EPA-600/3-77-001a
January 1977
Ecological Research Series
                INTERNATIONAL CONFERENCE
               ON PHOTOCHEMICAL OXIDANT
                POLLUTION AND ITS CONTROL
                                               I
                               Office of Research and Development
                              U.S. Environmental Protection Agency
                          Research Triangle Park, North Carolina 27711

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                 RESEARCH REPORTING SERIES

 Research reports of the Office of Research and Development, U.S. Environmental
 Protection  Agency, have  been grouped into five  series. These five  broad
 categories  were established to facilitate further development and application of
 environmental technology.  Elimination of traditional grouping was consciously
 planned to  foster technology transfer and  a maximum interface in related fields
 The five series are:

     1.    Environmental Health Effects Research
     2.    Environmental Protection Technology
     3.    Ecological Research
     4.    Environmental Monitoring
     5.    Socioeconomic Environmental Studies

 This report has been assigned to the ECOLOGICAL RESEARCH series. This series
 describes  research on the effects  of pollution on humans, plant and animal
 species, and materials.  Problems  are assessed for their long- and short-term
 influences.  Investigations include formation, transport, and pathway studies to
 determine the fate of pollutants and their effects. This work provides the technical
 basis for setting standards to minimize undesirable changes in living organisms
 in the aquatic, terrestrial, and  atmospheric environments.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.

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                                                   EPA-600/3-77-OOU
                                                   January 1977
                 INTERNATIONAL CONFERENCE
                            ON
              PHOTOCHEMICAL OXIDANT POLLUTION
                      AND ITS CONTROL
                  Proceedings:  Volume I
Hosted by the United States Environmental Protection Agency
                   September 12-17, 1976
                  Raleigh, North Carolina

         Coordinated by the Triangle Universities
                Consortium on Air Pollution

                   with the patronage of
   Organization for Economic Cooperation and Development
                         Edited by

                     Basil Dimitriades
        Environmental Sciences Research Laboratory
           Research Triangle Park, N. C.   27711
        Environmental Sciences Research Laboratory
            Office of Research and Development
           U. S. Environmental Protection Agency
      Research Triangle Park, North Carolina   27711

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                                  DISCLAIMER
     This report has been reviewed by the Environmental Sciences Research
Laboratory, U.S. Environmental Protection Agency, and approved for pub-
lication.  Approval does not signify that the contents necessarily reflect
the views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.

     In general, the texts of the papers included in this report have been
reproduced in the form submitted by the authors.

     Any papers included in the Program arid not included herein were not
submitted for publication.
                                     11

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                                   PREFACE

     Since the late 1940's when the first studies of atmospheric pollution
began, photochemical smog has been evolving into a full-fledged problem with
an enormously strong and complex impact upon man's lifestyle.  Smog is no
longer a subject of mainly academic interest.   Its presence and consequences
are now fully felt by the layman and perhaps most painfully by the automobile
user.  The use of automobiles is being restricted in the large urban centers
in the U. S., and even more restrictive measures including gasoline rationing
have been considered.  The merits of the economic incentives traditionally
associated with industrial growth are now being seriously questioned, and
pressures grow stronger for a review and a more realistic appraisal of the
environmental, energy, and industrial growth priorities.  Such a strong and
multifaceted impact of the photochemical pollution problem makes it imperative
that all judgment regarding the causes, occurrence, and solution or alleviation
of the problem be made responsibly and with the highest degree of confidence.
Thus, while it is extremely important that the health and welfare of the people
be protected, it is equally important to ascertain that such protection is
really achieved and that the health danger is  not traded for other equally
bad or worse problems.

     Intensive studies conducted in the past 3-4 years have resulted in an
abundance of suggestive evidence that in part  supported and in part refuted
the earlier understanding, but did not resolve all existing issues.  Thus, the
international scientific community is still divided on the issue of the justi-
fication of the 0.08-ppm ambient air quality standard for oxidant, one objection
arising from the questionable achievability of such a standard.  A newly revived
issue of major importance pertains to the relative roles of the hydrocarbon
and nitrogen oxide precursors in the urban and rural oxidant formation processes.
The viewpoint of the U.S. Environmental Protection Agency supporting maximum
control of the hydrocarbon and limited control of the N0x emissions is challenged
in several Conference papers.  More specific issues raised by the new evidence,
and debated in the Conference, are the achievability of the ambient oxidant
standard, the role of stratospheric ozone, the role of the natural ozone
precursors, the utility of current air quality simulation models, and the
significance of short- and long-range photochemical pollution transport.

     Aside from the debate on the above issues, the Conference will gather and
bring into focus the latest developments in the areas of physical-chemical
research methodology, biological effects of oxidants, and emission control
methods.  It was felt that inclusion of such widely diverse subject areas
would be essential for examining the balance,  rationality, and effectiveness
of the entire oxidant control effort.
                                     m

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     The Conference Is expected to be extremely valuable to the U.S. Environ-
mental Protection Agency in that it will  provide a forum for presenting the
Agency's evolving viewpoint on oxidant control  strategies, and for sounding out
scientific receptivity to this viewpoint.   The  Conference is of value also to
the international community of scientists  and government administrators in
that it will provide an opportunity for comparing the problems, experiences,
and control policies of one country with  those  of others.  Considering the now
established international range of pollution transport, and the implications
of oxidant-related control  upon international trade, such interaction among
countries is more than justified.   For these reasons the organization of the
Conference was undertaken by the U.S. Environmental  Protection Agency, with
the patronage of the Organization  for Economic  Cooperation and Development.
                                        B.  Dimitriades
                                     IV

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                                   CONTENTS


PREFACE 	    Hi

ACKNOWLEDGMENT 	    xv


SESSION 1  - ANALYTICAL METHODS FOR OXIDANTS AND 	      1
            PRECURSORS - I
            ChcuAman:  K.H. Becker

 1-1      METHODOLOGY FOR STANDARDIZATION OF ATMOSPHERIC 	      3
          OZONE MEASUREMENTS
          J.A. Hodgeson, E.E. Hughes, W.P.  Schmidt, and
          A.M. Bass

 1-2      ULTRAVIOLET PHOTOMETER FOR OZONE  CALIBRATION 	     13
          A.M. Bass, A.E. Ledford, Jr., and J.K. Whittaker

 1 -3      HYDROCARBON AND HALOCARBON MEASUREMENTS:  	     19
          SAMPLING AND ANALYSIS PROCEDURES
          R.B. Denyszyn, L.T. Hackworth, P.M.  Grohse, and
          D.E. Wagoner


SESSION 2  - ANALYTICAL METHODS FOR OXIDANTS AND 	     29
            PRECURSORS - II
            ChcUsunan:  K.H. Becker

 2-1      A NEW CHEMILUMINESCENT OLEFIN DETECTOR FOR 	     31
          AMBIENT AIR
          K.H. Becker, U. Schurath, and A.  Wiese

 2-2      GC-CHEMILUMINESCENCE METHOD FOR THE  ANALYSIS OF 	     41
          AMBIENT TERPENES
          R.L. Seila

 2-3      MEASUREMENTS OF SULFATE, INORGANIC GASEOUS NITRATE 	     51
          AND OTHER CONSTITUENTS IN THE ATMOSPHERE
          T. Okita

 2-4      A PORTABLE INSTRUMENT FOR THE CALIBRATION OF OZONE 	     59
          ANALYZERS BY OPTICAL ABSORPTION MEASUREMENTS
          K.H. Becker, A. Heindrichs, and U. Schurath

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 2-5      STATUS OF CALIBRATION METHODS FOR OZONE MONITORS	     67
          R.J. Paur, R.K. Stevens, and D.L. Flamm


SESSION 3 - SOURCES OF TROPOSPHERIC OZONE - I	     73
            ChjaAjma.ni  R.A. Rasmussen

 3-1      METEOROLOGICAL CONDITIONS CONDUCIVE TO HIGH LEVELS 	 75
          OF OZONE
          T.R. Karl and G.A. DeMarrais

 3-2      OZONE IN RURAL AND URBAN AREAS OF NEW YORK STATE - ...,	     89
          PART I
          P.Coffey, W. Stasiuk, and V. Mohnen

 3-3      OZONE MEASUREMENT AND METEOROLOGICAL ANALYSIS OF	     97
          TROPOPAUSE FOLDING
          V.A. Mohnen, A. Hogan, E. Danielsen, and P. Coffey

 3-4      METEOROLOGICAL FACTORS CONTROLLING PHOTOCHEMICAL 	    109
          POLLUTANTS IN SOUTHEASTERN NEW ENGLAND
          R.A. Dobbins, J.L. Nolan, J.P. Qkolowicz, and
          A.J. Gilbert
SESSION 4 - SOURCES OF TROPOSPHERIC OZONE - II .........................    119
                       R.A. Rasmussen
 4-1      AN ASSESSMENT OF THE CONTINENTAL LOWER TROPOSPHERIC ..........    121
          OZONE BUDGET
          R. Chatfield and R.A. Rasmussen

 4-2      URBAN KINETIC CHEMISTRY UNDER ALTERED SOURCE CONDITIONS .....    137
          L.A. Farrow, I.E. Graedel , and T.A. Weber

 4-4      THE EFFECT OF OZONE LAYERS ALOFT ON SURFACE '. . . . ...............    145
          CONCENTRATIONS
          T.N. Jerskey, T.B. Smith, and W.H. White


SESSION 5 - SOURCES OF TROPOSPHERIC OZONE - III .........................    155
            ChcuAman:  R.A. Rasmussen

 5-1      OZONE CONCENTRATIONS IN POWER PLANT PLUMES: .... ..............    157
          COMPARISON OF MODELS AND SAMPLING DATA
          T.W. Tesche, J.A. Ogren, and D.L. Blumenthal

 5-2      OZONE AND NITROGEN OXIDES IN POWER PLANT PLUMES .............    173
          D. Hegg, P.V. Hobbs, L. Radke, and H. Harrison

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 5-3      THE ANALYSIS OF GROUND-LEVEL OZONE DATA FROM 	    185
          NEW JERSEY, NEW YORK, CONNECTICUT, AND MASSACHUSETTS:
          DATA QUALITY ASSESSMENT AND TEMPORAL AND
          GEOGRAPHICAL PROPERTIES
          W.S. Cleveland, B. Kleiner, J.E. McRae, and R.E. Pasceri

 5-4      CHEMICAL AND METEOROLOGICAL ANALYSIS OF THE MESOSCALE 	    197
          VARIABILITY OF OZONE CONCENTRATIONS OVER A SIX-DAY
          PERIOD
          W.D. Bach, Jr., J.E. Sickles, II, R. Denyszyn, and
          1W.C. Eaton

 5-5      OZONE AND HYDROCARBON MEASUREMENTS IN RECENT OXIDANT 	    211
          TRANSPORT STUDIES
          W.A. Lonneman
SESSION 6 - OZONE/OXIDANT TRANSPORT - I 	    225
            Chairman:  A.P. Altshuller

 6-1      TRANSPORT OF OZONE BY UPPER-LEVEL LAND BREEZE - AN 	    227
          EXAMPLE OF A CITY'S POLLUTED WAKE UPWIND FROM ITS CENTER
          E.K. Kauper and B.L. Niemann

 6-2      OZONE FORMATION IN THE ST. LOUIS PLUME 	    237
          W.H. White, D.L. Blumenthal, J.A. Anderson, R.B. Husar,
          and W.E. Wilson, Jr.

 6-3      LONG RANGE AIRBORNE MEASUREMENTS OF OZONE OFF THE 	    249
          COAST OF THE NORTHEASTERN UNITED STATES
          G.W. Siple, C.K. Fitzsimmons, K.F. Zeller, and
          R.B. Evans

 6-4      AIRBORNE MEASUREMENTS OF PRIMARY AND SECONDARY 	    259
          POLLUTANT CONCENTRATIONS IN THE ST. LOUIS URBAN PLUME
          N.E. Hester, R.B. Evans, F.G. Johnson, and
          E.L. Martinez

 6-5      OZONE IN HAZY AIR MASSES 	    275
          R.B. Husar, D.E. Patterson, C.C. Paley and
          N.V. Gillani
SESSION 7 - OZONE/OXIDANT TRANSPORT - II 	    283
            Ckcuxman:  A.P. Altshuller

 7-1      THE TRANSPORT OF PHOTOCHEMICAL SMOG ACROSS THE 	    285
          SYDNEY BASIN
          R. Hyde and G.S. Hawke

 7-2      OXIDANT LEVELS IN ALBERTA AIRSHEDS 	    299
          H.S. Sandhu

                                      vii

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 7-3      AN INVESTIGATION OF LONG-RANGE TRANSPORT OF	    307
          OZONE ACROSS THE MIDWESTERN AND EASTERN
          UNITED STATES
          G.T. Wolff, P.J. Lioy, G.D. Wright, R.E. Meyers,
          and R.T. Cederwall

 7-4      OXIDANT AND PRECURSOR TRANSPORT SIMULATION IN	    319
          THE RESEARCH TRIANGLE INSTITUTE SMOG CHAMBERS
          J.E. Sickles, II, L.A. Ripperton, and W.C. Eaton

 7-5      OZONE EPISODES ON THE SWEDISH WEST COAST 	    329
          P. Grennfelt
SESSION 8 - IMPACT OF STRATOSPHERIC OZONE 	    339
            Ckcusunan:  R. Guicherit

 8-1      OZONE OBSERVATIONS IN AND AROUND A MIDWESTERN 	    341
          METROPOLITAN AREA.
          G. Huffman, G. Haering, R. Bourke, P. Cook, and M. Sillars

 8-2      A "TEXAS SIZE" OZONE EPISODE TRACKED TO ITS SOURCE	    353
          J.W.  Hathorn, III and H.M. Walker

 8-3      APPLICATION OF 1960's OZONE SOUNDING INFORMATION 	    381
          TO 1970's SURFACE OZONE STUDIES
          P.R.  Sticksel

 8-4      THE ROLE OF STRATOSPHERIC IMPORT ON TROPOSPHERIC 	    393
          OZONE CONCENTRATIONS
          E.R.  Reiter
SESSION 9 - THEORIES ON RURAL OZONE/OXIDATES ..........................    411
                       B.  Dimitn'ades
 9-1      RESEARCH TRIANGLE INSTITUTE STUDIES OF HIGH OZONE ...........    413
          CONCENTRATIONS IN NONURBAN AREAS
          L.A. Ripperton, J.J.B. Worth, F.M. Vukovich,
          and C.E. Decker

 9-2      IMPORTANT FACTORS AFFECTING RURAL OZONE CONCENTRATION .......    425
          F.L. Ludwig, W.B. Johnson, R.E.  Ruff, and
          H.B. Singh

 9-3      A MECHANISM ACCOUNTING FOR THE PRODUCTION OF OZONE IN .......    439
          RURAL POLLUTED ATMOSPHERES
          M. Antell

 9-4      NET OZONE FORMATION IN RURAL ATMOSPHERES ....................    451
          T.Y. Chang and B. Weinstock
                                     vm

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 9-5      THE KINETIC OZONE PHOTOCHEMISTRY OF NATURAL .................    467
          AND PERTURBED NONURBAN TROPOSPHERES
          T.E. Graedel and D.L. Allara


SESSION 10 - PHYSIOLOGICAL EFFECTS OF OXIDANTS - I ....................    475
                        J. Knelson
10-1      ON THE RELATIONSHIP OF SUBJECTIVE SYMPTOMS TO ...............    477
          PHOTOCHEMICAL OXIDANTS
          I. Mizoguchi, K. Makino, S. Kudou and R. Mikami

10-2      EFFECTS OF OZONE PLUS MODERATE EXERCISE ON PULMONARY ........    495
          FUNCTION IN HEALTHY YOUNG MEN
          B. Ketcham, S. Lassiter, E. Haak, and J.H. Knelson

10-3      EFFECTS OF OZONE AND NITROGEN DIOXIDE EXPOSURE OF ...........    505
          RABBITS ON THE BINDING OF AUTOLOGOUS RED CELLS TO
          ALVEOLAR MACROPHAGES
          J.G. Hadley, D.E. Gardner, D.L. Coffin, and D.B. Menzel

10-4      RELATIONSHIPS BETWEEN NITROGEN DIOXIDE CONCENTRATION, .......    513
          TIME, AND LEVEL OF EFFECT USING AN ANIMAL INFECTIVITY
          MODEL
          D.E. Gardner, F.J. Miller, E.J. Blommer, and
          D.L. Coffin

10-5      DEVELOPMENT OF OZONE TOLERANCE IN MAN .......................    527
          M. Hazucha, C. Parent, and D.V. Bates
SESSION 11 - PHYSIOLOGICAL EFFECTS OF OXIDANTS - II 	    543
             Ckalfiman:  J. Knelson

11-1      TOXIC INHALATION OF NITROGEN DIOXIDE IN CANINES 	    545
          T.L.  Guidotti and A.A.  Liebow

11-2      THE EFFECT OF OZONE ON THE VISUAL EVOKED POTENTIAL 	    555
          OF THE RAT SUPERIOR COLLICULUS AND VISUAL CORTEX
          B.W.  Berney, R.S. Dyer, and Z. Annau

11-3      HEALTH EFFECTS OF SHORT-TERM EXPOSURES TO N02-03 	    565
          MIXTURES
          E. Ehrlich, J.C. Findlay, J.D. Fenters, and
          D.E.  Gardner

11-4      BIOCHEMICAL INDICES OF NITROGEN DIOXIDE INTOXICATION 	    577
          OF GUINEA PIGS FOLLOWING LOW LEVEL-LONG TERM EXPOSURE
          B. Menzel, M.B. Abou-Donia, C.R. Roe, R. Ehrlich,
          D.E.  Gardner, and D.L.  Coffin
                                      IX

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11-5      BENEFIT EFFECTIVE OXIDANT CONTROL 	    589
          R.A. Bradley, M. Dole, Jr., W. Schink, and S. Storelli


SESSION 12 - EFFECTS OF OXIDANTS ON VEGETATION - I	    599
             Chairman:  W.W. Heck

12-1      OZONE INDUCED ALTERATIONS IN PLANT GROWTH AND 	    601
          METABOLISM
          D.T. Tingey

12-2      OXIDANT LEVELS ON REMOTE MOUNTAINOUS AREAS OF 	    611
          SOUTHWESTERN VIRGINIA AND THEIR EFFECTS ON
          NATIVE WHITE PINE (PINUS STROBUS L.)
          E.M. Hayes, J.M. Skelly, and C.F. Croghan

12-3      THE EFFECTS OF OZONE ON PLANT-PARASIT1C NEMOTODES 	    621
          AND CERTAIN PLANT MICROORGANISM INTERACTIONS
          D.E. Weber
SESSION 13 - EFFECTS OF OXIDANTS ON VEGETATION - II 	    633
             Chairman:  W.W. Heck

13-1      GROWTH RESPONSE OF CONIFER SEEDLINGS TO LOW OZONE 	    635
          CONCENTRATIONS
          R.G. Wilhour and G.E. Neely

13-2      MACROSCOPIC RESPONSE OF THREE PLANT "SPECIES" TO 	    647
          OZONE, PAN, OR OZONE + PAN
          D.D. Davis and R.J.  Kohut

13-3      RELATIVE SENSITIVITY OF EIGHTEEN HYBRID COMBINATIONS 	    655
          OF PINUS TAEDA L. TO OZONE
          L.W. Kress and J.M.  Skelly

13-4      EFFECTS OF OZONE AND SULFUR DIOXIDE SINGLY AND IN	    663
          COMBINATION ON YIELD, QUALITY, AND N-FIXATION OF
          ALFALFA
          G.E. Neely, D.T. Tingey and R.G. Wilhour


SESSION 14 - REACTIVITY AND ITS USE IN OXIDANT-RELATED CONTROL	    675
             Chairman:  J.G. Calvert

14-1      MULTIDAY IRRADIATION OF NOX ORGANIC MIXTURES 	    677
          W.A. Glasson and P.H. Wendschuh

14-2      HYDROCARBON REACTIVITY AND THE ROLE OF HYDROCARBONS	    687
          OXIDES OF NITROGEN AND AGED SMOG IN THE PRODUCTION
          OF PHOTOCHEMICAL OXIDANTS
          J.N. Pitts, A.M. Winer, G.J. Doyle, K.R. Darnall  and A.C. Lloyd

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14-3      APPLICATION OF REACTIVITY CRITERIA IN OXIDANT-	     705
          RELATED EMISSION CONTROL IN THE USA
          B. Dimitriades and S.B. Joshi

14-4      PHOTOCHEMICAL REACTIVITY CLASSIFICATION OF 	     713
          HYDROCARBONS AND OTHER ORGANIC COMPOUNDS
          F.F. Farley


SESSION 15 - ATMOSPHERIC CHEMISTRY AND PHYSICS 	     727
             Chairman:  J.G. Calvert

15-1      DECOMPOSITION OF CHLORINATED HYDROCARBONS UNDER 	     729
          SIMULATED ATMOSPHERIC CONDITIONS
          F. Korte and H. Parlar
 r
15-2      PHOTOOXIDATION OF THE TOLUENE-N02-02-N2 SYSTEM IN A 	     737
          SMALL SMOG CHAMBER
          H. Akimoto, M. Hoshino, G. Inoue, M.  Okuda , and
          N. Washida

15-3      THE CHEMISTRY OF NATURALLY EMITTED HYDROCARBONS 	     745
          B.W. Gay, Jr. and R.R. Arnts

15-4      MEASUREMENT OF PHOTONS INVOLVED IN PHOTOCHEMICAL 	     753
          OXIDANT FORMATION
          D.H. Stedman, R.B. Harvey,  and  R.R. Dickerson

15-5      ACTIVE SOLAR FLUX AND PHOTOLYTIC RATE IN THE 	     763
          TROPOSPHERE
          J.T. Peterson, K.L. Demerjian, and K.L. Schere


SESSION 16 - MATHEMATICAL MODELS OF OZONE/OXIDANT AIR QUALITY - I ....     775
             Chairman:  K. Deme rj i a n

16-1      PHOTOCHEMICAL AIR QUALITY SIMULATION  MODELLING: 	     777
          CURRENT STATUS AND FUTURE PROSPECTS
          K.L. Demerjian

16-2      THE SYSTEMS APPLICATIONS, INCORPORATED URBAN AIRSHED 	     795
          MODEL:  AN OVERVIEW OF RECENT DEVELOPMENTAL WORK
          S.D. Reynolds


SESSION 17 - MATHEMATICAL MODELS OF OZONE/OXIDANT AIR QUALITY - II ...     803
             Chairman:  K. Demerjian

17-1      A SURVEY OF APPLICATIONS OF PHOTOCHEMICAL MODELS 	     805
          J.E. Summerhays
                                      XI

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17-2      TESTS OF THE DIFKIN PHOTOCHEMICAL DIFFUSION MODEL 	     817
          USING LOS ANGELES REACTIVE POLLUTANT PROGRAM DATA
          G.H. Taylor and A.Q. Eschenroeder

17-3      DEVELOPMENT OF A MARKET CHAIN MODEL FOR PHOTOCHEMICAL 	     827
          OXIDANT PREDICTION
          J.R. Martinez

17-4      A PRELIMINARY INVESTIGATION OF THE EFFECTIVENESS OF AIR ....     837
          POLLUTION EMERGENCY PLANS
          W.F. Dabberdt and H.B.  Singh


SESSION 18 - OXIDANT-PRECURSOR RELATIONSHIPS AND THEIR INTERPRETATION .     849
             IN TERMS OF OPTIMUM STRATEGY FOR OXIDANT CONTROL - I
             ChcuAman:  J.N. Pitts

18-1      A "J" RELATIONSHIP FOR TEXAS 	     851
          H.M. Walker

18-2      AN ALTERNATIVE TO THE APPENDIX-J METHOD 	     871
          FOR CALCULATING OXIDANT- AND N02- RELATED CONTROL
          REQUIREMENTS
          B. Dimitriades

18-3      COMBINED USE OF MODELING TECHNIQUES AND SMOG CHAMBER 	     881
          DATA TO DERIVE OZONE-PRECURSOR RELATIONSHIPS
          M.C. Dodge

18-4      OUTDOOR SMOG CHAMBER STUDIES:  EFFECT OF DIURNAL 	     891
          LIGHT DILUTION AND CONTINUOUS EMISSION ON OXIDANT
          PRECURSOR RELATIONSHIPS
          H.E. Jeffries, R. Kamens, D.L.  Fox, and B.  Dimitriades

18-5      USE OF TRAJECTORY ANALYSIS FOR DETERMINING EMPIRICAL 	     903
          RELATIONSHIPS AMONG AMBIENT OZONE LEVELS AND METEOROLOGICAL
          AND EMISSION VARIABLES
          E.L. Meyer, Jr., W.D. Freas, III, J.E. Summerhays, and
          P.L. Youngblood


SESSION 19 - OXIDANT-PRECURSOR RELATIONSHIPS AND THEIR 	     915
             INTERPRETATION IN TERMS OF OPTIMUM STRATEGY FOR
             OXIDANT CONTROL - II
             CficuAman:  E.L. Meyer

19-1      REPORT ON OXIDANTS AND THEIR PRECURSORS IN CANADA 	     917
          L. Shenfeld

19-2      PRECURSOR CONCENTRATION AND OXIDANT FORMATION IN SYDNEY 	     927
          G.H. Allen, K. Post, B.S. Haynes, and R.W.  Bilger

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19-3      SMOG POTENTIAL OF AMBIENT AIR, SAMPLED AT DELFT ............     943
          NETHERLANDS:  THE EFFECT OF INCREASING NOX CONCENTRATION
          J. van Ham, and H. Nieboer

19-4      SUMMARY:  A PRELIMINARY INVESTIGATION OF EXPECTED ..........     955
          VISIBILITY IMPROVEMENTS IN THE LOS ANGELES BASIN FROM
          OXIDANT PRECURSOR GASES AND PARTICULATE EMISSION CONTROLS
          C.S. Burton, T.N. Jerskey, and S.D. Reynolds


SESSION 20 - CONTROL OF OXIDANT PRECURSOR EMISSIONS - I ..............     969
                        R.W. Bilger
20-1      TRAFFIC MANAGEMENT AS A MEANS OF OXIDANT PRECURSOR  .........     971
          CONTROL FROM LOW-SPEED SATURATED TRAFFIC
          R.B. Hamilton and H.C. Watson

20-3      CONTROL OF VEHICLE REFUELING EMISSIONS .....................     989
          A.M. Hochhauser and L.S. Bernstein
SESSION 21 - CONTROL OF OXIDANT PRECURSOR EMISSIONS - II 	    1001
             Chainman:  R.W. Bilger

21-1      NOX CONTROL TECHNOLOGY FOR STATIONARY SOURCES 	    1003
          G.B. Martin and J.S. Bowen

21-2      EMISSION ESTIMATES OF N02 AND ORGANIC COMPOUNDS FROM 	    1015
          COAL-FIRED BED COMBUSTION
          P.E. Fennelly

21-3      EMISSIONS ASSESSMENT OF THE CHEMICALLY ACTIVE FLUID 	    1025
          BED (CAFB) PROCESS
          A.S. Werner, R.M. Bradway, D.F. Durocher, S.L. Rakes,
          and R.M. Statnick

21-4      NOX CONTROL BY ABSORPTION 	    1035
          G. Sakash

21-5      DEVELOPMENT OF A LOW EMISSIONS PROCESS FOR ETHYLENE 	    1039
          DICHLORIDE PRODUCTION
          W.S. Amato, B. Bandyopadhyay, B.E. Kurtz, and R.H. Fitch


SESSION 22 - AIR QUALITY AND EMISSION TRENDS 	    1051
             Chcusuman:  R.E. Neligan

22-1      THE IMPACT OF EMISSIONS CONTROL TECHNOLOGY ON 	    1053
          PASSENGER CAR HYDROCARBON EMISSION RATES AND PATTERNS
          F. Black
                                     xi

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22-2      CONTROL OF OXIDANTS IN SYDNEY	    1069
          D. Iverach and M.G. Mowle

22-3      OXIDANT AND PRECURSOR TRENDS IN THE METROPOLITAN .,	    1077
          LOS ANGELES REGION
          J. Trijonis, T. Peng, G. McRae, and L. Lees

22-4      COMPARISON OF PAST AND PROJECTED TRENDS IN OXIDANT 	    1095
          CONCENTRATIONS AND HYDROCARBON EMISSIONS
          R.M. Angus, E.W. Finke, and J.H. Wilson

22-5      TRENDS IN AMBIENT LEVELS OF OXIDANT AND THEIR POSSIBLE 	    1103
          UNDERLYING EXPLANATIONS
          E.L. Martinez, N.C. Possiel, E.L. Meyer, L.G. Wayne,
          K.W. Wilson, and C.L. Boyd


SESSION 23 - ON THE OZONE/OXIDANT CONTROL STRATEGY IN U.S	    1113
             CkcuJunan:  A.B. Bromley

23-1      TRENDS IN PHOTOCHEMICAL OXIDANT CONTROL STRATEGY	    1115
          J. Padgett

23-2      PROBLEMS WITH CONVERTING STATE-OF-THE-ART PHOTOCHEMISTRY ...    1123
          TO STATE LEVEL CONTROL STRATEGIES
          W. Bonta and J. Paisie

23-3      OXIDANT CONTROL UNDER SECTION 110 OF THE CLEAN AIR ACT 	    1135
          J.L. Pearson

23-4      OXIDANT CONTROL STRATEGY:  RECENT DEVELOPMENTS	    1143
          B. Dimitriades

23-5      CONTROL REGULATIONS FOR STATIONARY SOURCES OF HYDROCARBONS .    1155
          IN THE UNITED STATES
          R.T. Walsh

          PREPARED COMMENTS ON JAPANESE PHOTOCHEMICAL AIR QUALITY ....    1167
          STANDARDS AND CONTROL STRATEGIES
          Professor R. Kiyoura
                                     xiv

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                                ACKNOWLEDGMENT

     The assistance of the Conference Program Committee members in organizing
the technical program of the Conference is gratefully acknowledged.   Program
Committee members were:   Dr. A.P.  Altshuller, EPA, USA (Chairman); Dr.  K.H.
Becker, U.  Bonn, Germany; Dr.  R.W.  Bilger, U. Sydney, Australia;  Dr.  J.C.
Calvert, Ohio State U.,  USA; Dr.  B.  Dimitriades,  EPA, USA;  Mr.  M.  Feldstein,
San Francisco, Calif., USA; Mr.  D.R.  Goodwin, EPA, USA; Dr.  R.  Guicherit,
IGTNO, Netherlands; Dr.  A.B. Bromley, OECD, France; Dr. M.  Hashimoto, Environ-
ment Agency, Japan; Dr.  J. Knelson,  EPA, USA; Mr.  R.E.  Neligan, EPA,  USA;
Mr. J. Padgett, EPA, USA; Dr.  J.M.  Pitts, U.  California, USA;  Dr.  R.A.  Rasmussen,
Washington  State U., USA; and  Mr.  J.O.  Smith, EPA, USA.

     Conference arrangements were  made  by the Triangle  Universities  Consortium
on Air Pollution, under  the direction of Dr.  Laurence Kornreich,  through
Research Grant #800916-0451.
                                      xv

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                     SESSION 1
ANALYTICAL METHODS FOR OXIDANTS AND PRECURSORS - I
                         K.H. Becker
                University of Bonn

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                                                                              1-1
                      METHODOLOGY FOR STANDARDIZATION OF
                        ATMOSPHERIC OZONE  MEASUREMENTS

         J.  A.  Hodgeson, E. E. Hughes, W.  P.  Schmidt, and A.  M. Bass*


ABSTRACT

      ?neJLAjminany i.nto.n.c.ompaAi^on& have, be.e.n  made, among 4eue/ut£ te.chyu.qau
-the. cati.bnati.on o^ atmoApheAi.c ozone, monitor.   The^e pfioce.duAeA -include, the.  1
peAce.nt  neuJAal bu^eAe-d potai>i>iwn todi.de. method;  a modification o& thiA
method e.mptoyi.ng 0.1  motan. bofii.c aci.d fiatheA than the. ph.oAph.ate bu^eA; a  3-
mzteA dou.bie.-be.am u£tAavi.olet photome^eA; and gat> pha&e. tittettion.  The. potai>-
.6.a(.i7i  i.odi.de. tie.aQe.nt with bosiic add gave  a mo tie,  Atabie. coiofi de.ve.l.opme,nt and
much  cJLo&eA agn.e.e.mant w+tk the. ultAavtotct me,ai>uA.m than that obtaine.d
wtth  the. nuWwJL bu^eAe,d x.e.age.nt.  Ozone, catibtiation data with the. 3-mzte.ti
photomete.1  agreed within 1 and 2 poAcent  with gad phaAe. tittLOtion and vJLtxa.-
vi-oLoJi photometAic ozone. me.ai>uAe.me.nt{> x.e.&pe.ctiveJ.y made, at the. EnviAonme.ntat
Px.ote.ctA.on  Agency faacltity in Re-ieaAeh Triangle,  Vatik,  Mo-^th Canotina.


                                 INTRODUCTION

      Atmospheric ozone (03) monitors have normally been calibrated against
manual idometric techniques.   The Environmental  Protection Agency (EPA) refer-
ence  calibration procedure employs a 1 percent neutral buffered potassium
iodide (NBK1)  reagent (1).  The accuracy  and reproducibility of iodmetric
calibration procedures have been the subject of  controversy for several years.
In a  recent example which received considerable  publicity, 03 measurements in
the city of Los  Angeles were discovered to be consistently biased 30 percent
lower than  measurements in surrounding counties.   Laboratory studies conclu-
sively demonstrated that the cause of the bias was the use of two different
iodometric  calibration procedures (2).  In data  obtained earlier this year and
not given here,  simultaneous measurements were made by NBKI  with two sets of
samplers off a common manifold.   One set  of  results obtained indicated higher
levels than the  other by 30 percent.  By  interchanging reagents and components
the difference appeared to be attributable to an impinger effect.

      Current activities of the National Bureau of Standards  (NBS) have focused
on the establishment  of definitive methodologies for the accurate measurement
of 03 in the subpart  per million range for the purpose of calibrating constant
03 generators.   Analytical techniques currently  under study are the EPA refer-
*National Bureau of Standards,  Washington, D.C.

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ence method which is a modified iodometric procedure suggested by Flamm (3).
The method employs boric acid (BA) rather than phosphate buffer to control  pH.
It measures 03 by ultraviolet (UV) absorption with a 3-meter double-beam
photometer (4), and by gas phase titration (GPT) of 03 with known concentra-
tions of nitric oxide (NO) (5).   In this paper preliminary results of compari-
sons of these various 03 calibration techniques are presented.


                                EXPERIMENTAL

     Some exceptions were employed to the iodometric technique as described.
Midget impingers were employed rather than the illustrated Mae West-type
bubblers.  We employed a calibrated wet test meter downstream of the impingers
to determine the integrated volume of air sampled.  This approach gives more
accurate and reproducible measurements of sample volume and does not require
fine flow control devices.  Finally, we measured the absorbance at a fixed
time of 5 minutes after ending sample collection, because of a slow color
development observed in the NBKI reagent.

     The wet test meter was calibrated gravimetrically by metering a fixed
volume of air from a compressed air cylinder and measuring the weight loss of
the cylinder with a Voland Precision Balance, Model 1115-DN.  As an additional
check during one of the experiments, the wet test meter measurement was com-
pared with the volume measured by means of a soap bubble meter connected to
the inlet of the sample probe.  These measurements agreed within 1 percent.

     The spectrophotometer employed was a Beckman Model DU with a Guilford
Model 222 digital absorbance readout attachment.  Checks on the photometric
accuracy have been made with NBS optical glass filters which have certified
absorbance values at specified wavelengths,   This instrument has been periodic-
ally calibrated over several years with standard iodine solutions and has
remained constant with an average calibration factor of 9.812 microliters of
03 per absorbance unit.   This value corresponds to an absorption coefficient
at 352 nonometers (nm) for molecular iodine of 24,930 liters/mole-cm (log
base 10).  It compares favorably with a value of 24,890 j^ 100 reported in
another study (6).

     The 03 source was a variable photolytic generator (7).  The clean air
source was an Aadco Model 737 pure air generator.  The reagents employed for
the NBKI procedure were ACS reagent grade granular KI, potassium dihydrogen
phosphate (KH2P04) certified ACS grade, and anhydrous disodium hydrogen phos-
phate (Na2HP04) analytical reagent.  The boric acid modified reagent also con-
tained 1 percent KI of the same grade and 0.1 molar boric acid ACS-CP grade.
The spectrophotometer calibration curve showed no evidence of a measurable
iodine demand for either of the reagents.

     The primary UV photometer was a 3-meter double-beam instrument specific-
ally constructed at NBS for the purpose of 03 calibration in the subparts per
million (ppm) range (4).  The other UV system was a commercially available
Dasibi Monitor Model 1003-AH.  In work at NBS this instrument has been used
primarily as a secondary transfer standard.   The iodometric measurements and

-------
 the  UV photometric measurements are currently measured in different labora-
 tories at NBS.  The  Dasibi instrument was used as a transfer standard to re-
 late 03 measurements obtained in different laboratories.  The GPT apparatus
 has  been described previously (5).
                           RESULTS AND DISCUSSION

EVALUATION OF THE BORIC ACID -POTASSIUM IODIDE REAGENT

     There has been considerable lack of interlaboratory reproducibility in
application of the NBKI technique (8, 9).  Paur (10) has summarized a number
of recent studies in which the relationship of measurements by the NBKI
technique was compared to measurements of 03 by UV photometry or by GPT.  The
ratio of measurements by NBKI to 03 measurements by either of these techniques
has varied over a range from 1.0 to 1.2.   One particular problem with this
iodometric technique is the slow color development observed after the 03 is
collected.  Variable results are thus obtained if the time of the absorbance
measurement is not controlled.

     Flamm (3) has recently performed an evaluation of iodometric techniques.
He used different buffering systems and observed an absence of the slow color
development either in the absence of a buffering agent or with the addition of
0.1 molar boric acid.  The addition of 0.1 molar boric acid stabilizes the pH
of the solution at approximately 5.3.  With the boric acid-KI (BAKI) reagent,
Flamm observed 03 measurements which were 20% lower than those obtained with a
NBKI reagent.  Measurements with boric acid reagent were in essential agreement
with a Dasibi 03 photometer, modified such that 03 measurements with GPT
measurements are obtained (10).

     We made a reagent as described by Flamm and studied the variation in ab-
sorbance after sample collection for both this reagent and the neutral NBKI
reagent.   The results of this study are shown in Figure 1.   An 03 sample of
0.35 ppm was collected for 10 minutes.  The initial time in Figure 1 corres-
ponds to the end of the sample collection.  The color obtained with the BAKI
reagent is indeed stable and the initial  absorbance at 4 minutes is approxi-
mately 22 percent lower than that obtained in the NBKI reagent.   The slow
color development observed with the NBKI  is apparently a result of a secondary
reaction which slowly releases iodine.

     Based on the results shown in Figure 1, 03 measurements with the NBKI
reagent are approximately 22 percent higher than with the boric acid modifica-
tion, assuming that the absorption coefficient of iodine is the same in both
reagents.  The absorption coefficients of iodine in both reagents were meas-
ured, and the values obtained agreed within 1 percent.  We observed a slow
color development in the unexposed BAKI reagent (0.003 to 0.27 in a few days)
when the absorbance was measured against distilled water as a reference.
Therefore, in all our analyses the absorbance measurement was made against
unexposed reagent as a blank.

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      OQ

      O
      CO
      OQ
         .155
         .150
         .145
         .140
.135
          .130
          .125
          .120
                                      l__ J	
   [03]  =  0.35 ppm

O  NEUTRAL BUFFERED  Kl  REAGENT

x  Kl REAGENT WITH 0.1 M
   BORIC ACID
                 XXXX X

                	I
                     10
                    20
              30
            t, min
40
50
60
         Figure 1.  Absorbance versus time  after sample collection.

COMPARATIVE OZONE  MEASUREMENTS

     We want to emphasize in the beginning that the  comparative data  obtained
thus  far  are limited  in number and that some of the  absolute results  reported
here  are  preliminary  in nature.   However, in spite  of  the preliminary nature
of these  data, we  present what has been obtained so  far  and feel that some
interesting conclusions can be drawn  therefrom.

-------
     The method for making the comparative measurements between different lab-
oratories was to use the Dasibi instrument as a transfer standard.  In this
role the instrument has performed remarkably well in that it has maintained
essentially the same calibration with respect to iodmetric measurements in the
same laboratory over the past two years.

     In the first comparisons given below, the Dasibi instrument was calibrated
with both KI reagents.  In these comparative data the Dasibi meter readings
were converted to UV photometric 03 concentrations by Equation 1.  The physi-
cal path length (71 cm) of the Dasibi is assumed to be the same as the otpical
path length.  Also, the gas temperature inside the optical cell is assumed to
be the same as the measured temperature adjacent to the cell in the instrument.
                     6
                   10 P T
where:   k = 308.6 crrf  atirf  (log base e), the 253.7 nm 03 absorption
             coefficient at 273 K and 1 atmosphere.

         L = 71 cm, the physical path length

     P0J0 - 1 atm and 273 K

        I  = Dasibi Span Factor

        Al = Dasibi Meter Reading

By substituting the above values, Equation 2 reduces to
[03]
             DAS
                        -  Al)
                                                                       (2)
where T is the temperature inside the optical cell in kelvins and P is the
barometric pressure in mm mercury (Hg).  For all the data in Table 1, the
value used for T (313 K) was approximately the average temperature of the
optical cells with the instrument in continuous operation.

     The comparative data obtained are given in Table 1.   The two idometric
reagents were used sequentially at the same 03 concentration and in the same
sampling apparatus.

     Ozone concentrations measured by the NBKI technique, [03]NBKI> and 03
concentrations measured by the boric acid version, [03]g/\Ki, were both fitted
to the 03 Dasibi measurements by linear regression analysis.
[03]NBKI = (1.35+0.01) [03]DAS - (0.0015+0.003)

           (1.10+0.01) [03]DAS + (0.001  +0.003)
[031BAKI
                                                                       (3)

                                                                       (4)
An excellent fit was obtained in both cases with no observable deviation from
linearity over the range of concentrations measured.  The zero intercepts are
negligible.   The relation between the two iodometric techniques is:
                                      7

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            TABLE 1.   CALIBRATION OF NBS-DASIBI  BY  IODOMETRIC METHODS

Date
8-19-76


8-20-76



8-28-76





8-31-76






L ^ DAS, ppm
.289
.1725
.4955
.094
.233
.378
.130
.256
.3415
.343
.462
.201
.136
.476
.043
.119
.220
.323
.413
.412
Neutral Buffered
Kl , ppm
.383
.227
.668
.128
.313
.513
.176
.345
.458
	
	
	
	
	
	
	
	



Boric Acid
KI, ppm
.308
.181
.540
.108
.263
.422
—
.285
.380
.379
.507
.225
.153
.520
.046
.132
.241
.354
.462
.461

         [03]NBKI = (1.23 ±0.03) [03]BAKI                             (5)

Flamm (3) observed a value of 1.20 for the ratio of NB to BA node-metric
measurements.

     On days intervening with those on which iodometric measurements were
made, the Dasibi was calibrated against the NBS 3-meter double beam photometer,
Multiple analyses were made at several concentrations and the averaged data
are presented in Table 2.


                                      8

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                 TABLE  2.   CALIBRATION  OF  DASIBI  WITH  NBS
                            3-METER  PHOTOMETER

[03] DAS, ppm
.02531
.0989
.1695
.2999
.3578
.5192
.5193
.5238
1.0010
1.4813
[0,] UV, ppm
.02157
.1001
.1733
.3006
.3688
.5265
.5245
.5372
1.0275
1.5045

     A  linear regression analysis of these data yielded,

          [03]uv =  (1.020+0.004) C03]DAS -  (0.001 +0.002)             (6)

This fit  also showed good linearity with a negligible intercept.  By combining
Equation  6 with the previous results, the following relations were obtained:

          [03]NBKI  = (1.32+0.02) [03]uv                                (7)

          [03]BAKI  = (1.08+0.02) [03]uv                          -      (8)

     In order to obtain additional comparative data, the NBS Dasibi instrument
was transported to EPA's Research Triangle Park facility.  Simultaneous 03
comparisons were made  at the EPA Environmental  Monitoring and Support Labora-
tory, where concurrent evaluations of the GPT method and a modified Dasibi
photometer (10)  were being performed.   The comparison  was made  on a single  date
(8/24/76) using a common 03  sampling manifold.   The 03 generator was  cali-
brated at several  fixed levels  by GPT,  and simultaneous  measurements  were made
at these same levels with  the NBS Dasibi and the modified EPA Dasibi  photom-
eter.   The data obtained are given in Table 3.

     The NBS Dasibi 03 readings in the first column were corrected to equi-
valent 03 measurements with  the NBS 3-meter photometer by Equation 6.   Analy-
sis of the data yielded

         [03]QpT,  EPA  = (1.01 + 0.02) [03]uv, NBS + (0.011  + 0.003)     (9)

         [03]uy, EPA = (0.98 +  0.01)  [03]uv, NBS + (0.003 + 0.001)     (10)

The agreement obtained on the whole was excellent among the three 03 measure-
ments, considering the limited time and data available during this one-day
comparison.

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                  TABLE 3.  OZONE COMPARATIVE MEASUREMENTS AT
                          EPA-RESEARCH TRIANGLE PARK
  [03]DAS, NBS,ppm              E03], NBS.ppm             IM. EPA,ppm
0.053
0.125
0.203
0.285
0.371
0.456
0.619
0.061
0.142
0.223
0.309
0.390
0.481
— — —
0.056
0.127
0.205
0.290
0.374
0.459
0.620

                           SUMMARY AND CONCLUSIONS

     The UV photometric measurements obtained at NBS agree within 1  and 2 per-
cent using GPT and UV photometric measurements respectively obtained at EPA-
Research Triangle Park.  This is in accord with results obtained in  other
works (6, 10, 11).  Additional comparative data will be obtained to  attempt to
reduce the small uncertainty remaining.

     The 1 percent KI solution with 0.1  molar BA gives a stable color develop-
ment.  Measurements with this reagent are in closer agreement with UV photo-
metric measurements than measurements obtained with the neutral phosphate
buffered system.  The BA iodometric measurements obtained here were  22 percent
lower than measurements by NBKI and 8 percent higher than 03 measurements
obtained with the NBS 3-meter photometer.

     We regard the absolute relations of either of the iodometric measurements
to the UV photometric measurements as preliminary at this point and  intend to
obtain more data before reaching final conclusions.  The iodometric  measure-
ments in relation to UV contradict to some degree other data which have been
obtained.  Flamm (3) and Paur (unpublished data) have observed closer agree-
ment between the boric acid iodometric measurements and UV photometry.  The
NBKI results obtained were 35 percent higher than UV^which is outside of the
1.0-1.2 ratio range observed in other studies (10).  An apparent impinger
effect in analyses obtained by the NBKI  procedure was noted in the introduc-
tory remarks.  The impinger set used to obtain the data above was the set
which apparently produced higher results.  Impinger effects have been reported
previously (9).   Whether the impinger design or materials in fact affects the
results, and whether an impinger effect applies to the BAKI reagent  are ques-
tions to be answered by additional studies.
                                      10

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                               ACKNOWLEDGEMENT

     The authors are particularly grateful  to Mike Beard of the Quality Assur-
ance Branch, Environmental  Monitoring and Support Laboratory,  EPA-Research
Triangle Park for the assistance he provided in the 03 comparisons  by ultra-
violet photometry and gas phase titration.


                                 DISCLAIMER

     Certain commercial equipment,  instruments, or materials are identified in
this paper in order to adequately specify the experimental  procedure.   In no
case does such identification imply recommendation or endorsement by the
National Bureau of Standards, nor does it imply that the material or equipment
identified is necessarily the best  available for the purpose.


                                 REFERENCES

    1.   Environmental Protection Agency, Federal Register^, No. 228,
         22384  (November 25, 1971 ).

    2.   "Comparison of Oxidant Calibration Procedures," Final Report
         of Ad Hoc Oxidant Measurement Committee, California Air
         Resources Board, Sancramento, CA., 3 February 1975.

    3.   Daniel Flamm, preliminary report to the Environmental
         Sciences Research Laboratory, Environmental Protection Agency,
         Research Triangle Park, N.C., August 1976.

    4.   A. M. Bass, A. E.  Ledford, Jr., and J. K. Whittaker, "Ultra-
         violet Photometer for Ozone Calibration," preprint for
         International Symposium on Photochemical Oxidant Pollution
         and Its Control, Raleigh,  N.C., 12-17 September 1976.

    5.   K. A. Rehme, B. E. Martin, and J.  A. Hodgeson, "Tentative Method
         for the Calibration of Nitric Oxide, Nitrogen Dioxide and Ozone
         Analyzers by Gas Phase Titration," EPA Report No.  R2-73-246, U. S.
         Environmental Protection Agency, Office of Research and Develop-
         ment, Washington,  D.C. 20460.

    6.   J. A. Hodgeson, C. B.  Bennett, H.  L. Kelly, and B. A. Mitchell,
         "Ozone Measurements by lodometry,  Ultraviolet Photometry and
         Gas-Phase Titration,"  publication preprint, submitted to
         Analytical Chemistry,  1976.

    7.   J. A. Hodgeson, R. K.  Stevens, and B. E. Martin, ISA Trans.
         11, 161 (1972).

    8.   J. B. Clements, "Summary Report:  Workshop on Ozone Measurements
         by the Potassium Iodide Method," EPA-650-4-75-007, U. S. Environ-
                                      11

-------
mental Protection Agency, Office of Research and Development,
Washington, D.C.  20460, February 1975.

H. C. McKee, R.  E.  Childers, and Van B.  Parr, "Collaborative Study
of Reference Method for Measurement of  Photochemical  Oxidants in
the Atmosphere (Ozone-Ethylene Chemiluminescent Method),  EPA-650/
4-75-016, U. S.  Environmental  Protection Agency, Office of Research
and Development,  Washington, D.C.  20460, February 1975.
                            12

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                                                                            1-2
                 ULTRAVIOLET  PHOTOMETER  FOR  OZONE  CALIBRATION

             A. M. Bass, A. E. Ledford,  Jr.,  and J.  K.  Whittaker*
ABSTRACT
     In order to provide, a ^acitcty  far photometric,  ozone  me.abu.re.me.nts,  me  have.
designed and constructed a do able.-beam photometer  fan  ozone.  concentration^  in
the range 0.025 - 1.0 ppm.  The. bampte path tength  in  tkL& instrument. U> app/tox-
ima.te.lij 300 cm.   The -instrument, measures changes -in  ozon.ize.d-a.iA bampte  tranb-
         oft mercury radiation at 253.7 nanometers where  the  pkoto-a.bbon.ptA.on
     -section o{, ozone. ha-s been welt determined.
     Radiation at wavelengths other than  253.7  nanometers  ^rom  the mercury tamp
Ls removed by passing the. Light through a narrow-band interference fitter.   The
tight is cottimot.ed and passed through a  beam sptitter whi.ch  directs  approxi-
mat.ety equat intensity beams through the  tivo celts.  Clean air  falows  through one
celt into the ozone generator and then the. ozonize.d  air  {^tows through the second
cett.  The tight beams are recombined on  the fiace  o^ a photo multiplier tube used
in the photon counting mode.  A rotating  chopper atlows  the two beams to  be.
detected se.quentAal.ty so tliat the transmissions o^ the two cetls  may  be directty


           indicate thai measurements may be made  at the 0.05 ppm te.veL with a
          ~j& }Q% or better.

                                 INTRODUCTION
     Tests
preci.si.on
     The oxidation of iodide to iodine by ozone  (03),  in  a  properly prepared
solution of potassium iodide (KI), is the basis  for  the  reference  method speci-
fied by the Environmental Protection Agency  (EPA)  for  the calibration  of atmos-
pheric monitors (1).  Recent comparative measurements  (2) of the specific
iodometric methods have raised serious doubts  as  to  the  accuracy and reproduci-
bility of iodometric calibration procedures.   The  report  of the  California Air
Resources Board recommended that oxidant analyzers in  California should be
calibrated by an ultraviolet (UV) photometric  method rather than by the ioda-
metric method (2).  In May 1975 this recommendation was  accepted for that
state's monitoring network.  At the present  time  the EPA  is considering two
candidate methods, gas phase titration (GPT) and  UV  photometry as  replacements
for the 1% neutral-buffered potassium iodide (NBKI)  procedure, the current
Federal Reference Method for calibration of  pollutant  monitors (1).

     In order to provide a facility at NBS for the measurement of  03 concentra-
tions, independently of GPT based on a nitric  oxide  (NO)  standard, an  ultra-
'"National Bureau of Standards, Washington, DC
                                      13

-------
violet photometer with the desired sensitivity for 03 measurements at ambient
concentrations was set up (3).  The desired performance for the photometer was
capability for measurement of 03 concentrations over the range 0.05 ^ 1.0 parts
per million (ppm) with an accuracy of approximately 0.005 ppm over the entire
range.

                                 EXPERIMENTAL

     The photometric measurement method is based on the application and the
validity of the Beer-Lambert Law:
          1=1  exp
                      -273 cPkl
                         ~TT~"
                        10 T
                                               (1)
where:
          c is given in ppm (parts per million by volume).
          k is 308.5 cnT^atnT1 (log base e), the ozone absorption coefficient (4)
               at 253.7 nm, 273 K, and 1 atmosphere.
          L is the path length, cm.
          P is the total  pressure, atm.
          T is the temperature of the cell,  °K.
          I/I  is the transmittance (Tr) of  the  sample.

     The design of the photometer is based principally on the accuracy require-
ment, 10% at 0.05 ppm.  The quantities k, L, P,  T appearing in the equation are
all known or can be measured to within 1 or  2 percent.  Thus the accuracy of the
concentration measurement is mainly determined by the accuracy of the trans-
mittance measurement.  The error in the transmittance measurement may be ex-
pressed as
          AC
           C
ATr
 Tr
                      1
                                                              (2)
It was estimated that the transmittance measurement could be made with a pre-

             of about .0005 by using photon counting.   For a concentration of
cision

0.05 ppm these conditions imply a transmittance of 0.995 which can be achieved
in an absorbing path of approximately 3 m.

     The design that was selected for the photometer is shown in Figure 1.  It
was decided that a double-beam arrangement would provide greater precision in
the measurement through elimination of the effect of variability of the UV
source.   The cells of the photometer are made of 1-1/2" diameter pyrex pipe;
teflon gaskets are used to make vacuum-tight seals for the fused silica windows.
The light from a low pressure mercury discharge lamp is passed through a narrow-
band interference filter in order to isolate the 253.7 nanometers (nm) emission
line.  The light is collimated by a fused silica lens and passed through a
partially-transmitting neutral density filter which serves as a beam splitter.
The two beams then pass through the two absorption cells.  Adjustable aperturei
stops limit the diameter of the beams to ensure that there are no reflections
from inner walls of the cells.  The light beams emerge from the cells and are
recombined on the face of a photomultiplier tube by another partially reflecting
filter.
                                     14

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                   STOP
                                 S A v P ' E CELL
           MIRROR
       Figure 1.  Double beam ultraviolet photometer for measurement of
                            ozone concentrations.

     The differential UV absorption method of photometry adopted for 03 con-
centration measurements requires the precise and accurate measurement of two
light intensities—one for each cell.  Photon counting techniques for these
intensity measurements using a UV sensitive tube with excellent single photo-
electron resolution were used.  If such a tube is cooled to about -20°C, the
dark count rate is a few counts per second.  Utilizing high-speed electronics
and very precise timing methods it is possible to obtain accurate and statis-
tically well-characterized pulse counts corresponding to incident light in-
tensity on the photomultiplier.  This method may be preferable to analog tech-
niques which are more subject to instability, drift, and uncertain amounts of
non-linearity.

     The mercury vapor lamp is energized either by a 10 KHz square-wave power
oscillator or by a 60 Hz commercial power supply.   Light passing through each
sample cell is alternately allowed to fall on the photomultiplier by means of a
light chopper.  A chopper blade with a single hole is driven by a hysteresis
synchronous motor at a preselected rate (approximately 23 Hz) chosen to be
unrelated to any harmonic or subharmonic of the line frequency.  Light emitting
diode-phototransistor pairs are used to sense the position of the hole in the
chopper; the signal from the phototransistor triggers a discriminator to start
the timing and counting cycle for each sample tube.

     A logic system, triggered by the discriminators, controls the pulse count-
ers associated with each sample tube.  In order to ensure precise counting time
as the photomultiplier is exposed to each tube, an electronic gate is used to
ensure that the photomultiplier is fully (and not merely partly) exposed to the
light beam passing through the sample.

     The photomultiplier tube which must be selected for gain, low dark count
rate and, most importantly, negligible afterpulsing, detects the photons as they
                                      15

-------
arrive.  This type of tube, with outstandingly good single photon resolution, is
essential for this measurement.

     The pulse output from the photomultiplier is amplified 100 times by direct-
coupled amplifiers and the pulses are detected by a high-speed pulse amplifitude
discriminator.  Pulse counting is performed  by convential  100 MHz pulse counters
and a rough guide of overall pulse rate is provided by a rate meter.

     Counting time is determined by a preset counter which counts the revolu-
tions of the chopper blade past  the light-emitting diode (LED) phototransistor
pairs.   At the end of a counting interval, the results are printed out and the
sequence repeats.

     House air, dried and filtered, flows through one cell (reference cell),
then into an 03 generator (5) from which ozonized air flows through the second
cell (sample cell).   The measurement is made by comparing  the ratio of the
signals transmitted  by the two cells in the  presence and in the absence of 03.

This procedure provides the transmittance (Tr = -j—), and the 03 concentration is

determined by application of the Beer-Lambert Law^ as discussed above.  Since
the mercury lamp is  viewed, nearly simultaneously, through both cells, fluc-
tuations in lamp intensity do not affect the measurement.   Any impurities present
in the  air stream are observed in both cells and do not interfere with 03
determination.

                                    RESULTS

     The performance of the photometer has been determined over the 03 con-
centration range 0.020 to 1.500  ppm.  At each of the measured concentrations the
standard deviation was of the order of 0.005 ppm or less.   A comparison of the
photometric measurements with those obtained by the iodometric and GPT methods
is presented at this Conference  in the paper by J. A. Hodgeson, et al. (6).

                                  REFERENCES

1.   "Reference*Method for the Measurement of Photochemical Oxidants  Corrected
     for Interferences due to Nitrogen Oxides and Sulfur Dioxide," Federal
     Register 36., 8195-8197 (30  April 1971).

2.   (a)  "Comparison of Oxidant Calibration Procedures,"  report of the Ad Hoc
          Oxidant Measurement Committee of the California  Air Resources Board,
          Sacramento, CA (20 Feb. 1974).

