r/EPA
              United Stales
              Environmental Protection
              Agency
               Office of Research and
               Development
               Washington DC 20460
  EPA/600/AP-93/004a
  December 1993
  External Review Draft
Air Quality
Criteria for
Ozone and
Related
Photochemical
Oxidants
Review
Draft
(Do Not
Cite or
Quote)
             Volume I  of
                             Notice
               This document is a preliminary draft. It has not been formally
              released by EPA and should not at this stage be construed to
              represent Agency policy. It is being circulated for comment on its
              technical accuracy and policy implications.

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TECHNICAL REPORT DATA
(fieae read Instructions on iht reverie btfort comple
1. REPORT NO.
EPA/60Q/AP-93/Q04a
2.
4, TITLE AND SUBTITLE
Air Quality Criteria for Ozone and Related
Photochemical Oxidants - Volume I of III
7. AUTMOR(S)
B. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Criteria and Assessment Office (MD-52)
Office of Health and Environmental Assessment, ORD
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
12. SPONSORING AQENCY NAME AND ADC
Office of Health and Enviror
Office of Research and Devel
U.S. Environmental Protectic
Washington, D.C. 20460
IRESS
mental Assessment (RD-689)
opment
m Agency
3.
S. REPORT DATE
December 1993
«. PERFORMING ORGANIZATION CODE
*. PERFORMINO ORGANIZATION REPORT NO,
BCftO-R-0746
10.PROORAM CLEMENT NO,
11. CONTHACT/QRANT NO,
t*.TVre OF REPORT AND PERIOD COVERED
External Review Draft
14. SPONSORING AGENCY CODE
600/21
IS. SUPPLEMENTARY NOTES
i«. ABSTRACT jj^ y «, Environmental Protection Agency (EPA) promulgates the National Ambient Air
Quality Standards (NAAQS) on the basis of scientific information contained in air quality criteria
documents. The previous ozone (O3) criteria document, Air Quality Criteria for Ozone and
Other Photochemical Oxidants, was released in August 1986 and a supplement, Summary of
Selected New Information on Effects of Ozone on Health and Vegetation, was released in January
1992. These documents were used as the basis for a March 1993 decision by EPA that revision
of the existing 1-h NAAQS for Oj was not appropriate at that time. That decision, however,
did not take into account some of the newer scientific data that became available after completion
of the 1986 criteria document. The purpose of this revised air quality criteria document for 63
and related photochemical oxidants is to critically evaluate and assess the latest scientific data
associated with exposure to the concentrations of these pollutants found in ambient air.
Emphasis is placed on the presentation of health and environmental effects data; however, other
scientific data are presented and evaluated in order to provide a better understanding of the
nature, sources, distribution, measurement, and concentrations of O3 and related photochemical
oxidants and their precursors in the environment. Although the document is not intended to be
an exhaustive literature review, it is intended to cover all pertinent literature available through
the end of 1993.
17.
1. DESCRIPTORS
• KEY WORDS AND DOCUMENT ANALYSIS
b. IDENTIFIERS/OPEN ENDED TERMS
>
18. DISTRIBUTION STATEMENT
Release to Public
1i, SECURITY CLASS (This Krporr/
Unclassified
20. SECURITY CLASS {Thiipagej
Unclassified

c. COS ATI FieWGioup

21, NO. Of PAGES
457
22. PRICE
f PA F«r» 2220-1 (R«v. 4-77)    pntviou* COITION i» OBSOLETE

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RAFT-DO NOT QUOTE OR CITE                            EPA/600/AP-93/004a
                                                       December 1993
                                                       External Review Draft
              Air Quality  Criteria for  Ozone
        and Related  Photochemical  Oxidants
                         Volume I of
                                 NOTICE
                This document is a preliminary draft. It has not been formally
                released by EPA and should not at this stage be construed to
                represent Agency policy. It is being circulated for comment on
                Its technical accuracy and policy implications.
                  Environmental Criteria and Assessment Office
                  Office of Health and Environmental Assessment
                      Office of Research and Development
                     U.S. Environmental Protection Agency
                      Research Triangle Park, NC 27711
                                                    Printed on Recycled Paper

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                                  DISCLAIMER

     This document is an external draft for review purposes only and does not constitute
U.S. Environmental Protection Agency policy. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
 December 1993                         I-ii       DRAFT-DO NOT QUOTE OR CITE

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                                      PREFACE

     In 1971, the U.S. Environmental Protection Agency (EPA) promulgated National
Ambient Air Quality Standards (NAAQS) to protect the public health and welfare from
adverse effects of photochemical oxidants.  In 1979, the chemical designation of the
standards was changed from photochemical oxidants to ozone (Oj). This document,
therefore, focuses primarily on the scientific air quality criteria for O3 and, to a lesser extent,
for other photochemical oxidants like hydrogen peroxide and the peroxyacyl nitrates.
     The EPA promulgates the NAAQS  on the basis of scientific information contained in
air quality criteria documents.  The previous O3 criteria document, Air Quality Criteria for
Ozone and Other Photochemical Oxidants,  was released in August 1986 and a supplement,
Summary of Selected New Information on Effects of Ozone on Health and Vegetation, was
released hi January 1992.  These documents were used as the basis for a March 1993
decision by EPA that revision of the existing 1-h NAAQS for O3 was not appropriate at that
time.  That decision, however, did not take into account some of the newer scientific data
that became available after completion of the 1986 criteria document.  The  purpose of this
revised air quality criteria document for O3 and related photochemical oxidants is to critically
evaluate and assess the latest scientific data associated with exposure to the concentrations of
these pollutants found in ambient air.  Emphasis is placed on the presentation of health and
environmental effects data; however, other scientific data are presented and evaluated in
order to provide a better understanding of the nature, sources, distribution, measurement,
and concentrations of 63 and related photochemical oxidants and their precursors  in the
environment.  Although the document is  not intended to be an exhaustive literature review, it
is  intended to cover all pertinent literature available through the end of 1993.
     This document was prepared and peer reviewed by experts from various state and
Federal governmental offices, academia,  and private industry for use by EPA to support
decision making regarding potential risks to public health and welfare.  The Environmental
Criteria and Assessment Office of EPA's Office of Health and Environmental Assessment
acknowledges with appreciation the contributions provided by these authors and reviewers as
well as the diligence of its staff and  contractors in the preparation of this document at the
request of the Office of Air Quality Planning and Standards.
December 1993                           T_«;       DBAFT-nn NOT nTTrrrn r\o

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 Previous Page Blank
                  Air Quality Criteria for Ozone
                 and Other Photochemical Oxidants
                       TABLE OF CONTENTS

                            Volume I

1.  EXECUTIVE SUMMARY	     1-1

2.  INTRODUCTION	     2-1

3.  TROPOSPHERIC OZONE AND ITS PRECURSORS	     3-1

4.  ENVIRONMENTAL CONCENTRATIONS, PATTERNS, AND
   EXPOSURE ESTIMATES	     4-1


                            Volume n

5.  ENVIRONMENTAL EFFECTS OF OZONE AND
   RELATED PHOTOCHEMICAL OXIDANTS	     5-1

APPENDED 5A: COLLOQUIAL AND LATIN NAMES	     5A-1


                            Volume HI

6.  TOXICOLOGICAL EFFECTS OF OZONE AND RELATED
   PHOTOCHEMICAL OXIDANTS	     6-1

7.  HUMAN HEALTH EFFECTS OF OZONE AND RELATED
   PHOTOCHEMICAL OXIDANTS  .	,     7-1

8.  EXTRAPOLATION OF ANIMAL TOXICOLOGICAL DATA
   TO HUMANS	     8-1

9.  INTEGRATIVE SUMMARY OF OZONE HEALTH EFFECTS  	     9-1

APPENDIX A;  GLOSSARY OF TERMS AND SYMBOLS  	     A-l
December 1993                     I_v      DRAFT-DO NOT OTTOTR m? rrra

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                          TABLE OF CONTENTS
                                                                  Page
LIST OF TABLES  	      I-xiii
LIST OF FIGURES	      I-xvii
LIST OF ABBREVIATIONS AND ACRONYMS .	      I-xxiii
AUTHORS, CONTRIBUTORS, AND REVIEWERS	      I-xxvii
U.S. ENVIRONMENTAL PROTECTION AGENCY PROJECT TEAM
FOR DEVELOPMENT OF AIR QUALITY CRITERIA FOR OZONE
AND RELATED PHOTOCHEMICAL OXIDANTS  .	      I-xxxiii


1.   EXECUTIVE SUMMARY	     1-1

2.   INTRODUCTION	     2-1
    2.1   LEGISLATIVE BACKGROUND	     2-2
    2.2   REGULATORY BACKGROUND  	     2-2
    2.3   SUMMARY OF MAJOR SCIENTIFIC TOPICS
         PRESENTED	     2-6
         2.3.1   Air Chemistry	     2-6
         2.3.2   Air Quality	     2-6
         2.3.3   Environmental Effects 	     2-7
         2.3.4   Health Effects	     2-7
    2.4   ORGANIZATION AND CONTENT OF THE DOCUMENT ...     2-8
    REFERENCES .	     2-11

3.   TROPOSPHERIC OZONE AND ITS PRECURSORS	     3-1
    3.1   INTRODUCTION	     3-1
    3.2   TROPOSPHERIC OZONE CHEMISTRY	     3-2
         3.2.1   Background Information	     3-2
         3.2.2   Structure of the Atmosphere 	     3-4
                3.2.2.1 Vertical and Horizontal Mixing in
                       the Atmosphere	     3-5
                3.2.2.2 Formation of Stratospheric Ozone	     3-5
         3.2.3   Tropospheric Ozone in the Unpolluted Atmosphere  . .  .     3-8
                3.2.3,1 Tropospheric Hydroxyl Radicals	     3-9
                3,2.3.2 Tropospheric Nitrogen Oxides Chemistry  ....     3-10
                3.2.3.3 The Methane Oxidation Cycle	     3-13
                3.2.3.4 Cloud Processes in the
                       Methane-Dominated Troposphere	     3-20
         3.2.4   Photochemistry of the Polluted Atmosphere	     3-20
                3,2.4,1 Tropospheric Loss Processes of
                       Volatile Organic Compounds	     3-22
                3.2.4.2 Chemical Formation of Ozone in Polluted
                       Air	     3-39
                3.2.4.3 Hydrocarbon Reactivity with Respect to
                       Ozone Formation	     3-44
December 1993
T .^:
        rvp A TJT_nr» Krrvr nTTnrn rvn

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                         TABLE OF CONTENTS (coot'd)
                                                                      Page

          3.2.5   Photochemical Production of Aerosols  	    3-47
                 3.2.5.1  Phase Distributions of Organic Compounds  . . .    3-48
                 3.2.5.2  Acid Deposition  .  .	    3-50
    3.3    METEOROLOGICAL PROCESSES INFLUENCING OZONE
          FORMATION AND TRANSPORT	    3-53
          3.3.1   Meteorological Processes  	    3-53
                 3.3.1.1  Surface Energy Budgets	    3-53
                 3.3.1.2  Planetary Boundary  Layer  	    3-55
                 3.3.1.3  Cloud Venting	    3-59
                 3.3.1.4  Stratospheric-Tropospheric Ozone
                         Exchange	    3-60
          3.3.2   Meteorological Parameters	    3-61
                 3.3.2.1  Sunlight	    3-62
                 3.3.2.2  Temperature	    3-63
                 3.3.2.3  Wind Speed	    3-70
                 3.3.2.4  Air Mass Characteristics	    3-74
          3.3.3   Normalization of Trends	    3-75
    3.4    PRECURSORS OF OZONE AND OTHER OXTOANTS	    3-77
          3.4.1   Sources  and Emissions of Precursors  	    3-77
                 3.4.1,1  Introduction	    3-77
                 3.4.1.2  Nitrogen Oxides  	    3-78
                 3.4.1.3  Volatile Organic Compounds	    3-89
                 3.4.1.4  Relationship of Summertime Precursor
                         Emissions and Ozone Production	    3-99
          3.4.2   Concentrations of Precursor Substances in Ambient
                 Air	    3-101
                 3.4.2.1  Nonmethane Organic Compounds	    3-101
                 3.4.2.2  Nitrogen Oxides	    3-106
                 3.4.2.3  Ratios of Concentrations of Nonmethane
                         Organic Compounds and Nitrogen Oxides ....    3-107
          3.4.3   Source Apportionment and Reconciliation	    3-108
                 3.4.3.1  Source Apportionment	    3-108
                 3.4.3.2  Source Reconciliation	    3-113
    3.5    ANALYTICAL METHODS FOR OXIDANTS AND
          THEIR PRECURSORS	    3-115
          3.5.1   Sampling and Analysis of Ozone and Other
                 Oxidants	 .	    3-115
                 3.5.1.1  Ozone .... . . . .... . .	    3-115
                 3.5.1.2  Peroxyacetyl Nitrate and Its Homologues ....    3-129
                 3.5.1.3  Gaseous Hydrogen Peroxide	    3-134
          3.5.2   Sampling and Analysis of Volatile Organic
                 Compounds		    3-138
                 3.5.2.1  Introduction	    3-138
                 3.5.2.2  Nonmethane Hydrocarbons	    3-139

December 1993                        I-viii      DRAFT-DO NOT QUOTE OR CITE

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                          TABLE OF CONTENTS (cont'd)
                                                                         Page

                  3.5.2.3  Carbonyl Species ...................     3-148
                  3.5.2.4  Polar Volatile Organic Compounds ........     3-151
          3.5.3    Sampling and Analysis of Oxides of Nitrogen  .......     3-152
                  3.5.3.1  Introduction  ...... . ...............     3-152
                  3.5.3.2  Measurement of Nitric Oxide  ..... ......     3-153
                  3.5.3.3  Measurements for Nitrogen Dioxide  .......     3-157
                  3.5.3.4  Calibration Methods   ...... ..........     3-166
    3.6   OZONE AIR QUALITY MODELS ...................     3-167
          3.6.1    Definitions, Description,  and Uses .... .........  .     3-168
                  3.6.1.1  Grid-Based Models .......... ........     3-169
                  3.6.1.2  Trajectory Models ... ...............     3-170
          3.6.2    Model Components .... ...................     3-173
                  3.6.2.1  Emissions Inventory  . . ...............     3-173
                  3.6.2.2  Meteorological Input to Air Quality
                          Models  .........................     3-175
                  3.6.2.3  Chemical Mechanisms ................     3-182
                  3.6.2.4  Deposition Processes .................     3-184
                  3.6.2.5  Boundary and Initial  Conditions  ..........     3-187
          3.6.3    Urban and Regional Ozone Air Quality Models ......     3-188
                  3.6.3.1  The Urban Airshed Model .............     3-195
                  3.6.3.2  The Regional Oxidant Model ............     3-196
                  3.6.3.3  The Regional Acid Deposition Model  ......     3-201
          3.6.4    Evaluation of Model Performance .............  .     3-202
                  3.6.4.1  Model Performance Evaluation
                          Procedures .......................     3-203
                  3.6.4.2  Performance Evaluation of Ozone Air
                          Quality Models  ....................     3-205
                  3.6.4.3  Data Base Limitations ................     3-207
          3.6.5    Use of Ozone Air Quality Models for Evaluating
                  Control Strategies ........................     3-209
          3.6.6    Conclusions . . ..........................     3-211
    3.7 SUMMARY AND CONCLUSIONS ....................     3-212
          3.7.1    Tropospheric Ozone Chemistry ................     3-212
                  3.7.1.1  Ozone in the Unpolluted Atmosphere .......     3-212
                  3.7.1.2  Ozone Formation in the Polluted
                          Troposphere ......................     3-212
          3.7.2    Meteorological Processess Influencing Ozone
                  Formation and Transport ....................     3-215
                  3.7.2.1  Meteorological Processes ..............     3-215
                  3.7.2.2  Meteorological Parameters .............     3-216
                  3.7.2.3  Normalization of Trends  ......... .....     3-217
          3.7.3    Precursors   .....  . ......................     3-217
                  3.7.3.1  Nitrogen Oxides Emissions .............     3-217
                  3.7.3.2  Volatile Organic Compound Emissions ......     3-218
December 1993                           T ;~      npA*5T_rw-v -vrrvr

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                        TABLE OF CONTENTS (cont'd)
                 3.7.3.3  Concentrations of Volatile Organic
                        Compounds in Ambient Air	    3-219
                 3.7.3.4  Concentrations of Nitrogen Oxides in
                        Ambient Air	    3-219
                 3.7.3.5  Source Apportionment and Reconciliation  ....    3-220
         3.7.4    Analytical Methods for Oxidants and Their
                 Precursors	    3-221
                 3.7.4.1  Oxidants	    3-221
                 3.7.4.2  Volatile Organic Compounds	    3-223
                 3.7.4.3  Oxides of Nitrogen	    3-224
         3.7.5    Ozone Air Quality Models	    3-225
                 3.7.5.1  Definitions, Descriptions, and Uses	    3-225
                 3.7.5.2  Model Components  	    3-226
                 3.7.5.3  Evaluation of Model Performance	    3-227
                 3.7.5.4  Use of Ozone Air Quality Model for
                        Evaluating Control Strategies   .	    3-227
                 3.7.5.5  Conclusions  .... *	    3-228
    REFERENCES	    3-229

4.   ENVIRONMENTAL CONCENTRATIONS, PATTERNS, AND
    EXPOSURE ESTIMATES	    4-1
    4.1   INTRODUCTION	    4-1
         4.1.1    Characterizing Ambient Ozone Concentrations  ......    4-2
         4.1.2    The Identification and Use of Existing Ambient
                 Ozone Data	    4-6
    4.2   TRENDS IN OZONE CONCENTRATIONS	    4-9
         4.2.1    Trends in Ambient Ozone Concentrations  	    4-9
    4.3   SURFACE OZONE CONCENTRATIONS	    4-19
         4.3.1    Introduction	    4-19
         4.3.2    Urban Area Concentrations	    4-21
         4.3.3    Nonurban Area Concentrations	    4-34
                 4.3.3.1  Pristine Areas	    4-34
                 4.3.3.2  Urban-Influenced Nonurban Areas  .	    4-39
    4.4   DIURNAL VARIATIONS IN OZONE CONCENTRATIONS  .  .    4-54
         4.4.1    Introduction  	    4-54
         4.4.2    Urban Area Diurnal Patterns	    4-55
         4.4.3    Nonurban Area Diurnal Patterns	    4-60
    4.5   SEASONAL PATTERNS IN OZONE CONCENTRATIONS . .  .    4-67
         4.5.1    Urban Area Seasonal Patterns	    4-67
         4.5.2    Nonurban Area Seasonal Patterns 	    4-67
         4.5.3    Seasonal Pattern Comparisons with "Pristine" Sites  . .  .    4-69
    4.6   SPATIAL VARIATIONS IN OZONE CONCENTRATIONS . .  .    4-70
         4.6.1    Urban-Nonurban Area Concentration Differences .....    4-70
         4.6.2    Concentrations Experienced at High-Elevation Sites ...    4-71

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Previous Page Blank
                          TABLE OF CONTENTS (cont'd)
           4.6.3    Other Spatial Variations in Ozone Concentrations  ....     4-74
      4.7   INDOOR OZONE CONCENTRATIONS	     4-82
      4.8   ESTIMATING EXPOSURE TO OZONE	     4-83
           4.8.1    Introduction	 .	     4-83
           4.8.2    Fixed-Site Monitoring Information Used To Estimate
                   Population and Vegetation Exposure	     4-87
           4.8.3    Personal Monitors	     4-90
           4.8.4    Population Exposure Models  ,	     4-90
           4.8.5    Concentration and Exposures Used  in Research
                   Experiments	     4-92
      4.9   CONCENTRATIONS OF PEROXYACETYL NITRATES IN
           AMBIENT ATMOSPHERES	     4-95
           4.9.1    Introduction	     4-95
           4.9.2    Urban Area Peroxyacetyl Nitrate Concentrations	     4-96
           4.9.3    Concentration of Peroxyacetyl Nitrate and
                   Peroxypropionyl Nitrate in Rural Areas	     4-100
      4.10  CONCENTRATION AND PATTERNS OF  HYDROGEN
           PEROXIDE IN THE AMBIENT ATMOSPHERE	     4-102
      4.11  CO-OCCURRENCE OF OZONE	     4-103
           4.11.1   Introduction  	     4-103
           4.11.2   Nitrogen Oxides	     4-104
           4.11.3   Sulfur Dioxide	     4-105
           4.11.4   Acidic Sulfate Aerosols	     4-106
           4.11.5   Acid Precipitation	     4-108
           4.11.6   Acid Cloudwater  	     4-110
      4.12  SUMMARY	     4-111
      REFERENCES	 .     4-124
  December 1993                        I-*,'      DRAFT-DO NOT niTrvrn nt»

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                                LIST OF TABLES
Number                                                                    Page

2-1      National Ambient Air Quality Standards for Ozone	       2-3

3-1      Estimated Emissions of Methane, Nonmethane
         Organic Compounds, Nitrous Oxide, and Oxides
         of Nitrogen into the Earth's Atmosphere from
         Biogenic and Anthropogenic Sources  ...................       3-21

3-2      Calculated Tropospheric Lifetimes of Selected
         Volatile Nonmethane Organic Compounds Due to
         Photolysis and Reaction with Hydroxyl and NO3
         Radicals and with Ozone	       3-24

3-3      Calculated Incremental Reactivities of Selected
         VOCs as a Function of the VOC/NOX Ratio for an
         Eight-Component VOC Mixture and Low-Dilution
         Conditions	       3-47

3-4      Rates of Increase of Peak Ozone with Diurnal Maximum
         Temperature for T  < 300 K and T > 300 K, Based on
         Measurements for April 1 to September 30, 1988	       3-67

3-5      Recent Studies Examining Trends in Ozone Data After Removal of
         Variability Associated with Meteorological Factors	       3-77

3-6      Source Categories Used To Inventory  Nitrogen Oxides
         Emissions	       3-79

3-7      1991  Emission Estimates for Manmade Sources of Nitrogen
         Oxides in the United States	       3-81

3-8      Recent Trends in Nitrogen Oxides Emissions for Major
         Manmade Source Categories	       3-84

3-9      Comparison of Estimates of Nitrogen  Oxides Emissions
         from  Manmade  Sources in the United States	       3-86

3-10     Annual Nitrogen Oxides Emissions from Soils by
         U.S. Environmental Protection Agency Region   	       3-88

3-11     Estimated 1991  Emissions of Volatile  Organic Compounds
         from Manmade  Sources in the United States	       3-90

3-12     Recent Trends in Emissions of Volatile Organic Compounds
         from  Major Categories of Manmade Sources	       3-93

December 1993  o-—J:-	LI—i- T.^ii     DRAFT-DO NTOT OTTOTR nu PTTTT

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                            LIST OF TABLES (cont'd)

Number                                                                  Page

3-13     Annual Biogenic Hydrocarbon Emission Inventory for the
         United States	       3-96

3-14     Annual Biogenic Hydrocarbon Emission Inventory by Month
         and U.S. Environmental Protection Agency Region for the
         United States	       3-98

3-15     Performance Specifications for Automated Methods of Ozone
         Analysis	       3-117

3-16     Reference and Equivalent Methods for Ozone Designated
         by the U.S. Environmental Protection Agency	       3-118

3-17     List of Designated Reference and Equivalent Methods for
         Ozone	       3-119

3-18     Performance Specifications for Nitrogen Dioxide Automated
         Methods	       3-158

3-19     Comparability Test Specifications for Nitrogen Dioxide	       3-158

3-20     Reference and Equivalent Methods for Nitrogen Dioxide
         Designated by the U.S. Environmental Protection Agency	       3-159

3-21     Grid-Based Urban and Regional Air Pollution Models:   Overview
         of Three-Dimensional Air Quality Models	       3-190

3-22     Grid-Based Urban and Regional Air Pollution Models:   Treatment
         of Emissions and Spatial Resolution	       3-191

3-23     Grid-Based Urban and Regional Air Pollution Models:  Treatment
         of Meteorological Fields, Transport and Dispersion	       3-192

3-24     Grid-Based Urban and Regional Air Pollution Models:  Treatment
         of Chemical Processes	       3-193

3-25     Grid-Based Urban and Regional Air Pollution Models:  Treatment
         of Cloud and Deposition Processes	       3-194

3-26     Regional Oxidant Model Geographical Domains	       3-197
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                             LIST OF TABLES (cont'd)

Number                                                                    Page

3-27     Applications of Photochemical Air Quality Models to Evaluating
         Ozone  	      3-210

4-1      Ozone Monitoring Season by State	       4-8

4-2      Summary by Forestry and Agricultural Regions for Ozone Trends
         Using the W126 Exposure Parameter Accumulated on a Seasonal
         Basis	 . . .	      4-18

4-3      The Highest Second Daily Maximum One-Hour Ozone
         Concentration by Metropolitan Statistical Area for the Years
         1989 to 1991	      4-22

4-4      Summary of Percentiles of Hourly Average Concentrations for
         the April-to-October Period	      4-25

4-5      The Highest Second Daily Maximum Eight-Hour Average Ozone
         Concentration by Metropolitan Statistical Area for the Years
         1989 to 1991	      4-27

4-6      Seasonal (April to October) Percentile Distribution
         of Hourly  Ozone Concentrations, Number of Hourly
         Mean Ozone Occurrences Greater Than or Equal to 0.08
         and Greater Than or Equal to 0,10, Seasonal Seven-Hour
         Average Concentrations, and W126 Values for Sites in
         Selected Class I Areas with Data Capture Greater
         Than or Equal to 75%  	      4-36

4-7      Seasonal (April to October) Percentile Distribution
         of Hourly  Ozone Concentrations, Number of Hourly
         Mean Ozone Occurrences Greater Than or Equal to 0.08
         and Greater Than or Equal to 0.10, Seasonal Seven-Hour
         Average Concentrations, and W126 Values for Three
         "Clean" National Forest Sites with Data Capture
         Greater Than or Equal to 75%   	      4-37

4-8      The Value of the W126 Sigmoidal Exposure Parameter
         Calculated Over the Annual Period	      4-38

4-9      The Value of the Ozone Season  (Seven-Month) Average
         of the Daily Seven-Hour (0900 to 1559 Hours)
         Concentration	      4-40
December 1993                         T-™      DRAFT-DO NOT OUOTE OH HTTP

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                             IJST OF TABLES (cont'd)

Number                                                                   Page

4-10     Summary of Percentiles, Number of Hourly Occurrences
         Greater Than or Equal to 0.10 ppm, and Three-Month
         SUM06 Values for Selected Rural Ozone Monitoring
         Sites in 1989 (April to October)	       4-42

4-11     Summary of Percentiles of Hourly Average Concentrations
         for Electric Power Research Institute Sulfate Regional
         Experiment Sites/ERAQS Ozone Monitoring
         Sites   	       4-43

4-12     Seven-Hour Growing Season Mean, W126 Values, and
         Number Greater Than or Equal to 80 ppb for Selected
         Eastern National Dry Deposition Network Sites	       4-45

4-13     Summary of Percentiles for National Dry Deposition
         Network Monitoring Sites   	       4-48

4-14     Description of Mountain Cloud Chemistry Program
         Sites	       4-72

4-15     Seasonal (April to October) Percentiles, SUM06, SUM08,
         and W126 Values for  the Mountain Cloud Chemistry
         Program Sites	       4-73

4-16     Summary Statistics for 11 Integrated Forest
         Study Sites	       4-76

4-17     Quarterly Maximum One-Hour Ozone Values at
         Sites in and Around New Haven, Connecticut, 1976	       4-78

4-18     Summary of Reported Indoor-Outdoor Ozone
         Ratios	       4-84

4-19     Summary of Measurements of Peroxyacetyl Nitrate and
         Peroxypropionyl Nitrate in Urban Areas 	       4-98

4-20     Summary of Measurements of Peroxyacetyl Nitrate and
         Peroxypropionyl Nitrate in Rural Areas	       4-101
December 1993                         I-xvi     DRAFT-DO NOT QUOTE OR CITE

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                                 1JST OF FIGURES

Number                                                                      Page

3-1       The cyclic reactions of tropospheric nitrogen oxides  	        3-13

3-2       Atmospheric reactions in the complete oxidation
          of methane	       3-17

3-3       Cyclic reactions of methane oxidation to formaldehyde,
          conversion of nitric oxide to nitrogen dioxide, and concomitant
          formation of ozone in the atmosphere	        3-19

3-4       Major steps in production of ozone in ambient air	        3-40

3-5       Time-concentration profiles for selected species during
          irradiations of an NOx-propene-air mixture in an indoor
          chamber with constant light intensity ,	        3-41

3-6       Time-concentration profiles for selected species during
          irradiations of an NOx-propene-air mixture in an outdoor
          chamber with diurnally varying light intensity	        3-42

3-7       Surface radiation budget for short-wave and long-wave radiation . .        3-54

3-8       The number of reports of ozone concentrations ^120 ppb at
          the 17 cities studied in Samson et al. (1988)	        3-63

3-9       A scatter plot of maximum daily ozone concentration in Atlanta,
          Georgia, and New York, New York, versus maximum daily
          temperature	       3-64

3-10      A scatter plot of maximum daily ozone concentration in Detroit,
          Michigan, and Phoenix, Arizona, versus maximum daily
          temperature	       3-65

3-11      A scatter plot of maximum ozone concentration versus maximum
          daily temperature for four nonurban sites	       3-65

3-12      The frequency of 24-h trajectory transport distance en route to
          city when ozone was & 120 ppb in four Southern U.S. cities
          compared with the percent frequency distribution for all 17 cities
          of a nationwide study, 1983 to 1985	       3-71
December 1993                          I-xvii      DRAFT-DO NOT nTTrvrn nt»

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                             LIST OF FIGURES (cont'd)

Number

3-13     The frequency of 24-h trajectory transport distance en route to
         city when ozone was S120 ppb in four New England cities
         compared with the percent frequency distribution for all 17 cities
         of a nationwide study, 1983 to 1985 . ,	       3-71

3-14     The root-mean-square-difference between CLASS
         observations and profiler observations as a function of height
         above ground level	 ..'..,	       3-72

3-15     The root-mean-square-difference between CLASS
         observations and lidar observations as a function of height
         above ground level		       3-73

3-16     Model of ozone levels using regression techniques	 .       3-76

3-17     Simulated versus observed ozone levels using regression
         techniques on an independent data set obtained in summer 1992
         in Atlanta, Georgia	       3-76

3-18     The 50 largest sources of nitrogen oxides (power plants) in the
         United States	       3-82

3-19     Nitrogen oxides emissions from manmade sources in the
         10  U.S. Environmental Protection Agency regions of the
         United States,  1991		       3-82

3-20     Changes in nitrogen oxides emissions from manmade sources in
         the United States, 10-year intervals, 1940 through 1990	       3-83

3-21     Growth in nitrogen oxides emissions from stationary source
         fuel combustion and transportation from 1940 through
         1990		.	       3-83

3-22     Changes in emissions of volatile organic compounds from major
         manmade sources in the United States, 10-year intervals, 1940
         through 1990	       3-92

3-23     Changes in emissions of volatile organic compounds from major
         manmade sources, 1940 through 1990 . .-...	       3-92

3-24     Estimated biogenic emissions of volatile organic compounds in
         the United States as  a function of season	       3-100
December 1993                         I-xviii     DRAFT-DO NOT QUOTE OR CITE

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                             LIST OF FIGURES (cont'd)

Number                                                                     Page

3-25     Example of EKMA diagram for high-oxidant urban area	       3-172

3-26     Regional oxidant model superdomain with modeling domains ....       3-198

4-1      National trend in the composite average of the second highest
         maximum one-hour ozone concentration at both NAMS and all
         sites with 95% confidence intervals, 1982 to  1991	       4-10

4-2      The annually averaged composite diurnal curves for the following
         sites that changed from nonattainment to "attainment status:"
         Montgomery County, Alabama; Concord, California;
         Louisville, Kentucky; and Dade County, Florida, for the
         period 1987 to 1990	       4-13

4-3      A summary of the seasonal (January to December) averaged
         composite ozone diurnal curve and integrated exposure W126
         index for the Los Angeles, California, site for the period 1980
         to 1991	       4-14

4-4      United States map of the highest second daily maximum one-hour
         average ozone concentration by Metropolitan Statistical Area,
         1991	       4-21

4-5      The relationship between the second highest daily maximum
         hourly average ozone concentration and the maximum three-
         month SUM06 value and the second highest daily maximum
         eight-hour average concentration and the maximum three-
         month SUM06 value for specific site years at rural
         agricultural sites for the  1980-to-1991 period	       4-31

4-6      The relationship between the second highest daily maximum
         hourly average ozone concentration and the maximum three-
         month SUM06 value and the second highest daily maximum
         eight-hour average concentration and the maximum three-
         month SUM06 value for specific site years at rural forested
         sites for the 1980-to-1991 period	       4-32

4-7      The location of National Dry Deposition Network monitoring sites
         as of December 1990	,	,	       4-44

4-8      The kriged 1985 to 1986 maximum seven-hour and twelve-hour
         average concentrations of ozone across the United States  	       4-52


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                             LIST OF FIGURES (cont'd)

Number                                                                     Page

4-9      The kriged estimates of the W126 integrated ozone exposure index
         for the eastern United States for 1988 and 1989	       4-53

4-10     The comparison of the seasonal diurnal patterns using 1988 data
         for Jefferson County, Kentucky, and Oliver County, North
         Dakota	       4-56

4-11     Diurnal behavior of ozone at rural sites in the United States
         in July	       4-57

4-12     Diurnal pattern of one-hour ozone concentrations on July 13, 1979,
         Philadelphia, Pennsylvania	       4-58

4-13     Diurnal and one-month composite diurnal variations in ozone
         concentrations, Washington, District of Columbia, July 1981 ....       4-59

4-14     Diurnal and one-month composite diurnal variations in ozone
         concentrations, St.  Louis County, Missouri, September 1981 ....       4-60

4-15     Diurnal and one-month composite diurnal variations in ozone
         concentrations, Alton, Illinois, October 1981 (fourth quarter) ....       4-61

4-16     Composite diurnal patterns of ozone concentrations by quarter,
         Alton, Illinois, 1981	       4-62

4-17     Quarterly composite diurnal patterns of ozone concentrations
         at selected sites representing potential for exposure of major
         crops, 1981	       4-63

4-18     Composite diurnal  ozone pattern at a rural National Crop Loss
         Assessment Network site in Argonne, Illinois, August 6 through
         September 30, 1980	       4-64

4-19     Composite diurnal  ozone pattern at selected National Dry
         Deposition Network sites	       4-65

4-20     Composite diurnal  pattern at Whiteface Mountain, New York, and
         Mountain Cloud Chemistry Program's Shenandoah National
         Park  site for May to September 1987 	       4-66

4-21     Seasonal variations in ozone concentrations as indicated by
         monthly averages and the one-hour  maximum in each month at
         selected sites,  1981	       4-68

December 1993                          I-xx      DRAFT-DO NOT QUOTE OR CITE

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                            LIST OF FIGURES (cont'd)

Number

4-22     Seven- and 12-hour means at Whiteface Mountain and
         Shenandoah National Park for May to September 1987 and
         integrated exposures at Whiteface Mountain and
         Shenandoah National Park for May to September 1987	       4-74

4-23     Integrated  exposures for three non-Mountain Cloud Chemistry
         Program's Shenandoah National Park sites, 1983 to 1987	       4-75

4-24     Maximum one-hour ozone concentrations (in parts per billion) and
         average 8:00 a.m. through 8:00 p.m. strong acid concentrations
         (expressed as micrograms per cubic meter of sulfuric acid) for
         each day that pulmonary function data were collected at
         Fairview Lake camp in 1988	       4-89

4-25     Maximal one-hour ozone concentrations at Fairview Lake during
         the study period	       4-89

4-26     The number of occurrences for each of the seven categories
         described in text  	       4-95

4-27     The co-occurrence pattern of ozone and sulfuric acid for
         July 25, 1986	       4-107

4-28     Sulfate, hydrogen ion, and ozone measured at Breadalbane Street
         (Site 3) during July and August, 1986, 1987,  and 1988  .......       4-108
December 1993                          I-xxi     DRAFT-DO NOT QUOTE OR CITE

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ADOM
AGL
AQCD
AUSPEX
CAA
CAL-RAMS
CASAC
CBM
CCM
CFC(s)
CFR
CI
CIT

CL
CTWM
3-D
DIAL
DOAS
DWM
EKMA
EMS
EPA
EPRI
EPS
FDDA
GMEP
GRIDS
GTP
HCFC(s)
IR
K
LMOS
LT
LIST OF ABBREVIATIONS AND ACRONYMS

 Acid Deposition and Oxidant Model
 Above ground level
 Air Quality Criteria Document
 Atmospheric Utility Signatures, Predictions, and Experiments
 Clean Air Act
 Coast and Late Regional Atmospheric Modeling System
 Clean Air Scientific Advisory Committee
 Carbon Bond Mechanism (has several versions)
 Community Climate Model
 Chlorofluorocarbon(s)
 Code of Federal Regulations
 Chemical ionization
 California Institute of Technology/Carnegie Institute
   of Technology Model
 Chemiluminescence
 Complex Terrain Wind Model
 Three-dimensional
 Differential absorption lidar
 Differential optical absorption spectrometry
 Diagnostic Wind Model
 Empirical Kinetic Modeling Approach (has several versions)
 Emissions Modeling System
 U.S. Environmental Protection Agency
 Electric Power Research Institute
 Emissions Preprocessor System
 Four-dimensional data assimilation
 Geoeoded Model of Emissions  and Projections
 Topography database operated by U.S. EPA
 Gas-phase titration
 Hydrochlorofluorocarbon (s)
 Infrared radiation; in Section 3.2., "incremental reactivity"
 Degrees Kelvin
 Lake Michigan Oxidant Study
 Local time
December 1993
                   I-xxiii     DRAFT-DO NOT QUOTE OR CITE

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               LIST OF ABBREVIATIONS AND ACRONYMS (cont'd)
M
MASS
MIDROXA
MM4/MM5
MOBILES
MODELS 3

NAAQS
NAPAP
NBS
NCAR
NECRMP
NEROS1
NEROXA
NIST
NMHC(s)
NMOC(s)
NO2
03
OAQPS
PAMS
PAN
PANs
PEL
PLANR
PF/TPLIF
PSD(s)
PVOC(s)
RADM
RAPS
RMSD
ROG
ROM
Third body in atmospheric chemical reactions; absorbs energy
Dynamic wind model used in STEM-n
Midwest domain of the ROM
Mesoscale Model, versions 4 and 5
U.S. EPA emissions model for mobile sources (version 5)
Modeling framework that consolidates all of U.S. EPA's
 3-D photochemical air quality models
National Ambient Air Quality Standard(s)
National Acid Precipitation Assessment Program
National Bureau of Standards; has been renamed NIST
National Center for Atmospheric Research
Northeast Corridor Regional Modeling Project
Northeast Regional Oxidant Study; a northeast domain of the ROM
A northeast domain of the ROM
National Institute of Standards and Technology
Nonmethane hydrocarbon(s)
Nonmethane organic compound(s)
Nitrogen dioxide
Ozone
Office of Air Quality Planning and Standards
Photochemical Aerometric Monitoring System
Peroxyacetyl nitrate
Peroxyacyl nitrates
Planetary boundary layer
Practice for Low-cost Application in Nonattainment Regions
Photofragmentation TPLIF
Passive sampling device(s)
Polar volatile organic compound(s)
Regional Acid Deposition Model (has several versions)
Regional Air Pollution Study (Illinois and Missouri)
Root-mean-square difference
Reactive organic gas(es)
Regional Oxidant Model (has several versions)
December 1993
                  I-xxiv     DRAFT-DO NOT QUOTE OR CITE

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               LIST OF ABBREVIATIONS AND ACRONYMS (cont'd)
ROMNET

SAB
SAPRC

SARMAP
SCAQS
SCCCAMP

SEROS1
SEROXA
SIP(s)
SJVAQS
SOS
SRM(s)
STEM-H
SUPROXA
TDLAS
TEA
TPL1F
TTFMS
UAM
UV
UV-B
VMT
VOC(s)
A northeast domain of the ROM; also, Regional Ozone Modeling for
 Northeast Transport program
Science Advisory Board
Statewide Air Pollution Research Center, University
 of California, Riverside
SJVAQS/AUSPEX Regional Model Adaptation Project
South Coast Air Quality Study (California)
South Central Coast Cooperative Aerometric Monitoring Program
 (California)
A southeast domain of the ROM
A southeast domain of the ROM
State Implementation Plan(s)
San Joaquin Valley Air Quality Study
Southern Oxidant Study
Standard Reference Material(s)
Sulfur Transport Eulerian Model (version n)
Super domain of the ROM
Tunable-diode laser absorption spectroscopy
Triethanolamine
Southern domain of the ROM
Two-photon laser-induced fluorescence
Two-tone frequency-modulated spectroscopy
Urban Airshed Model (has several versions)
Ultraviolet radiation
Ultraviolet radiation of wavelengths 280 to 320 nanometers
Vehicle miles traveled
Volatile organic compound(s)
December 1993
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                  AUTHORS, CONTRIBUTORS, AND REVIEWERS

                       CHAPTER 1. EXECUTIVE SUMMARY

 Principal Authors

 Mr. James A. Raub—Environmental Criteria and Assessment Office (MD-52),
 U.S. Environmental Protection Agency, Research Triangle Park, NC  27711

 Mr. William G. Ewald—Environmental Criteria and Assessment Office (MD-52),
 U.S. Environmental Protection Agency, Research Triangle Park, NC  27711

 Dr. J.H.B. Garner—Environmental Criteria and Assessment Office (MD-52),
 U.S. Environmental Protection Agency, Research Triangle Park, NC  27711

 Dr. Judith A. Graham—Environmental Criteria and Assessment Office (MD-52),
 U.S. Environmental Protection Agency, Research Triangle Park, NC  27711

 Ms. Beverly E. Tilton—Environmental Criteria and Assessment Office (MD-52),
 U.S. Environmental Protection Agency, Research Triangle Park, NC  27711


                           CHAPTER 2. INTRODUCTION

 Principal Author

 Mr. James A. Raub—Environmental Criteria and Assessment Office (MD-52),
 U.S. Environmental Protection Agency, Research Triangle Park, NC  27711


           CHAPTER 3.  TROPOSPHERIC OZONE AND ITS PRECURSORS

 Principal Authors

 Dr. A. Paul Altshuller—Environmental Criteria and Assessment Office (MD-52),
 U.S. Environmental Protection Agency, Research Triangle Park, NC  27711

 Dr. Roger Atkinson—Statewide Air Pollution Research Center, University of California,
 900 Watkins Avenue, Riverside, CA  92521

 Mr. Michael W. Holdren—BatteUe, 505 King Avenue, Columbus, OH 43201

 Dr. Thomas J. Kelly—Battelle, 505 King Avenue,  Columbus, OH 43201-2693
 December 1993                        l-xxvu     DRAFT-DO NOT QUOTE OR CITE

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              AUTHORS, CONTRIBUTORS, AND REVIEWERS (cont'd)
Dr. Charles W. Lewis—Atmospheric Research and Exposure Assessment Laboratory
(MD-47) U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Perry J. Samson—Department of Atmospheric, Oceanic, and Space Sciences, University
of Michigan, 2455 Hayward Street, Ann Arbor, MI  48109

Dr. John H. Seinfeld—Division of Engineering and Applied Science, California Institute of
Technology, 391 South Holliston Avenue, Pasadena, CA  91125

Dr. Joseph Sickles JJ—Atmospheric Research and Exposure Assessment Laboratory (MD-75),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Ms. Beverly E. Tilton—Environmental Criteria and Assessment Office (MD-52),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Halvor (Hal) Westberg—Department of Civil and Environmental Engineering,
Washington State University, Pullman, WA  99164
Reviewers

Dr. A. Paul Altshuller—Environmental Criteria and Assessment Office (MD-52),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Mr. Robert R. Arnts—Atmospheric Research and Exposure Assessment Laboratory (MD-84)
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Mr. Frank M. Black—Atmospheric Research and Exposure Assessment Laboratory (MD-46),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Joseph J. Bufalini—Atmospheric Research  and Exposure Assessment Laboratory
(MD-84), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Daewon Byun—Atmospheric Research and Exposure Assessment Laboratory (MD-80),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Jason K, S. Ching—Atmospheric Research and Exposure Assessment Laboratory
(MD-80), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Kenneth L. Demerjian—Atmospheric Sciences Research Center (SUMY-Albany),
100 Fuller Road, Albany NY 12205

Dr. Robin L. Dennis—Atmospheric Research and Exposure Assessment Laboratory (MD-80),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

December 1993                       I-xxviii    DRAFT-DO NOT QUOTE OR CITE

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              AUTHORS, CONTRIBUTORS, AND REVIEWERS (cont'd)
Dr. Basil Dimitriades—Atmospheric Research and Exposure Assessment Laboratory (MD-75),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Marcia C. Dodge—Atmospheric Research and Exposure Assessment Laboratory
(MD-84), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Mr. Chris Geron—Atmospheric Environmental Engineering Laboratory (MD-62),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Michael W. Gery—Atmospheric Research Associates,  160 North Washington Street,
Boston, MA  02114

Dr. James M. Godowitch—Atmospheric Research and Exposure Assessment Laboratory
(MD-80), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Jimmie W. Hodgeson—Atmospheric Research and Exposure Assessment Laboratory
(MD-84), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Harvey E. Jeffries—Department of Environmental Sciences and Engineering, School of
Public Health, CB #7400, University of North Carolina, Chapel Hill, North Carolina
27599-7400

Dr. Douglas R. Lawson—Energy and Environmental Engineering Center,  Desert Research
Institute, Reno, NV 89506

Dr. Charles W. Lewis—Atmospheric Research and Exposure Assessment Laboratory
(MD-47), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Mr. William A. Lonneman—Atmospheric Research and Exposure Assessment Laboratory
(MD-84), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. William A. McClenny—Atmospheric Research and Exposure Assessment Laboratory
(MD-44), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Mr. Frank F.  McElroy—Atmospheric Research and Exposure Assessment Laboratory
(MD-77), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Mr. Thomas B. McMullen—Office of Air Quality Planning and Standards (MD-14),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Edwin L.  Meyer—Office of Air Quality Planning and Standards (MD-14),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711
December 1993                         I-xxix     DRAFT-DO NOT QUOTE OR CITE

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              AUTHORS, CONTRIBUTORS, AND REVIEWERS (cont'd)
Mr. David C. Misenheimer—Office of Air Quality Planning and Standards (MD-14),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Mr. J. David Mobley—Office of Air Quality Planning and Standards (MD-14),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Will Ollison—American Petroleum Institute, 1220 L Street NW, Washington, DC  20005

Dr. Kenneth Olszyna—Tennessee Valley Authority, CEB 2A, Muscle Shoals, AL 35660

Mr. Thomas E. Pierce—Atmospheric Research and Exposure Assessment Laboratory
(MD-80), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Mr. Larry J. Purdue—Atmospheric Research and Exposure Assessment Laboratory (MD-56),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Mr. Kenneth A. Rehme—Atmospheric Research and Exposure Assessment Laboratory
(MD-77), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Harold G. Richter—Private consultant, 8601 Little Creek Farm Road, Chapel Hill, NC
27516

Mr. Shawn J. RoseUe—Atmospheric Research and Exposure Assessment Laboratory
(MD-80), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Mr. Kenneth L. Schere—Atmospheric Research and Exposure Assessment Laboratory
(MD-80), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Jack H. Shreffler—Atmospheric Research and Exposure Assessment Laboratory (MD-75),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Joseph Sickles n—Atmospheric Research and Exposure Assessment Laboratory (MD-75),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Mr. Robert L. Seila—Atmospheric Research and Exposure Assessment  Laboratory (MD-84),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Ms. Beverly E. TUton—Environmental Criteria and Assessment Office (MD-52),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Fred  Vukovich—Private consultant, 7820 Harps Mill Road, Raleigh, NC 27615

Mr. Richard A. Wayland—Office of Air Quality Planning and Standards (MD-14),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

December 1993                        I-xxx     DRAFT-DO NOT QUOTE OR CITE

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           CHAPTER 4.  ENVIRONMENTAL CONCENTRATIONS, PATTERNS,
                             AND EXPOSURE SiTIMATlS

   Principal Authors

   Dr. Allen S. Lefohn—A.S.L, & Associates,  111 Last Chanee Gulch, Suite 4A,
   Helena, MT 59601

   Dr. A. Paul Altshuller—Environmental Criteria and Assessment Office (MD-52),
   U.S. Environmental Protection Agency, Research Triangle Park, NC  27711
   Reviewers

   Dr. Thomas C. Curran—Office of Air Quality Planning and Standards (MD-12),
   U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

   Mr. Gary F. Evans—Atmospheric Research and Exposure Assessment Laboratory (MD-56),
   U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

   Mr. William G. Ewald—Environmental Criteria and Assessment Office (MD-52),
   U.S. Environmental Protection Agency, Research Triangle Paric, NC 27711

   Mr. Warren P. Freas—Office of Air Quality Planning and Standards (MD-14),
   U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

   Dr. Jon Heuss—General Motors Research and Development Center, Warren, MT 48090

   Dr. Nelson Kelly—Environmental Sciences Department, General Motors Research and
   Development Center, Warren, MI  48090

   Dr. Paul J. Lioy—Department of Environmental and Community Medicine, UMDNJ-Robert
   Wood Johnson Medical School, Piscataway, NY  08854

   Mr. Thomas R.  McCurdy—Office of Air Quality Planning and Standards (MD-12),
   U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

   Mr. Cornelius J. Nelson—Atmospheric Research and Exposure Assessment Laboratory
   (MD-56), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

   Dr. William Parkhurst—Tennessee Valley Authority, CEB 2A, Muscle Shoals, AL 35660

   Mr. Harvey M. Richmond—Office of Air Quality Planning and Standards (MD-12),
   U.S. Environmental Protection Agency, Research Triangle Park, NC 27711
   December 1993                        I-xxxi     DRAFT-DO NOT QUOTE OR CITE

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                 U.S. ENVIRONMENTAL PROTECTION AGENCY
        PROJECT TEAM FOR DEVELOPMENT OF AIR QUALITY CRITERIA
            FOR OZONE AND RELATED PHOTOCHEMICAL OXIDANTS
Scientific Staff

Mr, James A. Raub—Health Scientist, Environmental Criteria and Assessment Office
(MD-52), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. A. Paul Altshuller—Physical Scientist, Environmental Criteria and Assessment Office
(MD-52), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Mr. William G. Ewald—Health Scientist, Environmental Criteria and Assessment Office
(MD-52), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. J.H.B. Garner—Ecologist, Environmental Criteria and Assessment Office (MD-52),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Judith A. Graham—Associate Director, Environmental Criteria and Assessment Office
(MD-52), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Ms. Ellie R. Speh—Secretary, Environmental Criteria and Assessment Office (MD-52),
U.S. Environmental  Protection Agency, Research Triangle Park, NC 27711

Ms. Beverly E. Tilton—Physical Scientist, Environmental Criteria and Assessment Office
(MD-52), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711
Technical Support Staff

Mr. Douglas B. Fennell—Technical Information Specialist, Environmental Criteria and
Assessment Office (MD-52), U.S. Environmental Protection Agency, Research Triangle Park,
NC 27711

Mr. Allen G. Hoyt—Technical Editor and Graphic Artist, Environmental Criteria and
Assessment Office (MD-52), U.S. Environmental Protection Agency, Research Triangle Park,
NC 27711

Ms, Diane H. Ray—Technical Information Manager (Public Comments), Environmental
Criteria and Assessment Office (MD-52), U.S. Environmental Protection Agency, Research
Triangle Park, NC 27711

Mr. Richard N. Wilson—Clerk, Environmental Criteria and Assessment Office (MD-52),
U.S. Environmental Protection Agency, Research Triangle Park, NC  27711
December 1993                       I-xxxiii     DRAFT-DO NOT QUOTE OR CITE

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                 U.S. ENVIRONMENTAL PROTECTION AGENCY
        PROJECT TEAM FOR DEVELOPMENT OF AIR QUALITY CRITERIA
            FOR OZONE AND RELATED PHOTOCHEMICAL OXIDANTS
                                     (cont'd)
Document Production Staff

Ms. Marianne Barrier—Graphic Artist, ManTech Environmental, P.O. Box 12313,
Research Triangle Park, NC 27709

Mr. John R. Barton—Document Production Coordinator, ManTech Environmental
Technology, Inc., P.O. Box 12313, Research Triangle Park, NC  27709

Ms. Lynette D. Cradle—Lead Word Processor, ManTech Environmental Technology, Inc.,
P.O. Box 12313, Research Triangle Park, NC 27709

Ms. Jorja R. Followill—Word Processor, ManTech Environmental Technology, Inc.,
P.O. Box 12313, Research Triangle Park, NC 27709

Ms. Wendy B. Lloyd—Word Processor, ManTech Environmental Technology, Inc.,
P.O. Box 12313, Research Triangle Park, NC 27709

Mr. Peter J. Winz—Technical Editor, Mantech Environmental Technology, Inc.,
P.O. Box 12313, Research Triangle Park, NC 27709
Technical Reference Staff

Mr. John A. Bennett—Bibliographic Editor, ManTech Environmental Technology, Inc.,
P.O. Box 12313, Research Triangle Park, NC 27709

Ms. S. Blythe Hatcher—Bibliographic Editor, Information Organizers, Inc., P.O. Box 14391,
Research Triangle Park, NC 27709

Ms. Susan L. McDonald—Bibliographic Editor, Information Organizers, Inc.,
P.O. Box 14391, Research Triangle Park, NC 27709

Ms. Carol J. Rankin—Bibliographic Editor, Information Organizers, Inc., P.O. Box 14391,
Research Triangle Park, NC 27709

Ms. Deborah L. Staves—Bibliographic Editor, Information Organizers, Inc.,
P.O. Box 14391, Research Triangle Park, NC 27709

Ms. Patricia R. Tierney—Bibliographic Editor, ManTech Environmental Technology, Inc.,
P.O. Box 12313, Research Triangle Park, NC 27709
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 i                                 2.   INTRODUCTION
 2
 3
 4          The photochemical oxidants found in ambient air in the highest concentrations are
 5     ozone (O3) and nitrogen dioxide (NC^).  Other oxidants,  such as hydrogen peroxide and the
 6     peroxyacyl nitrates, have also been observed, but in lower and less certain concentrations.
 7     In 1971, the U.S. Environmental Protection Agency (EPA) promulgated National Ambient
 8     Air Quality Standards (NAAQS) to protect the public health and welfare from adverse effects
 9     of photochemical oxidants. In 1979, the chemical designation of the standards was changed
10     from photochemical oxidants  to O3.  This document, therefore, focuses primarily on the
11     scientific air quality criteria for O3 and, to a lesser extent, for hydrogen peroxide and  the
12     peroxyacyl nitrates, particularly peroxyacetyl nitrate. The scientific air quality criteria for
13     N02 are discussed in a separate  document (U.S. Environmental Protection Agency,  1993),
14          The previous O3 criteria document, Air Quality Criteria for Ozone and Other
15     Photochemical Oxidants (U.S. Environmental Protection  Agency,  1986) was released by
16     EPA in August 1986 and a supplement, Summary of Selected New Information on Effects of
17     Ozone on Health and Vegetation (U.S. Environmental Protection Agency, 1992), was
18     released in January 1992. These documents were used as the basis for a March 1993
19     decision by EPA that revision of the existing 1-h NAAQS for O3 was not appropriate  at that
20     time.  That decision did not take into account newer scientific data that became available
21     after completion of the 1986  criteria document.  The purpose of this document is to
22     summarize the air quality criteria for O3 available in the  published literature through the end
23     of 1993.  This review was performed in accordance with provisions of the Clean Air Act
24     (CAA) to provide the scientific basis for periodic reevaluation of the O3 NAAQS.
25          This chapter provides a general introduction to the legislative and regulatory
26     background for decisions on the O3 NAAQS, as well as a general summary of the
27     organization, content,  and major scientific topics presented in this document.
28
29
30
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 1     2.1   LEGISLATIVE BACKGROUND
 2          Two sections of the CAA govern the establishment, review, and revision of the
 3     NAAQS.  Section 108 (U.S. Code,  1991) directs the Administrator of EPA to identify
 4     ubiquitous pollutants that may  reasonably be anticipated to endanger public health or welfare
 5     and to issue air quality criteria for them.  These air quality criteria are to reflect the latest
 6     scientific information useful in indicating the kind and extent of all identifiable effects on
 7     public health or welfare that may be expected from the presence of the pollutant in ambient
 8     air.
 9          Section 109(a) of the CAA (U.S. Code, 1991) directs the Administrator of EPA to
10     propose and promulgate primary and secondary NAAQS for pollutants identified under
11     Section  108, Section 109(b)(l) defines a primary standard as one the attainment and
12     maintenance of which, in the judgment of the Administrator and based on the criteria and
13     allowing for an adequate margin of  safety, is requisite to protect the public health.  The
14     secondary standard, as defined in Section 109(b)(2), must specify a level of air quality the
15     attainment and maintenance of which, in the judgment of the Administrator and based on the
16     criteria, is requisite to protect the public welfare from any known or anticipated adverse
17     effects associated with the presence  of the pollutant in ambient air.
18          Section 109(d) of the CAA (U.S. Code, 1991) requires periodic review and, if
19     appropriate, revision of existing criteria and standards. If, in the Administrator's judgment,
20     the EPA's review and revision of criteria make appropriate the proposal of new or revised
21     standards, such standards are to be revised and promulgated in accordance with
22     Section  109(b). Alternatively, the Administrator may find that revision of the standards is
23     inappropriate and conclude the review by leaving the existing standards unchanged.
24
25
26     2.2   REGULATORY BACKGROUND*
27          On April 30, 1971, the EPA promulgated primary and secondary NAAQS for
28     photochemical oxidants under  Section 109 of the CAA (Federal Register,  1971). These were
29      This text is excerpted and adapted from the Praposed Decision on the National Ambient Air Quality
30      Standards for Ozone (Federal Register, 1992).
31
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 ]      set at an hourly average of 0.08 ppm total photochemical oxidants not to be exceeded more
 2      than 1 h per year.  On April 20, 1977, the EPA announced (Federal Register, 1977) the first
 3      review and updating of the 1970 Air Quality Criteria Document (AQCD) for Photochemical
 4      Oxidants in accordance with Section  109(d)  of the CAA.  In preparing the AQCD, the EPA
 5      made two external review drafts of the document available for public comment, and these
 6      drafts were peer reviewed by the Subcommittee on Scientific Criteria for Photochemical
 7      Oxidants of EPA's Science Advisory Board  (SAB).  A final revised AQCD for 03 and other
 8      photochemical oxidants was published on June 22,  1978.
 9           Based on the 1978 revised AQCD and taking into account the advice and
10      recommendations of the Subcommittee, and the comments  received from the public, the EPA
11      announced (Federal Register, 1979) a final decision to revise the NAAQS for photochemical
12      oxidants on February 8,  1979.  The final ruling revised the level of the primary standard
13      from 0,08 ppm to 0.12 ppm, set the secondary standard identical to the primary standard,
14      changed the chemical designation of the standards from photochemical oxidants to O3, and
15      revised the definition of the point at  which the standard is  attained to "when the expected
16      number of days per calendar year with maximum hourly average concentrations above
17      0.12 ppm is equal to or less than one" (see  Table 2-1).
18
          TABLE 2-1.  NATIONAL AMBIENT  AIR QUALITY STANDARDS FOR OZONE
       Date of Promulgation          Primary and Secondary NAAQS      Averaging Time
       February 8; 1979                 0. 12 ppma (235 ^g/m3)                1 hb
       al ppm = 1962 jtg/m3, 1 pglm  = 5.097 X IO"4 ppm @ 25 °C, 760 mm Hg.
        The standard is attained when the expected number of days per calendar year with a maximum hourly average
        concentration above 235 ng/m (0, 12 ppm) is equal to or less than one.
 1          On March 17, 1982, in response to requirements of Section 109(d) of the CAA, the
 2     EPA announced (Federal Register, 1982) that it was undertaking plans to revise the existing
 3     1978 AQCD for O3 and other photochemical oxidants, and on August 22, 1983, it announced
 4     (Federal Register,  1983) that review of the primary and  secondary NAAQS for O3 had been
 5     initiated.  Public peer-review workshops on draft chapters of the revised AQCD were held on
 6     December 15-17, 1982, and on November 16-18, 1983.  The EPA considered comments

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 1     made at both workshops in preparing the first external review draft that was made available
 2     (Federal Register, 1984) on July 24, 1984, for public review.
 3          On February 13, 1985 (Federal Register, 1985), and on April 2, 1986 (Federal
 4     Register, 1986), the EPA announced two public meetings of the Clean Air Scientific
 5     Advisory Committee (CASAC)  of EPA's SAB to be held on March 4-6, 1985, and on April
 6     21-22,  1986, respectively.  At these meetings, the CASAC reviewed  external review drafts
 7     of the revised AQCD for 03 and other photochemical oxidants.  After completion of this
 8     review, the CASAC sent the Administrator of EPA a closure letter, dated October 22, 1986,
 9     indicating that the document "represents a scientifically balanced and defensible summary of
10     the extensive scientific literature."  The EPA released the final draft document in August
11     1986.
12          The first draft of the Staff Paper "Review of the National Ambient Air Quality
13     Standards for Ozone:  Assessment of Scientific and Technical Information" was reviewed by
14     CASAC at the public meeting on April 21-22, 1986.  At that meeting, the CASAC
15     recommended that new information on prolonged exposure effects of 03 be considered in a
16     second draft of the Staff Paper prior to closure. The CASAC reviewed this second draft and
17     also  a presentation of new and emerging information on the health and welfare effects of
18     O3 at a public review meeting held on December 14-15, 1987.  The CASAC concluded that
19     sufficient new information existed to recommend incorporation of relevant new data into a
20     supplement to the 1986 AQCD  (O3 Supplement) and in a third draft of the Staff Paper,
21          A draft O3 Supplement, "Summary of Selected New Information on Effects of Ozone
22     on Health and Vegetation:  Draft Supplement to Air Quality Criteria for Ozone and Other
23     Photochemical Oxidants," and the revised Staff Paper were made available to CASAC and to
24     the public for review  in November 1988. The O3 Supplement reviewed and evaluated
25     selected literature concerning exposure- and concentration-response relationships observed for
26     health effects in humans and experimental animals and for vegetation effects.  This literature
27     appeared as peer-reviewed journal  publications or as proceedings papers from 1986 through
28     late  1988.
29          On December 14-15, 1988, CASAC held a public meeting to review these documents.
30     The  CASAC sent the Administrator a closure letter dated May  1, 1989,  indicating that the
31     draft O3 Supplement, along with the 1986 AQCD, and the draft Staff Paper "provide an

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 1     adequate scientific basis for the EPA to retain or revise the primary and secondary standards
 2     of ozone."  The CASAC concluded that  it would be some time before enough new
 3     information on the health effects of miillihour and chronic exposure to O3 would be
 4     published in scientific journals to receive full peer review and, thus, be suitable for inclusion
 5     in a criteria document.  The CASAC further concluded that such information could better be
 6     considered in the next review of the Qj NAAQS. A final version of the O3 Supplement has
 7     been published (U.S. Environmental Protection Agency,  1992).
 8          On October 22, 1991, the American Lung Association and other plaintiffs filed suit to
 9     compel the EPA to complete the review  of the criteria and standards  for O3 in accordance
10     with the CAA.  The U.S. District  Court for the Eastern District of New York subsequently
11     issued an order requiring the EPA to announce its proposed decision  on whether to revise the
12     standards for O3 by August 1, 1992, and to announce its final decision by March 1, 1993.
13          The proposed decision on O3 appearing in the Federal Register  on August 10, 1992
14     (Federal Register, 1992), indicated that revision of the existing 1-h NAAQS was not
15     appropriate at that time.  A public hearing on this proposal took place on September 1, 1992,
16     at the EPA Education Center in Washington, DC, and public comments were received
17     through October 9, 1992.  The final decision was published in the Federal Register on
18     March 9, 1993  (Federal Register,  1993). This decision does  not take into consideration a
19     number of recent studies on the health and welfare effects of O3 that have been published
20     since the last literature review in early 1989.  The EPA estimates that approximately 3 years
21     will be necessary to (1) incorporate the new studies into  a revised criteria document,
22     (2) complete mandated CASAC review,  (3) evaluate the  significance  of the key information
23     for regulatory decision-making purposes, and (4) publish a proposed  decision on the
24     O3 NAAQS in the Federal Register.
25          As stated in the 1993 final decision, the EPA's Environmental Criteria and Assessment
26     Office in Research Triangle Park,  NC, is proceeding as  rapidly as possible with the next
27     periodic review of the air quality criteria for O3. Under the processes established in
28     Sections 108 and 109 of the CAA and refined by the EPA and CASAC, the EPA began by
29     announcing the commencement of the review in the Federal Register. After assessing and
30     evaluating the pertinent new studies, the  EPA has prepared a preliminary draft of a revised
31     criteria document and subjected it  successively to review at expert peer-review workshops.

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 1     Comments received at the workshops were used to revise the preliminary draft for external
 2     review.  Once the public and CASAC have reviewed the external review draft of die revised

 3     criteria document, thus providing a preliminary basis for review of the existing standards,

 4     EPA's Office of Air Quality Planning and Standards (OAQPS) will complete their
 5     preparation of a draft Staff Paper assessing the most significant information contained in the

 6     draft criteria document and will develop recommendations for revisions, if appropriate, to the

 7     NAAQS for O3. Subsequent reviews by the public and by CASAC will occur, as warranted.
 8

 9

10     2.3   SUMMARY OF MAJOR SCIENTIFIC TOPICS PRESENTED

11          A number of separate topics and issues are addressed in this revised O3 criteria

12     document. Some of the key topics and issues addressed are highlighted below by document

13     section.
14

15     2.3.1   Air Chemistry

16           • What concerns  still exist regarding precision and accuracy of measurements
17             of O3 and its precursors?
18
19           • What is the order of magnitude of current estimates of natural emissions of
20              O3 precursors and emissions from anthropogenic sources and their relevance
21             to tropospheric O3 photochemistry?
22
23           • What new scientific information exists on the roles of meteorologic and
24              climatologic factors in O3 formation and transport?
25
26           • Are the reaction pathways of all major precursors  to O3 understood?  Have
27             all major reaction products been identified?  How  are the reactions  and
28             products represented in air quality models?
29
30           • What is the status of development, application, evaluation, and verification
31              of air quality models?
32
33
34     2.3.2   Air  Quality

35           •  What are the trends and geographic differences in O3 concentrations across
36              the United States?
37
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 ]             • What are diurnal and seasonal patterns of 1-h average O3 concentrations for
 2              urban and nonurban sites, for aUainment versus nonattainment areas?
 3
 4            • What is known about patterns of co-occurrence of O3 with other pollutants
 5              in the atmosphere?
 6
 7            • What O3 exposure assessment data are available for agricultural crops and
 8              for forests?
 9
10            • To what level and to what extent are humans typically exposed to O3 in the
11              course  of normal everyday activities?
12
13
14     2.3.3   Environmental Effects

15            • What are the effects of ambient O3 concentrations on vegetation  (i.e.,
16              agricultural and horticultural crops; urban landscape trees, shrubs,  and
17              flowers; forest tree species)?
18
19            • What characteristics of air quality (e.g., summary statistics) are relevant to
20              these effects on vegetation?
21
22            • What are the long-term effects of O3 exposures on natural ecosystems?
23
24            • Is there important new information on the effects of O3 on nonbiological
25              materials?
26
27
28     2,3.4   Health Effects

29            • What O3 concentration and  exposure duration relationships exist for effects
30              on lung structure, function, and host defense mechanisms and what are the
31              important modifiers of these effects?
32
33            • What are the mechanisms of O3-induced lung injury?
34
35            • Can dosimetry models predict human population responses to O3 on the
36              basis of laboratory animal data?
37
38            • Does long-term exposure to O3 lead to the development of chronic lung
39              disease or to an increased frequency  or exacerbation of other chronic
40              respiratory outcomes?
41
42            • What segment(s) of the population are most  susceptible to effects from
43              exposure to O3?
44
45


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 1     2.4   ORGANIZATION AND CONTENT OF THE DOCUMENT
 2          This document critically evaluates and assesses scientific information on the health and
 3     welfare effects associated with exposure to the concentrations of Oj and related
 4     photochemical oxidants in ambient air. Although the document is not intended to be an
 5     exhaustive literature review,  it is intended to cover all pertinent literature through 1993.  The
 6     references cited in the document should be reflective of the state of knowledge on those
 7     issues most relevant to review of the NAAQS for 63, now set at 0.12 ppm for 1 h.
 8     Although emphasis is placed  on the presentation of health and welfare effects data, other
 9     scientific data will be presented and evaluated in order to provide a better understanding of
10     the nature, sources,  distribution, measurement, and concentrations of O3 and related
11     photochemical oxidants in ambient air, as well as the characterization of population exposure
12     to these pollutants.
13          To aid in the development  of this document, summary tables of the relevant published
14     literature have been provided to  supplement a selective discussion of the literature.  Most of
15     the scientific information selected for review and comment in the text comes from the more
16     recent literature published since  completion of the previous O3 criteria document (U.S.
17     Environmental Protection Agency, 1986). Some of these newer studies were briefly
18     reviewed in the supplement to that document (U.S. Environmental Protection Agency, 1992)
19     but more intense evaluation of these studies has been included. Emphasis is placed on studies
20     conducted at or near O3 concentrations found in ambient air.  Other studies, however, are
21     included if they contain unique data, such as the documentation of a previously  unreported
22     effect or of a mechanism of an effect; or if they were multiple-concentration studies designed
23     to provide exposure-response relationships. Generally, O3 concentration is not an issue for
24     human clinical or epidemiology  studies; however, for animal toxicology studies, typically
25     only those studies conducted at less than  1 ppm Oj are considered. Studies that are
26     presented in the previous criteria document and whose data were judged to be significant
27     because of their usefulness in deriving the current NAAQS are briefly discussed in the text.
28     The reader should, however, consult the  more extensive discussion of these "key" studies in
29     the  previous document.  Other, older studies are also discussed in the text if they were
30     judged to be (1) open to reinterpretation  because of newer data, or (2) potentially useful in
31     deriving revised standards for 03.  Generally, only published information that has undergone

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 1     scientific peer review is included in the criteria document.  Some newer studies not published
 2     in the open literature but meeting high standards of scientific reporting and review have been
 3     included.
 4          Certain issues of direct relevance to standard setting are not explicitly addressed in this
 5     document, but are instead analyzed in documentation prepared by OAQPS as part of its
 6     regulatory analyses.  Such analyses include (1) a discussion of what constitutes an "adverse
 7     effect" and delineation of particular adverse effects that the primary and secondary NAAQS
 8     are intended to protect against, (2) exposure analyses and assessment of consequent risk, and
 9     (3) a discussion of factors to be considered in determining an adequate margin of safety.
10     Key points and conclusions from such analyses are summarized in the Staff Paper prepared
11     by OAQPS and reviewed by CAS AC.  Although scientific data contribute significantly to
12     decisions regarding the above  issues, their resolution cannot be achieved solely on the basis
13     of experimentally  acquired information.  Final decisions on items (1) and (3) are made by the
14     Administrator,  as  mandated by the CAA.
15          A fourth issue directly pertinent to standard setting is identification of populations at
16     risk, which is basically a determination by EPA of the subpopulation(s) to be protected by
17     the promulgation of a given standard. This issue is addressed only partially in this
18     document.  For example, information is presented on factors, such as preexisting disease,
19     that may biologically predispose individuals and subpopulations to adverse effects from
20     exposures to O3.   The identification of a population at risk, however, requires information
21     above and beyond data on biological predisposition, such as information on levels of
22     exposure, activity patterns, and personal habits.  Such information is included in the Staff
23     Paper developed by OAQPS.
24           The structure of this document includes,  first,  an Executive Summary and  Conclusions
25     (Chapter 1) providing a concise presentation of key information and conclusions from all
26     subsequent chapters.  This is followed by this  brief Introduction (Chapter 2)  containing
27     information on the legislative  and regulatory background for review of the 03 NAAQS, as
28     well as an overview of the organization  of this document.  Chapter 3 provides information on
29     the chemistry,  sources,  emissions, measurement, and transport of O3 and related
30     photochemical  oxidants and their precursors, whereas Chapter 4 covers environmental
31     concentrations, patterns, and exposure estimates of O3 and oxidant air quality. This is

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1     followed by Chapter 5, dealing with environmental effects of Oj and related photochemical
2     oxidants.  Chapters 6, 7, and 8 discuss, respectively, animal lexicological studies, human
3     health effects, and extrapolation of animal lexicological data to humans.  The last chapter,
4     Chapter 9, provides an integrative, interpretive evaluation of health risks associated with
5     exposure to O3.
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 1     REFERENCES
 2
 3     Federal Register. (1971) National primary and secondary ambient air quality standards. F. R. (April 30)
 4            36: 8186-8201.
 5
 6     Federal Register. (1977) Review of the photochemical oxidantand hydrocarbon air quality standards. F. R.
 7            (April 20) 42: 20493-20494.
 8
 9     Federal Register. (1979) National primary and secondary ambient air quality standards: revisions to the national
10            ambient air quality standards for photochemical oxidants. F. R. (February 8) 44: 8202-8221.
11
12     Federal Register. (1982) Air quality criteria document for ozone and other photochemical oxidants. F. R,
13            (March  17)47: 11561.
14
15     Federal Register. (1983) Review of the national ambient air quality standards for ozone. F. R.  (August 22)
16            48:38009.
17
18     Federal Register. (1984) Draft air quality criteria document for ozone and other photochemical oxidants. F. R.
19            (July 24) 49: 29845.
20
21     Federal Register, (1985) Science Advisory Board; Clean Air Scientific Advisory Committee; open meeting. F. R.
22            (February 13) 50: 6049.
23
24     Federal Register. (1986) Science Advisory Board; Clean Air Scientific Advisory Committee; open meeting. F. R.
25            (April 2)51: 11339.
26
27     Federal Register. (1992) National ambient air quality standards for ozone; proposed decision. F. R. (August 10)
28            57: 35542-35557.
29
30     Federal Register. (1993) National ambient air quality standards for ozone—final decision. F. R. (March 9)
31            58: 13008-13019,
32
33     U.S. Code. (1991) Clean Air Act, §108, air quality criteria and control  techniques, §109, national ambient air
34            quality standards. U.S. C. 42: §§7408-7409.
35
36     U.S. Environmental Protection Agency. (1986)  Air quality criteria for ozone and other photochemical oxidants,
37            Research Triangle Park, NC: Office of  Health and Environmental Assessment, Environmental Criteria
38            and Assessment Office; EPA report nos. EPA-600/8-84-020aF-eF. 5v. Available from: NTIS,
39            Springfield, VA; PB87-142949.
40
41     U.S. Environmental Protection Agency. (1992)  Summary of selected new information on effects of ozone on
42            health and vegetation: supplement to 1986 air quality criteria for ozone and other photochemical oxidants.
43            Research Triangle Park, NC: Office of  Health and Environmental Assessment, Environmental Criteria
44            and Assessment Office; EPA report no. EPA/600/8-88/105F. Available from: NTIS, Springfield, VA;
45            PB92-235670.
46
47     U.S. Environmental Protection Agency, (1993)  Air quality criteria for oxides of nitrogen. Research Triangle
48            Park, NC: Office of Health and Environmental Assessment, Environmental Criteria and Assessment
49            Office; EPA review draft no. EPA/600/8-91/049F.
50
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 i      3.  TROPOSPHERIC OZONE AND ITS PRECURSORS
 2
 3
 4     3.1   INTRODUCTION
 5          Ozone and other oxidants found in ambient air, such as the peroxyacyl nitrates and
 6     hydrogen peroxide, are formed as the result of atmospheric physical and chemical processes
 7     involving two classes of precursor pollutants, volatile organic compounds (VOCs) and
 8     nitrogen oxides (NOX). The formation of ozone and other oxidants from these precursors is
 9     a complex, nonlinear function of many factors,  including the intensity and spectral
10     distribution of sunlight; atmospheric mixing and related meteorological conditions; the
11     concentrations of the precursors hi ambient air and, within reasonable concentration ranges,
12     the ratio between VOC and NOX (VOC/NOj); and the reactivity of the organic precursors.
13          An understanding of the atmospheric chemistry and meteorological parameters and
14     processes responsible for the formation and occurrence of elevated concentrations of ozone in
15     ambient air is basic to the formulation of strategies and techniques for its abatement. Such
16     an understanding is required for representing those parameters and processes adequately in
17     predictive models used to determine the emission reductions needed for complying with the
18     NAAQS for ozone. In addition, the identification and quantification of ozone  precursors in
19     ambient air is essential, along with emission inventories or emission models, or both, for the
20     development, verification, and refinement of photochemical air quality models and for
21     comparisons of ambient concentrations with emission inventories as a check on the accuracy
22     of measurements and of inventories.
23          Product identification and quantification of yields, in chambers and in ambient air, are
24     helpful in the verification of photochemical air  quality models and in testing theoretical
25     chemical mechanisms.  Likewise, product identification and quantification are  useful in
26     determining the need for research on the potential effects of the simultaneous or sequential
27     co-occurrence with ozone and related oxidants of multiple air pollutants.
28          The ability to measure ozone and its precursors,  its reaction products, and the products
29     of the atmospheric reactions of its respective precursors is essential for (1) understanding
30     atmospheric chemistry of ozone formation, (2)  for verifying chemical mechanisms, (3) for

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 1     verifying models, (4) for quantifying emission rates, and (5) for adequately characterizing
 2     exposure-response factors for both biological and nonbiological receptors.
 3          For these reasons, this chapter presents information on a broad range of topics.  The
 4     chapter describes the chemical processes by which ozone and other photochemical oxidants
 5     are formed in ambient air (Section 3.2). It also characterizes the nature of the precursors in
 6     terms of their sources and emissions into the atmosphere and their concentrations in ambient
 7     air (Section 3.4), and methods by which their concentrations in ambient air are measured
 8     (Section 3.5).
 9          In addition to information on the chemistry of oxidants and their precursors, the chapter
10     includes a discussion of meteorological processes (Section  3.3) that contribute to the
11     formation of ozone and other oxidants and that govern their transport and  dispersion once
12     formed. Finally, an overview is given (Section 3.6) of models of the relationships between
13     precursor emissions and ozone formation in the atmosphere.
14          Readers are referred to other sources (e.g., Finlayson-Pitts and Pitts, 1986; Seinfeld,
15     1986; U.S. Environmental Protection Agency,  1986; National Research Council, 1991) for
16     additional information on the chemical and physical aspects of photochemical air pollution.
17
18
19     3.2   TROPOSPHERIC OZONE CHEMISTRY
20     3.2.1   Background Information
21          Ozone is formed photochemically in the stratosphere and transported downward,
22     leading to the presence of Qj at low concentrations in the  natural, or "clean", troposphere.
23     The presence of Og at low concentrations in the "clean" troposphere, in the absence of
24     perturbations caused by human activities, is highly important since O3 is a precursor to the
25     hydroxyl (OH) radical, the key intermediate species in the tropospheric degradation of VOCs
26     emitted into the atmosphere. Although Q$ at low concentrations is an integral part of the
27     "clean" troposphere, its presence at higher concentrations  is detrimental.
28          The chemical processes occurring in the atmosphere  that lead to the  formation of ozone
29     and other photochemical air pollutants are complex. Tropospheric ozone is formed as a
30     result of (1)  emissions  of NOX and VOCs into the atmosphere from anthropogenic and
31     biogenic sources; (2) transport of these emissions and their reaction products; and

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 1      (3) chemical reactions occurring in the atmosphere concurrent with transport and dispersion
 2      of the emissions, leading to the formation of O3 and other photochemical oxidants  such as
 3      peroxyacetyl nitrate (PAN), nitric and sulfuric acids, and to other compounds such as
 4      formaldehyde  (HCHO) and other carbonyl compounds, and paniculate matter.  Additionally,
 5      deposition of gases and particles along the trajectory occurs to reduce the concentrations of
 6      precursors and products in the atmosphere, but may lead to adverse impacts on the earth's
 7      environment.
 8           The chemical process leading to the chemical formation of O3 in the troposphere
 9      involves the photolysis of NO2 to yield nitric oxide (NO) and a ground-state oxygen atom,
10
                                     N02 +  hv -» NO + O^P),                         (3-1)
11
12     which then  reacts with molecular oxygen to form O3:
13
                                   O(3P) +  O2 * M -» O3 + M.                        (3-2)
14
15     The NO and O3 react to reform NO2:
16
                                      NO + O3  -» NO2  + O2.                          (3-3)
17
18     The presence  of reactive VOCs leads to  the conversion of NO to NO2 without the
19     intermediary of 03 (Reaction 3-3), and the photolysis of NO2 then leads to the formation of
20     elevated levels of O3:
21

                                             vex:
                                         NO	+ NO2                                (3-4)
22
23           The photochemical cycles leading to O3 production are best understood through a
24     knowledge  of the chemistry of the atmospheric oxidation of methane, which can be viewed as
25     being the chemistry of the clean, or unpolluted,  troposphere (although this is also  a
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 1     simplification, since vegetation releases large quantities of complex VOCs into the
 2     atmosphere).  Although the chemistry of the VOCs emitted from anteopogMiK and biogenic
 3     sources in polluted urban and rural areas is more complex, a knowledge of the methane
 4     oxidation reactions aids in underatauding toe ebej»cal processes oecwring in $a& poliaJed
 5     atmosphere because the underlying chemical principles are the same,
 6          This section first describes the structure of the atmosphere, and then discusses the
 7     formation of the OH radical, the key intermediate species in the chemistry of the
 8     troposphere; and tropospheric NOX chemistry. The photochemical formation of tropospheric
 9     O3 from the oxidation of methane is then discussed in some detail since, as noted above, the
10     methane oxidation cycle serves as a model for the photochemical  formation of O3 from the
11     more complex nonmethane VOCs emitted into the atmosphere from anthropogenic and
12     biogenic sources.  In  Section 3.2.4, the chemistry of the major classes of nonmethane VOCs
13     and the formation  of O3 from these VOCs are discussed.  Finally, in Section 3.2.5, the
14     photochemical formation of aerosols is briefly discussed, since the same processes that lead
15     to the formation of elevated levels of 03 {over those present in the "clean" troposphere)
16     result in the formation of paniculate matter, leading to visibility degradation, and in the
17     formation of atmospheric acidity.
18
19     3.2.2   Structure  of the Atmosphere
20          The earth's atmosphere is composed of a number of layers (Mcflveen, 1992). For the
21     purposes of this chapter, those of importance are the troposphere and the stratosphere, and
22     the boundary between them, which is the tropopause.
23          The troposphere extends from the earth's surface to the tropopause, which is at  «10 to
24     18 km altitude, depending on the latitude and season. The altitude of the tropopause is
25     greatest in the tropics and lowest in the wintertime polar regions, with an average altitude of
26      »14 km. The temperature in the troposphere decreases with increasing altitude from an
27     average of 290 K at the earth's surface to *210 to 220 K at the  tropopause, and the pressure
28     decreases from »760 torr at the earth's surface to  * 100 torr at  the tropopause.
29          The stratosphere extends from the tropopause to an altitude of »50 km. In the
30     stratosphere, the temperature increases with increasing  altitude from »210 to 220 K at the
31     tropopause to * 270 K at the top of the stratosphere.  The pressure in the stratosphere

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 1      decreases with increasing altitude from »100 torr at the tropopause to »1 torr at the top of
 2      the stratosphere.
 3
 4      3.2.2.1   Vertical and Horizontal Mixing in the Atmosphere
 5           In the troposphere, temperature generally decreases with increasing altitude.
 6      As discussed in Section 3.3., the lowest 1 to 2 km of the troposphere is influenced by the
 7      planetary boundary layer and, in certain locales, by inversion layers. These boundary and
 8      inversion layers inhibit the vertical movement of pollutants into the free troposphere.  Above
 9      inversion and boundary layers, vertical mixing in the "free" troposphere  has a time scale of
10     «10 to 30 days (Langner et al., 1990; World Meteorological Organization, 1990a),
11           Because temperature increases  with increasing altitude in the stratosphere, vertical
12     mixing in the stratosphere is slow, with a time scale of the order of months to a few years.
13           Horizontal mixing in the troposphere occurs both within and between the hemispheres.
14     The time scale for mixing between the northern and southern hemispheres is »1 year
15     (Cicerone, 1989; Singh and Kanakidou, 1993).  Transport within a hemisphere is more rapid
16     (Graedel  et al., 1986a), and local, regional, and global transport distances of < 100 km,
17     100 to 1,000 km, and  > 1,000 km, respectively, are observed.  For a wind speed of
18     15 km h"1 («4 m s"1), transport times over these local, regional, and global distances are
19     a few hours, a few hours to a few days,  and ^ 10 days, respectively.
20
21      3.2.2.2   Formation of Stratospheric Ozone
22          At altitudes between approximately 20 and 35 km, the stratosphere has a layer of air
23     containing O3 at  mixing ratios up to approximately 10 ppm.  The sun emits radiation
24      > 170 nm, and this radiation impacts the upper levels of the atmosphere. The bulk
25     composition of the atmosphere (78.1% N2, 21.0% O2, 0.9% Ar, 0.03% CO2, with variable
26     trace gas concentrations) is invariant up to >50 km (Mcllveen, 1992), and the shorter
27     wavelength radiation (175 to 240 nm) is  absorbed by molecular oxygen (O^) in the
28     stratosphere, leading to dissociation  into two ground-state oxygen atoms, OfP),
29
                                        02  - hv -+2 0(3P),                            (3-5)
30

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 1     followed by the reaction of O(3P) atoms with QJJ in the presence of a third-body, M, to form
 2     ozone.
 3
                            OfP) + O2 + M -» O3 + M (where M » air)                 (3-2)
 4
 5     Ozone also photolyzes, at wavelengths <360 nm (DeMore et al., 1992),
 6
                                        O3 +  h? - O2 + O                             (3-6)
 7
 8     where the oxygen atom produced can be in the ground state, O(~P), or electronically excited
 9     state, O^D).  The O(1D) atoms produced are deactivated to the ground state O(3P) atom by
10     N2, O2, CO2, and Ar
11
                    OOD)  + M -* O<3P) + M          (where M =  N2, O2, COj)         (3-7)
12
13     The reaction of O(3P) atoms with O^ is the termination step of this reaction sequence,
14
                                       O(3P) + 03 -» 2  O2.                            (3-8)
15
16          These reactions, called the Chapman reactions (Chapman, 1930), are responsible for the
17     layer of ozone found in the  stratosphere.  Because the stratospheric ozone layer absorbs the
18     sun's radiation below =290 nm, only radiation of wavelengths ^290 nm can penetrate into
19     the troposphere and impact the earth's surface. Any depletion of the stratospheric ozone
20     layer allows shorter wavelength  ultraviolet radiation to be transmitted through the
21     stratosphere and into the troposphere.
22          In addition to the biological effects expected from increased UV-B radiation (280 to
23     320  nm),  increased penetration of UV-B into the troposphere can lead to changes in
24     tropospheric ozone.  Model calculations indicate that 63 in the troposphere could increase
25     with increasing UV-B in urban and rural areas impacted by anthropogenic NOX emissions
26     (Gery et al., 1988; Liu and Trainer,  1988; Thompson et al.,  1989; Thompson,  1992), but

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 1      could decrease with increasing UV-B in remote tropospheric areas characterized by low NOX
 2      levels (Liu and Trainer, 1988; Thompson et al., 1989). Besides the implications of long-
 3      term trends in stratospheric O3 concentrations leading to corresponding changes in the
 4      intensity of UV-B radiation impacting the troposphere, short-term changes, including daily
 5      changes, in stratospheric ozone levels lead to short-term changes in the rates of photolysis of
 6      several important species,  including the photolysis of formaldehyde to produce radicals and
 7      of 03 to form the OH radical. These changes in photolysis rates affect the formation rates
 8      and ambient concentrations of key radical intermediates, specifically of the OH radical, in the
 9      troposphere. Information  concerning such short-term changes in stratospheric
10      03 concentrations is needed as input to urban and regional airshed computer models of
11      photochemical air pollution formation.
12           In the clean atmosphere, stratospheric ozone is also influenced by the emission of N2O
13      from soils and oceans (World Meteorological Organization, 1992). Because N2O is
14     chemically inert in the troposphere and does not photolyze (Prinn et al., 1990), it is therefore
15     transported into the stratosphere, where it undergoes photolysis and also reacts with O(*D)
16     atoms (DeMore et al., 1992;  Atkinson et al., 1992a).  The reaction of N2O with the O(:D)
17     atom is the major source of stratospheric NO,  which then participates in a series of reactions
18     known as the NOX catalytic cycle (Crutzen,  1970; Johnston, 1971).
19
                                       NO + O3 -* NO2 + O2                           (3-3)
20
                                    NO2 + O(3P)  -» NO  + O2                           (3-9)
       Net;                            O(3P)  +  03 -* 2 O,
21
22     The Chapman reactions and the NOX catalytic cycle reactions control the ozone
23     concentrations in the lower "clean" stratosphere.
24          Additional reaction sequences leading to the removal of stratospheric ozone arise from
25     the C1OX and BrOx catalytic cycles, which result when chlorine- and bromine-containing
26     organic compounds are emitted into the atmosphere.  These O3-depleting compounds include

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 1     the chlorofluorocarbons (CFCs), hydrocMorofluorocarbons (HCFCs), carbon tetrachloride
 2     (CC^), methyl chloroform, halons, and methyl bromide (Anderson et al., 1991; Rowland,
 3     1990, 1991; World Meteorological Organization, 1992). Analogous to N2O, the CFCs,
 4     CC^, and certain halons (CF3Br and CF2ClBr) are inert in the troposphere and are
 5     transported into the stratosphere, where they photolyze to generate Cl or Br atoms (World
 6     Meteorological Organization, 1992).  Methyl bromide and the HCFCs react to a large extent
 7     in the troposphere,  so that only a fraction of these Cl- and fir-containing species that are
 8     emitted into the troposphere are transported into the stratosphere (World Meteorological
 9     Organization, 1990b, 1992).
10
11     3.2.3   Tropospheric Ozone in the Unpolluted Atmosphere
12          As noted in Section 3.2,1, ozone is present in the troposphere, even in the absence of
13     human activities. The presence of ozone in the clean, unpolluted, troposphere is the result of
14     downward transport from the stratosphere and in situ production from the oxidation of
15     methane (National Research Council, 1991), emitted from swamps and wetlands, in the
16     presence of natural sources of NOX (emissions from soils,  lightning, and downward transport
17     from the stratosphere).  It is believed that on a global basis the photochemical formation of
18     ozone in the "clean" troposphere would be approximately balanced by its destruction (Logan,
19     1985; World Meteorological Organization, 1992; Ayers et al., 1992).  In the clean,
20     unpolluted lower troposphere, the ozone mixing ratios are in the range 10 to 40 ppb
21     (Oltmans,  1981; Logan, 1985), with higher mixing ratios of »100 ppb in the upper
22     troposphere (Logan, 1985).  A reasonable estimate for background O3 mixing ratios near
23     sea-level in the United States is 20 to 35 ppb (U.S. Environmental Protection Agency, 1989)
24     (see Chapter 4). Because of the decrease of total pressure with increasing  altitude,  the ozone
25     concentration in the "clean" troposphere may be taken to be reasonably independent of
26     altitude at *7 x 1011 molecule cm"3.  Transport of 03 from polluted urban areas (see
27     Section 3.3) impacts the "clean" troposphere and leads to  O3 concentrations in the
28     troposphere that have been increasing with time over the past few decades  (Logan,  1985).
29
30
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 1     3.2.3.1   Tropospheric Hydroxyl Radicals
 2          It is now recognized that the key reactive species in the troposphere is the hydroxyl
 3     (OH) radical, which is responsible for initiating the degradation reactions of almost all
 4     VOCs. In the presence of NO, these OH radical reactions with VOCs lead to the formation
 5     of O3 and hence to O3 concentrations above those encountered in the "clean"  troposphere.
 6     The OH radical is produced from the ultraviolet photolysis of 03.  Ozone photolyzes in the
 7     ultraviolet at wavelengths < 320 nm to generate the electronically excited O(  D) atom
 8     (DeMore et al., 1992; Atkinson et al., 1992a),
 9
                                      03  +  hy -* O2  +  O^D)                          (3-6a)
10
11     The 0(LD) atoms are either deactivated to the ground state O( P) atom by Reaction 3-7 or
12     they react with water vapor to form the OH radical:
13
                                       O(ID) + HjO -»  2 OH                           (3-10)
14
15     The O(3P) atoms formed directly in the photolysis of 03 or formed from deactivation of
16     O(*D) atoms (Reaction 3-7) reform 03 through Reaction 3-2.  At room temperature and 50%
17     relative humidity, 0.2 OH radicals are formed per O(*D) atom generated from the photolysis
18     of ozone.  Hydroxyl radical production from reactions (3-6a) and (3-10) is balanced by
19     reaction of the OH radical with CO and methane.  Because the water vapor mixing ratio
20     decreases with increasing altitude in the troposphere (Logan et al.,  1981; World
21     Meteorological Organization, 1992), whereas the ozone mixing ratio generally increases with
22     increasing altitude, the OH radical concentration is expected to be reasonably independent of
23     altitude (Dentener and Crutzen, 1993).
24          A knowledge of ambient tropospheric OH radical concentrations is needed to test our
25     understanding of tropospheric chemistry and allow the lifetimes of chemical compounds to be
26     reliably calculated.  Since, as shown below in Section 3.2.3.3, OH and HO2  radicals are
27     interrelated through a series of reactions, concurrent measurements of OH  and HO2 radical
28     concentrations are a further test of our knowledge of tropospheric chemistry.  Only in the
29     past few years have measurements been made of lower tropospheric OH radical
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 1     concentrations (see, for example, Felton et si,  199Q; Hofj^mahaMS et al,, 1991; MseJe and
 2     Tanner, 1991; Mount and Eisele, 1992; Comes fit«L, 1992; Maid et a!.s  1992). The limited
 3     data available show that, as expected, the OH radical concentrations exhibit a diurnal profile,
 4     with daytime maximum concentrations of several  x 106 motaeajfe eM3.  A global, annually,
 5     seasonally, and diurnaUy averaged topospheric ;QH laslieaJ s^&®faj$m can tlso be derived
 6     from the estimated emissions and measured atmesj&eric e^no^tratjoft
 7     (CH3CCl3> and the rate constant for the reaction of the OH radical with
 8     (its major tropospberic loss process). Using this method, Man et al. (1992) have d&riv^d a
 9     24-h average OH radical concentration ©f 8 x 10  molecule cm"  (equivalent to a 12'h
10     daytime average of 1.6 x 1Q6 molecule cm"3).  Ambient air measurements of the decays of
11     nonmethane hydrocarbons in urban plumes (Hate et al,, 1993) give OH radical
12     concentrations of a similar magnitude as direct tropospheiic measurements and globally
13     averaged estimates.
14
15     3.2.3.2  Tropospherk Nitrogen Oxides Chemistry
16          The presence of oxides of nitrogen is nejoessary for the ft>rmatiQn of Oj from the
17     oxidation of methane and other VOCs.  Sources of trop^spheric NOX include downward
18     transport from the stratosphere, in situ formation from lightning (National Research  Council,
19     1991; World Meteorological Organfeatioji, 1992) (Section 3.4.1.2), and emission from soils
20     (National Research Council, 1991; World M«*KMaalo|Krt Organisation,  1992). Recent
21     measurements show that the NOX concentrations over maritime areas increase slightly with
22     increasing altitude, from »15 ppt in the marine boundary layer (Carroll et al., 1990) to
23     *30 to 40 ppt at 3 to 7 km altitude (Ridley et  at, 1989; Carroll et al., 1990). Significantly
24     higher NOX concentrations (** 100 ppt) have been observed in the boundary layer over
25     relatively unpolluted continental areas (Carroll et al,,  1990), with the NOX concentrations
26     decreasing with increasing altitude to »50 ppt at 3 to 7 km (Ridley et al., 1989; Carroll
27     etal.,1990).
28          In the troposphere, NO, NO2, and 03 are interrelated by the following reactions:
29
                                       NO + O3 -* NOj + O2                           (3-3)
30

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 2
                                   NO2 + hi* -* NO  * O(3P)                         (3-1)
                                          O2 * M -> O3 + M                       (3-2)
 3     Because Reaction 3-2 is fast (the lifetime of an O(3P) atom at 298 K and 760 torr of air is
 4     *> 10"s s), the ozone concentration at photoequilibrium is given by,
 5
                                     [OJ = J.praj/kJNQ]                         (3-H)
 6
 7     where Jj and k3 are the photolysis rate of NO^ («0.5 min"  for an overhead sun) and the
 8     rate constant for the reaction of NO with O3, respectively.
 9          There are other important reactions involving NOX.  The reaction of NO2 with O3 leads
10     to the formation  of the nitrate (NO,) radical,
11
                                     NO2 + O3 -* NO3 + O2                         (3-12)
12
13     which in the lower troposphere is nearly in equilibrium with dinitrogen pentoxide (N2O5):
14
                                                 M
                                      NO3 + NO2 ^ N2OS                    (3-13, -3-13)

15     However, because the NOj radical photolyzes rapidly [with a lifetime of «»5 s for an
16     overhead sun (Atkinson et al., 1992a)],
17
                                          • - •- NO + O2      (10%)             (3-14a)
                         N03+hv -
                                          ! - * N02 + 0(V)   (90%)             (3-14b)
18
19
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 1     its concentration remains low during daylight hours, but can increase after sunset to
                                       7          If)             ^
 2     nighttime concentrations of <5 x 10  to 1 x 10  molecule cm  (<2 to 430 ppt) over
 3     continental areas influenced by anthropogenic emissions of NOX (Atkinson et al., 1986),
 4     Nitrate radical concentrations over marine areas are low because NOX concentrations are low
 5     over lower tropospheric marine areas (Noxon, 1983), and an NO3 radical mixing ratio of
 6     0,25 ppt has been measured at 3 km altitude in Hawaii {Noxon, 1983).  Atkinson (1991) has
 7     suggested the use of a 12-h nighttime average NO3 radical concentration of 5 X 10
                  -3
 8     molecule cm  in the lower troposphere over continental areas, with an uncertainty of a factor
 9     of «10,
10         The tropospheric chemical removal processes for NOX involve the daytime reaction of
11     NO2 with the OH radical and the nighttime wet and dry deposition of N2O5 to produce nitric
12     acid (HNO3),
13
                                                 M
                                       OH  + NO2 ™ HNO3                          (3-15)

                                            ILO
                                      N205	* HNO3                             (3-16)
14
15     Gaseous nitric acid formed from Reaction 3-15 undergoes wet and dry deposition, including
16     combination with gaseous ammonia to form paniculate phase ammonium  nitrate. The
17     tropospheric lifetime of NOX due to chemical reaction (mainly Reaction 3-15) is »1 to
18     2 days.  The tropospheric NO^ reactions  are  shown schematically in Figure 3-1 below:
19     It should be noted  that OH radicals can also react with NO to produce nitrous acid (HONO):
20

                                       OH + NO ^ HONO                          (3-17)

21     In urban areas, HONO can also be formed during nighttime hours (Harris et al., 1982; Pitts
22     et al., 1984a; Rodgers and Davis, 1989), apparently from the heterogeneous hydrolysis of
23     NC>2 or NOX, or both (Sakamaki et al., 1983; Pitts et al., 1984b; Svensson et al., 1987;
       December 1993                         3-12      DRAFT-DO NOT QUOTE OR CITE

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                                       HNO,
       Emission
       Figure 3-1. The cyclic reactions of tropospheric nitrogen oxides.
                                                                    *  N205
                                                                                wet/dry
                                                                                deposition
                                                                             HNO3
 1
 2
 3

 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
Jenkin et al., 1988; Lammel and Perner, 1988; Notholt et al., 1992a,b). The photolysis of
HONO during the early morning hours,
                             HONO + h»> -» OH + NO
(3-18)
can thus become an important source of OH radicals, leading to die rapid initiation of
photochemical activity (Harris et al., 1982).

3.2.3.3   The Methane Oxidation Cycle
     Methane is emitted into the atmosphere from swamps and wetlands, as well as from
ruminants (Fung et al., 1991a; World Meteorological Organization, 1992).  The major
tropospheric removal process for methane is by reaction with the OH radical,  with methane
lifetime equal to
                                    (k2t [OH])
                                             -l
(3-19)
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                                       343      DRAFT-DO NOT QUOTE OR CITE

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 1     where k2i is the rate constant for Reaction 3-21 and JOH] is the (variable) atmospheric
 2     OH radical concentration.  The calculated lifetime of methane in the troposphere is *» 10 to
 3     12 years. As for other saturated organic compounds, the OH radical reaction with methane
 4     proceeds by H-atom abstraction from the C-H bonds to form the methyl radical:
 5
                                    OH + CH, - Hp + ^Hj.                        #-20)
 6
 7     In the troposphere, the methyl radical reacts solely with ©2 to yield the mefiiyl peroxy
 8     (CH3O£) radical (Atkinson et al., 1992a):
 9

                                       CHs + 02 ^ CHjO'                           (3-21)

10          In the troposphere, the methyl peroxy radical can react with NO, NO^, HO2 radicals,
11     and other organic peroxy (RO^) radicals, with the reactions with NO and HO2 radicals being
12     the most important (see, for example, World Meteorological Organization, 1990b).  The
13     reaction with NO leads to the formation of the methoxy (CH3Q) radical,
14
                                  CH3O; + NO  -» O^O  f NO2.                       (3~22)
15
16          The reaction with the HO2 radical leads to the formation of methyl hydroperoxide,
17
                                 CHjOj + HO2 - CHgOOH + O2,                     (3-23)
18
19     which can photolyze or react with the OH radical (Atkinson et al., 1992a):
20
                                  CHjOOH  + hv -» CHjO + OH                      (3-24)
21
22
       December 1993                         3-H      DRAFT-DO NOT QUOTE OR CITE

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                                                    * H20 -i- CH3Oj                (3-25a)

                        OH + CH3OOH -------- -j

                                               - + H2O + CH2OOH              (3-25b)
                                                                fast
                                                          HCHO + OH
 1
 2      Methyl hydroperoxide also undergoes wet and dry deposition or incorporation into cloud
 3      water, or both.  The lifetime of methyl hydroperoxide in the troposphere due to photolysis
 4      and reaction with the OH radical is calculated to be =2 days.  Methyl hydroperoxide is then
 5      a temporary sink of radicals, with its wet or dry deposition being a tropospheric loss process
 6      for radicals.
 7           The only important reaction for the methoxy radical in the troposphere is with O2 to
 8      form formaldehyde (HCHO) and the HO2 radical,
 9
                                  CH36 * O2 -» HCHO +• HO2.                       (3-26)
10
1 1           Formaldehyde is a "first-generation" product that reacts further, by photolysis:
12
                                           . - P* H2 + CO     (55%)             (3-27a)
                         HCHO + hv - 1
                                           i - *H + HCO    (45%)             <3-27b)
13
14     where the percentages are for overhead sun conditions (Rogers, 1990); and also by reaction
15      with  the OH radical,
16
                                   OH  + HCHO -*  HjO + HCO                       (3-28)
17
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 1     In the troposphere, the H atom and HCO (formyl) radical produced in these processes react
 2     solely with O2 to form the HO2 radical:
 3
                                   H + 0^ - M -* H02 + M                       (3-29)
                                    HCO  + O2 -* HO2  + CO                        (3-30)
 5
 6     The lifetimes of HCHO due to photolysis and OH radical reaction are *4 h and 1.5 days,
 7     respectively, leading to an overall lifetime of » 3 h for overhead sun conditions.
 8         The final step in the oxidation of methane in the earth's atmosphere involves the
 9     oxidation of carbon monoxide by reaction with the OH radical (the only tropospheric reaction
10     of CO) to form CO2:
11
12
                                     OH + CO - H + CO2                          (3-31)
                                    H + O2 + M -* HO2 + M                        (3-29)
13
14     The lifetime of CO in the lower troposphere is »2 mo.
15          The overall reaction sequence leading to CO2 formation, through the HCHO and CO
16     intermediate products, is shown in Figure 3-2.
17          There is competition between NO and the HC^ radical for reaction with the CH3O2
18     radical, and the reaction route depends on the rate constants for these two reactions and the
19     tropospheric concentrations of HOs radicals and NO. The rate constants for the reaction of
20     the CH302 radicals with NO (Reaction 3-22) and HO2 radicals (Reaction 3-23) are of
21     comparable magnitude (Atkinson et al., 1992a).  Based on the expected HO2 radical
22     concentration in the troposphere, Logan et  al. (1981) calculated that the  reaction of the
23     CH3O^ radical with NO dominates for NO  mixing ratios of > 30 ppt (equivalent to an NO
                              o            3
24     concentration of > 7 x 10  molecule cm"  in the lower troposphere).  For NO mixing ratios
25     <30 ppt, the reaction of the CH3O2 radical with HO2 dominates.
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                                   OH + CH4 + H2O + CH3
                                                      02
                  wetfdry deposition -— CH3OOH
                                       OH
                                                  HCHO
                                               HO**10H,
                                               HOf
                                              I
                                             CO
                                               OH
                                             CO,
      Figure 3-2. Atmospheric reactions in the complete oxidation of methane.
 1
 2
 3
 4

 5
 6
 7
     Hydroperoxy radicals formed from., for example, Reactions 3-26, 3-29, and 3-30 can
react with NO, O3, or themselves, depending mainly on the concentration of NO. The
reaction with NO leads to regeneration of the OH radical,
                            HO2 +• NO -*OH + NO2,
(3-32)
whereas the reactions with 03 and HO2 radicals lead to a net destruction of tropospheric 03:
                            HO
                                                      O
                                                        2
(3-33)
 9
10
11
                                   HO2  + O3 -* OH  +  2 O2
                                                                          (3-34)
This net loss of tropospheric O3 occurs because the photolytic production of the OH radical
from O3, via the intermediary of the O( D) atom, represents a loss process for tropospheric
       December 1993
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 1     ozone.  Hence the absence of any Qj formation from the methane oxidation cycle is
 2     equivalent to a net ozone loss.  Using the rate constants reported for Reactions 3-32 and 3-34
 3     (Atkinson et al., 1992a) and the tropospheric ozone mixing ratios given above, it is
 4     calculated that the HO2 radical reaction with NO dominates over reaction with O3 for NO
 5     mixing ratios > 10 ppt.  The rate constant for Reaction 3-33 is such that an NO mixing ratio
 6     of this magnitude also means that the HO2 radical reaction with NO dominates over the self-
 7     reaction of HO2 radicals.
 8          There are therefore two regimes, depending on the fate of HQ^ and CH3O2 radicals:
 9     (1) a high-NO regime hi which HO2 and CH3O2 radicals react with NO to convert NO to
10     NO2, regenerate the OH radical and, through the photolysis of NO2, produce O3; and
11     (2) a low-NO regime in which HO2 and CH3O2 radicals combine (Reaction 3-23) and HO2
12     radicals undergo self-reaction and react with O3 (Reactions 3-33 and 3-34), leading to a net
13     destruction of O3 and inefficient OH radical regeneration (see  also Ehhalt et al., 1991; Ayers
14     etal., 1992).
15          Under high-NO conditions, the oxidation of methane leading to the formation of HCHO
16     can be written as the net reaction,
17
                   OH + CH4  + 2 NO + 2 Oj  = HjO •*• HCHO  + 2 NO2 +  OH,        (3-35)
18
19     showing the conversion of two molecules of NO to NO2 and regeneration of the OH radical.
20     Because NO2 photolyzes to form O-j in the presence of O2,
21

                                   N02 + hv -5?-» NO + 03,                     (3-1,3-2)
22
23     the oxidation of methane to HCHO under high-NO conditions can be written as,
24
                         OH + CH4 * 4 O2 = HjO +  HCHO  + 2 O3 +  OH,             (3-36)
25
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1
2
3
4
showing the formation of ozone from methane oxidation in the troposphere.  The reaction
cycles oxidizing methane to formaldehyde, converting NO to NO2, and forming ozone are
shown schematically in Figure 3-3.
                          HNO.
                                                               emission
                         emission
                                                                 HNOj
       Figure 3-3. Cyclic reactions of methane oxidation to formaldehyde, conversion of nitric
                  oxide to nitrogen dioxide, and concomitant formation of ozone in the
                  atmosphere.
 1          In a similar manner, under high-NO conditions, the photolysis of HCHO and its
 2     reaction with the OH radical is given approximately by:

         0,2 OH + HCHO  +  0.92 NO  -*? CO  + 0.44 H^  + 0.2 H/) + 0.92 NO2 + 0.92 OH

                                                                                    (3-37)
 3     Formaldehyde photooxidation is thus a  source of HO2 radicals (and of OH radicals in high-
 4     NO conditions) (Ehhalt et al., 1991), especially in urban areas where its concentration is
 5     elevated because it is produced during the  oxidation of anthropogenic nonmethane VOCs
 6     (Finlayson-Pitts and Pitts, 1986).
 7          Nitric oxide mixing ratios are sufficiently low in the lower troposphere over marine
 8     areas that oxidation of methane will lead to a net destruction of 03 (low-NO conditions),  as
 9     discussed by Carroll et al,  (1990) and Ayers et al. (1992). However, in the upper
10     troposphere and over continental areas  impacted by NOX emissions from combustion sources,
       December 1993
                                        3-19
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 1     NO inixing ratios are high enottgh (high NQ^coadMons} for methane oxidation to leal lo
 2     ozone fomiation (Carroll et al., 1990; WviM Me*e»^|peal OrgarazaiiQit, l§92s),
 3
 4     3.2.3.4   Cloud Processes in the Methane-Dominated Troposphere
 5          In addition to the dry and wet deposition of certain products of the
 6     photooxidation (for example, wet and dry deposition of nitric acid aad
 7     [Atkinson, 1988 and references therein; Hellpointner and Gab, 1989]), cloud processes cam
 8     have significant effects on the gasiphase chemisGy of the "clean19 tepc«SftoeiB 
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             TABLE 3-1. ESTIMATED EMISSIONS OF METHANE, NONMETHANE
           ORGANIC COMPOUNDS, NITROUS OXIDE, AND OXIDES OF NITROGEN
              (NO + N02) INTO THE EARTH'S ATMOSPHERE FROM BIOGENIC
                              AND ANTHROPOGENIC SOURCES

Chemical
CH4b
NMOCC
N2O (as N)d
NOX (as N)e
Emissions
Biogenic Sources
«150
«1,000
~7
= 10
(Tg/year8)
Anthropogenic Sources
= 350
»100
= 6
«40
       "Teragram = 10  g; or * 10  metric tons.
       Fung et al (1991a); World Meteorological Organization (1992). Emissions from ruminants, rice paddies, and
       biomass burning are considered as anthropogenic emissions.
       cLogan et al. (1981); World Meteorological Organization (1992), with biogenic emissions being assumed to be
       50% isoprene and 50% monoterpenes.
       dPrinnetal. (1990).
       National Research Council (1991); World Meteorological Organization (1992); biogenic sources =50% from
       soils; *s5Q% from lightning.
 1      of nonmethane VOCs from anthropogenic sources, large quantities of biogenic nonmethane
 2      VOCs (mainly of isoprene and monoterpenes) are emitted, both in polluted and nonpolluted
 3      areas, into the atmosphere from vegetation (see, for example, Isidorov et al., 1985; Lamb
 4      et al., 1987; Winer et al., 1991a,b).
 5           Analogous to the photooxidation of methane, the interaction of NOX with nonmethane
 6      VOCs from anthropogenic and biogenic sources under the influence of sunlight leads to the
 7      formation of photochemical air pollution (National Research Council, 1991).  In urban areas,
 8      emissions of NOX and VOCs from human activities (combustion sources, including
 9      transportation; industrial sources; solvent usage; landfills; etc.) dominate over biogenic
10      sources (National Research Council, 1991; Chameides et al,, 1992). However, the emissions
11      of VOCs from vegetation have been implicated in the formation of photochemical air
12      pollution in urban (Chameides et al., 1988; 1992) as well as rural (Trainer et al., 1987;
13      Roselle et al., 1991; Chameides et al., 1992) areas.
14          In essence, the chemistry of the polluted urban and regional atmosphere is an extension
15      of that of the clean, methane-dominated troposphere, with a number of additional

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 1     complexities because of the number and types of VOCs emitted from anthropogenic and
 2     biogenic sources.  At least in certain urban areas, the NMOC content of ambient air is
 3     similar to the composition of typical gasolines (Mayrsohn and Crabtree, 1976; Mayrsohn
 4     et aL, 1977; Harley et al., 1992; see Section 3,4.3).  For example, gasolines typically
 5     consist of  *55 to 65% alkanes, »5 to 10% alkenes, and  »25 to 35% aromatic
 6     hydrocarbons (Lonneman et al., 1986; Sigsby et al., 1987), whereas in Los Angeles the
 7     ambient urban air composition is »50 to 55% alkanes, »5 to 15% alkenes,  » 25 to 30%
 8     aromatic hydrocarbons, and *5 to 15% earbonyls (Grosjean and Fung, 1984; California Air
 9     Resources Board, 1992).  Emissions of NOX and VOCs are dealt with in detail in
10     Section 3.4.1.
11
12     3.2.4.1  Tropospheric Loss Processes of Volatile Organic Compounds
13          The chemical loss processes of gas-phase VOCs include photolysis and chemical
14     reaction with the OH radical during daylight hours, reaction with the NO3 radical during
15     nighttime hours,  and reaction with O3) which is often present throughout the 24-h period
16     (Atkinson,  1988).
17          As discussed earlier,  photolysis of chemical compounds in the troposphere is restricted
18     to the wavelength region above »290 nm. Because of the strength of chemical bonds, the
19     tropospheric wavelength region in which  photolysis can occur  extends from **290 to
20     ^800  nm, and this wavelength region is  often referred to as the "actinic" region.  For
21     photolysis to occur, a chemical compound must be able to absorb radiation in the actinic
22     region (and hence have a non-zero absorption cross-section, ^, is
25     defined as  (number of molecules of the chemical undergoing change)/(number of photons of
26     light absorbed).  The photolysis rate, kphotoiysis> ft>r the process,
27
                                         C + hv -» products                             (3-38)
28
29     is given by,
30

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                                               }  'x *x *. <*•                         (3-39)
 1
 2      where Jx is the radiation flux at wavelength X, and trx ^d «^x are tne absorption cross-section
 3      and photolysis quantum yield, respectively, at wavelength X.  Photolysis is therefore a
 4      pseudo-first-order process (depending on the radiation flux and spectral distribution) and the
 5      lifetime of a chemical with  respect to photolysis is  given by:
 6
                                        T      = *                                   *•    '
                                         phololy»i«
 1
 8          For the reaction of a VOC with a reactive species, X (for tropospheric purposes,
 9     X = OH, NO3, and O3), the lifetime for the reaction process, C + X -» products, is given
10     by:
11
                                          TX =  (kJXD-                              (3-41)
12
13     and depends on the concentration of the reactive species X and the rate constant (kx) for
14     reaction of the VOC with X. In general, the ambient atmospheric concentrations of OH
15     radicals, NO3 radicals, and O3 are variable, depending on tune of day, season, latitude,
16     altitude, etc.  For the purpose of comparing lifetime calculations for various classes  of
17     VOCs, average ambient tropospheric concentrations of these three species are often used.
18     The concentrations used here have been presented in the sections above and are:  OH
19     radicals, a 12-h average daytime concentration of 1.6 X 106 molecule cm"3 (equivalent to a
20     24-h average concentration of 8 x 10s molecule cm"3)  (Prinn et al., 1992); isTCXj radicals, a
21      12-h nighttime average concentration of 5 x 10 molecule cm"  (Atkinson, 1991);  and 03, a
22      24-h average of 7 x 1011 molecule cm"3 (30 ppb) (Logan, 1985).
23          The major classes of VOCs are the alkanes, alkenes (including alkenes from biogenic
24      sources), aromatic hydrocarbons, carbonyl compounds, alcohols, and ethers (see California
25      Air Resources Board,  1992). The calculated lifetimes with respect to the individual
26      atmospheric loss processes of compounds representing a range of reactivities in each class
27      are given in Table 3-2, Note that the lifetimes given are dependent on the reaction rate

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          TABLE 3-2. CALCULATED TROPOSPHERIC LIFETIMES OF SELECTED
        VOLATILE NONMETHANE ORGANIC COMPOUNDS DUE TO PHOTOLYSIS
       AND REACTION WITH HYDROXYL AND NO3 RADICALS AND WITH OZONE
Organic
n-Butane
2-MethyIbutane
n-Octane
Ethane
Propene
Isoprene
Limonene
Benzene
Toluene
m-Xylene
Formaldehyde
Acetaldehyde
Acetone
2-Butanone
Methanol
Ethanol
Methyl f-butyl ether
Ethyl r-butyl ether
Methylglyoxal

OH
5.7 days
3.7 days
1.7 days
1.7 days
6.6 h
1.7 h
l.Oh
12 days
2.4 days
7.4 h
1 .5 days
11 h
66 days
13 days
15 days
4.4 days
4.9 days
1.6 days
10 h
Lifetime Due
NO3
2.8 years
290 days
250 days
230 days
4.9 days
0.8 h
3 min
>4 years
1.9 years
200 days
80 days
17 days
—
—
> 77 days
> 50 days
—
—
—
to Reaction with
03
>4,500 years
> 4,500 years
> 4,500 years
10 days
1.6 days
1.3 days
2.0 h
>4.5 years
>4.5 years
>4.5 years
>4.5 years
>4.5 years
>4.5 years
>4.5 years
—
—
—
—
>4.5 years

hv










4h
6 days
60 days





2h
      Sources: Lifetimes resulting from reaction with OH, NO3, and 03 were calculated using rate constants given in
      Atkinson and Carter (1984) and Atkinson (1989, 1991, 1993); data for photolysis lifetimes are from Horowitz
      and Cdvert (1982), Meyrahn et al. (1982; 1986), Plum et al. (1983), and Rogers (1990).g The OH radical
      radical, and O3 concentrations used (molecule cm" were: OH, 12-h average of 1.6 X 10 ; NQj, 12-h average
      of 5  X 108; 03, 24-h average of 7 x 1011.
1     constants and the assumed ambient concentrations of OH radicals, NOj radicals, and 03.
2     Uncertainties in the ambient concentrations of the reactive species translate directly into
3     corresponding uncertainties in the lifetimes
      December 1993
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 1           The following brief discussions of the tropospheric chemistry of the important classes
 2      of VOCs are based on the recent review and evaluation article of Atkinson (1993), and that
 3      article should be consulted for further details of the tropospheric reactions of VOCs,
 4
 5      3.2.4.1.1   Alkanes
 6           Since gasoline and diesel fuels contain alkanes of carbon number C4 to SC15, a large
 7      number of alkanes are present in ambient air (see, for example, Grosjean  and Fung, 1984;
 8      California Air Resources Board, 1992; Section 3.4). Table 3-2 shows that the only
 9      important tropospheric loss process for the alkanes is by reaction with the OH radical, with
10      calculated lifetimes of the 03 to C10 alkanes ranging from ~ 1 to 15 days. As for methane,
11      the OH radical reaction proceeds by H-atom abstraction from the various  C-H bonds.  The
12      nighttime reactions of the NO3  radical with alkanes (calculated to be generally of minor
13      importance, but see Penkett et al. [1993]) also proceed by initial H-atom abstraction.  For an
14     alkane (RH) the initially formed radical is an alkyl radical (R):
15
                                      OH +  RH -» H,O  + R,                          (3-42)
16
17     which rapidly adds O2 to form an alkyl peroxy (RO^) radical,

                                          R  + 02 ^ RO;,                              (3-43)

18     with the simplest of the RO£ radicals being the methylperoxy radical, described in
19     Section 3.2.3.3 dealing with methane oxidation.  Alkyl peroxy radicals (RO^) can react with
20     NO, NO2, HO2 radicals, and other organic peroxy radicals (
21
                                     ROj + NO -* RO + NO,;
22
                                      RO* + NO2 ** ROONO2;                         (3-45)
23
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                                    ROj + HO2 - ROOH + O2;                        (3-46)
 1
                                  ROj + R'Oj -* RO + R'6 + 02;                     (3"47a)
 2
                           ROj + R'Oj -» a carbonyl  + (1 - ct)  ROH * O2              (3-47b)
                                        + products of R'Oj.
 3
 4     The reactions with organic peroxy radicals are expected to be of less importance in the
 5     troposphere than the other reactions listed.  Since low NO conditions occur even in air
I 6     masses in urban areas, the HO2 radical reactions  with RO2 radicals and the subsequent
 7     chemistry must be considered. However, because of space constraints and a general lack of
 8     knowledge concerning the tropospheric chemistry of R02 radicals under low-NO conditions,
 9     only the reactions occurring under high-HO conditions are presented and discussed here.  For
10     the SC3 alkyl peroxy radicals, in addition to the reaction pathway leading to NO-to-NQj
11     conversion (Reaction 3-44a), a second reaction pathway leading to formation of an alkyl
12     nitrate becomes important:

                                        ROj + NO ^ RONO2                          (3-44b)

13     For a given alkyl peroxy radical, the alkyl nitrate yield  increases with increasing pressure
14     and with decreasing temperature (Carter and Atkinson,  1989a).
15          Analogous to the case  for the  methoxy radical, those alkoxy radicals (RO^) formed
16     from the higher alkanes that have an abstractable H atom can react with 02 to form the HO2
17     radical and a carbonyl; for example,
18
                              (CH^CHO + O2 -* CH3C(O)CH3 + HO2                  (3-48)
19
20     In addition, unimolecular decomposition by C-C  bond scission and unimolecular
21     isomerization via a six-member transition state (Atkinson and Carter,  1991; Atkinson, 1993)
22     can be important for the larger alkoxy radicals.  For example, the following chemistry can
23     occur for the 1-pentoxy radical:
       December 1993                           3-26      DRAFT-DO NOT QUOTE OR CTTB

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                    decomposition           O2            isomerization
                                                             CH3CHCH£H/M2OH
                     +                        +
                                             H02
 1
 2     with the alkyl radicals C4H^ and HOCH2CH2CH2CHCH3 undergoing further reaction,
 3          The majority of the reaction rate constants and reaction pathways in the alkane
 4     degradation schemes are assumed by analogy with the chemistry of CrC3 alkyl, alkyl
 5     peroxy, and alkoxy radicals (Atkinson, 1990, 1993; Carter, 1990; Atkinson et al., 1992a).
 6     A number of areas of uncertainty still  exist for the tropospheric chemistry of the alkanes
 7     (Atkinson, 1993). These include (a) the relative importance of alkoxy radical reaction with
 8     O2, decomposition and isomerization,  and the reactions occurring subsequent to the
 9     isomerization reaction; (b) the formation of alkyl nitrates from the reactions of the peroxy
10     radicals with NO; and (c) reactions of the alkyl peroxy radicals with HO^ and other peroxy
11     radicals, reactions that can  be important  in the nonurban troposphere.
12
13     3.2.4.1.2   Alkenes (Anthropogenic and Biogenic)
14          The alkenes emitted from anthropogenic sources are mainly ethene, propene, and the
15     butenes, with lesser amounts of the ^C5 alkenes.  The major biogenic alkenes emitted from
16     vegetation are isoprene  (2-methyH,3-butadiene) and C^ft^ monoterpenes (Isidorov  et al.,
17     1985; Winer et al., 1992),  and their tropospheric chemistry is currently the focus of much
18     attention (see, for example, Hatakeyama et al., 1989, 1991; Arey et al., 1990; Tuazon and
19     Atkinson,  1990a; Pandis et al., 1991;  Paulson et al., 1992a,b; Paulson and Seinfeld,  1992a;
20     Zhang et al.,  1992; Hakola et al.,  1993a,b).
21          As evident from Table 3-2, the alkenes react with  OH and NO3 radicals and O3. All
22     three processes are important atmospheric transformation processes, and all three reactions
23     proceed by initial addition to the > C=C < bond(s).  These reactions are  briefly discussed
24     below.

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 1      Hydroxyl Radical Reactions
 2          As noted above, the OH radical reactions with the aJkenes proceed mainly by OH
 3      radical addition to the  > C=C < bond(s). For example, the OH radical reaction with
 4      propene leads to the formation of the two OH-containing radicals,
 5
                    OH + CH3CH=CH2   CHjCHCO^CHj and CI^CHCHpH.        (3-49)

 6     The subsequent reactions of these radicals are similar to those of the alkyl radicals formed by
 7     H-atom abstraction from the alkanes. Taking the CH3 CHCH2OH radical as an example,
 8     under high-NO conditions, the following chemistry occurs:
 9
                CH3CHCHpH
                                                NO
                                                       + NO2
                                           /         \
                                        /          \
                                 decomposition           \
                                                         \
                                                   GHqqO)CH^OH +
                          HCHO + HO2
10
11     The underlined species represent products that, although stable, can undergo further reaction;
12     and hence they can lead to "second-generation" products.  For the simple £C4 alkenes, the
13     intermediate OH-containing radicals appear to undergo mainly decomposition at room
14     temperature and atmospheric pressure of air.  Hence for propene, the "first-generation"
15     products of the OH radical reaction in the presence of NO are HCHO and CH3CHO,
16     irrespective of which OH-containing radical is formed.
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 1           However, this is not the case for the more complex alkenes of biogenic origin.  The
 2      product studies of Tuazon and Atkinson (1990a) and Paulson et al. (1992a) for the OH
 3      radical reaction with isoprene in the presence of N(\ show that the products expected from
 4      reaction schemes analogous to that shown above for propene (i.e., HCHO + methyl vinyl
 5      ketone [CH3C(O)CH=CH2] and HCHO + methacrolein [CH2=C(CH3)CHO], arising from
 6      initial OH radical addition to the CH2=CH- and CH2=C < bond, respectively) do noi
 7      account for the entire reaction pathways.  The product yields obtained from the studies of
 8      Tuazon and Atkinson (1990a) and Paulson et al. (1992a) are (Atkinson, 1993): methyl vinyl
 9      ketone, 34%; methacrolein,  24%; 3-methylfuran, 5%; organic nitrates,  «12%; and
10     unidentified carbonyl compounds, **25%.  The HCHO  yield was consistent with being a
11      co-product formed with methyl vinyl ketone and methacrolein (Tuazon and Atkinson, 1990a),
12      Aerosol formation for isoprene  photoxidation has been shown to be of negligible importance
13      under atmospheric conditions (Pandis et al.5 1991; Zhang et al., 1992).
14          To date, few quantitative product studies have been carried out for the monoterpenes
15      (Arey et al., 1990; Hatakeyama et al., 1991; Hakola et al., 1993a,b).  Arey et al. (1990) and
16     Hakola et al. (1993a,b) have observed the C7-C10 carbonyl compounds expected by analogy
17     with the reaction scheme shown above for propene., but  with total carbonyl formation yields
18     of £50%.  These data (Arey et al., 1990; Hakola et al., 1993a,b) indicate the formation of
19     other products in significant, and often dominant, yields. Hatakeyama et al. (1991) used
20     Fourier transform infrared (FTIR) absorption spectroscopy and reported carbonyl compounds
21      to be formed in high yield from a-pinene and /?-pinene, in apparent disagreement with the
22     data of Arey et al. (1990) and Hakola et al. (1993b).  While Hatakeyama et al. (1991)
23     ascribed these carbonyl products to those expected from oxidative cleavage of the >C=C<
24     bonds, it is possible that the yields reported for these carbonyls  included contributions by
25     other, as yet unidentified, carbonyl-containing products.
26
27     Nitrate Radical Reactions
28          The NO3 radical reactions proceed by reaction schemes generally similar to the OH
29     radical reactions, except that when NO3 radicals are present, NO concentrations are low (see
30     above) and RO2  +  RQ2  and RO2  + HO2 radical reactions are expected to dominate over
31     RO2  + NO reactions.  For propene the initial reaction  is  (Atkinson,  1991),

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                 N0
                                                and CHjCHtONO^CHj,      (3-50)
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
followed by a series of reactions that are expected (Atkinson, 1991) to lead to the formation
of, among others, carbonyls and mtrato-carbonyls (for example, ECHO, CHjCHO,
CH3CH(ONO2)CHO, and CH3C(O)CH2ONO2 from propene). Few data are presently
available concerning the products and detailed mechanisms of NC^-alkene reactions
(Atkinson, 1991, 1993 and references therein). In particular, the reaction products and
mechanisms for the NO3 radical reactions with isoprene and the monoterpenes are still not
quantitatively understood (Kotzias et al., 1989; Barnes et ah, 1990; Hjorth et ah, 1990;  Skov
etal., 1992).