     (b)  "Interagency Comparison of Iodometric Methods for Ozone Determina-
          tion," W.  B. DeMore, J. C. Romanovsky, M. Feldstein, W. J.  Hamming,
          and P. K.  Mueller, in  "Calibration in Air Monitoring," ASTM Special
          Tech. Publ. 598, pp. 131-143 (Philadelphia, 1976).

3.   J. B. Clements, "Summary Report:  Workshop on Ozone Measurements by the
     Potassium Iodide Method," EPA-650/4-75-007, U. S. Environmental  Protection
     Agency, Washington, D. C.   20460, February 1975, 36  pp.
                                      16

-------
4.   The value of k used in this work (308.5 cm^atnr1) is based on an evalua-
     tion by R. Hampson and D. Garvin of measurements reported in the published
     literature:

     (a)  Inn, E. C. Y. and Y. Tanaka, J. Opt.  Soc. Am. 43_, 870 (1953).

     (b)  Hearn, A. 6., Proc.  Phys. Soc. 78, 932 (1961).

     (c)  DeMore, W. B. and 0. Raper, J. Phys.  Chem. 68, 412 (1964).

     (d)  Griggs, M., J. Chem. Phys. 49, 857 (1968).

     (e)  Simons, J. W., R. J. Paur, H.  A.  Webster and E.  J. Bair, J. Chem.
          Phys. 59, 1203 (1973).

     (f)  Becker, K. H., U. Schurath, and H. Seitz, Int. J. Chem. Kinet. 6., 725
          (1974).

5.   Hodgeson, J. A., R. K. Stevens, and B.  E.  Martin, ISA Trans. 11, 161
     (1972).

6.   Hodgeson, J. A., E. E. Hughes, and A.  M. Bass, "Methodology for Standardi-
     zation of Atmospheric Ozone Measurements," preprint for International
     Symposium on Photochemical  Oxidant Pollution and its  Control, Raleigh, NC,
     12-17 September 1976.
                                      17

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                                                                                1-3
                    HYDROCARBON  AND HALOCARBON MEASUREMENTS:
                        SAMPLING AND ANALYSIS PROCEDURES

        R.  B.  Denyszyn, L. T.  Hackworth, P. M. Grohse,  and D. E. Wagoner*

ABSTRACT

     VaAinQ the. AummeA and  ^ati o& 1975 appAox.imate.tij 3000 hydAocoAbon,  500
kaJLoc.aA.bon, and 100 het^eAocyctic anatyAeA weAe. peA^oAme,d -in the, atmoApheAic.
chemiAtAy  taboAatoAy o& the. ReAe.aAch TAiangie. InAtitiite..   VuAing thu,  peAiod
vaAiouA  quality aon.tA.ol. pAoce.duAej> weAe. de.ve,£ope.d to e.vatu.ate. the. Aampting and
analytical method!, aAe.d to  deteAmine. conce.ntAationA  ofc vatiouA hydAocatbon and
hatocoAbon 4pecxe4 -in amb-lznt aiA cu> weJLt OA ui bmoQ c.hambeA bamptnA .   TzAtA
u)eA£ poA^oAmid on:  (a) the. Atab+jUty oft hydAOdOAbonA  tn Jt^ton Aampting bag*;
(b) peAme.dtA.on ofa hydAoc.aAbon and hatocaAbonA -into  TudtoA bag*;  (c) the. Ata-
           zeJio aJjt and btandoAd Aampte^> -in Te.diaA ba.g-4 beting t>hLppo,d  batwuAe.d
                to a btaA  o{, 5%  uiith 5 1 Ae.£ative. ktandaAd de.vtation.
                M. conce.ntAation6  o^ >10 ppb, C2-C5~hydAocaAbon& me.OAaAe.me.nt!>,
                21 AeJLattve. AtandaAd de.vtation  can  be. achte.ve.d.

                The. Ae.latA.ve. AtandaAd de.vtation ofi  FAe.on 11 me.aAuAe.me.ntt>  at the.
                Re^e.oAch TAiangle.  InAtttute. aAe. pAe^entiy 31.

                The. Atabtttty  ofa both Ae.active.  and  LLnAe.ac.tive. hydAocoAbonA at the.
                1-10 ppb conce.ntAation Aange. WOA  e.valu.ate.d tn Te.dlaA  bagA in the.
                doAlz &OA a 1-we.e.k  peAtod.
                SeJLe.cte.d hydAocaAbonA and hetejiocycLic compounds
                ceJLte,nt AtabJJLity in Te.^ton bagA in  the. daAk.
           9     Contamination  o^  Te.dlaA bagA ^-itte.d ulith hydAocaAbon--(iAe.e. aiA U
                viAtuaULy ne.Qtigi.bte. $OA hydAocoAbon and Aome. hatocoAbonA up to
                & dayA.

                                   INTRODUCTION

     During  the summer and  fall  of 1975 approximately 3000 hydrocarbon,  500
*Research Triangle Institute,  Research Triangle Park,  North Carolina.

                                        19

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halocarbon, and 200 heterocyclic analyses were performed in the atmospheric
chemistry laboratory at Research Triangle Institute (RTI).   Both ambient air and
smog chamber samples were included.   In order to establish  the credibility of
these analyses quality control (QC)  procedures were developed that have estab-
lished the accuracy and precision of the procedures.   These QC procedures have
also lead to improvement in the sampling arid analytical  techniques.

     Accuracy (bias) and precision (relative standard deviation) in  hydrocarbon
measurements result from attention to four parts of the  measurement  procedures:
sampling analysis, instrument calibration, sample collection, and personnel
training.  If optimum procedures are applied, gas samples containing hydrocar-
bons or halocarbons are stable enough to allow remote analysis; measurement
errors can be avoided; and a relative standard deviation of 2 percent is
possible in the 10-100 ppb concentration range.   If any  of  the critical pro-
cedures are not followed, this precision is degraded.

                              ANALYSIS PROCEDURES

     Analysis is performed with a modified gas chromatograph (GC), the selection
of which is of critical importance.   A suitable GC must  have detectors and
signal processing electronics with proven long-term stability and must be
sufficiently rugged to hold up under the rigors of continuous repetitive analysis,
It is advantageous that the GC have  an interface for direct coupling to a data
processing computer.  Additionally,  the GC columns should be selected for low
bleed since ambient air analysis requires the maximum detectability.  The
elution peaks should be well' separated in order to provide  maximum information
from the analysis.

     The specific GC employed for the hydrocarbon halocarbon analysis was the
Perkin-Elmer Model 900 with dual flame ionization detectors (FID) and two
electrometers.  The controls were modified to allow independent operation of
the detectors so as to facilitate rapid adjustment for analyses that require
different flow rates and column temperatures.  The valving  system shown sche-
matically in Figure 1 was built to allow the introduction of cryogenically
trapped samples into the GC.  Flexibility of the sample  injection system is such
as to accommodate samples with both  ppm and ppb concentrations.  This flexi-
bility is achieved by replacing the  secondary trap (liquid  nitrogen  trap) with a
sample loop.  The GC electronics interfaces with a Hewlett  Packard 3352B data
system.

     Since hydrocarbon concentrations in ambient air are much too low for
detection with direct injection gas  chromatography, sample  concentration is
required.  Concentration is usually  accomplished for lower  molecular weight
compounds with cryogenic traps although the choice of cryogen varies among
laboratories.  The primary requirement of the concentration procedure is that it
be quantitative—recovery must closely approximate to 100 percent.

     In order to avoid the condensation of oxygen that occurs in a liquid
nitrogen trap, liquid oxygen, which  boils at a higher temperature than liquid
nitrogen was used in our traps.  The collection efficiency  of the liquid oxygen
traps was evaluated by testing them  with ethylene and propane.  When ethylene in
                                      20

-------
                                        Detei tor
              ,11 r i e •  rid s
>nt

 \
                                                     \
         Figure 1.   Valving for thermally controlled injection system.

air was passed through two traps in series, the first trap gave 4.0 ppb  in
subsequent analysis while the second trap gave 0.3  ppb.  This indicates  a
collection efficiency of 93 percent for ethylene and, therefore, much better
efficiences for compounds with higher boiling temperatures.   In a similar
experiment with propane, a collection efficiency of .greater than 99 percent was
obtained.  Collection efficiences decreased at flow rates above 100 nrn/min and
with total sample volumes in excess of 500 mi as seen in Figure 2.
                  1OO -

                  90 -

                  80 -

                  70 -

                  60 -

                  50 .
                        100
                             250
                                       500
                                                  750
                                                           1000
       Figure  2.   Dependence  of  collection efficiency on volume of sample.


     This sample concentration and analysis system was  quantitative  for  C2-C10
hydrocarbons when the above procedures were followed.

                                  CALIBRATION

     The accuracy and precision of the analytical step  was  determined  with  the
complex permeation tube system shown  in  Figure  3.   In this  system,  carrier  and
dilution air were catalytically cleaned  of hydrocarbons and other pollutants
and mixed with accurate concentrations of dopant  gases  over broad concentration
ranges.  Calibration gases were propylene and n-butane.  Calibration was per-
formed using a 180 cm x 0.32 cm outside  diameter  (OD) column packed  with 100-120
mesh n-octane Durapak maintained  at 19°C with a helium  flow of 20 m£/min.   Each
concentration level was measured  a minimum of four  times.
                                      21

-------
                                                             in
                                                               .
                                                            L,
                Figure 3.  Permeation tube calibration system.
     In these tests,  a precision  of 5  percent  was  obtained  in  measuring  con-
centrations.   As may  be seen in Figure 4,  the  relative  standard  deviation
appears to decrease with increasing concentration  with  a  nearly  linear depen-
dence.   The relative  bias of the  measurements  plotted  in  Figure  5  showed no  such
dependence.  The bias for propylene is positive  and  that  for  butane  is negative;
the average deviation is +5 percent,  respectively.

                               SAMPLE  COLLECTION

     Sample collection bags made  of Teflon and Tedlar  are commonly used  in
atmospheric chemistry.  Their purported attributes  include  ease  of handling,
durability, chemical  passivity, and low cost.  Reported shortcomings  include
fragility, permeability, and the  outgassing of various  photolytic  compounds  by
the polymeric materials of which  the bags  are  made.  Outgassing  has  been ob-
served at RTI and at  other laboratories.

     While compounds  in the C2-C5 molecular weight range  mixed with  air  are
stable in both Tedlar and Teflon  bags, the more  serious outgassing of Tedlar  has
led us to use Teflon  bags for samples  containing high  molecular  weight hydro-
carbons, heterocyclics, and sulfur-containing  compounds such  as  dimethyl sulfide
and thiophene.

     Several  interesting phenomena that could  result in errors have  been ob-
served in using Tedlar bags.  Acetylene (in concentrations  >  100 ppb) is ab-
sorbed by Tedlar and  released when the bag is  heated.   If hydrocarbon mixtures
are blended in oxygen-nitrogen mixtures obtained by  liquid  boil  off rather than
in catalytically cleaned air, the hydrocarbon  concentration changes  due  to
permeation of the bag by oxygen in establishing  partial pressure equilibrium
with the ambient air.  Data indicating this activity are  illustrated  in  Figure
6.
                                      22

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o

+J
(O


O>
     6 -


     5


     4 H


     3


     2
                                          X  Propylene
                                          O  Butane
                10        20        30       40        50       60

                    Concentration Analyzed (ppb V/V)


    Figure 4.  Precision and its relationship  to  concentration.
10.
 8'
O ro
i. >
4-

1-
O
      6'
      8.

     10.
                          X Propylene
                          O Butane
                in       20        30        40        50

                    Concentration  Analyzed (ppb V/V)


      Figure 5.  Bias and  its relationship  to concentration.
                                                          60
                                 23

-------
o>
c:
CU
CU
<_)
     CO

      s_
      o



      en
      fO
     CO

      CU
      c:
      OJ

     ^
     +->
      CU
      (_)
     
                                              O
                                                                   LD


                                                                   O
                                                                                        
                               (A/A)
                                        24

-------
     The stability without light of both reactive (trans-2-butene)  and non-
reactive (acetylene) hydrocarbon mixtures in Tedlar bags was tested for a 1-
month interval.   Filled Tedlar bags were stored in aluminum suitcases for
periods of up to 23 days.   Initial  hydrocarbon concentrations were  70 ppb;  after
23 days, the concentrations of trans-2-butene and acetylene were 62 ppb and 56
ppb, respectively; losses  were 11  percent and 20 percent.   In a test using
acetylene and exposed to light, the data of Figure 7 were obtained.  As shown,
the average deviation is 6 percent from the mean concentration.  For the 12 ppb
sample used in this test,  on the 5th,  6th, and 14th day the concentrations  were
11.5, 11.0, and  14.0 ppb,  respectively.

                                                CoH^  Mean  Concentration  11.5

>
^>
-Q
CL
CL
m.
12 •
1 0 .
8 -
6
1+
Average
o
• .
_i. _ _ -- 	
Dash Lin
from Mea
                   0800   1600    2"+00    0800   1600

                       9/17/75    TIME     9/18/75
                 Figure  7.   Stability  of  acetylene  in  Tedlar  bags.

     Additional stability tests were performed by exposing the sample bags to
the contaminated transportation environment such as associated with a field
collection program.  Tedlar bags with control samples of hydrocarbon-free air
were shipped by United Parcel Service and air freight to various sampling
stations and then returned to the laboratory.  Eight days of travel time lapsed.
Test results are given in Table 1.  In this test the bags were exposed to var-
ious temperatures and unusually high concentrations of hydrocarbons in the
ambient air.

     In contrast to hydrocarbons, halocarbon sampling is much more susceptible
to contamination.  In normal laboratory air the concentration of Freon 11 is
several ppb so that even the fraction of a milliliter of laboratory air trapped
in a Swagelock fitting may invalidate data in a sample.  The permeati
for 1,1,1-trichloroethane and tetrachloroethylene through Tedlar are much
high to use bags for sample collection.  Stainless steel containers are
halocarbon sampling by many research groups but their high cost is prohibitive
for extensive sampling programs.
rates
  too
used for
     Aluminum sample containers (Altech Associates) appear to be excellent
containers for sampling and storing both hydrocarbon and halocarbon samples.
The results of a 1-month test of aluminum sample containers are given in Table
2.  Both Freon 11 mixtures and undoped air were used.  These aluminum cans have
been found to be usable with heterocyclic compounds such as furan but serious
wall interactions have been observed with sulfur compounds.  The concentration
of thiophene, for example, decreased 29 percent in 4 days.  However their low
                                      25

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          TABLE 1.  STABILITY OF HYDROCARBON FREE AIR IN TEDLAR BAGS
Species
ethane/ethylene
propane
propylene
acetylene
n-butane
butene-1
isobutane
isopentane
cyclopentane
n-pentane
toluene
o-xylene
freon 11
cci4
trichloroethane
tetrac hi oroethyl ene
Bag
Concentration
ppb (V/V)
2.1
0.4
0.1
0.4
N.D.
N.D.
N.D.
N.D.
N.D.
0.0
1.2
0.6
13.5 ppt (V/V)
N.O.
0.3
<40.0
Cylinder Gas
Concentration
ppb (V/V)
2.1
0.4
0.1
0.5
N.D.
N.D.
N.D.
N.D.
N.D.
N.D.
1.1
0.8
N.D.
N.D.
N.D.
N.D.
                   N.D. = not detectable.

                      TABLE  2.   FREON 11  IN ALUMINUM CANS
4-8-76
4-9-76
4-22-76
4-23-76
4-30-76
5-4-76


307 ppt
300
304
298
288
290
MEAN 298
S. OW 7.5

4.0

8.9
10.3
8.8
8.0
2.8
cost, convenience in use, and stability for most compounds indicate that alumi-
num cans are generally excellent for sample collection.

     Teflon bags are also recommended for sample collection.  Wall interactions
and permeation rates are low.  However there is considerable variability in  the
quality of the bags.  Some give off compounds that are detected with the FID and
the electron capture detector.  Because this outgassing varies with the batch,
and is usually less than with Tedlar, it is necessary to condition Teflon bags
with ozone and to analyze for background before being used for sampling.  Table
3 gives data illustrating the excellent stability in the dark of various mix-
tures contained in Teflon bags.

                               PERSONNEL FACTORS

     Training of personnel is important in operating a sampling program that is

                                      26

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            TABLE  3.   STABILITY OF VARIOUS COMPOUNDS IN TEFLON  BAGS


                                          Net Loss After 3 Days


                       Dimethyl Sulfide               1%

                       Thiophene                   5*

                       Dimethyl Disulfide             5%

                       Methyl Mercaptan               7%

                       Furan                     14S

                       p-Xylene                   14"J

                       Pyrrole                   23"
to obtain  accurate  and precise data.  This training must  include  familiarization
with GC and  review  of the various pitfalls that result  in  errors.   Measurement
of trace quantities of various atmospheric contaminants requires  much attention
to detail.   Gas  regulators with rubber diaphragms cannot  deliver  pure gases,
small  leaks  will  result in errors.  Personnel must learn  to  discern bad from
good data, and every phase of the measurement program must be given the required
attention.
                                   CONCLUSIONS

     Hydrocarbon and  halocarbon  measurements can be made accurately  and  pre-
cisely if proper attention  is  given to the analysis procedures,  calibration,
sample collection,  and  personnel  training.  When this is done, C2-C5  hydro-
carbons at < 10 ppb concentrations can be measured with a bias of  5  percent and
a relative standard deviation  of 5 percent.   For concentrations  above 10 ppb,
the bias is the same  but  the  relative standard deviation improves  to  2 percent.
Analysis of samples should  be  made within one week of collection and  when
possible, on-site analysis  is  preferable.
                                       27

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                     SESSION 2
ANALYTICAL METHODS FOR OXIDANTS AND PRECURSORS - II
                         K.H. Becker
                University of Bonn
                        29

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                                                                            2-1
                   A NEW  CHEMILUMINESCENT  OLEFIN  DETECTOR
                                FOR  AMBIENT AIR

                  K. H. Becker,  U.  Schurath,  and  A.  Wiese*
ABSTRACT
     \n tns&uwent faor continuous monitoring  o& re.active. hydrocarbons -in
ambi.e.nt air -in the. parts putt bWiion  concentration  Aange. -is  de.scribe.d.   The.
new anal.yti.cal. method ts base.d upon the.  chemilum-ine.sce.nt oUt^in — ozone, re-
action.  The. chemilumine^ce.nt ole-i-in  detectoA has been  te.ste.d at ground le.ve.1
para-ULeJL to an automatic. Gas Chromatograph, aboard  an airplane.,  and as a
detector adapted to a. gas chromato graphic  column.   Applications  o& the. new
histAu.me.nt {,01 air pollution control  are. discussed.


                                 INTRODUCTION

     In order to control photochemical oxidant precursors and their transport
over long distances, there is an urgent  need  for a  simple technique capable of
measuring "reactive hydrocarbons" continuously, with high sensitivity,  and
good time resolution.  The term  "reactive  hydrocarbons"  is generally applied
to the total amount of organic gaseous material, as measured by a Flame loni-
zation Detector (FID), less methane,  which is  considered unreactive in photo-
chemical smog.   It might, however, be more appropriate  to measure the reactiv-
ity of the hydrocarbons towards  ozone (03) to obtain an  indicator of their
smog forming potential.  It has  been  shown in  a number  of field  studies (1,2)
in urban areas with unspecified  emission sources that ethylene and propene are
by far the most abundant unsaturated  hydrocarbons which  at the same time
represent the most reactive organics  with  respect to photo-oxidant formation.
Reactivity of organics is measured as rate constant times concentration.   Sat-
urated hydrocarbons, although most present at higher concentrations are less
reactive.  A suitable measure of the  total olefin amount in  ambient air may be
that of the intensity of the chemiluminescent reaction  with  03,  as measured in
a "reversed" chemiluminescent 03 analyzer  which uses ozonized oxygen as re-
agent gas.  The relative quantum yields  of the most abundant olefins, ethylene
and propene, could also be a good "weighing"  factor of  their relative reactiv-
ity as smog precursors.

     The paper describes a rather simple chemiluminescent olefin detector
which has been field tested as a continuous monitor of  reactive  hydrocarbons
in ambient air at ground level,  in parallel with an automatic Gas Chromato-
graph (GC) (Siemens U 180).  Another  version  of the detector has been success-
fully used for olefin measurements in plumes  aboard an  airplane  up to an
*Institut fur Physikalische Chemie der  Universitat  Bonn,  Bonn,  Germany.

                                      31

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altitude of 3000 meters.   And the instrument was also adapted to a gas chroma-
tographic column for the selective detection of unsaturated hydrocarbons.   A
similar technique has previously been used elsewhere (3).   Part of the present
work has previously been published (4,5).


                                EXPERIMENTAL

     The construction and principle of operation of the chemiluminescent
olefin detector are evident from the schematic diagram (Figure 1), which shows
the version used for airborne measurements.   Ozonized oxygen from a silent
discharge ozonizer (2.5 liter/hour) and sample air (60 liter/hour) are drawn
into a mixing chamber (volume 230 ml) by a small diaphragm pump which is
protected against 03 by an activated charcoal filter.   A chamber pressure of
400-500 torr was found satisfactory.  The mixing chamber is mounted in front
of a photomultiplier tube (EMI-9635 QB) which, by its low quantum efficiency
above 600A, essentially eliminates interference by nitrogen oxide (NO) from
its chemiluminescent reaction with 03.   The reaction chamber was drilled from
solid teflon contained in a light-tight metal cylinder.   Teflon has the ad-
vantage of an extremely good optical reflectivity at short wavelengths,
thereby increasing the sensitivity of the detector.

     The instrument was calibrated  using  a  425  liter evacuable   glass  cylinder
as mixing chamber.  The container was  filled with ambient  or pure synthetic
air and spiked with the olefins by means  of a precision gas  syringe.   Mixing
was achieved by a built-in teflon fan.

     To increase the  long term stability  of the detector background  signal
(photomultiplier dark current plus  background chemiluminescence), the
photomultiplier and reaction chamber could be thermostat!zed.  This procedure
was not necessary for shorter periods of operation, e.g., aboard an aircraft.

     The sensitivity of the detector towards various olefins not only depends
on the relative quantum yields of the chemiluminescent reactions, but also on
the flow rate and total pressure in the chamber.  Typical sensitivities, rela-
tive to ethylene taken as unity, were 2.5 for propene, 6.4 for trans-2-butene,
3.0 for cis-2-butene, and 4.4 for 1,3-butadiene.

     To eliminate sensitivity changes due to relative humidity effects, an air
filter filled with Sicapent (phosphorus pentoxide on a solid support) was
found most satisfactory.   The detector zero was checked at intervals by
switching a molecular sieve filter of suitable pore size to eliminate olefins.


                                   RESULTS

     Our prototype chemiluminescent olefin detector for air analysis at ground
level has been in continuous operation since May 1975.   Maintenance amounts to
changing the Sicapent filter every 5 days, and the ozonizer oxygen supply tank
every 100 days.
                                      32

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      An  8  hour  recording  by  the  detector  is  compared with  the  ethylene  concen-
 tration  as measured  by  a  Siemens  U  180  automatic  GC  (Figure  2).  This GC  per-
 forms  a  complete  analysis  every  15  minutes,  averaging  over 10  minutes by  a
 preconcentration  technique.   The  comparison  shows  a  good correspondence be-
 tween  the  detector output  and the ethylene concentration which  is  by far  the
 most  abundant olefin  in ambient  air.  The continuous recording  shows fine
 structure  of the  concentration-time profile which is lost  in the averaging
 process  of  the GC analysis.   Interpretation of the chemiluminescent detector
 recordings  is also much easier than would be an evaluation of the sometimes
 confusing  information contained in a complete GC analysis  of the light  hydro-
 carbons every 15 minutes.

     The high sensitivity and short time constant  (about 3s) of the chemilumi-
 nescent  olefin detector make  it a valuable tool for continuous airborne meas-
 urements of reactive hydrocarbons.  Figure 3 shows a recording obtained on a
 first test flight in the Cologne-Bonn area.   The flight level was changed after
 passing over a lignite burning thermal power station from  4000 feet to  2600
 feet (3800 to 2600 feet above ground).  An extremely strong olefin signal
 corresponding to  a maximum of 700 ppb ethylene equivalents was obtained above
 a petrochemical  plant.  It had been shown on a previous flight (6) under  clear
weather conditions that the 03 concentration increased considerably above
 average about 20  km downwind  of the petrochemical plant, at a flight level of
 2500 feet.   The effect was less pronounced at lower and higher altitudes.

     The performance  of the instrument  as a GC detector is shown in Figures 4,
 5, and 6.   In this mode the GC column outflow is blended with 60 liter/hour of
 argon before analysis to reduce the residence time in  the  reaction chamber
 which was  run at  atmospheric  pressure.  Figure 4 compares  analyses of identi-
 cal mixtures of alkanes and olefins in  synthetic air (concentrations of the
 order 50-100 ppm), as measured with a conventional FID, and with oTefin de-
 tector.  Peak-overlapping with alkanes  is completely eliminated.   Figure  5
 shows the  chemiluminescent detector response for car exhaust gas after  separa-
 tion on  a  GC column.  Again,  only the olefins are detected.  Analysis of
 ambient  olefins by GC with the new detector requires pre-concentration.   A
 typical  olefin analysis of ambient air  is shown in Figure  6.   It clearly
 corroborates our  previous  statement that ethylene  and  propene  are  a good
 measure  of the total  olefin content in  ambient air under normal conditions.
                                  CONCLUSIONS

      It has been shown that  unsaturated  hydrocarbons  can be measured  continu-
ously in ambient air and in  smog  chamber experiments  (7) with this  inexpensive
rugged chemiluminescent detector.  The output of the  instrument is  a  useful
measure of the total olefin  content of the atmosphere, with weighing  factors
of 2.5 for propene, 6.4 for  trans-2-butene, 3.0 for cis-2-butene, and 4.4 for
1,3-butadiene relative to ethylene as unity, taking account of the  higher
photochemical reactivity of  the higher olefins.  One  version of the detector
has been used successfully for airborne  measurements  of reactive  hydrocarbons
above an industrialized area with distinct sources of olefins.  The instrument
is also useful as a specific GC detector for unsaturated hydrocarbons which
need  not be separated from alkanes.

                                      35

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Figure 4.   Chemiluminescent olefin analyzer as GC detector  in  comparison
           with  an  FID:  Analysis of a synthetic air sample (olefin  con-
           centration  in the 50 - 100 ppm range).
37

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             detector.
                                  38

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         5         /»          3          2         1          0   [mini
 Figure  6.   GC  analysis of a pre-concentrated air sample by the  chemilumi-
            nescent olefin detector.
                                    39

-------
                               ACKNOWLEDGEMENT

     This work was supported by the "Bundesminister des  Innern"  as part of
a program on photochemical  air pollution  control  in the  German  Federal
Republic.
                                 REFERENCES

    1.    H.  H.  Westberg,  R.  A.  Rasmussen,  and M.  Holdren.   Gas  Chromato-
         graphic Analysis of Ambient Air for Light  Hydrocarbons Using a
         Chemically Bounded  Stationary Phase.  Anal.  Chem.  46:1852,  1974.

    2.    W.  A.  Lonneman,  S.  L.  Kopczynski, P. E.  Darley,  and F. D.  Sutter-
         field.   Hydrocarbon Composition of Urban Air Pollution.   Env.  Sci.
         Technol.  8:229,  1974.

    3.    W.  Bruening and  F.  J.  M.  Concha.  Selective Detector for Gas
         Chromatography Based on the Chemiluminescence of Ozone Reactions,
         J.  Chromatog.  112:253, 1975.

    4.    U.  Schurath, A.  Wiese, and K.  H.  Becker.  Ein Chemilumineszen-
         zanalysator fur  ungesattigte Kohlenwasserstoffe  in der Atmosphare.
         Staub - Reinhalt. Luft, 1976,  in  press.

    5.    K.  H.  Becker,  Ulrich Schurath, and Andreas Wiese.   Gas Chromato-
         graphic Detector for Olefins.   Anal. Chem.,  1976,  in press.

    6.    W.  Fricke and H. W. Georgii,  private communication.

    7.    K.  H.  Becker,  F. Bahe, W.  Janek,  J. Lobel, U. Schurath, W.  W...Wendler,
         and A.  Wiese.   Untersuchungen uber Smogbildung,  insbesondere uber
         die Ausbildung von  Photooxidantien als Folge der Luftverunreinigungen
         in  der BRD.  Annual Report 1975.   University of  Bonn,  May 1976.
                                     40

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                                                                             2-2
  GC-CHEMILUMINESCENCE  METHOD FOR THE ANALYSIS OF AMBIENT TERRENES

                               R. L. Seil a*

ABSTRACT

     A method {^on, the., quantitative. and qualitative. anaty^iA o^ ambient te.Ape.neJ>
•it, dej>cAibe.d and e.val.uate.d.   Sampled  o& ambient ait c.otie.cte.d on a t>oLid adbotb-
e.nt ate. de^otbe.d Into a cA.yoge.nlc. ttap fact In j e.ction Into a got, c.htomatogtaphic.
cotamn.  k^teji Ae.pan.at.ion  by the. column,  the. Aampte. u> 6piit fiot £Jjnuitane.O(Li>
detection by ^lame. ionization and ozone, c.ke,mit(mine.t>c.e,nc.e..  The. chemitumineA-
ce.nce. dzte.ctot -it, a modi&ie.d comme.tc.ial. amb.ie.nt nittoge.yi ozidz-oicidzA oft
ge,n monitor,  Re^ponAe.  data fio-i a vasu.ety o& teA.pe.nic hydAocajibonA, and the.
        o& &ome. ambient anaiy^e^ ate.  ?ie.ponte.d.
                             INTRODUCTION

     The contribution  of natural  hydrocarbons emitted from trees and  other
vegetation to the  formation  of photochemical oxidants is a continuing subject of
debate and study.   Rasmussen,  et  al .  (1) report that monoterpenes and isoprene
are the major compounds  released  to  the atmosphere from plants.  The  research of
Grimsrud et al.  (2)  indicate that terpenes are very reactive with short  re-
sidence times in the atmosphere.   These findings suggest that natural  hydro-
carbons may be  important precursors  for the reactions which form 03 in rural
atmospheres .

     In order to more  fully  understand the relationship between biomass  and
rural 03 concentrations,  varied and  reliable analytical methods for the  identi-
fication and quantisation of terpenes are desirable.  Gas chromatography (GC)
with flame ionization  detection (FID) has been the method used by most previous
investigators (1,  3, 4,  5, 6).  The  inherent problem with this method is that
the FID does not provide a definitive qualitative analysis, since it  does not
enable identification  of specific organic compounds (7).  Experience  in  the
Environmental Protection Agency (EPA), Environmental Sciences Research Labora-
tory (ESRL) has been that the  GC  resolution of terpenes from the ever present
very dilute automobile exhaust in rural air is very difficult.  This  problem  has
been overcome by the use of  two detectors.

     There is a problem  of uncertainty concerning the results of detailed
hydrocarbon analyses of  relatively clean rural air samples collected  in  Tedlar
bags due to contaminants from  the polyvinyl fluoride film (11).  Another problem
of using bags for  sampling rural  air for terpene analysis is that the ambient 03
in the bags reacts  quickly with terpenes during the time interval between
 *U.  S.  Environmental Protection Agency, Research  Triangle  Park, North Carolina.

                                       41

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collection and analysis.  For these reasons and the fact that the  concentration
of large volumes of air is necessary for the analysis of low ambient  terpene
concentrations, it was decided to assemble and test a GC method which would
employ a solid adsorbent for sampling large volumes and would simultaneously
measure the FID and chemiluminescent responses of these samples.

     Ozone chemiluminescence measurement of olefins has been performed by
Quickert, et al. (8) who evaluated the direct response of  a modified  commercial
03 monitor to several selected olefins but not to terpenes.  Mil born, et  al.  (9)
used the same instrument as a total olefin monitor for ambient measurements.
McClenny, et al. (10) measured the chemiluminescent response of various olefins
with 03 and demonstrated the feasibility for analysis of vinyl chloride and
related compounds by using a combination of GC and 03 chemiluminescence.   A
commercial instrument manufacturer under contract to EPA has produced a proto-
type vinyl chloride analyzer using this method.
                                 EXPERIMENTAL
INSTRUMENTATION
     A schematic of the flame ionization-chemiluminescence chromatographic
system used for terpene analysis is provided in Figure 1.  It consists basically
of two components—a Perkin Elmer 900 GC with FID and a Bendix Model 8101-B N0x
chemiluminescence analyzer.
                TENAX DESORPTION UNIT
                                  HELIUM
CARRIER
 GAS
                                      AIR
                                                            CHEMILUMINESCENT

                                                               ANALYZER
        Figure 1.   Schematic of FID-chemiluminescent gas chromatoqraph.

     The NO  analyzer used  as  a chemiluminescence detector was  modified in
several respects.  The photomultiplier tube was  replaced with one  from a Bendix
03 chemiluminescence analyzer.  The red interference  filter  between  the photo-
                                      42

-------
multiplier tube and the reaction chamber was replaced with a transparent glass
window.  The glass capillary which controls the flow of ambient air into the
reaction chamber at a rate of approximately 150 ml min"1 was replaced with one
identical to the one used to restrict the 03 flow into the reaction chamber to
20 ml min-1.  This capillary gave a carrier gas inlet flow rate of 27 ml min"1.
The same pump which comes with the instrument was used to operate the reaction
chamber at a pressure of 50 Torr.  The 03 air supply pressure switch used to
energize the 03 generator at 18 pounds per square inch gauge (psig) was adjusted
to allow operation at a pressure of 8 psig.  A 35 liter tank was placed in the
vacuum line between the pump and the reaction chamber to act as a ballast.

     The outputs from the FID amplifier and chemiluminescence analyzer were 1 mv
and 10 mv respectively and were connected to a strip chart recorder operated at
a chart speed of 1.27 cm min'1.

CHROMATOGRAPHIC CONDITIONS

     The GC column employed was 120 cm x 2.36 mm inside diameter (ID) ss OPN/Porasil
C, 80/100 mesh (Waters Associates).  The carrier gas was helium at a flow rate
of 50 ml min"1.  The column and FID detector temperatures were 120°C and 160°C
respectively.  After splitting, the carrier flow rate to the FID was 23 ml min"1
and the flow rate to the chemiluminescence detector was 27 ml min-1.  The FID
air and hydrogen flows were 472 ml min"1 and 49 ml min"1 respectively.  A cryo-
genic trap, consisting of 0.5 ml of Chromosorb 750 in a 27 cm x 2.36 mm ID
section of ss tubing, was used to trap the sample before injection onto the
column.  Liquid oxygen was the cryogen.  A Seiscor six port gas sampling valve
was used for flow diversions involved in sample trapping and injection.  The
valve was placed in the GC oven with the column at a temperature of 120°C.
SAMPLING

     Tenax GC (2,6 diphenyl-p-phenyleneoxide polymer, Alltech Associates) 60/80
mesh was the adsorbent used for collecting ambient samples.  Stainless steel
tubes, 14 cm x 6.35 outside diameter (OD), containing 3.8 ml of Tenax and glass
wool plugs were the sampling cartridges.  Before use the cartridges were con-
ditioned under helium flow at 350°C for at least 24 hours.

     A Thomas pump connected to a two port manifold to which two Tenax cart-
ridges could be attached for duplicate sampling constituted the sampling ap-
paratus.  The air flow rate was measured with a calibrated rotometer and ad-
justed as necessary when ambient samples were collected.

     A special Tenax desorption unit was fabricated from a Perkin Elmer liquid
injection port.   This design has been described by Bellar, et al. (12).  The
exit of the desorption unit was connected to the sampling valve to which the
cryogenic trap was attached.  The valve plumbing was reverse that of common GC
valve plumbing.   In the valve off position, the carrier gas flows through the
cryogenic trap to the column.  Only when the valve is actuated does helium from
the desorption unit flow through the cryogenic trap.  This arrangement was used
to prevent contamination of the cryogenic trap from a Tenax cartridge in the
desorption unit.   Samplers were desorbed at 250°C while purging the cartridge

                                      43

-------
with helium at 47 ml mirr1 for 15 minutes.

CHEMICALS

     Terpenes liquid samples were obtained from Glidden-Durkee, Aldrich and
Chemical Samples Company.

                       RESULTS AND DISCUSSION

     Before the instrumentation was assembled, a preliminary experiment was
performed to determine if some terpenes would chemiluminesce when reacted with
03.  This work was done using the apparatus as described by McClenny, et al.
(10).  Bag samples of a-pinene, 3-pinene, myrcene, y-terpinene, and d-limonene
were sampled and did provide chemiluminescent response.  This suggested that a
GC-chemiluminescence method for terpenes was feasible.

     The chemiluminescent responses of selected terpenes were evaluated by
injecting masses varying from 0.08 yg to 1.08 yg into the FID-chemiluminescence
chromatograph.  Samples were cryogenically trapped from bag standards prepared
by microliter syringe injections into nitrogen.  This gave initial terpene
concentrations of 3 to 4 ppm.  Lower bag concentrations were produced by with-
drawing and adding nitrogen to the bags.  The FID analyses of the diluted bags
were used to calculate the terpene dilution concentrations by multiplying the
FID response times the terpene FID response factors obtained from the initial
known bag samples.  Sample masses were also changed by varying the sample volume
between 8 and 100 ml.

     Figure 2 is a graphical representation of the results of the response
study.   The concentrations on the abscissa were calculated from the known
samples masses and a presumed total sample volume of 15 liters.  The chemi-
luminescent response was determined by measuring peak area by the height times
width at half-height method.  This area (mm2) response was divided by 100 to
give the relative response depicted by the ordinate of the graph.  Most of the
curves  are not straight lines.   Myrcene and 3-pinene points appear to fall on a
straight line, while the other compounds show a slight decrease of sensitivity
with increasing concentration.

     The chemiluminescence sensitivity varied considerably from compound to
compound as can be seen by the curves in Figure 2.  Sensitivities were measured
by a linear regression calculation of the slope of the area response versus
concentration for the straight portion of the curves—generally at concentra-
tions below 5 ppb.  The slopes were converted to the accepted sensitivity units
of millivolt second/yg (7).  The minimum detectable masses were calculated by
dividing the minimum detectable area by the sensitivity for each compound. "The
minimum detectable area was the peak area for a recorder deflection of twice the
noise level.  The noise level was 0.008 mv and the minimum detectable area was
30 mm2  or 0.57 mv • sec.  The minimum detectable concentrations were calculated
from the known minimum detectable masses and an assumed sample volume of 15
liters.  Table 1 summarizes the sensitivity and detectability results.

     The sensitivity of chemiluminescent detection was improved considerably
(approximately 47 percent) by operating the chemiluminescent reaction chamber at

                                      44

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              70
           0
           a.
                        CONCENTRATION ppb CARBON
                                T  r~ "~r  r
                      0  10  20  30  40 SO  60  70  80
                       20  30  40  50   60   70  80   90  100 110 120
                             CONCENTRATION, ppb CARBON

    Figure  2.   Chemiluminescent response versus concentration* for selected
   terpenes.   (*A  sample  volume of 15  liters drawn through Tenax was assumed
                      for the concentration calculations.)

reduced (50 Torr) rather than  ambient  pressure.

     Table 2 is a comparison of  terpene relative  chemiluminescence  sensitivities
and their ozonolysis rates.  There is  a general positive correlation  of in-
creased sensitivity with increased ozonolysis  rate  (2).

     The efficiency of the Tenax cartridges was evaluated by  two  methods.   A bag
of low concentration a-pinene, 3-pinene, d-limonene,  and myrcene  was  prepared.
                                      45

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      TABLE 1.  CHEMILUMINESCENCE SENSITIVITY, MINIMUM DETECTABLE
             MASS AND CONCENTRATION FOR SELECTED TERRENES
                           *
 Compound        Sensitivity        Minimum Detectable     Minimum Detectable
                                         Mass                   Cone.
Camphene
Myrcene
d-Limonene
y-Terpinene
a-Pinene
A3-Carene
B-Pinene
256.9
208.0
82.7
58.6
50.7
37.0
3.4
0.0022 yg
0.0027 yg
0.0069 yg
0.0097 yg
0.0112 yg
0.0153 pg
0.1665 yg
.03
.03
.08
0.11
0.13
0.18
1.97

*
  Millivolt • second per microgram


  Parts per billion.  Concentrations based on 15 liter sample volume

        TABLE 2.  CHEMILUMINESCENCE RELATIVE SENSITIVITES AND RELATIVE
                     OZONOLYSIS RATE OF SELECTED TERRENES
Compound                Relative Sensitivity      Relative Ozonolysis Rate
Camphene
Myrcene
d-Limonene
Y-Terpinene
a-Pinene
A3-Carene
g-Pinene
5.1
4.1
1.6
1.2
1.0
0.73
0.067
--
8.6
4.4
1.9
1.0
0.83
0.25

A 25 liter sample was drawn through two Tenax cartridges in series.  These
cartridges were analyzed.  The analysis of a two liter cryogenic sample
directly from the bag provided a measurement of the actual  bag concentrations.
Comparison of the cryogenic analysis and Tenax analyses responses gave the Tenax
cartridge efficiency.  A comparison of the responses of the front and back
cartridges by the fo™ul. (1  -         .                 )  X 10CK .Iso produced

a trapping efficiency.   The results of this experiment are presented in Table 3.


     The  fact  that the Tenax  adsorption efficiency  for  C10  terpenes  is  not

                                      46

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              TABLE 3.  COMPARISON OF TENAX ADSORPTION EFFICIENCY
          DETERMINED BY TWO METHODS FOR  FOUR TERPENES OF VARYING SAMPLE SIZE
Compound             Bag Concentration,    Efficiency,         Efficiency,
                            ppb            Tenax Versus        Front Cartridge
                                           Cryogenic           Versus Back
                                           Analysis            Cartridge
a-Pinene
g-Pinene
d-Limonene
Myrcene
.30
.59
.87
2.15
57%
63%
69%
33%
74%
70%
64%
28%

greater than 90 percent  for a 25  liter volume is surprising and not what one
would expect from reviewing some  of the  literature on Tenax (13-18).

     A high efficiency of desorption (> 95 percent) of Tenax adsorbents was
verified several times by trapping cryogenically a second consecutive 15 minute
sample from a cartridge.  Comparison of the first desorption analysis with the
second indicated that practically all  of the adsorbed species had been removed.

     Chemiluminescence interference by aromatic hydrocarbons was evaluated by
analyzing automobile exhaust.   There was no interference in the terpene re-
tention time region.  This result agrees with the results of Hilborn, et al.  (9)
and McClenny, et al. that aromatic compounds do not respond to ozone chemi-
luminescence (10).

     The major source of error of this method arises from a sampling technique
which employs Tenax.  The problems with Tenax are contamination and adsorption
efficiency.

     Three types of blank analyses were performed to check Tenax background.
Cartridges were analyzed at the end of conditioning, after conditioning
and cooling, and after sampling prepurified nitrogen (Linde).   The
analysis of a cartridge at the end of conditioning revealed zero back-
ground on both the FID and chemiluminescent responses at the amplifier
attenuations used for ambient analyses (FID-16X, Chemiluminescence -
2X).  The cartridge was removed from the desorption unit and allowed to
cool for 15 minutes  while continuing the helium purge flow.  The subse-
quent chemiluminescent response revealed two small  peaks, comparable in
magnitude to the minimum detectability.  One peak retention time coin-
cided with that of A3-carene.   The FID chromatogram revealed general
contamination, but again of a magnitude corresponding to minimum de-
tectable peaks.   The 30 liter prepurified nitrogen sample displayed
general  FID contamination of low magnitude.  The chemiluminescent
response showed very small peaks at ct-pinene and myrcene and two small

                                     47

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unknown peaks in the retention region of terpenes and three very signi-
ficant peaks at retention time zero to one minute.   The two small  un-
known peaks were major peaks in all the later ambient samples and  were
confirmed to be Tenax artifacts by their absence from cryogenic concen-
tration analyses of two ambient bag samples.

     The error due to the uncertainty of Tenax adsorption efficiency
under ambient sampling conditions is difficult to access and will  be
more thoroughly investigated.   The data of Table 3 indicate an effi-
ciency of 60 to 70 percent.

     The reproducibility error expressed as percentage standard de-
viation was calculated from peak height measurements of four peaks from
eight duplicate ambient analyses.  The average percent standard de-
viations were ± 20 percent and + 22 percent for the FID and chemilumi-
nescent responses respectively.  The chemiluminescence and FID reproduci-
bility of the chromatograph without Tenax adsorption and desorption were
both ± 10 percent.  The lack of any reproducibility difference between
the chemiluminescent and FID responses and the large reproducibility
discrepancy of the method with and without Tenax indicate that Tenax is
a large source of reproducibility error.

     Ten duplicate day time ambient samples were collected and analyzed.
Six were from a small group of loblolly pines (Pinus taeda L.) behind
the EPA/RTP Environmental Research Center.  The other four were from an
18 year old, rural, homogeneous stand of loblolly pine.  The chemilumi-
nescence chromatograms of all  of the samples showed only two peaks
corresponding to previously analyzed known terpenes.  The two peaks were
a-pinene and myrcene, y-terpinene.  Their concentrations were all  less
than 2 ppb.

                                  CONCLUSIONS

     The method described herein has the advantage of simultaneous
measurement of FID and 03 chemiluminescent responses for GC samples.
This double measure provides for a more confident identification and quantit-
ation of terpenes in ambient air.

     The disadvantage is that this method employs Tenax, which has been shown to
have adsorption efficiency and contamination problems, as a solid adsorbent for
concentrating ambient samples.  If the use of Tenax proves to be too great a
problem, direct ambient cryogenic sampling of smaller volumes can be used as the
concentration technique.

                               ACKNOWLEDGEMENT

     The author wishes to acknowledge the assistance of Dr. William McClenny of
the U.S. EPA Environmental Sciences Research Laboratory.

                                   REFERENCES

1.  Rasmussen, R.A. What Do the Hydrocarbons from Trees Contribute to Air

                                     48

-------
    Pollution?  J. APCA, 22 (7):   537-543, 1972.

2.  Grimsrud, E.P., Westberg, H.H.,  Rasmussen,  R.A.  Atmospheric Reactivity
    of Monoterpene Hydrocarbons,  N02 Photooxidation  and Ozonolysis.   In:
    Proceedings of the Symposium on  Chemical  Kinetics Data for the Upper  and
    Lower Atmosphere, International  Journal  of  Chemical Kinetics Symposium
    No. 1, 1975.  pp. 183-195.

3.  Rasmussen, R.A., Werrt, F.W.  Volatile Organic  Material  of Plant Origin in
    the Atmosphere.  Proc. Nat.  Acad.  Sci.,  53:   215-220,  1964.

4.  Rasmussen, R.A. Isoprene:  Identified as  a  Forest-Type Emission  to the
    Atmosphere.  Environ.  Sci.  Techno!., 4(8):  667-671,  1970.

5.  Rasmussen, R.A., Holdren, M.W. Analyses  of  C5 to C10  Hydrocarbons  in
    Rural Atmospheres.  APCA 65th Meeting, paper  # 72-19,  June, 1972.

6.  Tyson, B.J., Dement, W.A.,  Mooney, H.A.  Volatilisation of Terpenes from
    Salvia Mellifera.  Nature,  252  (5479):  119-120, 1974.

7.  McNair, H.M., Bonelli, E.J.  Basic Gas Chromatography.   Varian Aerograph,
    Walnut Creek, CA, 1969, pp.  118, 87-89.

8.  Quickert, N., Findlay, W. J., Monkman, J.L. Modification of a Chem-
    iluminescent Ozone Monitor for  the Measurement of Gaseous Unsaturated
    Hydrocarbons.  The Science  of the Total  Environment 3(4): 323-328, 1975.

9.  Hilborn, J.C., Findlay, W.J., Quickert,  N.  The Application of Chem-
    iluminescence to the Measurement of Relative  Hydrocarbons in Ambient
    Air.   In:  Proceedings of the International Conference on Environmental
    Sensing and Assessment, Las  Vegas, Nevada,  1975, 24-2.

10. McClenny, W.A., Martin, B.E., Bumgardner,  R.E.,  Stevens, R.K., O'Keeffe,
    A.E.  Detection of Vinyl Chloride and Related  Compounds by a Gas  Chroma-
    tographic, Chemiluminescence Technique.   Environ. Sci.  Technol.,  10(8):
    810-813, 1976.

11. Seila, R.L., Lonneman, W.A.,  Meeks, S.A.  Evaluation of Polyvinyl  Fluoride
    as a  Container Material for  Air  Pollution  Samples.   J.  Environ.  Sci.
    Health—Environ. Sci.  Eng.,  All(2):  121-130, 1976.

12. Bellar, T.A., Lichtenberg,  J.J.  Determining Volatile  Organics at  Micro
    gram-per-Litre Levels  by Gas  Chromatography.   J. American Water  Works
    Assn., 66(12):  739-744, 1974.

13. Bertsch, W., Chang, R.C., Zlatkis, A.  The  Determination of Organic
    Volatiles in Air Pollution  Studies:  Characterization  of Profiles.
    J. Chromatog. Sci., 12(4):   175-182, 1974.

14. Pellizzari, E.D., Development of Method  for Carcinogenic Vapor Analysis
    in Ambient Atmospheres.  EPA-650/2-74-121,  U.S.  EPA,  Research Triangle
    Park, NC, 1974, 148 pp.


                                     49

-------
15. Pellizzari, E.D., Development of Analytical  Techniques  for Measuring
    Ambient Atmospheric Carcinogenic Vapors.   EPA-600/2-75-076, U.S.  EPA,
    Research Triangle Park, NC, 1975, 187 pp.

16. Pellizzari, E.D., Bunch, J.E., Carpenter,  B.H.,  Sawicki,  E. Collection
    and Analysis of Trace Organic Vapor Pollutants  in Ambient Atmospheres,
    Technique for Evaluating Concentration of  Vapors by Sorbent Media.
    Environ. Sci. Techno!. 9(6):   552-555, 1975.

17. Ibid, Thermal Desorption of Organic Vapors from  Sorbent Media.   Environ.
    Sci. Technol. 9(6):  556-560, 1975.

18. Pellizzari, E.D., Bunch, O.E., Berkley, R.E., McRae, J. Determination
    of Trace Hazardous Organic Vapor Pollutants  in Ambient  Atmospheres  by
    Gas Chromatograph/Mass Spectrometry/Computer.  Anal. Chem.  48(6):   803-
    806, 1976.
                                     50

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                                                                            2-3
                MEASUREMENTS  OF  SULFATE,  INORGANIC GASEOUS NITRATE
                     AND OTHER CONSTITUENTS  IN  THE ATMOSPHERE

                                     T.  Okita*

 ABSTRACT
                        made.  ofa Aiit&ate.,  gaA&ouA  nit/tote. and otheA.
•in the.  atmo&pk&ii -in  Tokyo and W>  Aiinnounding atea.   GOA&OUA nWiata conce.n-
tsiationA weAe  higheA.  -in Aumm&i than in uiinteA and c.owieJLatz.d dtoboLy with tho&e.
Of) oxidantA. Sul^ata-to-Aul^usi dioxide, conc-antsiation fiatioA did not appeal to
dosuieJLcite. with oxMant c.onc.e.ntn.ationA, and thzy  v&tizd uiith ti&tative. humidity.

                                   INTRODUCTION

      In photochemical  air pollution various types of pollutants are produced,
including oxidants.   They exert  adverse  effects  on human health, plants, etc.

      In this report,  results from measurements of sulfate, inorganic gaseous
nitrate (probably nitric acid vapor) and other constituents, conducted in Tokyo
and  its surrounding area, are presented  and compared with measurements of
oxidants.

                              ANALYTICAL PROCEDURES

MEASUREMENT OF NITRATE

      Ambient gaseous  nitrate was measured by collecting it first on a Sodium
Chloride (NaCl )-impregnated  filter from  which it was subsequently extracted and
analysis was made for it.  For preparation of the NaCl -impregnated filter, a
circular Toyo  51A cellulose  filter 5 cm  in diameter was soaked with a 5% aqueous
solution of NaCl, and was dried  using an infrared lamp in a chamber free from
nitrogen dioxide  (N02) and nitric acid gases.  The filter was then stored in a
silica  gel desiccator.

      For ambient air  sampling, either a  Millipore FHLP Teflon filter or a Sumi-
tomo  FP Teflon  filter 47 mm  in diameter  along with an NaCl -impregnated filter
were  placed in  separate filter holders.   They were connected in series, with the
FHLP  filter upstream  from the NaCl-impregnated filter.  The inside walls of the
holders were coated with Teflon  and the  filter holders were heated by a 30-W
tape  heater wound around the holder.  The air was sampled through the filters at
*Department of Community Environmental Sciences, the  Institute  of Public Health,
 Tokyo, Japan.

                                      51

-------
 a metered flow rate of about 20 1 mirr1.  Participate and gaseous nitrates were
 collected on the FHLP and Nad-impregnated filters, respectively.

      For measurement, the gaseous nitrate collected on the Nad-impregnated
 filter was extracted into 30 ml of hot water.  Then 20 ml of the extract was
 used  for the nitrate measurement.  The particulate nitrate collected on the FHLP
 filter was ultrasonically extracted into 30 ml of warm water.  In either case
 the nitrate in solution was reduced to nitrite by hydrazine in alkaline solu-
 tion.  The resultant nitrite was determined by reacting it with Griess-Romijn
 reagent (1) as modified by the technique as described in Ota et al.  (2).

      Efficiency of nitric acid collection on the Nad-impregnated filter was 90-
 100%  (mean efficiency 96.6%) for sampling flow rate of 20 1 min'1.  Interference
 from  0.1 ppm of N02 was equivalent to about 1 ygnr3 of nitrogen in the form of
 nitrate ion (NOs).  It was not enhanced by the presence of 03.  Interferences
 from  peroxyacetylnitrate (PAN) and organic nitrates were negligible.

      For particulate ammonium nitrate (deposited on the FHLP filter), ultrasonic
 extraction of nitrate from the filter in warm water was the most efficient
 extraction procedure, the efficiency being almost 100%.  Loss of nitric acid
 vapor on the FHLP filter was kept low (1-4%) by heating the filter holder with
 a 30-W tape heater.  Efficiency of particle collection by the FHLP filter has
 been  reported at 99.99%, even for the size corresponding to the penetration
 maximum (3).

 MEASUREMENT OF S02, N02, AND SULFATE (SOi;2)

      Ambient S02 and N02 were measured using automated electric conductivity and
 colorimetric (Saltzman) analyzers, respectively.  Particulate sulfates were
 collected on fiber glass filters and measured nephelometrically.

                                     RESULTS

 CORRELATIONS BETWEEN NITRATES, N02, AND OXIDANT CONCENTRATIONS

      During 1973-1976,  measurements of ambient gaseous and particulate nitrates
were conducted at the Institute of Public Health (IPH) and the Tokyo Metro-
 politan Institute of Environmental Control (TMIEC), located, respectively, in
 downtown Tokyo, and at Mt.  Tsukuba (altitude 876 m) which lies about 80 km NNE
 of downtown Tokyo (4).

      Figure 1  shows the relationship of gaseous nitrate concentrations (measured
 at the IPH between 10 a.m.  and 5 p.m.) and daily maximum oxidant concentrations
measured at the Meguro Air Monitoring Station located about 3.5 km from the IPH
 (during the period of July 25 to August 30, 1975).  The data of Figure 1 indi-
cate that the concentration of gaseous nitrate increases with increasing oxidant
 concentration.  Such a correlation between gaseous nitrate and oxidant was also
 found by our measurements in the summer of 1973 (4).  Figure 2 shows the rela-
 tionship between the concentrations of gaseous nitrate and N02 measured by the
 sodium arsenite method (5).  There was a tendency for high gaseous nitrate
concentrations  to occur with high N02 concentrations in downtown Tokyo, but at
Mt.  Tsukuba the gaseous nitrate concentrations were much higher than" were those

                                      52

-------
 of N02.   As shown in Figure 3,  there  was  no correlation  between  participate
 nitrate  and oxidant concentrations  at the IPH  site  in  the  summer of 1975.

0.15

Q.
Q.
|0.10
•+-•
c
§
o
§0.05
"3
O
n
X
X
X K
X X
XX X
x x
X X
X
X
XX X
XXXX W
X XXX X
•x
                                            30

                                          o
                                          'a
                                          *-•
                                          c
                                          0)
                                               XX  X
                                                 «• .t) .
    Gaseous  NQjN Concentration /x.gm*
   Figure  1.   Relationship  of gaseous
   N03 concentration at  the  Institute
   of Public  Health versus  daily maxi-
      mum oxidant concentrations.
                                             Q^Lj^Li- •; ••••  .   .	:	
                                             °0      _ 2         A        (
                                           Gaseous NKjN Concentration  fig m"1
                                         Figure 2.  Relationship between NO
                                           and gaseous N0~ concentrations.
                                          X IPH (July 25 - August 30, 1975)
                                        t Mt.  Tsukuba  (June  25  -  July 3,  1975)
     Figure 4 shows the relationship between daily mean concentrations of
gaseous and particulate nitrates measured at the IPH and TMIEC sites in January
of 1976.  Comparison of Figure 4 with Figures 1 and 3 indicates that, whereas
there was only a small seasonal change of the concentration of particulate
nitrate, the mean gaseous nitrate concentration in summer was about five times
that in winter in downtown Tokyo.  To further study the seasonal variation of
gaseous nitrate concentration, additional measurements were made between October
13 and 17, 1975, at Mt. Tsukuba.  These_measurements indicated that the mean N02
and both the gaseous and particulate N03 concentrations were 4.3, 0.4 and 1.5
ugnr3, respectively.  Comparison of these results with those shown in Figure 2
reveals that the gaseous nitrate concentrations were much lower in autumn than
in early summer, whereas N02 showed an opposite pattern.
CORRELATIONS BETWEEN S0i;2/S02,
                               N0^/N02 AND OXIDANT CONCENTRATIONS
     In the period June 25 to July 7, 1975 a survey of atmospheric constituents
was^conducted in a large area surrounding Tokyo (Figure 5).  The data examined
                                        and NOs1.   Figure 6 indicates the day-
included measurements of SO?, NO
SO;2
to-day variation of daily mean values for S0^2-S/S02-S, N03-N/N02-N, oxidant
concentration and relative humidity at Kumagaya, Ichihara and Kawasaki.  These
                                     53

-------
0.15

E
Q.
a.
c
50.10
TJ
ll
1
c
o
50.05
XJ
&
n
X
X X
X X
xx x



X X
X X
X X
X
X X
X XXX X
X XXX X
X
                       246
                Particulate  NQjN  Concentration
8
 Figure 3.   Relationship of participate HO^ concentration  at
       IPH  versus daily maximum oxidant concentration.
cn
0
"oj
to*
u
5
u
z
in
o
rn fj
(5 U(
X
X

•»" "
..•»«
x«
ox o
o
0 °
o
.0
D 1 2
             Particulate  NO}N Concentration
Figure 4.   Relationship between daily mean concentrations  of
     gaseous and particulate NOs on January 1-24,  1976.
     X IPH
     o Tokyo Metropolitan Institute of Environmental  Control
                             54

-------
 values  show  that  SOi;2-S/S02-S  correlates well with  humidity  rather  than  with
 oxidant level.  The  N03-N/N02-N,  on  the other hand,  shows  some  correlation  with
 oxidant level.  The  author  found  that  nitric acid vapor  is collected  on  glass
 fiber filter and  thus  a  portion of particulate  nitrate comes  from nitric acid
 vapor in  the atmosphere.
                          oKUMAGAYA
                                olGUSA
                             TOKYO ._„>
                                  ol.PH.
                                         .MT.TSUKUBA
         Figure 5.   Area surrounding Tokyo where survey of atmospheric
              constituents was conducted June 25 - July 7, 1975.