Ozone Reactions
     The O3 reactions also proceed by addition of O3 to the alkene, to form an energy-rich
ozonide that rapidly decomposes to form carbonyls and energy-rich biradicals [ ] ,
                     03 +
                                                       JQIQ + [CH^CHOO]
The energy-rich biradicals, [CH2OO]  and [CH3CHOO] , undergo collisional stabilization or
decomposition:

                                                     decomposition.
                                                                                 (3-51a)
                                                                           (3-5Ib)
19
       December 1993
                                       3-30      DRAFT-DO NOT QUOTE OR OTE

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 1     There are still significant uncertainties concerning the reactions of the energy-rich biradicals
 2     (see, for example, Hone and Moortgat, 1991; Atkinson, 1990, 1993), with recent studies
 3     showing the production of OH radicals in high yields for several alkenes (Niki et al., 1987;
 4     Paulson et al., 1992a; Atkinson et al., 1992b; Paulson and Seinfeld, 1992b; Atkinson and
 5     Aschmann, 1993),
 6          For isoprene, the major products are methacrolein and methyl vinyl ketone (Kamens
 7     et al., 1982; Niki et al., 1983; Paulson et al,, 1992b).  Paulson et al. (1992b) derived
 8     OH radical and O(3P) atom formation yields of 0.68 ± 0.15 and 0.45 ± 0.2, respectively,
 9     from the O3 reaction with isoprene, indicating the dominance of secondary reactions.
10     However, Atkinson et al. (1992b) derived a significantly lower OH radical formation yield of
11     0.27 (uncertain to a factor of «1.5).  Clearly, further studies of this important reaction are
12     needed.
13          The only quantitative studies of the gas-phase  O3 reactions with the monoterpenes are
14     those of Hatakeyama et  al. (1989) for a- and 0-pinene and Hakola et al. (1993a,b) for a
15     series of monoterpenes.  Additionally, Atkinson et al, (1992b) derived OH radical formation
16     yields from these reactions under atmospheric conditions.
17          Several groups  (Gab et al., 1985; Becker et al., 1990, 1993; Simonaitis et al.,  1991;
18     Hewitt and Kok, 1991) have reported the formation of H2O2 and organic peroxides from
19     O3 reactions with alkenes.  However, there are significant disagreements in the quantitative
20     results reported by Becker et al. (1990, 1993) and Simonaitis et al. (1991).
21
22     3,2.4.1.3  Aromatic Hydrocarbons
23          The most abundant aromatic hydrocarbons in urban atmospheres are benzene, toluene,
24     the xylenes, and the  trimethylbenzenes (Grosjean and Fung, 1984; California Air Resources
25     Board,  1992).  As shown in Table 3-2, the only tropospherically important loss process for
26     benzene and the alkyl-substituted benzenes is by reaction with the OH radical.  For the alkyl-
27     substituted benzenes, the OH radical reactions proceed by two pathways: H-atom abstraction
28     from the C-H bonds of the alkyl substituent group(s) and OH radical addition to the aromatic
29     ring, as shown here, for p-xylene,
30
        December 1993                          3-31       DRAFT-DO NOT QUOTE OR CITE

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1
2
3
4
5
                                     CH,
                                     CH,
                                                                                    (3-52a)
                                                                                    (3-52b)
with the OH radical addition pathway being reversible above « 325 K (Atkinson, 19&9).
     The radical formed in Reaction 3-52a reacts analogously to an alkyl radical (Atkinson,
1993), leading in the presence of NO to aromatic aldehydes and organic nitrates:
                                    0
                                       M
                                       ™
                                                  1 NO
                                                            NO
                                                   a,
                                           CH3C6H4QIQ + HO2
                                             (p-tolualdehyde)
1     The OH-containing radical formed in Reaction 3-52b can undergo reaction with both NO2
2     and O2-  Knispel et al. (1990) reported rate constants for the reactions of NC>2 and O2 with
3     the OH-containing radicals formed from benzene and toluene.  The magnitude of the rate
4     constants they obtained implies that in the troposphere the major reactions of these radicals
5     will be with C>2. However, laboratory  studies conducted under a range of NO2
                1993                          3-32       DRAFT-DO NOT QUOTE OR CITE

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 1      concentrations such that the expected reactions varied from being mainly with O2 to being
 2      mainly with NO2 showed no obvious change in the major ring-addition product yields
 3      (Atkinson et al.s 1989).  The data of Atkinson et al. (1989), obtained from the OH radicai-
 4      initiated reactions of benzene and toluene, may indicate that the product yields from the
 5      O2 and NO2 reactions with these radicals are fairly similar. The present uncertainties
 6      concerning the fate of these radicals need to be resolved before a detailed  mechanism of the
 7      tropospheric degradation of aromatic hydrocarbons can be constructed.
 8           Despite these uncertainties, however, products from the OH radical addition pathway
 9     have been identified and their formation yields determined (Atkinson, 1993, and references
10     therein). The major products identified from the OH radical addition pathway are phenolic
11      compounds (for example, phenol from benzene and o-, m- and p-cresol from toluene) and
12     a-dicarbonyls (glyoxal, methylglyoxal, and 2,3-butanedione) arising from  cleavage of the
13     aromatic ring (see, for example, Atkinson, 1990, 1993, and references therein).  Significant
14     fractions (S50% for benzene, toluene, and the xylenes) of the reaction products are,
15     however, still not accounted for.
16
17     3.2.4.1.4  Carbonyl Compounds
18          As noted above, the OH radical reactions with the alkanes, alkenes,  and  aromatic
19     hydrocarbons lead, often in large yield,  to the formation of carbonyl compounds. Likewise,
20     carbonyls are formed during  the reactions of NO3 radicals and O3 with alkenes.  As a first
21     approximation, the carbonyl compounds of tropospheric interest are:  formaldehyde (see
22     Section 3.2.3.3), acetaldehyde, and the higher aliphatic aldehydes;  benzaldehyde; acetone,
23     2-butanone, and the higher ketones; and simple dicarbonyls such as glyoxal, methylglyoxal,
24     and 2,3-butanedione.
25          The tropospheric photooxidation of isoprene leads to the  formation of methyl vinyl
26     ketone (CH3C(O)CH=CH2)  and methacrolein (CH3C(CHO)=CH2). The OH radical-
27     initiated reactions of these two carbonyl compounds in the presence of NOX have been
28     studied by Tuazon and Atkinson (1989,  1990b).
29          The tropospherically important loss processes  of the carbonyls not containing  > C=C <
30     bonds are photolysis and reaction with the OH radical.  As shown in Tables 3-2, photolysis
31     is a major tropospheric loss process for the simplest aldehyde (HCHO) and the simplest

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 1     ketone (CH3C(O)CH3), as well as for the dicarbonyls.  For the higher aldehydes and
 2     ketones, the OH radical reactions are calculated to be the dominant gas-phase loss process
 3     (Table 3-2). For acetaldehyde, the reaction proceeds by H-atom abstraction from the -CHO
 4     group to form the acetyl (CH3CO) radical,
 5
11
                               OH  +  CH3CHO -» HjO  + CH.CO,
 6
 7     which rapidly adds O2 to form the acetyl peroxy radical:

                                  CHjCO + O2 ^ CH3C(0)00.                      (3-54)

 8     This O2 addition pathway is in contrast to the reaction of O2 with the fonnyl (HCO) radical
 9     formed from HCHO, which reacts by an H-atom abstraction pathway (Reaction 3-30). The
10     acetyl peroxy radical reacts with  NO and
                              CH3C(O)OO + NO^ CH3C(O)O + NO2                  (3-55)
                                                    [fast
                                                    I
                                                 CH3 + CO2;
                                               M
                                           NO2 ** CH3C(O)OONO2!            (3-56, -3-56)

12     with the NO2 reaction forming the thermally unstable peroxyacetyl nitrate (PAN). The
13     higher aldehydes also lead to PANs (Roberts, 1990); for example, propionaldehyde reactions
14     lead to the formation of peroxypropionyl nitrate (PPN).  While the rate constant at
15     atmospheric pressure for the thermal decomposition of PAN (Atkinson et-al., 1992a) is such
16     that the lifetime of PAN with respect to thermal decomposition is *30 min at 298 K in the
17     lower troposphere, the thermal lifetime of PAN is calculated to be several hundred years in
18     the upper troposphere.  Reaction with OH radicals or photolysis, or both, will therefore
19     dominate as the PAN loss processes in the upper troposphere (Atkinson et al., 1992a).
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 1           The transport of PAN out of urban areas into colder air masses (for example, to higher
 2     altitude) leads to PANs becoming a temporary reservoir of NOX and allowing for the long-
 3     range transport of NOX to less polluted areas.  Release of NQj in these less polluted areas
 4     via reaction (-3-56), with subsequent photolysis of NO2, then leads to O3 formation and the
 5     pollution of remote areas.
 6          Since the CH3 radical formed from the NO reaction with the acetyl peroxy radical leads
 7     to HCHO  formation, the OH radical reaction with acetaldehyde forms formaldehyde.  The
 8     same process occurs for propionaldehyde, which reacts to form CH3CHO and then HCHO.
 9     Benzaldehyde appears to behave as a phenyl-substituted aldehyde with respect to its OH
10     radical reaction,  and the analog to PAN is then peroxybenzoyl nitrate, PBzN
11     (C6H5C(O)OONO2).
12          The formation of formaldehyde from acetaldehyde, and of acetaldehyde and then
13     formaldehyde from propionaldehyde, are examples of "cascading", in which the
14     photochemical degradation of emitted VOCs leads to the formation of further VOCs,
15     typically containing fewer carbon atoms than the precursor VOC.  This process continues
16     until the degradation products are removed by wet and dry deposition or until CO or CO2  are
17     the degradation products.  The reactions of each of these VOCs (i.e., the initially emitted
18     VOC and  its first-, second-, and successive-generation products) in the presence of NO
19     (high-NO  conditions) can lead to the formation of O3.
20          As discussed in Section 3.2.3.3 for formaldehyde, the photolysis of carbonyl
21     compounds can lead to the formation of new radicals that result in enhanced photochemical
22     activity.  The OH radical reactions of the ketones are generally analogous to the reaction
23     schemes for the alkanes and aldehydes.
24
25     3.2.4.1.5   Alcohols and Ethers
26          A number of alcohols and ethers are used in present-day and reformulated gasolines and
27     in alternative fuels.  The alcohols include methanol, ethanol, and tert-butyl alcohol, and the
28     ethers include methyl tert-butyl ether and ethyl /erf-butyl ether.  Table 3-2 shows that in the
29     troposphere these VOCs react only with the OH radical.  These OH radical reactions proceed
30     by H-atom abstraction from the C-H bonds (and to a minor extent from the O-H bonds in  the
31     alcohols).  For example, for methanol

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                                  OH + CHjOH -* Hp + O^O             (15%)  (3-57a)
                                 OH + CH3OH - Hp + CHjOH            (85%)  (3-57b)
 1
 2     In the troposphere, both of the CH3O and CH2OH radicals react only with 0^ to form
 3     formaldehyde.
 4
                                  CH30 + O2 - HCHO  + HO2                       (3-58)
 5
                                  CHjQH  + O2 - HCHO  + HO2                      (3-59)
 6
 7     The overall reaction is then:
 8
                           OH + CH3OH  + O2 -* HjO + HCHO + HO2               (3-60)
 9
10     The reaction  sequence for ethanol is similar (Atkinson, 1993).  Product studies of the OH
11     radical-initiated reactions of methyl ten-butyl ether and ethyl te/t-butyl ether in the presence
12     of NOX have been carried out by Taper et al. (1990), Smith et al. (1991, 1992), Tuazon et al.
13     (1991), and Wallington and Japar (1991).  The major products from methyl te/t-butyl ether
14     are ten butyl formate, formaldehyde, and methyl acetate [CH3C(O)OCH3]; and from ethyl
15     ten-butyl ether, rm-butyl formate, ten-butyl acetate, formaldehyde, acetaldehyde, and ethyl
16     acetate.  The available product data and the reaction mechanisms have been reviewed by
17     Atkinson (1993) and that reference should be consulted for further details.
18          In addition to the use of alcohols  and ethers in gasolines and alternative fuels,
19     unsaturated alcohols  have been reported as emissions from vegetation (Arey et al., 1991a;
20     Goldan et al., 1993), and kinetic and product studies have begun to be reported for these
21     biogenic VOCs (Grosjean et  al.,  1993).
22
23
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 1      3.2.4.1.6   Primary Products and Areas of Uncertainty for the Tropospkeric Degradation
 2                 Reactions of VOCs

 3           The tropospheric degradation reactions of the alkanes, alkenes (including those of

 4      biogenic origin), aromatic hydrocarbons, carbonyls (often formed as products of the

 5      degradation reactions of alkanes, alkenes, and aromatic hydrocarbons) and other oxygenates

 6      have been briefly discussed above.  The "first-generation" products of the alkanes, alkenes,

 7      and aromatic hydrocarbons are as follows (unfortunately, complete product distributions have

 8      not been obtained for most of the VOCs studied):

 9

10     Alkanes
11             •  Carbonyl compounds (i.e., aldehydes and ketones) are formed as major
12               products for the smaller (^C4 alkanes).
13
14            •  Alkyl nitrates are formed from the >C3 alkanes studied to date. The yields
15              increase with the size of the alkane from  =4% for propane to =30% for
16              n-octane.
17
18            •  5-Hydroxycarbonyls are expected to be formed after the alkoxy radical
19              isomerization reaction.  To date,  no direct evidence for the formation of
20              these compounds exists. For the larger alkanes, the formation yields of
21               these compounds could be high.
22
23            •  AIM hydroperoxides are formed under low-NO conditions.
24
25            •  Alkyl peroxynitrates (ROONO^ are formed but have short lifetimes (a few
26              seconds at 298 K) due to thermal decomposition.
27
28            •  Alcohols are formed from the combination reactions of the peroxy radicals
29              under low-NO conditions. These compounds are expected to be formed in
30              low overall yield in the troposphere.
31

32          The major uncertainties in the atmospheric chemistry of the alkanes concern the

33     formation of alkyl nitrates from the reactions of the peroxy radicals with NO

34     (Reaction 3-44b) and the reactions of the alkoxy radicals in the troposphere.  These

35     uncertainties affect the amount of NO to NO^ conversion occurring and hence the amounts of
36     O3 which are formed during the NOx-air photooxidations of the alkanes.

37

38

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 1     Alkenes
 2            •  Carbonyl compounds (aldehydes and ketones) are formed as major products
 3              of the OH radical, NO3 radical, and 03 reactions.
 4
 5            •  Organic acids are formed from the O3 reactions, but possibly in low yield.
 6
 7            •  Hydroxynitrates and nitratocarbonyls are formed from the OH radical
 8              reactions and NO3 radical reactions, respectively.  The hydroxynitrates are
 9              formed in low yield from the OH radical reactions, while the
10              nitratocarbonyls may be major products of the NQj radical reactions.
11
12            •  Hydroxycarbonyls and carbonyl-acids are also expected to be formed,
13              although few, if any, data exist to date.
14
15            •  Decomposition products are produced from the initially energy-rich
16              biradicals formed in the 03 reactions; these include CO, CO2, esters,
17              hydroperoxides, and, in the presence of NOX, peroxyacyl nitrates
18              (RC(O)OONO2; PANs).
19

20          The major areas of uncertainty concern the products and mechanisms of the

21     O3 reactions (in particular, the radical yields from these reactions that affect the

22     03 formation yields from the NOx-air photooxidations of the alkenes) and the reaction

23     products  and mechanisms of the OH radical reactions with the alkenes containing more than

24     four carbon atoms.

25

26     Aromatic Hydrocarbons

27            •  Phenolic compounds, such as phenol and cresols, have been observed as
28              major products of the atmospheric reactions of the aromatic hydrocarbons
29              under laboratory conditions.
30
31            •  Aromatic aldehydes, such as benzaldehyde, are formed in £10% yield.
32
33            •  a-Dicarbonyls, such as glyoxal, methylglyoxal, and biacetyl, are formed in
34              faniy high (10 to 40%) yields.  These dicarbonyls photolyze rapidly to form
35              radicals and are therefore important products with respect to the
36              photochemical activity of the aromatic hydrocarbons.
37
38            •  Unsaturated carbonyl or hydroxycarbonyl compounds,  or both, are formed,
39              although there is little direct information concerning the formation of these
40              products.
41
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 1          There is a lack of knowledge as to the detailed reaction mechanisms and reaction
 2     products for the aromatic hydrocarbons under tropospheric conditions, (i.e., for the NOX
 3     concentration conditions encountered in urban and rural areas.). It is possible that the
 4     products observed in laboratory studies, and their formation yields, are not representative of
 5     the situation in the troposphere. This then leads to an inability to formulate detailed reaction
 6     mechanisms for the atmospheric degradation reactions of the aromatic hydrocarbons, and the
 7     chemical mechanisms used in urban airshed models must then rely heavily on environmental
 8     (or "smog") chamber data.
 9
10     Oxygenated Compounds
11            • The products observed from the atmospheric photooxidations of oxygenated
12              organics are carbonyls, organic acids (RC(O)OH), esters, alcohols, and, in
13              the presence of NOX, PANs.
14
15
16          The major area of uncertainty concerns the importance of photolysis of carbonyl
17     compounds in the troposphere, and the products formed.  In particular, there is a lack of
18     information concerning the absorption cross-sections and photoodissociation quantum yields
19     for most of the aldehydes and ketones other than formaldehyde, acetaldehyde, and acetone.
20
21     3.2.4.2  Chemical Formation of Ozone in Polluted Air
22     3.2.4,2.1   Major Steps in Ozone Formation
23          As discussed earlier, NOX, and VOCs interact under the influence of sunlight to form
24     O3 and other photochemical air pollutants. The major steps hi this process are the
25     conversion of NO to NO2 by peroxy radicals, with the photolysis of NO2 leading to
26     O3 production.  In the absence of a VOC, Reactions  3-1 through 3-3,
27
                                       NO + 03 - N02  + 02                            (3-3)

                                       N02  + h? 2? NO  + 03                       (3-1, 3-2)

28
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1     lead to no net formation of O3.  The reaction of a VOC with the OH radical, or its
2     photolysis, leads to the formation of HO2 and organic peroxy (RO^ radicals, which react
3     with NO under high-NO conditions:
                            VOC(+ OH, h?) -H? RO,
                                                                                 (3-61)
                                   RO2 + NO -* RO + NO2
                                   NO,
                                  + hv 5? NO  + O,
  (3-44a)

(3-1, 3-2)
4
5
6
7
8
9
          Net:
VOC(+ OH, hv)  -»2 RO, + O3
   (3-62)
with the alkoxy (RO) radical producting further HO2 or RO2 radicals, or both, and, hence,
further production of O3.  This process is shown schematically in Figure 3-4.
                              VOC
      Figure 3-4. Major steps in production of ozone in ambient air (R — H, alkyl or
                 substituted alkyl, or acyl).
      December 1993
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 1
 2
 3
 4
 5
 6
 7
     The general time-concentration profiles for selected species during irradiation of an
NOx-VOC-air mixture are shown in Figure 3-5 for a constant light intensity and in
Figure 3-6 for diurnally varying light intensity. These general features of an NMOC-NOX-
air irradiation are described by the following reactions:
(a) The conversion of NO to NO2 occurs through the oxidation reactions,
                                   organic! +  OH, hi>, O3) -* RO2
                                     RO3 + NO -+ RO + NO2
                                      RO 2? carbonyl * HO2
                                                                               (3-63)
                                                                              (3-44a)

                                                                               (3-64)
 8
 9
10
                   0.60,
                   0.50
                   0.40*'
                   0.30
                   0.20
                   0.10C1
                   0.00 g
                       O Ozone    A  NO
                       D NO2      o  Propene
                       X PAN
                                                    3.0
                                                  Tlme(h)
       Figure 3-5.  Time-concentration profiles for selected species during irradiations of an
                   NOx-propene-air mixture in an indoor chamber with constant light
                   intensity.
       December 1993
                                        3-41
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                0.80,
                0.6CH
                0.00
                          O Ozone     A  NO
                          D NO2+PAN O  Propene
                          X PAN
                             8.0
10.0
                                         12.0
                                       Time(h)
14.0
16.0
18.0
      Figure 3-6.  Time-concentration profiles for selected species during irradiations of an
                  NOx-propene-air mixture in an outdoor chamber with diumally varying
                  light intensity.
 1
 2
 3
 4
                                   HO2 + NO -» OH * NO2
                                                                           (3-32)
(b)  The maximum concentration of NO2 is less than the initial NO + NO2 concentration
because NO2 is removed through the reaction,
                                      OH + NO2   NO3
                                                                           (3-15)
 5
 6
 7
 8
 9
10
11
(c)  The O3 concentration increases with the NO2/NO concentration ratio, and O3 formation
ceases when NO2 (and hence NOX) has been removed by reaction.

(d)  Formation of PAN occurs by Reaction 3-56. Because of Reactions 3-55 and 3-56, the
PAN concentration also increases with the NOj/NO concentration ratio, and PAN formation
also ceases when NOX has been depleted.
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 1      (e)  The removal processes for NOX are by reaction of NO2 with the OH radical to form
 2      nitric acid (Reaction 3-16), the formation of organic nitrates from the ROO + NO reaction
 3      pathway 3-42b, and the formation of PAN through Reaction 3-56,  The initially present NOX
 4      is converted to organic nitrates, nitric acid, and thermally unstable PAN(s).  At ambient
 5      temperature,  the PAN(s) will gradually thermally decompose to yield NO2 and the
 6      acylperoxy radicals;  hence the ultimate fate of NOX will be to form nitric acid and organic
 7      nitrates.
 8
 9      3.2.4.2.2  Effects of Varying Initial Nitrogen Oxide and Nonmethane VOC
10                 Concentrations
11           As discussed above,  NOX and VOC interact in sunlight to form O3 and other
12      photochemical air pollutants. The formation of O3 from the NOX and VOC precursors is
13      nonlinear with respect to the precursor emissions (or ambient concentrations) and, as
14      discussed in detail in Section 3.6, computer models incorporating emissions, meteorology,
15      and chemistry are necessary for a full understanding of the complexities of the NOX-VOC-O3
16      system. The  effects of high versus low VOC/NOX ratios and of VOC versus NOX emission
17     reductions are also discussed in Section 3.6.
18
19     3.2,4.2.3   Effects of Biogenic Nonmethane  VOC Emissions
20          Biogenic VOC emissions can be important in urban and rural areas (Trainer et al.,
21      1987; Chameides et al., 1988, 1992; Roselle et al., 1991) and can contribute to O3 formation
22     in much the same way as  anthropogenic VOCs.  Modeling simulations in which urban
23     biogenic VOC emissions are first included and then excluded from the calculations generally
24     indicate little effect of the biogenic emissions on the predicted 03 levels; this is not
25     unexpected from the shape of the O3 isopleths at high VOC/NOX ratios (see, for example,
26     Chameides et al.,  1988, and Section 3.6).  However,  results of modeling studies in which
27     anthropogenic VOC emissions are removed  from the simulations (but anthropogenic NOX
28     emissions are left unaltered) suggest that anthropogenic NOX together with biogenic VOCs
29     may form sufficient O3 to exceed the National Ambient Air Quality  Standards (NAAQS), at
30     least in certain areas (Chameides et  al., 1988). Thus, as discussed for the Atlanta, GA?
31      region (Chameides et al., 1988), NOX control may be more favorable than VOC  control in
32     urban areas with substantial biogenic NMOC emissions.
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 1          While it is known that isoprene is reactive with respect to the formation of
 2     63 (Section 3.2.4.3) and that the monoteipenes react rapidly with OH radicals, NO3 radicals,
 3     and O3, the ozone-forming potentials of the various monoterpenes emitted into the
 4     atmosphere are not known.
 5
 6     3.2.4.3  Hydrocarbon Reactivity with Respect to Ozone Formation
 7          As discussed in Section 3.2.4, VOCs are removed and transformed in the troposphere
 8     by photolysis and by chemical reaction with OH radicals, NO3 radicals, and O3. In the
 9     presence of sunlight, the degradation reactions of the VOCs lead to the conversion of NO to
10     NO2 and the formation of O3 and various organic products.  However, different VOCs react
11     at differing rates in the troposphere because of their differing tropospheric lifetimes
12     (Table 3-2). The lifetimes of most VOCs with respect to reaction with OH radicals and
13     O3 are in the range  »1 h to =10 years.  In large part because of these differing
14     tropospheric lifetimes and rates of reaction, VOCs exhibit a range of reactivities with respect
15     to the formation of 03 (Altshuller and Bufalini, 1971, and references therein).
16          A number of "reactivity scales" have been developed over the years (see, for example,
17     Altshuller and Bufalini, 1971, and references therein; Daniall et al., 1976), including the rate
18     of VOC disappearance  in NOx-VOC-air irradiations, the rate of NO to NO2 conversion in
19     NOx-VOC-air irradiations, 03 formation in NOx-single VOC-air irradiations, eye irritation,
20     and the rate constant for reaction of the VOC with the OH  radical.  It appears, however, that
21     a useful definition of "reactivity" is that of "incremental reactivity" (IR), defined as the
22     amount of O3 formed per unit of VOC added or subtracted from the VOC mixture in a given
23     air mass under high-NO conditions (Carter and Atkinson, 1987, 1989b):
24
                                        IR = A[03]/AfVOC]                            (3-65)
25
26     at the limit of A [VOC] -* 0. The concept of incremental reactivity and some further details
27     of this approach are illustrated by the general reaction mechanism for the photooxidation of
28     an alkane, RH:
                                       OH + RH: -*  R.O + R                          C3-42)
29
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                                     R * O7 -» RO2                           (3-43)
                                  RO2 - NO -» RO  * NO2                      (3-44a)
                                   RO - carbonyl + HO2
                                  HO2 + NO -» OH + NO2                       (3-32)
 4
 5    The net reaction,
 6    can be viewed as involving the two separate reaction sequences;
 7
 8    (1)  Formation of organic peroxy (RO^) radicals from the reactions,

                                         OH + RH ^ H2O + R
                                           R + O2 -* RO2
                             Net:        OH + RH ' -*• RO2
 9
10    and (2) Conversion of NO to NO2 and the formation of O3 and other products,
11
                                               NO -* RO + NO2

                                          RO ^ carbonyl + H02

                                         HO2 +• NO -* OH + NO2
                        OH + RH + 2 NO  ? carbonyl + 2 NO2  * OH,             (3-66)
                           Net:     ROj + 2 NO -+- carbonyl + 2 NO2 + OH

12


       December 1993                        3.45      DRAFT-DO NOT OUOTE OR CITF

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 1     The photolysis of NO2 then leads to O3 formation (Reactions 3-1 and 3-2).  The first reaction
 2     sequence determines how fast RO^ radicals are generated from the VOC, and has been
 3     termed the "kinetic reactivity" (Carter and Atkinson, 1989b). For the case given above,
 4     where the only reaction of the VOC is with the OH radical, the kinetic reactivity depends
 5     solely on the OH radical reaction rate constant. The second reaction sequence, leading to
 6     NO to NO2 conversion, regeneration of OH radicals, and the formation of product species
 7     determines the efficiency of formation of O3 from the ROj radicals formed from the first
 8     reaction sequence, and has been termed the "mechanistic reactivity" (Carter and Atkinson,
 9     1989b).  The second reaction sequence can be represented as:
10
                             RO2 + aNO -» 0 NO2 +  7OH + 6 products.                 (3-67)
11
12          In general, the faster a VOC reacts in the atmosphere, the higher the incremental
13     reactivity. However, the chemistry subsequent to the initial reaction does affect the ozone-
14     forming potential of the VOC. Thus, the existence of NOX sinks in the reaction mechanism
15     (low values of 0 or values of a-0  > 0) lead to a decrease in the amount of 03 formed.
16     Examples of NOX sinks are the formation of organic nitrates and PANs (which are also sinks
17     for radicals).   The generation or loss of radical species can lead to a net formation or net loss
18     of OH radicals (7 > 1 or < 1, respectively).  This in turn leads to an enhancement or
19     suppression of radical concentrations in the air parcel and to an enhancement or suppression
20     of the overall reactivity of all VOCs in that air parcel by affecting the rate of formation of
21     RQz radicals.
22          These effects vary in importance depending on the VOC/NOX ratio.  Nitrogen oxides
23     sinks are most important at high VOC/NOX ratios (NOx~limited), affecting the maximum
24     ozone formed; while the formation or loss of OH radicals is most important at low
25     VOC/NOX ratios, affecting the initial rate at which ozone is formed (Carter and Atkinson,
26     1989b).  In addition to depending on the VOC/NOX ratio (Table 3-3), incremental reactivity
27     depends on the composition of the VOC  mixture and on the physical conditions encountered
28     by the air mass (including the dilution rate, light intensity, and spectral distribution  (Carter
29     and Atkinson, 1989b; Carter, 1991).


       December 1993                          3-46       DRAFT-DO NOT QUOTE OR CITE

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         TABLE 3-3. CALCULATED INCREMENTAL REACTIVITIES OF SELECTED
       VOCs AS A FUNCTION OF THE VOC/NO, RATIO FOR AN EIGHT-COMPONENT
                                              x
                    VOC MIXTURE" AND LOW-DILUTION CONDITIONS
VOC/NOX Ratio (ppm C/ppm)
NMOC
CO
Ethane
n-Butane
rt-Octane
Bthene
Propene
ftww-2-Butene
Benzene
Toluene
m-Xylene
Fonnaldehyde
Acetaldehyde
Methanol
Ethanol
Urban Mixa
4
0,011
0.024
0.10
0.068
0.85
1.28
1.42
0,038
0.26
0.98
2.42
1 34
0.12
0.18
0.41
8
0.022
0.041
0.16
0.12
0.90
1.03
0.97
0.033
0.16
0.63
1.20
0.83
0.17
0,22
0.32
16
0.016
0.018
0.069
0.027
0.33
0.39
0,31
-0.002
-0.036
0.091
0.32
0.29
0.066
0.065
0.088
40
0.005
0.007
0,019
-0.031
0.14
0.14
0.054
-0.002
-0.051
-0.025
0.051
0.098
0.029
0.006
0.011
      "Eight-component VOC mixture used to simulate NMOC emissions in an urban area.
      Source:  Carter and Atkinson (1989b).


 1     3.2.5   Photochemical Production of Aerosols
 2          The chemical processes involved in the formation of O3 and other photochemical
 3     pollutants from the interaction of NOX and VOCs lead to the formation of OH radicals and
 4     the formation of oxidized VOC reaction products that are often of lower volatility than the
 5     precursor VOC. The OH radicals that oxidize the VOCs and lead to the generation of RO2
 6     radicals and conversion of NO to NC^ (with subsequent photolysis of NO2 form O3) also
 7     react with NO2 and SO2 to form nitric and sulfuric acids, respectively, which become
 8     incorporated into aerosols as particulate nitrate and sulfate.  The low-volatility VOC reaction
 9     products can condense onto existing particles in the atmosphere to form secondary organic
10     aerosol matter. Hence ozone formations acid formation, and secondary aerosol formation in

      December 1993                        3.47      DRAFT-DO NOT OUOTR OP rrm

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 1     the atmosphere are so related that controls aimed at reducing O3 levels will impact
 2     (positively or negatively) acid and secondary aerosol formation in the atmosphere.
 3
 4     3.2.5.1   Phase Distributions of Organic Compounds
 5          Chemical compounds are emitted into the atmosphere in both gaseous and particle-
 6     associated forms.  The emissions from combustion sources (for example, vehicle exhaust) are
 7     initially at elevated temperature, and compounds that may be in the particle phase at ambient
 8     atmospheric temperature may be in the gas phase when emitted. In addition, atmospheric
 9     reactions  of gas-phase chemicals can lead to the formation of products that then  condense
10     onto particles (or self-nucleate) (Pandis et al.,  1991; Wang et al,, 1992; Zhang et al., 1992).
11     Measurements of ambient atmospheric gas- and particle-phase concentrations of  several
12     classes of organic compounds indicate that the phase distribution depends on the liquid-phase
13     vapor pressure, PL (Bidleman, 1988;  Pankow and Bidleman, 1992). The available
14     experimental data and theoretical treatments show that, as a rough approximation, organic
IS     compounds with liquid-phase vapor pressures  > 10  torr at ambient temperature are mainly
16     in the gas phase (Bidleman,  1988). As expected, the gas-particle phase distribution in the
17     atmosphere depends on the ambient temperature, with the chemical being more particle-
18     associated at lower temperatures.  The gas-to-particle adsorption-desorption process can be
19     represented as,
                                          A + TSP 
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 1          Gaseous and paniculate species in the atmosphere are subject to wet and dry deposition,
 2     Dry deposition refers to the uptake of gases and particles at the earth's surface by vegetation,
 3     soil, ami water, including lakes, rivers, oceans, and snow-covered ground.  Wet deposition
 4     refers to the removal of gases and particles from the atmosphere through incorporation into
 5     rain, fog, and cloud water, followed by precipitation to the earth's surface.  These processes
 6     are discussed further in Section 3.6.
 7          For gases, dry deposition is important primarily for HNOj,  SO2,  and H2C>2 as well as
 8     for O3 and PAN; while wet deposition is important for water-soluble gases such as HNOj,
 9     H202, phenols, and,  under atmospheric conditions, SO2.  Dry deposition of particles depends
10     on the particle size; those of mean diameter =0.1 to 2.5 pm have lifetimes with respect to
11     dry deposition of »10 days (Graedel and Weschler, 1981; Atkinson, 1988), sufficient for
12     long-range transport.  However, particles are efficiently removed from the atmosphere by
13     wet deposition (Bidleman, 1988).
14          Particles  can form in the atmosphere by condensation or by coagulation, occurring
15     generally by the latter in urban and regional areas.  The photooxidation reactions of VOCs
16     generally lead  to the formation of more oxidized and less  volatile product species.  When the
17     vapor pressures exceed the saturated vapor pressure, or the vapor pressure is < 10"6 Torr,
18     the products will become particle-associated (Pandis et al., 1991, 1992),  Accumulation-size
19     particles are in the size range 0.08 to 2.5 pm diameter (Whitby et al.,  1972).
20          In urban  areas, the major sources of paniculate matter (Larson et al., 1989; Solomon
21     et al.,  1989; Wolff et al., 1991; ffildemann et al.,  1991a,b; Rogge et al., 1991, 1993; Chow
22     etal.,  1993) are:
23
24          •  Direct emissions of elemental carbon from, for example, diesel-powered vehicles
25              (Larson et al., 1989);
26
27          •  Direct emissions of primary organic carbon from, for example, meat cooking
28              operations, paved road dust, and wood-burning fireplaces and other combust! «n
29              sources (ffildemann  et al.,  1991a,b; Rogge et al., 1991, 1993);
30
31          •  Secondary organic material formed in the atmosphere from the atmospheric
32              photooxidations of gas-phase NMOC (Turpin and Huntzicker, 1991; Pandis et al.,
33              1992);
34

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 1          •  The conversion of NO and NO2 to nitric acid, followed by neutralization by
 2             ammonia or through combination with other cations to form aerosol nitrates:
 3
                             NH3(gas)  + HNO3(gas) -* NH4NO3(aerosol);
 4
 5          •  The conversion of SO2 (and other sulfur-containing species) to sulfuric acid, which
 6             has sufficiently low volatility to go to the aerosol phase; and
 7
 8          •  Emission into the atmosphere of "fine dust",  for example, of crustal material.
 9
10          Because the fine-particle size range is the  same magnitude as the wavelength of visible
11     light, paniculate matter present in the atmosphere leads to light scattering and absorption,
12     and hence to visibility reduction (see, for example, Larson et al., 1989; Eldering  et al.,
13     1993).
14
15     3.2.5.2  Acid Deposition
16          As noted above, the chemical processes involved in the formation of O3 and other
17     photochemical pollutants from the interaction of NMOC and NOX also lead to the formation
18     of acids in the atmosphere.  The two  major acidic species in ambient air are  nitric acid and
19     sulfuric acid, arising from the atmospheric oxidation of NOX and SO2, respectively.  Reduced
20     sulfur compounds emitted from biogenic sources and certain anthropogenic sources  may also
21     lead to  SC>2 or sulfonic acids, or bom (Tyndall and Ravishankara, 1991).
22          The major sulfur-containing  compound emitted into the atmosphere from anthropogenic
23     sources is sulfur dioxide, SO2.  In the troposphere, the important loss processes of  S02 are
24     dry deposition (Atkinson, 1988, and references therein), reactions within cloud water, and
25     gas-phase reaction with the OH radical.  The rate constant for the reaction of SO2 with the
26     OH radical is such that the lifetime of SO2 with respect  to gas-phase reaction with the OH
27     radical  is «15 days.  The reaction proceeds by (Stockwell and Calvert,  1983; Atkinson
28     etal.,  1992a),
29
                                                   M
                                        OH +  S02 ™ HOS02                           (3-70)

30
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                                    HOSO2  -  Oj -» HO2 + SO3                        (3-71)
 1
                                       SO3 - H2O - H2SO4.                          (3-72)
 2
 3      The reaction of SO3 with water vapor is slow in the gas-phase (Atkinson et al,5 1992a) and
 4      hence this may be a heterogeneous reaction.  Because of its low vapor pressure, H2SO4
 5      exists in the aerosol or particle phase in the atmosphere,
 6           Dry deposition is an important atmospheric loss process for SO2, since SO2 has a fairly
 7      long lifetime due to gas-phase chemical processes and has a high deposition velocity.
 8     A lifetime in relation to dry deposition of 2 to 3 days appears reasonable (Schwartz, 1989).
 9          Sulfur dioxide is not very  soluble in pure water (Schwartz,  1989). However, the
10     presence of pollutants such as H2O2 or O3,  or both, in the aqueous phase displaces the
11      equilibrium and allows gas-phase SO2 to be incorporated  into cloud,  rain, and fog water,
12     where it is  oxidized rapidly (Schwartz,  1989; Pandis and  Seinfeld, 1989, and references
13     therein):
                                       SO2(gas) ?* SO2(aqu)                          (3-73)
14
                          SO2(aqu) + H2O ** HSO3" + H+  *± SO32"  + 2 H+             (3-74)
15
                                 HSO3" + HjO2  -* SQ42~ * H* + H/)                   (3-75)
16
                                      SOj~ - O3 -* SO42" +  O2                        (3-76)
17
18     In addition, aqueous sulfur can  be oxidized in a process catalyzed by transition metals such
19     as iron(m)  [Fe3+] and manganese(n) [Mn2^] (Graedel et al., 1986b; Weschler et al., 1986;
20     Pandis and  Seinfeld, 1989).
21
                                       SO?' -  1/2 02 - SOf                          (3-77)
22

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 1     The oxidation rate of aqueous sulfur by O3 decreases as the pH decreases (i.e., as the acidity
 2     increases) and this oxidation route is therefore self-limiting and generally of minor
 3     importance in the atmosphere.  The oxidation of SO2 by H2O2 appears to be the dominant
 4     aqueous-phase oxidation process of SO2 (Chandler et al.,  1988; Gervat et al.s 1988;
 5     Schwartz, 1989; Pandis and Seinfeld, 1989; Fung et al., 1991b), although the transition
 6     metal-catalyzed oxidation of SO2 may also be important (Jacob et al., 1989).  It should be
 7     noted that aqueous-phase H2O2 arises,  in part, from the absorption of HO2  radicals and H2O2
 8     into the aqueous phase, with HO2 radicals being converted into H2O2 (see also Zuo and
 9     Hoigne, 1993).
10          The oxidation of SO2 to sulfate in clouds and fogs is often much faster than the
11     homogeneous gas-phase  oxidation of SO2 initiated by reaction with the OH radical.  The gas-
12     phase oxidation rate is * 0.5 to 1 %  h"1, while the aqueous-phase  (cloud) oxidation rate may
13     be as high as 10 to 50% h"1 (Schwartz, 1989).
14          The oxidation of NOX to nitric acid and nitrates was discussed in Section 3.2.3 above.
15     During daylight hours, oxidation occurs by the gas-phase reaction of NO2 with the OH
16     radical:
17

                                         OH  * NO2 ^ HNO3                           (3-15)

18
19     with the lifetime of NO2 due to Reaction 3-15 calculated to be  »1.4 days.  Nitric acid is
20     removed from the troposphere by wet  and dry deposition, with wet deposition being efficient.
21     During nighttime hours, NO2 can be convened into NO3  radicals and N2O5:
22
23
24
                                       N02 + O3-> N03  + 02                          (3-12)
                                                    M
                                        N03 - N0: ^ N205,                     (3-13, -3-13)
        December 1993                          3-52      DRAFT-DO NOT QUOTE OR CITE

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 1     with N205 undergoing wet or dry deposition, or both. The reader is referred to Schwartz
 2     (1989) for- further discussion of the conversion of NOX to nitrate and nitric acid and acid
 3     deposition.
 4
 5
 6     3.3   METEOROLOGICAL PROCESSES INFLUENCING OZONE
 7           FORMATION AND TRANSPORT
 8          Day-to-day variability in ozone (O3) concentrations is, to a first approximation, the
 9     result of day-to-day variations in meteorological conditions. This section presents a succinct
10     overview of those atmospheric processes that affect the concentrations of ozone and other
11     oxidants in urban and rural areas.  Included in this list of processes are the vertical structure
12     and dynamics of the planetary boundary layer (PEL); transport processes, including
13     thermally-driven mesoscale circulations such as lake and sea breeze circulations; complex
14     terrain effects on transport and dispersion; vertical exchange processes; deposition and
15     scavenging; and meteorological controls on biogenic emissions and dry deposition.
16
17     3.3.1   Meteorological Processes
18     3.3.1.1   Surface Energy Budgets
19          Knowledge of the surface energy budget is fundamental to an understanding of the
20     dynamics of the planetary boundary layer (PEL). The PEL is defined as that layer of the
21     atmosphere in contact with the surface of the earth and that is directly influenced by the
22     surface characteristics.  In combination with synoptic winds, it provides the forces for the
23     vertical fluxes of heat, mass and momentum.  The accounting of energy inputs and outputs
24     provides a valuable check on modeled PEL dynamics.
25          Figure 3-7 illustrates the surface radiation budget for short-wave (wavelength roughly
26     <0.4 fjtm) and long-wave radiation.  The radiation budget for the surface can be described in
27     terms of its components as:
28
                             Q8fc = Ki  - KT + LI - Lf + QH + QE                (3-78)
29
       December 1993                         3-53      DRAFT-DO NOT QUOTE OR CITE

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                                                                             Latent
                                                                              and
                                                                            Sensible
                                                                              Heat
      Figure 3-7.  Surface radiation budget for short-wave (7 > 0.4 /im) and long-wave
                  radiation. The surface radiation budget is driven by the input of short-
                  wave radiation (1).  This direct input is reduced by scatter (2) and
                  absorption passing through the atmosphere.  That amount that remains can
                  be absorbed or reflected at the surface. The reflected light (3) can also be
                  scattered back to the surface (4).  The short-wave energy absorbed at the
                  surface will ultimately be emitted back to the atmosphere as long-wave
                  radiation (5).  The atmosphere absorbs much of this radiation and radiates
                  it back to the surface (7) and out to space (6). This energy cycle is
                  completed as some of the absorbed energy is transmitted to the atmosphere
                  as sensible and latent heat (8).
1     where Kl is the incoming short-wave radiation, Kt is the outgoing short-wave radiation,

2     Li  is the incoming long-wave radiation from the atmosphere, Lt is the outgoing long-wave

3     radiation, and QH and QE are the heat flux and latent heat flux to the soil, respectively,

4     On  a global annual average, Qsfc is assumed to be near zero (i.e., the planet is not heating or

5     cooling systematically, an assumption clearly being questioned with the growing debate on

6     climatic change).  On a day-to-day basis, however, Qsfc will certainly vary from zero and

7     will cause changes in surface temperature.  Cloud cover, as an example, will reduce the

8     amount of short-wave radiation reaching the surface and  will  modify all the subsequent

9     components of the radiation budget.  Moreover, the redistribution of energy through the PEL
      December 1993
3-54
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 1     creates thermodynamic conditions that influence vertical mixing.  The treatment of energy
 2     budgets has been attempted on the scale of individual urban areas. These studies are
 3     summarized by Oke (1987).
 4          For many of the modeling studies of the photochemical production of ozone, the
 5     vertical mixing has been parameterized by a single, well-mixed layer. However, because
 6     this is a great simplification of a complex structure, and because the selection of rate and
 7     extent of vertical mixing may influence local control options, it behooves future modeling
 8     and observational studies to address the energy balances so that more realistic simulations can
 9     be  made of the structure of the PEL.
10
11     3.3.12  Planetary Boundary Layer
12          The concentration of an air pollutant depends significantly on the degree of mixing that
13     occurs between the time a pollutant or its precursors are emitted and the arrival of the
14     pollutant at the receptor.  Atmospheric mixing is the result of either mechanical turbulence,
15     often associated with wind shear, or thermal turbulence, associated with vertical
16     redistribution of heat energy. The potential for thermal turbulence can be characterized by
17     atmospheric stability.  The more stable the air layer the more work is required to move air
18     vertically.
19          As air is moved vertically through the atmosphere, as might happen  in a convective
20     thermal, its temperature will decrease with height as the result of adiabatic expansion.  It is
21     the comparison of how  the temperature should change with height in the absence of external
22     heating or  cooling against the actual temperature change with height that is a measure of
23     atmospheric stability.  Those layers of the atmosphere where temperature  increases with
24     height (inversion layers) are the most stable as air, cooling as it rises, then becomes denser
25     than its new  wanner environment.  In an atmospheric layer with relatively low turbulence,
26     pollutants do not redistribute vertically as rapidly as they do in an unstable layer.  Also,
27     because a stable layer has a relatively low rate of mixing, pollutants in a lower layer will not
28     mix through it to higher altitudes.
29          The stability of the atmosphere is often measured through computation of potential
30     temperature, q, as
31

       December  1993                           3-55      DRAFT-DO NOT QUOTE OR CITE

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                                                      -R/c.
                                                  r>
                                            e =

 i
 2     where 9 is the virtual potential temperature, P is the pressure of the air parcel, P0 is the
 3     reference pressure to which the air parcel will be moved (usually 1,000 mb), R is the gas law
 4     constant, and cp is the specific heat of air at constant pressure.  The faster 6 increases with
 5     height, the less the potential for mixing.
 6          A stable layer can also act as a trap for air pollutants lying beneath it.  Hence, an
 7     elevated inversion is often referred to as a "trapping" inversion. On the other hand, if
 8     pollutants are emitted into a stable layer aloft, such as might occur from an elevated stack,
 9     the lack of turbulence will keep the effluents from reaching the ground while the inversion
10     persists.
11          Traditionally, atmospheric mixing has been treated through use of a mixing height,
12     which is defined as the base of an elevated inversion layer.  In this model, the ozone
13     precursors are mixed uniformly through the layer below the mixing height.  As this layer
14     grows it both entrains remnant ozone from previous days and redistributes fresh emissions
15     aloft.  The vertical mixing profile through the lower layers of the atmosphere is assumed to
16     follow a typical and predictable cycle on a generally clear day. In such a situation a
17     nocturnal surface inversion would be expected to form during the night as Lt exceeds Li.
18     This surface layer inversion persists until surface heating becomes significant, probably two
19     or three hours after sunrise.  Pollutants initially trapped in the surface inversion may cause
20     relatively high, local concentrations,  but these concentrations will decrease rapidly when the
21     surface inversion is broken by surface heating.  The boundary formed between the rising,
22     cooling air of the growing mixing layer and that of the existing PEL is often sharp and can
23     be observed as an elevated temperature inversion.
24          Elevated temperature  inversions, when the base is above the ground, are also common
25     occurrences (Hosier, 1961; Holzworth, 1974).  This condition can form simply as the result
26     of rapid vertical mixing from below, but is exacerbated in regions of subsiding air when the
27     sinking air warms to a point such that it is warmer than the rising (and cooling) underlying
28     air.  Since these circumstances are associated with specific synoptic conditions, they are  less
29     frequent than the ubiquitous nighttime radiation inversion.  An  elevated inversion is
       December 1993                          3-56      DRAFT-DO NOT QUOTE OR CITE

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 1     nevertheless a very significant air pollution feature, because it may persist throughout the day
 2     and thus restrict vertical mixing.
 3          When compared to a source near the surface and the effects of a radiation (surface)
 4     inversion, the pollutant dispersion pattern is quite different for an elevated source plume
 5     trapped in a layer near the base of an elevated inversion.  This plume will not be in contact
 6     with the ground surface in the early morning hours because there is no mixing through the
 7     surface radiation inversion.  Thus, the elevated plume will not affect surface pollutant
 8     concentrations until the mixing processes become strong enough to reach the altitude of the
 9     plume. At that time, the plume may be mixed downward quite rapidly in a process called
10     fumigation.  During  fumigation, surface ozone concentrations will increase if the morning
11     ozone  concentration  is higher aloft than at the ground,  and if insufficient scavenging by NO
12     occurs at ground-level. In fact, the rapid rise in ozone concentrations in the morning hours
13     is often the result of vertical (downward) transport from an elevated reservoir of ozone.
14     After this initial increase, surface concentrations can continue to  increase as a result of
15     photochemistry or transport of ozone-rich air to the receptor, or both.
16          When surface heating decreases in the late afternoon and early evening, the surface
17     inversion will form again under most conditions.  The fate of the elevated inversion is less
18     clear,  however.  While ozone and its precursors have been mixed vertically, the reduction of
19     turbulence and mixing at the end of the daylight hours leaves ozone in a remnant layer that is
20     often without a well-defined thermodynamic demarcation.   This layer is then transported
21     through the night, often to regions far removed from pollution sources,  where its pollutants
22     can influence concentrations at remote locations the next morning as mixing entrains the
23     elevated remnant layer.  This overnight transport can be aided by the development of a
24     nocturnal jet that forms many nights at the top of the surface inversion layer.
25          Geography can have a significant impact on the dispersion of pollutants (e.g., along the
26     coast of an ocean or one of the Great Lakes). Near the coast or shore,  the temperatures  of
27     land and water masses can be different,  as can the temperature of the air above such land and
28     water masses.  When the water is warmer than the land, there is  a tendency toward reduction
29     in the  frequency of surface inversion conditions inland over a relatively narrow coastal strip
30     (Hosier, 1961).  This in turn tends to increase pollutant dispersion in such areas.  The
31     opposite condition also occurs if the water is cooler than the land, as in summer or fall.

       December 1993                          3.57       DRAFT-DO NOT QUOTE OR CITE

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 1     Cool air near the water surface will tend to increase the stability of the boundary layer in the
 2     coastal zone, and thus decrease the mixing processes that act on pollutant emissions.  These
 3     conditions occur frequently along the New England coast (Hosier, 1961).  Similarly,
 4     pollutants from the Chicago area have been observed to be influenced by a stable boundary
 5     layer over Lake Michigan (Lyons and Olsson, 1972), This has been observed especially in
 6     summer and fall when the lake surface is most likely to be cooler than the air that is carried
 7     over it from the adjacent land.
 8          Sillman et al. (1993) investigated abnormally high concentrations of O3 observed in
 9     rural locations on the shore of Lake Michigan and on the Atlantic coast in Maine, at a
10     distance of 300 km or more from major anthropogenic sources.  A dynamical-photochemical
11     model was developed that represented formation of O3 in shoreline environments and was
12     used to simulate case studies for Lake Michigan and the northeastern United States.  Results
13     suggest that a broad region with elevated O3, NOX, and VOC forms as the Chicago plume
14     travels over Lake Michigan, a pattern consistent with observed O3 at surface monitoring
15     sites. Near-total suppression of dry deposition of Oj and NOX over the lake is needed to
16     produce high O3. Results for the east coast suggest that the observed peak O3 can only be
17     reproduced by a model that includes suppressed vertical mixing and deposition over water,
18     2-day transport of a plume from New York, and  superposition of the New York and Boston
19     plumes.  Hence, the thermodynamics associated with the water bodies seem to play a
20     significant role in some regional-scale episodes of high ozone concentrations.
21          There is concern that the strict use of mixing height unduly simplifies the complex
22     atmospheric processes that redistribute pollutants within urban areas.  There  is growing
23     evidence that some ozone precursors may not be  evenly redistributed over some urban areas
24     in cases where  the sources are relatively close to the urban area and atmospheric mixing is
25     not strong enough to redistribute the material over a short travel time.  In these cases, it is
26     necessary to treat the turbulent structure of the atmosphere directly and acknowledge the
27     vertical variations in mixing.  Methods that are being used to investigate these processes
28     include the use of a diffusivity parameter to express the potential for mixing as a function of
29     height.  A  simple expression of how the mean concentration, x, changes with time, t,  in an
30     air parcel, assuming all concentrations are homogeneous in the horizontal, is:
        December 1993                           3-58       DRAFT-DO NOT QUOTE OR CITE

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 1     where w 'x ' is the vertical turbulent eddy flux of pollutant.  The term on the right hand side
 2     of the equation changes mean concentration through flux divergence; i.e., turbulence either
 3     disperses the pollutant to or from the point being considered.  The problem with this
 4     representation is that the flux divergence term is virtually impossible to measure directly.
 5           The turbulent eddy flux needed to understand the vertical distribution of ozone and its
 6     precursors  is often parameterized in photochemical models, if included at all, through use of
 7     eddy diffusivity. The eddy diffusivity is set using an analogy to mixing length theory as
                                                                                         (3-81)
 8      which allows estimation of flux divergence from measured or estimated vertical gradients in
 9      concentration and estimation of the eddy diffusivity.  The selection of diffusivity is often
10      somewhat arbitrary, but can be related to the eddy diffusivity for heat or momentum, or
11      both, depending on circumstances.  Large values result in rapid mixing. Thus, the
12      appropriate selection of eddy diffusivity is necessary to simulate whether elevated plumes
13      will enter an urban airshed.
14           Another method uses a technique called "large-eddy simulation"  to recreate the
15      probability of redistribution within the mixing height.
16           Both these techniques  require meteorological information that is  not normally available
17      from the National Weather Service, but that is now becoming available as part of several
18      ozone field experiments.
19
20      3.3.1.3   Cloud Venting
21           Vertical redistribution of ozone out of the PEL is achieved by the venting of pollutants
22      in clouds.  Clouds represent the top-most reaches of thermals of air rising through the PEL
23      and can act simply  as chemical reactors for soluble pollutants, returning the "processed" air
24      to the PEL; or if convection is sufficiently vigorous, they can result in physical redistribution

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 1     of ozone and its precursors from the PEL (Greenhut, 1986; Dickerson et al., 1987). Clouds
 2     also act to influence photolysis rates and chemical transformation rates.
 3          Greenhut (1986) showed that the net ozone flux in the cloud layer was a linear function
 4     of the difference in ozone concentration between the boundary layer and the cloud layer.
 5     Ozone fluxes between clouds were usually smaller than those found within clouds, but the
 6     slower rate is at least partially offset by the larger region of cloud-free air relative to cloudy
 7     air.
 8          Large clouds, such as cumulonimbus, offer considerably more potential for
 9     redistribution of ozone and its precursors. Additionally, the cumulonimbus clouds are also
10     associated with precipitation, a scavenger of pollutants, and with lightning, a potential source
11     for nitrogen oxides. Using carbon monoxide (CO) as a tracer, Dickerson et al. (1987) and
12     Pickering et al. (1990) have illustrated the redistribution potential of cumulonimbus cloud
13     systems. Lyons et al. (1986) provided an illustration of the potential for groups of
14     cumulonimbus clouds to vent the polluted boundary layer.
15          The role of cloud venting is thought to be largely a cleansing process for the boundary
16     layer, although a portion of the material lifted into the free troposphere could be entrained
17     back to the surface in subsequent convection.  Aircraft observations have documented
18     frequently the occurrence of relatively high ozone concentrations above lower-concentration
19     surface layers (e.g., Westberg et al., 1976).  This is a clear indication that ozone is
20     essentially preserved in layers above the surface and can be transported over relatively long
21     distances even when continual replenishment through precursor reactions is not a factor, such
22     as at night.
23
24     3.3.1.4  Stratospheric-Tropospheric Ozone Exchange
25          The fact that O3 is formed in the stratosphere, mixed downward, and incorporated into
26     the troposphere, where it forms a more or less uniformly mixed background concentration,
27     has been known in various degrees of detail for many years (Junge, 1963). The mechanisms
28     by which stratospheric air is mixed into the troposphere have been examined by a number of
29     authors, as documented previously by EPA (U.S. Environmental Protection Agency, 1986,
30     and references therein).
        December 1993                          3-60       DRAFT-DO NOT QUOTE OR CITE

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 1          There is little evidence that ozone from the stratosphere contributes in any substantial
 2     way to either peak urban ozone values or regional episodes of elevated ozone levels (Johnson
 3     and Viezee,  1981; Ludwig et al., 1977; Singh et al., 1980; and Viezee et al., 1979).
 4     Johnson and Viezee (1981) concluded that the ozone-rich intrusions studied sloped downward
 5     toward the south. In terms of dimensions, the average crosswind width (north to south) at an
 6     altitude of 5.5 kilometers (ca. 18,000 feet or 3.4 miles) for six spring intrusions averaged
 7     226 kilometers (364 miles), and for four fall tropopause  fold systems, 129 kilometers
 8     (208 miles).  Ozone concentrations at 5.5 kilometers (ca 18,000 feet or 3.4 miles) average
 9     108 ppb in the spring systems and 83 ppb in the fall systems.  From this and other research
10     described  in the previous criteria document for O3 and other photochemical oxidants (U.S.
11     Environmental Protection Agency, 1986),  Viezee and coworkers (Viezee and Singh, 1982;
12     Viezee et  al., 1983) concluded that (1) direct ground-level impacts by stratospheric O3 may
13     be infrequent, occurring < 1 % of the time; (2) that  such ground-level events are short-lived
14     and episodic; and (3) that they are most likely to be associated with Qj concentrations
15      ^0.1 ppm.  (See U.S. Environmental Protection Agency [1986] for additional details).
16          Using the  Be-to-O3 ratio as an indicator of O3 of stratospheric origin and sulfate
17     (SO4=) concentrations as a tracer for anthropogenic sources, Altshuller (1987) estimated
18     stratospheric contributions of ozone in the range 0 to 40 ppb (0 to 95% of observed 63) at
19     ground level at Whiteface Mountain, NY, for July  1975  and mid-June to mid-July 1977.
20     Monthly average stratospheric contributions were estimated at 5 to 10 ppb. He also
21     examined  extant Be and O3 data for a number of lower-elevation rural locations in the
22     western, midwestern, and southeastern United States, and calculated stratospheric or upper
23     tropospheric contributions at 6 to 8 ppb. He concluded that his calculated values for such
24     contributions should be viewed with caution and regarded probably as upper limits because of
25     scatter in  the 7Be and corresponding O3 data that hindered definition of the 7Be-to-O3 ratio.
26     He also concluded that removal and dilution processes result in the loss of most stratospheric
27     O3 before it reaches ground level (Altshuller, 1987).
28
29     3.3.2  Meteorological Parameters
30          This section focuses on analyses of data from previous and ongoing measurement
31     programs  to address two driving questions:  (1) are there meteorological parameters which

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 1      are systematically associated with ozone levels; and (2) are relationships between ozone and
 2      meteorological parameters sufficiently strong such that meteorological fluctuations can be
 3      filtered from the data to allow examination of longer-term trends?
 4           The meteorological factors that theoretically could influence surface ozone levels
 5      include ultraviolet radiation, temperature,  wind speed, atmospheric mixing and transport, and
 6      surface scavenging.  The following examines the theoretical basis for each of these and
 7      identifies to what degree empirical evidence supports the  hypotheses.
 8
 9      3.3.2.1   Sunlight
10           Ultraviolet (UV) radiation plays a key role in initiating the photochemical processes
11      leading to ozone formation. Sunlight intensity (specifically the UV portion of sunlight)
12      varies with season and latitude but the latter effect is strong only during the winter months,
13      The importance of photolysis to the formation of O3 provides a direct link between O3 and
14      time of year.  However, during the summer, the maximum UV intensity is fairly constant
15      throughout the contiguous United States and only the duration of the solar day varies to  a
16      small degree with latitude.
17           The effects of light intensity on individual photolytic reaction steps and on the overall
18      process of oxidant formation have been studied in the laboratory (Peterson, 1976; Demerjian
19      et al., 1980).  Early studies, however, employed constant light intensities, in  contrast to the
20      diurnally varying intensities that occur in the ambient atmosphere. The diurnal variation of
21      light intensity was subsequently studied as a factor in photochemical oxidant formation (e.g.,
22      Jeffries et al., 1975, 1976). Such studies showed that the effect of this factor varies with
23      initial reactant concentrations.  Most important was the observation that similar NMOC/NOX
24      systems showed different oxidant-forming potential depending on  whether studies of these
25      were conducted using constant or diurnal light.  This led to incorporation of the effects of
26      diurnal or variable light into photochemical models  (TUden and Seinfeld, 1982).
27           There is little empirical evidence in the literature, however,  linking day-to-day
28      variations in observed UV radiation levels with variations in ozone levels.  Samson  et al.
29      (1988) illustrated that the number of O3 concentrations exceeding 120 ppb did not track  well
30      with potential solar radiation,  as shown in Figure 3-8.  Although  variations in day-to-day
31      concentrations could well be influenced by cloud cover or attenuated by haze, the seasonal

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                                                  Annual Variation
                                                      in Solar
                                                  ts Radiation
                                                                TOO
                                                                      600
                                                                      500
                                                                          u
                                                                      400
                                                                          o
                                                                          1
                                                                      300
                                                                      200 O
                                                                      100
                         0_ itkffi^maipmiipiipaiapaHfflaH^^                        I   0
                          1 I  J 1 IT in T 1 T V t 1 plTT^m j  i^  rmT^ ( rpij   v
                         14 16 18  20  22 24 26 28 30 32 34 36 38 40 42 44 46

                                         Week of Year
      Figure 3-8.  The number of reports of ozone concentrations > 120 ppb at the 17 cities
                  studied in Samson et al. (1988).  (1 April = week 14, 1 May = week 18,
                  1 June = week 22, 1 July = week 27,1 August = week 31, 1 September =
                  week 35, 1 October = week 40, 1 November — week 44). A representation
                  of the annual variation in solar radiation reaching the earth's surface at
                  40 °N latitude (Units=cal cm"2) is shown.

      Source:  Samson et al. (1988).
1

2

3

4

5

6

7
peak in ozone concentrations usually lags the peak in potential solar radiation that occurs at
the Summer Solstice on or about June 23.


3.3.2.2   Temperature
     There is a demonstrable association between tropospheric ozone concentrations and
tropospheric temperature.  Numerous studies done over more than a decade have reported
that successive occurrences or episodes of high temperatures characterize seasonally high
      December 1993
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 1     ozone years (e.g., Clark and Karl,  1982; Kelly et al.,  1986).  The relationship has been
 2     observed for the South Coast Air Basin of California (Kuntasal and Chang, 1987), and in
 3     New England (Wolff and Lioy, 1978; Atwater, 1984; Wackier and Bayly, 1988), as well as
 4     elsewhere.
 5          Figures 3-9 and 3-10 show the daily maximum ozone concentrations versus maximum
 6     daily temperature for summer months (May to October) 1988 to 1990, for, respectively,
 7     Atlanta, Georgia, and New York City, New York; and for Detroit, Michigan, and Phoenix,
 8     Arizona. There appears to be an upper-bound on ozone concentrations that increases with
 9     temperature.  Likewise, Figure 3-11 shows that a similar qualitative relationship exists
10     between ozone and temperature even at a  number of rural locations.
11
                      8
                     •a
                     D
                      |
                      I
240
210


150
120
 90
 60
 30
  0
                              Atlanta, Georgia
                                  10
                                        15
                       20
                              25
                     I
                      E
                     I
                               New York, New York
                                                 ' o"«8cr
                                                             30
          35
                                                                          40
                                 10     15     20      25     30     35
                                      Maximum Temperature, "C
                                                  40
       Figure 3-9.  A scatter plot of maximum daily ozone concentration in Atlanta, Georgia,
                   and New York, New York, versus maximum daily temperature.
       December 1993
                       3-64
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                     240

                   .£ 210

                   *«
                      120

                      90

                      80

                      30-
                      210

                      180

                      150

                      120

                      BO

                      80

                      30

                       0
                 [Detroit, Michigan)
                             10
                                   15
                 Phoenix, Arizona
                                         20
                                              25
                                                      •w
                                 'a o "o"
                                 *er—r--
                                                          35
                                                               40

                                      •ff-8-.
                                       o


                             10
                                   15
                                         20
                                              25
                                                               40
                                 Maximum Temperature. °C
figure 3-10.  A scatter plot of maximum daily ozone concentration in Detroit, Michigan,
             and Phoenix, Arizona, versus maximum daily temperature.
             • Ann Arbor, MI
Wllllamsport, PA
                              Mammoth Cave, KY o McKensle City , NO
                210
                160-
                150-
            a>
            I
            |
            1
120
                90-
                eo

                30
                                TJ~V£l3Li'  «i
                                 • dK« t_>-  nil a
                                                           > -.»
                         10     15     20      25     30      35
                               Maximum Daily Temperature, °C
                                                 40
Figure 3-11.  A scatter plot of maximum ozone concentration versus maximum daily
             temperature for four nonurban sites.  The relationship with temperature is
             still apparent, although the slope is reduced from that of the urban areas.
December 1993
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 1          The notable trend in these plots is the apparent upper-bound to ozone concentrations
 2     because a function of temperature.  It is clear that at a given temperature there is a wide
 3     range of possible concentrations because other factors, (e.g., cloudiness, precipitation, wind
 4     speed) can reduce the ozone production.  The upper bound presumably represents the
 5     maximum concentration achieved under the most favorable conditions. Table 3-4 lists the
 6     results of a statistical regression performed on the paired O3-temperature data used in
 7     Figures 3-9 and 3-10 with separate slopes listed for temperatures above and below 30 °C.
 8     Results show that for T >  30 °C the (^-temperature relationship is statistically significant at
 9     all sites. The rate of increase is 3 to 5 ppb/°C at rural sites and ranges from 7 to 12 ppb/°C
10     at the three eastern U.S. urban sites (New York, Detroit and Atlanta). At two western  sites,
11     Williston, North Dakota, and Billings, Montana, there is a much weaker dependence on
12     temperature, possibly reflecting the lower level of anthropogenic activity.  At a third western
13     site, Medford,  Oregon, the O3-temperature relationship is comparable to that at rural eastern
14     sites.
15          Relationships between peak O3 and temperature have also been recorded by Wunderli
16     and Gehrig (1991) for three locations  in Switzerland.  At two sites  near Zurich, peak
17     O3 increased 3 to 5 ppb/°C for diurnal average temperatures between 10 and 25 °C, and
18     little change in peak O3 occurred for temperatures below  10 °C. At the third site, a high-
19     altitude location removed from anthropogenic influence, showed much less variation of
20     Oj with temperature was observed.
21          The hypotheses for this correlation include, but are not necessarily limited to:
22            1.  Reduction in photolysis rates at low temperatures;
23
24            2.  Reduction in I^O concentrations at low temperatures
25
26            3.  Thermal decomposition of PAN and its homologues;
27
28            4.  Increased anthropogenic emissions of reactive hydrocarbons or NOX or
29                both;
30
31            5.  Increased natural emissions of reactive hydrocarbons; and
32
33            6.  Relationships between high temperatures and stagnant circulation patterns.
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            TABLE 3-4.  RATES OF INCREASE OF PEAK OZONE WITH DIURNAL
        MAXIMUM TEMPERATURE (ppb/°C) FOR T  < 300 K (27 °C) AND T > 300 K,
             BASED ON MEASUREMENTS FOR APRIL 1 TO SEPTEMBER 30, 1988

Location
Urbanized Regions:





Nonurban Sites;










NY-NJ-CT
Detroit
Atlanta
Phoenix
Southern California

Williamsport, PA
Saline, MI
Mammoth Cave, KY
Kentucky, cleanest site 3
Williston, ND
Billings, MT
Medford, OR
T <
A03/AT

1.5
1.4
3.2
—
11.3

1.2
0.8
0.1
0.3
0.2
0.1
0.5
300 K
T-statistic

-5.2
-6.4
-4.2
__
-8.9

-5
-3.5
-0.3
-0.7
-1
-0.5
-2.6
T >
A03/AT

8.8
4.4
7.1
1.4
_

4
3.1
4.4
3.4
0.8
0.7
3.3
300 K
T-statistic

-:.4
-6.3
-5.9
-4.1
—

-7.4
-4.9
-7.3
-6.6
-3.7
-2.2
-13.7
       Source:
 1         The relationship with temperature is well known, but not yet reproduced by air quality
 2     models.  While it has been argued that this striking relationship with temperature is an
 3     indirect result of the stagnant synoptic meteorological conditions that lead to higher ozone
 4     levels, the correlation is not strong with other parameters of stagnation, notably wind speed,
 5     as is discussed later.
 6
 7     3.3.2.2.1  Reduction in Photolysis Rates
 8         It is possible that on a seasonal scale the correlation between temperature and ozone
 9     may be an indirect correlation with UV radiation variability.  This is insufficient, however,
10     to explain the day-to-day correlation between the two variables.
       December 1993
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 1          Changes in photolysis rates and in H2O concentrations are related in that both are
 2     linked to the supply of OH radicals which determines the rate of ozone production in polluted
 3     environment.  A reduction in either photolysis rates or H2O would reduce the source of OH
 4     radicals.  Calculations by Sillman and Samson (1993) showed that the difference between
 5     summer and fall photolysis rates (at 40° N latitude) has a significant impact on the rate of
 6     ozone production in urban photochemical  simulations, roughly equal to the impact of PAN
 7     thermal decomposition (discussed below). However the impact of photolysis rates and of
 8     water vapor was much lower in simulations for polluted rural environments. In the
 9     simulations by Silknan et al. (1993) ozone production in urban environments was limited
10     largely by the supply of OH radicals  to react with hydrocarbons; whereas in rural
11     environments the limiting factor was  the source of NOX.  Consequently photolysis rates and
12     H2O had less impact on ozone production in rural environments.
13
14     3.3.2.2.2  Thermal Decomposition  of Peroxyacetyl Nitrate
15          Temperature-dependent photochemical rate constants provide a link between 03 and
16     temperature (Sillman et al.,  1990a; Cardelino and Chameides, 1990). The reason for the
17     decline in O3 in rural areas when the PAN decomposition rate decreases is that PAN
18     apparently represents a major sink for NOX in rural environments.  When the rate of PAN
19     decomposition is decreased NOX drops sharply while OH and HO2 remain largely unaffected.
20     Consequently, the rate of the important HO^ + NO reaction (see Section 3.2) shows a
21     substantial decrease.
22          The photochemical response in  an urban environment is fundamentally different,
23     although the final  result, a decrease in O3 with temperature,  is similar.  The impact of PAN
24     in urban environments is attributable  to its role as a sink for odd hydrogen rather than to its
25     effect on NOX (Cardelino and Chameides, 1990). Sillman et al. (1990a) have shown that the
26     well-known division of ozone photochemistry  into NOx-sensitive and VOC-sensitive regimes
27     is associated with  the relative magnitude of odd-hydrogen sinks.  In the NOx-sensitive
28     regime, typical  of rural areas, the major sink of odd hydrogen consists of formation of
29     peroxides.  Ozone formation is relatively  insensitive to the magnitude of odd hydrogen
30     sources since the peroxide sink varies with the square of the HO2 concentration and provides
31     partially  buffers the effect of a change in  sources.  At higher NOX concentrations or lower

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 1     VOC/NOX ratios, the dominant sink for odd hydrogen is formation of HNO3.  The rate of
 2     odd hydrogen formation assumes a much greater importance since the buffering effect of
 3     peroxide formation and other OH-HC>2 interactions is lost.  Formation of Oj becomes
 4     strongly sensitive to odd hydrogen formation rates, and to VOC concentrations as sources of
 5     odd hydrogen.
 6          Sillman and Samson (1993) found that the thermal decomposition of PAN was enough
 7     to explain an increase of 1 to 2 ppb peak ozone per degree C increase in temperature in rural
 8     locations in the eastern  United States, based on photochemical simulations. This increase
 9     represents a  significant  fraction of the observed increase in peak ozone with temperature
10     (3 ppb per degree,  Figure 3-11) but is significantly less  than the observed increase.
11
12     3.3.2.2.3   Increased Anthropogenic Emissions
13          It has recently been suggested that emission rates for anthropogenic hydrocarbons
14     (VOC) also increase with temperature (U.S Environmental  Protection Agency, 1989; Stump
15     et al., 1992). Increased VOC emissions might be expected to cause increased rates of ozone
16     production only in  urban areas where ozone is sensitive to VOC, and would be less lively to
17     have impact on rural areas. However, NOx-sensitive urban areas and most rural areas would
18     also show increased ozone production with temperature  if NOX emissions also were to
19     increase with temperature. There is  no direct evidence for an increase in NOX emissions
20     with temperature but power plant loads tend to be highest when temperatures are high.
21     Because power plants are a major source of NOx, the increased power plant load would also
22     lead to increased NOX emissions.   Quantitative estimates are needed to determine the impact
23     of this effect.
24
25     3.3.2.2.4   Increased Natural Emissions
26          Fjnissions of  biogenic hydrocarbons increase sharply  with temperature (Lamb et al.,
27     1987). In ambient temperatures from 25 to 35 °C the rate of natural hydrocarbon emissions
28     from isoprene-emitting  deciduous trees increased by  about a factor of four.  From coniferous
29     trees the increase was on the order of one and a half times.
30          Recently Jacob et al. (1933) found that the photochemistry of ozone production in a
31     polluted rural environment (Blue Ridge Mountains, VA) is significantly different in

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 1     September and October when natural emissions from deciduous forests have ceased.  The
 2     difference in chemistry between summer and fall leaf production may also have an impact on
 3     the ozone-temperature correlation.
 4
 5     3.3.2.2.5  Correlation with Stagnation
 6          Recently Jacob et al. (1993) found that model-simulated ozone formation in the rural
 7     United States shows a tendency to increase with temperature based solely on the difference in
 8     atmospheric circulation between relatively warm and relatively cool days.  The model-
 9     simulated ozone-temperature correlation was less than observed but large enough to represent
10     a significant component of the observed correlation.  However, the temperature-meteorology
11     correlation identified by Jacob et al. (1993) was based on simulated meteorology from a
12     General Circulation Model rather than on direct observations.  It would be interesting to see
13     whether the correlation between ozone, temperature and atmospheric circulation predicted by
14     Jacobs et al. (1993) can be verified in terms of meteorological observations.
15
16     3.3.2.3  Wind Speed
17          Ozone is expected to be influenced by wind speed because lower wind speeds should
18     lead to reduced ventilation and the potential for greater buildup of ozone and its precursors.
19     Abnormally high temperatures are frequently associated with high barometric pressure,
20     stagnant circulation, and suppressed vertical mixing resulting from subsidence  (Mukammal
21     et al., 1982), all of which may contribute to elevated 03 levels.  However, in reality this
22     relationship varies from one part of the country to another.  Figure 3-12 shows the frequency
23     of 24-h trajectory transport distances to southern cities on days with resulting concentrations
24     of O3 S 120 ppb (Samson et al., 1988).  The frequency for southern cities is biased toward
25     lower wind speeds.  A similar plot for cities in the northeast United States (Figure 3-13)
26     shows an opposite pattern, in which the bias is toward higher wind speeds than normal.  It is
27     unclear how much  meteorological information is needed in order to perform accurate
28     urban-area ozone simulations using advanced photochemical models.  To understand the
29     significance of variations between upper-air wind measurements during the Southern Oxidant
30     Study (SOS) 1992 Atlanta Intensive, an intercomparison test of the precision of upper-air
31     measurements was conducted. Collocated measurements were made at an SOS measurement

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                       50   150250350   «0  6SO   6SO   750
                                    Distance traveled, km
                                                                •1,000
Figure 3-12. The frequency of 24-h trajectory transport distance en route to city when
             ozone was >120 ppb in four Southern U.S. cities compared with the
             percent frequency distribution for all 17 cities (scale on right) of a
             nationwide study,  1983 to 1985.

Source: Samson et al. (1988).
                            I D Provictonai  m Portland,   m Boston
                            i             ME
                            i • New Haven  ^ AIM? atiss
                                                                16
                                                                10
                       SO  1S02XI3504SC5608607508S0950  >1JX)0
                                    Distance traveled, km

Figure 3-13.  The frequency of 24-h trajectory transport distance en route to city when
              ozone was  > 120 ppb in four New England cities compared with the
              percent frequency distribution for all 17 cities (scale on right) of a
              nationwide study, 1983 to 1985.

Source: Samson et al. (1988).
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1     site using a boundary-layer lidar; a wind profiler; and a rawinsonde balloon. There was
2     generally good agreement between the profiler and rawinsonde although some large outliers
3     existed.  Figure 3-14 illustrates that the root mean square difference (RMSD) varied with
4     altitude.  The RMSD reached a minimum near 1,200 m AGL of about 2 ml sec, rising to
5     over 3 m/sec near the surface and above 1,200 m AGL.  Figure 3-15 illustrates the RMSD
6     for the lidar comparison with CLASS observations.  There is slightly greater RMSD at all
7     heights than for the profiler-rawinsonde comparison, with a relative minimum observed at
8     about 1,200 m.
9
          2,000
                                                              •••	Maximum
                                                                     RMSD
                                           6             9
                                            RMSD, m/sec
      Figure 3-14.  The root-mean-square-difference (RMSD) between CLASS observations
                   and profiler observations as a function of height above ground level.
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            2,000
                                             6             s
                                              RMSD, m/sec
       Figure 3-15.  The root-mean-square-difference (RMSD) between CLASS observations
                    and lidar observations as a function of height above ground level.
 1
 2
 3
 4
 5
 6
 1
 8
 9
10
     Although the measurements were significantly correlated, the results illustrate that there
was still considerable disagreement between methods. The profiler had better precision than
the lidar had although the differences were negligible if the first four runs were excluded
from the data set for reasons stated before.  The profiler obtained values biased slightly
higher than the CLASS system (+0.2 m/s), while the lidar system was biased low (-0.3 m/s
or -0.5 m/s). The statistical comparisons of both the profiler and the boundary-layer lidar
with the rawinsonde system suggest that variations in wind speed at a particular level (based
on S) must be larger than about 3 m/s to be considered significant.
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 1     3.3.2.4   Air Mass Characteristics
 2          In meteorology, an "air mass" is a region of air, usually of multistate dimensions, that
 3     exhibits similar temperature, humidity and/or stability characteristics. Air masses are created
 4     when air becomes stagnant over a "source region" and subsequently  takes on the
 5     characteristics of the source region.  Similarly, when dealing with air pollution meteorology
 6     it is possible to identify a "chemical air mass" as a region of air that has become stagnant
 7     over an emissions source area.  Air that was stagnant over,  say, the center of Canada will
 8     exhibit relatively cold, dry conditions and will be relatively  devoid of pollutants.  Air that
 9     resides over the industrial regions of the midwestern  United States will exhibit low visibility
10     and, often, high ozone levels on a regional scale.  Meteorological processes play an
11     important role in determining the  amount of "accumulation" of ozone and its precursors that
12     occurs under such stagnant conditions.
13          Episodes of high ozone concentrations in urban areas are often associated with high
14     concentrations of ozone in the surroundings.  This accumulated ozone forms under the same
15     atmospheric conditions that lead to high ozone levels in urban areas, and exacerbates the
16     urban problem by supplying relatively high ozone and precursor concentrations to the urban
17     area from upwind.  The transport of ozone and its precursors beyond the urban scale
18     (^50 km) to neighboring rural and urban areas has been well documented  (e.g., Wolff
19     et al.,  1977a,c; Wolff and Lioy, 1978; Clark and Clarke, 1982; Sexton,  1982; Wolff et al.,
20     1982).  A summary of these reports was given in the 1986 ozone criteria document (U.S.
21     Environmental Protection Agency, 1986) and will not be reiterated here. The phenomena of
22     high nonurban ozone levels was long-ago illustrated by Stasiuk and Coffey (1974) for
23     transport within New York State; by Ripperton et al. (1977), for sites in the Middle Atlantic
24     States; and by Samson and Ragland (1977) for the midwestern United Stales.
25          These areas of ozone accumulation are characterized by:
26            1.  Synoptic-scale subsidence of air in the free troposphere, resulting in
27               development of an elevated inversion layer;
28
29            2.  Relatively low wind speeds associated with the weak horizontal pressure
30               gradient around a surface high pressure system;
31
32            3.  Lack of cloudiness;  and
33
34            4.  High temperatures.

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 1          On occasion, ozone at levels greater than 120 ppb can occur in rural areas far removed
 2     from urban or industrial sources.  Ozone levels at the summit of Whiteface Mountain
 3     exceeded this value during the summer of 1988 when ozone accumulated across a wide
 4     expanse of the eastern United States at levels 5:120 ppb.  Nonetheless, even when the
 5     regional  accumulation is at a level below the current ozone NAAQS, the increment needed to
 6     bring the level above the NAAQS in an urban area is not large.
 7          The identification, and understanding of the transport of photochemical ozone and other
 8     oxidants and their precursors by weather systems represent a significant advance in
 9     comprehending photochemical air pollution and the potential extent of  its effects.
10     Considerable progress has been made in the development of long-range photochemical
11     modeling techniques so that the likely impact of synoptic systems can be anticipated.  Such
12     tools are very much in the research  stage, however, because the local  impact of ozone and
13     other oxidants results from a complex interaction of distant and local precursor sources,
14     urban plumes, mixing processes,  atmospheric chemical reactions, and general meteorology.
15
16     3.3.3   Normalization of Trends
17          The degree to which meteorological factors can be "normalized"  out of the ozone
18     concentration and "trends" data depends in large part on the strength of the relationships
19     between  ozone  and meteorological components.  As part of the Southern Oxidants Study
20     (SOS) Atlanta Intensive  field campaign, an attempt was made to model statistically the ozone
21     levels in Atlanta to build a predictive tool for forecasting days of specialized measurement.
22     Figure 3-16 shows the fit of the data used to create the model to the model simulations.
23     Figure 3-17 shows the fit obtained from independent data collected in  1992.
24          This model was used successfully to predict next-day ozone levels in Atlanta. Ozone
25     levels in a number of American cities should be analyzed using regression tools such as this
26     to normalize meteorological variability. Through such analyses, it is possible that trends, if
27     any, represented as systematic deviations from the model may become observable.
28     A summary of other techniques for removing meteorological variability is contained in the
29     recent monograph from  the National Research Council (1991).  Table  3-5 lists  a sample of
30     studies aimed at evaluation of ozone trends.
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                     200
                                       80      120
                                     Og (observed), ppb
Figure 3-16. Model of ozone levels using regression techniques. The use of wind speed,
            temperature and previous-day ozone provided a means to forecast ozone
            levels.
                     200
                                40      80      120
                                     Oj (observed), ppb
                        200
Figure 3-17.  Simulated versus observed ozone levels using regression techniques on an
             independent data set obtained in summer 1992 in Atlanta, Georgia.
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            TABLE 3-5.  RECENT STUDIES EXAMINING TRENDS IN OZONE DATA
                      AFTER REMOVAL OF VARIABILITY ASSOCIATED
                              WITH METEOROLOGICAL FACTORS
       Study
          Variables
                 Approach
       Jones et al. (1988)
       Pollock et al. (1988)
       Kuntasal and Chang (1987)
        Wakim (1989)
        Chock et al, (1982)
       Kumar and Chock (1984)
        Korsog and Wolff (1991)
Surface Temperature
Surface Temperature
850 mh Temperature
Surface Temperature
Surface Temperature, windspeed,
relative humidity, sky cover, wind
direction, dew point temperature,
sea level pressure, precipitation.

Surface Temperature, windspeed,
relative humidity, sky cover, wind
direction, dew point temperature,
sea level pressure, precipitation.

Surface Temperature, windspeed,
relative humidity, sky cover, wind
direction, dew point temperature,
sea level pressure, precipitation.
       Compared number of days with
       ozone concentrations above
       120 ppb to days with temperature
       above 30 °C,

       Compared number of days with
       ozone concentrations above
       105 ppb to days with temperature
       above 30 °C,

       Regression of ozone versus
       temperature for southern
       California.

       Regression of ozone versus
       temperature for Houston, New
       York and Washington, DC.

       Regression versus a variety of
       meteorological parameters.
       Regression versus a variety of
       meteorological parameters.
       Regression versus a variety of
       meteorological parameters.
       Source:  National Research Council (1991).
1     3.4   PRECURSORS  OF OZONE AND OTHER OXIDANTS

2     3.4.1   Sources and Emissions of Precursors
3     3.4.1.1   Introduction
4           As described earlier in Section 3,2, 03 is formed in the atmosphere through a series of
5     chemical reactions that involve volatile organic compounds (VOC) and the oxides of nitrogen
6     (NO and NO^ = NOX).  Control of 03 depends on reducing emissions of VOC or NOX or
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 1     both. In addition, models used to determine reductions needed require accurate emission
 2     inventories. Thus, it is important to understand the sources and source strengths of these
 3     precursor species in order to devise the most appropriate oxidant control strategies. In the
 4     following sections, anthropogenic and biogenic NOX and VOC sources will be described and
 5     best estimates of their current emission levels and trends will be provided.  Confidence levels
 6     for the assigned source strengths will be discussed.
 7          Both English and metric units have been utilized in emission inventories.  Thousands or
 8     millions of short tons are the common scales in the English system.  The metric unit most
 9     often employed is millions of metric tons, which is equivalent to teragrams (Tg).  To convert
10     English tons to teragrams, multiply English tons by 0.907  x 10"6.  For consistency,
11     teragrams have been employed throughout the ensuing discussion.
12
13     3.4.1.2   Nitrogen Oxides
14     3,4.1.2.1  Manmade Emission  Sources
15          Anthropogenic oxides of nitrogen sources are associated with combustion processes.
16     The primary pollutant is nitric oxide, which is formed from nitrogen and oxygen atoms that
17     are produced at high combustion temperatures when air is  present.  In addition, NOX is
18     formed from nitrogen contained in the combustion fuel.  Major NOX source categories
19     include transportation, stationary source fuel combustion, industrial processes, solid waste
20     disposal and some miscellaneous combustion related activities. Table 3-6 provides a more
21     detailed summary of each of these source categories.  The transportation category includes
22     gasoline- and diesel-powered motor vehicles, aircraft, railroads, vessels, and off-highway
23     vehicles.  Electric utilities, industrial boilers, commercial/institutional boilers, and industrial
24     furnaces and space heaters comprise the Stationary Source Fuel Combustion Category.
25     Industrial processes include petroleum refining and paper,  glass,  steel, chemical, and cement
26     production. The incineration and open burning of wastes leads to the emissions of NOX in
27     the solid waste disposal category. The miscellaneous sources category includes prescribed
28     forest slash burning, agricultural burning, coal refuse burning, and structure fires.  It should
29     be noted at this point that, even though NO is the primary pollutant, oxides of nitrogen
30     emission inventories are quantified relative to NO2 (mol. wt = 46).
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o
8
1
h- '
VO
VO
u>







TABLE 3-6.

Transportation
Highway vehicles
Gasoline-powered
Passenger cars
Light trucks - 1
Light trucks - 2
Heavy duty vehicles
Motorcycles


SOURCE CATEGORIES USED TO INVENTORY NITROGEN OXIDES EMISSIONS
Stationary Source Fuel
Combustion
Coal
Electric utilities
Industrial
Commercial-institutional
Residential





Industrial Processes
Pulp mills
Organic chemicals
Ammonia
Nitric acid
Petroleum refining
Glass
Cement
Lime
Iron and steel

Solid Waste Disposal Miscellaneous
Incineration Forestries
Open burning Other burning







0
o
I
I
       Diesel-powered
        Passenger cars
        Light trucks
        Heavy duty vehicles


       Aircraft
       Railroads
       Vessels
       Farm machinery
       Construction machinery
       Industrial machinery
       Other off-highway vehicles
Fuel oil
  Electric utilities
  Industrial
  Commercial-institutional
  Residential

Natural gas
  Electric utilities
  Industrial
  Commercial-institutional
  Residential
Wood
  Industrial
  Residential

Other Fuels
  Industrial residential
     Source:  U.S. Environmental Protection Agency (1992).

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 1          Quantifying NOX emissions in all of these categories generally requires multiplying an
 2     emission factor and an activity level.  Nitrogen oxides emission factors are obtained from
 3     Compilation of Air Pollution Factors, AP-42 (U.S. Environmental Protection Agency, 1985),
 4     and from the current mobile source emission factor model (e.g., MOBILES) recommended
 5     by the U.S. Environmental Protection Agency. Activity levels are derived from information
 6     sources that provide consumption levels. This takes the form of fuel type and amount
 7     consumed for stationary sources and, for transportation sources, the number of vehicle miles
 8     traveled (VMT).  Point source emissions are tallied at the individual plant level.  These
 9     plant-by-plant NOX emissions are first summed at the state level and then state totals are
10     added to arrive at the national emissions total. Data on VMT are published for three road
11     categories—highways, rural roads,  and urban streets.
12          Table 3-7 provides a summary of the most recent estimate of NOX emissions from the
13     various categories  mentioned previously (U.S. Environmental Protection Agency, 1993b).
14     The 1991 total is 21.39 Tg of NOX emissions in the United States. Slightly less than half of
15     the emissions (10,36 Tg) is associated with the stationary source fuel combustion category.
16     Transportation-related activities are the second largest source, accounting for about 45%  of
17     the national total.  The remaining 7% of emissions is divided between the industrial
18     processes,  solid waste disposal, and miscellaneous sources categories. The two largest single
19     NOX emission sources are electric power generation and highway vehicles.
20          Because of the dominance of the electric utility and transportation sources, the
21     geographical  distribution of NOX emissions is related to areas with a high density of power
22     generating  stations and urban regions with high traffic densities.  Figure 3-18 shows the
23     location of the 50 largest electric power generating sources of NOX in the United States.  The
24     majority of these power plants are concentrated in the upper Mississippi-Ohio River corridor.
25     Because of this congregation of large point sources, 69% of U.S.  NOX emissions occur
26     within U.S. Environmental Protection Agency Regions 3, 4, 5, and 6 (Figure 3-19). It is
27     interesting  to compare the annual NOX emissions from a large electrical generating plant with
28     the yearly  transportation-related emissions  in a major metropolitan region.  The largest utility
29     plants  currently release between 0.06 and 0,09 Tg of NOX annually, which compares to
30     approximately 0.12 Tg of NOX emitted by transportation sources in the Atlanta urban area
31     (U.S. Environmental Protection Agency, 1993b).

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             TABLE 3-7. 1991 EMISSION ESTIMATES FOR MANMADE SOURCES
       	OF NITROGEN OXIDES IN THE UNITED STATES	
        Source Category	Emissions (Tg)	
        Transportation                                                                9.7
          Highway Vehicles                                   7,20
          Off-Highway Vehicles                               2.51

        Stationary Fuel Combustion                                                   10.6g
          Electric Utilities                                    6.74
          Industrial                                           3.27
          Other                                              0.68
        Industrial Processes                                                           0.80
        Solid Waste Disposal                                                         0.07
        Miscellaneous                                                                0.12
          Forest Burning
          Other Burning
          Miscellaneous Organic Solvents
        Total of All Sources                                                         21.39
       Source:  U.S. Environmental Protection Agency (1993b).
 1     3.4,1.2.2   Trends in Nitrogen Oxides Emissions
 2          Estimates of NOX emissions date back to 1900, when approximately 2.3 Tg were
 3     emitted into the atmosphere in the United States (U.S. Environmental Protection Agency,
 4     1992).  Figure 3-20 summarizes the growth in NOX emissions at 10-year intervals since the
 5     1940s.  Emissions grew rapidly until the 1970s and then leveled off at about 20 Tg/year.
 6     Currently, greater than 90% of the national NOX emissions result from transportation
 7     activities and stationary fuel combustion.  Figure 3-21 illustrates the growth in each of these
 8     categories over the  last 50 years.  Transportation-related NOX emissions grew steadily until
 9     the 1980s and then  exhibited a moderate decrease.  Emissions of NOX from fuel combustion
10     sources have increased continually from 1940 to the present time.
11          Recent trends  in the major NOX emission categories are shown in Table 3-8. Between
12     1987 and 1991, the most recent 5 years for which NOX emission estimates are available,
13     transportation-related emissions have remained essentially constant, while the stationary
14     source NOX emissions have increased about 10%.

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                                                                 Legend

                                                                to 100 Tg/year
                                                              45 to 65 Tg/year
                                                            & 35 to 45 Tg/year
                                                            * 25 to 35 Tg/year

Figure 3-18.  The 50 largest sources of nitrogen oxides (power plants) in the United
             States.

Source:  U,S, Environmental Protection Agency (1992).
Figure 3-19.  Nitrogen oxides emissions (Tg) from manmade sources in the 10 U.S.
             Environmental Protection Agency regions of the United States, 1991.
Source:  U.S. Environmental Protection Agency (1993b).
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                  20
                   15 +
                   10 +
                        1940      1950      1980      1970     1980      1990
                                           Years
Figure 3-20.  Changes in nitrogen oxides emissions from manmade sources in the United

             States, 10-year intervals, 1940 through 1990.


Source: U.S. Environmental Prelection Agency (1992).
         12
          10
               1940
1950
1960      1970      1980      1990
    Years
Figure 3-21. Growth in nitrogen oxides emissions from stationary source fuel

             combustion (SF) and transportation (TR) from 1940 through 1990.


Source: U.S. Environmental Protection Agency (1992).
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       TABLE 3-8.  RECENT TRENDS IN NITROGEN OXIDES EMISSIONS FOR MAJOR
                           MANMADE SOURCE CATEGORIES (Tg)
Year
1991
1990
1989
1988
1987
Transportation
9,7
9.9
9.7
9.9
9.7
Stationary Source
Fuel Combustion
11.0
10.7
10.7
10.6
10.1
       Source: U.S. Environmental Protection Ageney (1993).


 1          Transportation and stationary source fuel combustion will likely show downward trends
 2     in their NOX emissions during the next 20 years.,  This will result from new provisions in the
 3     Clean Air Act passed in 1990.  Emission limits for electric utility boilers have been
 4     prescribed to reduce acidic deposition; automobile tailpipe emission standards will be
 5     tightened; and current technology-based applications will be required for industrial boilers
 6     (non-utility) in 03 nonattainment areas. In addition, the average grams of NOX per mile
 7     from passenger cars is expected to decrease because of new on-board diagnostic systems and
 8     expanded inspection and maintenance requirements.
 9          As a result of new emission limits and revised performance standards, NOK emissions
10     from electric utilities are expected to decrease by 16% by the year 2000.  Control
11     requirements in the industrial non-utility sector are expected to reduce NOX emissions by
12     10% during the 1990 to 2000 time span.  Projections based on vehicle miles travelec and
13     emission factors from the MOBILE model suggest nearly a 50% decrease in NOX emissions
14     from highway vehicles between 1990 and 2000 (U.S. Environmental Protection Agency,
15     1992).
16
17     3.4.1.2.3   Uncertainty of Anthropogenic Nitrogen Oxides Emission Estimates
18          Because  a large proportion of the U.S NOX emissions are derived from distinct point
19     sources, it is generally believed that published estimates are very reliable.  For example, the
20     NAPAP NOX  inventory for U.S. emissions in 1985  (18.6 Tg) was assigned a 90% relative
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 1     confidence interval in the range of 6 to 11 % (Placet et al., 1991). This confidence level was
 2     based on judgments used to assign uncertainty to component inputs of emission models and
 3     on statistical assumptions used to aggregate uncertainty values.
 4          Sources of error are associated with both the emission factors and the activity levels
 5     utilized in the inventorying process.  Emission factors provide quantitative estimates of the
 6     average rate of emissions from many sources. Consequently,  these factors are best applied
 7     to a large number of sources over relatively long time periods. In other words, an NOX
 8     emission estimate for a single point source on a particular day in  1990 may be highly
 9     inaccurate; but  the emission value for this same source for the entire year of 1990 could be
10     very good. It appears that the emission factors assigned to the transportation sectors may be
11     the most  uncertain.  This results from their having been derived from mobile source  models
12     that require multiple inputs.  This type of model requires information on temperatures,
13     vehicle speeds,  gasoline volatility, and several other parameters.
14          Recent attempts to validate NOX emission factors or inventories, or both, have involved
15     comparing ambient NOX concentrations with values predicted  using emissions-based models.
16     These have generally taken one of two forms: (1) comparisons between NOX concentrations
17     measured in a tunnel and those predicted from emission  factors, activity levels, and dilution
18     factors in the tunnel; or (2) whole-city integration procedures  in which ambient NOX
19     concentrations are compared to ambient NOX levels that have  been predicted using a  model
20     such as the Urban Airshed Model.  The latter approach has been  applied in the South Coast
21     Air Basin (Fujita et al., 1992). It was reported that measured and predicted NOX
22     concentrations agreed within 20% for a 2-day period in August 1987.  Likewise,  the results
23     from tunnel studies have shown good agreement between predicted and measured NOX
24     concentrations.  It is important to keep in mind that ambient NOX levels predicted using a
25     modeling method cannot be assigned true value status.  There could be as much or more
26     uncertainty in the model outputs as there is in the emission inputs that are being tested.  The
27     fact, however, that an emissions-based model predicts ambient concentrations that are close
28     to those measured tends to lend credence to the NOX emission estimates.
29          In addition, NOX  inventory  validation has involved comparing annual emission estimates
30     reported  by different groups.  Table 3-9 shows several annual U.S. NOX emission estimates.
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        TABLE 3-9.  COMPARISON OF ESTIMATES OF NITROGEN OXIDES EMISSIONS
                     FROM MANMAPE SOURCES IN THE UNITED STATES
                                                     Emissions/year (Tg)
        Inventory*                              1982                        1985
        NAPAP                                 —                         18.6
        EPA                                   19.6                        19.8
        MSCET                                18.8                        18.2
        EPRI	20/7	        —  	

       *NAPAP = National Acid Precipitation Assessment Program.
        EPA = U.S. Environmental Protection Agency.
        MSCET = Month and state current emissions trends.
        EPRI = Electric Power Research Institute.
       Source:  U.S. Environmental Protection Agency (1993a),
 1     In 1982, the estimates vary by less than 12% and this decreases to about 9% in the 1985
 2     comparison.
 3
 4     3.4,1.2.4   Natural Emissions
 5          Natural sources of NOX include lightning, soils, wildfires, stratospheric intrusion, and
 6     the oceans. Of these, lightning and soils are the major contributors. The custom is to
 7     include emissions from all soils in the biogenic or natural category even though cultivated
 8     soil emissions are in a sense anthropogenic; cultivated soils also appear to produce higher
 9     emissions than those from undisturbed forest and prairie soils, as discussed later.  Although
10     NOX emitted from large wildfires can be significant on a regional scale, overall this source is
11     considered to be of minor importance for the United States.  Injection of NOX into the upper
12     troposphere via subsidence from the stratosphere is estimated at less than 0.1 Tg/year for all
13     of North America.  Because of the relatively short lifetime of NOX (1 to 3 days) and a small
14     flux out of sea water, transport of NOX from oceans is thought to be a negligible source in
15     the United States.
16
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 1          Lightning. Lightning produces high enough temperatures to allow N2 and O2 io be
 2     converted to nitric oxide.  Two methods have been employed to estimate the NOX source
 3     strength from lightning:
 4          (1)   Multiply the frequency of lightning flashes by the energy dissipated per flash and
 5                the NO production per unit of energy dissipated; or
 6
 7          (2)   Relate NOX production to nitrate deposition in remote areas where lightning-
 8                produced NOX is thought to be the dominant nitrate precursor.
 9
10     Method (1) yields an annual NOX production of approximately 1.2 Tg for North America
11     (Placet et al., 1991). The deposition-based estimate (Method 2) gives a somewhat larger
12     value of 1.7 Tg/year (Placet et al,, 1991).  The NAPAP inventory included lightning-
13     produced NOX on a gridded 10° x 10° latitude-longitude scale.   Most of the continental
14     United States fits within 30 to 50° N latitude and 80 to 120° W longitude.   The estimated
15     annual lightning-produced NOX for this region (continental United States) is about 1.0 Tg.
16     Roughly 60% (0.6 Tg) of this NOX is generated over the southern tier of states (30 to 40° N
17     latitude;  80 to 120° W longitude).
18
19          Soils.  Both nitrifying and denitrifying organisms in the soU can produce NOX.  The
20     relative importance  of these two pathways is probably highly variable from biome to biome.
21     Nitric oxide is the principal NOX species emitted from soils, with emission rates depending
22     mainly on fertilization levels and soU temperature. Several reports have noted a large
23     increase in NOX emissions from agricultural soils treated with nitrate-containing fertilizers
24     (Johansson and Granat, 1984; Kaplan et al., 1988; Johansson, 1984). Measurements of soil
25     NOX emissions  have established that the relationship with temperature is exponential,
26     consisting of approximately a two-fold increase for each 10 °C rise in temperature (Williams
27     et al., 1992; Valente and Thornton, 1993).
28          Inventorying soU NOX emissions is difficult because of the large temporal and spatial
29     variability in emissions.  The existing inventories have been developed using emission
30     algorithms that are functions of soil temperature and land-use type.  Two broad, land-use
31     categories—natural and agricultural—have been assigned. The natural soils are broken down
32     into biome types, and the agricultural soils subdivided according  to fertilizer applications.
33     The highest biogenic NO emissions are in corn-growing regions of the midwest  (Nebraska,

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 1     Iowa, and Illinois) during summer months.  Of the total U.S. biogenic emissions of NO from
 2     soils, 85% occur during the spring and summer months.
 3         Table 3-10 provides a summary of the annual soil NOX emissions from the ten U.S.
 4     Environmental Protection Agency regions. Approximately 60% of this NOX is emitted in
 5     Regions 5, 7, and 8 (see Figure 3-19), which contain the central U.S. com belt. The total
 6     estimate for U.S. soil emissions is 1.2 Tg.
 7
          TABLE 3-10.  ANNUAL NITROGEN OXIDES EMISSIONS (Tg) FROM SOILS
       	BY U.S. ENVIRONMENTAL PROTECTION AGENCY REGION	
        U.S. Environmental Protection Agency Region               NOX Emissions
                        1, 2, and 3                                   0.05
                             4                                        0.11
                             5                                        0.26
                             6                                        0.18
                             7                                        0.27
                             8                                        0.21
                             9                                        0.04
                            10                                       0.01
                          Total                                      1.2
       Source: Placet et al. (1991).
 1     3.4.1.2.5  Uncertainty in Estimates of Natural Nitrogen Oxides Emissions
 2         As indicated previously, inventorying NOX produced from lightning requires
 3     multiplying the number of flashes by average energy factors. No attempt has been made to
 4     assign confidence limits to these variables.  A measure of the uncertainty associated with
 5     lightning-produced NOX is provided, however, by comparing emission estimates generated
 6     independently. Two estimates of the amount of lightning-generated, summertime NOX in the
 7     southeastern United States (2.4 and 8.5  x 10"2 Tg) varied by approximately a factor of four
 8     (Placet etal., 1991).
 9         Sources of uncertainty when inventorying NOX emissions from soils include:
10     (1) land-use assignments;  (2) soil temperature; and (3) emission algorithm development.
11     Confidence levels assigned to categories 1 and 2 are about ±50%. The emission algorithm
12     is developed from field measurements of NOX emission rates versus temperature for various
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 1     land-use categories.  Measurement accuracy is approximately ±30%. However, because of
 2     the natural variability of NOX emissions within a specific soil category, uncertainty in the
 3     exponential relationship that relates emission rate to temperature is estimated to be in the
 4     range of a factor of two to four.
 5
 6     3.4.1.2.6   Comparison of Emissions from Manmade and Natural Sources
 7          On an annual basis, natural sources (lightning and soils) contribute approximately
 8     2.2 Tg of NOX to the troposphere over the United  States.  This compares to the 1990
 9     anthropogenic emission estimate of 19.4 Tg. Annual NOX emissions from soils (1.2 Tg) are
10     about 6% of the manmade emissions in the United States. This percentage increases  to about
11     14% when the comparison includes only summer months (July, August, and September).
12     Even larger biogenic contributions can occur in certain regions of the United  States.  For
13     example, it is estimated that biogenic NOX emissions from soils account for about 19% of
14     summertime NOX emissions in Tennessee (Valente and Thornton, 1993) and actually  exceed
15     emissions from manmade  sources during the summer months in the states of Nebraska and
16     South Dakota (Williams et al., 1992).
17
18     3.4.1.3  Volatile Organic Compounds
19     3.4.1.3.1   Manmade Emission Sources
20          Volatile organic compounds are emitted into  the atmosphere by evaporative and
21     combustion processes.  Many hundreds of different organic species are released from a large
22     number of source types. The species commonly associated with atmospheric  O3 production
23     contain from 2 to about 12 carbon atoms.  They can be true hydrocarbons, which possess
24     only carbon and hydrogen atoms (e.g., alkanes, alkenes,  and aromatics), or substituted
25     hydrocarbons that contain a functional group such  as alcohol, ether, carbonyl, ester, or
26     halogens.  Methane has been largely ignored because its atmospheric oxidation rate is very
27     slow compared to the higher-molecular-weight organics.
28          In 1991, the total U.S. emissions of VOCs was estimated to be 21.0 Tg (U.S.
29     Environmental Protection  Agency, 1993b).  The two largest source categories were industrial
30     processes (10.0 Tg) and transportation (7.9 Tg). Lesser contributions were attributed to
31     waste disposal and recycling (2.0 Tg), stationary source fuel combustion (0.7 Tg), and

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1     miscellaneous area sources (0.5 Tg). Table 3-11 provides a more detailed breakdown of
2     VOC source contributions. Within the industrial category, solvent utilization, petroleum

3     product storage and transfer, and chemical manufacturing are the major contributors.

4     Volatile organic compounds released from highway vehicles account for almost 75 % of the

5     transportation-related emissions.
6

            TABLE 3-11. ESTIMATED 1991 EMISSIONS OF VOLATILE ORGANIC
            COMPOUNDS FROM MANMADE SOURCES IN THE UNITED STATES

      	Source Category	Emissions (Tg)
       Transportation                                                           7.87
           Highway Vehicles                                       6.00
           Off-Highway Vehicles                                    1.87
       Stationary Fuel Combustion                                                0.68
           Electric Utilities                                         0.03
           Industrial                                              0.26
           Other                                                  0.39
       Industrial Processes                                                       9,97
           Chemical Manufacture                                   1.61
           Petroleum and Related Industries                          0.68
           Solvent Utilization                                       5.50
           Petroleum Product Storage and Transport                   1.69
           Other                                                  0.49
       Waste Disposal and Recycling                                             2.01
       Miscellaneous                                                           0.51
      ^	TOTAL ALL SOURCES	       21.04

      Source: U.S. Environmental Protection Agency (1993).
1          Speciated hydrocarbon emissions from manmade sources were reported in the 1985
2     NAPAP Emissions Inventory.  Emissions of each main hydrocarbon family exceeded 1 Tg.
3     Alkanes comprised about 33%, aromatics 19%, and alkenes 11 % of anthropogenic VOC
4     emissions in the  1985 inventory (Placet et al., 1991).  None of the major oxygenated
5     hydrocarbon groups (e.g., carbonyls, organic acids, phenols) listed in the speciated inventory
6     exceeded 1 Tg.  The carbonyl group, which included formaldehyde, higher aldehydes,



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 1     acetone, and higher ketones, was the largest contributor of oxygenated hydrocarbons at
 2     0.73 Tg.
 3
 4     3.4.1.3.2   Trends in Emissions
 5          Emissions of nonmethane VOCs peaked in the early 1970s and have decreased
 6     continually since that time. Emissions of VOCs increased from 15.5 Tg in 1940 to 27.4 Tg
 7     in 1970, and now are estimated to be back down to approximately the same level as in 1940
 8     (U.S. Environmental Protection Agency, 1992). Figure 3-22 illustrates these changes  at
 9     10-year intervals from 1940 to 1990. Up until 1970, highway vehicles were the major
10     source of VOC emissions.  As more and better emission controls have been adopted on
11     automobiles, however, emissions from the transportation sector have dropped below those
12     from industrial processes, the category which is now the leading contributor of VOC
13     emissions to the atmosphere.  Transportation, industrial processes, and the miscellaneous
14     burning and  solvent use categories have accounted for 83 to 93% of VOC emissions over the
15     past 50 years.  Figure 3-23 shows the emission trends for these three categories. The
16     transportation-related emissions of VOCs are currently  estimated to be at about the same
17     level as in 1940. Industrial process VOC emissions nearly tripled between 1940 and 1980,
18     followed by  a small decline in more recent years.  The miscellaneous category has exhibited
19     a decrease in emissions from 4.5 Tg in 1940 to a 1990 level estimated at 2.8 Tg/year.
20          Trends for the dominant VOC emissions categories over the last 5 years are shown in
21     Table 3-12.  Projections for the year 2000 forecast a 62% reduction in VOC emissions from
22     highway vehicles compared to 1990 levels. The major reduction in the transportation  area
23     wUl contribute to an overall 25% decrease in total national VOC emissions between 1990 and
24     2000 (U.S. Environmental Protection Agency,  1992).
25
26     3.4.1.3.5   Uncertainty in Estimates of Emissions from Manmade Sources
27          It has proven difficult to  determine the accuracy of VOC  emission estimates.  Within an
28     area source such as  an oil refinery, emission factors and activity levels are assigned for
29     thousands  of individual sources (e.g., valves, flanges, meters, and processes) and emission
30     estimates for each of these sources are summed to produce the emissions total.  Since  it
31     would  be impractical to determine an emission  factor for each of these sources within  a

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                    1940
1950
1960      1970
    Years
1960
1990
Figure 3-22.  Changes in emissions of volatile organic compounds from major manmade
             sources in the United States, 10-year intervals, 1940 through 1990.

Source:  U.S. Environmental Protection Agency (1992).

              14-
               12
              10
             111
             r
             s
             o
             3. 4
             'S
             I
                                                           Transportation     i
                                                           Industrial Processes |
                                                           Mlsceliarwous     i
                    1940
1050
1060       1970
     Yaan
1980
1990
Figure 3-23. Changes in emissions of volatile organic compounds from major manmade
             sources, 1940 through 1990.

Source:  U.S. Environmental Protection Agency (1992).
December 1993
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                 TABLE 3-12. RECENT TRENDS IN EMISSIONS OF VOLATILE
                     ORGANIC COMPOUNDS FROM MAJOR CATEGORIES
                                  OF MANMADE SOURCES (Tg)
Year
1991
1990
1898
1988
1987
Transportation
7.87
8.07
8.26
9.15
9.29
Industrial Processes
7.86
9.96
9.92
10.00
9.65
Waste Disposal
and Recycling
2.01
2.05
2.08
2.10
2.05
       Source:  U.S. Environmental Protection Agency (1993).


 1     refinery individually, average emission factors for the various source categories are utilized.
 2     This can lead to substantial error if the individual sources deviate from the assigned average
 3     factor.   Even more troublesome are area sources that include a large evaporative emissions
 4     component.  These sources are dependent upon environmental factors such as temperature,
 5     which add to the difficulty in establishing reliable emission estimates.  Such sources fall into
 6     a miscellaneous solvent evaporation category, which includes emissions from processes such
 7     as dry cleaning, degreasing, printing, autobody repair, furniture manufacture, and motor
 8     vehicle manufacture.
 9          Assigning accurate VOC emission estimates to the mobile source category has proven
10     troublesome, as well.  Models are  used that incorporate numerous input parameters, each of
11     which has some degree of uncertainty.   For example, activity models are employed to
12     characterize the mobile source fleet.  This includes the number of vehicles in various
13     categories (e.g., gasoline fueled, diesel fueled, catalyst equipped, non-catalyst equipped,
14     etc.), miles accumulated per year for each type of vehicle,  and ages of the vehicles. Vehicle
15     registration statistics are employed for category assignment. Errors can arise because
16     registration data are not always up to date and unregistered vehicles are completely omitted.
17     Military vehicles, foreign-owned automobiles, and old "junkers"  that are on the highways but
18     not registered do not get included in the inventorying process.  The activity models assume
19     vehicles of the same age accumulate mileage at the same rate.  This is probably not correct,

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 1     and there is a need to assess the uncertainty in this assumption thorough a systematic
 2     collection of vehicle type-age-mileage accumulation statistics.  Recent developments in
 3     remote sensing have permitted more accurate measurement of hydrocarbon exhaust emissions
 4     from on-road vehicles (Stedman et al., 1990).  These studies have demonstrated a highly
 5     skewed distribution, with the majority of VOC emissions coming from  about 20% of the
 6     automobiles.  Emission factors developed from laboratory dynamometer testing most likely
 7     do not properly account for the high-emitting vehicle contribution (Pitchford and Johnson,
 8     1993). In many cases,  these high emitters are older cars that are poorly maintained.
 9     In order to reduce this source of uncertainty, it may be necessary to reassess the life spans
10     assigned to vehicles.  Vehicles manufactured more than 25 years prior to the present time
11     (1993) are not included in the inventory. However, these older vehicles are likely to be high
12     emitters,  and if they are under-represented in the model, emissions will be underestimated.
13     Activity models provide data in terms of national averages.  This can contribute to
14     inaccuracies in emissions  estimates if a particular region varies from the national average in
15     terms of vehicle types,  age, or vehicle miles traveled.
16          Ambient measurements of VOCs and NOX have been employed in order to better define
17     uncertainty levels in VOC inventories.  Some of the earliest work was carried out in the
18     Atlanta area in the 1980s. Using a simple model and measured ambient VOC and NOX
19     concentrations,  it was shown that ambient NOX levels were consistent with the urban NOX
20     emission estimates; but measured ambient VOC concentrations were as much as a factor of
21     six greater than predicted (Westberg and Lamb, 1985). More recently, experiments carried
22     out in tunnels have demonstrated a poor relationship between measured VOC emission
23     factors and those derived from automotive emission models.  In a study designed to verify
24     automotive emission inventories for the South Coast Air Basin, measurements in the
25     Van Nuys Tunnel indicated that automotive VOC emissions were a factor of four larger than
26     predicted using emission models (Herson et al., 1990). Improvements in mobile source
27     emission models have resulted in somewhat higher emission estimates that have now reduced
28     the discrepancy with ambient data to about a factor of 2.5 (Fujita et al., 1992; Cadle et al.,
29     1993). It is clear that the relationship between emission inventories and ambient
30     concentrations of NOX and VOCs warrants further study.  In addition to improving the
31     mobile source emission inventories, it will be necessary to place uncertainty bounds on

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 1     stationary source inventories.  Whether stationary source emissions of VOC are
 2     underpredicted using current emission inventory methodology is not known (Finlayson-Pitts
 3     and Pitts, Jr., 1993).
 4
 5     3.4.1.3.4  Biogenic Emissions
 6          Vegetation emits significant quantities of reactive VOCs into the atmosphere.  Many of
 7     these biogenic VOCs may contribute to Oj production in urban (Chameides et al., 1988) and
 8     rural (Trainer et al., 1987) environments.  The VOC emissions of primary interest are
 9     isoprene and the monoterpenes (e.g., a-pinene, jS-pinene, myrcene, limonene, etc.), which
10     are hydrocarbons.  Recent field measurements have shown that a  variety of oxygenated
11     organics are also emitted from plants (Winer et al., 1992).  A thorough discussion of
12     biogenic emissions and their implication for atmospheric chemistry has been published
13     recently by Fehsenfeld et al. (1992), who reviewed (1) the techniques used to measure VOC
14     emissions from vegetation; (2) laboratory emissions studies that have been used to relate
15     emission rates to temperature  and light intensity; (3) development of emission models; and
16     (4) the use of emission models in the preparation of emission inventories.
17          Over the past  10 years, a number of regional and national biogenic emission inventories
18     have been reported  (Zimmerman, 1979; Winer et al., 1983; Lamb et al., 1985; Lamb et al.,
19     1987; Lamb et  al.,  1993).  These inventories are based on algorithms that relate VOC
20     emissions from a particular vegetation class  to ambient temperature, land-use, and, in the
21     case of isoprene, photosynthetically active radiation. Most biogenic VOC emissions from
22     vegetation increase  exponentially with temperature. Isoprene emissions are light-dependent,
23     being minimal at night and increasing with solar intensity during  the day.  Deciduous
24     vegetation is the dominant source of isoprene; whereas coniferous trees emit primarily
25     monoterpenes.  Other things being equal, isoprene is emitted at a much higher rate than the
26     monoterpenes.  For example,  in a southern forest of mixed pine and hardwoods, the isoprene
27     emission rate from an oak tree is about 10 times larger than the flux of a-pinene from an
28     adjacent loblolly pine during the  midday period.
29          The most recent biogenic VOC emissions estimate for the United States totals
30     29 Tg/year (Lamb et al,, 1993).  This estimate includes 5.9,Tg isoprene, 4.4 Tg a-pinene,
31     6.5 Tg  other monoterpenes, and 12.3 Tg other VOCs.  Table 3-13 provides a summary of

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                TABLE 3-13.  ANNUAL BIOGENIC HYDROCARBON EMISSION INVENTORY FX)R
                                       THE UNITED STATES (Tg)



Compound
Isoprene
ot-pinene
Other terpenes
Other VOCs
Total
Percent of Total


Oak
Forests
2.31
0.19
0.41
1.12
4.03
13.9

Other
Deciduous
Forests
1.01
0.23
0.44
0.88
2.56
8.8


Coniferous
Forests
0.61
2.07
3.08
2.72
8.48
29.2


Scrub-
lands
1.17
0.78
1.41
2.49
5.85
20.1
Land Use

Grass-
lands
0.49
0.13
0.24
0.45
1.31
4.5


Crop-
lands
0.2
0.85
0.81
4.51
6.37
21.9


Inland
Waters
0.02
0.06
0.06
0.07
0.21
0.7


Urban
Areas
0.08
0.04
0.06
0.08
0.26
0.9



U.S. Total
5.9
4.4
6.5
12.3
29.1

w  Source:  Lamb et al. (1993).

ON

-------
 1     the contributions from the various vegetation categories.  In preparing this inventory,
 2     algorithms were developed that related VOC emissions to temperature and light for each of
 3     the biomass categories shown in the table.  On a national scale, coniferous forests are the
 4     largest vegetative contributor because of their extensive land coverage.  The category, "other
 5     VOCs," is the dominant biogenic hydrocarbon contributor to the national total.  From the
 6     standpoint of inventory accuracy, this is somewhat unfortunate because the identities of most
 7     of the "other VOCs" are uncertain.  This classification has carried over from the extensive
 8     field measurement program conducted by Zimmerman (1979) and coworkers in the
 9     mid-1970s.  The category, other VOCs, includes peaks that showed up in sample
10     chromatograms at retention times that could not be matched to known hydrocarbons.  It is
11     likely that if the Zimmerman study were repeated today, most of the species making up this
12     "other VOCs" category could be identified.  Recent field studies have made use of GC-MS
13     techniques that were not available to Zimmerman in the 1970s.
14          Biogenic emissions vary by season because of their dependence on temperature and
15     vegetational  growth.  In addition, the southern tier of states is expected to produce more
16     biogenic emissions than those in the north because of higher average temperatures.
17     Table 3-14 shows a spatial and temporal breakdown of U.S. biogenic emissions.
18     Summertime emissions comprise more than half of the annual totals in all regions. Federal
19     Regions IV and VI in  the southcentral and southeastern United States have the highest
20     biogenic hydrocarbon emission rates.
21
22     3.4.1.3.5   Uncertainty in Estimates of Biogenic Emissions
23          Sources of error in the biogenic inventorying process arise from uncertainties in
24     (1) emission measurements; (2) determination of biomass densities; (3) land-use
25     characterization; and (4) measurement of light intensity and temperature. Within each of
26     these categories the error is relatively small. However, when  emission measurements are
27     combined with temperature or light intensity or both into a single algorithm, the uncertainty
28     increases greatly. This results from the fact that temperature and light are only surrogates
29     for the real physiological processes that control biogenic emissions.  Emission rate and
30     ambient temperature can be highly correlated for data collected from one tree branch over a
31     24-h period; but, when these data are combined with measurements from other branches and

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TABLE 3-14. ANNUAL BIOGENIC HYDROCARBON EMISSION INVENTORY BY MONTH AND
 U.S. ENVIRONMENTAL PROTECTION AGENCY REGION FOR THE UNITED STATES (Tg)
ff
h— »
$
U)







oo

o
8
I
1
8
U.S. Environmental Protection Agency Region
Month
1
2
3
4
5
6
7
8
9
10
11
12
Total
Source: Lamb

3
0.018
0.017
0.071
0.169
0.206
0.427
0.441
0.439
0.123
0.069
0.066
0.018
2.1
et al. (1993).

4
0.092
0.139
0.428
0.460
0.475
0.874
0.903
0.903
0.461
0.286
0.162
0.080
5.3


5
0.004
0.004
0.067
0.189
0.240
0.550
0.568
0.568
0.137
0.066
0.063
0.004
2.5


6
0.084
0.123
0.519
0.567
0.586
1.146
1.184
1.184
0.561
0.394
0.174
0.073
6.6


7
0.007
0.007
0.078
0.211
0.226
0.508
0.524
0.524
0.136
0.026
0.025
0.007
2.3


8
0.022
0.02
0.108
0.303
0.362
0.809
0.836
0.820
0.280
0.290
0.110
0.022
4.0


9
0.060
0.054
0.113
0.320
0.331
0.710
0.734
0.734
0.357
0.369
0.130
0.060
4.0


10
0.043
0.039
0.102
0.202
0.208
0.424
0.438
0.438
0.212
0.219
0.109
0.043
2.5


Total
0.3
0.4
1.5
2.4
2.6
5.5
5.6
5.6
2.3
1.7
0.8
03
29.1


Percent
of Total
1.1
1.4
5.1
8.3
9.1
18.7
19.3
19.3
7.8
5.9
2.9
UL




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 1     other trees the correlation is not nearly as good.  The uncertainty associated with the
 2     algorithms used to generate the U.S. inventory described previously is estimated to be a
 3     factor of three (Lamb et al., 1987).  Since other sources of error in the inventorying process
 4     are much smaller, a factor of three is the current best estimate of the overall uncertainty
 5     associated with biogenic VOC inventories.  However, this may be a lower limit if it is shown
 6     that oxygenated species are emitted in significant quantities by vegetation.  Emission
 7     measurement methods employed in the past have not been adequate for quantifying polar,
 8     oxygenated organics.
 9
10     3.4,1.3.6   Comparison  of Manmade and Biogenic Emissions
11          The most recent anthropogenic and biogenic VOC emissions estimates for the United
12     States indicate that natural emissions (29 Tg) exceed manmade emissions (21 Tg). However,
13     in a recent National Research Council review it was concluded that emissions from manmade
14     sources are currently underestimated by a significant amount (National Research Council,
15     1991). Since uncertainty in both biogenic and anthropogenic VOC emission inventories is
16     large, it is not possible to establish at this time whether the contribution of emissions from
17     natural or manmade sources of VOCs is larger.
18
19     3.4.1.4  Relationship of Summertime Precursor  Emissions and Ozone Production
20          Peak O3 levels are recorded in most regions of the country during the summer months
21     of June, July, and August. From the foregoing discussion, it is obvious that natural
22     emissions of NOX and VOCs peak during this same  time frame. Biogenic emissions are very
23     dependent on temperature; and as ambient temperatures rise during the summer months, NOX
24     and VOC emissions reach a maximum.   Figure 3-24 clearly demonstrates this for biogenic
25     VOC emissions, and a plot of monthly biogenic NOX emissions would show a similar
26     pattern. Well over 50%  of biogenic NQX and VOC emissions occur during the period of
27     maximum photochemical activity.
28          Seasonal changes in anthropogenic emissions of NOX are believed to be relatively small.
29     The transportation sector produces slightly less NOX during the wanner months, but there is
30     probably a small increase from the stationary source category because of higher summertime
31     power demands.  Since these are the major U.S. sources of NOX and changes in  seasonal

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                Dec.
                 Nov.
                    01234
                                          Total NMHC Emissions fTg)
       Figure 3-24.  Estimated biogenic emissions of volatile organic compounds in tbe
                    United States as a function of season.
       Source: Fehsenfeld et ai, (1992),
 1     emissions tend to offset each other, there is no reason to expect that NOX emissions will vary
 2     significantly by season on the national level. Evaporative emissions of VOCs are enhanced
 3     during the warm summer months.  Because evaporation is an important component of
 4     anthropogenic VOC emissions, there should be a summertime increase.  In 1987, U.S. VOC
 5     emissions during June, July, and August were estimated to exceed annual monthly average
 6     VOC emissions by about 17% (U.S. Environmental Protection Agency, 1992),  This is a
 7     very small change relative to the uncertainty associated with VOC emission estimates. In the
 8     NAPAP inventory, VOC emissions from manmade sources  were considered to be almost
 9     independent of season (Placet et al., 1991).
10         Increases in O3 precursor emissions during the peak O3 season will have a tendency to
11     enhance O3 production. Ozone production in rural areas is usually NO^-limited (Fehsenfeld
12     et al,, 1992).  Thus, enhanced summertime emissions of NOX from soils and lightning will
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 1     add NOX to the atmosphere in rural regions, which in turn will lead to the production of
 2     more O3.  Larger summertime emissions of VOCs will enhance O3 production in urban
 3     areas.  Biogenic VOC sources in the vicinity of urban areas can contribute significant
 4     quantities of reactive hydrocarbons to the urban 63 precursor mix (CardeUno and Chameides,
 5     1990).
 6
 1     3.4.2   Concentrations of Precursor Substances in Ambient Air
 8          The volatile organic compounds (VOCs), excluding methane, often are referred to as
 9     nonmethane organic compounds (NMOCs). The class of NMOCs  most frequently analyzed
10     in air are the nonmethane hydrocarbons (NMHCs).  The NMHC measurements often provide
11     an acceptable approximation of the NMOCs.  The NMHCs and the nitrogen oxides (NOX)
12     within  urban areas tend to have morning concentration peaks.  These result from vehicular
13     traffic in combination with limited mixing depths.  Later in the morning into the afternoon
14     hours,  concentrations of NMHCs and NOX decrease, but to varying extents (Purdue et al.,
15     1992) because of increases in mixing depths and consequent increases in dilution volumes.
16     Photochemical atmospheric reactions also can rapidly convert nitric oxide (NO) to nitrogen
17     dioxide, and hydrocarbons to carbonyls,  PANs, and other products (Sections 3.2.4, 3.4.2.1,
18     and 4.9).  Late afternoon and early evening peaks might be expected in NMHC and NOX
19     concentrations  because of increased vehicular traffic at urban locations, but such increases
20     often are not discernible (Purdue et al., 1992).  This effect probably results from the
21     presence of substantial mixing depths in the warmer months that persist through these hours
22     in many urban locations.
23          Because of the emphasis on early morning inputs of NMOCs and NOX for models such
24     as EKMA, most of the measurements available emphasize the 6 to 9 a.m. period.  The
25     variations in the concentrations of NMOCs and NOX, their ratios, and the composition of
26     NMOCs are important factors in the generation of O3 and other photochemical products.
27
28     3.4.2.1  Nonmethane Organic Compounds
29          In earlier measurements based on gas chromatographic analyses made during a number
30     of different studies in urban areas over the years between 1969 and 1983, the mean 6 to
31     9 a.m. NMHC concentrations were reported to range from 0.324 to 3.388 ppm C (U.S.

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 1     Environmental Protection Agency, 1986),  The highest NMHC concentrations were those
 2     measured at sites in Los Angeles.
 3          A program for analysis for NMOCs and NOX in the months of June through September
 4     was conducted in a considerable number of U.S. cities during the 1980s. The results
 5     obtained from measurements made during the 6 to 9 a.m. period at sites in 22 cities in 1984
 6     and 19 cities in 1985 have been subjected to statistical analysis and interpretation (Baugues,
 7     1986). The total NMOC measurements throughout the June through September periods in
 8     these cities were obtained by the cryogenic preconcentration-direct flame ionization method
 9     (PDFJD) (McElroy et al.,  1986). In addition, during about 15% of the 6 to 9 a.m. periods,
10     canister samples were collected for subsequent gas chromatographic analysis (Seila et al.,
11     1989). In 1984, the lowest median NMOC value obtained was 0.39 ppm C from
12     measurements in Charlotte, NC, while the highest median NMOC value obtained was
13     1.27 ppm C from measurements in Memphis, TN.  In 1985, the lowest median NMOC value
14     obtained was 0.38 ppm C from measurements in Boston, MA, while the highest median
15     NMOC value obtained was 1.63 ppm C in Beaumont, TX.  The overall median values from
16     all urban sites were approximately 0.72 ppm C in 1984 and 0.60 ppm C in 1985 (Baugues,
17     1986). The gas chromagraphic analyses made on samples collected in 1984, 1985, and 1986
18     have been reported (Seila et al., 1989). The more abundant individual hydrocarbons include
19     C2~Cg alkanes, C2-C5 alkenes, Cg-Cp aromatics, and acetylene.  Based on the 48 most
20     abundant concentrations, the overall median concentrations by class of hydrocarbon
21     (NMHCs) were as follows: paraffins, 0.266 ppm C, 60% of total; aromatics, 0,166 ppm C,
22     26% of total; olefins,  0.047 ppm C, 11 % of total; and acetylene, 0.013 ppm C, 3 % of the
23     48 hydrocarbons measured (Seila et al., 1989).  Additional individual NMHCs summing to
24     about 0.100 ppm C were detected at concentrations  £0.002 ppm C each. Most of these
25     compounds were identified by class but not by structure.
26          Detailed hydrocarbon analyses for C2-C10 NMHCs were obtained during the
27     17 intensive days of the Southern California Air Quality Study (SCAQS) in  1987 (Lonneman
28     et al., 1989; Rasmussen, 1989; Stockberger et al.,  1989). The average percentage ambient
29     composition from eight southern California sites  during 11 intensive sampling days of the
30     summer of 1987 by class of NMHCs were as follows: paraffins, 53.4; aromatics, 27.2;
31     olefins, 12.1; carbonyls, 7.7 (Main and Lurmann, 1992).