                                    REFERENCES

1.   Mull in, J.B. and J.  P. Riley.  The spectrophotometric determination of
     nitrate in natural waters, with particular reference to sea water.  Analyt.
     Chem. Acta 12, 1955. pp. 464-480.

2.   Ota, T., R. Ishibashi and M. Osaki.  Determination of nitrate ion using
     hydrazine reduction  technique.  J. Japan Soc. Air Pollution 1, 1970.  pp.
     72 (in Japanese).

3.   Liu, B.Y.H. and K. W. Lee.  Efficiency of membrane and nucleopore filters
     for submicrometer aerosols.  Particle Technology Laboratory Publication No.
     266, 1975.

4.   Okita, T. and S.  Morimoto.  Measurement of nitric acid and particulate
     nitrate in the atmosphere.  Preprint of Autumnal Meeting of Met. Soc. of
     Japan, 143, 1973 (in Japanese).

5.   U. S. Environmental Protection Agency.  Ambient air quality standards.
     Reference method for determination of nitrogen dioxide.  Federal Register
                                      55

-------
     38, 1973.   pp.  15174-91.

6.    Environment Agency of Japan,  Study Committee of Contaminated Precipitation.
     Report of Study of Contaminated Precipitation in 1975, 1976.  (in Jap-
     anese) .
o -
/I
M








40
30
1
3 20
1

O* 10

n
\
R-H- KUMAGAYA ' .
\fl}) I
i
/ •
/ \
f
90, ' '
\ { \
1 Rs / I
\\ '' \ "
-Xk^-'A >• •
A A- -

^^L O LI ^r ^i
-70 *xj /

1 1 1 1 1 1 1
016


014


012
to
en
Q10 &
*. N; "g
008 ^ I1
^ z
Q06 ^ ~
v-x 2
\
C/3 i rt
004 O
i

jy}

KUMAGAYA



- Ox

(pphm)

-8 ft R N
. t
' i
/ \
/ 1C l
'H -^Xx '


, t i i i i i



RN
X
•2.
010 2

o
u 1
0.08 '
<§
Q06 ^
\
004 O
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1
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0.02 if

V_-*
002 1* ° 25 26 30 1 2 3 7 °
^ JUNE JULY
n
25 26 30 1 2 3 7
JUNE JULY





40
^ 30
c/)
i 20
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10

0
rioo o
R H '\
Rs / i
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9°\ / \ -
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9
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ICHIHARA
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(pphm)'V
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0.08
0.06

Oj04
0.02


       25  26  30  1   2   3   7

     JUNE         JULY
  25   26  30  1   23    7

JUNE         JULY
      Figure  6.   Day  to  day  variations  of Rc.,  R ,  oxidant concentration
                and  relative humidity--Kumagaya and Ichihara.
                                     56

-------
Oo
3
C/l

20 -
    10
o 0.4 6
VK
R.H.
^l KAWASAKI
' \\
\
-90 V
\ Rs
1 o
\ /\R.H.-
f /®T-*
\ J \ '
\ /s> 20
Z
1
d* 10
z
0 -u
KAWASAKI




' Ox
( pphm) 0
y \
"/X .^-"x "
yx^x\ c^*^* \
o \ N
\ ^^--o
	 LJ 	 1 	 1 	 ifl- —0^ 	 1 	 1 	
        25  26  30   1   2   3   7

      JUNE          JULY
                                            25  26  30  1   2   3   7

                                          JUNE         JULY
     Figure 6.   Day  to  day variations of R  , R  . oxidant  concentration
                      and relative humidity--Kawasaki.
                                                                          • 0.20
                                                                        o.io
                                      57

-------
                                                                            2-4
        A PORTABLE  INSTRUMENT  FOR  THE  CALIBRATION OF OZONE ANALYZERS
                     BY OPTICAL  ABSORPTION  MEASUREMENTS

                K. H. Becker, A. Heindrichs,  and  U.  Schurath*


ABSTRACT

     An -inA&uunent  ^on na.pi.d c&tibfiCLtionA o^  ozone, analyzes, oveA the. conc.e.n-
tsiation fianQe,  10 ppb to -ieve/io£  ppm u, deAcsubed.  It tnctudeA a photoc.he.micj&t
ozone- 4ouA.ce.  The.  ozone. conce.ntMtA.on u* catcalate^d ^fiom the. optical, ab^o-tp-
tion o£ monochromatic 253.7 nanometer  mediation,  06 me.cu>uAe.d -in a. tubuJLaSi ab-
boiption ceJUi.  Due. to  fvapid iej>pon&e.,  the. -in&tnwment  pavticu£ci>i£y
i>iiLte.d fion. the. catibtt&tion o&  c.hemitLwine.Ac.e.nt ozone. ayiaLyzeAb m£h bhoht tune.
                                 INTRODUCTION

     Ozone measurements in  Europe  indicated  in  1973 that the ozone (03) con-
centration was frequently considerably  higher than the natural background con-
centration of 20 to 40 ppb  at  ground  level,  and on some occasions exceeded
the 200 ppb level above which  health  effects  are manifest (1).  This releva-
tion initiated an international  program for  the investigation of the oxidant
situation in a number of European  countries  with the aim of recommending
control strategies.  Since  then  the number of monitoring stations for 03 in
the German Federal Republic and  other European  countries was considerably
increased.  Nearly all 03 analyzers in  the stations are based on the chemilumi-
nescent reaction of 03 with ethylene  which is particularly suited for continu-
ous monitoring.  Such analyzers  are not by principle absolute detectors and
must be calibrated.  Furthermore,  sensitivity changes must be anticipated
under continuous operating  conditions.   These changes cannot be totally elimi-
nated by re-calibrations with  a  built-in 03  generator which can lack stability.
In addition, 03 losses can  occur in the sampling line and dust filter.

     Calibrations of 03 analyzers  are usually made by comparison with the
hydrogen iodide (HI) method.   The  stoichiometry of this wet chemical reaction,
at 03 concentrations below  500 ppb, is  approximately the following (2,3):

         03 + 2 I" + 2 H+ + I2 + H20  +  02                               (1)

     The procedure, apart from its well known error sources (4), has all the
disadvantages of an integrating  method:  the  calibration is time consuming and
must be performed with an 03 source of  highly constant output, whereas  an ad-
vantage of chemiluminescent analyzers is, in  particular, their short response
time.	
*Institut fur Physikalische Chemie der  Universitat Bonn, Bonn, Germany.

                                      59

-------
     This paper presents a reliable technique for the calibration of 03 anal-
yzers which eliminates the disadvantages of wet chemical methods.  It measures
optical absorption by 03 using an ultraviolet means, a method frequently used
in laboratory experiments (5,6).


                        THE PRINCIPLE OF MEASUREMENT

     The highest absorption coefficient of 03 in the Hartley band nearly
coincides with the wavelength 253.7 nanometers (nm) of the mercury resonance
line.  The absorption obeys Beer's law, due to the continuous nature of the
absorption spectrum in this region.   The recommended value of the absorption
coefficient at 253.7 nm is defined by Equation 2.

         log10(I/I0) - k x p 273/T                                     (2)

(T = temperature in K, x = absorption path in cm;  p = ozone pressure in atmo-
spheres), is k = 133.9 atirr^crrr1  (7).   This value obtains support from numer-
ous determinations (8) and agrees well with k = 134.5 atm-^cnr1 measured in
this laboratory (5).  At an optical  path length of 3 m and 20°C, 100 ppb 03
causes an intensity reduction of 0.89% relative to pure synthetic air.   Weak
intensity reductions can be measured reliably at 253.7 nm, provided a low
pressure mercury lamp of sufficient stability is used.  The suitable concen-
tration range of 10 to 500 ppb 03 can thus be covered.


                                EXPERIMENTAL

     The experimental setup is shown schematically in Figure 1.  Ozone is pro-
duced in synthetic air by means of a simple but efficient photochemical 03
generator with an elliptical reflector.  The sampling gas then flows through
a light protected glass tube of 1500 mm length.  Radiation from a low pressure
mercury lamp (Oriel type C-13-61) in a brass housing is collimated along the
axis of the tube through a metal  capillary.  The light is reflected at the far
end of the glass tube by a quartz triple prism which has the advantage over a
plane mirror that the angle of reflection is always 180°.  Therefore no adjust-
ment of the prism is necessary, and the intensity of the reflected light is
nearly independent of the angle of incidence on the prism surface.,  The return-
ing light beam is deflected 90° by a plane mirror through a quartz window and
interference filter for 253.7 nm on the cathode of a photomu'ltiplier tube (EMI
9665 B).  The light reaching the photomultiplier is better than 99.9% monochro-
matic since 95% of the lamp output is at 253.7 nm, and the interference filter
blocking ratio is 1:104.  The effective absorption path is 3100 mm.  All metal
parts exposed to the gas stream are teflon coated.  The volume of the optical
cell including both the entrance and the exit chambers is 180 ml, giving a
residence time of 11 s at a typical  flow rate of 1000 ml/min.  Decay measure-
ments in the absorption cell at stopped flow resulted in a lifetime of 70
min., increasing to 100 min. after 1 hour exposure to ozonized air.  The
systematic error due to heterogeneous decomposition of ozone in the cell is
therefore less than 0.3%.
                                      60

-------
     To determine 03 in the concentration range below 500 ppb, intensity
 reductions below 4.35% must be measured.  A well stabilized high voltage
 supply for the photomultiplier tube, and a stable light source are therefore
 needed.  A selected low pressure mercury lamp of the above-mentioned type was
 found adequate after a short period of conditioning, and at a constant line
 voltage.  Intensity changes below 5% are conveniently measured by compensating
 95% of the voltage across the photomultiplier anode resistor at full intensity
 IG with a battery.  The remaining signal is amplified and displayed on a strip
 chart recorder which is then deflected full scale at 5% optical absorption.


              CALIBRATION OF A CHEMILUMINESCENT OZONE ANALYZER

     A Bendix 03 analyzer, Model 8002, was calibrated in the 500 ppb range and
 below.  The coupling of the analyzer to the optical measuring cell is shown in
 Figure 1.   Both instruments were run with time constants of 1 s.  The synthetic
 air flow rate was 108 liter/hour.  The calibration procedure is illustrated by
 the strip chart recordings of the signals from both instruments in Figure 2.
 Stepwise changes of the 03 concentration in the sampling gas were achieved by
 shielding or unshielding part of the mercury lamp in the 03 generator.  The
 intensity I0 was checked in between the measurements by completely shielding
 the mercury lamp in the generator.   A drift of I0 could thus be taken into
 account by linear interpolation.  The calibration of the 03 analyzer, as de-
 picted by the recordings in Figure 2, was completed within 11  minutes.  Figure
 3 shows the resulting plot of chemiluminescent analyzer signal versus the
 optically measured 03 concentration, as calculated from the recordings by
means of Equation 2.   The slope of the straight line gives the sensitivity of
 that particular analyzer as 1.88 V per ppm 03, with a standard deviation of
+ 2.5%.


              COMPARISON WITH THE POTASSIUM IODIDE (KI) METHOD

     The potassium iodide (KI) method is widely considered an absolute method
 for 03 measurements,  since, under suitable conditions, the stoichiometry given
by Equation 1 is closely obeyed.  In practice, however, the KI method often
 leads to serious errors, as was shown recently on occasion of a monitoring
program in the U.S.  (9).   (One of the probable reasons for such errors is that
the sensitivity of chemiluminescent analyzers is reduced by a factor of nearly
2 when oxygen is used as test gas instead of synthetic or purefied air (10).)
The precision of the  optical method for 03 determination depends, in principle,
only upon  the reliability of the absorption coefficient at 253.7 nm used in
 Equation 2.   Determinations of the absorption coefficient are based on ele-
mentary physical measurements such as the length of the absorption path, the
pressure of 03, and the temperature.  The relatively wide error limits of the
absorption coefficient, +_ 1.5%, are mainly due to the difficulties inherent in
the production and handling of pure 03.  The 03 concentration is deduced from
the pressure increase after complete decomposition into molecular oxygen.

     A direct comparison between optically measured 03 in synthetic air and
measurements by the KI method resulted in good agreement between the two
methods.


                                      61

-------An error occurred while trying to OCR this image.

-------
 -p

 00.8
 0)
 N

^0.6
 0)

 OQ.4
 N
 o
 O
   0.2
tn
-H
                100     200     300     400  ppb

                      ozone concentration

 Figure 2.  Calibration of a chemiluminescent ozone analyzer,  (a) Absorp-
 tion by ozone at 253.7 nm in the cell, (b)  Corresponding signal of the
 chemiluminescent ozone analyzer in series with the cell.
                           63

-------
 CAP


 e
ro
LT)
04
  *

-M
 C
 O
•H
-P
 C^
 JH
 O
 w
   4


   3


   2


   1



   O
 S  °-8
      .6
 c
 O
 N
 O
 C
 Cn
-H
0.4
    0.2
                           /•»*
                 2468
                    time  (minutes)
                                          10
Figure 3.  Calibration curve,  calculated from the recordings in Figure 2,


                               64

-------
                               ACKNOWLEDGEMENT

     The authors express their thanks to J. Lobe! and A. Wiese for their valu-
able assistance.  The 03 meter was developed as a part of a research programme
on photochemical smog formation in the German Federal Republic, supported by
the "Bundesministerium des Innern."

                                  REFERENCES

 1.  Becker, K. H., and U.  Schurath.   Entsteht Photochemischer "Smog" in der
     Bundesrepublik Deutschland?  Umschau 73:310, 1973.
 2.  Leithe, W.  Die Analyse der Luft und ihrer Verunreinigungen in der
     freien Atmospha're und am Arbeitplatz.   Wissenschaftliche Verlagsgesell-
     schaft mbH, Stuttgart, 1968.
 3.  Methods of Air Sampling and Analysis.   Published by American Public Health
     Association, 1015 Eighteenth  Street, N. W., Washington, D. C., 1972.
 4.  Perry, E.  P.,  and D.  H.  Hern.   Stoichiometry of ozone-iodine reaction:
     Significance of iodate formation.   Envir.  Sci.  Technol.  7:65 and 647,  1973.
 5.  Becker, K. H., U. Schurath, and H.  Seitz.   Ozone-Olefin Reactions in  the
     Gas Phase.  1.  Rate  Constants and Activation Energies.  Int. J. Chem.
     Kinet.  VI:725-739,  1974.
 6.  Hames, P.  Thesis, Technische  Universitat Munchen/DECHEMA Institut
     Frankfurt, 1975.
 7.  Hampson, R. F., Editor.   Survey of photochemical and rate data for twenty-
     eight reactions of interest in atmospheric chemistry.   J. Phys.  Chem.
     Ref.   Data 2:267-311,  1973.
 8.  Hudson, R. D.   Critical  review of  ultraviolet photoabsorption cross
     sections for molecules of astrophysical interest.   Rev.  Geophys.  Space
     Phys.   9:305,  1971.
 9.  Stephens,  Edgar R.,  and Arthur M.  Winer.   The Oxidant  Measurement
     Discrepancy.  California Air  Environment 6(1),  1975/76.
10.  Schurath,  U.,  and W.  Wendler.   liber die Verwendbarkeit von ozonhaltigem
     Sauerstoff zur Kalibrierung von  Ozonanalysatoren.   Staub-Reinhalt.
     Luft  35 (9):329-310,  1975.
                                      65

-------
                                                                              2-5
               STATUS OF CALIBRATION METHODS  FOR  OZONE MONITORS

                  R. J. Paur, R. K. Stevens,  and  D.  L.  Flamm*
 ABSTRACT
      The n neutral-bu^ered potaAAium i.odide  federal Reference Method &or
 calibrating ozone. monAton, kcu> been widety  criticized ^or itA  A&iong bttoad ab*ox.ption band £n the. 200-300
 nanome.teA ie.Q4.on.   The. go* pha^e. titnation  te.c.hntqu.e. nztia.* on the. weJtt known
 ie.acti.on o& n-l&iogen oxA.de. wtctfi ozone.  Go* pfuue tAtAa&ion and ul&iav-ioJlLet
 photometry yieJLd compa^ab£e sie.aZt& oveA an ozone, conce-ntsiation stange. ofi 0.05
 to 0.7 ppm.  Re.ce.ntty, undeA Environmental.  Vnotz.ctA.on Agency t>pon*ouhip, a
 modsifii.e.d potaAAium iodide, method ha* been developed.   In ptieJLimjian.y 6tu.die.-i>,
 the. new method appeau to be accurate and precise over the ozone concentration
 fiange o$ 0.1 to 1.0 ppm.


                                 INTRODUCTION

      The Federal Reference Method for determining ozone (03) concentrations in
 synthetic atmospheres used to calibrate 03  monitors  is the U neutral-buffered
 potassium iodide (1% NBKI) procedure as described in the Federal Register 36
 (228):   22384-22397, November 25, 1971.  This  calibration method is based on
 the spectrophotometric determination of iodine released from an NBKI absorbing
 solution of 03.

      The 1% NBKI method has been widely criticized for its inconsistent re-
 sults.   (See Figure 1.)  In late 1973 it was discovered that state and local
 agencies in the Los Angeles area were obtaining significantly different esti-
 mates of 03 concentrations in that area.  These differences were traced to
 different KI calibration methods used by the various agencies.  As a result of
 those findings, some half dozen studies have been carried out since mid 1974
 to determine the accuracy of various KI methods.   The results of some of these
 studies are summarized in Table 1.
*R. J. Paur, R. K. Stevens,  Environmental  Protection Agency, Research  Triangle
 Park, North Carolina.
 D. L. Flamm, Texas A&M  University,  College Station, Texas.


                                       67

-------
    tn
I .20 -
1 . IE-
i—
0.
^1.12-
3
" 1 . 0B -
1 I .0H-

1.00-
0 . as -
c
r
CDMPRRI5QN DF Kl Nl


\
*'T

In
. a

M



4


'{ i



a 3~ m 3^ m 3-
n — — rvi
"^ •>» •** -s "* "«»
m 3- 3- 3- 3- 3-








TH EPT

*




4


j



m 3-
rvi
3- ui



.,,



m
Url
                                           DflTE
     Figure 1.   Comparison of potassium iodide with gas phase titration.


     Table 1 illustrates that the 1% NBKI method run under dry conditions
(i.e. the Federal Reference Calibration Method) gives results approximately
10% greater than ultraviolet (UM) photometry or gas phase titration (GPT).   It
should be remembered that all of these studies were run under ideal conditions,
and that in normal usage the precision of the method may well be less than
that indicated by the Table.

     In addition to the KI studies, the U.S.  Environmental  Protection Agency
(EPA) and other groups have examined several  other methods  for determining the
03 content of calibration atmospheres.  Two of these methods, LIV photometry
and GPT, have been in use for some time and are generally considered to be
valid methods.  A third method, 1% boric acid buffered potassium iodide (1%
BAKI) is new and is in the preliminary stages of evaluation.


                           ULTRAVIOLET PHOTOMETRY

     Ozone lends itself to UV photometry due to its strong  broad absorption
band in the 200 to 300 nanometer (nm) region.  The peak of  this band very
nearly coincides with the 254 nm radiation of low pressure  mercury (Hg) dis-
charges.  In spite of the high absorptivity of 03 at 254 nm (133.9 cm-1
atm s base 10), the UV photometer must have capability to  resolve changes in
transmittance of less than 1 part in 104 if ozone concentrations to within 5
                                      68

-------
  TABLE 1.  COMPARISON OF VARIOUS KI DETERMINATIONS WITH UV PHOTOMETRY OR GAS
                                PHASE TITRATION

Study
Baumgardner, et al
Baumgardner, et al
Baumgardner, et al
Baumgardner, Paur
Baumgardner, Paur
Baumgardner, Paur
Baumgardner, Paur
CARB, El Monte
Hodgeson
Beard
Smith
Hughes
KI Method
V/o NBKI
2% NBKI
2% NBKI
1% NBKI
1% NBKI
2% NBKI
2% NBKI
1% NBKI
2% NBKI
2% UBKI
V/o NBKI
1% NBKI
1% NBKI
1% NBKI
Reference
Method
GPT
GPT
GPT
GPT
GPT
GPT
GPT
UV
UV
UV
UV
GPT
GPT
GPT
Ratio0
1.01
1.04
0.61
1.05
1.12
1.13
1.18
1.25
1.29
0.96
1.11
1.08
1.11
1.0
KI
Reference
+ 0.04
+ 0.03
+ 0.04
+ .05
+ .07
+ .03
+ .05
a
a
a
+_ .01
+ .035
+ .02
b
03Conc.
Range, ppm
0.1 - 0.5
0.1 - 0.5
0.1 - 0.5
0.4
0.4
0.4
0.4
0.1 - 0.8
0.1 - 0.8
0.1 - 0.8
0.05-10.1
0.08- 0.8
0.2 - 0.4
0.2 - 0.4
Relative
Humidity
0
0
0
0
40-60%
0
40-60%
50%
50%
50%
0
0
0
0

a.  These workers also report intercept data which indicates a constant
    additive bias.
b.  Variable depending on sampling time and color development time.
c.  There is no absolute standard for ozone in the sub-part-per-million range.
    Therefore, precision of calibration procedures is determined by the
    reproducibility of measurements while the stability of the ozone
    concentration is monitored by ambient air ozone monitors.  The accuracy
    of ozone calibration procedures at the sub-ppm level  is estimated from
    the degree of agreement between two or more procedures that are accurate
    at ozone concentrations which can be monitored manometrically.  UV
    photometry and gas phase titration are methods of high precision; they
    are accurate at high ozone concentrations; they agree well at sub-ppm
    ozone concentrations so they are assumed to be accurate at low concen-
    trations.   For these reasons the results of most potassium iodide studies
    are reported in terms of KI values relative to UV photometry or gas
    phase titration values.

                                      69

-------
ppb using a pathlength consistent with an easily portable instrument are to be
measured.  At least one such photometer, which with minor modifications
appears to have the capacity for suitable accuracy, is commercially available.


                             GAS PHASE TITRATION

     Gas phase titration techniques rely on the well  known reaction of CL with
nitric oxide (NO):
nNO
                                  (n - m)NO
The reaction can be monitored by determining either the amount of NO consumed
or the amount of nitrogen dioxide (N02) produced.   Standard reference materials
(SRM) for NO are available from the National Bureau of Standards  (NBS) in the
form of cylinders containing 50 to 100 ppm NO in nitrogen (N).   A nitrogen
dioxide (N02) SRM is available in the form of a permeation tube.   In addition
to NO and/or N02 standards of known accuracy, GPT methods generally require
accurate flow measurements to determine the degree of dilution of the standard
in the calibration system.

     Figure 2 presents a typical comparison of 03 concentrations  determined by
UV photometry and GPT.  The slope of the curve is approximately unity and the
small scatter about the curve attests to the precision of both analyses.
Results similar to those in Figure 2 have been obtained in several  laboratories
and are summarized in Table 2.
        a:
        LJ
        LJl
        a:
        in
        en
        in
         V.
        31
        CL
        a.
         ^,
        n
        a
   0.B--


   0.7-


   0.E-


   0.S-


   0.H-


   0.3-


   0.2-


   0.1-
            0.0
                    CDMPRRI5DN  DF  EPT  RND  UV
                    DZDNE  DETERMINATIONS
                     SLOPE  - I.003
              -  I
1    E/30/7S
2   7/0 I/7S
3   7/02/7S
H   7/03/7S
               0.0   0.1   0.2   0.3   0.H   0.S   0.E   0.7  0 . B

                          D3/PPM/UV   PHDTDMETER

  Figure 2.    Comparison of gas phase  titration  and UV  ozone determination.
                                      70

-------
            TABLE  2.   COMPARISON  OF OZONE DETERMINATIONS BY GAS PHASE
                          TITRATION WITH UV  PHOTOMETRY
  Study
03 Con.
Range, ppm
                                               Results
  Paur*



  DeMore


  Hodgeson


  Stedman
0.06 - 0.7



0 - 1


0 - 10
       = 0 -009 ± -004)  (°3)uv-  (°-002 ± °-002)

(03)= (1.001  + .007)  (03)uv-  (0.005+0.003)

               + -02)  (03)uv


               - '02)  (°3)uV

                   yv
QpT

GPT
              (°3)
              (Q3)GPT= d.o)  (O3)
  *  Two  separate  4-day  studies  using  different NO standards and different
    system  flows.
                         BORIC ACID POTASSIUM IODIDE

     The ]% boric acid potassium iodide (BAKI) method is similar to the 1%
NBKI method except for replacing the phosphate buffer with 0.1 M boric acid.
The results obtained from the BAKI method differ from the NBKI results in
several important aspects.

     The NBKI method yields results some 10 percent greater than the BAKI
method at the 0.5 and 1.0 ppm levels.   In studies conducted at Texas A&M Univ-
ersity, the BAKI results were in good (+_ 3 percent) agreement with a Dasibi  03
monitor set up to run as an absolute photometer.   This Dasibi instrument was
later compared with an 03 calibration system at EPA headquarters in Research
Triangle Park, N.C. (EPA/RTP) and results agreed to within + 2 percent.

     The color development of the NBKI method continues for some 15-30 minutes
or more after completion of sampling,  and by the end of color development the
NBKI results may be more than 20% greater than the photometer results.  In
contrast the BAKI color development appears to be stable by the time the
absorbing solution can be transferred to curvettes.  The change in absorbance
in the NBKI method may be due to decomposition of an intermediate species
formed during sampling.   A preliminary study of this phenomena indicates that
decomposition of hydrogen peroxide occurs at approximately the same rate as  is
required to explain the time dependence of the absorbance.

     The Texas A&M studies  also indicate that the BAKI method yields the same
                                      71

-------
results when using fritted bubblers as when using "midget impingers"; the NBKI
method has been criticized for yielding different results with different kinds
of absorber glassware.

     A preliminary study of the BAKI method has been carried out in the EPA/RTP
laboratories to compare BAKI results with an 03 calibration system that utilizes
both GPT and UV photometry to provide a reliable estimate of the 03 concentra-
tion.  For 50 data points (29 at ~500 ppb, (5 at ~250 ppb and 15 at ~120 ppb),
the average ratio of BAKI results to photometric results was 1,.016 with a
standard deviation for the ratio of 3 percent.

     The new BAKI method is currently being examined with respect to its
stability under changes in relative humidity.   Further studies will examine
the sensitivity of the method to impurities in  the reagents.  This last point
is of particular interest since the BAKI results were approximately 10% lower
than the photometric results at the 0.1 ppm level in the Texas A&M study; the
ratio of BAKI results to UV photometry results  did not show any discernible
concentration dependence in the EPA/RTP results.
                                      72

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            SESSION 3
SOURCES OF TROPOSPHERIC OZONE - I
               R.A. Rasmussen
   Washington State University
               73

-------
                                                                             3-1
            METEOROLOGICAL CONDITIONS CONDUCIVE TO HIGH LEVELS  OF  OZONE

                          T.  R.  Karl and G. A. DeMarrais*

ABSTRACT

     AeJtome.t'Lic  data aAe. c.onAtd&fie,d ^on. two tocationA:  Los kngeJLeA  and St.
louM>.  NumesiouA  AtudteJ* o&  photochemical. oxA.da.nt, o{te.n catie.d  Loi>  AngeJLeJ,
-6mog, one.  brought together to de.pi.ct the me.tz.osiologtc.al. e.^e.ctA  on ozone, con-
ce,ntsiattonA.   Re.ce.ntty obtaA,ne.d data fifiom the. Envvionme.ntal. P?iote.ction  Agenct/'^
Regional kin.  Pottu.tion Study OA.Q. Au.bje.cte,d to fm.QtieAbi.on anatyAeA  to &oit oat
the. mzte.oMl.ogi.cal. vaJtiableA that asie. conducive, to high. te.ve.&> ofa  AuAfaace
ozone..

                                   INTRODUCTION

     The  ozone/oxidant problem, starting with a plant damage  investigation (1),
has been studied for 30 years.   The photochemical aspects were partially under-
stood a quarter-century ago  (2).  Beginning with specialized  forecasts  in 1952
and daily  forecasts in 1953, the meteorologist was predicting  when ozone con-
centrations [03] would be bothersome to people (3).   By 1954,  there  was a
compendium on the meteorological aspects of the ozone problem  in  Los Angeles
(4) and a  report on one of the largest field programs on the  three dimensional
variation  of  oxidant and meteorology in the LA Basin  (5).  Space  limitations
prevent the enumeration of all  the field studies that have been  conducted,
but the spatial  coverage and results indicate that high [03]  are  a nationwide
affliction.

     Observed levels of [03] are higher in California than in  the  rest  of the
nation.  The  literature on the meteorological aspects of the  ozone problem in
California, particularly in  the LA Basin, is plentiful, but a  composite pic-
ture does  not exist.  Such a picture, based on existing information, is pre-
sented in  this paper and will be referred to as the Pipe-Mix  Model.

     A second major section  of this report is an examination  of  various meteor-
ological variables related to [03] for a 25-station network in St. Louis (STL).
This data  set was chosen for study because of the high quality and large quantity
of aerometric data within an urban and rural environment outside  the LA area.

               THE PIPE-MIX MODEL OF THE LOS ANGELES OXIDANT PROBLEM

     A review of the literature indicated that an understanding  of various
*Environmental Protection Agency,  Research Triangle Park, North Carolina.
 The authors are on assignment with  EPA from the National Oceanic and Atmospheric
 Administration, U.S. Department of  Commerce.

                                       75

-------
parts of the ozone problem in LA existed.   There  are  two main  meteorological
processes contributing directly to the problem—horizontal  transport and vertical
mixing (abundant solar radiation away from the  immediate coast is  an everyday
phenomenon in the Basin in the summer, so  its  contribution  to  [03] does not
vary).  The horizontal transport aspect has been  called the "pipe  reactor
effect" (6).  Vertical mixing accounts for the  mixing of air aloft with that
at the surface.   The detailed descriptions and  pictorial presentations that
follow are called the Pipe-Mix Model  (July conditions are presented).

     The basic elements in the Pipe Reactor Effect (Figure  1)  are:

     •    The average wind speed in the Basin  is  7 mph (7).

     •    Sunlight is of sufficient intensity  to  initiate photochemical reactions
          early in the morning (8).

     •    Production exceeds destruction of ozone in  this contaminated layer
          during the period 2 to 7 hours after  the photochemical  reaction is
          initiated (9).   The time when the production first exceeds destruction
          (in the summer)  is around 8 a.m. (8).

     •    The daytime surface wind patterns are so persistent  that the reactive
          air mass moving  downwind under the subsidence inversion  can be
          considered as moving in a pipe (6).

     This pipe reactor effect means:

     •    Primary emissions in upstream locations result in problems further
          down the pipe,  and

     •    The resulting [03] are cumulative.

     The basic elements in the Vertical Mixing  Effect (Figure  2)  are:

     •    There is a reservoir of ozone aloft  that can be brought  down by
          vertical mixing.  In 1954,  ozone aloft  was  restricted to the volume
          below the inversion base (5), but now the inversion  is  a major re-
          servoir of ozone aloft (10, 11,  12).

     •    The reservoir extends from Coastal Ventura  and Los Angeles County
          to the mountains north and east  of Los  Angeles.  Its presence to
          the west and northwest of Los Angeles was shown by Lea  (10).  The
          movement from Los Angeles to Coastal  Ventura County  was  shown to
          occur by Kauper  and Niemann (13).  Winds aloft data  during night-
          time hours for Santa Monica and  Long  Beach  (14) show that this
          movement is a frequent occurrence.  During  the day the movement
          is in the opposite direction and the  highest concentrations in the
          Basin are generally over the eastern  part (11, 12).

     t    [03] aloft remain relatively high throughout the  night  (10, 15, 16),
          as there is very little ozone destruction aloft.
                                     76

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     •    [03] aloft vary spatially and from day to day (10, 11, 12, 15).
          The spatial variations are due to the various methods and places
          through which the ozone gets into the layer aloft (10, 11, 17).
          Prediction techniques based on historical data (18, 19, 20) show
          that the highest ground level concentrations occur when the 500-mb
          level (on the average, about 5.6 km above the surface) is relatively
          high, is warm, and is marked by a weak pressure gradient.  This
          condition would likewise mean that the air aloft is stagnant (ozone
          accumulates).  Variations in rates of accumulation account for day-
          to-day differences in concentrations aloft.

      •    Vertical mixing extends to much greater heights over the eastern
           than over the western part of the Basin during the day (11, 12, 21).
           Climatological  data (7) for the Basin show the average diurnal
           temperature ranges are 10° to 15°F in the western areas, whereas
           they are 30° to 38°F in a very large part of the eastern section.
           Surface-based inversions with negligible vertical mixing occur  almost
           every night where the range of temperatures is large and are relatively
           infrequent in the west in July.

      •    Vertical mixing that gives a dilution benefit when it mixes surface
           air with cleaner air aloft is a detriment when the concentrations
           aloft are higher than those at the surface.  In the western part>
           of the Basin, because the increase in mixing height is small during
           the day (22) and because the [03] in the affected volume aloft  are
           relatively low, the ground level concentrations are not increased
           markedly in the typical situation (occasionally easterly winds
           aloft move the higher concentrations to the west and vertical mixing
           brings the high concentrations to the ground) (16).  In the east,
           where the daytime mixing occurs to greater heights and the [03] aloft
           are relatively high, the ground level concentrations can be increased
           markedly.

      The combined parts of the pipe-mix model demonstrate the synergistic
effect of the two meteorological parameters, horizontal transport and vertical
mixing, in the observed levels of  [03] in the area.

      METEOROLOGICAL CONDITIONS RELATED TO OZONE CONCENTRATIONS IN ST. LOUIS

 DATA

      As part of the Environmental Protection Agency's (EPA) Regional Air
 Pollution Study (RAPS) in St. Louis, a network of 25 Regional Air Monitoring
 Stations (RAMS) continuously record aerometric data.  Surface measurements
 of [03], wind direction and speed, and global radiation (global radiation is
 defined as the total of direct plus diffuse sky radiation received by a unit
 horizontal surface), as well as the vertical temperature gradient near the
 surface (5 to 30 meters), were derived from the RAMS network during the period
 July 1, 1975 through September 15, 1975.  The locations of the stations in
 the network and their associated land use are shown in Figure 3.
                                      79

-------
                                               122
                  INDUSTRIAL. GENERALLY IS STORIES •
                  RESIDENTIAL, GENERALLY 2 STORIES

                  COMMERCIAL. > 10 STORIES

                  SINGLE FAMILY DWELLING 1 STORY
                  UNDEVELOPED OR AGRICULTURAL
                  AREA
118
                                                                          •
                                                                          123
               01  23 45
           MILES
                 0 1 2
                           10
         KILOMETERS
                                               124
                                               •
        Figure 3.   Station locations  and land use  in  the St. Louis area
                          (modified from Reference  23).

     Additional data were acquired from the National Weather Service at  Lam-
bert Airport,  which is approximately  5 km northeast of  Station 120.   Synoptic
charts of various  other meteorological  variables, prepared  by the National
Meteorological  Center, were also  employed.

     In the  RAMS  network each station  was visited at least  twice weekly  for
routine maintenance.  The data from each station were checked by computer
programs (24)  and by visual inspection to eliminate erroneous values.

RESULTS OF THE ANALYSIS

     A stepwise regression technique  was employed as a  means of sorting  out
the role played by various meteorological variables with regard to surface

                                        80

-------
[03].  At each  station ozone concentration was used as the  dependent variable.
Table 1 lists all  the variables subject to entry into the regression equations,
      TABLE  1.   VARIABLES SUBJECT TO  ENTRY INTO THE REGRESSION EQUATION
           [03]


           TMAX

           WS
AVERAGE OZONE CONCENTRATION (ppb) BETWEEN 1000
AND 1500 LOCAL DAYLIGHT TIME (LOT).

DAILY MAXIMUM TEMPERATURE AT LAMBERT AIRPORT (°C).

AVERAGE SURFACE WINDSPEED (m/sec) ACROSS THE RAMS
NETWORK BETWEEN 0800 AND 1500 LOT

SQUARE ROOT OF THE NUMBER OF DAYS SINCE THE LAST
MEASURABLE PRECIPITATION OCCURRED AT LAMBERT
AIRPORT

SQUARE ROOT OF 10 TIMES THE AVERAGE GLOBAL RADIA-
TION (lang/min) BETWEEN 0800 AND 1500 LOT DETERMINED
FROM STATIONS 103, 104, 107, 114,  118, AND 122.

SQUARE ROOT OF THE NUMBER OF DAYS SINCE THE LAST
COLD FRONT PASSED ST. LOUIS

HEIGHT OF THE 500 mb SURFACE (FEET ABOVE SEA LEVEL)
OVER ST. LOUIS AT 0700 LOT

24-HOUR CHANGE (FEET) IN THE HEIGHT OF THE 500-mb SUR-
FACE FROM THE  PREVIOUS 0700 LOT OBSERVATION.
           AT       - TEMPERATURE (°C) AT 30 METERS MINUS THE TEMPERA-
                     TURE AT 5 METERS AVERAGED ACROSS STATIONS 109, 111,
                     AND 112 DURING THE PERIOD 1000 TO 1500 LOT.

           YNRAIN   -- REPRESENTS WHETHER OR NOT MEASURABLE PRECIPI-
                     TATION FELL BETWEEN 1000 AND 1500 LOT. THE VAR-
                     IABLE EQUALS 1 IF IT DID OCCUR AND 0  IF IT DID NOT
                     OCCUR.

           WD       - FRACTION OF TIME DURING THE PERIOD  0800 TO 1500 LOT
                     WHEN THE SURFACE WIND BLEW > 1 m/sec FROM THE EIGHT
                     SECTORS LISTED BELOW. WIND DIRECTION WAS DETERMINED
                     BY AVERAGING ALL 25 STATIONS.
VARIABLE
N
NE
E
SE
SECTOR (+22.5°)
360°
45°
90°
135°
VARIABLE
S
SW
W
NW
SECTOR (+22.5°)
180°
225°
270°
315°
           CALM     -- FRACTION OF TIME DURING THE PERIOD 0800 TO 1500 LOT
                     WHEN THE SURFACE WIND SPEED IN THE RAMS NETWORK
                     AVERAGED < 1 m/sec.

           VORT500  -- AVERAGE VORTICITY (sec-1) AT 500 mb OVER ST. LOUIS BASED
                     ON THE 0700 AND 1900 LOT 500-mb VORTICITY CHARTS.

           AVORT500 -- 12-HOUR CHANGE IN VORTICITY (sec'1) AT 500 mb BETWEEN
                     0700 AND 1900 LOT.
                                       81

-------
     Table 2 lists the importance of each variable at the various stations as
determined by their F ratios (25) in the final step of the regression technique.
The F ratio associated with each independent variable is a measure of the
additional variance explained by the variable not accounted for by the other
variables already in the regression equation.  In this technique, F ratios were
computed for each variable and a step was made by the inclusion of a variable
with a significant F ratio or the deletion of a variable when its F ratio had
become insignificant due to the inclusion of other variables.  The final step
occurred when the remaining variables (those without ranks in Table 2) had
F ratios that were statistically insignificant at the 1% significance level
(25).   The signs (+ or -) in Table 2 on top of each ranked variable indicate
the sign of the coefficient in the final equation.  For wind direction (WD)
the significant sector is listed above the rank along with its sign.  At some
stations there are two significant wind directions.  For these stations the rank
is listed for the more significant of the two.  It should be noted that for the
three  variables, global  radiation (/RAD), the number of days since the last
frontal  passage (/FRONT), and the number of days since the last measurable
precipitation occurred (/PRECIP), the square roots of the variables were_
found  to be more effective predictors of average ozone concentrations [(L]
than linear predictors.
an approach.   In general
and shortly after the passage of a front
to several  days after their occurrence.
is not linearly correlated to [03] in STL
                                               3-
There are sound physical reasons for this type of
 meteorological conditions change rapidly during
                or a significant rainfall, as opposed
                One reason why the global radiation
                 is because often the most intense
global  radiation occurs when dispersion is good, i.e., after a frontal passage.

 TABLE 2.  THE  RELATIVE  IMPORTANCE OF  VARIOUS VARIABLES  IN  THE FINAL  STEP  OF
                            THE REGRESSION EQUATION
*%,

TMAX
WS
WD

^PRECIP
HT 500
^RAD
CALM
VORT 500
CFRONT
HT500
T
YN RAIN
	 	 1
a VORT 500
VARIANCE
EXPLAINED
BY RANKED
VARIABLES
SAMPLE
SIZE
101

1
4
-S
2

3







h •
59
53
102

1
2




3






64
69
103

1
2
S
4

3

5






80
"
104

1
3


2
5


4



1
77
50
105

4
3


2
5
1




6
'
75
57
106

4
2

"

1
3






65
61
107

1
2
-S
*NW
4

3





5


71
51
_
108

1
2
-S
rSW
4



3
5


1"

r
67
65
109

1
3


2


4
h





64
e,
110

1
3
-S
-SW
4

2


5





71
59
111


3
tNW
*W
4


1
2
5




t
69
56
112


4
-SW
6


1
>
2



5
3

84
41
113

3
5
+ SE

4

1
4

2

6

68
63
114

1
2
*SW
6

"

7
:


,
3


69
61
115

4
2
+SW
3


5
1






75
36
116

1
4
-S
2

3








67
43
117

1
3


2


5



4

65
48
118



+NE
-S
3

1
2


5
4



87
29
119

I 2
4
*NE
1

3








66
64
120

6
2


5
3
1


4


- -
88
37
122

4
2
1
~:
l.?3
I
-S
	
--
2

124

+ NW
2


125

6
3
	
	 (_ _
                                                               -  +-—I
                                                               55 , 40
                                                                     85  40   81
                                                                     28 j  34   44
                                      82

-------
     It is immediately apparent that the importance of each variable can vary
considerably from station to station.   Some of this variability can be attri-
buted to the fact that data were available at some stations and not others
on any given day.  However, in general  the maximum temperature (TMAX) and
the wind speed (WS) are the most important predictors of [03] in the RAMS
network.  WS is important since it has  the direct effect of diluting the
pollutant.  Looking more closely at Table 2, it appears that WS is of less
importance as a predictor of [03] at rural stations.   However, at these
stations the effects of dilution, low concentrations  at high wind speeds, and
high concentrations at low wind speeds  are combined with the effects of
advection from the city to give a non-linear relationship with [03].
     There are several reasons for TMAX showing up as an important variable.
Laboratory results have shown that ozone production is temperature dependent
(26).  However, the maximum temperature is a surrogate for various other
meteorological variables.  The most obvious one in the summertime is global
radiation.  There is a significant positive correlation between /RAD and TMAX.
The maximum temperature is also related to changes in air masses.  For example,
a cold frontal passage with its good dispersion characteristics and cleaner
air is followed by several days with lower daily maximum temperatures.  Addi-
tionally, lower maximum temperatures are observed with rain falling within
the tjme span between 1000 and 1500 LOT, which is the time span used to obtain
the [
-------
o
LL
LL
LLJ
O
CJ
CC
CC
O
O
             SITE 102, NORTH (345°) OF DOWNTOWN
            NE    E   SE    S    SW   W    NW CALM
        N
                       NE
              SE
                                SW
W
NW  CALM
               .5
               .4
               3
               2
               1
               0
                1
                2
                3
               4
               .5
    .5
     4
     3
    .2
     1
    0
    .1
     2
    -3
     4
    -5
            SITE 118, SOUTH (190°) OF DOWNTOWN
            NE    E    SE    S    SW   W   NW
                                                        CALM
DISTANCE = 16km
   I     I     I    I
                                        I
                                             I
            NE   E    SE    S   SW    W   NW  CALM
            SITE 121, NORTHWEST (335°) OF DOWNTOWN
            ME    E    SE   S    SW   W   NW  CALM
              .b
              A
              .3
              .2
              .1
              0
              -.1
              -.2
              - 3
              - 4
              - 5
                      I    I     I
                      I     I
                   N  55
                   DISTANCE = 27 km
              .5
              .4
              3
              2
              .1
              0
              -.1
               2
              -3
              -.4
              -5
       N
            NE
                                     W
                                         NW  CALM
                            :    SE    S    SW
                                WIND DIRECTION
Figure 4.  Correlation coefficients  of  the  daily frequency distribution of
  wind direction  (WD)  and calm (CALM) with  ozone concentrations  -  shaded;
   equally weighted  average correlation  coefficients derived  from  all  25
stations - unshaded.   Distance is given  from downtown St. Louis  at Stations
                             102, 118, and 121.
                           84

-------
and /RAD".  The height^ of the 500-mb surface HT500 serves much the same pur-
pose in explaining [03] as does TMAX.  In fact, four out of five times when
HT500 ranked as the most significant variable in the regression equation,
TMAX did not even rank significantly as an important variable.  It was somewhat
surprising to see /PRECIP rank high in significance so often.  However, it
should be noted that /PRECIP shows a significant correlation with /RAD
(approximately 0.45).  Upon further investigation of the results in Table 2,
the question arises of why the variable YNRAIN, which represents whether or
not measurable precipitation occurred (Table 1), ranked so few times as compared
to /PRECIP.  YNRAIN is even more strongly correlated with /RAD" (approximately
-0.65) than is /PRECIP.  In addition, both YNRAIN and /PRECIP are signifi-
cantly correlated with the same variables included in the regression analyses.
These results suggest that /PRECIP accounts for a process not accounted for
by YNRAIN.  A plausible explanation for this is:  summertime rainfall in STL
(which is mostly convective) inhibits ozone production during the daytime,
but in addition, after the rainfall, several days must pass before the return
of meteorological conditions that are conducive to high levels of ozone.  The
variable /RAD, which is the driving mechanism for ozone production, frequently
takes a "back seat" to the various other meteorological variables.  Many of
the reasons for this have already been cited.  Primarily, the day-to-day var-
iance in the global radiation received at the surface is highly correlated
with other meteorological variables, TMAX, HT500, /PRECIP, YNRAIN, but in
addition, these variables also represent other meteorological factors that
influence [fi"3].

     The remaining variables in Table 2 deserve brief comment.  First, it
should be noted that sometimes the variable CALM, representing near calm
winds, was included in the regression equations even when WS was already in
the equation.   Second, the stability_very close to the ground (AT) appears
to play a minor role in explaining [03] when other variables are used in
combination with this variable.  Third, there is no apparent physical reason
for the sign of the vorticity at 500-mb (VORT500) at Stations 107, 118, and
125 to be positive.  Lastly, at Station 112, when HT500 and AHT500 were both
in the same equation, the coefficient of AHT500 was negative.  This indicates
a tendency for higher concentrations as the 500-mb ridge begins to break down.

                                   CONCLUSIONS

     Data has  been analyzed from two metropolitan areas of differing climates.
In each area there was a dense network of high-quality data.   The following
conclusions were reached from our analyses.

     The proposed Pipe-Mix Model  shows there are two meteorological  processes,
horizontal transport and vertical  mixing, contributing to the LA ozone problem.
The horizontal transport involves fairly well-known sources and photochemical
reactions, whereas the vertical mixing involves a source of "second-hand"
ozone that varies in concentration.

     In the STL area, the combination of a few meteorological variables can
explain, on the average, about 70% of the day-to-day variance in average
ozone concentrations during hours of peak concentrations.  Various combinations
of the following variables were effective in this regard:  (a) the daily


                                      85

-------
maximum temperature,  (b)  the wind speed,  (c)  the  wind  direction,  (d)  the
number of days since  the  last measurable  precipitation occurred,  (e)  the
global radiation, and (f) the height of the  500-mb  surface.   Furthermore,  it
was confirmed that the near-surface advection of  ozone and/or its  precursors
from the city does contribute to high ozone  levels  downwind  of the city.
                                  REFERENCES

 1.    Middleton, J.T., J.B. Kendrick, and H.W. Schwalm.  Injury to Herbaceous
      Plants by Smog or Air Pollution.  Plant Disease Reporter, 34 (9): 245-252,
      1950.

 2.    Haagen-Smit, A. J.  Chemistry and Physiology of Los Angeles Smog.  Ind.
      Eng. Chem. 44 (6): 1342-1346, 1952.

 3.    Kauper,  E.K., R.G. Holmes, and A.B. Street.  Meteorological Variables
      and Objective Forecasting Techniques Relating to the Air Pollution Pro-
      blem in  Los Angeles.  Technical Paper No. 15, Air Pollution Control
      District, Los Angeles, California, 1955.  15 pp.

 4.    Neiburger, M. and J. Edinger.  Meteorology of the Los Angeles Basin.
      Report No. 1, Southern California Air Pollution Foundation, Los Angeles,
      California, 1954.  97 pp.

 5.    Renzetti, N.A., Editor.  Aerometric Survey of the Los Angeles Basin.
      August-November 1954.  Report No. 9, Air Pollution Foundation, Los
      Angeles, California, 1955. 334 pp.

 6.    Tiao, G.C., G.E.P. Box, and W.J. Hamming.  Analysis of Los Angeles
      Photochemical Smog Data:  A Statistical Overview.  J. Air Poll. Control
      Assoc.,  25 (3): 260-268, 1975.

 7.    U.S. Weather Bureau.  Climatography of the United States No. 86-4 (De-
      cennial  Census, California, 1951-1960).  U.S. Dept. of Commerce, Washington,
      D.C., 1964.  216 pp.

 8.    Hamming, W.J., R.L. Chass, J.E. Dickinson, and W.G. MacBeth.  Motor
      Vehicle  Control and Air Quality The Path to Clean Air for Los Angeles.
      Presented at the Meeting of the Air Pollution Control Association,
      Paper No. 73-73, Chicago, Illinois, June 1973.  19 pp.

 9.    Middleton, J.T. and A.J. Haagen-Smit.  The Occurrence, Distribution
      and Significance of Photochemical Air Pollution in the U.S., Canada,
      and Mexico.  J. Air Poll. Control Assoc., 11 (3): 129-134, 1961.

 10.   Lea, D.A.  Vertical Ozone Distribution in the Lower Troposphere Near
      an Urban Pollution Complex.  J. Appl. Meteor., 7: 252-267., 1968.

 11.   Edinger, J.G.  Vertical Distribution of Photochemical Smog in Los Angeles
      Basin.   Environ. Sci. Technol., 3: 247-252, 1973.


                                     86

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12.  Gloria, H.R., G. Bradburn, R.F.  Reinison, J.N.  Pitts Jr.,  J.V.  Behar
     and L. Zafonte.  Airborne Survey of Major Air Basins in California.
     J. Air Poll. Control Assoc., 24  (7): 645-652, 1973.

13.  Kauper, E.K. and B.L. Niemann.   Los Angeles to Ventura Over Water Ozone
     Transport Study.  Report prepared for California Air Resources  Board by
     Metro Monitoring Services, Covina, California, 1975.  54 pp.

14.  DeMarrais, G.A., G.C. Holzworth  and C.R.  Hosier.  Meteorological  Sum-
     maries Pertinent to Atmospheric  Transport and Dispersion Over Southern
     California.  Technical Paper No. 54.  U.S.  Weather Bureau, Washington,
     D.C., 1965.  86 pp.

15.  Blumenthal, D.L., W.H. White, R.L. Peace  and T.B. Smith.  Determination
     of the Feasibility of the Long-Range Transport of Ozone or Ozone  Precursors.
     Final Copy (draft copy) prepared by the Environmental Protection  Agency
     by Meteorology Research, Inc.,  Altadena,  California, 1974.  86  pp.  plus
     2 appendices.

16.  Air Resources Board.  California Air Quality Data, April,  May,  June
     1974.  Vol. VI, No. 2.  Sacremento, California, 1974.  83  pp.

17.  Miller, A. and C.D. Ahrens.   Ozone Within and Below the West Coast
     Temperature Inversion.  Dept. of Meteorology Report No. 6, San  Jose
     State College, San Jose, California, 1969.   74 pp.

18.  Kauper, E. K., D. F. Hartman, and E. G. Roberts.  Air Pollution Fore-
     casts for Los Angeles, Using an  Objective Method.  Manuscripts  of Los
     Angeles Air Pollution Control District, California,  1964.   16 pp.

19.  Zeldin, M.D.  Ozone Forecast Model.  Manuscript of San Bernardino Air
     Pollution Control District,  California, 1974.  4 pp.

20.  Air Resources Board (2).  California Air  Quality Data, October, November,
     December 1974.  Vol. VI, No. 4,  Sacramento, California, 1974.  94 pp.

21.  Lust, D.  Semi-Annual Report on  Operation of Environmental Meteorologi-
     cal Support Unit in Los Angeles.  Inter-Office Communication of National
     Weather Service dated August 9,  1972.

22.  Lust, D.  Inversion Base Heights and Temperatures, Los Angeles  Airport
     and El Monte.  Manuscript of Weather Service Forecast Office, Los Angeles,
     California,  1976.  3 pp.

23.  Auer, A.H.  Metropolitan Land Use in the  Metropolitan St.  Louis Area.
     Report No. AS116, Dept. of Atmospheric Science, Univ. of Wyoming, 1975.
     30 pp.

24.  Jurgens, R. B. and R. C. Rhodes.  Quality Assurance  and Data Validation
     for the Regional Air Monitoring  System of the St. Louis Regional  Air
     Pollution Study.  In:  Proceedings of the EPA's Conference on Environ-
     mental Modeling and Simulation,  Cincinnati, Ohio, 1976 (in press).

                                     87

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 25.   Panofsky, H.A. and G. W. Brier.  Some Applications of Statistics to
      Meteorology.  The Pennsylvania State University, University Park, Penn-
      sylvania, 1958.  224 pp.

26.  Alley, F.C.  and L.A.  Ripperton.   The Effect of Temperature on  Photo-
     chemical  Oxidant  Production in  a  Bench  Scale Reaction  System.   J.  Air
     Poll.  Control  Assoc.,  11  (12):  562-565,  584, 1961.

27.  Brooks, C.P.  and  N.  Carruthers.   Handbook  of Statistical  Methods  in
     Meteorology.   Her Majesty's Stationary  Office, London,   1953.   pp.  210-241
                                      88

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                                                                              3-2
               OZONE IN RURAL AND URBAN AREAS  OF NEW YORK STATE

                                    PART  I

                       P.  Coffey, W. Stasiuk,  V.  Mohnen*
ABSTRACT
     Ozone, c.onc.e.ntA.ationA have. be.e,n mea^uA.e.d at nuJwJi and. uAban A-iteA  -in
New Void State,  ^on the, tat>t Ae.veA.al ye,au.   MoAt o& the. ozone, fiound at
theAe, AiteJ> it,  the, A£Au£t o& tang tiange. tAanApoAt pfioaeAAeA and not toc,at
photo ah em-inal. ge.neAation.  Pe/iiodA o£ high  ozone, conc.e.ntx.ationA oJio, Ae.gtonal.
i.n natuJie, and ajie, aAAociate,d wtth high pA&AAuAe. we.atheA. AyAtemA.  The.
ox-ide. and pafittciitate. matteA pfiodu.c.e.d -In uAban oAeoi deA&ioi/A ozone, and
the^e. aSie.aA te.nd to e.x.pesu.e.nc.e. ^eweA hout&  o& ozone. conc.e.ntSLatLonA
o& SO ppb than  do the. Ausial atie.at>.  Howe.veA.,  on occasion, ozone. appe,asu> to
be. ge,neAate,d -in the. usiban ptime. -In c,xce44 ofa the. psie.vattt.ng bac.kgfiou.nd ozone.
C-onc-e.ntA.ation&.   The, magnitude, ofi the, con&itbtition ofi ozone. -60 ge,neAate,d to
the. ov&ioitt ozone. teveJLb -in the. aJji muA.e.
       ^6 both  vanMibtn and
                                 INTRODUCTION

     Several years  ago, the Division of  Air  Resources of the New York  State
Department  of  Environmental Conservation and the Atmospheric Sciences  Re-
search Center  of the State University of New York initiated a continuing
study designed to investigate the sources of the ozone being found  in  New
York State  and the  northeastern United States.

      Quite frequently, starting in late spring and continuing throughout
the summer, ozone concentrations in excess of the National Ambient  Air
Quality  Standard (80 ppb not to be exceeded  more than one hour per  year)
were being  recorded at urban monitoring  sites in New York State.  While
these urban sites usually recorded ozone concentration patterns which
correspond  to  the classical diurnal cycle characteristic of local
photochemical  generation and subsequent  distruction, there was evidence
that the  problem was more complex.  Earlier  studies by New York State  (1)
in the mid-1960' s,  using the cracking of rubber as an indicator of  ozone,
indicated that ozone concentrations were higher in the rural areas  than
in the urban areas.  The results were reinforced' by Johnston (2) and
Richter  (3) who,  in the early 1970's, measured high concentrations  of
ozone in  rural  Maryland and West Virginia, respectively.
*Bureau of  Technical  Services, Division  of Air Resources, New  York  State
 Department of  Environmental Conservation,  Albany, New York.

                                       89

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                                STUDY DESIGN

     The ozone study was designed to collect and analyze ozone data over a
large area from both stationary surface sites and instrumented aircraft.  To
supplement existing urban monitors situated in the larger cities of New York
State, several sites were added.

     The summit atmospheric physics laboratory at Whiteface Mountain (Eleva-
tion 4,980 feet) in the northern Adirondack Mountains of New York was chosen
to be a permanent site.  This laboratory, operated by the Atmospheric Sciences
Research Center of the State University of New York,  is situated in a very re-
mote area of the Northeast well over 100 miles from the nearest sizable urban
area.  The elevation of the site, which is above the  tree line, is sufficient
to place it above the summertime nocturnal inversion  layer, yet low enough so
that it remains well within the daytime surface mixing layer.

     A temporary rural elevated site was set up in a  fire tower 40 feet above
the summit of Mount Utsayantha (elevation 3,200 feet) located in Delaware
County approximately 180 miles south of Whiteface Mountain.  This site has
the same meteorological characteristics as the Whiteface site.