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 1          In Atlanta, GA, during the summer of 1990, hydrocarbon concentrations were
 2     measured at six sites with automated gas chromatographs.  Results were reported on
 3     54 hydrocarbons, with 24-h average concentrations ranging from 0.186 ppm C to
 4     0.397 ppm C (Purdue et al., 1992).
 5          A comparison of NMHC measurements made by gas chromatographic analyses  over a
 6     period of years in Los Angeles and in the New York City area has been reported (Lonneman
 7     and Seila, 1993). In the Los Angeles area, the NMHC concentrations averaged  2.81 ppm C
 8     in 1968, compared to 1.02 ppm C in  1987.  In the New York City area, the NMHC
 9     concentrations averaged about 1.1 ppm C in 1969, compared to 0.62 ppm C from 1986 to
10     1988.  In both the Los  Angeles and New York areas, there were significant decreases in
11     NMHC concentrations as well as compositional changes in NMHCs during these years, with
12     increases observed in the percentage of paraffin hydrocarbons and decreases in the
13     percentage of aromatic  hydrocarbons  and acetylene (Lonneman and Seila, 1993).
14          Aldehydes and ketones occur in urban air as ozone-oxidant precursors from emissions
15     such as vehicular exhaust,  and as products of reactions of OH radicals with NMHCs,
16     reactions of alkenes with Oj, and, at  night, reactions with NOj radicals.  Early morning
17     aldehyde concentrations have been predicted to result to a greater extent from atmospheric
18     reactions of alkenes than from emission of vehicular exhaust (Altshuller, 1993).  During the
19     day, aldehydes and ketones are rapidly produced from reactions of OH radicals with  aliphatic
20     and aromatic hydrocarbons and of alkenes with O3. Carbonyl concentrations tend to increase
21     through the daytime hours (Grosjean, 1982, 1988; Grosjean et al., 1993).
22          Measurements of ambient air concentrations of carbonyls indicate the total  loading of
23     aldehydes and ketones from all processes.  Ambient urban air concentrations  of formaldehyde
24     and total aldehydes were tabulated for the 1960 to 1981 period (Altshuller, 1983a).
25     Subsequent studies by DNPH-HPLC  techniques (Section 3.5.2.3.4) have consistently shown
26     that formaldehyde and acetaldehyde are the most abundant aldehydes; however,  a number of
27     other carbonyls—including propanal,  acrolein, acetone, butanal, crotonaldehyde, methyl ethyl
28     ketone, pentanal, hexanal, benzaldehyde, and tolualdehyde—also have been measured (Fung,
29     1989; Grosjean 1982, 1988,  1991; Kalabokas et al., 1988; Zweidinger et al., 1988).   The
30     ratios of formaldehyde  to acetaldehyde concentrations (ppbv) can vary from less than 0.5 in
31     cities in Brazil, where there  is high use of ethanol fuels, up to 4.0 to  5.0 at a few urban sites

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 1     (Grosjean et al., 1993).  However, at most urban sites, the ratios of formaldehyde to
 2     acetaldehyde concentrations occur in the 1.0 to 3.0 range.
 3          A compilation of the maximum, average range of formaldehyde concentrations from
 4     many studies in Southern California carried out between  1960 and 1989 is available
 5     (Grosjean, 1991).  A downward trend in formaldehyde concentrations occurs, probably
 6     because of decreased production from precursor alkenes and decreased emission in vehicular
 7     exhaust (Sigsby et al,, 1987; Dodge, 1990).  For example, the maximum formaldehyde
 8     concentrations decreased from above 100 ppbv in the 1960s down to the 10 to 30 ppbv range
 9     during the last decade (Grosjean, 1991).  In other U.S. cities in the early 1980s, the
10     maximum formaldehyde concentrations ranged  from 5 to 45 ppb (Salas and Singh, 1986),
11          Several studies have reported concurrent morning hydrocarbon and carbonyl
12     concentrations in downtown Los Angeles,  CA (Grosjean  and Fung, 1984); Raleigh, NC
13     (Zweidinger et al., 1988); and Atlanta, GA (Shreffler, 1992; Grosjean et al., 1993). The
14     average percentage of carbonyls relative to total NMHCs were reported as follows; Los
15     Angeles, 3%;  Raleigh, 2%; and Atlanta,  ^2% (formaldehyde + acetaldehyde
16     concentrations) at two different sampling sites.  In SCAQS, carbonyls were measured at eight
17     sites in summer and five in fall of 1987 (Fung, 1989; Fujita et al., 1992).  The average
18     percentage of Cj to C6 carbonyls relative to  NMHCs in summer was 7.6%  and in fall was
19     3.7%.
20          Compilations of NMHC concentrations of nonurban and remote locations are available
21     (U.S. Environmental Protection Agency,  1986; AltshuUer,  1989a). Total NMHC
22     concentrations reported ranged from less than 0.01  to 0.14 ppm  C.  At remote locations over
23     the Pacific, NMHC concentrations generally were less than 0.01 ppm C.  Over both
24     continental and oceanic locations there can be contributions from biogenic sources of
25     NMHCs.
26          Interest in the contribution of biogenic hydrocarbons has existed for many years and
27     earlier work has been reviewed (Altshuller, 1983b). Photochemical modeling in the United
28     States predicts significant effects of biogenic hydrocarbons on O3 production (Chameides
29     et al., 1988; Roselle  et al., 1991).  Similar modeling of the effect of biogenic hydrocarbons
30     on O3 production within urban plumes over southeastern England predicted a 2 to 8 ppb
31     increase in plume and background O3 concentrations (MacKenzie et al.,  1991).  Because of

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 1     lower emissions of biogenic and lower overall NMOC/NOX ratios, O3 production over
 2     southeastern England is predicted to be limited by the availability of anthropogenic
 3     hydrocarbons,
 4          Compilations of results of earlier measurements of isoprene and terpene concentrations
 5     are available (Altshuller, 1983b; U.S. Environmental Protection Agency,  1986).  Average
 6     concentrations  of isoprene ranged from 0.001 to 0.020 ppm C and terpenes from 0.001 to
 7     0.030 ppm C.  When concurrent measurements of biogenic and anthropogenic NMHCs
 8     were available, the biogenic NMHCs usually constituted much less than 10% of the total
 9     NMHCs (Altshuller,  1983b).
10          Among more recent studies are two investigations of terpene and isoprene emissions in
11     the central valley of California and in Louisiana (Arey et al., 1991; Khalil and Rasmussen,
12     1992).  Both studies reported a large number of individual terpenes as measured using
13     enclosure  methods.  When ambient air measurements were made, most of the terpenes
14     measured  in the enclosures were not detectable (Khalil and Rasmussen, 1992).  In ambient
15     air, isoprene was the predominate  hydrocarbon, accounting on average for 70%  of the
16     biogenic species and  36% of NMOCs. It is concluded that the bag enclosure method can
17     lead to large overestimates in biogenic emissions (Khalil and Rasmussen,  1992).
18          In two other recent studies in deciduous forests, the isoprene oxidation products were
19     measured  as well as isoprene itself (Pierotti et aL, 1990; Martin et al., 1991).  Both studies
20     report the ambient concentrations of methacrolein and methyl vinyl ketone.  In the
21     investigation in a central Pennsylvania deciduous forest in the summer of 1988, average
22     midday concentrations of isoprene were in the 0.005 to 0.010 ppm C range; whereas the
23     corresponding  concentrations of methacrolein and methyl vinyl ketone were in the 0.001 to
24     0.002 ppm C range (Martin et al., 1991). In the  study conducted in California forests with
25     samples collected  between  1200 and 1600 LT in late spring and  summer, the upper quartile
26     of isoprene concentrations  was within the 0.010 to 0.025 ppm C range, whereas methacrolein
27     concentrations  were within the 0.001 to 0.003 ppm C range, and methyl vinyl ketone
28     concentrations  were within the 0.0005 to 0.0015 ppm C range (Pierotti et al., 1991).
29          Higher-molecular-weight semivolatile  carbonyls have been measured in a number of
30     rural-remote areas  (Juttner, 1986;  Yokouchi et al., 1990; Nordek et al., 1992; Ciccioli et al.,
31     1993).  The compounds identified include C5-C12 aliphatic aldehydes, aliphatic ketones, and

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 1     aromatic aldehydes. Comparisons of the measurement of these carbonyls relative to aromatic
 2     hydrocarbons in two studies indicated higher carbonyl concentrations and much lower
 3     aromatic hydrocarbon concentrations in the rural-remote sites compared to the urban areas
 4     (Yokouchi et al., 1990; Ciccioli et al., 1993).  Widely varying natural sources have been
 5     associated with these carbonyls, including emissions from forest species (Nordek et al.,
 6     1992) and short vegetation (Ciccioli et al., 1993) and as secondary products of natural
 7     emissions of terpenes (Ciccioli et al., 1993) or oleic acid (Yokouchi et al.,  1990).  Among
 8     other oxygenates reported to be of natural origin are higher-molecular-weight alcohols
 9     (Juttner,  1986; Nordek et al.,  1992; Goldan et al., 1993). These oxygenates contribute to
10     the "other VOCs" category in the biogenic emissions inventory (Section 3.4.1.3,4).
11          In an urban-scale study in Atlanta,  GA, during the summer of 1990 (as part of the
12     Southern Oxidant Study), isoprene concentrations rose in late morning and into the afternoon,
13     with early evening peaks observed at residential and rural-residential sites (Purdue et al.,
14     1992). A similar diurnal profile for isoprene was observed at a Pennsylvania forest site
IS     (Martin et al., 1991).  The median concentration at the sampling sites in Atlanta early in the
16     evening ranged from 0.006 to 0.020 ppm C. The isoprene as a percentage of total NMHCs
17     in the early evening ranged among the sites from 2 to 12% (Shreffler, 1992).
18
19     3.4.2.2  Nitrogen Oxides
20          Measurements of NOX were obtained with continuous NOX analyzers at sites  in  22 and
21     19 U.S. cities during the months of June through September of 1984 and 1985, respectively.
22     These results have been evaluated and the 6 to 9 a.m. values tabulated (Baugues,  1986).
23     In 1984, the lowest median NOX concentration of 0.010 ppm was obtained from
24     measurements in West Orange, TX; while the highest median NOX concentration of
25     0.088 ppm was obtained from measurements in Memphis, TN.  In 1985, the lowest median
26     NOX concentration of 0.005 ppm was obtained from measurements in West Orange, TX;
27     while the highest median NOX concentration of 0.100 ppm was obtained from  measurements
28     in Cleveland, OH. The median NOX concentration values for sites in most of these cities in
29     1984 and 1985 ranged between 0.02 and 0.08 ppm.  Because of high vehicular emission rates
30     and shallow  mixing depths, the median 6 to 9 a.m. concentration values  in many of these
31     cities exceeded the annual average NOX  values of 0.02 to 0.03 ppm in U.S. metropolitan

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 1     areas between 1980 and 1989 (U.S. Environmental Protection Agency, 199la).  In the 1990
 2     Atlanta study, average summer NOX concentration values at the six study sites ranged from
 3     0.011 to 0.026 ppm (Purdue et al., 1992).
 4          At nonurban sites, NOX concentrations have been reported as mean 24-h seasonal or
 5     annual NOX values.  The available results have been compiled for work reported through
 6     1983 (Altshuller, 1986).  The average seasonal or annual NOX concentrations ranged from
 7     less than 0.005 to 0.015 ppm. At remote sites in the earlier investigations, monthly average
 8     NOX concentrations were less than 0.001 ppm. In more recent work, the statistics on NOX
 9     concentrations have been reported for several relatively remote U.S.  sites (Fehsenfeld et al.,
10     1988). The 24-h average NOX concentrations  and the range in the central 90% of values
11     were as follows: Point Arena, CA,  spring 1985, 0.0004 ppm, 0.0007 to 0.001 ppm; Niwot
12     Ridge, CO, summer 1985,  0.0005 ppm, 0.0001 to 0.002 ppm; and Scotia, PA, summer
13     1986, 0.002 ppm, 0.0007 to 0.009 ppm. It should be noted that each of these sites can be
14     subject to anthropogenic influences, thus accounting for the higher NOX values.  For
15     example, at Niwot Ridge, CO, with upslope flow from the Denver-Boulder, CO, urban area,
16     higher NOX concentrations  are measured. Nitrogen oxide concentrations at or below
17     0.0001 ppm occur at other remote surface locations (Fehsenfeld et al., 1988).
18
19     3.4.2.3   Ratios of Concentrations of Nonmethane Organic Compounds and Nitrogen
20              Oxides
21          The ratios of 6 to 9 a.m. NMOC/NOX have been obtained from the measurements in
22     the U.S. cities discussed above (Baugues, 1986).  In  1984, the lowest median NMOC/NOX
23     ratio of 9.1 was obtained in Cincinnati, OH, and the highest median  NMOC/NOX ratio of
24     37.7 was obtained in Texas City, TX.  In 1985, the lowest median NMOC/NOX ratio of
25     6.5 was obtained in Philadelphia, PA, whereas the highest median NMOC/NOX ratio of
26     53.2 was obtained in Beaumont,  TX. The range in daily 6 to 9 a.m. NMOC/NOX ratios
27     within a given city is large, with 10th percentile to 90th percentile NMOC/NOX ratios
28     varying usually by factors of 2 to 4 and at  several sites by factors of 5 to 10 (Baugues,
29     1986). There appears to be a tendency for higher NMOC/NOX ratios in the cities included in
30     the southeastern (9) and southwestern (15)  United States than in the northeastern (7) and
31     midwestem United States (7) (Altshuller, 1989b). The NMOC-to-NOx ratios at rural sites

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 1     tend to be higher than the mean NMOC-to-NOx ratios in urban locations, with mean values
 2     at several rural sites ranging between 20 and 40 (AJtshuller, 1989b).
 3         In SCAQs, the ambient NMOC (NMHCs + carbonyl)/NOx ratios averaged 8.8 in
 4     summer and 6.9 in the fall of 1987 (Fujita et al., 1992).  However, the six intensive days in
 5     fall between November 11 and December 11 were not characterized by elevated
 6     03 concentrations (Zeldin, 1992). These ambient ratios were 2 to 2.5 times higher than the
 7     corresponding emission inventory ratios. Discrepancies as large or larger have been
 8     previously discussed for urban and rural NMHC/NOX ambient-to-emission ratios in the
 9     eastern United States (Allshuller,  1989b).
10         A trend analysis of NMHC/NOX ratios in the South Coast Air Basin is available for the
11     1976 to 1990 period (Fujita, 1992).  The ratios were consistently higher in summer than fall.
12     These  ratios started decreasing slowly during the 1980s from maximum ratios of about 12 in
13     summer and 9 in fall down to 8.5 in summer and 7 in fall by 1990. The ambient-to-emission
14     inventory ratios over this period ranged from as high as 3.4 in summer to 1.7 in winter
15     (Fujita, 1992).
16         Interest in the 6 to 9 a.m. NMOC/NOX ratios is associated with their use in the EKMA
17     type of trajectory model (Section 3.6.1.2). The analysis at 10 eastern and midwestera sites
18     of upper-quartile O3 days relative to other O3 days indicated a significant difference
19     (p ^ 0.10) by the two-sample Wilcoxon Rank Sum  test at four of the 10 sites with
20     NMOC/NOX ratios (Wolff and Korsog, 1992). However, the correlation of NMOC/NOX
21     ratios  with maximum 1-h O3 concentrations was very weak. It was concluded that the use of
22     the 6 to 9 a.m. NMOC/NOX ratio in EKMA will not provide sufficient information to
23     distinguish among NMOC, NOX,  or combined VOC-NOX strategies as optimum strategies for
24     urban  areas.
25
26     3.4.3   Source Apportionment and Reconciliation
27     3.4.3.1   Source Apportionment
28         Source apportionment refers to determining the quantitative contributions of sources to
29     ambient air pollutant concentrations.  In principle, it includes two fundamentally different
30     approaches, source-oriented and receptor-oriented.  In the source-oriented approach, a
31     mathematical dispersion model is  applied to an emissions inventory and meteorological data

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 I     to produce an estimate of ambient pollutant concentrations that can be expected at a specified
 2     point in space and time. In contrast, the receptor-oriented approach depends on simultaneous
 3     ambient concentration measurements of a variety of pollutant species,  and a knowledge of the
 4     relative amounts of the species (source profiles) that are present in the emissions of the
 5     sources that are potential contributors.  A mathematical receptor model operates on the
 6     source profile and ambient species concentration information to deconvolute the ambient
 7     concentrations into their source contributions, without the need of emissions inventory or
 8     meteorological information.  Indeed, the desire to avoid the latter two kinds of information,
 9     whose acquisition is often problematical, has been an important motivation in the
10     development of the receptor-oriented approach.
11          Although source apportionment in its general sense embraces both approaches, in recent
12     years it has come to be regarded as synonymous with the receptor-oriented approach
13     (receptor modeling).  The equivalence  of source apportionment and receptor modeling is
14     assumed in the following.  The most recent review of the field of receptor modeling has been
15     given by Gordon (1988).
16          Because tropospheric O3 is a secondary pollutant, the natural role of receptor modeling
17     is in determining the quantitative source contributions of the VOC precursors of O3.
18     Historically, receptor modeling was first developed in the 1970s for the apportionment of
19     ambient aerosol, and aerosol applications since then have been more extensive than VOC
20     applications.  The aerosol and VOC areas of receptor modeling application have more
21     similarities than  differences, however,  so that much of the mathematical apparatus that has
22     been developed for aerosol problems is readily adaptable to VOCs.
23          For reasons that will become apparent, the separation of emissions sources into
24     anthropogenic and biogenic classes is a natural division for VOC receptor modeling and is
25     used in the following.
26
27     3.4.3.1.1  Manmade Sources of Volatile Organic Compounds
28          A principal approach for receptor modeling of anthropogenic VOC sources is that of
29     "mass balance".  In this approach, a particular linear combination of source profiles is sought
30     that best approximates (in a linear least-squares sense) the profile of VOC species
31     concentrations measured in  an ambient sample.   Here a VOC  source profile is defined as the

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 1     set of numbers giving the fractional amounts (abundances) of individual species in the
 2     emissions from the source.  The profile may be normalized to the sum of the abundances of
 3     all VOC species emitted by the source or to a sum over some arbitrary subset of species.
 4     For the linear combination of profiles that gives the best fit, the coefficients are the source
 5     strengths (in the same units as  the measured ambient concentrations) associated with each of
 6     the included source profiles.
 7          Early efforts to use various versions of the mass balance approach include Ehrenfekl
 8     (1974), in Los Angeles; Mayrsohn and Crabtree (1976) and Mayrsohn et al. (1977), in
 9     Los Angeles; and Nelson et al. (1983), in Sydney, Australia.
10          Of these studies, the work of Mayrsohn et al. (1977) is the most comprehensive—
11     900 samples from eight sites collected during June to September, 1974. The average results
12     were:  automotive exhaust,  53%; whole gasoline evaporation, 12%; gasoline headspace
13     vapor, 10%; commercial natural gas, 5%; geogenic natural gas, 19%; liquefied natural gas,
14     1 %. The percentages are for NMHCs through C10 (i.e., not all of the total VOCs).
15          The estimates for the first three vehicle-related  sources together account for 75% of the
16     ambient NMHCs, which is  the approximate percentage estimated in the other studies listed.
17     Geogenic natural gas is obviously not anthropogenic but is included here for completeness.
18     Its strength (19 %) is striking.  It seems unlikely that a contribution this large would be
19     typical of other locales lacking a petroleum-related geology. In any case, accounting for the
20     urban atmospheric concentrations of ethane and propane (the main NMHC constituents of
21     natural gas) has remained an unsatisfactorily resolved problem, so that the 19% result for
22     geogenic natural gas has to  be  regarded skeptically.
23          Although old, these early studies are of more than just historical interest.  In one
24     respect, they are superior to more recent studies in their recognition of two distinctly
25     different kinds of gasoline evaporation: (1) headspace vapor, which represents the partial
26     evaporation of gasoline in situations such as storage tank evaporation or vehicle diurnal
27     evaporation, and is characterized by an enrichment of high  volatility species; and (2) whole
28     gasoline emissions, which can  arise from spillage, leakage, and vehicle hot-soak emissions,
29     and has a composition resembling liquid gasoline itself.  The implications of this are
30     discussed below.
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 1          In the mid-1980s, a useful degree of standardization was incorporated into the mass
 2     balance approach by the introduction of EPA's Chemical Mass Balance (CMS) software.
 3     The current version, CMB7 (Watson et al.,  1990), embodies a comprehensive treatment of
 4     error (including uncertainty in both ambient data and source profiles) and many diagnostics
 5     (including profile collinearity), and has been used frequently in recent VOC receptor
 6     modeling studies.
 7          Recent studies include Wadden et al. (1986), in Tokyo;  O'Shea and Scheff (1988), in
 8     Chicago; Aronian et al.  (1989), in Chicago; Sweet and Vermette (1992), in Chicago and East
 9     St. Louis, IL; Harley et al. (1992), in Los Angeles; Kenski et al.  (1993), in Chicago;
10     Beaumont, TX; Detroit; Atlanta; and Washington, DC;  Spicer et al. (1993), in Colombus,
11     OH; and Lewis et al. (1993), in Atlanta.
12          The source categories covered by these studies taken together include vehicle exhaust,
13     gasoline evaporation (whole gasoline and  headspace vapor), industrial emissions (refineries,
14     coke ovens, chemical plants), architectural coatings, dry cleaning, wastewater treatment,  auto
15     painting, industrial solvents/degreasers, graphic arts (printing), and natural gas.  Each study
16     gives estimates for the percentage contributions to measured ambient VOC (or related
17     quantity) for a selected subset of these source categories.  The one exception is the work of
18     Sweet and Vermette (1992), which estimates the percentage source contributions to individual
19     species, rather than to total VOC.  Such species apportionment is always available from the
20     CMB calculations, but is often not explicitly reported.
21          Usually the source profiles used were generic; that is, from compilations (e.g., U.S.
22     EPA, 1991) of source measurements taken elsewhere.  The work of Lewis et al. (1993) is
23     unique in the use of profiles extracted from the ambient air data themselves.
24          Generally,  for these urban-based studies, vehicle exhaust is found to be the dominant
25     contributor to ambient VOC. Exceptions are  the Tokyo results of Wadden et al. (1986),
26     which show an unreasonably  small average contribution of 7%, and the Beaumont results of
27     Kenski et al. (1993) at 14%.  For all the  rest, the average vehicle exhaust results  fall in the
28     range (45 ±  15%).
29          The results for gasoline evaporation contribution estimates are much less satisfactory.
30     This is because the recent studies, with the exceptions of Harley et al. (1992) and Lewis
31     et al. (1993), included a gasoline  headspace vapor profile but not a whole gasoline profile in

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 1     their calculations.  The latter two studies suggest that this omission is a serious error.  For
 2     example, Harley et al. (1992) find a remarkably large whole gasoline contribution (nearly the
 3     same as that of vehicle exhaust); and Lewis et al. (1993) find a whole gasoline contribution
 4     that is about 20% that of vehicle exhaust.  Both, however, find a whole gasoline contribution
 5     about four times greater than the headspace contribution. Because vehicle exhaust and whole
 6     gasoline profiles are  quite similar (except for the very light species that are absent in gasoline
 7     but present in exhaust as combustion products), excluding the whole  gasoline profile will
 8     tend to overestimate  the exhaust contribution.  Although this error may not greatly affect the
 9     total mobile source-related emissions estimate, it is misleading with regard to implied control
10     strategies.
11          Beyond the ubiquitous vehicle-related contributions, other anthropogenic source
12     contribution estimates tend to be smaller or locale-specific.
13
14     3.4.3.1.2  Biogenic Sources of Volatile Organic Compounds
15          The possible role of biogenic VOC emissions in O3 formation is being considered much
16     more seriously now (Chameides et al., 1988) than was the case a decade ago.  Because of
17     the severe experimental problems in accurately measuring biogenic emissions directly,
18     receptor modeling approaches are of considerable interest.  Compared with anthropogenic
19     sources, however, the application of receptor modeling methodology to biogenic sources has
20     been very limited. The principal reason is that it has not been possible to find VOC species
21     that are simultaneously (1) distinctive components of biogenic emissions,  (2) emitted in an
22     approximately fixed proportion to the total VOC biogenic emissions, and (3) relatively
23     unreactive.  Without these conditions, the construction of a credible stable biogenic  source
24     profile is not possible, and, consequently,  the CMB  approach is unusable.
25          In this situation, a crude form of receptor modeling has been used in which the ambient
26     concentration of a VOC species, whose only source  is thought to be  biogenic, is divided by
27     the estimated abundance of the  species in the total VOC biogenic emissions. Typical
28     candidates include isoprene (deciduous emission) and the terpenes a- and j8-pinene
29     (coniferous emission), 6-caranene, and limonene.  Because these are  all highly reactive, any
30     such estimate can only be regarded as a lower limit of the contribution that biogenic
31     emissions make to total ambient VOC, if the loss resulting from atmospheric transformation

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 1     is not taken into account.  As an example, Lewis et al. (1993) used isoprene, the most
 2     prominent biogenic species measured in downtown Atlanta during summer 1990, to infer a
 3     lower limit of 2 %  (24-h average) for the biogenic percentage of total ambient VOC at that
 4     location. Isoprene emissions have a strong diurnal dependence.  Lower limits for biogenic
 5     emissions at other  hours, inferred from average isoprene concentrations, were:  1 % at 8 am,
 6     5% at noon, 6% at 4 pm, 2% at 9 pm.
 7          The recent review article by Fehsenfeld et al. (1992) lists other prominent biogenic
 8     species, and calls attention to the newly recognized importance of alcohols such as methanol
 9     as biogenic primary emissions.  Goldan et al.  (1993) have reported the C5 alcohol,
10     2-methyl~3-buten-2-ol ("methyl butenol"), to be the most abundant VOC of biogenic origin
11     present in a predominantly lodgepole pine forest in Colorado.
12          A more sophisticated form of biogenic receptor modeling involves the radiocarbon
13     isotope 14C.  The approach depends on the fact that 14C constitutes a nearly fixed fraction
                         1 *t                                                            t A
14     (approximately 10" ) of all carbon present throughout the biosphere.  In contrast, the   C in
15     dead organic material older than 40,000 years, certainly the case for fossil fuels, has been
16     reduced by at least 99 % through radioactive decay. This leads to a simple estimate of the
17     biogenic fraction of a carbon-containing sample given by fg/f0 , where fg is the   C fraction
18     in the sample, and f0 is the 14C fraction in living material.  Besides its conceptual simplicity,
19     the approach is appealing for VOC apportionment because 14C retains its identity in the
20     reaction products that may result from atmospheric transformation  of reactive VOC.  The
21     method appears to be reliable for paniculate phase organics (Lewis et al., 1988; Lewis  et al.,
22     1991a), but is still under development for VOC applications (Klouda et al., 1993).
23
24     3.4.3.2  Source Reconciliation
25          Source reconciliation refers to the comparison of measured ambient VOC concentrations
26     with emissions inventory estimates of VOC source emission rates for the purpose of
27     validating the inventories. Because concentrations and emission rates are specified in
28     different units, the comparisons are done  in terms of percentages:  the percentage of a
29     source's  contribution to ambient total VOC as estimated by  receptor modeling versus the
30     source's  emission rate  as a percentage of the inventory's total VOC emission rate.
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 1          Nearly all the receptor modeling studies listed above have included such a percentage
 2     comparison.  Typically, the agreement is quite good for vehicle exhaust, generally the
 3     dominant VOC source in urban airsheds. Gasoline evaporation comparisons are much less
 4     consistent, at least partly for the reasons already indicated. Typically, there is at least
 5     qualitative agreement for the other anthropogenic sources: They are small in the inventory,
 6     and the receptor-estimated contributions are small,  An interesting exception is refinery
 7     emissions in Chicago (Scheff and Wadden, 1993), for which the receptor estimate was 7%,
 8     five times greater than the inventory estimate.  Another is the significant (5 to 20%) natural
 9     gas/propane contribution estimated in Los Angeles, Columbus, and Atlanta but not reflected
10     in their inventories.  The few biogenic source estimates provided by receptor modeling are
11     generally smaller than those given in emissions inventories, at least partly because of the
12     reactivity problem already referred to.  Credible   C measurements on VOC samples would
13     be extremely helpful in validating the magnitude of the biogenic component of emissions
14     inventories.
IS          Lewis et al. (1993) has noted that comparisons based on percentages are quite
16     insensitive for dominant source components,  and the comparisons are more dependent on
17     how "total VOC" is defined than is often appreciated (the definition varies for the studies
18     listed).  Thus, unfortunately, the generally good agreement (receptor versus inventory
19     estimates) found for vehicle exhaust does not translate into a definitive judgment on the
20     current concern that this source component may be significantly underestimated in existing
21     inventories.  For example, if the emission rate of vehicle exhaust in a typical inventory were
22     arbitrarily doubled, the resulting change in the percentage of this component in the inventory
23     is well within the range of what can be produced in the receptor estimate by merely  choosing
24     a different definition of "total VOC" from plausible alternatives. Such alternatives relate to
25     questions such as which subset of hydrocarbons are summed. Whether unidentified
26     chromatographic components are included in the sum, etc. In the future, this situation can
27     be improved by more consistency in the total VOC definition and by transforming the
28     receptor modeling results from a concentration-based representation to an emission-rate one.
29     This unavoidably involves introducing some  limited meteorological information (Lewis et al.,
30     1991b).
31

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 1     3.5   ANALYTICAL METHODS FOR OXIDANTS AND THEIR
 2           PRECURSORS
 3     3.5.1   Sampling and Analysis of Ozone and Other Oxidants
 4     3.5.1.1   Ozone
 5     3.5.1.1.1  Introduction
 6          The measurement of O3 in the atmosphere has been a subject of research for decades
 7     because of the importance of this compound in atmospheric chemistry and because of its
 8     potential and demonstrated effects on human health and welfare.
 9          Because of the importance of 03 in the air of populated regions, widespread
10     O3 monitoring networks have been operated for many years, and the development of
11     measurement and  calibration approaches for O3 has been extensively reviewed (e.g., U.S.
12     Environmental Protection Agency,  1986). This section focuses on the measurement of ozone
13     in the ambient atmosphere at ground level, and summarizes the current state of ambient
14     O3 measurement and calibration.  No attempt is made here to cover the full history of
15     development of these methods, since that has been documented elsewhere (e.g., U.S.
16     Environmental Protection Agency,  1978, 1986).  Instead, this section concentrates on those
17     methods currently used and  on new developments and novel approaches to O3 measurement.
18          Although no method is totally specific for 03, current methods for 03 must be
19     distinguished from earlier methods that measured "total oxidants".  The wet chemical
20     methods used earlier for total oxidants have been replaced for essentially all ambient
21     measurements by  two more  specific instrumental methods based on the principles of
22     chemiluminescence and ultraviolet (UV) absorption spectrometry. These two approaches are
23     described below.  In addition,  recent developments in spectroscopic measurements, in other
24     chemical approaches, and in passive sampling devices for O3 are described.
25
26     3.5.1.1.2   Chemiluminescence Methods
27          Gas-Phase Chemiluminescence.  The most common chemiluminescence method for
28     O3 is direct gas-phase reaction of O3 with an olefin to produce electronically  excited
29     products, which decay with  the emission of light.  This approach was first used nearly
30     30 years ago for chemical analysis by Nederbragt (Nederbragt et al.,  1965), and development
31     of a portable monitor (Warren and Babcock, 1970) and application to atmospheric

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 1     measurements (Stevens and Hodgeson, 1970) followed soon after.  Typically, an O3 monitor
 2     based on this approach functions by mixing a constant flow of about 1 L/min of sample air
 3     with a small constant flow (»50 cm3/min) of ethylene. Mixing occurs in a small inert
 4     reaction chamber fitted with a sealed window through which light can pass to the
 5     photocathode of a photomultiplier tube.  Electronically excited formaldehyde molecules,
 6     generated by a small fraction of the O3-ethylene reactions, produce a broad band of emission
 7     centered  at 430 nm.  The emission intensity is linearly proportional to the O3 concentration
 8     over the range of 0.001 ppm to at least 1 ppm.  Calibration of the monitor with a known
 9     ozone source provides the relationship between monitor response and ozone concentration.
10     Detection limits of 0.005  ppm and a response time of less than 30 s are easily attained, and
11     are typical of currently available commercial instruments.
12          Although no interference has been found from common atmospheric pollutants, a
13     positive interference from atmospheric water vapor has been reported (California Air
14     Resources Board,  1976; Kleindienst et al., 1993 and references therein) and has recently
15     been confirmed (Kleindienst et al., 1993). The recent results indicate a positive interference
16     of about  3% per percent H2O by volume at 25 °C. The results of Kleindienst et al. (1993)
17     were obtained at ozone concentrations of 0.085 to 0.32 ppm, and at I^O concentrations of
18     1 to 3%  (i.e., dew point temperatures of 9 to 24 °C).  It has been estimated that the
19     interference of water in ethylene chemiluminescent measurements at 30 °C and 60% relative
20     humidity could be as high as 13 ppbv of Oj, or 11 % of the O3 reading at 120 ppbv
21     (Kleindienst et al., 1993). Calibration with known O3 concentrations in air of temperature
22     and humidity similar to that of the sample air can minimize this source of error.
23          A separate potential problem with the ethylene chemiluminescent method is leakage of
24     the pure  ethylene reagent gas. Because ozone and hydrocarbon measurements are often
25     co-located for monitoring purposes, leakage of ethylene could cause difficulty in obtaining
26     valid  measurements of total nonmethane hydrocarbons (TNMHC) in ambient air.
27          The measurement principle set forth by EPA for compliance monitoring for O3 is the
28     chemiluminescence method using ethylene (Federal Register,  1971).  Methods of testing and
29     the required performance specifications that commercial O3 monitors must meet to be
30     designated a reference or equivalent method are documented (Federal Register, 1975).
31     A monitor may be designated a reference method if it employs gas-phase chemiluminescence

       December 1993                          3-116      DRAFT-DO NOT QUOTE OR CITE

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1     with ethylene as the measuring principle and achieves the required performance
2     specifications.  An equivalent method must show a consistent relationship with the reference
3     method and must meet the required performance specifications.  Table 3-15 shows those
4     specifications for Oj monitors. Note that ethylene chemiluminescence monitors typically have
5     response times far superior to that required in Table 3-15.
6
             TABLE 3-15. PERFORMANCE SPECIFICATIONS FOR AUTOMATED
      ^	METHODS OF OZONE ANALYSIS	

      Performance Parameter                Units                     Specification
      Range                              ppm                     0 to 0.5
      Noise                               ppm                        0.005
      Lower detectable limit                 ppm                        0.01
      Interference equivalent
        Each interference                   ppm                        ±0.02
        Total interference                   ppm                        0.06
      Zero drift,  12 and 24 h                ppm                        ±0.02
      Span drift,  24 h
        20% of upper range limit              %                         ±20.0
        80% of upper range limit              %                         ±5,0
      Lag time                             min                         20
      Rise time                             min                         15
      Fall time                             min                         15
      Precision
        20% of upper range limit            ppm                        0.01
        80% of upper range limit            ppm                        0.01
      Source:  Federal Register (1975); Code of Federal Regulations (1975); cited in U.S. Environmental Protection
             Agency (1986).
1          The list of commercial O3 monitors designated as reference or equivalent methods by
2     EPA is shown in Table 3-16 (updated as of February 8, 1993).  Details on three monitors not
3     described in the 1986 EPA criteria document for ozone and other oxidants are presented in
4     Table 3-17. All of the reference methods are ethylene chemiluminescence instruments, as
5     required by the definition of a reference method.  The equivalent methods are based on either
6     gas-solid chemiluminescence or UV absorption analyzer measurements. Those methods are
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          TABLE 3-16.  REFERENCE AND EQUIVALENT METHODS FOR OZONE
         DESIGNATED BY THE U.S. ENVIRONMENTAL PROTECTION AGENCY8
Method
(Principle)
Reference Methods
(Ethylene Chemiluminescence)
Beckman 950A
Bendix 8002
CSI2000
McMillan 1100-1
McMillan 1100-2
McMillan 1100-3
Meloy OA325-2R
Meloy OA350-2R
Monitor Labs 841 OE
Equivalent Methods
(UV Absorption)
Advanced Pollution Instr. 400
Dasibi 1003- AH, -PC, -RS
Dasibi 1008-AH,-PC,-RS
Environics 300
Lear-Siegler ML9810
Monitor Labs 8810
PQ Ozone Corp. LC-12
Thenno Electron 49
Equivalent Methods (Gas/Solid CL)
Philips PW9771
Designation
Number


RFOA-0577-020
RFOA-0176-007
RFOA-0279-036
RFOA-1076-014
RFOA-1076-015
RFOA-1076-016
RFOA-1075-003
RFOA-1075-004
RFOA-1 176-017


EQOA-0992-087
EQOA-0577-019
EAOA-0383-056
EQOA-0990-078
EQOA-0193-091
EQOA-0881-053
EQOA-0382-055
EQOA-0880-047

EQOA-0777-023
Method
Code


020
007
036
514
515
016
003
004
017


087
019
056
078
091
053
055
047

023
     aAs of February 1993.
1

2

3

4

5
described below. A gas-liquid chemiluminescence analyzer for O3, which was submitted for

EPA equivalency during 1993, is also described below.


    Gas-Solid Chemiluminescence,  The reaction of O3 with Rhodamine-B adsorbed on

activated silica gel produces chemiluminescence in the red region of the visible spectrum.

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                TABLE 3-17.  LIST OF DESIGNATED REFERENCE AND EQUIVALENT METHODS FOR OZONEa
1
cr
CD
vo
0
o
I
I
3
                                                                                              Federal Register
Designation
Number
Identification
Source
Manual
or Auto
Ref. or
Equiv.
Vol.
Page
Notice
Date
     EQOA-0990-078
~   EQOA-0992-087
"Environics Series 300 Computerized Ozone
Analyzer," operated on the 0-0.5 ppm range, with
the following parameters entered into the analyzer's
computer system:
Absorption Coefficient = 308 ± 4
Flue Time = 3 Integration Factor = 1
Offset Adjustment = 0.025 ppm
Ozone Average Time = 4
Signal Average + 0
Temp/Press  Correction =  On
and with or  without the RS-232  Serial Data
Interface

"Advanced Pollution Instrumentation, Inc. Model
400 Ozone Analyzer,"  operated  on any full-scale
range between 0-0.1 ppm  and 0-1 ppm, at any
temperature  in the range of 5 to 40 °C, with the
dynamic zero and span adjustment features set
OFF, with a 5-micron TFE filer element installed
in the rear-panel filter assembly, and with or
without any  of the following options:
Internal Zero/Span (IZS)
Rack Mount with Slides
RS-232 with Status Outputs
Zero/Span Valves
                                                                    Environics, Inc.
                                                                    165 River Road
                                                                    West Willington, CT
                                                                    06279
Auto
Equiv.
55
                                                                                                                          38386  09/18/90
                                                                    Advanced Pollution
                                                                    Instrumentation, Inc.
                                                                    8815 Production Avenue
                                                                    San Diego, CA  92121-
                                                                    2219
                                                                                           Auto
        Equiv.
              57
        44565  09/28/92
n

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       TABLE 3-17 (cont'd). LIST OF DESIGNATED REFERENCE AND EQUIVALENT METHODS FOR OZONE*
                                                                                                                   Federal Register
 Designation
 Number
Identification
Source
Manual
or Auto
Ref. or
Equiv.
Vol.
Page
Notice
 Date
 EQOA-0193-091    "Lear Siegler Measurement Controls Corporation
                   Model ML9810 Ozone Analyzer," operated on any
                   full-scale range between 0-0.050 ppmb and 0-1.0
                   ppm, with auto-ranging enabled or disabled, at any
                   temperature in the range of 15 °C to 35 °C, with a
                   5-micron Teflon filter element installed in the Miter
                   assembly behind the secondary panel, the  service
                   switch on the second panel set to the In position;
                   with the following menu choices selected:
                   Calibration; Manual or Timed:  Diagnostic Mode:
                   Operated; Filter Type: Kalman; Pres/Temp/Flow
                   Comp: On; Span Comp: Disabled;
                   With the  50-pin I/O board installed on the rear
                   panel configured at any of the following output
                   range  settings:
                   Voltage, 0.1 V, IV, 5V, 10V;
                   Current, 0-20 mA, 2-20 mA, 4-20 mA; and with
                   or without any of the following options:  Valve
                   Assembly for External Zero/Span (EZS) Rack
                   Mount Assembly
                   Internal Floppy Disk Drive
                             Lear Siegler Measurement
                             Controls Corp.
                             74 Inverness Drive East
                             Englewood, CO
                             80112-5189
                Auto
        Equiv.
           58
          6964  02/03/93
"Designated since publication of the 1986 EPA criteria document for ozone and other photochemical oxidants.
 Users should be aware that designation of this analyzer for operation on any full-scale range less than 0.5 ppm is based on meeting the same absolute
 performance specifications required for the 0-0.5 ppm range. Thus, designation of any full-scale range lower than the 0-0.5 ppm range does not imply
 commensurably better performance than that obtained on the 0-0.5 ppm range.

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 1     This was the first chemiluminescence method ever developed for ambient O3 measurement
 2     (Regener, 1960, 1964).  The emitted light intensity is linearly related to the
 3     63 concentration, and the detection limit can be as low as 0.001 ppm. No direct
 4     interferences from other gas-phase pollutants are known; however, decay  of the sensitivity
 5     because of surface aging  can occur (Hodgeson et al.,  1970). Addition of gallic acid to the
 6     surface stabilizes the response characteristics, apparently by allowing direct reaction of
 7     03 with the gallic acid, rather than with the Rhodamine-B (Bersis and Vassiliou,  1966).
 8     A commercial analyzer (Phillips Model PW9771) based on this approach  has been designated
 9     an equivalent method for ambient ozone (see Table 3-16), but gas-solid chemUuniinescence is
10     currently rarely used for  ambient measurements.
11
12          Gas-Liquid Chemiluminescence.  A recently developed commercial monitor uses the
13     chemiluminescent reaction of ozone with the dye eosin-Y in solution (Topham et  al., 1993).
14     The monitor functions by exposing a fabric wick, wetted with the eosin-Y solution, to a flow
15     of sample air within view of a red-sensitive photomultiplier tube.  The monitor, designated
16     the LOZ-3, is compact, portable, and requires no reagent gases.  The LOZ-3 provides very
17     fast response:  a lag time  of 2 s, rise time of 3 s, and fall time  of 2 s, all  relative to a step
18     change of 400 ppbv ozone, are reported (Topham et al., 1993).  Instrument noise at zero and
19     at 382 ppbv ozone is 0.05 ppbv or less, calculated as the standard deviation of 25 successive
20     2-min averages.  The precision of the LOZ-3 is reported to be 0.80 ppbv at 100 ppbv ozone,
21     and as 1.87 ppbv at 400 ppbv ozone, both calculated  as one standard deviation of six
22     repeated measurements at these levels (Topham et al., 1993).  The instrument provides linear
23     response up to 200 ppbv, with a gradually decreasing slope of the response curve above that
24     level.  Temperature and pressure sensitivity are corrected by internal circuitry (Topham
25     et al., 1993).  An initial large positive interference from SQj is reported, which becomes
26     smaller and negative as the eosin solution ages; and a positive  interference from CC^ is also
27     present.  Topham et al. (1993) report that a pretreatment technique applied to the eosin
28     reagent solution minimizes both of these interferences.  Several of the performance
29     characteristics of the LOZ-3 are impressive, but verification of the reported interference
30     levels  and the effectiveness of temperature and pressure corrections  appears to be needed.
31     This method was submitted for EPA equivalency certification during 1993.

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 1     3.5.1,1.3   VUmviolet Photometry
 2          This method is based on the fact that 03 has a reasonably strong absorption band with a
 3     maximum near 254 nm, coinciding with the strong emission line of a low-pressure mercury
 4     lamp.  The molar absorption coefficient at the mercury line is well known, the accepted
 5     value being 134 (±2) M^cm"1 in base 10 units at 0 °C and 1 atmosphere pressure (Hampson
 6     et al., 1973). Ultraviolet absorption has frequently been used to measure O3 in laboratory
 7     chemical and kinetics studies. Ultraviolet photometry was also used for some of the first
 8     atmospheric O3 measurements, but the early instruments suffered from poor precision
 9     because of the small absorbances being measured (U.S. Department of Health, Education,
10     and Welfare, 1970).
11          Modern digital electronics have now  solved the precision problems resulting from
12     measurement of small absorbances,  and several commercial O3 monitors now employ
13     UV photometry.  Several instruments based on this principle have been designated by EPA
14     as equivalent methods for ambient ozone (Tables 3-16 and 3-17).  Ultraviolet photometry is
15     now the predominant method for assessing compliance with the NAAQS for Oj. The
16     commercial monitors use pathlengths of 1 m or less, and operate in a sequential single-beam
17     mode. Transmission of 254 nm light through the sample air is averaged over a short period
18     of time (as short as a few seconds), and is compared to a subsequent transmission
19     measurement on  the same air stream from  which O3 has been selectively removed by a
20     manganese dioxide scrubber. The electronic comparison of the two signals can be converted
21     directly into a digital readout of the O3 concentration.  The method is in principle absolute,
22     since the absorption coefficient and  pathlength are accurately known and the measured
23     absorbance can be converted directly to a concentration.
24          Commercial UV photometers for ambient ozone measurements have detection limits of
25     approximately 0.005 ppm.  Time response depends on the averaging time used, but is
26     typically < 1 min.  Long-term precision can be within ±5%. The method has the advantage
27     of requiring no gas supplies, and commercial instruments are compact and reasonably
28     portable.  Sample air flow control is not critical, within the limitations of the MnO2
29     scrubber.  Since  the measurement is absolute, UV photometry is also used to assay
30     O3 calibration standards  as described below (Section 3.5.1.1.5).  Ambient air monitors using
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 1     UV photometry are generally calibrated with standard Oj mixtures to account for losses of
 2     O3 in sampling lines.
 3          A potential disadvantage of UV photometry is that any atmospheric constituent that
 4     absorbs 254 nm light and is removed fully or partially by the manganese dioxide scrubber
 5     will be a positive interference in O3 measurements.  Potential interferents include aromatic
 6     hydrocarbons, mercury vapor, and sulfur dioxide. A recent study (Kleindienst et al., 1993)
 7     demonstrated that toluene and possibly aromatic reaction products, such as benzaldehyde,
 8     produce positive interferences in UV photometric ozone measurements.  This result was
 9     found using photochernically  reactive mixtures of toluene and NOX, at concentrations a factor
10     of two to five higher than those expected in polluted urban air.  Consideration of the relative
11     absorption coefficients of O3  and the aromatics indicates that at higher humidities toluene can
12     cause an interference of 0.1 ppbv O3 per ppbv of toluene, whereas benzaldehyde may cause
13     an interference as high as 5 ppbv O3 per ppbv benzaldehyde (Kleindienst et al,,  1993). This
14     interference may be humidity dependent.  t In earlier work at very low humidities, no
15     interference was observed with toluene ai^d only a very small interference was observed with
16     benzaldehyde  (Grosjean and Harrison, 19J85). However, even at very low humidities these
17     investigators observed significant interferences from  styrene, cresols, and nitrocresols.
18     Evaluation of aromatic interference is limited by a lack of appropriate absorption spectra in
19     the 250 nm range, and by a lack of ambient  measurements of most of the aromatic
20     photochemical reaction products.  The us^ of ethylene chemiluminescence monitors in areas
21     where aromatic concentrations are substantial is suggested (Kleindienst et al., 1993).
22          The same study found no consistent]effect of ambient water vapor on measured
23     O3 concentrations using UV photometry, |in contrast to the effect noted using ethylene
24     chemiluminescence (Kleindienst et al., 1993). However, short-term disturbances in UV
25     photometric O3 readings were observed when the humidity of the sample air was changed
26     substantially within a few seconds.  This finding corroborates the observations of Meyer
27     et al. (1991) in an earlier study that indicated microscopic irregularities in the UV cell
28     windows as the cause of such disturbances.  This effect should be absent in UV photometric
29     measurements of ambient O3  at the ground, but could be important in other applications,
30     such as measuring vertical O3 profiles from an aircraft (Kleindienst et al., 1993).
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 1          A different approach to evaluating potential interferences in ozone measurements has
 2     been taken by Leston and OUison (1993), These investigators examined ambient ozone data
 3     from instruments of different measurement principles co-located at monitoring sites.  The
 4     focus of their study is the ozone "design value", the fourth highest daily maximum hourly
 5     value from a monitoring station within an urban area, which is established in the 1990 Clean
 6     Air Act Amendments as the basis for classification of the area relative to  attainment of the
 7     NAAQS for ozone.  Leston and OUison (1993) examined hourly ozone concentration data
 8     from co-located UV and ethylene chemiluminescence instruments, from 1989 and 1990 at a
 9     site in Madison, CT,  and from shorter periods at sites in East Hartford, CT, and
10     Mobile, AL.  They also examined 11 winter days of simultaneous ozone data from UV and
11     Luminox LQZ-3 instruments, from Long Beach, CA.  Leston and OUison (1993) reported
12     positive biases in the  UV data of 20 to 40 ppbv  Oj during "hot, humid, hazy conditions
13     typical of design value days," They proposed that most ozone data and all design values are
14     biased  high by known and suspected interferences, and that those interferences are
15     exacerbated by water vapor.  Leston and OUison (1993) argue that the interference in UV
16     measurements from benzene derivatives (e.g., styrene,  cresols, benzaldehyde, nitro-
17     aromatics) is poorly accounted for. For example, of these compounds, only styrene is
18     measured in the PAMS VOC monitoring network (Leston and Ollison, 1993).
19          Interferences of the magnitude suggested by Leston and Ollison  (1993) clearly would
20     have serious implications for monitoring of ambient ozone.  It is difficult to estimate whether
21     interferences in the UV method could be as high as suggested, in part because data are
                                           i
22     lacking on the ambient levels of potential interferents.  Many potential interferents are
23     photochemically reactive, and it is questionable whether such compounds could co-exist with
24     ozone in  sufficient quantities to constitute a significant interference. What is clear is that full
25     evaluation of interferences in UV and ethylene chemiluminescence methods will require
26     simultaneous measurements  of ozone, humidity, temperature, and speckled organic
27     compounds, and perhaps of other meteorological parameters and potential interferents.
28
29     3.5.1.1.4  Spectroscopie Methods for Ozone
30          Spectroscopie methods have the potential to provide direct, sensitive, and specific
31     measurements representative of broad areas, rather than of single monitoring sites. This

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 1     potential has led to investigation of spectroscopic approaches, primarily differential optical
 2     absorption spectrometry (DOAS), for ozone measurement.  Differential optical absorption
 3     spectrometry measures the absorption through an atmospheric path (typically 0.5 to 1.5 km)
 4     of two closely spaced wavelengths of light from an artificial source.  One wavelength is
 5     chosen to match an absorption line of the compound of interest, and the other is close to but
 6     off that line, and is used to account for atmospheric effects. Platt and Perner (1980) reported
 7     measurements of several atmospheric species, including ozone, by DOAS, and various
 8     investigators have applied the technique since then (Stevens et al., 1993, and references
 9     therein). Stevens et al. (1993) describe testing of a commercial DOAS instrument in North
10     Carolina in the fall of 1989.  Ozone was measured using wavelengths between 260 and
11     290 nm, over a 557-m path.  A detection limit for ozone of 1.5 ppbv was reported, based on
12     a 1-min averaging time (Stevens et al.,  1993).  Comparison of DOAS results to those from a
13     UV absorption instrument showed (DOAS ozone) = 0.90 x (UV ozone) — 2.5 ppbv, with a
14     correlation coefficient (r2) of 0.89, at ozone levels up to 50 ppbv.  The sensitivity, multiple
15     analytical capability, stability, and speed of response of the DOAS method are attractive,
16     though further intercomparisons and interference tests are recommended (Stevens et al.,
17     1993).
18
19     3.5,1.1.5  Passive Samplers for Ozone
20          A passive sampler is one that depends on diffusion of the analyte in air to a collecting
21     or indicating medium.  In general, passive samplers  are not adequate for compliance
22     monitoring purposes because of limitations in specificity and averaging time.  However,
23     passive sampling devices (PSDs) for O3 are of value as a means of obtaining personal human
24     exposure data for O3 and as a means of obtaining long-term O3 measurements in areas where
25     the use of instrumental methods is not feasible.  Estimation of long-term population exposure
26     and ecological monitoring for vegetation effects of ozone in remote areas are examples of me
27     latter application.  Passive sampling devices have the advantages of simplicity, small size,
28     and low cost, but may also present disadvantages,  such  as poor precision, loss of
29     effectiveness during use or storage, and interference from other atmospheric constituents.
30     Passive samplers for measuring O3 at ambient concentrations are now commercially
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 1     available.  No PSD has been fully validated, however, to the point of acceptance as an
 2     equivalent method for O3.
 3          The Ogawa PSD for O3 (Ogawa, Inc., Pompano Beach, FL) contains 0.1 mL of a
 4     solution of sodium nitrite and sodium carbonate in glycerine on glass fiber filter paper. The
 5     nitrite ion reacts with O3 to form nitrate.  Following exposure, the PSDs are analyzed by
 6     extraction of the nitrate with deionized water, followed by ion chromatographic analysis.
 7     In a comparative ambient O3 study over 24 weeks, this PSD demonstrated agreement within
 8     about 10% with the weekly real-time measurements taken by a UV O3 monitor (Mulik et al.,
 9     1991). Extension of these  measurements to a full year produced  similar results (Mulik et al.,
10     1991). The standard  deviation of weekly average measurements by three collocated PSD
11     samplers ranged from about ±1  to ±6 ppb, at weekly average Oj levels of 12 to 45 ppb
12     (Mulik et al. 1991).   The Ogawa PSD was also used in a study of personal exposure to
13     indoor and outdoor O3, showing a correlation of r = 0.91, and relative errors of 15 %
14     (daytime) and 25% (nighttime) relative to UV photometric data (Liu et al., 1992).
15          Another PSD for O3 has been developed that is based on the use of a colorant that
16     fades when exposed to O3 (Grosjean and Hisham,  1992; Grosjean and Williams, 1992).  The
17     plastic badge-type PSD contains  a diffusion barrier and a colorant-coated filter as the
18     O3 trap.  The colorant used is indigo carmine (5,5'-disulfonate sodium salt of indigo, X max
19     = 608 nm).  With a plastic grid or Teflon filter as the diffusion barrier, detection limits of
20     30 ppb-day and 120 ppb-day, respectively, are achieved. Interferences from NO2,
21     formaldehyde, and PAN are 15,  4, and 16%, respectively, of the ambient interferant
22     concentrations.  For sampling ambient O3 in most locations, these interferences are probably
23     negligible (Grosjean and Hisham, 1992).  Following sampling, the color change is measured
24     by reflectance spectroscopy and  no chemical analysis is required.  The reported shelf life is
25     3  mo prior to O3 exposure and 12 mo after 63 exposure (Grosjean and Hisham,  1992).
26          Field tests of the indigo carmine PSD were conducted at five forest locations in
27     California in the summer of 1990 (Grosjean and Williams, 1992). During these  tests,
28     ambient ozone ranged up to 250 ppbv; 3-day average ozone values at the sites ranged from
29     40 to 88 ppbv.  The precision of the measurements was ±12% based on 42 sets of collocated
30     samplers,  over sampling durations of 3 to 30 days. The color change in the PSD was highly
31     correlated (R = 0.99) with ozone dose as measured by UV photometry.  No effect of

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 1     ambient temperature or humidity variations was observed, and the total interference caused
 2     by other pollutants (NC^, PAN, aldehydes) was less than 5 %.
 3          A third PSD for ozone has also been recently developed, based on color formation from
 4     the reaction of O3 with an aromatic amine (Kirollos and Attar,  1991).  The ChromoSense™
 5     direct-read passive dosimeter is a credit-card-sized device that changes color proportionally to
 6     the integrated dose of exposure of the specific toxic material for which it was designed (U.S.
 7     Patent 4,772,560). The dosimeter consists of an outer polyester pouch that encloses a
 8     polymeric plate with a sorbant and membrane.  A filtering layer is coated on the membrane
 9     to reduce the sensitivity of the detection process to nitrogen dioxide.  The chromophoric
10     layer, consisting of an aromatic amine that can react with ozone and form color, is
11     encapsulated so as to create a very high surface area.  A polymeric barrier separates the
12     chromophore from a UV-absorbing layer to reduce their interaction.  The UV absorber (in a
13     polymeric matrix) helps stabilize the chromophore toward intense light exposure when the
14     device is used outdoors.  The transparent polymeric plate keeps the wafer flat and allows
15     uninterrupted optical viewing of the color of the reference and the sample area.
16     An electronic reading device measures color on both the exposed (sample) and unexposed
17     (reference) areas, and displays a digital reading that is proportional to the log of the 03 dose.
18     Visible color is formed at doses as low as 20 ppb-h.  No interference from NC^  is observed
19     at NO2 concentrations up to 350 ppb, and only a  small effect of ambient humidity has been
20     reported (Kirollos and Attar,  1991).  No data on precision have yet been reported.
21
22     3.5.1.1.6   Calibration Methods for Owm
23          Since it is an unstable molecule and cannot be stored,  O3 must be generated at the time
24     of use to produce calibration mixtures.  Electrical discharges in air or oxygen readily
25     produce O3, but at concentrations  far too high for calibration of ambient monitors.
26     Radiochemical methods are expensive and require the use of radioactive sources,  with
27     associated safety requirements.  For calibration purposes, low levels of 63 are nearly always
28     generated by photolysis of oxygen at wavelengths < 200 nm.  Placing a mercury  lamp near a
29     quartz tube through which air is flowing produces small amounts of O3  in the airstream.
30     Commercial O3 sources based on this approach typically adjust the lamp current to  control
31     the amount of light transmitted, and thus the  Oj produced.

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 1          Once a stable, low concentration of O3 has been produced from a photolytic generator,
 2     that 03 output must be established by measurement with an absolute reference method. The
 3     original reference calibration procedure promulgated by EPA in 1971 (Federal Register,
 4     1971) was an iodometric procedure, employing 1 % aqueous neutral buffered potassium
 5     iodide (NBKI).  A large number of studies conducted in the 1970s revealed several
 6     deficiencies with KI methods, the most notable of which were poor precision or
 7     interlaboratory comparability and a positive bias of NBKI measurements  relative to
 8     simultaneous absolute UV absorption measurements.
 9          Following investigations of problems with the NBKI method, EPA  evaluated four
10     potential reference calibration procedures and selected UV photometry on the basis of
11     superior accuracy and precision and simplicity of use (Retime et al., 1981). In 1979, UV
12     photometry was designated the reference calibration procedure by EPA (Federal Register,
13     1979).
14          The measurement principle of UV O3 photometers used as reference standards is
15     identical to that of O3 photometers used for ambient measurements (see Section 3.5.1.1.3).
16     A laboratory photometer used as a reference standard will typically contain a long-path cell
17     (1 to 5 m) and employ sophisticated digital techniques for making effective double-beam
18     measurements of small absorbances at low O3 concentrations.
19          A primary reference standard is a UV photometer that meets the requirements set forth
20     in the 1979 revision designating  UV photometry as the reference method (Federal Register,
21     1979). Commercially available O3 photometers that meet those requirements may function as
22     primary standards.  The EPA and the National Institute of Standards and Technology (NIST,
23     formerly National Bureau of Standards [NBS]) have established a nationwide network of
24     Standard Reference Photometers (SRPs) that are used to verify local primary standards and
25     transfer standards.  A secondary or transfer standard is a device or method that can be
26     calibrated  against the primary standard, and then moved to another location for calibration of
27     03 monitors.  Commercial UV photometers for Oj are often used as secondary or transfer
28     standards, as are commercial photolytic ozone generators and apparatus for the gas-phase
29     titration of O3 with nitric oxide (NO).
30          The latter method, gas-phase titration (GPT)  of 03 with NO (NO + O3 -* NO2 + O2),
31     is a direct and absolute means of determining Oj, provided NO is in excess so that no side

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 1     reactions occur. Under such conditions, GPT has the advantage that measurement of the NO
 2     or O3 consumed or the NO2 produced gives a simultaneous measurement of the other two
 3     species. All three modes have been used, and this method is often used for calibration of
 4     NO/NOX analyzers.  Gas-phase titration has been compared to UV photometry in several
 5     studies. The most detailed study is that of Fried and Hodgeson (1982), who used an NBS
 6     primary standard UV photometer, highly accurate flow measurements, photoacoustic
 7     detection of NC^, and NBS (now NIST) Standard Reference Materials as sources of NO and
 8     NO2, That study showed that decreases in O3 as measured by the UV method averaged
 9     3.6% lower than the corresponding decrease in NO and increase in NO2 measured
10     independently. Because of uncertainty about  the origin of the small bias relative to UV
11     photometry, GPT is used as a transfer standard but not as a primary reference standard.
12
13     3.5.1.2  Peroxyacetyl Nitrate and Its Homologues
14          During laboratory organic photooxidation studies, Stephens et al. (1956a,b) determined
15     the presence of a number of alkyl nitrates and an unidentified species called "Compound X".
16     The presence  of "Compound X" in the atmosphere of Los Angeles was confirmed by Scott
17     et al, (1957).  In later work (Stephens et al.,  1961) its structure was determined and
18     "Compound X" was  named peroxyacetyl nitrate (PAN).  Since the discovery of PAN much
19     effort has been directed toward its atmospheric measurement.  In the following subsections
20     PAN measurement and calibration techniques are described.  The discussion on measurement
21     techniques includes a summary description, identifies limits of detection, specificity
22     (interferences), reproducibility and accuracy of each method. The relative merits of each
23     method are also presented.  The subsection on calibration techniques includes those methods
24     most often employed during ambient air measurement studies.
25
26     3.5.1.2.1   Measurement Methods
21          Two methods have been generally employed to make atmospheric measurements of
28     PAN.  These methods are infrared spectroscopy  (IR) and gas chromatography (GC).
29     Infrared spectroscopy permits the sampling and analysis to be conducted in real time.  Since
30     PAN is very reactive in the gas phase and exhibits surface adsorptive effects, the minimal
31     contact time offered  by IR makes this method very attractive.  However, IR instrumentation

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 1     is expensive and complex and requires a good deal of space.  On the other hand, gas
 2     chromatography is inexpensive and requires minimal space and operator training.  A PAN
 3     GC can be set up  to automatically sample and analyze air every 10 to 15 min. Application
 4     of these methods for obtaining ambient concentrations of PAN has recently been reviewed by
 5     Roberts (1990).
 6
 7          Infrared Spectroscopy.  Conventional long-path infrared spectroscopy and FI1R have
 8     been used to detect and measure atmospheric PAN.  Sensitivity is enhanced by the use of
 9     FUR.  The most frequently used IR bands have been assigned and the absorptivities reported
10     in the literature (Stephens, 1964; Bruckmann and WiUner, 1983; Holdren and Spicer,  1984;
11     Niki et al., 1985;  Tsatkani et al., 1989) permit the quantitative analysis of PAN without
12     calibration standards.  Tuazon et al. (1978) have described an FTIR system operable at
13     pathlengths up to 2 km for ambient measurements of PAN and other trace constituents.  This
14     system employed an eight-mirror multiple reflection cell with a 22.5-m base path.  The
15     spectral windows  available at pathlengths of 1 km were 760 to 1,300, 2,000 to 2,230 cm"1.
16     Thus, PAN could be detected by the bands at 793 and  1,162 cm"1. The 793  cm"1 band is
17     characteristic of peroxynitrates, while the 1,162 cm"1 band is reportedly caused by PAN only
18     (Stephens, 1969; Hanst et al., 1982),  Tuazon et al. (I981a,b) reported ambient
19     measurements with this system during a smog episode in Claremont, California, in 1978.
20     Maximum daily PAN concentrations ranged from 6 to 37 ppb over a 5-day episode.
21     A detection limit for PAN was 3 ppb at a pathlength of ~ 1 kilometer.  Hanst et al. (1982)
22     modified the FTIR system used by Tuazon by changing it from an eight-mirror to a
23     three-mirror cell configuration and by considerably reducing the cell volume. A detection
24     limit for PAN was increased to 1 ppb at a similar pathlength.
25          The limited sensitivity (-1 ppb) and the complexity of the above FITR systems have
26     generally limited their field use to urban areas such as Los Angeles. More recently,
27     cryogenic sampling and matrix-isolation FITR has been used to measure PAN in 15-L
28     integrated samples of ambient air. The matrix isolation technique has a theoretical level of
29     detection of -50 ppt (Griffith and Schuster, 1987).
30
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 1          Gas Chromatography-Electron Capture Detection.  Peroxyacetyl nitrate is normally
 2     measured by using a gas chromatograph coupled to an electron capture detector (GC/ECD).
 3     The method was originally described by Darley et al. (1963) and has subsequently been
 4     refined and employed by scientists over the years. Key features of the method remain
 5     unchanged. The column and detector temperatures are kept relatively low (—50 ° and
 6     100 °C, respectively) to minimize PAN thermal decomposition. Short columns of either
 7     glass or Teflon are generally used (1 to 5 ft in length). Finally, column packing normally
 8     includes a Carbowax stationary phase coated onto a deactivated solid support. Using packed
 9     columns, detection limits of 10 ppt have been reported using direct sampling with a 20-mL
10     sample loop (Vierkorn-Rudolph et al., 1985). Detection limits were further extended  to 1 to
11     5 ppt using cryogenic enrichment of samples (Vierkorn-Rudolph et al., 1985; Singh and
12     Salas, 1983).  These studies have found only slight overall losses of PAN (10 to 20%)
13     associated with cryosampling, provided samples are warmed only to room temperature during
14     desorption.
15          Recently, improved precision and sensitivity have been reported using fused-silica
16     capillary columns instead of packed columns (Helmig et al.,  1989; Roberts et al., 1989).
17     Signal-to-noise enhancement of 20 has been claimed (Roberts et al., 1989).
18
19          Gas Chromatography-AUernate Detection.  As noted earlier, PAN is readily reduced to
20     NO in the gas phase.  To separate PAN, NO, and NO2, Meyrahn  et al. (1987) have coupled
21     a GC with a molybdenum converter; and used a chemiluminescent analyzer to measure PAN
22     as NO.  Using a 10 mL sample loop, a detection limit of 10 ppb was reported.
23          A luminol-based detector has also shown sensitivity to PAN.  Burkhardt et al. (1988)
24     used gas chromatography and a commercially available luminol-based instrument (i.e.,
25     Scintrex LMA-3 Lummox) to detect both NO2 and PAN. Using a sampling interval of 40 s,
26     linear response was claimed from 0,2 to 170 ppb NO2 and from 1  to  65 ppb PAN. Although
27     the PAN calibration was nonlinear below 1 ppb, a detection level of 0.12 ppb was reported.
28     Drummond et al. (1989) have slightly modified the above approach by converting the PAN
29     from the GC column to NO2 and measuring the resulting NO2  with a luminol-based
30     instrument.
31

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 1     3.5.1.2.2   Peroxyacetyl Nitrate Stability
 2          Peroxyacetyl nitrate is an unstable gas and is subject to surface-related decomposition as
 3     well as thermal instability.  Peroxyacetyl nitrate exists in a temperature-sensitive equilibrium
 4     with the peroxyacetyl radical and NO2 (Cox and Roffey, 1977). Increased temperature
 5     favors the peroxyacetyl radical and NO2 at the expense of PAN.  Added NO2 should force
 6     the equilibrium toward PAN and enhance its stability. In the presence of NO, peroxyacetyl
 7     radicals react rapidly to form NO2 and acetoxy radicals, which decompose in O2 to radicals
 8     that also convert NO to NO2.  As a result, the presence of NO acts to reduce PAN stability
 9     and enhance its decay rate (Lonneman et al., 1982).  Stephens (1969) reported that
10     appreciable PAN loss in a metal sampling valve was traced to decomposition on a silver-
11     soldered joint. Meyrahn et al. (1987) reported that PAN decayed according to first-order
12     kinetics at a rate of 2 to 4%/h in glass vessels and they suggested first-order decay as the
13     basis for a proposed method of in-field PAN calibration.  In contrast, Holdren and Spicer
14     (1984)  found that without NO2 added, 20 ppb PAN decayed in Tedlar bags according to
15     first- order kinetics at a rate of 40%/h.  The addition of 100 ppb NO2 acted to stabilize the
16     PAN (20 ppb) in the Tedlar bags.
17          A humidity-related difference in GC-ECD response has been reported (Holdren and
18     Rasmussen, 1976).  Low responses  observed at humidities below 30% and PAN
19     concentrations of 10 and 100 ppb, but not 1,000 ppb, were attributed to sample-column
20     interactions,  A humidity effect was alluded to by Nieboer and Van Ham (1976) but details
21     were not given. No humidity effect was observed by Lonneman (1977).  Watanabe and
22     Stephens (1978) conducted experiments at 140 ppb and did not conclude that the reduced
23     response was from faults in the detector or the instrument.  They concluded that there was no
24     column-related effect, and they observed surface-related sorption by PAN at 140 ppb in dry
25     acid-washed glass flasks.  They recommended that moist air be used to prepare PAN
26     calibration  mixtures to avoid potential surface-mediated effects.
27          Another surface-related effect  has been reported for PAN analyses of remote marine air
28     (Singh and Viezee, 1988).  Peroxyacetyl nitrate concentrations were found to increase by
29     20 to 170 ppt, an average factor of 3, when the sample was stored in a  glass vessel  for 1 to
30     2 min prior to analysis. This effect remains to be explained.
31

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 1     3.5.1.2,3  Preparation and Calibration
 2          Because PAN is unstable, the preparation of reliable calibration standards is difficult.
 3     The more promising methods are described here.  The original method used the photolysis of
 4     ethyl nitrite in pure oxygen (Stephens, 1969). When pure PAN is desired, the reaction
 5     mixture must be purified, usually by chromatography, to remove the major by-products,
 6     acetaldehyde and methyl and ethyl nitrates (Stephens et al.s 1965). For GC calibration,
 7     purification is unnecessary; the PAN concentration in the reactant matrix is established from
 8     the IR absorption spectrum and subsequently diluted to the parts-per-billion working range
 9     needed for calibration purposes (Stephens and Price, 1973).
10          Static mixtures of molecular chlorine, acetaldehyde, and NO2 in the ratio of 2:4:4 can
11     be photolyzed in the presence of a slight excess NO2 to give  a near-stoichiometric yield of
12     PAN (Gay et al.,  1976).  This method was adapted by Singh and Salas (1983) and later by
13     Grosjean et al. (1984) using photolytic reactors to provide continuous PAN calibration units
14     at concentrations between 2 and 400 ppb. In the former approach, the PAN concentration is
IS     established by measuring the change in acetaldehyde concentration across the reactor.  In the
16     latter,  the PAN concentration is established by measuring the acetate in an alkaline bubbler
17     where  PAN is hydrolyzed.
18          A static technique involving the photolysis of acetone hi the presence of NO2 and air at
19     250 nm has been reported to produce a constant concentration of PAN (Meyrahn et al.,
20     1987; Wameck and Zerbach,  1992).  A Penray mercury lamp is inserted into a mixture of
21     10 ppm NO2 and 1 % acetone and irradiated for 3 min to yield 8.9 ±  0.3 ppm PAN.
22          Peroxyacetyl nitrate can be synthesized in the condensed phase by the nitration of
23     peracetic acid in hexane (Helmig et al., 1989), heptane (Nielsen et al., 1982),  octane
24     (Holdren and Spicer, 1984), or /z-tridecane (Gaffney et al., 1984). Purification of PAN in
25     the liquid phase is needed using the first two methods.  The resulting  PAN-organic solution
26     can be stored at -20 to -80  °C with losses of less than 3.6%/mo and can be injected directly
27     into a vessel containing air to produce a calibration mixture.  The  PAN concentration is
28     normally established by FTIR analysis of the solution or the resulting PAN-air mixture.
29          Peroxyacetyl nitrate readily disassociates to NO, and chemiluminescence NOX analyzers
30     have near-quantitative response to PAN.  Thus under some circumstances, chemiluminescent
31     NOX response can be used for PAN calibration.  One method uses the difference in NOX

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 1     signal measured upstream and downstream of an alkaline bubbler (Grosjean and Harrison,
 2     1985a). Joos et al. (1986) have coupled a chemiluminescence NOX analyzer with a GC
 3     system to permit calibration of the BCD response by reference to the chemiluminescence
 4     NOX analyzer that has been calibrated by traditional methods.
 5          As noted previously, NO in the presence of PAN is converted to NO2. Approximately
 6     four molecules of NO can react per molecule of PAN.  Lonneman et al. (1982) devised a
 7     PAN calibration procedure based on the reaction of PAN with NO in the presence of
 8     benzaldehyde, which is added to control unwanted radical chemistry and improve precision.
 9     Using this approach and an initial NO-to-PAN ratio between 10 and 20 to 1, the change in
10     NO concentration is monitored with a chemiluminescence NO analyzer, the change in PAN
11     GC-ECD response is monitored, and the resulting ratio (i.e., ANO/APAN) is divided by the
12     stoichiometric factor of 4.7 to arrive at & calibration factor for the BCD.
13          Peroxyacetyl nitrate and n-propyl nitrate  (NPN) have similar BCD responses.  Serial
14     dilution of the more stable compound, NPN, has been used for field operations
15     (Vierkorn-Rudolph et al., 1985).  This approach is not recommended for primary calibration,
16     however, because it does not permit verification of quantitative delivery of PAN to the
17     detector (Stephens and Price, 1973).
18
19     3.5.1.3  Gaseous Hydrogen Peroxide
20          Although O3 has long been considered to be the primary oxidant affecting air quality,
21     atmospheric chemists recently have identified H2O2, a photochemical reaction product as
22     another oxidant that may also play a significant role in diminishing air quality.  In order to
23     assess the role of atmospheric H2O2, good measurement methods are needed.  Early
24     measurements in the 1970s reported H2O2 concentrations ranging from 10 to 180 ppb (Gay
25     and Bufalini,  1972  a,b; Kok et al., 1978 a,b).  However, these measurements are in error
26     because of artifact formation  of H2O2 from reactions of absorbed gaseous 03 (Zika and
27     Saltzman, 1982; Heikes et al., 1982, Heikes, 1984).  Modeling results also indicate that
28     H2O2 atmospheric concentrations should be on the order of 1 ppb (Chameides and Tan,
29     1981; Logan et al., 1981).
30          In the following section, the discussion focuses on those sampling and analytical
31     methods most frequently used within the last decade to determine atmospheric levels of

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 1     H2O2.  The measurement techniques are described and limits of detection, specificity
 2     (interferences) reproducibility and accuracy are discussed.
 3
 4     3.5.1.3.1   Measurement Methods
 5          In-situ measurement methods that have been employed for determining gaseous H2O2
 6     include both FUR and tunable diode laser absorption spectrometry (TDLAS).  Four methods
 7     involving sample collection via wet chemical means and subsequent analysis via
 8     chemiluminescent or fluorescent detection have also been frequently used. These methods
 9     are the (1) luminol; (2) peroxyoxalate; (3) enzyme-catalyzed (peroxidase); and (4) benzoic
10     acid-fenton reagent methods.  Application of most of these methods for obtaining ambient
11     concentrations of H2O2 has recently been reviewed by Sakugawa et al. (1990) and Gunz and
12     Hoffmann (1990).
13
14          In-Situ Methods,  Fourier transform infrared spectroscopy was employed in the early
15     1980's for atmospheric measurements (Tuazon et al., 1980; Hanst et al., 1982).  Even
16     though the FTIR is very specific for H2O2, it saw limited use because of the high detection
17     level of -50 ppb when using a 1-km path length. The TDLAS also has very high specificity
18     for H2O2 and was subsequently evaluated and shown to have a much improved detection
19     limit of 0.1 ppb when  using scan averaging times of several minutes (Slemr et al.,  1986;
20     MacKay and Schiff,  1987; Schiff et al., 1987).
21
22          Wet Chemical Methods.  Numerous wet chemical techniques for measuring H2O2 have
23     been reported. However, discussion in this section is limited to the four approaches most
24     frequently used by researchers.
25
26          Luminol Method. Hydrogen peroxide concentrations in the atmosphere have been
27     determined by the chemiluminescent response obtained from the catalyzed oxidation of
28     luminol (5-amino-2,3-dihydro-l,4-phthalazinedione) by H2O2.  Copper (II) (Armstrong and
29     Humphreys, 1965; Kok et al., 1978 a,b; Das et al.,  1982), as well as hem in, a blood
30     component (Yoshizumi et al., 1984), have been reported  as catalysts for the luminol-based
31     H2O2 oxidation.  Method sensitivity of —0.01 ppb has been achieved. Interference from

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 1     O3, SO2, metal ions and high pH have been reported along with ways to mitigate these
 2     effects (Heikes et al., 1982; Zika and Saltzman, 1982; Ibusuki,  1983; Lazaras et al., 1985;
 3     Aoyanagi and Mitsushima, 1987; Hoshino and Hinze, 1987).
 4
 5          Peroxyoxalate Method. The peroxyoxalate chemiluminescence method has also been
 6     employed by a number of researchers (Rauhut et al., 1967; Scott et al., 1980; Klockow and
 7     Jacob, 1986). Hydrogen peroxide reacts with bis(2,4,5-trichloro-6-phenyl)-oxalate to form a
 8     high-energy dioxetanedione (Stauff and Jaeschke, 1972).  The chemiluminescenee is
 9     transmitted to the fluorophore, perylene, which emits light upon return to the ground state.
10     Method sensitivity of —0.01  ppb is achieved and no interferences are observed from O3 and
11     metal ions. A signal depression has been reported for trace levels of nitrite (> 10*  M),
12     sulfite (> 10"4 M),  and formaldehyde (> 10"3 M) (Klockow and Jackob, 1986).
13
14          Enzyme-Catalyzed  Method (Peroxidase). This general method involves three
15     components:  a  substrate that is oxidizable; the enzyme, horseradish peroxidase (HRP); and
16     hydrogen peroxide.  The production or decay  of the fluorescence intensity of the substrate or
17     reaction product is  measured  as it is oxidized by H2O2, catalyzed by HRP.  Some of the
18     more widely used chromogenic substrates have been scopoletin (6-methoxy-7-hydroxy-l,2-
19     benzopyrone) (Andreae,  1955; Perschke and Broda, 1961); 3-(p-hydroxphenyl)propionic acid
20     (HPPA) (Zaitsu and Okhura,  1980); leuco crystal violet (LCV)  (Mottola et al., 1970); and
21     p-hydroxyphenylacetic acid (POPHA) (Guilbault et al., 1968).
22          Of the chromogens used, POPHA is one of the better indicating substrates.  Hydrogen
23     peroxide oxidizes the peroxidase and is itself reduced by electron transfer from POPHA.
24     The POPHA radicals form a  dimer that is highly fluorescent.  Since the chemical reaction is
25     sensitive to both H2O2 and organic peroxides, a dual channel system with a H2O2 removal
26     step (use of catalase) is used  to distinguish H2O2 from organic peroxides (Lazarus et al.,
27     1985; Wei and Weihan,  1987; Dasgupta and Hwang, 1985; Kok et al., 1986).
28          The peroxidase-POPHA-fluorescence technique has been used by several groups to
29     measure gas-phase  H2O2 concentrations (Lazarus et al., 1986; Tanner et al., 1986; Heikes
30     et al., 1987; Van Valin et al., 1987; Dasgupta et al., 1988). Method detection levels range
31     from 0.01 to 0.1 ppb.  However, artifact formation does occur as a result of the reaction of

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 1     dissolved O3 in the collection devices (Staehelin and Hoigne, 1982; Heikes, 1984; Gay et al,,
 2     1988).  To overcome the O3 interference researchers have used NO to eliminate 03 (Tanner,
 3     1984; Tanner et al., 1986; Shen et al., 1988).
 4
 5          Fenton Reagent-Isomeric Hydroxybenzoic Acids Method. This technique involves the
 6     formation of aqueous OH radicals from the reaction of Fenton reagent (Fe(n) complex) with
 7     gaseous H2O2.  The OH radicals in turn react with benzoic acid (hydroxyl radical scavenger)
 8     to form isomeric hydroxybenzoic acids (OHBA). The OHBA fluoresces weakly at the pH
 9     necessary to carry out the above reactions.  Fluorescence is enhanced by adding NaOH to the
10     product stream (Lee et al., 1990) or by using a low pH Al(in) fluorescence enhancing
11     reagent (Lee et al., 1993).
12
13     3.5.1.3.2   Comparison of Methods
14          The above techniques have been shown to measure H2O2 in the atmosphere with
15     detection levels of «0.1 ppb. Kleindienst et al. (1988) have compared  several of these
16     techniques using three sources of H2O2: (1) zero air in the presence and absence of common
17     interferences, (2) steady-state irradiations of hydrocarbon-NOx mixtures, and (3) ambient air.
18     The measurements were conducted simultaneously from a common manifold.  For pure
19     samples in zero air, agreement within 23% was achieved among methods over a
20     concentration range of 0.06 to 128 ppb.  A negative SO2 interference was caused with the
21     luminol technique. During the irradiation experiment, significant concentrations of organic
22     peroxides were generated and the agreement among techniques for H2O2 was very poor. For
23     ambient measurements,  the methods agreed reasonably well with an average deviation of
24     30% from the mean values.
25          Atmospheric intercomparison studies have also been conducted as  part of the Carbon
26     Species Methods Comparison Study  (Calif, 1986).  The results of the study indicated that the
27     wet chemical methods still suffer from sampling artifacts and interferences from other
28     atmospheric constituents (Dasgupta et al., 1990; MacKay et al., 1990; Kok et al., 1990;
29     Sakugawa et al., 1990; Tanner et al., 1990).  It is clear from the above studies that further
30     comparisons of techniques are needed to resolve questions of errors and provide improved
31     measurement techniques.

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 1     3.5.1.3.3   Calibration Methods
 2          The most frequently used method for generating aqueous standards is simply the serial
 3     dilution of commercial grade 30% H2O2/water.  The dUute solutions of H2O2 as low as 10"4
 4     have been found to be stable for several weeks if kept in the dark (Armstrong and
 5     Humphreys, 1965). The stock H2O2 solution is standardized by iodometry (Allen et al.,
 6     1952; Hochanadel, 1952; Cohen et al., 1967) or, more recently, by using standardized
 7     permanganate solution (Lee et al., 1991).
 8          Gaseous H2O2 standards are not as easily prepared and stability problems require use of
 9     standard mixtures immediately.  One method makes use of the injection of microliter
10     quantities of 30% H2O2 solution into a metered stream of air that flows into a Teflon bag.
11     The amount of H2O2 in the gas phase is determined by the iodometric titration method
12     (Cohen and Purcell, 1967). Gas-phase H2O2 standards have also been generated by
13     equilibrating N2 with an aqueous H2O2 solution of known  concentration that is maintained at
14     constant temperature.  Equilibrium vapor pressures and corresponding gas-phase
15     concentrations are calculated using Henry's law constant (Lee et al., 1991).
16
17     3.5.2   Sampling and Analysis  of Volatile Organic Compounds
18     3.5.2.1  Introduction
19          The term volatile organic compounds (VOCs) generally refers to gaseous organic
20     compounds that have a vapor pressure greater than 0.15 mm and generally have a carbon
21     content ranging from Ct through C12.  As discussed in Sections 3.2 and 3.4, VOCs are
22     emitted from a variety of sources and play a critical role in the photochemical formation of
23     03 in the atmosphere.
24          The U.S. Environmental Protection Agency (EPA) recently revised the ambient air
25     quality surveillance regulations in Title 40 Part 58 of the Code of Federal Regulations to
26     include, among other activities, the monitoring of volatile  organic compounds.  The revisions
27     require states to establish additional air monitoring stations as part of their existing State
28     Implementation Plan (SIP) monitoring networks.  Authority for requiring the enhanced
29     monitoring is provided for in Title I, Section 182 of the Clean Air Act Amendments of 1990.
30          The term nonmethane organic compounds (NMOC) is also frequently used and refers to
31     a subset of VOCs, since it excludes the compound methane. Numerous sampling, analytical,

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 1     and calibration methods have been employed to determine NMOCs in ambient air.  Some of
 2     the analytical methods utilize detection techniques that are highly selective and sensitive to
 3     specific functional groups or atoms of a compound (e.g., formyl group of aldehydes,
 4     halogen), while others respond in a more universal manner; that is, to the number of carbon
 5     atoms present in the organic molecule.  In this overview of the most pertinent measurement
 6     methods, NMOC have been arranged in three major classifications:  nonmethane
 7     hydrocarbons (NMHC), carbonyl species, and polar volatile organic compounds (PVOCs).
 8     Measurement and calibration procedures are discussed for each classification.
 9
10     3.5.2.2  Nonmethane Hydrocarbons
11          Nonmethane hydrocarbons  (NMHC) constitute the major portion of NMOC in ambient
12     air.  Traditionally, NMHC have  been measured by methods that employ a flame ionization
13     detector (FID) as the sensing element.  This detector was originally developed for gas
14     chromatography and employs a sensitive electrometer that measures a change in ion intensity
15     resulting from the combustion of air containing organic compounds.  Ion formation is
16     essentially proportional to the number of carbon atoms present in the organic molecule
17     (Sevcik,  1975). Thus, aliphatic, aromatic, alkenic, and acetylenic compounds aU respond
18     similarly to give relative responses of 1.00 ± 0.10 for each carbon atom present in the
19     molecule (e.g., 1 ppm hexane = 6 ppm C;  1 ppm benzene = 6 ppm C;  1 ppm propane =
20     3 ppm C).  Carbon atoms bound to oxygen, nitrogen, or halogens give reduced relative
21     responses (Dietz, 1967). Consequently, the FID, which is primarily used as a hydrocarbon
22     measuring method, should more  correctly be viewed as an organic carbon analyzer.
23          In the following sections, discussion focuses on the various methods utilizing this
24     detector to measure total nonmethane organics.  Methods in which no compound speciation is
25     obtained are covered first.  Methods for determining individual organic compounds are then
26     discussed.
27
28     3.5.2,2,1  Nonspeciation Measurement Methods
29          The original EPA reference method for nonmethane organic compounds, which was
30     promulgated in 1971, involves the gas chromatographic separation of methane (CH^ from
31     the remaining organics in an air  sample (Federal Register, 1971).  A second sample is

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 1     injected directly to the flame ionization detector without methane separation.  Subtraction of
 2     the first value from the second produces a nonmethane organic concentration.
 3          A number of studies of commercial analyzers employing the Federal Reference Method
 4     have been reported  (Reckner, 1974; McElroy and Thompson, 1975; Harrison et al., 1977;
 5     Sexton et al., 1982).  These studies indicated an overall poor performance of the commercial
 6     instruments when either calibration or ambient mixtures containing NMOC concentrations
 7     less than 1 ppm C were used.  The major problems associated with using these NMOC
 8     instruments have been reported in an EPA technical assistance document (U.S.
 9     Environmental Protection Agency, 1981). The technical assistance document also suggests
10     ways to reduce the effects of existing problems.  Other nonspeciation approaches to the
11     measurement of nonmethane organics have also been investigated.  These approaches have
12     been discussed in the 1986 EPA air quality criteria document (U.S. Environmental Protection
13     Agency, 1986). Again, these approaches are also subject to the same shortcomings as the
14     EPA reference method (i.e., poor performance below 1 ppm C of NMHC).
15          More recently, a method has been developed for  measuring NMOC directly and
16     involves the cryogenic preconcentration of nonmethane organic compounds and the
17     measurement of the revolatilized NMOCs using flame  ionization detection (Cox et al., 1982;
18     Jayanty et al.,  1982).  This methodology has been formalized and is referred to as Method
19     TO-12 and is published in a compendium of methods for air toxics (Winberry et  al., 1988).
20     The EPA recommends this methodology for  measuring total NMOC and has incorporated it
21     into tiie Technical Assistance Document far SampUng and Analysis of Ozone Precursors
22     (U.S. Environmental Protection Agency, 1991).
23          A brief summary of the method is as follows, A whole air sample is drawn through a
24     glass bead trap that is cooled to approximately —185 °C using liquid  argon.  The cryogenic
25     trap collects and concentrates the NMOC, while allowing the methane, nitrogen,  oxygen,
26     etc., to pass through the trap without retention.  After  a known volume of air has been
27     drawn through the trap, carrier gas is diverted to the trap first to remove residual air and
28     methane. When the residual gases have been flushed from the trap, the cryogen is removed
29     and the temperature of the trap is ramped to approximately 100 °C. The revolatilized
30     compounds pass directly to a  flame ionization detector (no analytical column). The
31     corresponding  signal is integrated over time  (several minutes) to obtain a total FID response

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 1     from the NMOC species. Water vapor, which is also preconcentrated, causes a positive shift
 2     in the FID signal.  The effect of this shift is minimized by optimizing the peak integration
 3     parameters.
 4          The sensitivity and precision of Method TO-12 are proportional to the sample volume.
 5     However, ice formation in the trap limits sampling volumes of «>500 cc.  The detection level
 6     is 0.02 ppm C (with a signal-to-noise ratio, S/N, of 3) and the precision at 1 ppm C and
 7     above has been determined to be S 5 %.  The instrument response has been shown to be
 8     linear over a range of 0 to 10 ppm C.  Propane gas certified by the National Institute of
 9     Standards and Technology (NISI) is normally used as the calibrant.  Accuracy at the method
10     quantitation  level (S/N  = 10) is ±20%.
11
12     3.5.2,2.2   Speciation  Measurement Methods
13          The primary measurement technique utilized for NMOC speciation is gas
14     chromatography (GC).  Coupled with flame ionization detection,  this analytical method
15     permits the separation and identification of many of the organic species  present in ambient
16     air.
17          Separation of compounds is accomplished by  means of both packed and capillary GC
18     columns.  If high resolution is not required and large sample volumes are to be injected,
19     packed columns are employed.  The traditional packed column may contain either (1) a solid
20     polymeric adsorbent (gas-solid chromatography) or (2) an inert support, coated with a liquid
21     (gas-liquid chromatography).  Packed columns containing an adsorbent substrate  are normally
22     required to separate C2 and C3 compounds.  The second type of column can be a support-
23     coated or wall-coated open tubular capillary column.  The latter column has been widely
24     used for environmental analysis because of its superior resolution and broader applicability.
25     The wall-coated capillary column consists of a liquid stationary phase coated or bonded
26     (cross-linked) to the specially treated glass or fused-silica tubing.  Fused-silica tubing is most
27     commonly used because of its physical durability and flexibility.  When a complex mixture is
28     introduced into a GC column, the carrier gas (mobile phase) moves the  sample through the
29     packed or coated capillary column (stationary phase).  The chromatographic process occurs
30     as a result of repeated sorption-desorption of the sample components (solute) as they move
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 1     along the stationary phase.  Separation occurs as a result of the different affinities that the
 2     solute components have for the stationary phase.
 3          As described in the previous ozone criteria document (U.S. Environmental Protection
 4     Agency, 1986), the GC-FID technique has been used by numerous researchers to obtain
 5     ambient NMOC data.  Singh (1980) drew on the cumulative experience of these researchers
 6     to prepare a guidance document for state and local air pollution agencies interested in
 7     obtaining speciation data.  In general, most researchers  have employed two gas
 8     chromatographic units to carry out analyses of NMOC species in ambient air. The more
 9     volatile organic compounds (C2 through C5) are generally measured on one unit using
10     packed-column technology, while the other GC separates the less volatile organics using a
11     capillary column.  In typical chromatograms of urban air, all major peaks are identified and,
12     on a mass basis, represent from 65 to 90% of the measurable nonmethane organic burden.
13          Identification of GC peaks is based upon matching retention times of unknown
14     compounds with those of standard mixtures. Subsequent verification of the individual species
15     is normally accomplished with gas chromatographic-mass  spectrometric (GC-MS) techniques.
16     Compound-specific detection systems, such as electron capture, flame photometry, and
17     spectroscopic techniques, have also been employed to confirm peak identifications.  The peak
18     matching process is far from being a trivial task.  Ambient air chromatograms are often very
19     complex (> 200 peaks/run) and require a good deal of manual labor to assure that the peak
20     matching process is being carried out correctly by the resident peak identification/
21     quantification software. Efforts to improve upon the accuracy of peak assignment and
22     diminish the labor hours normally associated with the objective have recently been reported.
23     Silvestre et al. (1988) developed an off-line spreadsheet program that is menu-driven and
24     used to identify and edit a chromatogram containing 200 peaks within 15 minutes. The
25     accuracy of peak assignment was typically better than 95%. Mason et al. (1992) developed  a
26     novel algorithm, which is embedded within the Harwell MatchFinder software package, and
27     have demonstrated its potential for enhancing peak identification in complex chromatograms.
28     The authors indicate that the software could be used to batch process large volumes of
29     chromatographic data.  A commercial software package from Meta Four Software, Inc., was
30     recently employed during the Atlanta Ozone Precursor Monitoring Study to batch process
31     chromatographic data from over 6,000 GC runs (Purdue et al., 1992).  This  software was

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 1     also used to validate peak identities from two GC databases and was shown to improve peak
 2     identities from the originally processed data by 10 to 20% (Holdren et al,, 1993).
 3          Because the organic components of the ambient atmosphere are present at parts-per-
 4     billion levels or lower, sample preconcentration is necessary to provide sufficient material for
 5     the GC-FDD system. The two primary techniques utilized for this purpose are the use of
 6     solid adsorbents and cryogenic collection.  The more commonly used sorbent materials are
 7     divided into three categories:  (1) organic polymeric adsorbents, (2) inorganic adsorbents,
 8     and (3) carbon adsorbents.  Primary organic polymeric adsorbents used for NMOC analyses
 9     include the materials Tenax®~GC and XAD-2®.  These materials have a low retention of
10     water vapor and,  hence, large volumes of air can be collected.  These materials do not,
1 1     however, efficiently capture highly volatile compounds such as C^. to  ^5 hydrocarbons,  nor
12     certain polar compounds such as methanol and acetone. Primary inorganic adsorbents are
13     silica gel, alumina, and molecular sieves.  These materials are more polar than the organic
14     polymeric adsorbents and are thus more efficient for the collection of the more volatile and
15     polar compounds.  Unfortunately, water  is also efficiently collected, which in many instances
16     leads to rapid deactivation of the adsorbent. Carbon adsorbents are less polar than the
17     inorganic adsorbents and, as a result, water adsorption by carbon  adsorbents is a less
18     significant problem. The carbon-based materials also  tend to exhibit much stronger
19     adsorption properties than organic polymeric adsorbents; thus, lighter-molecular-weight
20     species are more easily retained.  These  same adsorption effects result, however, in
21     irreversible adsorption of many compounds.  Furthermore, the very high thermal desorption
22     temperatures required (350 to 400 °C) limit their use  and also may lead to degradation of
23     labile compounds.  The commonly available classes of carbon adsorbents include:
24     (1) various conventional activated carbons; (2) carbon molecular sieves (Spherocarb®,
25     Carbosphere®, Carbosieve®);  and (3) carbonaceous polymeric adsorbents (Ambersorb®
26     XE-340, XE-347,  SE-348).
27          Although a number of researchers have employed solid adsorbents for the
28     characterization of selected organic species in air, only a few attempts have been made to
29     identify and quantitate the range of organic compounds from C^ and above. Westberg et al.
30     (1980) evaluated several carbon and organic polymeric adsorbents and found that Tenax®-GC
31     exhibited good collection and recovery efficiencies for sC6 organics; the remaining
                                                                   r»r» xTrvr rvnrvrTJ r\o

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 1     adsorbents tested (XAD-4®, XE-340®) were found unacceptable for the lighter organic
 2     fraction.  The XAD-4® retained ^ C2 organic gases, but it was impossible to desorb these
 3     species completely without partially decomposing the XAD-4®.  Good collection and
 4     recovery efficiencies were provided by XE-340® only for organics of C4 and above.  Ogle
 5     et al. (1982) used a combination of adsorbents in series and designed an automated GC-FID
 6     system for analyzing €2 through C10 hydrocarbons. Tenax-GC® was utilized for Cg and
 7     above; whereas Carbosieve S® trapped C3 through €5 organics.  Silica gel followed these
 8     adsorbents and effectively removed water vapor while passing the C2 hydrocarbons onto a
 9     molecular-sieve 5A adsorbent. More recently, Levaggi et al. (1992) have used a
10     combination of adsorbents in series for analyzing C2 through C10 hydrocarbons. Tenax GR,
11     Carbotrap, and Carbosieve S-ffl were evaluated.  At room temperature collection, excellent
12     recovery efficiencies were obtained for all species except acetylene (breakthrough begins
13     after 220 cc).  Smith et al. (1991) evaluated a commercially available GC system
14     (Chrompack, Inc.) and found that a Carbotrap C, Carbopack B, and Carbosieve S-ffl
15     combination was effective for all C2 and above species if the trap temperature was
16     maintained at —30 °C during collection (600 cc).  The above researchers also caution that
17     artifact peaks do occur during thermal desorption and recommend closely screening the
18     resulting data.
19          The preferred method for obtaining NMOC data is cryogenic preconcentration (Singh,
20     1980).  Sample preconcentration is accomplished by directing air through a packed trap
21     immersed in either liquid oxygen (b.p. -183 °C) or liquid argon (b.p. -186 °C).  For the
22     detection of about  1 ppb C of an individual compound, a 250-cc  air sample is normally
23     processed. The collection trap is generally filled with deactivated 60/80 mesh glass beads
24     (Westberg et al., 1974), although coated chromatographic supports have also been used
25     (Lonneman et al.,  1974).  Both of the above cryogens are sufficiently warm to allow air to
26     pass completely through the trap, yet cold enough to collect trace organics efficiently.  The
27     use of cryogenic preconcentration for collection of volatile organic compounds in general was
28     automated to allow sequential hourly updates of gas chromatographic data (McClenny et al.,
29     1984), leading to the initial configuration of what are now referred to as "auto GCs" for
30     ozone precursor monitoring.  The cryogenic collection procedure also condenses water
31     vapor.  An air volume of 250 cc at 50% relative humidity and 25 °C contains approximately

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 1     2.5 rag of water, which appears as ice in the collection trap. The collected ice at times will
 2     plug the trap and stop the sample flow; furthermore, water transferred to the capillary
 3     column during the thermal desorption step occasionally causes plugging and other deleterious
 4     column effects. To circumvent water condensation problems, Pleil et al. (1987) have
 5     characterized the use of a Nafion® tube drying device to remove water vapor selectively
 6     during the sample collection step.  Although hydrocarbon species are not affected, polar
 7     organics are partially removed when the drying device is used. Burns et al. (1983) also
 8     showed that partial loss or rearrangement of monoterpenes,  or both (e.g.,  a-pinene,
 9     limonene),  occur when the Nafion® tube is used to reduce water vapor.
10          The EPA has recently provided technical guidance for measuring volatile organic
11     compounds that is based on the above  studies as well as emerging and developing technology
12     (U.S. Environmental Protection Agency, 1991). Guidance for the use of automated gas
13     chromatography sampling and analysis for VOCs has been derived from experience gained
14     from application of this technology during an ozone precursor study conducted by the EPA in
15     Atlanta, GA, during the summer of 1990 (Purdue et al., 1992).  For that study, an
16     automated GC system developed and manufactured by Chrompack, Inc., and modified for
17     ozone percursor monitoring (McClenny et al., 1991) was used to obtain hourly VOC
18     measurements.  The GC system was equipped with  a preconcentration adsorption trap, a
19     cryofocusing secondary trap, and a single analytical column. The study was focused on the
20     identification and quantitation of 55 ozone precursor compounds, and resulted  in accounting
21     for 65  to 80 % of the total NMOC mass. Sample volumes of 600 cc were used and a
22     detection level of 0.1 ppb C was reported.  External auditing indicated accuracy of ±30% at
23     challenge concentrations of 2 ppb  C  (17-component audit mixture).
24          The study also revealed several weaknesses.  First of all, excessive amounts of liquid
25     cryogen were consumed in carrying  out the measurements.  The inferior quality of the
26     cryogen containers and poor delivery schedules resulted in reduced data capture. Secondly,
27     because of the single-column approach, numerous target species either co-eluted or were
28     poorly resolved.  Finally, several significant  artifact peaks co-eluted with the target species
29     and therefore biased the reported concentrations of those species as well as the total NMOC
30     (by summation of peaks).
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 1          Based upon these deficiencies, the EPA has challenged commercial GC instrument
 2     makers with improving the current state of the art. One result has been the evolution of
 3     systems that require no liquid cryogen for operation, yet provide sufficient gas
 4     chromatographic resolution of target species (McClenny, 1993; Holdren et al., 1993).
 5     A recent comparison study of automated gas chromatographs at Research Triangle Park with
 6     five participating vendors has indicated that the newer auto GC designs use cryogens more
 7     efficiently (Purdue, 1993).
 8          In addition to direct sampling via preconcentration with sorbents and cryogenic
 9     techniques, collection of whole air samples is frequently used to obtain NMOC data. Rigid
10     devices such as syringes,  glass bulbs, or metal containers and non-rigid devices such as
11     Tedlar* and Teflon®  plastic bags are often utilized during sampling.  The primary purpose of
12     whole-air collection is to  store an air sample temporarily until subsequent laboratory analysis
13     is performed.  The major problem with this approach is assuring the integrity of the sample
14     contents prior to analysis. The advantages and disadvantages of the whole air collection
15     devices have been previously summarized in the 1986 air quality criteria document (U.S.
16     Environmental Protection Agency, 1986).
17          The canister-based method is the preferred means for collecting VOCs and  is described
18     as part of the "EPA Compendium of Methods for the Determination  of Toxic Organic
19     Compounds in Ambient Air"  (Compendium Method TO-14).  McClenny et al. (1991)
20     recently reviewed the canister-based method and have discussed basic facts about the
21     canisters, described canister cleaning procedures,  contrasted the canister collection system
22     versus solid adsorbents, and  discussed the storage stability of VOCs in canisters.  Although
23     storage stability studies have indicated that many target VOCs can be stored with good
24     integrity over time periods of at least 7  days, there are still many VOCs for which there are
25     no stability data (Pate et al., 1992; Oliver et al., 1986; Holdren et al., 1987;  Westberg et al.,
26     1981;  Gholson  et al., 1990; Westberg et al.,  1984). Coutant (1993)  has developed a
27     computer-based model for predicting adsorption behavior and vapor-phase losses in
28     multicomponent systems, based on the potential for physical adsorption as well as the
29     potential for dissolution in condensed water for canister samples collected at high humidities,
30     At present, the database for the model contains relevant physicochemical data for
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 1     78 compounds (including water) and provisions for inclusion of up to 120 additional
 2     compounds are incorporated in the software,
 3
 4     3.5.2.2.3  Calibration Methods
 5          Calibration procedures for NMOC instrumentation require the generation of dilute
 6     mixtures at concentrations expected to be found in ambient air.  Methods for generating such
 7     mixtures are classified as static or dynamic systems.
 8          As described in the previous ozone criteria document (U.S. Environmental Projection
 9     Agency, 1986), static systems are generally preferred for quantitating NMOCs.  The most
10     commonly used static system is a compressed gas cylinder containing the appropriate
1 1     concentration of the compound of interest.  These cylinder gases may also be diluted with
12     hydrocarbon-free air to provide multi-point calibrations.  Cylinders of calibration gases and
13     hydrocarbon-free air are available commercially.  Also, some standard gases such as propane
14     and benzene, as well as a 17-component ppb mixture, are available from the National
15     Institute of Standards and Technology (NIST) as certified standard reference materials
16     (SRM).  Commercial mixtures are generally referenced against these NIST standards. In its
17     recent technical assistance document for sampling and analysis of ozone precursors, EPA
18     recommended propane  (or benzene)-in-air standards for calibration (U.S. Environmental
19     Protection Agency, 1991).  Some commercially available propane cylinders have been found
20     to contain other hydrocarbons (Cox et al., 1982), so that all calibration data should be
21     referenced to NIST standards.
22          Because of the uniform carbon response of a GC-FID system (±10%) to hydrocarbons
23     (Dietz, 1967), a common response factor is assigned to both identified and unknown
24     compounds obtained from the speciation systems. If these compounds are oxygenated
25     species,  an underestimation of the actual concentrations will be reported.  Dynamic
26     calibration systems are employed when better accuracy is needed for these oxygenated
27     hydrocarbon species.  Dynamic systems are normally employed to generate in situ
28     concentrations of the individual compound of concern and include devices such as permeation
29     and diffusion tubes and syringe delivery systems.
30
31
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 1     3.5,2.3   Carfoonyl Species
 2          Historically, the major problem in measuring concentrations of carbonyls in ambient air
 3     has been to find an appropriate monitoring technique that is sensitive to low concentrations
 4     and specific for the various homologues.  Early techniques for measuring formaldehyde, the
 5     most abundant aldehyde, were subject to many interferences and lacked sensitivity at low
 6     parts-per-billion concentrations.  The 1986 air quality criteria document described two
 7     methods frequently used:  the chromotropic acid (CA) method for formaldehyde and the
 8     3-methyl-2-benzothiazolone hydrazone (MBTH) technique for total aldehydes (U.S.
 9     Environmental Protection Agency, 1986). However, spectroscopic methods, on-line
10     colorimetric methods, and the high-performance liquid chromatography (HPLC) method
11     employing 2,4-dinitrophenylhydrazine (DNPH) derivatization are the preferred methods
12     currently used for measuring atmospheric levels of carbonyl species.
13
14     3.5.2.3.1   Spectroscopic Methods
15          Three spectroscopic methods have been used to make measurements for atmospheric
16     levels of formaldehyde and were recently intercompared at an urban site in California
17     (Lawson et al., 1990).  The Fourier Transform  Infrared Spectroscopy (FUR) method used
18     gold-coated 30-cm-diameter mirrors and a total  optical path of 1,150 m. The 2781.0 cm"
19     "Q-branch" adsorption peak was used to measure HCHO.  The limit of detection was 3 ppb,
20     and the measurement errors were within ±3 ppb. The Differential Optical Absorption
21     Spectroscopy  (DOAS) method was operated at an 800-m pathlength, and an absorption peak
22     at 339 nm was used to measure HCHO; NO^ and HONO spectral features were subtracted.
23     The limit of detection was 4.5 ppb; the experimental error was ±30%.  A Tunable Diode
24     Laser Absorption Spectroscopy (TOLAS) method was operated at a pathlength of 150 m.
25     Laser diodes were mounted in a closed-cycle helium cryocooler with a stabilizing heater
26     circuit for constant temperature control.  Radiation from the diode was collected and focused
27     into the sampling by reflective optics. Formaldehyde absorption was measured at
28     1,740 cm"1. The limit of detection was 0.1 ppb and the measurement errors were within
29     ±20 %.  Additional information on F1TR and DOAS has been reported by Winer et al.,
30     1987; Atkinson et al., 1988; and Biermann et al., 1988. A more complete description of
31     TOLAS is given by MacKay et al.,  1987.

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 1     3.5.2,3.2   On-line Colorimetric Method
 2          A wet chemical method based upon the derivatization of HCHO in aqueous solution to
 3     form a fluorescent product was recently developed by Kelly et al. (1990).  The detection of
 4     fluorescent product was made more sensitive by using intense 254 nm light from a mercury
 5     lamp for excitation. This procedure allowed the use of a simple and efficient glass coil
 6     scrubber for collection of gaseous HCHO. A detection limit of 0.2 ppb was obtained when
 7     using a response time  of 1 min. The instrument is portable and highly selective for HCHO.
 8
 9     3.5.2.3.3   High-Performance Liquid ChromcUography-2,4~DinUrophenylhydra&ne Method
10          The preferred and most current method for measuring aldehydes in ambient air is one
11     involving derivatization of the aldehydes concurrent with sample collection, followed by
12     analysis using high-performance liquid chromatography (HPLC).  This method takes
13     advantage of the reaction of carbonyl compounds with 2,4-dinitrophenylhydraaane (DNPH) to
14     form a 2,4-dinitrophenylhydrazone:
15
                   RR'C=O +  NHyNHC^CNO^ -» Hp + RR'C=NNHC6H3(NO2)2      (3-82)
16
17     Because DNPH is a weak nucleophile, the reaction is carried out in the presence of acid in
18     order to increase protonation of the carbonyl.
19          In this method, atmospheric sampling was initially conducted with micro-impingers
20     containing an organic  solvent and aqueous, acidified DNPH reagent (Papa and Turner, 1972;
21     Katz, 1976; Smith and Drummond, 1979; Fung and Grosjean, 1981).  After sampling was
22     completed, the hydrazone derivatives were extracted and the extract was washed with
23     deionized water to remove the remaining acid and unreacted DNPH reagent. The organic
24     layer was then evaporated to dryness, subsequently dissolved in a small volume of solvent,
25     and analyzed by reversed-phase liquid chromatographic techniques employing an ultraviolet
26     (UV) detection system (360 nm).
27          An unproved procedure was subsequently reported that is much simpler than the above
28     aqueous impinger method (Lipari and Swarin,  1982; Kuntz et al., 1980; Tanner and Meng,
29     1984).  This scheme utilizes a midget impinger containing an acetonitrile solution of DNPH
30     and an acid catalyst.   After sampling, an aliquot of the original collection solution is directly

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 1     injected into the liquid chromatograph.  This approach eliminates the extraction step and
 2     several sample-handling procedures associated with the DNPH-aqueous solution; and
 3     provides much better recovery efficiencies.  This method has been formalized by the EPA as
 4     Compendium Method TO-5 (Winberry et al,, 1988).  The TO-5 Method has been further
 5     modified to include the use of DNPH-impregnated solid adsorbent rather than DNPH
 6     impinger solutions as the collection medium. This modification and associated sampling
 7     conditions are referred to as EPA Method TOIL The methodology can be easily used for
 8     long-term (1 to 24 h) sampling of ambient air.  Sampling rates  of 500 to 1,200 cc/min can be
 9     achieved and detection levels of 1 ppbV can be attained with sampled volumes of 100 L.
10     The method currently calls for the use of SepPak® silica gel material as the sorbent material.
11     However,  researchers have noted that O3 present in ambient air reacted more easily with
12     carbonyl compounds collected on DNPH-coated silica gel cartridges than on DNPH-coated
13     C18 bonded silica material. To eliminate this interference problem, these researchers used an
14     ozone scrubber (Arnts et al.,  1989). The TO11 Method has been included in EPA's
15     Technical Assistance Document for SampUng and Analysis of Ozone Precursors (U.S.
16     Environmental Protection Agency,  1991).
17
18     3.5.2.3.4   Calibration of Carbonyl Measurements
19          Because they are reactive compounds,  it is extremely difficult to make stable calibration
20     mixtures of carbonyl species in pressurized gas cylinders.  Although gas-phase standards are
21     available commercially, the vendors do not guarantee long-term stability and accuracy.
22          Formaldehyde standards are generally prepared by one of several methods.  The first
23     method utilizes dilute commercial formalin (37% HCHO, w/w). Calibration is accomplished
24     by the direct spiking into sampling impingers of the diluted mixture or by evaporation into
25     known test volumes, followed by impinger collection. Formaldehyde can also be prepared
26     by heating known amounts of paraformaldehyde, passing the effluent gases through a
27     methanol-liquid nitrogen slush trap to remove impurities, and collecting the remaining
28     HCHO. Paraformaldehyde permeation tubes have also been used (Tanner and Meng, 1984).
29          For the higher-molecular-weight carbonyl species, liquid solutions can be evaporated or
30     pure vapor can be generated in dynamic gas-flow systems (permeation tubes, diffusion tubes,
31     syringe delivery systems, etc.).  These test atmospheres are then passed through the

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 1     appropriate collection system and analyzed  A comparison of these data, with the direct
 2     spiking of liquid carbonyl species into the particular collection system, provides a measure of
 3     the overall collection efficiency.
 4
 5     3.5.2.4   Polar Volatile Organic Compounds
 6          The VOCs discussed earlier in this chapter (Section 3.5.2.2) have included aliphatic,
 7     aromatic, alkenic, and acetylenic hydrocarbons.  These compounds are relatively nonpolai,
 8     nonreactive species, and measurement methods have been easily applied in determining
 9     ambient concentrations.
10          Recently, attention has also been directed toward the more reactive oxygen- and
11     nitrogen-containing organic compoundss in part by the inclusion of many of these compounds
12     on a list of 189 hazardous air pollutants specified in the 1990 Clean Air Act Amendments.
13     Many of these compounds are directly emitted from a variety of industrial processes, mobile
14     sources, and consumer products, and some are also formed in the atmosphere by
15     photochemical oxidation of hydrocarbons.  However, as indicated earlier in this document,
16     very few ambient data exist for these species. These compounds have been collectively
17     referred to as polar VOCs (PVOCs), although it is their reactivity and water solubility, more
18     than simple polarity, that make their measurement difficult with existing methodology.
19          Two approaches  have been utilized in developing analytical methods for PVOCs.  One
20     approach has incorporated the use of cryogenic trapping techniques similar to those discussed
21     earlier for the nonpolar hydrocarbon species;  the second approach has utilized adsorbent
22     material for sample preconcentration.  To be effective for sensitive ppb measurement of
23     PVOCs, both approaches require some type of water management system to mitigate the
24     adverse effects that water has on the chromatography and detector sensitivity and reliability.
25     Several researchers have reported the use of cryogenic trapping with two-dimensional
26     chromatography to selectively remove water  vapor from the analytical process (Pierotti,
27     1990; Caidin and Lin, 1991). Although this column "heart  cutting" technique has been
28     successful for selected compounds, additional studies are needed to determine its potential
29     use for the wide range of PVOCs.  Ogle et al. (1992) developed a novel water management
30     system based upon the condensation of moisture from the saturated carrier gas  stream during
31     thermal desorption of a cryogenic trap.  The moisture management system was found to be
32     effective for reducing  the amount of water delivered to the column during laboratory analyses
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 1     of spiked mixtures. However, the system has not yet been extended to field monitoring.
 2     Gordon et al.  (1989) have used cryogenic trapping and gas chromatography/mass
 3     spectrometry techniques to demonstrate the potential of chemical ionization (CI) within an ion
 4     trap to detect PVOCs.  The water vapor present in the sample served as the CI reagent gas
 5     and appeared to be an effective reagent gas; however,  deleterious chroinatography results
 6     were also encountered.  The authors concluded  that further laboratory work is needed before
 7     this methodology can be applied to ambient air  monitoring.  Martin et al. (1991) also
 8     reported the use of cryogenic trapping with a GC-FID system to measure ambient levels of
 9     isoprene and two of its oxidation products, methacrolein and methylvinyl ketone (detection
10     level of 0.5 ppb).  The water vapor was selectively removed by using a potassium carbonate
11     (I^COj)  trap ahead of the cryogenic trap.  Frequent replacement of the K2C03 trap was
12     required.
13          The use of solid adsorbents for sample preconcentration of PVOCs has been reported
14     by Kelly  et al. (1993). The analytical method was used  extensively at two field sites that
15     were formerly used in EPA's Toxic Air Monitoring Study (TAMS). The analytical method
16     consisted of gas chromatographic separation of  PVOCs with quantification by a ion trap mass
17     spectrometer. A two-stage adsorbent trap containing Carbopack B and Carbosieve S-ffl
18     (Supelco  catalog number 2-0321) was used to separate water vapor  from  the PVOCs. The
19     optimum room temperature trapping and drying procedure consisted of a 320-cc sample
20     (100 cc/min) followed by a dry nitrogen purge  of 1,300  cc (100 cc/min). The trap was then
21     backflushed and thermally desorbed with helium at 220 °C.  A 5-min 260 °C trap bakeout
22     followed each collection-analysis cycle. The target list contained 14 PVOCs, including
23     alcohols, ethers, esters, and nitrile species.  Individual detection limits ranged from 0.2 to
24     1 ppb.
25
26     3.5.3   Sampling and Analysis of Oxides of Nitrogen
27     3.5.3.1  Introduction
28          The measurement of oxides of nitrogen in ambient air is of interest because  of the role
29     that certain of those compounds play as precursors to  ozone and because nitrogen dioxide
30     (NO2) has been shown to elicit health effects.  The primary nitrogen oxides emitted from
31     combustion sources are nitric oxide (NO) and nitrogen dioxide (NOj).  Collectively these

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 1      two compounds are called NOX, They contribute to ozone formation by means of reactions
 2      discussed in Section 3.2.  As a result, measurement of NOX is important in efforts to
 3      understand and control ozone and NO2 in ambient air.
 4           The atmospheric photochemistry that produces ozone also results in conversion of NO
 5      and NO2 to products such as nitric acid (HNO3), nitrous acid (HONO), peroxyacetyl nitrate
 6      (CH3C(O)O2NO2; PAN), organic nitrates, and other species.  The total of all of these labile
 7      nitrogen species in air, NOX included, is termed NOy.  Such compounds may be labile via
 8      photolysis (e.g., HONO)  or thermal decomposition (e.g., PAN), and may be toxic,  irritating,
 9      or acidic. However, in general they do not play the same critical role that NO2 and NO play
10      as ozone precursors. For that reason, this section focuses on measurement methods for NO
11      and NO2, as the primary  ozone precursors among the nitrogen oxides.  The nitrogen oxides
12      other than NOX may be important, however, as interferents in efforts to measure  NO and
13      NO2. These non-NOx species are considered in this section in that regard.
14          Measurements of NOX may involve measurements of NO, of NO2, or of the sum of
15      NOX. Nitrogen dioxide, but not NO, is a criteria air pollutant, and thus reference and
16     equivalent methods are specified for NO2 measurements.  In this section, the current state of
17     measurement methods for NO and NO2 will be summarized separately.  Such methods in
18     some cases rely on measurements of total NOX,  or at least an approximation of NOX.  This
19     discussion focuses on current methods and on promising new technologies; but no attempt is
20     made here to cover the extensive history of development of these methods. More detailed
21      discussions of such methods may be found elsewhere (U.S. Environmental Protection
22     Agency, 1993; National Aeronautics and Space Administration, 1983).  Wet chemical
23      methods are no longer commonly used and are not discussed here; a review  of such methods
24     is given by Purdue and Hauser (1980).
25
26     3.5.3.2  Measurement  of Nitric Oxide
27     3.5.3.2.1   Gas-phase Chemiluminescence Methods
28          By far the most common method of NO measurement is gas-phase Chemiluminescence
29     (CL) with 03.  In this method, excess 03 is added to air containing NO in a darkened,
30     internally reflective chamber viewed by a photomultiplier tube.  A small portion  of the
31     NO reactions with O3 produce electronically excited NO2 molecules, which decay by

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 1     emission of light of wavelengths longer than 600 nm. The emitted light is detected by a red-
 2     sensitive photomultiplier tube, through an optical filter that prevents passage of wavelengths
 3     shorter than 600 nm.  This optical filtering minimizes interference from chemiluminescence
 4     produced by Qj reactions with other species (e.g., hydrocarbons).  The excited NO2 is
 5     readily quenched in air, so that in typical instruments air and O3 are mixed at reduced
 6     pressure (i.e., at least 20 in. of Hg vacuum).  The intensity of the emitted light is linearly
 7     proportional to the NO content of the sample air over several orders of magnitude in
 8     concentration.
 9          Commercial CL instruments for continuous measurement of NO are available from
10     several manufacturers.  The chemiluminescence approach is also an EPA-designated
11     measurement principle for measuring ambient NO2; it requires a means of converting NO2 to
12     NO for detection.  The complexities of this conversion are discussed in Section 3.5.3.3, on
13     NO2 methods.   The commercial NO monitors typically are claimed to have detection limits
14     of a few parts per billion by volume in air (ppbv) with response time of a few minutes.
15     Field evaluations of several commercial instruments have indicated that minimum levels of
16     detection for NO2 are 5 to 13 ppbv (Michie et a!., 1983; Holland and McElroy,  1986).
17     However, more recent evaluations have indicated better performance.  Rickman et al. (1989)
18     reported detection limits of 0.5 to 1 ppbv, and precision of ±0.3 ppbv, from laboratory and
19     field evaluations of two commercial instruments operated on their 50 ppbv full-scale ranges.
20     Commercial NO analyzers are portable and quite reliable, and are now commonly used in
21     ambient air monitoring networks.
22          Commercial NO analyzers may not have sensitivity sufficient for surface measurements
23     in rural or remote areas, or for airborne measurements. As a result, several investigators
24     have devised modifications to commercial instruments to improve their sensitivity and
25     response time (Delany et al., 1982; Tanner et al., 1983, Dickerson et al., 1984,  Kelly et al.,
26     1986).  Those modifications include:  (1) operating at low pressure and high sample flow
27     rate; (2) using a larger, more reflective reaction chamber that promotes mixing of the
28     reactants close to the photomultiplier tube; (3) increasing the O3  supply; for example, by use
29     of oxygen in the O3 source; (4) cooling of the photomultiplier to reduce noise; (5) adopting
30     photon counting techniques for light detection; and (6) adding a prereactor to obtain a more
31     stable and appropriate background signal. Commercial instruments modified in these ways

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 1     are generaUy reported to have detection limits of 0,1 ppbv or less, with response times of
 2     30 s or less.
 3          Research-grade NO instruments specially designed for ultra-high sensitivity have also
 4     been built for use in remote ground-level or airborne applications (e..g, Ridley and Hewlett,
 5     1974; Kley and McFarland, 1980; Kelly et al., 1980; Helas et al., 1981; Drummond et al.,
 6     1985; Tones, 1985; Kondo et al., 1987; Parrisn  et al., 1990).  These instruments typically
 7     have detection limits of 10 ppt (i.e., 0.01 ppbv) or less, with response times from a few
 8     seconds to 1  min.
 9          A number of studies indicate that the chemiluminescence method is essentially specific
10     for NO.  Operation at reduced pressure prevents interference resulting from quenching by
11     water vapor (Michie et al., 1983; Drummond et  al., 1985). In air samplings no significant
12     interferences have been found in NO detection from sulfur-, chlorine-, and nitrogen-
13     containing species (Joshi and Bufalini, 1978; Sickles and Wright, 1979; Grosjean and
14     Harrison,  1985; Fahey et  al., 1985). However,  H2S and possibly other sulfur-containing
15     compounds from seawater have been reported to give false NO signals (Zafiriou and True,
16     1986). This effect should not be important for ambient air measurements.  Fahey et al.
17     (1985) and Drummond et al. (1985) also reported no significant NO interference from a
18     variety of other nitrogen-containing  species, including NO2, HNO3, PAN, N2O5, NH3,
19     HCN, N2O,  and HO2NO2; as well as no interference from methane, propylene, and
20     hydrogen peroxide.
21          Several ambient air intercomparisons have  been done of chemiluminescence NO
22     instruments (Walega et al., 1984; Hoell et al., 1987;  Fehsenfeld et al., 1987; Gregory et al.,
23     1990), These studies have focused on high-sensitivity research instruments, rather than the
24     commercial instruments used for widespread ambient air measurements. These studies have
25     shown excellent agreement among the CL NO instruments, even at NO levels in the low ppt
26     range (Hoell et al., 1987; Gregory et al., 1990).  These results support the validity of the CL
27     approach for NO.  Good  agreement has also been found between CL measurements and
28     spectroscopic NO measurements in these studies (see Section 3.5.3.2.2).
29
30
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 1     3.5.3.2.2   Spectroscopic Methods for Nitric Oxide
 2          Direct Spectroscopic methods for NO include two-photon laser-induced fluorescence
 3     (TPIIF), tunable-diode laser absorption spectroscopy (TOLAS), and two-tone frequency-
 4     modulated spectroscopy (TTFMS). The primary characteristics of these methods are their
 5     very high sensitivity and selectivity for NO,  For example, a detection limit of 10 ppt has
 6     been quoted for TPLIF with a 30-s integration time, with no significant interferences from
 7     atmospheric species (Davis et al., 1987).  An accuracy of ±16% as a 90% confidence limit
 8     has been calculated for NO measurement by TPLIF from an aircraft (Davis et al., 1987).
 9     The TOLAS method is similarly highly selective for NO and achieves a detection limit of
10     0.5 ppbv (Schiff et al., 1983).  The response time  of the TOLAS instrument is about 1 min
11     for NO, and is limited by stabilization of concentrations with the large surface area of the
12     multi-pass White cefl.  The newest method is TTFMS, which appears in laboratory studies to
13     be very sensitive, fast, and selective.  With a 100-m path length in a 20-torr multiple-pass
14     cell, and a 1-min averaging time, the detection limit of NO is estimated to be 4 ppt (Hansen,
15     1989).
16          Spectroscopic methods have compared well with the CL method for NO in  ambient
17     measurements.  Walega et al.  (1984) reported good agreement between CL and TOLAS
18     results for NO in laboratory air, in ambient air,  and even in downtown Los Angeles air.
19     Gregory et al. (1990) reported comparisons of TPLIF and CL NO methods in airborne
20     measurements.  Agreement at levels below 20 ppt  was within the expected accuracy and
21     precision of the instruments (i.e., within 15 to 20 ppt).
22          The major drawbacks of these Spectroscopic methods are their complexity,  size, and
23     cost.  Although possessing remarkable characteristics, these methods are restricted to
24     research applications.  The TTFMS approach, in fact, is still hi the laboratory development
25     stage.
26
27     3.5.3.2.3  Passive Samplers
28          At present no passive sampler exists that directly measures NO. Instead, passive
29     samplers developed for NO2 have been adapted for NO measurement, using an oxidizing
30     material that converts  NO to NO2.  Palmes tubes (Palmes and Tomczyk, 1979) have been
31     adapted for NO measurement  by using two tubes in parallel.  One tube collects NO2 on a

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 1     triethanolamine (TEA)-coated grid, while the other collects NO2 on a TEA grid, plus NO
 2     oxidized by a chromic acid-coated surface.  The grids are then extracted and analyzed for
 3     NO2 ion.  Nitric oxide is determined by difference between the two results, after accounting
 4     for the different diffusivities of NO and NO2.  The sampling rates depend on temperature
 5     and air velocity.  The tubes cannot be used for periods longer than 24 h, and are intended for
 6     use at ppm NO levels important in the workplace (e.g., 2 to 200 ppm • h).  Applicability to
 7     ambient NO levels has not been demonstrated.
 8          A more sensitive passive sampler for NO has been reported (Yanagisawa and
 9     Nishimura,  1982) that uses the same TEA chemistry, with CrO^ as the NO oxidizer.
10     A detection limit of 70 ppbv-h has been reported.  As with any currently available passive
1 1     sampler, the disadvantages of the method are the potential for interferences, relatively poor
12     precision, and low sensitivity for ambient air measurements.
13
14     3.5J3J  Measurements for Nitrogen Dioxide
15     3.5,3.3,1   Gas-phase Chemiluminescence Methods
16          In 1976, the gas-phase chemiluminescence approach described above for NO detection
17     was designated as the measurement principle on which U.S. EPA reference methods for
18     ambient NO2 must be based. The CL method thus filled the vacancy left by withdrawal of
19     the Jacobs-Hocnheiser method, because of technical problems, in 1973.  To be designated as
20     a reference method, an NO2 detection method must  use the CL approach and  be calibrated
21     by the specified methods (gas-phase titration of NO  with O3, or use of an NO2 permeation
22     device). In addition the  instrument must meet the performance specifications  shown in
23     Table 3-18.  An equivalent method, either manual or automated, must meet certain
24     requirements for comparability with a reference method when measuring simultaneously in a
25     real atmosphere. Those  comparability requirements are shown in Table 3-19.  An automated
26     equivalent method must also meet the performance requirements shown in Table 3-18.
27          The selection of the ozone CL method as the reference measurement principle for
28     ambient NO2 was the result of comparison tests of CL and wet chemical methods.
29     Chemiluminescence analyzers were found superior to the  wet chemical methods in response
30     time, zero and span drift, and overall operation, although agreement among all the methods
31     tested was good, at the NO2 spike levels provided (Purdue and Hauser, 1980).  Table 3-20
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            TABLE 3-18.  PERFORMANCE SPECIFICATIONS FOR NITROGEN
     	DIOXIDE AUTOMATED METHODS
     Performance Parameter                                  Units           NO2
     Range                                     '           ppm           0-0.5
     Noise
       0% upper range limit                                  ppm             0.005
       80% upper range limit                                 ppm             0.005
     Lower detectable limit                                   ppm             0,01
     Interference equivalent
       Each interferant (SO2,NO,NH3,H2O                      ppm           ±0.02
       Total interferant                                       ppm           ,<.0.04
     Zero drift, 12 and 24 hours                               ppm           ±0.02
     Span drift, 24 hours
       20% upper range limit                                  %            ±20.0
       80% upper range limit                                  %            ±5.0
     Lag time                                               min            20
     Rise time                                               min            15
     Fall time                                               min            15
     Precision
       20% upper range limit                                 ppm             0.02
       80% upper range limit                                 ppm             0.03

     Source:  Code of Federal Regulations, Ambient Air Monitoring Reference and Equivalent Methods,
            C.F.R. Title 40, Part 53.
                 TABLE 3-19. COMPARABILITY TEST SPECD7ICATIONS
      	 FOR NITROGEN DIOXIDE
               Nitrogen Dioxide                            Maximum Discrepancy
           Concentration Range (ppm)                          Specification (ppm)
      Low                   0.02 to 0.08                           OG2
      Medium               0.10 to 0.20                           0.02
      High                  0.25 to 0.35                           0.03
1     lists the methods currently designated (as of February 1993) by U.S. EPA as reference and
2     equivalent methods for ambient NQj. Three wet chemical methods are shown as equivalent
3     methods, but these are rarely used for ambient air measurements,
4         The ozone chemiluminescence method does not measure NO2 directly, because the
5     chemiluminescence is produced by reaction of NO with O3.  As a result, NO2 must first be

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              TABLE 3-20. REFERENCE AND EQUIVALENT METHODS FOR
                     NITROGEN DIOXIDE DESIGNATED BY U.S. EPAa
Method
Reference Methods (Continuous CL Analyzers)
Advanced Pollution Instrumentation 200
Beckman952A
Bendix 8101-B
Bendix 8101-C
CSI1600
Dasibi 2108
Lear Siegler ML9841
Meloy NA53OR
Monitor Labs 8440E
Monitor Labs 8840
Monitor Labs 8841
Philips PW9762/02
Thermo Electron 14B/E
Thermo Electron 14D/E
Thermo Environmental 42
Equivalent Methods (Wet Chemical)
Sodium arsenite
Sodium arsenite/Technicon n
TGS-ANSAb
Designation
Number
RFNA-0691-082
RFNA-01 79-034
RFNA-0479-038
RFNA-0777-022
RFNA-0977-025
RFNA-1 192-089
RFNA-1292-090
RFNA-1078-031
KFNA-0677-021
RFNA-0280-042
RFNA-0991-083
RFNA-0879-040
RFNA-0179-035
RFNA-0279-037
RFNA-1289-074
EQN-1277-026
EQN-1277-027
EQN-1277-028
Method
Code
082
034
038
022
025
089
090
031
021
042
083
040
035
037
074
084
084
098
      aAs of February 1993.
       Triethanolamine-guajacol-sulfite with 8-amino-l-naphthalene-suIfonic acid ammonium salt.
1     reduced to NO for detection. In principle, such a reduction should readily result in
2     measurement of NO + NO2 (i.e., NOX), and allow indirect measurement of NC«2 by
3     difference between NO and NOX responses, measured either sequentially, or simultaneously
4     by separate detectors.  In practice, however, selective measurement of NOX by this approach
5     has proven very difficult.
6          Several methods have been employed to convert NO2 to NO, including catalytic
7     reduction with heated  molybdenum or stainless  steel, reaction with CO over a gold catalyst
8     surface, reaction with ferrous sulfate (FeSO4) at room temperature, reaction with carbon at
9     200 °C, and photolysis of NO2 at wavelengths  of 320 to 400 nm (Kelly et al., 1986).  It has

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 1     been found in many separate investigations that the heated converters reduce NC>2 to NO
 2     effectively, but also reduce other NOy species as well (e.g., Winer et al., 1974; Cox, 1974;
 3     Joseph and Spicer, 1978; Grosjean and Harrison,  1985; Fahey et al., 1985).  Efficiencies of
 4     conversion near 100% are reported in these studies for N^ and for NOy species such as
 5     HNO3, HONO, PAN, and organic nitrates.  This finding is particularly important for
 6     widespread monitoring networks that use commercial instruments, because such instruments
 7     without exception use heated catalytic converters (typically molybdenum).  Thus, such
 8     instruments measure not NO and NOX, but more nearly NO and total NOy.  The NO2 value
 9     inferred from such measurements may be significantly in error (see below), and may in turn
10     affect the results of models of ambient ozone. The completeness of the measured NO value
11     is also questionable because, for example, HN03  is readily lost to surfaces, and, in ambient
12     sampling,  may be removed within the sampling system before reaching the heated converter.
13          Other conversion methods for NO2 have been tried in an effort to achieve higher
14     selectivity. Ferrous sulfate  (FeSO4) has been used for ambient NO2 measurements using
15     high-sensitivity research grade CL instruments (e.g., Kelly et al.,  1980; Helas et al., 1981;
16     Dickerson et al,, 1984). This material is an efficient reducer of NO2,  but has also been
17     found to convert a portion of PAN, and possibly a portion of HONO and organic nitrates
18     (Fehsenfeld et al., 1987). Memory effects and reduction in efficiency  can occur because of
19     humidity effects  (Fehsenfeld et al., 1987). As a result of these characteristics, use of FeSO4
20     has given  high readings in comparison with spectroscopic instruments and the photolytic NO2
21     converter, and likely results in overestimating ambient NOX by a significant amount
22     (Fehsenfeld et al., 1987; Ridley et al., 1988a; Gregory et al., 1990).  Ferrous sulfate has
23     never been used in commercial NOX instruments, and is no longer used in research
24     measurements.
25          The  most specific method for converting NO2 to NO is photolysis (Hey and
26     McFarland, 1980).  In this approach, ambient NO2 is photolyzed to NO by a xenon arc
27     lamp.  The method does not produce NO from the major potential interferents present in air
28     (i.e., HNO3,  PAN, and organic nitrates), but less abundant NOy species such as HONO or
29     HO2NO2 may interfere. A detailed description of steps to minimize such interferences is
30     given by Ridley et al. (1988b).  As currently  used, the photolytic converter appears to be
31     essentially specific for NO2. However, it does not provide complete conversion of NO2.

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 1     Conversion efficiencies are 50 to 60% with a new lamp, and may decline to 20% over the
 2     course of several weeks (Parrish et al,, 1990). Thus the conversion efficiency must be
 3     repeatedly calibrated. This approach has not been implemented with commercial NO
 4     detectors, but has been implemented with research-grade CL NO instruments for studies of
 5     NOX and NOy chemistry at a variety of locations (e.g., Parrish et al.s 1990; Trainer et al.,
 6     1991; Parrish et al., 1992).  The photolytic method has compared well with other techniques,
 7     including spectroscopic methods, even at NO2 levels as low as 0.05 ppbv (Gregory et al.,
 8     1990).
 9          As noted above, the commercial CL analyzers used for most ambient air NO and NOX
10     measurements actually measure  more nearly NO and NOy.  The magnitude of the resulting
1 1     overestimation of NO2 determined by difference obviously depends on the portion of NOy
12     that is NOX.  The smaller the portion of NOy that is NOX, the greater will be the error in the
13     NO2 determined by difference.  In remote areas, where NOX has undergone extensive
14     conversion to other products during transport from a source region, NOX may contribute a
15     small fraction of NOy,  In urban areas, close to sources, NOX may comprise nearly all of
16     NOy. For example, in measurements at Point Arena, California,  Parrish et al. (1992) report
17     NOx/NOy ratios averaging 0.3 in air of marine origin, and 0.75 in air subject to continental
18     influence. Clearly, although the commercial CL instruments are designated as reference
19     methods for NO2, the great majority of existing ambient air data for NOj or NOX are biased
20     high, because of the inclusion of some portion of other NOy species. The magnitude of this
21     bias  may not be large in urban areas, but in any case it is unknown at this time,
22
23     3.5.3.3.2   Luminol Chemiluminescence Method
24          This approach is based on the chemiluminescent reaction of gaseous NO2 with the
25     surface of an aqueous solution of luminol (5-amino-2,3-dihydro-l ,4-phthaJazinedione).
26     Emission occurs primarily between 380 and 520 nm. In commercial instruments, luminol
27     solution flows down a fabric wick that lies vertically on a clear window viewed by a
28     photomultiplier tube. Nitrogen dioxide in sample air passing over the wick produces light,
29     the intensity of which is proportional to the NO2 concentration.  Commercial instruments
30     using this approach are compact, light, and relatively inexpensive, and can provide detection
31     limits as low as 0.01 ppbv with response times below 30  s. The  instrument has the
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 1     advantage of detecting NO2 directly.  However, several difficulties have had to be dealt with
 2     in developing the method.
 3          Original reports of the approach (Maeda et al., 1980) indicated positive interferences
 4     from O3 and SO2 and a negative one from CO2. Reformulation of the luminol reagent
 5     solution has minimized, though not fully eliminated, those interferences (Wendel et al,,
 6     1983; Schiff et al., 1986).  Reported effects include a slight negative response from NO, and
 7     sensitivity to PAN, HONO, and O3 (Wendel et al., 1983; Schiff et al., 1986; Rickman et al.,
 8     1989; Kelly et al., 1990; Spicer et al., 1991). Response to NO2 may be nonlinear at low
 9     concentrations (Kelly et al.,  1990), although recent reformulation of the reagent has
10     apparently reduced this behavior (Busness, 1992).  Evaluation of the luminol NOj monitor
11     indicates that great care must be taken in using and calibrating the instrument in order to
12     achieve good precision and accuracy in ambient measurements (Kelly et al.,  1990).  The
13     monitor has been widely used as a research  tool, but has not been widely used in ambient air
14     monitoring and has not been designated an equivalent method for NCX^
15          An 03 scrubber is available to eliminate the 03 interference noted above, but was also
16     found to remove a portion of the NO2 (Kelly et al., 1990).  The lumdnol approach has also
17     been modified to measure NO, by using a CrO3 converter that oxidizes NO to NO^ for
18     detection. Thus NO is detected by difference.  This method has the potential for
19     measurement  of total NOX; however, evaluations of the CrO^ converter arc still underway at
20     several laboratories.  Given the known interferences in the luminol approach, careful
21     evaluation of this method must be completed before it gains acceptance as an NO
22     measurement  method.
23          An  adaptation of the commercial luminol NO^ detector has been reported to provide
24     measurements of total NOy, NO2, and NOX (Drummond et al.,  1993). This adaptation,
25     called the LNC-3M, uses a commercial luminol instrument for NO2 detection, with a
26     CrO3 converter for NOX detection.  The NOX measurement must be corrected for the few
27     percent of the ambient NO2 that is lost in the CrO3 converter (Drummond et al., 1993). The
28     NOy measurement is achieved using a stainless steel converter maintained at 400 °C.  Tests
29     indicate that this converter provides a more complete conversion of alkyl nitrates, and
30     consequently a more complete measurement of NOys than is provided by either the heated
31     molybdenum converters used in commercial ozone CL NOX  detectors or the gold converters

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 1     with CO addition used in research instruments (Druramond et al., 1993),  The LNC-3M adds
 2     a small amount of NO2 to the sample to eliminate the nonlinearity at low concentrations, and
 3     uses a zeroing scrubber that greatly reduces the interference from PAN. However, this
 4     scrubber must be replaced weekly when in continuous use (Drummond et al., 1993).
 5
 6     3,5.3.3.3   Spectroscopic Methods
 1          Several spectroscopic approaches to NO2 detection have been developed:  TDLASS
 8     TTFMS, differential optical absorption (DOAS), and differential absorption lidar (DIAL) are
 9     absorption methods that have been used. The TOLAS method is probably the most
10     commonly used spectroscopic NO2 method. It can provide high selectivity for NO2, with a
11     detection limit of 0.1 ppbv, accuracy of ±15 percent, and a response time on the order of
12     1 min because of the White cell (Mackay and Schiff, 1987).  The DOAS method is an
13     open-path long-pathlength system.  The detection limit for NO2 with a 0.8-km pathlength and
14     12-min averaging time has been reported as 4 ppbv, with measurement accuracy reported as
15     ±10% (Biermann et al., 1988).  However, recent improvements  have resulted in a
16     commercial DOAS instrument capable of an NO2 detection limit of 0.6 ppbv, based on a
17     557-m path and a  1-min averaging time (Stevens et al., 1993).  The detection limit for NO2
18     by the DIAL technique has been reported as  10 ppbv with a 6-km pathlength (Staehr et al.,
19     1985). The novel TTFMS method noted above for NO is reported  to have an NC^ detection
20     limit of 0.3 ppt, but is not fully proven for ambient measurements.
21          Fluorescence methods have also been used for NO^, including photofragmentation
22     TPLJF (PF/TPUF) (Davis, 1988). This method uses two cells hi which NO is measured  by
23     TPLIF. In one of the cells, an excimer laser emitting at 353 nm photolyzes NO2 to NO for
24     detection.  Thus NO2 is ultimately measured, by difference, as NO, but the NO is  formed
25     directly by photolysis of NO2. With a 2-min integration time, an NO2 detection limit of
26     12 ppt is reported. The method  is highly selective for NO2, since an interferant would have
27     to photolyze to produce NO.  Several potential atmospheric species have been ruled out in
28     this regard (Davis, 1988).
29          The drawbacks of most of these methods are, as noted earlier, complexity, size, and
30     cost.  At present these factors outweigh the obvious advantages of the sensitivity and
31     selectivity of these spectroscopic methods, and have largely restricted the use of these

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 1     NO2 methods to specific research applications or to their use as reference methods in
 2     intercomparisons.  In such intercomparisons, absorption measurements have been most
 3     commonly used.  The TOLAS method has been used in ground-level comparisons with
 4     O3 CL and luminol instruments to provide specific NO2 measurements (Walega et al., 1984;
 5     Sickles et al., 1990; Fehsenfeld et al., 1990), and in an airborne comparison with PF/TP1IF
 6     and O3 CL instruments (Gregory et al., 1990b),  A finding of these studies was that the
 7     TDLAS consistently read higher than other established methods at very low NO2 levels (i.e.,
 8     <0.4 ppbv)  (Fehsenfeld et al., 1990; Gregory et al., 1990b).
 9          The spectroscopic NO2 method most fully developed beyond the research stage is the
10     DOAS technique.  Stevens et al.  (1993) report testing of a commercial DOAS instrument in
11     North Carolina over 17  days in the fall of 1989. The DOAS measured NO2 using
12     wavelengths  between 400 and 460 nm? and achieved a detection limit of 0.6 ppbv, as noted
13     above.  Simultaneous measurements of ozone,  sulfur dioxide, formaldehyde, and nitrous acid
14     were also provided by the DOAS instrument.  Comparison of the DOAS NC^ results to those
15     from a commercial CL detector showed (DOAS NO^ = 1.14 X (CL NO^ + 2.7 ppbv,
16     with a correlation coefficient (r2) of 0.93, at NC^ levels up to 50 ppbv (Stevens et al.,  1993).
17     The sensitivity, stability, response time, and multicomponent capability are the primary
18     advantages of the DOAS approach.  Further intercomparisons and interference tests are
19     recommended (Stevens et al,  1993).
20
21     3.5.3.3,4   Passive Samplers
22          Passive samplers are attractive,  inexpensive, and simple means to obtain long-term or
23     personal exposure data for NO2 or NOX. The simplest passive sampler for NO2 is the
24     nitration plate, which is essentially an open dish containing filter paper impregnated with
25     TEA.  Nitrogen dioxide diffuses to the paper,  and is extracted later as NO2~ for analysis.
26     No diffusion barrier exists in this approach, or in a similar approach using a candle-shaped
27     absorber (Kosmus, 1985); consequently, results are very subject to ambient conditions and
28     give at best a qualitative indication of NO2 or NOX.
29          Addition of a diffusion barrier to the nitration plate concept has led to badge-type
30     passive samplers for NO2 (e.g., Mulik and Williams, 1986, 1987; Mulik et al.,  1989,  1991).
31     In general, such devices use perforated screens, plates, or filters as diffusion barriers on  the

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 1     chemically reactive material, which may be exposed on one or both sides, depending on the
 2     application. Extraction of the sorbent then allows measurement of the NO2 collected,
 3     typically as NO2" ion.  Such a device using TEA as the active material gave very good
 4     agreement relative to a CL analyzer in laboratory tests with NO2 at 10 to 250 ppbv (Mulik
 5     and Williams, 1987).  However, interferences from PAN and HONO (the latter both in
 6     outdoor and indoor air) are expected (Sickles and Michie, 1987).  Comparison of ambient
 7     NO2 results in the 5 to 25 jig/m range (i.e., about 2.5 to 12.5 ppbv) from the passive
 8     device to those from TDLAS showed good agreement on average values, but a correlation
 9     coefficient (r) of only 0.47 on daily values (Mulik et al., 1989).
10          Badge-type personal samplers for NO2 have also been developed by Yanagisawa and
11     Nishimura (1982) (YN) and by  Cadoff and Hodgeson (1983)  (CH). Triethanolamine is used
12     as the active collecting medium in both samplers, and both use colorimetry as the analytical
13     method for detection of NO2 ,   The samplers differ in that the YN device uses  TEA coated
14     on a cellulose filter with  a Teflon® filter as a diffusion barrier; whereas the CH sampler uses
15     TEA coated on a glass fiber filter with a polycarbonate filter as a diffusion barrier.
16     Detection limits are reported to be 0.07 ppm-h (Yanagisawa and Nishimura,  1982) and
17     0,06 pprn-h (Cadoff and  Hodgeson,  1983).  Interferences from PAN and HONO  are expected
18     (Sickles and Michie, 1987); likewise, the  devices are sensitive to the speed of ambient air
19     movement.
20          Palmes tubes  have been developed for NO2 measurement and adapted to NO
21     measurement as described above. The device has been used  for workplace and personal
22     exposure monitoring (Wallace and Ott, 1982), but  not for ambient air measurements.
23     A detection limit of 0.03 ppm-h can be achieved if ion  chromatography is  used to determine
24     the extracted NO2" (Mulik and Williams,  1986). Adsorption of NO2 to the tube walls may
25     raise this limit considerably (Miller, 1988),  but this effect can be counteracted  by use of
26     stainless  steel tubes.  The device is sensitive to temperature and wind speed; and PAN and
27     HONO are likely interferences  (Sickles and Michie,  1987).  In a comparison with two
28     commercially produced NO2 passive samplers, the Palmes tube showed reasonable accuracy
29     and precision at loadings of 1 to 80 ppm-h.  However, the commercial devices were designed
30     for use at relatively high loadings; therefore, this comparison does not support the use of
31     Palmes tubes for ambient air monitoring.  The Palmes tubes  have the same disadvantages as
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 1     other passive devices for NO2, namely, poor precision, insufficient sensitivity, temperature
 2     dependence, and considerable interferences in ambient sampling.
 3
 4     3.5.3.4  Calibration Methods
 5          Calibration of NO measurement methods is done using standard cylinders of NO in
 6     nitrogen. Typical NO concentrations in such cylinders are 1 to 50 ppmv.  Dilution of such
 7     standards with clean air using mass flow controllers can accurately provide NO
 8     concentrations in the ambient (i.e., 1 to 100 ppbv) range for calibration.  Nitric oxide
 9     standards are  available as Standard Reference Materials (SRMs) from the National Institute
10     of Standards and Technology (NIST), and as commercially available Certified Reference
11     Standards.  Commercially available certified NO standards have been shown to be stable and
12     accurate in the certified concentrations.
13          Standard cylinders of N02  in nitrogen or air are sometimes used for NO2 calibration.
14     These standards are commercially available, and are readily diluted to ppbv levels in the
15     same manner as for NO  standards.  However, instability of the N02 levels in  such standards
16     has been reported,  and caution must  be used in relying on NO2 standards as the primary
17     means  of calibration.
18          Two calibration methods for NO2 are specified in the Code of Federal Regulations
19     (1987) for calibration of ambient NO2 measurements.  Those methods are permeation tubes
20     and gas-phase titration.
21          An NO2 permeation tube is an  inert enclosure, generally of Teflon®, glass and Teflon®,
22     or stainless steel and Teflon®, that contains liquid NO2.  As long as liquid NO2 is present,
23     NO2 will permeate through the Teflon® at a rate that depends on the temperature of the tube.
24     Maintaining the permeation tube at a constant temperature (i.e., ±0.1 °C) results in
25     permeation of NO2 at a constant rate. Dilution  of the emitted NO2 with a flow of dry air or
26     N2 results in known low NO2 concentrations for calibration.  Nitrogen  dioxide permeation
27     tubes are supplied as SRMs by NIST, and tubes are commercially available with  a wide
28     range of permeation rates. Permeation tubes are small, simple, reliable, and relatively
29     inexpensive, although constant temperature ovens and dilution systems are required to obtain
30     good results.  Nitrogen dioxide  permeation tubes are susceptible to moisture, and changes in
31     permeation rate or emission of other species (HNO3, HONO, NO) may occur if they are not

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 1     kept dry. As with NO2 cylinder standards, the NO2 permeation tube requires care as a
 2     calibration method for NO2.
 3          Gas-phase titration (GPT) uses the rapid reaction of NO with 03 to produce NO2 with
 4     1:1 stoichiometry. In practice, excess NO generated from a standard cylinder containing
 5     50 to 100 ppmv NO is reacted with Oj from a stable source. The resultant decrease in NO
 6     concentration, usually measured on the NO channel of a chemiluminescence NOX analyzer,
 7     equals the concentration of NO2 generated. Varying amounts of NO2 can be produced by
 8     varying the amount of O3.
 9
10
11     3.6  OZONE AIR QUALITY MODELS
12          To plan control strategies to achieve compliance with the  National Ambient Air Quality
13     Standard (NAAQS) for ozone at some future date it is necessary to predict how ozone
14     concentrations  change in response to prescribed changes in source emissions of precursor
15     species;  the oxides of nitrogen (NOX) and volatile organic compounds (VOCs). This
16     assessment  requires an air quality model, which in the case of ozone prediction is often
17     called a photochemical air quality model.  The model in effect  is used to determine the
18     emission reductions needed to achieve the ozone air quality standard.  For at least a decade,
19     the U.S. Environmental Protection Agency (EPA) has offered guidelines on the selection of
20     air quality modeling techniques for use in State Implementation Plan (SIP) revisions,  new
21     source reviews, and studies aimed at the prevention of significant deterioration of air quality.
22          Ozone air quality models provide the ability to address "what if' questions, such as
23     what if emissions of VOCs or NOX or both are reduced? The  model can be used as an
24     experiment that cannot be run in the atmosphere. Sensitivity questions can be asked, such as
25     how important is emissions change A relative to emissions change B, or what is the effect of
26     an X% uncertainty in a certain  chemical reaction rate constant on the ozone levels predicted.
27          Models are the ultimate integrators of our knowledge of the comprehensive chemistry
28     and physics of the atmosphere.  As such, they are an indispensable tool for understanding the
29     complex interactions of transport, transformation, and removal in the atmosphere.  Models
30     assist in the design of field measurement programs and are essential  in the interpretation of
31     data from such programs.

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 1          The purpose of Section 3,6 is to review briefly the main elements of ozone air quality
 2     models, to describe several of the current models, to discuss how one evaluates the
 3     performance of these models, and to present examples of the use of the models for
 4     determining VOC and NOX control strategies.
 5

 6     3.6.1    Definitions, Description,  and Uses

 7          Air quality models are mathematical descriptions of the atmospheric transport,
 8     diffusion, removal, and chemical reactions of pollutants.  They operate  on sets of input data
 9     that characterize the emissions, topography, and meteorology of a region and produce outputs

10     that describe air quality in that region.  Mathematical models for photochemical air pollution
11     were first developed in the early 1970s  and have been improved, applied, and evaluated since
12     that time. Much of the history of the field is described in reviews by Tesche  (1983),

13     Seinfeld (1988), and Roth et al. (1989).
14          Photochemical air quality models include treatments of the important physical and
15     chemical processes that contribute to ozone formation in and downwind of urban areas.
16     In particular, such models contain a representation of the following phenomena (Roth et al.s
17     1989):
18          •     Precursor emissions.  The spatial and temporal characteristics of reactive
19                hydrocarbon, carbon monoxide (CO), and NOX emissions sources must be
20                supplied as inputs to the model. Hydrocarbon emissions are generally
21                apportioned into groups (e.g., alkanes, alkenes, aromatics, etc.) according to the
22                speciation requirements of the chemical kinetic mechanism embedded in the
23                model.
24
25          •     Pollutant transport.  Once the ozone precursors are emitted into the atmosphere,
26                they are transported by the  wind.  When ozone is formed, it is also subject to
27                transport by the wind. Grid-based models require the preparation of three-
28                dimensional, time-varying fields of the wind speed and direction.  These values
29                must be specified for each grid cell.  Cloud venting and cloud mixing processes
30                that are important on the regional scale can also be included in the pollutant
31                transport description.
32
33          •     Turbulent diffusion.  Ozone and its precursors are also subject to  turbulence-
34                related dispersion processes that take place on a subgrid scale. These turbulent
35                diffusion effects are usually represented in grid-based models by the so-called
36                gradient transport hypothesis, where the pollutant flux is assumed to be
37                proportional to the spatial gradient in the concentration field. The turbulent


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 1                diffusivities employed in the model are dependent on atmospheric stability and
 2                other meteorological variables,
 3
 4          •     Chemical reactions.  Ozone results from chemical transformations involving
 5                reactive organics and NOX  (See Section 3.2). A chemical kinetics mechanism
 6                representing the important reactions that occur in the atmosphere is employed to
 7                estimate the net rate of change of each pollutant simulated by the model,
 8                Description of chemical reactions  requires actinic flux, cloud cover, temperature,
 9                and relative humidity.
10
11          •     Removal processes.  Pollutants are removed from the atmosphere via interactions
12                with surfaces at the ground, so-called  "dry deposition," and by precipitation,
13                called "wet deposition."
14
15          Guidelines issued by U.S. EPA (U.S. Environmental Protection Agency, 1986a)
16     identify two kinds of photochemical model: The grid-based Urban Airshed Model (UAM) is
17     the recommended  model for modeling ozone over  urban areas and the trajectory model
18     EKMA (empirical kinetics modeling approach) is identified as an acceptable approach. The
19     1990 Clean Air Act Amendments mandate that three-dimensional, or grid-based, air quality
20     models, such as UAM, be used in SIPs for ozone  nonattainment areas designated as extreme,
21     severe, serious, or multistate moderate (U.S.  Environmental Protection Agency, 1991b).
22
23     3.6.1.1  Grid-Based Models
24          The basis for grid-based air quality models is the atmospheric diffusion equation, which
25     expresses the conservation of mass of each pollutant in a turbulent fluid  in which chemical
26     reactions occur (Seinfeld, 1986). The region  to be modeled is bounded  on the bottom by the
27     ground, on the top by some height that characterizes the maximum extent of vertical mixing,
28     and on the sides by east-west and north-south boundaries. The choice of the size of the
29     modeling domain  will depend on the spatial extent of the ozone problem, including the
30     distribution of emissions in  the region, the meteorological conditions, and, to some extent,
31     the computational resources available.  This space is then subdivided into a three-dimensional
32     array of grid cells.  The horizontal dimensions of  each cell are usually a few kilometers for
33     urban applications up to tens of kilometers for regional applications.  Some older grid-based
34     models assumed only a single, well-mixed vertical cell extending from the ground to the
35     inversion base; current models subdivide the region  into layers.  Vertical dimensions can

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 1     vary, depending on the number of vertical layers and the vertical extent of the region being
 2     modeled.  A compromise generally must be reached between the better vertical resolution
 3     afforded by the use of more vertical layers and the associated increase in computing time.
 4     Although aerometric data, such as the vertical temperature profile, that are needed to define
 5     the vertical structure of the atmosphere are generally lacking, it is still important to use
 6     enough vertical layers  so that vertical transport processes are accurately represented.
 7          There are practical  and theoretical limits to the minimum horizontal grid cell size,
 8     Increasing  the number of cells increases computing and data acquisition effort and costs.
 9     In addition, the choice of the dimension of a grid cell implies that the input data information
10     about winds, turbulence, and emissions, for example,  are resolved to that scale.  The spatial
11     resolution of the concentrations predicted by a grid-based model corresponds to  the size of
12     the grid cell.  Thus, effects that have spatial scales smaller than those of the grid cell cannot
13     be resolved.   Such effects include the depletion of ozone by reaction with nitric oxide (NO)
14     near strong sources of NOX like roadways and power plants.
15          Several grid-based photochemical air quality models have been developed to simulate
16     ozone production in urban areas or in larger regions.  They differ primarily in their treatment
17     of specific atmospheric processes, such as chemistry, and in the numerical procedures used
18     to solve the governing system of equations,  They will be reviewed in Section 3.6.3.
19
20     3.6.1.2   Trajectory Models
21          In the trajectory  model approach, a hypothetical air parcel moves through  the area of
22     interest along a path calculated from wind trajectories. Emissions are injected into the air
23     parcel and undergo vertical mixing and chemical transformations. The data requirements for
24     trajectory models include:  (1) initial concentrations of all relevant pollutants and  species;
25     (2) rates of emissions  of VOC and NOX precursors into the parcel along its trajectory;
26     (3) meteorological characteristics such as wind speed and direction needed to define the path
27     of the air parcel through the region; (4) mixing depth; and (5) solar ultraviolet radiation.
28     Basic limitations of trajectory models include neglect of horizontal wind shear,  and neglect of
29     cell volume changes resulting from convergence and divergence of the wind field (liu and
30     Seinfeld,  1975).
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 1          Trajectory models provide a dynamic description of atmospheric source-receptor
 2     relationships that  is simpler and less expensive to derive than that obtained from grid models.
 3     Trajectory models are designed to study the photochemical production of ozone in the
 4     presence of sources and vertical diffusion of pollutants; otherwise the meteorological
 5     processes are highly simplified.
 6          A simple trajectory model is used in the empirical kinetic modeling approach
 7     (BKMA)(Dodge,  1977a).  This modeling approach relates the maximum level of ozone
 8     observed downwind of an urban area to the levels of VOC and NOX observed in the urban
 9     area.  It is based  on the use of a simple, one-cell moving box model. As the box moves
10     downwind, it encounters  emissions of organics and NOX that are assumed to be uniformly
1 1     mixed within the  box.  The height of the box is allowed to expand to account for the breakup
12     of the nocturnal inversion layer.  As the height of the box increases,  pollutants above the
13     inversion layer are transported into the box. The model is first used to generate a series of
14     constant ozone lines (or isopleths) as depicted in Figure 3-25. The isopleths show the
15     downwind, peak  1-h ozone levels as a function of the concentrations  of VOC and NOX for a
16     hypothetical urban area.  These isopleths were generated by carrying out a large number of
17     model simulations in which the initial concentrations and anthropogenic emissions of VOC
1 8     and NOX were varied systematically while all other model inputs were held constant.  When
19     it was first conceived,  EKMA employed a very simple, highly empirical chemical mechanism
20     and the isopleths  generated were for a hypothetical situation in Los Angeles.
21     As understanding of the chemical processes responsible for ozone formation increased, the
22     EKMA model was updated to include more complete representations of atmospheric
23     chemistry.  Although EKMA has employed the CBM-IV mechanism, the same mechanism
24     that is currently being  used in several grid-based models, the most recent version allows the
25     input of any mechanism.  The EKMA method is now used to generate city-specific isopleth
26     diagrams using information on emissions, transport, and dilution that are appropriate to the
27     particular city being modeled.
28          City-specific ozone isopleths can be used to estimate the reduction in nonmethane
29     hydrocarbon (NMHC) or NOX levels, or both, needed to achieve the NAAQS for ozone in a
30     specific urban area.  The first step is to determine the early-morning NMHC/NOX ratio for
31     the urban area in question and the maximum 1-h downwind O3 concentration. Both the
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       0.28
       0.24 -
       0.20 -
       0.16 -
       0.12
       0.08 -
       0.04
           0     0.2     0.4     0.6    0.6     1.0     1.2     1.4     1.6     1.8
                           Nonmethane Hydrocarbon Concentration, ppm

       Figure 3-25. Example of EKMA diagram for high-oxidant urban area.
       Source: Derived from U.S. Environmental Protection Agency (1986b).
                                       0.28
                                       0.24
                                       0.20
                                     - 0.16
                                     - 0.12
                                     - 0.08
                                       0.04
 1      NMHC/NOX ratio and the peak ozone concentration are obtained from air monitoring data.
 2      These two values define a point on the isopleth surface and from this point, the percentage
 3      reductions in NMHC or NOX, or both, needed to achieve the ozone NAAQS can be
 4      determined.
 5           As examination of Figure 3-25 reveals, for an NMHC concentration of 0.6 ppmC, for
 6      example, increasing NOX leads to increased Qj until NMHC/NOX ratios of about 5:1 to 6:1
 7      are reached;  further NOX increases, leading to lower NMHC/NOX ratios, inhibit
 8      O3 formation. Thus, in this example, there is a "critical" ratio (in the range of 5:1 to 6:1) at
 9      which the NOX effect on 03 changes direction. Besides this "critical" ratio,  an "equal
10      control" NMHC/NOX ratio  also exists, above which the reduction of NOX is  more beneficial
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 1      in terms of O3 reduction than an equal percentage reduction in NMHC.  This ratio, for the
 2      isopleths shown in Figure 3-25, is roughly 8:1 to 9:1 for low levels of control, and as high
 3      as 20:1 for the levels of control needed to reduce O3 to 0,12 ppm.  Thus, for this particular
 4      case (Figure 3-25), the chemical mechanism modeling evidence suggests that (1) NOX control
 5      will increase the peak downwind O3 concentration at NMHC/NOX ratios of between 5:1 and
 6      6:1 or lower; (2) both NOX control and NMHC control will be beneficial at somewhat higher
 7      ratios, with control of NMHC being more effective; and (3) for ratios above 20:1, NOX
 8      control is relatively more effective in reducing O3 to attain the ozone NAAQS.
 9           The EKMA-based method for determining control strategies has  some limitations, the
10      most serious of which is that predicted emissions reductions are critically dependent on the
11      initial NMHC/NOX ratio used in the calculations. This ratio cannot be determined with any
12      certainty and it is expected to be quite variable in an urban area.  Another limitation is that
13      trajectory models have limited spatial and temporal scopes of application.  They are generally
14      1-day models, simulating only one cell at a time. Another problem with the use of morning
15      NMHC/NOX ratios is the failure to account for photochemical evolution as urban emissions
16      are carried downwind. As demonstrated in simulations by Milford et  al. (1989) and in smog
17      chamber studies by Johnson and Quigley  (1989), an urban plume that  is in the VOC-
18      controlling regime (low NMHC/NOX ratio) near city center can move increasingly into the
19      NOx-controUing regime  (high NMHC/NOX ratio) as the air parcels age and move downwind.
20     This progression occurs  because NOX is photochemically removed from  an aging plume more
21      rapidly than VOC, causing the VOC/NOX ratio to increase.  As demonstrated  by Milford
22      et al.  (1989), the implication of this evolution is that different locations in a large urban area
23      can show very different  ozone sensitivities to VOC and NOX changes. Because of this and
24     other drawbacks, the 1990 Clean Air Act Amendments require that grid-based models be
25      used in most ozone nonattainment areas.
26
27     3.6.2   Model Components
28      3.6.2.1   Emissions Inventory
29          The spatial and temporal characteristics of VOC and NOX emissions  must be supplied
30     as inputs to a photochemical air quality model.  Emissions from area and point sources are
31     injected into ground-level grid cells, and  emissions from large point sources are injected into

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 1     upper-level cells.  Total VOC emissions are generally apportioned into groups of chemically
 2     similar species (e.g., alkanes, alkenes, aromatics, etc.) according to the requirements of the
 3     chemical mechanism.  This apportionment may be accomplished using actual emission
 4     sampling and analysis or be based on studies of similar emission sources.  Recognition of
 5     potential undercounting in existing inventories  has spurred efforts to improve the accuracy of
 6     emissions inventories. In fact, at present the emissions inventory is the most rapidly
 7     changing component of photochemical models. It has been recognized that both mobile and

 8     stationary source components have been highly uncertain, and there is significant ongoing
 9     effort to improve the accuracy of emissions inventories.
10          Some emissions terminology is as follows (Tesche, 1992):
11          •     Emissions data - the primary information used as input to emissions models,
12
13          •     Emissions model - the integrated collection of calculational procedures, or
14                algorithms, properly encoded for computer-based computation.
15
16          •     Emissions estimates - the output of emissions models; used as input to
17                photochemical models.
18
19          •     Emissions inventory - the aggregated set of emissions estimate files.
20
21          •     Emissions model evaluation - the testing of a model's ability to produce accurate
22                emissions estimates over a range of source activity and physicochemical and
23                meteorological conditions.
24

25     Emissions input requirements for the UAM, for example, include:
26          •     Spatial allocation of precursor  emissions (VOC, NOX, CO):
27                —     Actual location of individual point sources;
28                —     Spatial allocation by gridding surrogates;
29                —     Assignment of surrogates to other categories.
30
31          •     Stack parameters for point sources:
32                —     Temperature, height, diameter, exit velocity.
33
34          •     Speciation of VOC emissions for CBM-IV mechanism:
35                —     Region-specific speciation profiles;
36                —     EPA default speciation profiles,
37
38          •     Temporal allocation of precursor emissions:
39                —     Operating schedules for individual point sources;
40                —     Assignment of diurnal profiles for area and mobile sources.

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 1          The emissions inventory component of modeling is moving in the direction of the use
 2     of emissions models rather than inventories. Emissions models are being developed for the
 3     Lake Michigan Oxidant Study (LMOS) and the San Joaquin Valley Air Quality Study
 4     (SJVAQS) and the Atmospheric Utility Signatures, Predictions, and Experiments (AUSPEX),
 5     designated as the SJVAQS/AUSPEX Regional Model Adaptation Project (SARMAP) studies.
 6     The consistency of existing inventories was improved in 1990 when U.S. EPA released the
 7     Emissions Preprocessor System (EPS) as a component of the UAM (U.S. Environmental
 8     Protection Agency, 1990d).  The EPS was updated in 1992 to EPS Version 2 (EPS2). It is
 9     an emissions model that considers spatial and temporal disaggregation factors, speciation
10     data, and meteorological data to convert daily emissions estimates for each point source and
11     for area source categories and mobile source emissions factors computed by the EPA
12     MOBILES model into hourly, gridded speciated estimates needed by a photochemical grid
13     model.
14          A step beyond the EPS is the Emissions Modeling System (EMS) (Tesche, 1992),  The
15     EMS1 utilizes emissions estimation and information processing methods to provide gridded,
16     temporally resolved, and chemically speciated base year emissions estimates for all relevant
17     source categories; to provide flexibility in forecasts of future year emissions rates; and to
18     provide modular code design facilitating module updating and replacement.  The EMS
19     provides for easy substitution of alternative assumptions, theories, or input parameters (e.g.,
20     emissions factors, activity levels, spatial distributions) and facilitates sensitivity and
21     uncertainty testing.
22
23     3.6.2.2  Meteorological Input to Air Quality Models
24          Grid-based air quality models require, as input, the three-dimensional wind field for the
25     episode being simulated.  This input is supplied by a so-called meteorological module.
26     Meteorological modules for constructing wind fields for air quality models Ml into  one of
27     four categories (Tesche, 1987; Kessler, 1988):
28
29          •      Objective analysis procedures that interpolate observed surface and aloft wind
30                 speed and direction data throughout the modeling domain.
31      The EMS has been renamed the GMEP (Geocoded Model of Emissions and Projections).
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 1          •     Diagnostic methods in which the mass continuity equation is solved to determine
 2                the wind field.
 3
 4          •     Dynamic, or prognostic, methods based on numerical solution of the governing
 5                equations for mass, momentum, energy, and moisture conservation along with
 6                the thermodynamic state equations on a three-dimensional, finite-difference
 7                mesh.
 8
 9          •     Hybrid methods that embody elements from both diagnostic and prognostic
10                approaches.
12     3.6.2.2 .1  Objective Analysis
13          Objective wind-field analysis involves the interpolation and extrapolation of wind speed
14     and direction measurements (collected at a number of unequally spaced monitoring stations)
15     to grid points throughout the region (Goodin et al., 1980).  For flat terrain settings away
16     from complex mesoscale forcings, this class of techniques may provide an adequate method
17     for estimating the wind field, provided that appropriate weighting and smoothing functions
18     are used (Haltiner, 1971). For complex terrain or coastal-lake environments, however, it is
19     tenuous to interpolate between and extrapolate from surface observational sites except with an
20     unusually dense monitoring network. In most cases, the routinely available rawinsonde
21     network sounding data are even more severely  limited because of the large distances (300 to
22     500 km) between sites and because soundings are made only every 12  h.  The limitations of
23     even the best available data sets are most severe above the surface layer, where upper-level
24     observations  are less frequent and more expensive to obtain.  It will remain economically
25     unfeasible to obtain sufficiently dense atmospheric observations to allow any direct objective
26     analysis  scheme to provide the required detail and accuracy necessary for use in advanced,
27     high-resolution photochemical models.
28
29     3.6.2.2.2  Diagnostic Modeling
30          In diagnostic wind modeling, the kinematic details of the flow are estimated by solving
31     the mass conservation equation.  Dynamic interactions such as turbulence production and
32     dissipation and the effects of pressure gradients are parameterized.  Various diagnostic wind
33     models have been developed, many employing the concepts introduced by Sherman (1978)
34     and Yocke (1981).

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 1           In recent years, attempts have been made to combine the best features of objective
 2      analysis and pure diagnostic wind modeling.  The current release of U.S. EPA's UAM-IV
 3      includes the Diagnostic Wind Model (DWM) as the suggested wind-field generator for this
 4      urban-scale photochemical model. The DWM (U.S. Environmental Protection Agency,
 5      1990c) is representative of this class of hybrid objective-diagnostic models.  The DWM
 6      combines the features of the Complex Terrain Wind Model (CTWM) (Yocke, 1981) and the
 7      objective wind interpolation code developed at the California Institute of Technology (Goodin
 8      et al.,  1980).  In the DWM, a two-step procedure is normally followed.  First, a
 9      "domain-scale" wind is estimated from available surface and upper-air synoptic data.  This
10     initial field consists of a single wind vector (e.g., horizontal homogeneity) for each elevation.
11      The domain-scale wind is adjusted using procedures derived from the CTWM for the
12      kinematic effects of terrain such as lifting, blocking, and flow acceleration.
13      Thermodynamically generated influences such as mountain-valley winds are parameterized.
14     This first step produces a horizontally varying field of wind speed and direction for each
15      vertical layer within the DWM modeling domain.  Typically, 10 to  12 vertical layers are
16     used.  In the second step, available hourly surface and upper air measurements are
17     objectively combined with the step 1  hourly diagnostic flow fields to produce a resultant
18     wind field that matches the observations at the monitoring points and obeys the general
19     constraints of topography in regions where data are absent. The DWM contains a number  of
20     user-specified options whereby different final flow fields may be produced, depending upon
21      selection of various smoothing and weighting parameters.  The final output of the DWM is a
22     set of hourly averaged horizontal wind fields for each model layer.
23          Diagnostic models may invoke scaling algorithms that propagate the influence of the
24     surface-flow field into upper levels according to the local height of the inversion and the
25     Pasquill-Gifford-Turner stability category for the hour.  Once the winds are created by
26     DWM, they must be  "mapped" onto the photochemical model's vertical grid structure. This
27     function is normally accomplished in a two-step process.  First, the DWM winds are
28     interpolated onto the photochemical model grid using simple linear interpolation. Second,
29     the three-dimensional divergence is computed in each grid cell and an iterative scheme is
30     used to minimize this divergence to a user-specified level.  Typically, the output consists of
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 1     "non-divergent" x- and y-direction wind components for direct input to the photochemical
 2     model.
 3          Among the advantages of the diagnostic modeling approach are its intuitive appeal and
 4     modest computing requirements.  The method generally reproduces the observed wind values
 5     at the monitoring locations and provides some information on terrain-induced airflows in
 6     regions where local observations are absent.  In addition, one may calibrate diagnostic model
 7     parameters for a particular locale based on site-specific field measurements.  However, there
 8     are several disadvantages. Diagnostic models cannot represent complex mesoscale
 9     circulations, unless these features are well-represented by surface and aloft observations.
10     Often the vertical velocities produced by a diagnostic model are unrealistic and, in regions of
11     complex terrain, local horizontal flow velocities may often be an order of magnitude too high
12     (Tesche et al., 1987).  Since the diagnostic model is not time-dependent, there is no inherent
13     dynamic consistency in the winds from  one hour to the next. That is, calculation of the flow
14     field at hour 1200, for example,  is not influenced by the results of the 1100 hour winds.
IS     This is a particular problem in applications involving important flow regimes such as land-
16     sea breezes, mountain-valley winds, eddy circulations,  and nocturnal valley jets, that take
17     several hours to develop and whose three-dimensional character is poorly characterized by
18     even the most intensive sampling networks.
19
20     3,6.2,2.3   Prognostic Modeling
21          In prognostic meteorological modeling, atmospheric fields are  computed based on
22     numerical solutions of the coupled, nonlinear conservation equations of mass, momentum,
23     energy, and moisture.  Derivations of these equations are presented extensively in the
24     literature (see, for example, Haltiner, 1971; Pielke,  1984; Seinfeld, 1986; Cotton and
25     Anthes, 1989).  Many prognostic models have  been  developed for computing mesoscale wind
26     fields, as shown in the recent survey by Pielke (1989); and they have been applied to a
27     variety of problems, including the study of land-sea  and land-lake circulations.  Available
28     prognostic models range from relatively simple one-dimensional representations to complex
29     three-dimensional codes.
30          Prognostic wind models are attractive because they explicitly address the various
31     physical processes governing atmospheric flows.  Consequently, they have the potential for

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 1     describing a number of wind regimes that are particularly relevant to air pollution modeling,
 2     such as flow reversal, daytime upslope flows, wind shear,  and other mesoscale thermally
 3     induced circulations.  Drawbacks of prognostic models include the need to gather detailed
 4     data for model performance testing and the large computational costs.  Indeed, prognostic
 5     models may require as much or more  computer time than regional-scale photochemical
 6     models. More intensive data sets are  needed to evaluate prognostic models than for
 7     diagnostic models,  but this is not necessarily a  disadvantage; rather,  it provides the modeler
 8     and decision-maker with a far better basis for judging the adequacy of the model than can be
 9     achieved with objective or diagnostic models.
10          Summaries of prognostic models available for use in air quality modeling are presented
11     extensively in the literature (e.g., Pielke, 1989; Benjamin and Seaman, 1985; McNally,
12     1990; Stauffer et al., 1985;  Stauffer and Seaman, 1990; Ulrickson, 1988; Wang and Warner,
13     1988; and Yamada et al,, 1989).  From these reviews, two models stand out as representing
14     the present state-of-science in applications-oriented prognostic modeling. These are the
15     Mesoscale Model Versions 4 and 5 (MM4/MM5) developed by Pennsylvania State University
16     and the National Center for Atmospheric Research (NCAR) (Anthes and Warner, 1978;
17     Anthes et al., 1987; Zhang et al., 1986; Seaman, 1990; Stauffer and Seaman,  1990), and the
1 8     Coast and Lake Regional Atmospheric Modeling System (CAL-RAMS) (Tripoli and Cotton,
19     1982; Pielke, 1974, 1984, 1989; Lyons et al.,  1991).
20          Two ongoing regional ozone modeling programs in the U.S. (i.e., LMOS and
21     SARMAP) are using prognostic models to drive regional ozone models.  Part  of the U.S.
22     EPA's long-range plan (in the Office  of Research and Development) for model development
23     is to construct a "third"  generation modeling framework referred to  as MODELS 3 (Dennis,
24     1991). This modeling system will consolidate  all of the agency's three-dimensional models.
25     The current plan calls for meteorological inputs to the MODELS 3 system to be supplied by
26     prognostic models. The MM4 model  (the hydrostatic version of MM5) is presently being
27     examined by U.S.  EPA for this purpose.
28          Activities are currently underway in the Lake Michigan Oxidant Study (LMOS) to
29     supply prognostic model fields to U.S. EPA's  Regional Oxidant Model (ROM) for use in
30     simulating regional ozone distributions in four  multiple-day ozone episodes extensively
31     monitored during the 1991 field program in the midwest.  The U.S. EPA will be exercising
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 1     ROM2.2 (version 2,2) with fields obtained from CAL-RAMS (Lyons et al., 1991) to
 2     examine whether prognostic model output gives improved regional ozone estimates (Guinnup
 3     and Possiel, 1991).
 4          The SARMAP program is the modeling and data analysis component of a multiyear
 5     collaboration between two projects, the San Joaquin Valley Air Quality Study (SJVAQS) and
 6     the Atmospheric Utility Signatures, Predictions, and Experiments Study (AUSPEX). The
 7     major near-term objective of SARMAP is to understand the processes that lead to high ozone
 8     concentrations in the San Joaquin Valley of California.  An overview of the regional
 9     meteorological and air quality modeling approach of SARMAP is described by  Tesche
10     (1993).  For SARMAP,  the MM5 model was chosen as the "platform" prognostic
11     meteorological model because of its broad application history, its demonstrated reliability on
12     large domains requiring  spatially and temporally varying boundary conditions, and its
13     capability for four-dimensional data assimilation (FDDA) (see Section 3.6.2.2.4)—needed for
14     longer-range simulations. All of these attributes are crucial to the success of mesoscaie
15     meteorological modeling.
16          Prognostic models  are beEeved to provide a dynamically consistent, physically realistic,
17     three-dimensional representation of the wind and other meteorological variables at scales of
18     motion not resolvable by available observations.  However, the  meteorological fields
19     generated by a prognostic model do not always agree with  observational data.  Numerical
20     approximations, physical parameterizations, and initialization problems are among the
21     potential sources of error growth in model forecasts that can cause model solutions to deviate
22     from actual atmospheric behavior.  Described below are methods that have been devised over
23     the past 20 years to mitigate these problems.
24          "Post-processing" refers to methods whereby output fields from prognostic models are
25     selectively  adjusted through a series of objective techniques with the aim of improving the
26     realism of the resultant fields.  Examples of this procedure (sometimes referred to as
27     objective combination) are given by Cassmassi et al. (1990) in the Los Angeles Basin,
28     Kessler and Douglas (1989) in the South Central Coast Air Basin, and Moore et al. (1987) in
29     the San Joaquin Valley.
30          Ideally, a prognostic  model should be initialized with spatially varying, three-
31     dimensional fields  (i.e., wind, temperature, moisture) that  represent the state of the

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 1     atmosphere at the initial simulation time  A prognostic model that is initialized with such
 2     fields, however, can generate large non-meteorological "waves" when the initial conditions
 3     do not contain a dynamic balance consistent with the model formulation (Hoke and Ant lies,
 4     1976; Errico and Bates, 1988).  The objective of an initialization procedure is to bring the
 5     initial conditions into dynamic balance so that the model can integrate forward with a
 6     minimum of noise and a maximum of accuracy (Haltiner and Williams, 1980). Dynamic
 7     initialization makes use of a model's inherent adjustment mechanism to bring the wind and
 8     temperature into balance prior to the initial simulation time.  In this technique, a
 9     "pre-simulation" integration of the model equations produces a set of dynamically balanced
10     initial conditions.  By allowing the simulation to begin with a balanced initial state, this
11     technique reduces the generation of meteorological noise and thus improves the quality of the
12     simulation.
13
14     3.6.2.2.4   Four-Dimensional Data-Assimilation Techniques
15          Four Dimensional Data Assimilation (FDDA) refers to a class of procedures in which
16     observational data are used to enhance the quality of meteorological model predictions
17     (Harms et al., 1992).  The most common use of FDDA today in applications-oriented models
18     is known as Newtonian relaxation, or simply as "nudging".  With this method, model
19     estimates at a particular time interval are adjusted toward the observations by adding artificial
20     tendency terms to the governing prognostic  equations. The objective of this method is to
21     improve prognostic model estimates through the use of valid, representative observational
22     data. As an example of mis procedure, a linear term is added to the momentum equations to
23     "nudge" the dynamic calculation towards the observed state at each time step in regions
24     where data are available.  The FDDA procedures may be thought of as the joint use of a
25     dynamic meteorological model in conjunction with observed data (or analysis fields based on
26     these data) in such a manner that the prognostic equations provide temporal continuity and
27     dynamic coupling of the hourly fields of monitored data (Seaman, 1990).
28          A recent example of the use of FDDA in regional-scale applications with the
29     MM4/RADM model is given by Stauffer and Seaman (1990). Attempts to apply FDDA in
30     support of urban-scale photochemical grid modeling are described by Tesche et al. (1990b)
31     and McNally (1990) for the San Diego Air  Basin and by Stauffer et al. (1993) for the Grand

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 1     Canyon region of Arizona. Currently, FDDA is being used in the CAL-RAMS simulations
 2     in the LMOS program (Lyons et al.,  1991) and in the MM5 simulations for SARMAP
 3     (Seaman, 1992).
 4
 5     3.6.2.3  Chemical Mechanisms
 6          A chemical kinetic mechanism (a set of chemical reactions), representing the important
 7     reactions that occur in the atmosphere, is used in an air quality model to estimate the net rate
 8     of formation of each pollutant simulated  as a function of time.
 9          Various grid models employ different chemical mechanisms.  Because so many VOCs
10     participate in atmospheric chemical reactions, chemical mechanisms that explicitly treat each
11     individual VOC component are too lengthy to be incorporated into three-dimensional
12     atmospheric models.  Lumped mechanisms are therefore used (e.g., Lurmann et al., 1986;
13     Gery et al., 1989; Carter, 1990; Stockwell et ai, 1990).  These lumped mechanisms are
14     highly condensed and do not  have die ability to follow explicit chemistry because of this
15     lumping. Lumped-molecule mechanisms group VOCs by chemical classes (alkanes, alkenes,
16     aromatics, etc.).  Lumped-structure mechanisms group VOCs according to cartxm structures
17     within molecules. In both cases, either a generalized (hypothetical) or surrogate (actual)
18     species represents all species within a class.  Organic product and  radical chemistry is limited
19     to a few generic  compounds to represent all products; thus, chemistry after the first oxidation
20     step is overly uniform. Some mechanisms do not conserve carbon and nitrogen mass. Some
21     molecules do not easily "fit"  the classes  used in the reduced mechanisms.  Because different
22     chemical mechanisms follow  different approaches to "lumping," and because the developers
23     of the mechanisms made different assumptions about how to represent chemical processes
24     that are not well understood, models can produce somewhat different results under similar
25     conditions (Dodge, 1989).
26          No single chemical mechanism is currently considered "best."  Both UAM-IV and
27     ROM utilize the CBM-IV mechanism, which, along with the SAPRC (Statewide Air
28     Pollution Research Center, University of California, Riverside) and RADM mechanisms,  is
29     considered  to represent the state-of-the-science (Tesche et al., 1992; National Research
30     Council, 1991).  Agreement  among mechanisms is better for ozone than for other secondary
31     pollutants (Dodge, 1989,  1990; National Research Council, 1991), raising concern that the

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 1     mechanisms may suffer from compensating errors   These mechanisms are at least 5 years

 2     old and often tested on much older smog chamber data.

 3          The chemical mechanisms used in existing photochemical ozone models contain

 4     uncertainties that may limit the accuracy of their predictions.  The reactions that are included

 5     in these mechanisms generally fall into one of three categories:

 6          (1)    Reactions for which the magnitude of their rate constants and their product
 7                 distribution is well known. These include mostly the inorganic reactions and
 8                 those for the simple carbonyls.
 9
10          (2)    Reactions with  known rate constants and known products but uncertain product
11                 yields.  These are mostly organic reactions, and the actual product yields
12                 assumed may vary among mechanisms.
13
14          (3)    Reactions with  known rate constants but unknown products.  Each mechanism
15                 assumes its own set of products for reactions in this class.  This class includes
16                 aromatic oxidation reactions.

17

18          Most inorganic gas-phase processes are understood.  Regarding classes of VOCs the

19     following general comments can be made:
20          •      Unbranched alkanes comprise approximately one-half of the carbon emissions in
21                 urban areas.  Reaction rates are relatively slow.  The only important reaction is
22                 with the hydroxyl radical.  For alkanes C4 or below, the chemistry is well
23                 understood and the reaction rates are slow.  For C5 and higher alkanes the
24                 situation is more complex because few reaction products have been found.
25
26          •      Branched alkanes have rates of reaction that are highly dependent on structure.
27                 Rate constants  have been measured for only a few of the branched alkanes and
28                 reaction produces for this class of organics are not well characterized.
29
30          •      Alkenes are highly reactive with hydroxyl, ozone, and the  NO3 radical.  Most
31                 rate constants of these  reactions are known.  Alkenes make up about 15 % of the
32                 emitted carbon and constitute about 20 % of the hydrocarbon reactions in urban
33                 areas.  Ozone reaction products are not well characterized, and the mechanisms
34                 are poorly understood.  Mechanisms  for the NO3 radical are also uncertain.
35
36          •      Aromatics constitute about 15%  of the carbon compounds emitted and 20% of
37                 the hydrocarbons reacting in urban areas.  Aromatics have been frequently
38                 studied, but only a few reaction products have been well characterized.
39                 Aromatics act as  strong NOX sinks under low NOX conditions.
40
41          Mechanisms used in photochemical air quality models thus have uncertainties, largely

42     attributable to a lack of fundamental data on products and product yields.  The missing

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 1     information necessitates that assumptions be made.  Current mechanisms provide acceptable
 2     overall simulation of ozone generation in smog chamber experiments.  Specific VOCs may,
 3     however, be simulated poorly, and products other than ozone may not be accurately
 4     simulated.  Existing mechanisms are mostly applicable to single-day, high NOX conditions
 5     because those are the conditions of almost all smog chamber experiments. Low NOX
 6     condition simulations are less well verified. Fundamental kinetic data are needed on the
 7     photooxidation of aromatics, higher alkanes, and higher alkenes to fill in  areas of uncertainty
 8     in current mechanisms.  Whereas these uncertainties are important and require continued
 9     research to remove, the uncertainties are likely not such that general conclusions about the
10     relative roles of hydrocarbons and NOX in ozone formation will be changed by new data.
11
12     3.6.2.4  Deposition Processes
13          Species are removed from the atmosphere by interaction with ground-level  surfaces,
14     so-called dry deposition;  and  by absorption into airborne water droplets followed by transport
15     of the water droplets, wet deposition.  Dry deposition is an important removal process for
16     ozone and  other species on both the urban and regional scales and is included in  all urban-
17     and regional-scale models as a contribution to the ground-level flux of pollutants. Wet
18     deposition  is a key removal process for gaseous species on the regional scale and is included
19     in regional scale acid deposition models.  Urban-scale photochemical models have generally
20     not included a treatment of wet deposition  as ozone episodes  do  not occur during periods of
21     significant clouds or rain.
22
23     3.6.2.4.1   Dry Deposition
24          It is generally impractical to simulate, in explicit detail, the complex of multiple
25     physical and chemical pathways that result in dry deposition to individual surface elements.
26     Because of this, the  usual practice has been to adopt simple parameterizations mat consolidate
27     the multitude of complex processes.  For example, it is generally assumed that the dry
28     deposition flux is proportional to the local pollutant concentration [at a known reference
29     height (zr), typically 10 m], resulting in the expression F =  -v^C, where F represents the
30     dry deposition flux (the amount of pollutant depositing to a unit  surface area per unit time)
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 1     and C is the local pollutant concentration at the reference height.  The proportionality
 2     constant, vd> has units of length per unit time and is known as the deposition velocity.
 3          It is customary to interpret the dry deposition process in terms of the electrical
 4     resistance analogy, where transport of material to the surface is assumed to be governed by
 5     three resistances in series: the aerodynamic resistance  (ra), the quasi-laminar layer resistance
 6     (rb), and the surface or canopy resistance (rs) (Wu et al., 1992).  The aerodynamic resistance
 7     characterizes the turbulent transport through the atmosphere  from reference height zr down to
 8     a thin layer of stagnant air very near  the surface.  The molecular-scale diffusive transport
 9     across the thin quasi-laminar sublayer near the surface  is characterized by rb. The chemical
10     interaction  between the surface and the pollutant of interest once the gas molecules have
11     reached the surface is characterized by rc.  The total resistance (rr) is the sum of the three
12     individual resistances, and is, by definition, the inverse of the deposition velocity,
13     M'vd=rt=ra'>rrbJt~rs' Note that the deposition velocity  is small when any one of the
14     resistances is large. Hence, either meteorological factors or the chemical interactions on the
15     surface  can govern the rate of dry deposition.
16           Dry deposition velocities of HNO3 and SO2 are typically  ~2 cm s~ , and those of
17     O3 and  peroxyacetyl nitrate (PAN) are generally approximately 0.5 cm s"  and «* 1 cm s" ,
18     respectively (see, for example, Dolske and Gate, 1985; Colbeck and Harrison, 1985; Huebert
19     and Robert, 1985; Shepson et al., 1992).  With a 1-km-deep inversion or boundary layer, the
20     time-scale  for dry deposition is of the order of 1 day for a deposition velocity of 1 cm s"1,
21     and dry deposition is important for those chemicals with high or fairly high deposition
22     velocities and long or fairly long lifetimes ( > 10 days) due to photolysis and chemical
23     reaction (for example,  HNO3, SO2> and H2O2, as well as 03 and PAN).
24           A number of researchers have reviewed the deposition literature and provided
25     summaries of deposition velocity  data. The rank ordering of deposition velocity values
26     among pollutant species based on several such studies  is summarized as follows:
27           McRae and Russell (1984):
28           HNO3 > SO2 > NO2 » O3 > PAN  > NO
29           Derwent and Hov (1988):
30           HNO3 > SO2 = O3  > NO2 > PAN
31

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 1          McRae et al. (1982b):
 2          O, > NO2 > PAN > NO > CO
 3          Chang et al. (1987»:
 4          HNO3 > H2O2 >  NH3  > HCHO > O3 = SO2 = NO2 = NO >  RCHO
 5
 6          There is general agreement that HNO^ is removed at the highest observed rates, which
 7     is consistent with the relative deposition rates observed by Huebert and Robert (1985) and
 8     which suggests that the surface resistance of HNQij is essentially zero.  Most of the surveys
 9     are roughly consistent with the relative deposition velocity ordering seen in the experiments
10     of Kin and Chamberlain  (1976):  diffusion-limited acids > SO2 > NO2 « O3 > PAN >
11     NO > CO. This suggests surface resistance values should be ordered approximately as:
12     CO > NO > PAN > O3 *  NO2 > SO2 > HNO3 = 0.
13          There are a significant number of other gases for which there are no surface resistance
14     data and for which values must be estimated using engineering judgment.  The values should
IS     be consistent with the existing experimental values for vegetative surfaces, and should
16     preserve the apparent rank ordering among the pollutant species (discussed above). For
17     ozone, surface resistance values by land-use type and season recommended by  Sheih et al.
18     (1986) and Wesely (1988) are  appropriate. For NO, NO2, NH3, H2O2, HCHO, and
19     CH3CHO, the surface resistance values for each land use can be estimated from that for SO2
20     (Wesely, 1988),  except that different proportionality factors should be used for NO and NO2.
21
22     3.6.2.4.2   Wet Deposition
23          Wet deposition refers to  the removal  of gases and particles from the atmosphere by
24     precipitation events, through incorporation of gases and particles into rain, cloud, and fog
25     water followed by precipitation at the earth's surface.  Removal of gases and particles during
26     snow falls is also wet deposition.  Wet removal of gases arises from equilibrium partitioning
27     of the chemical between the gas and aqueous phases (Bidleman, 1988; Mackay, 1991). This
28     partitioning can be defined by means of a washout ratio,  Wg, with Wg -  [C\rainl\C\cdr,
29     where [Qrain and \C\air are the concentrations of the chemical in the aqueous and gas
30     phases, respectively.  Since Wg is the inverse of the air/water partition coefficient, J5Taw, then
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 1     (Mackay, 1991) Wg = RT/H, where R is the gas constant, T is the temperature, and H is the
 2     Henry's Law Constant.
 3          Particles, and particle-associated chemicals, are efficiently removed from the
 4     atmosphere by precipitation events,  and the washout ratios for particles, Wp, are typically in
 5     the range 104-106 (Eisenreich et al., 1981; Bidleman,  1988).  Wet deposition is important for
 6     particles (and particle-associated chemicals) and for those gas-phase compounds with washout
 7     ratios of Wg S 1(T. Examples of such gaseous chemicals are HNO3, H2O2, phenol, and
 8     cresols, all of which are highly soluble in water. Formaldehyde is present in the aqueous
 9     phase as the glycol, H2C(OH)2, and has an effective washout ratio of 7 x  103 at 298 K
10     (Betterton and  Hoffmann, 1988; Zhou and Mopper, 1990).  Note that the importance of wet
1 1     deposition may depend on whether the chemical is present in the gas phase or is particle-
12     associated.  For example, the gas-phase alkanes have  low values of Wg and are inefficiently
13     removed by wet deposition, while the particle-associated alkanes are efficiently removed by
14     wet deposition (Bidleman, 1988), through removal of the host particles.
15
16     3.6.2.5  Boundary and Initial Conditions
17          When a grid-based photochemical model is applied to simulate a past pollution episode,
18     it is necessary  to specify the  concentration fields of all the species computed by the model at
19     the beginning of the simulation. These concentration  fields are called the initial conditions.
20     Throughout the simulation it  is necessary to specify the species concentrationSj called the
21     boundary conditions, in the air entering the three-dimensional geographic domain.
22          Three general approaches for  specifying boundary conditions for urban-scale
23     applications can be identified:  (1) Use the output from a regional-scale photochemical
24     model; (2) use objective or interpolative techniques with ambient observational data; or,
25     (3) for urban areas sufficiently isolated from significant upwind sources, use default regional
26     background values and expand the area that is modeled.
27          In the ideal case, observed data  would provide information about the concentrations for
28     all the predicted species at the model's boundaries. An alternative approach is to use
29     regional models to set boundary and initial  conditions.  This is, in fact, preferred when
30     changes in these conditions are to be forecast.  In any event, simulation studies should use
3 1     boundaries that are far enough from the major source areas of the  region that concentrations
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 1     approaching regional values can be used for the upwind boundary conditions. Boundary
 2     conditions at the top of the area that is being modeled should use measurements taken from
 3     aloft whenever they are available.  Regional background values are often used in lieu of
 4     measurements.  An emerging technique for specifying boundary conditions is the use of a
 5     nested grid, in which concentrations from a  larger, coarse grid are used as boundary
 6     conditions for a smaller, nested grid with finer resolution. This technique reduces
 7     computational requirements compared to those of a single-size, fine-resolution grid.
 8          Initial conditions  are determined mainly with ambient measurements, either from
 9     routinely collected data or from special studies.  Where spatial coverage with data is sparse,
10     interpolation can be used to distribute the surface ambient measurements. Because few
11     measurements of air quality data are made aloft, it is generally assumed that species
12     concentrations are initially uniform in the mixed layer and above it.  To ensure  that  the
13     initial conditions do not dominate the performance statistics, model performance should not
14     be assessed until the effects of the initial conditions have been swept out of the grid.
15
16     3.6.3    Urban and Regional Ozone Air  Quality Models
17          Grid-based models that have been widely used to evaluate ozone and acid deposition
IS     control strategies are:
19          «     The Urban Airshed Model (UAM), developed by Systems Applications, Inc., has
20                been,  and  is continuing to be, applied to urban areas throughout the country,
21                It is described in Section 3.6.3.1. The current U.S. EPA-approved version is
22                UAM-IV.  The UAM-V, which has been developed for the Lake Michigan
23                Oxidant Study  (LMOS), is a nested regional-scale model.
24
25          •     The California Institute of Technology/Carnegie Institute of Technology (CIT)
26                model has been applied to California's South Coast Air Basin (McRae et al.,
27                1982a,b; McRae and Seinfeld, 1983; Milford et al., 1989; Harley et al., 1993).
28
29          •     The Regional Oxidant Model (ROM), developed by U.S. EPA,  has been applied
30                to the northeastern and southeastern United States (Schere and Way land,
31                1989a,b).  It is described in Section 3.6.3.2.
32
33          •     The Acid Deposition and Oxidant Model (ADOM) was developed by ENSR
34                Consulting and Engineering for the Ontario Ministry of the Environment and
35                Environment Canada (Venkatrani et al.,  1988) and the German
36                Umweldbundersamdt. Its primary application has been to acidic deposition.
37

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 1          •     The Regional Acid Deposition Model (RADM) was developed by the National
 2                Center for Atmospheric Research (NCAR) and the State University of Nev  York
 3                for the National Acid Precipitation Assessment Program (NAPAP),  The primary
 4                objective of RADM applications is the calculation of changes in sutftir and
 5                nitrogen deposition over the eastern United States and southeastern Canada
 6                resulting from changes in emissions (National Acid Precipitation Assessment
 7                Program, 1989). See Section 3.6.3.3 for a description  of RADM.
 8          A summary of the major applications of the above air quality models, including the
 9     Sulfur Transport Eulerian Model (STEM-II) „ is presented in Table 3-21.  All of the models
10     are nominally based on a 1-h time resolution.  The horizontal spatial resolutions vary from
11     5 to  120 km.  Typical spatial resolutions used in past model applications are summarized in
12     Table 3-22.  It is important to note that the spatial scale at which a  model is applied is
13     governed by the manner in which physical processes are treated and the spatial scale of the
14     inputs. The regional models can have a vertical resolution on the order of 10 to 15 layers
15     extending up to 6 to 10 km in order to treat vertical redistribution of species above the
16     planetary boundary layer. This increased vertical resolution often comes at the expense of
17     decreased horizontal resolution.  Urban models typically have two to five layers extending up
18     to 1,000 to 2,000 m. The treatment of meteorological fields by the six models is
19     summarized in Table 3-23.  Generally the treatment of meteorology is separate from the air
20     quality model itself, and models can employ wind fields prepared by different approaches as
21     long as consistent assumptions, such as non-divergent wind field, are  employed in each
22     model.  The regional models, ROM, RADM, ADOM,  and STEM-IT, treat the vertical
23     redistribution of pollutants resulting from the presence of cumulus clouds.  Table 3-24
24     summarizes the gas-phase chemical mechanisms incorporated  into the six models.  Generally
25     three chemical mechanisms are used in the models:  (1) CBM-IV used in ROM and UAM;
26     (2) versions of the SAPRC mechanism used in ADOM, STEM-H, and CIT; and (3) the
27     RADM mechanism. Of the three chemical mechanisms, RADM is the largest and CBM-IV
28     is the smallest.  Aqueous-phase chemistry is currently treated only in the regional models.
29     Cloud processes are treated in the three regional models,  RADM,  ADOM, and STEM-II
30     (Table 3-25). Cumulus venting and solar attenuation are treated in ROM.  Layer 3 depths
31     are also influenced by cloud thickness. At present, only RADM, ADOM and STEM-n treat
32     wet deposition.  The treatment of dry  deposition in the models is also summarized in
33     Table 3-25.

       December 1993                          1.1 so     DRAFT-T>O NOT OTTOTP nv rrrn

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Model
                   TABLE 3-21.  GRID-BASED URBAN AND REGIONAL AIR POLLUTION MODELS:
                            OVERVIEW OF THREE-DIMENSIONAL AIR QUALITY MODELS
       Major Applications
                                      Major References for
                                        Model Formulation
   Selected References for Model Performance
        Evaluation and Application
UAM
CIT
ROM
RADM
ADOM
STEM-H
Urban and nonurban areas in the
United States and Europe
Los Angeles Basin
Eastern United States
(E of 99° W longitude)

Eastern North America
Eastern North America and
Northern Europe
                               Reynolds et al. (1973, 1974, 1979)
                               Tesche et al. (1992)
                               U.S. Environmental Protection Agency
                               (1990a-e)
                               Scheffe and Morris (1993)
                               McRae et al, (1982a)
                               Lamb (1983)
                               Chang et al. (1987)
                               Venkatram et al. (1988)
Philadelphia area, Kentucky, and    Cannichael et al. (1986)
northeastern United States, central
Japan
Tesche et al. (1992)
McRae and Seinfeld (1983)
Russell et al. (1988a,b)
Harley et al. (1993)

Schere and Wayland (1989a,b)
Meyer et al. (1991)

Middleton et al. (1988, 1993)
Middleton and Chang (1990)
Dennis et al. (1993a)
Cohn and Dennis (1994)

Venkatram et al. (1988)
Macdonald et al. (1993)
Karamchandani and Venkatram (1992)
Cannichael et al. (1991)
Saylor et al. (1991)

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If   Model
                        TABLE 3-22.  GRID-BASED URBAN AND REGIONAL AIR POLLUTION MODELS:
                                     TREATMENT OF EMISSIONS AND SPATIAL RESOLUTION
                   Emitted Species
Point-Source Emissions
                                                                       Area-Source Emissions
Vertical Resolution
UAM       SO2, sulfate, NO, NO2, CO,
            NH3, and 8 classes of ROG
            and PM(4 size classes)


CIT         SO2, sulfate, NO, NO2, CO,
            NH3, and 6 classes of ROG
            and PM(4 size classes)
                                             Released into grid cell in layer
                                             corresponding to plume rise in
                                             UAM; treated with a reactive
                                             plume model in PARIS

                                             Treated with a plume model
                                             with simple NOX and O3
                                             chemistry
                                                                    Grid-average with resolution
                                                                    ranging from 4 km  x 4 km to
                                                                    10 km X 10 km in past
                                                                    applications

                                                                    Grid-average with 5 km x
                                                                    5 km resolution in past
                                                                    applications
                                                    Typically, 5-6 layers up to about 1.5 km
                                                    Five layers up to about 1.5 km
     ROM        CO, NO, NO2, and 8 classes   Released into grid cell in layer  Grid-average with 18.5 km X   Three layers up to about
                 of ROG                     corresponding to plume rise     18.5 km resolution in present   4 km
                                                                        applications
.o

5    RADM
            SO2, sulfate, NO, NO2, CO,    Released into grid cell in layer   Grid-average with 80 km X
            NH3, and 12 classes of ROG    corresponding to plume rise     80 km resolution in past
                                                                    applications
                                                    Fifteen layers up to about 16 km
1
3
ADOM      SO2, sulfate, NO, NO2,NH3,   Released into grid cell in layer   Grid-average with resolution    Twelve layers up to about 10 km
            and 8 classes of ROG and PM   corresponding to plume rise     ranging from 60 km X 60 km
                                                                    to about 120 km X 120 km in
                                                                    past applications


STEM-n     SO2, sulfate, NO, NO2, NH3,   Released into grid cell in layer   Grid-average with resolution    Ten to 14 layers up to about 6 km
            and 8 classes of ROG          corresponding to plume rise     ranging from 10 km X 10 km
                                                                    to 56 km X 56 km in past
                                                                    applications
0

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Model
                    TABLE 3-23.  GRID-BASED URBAN AND REGIONAL AIR POLLUTION MODELS:
                     TREATMENT OF METEOROLOGICAL FIELDS, TRANSPORT AND DISPERSION
              Meteorology
               Transport
               Turbulent Diffusion
UAM
CIT
ROM
RADM
ADOM
STEM-n
Constructed through data interpolation or   3-D wind field.  Finite difference numerical Vertical turbulent diffusion function of atmospheric
calculated with land-sea breeze or complex  technique.                              stability and friction velocity. Constant horizontal
terrain wind model.                                                             turbulent diffusion coefficient.
Constructed through data interpolation with  3-D wind field.  Finite element numerical
diagnostic wind model                   technique.
Constructed through data interpolation.
3-D wind field with vertical transport
through cumulus clouds.  Finite difference
numerical technique.
Calculated with Community Climate Model  3-D wind field with vertical transport
(CCM) and MM4                        through cumulus clouds. Finite difference
                                       numerical technique
Constructed through data interpolation in
combination with prognostic planetary
boundary-layer model.

Calculated with dynamic wind model
(MASS) or constructed through data
interpolation.
3-D wind field with vertical transport
through cumulus clouds.  Cubic spline
numerical technique.

3-D wind field with vertical transport
through clouds.  Finite element numerical
technique.
Vertical turbulent diffusion function of atmospheric
stability and friction velocity.  Horizontal turbulent
diffusion function of mixing height and convective
velocity scale.

Vertical turbulent diffusion function of atmospheric
stability. Horizontal turbulent diffusion function of
atmospheric stability, convective cloud cover and
velocity scale, and the depths of the boundary layer
and clouds.

Vertical turbulent diffusion function of atmospheric
stability and wind shear. No horizontal turbulent
diffusion.

Vertical turbulent diffusion calculated from planetary
boundary layer model.  No horizontal turbulent
diffusion.

Vertical turbulent diffusion function of atmospheric
stability and surface roughness.  Horizontal turbulent
diffusion proportional to vertical turbulent diffusion.

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I  —
     Model
 TABLE 3-24.  GRID-BASED URBAN AND REGIONAL AIR POLLUTION MODELS:
                      TREATMENT OF CHEMICAL PROCESSES
                 Gas-Phase Chemistry
                                                                                        Aqueous- Phase Chemistry
U)
UAM


CIT


ROM


RADM



ADOM
-    STEM-0
o
Eighty-seven reactions among 36 species including NOX, 03,  No treatment of aqueous-phase chemistry.
ROG, and SO2 (CBM-IV) (Gery et al., 1988, 1989)

One hundred-twelve reactions among 53 species including     No treatment of aqueous-phase chemistry.
NOX, O3, ROG, and SO2 (Lurmann et al., 1986)

Eighty-seven reactions among 36 species including NOX, O3,  No treatment of aqueous-phase chemistry.
ROG, and SO2 (CBM-IV)
                       One hundred fifty-seven reactions among
                       59 species including NOX ,  O3, ROG, and SO2 (Stockwell
                       et al., 1990)
                                                    Forty-two equilibria and five reactions for SO2 oxidation.
One hundred-twelve reactions among 53 species including     Fourteen equilibria and five reactions for SO2 oxidation
NOX, O3, ROG, and SO2 (Lurmann et al.,  1986)

One hundred-twelve reactions among 53 species including     Twenty-six equilibria and about 30 reactions for SO2 and NOX
NOX, O3, ROG, and SO2 (Lurmann et al.,  1986)            oxidation, radical chemistry, and transition metal chemistry.
I
2

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     Model
                         TABLE 3-25.  GRID-BASED URBAN AND REGIONAL AIR POLLUTION MODELS:
                                       TREATMENT OF CLOUD AND DEPOSITION PROCESSES
                       Cloud Processes
                                                  Wet Deposition
                   Dry Deposition
D
O

I
UAM

CIT


ROM

RADM
     ADOM
     STEM-n
No treatment of cloud processes.


No treatment of cloud processes.


No treatment of cloud processes, except
vertical transport treatment.
                                                      No treatment of wet deposition
                                                      No treatment of wet deposition.
                                                      No treatment of wet deposition
                Treatment of (1) precipitating cumulus    Calculated from precipitation rate and
                clouds, (2) precipitating stratus clouds and cloud average chemical composition.
                (3) fair-weather cumulus clouds based on  No below-cloud scavenging.
                precipitation amount, temperature, and
                relative humidity vertical profiles. Use of
                cloud-averaged properties for aqueous
                chemistry.
            Treatment of (1) cumulus clouds and
            (2) stratus clouds based on precipitation
            amount (for stratus clouds), temperature,
            and relative humidity vertical profiles.
            Vertical resolution for cloud chemistry.

            Treatment of clouds with the Advanced
            Scavenging Module based on cloud base
            height,  precipitation rate, and surface
            temperature.
                                      Calculated from precipitation rate and
                                      vertically weighted cloud average
                                      chemical composition, below-cloud
                                      scavenging included.
Dry deposition velocity approach; function of wind
speed, friction velocity, land type, and species.

Dry deposition velocity approach; function of
atmospheric stability, wind speed, land type, and species.

Resistance transfer approach; function of land type, wind
speed, atmospheric stability, and species.

Resistance transfer approach; function of atmospheric
stability, wind speed, season, land type, insolation,
surface wetness, and species.
Resistance transfer approach; function of atmospheric
stability, wind speed, land type, season, insolation, and
species.
                                      Calculated with the Advanced Scavenging  Resistance transfer approach; function of atmospheric
                                      Module.  Treats cloud water, rain water,   stability, land type, wind speed, and species.
                                      and snow; below-cloud scavenging
                                      included.
8
n

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 1           More detailed descriptions will now be  presented for UAM, ROM, and RADM.  The
 2      UAM is described as it is officially specified by EPA as a grid-based model for urban-scale
 3      ozone control strategy determination. Its regional-scale ozone model, ROM is being used by
 4      U.S. EPA to evaluate ozone control measures for the eastern United States and to provide
 5      boundary conditions for urban area simulations using UAM.  Representative of a
 6      comprehensive state-of-the-science ozone/acid deposition model, RADM has been used to
 7      evaluate combined ozone and acid deposition abatement strategies for the northeastern United
 8      States and Canada.
 9           The U.S. Environmental Protection Agency is embarking on a project to produce the
10      next generation of photochemical models, termed MODELS 3 (Dennis et al., 1993b).  This
11      group of models will be flexible (scalable grid and domain), will be modular (modules with
12      interchangeable data structure), will have uniform input/output across subsystems, and will
13      contain advanced analysis and visualization features. The models will be designed to take
14     advantage of the latest advances in computer architecture and software.
15
16      3.6.3.1   The Urban Airshed Model
17           The UAM is the most widely applied and broadly tested grid-based photochemical air
18      quality model. The model is described in a number of sources, including a multi-volume
19      series of documents issued by the U.S. Environmental Protection Agency (U.S.
20     Environmental Protection Agency, 1990a,b,c,d,e) and a comprehensive evaluation by Tesche
21      et al. (1992).  Current versions include provisions enabling the user to model transport and
22     dispersion within both the mixed and inversion layers.  The computer codes have been
23     structured to allow inclusion of up to 10 vertical  layers of cells and any number of cells in
24     the horizontal directions.
25          The original UAM developed by Reynolds et al. (1973) simulated the dynamic behavior
26     of six pollutants:  reactive and unreactive hydrocarbons, NO, NOj, ozone, and CO.  Since
27     1977, the UAM has employed various versions of the Carbon-Bond Mechanism.  Currently,
28     the model utilizes the CBM-IV Mechanism (Gery et al., 1988, 1989), which treats
29     36 reacting species. Reactive organic compounds include alkanes,  alkenes, aromatics, and
30     aldehydes; while nitrogen-bearing species include nitrous acid (HONO), nitric acid (HNO3),
31     and peroxyacetyl nitrate (PAN).

       December 1993                          3.19S      DRAFT-DO NOT OTTOTR OP rrm

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 1     3.6.3.2  The Regional Oxidant Model
 2          The ROM was designed to simulate most of the important chemical and physical
 3     processes that are responsible for the photochemical production of 03 over regional domains
 4     and for multiple 3-day episodes of up to IS days in duration. These processes include
 5     (1) horizontal transport,  (2) atmospheric chemistry and subgrid-scale chemical processes,
 6     (3) nighttime wind shear and turbulence associated with the low-level nocturnal jet, (4) the
 7     effects of cumulus clouds on vertical mass  transport and photochemical reaction rates,
 8     (5) mesoscale vertical motions induced by terrain and the large-scale flow, (6)  terrain effects
 9     on advection, diffusion,  and deposition, (7) emissions of natural and anthropogenic ozone
10     precursors, and (8) dry deposition.  The processes are mathematically simulated in a three-
11     dimensional Eulerian model with three vertical layers, including the boundary layer and the
12     capping inversion or cloud layer.  The ROM geographical domains are summarized in
13     Table 3-26 and illustrated  in Figure 3-26.
14          Meteorological data are used to objectively model regional winds and diffusion. The
15     top three model layers of ROM are prognostic (predictive) and  are free to locally expand and
16     contract in response to changes in the physical processes occurring within them.  During an
17     entire simulation period, horizontal advection and diffusion and gas-phase chemistry are
18     modeled in the upper three layers. Predictions from layer 1 are used as surrogates for
19     surface concentrations.  Layers 1  and 2 model the depth of the well-mixed layer during the
20     day.  Some special features of layer 1 include the modeling of (1) the substantial wind shear
21     that can exist in the lowest few hundred meters  above ground in local areas where strong
22     winds exist and the surface heat flux is weak; (2) the thermal internal boundary layer that
23     often exists over large lakes or near sea coasts;  and (3) deposition onto terrain features that
24     protrude above the layer.  At night, layer 2 represents  what remains of the daytime mixed
25     layer.  As  stable layers  form near the ground and suppress turbulent vertical mixing, a
26     nocturnal jet forms above the stable layer and can transport aged pollutant products and
27     reactants considerable distances.  At night, emissions from tall  stacks and warm cities are
28     injected directly into layers 1 and 2. Surface emissions are specified as a mass flux through
29     the bottom of layer 1.  During the day, the top  model  layer, layer 3, represents the synoptic-
30     scale subsidence inversion characteristic of high ozone-concentration periods; the base of
31     layer 3 is typically 1 to 2 km above the ground. Relatively clean tropospheric air is assumed

       December 1993                          3-196      DRAFT-DO NOT QUOTE OR CITE

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    TABLE 3-26. REGIONAL QXTOANT MODEL GEOGRAPHICAL DOMAINS

GENERAL INFORMATION:

   ROM grid cells are 1/4° longitude and 1/6° latitude in size or approximately 18.5 km. Actual domain
names are included in parenthesis after the general geographical description. In addition, all domains can be
run independently or windowed from the "super" domain.

SUPER DOMAIN (SUPROXA)

     99.00 W to 67.00 W Longitude
     26.00 N to 47.00 N Latitude
     128  X 126 Grid Cells (columns X rows)

NORTHEAST DOMAIN (NEROXA)

     89.00 W to 67.00 W Longitude
     35.00 N to 47.00 N Latitude
     88 X 72 Grid Cells (columns X rows)

MIDWEST DOMAIN (MIDROXA)

     97.00 W to 78.00 W Longitude
     35.00 N to 47.00 N Latitude
     76 X 72 Grid Cells (columns X rows)

SOUTHEAST DOMAIN (SEROXA)

     98.75 W to 76.25 W Longitude
     27.67 N to 37.67 N Latitude
     90 X 60 Grid Cells (columns x rows)

SOUTHERN DOMAIN (TEXROXA)

     99.00 W to 81.00 W Longitude
     26.00 N to 37.67 N Latitude
     72 X 70 Grid Cells (columns X rows)

NORTHEAST DOMAIN (ROMNET)

     85.00 W to 69.00 W Longitude
     36,33 N to 45.00 N Latitude
     64 X 52 Grid Cells (columns X rows)

NORTHEAST DOMAIN (NEROS1)

     84.00 W to 69.00 W Longitude
     38.00 N to 45.00 N Latitude
     60 X 42 Grid Cells (columns X rows)

SOUTHEAST DOMAIN (SEROS1)

     97.00 W to 82.00 W Longitude
     28.00 N to 35.00 N Latitude
     60 X 42 Grid Cells (columns X rows)
December 1993                          1.107      DRAFT-DO NOT OTTOTF. OR rrm

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                    W97Se9S94939Z01908988S78e8S8A83B28160797S777675747372717068asa7
                  99 98 97 98 96 M 93 92 91 90 SB 88 87 M 85 84 83 82 Bl 80 79 78 77 78 75 74 73 72 71 70 68 88
                                                Longitude

       Figure 3-26. Regional oxidant model superdomain with modeling domains.
       Source: R. Wayland, U.S. Environmental Protection Agency (1993).
 1     to exist above layer 3 at all times and stratospheric intrusion of O3 is assumed to be
 2     negligible.  If cumulus clouds are present, an upward flux of Oj and precursor species is
 3     injected into the layer by penetrative convection. At night,  O3 and the remnants of other
 4     photochemical reaction products may remain in this layer and be transported long distances
 5     downwind.  These processes are modeled in layer 3.
 6          When cumulus clouds are present in a layer 3 cell, the upward vertical mass  flux from
 7     the surface is partially diverted from injection into layer 1 to injection directly into the
 8     cumulus cloud of layer 3. In the atmosphere, strong thermal vertical updrafts, primarily
 9     originating near the surface in the lowest portion of the mixed layer, feed growing fair-
10     weather cumulus clouds with vertical air currents that extend in one steady upward motion
       December 1993
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 1     from the ground to well above the top of the mixed layer.  These types of clouds are termed
 2     "Mr-weather cumulus" since atmospheric conditions are such that they do not grow to the
 3     extent that precipitation forms.  The dynamic effects of this transport process and daytime
 4     cloud evolution can have significant effects on the chemical fate of pollutants.  Within the
 5     ROM system, a submodel parameterizes the above cloud flux process and its impact on mass
 6     fluxes among all the model's layers.  In the current implementation of the chemical kinetics,
 7     liquid-phase chemistry is not included, and thus part of the effects from the cloud flux
 8     processes are not accounted for  in the simulations.  The magnitude of the mass flux
 9     proceeding directly from the surface layer to the cloud layer is modeled as being proportional
10     to the observed amount of cumulus cloud coverage and inversely proportional to the observed
11     depth of the clouds.
12          Horizontal transport within the ROM system is governed by hourly wind fields that are
13     interpolated from periodic wind observations made from upper-air soundings and surface
14     measurements.  During the nighttime simulation period, the lowest few hundred meters of
15     the atmosphere above the ground may become stable as  a radiation inversion forms. Wind
16     speeds increase just above the top of this layer, forming the nocturnal jet. This jet is capable
17     of carrying O3, other reaction products, and emissions injected aloft considerable distances
18     downwind.  This phenomenon is potentially significant in modeling regional-scale air quality
19     and is implicitly treated by the model, where the definition of layer  1 attempts to account
20     for it.
21          The ROM system requires five types of  "raw" data inputs: air quality, meteorology,
22     emissions, land use, and topography.
23          Air quality data required by  the ROM include initial conditions and boundary
24     conditions.  The model is initialized several (usually 2 to 4)  days before the start of the
25     period of interest (called an "episode,"  usually around 15 days long) with clean tropospheric
26     conditions for all species.  Ideally, the  initial condition field will have been transported out of
27     the model domain in advance of the portion of the episode of greatest interest. Upwind
28     lateral boundary conditions for  O3 are updated every  12 h based on measurements, except for
29     the large superdomain, where tropospheric background values are used. Other species
30     concentrations at the boundaries, as well as all species at the top of the modeling domain, are
31     set to tropospheric clean-air concentrations.

       December  1993                          1-1QQ      DRAFT-DO NOT OTTOTR OP rrm

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 1          Meteorological data are assimilated by the first stage of preprocessors.  These data
 2     contain regular hourly observations from U.S. National Weather Service surface stations (and
 3     from similar stations in Canada as necessary), including wind speed and direction, air
 4     temperature and dew point, atmospheric pressure, and cloud amounts and heights, Twice-
 5     daily sounding data from the upper-air observation network are also included in the
 6     meteorological database.  Upper-air meteorological parameters include atmospheric pressure,
 7     wind speed and direction, and air temperature and dew point. Finally, both buoy and
 8     Coastal Marine Automated Station data are used; parameters typically reported are wind
 9     speed and direction, and air and sea temperatures.
10          Emissions data for the primary species are input to the ROM system as well.
11     Originally these data were provided from the National Acid Precipitation Assessment
12     Program  1985 emissions inventory with 18.5-km spatial resolution. Most recently, the
13     interim regional inventory is being widely used to support current applications of the ROM,
14     It represents an update and improvement to the NAPAP inventory and is being used to
15     support State Implementation Plan modeling until State inventories are approved (U.S.
16     Environmental Protection Agency,  1993a,b).  Species included are CO, NO, NO^, and ten
17     hydrocarbon reactivity categories.  Natural hydrocarbons are also input, including isoprene
18     explicitly, monoterpenes divided among the existing reactivity classes, and unidentified
19     hydrocarbons. The chemical mechanism in ROM is the CBM-IV as previously described.
20          Land-use input data consist of 11  land-use categories in 1/4-degree longitude by
21     1/6-degree latitude grid cells. The data are more than 20 years old and represent a
22     weakness.  Data are provided for the United States and Canada as far as 55° N. The land-
23     use categories are (1) urban land, (2) agricultural land, (3) range land, (4) deciduous forests,
24     (5) coniferous forests, (6) mixed-forest wetlands,  (7) water, (8) barren land, (9) nonforested
25     wetland,  (10) mixed agricultural land and range land, and (11) rocky, open places occupied
26     by low shrubs and lichens.  Land-use data are used to obtain biogenic emissions estimates as
27     a function of the area of vegetative land cover, and for the determination of surface heat
28     fluxes.
29          Topography input data consist of altitude matrices of elevations in a 7.5°  x 7.5° grid.
30     The data are obtained from the GRIDS database operated by U.S. EPA's Office of
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 1     Information Resources Management. Topography data are used in the calculation of layer
 2     heights.
 3
 4     3.6.3.3  The Regional Acid Deposition Model
 5          The Regional Acid Deposition Model was initially developed at the National Center for
 6     Atmospheric Research (NCAR) for U.S, EPA, and subsequently refined and improved at the
 7     State University of New York at Albany (SUNYA). The model is an Eulerian transport,
 8     transformation, and removal model that includes a treatment of the relevant physical and
 9     chemical processes leading to acid deposition and the formation of photochemical oxidants.
10     As summarized in Tables 3-21 through 3-25, these processes include atmospheric transport
11     and mixing, gas-phase and aqueous-phase chemical transformations, dry deposition, and
12     cloud mixing  and scavenging.
13          Chemical trace species are transported  and diffused through the three-dimensional
14     RADM grid using externally specified meteorological data.  The RADM uses hourly three-
15     dimensional fields of horizontal winds, temperature, and water vapor mixing ratio calculated
16     by the meteorological model MM4 with four-dimensional data assimilation (FDDA).
17     In addition, RADM requires two-dimensional,  hourly fields  of surface temperature, surface
18     pressure, and precipitation rates over the model domain. Kuo et al. (1985) found that to
19     calculate accurate mesoscale trajectories, at least 3-h temporal resolution is desirable, and the
20     12-h resolution of upper air observations is inadequate.  Recent verification studies with
21     30 meteorological episodes by Stauffer and Seaman (1990) further support the use of MM5
22     data with FDDA.  Using meteorology generated from a dynamically consistent
23     meteorological model can introduce errors caused by simulation errors associated with the
24     meteorological model.  These uncertainties can be quantified through objective verification
25     studies with observed data (Anthes et al., 1985; Stauffer and Seaman, 1990).
26          The RADM2 chemical mechanism has been described  by Stockwell et al. (1990),
27     Chang et al. (1991),  Carter and Lurmann (1990), and Stockwell and Lurmann (1989). For
28     RADM2, the VOCs are aggregated into 12 classes of reactive organic species.  Each
29     category of VOC is represented by several model species that span the required range for
30     reaction with the OH radical. Most emitted organic compounds are lumped into surrogate
31     species of similar reactivity and molecular weight, although organic chemicals with large

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 1     emissions are treated as separate model species even though their reactivities may be similar.
 2     Categories of VOCs with large reactivity differences and complicated secondary chemistries
 3     are represented by larger numbers of intermediates and stable species.  During the
 4     aggregation of organic species, the principle of reactivity weighting is followed to attempt to
 5     account for differences in reactivity.
 6
 7     3.6.4   Evaluation of Model  Performance
 8          Air quality models are evaluated by comparing their predictions with ambient
 9     observations. Because a model's demonstration of attainment of the ozone NAAQS is based
10     on hypothetical reductions of emissions from a base-year-episode simulation, the accuracy of
11     the base-year simulation is necessary,  but not sufficient. An adequate model should give
12     accurate predictions of current peak ozone concentrations and temporal and spatial ozone
13     patterns.  It should also respond accurately to changes in VOC and NOX emissions, to
14     differences hi VOC reactivity, and to  spatial and temporal changes in emissions patterns for
15     future years.
16          Model performance can be evaluated at several levels.  The important sub-models, the
17     emissions  model, the meteorological model, and the chemical mechanism, can be
18     independently evaluated, and the model as a whole can be evaluated. Evaluation of
19     emissions  models can be carried out with special measurements designed to isolate the effects
20     of emissions from a particular source  category, such as tunnel studies (Pierson et al., 1990)
21     or on-road surveillance of motor vehicles (Lawson et al., 1990) to evaluate the accuracy of
22     motor vehicle emissions models. Meteorological sub-models can be evaluated from the
23     results of tracer experiments.  Chemical mechanisms have traditionally been developed and
24     evaluated on the basis of smog chamber experiments.  A question that merits continued
25     attention is how well chemical mechanisms developed with reference to smog chamber data
26     perform when simulating the ambient  atmosphere.   As noted in this  section, comparisons of
27     observed and predicted concentrations for all important precursors, intermediates, and
28     products are important in assessing the accuracy of a chemical mechanism.
29
30
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 1      3.6.4.1   Model Performance Evaluation Procedures
 2           Specific numerical and graphic procedures have been recommended for evaluation of
 3      the accuracy of grid-based photochemical models (Tesche et al., 1990b).  The methods
 4      suggested include the calculation of peak prediction accuracy; various statistics based on
 5      concentration residuals; and time series of predicted and observed hourly concentrations.
 6      Four numerical measures  appear to be most helpful in  making an initial assessment of the
 7      adequacy of a photochemical simulation (Tesche et al., 1990b):
 8
 9          •     The paired peak prediction accuracy.
10
11           •     The unpaired peak prediction accuracy.
12
13          •     The mean normalized bias.
14
15          •     The mean absolute normalized gross error,
16
17          Accurate matching of ozone alone may not be sufficient to ensure that a model is
18     performing accurately. The possibility of compensatory errors  must be recognized in which
19     two or more sources of error interact in such a way that ozone is predicted accurately, but
20     for the wrong reasons. The inaccuracies offset each other in part.   The modeling effort
21     should be designed to minimize the likelihood of the presence of compensatory errors,
22          Evaluation of model performance for precursor and intermediate species as well as  for
23     product species other than ozone, when ambient concentration data for these species are
24     available, significantly improves the chances that a flawed model will be identified.
25     Comparisons of observed and predicted concentrations for all important precursors,
26     intermediates, and products involved in photochemical air pollution—such as individual
27     VOCs, nitric oxide, nitrogen dioxide, PAN, ozone, H2O2, nitrous acid (HONO), and HNO3
28     —are useful in model evaluation, especially with respect to the chemistry component of the
29     model (Jeffries et al., 1992).  Comparisons of predictions and observations for total organic
30     nitrates (mainly PAN) and inorganic nitrates (HNO3 and nitrate aerosol) can be used to test
31     qualitatively whether the emissions inventory has the correct relative amounts of VOCs and
32     NOX.  However, to include HNO3 and nitrate aerosol  in the data set for model comparisons,
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 1     the model should include an adequate description of the HNO^ depletion process associated
 2     with aerosol formation.
 3          Adequate model performance for several reactive species increases the assurance that
 4     correct ozone predictions arc not a result of chance or fortuitous cancellation of errors
 5     introduced by various assumptions.  Multispecies comparisons could be the key in
 6     discriminating among alternative modeling approaches that provide similar predictions of
 7     ozone concentrations.
 8          As noted above, photochemical models have the potential to produce nearly the right
 9     ozone concentrations when performance is evaluated,  but do so because two or more flaws
10     were compensating each other. The existence of compensating errors in many modeling
11     applications is suspected because most applications to date have used emission inventories
12     whose validity is now in question (National Research  Council, 1991). Underestimation of
13     VOC emissions from motor vehicles may be responsible for the lack of agreement between
14     inventories and ambient concentration data (Baugues,  1986; Lawson et al., 1990; Pierson
15     et al., 1990; Fujita et al., 1992).  Underestimation of emissions from other sources is also a
16     possibility. One potentially underestimated VOC source is vegetation, which naturally emits
17     VOCs.  An underestimation of VOC emissions could  be compensated for by underestimation
18     of mixing height or wind speed or by overestimation of boundary concentrations of ozone or
19     precursors or by inaccurate chemistry modules.  Boundary concentrations (which can be
20     obtained from measurements or regional models or by assuming background concentrations,
21     as discussed in  Section 3.6.2.6) are often poorly defined.
22          If only a routine database is available for modeling ozone in an urban area, then there
23     are several areas of concern that require attention (Roth, 1992):
24
25          •     Air quality aloft - Most likely these data will not be available. These
26                measurements  are important and instrumental for diagnostic analysis of model
27                simulations.
28
29          •     Boundary  conditions - If the possibility of significant transport into the region
30                exists, and the data are not  available, the boundary conditions become a variable
31                that allows the introduction  of compensatory errors if the emissions are
32                inaccurate. An approach to circumvent this problem is to define the region in a
33                way so that the boundaries become a much less significant issue.
34

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 1          •     Ambient VOC data - These are generally not routinely available.  In their
 2                absence, evaluation of model performance is hampered.
 3
 4          •     Meteorological data aloft - Very often there are only surface measurements and a
 5                few soundings from which to extrapolate the needed data.
 6
 7          If any of these four areas is missing from the database, the performance evaluation and
 8     subsequent model application must be adequately planned to minimize the possibility of
 9     compensatory errors.
10
11     3.6.4.2  Performance Evaluation of Ozone Air Quality Models
12     3.6.4.2.1   Urban Airshed Model
13          The UAM has been applied to many urban areas in the United States and Europe, and
14     most of these studies have included some form of performance evaluation. (See summary in
15     Tesche et al., 1992, Table 6-2.) Thus, there is a growing body of information concerning
16     the accuracy of the model's predictions.  (UAM itself was continuing to undergo revision.)
17     Evaluations of UAM's performance have been carried out for a number of geographic areas.
18     Evaluations carried out since 1985 have indicated mean discrepancies between predicted and
19     measured ozone values of 20 to 40% of the observations, when paired in space and time
20     (Roth et al., 1989). The prediction of peaks exhibits relative errors that are  smaller than the
21     average error, with a tendency toward underprediction (Roth et al.,  1989).  The
22     discrepancies between predicted and measured NO2  in UAM applications are on the order of
23     30 to 50% with no improvement over the history of modeling applications (Roth et al.,
24     1989).  Underprediction of NO2 by UAM has been typical,  generally on the order of 20 to
25     40% (Roth etal., 1989).
26
27     3.6.4.2.2   Regional Oxidant Model
28          A primary role of the ROM model is to estimate boundary conditions for use by the
29     Urban Airshed Model in evaluating hydrocarbon and NOX reduction strategies for urban
30     areas in the eastern United States, especially in areas where transport is a significant element
31     (U.S. Environmental Protection Agency, 1990f).  Analysis of regional ozone abatement
32     strategies is also a major role of the ROM model (Possiel et al., 1990).

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 1          The ROM has been used in a U.S, EPA program, the Regional Ozone Modeling for
 2     Northeast Transport (ROMNBT) program, to assess the effectiveness of various regional
 3     emission control strategies in lowering O3 concentrations to nationally mandated levels for
 4     the protection of human health, forests, and crops (Meyer et al., 1991). As part of the
 5     ROMNET program, the ROM is also being used to provide regionally consistent initial and
 6     upwind boundary conditions to smaller-scale urban models for simulations of future-year
 7     scenarios.
 8          The most complete testing of ROM2.0 was accomplished in an evaluation with the
 9     50-day (My 12 to August 31, 1980) NBROS database (Schere and Wayland, 1989a,b). The
10     model underestimated the highest values and overestimated the lowest. It showed good
11     performance (an overall 2% overproduction) in predicting maximum daily 03 concentrations
12     averaged over aggregate groups of monitoring stations. A key indicator of model
13     performance on the regional scale is the accuracy of simulating the spatial extent and
14     location, as well as the magnitude, of the pollutant concentrations  within plumes from
15     significant source areas.  In ROM2.0 performance analyses, plumes from the major
16     metropolitan areas of the Northeast Corridor, including Washington, DC; Baltimore;
17     New York; and Boston, could be clearly discerned in the model predictions under episodic
18     conditions. Generally the plumes were well characterized by  the model, although there was
19     evidence of a westerly transport bias and underprediction of O3 concentrations near the
20     center of the plume.  Using aircraft data, ROM2.0 was found to underpredict the regional
21     tropospheric burden of ozone.
22          The evaluation of ROM2.1 (Pierce et al., 1990), unlike  that of ROM2.0, was based on
23     routinely archived data from state and local agency monitoring sites rather than on an
24     intensive field-study period.  The evaluation consisted of the comparison of observed and
25     predicted O3 concentrations during selected episodes (totaling 26 days) of high ozone
26     observed during the summer of 1985.  Evaluation showed that ROM2.1 underestimated the
27     highest values and slightly overestimated the lowest; underestimates of the upper percentiles
28     tended to be more prevalent in the southern and western areas of the ROMNET domain
29     (Table 3-26). The model showed good performance (an overall 1.4% overprediction) in
30     predicting maximum daily O3 concentrations averaged over aggregate  groups of monitoring
31     stations; and it  appears to correct for the westerly transport bias of high-ozone plumes in the

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 1      Northeast Corridor seen in ROM2.0.  As with ROM2.0, model performance degraded as a
 2      function of increasingly complex mesoscale wind fields.
 3
 4      3.6.4.3   Data Base Limitations
 5           As previously mentioned, the use of routine air quality and meteorological data requires
 6      that a number of assumptions be made about key model inputs. While intensive field studies
 7      are desirable during ozone episodes to acquire the full set of data required, three key
 8      problems arise:  such studies are expensive and,  therefore, are limited in number; the time
 9      required to cany out field studies usually exceeds the time available; and most field studies
10     have not captured the worst ozone episodes.  Since U.S. EPA guidance emphasizes planning
11      to meet worst-case conditions, field data must often be manipulated to approximate highest
12      ozone concentrations.  Such adjustments invariably increase uncertainty in model projections.
13           Studies that have, or will, provide data for model evaluation include:  the St. Louis
14     Regional Air Pollution Study (RAPS) conducted  in 1975-1976; the Northeast Corridor
15     Regional Modeling Project (NECRMP) conducted in 1979 and 1980; the South Central Coast
16     Cooperative Aerometric Monitoring Program (SCCCAMP) conducted in  1985; the South
17     Coast Air Quality Study (SCAQS) conducted in  1987; studies in Sacramento and San Diego
18      in 1990; SJVAQS/AUSPEX conducted in 1990;  the Lake Michigan Oxidant Study (LMOS)
19     conducted in 1990 and 1991; the Southern Oxidant Study (SOS) conducted in 1991 and 1992;
20     arid a Gulf Coast study planned for 1993.
21           In most cases, field studies have not coincided with periods in which ozone
22     concentrations have attained values as high as the design values.  Given the low probabilities
23     of occurrence of the most adverse meteorological conditions and the fact that field studies
24     typically acquire data for two or three ozone episodes, obtaining a design value concentration
25     during the course of a field study is unlikely.
26          The U.S. EPA recommends that the five highest daily maximum ozone concentrations
27     at a design-value site, selected from the three most recent years, be modeled if EKMA is
28     used for a SIP (U.S. Environmental Protection Agency,  1989b).  Because EKMA's  data
29     requirements are minimal, it can be applied to the worst episodes. In contrast, the number
30     of episodes available for grid-based modeling is  less than desirable in all areas. In addition,
31     any available intensive databases often do not include the worst-case meteorology; intensive

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 1     databases typically restrict modeling to two or three ozone episodes having a duration of 2 to
 2     3 days each.  Moreover, the intensive databases never encompass the fall range of
 3     meteorological conditions of interest (if ozone exceedances occur in an area under different
 4     meteorological conditions, the relative effectiveness of different control strategies might vary
 5     with the different meteorological conditions). The U.S. EPA spells out procedures for
 6     episode selection for use with grid-based models (U.S.  Environmental Protection Agency.
 7     1991b).
 8          Because the number of intensive databases is limited both in terms of episodes and
 9     regions, U.S. EPA has investigated the feasibility of applying UAM without conducting
10     intensive field studies (Scheffe and Morris, 1990a,b).  These studies, known as the Practice
11     for Low-cost Application in Nonattainment Regions (PLANE), were conducted for
12     New York, Philadelphia, Atlanta,  Dallas-Fort Worth, and St. Louis.  Of the five cities
13     studied, St. Louis, New York, and Philadelphia had intensive databases available.
14     Simulations were carried out using both routine and intensive databases for St. Louis and
15     Philadelphia, Model performance using routine data was much better for St. Louis than for
16     Philadelphia (Scheffe and Morris,  1990a,b).  Scheffe and Morris (1990a,b) caution that the
17     differing results may be complicated by the quality of the databases, but they speculate that
18     model performance using routine databases for Philadelphia might have been poorer because
19     of regional transport.  Performance  statistics  for all four applications using routine data were
20     consistent with other UAM applications (Scheffe and Morris, 1990a,b); however, the paucity
21     of data in the routine databases precluded any investigation of the possibility that
22     compensating errors occurred.
23           Scheffe and Morris (1990a,b) note that the PLANE lack of air quality data was
24     addressed by extending the length of the simulations and expanding  the upwind boundary,
25     which, in effect, increased the need for accurate emissions inventories (boundary conditions
26     could also be obtained through use of EOM). For PLANE applications, gridded emissions
27     were created from routine county-level emission inventories by utilizing an emissions
28     program that made use of surrogate information,  such  as population distribution.
29
30
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 1      3.6.5   Use of Ozone Air Quality Models for Evaluating Control Strategies
 2           Photochemical air quality models are used for control strategy evaluation by first
 3      demonstrating that a past episode, or episodes, can be adequately simulated and then
 4      reducing hydrocarbon or NOX emissions or both in the model inputs and assessing the effects
 5      of these reductions on ozone in the region.  Ozone concentrations can be decreased by
 6      reducing either VOC or NOX concentrations to sufficiently low levels.  Controlling VOC
 7      emissions always delays ozone formation and  reduces the amount of ozone formed.
 8      Controlling highly reactive VOCs in areas exhibiting low VOC-to-NOx ratios delays and
 9      reduces ozone formation most effectively.  The effects of NOX emissions reductions on ozone
10      concentrations vary because NOX is an atypical precursor:  though it is necessary for ozone
11      formation, fresh NO emissions remove ozone, and high concentrations of NOX retard the rate
12      of ozone formation by removing radicals.   Control of NOX tends to accelerate the rate of
13      ozone formation; however, its effects on peak ozone concentration depend upon the location
14     and timing of the control and upon ambient concentrations of VOCs and NOX, which vary
15      widely in  time and space, even within a single urban area during one day.
16          Grid modeling applications are currently underway by or for State agencies for
17     approximately 20 areas within the United States to support regional ozone SIP revisions.
18            An immediate problem faced for almost all urban areas is that even if an  adequate
19     number of episodes exist, the episodes may not include the most adverse ozone levels.
20     An inherent question in using a less adverse episode to develop control strategies is how
21      these strategies extrapolate to a more severe set of conditions.  There is no clear answer to
22     this question at this point. At present, control strategies, evaluated using grid-based models,
23     are determined based on available episodes that have the largest amount of data whether or
24     not these episodes contain the highest ozone concentration achieved. Another issue is that
25     the form of the NAAQS for ozone does not correspond with the output from a grid-based
26     model.  The model output does not provide a direct answer to whether an area will meet the
27     standard in its current statistically based form.
28          Table 3-27 summarizes a number of recent ozone control strategy evaluations for
29     different areas of the United States.   Some general observations can be made concerning
30     issues that have arisen  in control strategy exercises, particularly as they relate to problems
31     associated with different areas of the country (Roth, 1992). In California, model results

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      TABLE 3-27.  APPLICATIONS OF PHOTOCHEMICAL AIR QUALITY MODELS TO
                                       EVALUATING OZONE
       Investigators
     Region/Episode
   Model Used
     Strategies Evaluated
       Chu et al. (1992)
       Chu and Cox (1993)
       Roselle et al. (1992)
       Mathur and Schere (1993)
       Possiel et al. (1993)
       Possiel and Cox (1993)

       Milford et al, (1992)
       Rao (1987)
       Rao et al. (1989)
       Rao and Sistla (1993)
       Scheffe and Morris
       (1990a,b)
       Possiel et al. (1990)
Eastern U.S./
July 2-10, 1988
Northeastern U.S./
July 1-12, 1988

Northeastern U.S./
July 2-17, 1988

New York Metropolitan
area/
5 days in 1980
New York
St. Louis
Atlanta
Dallas-Ft. Worth
Philadelphia
Northeastera U.S./
July 2-17, 1988
       Roselle and Schere (1990)  Northeast U.S./
       Roselle et al. (1991)       July 12-18, 1980
       Dunker et al. (1992a,b)
       Milford et al. (1989)
Los Angeles
New York
Dallas-Ft. Worth

South Coast Air Basin
ROM2.2
ROM2.2
ROM
UAM/RQM2A
UAM
ROM
                       ROM2.1
UAM
Across-the-board NOX/VOC
reductions.
Estimate ozone reductions per
1990 Clean Air Act Amendments

Analysis of effect of NO,
reductions.

Evaluation of 1988 SIPs and
VOC/NOX strategies

Use of UAM for demonstrating
attainment with routinely
available data
Ozone control strategies in
Northeast

Sensitivity of ozone in Northeast
to biogenic emissions

Effects of alternate fuels and
reformulated gasolines on ozone
levels

Effects of systematic VOC and
NOX reductions
       Middleton et al. (1993)
Eastern U.S. and
Southeastern Canada
RADM
2010 emissions projections
1      indicate that ozone has been underestimated, most likely because VOC emissions from motor
2      vehicles have been seriously underestimated.  The underestimation was hidden by adjusting
3      other model inputs within their range of uncertainty.  In Atlanta, it has been estimated that
4      approximately 60% of the VOC inventory is of biogenic origin, and the variation of
5      anthropogenic emissions reductions required to achieve ozone attainment within the
6      uncertainty range of the biogenic emissions  is on the order of 20%.  The uncertainty range of
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 1     the biogenic VOC emissions needs to be reduced to obtain tighter control strategy estimates,
 2     Studies with ROM and UAM tend to indicate that NOX control is beneficial in the northeast.
 3     While it is unlikely that this general  conclusion will be altered by more refined data, there
 4     are still significant uncertainties concerning regionwide boundary conditions and the extent of
 5     influence of emissions in upwind regions on air quality in the major eastern metropolitan
 6     areas.
 7
 8     3.6.6    Conclusions
 9          The 1990 amendments to the Clean Air Act have mandated the use of photochemical
10     grid models for demonstrating how most ozone nonattainment areas can attain the NAAQS.
11     Predicting ozone is a complex problem.  There are still many uncertainties in the models;
12     nonetheless models are necessary and essential for regulatory analysis and constitute one of
13     the major tools for attacking the ozone problem.  These models have developed considerably
14     in the past 10 years.  However, their usefulness is constrained by limited databases for
15     evaluation and from having to rely on hydrocarbon emissions data that may be inaccurate.
16     Comparison of model predictions against ozone measurements, while necessary, is not a
17     robust  test of a model's  accuracy. Ideally, one should evaluate performance  against more
18     extensive sets of species such as individual VOCs, NOX, and NOy. Compensating errors in
19     input information to a model and within the model formulation can cause an ozone model to
20     generate  correct ozone predictions for the wrong reasons.  Therefore, model evaluation
21     indicators are needed to demonstrate the reliability of a prediction before the model can be
22     effectively used in making control strategy decisions.  Models can be effectively used in a
23     relative sense to rank different control alternatives in terms of their effectiveness in reducing
24     ozone and to indicate the approximate magnitude of improvement in peak ozone levels
25     expected under various control  strategies.  To do sos there must be a sound emissions model
26     and  data and an adequate database on which to construct the modeling.  Grid-based ozone air
27     quality modeling is superior to the available alternatives for ozone control planning, but if the
28     model is not evaluated sufficiently, one can be misled. The goal is to minimize the chances
29     of its incorrect use.
30
31
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 1     3.7  SUMMARY AND CONCLUSIONS
 2     3.7.1   Tropospheric Ozone Chemistry
 3     3.7.1.1   Ozone in the Unpolluted Atmosphere
 4          Ozone is found in the stratosphere, the "free" troposphere, and the planetary boundary
 5     layer (PEL) of the earth's atmosphere.  In the stratosphere, the uppermost layer, O3 is
 6     produced through cyclic reactions that are initiated by the photolysis of molecular oxygen by
 7     short-wavelength radiation from the sun and are terminated by the recombination of
 8     molecular oxygen and ground-state oxygen atoms.
 9          In the "free" troposphere, O3 occurs as the result of incursions from the stratosphere;
10     upward venting  from the PEL (which is the layer next to the earth, extending to altitudes of
11     ~ 1 to 2 km)  through certain  cloud processes; and photochemical formation from precursors,
12     notably methane, carbon monoxide, and nitrogen oxides,
13          Ozone is present in the PEL as the result of downward mixing from the stratosphere
14     and free troposphere and as the result of photochemical processes occurring within the PEL.
15     The photochemical production of O3 and other oxidants found at the earth's surface is the
16     result of atmospheric physical and chemical processes involving two classes of precursor
17     pollutants, reactive volatile organic compounds (VOCs) and (NOX).  The formation of O3 and
18     other oxidants from its precursors is a complex, nonlinear function of many factors,
19     including the  intensity and spectral distribution of sunlight; atmospheric mixing and related
20     meteorological conditions; the reactivity of the mixture of organic compounds in ambient air;
21     the concentrations of precursor compounds in ambient air; and, within reasonable
22     concentrations ranges,  the ratio between the concentrations of reactive VOCs and NC^.
23          In the free troposphere and in relatively "clean" areas of the PEL, methane is the chief
24     organic precursor to in situ photochemical production of O3 and related oxidants.  The major
25     tropospheric removal process for methane is by reaction with OH radicals.  In the complex
26     cyclic reactions  that result in  oxidation of methane, there can be a net increase in 03 or a net
27     loss of 03, depending mainly upon the NO concentration.
28
29     3.7.1.2  Ozone Formation  in the Polluted Troposphere
30          The same  basic processes by which methane is oxidized occur in the atmospheric
31     oxidative degradation of other, even more reactive and more complex VOCs. The only

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 1     significant initiator of the photochemical formation of ozone in the troposphere is the
 2     photolysis of NO2, yielding NO and a ground-state oxygen atom that reacts with molecular
 3     oxygen to form O3.  The O3 thus formed reacts with NO, yielding 02 and NO2. These
 4     cyclic reactions attain equilibrium in the absence of VOCs,  In the presence of VOCs,
 5     however, the equilibrium is upset, resulting, through a complex series of chain reactions, in
 6     a net increase in O3.
 7          The key reactive species in the troposphere is the hydroxyl (OH) radical, which is
 8     responsible for initiating the oxidative degradation reactions of almost all VOCs. As in the
 9     methane oxidation cycle,  the conversion of NO to NO2 during the oxidation of VOCs is
10     accompanied by the production of O3 and the efficient regeneration of the OH radical. The
11     O3 and PANs formed in polluted atmospheres increase with the NO2/NO concentration ratio.
12          At night, in the absence of photolysis of reactants, the simultaneous presence of 03 and
13     NO2 results in the formation of the nitrate radical, NO3.  The reaction with nitrate radicals
14     appears to constitute a major sink for alkenes,  cresols, and some other compounds, although
15     alkyl nitrate chemistry is  not well characterized.
16          Most inorganic gas-phase processes, that is, the nitrogen cycle and its interrelationships
17     with O3 production, are well understood.  The chemistry of the VOCs in ambient air,
18     however, is not as well understood.  The chemical loss processes of gas-phase VOCs, with
19     concomitant production of O3, include reaction with OH,  NO3, O3, and photolysis.
20          The major classes of VOCs in ambient air are:  alkanes, alkenes (including alkenes
21     from biogenic sources), aromatic hydrocarbons, carbonyl  compounds, alcohols, and ethers.
22     A wide range of lifetimes in the atmosphere, from minutes to years, characterize the VOCs.
23          The only important  reaction of alkanes is with OH radicals.  For alkanes having
24     carbon-chain lengths of four or less  (C5 alkanes the situation is more complex because few reaction
26     products have been found. Branched alkanes (e.g., isobutane) have rates of reaction that are
27     highly dependent on  structure. It is difficult to represent reactions of these VOCs
28     satisfactorily in the chemical mechanisms of air quality models.  Stable products of alkane
29     photooxidation are known to include carbonyl compounds, alkyl nitrates, and
30     5-hydroxycarbonyls.  Major uncertainties in the atmospheric chemistry of the alkanes concern
31     the chemistry of alkyl nitrate formation; these uncertainties affect the amount of NO-to-NO^

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 1     conversion occurring and hence the amounts of O3 formed during photochemical degradation
 2     of the alkanes.
 3          Alkenes react in ambient air with OH and NO^ radicals and with 03.  All three
 4     processes are important atmospheric transformation processes, and all proceed by initial
 5     addition to the >C=C< bond(s).  Products of alkene photooxidation include carbonyl
 6     compounds, hydroxynitrates and nitratocarbonyls, and decomposition products from the
 7     energy-rich biradicals formed in alkene-O3 reactions.  Major uncertainties in the atmospheric
 8     chemistry  of the alkenes concern the products and mechanisms of their reactions with O3,
 9     especially  the radical yields (which affect the O3 formation yields).
10          The only troposphericaUy important loss process for aromatics (benzene and the alkyl-
11     substituted benzenes) is by reaction with the OH radical,  followed by H-atom abstraction or
12     OH radical addition.  Products of aromatic hydrocarbon photooxidation include phenolic
13     compounds, aromatic aldehydes, a-dicarbonyls  (e.g., glyoxal), and unsaturated carbonyl or
14     hydroxycarbonyl compounds or both. Aromatics appear  to act as strong NOX sinks under
15     low NOX conditions.  Major uncertainties in the atmospheric chemistry of aromatic
16     hydrocarbons are mainly with regard to reaction mechanisms and reaction products under
17     ambient conditions (i.e., for NOX concentration conditions that occur in urban and rural
18     areas).  These uncertainties impact on the representation  of mechanisms in models.
19          Tropospherically important loss processes for carbonyl compounds not containing
20      >C=C<  bonds are photolysis and reaction with the OH radical; those that contain such
21     bonds can undergo the same reactions as alkenes.  Photolysis is the major loss process for
22     HCHO (the simplest aldehyde) and acetone (the simplest ketone), as well as for the
23     dicarbonyls.  Reactions with OH radicals are calculated to be the dominant gas-phase loss
24     process for the higher aldehydes and ketones.  Products formed and the importance of
25     photolysis are major uncertainties in the chemistry of carbonyl compounds.
26          Alcohols and ethers in ambient air react only with the  OH radical, with the reaction
27     proceeding primarily via H-atom abstraction from the C-H bonds in these compounds.
28          It should be noted that the photooxidation reactions of  VOCs can lead to the formation
29      of participates in ambient air.  The chemical processes involved in the formation of O3 and
30      other photochemical pollutants lead to the formation of OH radicals and the formation of
31      oxidized VOC reaction products that are of low enough volatility to be present as organic

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 1     paniculate matter.  Hydroxyl radicals that oxidize VOCs also react with NO2 and SO2 to
 2     form nitric and sulfuric acids, respectively, which become incorporated into aerosols as
 3     participate nitrate and sulfate.  Controls aimed at reducing ozone will impact—positively or
 4     negatively—acid and secondary aerosol formation in the atmosphere.
 5
 6     3.7.2    Meteorological Processess Influencing Ozone Formation  and
 7              Transport
 8     3.7.2.1  Meteorological Processes
 9          The surface energy (radiation) budget of the earth strongly influences the dynamics of
10     the planetary boundary layer (PEL).  In combination with synoptic winds, it provides the
11     forces  for the vertical fluxes of heat,  mass, and momentum. The redistribution of energy
12     through the PEL creates thermodynamic conditions that influence vertical mixing.  Energy
13     balances require study so that more realistic simulations can be made of the structure of the
14     PEL.
15          Day-to-day variability in ozone  concentrations depends heavily on day-to-day variations
16     in meteorological conditions.  For example, the concentration of an air pollutant depends
17     significantly on the degree of mixing that occurs between the time a pollutant or its
18     precursors are emitted and the arrival of the pollutant at the receptor.  Inversion layers
19     (layers in which temperature increases with height above ground level) are prominent
20     determinants  of the degree of atmospheric vertical mixing and thus the degree to which ozone
21     and other pollutants will be dispersed or accumulate.  Ozone left in a layer aloft, as the result
22     of reduced turbulence and mixing at the end of daylight hours, can be transported  through
23     the night, often to  areas far removed  from pollution sources. Downward mixing on the
24     subsequent day can result in increases in local concentrations from the transported ozone.
25          Growing evidence indicates that the strict use of mixing heights in modeling is an
26     oversimplification  of the complex processes by which pollutants are redistributed within
27     urban areas;  and that it is necessary to treat the turbulent structure of the atmosphere directly
28     and acknowledge the vertical variations in mixing.
29          Geography can significantly affect the dispersion of pollutants along the  coast or shore
30     of oceans and lakes.  Temperature gradients between bodies of water and land masses
31     influence the incidence of surface conditions.  The thermodynamics of water bodies (e.g.,

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 1     Lake Michigan and the Atlantic Ocean off the coast of Maine) may play a significant role in
 2     some regional-scale episodes of high ozone concentrations.
 3          An "air mass" is a region of air, usually of multistate dimensions, that exhibits similar
 4     temperature, humidity, and stability characteristics.  Episodes of high ozone concentrations in
 5     urban areas are often associated with high concentrations of ozone in the surroundings.
 6          The transport of ozone and its precursors beyond the urban scale (^50 km) to
 7     neighboring rural and urban areas has been well documented and was described in the 1986
 8     EPA criteria document for O3.  Areas of ozone accumulation are characterized by:
 9     (1) synoptic-scale subsidence of air in the free tropopsphere, resulting in development of an
10     elevated inversion layer; (2) relatively low wind speeds associated with the  weak horizontal
11     pressure gradient around a surface high pressure system;  (3) a lack of cloudiness; and
12     (4) high temperatures.
13
14     3.7.2.2  Meteorological Parameters
15          Ultraviolet (UV) radiation from the sun plays a key role in initiating the photochemical
16     processes leading to ozone formation and affects individual photolytic reaction steps.  There
17     is little empirical evidence in the literature, however, linking day-to-day variations in
18     observed UV radiation levels with variations in O3 levels.
19          An association between tropospheric ozone concentrations and tropospheric temperature
20     has been demonstrated.  Plots of daily maximum ozone concentrations versus maximum daily
21     temperature for summer months of 1988 to  1990 for four urban areas, for example, show an
22     apparent upper bound on ozone concentrations that increases with temperature.  A similar
23     qualitative relationship exists at a number of rural locations.
24          The relationship between wind speed and ozone buildup varies from one part of the
25     country to another. Research done during the Southern Oxidant Study  (in the "Atlanta
26     intensive" field study) indicates that variations in wind speed at a particular level above
27     ground must be larger than about 3 m/s to be considered significant. This  may limit the
28     accuracy of urban-area ozone simulations using photochemical models.
29
30
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 1     3.7.2.3  Normalization of Trends
 2          Statistical techniques (e.g., regression techniques) can be used to help identify real
 3     trends  in ozone concentrations,  both intra-annual and inter-annual, by normalizing
 4     meteorological variability.  In the Southern Oxidant Study, for example, regression
 5     techniques were successfully used to forecast ozone levels to ensure that specialized
 6     measurements were made on appropriate days.
 7
 8     3.7.3    Precursors
 9     3.7.3.1  Nitrogen Oxides Emissions
10          Anthropogenic oxides of nitrogen are associated with combustion processes.  The
11     primary pollutant emitted is nitric oxide (NO) formed at  high combustion temperatures from
12     the nitrogen and oxygen in air and from nitrogen in the combustion fuel.  Emissions of NOX
13     in 1991 in the United States totaled 21.39  Tg.  The two  largest single NOX emission sources
14     are electric power generation and highway vehicles. Emissions of NOX are therefore highest
15     in areas having a high density of electric-power-generating stations and in urban regions
16     having high traffic densities.  Between  1987 and 1991, transportation-related emissions
17     remained essentially constant, while stationary source NOX emissions increased about 10%.
18          Natural NOX sources include stratospheric intrusion, oceans, lightning, soils,  and
19     wildfires. Lightning and soil emission  are the only two  significant natural sources of NOX in
20     the United States. The estimated annual lightning-produced NOX for the continental United
21     States  is —1.0 Tg, about 60% of which is generated over the southern states.  Both
22     nitrifying and denitrifying organisms in the soil can produce NOX, principally NO. Emission
23     rates depend mainly on fertilization levels  and soil temperature.  Inventorying  soil  NOX
24     emissions is difficult because of large temporal and spatial variability, but the  nationwide
25     total has been estimated at  1.2 Tg/year, of which about 85% is emitted in spring and
26     summer. About 60% of the total soil NOX is emitted in  the area of the country containing
27     the central corn belt.
28          Combined natural sources contribute about 2.2 Tg  of NOX to the troposphere over the
29     continental United States. Uncertainties in natural NOX  inventories are much larger,
30     however, than for anthropogenic NOX emissions.  Because a large proportion of
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 1     anthropogenic NOX emissions come from distinct point sources, published annual estimates
 2     are thought to be very reliable.
 3
 4     3.7.3.2  Volatile Organic Compound Emissions
 5          Hundreds of volatile organic compounds, commonly containing from 2 to about
 6     12 carbon atoms, are emitted by evaporative and combustion processes from a large number
 7     of source types.  Total U.S. VOC emissions in 1991  were estimated at 21.0 Tg.  The two
 8     largest source categories were industrial processes (10.0 Tg) and transportation (7.9 Tg).
 9     Emissions of VOCs from highway vehicles accounted for almost 75 % of the transportation-
10     related emissions; studies have shown that the majority  of these VOC emissions come from
11     about 20% of the automobiles in service, many, perhaps most, of which are older cars that
12     are poorly maintained.
13          The accuracy of VOC emission estimates is difficult to determine, both for stationary
14     and mobile sources.  Within major point sources, deviations of emission rates from
15     individual sources from assigned average factors can  result in error for the entire point
16     source. Evaporative emissions, which depend on temperature and other environmental
17     factors, compound the difficulties of assigning accurate emission factors. In assigning VOC
18     emission estimates to the mobile source category, models are used that incorporate numerous
19     input parameters (e.g., type of fuel used, type of emission controls, age of vehicle), each of
20     which  has some degree of uncertainty.
21          Vegetation emits significant quantities of VOCs into the atmosphere, chiefly
22     monoterpenes and isoprene, but also oxygenated VOCs, according to recent studies.  The
23     most recent biogenic VOC emissions estimate for the United States showed annual emissions
24     of 29.1 Tg/year. Coniferous forests are the largest vegetative contributor on a national basis,
25     because of their extensive land coverage.  Summertime biogenic emissions comprise more
26     than half of the annual totals in all regions because of their dependence on temperature and
27     vegetational growth.  Biogenic emissions are, for those reasons, expected to be higher in the
28     southern states than in the northern.
29          Uncertainties in  both biogenic and anthropogenic VOC emission inventories prevent
30     establishing the relative contributions of these two categories.
31

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 1     3.7.3.3   Concentrations of Volatile Organic Compounds in Ambient Air
 2          The VOCs most frequently analyzed in ambient air are the nonmethane hydrocarbons
 3     (NMHCs).  Morning concentrations (6:00 a.m. to 9:00 a.m.) have been measured most often
 4     because of the use of morning data in EKMA and in air quality simulation models.  Major
 5     field studies in 22 cities in 1984 and 19 cities in  1985 produced NMHC measurements
 6     showing median values ranging  from 0.39 ppm C to 1.27 ppm C for 1984; and ranging from
 7     0.38 ppm C to 1.63 ppm C in 1985.  Overall median values from all urban sites were about
 8     0.72 ppm C in 1984 and 0.60 ppm C in 1985.
 9          Comparative data over two decades (1960's through 1980's) in the Los Angeles and
10     New York City areas showed decreases in NMHC concentrations in those areas.
11     Concomitant compositional changes were observed over the two decades, with increases
12     observed in the percentage of alkanes and decreases  in the percentage of aromatic
13     hydrocarbons and acetylene.
14          Concurrent measurements  of anthropogenic and biogenic NMHCs have shown that
15     biogenic NMHCs usually constituted much less than 10% of the total NMHCs. For
16     example, average isoprene concentrations ranged from 0.001 to 0.020 ppm C and terpenes
17     from 0.001 to 0.030 ppm C.
18
19     3.7.3.4  Concentrations of Nitrogen Oxides in Ambient Air
20          Measurements of NOX at sites in 22 and 19 U.S. cities in 1984 and 1985, respectively,
21     showed that median NQX concentrations ranged from 0.02 to 0.08 ppm in most of these
22     cities.  The 6-to-9 a.m. median concentrations in many of these cities exceeded the annual
23     average NOX values of 0.02 to 0.03 ppm found in U.S. metropolitan areas between 1980 and
24     1989.  Nonurban NQX concentrations, reported as average seasonal or annual NOx, range
25     from < 0.005 to 0.015 ppm.
26          Ratios of 6-to-9 a.m. NMOC to NOX are higher in southeastern and  southwestern
27     U.S. cities than in northeastern  and midwestern U.S. cities, according to data from EPA's
28     multi-city studies conducted in 1984 and 1985.  Median ratios ranged from 9.1 to 37.7 in
29     1984; in 1985, median ratios  ranged from 6.5 to 53.2 in the cities studied. Rural
30     NMOC/NOX ratios tend to be higher than urban  ratios.  Morning (6-to-9 a.m.) NMOC/NOX
31     ratios are used in the EKMA-type of trajectory model. Trends from 1976 to 1990 show

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 1     decreases in these ratios in the South Coast Air Basin of California.  The correlation of
 2     NMOC/NOX ratios with maximum 1-h O3 concentrations, however, was weak in a recent
 3     analysis.
 4
 5     3.7.3.5  Source Apportionment and Reconciliation
 6          Source apportionment (now regarded as synonymous with receptor modeling) refers to
 7     determining the quantitative contributions of various sources of VOCs to ambient air
 8     pollutant concentrations.  Source reconciliation refers to the comparison of measured ambient
 9     VOC concentrations with emissions inventory estimates of VOC source emission rates for the
10     purpose of validating the inventories.
11          Early studies in Los Angeles employing a "mass balance" approach to receptor
12     modeling showed the following estimated contributions of respective sources to ambient air
13     concentrations of NMOCs through CIO;  automotive exhaust,  53%; whole gasoline
14     evaporation, 12%; gasoline headspace vapor, 10%; commercial natural gas, 5%; geogenic
15     natural gas, 19%; and liquefied  natural gas, 1 %.  Recent studies in eight U.S. cities showed
16     that vehicle exhaust was the dominant contributor to ambient VOCs (except in Beaumont,
17     TX, with 14% reported).  Estimates of the contributions of gasoline evaporation differ in
18     methodology; the more appropriate methods used result in estimates of large whole gasoline
19     contributions, i.e., equal to vehicle exhaust in one study and 20% of vehicle exhaust in a
20     second study.
21          The chemical mass balance approach used for estimating anthropogenic VOC
22     contributions to ambient air cannot be used for receptor modeling of biogenic sources.
23     A modified approach, applied to 1990 data from a downtown site in Atlanta, indicated a
24     lower limit of 2% (24-h average) for the biogenic percentage of total ambient VOCs at that
25     location (isoprene was used as the biogenic indicator species).  The percentage varies during
26     the 24-h period because of the diurnal (e.g., temperature, light intensity) dependence of
27     isoprene concentrations.
28          Source reconciliation data  have shown disparities between emission inventory estimates
29     and receptor-estimated contributions.  For biogenics, emission estimates are greater than
30     receptor-estimated contributions. The reverse has been true for natural gas contributions
31     estimated for Los Angeles, Columbus, and Atlanta;  and for refinery emissions in Chicago.

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 1     3.7.4   Analytical Methods for Oxidants and Their Precursors
 2     3.7.4.1   Oxidants
 3          Current methods used to measure O3 are chemiluminescence (CL), ultraviolet (UV)
 4     absorption spectrometry, and newly developed spectroscopic and chemical approaches,
 5     including chemical approaches applied to passive sampling devices for 03.
 6          The CL method, designated as the reference method by EPA, involves the direct gas-
 7     phase reaction of ozone with an alkene (ethylene) to produce electronically excited products,
 8     which decay with the emission of light.  Detection limits of 0.005 ppm and a response time
 9     of less than 30 s are typical of currently available commercial instruments.  A positive
10     interference from atmospheric water vapor was reported in the 1970s and has recently been
11     confirmed.  Proper calibration can minimize this source of error.
12          Commercial UV photometers for measuring ozone have detection limits of about
13     0.005 ppm, long-term precision within about ±5%, and a response time of < 1 min. Ozone
14     has a fairly strong absorption band with a maximum near 254 nm; its molar absorption
15     coefficient at that wavelength is well known. Since the measurement is absolute, UV
16     photometry is also used to calibrate O3 methods.
17          A potential disadvantage of UV photometry is that atmospheric constituents  that absorb
18     254 nm radiation (and that are removed fully or partially by the  manganese dioxide scrubber
19     used in UV O3 photometers) will be a positive interference in Oj measurements.
20     Interferences have been reported in two recent studies but assessment of the potential
21     importance of such interferences (e.g., toluene, styrene, cresols, nitrocresols) is hindered by
22     lack of absorption spectra data in the 250 nm range and by lack of ambient measurements of
23     most of the aromatic photochemical reaction products.
24          Differential optical absorption spectrometry (DOAS) has been used to measure ambient
25     O3, but further intercomparisons with other methods and interference tests are recommended.
26     Passive sampling devices (PSDs) permit acquisition of personal human exposure data and of
27     ozone monitoring data in areas where the use of instrumental methods is not feasible. Three
28     PSDs are commercially available. All employ solid absorbents that react with Q$.
29          Calibration of O3 measurement methods (other than PSDs) is done by UV spectrometry
30     or by gas-phase titration (GPT) of Oj with NO.  Ultraviolet photometry is the reference
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 1     calibration method approved by EPA. Ozone is unstable and must be generated in situ at
 2     time of use to produce calibration mixtures.
 3          Two methods have been generally employed to measure atmospheric peroxyacetyl
 4     nitrate (PAN) and its higher homologues (PANs):  infrared spectroscopy (TR) and gas
 5     chromatography (GC) using an electron capture detector (BCD). A third method, less often
 6     used, couples GC with a molybdenum converter that reduces PAN to NO in the gas phase
 7     and subsequently measures the NO with a chemiluminescence analyzer.  Peroxyacetyl nitrate
 8     and the higher PANs are normally measured by GC-ECD.  Detection limits have been
 9     extended to 1 to 5 ppt using cryogenic enrichment of samples and specified desorption
10     procedures that limit losses associated with cryosampling. Because PAN is unstable
11     (explosive, and subject to surface-related decomposition), the preparation of reliable
12     calibration standards is difficult.  Methods devised to generate calibration standards include
13     photolysis of static concentrations of gases,  nitration of peracetic acid in single hydrocarbons,
14     and analysis of PAN as NO under specified conditions of the dissociation of PAN into its
15     precursors.
16          Early measurements of 10 to 80 ppb hydrogen peroxide (I^Oz) reported in the 1970s
17     have been found to be in error because of artifact formation of H2O2 from reactions  of
18     absorbed gaseous O3, Modeling results also indicate that lower levels of H2O2 occur in the
19     atmosphere, on the order of 1 ppb.
20          In-situ measurement methods for H2O2 include FUR and tunable diode laser absorption
21     spectrometry (TOLAS).  The FITR method is specific  for H2O2 but has a high detection
22     level of ~50 ppb (using a 1-km path length). The TOLAS method  is also specific and has a
23     detection level of 0.1 ppb over averaging times of several minutes.  Four frequently  used wet
24     chemical methods for measurement of H2O2 are available.  All involve the oxidation of a
25     substrate followed by instrumental detection and quantification of the resulting
26     chemiluminescence or fluorescence.  Detection limits are comparable to those of FTIR and
27     TOLAS, but interferences are common and must be obviated or minimized with specified
28     procedures.
29           Calibration of methods for gaseous H202 measurement requires the immediate  use of
30     standard  mixtures prepared by one of several wet chemical methods.
31

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 1     3.7.4.2   Volatile Organic Compounds
 2          Increased monitoring of volatile organic compounds is required under Title I, Section
 3     182, of the Clean Air Act Amendments of 1990 because of their role as precursors to the
 4     formation of O3 and other photochemical oxidants.  Volatile organic compounds (VOCs) are
 5     those gaseous organic compounds that have a vapor pressure greater than 0.15 mm and
 6     generally have a carbon content ranging from Cl through C12.  They include methane;
 7     nonmethane organic compounds (NMOC); nonmethane hydrocarbons (NMHC); polar,
 8     oxygenated hydrocarbons  (PVOC); and reactive organic gases (ROG), which can include all
 9     of the subcategories listed here.
10          Traditionally, NMHCs have been measured by methods that employ a flame ionization
11     detector (FID) as the sensing element that measures a change in ion intensity resulting from
12     the combustion of air containing organic compounds.  The method recommended by EPA for
13     total NMOC measurement involves the cryogenic preconcentration of nonmethane organic
14     compounds and the measurement of the revolatilized NMOCs using FID.  The main
15     technique for speciated NMOC/NMHC measurements is cryogenic preconcentration followed
16     by GC-FID,   Systems  for sampling and analysis of VOCs have now been developed that
17     require no liquid cryogen  for operation, yet provide sufficient resolution of species.
18          Stainless steel canisters have become the containers  of choice for collection of whole-air
19     samples for NMHC/NMOC data. Calibration procedures for NMOC instrumentation require
20     the generation, by static or dynamic systems, of dilute mixtures at concentrations expected to
21     occur in ambient air.
22          Preferred methods for measuring carbonyl species (aldehydes and ketones) in ambient
23     air are spectroscopic methods; on-line colorimetric methods; and the high-performance liquid
24     chromatography (HPLC) method employing 2,4-dinitrophenylhydrazine (DNPH)
25     derivatization in a silica gel cartridge.  The most common method in current use for
26     measuring aldehydes in ambient  air is the HPLC-DNPH method. Use of an O3 scrubber has
27     been recommended to  prevent interference in this method by O3 in ambient air.  Carbonyl
28     species are reactive, making preparation of stable calibration mixtures difficult; but several
29     methods are  available.
30          Impetus for the development of methods for measuring the more reactive oxygen- and
31     nitrogen-containing organic  compounds has come from their roles as precursors or products

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 1     of photochemical oxidation but also from the inclusion of many of these compounds on the
 2     list of hazardous air pollutants in the  1990 Clean Air Act Amendments.  Measurement of
 3     these polar volatile organic compounds (PVOCs) is difficult because of their reactivity and
 4     water solubility.  Methods are still in development.
 5
 6     3.7.4.3   Oxides of Nitrogen
 7          Nitric oxide (NO) and nitrogen dioxide (NO^ comprise the oxides of nitrogen (NOX)
 8     involved as precursors to ozone and other photochemical oxidants.
 9           The most common method of NO measurement is the gas-phase chemiluminescent
10     (CL) reaction with ozone.  The CL method  is essentially specific for NO.  Commercial NO
11     monitors have detection limits of a few parts per billion by volume (ppbv) in ambient air.
12     Commercial NO analyzers may not have sensitivity sufficient for surface measurements in
13     rural or remote areas, or for airborne measurements. Direct spectroscopic methods for NO
14     exist that have very high sensitivity and selectivity for NO.  Major drawbacks of these
15     methods are their complexity, size, and cost, which restrict these methods to research
16     applications.  No passive sampling devices (PSDs) presently exist for measurement of NO.
17          Chemiluminescence (CL) analyzers are the method of choice for NO2 measurement,
18     even though they do not measure NO2 directly.  Minimum detection levels for NO2 have
19     been reported to be 5 to 13 ppb, but more recent evaluations have indicated  detection limits
20     of 0.5 to 1 ppbv.  Reduction of N02 to NO is required for measurement.  In practice,
21     selective measurement of NOX by this approach has proved difficult. Commercial
22     instruments that use heated catalytic converters to reduce NO2 to NO measure  not NO and
23     NOX, but more nearly NO and total NOy.  Thus, the NO2 value inferred from such
24     measurements may be significantly in error, which may in turn affect the results of modeling
25     of ambient ozone.
26          Several  spectroscopic approaches to NO2 detection have been developed.   As noted
27     above for NO, however, these methods have major drawbacks that include their complexity,
28     size, and cost, which outweigh at present the advantages of their sensitivity  and selectivity.
29     Passive samplers for NO2 exist, but are still in the developmental  stage for ambient air
30     monitoring.
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 1          Calibration of methods for NO measurement is done using standard cylinders of NO in
 2     nitrogen.  Calibration of methods for NO2 measurement include: use of cylinders of NO2 in
 3     nitrogen or air; use of permeation tubes; and gas-phase titration.
 4
 5     3.7.5   Ozone Air Quality Models
 6     3.7.5.1  Definitions, Descriptions, and Uses
 7          Photochemical air quality models are used to predict how O3 concentrations change in
 8     response to prescribed changes in source emissions of NOX and VOCs.  They are
 9     mathematical descriptions of the atmospheric transport, diffusion, removal, and chemical
10     reactions of pollutants.  They operate  on sets of input data that characterize the emissions,
11     topography, and meteorology of a region and produce outputs that describe air quality in that
12     region.
13          Two kinds of photochemical models are recommended in guidelines issued by EPA:
14     The grid-based Urban Airshed Model  (UAM) is recommended for modeling O3 over urban
15     areas;  and EKMA  (the Empirical Kinetics Modeling Approach) is identified as an acceptable
16     approach under certain circumstances.  The 1990 Clean Air Act Amendments mandate the
17     use of  three-dimensional (grid-based) air quality models such as UAM in developing SIPs
18     (State Implementation Plans) for areas designated as extreme, severe, serious, or multistate
19     moderate.
20          In grid-based air quality models, the region to be modeled (the modeling domain) is
21     subdivided into a three-dimensional array of grid cells.  Pertinent atmospheric processes and
22     chemical reactions  are represented for each cell.
23          In trajectory models, such as EKMA, a hypothetical air parcel moves through the area
24     of interest along a  path calculated from wind trajectories.  Emissions are injected into the air
25     parcel  and undergo vertical mixing and chemical  transformations.  Trajectory models provide
26     a dynamic description of atmospheric  source-receptor relationships that is simpler and less
27     expensive to derive than that obtained from grid models, but meterological processes are
28     highly  simplified in trajectory  models
29          The EKMA-based method for determining 03 control strategies has some limitations,
30     the most serious of which is that predicted emissions reductions are  critically dependent on
31     the initial NMHC/NOX ratio used in the calculations. This ratio cannot be determined with

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 1     any certainty and is expected to be quite variable in an urban area.  Grid-based models have
 2     their limitations as well.  These are pointed out subsequently.
 3
 4     3.7.5.2  Model Components
 5          Spatial and temporal characteristics of VOC and NOX emissions are major inputs to a
 6     photochemical air quality model.  Greater accuracy in emissions inventories is needed, for
 7     biogenics and for both mobile and stationary source components. Grid-based air quality
 8     models also require as input the three-dimensional wind field for the photochemical episode
 9     being simulated. This input is supplied by "meteorological modules" which fall into one of
10     four categories:  (1) objective analysis procedures; (2) diagnostic methods; (3) dynamic, or
11     prognostic, methods; and (4) hybrid methods that embody elements from both diagnostic and
12     prognostic approaches.   Prognostic models are believed to provide a dynamically consistent,
13     physically realistic, three-dimensional representation of the wind and other meteorological
14     variables at scales  of motion not resolvable by available observations.  Outputs of prognostic
15     models do  not always agree with observational data, but methods have been devised to
16     mitigate these problems.
17          A chemical kinetic mechanism (a set of chemical reactions), representing the important
18     reactions that occur in the atmosphere, is  used in  an air quality model to estimate the net rate
19     of formation  of each pollutant simulated as a function of time.  Chemical mechanisms that
20     explicitly treat each individual VOC component of ambient air are too lengthy to be
21     incorporated  into three-dimensional atmospheric models. " Lumped" mechanisms are
22     therefore used.  The chemical mechanisms used in existing photochemical O3 models contain
23     uncertainties  that may limit the accuracy of their predictions. Because of different
24     approaches to "lumping" of reactions,  models can produce somewhat different results under
25     similar conditions.  Both the UAM (UAM-IV) and EPA's Regional Oxidant Model (ROM)
26     use the Carbon-Bond Mechanism-IV (CMB-IV).  The CBM-IV and the SAPRC and RADM
27     mechanisms (Statewide Air Pollution Research Center, and Regional Acid Deposition Model,
28     respectively)  are considered to represent the state-of-the-science.
29          Dry deposition, the removal of chemical species from the atmosphere by interaction
30     with ground-level  surfaces, is an important removal process  for ozone on both urban and
31     regional  scales; and is included in all urban- and regional-scale models. Wet deposition (the

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 1     removal of gases and particles from the atmosphere by precipitation events) is generally not
 2     included in urban-scale photochemical models, since O3 episodes do not occur during periods
 3     of significant clouds or rain,
 4          Concentration fields of all species computed by the model must be specified at the
 5     beginning of the simulation; these concentration fields are called the initial conditions.  These
 6     initial conditions are determined mainly with ambient measurements,  either from routinely
 7     collected data or from special studies; but interpolation can be used to distribute the surface
 8     ambient measurements.
 9
10     3.7.5.3   Evaluation of Model Performance
11           Air quality models are evaluated by comparing their predictions with ambient
12     observations.  An adequate model should give accurate predictions of current peak
13     O3 concentrations and temporal and spatial O3 patterns.  It should also respond  accurately to
14     changes in VOC and NOX emissions, to differences in VOC reactivity, and to spatial and
15     temporal changs in emissions patterns for future years.  Likewise, multispecies  comparisons
16     could be the key in discriminating among alternative modeling approaches that provide
17     similar predictions of O3 concentrations.  Adequate model performance for several reactive
18     species increases the assurance that correct ozone predictions are not a result of chance or
19     fortuitous cancellation of errors introduced by various assumptions.
20          If only a routine database is available for modeling O3 in an urban area, then several
21     concerns require attention relative to model performance evaluation:  air quality aloft,
22     boundary conditions, ambient VOC data, and meteorological data aloft. If any  of these four
23     areas is missing from the database,  the performance evaluation and subsequent model
24     application must be adequately planned to minimize the possibility of compensatory errors.
25
26     3.7.5.4   Use of Ozone Air Quality Model for Evaluating Control Strategies
27          Photochemical air quality models are used for control strategy evaluation by first
28     demonstrating that a past episode, or episodes, can be adequately simulated and then
29     reducing hydrocarbon or NOX emissions or both in the model inputs  and assessing the effects
30     of these reductions on O3 in the region.  The adequacy  of control strategies  based on grid-
31     based models depends in part on the nature of input data for simulations and model

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 1     validation, on input emissions inventory data, and on the mismatch between model output
 2     and the current form of the NAAQS for Qj.
 3          Grid-based models that have been widely used to evaluate control strategies for 03 or
 4     acid deposition, or both, are: (1) the Urban Airshed Model; (2) the California Institute of
 5     Technology/Carnegie Institute of Technology (CIT) model; (3) the Regional Oxidant Model
 6     (ROM); (4) the Acid Deposition and Oxidant Model (ADOM); and (5) the Regional Acid
 7     Deposition Model (RADM).
 8
 9     3.7.5.5   Conclusions
10          Urban air quality models are becoming readily available for application and have been
11     applied in recent years in  several urban areas.  Significant progress has also been made in the
12     development of regional models and the integration of state-of-the-art prognostic
13     meteorological models as  drivers.
14          There are still many uncertainties in photochemical air quality modeling.  Prime among
15     these are emission inventories,  However, models are essential for regulatory analysis and
16     constitute one of the major tools for attacking the 03 problem.  Grid-based 03 air quality
17     modeling is superior to the available alternatives for O3 control planning, but the chances of
18     its incorrect use must be minimized.
19
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 1     REFERENCES
 2
 3     AIRS, Aerometric Information Retrieval System [database]. (1992) [Data on NOX], Research Triangle Park, NC:
 4            U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards.
 5
 6     Allen, A. O.; Hochanadel, C. J,; Ghormley, J. A.; Davis, T, W. (1952) Decomposition of water and aqueous
 7            solutions under mixed fast neutron and gamma radiation. J. Phys. Chem. 56: 575-586.
 8
 9     Altshuller, A. P. (1975) Evaluation of oxidant results at CAMP sites in the United States. J. Air Pollut. Control
10            Assoc. 25: 19-24.
11
12     Altshuller, A. P. (1983) Review: natural volatile organic substances and their effect on air quality in the United
13            States, Atmos, Environ, 17:  2131-2165.
14
15     Altshuller, A. P. (1986) The role of nitrogen oxides in nonurban ozone formation in the planetary boundary layer
16            over N America, W Europe and adjacent areas of ocean. Atmos. Environ. 20: 245-268.
17
18     Altshuller, A. P. (1989a) Sources  and levels of background ozone and its precursors and impact at ground level.
19            In: Schneider,  T.; Lee, S, D.; Wolters, G. J, R,; Grant, L. D., eds. Atmospheric ozone research and its
20            policy implications: proceedings of the 3rd US-Dutch international symposium; May 1988; Nijmegen,
21            The Netherlands. Amsterdam, The Netherlands: Elsevier Science Publishers; pp. 127-157. (Studies in
22            environmental  science 35).
23
24     Altshuller, A. P. (1989b) Nonrnethane organic compound to nitrogen oxide ratios and organic composition in
25            cities and  rural areas. JAPCA 39: 936-943.
26
27     Altshuller, A. P.;  Bufalini, J. J. (1971)  Photochemical aspects of air pollution: a review. Environ. Sci. Technol.
28            5: 39-64.
29
30     Altshuller, A. P.;  Leng, L. J.  (1963) Application of the 3-methyI-2-benzothiazolonehydrazone method for
31            atmospheric analysis of aliphatic aldehydes. Anal. Chem. 35: 1541-1542.
32
33     Altshuller, A. P.;  McPherson, S. P. (1963) Spectrophotometric analysis of aldehydes in the Los Angeles
34            atmosphere. J. Air Pollut. Control Assoc. 13: 109-111.
35
36     AltshuUer, A. P.;  Miller, D. L.; Sleva, S. F. (1961) Determination of formaldehyde in gas mixtures by the
37            chromotropic acid method. Anal.  Chem.  33: 621-625.
38
39     Anderson, J. G.; Toohey, D. W.; Brune, W. H. (1991) Free radicals  within the Antarctic vortex: the role of
40            CFCs in Antarctic ozone loss. Science (Washington, DC) 251: 39-46.
41
42     Andreae, W. A. (1955) A sensitive method for the estimation of hydrogen peroxide in biological materials.
43            Nature (London) 175:  859-860.
44
45     Anthes, R. A,; Warner, T. T. (1978) Development of hydrodynamic models suitable for air pollution and other
46            mesometeorological studies. Mon. Weather Rev. 106: 1045-1078.
47
48     Anthes, R. A.; Kuo, Y. H.; Baumheroer, D. P.; Errico, R. M.; Bettge, T.  W. (1985) Predictability of
49            mesoscale atmospheric motions. Adv. Geophys. 28B: 159-202.
50
51     Anthes, R. A.; Hsie, E. Y.; Kao, Y. H. (1987) Description of the Penn State/NCAR mesoscale model version
52            4 (MM4). Boulder, CO: National Center for Atmospheric Research; NCAR technical note 282.
53
         December 1993                              3-229       DRAFT-DO NOT OTTOTP nu rrro

-------
 1     Aoyanagi, S.; Mitsumisha, H. (1985) Determination of hydrogen peroxide by chemiluminescence. Jpn. Kokai
 2            Tokkyo Koho 62-123336 (CA 107: 93083V, 1987)
 3
 4     Arey, J.; Atkinson, R,; Aschmann, S. M. (1990) Product study of the gas-phase reactions of monoterpenes with
 5            the OH radical in the presence of NOX. J. Geophys. Res, 95: 18539-18546.
 6
 7     Arey, J,; Winer, A. M.; Atkinson, R,; Aschmann, S. M.; Long, W. D.; Morrison, C. L. (1991a) The emission
 8            of (Z)-3-hexen-l-ol,  (Z)-3-hexenylacetate and other oxygenated hydrocarbons from agricultural plant
 9            species. Atroos. Environ. Part A 25: 1063-1075,
10
11     Arey, J.j Winer, A. M.; Atkinson, R.; Aschmann, S. M.; Long, W. D.; Morrison, C. L,; Olszyk, D. M.
12            (1991b) Terpenes emitted from agricultural species found in California's Central Valley. J, Geophys.
13            Res. [Atmos.] 96: 9329-9336.
14
15     Armstrong, W. A.; Humphreys, W. G. (1965) A L.E.T.  independent dosimeter based on the chemiluminescent
16            determination of H2O2. Can. J. Chem, 43: 2576-2584.
17
18     Aronian, P. F.; Scheff, P. A.; Wadden, R. A. (1989) Wintertime source-reconciliation of ambient organics.
19            Atmos. Environ. 23: 9U-920.
20
21     Atkinson, R. (1988) Atmospheric transformations of automotive emissions. In: Watson, A. Y.; Bates, R. R.;
22            Kennedy, D., eds. Air pollution, the automobile,  and public health. Washington, DC; National Academy
23            Press; pp. 99-132.
24
25     Atkinson, R. (1989) Kinetics and mechanisms of the gas-phase reactions of the hydroxyl radical with organic
26            compounds. In: Journal of physical and chemical  reference data: v. 1. Washington, DC; pp. 1-246.
27
28     Atkinson, R. (1990) Gas-phase tropospheric chemistry of organic compounds: a review. Atmos. Environ.
29            Part A 24:  1-41.
30
31     Atkinson, R. (1991) Kinetics and mechanisms of the gas-phase reactions of the NO) radical with organic
32            compounds. J. Phys. Chem. Ref. Data 20: 459-507.
33
34     Atkinson, R. (1993) Gas-phase tropospheric chemistry of organic compounds. J. Phys. Chem. Ref, Data:
35            in press.
36
37     Atkinson, R.; Aschmann, 5. M. (1993) OH radical  production from the gas-phase reactions of 03 with a series
38            of alkenes under atmospheric conditions. Environ. Sci. Techno!.: in press.
39
40     Atkinson, R.; Carter, W. P. L. (1984) Kinetics and mechanisms of the gas-phase reactions of ozone with organic
41            compounds under atmospheric conditions. Chem.  Rev. 84: 437-470.
42
43     Atkinson, R.; Carter, W. P. L. (1991) Reactions of alkoxy radicals under atmospheric conditions: the relative
44            importance of decomposition versus reaction with O2. J. Atmos. Chem.  13: 195-210.
45
46     Atkinson, R.; Winer, A. M., principal investigators. (1988) Measurements of NOj, HONO, NO3, HCHO, PAH,
47            nitroarenes and paniculate mutagenic activities during the carbonaceous species methods comparison
48            study. Final report Sacramento, CA: California Air Resources Board; report no. ARB-R-88/366.
49            Available from: NTIS, Springfield, VA; PB88-247481.
50
51     Atkinson, R.; Winer, A.  M.; Pitts, J N., Jr. (1986) Estimation of night-time N2O5 concentrations from ambient
52            NO2 and NOg radical concentrations and the role of N2O3 in night-time chemistry. Atmos. Environ.
53            20: 331-339.
54


         December 1993                              3-230      DRAFT-DO NOT QUOTE OR CTTB

-------
 1     Atkinson, R.; Aschmann, S. M.; Arey, J.; Carter, W. P. L. (1989) Formation of ring-retaining products from
 2            the OH radical-initiated reactions of benzene and toluene. Int. J. Chem. Kinet, 21: 801-827.
 3
 4     Atkinson, R.; Baulch, D. L.; Cox, R. A.; Hampson, R, P., Jr.; Ken-, J. A.; Troe, J. (1992a) Evaluated kinetic
 5            and photochemical data for atmospheric chemistry: supplement IV, J. Phys. Chem. Ref. Data
 6            21: 1125-1568.
 7
 8     Atkinson, R.; Aschmann, S. M.; Arey, I.; Shorees,  B.  (1992b) Formation of OH radicals in the gas phase
 9            reactions of O* with a series of terpenes. J. Geophys. Res. [Atmos.] 97: 6065-6073.
10
11     Ayers, G. P.; Penkett, S. A.; Gillett, R.  W.; Bandy, B.; Galbally, I. E.; Meyer, C. P.; Elsworth, C. M.;
12            Bentley, S. T.; Forgan, B. W. (1992) Evidence for photochemical control of ozone concentrations in
13            unpolluted marine air. Nature (London) 360: 446-449.
14
15     Bach, W. D., Jr. (1975) Investigation of ozone and ozone precursor concentrations at nonurban locations in the
16            eastern United States. Phase H. Meteorological analyses. Research Triangle Park, NC:
17            U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards; EPA report
18            no. EPA-450/3-74-034a.  Available from: NTIS, Springfield, VA; PB-246899,
19
20     Barnes, I.; Bastian, V.; Becker, K. H.; long, Z. (1990) Kinetics and products of the reactions of NOj with
21            monoalkenes, dialkenes, and monoterpenes. J. Phys. Chem.  94; 2413-2419,
22
23     Bass, A.  M.; Glasgow,  L. C.; Miller, C.; Jesson, J. P.; Filkin, D. L. (1980) Temperature dependent absorption
24            cross sections for formaldehyde (CH2O): the effect of formaldehyde on stratospheric chlorine chemistry.
25            Planet. Space Sci. 28: 675-679.
26
27     Baugues, K. (1986) A review of NMOC, NOX and NMOC/NOX ratios measured in 1984 and 1985.
28            Research Triangle Park, NC: U.S. Environmental Protection Agency, Office of Air Quality Planning and
29            Standards; EPA report no. EPA-450/4-86-015. Available from: NTIS, Springfield, VA;
30            PB87-166963/HSU.
31
32     Beck, M. B, (1987) Water quality modeling:  a review of the analysis of uncertainty. Water Resour. Res.
33            23: 1393-1442.
34
35     Becker, K. H.; Brockmann,  K. J.; Bechara, J. (1990) Production of hydrogen peroxide in forest air by reaction
36            of ozone with terpenes. Nature (London) 346: 256-258.
37
38     Becker, K. H.; Bechara, J.; Brockmann, K. J. (1993) Studies on the formation of H2O2 in the ozonolysis of
39            alkenes. Atmos. Environ. Part A 27:  57-61.
40
41     Bell, G. B. (1960) Meteorological conditions during oxjdant episodes in coastal San Diego County in October and
42            November, 1959. Sacramento, CA: State of California, Department of Public Health.
43
44     Benjamin, S. G.; Seaman, N. L. (1985) A simple scheme for objective analysis in curved flow. Mon. Weather
45            Rev,  113: 1184-1198.
46
47     Bersis, D.; Vassiliou, E. (1966) A chemiluminescence method for determining ozone. Analyst (London)
48            91: 499-505.
49
50     Betterton, E, A.; Hoffmann, M.  R, (1988) Henry's  law constants of some environmentally important aldehydes.
51            Environ. Sci. Technol. 22: 1415-1418.
52
53     Bidleman, T. F, (1988) Atmospheric processes. Environ. Sci. Technol. 22: 361-367.
54


         December  1993                              3-231       DRAFT-DO  NOT QUOTE OR OfTP.