      A third temporary rural site was operated in a  remote conifer
forested valley area known as the "Pack Forest."  This site (Elevation
800 feet) was approximately 55 miles south of Whiteface.  Unlike the
other two rural sites, the Pack Forest location was typically under the
nocturnal inversion layer.  The location of these rural sites and several
urban sites used during the study is shown in Figure  1.
                               OZONE STUDY SITES
                                      IN
                                NEW YORK STATE
                                          (N.YC.)
           Figure 1.   Locations of various sites in New York State.
                                     90

-------
       In  addition  to  the  above mentioned  fixed  location  sites,  instrumented
 helicopter  and  airplane flights were made on  both a  local and long-range
 basis.
                                   RESULTS

      The  Whiteface  station,  because  of  its  isolation  from  urban areas,  pro-
 duced ozone  data which  was unperturbed  by local  anthropogenic  sources.   The
 monthly average ozone concentrations  at this  site  for 1973 and part  of  1974
 are shown in Figure 2.   The  classical springtime rise is evident,  as is the
 fall  and  winter low.  While  not  evident in  this  figure, the month  of highest
 ozone concentration is  very  dependent on year by year climate  variations.
 For example, while  the  1973  highest  average ozone  concentrations were measured
 for August,  the highest month  in 1974 was June.  This coincided with a  shift
 in  1974 climatic conditions  producing winter-like  weather  patterns over the
 northeastern United States after June of that year.
                        701
                        60
                        SO
                        40
                      N 30-
                      O
                        20-
                        10-
                          JFMAMJJASONDJFMAM

                                   1973         I   1974
           Figure 2.   Average monthly ozone concentrations recorded
                         at summit of Mount Whiteface.
                       EFFECT OF NOCTURNAL INVERSION

     In Figure 3, ozone concentrations at the Whiteface site are compared
with those at the Pack Forest site from August 6, 1973 to August 17, 1973.
The Pack Forest valley site, which is under the nocturnal inversion, recorded
distinct diurnal variations in ozone concentration which look very much like
the classical case of local daytime photochemical ozone generation and subse-
quent nighttime destruction.  However, the lack of local anthropogenic
sources and the existence of high concentrations of ozone above the nocturnal
                                      91

-------
 inversion layer as  seen from the Whiteface  data  suggests  a different mecha-
 nism (4).   That is,  the ozone seen  at both  sites  is  generated elsewhere and
 transported over long distances  to  these locations.   The  distinct diurnal
 variation at the Pack Forest site is  caused by local  nighttime destruction of
 ozone under the nocturnal  inversion layer by reaction with gases  such as ni-
 tric oxide and terpenes,  by contact with the surface and  by reaction with  par-
 ti cul ate matter. The daytime breakup of the inversion layer allows ozone
 replenishment from  the ozone reservoir above this layer.
  .16


  .14


  .12
 I .06-1
 i

  04


  .02
WHITEFACE
PACK FOREST
   8/6/73
    NOON
                             10
                                                13
                                                      14
                                                            15
                                                                         17
                                     DAYS
         Figure  3.
     Ozone Concentrations at Whiteface and Pack l-orest
     from August 6, 1973 to August 17, 1973.
     That this mechanism is responsible for diurnal  ozone fluctuations in
urban areas can also be demonstrated.

     Approximately 25 miles to the south and east of the Pack Forest  is  loca-
ted the city of Glens Falls (population 18,500).  Its ozone concentrations
are almost identical to those found at the Pack Forest site.  The relation-
ship between these two sites is illustrated in Figure 4 on an hourly  average
basis for the month of July, 1973.  Note also on this figure the Whiteface
hourly average which exhibits a reverse diurnal.  Evidently, the ozone con-
centration at Whiteface experiences a daytime minimum due to the influx  of
ozone depleted air from under the nocturnal inversion.  During the winter
months when the snow covered mountain summit is typically under the nocturnal
inversion, the summit ozone diurnal fluxuation is reversed as would be expec-
ted.

                            LONG RANGE TRANSPORT

     That long range transport of ozone occurs on a massive scale is  sugges-
ted by Figure 5.  In this figure, continuous ozone data from the Whiteface
site for the first 17 days of August, 1973 is presented for comparison with
the rural Utsayantha site and the urban site of Syracuse, New York.   The
missing ozone data is a result of malfunctions in the data transmission  sys-
tem of the continuous air monitoring network.  Despite a separation of 180
                                      92

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                              HOURLY AVERAGES FOR JULY  73
                                           WHITEFACE
                                           PACK FOREST
                                           GLENS  FALLS
                       0   2   4   6  8  (0  12  14 (6  18  20  22  24
                                        HOURS

            Figure  4.   Hourly ozone averages at Whiteface,  Pack Forest
                       and Glens Falls sites for July, 1973.
  t4-
  .12-
  .10
  08-
  .06
i
               .WHITEFACE
                  SYRACUSE
  ,12
  .10
  .01
  oc
  .04-
  02
   0
WHITEFACE
UTSAYANTHA
        12 Z
       NOON
                 789
                      DAYS
                               IO   II    12    13   14   15    16    17
  Figure  5.   Comparison of ozone concentration at Whiteface site with  that at
              Utsayantha and Syracuse  sites  for the first 17 days
                                 of August,  1973.
                                       93

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miles between the two rural  stations (Utsayantha and Whiteface),  the ozone
levels at both sites are nearly equal  and exhibit the same variations.

      Of perhaps more interest are the comparisons of the urban ozone concen-
trations at Syracuse with the rural  concentrations at Whiteface.   The typical
diurnal ozone pattern is seen in the urban areas with nighttime values
usually reduced to zero by reaction  with nitric oxide.   A close examination
of this figure shows that the urban  daily maximum ozone values apparently
are high when non-urban ozone values are high and are low when non-urban
values are low.  We have reported similar relationships for Whiteface,
Glens Falls and Montreal, Canada (5).   This strengthens the hypothesis
that the urban ozone observed in New York State may be more the resultant
of a physical process of transport and mixing than of local photochemical
generation.

                                  WEATHER

      Episodes of high ozone concentrations are associated with high pressure
systems.  Ozone concentrations rise  as the center of the high moves south-
east of the area during which time the surface winds blow from the south-
west quadrant.  Elevated sulfate concentrations are also associated with
these systems (5,6).

                                URBAN OZONE

      It has been shown by Coffey and Stasiuk (7) that urban areas experience
fewer hours in excess of the 80 ppb ozone standard than do rural areas.
Figure 6 illustrates this point for the cities of New York, Mamaroneck,
Buffalo, Glens Falls and the rural sites at Whiteface and  the Pack Forest.
Apparently, the destruction of ozone by nitric oxide tends to be greater
than the photochemical generation of ozone within the urban area.

                             URBAN OZONE PLUME

     Figure 6 is interesting in that all the sites but one experience ozone
maximums of around  135 ppb.  The site at Mamaroneck, however, experiences
several hours of ozone concentrations significantly higher.  This site  is
approximately 20 miles from New York City and typically downwind during  an
ozone episode.  An explanation of these high ozone concentrations is that on
occasion when reaching the Mamaroneck area, the urban plume from the New York
City area  has depleted its nitric oxide content and has become a net producer
of ozone.  This argument is reinforced by Figure 7 - an ozone concentration
isopleth of the northeastern area drawn from data supplied by 95 ozone  report-
ing stations  in the region.  Several ozone plumes are evident as is the  re-
gional nature of the ozone problem.

                                CONCLUSIONS

     The diurnal fluctuations in ozone concentration observed at surface sites
is largely the resultant of local meteorological parameters and not local pho-
tochemical generation.  Above the nocturnal inversion ozone a high concentra-
tion persists throughout the night and serves to replenish the surface  ozone


                                     94

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                      20-


                      (0
                      20


                      10
                       0

                      20
                    S  0
                      10
                       0

                      20
                     •

                    I
                      10
                      30


                      20
                                    MAMARONECK
                                     NEW YORK
                                    BUFFALO
                                   GLENS FALLS
                                   PACK FOREST
                                   WHITEFACE
                        80 90 I 0 110 120 <30 MO 150 ifcO <>0 180 190

                                    OZONE ppb
Fiaure 6
  9     '
         Frequency  distribution of ozone concentrations  in  excess of 80 ppb
                          from 7/1/73 to 8/22/73.
             OZONE ISOPLETHS

                 6/23/75
Figure 7   3-4 P.M. ozone  concentration isopleths of  several  northeastern
                            states for June 23, 1975.
                                      95

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concentrations during the daylight hours.

     The ozone problem is a regional  one,  episodic in  nature associated with
high pressure systems.

     Urban areas tend to have less ozone than  do  rural  areas,  however,  ozone
plumes have been measured downwind of the  larger  urban areas.   The  relative
contribution of ozone generated in urban plumes to the overall  ozone concen-
trations associated with high pressure systems is unknown.   Similarly,  the
relative contribution of ozone from the stratosphere  and  ozone  produced from
naturally emitted precursors is also  uncertain.   Resolution  of  the  reasons
for elevated ozone concentrations  in  these air masses  is  needed since the
levels are greater than the federal  ambient air quality standard.
                                REFERENCES

(1)   Statistical  Analyses  of Data  from  Effects  Stations  in  New  York  State,
     January-December,  1969.   New  York  State  Department  of  Environmental
     Conservation,  Report  No.  BAQS 24.

(2)   Johnston,  et.al.,  "Investigation of  High Ozone  Concentrations in  the
     Vicinity of  Garrett County, Maryland and Preston  County, West Virginia,1
     Research Triangle  Institute publication, January, 1973.
     NTIS #PB-218540.

(3)   Richter, H.G.,   "Special  Ozone and Oxidant Measurements  in  Vicinity of
     Mount Storm,  West  Virginia,"  Research  Triangle  Park, North  Carolina,
     Research Triangle  Institute,  October,  1970.

(4)   Coffey,  P.E.,  Stasiuk,  W.N.,  "Evidence of  Atmospheric  Transport of
     Ozone into Urban Areas,"  Environmental Science  and  Technology,
     Volume 9,  No.  1, p. 59.   January,  1975.

(5)   Stasiuk, W.N.,  Coffey,  P.E. and McDermott, R.F.,  "Relationships
     Between  Suspended  Sulfates  and Ozone at  a  Non-Urban Site."   Paper
     No.  75-62.7  presented at  68th National Annual Meeting  of the Air
     Pollution  Control  Association, Boston, Massachusetts,  June,  1975.

(6)   Quickert,  N.,  Wallworth,  B. and L. Dubois, "Characterization of an
     Episode  with Elevated Ozone Concentrations."

(7)   Coffey,  P.E.,  Stasiuk,  W.N.,  "Urban  Ozone:   Its Local  and  Extraregional
     Components."   Presented at  the 79th  National Annual  Meeting  of  AICHe,
     Houston, Texas,  March,  1975.
                                     96

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                                                                           3-3
                      OZONE MEASUREMENT AND METEOROLOGICAL
                         ANALYSIS OF TROPOPAUSE FOLDING

              V.  A.  Mohnen, A.  Hogan, E.  Danielsen, and P. Coffey*

 ABSTRACT
      Ozone me.aAusie.me.ntA  made. at hOMQJioJL AuA&ace. AtationA in Mew Vofik and
 Mat>AachiK>ettA  i>how typical continental diusinal vacation; a moantaintop
 (850  mb}  station in the.  same. fie.gion experienced veAy little. diuAnal
 vafiiation.   The,  moataintop ozone, concentration atoat/4 exceeds that o& the,
 AuA^ace. stations,  and thib concentnation &ie.nd is predictable. by
 met.e.otio ioQical analysis.   The nesultA o& thus. nx.peJiimn.n&> indicate, that the.
 ozone. souAce level Liu  above. 850 mb.  ftight e.xpeAijme,ntt> have.
 that  significant downward tAanApotit ofa ozone, fatiom the. ioweA
 accompanies  a  tA.opo&pke.?iic faotd,  and that thi& ozone.-e.n?iiche,d OAJI may n,e,ack
 the. ^uut^ace. and/on remain in the. middle.
                                  INTRODUCTION

     Vertical  profiles  of  ozone mixing ratio, averaged to remove the
fluctuations,  are  consistent with a net production in the upper stratosphere
and a  net  destruction at the earth's surface (1,2).   From this results an
average  background concentration for the "natural" ozone.  Ozone concentra-
tions  that far exceed this average, and that are not caused by a sudden
increase in  downward transport, are caused by photochemical production of
ozone  in the lower part of the  troposphere from precursor gases of
anthropogenic  origin.   Downward transport of ozone from the stratosphere
to the troposphere occurs  when  the boundary between  the stratosphere and
the troposphere deforms, becomes vertical in the core of the jet stream, and
then folds beneath the  jet core.   Danielsen (3) concluded after completing
several  case studies of large-scale cyclogenesis that "tropopause folding"
was an integral  part of cyclogenesis and that, therefore, the net seasonal
and annual  transport of mass could be estimated by multiplying the mass
transport  per  cyclogenesis times  the number of cyclogenetic events.  This
estimate of  4.3 x  1020  gm:year  -1 implied that a mass comparable to the
entire norther hemishperic stratosphere was exchanged in one year, the
outflow  being  from the  lower stratosphere on the cyclonic side of the jets,
the inflow implied at higher elevation on the anticyclonic side of the
jets.  Table 1  summarizes  the current estimates on globally averaged ozone
*V.A. Mohnen and A. Hogan, State University  of  New York  at Albany, Atmospheric
Sciences Research Center.
E. Danielsen, National Center  for Atmospheric  Research,  Boulder, Colorado.
P. Coffey, New York State  Department  of  Environmental  Conservation, Albany,
New York.

                                      97

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                                TABLE  1.   SUMMARY
ESTIMATED STRATOSPHERIC OUTFLOW NORTHERN HEMISPHERE

  (1959) 4 x 1020 gm/year

STRATOSPHERIC MASS

  Ms = [4.5 + 0.5 cos |^ (t - lf|)]  x  1020  gm

  (1964) OUTFLOW DERIVED FROM Sr90 DEPOSITION IN  1960  + 1963


  ^    =    [3.6 + 1.8 cos -^ (t -  ^j|)] x 1020  gm/year
    outflow

               OZONE MASS MIXING RATIO IN LOWER STRATOSPHERE

XQ  = [1.3 + 0.3 cos |^ (t - ^j|-)] x lO'6 gm/gm


ANNUAL OUTFLOW OF OZONE

               4.7 x 1014 gm 03

               5.8 x 1036 molecules

AVERAGE FLUX

               7 x 1010 molecules cm"2 sec"1

PAETZOLD 1955                  FABIAN  + JUNGE 1970               REGENER 1957

  4 x 1010                      (4 - 7.6) x 1010               (12 -  16) x 1010

OZONE TRANSPORT IN SPRING 5 TIMES TRANSPORT IN FALL.


(Danielsen and Mohnen, 1976)
                                      98

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fluxes (4).

     Taba (5) reviewed the World Meteorological  Organization Congress on
ozone observations, which concluded that in a major portion, daily and seasonal
variations in ozone concentrations were due to meteorological  phenomena.  More
recent reviews of the ozone literature (6-7) support this conclusion.

     It is quite obvious that the average ozone concentration  observed in
the planetary boundary layer is governed by more than one mechanism:

   •  Cyclogenetic events and subsequent further transport of
      stratospheric air to the ground.  (Depends on season and
      geographic latitude as far as the jet stream is concerned,
      and on atmospheric stability with regard to vertical transport.)
   •  Photochemical production within the planetary boundary layer
      or in the lowest troposphere.  (Depends on season, geographic
      latitude, atmospheric stability and, most importantly, on the
      concentration of anthropogenic precursor gases such as oxides of
      nitrogen and reactive hydrocarbons.)
    •  Destruction on the earth's surface.  (Depends strongly on the
      type of surfaces.  Values between 0.01 to 2 cm-s l have been
      found for surface destruction rates; i.e., they can differ by a
      factor as high as two hundred.)

     It can be expected, therefore, that the average ozone concentration
differs from region to region.  Background ozone measurements within the
planetary boundary layer for the purpose of establishing realistic air
quality standards must be made on a regional basis.  The "region" is
defined by climatology, geographic latitude, topography, type of surface,
etc.

     The Atmospheric Sciences Research Center (ASRC) and the New York State
Department of Environmental Conservation have collaborated in operating a
series of ozone observations in rural and urban New York State for several
years.  Station descriptions can be found in Coffey and Stasiuk (8).   This
analysis of ozone background concentration will  be confined to the ASRC
Whiteface Mt. (4860 ft.) and Schenectady County Airport stations, the
Pittsfield, Mass, station operated by the Department of Public Health,
Commonwealth of Massachusetts, and the Albany-Rensselaer station operated
by the New York State Department of Environmental Conservation.  The secular
variation of ozone (1974 data) for these four stations is presented in Figure
la.

     The data are consistent with the classical  concept of increased ozone
transport from the stratosphere to the troposphere during the spring
("springtime rise" of ozone).  Further mixing down to the ground is enhanced
during the summer months, as indicated by the increase in afternoon mixing
height measured at the Albany Airport (Figure Ib).

     A positive correlation between afternoon mixing height and ozone
concentration suggests ozone transport from aloft into the planetary boundary
layer.  It is also interesting to note that the monthly averaged ozone

                                      99

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                   40
                 Hi 3O
                 8:
^20
o
N
O

  10
                         V/HITEFACE MTN.(~SOOO FEET)  PITTS Ft ELD
                         SCHENECTADY   RENSSELAER
                                              Uj
                                              ^
                                              O
                                              s
                                              UJ
                                              to
                                                                UJ
                                                                O
                4  5   6   7  8
                 MONTH 1974
                                                    1O II  12
                    Figure  la.   Secular variation of ozone.
  18

  16

O 14

* 12
                 LU
                    6

                    4

                    2

                    0
                                                   AFTERNOON
                                  MORNING
                                                                to
                                                                G
                                                                3:
                                                                Uj
                                                                Cc
                                                                Uj
a:
i-
2:
O
§
                         /   2  3  4  5  6   7   8   9   IO  II  12

                                  MONTH 1974
                   Figure Ib.   Mixing height, Albany airport.


concentration for Whiteface Mt.  (4860  ft.  or  850  mb) was always highest
(except March 1974 for the Pittsfield  station;  however,  March is not a
"photochemical" month) of all the stations.   To further  substantiate the
transport mechanism from aloft as the  main source of ozone for this region
(versus the photochemical mechanism  observed  in other  regions), we have
plotted the "normalized" ozone diurnal  in  Figure  2a for  the four stations.

     Also plotted in Figure 2b are the normalized diurnal  variation of
(horizontal) windspeeds.  Maximum wind speed  results  in  maximum vertical
                                      100

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            w

          32.2'
          PPB
                     I
                     3
                     5

                     0^
                     N.
                     OJ
           28.JJ
                                                              32J5\
                                                               9.7
                            42.9'
                             15.21
                                                                       00
                                                                       N
               1574 ANNUAL  ONE HOUR  AVERAGES

              Figure 2a.  Normalized diurnal  variation  of ozone,
                    Whiteface Mtn.  Rensselaer.  Pittsfield.
                                                  W
W R P
28




— J
^
S
Cc
5
S
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-------
     Figure 3 shows the mean hourly ozone concentrations observed at
Whiteface Mt. and Schenectady County Airport during the period 21-31 July
1975.  The 850 mb potential temperatures from the National Oceanic and
Atmospheric Administration radiosonde at Albany Airport are noted on the
same axis.  This short data run is used to facilitate display of hourly
values; daily or twice daily means suppress some important short-term
trends in ozone concentration.   Examination of Figure 3 shows an unmistakable
parallel in the trends in ozone concentration at Whiteface Mt. (altitude
<<850 mb) and in the 850 mb potential  temperature reported for Albany, some
120 miles south of Whiteface Mt.  At this level, an increase in air temperature
(and/or potential temperature)  would be indicative of subsiding air.  A
warming trend should then be accompanied by increasing ozone concentration,
and a cooling trend should be accompanied by steady, or decreasing, ozone
concentration.   This is the general case for the Whiteface Mt., observations.
It is again obvious that the Schenectady ozone concentration appears to
approach, but never exceeds, the Whiteface Mt. ozone concentration.  For the
northeastern region of New York State,  we can therefore reiterate the importance
of meteorological mixing processes as the dominant parameter governing the
diurnal behavior of surface ozone concentrations.

     We have further substantiated these findings through occasional airplane
flights (equipped with chemiluminescence ozone detectors) over New York State
to levels up to 12,000 ft.  While the source of ozone observed at. the four
stations must be "uniformly" distributed at elevated levels (certainly above
the 850 mb level and therefore  above the planetary  boundary  layer), we
cannot yet establish a link between ozone-rich  stratospheric air mass
intrusions and high surface ozone concentrations.

     However, the first large-scale experiments have been initiated in
collaboration with the National Center for Atmospheric Research (NCAR).  Data
from three examples of tropopause folding have been collected and analyzed
that demonstrate the vertical  ozone transport.  The measurements were made
in Project DUSTORM during April 1975.  Large scale cyclogenesis was predicted
and the NCAR aircraft first traversed the folded tropopause at 21,000 ft.,
flying perpendicular to the wind.  After the limits of the zone were
determined, the plane turned back and reentered the zone.  Three upwind-
downwind sampling flights were  made—one near the warm boundary, one in
the center, and one near the cold boundary.   Then the aircraft ascended to
25,000 ft.  and  this flight pattern was  repeated.  On the same day, an
observer traversed the same storm system on a commercial aircraft, making
ozone measurements at approximately 39,000-41,000 ft.  Figure 4 shows the
vertical  cross-sections along Electra and commercial airline flight paths
normal  to folded tropopause and jet streams.  Isotachs are drawn at
10 m-sec"1  intervals (solid lines).  Folded tropopause (dashed lines) is
also indicated  in Figure 4.

     Figure 5 shows the locations of jet and Electra flight paths at 0000
GMT on the 26th and 27th of April 1975.  Dashed line denotes trajectory of
ozone-rich air  from 26th to 27th.  Figure 6 shows the time profiles of
ozone number mixing ratio, wind speed,  and temperature measured along commercial
flight path on  26 April 1975.   Tropopause level  (dashed line) is from
conventional  tropopause analysis charts (provided to us by P. Falconer, NOAA).

                                     102

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           dW31 lOd
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                         c
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                                       co
 add OIlVd 9NIXIN fcO
                103

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                                                  x-   AIRLINE FLIGHT LEVEL
                                              f 7!km
                                              v       FLIGHT LEVELS
                                                   =	6.4km
Figure 4.   Vertical  cross-sections  along Electra and commercial  airline flight
            paths normal  to folded  tropopause and jet streams.


      The preliminary evidence presented here from the Electra and commercial
 flight  data obtained during the operation of Project DUSTORM confirms  the
 concept of tropopause folding and  the assumption that ozone-rich air is
 transported into  the troposphere with each major cyclonic development, and
 that  this ozone-rich air,  although diluted by mixing with tropospheric air,
 can reach the  surface of the earth.  The surface deposition pattern is
 strongly asymmetrical due  to the narrowness of  the  folded structure and
 the strong deformations in the descending air.  Some local regions may be
                                      104

-------
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                           106

-------
8dd OI1VN 9NIXIN 3NOZO
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                            107

-------
influenced by this ozone-rich layer for just two or three hours, others for
one or two days.  More research is necessary to quantify the effects of this
ozone source on the surface ozone chemistry.

                                  REFERENCES

1.  Junge, C.E., "Global  ozone budget and exchange  between stratosphere
      and troposphere."  Tellus XIV,  363-377 (1962).

2.  Fabian, P., "A theoretical investigation of tropospheric ozone and
      stratospheric-tropospheric exchange processes."   Pure and Appl.
      Geophys., 106-108,  1027 (1973).

3.  Reed, R.J. and E.F. Danielsen, "Fronts in the vicinity of the
      tropopause."  Arch.Meteor.Geophys.Biobl., SA, B11, 1-17 (1959).

4.  Danielsen, E.F.  and V.A.  Mohnen,  "Ozone measurements and meteorological
      analysis of tropopause folding."  International  Symposium on Ozone,
      Dresden (Aug.  1976).

5.  Taba, H., "Ozone observations and their meteorological applications."
      Technical Note No.  36,  World Meteorological Organization, Geneva
      (1961).

6.  Vassy, A., "Atmospheric ozone."  Advances in Geophysics, Vol. 11,
      115-173.  Academic  Press, N.Y.   (1965^

7.  Reiter, E.R., Atmospheric Transport Processes.   Part 2:  Chemical  Tracers.
      AEC Div. of Technical Information (1971).

8.  Coffey, P.E. and W.N.  Stasiuk, "Evidence of tropospheric transport of
      ozone into urban areas."  Environmental Science  and Technology,
      Vol. 9, No. 1, p. 59  (Jan. 1975).
                                    108

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                                                                             3-4
          METEOROLOGICAL FACTORS CONTROLLING PHOTOCHEMICAL  POLLUTANTS  IN
                             SOUTHEASTERN NEW ENGLAND

            R.  A.  Dobbins,  J.  L. Nolan, J. P. Okolowicz, A.  J.  Gilbert*

ABSTRACT

      The. ozom me.aAuSie.me.ntA  in AouuthzaAteAn Ne.u) England fatiom  May to  Se,pte,m-
boji 1975 weAe.  examined  (&Ltk the. did oft data on ground le,vel. mutwiotogy,
not radiation, and nearby  fi.adioi>ondej>.  Ike, ozone. c.once,ntsiationA at -6euen
4-c£e/4 in tki&  Ae,gion  fluctuate, e.&Ae,ntially in unison 04 Mould  OCC.UA. i
pollutant IMOA  pfLimasiily tA.anApotite.d -into the, siagton.  The,  cle.afi-Me.atheA
diufinal cycle,  normally  &kowi>  ve,iy low conce,nttation-& pfii.au to  £untiit>e. and
the, daiJLy maximum oceans during late, a&tesinoon.  OccaA-ional daily maximum
fLe,ading^> one, obAeAve,d to OC.CILI afate.fi &u.n&e,nt  and
dtheA condition* aste,  faavotiable,.   A machaniAm Lb ofifieAnd in e-zplanatton ofa
the. diutnal cycle, that    con&iAte,nt w-Lth the, ob£e.fivationA -^e,po^te,d by othe,-U.

                                   INTRODUCTION

       In  this  paper we examine the  effect of  transport  and meteorological
conditions  on  photochemical air pollution  in  southeastern  New England during the
period from May through September 1975.  Ground level ozone (Oq) measurements
at seven  sites in Massachusetts, Connecticut and Rhode  Island  (Figure 1),
along with the appropriate meteorological data, provide the basis  for this
study.  The sites represent small cities (Providence, Fall  River)  and rural
areas (Groton, Eastford,  Scituate, Fairhaven, Medfield) on the northern
terminus  of the northeast  corridor.  The ozone measurements  at the  sites
were made using the  gas-phase chemiluminescence technique  as  prescribed by
the U.S.  Environmental  Protection Agency (EPA) (1), and the quality  assurance
procedure was  carried out  for each instrument following the EPA guidelines
(2).  This quality  assurance  program in Rhode Island included  daily  a zero
check, a  single span  point each week and a multipoint calibration  once a
month.  From 20 May  1975 through 14 November 1975 the EPA  Region  I  labora-
tory conducted monthly  audits of Massachusetts, Connecticut,  and Rhode Island
sites including Eastford,  Connecticut and Providence and Scituate,  Rhode
Island.   Dr. Thomas  Spittler, reporting on the results  of  these audits,
concluded that the  ozone data from the region was of good  quality  (3).
Continuous nitrogen  dioxide (NO?) measurements were made in  Providence using
*R. A. Dobbins,  Brown  University, Providence, Rhode  Island.
 J. L. Nolan,  J.  P.  Okolowicz, State of Rhode Island,  Department of Health,
Providence,  Rhode Island.
 A. J. Gilbert,  New  England Consortium for Environmental  Protection,  Providence,
Rhode  Island.

                                      109

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the Lyschkow modification of the Saltzman method.   The  instrument  was  zeroed
every day and standards were run once a month.   Baseline  drift  was significant
but linearly corrected when reducing the data;  therefore,  the data is  of good
quality.
   1
   2
   3
   4
   5
   6
   7
Eastford
Groton
Scituate
Providence
Medfield
Fall River
Fairhaven
             Figure 1.   Location  of Regional  Ozone  Monitoring  Sites.


      Our examination of the ozone readings was facilitated by the use of a
simple atmospheric total radiation meter.   The device consisted of two flat
stainless disks with copper-constantan thermocouples mounted to measure their
temperature difference.  One polished disk, which assumed air temperature,
was shaded by three horizontal aluminum wafers that formed a radiation shield.
The second disk was painted with flat black paint to achieve a high emissivity
and was located on the top wafer so as to command a clear view of the sky.
The temperature difference between the disks was controlled by both radiation
and convection; therefore, the thermocouple output has no quantitative signi-
ficance.  Nevertheless, the record does provide excellent qualitative differ-
entiation among the following types of atmospheric radiation histories:  (a)
strong insolation as indicated by a noontime deflection of about +15°C with a
moderate turbulent noise component; (b) zero net
neutral stability; and (c) a negative deflection
of outgoing radiation from the earth's surface.
found to correlate perfectly with the occurrence
or low level inversion as revealed by radiosonde
Massachusetts.
                                           radiation  flux leading to
                                           of  2.5  to  4.0°C indicative
                                           The negative  readings  were
                                           of  either  a surface-based
                                           observations  at Chatham,
     Air parcel trajectories for the 500 meter level were calculated using the
computer program developed by Heffter and Taylor (4).   This program used
observed winds to calculate the prior position at six-hour intervals of an
air parcel located over Providence at a specified time.  The winds used in
the calculation apply to the 300 to 700 meter altitude band that is typical
of the middle level of the daytime convective boundary layer in our region.
The observed wind vector at a point on the surface or above the surface is
assumed constant for six-hour time periods, and the parcel wind vector at
each three-hour period is found by interpolation from all wind vectors observed
                                     110

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within 300 nautical miles.  The individual wind observations are weighted in
accordance with their distance and upwind/downwind locations from the time-
dependent position of the specified air mass.   The assumption of stepwise
steadiness may not be suitable if, for example, a time-dependent pressure field
is present or a frontal system traverses the region.   The procedure involving
weighting factors for the interpolation procedure is  not known to have been
tested.  Therefore, we consider the trajectories to be estimates and, in this
study, we applied two additional criteria.  The estimated trajectory was
considered valid only if (a) the number of available  observed winds was greater
than five and (b) the estimated trajectory was consistent with the surface
wind observed at the National Weather Service at Warwick, Rhode Island.

                                  OBSERVATIONS

     The graph of the daily average ozone concentrations for five of the seven
sites during the month of June 1975 (Figure 2) demonstrates the strong corre-
lation of ozone concentrations throughout the region.   This situation suggests
that ozone concentrations in southeastern New England are, in large part, the
result of advection into the region.   On a daily basis, the transport mechanism
results in ozone peaks occurring at approximately the same time and magnitude
"hroughout the region, especially on  days having high sustained wind speeds.

     Air parcel trajectories were examined for those  days having a daily ozone
concentration greater than  .055 ppm at Providence.  The trajectories in
Figure 3 have arrival times closely corresponding to the occurrence of the
ozone peak at Providence.  The trajectories indicate  that 90 percent of the
air flows in question arrive from the southwest quadrant traveling northeast.
In examining the air flows from the southwest, we find that 60 percent of these
trajectories are generated by relatively large Bermuda highs.  The remaining
40 percent of the southwest flows are generated by more complex weather systems,
such as approaching cold fronts and/or low pressure systems situated to the
north of the New England region.  The northeasterly air flow indicated in Figure 3
is actually the reversal of air flowing from the southwest through the region.
The arrival of a "back door" cold front (from the northeast) results in this
air, with a high 03 concentration, being transported  towards the southwest,
again passing through the region.  This may be an example of the inability of
the trajectory model to deal with such discontinuities.  In tracing the air
flows back 48 hours prior to their arrival at Providence, we find that 73 percent
of the trajectories lie along the "Northeast Corridor."  These trajectories
correspond to the occurrence of the highest concentrations of 03 in the south-
eastern New England region during the period under study.

     To demonstrate the variation of ozone increase in the morning hours, the
0300-0500 EST ozone average was plotted versus the 0800-1000 EST average at
both Providence and Scituate for selected conditions.   The 0300-0500 period
was chosen to represent the ozone value just prior to sunrise, and the 0800-1000
interval was believed to be too early for any significant local ozone production.
These data were plotted for mornings  following low level or surface-based
inversion (chosen with both radiosonde and radiometer data) and for mornings
following cloudy nights (selected with climatological  and radiometer data)
for both Providence and Scituate.  A least mean squares line was then fit to
                                     111

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 .10-.
 .08"
.06
 .Oh"
 .0?
 KLY  to SYMBOLS
	Providence
— Scituate
H+H Groton
+ + -«• Fall  River
    Eastford
     PPM
                                      DATE
                                               7<
                           10
?0
                   Figure 2.  Daily 03 averages,  June  1975.
each set of data in  Figure  4, with the slope of each line representing the
average ratio of the pre-sunrise  to post-sunrise 03 reading.  After sunrise
there was very little change  in 03 concentration at either Scituate or Provi-
dence under the cloudy night  condition.  However, when radiation inversions
were present prior to sunrise, the post-sunrise 63 concentration at Scituate
increased by a factor of three and at Providence by a factor of ten.

     In figures 5a and 5b we  have graphed several pollutant concentrations
(hourly averages)  on the same chart as the radiometer temperature difference.
Figure 5a illustrates several features that are typical of a clear sky diurnal
ozone cycle in our region.  Ozone builds up during the first clear day to
a level of 0.035 ppm and falls to zero soon after sunset.  During the second
sunny day the peak ozone reading  of 0.055 ppm occurs at 1400-1500 hours EST
and again decreases  sharply after sunset.  In Figure 5b the radiometer indicates
a partly cloudy day, and the  peak 03 reading of 0.12 ppm at noon is followed
by a long period during which the reading is 0.05 ppm.  This level persists
until midnight during the night,  when the radiometer shows no temperature
                                    112

-------
                                                £"/:> - o >co
                                                      Ai,Y  to 6YM3CL3

                                              •        o Trajectory
                                                             endpoint
                                                      ^ 1^-hour  interval
                                                             position
                                                    — Estimated
                                                             trajectory
                                             -/?oo
  Figure 3.   Air parcel  trajectories daytime 03 peaks, May - September 1975,
difference; the sky is  therefore overcast.  After midnight the ozone  reading
drops to 0.015 ppm and  does  not increase after sunrise, when cloudiness  remains
high.  These 03 concentration  cycles are typical of clear and cloudy  weather
in our region.  Note that  in Figure 5b the N02 concentration remains  low and
does not decrease when  the 03  readings increase dramatically during the  first
partly cloudy day.

     Table I is a list  of  seven dates on which ozone peaks occurred during  the
nighttime hours.   In each  case the daytime concentrations were significantly
lower than the standard while  the peak nighttime value was over or near  the
standard.  A comparison of the trajectories (Figure 6)
showed that on each occasion the trajectory originated
the southeastern New England region was cloudy all day
seems to indicate that  the ozone was formed in the sunny area and combined
with clouds as it was advected into southeastern New England.  This weather
condition was commonly  associated with the approach of a cold front to our
region, but other more  complex weather systems produced similar results.  As
was the case for the daytime peaks, the majority (85 percent) of the  wind
flows on these nights were from the southwest quadrant.  Additionally, 70
percent of the trajectories were found to lie along the eastern seaboard.
with the weather maps
in a clear area while
and evening.   This
                                    113

-------
 .Oil 5-
 .030'
                                      X
                                    Scituate  - after cloudy  night (O)
 .01')-
          *        -—-"^
  Scituate -  after inversion (-J-)
           ~A        +


Providence -  after inversion (•)
' ^^ -™
,0is

.030

.oV,

I
.0 0

1
.07'


      Figure 4.   Average  03  concentrations, ppm.  Providence arid Scituate
                            pre- vs. post-sunrise.


                                  DISCUSSION

     The formation  of  ozone  in the atmosphere over Los Angeles has been recently
discussed by Calvert  (5), who shows that the rate controlling reactions
involve:  (a)  the photolysis  (Kj of N02 to form 0 and nitric oxide (NO) which
is followed by the  rapid  formation of 03, arid (b) the recombination (K3) of
03 and NO to form N02  and 02.  Thus, Calvert shows that, within a given air
parcel,  the relationship  for  the concentration ratio is given by
          [03]  [NO]
                                                              (1)
between the hours  of  0900  and  1400 local time.  The increasing solar inten-
sity during the daylight hours  causes 03 to reach peak levels in the after-
noon hours because,  in  part, the radiation-dependent K: is then a maximum.
We find many cases where there  is a similarity between the 03 diurnal cycle
in our region and  the Los  Angeles Basin, suggesting that the above reaction
sequence describes our  03  concentrations.  However, the basic mechanics that
caused the diurnal 03 in southeastern New England are entirely different.
These mechanisms must also be  consistent with the previous observations:
the nearly coincident daily Q3  averages at five locations as shown in Figure 2;
the occurrence of  nighttime high levels of 03 only under conditions of cloud-
iness; and finally,  the occurrence of increasing daytime levels of 03 under
clear skies when the  N02 concentrations are negligible.
                                     114

-------
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t I
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           115

-------
  TABLE 1.  CLOUDY NIGHTS WITH 03 PEAKS:  TIME  AND MAGNITUDE  OF  PEAKS  (ppm)
              Prov.     Scit.     Grtn.     F.R.     Estfd.     Fhvn.     Med.
May
12-13
June
3-4
June
29-30
July
4-5
Aug.
13-14
Aug.
21-22
Sept.
11-12
0200
.059
2300
.074
2300
.054
0000
.113
0000
.093
0000
.098
2000
.108
No
Data
2300
.054
0000
.049
2300
.088
2200
.093
2200
.084
No
Data
2200
.070
0100
.070
0200
.070
No
Night
2000
.140
2200
.130
No
Data
2100
.071
2300
.079
2200
.057
0100
.121
0000
.094
1900
.099
2000
.124
No
Data
2000
.045
0000
.061
No
Data
2000
.115
2300
.100
2100
.125
Mo
Data
Mo
Data
No
Data
No
Data
0100
. 1 35
1900
.125
1900
.103
No
Data
No
Data
No
Data
No
Data
0000
.095
0000
.100
2100
.138
     Based on these observations,  we  conclude  that long distance  transport
is the major source of 03 observed in our region.   We further hypothesize
that the depletion of ozone by reaction on the earth's surface with substances
that are readily oxidized is an important factor that influences  its concen-
tration in the surface layer.   These  effects  are the dominant factors that
control ozone levels in our area and  that account  for a diurnal  cycle that is
strongly dependent upon the atmospheric stability.  Some common sequences
that we observe that are explained by this hypothesis are the following:
(a) Clear Night Condition—Following  a clear  day,  high concentrations of
ozone may be advected into our region.  During a cloudless night, strong out-
going radiation results in the formation of a  nocturnal surface layer that
is of depth equal  to about 100 meters (6, 7).   Within this confined layer,
the ozone is reduced to marginally detectable  levels by surface depletion
reactions.   Presumably high levels of  ozone exist above the surface  layer
and  then escape detection by the monitoring devices whose intake ducts are
typically  ten meters above  the surface.   Rural versus  urban readings do
differ because traffic-generated NO may be injected at ground level  into the
stable nocturnal  surface  layer by early morning traffic; thus urban  03 readings
will  be generally  lower  than rural readings.  Within  two-three hours after
sunrise, the  nocturnal inversion is dispersed by  solar heating of  the earth's
surface.   Morning  ozone  readings rapidly  increase when the 03 above  the dis-
integrating  inversion  is  allowed to reach  the ground  through a fumigation
process; (b)  Cloudy Night Condition—A heavy  layer of  cloudiness present


                                     116

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                                                      KEY to SYMBOLS

                                                     O  Trajectory
                                                             endpoint
                                                     ^  12-hour  interval
                                                             position
S//3-/?oo

  Figure  6.   Air  parcel  trajectories nighttime 03 peaks May - September 1975.

 during nighttime hours  results in a neutral atmosphere boundary layer whose
 typical  height is  500-1000 meters.  If the cloudiness follows a clear day,
 the 03 levels at the  surface can be high because of advection from sources
 outside  our region.   The  03 concentration is totally controlled by the levels
 resulting from advection.  Surface depletion reactions play a minor role because
 mixing from aloft  is  unimpeded by any stable layer near the surface.   These
 two sequences are  illustrated by the pre-sunrise/post-sunrise 03 ratios in
 Figure 4 and by  the correlation between the radiometer output and 03  concen-
 trations shown in  Figure  5.

                                     SUMMARY

      We  conclude that the ozone concentrations in southeastern New England
 result primarily from the transport of this pollutant into this region from
 distant  sources.  A study of air mass trajectories indicates that the ozone
 usually  is  transported  from the southwest direction.  The 03 violations occur
 even when the morning N02 levels are low, suggesting that the local photolytic
 effect does not  contribute to the 03 peak.

      We  propose  that  under clear skies, surface depletion reactions occurring
 within the  nocturnal  inversion layer cause the low 03 readings that are observed
 prior to sunrise.  After  sunrise, when the inversion is broken up by solar
 heating, the 03  existing  aloft is allowed to fumigate the surface, causing
 a rapid  increase in ozone concentrations.  Nighttime high levels of ozone
 directly reflect the  influence of long distance transport under conditions
 when the cloudiness prevents the formation of a nocturnal inversion,  and the
                                     117

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unimpeded mixing diminishes the relative importance of the surface depletion
reaction.

     This proposed mechanism involving surface depletion reactions is con-
sistent with the observations of others.  It may explain why Calvert found
Equation 1 invalid during the early morning hours in the Los Angeles Basin
and why he and others have observed 03 concentrations increasing with alti-
tude in the early morning hours under clear skies.   The surface depletion
reaction mechanism combined with transport is also  consistent with the rural
03 readings at Wilmington, Ohio, reported by Lonneman et al. (8); these read-
ings increased dramatically during morning hours without a significant decrease
of the very low level of N02 that was observed.

                                ACKNOWLEDGEMENTS

     The authors wish to acknowledge the assistance of Larry Niemeyer and Dale
Coventry of the U. S. Environmental Protection Agency, Research Triangle Park,
North Carolina, in running the air parcel trajectories model; Marvin Rosen-
stein, U. S. Environmental Protection Agency, Region I, for providing the
radiosonde data; and Arnold Leriche, U.  S. Environmental Protection Agency,
Region I, for the air quality data.  Financial support was supplied by the
New England Consortium for Environmental Protection for A. J. Gilbert and
J. P. Okolowicz.

                                   REFERENCES

1.   Appendix D, "National Primary and Secondary Ambient Air (Juality Stand-
     ards," Federal  Register, Vol. 36, No. 84, Part II, Friday, April 30, 1971.

2.   EPA-R4-73-028c, Guidelines for Development of  a Quality Assurance Pro-
     gram (Photochemical Oxidants), June 1973.

3.   Spittler, T.  M., "Report on Ozone Field Audits for 1975 Summer Ozone
     Study," N. E. Region APCA Monthly,  Hartford, Conn., April  1976.

4.   Heffter, J. L.  and Taylor, A. D., "A Regional-Continental  Scale Transport
     Diffusion and Deposition Model," NOAA Technical Memorandum, ERL ARL-50,
     June 1975.

5.   Calvert, J. G., "The Theory of Ozone Generation in the Los Angeles
     Atmosphere,"  Environmental Science  and Technology, Vol. 10, 1976, p. 248.

6.   Yamada, T. and  Mellor, G., "A Simulation of the Wangara Atmospheric
     Boundary Layer  Data," Journal of Atmospheric Sciences, Vol. 32, 2309,
     1975.

7.   Shaw, N. A.,  "Acoustic Sounding of  the Atmosphere," Ph.D.  Thesis, Uni-
     versity of Melbourne, Australia, 1971.

8.   Lonneman, Buffalini & Seila, "PAN and Oxidant  Measurements in Ambient
     Atmospheres," Environmental Science and Technology, Vol. 10, 1976,
     p.  374.


                                     118

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             SESSION 4
SOURCES OF TROPOSPHERIC OZONE - II

     Ckcuxman:  R.A. Rasmussen
    Washington State University
                119

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                                                                               4-1
                              AN ASSESSMENT  OF  THE
                  CONTINENTAL LOWER TROPOSPHERIC OZONE BUDGET

                       R.  Chat-field and R.  A.  Rasmussen*
ABSTRACT

     Severai di^erent regime* oft photoc.hem-if>try and transport are nece**ary
to ducAA.be. the. di^erent pattern* o& dinmai ozone. variation  ob*erved hi
rurai  area* 0f) eastern North America.  One  chemicai regime may govern ozone.
concentrati.on &or day* then,  within hour*,  -Lt may be. dispiaced by another
regime a*  precursor concentration*, atmo*pheric n\4.XA.n.Q, and AadLcution dkange.
because o& wind* and we.atheA.   The^,e. n.e.g-ime.-i>  inc.lu.de.:    (a) expo^uAe o& the.
OAA'A  4uA)$ace layeA to &iopot>pheAA.c background ozone.;   (b) duoM> to produce. e.nhanc.e.d oxi-dant  le.ve.lA outi>i.de. any indi.vi.duaf.
urban  pJtume..
     Thue. re.gime^> are. iLtw&tratcd Mith cat>e. -t>tudi.e^> 4 ejected 04  arc.kejtype.ts
many day*  o& inte.n&i.\>e. Aampting -in the. midweAt and northe.at>t o{, the. Unite.d
State.*.  V-Uti.nct patteAnA  ofa ozone, be.havi.or are. i.ntnrpre.te.d ut>i.ng faliioro-
carbon and hydrocarbon me.a&ure.me.ntA .  . VeJiaJJ,e.d gad -chromato graphic anaty-dis
i.ndivi.duai hydrocarbon* ducri.be. oxi-dant pre.cur*or JLe.ve.lA.  ftuoro carbon
me.aAure.mentt> describe, direct urban contami.natA.on and the. de.gre.e. o& accumula
tion o{, anthropoge.ni.c e.miAi>i,ont> on a re.gi.onai
     The. tropo*pheri-c background appe.art> to  be. about BQ% greateA than pre.-
        reported and there, is  e.vi.de.nc.e. {on e.a&t-wut at, weJLi a*  north-touth
            o{, the. me.an background aero** the. contine-nt.  Thue. condu*-ion*
      ^rom a re.anaiy*i^, o^ the. e.xte.n*i.ve. ozone. *ounding program* o&  the.
     We present a briefi as*e**ment of, the deveiopments -in other descri.pt-
Of) the rurai ozone budget  over the iast *i.x  year*  and *ugge*t dir.ecti.on*
future, more detailed modeiing nLinhi-k
                                  INTRODUCTION

     In  1970,  the ozone budget of the nonurban  troposphere seemed  about to be
expressed  with reasonable numerical precision.   Fabian and Junge in that year
*Washington State University, Pullman, Washington.

                                        121

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described a simple model, applicable outside urban areas, based on production
of ozone in the stratosphere and on destruction at the earth's surface.  On
the basis of this model, all that seemed necessary to predict human exposure
was better quantitation of boundary layer micrometeorology and surface reac-
tivity.  However, since 1970, a quantitative description of ozone concentra-
tions, reactions, and fluxes has become much less definite—the ozone budget
over and outside of the population centers of the mid-latitudes of the U.S.
appears to be much less understood.   Certain realizations have produced this
indefiniteness:

     •   The long distance transport of oxidant pollution in urban and in-
         dustrial plumes has been documented.   For example,  the work of
         Cleveland et al.  (1976), Westberg (1976), and Spicer (1976) suggests
         that the plume of the New York City area may determine oxidant expo-
         sure in Boston, nearly 300 km distant.

     •   Measurements of high rural  oxidant levels, outside  the boundaries of
         distinct urban plumes, have repeatedly been reported.  These levels
         have been described in terms of smog-like chemistry acting on regional
         accumulations of oxidant precursors (Robinson and Rasmussen, 1976;
         Ripperton,  et al.,  1974) or in terms  of ozone of stratospheric origin
         (Coffey and Stasiuk, 1976).

     t   Levy (1971) has suggested that natural  atmospheric  processes produce
         radicals from methane oxidation even  in clean-environments.  The de-
         tails of this chemistry are still not adequately modeled; but, it is
         recognized that the process can produce or destroy  ozone faster than
         transport to the earth's surface can  destroy ozone  (Crutzen, 1974).
         Chameides and Walker (1973,  1976) have suggested that this chemistry
         may produce much of the ozone of the  troposphere.

     •   The prevalence of significant levels  of non-methane hydrocarbons and
         other trace gases in rural  areas has  been demonstrated (Rasmussen, et
         al., 1976).  It is  not yet clear to what extent these gases may be
         responsible for modulating the surface ozone budget.   Some compounds
         reduce ozone; others probably participate in free-radical chemistry
         processes that produce ozone.

     t   Our understanding of the natural range in the level of background
         tropospheric concentrations of ozone  based on older methods of meas-
         urement has been questioned by the use of more accurate surface and
         airborne instruments.   Chatfield and  Harrison (1976c) have suggested
         that mid-tropospheric background ozone levels may be as much as 60%
         higher than estimated 1970.

     This paper describes both the certainties and uncertainties of the tropo-
spheric ozone budget.  The following section sketches the photochemical and
meteorological conditions affecting ozone transport and chemistry.  Then
observations characterizing mid- and lower-tropospheric ozone levels, which
are free from boundary layer complexities, are presented.  Three case studies
of surface ozone variation with concurrent levels of hydrocarbon species and
transport patterns are included.  These case studies illustrate the alternate


                                     122

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importance of (a) vertical  mixing of tropospheric air,  (b)  natural  photochemi-
cal processes in the boundary layer, and (c)  enhanced photochemical  production
of ozone due to anthropogenic emissions  outside the boundaries  of urban plumes.

                        OZONE CHEMISTRY AND TRANSPORT

     In order to understand the variability of the concentrations of ozone
observed near the earth's surface, we must appreciate the physical and chemi-
cal processes that govern its concentration in the boundary layer and the
troposphere  as a whole.  Humans and plants, both sensitive to anomalously high
ozone concentrations, have always lived within a few meters of the earth's
surface.  For this reason, our exposure to ozone has been within a very thin
region of the atmosphere—the boundary layer.   This layer is the region where
ozone behavior is the most complex.   Within the boundary layer (often consid-
ered equivalent to the "mixed layer") the chemistry and transport behavior of
ozone is quite distinct from the rest of the troposphere.

     First, within the limits of the boundary layer there are large sinks for
atmospheric  ozone.  For three decades it has been apparent that the earth's
surfaces, whether or not covered by vegetation, reduce ozone readily at vari-
ous rates.  Summaries of the importance of this sink may be found in Galbally
(1974) and in Fabian and Junge (1970).   The ocean's surface has much less
ability to destroy ozone; its rate of destruction is still not well estimated
(Regener, 1973).  More recently, it has become apparent that trace gases
emitted from natural biogenic sources and man's activities also effectively
reduce ozone close to their surface sources.   On the other hand, some of these
gases, the hydrocarbons and nitrogen oxides, participate in reactions that
resemble smog chemistry in great dilution.  Many hydrocarbons, like isoprene,
are measureable only within the earth's boundary layer, apparently indicating
that they oxidize before they can travel far vertically.  Others, like methane,
appear to be distributed rather evenly throughout the troposphere (Ehhalt,
1972).   Currently, the significance to the ozone budget of the photochemical
reactions of these hydrocarbons is subject to considerable uncertainty.  Levy
(1972) and Crutzen (1974) have suggested that the oxidation of methane in the
unpolluted lower atmosphere could contribute to or could destroy significant
amounts of ozone.  Chameides and Walker (1973) have taken the stronger posi-
tion that photochemical oxidation of methane supplies the major source of
tropospheric ozone.   The ozone produced in their photochemical model dominates
over transport and vertical diffusion in controlling ozone concentrations in
the surface layer of the atmosphere (1976).   Crutzen's (1974) description of
the relevant reaction chains points out that various small changes in reaction
rate coefficients and other model parameters  change the destruction rate
significantly and even allow for a net sink for ozone.   Other hydrocarbons in
addition to methane oxidize by means of radical-propagated reactions which may
produce and/or destroy ozone via similar reaction pathways.  While non-methane
hydrocarbons are 3 to 4 orders of magnitude less concentrated in the boundary
layer than methane, most of them are 2 to 4 orders of magnitude more reactive
(Pitts, et al., 1976).   The net result is that these species may contribute as
significantly as methane to ozone formation.   Graedel et al. (1976) have in-
cluded isoprene and a-pinene in one reaction scheme; more ozone was generated
from these hydrocarbons than from methane.
                                     123

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     Three results of recent work stand out:  (a) Chemical reactions produce
or  destroy ozone in the troposphere, (b) The variability of meteorology  (sun-
light, temperature, vertical mixing, and water vapor) and source strengths of
precursors (hydrocarbons and nitrogen oxides) may vary so to allow both  net
production and destruction at different times, (c) Ozone-modulating chemistry
is  most active within the boundary layer; the boundary layer and the lower
troposphere should be modeled as separate but interacting systems.


                        BACKGROUND TROPOSPHERIC OZONE

     Systematic data on the variability of the ozone concentrations represent-
ative of the atmosphere above the boundary layer (90% of the troposphere) and
away from densely populated areas are scarce.   The data available until  re-
cently was incidental  information obtained from programs designed to character-
ize surface ozone levels in urban air with little attention  given to the ozone
levels above the boundary layer.   The ozone data available for mid-troposphere
profiles was also peripheral  since most of it came from ozone sounding programs
designed to characterize stratospheric ozone.   However, the  latter programs
provide an acceptable  random sample of varying ozone levels  characteristic of
different weather situations  and geographical  locations obtained with  instru-
ments whose measurements are  readily comparable.

     Hering and Borden (1964a,  1964b, 1965, 1967) reported an extensive  series
of ozone soundings  of  the troposphere and stratosphere launched from 1963 to
1965.  However they cautioned that errors in their method could be quite
significant for the tropospheric portions of the soundings.   Continuation of
that ozone sounding program from 1966 to mid-1969 demonstrates the nature of
one of these errors.   Earlier ozone measurements used instruments based  on the
chemiluminescent reaction of ozone with rhodamine dye (CL instruments).   The
later ozonesonde studies used a Mast-type buffered KI electrochemical  method
(EC instruments).  An  analysis  comparing the standardization of the instruments
as well as the statistics of the ozone concentrations obtained from each type
of instrument suggested that the EC instruments  give more reproducible (pre-
cise) estimates of the tropospheric ozone.   The  better data  obtained by  the  EC
instruments in the second phase of the ozonesonde program are not very well
known.   This is unfortunate since the second data set apparently provides more
information about the  true variation of ozone in the mid-troposphere than does
the first, larger data set.   Chatfield and Harrison (1967c)  reported that
these EC instrument estimates may be more accurate estimates of free-
tropospheric ozone.  If Chatfield and Harrison's analysis of the two data sets
is correct, estimates  of tropospheric ozone based on Hering  and Borden's
earlier work should be raised by 50 to 60 percent.

     Vertical profiles of ozone for the six stations that launched EC-type
ozonesondes from 1966  to 1969 are shown in Figure 1.  The ozone concentration
profiles are the means of numerous soundings measuring the ozone above the
stations named.  The stations extended from the Canal Zone at 9°N to Goose Bay
at 53.5°N.  All of the stations are located within a few degrees longitude of
the 75th meridian which passes  through the East Coast of North America.   The
data analyzed are for  the summer season.  Consequently, the  tropopause,  above
which ozone increases  dramatically, is high, i.e., at Goose  Bay, 9 km and, for


                                     124

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the tropical stations, over 14 km.   For the three  stations  north  of  30°N, the
ozone profiles are nearly vertical.   This constancy  of ozone  concentration
suggests either that there is little net diffusive transport  in the  vertical
or that the baroclinic eddies which  produce the  diffusive  transport  in
mid-latitudes are not well modeled by K-theory.  The vertical  variation  in  the
southern latitudes is a seasonal feature:  in March  for example,  ozone is con-
stant or decreases with height at these same stations.   Transport by Hadley-
cell motions and eddy motions described by Newell  (1969) seems to be the most
reasonable explanation.

        CANAL   G.TURK    KENNEDY   WALLOPS   BEDFORD  GOOSE  BAY
          9.0 N
21.5 N
28.5N
37.5 N
42.5N
53.3N
      0 20 40    20 40   20 40   20 40    20 40
                                        40
                                          120
                            OZONE MIXING RATIO,  ppb
Figure 1.   Averaged soundings  of ozone  concentration  (in  ppbv) above  the
listed stations.   Electrochemical  sondes  launched  during  the  summer seasons
of the years 1966 through 1969 contributed to  these means.  The data  for the
lowest kilometer  are not well  estimated.

     Figure 2 shows tropospheric ozone  in a way  that  compares north-south
variations among  stations.   The data  used to generate this  figure  used  EC
ozonesonde reports for the  layer 2 to 3 km above the  earth's  surface.   The
lower layers of the atmosphere are made more complex  by boundary layer, local
chemistry and transport features.   Bedford, Massachusetts,  42.5°N, and  Wallops
Island, Virginia, 37.7°N, probably have additional  complexities derived from
large anthropogenic oxidant and S02 sources upwind (S02,  for  example, produced
low instrument readings).

     Certain aspects of Figure 2 argue  persuasively that  the  stratosphere is
the predominant origin of free-tropospheric ozone  in  the  mid-latitudes.  The
left wall  of Figure 2 shows a  maximum ozone value  at  about  35°N in the  month
of January.  As the year progresses,  this maximum  retreats  northward  to about
43°N, where it stays from March until  September, and  then advances to a lower
latitude through  the end of the year.   The movement of this ridge  of  highest
ozone values corresponds well  to the  retreat and advance  of the mean  position
of the lower-tropospheric position of the polar  front.  It  is this frontal
region to which Danielsen's (1970) description of  stratospheric injections
into the troposphere applies.   The value  of the  summer ozone  maximum  is also
                                     125

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                                               t, month
 Figure 2.  Time-latitude cross-section of ozone (ppbv) measured between 2
 and 3 km by sondes launched from the stations listed in Figure 1.  These
 stations lie within a north-south band running through the Eastern U.S.

reasonable in that only in the spring is the lower stratosphere in the mid-
latitudes replenished with ozone from the tropical upper stratosphere.   Injec-
tions from the stratospheric reservoir are also most likely to occur in  the
highly contorted tropospheric westerlies that are characteristic: of spring
weather.
     Latitudinal variation is likely to be the most important type of varia-
tion, given the tendency of the winds to blow zonally.   However, in Figure 3,
contours of tropospheric ozone in the mid-troposphere,  between 3 and 7 km, are
drawn for all the stations reporting CL ozonesonde observations.  The con-
toured ozone concentrations of ozone depicted have been raised by a factor of
approximately 1.6 so as to agree with the results of the EC sonde data.  The
data seem to suggest an east-west variation in annual mean ozone.   The chemi-
cal and dynamical explanations have been discussed by Chatfield and Harrison,
(1967d).