-------
 1     Biermann, H. W.; Tuazon, E. C.; Winer, A. M.; Wallington, T. J.; Pitts, J, N., Jr. (1988) Simultaneous
 2            absolute measurements of gaseous nitrogen species in urban ambient air by long pathlength infrared and
 3            ultraviolet-visible spectroscopy. Atmos. Environ. 22: 1545-1554.
 4
 5     Bjerlcnes, J. (1951) Extratropical cyclones. In: Malone, T. F., ed. Compendium of meteorology. Boston, MA:
 6            American Meteorological Society; pp. 577-598.
 7
 8     Blake, N. J.;  Penkett, S. A.; Clemitshaw, K.  C.; Anwyl, P.; Lightman, P.; Marsh, A. R. W.; Butcher, G.
 9            (1993) Estimates of atmospheric hydroxyl radical concentrations from the observed decay of many
10            reactive hydrocarbons in well-defined urban plumes, J. Geophys. Res. [Atmos.] 98: 2851-2864.
11
12     Brost, R. A. (1988) The sensitivity to input parameters of atmospheric concentrations simulated by a regional
13            chemical model. J. Geophys. Res. [Atmos.] 93: 2371-2387.
14
15     Bruckmann, P. W.; Willner, H. (1983) Infrared spectroscopic study of peroxyacetyl nitrate (PAN) and its
16            decomposition products. Environ. Sci. Techno]. 17: 352-357.
17
18     Burkhardt, M. R.; Maniga, N. I.; S ted man, D. H.; Paur, R. J. (1988)  Gas chromatographic method for
19            measuring nitrogen dioxide and peroxyacetyl nitrate in air without compressed gas cylinders. Anal,
20            Chem. 60:  816-819.
21
22     Burns, W. F.; Tingey, D. T.; Evans, R. C.; Bates, E. H. (1983) Problems with a Nafion membrane dryer for
23            drying chromatographic samples. J, Chromatography 269: 1-9,
24
25     Burton, C. S.; Bekowies, P. J.; Pollack, R. I.; Cornell, P. (1976) Oxidanfozone ambient measurement methods:
26            an assessment and evaluation. Washington, DC: American Petroleum Institute, Office of the General
27            Counsel; report no. EF76-111R.
28
29     Busness, K. (1992) unpublished data. RichJand, WA: Pacific Northwest Laboratory.
30
31     Cadle, S. H.; Gorse, R, A.; Lawson, D. R. (1993) Real-world vehicle emissions : a summary of the third annual
32            CRC-APRAC on-road vehicle emissions workshop. Air Waste 43: 1084-1090.
33
34     Cadoff, B. C.; Hodgeson, J. (1983) Passive sampler for ambient levels of nitrogen dioxide. Anal. Chem.
35            55: 2083-2085.
36
37     California Air Resources Board. (1976) A study of the effect of atmospheric humidity on analytical oxidant
38            measurement methods. Presented at: 15th conference [on] methods in air pollution studies; January;
39            Long Beach, CA. Sacramento, CA: Air and Industrial Hygiene Laboratory.
40
41     California Air Resources Board. (1992) Analysis of the ambient VOC data collected in the southern California
42            Air Quality Study [final report]. Sacramento, CA: California Air Resources Board; contract no.
43            A8320-130.
44
45     Cardelino, C. A.; Chameides, W. L. (1990) Natural hydrocarbons, urbanization, and urban ozone. J. Geophys.
46            Res. 95: 13,971-13,979.
47
48     Cardin, D, B.; Lin, C.  C.  (1991) Analysis of selected polar and non-polar compounds in air using automated
49             2-dimensional chromatography. Presented at: the  1991 U.S. EPA/A&WMA international symposium on
50             measurement of toxic and related air pollutants; May; Research Triangle Park, NC. Pittsburgh, PA: Air
51             and Waste  Management Association; pp. 552-557.
52
53      Carmichael, G. R.; Peters, L. K.; Kitada, T,  (1986) A second generation model for regional-scale
54             transport/chemistry/deposition. Atmos. Environ. 20: 173-188.


         December 1993                              3-232      DRAFT-DO NOT QUOTE OR CITE

-------
 1     Cannichael, G. R.; Peters, L. K.; Saylor, R. D. (1991) The STEM-II regional scale acid deposition and
 2            photochemical oxidant model—I: an overview of model development and applications. Atmos. Environ.
 3            Part A 25: 2077-2090,
 4
 5     Carroll, M. A.; Hastie, D. R.; Ridley, B. A.; Rodgers, M. O.; Torres, A. L.; Davis, D. D.; Bradshaw, J. D.;
 6            SandholmS. T.; Schiff, H. I.j Karecki, D. R,; Harris, G. W.; Mackay,  G. I.; Gregory, G. L.; Condon,
 7            E. P.; Trainer, M.; Hubler, G.; Montzka, D. D.; Madronich, S.; Albritton, D. L.; Singh, H. B.; Beck,
 8            S, M.; Shipham, M. C.; Bachmeier, A. S. (1990) Aircraft measurement  of NOX over the eastern Pacific
 9            and continental United States and implications for ozone production. J. Geophys. Res. [Atmos.]
10            95: 10,205-10,233.
11
12     Carter, W. P. L. (1990) A detailed mechanism for the gas-phase atmospheric reactions of organic compounds.
13            Atmos. Environ. Part A 24: 481-518.
14
15     Carter, W. P. L. (1991) Development of ozone reactivity scales for volatile organic compounds. Research
16            Triangle Park, NC: U.S. Environmental protection Agency; report no. EPA/3-91/050. Available from:
17            NTIS, Springfield, VA.
18
19     Carter, W. P. L.; Atkinson, R.  (1987) An experimental study of incremental hydrocarbon reactivity. Environ.
20            Sci. Technol. 21:  670-679.
21
22     Carter, W. P. L.; Atkinson, R.  (1989a) Alkyl nitrate formation from the atmospheric photooxidation of alkanes;
23            a revised estimation method. J. Atmos. Chein. 8:  165-173.
24
25     Carter, W. P. L.; Atkinson, R.  (1989b) Computer modeling study of incremental hydrocarbon reactivity.
26            Environ. Sci. Technol. 23: 864-880.
27
28     Carter, W. P. L.; Lurmann, F.  W. (1990) Evaluation of the RADM gas-phase chemical mechanism. Research
29            Triangle Park, NC: U.S. Environmental Protection Agency, Atmospheric Research and Exposure
30            Assessment Laboratory; EPA report no. EPA-600/3-90-001. Available from:  NTIS, Springfield, VA;
31            PB90-164526/HSU.
32
33     Carter, W. P. L.; Lloyd,  A. C.; Sprung, J. L.; Pitts, J. N., Jr. (1979) Computer modeling of smog chamber
34            data: progress in validation of a detailed mechanism for the photooxidation of propene and n-butane in
35            photochemical smog. Int. J. Chem. Kinet.  11: 45-101.
36
37     Carter, W. P. L.; Winer,  A. M.; Pitts, J. N., Jr. (1982) Effects of kinetic mechanisms and hydrocarbon
38            composition on oxidant-precursor relationships predicted by the EKMA isopleth technique. Atmos.
39            Environ. 16: 113-120.
40
41     Cassmassi, I.; Mitsutom.i, S.; Shepherd, M. (1990) Three-dimensional wind fields for use in the urban airshed
42            model. Presented at: Tropospheric ozone and the environment I;  March; Los Angeles, CA. Pittsburgh,
43            PA: Air and Waste Management Association.
44
45     Chameides, W. L.; Tan, A. (1981)  The two-dimensional diagnostic model for tropospheric OH: an uncertainty
46            analysis. J, Geophys. Res. C: Oceans Atmos. 86: 5209-5223.
47
48     Chameides, W. L.; Lindsay, R. W.; Richardson, J.; Kiang, C. S. (1988) The role of biogenic hydrocarbons in
49            urban photochemical smog:  Atlanta as a case study. Science (Washington, DC) 241: 1473-1475.
50
51     Chameides, W. L.; Fehsenfeld, F.;  Rodgers, M. O.; Cardelino, C.; Martinez, J.; Parrish, D.;  Lonneman, W.;
52            Lawson, D. R.; Rasmussen, R. A.; Zimmerman, P.; Greenberg, J.; Middleton, P.; Wang, T. (1992)
53            Ozone precursor relationships in the ambient atmosphere. J. Geophys. Res. [Atmos.] 97: 6037-6055.
54


         December 1993                              3-233       DRAFT-DO NOT DTTDTP np nrrn

-------
 1     Chandler, A. S.; Choiuarton, T. W.; Dollard, G. J.; Eggleton, A. E. J.; Gay, M. J.; Hill, T. A.;
 2            Jones, B. M. R.; Tyler, B. J.; Bandy, B. L; Penkett, S. A. (1988) Measurements of H2O2 and SO2 b
 3            clouds and estimates of their reaction rate. Nature (London) 336: 562-565.
 4
 5     Chang, J. S,; Brost, R, A.; Isaken, I. S. A.; Madronkii, S.; Middleton, P.; Stoekwell, W. R.; Wdcek, C, J.
 6            (1987) A three-dimensional Eulerian add deposition model: physical concepts and formulation,
 7            J. Geophys. Res. 92: 14,681-14,700.
 8
 9     Chang, Y. S.; Carmichael, G. R.; Kurita, H.; Ueda, H. (1989) The transport and formation of photochemical
10            oxidants in central Japan.  Atmos. Environ. 23; 363-393.
11
12     Chang, J. S.; Middleton, P. B.; Stockwell,  W. R.; Walcefc, C. J.; Pleim, L E.; Lansford, H. H.; Binkowski,
13            F. S.; Madronich, S.; Seaman, N. L.; Stauffer, D. R. (1991) The regional acid deposition model and
14            engineering model. In: Irving, P. M., ed. Acidic deposition: state of science and technology, volume I,
15            emissions, atmospheric processes, and deposition. Washington, DC: The U.S. National Acid Precipitation
16            Assessment Program. (State of science and technology report no. 4).
17
18     Chapman, S. (1930) A theory of upper atmospheric ozone. Q. J. R. Meteorol. Soc. 3: 103-125.
19
20     Chock, D. P.; Kumar, S.; Herrmann, R. W. (1982) An analysis of trends in oxidant air quality in the south coast
21            air basin of California. Atmos. Environ. 16: 2615*2624.
22
23     Chow, J.  C.; Watson, J. G.; Lowenthal, D. H.; Solomon, P. A.; Magliano, K. L.;  Ziman, S. D.; Richards,
24            L. W. (1993) PM10 and PM2 5 compositions in California's San Joaquin Valley. Aerosol Sci. Technol.
25            18: 105-128.
26
27     Chu, S. H.; Cox, W. M. (1993) Differences in regional ozone responses to precursor reductions as demonstrated
28            in a regional oxidant model. Presented at: AMS conference on the role of meteorology in managing the
29            environment in the 1990's; January; Scottsdale, AZ. Boston, MA: American Meteorological Society,
30
31     Chu, S. H.; Meyer, E. L.; Cox, W. M.; Scheffe, R. D.  (1992) The response of regional ozone to VOC and
32            NOX emissions reductions: an analysis for the eastern United States based on regional oxidant modeling.
33            Presented at: specialty conference on tropospheric ozone, nonattaimnent, and design value issues;
34            October; Boston, MA. Pittsburgh, PA: Air and Waste Management Association.
35
36     Cicerone, R. J. (1989) Analysis of sources  and sinks of atmospheric nitrous oxide (N2O). J. Geophys. Res.
37            [Atmos.] 94: 18,265-18,271.
38
39     Clark, T. L-, Karl, T. R. (1982) Application of prognostic meteorological variables to forecasts of daily
40            maximum one-hour ozone concentrations in the northeastern United States. J. Appl. Meteorol.
41            21: 1662-1671.
42
43     Clark, T. L-; Clarke, J, F.; Possiel, N. C.  (1982) Boundary layer transport of NOX and O3 from Baltimore,
44            Maryland—a case study. Presented at: 75th annual meeting of the Air Pollution Control Association;
45            June; New Orleans, LA. Pittsburgh, PA: Air Pollution Control Association;  paper no. 82-24.3.
46
47     Clarke, J. F.; Ching, J. K. S.; Brown, R. M.; Westberg, J.; White, J. H. (1982) Regional transport of ozone.
48            Presented at: Third conference on air pollution meteorology. Boston, MA: American Meteorological
49            Society; paper no.  1.1.
50
51     Cleveland, W. S.; Guarino, R.; Kleiner, B.; McRae,  J, E.; Warner, J. L. (1976a) The analysis of the ozone
52            problem in the northeast United States. In: Specialty conference on: ozone/oxidants-interactions with the
53            total environment; March; Dallas, TX. Pittsburgh, PA: Air Pollution Control Association; pp. 109-119.
54


         December 1993                               3-234      DRAFT-DO  NOT QUOTE OR CTTE

-------
 1     Cleveland, W. S.; Kleiner, B,; McRae, J. E.; Warner, J. L. (1976b) Photochemical air pollution: transport from
 2            New York City area into Connecticut and Massachusetts. Science (Washington, DC) 191: 179-181.
 3
 4     Code of Federal Regulations. (1987) Ambient air monitoring reference and equivalent methods. C. F. R.
 5            40: §53.
 6
 7     Coffey, P, E,; Stasiuk, W. N. (1975) Evidence of atmospheric transport of ozone into urban areas. Environ.
 8            Sci. Technol. 9: 59-62.
 9
10     Cohen, I. R.; Purcell, T, C. (1967) Spectrophotometric determination of hydrogen peroxide with 8-quinolinol.
11            Anal. Chem. 39: 131-132.
12
13     Cohen, I. R.; Purcell, T. C.; Altshuller, A. P. (1967) Analysis of the oxidant in photooxidation reactions.
14            Environ. Sci. Technol. 1: 247-252.
15
16     Cohn,  R. D.; Dennis, R, L. (1994) The evaluation of acid deposition models using principal component spaces,
17            In press.
18
19     Colbeck, I.; Harrison, R. M. (1985) Dry deposition of ozone:  some measurements of deposition velocity and of
20            vertical profiles to 100 metres. Atmos.  Environ. 19: 1807-1818.
21
22     Comes, F. J.; Armerding, W.; Grigonis, R,; Herbert, A.; Spiekermann, M.; Walter, J. (1992) Tropospheric
23            OH: local measurements and their interpretation. Her.  Bunsen-Ges. Phys. Chem. 96: 284-286.
24
25     Cotton, W. R.; Anthes, R. A. (1989) Storm and cloud dynamics. New York, NY: Academic Press.
26
27     Countess, R.  J.;  Wolff, G. T.; Whitbeck, M. R. (1981) The effect of temperature on ozone formation in the
28            propene/nitrogen dioxide/air system. J. Environ. Sci. Health Part A 16: 1-8.
29
30     Coutant, R. W. (1993) Theoretical evaluation of stability of volatile organic chemicals and polar volatile organic
31            chemicals in canisters [final report]. Columbus, OH: Battelle Columbus Laboratory; EPA contract
32            no. 68-DO-0007, WA-45.
33
34     Cox, R. A. (1974) The photolysis of gaseous nitrous acid. J. Photochem. 3: 175-188.
35
36     Cox, R. A.; Roffey, M. J. (1977) Thermal decomposition of peroxyacetylnitrate in the presence of nitric oxide.
37            Environ. Sci. Technol. 11: 900-906.
38
39     Cox, R. D.; Balfour, W, D.; Langley, G. J. (1982) Quality control for ambient level hydrocarbon sampling and
40            analysis. Presented at: 75th annual meeting of the Air Pollution Control Association; June;
41            New  Orleans, LA. Pittsburgh, PA: Air Pollution Control Association; paper no. 82-23.2.
42
43     Crutzen, P. J. (1970) The influence of nitrogen oxides on the atmospheric ozone content. Q. J. R. Meteorol.
44            Soc. 96: 320-325.
45
46     Danielsen, E.  F. (1968) Stratospheric-tropospheric exchange based on radioactivity, ozone and potential vorticity.
47            J. Atmos. Sci.  25: 502-518.
48
49     Danielsen, E.  F. (1980) Stratospheric source for unexpectedly  large values of ozone measured over the Pacific
50            Ocean during Gametag, August 1977. J. Geophys. Res. C: Oceans Atmos. 85: 401-412.
51
52     Danielsen, E.  F.; Mohnen, V.  A. (1977) Project Duststonn report: ozone transport, in situ measurements, and
53            meteorological analyses of tropopause folding. J. Geophys. Res. 82: 5867-5877.
54


         December 1993                              3-235       DRAFT-DO NOT OTTOTFi nw rrrr:

-------
  1     Darley, E. F.; Kettner, K. A.; Stephens, E. R, (1963) Analysis of peroxyacyl nitrates by gas chromatography
  2             with electron capture detection. Anal. Cham. 35: 589-591.
  3
  4     Daraall, K. R.; Lloyd, A. C.; Winer, A. M.; Pitts, J. N., Jr. (1976) Reactivity scale for atmospheric
  5             hydrocarbons based on reaction with hydroxyl radical. Environ. Sci. Technol. 10: 692-696.
  6
  7     Das, T. N,; Moorthy, P.  N.; Rao, K. N. (1982) Cbemiluminescent method for the determination of low
  8             concentrations of hydrogen peroxide. J. Indian Chem. Soc. 59: 85-89.
  9
10     Dasgupta, P. K.; Hwang, H. (1985) Application of a nested loop system for the flow injection analysis of trace
11             aqueous peroxide. Anal. Chem. 57: 1009-1012.
12
13     Dasgupta, P. K.; Dong, S.; Hwang, H.; Yang, H. C.; Genfa, Z. (1988) Continuous liquid-phase fluorometry
14             coupled to a diffusion scrubber for the real-time determination of atmospheric formaldehyde, hydrogen
15             peroxide and sulfur dioxide. Atmos. Environ.  22: 949-963.
16
17     Dasgupta, P. K.; Dong, S.; Hwang, H. (1990) Diffusion scrubber-based field measurements of atmospheric
18             formaldehyde and hydrogen peroxide. Aerosol Sci. Technol. 12: 98-104.
19
20     Davis, D. D. (1988) Atmospheric nitrogen oxides, their detection and chemistry. In: Third year report to
21             Coordinating Research Council. Atlanta, GA:  Georgia Institute of Technology; pp. 1-13.
22
23     Davis, D. R.; Jensen, R.  E. (1976) Low level ozone and weather systems. In: Specialty conference on
24             ozone/oxidants—interactions with the total environment; March; Dallas, TX. Pittsburgh, PA: Air
25             Pollution Control Association; pp. 242-251.
26
27     Davis, D. D.; Bradshaw,  J. D.,* Rodgers, M. O.; Sandholm, S. T.; KeSheng, S. (1987) Free tropospheric and
28             boundary layer measurements  of NO over the central and eastern North Pacific Ocean. J. Geophys. Res.
29             [Atmos.] 92: 2049-2070.
30
31     De Santis, P.; Febo, A.; Penino, C,; Possanzini, M.; Liberti, A. (1985) Simultaneous measurements of nitric
32             acid, nitrous acid, hydrogen chloride and sulfur dioxide in air by means of high-efficiency annular
33             denuders. In: Proceedings of the ECE workshop on advancements in air pollution monitoring and
34             procedures;  June; Freiburg, Federal Republic of Germany. Bonn, Federal Republic of Germany: Federal
35             Ministry of the Interior, pp. 68-75.
36
37     Delany, A. C.; Dickerson, R. R.; Melchior, F. L., Jr.; Wartburg, A. F. (1982) Modification of a commercial
38             NO. detector for  high sensitivity. Rev.  Sci. Instrum. 53:  1899-1902.
39
40     Demerjian, K. L.; Schere, K. L.; Peterson, J. T. (1980) Theoretical estimates of actinic (spherically integrated)
41             flux and photolytic rate constants of atmospheric species in the lower troposphere. In: Pitts, J. N., Jr.;
42             Metcalf, R.  L.; Grosjean. D., eds. Advances  in environmental science  and technology: v. 10. New York,
43             NY: John Wiley & Sons; pp. 369-459.
44
45     DeMore, W. B.; Sander,  S. P.; Golden, D. M.; Hampson, R. F.; Kurylo, M.  J.; Howard, C. J.; Ravishankara,
46             A. R.; Kolb, C. E.; Molina, M. J. (1992) Chemical kinetics and photochemical data for use in
47             stratospheric modeling, Pasadena, CA:  NASA Panel for Data Evaluation, Jet Propulsion Laboratory;
48             publication no.  92-20.
49
50     Dennis, R. (1991) EPA's new models-3. Presented at: Tropospheric ozone and the environment II: effects,
51             modeling and control; November; Atlanta, GA. Pittsburgh, PA: Air and Waste Management Association.
52
53     Dennis, R. L,;  Downton, M. W. (1984) Evaluation of urban photochemical models for regulatory use. Atmos.
54            Environ. 18: 2055-2069.


         December 1993                              3-236      DRAFT-DO NOT  QUOTE OR CITE

-------
 1     Dennis, R. L.; McHenry, J. N.; Barchet, W. R.; Binkowski, F. S.; Bynn, D. W. (1993a) Correcting RADM's
 2            sul fate underprediction: discovery and correction of model errors and testing the corrections through
 3            comparisons against field data. Atmos. Environ. Part A 27: 975-997.
 4
 5     Dennis, R. L; Bynn, D. W.; Novak, I. H.; Coates, C. J.; Galuppi, K. I. (1993b) Hie next generation of
 6            integrated air quality modeling: EPA's Models-3, Presented at: the international conference on regional
 7            photochemical measurement and modeling studies; November; San Diego, CA. Pittsburgh, PA: Air and
 8            Waste Management Association.
 9
10     Dentener, F. J.; Crutzen, P. J. (1993) Reaction of N2O5 on tropospheric aerosols: impact on the global
11            distribution of NOX, O3, and OH. J. Geophys. Res. 98: 7149-7163.
12
13     Derwent, R.; Hov,  O. (1988) Application of sensitivity and uncertainty analysis techniques to a photochemical
14            ozone model. J. Geophys. Res. [Atmos.] 93: 5185-5199.
15
16     Dickerson, R. R. (1984) Measurements of reactive nitrogen compounds in the free troposphere. Atmos. Environ.
17            18:  2585-2593.
18
19     Dickerson, R. R.; Delany, A. C.; Wartburg,  A. F. (1984) Further modification of a commercial NOX detector
20            for high sensitivity. Rev. Sci. Instrum. 55: 1995-1998.
21
22     Dickerson, R. R.; Huffman, G. J.; Luke, W. T.; Nunnermacker, L- J.; Pickering, K. E.; Leslie,  A.  C. D.;
23            Lindsey.  C.  G.; Slinn, W. G. N,; Kelly, T. J.; Damn, P.  H,; Delany, A. C.; Greenberg,  J. P.;
24            Zimmerman, P. R.; Boatman, J. F.; Ray,  J. D.; Stedman, D. H. (1987) Thunderstorms: an important
25            mechanism  in the transport of air pollutants. Science (Washington, DC) 235: 460-465.
26
27     Dietz, W. A, (1967) Response factors for gas chromatographic analyses. J. Gas Chromatogr. 5: 68-71.
28
29     Dimitriades, B. (1970) On the function of hydrocarbon and nitrogen oxides in photochemical smog formation.
30            Washington, DC: U.S. Department of the  Interior, Bureau of Mines; report DO. BM-RI-7433. Available
31            from: NTIS, Springfield, VA; PB-196680.
32
33     Dimitriades, B. (1972) Effects of hydrocarbon and nitrogen oxides on photochemical smog formation. Environ.
34            Sci. Technol. 6: 253-260.
35
36     Dimitriades, B. (1977) Oxidant control strategies.  Part I. Urban oxidant control strategy derived from existing
37            smog chamber data. Environ. Sci. Technol. 11: 80-88.
38
39     Dodge, M.  C. (1977a) Combined use of modeling techniques and smog chamber data to derive ozone-precursor
40            relationships. In: Dimitriades, B., ed. International conference on photochemical oxidant pollution and its
41            control—proceedings: volume II; September 1976; Raleigh, NC. Research Triangle Park, NC: U.S.
42            Environmental Protection Agency, Environmental Sciences Research Laboratory; pp. 881-889; EPA
43            report no. EPA-600/3-77-001b. Available from: NTIS, Springfield, VA; PB-264233.
44
45     Dodge, M.  C. (1977b) Effect of selected parameters on predictions of a photochemical model.
46            Research Triangle Park, NC: U.S. Environmental Protection Agency, Environmental Sciences Research
47            Laboratory;  EPA report no. EPA-600/3-77-048. Available from: NTIS, Springfield, VA; PB-269858.
48
49     Dodge, M.  C. (1989) A comparison of three  photochemical oxidant mechanisms. J. Geophys. Res. [Atmos.]
50            94:5121-5136.
51
52     Dodge, M.  C. (1990) Formaldehyde production in photochemical smog as predicted by three state-of-the-science
53            chemical oxidant mechanisms. J. Geophys. Res. 94: 5121-5136.
54


         December 1993                              i.m      DRAFT-DO NOT  OTTOTR HP  rrm

-------
 1     Dolske, D. A.; Gatz, D. F. (1985) A field Intel-comparison of methods for the measurement of particle and gas
 2            dry deposition. J. Geophys. Res, 90: 2076-2084.
 3
 4     Douglas, S. G.; Kessler, R. C.; Carr, E. L. (1990) User's guide for the urban airshed model, v, ffl: user's
 5            manual for the diagnostic wind model (version 1.1). San Rafael, CA: U.S. Environmental Protection
 6            Agency; SYSAPP-90/018c.
 7
 8     Drummond, J. W,; Volz, A.; Ehhalt, D. H. (1985) An optimized chemiluminescence detector for tropospheric
 9            NO measurements. J. Atmos. Chem. 2: 287-306.
10
11     Drummond, J.; Sclriff, H.; Karecki,  D.; Mackay, G. (1989) Measurements of NOj, O3, PAN, HNO3> fyOj,
12            and H2CO during the southern California air quality study. Presented at: die 82nd annual meeting and
13            exhibition of the Air and Waste Management Association; June; Anaheim, CA. Pittsburgh, PA: Air and
14            Waste Management Association; report no.  89-139.4.
15
16     Drummond, J. W.; Shepson, P. B.; Mackay, G. I.; Schiff, H. I. (1993) Measurements of NOy, NOX, and
17            NO2 using a new converter-sequencer and sensitive Uiminox detection. In: proceedings of the 1992 U.S.
18            EPA/A&WMA international symposium on measurement of toxic and related air pollutants. Pittsburgh,
19            PA: Air and Waste Management Association; publication no. VIP-25; EPA report no.
20            EPA/600/R-92/131; pp. 750-755.
21
22     Dunker, A. M. (1980) The response of an atmospheric reaction-transport model to changes in input functions.
23            Atmos. Environ. 14: 671-679.
24
25     Dunker, A. M. (1984) The decoupled direct method for calculating sensitivity coefficients in chemical kinetics.
26            J. Chem. Phys. 81: 2385-2393.
27
28     Dunker, A. M.; Schleyer, C. H.;  Morris, R. E.; Pollack, A. K. (1992a) Effects of methanol/gasoline blends
29            used in flexible/variable fuel vehicles on urban air quality in year 2005/2010—auto/oil air quality
30            improvement research program. Presented at: 85th annual meeting and exhibition of the Air and Waste
31            Management Association;  June; Kansas City, MO. Pittsburgh, PA: Air and Waste Management
32            Association; paper no. 92-119.06.
33
34     Dunker, A. M.; Morris, R. E.; Pollack, A. K.; Cohen, J. P.; Schleyer, C. H.;  Chock, D. P. (1992b) Effects of
35            aromatics, MTBE, olefins, and T90 on urban air quality in year 2005/2010—auto/oil air quality
36            improvement research program. Presented at: 85th annual meeting and exhibition of the Air and Waste
37            Management Association;  June; Kansas City, MO. Pittsburgh, PA: Air and Waste Management
38            Association; paper no. 92-119.03.
39
40     Durbin, P. A.; Hecht, T. A.; Whitten, G. Z. (1975) Mathematical modeling of simulated photochemical smog.
41            Washington, DC: U.S. Environmental Protection Agency,  Office of Research and Development; EPA
42            report no. EPA-650/4-75-026. Available from: NTIS, Springfield, VA; PB-246122.
43
44     Ehhalt, D. H.; Dom, H.-P.; Poppe, D. (1991) The chemistry of the hydroxyl radical in the troposphere.
45            Proc. R. Soc. Edinburgh,  Sect. B: Biol. Sci. 97:  17-34.
46
47     Ehrenfeld, J.  R. (1974) Analysis of the composition of the atmosphere in the Los Angeles basin. Washington,
48            DC: U.S. Environmental Protection Agency, Office of Research and Development; EPA report
49            no. EPA-650/2-74-105. Available from: NTIS, Springfield, VA; PB-239 466.
50
51     Eisele, F. L.; Tanner, D. J. (1991) Ion-assisted tropospheric OH measurements. J. Geophys. Res. [Atmos.]
52            96: 9295-9308.
53
         December 1993                              3-238       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Eisenreich, S. J,; Looney, B. B.; Thornton, J. D. (1981) Airborne organic contaminants in the Great Lakes
 2            ecosystem. Environ. Sci. Technol.  15: 30-38.
 3
 4     Eldering, A.; Larson, S. M,; Hall, J. R.; Hiissey, K, J.; Cass, G. R. (1993) Development of an improved image
 5            processing based visibility model. Environ. Sci. Technol. 27; 626-635.
 6
 7     Errico, R.; Bates, G. T.  (1988) Implicit normal-mode initialization of the PSU/NCAR mesoscale model. Boulder,
 8            CO: National Center for Atmospheric Research; NCAR technical note 312.
 9
10     Fabian, P.; Pruchniewicz, P.  G. (1977) Meridional distribution of ozone in the troposphere and its seasonal
11            variations. J. Geophys. Res. 82: 2063-2073.
12
13     Fahey, D. W.; Eubank, C. S,; Hubler, G,; Fehsenfeld, F. C. (1985) Evaluation of a catalytic reduction
14            technique for the measurement of total reactive odd-nitrogen NOL in the atmosphere. J.  Atmos. Chem.
15            3: 435-468.
16
17     Federal Register. (1971) National primary and secondary ambient air quality standards. F. R. (April 30)
18            36: 8186-8201.
19
20     Federal Register. (1975) Ambient air monitoring reference and equivalent methods. F. R. (February 18)
21            40: 7042-7070.
22
23     Federal Register. (1979a) National primary and secondary ambient air quality standards:  calibration of ozone
24            reference methods. F. R. (February 8) 44: 8221-8233.
25
26     Federal Register. (1979b) Data collection for 1982 ozone implementation plan submittals. F. R. (November 14)
27            44: 65667-65670.
28
29     Federal Register. (1990) F. R. (September  18) 55: 38386.
30
31     Federal Register. (1992) F. R, (September  28) 57: 44565.
32
33     Federal Register. (1993) F. R. (February 3) 58: 6964.
34
35     Fehsenfeld, F. C.; Dickerson, R. R.; Hubler, G.; Luke, W. T.; Nunnermacker, L. J.; Williams, E. J.;
36            Roberts, J. M.; Calvert, J. G.; Curran, C. M.; Delany, A. C.;  Eubank, C. S.; Fahey, D. W.;
37            Fried, A.; Gandrud, B. W.; Langford, A. O,; Murphy, P. C.;  Norton, R. B.; Pickering, K. E.;
38            Ridley,  B. A. (1987) A ground-based intercomparison of NO, NOX, and NCL measurement techniques.
39            J. Geophys.  Res. [Atmos.] 92: 14710-14722.
40
41     Fehsenfeld, F. C.; Parrish, D. D.; Fahey, D. W. (1988) The measurement of NOX in the non-urban troposphere.
42            In: Isaksen,  I.  S. A., ed. Tropospheric ozone; regional and global scale interactions. Dordrecht, The
43            Netherlands: D. Reidel  Publishing; pp.  185-215.
44
45     Fehsenfeld, F, C.; Drummond, J. W.; Roychowdhury, U. K.; Galvin, P. J.; Williams, E. J.; Buhr, M. P.;
46            Parrish, D. D.; Hubler, G.; Langford, A. O,; Calvert, J. G,; Ridley, B. A.; Grahek, F.; Heikes, B. G.;
47            Kok, G. L.; Shelter, J.  D.; Walega, J. G.; Elsworth, C. M.; Norton, R. B.; Fahey, D. W.;
48            Murphy, P.  C.; Hovermale, C.; Mohnen, V. A.; Demerjian, K. L.; Mackay, G. I.; Schiff, H. I. (1990)
49            Intercomparison of NO2 measurement techniques. J. Geophys. Res. [Atmos.] 95: 3579-3597.
50
51     Fehsenfeld, F.;  Calvert, J.; Fall, R.; Goldan, P.; Guenther, A.  B.; Hewitt, C. N.; Lamb, B.; Liu, S.; Trainer,
52            M.; Westberg, H.; Zimmerman,  P. (1992) Emissions of volatile organic compounds from vegetation and
53            the implications for atmospheric chemistry. Global Biogeochem. Cycles 6: 389-430.
54
         December 1993                              I.TIQ       nBAFT.no xrnr niTnTc r\r>

-------
 1     Feltan, C. C.; Sheppard, J. C.; Campbell, M. J. (1990) The radiochemical hydroxyl radical measurement
 2            method. Environ. Sci. Technol. 24: 1841-1847.
 3
 4     Finlayson-Pitts, B. J.; Pitts, J. N., Jr. (1986) Atmospheric chemistry: fundamentals and experimental techniques.
 5            New York, NY:  John Wiley & Sons.
 6
 7     Flnlayson-Pitts, B. J.; Pitts, J. N., Jr. (1993) Atmospheric chemistry of tropospheric ozone formation: scientific
 8            and regulatory implications. Air Waste 43: 1091-1100.
 9
10     Flamm, D. L. (1977) Analysis of ozone at low concentrations with boric acid buffered KI. Environ. Sci.
11            Technol.  11: 978-983.
12
13     Fox, D, G. (1981) Judging air quality model performance. Bull. Am. Meteorol. Soc. 62: 599-609.
14
15     Freas, W. P.; Martinez,  E. L.; Meyer, E. L.; Possiel, N. C.; Sennett, D. H.; Summerhays, J. E. (1978)
16            Procedures for quantifying relationships between photochemical oxidants and precursors: supporting
17            documentation. Research Triangle Park, NC: U.S. Environmental Protection Agency, Office of Air
18            Quality Planning and Standards; EPA report no. EPA-450/2-77-021b. Available from: NTTS,
19            Springfield, VA; PB-280058.
20
21     Fried, A.; Hodgeson, J.  (1982) Laser photoacoustic detection of nitrogen dioxide in the gas-phase titration of
22            nitric oxide with ozone. Anal. Chem. 54: 278-282.
23
24     Fujita, E. M.; Croes, B. E.;  Bennett, C. L.; Lawson, D. R.; Lurmann, F. W.; Main, H. H. (1992) Comparison
25            of emission inventory and ambient concentration ratios of CO, NMOG, and NOX in California's south
26            coast air basin. J. Air Waste Manage. Assoc. 42: 264-276.
27
28     Fung, K.; Grosjean, D. (1981) Determination of nanogram amounts of carbonyls as 2,4-dinitrophenylhydrazones
29            by high-performance  liquid chromatography. Anal. Chem. 53: 168-171,
30
31     Fung, I.; John, J.;  Lerner,  J.; Matthews, E.; Prather, M.; Steele, L. P.; Fraser, P. J. (1991a) Three-dimensional
32            model synthesis of the global methane cycle. J.  Geophys.  Res. [Atmos.] 96: 13,033-13,065.
33
34     Fung, C. S.;  Misra. P. K.; Bloxam, R.; Wong, S. (1991b) A numerical experiment on the relative importance of
35            H2O2 and O3 in  aqueous conversion of SO2 to SO 74. Atmos. Environ. Part A 25: 411-423.
36
37     Gab, S.; Hellpointner, E.; Turner, W. V.; Korte, F. (1985) Hydroxymethyl hydroperoxide and
38            bisfhydroxymethyl) peroxide from gas-phase ozonolysis of naturally occuring alkenes. Nature (London)
39            316: 535-536.
40
41     Gaffney, J. S.; Fajer, R.; Senum, G. I. (1984) An improved procedure for high purity gaseous peroxyacyl nitrate
42            production: use of heavy lipid solvents. Atmos. Environ. 18: 215-218.
43
44     Garland, J. A. (1976) Dry deposition of SC^ and other gases. In:  Engelmann, R. J.; Sehmel, G. A., eds.
45            Atmosphere-surface exchange of particulate and gaseous pollutants (1974): proceedings of a symposium;
46            September  1974; Richland, WA. Washington, DC: U.S. Energy Research and Development
47            Administration.
48
49     Garland, J. A.; Penkett,  S. A. (1976) Absorption of peroxy acetyl nitrate and ozone by natural surfaces.
50            Atmos. Environ. 10: 1127-1131.
51
52
         December 1993                               3-240       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Gay, B. W.7 Jr.; Bufalini, J. J. (1972a) Hydrogen peroxide in the urban atmosphere. In: Photochemical smog
 2            and ozone reactions: proceedings of the 161st meeting of the American Chemical Society; March-April;
 3            1971; Los Angeles, CA. Washington, DC: American Chemical Society; pp. 255-263. (Gould, R. F., ed.
 4            Advances in chemistry series: v. 113),
 5
 6     Gay, B. W., Jr.; Bufalini, J. J. (1972b) Hydrogen peroxide in the urban atmosphere. Environ. Lett. 3: 21-24.
 7
 8     Gay, B. W., Jr.; Noonan, R. C.; Bufalini, J. J.; Hanst, P. L. (1976) Photochemical synthesis of peroxyacyl
 9            nitrates in gas phase via chlorine-aldehyde reaction. Environ, Sci. Technol. 10: 82-85.
10
11     Gay, B. W.; Meeks, S.; Bufalini, J. I. (1988) Peroxide formation and detection in various systems. Presented at:
12            196th meeting of the American Chemical Society; Los Angeles, CA. 28: 93-94.
13
14     Gervat, G. P.; Clark, P.  A.; Marsh, A. R. W.; Teasdale, I.; Chandler, A. S.; Choularton, T. W.; Gay, M. J.;
15            Hill, M. K.; Hill, T. A. (1988) Field evidence for the oxidation of SOj by H2O2 in cap clouds. Nature
16            (London) 333: 241-243.
17
18     Gery, M. W.; Whitten, G. Z.; Killus, J. P. (1988) Development and testing of the CMB-IV for urban and
19            regional modeling. Research Triangle Park, NC: U.S. Environmental Protection Agency, Atmospheric
20            Sciences Research Laboratory; EPA report no. EPA-600/3-88-012. Available from: NTIS, Springfield,
21            VA; PB88-180039.
22
23     Gery, M. W.; Whitten, G. Z.; Killus, J. P.; Dodge, M. C. (1989) A photochemical kinetics mechanism for
24            urban and regional scale computer modeling. J. Geophys. Res. [Atmos.] 94; 12,925-12,956.
25
26     Gholson, A. R.; Jayanty, R. K. M.; Storm, J. F. (1990) Evaluation of aluminum canisters for the collection and
27            storage of air toxics. Anal.  Chem. 62: 1899.
28
29     Gipson, G.  L. (1984) Guideline for using the carbon-bond mechanism in city-specific EKMA (empirical kinetics
30            modeling approach). Research Triangle Park, NC: U.S. Environmental Protection Agency, Office of Air
31            Quality Planning and Standards; EPA report no. EPA-450/4-84-005. Available from:  NTIS, Springfield,
32            VA; PB84-198910.
33
34     Gipson, G. L.; Freas, W. P.; Kttly, R. F.; Meyer, E. L. (1980) Guideline for use of city-specific EKMA in
35            preparing ozone SIPs [draft]. Research Triangle Park, NC: U.S. Environmental Protection Agency,
36            Office of Air Quality Planning and Standards; EPA report no. EPA-450/4-80-027. Available from: NTIS,
37            Springfield, VA; PB81-118739.
38
39     Goldan, P.  D.; Kuster, W. C.; Fehsenfeld, F. C.; Montzka, S.  A. (1993) The observation of a C5 alcohol
40            emission in a North American pine forest. Geophys. Res. Lett. 20: 1039-1042.
41
42     Goodin, W. R.; McRae,  G. J.; Seinfeld, J. H. (1980) An objective analysis technique for constructing
43            three-dimensional urban-scale wind fields. J. Appl. Meteorol, 19: 98-108.
44
45     Gordon, G. E. (1988) Receptor models. Environ.  Sci. Technol. 22:  1132-1142.
46
47     Gordon, S. M.; Miller, M. (1989)  Analysis of ambient polar volatile organic compounds using chemical
48            ionization-ion trap detector. Research Triangle Park, NC: U.S. Environmental Protection Agency,
49            Atmospheric Research and  Exposure Assessment Laboratory; EPA report no. EPA/600/3-89/070.
50            Available from: NTIS, Springfield, VA; PB90-106451.
51
52     Graedel, T. E.; Weschler, C. J. (1981) Chemistry within aqueous atmospheric aerosols and raindrops.
53            Rev. Geophys. Space Phys. 19: 505-539.
54


         December 1993                              I.OAI        DRAFT-DO NOT OTIOTR mt PTTF

-------
 1     Grade], T. E.; Hawkins, D. T.; Claxton, L. D. (1986a) Atmospheric chemical compounds: sources, occurrence,
 2            and bioassay. Orlando, FL: Academic Press, Inc.
 3
 4     Graedel, T. E.; Mandich, M. L; Weschler, C. J. (1986b) Kinetic model studies of atmospheric droplet
 5            chemistry: 2, homogenous transition metal chemistry in raindrops. J. Geophys. Res. [Atmos.]
 6            91:5205-5221.
 7
 8     Greenhut, G. K. (1986) Transport of ozone between boundary layers and cloud layer by cumulus clouds.
 9            J. Geophys. Res. [Atmos.] 91: 8613-8622.
10
11     Gregory, G. L.; Hoetl, J. M., Jr.;  Torres, A. L.; Carroll, M. A.; Ridley, B. A.; Rodgers, M. O.; Bradshaw,
12            J.; Sandholm, S.; Davis, D. D. (1990s) An Intel-comparison of airborne nitric oxide measurements:
13            a second opportunity. J. Geophys. Res. [Atmos.] 95: 10129-10138.
14
15     Gregory, G. L.; Hoell, J. M., Jr.;  Carroll, M. A.; Ridley, B. A.; Davis, D. D.; Bradshaw, J.; Rodgers, M. O.;
16            Sandholm, S. T.; Schiff, H. I.; Hastie, D. R.; Karecki, D. R.; Mackay, G. I.; Harris, G. W.;
17            Torres, A. L.; Fried, A. (1990b) An intercomparison of airborne nitrogen dioxide instruments. J.
18            Geophys. Res. [Atmos.] 95: 10103-10127.
19
20     Griffith, D. W. T.;  Schuster, G. (1987) Atmospheric trace gas analysis using matrix isolation-Fourier transform
21            infrared spectroscopy. J. Atmos. Chern. 5: 59-81.
22
23     Grosjean, D.  (1982) Formaldehyde and other carbonyls in Los Angeles ambient air. Environ. Sci. Technol.
24            16: 254-262.
25
26     Grosjean, D.; Fung, K. (1984) Hydrocarbons and carbonyls in Los Angeles air. J, Air Pollut. Control Assoc.
27            4: 537-543.
28
29     Grosjean, D.; Harrison, J. (1985a) Peroxyacetyl nitrate: comparison of alkaline hydrolysis and
30            chemiluminescence methods. Environ. Sci. Technol.  19: 749-752.
31
32     Grosjean, D.; Harrison, J. (1985b) Response of chemiluminescence NOX analyzers and ultraviolet ozone
33            analyzers to organic air pollutants. Environ. Sci. Technol. 19: 862-865.
34
35     Grosjean, D.; Hisham, M. W. M.  (1992) A passive sampler for atmospheric ozone. J. Air Waste Manage.
36            Assoc.  42:  169-173.
37
38     Grosjean, D.; Parmar, S, S. (1990) Interferences from aldehydes and peroxyacetyl nitrate when sampling urban
39            air organic acids on alkaline traps. Environ. Sci. Technol. 24: 1021-1026.
40
41     Grosjean, D.; Williams, E. L. (1992) Field tests of a passive sampler for atmospheric ozone at California
42            mountain forest locations. Atmos. Environ.  Part A 26: 1407-1411.
43
44     Grosjean, D.; Fung, K.; Collins, J.; Harrison, J.; Breitung, E. (1984) Portable generator for on-site calibration
45            of peroxyacetyl nitrate analyzers. Anal. Chem. 56: 569-573.
46
47     Grosjean, D.; Williams,  E. L., II;  Grosjean, E. (1993) A biogenic precursor of peroxypropionyl nitrate:
48            atmospheric oxidation of ctr-3-hexen-l-oI. Environ. Sci. Technol. 27: 979-981.
49
50     Grosjean, E.; Williams, E. L., II;  Grosjean, D. (1993) Ambient levels of formaldehyde and acetaldehyde in
51            Atlanta, Georgia. Air Waste 43: 469-474.
52
53     Guilbault, G. G.; Brignac, P. J., Jr.; Juneau,  M. (1968) New substrates for die fluorometric determination of
54            oxidative enzymes. Anal. Chem.  40: 1256-1263.


         December 1993                              3-242       DRAFT-DO NOT QUOTE  OR CITE

-------
 1     Guinmip, D.; Possiel, N. (1991) Woikplan for regional ozone modeling to support the Lake Michigan ozone
 2            study. Research Triangle Park, NC: U.S. Environmental Protection Agency, Office of Air Quality
 3            Planning and Research.
 4
 5     Gunz, D. W.; Hoffmann, M, R. (1990) Atmospheric chemistry of peroxides: a review. Atraos. Environ. Part A
 6            24: 1601-1633.
 7
 8     HakoJa, H.; Shorees, B.; Arey, J.; Atkinson, R. (1993a) Product formation from the gas-phase reactions of OH
 9            radicals and O3 with 0-phelIandrene, Environ, Sci. Technol. 27: 278-283.
10
11     Hakola, H.; Arey, J.; Aschmann, S. M.', Atkinson, R. (1993b) Product formation from the gas-phase reactions
12            of OH  radicals and O3 with a series of monoterpenes. J.  Atmos. Chcm.: in press.
13
14     Haltiner,  G. J.  (1971) Numerical weather prediction. New York, NY: John WUey.
15
16     Haltiner,  G. J.; Williams, R. T. (1980) Numerical prediction and dynamic meteorology. 2nd ed. New York, NY:
17            John Wiley.
18
19     Hampson, R. F.; Braun, W.; Brown, R. L.; Garvin, D.; Herron, J. T.; Huie, R. E.; Kurylo, M. T.; Laufer,
20            A. H.; McKinley, J. D.; Okabe, H.; Scheer, M. D.; Tung, W. (1973) Survey of photochemical and rate
21            data for twenty-eight reactions of interest in atmospheric chemistry. J. Phys. Chem. Ref. Data 2:
22            267-311.
23
24     Haney, J. L. (1986) Overview of the urban airshed model validation of 25-26 October 1985 for the Phoenix
25            carbon monoxide (CO) study. San Rafael, CA: Systems Applications, Inc.; report no. SYSAPP-86/126.
26
27     Haney, J. L.; Braver-man, T. N. (1985) Evaluation and application of the urban airshed model in the Philadelphia
28            sir quality control region. Research Triangle Park, NC: U.S. Environmental Protection Agency, Office of
29            Air Quality Planning and Standards; EPA report no. EPA-450/4-85-003. Available from; NTIS,
30            Springfield, VA; PBS5-246056/HSU.
31
32     Hansen, D. A.  (1989) Measuring trace gases with FM spectroscopy. EPRI J. 14(4): 42-43.
33
34     Hanst, P. L.; Wilson, W. E.; Patterson, R. K.;  Gay,  B. W., Jr.; Chaney, L. W.; Burton, C. S. (1975)
35            A spectroscopic study of California smog. Research Triangle Park, NC: U.S. Environmental Protection
36            Agency, National Environmental Research Center; EPA report no. EPA-650/4-75-006. Available from:
37            NTIS,  Springfield, VA; PB-241022.
38
39     Hanst, P. L.; Wong, N. W.; Bragin, J. (1982) A long-path infra-red study of Los Angeles smog. Atmos.
40            Environ.  16: 969-981.
41
42     Hard, T. M.j Mehrabzadeh, A. A.;  Chan, C. Y.; O'Brien, R. J. (1992) PAGE measurements of tropospheric
43            OH with  measurements and model of interference. J. Geophys. Res. 97: 9795-9817.
44
45     Harley, R. A.; Hannigan, M. P.; Cass, G. R. (1992) Respeciation of organic gas emissions and the detection of
46            excess  unburned gasoline in the atmosphere. Environ. Sci. Technol. 26: 2395-2408.
47
48     Harley, R. A.; Russell, A. G.; McRae, G. J.; Cass, G. R.; Seinfeld, J. H. (1993) Photochemical modeling of
49            the Southern California Air Quality Study. Environ. Sci. Technol. 27: 378-388.
50
51     Harms, D. E.;  Raman, S.; Madala, R. V, (1992) An  examination of four-dimensional data-assimilation
52            techniques for numerical weather prediction. Bull. Am. Meteorol. Soc.  73: 425-440.
53
        December 1993                              WAX       DRAFT-nn NOT nnnTR HP rrm

-------
 1     Harris, G. W.; Carter, W.  P, L.; Winer, A. M,; Pitts, J. N,, Jr.; Platt, U.; Peraer, D. (1982) Observations of
 2            nitrous acid in the Los Angeles atmosphere and implications for predictions of ozone-precursor
 3            relationships. Environ. Sci. Technol. 16; 414-419,
 4
 5     Harrison, J. W.;  Timmons, M. L.; Denyszyn, R. B.; Decker,  C. E. (1977) Evaluation of the EPA reference
 6            method for measurement of non-methane hydrocarbons. Research Triangle Park, NC: U.S.
 7            Environmental Protection Agency, National Environmental Research Center; EPA report no.
 8            EPA-600/4-77-033. Available from: NTTS,  Springfield, VA; PB-278296,
 9
10     Hatakeyama, S.;  Izumi. K.; Fukuyama, T.; Akimoto, H. (1989) Reactions of ozone with a-pinene and 0-pinene
11            in air: yields of gaseous and particulate products. J. Geophys. Res. [Atmos.] 94: 13,013-13,024.
12
13     Hatakeyama, S.;  Izumi, K.; Fukuyama, T.; Akimoto, H.; Washida, N. (1991) Reactions of OH with
14            a-pinene and /3-pinene in air estimate  of global CO production from the atmospheric oxidation of
15            terpenes. J. Geophys. Res. [Atmos.] 96: 947-958.
16
17     Hauser, T. R.; Cummins, R. L. (1964) Increasing sensitivity of 3-methyl-2-beozothiazolone hydrazone test for
IS            analysis of aliphatic aldehydes  in air. Anal. Chem, 36: 679-681.
19
20     Hecht, T.  A.; Seinfeld,  J. H. (1972) Development and validation of a generalized mechanism for photochemical
21            smog. Environ.  Sci. Technol. 6: 47-57.
22
23     Heikes, B. G. (1984) Aqueous H2O2 production from 03 in glass impingers. Atmos. Environ. 18: 1433-1445.
24
25     Heikes, B. G.; Lazrus,  A.  L.; Kok, G. L.; Kunen, S. M.; Gandrud, B. W.; GiUin, S. N.; Sperry, P. D. (1982)
26            Evidence for aqueous phase hydrogen peroxide synthesis in the troposphere. J. Geophys. Res. C: Oceans
27            Atmos. 87: 3045-3051.
28
29     Heikes, B. G.; Kok, G. L.; Walega, J. G.; Lazrus, A. L. (1987) HjC^, 03 and SO2 measurements  in the lower
30            troposphere  over the eastern United States during fall.  J. Geophys, Res. 92: 915-931.
31
32     Helas, G.; Flanz, M.; Warneck, P. (1981) Improved NOX monitor for measurements in tropospheric clean air
33            regions. Int. J. Environ. Anal. Chem.  10: 155-166.
34
35     Hellpointaer, E.; Gab, S. (1989) Detection of methyl, hydroxymethyl and hydroxyethyl hydroperoxides in air and
36            precipitation. Nature (London) 337: 631-634.
37
38     Helmig, D.; Mueller, J.; Klein, W. (1989) Improvements in analysis of atmospheric peroxyacetyl nitrate (PAN).
39            Atmos. Environ. 23: 2187-2192.
40
41     Herron, J. T.; Huie, R. E. (1978) Stopped-flow studies of the mechanisms of ozone-alkene reactions in the gas
42            phase: propene  and isobutene.  Int. J. Chem. Kinet. 10: 1019-1041.
43
44     Hewitt, C. N.; Kok, G. L. (1991) Formation and occurence of organic hydroperoxides in the troposphere:
45            laboratory and field observations. J, Atmos. Chem. 12: 181-194.
46
47     Hildemann, L. M.; Markowski, G. R.; Cass, G. R, (1991a) Chemical composition of emissions from urban
48            sources of fine organic aerosol. Environ. Sci. Technol. 25: 744-759.
49
50     Hildemann, L. M.; Mazurek, M. A.; Cass, G. R.; Simoneh, B. R. T. (1991b) Quantitative characterization of
51            urban sources of organic aerosol by high-resolution gas chromatography. Environ. Sci. Technol.
52            25: 1311-1325.
53
         December 1993                              3-244       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Hill, A, C.; Chamberlain, E. M,, Jr. (1976) The removal of water soluble gases from the atmosphere by
 2            vegetation. In: Engelmaon, R. J.; Sehtnel, G. A., eds. Atmosphere-surface exchange of participate and
 3            gaseous pollutants (1974): proceedings of a symposium; September 1974; Richland, WA. Washington,
 4            DC: U.S. Energy Research and Development Administration.
 5
 6     Hjorth, J.; Lohse, C.; Nielsen, C. J.; Skov, H.; Restelli, G. (1990) Products and mechanisms of gas-phase
 7            reactions between NO3 and a series of alkenes. J. Phys. Chem. 94: 7494-7500.
 8
 9     Hochanadel, C. I. (1952) Effects of cobalt ?-radiation on water and aqueous solutions. J. Phys. Chem.
10            56: 587-594.
11
12     Hodgeson, J. A.; Krost,  K. J.; O'Keeffe, A. E.; Stevens, R.  K. (1970) Chemiluminescent measurement of
13            atmospheric ozone: response characteristics and operating variables. Anal. Chem. 42: 1795-1802.
14
15     Hodgeson, J, A.; Hughes, E. E.; Schmidt, W. P.; Bass, A. M. (1977) Methodology for standardization of
16            atmospheric ozone measurements. In: Dimitriades, B., ed. International conference on photochemical
17            oxidant pollution and its control—proceedings: volume I; September 1976; Raleigh, NC. Research
18            Triangle Park, NC: U.S. Environmental Protection Agency, Environmental Sciences Research
19            Laboratory; pp. 3-12; EPA report no. EPA-600/3-77-001a. Available from: NTIS, Springfield,  VA;
20            PB-264232.
21
22     HoeU, J. M., Jr.; Gregory, G. L.; McDougal, D. S.; Torres, A. L.; Davii, D. D.; Bradshaw, J.;
23            Rodgers, M. O.; Ridley, B. A.;  Carroll, M. A. (1987) Airborne intercomparison of nitric oxide
24            measurement  techniques. J. Geophys. Res. [Atmos.] 92: 1995-2008.
25
26     Hofzumahaus,  A.; Dora, H.-P.; Callies, J.; Platt, U.; Ehhalt, D. H. (1991) Tropospheric OH concentration
27            measurements by laser long-path absorption spectroscopy.  Atmos. Environ. Part A 25: 2017-2022.
28
29     Hoke, J.  E,; Anthes,  R. A. (1976) The initialization of numerical models by a dynamic initialization technique.
30            Mon. Weather Rev. 104: 1551-1556.
31
32     Holdren, M. W.; Rasmussen, R. A. (1976) Moisture anomaly in analysis of peroxyacetyl nitrate (PAN).
33            Environ. Sci.  Technol. 10: 185-187.
34
35     Holdren, M. W.; Smith, D. L. (1987) Stability of volatile organic compounds  while stored in SUMMA polished
36            stainless steel canisters [final report]. Columbus, OH: Battelle Columbus Laboratory; EPA contract
37            no. 68-02-4127, WA-13.
38
39     Holdren, M. W.; Spicer, C. W. (1984) Field compatible calibration procedure for peroxyacetyl nitrate.  Environ.
40            Sci. Technol. 18: 113-116.
41
42     Holdren, M.; Spicer,  C.; Sticksel, P.; Nepsund, K.; Ward, G.; Smith, R. (1982) Implementation and analysis of
43            hydrocarbon grab samples from Cleveland and Cincinnati 1981 ozone monitoring study. Chicago,  IL:
44            U.S. Environmental Protection Agency, Region V; EPA report no. EPA-905/4-82-001. Available from:
45            NTIS,  Springfield, VA; PB83-197673.
46
47     Holdren, M. W.; Smith, D. L.; Pollack, A. J.; Pate, A.  D.  (1993) The 1992 field study/demonstration of
48            automated gas chromatographs in Connecticut and other laboratories [final report]. Columbus, OH:
49            Battelle Columbus Laboratory; EPA contract no.  68-DO-0007, WA-36.
50
51     Holland, D. M.; McElroy, F. F. (1986)  Analytical method comparisons by estimates of precision and lower
52            detection limit. Environ. Sci. Technol. 20:  1157-1161.
53
         December 1993                              l_ix«       ni? ABT.no WAT nTTrvrn nra rrrrn

-------
 1     Holzworth, G. C, (1964) Estimates of mean maximum mixing depths in the contiguous United States, Mon,
 2            Weather Rev, 92: 235-242.
 3
 4     HoLzworih, G. C. (1972) Mixing heights, wind speeds, and potential for urban air pollution throughout the
 5            contiguous United States. Research Triangle Park, NC: U.S. Environmental Protection Agency, Office of
 6            Air Programs; publication no. AP-101. Available from: NTIS, Springfield, VA; PB-207103,
 7
 8     Horie, O.; Moortgat, G. K. (1991) Decomposition pathways of the excited Criegee intermediates in the
 9            ozonolysis of simple alkenes. Atmos. Environ. Part A 25: 1881-1896.
10
11     Horowitz, A.; Calvert, J. G. (1982) Wavelength dependence of the primary processes in acetaldehyde photolysis.
12            J. Phys. Chem.  86: 3105-3114.
13
14     Hoshino, H.; Hinze, W. L. (1987) Exploitation of reversed micelles as a medium in analytical
15            chemiluminescence measurements with application to the determination of hydrogen peroxide using
16            Luminol. Anal.  Chem. 59: 496-504.
17
18     Hosier, C. R. (1961) Low-level inversion frequency in the contiguous United States. Mon. Weather Rev.
19            89: 319-339.
20
21     Huebert, B, J.; Robert,  C, H. (1985) The dry deposition of nitric acid to grass. J. Geophys. Res.  [Atmos.]
22            90: 2085-2090.
23
24     Ibusuki, T. (1983) Influence of trace metal ions on the determination of hydrogen peroxide in rainwater by using
25            a chemiluminescent technique. Atmos. Environ. 17: 393-396.
26
27     Isidorov, V. A.; Zenkevich, I. G.; loffe, B. V. (1985) Volatile organic compounds in the atmosphere of forests.
28            Atmos. Environ. 19: 1-8.
29
30     Jacob, D. J.; Gottlieb, E. W.; Prather, M. J. (1989) Chemistry of a polluted cloudy boundary layer.  J.  Geophys.
31            Res. [Atmos.] 94: 12,975-13,002.
32
33     Jacob, D. J.; Logan, J.  A.; Yevich, R, M.; Gardner, G. M.; Spivakowsky, C. M.; Wofsy, S. C.; Monger, W,;
34            Sillman, S.; Prather, M. J. (1993) Climatological simulation of summertime ozone over North America.
35            J. Geophys. Res.: in press.
36
37     Jaffee, R. J.; Smith, F.  C., Jr.; West, K.  W. (1974) Study of factors affecting reactions in environmental
38            chambers: final  report on phase HI. U.S. Environmental  Protection Agency, Office of Research and
39            Development.
40
41     Japar, S. M.; Wallington, T. J.; Richert, J. F. O.; Ball, J. C. (1990) The atmospheric chemistry of oxygenated
42            fuel additives: r-butyl alcohol, dimethyl ether, and methyl /-butyl ether. Int. J. Chem. Kinet.
43            22: 1257-1269.
44
45     Jayanty, R. K. M.; Blackard, A.; McElroy, F. F.; McClenny, W. A. (1982) Laboratory evaluation of non
46            methane organic carbon determination in ambient air by cryogenic preconcentration and flame ionization
47            detection. Research Triangle Park, NC: U.S.  Environmental Protection Agency,  Environmental
48            Monitoring Systems Laboratory; EPA report no. EPA-600/4-82-019. Available from: NTIS, Springfield,
49            VA; PB82-224965.
50
51     Jeffries, H.; Fox, D.; Kamens, R. (1975) Outdoor smog chamber studies: effect of hydrocarbon reduction on
52            nitrogen dioxide. Washington, DC: U.S. Environmental Protection Agency, Office of Research and
53            Development; EPA report no. EPA-650/3-75-011. Available from: NTIS, Springfield, VA; PB-245829.
54


         December 1993                              3-246       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Jeffries, H.; Fox, D.; Kamens, R. (1976) Outdoor smog chamber studies; light effects relative to indoor
 2            chambers. Environ. Sci. Technol, 10:  1006-1011.
 3
 4     Jeffries, H. E,; Sexton, K. G.; Salmi, C, N, (1981) The effects of chemistry and meteorology on ozone control
 5            calculations using simple trajectory models and the EKMA procedure. Research Triangle Park, NC:
 6            U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards; EPA report
 7            no. EPA-450/4-S1-034. Available from: NTIS, Springfield, VA; PB82-234170.
 8
 9     Jeffries, H. E.; Gery, M.; Carter, W. P. L. (1992) Protocols for evaluating oxidant mechanisms for urban and
10            regional modeling. Research Triangle Park, NC: U.S. Environmental Protection Agency; EPA report
11            no. EPA-600/R-92/112. Available from: NTIS, Springfield, VA; PB92-205848.
12
13     Jenkin, M. E.; Cox, R. A,; Williams, D. J. (1988) Laboratory studies of the kinetics of formation of nitrous acid
14            from die thermal reaction of nitrogen dioxide and water vapour. Atmos. Environ. 22: 487-498.
15
16     Johansson, C. (1984) Field measurements of emission of nitric oxide from fertilized and unfertilized forest soils
17            in Sweden. J. Atmos. Chem. 1: 429-442.
18
19     Johansson, C.; Granat, L. (1984) Emission of nitric oxide from arable land. Tellus 36 B: 26-37.
20
21     Johnson, G. M.; Quigley, S. M. (1989)  A universal monitor for photochemical smog. Presented at: 82nd annual
22            meeting and exhibition of the Air and Waste Management Association; June; Anaheim, CA. Pittsburgh,
23            PA: Air and Waste Management Association;  paper no. 89-29.8.
24
25     Johnson, W. B.; Viezee, W. (1981) Stratospheric ozone in the lower troposphere—I. presentation and
26            interpretation of aircraft measurements. Atmos. Environ. IS: 1309-1323.
27
28     Johnson, D. F.; Kok, G. L.; Sonner, R. J. (1981) Improved chromatographic acid technique for the
29            determination of formaldehyde. In: Grosjean, D.; Kok, G. L.. eds. Intel-laboratory comparison study of
30            methods for  measuring formaldehyde and  other aldehydes in ambient air: final report. Atlanta, GA:
31            Coordinating Research Council.
32
33     Johnston, H. (1971) Reduction of stratospheric ozone by nitrogen oxide catalysts from supersonic transport
34            exhaust. Science (Washington, DC) 173: 517-522.
35
36     Tones, K,; Militana, L,; Martini, J. (1989) Ozone trend analysis  for selected urban areas in the continental U.S.
37            Presented at: the 82nd annual meeting and exhibition of the Air and Waste Management Association;
38            June; Anaheim, CA. Pittsburgh, PA: Air  and  Waste Management Association; paper no. 89-3.6.
39
40     Joos, L.  F.; Landolt, W.  P.; Leuenoerger, H. (1986)  Calibration of peroxyacetyl nitrate measurements with an
41            NOX analyzer. Environ. Sci. Technol. 20: 1269-1273.
42
43     Joseph, D. W.; Spicer, C. W. (1978) Chemiluminescence method for atmospheric monitoring of nitric acid and
44            nitrogen oxides. Anal. Chem.  50: 1400-1403.
45
46     Joshi, S. B.; Bufalini, J. J. (1978) Halocarbon interferences in chemiluminescent measurements  of NOX. Environ.
47            Sci. Technol. 12: 597-599.
48
49     Junge, C. E. (1963) Air chemistry and radioactivity. New York, NY: Academic Press. (Van Mieghem, J.;
50            Hales, A. L., eds. International geophysics series: v. 4).
51
52     Kamens, R. M.; Gery, M. W,; Jeffries, H. E.; Jackson, M.; Cole, E. I. (1982) Ozone-isoprene reactions:
53            product formation and aerosol potential. Int. J. Chem. Kinet. 14: 955-975.
54


         December 1993                               3-247      DRAFT-DO NOT QUOTE OR CTTP

-------
 1     Kaplan, W. A.; Wofsy, S, C.; Keller, M.; Da Costa, J. M. (1988) Emission of NO and deposition of O3 in a
 2            tropical forest system, J. Geophys. Res. [Atmos.] 93: 1389-1395.
 3
 4     Karamchandani, P.; Venkatram, A. (1992) The role of non-precipitating clouds in producing ambient sulfete
 5            during summer: results  from simulations with the Acid Deposition and Oxidant Model (ADOM) Atmos.
 6            Environ. Part A 26: 1041-1052.
 7
 8     Katz, M. (1976) Nitrogen compounds and oxidants. In: Stem, A. C., ed. Air pollution: v. ffl, measuring,
 9            monitoring, and surveillance of air pollution. 3rd ed. New York, NY: Academic Press; pp. 259-305.
10
11     Kelly, T. J. (1986) Modifications of commercial oxides of nitrogen detectors for improved response. Upton, NY:
12            U.S. Department of Energy, Brookhaven National Laboratory; report no. BNL-38000. Available from:
13            NTIS, Springfield, VA; DE86010536.
14
15     Kelly, T. J.; Barnes, R. H, (1990) Development of real-time monitors for gaseous formaldehyde [final report].
16            Research Triangle Park, NC: U.S. Environmental Protexction Agency, Atmospheric Research and
17            Exposure Assessment Laboratory; EPA report no. EPA/600/3-90/088. Available from: NTIS,
18            Springfield, VA; PB91-126029.
19
20     Kelly, T. J.; Stedman, D. H.; Ritter, J. A.; Harvey, R. B. (1980) Measurements of oxides of nitrogen and nitric
21            acid in clean air. J. Geophys. Res. 85: 7417-7425.
22
23     Kelly, N. A.; Wolff, G. T.; Fennan, M. A. (1982) Background pollutant measurements in air masses affecting
24            the eastern half of the United States—I. air masses arriving from the northwest. Atmos. Environ.
25            16: 1077-1088.
26
27     Kelly, N. A.; Fennan, M. A.; Wolff, G. T. (1986) The chemical and meteorological conditions  associated with
28            high and low ozone concentrations in southeastern Michigan and nearby areas of Ontario. J. Air Pellut.
29            Control Assoc. 36:  150-158.
30
31     Kelly, T. J.; Spicer, C. W.; Ward, G. F. (1990) An assessment of the luminol chemiluminescence technique; for
32            measurement of NCs in ambient air. Atmos. Environ. Part A 24: 2397-2403.
33
34     Kelly, T. J.; Callahan, P. J.; Pleil, J.; Evans,  G. F. (1993) Method development and field measurements for
35            polar volatile organic compounds in ambient air. Environ. Sci. Techno!. 27: 1146-1153.
36
37     Kenski, D. M.; Wadden, R. A.; Scheff, P. A.; Lonneman, W. A. (1993) A receptor modeling approach to VOC
38            emission inventory validation in five U.S. cities. Presented at: 86th annual meeting of the Air and Waste
39            Management Association; June; Denver, CO. Pittsburgh, PA: Air and Waste Management Association;
40            paper no. 93-WP-100.04.
41
42     Kessler, R. C. (1988) What techniques are available for generating windfields? Presented at: Conference on
43            photochemical modeling as a tool  for decision makers; ???; ???. Pasadena,  CA: California Air Resources
44            Board.
45
46     Kessler, R. C.; Douglas, S. G. (1989) Numerical simulation of mesoscale airflow in the South Central Air Coast
47            Basin. San Rafael, CA: Systems Applications, Inc.; paper no. SYSAPP-89/108.
48
49     Khalil, M. A. K.; Rasmussen, R. A. (1992) Forest hydrocarbon emissions:  relationships between fluxes and
50            ambient concentrations. J. Air Waste Manage, Assoc. 42: 810-813.
51
52
         December 1993                              3-248       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Killus, J. P.; Meyer, J. P.; Durran, D, R.; Anderson, G. E.; Jerskey, T. N.; Reynolds, S. D.; Ames, J. (1980)
 2            Continued research in mesoscale air pollution simulation modeling: volume 5—refinements in numerical
 3            analysis, transport, chemistry, and pollutant removal, San Rafael, CA:  Systems Applications, Inc.; EPA
 4            contract no. 68-02-2216.
 5
 6     Kirollos, K. S,; Attar, A. J. (1991) Direct-read passive dosimetry of nitrogen dioxide and ozone. In: proceedings
 7            of the 1991 EPA/A&WMA international symposium on measurement of toxic and related air pollutants;
 8            May; Durham, NC. Pittsburgh, PA: Air and Waste Management Association; publication no. VIP-25;
 9            EPA report no, EPA-600yR-92/131,
10
11     Klehdienst, T,  E.; Shepson, P. B.; Hodges, D. N,; Nero, C. M.; Dasgupta, P. K.; Huang, H.; Kok, G. L.;
12            Lind, J. A.; Lazrus, A. L.; Mackay, G. I.; Mayne, L. K.; Schiff, H. I. (1988) Comparison of
13            techniques for measurement of ambient levels of hydrogen peroxide. Environ. Sci. Technol. 22:  53-61.
14
15     Kleindienst, T.  E.; Hudgens, E. E.; Smith, D. F.; McElroy, F. F.; Bufalini, J. J. (1993) Comparison of
16            chemiluminescence and ultraviolet ozone monitor responses in the presence of humidity and
17            photochemical pollutants. Air Waste 43: 213-222.
18
19     Kley, D.; McFarland, M, (1980) Chemiluminescence detector for NO and NOj. Atmos. Technol. 12: 63-69.
20
21     Kley, D.; Drummond, J. W.; McFarland, M,; liu, S. C. (1981) Tropospheric profiles of NOr. J. Geophys.
22            Res. 86: 3153-3161.
23
24     Klockow, D.; Jacob, P. (1986) The peroxyoxalate chemiluminescence and its application to die determination of
25            hydrogen peroxide in precipitation. In: Jaeschke, W., ed. Chemistry of multiphase atmospheric systems.
26            Berlin,  Germany: Springer-Verlag; pp. 117-130 (NATO Advanced Science Institutes series, v. G6).
27
28     Klouda, G. A.; Norris, J. E.; Currie, L.  A.; Rhoderick, G. C.; Sams, R. L.; Dorko, W. D.; Lewis, C. W.;
29            Lonneman, W.  A.; Seila, R. L.;  Stevens, R. K. (1993) A method for separating volatile organic carbon
30            from. O.lm of ait to identify sources of ozone precursors via isotope ( C) measurements,
31            In: proceedings of the EPA/A&WMA international symposium on the measurement of air toxic and
32            related air pollutants; May; Durham, NC. Pittsburgh, PA: Air and Waste Management Association.
33
34     Knispel,  R.; Koch, R,; Siese, M.; Zetzsch, C. (1990) Adduct formation of OH radicals with benzene, toluene,
35            and phenol and consecutive reactions of the adducts with NOX and O2. Ber. Bunsen-Ges. Phys. Chem.
36            94: 1375-1379.
37
38     Kok, G.  L.; Daraall, K. R.; Winer, A. M.; Pitts, J. N., Jr.; Gay, B. W. (1978a) Ambient air measurements of
39            hydrogen peroxide in the California south coast air basin. Environ, Sci. Technol. 12: 1077-1080.
40
41     Kok, G.  L.; Holler, T. P.; Lopez, M. B.; Nachtrieb, H. A.; Yuan, M. (1978b) Chemilummescent method for
42            determination of hydrogen peroxide in the ambient atmosphere. Environ. Sci. Technol, 12:  1072-1076.
43
44     Kok, G.  L.; Thompson, K.; Lazrus, A. L.; McLaren, S. E. (1986) Derivatization technique for the
45            determination of peroxides in precipitation. Anal. Chem. 58:  1192-1194.
46
47     Kok, G.  L.; Walega, J. G.; Heikes, B. G.; Lind, J.  A.; Lazrus, A. L. (1990) Measurements of peroxide and
48            formaldehyde in Glendora, California. Aerosol Sci. Technol.  12: 49-55.
49
50     Kondo, Y.; Matthews, W. A.; Iwata, A.; Morita, Y,; Takagi, M. (1987) Aircraft measurements of oxides of
51            nitrogen along the eastern rim of the Asian continent: winter observations,  J. Atmos. Chem. 5: 37-58.
52
         D«rp.mhp,r 1QQ^                               i 1*0       TYDATJT TV"» xirvr rvfrrvra rvn /"ITU

-------
 1     Korshover, J. (1967) Climatology of stagnating anticyclones east of the Rocky Mountains, 1936-1965.
 2            Cincinnati, OH; U.S. Department of Health, Education and Welfare, Public Health Service; FHS
 3            publication no. 999-AP-34. Available from: NT1S, Springfield, VA; PB-174709.
 4
 5     Korshover, J. (1976) Climatology of stagnating anticyclones east of the Rocky Mountains, 1936-1975.
 6            Boulder, CO: National Oceanic and Atmospheric Administration, Environmental Research Laboratories;
 7            NOAA report no. TM ERL ARL-55. Available from; NTIS, Springfield, VA; PB-257368.
 8
 9     Korsog, P. E.; Wolff, G. T. (1991) An examination of urban ozone trends in the northeastern U.S. (1973-1983)
10            using a robust statistical method. Atmos, Environ.  Part B 25; 47-57.
11
12     Kosmus, W. (1985) Summation method for monitoring nitrogen oxides. Int. J. Environ. Anal. Chem.
13            22: 269-279.
14
15     Kotzias, D.;  Hjorth, J. L.; Skov, H. (1989) A chemical mechanism for dry deposition—the role of biogenic
16            hydrocarbon (terpene) emissions in the dry deposition of Oj, SO2 and NOX in forest areas, Toxicol.
17            Environ. Chem. 20-21: 95-99.
18
19     Kumar, S.; Chock, D. P. (1984) An update on oxidant trends in the south coast air basin of California. Atmos.
20            Environ. 18: 2131-2134.
21
22     Kuntasd, G.; Chang, T.  Y. (1987) Trends and relationships of Q$, NOX  and HC in the south coast air basin of
23            California. JAPCA 37: 1158-1163.
24
25     Kuntz, R.; Lonneman, W.; Namie, G.; Hull, L. A. (1980) Rapid determination of aldehydes in air analyses.
26            Anal. Lett. 13: 1409-1415.
27
28     Kuo, Y.-H.; Skumanich, M.; Haagenson, P. L.; Chang, J. S. (1985) The accuracy of trajectory models as
29            revealed by the observing system simulation experiments. Mon. Weather Rev. 113: 1852-1867,
30
31     Lamb, R. G. (1976) Continued research in mesoscale air pollution simulation modeling: volume HI—modeling of
32            microscale phenomena. Research Triangle Park, NC: U.S. Environmental Protection Agency,
33            Environmental Sciences Research Laboratory; EPA report no. EPA-600/4-76-016C. Available from:
34            NTIS, Springfield, VA; PB-257528.
35
36     Lamb, R. G. (1977) A case study of stratospheric ozone affecting ground-level oxidant concentrations. J. Appl.
37            Meteorol.  16: 780-794.
38
39     Lamb, R. G, (1983) Regional scale (1000 km) model of photochemical air pollution. Part 1. Theoretical
40            formulation. Research Triangle Park, NC: U.S. Environmental Protection Agency, Environmental
41            Sciences Research Laboratory; EPA report no. EPA-600/3-83-035. Available from: NTTS,
42            Springfield, VA; PB83-207688.
43
44     Lamb, S, I.; Petrowski, C.; Kaplan, I. R.; Simoneit, B. R. T. (1980) Organic compounds in urban atmospheres:
45            a review of distribution, collection and analysis. J. Air Pollut. Control Assoc. 30: 1098-1115.
46
47     Lamb, B.; Westberg, H.; Allwine, G.; Quarles, T. (1985) Biogenic hydrocarbon emissions from deciduous and
48            coniferous trees in the United States. J. Geophys. Res. 90: 2380-2390.
49
50     Lamb, B.; Guenther, A.; Gay, D.; Westberg, H. (1987) A national inventory of biogenic hydrocarbon emissions.
51             Atmos. Environ. 21:  1695-1705.
52
53     Lamb, B.; Gay, D.; Westberg, H.; Pierce, T. (1993) A biogenic hydrocarbon emission inventory for  the U.S.A.
54            using a. simple forest canopy model. Atmos. Environ. 27A: in press.


         December 1993                              3-250      DRAFT-DO NOT QUOTE OR CITE

-------
 1     Lammel, G.; Perner, D. (1988) The atmospheric aerosol as a source of nitrous acid in the polluted atmosphere.
 2            J. Aerosol Sci. 19; 1199-1202.
 3
 4     Langner, J.; Rodhe, H.; Olofsson, M. (1990) Parameterization of subgrid scale vertical transport in a global
 5            two-dimensional model of the troposphere. J. Geophys. Res. 95;  13691-13706.
 6
 7     Larson, S, M.; Cass, G. R.; Gray, H. A. (1989) Atmospheric carbon particles and the Los Angeles visibility
 8            problem. Aerosol Sci. Technol. 10: 118-130.
 9
10     Lavoie, R. L. (1972) Mesoscale numerical model of lake-effect storms. J. Atmos. Sci. 29: 1025-1049.
11
12     Lawson, D. R.; Groblicki, P. J.; Stedman, D. H.; Bishop, G. A.; Guenther, P. L. (1990) Emissions from in-use
13            motor vehicles in Los Angeles: a pilot study of remote sensing and the inspection and maintainence
14            program. J. Air Waste Manage. Assoc. 40: 1096-1105.
15
16     Lazrus, A. L.; Kok, G. L,; Gitlin, S. N.; Lind, J. A.; McLaren, S. E. (1985) Automated fluorometric method
17            for hydrogen peroxide in atmospheric precipitation. Anal. Chem.  57: 917-922.
18
19     Lazrus, A. L.; Kok, G, L.; Lind, J. A.; Gitlin, S. N.; Heikes, B. G.; Shelter, R. E. (1986) Automated
20            fluorometric method for hydrogen peroxide in air. Anal. Chem. 58:  594-597.
21
22     Lee, J, H.; Chen, Y.; Tang, I. N. (1991) Heterogeneous loss of gaseous H2O2 in an atmospheric air sampling
23            system. Environ. Sci. Technol. 25: 339-342.
24
25     Leighton, P. A. (1961) Photochemistry of air pollution. New York, NY: Academic Press.
26
27     Lelieveld, J.;  Crutzen, P.  J. (1990) Influences of cloud photochemical processes on tropospheric ozone. Nature
28             (London) 343: 227-233.
29
30     Lelieveld, J.;  Crutzen, P.  J. (1991) The role of clouds in tropospheric photochemistry. J. Atmos. Chem.
31             12: 229-267.
32
33     Leston, A.; Ollison, W. (1993) Estimated accuracy of ozone design values: are they compromised by method
34            interferences? In: transactions of the AWMA specialty conference: tropospheric ozone, nonattainment,
35            and design value issues; October, 1992; Boston, MA. Pittsburgh, PA: Air and Waste Management
36            Association.
37
38     Levaggi, D. A.; Oyung, W.; Zerrudo, R. (1992) Noncryogenic concentration of ambient hydrocarbons for
39            subsequent nonmethane and volatile organic  compound analysis. Presented at: the international
40            symposium on measurement of toxic and related air pollutants. Pittsburgh, PA:  Air and Waste
41            Management Association.
42
43     Lewis, C. W.; Conner, T. L. (1991) Source reconciliation of ambient volatile organic compounds measured in
44            the Atlanta 1990 summer study: the mobile source component. Presented at: A&WMA specialty
45             conference on emission inventory issues in the 1990's; September; Durham, NC. Pittsburgh,  PA: Air and
46             Waste Management Association; paper no. VIP-22; pp. 514-523.
47
48     Lewis, C. W.; Baumgardner, R. E.; Stevens, R. K.; Claxton, L. D.; Lewtas, J. (1988) Contribution of
49            woodsmoke and motor vehicle emissions to ambient aerosol mutagenicity. Environ. Sci. Technol.
50             22: 968-971.
51
52
         December 1993                              ijjti       DBAFT.nn isrrvr mm-rc rm

-------
 1     Lewis, C. W.; Stevens, R, K.; Zweidinger, R. B,; Claxton, L. D.; Barraclough, D,; Klouda, G, A. (1991)
 2            Source apportionment of mutagenic activity of fine particle organics in Boise, Idaho, Presented at:
 3            84th annual meeting and exhibition of the Air and Waste  Management Association; June;
 4            Vancouver, BC, Canada, Pittsburgh, PA: Air and Waste  Management; paper no, 91-131,3,
 5
 6     Lewis, C. W.; Conner, T. L.; Stevens, R, K.; Collins, J. P.; Henry, R, C. (1993) Receptor modeling of volatile
 7            hydrocarbons measured in the 1990 Atlanta ozone precursor study. Presented at: 86th annual meeting of
 8            the Air and Waste Management Association; June; Denver, CO. Pittsburgh, PA: Air and Waste
 9            Management Association; paper no. 93-TP-58.04.
10
11     Lindsay, R. W.; Richardson, J. L; Chameides, W. L. (19S9) Ozone trends in Atlanta, Georgia: have emission
12            controls been effective? JAPCA 39: 40-43.
13
14     LJpari, P.; Swarin, S. J. (1982) Determination of formaldehyde and other aldehydes in automobile exhaust with
15            an improved 2,4-dinitrophenylhydrazine method.  J. Chromatogr.  247: 297-306.
16
17     Uttman, F. E.; Benoliel, R. W. (1953) Continuous oxidant recorder.  Anal. Chem.  25: 1480-1483.
18
19     Liu, M.-K.; Seinfeld, J. H. (1975) On the validity of grid and trajectory models of urban air pollution.
20            Atmos. Environ. 9: 555-574.
21
22     Liu, S. C.; Trainer, M. (19S8) Responses of the tropospheric ozone and odd hydrogen radicals to column ozone
23            change. J. Atmos. Chem. 6: 221-233.
24
25     liu, L.-J. S,; Koutrakis, P.; Sun, H. S.; Mulik, J. D.; Burton, R. M. (1992) Use of personal measurements for
26            ozone exposure assessment—a pilot study. In: proceedings of the 1992 EPA/A&WMA international
27            symposium on measurement of toxic and related  air pollutants; May; Durham.  Pittsburgh, PA: Air and
28            Waste  Management Association: publication no.  VIP-25; EPA report no. EPA-600/R-92/131;
29            pp. 962-967.
30
31     Logan, J.  A, (1985) Tropospheric ozone:  seasonal behavior, trends, and anthropogenic influence. J. Geophys.
32            Res. [Atmos.] 90: 10463-10482.
33
34     Logan, J.  A. (1989) Ozone in rural areas  of the United States. J. Geophys. Res. 94: 8511-8532.
35
36     Logan, J,  A.; Prather, M. J.; Wofsy, S, C.; McElroy, M. B. (1981) Tropospheric chemistry: a global
37            perspective. J. Geophys. Res. C: Oceans Atmos. 86: 7210-7254.
38
39     Lonneman, W, A. (1977) PAN measurement in dry and  humid atmospheres. Environ.  Sci. Technol.
40            11: 194-195.
41
42     Lonneman, W. A.; Seila,  R. L. (1993) Hydrocarbon compositions in Los Angeles and New York 20 years later.
43            Presented at: die international symposium on Measurement of Toxic and Related Air Pollutants.
44            Pittsburgh, PA: Air and Waste Management Association.
45
46     Lonneman, W. A.; Kopczynski, S. L.; Dariey, P. E.; Sutterfield, F. D. (1974) Hydrocarbon composition of
47            urban air pollution. Environ. Sci. Technol. 8: 229-236.
48
49     Lonneman, W. A.; Bufalini, J. J.; Kuntz, R. L.; Meeks, S. A. (1981) Contamination from fluorocarbon films.
50            Environ. Sci. Technol. 15: 99-103.
51
52     Lonneman, W. A.; Bufalini, J. J.; Namie, G. R. (1982) Calibration procedure for PAN based on its thermal
53            decomposition in the presence  of nitric oxide. Environ. Sci. Technol, 16: 655-660.
54


         December  1993                              3-252       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Loimeman, W. A.; Seila, R. L.; Meeks, S. A. (1986) Non-methane organic composition in the Lincoln Tunnel.
 2            Environ. Sci. Technol, 20: 790-796.
 3
 4     Ludwig, F. L.; Reiter, E.; Shelar, E.; Johnson, W. B. (1977) The relation of oxidant levels to precursor
 5            emissions and meteorological features; v. I, analysis and findings. Research Triangle Park, NC;
 6            U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards; EPA report no.
 7            EPA-450/3-T7-022a. Available from: NITS, Springfield, VA; PB-275001.
 8.
 9     Lunnantt,  F. W.; Lloyd, A. C.; Atkinson, R. (1986) A chemical mechanism for use in long-range transport/acid
10            deposition computer modeling. J. Geophys. Res. [Atmoa.] 91: 905-910, 936.
11
12     Lynn, D. A.; Steigerwald, B. J.; Ludwig, J. H. (1964) The November-December 1962  air pollution episode in
13            the eastern United States.  Cincinnati, OH: U.S. Department of Health, Education, and Welfare, Public
14            Health Service; PHS publication no. 999-AP-7.  Available from:  NTIS, Springfield, VA; PB-168878.
15
16     Lyons, W. A.; Olsson, L. E.  (1972) Mesoscale air pollution transport in the Chicago lake breeze. J. Air Pollut.
17            Control Assoc. 22: 876-881.
18
19     Lyons, W. A.; Calby, R. H,; Keen, C. S. (1986) The impact of mesoscale convective systems on regional
20            visibility and oxidant distributions during persistent elevated pollution episodes. J. Clim. Appl. Meteorol.
21            25: 1518-1531.
22
23     Lyons, W. A.; Tremback, C. J.; Tesche, T. W. (1991) Lake Michigan  ozone study prognostic modeling: model
24            performance evaluation and sensitivity testing. Crested Butte/ Fort Collins, CO:  Alpine Geophysics,
25            ASTeR, Inc.
26
27     Macdonald, A. M.; Bank, C. M.; Leaitch, W.  R.; Puckett, K. J. (1993) Evaluation of the Eulerian Acid
28            Deposition and Oxidant Model (ADOM) with summer 1988 aircraft data. Atmos. Environ. Part A
29            27: 1019-1034.
30
31     Mackay, D. (1991) Multimedia environmental models:  the fugacity approach. Chelsea, MI: Lewis Publishers.
32
33     Mackay, G. I.; Schiff, H. I. (1987a) Methods comparison measurements during the carbonaceous species
34            methods comparison study, Glendora, California, August 1986:  tunable diode laser absorption
35            spectrometer measurements of HCHO, H2O2 and HNO3. Sacramento, CA: California State Air
36            Resources Board; report no. ARB-R-87/318. Available from; NTIS, Springfield, VA;
37            PB88-133269/XAB.
38
39     Mackay, G. L; Schiff, H. I. (1987b) Reference measurements of HNOj and NOj by tunable diode laser
40            absorption spectroscopy. In: Proceedings of the 1987  EPA/APCA symposium on measurement of toxic
41            and related air pollutants; May; Research Triangle Park, NC. Pittsburgh, PA: Air Pollution Control
42            Association; pp. 367-372; EPA report no. EPA-600/9-87-010. Available from: NTIS, Springfield, VA;
43            PB88-113402. (APCA publication VIP-8).
44
45     Mackay, G. L; Mayne,  L. K.; Schiff, H. I. (1990) Measurements of H2O2 and HCHO by tunable diode laser
46            absorption spectroscopy during the 1986 carbonaceous species methods comparison study in Glendora,
47            California. Aerosol Sci. Technol. 12: 56-63.
48
49     Maeda, Y.; Aoki, K.; Munemori, M. (1980) Chemiluminescence method for the determination of nitrogen
50            dioxide. Anal. Chem. 52: 307-311.
51
52     Manos, D. M.;  Volltrauer, H. N.; Allen, J.; Burch, D. E.; Chudy, L S.; Pembrook, J. D. (1982) Totally
53            optical ambient NMHC monitor. Research Triangle Park,  NC: U.S. Environmental Protection Agency;
54            EPA contract no. 68-02-3292.


         December 1993                              i_/>*i       nuATJT-nn xmr rvrTrvrc  r\t>

-------
 1     Martin, R. S.; Westberg, H.; Allwine, E.; Ashman, L.; Farmer, J. C.; Lamb, B. (1991) Atmos. Chem.
 2            13: 1-32.
 3
 4     Martinez, R. L; Herron, J. T. (1988) Stopped-flow studies of the mechanisms of ozone-alkene reactions in the
 5            gas phase: rrons-2-butene, J. Phys. Chem. 92: 4644-4648.
 6
 7     Mason, J.  P.; Kirk, I.; Windsor, C. G.; Tipler, A.; Spragg, R. A.; Rendle, M.  (1992) A novel algorithm for
 8            chromatogram matching in qualitative analysis, J. High Resolut. Chromatogr. 15: 539-547.
 9
10     Mast, G. M.; Saunders, H. E. (1962) Research and development of the instrumentation of ozone sensing.
11            ISA Trans. 1:325-328.
12
13     Mathur, R.; Schere, K.  L. (1993) A regional modeling analysis of the dependencies of atmospheric oxidants to
14            perturbations in NOX and hydrocarbon emissions. Presented at: AMS special session on atmospheric
15            chemistry; January; Anaheim, CA. Boston, MA: American Meteorological Society.
16
17     Mayrsohn, H.; Crabtree, J. H. (1976) Source reconciliation of atmospheric hydrocarbons. Atmos. Environ.
18            10: 137-143.
19
20     Mayrsohn, H.; Crabtree, J. H.; Kuramoto, M.; Sothern, R. D.; Mano, S. H. (1977) Source reconciliation of
21            atmospheric hydrocarbons 1974. Atmos. Environ. 11: 189-192.
22
23     McClenny, W. A. (1993) Instrumentation to meet requirements for measurement of ozone precursor
24            hydrocarbons in the U.S. A. In: Proceedings of the international conference on volatile organic
25            compounds; October; London, United Kingdom,
26
27     McClenny, W. A.; Pleil, J. D.; Holdren, M. W.; Smith, R. N. (1984) Automated cryogenic preconcentration
28            and gas chromatographic determination of volatile organic compounds in air. Anal. Chem.
29            56: 2947-2951.
30
31     McClenny, W. A.; Pleil, J. D.; Evans, G. F.;  Oliver, K. D.; Holdren, M. W.;  Winberry, W. T. (1991a)
32            Canister-based method for monitoring toxic VOCs in ambient air. J, Air Waste Manage. Assoc.
33            41: 1308-1318.
34
35     McClenny, W. A.; Yarns, J. 1.; Daughtridge, J. V. (1991b) The emergence of automated gas chromatographs as
36            air quality network monitors for volatile organic compounds. Presented at: the 84th annual meeting and
37            exhibition of the Air and Waste Management Association; June; Vancouver, BC, Canada. Pittsburgh,
38            PA: Air and Waste Management Association.
39
40     McElroy, F. F.; Thompson, V. L.  (1975) Hydrocarbon measurement discrepancies among various analyzers
41            using flame-ionization detectors. Research Triangle Park, NC: U.S. Environmental Protection Agency,
42            Environmental Monitoring and Support Laboratory; EPA report no. EPA-600/4-75-010. Available from:
43            NTIS, Springfield, VA; PB-247821.
44
45     McElroy, F. F.; Thompson, V. L,; Holland, D. M.; Lonneman, W. A.;  Seila, R. L, (1986) Cryogenic
46            preconcentration-direct FID method for measurement of ambient MMOC: refinement and comparison
47            with GC speciation. J. Air Pollut. Control Assoc. 36: 710-714.
48
49     Mcllveen, R. (1992) Fundamentals of weather and climate.  London, United Kingdom: Chapman and Hall.
50
51     McNally, D. E. (1990)  Incorporation of four-dimensional data assimilation into the Colorado State University
52            mesoscale model.  Davis, CA: University of California, Department of Land, Air and Water; project  no.
53            UCD201,
54


         December 1993                              3-254       DRAFT-DO NOT QUOTE OR CITE

-------
 1     McRae, G, J.; Russell, A. G. (1984) Dry deposition of nitrogen-containing species. In: Hicks, B. B., ed.
 2            Deposition both wet and dry. Boston, MA: Butterworths. (Teasley, J. I., ed. Acid precipitation; v. 4).
 3
 4     McRae, G. J.; Seinfeld, J. H, (1983) Development of a second-generation mathematical model for urban air
 5            pollution—n. evaluation of model performance, Atmos. Environ, 17: 501-522.
 6
 7     McRae, G. J.; Goodin, W. R.; Seinfeld, J. H. (1982a) Development of a second-generation mathematical model
 8            for urban air pollution—I. model formulation. Atmos. Environ. 16: 679-696.
 9
10     McRae, G. J.; Goodin, W. R.; Seinfeld, J. H. (1982b) Mathematical modeling of photochemical air pollution.
11            Pasadena,  CA: California Institute of Technology; Environmental Quality Laboratory report no. 18.
12
13     Meyer, C. P.; Elsworth, C. M.; Galbally, I. E. (1991a) Water vapor interference in the measurement of ozone
14            in ambient air by ultraviolet absorption. Instrum.  62: 223.
15
16     Meyer, E. L.; Possiel, N. C.; Doll, D. C.; Baugues, K.  A.; Baldridge, K. W. (1991b) A summary of ROMNET
17            results and outputs. In: Proceedings of the seventh joint AMS/A&WMA conference on applications of air
18            pollution meteorology; January; New Orleans, LA. Pittsburgh, PA; Air and Waste Management
19            Association; pp. 246-249.
20
21     Meyrahn, H.; Moortgat, G. K.; Waraecfc, P. (1982) The photolysis of acetaldehyde under atmospheric
22            conditions. In: 15th informal conference on photochemistry; June-July; Stanford, CA.
23
24     Meyrahn, H.; Pauly, J.;  Schneider,  W.; Warneck,  P. (1986) Quantum yields for photodissociation of acetone in
25            air and an estimate for the life time of acetone in the lower troposhere. J. Atmos. Chem. 4: 277-291.
26
27     Meyrahn, H.; Helas, G.; Warneck,  P. (1987) Gas chromatographic determination of peroxyacetyl nitrate: two
28            convenient calibration techniques. J. Atmos. Chem. 5: 405-415.
29
30     Michie, R. M., Jr.;  Sokash, J. A.; Fritschel, B. P.; McElroy, F. F.; Thompson, V, L. (1983) Performance test
31            results and comparative data for designated reference methods for nitrogen dioxide. Research Triangle
32            Park, NC: U.S. Environmental Protection Agency, Environmental Monitoring Systems Laboratory; EPA
33            report no.  EPA-600/4-83-019.  Available from: NTIS, Springfield, VA; PB83-200238.
34
35     Middleton, P.; Chang, J. S. (1990) Analysis of RADM gas concentration predictions using OSCAR and NEROS
36            monitoring data.  Atmos. Environ. Part A 24: 2113-2125.
37
38     Middleton, P.; Chang, J. S.; del Corral, J. C.; Geiss, H.; Rosinski, J,  M.  (1988) Comparison of RADM and
39            OSCAR precipitation chemistry. Atmos. Environ. 12: 1195-1208.
40
41     Middleton, P.; Chang, J. S.; Beauharnois, M.; Hash, L.; Binkowski, F. (1993) The role of nitrogen oxides in
42            oxidant production as predicted by the Regional Acid Deposition Model (RADM) J. Water Air  Soil
43            Pollut. 67: 133-159.
44
45     Miksch, R, R.; Anthon,  D. W. (1982) A recommendation for combining the standard analytical methods for the
46            determinations of formaldehyde and total aldehydes in air. Am. Ind. Hyg. Assoc. J. 43: 362-365.
47
48     Milford, J. B.; Russell, A. G.; McRae, G. J. (1989) A new approach to photochemical pollution control:
49            implications of spatial patterns in pollutant responses to reductions in nitrogen oxides and reactive organic
50            gas emissions. Environ. Sci. Technol.  23: 1290-1301.
51
52
         December 1993                              v>«       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Milford, J. B,; Gao, D.; Odman, M. T.; Russell, A. G.; Possiel, N. C.; Scheffe. R. D.; Pierce, T, E.; Schere,
 2            K. L, (1992) Air quality responses to NO^ reductions: analysis of ROMNET results. Presented at: 85th
 3            annual meeting and exhibition of the Air and Waste Management Association; June; Kansas City, MO.
 4            Pittsburgh, PA: Air and Waste Management Association; paper no. 92-89.2.
 *J
 6     Miller, D. P. (1988) Low-level determination of nitrogen dioxide in ambient air using the Palmes Tube.
 7            Atmos. Environ. 22: 945-947.
 8
 9     Moore, G. E.; Daly, C.; Liu, M. K. (1987) Modeling of mountain-valley wind fields in the Southern San
10            Joaquin Valley, California. J. Clim. Appl. Meteorol. 26: 1230-1242.
11
12     Moore, G. E.; Morris, R.  E.; Douglas, S. G. (1988) Application of a regional oxidant model to central
13            California. San Rafael, CA: Systems Applications, Inc.
14
15     Mottola, H. A.; Simpson,  B. E.; Gorin, G. (1970) Absorptiometric determination of hydrogen peroxide in
16            submicrogram amounts with leuco crystal violet and peroxidase as catalyst. Anal. Chem. 42: 410-411.
17
18     Mount, G. H.; Eisele, F. L. (1992) An intercomparison of tropospheric OH measurements  at Fritz Peak
19            Observatory, Colorado. Science 256: 1187-1190.
20
21     Mueller, P. K.; Hidy, G. M, (1983) Ths sulfate regional experiment (SURE): report of findings. Palo Alto, CA:
22            Electric Power Research Institute; EPRI report no. EA-1901. 3v.
23
24     Mukammal, E. L; Neumann, H. H.; Gillespie, T. J. (1982) Meteorological conditions associated with ozone in
25            southwestern Ontario, Canada.  Atmos. Environ. 16: 2095-2106.
26
27     Mulik, J. D.; Williams, D. (1986) Passive sampling devices for NO2- In: Proceedings of the  1986 EPA/APCA
28            symposium on measurement of toxic air pollutants; April; Raleigh, NC. Pittsburgh, PA: Air Pollution
29            Control Association; pp. 61-70; EPA report no. EPA-600/9-86-013. Available from: NTIS,
30            Springfield, VA; PB87-182713. (APCA publication VIP-7).
31
32     Mulik, J. D.; Williams, D. E. (1987) Passive sampling device measurements of NO2 in ambient air.
33            In: Proceedings of the 1987 EPA/APCA symposium on measurement of toxic and related air pollutants;
34            May; Research Triangle Park,  NC.  Pittsburgh, PA: Air Pollution Control Association; pp. 387-397; EPA
35            report no. EPA-600/9-87-010.  Available from: NTIS, Springfield, VA; PB88-113402. (APCA publication
36            VIP-8).
37
38     Mulik, J. D.; Lewis, R. G.; McClenny, W. A. (1989) Modification of a high-efficiency passive sampler to
39            determine nitrogen dioxide or formaldehyde in air. Anal. Chem. 61: 187-189.
40
41     Mulik, J. D.; Varns, J. L,; Koutrakis, P.; Wolfson, M.; Bunyaviroch, A.; Wiffiams, D. D.;  Kronmiller, K. G.
42            (1991) Using passive sampling devices to measure  selected air volatiles for assessing ecological change.
43            In: Measurement of toxic and related air pollutants: proceedings of the 1991 U.S. EPA/A&WMA
44            international symposium, v. 1. Pittsburgh, PA: Air & Waste Management Association; pp. 285-290.
45            A&WMA no. Vff-21; EPA report no. EPA/600/9-91/018.
46
47     National Acid Precipitation Assessment Program. (1989) Models planned  for use in the NAPAP integrated
48            assessment program. Washington, DC: National Acid Precipitation Assessment Program.
49
50     National Aeronautics and Space Administration. (1983) Assessment of techniques for measuring tropospheric
51            NxOy: proceedings of a workshop; August 1982; Palo Alto, CA. Hampton, VA: Langley Research
52            Center; NASA conference publication NASA-CP-2292, Available from: NTIS,  Springfield, VA;
53            N84-13706.
54


         December 1993                              3-256      DRAFT-DO NOT QUOTE OR CITE

-------
 1     National Research Council. (1976) Vapor-phase organic pollutants: volatile hydrocarbons and oxidation products.
 2            Washington, DC; National Academy of Sciences.
 3
 4     National Research Council. (1991) Rethinking the ozone problem in urban and regional air pollution.
 5            Washington, DC: National Academy Press.
 6
 7     Nederbragt, G. W.; van der Horst, A.; van Duijn, J. (1965) Rapid ozone determination near an accelerator,
 8            Nature (London) 206: 87.
 9
10     Neiburger, M.; Johnson, D. S.; Chien, C.-W. (1961) Studies of the structure of the atmosphere over the eastern
11            Pacific Ocean in summer: I. the inversion over the eastern north Pacific Ocean. Berkeley, CA:
12            University of California Press. (University of California publications in meteorology: v. 1, no. 1).
13
14     Nelson, P. F.; Quigley, S.  M.; Smith, M.  Y. (1983) Sources of atmospheric hydrocarbons in Sydney:
15            a quantitative determination using a source reconciliation technique. Atmos. Environ. 17: 439-449.
16
17     Nicksic, S. W.; Harkins, J.; Mueller, P. K. (1967) Some analyses for PAN and studies of its structure.
18            Atmos. Environ. 1: 11-18.
19
20     Nieboer, H.; Van Ham, J.  (1976) Peroxyacetyl nitrate (PAN) in relation to ozone and some meteorological
21            parameters  at Delft in The Netherlands. Atmos. Environ. 10: 115-120.
22
23     Nielsen, T.; Hansen, A. M.; Thomsen, E.  L. (1982) A convenient method for preparation of pure standards of
24            peroxyacetyl nitrate for atmospheric analyses. Atmos. Environ. 16: 2447-2450.
25
26     Niki, H.; Maker, P. D.; Savage, C. M.; Breitenbach, L. P. (1983) Atmospheric ozone-olefin reactions. Environ.
27            Sci. TechnoL 17: 312A-322A.
28
29     Niki, H.; Maker, P. D.; Savage, C. M.; Breitenbach, L. P. (1985) An FTTR spectroscopic study of the reactions
30            Br +  CH3CHO -* HBr + CH3CO and CH3C(O)OO + NOj *- CH3C(O)OONO2 (PAN). Int. J. Chem.
31            Kinet.  17: 525-534.
32
33     Niki, H.; Maker, P. D.; Savage, C. M.; Breitenbach, L, P.; Hurley, M. D. (1987) FUR spectroscopic study of
34            the mechanism for  the gas-phase reaction between ozone and tetramethylethylene. J. Phys. Chem.
35            91: 941-946.
36
37     Notholt, J.; Hjorth, J.; Raes, F. (1992a) Formation of HNO2 on aerosol surfaces during foggy periods in the
38            presence of NO and NO,. Atmos. Environ. Part A 26: 211-217.
39
40     Notholt, J.; Hjorth, J.; Raes, F.; Schrems, O. (1992b) Simultaneous field measurements of HNO2, CH2O and
41            aerosol. Ber. Bunsen-Ges. Phys. Chem. 96: 290-293.
42
43     Noxon, J. F. (1983) NC>3 and NO2 in the mid-Pacific troposphere. J, Geophys. Res. C: Oceans Atmos.
44            88: 11017-11021.
45
46     O'Shea, W. J.; Scheff, P. A. (1988) A chemical mass balance for volatile organics in Chicago. JAPCA
47            38: 1020-1026.
48
49     Ogle, L. D.; Hall,  R. C.; Crow, W. L.; Jones, A. E.; Gise, J. P. (1982) Development of preconcentration and
50            chromatographic procedures for the continuous and unattended monitoring of hydrocarbons in ambient
51            air. Presented at: 184th national meeting of the  American Chemical Society; September;
52            Kansas City, MO. Austin, TX:  Radian Corporation.
53
         December 1993                              IJJVT       DRAFT-DO NOT OTIOTR OB

-------
 1     Ogle, L. D.; Brymer, D. A,; Jones, C. J.; Nahas, P. A. (1992) Moisture management techniques applicable to
 2            whole air samples analyzed by method TO-14, In: Proceedings of the 1992 U.S. EPA/A&WMA
 3            international symposium on measurement of toxic and related air pollutants; May;
 4            Research Triangle Park, NC. Pittsburgh, PA: Air and Waste Management Association; pp. 25-30.

 6     Oke, T. R. (1978) Boundary layer climates. London, United Kingdom: Methuan.
 7
 8     Olansky, A. S,; Deming, S. N. (1976) Optimization and interpretation of absorbance response in the
 9            determination of formaldehyde with chromotropic acid. Anal. Chim.  Acta 83: 241-249.
10
11     Oliver, K. D.; Pleil, J.  D.; McClenny, W. A. (1986) Sample integrity of trace level volatile organic compounds
12            in ambient air stored hi SUMMA polished canisters. Atmos, Environ. 20: 1403.
13
14     Oltmans, S. J. (1981) Surface ozone measurements in clean air. J. Geophys.  Res. C: Oceans Atmos.
15            86: 1174-1180.
16
17     Palmes, E. D.; Tomczyk, C. (1979) Personal sampler for NOX.  Am. Ind. Hyg. Assoc. J. 40: 588-591,
18
19     Pandis, S. N.; Seinfeld, J. H. (1989) Sensitivity analysis of a chemical mechanism for aqueous-phase atmospheric
20            chemistry, J. Geophys.  Res. [Atmos.] 94: 1105-1126.
21
22     Pandis, S. N.; Paulson, S. E.; Seinfeld, J. H.; Flagan, R. C.  (1991) Aerosol formation in the photooxidation of
23            isoprene and 0-pinene. Atmos. Environ. Part A 25: 997-1008.
24
25     Pandis, S. N.; Harley, R. A.; Cass, G. R.; Seinfeld, J. H. (1992) Secondary organic aerosol formation and
26            transport. Atmos. Environ. Part A 26: 2269-2282.
27
28     Pankow, J. F.; Bidleman, T. F. (1991) Effects of temperature, TSP and per  cent non-exchangeable material in
29            determining the gas-particle partitioning  of organic compounds. Atmos. Environ. Part A 25:  2241-2249.
30
31     Pankow, J. F.; Bidleman, T. F. (1992) Interdependence of the slopes and intercepts from log-log correlations of
32            measured gas-particle partitioning and vapor pressure-I. Theory and analysis of available data. Atmos
33            Environ. Part A 26: 1071-1080.
34
35     Papa, L. J.; Turner, L. P. (1972) ChromatograpMc determination of carbonyl compounds as their
36            2,4-dinitrophenylhydrazones: U. high pressure liquid chromatography. J.  Chromatogr. Sci. 10: 747-750.
37
38     Parrish, D. D.; Hahn, C. J.; Fahey, D. W.; Williams, E. J.; Bellinger, M. J.; Hubler, G.; Buhr, M. P.;
39            Murphy, P. C.; Trainer, M.; Hsie, E. Y.; Liu, S. C.; Fehsenfeld, F. C. (1990) Systematic variations in
40            the concentration of NOK (NO plus NOj) at Niwot Ridge, Colorado. J. Geophys. Res. [Atmos.]
41            95: 1817-1836.
42
43     Parrish, D. D.; Hahn, C. J.; Williams, E. J.; Norton, R. B.; Fehsenfeld, F. C. (1992) Indications of
44            photochemical histories of Pacific air masses from measurements  of atmospheric trace species at
45            Point Arena, California. J. Geophys. Res [Atmos.] 97: 15,883-15,901.
46
47     Pate, B.; Jayanty, R. K. M.; Peterson, M. R.; Evans, G. F. (1992) Temporal stability of polar organic
48            compounds in stainless steel canisters. J. Air Waste Manage. Assoc.  42: 460-462.
49
50     Paulson, S. E.; Seinfeld, J.  H.  (1992a) Development and evaluation of a  photooxidation mechanism  for isoprene.
51             J. Geophys. Res. [Atmos.] 97: 20,703-20,715.
52                                                                                                   *
53     Paulson, S. E.; Seinfeld, J.  H.  (1992b) Atmospheric photochemical oxidation of  1-octene: OH, 03 and OfT)
54             reactions. Environ. Sci. Technol. 26: 1165-1173.


         December  1993                               3-258       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Paulson, S. E,; Flagan, R, C,; Seinfeld, J. H. (1992a) Atmospheric photooxidation of isoprene part I: the
 2            hydroxyl radical and ground state atomic oxygen reactions. Int. J. Chem. Kinet. 24: 79-101.
 3
 4     Paulson, S. E.; Flagan, R. C.; Seinfeld, J, H. (1992b) Atmospheric photooxidation of isoprene part II: the
 5            ozone-isoprene reaction. Int. J. Chem. Kinet. 24: 103-125.
 6
 7     Penkett, S. A.; Blake, N. J.; lightman, P.; Marsh, A. R. W.; Anwyl, P.; Butcher, G.  (1993) The seasonal
 8            variation of nonmethane hydrocarbons in the free troposhere over die north Atlantic Ocean: possible
 9            evidence for extensive reaction of hydrocarbons with the nitrate radical. J. Geophys. Res. 98: 2865-2885.
10
11     Penner, J. E.; Council, P. S.; Wuebbles, D, J.; Covey, C. C. (1988) Climate change and its interactions with air
12            chemistry: perspectives and research needs. Research Triangle Park, NC: U.S. Environmental Protection
13            Agency,  Atmospheric Sciences Research Laboratory; EPA report no. EPA/600/3-88/046. Available from:
14            NTIS, Springfield, VA; PB89-126601/XAB.
15
16     Perschke,  H.; Broda, E.  (1961) Determination of very small amounts of hydrogen peroxide. Nature (London)
17            190: 257-258.
18
19     Peterson, J. T. (1976) Calculated actinic fluxes (290-700 nm) for air pollution photochemistry applications.
20            Research Triangle Park, NC: U.S. Environmental Protection Agency, Environmental Sciences Research
21            Laboratory; EPA report no. EPA-600/4-76-025. Available from: NTIS, Springfield, VA; PB-255819.
22
23     Pickering, K, E.; Thompson, A. M.; Dickerson, R. R.; Luke, W. T.; MacNamara, D. P.; Greenberg, J. P.;
24            Zimmerman,  P. R. (1990) Model calculations of tropospheric ozone production potential following
25            observed convective events. J. Geophys. Res. [Atrnos.] 95: 14,049-14,892.
26
27     Pielke, R. A. (1974)  A three-dimensional numerical model of the sea breeze over South Florida. Mon. Weather
28            Rev, 102: 115-139.
29
30     Pielke, R. A. (1984)  Mesoscale meteorological modeling. Orlando, FL: Academic Press.
31
32     Pielke, R. A. (1989)  Status of subregional and mesoscale models, v. 2: mesoscale meteorological models in the
33            United States. Fort Collins,  CO: Electric Power Research Institute; report no. EN-6649, v. 2.
34
35     Pierce, T. E.; Schere, K. L.; Doll, D. C; Heilman, W. E. (1990) Evaluation of the regional oxidant model
36            (version 2.1)  using ambient and diagnostic simulations. Research Triangle Park, NC: U.S. Environmental
37            Protection Agency, Atmospheric Research and Exposure Assessment Laboratory; EPA report no.
38            EPA-600/3-90/046. Available from: NTIS, Springfield, VA; PB90-225293/HSU.
39
40     Pierotti, D. J. (1990) Analysis of trace oxygenated hydrocarbons in the environment. J. Atmos. Chem,
41            10:373-382.
42
43     Pierson, W. R.; Gertler, A.  W.; Bradow, R. L.  (1990) Comparison of the SCAQS tunnel study with other
44            on-road vehicle emission data. J. Air Waste Manage. Assoc. 40: 1495-1504.
45
46     Pitts, J. N., Jr.;  Biermann, H. W.; Atkinson, R.; Winer, A. M. (1984a) Atmospheric implications of
47            simultaneous nighttime measurements of NO-, radicals and HONO. Geophys. Res. Lett. 11: 557-560.
48
49     Pitts, J. N., Jr.;  Sanhueza, E.; Atkinson,  R.; Carter, W. P. L.; Winer, A. M.; Harris,  G, W.; Plum, C. N.
50            (1984b) An investigation of the dark formation of nitrous acid in environmental chambers. Int. J. Chem.
51            Kinet. 16: 919-939.
52
53
         December 1993                              i.?so       DRAFT-DO NOT OTIOTR nrc OTP.