            TROPOSPHERIC BACKGROUND AS SAMPLED BY GROUND STATIONS

     The deleterious effects of high ozone are most important near the ground;
but, the complex chemistry and transport occurring within the boundary layer
make ozone levels difficult to study.  Aircraft and balloon soundings allow
more extensive characterization of ozone formation and movement within this
mixed layer, and have been quite useful in the past few years.  However,
another way to reduce the complexity of ozone behavior near the surface  is
intensive—that is frequent-measurement of ozone, hydrocarbon, and oxidant
precursors, as well as tracers that give information about the origin of the
                                     126

-------
 ozone sampled.   For example,  fluorocarbon tracers  clearly  identify  the  extent
 to which ozone  may have had an urban origin.
                      CONTOURS OF OZONE   ppb  at 3 to 7 km

 Figure 3.  Continental ozone background.  Isopleths of ozone concentration
 (ppbv) derived from chemiluminescent ozonesonde ascents above the nine
 stations marked*.  These isopleths are drawn for annual mean ozone; various
 seasons may exhibit somewhat different ozone climatology.


     One such period during which a surface site was apparently exposed to
clean tropospheric air is shown in Figure 4.  The data were obtained at a farm
site near Elkton crossroads in southwestern Missouri, just northwest of the
Ozark Mountains.  The fluorocarbon-11 (F-ll) trace at the top of the figure is
representative of uncontaminated urban emissions.  Indeed, 115 ppt of F-ll was
the minimum observable background level  for surface air at that time period
and altitude.  As the radiation trace at the bottom of the figure shows, con-
ditions were generally overcasted.   The  movement of warm Gulf air into the
area during the afternoon resulted in showers in the early evening.   One
squall  line thunderstorm (not associated with a deep 500-mb though)  passed
over the area at about 2200 CDT on the 25th.   Intense stirring of clean middle
tropospheric air to the surface occurred for the F-ll  trace dipped to 105 ppt.
The lack of any significant change in ozone level suggests that the  ozone con-
centration overhead was similar to the concentration at the surface.   The
vertical ozone profiles shown in Figure  1 for stations north of 30°N latitude
also suggest that the overhead ozone level  does  not normally change  dramatic-
ally with altitude during the summer season.   Total  non-methane hydrocarbons
also decreased during this period from 50 to 30  yg  nf3.

     The ozone trace contained between August 25-26,  1976, is  a typical
pattern for windy, low-radiation situations  in  rural  areas.   The  general  ozone
level  varied irregularly between 30 and  47  ppb,  and there was  little indica-
                                     127

-------
               200




              I 175



              i 150
              o
              UJ
              cr
              Lx
                125



                100
8/25
                   '8/26
                                                           200
                                        50
                                          -,95
                                                           00 _
                                                              45
                                                           50 J20
                                              HOURS
 Figure 4.   Variation  in  ozone,  hydrocarbon,  and fluorocarbon levels observed
 during stormy weather near Elkton crossroads in southwestern Missouri.

 tion  of a  diurnal cycle.


      How do these surface  concentrations compare to the tropospheric ozone
 background illustrated in  Figure  2?  The latitude of Elkton, Missouri, is
 closest to Wallops Island, Virginia (37.5°N).  The mid-tropospheric ozone con-
 centration observed with the Wallops ozonesondes reported approximately 55 ppb
 of ozone in August and 50  ppb in  September.  Since Elkton is 17° west  of
 Wallops Island, the evidence summarized in Figure 3 suggests that we should
 subtract approximately 5 ppb.  In short, the agreement between sounding data
 and remote site data is consistent with the  interpretation that, the surface
 ozone  observed at Elkton under windy, low radiation conditions is primarily
 derived from overhead replenishment of the ozone in the troposphere.

     Such agreement is partly accidental since the standard deviation  of the
 tropospheric ozone background at  one location and season is 0.2 to 0.3 of the
 mean,  as measured by the EC ozonesondes.  The variability includes the range
 of true climatic variability of ozone as well as instrumental variability of
 the ozone data analyzed by Chatfield and Harrison (1967d).   The variation on
 the ozone levels from the climatology of the lower atmosphere suggested by
 Figure 2 may persist for weeks, as observations at the same site in successive
years indicate.  That is to say, ozone displays "weather" just as do rain and
 temperature.  Perhaps the most variation occurs in the spring, when the pre-
valence of blocking highs and cut-off lows create weather patterns which are
conducive to stratospheric injections of ozone into the troposphere (Danielsen
1976).  In certain cases, it appears that stratospheric injections followed by
strong cumulonimbus downdrafts can produce hour-long periods when surface
ozone concentrations are observed at levels of hundreds of ppb (Lamb,  1976)
                                     128

-------
 and shorter periods  when ozone can approach 600 ppb (Attmannspacher and
 Hartsmannsgruber,  1973).   Davis and Jensen (1976) have recently summarized
 practical  techniques for forecasting high ozone levels.

               NATURAL PHOTOCHEMICAL OZONE IN THE BOUNDARY LAYER

      The significance of the photochemical production of ozone within the
 lower troposphere  has been a point of controversy in recent years (Chameides
 and Walker 1973,  1976; Chameides and Stedman, 1975; Fabian, 1974).  Presuma-
 bly, there is a greater likelihood of significant photochemistry occurring in
 the boundary layer with its higher concentrations of oxidant precursors
 than in the free  troposphere.  The evidence for significant photochemis-
 try occurring in  the mixed layer outside urban plumes in situations of
 relatively clean  environments has been poorly documented.

      Several days  after the storms that characterized the August 25-27 weather
 at Elkton, Missouri, passed, the weather became sunny and the air relatively
 clean as shown in  Figure 5.  On the 30th, a weak cold front passed through the
 area in the early  morning hours without bringing rain, although a few clouds
 persisted.  Fluorocarbon levels gradually increased from 115 ppt in the after-
 noon although they remained below 125 ppt until midnight.  Ozone showed a
 typical diurnal  variation for clear weather with a broad maximum in the middle
 and late afternoon.   The peak ozone hourly values reached 56 ppb, an increase
 of 28 ppb  from that  morning at 0900 CDT, which was about the time of the
 frontal passage.
                        200
                       a 175
                         150
o
u

k.
                         125
                         100
                          0,
                                                  200
                             8/30
            • FREONS
            ° H C (TRAILER)
            QHC (WOODS)
            • OZONE
            A RADIATION
                                       12
                                          16   20
                                                  50
                                                     95
                                                  00
                                                     45
                                                  50 J20
                                                       E
                                                       o>
                                                       a.
Figure 5.  Fair weather diurnal  variation  pattern  of ozone levels contrasted
with hydrocarbon and fluorocarbon  levels observed  near Elkton,  Missouri.   The
afternoon maximum in ozone may be  due  to local  photochemistry.
                                      129

-------
     The hydrocarbon composition of the atmosphere was consistent with unpol-
 luted rural air with 30 to 50 yg m 3.  Total non-methane hydrocarbons (exclu-
 ding oxygenated species) were usually about 50 yg m 3 in the afternoon.   A
 typical afternoon sample was composed of about 10 yg m"3 of natural gas
 alkanes, 2.5 yg m~3 aromatics, 2.0 yg m 3 i-butane and n-pentane, 7.3 yg m~3
 of isoprene, and 6.5 yg m 3 of four_unknown but prevalent hydrocarbons of
 apparently rural origin and 20 yg m 3 of other hydrocarbons, about half of
 which were statistically associated with rural unknown hydrocarbons.  These
 identifications were made on the basis of gas chromatographic separations
 described in Rasmussen, Chatfield, and Holdren (1976).  In summary, the hydro-
 carbon composition of the atmosphere was dominated by rural hydrocarbons with
 very dilute traces of some anthropogenic hydrocarbons.

     The levels of hydrocarbons present were sufficient to produce the 28 ppb
 ozone increase observed during the day.   Since it is theoretically possible to
 produce from each oxidized atom of carbon 3 or 4 radicals, and hence 3 or 4
 ozone molecules, the 7.3 yg m~3 of photochemically reactive isoprene could
 produce 28 ppb of ozone if it were to react completely.  In addition, isoprene
 reacts so much more rapidly with hydroxide radicals than does methane that, at
 the concentrations observed, it creates  almost twice as many radicals as
 methane (Pitts, et al., 1976).   In reality, there are many reactions that de-
 stroy ozone and the necessary radical precursors.  Also the flux of ozone into
 or out of the boundary layer, both with  the free atmosphere and with the
 ground, are unquantified parameters affecting the resultant ozone concentra-
 tions.   Only intricate photochemical  modeling will be able to balance all of
 these effects.

     While atmospheric chemistry processes within clean continental air can
 plausibly produce ozone, one of the authors has argued elsewhere that many
 pieces of evidence that seem to confirm photochemistry also confirm transport
 arguments (Chatfield and Harrison 1976a).   Solar radiation, for example,
 governs meteorological processes (such as convective mixing) as well as  photo-
 chemical  rates.  Conclusive observational  evidence for photochemical ozone
 formation in rural atmosphere remains to be presented.


                       REGIONAL OXIDANT PHOTOCHEMISTRY

     Perhaps the most problematic portion of the current understanding of the
 lower tropospheric continental  ozone budget is assessing the extent to which
 urban and industrial hydrocarbon precursors may increase oxidant production on
 regional  or sub-continental scales.  Recently there has been considerable
 attention given to oxidant production in urban and industrial plumes.  These
studies show very clearly marked pollutant episodes occurring outside cities.
 Other contributors to this conference have described in greater detail the
 theoretical  and observational features of these urban plumes.  However,  there
 is a larger problem of regional air pollution episodes.  Our measurements at
 Elkton, a site specifically chosen to represent clean air in the far Midwest,
suggest that the air within the boundary layer even at this very rural site is
almost never entirely free of anthropogenic emissions.

     Often,  rural air is so well mixed horizontally that the plumes of small

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to modest size (10,000 to 70,000 population) cities can not be distinguished
50 km downwind.  Husar, et al. (1976) has noted the regional accumulation of
visibility-degrading aerosol into regional "blobs" shifted by synoptic winds.
Currently, such aerosol-haze is believed to be due to secondary heterogeneous
photochemical reactions involving either hydrocarbons or sulfates, or both.

     Our example of apparent regional air pollution episode comes from ground
station studies conducted near Glasgow, Illinois, 104 km NNW of the St. Louis
Gateway arch in July 1975.  The studies at this site were conducted just prior
to the Elkton studies.

     The meteorology and trace chemistry conditions leading to this episode
are shown in Figure 6.  Both the time variation of the F-ll concentrations and
total non-methane hydrocarbon (TNMHC) levels at the Glasgow site are shown.
The correlation for F-ll spikes—indicators of urban plumes-and TNMHC spikes  is
very good, though not perfect.  The line drawn at 115 ppt represents the mini-
mum F-ll concentrations observed as Glasgow, Illinois, or Elkton, Missouri.
The passage of urban air with higher levels of F-ll extend upward from this
background level as spikes.  Besides the minimum  background representative
of the cleanest air, there is a daily background  suggested by the minimum
concentrations attained each day when the site was most nearly free of
urban plumes.
            250
            200-
            150-
                                                                   250
ACCUMULATION
    OVER
 BACKGROUND
                                                                  15
Figure 6.  Regional accumulation of fluorocarbon-11 and non-methane hydrocar-
bon sampled on a farm 110 km north of St. Louis during the first two weeks of
August 1975.   The fluorocarbons spike to high levels when plumes of urban air
are sampled;  hydrocarbons show a similar behavior.  There is also a gradual
increase in minimum daily fluorocarbon concentrations from August 3 to August
13.  On these dates, new high-pressure systems entered the area.
                                     131

-------
     A subtle but important feature of the data gathered at Glasgow is the
 slow increase in this general level of the daily F-ll background from 117 ppt
 on  August 2 to  130 ppt on August 12, and the subsequent more rapid decline to
 118 ppt on August 13.  The rise was not due to instrumental drift.   Instead
 the rise in the F-ll background represents the accumulation of emissions in
 the air over the Midwest during this period.   Of course, our site at Glasgow
 never sampled the same air parcel twice; but, the Eulerian description of the
 site portrays fluorocarbon buildup in a manner fairly representative of air
 parcels moving within a stagnant southward-drifting high-pressure system.   The
 last frontal  passage bringing in new air from the northwest was  on  August 2.
 During the following time lapse the air mass  drifted from the industrial
 Midwest into the Glasgow site where it peaked August 12-14.

     Somewhat similar accumulative behavior is  evident for the TNMHC loading
 of  the atmosphere shown in Figure 2, despite  the greater variability that is
 evident for these reactive substances.   It is likely that nitrogen  oxides also
 increased during this period, but the Washington State University trailer did
 not measure them.

     Figure 7 shows  in detail the ozone, F-ll,  and TNMHC variations observed
 on August 12.   About midnight, the St.  Louis  plume passed over the  station
 according to the evidence of the surface winds  and the F-ll  readings monitored
 at the trailer site.   The surface winds then  swung south to the  west-southwest
 from 0300 CDT until  1500 CDT; during this period it would have been nearly im-
 possible for the site to be exposed to the St.  Louis plume.   By  1600 CDT, the
wind turned again to flow from the south, and within 4 hours the sampling sta-
 tion was again directly exposed to St.  Louis  air.   At 2000 CDT the  plume-
 generated oxidant rose to over 100 ppb and then dropped quickly.

     The interim period of west-southwest winds shows ozone behavior equally
 as  interesting as the 100 ppb spike.  During the interim period ozone reached
 90  ppb for one hour, and remained at a level  of over 85 ppb for 5 hours out-
 side any identifiable urban plume.

     The hydrocarbon chemistry of this day shows a mixture of anthropogenic
 and natural emissions.  TNMHC averaged around 80 yg m~3.  Gas chromatographic
 analysis of the ambient air samples taken in the afternoon show about 17.4 yg
 m"3 natural gas hydrocarbons, 6.4 yg m~3 of aromatics, 4.4 yg nf3 of automotive
 fuel vapors (e.g. pentane, octane), 4.3 yg m-3 of automotive exhaust emissions
 (ethylene, propene,  n-butane), 6.8 yg m~3 of isoprene, 10.0 yg m~3  of unknown
 compounds of suspected rural origin, and 29.0 yg nr3 of other compounds.

     Not all  of the days during this interim period showed such high ozone
 levels outside of the plume episodes.  The previous day showed only 60 ppb of
 ozone at maximum in  conjunction with 60 yg m"3 of hydrocarbons.   Ozone levels
 might have risen further, but in the early afternoon clouds cut off the solar
 radiation, and ozone began to decline immediately.  Also there were differ-
 ences in the hydrocarbon concentration which may have affected oxidant pro-
 duction; i.e., there were lower concentrations of isoprene, and other rural
 unknown compounds, and natural gas alkanes.  Other reports of elevated ozone
 distributions in the Eartern United States suggest the possibility of region-
wide production of oxidant.  One particularly interesting set of ozone meas-

                                     132

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                       250
                       225
                       200
                           1 8/12
                             REGIONAL AIR
                          POLLUTION   EPISODE
                                              1 8/13


                                             1 FREONS
                                             • HC
                                             ' OZONE
                                             . RADIATION
                                                       150
                                                       200
 Figure  7.   Elevated  ozone  levels  related  to  regional  accumulations of oxidant
 precursors  by August 12  in  Glasgow,  Illinois.   The  F-ll  spikes  at 0 and 20
             influx  of urban  air  from  St.  Louis with  accompanying increased
                Between these  spikes, F-ll  remains at  levels  significantly above
CDT indicate
ozone levels
 the minimum  background  value  of  115  ppt.   It  is  suspected  that  similarly ele-
 vated  levels of  hydrocarbons  and oxides  of nitrogen  may  have  produced the
 high midday  ozone.

 urements was made at 500 m above  the ground between  Canton, Ohio,  and the
 Black Hills of South Dakota in the summer  of  1974.   The  observed ozone con-
 centration dropped from 70 ppb over  the  rural areas  of Ohio early  in  the
morning to 40 ppb over the rural  Great Plains late in the  evening  on  the  same
 day.  This measurement suggests  a substantial east-west  gradient in ozone, but
 other considerations prevent  our  accepting this  gradient as representative of
 regional photochemistry acting solely on anthropogenic or  natural  emissions.
The 70 ppb measurement was made early in the  morning, and  there is no data or
estimate of the level to which it could  have  risen in the  afternoon.   Photo-
 chemical considerations would allow  even larger  ozone gradients due to anthro-
 pogenic emissions producing more  ozone to  add to the 70  ppb value.  However,
 the distance scale is also a  synoptic distance scale, so that ozone differences
might be attributed to different  ozone "weather":  that  is, the ozone gradient
may reflect mid-tropospheric  ozone variations or other weather effects  rather
than differing surface emissions.  For these  reasons it  is important  that
measurements on this larger synoptic scale be repeated.
                                 CONCLUSIONS

     Substantial uncertainties exist in quantifying the significance of the
                                     133

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 different sources of ozone or contributions of ozone precursors in the lower
 tropospheric ozone budget over continents.  There is a clear need to model
 both transport and chemistry in the lowest few kilometers of the atmosphere.
 Both chemical and meteorological parameters for models on this scale are rela-
 tively  uncertian.  It appears that separate and interrelated models should be
 constructed for:

     (1) The boundary layer.  Emissions and photochemistry of non-methane
         hydrocarbons allow ozone levels to change significantly within a day,
         but other important precursor transport processes may occur over sev-
         eral days.

     (2) The "free" lower troposphere.  The interaction between local photo-
         chemistry and synoptic-scale transport must be qualified.

     Verbal models of ozone variation near the surface may allow for different
 regimes of transport-dominated and photochemistry-dominated patterns of ozone
 concentration gradients or distributions to develop.  In summary they are:

     (1) Clean, strongly mixed troposphere.  Ground level ozone from 15 to 70
         ppb determined by the ozone concentration of mid-troposphere.  This
         mid-tropospheric concentration may be summarized by latitude and
         season, as in Figure 3, but it is a "climatology" of ozone subject to
         ozone "weather."

     (2) Clean, diurnally mixed troposphere.  Both photochemistry and diurnal
         boundary-layer mixing give adequate descriptions of the ozone be-
         havior.  Models should incorporate both parameters quantitatively.

     (3) Urban plumes.  Individual urban plumes frequently modify ozone con-
         centrations in the lowest kilometer of the troposphere of the Eastern
         United States.  Large plumes may  travel 200 to 300 km before losing
         their character.  Their composition produces variations in the ozone
         pattern different than rural air; however, additions of rural hydro-
         carbons like isoprene may rekindle ozone production particularly in
         older plumes.

     (4) Regional oxidant production.  The trailing portions of slowly migra-
         tory high pressure systems accumulate ozone and oxidant precursors
         not attributable to a single urban area.  There is a need for models
         of the photochemistry of these situations.  The relationship of area
         wide production of oxidants with  the development of photochemical
         aerosol-haze patterns described as "blobs" through the Midwest needs
         better study.


                                  REFERENCES

Attmannspacher,  W.,  and R.  Hartmannsgruber.  1973.  On Extremely High Values
     of Ozone Near the Ground.   Pure and Applied Geophys.  106-108:1091-1096.

Chameides,  W.  L., and Donald H.  Stedman.   1976.   Ozone Formation from NOY in
     Clean Air.  Environ. Sci.  Tech.  19(2):150-153.


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Chameides, W., and J. C. G. Walker.  Dec. 20, 1973.  A Photochemical Theory of
     Tropospheric Ozone.  J. Geophys. Res.  78:8751-8760.

Chameides, W., and J. C. G. Walker.  1976.  A Time-Dependent Model for Ozone
     Near the Ground.  J. Geophys. Res.  81(3):413-420.
Chatfield, R. B., and H. Harrison.  1976a.  Tropospheric Ozone: Mixing vs.
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Chatfield, R. B., and H. Harrison.  1976b.  Proceedings of the Specialty Con-
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Chatfield, R. B., and H. Harrison.  1976c.  Tropospheric Ozone, I:  Evidence
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Chatfield, R. B., and H. Harrison.  1976d.  Tropospheric Ozone, II:  Varia-
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Cleveland, W. S., B. Kleiner, J. E. McCrae, and J. L. Warner.  1976.  Photo-
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Coffey, P. E., and W. N. Stasiuk.  Jan. 1976.  Evidence of Atmospheric Trans-
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Crutzen, Paul J.  1974.   Photochemical  Reactions Initiated by and Influencing
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Danielsen, E. F., e t a 1.  1970.   Observed Distribution of Radioactivity,
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Davis,  D. R., and R. E.  Jensen.   March, 1976.  Low Level Ozone and Weather
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Ehhalt, D. H.  1974.  The Atmospheric Cycle of Methane.  Tellus.  26(l-2):58-
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Fabian, P.  1974.   Comments on 'A Photochemical  Theory of Tropospheric Ozone.'
     by W. Chameides and J. C. G. Walker, J.  Geophys. Res.  79(27):4124-4125.
Fabian,  P.,  and C.  E. Junge.  1970.  Global  Rate  of  Ozone  Destruction  at  the
     Earth's Surface.  Arch.  Met  Geoph.  Biokl.  19(Ser.  A):161-172.

Graedel, T., and  D.  L. Allara.   March, 1976.  The  Kinetic  Photochemistry  of
     Natural and  Perturbed  Remote Tropospheres.   Submitted  for  publication.

Hering,  Wayne S., and Thomas  R.  Borden,  Jr.  Ozonesonde  Observations  Over
     North America,  AFCRL-64-30(I-IV), Air Force  Cambridge  Research  Labora-
     tories, Meteorology Laboratory  Research Project 8631.   Environmental
     Research Papers.  No.  133:279.

Husar,  R. B., N.  V.  Gillani,  J.  D. Husar, and C.  C.  Paley.   March  1976.   Hazy
     Air Masses Over the Continental United  States.  Submitted  for publica-
     tion.

Lamb,  Robert G.   1976.   Personal communication of an analysis of an ozone  epi-

                                     135

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     sode in Santa Rosa, California occurring in November, 1975.

Levy, H. H.  1971.  Normal Atmosphere:  Large Radical and Formaldehyde Concen-
     trations Predicted.  Science.  173:141,

Levy, H. H.  1974.  Photochemistry of the Troposphere.  Advances in Photochem-
     istry.  370-524.
Newell, R. E., D. G. Vincent and J. W. Kidson.  1969.  Interhemispheric Mass
     Exchange from Meteorological and Trace Substance Variations.  Tell us.
     21(5):641-647.

Rasmussen, R. A., R. B. Chatfield, and M. Holdren.  1976a.  Hydrocarbon Levels
     Observed in a Midwest Rural Open-Forested Area.  Report being submitted
     to the Coordinating Research Council.  Contract No. CAPRAC-11.

Rasmussen, R. A., R. B. Chatfield, and M. Holdren.  1976b.  Hydrocarbon and
     Oxidant Chemistries Observed at a Site near St. Louis.  Report being sub-
     mitted to the Environmental Protection Agency.  Contract; No. 68-02-2254.

Regener, V. H.  1974.  Destruction of Atmospheric Ozone at the Ocean Surface.
     Arch. Met Geoph. Biokl.  23(Ser. A):131-135.

Ripperton, L. A., J. B. Tommerdahl, and J. J. B. Worth.  1974.  Proceedings of
     the Annual  Meeting of the APCA, Denver, Colorado, June 9-13, 1974.

Robinson, E., and R. A. Rasmussen.  March 1976.   Identification of Natural and
     Anthropogenic Rural Ozone for Control Purposes.  Proceedings of the
     Specialty Conference on Ozone/Oxidants - Interactions with the Total En-
     vironment.   APCA.

Spicer, Chester W.  1976.  Ozone and Hydrocarbon Measurements by Batelle.
     Proceedings of the Northeast Oxidant Transport Symposium held at Research
     Triangle Park, North Carolina on January 20-21, 1976.

Westberg, H.  H.   1976.   Ozone and Hydrocarbon Measurements by W.S.U.  Proceed-
     ings of the Northeast Oxidant Transport Symposium held at Research Tri-
     angle Park, North  Carolina on January 20-21, 1976.

Westberg, H.  H., K. J.  Allwine, and D. Elias.  March 1976.  Vertical Ozone
     Distribution above Several Urban and Adjacent Areas across the U. S.
     Proceedings of the Specialty Conference on  Ozone/Oxidants - Interactions
     with the Total Environment.  APCA.
                                     136

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                                                                            4-2
                            URBAN KINETIC CHEMISTRY
                        UNDER ALTERED SOURCE CONDITIONS

                 L.  A.  Farrow, T. E. Graedel, and  T.  A.  Weber*
ABSTRACT
     The. e.iie.ct oft alteAe.d Aoufi.ce. generation rates  on ozone, conce.ntratA.onA in
northern New 3e.ue.ij has been as&es&e.d by a. /setx.e-6 oft  de.tcuiie.d photoch2.mic.aJL
coitcuLati-onA.   The. Sunday E^e.ct, -in (Mk4.dk me.asure.d Sunday ozone, concentra-
tion!, in ceAtain u/iban aA.e.as are. AimiJLar to those, occurring on wotikdays de.-
Apite. marke.dl.y di6fie.re.nt mo ton. ve.hicte. emissions, is  succe.ssfiutty Ae.produ.ced.
The. concept ofi functional. oxyge.n gioupA iA introduced and a^ed to i>kow that
the. Sunday e.^e.ct sieAuJLtb ^ofun the. tight balance, between ozone pftodu.ctA.on
through  ni&iic oxA.de. photo dissociation and oxygen &cave.nging by nitric otu.de,,
faswm the. a.dve.ctian o£ ozone, ^fiom. £e^4 uA.ban a/tea^,  and {,fiom the. incofiponation
o& i,imitaA. quantities ofa ozone. pre.e.XASting above, the.  morning mxjced layeA.


                                 INTRODUCTION

     The chemical  generation and destruction of ozone in the urban troposphere
is known to be inextricably connected with the atmospheric chemistry of hydro-
carbons  (HC)  and oxides of nitrogen (NOX).  Despite this connection, however,
ambient  air quality data (Paskind and Kinosian, 1974) and smog chamber studies
(Dimitriades,  1975) have not shown a simple relationship between ozone and its
precursors.   An  example of the complexity of the problem is the Sunday Effect
(the only altered source condition for which substantial quantities of air
quality  data are available), in which Sunday ozone  concentrations in certain
urban areas  are  similar to those occurring on workdays despite markedly dif-
ferent motor vehicle emissions (Bruntz, et a!., 1974; Cleveland, et al.,
1974).

     This  paper  presents the results of detailed chemical kinetic computations
representing workdays and Sundays in Hudson County, New Jersey.   The computa-
tional  techniques  are applied to the Sunday Effect, which is shown to be a
consequence of the chemistry and meteorology of the urban troposphere.


                           COMPUTATIONAL FORMULATION

     Calculation of the diurnal chemical concentrations in the urban tropo-
sphere is  based  on a chemistry of 143 reactions in  76 species.   Extensive
*Bell Laboratories, Murray Hill, New Jersey.

                                      137

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descriptions of the chemistry of oxides of nitrogen,  hydrocarbons,  and sulfur
compounds are included in the reaction set,  as  is  a representation  of the •
heterogeneous interactions between gas phase radicals and the  atmospheric
aerosol.   This chemical formulation is described in detail  by  Graedel, et al.,
(1976) (hereafter termed "Paper I").   As  has been  discussed previously (Paper
I), no chemical set can be considered a complete representation  of  tropospheric
photochemistry.  The excellent agreement with data that results, however,
indicates that our formulation, at the very least, captures the essential
processes which control that chemistry.

     The computational architecture that is utilized is based on a 3x1 matrix
of geographical areas, in which each matrix element is rectangularized trans-
formation of the dimensions of a county; those represented are (from west to
east), Morris County, New Jersey, Essex County, New Jersey, and Hudson County,
New Jersey.  Since available emission inventories for the region are compiled
on a county-wide basis, each of the counties is treated as a "reaction volume"
with source terms corresponding to the emission data.  Emissions attributable
to mobile sources are varied in accordance with local traffic density functions
and those for power plants in accordance with energy generation patterns.
Other emissions are regarded as constant with time.  For computations with
varied source conditions, all sources are multiplied by the same reduction or
enhancement factor; diurnal emission patterns are preserved.

     The flow of gases from one matrix element to the next is controlled by
the local wind velocity and direction.  In the computations presented here, we
utilize an average diurnal wind flow pattern derived from measurements at
Newark Airport (Essex County) on summer days, of normal convective mixing.  The
variations in mixing height are specified by a function derived from lidar
measurements of the atmospheric aerosol.   The chemical species within each
reaction volume are assumed to be fully mixed.

     Several differences exist between the workday and Sunday computations.
The most important is the marked difference in motor vehicle emissions and
power generation functions for Hudson County.  Atmospheric aerosol  concen-
trations are lower on Sundays and, perhaps as a result, the solar radiation at
ground level is somewhat higher (Cleveland et al., 1974).  In addition to its
meteorological effects, the change in aerosol concentration reduces the hetero-
geneous interactions which have important effects on tropospheric chemistry
(Farrow, et al., 1975; Graedel, et al., 1975).   The increased solar radiation
increases the rate of the photosensitive reactions included in the chemical
set.
                    RESULTS OF SUNDAY EFFECT CALCULATIONS

     Computations of the kinetic chemistry of the urban troposphere have been
performed for Morris, Essex, and Hudson Counties, New Jersey, for both work-
days and Sundays.  The workday computations have been described in detail in
Paper I, and the agreement with a wide variety of air quality data for Hudson
County (across the Hudson River from Manhattan) have been judged to be good.
For the Sunday computation, there are insufficient days with appropriate
characteristics (i.e. full sun, summer, westerly wind direction, wind speed


                                    138

-------
 within  the  central  50%  of  all  values)  to  permit a direct  comparison between
 data  and  computational  results.   It  is possible, however, to make general com-
 parisons  with  less  stringently stratified data.  Figure la shows the computed
 diurnal ozone  (03)  concentrations for workdays and Sundays.  The Sunday com-
 putation  reproduces two important characteristics of the  Sunday ozone data
 illustrated by Bruntz, et al, (1974):  the virtual  equivalence of the after-
 noon ozone peak, and the higher ozone values on Sunday morning.   The ozone
 computations show higher Sunday evening values not reflected in the data;  this
 discrepancy may be a result of inadequate representation of the heavy traffic
 flow from New Jersey shore points to the metropolitan area that occurs  on
 summer Sunday evenings.

     The reduction in the ozone precursors nitric oxide (NO)  and nitrogen
 dioxide (N02) on Sundays is snown in Figures Ib and Ic.   Similar reductions
 occur in air quality data (Cleveland, et al.,  1974),  and are  representative  of
 concomitant reductions in other species such as carbon monoxide (CO) and
 nonmethane hydrocarbons.

     The results can be succinctly summarized:  The computations have suc-
 ceeded in reproducing the ozone Sunday Effect, while  simultaneously demon-
strating the reduction in primary emittants  known to  occur on Sunday.


                          FUNCTIONAL GROUP ANALYSIS

     The Sunday Effect is intriguing because of its defiance  of the intui-
 tively anticipated precursor-product relationship between  ozone-producing
species and ozone itself.  Having duplicated the Sunday Effect computation-
ally, we then proceeded to deduce a unifying analytical  technique that  not
only demonstrates why the Sunday Effect occurs, but offers potential insight
into a wide variety of other atmospheric chemical  regimes.  The initial  step
is to divide the oxygen-containing species into groups on  the basis of  the
function of the incorporated oxygen in photochemical  reactions.   Four groups
are distinguished:   fixed oxygen (0), accessible oxygen (aO),  dissociative
oxygen (60), and odd oxygen (oO).

     The chemical species assigned to each group depend on the chemical  detail
of the analysis.   In this study, odd oxygen  includes  0(3P) (indicated through-
out as 0), 0(1D), and 03.  Dissociative oxygen includes  those species that
photodissociate to produce odd oxygen; N02 and nitrous oxide  (N20)  comprise
the 60 subgroup in this study.  Accessible oxygen species  are those that can
donate an oxygen atom to permit the formation  of 60 in a single reaction step;
in our study this group comprises nine R02 radicals,  nitric acid (HN03), H02,
nitrogen pentaoxide (N205), and N03.

                              N02 ^ NO + 0

                              N20 ^ N2 + 0( D).

 (We note that recent experimental results indicate  that N20 photodissociation
does not occur in the lower troposphere [Stedman,  et  al.,  1976].  The effect


                                     139

-------
         o
           102
         OJ
         0.
         0.
           K)'
                           SUNDAY
            K) I	1	1  .  I	1	1	1	1	1	L__L__L__J
              0  2   4 f 6    8   10  12   14   16   16 f 20  22  t4
                                 MR OF DAY
Figure 1.   Computed  diurnal  concentration patterns  for workdays and
            Sundays in  Hudson County, New Jersey.
                                  140

-------
 of  its  inclusion  in the  calculation  at  rates previously  thought  to  be  correct
 has negligible effect  on  any  of  the  results discussed  herein.)   Tfie triple
 letter  designations in Figure 2  are  group  transition rates  that  are not  the
 result  of  gas phase chemistry.   Rates SMx  represent the  sums  of  all  source
 emission and meteorological rates  contributing  to  changes in  the group
 concentration (note that  rates SMx may be either positive or negative),  and
 rates ARx  represent group concentration changes because  of heterogeneous
 reactions with atmospheric aerosols  (Paper I).   No triple letter rates are
 indicated  in Figure 2 for cf>0, since  oxygen (02) dominates the <|>0 concentration
 and is negligibly affected by SMF or ARF processes; since we neglect hetero-
 geneous processes for N02 and N20, rate ARD does not exist.
                         S,M  AR
                               t,
S,M  AR
                                                                       ARO
  Figure 2.   The functional oxygen group diagram.  The symbol S refers  to
              emissions sources.  M to meteorological sources and sinks, and
              AR to removal by aerosol incorporation.

     The relative magnitudes of the group transition rates are very different.
Figure 3 presents functional group diagrams for workday and Sunday at 12 a.m.
Several features are immediately apparent.  The first is that the dominant
rates are DO and OD, and that they balance to better than 1% for both calcula-
tions.  Secondly, the net rates for group transition from 4>0 to 50 are clearly
positive.  Finally, while the magnitudes of the bypass group transition rates
are less than those along the central "backbone" of the diagram, they are of
potential significance in view of the net rates along the backbone.   The same
consideration applies to the SMx rates.   (For this problem, sources furnish
only fixed oxygen;  the SMx rates are thus solely meteorological.)  Aerosol
effects are small relative to the other group transition rates.   A general
decrease in nearly all the rates is evident when comparing Sunday with work-
days.  This decrease results from the decreased emissions of NO, the building
block compound that carries the oxygen from group to group, and of reactive
hydrocarbons, the precursors of the radicals responsible for most of the group
transitions.   Despite the decreased rates, the strong feedback among the
                                     141

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                   13  48
183




t







<*>

I






390 p 360 m 13178 ^
0 „ 117 a° . 129 S° .13113

2
69
14
85
1
40
|

c

11







>0

i





i



k





i



















                   WORKDAY, 12 A.M.
                    7   48
                   103   0
                   SUNDAY, 12 A.M.
Figure 3.   Functional oxygen group diagram at 12  a.m. for workdays and
           Sundays, Hudson County, New Jersey.
                               142

-------
 reactive  atmospheric  compounds  enables  the  overall  chemistry  to  retain  its
 basic weekday  structure.

      It can be seen from Figure 3 that the group transition rates DO and OD,
 although markedly larger on workdays, have a similar net rate, which represents
 the close balance between

                              N02 ^ NO + 0

                              NO + 03 -> N02 + 02.

The SMO rate is the largest of those remaining and is virtually identical
weekdays and Sundays.   This term represents not only the ozone advected into
Hudson County from the less urban areas upwind, but also that which enters the
"reaction volume" as the rising height incorporates preexisting "fossil" ozone
 (Ripperton, 1974) from above.  This incorporation was shown in Paper I to be
consistent with air quality data, and provides a vital carryover buffer against
the day-to-day perturbations of ozone precursors.

     The early morning excess in ozone concentrations on Sundays reflects the
ozone reductions that occur when rush hour NO emissions enhance the rate of
ozone scavenging by NO.  These reductions, combined with the slightly higher
solar flux levels present on Sundays, produce a somewhat higher value net rate
of ozone production on Sunday mornings than on workday mornings.  A further
factor inhibiting net ozone production on workdays is the increased rate of
the ozone scavenging reaction

                             N02-» +  03 •* N03 + 02

caused by the higher N02 concentrations.  The inhibitory factors are eventu-
ally overcome by the workday presence of 60 (i.e.  N02 + N20); the result is
virtual equality of resulting peak ozone.


                                 CONCLUSIONS

     Functional group analysis of oxygen in the troposphere has demonstrated
that the Sunday effect in urban areas results from the tight balance between
ozone production through N02 photodissociation and ozone scavenging by NO,
from the advection of ozone from less urban areas, and from the incorporation
of similar quantities  of ozone preexisting above the morning mixed layer.  The
higher levels of N02 on workdays increase the rates of the NO-N02-03 shuttle
reactions, but do not significantly alter the similar behavior of odd oxygen
on workdays and Sundays.   The increased levels of NOX on workdays have other
consequences, however.  The advective transport of NOX is enhanced relative to
Sundays (as seen in the increased group transition rate SMD), with a concomit-
ant expansion of the downwind impact of the urban area.   In addition, the
rates of secondary reactions are higher on workdays, resulting in higher con-
centrations of organic and inorganic nitrates and concomitant increases in the
potential  of the atmosphere to cause lachrymation.
                                     143

-------
     The success of the calculations and analysis  performed thus  far in deriv-
ing results consistent with field data for two cases of differing source con-
ditions suggests further studies on the changes in ozone concentrations as
anthropogenic emissions are varied over reasonable limits.   Such  work is now
proceeding and will be reported subsequently.
                                 REFERENCES

Bruntz, S. M., W. S. Cleveland, T.  E.  Graedel,  B.  Kleiner, and J.  L.  Warner.
Ozone Concentrations in New Jersey  and New York:   Statistical  Association with
Related Variables.  Science, 186, 257-259, 1974.

Cleveland, W. S., T. E. Graedel, B.  Kleiner,  and  J.  L.  Warner.  Sunday and
Workday Behavior of Photochemical Air  Pollutants  in  New Jersey and New York.
Science, 186, 1037-1038, 1974.

Dimitriades, B.   Chamber Studies, Scientific  Seminar on Automotive Pollutants.
EPA-600/9-75-003, Environmental Protection Agency, Washington, D.C.,  1975.

Farrow, L. A., T. E. Graedel, and T. A.  Weber.   The  Effect of Aerosols on the
Free Radical Chemistry of the Lower Atmosphere.   Removal  of Trace  Contaminants
from the Air.  ACS Symposium Series,  17, 17-27,  1975.

Graedel, T. E.,  L. A.  Farrow, and T. A.  Weber.   Kinetic Studies of the Photo-
chemistry of the Urban Troposphere.  Atmospheric  Environment (in press), 1976

Graedel, T. E.,  L. A.  Farrow, and T. A.  Weber.   The  Influence of Aerosols on
the Chemistry of the Troposphere.  Int.  J. Chem.   Kinetics Symp.,  1,  581-594,
1975.

Paskind, J., and J.  R.  Kinosian.  Hydrocarbon,  Oxides  of Nitrogen, and Oxidant
Pollutant Relationships in the  Atmosphere over  California Cities.   Paper
presented at 67th Annual Meeting, Air  Pollution  Control  Association,  Denver,
Colorado, June 9, 1974.

Ripperton, L. A., Eastern United States  High  Ozone Concentration:   Chemical
Aspects.  Clean  Air. 4, (16), 79-82,  1974.

Stedman, D. H.,  R. J.  Cicerone, W.  L.  Chameides,  and R.  B. Harvey.  Absence
of N20 Photolysis in the Troposphere.   J. Geophys. Res.,  81, 2003-2004, 1976.
                                     144

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                                                                             4-4
           THE EFFECT OF OZONE  LAYERS  ALOFT ON SURFACE CONCENTRATIONS

            T. N. Jerskey, T. B.  Smith,  S.  L.  Marsh, and W. H. White

 ABSTRACT
      Pottutant layeAA alo&t  in the.  Lot  hnge,ieJ> Boi-m M&te, hound to
 a vcwiity o^ me.c.haniAmt> ind.udi.ng heating  ofc mountain AtopeA, conveAgence  zone.4,
 and plumed &x,om Atationafiy AouSLC.eA.   Aged  pottutantA te,nd to acc.umul.ate.  ato^t
 atong fioothittb during the, late, afiteJinoon.   UndeA. Stagnant itiind condition*  thue,
 layeAA o& ozone, and otheA product*  o^ photoc.hejntc.al. Ae,actiont> may Ae,matn hi the.
 an.ua and c.on&iibtit£. to high  ^uA^ace ozone,  conaen.fruttuM.6 atong tha  ^oothittt, on
 the. Bottoming day.  Examination o&  the,  c.he,m.i&tA.y o^ ?ie.e.ntA.ainme,nt AuggeJitA  that
 thu inteA.me,diate, ptioductA o^ photoc.he,mi.c,at fi^ac^tion^ [t>u,c,h a& ni&iouA  actd  and
 alde.hyde^>] c.an ac,c.eJL&iat& the. tiate.  o& ozone, ^oftmation.   Thi& e,ntAjatnme.nt pfioc,&
 may c.ontsU.but.(i AubAtantialiy to the, gsiound-l.e,ve,l. ozone, c.onc.e.n&iation undeA
 e,piAode. condition^.

                                   INTRODUCTION

      This paper presents evidence that,  under the stagnant wind conditions  that
 characterize episode periods, ozone layers aloft can account for a  substantial
 portion of the surface ozone concentrations in the Los Angeles Basin.  The  data
 analyzed were obtained during the Three-Dimensional Gradient Study  (Blumenthal
 et a!., 1974).  Below we discuss  possible  mechanisms for the formation of
 pollutant layers aloft and analyze  their possible effects on surface concentrations

                              SOURCES OF  LAYERS ALOFT

      An examination of a large number of layers aloft indicates that the fol-
 lowing mechanisms may be responsible for their formation in the Los Angeles
 Basin:   (a)  convergence of the windfields,  (b) flow up heated mountain slopes,
 (c)  undercutting by the sea  breeze,  (d)  plumes from stationary sources,  and (e)
 formation of a radiative inversion.   With  the exception of the first two me-
 chanisms, the layers formed  are near the surface and can be incorporated readily
 into the mixed layer on the  following day.   When layers aloft form  by  conver-
 gence of the windfields, the pollutants  are often carried far above the  in-
 version base and generally have a low probability of becoming entrained  on  the
 following day.  Also, layers formed by  upslope flow often are carried  far  above
 the  base of  the inversion; but, because  of the heating occurring on the  mountain
 slopes  on the following day, these  layers  can be entrained and affect  surface
 concentrations along the foothills.
*Jerskey, Systems Applications,  Inc., San Rafael, California.
 Smith, Marsh, and White,  Meteorology Research, Inc., Altadena,  California.

                                      145

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     Pollutants carried into elevated layers  during  the  afternoon  are  subject to
transport by the prevailing winds at those  levels  during the  night.   Depending
on wind direction and speed, the pollutants in  the layers aloft may  be carried
inland over the desert and diffused, may be carried  toward the coastal areas, or
may remain in the foothill areas until the  next morning.  The worst  pollution
episode conditions are associated with the  lack of transport  of the  layers aloft
away from the foothill areas.   Under these  conditions,  the material  aloft
remains undiluted and is available for entrapment into  the mixed  layer on the
following day.

               IMPACT OF LAYERS ALOFT ON SURFACE CONCENTRATIONS

     The object of this phase of our analysis was  to determine the impact of
the layers of pollutants aloft on concentrations within the mixed  layer as the
inversion rises to entrain the material aloft.   In our approach we assumed that
all the material aloft in the morning profile up to the midday inversion height
was entrained.

     For the eight days on which a sufficient overlap existed between the
morning and midday measurement locations, we tabulated coefficients  for the
correlation between the mass of entrained pollutants and the  change  of the
pollutant mass  loadings between the morning and midday flights.  The correlation
coefficients varied considerably over the eight days.  Furthermore a high
correlation coefficient did not appear to be related to the quantity of pol-
lutant entrained from aloft or the pollutant concentration on a particular day.
Upon closer inspection of the data, we found that the entrained ozone did appear
to be correlated with the difference between the mass loading in the morning and
at midday.  A similar conclusion could not be drawn for aerosol mass or carbon
monoxide, even  when the change in mass loading  was modified to account for
emissions into  the air parcel.  Instead of considering the mass entrained at
individual locations, the average mass entrained for the entire basin can be
calculated.  By averaging the difference between the morning  and midday loading
over the basin, one can minimize the variation  of measurements from location to
location.  Furthermore, averaging over all  the  measurements minimizes the effect
of advection, particularly for a secondary pollutant like ozone, whose spatial
variations in concentration are relatively small compared with those of primary
pollutants.  The mean values of the entrained ozone mass loading arid the dif-
ference between the morning and midday mass loadings for the  eight days studied
are plotted in  Figure 1.  The correlation coefficient for the eight  days was
0.78.

     Because of the relative location of Cable  and Rial to and the  routes flown
by the aircraft, the time delay between measurements made at  the two locations
(typically 90 minutes) was approximately the time  required for an  air parcel to
be advected between them.  For this portion of the data set we again calculated
the mass entrained from aloft (using the vertical  ozone distribution at the
beginning of the trajectory measured at Cable)  and the change of the mass
loading in the  mixed layer calculated for Cable and Rial to.  Morning and midday
trajectories between Cable and Rialto were  available for eight days  in 1973.
Afternoon trajectories were not considered  since the depth of the  mixed layer
generally decreased along the trajectory during this time period.   By comparing
the change in the ozone mass loading with the ozone entrained from aloft (see

                                     146

-------
          220


          200

          180
        1*160
        i
        D>
       £ 140
        re
        °
        VI
        V)
        a,
120

100


 80
       5  60
           40

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                  1
                           l
                          1
          1
                                             l
               l
  0
                 10   20   30
40   50  60    70

 Ozone Entrained--mg m
80   90
   -2
100  110 120
        Figure 1.  The change in ozone mass loading as a function of
              the mass of ozone entrained from the mixed layer.
Figure 2) we confirmed the observation that high ozone concentrations at Rialto
are correlated with high ozone concentrations aloft.

     Further evidence that the layers aloft have an impact on the concentration
of ozone in the mixed layer is provided by an analysis of the surface concen-
trations for July 25, 1973, a day when ozone concentrations reached a level of
0.5 ppm at Upland (near Cable).  Figure 3 shows the vertical sounding at Cable
at about 0830 Pacific Daylight Time (PDT) on July 25.  Substantial ozone con-
centrations were found aloft, peaking at over 0.2 ppm at a height of 2100 feet
mean sea  level (msl).  The sounding also shows a rapid decrease in b
                                                                     scat
above 1800 ft msl,  indicating a very shallow surface mixing layer.   Figure 4a
shows the surface ozone concentrations from the California Air Resources Board
(ARB) pollution network for the period from 0900-1000 PDT on July 25.  Peak
values of 0.15 ppm in the basin occurred in the Upland area but generally high
values existed along the entire foothill area from San Bernardino (SBD)  to
                                     147

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                                         8/23
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                                                    •
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                              8/23
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                 A
                          •  MORNING TRAJECTORY

                          A  MIDDAY TRAJECTORY
           7/18
                  7/25
                  A
                            I
                                                    I
                                       I
         20    40     60     80    100    120   140
                                              _o
                        Entrained Ozone--mg  m c
                                                          160   180    200
    Figure 2.  The change in ozone mass loading along the trajectory from
            Cable to Rialto as a function of the ozone entrained.

Burbank (BUR).   By 1200-1300 PDT (Figure 4b) the ozone concentrations along the
foothills had increased at a time when the mixed layer at Cable had increased to
2500 ft msl,  incorporating much of the pollutants aloft.   At this time there was
also evidence of new ozone production in the central  Los  Angeles area (CAP).
Subsequently  these new ozone concentrations were carried  northeastward to the
foothill area and mixed with the existing high ozone  concentrations to produce
levels as high  as 0.5 ppm at Upland during the hours  from 1600 to 1700 PDT.

     These data suggest that the high ozone concentrations observed along the
foothills were  influenced by the downward mixing of pollutants from aloft as
surface heating caused the inversion base to rise and entrain these materials.
Although ozone  is mixed downward into the mixed layer, we believe that the
intermediate  products (such as aldehydes and nitrous  acid) of the photochemical
reactions are responsible for the high ozone concentrations observed along the
                                     148

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Temperature
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40*
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_50 bjcat
45* Temperature
                                                                  76-002
           Figure 3.  Vertical sounding at Cable Airport (Upland),
                          July 25, 1973 (0830 PDT)

foothills.  The effect of these intermediate products on the ozone  formation
rate is illustrated by the numerical simulation of a smog chamber experiment
using the Hecht et al. (1974) kinetic mechanism (see Figure 5).  In Case 1  (see
Table 1) the simulation was performed without any initial ozone or  aldehyde
concentration.  Case 2, with the initial ozone concentration at 0.42 ppm, showed
little change in the final ozone concentration.  However, when the  aldehydes
were carried over (Case 3), the ozone production rate was accelerated initially,
leading to higher ozone concentrations at early times.  The photolysis of
aldehydes produces radicals that react with nitri oxide to give nitrogen dioxide
(N02).  Thus these intermediate products accelerate the formation of ozone  by
increasing the concentration of N02.

                            SUMMARY AND CONCLUSIONS

     Layers of ozone aloft can be formed by one of several mechanisms.  Once
these layers are formed the impact they have on surface concentrations on the
following day depends on the strength and direction of the winds aloft.  Under
stagnant conditions the layers can remain overnight where they were formed.  On
the following day surface heating causes these layers to be entrained into  the
mixed layer, where they can contribute a substantial fraction of the ozone
concentration on that day.  Hence, a knowledge of the winds aloft can serve as a
forecasting tool for prediction episode conditions.
                                     149

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              TABLE 1.  INITIAL POLLUTANT CONCENTRATIONS (IN PPM)
                       FOR THE RESULTS SHOWN IN FIGURE 5
    Pollutant
Case 1
Case 2
Case 3
NO
N02
PAN
Ozone
Propylene
Formaldehyde
Acetaldehyde
Propionaldehyde
0.94
0.13
0
0
1.04
0.02
0
0
0.94
0.13
0
0.42
1.04
0.02
0
0
0.94
0.13
0
0
1.06
0.25
0.17
0.03

     These results suggest that air quality simulation models must take into
account the three-dimensional structure of pollutant concentrations in order to
predict episode conditions.

                                ACKNOWLEDGMENTS

     This study was carried out under the support of the California Air Re-
sources Board (ARE) as part of a study to examine the data from the Three-
Dimensional Gradient Study.   Mr. Gary Palo and Mr.  C. L. Bennett of the ARB
served as contract monitors and contributed significant inputs in regard to the
ARB problems and interests in the study.
                                  REFERENCES

Blumenthal, D. L., et al. Three Dimensional Pollutant Gradient Study.  1972-
     1973 Program.  MRI 74 FR-1262, ARB-631 and ARB-2-1245, 1974.  Meteorology
     Research, Incorporated, Altadena, California.
Hecht, T. A., J. H. Seinfeld, and M. C. Dodge.  Further Development of a
     Generalized Kinetic Mechanism for Photochemical Smog, Environ. Sci.
     nol. , Vol. 8, p. 327.
                                              Tech-
                                     153

-------
             SESSION 5
SOURCES OF TROPOSPHERIC OZONE - III
                R.A. Rasmussen
    Washington State University
                155

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                                                                             5-1
                  OZONE CONCENTRATIONS IN POWER PLANT PLUMES:
                    COMPARISON OF MODELS AND SAMPLING DATA

               T.  W.  Tesche,  J.  A.  Ogren, and D. L. Blumenthal*
ABSTRACT
     F/te£d measurements  and modi-Ling studies have, been carried  out to  investi-
gate reports that ozone,  may be generated -in plumes farom large power plants -in
concentrations  exceeding amb-ient levels.  Analyst o{ aerometric data  firom
three Western poweA plants consistently revealed ozone depletion w/ctn/en the
p£ume /en the. vicinity o& the. stack and a gx.adu.aJL -increase /en ozone. concentra-
tion to approximately background levels fiasi dom.u),ind.  Wo ozone. ge,ne.siation wa&
ob4eA.ued -in the. p£ume-4 Atu.die.d.   Exte.nt»ive. mode.1. vaLida£ion Atudie.* with the.
Re.active, Plume.  Mode£ we^ie peA|$oAmed.   CompastU>on o^ mode.1. psie.dictionA  and mea-
-iu/ied plume. c.onc.e,n&ia£ion-{> -indicatzd that the. mode.1. AJ> a aie^a£ tool. ^on. Atudy-
/tng AeacXtue p£ume-6.   To deteAm/cne whetne-A tne mode£ coa£d be a6ed to  ievea£
conditions ^on.  which ozone, might be generated /en plwn&>, hypothetical.  Ace.nasiio&
.involving  di^eAant. ambi&nt hydrocarbon i.nv weAe.  i.nveA£igate.d.  for vary
high hydrocarbon  concentrations  (6 ppm as methane.} the. model does predict net
ozone  formation ok approximately 6-12 percent aboue  background levels.  The
Limitations and implications ofa this result are discussed.


                                 INTRODUCTION

     The possibility  of  ozone formation above ambient concentrations in  power
plant plumes has  recently been raised by several  investigators  (1,2).   To
better understand  the  factors affecting the behavior of ozone in  power plant
plumes, the Electric  Power Research Institute (EPRI) contracted with Meteoro-
olgy Research,  Inc.,  (MRI) and Systems Applications, Inc., (SAI)  to perform at
three Western United  States  power plants to determine the behavior of  ozone in
the plumes, and to  support a validation study of the Reactive Plume Model (RPM),
originally developed  to  study reactive power plant plumes under various  envir-
onmental conditions.   Because the results  of the EPRI study are presented in
greater detail  elsewhere (3,4),  only  the essential findings are reviewed here.
The primary emphasis  of  this paper concerns the modeling results  obtained with
RPM.
*T. W. Tesche, Systems  Applications,  Inc., San Rafael, California.   J.  A.  Ogren
 and D. L. Blumenthal,  Meteorology Research, Inc., Altadena,  California.
                                      157

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                          FIELD MEASUREMENT PROGRAM

     Airborne plume sampling was conducted in August and October 1975, primar-
 ily with the MRI Cessna 206, which was instrumented to measure and record con-
 tinuously ozone (03), nitric oxide (NO), nitrogen oxides (NOX), sulfur dioxide
 (S02), light scattering coefficient,  condensation nuclei, temperature, dew
 point, turbulence, pressure (altitude), and position.   Sulfate aerosol and
 hydrocarbon (HC) samples were obtained for later chemical analysis.  Support-
 ing ground-based measurements included winds aloft (using pibals) and ultra-
 violet solar radiation.   In addition, a Douglas B-23 (operated by the Univer-
 sity of Washington), instrumented similarly to the Cessna 206, was used to
 collect supplemental plume data during part of the program.

     Aerometric measurements were made at the following power plants:  Four
 Corners, Farmington, New Mexico (coal-fired, dry environment); Cunningham,
 Hobbs, New Mexico (gas-fired, dry environment); and Wilkes,  Longview, Texas
 (gas-fired, humid environment).  Data from coal-and oil-fired plants in humid
 environments were also analyzed along with the data from the plants  listed
 above to provide a comprehensive basis for studying the behavior of ozone in
 power plant plumes.   In  all of the cases studied, ozone depletion within the
 plume occurred near the  plant, followed by a gradual  increase to background
 levels as ambient air was entrained in the plume.

     A typical ozone profile is shown in Figure 1.   The plume is readily iden-
 tified by the elevated S02 concentrations.  High values of NO., NOX, and bscat
 were also associated with the plume.   Ozone concentrations in the plume were
 well below background levels.   Depletion of ozone relative to background was
 observed wherever the plume was distinguishable from background concentrations,
 although the deficit was very small at far downwind distances.  Another example
 of plume concentration data is presented in Figure 2.   This  plume isopleth
 characterization is based on ozone measurements at five altitudes.  The plume
 contained high NO and NOX concentrations, and a pronounced ozone deficit.  How-
 ever, an ozone layer with high concentrations was observed above the plume.
 Analysis of the data collected on this day revealed that the ozone layer was
 not associated with the  plume, and was probably caused by the advection and
 aging of pollutants emitted upwind of the sampling area.  Clearly, without
 supporting measurements  upwind of the plant, and well  outside of the plume, it
would be possible to misinterpret some of the ozone profiles used to create
 Figure 2 as evidence of  ozone formation on the edges  of the  plume.


                 MATHEMATICAL  MODELING  OF  POWER  PLANT  PLUMES

      Recently, the  California  Air  Resources  Board sponsored  the  development  of
 a package of  three  numerical models  to  characterize both the  physical  and
 chemical transformations of power  plant plumes  (5).  One of  these - the  Reac-
 tive  Plume Model  (RPM) -was an integral  part  of the EPRI study.

 THE REACTIVE  PLUME  MODEL  (RPM)

      RPM was  developed to study the  complexities of plume photochemistry  in
 detail; transport and dispersion are  treated in  a less  rigorous  fashion.   The


                                      158

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model employs a refined version of the lumped-hydrocarbon, Hecht-Seinfeld-
Dodge photochemical mechanism (6).  For generality, the kinetic mechanism has
been augmented with a set of provisional sulfur oxidation reactions in order to
simulate the environment of power plant plumes contain sulfur emissions.   The
model is based upon a mass balance for pollutant species involved in plume
photochemistry.   Within a Lagrangian air parcel moving downwind, photochemical
reactions are modeled by accounting for:


     •   The mass of a given pollutant emitted from the stack - initial
         conditions

     •   The mass of a given pollutant entrained from the ambient air as  the
         plume expands - boundary conditions

     •   The mass of a given pollutant created or destroyed due to reactions
         within the air parcel - chemical reactions.

Plume dilution is prescribed in RPM either from measurement or theory.   Esti-
mates of dilution rates can be based on measured plume widths and mixing  depths;
alternatively, the model can compute the dilution of pollutants by a Gaussian
formula using dispersion coefficients estimated from either the standard
Pasquill-Gifford method (7), the modified Bowne scheme (8), or a recent method
based upon similarity theory (5).   The speed at which the parcel is transported
downwind is specified from wind measurements aloft via pibal records.  Reliance
is placed upon aircraft measurements to determine the pollutant concentrations
as close to the stack as possible (the initial conditions) and to record  the
temporal and spatial variation in background pollutant concentrations (boundary
conditions).  Finally, average concentrations of pollutants measured by air-
craft within the plume are used for comparison with model predictions.


                           RPM VALIDATION STUDIES

     One objective of the EPRI program was to provide a data base suitable for
determining RPM's accuracy in simulating the behavior of reactive power plant
plumes.   Consequently, a large number (sixteen) of model verification studies
were carried out with the EPRI field data.  One set of comparisons between
predictions and measurements is presented here.

     On August 28, 1975, the Four Corners plume was sampled by the MRI aircraft.
At distances of 5, 21, 60, and 87 km downwind of the plant, the plume was
characterized with horizontal traverses at three different altitudes and  with
vertical spirals.  Concentrations of S02 in the Four Corners plume were identi-
fiable at all four sampling distances.   Maximum S02 concentrations within the
core of the plume exceeded 1 ppm at 5 km and declined with increasing distance
from the plant,  falling to 0.04 ppm at 87 km.  The observed S02 concentrations
outside the plume were 0.01 ppm or less.

     Ozone concentrations outside the plume were in the 0.04 to 0.05 ppm  range,
increasing slightly with the increase in solar insolation during the morning.
While ozone concentrations within the plume were depressed relative to those


                                     161

-------
 outside at all  distances, the absolute ozone concentrations  in  the plume in-
 creased with distance downwind,  from a minimum of 0.01  ppm or less at 5 km to
 0.04 ppm at 87  km.   Background reactive HC levels were  estimated to be 0.027
 ppm by volume (approximate 0.16  ppm as methane).   The mean wind speed ranged
 from 1.2 to 5.0 meters per second.

      The RPM simulation for this day was  carried  out for a distance of 100 km
 from the stack.   Predicted NO, N02, 03 and S02 concentrations,  designated by
 the symbol "0", are presented in Figures  3 through 6.   Background and plume
 measurements, designated  by "B"  and "M" respectively, are  also  plotted in the
 figures.   Nitric oxide predictions  (Figure 3)  exhibit excellent agreement with
 the data.   After approximately 24 km,  NO  levels in  the  plume  are  depressed to
 approximately background  levels.  In  addition, N02  predictions  (Figure 4) are
 also in good agreement with the  data.   On  the  other hand,  ozone predictions
 exceed measured  values by approximately 30 percent  far  downwind of the stack.
 As  may be  seen  in Figure  5, the  measured  concentrations  increase  gradually;  at
 84  km the  measured  plume  ozone is just slightly less  than  the background.   In
 Figure 6 very good  agreement exists  between  predicted and  measured S02 con-
 centrations  over a  relatively  wide  range  of  values.

      Based on the RPM validation studies  conducted  to date, it  is  possible to
 make a preliminary  assessment  of the  model's validity and  utility.   RPM is
 capable of predicting the dilution  of  conservative  pollutants and  tracer
 material quite well.   For reactive  primary pollutants such as NO  and  S02, pre-
 dictions are generally in good agreement with  measurements.  Model  predictions
 of  secondary pollutants such  as  N02  and 03  are strongly  influenced by  the con-
 centrations  of  reactive HC in  the ambient  atmosphere.  There appears  to be a
 tendency for the model  to overpredict  N02  and  03  concentrations when  high
 background HC concentrations  are present.   However,  at present,  it is  not
 clear whether there  are factors  involved  in  the N02  and  03 overpredictions
 other than high  HC  estimates.  From  RPM simulations  for  which the  assumed HC
 concentrations are  believed to be reasonably accurate, we estimate that the
 accuracy of  the  Model  for 03 predictions  at  large downwind distances  is  within
 +_ 25 percent.   In general,  the overall predictive capability of the model
 appears  to be commensurate  with  the  ability  of present sampling methods  (9)  to
 characterize the unsteady nature of  power  plant plumes.


                     OZONE FORMATION  IN POWER PLANT  PLUMES

      To determine if RPM  is  capable  of identifying  conditions for  which ozone
 in  excess  of background concentrations may  be  formed  in  plumes, two basic
 simulations  were carried  out.  First,  the  photochemical  model CHEMK was  used
 to  predict initial  background  concentration  variations throughout  the  day.*
 Then,  with the predicted  background  concentrations  as inputs, RPM  was  exercised
 to  study how the predicted plume ozone  levels  varied  relative to  the  predicted
*Due to numerical  instabilities in the integration algorithm, it is not possi-
 ble to conduct a  "background simulation"  with RPM.   Instead, another model,
 CHEMK, incorporating the same kinetic reaction steps as  RPM, was used to sim-
 ulate the temporal  changes in the background pollutant concentration (10).

                                     162

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background.  If the plume concentrations exceed background levels, this would
suggest that the model is simulating a condition for which ozone generation in
the physical environment might occur.

      Two  hypothetical  scenarios  involving different ambient HC concentrations
were  investigated.   In one  case  HC was approximately 6.0  ppm as methane;  in
the other HC was reduced to 0.6  ppm  as methane.  Initial  conditions similar
to what might  be expected in an  urban air atmoshpere were chosen for  the
simulations.   Dispersion characteristics and  initial pollutant concentrations
were  chosen to be identical  to those observed for the Four Corners Plume on
August 28, 1975.  Wind speeds varied between  1.2 and 5.0 meters per second.

      The  following simulations were carried out for both scenarios:

      •    Using the CHEMK photochemical model, the initial ambient concentra-
          tions reacted for 6 hours leading to a predicted variation in back-
          ground concentrations.

      •    RPM was exercised using as inputs the time-varying background con-
          centrations of NO,  N02, 03, olefins, paraffins, aldehydes, aromatics,
          and S02 predicted by CHEMK.

Results of the simulations are presented in Figures 7 and 8.   The curves in
the figures give the background ozone concentrations predicted by CHEMK and
the plume ozone concentrations predicted by RPM using computed CHEMK back-
grounds for NO, N02, 03,  S02, and the four lumped HC groups - olefins, alde-
hydes, aromatics, and paraffins.  In Figure 7, the low HC case, predicted
plume ozone concentrations exceed predicted background levels  by about 0.005
to 0.010  ppm between simulation times of 60 and 180 minutes.   Before and after
this period the plume is  observed to have an  ozone deficit relative to the
background.  On the other hand, the case of highly reactive HC backgrounds
(Figure 8) is associated with an ozone bulge of 0.030 ppm (approximately 12
percent above background) occurring midway through the simulation.   In fact,
with the  exception of the ozone deficit occurring in the first 20 minutes of
the simulation, the plume ozone levels exceed predicted ambient levels by
0.015 to  0.030 ppm (6 to 12 percent above ambient) throughout the simulation.
Thus, for the initial and background conditions used in the high HC background
example,  RPM predicts net ozone generation in the plume relative to the pre-
dicted background ozone level given by CHEMK.

      From this case study it appears that for ambient reactive HC concentra-
tion  levels on the order of 6.0 ppm as methane, RPM predicts plume ozone con-
centrations approximately 6 to 12 percent higher than the predicted background
concentrations derived from a smog chamber photochemical model.  While this
result suggests that for high background HC conditions the models do predict
slight ozone formation, the  results of this case study are too limited to con-
firm or refute an ozone formation hypothesis  in the real environment because
important phenomena that affect background and plume pollutant concentrations
(e.g., emissions from other sources, surface  pollutant removal processes) were
not included in the simulations.  One way to  include these phenomena and
perhaps to derive a more general result would be to use a more sophisticated
photochemical model that treats plume and background reactions simultaneously,


                                     167

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and accounts for source emissions and pollutant removal  processes.
                                 CONCLUSIONS

     From the results of field studies, data analysis and a review of the
literature, we conclude that formation of ozone in power plant plumes above
ambient concentrations is not a common occurrence if it occurs at all.  In
all of the plumes studied during the EPRI program the ozone observed in the
plume can be explained by entrainment of ambient ozone and ozone precursors.

     It appears that for certain special conditions RPM does predict plume
ozone concentrations slightly in excess (6 to 12 percent) of background levels.
These conditions involve the entrainment of high ambient reactive HC concen-
trations (6.0 ppm as methane).  However, the computer simulations yielding
this result are only the first step in examining the ozone formation hypothesis.

     In attempting to determine the contribution of a given power plant to
regional ozone concentrations, one should examine the plume and the plant site
for conditions that may be conducive to ozone formation.   These include a
major HC source in the immediate vicinity of the plant or high HC emissions
from the plant itself.  If conditions potentially conducive to ozone formation
in the plume are encountered, models capable of predicting photochemical re-
actions may be of value in assessing the situation.


                              ACKNOWLEDGEMENTS

     The authors express their sincere thanks to the many individuals who con-
tributed to various aspects of this program, particularly Dr.  W. H. White and
Mr. J.  Anderson (MRI) and Drs. M.  K. Liu, G. Z. Whitten,  and P. M. Roth, and
Mr. M.  A. Yocke (SAI).  This study was supported by the Electric Power Research
Institute under Contract No. RP-572, under the direction  of Mr. Charles
Hakkarinen.
                                 REFERENCES

 1.   Davis,  D.  D. ,  G.  Smith,  and  G.  Kletuber,  Trace  Gas  Analysis  of Power Plant
3.
    Plumes Via Aircraft Measurement:
    186, 1974, pp.  733-736.
                                       0~,  NO  ,  S0?  Chemistry,  Science,  Vol
                                        cs
     Buffi ngton,  P.  D.  and  E.  A.  Bartczak,  Ozone:   Chemical  Action  and Reaction
     in  the  Lower Level  Transport Winds,  Presented  at  the  68th  Annual  Meeting
     of  the  Air Pollution Control  Association,  Boston,  Massachusetts,  June
     1975.

     Ogren,  J. A.,  D.  L. Blumenthal,  and  W.  H.  White,  Study  of  Ozone Formation
     in  Power Plant  Plumes,  Presented at  the Ozone/Oxidants:   Interactions
     with  the Total  Environment  meeting,  Air Pollution  Control  Association II-
     5 Committee,  Dallas, Texas,  March  10-12,  1976.
                                      170

-------
 4.   Determination  of the Feasibility'of Ozone Formation in Power Plant
     Plumes,  Report to the Electric Power Research  Institute prepared by
     Systems  Applications, Inc.,  and Meteorology Research,  Inc.,  contract
     No.  RP-572,  May 1976.
 5.   Liu, M.  K.,  D. Durran, P.  Mundkur, M.  Yocke, and J. Ames, The Chemistry,
     Dispersion,  and Transport of Air Pollutants Emitted from Fossil Fuel
     Power Plants in California:   Data Analysis and Emission Impact Model,
     Report EF76-18 to the California Air Resources Board by Systems Applica-
     tions, Inc.  San Rafael, California, May 1976.

 6.   Meet, T.  A., J. H.  Seinfeld, M. C. Dodge, Further Development of a
     Generalized  Kinetic Mechanism for Photochemical Smog,  Environ. Sci. Tech.
     Vol. 8,  1974,  pp. 237-339.

 7.   Slade, D.  H.,  ed.,  Meteorology and Atomic Energy 1968, U.S.  Atomic Energy
     Commission  Publication TID-24190, 1968.

 8.   Bowne, N.  E.,  Diffusion Rates, Journal of the Air Pollution Control
     Association, Vol. 24, No.  9, September 1974.

 9.   Tesche,  T. W., G. Z. Whitten, M. A. Yocke, M.  K. Liu,  Theoretical Numeri-
     cal, and Physical Techniques for Characterizing Power Plant Plumes.
     Report EC-144 to the Electric Power Research Institute by Systems Appli-
     cations, Inc., San Rafael, California, October 1975.

10.   Whitten,  G.  Z., Rate Constant Evaluations Using a New Computer Modeling
     Scheme,  Paper presented at the 167th National  Meeting of the American
     Chemical  Society, April 1974.
                                     171

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                                                                             5-2
ABSTRACT
                OZONE AND NITROGEN OXIDES  IN  POWER  PLANT PLUMES

              D.  Hegg,  P.  V.  Hobbs, L. F.  Radke,  and  H.  Harrison*
             aAe.  pAe.Aente.d o& aiAboAne. me.at>uAme.nti>  taken -in the. plumed o& two
coal- and two gaA-faiAe-d pow  w>eAe made. o& the, conce.ntAo
tion o^ nitAi.c  oxA.de.,  ni\tAoge.n dioxide., ozone, and Aul&uA dioxA.de., tempe.AatuAe.,
Ae.lative. humidity,  and ultAav-iolet Aadtation.   Ozone, conce.ntAati.onA exceeding
thote. ofa the. AuAAounding ambient aiA we.Ae. not &ound  in thcAe. plumes, which
we.Ae. obAeAve.d out to  diAtanceA o^ 90 km  (4 houAA tAave.1 time.} ^Aom- the. AtockA.
AnalyAiA o& the. plume. che.miAtn.y &ugge.At!> that,  oveA  dLbtanzeA and time. i,c.aleA
within which. plwneA one. di^eAentiable. fitiom  background (the. vie.ati-{si.eX.d} , the.
che.m&iy JJ* Qe.neMUULy contftolZe.d by the. ^utfe-6  at which the. plumes m/tx
the. ambtent CUA. natheA. than by chejnicoit ki.netA.cJ,.  Con&e.que.ntty , on the&e.
-6ca£e4, the. iate.t> o&  conveAAton oft nitric oxide, to nitAOQen dioxide, i
and the nitAoge.n  dio xi.de. /nitAi.c oxi.de. nation aAe. malt (the. highest fiatio
me.a£(Lfie.d WOA 4.3}.  ThiA analy&i^  con&iAte.nt with the. absence o{, ob&eAv-
able. ozone. ge.neAation i.n the. ne.aji- ^i.eJLd^ ofi  the. poweA plant plumes Atudie.d.
                                 INTRODUCTION

     The possibility  of ozone (03) formation, perhaps  in  excess of federal
standards, in  the  near field plumes (the distance  over which the plume is dif-
ferentiable from the  background) of fossil --fueled  power plants has been sug-
gested by the  observations of Davis et al.  (1974)  at the  Morgantown, Maryland,
coal-fired power plant.   However, in other  studies,  ozone at concentrations
above the ambient  background levels has not been detected in power plant plumes
(Teshe et al . ,  1976).

     In this paper we present the results of field studies of the plumes from
two coal and two gas-fired power plants.  The two  coal-fired plants were the
Pacific Power  and  Light Plant at Centralia, Washington, and the Four Corners
Plant at Farmington,  New Mexico.  The gas-fired plants were the Cunningham
Plant at Hobbs, New Mexico, and the Wilkes  Plant at  Longview Texas.  Airborne
measurements were  made of the concentrations of nitric oxide (NO), nitrogen
dioxide (N02),  QS, and sulfur dioxide (S02), temperature, relative humidity,
ultra-violet radiation,  and condensation nucleus concentrations.  Data were
collected in thirty flights over an S-month period and parameters needed to
specify the nitrogen  oxides (N0x)-ozone chemistry  of the  plumes were derived.
The data consisted primarily of ambient and plume  03 concentrations, plume
*University of  Washington, Seattle, Washington.

                                      173

-------
center-line and plume average N02/N0 ratios, plume center-line and plume average
NO to NO  conversion rates, and the correlations of N02/N0 with NO  across the
plume.  We conclude that at the spatial resolution of our measurements (? 150
m) the NOX-03 chemistry is commonly controlled by the rate of mixing of a plume
with the ambient air, rather than by kinetic rate constants.   Consequently,
the macroscopic conversion rate of NO to N02 is slow and the  N02/N0 ratios re-
main too low to permit ozone generation in the near-field plume.   A full  account
of the work summarized in this paper, including all  field data, has been  given
by Hegg et al.  (1976).


                               INSTRUMENTATION

     The University of Washington's (U.W.) B-23 aircraft was  used for most of
the sampling, but some data were gathered by a Cessna 206 operated by Meteor-
ology Research, Inc. (Ogren et al., 1976).  In addition to an extensive set
of meteorological  and aerosol  sizing instruments (Hobbs et al., 1976), the
U.W.  sampling aircraft also carried a Meloy 160-2A sulfur analyzer, a Monitor
Labs 8440 chemiluminescent NOX analyzer, a Monitor Labs 8410A ozone analyzer
and an Eppley untrviolet radiometer.  The sulfur analyzer was periodically
calibrated against a Meloy CS10-2 calibration source (permeation  tube), and
the NOX and ozone analyzers were calibrated against  a Monitor Labs 8500 cali-
bration source (which was ultimately calibrated against gas-phase titration
for NO  and against buffered potassium iodide for ozone).
      A


                         FIELD RESULTS AND ANALYSIS

     Ozone concentrations higher than in the surrounding ambient  air were
never observed in the power plant plumes that we studied.   We did observe
three episodes (on October 10, 11,  and 13, 1975) of  very high 03  levels (^120
ppb) in the plume of the Wilkes plant at Longview, but detailed analysis  (Hegg
et al., 1976) of the background 03  field, including  its vertical  structure,
revealed that the high concentrations in the plume on these occasions were
caused by the advection of high ambient blobs of 03  into the  plume,

     The amount of 03 that can exist in photochemical steady-state with a
given quantity of NOX is directly related to the ratio of N02/N0  (Steadman
and Jackson, 1974).   For a system of either NOX p"ius hydrocarbons (HC), or
NOX plus HC plus  S02, it has been shown experimentally that 03 generation
will  not occur to any appreciable extent until the N02/N0 ratio rises to
about 10 (Kocmond et al., 1975).   Therefore, the ratios of N02/N0 in power
plant plumes give an indication of the near-field ozone generating capability.
Since the NOX emitted from power plants is mostly NO, the conversion rate of
NO to N02 is also an important parameter.

     In the above discussion,  we have tacitly assumed that the plumes are close
to photochemical  steady-state.  This, at first glance, appears to be plausible
because the fast rate constants of the NOX-03 system result in a  very short
relaxation time to steady-states, about 1 minute at  typical plume concentra-
tions of NO (0.050 ppm and 03  (0.015 ppm) for typical temperatures and UV
radiation levels.   Indeed, the NOX-03 system has been shown to be in

                                     174

-------
photochemical steady-state for well-mixed ambient air (Steadman and Jackson,
1974).  However, a diffusing plume may not be in macroscopic photochemical
equilibrium because diffusive mixing times over the spatial scale of the
plume may be short compared to the chemical relaxation times.   Indeed, over
a small enough spatial scale, the mixing times do become short compared to
chemical relaxation times.  The relative size of this sub-scale to the plume
mixing scale determines the extent to which a plume is macroscopically in
a steady-state.  We must  therefore consider this problem in more detail.

     A plume of NO , initially mostly NO, interacting with ambient air con-
taining 0  (or anyxother  species of comparable reactivity with NO) may be
viewed as a bimolecular reaction, with initially unmixed reactants, in a
turbulent fluid.  This problem has been treated theoretically with some success;
also, some laboratory results are available (O'Brian, 1974; Hill, 1976).
Assuming that the bimolecular reaction is fast compared to mixing times over
the scale of the plume (for NO + 03 ->N02 + 02, Tn : 1 minute for typical NO
                                                 3
concentrations near 0.05  ppm), the reactant species become spatially segre-
gated with the reaction occurring entirely within a relatively narrow reaction
zone between the two spatial  regions.   Figure 1  illustrates this view of the
plume.  The width of the  reaction zone is essentially the spatial sub-scale
over which the mixing time is comparable to the chemical relaxation time.   The
well known ozone deficits associated with power plant plumes are, in fact,
manifestations of spatial segregation of reactant species.   Figure 2 shows an
example of this effect which suggests that the width of the reaction zone is
indeed small  compared to  the plume radius.   Thus, over the spatial scale of
the plume, the mixing time is long compared to the chemical relaxation time
and most of the volume of a plume should be in local photochemical steady-
state.

     The time required to mix the initially separated reactants  (NO and 03)
over the whole plume is longer than that required for reactions  between NO and
03 to take place in the sub-scale.   Therefore, the macroscopic rate of reaction
is controlled by the rate of mixing of the  plume with the ambient air, rather
than by the kinetic rate constant for the reaction.   The plume chemistry is
therefore diffusion controlled.

     Evidence for the diffusive control  of  the plume chemistry can be obtained
by considering the spatial distribution  of  the N02/N0 ratio in the plume.
Since N02 is  the product of the reaction of NO and 03, the  ratio of N02/N0
should be highest at the reaction zone;  for a biomolecular diffusion-controlled
reaction, this zone should be located at the edge of the plume between the
regions of high NO and 03 (Figure Ib).   Assuming this to be the  case, the
ratio of N02/N0 should then be negatively correlated with the  total concen-
tration of NO  (which we employed as a plume tracer and assumed to be con-
served in the plume).

     Table 1  shows the results of a correlation analysis of N02/N0 with NOX
in the power plant plumes we have investigated.   In fourteen out of eighteen
cases there was a negative correlation between N02/N0 and NOX  indicating that
the plumes were indeed generally diffusion  controlled.  However, on three
occasions there were significant positive correlations between N02/N0 and NOX,

                                     175

-------
                                               5000
                                             „ 2500
                                                       (a) Nitric oxide
                                                                     I KM
                  (a)
                                               200
                                                100
                                                        (b) Ozone
                                                                     I KM
                 (b)

 Figure  1.   Diagrams  for a bimolecular
 reaction  in a turbulent plume:  (a)
 shows a cross-sectional  view of the
 plume.   The reaction zone is an
 annul us of area  A  and width LR.  The
 interior  of the  plume, where the
 concentration of NO  is high, has area
 B.   Area  C is the  exterior region of
 ozone.   E  is a mixing turbulent eddy
 of  velocity VV and scale A.   (b) shows
 concentrations of  the gases across
 section (a).
which indicates that in some situations the
controlled.  This is not surprising in view
scales for atmospheric mixing,, and it is to
gradients of NOx become small over both the
and the macroscale of the plume.
                                         Figure 2.  Profiles  of  nitric  oxide
                                         and ozone across  the plume  of  the
                                         Four Corners coal-fired power  plant
                                         on 16 October  1975.   The range was
                                         1 km downwind  from the  stack and
                                         the altitude was  1950 m.
                                            plume chemistry may be  chemically
                                            of the variability in the  time
                                            be expected when concentration
                                            spatial scale of the measurements
     The degree to which the plumes are in chemical steady state may
sidered in terms of the three fast reactions:
                                                                      be con-
         NO  + hv
                        NO + 0
                                               (1)
         0 + 02 +
0
                               M
(2)
                  k,
         NO + 03 —-*-* N02 + 02                                          (3)

where the k's are rate constants and ka = 8.0 x  TO"3  (x  <  400  nm),  k2  = 1.1  x
                                     176

-------
      TABLE 1.  CORRELATION OF N02/N0 WITH NOX IN POWER PLANT PLUMES

Date
6/16/75
M
n
7/29/75
ii
8/20/75
n
10/10/75
M
10/11/75
ii
10/17/75
n
M
n
10/30/75
10/31/75
II

Power Plant *™*°
Centralia* 0.8
1.6
4.8
0.8
1.6
0.2
3.2
Longview t 5.0
3.0
3.0
10
Farmington* 20
40
70
10
Centralia* 8.0
2.4
5.6

Correlation
Coefficient
(Vxy)
-0.75
-0.92
-0.94
-0.87
-0.90
-0.57
-0.51
+0.98
+0.10
-0.76
+0.99
-0.91
-0.91
-0.54
+0.80
-0.74
-0.80
-0.69

Significance
Level (%)
> 90
> 90
> 98
> 95
> 99
> 75
> 50
98
< 50
> 90
99
> 90
> 95
> 50
80
> 80
80
> 80

Data Source
Hegg et al .
(1976)
M
M
n
n
M
n
M
Ogren et al .
(1976)
M
n
Hegg et al .
(1976)
n
M
Ogren et al .
(1976)
Hegg et al .
(1976)
M
II

* Coal-fired
T Gas-fired
                                   177

-------
 10-3U exp(500/T),  and k3 =  1.7  x 1CT12  exp(-1310/T)  (Crutzen,  1974).   If the
 system is in the photostationary state,  then:

          H = (N02) ka/k3(NO)(03) =  1                                    (4)

 (Steadman and Jackson, 1974).   Because  values  for all  of the  parameters  in
 Equation (4) can be determined  from our airborne  measurements, departures of
 the measured ty from unity are  indicators of departure  from chemical  steady
 state at the spatial  scales of  the  measurements.   Moreover, departures of ^
 from unity are explicable in terms  of the relative size of the reaction  ozone
 compared to the size  of the plume.

      Before displaying these departures, however, we wish to  consider the de-
 pendence of \i> on the  width  of the reaction zone (expressed in terms  of the
 ratio of the time scale of  the  chemical  kinetics  to the time  scale of plume
 mixing).  Consider a simple bimolecular reaction:


              A + B ^> C .                                              (5)

 where k is the chemical  rate constant.   Then,
          (jy\      0_n     	
          dt    \* 8 r*

where Kr is an eddy diffusion coefficient along the radius of a cylindrical
plume, and  the bars indicate the effect of correlated concentration fluctua-
tions.  If  the effect of  correlated concentration fluctuations on the chemical
kinetics is negligible for fast chemistry, Equation 6 can be approximated as:


         <±A = M   _5
         •df - TD - XC

where T. is the kinetic time scale and T  is a diffusive time scale defined
by:    C                                D


         K  32A =  K   A = V  TTA                                        , .
          rW?~  r FT- Yr2T 2  '                                      I8j
                          v  TD

Tn is a time scale characteristic of the mixinq over some sub-scale (LD) of  the
 U                                                                    K
plume, T  is the turbuieni time scale over the spatial  scale R (Figure  la) and

V  is the turbulent velocity fluctuation.   The value of B is given by;


                Tl                                                      (9)
                 D

Integrating (7) over the chemical time scale:
                                      178

-------
          ln/=  0^-  1                                              (10)
             Ho      TD
 and

          A  = AQ exp{g TC/TD +  1}  .                                     (11)

 Hence,

          $  = a  _I = a exp{_3 T /,  +  1}                             (12)
              K3   AB              L  u

      Values  of ^  and tp/Tn from our field data are  listed in Table 2.  The
 value of  TC was determined from the formula of Steadman and Jackson  (1974),
 namely:

          T   - (\s  + ic fNi~n + k (r\ \\~                                  (~\i\
          T p  — IK'K —^INUyrls—^Ugyj                                   V ' ^ /

 The value of TD was approximated as:


          TD  = R/2V£                                                    (14)

 where R is  the radius of the plume, VE - 0.4 If and U is the mean wind  velocity
 (Pasquill,  1974).   The data in Table 2 were fitted  to Equation 12 and  a and e
 determined as regression coefficients.  The values were found to be stable
 with values  of:   a = 0.2 +_ 0.03 and 3 - 4 +. 1.  The multiple correlation coef-
 ficient of the regression was found equal to 0.61.  We conclude that observed
 departures from the photostationary state can indeed be explained by the rela-
 tive size of a plume reaction zone and that the plume chemistry is, in fact,
 diffusion controlled.

     If the  plume chemistry is diffusion controlled, the net conversion rate
 of NO to N02 will  be considerably slower than that  inferred from chemical
 kinetics.   Furthermore, the value of the ratio N02/N0 should, and does, remain
 low.  Conversion rates of NO to N02 were calculated for the plume centerline
 and for the plume as a whole using the formula

          (N02).  + y(NO).    (N02)f
              1  .  ,  .  1  =      T                                      f-\Z\
          (1 - Y)  (N0)i     (N0)f                                       (^>

where y "is the fraction of NO converted to N02 and  the subscripts i and f
 refer to the initial and final times, respectively, that the concentrations
were measured.  (Note that Equation 15 assumes that NOX is conserved.)  Meas-
 ured values  for the 50% conversion times of NO to N02 are shown in Table 3.
The 50% NO to N02  conversion times for the centerline of the plume are plotted
 in Figure 3, where it can be seen that the conversion rate decreases approxi-
mately inversely as the square of the travel time from the stack; this result
 is consistent with our previous conclusion that the plume chemistry is diffu-
 sion controlled.

     Ratios of N02/N0 measured during this study are quite low (Tables 4 and

                                     179

-------
TABLE 2.  VALUES OF TC/TD AND CORRESPONDING VALUES OF
Date   Power Plant
TC/TD

                                     ^ (obsen/ed)  (ca]cuiated)
10/17/75
n
10/31/75
n
10/11/75
II
10/31/75
10/30/75
10/16/75
n
10/30/75
Farming ton
n
Central ia
II
Longview
n
Central ia
n
Farmington
n
Central ia
20
40
2.4
5.6
3
10
21
0.8
17
30
18
0.034
0.002
1.17
0.44
0.17
0.18
0.39
0.88
0.005
0.010
0.45
2
3

1


1

13
16
1
,860
,718
429
,215
721
648
,200
358
,700
,300
,144
6
9
9
9
7
7
9
10
5
5
10
0.60
0.64
0.13
0.14
0.13
0.12
0.17
0.15
0.54
0.37
0.18
+_ 0,
+ 0.
+ 0..
± °-
± °-
+ 0.
± °-
+ 0.
± °-
+ 0.
1 °-
19
11
05
03
02
02
05
03
06
05
03
0
0
0
0
0
0
0
0
0
0
0
.47
.43
.01
.12
.30
.29
.14
.03
.52
.51
.12

 TABLE 3.  TIMES REQUIRED FOR 50% OF NO TO BE CONVFRTED
              TO N02 IN POWER PLANT PLUMES

Date
6/16/75
n
7/29/75
8/20/75
10/11/75
10/17/75
10/31/75
11/4/75
11/5/75
Power Plant
Central ia
n
n
M
Longview
Farmington
Central ia
n
n
Travel Time
(min)
5.0
14
23
30
18
96
7.9
14
2.3
50% Conversion
Time Along
Center line (min)
5.9 -
7.6
Indeterminate
n
366 -
24 -
119 -
11.6 -
29 -
2 -

1002
53
160
120
320
3.4
Average 50%
Conversion Time
for Plume (min)
3.6 - 4.3
Indeterminate
n
ii
48 - 82
93 - 126
Indeterminate
—
3.3 - 16.7
                          180

-------
                    1000
                   0)

                   ~ 100

                   o
                   o

                  8?
                   fc  10

                   
-------
       TABLE 4.  N02/N0 RATIOS ALONG THE CENTERLINE OF THE PLUME FROM THE

                  CENTRALIA COAL POWER PLANT ON 30 OCTOBER 1975

Range
(km)
0.8
8.0
17.6
22.4
38.4
Travel Time
(min)
1.4
14
22
39
65
NO
(ppm)
0.42
0.099
0.065
0.055
0.039
N02/N0
0.33
1.3
1.9
4.3*
2.6

 *Highest ratio observed in study.


    TABLE 5.  PLUME AVERAGE N02/N0 RATIOS WITH CORRESPONDING TRAVEL TIMES

              FOR VARIOUS FLIGHTS AT THE CENTRALIA COAL POWER PLANT

Date
7/29/75
II
6/16/75
II
II
8/20/75
II
11/5/75
M
Travel Time
(min)
15
30
3.3
6.7
20
3.5
60
1.5
3
NOX
(ppm)
0.13
0.07
0.27
0.11
1.05
0.38
0.06
0.07
0.05
N02/N0
0.25 + 0.03
0.27 + 0.05
0.24 + 0.02
1.14 + 0.07
1 . 08 + 0.14
0.27 + 0.01
0.26 + Q.03
0.47 + 0.07
0.70 + 0.10

would be inferred from chemical  kinetics.   The highest value of N02/N0 was
4.3, which is consistent with our observation that ozone was not generated in
the power plant plumes that we studied.


                              ACKNOWLEDGEMENTS

     This research was supported by contracts RP572-3-1  and RP330-1  from the
Electric Power Research Institute.

                                 REFERENCES

 1.   Crutzen,  P.  J.  1974.   Photochemical Reactions  Initiated By  and  Influencing
     Ozone  in  Unpolluted Tropospheric Air.  Tellus.  26:  47-56.

                                     182

-------
 2.  Davis, D. D., G. Smith and G.  Klauber 1974.   Trace  gas  analysis  of  Power
     Plant Plumes via Aircraft Measurement.   Science.  186:  733-735.

 3.  Hegg, D. A., P. V.  Hobbs and L.  F.  Radke 1976.   Reactions  of  Nitrogen
     Oxides, Ozone and Sulfur in Power Plant Plumes.   Final  Report Under
     Contract RP 572-3-1  And Interim  Report  Under Contract RP 330-1 prepared
     for the Electric Power Research  Institute,  3412  Hill view Avenue,  Palo
     Alto, California  94304.

 4.  Hill, J. C. 1976.  Homogeneous Turbulent Mixing  with Chemical  Reaction.
     Ann. Rev. Fluid Mech.  8:  135-161.

 5.  Hobbs, P. V., L. F.  Radke and  E.  E.  Hindman  II  1976.  An Integrated Air-
     borne Particle-Measuring Facility and Its Preliminary Use  in  Atmospheric
     Aerosol Studies.  J. Aerosol Sci.  7:  195-211.

 6.  Kocmond, W.C., D.B.  Kittelson, J.Y.  Young and K.L.  Demerjian, 1975.
     Study of Aerosol Formation in  Photochemical  Air  Pollution.   EPA  Report
     No. 65013-75-007.

 7.  O'Brian, E. E. 1974,  Turbulent  Diffusion of Rapidly Reacting Chemical
     Species.  Adv. in Geoph.  18b:  341-348.

 8.  Ogren, J. A., S. A.  Muller, M. E. Thistlewaite,  J.  A. McDonald,  W.  R.
     Kiruth, M.  E. Drehsen, J. A. Nuebuck and S.  B. Bristow  1976.   Data  Volume,
     Determination of the Feasibility  of  Ozone Formation in  Power  Plant  Plumes.
     Meteorology Research Inc.  Report MRI 76-FR-1388.

 9.  Pasquill, F.  1974.  Atmospheric  Diffusion.  2nd Ed., Halstad Press,  New
     York.

10.  Steadman, D. H. and  J. 0. Jackson.  1974.  The Photostationary State in
     Photochemical Smog.   Paper presented at CODATA Chemical Kinetics  Meeting,
     Detroit, Michigan.

11.  Tesche, K.  W., G. Z. Whitten,  M.  A.  Yoche and M.  K.  Liu. 1976.   Theoretical
     Numerical and Physical Techniques for the Characterization of Power Plant
     Plumes.  Electric Power Research  Institute,  Topical  Rpt. EC-144.
                                     133

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                                                                            5-3
          THE ANALYSIS  OF  GROUND-LEVEL OZONE DATA FROM NEW JERSEY,
                NEW  YORK,  CONNECTICUT, AND MASSACHUSETTS:  DATA
                      QUALITY ASSESSMENT AND TEMPORAL AND
                            GEOGRAPHICAL PROPERTIES

                  W.  S.  Cleveland,  B. Kleiner, J. E. McRae,
                              and R.  E.  Pasceri*
ABSTRACT

     Hourly,  ground-level ozone, measurements firom 47 suites in eastern New
Vork, northern  Went Jersey,  Conne.dtic.uut,  and Massachusetts firom May  7, 1974
to September  SO,  1974,  are analyzed,   (/arious techniques fior assessing  data
quality and uniform calibration show the. data to be OjJ high retiabiJLitiy {,or
yielding i.n^ormati,on  on the. ozone. problem in the. fio.Qi.on.  Statistical analyses
show that ni.ghttane concentration*,  negative, to those ducting the. day, are
highest in MaAAachuA&ttA.  The. i»Lt  diA&vibuution ofi daMLy maxAjnum conce.ntn.a-
tion (Vie. hi.ghut  i.n the. Stmfiosid-Gie.e.nwi.ch ie.gi.on o& Aouth Connecticut  and
ne.xt hi.ghut  -in a ie.gi.on to the. e.aAt and notithe.aAt oft Sta.m&otLd-Gsie.e.nW'ich.
Jkue. n.
  • vJtt&, together with otheA anaJLyAeA, demonstrate, that photochemical. aiA potation sizAuutting fiiom primary e.miAi>i,on& in the. Wew Vork City metro- politan area. JU> transported by prevailing Minds on a 300 km northeast trajec- tory through Connecticut as &ar as northeastern Massachusetts. INTRODUCTION This paper presents an analysis of ambient ground-level ozone measure- ments from a region of the northeastern United States covering eastern New York, northern New Jersey, Connecticut, and Massachusetts. The data consist of hourly averages from May 1, 1974, to September 30, 1974, at 41 sites. Their quality and uniform calibration assessed, their diurnal behavior is analyzed, and the geographical variation in concentrations over the region is described. The ozone data, gathered at monitoring site locations shown in Table 1 and Figure 1, were provided by the following agencies: New Jersey sites — New Jersey Department of Environmental Protection; New York sites (except Yonkers) — New York State Department of Environmental Conservation; Yonkers — Boyce Thompson Institute; Connecticut sites — Connecticut Department of Environ- mental Protection; Massachusetts sites — Massachusetts Department of Public Health. *W. S. Cleveland, B. Kleiner, J. E. McRae, J. L. Warner, Bell Laboratories, Murray Hill, New Jersey. R. E. Pasceri, New Jersey Department of Environ- mental Protection, Trenton, New Jersey. 185

  • -------
     TABLE 1.   SUMMARY  OF  OZONE  DATA AT 41 SITES  IN THE NORTHEASTERN UNITED STATES
     FOR 1974.   ALL  OZONE  CONCENTRATIONS ARE  IN PPB.
     Column   Description
    
       1      Site  name
       2      State (J = New  Jersey, Y = New York, C = Connecticut, and M =
             Massachusetts).
       3      Site  letter  (the  site letter together with the state allows
             identification  of the location in Figure 1).
       4      Maximum hourly  reading from May to September with suspect values
             shown by a *.
       5      Number of days  from May to September with valid daily maxima (i.e.,
             maximum hourly  concentration from 0800 to 2400 EST).
       6      Median of the daily maxima for June to August.
       7      Upper quartile  of daily maxima for June to August (one site omitted)
       8      Ratio of upper  quartile of readings at 1500 hours EST from May 15
             to August 15 to upper quartile of readings at 0100 hours EST from
             May 15 to August  15.
     Name
    
     Asbury Park
     Somerville
     Chester
     Bayonne
     Elizabeth
     Newark
     Welfare Island
     Yonkers
     Eisenhower Park
     Babylon
     Mamaroneck
     Greenwich
     Stamford Farms
     Stamford Trailer
     Bridgeport
     Danbury
     New Haven
     Waterbury
     Morris
     Deep River
    Middletown
     New Britain
     Groton
     Hartford
    Windsor
     Eastford
    Springfield
    State  Code  Maximum  Days  Median  Quartile   Ratio
      J
      J
      J
      J
      J
      J
      Y
      Y
      Y
      Y
      Y
      C
      C
      C
      C
      C
      C
      C
      C
      C
      C
      C
      C
      C
      C
      C
      M
    A
    S
    C
    B
    E
    N
    W
    Y
    E
    B
    M
    G
    S
    D
    N
    W
    M
    d
    m
    n
    g
    H
    W
    E
    S
     176
     196
     170
     208*
      98
     140
     185
     132
     154
     207*
     165
     270
     250
     240
     250
     270
     302
     252
     225
     202
     365
     240
     244
     306
     234
     197
     108
    (conti
      121
      114
       90
      122
       95
      125
      115
      148
       48
      109
      120
      133
       63
      136
      137
       89
       94
       76
       90
       57
      105
      119
      110
      135
      103
       56
      131
    nued)
     59
     58
     90
     80
     50
     47
     81
     56
     55
     72
     62
    100
     97
     91
     80
     81
     76
     75
     85
     94
     80
     82
     74
     68
     60
     85
     34
     82
     81
    110
    100
     64
     63
    102
     80
    
    111
     89
    140
    145
    134
    116
    120
    127
    112
     99
    117
    122
    124
    113
    103
     82
     96
     48
    2.2
    5.5
    1.7
    4.8
    4.7
    5.6
    5.3
    3.4
    4.5
    3.5
    8.3
    3.7
    3.1
    5.6
    4.1
    4.8
    3.7
    5.1
    2.9
    2.6
    3.1
    2.5
    2.7
    2.9
    4.8
    2.7
    1.9
                                         186
    

    -------
    TABLE 1.   (continued)
       Name
    State  Code  Maximum  Days  Median  Quartile  Ra ti o
    Worchester
    Fitchburg
    Fall River
    Lowel 1
    Quincy
    Boston
    Cambridge
    Waltham
    Medford
    Kingston
    Pittsfield
    Rensselaer
    Schenectady
    Glens Falls
    M
    M
    M
    M
    M
    M
    M
    M
    M
    Y
    M
    Y
    Y
    Y
    W
    F
    f
    L
    Q
    B
    C
    w
    M
    K
    P
    R
    S
    G
    250
    174
    214
    145
    173
    136
    130
    116*
    166
    159
    166
    128
    128
    127
    — . . M .-_
    128
    136
    94
    135
    102
    84
    95
    92
    76
    123
    109
    106
    116
    115
    66
    65
    73
    63
    62
    36
    54
    42
    52
    64
    65
    60
    56
    64
    86
    87
    109
    86
    79
    56
    74
    59
    79
    91
    84
    78
    72
    84
    1.8
    2.1
    1.5
    2.5
    2.0
    2.0
    1.9
    2.4
    3.1
    3.0
    2.2
    2.9
    2.4
    2.5
    
    Figure 1.  Site letters in column 3 of Table 1 are shown at site locations
                                         187
    

    -------
         With the exception of the Boyce Thompson Institute unit, all  monitors
    were of the gas phase, ozone-ethylene type.   Some of the commercial types used
    (Bendix, REM) have been recently examined by Clark, et al., who also briefly
    reviewed the development history of the ozone-ethylene detector (1).   Field
    tests of various ozone and oxidant analyzers have been reported by Stevens,
    et al. (2,3).  The cooperating agencies have found that the various commer-
    cial brands of analyzers are equivalent with regard to the accuracy needed for
    air monitoring networks.  Boyce Thompson Institute employed the colorimetric
    method for oxidants determination with a dichromate scrubber to avoid sulfur
    dioxide interference (4).
    
         Each monitoring agency, operating independently, utilized a variety of
    analyzers, field calibration techniques and schedules.  Generally, however,
    all field calibrations were referred to the federal reference method utilizing
    the reaction of oxidants with neutral, buffered potassium iodide (5).   In
    addition, the Connecticut, New Jersey, and New York agencies participated with
    their EPA Region II laboratory in a joint ozone calibration on June 21, 1974
    (6).  Previously, on June 14-17, the EPA laboratory had calibrated their
    Bendix 016059 calibrator at the National Bureau of Standards, Washington, D.
    C., which utilized the federal reference method.   Efforts toward standardizing
    ozone calibration techniques have been reported by Hodgeson, et al (7).
    
    
                            DATA QUALITY AND CALIBRATION
    
         No detailed investigation of ambient air quality data can omit the impor-
    tant consideration of data quality (8).  A number of nonstatistical considera-
    tions make it plausible that the data are of high quality.  The first is the
    reliability and relative ease of maintenance of the chemiluminescent monitors
    (3).  The second is the high frequency of site visits by agency personnel and
    the data review programs carried out by all  agencies.  Third, the  uniformity
    of calibration was greatly enhanced among the New Jersey, New York, and Con-
    necticut agencies by the joint calibration program of June 21, 1974,  described
    in the introduction.   While such considerations inspire confidence in the
    data, it is still desirable to use statistical methodology for further veri-
    fication. In this section the particular techniques that have been used in
    assessing the ozone data are described.
    
         Bad data, particularly if caused by transmission errors, often have
    little regard for the measurement scale.  Thus, the first step in  our data
    quality assessment was to calculate the largest hourly reading at  each site
    and inspect the data for a time interval containing the maximum.  In a number
    of cases, transmission errors were detected; in a few cases, correctly trans-
    mitted numbers were discarded as unlikely because of a lack of validation from
    other sites.  In three cases, suspicion was  raised but there was no proof of
    bad data.  These values were retained with the notation that something might
    be wrong.  A typical  example was recorded in Waltham, Massachusetts, on August
    7, 1974;  24-hourly values in ppb starting at 0100 hours EST were 0, 10, 20,
    10, 20, 30, 40, 50, 50, 100, 120, 100, 80, 70, 40, 40, 50, 40, 40, 40, 30, 30,
    20, 10.  The readings were not terribly unusual;  but, in comparison with
    measurements for the day at other sites, were atypical.  At other  sites, there
    was relatively little photochemical activity measured; the highest reading
    being 70 at Cambridge.
    
                                         188
    

    -------
         Table  1  lists the maxima for  the  41 sites to show the highest concentra-
     tions  of  ozone  in the region.  The three suspect values are indicated.   For
     these  sites,  the second  highest  readings in ppb are  167 (Bayonne), 112  (Wal-
     tham), and  201  (Babylon).
    
         If the data at a particular site  contains an undue amount of measurement
     noise, then it  is to be  expected that  the variation  of the measurements
     through time  will not correspond well  with those at  other sites.  For each
     day, the  maximum of the  hourly averages from 0800 to 2400 was calculated  for
     each site.  Correlation coefficients, with 5% trimming at points along the two
     principal components, between all  pairs of sites were computed for the  square
     roots  of  these  daily maxima  (9).   The  trimming is a  statistical device which
     prevents  a  small fraction of the data  having an undue influence on the  corre-
     lations,  which  are meant to summarize  the general behavior.  The sample distri-
     bution of the square roots is approximated well by a normal probability plots
     for each  of the 41 sites (10).   Although in a few cases, such as Bridgeport,
     the square root maxima are skewed  to the right, the  square roots provide  a
     more satisfactory plot than logs or the untransformed data.
    
         Since distance between sites  must be taken into account in assessing the
     levels of the correlations, correlations between all pairs of sites are
     plotted against inter-site distances in Figure 2.  Moving statistics have been
     superimposed  on the plot to summarize  the behavior of the plotted points.  The
     middle curve  summarizes  the middle of  the distribution of correlations  given
     distance, the upper curve summarizes the upper tail  of the distribution,  and
     the lower curve summarizes the lower tail.  The correlations tend to be quite
     large  for small distances, and,  as has previously been observed, tend to
     decrease  with increasing distance  (11).  The only site with unusually low
     values, given distance to other  sites, is Asbury Park.  In fact, all correla-
     tions  below 0.2 involve  this site.  A  careful study  of the Asbury Park  data
     led to the conclusion that the site location, and not data quality, was
     responsible for the low  values.  This  conclusion is  discussed further in  the
     final  section of this paper.
    
         One  of the most elusive questions for statistical methodology to investi-
     gate is thart  of uniform  calibration, particularly between different agencies.
    Respite the joint calibration described earlier, it  was desirable to use  the
     data to conduct further  checks.  The distributions of daily maxima at pairs of
     sites were compared by an empirical quantile-quantile (EQQ) plot (12, 13).
     This analysis was complicated, however, because even if two sites are located
     within a  few  miles of one another  and  even if calibration is exactly the  same,
     the two sites do not have to have  the  same ozone concentrations, since  local
     primary emissions can substantially influence ozone  levels (14).  However, the
     philosophy invoked is that if there is a major discrepancy between two  close
     sites  for which an explanation cannot  be found, then the calibration is
     questioned.
    
         To eliminate distortions due  to missing data, the distributions of daily
     maxima at two sites were compared  only for days when both sites have all  daily
     maxima.   X-j,  for i = l,...,n, is the ordered daily maxima (Xi is the smallest,
     X2 is  the next smallest, etc.) from one site, and Yi the ordered maxima for
     the second site.  The EQQ method of comparing the ozone levels at the two
    
    
                                         189
    

    -------
        08
        06 •
      C
      O
      L.
      i,
      O
        0.4 •
        02 •
        0 0
                 000  O
                           100
                                                              300
      Figure 2.
                               200
                          Distance - km
    Correlations of square root daily maximum ozone concentrations
    between all  pairs of the 41 sites are plotted against the dis-
    tances between sites.  Moving statistics have been superimposed
    to summarize the information on the plot.
                                                                               400
    sites consists of plotting Y-j versus X-j.  If the plotted points lie near  the
    line Y=X, the two distributions are nearly the same.  These plots were made
    for a large number of pairs of nearby sites and only one major discrepancy was
    found.   Figure 3 shows the EQQ plot for Mamaroneck, maintained by the New York
    State Department of Environmental Conservation, and Stamford Trailer, which is
    24 km from Mamaroneck and is maintained by the Connecticut Department of
    Environmental Protection.  The points on the EQQ plot lie well below the  line
    Y=X, indicating that Stamford has considerably higher ozone levels.  The
    result in the next section that ozone measurements in the region are highest
    in Connecticut carries with it important conclusions about the nature of  the
                                         190
    

    -------
    photochemical  air  pollution  problem in the region.  It is, therefore,  import-
    ant to investigate further whether the recorded Connecticut concentrations  are
    too high as  a  result  of faulty calibration.
    
         An important  factor for consideration is that Mamaroneck is in the  vicin-
    ity of strong  automobile emissions of nitric oxide, which would tend to  reduce
    the ozone concentrations (14).   An example of the effect of these emissions
    is, as shown in the next section,  that Mamaroneck has the lowest nighttime
    ozone concentrations  of the  41  sites.   In order to compare the Connecticut
    data in other  ways, EQQ plots  have been made in Figure 3 comparing Fall  River,
    Massachusetts, with Groton,  Connecticut; and Babylon, New York, with Bridgeport,
    Connecticut. Groton,  located in eastern Connecticut appears to agree quite
    well with Fall River.   Babylon,  like  many of the Connecticut sites, lies  in  a
    region where prevailing winds  reach after crossing the center of the New  York
    City metropolitan  area  and has  ozone  concentration distributions much  like
                                                Z 140
                                                >
                                                s
                 50    100    150   200
                    Stamford Trailer
        100   140
         Groton
                                                                         220
                                                c
                                                c
                                                O BO-
                                                X
                                                <0
                                                m
                      80    120
                      Bridgeport
    40    80   120   160
      Stamford Trailer
      Figure 3.   Empirical quartile-quartile  plots of daily maximum ozone con-
                 centrations  (ppb)  for  four  pairs  of sites.
                                         191
    

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    that of many of the Connecticut sites.   Levels in Babylon agree quite well
    with those in most of Connecticut, and are only slightly lower overall than
    the levels in the Stamford-Greenwich region, which, as will  be shown, are the
    highest in the state of Connecticut.  For example,  the EQQ plot in Figure 3
    comparing Babylon and Bridgeport shows  the two sites to have very similar
    distributions.  The fourth EQQ plot in  Figure 3 compares the distributions of
    daily maxima at Bayonne, New Jersey, and Stamford Trailer for all days from
    May to September when the resultant wind direction  at 1000 and 1300 hours EST
    at La Guardia Airport is between 0° and 180°.   The  two sites have very similar
    concentration distributions for such days which lends credence to uniform
    calibration between new Jersey and Connecticut.
    
         A final verification for the Connecticut data  comes from an aircraft
    flight on August 1, 1974, in which ozone was measured over the state of
    Connecticut (15).  The aircraft measurements gave no indication of Connecticut
    ground station measurements being too high.  For example, at 1606 hours EST
    the aircraft 1000 ft.  over Bridgeport was measuring 135 ppb while the ground
    station average from 1600-1700 hours EST was 110 ppb.
    
    
                      DIURNAL VARIATION OF  OZONE CONCENTRATIONS
    
         The diurnal variation at each of the 41 sites  was studied by calculating
    and plotting the upper quartiles for each hour of the day from May 15 to
    September 15.   One noticeable feature was the reduction in the amount of
    diurnal variation in the upper quartiles at the Massachusetts sites.   In Table
    1  the ratios of the upper quartiles at  1500 divided by the upper quartiles at
    0100 are given.  The ratio tends to decrease with increasing distance from the
    New York City metropolitan region.  In  particular,  the Massachusetts values
    appear to be the lowest.  One site, Mamaroneck, has an unusually large ratio,
    caused, presumably, by local sources of primary emissions which appear to
    reduce the ozone levels overall, but which have a particularly strong influ-
    ence on nighttime levels.  Mamaroneck has the lowest upper quartile at 0100
    for all 41 sites.
                   GEOGRAPHICAL VARIATION OF OZONE CONCENTRATIONS
    
         A detailed comparison of the 41  ozone concentration distributions at the
    sites would be easier if there were not missing values.   Missing data can lead
    to distortion in the comparison of distributions unless  special care is taken.
    To illustrate this, consider two nearby sites with nearly the same ozone con-
    centration distributions.   Suppose the first has all data from May through
    September; but, for the second, the data is missing for  the first two weeks in
    May when the maxima are at their lowest for the season.   Then a comparison of
    all data at site one with all data at site two would leave the false impres-
    sion that site two has a higher ozone distribution.  In  a previous section,
    each comparison of distributions to check calibration involved only two sites.
    But in this section, the goal is to compare the 41 distributions simultane-
    ously. The number of days with no missing data at all sites is extremely
    small, so it is necessary to compare distributions of values over different
    sets of days. Thus a statistical technique was developed to determine which
    
    
                                         192
    

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     aspects of the daily maxima at each site were reliable for all sites, except
     for the upper quartile at Eisenhower Park.  Thus these values, given in Table
     1, are regarded as valid for comparing the dependence of ozone levels on
     geographical location. One result, somewhat unexpected before this analysis
     was carried out, is that Eastford and Deep River, despite having only about
     one month of data, are usable in the geographical comparison.  However, it was
     found that the largest reading at each site could not be used for comparing
     ozone concentration distributions at different sites.
    
         Analysis of the data revealed that the ozone levels taper off at the
     beginning and end of the May to September period.  Since data at a site tends
     to be missing in stretches of several days, rather than isolated days, and
     since a number of sites have missing data for large stretches of days at the
     beginning and end of the season, it makes comparison of distributions even
     more difficult if the whole period May-September is included.  For this reason
     only the months June-August were used in computing the medians and upper
     quartiles.
    
         In Figure 4 the upper quartiles are plotted against geographical location.
     The region of highest ozone concentrations is in the Greenwich-Stamford region
     of southwestern Connecticut, while the next highest are in a belt which spreads
     out from there to the east and northeast.  The five sites with the lowest
     upper quartiles and medians are Boston, Waltham, Springfield, Newark, and
     Elizabeth.
    Figure 4.   Upper quartiles of daily maximum ozone concentrations from June
               to August at each site are plotted against geographical  locations,
               The values are coded by numbers: 0=79 ppb or less; 1=80-99 ppb;
               2=100-114 ppb; 3=115-129 ppb; 4=130 ppb or more.
                                         193
    

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                                       SUMMARY
    
         Hourly  average, ground-level ozone measurements from 41 sites in eastern
    New York, northern New Jersey, Connecticut, and Massachusetts for the time
    period May 1,  1974, to September 30, 1974, have been analyzed.  The quality
    and uniform  calibration of the data were assessed by several statistical
    procedures.  In a few cases short stretches of data were invalidated,  A
    discrepancy  between the Mamaroneck and Stamford Trailer sites, which brought
    the uniformity of calibration between New York and Connecticut into question,
    was resolved by the conclusion that local primary emissions were reducing the
    ozone concentrations in Mamaroneck substantially.  The general conclusion is
    that the ozone data are of high quality and reliable for examining the problem
    of ozone pollution.
    
         An analysis of diurnal behavior revealed that diurnal variation tends to
    decrease (i.e. nighttime values are closer to daytime values) with increasing
    distance from the New York City metropolitan region.  Nighttime values, rela-
    tive to the  daytime values, were particularly high in Massachusetts.
    
         An analysis of the geographical variation in ozone concentrations showed
    that the lowest concentrations are in Boston, Waltham, Springfield, Newark,
    and Elizabeth.  All five sites are located next to high traffic density
    arteries, and therefore have large emissions of nitric oxide that reduce the
    ozone levels. Since this depression of the levels drastically reduces the
    information  content in data from such areas, it is recommended that future
    placement of ozone monitors not be immediately adjacent to high traffic den-
    sity roadways.
    
         The highest ozone concentrations are in the Stamford-Greenwich region of
    Connecticut while the next highest are in a region to the east and northeast
    of Stamford-Greenwich.
    
    
                                     CONCLUSIONS
    
         This paper and other publications directly dealing with transport of
    photochemical air pollution provides strong evidence that photochemical  air
    pollution resulting from primary emissions in the New York City metropolitan
    area is transported by prevailing winds on a 300 km northeast trajectory
    through Connecticut and as far as northeastern Massachusetts (16,17).  This
    occurrence accounts for southwestern Connecticut having the highest ozone
    concentrations in the region.   Thus, it would appear that, similar to the Los
    Angeles Basin, the chemistry of ozone production is such that areas downwind
    of strong precursor emissions have the highest ozone concentrations (18,19).
    
         The phenomenon of transport provides the explanation for the low correla-
    tion of ozone daily maxima at Asbury Park with those at other sites.  Asbury
    Park is the only site which is both south to southeast of the New York City
    metropolitan area and in a region which is downwind of the area on a signifi-
    cant number of days.   Thus Asbury Park has its highest ozone concentrations
    when the wind is from the northwest and north, while the majority of other
    sites, which lie to the east and northeast, have their highest ozone concen-
    
                                         194
    

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    trations when the wind is from the west and southwest.
    
         Transport also provides the explanation for the  high nighttime ozone
    concentrations in Massachusetts relative to those during the day.  The distance
    between the New York City metropolitan area and eastern Massachusetts is such
    that the effects of transport, in the form of high ozone concentrations, often
    occur in eastern Massachusetts during the time period from 1900 to 2400 hours.
    
    
                                     REFERENCES
    
     1.  Clark, T. A., R.  E. Baumgardner, R. K. Stevens,  and K. J. Krost.  Evalua-
         tion of New Ozone Monitoring Instruments by Measuring in Non-Urban Atmos-
         pheres.  Instrumentation for Monitoring Air Quality.  ASTM STP 555.
         American Society for Testing and Materials, Philadelphia, Pennsylvania,
         1974.
    
     2.  Stevens, R.  K., J.  A. Hodgeson, L.  F. Ballard, and C.  E. Decker.  Ratio
         of Sulfur Dioxide to Total Gaseous Sulfur Compounds and Ozone to Total
         Oxidants in the Los Angeles Atmosphere - An Instrument Evaluation Study.
         Determination of Air Quality, G. Mamantov and W. 0. Shults, eds., Plenum
         Publishing Co., New York, 1972.
    