-------
 1     Placet, M.; Battye, R. E.; Fehsenfeld, F. C.; Bassett, G, W. (1991) Emissions involved in acidic deposition
 2            processes. In; Irving, P. M., ed. Acidic depostion; state of science and technology, volume I, emissions,
 3            atmospheric processes, and deposition. Washington, DC: The U.S. National Acid Precipitation
 4            Assessment Program. (State of science and technology report no. 1),
 *?
 6     Platt, U.; Pemer, D.  (1980) Direct measurement of atmospheric CH2O, HNO2, O3, and SC»2 by differential
 7            optical absorption in the near UV. J. Geophys. Res. 85: 7453-7458.
 8
 9     Pleil, J. D.; Oliver, K. D.; McClenny, W. A. (1987) Enhanced performance of Nafion dryers in removing water
10            from air samples prior to gas chromatographic analysis. JAPCA 37; 244-248,
11
12     Plum, C. N.; Sanhueza, E.; Atkinson, R.; Carter, W, P. L.; Pitts, J. N., Jr. (1983) OH radical rate constants
13            and photolysis rates of a-dicarbonyls. Environ, Sci, Technol, 17: 479-483.
14
15     Possiel, N. C.;  Cox, W. M. (1993) The relative effectiveness of NO, and VOC strategies in reducing northeast
16            U.S. ozone concentrations. J. Water Air Soil Pollut. 67: 161-179.
17
18     Possiel, N. C.;  Doll,  D. C.; Baugues, K. A.; Baldridge, E, W.; Wayland, R. A. (1990) Impacts of regional
19            control strategies on ozone in the northeastern United States. Presented at: 83rd annual meeting and
20            exhibition of the Air and Waste Management Association; June; Pittsburgh, PA. Pittsburgh, PA: Air and
21            Waste Management Association; report no 90-93.3.
22
23     Possiel, N. C.;  Wayland, R. A.; Wilson, J. H., Jr.; Laich, E. J.; Mullen, M. A. (1993) Predicted impacts  of
24            1990 CAAA controls on northeast U.S. ozone levels. Washington, DC: U.S. Environmental Protection
25            Agency, Office of Air Quality Planning and Standards.
26
27     Price, J.  H. (1976) A study of factors associated with high urban ozone concentrations in Texas. In:  Specialty
28            conference on ozone/oxidants—interactions with the total environment. Pittsburgh, PA: Air Pollution
29            Control Association; pp. 282-292.
30
31     Prinn, R,; Cunnold, D.; Rasmussen, R.; Simmonds, P.; Alyea, F.; Crawford, A.; Fraser, P.; Rosen, R. (1990)
32            Atmospheric emissions and trends of nitrous oxide deduced from 10 years of ALE-GAGE data.
33            J. Geophys. Res. 95: 18369-18385.
34
35     Priori, R.; Cunnold, D.; Simmonds, P.;  Alyea, F.; Boldi, R.; Crawford, A.; Fraser, P.; Gutzler, D.;
36            Hartley, D.; Rosen, R.; Rasmussen, R. (1992) Global average concentration and trend for hydroxyl
37            radicals deduced from ALE/GAGE trichloroethane (methyl chloroform) data for 1978-1990. J. Geophys.
38            Res. [Atmos.] 97: 2445-2461.
39
40     Purdue, L. J. (1993) Continuous monitoring of VOC precursors. Research Triangle Park, NC: U.S.
41            Environmental Protection Agency, Atmospheric Research  and Exposure Assessment Laboratory; EPA
42            report no. EPA/600/A-93/045. Available from: NTIS, Springfield, VA; PB93-167211.
43
44     Purdue, L. J.; Hauser, T. R. (1980) Review of U.S. Environmental Protection Agency NO^ monitoring
45            methodology requirements. In: Lee, S. D., ed. Nitrogen oxides and their effects on health. Ann Arbor,
46            MI: Ann Arbor Science Publishers, Inc.; pp. 51-76,
47
48     Purdue, L. J.; Dayton, D. P.; Rice, J.; Bursey, J.  (1991) Technical assistance document for sampling and
49            analysis of ozone precursors. Research Triangle Park, NC: U.S. Environmental Protection Agency; EPA
50            report no. EPA/600-8-91-215. Available from: NTIS, Springfield, VA; PB92-122795.
51
52
         December 1993                               3-260       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Purdue, L. J.; Reagan, 3. A.; Lonneman, W. A.; Lawlass, T. C.; Drago, R. J.; Zalaquet. G, M.;
 2            Holdren, M. W.; Smith, D. L.; Pate, A. D.; Buxton, B.  E.; Spicer, C. W. (1992) Atlanta ozone
 3            precursor monitoring study data report. Research Triangle Park, NC: U.S. Environmental Protection
 4            Agency, Atmospheric Research  and Exposure Assessment Laboratory; EPA report no.
 5            EPA-600/R-92-157. Available from: NTIS, Springfield, VA; PB92-2206S6/REB.
 6
 7     Rao, S. T. (1987) Application of the urban airshed model to the New York metropolitan area. Research Triangle
 8            Park, NC: U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards; EPA
 9            report no.  EPA-450/4-87-011. Available from: NTIS, Springfield, VA; PB87-201422/HSU.
10
11     Rao, S. T.; Sistla, G. (1993) Efficacy of nitrogen oxides and hydrocarbons  emissions controls in ozone
12            attainment strategies as predicted by the urban airshed model. Int. J. Water Air Soil Pollut. 67: 95-116.
13
14     Rao, S. T.; Sistla, G.; Twaddell, R. (1989) Photochemical modeling analysis of emission control strategies in the
15            New York metropolitan area. Washington, DC: U.S. Environmental Protection Agency; report no.
16            EPA-230/2-89/026.
17
18     Rauhut, M. M.; Bollyky, L. J.; Roberts, B. G.; Loy, M.; Whitman, R. H.; lannotta, A. V.; Semsel, A. M.;
19            Clarke, R. A. (1967)  Chenriluminescence from reactions  of electronegatively substituted aryl oxalates
20            with hydrogen peroxide and fluorescent compounds. J. Am. Chem.  Soc. 89: 6515-6522.
21
22     Reckner, L. R. (1974) Survey of users of the EPA-reference method for measurement of non-methane
23            hydrocarbons in ambient air. Washington, DC: U.S. Environmental Protection Agency, Office of
24            Research and Development; EPA report no. EPA-650/4-75-008. Available from NTIS, Springfield, VA;
25            PB-247515.
26
27     Regener, V. H. (1960) On a sensitive method for the recording of atmospheric ozone. J. Geophys. Res.
28            65: 3975-3977.
29
30     Regener, V. H. (1964) Measurement of atmospheric ozone with the chemiluminescent method. J. Geophys. Res.
31            69: 3795-3800.
32
33     Rehme, K.  A.; Puzak, J. C.;  Blftrtt, M. E.; Smith, C. F.; Paur,  R. J.  (1981) Evaluation of ozone calibration
34            procedures [project summary]. Research Triangle Park, NC: U.S. Environmental Protection Agency,
35            Environmental Monitoring Systems Laboratory; EPA report no. EPA-600/S4-80-050. Available from:
36            NTIS, Springfield, VA; PB81-11891L
37
38     Reiter, E. R. (1963) A case study of radioactive fallout. J. Appl. Meteorol. 2: 691-705.
39
40     Reiter, E. R. (1975) Stratospheric-tropospheric exchange processes. Rev. Geophys. Space Phys. 13: 459-474.
41
42     Reiter, E. R.; Mahlman, J, D. (1965) Heavy radioactive fallout over the southern United States, November 1962.
43            J. Geophys. Res. 70:  4501-4520.
44
45     Reynolds, S. D.; Roth, P. M.; Seinfeld, J.  H. (1973) Mathematical modeling of photochemical air pollution—L
46            formulation of the model. Atmos. Environ. 7:  1033-1061.
47
48     Reynolds, S. D.; Liu, M-K.; Hecht, T.  A.;  Roth, P. M.; Seinfeld, J. H. (1974) Mathematical modeling of
49            photochemical air pollution—HI. evaluation of the model. Atmos. Environ. 8: 563-596.
50
51     Reynolds, S. D.; Tesche, T. W.; Reid,  L. E. (1979) An introduction to the SAI airshed model and its usage.
52            San Rafael, CA: Systems Applications, Inc.; report no. SAI-EF79-31.
53
        December 1993                              3-?fi1       DRAFT-DO NOT OUOTH OP fTTR

-------
 1     Rickman, E. E., Jr.; Green, A. H.; Wright, R. S.; Sickles, J. E., n. (1989) Laboratory and field evaluations of
 2            extrasensitive sulfur dioxide and nitrogen dioxide analyzers for acid deposition monitoring.
 3            Research Triangle Park, NC:  Research Triangle Institute; RTT report no. RTI/3999/18-04F.
 4
 5     Ridley, B. A.; Hewlett, L. C. (1974) An instrument for nitric oxide measurements in the stratosphere. Rev. Sci.
 6            Instrum. 45: 742-746.
 7
 8     Ridley, B. A.; Carroll, M. A.; Torres, A. L.; Condon, E. P.; Sachse, G. W,; Hill, G.  F.; Gregory, G. L.
 9            (1988a) An intercomparison of results from ferrous sulfate and photolytic converter techniques for
10            measurements of NOX made during the NASA GTE/CITE 1  aircraft program. J. Geophys. Res. [Atmos.]
11            93: 15,803-15,811.
12
13     Ridley, B. A.; Carroll, M. A.; Gregory, G. L,; Sachse, G. W. (1988b) NO and NC^ in the troposphere:
14            technique and measurements in regions of a folded tropopause. J. Geophys. Res. [Atmos.] 93:
15            15813-15830.
16
17     Ridley, B. A.; Carroll, M. A.; Dunlap, D. D.; Trainer, M.;  Sachse, G, W,; Gregory, G. L.; Condon, E. P.
18            (1989) Measurements of NOX over the eastern Pacific ocean and southwestern United States during the
19            spring 1984 NASA GTE aircraft program. J. Geophys. Res. [Atmos.] 94: 5043-5067.
20
21     Riggan, R. M. (1983) Technical assistance document for sampling and analysis of toxic organic compounds  in
22            ambient air. Research Triangle Park, NC: U.S. Environmental Protection Agency, Environmental
23            Monitoring Systems Laboratory; EPA report no. EPA-600/4-83-027. Available from: NITS,
24            Springfield, VA; PB83-239020,
25
26     Ripperton, L. A.; Worth, J. J. B.; Vukovich, F, M.; Decker, C. E. (1977) Research Triangle Institute studies of
27            high ozone concentrations in nonurban areas. In: Dimitriades, B.,  ed. International conference on
28            photochemical oxidant pollution and its control—proceedings: volume I; September 1976; Raleigh, NC.
29            Research Triangle Park,  NC:  U.S. Environmental Protection Agency, Environmental Sciences Research
30            Laboratory; pp. 413-424; EPA report no. EPA-600/3-77-001a. Available from:  NTIS, Springfield, VA;
31            PB-264232.
32
33     Roberts, J. M. (1990) The atmospheric chemistry of organic nitrates. Atmos. Environ. Part A 24: 243-287.
34
35     Roberts, J. M.; Fajer, R, W.; Springston, S. R. (1989) Capillary gas chromatographic separation of alkyl nitrates
36            and peroxycarboxylie nitric anhydrides. Anal. Chem.  61: 771-772.
37
38     Robinson, E. (1952) Some air pollution aspects of the Los Angeles temperature inversion. Bull. Am. Meteoroi,
39            Soc. 33: 247-250.
40
41     Rodgers, M. O.; Davis, D. D. (1989) A UV-photofragmentation/laser-induced fluorescence sensor for the
42            atmospheric detection of HONO. Environ. Sci. Technol. 23: 1106-1112.
43
44     Rogers, J. D. (1990) Ultraviolet absorption cross sections and atmospheric photodissociation rate constants of
45            formaldehyde. J. Phys. Chem. 94: 4011-4015.
46
47     Rogge, W. F.; Hildemann, L. M.; Mazurek, M. A.; Cass, G. R.; Simoneit, B. R. T. (1991) Sources of fine
48            organic aerosol. 1. Charbroilers and meat cooking operations. Environ, Sci. Technol. 25: 1112-1125.
49
50     Rogge, W. F.; Hildemann, L. M.; Mazurek, M. A.; Cass, G. R.; Simoneit, B. R. T. (1993) Sources of fine
51            organic aerosol. 2. Noncaudyst and catalyst-equipped automobiles and heavy-duty diesel trucks. Environ.
52            Sci. Technol. 27: 636-651.
53
         December 1993                              3-262       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Roselle, S, J.; Schere, K. L. (1990) Sensitivity of EPA regional oxidant model to biogenic hydrocarbon
 2            emissions. Presented at: the 83rd annual meeting and exhibition of the Air and Waste Management
 3            Association; June; Pittsburgh, PA, Pittsburgh, PA: Air and Waste Management Association; paper no.
 4            90-94.4.
 5
 6     Roselle, S. J.; Pierce, T. E.; Schere, K. L. (1991) The sensitivity of regional ozone modeling to biogenic
 7            hydrocarbons. J. Geophys. Res. [Atmos.] 96: 7371-7394.
 8
 9     RoseUe, S, J.; Schere, K. L.; Chu, S. H. (1992) Estimates of ozone response to various combinations of NOX
10            and VOC reductions in the eastern United States. Presented at: 1992 quadrennial ozone symposium; June;
11            Charlottesville, VA,
12
13     Roth, P.  (1992) Using photochemical models in developing attainment strategies: perspectives and problems.
14            In: Proceedings of the Electric Power Research Institute photochemical modeling workshop; August;
IS            Cambridge, MA, Palo Alto, CA: Electric Power Research Institute.
16
17     Roth, P.  M,; Blanchard, C, L.; Reynolds, S. D. (1989) The role of grid-based, reactive air quality modeling in
18            policy analysis: perspectives and implications, as drawn from a case study. Research Triangle Park, NC:
19            U.S. Environmental protection Agency, Atmospheric Sciences Division; contract no. 68-01-6849.
20
21     Rom, P.  M.; Blanchard, C. E.; Reynolds, S, D, (1990) The role of grid-based reactive air quality modeling in
22            policy analysis: perspectives and implications, as drawn from a case study. Research Triangle Park, NC:
23            U.S. Environmental Protection Agency, Atmospheric Research and Exposure Assessment Laboratory;
24            EPA report no. EPA-600/3-89-082. Available from: NTTS, Springfield, VA; PB90-187204/HSU.
25
26     Rowland, F. S. (1990) Stratospheric  ozone depletion by chlorofluorocarbons. Ambio 19: 281-292.
27
28     Rowland, F. S. (1991) Stratospheric  ozone depletion. Annu. Rev.  Phys. Chem. 42: 731-768.
29
30     Rubino, R. A.; Bruckman, L,; Magyar, J. (1976) Ozone transport. J. Air Pollut. Control Assoc. 26: 972-975.
31
32     Russell, A. G.; McCue, K.  F.; Cass, G. R. (1988a) Mathematical modeling of the  formation of
33            nitrogen-containing air pollutants. 1. Evaluation of an Eulerian photochemical model. Environ, Sci.
34            Technol. 22: 263-271.
35
36     Russell, A. G,; McCue, K.  F.; Cass, G, R. (1988b) Mathematical modeling of the  formation of
37            nitrogen-containing pollutants. 2. Evaluation of the effect of emission controls. Environ. Sci. Technol.
38            22: 1336-1347.
39
40     Sakamaki, F.; Hatakeyama, S.; Akimoto, H. (1983) Formation of nitrous acid and nitric oxide in the
41            heterogeneous dark reaction of nitrogen dioxide and water vapor in a smog  chamber. Int. J. Chem.
42            Kinet. 15: 1013-1029.
43
44     Sakugawa, H.; Kaplan, I. R. (1990)  Observation of the diurnal variation of gaseous I^O2 in Los Angeles air
45            using a cryogenic collection method. Aerosol Sci. Technol. 12: 77-85.
46
47     Sakugawa, H.; Kaplan, I. R.; Tsai, W.; Cohen, Y. (1990) Atmospheric hydrogen peroxide: does it share a role
48            with ozone in degrading air quality? Environ. Sci. Technol. 24:  1452-1462.
49
50     Salo, A.  E.; Witz, S.; MacPhee, R.  D. (1975) Determination of solvent vapor concentrations by total combustion
51            analysis: a comparison of infrared with flame ionization detectors. Presented at: 68th annual meeting of
52            the Air Pollution Control Association; June; Boston,  MA. Pittsburgh,  PA: Air Pollution Control
53            Association; paper no. 75-33.2.
54


         December  1993                               3,210      DRAFT-DO NOT OTTOTR OP

-------
 1     Samson, P. J.; Ragland, K. W. (1977) Ozone and visibility reduction in the Midwest: evidence for large-scale
 2            transport. J. Appl. Meteorol.  16: 1101-1106.
 3
 4     Samson, P. J.; Shi, B.; Milford, J. (1988) A meteorological investigation of high ozone values in American
 5            cities. Office of Technology Assessment, U.S. Congress,
 6
 7     Sawicki, E.; Mauser, T. R.; Stanley, T. W.; Elbert, W, (1961) The 3-methyl-2-benzothiazolonehydrazone test:
 8            sensitive new methods for the detection, rapid estimation, and determination of aliphatic aldehydes. Anal.
 9            Chem. 33: 93-%.
10
11     Saylor, R. D.; Peters,  L. K.; Mathur, R. (1991) The STEM-n regional-scale acid deposition and photochemical
12            oxidant model—HI. a study of mesoscale acid deposition in the lower Ohio River Valley. Atmos,
13            Environ. Part A 25: 2873-2894.
14
15     Scheff, P. A.; Wadden, R. A (1993) Receptor modeling of volatile organic compounds. I. Emission inventory
16            and validation. Environ, Sci. Technol. 27: 617-625.
17
18     Scheffe, R. D.; Morris, R. E. (1990a) Assessment of ozone precursor control measurements using the urban
19            airshed model in EPA's 5-city UAM study. Presented at: 83rd annual meeting and exhibition of the Air
20            and Waste Management Association; June; Pittsburgh, PA. Pittsburgh, PA: Air and Waste Management
21            Association; paper no 90-93.4.
22
23     Scheffe, R. D.; Morris, R. E. (1990b) Overview of EPA's 5-city UAM study. In: Berglund, R. L.; Lawson,
24            D. R.; McKee, D. J., eds. Transactions: tropospheric ozone and the environment, papers from an
25            international conference. Pittsburgh, PA: Air and Waste Management Association; pp. 611-621.
26
27     Scheffe, R. D.; Morris, R. E. (1993) A review of the development and application of the Urban Airshed Model.
28            Atmos. Environ.  Part A 27: 23-39.
29
30     Schere, K. L.; Wayland, R. A. (1989a) Development and evaluation of the regional oxidant model for the
31            northeastern United States. In: Schneider, T.; Lee, S. D.; Welters, G. J. R.;  Grant, L, D., eds.
32            Atmospheric ozone research and its policy implications: proceedings of the 3rd US-Dutch international
33            symposium; May 1988; Nijmegen, The Netherlands. Amsterdam, The Netherlands: Elsevier Science
34            Publishers; pp. 613-622. (Studies in environmental science 35).
35
36     Schere, K. L.; Wayland, R. A. (1989b) EPA regional oxidant model (ROM2.0): evaluation on 1980 NEROS
37            data bases.  Research Triangle Park, NC: U.S. Environmental Protection Agency, Atmospheric Research
38            and Exposure Assessment  Laboratory; EPA report no. EPA/600/3-89/057. Available from: NTIS,
39            Springfield, VA;  PB89-200828/HSU.
40
41     Schiff, H. L; Hastie, D. R.; Mackay, G. I.; Iguchi, T.; Ridley, B. A. (1983) Tunable diode laser systems for
42            measuring trace gases in tropospheric air: a discussion of their use and the sampling and calibration
43            procedures for NO, NO2,  and HNO-j. Environ. Sci. Technol. 17: 352A-364A.
44
45     Schiff, H. I.; Mackay, G. I.; Castledme, C.; Harris, G. W.; Tran, Q. (1986) A sensitive direct measurement
46            NO2 instrument. In: Proceedings of the 1986 EPA/APCA symposium on measurement of toxic air
47            pollutants; April; Raleigh, NC. Pittsburgh, PA: Air Pollution Control Association; pp. 834-844; EPA
48            report no. EPA-600/9-86-013. Available from: NTIS, Springfield, VA; PB87-182713. (APCA publication
49            VIP-7).
50
51     Schiff, H. L; Harris, G.  W.; Mackay, G. I. (1987) Measurement of atmospheric gases by laser absorption
52            spectrometry. Am. Chem. Soc.  Symp. Ser. 349: 274-288.
53
         December 1993                              3-264       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Schrenk, H. H.; Heimann, H.; Clayton, G. D.; Gafafer, W. M.; Wexler, H. (1949) Air pollution in Donora,
 2            PA. Epidemiology of the unusual smog episode of October 1948: preliminary report. Washington, DC:
 3            Public Health Service; Public Health Service bulletin no. 306.
 4
 5     Schwartz, S. E. (1989) Acid deposition: unraveling a regional phenomenon. Science (Washington, DC)
 6            243: 753-763.
 7
 8     Scott, W. E.; Stephens, E. R.; Hanst, P. L.; Doerr, R. C. (1957) Further developments in the chemistry of the
 9            atmosphere. Proc. Am. Pet. Inst. Sect, 3; 37: 171-183.
10
11     Scott, G.; Seitz, W. R.; Ambrose, J. (1980) Improved determination of hydrogen peroxide by measurement of
12            peroxyoxalate. Anal. Chem. Acts 115: 221-228.
13
14     Seaman, N. L. (1990) Meteorological modeling applied to regional air-quality studies using four-dimensional data
15            assimilation. In; Proceedings of the IBM summer institute on environmental modeling;  July; Oberlech,
16            Austria.
17
18     Seaman, N. L. (1992) SARMAP meteorological model development and testing: annual report. California Air
19            Resources Board.
20
21     Sehmel, G, A. (1980) Particle and gas dry deposition: a review. Atmos. Environ. 14: 983-1011.
22
23     Seigneur, C.; Tesche, T. W.; Roth, P. M.; Reid, L. E. (1981) Sensitivity of a complex urban  air quality model
24            to input data. J. Appl, Meteorol.  20: 1020-1040.
25
26     Seila, R. L.; Lonneman, W. A.; Meeks,  S. A. (1976) Evaluation of polyvinyl fluoride as a container material for
27            air  pollution samples. J. Environ. Sci. Health Part A 11: 121-130.
28
29     Seila, R. L.; Lonneman, W. A.; Meeks,  S. A. (1989) Determination of Cj to Cj^ ambient air hydrocarbons in
30            39 U.S. cities from 1984 through 1986. Research Triangle Park,  NC: U.S. Environmental Protection
31            Agency, Atmospheric Research and Exposure Assessment  Laboratory; EPA report no.
32            EPA/600/3-89/058. Available from: NTIS,  Springfield, VA; PB89-214142/HSU.
33
34     Seinfeld, J. H. (1986) Atmospheric chemistry and physics of air pollution. New York,  NY: John Wiley & Sons.
35
36     Seinfeld, J. H. (1988) Ozone air quality models: a critical review. JAPCA 38: 616-645.
37
38     Sevcik, J. (1975) Detectors in gas chromatography. New York, NY: American Elsevier Publishing
39            Company, Inc.
40
41     Sexton, K.  (1982) Evidence of an additive effect for small city plumes. Presented at: 75th annual meeting of the
42            Air Pollution Control Association; June; New Orleans, LA. Pittsburgh, PA: Air Pollution Control
43            Association; paper no.  82-31.4.
44
45     Sexton, K.; Westberg, H. (1980) Elevated ozone concentrations measured downwind of the Chicago-Gary urban
46            complex. J. Air Pollut. Control Assoc. 30:  911-914.
47
48     Sexton, F. W.; Micble, R. M., Jr.; McElroy, F. F.; Thompson, V. L. (1982) A comparative evaluation of seven
49            automated ambient nonmethane organic compound analyzers. Research Triangle Park, NC:
50            U.S. Environmental Protection Agency, Environmental Monitoring Systems Laboratory; EPA report
51            no. EPA-600/4-82-046. Available from: NTIS, Springfield, VA; PB82-230798.
52
53
        December 1993                              3-2fi5       DRAFT-DO NOT QUOTE OR CITE

-------
 1     SheLh, C, M.; Wesely, M. L.; Walcek, C. J. (1986) A dry deposition module for regional acid deposition.
 2            Research Triangle Park, NC: U.S. Environmental Protection Agency, Atmospheric Sciences Research
 3            Laboratory; EPA report no. EPA/600/3-86/037, Available from: NTIS, Springfield, VA;
 4            PBS6-218104/HSU.
 5
 6     Shen, J.; Tanner, R. L.; Kelly, T.  J. (1988) Development of techniques for measurement of gas phase hydrogen
 7            peroxide. New York, NY:  Brookhaven National Laboratory, report no. BNL-52138.
 8
 9     Shepson, P. B.; Bottenheim, J, W.; Hastie, D. R.; Venkatram, A,  (1992) Determination of the relative ozone
10            and PAN deposition velocities at night. Geophys. Res.  Lett. 19: 1121-1124.
11
12     Sherman, C. A. (1978) A mass-consistent model for wind fields over complex terrain. J, Appl. Meteorol.
13            17:312-319.
14
IS     Shreffler, J, H. (1992) A survey of data from the continuous sites of the 1990 Atlanta ozone precursor study.
16            Research Triangle Park, NC: U.S. Environmental Protection Agency, Atmospheric Research and
17            Assessment Laboratory; EPA report no. EPA-600/R-92/172.
18
19     Shreffler, J. H.; Evans, R. B. (1982) The surface ozone record from the regional air pollution study, 1975-1976.
20            Atmos.  Environ. 16:  1311-1321.
21
22     Sickles, J. E., II; Michie, R.  M. (1987) Evaluation of the performance  of sulfation and nitration plates.
23            Atmos.  Environ. 21:  1385-1391.
24
25     Sickles, J. E., II; Wright, R. S. (1979) Atmospheric chemistry of selected sulfur-containing compounds: outdoor
26            smog chamber study—phase 1. Research Triangle Park, NC: U.S. Environmental Protection Agency,
27            Environmental Sciences Research Laboratory; pp. 45-49; EPA report no. EPA-600/7-79-227. Available
28            from: NTIS, Springfield, VA; PB81-141525.
29
30     Sickles, J. E., H; Grohse, P.  M.; Hodson, L. L.; Salmons, C. A.; Cox, K. W.; Turner,  A. R.; Estes, E. D.
31            (1990) Development of a method for the sampling and analysis of sulfur dioxide and nitrogen dioxide
32            from  ambient air. Anal. Chem. 62: 338-346,
33
34     Sigsby, J. E., Jr.; Tejada, S.; Ray, W.; Lang, J. M.; Duncan, J. W. (1987) Volatile organic compound
35            emissions from 46 in-use passenger cars. Environ.  Sci. Technol. 21: 466-475.
36
37     Sillman, S.; Samson, P. J. (1993) The impact of temperature on oxidant photochemistry in urban, polluted rural
38            and remote environments. J. Geophys. Res.: submitted.
39
40     Sillman, S.; Samson, P. J.; Masters, J. M. (1993)  Ozone formation in urban plumes transported over water:
41            photochemical model  and case studies in the northeastern and midwestern U.S. J. Geophys. Res.
42            98: 12,687-12,699.
43
44     Simonaitis, R.;  Olszyna, K. J.; Meagher, J. F. (1991) Production of hydrogen peroxide and organic peroxides in
45            the gas phase reactions of ozone with natural alkenes. Geophys. Res. Lett. 18: 9-12.
46
47     Singh, H. B.  (1980) Guidance for the collection and use of ambient hydrocarbon species data in development of
48            ozone control strategies. Research Triangle Park, NC:  U.S. Environmental Protection Agency, Office of
49            Air Quality Planning  and Standards; EPA report no. EPA-450/4-80-008. Available from: NTIS,
50            Springfield, VA; PB80-202120.
51
52     Singh, H. B.; Kanakidou, M. (1993) An investigation of the atmospheric sources and sinks  of methyl bromide.
53            Geophys. Res. Lett. 20:  133-136.
54


         December 1993                               3-266       DRAFT-DO NOT  QUOTE OR CITE

-------
 1     Singh, H. B.; Salas, L. J. (1983) Methodology for the analysis of peroxyacetyl nitrate (PAN) in die unpolluted
 2            atmosphere. Atmos. Environ. 17: 1507-1516.
 3
 4     Singh, H. B.; Viezee, W. (1988) Enhancement of PAN abundance in the Pacific marine air upon contact with
 5            selected surfaces. Atmos. Environ. 22: 419-422.
 6
 7     Singh, H. B.; Viezee, W.;  Johnson, W.  B.; Ludwig, F. L. (1980) The impact of stratospheric ozone on
 8            tropospheric air quality. J. Air Pollut, Control Assoc. 30: 1009-1017.
 9
10     Skov, H.; Hjorth, I.; Lohse, C.; Jensen, N. R.; Restelli, G. (1992) Products and mechanisms of the reactions of
11            the nitrate radical (NO3) with isoprene, 1,3-butadiene and 2,3-dimethyl-l,3-butadienein air.
12            Atmos. Environ, Part A  26: 2771-2783.
13
14     Slemr, F.; Harris, G. W.; Hastie, D. R.; Mackay, G. L;  Schiff, H. I.  (1986) Measurement of gas phase
15            hydrogen peroxide in air by tunable diode laser absorption spectroscopy. J. Geophys, Res.
16            91: 5371-5378.
17
18     Smith, R. A.; Drummond,  I. (1979) Trace determination of carbonyl compounds in air by gas chromatography of
19            their 2,4-dim'trophenylhydrazones. Analyst (London) 104: 875-877.
20
21     Smith, D. F.; Kleindienst, T. E.; Hudgens, E. E.; Mclver, C. D.; Bufalini, J. J. (1991) The photoxidationof
22            methyl tertiary bulyl ether. Int. J. Chem. Kinet. 23: 907-924.
23
24     Smith, D. L.; Holdren, M. W.;  McClenny, W. A. (1991) Design and operational characteristics of the
25            Chrompack model 9000  as an automated gas chromatograph. Presented at: the international symposium
26            on management of toxic  and related air pollutants. Pittsburgh, PA: Air and Waste Management
27            Association.
28
29     Smith, D. P.; Kleindienst, T. E.; Hudgens, E. E.; Mclver, C. D.; Bufalini, J. J. (1992) Kinetics and mechanism
30            of the atmospheric  oxidation of ethyl Wrr-butyl ether. Int. J. Chem. Kinet. 24: 199-215.
31
32     Solomon, P. A.; Fall,  T.; Salmon, L.; Cass, G. R.; Gray, H. A.; Davidson, A.  (1989) Chemical characteristics
33            of PM10 aerosols collected in the Los Angeles area. JAPCA 39: 154-163.
34
35     Spicer, C. W.; Joseph, D.  W.; Sticksel, P.  R.; Ward, G. F. (1979) Ozone sources and  transport in the
36            northeastern United States. Environ. Sci. Technol. 13: 975-985.
37
38     Spicer, C. W.; Joseph, D.  W.; Sticksel, P.  R. (1982) An investigation of the ozone plume from a small city.
39            J, Air Pollnt. Control Assoc. 32: 278-281.
40
41     Spicer, C. W.; Ward,  G. F.; Kenny, D. V.; Leslie, N. P.; Billick, I. H. (1991)  Measurement of oxidized
42            nitrogen compounds in indoor air. Presented at: Measurement of toxic and related air pollutants; May;
43            Durham, NC. Pittsburgh, PA: Air & Waste Management Association; EPA report no.
44            EPA-60d>9-91-018. A&WMA publication no.  VIP-21; pp. 103-108.
45
46     Spicer, C. W.; Buxton, B.  E.; Holdren, M. W.; Kelly, T. J.; Rust, S. W.; Ramamurthi, M.; Smith,  D. L.;
47            Pate, A. D.; Svcrdrup, G, M.; Chuang, J. C.; Shah, J. (1993) Variability and source attibutionof
48            hazardous urban air pollutants, Columbus field study. Research Triangle Park, NC: U.S. Environmental
49            Protection Agency, Atmospheric Research and Exposure Assessment Laboratory; EPA contract no.
50            68-D-80082.
51
52     Staehelin, J.; Hoigne, J. (1982) Decomposition of ozone in water:  rate of initiation by hydroxide ions and
53            hydrogen peroxide. Environ. Sci, Technol. 16: 676-681.
54


         December 1993                               3-267       DRAFT-DO NOT QUOTE OB rrra

-------
 1     Staffer, W.; Lahmana, W.; Weitkamp, C. (1985) Range-resolved differential absorption lidar. optimization of
 2            range and sensitivity, Appl. Opt. 24: 1950-1956.
 3
 4     Stair, R.  (1961) The spectral radiant energy from the sun through varying degrees of smog at Los Angeles.
 5            In: Proceedings of the 3rd national air pollution symposium; 1955; Pasadena, CA; pp. 48-54.
 6
 7     Stasiuk, W. N., Jr.; Coffey, P. E. (1974) Rural and urban ozone relationships in New York State. J. Air Pollut.
 8            Control Assoc. 24: 564-568,
 9
10     Stauff, J.; Jaeschke, W. (1972) Chemiluminszenz des 'Dioxetandions', Z. Naturforsch. 27b: 1434-1435.
11
12     Stauffer,  D. R.; Seaman, N. L. (1990) Use of four-dimensional data assimilation in a limited area mesoscale
13            model. Part I: experiments with synoptic data. Mon. Weather Rev.  118: 1250-1277.
14
15     Stauffer,  D. R.; Warner, T. T.; Seaman, N. L.  (1985) A Newtonian "nudging" approach to four dimensional
16            data assimilation: use of SESAME-IV data in a mesoscale model. Presented at: 7th conference on
17            numerical weather prediction; Montreal, Canada.
18
19     Stauffer,  D. R.; Seaman, N, L,; Warner, T. T.; Lario, A. M.  (1993) Application of an atmospheric simulation
20            model to diagnose air-pollution transport hi the Grand canyon region of Arizona. Chem, Eng. Commun.
21            121: 9-25.
22
23     Stedman, D. H.; Bishop, G. A.; Peterson, J. E.; Guenther, P.  L.; McVey, I. F.; Beaton, S. P. (1990) On-road
24            carbon monoxide and hydrocarbon remote sensing in die Chicago area. Illinois Department of Natural
25            Resources report no. ILEN/RE-AQ-91/14.
26
27     Stephens, E. R. (1964) Absorptivities for infrared determination of peroxyacyl nitrates. Anal. Chem.
28            36: 928-929.
29
30     Stephens, E. R. (1969) The formation, reactions, and properties of peroxyacyl nitrates (PANs) in photochemical
31            air pollution. In: Pitts, J.  N., Jr.; Metcalf, R.  L., eds.  Advances hi environmental science and
32            technology: v. 1. New York, NY:  Wiley4nterecience; pp. 119-146.
33
34     Stephens, E. R.; Price, M. A. (1973) Analysis of an important air pollutant: peroxyacetyl nitrate. J. Chem.
35            Educ. 50: 351-354.
36
37     Stephens, E. R.; Hanst, P. L.; Doerr, R. C.; Scott, W. E.  (1956a) Reactions of nitrogen dioxide and organic
38            compounds in air. Ind. Eng. Chem. 48:  1498-1504.
39
40     Stephens, E. R.; Scott, W. E.; Hanst, P. L.; Doerr, R. C.  (1956b) Recent developments hi  the study of the
41            organic chemistry of the atmosphere. Proc. Am. Pet. Inst. Sect. 3 36: 288-297.
42
43     Stephens, E. R.; Darley, E. F.; Taylor, O. C.; Scott, W. E. (1961) Photochemical reaction products hi air
44            pollution. Int. J. Air Water Pollut. 4: 79-100.
45
46     Stephens, E. R.; Burieson, F. R.; Cardiff, E. A. (1965) The production of pure peroxyacyl nitrates.
47            J. Air Pollut. Control Assoc. 15: 87-89.
48
49     Stevens,  R. K.; Hodgeson, J. A.  (1973) Applications of chemiluminescent reactions to the measurement of air
50            pollutants. Anal. Chem. 45: 443A^t49A.
51
52     Stevens,  R. K.; Drago, R. J.; Mamane,  Y. (1993) A long path differential optical absorption spectrometer and
53            EPA-approved fixed-point methods intercoraparison. Atmos, Environ. Part B 27: 231-236.
54


         December 1993                               3-268       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Sticksel, P. R.; Spicer, C. W.; Westberg, H. (1979) Ozone plumes from small cities and airborne observations
 2            of ozone in a moving high pressure system. Presented at: 72nd annual meeting of the Air Pollution
 3            Control Association; June; Cincinnati, OH, Pittsburgh, PA: Air Pollution Control Association; paper
 4            no. 79-58.6.
 5
 6     Stockwell, W. R.; Calvert, J. G. (1983) The mechanism of the HO-SOj reaction. Atmos. Environ.
 7            17:2231-2235.
 8
 9     Stockwell, W. R.; Lurmann, F. W. (1989) Intel-comparison of the ADOM and RADM gas-phase chemical
10            mechanisms. Palo Alto, CA: Electric Power Research Institute.
11
12     Stockwell, W. R.; Middleton, P.; Chang, J.  S.; Tang, X. (1990) The second generation regional acid deposition
13            model chemical mechanism for regional air quality modeling. J. Geophys. Res. [Atmos.]
14            95: 16,343-16,368.
15
16     Stump, F. D.; Knapp, K. T.; Ray,  W. D.; Snow, R.; Burton, C. (1992) The composition of motor vehicle
17            organic emissions under elevated temperature summer driving conditions (75 to 105 °F). J. Air Waste
18            Manage. Assoc. 42:  152-158.
19
20     Svensson, R.; Ljungstroem, E.; Lindqvist, O. (1987) Kinetics of die reaction between nitrogen dioxide and water
21            vapour. Atmos. Environ. 21:  1529-1539.
22
23     Sweet, C. W.; Vermette, S. J. (1992) Toxic volatile organic compounds in urban air in Illinois. Environ. Sci.
24            Technol. 26: 165-173.
25
26     Tanner, R. L. (1984) Chemical transformations in acid rain; vol. I.: new methodologies for sampling and
27            analysis of gas phase peroxide. New York, NY: Brookhaven National Laboratory; report no.
28            BNL-35953. Available from: NTIS,  Springfield, VA; PB85-17345.
29
30     Tanner, R. L.; Meng, Z, (1984) Seasonal variations in ambient atmospheric levels of formaldehyde and
31            acetaldehyde. Environ. Sci. Technol. 18: 723-726.
32
33     Tanner, R. L.; Shen, J. (1990) Measurement of hydrogen peroxide in ambient air by impinger and diffusion
34            scrubber. Aerosol Sci. Technol. 12:  86-97.
35
36     Tanner, R. L.; Daum, P. H.; Kelly, T. J, (1983) New instrumentation for airborne acid  rain research.
37            Int. J. Environ. Anal. Chem.  13: 323-335.
38
39     Tanner, R. L.; Markovits, G.  Y.; Ferreri, E. M.; Kelly, T. J. (1986) Sampling and determination of gas-phase
40            hydrogen peroxide following removal of ozone by gas-phase reaction with nitric oxide. Anal. Chem.
41            58: 1857-1865.
42
43     Tejada, S. B.; Sigsby, J. E, (1988) Identification of chromatographic peaks using Lotus 1-2-3. J. Chromatogr.
44            Sci. 26: 494-500.
45
46     Tesche, T. W. (1983) Photochemical dispersion modeling: review of model concepts and applications studies.
47            Environ. Int. 9: 465-489.
48
49     Tesche, T. W. (1987) Photochemical modeling of 1984 SCCCAMP oxidant episodes: protocol for model
50            selection, adaptation, and performance evaluation. Washington, DC: U.S. Environmental Protection
51            Agency.
52
         December 1993                              i.9#i       DRAFT-DO NOT OTTOTP nw  rrrp

-------
 1     Tesche, T. W. (1992) Emissions modeling: status and new directions. In: Proceedings of the Electric Power
 2            Research Institute photochemical modeling workshop; August; Cambridge, MA. Palo Alto, CA: Electric
 3            Power Research Institute.
 4
 5     Tesche, T. W. (1993) Workplan for the development and application of the SARMAP modeling system.
 6            Sacramento, CA: California Air Resources Board; report no. AG-90/TS35,
 7
 8     Tesche, T. W.;  Seigneur, C.; Reid, L. E.-, Roth, P. M.; Oliver, W. R.; Cassmassi, J. C. (1981) The sensitivity
 9            of complex photochemical model estimates to detail in input information. Research Triangle Park, NC:
10            U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards; EPA report
11            no. EPA 450/4-81-031 A. Available from: NTIS, Springfield, VA; PB82-23418S.
12
13     Tesche, T. W.;  Haney, J. L.; Morris, R. E> (1987) Performance evaluation of four grid-based dispersion models
14            in complex terrain.  Atmos. Environ. 21: 233-256.
15
16     Tesche, T. W.;  Balentine, H.; Fosdick, E. (1990a) Ozone modeling protocol for the San Diego air quality study.
17            San Diego, CA: San Diego County Air Pollution Control District.
18
19     Tesche, T. W.;  Georgopoulos, P.; Seinfeld, J. H.; Cass, G.; Lunnann, F. W.; Roth, P. M. (1990b)
20            Improvement of procedures for evaluating photochemical models. Sacramento,  CA: California Air
21            Resources Board.
22
23     Tesche, T. W.;  Roth, P. M.; Reynolds, S. D.; Lurmann, F, W. (1992) Scientific assessment of the urban
24            airshed model (UAM-IV). Washington, DC: American Petroleum Institute; report no. API-300-92,
25
26     Thompson, A. M. (1992) The oxidizing capacity of the Earth's atmosphere: probable past and future changes.
27            Science  (Washington, DC) 256: 1157-1165.
28
29     Thompson, A. M.; Stewart, R. W.; Owens, M. A.; Herwehe, J. A, (1989) Sensitivity of tropospheric oxidants
30            to global chemical and climate change. Atmos. Environ. 23: 519-532.
31
32     Tiao, G. C.; Box, G. E. P.; Hamming, W. J. (1975) Analysis of Los Angeles photochemical smog data:
33            a statistical overview. J. Air Pollut. Control Assoc. 25: 260-268.
34
35     TUden, J. W.; Seinfeld, I. H. (1982) Sensitivity analysis of a mathematical model for photochemical air
36            pollution. Atmos. Environ. 16: 1357-1364.
37
38     Tilden, J. W.; Costanza, V.;  McRae, G. J.; Seinfeld, 3. H.  (1981) Sensitivity analysis of chemically reacting
39            systems. In: Ebert,  K. H,; Deuflhard, P.; Jager, W., eds. Modelling of chemical reaction systems,
40            proceedings of an international workshop. Berlin,  Germany: Springer-Verlag; pp. 69-91.
41            (Springer-Verlag series in chemical physics, v,  18).
42
43     Topham, L. A.; Mackay, G. L; Scbiff, H. I. (1993) Performance assessment of the portable and lightweight
44            LOZ-3 chemiluminescence type ozone monitor. In: proceedings of the 1992 EPA/AWMA international
45            symposium on measurement of toxic and related air pollutants. Pittsburgh, PA: Air and Waste
46            Management Association; publication no. VIP-25; EPA report no. EPA/600/R-92/131; pp. 745-749.
47
48     Torres, A. L. (1985) Nitric oxide measurements at a nonurban eastern United  States site: Wallops instrument
49            results from July 1983 GTE/CITE mission. J. Geophys. Res. [Atmos.] 90: 12875-12880.
50
51     Trainer,  M.; Williams, E. J.; Parrish, D. D.; Buhr, M. P.; Allwine, E. J.; Westberg, H. H.; Fehsenfeld, F. C.;
52            Liu, S.  C. (1987) Models and observations of the impact of natural hydrocarbons on rural ozone. Nature
53             (London) 329: 705-707.
54


         December 1993                             3-270      DRAFT-DO NOT QUOTE OR OTB

-------
 1     Trainer, M.; Buhr, M. P.; Cumin, C, M.; Fehsenfeld, F. C.; Hsie, E. Y.; Uu, S. C.; Norton, R. B.; Parrish,
 2            D. D.j Williams, E. J. (1991) Observations and modelling of the reactive nitrogen photochemistry at a
 3            rural site. J. Geophys. Res. [Atmos.] 96: 3045-3063.
 4
 5     Tripoli, G. J.; Cotton, W. R. (1982) The Colorado State University three-dimensional cloud mesoscale model:
 6            part I. general theoretical framework and sensitivity experiments. J. de Rech. Atmos. 16: 185-195.
 7
 8     Tsalkani, N.; Tonpance, G.  (1989) Infrared absorptivities and integrated band intensities for gaseous peroxyacetyl
 9            nitrate (PAN). Atmos. Environ. 23: 1849-1854.
10
11     Tuazon, E. C.; Atkinson, R. (1989) A product study of the gas-phase reaction of methyl vinyl ketone with the
12            OH radical in the presence of NOX. Int. J.  Chem. Kinet. 21: 1141-1152.
13
14     Tuazon, E. C.; Atkinson, R. (1990a) A product study of the gas-phase reaction of isoprene with the OH radical
15            in the presence of NOX. Int. J. Chem. Kinet. 22: 1221-1236.
16
17     Tuazon, E. C.; Atkinson, R. (1990b) A product study of the gas-phase reaction of methacrolein with the OH
18            radical in the presence of NO,. Int. J. Chem. Kinet. 22: 591-602.
19
20     Tnazon, E. C.; Graham, R. A.;  Winer, A. M.; Easton, R, R.; Pitts, J. N., Jr.; Hanst, P. L. (1978) A kilometer
21            pathlength Fourier-transform infrared system for the study of trace pollutants in ambient and synthetic
22            atmospheres. Atmos. Environ. 12; 865-875.
23
24     Tuazon, E. C.; Winer, A. M.; Graham, R. A.; Pitts, J. N., Jr. (1980) Atmospheric measurements of trace
25            pollutants by kilometer-pathlength FT-IR spectroscopy. Adv. Environ. Sci. Technol.  10: 259-300.
26
27     Tuazon, E. C.; Winer, A. M.; Graham, R. A.; Pitts, J. N., Jr. (198la) Atmospheric measurements of trace
28            pollutants:  long path Fourier transform infrared spectroscopy. Research Triangle Park,  NC:
29            U.S. Environmental Protection Agency, Environmental Sciences Research Laboratory;  EPA report no.
30            EPA-600/3-81-026. Available from: NTIS, Springfield, VA; PB81-179848.
31
32     Tuazon, E. C.; Winer, A. M.; Pitts, J. N., Jr. (198Ib) Trace pollutant concentrations in a multiday smog
33            episode in  the California South Coast Air Basin by long path length Fourier transform infrared
34            spectroscopy. Environ. Sci. Technol. 15: 1232-1237.
35
36     Tuazon, E. C.; Carter, W. P. L.; Aschmann, S. M.; Atkinson, R.  (1991) Products of the gas-phase reaction of
37            methyl /erf-butyl ether with the OH radical in the presence of NOK. Int. J. Chem. Kinet. 23:  1003-1015.
38
39    Turpin, B. J.; Huntzicker, J. J.  (1991) Secondary  formation of organic aerosol in the Los Angeles basin:
40            a descriptive analysis of organic and elemental carbon concentrations. Atmos. Environ. Part A
41            25:207-215.
42
43      Tyndall, G. S.; Ravishankara, A. R. (1991) Atmospheric oxidation of reduced sulfur species. Int. J. Chem.
44           Kinet. 23:  483-527.
45
46    U.S. Congress. (1989) Catching our breath: next steps for reducing urban ozone. Washington, DC: Office of
47            Technology Assessment; report no. OTA-O-412. Available from: NTIS,  Springfield, VA; PB90-130451.
48
49    U.S. Department of Commerce. (1968) Climatic atlas of the United States. Asheville, NC: National Climatic
50            Center [reprinted (1977) by the National Oceanic and Atmospheric Administration].
51
52     U.S. Department of Health, Education, and Welfare. (1965) Selected methods for the measurement of air
53           pollutants. Durham, NC: National Air Pollution Control Administration; Public Health Service
54            publication no. 999-AP-ll. Available from:  NTTS,  Springfield, VA; PB-169677.


         December 1993                              3-271       DRAFT-DO NOT QUOTE OR CITE

-------
 1     U.S. Department of Health, Education, and Welfare. (1970) Air quality criteria for photochemical oxidants.
 2            Washington, DC: National Air Pollution Control Administration; publication no. AP-63. Available from:
 3            NTIS, Springfield, VA; PB-190262/BA.
 4
 5     U.S. Environmental Protection Agency. (1977) Uses, limitations and technical basis of procedures for quantifying
 6            relationships between photochemical oxidants and precursors. Research Triangle Park, NC: Office of Air
 7            Quality Planning and Standards; EPA report no. EPA-450/2-77-021a. Available from: NTTS, Springfield,
 8            VA; PB-278142.
 9
10     U.S. Environmental Protection Agency. (1978) Air quality criteria for ozone and other photochemical oxidants,
11            Research Triangle Park, NC: Office of Health and Environmental Assessment, Environmental Criteria
12            and Assessment Office; EPA report no. EPA-600/8-78-004. Available from: NTIS, Springfield, VA;
13            PB80-124753.
14
15     U.S. Environmental Protection Agency, (1981) Technical  assistance document for the calibration and operation of
16            automated ambient non-methane organic compound analyzers. Research Triangle Park, NC:
17            Environmental Monitoring Systems Laboratory; EPA report no. EPA-600/4-81-015, Available from:
18            NTIS, Springfield, VA; PB82-147406.
19
20     U.S. Environmental Protection Agency. (1984) User's manual for OZIPM2: ozone isopleth plotting with optional
21            mechanisms/version 2. Research Triangle Park, NC: U.S. Environmental Protection Agency; EPA report
22            no. EPA-450/4-84-024.
23
24     U.S. Environmental Protection Agency. (1985) Compilation of air pollutant emission factors, volume I: stationary
25            point and area sources; volume II: mobile sources. 4th ed. Research Triangle Park, NC: Office of Air
26            Quality Planning and Standards; EPA  report no. AP-42-ED-4-VOL-1 and AP-42-ED-4-VOL-2. Available
27            from: NTIS, Springfield, VA; PB86-124906 and PB87-205266.
28
29     U.S. Environmental Protection Agency. (1986a) Guideline on air quality models (revised).
30            Research Triangle Park, NC: Office of Air Quality Planning and Standards; EPA report no.
31            EPA-450/2-78/027R. Available from:  NTIS, Springfield, VA;  PB86-245248.
32
33     U.S. Environmental Protection Agency. (1986b) Air quality criteria for ozone and other photochemical oxidants.
34            Research Triangle Park, NC: Office of Health and Environmental Assessment, Environmental Criteria
35            and Assessment Office; EPA report nos. EPA-600/8-84-020aF-eF. 5v. Available from: NTIS,
36            Springfield, VA; PB87-142949.
37
38     U.S. Environmental Protection Agency.  (1989a) User's guide to MOBILE4 (Mobile Source Emission Factor
39            Model), Ann Arbor, MI: Office of Mobile Sources; EPA report no. EPA-AA-TEB-89-01. Available
40            from: NTIS, Springfield, VA; PB89-164271.
41
42    U.S. Environmental Protection Agency.  (1989b) Procedures for applying cUy-specific EKMA.
43           Research Triangle Park, NC: U.S. Environmental Protection Agency, Office of Air Quality Planning and
44           Standards; EPA report no. EPA-450/4-91-013. Available from: NTIS, Springfield, VA;
45           PB90-256777/HSU.
46
47    U.S. Environmental Protection Agency.  (1990a) User's guide for the Urban Airshed Model, v. I: user's manual
48           for UAM (CB-IV). Research Triangle Park, NC:  U.S. Environmental Protection Agency;  EPA report
49           no. EPA-450/4-90-007A(R).
50
51     U.S. Environmental Protection Agency. (199%) User's guide for the Urban Airshed Model, v. H.
52           Research Triangle Park, NC: U.S. Environmental Protection Agency; EPA report no.
 53           EPA-450/4-90-007B(R).
 54


         December 1993                              3-272      DRAFT-DO NOT QUOTE OR  CITE

-------
 1     U.S. Environmental Protection Agency. (1990c) User's guide to the Urban Airshed Model, v. Ill: user's manual
 2            for the diagnostic wind model. Research Triangle Park, NC; U.S. Environmental Protection Agency;
 3            EPA report no. EPA-450/4-90-007C(R).
 4
 5     U.S. Environmental Protection Agency. (1990d) User's guide for the Urban Airshed Model, v. IV: user's manual
 6            for the emissions preprocessor system 2.0. Part A: core FORTRAN system.
 7            Research Triangle Park, NC:  U.S. Environmental Protection Agency; EPA report no.
 8            EPA-450/4-90-007D(R).
 9
10     U.S. Environmental Protection Agency. (1990s) User's guide for the Urban Airshed Model, v. IV: user's manual
11            for the emissions preprocessor system 2.0. Part B: interface and emission display system.
12            Reserach Triangle Park, NC:  U.S. Environmental Protection Agency; EPA report no.
13            EPA-450/4-90-007D(R).
14
15     U.S. Environmental Protection Agency. (1990f) User's guide for the Urban Airshed Model, v. V: description
16            and operation of the ROM-UAM interface program system. Research Triangle Park, NC: U.S.
17            Environmental Protection Agency; EPA report no. EPA-450/4-90-007E(R).
18
19     U.S. Environmental Protection Agency. (1991a) National air quality and emissions treads report, 1989.
20            Research Triangle Park, NC:  Office of Air Quality Planning and Standards; EPA report no.
21            EPA/450/4-91/003. Available from: NTIS, Springfield, VA; PB91-172247/XAB.
22
23     U.S. Environmental Protection Agency. (1991b) Guideline for regulatory application of the urban airshed model.
24            Research Triangle Park, NC: U.S. Environmental Protection Agency, Office of Air Quality Planning and
25            Standards; EPA report no. EPA-450/4-91-013. Available from: NTIS, Springfield, VA;
26            PB92-108760/HSU.
27
28     U.S. Environmental Protection Agency. (1991c) Volatile organic compound (VOC)/particuIate matter (PM)
29            speciation data system, version 1.4. Research Triangle Park, NC: U.S. Environmental Protection
30            Agency, Office of Air Quality Planning and Standards; EPA report no. EPA-450/4-91-027.
31
32     U.S. Environmental Protection Agency. (1992) National air pollutant emission estimates, 1900-1991.
33            Research Triangle Park, NC: Office of Air Quality Planning and Standards; EPA report no.
34            EPA/454/R-92/013. Available from: NTIS, Springfield, VA; PB93-157808/XAB.
35
36     U.S. Environmental Protection Agency. (1993a) Regional interim emission inventories (1987-1991), v. I:
37            development methodologies. Research Triangle Park, NC; U.S. Environmental Protection Agency;
38            EPA report no. EPA-454/R-93-021a.
39
40     U.S. Environmental Protection Agency. (1993b) Regional emission inventories (1987-1991), v. II: emission
41            summaries. Research Triangle Park, NC:  U.S. Environmental Protection Agency; EPA report no.
42            EPA-454/R93-021b.
43
44     U.S. Environmental Protection Agency. (1993c) Air quality criteria for oxides of nitrogen.
45            Research Triangle Park, NC: Office of Health and Environmental Assessment, Environmental Criteria
46           and Assessment Office; EPA review draft no, EPA/600/8-91/049F.
47
48     Ulrickson, B. L. (1988) Mesoscale circulations in the Los Angeles Basin: a numerical modeling study [Ph.D.
49            dissertation]. Seattle, WA: University of Washington.
50
51     Valente, R. J.; Thornton, F. C. (1993) Emissions of NO from soil at a rural site in central Tennessee.
52           J. Geophys. Res. 98: 16,745-16,753.
53
         December 1993                             3-273       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Van de Wiel, H. J,; Reijoders, H. F. R.; Seifert, R.; Giea, H.; Lanting, R, W,; Rudolf, W, (1979) International
 2            comparative programme on ozone reference methods. Atmos. Environ. 13: 555-557.
 3
 4     Van Valin, C. C.; Ray, J. D.; Boatman, J.  F.; Guater, R. L. (1987) Hydrogen peroxide in air during winter
 5            over the south-central United States. Geophys. Res. Lett. 14: 1146-1149.
 6
 7     Vaughan, W, M,; Chan, M.; Cantrell, B.; Pooler, F. (1982) A study of persistent elevated pollution episodes in
 8            the northeastern United States. Bull, Am. Meteorol. Soc. 63: 258-266.
 9
10     Venkatram, A.; Karamchandani, P. K.; Misra, P. K. (1988) Testing a comprehensive acid deposition model.
11            Atmos. Environ. 22: 737-747.
12
13     Vierkorn-Rudolph, B.; Rudolph, J.; Diederich, S. (1985) Determination of peroxyacetylnitrate (PAN) in
14            unpolluted areas. Int. J. Environ. Anal. Chem. 20: 131-140.
15
16     Viezee, W.; Singh, H. B.  (1982) Contribution of stratospheric ozone to ground-level ozone concentrations-
17            a scientific review of existing evidence. Research Triangle Park, NC: U.S. Environmental Protection
18            Agency, Environmental Science Research Laboratory; EPA grant CR-809330010.
19
20     Viezee, W.; Johnson, W.  B.; Singh, H. B. (1979) Airborne measurements of stratospheric ozone intrusions into
21            the troposphere over the United States: final report. Atlanta, GA:  Coordinating Research Council; SRI
22            project 6690; CRC-APRAC project no. CAPA-15-76.
23
24     Viezee, W.; Johnson, W.  B.; Singh, H. B. (1983) Stratospheric ozone in the lower troposphere—n. assessment
25            of downward flux and ground-level impact. Atmos. Environ. 17: 1979-1993.
26
27     Vukovich, F. (1977) Review and analysis. In: International conference on oxidants, 1976—analysis of evidence
28            and viewpoints: part V, the issue of oxidanl transport; September  1976. Research Triangle Park, NC:
29            U.S. Environmental Protection Agency, Environmental Sciences Research Laboratory; EPA report no.
30            EPA-600/3-77-117. Available from: NTIS, Springfield, VA; PB-278750.
31
32     Vukovich, F. M.; Bach, W. D., Jr.; Crissman, B. W.; King, W. J. (1977) On the relationship between high
33            ozone in the rural surface layer and high pressure systems. Atmos. Environ. 11: 967-983.
34
35     Wadden, R. A.; Uno, I.;  Wakamatsu, S. (1986) Source discrimination of short-term hydrocarbon samples
36            measured aloft. Environ. Sci. Technol. 20: 473-483.
37
38     Wakim, P. G. (1989) Temperature-adjusted ozone trends for Houston, New York and Washington, 1981-1987.
39            Presented at: the 82nd annual meeting and exhibition of the Air and Waste Management Association;
40            June; Anaheim, CA. Pittsburgh, PA: Air and Waste Management Association; paper no. 89-35.1.
41
42     Walcek,  C. J.; Brest, R.  A.; Chang, J. S.; Wesely, M. L.  (1986) SC^, sulfate and HNC^ deposition velocities
43            computed using regional landuse and meteorological data. Atmos. Environ. 20: 949-964.
44
45     Walega,  J. G.; Stedman,  D.  H.; Shelter, R. E.; Mackay, G. I.; Iguchi, T.; Schiff, H. I. (1984) Comparison of a
46           chemiluminesceat and a tunable diode laser absorption technique for the measurement of nitrogen oxide,
47           nitrogen dioxide,  and nitric acid. Environ. Sci. Technol. 18: 823-826.
48
49     Wallace, L. A.;  Ott, W. R. (1982) Personal monitors: a state-of-the-art survey. J. Air Pollut. Control Assoc.
50           32:601-610.
 51
 52     Wellington, T. J.; Japar,  S. M. (1991) Atmospheric chemistry of diethyl  ether and ethyl tert-butyl ether.
 53            Environ.  Sci. Technol. 25: 410-415.
         December 1993                              3-274      DRAFT-DO NOT QUOTE OR CTIE

-------
 1     Wang, W.; Warner, T. T. (1988) Use of four-dimensional data assimilation by Newtonian relaxation and
 2            latent-heat forcing to improve a masoscale-model precipitation forecast: a case study. Mon. Weather Rev.
 3            16:2593-2613,
 4
 5     Wang, S.-C.; Paulson, S. E.; Grosjean, D,; Flagan, R. C.; Seinfeld, J. H. (1992) Aerosol formation and growth
 6            in atmospheric organic/NOx systems-I. Outdoor smog chamber studies of €7- and C8- hydrocarbons.
 7            Atmos. Environ. Part A 26: 403-420.
 8
 9     Wameck, P. (1991) Chemical reactions in clouds. Fres. J. Anal. Chem. 340: 585-590.
10
11     Wameck, P. (1992) Chemistry and photochemistry in atmospheric water drops. Ber. Bunsen-Ges. Phys. Chem.
12            96:454-460.
13
14     Wameck, P.; Zerbach, T. (1992) Synthesis of peroxyacetyl nitrate in air by acetone photolysis. Environ. Sci.
15            Technol.  26: 74-79.
16
17     Warren, G. J.; Babcock,  G. (1970) Portable ethylene chemiluminescence ozone monitor. Rev. Sci. lustrum,
18            41:280-282.
19
20     Watanabe, I.; Stephens, E. R. (1978) Reexamination of moisture anomaly in analysis of peroxyacetyl nitrate.
21            Environ.  Sci. Technol.  12: 222-223.
22
23     Watson, J. G.; Robinson, N. P.;  Chow, J. C.; Henry, R. C.; Kim, B.; Meyer, E. L.; Nguyen,  Q. T.;
24            Pace, T, G. (1990) Receptor model technical series, v. m (1989 revision) CMB7 user's  manual.
25            Research Triangle Park, NC: U.S. Environmental Protection Agency, Office of Air Quality Planning and
26            Standards; EPA report no. EPA-450/4-90-004. Available from: NTTS, Springfield, VA: PB90-185067.
27
28     Wayne, R. P. (1991) Chemistry of atmospheres: an introduction to the chemistry of the atmospheres of earth, the
29            planets, and their satellites. 2nd ed. Oxford, United Kingdom: Oxford University Press.
30
31     Wei, L.; Weihan, S. (1987) Automated method for determination of hydrogen peroxide in air and atmospheric
32            precipitation. Huanjing Huaxue 6: 23-29. (CA 109: 16299;  1988).
33
34     Wendel, G. J.; Stedman, D. H.;  Cantrell, C. A.; Damrauer, L.  (1983) Luminol-based nitrogen dioxide detector.
35            Anal. Chem. 55: 937-940.
36
37     Weschler, C. J.;  Mandich, M.  L.; Graedel, T. E, (1986) Speciation, photosensitivity, and reactions of transition
38            metal ions in atmospheric droplets. J. Geophys. Res. [Atmos.j 91: 5189-5204.
39
40     Wesely, M. L. (1988) Improved  parameterizations for surface resistance to gaseous dry deposition in
41            regional-scale, numerical models. Research Triangle Park, NC: U.S. Environmental Protection Agency,
42            Atmospheric Sciences Research Laboratory; EPA report no. EPA/600/3-88/025. Available from: NTIS,
43            Springfield, VA; PB88-225099/AS.
44
45     Wesely, M. L.; Eastman, J. A,;  Stedman, D. H.; Yalvac, E.  D. (1982) An eddy-correlation measurement of
46            NO2 flux to vegetation and comparison to 03  flux. Atmos. Environ. 16: 815-820.
47
48     Westberg, H.; Lamb, B.  (1985) Ozone production and transport in (he Atlanta, Georgia, region.
49            Research Triangle Park, NC: U.S. Environmental Protection Agency, Atmospheric  Sciences Research
50            Laboratory;  EPA report no. EPA-600/3-85-013. Available from: NTIS, Springfield, VA; PB85-173839.

52     Westberg, H. H.; Rasmussen, R. A.; Holdren, M. (1974) Gas chromatographic analysis of ambient air for light
53            hydrocarbons using a chemically bonded stationary phase. Anal. Chem. 46: 1852-1855.
54


         December  1993                              3-275       DRAFT-DO NOT  QUOTE OR CITE

-------
 1     Westberg, H.; Allwine, K. J.; Elias, D, (1976) Vertical ozone distribution above several urban and adjacent rural
 2            anas across die United States. In: Specialty conference on: ozone/oxidants—interactions with the total
 3            environment; March; Dallas, TX. Pittsburgh, PA: Air Pollution Control Association; pp. 84-95.
 4
 5     Westberg, H.; Allwine, K.; Robinson, E. (1978a) Measurement of light hydrocarbons and oxidant transport:
 6            Houston study 1976. Research Triangle Park, NC: U.S. Environmental Protection Agency,
 7            Environmental Sciences Research Laboratory; EPA report no. EPA-600/3-78-062. Available from: NTTS,
 8            Springfield, VA; PB-285891.
 9
10     Westberg, H.; Allwine, K. J.; Robinson, E. (1978b) Hie transport of oxidant beyond urban areas: light
11            hydrocarbon and oxidant data, New England study, 1975. Research Triangle Park, NC:
12            U.S. Environmental Protection Agency, Environmental Sciences Research Laboratory; EPA report
13            no.  EPA-600/3-78-006. Available from: NTIS, Springfield, VA; PB-277043.
14
15     Westberg, H. H.; Holdren, M. W.; HUl, H. H. (1980) Analytical methodology for the identification  and
16            quantification of vapor phase organic pollutants. New York, NY:  Coordinating Research Council;
17            CRC-APRAC project no. CAPA-11-71.
18
19     Westberg, H.; Sexton, K.; Roberts, E. (1981a) Transport of pollutants along the western shore of
20            Lake Michigan. J. Air Pollut. Control Assoc. 31: 385-388.
21
22     Westberg, H. H.; Holdren, M. W.; Hill, H. H. (1981b) Analytical methodology for the identification and
23            quantitation of vapor phase organic pollutants [final report]. Pullman, WA: Washington State University;
24            CRC-APRAC project no. CAPA-11-17.
25
26     Westberg, H.; Lonneman, W.; Holdren, M. (1984) Analysis of individual hydrocarbon species in ambient
27            atmospheres: techniques and data validity. In: Keith, L. H., ed. Identification and analysis of organic
28            pollutants in air. Woburn, MA: Butterworth; pp. 323-327.
29
30     Wbitby, K. T.; Husar, R. B.; Liu, B. Y. H. (1972) The aerosol size distribution of Los Angeles smog. J.
31            Colloid Interface Sci. 39: 177-204.
32
33     Whitten, G. Z.; Hogo, H. (1977) Mathematical modeling of simulated photochemical smog.
34            Research Triangle Park, NC: U.S. Environmental Protection Agency, Environmental Sciences Research
35            Laboratory; EPA report no. EPA-600/3-77-011. Available from:  NTIS, Springfield, VA; PB-263348.
36
37     Whitten, G. Z.; Hogo, H. (1981) Comparative application of the EKMA in the Los Angeles area.
38            Research Triangle Park, NC: U.S. Environmental Protection Agency, Office of Air Quality Planning and
39            Standards; EPA report no. EPA-450/4-81-031d. Available from:  NTIS, Springfield, VA; PB82-234204.
40
41     Wight, G. D,; Wolff, G. T.; lioy, P.  J.; Meyers, R. E.;  CederwaJl, R.  T. (1978) Formation and transport of
42            ozone in the northeast quadrant of the United States. In: Morris,  A. L.;  Barras,  R. C., eds. Air quality
43            meteorology and atmospheric ozone: a symposium sponsored by ASTM  Committee D-22 on  Methods of
44            Sampling and Analysis of Atmospheres; July-August 1977; Boulder, CO. Philadelphia, PA: American
45             Society for Testing and Materials; pp.  445-457; ASTM special technical publication 653.
46
47    Williams, E. L., II; Grosjean, D. (1990) Removal of atmospheric oxidants with annular denuders. Environ.
48             Sci. Technol. 24: 811-814.
49
50     Williams, E.; Guenther, A.; Fehsenfeld, F. (1992) Inventory of U.S. soil emissions. J.  Geophys. Res.
51             97:7511-7519.
52
53     Winer, A.  M. (1983) Investigation of the role of natural hydrocarbons in photochemical smog formation in
54            California: final report. Sacramento, CA: California Air Resources Board; contract no. AO-056-32.


         December  1993                              3-276       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Winer, A, M.; Peters, J. W.; Smith, J. P.; Pitts, I. N., Jr. (1974) Response of commercial chemiluminescent
 2            NO-NOj analyzers to other nitrogen-containing compounds. Environ. Sci. Technol. 8; 1118-1121.

 4     Winer, A. M.; Breuer, G. M.; Carter, W. P. L.; Darnall, K. R.; Pitts, J. N., Jr. (1979) Effects of ultraviolet
 5            spectral distribution on the photochemistry of simulated polluted atmospheres. Atmos. Environ.
 6            13:989-998.
 7
 8     Winer, A. M.; Atkinson, R.; Arey, J.; Biermann, H. W.; Harger, W. P.; Tuazon, E. C.; Zielinska, B. (1987)
 9            The role of nitrogenous pollutants in the formation of atmospheric mutagens and acid deposition.
10            Sacramento, CA: California Air Resources Board; report no. ARB-R-87/308. Available from: NTIS,
11            Springfield, VA; PB87-222949.
12
13     Winer, A. M.; Arey, J.; Atkinson, R,; Aschmann, S. M.; Long, W. D.; Morrison, C. L.; Olszyk, D. M.
14            (1992) Emission rates of organks from vegetation in California's Central Valley. Atmos. Environ.
15            Part A 26: 2647-2659.
16
17     Wolff, G. T.; Korsog, P. E. (1992) Ozone control strategies based on die ratio of volatile organic compounds to
18            nitrogen oxides. J. Air Waste Manage. Assoc.  42: 1173-1177.
19
20     Wolff, G. T.; Lioy, P. J, (1978) An empirical model for forecasting maximum daily ozone levels in the
21            northeastern U.S. J. Air Pollut. Control Assoc. 28: 1034-1038.
22
23     Wolff, G. T.; Lioy, P. J. (1980) Development of an ozone river associated with synoptic scale episodes in the
24            eastern United States. Environ. Sci. Technol. 14:  1257-1260.
25
26     Wolff, G. T.; Lioy, P. J.; Meyers, R. E.;  Cederwall,  R.  T.; Wight,  G. D.; Pasceri, R. E.; Taylor, R. S.
27            (1977a) Anatomy of two ozone transport episodes in the Washington, D.C.,  to Boston, Mass., corridor.
28            Environ. Sci.  Technol. 11: 506-510.
29
30     Wolff, G. T.; Lioy, P. J.; Wight, G. D.; Meyers, R. E.; Cederwall, R.  T.  (1977b) An investigation of
31            long-range transport of ozone across the midwestern and eastern United States. Atmos. Environ.
32            11:797-802.
33
34     Wolff, G. T.; Lioy, P. J.; Wight, G. D.; Pasceri, R. E. (1977c) Aerial investigation of the ozone plume
35            phenomenon.  J. Air Pollut. Control Assoc. 27: 460-463.
36
37     Wolff, G. T.; Lioy, P. J.; Wight, G. D.; Pasceri, R. E. (1977d) Aerial investigation of photochemical oxidants
38            over the northeast In: Bufalini, J. J.; Lonneman, W. A., eds. Proceedings of symposium on 1975
39            northeast oxidant transport study; January 1976; Research Triangle Park, NC. Research Triangle Park,
40            NC: U.S. Environmental Protection Agency, Environmental Sciences Research Laboratory; pp. 70-86;
41            EPA report no. EPA-600/3-77-017. Available  from: NTlS, Springfield, VA; PB-265370.
42
43     Wolff, G. T.; Ferman,, M. A.; Monson, P. R. (1979) The distribution of beryllium-7 within high-pressure
44            systems in the eastern United States. Geophys. Res.  Lett  6: 637-639.
45
46    Wolff, G. T.; Lioy, P. J.; Wight, G. D. (1980) Transport of ozone associated with an air mass. J. Environ.  Sci.
47           Health Part A 15: 183-199.
48
49    Wolff, G. T.; Kelly, N. A.; Ferman, M. A.  (1981) On the sources of summertime haze in the eastern
50           United States.  Science (Washington, DC) 211: 703-705.
51
52    Wolff, G. T.; Kelly, N. A.; Ferman, M. A.  (1982) Source regions of summertime ozone and haze episodes  in
53           the eastern United States. Water Air Soil Pollut 18: 65-81.
54


         December 1993                               3-277      DRAFT-DO NOT QUOTE OR CITE

-------
 1     Wolff, G. T.; Ruthkosky, M, S.; Stroup, D. P.; Korsog, P. E. (1991) A characterization of the principal
 2            PM-10 species in Claremoni (summer) and Long Beach (fall) during SCAQS. Atmos. Environ. Part A
 3            25:2173-2186.
 4
 5     World Meteorological Organization, (I990a) Scientific assessment of stratospheric ozone: 1989, v. 1.
 6            Geneva, Switzerland: World Meteorological Organization; report no. 20; pp. 331-332.
 7
 8     World Meteorological Organization. (1990b) Scientific assessment of stratospheric ozone: 1989, v. TT.
 9            Geneva, Switzerland: World Meteorological Organization; report no. 20.
10
11     World Meteorological Organization, (1992) Scientific assessment of ozone depletion: 1991. Geneva, Switzerland:
12            World Meteorological Organization; report no. 25.
13
14     Wu, Y.-L.; Davidson, C. I.; Dolske, D. A.; Sherwood, S. I. (1992) Dry deposition of atmospheric
IS            contaminants: the relative importance of aerodynamic, boundary layer, and surface resistances. Aerosol
16            Sci. Technol. 16: 65-81.
17
18     Wunderli, S.; Gehrig, R. (1991) Influence of temperature on formation and stability of surface PAN and ozone.
19            A two year field study in Switzerland. Atmos. Environ. Part A 25: 1599-1608.
20
21     Yamada, T.; Kao, C. J.; Bunker, S. (1989) Airflow and air quality simulations over the western mountainous
22            region with a four-dimensional data assimilation technique. Atmos. Environ. 23: 539-554,
23
24     Yanagisawa, Y.; Nishimura, H. (1982) A badge-type personal sampler for measurement of personal exposure to
25            NO? and NO in ambient air. Environ. Int. 8: 235-242.
26
27     Yocke, M. A (1981) A three-dimensional wind model for complex terrain [Ph.D. dissertation]. Berkeley, CA:
28            University of California.
29
30     Yoshizumi, K.; Aoki, K.; Nouchi, I.; OMta, T.; Kobayashi, T.; Kamakura, S.; Tajima, M. (1984)
31            Measurements of die concentration in rainwater and of the Henry's Law constant of hydrogen peroxide.
32            Atmos. Environ.  18: 395-401.
33
34     Zafiriou, O. C.; True, M. B. (1986) Interferences in environmental analysis of NO by NO plus Oj detectors:
35            a rapid screening technique. Environ. Sci. Technol. 20: 594-596.
36
37     Zaitsu, K.; Ohkura, Y. (1980)  New fluorogenic substrates for horseradish peroxidase: rapid and sensitive assays
38            for hydrogen peroxide and the peroxidase. Anal. Biochem.  109: 109-113.
39
40     Zhang, D.-L.; Chang, H.-R.; Seaman, N. L.; Warner, T. T.;  Fritsch, J. M. (1986) A two-way interactive
41            nesting procedure with variable terrain resolution. Mon. Weather Rev. 114: 1330-1339.
42
43      Zhang, S.-H.; Shaw, M.; Seinfeld, J. H.;  Flagan, R. C. (1992) Photochemical aerosol formation from
44           a-pinene- and 0-pinene. J. Geophys. Res. [Atmos.] 97: 20,717-20,729.
45
46     Zhou, X,; Mopper, K. (1990) Apparent partition coefficients of 15 carbonyl compounds between air  and seawater
47            and between air and freshwater; implications for air-sea exchange. Environ. Sci. Technol. 24: 1864-1869.
48
49     Zika. R. G.; Saltzman, E. S. (1982) Interaction of ozone and hydrogen peroxide in water: implications for
50            analysis of Hj^ in air. Geophys. Res. Lett. 9: 231-234.

52
         December 1993                              3-278       DRAFT-DO NOT QUOTE OR CITE

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1     Zimmerman, P. R. (1979) Testing of hydrocarbon emissions from vegetation, leaf litter and aquatic surfaces, and
2           development of a methodology for compiling biogenic emission inventories: final report. Research
3           Triangle Park, NC: U.S. Environmental Protection Agency, Office of Air Quality Planning and
4           Standards; EPA report no, EPA-4SO/4-79-004. Available from: NTIS, Springfield, VA; PB-296070.
5
6     Zuo, Y.; Hoigne, J. (1993) Evidence for photochemical formation of HjC^ and oxidation of SO^ in authentic fog
7           water. Science (Washington, DC) 260: 71-73.
8
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 i             4.   EPWIRONMENTAL CONCENTRATIONS,
 2              PATTERNS, AND EXPOSURE ESTIMATES
 3
 4
 5     4.1   INTRODUCTION
 6          The ubiquity and toxicity of ozone (O3) are well documented (U.S. Environmental
 7     Protection Agency, 1986a).  Its effects on humans, animals, and vegetation have received
 8     extensive examination and are discussed later in this document (Chapters 5 through 9).
 9     As indicated in the previous O3 criteria document (U.S. Environmental Protection Agency,
10     1986a), most of the human and welfare effects research has focused on evaluating the
11     impacts on health or vegetation of exposure to O3  that mimic ambient O3 exposures (e.g.,
12     matching the occurrence of hourly average concentrations or more prolonged times of
13     exposure). The concentration information extensively monitored in the United States can be
14    useful for both linking anthropogenic emissions of O3 precursors with the protection of health
15     and welfare  (i.e., determining compliance with air standards) and also to augment exposure
16    assessment and epidemiology studies.  Therefore, as in previous criteria documents, the
17    major emphasis in this chapter will be on characterizing and summarizing the extensive
18    O3 monitoring data collected under ambient conditions. Although most of the O^ air quality
19    data summarized  were gathered for compliance and enforcement purposes, the hourly
20    averaged 03 information can be used for determining patterns and trends and as inputs to
21     exposure and health assessments (e.g., U.S. Environmental Protection Agency, 1992a;
22    Lefohn et al., 1990a).  In the sections that follow, the hourly averaged ambient 03 data have
23     been summarized in different ways to reflect the interests of those who wish to know more
24     about the potential for O3 to affect humans and their environment.
25          Trend patterns for 03  over several periods of time are described in Section 4.2.  The
26     trends for O^ have been summarized by the U.S. EPA (1993) for the period 1983 to 1992.
27     In addition,  trends analysis  for specific regions of the United States have been performed by
28     several investigators.  In some cases, attempts have been made to adjust for meteorological
29     variation. In Section 4.3, the hourly averaged concentration information from several
30     monitoring networks has been characterized for urban and  rural areas. The diurnal variation
31     (Section 4.4) occurring at urban and rural locations, as well as seasonal patterns are also
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 1     described. Specific focus is provided on O3 monitoring sites that are isolated from
 2     anthropogenic sources of ozone precursors because these locations form the "basis for
 3     comparison" for 03 concentrations and exposures. In many cases, it is important to know
 4     O3 exposure regimes experienced at isolated areas so that the regimes can be compared with
 5     those that are used in control treatments in experimental studies.  In Section 4.5, the seasonal
 6     patterns of exposure are discussed.  The hourly average concentration information is used in
 7     Section 4.6 to compare the spatial variations that occur in urban areas with those in nonurban
 8     areas, as well as in high-elevation locations.  For comparing indoor to outdoor O^ exposures
 9     or concentrations, information is provided in Section 4.7 on the latest data on indoor/outdoor
10     ratios.
11          Section 4.8 describes efforts to estimate accurately both human and vegetation exposure
12     to O3.  Examples are provided on how both fixed-site monitoring information,  as well as
13     human exposure models, are used to estimate risks associated with 63 exposure.  A short
14     discussion is provided on the importance of hourly average concentrations, used in the human
15     health and vegetation experiments, mimicking as closely as possible "real world"  exposures.
16          As indicated in the previous O3 criteria document (U.S. Environmental Protection
17     Agency, 1986a), O3 is  the only photochemical oxidant other man nitrogen dioxide that is
18     routinely monitored and for which a comprehensive aeromerric data base  exists.  Data for
19     peroxyacetyl nitrate (PAN) and hydrogen peroxide (H2O2)  have been obtained  as part of
20     special research investigations. Consequently, no data on nationwide patterns of occurrence
21     are available for these non-O3 oxidants; nor are extensive data available on the correlations
22     of levels and patterns of these oxidants with those of O3.  Sections 4.9 and 4.10 summarize
23     the data available for these other oxidants.  Section 4.11 describes the cooccurrence patterns
24     of O3 with nitrogen dioxide, sulfur dioxide, acidic aerosols, acidic precipitation, and acid
25     cloudwater.
26
27     4.1.1   Characterizing Ambient Ozone Concentrations
28          For purposes of using air quality data for assessing human health and vegetation effects,
29     it is important to distinguish among concentration, exposure, and dose.  For human health
30     considerations, Sexton and Ryan (1988) provide the following definitions, as described in the
31     Air Quality Criteria for Carbon Monoxide (U.S. Environmental Protection Agency, 1991):

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 1            1.  The concentration of a specific air pollutant is the amount of that material
 2               per unit volume of air. Air pollution monitors measure pollutant
 3               concentrations, which may or may not provide accurate exposure estimates.
 4
 5            2.  The term exposure is defined as any contact between an air contaminant of
 6               a specific concentration and the outer (e.g., skin) or inner (e.g., respiratory
 7               tract epithelium) surface of the human body. Exposure implies the
 8               simultaneous occurrence of the two events.
 9
10
11     The concentration of an airborne contaminant that is measured in an empty room is not
12     exposure. However, a concentration measured in a room with people present is considered
13     to be a measurement of exposure.  A measured concentration is a surrogate for exposure
14     only to the degree to which it represents concentrations actually experienced by individuals.
15     Exposure is defined as the pollutant concentration at the point of  contact between die body
16     and the external environment, while dose is defined as the amount of pollutant that actually
17     crosses one of the body's boundaries and reaches the target tissue.
18           For vegetation, similar to human health considerations, concentrations of airborne
19     contaminants are considered to represent exposure when contacts with them are experienced
20     by a plant.  As indicated in Chapter 5 (see Section 5.5), dose has been defined historically by
21     air pollution vegetation researchers as ambient air quality concentration multiplied  by time
22     (O'Gara, 1922).  However, a more rigorous definition is required. Runeckles (1974)
23     introduced the concept of "effective dose" as the amount or concentration of pollutant that
24     was adsorbed by vegetation, in contrast to that present in the ambient air.  Fowler and Cape
25     (1982) developed this concept further and proposed that the "pollutant adsorbed dose" be
                             2
26     defined in units of g m"  (of ground area or leaf area) and could  be obtained as the product
27     of concentration, time, and stomatal (or canopy) conductance for the gas in question. Taylor
28     et al.  (1982) suggested internal flux (mg m" If1) as a measure of the dose to which plants
29     respond.  For the purposes of vegetation, this chapter has adopted the concept that dose is
30     the amount of pollutant absorbed by the plant.
31           In  order to characterize the specific doses responsible for affecting human health and
32     vegetation,  there has to be a  linkage between exposure and the actual dose. Unfortunately,  it
33     is difficult to predict this relationship without detailed modeling.  For example, the sensitivity
34     of vegetation as a function of time of day or period of growth, as well as edapiric conditions,
35     may result in plants being exposed to high O3 concentrations with little resultant injury or
        December 1993                           4.3       DRAFT-DO NOT QUOTE OR CITE

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 1     damage, while more moderate levels of O3 exposures result in injury (Showman, 1991).
 2     Because (1) not enough is known to quantify the links between exposure and dosage and
 3     (2) routine monitoring for O3 is summarized as hourly average concentrations (i.e., potential
 4     exposure), most of the information provided in this chapter is characterized in terms of
 5     concentration and exposure.
 6          As indicated in the human health and vegetation chapters (Chapters 7 and 5), for many
 7     years, air pollution specialists have explored alternative mathematical approaches for
 8     summarizing ambient air quality information in biologically meaningful forms that can serve
 9     as surrogates for dose. At present, for human health effects purposes, 03 is usually
10     characterized in terms of the daily maximum (i.e., the highest hourly  average concentration
11     for the day).  In addition, recent human health concern about 63 exposures for extended
12     periods has resulted  in the summarization of hourly average concentrations of O3 in terms of
13     4- to 8-h daily maximum concentrations (see Chapter 7 for further discussion).
14          For vegetation, as indicated in Chapter 5 (Section 5.5), extensive research has focused
15     on identifying indicators  of exposure with a firm foundation on biological principles. Many
16     of these indicators have been based on research results indicating that the  magnitude of
17     vegetation responses to air pollution is determined more as a function of the magnitude of the
18     concentration than the length of the exposure  (U.S. Environmental Protection Agency,
19     1986b; U.S. Environmental Protection Agency, 1992b).  Short-term,  high concentration
20     O3 exposures have been identified by many researchers as being more important than
21     long-term, low concentration exposures for induction of effects on vegetation (see Chapter 5
22     for further discussion). Similarly, for human health considerations, results using controlled
23     human exposures  have shown the possible importance of concentration in relation to duration
24     of exposure and ventilation rate.  The product of O3 concentration multiplied by exposure
25     duration was shown to be an imprecise indicator of O3 toxicity when the rate of O3
26     inhalation was increased (DeLucia et al., 1978).  Folinsbee et al. (1978) and Silverman et al.
27     (1976) observed that O3  toxicity was better represented by an effective dose expressed as the
28     product of concentration, exposure duration, and ventilation. Adams et al. (1981) examined
29     the effective dose concept and concluded that O3 concentration was of greater importance in
30     affecting pulmonary function decrement than  either ventilation or exposure duration.
31     Pulmonary function research results reported  by Hazucha et al.  (1990) have also revealed

       December 1993                           4-4       DRAFT-DO NOT QUOTE OR CITE

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 1     that concentration may be more important than duration.  Horstman et al. (1990) reported
 2     that O3 concentration was slightly more influential than exposure duration for inducing
 3     FEVi o responses.  Lung function modelling results reported by Larsen et al. (1991) appears
 4     to agree with previous reports that concentration is one of the most important components of
 5     exposure and that the higher hourly average concentrations should be weighted differently
 6     than the lower ones.
 7          Long-term average concentrations initially were used to describe O^ exposures when
 8     assessing vegetation effects (Heck et al., 1982).  However, as evidence began to mount that
 9     higher concentrations of O3 should be given more weight than lower concentrations (see
10     Section 5.5 for further details), the following specific concerns about the use of a long-term
11     average to summarize exposures of Qs began appearing in the literature:  (1) the use of a
12     long-term average failed to consider the impact of peak concentrations, as well as duration;
13     (2) a large number of hourly distributions within a 7-h (0900 to 1559 h) window could be
14     used to generate the same 7-h seasonal mean;  and (3) high hourly average concentrations
15     (e.g., values greater than 0.10 ppm) occurred outside of a fixed 7-h window.
16          In summarizing the hourly average concentrations in this chapter, specific attention is
17     given to the relevance of the exposure indicators used. For  example, for human health
18     considerations, concentration (or exposure)  indicators such as the daily maximum 1-h average
19     concentrations, as well as the number of daily maximum 4-h or 8-h average concentrations
20     are used to characterize information hi the population-oriented locations. For vegetation,
21     several different types of exposure indicators are used. For example, much of the National
22     Crop Loss Assessment Network (NCLAN)  exposure information is summarized in terms of
23     the 7-h  average concentrations.  However, because peak-weighted, cumulative indicators
24     (i.e., exposure parameters that sum the products of hourly average concentrations multiplied
25     by time over an exposure period) have shown considerable promise in relating exposure and
26     vegetation response (see Section 5,5), several exposure indicators that use either a threshold
27     or a sigmoidally weighting scheme are used in this chapter to provide insight concerning the
28     O3 exposures that are experienced at a select  number of rural monitoring sites in the United
29     States.  The peak-weighted cumulative exposure indicators used in this chapter are SUM06
30     (the sum of all hourly average  concentrations equal to or greater than 0.06 ppm), SUM08
31     (the sum of all hourly average  concentrations equal to or greater than 0.08 ppm), and W126

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 1     (the sum of the hourly average concentrations that have been weighted according to a
 2     sigmoid function [see Lefohn and Runeckles, 1987] that is theoretically based on a
 3     hypothetical vegetation response) are used.
 4          The exposure indicators used for human health considerations are in concentration units
 5     (i.e., ppm), whereas the indicators used for vegetation are in both ppm (e.g., 7-h seasonal
 6     average concentrations) and ppm-h (e.g., SUM06, SUM08, and W126).  The magnitude of
 7     the peak-weighted cumulative indicators at specific sites can be compared with those values
 8     experienced at pristine areas. In some cases, to provide more detailed information about the
 9     distribution patterns for specific O3 exposure regime, the percentUe distribution of the hourly
10     average concentrations (in units of ppm) is given. For further clarification of the
11     determination and rationale for the exposure indicators that are used for assessing human
12     health and vegetation effects, the reader is encouraged to read Chapters 5 (Section 5.5)
13     and 7.
14
15     4.1.2   The Identification and Use of Existing Ambient Ozone Data
16          Information is readily available from the database supported by a network of monitoring
17     stations that were established to determine the compliance with the National Ambient Air
18     Quality Standard for O3.  Most of the data presented in this chapter were obtained from data
19     stored in the EPA's computerized Aerometric Information Retrieval System (AERS) and were
20     collected after 1978.  As pointed out in the previous criteria document for  O3 and other
21     photochemical oxidants (U.S. Environmental Protection Agency, 1986a), there was some
22     difficulty in interpreting the Og data obtained at most  sites across the United States prior to
23     1979 because of calibration problems.
24          In the United States,  O3 hourly average concentrations are routinely monitored through
25     the National Air Monitoring Network, consisting of three types of sites. The National Air
26     Monitoring Station (NAMS) sites are located in areas where the concentrations of O$  and
27     subsequent potential human exposures are expected to be high.  Criteria for these sites have
28     been established by regulation to meet uniform standards of siting, quality  assurance,
 29     equivalent analytical  methodology, sampling intervals, and instrument selection to assure
 30     consistency among the reporting agencies.  For O3, NAMS sites are located only in urban
 31     areas with populations exceeding 1  million.  The other two types of sites are States and Local

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 1     Air Monitoring Stations (SLAMS) and Special Purpose Monitors, which meet the same rigid
 2     criteria for the NAMS sites out may be located in areas which do not necessarily experience
 3     high concentrations in populated areas.
 4          For O3, the reporting interval is 1 h, with the instruments operating continuously and
 5     producing an integrated hourly average measurement.  In many cases, the U.S.
 6     Environmental Protection Agency summarizes air quality data by an 03 "season."  Table 4-1
 7     summarizes the O3 "season" for the various states in the United States.
 8          In this chapter,  data are analyzed for the purpose of providing focus on specific issues
 9     of exposure-response relationships that are considered in later effects chapters.  The  analyses
10     proceed from a national picture of peak annual averages in Metropolitan Statistical Areas,
11     through national 10-year and 3-year trends, to characteristic seasonal and diurnal patterns at
12     selected stations, and a brief examination of the incidence of episodic 1-h levels.  Although
13     there are O3 data collected from  monitoring stations not listed in AIRS, the major source of
14     information was derived from ambient air concentrations from monitoring sites operated by
IS     the State and local air pollution agencies who report their data to AIRS.  Because
16     meteorology affects the identification of trends, methodologies which adjust for meteorology
17     are described.
IS          To obtain a better understanding of the potential for ambient O3 exposures to affect
19     human health and vegetation, hourly average concentration information was summarized for
20     urban versus rural (forested and agricultural) areas in the United States.  A land use
21     characterization of "rural" does not imply that any specific location is isolated from
22     anthropogenic influences.  For example, Logan (1989) has noted that hourly average
23     03 concentrations above 0.08 ppm are common in rural areas of the eastern United  States in
24     spring and summer, but are unusual at remote western sites.  Consequently, for comparing
25     exposure regimes that may be characteristic of clean locations in the United States with those
26     that are urban influenced (i.e., located in either urban or rural locations), this chapter
27     characterizes data collected from those stations whose locations appear to be isolated from
28     large-scale anthropogenic  influences.
29          For the most part, research on O^ concentrations is clearly divided between ambient air
30     environments and indoor air environments, although some exposure studies use personal
31     monitors to measure continuous  O3 concentrations in both situations. Long-term

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         TABLE 4-1. OZONE MONITORING SEASON BY STATE
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
D.C.
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
aAQCR numbers 4,
bAQCR numbers 1,
Begin
March
April
January
March
January
March
April
April
April
January
March
January
April
April
April
April
April
April
January
April
April
April
April
April
March
April
5, 7, 10, and
2, 3, 6, 8, 9,
End
November
October
December
November
December
September
October
October
October
December
November
December
October
October
October
October
October
October
December
October
October
October
October
October
November
October
n.
and 12.
State
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texasa
Texasb
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming

J3egin
June
April
January
April
April
January
April
April
May
April
March
April
April
April
April
June
April
January
March
May
April
April
April
April
April
April

End
September
October
December
October
October
December
October
October
September
October
November
October
October
October
October
September
October
December
October
September
October
October
October
October
October
October

December 1993
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       (multiple-year) patterns and trends are available only from stationary ambient monitors; data
 1     on indoor concentrations are collected predominantly in selected settings during
 2     comparatively short-term studies. Data from the indoor and outdoor environments are
 3     reviewed here independently.
 4
 5
 6     4.2   TRENDS IN OZONE CONCENTRATIONS
 7     4.2.1   Trends in Ambient Ozone Concentrations
 8          Ozone concentrations and thus, exposure, change from year to year.  Ambient trends
 9     during the 1980s were heavily influenced by varying meteorological conditions (U.S.
10     Environmental Protection Agency, 1993).  High Og levels occurred in 1983 and 1988 in
11     some areas of the United States.  These levels were more than likely attributable in part to
12     hot, dry, stagnant conditions.  However, 03 levels in  1992 were the lowest of the 1983 to
13     1992 period (U.S. Environmental Protection Agency,  1993).  These low levels may have
14     been due to less favorable meteorological conditions for O3 formation,  as well as recently
15     implemented control measures.  Nationally, the summer of 1992 was the third coolest
16     summer on record (U.S. Environmental Protection Agency, 1993). The U.S. EPA (1993)
17     has recently reported a 21 % improvement in Oj levels between 1983 and 1992, which in part
18     may be attributed to relatively high levels in 1983, compared to the low Qj exposure year
19     from the period 1989 through 1992. However, new statistical techniques accounting for
20     meteorological influences have been used by the U.S. EPA and they appear to suggest an
21     improvement (independent of meteorological considerations) of 10% for the 10-year period,
22     1983 to 1992.
23          The  U.S. Environmental Protection Agency summarizes trends for the National
24     Ambient Air Quality Standards  (NAAQS) for the most current 3- and 10-year periods.
25     In order to be included in the 10-year trend analysis in the annual National Air Quality and
26     Emissions Trend Report (U.S. Environmental Protection Agency, 1993) a station must report
27     valid data for at least eight of the last ten years.  A companion analysis of the most recent
28     three years requires valid data in all three years. Analysis in the above report covers the
29     periods  1983 to 1992 and 1990 to 1992, respectively; 509 sites met the 10-year period


       December 1993                          4.9       DRAFT-DO NOT QUOTE OR CITE

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 1     criteria, 672 sites are included in the 1990 to 1992 data base.  The NAMS sites comprise
 2     196 of the long-term trends sites and 222 of the sites in the 3-year data base.
 3          Figure 4-1 displays the 10-year composite average trend for the second highest daily
 4     maximum hourly average concentration during the O^ season for the 509 trend sites and the
 5     subset of 196 NAMS sites. The 1992 composite average for the 509 trend sites is 21 %
 6     lower than the 1983 average and 20% lower for the subset of 196 NAMS sites. The 1992
 7     value is the lowest composite average of the past ten years (U.S. Environmental Protection
 8     Agency, 1993). The 1992 composite average is significantly less than all the previous nine
 9     years,  1983 to 1991.  As discussed in U.S. EPA (1992a), the relatively high
10     O3 concentrations in 1983 and 1988 were likely attributable in part to hot, dry stagnant
11     conditions in some  areas of the country that were especially conducive to O3 formation.





p
t
c
o
1
I




vs. 10
0.16-
0.14-

04 O
.If.
0.10-


0.08-
0.06-
0.04

0.02-
nnn



^SiL ''.3J^lx.
^^**«<3p"— *.- .--ii^'^V NAAQS
* "1 	 	 £•§— •*" •5k
1 	 ~f*-| 	 :^""--~~^_




A All Sites (509) • NAMS Sites (196)



                       1983   1984  1985  1986   1987  1988  1989   1990  1991  1992

        Figure 4-1. National trend in the composite average of the second highest maximum
                   1-h ozone concentration at both NAMS and all sites with 95% confidence
                   intervals, 1982 to 1991.
        Source: U.S. Environmental Protection Agency (1993).
        December 1993
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DRAFT-DO NOT QUOTE OR CITE

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 1          Between 1991  and 1992, the composite mean of the second highest daily maximum
 2      1-h O3 concentrations decreased 7% at the 672 sites and 6% at the subset of 222 NAMS
 3      sites.  Between 1991 and 1992, the composite average of the number of estimated
 4      exceedances of the O3 standard decreased by 23% at the 672 sites, and 19% for me
 5      222 NAMS sites. Nationwide VOC emissions decreased 3% between 1991 and 1992 (U.S.
 6      Environmental Protection Agency, 1993),
 7          The composite average of the second daily maximum concentrations decreased in eight
 8      of the ten EPA Regions between 1991 and 1992, and remained unchanged in Region vn.
 9      Except for Region vn, the 1992 regional composite means are lower than the corresponding
10      1990 levels.
11          Investigators have explored methods for investigating techniques for adjusting Q3 trends
12      for meteorological influences (Stoeckenius and Hudischewskyj,  1990; Wakim, 1990; Shively,
13      1991; Korsog and Wolff, 1991; Lloyd et al., 1990; Davidson, 1993; Cox and Chu, 1993).
14     Stoeckenius and Hudischewskyj (1990) used a classification method to group days into
15      categories according to the magnitude of O3 and similarity of meteorological conditions
16     within each defined group. Adjusted 63 statistics for each year were computed from the
17     meteorologically grouped data and the yearly frequency of occurrence of each group relative
18     to its  long-term frequency was described.  Wakim (1990) used standard regression analysis to
19     quantify the effect of daily meteorology on 63. Adjusted O3 statistics were calculated by
20     adding the expected O3 statistic for a year with typical meteorology to the average of the
21     regression residuals obtained for the adjusted year.  Shively (1991) described a model in
22     which the frequency of exceedance of various 03 thresholds was modeled as a  non-
23     homogeneous Poisson process where the parameter is a function of time and meteorological
24     variables. Kolaz and Swinford (1990) categorized 03 days as "conducive" or "non-
25     conducive" based on selected meteorological conditions within the Chicago area.  Within
26     these  categories, the meteorological intensity of days conducive to daily exceedances of the
27     NAAQS for O3 was calculated and used to establish  long-term  trends in the annual
28     exceedance rate.
29           Recently,  Cox and Chu (1993) have modeled the daily maximum 03 concentration
30     using a Weibull distribution with a fixed shape parameter and a scale parameter, the
31     logarithm of which varies as a linear function of several meteorological variables and a

       December 1993                         4-11      DRAFT-DO NOT QUOTE OR CITE

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 1      yearly index.  The authors tested for a statistically significant trend term to determine if an
 2      underlying meteorologically adjusted trend could be detected. Overall the measured and
 3      modeled predicted percentiles tracked closely in the northern latitudes but performed less
 4     well in southern coastal and desert areas.  The results suggested that meteorologically
 5      adjusted upper percentiles of the distribution of daily maximum 1-h O3 are decreasing  in
 6     most urban areas over the period 1981 through 1991.  The median rate of change was
 7      —1.1% per year, indicating that 03 levels have decreased approximately 11 % over this time
 8     period.  The authors reported that trends estimated by ignoring the meteorological component
 9     appear to  underestimate the rate of improvement in Qj primarily because of the uneven year-
10     to-year distribution of meteorological conditions  favorable to Oj formation.
11           Lefohn et al. (1993a) focused on a potentially useful method for identifying monitoring
12     sites whose improvement in Qj exposures may be attributed more to  the implementation of
13     abatement control strategies than meteorological changes.  As has been pointed out
14     previously, meteorology plays an important role in affecting the O3 concentrations that are
IS     contained in the tail of the 1-h distributions, as indicated by the successful predictive
16     application of the exponential-tail model to distributions (California Air Resources Board,
17     1992),  Because meteorology plays such an important role in affecting the tail of the 1-h
18     distribution at a specific site, changes in "attainment" status would be expected not to affect
19     changes in the entire distribution pattern and thus, the average diurnal pattern.  Lefohn et al.
20     (1993b) investigated the change in the annual averaged diurnal pattern as changes in
21     O3 levels occurred.  The authors reported that although the  amplitude of the diurnal patterns
22     changed,  there was little evidence for consistent changes in  the shape of the annual diurnal
23     patterns (Figure 4-2). In a follow-up to this analysis, Lefohn et al. (1993a) reported that
24     25 of the 36 sites that changed compliance status across years  showed no statistically
25     significant change in the shape of the average diurnal profile (averaged by Qj season).
26     In addition, the authors  reported that for 71 % (10 out of 14) of the sites in southern
27     California and Dallas-Fort Worth, Texas, that showed improvement  in 03 levels (i.e.,
28     reductions in  the number of exceedances over the years), but still remained in
29      "nonattainment," a statistically significant change in the shape of the seasonally averaged
30      diurnal profile occurred (Figure 4-3). Thus, the authors noted that for the southern
31      California and Dallas-Fort Worth sites, which showed improvements in O3 levels, changes

        December 1993                           4-12      DRAFT-DO NOT QUOTE OR CITE

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                          Annual
              1  3 5 7  9 11  13 15 17 19 21 23
                  -1987 -»-1988--*-1989
                                 -1990
           0.08 1
                 Louisville, KY
                    Annual
               1  3  5  7 9 11 13 15 17 19 21 23
                  -1987 -*-1988 -e-1989
                                 -1990
                                                              Annual
                                                   1  3  57 9  11 13 15 17 19 21 23
     -1987 -«-198B -0-1989
-1990
         Dade Co., FL
   (d)      Annual
                                                         1  3 57  9 11  13 15 17 19 21 23
     -1987-^1988 -0-1989
-1990
      Figure 4-2.  The annually averaged composite diurnal curves for the following sites that
                  changed from nonattainment to "attainment status:" (a) Montgomery
                  County, AL, (b) Concord, CA, (c) Louisville, KY, and (d) Dade County,
                  FL for the period 1987 to 1990. The darkened curve in each figure
                  identified the year in which the greatest number of daily maximum 4-h
                  average concentrations ^0.08 ppm occurred.
      Source:  Lefohn et al. (1993b).
1
2
3
4
5
6
7
were observed in the seasonally averaged diurnal profiles, while for the sites moving between
"attainment" and "nonattainment" status, such a change in shape was generally not observed.
Lefohn et al. (1993a) pointed out that it was possible that meteorology played a more
important role in affecting attainment status than changes in emission levels.
     Historically, the long-term O3 trends in the United States characterized by the U.S.
Environmental Protection Agency have emphasized air quality statistics that are closely
      December 1993
                                        4-13
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          0.08
                 3  57  911 1'3 1'5  17  1'9 2?1
                               Hour
                    1980-*-  1981-0-  1990  -^  1991
19BO  19&2  10&4  19'86  1968  1990
             Year
      Figure 4-3.  A summary of the (a) seasonal (January to December) averaged composite
                  ozone diurnal curve and (b) integrated exposure W126 index for the
                  Los Angeles, CA site for the period 1980 to 1991.
      Source: Lefbhn et al. (1993a).
 1      related to tile NAAQS.  A recent report by the National Academy of Sciences (NAS) (NRC,
 2      1991) stated that the principal measure currently used to assess 03 trends is highly sensitive
 3      to meteorological fluctuations and is not a reliable measure of progress in reducing O3 over
 4      several years for a given area.  The NAS report recommended that "more statistically robust
 5      methods be developed to assist in tracking progress in reducing ozone."  The NAS report
 6      points out that most of the trends analyses are developed from violations of standards based
 7      on lower concentration cutoffs or using percentile distributions. Because of the interest by
 8      the EPA in tracking trends in the quality of air people breathe when outdoors, most of the
 9      above measures have some association with the existing NAAQS, in the form of either
10      threshold violations or O3 concentrations.
11           Several of the alternative examples provided in the NAS report were described
12      previously by Curran and Frank (1990).  Several of the examples mentioned  in the NAS
13     report involved threshold violations:  the number of days on which the maximum
14     O3 concentration was above  0.12 ppm (Jones et al., 1989; Kolaz and Swinford, 1990;
15     Wakiin, 1990); the number of times during the year that the daily summary statistics
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 1      exceeded 0.08 ppm or 0.105 ppm (Stoeckenius, 1990); and the number of days in California
 2     when the O3 concentration exceeded 0,20 ppm (Zeldin et al.,  1990).  Several other
 3     O3 concentration measures are described in the NAS (NRC, 1991) report.
 4          As an alternative to the way in which the U.S. EPA historically implemented its trends
 5     analysis, the EPA (1992a) used percentiles in the range from 50th percentile (or median) to
 6     the 95th percentile.  The U.S. EPA (1992a) reported that the pattern for the 10-year trends
 7     (1982 to 1991) using the various alternative O3 summary statistics were somewhat similar,
 8     There was a tendency for the curves to become flatter in the lower percentiles. The peak
 9     years of 1983 and 1988 were still evident in the trend lines for each indicator.  The increase
10     of 8% recorded in the annual second-highest daily maximum 1-h concentration between 1987
11     and 1988 was also seen in the 95th and 90th percentile concentrations.  The lower percentite
12     indicators had smaller increases of 3 to 4%.  The percent change between 1982 and 1991 for
13     each of the summary statistics follows: annual daily maximum  1-h concentration (—11 %),
14     annual second daily maximum 1-h concentration (-8%), 95th percentile of the daily
15     maximum 1-h concentrations (-5%),  90th percentile (-4%), 70th percentile (-1%), 50th
16     percentile, or median of the daily maximum 1-h concentrations  (+1 %), and the annual mean
17     of the daily maximum 1-h concentrations (-1 %).
18          Besides the U.S. Environmental Protection Agency, additional investigators have
19     assessed trends at several locations in the United States (e.g., Kuntasal and Chang,  1987),
20     (Gallopoulos et al.,  1988; Korsog and Wolff,  1991; Lloyd et al., 1990; Rao et al.,  1992;
21     Davidson, 1993). For example, Kuntasal and Chang (1987) performed a basin-wide air
22     quality trend analysis for the South Coast Air Basin of California using multi-station
23     composite daily maximum-hour average ambient concentrations for the third quarter from
24     1968 to 1985.  Basin-wide ambient Oj concentrations appeared to show  downward  trends for
25     the period 1970 to 1985, but because of high fluctuations, it was difficult to delineate trends
26     for shorter periods. The meteorology (850 mb temperature)-adjusted O3 showed a  more
27     consistent downward trend than did unadjusted O3.  Korsog and Wolff (1991) examined
28     trends from 1973 to 1983 at eight major population centers in the northeastern United States,
29     using a robust statistical method.  The 75th percentile was shown to be a good statistic for
30     determining trends and was used for analysis  of the trends.  The surface temperature and
31     upper air temperature variables were  found to be the best predictors of (>3 behavior.  Two

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 1      regression procedures were performed to remove the variability of meteorological conditions
 2      conducive to high O3 (i.e,, O3 concentrations  >0.08 ppm).  The results of the analysis
 3      showed that there has been a decrease of a few ppb on a yearly basis for the majority of the
 4     sites investigated by the authors.
 5           Lloyd et al. (1989) investigated the improvement in 03 air quality from 1976 to 1987 in
 6     the South Coast Air Basin of California. The authors reported that when the trend in total
 7     exceedance hours of a consistent set of Basin air monitoring stations was considered, the
 8      "improvement over the period of investigation was substantial.  The authors reported that the
 9     number of station hours at or above the Stage I Episode Level (0.20 ppm, 1-h average) had
10     decreased by about two-thirds  over the period 1976 to 1987.  Davidson (1993) reported on
11      the number of days on which O3 concentrations at one or more stations in the South Coast
12     Air Basin exceeded the federal standard and the number of days reaching Stage I episode
13     levels, for the months of May through October in the years from 1976 to 1991.  The author
14     reported that the number of Basin days exceeding the federal standard declined at an average
15     annual rate of 2.27 days per year over the period.  In addition, the number of Basin days
16     with Stage I episodes declined at an average annual rate of 4.70 days per year over the
17     period 1976 to 1991.  Rao et al. (1992) demonstrated the use of some statistical methods for
18     examining trends in ambient O3 air quality downwind of major urban areas.  The authors
19     examined daily maximum 1-h O3 concentrations measured over New Jersey, metropolitan
20     New York City, and Connecticut for the period 1980 to 1989. The analyses indicated that
21     although there has been  an improvement in O3 air quality downwind of New York City,
22     there has been little change in O3 levels upwind of New York City during this 10-year
23     period.
24          Lefhon and Runeckles (1987) proposed a sigmoidal weighting function that was used in
25     developing a cumulative integrated exposure index (W126):
26
                                     w  =  	*   .  .   ,                         (4-1)
                                           [1  + M x  exp('A x **}
 27      where:     M and  A are positive arbitrary constants,
 28                 Wj = weighting factor for concentration i, and
 29                 Cj = concentration i.

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 1      Lefohn et al. (1988) reported the use of the sigmoidally weighted index with constants,
 2      M and A, 4,403 and 126 ppm , respectively. The authors referred to the index as W126.
 3      The values were subjectively determined to develop a weighting function that (1) included
 4      hourly average concentrations as low as 0.04 ppm, (2)  had an inflection point near
 5      0.065 ppm, and (3) had an equal weighting of 1 for hourly average concentrations at
 6      approximately 0.10 ppm and above.  To determine the value of the index, the sigmoidal
 7      weighting function at CL was multiplied by the hourly average concentration, Cj,  and summed
 8      over all relevant hours. The index included the lower, less biologically effective
 9      concentrations in the integrated exposure summation.  The weighting function has been used
10     to describe the relationship between 03 exposure and vegetation response (e.g., Lefohn
11      et al., 1988; Lefohn et al., 1992a).
12          Lefohn and Shadwick (1991), using the W126 sigmoidally weighted exposure index,
13     assessed trends in O3 exposures at rural sites in me United States over 5- and 10-year periods
14     (1984 to 1988 and 1979 to 1988, respectively) for forestry and  agricultural regions of the
15     United States.  Although their analysis did not explore the effects on trends of the lower
16     O3 exposure period 1989 to 1992, their analysis did  reflect the  effect of the higher
17     03 exposure years (1983 and 1988).  To compare the exposure index values  across years,  a
18     correction for missing data was applied for each pollutant. The corrections were determined
19     for each site on a monthly basis.  The Kendall's K statistic (Mann-Kendall test)  was used to
20     identify linear trends.  Estimates of the rate of change (slope) for the index were calculated.
21     Table 4-2 summarizes the results of the analysis.  For sites distributed by forestry regions,
22     there were more positive than negative slope estimates for the 5-year analysis of sites in the
23     Southern, Midwest, and Mid-Atlantic regions.  For the 10-year analysis, the above was true
24     except for the Mid-Atlantic seasonal analysis, where there was  one positive and one negative
25     significant trend. In the Southern region, 38%  of the sites showed significant trends.  For the
26     sites in the Northeastern region, few sites showed a significant  trend.  There were
27     considerably fewer sites in the remaining regions than in the four forestry  regions above.
28     Hence, for these regions, no significance was assigned to the differences in the  number of
29     negative and positive slope estimates in the tables.  Similar to the results reported for the
30     forestry regions, most of the sites in the agricultural regions showed no Oj trends.
        December 1993                          4.17      DRAFT-DO NOT OTTOTR OP rim?

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 TABLE 4-2.  SUMMARY BY FORESTRY AND AGRICULTURAL REGIONS FOR
 OZONE TRENDS USING THE W126 EXPOSURE PARAMETER ACCUMULATED
                        ON A SEASONAL BASIS8
Forestry
Five- Year Trends
Not Significant

South
Midwest
West
Pacific
Northwest
Plains
Northeast
Mid-Atlantic
Rocky
Mountains
All

Pacific
Mountain
Northern
Plains
Lake States
Cora Belt
Northeast
Appalachian
Southeast
Delta State
Southeastern
Plains
All

53
38
10
4
3
14
12
5
139


Not
14
5
3
10
20
26
27
16
9
9
139

(16)
(1)
(0)
(2)
(0)
(0)
(0)
(2)
(21)

Five-Year
Significant
(2)
(2)
(0)
(0)
(1)
(0)
(9)
(5)
(0)
(2)
(21)
Significant
-
0
0
0
0
0
1
0
0
1

Trends
+
14
7
3
0
0
0
3
1
28
Agricultural

Significant
-
0
0
0
0
0
1
0
0
0
0
1
+
3
1
0
1
3
3
14
1
2
0
28
Ten- Year Trends
Not Significant

13
20
4
2
2
7
4
2
54

Ten-Year
Not Significant

6
2
2
5
11
11
8
4
4
1
54
Significant
-
1
1
2
0
0
1
1
0
6

Trends
+
7
6
1
0
0
1
1
1
17


Significant
-
2
0
0
0
1
2
0
1
0
0
6
+
1
1
0
1
2
2
8
0
1
1
17
aNumbers in parentheses in the "Not Significant" column under "Five-year trends" are the number of sites with
 exactly 3 years of data.
Source: Lefhon and Shadwick, 1991.
December 1993
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 1     However, in the Appalachian agricultural region, as many as 50% of the sites showed a
 2     pronounced indication of a trend.  A predominance of positive significant trends for both the
 3     5- and 10-year analyses was observed. In the other agricultural regions, there were
 4     approximately an equal number of positive and negative significant 5- and 10-year trends.
 5     The O3 results produced patterns that were not pronounced enough to draw more than
 6     tentative conclusions for the 10-year analysis.  For the 5-year analysis, there was still not a
 7     strong indication of an O3 trend.  However, when significant trends were observed, they
 8     were almost always positive.  This can be attributed to eastern O3 levels that were  generally
 9     higher in 1988 than in previous years.
10
11
12     4.3   SURFACE OZONE CONCENTRATIONS
13     4.3.1   Introduction
14          Ozone is an omnipresent compound that is measured at levels above the minimum
15     detectable level at all monitoring locations in the world (Lefohn et al., 1990b).  Stratospheric
16     sources of O3 play an important role in determining the O3 concentrations at remote  sites that
17     are isolated from either local generation of O3 or the transport of 03 or its precursors (Singh
18     et al., 1978).  The occasional occurrence of stratospheric injection of O3, at specific  times
19     and in certain locations, is accepted and may be responsible for some of the rare occurrences
20     of elevated levels that have been observed at both some high- and low-elevation remote sites.
21     Altshuller (1989) attributes approximately 10 ppb of surface-level Q^ concentration to
22     stratospheric intrusion.
23          For purposes of comparing how Oj levels have changed over time, it would be
24     interesting to know how current levels compare to natural background levels.  However,
25     estimations of natural background O3 concentrations are  difficult to make.  The definitions of
26     natural background and use of the information are subject to much uncertainty. It is
27     difficult, if not impossible, to determine whether any geographic location on Earth is free
28     from human influence (Finlayson-Pitts and Pitts, 1986).  Finlayson-Pitts and Pitts (1986)
29     have noted that photochemical production via naturally occurring NOX-NMOC (non-methane
30     organic compounds) or carbon monoxide reactions in sunlight may be more important than
31     injection of O3 from the stratosphere.  Natural emissions can influence O3 exposures

       December 1993                          4-19      DRAFT-DO NOT QUOTE OR CITE

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 1     observed at remote sites (Chameides et al., 1988; Zimmerman, 1979; Trainer et al,, 1987).
 2     Citing indirect evidence for the possible importance of natural emissions, Lindsay et al.
 3     (1989) have emphasized that additional research is required to assess the role that natural
 4     hydrocarbons might play in urban and regional O3 episodes.
 5          Ozone concentrations at a specific location are influenced by local emissions and by
 6     long-range transport from  both natural and anthropogenic sources.  In addition, levels are
 7     also influenced by variables such as wind, solar insolation, vertical exchange rates, and the
 8     nature of the surface.  For a more complete discussion,  see Chapter 3.
 9          It is possible for urban emissions, as well as O3 produced from urban area emissions,
10     to be transported  to more  rural downwind locations.  This can result in elevated
11     O3 concentrations at considerable distances from urban centers (Wolff et al., 1977; Husar
12     et al., 1977; Wight et al.,  1978;  Vukovich et al.,  1977; Wolff and Lioy, 1980; Pratt et al.
13     1983; Logan,  1985; Altshuller, 1986; U.S. Environmental Protection Agency, 1986a; Kelly
14     et al., 1986; Pinkerton and Lefohn, 1986; Lefohn et al., 1987a; Logan, 1989; Lefohn and
15     Lucier, 1991; Taylor and  Hanson, 1992).  For example, on over 40%  of the 98 days that the
16     maximum 1-h O3 concentrations exceeded 0.120 ppm, the highest value was measured
17     downwind of St.  Louis at  one of the rural sites, which was located approximately 50 km
18     from downtown St. Louis (Altshuller, 1986). Urban O3 concentration values are often
19     depressed because of titration by nitric oxide (Stasiuk and Coffey,  1974). Reagan (1984) and
20     Lefohn et al. (1987a) have observed this phenomenon where Oj exposures at center-city sites
21     were lower than  some rural locations. Because of the absence of chemical scavenging,
22     O3 tends to persist longer in  nonurban than in  urban areas (U.S. Environmental Protection
23     Agency, 1986a; Coffey et al., 1977; Wolff et al., 1977; Isaksen et al., 1978).
24           The distribution of O3 or its precursors at a rural  site near an urban source is affected
25     by wind direction (i.e., whether the rural site is located up- or down-wind from the source)
26      (Kelly et al.,  1986; Lindsay and Chameides, 1988).  Thus, it may be difficult to apply land-
27     use designations  to the generalization of exposure regimes that may be experienced in urban
28     versus rural areas.  Because  of this, it is difficult to identify a set of unique Oj distribution
29      patterns that adequately describe exposures experienced at monitoring  sites in rural locations
30      (Lefohn et al., 1990a).
 31

        December 1993                           4-20       DRAFT-DO NOT QUOTE OR CITE

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1     4.3.2   Urban Area Concentrations
2          Figure 4-4 shows the highest second daily maximum 1-h average O3 concentrations in
3     1991 across the United States. The highest second daily maximum 1-h O3 concentrations by
4     Metropolitan Statistical Area (MSA) for the years 1989 to 1991 are summarized in
5     Table 4-3.  The highest O3 concentrations are observed in southern California, but high
6     levels also persist in the Texas Gulf Coast, Northeast corridor and other heavily populated
7     regions in the United States.
       Figure 4-4. United States map of the highest second daily maximum 1-h average ozone
                  concentration by Metropolitan Statistical Area, 1991.
       Source: U.S. Environmental Protection Agency (1992a),
 1          Lefohn (1992a) reported that for many urban sites that experience high second daily
 2     maximum 1-h average values (i.e, > 0.125 ppm), most are associated with a few episodes.
 3     Monitoring sites in polluted regions tend to experience frequent hourly average
 4     O3 concentrations at or near minimum detectable levels and high O^ concentrations.  The
 5     percentile summary information for some of these sites shows that although some of the
 6     highest hourly average concentrations occur at these locations, their occurrence is infrequent
 7     (Table 4-4).  For example, O3 monitoring sites at Delmar (CA), Stratford (CT), Madison
 8     (CT), Baton Rouge (LA), Bayonne (NJ), New York (NY), Babylon (NY), Harris County
       December 1993                          4-21      DRAFT-DO NOT QUOTE OR CITE

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   TABLE 4-3.  THE HIGHEST SECOND DAILY MAXIMUM ONE-HOUR OZONE
     CONCENTRATION BY METROPOLITAN STATISTICAL AREA (MSA) FOR
                                     THE YEARS 1989 TO  1991
                                             (Unite are ppm)
MSA
                                      1989  1990  1991
                    MSA
                                                         1989  1990  1991
Akron, OH
Albany-Schenectady-Troy, NY
Albuquerque, NM
Alientown-Bethlehem, PA-NJ
Altoona,PA
Anaheim-Santa Ana, CA
Anderson, IN
Anderson, SC
AnnArhor, Ml
               NeeiMh, WI
Asheville, NC
Atlanta, GA
Atlantic City, NJ
Augusta. GA-SC
Aurora-Elgin, IL
Austin, TX
Bakersfield, CA
Baltimore, MD
Baton Rouge, LA
Beaumont-Port Arthur, TX
Beaver County, PA
Bellingham, WA
Benton Harbor, MI
Bergen-Passaic, Nl
Billings, MT
Birmingham, AL
Boston, MA
Boulder-Longmont, CO
Bradenton, FL
Brazoria, TX
Bridgeport-Milford, CT
Brockton, MA
 Buffalo, NY
 Canton, OH
 Cedar Rapids, LA
 Champaign-Urbana-Rantoul, IL
 Charleston, SC
 Charleston, WV
 Chartotte-Gattonia-RockHill, NC-SC
 Chattanooga, TN-GA
 Chicago, IL
 Chico, CA
 Cincinnati, OH-KY-IN
 Cleveland, OH
 Colorado Springs, CO
 Columbia, SC
 Columbus, GA-AL
 Columbus, OH
 Corpus Christi, TX
 Cumberland, MD-WV
 Dallas, TX
 Danbury, CT
 Davenport-Rock. Island-Moline, 1A-1L
 Dayton-Springfield, OH
0.14   0.11  0.13     Decatur, IL                            0.09   0.09  0.10
0.10   0.11  0.10     Denver, CO                            0.11   0.11  0.11
0.10   0.10  0.09     DesMoines, IA                         0,08   0.07  0.07
0.10   0.11  0.12     Detroit, MI                            0.14   0.12  0.13
0.10   0.10  0.11     Duluth, MN-WI                         0.06
0.24   0.21  0.20     Eau Claire, WI                               0.06
0.10                 El Paso, TX                            0.14   0.14  0.13
           0.09     Elmira, NY                            0.09   0.10  0.10
0.10   0.09  0.11     Erie, PA                               0.12   0.10  0.11
0.10   0.08  0.09     Eugene-Springfield, OR                   0.08   0.09  0,09
0.08   0.09  0.08     Evansviile, IN-KY                       0.12   0.11  0.12
0.12   0.15  0.13     Fayetteville, NC                         0.11   0.10  0.10
0.12   0.16  0.14     Flint, MI                              0.10   0.10  0.10
0.10   0.11  0.10     Fort Collins, CO                        0.09   0.10  0.09
0.11   0.09  0.13     Ft. Lauderdale-Hollvwood-Pompano.FL     0.12   0.10  0.10
0.11   0.11  0.10     Fort Myers-Cape Coral, FL               0.10   0.08  0.08
0.16   0.16  0.16     Fort Wayne, IN                         0.12   0.09  0.10
0.13   0.14  0.16     Fort Worth-Arlington, TX                0,13   0.14  0.15
0.16   0.18  0.14     Fresno, CA                            0.15   0.15  0.16
0.15   0.15  0.13     Galveston-TexasCity, TX                0.14  0.15  0.15
0,10   0,10  0.11     Gary-Hammond, IN                     0.11   0.12  0.12
0.05   0.08  0.07     Grand Rapids, MI                       0.13   0.14  0.15
           0.12     Greetey, CO                           0.10  0.11  0.10
0,12  0.13  0.14     Green Bay, WI                         0.09  0.09  0.10
0,08                Greensboro-WinstonSalem-High Point, NC   0.10  0.12  0.11
0.12  0.13  0.11     Greenville-Spartanburg, SC               0.10  0.11  0.11
0.12  0.11  0.13     Hamilton-Middletown, OH                0.11  0.13  0.12
0.11   0.10  0.10     Hanisburg-Lebanon-Catlisle.PA           0.11  0.12  0.11
0.10  0.10  0.10     Hartford,  CT                           0.14  0.15  0.15
      0,15  0.13     Hickory, NC                                 0.09
0.18  0,16  0.15     Honolulu, HI                          0.05  0.05  0.05
0.13  0.12  0.15     Houma-Thibodaux, LA                  0.11  0.12  0,10
0.11  0.11  0.11     Houston, TX                           0.23  0.22  0.20
0.12  0.11  0.12     Hu«ington-A»hUnd,WV-KY-OH          0.12  0.14 0.14
 0,08  0.07  0.08     Himtsville, AL                         0.09  0.09  0.11
 0.09  0.09  0.08     Indianapolis, IN                        0.12  0.11   0.11
 0.09  0.10  0.09     Iowa City, IA                          0.09  0.09  0.06
 0.10  0.12  0.12     Jackson, MS                           0.09  0.10  0.09
 0.13  0.12  0.12     Jacksonville, FL                        0.11  0.11   0.10
 0.11  0.12  0.10     Jamestown-Dunkirk, NY                       0.08  0.10
 0.12  0.11  0.13     Janesville-Beloit, WI                     0.12  0.09  0.11
 0.10  0.12  0.09     Jersey City, NJ                          0.12  0.18  0.14
 0.12  0.15  0.14     Johnson City-Kingsport-Bristol, TN-WV      0.11  0.12  0.12
 0,12  0.12  0.13     Johnstown, PA                          0.10  0.10  0.11
 0.09  0.09  0.09     Joliel, IL                              0.10  0.09  0.12
 0.10  0.11  0.11     Kalamazoo.MI                                    0.08
 0.09  0.11  0,10      Kansas City MO-KS                     0.11  0.11  0.12
 0.11  0.11  0,12     Kenosha, WI                           0.13  0.11  0.15
 0.10  0.10  0.11      Knoxville,TN                          0.10  0.12  0.11
      0.09  0.10      Lafayette, LA                          0.10  0.11  0.08
 0.13  0.14  0,12      Lafayette, IN                           0.09  0.10
 0.13  0.15  0.14      Lake Charles, LA                       0.13  0.13  0.12
 0.11   0.10  0.10     Lake County, IL                        0.13  0.10  0.12
 0.15 0.12  0,12     Lancaster, PA                          0.10  0.10  0.12
 December 1993
                 4-22
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 TABLE 4-3 (cont'd). THE HIGHEST SECOND DAILY MAXIMUM ONE-HOUR
      OZONE CONCENTRATION BY METROPOLITAN STATISTICAL
              AREA (MSA) FOR THE YEARS 1989 TO 1991
                         (Units are ppra)
MSA
Lansing-East Lansing, Ml
La& Cruces, NM
Las Vegas, NV
Lawrence-Haverhm, MA-NH
Lexington-Fayette, KY
Lima, OH
Lincoln, NE
Little Rock-North Little Rock, AR
Longview-Marshall, TX
Lorain-Elyria, OH
Los Angeles-Long Beach, CA
Louisville, KY-1N
Lynchburg, VA
Madiion, WI
Manchester, NH
Medford, OR
Melbourne-Titusville-PalmBay, FL
Memphis, TN-AR-MS
Miami-Hialeah. FL
Middlesex-Somerset-Hunlerdon, NJ
Middletown, CT
Milwaukee, WT
Minneapolis-St. Paul, MN-WI
Mobue, AL
Modesto, CA
Monmouth-Ocean, NJ
Montgomery, AL
Muskegun, Ml
Nashua, NH
Nashville, TN
Nassau-Suffolk, NY
New Bedford, MA
New Haven-Meriden, CT
New London-Norwich, CT-RI
New Orleans, LA
New York, NY
Newark, NJ
Niagara Falls, NY
Norfolk- Virginia Beach-Newport News, VA
Oakland, CA
Oklahoma City, OK
Omaha, NE-1A
Orlando, FL
Owensboro, KY
Oxnard-Ventura, CA
Perkerburg-Marietta, WV-OH
Pascogoula, MS
Pensacola, FL
Peoria, IL
Philadelphia. PA NJ
Phoenix, AZ
Pittsburgh, PA
Pittsfield, MA
Portland, ME
1989 1990 1991
0,10 0.10 0.11
0.11 0.10 0.10
0.11 0.11 0.09
0.12 0.10 0.13
0.11 0.11 0.10
0.10 0.10 0.10
0.06 0,07 0.07
0.09 0,10 0.10
0.10 0.13 0.11
0.12 0.09 0.10
0.33 0.27 0.31
0.11 0.13 0.13
0.10 0.09
0.10 0.08 0.11
0.10 0.10 0.10
0.09 0.10 0.07
0.10 0.09 0.09
0.12 0.12 0.11
0.12 0.11 0.12
0.13 0.15 0.13
0.17 0.16 0.17
0.15 0.13 0.18
0.10 0.10 0.09
0.10 0.11 0.09
0.13 0.12 0.11
0.14 0.14 0.15
0.08 0.10 0.09
0,14 0.13 0.15
0.09 0.10 0.11
0.14 0.13 0.12
0.15 0.14 0.18
0.12 0,13 0.13
0.15 0.16 0.18
0.14 0.16 0.14
0.11 0.11 0.11
0.13 0.16 0.18
0.13 0.13 0.14
0.10 0.10 0.10
0.10 O.U 0.11
0.13 0.12 0.12
0.11 0.11 0.11
0.10 0.08 0.08
0.11 0.12 0.10
0.10 0.11 0.09
0.17 0.15 0.16
0.12 0.11 0.12
0.10 0.11 0.10
0.09 0.12 0.11
0.11 0.09 0.10
0.16 0.14 0.16
0.11 0.14 0.12
0.13 0.11 0.12
0.09 0.11 0.10
0.13 0,13 0.14
MSA
Portland, OR-WA
Portsmoulh-Dover-Rochester, NH-ME
Poughkeepsie, NY
Providence, RI
Provo-Orem, UT
Racine, WI
Raleigh-Duiham, NC
Reading, PA
Redding, CA
Reno, NV
Richmond-Petersburg, VA
Riverside-San Bernardino, CA
Roanoke, VA
Rochester, NY
Rockford, IL
Sacramento, CA
St. Louis, MO-EL
Salinas-Seaside-Monterey, CA
Salt Lake CHy-Ogden, UT
San Antonio, TX
San Diego, CA
Sao Francisco, CA
San Jose, CA
San Juan, PR
Santa Barbara Santa Maria-Lompoc, CA
Santa Cruz, CA
Santa Fe, NM
Santa Rosa-Petaluma, CA
Sarasota, FL
Scranton-Wilkeg-Barre, PA
Seattle, WA
Sharon, PA
Sheboygan, WI
Shreveport, LA
South Bend-Mishawak*, IN
Spokane, WA
Springfield, IL
Springfield, MO
Springfield, MA
Stamford, CT
SteubenviUe-Weirton, OH-WV
Stockton, CA
Syracuse, NY
Tacoma, WA
Tallahassee, FL
Tampa St. Peteraburg-Clearwater, FL
Terre Haute, IN
Toledo, OH
Trenton, NJ
Tucson, AZ
Tulsa, OK
Utica-Rome, NY
Vallejo-Fafafield-Napa, CA
Vancouver, WA
1989 1990 1991
0.09 0.15 0.11
0.11 0.10 0.13
0.08 O.U 0.13
0.13 0.14 0.16
0.11 0.09 0.08
0.14 0.11 0.14
0.11 0.12 0.11
0.11 0.11 0.12
0.09 0.09 0.08
0.10 0.14 0.09
0.11 0.12 0.12
0.28 0.30 0.25
0.10 0.09 0,10
0.11 0.11 0.11
0.10 0.09 0.09
0.14 0.16 0,16
0.13 0.13 0.12
0.11 0.09 0.09
0.15 0.12 0.11
0.11 0,10 0.11
0.19 0.17 0.18
0.09 0.06 0.07
0.13 0.12 0.12
0.06 0.07 0.08
0.16 0.13 0.10
0.08 0.08 0,10
0.05 0.08 0.08
0.10 0.08 0.10
0.10 0.10 0.10
0.11 0.11 0.13
0.09 0,13 0.11
0.11 0.10 0.11
0.11 0.11 0.16
0.12 0,12 0.11
0.10 0.10 0.11
0.07 0.08
0.11 0,10 0.10
0,09 0.08 0.08
0.13 0.12 0.13
0.16 0.14 0.15
0.11 0.09 0.12
0,11 0.12 0.11
0.10 0.11 0.11
0.09 0.13 0.09
0,07 0.05
0.10 0.11 0.11
0.11 0.11 0.10
0.11 0.10 0.12
0.14 0.14 0,15
0.10 0.10 0.09
0.12 0.12 0.12
0.09 0.10 0,10
0.11 0.10 0.11
0.09 0,11 0.10
December 1993
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         TABLE 4-3 (cont'd). THE HIGHEST SECOND DAILY MAXIMUM ONE-HOUR
               OZONE CONCENTRATION BY METROPOLITAN STATISTICAL
                         AREA (MSA) FOR THE YEARS 1989 TO 1991
                                        (Units are ppm)
MSA
Victoria, TX
Vinelund-Millvile-Bridgetori, NJ
Visdia-TuUre-Porterville, CA
Washington, DC-MD-VA
W. Palm Beach-Boca Raton-Delray, FL
Wheeling, WV-OH
Wichita, KS
Williamsport, PA
1989
0,10
0,13
0.15
0.13
0.11
0.11
0.09
0.08
1990
0.07
0.13
0.14
0.13
0.09
0.11
0.10
0.09
1991
0.10
0.12
0.12
0.14
0.09
0.11
0.10
0.10
MSA
Wilmington, DE-NJ-MD
Wilmington, NC
Worcester, MA
York, PA
Youngtfown-Warren, OH
Yuba City, CA
Yuma, AZ
1989
0.
0.
0.
0.
0
13
10
10
.11
.01
1990
0.14
0.09
0.12
0.12
0.10
0.09
0.09
1991
0.15
0.14
0.11
0.12
0.10
0.09
 1      (TX), and Bayside (WI) exhibit maximum hourly average concentrations above 0.125 ppm;
 2      however, only 1 % of the hourly average concentrations generally exceed 0.100 ppm.
 3      Although for human health considerations, the occurrence of a second daily maximum hourly
 4      average concentration is important, the table illustrates the point that, for the sites listed, the
 5      occurrence of high hourly average concentrations is infrequent and that they are associated
 6      with occasional episodes.
 7          As indicated in the Introduction, interest has been expressed  in characterizing
 8      03 exposure regimes for sites experiencing daily maximum 8-h concentrations above specific
 9      thresholds (e.g.,  0.08 or 0.10 ppm).  Table 4-5 summarizes the highest second daily
10      maximum 8-h average O3 concentrations by MSA for the years 1989 to 1991.  The data have
11      been reported for the 03 season as summarized in Table 4-1.  In some cases, high
12     concentrations occur in the fall and winter periods as well as the summertime.  Analyses
13      reported by Rombout et al. (1986, 1989), Berglund et al. (1988),  and Lioy and Dyba (1989)
14     documented the occurrence, at some sites, of multihour periods within a day of 63 at levels
15     of potential health effects.  While most of these analyses were made using monitoring data
16     collected from sites in or near nonattainment areas, the analysis of Berglund et al. (1988)
17     showed that at five  sites, two in New York state, two in rural California, and one in rural
18     Oklahoma, an alternative O3 standard of an 8-h average of 0.10 ppm would be exceeded
 19     even though the existing 1-h standard would not be.  Berglund et  al. (1988) described the
20     occurrence at these five sites,  none of which was in or near a nonattainment area, of
21     O3 concentrations showing only moderate peaks but showing multihour levels above

       December 1993                          4-24      DRAFT-DO NOT QUOTE OR CITE

-------
TABLE 4-4.  SUMMARY OF PERCENTILES OF HOURLY AVERAGE
  CONCENTRATIONS FOR THE APRIL-TO-OCTOBER PERIOD
                    (Units are ppm)
1— »
^O AIRS Site Name
060370016 Glendora, CA


060595001 La Habra, CA


060710005 San Bernardino County, CA


060731001 Del Mar, CA


fa.
^ 090013007 Stratford, CT
Lf\

090093002 Madison, CT
j_j
w
EH 220330003 Baton Rouge, LA
H-j
0
o
2 340170006 Bayonne, NJ
^*n
s
O 360610063 New York, NY
c|
H
Year
1989
1990
1991
1989
1990
1991
1989
1990
1991
1989
1990
1991

1989
1990
1991
1989
1990
1991
1989
1990
1991

1989
1990
1991
1989
1990
1991
Min.
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000

0.001
0.001
0.000
0.001
0.000
0.000
0.000
0.000
0.000

0.001
0.001
0.001
0.000
0.000
0.002
10
0.000
0.000
0.000
0.000
0.000
0.000
0.020
0.020
0.020
0.020
0.020
0.020

0.008
0.010
0.007
0.008
0.008
0.007
0.001
0.000
0.002

0.001
0.001
0.002
0.015
0.014
0.015
30
0.020
0.010
0.010
0.010
0.010
0.010
0.050
0.040
0.040
0.040
0.030
0.040

0.024
0.023
0.019
0.022
0.023
0.023
0.009
0.011
0.010

0.008
0.009
0.011
0.028
0.029
0.029
50
0.030
0.030
0.020
0.030
0.020
0.020
0.060
0.060
0.060
0.040
0.040
0.050

0.036
0.033
0.030
0.033
0.033
0.034
0.021
0.023
0.020

0.021
0.022
0.024
0.040
0.039
0.041
70
0.060
0.050
0.050
0.040
0.040
0.040
0.090
0.080
0.080
0.050
0.050
0.050

0.046
0.044
0.042
0.043
0.043
0.045
0.034
0.038
0.031

0.036
0.036
0.038
0.051
0.051
0.056
90
0.120
0.110
0.100
0.070
0.070
0.070
0.140
0.120
0.120
0.070
0.060
0.060

0.064
0.059
0.060
0.059
0.063
0.065
0.059
0.063
0.054

0.059
0.058
0.065
0.073
0.074
0.082
95
0.150
0.140
0.140
0.090
0.090
0.090
0.160
0.150
0.140
0.080
0.070
0.070

0.077
0.068
0.074
0.070
0.075
0.082
0.069
0.079
0.067

0.074
0.073
0.082
0.086
0.090
0.096
99
0.220
0.200
0.200
0.140
0.140
0.130
0.200
0.180
0.190
0.120
0.100
0.100

0.115
0.100
0.110
0.103
0.107
0.123
0.094
0.109
0.092

0.099
0.106
0.110
0.110
0.116
0.123
Max.
0.340
0.290
0.320
0.260
0.210
0.210
0.270
0.330
0.270
0.250
0.170
0.150

0.202
0.176
0.157
0.149
0.197
0.193
0.168
0.187
0.134

0.147
0.185
0.167
0.134
0.175
0.177
Number of Observations
4,874
4,888
4,907
4,875
4,887
4,899
4,871
4,899
4,905
4,814
5,060
5,017

4,673
3,853
4,794
4,272
4,477
4,814
4,964
5,000
4,905

4,815
4,939
4,943
4,825
4,707
4,910

-------
 I
                       TABLE 4-4 (cont'd).  SUMMARY OF PERCENTILES OF HOURLY AVERAGE
                               CONCENTRATIONS FOR THE APRIL-TO-OCTOBER PERIOD
                                                           (units are ppm)
AIRS Site
                            Name
                                              Year
                                                Min.
                                                              10
                                                                     30
                                SO
                               70
                                                                                            90
                                                                                                   95
                                             99
                                                                                                                Max.
                                                                                                                         Number of Observations
 U>
361030002 Babylon, NY 1989
1990
1991
0.001
0.000
0.001
0.004
0.006
0.005
0.015
0.017
0.018
0.027
0.027
0.030
0.039
0.040
0.044
0.060
0.060
0.067
0.073
0.075
0.081
0.101
0.105
0.111
0.156
0.146
0.217
4,407
4
4
,876
,873
     482010024
     550790085
             Harris County, TX
             Bayside, WI
1989
1990
1991