     3.  Stevens, R. K., T. A. Clark, C. E. Decker, and  L.  F.  Ballard.
         Field Performance Characteristics of Advanced Monitors for Oxides of
         Nitrogen, Ozone,  Sulfur Dioxide, Carbon Monoxide, Methane, and Nonmethane
         Hydrocarbons.  APCA Meeting, Miami, Florida, June 1972.
    
     4.  Jacobson, J.  S.  and G.  D.  Salottolo.   Photochemical Oxidants in the New
         York-New Jersey Metropolitan Area.   Atmos.  Env.  9, 1975, pp.  321-322.
    
     5.  U.  S.  Environmental Protection Agency.  National Primary and Secondary
         Air Quality Standards,  Federal  Register 36, 1971, pp.  8186-8201.
    
     6.  Brown,  R. M.,  G.  Wolff,  and J.  A.  Spatola.   Results of the Cooperative
         Ozone  Calibration.   Environmental  Protection Agency Region II, Edison,
         New Jersey,  July  21,  1974.
    
     7.  Hodgeson, J.  A.,  R.  K.  Stevens, and B.  E.  Martin.  A Stable Ozone Source
         Applicable as  a Secondary Standard for Calibration of Atmospheric Moni-
         tors.  ISA Transactions,  II, No.  2,  1972,  pp.  161-167.
    
     8.  Nehls,  G. J.  and  G.  G.  Akland.   Procedures for Handling Aerometric Data.
         J.  Air.  Poll.  Control  Assoc.,  23,  1973,  pp. 180-184.
    
     9.  Gnanadesikan,  R.,  and J.  R.  Kettenring.   Robust Estimates, Residuals, and
         Outlier Detection  with  Multiresponse Data.   Biometrics, 28, 1972, pp.  81-
         124.
    
    10.  Kempthorne,  0.  and  L.  Folks.   Probability, Statistics, and Data Analysis.
         Iowa State University Press, 1971,  pp.  220-221.
                                         195
    

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    11.   Bruntz, S.  M. ,  W.  S.  Cleveland, T.  E. Graedel, B. Kleiner, and J. L.
         Warner.  Ozone  Concentrations in New Jersey and New York:  Statistical
         Association with Related Variables.  Science 186, October 18, 1974, pp.
         257-259.
    
    12.   Wilk, M. B. and R.  Gnanadesikan.  Probability Plotting Methods for the
         Analysis of Data.   Biometrika, 55,  1968.   pp.  1-17.
    
    13.   Cleveland,  W.  S.,  T.  E.  Graedel, B. Kleiner, and J.  L. Warner.  Sunday
         and Workday Variations in Photochemical Air Pollutants in New Jersey and
         New York.   Science, 186, December 13, 1974.  pp. 1037-1038.
    
    14.   Graedel, T. E., and L. A. Farrow.  Ozone:  Involvement in Atmospheric
         Chemistry and Meteorology.  Ozone Chemistry and Technology.   Franklin
         Institute Research Laboratories, Philadelphia, 1975.
    
    15.   Wolff, G.,  W.  Stasiuk, P. Coffey, and R.  Pasceri.  Aerial Ozone Measure-
         ments Over  New  Jersey, New York, and Connecticut, presented at APCA
         Annual Meeting, Boston,  1975.
    
    16.   Cleveland,  W.  S.,  B.  Kleiner, J. E. McRae, and J. L. Warner.  Photo-
         chemical Air Pollution:   Transport from the New York City Area into
         Connecticut and Massachusetts.  Science,  19, 1976.   pp. 179-181.
    
    17.   Cleveland,  W.  S.,  B.  Kleiner, J. E. McRae, and J. L. Warner.  The
         Analysis of Ground-Level Ozone Data from New Jersey, New York, Connecti-
         cut, and Massachusetts:   Transport from the New York City Metropolitan
         Area.  Proceedings of the Fourth symposium on Statistics and the Environ-
         ment. American  Statistical Association, Washington,  D. C., 1976.
    
    18.   Altshuller, A.  P.   Evaluation of Oxidant Results at CAMP Sites in the
         United States.   J.  Air.  Pollut. Control Assoc., 25,  1975.  pp. 19-24.
    
    19.   Tiao, G. C., G.  E.  P.  Box, and W. J.  Hamming.   Analysis of Los Angeles
         Photochemical Smog Data:  A Statistical Overview.  J.  Air.. Pollut.
         Control Assoc., 25, 1975.  pp. 260-268.
                                         196
    

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                                                                                   5-4
                      CHEMICAL  AND METEOROLOGICAL ANALYSIS OF THE
                     MESOSCALE  VARIABILITY OF OZONE  CONCENTRATIONS
                                  OVER A SIX- DAY PERIOD
    
          W.  D.  Bach, Jr., J.  E.  Sickles, II, R. Denyszyn and W. C. Eaton
    
    
    ABSTRACT
    
         The. Reieat.cn Tfu.angie. InAtttate. conducted  low aititu.de. aiACAa^t
    oveA e.aAt Texai,  mo At ofa LoulAtana,  and adjacent ofie.aA Ofj the. Guifi  o^  Mexico
    to ^investigate. the. aAe.ai e.xte.nt oft htgh ozone. conce.ntAationA .  Ozone, concen-
    tAa£ionA wete con£tnuou6£i/ me.aAuAe.d aJLong the. ^Light pathA and at ground Ata-
    tionA at CofipuA ChfuAti, Pofit O'Connor, huAtin, Houston, and Vont AAthuA,
    Je.~x.aA and at Ve.HiddQ.n-, LouiAtana.
    
         On  Octobe.fi 19, 7975,  a htgh p^e44uAe Ay&tejm developed oue^ the. a/^ea and
               motion, began to  de.ve.lop a Atabl.e. iaye.fi o^ oJji ato{t.  Ozone,  concen-
              -in  exce.6-6 o^ HO  yg/m3 wete ^oand oueA e.&t>t Texai and ove/i u}ute.x.n
                 Ai the. ptieA&uAe. AyAtejm deue^oped and moved ea4^wow.d the. ne.x.t day,
    the. highest  ozone, wai meaiu/ied oveji weAteJin LoiuAtana.  Ozone. conce.ntn.ationA
              above 760 yg/m3 at 300 meteAi, oveA. the. 6u£^ o^ Mexico and  inland,  bat
               to 110 yg/m3 above the. stable, iaye.fi.  Ozone. me.at>(Vte,me.ntt>  at  the.
    gtiound monttofving ioc.at4.onA  ag/teed wtth the. tA.e.ndt> o^ the. oJjibonno,  me.aAuAe.me.ntt>,
              paAc.eJL iAaj e.ctoAie^  aAAivtng at ground AtationA OA at
    potntA  aiong the. ^tight ttacki,  weAe. computed to de.AcAi.bo. the. hotiizontai motion
    Of) the.  atmoApheAic. boundoAy iaye.fi.   Ttme.-aitUude.  CAOAA Ae.ctionA o&  pote.ntiai
    te.mpeAatuAe. at Lake. ChauJLuA,  LomiA-iana, 4/iowed a dynamic. atmoApheAic boundary
    iayeA.
    
         The.  occuM.e.nce.A 0(J htgh  ozone. conce.ntAationA  and ozone. gfiadie.ntA  wtthtn
    thiA ep-c6ode weAe. examined conAtdeAtng the. ozone. pfi&cuAAofi ejn^AtonA and the.
    mete.oAoiog4.cai Actuation.  Ozone. pfie.cuAf,ofi ejru.AAi.onA  -in the. Atudy afie.a and
    timite.d ve.ntHation aAe. pfiimaAiZy fie.ApoMi.bie. fiofi  maintaining the. high ozone.
    conce.ntAationA untii cie.ane.fi  aiA -iA tAanApoAte.d -into  the. ne.Qi.on.
                  »
    
                                      INTRODUCTION
    
         Until  about ten years ago, ozone  (03),  a  principal constituent of photo-
    chemical  smog, was thought to occur in high concentrations only in  urban areas
    where the precursor materials — hydrocarbons (HC)  and oxides of nitrogen (NOX)
    — were  abundant in automotive exhaust.  Nonurban ozone concentrations  typically
    ranged  from 40 to 120 yg/m3,  below the present National Ambient Air  Quality
    *Research  Triangle Institute,  Research Triangle  Park, North Carolina.
    
    
                                            197
    

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    Standard (NAAQS) of 160 yg/tn3 (1).  Recent measurements have shown that ozone
    concentrations frequently exceed the NAAQS at numerous nonurban locations in
    different parts of the United States (2-5).  In most instances, the evidence
    indicates that horizontal transport of ozone and the in situ generation/destruc-
    tion cycle of ozone are primary contributors to the high concentrations.
    
         Hydrocarbon emission densitites in several counties along the northern
    Gulf Coast are in the 95th to 98th percentile of all counties in the United
    States, due in large to the petrochemical industry of the area (6),  The abund-
    ance of hydrocarbons in the atmosphere suggests that generation of photochemi-
    cal oxidants may be a problem in and downwind of the urban industrial centers.
    
         In studies conducted by the Texas Air Control Board (7-9), hourly ozone
    concentrations greater than 160 yg/m3 were measured in nonurban areas of east
    and southeast Texas and along the coast of the Gulf of Mexico,   High ozone con-
    centrations were found upwind of urban areas, in onshore flow from the Gulf of
    Mexico, and in pine forests a hundred miles or more from the principal hydro-
    carbon emissions areas.  Neither the spatial extent of the region of high ozone
    concentration nor the sources of high ozone concentrations were determined.
    
         In response to the Environmental Protection Agency's interest in develop-
    ing strategies to control urban oxidants including ozone, the Research Triangle
    Institute conducted a field program of surface and airborne measurements to
    investigate and document the occurrences and the area! extent of regions of
    high ozone concentration in the northern Gulf Coast area of Texas and Louisiana.
    The program began June 25 and continued through October 31, 1975.
    
         This analysis considers one episode of high ozone concentration at the
    ground and aloft that shows a strong dependence of the observed ozone concen-
    trations upon slowly changing meteorological conditions.   Some of the measured
    concentrations are not identified with urban precursors and may represent a
    natural event, further complicating the problems of oxidant control.
    
    
                            DATA ACQUISITION AND ANALYSES
             fe
    GROUND STATION MEASUREMENTS
    
         RTI established a base station at the Beauregard Parrish Airport, DeRidder,
    Louisiana,  a nonurban location 50 miles north of Lake Charles.   Ozone, oxides
    of nitrogen, sulfur dioxide, and total suspended particulate (TSP) were contin-
    uously monitored.   Grab samples were taken for later analysis of selected
    hydrocarbon and halocarbon species.  The Texas Air Control  Board provided
    hourly ozone data measured at their Nederland (Port Arthur-Beaumont), Houston
    (Aldine), Austin,  and Corpus Christi, Texas locations.  These locations are
    generally considered more urban-industrial than nonurban since they are near
    large hydrocarbon  emission areas (Figure 1).  Ozone measurements at Port
    O'Connor, Texas, were provided by the DuPont Company.   All  of these locations
    were routinely audited by EPA and RTI as a part of an independent quality
    assurance program.
                                          198
    

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                                                     •^
                                                       I
                          AUSTIN
                                            \   • '~-ft  r          \
    
                                         DeRIDOjER ^;,., :;j; ^   »_A
                                    HOUSTON  .
                                          -.T^----^-s    xu
                                          'NEDERLAND   ^^'"-o "-jC1
                                 PORT O'CONNOR
                         ',    ,-;'-j^fCORPUS CHRISTI
                                                           | > 10
                                                         vl >ioo
                                HYDROCARBON EMISSION  DENSITY
                                     (tons / mi2 / yr )
                  Figure 1.  Hydrocarbon  emission  density by county.
    AIRCRAFT MEASUREMENTS
    
         RTI operated a twin engine  aircraft from the DeRidder base station.  The
    ozone, oxides of nitrogen,  air temperature,  and dewpoint temperature were con-
    tinuously monitored and the data digitized at 30-second intervals.  Similar
    measurements were made aboard the EPA B-26 research aircraft.  These aircraft
    provided spatial coverage unavailable from any other source.
    
         Flight plans were designed  to investigate specific problems of the Gulf
    Coast area, including a pair of  area!  survey flights.   The survey flights were
    conducted on successive days when similar meteorological conditions were expec-
    ted.  Additional flights were designed during the field program to investigate
    specific situations that developed or were indicated by meteorological condi-
    tions or air quality data.   Flight protocols called for a low pass over the
    DeRidder ground station after takeoff and again before landing to cross-check
    the aircraft and ground-based measurements.   When directed, the aircraft were
    used to obtain vertical profile  data in 1000 to 2000 feet vertical increments
    during both ascent and descent over a given  location.
                                           199
    

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    AIR PARCEL TRAJECTORIES ANALYSES
    
         Approximate trajectories were computed for air parcels arriving at selected
    positions along the flight track when the aircraft was in the vicinity.  Those
    computations used 12-hourly wind data from the regular rawinsonde network,  aver-
    aged vertically over the lowest 2 km of the atmosphere.   Parcel  displacements
    were integrated at 2-hour intervals over a 48-hour period to give the trajec-
    tories.
    
    CROSS SECTION ANALYSES
    
         Time-altitude cross sections of potential temperature, 9,  and the southerly
    wind component, v, were developed for the Lake Charles rawinsonde location,
    which is typical of the conditions in the coastal  area during the period.   Po-
    tential temperature is conserved in adiabatic processes,  and it is a good  indi-
    cator of atmospheric changes.  Descending e-isopleths with increasing time
    indicate descending motion and/or advection of cooler air.   Furthermore, as the
    vertical gradient of e increases, atmospheric stability increases, and the
    vertical mass transfer is inhibited.
    
    FLIGHT ANALYSES
    
         Altitude corrections were applied to airborne ozone measurements in accor-
    dance with test results in the EPA-Las Vegas Environmental  Test Chamber.  The
    corrected ozone data showed excellent continuity of trends  at 2-minute inter-
    vals, so the concentrations at 10-minute intervals along  the flight track were
    plotted.  Concentrations of oxides of nitrogen were seldom above the detectabil-
    ity of the chemiluminescent instruments, so those numerical data were of little
    value.
    
    
                                     CASE STUDY
    
    OVERVIEW
    
         On October 16, a tropical storm moved inland about 150 miles east of De
    Ridder.  Over the next two days a ridge of high pressure  moved southeastward
    causing clearing skies, cooler temperatures, and a northwesterly flow of air.
    By the evening of October 18, the ridge had expanded and  covered much of the
    coastal area.  The atmosphere at Lake Charles was  well-mixed to approximately
    1.7 km (Figure 2).   Above that, a large-scale subsiding motion  associated with
    the ridge had begun to develop a stable layer.  An anticyclonic circulation
    pattern of a high pressure system began to develop on the morning of October
    19.  The subsidence continued, lowering the mixing height and inversion layer
    to 1.0 km on the morning of October 21.   Thereafter, the  subsidence diminished
    and wanner air returned with a southerly flow.  The stable layer began to  rise,
    but its intensity did not diminish until the afternoon of October 22.  By  the
    morning of October 23, the stable layer was effectively broken  and vertical
    mixing was no longer confined.  This  sequence of events is  typical of transient
    anticyclonic systems.
    
         During this period the maximum afternoon hourly ozone concentrations were
    generally high at urban and nonurban  locations until the  high pressure ridge or
    center passed eastward (Table 1).  Thereafter, the afternoon ozone concentrations
                                          200
    

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                                   20     21     22
    
                                      DATE, OCTOBER 1975
                                                     23     24
    Figure 2.   Time-altitude cross section of potential temperature at Lake Charles,
               Louisiana.  Temperature inversion is stippled.
                 TABLE 1.  MAXIMUM AFTERNOON  OZONE  CONCENTRATIONS  (yg/rrT)
    
    Location
    Corpus Christi
    Port 0' Connor
    Austin
    Houston
    Nederland
    DeRidder
    18
    112
    106
    128
    M*
    M
    109
    19
    224
    151
    154
    M
    M
    122
    20
    140
    133
    156
    136
    156
    256
    October
    21
    112
    98
    124
    138
    182
    210
    22
    88
    76
    108
    90
    120
    76
    23
    64
    22
    88
    84
    78
    22
    24
    50
    30
    62
    64
    60
    30
    
       ''Missing Data
    were perceptably  lower  as  the  onshore,  well-mixed flow developed and prevailed.
    An eastward migration of higher  ozone  concentrations  with  the pressure system
    is also apparent.
    
         The concentrations measured at  Corpus  Christi  and Port O'Connor on October
    19» at Austin on  October 19  and  20,  and at  DeRidder on October 20 and 21,  are
    among the  highest recorded at  those  locations  during  the study period.
    
                                          201
    

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    OCTOBER 19
    
         On the morning of October 19, a weak high pressure center developed within
    the ridge in southeastern Texas and western Louisiana.   The western half of
    a 2-day survey flight was initiated to investigate the gradient of ozone which
    might occur with the predominently northerly flow of air.   By mid-afternoon,
    the high pressure center was located to the south-southeast of Lake Charles,
    but the pressure gradient was weak.
    
         Air flow in the mixed layer had been northerly and was turning westerly
    during the day (Figure 3).  The predominance of a northerly flow even in a
    developing anticyclone indicates an unusual situation.   Anticyclonically-curved
    trajectories are expected with the transient high pressure system.   These tra-
    jectories had cyclonic curvature, suggesting that the high pressure system was
    being formed and had only recently begun to establish its  influence in the flow
    regime.
        Figure 3.
    Ozone concentrations along flight track
    maximum of hourly ozone concentrations
    trajectories with 12-hour positions (
    pressure isobars ( - ) for October  19, 1975,
     ),  the daily
    ),  air parcel
     ),  and surface
         The flight began at 1000 CDT, proceeded clockwise around the rectangular
    pattern at 650 m (^2000 ft MSL) before returning to DeRidder at 1700 CDT.   All
    measurements were made within the well-mixed boundary layer, capped by the in-
    version layer.
                                          202
    

    -------
         Ozone concentrations measured during the eastern half of the flight were
    of the order of 130 yg/m3, while in the western half, concentrations were most-
    ly at or above the NAAQS.  Cleraly, the western half of the flight shows an
    area-type distribution rather than a plume-type distribution of ozone developing
    from a localized source of precursors.
    
         The substantial decrease of ozone from the northwest to the northeast cor-
    ner of the flight does not seem related to hydrocarbon source areas along those
    trajectories.  The air arriving in the northwestern corner had a path roughly
    over the Oklahoma City area 24 to 36 hours before the aircraft reached this
    point.  The air arriving in the northeastern corner passed over the Tulsa,
    Oklahoma, area, also an oil refining area, 24 hours before.   On the southbound
    leg of the flight, the aircraft apparently passed through a narrow plume south-
    west of the Shreveport, Louisiana, area and measured ozone concentrations as
    high as 169 yg/m3 for a brief period.
    
         Upon return to DeRidder, the ozone concentrations and their gradients
    were quite similar to those measured upon departure 7 hours  previously.   This
    suggests that the ozone existed in a quasi-steady state in the afternoon bound-
    ary layer.   The higher ozone concentration of east Texas are not associated
    with specific ozone precursor source regions.   The urban-industrial regions
    make no discernable contribution to those concentrations.
    
    OCTOBER 20
    
         By the afternoon of October 20, the high  pressure center had moved to a
    position just north of Mobile, Alabama.  Central  pressures increased to 1023 mb
    as the circulation system developed.  A high pressure ridge  extended southeast-
    ward from the high center to the south  of the  flight area.  For the previous
    24 hours, southerly winds were reported at all  of the ground monitoring stations.
    Further away from the high pressure center more air movement had occurred at
    Austin and Houston than at DeRidder and Nederland.
    
         Of the ground stations, only DeRidder (256 yg/m3) showed ozone concentra-
    tions above NAAQS.  Surface trajectories showed that air arriving at DeRidder
    in the late afternoon had been in transit from the Nederland area for the past
    24 hours.  Concentrations measured at DeRidder were among the highest encountered.
    
         The eastern portion of the area survey blocks was flown at 650 m (^2000
    feet) counterclockwise along the path (Figure  4).   The subsidence inversion
    covered the Gulf Coastal plain from southern Texas to central Alabama.  Conse-
    quently, vertical motion probably was  restricted to 1.5 km (^5000 feet) or
    less but above flight level.   The area coverage was reduced  from the previous
    day for operational reasons.
    
         Ozone concentrations near 160 yg/m3 were  encountered on all legs of the
    flight and were persistent in the northern, western, and southern portions of
    the flight.   Again, eastern portions of the flight were lower than the other
    portions, but were higher by about 30 yg/m3 than on the previous day.   Concen-
    trations and concentration gradients over 4-hour intervals at DeRidder were
    continuous.
                                          203
    

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        Figure 4.  Ozone concentrations along flight track (	
                   maximum of hourly ozone concentrations ( (_} ),
                   trajectories with 12-hour positions (—&	),
                   pressure isobars (	) for October 20,  1975.
    ),  the daily
    air parcel
     and surface
         High ozone concentrations persisted during the period  of north  and westerly
    flow across areas of low emission densities.   The  influence of precursor emis-
    sion areas is not apparent.   Since flights remained below the subsidence inver-
    sion, downward transport of ozone into the boundary layer is unlikely.   The air
    parcels arriving in the northeastern corner of the flight suggests  an  increase
    of concentration with time.   Twenty-four hours previously the parcel was near
    the Arkansas-Louisiana border, roughly in the area where ozone concentrations
    on the order of 110 pg/m  were sampled^  At flight altitude 24 hours later,
    concentration on the order of 145 ug/m  were encountered.  Air parcels arriv-
    ing in the northwestern corner on this evening came from areas of east Texas
    where ozone concentrations were about equaj to the NAAQS.  Upon arrival, these
    concentrations increased to about 190 yg/m  , an increase of 30 yg/m .
    
         In the southwestern corner of the flight path, the trajectory  shows flow
    across Nederland to the sample point where it had  remained  nearly stagnant for
    about 12 hours.   Ozone concentrations at flight level  were  just below  the NAAQS
    but were the lowest measured during this part of the flight.
    
         The pattern of high ozone in the western part of the flight and lower in
    the eastern part persisted.   Concentrations were generally  higher throughout
    the flight.  The ground stations near the flight area indicate increasing ozone
    concentrations while Corpus  Christi  and Port O'Connor indicate a reduction in
    the maximum concentration as onshore flow returned there.
                                          204
    

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    OCTOBER 21
    
         On October 21, the high pressure center had proceeded further eastward
    leaving only a ridge line with a northeastward axis.  The air had begun to flow
    northward.  The mixing depth of Lake Charles rose from 1.2 km in the morning to
    1.45 km in the afternoon.   The potential temperature associated with the mixing
    depth, however, did not change, suggesting that overall ascent of the air was
    occurring.  Measurements of high ozone concentrations on the previous day at
    DeRidder, and the high concentrations already observed in the afternoon indi-
    cated that a flight was necessary.   The RTI aircraft left Lake Charles for
    Nederland then went 160 km south out over the Gulf of Mexico before returning
    to Lake Charles via Nederland and DeRidder, where a vertical profile was flown
    (Figure 5).
         Figure  5.  Ozone  concentrations along  flight  track  (.
    .),  the  daily
                   maximum of  hourly ozone  concentrations  ( {_}  ),  air  parcel
                   trajectories with 12-hour  positions  (	&	),  and surface
                   pressure  isobars  (	-)  for October 21,  1975.
    
         Ozone concentrations exceeded the NAAQS throughout the flight except at
    the southern tip  of the flight, where ozone briefly decreased by about 20 yg/m3.
    The over-water flight was made along the axis of the wind into Nederland out-
    bound at 100 m and returning at 425 m (^1400 feet).   Trajectories suggest that
    advection of air  having lower ozone concentrations into the Nederland area
    might have been expected within about 12 hours.   The ground level concentration
    in Nederland decreased over the next 12 hours;  but probably more in response
    to local nocturnal ozone destruction than in advection.  On the following day,
                                          205
    

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    the maximum ozone  concentration was 62 pg/m3  lower,  indicating  a  change  of air
    mass characteristics.
    
         Trajectories  also indicate that the air  reaching Nederlarid had  been carried
    out to sea, approximately 24 hours before  a reversal of wind  initiated a return
    flow into the Nederland area.  Though initially  it might  appear that the high
    ozone concentrations were associated with  air flow from the Gulf  of  Mexico, the
    trajectories analysis clearly shows that the  air is  only  returning after having
    passed over land-based sources of ozone and ozone precursors.
    
         In the vertical profile to approximatly  3 km at DeRidder (Figure 6),, ozone
    concentrations increased with altitude to  1.2 km.  Above  1.6  km,  ozone concen-
    trations decreased and remained constant,  thereafter, to  the  top  of  the  sound-
    ing.  The ambient  temperature decreased with  altitude to  1.6  km.  Over the next
    300 m, the temperature was isothermal and  the dewpoint temperature decreased by
    11.2°C.   During descent, ozone concentrations remained below  "110  yg/m3 above
    1.5 km.   In the next 300 m of descent, ozone  doubled to 216 ug/m3 and slowly
    decreased to 178 pg/m3 in the lowest 300 m of the air.  The aircraft tempera-
    tures agree closely with the late afternoon soundings taken at  Lake  Charles.
    On the return trip from DeRidder to Lake Charles, ozone concentrations also
    remained above the NAAQS between 300 and 600  m above the  ground.
                                  Temper a Lure , ( '(')
    
                              0    5    H)    1 r>    1'')
                                    I    I    I    I
                                              D Temp.
                                              O Ozone
                               I     I     1     I
                                                         10
                                                            01
                                                            T3
                                                            3
                              40    80   120  ^160   200   240
                                  Ozone,
    Figure 6.  Vertical profiles of ozone and temperature at DeRidder  at  1900 CDT
               October 21, 1975.
    
    
         On this day, trajectories arriving at Houston and Austin showed  a well-
    developed southerly flow, having been on the side of the high pressure system
                                          206
    

    -------
    for a longer time.  Afternoon concentrations in the Houston area were 137
    a fairly low value for that station, and concentrations at Austin had decreased
    to 124 pg/m3 from 159 ug/m3 on the previous day.
    
    OCTOBER 22
    
         By the afternoon of October 22, the influence of the high pressure ridge
    had weakened through the area.  The pressure gradient had increased and a
    strong onshore flow had developed through all levels of the atmosphere.  Ozone
    concentrations between 99 and 122 pg/m3 were measured during the EPA aircraft
    flight with no particular pattern to the concentrations measured (Figure 7).
    Ground level ozone concentrations at the four stations were comparable to those
    measured aloft indicating a relatively uniform distribution of ozone in the on-
    shore flow.
        Figure 7.   Ozone concentrations along flight track
    the daily
                                               ..,..._. _____ v       ,
                   maximum of hourly ozone concentrations ( \_/ ), air parcel
                   trajectories with 12-hour positions ( — & - ), and surface
                   pressure isobars  ( - ) for  October  22,  1975.
         The air parcel trajectories indicate a long fetch over water preceded by
    turning from a northeasterly flow into a southeasterly to southerly flow.   The
    ozone concentrations were slightly higher than background concentrations.   The
    turning of the trajectories from a northeastern into a southerly flow suggests
    that the air might have had an earlier origin over the Gulf Coast region.
                                          207
    

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    Mixing depth increased to about 1.8 km in the morning.   By afternoon the stable
    layer had risen to 2.2 km; but, the afternoon mixing depth reached only about
    1.8 km.  Warm air associated with the increased onshore flow left a relatively
    unstable column of air within the mixed layer.   The ventilation of the near
    coastal area had increased substantially and ozone concentrations decreased.
    
    OCTOBER 23, 24
    
         For the next two days, October 23 and 24,  strong onshore winds persisted
    exceeding 10 m/s through most of the first 2 km.   The lowest maximum ozone con-
    centrations reported during the measurement program occurred at Nederland and
    Houston.   The increased wind speeds reduced the local residence time of injec-
    ted ozone precursors, increased the turbulence  of the atmosphere giving better
    dispersion, and probably inhibited development  of the oxidant potential on the
    Texas Gulf Coast.
    
         Ozone concentrations between 68 and 93 ug/m3 were measured during an EPA
    flight on October 24 (Figure 8.   These values were consistent with concentra-
    tions found onshore at ground measurement stations.   The strong southerly flow
    at this time gave no indication of having had any recent history over any con-
    tinental  areas.
        Figure 8.   Ozone concentrations  along flight track (-
    -),  the  daily
                   	 — —...... —  _._..-, ...-,.._ „. — ^\~
                   maximum of hourly ozone concentrations ( \_/ ),  air parcel
                   trajectories with 12-hour positions (	£	), and surface
                   pressure isobars (	) for October  22,  1975.
                                         208
    

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                                     CONCLUSIONS
    
         The single episode of high, nonurban ozone clearly demonstrates that ozone
     concentrations exceed the NAAQS and persist for several days over a large
     (^50,000 mi2) area that has a low precursor emission and does not have an
     identifiable source region.  That area apparently expands with increased con-
     centrations and moves with the high pressure cell where vertical mixing is
     inhibited and horizontal transport is limited.
    
         The local changes of ozone concentrations in the northern Gulf Coast area
     are strongly affected by transient high pressure systems and the history of
     the arriving air.
    
         These findings are consistent with findings of other investigations that
     lead to the concept of a spent photochemical system developing in a slow-moving
     high pressure cell.  Therefore, in at least one case, the same concept applies
     to the northern Gulf Coast area.
                                  ACKNOWLEDGEMENTS
    
         This research was performed under Contract No. 68-02-2048 with the Office
    of Air Quality Planning and Standards, Environmental Protection Agency, Research
    Triangle Park, North Carolina.
    
    
                                      DISCLAMER
    
         The opinions expressed herein are those of the authors and are not neces-
    sarily those of the sponsoring agency.
    
    
                                     REFERENCES
    
    1.    Federal Register, National  Primary and Secondary Ambient Air Quality
         Standards, April 30, 1971.
    
    2.    Research Triangle Institute, Investigation of Ozone and Ozone Precursor
         Concentrations at Nonurban  Locations in the Eastern United States, Phase I,
         EPA-450/3-74-034, May 1974.
    
    3.    Stasiuk, W. N. and P. E. Coffey, Rural and Urban Ozone Relationships in
         New York State, JAPCA, 24,  564-568, 1974.
    
    4.    Research Triangle Institute.   Investigation of Rural Oxidant Levels as
         Related to Urban Hydrocarbon Control Strategies, EPA-450/3-74-035, March,
         1975.
    
    5.    Muller, P.  R., M.  H.  McCutchan, H.  P.  Milligan, Oxidant Air Pollution in
         the Central Valley,  Sierra  Nevada Foothills and Mineral King Valley of
         California, Atmos.  Environ.,  6:603-633, 1972.
                                          209
    

    -------
    6.   Personal Communication from Dr. E. L. Meyer, OAQPS, Environmental Protec-
         tion Agency.
    
    7.   Texas Air Control Board, Yellow Pine Study, 1975.
    
    8.   Johnson, D.  J., Texas Ambient Air Quality Continuous Monitoring Network,
         Texas Air Control Board, Air Quality Evaluation Division, 1973.
    
    9.   Wallis, R.,  J. H. Price, G.  K.  Tannahill, and J. P. Grise, Ozone Concen-
         trations in  Rural and Industrial-Urban Cities in Texas, Texas Air Control
         Board, Air Quality Evaluation Division, 1975.
                                          210
    

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                                                                               5-5
         OZONE AND  HYDROCARBON  MEASUREMENTS  IN  RECENT  OXIDANT  TRANSPORT STUDIES
    
                                   W. A.  Lonneman*
    ABSTRACT
    
          In Ae.ce.nt  yeou,  ^-ieJid Atudie.* weAe.  undertaken to  investigate, ozone- and
    ozone.-pAe.cuAt,oA tnanApoAt.  In thus. AtudieA  &l&> weAe colle.cte.d and ana-
    lyzed &OA kydAoc.aA.bon  concentration.   The. analytical AeAultA  indicate, tkat
    AuAal ambie.nt aiA dowwiind o& uAban centeAA  con&iAtA laAgel.y  ofa  diluted uAban
    mix.,  with lo&A  0& the.  moAe. Ae.acti.ve. hydAocaAbon  components.   HydAocaAbon and
    nitAogen oxA.de.* analyses at Wilmington, Ohi.o, indicate,  that high ozone. concen-
    tAation* OAC pAobably  due. to tAantpoAt pAocei>i>ei>  and aAe not  tke. AeAu£t o&
    local photochemical  ^oAmoution.
    
    
                                     INTRODUCTION
    
          In recent years field studies were conducted to investigate the extent of
    ozone  (03) and  03-precursor transport  downwind of urban areas.   These studies
    were  designed to provide better  assessment of the oxidant transport problem
    and to furnish  a data  base for planning future oxidant  control strategies.
    The study sites were located near large industrial  and  highly populated areas
    since  the anthropogenic origin of high  levels of  tropospheric 03 is expected
    to be  the most  significant and the only controllable source.
    
          In 1974, EPA and  EPA contractors  conducted  a study in Ohio.   A network of
    ground sampling sites  for 03 was established, principally in  Ohio but also in
    neighboring states.  Some of these sites,  mainly  those  operated  by RTI, were
    equipped with other  instrumentation for more  detailed pollutant  analysis.
    These  other activities included  the collection of bag samples for subsequent
    analyses of detailed hydrocarbons (HC)  by  the Environmental Sciences Research
    Laboratory (ESRL) mobile labs.   An aircraft was  used to follow urban plumes
    downwind of several metropolitan areas.   In addition to 03 and temperature
    measurements, the aircraft collected Tedlar bag  samples for detailed HC anal-
    ysis.   Clinton County  airport, an abandoned U. S.  Air Force base,  near Wil-
    mington, Ohio, was used as the base station for these studies.   The airport
    had very little air traffic and was ideally situated to sample urban plumes
    originating from nearby Dayton, Cincinnati, and Columbus.  The EPA-ESRL
    mobile laboratory which was located at  this site,  measured continuous diurnal
    profiles of several pollutants.  In addition, gas  chromatographic analysis
    of the collected air sample bags was performed for  detailed HC composition.
    *U.S. Environmental Protection Agency,  Research Triangle  Park,  North  Carolina.
    
    
                                         211
    

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          In  1975,  a similar field  study was  conducted  in  the  northeast.   This
     study was  undertaken  in order to  explain  the  high  nighttime  03  concentrations
     observed at several  sampling sites throughout  EPA  Region  I.   The  northeast
     area, including New  York and New Jersey, represents the most  highly  populated
     and industrialized section  of  the  United States.   Needless  to say, this  area
     provides a  critical  testing ground for transport phenomena  arid constitutes  the
     extreme  test of present oxidant control  strategy.   The sampling  network  in-
     cluded several  03 sampling  sites located throughout EPA Region I.  EPA con-
     tractors installed and  operated additional  sampling sites,  at Battelle facil-
     ities located  in Simsbury,  Connecticut,  and Washington State  University
     located  in  Groton, Connecticut.  The  ESRL-EPA  laboratory  was  located south  of
     Boston,  Massachusetts.   In  addition to these ground station laboratories,
     three aircraft  were  used to provide more extensive  coverage of 03 and HC
     precursor concentration,  including the transport of urban plumes  over the
     Atlantic.
    
          Detailed  reports  of the 1974  study  are presently available  as EPA reports
     (1,  2).   Reports of  the 1975 study should  be completed in the near future.
     The  purpose of  this  paper is to present  some results  from these  studies.
    
    
                                    EXPERIMENTAL
    
          The instruments employed  in the  ESRL  mobile laboratory are  listed in
     Table I.  Calibration procedures were used  frequently to ensure  the  quality of
     the  data collected.  Also for  quality control, the  calibration of the 03
     monitors was checked on a day-to-day  basis, often  by  an audit team.
    
                     TABLE 1.  MOBILE LABORATORY INSTRUMENT ARRAY
      Pollutant/detection objective
          Instrument
    Nitrogen oxides
    Total hydrocarbon, methane,
     carbon monoxide
    Total sulfur
    Ozone
    PAN
    Freon-11, carbon tetrachloride
    Visibility
    UV-Visible radiation
    Wind speed and direction
    Temperature and relative humidity
    TECO 14B
    Beckman 6800
    
    Meloy SA-120
    Bendix model 8000
    G.C.-Electron capture
    G.C.-Electron capture
    MRI-Integrating Nepholometer
    Eppley radiometer
    Bendix Aerovane system
    Hydrothermograph
         The  gas chromatographic procedures for detailed HC analysis are published
    elsewhere  (3).  A modification of the published cryogenic trapping  procedure
    was used  to concentrate larger air volumes and is graphically illustrated  in
    Figure 1.
                                         212
    

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     VALVE OPERATION
                         VALVE NORMAL
                   	VALVE ENERGIZED
                                              AIR SAMPLE IN
                                                                    VALVE B
       GCCOLUMN
                              TRAP
                                                                2.5 LITER
                                                                 TANK
                                                                       WALLACE-TIERNAN
                                                                        PRESSURE GUAGE
                              Figure 1.  Trapping system.
    
    
         For HC trapping we used the dual valve  system  illustrated  in  Figure 1.
    The vacuum gauge is a 0-200 torr Wallace-Tiernan  gauge.   Valve  A  is  connected
    to a high-speed rotary vacuum pump and  is opened  to evacuate  the  2.5-liter
    tank to 10-torr pressure  (about a  30-second  operation).   At  this  point,  valve
    A is closed.  A bag sample is connected  to port No.  1  of  valve  V^   The  trap
    is immersed in liquid 02.  Valve B is opened, and sample  from the  bag  is
    pulled through the system at a rate of  about 150  cm3/min.  When the  pressure
    setting on the vacuum gauge reaches 20  torrs, valve VT  is  energized, routing
    the air sample into the trap.  Samples  are collected over a  pressure differ-
    ential  of 20-170 torrs.   This calculates to  be (150/750)  (2500  C)  or about 500
    C of air sample.  Therefore, when  the pressure on the  gauge  reaches  170  torrs,
    valve MI is deenergized.  To inject the  sample, the cyrogen  is  removed,  and
    valve V2 is energized.  As illustrated  in Figure  1,  the trapped contents are
    front flushed onto the column; however,  the  trap  can be easily  modified  to
    back flush the trapped contents onto the G.C. column.
    
    
                               RESULTS AND  DISCUSSION
    
         The location in Wilmington, Ohio,  proposed to  be  an  ideal  rural sampling
    site, since it is surrounded by three major  metropolitan  areas.   The site is
    downwind of a major city regardless of wind  direction.  The  ground-level HC
    concentration of Wilmington was determined by collecting  30-minute-to-one-hour
    integrated bag samples during morning,  afternoon, and  evening periods.   On
    occasion, 24-hour diurnal studies were  conducted  for a  more  complete investi-
    gation of HC compositional and concentration  variations.   This  task  involved
    the use of an automated bag sampler to  collect 12 2-hour  integrated  samples.
                                         213
    

    -------
         A comparison of HC between urban and downwind rural areas involves the
    use of frequency plots of sample concentration versus the number of sample
    observations.  Unfortunately, during these studies, ground-level urban  samples
    were not collected in Cincinnati, Dayton, or Columbus; however, the HC  concen-
    tration at these sites is expected to be similar to other urban sites sampled
    in previous studies.   Frequency plots for Wilmington and for several urban
    areas previously studied are given in Figure 2.
        80
        70
        60
      a.
    
      <
      C/3
    50
      O 40
      I-
    
      o 30
      oc
      tu
      a.
        20
        10
         0 50  I50
                                                                      5100
    6100
                            600    900   1200   1500    1800   2100   3100   4100
                              SUM OF NON METHANE HYDROCARBON, ppb C
    Figure 2.   Distribution of the sum of nonmethane hydrocarbons  at  various  sampling
               sites during the 600-900 a.m. time period.
          If plots were available for these Ohio cities,  they would probably  be
     similar to that shown for the  St. Louis SLU profile,  since the size of the  St.
     Louis metropolitan area  is  comparable  to  these Ohio  cities.   The profiles  for
     Wilmington and St. Louis SLU are similar  except  for an approximate 5-6 fold
     dilution.  A similar dilution  factor may  be observed  by comparing average
     acetylene concentration  between the two sampling  sites.
    
          The percentage value given in parenthesis in  Figure 2 for each sampling
     site represents an estimate of total nonmethane HC as  vehicular  tailpipe emis-
     sions.  This estimation  was established from an average total nonmethane
     hydrocarbon/acetylene (TNMHC/C2H2) factor of 15.5, determined from previous
     tunnel or roadway samples collected in New York,  St.  Louis,  Denver, and
     Boston.  The value of 15.5 was calculated by averaging published factors of
     13.9 for New York tunnels (3)  and 15.0 for St. Louis  roadways  (4), with
     unpublished values of 16.0  for Denver  roadways and  17.0 for  ESostori tunnel
     samples.  The percentage calculation involved  the  ratio of the estimated
     vehicular emissions (average C2H2 X 15.5) to the  average of the  observed TNMHC.
     The difference between the  percentage  of  vehicular emission  and  100 represents
     HC from other urban HC sources, such as gasoline  evaporative, spillage emis-
     sion and industrial contribution.
                                         214
    

    -------
         No new or unidentified  HC  peaks,  except those resulting from bag out-
    gassing, were observed on  our G.C.  systems  during the analysis of bag samples
    collected during the study.  Naturally emitted  HC, such as the Cio terpenes,
    are resolved on our G.C. systems;  however,  none of these compounds were ever
    observed, at least at the  sensitivity  of  our instruments (1  ppbC).  The frequency
    distribution plots for these sampling  sites  were established from as few as 25
    sample points and may not  be exactly representative;  however,  a large sample
    size would probably not significantly  change the dimensions  of these curves.
    
         The analysis of bag samples collected  at McConnelsville (another sampling
    site operated by RTI during  the 1974 Midwest study,  located  100 miles east and
    somewhat north of Wilmington) resulted in a  distribution of  TNMHC similar to
    that observed at Wilmington.  Typically,  the average  TNMHC concentrations were
    higher during the morning  hours than during  the late  afternoon sampling
    periods. These results are given in Figure  3.   This  dilution effect between
    morning and afternoon samples was  observed  in every  urban area previously
    studied and is likely to be  the result of improved vertical  mixing resulting
    from surface heating during  afternoon  hours.
      30
      25
                       WILMINGTON.OHIO
      20
    c/3
    LU
    0.
    
    <
      15
    cc
    UJ
    CO
    5
    
    z
      10
                                                                MORNING SAMPLES
                                                                    700-900
    
                                                                EVENING SAMPLES
                                                                   1700-1900
                                                       McCONNELSVILLE.OHIO
                         100     200     300             0      100     200
                          TOTAL NON METHANE HYDROCARBON CONCFNTRATION ppbC
    300
      Figure 3.   Sum of nonmethane hydrocarbon  versus  number of samples for two
                 ground sites used in the  1974  Midwest Oxidant Transport Study.
                                         215
    

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         The composition of HC in samples collected at Wilmington and RcConnels-
    ville, as well as at other ground sites, and in aircraft samples collected
    downwind of urban areas generally indicated reduced olevin and aromatic con-
    tent.  Figure 4 illustrates this for total olefin content for a diurnal study
    of the Wilmington site on July 18, 1974.  The dashed line in the figure repre-
    sents the average olefin content of the TNMHC concentration for 42 samples of
    less than 10 ppbC C2H2 concentration observed at St. Louis, Denver, and New
    York sampling sites. At each sample period, the sample bag collected at
    Wilmington during the diurnal study showed lower olefin content.  The graph
    also illustrates reduced olefinic content during afternoon, undoubtedly the
    result of photochemical activity.
    
         A different illustration of olefin loss is shown in Figure 5.  In this
    figure, the estimated percent of olefin reacted was plotted, versus time.   The
    percent of olefin reacted was determined by ratioing the observed sum of
    olefin concentration in the sample to the estimated original olefin concen-
    tration.   The estimated original olefin concentration was determined by a cal-
    culation similar to one described earlier for vehicular TNMHC that uses C2H2
    concentration and an averaged olefin/C2H2 factor of 3.4 obtained from tunnel
    and roadway samples.  This calculation indicates that as much as 70 percent of
    the original olefin concentration has reacted by the late afternoon.
    
         Similar observations, differing in magnitude, were made for other diurnal
    studies conducted at Wilmington.  The results shown in Figures 2, 4, and 5
    suggest that the ambient air sampled in Wilmington was a diluted urban HC mix,
    with associated photochemical loss of the more reactive compounds during the
    transport process.
    
         It was stated earlier that low araomatic content of the TNMHC was also
    observed in Wilmington samples.  The G.C. elution of these aromatic compounds
    was interfered with by unknown peaks later identified as outgassing compon-
    ents from Tedlar bag surfaces.  These interfering peaks present serious
    problems for the accurate measurement of aromatic content and is an area we
    are presently investigating in our laboratories by evaluating alternate air
    sample containers.  These unknown peaks were not included in any of the TNMHC
    summations.  Acetaldehyde and acetone also were peaks identified as outgassing
    from Tedlar bag surfaces.  It is likely that both acetone and acetaldehyde are
    both components of these rural ambient atmospheres; however, quantitative
    evaluation of these ambient levels is impossible because of this inconsistant
    outgassing contribution.
    
         Ozone concentrations at Wilmington often exceeded the National Air Quality
    Standard of 80 ppb during the late afternoon and evening hours.  The late
    evening levels of ozone suggests transport; however, th,e possibility that
    morning levels of TNMHC and nitrogen oxices (NOX) at Wilmington are responsi-
    ble for afternoon 03 concentrations was investigated.  Figure 6 shows a plot
    of morning concentrations of TNMHC and NOX.  The solid line in the figure
    represents the 0.08 ppm 03 isopleth, determined by computer simulation of an
    atmospheric model developed by Dodge (5).  The model is based on a mixture of
    n-butane-propylene-NOx.  The 0.08 ppm isopleth was determined from the worst
    possible case of limited vertical mixing and no horizontal transport.
                                         216
    

    -------
     QC
    
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     <
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    20
    
    
    
    18
    
    
    
    16
    
    
    
    14
    
    
    
    12
    
    
    
    10
    
    
    
     8
    
    
    
     6
    
    
    
     4
    
    
     2
           —	URBAN AVERAGE FOR 42 SAMPLES AT 10 ppb ACETYLENE OR LESS	—
    0000    0200    0400    0600    0800    1000    1200    1400    1600
    
                                          TIME OF DAY
                                                                      1800
    2000   2200    2400
     Figure 4.   Diurnal  variation of average olefinic fraction of total  nonmethane
                 hydrocarbon, Wilmington,  Ohio,  July 18,  1974.
     a
     UJ
     o
     4
          0000    0200    0400   0600    0800   1000    1200    1400    1600    1800   2000    2200   2400
    
                                               TIME OF DAY
    
    
    Figure  5.   Diurnal variation of  the fraction of  olefins  reacted, Wilmington,
    
                Ohio,  July  18,  1974.
                                             217
    

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       30
    
    
       28
    
    
       26
    
    
       24
    
    
       22
    
    
       20
    
    .Q
    g  18
     x
    
    i  16
    
    
       14
    
    
       12
    
    
       10
    
    
       8
    
    
       6
    
    
       4
               20      40      60      80     100     120
                                         1 NMHC, ppb
    140
           160
                                                                          180
                                                                                 200
       Figure  6.   Wilmington,  Ohio,  1974 sum of nonmethane hydrocarbon versus
                   NOX   (600-900 a.m.).
    
    
         Of the 16 data pairs available  for  the month  of August, only two pairs
    fell  on the right-hand side of the 0.08  ppm 03  isopleths,  meaning that these
    HC and NOX levels were capable of producing 03  at  or above 0.08 ppm.   Ozone
    maximums observed on these  days are  shown  in  Table 2.
    
         TABLE 2.   OZONE MAXIMUMS FOR AUGUST,  1974,  DAYS WHERE MORNING NMHC
                AND NOX CONCENTRATIONS ARE KNOWN  IN  WILMINGTON,  OHIO-
    DATE
    5
    6
    8
    X 9
    10
    14
    16
    OZONE MAXIMUM, ppb
    63
    66
    63
    73
    70
    77
    85
    DATE
    19
    20
    21
    24
    25
    27
    X28
    OXONE MAXIMUM, ppb
    69
    93
    90
    94
    93
    96
    45
                                         218
    

    -------
         The dates of the two data points falling on the right-hand side of the
    0.08 ppm isopleth were August 9 and 28.  On these two days, the 03 standard
    was not exceeded.  On 7 of the other 14 days, however,  the Os  standard was
    either approached or exceeded.  These results suggest that local HC and NOX
    levels do not account for all local 03 observed and that a considerable
    portion of this 03 is transported from upwind sources.
    
         Other indications of the urban influence on downwind 03 air quality  are
    shown in Figures 7 and 8.   These figures were constructed from aircraft
    flights upwind and downwind of Columbus.  Figure 8 represents a square wave
    plume flight by RTI downwind of Columbus on July 21, 1974.  The acetylene
    profile was established from bag samples collected along perpendicular paths
    to the urban plume.  The ozone profile was drawn by averaging continuous 03
    concentrations measured along these paths.  This figure, demonstrates, in
    effect, a net 15 to 20 yg/m3 increase in 03 as far as 40 miles downwind of
    Columbus.
    
         Figure 8 represents a double-box type pattern as flown on July 9, 1974,
    during very stable atmospheric conditions.  The solid line was constructed
    from C2H2  measurements of bag samples collected parallel to wind direction.
    The dotted line represents C2H2 profile constructed from C2H2 measurements of
    bag samples collected at locations perpendicular to the wind direction. On
    this day,  the downwind urban effect on 03 air quality is even more signi-
    ficant.
    
         Results from the 1975 northeast study also show the effect of transported
    03 and 03  precursors.   The purpose of this study was not to investigate the
    transport of 03 from urban to rural sites, but to study the transport of 03
    and its precursors from one urban area into other urban areas.   In general,
    the study was concerned with the implementation of an effective transportation
    control plan designed to lower the 03 concentration when the 03 levels were
    already high upwind of the urban areas.   A complete analysis of the data is
    not presently available.   The ESRL mobile laboratory was located on Chicka-
    tawbut Hill, 10 miles south of Boston.   Typical profiles of 03 and other
    pollutants at the site are shown in Figure 9.   Ozone transport is evident by
    the observation of increasingly high 03 concentrations during nighttime hours.
    The evidence for urban origin of this 03 is a corresponding increase in the
    concentrations of C2H2 and peroxyacetylnitrate (PAN). Similar results were
    observed on other days.
    
         Aircraft measurements of 03 and precursor concentrations were made over
    the eastern coastal regions of Massachusetts.   Often, an urban plume contain-
    ing high levels of 03 was  followed hundreds of miles out over the Atlantic
    Ocean.   In an effort to investigate urban tracer relationships, C2H2 and
    corresponding 03 data were assembled for comparison.   On the basis of an
    analysis of samples collected over the Atlantic during late afternoons and
    evenings,  there appeared to be a linear relationship between these two pollut-
    ants.   Linear regression equations were determined for the data of three
    flights and for all the data points collected during these flights.  The
    results are recorded in Table 3.
                                         219
    

    -------
    
    
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    , 	 ^. 	
    •' ^"-->. OZONE
    — ., 	 —
    ~" T NET INCREASE 15-20 M9/m3
    OZONE STANDARD
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    200
    ISOn
    a.
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    50
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                  10
                         20
                                 30      40      50
                                    DISTANCE, miles	»
    Figure  7.   Air flight of 7/21/74, traverse  pattern over Columbus,  Ohio
       Figure  8.   Air flight of 7/9/74, box  pattern over Columbus, Ohio.
                                        220
    

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    120
    
    110
    
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     60
    
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     10
                                                                JULY 18  JULY 19
    
                                                     WIND SPEED:     7 mph   11 mph
    
                                                     WIND DIRECTION:  240°    240°
    S^«t»y     ~
         —t—.-^..    	
                                                                             1.5
    
                                                                             1.0
    
                                                                             0.5
                                                                                  o
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                                                                                  4
                                                                                  CC
    
                                                                                  e
         0100    0600      1200
                     JULY 18, 1975
                              1800      2400      0600      1200      1800
    
                                   TIME OF DAY          JULY 19, 1975
                                                                            2400
          Figure 9.  Diurnal  hourly  concentrations of Oa, CO, acetylene,  and
                     visibility,  Chikatawbut, July 18 and 19, 1975.
    
    TABLE 3.  CORRELATION  OF OZONE VERSUS ACETYLENE  OFR  EPA-LV  AIRCRAFT SAMPLES
                               BOSTON OXIDANT STUDY,  1975
    
    Sample
    Period
    
    August 14
    August 20
    August 27
    All samples
    Observations
    
    
    7
    7
    6
    66
    P
    
    
    0.91
    0.95
    0.94
    0.85
    Slope
    
    
    19.6
    15.9
    14.6
    19.4
    Intercept
    
    
    46.1
    38.1
    32.0
    31.0
    Os Range
    ppb
    
    53-186
    40-69
    58-99
    29-186
    C2H2
    Range,
    ppbC
    1.0-7.1
    0.3-1.5
    1.6-2.6
    0.2-7.1
         The correlation  coefficients between 03 and  C2H2  for these data sets are
    quite high, suggesting  a significant relationship.   The  comparison of slope
    and intercept for  the data sets is quite interesting.  A bold interpretation
    of these results would  suggest that the variation  of the slope values for
    these data sets may be  the result of variable chemical physical and chemical
    parameters such as initial concentration of HC and NOX,  HC/NOX ratios, ambient
    temperature, and sunlight intensity.
    
         On the other  hand,  the intercept could represent  background 03 when the
    C2H2 concentration is zero; or, in other words, the vehicular contribution is
    absent.  The 03 concentration represented by the  intercept could be due to
    natural and industrial  sources of HC and NOX.  Caution must be exercised when
                                          221
    

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    making such interpretation.  However, the values for the intercepts interest-
    ingly compare to background measurements of 30 ppb of ozone made over Maine on
    August 28, 1976.
    
         In recent months, we have commenced a study of natural HC emissions at a
    forested area west of Durham, North Carolina.   The vegetation at the site con-
    sists primarily of loblolly pine and has been used to perform micrometeoro-
    logical measurements to estimate mass and energy balance.  The purpose of our
    sampling program is to determine the composition of natural HC emissions.
    
         In preliminary studies to determine detailed HC composition, 03 bag
    samples were collected at various vertical heights below, within, and above
    the tree canopy.  Additional samples were collected at ground level, upwind
    and downwind of this forested area.  In some bag samples a~ and g-pinene at
    times myrcene and A-carene were observed, most frequently in samples collected
    within or below the tree canopy.   In these studies, a maximum of 87 ppbC a-
    pinene, 19 ppbC 3-pinene, 3.3 myrcene, and 4.8 ppbC A-carene were observed at
    ground level, suggesting that perhaps pine needle litter was the principal
    source..  Concurrent 03 measurements indicated a 40 ppb 03 level  above the tree
    canopy and 30 ppb 03 within or below the canopy.   The reduced level of 03 in
    the canopy suggests 03 removal by either surface deposition or terpene-
    ozonolysis mechanisms. Samples collected upwind and downwind of the forested
    area showed no difference in 03 concentration and only trace levels of terpene
    compounds in downwind samples.  These studies also suggested that terpene
    emissions and ambient temperature were directly related.
    
         More recently, simultaneous  diurnal studies  for HC and 03 were performed
    at two vertical  heights, one within and one above the tree canopy.   The
    results of these studies are not presently available.   Ultimately,  we plan to
    determine vertical  fluxes of these terpene hydrocarbons in an effort to evalu-
    ate emission strength.
    
    
                                     CONCLUSIONS
    
         Field studies  conducted in recent years to investigate rural 03 have
    indicated that the  high levels of 03 are of anthrophogenic origin,  transported
    from upwind sources.   The HC composition at rural Wilmington, Ohio, was simi-
    lar to the HC composition at urban sampling sites.   In fact the HC  sampled in
    these rural areas appeared to be  a diluted urban  HC mix depleted to some
    extent of the reactive olefinic hydrocarbons.   This loss of olefinic HC was
    probably the result of photochemical degradation.
    
         Acetylene and  corresponding  03 measurements  showed significant correla-
    tion in aircraft sampling programs of urban plumes over ocean bodies during
    the 1975 Northeast  Study.
    
    
                                     REFERENCES
    
     1.  Investigation  of Rural Oxidant Levels as  Related to Urban Hydrocarbon
         Control  Strategies, U.  S. Environmental Protection Agency, Publication
         EPA-450/3-75-036, 1975.
    
                                         222
    

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    2.  Transport of Oxidant Beyond Urban Areas, U. S.  Environmental  Protection
        Agency, Publication EPA-600/3-76-018, 1976.
    
    3.  Lonneman, W. A., S. L.  Kopczynski, P. E. Dorley, and  F.  D. Sutterfield,
        Environ. Sci. Technol.  8, 229, 1974.
    
    4.  Kopczynski, S.  L. , W.  A.  Lonneman, T. Winfield, and R. Seila, J.  Air  Poll
        Control Assoc., 25, 255 (1975).
    
    5.  Dodge, M.   Combined Use of Modeling Techniques  and Smog  Chamber  Data  to
        Derive Ozone-Precursors Relationships, these proceedings.
                                        223
    

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               SESSION 6
      OZONE/OX I DANT TRANSPORT - I
                 A. P. Altshuller
    Environmental Protection Agency
                  225
    

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                                                                                  6-1
                    TRANSPORT OF OZONE BY UPPER-LEVEL  LAND BREEZE -
               AN EXAMPLE OF A CITY'S POLLUTED WAKE  UPWIND FROM ITS CENTER
    
                           E. K. Kauper and B. L.  Niemann*
    
     ABSTRACT
                   Of) alficAa^t i>oundlnQ& avid tsiaveAAeA,  meoAuSLtng ozone, and the. at-
              tempeAatuAe. A-tAuctuAe. between the. C-oaAtai.  po>itA.ont> ofa Lot> knaeJLeA and
     (/e.ntuAa County to the. nonthwut weAe. made. duA-ing the. AummeA oft 7975.  W-tmii
     alofit weAe. .t>Ajnultane.ouAl.y obtained, and the. movemznt o& uppeA te.\)eJL ozone.
     layeAA weAe. de.ducte.d by mean-5 o{, tAaje.c£oAy anaiyt>eA ubtng thAe.e.-houAty A&ie.am-
     Line. chasitA.   The. uppeA £e.veJL {^tow, Ln the. JLayeAA containing the. ozone, maxima,
     4.ndie,ate,d that the. ozone, wcw brought oveJt the.  Ve.ntuA.a County coaAt&ne. fiiom
     the. Loi> Ange£e6 Bat>in,  euen though AuA^ace. wind SLe.posit£,  AJ>,  Mould t>how that no Lo& Angetu  c.onne.c.*tion WOA tnvolve.d.
    