1989
1990
1991
0.000
0.000
0.000

0.002
0.002
0.002
0.000   0.010
0.000   0.010
0.000   0.000

0.006   0.024
0.009   0.025
0.008   0.025
0.020
0.020
0.020

0.035
0.034
0.035
0.030
0.040
0.030

0.046
0.044
0.047
0.060
0.070
0.060

0.066
0.061
0.070
0.070
0.090
0.080

0.077
0.071
0.081
0.110
0.130
0.110

0.101
0.094
0.113
0.230
0.220
0.170

0.151
0.130
0.189
4,728
4,274
4,322

4,376
4,395
4,303
I
8
O

-------
       TABLE 4-5.  THE HIGHEST SECOND DAILY MAXIMUM EIGHT-HOUR
     AVERAGE OZONE CONCENTRATION BY METROPOLITAN STATISTICAL
                         AREA (MSA) FOR THE YEARS  1989 TO 1991
                                              (Units are ppm)
MSA
 1989  1990  1991     MSA
                                      1989  1990  1991
Akron, OH
Albany-Schenectady-Troy, NY
Albuquerque, NM
Alexandria, LA
Allentown-Bethlehem, PA-NJ
Altoona, PA
Anaheim-Santa Ana, CA
Anderson, IN
Anderson, SC
Ann Arbor, MI
Appleton-Oshkosh-Neenah, WI
Asheville, NC
Atlanta, OA
Atlantic dry, NJ
Augusta, OA-SC
Aurora-Elgin, IL
Austin, TX
Bakersfield, CA
Baltimore, MD
Baton Rouge, LA
Beaumont-Port Arthur, TX
Beaver County,  PA
BeUingham, WA
Benton Harbor, MI
Bergen Passaic,  NJ
Billings, MT
Biloxi-GuHport, TX
Birmingham, AL
Bismark, ND
Bloomington-Normal, IL
Boston, MA
Boulder-Longmont, CO
Bradenton, FL
Brazor'ia, TX
Bridgeport-Milford, CT
Brockton, MA
Buffalo, NY
Canton, OH
Carson City, NV
 Cedar Rapids, IA
 Champaign-Urbana-Rantou], IL
 Charleston, SC
Charleston, WV
Charlotte-Gastonia-Rock Hill, NC-SC
Charlottesville,  VA
 Chattanooga, TN-GA
 Chicago, IL
 Chieo, CA
 Cincinnati, OH-KY-IN
 Cleveland, OH
 Colorado Springs, CO
 Columbia, SC
 Columbus, OA-AL
 Columbus, OH
 Corpus Christ!,  TX
 Cumberland, MD-WV
 Dallas, TX
 Danbury, CT
0.109 0.097 0.102
0.087 0.091 0.089
0.078 0.089 0.077
0.077 0.076 0.074
0.091 0.098 0,112
0.077 0.090 0.094
0.146 0,135 0,110
0,084
           0.081
0,093 0,087 0.096
0.091 0,078 0,082
0.083 0.074 0.064
0.096 0.125 0.102
0,104 0.135 0.112
0.078 0.092 0.081
0,088 0,077 0.100
0.099 0,103 0.084
0.124 0.120 0.118
0.103 0.111 0.127
0.095 0.134 0.100
0.110 0.100 0.101
0.095 0.085 0.095
0.038 0.068 0.059
           0.098
0.093 0.097 0.106
0,56
           0.089
0.088 0.105 0.088
0.086 0.062 0.061
0.081 0.071 0.095
0.109 0.105 0.118
0.082 0.084 0.083
0.086 0.075  0.074
      0.101  0.107
0.139 0.114 0.121
0.110 0.106 0.107
0,085 0.096 0.097
0.098 0.098 0.099
0.070
0.078 0.057 0.066
0.084 0.080 0,077
0.094 0,084 0.074
0.087 0,083 0.099
0,089 0,100 0.094
0.076 0.089 0.091
0.091 0.094 0.083
0.101 0.084 0.106
0.081 0.083 0.074
0.106 0.119 0.115
 0.099 0,096 0.101
 0.072 0.065 0,068
 0.079 0.094 0.083
 0.068 0.075 0,083
 0.097 0.098 0.112
 0.083 0.085 0.075
      0.070 0,076
 0.101 0.115 0.095
 0.098 0.105 0.116
Davenport-Rock Island-Moline, IA-LL
Dayton-Springfield, OH
Decatur, E.
Denver, CO
Des Moines, IA
Detroit, MI
Duluth, MN-WI
Eau Claire, WI
El Paso, TX
Elmira, NY
Erie, PA
Eugene-Springfield, OR
Evansville, IN-KY
Fayetteville, NC
Hint, MI
Fort Collins, CO
Ft. Lauderdale-Hollywood-Pompano.FL
Fort Myers-Cape Coral, FL
Fort Wayne, IN
Fort Worth-Arlington, TX
Fresno, CA
Gatveston-Texas City, TX
Gary-Hammond, IN
Grand Rapids, MI
Greeley, CO
Green Bay, WI
Greensboro-Winston Salem-High Point, NC
Greenville-Spartanburg, SC
Harnilton-Middletown, OH
Harrisburg-Lebanon-Cariule, PA
Hartford, CT
Hickory, NC
Honolulu, HI
Houma-Thibodaux, LA
Houston, TX
Huntuigton-Ashland, WV-KY-OH
Hunteville, AL
Indianapolis, IN
Iowa City, IA
Jackson, MS
Jacksonville, FL
Jamestown-Dunkirk, NY
Janesville-Beloil, WI
Jersey City, NJ
Johnson City Kingnport-Bristol, TN-WV
Johnstown, PA
Joliet, IL
Kalamazoo, MI
Kansas City MO-KS
Kenosha, WI
Knoxvilie, TN
 Lafayette, LA
 Lafayette, IN
 Lake Charles, LA
 Lake County, IL
 Lancaster, PA
 Lansing-East Lansing, MI
 Las Cruces, NM
0.102 0.071 0.086
0.122 0.096 0.107
0.084 0.077 0.087
0,089 0,086 0,080
0.073 0,051 0.056
0.103 0.091 0.111
0.073 0.051
      0,049
0.083 0.087 0.080
0.075 0.080 0.094
0.092 0.088 0.093
0.061 0.077 0.070
0,097 0.094 0.107
0.089 0.088 0,085
0.093 0.086 0.090
0.076 0.076 0.077
0.089 0.078 0.064
0.084 0,070 0.062
0.105 0.091 0.096
0.098 0.116 0.116
0,116 0.105 0.119
0,102 0.096 0.094
0.102 0,122 0.101
0.119 0.107 0,124
0.080 0.080 0.081
0.095 0.074 0.079
0.083 0.100 0.087
0.088 0.091  0.085
0.095 0.111  0.105
0.091 0.108  0.100
0.114 0.109 0.112
      0.080
0.020 0.037  0.042
0.082 0,084 0.077
0.121 0.141  0,115
0.102 0.109 0.124
0,072 0,080 0.082
0.097 0.099 0.100
0.078 0.084 0.060
0.086 0,083 0.075
0,090 0.084 0.077
      0.068 0.082
0.097 0,081 0,090
0.105 0.128 0.117
0.083 0,100 0.080
0.082 0.090 0,099
0.082 0.070 0.091
            0.071
0.090 0.089 0.089
0.113 0.093 0.118
0,088 0.105 0,091
 0.080 0.086 0,075
 0.077 0,092 0.090
 0.088 0.084 0.096
 0.092 0.082 0.102
 0 085 0.089 0.096
 0.093 0.083 0.087
 0.074 0.082 0.074
 December 1993
                 4-27
          DRAFT-DO NOT QUOTE OR CITE

-------
            TABLE 4-5 (cont'd).  THE HIGHEST SECOND DAILY MAXIMUM
    EIGHT-HOUR AVERAGE OZONE CONCENTRATION BY METROPOLITAN
               STATISTICAL AREA (MSA) FOR THE YEARS 1989  TO 1991
                                             (Units are ppm)
MSA
                                      1989 1990  1991     MSA
                                                          1989  1990  1991
Las Vegas, NV
Lawrence-Haverhill, MA-NH
Lewigton-Aubum, ME
Lexington-Fayette, KY
Lima, OH
Lincoln, NE
Little Rock-North Litlle Rock, AR
Longview-Marshall, TX
Lorain-EJyria, OH
Los Angeles Long Beach, CA
Louisville, KY-1N
Lynchburg, VA
Madison, Wl
Manchester, NH
Medford, OR
Melbourne-Titusviile-Pulm Bay, FL
Memphis, TN-AR-MS
Miami-Hialeah, FL
Middlesex-Somerset-Hunlerdon, NJ
Middletown. CT
Milwaukee, WI
Minneapolis-Si. Paul, MN-WI
Mobile, AL
Modesto, CA
Monmouth-Ocean, NJ
Montgomery, AL
Muskegon, Ml
Nashua, NH
Nashville, TO
Nassau-Suffolk, NY
New Bedford, MA
New Haven-Meriden, CT
New London-Norwich, CT-R1
New Orleans, LA
New York, NY
Newark, NJ
Niagara Falls, NY
Norfolk-Virginia Beach-Newport Newg, VA
Oakland, CA
Oklahoma City, OK
 Omaha, NE-IA
 Orlando, FL
 Owensboro, KY
 Oxnard-Ventura, CA
 Parkersburg-Marietta, WV-OH
 Pascagoula, MS
 PensacoU, FL
 Peoria, 1L
 Philadelphia, PA-NJ
 Phoenix,  AZ
 Pittsburgh, PA
 PiiUfield, MA
 Portland, ME
 Portland, OR-WA
 Portsmouth-Dover-Rochester, NH-ME
 Poughkeepsie, NY
 Providence, Rl
0.084
0.104
0.089
0.097
0.088
0.057
0.077
0.076
0.096
0.188
0.096

0.089
0.084
0.063
0.082
0.077
0.090
0.097
0.086
0.060
0.083
0.089
0.082
0.170
0.093
0.083
0.079
0.098
0.076
0.075
0.106
0.101
0.088
0.091
0.060
0.089
0086
0.091
0.178
0.119
0.079
0.089
0.087
0.055
0.082 0.082 0.069
0.099 0.100 0,093
0.087 0.076 0.072
0.108 0.111 0.111
O.U9 0.117 0.125
0.115 0.100 0.118
0.090 0.077 0.079
0.079 0.098 0.062
0.101 0.106 0.091
0.118 0.107 0.122
0.066 0.081 0.071
0.139 0.100 0.119
0.072 0.095 0.110
0.093 0.102 0.107
0.099 0.115 0.121
0.104 0.101 0.106
0.108 0.122  0.128
0.128 0.127  0.115
0.075 0.086  0.079
0.111 0.119  0.133
0.108 0.107  0.119
0.082 0.092  0.095
0,089 0.095  0.089
0.091 0,091  0.083
0.089 0.090 0.089
 0.075 0.075 0.073
 0.096 0.082 0.075
 0.096 0.104 0.077
 0.147 0.119 0.129
 0.094 0.088 0,104
 0.082 0,092 0.077
 0.080 0.098 0.082
 0.087 0.075 0.088
 0.118 0.110 0.123
 0.086 0.096 0.094
 0.107 0.100 0.106
 0,075 0.094 0.095
 0.124 0.109 0.134
 0.071 0.111 0.092
 0.107 0.086 0.123
 0,079 0.085 0.101
 0.107 0.112 0.127
Provo-Orem, UT
Racine, WI
Raleigh-Durham, NC
Reading, PA
Redding, CA
Reno, NV
Richmond-Petersburg, VA
Riverside-San Bernardino, CA
Roanoke, VA
Rochester, NY
Rockford, &
Sacramento, CA
St. Louis, MO-IL
Salinas-Seaside-Monterey, CA
Salt Lake City-Ogden, UT
San Antonio, TX
San Diego, CA
San Francisco, CA
San Jose, CA
Sin Juan, PR
Santa Barbara-Santa Maria-Lompoc, CA
Santa Cruz, CA
Santa Fe, NM
Santa Rosa-Petaluma, CA
Sara sola, FL
Scranton-Wilkes-Barre, PA
Seattle, WA
Sharon, PA
Sheboygan,WI
Shreveport, LA
South Bend-Mishawafca, IN
Spokane, WA
Springfield, IL
Springfield, MO
Springfield, MA
Stamford, CT
Sleubenville-Weirton, OH-WV
Stockton, CA
Syracuse, NY
Tacoma, WA
Tallahassee, FL
Tampa-St. Petersburg-Clearwater, FL
Terre Haute, IN
 Toledo, OH
 Trenton, NJ
 Tucson, AZ
 Tulsa, OK
 Utka4tame, NY
 Vallejo-Fairfield-Napa, CA
 Vancouver, WA
 Victoria, TX
 Vineland-Millvile-Bridgeton, NJ
 Visalia-Tulare-Porterville. CA
 Washington, DC MD-VA
 W. Palm Beach-Boca Raton-Delray, FL
 Wheeling, WV-OH
 Wichita, KS
0.094 0.070 0.071
0.110 0.090 0.118
0.099 0.094 0.091
0.095 0.101 0.109
0.080 0.100 0.093
0.081 0.109 0.075
0.094 0.101 0.097
0.196 0.193 0.189
0.077 0.075 0.078
0.094 0.097 0.103
0.085 0.073 0.081
0.105 0.125 0.124
0.105 0.098 0.107
O.OB2 0.074 0.071
0.114 0.086 0.086
0.100 0.080 0.085
0.139 0.135 0.128
0.064 0.056 0.054
0.094 0.075 0,086
0.043 0.042 0.044
0.129 0.129 0.075
0.066 0.058 0.067
0.049 0,069 0.076
0.083 0.061 0.076
0.085 0.083  0.080
0.088 0.096  0.111
0.078 0.099  0.087
0.098 0.095  0.094
0.103 O.OS8  0.103
0.098 0.102  0,087
0.089 0.089  0.093
      0.060 0.060
0.085 0.082 0.087
0,075 0.061  0.069
0.123 0.113  0,117
0.113 0.112 0.115
0.094 0.075 0.098
0.086 0.093 0.090
 0.090 0.093 0.098
 0.077 0.094 0.077
 0.072
 0.088 0.085 0.083
 0.087 0.095 0.089
 0.093 0.084 0.107
 0.119 0.112 0.131
 0.074 0.084 0.080
 0.093 0.094 0.097
 0.082 0.094 0.091
 0.076 0.074 0.078
 0.058 0.080 0.042
 0.093 0.056 O.OS6
 0.122 0.106 0.108
 0.114 0.103 0.104
 0.106 0.110 0.114
 0.081 0.067 0.059
 0.086 0.089 0.093
 0.079 0.089 0.081
 December 1993
                 4-28
                         DRAFT-DO NOT QUOTE OR CITE

-------
               TABLE 4-5 (cont'd). THE HIGHEST SECOND DAILY MAXIMUM
          EIGHT-HOUR AVERAGE OZONE CONCENTRATION BY METROPOLITAN
                  STATISTICAL AREA (MSA) FOR THE YEARS 1989 TO 1991
                                        (Units are ppm)
MSA
Williamsport, PA
Wilmington, DE-NJ-MD
WUmingion, NC
Worcester, MA
1989 1990 1991
0,065 0.072 0,087
0.105 0.110 0.118
0.086
0.097 0.089 0.107
MSA
York, PA
Youngstown-Warren, OH
Yub* City, CA
Yuma, AZ
1989 1990 1991
0.091 0.108 0.103
0.088 0.085 0.101
0.084 0.076 0.084
0.080 0.075 0.070
 1     0.10 ppm.  Lefohn et al. (1993) have identified those areas in the United States for the
 2     period 1987 to 1989 where more than one occurrence of an 8-h daily maximum average
 3     concentration of 0.08 ppm was experienced, while an hourly average concentration equal to
 4     or greater than 0.12 ppm never occurred.
 5          A follow-up to the points made above is whether an improvement in O3 levels may
 6     produce distributions of 1-h O3 that result in a broader diurnal profile than those seen in
 7     high-oxidant urban areas where O3 regimes contain hourly average concentrations with
 8     sharper peaks. The result would be an increase in the number of exceedances of daily
 9     maximum 8-h average concentrations S0.08 ppm, when compared to those sites,
10     experiencing  sharper peaks, Lefohn et al. (1993b), using aerometric data at specific sites,
11     observed how O3  concentrations  change when the sites change compliance status.  One of the
12     parameters examined was 4-h daily maxima.  The number of exceedances for a specific daily
13     maximum average concentration  tended to decrease as fewer exceedances of the current 1-h
14    standard were observed at a given site.  The number of occurrences of the daily maximum
15    4-h average concentration >0.08 ppm and the number of exceedances of the current form of
16    the standard had a positive, weak correlation (r = 0.51).  Lefohn et al.  (1993a,b)  reported
17    few changes  in the shape of the average diurnal patterns as sites changed attainment status;
18     this may have explained why Lefohn et al. (1993b) could not find evidence that the number
19     of occurrences of the daily maximum 4-h average concentration ^0.08 ppm increased when
20     the sites experienced few high hourly average concentrations.
21          There has been considerable interest in possibly substituting one index for another when
22     attempting to relate O3 exposure with an effect.  For example, using 03 ambient air quality
23     data, McCurdy (1988) compared the number of exceedances of 0.125 ppm and the number of

       December 1993                          4-29     DRAFT-DO NOT QUOTE OR CITE

-------
 1      occurrences of the daily maximum 8-h average concentrations ^0.08 ppm and reported that
 2      a positive correlation (r = 0.79) existed between the second-highest 1-h daily maximum in a
 3      year and the expected number of days with an 8-h daily maximum average concentration
 4      >0.08 ppm O3. In this case, the predictive strength of using one O3 exposure index to
 5      predict another is not strong.
 6           Similar to analysis performed by McCurdy (1988), all of the hourly averaged data from
 7      rural agricultural and forested sites in the AIRS database were summarized into maximum
 8      3-mo SUM06, second highest daily maximum hourly average concentration, and second
 9      highest daily maximum 8-h average concentration exposure indices per year for the period
10     1980 to 1991.  For the rural agricultural sites, the correlation coefficient between the 3-mo
11      SUM06 and (a) second highest daily maximum hourly average concentration and (b) second
12      highest daily maximum 8-h average concentration was 0.650 and 0.739,  respectively
13      (Figure 4-5).  For the rural forested sites, the correlation coefficient between the 3-mo
14     SUM06 and (a) second highest daily maximum hourly average concentration and (b) second
15     highest daily maximum 8-h average concentration was 0.585 and 0.683,  respectively
16     (Figure 4-6).
17          One of the difficulties in attempting to use correlation analysis between indices for
18     rationalizing the substitution of one exposure index  for another for predicting an effect (e.g.,
19     SUM06 versus the second highest daily maximum hourly average concentration) is the
20     introduction of the error associated with estimating  levels of one index from another.  Lefohn
21     et al. (1989) have recommended that if a different exposure index (e.g., second  highest daily
22     maximum hourly average concentration) is to be compared to, for example, the  SUM06 for
23     adequacy  in predicting crop loss, then the focus should be on how well the  two  exposure
24     indices predict crop loss using the effects model that is a function of the most relevant index
25     and not on how well the indices predict one another.  Using data from both urban and rural
26     O3 monitoring sites in the midwestern United States that were located near  agricultural/
27     forested areas. Lefohn  et al. (1989) reported a large amount of scatter between the second
28     highest daily maximum hourly average concentration and the SUM06 indices. This large
29      scatter indicated considerable uncertainty when attempting to predict a value for SUM06,
        December 1993                           4-30      DRAFT-DO NOT QUOTE OR CITE

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                      0.40i
                              a)
                                                        o^bj
                              o  a  o D D
V.VAJ ^
(
0.25-
I0-20-
of 0.15-
4»*
40.10-
* 0.05
S
0.001
) 50 100 1f
3-Month SUM06 (ppm-h)
b)
r-0.739
a
D °

^*D ocna D D

,
0 50 100 1
                                                                       150
                                      3-Month   SUM06  (ppm-h)
      Figure 4-5. The relationship between the (a) second highest daily maximum hourly
                 average O3 concentration and the maximum 3-mo SUM06 value and (b) the
                 second highest daily maximum 8-h average concentration and the maximum
                 3-mo SUM06 value for specific site years at rural agricultural sites for the
                 1980-to-1991 period.
1     given a specific second highest daily maximum hourly average concentration value. The

2     authors reported mat for a given second highest daily maximum hourly average

3     concentration, the SUM06 values varied over a large range.  Lefohn et al. (1989) concluded

4     that such large uncertainty would introduce additional uncertainty when attempting to use the

5     predicted exposure index to estimate an effect.  The authors concluded that less error would
      December 1993
4-31
DRAFT-DO NOT QUOTE OR CITE

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          0.20^
                                                       r-0.585
        *
      CM
                             3-Month  SUM06 (ppm-h)
           0.15
                                                        r-0.683
                                                     0
                                SO             100
                              3-Month  SUM06 (ppm-h)
                              150
figure 4-6. The relationship between the (a) second highest daily maximum hourly
          average O, concentration and the maximum 3-mo SUM06 value and (b) the
          second highest daily maximum 8-h average concentration and the maximum
          3-mo SUM06 value for specific site years at rural forested sites for the
          1980-10-1991 period.
December 1993
4-32
DRAFT-DO NOT QUOTE OR OTE

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1     be introduced if either of the two indices were used directly in the development of an
2     exposure-response model.
3          As pointed out by the U.S. EPA (1986a), a familiar measure of 03 air quality is the
4     number or percentage of days on which some specific concentration is equalled or exceeded.
5     This measure, however, does not shed light on one of the more important questions
6     regarding the effects of O3 on both people and plants; that is, the possible significance of
7     high concentrations lasting 1 h or longer and then recurring on 2 or more successive days.
1          The recurrence of high Oj concentrations on consecutive days was examined for one
2     site in four cities by the U.S. EPA (1986a). The numbers of multiple-day events were tallied
3     by length of event (i.e., how many consecutive days) using data for the daylight hours (0600
4     to 2000 h) hi the second and third quarters of 1979 through 1981. These sites were selected
5     because they included areas known to experience high Oj concentrations (California),  and
 1     because they represent different geographic regions of the country (west, southwest, and
2     east).
3           Because of the importance of episodes and respites, EPA (1986a) commented on the
4     occurrences of the length of episodes and the time between episodes (respites). The agency
5     concluded that its analysis showed variations among  sites in the lengths of episodes, as well
6     as the respite periods.  In its discussion, the U.S. EPA (1986a) defined a day or series of
7     days on which the daily  1-h maximum reached or exceeded the specified level as an
8      "exposure"; the intervening day  or days when that level was not reached was called a
 9      "respite." Four O3 concentrations were selected:  0.06, 0.12, 0.18, and 0.24 ppm.  At the
10     Dallas site,  for example, the value equalled or exceeded 0.06 ppm for more than 7 days in a
11      row.  The Pasadena site experienced 10 such exposures, but these 10 exposure events
12     spanned 443 days; in Dallas, the 11 exposures involved only 168 days.  At the lowest
13      concentration (^0.06 ppm), the Dallas station recorded more short-term (^7 days)
14     exposures (45) involving more days (159) than the Pasadena station (14 exposures over
15     45 days)  because  the daily 1-h maximum statistic hi  Pasadena remained above 0.06 ppm for
16     such protracted periods.   At concentrations &0.12 ppm, the lengthy exposures at the
17     Pasadena site resolved into numerous shorter exposures, whereas in Dallas the exposures
18     markedly dwindled in number and duration.
19

       December 1993                          4.33      DRAFT-DO NOT QUOTE OR CITE

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 1      4.3.3   Nonurban Area Concentrations
 2      4.3.3.1   Pristine Areas
 3           For those attempting to compare O3 exposures experienced under ambient or
 4      experimental conditions with a reference point, it is important to identify the hourly average
 5      concentration regimes that occur in pristine areas.  The U.S. EPA (1989) has indicated that a
 6      reasonable estimate of annual average natural Qj background concentration near sea-level in
 7      the United States today  is from 0.020 to 0.035 ppm. This estimate included a 0.010 to
 8      0.015 ppm contribution from the stratosphere and a 0.01 ppm contribution from
 9      photochemically-affected biogenic non-methane hydrocarbons.  In addition, the U.S. EPA
10     (1989) estimated that an additional 0.010 ppm is possible from the photochemical reaction of
11      biogenic methane.  The U.S. EPA concluded that a reasonable estimate of natural
12      O3 background concentration for a 1-h daily maximum at sea-level in the United States
13      during the summer is on the order of 0.03 to 0.05 ppm (U.S. Environmental Protection
14     Agency, 1989).
15          Using measurements at a remote site in South Dakota, Kelly et al.  (1982) estimated the
16     background O3  in air masses entering the Midwest and eastern United States to be 0.020 to
17     0.050 ppm.  Pratt et al. (1983), using data from low-elevation rural sites in Minnesota and
18     North Dakota, reported that annual average concentrations for an 63 monitoring site in
19     LaMoure County, ND,  (400 m) for 1978 through 1981, ranged from 0.030 to 0.035 ppm,
20     while an O3 monitoring site in Traverse County, MN (311 m), had a range of 0.029 to
21     0.035 ppm.  Bower et al. (1989) reported that the remote northern Scotland site,  Strath
22     Vaich (270 m), had a 1987 to 1988 annual average O3 concentration of 0.031 ppm.
23          Lefohn and Jones (1986) have characterized several O3 monitoring sites, which
24     appeared to be isolated from major anthropogenic activities, independent of land use
25     designations (i.e., remote, rural, or urban), and reported that the data collected at these sites
26     show a tendency of few hourly mean O3 concentrations at or near the minimum detectable
27     level and few occurrences of hourly average concentrations above 0.08 ppm.  At these sites,
28     more than 90% of the hourly  average concentrations are greater than 0.015 ppm.  The
29     infrequent minimally detectable hourly mean concentrations occur because of weak surface
30     sink effects. The authors referred to these sites as being located in clean areas.
        December 1993                          4.34      DRAFT-DO NOT QUOTE OR CITE

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 1          Lefohn and Foley (1992) summarized O3 exposures experienced at several clean sites in
 2      the United States (Table 4-6). Redwood NP (CA), Olympic NP (WA), Glacier NP (MT),
 3      Sand Dunes NM (CO), Yellowstone NP (WY), Badlands NP (SD), and Theodore Roosevelt
 4      NP (ND) experienced no hourly average concentration ^0.08 ppm for the period April to
 5      October.  Logan (1989) has noted that O3  hourly average concentrations above 0.08 ppm are
 6      rarely  exceeded at remote western sites. In almost all cases for the above sites, the
 7      maximum hourly average concentration was  ^0.07 ppm.  In 1989, the maximum hourly
 8      average concentration experienced at the Redwood NP (CA) site was 0.046 ppm.
 9          Evans et al. (1983) summarized O3 hourly averaged data collected at eight stations
10      located in eight National Forests across the United States. The first three stations began
11      operations in 1976 (Green Mountain NF, Vermont; Kisatchie NF, Louisiana; and Custer NF,
12      Montana); the second three in 1978 (Chequamegon NF, Wisconsin; Mark Twain NF,
13      Missouri; and Croatan NF, North Carolina); and the last two  in 1979 (Apache NF, Arizona;
14     and Ochoco NF, Oregon),  For the period 1979 to  1983, hourly maximum average
15      concentrations occurring at the clean sites, Custer National Forest (MT), Ochoco National
16     Forest (OR), and Apache National Forest  (AZ), were similar to the exposures determined for
17     6 of the 7 clean sites characterized by Lefohn and Foley (1992).  In almost all cases,
18     (1) none of the sites experienced hourly average concentrations ^0.08 ppm and (2) the
19     maximum hourly average concentrations were in the range from 0.060 to 0.075 ppm.
20     Table 4-7 summarizes the percentUe distributions for  the three national forest sites.
21          Several clean sites were characterized by Lefohn et al. (1990b), using various exposure
22     indices.  One of the indices used was a sigmoidally weighted  cumulative exposure index
23     (W126),  which was described in Section 4.1.  The sigmoidal exposure (W126) values,
24     calculated over an annual period, are provided in Table 4-8.  The W126 values for Theodore
25     Roosevelt National Park, ND were in the range 6.48 to 8.03 ppm-h. The maximum hourly
26     average concentration reported at the site  was 0.068 ppm.  The W126 values at the Custer
27     National Forest, MT  and Ochoco National Forest, OR sites ranged from 5.79 to
28     22.67 ppm-h. The maximum hourly average concentrations measured at each site were
29     0.075 and 0.080 ppm, respectively.  The  W126 values calculated for the Custer National
30     Forest and Ochoco National Forest sites showed greater variability from year-to-year than the
31     values calculated for the South Pole, Barrow, and Theodore Roosevelt National Park sites.

       December 1993                          4.35      DRAFT-DO NOT QUOTE OR CITE

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 TABLE 4-6. SEASONAL (APRIL TO OCTOBER) PERCENHLE DISTRIBUTION
OF HOURLY OZONE CONCENTRATIONS, NUMBER OF HOURLY MEAN OZONE
   OCCURRENCES >0.08 AND ^0.10, SEASONAL SEVEN-HOUR AVERAGE
          CONCENTRATIONS, AND W126 VALUES FOR SITES IN
        SELECTED CLASS I AREAS WITH DATA CAPTURE
                  (Afl concentrations are in ppm units)












*».
ON



M
^•^
s*
2
i^
O
o

^*.
s

^
o
$
CEJ
3
A*
n
Class I Area
Redwood, CA


Olympic, WA





Glacier, MT


Yellowstone, WY


Badlands, SD


Great Sand
Dunes, CO

Theodore
Roosevelt, ND
Norm Unit

Point Reyes, CA


Arches, UT

Rocky Mountains,
CO

Site/ AIRS ID
Redwood NP
06015002

Olympic NP
530090012




Glacier NP
300298001

Yellowstone NP
560391010

Badlands NP
460711001

Sand Dunes NM
08003002

Theodore
Roosevelt NP
380530002

Point Reyes, NP
060410002

Arches NP
490190101
Rocky Mountain
NP
080690007
Year
1989
1990
1991
1982
1984
1986
1989
1990
1991
1989
1990
1991
1989
1990
1991
1989
1990
1991
1989
1990
1991
1984
1985
1986
1989
1989
1990
1991
1989
1990
1989
1990
1991
Min.
0.000
0.000
0.001
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.002
0.000
0.004
0.006
0.006
0.005
0.011
0.010
0.008
0.000
0.000
0.004
0.004
0.006
0.006
0.006
0.000
0.000
0.003
0.006
0.004
10
0.010
0.011
0.012
0.000
0.000
0.000
0.003
0.005
0.006
0.003
0.001
0.001
0.018
0.015
0.020
0.020
0.019
0.020
0.031
0.030
0.029
0.017
0.019
0.017
0.023
0.020
0.017
0.019
0.031
0.020
0.025
0.022
0.026
30
0.017
0.018
0.019
0.010
0.010
0.010
0.010
0.012
0.014
0.015
0.014
0.014
0.027
0.023
0.030
0.027
0.027
0.028
0.037
0.037
0.037
0.025
0.026
0.027
0.032
0.025
0.022
0.025
0.040
0.025
0.034
0.029
0.037
Percentiles (ppm)
50 70 90
0.022
0.023
0.025
0.010
0.010
0.020
0.015
0.018
0.019
0.026
0.026
0.027
0.036
0.029
0.037
0.034
0.032
0.034
0.041
0.041
0.043
0.032
0.032
0.033
0.039
0.031
0.025
0.030
0.045
0.027
0.039
0.034
0.043
0.027
0.027
0.031
0.020
0.020
0.020
0.022
0.023
0.024
0.036
0.035
0.036
0.044
0.036
0.042
0.041
0.037
0.040
0.045
0.045
0.048
0.039
0.038
0.039
0.045
0.036
0.029
0.034
0.050
0.031
0.043
0.038
0.048
0.034
0.035
0.038
0.030
0.020
0.040
0.030
0.030
0.033
0.046
0.044
0.046
0.051
0.043
0.048
0.049
0.044
0.047
0.050
0.051
0.055
0.047
0.046
0.047
0.054
0.041
0.036
0.040
0.056
0.036
0.051
0.046
0.055
95
0.038
0.038
0.041
0.030
0.020
0.040
0.035
0.034
0.036
0.050
0.047
0.049
0.056
0.046
0.051
0.053
0.048
0.050
0.051
0.055
0.058
0.050
0.049
0.050
0.058
0.045
0.040
0.043
0.059
0.039
0.055
0.049
0.059
99
0.041
0.043
0.045
0.040
0.030
0.040
0.046
0.043
0.044
0.058
0.052
0.056
0.063
0.053
0.057
0.060
0.054
0.056
0.056
0.061
0.065
0.059
0.054
0.056
0.065
0.058
0.046
0.048
0.065
0.045
0.070
0.058
0.074
Max.
0.046
0.053
0.054
0.060
0.050
0.060
0.065
0.064
0.056
0.067
0.066
0.062
0.071
0.060
0.064
0.071
0.063
0.066
0.063
0.070
0.077
0.068
0.061
0.062
0.073
0.080
0.063
0.072
0.083
0.055
0.098
0.070
0.095
Hours
No. ofObs. 2:0.08 2=0.10
4,624
4,742
4,666
4,704
4,872
4,776
4,220
4,584
4,677
4,770
5,092
5,060
4,079
4,663
4,453
4,840
4,783
4,584
4,436
4,624
4,130
4,923
4,211
4,332
4,206
4,577
4,856
4,588
4,260
4,639
4,366
4,091
4,730
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
2
0
9
0
21
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Seasonal W126
7-h (ppm) (ppm-h)
0.024
0.025
0.027
0.020
0.015
0.025
0.021
0.022
0.025
0.036
0.036
0.036
0.042
0.034
0.042
0.040
0.037
0.038
0.044
0.044
0.046
0.038
0.038
0.039
0.046
0.033
0.028
0.031
0.047
0.030
0.043
0.038
0.048
1.0
1.1
1.7
7.4
1.6
13.7
0.7
0.8
0.9
5.9
4.1
5.3
10.7
3.7
7.7
9.0
4.7
6.2
10.5
13.3
17.0
7.0
5.0
5.5
14.2
4.7
1.8
3.0
20.6
1.7
13.6
5.5
22.3

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I
OJ
.0
•J
o
o
 TABLE 4-7. SEASONAL (APRIL TO OCTOBER) PERCENTILE DISTRIBUTION OF HOURLY OZONE
   CONCENTRATIONS, NUMBER OF HOURLY MEAN OZONE OCCURRENCES ^0.08 AND ^0.10,
SEASONAL SEVEN-HOUR AVERAGE CONCENTRATIONS, AND W126 VALUES FOR THREE "CLEAN"
                  NATIONAL FOREST SITES WITH DATA CAPTURE ^75%
                           (All concentrations are in ppm units)
   Site
             AIRS ID
                                            Percentiles (ppm)
                          Year Min.
                          10
                                       30
50
70
90
95
                                                        99
Max.  No. of Obs.
  Hours    Seasonal W126
         7-h
2: .08  i.10  (ppm) (ppm-h)
Custer NF, MT 300870101



Ochoco NF, OR 4101301 1 1



Apache NF, AZ 040110110


1978 0.000
1979 0.010
1980 0.010
1983 0.010
1980 0.010
1981 0.010
1982 0.010
1983 0.010
1981 0.010
1982 0.015
1983 0.004
0.010
0.025
0.025
0.025
0.030
0.025
0.025
0.025
0.025
0.030
0.025
0.020
0.035
0.035
0.035
0.035
0.030
0.030
0.035
0.030
0.040
0.035
0.035
0.040
0.040
0.040
0.040
0.035
0.035
0.035
0.035
0.045
0.040
0.040
0.045
0.050
0.045
0.045
0.040
0.040
0.040
0.040
0.050
0.045
0.050
0.050
0.055
0.050
0.055
0.045
0.045
0.045
0.045
0.055
0.055
0.055
0.055
0.060
0.055
0.055
0.045
0.050
0.050
0.050
0.060
0.055
0.060
0.060
0.065
0.060
0.065
0.055
0.055
0.055
0.055
0.065
0.065
0.070
0.075
0.070
0.065
0.080
0.075
0.065
0.060
0.065
0.075
0.070
4,759
5,014
4,574
4,835
4,759
4,459
4,697
4,423
4,806
4,714
4,788
0
0
0
0
5
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.033 8.3
0.043 13.2
0.043 19.7
0.042 10.7
0.044 16.5
0.035 4.7
0.038 7.6
0.039 6.8
0.039 7.6
0.047 21.9
0.042 14.6
i

-------

f'
u>
oo
1
                                TABLE 4-8.  THE VALUE OF THE W126 SIGMOIDAL EXPOSURE
                                   PARAMETER CALCULATED OVER THE ANNUAL PERIOD
                                                          (Units in ppm-h)
                                        Elevation (m)    1976  1977  1978  1979   1980   1981   1982   1983   1984   1985    1986   1987
South Pole, Antarctica
Bitumount, Alberta, Canada
Barrow, AK
Theodore Roosevelt NP, ND
Custer National Forest, MT
Ochoco National Forest, OR
Birch Mountain, Alberta, Canada
2,835
350
11
727
1,006
1,364
850
2.65
2.99
2.60

14.08 22.67
19.54
19.73
3.72 3.01 2.41 3.54 2.76 4.09

2.60 3.15 2.36 2.79 2.03 2.46 3.69
8.03 6.69 6.48*
12.18
5.79 9.10 8.02

 White River Oil Shale Project, UT,
 U-4 1600
 Fortress Mountain, Alberta, Canada
 Apache National Forest, AZ
 Mauna Loa, HI
 Whiteface Mountain, NY
 Hohenpeissenberg, FRG
 American Samoa
                                               19.98  32.10

2,103                                                                     25.04  83.89
2,424                               81.39  10.24  27.18  17.48
3,397                               27.48  45.68  33.68  48.90 19.18    32.66  24.48
1,483                         86.50  68.30  33.75  32.03  37.82 42.94    41.36  32.07  58.33
 975      61.28 25.04  35.64  21.76  18.53  29.53  49.00  19.85 40.43
  82                               0.28   0.24   0.25   0.28  0.30    0.26  0.30   0.32
 Collection did not occur during the months of October, November, and December.
Source: Lefohn et al. (1990b).

-------
 1           As the W126 values increased, the magnitude of the year-to-year variability also
 2      increased. For 2 years of data, the W126 values calculated for the White River U-4 Oil
 3      Shale (UT) site were 19.98 and 32.10 ppm-h.  The maximum hourly concentration recorded
 4      was 0.079 ppm.  The W126 values calculated for the Apache National Forest, AZ site
 5      ranged from 10.24 to 81.39 ppm-h. The highest hourly average concentration was
 6      0.090 ppm.
 7           The 7-h (0900 to 1559 h) average concentration has been used by vegetation researchers
 8      to characterize O3 exposures experienced in plant chamber experiments (see Chapter 5).
 9      Because Oj concentrations are highest during the warm-season months and, at many low-
10      elevation sites, during daylight hours,  the 7-mo seasonal, 7-h (0900 to 1559 h) average
11      concentration is higher than annual average values.  Most remote sites outside North America
12      experience seasonal 7-h averages of 0.025 ppm (Table 4-9) (Lefohn et aL, 1990b). The
13      seasonal average of the daily 7-h average values for the South Pole, Antarctica, range from
14     0.024 to 0.027 ppm. The values range from 0.022 to  0.026 ppm at Barrow, Alaska.  In the
15     continental United States and southern Canada, values  range from approximately 0.028 to
16     0.050 ppm (Lefohn, 1990b).  At an O3 monitoring site at the Theodore Roosevelt National
17     Park in North Dakota, a 7-mo (April to October) average of the 7-h daily average          ;
18     concentrations of 0.038, 0.039,  and 0.039 ppm, respectively, was experienced in 1984,
19     1985, and 1986. These 7-mo seasonal averages (i.e.,  0.038 and 0.039 ppm) appear to be
20     representative of values  that may occur at other fairly  clean sites located in the United States
21     and  other locations  in the northern hemisphere.  In earlier investigations, Lefohn (1984)
22     reported 3-mo (June to August), 7-h averages of 0.048, 0.044, and 0.059 ppm  at remote
23     national forest sites at Custer, MT, Ochoco,  OR, and  Apache, AZ, respectively.
24
25     4.3.3.2   Urban-Influenced Nonurban Areas
26          It is difficult to identify a  set of unique O3 distribution patterns that adequately
27     describes exposures experienced at monitoring sites in nonurban locations because, as
28     indicated earlier, many nonurban sites in the United States are influenced by local sources of
29     pollution or long-range transport of 03 or its precursors.  Unlike the clean sites characterized
30     by Lefohn and Jones (1986),  Lefohn et al. (1990b), and Lefohn and Foley (1992),
        December 1993                          4.39       DRAFT-DO NOT QUOTE OR CITE

-------
                      TABLE 4-9.  THE VALUE OF THE OZONE SEASON (SEVEN-MONTH) AVERAGE OF
                              THE DAILY SEVEN-HOUR (0900 TO 1559 HOURS) CONCENTRATION
                                                             (Units in ppm)
     Site
Elevation (m)
1976  1977  1978   1979   1980  1981   1982   1983    1984    1985    1986    1987
 South Pole, Antarctica
 Bitumount, Alberta, Canada
 Barrow, AK
 Theodore Roosevelt NP, ND
 Custer National Forest, MT
 Ochoco National Forest, OR
 Birch Mountain, Alberta, Canada
 White River Oil Shale Project, UT,
U-4 1600
 Fortress Mountain, Alberta, Canada
Apache National Forest, AZ
MaunaLoa, HI
Whiteface Mountain, NY
Hohenpeissenberg, FRG
American Samoa
                                           2,835
                                             350
                                              11
                                             727
                                           1,006
                                           1,364
                                             850


                                           2,103
                                           2,424
                                           3,397
                                           1,483
                                            975
                                             82
                                      0.025  0.027        0.026   0.027  0.024   0.025
                                0.028
                                      0.022  0.025  0.024 0.024   0.022  0.026   0.022  0.026
                                                                 0.038  0.039   0.039*
                                0.043 0.044              0.042
                                      0.043  0.035  0.038 0.038
                                0.036
                                                   0.045 0.045
                                      0.054 0;©39  0.047  0.040
                                      0.035 0.039  0.034  0.038
                                0.049  0.046 0.040  0.034  0.041
             0.047  0.040  0.044  0.040  0.037 0.043  0.047  0.040
                                      0.010 0.010  0.011  0.009
                                                                0.041  0.050

                                                  0.035  0.035    0.034
                                                  0.044  0.043    0.043  0.045
                                                  0.043
                                                  0.012  0.010    0.011
M   Collection did not occur during the months of October, November, and December.
S  Source: Lefohn et al. (199®)),

-------
       urban-influenced nonurban sites sometimes show frequent hourly average concentrations near
 1      the minimum detectable level, but almost always show occurrences of hourly average
 2      concentrations above 0.10 ppm. The frequent occurrence of hourly average concentrations
 3      near the minimum detectable level is indicative of scavenging processes (i.e., NOX); the
 4      presence of high hourly average concentrations can be attributable to  the influence of either
 5      local generation or the long-range transport of O3.  For example, Evans et al. (1983)
 6      reported that the Green Mt. (VT) and Mark Twain (MO) national forest sites were influenced
 7      by long-range transport of O3. Environmental Protection Agency (1986a) reported that the
 8      maximum hourly average concentrations at Green Mt. (for the period 1977 to 1981) and
 9      Mark Twain (for the period 1979 to 1983) were 0.145 and 0.155 ppm, respectively.  Using
10     hourly averaged data from the AIRS database for a select number of rural  monitoring sites,
11      Table 4-10 summarizes the percentiles of the hourly average O3 concentrations, the number
12     of occurrences of the hourly average concentration ^0.10  ppm, and the 3-mo sum of all
13      hourly average concentrations ^0.06 ppm.
14          As part of a comprehensive air monitoring project sponsored by the Electric Power
15     Research Institute (EPRI), O3 measurements were made by the chemiluminescence method
16     from 1977 through 1979 at nine "nonurban" Sulfate Regional Experiment Sites (SURE) and
17     Eastern Regional Air Quality Study (ERAQS) sites in the eastern United States.   On the basis
18     of diurnal NOX patterns that indicated the influence of traffic emissions, five of the sites were
19     classed as "suburban;" the other four were classed as "rural."  The 03 data from these nine
20     stations are summarized  in Table 4-11. The sites are either influenced by  local sources or
21     transport of O3 or its precursors.  The maximum  hourly average concentrations are generally
22     higher than 0.125 ppm and the occurrence of hourly average concentrations near minimum
23     detectable levels indicates NOX scavenging processes.
24          As part  of its effort to provide long-term estimates of dry acidic deposition  across the
25     United States, the National Dry Deposition Network (NDDN)  operated more than 50 sites,
26     which include 41 in the  eastern United States and 9 in the  western United States, that
27     routinely recorded hourly average 03  concentrations. Figure 4-7 shows the locations of the
28     NDDN sites.   Edgerton  and Lavery (1992) have summarized the O3 exposures at some of the
29     sites for the period 1988 to  1990.  Table 4-12 summarizes the 7-h (0900 to 1559 h) growing
30     season average concentration (May to September) for selected  sites in the  Midwest and East.

       December 1993                           4-41      DRAFT-DO NOT QUOTE OR CITE

-------
 g
t
§
          TABLE 4-10, SUMMARY OF PERCENTILES, NUMBER OF HOURLY OCCURRENCES ^0.10 ppm,
            AND THREE-MONTH SUM06 VALUES FOR SELECTED RURAL OZONE MONITORING SITES
                                    IN 1989 (APRIL TO OCTOBER)
                                     (Concentration values in ppm)
AIRS Site Name
RURAL AGRICULTURAL
170491001 Effingham County, IL
180970042 Indianapolis, IN
240030014 Anne Arundel, MD
310550032 Omaha, NE
420070003 New Brighton, PA
510610002 Fauquier County, VA
RURAL FOREST
060430004 Yosemite NP, CA
360310002 Eaaex County, NY
470090101 Smoky Mountain NP, TN
511870002 ShenNP(DkyRdg),VA
RURAL OTHER
040132004 Scottsdale, AZ
350431001 Sandoval County, NM
370810011 OuUford County, NC
371470099 Fannville, NC
550270001 Horicon, WI
551390007 Oshkosh, WI
Min.

0.000
0,001
0.000
0.002
0.000
0.000

0.000
0.016
0.000
0.004

0.000
0.000
0.004
0.000
0.002
0.002
10

0.009
0.006
0.006
0.021
0.008
0.009

0.008
0.031
0.025
0.027

0.006
0.010
0.010
0.010
0.019
0.016
30

0.023
0.021
0.021
0.030
0.021
0.021

0.022
0.040
0.036
0.037

0.018
0.020
0.023
0.023
0.029
0.028
50

0.036
0.034
0.032
0.037
0.032
0.033

0.035
0.049
0.044
0.045

0.031
0.030
0.034
0.034
0.037
0.038
Percentiles (ppm)
70 90

0.046
0.046
0.045
0.047
0.043
0.045

0.049
0.056
0.053
0.054

0.045
0.040
0.046
0.044
0.047
0.048

0.063
0.063
0.064
0.062
0.062
0.061

0.065
0.066
0.065
0.065

0.062
0.060
0.063
0.062
0.062
0.063
95

0.070
0.072
0.073
0.067.
0.070
0.069

0.072
0.072
0.070
0.071

0.071
0.060
0.070
0.070
0.070
0.070
99

0.081
0.085
0.090
0.075
0.087
0.084

0.083
0.086
0.081
0.082

0.084
0.070
0.083
0.083
0.088
0.084
Max.

0.104
0.103
0.120
0.098
0.102
0.122

0.111
0.106
0.098
0.100

0.107
0.090
0.113
0.100
0.111
0.121
Number of
Hourly
Value*

4,600
4,592
4,360
4,160
5,055
5,050

4,853
4,792
4,764
4,454

5,070
5,059
4,853
4,833
4,142
4,206
Number of
Occurrence
i 20.10

1
3
10
0
4
5

3
4
0
1

4
0
2
2
11
3
Max. Uncorrected
3-moSUM06 Value
(ppm-h)

25.3
25.4
25.5
24.9
29.4
24.6

37.6
45.6
35.9
33.5

31.7
25.1
27.7
26.4
24.6
27.9

-------
TABLE 4-11. SUMMARY OF PERCENTILES OF HOURLY AVERAGE CONCENTRATIONS FOR ELECTRIC POWER
8 RESEARCH INSTITUTE SULFATE REGIONAL EXPERIMENT SITES (SURE)/ERAQS OZONE MONITORING SITES
I- (Units are ppm)
VO
VO
W SURE/ERAQS Name
Montague, MA
Scranton, PA
Indian River, DE
Duncan Falls, OH
f* Rockport, IN
Giles County, TN
2 Roanoke, IN
V Research Triangle Park, NC
8
3 Lewisburg, WV
H
O
0
O
Year
1978
1979
1978
1979
1978
1979
1978
1979
1978
1979
1978
1979
1978
1979
1978
1979
1978
1979



Min.
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.002
0.000



10
0.002
0.000
0.015
0.011
0.010
0.008
0.005
0.010
0.008
0.008
0.000
0.000
0.004
0.004
0.001
0.001
0.020
0.013



30
0.018
0.013
0.031
0.022
0.024
0.020
0.022
0.021
0.021
0.019
0.018
0.014
0.019
0.017
0.017
0.012
0.034
0.022



Percentiles
50 70
0.032
0.025
0.040
0.030
0.035
0.031
0.034
0.029
0.032
0.028
0.032
0.024
0.032
0.026
0.032
0.024
0.045
0.029



0.043
0.035
0.048
0.040
0.049
0.042
0.049
0.042
0.044
0.038
0.046
0.036
0.044
0.038
0.049
0.037
0.056
0.039



90
0.061
0.056
0.062
0.061
0.072
0.063
0.071
0.060
0.066
0.055
0.066
0.055
0.067
0.061
0.076
0.058
0.072
0.056



95
0.075
0.070
0.073
0.074
0.085
0.073
0.081
0.069
0.078
0.064
0.075
0.065
0.079
0.074
0.087
0.068
0.079
0.065



99
0.119
0.103
0.094
0.097
0.103
0.092
0.110
0.086
0.101
0.083
0.087
0.081
0.106
0.098
0.108
0.084
0.091
0.080



Max.
0.202
0.149
0.126
0.132
0.134
0.138
0.144
0.110
0.145
0.104
0.110
0.130
0.160
0.133
0.142
0.131
0.115
0.099



Number of
Observations
7,138
8,485
5,461
8,313
6,874
8,527
5,125
7,595
6,849
8,391
6,034
8,439
5,874
8,001
7,081
8,652
7,019
7,849




-------
                                                                               Upper
                                                                              Northeast
                                                                                Northeast
                                                                              South
                                                                             Central
      figure 4-7. The location of National Dry Deposition Network monitoring sites as of
                  December 1990.
      Source: Edgerton and Laveiy (1992).
 1      Fifty-nine percent of the monitoring sites listed in the table have been classified as
 2      agricultural and 36% as forested.  One site was classified as commercial. As noted by the
 3      U.S. EPA (1992a), 1988 was an exceptionally high 63 concentration year, when compared
 4      with 1989 and 1990.  The number of hourly 0^ concentrations &0.08 ppm is presented in
 5      the table.  Edgerton and Lavery (1992) have summarized O3 hourly average concentration
 6      data for several sites using the cumulative integrated exposure index, W126, as proposed by
 7      Lefohn and Runeckles (1987). Based on evidence presented in the literature relating
 8      O3 exposure with agricultural yield reduction, the index  was proposed as a way to weight the
 9      higher hourly average concentrations  greater than the lower values.  The data in the table
10     illustrate the large differences in cumulative exposure between those that occurred in 1988
       December 1993
4-44      DRAFT-DO NOT QWXl OK CITE

-------
TABLE 4-12.
SEVEN-HOUR GROWING SEASON MEAN, W126 VALUES, AND NUMBER ^80 ppb FOR
 SELECTED EASTERN NATIONAL DRY DEPOSITION NETWORK SITES
Cp 7-h Mean (ppb)
£
U>











**>
•k


0
e
2|
bL
o



o
o
»
Subregion
NUKTHKASST
Connecticut Hill
Washington's Crossing
Pennsylvania State University
Laurel Hill State Park
Beltsville
Cedar Creek State Park
UPPER NORTHEAST
Whiteface Mountain
Ashland
MIDWEST
Argonne National Lab
Vincennes
Oxford
UPPER MIDWEST
Unionville
Perkinstown
SOUTH CENTRAL
Sand Mountain
Georgia Station
Penyville
Research Triangle Park
Coweeta
Edgar Evins State Park
Horton Station


State

NY
NJ
PA
PA
MD
WV

NY
ME

n.
IN
OH

MI
WI

AL
OA
KY
NC
NC
TN
VA


Site

110
144
106
117
116
119

105
135

146
140
122.

124
134

152
153
129
101
137
127
120


Land Class

RF
RA
RA
RF
RA
RA

RF
RA

RA
RA
RA

RA
RA

RA
RA
RA
RC
RF
RF
RF


1988

55.0
—
59.0
62.7
—
59.8

43.5
—

61.1
62.0
65.3

	
—

	
—
65.2
62.3
55.6
—
62.3


1989

48.3
52.8
46.0
48.4
54.6
44.9

45.7
37.9

51.4
51.1
53.5

51.5
44.2

52.6
48.1
50.8
50.8
41.0
47.2
51.4


1990

45.3
52.4
51.0
48.6
55.5
48.2

42.3
35.3

46.3
50.9
51.7

47.4
38.8

63.6
62.6
—
—
47.9
56.1
54.4


1988

75.5
—
63.5
68.8
—
50.4

37.8
—

59.1
68.1
91.8

	
—

	
—
103.6
62.3
44.3
—
127.6


W126 (ppm-h)
1989

40.3
46.0
25.4
29.1
45.4
19.6

25.3
9.1

29.6
36.4
48.4

35.4
19.0

40.6
28.1
39.7
31.7
16.1
26.9
61.2


1990

36.8
43.7
42.7
31.0
45.7
24.3

31.2
8.7

21.6
35.8
46.4

30.7
11.6

68.7
69.7
—
—
21.3
44.5
70.6


1988

86.8
—
65.6
75.5
—
56.3

40.9
—

69.4
78.5
103.2

	
—

	
—
99.6
71.0

—
150.7


SUM06 (ppm-h)
1989

47.2
52.1
28.1
30.8
48.6
19.0

25.2
5.4

35.0
40.3
55.3

41.6
18.3

33.2
21.8
38.9
35.5

24.4
64.0


1990

35.8
48.4
45.0
32.1
49.4
23.2

29.0
5.8

25.7
41.2
51.7

31.6
7.6

83.4
77.7
—
—

49.2
82.8


SUM08 (ppm-h)
1988

44.3
—
32.3
41.6
—
27.0

17.0
—

32.3
36.7
56.8

	
—

	
—
39.7
20.5

—
60.2


1989

5.5
21.2
5.0
7.0
22.9
4.1

2.6
0.6

10.4
8.7
15.8

9.0
0.2

3.4
4.6
5.2
6.6

1.5
8.5


1990

3.3
21.3
11.6
8.0
21.9
6.5

8.4
0.8

3.6
11.8
17.2

7.1
0.0

24.0
28.4
—
—

8.2
9.2



-------
   TABLE 4-12 (cont'd).  SEVEN-HOUR GROWING SEASON MEAN, W126 VALUES, AND NUMBER £80 ppb FOR
	SELECTED EASTERN NATIONAL DRY DEPOSITION NETWORK SITES	
                                                 7-h Mean (ppb)          W126 (ppm-h)         SUM06 (ppm-h)        SUM08 (ppm-h)
Subregion                  State  Site   Land CUss*    1988  1989   1990    1988    1989    1990    1988    1989   1990   1988   1989    1990
SL»i)i.miKi>i taLkkiUlbk'i
Caddo Valley
Sumatra
If
AR
FL

150
156

RF
RF

- 46.2
- 39.8

49.5 -
46.3 —

18.5
17.8

21.0 —
20.0 -

15.6
16.5

25.2 -
17.4 -

0.2
1.0

2.3
0.9
t—  = No data or insufficient data.
 RA - Rural agricultural.
 RF = Rural forest.
 RC = Rural commercial.
Source: Edgerton and Lavery (1992).

-------
 1      and those that were experienced in 1989 and 1990.  The percentile of the hourly average
 2      concentrations is summarized in Table 4-13.  Although several of the monitoring sites are
 3      located in fairly remote locations in the eastern United States (based on land use
 4      characterization) the maximum hourly average concentrations reflect the transport of Oj or
 5      its precursors into the area.
 6           Taylor et al. (1992) have summarized the O3 exposures that were experienced at
 7      10 EPRI Integrated Forest Study sites in North America. The authors reported that in 1988
 8      all sites experienced maximum hourly average concentrations  SO. 08 ppm. In almost all
 9      cases, Hie sites experienced multiple occurrences above 0.08 ppm.  This implies that  although
10      the sites were located in remote forested areas, the sites experienced elevated O3 exposures
11      that were more than likely due to long-range transport of O^ or its precursors.
12           Ozone concentrations on a seasonal basis in the Shenandoah National Park exhibit some
13      features in common with both urban and rural areas. During some years, maximum  hourly
14     average concentrations exceed 0.12 ppm, although some sites in the Park exhibit a lack of
15     hourly average concentrations near minimum detectable level.  Taylor and Norby (1985)
16     have characterized Oj episodes, which they defined as  any day in which a 1-h mean
17     O3 concentration was >0.08 ppm. Based on a 4-year monitoring period in the Park, the
18     probability was 80% that any given episode during the growing season would last 2 or more
19     days, while the probabilities of episodes lasting for periods > 3, 4, and 5 days were 30, 10,
20     and 2%, respectively.  Single-day O3 episodes were infrequent. Taylor and Norby (1985)
21     noted that, given the frequency of respites, there was a 50% probability that a second
22     episode would occur within 2 weeks.
23          Because of a lack of air quality data collected at rural and remote locations, it has been
24     necessary to use interpolation techniques to estimate O3 exposures in nonurban areas. In the
25     absence of actual O3 data, interpolation techniques have been applied to the estimation of
26     O3 exposures across the United States (Reagan, 1984;  Lefohn et al., 1987a; Knudsen and
27     Lefohn, 1988). Kriging, a mathematical interpolation  technique, has been used to provide
28     estimates of seasonal O3 values for the National Crop Loss Assessment Network (NCLAN)
29     for 1978 through 1982 (May to September for each year) (Reagan, 1984). These values,
 30     along with updated values, coupled with exposure-response models, were used to predict
 31

       December 1993                           4.47      DRAFT-DO NOT QUOTE  OR CITE

-------
? TABLE 4-13. SUMMARY OF PERCENTILES FOR NATIONAL DRY DEPOSITION NETWORK MONITORING SITES
5 (Units are ppm)
3 Site No. Name
Year
Min.
10
30
Percentiles
50 70
90
95
99
Max. Number of Observations
W RURAL AGRICULTURAL SITES
106


116

119


122
k.
^
o
124

3 129
O
>
ri
-3 134
3
2 135
i
D 140
H
3
1
u
5 144
0
Pennsylvania State University, PA


Beltsville, MD

Cedar Creek, WV


Oxford, OH


Unionville, MI

PerryviUe, KY

Perkinstown, WI

Loring AFB/ Ashland, ME

Vincennes, IN


Washington Crossing, NJ

1988
1989
1990
1989
1990
1988
1989
1990
1988
1989
1990
1989
1990
1988
1989
1989
1990
1989
1990
1988
1989
1990
1989
1990
0.000
0.000
0.000
0.002
0.000
0.000
0.001
0.001
0.001
0.001
0.000
0.003
0.004
0.002
0.001
0.007
0.006
0.002
0.002
0.000
0.000
0.000
0.000
0.001
0.013
0.010
0.015
0.003
0.001
0.008
0.006
0.007
0.019
0.017
0.015
0.021
0.020
0.024
0.020
0.023
0.020
0.017
0.014
0.007
0.009
0.009
0.006
0.008
0.026
0.022
0.027
0.014
0.015
0.017
0.013
0.014
0.032
0.029
0.028
0.031
0.029
0.038
0.033
0.032
0.028
0.026
0.023
0.024
0.025
0.025
0.021
0.021
0.036
0.033
0.038
0.029
0.027
0.029
0.024
0.024
0.044
0.039
0.037
0.038
0.036
0.049
0.043
0.038
0.035
0.032
0.029
0.036
0.036
0.035
0.033
0.032
0.049
0.043
0.048
0.044
0.041
0.044
0.037
0.038
0.058
0.050
0.048
0.047
0.044
0.062
0.052
0.046
0.041
0.039
0.036
0.052
0.047
0.045
0.046
0.043
0.073
0.059
0.065
0.068
0.067
0.069
0.056
0.057
0.083
0.069
0.067
0.063
0.061
0.080
0.066
0.057
0.050
0.049
0.046
0.076
0.064
0.062
0.067
0.065
0.086
0.066
0.074
0.081
0.080
0.082
0.065
0.067
0.0%
0.077
0.077
0.071
0.069
0.094
0.072
0.062
0.056
0.055
0.051
0.089
0.072
0.073
0.078
0.079
0.114
0.082
0.090
0.096
0.103
0.108
0.082
0.085
0.117
0.092
0.092
0.086
0.084
0.110
0.086
0.071
0.065
0.063
0.068
0.104
0.085
0.089
0.100
0.104
0.143
0.104
0.120
0.131
0.137
0.134
0.172
0.116
0.221
0.109
0.116
0.113
0.105
0.143
0.102
0.085
0.074
0.103
0.088
0.120
0.112
0.110
0.159
0.148
4,716
5,089
5,056
5,062
4,597
4,938
5,044
5,025
4,746
5,073
5,077
5,041
5,065
4,061
4,787
5,029
5,063
5,067
5,080
4,908
5,065
5,084
5,053
5,058

-------
TABLE 4-13 (cont'd). SUMMARY OF PERCENTILES FOR NATIONAL DRY DEPOSITION NETWORK
                               MONITORING SITES
0*
8
h— i
i§
(Units are ppm)
Site No. Name
Year
Min.
10
30
Percentiles
50 70
90
95
99
Max. Number of Observations
RURAL AGRICULTURAL SITES (cont'd)



1
0
%
1
i
146 Argonne National Laboratory, IL
152 Sand Mountain, AL
153 Georgia Station, GA
RURAL FOREST SITES
105 Whiteface Movmtain, NY
110 Ithaca, NY
117 Laurel Hill, PA
120 Horton Station, VA
127 Edgar Evins State Park, TN
1988
1989
1990
1989
1990
1989
1990
1988
1989
1990
1988
1989
1990
1988
1989
1990
1988
1989
1990
1989
1990
0.000
0.000
0.000
0.000
0.000
0.002
0.002
0.000
0.003
0.005
0.005
0.002
0.001
0.001
0.000
0.001
0.010
0.002
0.004
0.000
0.001
0.004
0.005
0.004
0.020
0.021
0.014
0.021
0.016
0.022
0.018
0.025
0.025
0.022
0.012
0.009
0.009
0.031
0.032
0.032
0.017
0.019
0.019
0.019
0.017
0.031
0.035
0.025
0.034
0.026
0.030
0.028
0.034
0.036
0.033
0.025
0.020
0.020
0.045
0.043
0.044
0.028
0.032
0.032
0.029
0.028
0.041
0.045
0.034
0.044
0.034
0.038
0.036
0.043
0.044
0.041
0.036
0.031
0.030
0.057
0.050
0.052
0.037
0.041
0.046
0.041
0.039
0.051
0.057
0.045
0.056
0.044
0.047
0.046
0.055
0.052
0.049
0.050
0.043
0.042
0.067
0.059
0.059
0.047
0.052
0.073
0.061
0.057
0.065
0.074
0.062
0.073
0.062
0.059
0.060
0.080
0.065
0.063
0.076
0.061
0.060
0.084
0.070
0.071
0.062
0.067
0.085
0.070
0.065
0.072
0.080
0.069
0.084
0.074
0.066
0.069
0.090
0.071
0.069
0.092
0.069
0.071
0.096
0.076
0.075
0.067
0.073
0.103
0.088
0.077
0.082
0.093
0.082
0.102
0.098
0.078
0.086
0.103
0.081
0.081
0.119
0.087
0.086
0.114
0.085
0.084
0.077
0.085
0.146
0.126
0.097
0.097
0.117
0.118
0.144
0.129
0.093
0.115
0.126
0.101
0.093
0.156
0.110
0.109
0.145
0.103
0.097
0.090
0.109
5,037
5,055
5,033
4,509
5,068
3,540
4,814
5,051
4,698
5,016
4,827
5,064
5,075
5,007
4,697
5,032
5,012
4,976
5,066
5,060
5,027

-------
          TABLE 4-13 (cont'd).
SUMMARY OF PERCENTTLES FOR NATIONAL DRY DEPOSITION NETWORK
              MONITORING SITES
                 (Units are ppm)
£0 Site No.
RURAL
137


150

156

RURAL
101

Name
FOREST SITES (cont'd)
Coweeta, NC


Caddo Valley, AR

Sumatra, FL

COMMERCIAL SITE
Research Triangle Park, NC

Year

1988
1989
1990
1989
1990
1989
1990

1988
1989
Min.

0.001
0.001
0.000
0.002
0.002
0.001
0.000

0.000
0.000
10

0.010
0.007
0.008
0.005
0.004
0.012
0.011

0.004
0.004
30

0.022
0.016
0.018
0.016
0.015
0.022
0.023

0.020
0.019
Percentiles
50 70

0.034
0.025
0.029
0.028
0.029
0.030
0.033

0.035
0.030

0.047
0.037
0.043
0.041
0.041
0.040
0.043

0.050
0.042
90

0.065
0.055
0.059
0.057
0.057
0.057
0.057

0.072
0.063
95

0.072
0.061
0.064
0.063
0.065
0.065
0.063

0.084
0.071
99

0.094
0.071
0.072
0.075
0.077
0.075
0.072

0.111
0.083
Max. Number of Observations

0.145
0.094
0.085
0.102
0.094
0.098
0.118

0.137
0.121

4,182
4,275
5,046
5,046
5,078
4,700
4,444

5,030
4,893
^•4
3
«

-------
 1      agriculturally related economic benefits anticipated by lower O3 levels in the United States
 2      (Adams et al., 1985; Adams et al., 1989).
 3           Kriging is a statistical tool developed by Matheron (1963) and named in honor of D.G,
 4      Krige.  Although originally developed specifically for ore reserve estimation, kriging has
 5      been used for other spatial estimation applications, such as analyzing and modeling air
 6      quality data (Grivet, 1980; Faith and SheshensM, 1979). At its simplest, kriging can be
 7      thought of as a way to interpolate spatial data much as an automatic contouring program
 8      would. In a more precise manner, kriging can be defined as a best linear unbiased estimator
 9      of a spatial variable at a particular site or geographic area.  Kriging assigns low weights to
10     distant samples and vice versa, but also takes into account the relative position of the  samples
11      to each other and the site or area being estimated.
12           Figure 4-8 shows the average for the 1985 through 1987 period for the seasonal (April
13     to October) average of the daily maximum 7- and 12-h values across the United States, The
14     estimates made for the Rocky Mountain region bad  large uncertainties associated with them
15     because of a lack of monitoring sites.
16          Because of the importance of the higher hourly average concentrations in eliciting
17     injury  and yield reduction for agricultural crops (U.S. Environmental Protection Agency,
18     1986b; 1992b), kriging was used to predict  03 exposures in the eastern United States, using
19     the sigmoidally weighted W126 exposure index as described earlier hi this section. Lefohn
20     et al. (1992b) used the W126 index in its kriging to characterize the 63 exposures that
21     occurred during the period 1985-1989.  Figure 4-9  illustrates the integrated 03 exposure for
22     the 1988 and 1989 periods (data derived from work described in Lefohn et al.,  1992b),
23     Using the kriged data in the East, the 1988  exposures were the highest for the 5-year period,
24     while  1989 exhibited the lowest exposures.  The Oj gradient pattern analyses described by
25     Lefohn et al. (1992b) identified contiguous  areas  of persistent relatively high seasonal
26     O3 values.  The largest area extended from New  Jersey south to northern  Georgia and South
27     Carolina. This area was roughly bounded on the west by the Appalachian Mountains.
28     A second area, which exhibited persistent relatively high seasonal Oj exposures, was
29     centered over the Ohio River Valley in the  region near the Kentucky-Indiana-Ohio borders.
 30     Relatively low O3 exposures were found in Minnesota, Iowa, Wisconsin, Maine, Vermont,
 31

       December 1993                          4-51       DRAFT-DO NOT QUOTE OR CITE

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                 (a)
                 (b)
      figure 4-8.  The kriged 1985 to 1986 maximum (a) 7-h and (b) 12-h average
                  concentrations of ozone across the United States.
      Source:  Lefohn et al. (1990a).
1
2
3
4
New Hampshire, and Florida.  On a year-to-year basis, the analysis by Lefohn et al. (1992b)
Showed that regions that tended to be high for a specific year continued to experience
O3 exposures that were higher when compared to other regions.
      December 1993
                                        4-52
HOT
errs

-------
             (a)
             (b)
figure 4-9. Hie kriged estimates of the W126 integrated ozone exposure index for the
           eastern United States for (a) 1988 and (b) 1989.
Source: Lefohn et al.
December 1993
4-53      DRAFT-DO NOT QUOTE OR CITE

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 1      4.4   DIURNAL VARIATIONS IN OZONE CONCENTRATIONS
 2      4.4.1   Introduction
 3           By definition, diurnal variations are those that occur during a 24-h period.  Diurnal
 4      patterns of O3 may be expected to vary with location,, depending on the balance among the
 5      many factors affecting O3 formation, transport, and destruction.  Although they vary with
 6     locality, diurnal patterns for 63 typically show a rise in concentration from tow or levels
 7      near minimum detectable amounts to an early afternoon peak. The 1978 criteria document
 8      (U.S. Environmental Protection Agency, 1978) ascribed the diurnal pattern of concentrations
 9     to three simultaneous processes:  (1) downward transport of O3 from layers aloft;
10     (2) destruction of O3 through contact with surfaces and through reaction with nitric oxide at
11      ground level; and (3) in situ photochemical production of Oj (U.S. Environmental Protection
12      Agency, 1978; Coffey et al., 1977;  Mohnen et al., 1977; Reiter,  1977a).
13          The form of an average diurnal pattern may provide information on sources, transport,
14     ami chemical formation/destruction effects at various sites (Lefohn, 1992b).  Non transport
15     conditions will produce early afternoon peaks. However, long-range transport processes will
16     influence the actual timing of a peak from afternoon to evening or early morning hours.
17     Investigators have utilized diagrams mat illustrate composite diurnal patterns as a means  to
18     describe qualitatively the differences in O3 exposures between sites (Lefohn and Jones, 1986;
19     Bohm et al., 1991). Although it might appear mat composite diurnal pattern diagrams could
20     be used to quantify the  differences in O3 exposures between sites, Lefohn et al. (1990a)
21     cautioned their use for this purpose. The average diurnal patterns are derived from long-
22     term calculations of the hourly average concentrations, and the resulting diagram cannot
23     adequately identify, at most sites, the presence of high hourly average concentrations and
24     thus may not adequately be able to  distinguish 03 exposure differences among sites.  Logan
25      (1989) noted that diurnal variation of O3 did not reflect the presence of high hourly average
26      concentrations.
27          Unique families of diurnal average profiles exist and it is possible to distinguish
28      between two types of O3 monitoring sites.  A seasonal diurnal diagram provides the
 29      investigator with the opportunity to identify whether a specific O3 monitoring site has more
 30      scavenging than any other site.  Ozone is rapidly depleted near the surface below the
 31      nocturnal inversion layer (Berry, 1964), Mountainous sites, which are above the nocturnal

        December 1993                          4-54      DRAFT-DO NOT QUOTE OR CITE

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 1      inversion layer, do not necessarily experience this depletion (Stasiuk and Coffey, 1974).
 2      Taylor and Hanson (1992) reported similar findings using data from the Integrated Forest
 3      Study. For the low-elevation sites, the authors reported that intra-day variability was most
 4      significant due to the pronounced daily amplitude in O3 concentration between the pre-dawn
 5      minimum and mid-afternoon-to-early evening maximum.  The authors reported that the inter-
 6      day variation was more significant in the high-elevation sites.  Ozone trapped below the
 7      inversion layer is depleted by dry deposition and chemical reactions if other reactants are
 8      present in sufficient quantities (Kelly et al., 1984),  Above the nocturnal inversion layer, dry
 9      deposition generally does not occur and the concentration of O3 scavengers is generally lower
10     so that 63 concentration remains fairly constant (Wolff et al., 1987).  A flat diurnal pattern
11      is usually interpreted as indicating a lack of efficient scavenging of Qj and/or a lack of
12     photochemical precursors, whereas a varying diurnal pattern is taken to indicate the opposite.
13     With the composite diagrams alone, it is difficult to quantify the daily or long-term  exposures
14     of 63. For example, the diurnal patterns for two such sites are illustrated in Figure 4-10.
15     The Jefferson  County (KY) site is urban-influenced and experiences elevated levels of O3 and
16     NOX.  The Oliver County (ND) site is fairly isolated from urban-influenced sources and
17     hourly average O3 concentrations are mostly below 0.09 ppm.  The flat diurnal pattern
18     observed for the Oliver County site is usually interpreted as indicating a lack of efficient
19     scavenging of 03 and/or a lack of photochemical precursors, whereas the varying diurnal
20     pattern observed at the Jefferson County site may be interpreted to indicate the opposite.
21     Logan (1989)  has described the diurnal pattern for several rural sites in the United States
22     (Figure 4-11)  and noted that average daily profiles  showed a broad maximum from  about
23     noon until about 1800 LT at all the eastern sites, except for the peak of Whiteface Mountain.
24     Logan (1989)  noted that the maximum concentrations were higher at the SURE sites than at
25     the NAPBN sites in the east because the latter were situated in more remote or coastal
26     locations.
27
28     4.4.2   Urban Area Diurnal Patterns
29           The U.S. EPA (1986a) has discussed diurnal patterns for urban sites.  Figure 4-12,
 30      reproduced from the previous document, shows the diurnal pattern of 03 concentrations on
 31     July 13, 1979, in Philadelphia, Pennsylvania.  On this day a peak 1-h average concentration

        December 1993                           4.55       DRAFT-DO NOT QUOTE OR CITE

-------
            0.08-
            0.06-
                            Jefferson Co., KYI
                            Oliver Co., ND
                 1     3     5     7     9     11     13    15    17     19    21     23
                                                Hour
      Figure 4-10. Hie comparison of the seasonal diurnal patterns using 1988 data for
                   Jefferson County, KY and Oliver County, ND.
1     of 0.20 ppm, the highest for the month, was reached at 2:00 p.m., presumably as the result
2     of meteorological factors, such as atmospheric mixing and local photochemical processes.
3     The severe depression of concentrations to below detection limits (less than 0.005 ppm)
4     between 3:00 and 6:00 a.m. is usually explained as resulting from the scavenging of O3 by
5     local nitric oxide emissions.  In this regard, this station is typical of most urban locations.
6           Diurnal profiles of O3 concentrations can vary from day to day at a specific site,
7     however,  because of changes in the various factors that influence concentrations.  Composite
8     diurnal data (that is, concentrations for each hour of the day averaged over multiple days or
9     months) often differ markedly from the diurnal cycle shown by concentrations for a specific
10      day. In Figures 4-13 through 4-15, reproduced from the previous document, diurnal data for
11      2 consecutive days are compared with composite diurnal data (1-mo averages of hour-by-
12      hour measurements) at three different kinds of sites:  center city-commercial
       December 1993
4-56
DRAFT-DO NOT QUOTE OR CITE

-------
               50
               40

               30

               20
(a)
- AZ
m ^ /- 	 ^

— • 	 '~Ili;—*'x .
I l
1 '


--- — \ ^*"""*
,--' OR
i i
' MT
"*•••-.

'* **• ••» — _

i

_

—


                         4       8        12      16      20
                                  Time of Day (h)

figure 4-11. Diurnal behavior of ozone at rural sites in the United States in July.  Sites
            are identified by the state in which they are located,  (a) Western National
            Air Pollution Background Network (NAPBN); (b) Whiteface Mountain
            (WFM) located at 1.5 km above sea level; (c) eastern NAPBN sites; and
            (d) sites selected from the Electric Power Research Institute's Sulfate
            Regional Air Quality study. IN (R) refers to Rockport.

Source:  Logan (1989).
December 1993
DRAFT-DO NOT OTTOTR OP PTTP.

-------
            OL
            a.
            a
            03
            8
           8
            O
                                       I
                   12 1  23456789 10 11 fl  23  456789
                                              Noon
                      	a.m.	Hour of Day	p.m-
                         1011
      figure 4-12.  Diurnal pattern of 1-h ozone concentrations On July 13,1979,
                   Philadelphia, PA.
      Source:  U.S. Environmental Protection Agency (1986a).
1     (Washington, DC), rural-near urban (St. Louis, MO), and suburban-residential (Alton, EL).
2     Several obvious points of interest present themselves in these figures: (1) at some sites, at
3     least, peaks can occur at virtually any hour of the day or night but these peaks may not show
4     up strongly in the longer-term average data; (2) some sites may be exposed to multiple peaks
5     during a 24-h period; and (3) disparities, some of them large, can exist between peaks (the
6     diurnal date) and the 1-mo average (the composite diurnal data) of hourly O3 concentrations.
7          When diurnal or short-term composite diurnal O3 concentrations are compared with
8     longer-term composite diurnal 03 concentrations, the peaks are smoothed as the averaging
9     period is lengthened.  Figure 4-16 demonstrates the effects of lengthening the period of tune
       December 1993
4-58
DtAFT-DO NOT QUOffi OR CltE

-------
   0.12

   0.10

&0.08
.o
£ 0.06
         
-------
           o.ta
           0.10
            0.08-
            0.06-
         8
         i
         o
            0.04 —
            0.02-
                 Rural - Near Urban
                                  I   I   I  I   I
                                  -  Sept. 29-30
                                  -  1-month
                TT
                        I  I   I   I  I   I   I
               24    4    8    12    16   20   24    4    8    12    16   20   24
|< - a.m. — Noon- — p.m.
                                                     a.m. — Noon — — p.m. — •>]
      Figure 4-14.  Diurnal an«l 1-mo composite diurnal variations in ozone concentrations,
                   St. Lends County, MO, September 1981.
      Source:  U.S. Environmental Protection Agency (1986a).
1     4.4.3   Nonurban Area Diurnal Patterns
2          Non-urban areas only marginally affected by transported O3 usually have a flatter
3     diurnal profile than sites located in urban areas. Nonurban O3 monitoring sites experience
4     differing types of diurnal patterns (Bohm et at., 1991; Lefohn, 1992b). As indicated earlier,
5     O3 concentrations at a specific location are influenced by local emissions and by long-range
6     transport from both natural and anthropogenic sources.  Thus,  considerable variation of
7     O3 exposures among sites characterized as agricultural or forested is found and there is no
8     preference for maximum diurnal patterns to occur in either the second or third quarter.
       December 1993
                               4-60
DRAFT-ISO N€*t QUOTE OH CITE

-------
           0.12
           0.10-
            0.08
8
o
o
I
            0.06
            0.04
            0.02
                  I   I  I   I   I  I   I  I   I   I
                 Suburban - Residential
                                         !  !   t
    I  I   I   I
                   Oct. 11-12
                   1-month
       24   4    8    12    16   20   24    4
                                                          8    12    16
       |g - a.m -- Noon — p.m.
                                                     a.m. —  Noon — p.m. — \
                                          Hour of Day

      Figure 4-15.  Diurnal and 1-mo composite diurnal variations in ozone concentrations,
                   Alton, IL, October 1981 (fourth quarter).
      Source:  U.S. Environmental Protection Agency (1986a).
1          The diurnal patterns for several agricultural sites have been characterized (U.S.
2     Environmental Protection Agency, 1986a). Figures 4-17 and 4-18 show some typical
3     patterns of exposure.  As discussed by U.S. EPA (1986a), the six sites, whose diurnal
4     patterns are illustrated in Figure 4-16, represent counties with high soybean, wheat, or hay
5     production.  The figures show a distinct afternoon maximum with the lowest concentrations
6     occurring in the early morning and evening hours. Quarterly composite diurnal patterns
7     clearly show the division of the afternoon 03 concentrations into two seasonal patterns, the
8     low "winter" levels in the first and fourth quarters and the high "summer8 levels in the
9     second and third  quarters of the year.
      December 1993
                                     4-61
DRAFT-DO NOT QUOTE OR CTTE

-------


_<
D.
C
0
"05
C.
"c
8
c
o
O
0)
c
o
N



U.1U
0.09
0.08
0.07

0.06

0.05

0.04

0.03

0.02

0.01
0
I M M MM M M M Ml MM
— Alton, IL -
— —
i — —

— —

_ „-- \-,^ 3rd Q
-^
/ 	 	 	 \
— / s'' 2nd Q"--.> —
/ '"' \\
/•'' \\
~~ /"' \"i
/Xs
..-"" 4th Q"- . x^..._..-^
« 	 ^ 	 f/ ^.. ^^
Iimuij_ •-?T^-' ^*** 	
M i I M I M M M M M M M M
               24
10   12    14   16    18    20   22   24
                             a.m.
    Noon
       p.m.
                                           Hour of Day
       Figure 4-16. Composite diurnal patterns of ozone concentrations by quarter, Alton, IL,
                   1981.
 1          Remote forested sites experience unique patterns of 63 exposures (Evans et al., 1983;
 2      Lefohn, 1984). ITiese sites tend to experience a weak diurnal pattern, with hourly average
 3      03 concentrations that occur frequently in the range of 0.04 to 0.05 ppm.  Figure 4-19 shows
 4      diurnal patterns for several sites in the NDDN network that are located in forested areas.
 5      Several of the NDDN sites analyzed by Edgerton and Lavery (1992) exhibit fairly flat
 6      average diurnal patterns.  Such a pattern  is based on average concentrations calculated over
 7      an extended period.  On a daily basis, some variation in O3 concentration does occur from
 8      hour to hour and, in some cases, high hourly average concentrations are experienced either
 9      during daytime or nighttime periods (Lefohn and Mohnen, 1986; Lefohn  and Jones,  1986;
10     Logan, 1989; Lefohn et al., 1990c; Taylor et aL, 1992).
       December 1993
     4-62
DRAFT-DO NOT QUOTE OR CITE

-------
[ 0.09
5 0.08
i 0-07
f 0.08
^ 0.06
j 0.04
: o-03
5 OjOZ
3 0.01
0,
i
1 1 1 1 1 1 1 1
~ N. Little Roc»
-(a)
	 ifrtOi
_______ 4.U4 f^
- . 	 3rdO
....... JJh ft
*F*»..rr^%~H4sx'
i i i j i 1 i I
w 2 * e t
i i i i i i i i i i i i i i
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barter
uarter
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/ \_
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10 12 14 16 IB 20 22
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2}
-3)1
                                                            a.m.
                                                                         p.m.
  \j
  J
0.10
0.09
0.08
0.07
0.08
0.05
0.04
0.03
0.02
0.01
  0
         i  i i  i i i i i i iiiii  jiITiiiri
         ~  Sacramento, CA
           (c)
                                              0.10
                                              0.09
                                              0.08
                                              0.07
                                              OM
                                              0.05
                                              0.04
                                              0.03
                                              0.02
                                              0.01
        K-
            a.m.
    riTiiT i i i i i rrri  iiii  i i  i
    " Alton, IL
                                                     s,»--»..;fc,«^i,,«'
                                                     i  i i  i i'i"i i i M i i i  i i i i  i i  i
                                                    W4-
                        11 j 111 j_t n
                        14 18 18 20 22  24
                                            24
                                               K-
                                                           a.m,	9^-
                             p.m.
^> °'10
1 0.09
& 0.08
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g 0.08
g 0.05
g 0.04
O OJ»
®
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     o
           1  1 1  1 1  I 1  1
           CIaikCO.,OH
           (*)
                        1 f 1  1 1 1 1 1 1 1
          1 i ' 1 i L' 1' J.1 JJJJ JJ LUJ JJ
          -_g  ^  ^  g  10 12 14  18  18  »}  22
               8  10 12 14 18 18
             a.m,	^	p.m~
                Hour of Day, LSI
0.10
0.09
aoe
0.07
0.06
0.06
0.04
0.09
0.02
0.01
                                                     I  I I  I I  I I I I I  I I  I II I  I I  I I  I !  I
                                                  Edmond.OK
                                                  (0
                                          24
      I  I I  I I  I I  I M I  I I I I I I I I I  I I
  "242  4  §  8  10  12 14 18  18 20 22  2
                 ..  . ;>!<;	   p.m....	
                                                               Hour of Day, LSI
Figure 4-17.  Quarterly composite diurnal patterns of ozone concentrations at selected
              sites representing potential for exposure of major crops, 1981.
Source: U.S. Environmental Protection Agency (1986a).
December 1993
                                       4-63
                                                     DRAFT-DO NOT QUOTE OR CITE

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       Figure 4-18.  Composite diurnal ozone pattern at a rural National Crop Loss Assessment
                    Network site in Argonne, IL, August 6 through September 30, 1980.
       Source: U.S. Environmental Protection Agency (1986a).
 1           Lefohn et al. (1990c) characterized O3 exposures at high-elevation monitoring sites,
 2      The authors reported that a fairly flat diurnal pattern for the Whiteface Mountain summit site
 3      (WF1) was observed (Figure 4-20a), with the maximum hourly average concentrations
 4      occurring in the late evening or early morning hours.  A similar pattern was observed for the
 5      mid-elevation site at Whiteface Mountain (WF3).  The site at the base of Whiteface
 6      Mountain (WF4) showed the typical diurnal pattern expected from sites that experience some
 7      degree of Qj scavenging.  More variation in the diurnal pattern for the highest Shenandoah
 8      National Park sites occurred than for the higher elevation Whiteface Mountain sites, with the
 9      typical variation for urban-influenced sites in diurnal pattern at the lower elevation
10      Shenandoah  National Park site (Figure 4.20b).  Aheja and Li (1992), in their analysis of the
11      5 high-elevation Mountain Cloud Chemistry Program sites (see Section 4.6.2 for site
12     descriptions), noted the flat diurnal pattern typical of high-elevation sites  that has been
13      described previously in the literature.  Aneja and Li (1992) noted that the peak of the diurnal
       December 1993
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         60

         50
      -40
       CL
       o.
      ^ 30

      8 20
          10
••• 108 -Prince Edward, VA
ooo 119-Cedar Creek, WV
                     .8
                     O
                                         •
                                         8 o
                                             * •
                                  o   *•
                                     o
                   o o
                                                             o o
                       o
              2    4  ' 6  '  6 '  10 ' 1'2 '  1'4 ' 1'8 '  18  20   22  24
                                    Hour
          60-

          50
       V 30
       c
       o
       fi 20
          10-
••• 168-Glacier NP.MT
ooo 174 -Grand Canyon, AZ
               o o o o o o o
                                     ooooooooo
                                                           o o o
                 • • •
               2   4   6   8    10   12  14   16  18   20  22   24
                                     Hour
Figure 4-19. Composite diurnal ozone pattern at selected National Dry Deposition
           Network sites.

Source: Edgertan and Laveiy (1992).
December 1993
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                0   24   6  8  10  12 14  16 18  20  22  24
             0.00
             0.08-1
             0.06
^ 0.04-


« 0.03-J
             0.02-
             0.01-
             0.00
                  (b)
                                                               -SHI
                                                               -SH2
                                                               -SH3
                0   24   6   8   10   12  14  16  18  20  22  24
                                     Hour
Figure 4-20. Composite diurnal pattern at (a) Whiteface Mountain, NY, and
            (b) Mountain Cloud Chemistry Program's Shenandoah National Park site
            for May to September 1987.

Source: Lefohn et al. (1990c).
          1993
                            4-66      DRAFT-DO NOT QUOTS OR OTB

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 1     patterns over the period May to October (1986 to 1988) for the 5 sites occurred between
 2     1800 and 2400 h, while the minimum was observed between 0900 and 1200h. However, it
 3     is important to note that as indicated by Lefohn et al. (1990), the flat diurnal pattern is not
 4     observed  for all high-elevation sites.
 5
 6
 7     4.5   SEASONAL PATTERNS IN OZONE CONCENTRATIONS
 8     4.5.1   Urban Area Seasonal Patterns
 9          Seasonal variations in 63 concentrations in 1981 were described by the U.S. EPA
10     (1986a).  Figure 4-21 shows the 1-mo averages and the single 1-h maximum concentrations
11     within the month for eight sites across the nation.  The data from most of these sites exhibit
12     the expected pattern of high O3 in late  spring or in summer and low levels in the winter.
13     Data from Pomona (Figure 4-21c) and  Denver (Figure 4-21d) show summer maxima.
14     Tampa shows a late spring maximum but with concentrations in the fall (i.e., October)
15     approaching those of spring (June)  (Figure 4-2If). Dallas data also tend to be skewed toward
16     higher spring concentrations; but note that November concentrations are also relatively high
17     (Figure 4-2lh).  Because of seasonal changes in temperature, relative humidity, and storm
18     tracks from year to year, the general weather conditions in a given year may be more
19     favorable for the formation of 03 and other oxidants than during the prior or following year.
20     For example, 1988 was a hot and dry year during which some of the highest
21     O3 concentrations of the last decade occurred, while 1989 was a cold and  wet year in which
22     some of the lowest concentrations occurred (U.S. Environmental Protection Agency,  1992a).
23
24     4.5.2   Nonurban Area Seasonal Patterns
25          In the literature,  several investigators have reported on the tendency  for average
26     63 concentrations to be higher in the second versus the third quarter of the year for many
27     isolated rural sites (Evans et al., 1983; Singh et al., 1978). This observation has been
28     attributed to either stratospheric intrusions or an increasing frequency of slow-moving, high-
. 29     pressure systems that promote the formation of 03.  Lefohn et al. (1990b) reported that for
 30      several clean sites, the highest exposures occurred in the third quarter rather than in the
 31      second.  The results of this analysis will be  discussed in the Section 4.5.3.  Taylor et al.

       December 1993                          4-6?      DRAFT-DO NOT QUOTE  OR CITE

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                  OJE
                                            QMr
                       JFMAU4JA
                            Month of Yi
Figure 4-21.  Seasonal variations in ozone concentrations as indicated by monthly
             averages and the 1-h maximum in each month at selected sites, 1981.

Scarce:  U.S. Environmental Protection Agency (1986a).
                                        4-68
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 I      (1992) reported that for 10 forest sites in North America, the temporal patterns of Q, on
 2      quarterly or annual periods exhibited less definitive patterns.  Based on the exposure index
 3      selected, different patterns were reported.  The different patterns may be associated  with the
 4      observations by Logan (1989) that rural O3 in the eastern United States in the spring and
 5      summer is severely impacted by anthropogenic and possibly natural emissions of NOX and
 6      hydrocarbons and that O3 episodes occur when the weather is particularly conducive to
 7     photochemical formation of O3. Meagher  et al. (1987) reported for rural O3 sites in the
 8      southeastern United States that  the daily maximum 1-h average concentration was found to
 9      peak during the summer months.  Taylor and Norby (1985) reported that in the Shenandoah
10     National Park, the probability of a day occurring in which a 1-h mean O3 concentration was
11      >0.08 ppm was the same during the months of May,  June, and July, while the probability
12      was nearly 40% less in August. The probability of an episode during each of the remaining
13     months of the growing season was < 5 %.  The month of July experienced both the highest
14     frequency of episodes and the highest mean duration of exposure events.
IS          Aneja and LI (1992) reported that the maximum monthly ozone levels occurred in either
16     the spring or the summer (May to August), and the minimum occurred in the fall (September
17     and October).  The timing of the maximum monthly values differed across sites and years.
18     However, in 1988,  an exceptionally  high concentration O3 year, for almost all of the 5 sites,
19     June was the month in which the highest monthly average concentration occurred.  This was
20     the month in which the greatest number of O3 episodes occurred in the eastern United States.
21
22     4.5.3  Seasonal Pattern  Comparisons with  "Pristine"  Sites
23          Lefohn et al.  (1990b) have characterized the 63 concentrations that occurred at several
24     clean sites in the United States. The Theodore Roosevelt National Park, ND site experienced
25     its maximum in July for 1984  and 1985 and in May for 1986. Of the three western national
26     forest sites evaluated by Lefohn et al. (1990b), only Apache National Forest experienced its
 27     maximum monthly mean concentration in  the Spring.  The Apache National Forest site was
28     above mean nocturnal inversion height and no decrease of concentrations occurred  during the
29     evening hours.  This site also experienced the highest hourly maximum concentration, as
 30     well as the highest W126 03 exposures.  The Custer  and Ochoco  National Forest sites
 31     experienced most of their maximum monthly mean concentrations in the summer.  The White

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 1      River Oil Shale site in Colorado experienced its maximum monthly mean during the spring
 2      and summer months.
 3          The W126 sigmoidal weighting function index was also used to identify the month of
 4     highest O3 exposure.  A somewhat more variable pattern was observed than when the
 5     maximum monthly average concentration was used.  For some sites,  the winter/spring
 6     pattern was represented; for others, it was not. In some cases, the highest W126 exposures
 7     occurred earlier in the year than was indicated by the maximum monthly concentration.  For
 8     example, in 1979, the Custer National Forest site experienced its highest W126 exposure in
 9     April, although the maximum monthly mean occurred in August. In 1980, the reverse
10     occurred.
11         There was no consistent pattern for those sites located in the continental United States.
12     The Theodore Roosevelt National Park, Custer National Forest, Ochoco National Park, and
13     White River Oil Shale sites experienced their maximum Oj exposures during the spring and
14     summer months.  The sites experiencing their highest O3 exposures in the fall to spring
15     period did not necessarily experience the lowest 03 exposures.
16
17
18     4.6   SPATIAL VARIATIONS IN OZONE CONCENTRATIONS
19     4.6.1  Urban-Nonurban Area Concentration Differences
20          Diurnal concentration data presented earlier indicate that peak O3 concentrations can
21     occur later in the day in rural areas than in urban, with the distances downwind from urban
22     centers generally determining how much later the peaks occur.  Meagher et al. (1987)
23     reported that for five rural sites in the Tennessee Valley region of the southeastern United
24     States, O3 levels were found to equal or exceed urban values for the same region. Data
25     presented in the 1978 criteria document demonstrated that peak concentrations of Oj in rural
26     areas are generally lower than those in urban areas, but mat average concentrations in rural
27     areas are comparable to or even higher than those in urban areas (U.S.  Environmental
28     Protection Agency, 1978).  Reagan (1984) noted that Oj concentrations measured  near
 29     population-oriented areas were depressed in comparison with data collected in more isolated
 30     areas. As noted earlier, urban O3 values are often depressed because of titration by nitric
 31     oxide (Stasiuk and Coffey, 1974). In reviewing the National Crop Loss Assessment

       December 1993                          4^70      DRAFT-DO NOT QtJQTfi OR CTTB

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 1      Network's use of kriging to estimate the 7-h seasonal average O3 levels, Lefohn et ai.
 2      (1987a) found that the 7-h values derived from kriging for sites located in rural areas tended
 3      to be lower than the actual values because of the effect of using data from urban areas to
 4      estimate rural values.  In addition to the occurrence of higher average concentrations and
 5      occasionally higher peak concentrations of O3 in nonurban areas than in urban, it is well
 6      documented that O3 persists longer in nonurban than in urban areas (Coffey et al., 1977;
 7      Wolff et al., 1977; Isaksen et al., 1978).  The absence of chemical scavengers appears to be
 8      the main reason.
 9
10      4.6.2   Concentrations Experienced at High-Elevation  Sites
11           The distributions of hourly average concentrations experienced at high-elevation urban
12      sites are similar to those experienced at low-elevation areas.  For example,  the distribution of
13      hourly average concentrations for several Oj sites located in Denver were similar to
14     distributions observed at many low-elevation sites in the United States.  However, as will be
IS      discussed in Section 4.6.3, for assessing the possible impacts of Oj at high-elevation sites,
16     the use of absolute concentration (e.g., in units of micrograms per cubic meter) instead of
17     mixing ratios (e.g., ppm) may be an important consideration.
18          Lefohn et al. (1990c) have summarized the characterization of gaseous exposures at
19     rural sites in 1986 and 1987 at several Mountain Cloud Chemistry Program (MGCP) high-
20     elevation sites.  Aneja and Li (1992) have reported the ozone exposures for 1986 to 1988.
21     Table 4-14 summarizes the sites characterized by Lefohn et al. (1990c). Table 4-15
22     summarizes the exposures that occurred at several of the sites for  the period 1987 to 1988.
23     In 1987, the 7- and 12-h seasonal means were similar at the Whiteface Mountain WF1 and
24     WF3 sites (Figure 4-22a). The 7-h mean values were 0.0449 and 0.0444 ppm, respectively;
25     the 12-h mean values were 0.0454 and 0.0444 ppm,  respectively.  Note that, in some cases,
26     the 12-h mean was slightly higher  than the 7-h mean value.  This  resulted when the 7-h mean
27     period (0900 to 1559 h) did not capture the period of the day when the highest hourly mean
28     O3 concentrations were experienced.  A similar observation was made, using the 1987 data,
29     for the MGCP Shenandoah National Park sites.  The 7- and 12-h  seasonal means were
 30     similar for the SHI and SH2 sites  (Figure 4-22b). Based on cumulative indices, the
 31     Whiteface Mountain summit she (WF1) experienced a slightly higher exposure than the WF3

       December  1993                          4-71       DRAFT-DO NOT QUOTE OR CITE

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              TABLE 4-14.  DESCRIPTION OF MOUNTAIN CLOUD CHEMISTRY
                                      PROGRAM SITES
Site Elevation (m)
Howland Forest (HF1), ME
Mt. Moosilauke (MSI), NH
Whiteface Mountain (WFI), NY
Shenandoah Park (SHI), VA
Shenandoah Park (SH2), VA
Shenandoah Park (SH3), VA
Whitetop Mountain (WT1), VA
Mt, Mitchell (MMl), NC
Mt. Mitchell (MMl), NC
65
1,000
1,483
1,015
716
524
1,689
2,006
1,760
Latitude
45°
43°
44°
38°
38°
38°
36°
35°
35°
11'
59'
23'
37'
37'
37'
38'
44'
45'

18"
26"
12"
30"
45"
20"
15"

68°
71°
73°
78°
78°
78"
81°
82°
82°
Longitude
46'
48'
51'
20'
21'
21'
36'
17'
15'

28"
34"
48"
13"
28"
21"
15"

 1      site (Figure 4-22c).  Both the sum of the concentrations ^0.07 ppm (SUM07) and the
 2      number of hourly concentrations ^0.07 ppm were higher at the WFI site than at the WF3
 3      site. The site at the base of the mountain (WF4) experienced the lowest exposure of the
 4      three O3 sites.  Among the MGCP Shenandoah National Park sites, the SH2 site experienced
 5      marginally higher 03 exposures, based on the index that sums all of the hourly average
 6      concentrations (i.e., referred to as total dose in the figure) and  sigmoidal values, than the
 7      high-elevation site (SHI; Figure 4~22d); the reverse was true for the sums of the
 8      concentrations S0.07 ppm and number of hourly concentrations S0.07 ppm.
 9          When the Big Meadows, Dickey Ridge, and Sawmill Run Shenandoah National Park
10      data for 1983 to 1987 were compared, it was again found that the 7- and 12-h seasonal
11      means were insensitive to the different O3 exposure patterns. A better resolution of the
12      differences was observed when the cumulative indices were used (Figure 4-23).  There was
13      no evidence that the higher elevation, Big Meadows, site had consistently experienced higher
14     03 exposures lhan the lower elevation sites.  In 2 of the 5 years, the higher elevation site
15      experienced lower exposures than the Dickey Ridge and Sawmill Run sites, based on "total
16     dose" or sigmoidal indices. For 4 of the 5  years, the SUM07  index yielded the same result.
17          Taylor et al. (1992) indicate that forests experienced marked quantitative and qualitative
18     differences in Og exposure. The principal spatial factors underlying this variation were
       December 1993
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TABLE 4-15. SEASONAL (APRIL TO OCTOBER) PERCENTILES, SUM06, SUM08, AND W126
        VALUES FOR THE MOUNTAIN CLOUD CHEMISTRY PROGRAM SITES

2 Site Year
Co Howland Forest, ME 1987
g (HF1) 1988
Mt. Moosilauke, NH 1987
(MSI) 1988
Whiteface Mountain, NY 1987
(WF1) (36-031-0002) 1988
Whiteface Mountain, NY 1987
(WF3)
Whiteface Mountain, NY 1987
(WF4)
Mt. Mitchell, NC 1987
(MM1) 1988
1989
f- 1992
-4
•** Mt. Mitchell, NC 1987
(MM2) 1988
Shenandoah Park, VA 1987
M (SHI) 1988
5 Shenandoah Park, VA a!987
C (SH2)
1
o
X Shenandoah Park, VA 1987
^ (SH3) 1988
Q Whitetop Mountain, VA 1987
^ (WT1) 1988

Min.
0.000
0.000
0.006
0.010
0.011
0.014
0.010

0.000

0.008
0.011
0.010
0.005

0.017
0.009
0.000
0.006
0.003



0.000
0.006
0.011
0.000

10
0.013
0.012
0.027
0.026
0.029
0.025
0.025

0.011

0.034
0.038
0.038
0.036

0.032
0.029
0.023
0.024
0.027



0.018
0.020
0.038
0.030

30
0.021
0.021
0.036
0.033
0.037
0.033
0.033

0.023

0.044
0.054
0.047
0.043

0.042
0.041
0.036
0.036
0.040



0.029
0.031
0.051
0.046

50
0.028
0.028
0.045
0.043
0.046
0.043
0.039

0.031

0.051
0.065
0.054
0.048

0.049
0.050
0.044
0.047
0.049



0.037
0.040
0.059
0.058

70
0.035
0.036
0.053
0.055
0.053
0.056
0.047

0.041

0.058
0.075
0.059
0.053

0.056
0.060
0.054
0.058
0.059



0.047
0.051
0.066
0.068

90
0.046
0.047
0.065
0.076
0.067
0.078
0.064

0.056

0.067
0.095
0.068
0.063

0.067
0.080
0.069
0.077
0.071



0.061
0.067
0.078
0.084

95
0.052
0.054
0.074
0.087
0.074
0.089
0.075

0.065

0.074
0.106
0.072
0.069

0.073
0.092
0.076
0.087
0.077



0.068
0.076
0.085
0.094

99
0.065
0.076
0.086
0.113
0.087
0.110
0.091

0.081

0.085
0.126
0.081
0.081

0.083
0.110
0.085
0.103
0.086



0.080
0.097
0.096
0.119

Max.
0.076
0.106
0.102
0.127
0.104
0.135
0.117

0.117

0.105
0.145
0.147
0.096

0.096
0.162
0.135
0.140
0.145



0.108
0.135
0.111
0.163

No. Obs.
4,766
4,786
4,077
2,835
4,704
4,673
4,755

4,463

3,539
2,989
2,788
3,971

3,118
2,992
3,636
3,959
2,908



3,030
4,278
4,326
3,788

SUM06
5.9
10.9
45.0
51.9
62.0
65.8
45.4

23.8

59.4
145.1
54.8
37.8

47.0
68.7
54.2
80.9
55.7



23.1
52.3
147.7
133.8

SUM08
0.0
2.9
9.5
21.2
12.2
40.8
14.4

5.1

7.8
69.7
3.5
4.4

5.1
28.1
8.5
29.6
7.8
55.8


2.6
15.6
32.4
51.0

W126
7.7
11.6
40.1
43.4
49.5
56.5
40.3

21.3

46.5
116.6
40.7
36.7

37.4
57.7
42.0
67.2
41.8



19.2
44.2
105.7
102.8
§ .
Q Calculations based on a May to September season.
o
73



























-------
             0,00
                                          I 7h
                                          H2h
                   WF1
                            WF3
                                    WF4
                                   i7h
                                   [12h
                                                          SHI
                                                                   SHZ
                                                                           SH3
              200-
                                     Total Dosa
                                     Sigmoldal
                                     Sum * 0.07
             > 100
                                                     200-1 (d)
                                                   0)
                                                   c
                                                    '100-
                    WF1
                            WF3
                                     WF4
                                                           SH1
                                                                   SHZ
                                                                            SH3
      Figure 4-22.  Seven- and 12-h means at (a) Whiteface Mountain and (b) Shenandoah
                   National Park for May to September 1987 and integrated exposures at
                   (c) Whiteface Mountain and (d) Shenandoah National Park for May to
                   September 1987.
      Source:  Lefohn et al. (1990c).
1     elevation, proximity to anthropogenic sources of oxidant precursors, regional-scale
2     meteorological conditions, and airshed dynamics between the lower free troposphere and the
3     surface boundary layer.  Table 4-16 summarizes the exposure values for the ten EPRI
4     Integrated Forest Study Sites located in North America.
5
6     4.6.3   Other Spatial Variations in Ozone Concentrations
7          Despite relative intraregional homogeneity, evidence exists for intracity variations in
8     concentrations that are pertinent to potential exposures of human populations and to the
9     assessment of actual exposures sustained in epidemiologic studies.  Two illustrative pieces of
       December 1993
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                 May - September 1983
                               • ToM Doss
                               • SJgmokJal
                               G Sum 2 0.07
                                               300
                                               zoo-
                                               100
           June - September 1985
             Big Meadows  Dickey RMg« Sawmill Run
         (0)
• Total DOM
• StgmohU
D Sum » 0,07
         Big Meadows Dtefcey RUge Sawml Run
                  May-September 1984
                                  Total DOM
                                  SlamokJal
                                  Sim * 0.07
      300 n
                                                200-
                                                        May-September
          (d)
                            • Slgmoldal
                            Q Sun 2 0.07
                                       Run
        ol •"!  Jh=L_Jlb_
          Big Meadow* DtekeyRWga Sawmill Run
                             300 n
                                     May - September 1987
                                 (e)
                                                   • Total DOM
                                                   • SlgmoMal
                                                   Q Sum 2 0.07
figure 4-23. Integrated exposures for three non-Mountain Cloud Chemistry Program's
             Shenandoah National Park sites, 1983 to 1987.

Source: Lefohn et al. (199(te).
December 1993
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TABLE 4-16. SUMMARY STATISTICS FOR 11 INTEGRATED FOREST STUDY SITES
                          (All units are in ppb)
ff
H- '
vo Site
HIGH ELEVATION SITES
Whiteface Mountain, NY



Great Smoky Mountain NP



Coweeta Hydrologic Lab, NC
•^
ON

LOW ELEVATION SITES
W Huntington Forest, NY
£!
3
6
0
2 Howland, MA
9
H
8
Year

1987
1987
1988
1988
1987
1987
1988
1988
1987
1987
1988
1988

1987
1987
1988
1988

1987
1987
1988
1988
Quarter

2
3
2
3
2
3
2
3
2
3
2
3

2
3
2
3

2
3
2
3
24-h
(Ppb)

42
45
49
44
54
53
71
59
50
47
61
57

36
24
40
37

34
26
36
24
12-h
(Ppb)

43
44
50
43
52
51
70
57
48
44
59
54

42
32
46
46

39
32
41
30
7-h
(Ppb)

42
43
49
43
49
49
68
55
47
42
59
51

42
33
46
48

39
31
41
30
1-h Max.
(Ppb)

104
114
131
119
99
95
119
120
85
95
104
100

88
76
106
91

69
76
90
71
SUM06
(ppm-h)

13.2
30.1
33.5
22.6
57.1
34.3
126.3
74.7
32.4
24.1
81.6
63.6

9.8
5.4
19.2
18.6

1.9
3.8
8.1
1.7
SUM08
(ppm-h)

2.5
11.8
13.9
10.4
10.9
8.8
61.2
22.2
2.6
2.4
18.5
19.8

0.9
0.2
6.1
2.7

0.0
0.0
2.9
0.0

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           TABLE 4-16 (cont'd). SUMMARY STATISTICS FOR 11 INTEGRATED FOREST STUDY SITES
1
H- Site
5 LOW ELEVATION SITES (cont'd)
Oak Ridge, TN



Thompson Forest, WA



B.F. Grant Forest, GA

^
^
Gainseville, FL

o

H Duke Forest, NC
I
0
o
g
^ Nordmoen, Norway
§
~H
S
o
* aData were insufficient to calculate statistic.
n

Year

1987
1987
1988
1988
1987
1987
1988
1988
1987
1987
1988
1988
1987
1987
1988
1988
1987
1987
1988
1988
1987
1987
1988
1988




Quarter

2
3
2
3
2
3
2
3
2
3
2
3
2
3
2
3
2
3
2
3
2
3
2
3




24-h

42
29
40
32
36
30
32
32
32
33
47
32
42
29
35
20
38
52
54
38
32
14
22
11




12-h

53
44
57
47
43
36
39
39
46
52
63
47
53
44
48
29
48
59
69
51
40
18
28
15




7-h

50
41
58
51
41
34
37
36
48
54
64
48
50
41
51
30
52
50
75
54
41
20
29
16




1-h Max.

112
105
104
122
103
94
103
140
99
102
127
116
a
a

84
70
100
124
115
141
75
32
53
30



SUM06
(ppm-h)

39.5
24.3
26.4
19.7
10.7
10.3
8.1
13.5
26.1
31.3
53.1
24.1
a
a

23.4
1.9
29.2
a
a

52.9
2.4
0.0
0.0
0.0



SUM08
(ppm-h)

13.5
9.0
9.8
7.7
3.6
2.1
2.3
6.7
5.1
10.3
21.9
7.4
a
a

0.5
0.1
7.8
a
a

23.4
0.0
0.0
0.0
0.0



Source:  Adapted from Taylor et al. (1992).

-------
 1     data are presented in this section, one a case of relative homogeneity in a city with a
 2     population under 500,000 (New Haven, Connecticut) and one a case of relative in
 3     homogeneity of concentrations in a city of greater than 9 million population (New York
 4     City).
 5          As described in the previous version of the criteria document (U.S. Environmental
 6     Protection Agency, 1986a), the general similarity of the percentiles of the hourly average
 7     concentrations for a New Haven site, and two other monitoring stations in the county that
 8     were operating at the time, one in Derby, Connecticut, 9 miles west of New Haven, and one
 9     in Hamden, Connecticut, 6 miles north of New Haven, is evident.  Table 4-17  shows that the
10     data and time of the maximum hourly concentrations by quarter at these three sites are
11      similar.
12
        TABLE 4-17.  QUARTERLY MAXIMUM 1-H OZONE VALUES AT SITES  IN AND
                         AROUND NEW HAVEN, CONNECTICUT, 1976
                        (Chemiluminescence method, hourly values in ppm)
7 -* *-r
Quarter of Year

New Haven, CT
No. measurements
Max 1-h, ppm
Hour of day
Date
Derby, CT
No. measurements
Max 1-h, ppm
Hour of day
Date
Hamden, CT
No. measurements
Max 1-h, ppm
Hour of day
Date
1

10
0.045
11. -00 a.m.
3/29

11
0.015
11:00 p.m.
3/31

56
0.050
12:00 p.m.
3/29
2

1,964
0.274
2:00 p.m.
6/24

2,140
0.280
2:00 p.m.
6/24

2,065
0.240
3:00 p.m.
6/24
3

2,079
0.235
2:00 p.m.
8/12

2,187
0.290
2:00 p.m.
8/12

1,446
0.240
1:00 p.m.
7/20
4

66
0.066
10:00 p.m.
10/3

1,360
0.060
7:00 p.m.
12/20

286
0.065
3:00 p.m.
10/7
       Source:  U.S. Environmental Protection Agency (1986a).
        December 1993
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 1           The source of much of the O3 experienced in the New Haven, Connecticut, area is the
 2      greater New York area (e.g., Wolff et al., 1975; Cleveland et al.,  1976a,b) and an urban
 3      plume transported over the distance from New York City to New Haven would tend to be
 4      relatively well-mixed and uniform, such that intracity variations in New Haven would
 5      probably be minimal.
 6           As indicated in the previous version of the Criteria Document (U.S. Environmental
 7      Protection Agency, 1986a), intracity differences in 03 concentrations have also been reported
 8      by Kelly et al. (1986) for a 1981  study in Detroit, Michigan.  Ozone concentrations were
 9     measured for about 3 mo at 16 sites in the metropolitan Detroit area and in nearby Ontario,
10     Canada,  Values at 15 sites were  correlated with those at a site adjacent to the Detroit
11      Science Center, about 3  km north of the central business district in Detroit.  In general, the
12     correlation decreased as  distance from the Science Center site increased; and, in general, the
13     actual concentrations increased with distance from that site toward the north-northeast.  The
14     highest O3 concentrations were recorded at sites about 10 to 70 km north-northeast of the
15     urban core. At greater distances  or in other directions, 03 maxima decreased.
16          Concentrations of O3 vary with altitude and with latitude.  While a number of reports
17     contain data on O3 concentrations at high altitudes (e.g., Coffey et al., 1977; Reiter, 1977b;
18     Singh et al., 1977; Evans et al., 1985; Lefohn and Jones,  1986), fewer reports are available
19     that present data for different elevations at the same locality.  There appears to be no
20     consistent conclusion concerning  the relationship between O3 exposure and elevation.
21          Wolff et al. (1987) have reported, for a short-term study at High Point Mountain in
22     northwestern New Jersey,  that both the daily maximum and mid-day O3 concentrations were
23     similar at different altitudes, but that the O3 exposures increased with elevation.  Wolff et al.
24     (1987) conducted a study of the effects of altitude on 03 concentrations at three  sites located
25     at three separate elevations on High Point Mountain in northwestern New Jersey.  Data for
 26     several days indicate that in mid-May, when atmospheric mixing was good, vertical profiles
27     were nearly constant, with concentrations increasing only  slightly with elevation.  Likewise,
 28     the daily O3 maxima were similar at different elevations.  At night, however,
29     O3 concentrations were  nearly zero in the valley (i.e., the lowest-elevation site)  and increased
 30     with elevation.  Comparison of the O3 exposures at the three sites (number of hours
 31      > 0.08 ppm) showed that greater cumulative exposures were sustained at the higher

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 1      elevations.  Comparable data from an urban area (Bayonne, NJ) about 80 km southeast of
 2      High Point Mountain showed that the cumulative exposures were higher at all three of the
 3      mountain sites than in the urban area (Wolff et al., 1987). The investigators concluded from
 4      their concentration and meteorological data that elevated, mountainous sites in the eastern
 5      United States may be expected to be exposed to higher O3 exposures than valley sites
 6      throughout the year.
 7           Winner et al.  (1989) have reported that for three Shenandoah National Park sites (i.e.,
 8      Big Meadows, Dickey Ridge, and Sawmill Run), the 24-h monthly mean O3 concentrations
 9      tended to increase with elevation, but that the number of elevated hourly occurrences equal to
10     or above selected thresholds did not. The authors reported that the highest elevation site (Big
11      Meadows) experienced a smaller number of concentrations at or below the minimum
12     detectable level than did the other two sites.  The larger number of hourly average
13     concentrations that occurred at  or below the minimum detectable level at both Dickey  Ridge
14     and Sawmill Run resulted in lower 24-h averages at these sites.
15          Lefohn et al.  (1990c), characterizing the O3 exposures at several high-elevation sites,
16     reported that based on cumulative indices, the Whiteface Mountain summit site (WF1)
17     experienced a slightly higher exposure than the lower elevation Whiteface Mountain (WF3)
18     site.  The site at the base of Whiteface Mountain (WF4) experienced the lowest exposure of
19     the three O3 sites at Whiteface  Mountain.  Among the MCCP Shenandoah National Park
20     sites, the SH2 site experienced  higher O3 exposures than the high-elevation site (SHI).  The
21     "total dose" (the sum of all hourly average concentrations) and sigmoidal (W126) indices
22     were slightly higher at the SH2 than the SHI site. The data capture at  the two sites for the
23     5-mo period was similar.  However, the sum of the concentrations SO. 07 ppm and number
24     of hourly concentrations  SO. 07 ppm were slightly higher at the SHI than at the SH2  site.
 25     For the Whiteface Mountain sites, both the sum of the concentrations SO.07 ppm (SUM07)
 26     and the number of hourly concentrations S0.07 ppm were higher at the WF1 site than at the
 27     WF3 site.
 28           When the Big Meadows,  Dickey Ridge, and Sawmill Run Shenandoah National  Park
 29      data for 1983 to 1987 were compared, a higher resolution of the differences among the
 30      regimes was observed when the cumulative indices were used. No specific trend could be
 31      identified that showed the higher elevation, Big Meadows, site had consistently experienced

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 1      higher 03 exposures than the lower elevation sites. In 2 of the 5 years, the higher elevation
 2      site experienced lower exposures than the Dickey Ridge and Sawmill Run sites, based on
 3      "total dose" or sigmoidal indices.  For 4 of the 5 years, the SUM07 index yielded the same
 4      result.
 5           An important issue for assessing possible impacts of 03 at high-elevation sites that
 6      requires further attention is the use of mixing ratios (e.g., ppm) instead of absolute
 7      concentration (e.g., in units of micrograms per cubic meter) to describe 63 concentration.
 8      In most cases, mixing ratios (e.g., ppm) or mole fractions are used to describe
 9      63 concentrations. Lefohn  et al. (1990c) have pointed out that the manner in which
10     concentration is reported may be important when assessing the potential impacts of air
1 1      pollution on high-elevation forests. Concentration (in units of micrograms per cubic meter)
12     varies as a function of altitude. Although the change in concentration is small when the
13      elevational difference between sea level and the monitoring site is small, it becomes
14     substantial at high-elevation sites.  Given the same part-per-million value experienced at both
15     a high- and low-elevation site, the absolute concentrations (i.e., micrograms per cubic meter)
16     at the two elevations will be different.  Since both 03 and ambient air are gases, changes in
17     pressure directly affect their volume.  According to Boyle's law, if the temperature of a gas
18     is held constant, the volume occupied  by the gas varies inversely with the pressure (i.e., as
19     pressure decreases, volume increases). This pressure effect must be considered when
20     measuring absolute pollutant concentrations. At any given sampling location, normal
21     atmospheric pressure variations have very little effect on air pollutant measurements.
22     However, when mass/volume units of concentration  are used and pollutant concentrations
23     measured at significantly different altitudes  are compared, pressure (and hence volume)
24     adjustments are necessary.
25          These exposure considerations are trivial at low-elevation sites. However, when one
26     compares exposure-effects results obtained at high-elevation sites with those from low-
27     elevation sites, the differences may become significant (Lefohn et al.,  1990c).  In particular,
28     assuming that the sensitivity of the biological target is identical at both low and high
29     elevations, some adjustment will be necessary when attempting to link experimental data
30     obtained at low-elevation sites with air quality data monitored at the high-elevation stations.
 31
        December 1993                           4_ai       nuAFT-nn MOT nTTnrn rat

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 1      4.7   INDOOR OZONE CONCENTRATIONS
 2           Most people in the United States spend a large proportion of their time indoors,
 3      A knowledge of actual exposures of populations to indoor levels of 63 is essential for the
 4     interpretation and use of results associated with epidemiological studies.  However,
 5     essentially all routine air pollution monitoring is done on outdoor air.  Until the early 1970s,
 6     very little was known about the O3 concentrations experienced inside buildings.  The ratio of
 7     the indoor/outdoor O3 concentrations (I/O) is a parameter that has been widely used for
 8     studying the indoor and outdoor relationships, sources, and exposure patterns of O3.
 9     However, the data base on this subject is not large and a wide range of I/O Oj concentration
10     relationships can be found in the literature.  The only significant source of 03 in indoor
11     residential air is infiltration of outdoor 03, with ventilation rates affecting the flow of air
12     between indoor and outdoor (Zhang and Lioy, in press).
13          Reported I/O values for 03 are highly variable (U.S. Environmental Protection Agency,
14     1986a) and range from  <0.1 to 0.80±0.10 for various indoor environments and ventilation
15     rates (Weschler et al., 1989).  Unfortunately,, the number of experiments and kinds of
16     structures examined to date provide only limited data for use in modeling indoor exposures.
17     Data were summarized by Yocom (1982) describing studies of indoor-outdoor gradients in
18     buildings and residences for either O3 or photochemical oxidant.  This information was
19     presented in the previous  document (U.S. Environmental Protection Agency, 1986a).  The
20     results were highly variable. A relatively large number of factors can affect the difference in
21     O3 concentrations between the inside of a structure and the outside air.  In general, outside
22     air infiltration or exchange rates, interior air circulation rates, and interior surface
23     composition (e.g., rugs, draperies, furniture, walls) affect the balance between replenishment
24     and decomposition of O3  within buildings (U.S. Environmental Protection Agency, 1986a).
25     Although indoor concentrations of O3 will almost invariably be less than outdoors, the fact
26     that people spend more time indoors than outdoors may result in greater overall indoor
27     exposures.
 28           Cass et al. (1991) have discussed the importance of protecting works of art from
 29      damage  due to O3.  Based on experiments  that show that the fading of artists' pigments in
 30      the presence of 03 is directly related to  the product of concentration x duration of exposure,
 31      it appears that museum personnel face unusual challenges because indoor 03 exposure must

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 1      be reduced to very low levels in order to protect the collections from accumulated damage
 2      over periods of 100 years or more. Druzik et al. (1990) reported that in a survey of
 3      11 museums, galleries, historical houses and libraries in southern California, facilities with a
 4      high air exchange with the outdoors and no pollutant removal system have indoor
 5      O3 concentrations greater than two-thirds as high as outdoor concentrations. The author
 6      reported mat museums with conventional air conditioning systems showed indoor
 7      O3 concentrations about 30 to 40% of those outside, while museums with no forced
 8      ventilation system, where slow air infiltration provides the only means of air exchange, have
 9      indoor Qj levels typically 10 to 20% of those outdoors.  Several other studies have been
10      reported in the literature and Table 4-18 lists the I/O ratios reported from these efforts as
11      well as those from earlier years.
12           Automobiles and other vehicles constitute another indoor environment in which people
13      may spend appreciable amounts of time. As with buildings, the mode of ventilation and
14     cooling helps determine the inside concentrations.  The U.S. EPA (1986a) describes studies
15      for the I/O ratios. In one study reported by Contant et al. (1985), the I/O ratios from
16     49 measurements inside vehicles were 0.44 for the mean, 0.33 for the median, and 0.56 for
17     maximum concentrations measured.  Chan et al. (1991) reported an I/O ratio of 0.20 for
18     median in-vehicle concentrations (0.011 ppm) and time-matched fixed-site measurements
19     (0.051 ppm).
20          At present, there are no long-term monitoring data on indoor air pollutant
21     concentrations comparable to the concentration data available for outdoor locations.  Thus,
22     for estimates of the exposure of building or vehicle occupants to O3 and other photochemical
23     oxidants, it is necessary to rely on extrapolations of very limited I/O data.
24
25
26     4.8   ESTIMATING EXPOSURE TO OZONE
27     4.8.1   Introduction
28           It is important that accurate estimates of both human and vegetation exposure to 63 are
29     available for assessing the risks posed by the pollutant.  In the Introduction of this chapter,
30     the differences between concentration, exposure, and dose were discussed.  In this section,
31     examples are provided on how both fixed-site monitoring information, as well as human

       December 1993                          4-83       DRAFT-DO NOT QUOTE OR CITE

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 TABLE 4-18. SUMMARY OF REPORTED INDOOR-OUTDOOR OZONE RATIOS
Structure
Indoor-Outdoor Ratio
              Reference
Hospital
Residence
(with evaporative cooler)
Office
(air conditioned; 100% outside air
intake)
(air conditioned; 70% outside air
intake)
      0.67s
      0,60a

    0.80±0.10


    0.65 ±0.10
     Thompson et al. (1971)
     Thompson et al. (1973)

     Sabersky et al. (1973)


     Sabersky et al. (1973)
Office
Office/Lab
Residence
Residence
Two offices
Residence
(gas stoves)
(all electric)
Office
School Room
Residence
Residences (1 each)
(air conditioned)
(100% outside air; no air
conditioning)
Residences (12)
(air conditioned)
Residences (41)
Residences (6)
(window open)
(window closed)
(air conditioning)
Art Gallery
0.66
0.54
0.62
0.70
0.50-O.70
0.3
0.19
0.20
0.29
0. 19 (max. cone.)
0.10-0.25
0.00-0.09
1.0
0.21 (mean cone.)
0,12(med. cone.)
0.59 (max. cone.)
0.3
0.59±0.16
0.26 ±0.12
0.28 ±0.12
0.5
Shair and Heitner (1974)
Shair and Heitner (1974)
Hales et al. (1974)
Sabersky et al. (1973)
Sabersky et al. (1973)
Moschandreas et al. (1978)
Moschandreas et al. (1981)
Moschandreas et al. (1978)
Berk et al. (1980)
Berk et al. (1981)
Stock et al. (1983)
Contant et al. (1985)
Lebowitz et al. (1984)
Zhang and Lioy (In press)
Shaver et al. (1983)
December 1993
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             TABLE 4-18 (cont'd). SUMMARY OF REPORTED INDOOR-OUTDOOR
                                          OZONE RATIOS
        Structure
Indoor-Outdoor Ratio
          Reference
        Ait Gallery
        (three modes of ventilation in each
        24-h period: recirculation,
        mixture of recirculated and
        outside air, and 100% outside air)
        Museums

        Museum
        Museums
        (with high air exchange, but no
        air conditioning)

        (with no air conditioning and with
        low air exchange rate)

        (with natural convection-induced
        air exchange system)

        (with conventional air conditioning
        system but with, no activated
        carbon air filtration)

        (with activated carbon air
        nitration system)
    0.70±0.10
   (mean cone.)
Davies et al. (1984)
       0.45

   0.69-0,84 (1-h)
   0.50-0.87 (8-h)

   0.10-0,59(14i)
   0.10-0.58
Shaver et al. (1983)
Nazaroff and Cass (1986)
Dnuak et al. (1990)
   0.33-0.49 (1-h)
   0.28-0.40 (8-h)

   0.24-0.40 (1-h)
   0.25-0.41 (8-h)
   0.03-0.37 (1-h)
   0.03-0.31 (8-h)
        Measured as total oxidants.
 1      exposure models, are used to estimate risks associated with Oj exposure.  A short discussion
 2      is provided on the importance of hourly average concentrations,  used in the human health
 3      and vegetation experiments, mimicking as closely as possible "real world" exposures.
 4           Human exposure represents the joint occurrence of an individual being located at point
 5      (x,y,z) during time t, with the simultaneous presence of an air pollutant at concentration
 6     C*,y,z (t) (U.S. Environmental Protection Agency, 1991).  Consequently, an individual's
 7     exposure to an air pollutant is a function of location as well as time.  If a volume at a
 8     location can be defined such that air pollutant concentrations within it are homogeneous yet
 9     potentially different from other locations, the volume may be considered a
10     "microenvironment" (Duan, 1982).  Microenvironmente may be aggregated by location (i.e.,
       December 1993
                  DRAFT-DO NOT OTTOTR ntt rnrr

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 1     indoor or outdoor) or activity performed at a location (i.e., residential, commercial) to form
 2     microenvironment types.
 3          The Air Quality Criteria for Carbon Monoxide (U.S. Environmental Protection Agency,
 4     1991) discusses the difference between individual and population exposures.  The report
 5     notes that Sexton and Ryan (1988) define the pollutant concentrations experienced by a
 6     specific individual during normal daily activities as "personal" or "individual" exposures,
 7     A personal exposure depends on the air pollutant concentrations that are present in the
 8     location through which the person moves, as well as on the time spent at each location.
 9     Because time-activity patterns can vary substantially from person to person, individual
10     exposures exhibit wide variability (U.S. Environmental Protection Agency,  1991).  Thus,
11     although it is a relatively straightforward procedure to measure any one person's exposure,
12     many such measurements may be needed to quantify exposures for a defined group. The
13     daily activities of a person in time and space define his or her activity pattern.  Accurate
14     estimates of air pollution exposure generally require that an exposure model account for the
IS     activity patterns of the population of interest.
16           From a public health perspective, it is important to determine the "population
17     exposure," which is the aggregate exposure for a specified group of people (e.g., a
18     community or an identified occupational cohort).  Because exposures are likely  to vary
19     substantially between individuals, specification of the distribution of personal exposures
20     within a population, including the average value and the associated variance, is  often the
21     focus of exposure assessment studies.
22           In many cases, the upper tail of the distribution, which represents  those individuals
23     exposed to the highest concentrations, is frequently of special interest because the
24     determination of the number of individuals who experience elevated pollutant levels can be
25      critical for health risk assessments.  This is especially true for pollutants for which the
26      relationship between dose and response is highly nonlinear.  Runeckles and Bates (1991)
27      have pointed out the importance of peak concentrations in eliciting adverse human effects.
28      As indicated in the Introduction, results using controlled human exposures  have shown the
 29      possible importance of concentration in relation to duration of exposure and inhalation rate.
 30     The implication of the importance of concentration can be translated into the conclusion that
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 1      the simple definition of exposure as equal to concentration multiplied by time may be too
 2      simplified.
 3           Because, for most cases, it is not possible to estimate population exposure solely from
 4      fixed-station data, several human exposure models have been developed.  Some of these
 5      models include information on human activity patterns (i.e., the microenvironttients people
 6     visit and the times they spend there).  These models also contain submodels depicting the
 7      sources  and concentrations likely to be found in each microenvironment, including indoor,
 8      outdoor, and in-transit settings.
 9
10     4.8.2  Fixed-Site Monitoring Information Used To Estimate  Population
11              and Vegetation Exposure
12          For most cases, from the information provided in earlier sections in this chapter, fixed-
13     site monitors alone cannot accurately depict population exposures because (1) indoor and
14     in-transit concentrations of Gj may be significantly different from ambient  Qj concentrations,
15     and (2)  ambient outdoor concentrations of O3 that people come in contact with may vary
16     significantly from O3 concentrations measured at fixed-site monitors.  Fixed-site monitors
17     measure concentrations of pollutants in ambient air.  Ambient air as noted  by the EPA (1991)
18     is defined in the Code of Federal Regulations (1991) as air that is "external to buildings, to
19     which the general public has access."  But the nature of modem urban lifestyles in many
20     countries, including the United States, is that people spend an average of over 20 h per day
21     indoors (Meyer, 1983).  Reviews of studies summarized in Section 4.7 show that indoor
22     O3 concentration measurements vary significantly from simultaneous measurements in
23     ambient air.  The difference between indoor and outdoor air quality and the amount of time
24     people spend indoors reinforces the conclusion that, for most cases, using ambient air quality
25     measurements alone do not provide accurate estimates of population exposure.
26           For vegetation, in most cases, it is assumed that exposure is the same as the
27     concentration information provided at fixed monitors in the field (see Sections 5.5 and 5.6).
28     In some cases, because of (a) foliar scavenging and (b) height differences between the
29     vegetation canopy and pollutant monitor, the measured concentration is not equivalent to the
30     vegetation exposure.
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 1           A subgroup that has been studied by several investigators to assess the influence of
 2      ambient air pollution on their respiratory health and function is children attending summer
 3      camp.  Because children are predominantly outdoors and relatively active while at camp,
 4      they provide a unique opportunity to assess the relationships between respiratory health and
 5      function and concurrent air pollution levels.  Children may be at potentially increased risk
 6      from air pollution by virtue of their lifestyle patterns, which often involve several hours of
 7      outdoor exercise, regardless of air quality, during daylight hours.
 8           For campers, attempts have been made to estimate human exposure  to O3 using types
 9      of activity patterns (Mage et al., 1985); Paul et al., 1987). Mage et al. (1985) developed an
10      objective approach to estimate the  dose delivered to the lung of a 12-year-old camper by
11      using:  pulmonary minute volume  associated with a specific activity, the fractional
12      penetration beyond the trachea, and infiltration of ozone indoors. Lioy and Dyba (1989)
13      have applied the parameters used by Mage et al. (1985) to predict the delivered O3 dose over
14     a four-day episode period. The schedule of a hypothetical camper was matched to the actual
15     03 concentrations, and the predicted doses were estimated.
16          Several studies involving children attending summer camp  have been summarized hi
17     Chapter 7. In one study, Avol et  al. (1990) reported that 03 levels at a southern California
18     summer camp, located 190 km southeast of Los Angeles, rose gradually throughout each
19     day, displaying a "broad peak* between 1000 and 2000 h each day.  Daily maxima typically
20     occurred in late afternoon (1500 to 1700 h); subsequently, concentrations gradually declined
21     to non-zero overnight O3 levels of 0.025 to 0.050 ppm.  Spektor et al. (1991) investigated
22     the pulmonary function of 46 healthy children on at least 7 days for each child during a
23     4-week period at a northwestern New Jersey residential summer camp in 1988. The daily
24     levels of 1-h peak O3 and the 12-h average H+ concentrations are shown in Figure 4-24.
25     On 5 of these days, the  current NAAQS of 0.12 ppm was exceeded. The maximum hourly
26     concentration attained during the study was 0.150 ppm.  The year 1984 was a milder
27     O3 exposure year and Figure 4-25 summarizes the maximal 1-h O3 concentrations at
28     Fairview Lake during a 1984 study period (Spektor et al., 1988).
 29
 30
        December 1993                          4-88       DRAFT-DO NOT QUOTE OR CTTB

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                                 National Ambient
                     0       5      10      15      20
                                      Day Number

Figure 4-24.  Maximum 1-h ozone concentrations (in parts per billion) and average
             8:00 a.m. through 8:00 p.m. strong acid concentrations (expressed as
             micrograms per cubic meter of sulfuric acid) for each day that pulmonary
             function data were collected at Fairview Lake  camp in 1988. The
             correlation coefficient (r) between O3 and H+  was 0.56.

Source:  Spektor et al. (1991).
                       National Ambient Air Quality Standard

                                         Dates -1984
                                                            August
Figure 4-25. Maximal 1-h ozone concentrations at Fairview Lake during the study
             period.

Source: Spektor et al. (1988).
 December 1993
4-8Q
DRAFT-DO NOT QUOTE OR CITE

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 1     4.8.3   Personal Monitors
 2          A personal exposure profile can be identified by using a personal exposure monitor,
 3     McCurdy (1994) has described the development of personal exposure monitors by several
 4     companies. However, little data are available describing personal exposures for individuals
 5     using these monitors.  An example of a pilot study using a personal exposure monitor was
 6     described for assessing O3 exposure to 23 children by Liu et al. (1993). The authors
 7     collected indoor, outdoor, and personal 03 concentration data as well as time-activity data in
 8     State College, Pennsylvania. Results from the pilot study demonstrated that fixed-site
 9     ambient measurements may not adequately represent individual exposures.  Outdoor
10     O3 concentrations showed substantial spatial variation between rural and residential regions.
11     The  authors reported that the use of fixed-site measurements could result in an error as high
12     as 127%.  In addition, Liu et al.  (1993) reported that models based on time-weighted indoor
13     and  outdoor concentrations explained only 40% of the variability in personal exposures.
14     When the model used included observations for only those participants who spent the
15     majority of their day in or near their homes, an R of 0.76 resulted when estimates were
16     regressed on  measured personal exposures.  The authors concluded mat contributions from
17     diverse indoor and outdoor microenvironraents should be considered to estimate personal
18     O3 exposure  accurately. From these results, it is clear that additional data are needed to
19     better quantify the O3 exposures to which populations are exposed.
20
21     4.8.4   Population Exposure Models
22          The availability of personal exposure monitors has facilitated the use of the direct and
23     indirect approaches to assessing personal exposure.  Whether the direct or indirect approach
24      is followed, the estimation of population exposure requires a model.  Sexton and Ryan (1988)
25      suggest that most exposure models can be classified as one of three types: statistical,
26      physical, or physical-stochastic.
27          In the U.S. EPA (1991), all three types are discussed. The statistical approach requires
28      the  collection of data on human exposures and the factors thought to be determinants of
 29      exposure.  These data are combined in a statistical  model, normally a regression equation or
 30     an analysis of variance, to investigate the relationship between air pollution exposure
 31      (dependent variable) and the factors contributing to the measured exposure (independent

        December 1993                          4-90      DRAFT-DO NOT QUOTE  OR CITE

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 1      variables). If the study group constitutes a representative sample, the derived statistical
 2      model may be extrapolated to the population defined by the sampling frame.  In the physical
 3      modeling approach, the investigator makes an a priori assumption about the underlying
 4      physical processes that determine air pollution exposure and then attempts to  approximate
 5      these processes through a mathematical formulation. Because the model is chosen by the
 6      investigator, it may produce biased results because of the inadvertent inclusion of
 7      inappropriate parameters or the improper exclusion of critical components. Hie physical-
 8      stochastic approach combined elements of both  the physical and statistical modeling
 9      approaches.  The investigator begins by constructing a mathematical model that  describes the
10      physical basis for air pollution exposure.  Then a random or stochastic component (that takes
11      into account the imperfect knowledge of the physical parameters that determine exposure) is
12      introduced into the model.  The physical-stochastic approach limits the effect of
13      investigator-induced bias by the inclusion of the random component, and allows for estimates
14     of population distributions for air pollution exposure. Misleading results still may be
15     produced, however, because of poor selection of model parameters. In addition, the required
16     knowledge about distributional characteristics may be difficult to determine.
17          McCurdy (1994) has reviewed the current status of human exposure modeling.  The
18     author describes two distinct types of O3 exposure models: those that  focus narrowly on
19     predicting indoor O3 levels and those that focus on predicting 03 exposures on a community-
20     wide basis. The models that predict indoor O3 levels have been described by Sabersky et al.
21     (1973), Shair and Heitner (1974), Nazaroff and Cass (1986), and Hayes (1989, 1991).
22     McCurdy (1994) discusses four distinct models that predict 03 exposure on a community-
23     wide basis.  These models are:
24
25            1. pNEM/O3 based on the NEM  series of models  (Paul et al., 1986; Johnson
26               et al., 1990; McCurdy et al., 1991).
27
28            2. SAI/NEM (Hayes et al., 1984; Hayes and Lundberg, 1985; Austin et al.,
29               1986; Hayes et al., 1988; Hayes and Rosenhaum, 1988).
30
31            3. REHEX (Lurmann and Colome, 1991; Winer et al., 1989; Lurmann et al.,
 32               1989; Lurmann et al., 1990).
 33
 34            4. Event probability exposure model (EPEM) (Johnson et al., 1992).
 35
       December 1993                           4-Q1       DRAFT-DO  NOT QUOTE OR CTTE

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 1          McCurdy (1994) points out that ail four models are related to the NBM (National
 2      Ambient Air Quality Standards Exposure Model approach).  The NEM is an EPA exposure
 3      model developed in the 1980s (Bifler et at, 1981).  Outdoor air quality data are obtained
 4      from monitoring or modeling data.  In most applications of NEM, fixed-site monitoring data
 5      are used. The hourly average values are transformed by a suitable relationship so that they
 6      better  represent air quality outside of the various microenvironments of interest.  McCurdy
 7      (1994) points out that the important point of the NEM spatial dimension is that people can be
 8      assigned to a monitor using United States Census data.  In addition, community trips can be
 9      assigned among the districts, grid cells, or neighborhood types using Census data.  Thus,  the
10      NEM  model simulates the movement of people through space for work-trip purposes.
11      Interested readers are referred to McCurdy (1994) for further discussion of the pNEM
12      model.
13           The SAI/NEM is based on an earlier version of NEM.  The SAI version has more
14     districts, more monitoring input data, and a more detailed mass-balance model to predict
15      indoor O3 concentrations that pNEM/Oj or earlier versions.  The REHEX model adopted
16     some  of the NEM computer code but uses a more detailed geographic resolution.  Similar to
17     the NEM models and SAI/NEM, REHEX explicitly uses home/work trip data to "move"
18     people through the region during their day.  The REHEX calculates O3 exposure and dose
19     using discrete distributions of hourly averaged air quality.  The model contains an exposure-
20     response relationship that allows analysts to directly estimate discrete, hourly averaged
21     O3 dose levels in exposed individuals (McCurdy, 1994).  The author points out that the
22     Event Probability  Model (EPEM) does not provide distributions of Oj exposure for any
23     specified population group.  The model estimates the probability that a person selected at
24     random will experience a particular exposure situation.  The estimate is based on an
25     individual being outdoors for an entire hour. McCurdy (1994) notes that if a person were
26     outdoors for a shorter period,  he or she would not be counted. Vostal and Johnson (1993)
27     have  described  the use of the EPEM for the Houston, Texas area for the 1982 O3 season.
28
 29      4.8.5   Concentration and Exposures Used in Research Experiments
 30           It is important to adequately characterize the exposure patterns that result in vegetation
 31      and human health effects.  In  Chapter 5 (see Section 5.5), it has been pointed out that the

        December 1993                         4-92       DRAFT-DO NOT QUOTE OR CITE

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 1      hourly average concentrations used in many of the high treatment experimental studies did
 2      not necessarily mimic those concentrations observed under ambient conditions.  Although the
 3      ramifications of this observation on the effects observed is not clear, it was pointed out that
 4      the highest treatments used in many of the open-top chamber experiments were bimodal in
 5      the distribution of the hourly average concentrations. In other experiments designed to assess
 6      the effects of O3 on vegetation, constant concentration (i.e., square  wave)  exposures were
 7      implemented. As has been discussed in earlier sections of this Chapter, hourly average
 8      concentrations change by the hour and "square wave" exposure regimes do not normally
 9      occur under ambient conditions.  In addition to the exposures used at the highest treatment
10      levels, there is concern that the hourly average concentrations used in the  control treatments
11      may be lower than those experienced at isolated sites in the United  States or in other parts of
12      the world.  Although the ramifications of using such exposure regimes is unclear, there is
13      some concern that the use of such levels may result in an overestimation of vegetation yield
14     losses when compared to treatments greater than the control treatment (see Section 5.5 and
15      Lefohn and Foley, 1992).
16          For assessing the human health effects of Og exposure, a series of studies has explored
17     prolonged 6.6 h O3 exposures at low levels (i.e., 0.08 to 0.12 ppm) (Horstman, 1990).
18     McDonnell et al. (1991), using similar hourly average concentration regimes, have confirmed
19     the findings reported by Horstman et al. (1990).  All the research investigations using 6.6-h
20     durations have applied constant concentrations during the exposure period. If, as indicated  in
21     the Introduction of this chapter, concentration is more important than duration and ventilation
22     rate, different human health effects may occur as a result of different exposure regimes that
23     have identical 6.6-h average concentrations.  Because of this, it is important to explore the
24     different types of exposure regimes that occur under ambient conditions during an 8-h
25     episode.
26          Lefohn and Foley (1993) reported on an analysis of hourly average  data for
27     O3 monitoring sites  that (1) never experienced an exceedance of an hourly average
28     concentration equal  to or greater than 0.12 ppm and (2) experienced 8-h daily maximum
29     average concentrations greater than 0.08 ppm. For those monitoring sites that met the above
30     two criteria, they identified the number of times the 8-h daily maximum average
31     concentration exceeded 0,08 ppm during the monitoring year.  For the period 1987 to 1989,

       December 1993                           4-
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 1     there were 925 exposure regimes identified from 166 site-years of data that met the above

 2     criteria. The data were then organized into the following seven categories:

 3

 4            I.    The occurrence of 8-h daily maximum averages greater than 0.08 ppm
 5                 and less than 0.09 ppm;
 6
 7            n.    The occurrence of 8-h daily maximum averages greater than
 8                 0.08 ppm but less than or equal to 0.082 ppm, which contained
 9                 only hourly average concentrations greater than 0.08 ppm but less
10                 than or equal to 0.082 ppm;
11
12            m.   8-h daily maximum averages greater than 0.08 ppm, which
13                 contained hourly average concentrations less than 0.09 ppm;
14
15            IV.   8-h daily maximum averages greater than 0.08 ppm and less than
16                 0.09 ppm, which contained at least 1 hourly average concentration
17                 greater man or equal to 0.09 ppm but less than 0.10 ppm;
18
19            V.   8-h daily maximum averages greater than 0.08 ppm and less than
20                 0.09 ppm, which contained at least 1 hourly average concentration
21                 greater than or equal to 0.10 ppm;
22
23            VI.   8-h daily maximum averages  less than 0.08 ppm, which contained
24                 at least 1 hourly average concentration greater than or equal to
25                 0.09 ppm  but less than 0.10 ppm; and
26
27            VII. 8-h daily maximum averages less than 0.08 ppm, which contained
28                 at least  1 hourly average concentration greater man or equal to
29                 0.10 ppm,
30
31      Figure 4-26 summarizes the results of the analysis.  The results indicated that there was a

32      poor relationship between the value of the 8-h daily maximum average concentration and the

33      frequency of occurrence of hourly average concentrations within specific ranges (e.g.,

34      between 0.09 and 0.10 ppm).  In no case  could the authors  identify a monitoring site that

35      experienced the "square-wave" type of exposure that was described in Category n (i.e., the

36      occurrence of 8-h daily maximum averages greater than 0.08 ppm but less than or equal to

37      0.082 ppm, which contained only hourly average concentrations greater than 0.08 ppm but

 38      less than or equal to 0.082 ppm).  Lefohn and Foley (1993) concluded that the "square

 39      wave" exposures used  in the 6.6-h duration human health effects experiments were not found

 40      under ambient conditions.  The authors identified 453 additional exposure regimes, where the


        December 1993                          4-94      DRAFT-DO NOT QUOTE OR COTE

-------
                                          Categories
      Figure 4-26.  The number of occurrences for each of the seven categories described in
                  text.
      Source: Lefohn and Foley (1993).
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
8-h daily maximum average was less than 0.08 ppm but experienced maximum hourly
average concentrations greater than or equal to 0.09 ppm. Thus, if hourly average
concentrations ^0.08 ppm are of concern for affecting human health, there will be instances
where occurrences above this threshold are evident, but the 8-h average value is below
0.08 ppm.
4.9   CONCENTRATIONS OF PEROXYACETYL NITRATES IN
      AMBIENT ATMOSPHERES
4.9.1   Introduction
     The biological effects of PAN in human exposures, lexicological studies of animals,
and plant response and yield have been considered previously (U.S. Environmental
Protection Agency, 1986). Controlled human exposure studies involving Oj and O3 + PAN
December 1993                        4.0*      DRAFT-DO NOT OTTOTP rat rrm

-------
 1      are discussed elsewhere in this document (Section 7.2.6.3).  Some effects on respiratory
 2      parameters have been reported in one study, but not in others. However, the PAN
 3      concentrations used in these studies have been well above the maximum ambient
 4      concentrations usually experienced within die Los Angeles Basin many years ago (U.S.
 5      Environmental Protection Agency, 1986) and, most especially, above the maximum ambient
 6      concentrations in the more recent measurements considered in this section.
 7          The PANs are of importance as reservoirs for NC^ as  NOX is depleted relative to
 §      VOCs in plumes moving downwind into less polluted areas (Section 3.2.4). In performance
 9      evaluation of ozone air quality models, measured concentrations  of PANs are useful in model
10      evaluation (Section 3.6.4.2).
11          In the previous air quality criteria for O3 and other photochemical oxidants (U.S.
12      Environmental Protection Agency,  1986), extensive tabulations of PAN and peroxypropionyl
13     nitrate (PPN), CH3CH2C(O)OONO2, concentrations were given based on measurements
14     made between 1965 and 1981 based on references up to 1983.  In the present work,
15     references starting in 1983 up to the present are used for measurements of PANs in urban
16     and rural locations. The urban area measurements are from the United States, Canada,
17     France, Greece, and  Brazil.  The use of measurements from aboard serve to  illustrate or
IS'     support certain U.S.  results as well as  to demonstrate the widespread presence of PANs in
19     the atmosphere.
m
21     4.9.2   Urban Area Peroxyacetyl Nitrate Concentrations
22          The prior criteria document for ozone and other photochemical oxidants contains for
23     urban sites a number of tables tabulating measurements of PAN, peroxypropionyl nitrate
24     (PPN), the PPN to PAN ratios, and the PAN to 03 ratios (Altshuller, 1983;  U.S.
25     Environmental Protection Agency, 1986). Based on comparisons of PAN measurements in
 26     Eos Angeles in 1980 with those made  in the 1960s, it was uncertain whether PAN
 27     concentrations had decreased.  In tile Los Angeles area, the average and maximum PAN
 28     concentrations reported ranged from 1.6 to 31 ppb and from 6 to 214 ppb.  The wide
 29     variations at least in  part was associated with the range of years, different seasons,  and
 30     differing average times among  studies. The PPN to PAN ratios in Los Angeles on average
 31     ranged among studies from 0.15 to 0.2, whereas the PAN to O3 ratios on average ranged

                 1993                         4193      DRAFT-DO NOT QUOTfi

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 1      among studies from 0.04 to 0.2.  In the earlier PAN measurement results, studies conducted
 2      in die South Coast Air Basin of California predominated.
 3           The average PAN concentrations measured in other cities usually were lower than in
 4      the Los Angeles area, whereas the maximum PAN concentrations overlapped with the lower
 5      end of range in Los Angeles. The PPN and PAN ratios in other cities ranged from 0.1 to
 6      0.4, while the PAN to Oj ratios were in the 0.01 to 0.05 range.
 7           Seasonally, PAN to O3 ratios tended to be somewhat higher in the winter. The diurnal
 8      characteristics of O3 and of PAN were similar, but not identical.
 9           The recent urban area measurement results are tabulated in Table 4-19.  The earlier
10      maximum PAN concentrations reported usually were substantially higher than those given hi
11      Table 4-19.  A possible exception occurs for the Claremont, CA, results.  Measurements of
12      PAN and PPN were made in 1989 and 1990 at sites downwind of Los Angeles: Perrin,
13      90 km east-southeast, and Palm Springs, 120 km east of Los Angeles (Grosjean and
14     Williams, 1992).  The concentrations of PAN and PPN were high, and the concentration
IS     maxima occurred during the evening hours consistent with downwind transport from the
16     Los Angeles area rather man local sources.
17          In Southern California, the maximum PAN concentrations appear to be more evenly
18     distributed spatially during the fall than during the summer  (Williams and Grosjean, 1990).
19     At coastal  and central locations, the PAN maxima during the fall were comparable to those
20     observed at inland locations during the summer.
21          As observed previously, PAN concentrations in other U.S. cities as well as cities in
22     other countries tend to be substantially lower than in Los Angeles and its surrounding  urban
23     areas (Table 4-19).  An exception occurs for the measurements from Paris (Tsalkoni et al.,
24     1991).  Maximum PAN concentrations in the 20 to 35 ppb range were observed.
25          In recent measurements in Atlanta, GA,  at the Georgia Institute of Technology (GIT)
26     campus site made in 1992, not only were PAN and PPN measured, but very occasionally
27     peroxymethacryloyl nitrate (MPAN) CH.2=C(CH$ C(O)OONO2  was observed (Williams
28     et al.,  1993). Maximum diurnal concentrations of PANs and 63 occur in late afternoon and
29     early evening.  The average MPAN concentration was 0.3 ppb, and the maximum value was
30     0.5 ppb and constituted about 15 % of the concurrent PAN concentrations. MPAN is  a
31     product of the atmospheric photooxidation of local biogemc sources of isoprene.

       December 1993                         4.97      DRAFT-DO NOT QUOTE OR CITE

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TABLE 4-19. SUMMARY OF MEASUREMENTS OF PEROXYACETYL NITRATE
        AND PEROXYPROPIONYL NITRATE IN URBAN AREAS
I










t>
oi


g
g
H
§'

55
9
O
c
2
r>
Site
Long Beach, CA
Anaheim, CA
Los Angeles, CA
Burbank, CA
Azusa, CA
Claremont, CA
Perrin, CA
Palm Springs, CA
Downey, CA
Boulder, CO

Denver, CO
Houston, TX
Philadelphia, PA
Staten Island, NY
Atlanta, GA
Edmonton, Alberta,
Canada
Calgary, Alberta,
Canada
University of
Calgary, Alberta,
Canada
Simcoe, Ontario,
Canada
Months/
Year
6-12/1987
6-12/1987
6-12/1987
6-12/1987
6-9/1987
6-9/1987
6/1989 to 6/1990
6/1989 to 6/1990
2/1984
5-6 and
8-9/1987
3/1984
3/1984
4/1983
4/1983
7-8/1992
12/1983 to 4/1984

7/1981 to 2/1982

10/1980 to 8/1981


6/1980 to 3/1981

Number
of Days
Sampled
16
14
16
16
11
10
NAa
NAa
10
12
45
9
9
19
7
36
66

213

175


191

PAN
Concentration
(ppb)
Average/Mean
NAa
NAa
NAa
NAa
NAa
NAa
1.6
1.6
1.2
0.63
0.59
0.64
0.75
1.1
1.6
0.71


0.14

0.22


1.3

Maximum
16
19
13
19
13
30
9.1
7.6
6.7
2.0
3.8
2.0
7.9
3.7
5.5
2.9
7.5

6.6

2.4


5.6

PPN
Concentration
(ppb)
Average/Mean
NAa
NAa
NAa
NAa
NAa
NAa
NAa
NAa
0.06
0.08
0.07
0.02
0.045
0.14
0.21
0.14
NAa

NAa

NAa


NAa

Maximum
NAa
NAa
NAa
NAa
NAa
NAa
0.73
0.42
0.40
0.3
0.6
0.09
0.54
0.50
0.90
0.37
NAa

NAa

NAa


NAa

Reference
Williams and Grosjean (1990)
Williams and Grosjean (1990)
Williams and Grosjean (1990)
Williams and Grosjean (1990)
Williams and Grosjean (1990)
Williams and Grosjean (1990)
Grosjean and Williams (1992)
Grosjean and Williams (1992)
Singh and Salas (1989)
Ridley et al. (1990)

Singh and Salas (1989)
Singh and Salas (1989)
Singh and Salas (1989)
Singh and Salas (1989)
Williams et al. (1993)
Peake et al. (1988)

Peake and Sandhu (1983)

Peake and Sandhu (1983)


Corkum et al. (1986)


-------
S
>
              TABLE 4-19 (cont'd). SUMMARY OF MEASUREMENTS OF PEROXYACETYL NITRATE

                         AND PEROXYPROPIONYL NITRATE IN URBAN AREAS
1
s
u>
Site
Rio de Janeiro
Vila Isabel
PUC/RJ
Athens, Greece
Paris, France
Months/
Year
7/1985
7/1985
2-11/85
11/85-11/86
Number
of Days
Sampled
8
4
113
NAa
PAN
Concentration
(ppb)
Average/Mean
NAa
NAa
NAa
1.1
Maximum
5.4
3.3
3.7
20.5
PPN
Concentration
(ppb)
Average/Mean
NAa
NAa
NAa
NAa
Maximum
1.0
0.6
NAa
NAa
Reference
Tanner et al. (1988)
Tanner et al. (1988)
Tsani-Bazaca et al. (1988)
Tsalkani et al. (1991)
   *NA = Not available.
i

-------
 1          In a study in Rio de Janeiro made to investigate the effects of the use of ethanol or
 2     ethanol-containing fuel on PAN concentrations, the maximum PAN concentration reached
 3     5.4 ppb (Tanner et al., 1988). However, this maximum concentration is well below the
 4     maximum concentrations reported in and around Los Angeles, and it falls within the
 5     maximum PAN values reported for a number of other cities hi Table 4-19.
 6
 1     4.9.3  Concentration of Perox) acetyl Nitrate and Peroxypropionyl Nitrate
 2             in Rural Areas
 3          Prior measurements of nonurban PAN and PPN concentrations and PAN to 03 ratios
 4     are available (Altshuller,  1983; U.S. Environmental Protection Agency, 1986), At nonurban
 5     sites, not impacted by urban plumes, PAN and PPN concentrations are much lower than in
 6     urban areas.  Average PAN concentrations ranged between 0.1 and 1 ppb, while the PAN to
 7     03 ratios were at or below  1 %.
 8           Concentrations of PAN, PPN, and other PANs have been reported (Table 4-20) at
 9     Tanbark Flat, CA, 35 km northeast of Los Angeles, during 1989, 1990, and 1991 and at
10     Franklin Canyon, CA, 25 km west of Los Angeles, during 1991 (Grosjean and Williams,
11      1992; Grosjean et al., 1993).  As indicated by the results tabulated in Table 4-20, the
12     concentrations were high at these mountain sites,  the PPN to PAN ratios were relatively
13     high, and the concentration maxima occurred during the afternoon hours.  These
14    concentration levels of PAN and PPN are attributed to downwind transport from the
 15     Los Angeles urban area.  The MPAN, CH2  = C(CH3)C(0)OONO2, was very occasionally
 16     detected with average concentrations of 1.2 ppb at Tanbark Flat and  1.0 ppb at Franklin
 17     Canyon in 1991.
 18          At Tanbark Flat, the O3 and PAN diurnal concentration patterns were similar to those
 19     in upwind urban areas.  The PAN to O3 ratios at the Qj maximum were as follows:  1989,
 20     0.05; 1990, 0.08; 1991,  0.05—all the ratios are within the same range as at sites in urban
 21     areas in and around Los  Angeles.
 22          Other measurements of PAN and PPN or PAN are available over a period of years at
 23     Niwot Ridge, CO, just west of the Denver-Boulder area, at Point Arena, CA, and at a forest
 24     site, Scotia, PA (Ridley  et al., 1990).  The concentrations reported at all of these sites are
 25     much lower than the mountain sites in California. The Niwot Ridge site, which does show

       December 1993                         4-100      DRAFT-DO NOT QUOTE OR CTTE

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TABLE 4-20. SUMMARY OF MEASUREMENTS OF PEROXYACETYL NITRATE
        AND PEROXYPROPIONYL NITRATE IN RURAL AREAS
I
So
U)









^,
=5
—

o
W
^
|
g

s
O
cj


Site
Tanbark Flat, CA

Tanbark Flat, CA
Tanbark Flat, CA
Franklin Canyon, CA
Niwot Ridge, CO
Niwot Ridge, CO
Niwot Ridge, CO
Niwot Ridge, CO

Point Arena, CA
Point Arena, CA
Scotia, PA
Scotia, PA
Kananaskis Valley, Alberta,
Canada

Frijoles Mesa, NM

*NA = Not available.



Months/
Year
8-10/1989

8,9/1990
8/1991
9/1991
7/1984
6-7/1984
8-9/1984
6-7/1987

1/1984
Spring/1985
Summer/1986
6-8/1988
9/1979,
4/1982,
6-8/1982
10/1987-
1/1989



Number
of Days
Sampled
69

34
22
9
16
23
21
46

14
NAa
NAa
47
NAa


NAa




PAN
Concentration
(Ppb)
Average/Mean
2.9

4.8
2.8
1.6
0.28
»0.25
»0.25
0.81 (E)
0.21 (W)
0.12
0.05
»0.6
1.0
»0.5


0.26






Maximum
>16.1

22.0
12.8
7.0
2.3
NAa
NAa
3.2

1.1
NAa
NAa
NAa
2.3


1.9




PPN
Concentration
(ppb)
Average/Mean
0.75

0.76
0.43
0.18
0.016
NAa
NAa
0.08 (E)
0.01 (W)
0.005
NAa
NAa
NAa
NAa


NAa






Maximum
5.1

4.3
2.66
1.15
0.17
NAa
NAa
0.45

0.07
NAa
NAa
NAa
NAa


NAa






Reference
Williams and Grosjean
(1991)
Grosjean et al. (1993)
Grosjean et al. (1993)
Grosjean et al. (1993)
Singh and Salas (1989)
Fahey et al. (1986)
Fahey et al. (1986)
Ridley et al. (1990)

Singh and Salas (1989)
Ridley (1991)
Ridley (1991)
Buhr et al. (1990)
Paske et al. (1983)


Gafmey et al. (1993)





-------
 1      the effects of easterly upslope flow of air parcels from Denver-Boulder, are still low
 2      compared to the sites downwind of the urban Los Angeles area (Table 4-20).
 3          The PAN concentrations at the Scotia, PA, rural site in the eastern United States tend
 4      to be somewhat higher than the Niwot Ridge or Point Arena sites (Table 4-20). This
 5      difference may relate to higher regional precursor concentration levels.
 6
 7
 8      4.10  CONCENTRATION AND PATTERNS OF HYDROGEN PEROXIDE
 9            IN THE AMBIENT ATMOSPHERE
10          Efforts to measure hydrogen peroxide (H2O2> began in the 1970s, but the early reports
11      of H2O2 concentrations above 10 ppb and even 100 ppb appear to be in error because of the
12      artifact H2O2 generated within the presence of O3  (Section 3.5.1.3). Subsequent
13      measurements of H2O2 in the 1980s resulted in maximum H2O2 concentrations at or below
14     5 ppb and mean concentrations at or below 1 ppb (Sakugawa et al, 1990).
15          Studies comparing more recent methods for measuring H2O2,  which were conducted in
16     North Carolina, indicated differences among measurement methods in synthetic mixtures of
17     H202, including possible interferences, and in the ambient atmosphere of up to about ±25%
18     (Kleindienst et al., 1988). However, results from the same study from mixtures irradiated in
19     a smog chamber produced larger differences among methods, especially with the luminol
20     technique compared with the fluorescence techniques and with tunable-diode laser absorption
21     spectroscopy.  Another comparison  study was conducted in California, resulting in
22     differences in methods for measuring H^ varying by a factor or two (Lawson ^ al,, 1988).
23     In the measurements of H2O2 discussed below, the cryogenic fluorescence method or the
24     scrubber-coil fluorescence methods  were generally used.
25          Based on interpretation of a compilation of H2O2 measurements made between
26      1984  and 1988 at a number of urban locations, at rural/remote locations, and on aircraft
27     flights, it was concluded that the  higher H202 concentrations were  associated with the
28     following measurement conditions:  (1) in the afternoon hours, (2)  during summer months,
 29      (3) at rural locations, and (4) at lower latitudes (Sakugawa et al., 1990; Van Valin et al.,
 30      1987).  The H202 concentrations increase from the surface to the top of the boundary layer
 31      (Daum et al., 1990). Available values for mean H2O2 concentrations at U.S.  locations were

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 1      (1) summit of Whitetop Mountain, VA: summer, 0.80 ppb; winter, 0.15 ppb (Olszyna
 2      et al., 1988); (2) summit of Whiteface Mountain, NY: 1986, 0.6 ppb; 1987; 0.8 ppb
 3      (Mohnen and Kadlecek, 1989); and (3) Westwood,  CA:  summer, »1.0 ppb; winter,
 4      0.2 ppb (Sakugawa and Kaplan, 1989). At Westwood, the highest correlation with various
 5      parameters was found for solar radiation consistent with the higher H2O2 concentrations
 6      being observed in the afternoon during the late spring and early summer months (Sakugawa
 7      and Kaplan, 1989).  In the same study, the average H2O2 concentrations were observed to
 8      increase from Westwood, near the coast in the Los Angeles Basin, to Duarte (inland) and at
 9      Daggett in the Mohave Desert and at Sky Mountain and Lake Gregory in the San Bernadino
10      Mountains. The ratios of Oj to H2O2 concentrations at the these sites were & 100,
11      In subsequent measurements, the same relationship in H2O2 concentrations between
12      Westwood and the other California sites listed above was observed (Sakugawa and  Kaplan,
13      1993).  Unlike the results at several urban sites and other mountain sites, it was reported that
14      the highest diurnal H2O2 concentrations at Lake Gregory in the San Bernadino Mountains
15      were observed  during the nighttime hours (Sakaugawa and Kaplan, 1993).
16
17
18     4.11 CO-OCCURRENCE OF OZONE
19     4.11.1 Introduction
20          There have been several attempts to characterize air pollutant mixtures (Lefohn and
21     Tingey, 1984;  Lefohn et al., 1987b). Pollutant combinations can occur at or above a
22     threshold concentration either together or temporally separated from one another.  For
23     example, for characterizing the different types of cooccurrence patterns, Lefohn et al.
24     (I987b) grouped air quality data within a 24-h period starting at 0000 h and ending at
25     2359 h. Patterns that showed air pollutant pairs appearing at the same hour of the day at
26     concentrations equal to or greater than a minimum hourly mean value were defined as
27     simultaneous-only daily cooccurrences. When pollutant pairs occurred at or above a
28     minimum  concentration during the 24-h period, without occurring during the same hour, a
 29     sequential-only cooccurrence was defined.  During a 24-h period, if the pollutant pair
 30     occurred at or above the minimum level at the same hour of the day and at different hours
31     during the period, the cooccurrence pattern was defined as complex-sequential.

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 1     A cooccurrence was not indicated if one pollutant exceeded the minimum concentration just
 2     before midnight and the other pollutant exceeded the minimum concentration just after
 3     midnight.  As will be discussed below, studies of the joint occurrence of gaseous NCyC^
 4     and SO2/O3 have concluded mat (a) the cooccurrence of two-pollutant mixtures lasted only a
 5     few hours per episode, where an episode was defined by the threshold concentration used,
 6     and (b) the time between episodes is generally long (i.e., weeks, sometimes months) (Lefohn
 7     and Tingey, 1984; Lefohn et aL, 1987b).
 8          For exploring the cooccurrence of 03 and other pollutants (e.g., acid precipitation,
 9     acidic cloudwater, and acidic sulfate aerosols), there are limited data available.  In most
10     cases, routine monitoring data are not available from which to draw general conclusions.
11     However, published results are reviewed and summarized for the purpose of assessing an
12     estimate of the possible importance of cooccurrence patterns of exposure.
13
14     4.11.2  Nitrogen Oxides
15          Ozone occurs frequently at concentrations equal to or greater than 0.03 ppm at many
16     rural and remote monitoring sites in the United States (Evans et al.,  1983; Lefohn,  1984;
17     Lefohn and Jones,  1986).  Therefore, for many rural locations in the United States, the
18     cooccurrence patterns observed by Lefohn and Tingey (1984) for 63 and NC^ were defined
19     by the presence or absence of N02. As anticipated, Lefohn and Tingey (1984)  reported that
20     most of the sites analyzed experienced fewer than 10 cooccurrences  (when both pollutants
21     were present at an hourly average concentration &O.Q5 ppm). However, the authors did
22     note that several urban  monitoring sites in the southern California South Coast Air  Basin
23     experienced more than  450 cooccurrences.  The rural sites of Riverside,  Fontana, and
24     Rubidoux, California had more man 100 cooccurrences.  Denver, Colorado and San Jose,
25     California, also experienced more than 100 cooccurrences of O^NC^.  Lefohn and Tingey
26     (1984) reported that  for Rubidoux, because NO2 concentration maxima tended to peak in the
27     evenings or early morning, the cooccurrences were present at these times.  For more
28     moderate areas of the country, Lefohn et al. (1987b) reported that even with a threshold of
 29     0.03 ppm O3, the number of cooccurrences with NQ^ was small.
 30
 31

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 1      4.11.3  Sulfur Dioxide
 2           Because elevated SO2 concentrations are mostly associated with industrial activities
 3      (U.S. Environmental Protection Agency,  1992a), cooccurrence observations are usually
 4      associated with monitors located near these types of sources.  Lefohn and Tingey (1984)
 5      reported that for the rural and nonrural monitoring sites investigated, most sites experienced
 6      fewer than 10 cooccurrences of SO2 and  O3.  Only Rockport, Indiana and Paradise No, 21
 7      (Kentucky) had more than 40 cooccurrences during the monitoring period (48 and 45,
 8      respectively). The monitors at these two sites were influenced by the local sources. The
 9      authors noted that at Fontana, California, there were numerous 63 episodes above 0.05 ppm
10     and there was a high probability mat when the SO2 hourly average concentrations rose above
11      0.05 ppm, both pollutants would be present at levels equal to or greater than 0.05 ppm.
12          Meagher et al. (1987) reported that several documented O3 episodes at specific rural
13     locations appeared to be associated with elevated SO2 levels.  The investigators defined the
14     cooccurrence of O3 and SO2 to be when  hourly mean concentrations were equal to or greater
15     than 0.10 ppm and 0.01 ppm, respectively. Upon reviewing the hourly mean O3 and SO2
16     data used by Lefohn et al. (19S7b), in 1980 (using a threshold of 0.05 ppm for both
17     pollutants) the Paradise No. 23 (KY), Giles County (TN), Murphy Hill (reported as Marshall
18     Co.  by Meagher el al.,  1987) (AL), and  Saltillo (reported as Hardin Co. by Meagher et al.,
19     1987) (TN) sites experienced fewer than  7 days over a 153-day period for a cooccurrence of
20     any  form (i.e., simultaneous-only,  sequential, and complex-cooccurrence).  Thus, as reported
21     by Lefohn et al. (1987b), the cooccurrence pattern of 63 and SO2 was infrequent.
22           The above discussion was based on the cooccurrence patterns associated with the
23     presence or absence of hourly average concentrations of pollutant pairs.  Taylor el al. (1992)
24     have discussed the joint occurrence of O3, nitrogen, and sulfur in forested areas using
25     cumulative exposures of O3 with data on dry deposition of sulfur and nitrogen. The authors
26     concluded in their study that the forest landscapes with the highest loadings of sulfur and
27     nitrogen via dry deposition tended to be  the same forests with the highest average
28     O3 concentrations and largest cumulative exposure.  Although the authors concluded that the
29     joint occurrences of multiple pollutants in forest landscapes were important, nothing was
30     mentioned about the hourly cooccurrences of Og and SO2 or Oj and NO2.
31

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 1      4.11.4  Acidic Sulfate Aerosols
 2           Acid sulfates, which are usually composed of sulfuric acid, ammonium bisulfate, and
 3      ammonium sulfate, have been measured at a number of locations in North America.  Acidic
 4      sulfate and neutralized species can accumulate and range in concentration from 0 to 50 /*g/m3
 5      at a specific location or a number of locations simultaneously (lioy, 1989).  For many
 6      summertime studies, peaks of H2SO4 and/or H+ appear to be associated with the presence of
 7      a slow-moving high pressure system (Lioy and Waldman  (1989).  Acid sulfates are found
 8      primarily in the fine particle size range (<2.5 /im in diameter). Lioy (1989) reports that the
 9      acidic sulfate concentrations measured in the summertime can be found at 20 /ig/m for over
10      an hour and can be found at high concentrations of  10 to  20 pg/m3 for 6 to 24 h at one or
11      more sites (lioy, 1989).  Acidic sulfate aerosol concentrations  can occur at concentrations in
12      the summertime above 10 /*g/m for periods greater than 5 h (Lioy, 1989),  As has been
13      discussed earlier in this chapter, the highest O3 exposures for sites affected by
14     anthropogenically derived photoxidant precursors are expected  to occur during the late spring
15     and summer months. Thus, the potential for O3 and acidic sulfate aerosols to cooccur at
16     some locations in some form (i.e., simultaneously,  sequentially, or complex-sequentially) is
17     real. Our knowledge of the potential exposure of the cooccurrence of acidic sulfate aerosols
18     and O3 is limited because routine monitoring data for acidic aerosols are not available.
19     Information on the cooccurrence patterns is limited to research studies and some of the
20     results  of these studies is provided in this  section.
21          Spektor et al. (1991) investigated the effects of single- and multiday 03 exposures on
22     respiratory function in active normal children aged  8 to 14 years at a northwestern New
23     Jersey  residential summer camp in 1988.  During the investigation, the authors measured
24     daily levels of 1-h peak Oj and the  12-h average H+  concentrations. On 7 days the acid
25     aerosol concentrations (reported as H2S04) were higher than 10 /ig/m , reaching a 12-h
26     maximum of 18.6 /*g/m3. Figure 4-24 shows the relationship  between daily maximum
27     O3 and daily  12-h average H+ concentrations.  Thurston et al. (1992) have reported
28     occurrences in 1988 of maximum 24-h average concentrations of H+ as high as 18.7 ^g/m3
 29      (Buffalo, New York) and a maximum daily hourly average concentration of 0.164 ppm.
 30      Although lower than Buffalo, high O3 or  H+ values were reported by the investigators for
 31      Albany and White Plains, New York. It  is unclear whether the O3 or H+ maximum

        December 1993                          4406       DRAFT-DO NOT QUOTE OR CTTE

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 1      concentrations occurred simultaneously; however, it is clear that high concentrations could
 2      occur either sequentially, complex-sequentially, or simultaneously. Evidence exists in the
 3      literature indicating that hourly cooccurrences are experienced.  Raizenne and Spengler
 4      (1989) have described an episodic cooccurrence pattern in 1986 of high hourly averaged
 5      concentrations of O3 and H2SO4 that occurred at a residential summer camp located on the
 6      north shore of Lake Erie, Ontario, Canada (Figure 4-27). Thurston et al. (1994) have
 7      conducted a study of ambient acidic aerosols in the Toronto, Ontario metropolitan area in
 8      July and August of 1986, 1987, and 1988, and have reported on the fine particle
 9      (da<2.5 ^m) samples collected twice per day. The authors reported that their results
10      indicated that acidic aerosol episodes (i.e., H+ & 100 nmol/m ) occurred routinely during
11      the summer months and that H   peaks were correlated with sulfate episodes. Figure 4-28
                                          f\    i
12     illustrates the relationship among SO4  , H  , and O3.
13
                300
                290
                280
                260
«£  270
 oJ
*c  250
 O
 t5  240
 1  23°
 C  220
 o
 O  210
 I  200
 6  190
    180
    170
                                50
                                                                                  40
                                                                                  30
                                                                                      o
                                                                                   20
                                                                                   10
                                    8
                                    o
                                   O
                   7    8     9   10    11    12   13   14   15    16   17   18   1
                                               Time (h)
        Figure 4-27.  The co-occurrence pattern of O3 and H2SO4 for July 25, 1986.
        Source:  Raizenne and Spengler (1989).
        December 1993
im
                     MAT rmrvrc rm nrm

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                    1986
                                              1887
                                                                         1888
August
.My
                                                   AngiHt
JJy
                                                                              August
      Figure 4-28. Sulfate, hydrogen ion, and ozone measured at Breadalbane St. (Site 3)
                   during July and August, 1986,1987, and 1988.
      Source: Thurston et al. (1994),
 1      4.11.5  Acid Precipitation
 2           Concern has been expressed about the possible effects on vegetation from cooccurring
 3      exposures of O3 and acid precipitation (Prinz et al., 1985; National Acid Precipitation
 4      Assessment Program,  1987; Prinz and Krause, 1988).  Little information has been published
 5      concerning the cooccurrence patterns associated with the joint distribution of 03 and acidic
 6      deposition (i.e., H+). In a nonpeer-reviewed paper, Lefohn and Benedict (1983) reviewed
 7      the EPA's SAROAD monitoring data for 1977 through 1980 and, using National
 8      Atmospheric Deposition Program (NADP) and Electric Power Research Institute (EPRI) wet
 9     deposition data, evaluated the frequency distribution of pH events for 34 NADP and 8 EPRI
10     chemistry monitoring  sites located across the United States. Unfortunately, there were few
11      sites where O3 and acidic deposition were comonitored.
12          As a result, Lefohn and Benedict (1983) focused their attention on O3 and acidic
13     deposition monitoring sites that were closest to one another. In some cases, the sites were as
14     far apart as 144 km.  Using hourly O3 monitoring data, and weekly and event acidic
       December 1993
       4-108
                               DRAFT-DO NOT QUOTE OR CTTE

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 1      deposition data from the NADP and EPRI databases, the authors identified specific locations
 2      where the hourly mean Oj exposures were SO. 10 ppra and 20% of the wetfall daily or
 3      weekly samples were below pH 4.0.  Elevated levels of 03 were defined as hourly mean
 4      concentrations equal to or greater than 0.10 ppm. Although for many cases, experimental
 5      research results of acidic deposition on agricultural crops show few effects at pH levels
 6      above 3.5 (NAPAP, 1987), it was decided to use a pH threshold of 4.0 to take into
 7      consideration the possibility of synergistic effects of Oj  and acidic deposition.
 8           Based on their analysis, Lefohn and Benedict (1983) reported five sites where there
 9      may be the potential for agricultural crops  to experience additive, less than additive, or
10      synergistic (i.e., greater than additive) effects from elevated O3 and hydrogen ion exposures.
11      The authors stated that they believed, based on the available data, the greatest potential for
12     interaction between acid rain and O3 exposures in the United States, with possible effects on
13     crop yields, may be in the most industrial areas (e.g., Ohio and Pennsylvania).  However,
14     they cautioned that, because no documented evidence existed to show that pollutant
15     interaction had occurred under field growth conditions and ambient exposures, their
16     conclusions  should only be used as a guide for further research.
17          In their analysis, Lefohn and Benedict (1983) found no colocated sites.  The authors
18     rationalized that data from non-co-monitoring sites (i.e., O3 and acidic deposition) could be
19     used because O3 exposures are regional in nature.  However, work by Lefohn et al. (1988a)
20     has shown that hourly mean 03 exposures vary from location to location within a region and
21     that cumulative indices, such as the percent of hourly mean concentrations equal to or greater
22     than 0.07 ppm, do  not form a uniform pattern over a region.  Thus, extrapolating hourly
23     mean O3 concentrations from known locations to other  areas within a region may provide
24     only qualitative indications of actual 63 exposure patterns.
25          In the late 1970s and the 1980s, both the private sector and the government funded
26     research efforts to better characterize gaseous air pollutant concentrations and wet deposition.
27     The event-oriented wet deposition network, EPRI/Utility Acid Precipitation Study Program,
28      and the weekly oriented sampling network (NADP) provided information that can be
29      compared with hourly mean concentrations of O3 collected at several comonitored locations.
30      No attempt was made to include hydrogen ion cloud deposition information.  In some cases,
31     for mountaintop locations (e.g., Clingman's Peak, Shenandoah, Whiteface Mountain, and
        December 1993                          4.1 no      DRAFT-DO NOT OITOTR cm

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 1      Whitetop), the hydrogen ion cloud water deposition is greater than the hydrogen ion
 2      deposition in precipitation (Mohnen, 1988) and the cooccurrence patterns associated with
 3      O3 and: cloud deposition will be different than those patterns associated with Oj and
 4      deposition in precipitation.
 5           Smith and Lefohn (1991) explored the relationship between O3 and hydrogen ion in
 6      precipitation,  using data from sites which monitored both Qj and wet deposition
 7      simultaneously and within one minute latitude and longitude of each other.  The authors
 8      reported that individual sites  experienced years hi which both hydrogen ion deposition and
 9      total O3 exposure were at least moderately high (i.e., annual H+ deposition 5:0.5 kg ha"1
10      and an annual O3 cumulative sigmoidally-weighted exposure (W126) value  S50 ppm-h).
11      With data compiled from all sites, it was found that relatively acidic precipitation (pH £4.31
12     on a weekly basis or pH £4.23 on a daily basis) occurred together with relatively  high
13      O3 levels (i.e., W126  values SO.66 ppm-h for die same week or W126 values S0.18 ppm-h
14     immediately before or after a rainfall event)  approximately 20% of the time, and highly
15     acidic precipitation (i.e, pH  £4.10 on a weekly basis or pH £4.01 on a daily basis)
16     occurred together with a high 03 level (i.e., W126 values  ^1.46 ppm-h for the same week
17     or W126 values £0.90 ppm-h immediately before or after the rainfall event)  approximately
18     6% of the time. Whether during the same week or before, during, or after a precipitation
19     event, correlations between O3 level and pH (or H+ deposition) were weak to nonexistent.
20     Sites most subject to relatively high levels of both hydrogen ion and O3 were located in the
21     eastern portion of the United States, often in mountainous areas.
22
23     4.11.6  Acid Cloudwater
24          In addition to the cooccurrence of O3 and acid precipitation, results have been reported
25     on the cooccurrence of 03 and acidic cloudwater in high-elevation forests.  Vong and
26     Guttorp (1991) characterized the frequent O3-only and pH-only single-pollutant episodes, as
27     well as the simultaneous and sequential cooccurrences of O3 and acidic cloudwater.  The
28     authors reported that both simultaneous and sequential cooccurrences were observed a few
 29      times each month above cloud base.  Episodes were classified by considering hourly
 30      O3 average concentrations SO.07 ppm ami  cloudwater events with pH £3.2. The authors
 31      reported that simultaneous occurrences of 0$ and pH episodes occurred  2-3 times  per month

        Bteembar 1993                          4-110      DRAFT-DO NOT QUOTE OR CITE

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 1      at two southern sites (Mitchell, NC and Whitetop, VA) and the two northern sites (Whiteface
 2      Mountain, NY and Moosilauke, NH) averaged 1 episode/month. No cooccurrences were
 3      observed at the central Appalachian site (Shenandoah, VA), due to a much lower cloud
 4      frequency.  Vong and Guttorp (1991) reported that the simultaneous occurrences were
 5      usually of short duration (mean 1.5 h/episode) and were followed by an O3-only episode.
 6      As would be expected, O3-only episodes were longer than cooccurrences and pH episodes,
 7      averaging an 8-h duration.
 8
 9
10     4.12  SUMMARY
11           Ozone is an omnipresent compound that is measured at levels above the minimum
12     detectable level at all monitoring locations in the world.  Although all 03 and other
13     photochemical oxidant-induced effects on vegetation and ecosystems, as well as human
14     health, rely on an accurate determination of exposure through knowledge of O3 and other
15     photochemical oxidant concentrations, most of the human and welfare effects research is
16     focused on O3 exposures (e.g., hourly average concentration  and duration of exposure).
17     To obtain a better understanding of the potential for ambient  O3 exposures affecting human
18     health and vegetation, hourly average concentration information was summarized for urban,
19     rural forested, and rural agricultural areas in the United States.
20          The distribution of Oj  or its precursors at a rural site near an urban source is affected
21     by wind direction (i.e., whether the rural site is located up- or  down-wind from the source).
22     It is difficult to apply land-use designations to the generalization of exposure regimes that
23     may be experienced in urban versus rural areas, because the  land use characterization of
24     "rural"  does not imply that a specific location is isolated from anthropogenic influences.
25     Rather, the characterization  only implies the existing use of the land.  Because it is possible
26     for urban emissions, as well as O3 produced from urban area emissions, to be transported to
27     more rural downwind locations, elevated O3 concentrations can occur at considerable
28     distances from urban centers.  Urban O3 concentration values are often depressed because of
29     titration by nitric oxide.  Because of the absence of chemical scavenging, O3 tends to persist
30     longer in nonurban than in urban areas and exposures may be higher than in urban locations.
        December 1993                          4-111      DRAFT-DO NOT QUOTE OR CITE

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 1          For purposes of using air quality data for assessing human health and vegetation effects,
 2     it is important to distinguish among concentration, exposure, and dose.  For human health
 3     considerations, the following definitions are used:
 4
 5            1.  The "concentration" of a specific air pollutant is the amount of mat
 6               material per unit volume of air. Air pollution monitors measure pollutant
 7               concentrations, which may or may not provide accurate exposure estimates.
 8
 9            2.  The term "exposure" is defined as any contact between an air contaminant
10               of a specific concentration and the outer (e.g., skin) or inner (e.g.,
11               respiratory tract epithelium) surface of the human body.  Exposure implies
12               the simultaneous occurrence of the two events.
13
14          Similar to human health considerations for vegetation, concentrations of airborne
15     contaminants are considered to be exposure when they are experienced by a plant.  For the
16     purposes of vegetation, this chapter has adopted the concept mat dose is the amount of
17     pollutant absorbed by the plant.  Because most of the data presented in this chapter are from
18     fixed monitors, dose is not addressed.
19          For vegetation, as indicated in Chapter 5 (Section 5.5), extensive research has focused
20     on identifying exposure indices with a firm foundation on  biological principles.  Many of
21     these exposure indices have been based on research results indicating that the magnitude of
22     vegetation responses to air pollution is more an effect of the magnitude of the concentration
23     than the length of the exposure. For O3, the short-term, high concentration exposures have
24     been identified by many researchers as being more important than long-term, low
25     concentration exposures (see Chapter 5 for further discussion). Similarly, for human health
26     considerations, results using controlled human exposures have shown the possible importance
27     of concentration in relation to duration of exposure and inhalation rate.
28           In summarizing the hourly average concentrations in this chapter, specific attention is
29     given to the relevance of the exposure indices used.  For example, for human health
30      considerations, concentration (or exposure) indices such as the daily maximum 1-h average
 31      concentrations, as well as the number of daily maximum 4-h or 8-h average concentrations
 32      above a specified threshold, are used to characterize information in the population-oriented
 33      locations.  For vegetation, several different types of exposure indices are used.  Because
 34     much of the NCLAN exposure information is summarized in terms of 7-h average

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 1      concentrations, this exposure index is used.  However, because peak-weighted, cumulative
 2      indices (i.e., exposure parameters that sum the products of hourly average concentrations
 3      multiplied by time over an exposure period have shown considerable promise in relating
 4      exposure and vegetation response (see Section 5.5), several exposure indices that use either a
 5      threshold or a sigmoidally weighted scheme are used in this chapter to provide insight
 6      concerning the 03 exposures that are experienced at a select number of rural monitoring sites
 7      in the United States.  The peak-weighted cumulative exposure indices such as the SUM06
 8      (the sum of all hourly average concentrations equal to or greater than 0.06 ppm), SUM08
 9      (the sum of all hourly average concentrations equal to or greater than 0.08 ppm), and W126
10     (the sum of the hourly average concentrations that have been weighted according to a
11      sigmoid function that is theoretically based on a hypothetical vegetation response) are used.
12          Ozone hourly average concentrations have been recorded for many years by the State
13     and local air pollution agencies who report their data to the U.S. Environmental Protection
14     Agency. The 10-year (1983 to 1992) composite average trend for the second highest daily
15     maximum hourly average concentration during the 03 season for 509 trend sites and a subset
16     of 196 NAMS sites, shows that the 1992 composite average for the trend sites is 21 % lower
17     than the 1983 average and 20% lower for the subset of NAMS sites.  The 1992 value is the
18     lowest composite average of the past ten years.  The 1992 composite average is significantly
19     less than all the previous nine years, 1983 to 1991.  The relatively high Oj concentrations in
20     1983 and 1988 were likely attributable in part to hot, dry stagnant conditions in some areas
21     of the country that were especially conducive to O3 formation.
22          Between 1991 and 1992, the composite mean of the second highest daily maximum 1-h
23     03 concentrations decreased 1% at the 672 sites and 6% at the subset of 222 NAMS sites.
24     Between 1991 and 1992, the composite average of the number of estimated exceedances of
25     the O3 standard decreased by 23% at the 672 sites, and 19% at the 222 NAMS sites.
26     Nationwide VOC emissions decreased 3% between 1991 and  1992 (U.S. Environmental
27     Protection Agency, 1993). The composite average of the second daily maximum
28     concentrations decreased in eight of the ten EPA Regions between 1991 and 1992, and
29     remained unchanged in Region YE, Except for Region YE, the 1992 regional composite
30     means are lower than the corresponding 1990 levels.
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 1           Information is provided in the Chapter on methods used for investigating techniques for
 2      adjusting O3 trends for meteorological influences.  Historically, the long-term Oj trends in
 3      the United States characterized by the U.S. Environmental Protection Agency have
 4      emphasized air quality statistics that are closely related to the NAAQS. Information is
 5      provided on the use of alternative indices.  Besides the U.S. Environmental Protection
 6      Agency,  additional investigators have assessed trends at several locations in the United States
 7      and information is provided for both urban and rural areas.
 8           Interest has been expressed in characterizing  O3 exposure regimes for sites experiencing
 9      daily maximum 8-h concentrations above specific thresholds (e.g., 0.08 or 0.10 ppm).
10      Documented evidence has been published showing the occurrence, at some sites,  of
11      multihour periods within a day of G, at levels of potential health effects.  While most of
12      these analyses were made using monitoring data collected from sites in or near nonattainment
13      areas, one analysis showed that at five sites, two in New York state, two in rural California,
14     and  one in rural Oklahoma, an alternative O3 standard of an 8-h average of 0.10 ppm would
15     be exceeded even though the existing I-h standard would not be.  The study indicated the
16     occurrence at these five sites, none of which was in or near a nonattainment area, of
17     O3 concentrations showing only moderate peaks but showing multihour levels above
18     0.10 ppm.
19          An important question is whether an improvement in O^ levels would produce
20     distributions of 1-h O3 that result in a broader diurnal profile than those seen in high-oxidant
21     urban areas where O3 regimes contain hourly average concentrations with sharper peaks.
22     The result would be an increase in the number of exceedances of daily maximum 8-h average
23     concentrations ^0.08 ppm, when compared to those sites experiencing sharper peaks.  One
24     research effort observed, using aerometric data at specific sites, how 03 concentrations
25     change when the sites change  compliance status.  One of the parameters examined was 4-h
26     daily maxima.  The number of exceedances for a  specific dairy maximum average
27     concentration tended to decrease as fewer exceedances of the current 1-h standard were
28     observed at a given site.  The number of occurrences of the daily maximum 4-h average
 29      concentration 2:0.08 ppm and the number of exceedances of the current form of the standard
 30      had a positive, weak correlation (r = 0.51).  The investigators reported few changes in the
 31      shape of the average diurnal patterns as sites changed attainment status. The lack of a

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 1      change in shape may have explained why the investigators could not find evidence that the
 2      number of occurrences of the daily maximum 4-h average concentration 3:0.08 ppm
 3      increased when the sites experienced few high hourly average concentrations.
 4           There has been considerable interest in possibly substituting one index for another when
 5      attempting to relate O3 exposure with an effect.  For example, using O3 ambient air quality
 6      data, the number of exceedances of 0.125 ppm and the number of occurrences of the daily
 7      maximum 8-h average concentrations ^0.08 ppm have been compared with the result that a
 8      positive correlation (r = 0.79) existed between the second-highest 1-h daily maximum in a
 9      year and the expected number of days with an 8-h daily maximum average concentration
10      >0.08 ppm O3.  However, there was not much predictive strength in using one  63 exposure
11      index to predict another was not strong. Similarly, the maximum 3-mo SUM06, second
12      highest daily maximum hourly average concentration,  and second highest daily maximum 8-h
13      average concentration exposure indices were compared.   For the rural agricultural and forest
14     sites, the relationships among the indices were not strong.
15          One of the difficulties in attempting to use correlation analysis between indices for
16     rationalizing the substitution of one exposure index for another for predicting an effect  (e.g.,
17     SUM06 versus the second highest daily maximum hourly average concentration) is the
18     introduction of the error associated with estimating levels of one index from another.
19     Evidence has been presented in the literature for recommending that if a different exposure
20     index (e.g., second highest daily maximum hourly average concentration) is to be compared
21     to, for example, the SUM06 for adequacy in predicting crop loss, then the focus should be
22     on how well the two exposure indices predict crop loss using the effects model that is a
23     function of the most relevant index and not on how well the indices predict one  another.
24     Less error would be introduced if either of the two indices were used directly in the
25     development of an exposure-response model.
26           The U.S.  EPA has indicated that a reasonable estimate of natural O3 background
27     concentration near sea-level in the United States today, for an annual average, is from
28     0.020 to 0.035 ppm.  This estimate included a 0.010  to 0.015 ppm contribution from the
29     stratosphere and a 0.01 ppm contribution from photochemically-affected biogenic non-
30     methane hydrocarbons.  In addition, the U.S. EPA estimated that an additional 0.010 ppm is
31     possible from the photochemical reaction of biogenic  methane.  The U.S. EPA concluded

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 1     that a reasonable estimate of natural O3 background concentration for a 1-h daily maximum
 2     at sea-level in the United States during the summer is on the order of 0.03 to 0.05 ppm.
 3     Reviewing data from sites that appear to be isolated from anthropogenic sources, it has been
 4     reported that in almost all cases, (1) none of the sites experienced hourly average
 5     concentrations  SO.08 ppm and (2) the maximum hourly average concentrations were in the
 6     range from 0.060 to 0.075 ppm.  Using data from these sites, in the continental United States
 7     and southern Canada, the 7-mo (April to October) average of the 7-h daily average
 8     concentrations  range from approximately 0.028 to 0.050 ppm. At an 03 monitoring site at
 9     the Theodore Roosevelt National Park in North Dakota, 7-mo (April to October) averages of
10     the 7-h daily average concentrations of 0.038, 0.039, and 0.039 ppm, respectively, were
11     experienced in 1984, 1985, and 1986.  These 7-mo seasonal averages (i.e., 0.038 and
12     0.039 ppm) appear to be representative of values that may occur at other fairly clean sites in
13     the United States and other locations in the Northern Hemisphere.
14          Diurnal variations are those that occur during a 24-h period.  Diurnal patterns of
15     O3 may be expected to vary with location, depending on the balance among the many factors
16     affecting O3 formation, transport, and destruction.  Although they vary with locality, diurnal
17     patterns for 03 typically show a rise in concentration from low or levels near minimum
18     detectable amounts to an early  afternoon peak.  The diurnal pattern of concentrations can be
19     ascribed to three simultaneous processes:  (1) downward transport of Oj from layers aloft;
20     (2) destruction of O3 through contact with surfaces and through reaction with nitric oxide
21     (NO) at ground level; and (3) in situ photochemical production of 03.
22          Although it might appear that composite diurnal pattern diagrams could  be used to
23     quantify the differences of O3 exposures between sites, caution has been expressed in their
24     use for this purpose. The average diurnal patterns are derived from long-term calculations of
25     the hourly average concentrations, and the resulting diagram cannot adequately identify, at
26      most sites, the presence of high hourly average concentrations and thus may not adequately
27      be able to distinguish O3 exposure differences among sites.  Unique families  of diurnal
28      average profiles exist and it is possible to distinguish between two types of 03 monitoring
 29      sites.  A seasonal diurnal diagram provides the investigator with the opportunity to identify
 30      whether a specific O3 monitoring site has more scavenging than any other site. For low-
 31      elevation sites, intra-day variability is most significant due to the pronounced daily amplitude

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 1      in O3 concentration between the pre-dawn minimum and mid-afteraoon-to-early-evening
 2      maximum, while inter-day variation is more significant in the high-elevation sites.
 3           Seasonal variations in Qj concentrations in urban areas usually show the pattern of high
 4      O3 in late spring or in summer and low levels in the winter. Because of temperature,
 5      relative humidity, and seasonal changes in storm tracks from year to year, the general
 6      weather conditions in a given year may be more favorable for the formation of O3 and other
 7      oxidants than during the prior or following year.  For example, 1988 was a hot and dry year
 8      in which some of the highest Oj concentrations of the last decade occurred, while 1989 was
 9      a cold  and wet year in which some of the lowest concentrations occurred.
10          Several investigators have reported on the tendency for average Oj concentrations to be
11      higher in the second versus the third quarter of the year for many isolated rural sites.  This
12     observation has been attributed to either stratospheric intrusions or an increasing frequency of
13     slow-moving, high-pressure systems that promote the formation of Oj.  However, for several
14     clean rural sites, the highest exposures have occurred in the third quarter rather than in the
15     second.  For rural O3 sites in the southeastern United States, the daily maximum 1-h average
16     concentration was found to peak during the summer months.  For sites located in rural areas,
17     but not isolated from anthropogenic  sources of pollution, the different patterns may be
18     associated with anthropogenic emissions of NOX and hydrocarbons.
19          Concentrations of O3 vary with altitude and with latitude.  There appears to be no
20     consistent conclusion concerning the relationship between O3 exposure and elevation.
21     An important issue for assessing possible impacts of O3 at high-elevation sites that requires
22     further attention is the use of mixing ratios (e.g., ppm) instead of absolute concentration
23      (e.g.,  in units of micrograms per cubic meter) to describe O3 concentration. In most cases,
24     mixing ratios (e.g., ppm) or mole fractions are used to describe O3 concentrations.  The
25      manner in which concentration is reported may be important when assessing the potential
 26      impacts of air pollution on high-elevation forests.  Concentration (in units of micrograms per
 27      cubic  meter) varies as a function of altitude. Although the change in  concentration is small
 28      when  the elevational difference between sea level and the monitoring  site is small, it becomes
 29      substantial at high-elevation sites.  Given the same part-per-million value experienced at both
 30      a high- and low-elevation site, the absolute concentrations (i.e., micrograms per  cubic meter)
 31      at the two elevations will be different.  Since both pollutants and ambient air are gases,

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 1     changes in pressure directly affect their volume.  This pressure effect must be considered
 2     when measuring absolute pollutant concentrations.  Although these exposure considerations
 3     are trivial at low-elevation sites, when one compares exposure-effects results obtained at
 4     high-elevation sites with those from low-elevation sites, the differences may become
 5     significant.
 6          Most people in the United States spend a large proportion of their time indoors.  Until
 7     the early 1970s, very little was known about the O3 concentrations experienced inside
 8     buildings. Even to date, the data base on this subject is not large and a wide range of
 9     indoor/outdoor O3 concentration relationships can be found in the literature.  Reported I/O
10     values for O3  are highly variable.  A relatively large number of factors can affect the
11     difference in O3 concentrations between the inside of a structure and the outside air.
12     In general, outside air infiltration or exchange rates, interior air circulation rates, and interior
13     surface composition (e.g., rugs, draperies,  furniture, walls) affect the balance between
14     replenishment and decomposition of O3 within buildings. Indoor/outdoor O3 concentration
15     ratios generally fall in the range from 0.1 to 0.7 and indoor concentrations of O3 will almost
16     invariably be  less than outdoors.
17           It is important that accurate estimates of both human and vegetation exposure to 03 are
18     available for assessing the risks posed by the pollutant.  Examples  are provided on how both
19     fixed-site monitoring information and human exposure models are used to estimate risks
20     associated with O3 exposure.  A short discussion is provided on the importance of hourly
21     average concentrations, used in the human health and vegetation experiments, mimicking as
22      closely as possible the "real world" exposures.
23           In many cases, the upper tail of the distribution, which represents those individuals
24      exposed to the highest concentrations, is frequently of special interest because the
 25      determination of the number of individuals who experience elevated pollutant levels can be
 26      critical for health risk assessments.  This is especially true for pollutants for which the
 27      relationship between dose and response is highly nonlinear.
 28           Because, for most cases, it is not possible to estimate population exposure solely from
 29      fixed-station data, several human exposure models have been developed.  Some of these
 30      models include information on human activity patterns (i.e., the microenvironments people
 31      visit and the  times they spend there). These models also contain submodels depicting the

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 1      sources and concentrations likely to be found in each microenvironment, including indoor,
 2      outdoor, and in-transit settings.
 3           A subgroup that has been studied by several investigators to assess the influence of
 4      ambient air pollution on their respiratory health and function is children attending summer
 5      camp.  Because children are predominantly outdoors and relatively active while at camp,
 6      they provide a unique opportunity to assess the relationships between respiratory health and
 7      function and concurrent air pollution levels.  Examples are provided on the type of exposure
 8      patterns that children experience.
 9           A personal exposure profile can be identified by using a personal exposure monitor.
10      Little data are available for individuals using personal exposure monitors.  Results from a
11      pilot study demonstrated that fixed-site ambient measurements may not adequately represent
12      individual exposures. Outdoor Qj concentrations showed substantial spatial variation
13      between rural and residential regions.  The study showed that the use of fixed-site
14     measurements could result in an error as high as 127%. In addition, the study showed that
15     models based on time-weighted indoor and outdoor concentrations explained only 40% of the
16     variability in personal exposures.  The investigators concluded that contributions from
17     diverse indoor and outdoor microenvironments could estimate personal O3 exposure
18     accurately.
19          The field of human exposure modeling is relatively young, with the first rigorous
20     exposure modeling analyses appearing in the mid-1970s and the theoretical constructs
21     regarding human exposure to environmental pollution being published in the early 1980s.
22     Two distinct types of O3 exposure models exist: those that focus narrowly on predicting
23     indoor Qj levels and those that focus on predicting 03 exposures on a community-wide basis.
24     The following four distinct models address the prediction of 03 exposures on a community-
25     wide basis:
26            1. pNEM/C^ (bared on the NEM series of models)
27
28            2.  SAI/NEM
29
 30            3.  REHBX
31
 32            4.  Event probability exposure model (EPEM)
 33

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 1          It is important to adequately characterize the exposure patterns that result in vegetation
 2     and human health effects. In Chapter 5 (see Section 5.5), it has been pointed out that the
 3     hourly average concentrations used in many of the high treatment experimental studies did
 4     not necessarily mimic those concentrations observed under ambient conditions.  Although the
 5     ramifications of this observation on the effects observed is not clear, it was pointed out that
 6     the highest treatments used in many of the vegetation open-top chamber experiments were
 7     bimodal in the distribution of the hourly average concentrations.  In other experiments
 8     designed to assess the effects of C^ on vegetation, constant concentration (i.e., square wave)
 9     exposures  were implemented.  As has been discussed in earlier sections of this Chapter,
10     "square wave" exposure regimes do not normally occur under ambient conditions. Similar
11     "square wave" exposures have been used in human health effects studies. In addition to the
12     exposures used at the highest treatment levels for vegetation experiments, there is concern
13     that the hourly average concentrations used in the charcoal-filtered control treatments may be
14     lower than those experienced at isolated sites in the United States or in other parts of the
15     world.  Although the ramifications of using such exposure regimes is unclear, there is some
16     concern that the use of such levels may result in an overestimation of vegetation yield losses
17     when compared to treatments greater than the control treatment.
18           Published data on the concentrations of photochemical oxidants other than O3 in
19     ambient air are neither comprehensive nor abundant. A review of the data shows that PAN
20     and peroxypropionyl nitrate (PPN) are the most abundant of the non-Qj oxidants in ambient
21     air in the United States, other than the inorganic nitrogenous oxidants such as nitrogen
22     dioxide (NC^), and possibly nitric acid (HNO3). At least one study has reported that a
23     higher homologue of the series, peroxybenzoyl nitrate (PBzN), like PAN, is a kchrymator.
24     No unambiguous identification of PBzN in the ambient air of the United States has been
25     made.
26           Given the information available on PAN, the concentrations of PAN that are of most
27     concern are those to which vegetation could potentially be exposed, especially during
28     daylight hours in agricultural areas.  These are followed hi importance by concentrations
 29      both indoors and outdoors, in urban and nonurban areas, to which human populations could
 30      potentially be exposed.  Most of the available data on concentrations of PAN and PPN in
 31      ambient air are from urban areas.  The levels to be found in nonurban areas will be highly

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 1      dependent upon the transport of PAN and PPN or their precursors from urban areas, since
 2      the concentrations of the NOX precursors to these compounds are considerably lower in
 3      nonurban than in urban areas.
 4           There nave been several attempts to characterize air pollutant mixtures.  Pollutant
 5      combinations can occur at or above a threshold concentration either together or temporally
 6      separated from one another. Studies of the joint occurrence of gaseous NO2/O^ and SO2/O3
 7      have concluded that (a) the cooccurrence of two-pollutant mixtures lasted only a few hours
 8      per episode, and (b) the time between episodes is generally long (i.e, weeks, sometimes
 9      months). Using  hourly averaged data collected at rural sites for vegetation considerations,
10      the periods of cooccurrence represent  a  small portion of the potential plant growing period.
11      For human ambient exposure considerations, in most cases,  the simultaneous cooccurrence of
12      NO2/O3 was infrequent. However, for  several sites located in the southern California South
13      Coast Air Basin, more than 450 simultaneous cooccurrences of each pollutant, at hourly
14     average concentrations equal to or greater than 0.05 ppm, were present.  Although the focus
15      of cooccurrence  research has been on patterns associated with the presence or absence of
16     hourly average concentrations of pollutant pairs, some researchers have discussed the joint
17     occurrence of O3, nitrogen, and sulfur in forested areas, combining cumulative exposures of
18     O3 with data on dry deposition of sulfur and nitrogen.  One study reported that several forest
19     landscapes with  the highest dry deposition loadings of sulfur and nitrogen tended to
20     experience the highest average 03 concentrations and largest cumulative exposure. Although
21     the investigators concluded that the joint occurrences of multiple pollutants in forest
22     landscapes were important, nothing was mentioned about hourly cooccurrences of O3 and
23     SOj or Oj and NC^.
24           Our knowledge of the potential exposure of the cooccurrence of acidic sulfate aerosols
25     and O3 is limited because routine monitoring data for acidic aerosols are not available.
26     Information on the cooccurrence patterns is limited to research studies and some of the
27     results are provided in tins chapter. Acid sulfates, which are usually composed of sulfuric
28     acid, ammonium bisulfate,  and ammonium sulfate, have been measured at a number of
29     locations in North America. Acidic sulfate and neutralized species can accumulate and range
 30     in concentration from 0 to 50 pg/m3 at a specific location or a number of locations
                                                            •f               i
31      simultaneously.  For many summertime studies, peaks of H2SO4 and/or H  appear to be

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 1     associated with the presence of a slow-moving high pressure system.  Acid sulfates are found
 2     primarily in the fine particle size range (< 2.5 /*m in diameter). The acidic sulfate
 3     concentrations measured in the summertime can be found at 20 ^g/m for over an hour and
 4     can be found at high concentrations of 10 to 20 ^ig/m for 6 to 24 h at one or more sites,
 5     Acidic sulfate aerosol concentrations can occur at concentrations in the summertime above
 6     10 /*g/m for periods greater than 5 h.  The highest 63 exposures for sites affected by
 7     anthropogenically derived photoxidant precursors are expected to occur during the late spring
 8     and summer months. Thus, the potential for 03 and acidic sulfate aerosols to cooccur at
 9     some locations in some form (i.e., simultaneously, sequentially, or complex-sequentially) is
10     real and requires further characterization.
1 1           Concern has been expressed about the possible effects on vegetation from cooccurring
12     exposures of 03 and acid precipitation. One study explored the relationship between O3 and
13     hydrogen ion in precipitation, using data from sites which monitored both O3 and wet
14     deposition simultaneously and within one minute latitude and longitude of each other.  The
15     investigators reported that individual sites experienced years in which both hydrogen ion
16     deposition and total 63 exposure were at least moderately high (i.e., annual H   deposition
17      ^0.5 kg ha*1 and an annual 03 cumulative sigmoidally-weighted exposure (W126) value
18      ^50 ppm-h).  With data compiled from all sites, it was found that relatively acidic
19     precipitation (pH £4.31 on a weekly basis or pH £4.23 on a daily basis) occurred together
20     with  relatively high 63 levels (i.e., W126 values ^0.66 ppm-h for the same week or W126
21     values 5: 0. 18 ppm-h immediately before or after a rainfall event) approximately 20% of the
22     time, and highly acidic precipitation (i.e, pH £4,10 on a weekly basis or pH £4.01 on a
23     daily basis) occurred together with a high 03 level (i.e. , W126 values ^ 1.46 ppm-h for the
24      same week or W126 values  ^ 0.90 ppm-h immediately before or after the rainfall event)
25      approximately 6 % of the time.  Whether during the same week or before, during, or after a
26      precipitation event, correlations between C^ level and pH (or H+ deposition) were weak to
27      nonexistent. Sites most subject to relatively high levels of both hydrogen ion and 63 were
28      located in the eastern portion of the United States,  often in mountainous areas.
 29           The cooccurrence of Qj and acidic cloudwater in high-elevation forests has been
 30      characterized.  The frequent O3-only and pH-only single-pollutant episodes, as well as the
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1     simultaneous and sequential cooccurrences of 03 and acidic cloudwater, have been reported.
2     Both simultaneous and sequential cooccurrences were observed a few times each month
3     above cloud base.
4
5
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 1     REFERENCES
 2
 3     Adams, W. C.; Savin, W. M.; Christo, A. E. (1981) Detection of ozone toxicity during continuous exercise via
 4            the effective dose concept. J. Appl. Physiol: Respir. Environ, Exercise PhysLol, 51: 415-422.
 5
 6     Adams, R. M.; Hamilton, S. A.; McCari, B, A. (1985) An assessment of the economic effects of ozone on U.S.
 7            agriculture. J. Air Follut. Control Assoc. 35: 938-943.
 8
 9     Adams, R. M.; Glyer, J. D.; Johnson, S, L,; McCari, B. A. (1989) A reassessment of the economic effects of
10            ozone on U.S. agriculture. JAPCA 39: 960-968.
11
12     AltshuUer, A. P. (1983) Measurements of the products of atmospheric photochemical reactions in laboratory
13            studies and in ambient air-relationships between ozone and other products. Atmos. Environ.
14            17:2383-2427.
15
16     AltshuUer, A. P. (1986) The role of nitrogen oxides in nonurban ozone formation in the planetary boundary layer
17            over N America, W Europe and adjacent areas of ocean. Atmos. Environ. 20:  245-268.
18
19     AltshuUer, A. P. (1988) Some characteristics of ozone formation in the urban plume of St. Louis, MO. Atmos.
20            Environ. 22: 499-510.
21
22     AltshuUer, A. P. (1989) Sources and levels of background  ozone and its precursors and impact at ground level.
23            In: Schneider, T.; Lee, S. D.; Wolters, G. J. R.; Grant, L.  D., eds. Atmospheric ozone research and its
24            policy implications: proceedings of the 3rd US-Dutch international symposium; May 1988; Nijmegen,
25            The Netherlands. Amsterdam,  The Netherlands: Elsevier Science Publishers; pp. 127-157. (Studies in
26            environmental science 35).
27
28     Aneja, V. P.; Li, Z.  (1992) Characterization of ozone at high elevation in the eastern United States: trends,
29            seasonal variations, and exposure. J. Geophys. Res. 97: 9873-9888.
30
31     Austin, B. S.; Andersen, G. E.; Weir, B. R.; Seigneur, C, (1986) Further development and application of an
32            improved population exposure model. San Rafael, CA: Systems Applications, Inc.
33
34     Avol, E. L.; Trim, S. C.; Little, D. E.; Spier, C. E.; Smith, M. N.; Peng, R.-C.; Lmn, W. S.-,
35            Hackney, J. D.;  Gross, K. B.; D'Arcy, J. B.; Gibbons, D.; Higgins, I. T. T.  (1990) Ozone exposure
36           and lung function in children attending a southern California summer camp.  Presented at: 83rd annual
37           meeting and exhibition of the Air & Waste Management Association; June; Pittsburgh, PA.
38           Pittsburgh, PA: Air & Waste Management Association; paper no. 90-150.3.
39
40     Berglund, R. L.; Dittenhoefer, A. C.; Ellis, H. M.; Watts, B. J.; Hansen, J.  L. (1988) Evaluation  of the
41            stringency of alternative forms of a national ambient air quality standard for ozone. In: Wolff, G. T.;
42            Hanisch, J. L.; Schere, K., eds. Transactions of an APCA international specialty conference on the
43            scientific and technical issues facing post-1987 ozone control strategies; November,  1987; Hartford, CT.
44            Pittsburgh, PA: Air and Waste Management Association; pp. 343-369.
 45
46     Berk, J.  V.; Young, R.; Hollowell, C. D.; Tnriel, L; Pepper, J. (1980) The effects of energy-efficient
47            ventilation rates  on indoor air quality at an Ohio elementary school. Berkeley, CA: University of
48            California, Lawrence Berkeley Laboratory; report  no. EEB-VENT 80-9. Available from: NTTS,
49            Springfield, VA; LBL-10223.
 50
 51     Berk, J. V.; Young, R.  A.; Brown, S. R.; Hollowell, C. D. (1981) Impact of energy-conserving retrofits on
 52            indoor air quality in residential housing. Presented at: 74th annual meeting of the Air Pollution Control
 53            Association; June; Philadelphia, PA. Pittsburgh, PA: Air Pollution Control Association; paper
 54            no. 81-22.1.

          December 1993                              4-124       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Berry, C, R, (1964) Differences in concentrations of surface oxidant between valley and mountaintop conditions
 2            in the southern Appalachians. J, Air Pollut Control Assoc. 14: 238-239,
 3
 4     Biller, W. F.; Feagans, T. B.; Johnson, T. R.; Duggan, G. M.; Paul, R, A,; McCurdy, T.; Thomas, H. C.
 5            (1981) A general model for estimating exposures associated with alternative NAAQS. Presented at: the
 6            74th annual meeting of the Air Pollution Control Association; June; Philadelphia, PA. Pittsburgh, PA;
 7            Air Pollution Control Association.
 8
 9     Bohm, M.;  McCunc, B,; Vandetta, T.  (1991) Diurnal curves of Croposheric ozone in the western United States.
10            Atmos. Environ.  Part A 25: 1577-1590.
11
12     Bower, J. S.; Broughton, G. F. J.; Dando, M. T.;  Stevenson, K, J.; Lampert, J. E.; Sweeney, B. P.;
13            Parker, V. J.; Driver, G.  S.; Clark, A. G.; Waddon, C. J.; Wood, A. J.; Williams, M. L.  (1989)
14            Surface ozone concentrations in the U. K. in 1987-1988. Atmos. Environ. 23: 2003-2016.
15
16     Buhr, M. P.; Parrish, D. D.; Norton, R. B.; Fehsenfeid, F. C.; Severs, R. E.; Roberts, J. M. (1990)
17            Contribution of organic nitrates to die total reactive nitrogen budget at a rural eastern U.S. site.
18            J, Geophys. Res. [Atmos.] 95: 9809-9816.
19
20     California Air Resources Board. (1992) Technical support document for proposed amendments to  the criteria for
21            designating areas of California as nonattainment, attainment, or unclassified for state ambient air quality
22            standards. Sacramento, CA: California Environmental Protection Agency.
23
24     Cass, G. R.; Nazaroff, W. W.; Tiller, C.; Whitmore, P. M. (1991) Protection of works of art from damage due
25            to atmospheric ozone. Atmos. Environ. Part A 25: 441-451.
26
27     Chameides, W.  L.; Lindsay, R. W.; Richardson, J.;  Kiang, C. S. (1988) The role of biogenic hydrocarbons in
28            urban photochemical smog: Atlanta as a case study.  Science (Washington, DC) 241: 1473-1475.
29
30     Chan, C.-C.; Ozkaynak, H.; Spengler, J. D.; Sheldon, L. (1991) Driver exposure to volatile organic compounds
31            carbon monoxide, ozone and nitrogen dioxide under different driving conditions. Environ. Sci. Technol.
32            25: 964-972.
33
34     Cleveland,  W. S.; Kleiner, B.; McRae, J. E.; Warner, J. L. (1976a) Photochemical air pollution: transport from
35             New York City area into Connecticut and Massachusetts.  Science (Washington, DC) 191: 179-181.
36
37     Cleveland,  W. S.; Guarino, R.; Kleiner, B.; McRae, J. E.; Warner, J. L. (1976b) The analysis of  the ozone
38             problem in the northeast United States. In: Specialty conference on: ozone/oxidants-interactions with the
39             total environment; March; Dallas, TX. Pittsburgh, PA: Air Pollution Control Association; pp. 109-119.
40
41     Code of Federal Regulations. (1991) National primary and secondary ambient air quality standards, C. F. R.
42            40: §50.
43
44     Coffey, P.; Stasiuk, W.; Monnen, V.  (1977) Ozone in rural and urban areas of New York State: part I.
45            In; Dimitriades, B., ed. International conference on photochemical oxidant pollution and  its
 46            control—proceedings: volume I; September 1976; Raleigh, NC. Research Triangle Park,  NC;
 47            U.S. Environmental Protection Agency, Environmental Sciences Research  Laboratory; pp.  89-96;
 48            EPA report no.  EPA-600/3-77-001a. Available from: NTIS, Springfield, VA; PB-264232.
 49
 50     Contant, C. F., Jr.; Gehan, B. M.; Stock, T. H.;  Holguin, A. H.; Buffler, P.  A.  (1985) Estimation of individual
 51            ozone exposures using microenvironment measurements. In: Lee, S. D., ed. Transactions:  evaluation of
 52            the scientific basis for ozone/oxidants standards. An APCA international specialty conference;
 53            November, 1984; Houston, TX. Pittsburgh,  PA: Air Pollution Control Association; pp. 250-261.
 54


         December 1993                              4-125      DRAFT-DO NOT QUOTE OR CITE

-------
 1     Corkum, R.; Giesbrecht, W. W.; Bardsley, T.; Cherniak, E. A. (1986) Peroxyaeetyl nitrate (PAN) in the
 2            atmosphere at Simcoe, Canada. Atmos. Environ. 20: 1241-1248.
 3
 4     Cox, W. M.; Chu, S. H. (1993) Meteorologically adjusted ozone trends in urban areas: a probabilistic approach.
 5            Atmos. Environ. Part A 27: 1-10.
 6
 7     Curran, T. C.; Frank, N. H. (1990) Ambient ozone trends using alternative indicators. In: Berglund, R. L.;
 8            Lawson, D. R.; McKee, D. J., eds. Tropospheric ozone and the environment. Pittsburgh, PA; Air and
 9            Waste Management Association; pp. 749-759.
10
11     Daum, P. H.; Kleinman,  L.  L; Hill, A. J.; Lazrus, A. L.; Leslie, A. C. D.; Bushess, K.; Boatman, J. (1990)
12            Measurement and interpretation of concentrations of HjC^ and related species in the upper midwest
13            during summer. J. Geophys. Res. D:  Atmos. 95: 9857-9871.
14
15     Davidson, A. (1993) Update of ozone trends in California's South Coast Air Basin. Air Waste 43: 226-227.
16
17     Davies, T. D.; Ramer, B.; Kaspyzok, G.; Delany,  A, C. (1984) Indoor/outdoor ozone concentrations at a
18            contemporary art gallery. J. Air Pollut. Control Assoc. 31: 135-137.
19
20     DeLucia, A. J.; Adams, W. C. (1977) Effects of 03 inhalation during exercise on pulmonary function and blood
21            biochemistry. J. Appl. Physiol.: Respir, Environ, Exercise Physiol. 43: 75-81.
22
23     Druzik, J. R.; Adams, M. S.; Tiller, C.; Cass, G.  R. (1990) The measurement and model predictions of indoor
24            ozone concentrations in museums. Atmos. Environ. Part A 24: 1813-1823.
25
26     Duan, N.  (1982) Models for human exposure to air pollution. Environ. Int. 8: 305-309.
27
28     Edgerton, E. S.; Lavery, T. F. (1992) National dry deposition network fourth annual progress report, 1990.
29            Research Triangle Park, NC: U.S. Environmental Protection Agency, Atmospheric Research and
30            Exposure Assessment Laboratory; EPA contract no. 68-02-4451.
31
32     Evans, G.; Finkelstein, P.;  Martin, B.; Possiel, N.; Graves, M. (1983) Ozone measurements from a network of
33            remote sites. J. Air Pollut. Control Assoc.  33: 291-2%.
34
35     Evans, E. G.; Rhodes, R. C.; Mitchell, W. J.; Puzak, J. C.  (1985) Summary of precision and accuracy
36           assessments for the  state and local air monitoring networks: 1982. Research Triangle Park, NC:
37           U.S. Environmental Protection Agency,  Environmental Monitoring Systems Laboratory; EPA report
38           no.  EPA-600/4-85-031. Available from:  NHS, Springfield, VA; PB85-208171/HSU.
39
40     Fahey, D. W.; Hiibler, G,; Parrish, D. D.; Williams, E. J.; Norton, R. B.; Ridley, B. A.; Singh, H. B.;
41             Liu, S. C.; Fehsenfeld, F. C.  (1986) Reactive nitrogen species in the troposphere:  measurements of NO,
42            NOj, HNO3, particulate nitrate, peroxyacetyl nitrate (PAN), O3, and total reactive odd nitrogen (NOy)
43            at Niwot Ridge,  Colorado. J. Geophys. Res.  [Atmos.] 91: 9781-9793.
44
45     Faith, R.; Sheshinski, R. (1979) Misspecification of trend in spatial random-function interpolation with
 46            application to oxidant mapping. Palo Alto, CA: SLAM Institute for Mathematics and Society, Stanford
 47            University, technical report no. 28.
 48
 49     Finlayson-Pitts, B. J.; Pitts, J. N., Jr. (1986) Atmospheric chemistry: fundamentals and experimental techniques.
 50            New York, NY: John Wiley & Sons.
 51
 52
          December 1993                              4-126       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Folinsbee, L. J.; Drinkwater, B. L.; Bedi, J. F.; Horvafh, S. M. (1978) The influence of exercise on the
 2            pulmonary function changes due to exposure to low concentrations of ozone. In: Folinsbee, L. J.;
 3            Wagner, J.  A.; Borgia, J. F.; Drinkwater, B. L.; Oliner, I. A.; Bedi, J. F., eds.  Environmental stress:
 4            individual human adaptations. New York, NY: Academic Press; pp. 125-145,
 5
 6     Fowler, D.; Cape, J. N. (1982) Air pollutants in agriculture and horticulture. In: Unsworth, M. H.;
 1            Ormrod, D. P., eds. Effects of gaseous air pollution in agriculture and horticulture, London,
 8            United Kingdom: Butterworth Scientific; pp. 3-26,
 9
10     Gaffhey, J. S.; Marley, N. A.; Prestbo, E. W.  (1993) Measurements of peroxyacetyl nitrate at a  remote site in
11            the southwestern United States-tropospheric implications. Environ. Sci. Technol. 27: 1905-1910.
12
13     Gallopoulos, N. E,; Heuss, J. M.; Chock, D. P.; Dunker, A. M.; Williams, R, L; Wolff, G. T. (1988)
14            Progress and prospects in air pollution control and the need to strengthen its scientific base.
15            In: Wolff, O. T.; Hanisch, J. L.; Schere, K, L., eds. The scientific and technical issues being
16            post-1987  ozone control stategies. Pittsburgh, PA: Air and Waste Management Association.
17
18     Grivet, C. D. (1980) Modeling and analysis of air quality data. Palo Alto, CA: SIAM Institute for Mathematics
19            and Society, Stanford University; technical report no. 43.
20
21     Grosjean, D.; Williams, E. L., H (1992) Photochemical pollution at two southern California smog receptor sites.
22            J. Air Waste Manage. Assoe. 42: 805-809.
23
24     Grosjean, D.; Williams, E. L., II; Grosjean, E. (1993) Peroxyacyi nitrates at southern California mountain forest
25             locations. Environ. Sci. Technol. 27: 110-121.
26
27     Hales, C. H.; Rollinson, A. M.; Shair, F. H. (1974) Experimental verification of linear combination model for
28             relating indoor-outdoor pollutant concentrations. Environ. Sci. Technol. 8: 452.
29
30     Hayes, S. R. (1989) Estimating the effect of being indoors on total personal exposure to outdoor air pollution.
31             JAPCA 39: 1453-1461.
32
33     Hayes, S. R. (1991) Use of an indoor air quality model (IAQM) to estimate indoor ozone levels. J.  Air Waste
34             Manage. Assoc. 41:  161-170.
35
36     Hayes, S. R.;  Lundberg, G.  W. (1985) Further improvement and sensitivity analysis of an ozone population
37             exposure model. San Rafael, CA: Systems Applications, Inc.
38
39     Hayes, S. R.;  Rosenbaum, A. S. (1988) An examination of acute ozone health risk and exposure effects on
40            proposed SCAQMD rule 1109 using the SOCAB 6-7 June 1985 ozone episode.  San Rafael,  CA: Systems
41             Applications, Inc.
42
43     Hayes, S. R.;  Seigneur, C.;  Lundberg, G. W.  (1984) Numerical modeling of ozone population exposure:
44            application to a comparison of alternative ozone standards. San Rafael, CA: Systems Applications, Inc.
45
46     Hayes, S. R.;  Austin, B.  S,; Rosenbaum, A. S. (1988) A technique for assessing the effects of ROG and NO,
47            reductions on acute ozone exposure and health risk in the South Coast Air Basin. San Rafael, CA:
48            Systems Applications, Inc.
49
50     Hazucha, M. J.; Seal, E,; Folinsbee, L. (1990) Effects of steady-state and variable ozone exposure  profiles on
51            pulmonary function of man. Am. Rev. Respir. Dis.  141: A7L
52
53     Heck, W. W.; Taylor, 0. C.; Adams, R.; Bingham, G.; Miller, J.; Preston, E.; Weinstein, L. (1982)
54            Assessment of crop loss from ozone. J. Air Pollut, Control Assoc.  32: 353-361.


         December 1993                               4-127       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Holdren, M. W.; Spicer, C, W.; Hales, J. M. (1984) Peroxyacetyl nitrate solubility and decomposition rate in
 2            acidic water. Atmos. Environ. 18: 1171-1173.
 3
 4     Horstman, D, H.; Folinsbee, L, J.; Ives, P. J.; Abdul-Salaam, S,; McDonneH, W. F. (1990) Ozone
 5            concentration and pulmonary response relationships for 6,6-hour exposures with five hours of moderate
 6            exercise to 0.08, 0.10, and 0.12 ppm. Am, Rev. Respir. Die, 142: 1158-1163.
 7
 8     Husar, R.  B.; Patterson, D. E.; Paley, C. C.; Gillani, N. V. (1977) Ozone in hazy air masses.
 9            In: Dhnitriades, B., ed. International  conference on photochemical oxidant pollution and its control.
10            Proceedings: v. I.;  September, 1976;  Raleigh, NC. Research Triangle Park, NC: U.S. Environmental
11            Protection Agency, Environmental Sciences Research Laboratory; EPA report no. EPA-600/3-77-001 A.
12            Available from: NTIS, Springfield, VA; PB-264 232.
13
14     Isaksen, I. S. A.; Hov, O.; Hesstvedt, E. (1978) Ozone generation over rural areas. Environ. Sci. TechnoL
15            12: 1279-1284.
16
17     Johnson, T. R.; Paul, R. A.; Capel, J. E.; McCurdy, T. (1990) Estimation of ozone exposure in Houston using a
18            probabilistic version of NEM. Presented at: 83rd annual meeting and exhibition of the Air and Waste
19            Management Association; June; Pittsburgh, PA. Pittsburgh, PA:  Air and Waste Management Association;
20            paper no. 90-150.1.
21
22     Johnson, T. R.; Wijnberg,  L.; Capel, J, E.; Vostal, J. J. (1992) The use of activity diary data to estimate the
23            probability of exposure to air pollution. In: Berglund, R, L., ed. Tropospheric ozone and the
24            environment n. Pittsburgh, PA: Air and Waste Management Association.
25
26     Jones, K.; Militana, L,; Martini, J. (1989) Ozone trend analysis for selected urban areas in the continental U.S.
27            Presented at: the 82nd annual meeting and exhibition of the Air and Waste Management Association;
28            June; Anaheim, CA. Pittsburgh, PA: Air and Waste Management Association; paper no. 89-3.6.
29
30     Kelly, N. A.; Wolff, G. T.; Fennan, M. A.  (1982) Background pollutant measurements in air masses affecting
31             the eastern half of the United States—I. air masses arriving from the northwest. Atmos. Environ.
32             16: 1077-1088.
33
34    Kelly, N. A.; Wolff, O. T.; Fennan, M. A. (1984) Sources and sinks of ozone in rural areas. Atmos. Environ.
35             18:  1251-1266.
36
37    Kelly, T.  J.; Tanner, R. L.; Newman, L.; Galvin, P. J.; Kadlecek, J. A. (1984) Trace gas and aerosol
38            measurements at a remote site in the northeast U.S. Atmos. Environ. 18: 2565-2576.
39
40    Kelly, N. A.; Ferman, M. A.; Wolff, G. T. (1986) The chemical and meteorological conditions associated with
41             high and low ozone concentrations in southeastern Michigan and nearby areas of Ontario. J. Air Pollut.
42            Control Assoc. 36: 150-158.
43
 44     Kkindienst, T. E.; Shepson, P. B.; Hodges, D, N.; Nero,  C. M.; Arnts, R. R.; Dasgupta, P. K.; Hwang, H.;
 45            Kok, G. L.; JJnd, J. A.; Lazrus, A. L.; Mackay, G. L; Mayne, L. K.;  Schiff,  H. I. (1988) Comparison
 46            of techniques  for measurement of ambient levels of hydrogen peroxide. Environ. Sci. Technol.
 47            22:53-61.
 48
 49     Kleindienst, T. E.; Shepson, P. B.; Smith, D. F.; Hudgens, E. E.; Nero, C. M.; Cupitt, L. T.; Bufalini, J. J.;
 50            Claxton, L. D.  (1990) Comparison of mutagenic activities of several peroxyacyl nitrates. Environ. Mol.
 51            Mutagen.  16: 70-80.
 52
          December 1993                              4-128       DRAFT-DO NOT QUOTE OR CITE

-------
 1     Knudsen, H, P.; Lefohn, A. S. (1988) The use of geostatistics to characterize regional ozone exposures.
 2            In: Heck, W. W.; Taylor, 0. C.; Tingey, D. T., eds. Assessment of crop loss from air pollutants.
 3            London, United Kingdom: Elsevier Science;  pp. 91-105.
 4
 5     Kolaz, D. J.; Swinford, R. L. (1990) How to remove the influence of meteorology from the Chicago area ozone
 6            trend. Presented at: 83rd annual meeting and exhibition of the Air and Waste Management; June,
 7            Pittsburgh, PA. Pittsburgh, PA: Air and Waste Management; paper no. 90-97.5.
 8
 9     Korsog, P. E.; Wolff, G. T.  (1991) An examination of urban ozone trends in the northeastern U.S. (1973-1983)
10            using a robust statistical method. Atmos. Environ. Part B 25: 47-57.
11
12     Kress, L. W.; Miller, J. E. (1983) Impact of ozone on soybean yield. J. Environ. Qua!. 12: 276-281.
13
14     Kuntasal, G.; Chang, T. Y. (1987) Trends and relationships of  03, NO, and HC in the south coast air basin of
15            California. JAPCA 37: 1158-1163.
16
17     Larsen, R. I.; McDonnell, W. F.; Horstman, D. H.; Folinsbee, L. I. (1991) An air quality data analysis system
18            for interrelating effects, standards, and needed source reductions: part 11. a lognormal  model relating
19            human lung function decrease to Oj exposure. J. Air Waste Manage. Assoc. 41: 455-459.
20
21     Lawson, D. R. et al. (1988)  In: Proceedings of the 196th American Chemical Society National Meeting,
22            Los Angeles, Division of Environmental Chemistry, 28, 107.
23
24     Lebowitz, M. D.; Corman, G.; O'Rourke, M. K.; Holberg, C. J. (1984) Indoor-outdoor air pollution, allergen
25            and meteorological monitoring in an arid southwest area. J.  Air Pollut. Control Assoc. 34: 1035-1038.
26
27     Lefohn,  A.  S. (1984) A comparison of ambient ozone exposures for selected nomirban sites. Presented at: 77th
28            annual meeting of the Air Pollution Control Association; June;  San Francisco, CA. Pittsburgh, PA: Air
29            Pollution Control Association; paper no. 84-104.1.
30
31     Lefohn,  A. S. (1992a) Ozone standards and (heir relevance for  protecting vegetation. In: Lefohn,  A. S., ed.
32             Surface level ozone exposures and their effects on vegetation. Chelsea, MI: Lewis Publishers, Inc.;
33            pp. 325-359.
34
35      Lefohn,  A. S. (1992b) The characterization of ambient ozone exposures. In: Lefohn, A. S., ed. Surface-level
36            ozone exposures and (heir effects  on vegetation.  Chelsea, MI: Lewis Publishers, Inc.;  pp. 39-92.
37
38     Lefohn,  A. S.; Benedict, H. M. (1983) The potential for the interaction of acidic precipitation and ozone
39            pollutant doses affecting agricultural crops. Presented at: 76th annual meeting of the Air Pollution Control
40            Association; June; Atlanta, GA. Pittsburgh, PA: Air Pollution  Control Association; report no. 83-2.2.
41
42     Lefohn,  A. S.; Foley, J. K.  (1992) NCLAN  results and their application to the standard-setting process:
43            protecting vegetation from surface ozone exposures. J.  Air Waste Manage. Assoc.  42: 1046-1052.
44
45     Lefohn,  A. S.: Foley, J. K.  (1993) Establishing relevant ozone standards to protect vegetation and human health:
46            exposure/dose-response considerations. J. Air Waste Manage. Assoc. 43: 106-112.
47
48     Lefohn,  A. S.; Jones, C. K. (1986) The characterization  of ozone and  sulfur dioxide air quality data for assessing
49            possible vegetation effects. J. Air Pollut Control Assoc. 36: 1123-1129.
50
51     Lefohn, A. S.; Lucier, A. A. (1991) Spatial and temporal variability of ozone exposure in forested areas of the
52            United States and Canada:  1978-1988.  J. Air Waste Manage. Assoc. 41: 694-701.
53
          December 1993                               4-12Q       DRAFT-DO NOT QUOTE OR fTTR

-------
 1     Lefohn, A. S.; Mohnen, V. A. (1986) The characterization of ozone, sulfur dioxide, and nitrogen dioxide for
 2            selected monitoring sites in the Federal Republic of Germany. J. Air Pollut. Control Assoc.
 3            36: 1329-1337.
 4
 5     Lefohn, A. S.; Runeckles, V. C. (1987) Establishing standards to protect vegetation—ozone exposure/dose
 6            considerations. Atmos. Environ. 21: 561-568,
 7
 8     Lefohn, A. S.; Shadwick, D. S. (1991) Ozone, sulfur dioxide, and nitrogen dioxide trends at rural sites located
 9            in Ibe United States. Atmos. Environ. Part A 25: 491-501.
10
11     Lefohn, A, S.; Tingey, D. T. (1984) The co-occurrence of potentially phytotoxic concentrations of various
12            gaseous air pollutants. Atmos. Environ. 18: 2521-2S26.
13
14     Lefohn, A. S.; Knudsen, H. P.; Logan, J. A.; Simpson, J.; Bhumralkar, C. (1987a) An evaluation of the kriging
15            method to predict 7-h seasonal mean ozone concentrations for estimating crop losses. JAPCA
16            37:595-602.
17
18     Lefohn, A. S.; Davis, G. E.; Jones, C. K.; Tingey, D. T.; Hogsett, W. E. (1987b) Co-occurrence patterns of
19            gaseous air pollutant pairs at different minimum concentrations in the United States. Atmos. Environ,
20            21: 2435-2444.
21
22     Lefohn, A. S.;  Knudsen, H. P.; McEvoy, Jr., L. R. (1988a) The use of kriging to estimate monthly ozone
23             exposure parameters for the southeastern United States. Environ, Pollut. 53: 27-42.
24
25     Lefohn, A. S.;  Laurence, J. A.; Kohut, R. J. (1988b) A comparison of indices that describe the relationship
26             between exposure to ozone  and reduction in the yield of agricultural crops. Atmos. Environ.
27             22: 1229-1240.
28
29     Lefohn, A. S.; Runeckles, V. C.; Krupa, S. V.; Shadwick, D. S. (1989) Important consideratins for establishing
30             a secondary ozone standard to protect vegetation. JAPCA 39: 1039-1045.
31
32     Lefohn, A. S.; Benkovitz, C. M.; Tanner, R.  L.; Smith, L. A.; Shadwick, D. S. (1990a) Air quality
33             measurements and characterizations for terrestrial effects research.  In: Irving, P. M., ed. Acidic
34             deposition: state of science and technology, volume I, emissions, atmospheric processes, and deposition.
35             Washington, DC: The U.S. National Acid Precipitation Assessment Program. (State of science and
36             technology report no. 7).
3.7
38     Lefohn, A. S.; Krupa, S. V.; Winstanley, D. (1990b) Surface ozone exposures measured at clean locations
39            around the world. Environ. Pollut. 63: 189-224.
40
41      Lefohn, A. S.; Shadwick, D. S.; Mohnen, V. A. (1990c) The characterization of ozone concentrations at a select
42            set of high-elevation sites in the eastern United States. Environ. Pollut. 67: 147-178.
43
44     Lefohn, A. S.; Shadwick, D. S,; Somerville, M.  C.; Chappelka, A. H.; Lockaby, B. G.; Meldahl, R. S.
45            (1992a) The characterization and comparision of ozone exposure indices used in assessing the response of
46            loblolly pine to ozone. Atmos. Environ. Part A 26: 287-298.
47
48     Lefohn, A. S.; Knudsen, H. P.; Shadwick, D. S.; Hermann, K. A. (1992b) Surface ozone exposures in the
49            eastern United States (1985-1989). In: Flagler, R.  B., ed. Transactions of the Response of southern
 50            commercial  forests to air pollution specialty conference. Pittsburgh, PA: Air and Waste Management
 51             Association; pp. 81-93.
 52
 53     Lefohn, A. S.; Foley, J. K.; Shadwick, D. S.; Tilton, B.  E. (1993a) Changes in diurnal patterns related to
 54             changes in ozone levels. Air  Waste 43: 1472-1478.


          December  1993                              4-130       DRAFT-DO NOT QUOTE OR  CITE

-------
 1     Lefohn, A. S.; Foley, J. K.; Tilton, B. E. (1993b) Changes in ozone concentration regimes as a function of
 2            change in site attainment status. In: Berglund, R. L., set. Transactions of the tropospheric ozone,
 3            nonattainment and design value issues specialty conference. Pittsburgh, PA:  Air and Waste Management
 4            Association; in press.
 5
 6     Lindsay, R. W.; Chameides, W. L. (1988) High-ozone events in Atlanta, Georgia, in 1983 and  1984. Environ,
 7            Sci. Technol.  22; 426-431,
 8
 9     Lindsay, R. W.; Richardson, J. L; Chameides, W, L. (1989) Ozone trends in Atlanta, Georgia: have emission
10            controls been  effective? JAPCA 39: 40-43.
11
12     Lioy, P. J, (1989) Exposure assessment of oxidant gases and acidic aerosols, Annu, Rev. Public Health
13            10; 69-84.
14
15     Lioy, P. J.; Dyba, R. V. (1989) The dynamics of human exposure to tropospheric ozone. In: Schneider, T.;
16            Lee, S. D.; Wolters, G. J. R.; Grant, L. D,, eds.  Atmospheric ozone research and its policy
17            implications: proceedings of the 3rd US-Dutch international symposium; May 1988; Nijmegen, The
18            Netherlands. Amsterdam, The Netherlands: Elsevier Science Publishers; pp. 711-721. (Studies in
19            environmental science 35).
20
21     Lioy, P. J.; Waldman, J. M. (1989) Acidic sulfate aerosols: characterization and exposure. In: Symposium on
22            the health effects of acid aerosols; October 1987; Research Triangle Park, NC, Environ. Health Perspect.
23            79: 15-34.
24
25     Liu, L. J.; Koutrakis, P.; Suh, H. H.; Mulik, J. D.; Burton, R. M. (1993) Use of personal measurements for
26            ozone exposure assessment: a pilot study. Environ. Health Perspect. 101: 318-324.
27
28     Lloyd, A. C.; Lents,  J. M.; Green,  C.; Nemeth, P. (1989) Air quality management in Los Angeles: perspectives
29            on past and future emission control strategies. JAPCA 39: 696-703.
30
31     Logan, J. A. (1985) Tropospheric ozone: seasonal behavior, trends, and anthropogenic influence.  J. Geophys.
32            Res.  [Atmos.] 90:  10463-10482.
33
34     Logan, J. A. (1989) Ozone in rural areas of the United States. J. Geophys. Res. 94: 8511-8532.
35
36     Lurmann, F.; Colome, S. (1991) An assessment of current and future  human exposure to ozone in the South
37            Coast Air Basin. Santa Rosa, CA: Sonoma Technology.
38
39     Lurmann, F. W.; Coyner,  L.; Winer,  A. M.; Colome, S. (1989) Development of a new regional  human
40           exposure (REHEX) model and its application to the California south coast air basin. Presented at: 60th
41            annual meeting of the  Air and Waste Management Association; June; Anaheim, CA. Pittsburgh, PA: Air
42           and Waste Management Association; paper no. 89-27.5,
43
44    Lurmann, F. W.; Winer, A. M.; Colome, S. D. (1990) Development  and application of a new regional human
45            exposure (REHEX) model. In: Total exposure assessment methodology. Pittsburgh, PA: Air and Waste
46            Management Association; pp. 478-498.
47
48     Mage, D. T.; Raizenne, M.; Spengler, J. (1985) The assessment of individual human exposures to ozone in a
49            health study. In: Lee,  S. D., ed. Evaluation of the scientific bases for ozone/oxidants standards:
50            transactions of an APCA international specialty conference; November  1984; Houston,  TX. Pittsburgh,
51            PA:  Air Pollution Control Association; pp.  238-249; TR-4.
52
53     Matneron, G. (1963) Principles of geostatistics. Economic Geol. 58: 1246-1266.
54


         December 1993                               4-131       DRAFT-DO NOT QUOTE OR CITE

-------
 1     McCurdy, T. (1988) Relationships among ozone air quality indicators in urban areas. In: Wolff, G, T.; Hanisch,
 2            J. L.; Schere, K,, eds. Transactions of an APCA specialty conference on the scientific and technical
 3            issues facing post-1987 ozone control strategies; November, 1987; Hartford, CT, Pittsburgh, PA: Air and
 4            Waste Management Association; pp.  331-342,
 5
 6     McCurdy, T, (1994) Human exposures to ambient ozone. In: McKee, D. I., ed. Tropospheric ozone: human
 7            health and agricnltrual impacts. Chelsea, MI: Lewis Publishers; pp. 85-128.
 8
 9     McCurdy, T,; Johnson, T. R.; Capel, J.  E.; Paul, R. A. (1991) Preliminary analyses of ozone exposures in
10            Houston using pNEM/O3. Presented at; the 84th annual meeting and exhibition of the Air and Waste
11            Management Association; June; Vancouver, BC, Canada. Pittsburgh, PA: Air and Waste Management
12            Association; paper no. 91-141.1.
13
14     McDonnell, W. P.; Kehrl, H. R.; Abdul-Salaam, S.; Ives, P. J.; Folinsbee, L. J.;  Devlin, R. B.; O'Neil, J.  J.;
15            Horstman, D. H. (1991) Respiratory response of humans exposed to low levels of ozone for 6.6 hours.
16            Arch, Environ. Health 46: 145-150.
17
18     Meagher, J. P.; Lee, N.  T.; Valente, R. J.; Parkfanrst,  W. J. (1987) Rural ozone in the southeastern United
19            States.  Atmos. Environ, 21: 605-615.
20
21     Meyer, B. (1983) Indoor air quality. Reading, MA: Addison-Wesley Publishing Company, Inc.
22
23     Mohnen, V. A. (1988) Mountain cloud chemistry project—wet, dry and cloud water deposition. Research
24            Triangle  Park, NC: U.S. Environmental Protection Agency, Office of Research and Development,;
25            contract no. CR 813934-01-02.
26
27     Mohnen, V. A.;  Hogan, A.;  Coffey, P.  (1977) Ozone measurements in rural areas. J. Geophys. Res.
28            82:5889-5895.
29
30    Moschandreas, D. J,; Stark, J. W. C.; McFadden, J. E.; Morse,  S. S. (1978) Indoor air pollution in the
31            residential environment: volume I. data collection, analysis,  and interpretation. Research Triangle Park,
32            NC: U.S. Environmental Protection Agency, Environmental Monitoring and Support Laboratory; EPA
33            report  no. EPA-600/7-78-229a, Available from: NTIS, Springfield, VA; PB-290999.
34
35     Moschandreas, D. J.; Zabransky, J.; Pelton, D.  J. (1981) Comparison of indoor and outdoor air quality. Palo
36           Alto, CA: Electric Power Research  Institute; EPRI report no.  EA-1733.
37
38    National Acid  Precipitation Assessment Program. (1987) Interim assessment: the causes and effects of acidic
39           deposition, volume I, executive summary. Washington, DC; Office of the Director of Research.
40
41     National Research Council. (1991) Rethinking the ozone problem in urban and regional air pollution.
42            Washington, DC: National Academy Press.
43
44     Nazaroff, W.  W.; Cass, G. R. (1986) Mathematical modeling of chemically reactive pollutants in indoor air.
45            Environ, Sci. Technol. 20:  924-934.
46
47     O'Gara, P. J.  (1922) Sulfur dioxide and fume problems and their solution, (presented at the 14th semiannual
48            meeting  of the American Institute of Chemical  Engineers, Niagara Falls, Canada, June 19-22, 1922).
 49            Presented at: 14th semiannual meeting of the American Institute of Chemical Engineers; June; Niagara
 50            Falls,  Canada. Proceedings and  papers of the meeting summarized in J. Ind. Eng. Chem. 14: 744-745 by
 51            J, C. Olsen.
 52
 53     Olszyna, K. J.;  Meagher, J. F.; Bailey, E.  M. (1988)  Gas-phase, cloud and rain-water measurements of
 54            hydrogen peroxide at a high-elevation site. Atmos. Environ. 22: 1699-1706.


          December 1993                              4-132       DRAFT-DO NOT QUOTE OR OT1

-------
 1     Paul, R. A.; Biller, W. F.; McCurdy, T. (1987) National estimates of population exposure to ozone. Presented
 2            at: 80th annual meeting of the Air Pollution Control Association; June; New York, NY. Pittsburgh, PA:
 3            Air Pollution Control Association; paper no. 87-42.7.
 4
 5     Peake, £.; Sandhn, H. S.  (1983) The formation of ozone and peroxyacetyl nitrate (PAN) in the urban
 6            atmospheres of Alberta. Can. I. Chem. 61: 927-935.
 7
 8     Peake, £.; MacLean, M. A.; Sandhu, H. S. (1983) Surface ozone and peroxyacetyl nitrate (PAN) observations at
 9            rural locations in Alberta, Canada. 3. Air PolluL Control Assoc. 33: 881-883.
10
11     Peake, £.; MacLean, M. A.; Lester, P. F.; Sandhu, H.  S. (1988) Peroxyacetylnitrate (PAN) in the atmosphere
12            of Edmonton, Alberta, Canada. Atmos. Environ. 22: 973-981.
13
14     Pinkerton, J. E.; Lefohn,  A. S. (1986) Characterization  of ambient ozone concentrations in commercial
15            timberlands using available monitoring data. Tappi 69: 58-62.
16
17     Pitts, J. N., Jr.; Grosjean, D. (1978) Detailed characterization of gaseous and size-resolved particulate pollutants
18            at a south coast air basin smog receptor site: levels and modes of formation of sulfate,  nitrate and organic
19            particulates and their implications for control strategies [final report]. Sacramento, CA; California Air
20            Resources Board;  report no. ARB-R-5-384-79-100. Available from NTIS, Springfield,  VA; PB-301294.
21
22     Pratt, G. C.; Hendrickson, R. C.; Chevone, B. I.; Christopherson, D. A.; O'Brien, M. V.; Krupa, S. V. (1983)
23            Ozone and oxides of nitrogen in the rural upper-midwestern U.S.A. Atmos. Environ. 17: 2013-2023.
24
25     Prinz, B,; Krause, G. H.  M. (1988) State of scientific discussion about the causes of the novel forest decline in
26            the Federal Republic of Germany and surrounding countries. Presented at* 15th international meeting for
27             specialists in Air pollution effects on forest ecosystems; October; Interlaken, Switzerland. IUFRO.
28
29     Prinz, B.; Krause, G. H.  M.; Jung, K. D. (1985) Untersuchungen der LIS zur problematik der waldschaden.
30             In: Waldschaden—Theorie und Praxis auf der Suche nach Antworten, R. Oldenbourg Verlag, Munchen,
31             Wien; pp. 143-194.
32
33     Raizenne, M. E.; Spengler, J. D. (1989) Dosimetric model of acute health effects of ozone and acid aerosols in
34             children. In: Schneider, T.; Lee, S. D.; Welters, G. J. R.; Grant, L. D., eds. Atmospheric ozone
35             research and its policy implications: proceedings of the 3rd U.S.-Dutch international symposium;
36             May 1988; Nijmegen, The Netherlands. Amsterdam, The Netherlands: Elsevier Science Publishers:
37             pp. 319-329. (Studies in environmental science 35).
38
39    Rao, S. T.; Sistla, G.; Henry, R. (1992) Statistical analysis of trends in urban ozone air quality. J.  Air Waste
40            Manage. Assoc. 42: 1204-1211.
41
42     Reagan, J. (1984) Air quality data interpretation. In: Heck, W. W.; Taylor, O. C.; Adams, R. M.; Bingham,
43            G. E.; Miller, J.  E.; Preston, E. M.; Weinstein, L. H., eds. National Crop Loss Assessment Network
44            (NCLAN) 1982 annual report Corvallis, OR: U.S. Environmental Protection Agency, Corvallis
45            Environmental Research Laboratory; pp. 198-219; EPA report no. EPA-600/4-84-049. Available from:
46            NTIS,  Springfield, VA; PB84-169358/HSU.
47
 48     Reiter, E. R. (1977a) Review and analysis. In: Mohnen, V. A.; Reiter, E. R., eds. International conference on
 49            oxidants, 1976—analysis of evidence and viewpoints; part ID.  (he issue of stratospheric ozone intrusion.
 50            Research Triangle Park, NC: U.S. Environmental Protection Agency, Environmental Sciences Research
 51            Laboratory; pp. 67-117; EPA report no. EPA-6QO/3-77-115. Available from: NTIS, Springfield, VA;
 52            PB-279010.
 53
          December 1993                              4-1 "VI       DRAFT-DO NOT QUOTE OR  rrm

-------
 1     Reiter, E, R. (1977b) The role of stratospheric import on tropospheric ozone concentrations. In: Dimitriades, 6.,
 2            ed. International conference on photochemical oxidant pollution and its control—proceedings: volume I;
 3            September 1976; Raleigh, NC. Research Triangle Park, NC: U.S. Environmental Protection Agency,
 4            Environmental Sciences Research Laboratory; pp. 393-410; EPA report no. EPA-600/3-77-001a.
 5            Available from: NTIS, Springfield, VA; PB-264232.
 6
 7     Ridley, B, A. (1991) Recent measurements of oxidized nitrogen compounds in the troposphere. Atmos. Environ.
 8            Part A 25: 1905-1926.
 9
10     Ridley, B. A.; Shetter, J. D.; Walega, J. G.; Madnmich, S.; Elsworth, C. M.; Grahek, F. E.; Fehsenfeld,
11            F. C.;  Norton, R. B.; Parrish, D. D,; Hublers G.; Buhr, M.; WUHams, E. J.;  Allwine, E. J.;
12            Westberg, H. H. (1990) The behavior of some organic nitrates at Boulder and  Niwot Ridge, Colorado.
13            J. Geophys. Res. [Atmos.] 95: 13,949-13,961.
14
15     Rombout, P. J. A.; Lioy, P. J.; Goldstein, B. D, (1986) Rationale for an  eight-hour standard. J. Air Pollut.
16            Control Assoc. 36: 913-917.
17
18     Rombout, P. J. A.; Van Bree, L.; Heisterkamp, S. H.; Marra, M. (1989) The need for an eight hour ozone
19            standard. In: Schneider, T.;  Lee, S. D.; Wolters, G. J. R.; Grant, L. D., eds.  Atmospheric ozone
20            research and its policy implications: proceedings of the 3rd US-Dutch international symposium;
21            May 1988; Nijmegen, The Netherlands. Amsterdam, The Netherlands: Elsevier Science Publishers;
22            pp. 701-710. (Studies in environmental science 35).
23
24     Runeckles, V, C. (1974) Dosage of air pollutants and damage to vegetation. Environ, Conserv, 1: 305-308.
25
26     Runeckles, V. C.; Bates, D. V, (1991) The form of the ozone standard in relation to vegetation and health
27            effects. Presented at: the 84th annual meeting and exhibition of the Air and Waste Management
28            Association; June; Vancouver, BC, Canada. Pittsburgh, PA: Air and Waste Management Association;
29            paper no. 91-74.3,
30
31     Ryan, P. B.; Soczek, M. L.; Treitman, R. D.; Spengler, J.  D.; Billick, I. H. (1988) The Boston residential
32           NO2 characterization study—H. survey methodology and population concentration estimates. Atmos.
33           Environ. 22: 2115-2125.
34
35     Sabersky, R. H.; Sinema, D. A.; Shair, F. H.  (1973) Concentrations, decay rates, and removal of ozone and
36            their relation to establishing clean indoor air. Environ. Sci.  Technol. 7: 347-353,
37
38     Sakugawa, H.; Kaplan, I. R. (1989) I^Qj and Qj in the atmosphere of Los Angeles and its vicinity: factors
39            controlling their formation and their role as oxidants of SOj. J. Geophys. Res. D:  Atmos.
40            94: 12,957-12,973.
41
42     Sakugawa, H.; Kaplan, I. R. (1993) Comparison of I^Oj and O3 content in atmospheric samples in the
43            San Bernardino Mountains,  southern California. Atmos.  Environ 27A: 1509-1515.
44
45     Sakugawa, H.; Kaplan, I. R.; Tsai, W.; Cohen, Y. (1990) Atmospheric hydrogen peroxide: does it share a role
46            with ozone in degrading air quality? Environ. Sci. Technol. 24: 1452-1462.
47
48     SAROAD, Storage and Retrieval of Aerometric Data [data base]. (1985a) Data rile for 1976. Research Triangle
49            Park, NC: U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards. Disc;
 50            ASCT.
 51
 52     SAROAD, Storage and Retrieval of Aerometric Data [data base]. (1985b) [Data file for 1979]. Research Triangle
 53            Park, NC: U.S. Environmental Protection Agency,  Office of Air Quality Planning and Standards. Disc;
 54            ASCn.


          December 1993                              4-134       DRAFT-DO NOT QUOTE OR CTTE

-------
 1     SAROAD, Storage and Retrieval of Aerometric Data [data base]. (1985c) Data file for 1981. Research Triangle
 2            Park, NC: U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards. Disc;
 3            ASCn.
 4
 5     Sexton, K.; Ryan, P. B. (1988) Assessment of human exposure to air pollution: methods, measurements, and
 6            models. In:  Watson, A. Y.; Bates, R. R.; Kennedy, D., eds. Air pollution, the automobile, and public
 7            health. Washington, DC: National Academy Press; pp. 207-238.
 8
 9     Shaii, F. H.; Heitner, K. L. (1974) Theoretical model for relating indoor pollutant concentrations to those
10            outside. Environ. Sci. Technol. 8: 444-451.
11
12     Shaver,  C. L.; Cass, G. R.; Druzik, J. R. (1983) Ozone and ihe deterioration of works of art. Environ. Sci.
13            Technol.  17: 748-752.
14
15     Shepson, P. B.; Kleindienst, T. E.; Edney, E. O.; Nero, C. M.; Cupitt, L. T.; Claxton, L. D. (1986)
16            Acetaldehyde: the mutagenic activity of its photooxidation products. Environ. Sci. Technol.
17            20: 1008-1013.
18
19     Shively, T. S. (1991) An analysis of the trend in ground-level ozone using non-homogenous Poisson process.
20            Atmos. Environ. Part B 25: 387-395.
21
22     Showman, R. E.  (1991) A comparison of ozone injury to vegetation during moist and drought years. J. Air
23            Waste Manage. Assoc. 41: 63-64.
24
25     Silvernum, F.; Folinsbee, L. J.; Barnard, I.; Shephard, R. J. (1976) Pulmonary function changes in
26            ozone—interaction of concentration and ventilation. J. Appl. Physiol. 41: 859-864.
27
28     Singh, H. B.; Salas, L. J. (1989) Measurements of peroxyacetyl nitrate (PAN) and peroxypropionyl nitrate (PPN)
29             at selected urban, rural and remote sites. Atmos. Environ. 23: 231-238.
30
31     Singh, H. B.; Ludwig, F. L.; Johnson, W. B. (1977) Ozone in clean remote atmospheres: concentrations and
32             variabilities. New York,  NY: Coordinating Research  Council, Inc.; report no. CRC-APRAC
33             CAPA-15-76. Available from: NTIS, Springfield, VA; PB-272290.
34
35     Singh, H. B.; Ludwig, F. L.; Johnson, W. B. (1978) Tropospheric ozone: concentrations and variabilities in
36            clean remote atmospheres. Atmos. Environ. 12: 2185-2196.
37
38     Smith, W. J. (1981) New York State air monitoring data report for the northeast corridor regional modeling
39            project (NECREMP), June 1, 1980 to September  12, 1980. Albany, NY: New York State Department of
40            Environmental Conservation, Monitoring Instrumentation Engineering Section.
41
42     Smith, L. A.; Lefohn, A. S.  (1991) Co-occurence of ozone and wet deposited hydrogen ion in the United States.
43            Atmos. Environ. Part A 25: 2707-2716.
44
 45     Spektor, D. M.; JJppmann, M.; Lioy, P. J.; Thurston, G. D.; Citak, K.; James, D. J.; Bock, N.; Speizer,
 46            F. E.; Hayes, C. (1988) Effects of ambient ozone on respiratory function in active, normal children.
 47            Am.  Rev. Respir. Dis. 137: 313-320.
 48
 49     Spektor, D. M.; Thurston, G. D.; Mao, J.; He, D.;  Hayes, C.; lippmann, M. (1991) Effects of single- and
 50            multiday ozone exposures on respiratory function in active normal children. Environ. Res.  55: 107-122.
 51
 52     Stasiuk, W. N.,  Jr.; Coffey,  P. E. (1974) Rural and  urban ozone relationships in New York State, J. Air PoUut,
 53            Control ASSOG, 24: 564-568.
 54


         December 1993                              4-1 T?      DRAFT-DO NOT OTrOTP m? PTTP

-------
 I     Stack, T. H.; Holguin, A. H.; Selwyn, B. J.; Hsi, B. P.; Contant, C. F.; Buffler, P. A.; Kotdunar, D. J.
 2            (1983) Exposure estimates for die Houston area asthma and runners studies. In: Lee, S. D.;
 3            Mustafa, M. G.; Mehlman, M. A., eds. International symposium on the biomedical effects of ozone and
 4            related photochemical oxidanta; March 1982; Hnehurst, NC.  Princeton, NJ: Princeton Scientific
 5            Publishers, Inc.; pp. 539-548. (Advances in modern environmental toxicology: v. 5).
 6
 7     Stoeckenius, T.  E. (1990) Adjustment of ozone trends for meteorological variation. In: Berglund, R. L.;
 8            Lawson, D. R.; McKee, D. I., eds. Tropospheric ozone and the environment. Pittsburgh, PA: Air and
 9            Waste Management Association; pp. 781-800.
10
11     Stoeckenius, T.  E.; Hudischewskyj, A. B. (1990) Adjustment for ozone trends for meteorological variation.
12            San Rafael, CA: Systems Applications, Inc; paper no. SYSAPP-90/008.
13
14     Tanner, R. L.; Miguel, A. H.; de Andrade, J. B.; Gaffney, J, S.; Streit, G. E.  (1988) Atmospheric chemistry of
15            aldehydes: enhanced peroxyacetyl nitrate formation from ethanol-fueled vehicular emissions. Environ.
16            Sci. Technol. 22;  1026-1034.
17
18     Taylor, G. E., Jr.; Hanson, P. J. (1992) Forest trees and tropospheric ozone: role of canopy deposition and leaf
19            uptake in developing exposure-response relationships. Agric. Ecosyst, Environ, 42: 255-273.
20
21     Taylor, G. E., Jr.; Norby, R. J. (1985) The significance of elevated levels of ozone on natural ecosystems of
22             North America, In: Lee, S. D., ed. Evaluation of the scientific basis for ozone/oxidants standards:
23            proceedings of an APCA international specialty conference; November 1984; Houston, TX.
24            Pittsburgh, PA: Air Pollution Control Association; pp. 152-175. (APCA transactions: TR-4).
25
2.6    Taylor, G. E., Jr.; McLaughlin, S. B.; Shriner, D. S.  (1982) Effective pollutant dose. In: Unsworth, M. H.;
27            Ormrod, D. P., eds. Effects of gaseous air pollution in agriculture and horticulture. London, United
28            Kingdom: Butterworth Scientific; pp. 458-460.
29
30    Taylor, G. E.; Ross-Todd, B. M.; Allen, E.; ConkUn, P.; Edmonds, R.; Joranger, E.; Miller, E.; Ragsdale, L;
31            Shepard, J.; Silsbee, D.; Swank, W. (1992) Patterns of tropospehric ozone in forested landscapes of the
32            Integrated Forest Study. In: Johnson, D. W.; Lindberg, S. E., eds. Atmospheric deposition and forest
33            nutrient cycling—a synthesis of the Integrated Forest Study.  New York, NY: Springer-Verlag; pp. 50-71.
34
35     Thompson, C. R. (1971) Measurement of total oxidant levels at Riverside Community Hospital.  Arch. Environ.
36            Health 22: 514.
37
38     Thompson, C. R.; Hensel, E. G.; Kats, G. (1973) Outdoor-indoor levels of six air pollutants. J. Air Pollut,
39            Control Assoc. 23: 881-886.
40
41     Thurston, G. D.; Ito, K.; Kinney, P. L.; Lippmann, M. (1992) A multi-year study of air pollution and
42            respiratory hospital admissions in three New York State metropolitan areas: results for 1988 and
43            1989 summers. J. Exp. Anal. Environ. Epidemic!. 2: 429-450.
 44
 45     Thuraton, G. D.; Gorczynski, J. E., Jr.; Currie, J. H.; He, D.; Ito, K.; Lippmann, M.; Waldman, J.;
 46            Lioy, P. J.  (1994) The nature and origins of acid aerosol pollution measured in metropolitan Toronto,
 47            Ontario. Environ. Res,: in press.
 48
 49     Tingey, D. T.;  Hill, A. C. (1968) The occurence of photochemical phytotoxicants in the Salt Lake Valley. Utah
 50            Acad. Sci. Proc, 44:  387-395.
 51
 52     Trainer,  M.; Williams, E. J.; Parrish, D, D.; Buhr, M, P.; Allwine, E. J.; Westberg, H. H.; Fehsenfeld, F. C.;
 53            JJu, S. C. (1987) Models and observations of the impact of natural hydrocarbons on rural ozone. Nature
 54             (London) 329: 705-707.


          December 1993                               4-136      DRAFT-DO NOT QUOTE OR CITE

-------
 1     Tsalkani, N.; Perros, P.; Dutot, A. L.; Toupance, G, (1991) One-year measurements of PAN in the Paris basin;
 2            effect of meteorological parameters,  Atmos. Environ. Part A 25: 1941-1949.
 3
 4     Tsani-Bazaca, E.; Olavas, S.; Gusten, H. (1988) Peroxyacyl nitrate (PAN) concentrations in Athens, Greece.
 5            Atmos. Environ. 22: 2283-2286.
 6
 7     Tuazon, E. C.; Atkinson, R. (1990) A product study of OK gas-phase reaction of methacrolein with the OH
 8            radical in the presence of NOX. Int.  J. Chem. Kinet, 22: 591-602.
 9
10     U.S. Environmental Protection Agency. (1978) Air quality criteria for ozone and other photochemical oxidants.
11            Research Triangle Park, NC: Office of Health and Environmental Assessment, Environmental Criteria
12            and Assessment Office; EPA report  no. EPA-600/8-78-004, Available from: NT1S, Springfield, VA;
13            PB80-124753.
14
15     U.S. Environmental Protection Agency. (1986) Air quality criteria for ozone and other photochemical oxidants.
16            Research Triangle Park, NC: Office of Health and Environmental Assessment, Environmental Criteria
17            and Assessment Office; EPA report nos. EPA-60Q/8-84-020aF-eF. 5v. Available from: NTIS,
18            Springfield, VA; PB87-142949.
19
20     U.S. Environmental Protection Agency. (1988) Summary of selected new information on effects of ozone on
21            health and vegetation: draft supplement to air quality criteria for ozone and other photochemical oxidants.
22            Research Triangle Park, NC: Office of Health and Environmental Assessment, Environmental Criteria
23            and Assessment Office; EPA report no. EPA-600/8-88-105A. Available from: NTIS, Springfield, VA;
24            PB89-135123.
25
26     U.S. Environmental Protection Agency. (1989) Review of the national ambient air quality standards for ozone:
27            assessment of scientific and technical information. OAQPS staff paper. Research Triangle Park, NC:
28            Office of Air Qualify Planning and  Standards; EPA  report no. EPA-450/2-92/001. Available from: NTIS,
29            Springfield, VA; PB92-190446.
30
31     U.S. Environmental Protection Agency. (1990) Air quality criteria for carbon monoxide [external review draft].
32            Research Triangle Park, NC: Office of Health and Environmental Assessment, Environmental Criteria
33            and Assessment Office; EPA report no. EPA/600/8-90/045A. Available from: NTIS, Springfield, VA;
34            PB90-195587.
35
36     U.S. Environmental Protection Agency. (1992a) National air quality and emissions trends report,  1991. Research
37             Triangle Park, NC: U.S. Environmental Protection  Agency, Office of Air Quality Planning and
38             Standards; EPA report no. 450-R-92-001.
39
40    U.S. Environmental Protection Agency. (1992b) Summary of selected new information on effects of ozone on
41             health and vegetation: supplement to 1986 air quality criteria for ozone and other photochemical oxidants.
42             Research Triangle Park, NC: Office of Health and Environmental Assessment, Environmental Criteria
43             and Assessment Office; EPA report no. EPA/600/8-88/105F. Available from: NTIS, Springfield, VA;
44            PB92-235670.
45
46     U.S. Environmental Protection Agency. (1993) National air quality and emissions trends report, 1992. Research
47            Triangle Park, NC: Office of Air Quality Planning  and Standards; EPA report no. EPA/454-R-93-031.
48
49     Van Valin, C. C.; Ray, J.  D.; Boatman, J. F; Gunter, R. L.  (1987) Hydrogen peroxide in air during winter over
50            the south-central United States. Geophys. Res. Lett. 14: 1146-1149.
51
52     Viezee, W.; Johnson, W. B; Singh, H. B.  (1983) Stratospheric ozone in the lower troposphere - n. assessment
53            of downward flux and ground-level impact. Atmos. Environ. 17: 1979-1993.
 54


         December 1993                              4-137       D1AFT-DO NOT QUOTE OR CITE

-------
 1     Vong, R. J.; Guttorp, P. (1991) Co-occurrence of ozone and acidic cloudwater la high-elevation forests. Environ,
 2            Sci. Technol. 25: 1325-1329.
 3
 4     Vukovich, F. M.; Bach, W. D., Jr.; Crissman, B. W.; King, W. J. (1977) On the relationship between high
 5            ozone in the rural surface layer and high pressure systems. Atmoa. Environ. 11: 967-983.
 6
 7     Wakim, P. G.  (1990) 1981 to 1988: ozone trends adjusted to meteorological conditions for 13 metropolitan areas.
 8            Presented at: the 83rd annual meeting and exhibition of the Air and Waste Management Association;
 9            June; Pittsburgh, PA. Pittsburgh, PA: Air and Waste Management Association; paper no. 90-97.9.
10
11     Weschler, C. J.; Shields, H. C.; Naik, D. V. (1989) Indoor ozone exposures. JAPCA 39: 1562-1568.
12
13     Westberg, H.;  Allwine, K.; Robinson, E. (1978) Measurement of light hydrocarbons and oxidant transport:
14            Houston study 1976. Research Triangle Park, NC: U.S. Environmental Protection Agency,
15            Environmental Sciences Research Laboratory; EPA  report no. EPA-600/3-78-062. Available from: NT1S,
16            Springfield, VA; PB-285891.
17
18     Wight, G. D.; Wolff, G. T.; Lioy, P. J.; Meyers, R. E.; Cederwall, R. T. (1978) Formation and transport of
19            ozone in the northeast quadrant of the United States. In: Morris, A. L.;  Barras,  R. C., eds. Air quality
20            meteorology and atmospheric ozone: a symposium sponsored by ASTM  Committee D-22 on Methods of
21            Sampling and Analysis of Atmospheres;  July-August 1977; Boulder, CO. Philadelphia, PA: American
22            Society for Testing and Materials-, pp. 445-457;  ASTM special technical publication 653.
23
24     Williams, E. L., II; Grosjean, D. (1990) Southern California air quality study: peroxyacetyi nitrate.  Atmos.
25            Environ. Part A 24: 2369-2377.
26
27     Williams, E. L., II; Grosjean, D. (1991) Peroxypropionyl nitrate at a Southern California mountain forest site.
28            Environ, Sci. Technol. 25: 653-659.
29
30     Williams, E. L., II; Grosjean, E.; Grosjean, D. (1993)  Ambient levels of the peroxyacyl nitrates PAN, PPN, and
31            MPAN in Atlanta, Georgia, Air Waste 43: 873-879.
32
33     Winer, A, M.; Lurmann, F. W.; Coyner, L. A.; Colome, S.  D.; Poe, M. P. (1989) Characterization of air
34            pollution exposures in the California South Coast Air  Basin: application of a new regional human
35             exposure (REHEX) model. Riverside, CA: University of California at Riverside.
36
37     Winner, W. E.; Lefohn, A. S.;  Cotter, I. S.; Greitner,  C.  S.; Nellessen, J.; McEvoy, L. R., Jr.; Olson, R. L.;
38            Atkinson, C. J.; Moore, L. D. (1989) Plant responses to elevational gradients of pj exposures in
39            Virginia. Proc. Nad. Acad. Sci. U.S. A. 86: 8828-8832.
40
41      Wolff, G. T.; Lioy, P. J.  (1980) Development of an ozone river associated with synoptic scale episodes in the
42            eastern United States. Environ. Sci. Technol. 14: 1257-1260.
43
44     Wolff, G. T.; Stasiuk, W. N., Jr.; Coffey, P. E.; Pasceri,  R. E. (1975) Aerial ozone measurements over
45            New Jersey, New  York, and Connecticut Presented at: 68th annual meeting of (he Air Pollution Control
 46            Association; June; Boston, MA. Pittsburgh, PA: Air Pollution Control Association; paper no. 75-58.6.
47
 48     Wolff, G. T.; Lioy, P. J.; Wight, G. D.; Meyers, R. E.; Cederwall, R, T. (1977) An investigation of long-range
 49            transport of ozone across the midwestern and eastern  United States. In: Dimitriades, B., ed. International
 50            conference on photochemical oxidant pollution and its control—proceedings: volume I; September 1976;
 51            Raleigh, NC. Research Triangle Park, NC:  U.S. Environmental Protection Agency, Environmental
 52            Sciences Research Laboratory; pp.  307-317; EPA report no, EPA-600/3-77-001a. Available from: NTIS,
 53            Springfield, VA; PB-264232.
 54


          December  1993                              4-138      DRAFT-DO NOT QUOT1 OR CTffi

-------
 1     Wolff, G. T.; Lioy, P. J,; Taylor, R. S. (1987) The diurnal variations of ozone at different altitudes on a rural
 2            mountain in the eastern United States. JAPCA 37: 45-48.
 3
 4     Yocom, J. E. (1982) Indoor-outdoor air quality relationships:  a critical review. J. Air Pollut. Control Assoc.
 5            32:500-520.
 6
 7     Zeldin, M. D.; Cassmassi, J. C.; Hoggan, M. (1991) Ozone trends in the south coast air basin: an update,
 8            In: Berglund, R. L.; Lawson, D. R.; McKee, D. J., eds. Tropospheric ozone and the environment:
 9            papers from an international conference; March 1990; Los Angeles, CA. Pittsburgh, PA: Air & Waste
10            Management Association; pp. 760-771. (A&WMA transaction series no. TR-19).
11
12     Zhang, J.; lioy, P. J, (1994) Ozone in residential air: concentrations, I/O ratios, indoor chemistry, and
13            exposures. Indoor Air: in press.
14
15     Zimmerman, P. R. (1979) Determination of emission rates of hydrocarbons from indigenous species of vegetation
16            in the Tampa/St. Petersburg, Florida area. Atlanta, GA: U.S. Environmental Protection Agency,  Air
17            Programs Branch; EPA report no. EPA-904/9-77-028. Available from: HITS, Springfield, VA;
18            PB-297057.
         December 1993                              4-139       DRAFT-DO NOT QUOTE OR CITE

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