                                      INTRODUCTION
    
           Questions  regarding  the origin  of  high  ozone  values  in areas  of southern
     California assumed to  be upwind  of  the  Los  Angeles  Metropolitan area  have  long
    , been asked (1).  Answere,  using  surface  wind  flow maps, indicate that such occur-
     rences either were due to  local  sources  in  the Ventura County area  northwest  of
     Los Angeles, or  came from  off the  Pacific  Ocean  (2).  A second path,  that
     through the San  Franando Valley  to  the  interior  valleys of Ventura  County, has
     also been postulated.
    
          Recently,  more detailed analyses of ozone episode cases in Ventura County
     have suggested  the importance of ozone transport  aloft and subsequent fumiga-
     tion to the ground as a causative mechanism (3).  However, these analyses have
     been seriously  hampered by lack of wind, temperature and ozone profiles in
     Ventura County  and air mass trajectories of high  ozone concentration parcels
     aloft leaving  the Los Angeles area.
    
           To  document the three-dimensional  situation off the  southern California
     coast,  the  California Air Resources Board funded a  study of the over-water
     transport  of ozone in 1975  from which the data used  for this paper were
     derived (4).
                        GEOGRAPHICAL AND METEOROLOGICAL  SETTING
    
          The  project area of concern involved the  coastal portion of southern Cali-
     fornia, between West Los Angeles - Santa Monica and the Ventura County coast-
     line to the north and west of the Los Angeles  Basin.
     *E. K. Kauper, Metro Monitoring  Services,  Covina, California.
      B. L. Niemann, Teknekron  Inc.,  Berkeley,  California.
                                           227
    

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         Flights were conducted during the summer of 1975 under what would be con-
     sidered typical summer conditions.  A marine layer, usually capped by a stratus
     cloud deck, was present during all operations.   The height of the inversion and
     its  strength varied during the study, with high inversions the rule during the
     June 2-4 study period, moderately low inversions during the period of July 10-11,
     followed by a period with a deepening marine layer, July 14-18.
    
                                      EQUIPMENT
         The airborne sampling was conducted from a Piper PA28-140, with the tem-
    perature and ozone sampling intake located on the left side of the fuselage,
    away from the engine
    exhaust outlet.
         The sampling line, of 0.6 cm teflon, was kept short (1.2 m) to reduce the
    possibility of ozone loss due to wall effects.  The ozone monitor was a Dasibi
    1003AH, factory modified to provide reading update every 13 seconds, recorded
    on a Hewlett-Packard 680M strip chart recorder.
    
         The ozone sensor, together with the recording system,  was calibrated by
    the California Air Resources Board at its El Monte, California, facility.
    
         Winds aloft were measured by means of optical tracking, using theodolites,
    of 30 gram pilot balloons.   The balloons were inflated to a standard free-lift
    condition which gave a rate of rise averaging 600 ft/min (3 mps) from the sur-
    face to 5000 ft (1.5 km).
    
                                      OPERATIONS
    
         The aircraft followed the flight path shown in Figure  1, starting from
    Santa Monica Airport (SMO), climbing to 5000 ft  (1525 m) and then descending
    for a touch-and-go landing at Ventura County Airport, Oxnard (OXR).  The return
    trip to SMO was generally along the coast during good weather (VFR conditions);
    but when cloud cover required instrument flight, the path was along an inland
    route shown in Figure 1.
    
         These flights were performed every three hours during  the day, with one
    flight near midnight to monitor the nighttime conditions.
    
         An aircraft observer recorded temperature and altitude information during
    the climbing and descending phases of the flights, with ozone being recorded
    continuously throughout the flight.
    
         With the Dasibi instrument obtaining a reading every 13 seconds, the sam-
    pling rate in horizontal flight, corresponding to the aircraft's cruising
    speed of 120 mph, was one sample every 0.4 miles (0.6 km).   During climb and
    descent, the rate of altitude change was 300 feet per minute, giving an ozone
    reading at 65 ft (20 m) intervals.
    
         Winds aloft were measured at three locations, Los Angeles International
    Airport (LAX), Point Dume (DUM), and OXR, and were scheduled on the same time
    basis as the aircraft flights.
                                         228
    

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                       229
    

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                                       RESULTS
    
         The data obtained by the aircraft and the wind observation stations were
    plotted as vertical soundings, and placed on vertical  cross-sections  covering
    the route from Santa Monica to Oxnard.  Figure 2 presents soundings of tempera-
    ture and ozone at these two locations for a specific time.   There is some ques-
    tion regarding the ozone values as recorded between 1000 and 2000 ft over SMO;
    but the other data points appear to be valid.
    
         Cross sectional analysis of these data indicates  that layers of ozone-rich
    air exist aloft over the coastal route between the Los Angeles Basin and the
    Ventura County area.  These layers are mainly found just above the base of the
    main subsidence inversion, but also can be located within the stable layer of
    the inversion itself, as seen in Figure 2.
    
         Trajectory analysis was carried out, using the winds aloft data from the
    pilot balloon network, plus winds aloft data taken by  the Navy at Point Mugu
    (NTD).   Wind flow streamline maps for the various altitudes with the maximum
    ozone were used in this work.  Figure 3 represents the trajectory of the air
    parcel  found over Oxnard with a concentration of 0.45  ppm at 900 ft. (0.3 km)
    when the ozone maximum over Santa Monica was 0.31 ppm, at a similar height.
    
         For comparison, the trajectory taken by a surface air parcel arriving at
    OXR at the same time as the upper air parcel is also shown in Figure 3.  Its
    track into the coast at OXR from the west is characteristic of trajectories
    derived from the surface wind reports.
    
         To provide some sort of climatology of upper air  flow, trajectories of air
    containing the maximum ozone aloft over Oxnard were constructed daily for the
    1200 PDT time period.  Nine such trajectories were prepared, five of which
    followed a track along the coast between Santa Monica  Bay and the Ventura
    coastline, similar to that shown in Figure 3.   Three others were located along
    a San Fernando Valley - Thousand Oaks path, while only one could not be traced
    into the Los Angeles source region.
    
         Inspection of the conditions associated with the  individual trajectories
    indicates that the over-water trajectory from Los Angeles is more likely when
    the marine layer is shallow.  The trajectories which indicated movement into
    Ventura County from the San Fernando Valley were associated with the deeper
    marine layer conditions.
    
         A similar climatological approach to the ozone concentrations aloft,
    averaged for the project period, is shown in Figure 4.  The ozone values in-
    crease aloft during the day over both SMO and OXR, but stay near 0.10 ppm
    during the night,  rather than decreasing to near zero  as is the case for sur-
    face measurements.
    
         The most frequent winds aloft are shown in Figure 5, again for the project
    period.  It is evident that the easterly winds dominate the flow, especially at
    levels aloft above the surface.  For example at 1200 PDT, while the westerly
    sea breeze is blowing in the layer between the surface and 1000 ft at LAX and
    OXR, the flow aloft is easterly.  At Point Dume (DUM), midway between the Los
    
    
                                         230
    

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         CO
             Q    .2      .4    .6    .8
    70             BO
            TEMP ("F)
    90
                                        OXR
    Figure 2a.  Temperature  and  ozone  sounding (OXR), July 10,  1975,  1500  PDT.
                                         231
    

    -------
            30
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               0     .2     -4     .6    .8    1.0  70
    
                          03 (PPM)
    
    
    
                                         SMO
                                                       80
    
                                                   TEMP (°F)
    90
    Figure 2b.  Temperature and ozone sounding  (SMO),  July 10, 1975,  1500 PDT,
                                         232
    

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                                                             233
    

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             .25
    O.
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                  06
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                                         HOUR (PDT)
    
    
        Figure 4.  Average maximum  ozone above inversion base,  July  9-18, 1975.
                                          234
    

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     t-
          3000
          2000
          1000
           sfc.
         3000
     -   2000
    
     co
         1000
    (1107)    Easterly     1106(1410)  2204(1410)
    
                                     /
                                                           Westerly
    (1108)
                1405    0904(1406) 2204(2206)     2206
    1106(0904)   1104    2205(1406) 2510(2706)  .   2512
    3602(3605) 2202(1805) 2205(2710)  2706(2710)    2706
                    06
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    15
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          sfc.
                   06
                 09
                                         12
                                                   15
                                                 18
                   06
                 09
                                        12        15        18
    
                                               HOUR (PDT)
                                                                 2202
    
                                                                  /
                                                                      Easterly
                              0908
    
                               \
                                                                 2904
                                                                             2702
                                  \
                                                                           \
                                                                                           (a)
    23
    • 1107 / 2705 2505
    Easterly
    Westerly
    
    2903 2703
    1109 1107 1106" 2711 2505
    I
    3102 1402 1403 2709 2908
    • i ii • |
    \
    \
    m
    *
    \
    
    
    
    
    1112
    
    
    Easterly
    0904
    0906
    
    1102
    1
                                                                              23
                                                                 23
                                                                                           (b)
    /
    • 1409 2207
    •
    Easterly 1
    • 1106 1404 / 2208
    •
    • 1105 1106 2208 2210
    *
    1604 0603 I 2711 2510
    i t f i i
    2905
    ( 1
    2208
    1 1
    Westerly
    2515
    2710
    -•
    KEY:
    Wind Direction
    (10's of degs.)
    •
    Wind Speed, mph
    2204
    2704
    i i
                                                                                           (c)
       Figure  5.  Most frequent winds aloft,  June-July 1975;  (a)  OXR, NTD in  ():
                   (b)  DUM;  (c) LAX.
                                               235
    

    -------
    Angeles coastline and Ventura area, the westerly winds are not noted until well
    after 1200 PDT, even at the surface.
    
         Conditions shown in Figure 5 reinforce the idea that ozone layers aloft
    can easily be transported from the east (from Los Angeles) to the Ventura
    County coast.
    
                                     CONCLUSIONS
    
         On the basis of a three-dimensional  study of wind flow and ozone between
    the coastal portion of Los Angeles and Ventura County to the northwest, it is
    concluded that ozone rich layers exist aloft, and may be tracked as entities
    over the length of the study area.
    
         The most persistent ozone layer  was  found just above the base of the subsi-
    dence inversion characteristic of the southern California summer season.
    
         Trajectories of air containing the ozone aloft indicated a prior history
    over the Los  Angeles Basin.   (Surface wind-derived trajectories, on the other
    hand, give the impression that such a transport did not occur.)
    
         The persistence of the  ozone layers  aloft, and the upper flow indicating
    transport from the Los Angeles area during what is considered normal  summer
    conditions, leads to the conclusion that  such is the common situation, and that
    the reported  high ozone values at surface locations in Ventura County may well
    be the result of the surfacing of the aged photochemical pollution cloud  from
    Los Angeles.
    
    
                                      REFERENCES
    
    
     1.    Tubbs,  D.   Photochemical  Oxidant Air Pollution in Ventura County,
          2nd edition,  1965-1974,  Report  by the Ventura County Air Pollution
          Control  District,  1975,  115 pp.
    
     2.    Chaplin,  A.S.  and  R.R.  Russell.   A  Report on the Impact of the  Proposed
          Camarillo Airport  on the Air Quality of the Oxnard Plain, Environmental
          Systems  Div.  Litton Systems,  Inc.,  Camarillo,  CA.,  1970,  p.  3.9.
    
     3.    Sklarew,  R.C.,  and A.S.  Chaplin.  Analysis  of Formation of High Ozone
          Concentrations  in  Ventura  County, Report by the Environmental  Systems
          Division,  Xonies  Corporation, to Ventura County Air Pollution  Control
          District,  1975,  54 pp.
    
     4.    Kauper,  E.K.  and B.L.  Niemann.   Los  Angeles to Ventura Overwater Ozone
          Transport Study,  Report  to California Air Resources Board, Sacramento,
          CA, #ARB4-1126,  1975.
                                         236
    

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                                                                                6-2
                       OZONE  FORMATION  IN THE ST.  LOUIS URBAN PLUME
    
               W.H. White, D.L.  Blumenthal,  J.A.  Anderson, R.B. Husar and
                                     W.E. Wilson,  Jr.*
    
    ABSTRACT
    
         The. pottutant e.mLf>Atont>  ofa  me.tAopoLitan St.  LOUAJ> can cau/ie.
    ofa the, Fe.deAat Ambte.nt Standard  faoti ozone. 160 km oft mono, downultnd.  The.
    appaAe.nt ozone. yteJLd  ofa  the.  eAtimate.d hydAoc.aA.bon e.m.L&A  cJLoAe.  to the. the.osLe.tLc.aJL Atotc-htomztsitc. uppeA Urn-it.
    c.oncJLuAtonA aAe. dnawn ^ftom d^taiie.d obAe.sivationA  ofi the. St. Lou/a usiban
    ptume. made, by tAime.nte.d aJAcAa^t dusting the. AummeAi, ofa 1973, 1974, and  1975.
    
                                       INTRODUCTION
    
         Metropolitan  St. Louis  is a major urban-industrial center, encompass-
    ing coal-fired power  plants  with a combined capacity of 4600 megawatts (mw),
    oil refineries with a combined capacity  of 4.4 x 105 barrels/day, various
    other industry, and a population of about two million.  It is surrounded by
    flat, predominantly agricultural terrain, the nearest neighboring city of
    50,000 or more people being  135  km distant.  Due  to its isolation, the impact
    of St. Louis on ambient  air  quality is relatively easy to determine; air that
    has been modified  by  the aggregate emissions  of the metropolitan area forms
    a 30-50 km-wide urban plume  downwind.   The Fate of Atmospheric Pollutants
    Study (FAPS) showed that the  aerosol burden of this plume is often identifi-
    able 80 to 120 km  from the city  (1, 2, 3, 4).
    
         As part of Project  Midwest  Interstate Sulfur Transformation and Trans-
    port (MISTT), pilot balloons  and instrumented aircraft were used during the
    summers of 1973, 1974, and 1975  to quantify the three-dimensional flow of
    aerosols and trace  gases in  the  St. Louis urban plume (5).  The primary sampl-
    ing platform for the  program  was the MRI Cessna 206 (6).  In addition to
    extensive aerosol  and meteorological instrumentation, this single-engine
    plane carried continuous monitors  for ozone (03)  (chemiluminescence), nitric
    oxide (NO) and nitrogen  oxides (NO ) (chemiluminescence), and sulfur dioxide
    (S02) (electrochemical).  The flight pattern  of the sampling aircraft was
    designed to characterize cross wind sections  of the plume at discrete distances
    downwind of the city, and was established with the aid of an instrumented
    *W.H. White, D.L. Blumenthal,  J.A.  Anderson,  Meteorology Research, Inc.,
    Altadena, California.
    R. B. Husar, Washington University,  St.  Louis,  Missouri.
    W. E. Wilson, Jr., U.S. Environmental  Protection Agency, Research Triangle
    Park, North Carolina.
    
                                          237
    

    -------
    scout aircraft operated by Washington University (7).   Airborne operations
    were supported with half-hourly observations of winds  aloft obtained by mobile
    pilot balloon units operating in the sampling area.
    
         The use of a highly-mobile fixed-wing aircraft  as the primary sampling
    platform led to an improved understanding of pollutant transport and disper-
    sion at scales of 100 km or more.   In addition, the  design of the experiment
    made possible the study of transformations undergone by pollutants in the
    atmosphere at dilutions and time scales which are difficult to simulate in
    the laboratory.   The formation of aerosols and loss  of sulfur dioxide in the
    St. Louis urban plume are discussed elsewhere (7, 8).   In this paper, we will
    present some results on the formation and transport  of ozone, and discuss
    their implications for a control policy.
    
                                         RESULTS
    
         A plume of ozone concentrations well above background levels was en-
    countered directly downwind of St. Louis on most sampling days.  Ozone con-
    centrations within this plume often exceeded 0.2 ppm,  and concentrations in
    excess of 0.3 ppm were recorded.  Net production of 03 and/or nitrogen dioxide
    (N02) was often apparent less than 15 km downwind of major hydrocarbon (HC)
    sources near Wood River (chemical industry) and downtown St. Louis (motor
    vehicles).  Figure 1 shows profiles of ozone and oxidant (03 + N02) concen-
    trations measured immediately downwind of the metropolitan area under dif-
    ferent wind regimes.
    
         The geometry of the urban plume strongly depended on the prevailing wind
    direction.  Under northwesterly or southeasterly conditions, parallel plumes
    from Wood River and St. Louis could be distinguished in traverses immediately
    downwind of the metropolitan area.  The combined initial width of the two
    plumes was about 50 km.  Under southwesterly or northeasterly flow, the two
    plumes tended to overlap and merge into one.  The highest ozone concentra-
    tions were measured under these conditions, when the individual plumes rein-
    forced each other.  On two days in 1975, the wind held steady from the south-
    west all day long and the combined urban plume was mapped from St. Louis out
    to distances greater than 150 km.
    
         Figure 2 shows ozone and aerosol light-scattering coefficient (b   .)
    profiles recorded by the sampling aircraft during selected cross-wind tra-
    verses downwind of St. Louis on July 18, 1975.  Each traverse path was flown
    at three different altitudes, starting just, downwind of St. Louis at 0900
    Central Daylight Time (CDT) and finishing near Decatur, Illinois, at 1900 CDT.
    These horizontal traverses, together with vertical soundings such as that
    shown in Figure 3, documented a broad, shallow pollutant plume extending from
    St. Louis out past Decatur, 170 km to the northeast.  Outside the plume, ozone
    concentrations were fairly uniform and generally below the 0.08 ppm Federal
    Ambient Standard.  Within the plume, ozone concentrations exceeded the Feder-
    al Ambient Standard even at 160 km from the St. Louis  Arch.  At this distance,
    where concentrations outside the plume were 0.07 ppm or less, concentrations
    in the center of the plume remained as high as 0.12  ppm.
    
         The July 18 plume was mapped under hazy skies,  with some scattered thunder-
    
                                         238
    

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    Figure 1.   Horizontal  profiles  of  ozone  and oxidant concentrations downwind
               of metropolitan  St.  Louis  under four different wind regimes.  Pro-
               files  were  recorded  during  traverses along profile baselines at
               the following  altitudes  and times:  (clockwise from top) 610 m MSL,
               1145-1152 CDT,  12  August 1974; 455 m MSL, 0933-0952 CDT, 30
               July 1974;  760  m MSL 1451-1512 CDT, 28 July 1975; 455 m MSL, 1027-
               1048 CDT, 15 August  1974.   Arrows show average winds measured in
               mixing layer during  sampling  period; their lengths equal distance
               covered in  one  hour  at  average wind speed.
                                         239
    

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                                                               CHAMPA IGNN
    
    
                                                                     fv^-^j' URUANA
                  >,/-u  xi^.;
               MISSOURI  / II I.INOIS
                                         0            50
    
                                            KILOMCTTRS
                                                              A  POWER PLANT
                                                              •  REFINERY
    Figure 2.  Selected horizontal profiles of ozone concentration and light-
               scattering coefficient (b   ,) downwind of St. Louis on 18 July
               1975.  Profiles were recoruea during traverses along profile base-
               lines at the following altitudes and times:  (starting near city)
               455 m MSL, 0849-0907 CDT; 455 m MSL, 1157-1220 CDT; 610 m MSL,
               1348-1410 CDT; 760 m MSL, 1631-1656 CDT; 760 m MSL, 1804-1834 CDT.
               Spiral indicates location of vertical sounding shown in Figure 3.
    
    
    showers appearing toward evening.   The depth  of the mixed layer,  which was 0.3
    km at 0900 CDT, increased rapidly during the  morning,  and exceeded 1.0 km by
    early afternoon.  The continuing presence of  a low pressure trough over the
    western plains produced strong southwesterly  flow over the Missouri  and upper
    Mississippi valleys, which was documented in  the sampling area by a  total  of
    36 pilot balloon observations  carried out as  part of Project MISTT.   The mean
    transport vector (1) lay between 230° and 243  during  the middle  of  the day,
    at speeds of 20-36 km/hr.   At  these  speeds, among the  highest encountered
    during the program,  emissions  from the city would have aged roughly  5-7 hours
    by the time they were sampled  in the farthest passes.
    
         The general direction of  the airflow was corroborated by the alignment
    of power plant plumes in successive  traverses.  All of the major  (greater
    than 1,000 mw capacity) power  plants lying in and immediately upwind of the
                                         240
    

    -------
                              ; bSCAT
                    0      0 I
                    0   I   2
                    TEMPERATURE (C)
                                       TEMPERATURE
                                                               V
    02
    4
    15
    ppm
    lO-'m
    20
    OZONE
    
    l> Cf «T
    180  210  240 270   DIRECTION
    SPEED tm/s)   6   8  10
     Figure 3.   Vertical profiles of  ozone concentration, (bscaj-), temperature,
                and wind, measured  in late morning on 18 July 1975.   Profiles  of
                ozone, bsca£, and temperature were recorded during spiral  descent
                over Mt. Olive,  Illinois  (identified by spiral in Figure  2),  1130-
                1143 CDT.  Straight line  with temperature profile shows dry adia-
                batic lapse rate.   Wind profiles were derived from pilot  balloon
                released from Sorento,  Illinois, 15 km from Mt. Olive, at 1200 CDT.
                                    TEMPERATURE
                   0
                   0    I   2
                   TEMPERATURE (C)
                   IBO 210  240 2/0  DIRECTION
                    SPtfU (m/sl    6   8   10
    Figure 4.  Vertical profiles  measured in early afternoon  on  11  August 1975.
               Profiles of  ozone, bscat,  and temperature were recorded during spiral
               descent over Butler,  Illinois (identified by spiral  in Figure 5),
               1329-1343 CDT.   Wind  profiles were derived from pilot  balloon
               released from Taylorville, Illinois, 40 km northeast of Mt.  Olive,
               at 1330 CDT.
                                          241
    

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    area are noted in Figure 2.  The plumes from some of these plants can be
    identified in Figure 2 by their ozone deficits, which result from the scav-
    enging of the ambient ozone by plume NO (9).  The Coffeen plant, 85 km WNW
    of St. Louis, is the only major downwind pollutant source known to the authors
    which lies within the July 18 urban plume.
    
         Figure 5 shows selected ozone and b   .  profiles recorded on August 11,
    1975.  Sampling began upwind of St. Louis at 0800 CDT and continued downwind
    of the city until a line of thunderstorms moved into the sampling area at about
    1600 CDT.  At this time, the sampling aircraft had just completed a set of
    passes 145 km from the Gateway Arch, and the scout aircraft, which was not
    instrumented for ozone, had identified the  aerosol plume 100 km further down-
    wind.  In all sampling passes downwind of the city, ozone concentrations
    outside the urban plume were below the 0.08 ppm Federal Ambient Standard, while
    concentrations within the plume were substantially above.  Near Hillsboro,
    Illinois, 85 km from St. Louis, the ozone concentration reached 0.2 ppm in
    the middle of the day.
    
         Skies on August 11 were partly cloudy., with scattered cirrus present
    during the morning and early afternoon.  The mixing depth was about 0.3 km
    at 1000 CDT and reached 1.4 km by 1330 CDT  (Figure 4).  A weak low in western
    Nebraska triggered southwesterly flow in the lower atmosphere, at speeds
    somewhat below those of July 18.  The mean  transport vector lay between 221°
    and 243° during the middle of the day, at speeds in the range 16-30 km/hr.
    At these wind speeds, the sampling aircraft was progressing downwind at
    roughly the same rate as the air.
    
         A distinctive feature of the MISTT program was the characterization
    of pollutant concentrations and winds over  complete cross-sections of the
    urban plume.   From the measurements at a given cross-section, the horizontal
    mass flow rate of a pollutant across that cross-section can be calculated
    directly:
                   FLOW RATE =   u(x,z)   (C(x,y,z) - C(x,z)) dy dz,
                               J   A      J               0
    
    where x is distance downwind, y,z are cross-wind and vertical coordinates,
    u  is wind speed (from pilot balloon observations), C is pollutant  concentra-
    tion (from aircraft measurements), and  C  is average pollutant concentra-
    tion outside the plume (from aircraft measurements).  Figure 6 shows ozone
    flow rates from three different days, plotted against distance downwind of
    the city.  The quantities plotted are the flow rates of ozone in excess of
    background, and thus represent the specific contribution of metropolitan St.
    Louis to atmospheric loadings.
    
         The measurements for Figure 6 were not, in general, made in the Lagran-
    gian mode.  Moreover, the measureme-ts  at less than 50 km from the  city were
    all made in the morning, while the measurements at greater distances were
    all made in the afternoon.  It is, therefore, difficult to distinguish be-
    tween the contributions of solar elevation and atmospheric residence time
    to the increase in the ozone flow rate  over the first 100 km.  Nevertheless,
    it is of interest that the flow rates at 50 km or more from the city cluster
    in the range 95-125 T/hr.  These numbers may be taken as a rough estimate
    
    
                                         242
    

    -------
                        OZONF
                                                           CHAMPAIGN
                                                              A FJOWF:R PLANT
                                                              •  REFINERY
                                              KH.OME1EHS
                                                                            76-407
    
    Figure 5.  Selected horizontal profiles of ozone concentration  and  b
               downwind of St. Louis on 11 August 1975.   Profiles were  riSBfded
               during traverses of profile baselines at the following altitudes
               and times:  (starting upwind of city) 455  m MSL, 0744-0758  CDT;
               425 m MSL, 1019-1036 CDT; 610 m MSL, 1245-1310 CDT;  760  m MSL,
               1442-1508 CDT.  Spiral indicates location  of vertical sounding
               shown in Figure 4.
    
    for the rate at which ozone was formed in the atmosphere from the emissions
    of metropolitan St. Louis.
    
    
                                       DISCUSSION
    
         The St. Louis urban plume was mapped on a  total  of eight days  during
    the July 15-August 15, 1975, MISTT experiment,  and ozone was a  conspicuous
    indicator of the plume during this period.  Daytime ozone concentrations
    within the plume generally exceeded the 0.08 ppm Federal Ambient Standard,
    even on the most distant sampling runs.  Peak concentrations in the plume
    were typically twice those in the unmodified background air, and surpassed
    0.15 ppm on most sampling days.  (It should be  noted  that the object of Pro-
                                         243
    

    -------
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    -------
    ject MISTT was not to develop a climatology of the urban plume, but to mea-
    sure it in detail under conditions favorable for doing so, and sampling days
    were chosen according to this criterion.)  Earlier measurements by FAPS
    had also found excess ozone in the St. Louis urban plume on two days in
    April, 1973 (3).
    
         While upwind sources undoubtedly contribute to regional backgrounds at
    St. Louis, they clearly do not account for the excess concentrations of the
    urban plume, which were consistently found downwind of the city regardless
    of the wind regime.  On the two days discussed in detail in this paper, the
    nearest upwind city of any size was Springfield, Missouri, over 300 km from
    St. Louis with only about 100,000 people.  Nor is a stratospheric origin for
    the excess ozone any more likely; this would not explain the restriction of
    high concentrations to the mixed layer, and their alignment with the wind.
    Moreover, Figures 2 and 5 show that the excess ozone in the plume is associated
    with light-scattering aerosols, which would not be expected in a clean airmass
    subducted from the stratosphere.  The excess ozone concentrations downwind
    of St. Louis must be attributed directly to the emissions of the metropolitan
    area.
    
         The most obvious policy implication of the MISTT data is that ozone
    control strategies must, to be effective, be formulated on a regional scale.
    The 1975 experiment documented, in air 160 km from St. Louis, violations of
    the Federal Ambient Standard for ozone which were traceable to emissions from
    the metropolitan area.  Between 125 and 160 km downwind there was no signifi-
    cant decay in the flow rate of ozone and no significant increase in the cross-
    wind and vertical dimensions of the urban plume, so that violations of the
    standard probably extended much farther out.  None of the ground-level ozone
    monitors operated by the State of Illinois were situated in the path of the
    observed ozone plume, so that the airborne measurements can be compared with
    the standard network measurements only in the background air, where they were
    consistent (10).  Aircraft soundings in the plume (Figures 3 and 4) showed
    ozone concentrations to be quite uniform through the mixed layer, however,
    and it is probable that the high plume concentrations encountered aloft were
    experienced near the surface as well.
    
         The elevated ozone concentrations within the St. Louis urban plume were
    superimposed on background ozone levels which were themselves substantially
    above those associated with clean air (11).  On most sampling days, midday
    ozone levels outside the urban plume lay in the range 0.07-0.12 ppm.  It is
    clear that if the emissions of St. Louis can contribute to the ozone back-
    grounds of cities far downwind, then  much  of the  ozone  background  of St.  Louis
    itself may not be natural, but instead due to cities and industry far upwind
    of St. Louis.   There is some evidence that the composition of the upwind back-
    ground strongly affects the chemistry of the downwind plume.  For example,
    unusually high (for St. Louis) peak ozone concentrations were observed on
    July 28, 1975, a day of unusually high (for St. Louis) ozone backgrounds
    (Figure 1).
    
         The annual emissions of non-methane HC in metropolitan St. Louis are
    estimated at about 1.6 x 105 tonnes (10, 12, 13).  This corresponds to an
    average of 18-36 tons/hr, depending on whether emissions are spread out through
    
    
                                         245
    

    -------
    the day or concentrated in the daylight hours.   H.  M.  Walker has pointed out
    that if these figures are accurate then the formation  of 120 tons/hr of ozone
    in the St. Louis urban plume corresponds to a yield of one to two parts (by
    volume) ozone for each part (by volume as C) emitted HC (13).  This would be a
    much higher yield than is typically found in smog chamber studies (14).
    Possible explanations for the high apparent yield would include enhanced pro-
    duction at low concentrations in the absence of wall losses, and the partici-
    pation of incompletely-reacted HC products contributed by the background air.
    Hydrocarbon measurements taken during the recently-completed 1976 MISTT experi-
    ment may help to resolve this point.
    
         Whatever its origin, the high apparent ozone yield of HC in the St. Louis
    urban plume carries important implications for photochemical simulation models.
    If most of the ozone produced in the plume is attributable to free radicals
    and unreactive HC advected into the city from upwind sources, then the compo-
    sition of the background air is a critical input to a  simulation model.  This
    means that successful simulation on the mesoscale is dependent, via initial
    and boundary conditions, on successful simulation on the synoptic scale.
    Alternatively, if most of the ozone produced in the plume is attributable
    simply to the efficient utilization of HC emitted in metropolitan St.  Louis,
    then the ozone yield of these HC is near the theoretical stoichiometric upper
    limit of two to one (15) or four to one (13).  This means that the chain
    lengths of the reactions involving the more reactive HC species are determined
    primarily by the size of the initial HC molecule, and  not by a competition
    between chain-propagating and chain-terminating reactions as in present lumped
    kinetic photochemical models (16).
    
                                     ACKNOWLEDGEMENT
    
         This research  was supported by the U.S.  Environmental  Protection  Agency,
    Environmental  Sciences Research Laboratory, Aerosol Research Branch.
    
                                      REFERENCES
    
    
     1.    Haagenson, P.  L. and A.  L.  Morris. J. of Applied Meteorology 13:901,
           1974.
    
     2.    Stampfer, J. F. and J. A. Anderson.  Atmospheric Environment, 9:301,
           1975.
    
     3.    Breeding, R. J.  ,  P.  L.  Haagenson, J. A. Anderson, J.  P.  Lodge,  Jr.
           and J. F. Stampfer, Jr.  J. of Applied Meteorology 14:204, 1975.
    
     4.    Breeding, R. J., H. B. Klonis, J. P. Lodge, Jr., J. B. Pate, D.   C.
           Sheesley, T. R. Englert and D. R. Sears.   Atmospheric Environment
           10:181, 1976.
    
     5.    Wilson, Jr., W. E., R. J. Charlson, R. B. Husar, K. T. Whitby, and
           D. L. Blumenthal.  Proc. 69th Annual Meeting Air Pollution Control
           Assoc., Paper #76-30-06, June 1976.
                                         246
    

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     6.   White, W. H.,  J. A. Anderson, W.  R. Knuth, D.  L.  Blumenthal ,  J.  C.
          Hsiung and R.  B. Husar.  Final  Report to LJ.S.E.P.A.  on contract  number
          68-02-1919 by Meteorology Research, Inc., Altadena,  California,  1976.
    
     7.   Husar, R. B., J. D. Husar, N. V.  Gillani, S. B. Fuller, W. H. White,
          W. M. Vaughan and W. E. Wilson, Jr.  Proc. of the Div. Environmental
          Chemistry, 171st National ACS Meeting, New York,  April 1976.
    
     8.   White, W. H.,  J. A. Anderson, D.  L. Blumenthal, R.  B.  Husar,  N.  V.
          Gillani,  J.  D.  Husar and W.  E.  Wilson, Jr.  Science, 1976 (in Dress).
    
     9.   Ogren, J. A.,  D. L. Blumenthal, W.  H.  White, T. W.  Tesche and M.  K.
          Liu.  Proc.  Int'l.  Conf. on  Photochemical Oxidants  and its Control,
          Raleigh,  North  Carolina, 1976. ( in press)
    
    10.   Illinois  E.P.A.   1976.
    
    11.   Blumenthal,  D.  L.,  T.  B. Smith, W.  H.  White, S. L.  Marsh, D.  S.  Ensor,
          R. B. Husar, P.  S.  McMurry,  S.  L.  Heisler and P.  Owens.   Final  Report
          to California  Air Resources  Board  on contract number ARB 2-1245  by
          Meteorology  Research,  Inc.,  Altadena,  California,  1974.
    
    12.   U.S.E.P.A.  1976.
    
    13.   Walker,  H. M.   Proc. of the  Conf.  on Ozone/Oxidants, Air Pollution
          Control  Assoc.,  Dallas, March 1976.
    
    14.   Wilson,  W. E.,  Jr., D.  F. Miller,  A.  Levy and  R.  K.  Stone.   J. Air
          Pollution Control Assoc.  23:949,  1973.
    
    15.   Klauber,  G.  M.,  Ph.D.   thesis,  Johns Hopkins University, 1975
    
    16.   Hecht, T. A.,  J. H. Seinfeld and M. C. Dodge,   Environmental  Science
          and Technology   8:327,  1974.
                                         247
    

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                                                                                6-3
                  LONG RANGE AIRBORNE MEASUREMENTS OF OZONE  OFF  THE
                       COAST OF THE NORTHEASTERN UNITED STATES
    
            G.  W.  Siple,  C.  K.  Fitzsimmons, K. F. Zeller,  and R.  B.  Evans*
    
    
    ABSTRACT
    
          The. Envpont -in the. noitntQ.n.vi Unite.d  States  tn. the.
    •iuinmeA  ofi  7975.   An 4.nl>tA.me.nte.d ouAcA&fit w)o6 o6e.d to meo6u/ie ozone and nitsvic.
    Q->u.de.,  and to take, bag AampleA, among otheA paJiam&teAA.  kvi tfia^e.ctox.y anal-
    y&oA  indicate, that the. oJin. mo44 c.onta4.ning kigh ozone. c.onc.e.ntA.ationt> monJJ:otie.d
    ove.fi the. kttant-lc. Ocean 250 ItULometeAA e.a!>t oft Wew Vo^tk C^ty pa64ecf oveA that
    metA.opotitan an.e.a on the. mox.nJ.ng o& the. day the. mea
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                                 INSTRUMENTATION
         A field team from the U.S.  Environmental  Protection  Agency's  Environmen-
    tal Monitoring and Support Laboratory  at Las  Vegas,  Nevada,  (EMSL-LV)  partic-
    ipated in the^NOTS gathering extensive air  quality data with  the Long  Range
    Air Monitoring Aircraft (LORAMA) during August of 1975.   The  aircraft, a
    Monarch B-26, was modified to operate  as an air monitoring  platform.   The in-
    strumentation on board the aircraft is listed in Table 1.   Oxidant,  measured
    as ozone (Os), was monitored during each flight by a gas-phase  chemilumines-
    cent Bendix 8002, an instrument which  has proven reliable and precise  for
    field data collection.  Nitric oxide (NO) was measured with a TECO 14B single-
    channel gas-phase chemiluminescent analyzer,  modified for high  sensitivity
    and low noise.  This particular instrument  is designed to reliably measure
    NOX in the range of 5 parts per billion (ppb) fullscale;  but, this instrument
    Was not used to monitor total NOx or nitrogen dioxide (N02) at  any time dur-
    ing the study.  Other data routinely collected included coefficient of light
    scattering (b$cat), outside ambient temperature, dewpoint  temperature,  alti-
    tude, and navigational position.  Bag  samples were taken  at strategic  points
    on most flights for subsequent HC analysis  by gas chromatography.
    
         There are several important considerations with regard to  air pollution
    data collected by means of an airborne platform.  However,  these  are discussed
    in the literature (Hester et al., 1976) and are not  specified here.   It should
    be mentioned that detailed quality control  procedures were  an integral part  of
    the field work; instrument calibration was  performed on all  instruments before
    and after each day's flights, checking both zero and one  span level.   During
    flight, periodic zero input checks were made.   These calibration  data, along
    with altitude correction factors derived from environmental  chamber tests
    (Siple et al., 1976), were used to process  the data  into  useable engineering
    units.
                            TABLE  I.  LORAMA  INSTRUMENTATION
                     Parameter
     Outside Ambient Temperature
     Dewpoint  Temperature
     Particulate  Light Scattering
     Altitude
     Location
     Hydrocarbons
                Method/Instrument
    °3
    NO
    Chemi luminescence/Bendix 8002
    Chemi luminescence/TECO 14B modified
    for low noise/high sensitivity
    Integrated circuit/LX5700
    Hygrometer/Cambridge 13F-C3
    Integrating nephelometer/MRI 1550
    Integrated circuit/LX 3702A
    Digital DME/Collins DME-40
    Bag Samples (Tedlar)
                                         250
    

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                                MONITORING STRATEGY
         The  report of Cleveland et al.  (1976), based on ground-level ozone data,
     seems  to  strongly indicate the reality of the pollutant transport phenomenon
     in  the  northeastern U.S.  However, one might generally expect micro- and meso-
     scale  geographical, meteorological,  and anthropogenic irregularities within
     the study path to adversely affect conclusions concerning broad area phenomena
     such as pollutant transport over terrestrial areas.  In contrast, air quality
     monitoring over oceanic areas offers unique opportunities for experimental
     design  and data interpretation; the  relatively smooth ocean surface provides
     simplified conditions for the study  of pollutant dispersion.  The ocean is
     not recognized as a significant source of, or a sink for, photochemical oxi-
     dant activity.  Although complex interactions between oxidant and the ocean
     surface probably do occur, the exact nature of such interactions is not
     we!1-defined.
    
         Without such knowledge, and for the sake of simplicity, it can be assumed
     that transport and dispersion of oxidant and oxidant precursors by meteoro-
     logical means are primarily responsible for the ambient pollutant concentra-
     tions over marine areas.  Under these simplified conditions, the fate of pol-
     lutants originating in littoral areas can be described confidently.
    
    
         This report examines ozone data collected by the LORAMA over portions of
     the Atlantic Ocean off the northeastern seaboard.   Perhaps the most signifi-
     cant flight was #9,  performed on the afternoon of August 14, between 1430 and
     1745 Eastern Daylight Time (EOT).
    
                              RESULTS AND DISCUSSION
         Figure 1 shows the flight path for flight #9, which departed the Naval
    Air Station at South Weymouth (NZW) at about 1430 EOT on August 14.   The
    flight turned south, to begin a spiral over Vineyard Bay, between the Eliz-
    abeth Islands and Martha's Vineyard.  Figure 1 shows instantaneous ozone con-
    centrations in ppb every two minutes, as a function of position, time, and
    altitude.
    
         Figure 2 presents the vertical profiles of all data parameters  measured
    continuously; the spiral began at 2135 meters above mean sea level (m MSL)
    and descended to 60 m MSL.  One can notice two shallow temperature inver-
    sions; the base of the higher one is at approximately 1525 m MSL, the base
    of the lower is at approximately 1220 m MSL.  The ozone profile, the humid-
    ity profile, and the light scattering coefficient profile indicate distinct
    patterns related to these inversions.  However, one can note the rapid in-
    crease in ozone between 200 m MSL and 60 m MSL.  This increase would not
    appear to be related to a trapped polluted layer since the temperature pro-
    file indicates a near adiabatic lapse rate at these lower altitudes.   Sim-
    ilar measurements on numerous other flights over the ocean corroborate this
    observation.  This might signify that the air within the mixing layer over
    the ocean is not necessarily well-mixed.  Unfortunately, the TECO 14B was
                                         251
    

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                                                                            24)
                                                   94{'30m}
    
                                                  j_7+7 (1310m |>
    
                                               (1452)72 'A
    Figure  1.   Flight #9  (August 14,  1975):  Flight pattern  and ozone
                distribution map.
                                    252
    

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        SEA
       LEVEL
     SEA
    LEVEL
    0  20 40 60 80  100120140160180200
       CONCENTRATION, ppb
        -30 -20 -10   0   10  20
    
            TEMPERATURE,°C
                                                                      30  40
        SEA
       LEVEL
     SEA
    LEVEL
            0 10 20 30 40  50 60 70 80 90 100
              RELATIVE  HUMIDITY. %
                                      01  23456789
                                    SCATTERING COEFFICIENT, lO
                                     10
    Figure 2.  Flight #9 (August 14, 1975):   Vertical profiles of parameters
              for spiral  #1.
                                       253
    

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    non-operational on this particular day so there is little indication as to
    the NO precursor values at this point.
    
         At the completion of the spiral, the aircraft flew over Martha's Vine-
    yard then headed southward again at an altitude of 335 m MSL.  The ozone
    concentration continued to increase at this altitude and, at a point about
    130 km south of Martha's Vineyard, the aircraft turned east.  The ozone val-
    ues continued to rise for a short distance, peaking at 214 ppb, then de-
    creasing again.  Bag samples taken in this area showed relatively high con-
    centrations of acetylene (Environmental Protection Agency, 1976).  The air-
    craft traveled about 110 km in an easterly direction, then turned northward.
    The ozone concentration continued to decrease, although there were several
    minor maxima and minima along the way.  After passing the northern point of
    Cape Cod, the aircraft turned west, climbed to 490 m MSL and made a large
    circuit of eastern Massachusetts and the ocean just to the east of Boston,
    returning to NZW at about 1745 EOT.
    
         The ozone concentrations in the northern circuit (50 ppb to 80 ppb)
    were lower than in the southern circuit (100 ppb to 200 ppb).  In terms of
    ozone concentration, the air monitored in the southern circuit would appear
    to have a different history than that monitored in the northern circuit.
    If the spiral data taken near the beginning of the flight is a good indi-
    cator of the vertical profiles throughout the flight path (i.e., consider-
    ing the time difference during the flight), the altitude difference between
    the two circuits is of little consequence.
    
         Figure 3 illustrates a trajectory analysis calculated backwards in
    time from the coordinates of the southwest corner of flight #9 (bull's-
    eye).   This is the area where the highest ozone concentrations were re-
    corded.  The aircraft was in this locality at approximately 1530 EOT.
    Three individual trajectories are represented on the figure by the letters
    A, C, and D.  (These trajectories were prepared using the USAF ETAC tra-
    jectory program.)  The letter C represents the trajectory of an air mass
    between the altitudes of 300 m above ground level (AGL) and 600 m AGL,
    terminating at the bull's-eye at 0700 EOT on August 14.  The letter D rep-
    resents the trajectory of an air mass between the same altitudes terminat-
    ing at the bull's-eye at 1300 EOT.  Finally, the letter A represents the
    trajectory of an air mass between the same altitudes terminating at the
    bull's-eye at 1900 EOT.   The numbers associated with these letters indicate
    the number of 6-hour periods backward in a given trajectory.
    
         It should be noted before any further analysis is forthcoming that any
    such trajectory is not solely definitive; there is necessarily an error mar-
    gin which brackets the calculated path, compounding the error the further
    the trajectory recedes in time from the starting point.  The program which
    generates these positions attempts to provide macroscale behavior based on a
    collection of widespread microscale observations.
    
         Nonetheless, one can say that, in general, the air arriving at the
    bull's-eye portion of the flight path before and after flight #9 was from
    the northwest through west-northwest.  The indicated trajectories C and A
    pass over southern New York state and northern New Jersey; all trajectories
    pass over portions of Long Island.
    
                                         254
    

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        Figure 3.   Computer trajectories for air parcel  between 300 m AGL and
                   600 m AGL for August 14,  1975:   A terminates at   ©    at
                   1900 EOT; C terminates at  ©   at 0700 EOT; D terminates
                   at   ©   at 1300 EOT.
                                     ISOfEDT
    0500EDT
    Figure 4.   Hand-drawn trajectories for
               air parcels at surface level
               by time and space, terminat-
               ing at 1600 EOT August 14,
               1975.
                                              Figure 5.  Hand-drawn trajectories for
                                                        air parcels at 305 m AGL,
                                                        terminating at 1600 EOT
                                                        August 14, 1975.
                                         255
    

    -------
          Figures 4 through  7  were  prepared  by  hand  by  our  staff meteorologist
     and represent a best judgment  air  trajectory  analysis.  The basis  for  these
     trajectories is the  extensive  pibal  and radiosonde data collected  during the
     NOTS.   The trajectories in  Figure  4,  at surface level, indicate  generally
     westerly flow from early  in the  morning until late afternoon.  Figure  5, at
     305 m AGL, shows air flow generally  from the  west-southwest through  west-
     northwest.  The trajectories  in  Figure  5,  at  610 m AGL, show a more  north-
     westerly component for  the  air at  this  altitude.  These figures  appear to
     offer a rationale for the divergence  of measured ozone concentrations  in the
     different sectors of the  flight.   These air masses appear  to have  passed over
     land areas with different precursor  emission  potential; e.g., New  York City
     vs.  upstate Connecticut.
    
          Figure 7 is a combination of  the surface trajectory of Figure 4 and the
     305 m AGL trajectory of Figure 5.  Figure  7 represents a backward  trajectory
     from points on the flight pattern, suggesting the  ground area swept  by the
     column of air from the  surface to  305 m AGL from 0800  EOT  to 1600  EOT.  Al-
     though this is a subjective analysis  neglecting vertical motion  and  based
     only on limited data, it  can be  concluded  that  a sizeable  percentage of the
     air arriving at these points at  1600  EOT came from somewhere in  the  shaded
     areas  between the surface and  305  m  AGL.
                                                           160()EDT
                                             1600EDT
    
    Figure 6.   Hand-drawn trajectories for air parcels  at 610 m AGL,  terminating
               at 1600 EOT August 14,  1975.
    
         These subjective trajectories compare favorably with the computer-
    generated trajectories, and are consistent with the hypothesis that the high
    ozone air was influenced by urban  sources of ozone  and ozone precursors (e.g.,
    New York City, Newark), while the  low ozone air was influenced by more rural
    sources of these air contaminants  (e.g., upstate New York).  The paucity of
    wind data over marine areas and the inherent errors of trajectory analysis
    limit definitive conclusions regarding ozone and ozone precursor transport.
    
                                         256
    

    -------
     With due regard for these limitations  and  the  assumption of non-interaction
     of the ozone-ocean interface,  the  present  analysis  indicates that elevated
     ozone values were measured 250 km  downwind of  the New York City area.
                                                     1400MJ
                                                    "SLURf^CE
                                                           6IJIOEDT
    Figure 7.
          0800EDT  1100EDT
          SURFACE SURFACE1400EDT
                           SURFACE
    
    Combination of surface and 305 m AGL trajectories  showing  ground
    area swept by air arriving at the bull's-eye  at  1600  EOT
    August 14, 1975.
                                   CONCLUSIONS
         Ozone data collected from an airborne platform over  a  wide  area  off  the
    northeastern seaboard on August 14,  1975,  show two  basic  regimes:   high ozone
    (>0.08 ppm) in the southern sector of the  area,  low ozone  (<0.08 ppm)  in  the
    northern sector.   Vertical  profile information suggests that  ozone  may not  be
    well-mixed throughout the mixing depth over the  ocean.  Two separately-
    generated air parcel  trajectories imply that the high  ozone air  measured  in
    the southern flight sector passed over highly urbanized areas of New  York and
    New Jersey on the morning of August 14, whereas  the low ozone air measured  in
    the northern flight sector was over rural  areas  of  southern New  England on
    the same morning.  This suggests that ozone and/or  ozone  precursors have  been
    transported at least 250 km downwind from  a large source  area.
    
         Transport of air parcels over land surfaces will  undoubtedly have a
    greater dispersive effect on air concentrations  of  air parcel constituents
    than transport over marine surfaces.  However, under suitable meteorological
    conditions, transport winds could clearly  carry  an  air parcel from  the New
    York Metropolitan area as far as the Boston Metropolitan  area, the  oxidant
    burden of which exceeds the National Ambient Air Quality  Standard.
    
                                         257
    

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                                      REFERENCES
    
    Blumenthal, D.L., W.H. White, R.L. Peace, arid T.B.  Smith.   Determination
    of the Feasibility of the Long-Range Transport of Ozone or Ozone Precursors.
    Meteorology Research, Inc.  Prepared for the U.S. Environmental  Protection
    Agency, EPA-450/3-74-061, November 1974.
    
    Cleveland, W.S., B. Kleiner, J.E. McRae, and J.L. Warner.   Photochemical
    Air Pollution:  Transport from the New York City Area into Connecticut
    and Massachusetts.   Science, 191:179-181, 1976.
    
    Environmental  Protection Agency, Northeast Oxidant  Transport Symposium,
    Research Triangle Park, North Carolina, January 20-21, 1976 (to  be published)
    
    Hester, N.E.,  R.B.  Evans, D.T. Mage, J.L. Pierett,  G. W.  Siple,  and J. J.
    van Ee. Some Considerations in Collecting Valid Data with  Airborne Platforms.
    Proceedings of Specialty Conference on Air Pollution Measurement Accuracy
    as It Relates  to Regulation Compliance, Air Pollution Control  Association,
    Pittsburgh, 1976.
    
    Siple, G.W., C.K. Fitzsimmons, J.J. van Ee, and K.  F. Zeller.  Air Quality
    Data for the Northeast Oxidant Transport Study,  1975:  Final  Data Report.
    U.S.  Environmental  Protection Agency (to be published).
                                         258
    

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                                                                                6-4
                 AIRBORNE MEASUREMENTS OF PRIMARY AND SECONDARY  POLLUTANT
                        CONCENTRATIONS IN THE ST. LOUIS URBAN  PLUME
    
               N.  E. Hester, R. B. Evans, F. G. Johnson,  and E.  L. Martinez*
    
     ABSTRACT
                      4.nAtnume.nte.d mth aiA pollution monttoAf,  we.fie. uAtd to
     acteAize. the. uAban plume. o^ mzttopo titan St.  Loui6, t4l^^ouAi.   Maximum oxi-
     dant and paAticulate. c.onc.e.ntsiationt> we.fie. fiound we.lt downwtnd o{ the. cJ
     and. ove.fi nuAat aAe.at>.  The. maxima fan both  ozone, and  poAtic.ut.ate. weAe.
     fiound to coincide..  A paAc.e.1 ofi aiA, c.hoAacteAU,ttc. ofi  a peAiod oft htgh e.mit>-
     AionA due. to moaning fiu^k houA tAa^-ic., wai> di^c.oveAe.d  within the. uAban plume..
     PoweA plant plume.* AupeAimpoAe.d on the. uAban  plume. weAe. fiound to de.c.tie.a?>e.
     the. c.once.ntfLation ofi ozone. i.n the. uAban plume, fan du>tancu  a& Qtiz-at a* 60
     k-ilometeAt, .
    
                                       INTRODUCTION
    
          Several studies during the last 5 years  have shown ozone (Os) concentra-
     tions that exceeded the federal standards in  rural areas.  A recent study
     by the United States Environmental Protection Agency  of the  phenomena concluded
     that these high ozone values could not be attributed  to natural sources (EPA,
     1975).  The high ozone levels seemed to be  related to a combination of local
     man-made sources and the transport of ozone and ozone precursors into rural
     areas from upwind urban areas.
    
          As part of the Regional Air Pollution  Study (RAPS) personnel from the
     Environmental Monitoring and Support Laboratory, Las  Vegas,  Nevada, made a
     number of flights with instrumented helicopters to measure ozone and related
     parameters in the St. Louis, Missouri, urban  plume during  the summer of 1975
     (Allen 1973).  These measurements were requested by the EPA  Office of Air
     Quality Planning and Standards to aid in developing better criteria for the
     siting of monitoring stations for the reactive pollutants  nitrogen oxides
     (N0x, i.e., NO, N02) and ozone.  In this report, the results  of five flights
     made during July and August are discussed.  Further flights  in this program
     were conducted during the summer of 1976; however, the  data  have not yet been
     analyzed.
    *N.E. Hester, R.B. Evans,  F.G.  Johnson,  U.S.  Environmental Protection Agency,
    Las Vegas, Nevada   89114.
     E. L. Martinez, U.S. Environmental  Protection Agency, Research Triangle Park,
    North Carolina   27711.   (On  assignment  from  National Oceanic and Atmospheric
    Administration, U. S. Department  of Commerce.)
    
                                          259
    

    -------
         A close examination of the data from the 1975 flights provides insight
    into the chemical transformations which occur in urban plumes, and reveals
    the contribution of the city to the pollution problems of the surrounding
    rural areas.
    
                                      EXPERIMENTAL
    
    INSTRUMENTATION AND TECHNIQUE
    
         The helicopters used in this study were instrumented to measure ozone
    (03), nitric oxide (NO), total oxides of nitrogen (N0x), sulfur dioxide (S02),
    temperature, dewpoint, particulate light scattering, pressure altitude, air
    speed, compass heading, and navigational position.  A more detailed descrip-
    tion of the helicopters' capabilities, limitations, and instrumentation, and
    a description of the data collection and processing techniques have been pub-
    lished previously (Hester et al., 1975a, 1975b).
    
         The wind data used in this study were obtained from four stations which
    were operated continually by RAPS during the time the helicopter flights
    were made.  Wind measurements were taken by pilot balloons at approximately
    one-hour intervals.   The locations of these four stations, indicated as
    Pibal 141, 142, 143, and 144, are plotted on the map shown in Figure 1.  The
    wind data reported in Table 1 represent the mean and standard deviation of
    the speed and direction readings  taken between 0600 and 1800 Central Standard
    Time (CST) at all four pibal stations on the days of the experiments.
                  TABLE 1.  MEAN WIND SPEED AND DIRECTION BY DATE
                                          Wind Speed              Direction
       Date          Altitude (MSL)    (Mean 1 Std. Dev.)    (Mean 1 Std. Dev.)
    
    July 15, 1976      200M              5.7 MPS +_2.3          198° + 36
                       250M              5.9 MPS +_ 2.5           200 £ 37
                       3COM              5.8 MPS +_ 2.6           205 + 40
                       350M              5.7 MPS +_ 2.7           208 £ 43
    
    July 18, 1975      200M              8.0 MPS + 3.3           229 +_ 21
                       250M              8.6 MPS +_ 3.7           231 + 18
                       300M              9.2 MPS +_ 4.1           232 £ 16
                       350M             10.0 MPS +4.7           232 £ 15
    
    August 3, 1975     200M              5.9 MPS +_ 2.3            10 +_ 16
                       250M              6.0 MPS + 2.2            12 + 16
                       300M              6.3 MPS ^2.3            12 £ 16
                       350M              6.5 MPS ^ 2.5            12 £ 16
    
    August 6, 1975     200M              7.0 MPS +_ 2.9            30 + 18
                       250M              7.1 MPS + 2.8            31 £ 17
                       300M              7.1 MPS + 2.8            31 ^17
                       350M              6.9 MPS + 2.9            32 + 17
                                        260
    

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                                                         H
     WEMTZVILLE
                                               RAMS     5TOY
    
                                               108
                                      GRANITE CITY      f  COLLINSVILLE
    
                                               POWER  PLANT
                                  PIBAL
                                              PIBAL 144
                                                 PETROLEUM REFINERY COMPLEX
    
                                                     EDWARDSVILLE
                                               AST ST LOUIS
    
                                               CHEMICAL  REFINERY
    
                                            BREWERY    SCOTT AIR  FORCE BASE
    
                                                      BELLEVILLE
    
    
    
                                                PIBAL 143
                                                      SCALE  IN  KILOMETERS
          Figure 1.   St. Louis map with  aircraft flight patterns superimposed.
         Flight patterns  for  each  experiment were planned based  on  the  most recent
    forecast of wind speed  and  direction coupled with the most recent  pibal measure-
    ments from one or more  of the  four pibal stations.  The point chosen to begin
    each day's sampling flight  was,  by best estimate, along the  center!ine of the
    urban plume, and near the outer  edge of the metropolitan  area.   The first leg
    of each flight proceeded  with  the wind away from the city at an
    305 m (1,000 feet) mean sea  level (MSL).  Ground elevations in
    altitude of
    the St. Louis
    area are typically  120  to  180 m MSL.   The helicopter maintained  a  constant
    air speed of 111  kilometers  per hour (60 knots).  A maximum was  sought in
                                          261
    

    -------
     pollutant concentration as the aircraft proceeded.  On morning flights, the
     maximum in NO concentration was sought, and on afternoon flights, the maximum
     in ozone concentration was sought.  The first leg of each flight proceeded
     past the point of the pollutant maximum until pollutant levels had ceased to
     fall sharply.  At this point, a 180° turn was made.  In some flights, where
     it was desired to better define the plume, the return leg proceeded all the way
     back to the starting point.  However, most of the flights returned directly
     to the point of maximum pollutant concentration along the flight path, and then
     proceeded to fly a cross section of the urban plume.
    
         The cross sections were determined by flying flight legs at 90° to the wind
     direction at 305 m MSL until the outer boundaries of the plume were defined.   In
     some cases, the cross section revealed that the estimates of the position of the
     plume center!ine had been somewhat in error, and higher pollution levels were
     found.
    
         After the cross section was completed, the aircraft returned to the
     position of the maximum ozone or NO concentration and performed a vertical
     distribution of pollutants.
    
     RESULTS BY DATE
    
     July 15. 1975 (Afternoon)
    
         On this date, the wind was steady from the south (see Table 1) and the
     flight patterns shown on Figure 1 as AB and CD were flown.  The data from
     these flight patterns and from the vertical spiral are shown in Figures 2a,
     2b, and 2c.
    
         The data in Figure 2a from the flight down the plume axis, AB, revealed
     that the maximum ozone concentration (approximately 0.14 ppm) was 25 km downwind
     of B, the point closest to the city (approximately 40 km downwind of center
    of the city).   The ozone maximum corresponds with the maximum light scattering
    coefficient (B   .)  reading, and with NO and S02 levels that were so low that
    they were at the noise level of the instruments.  Near the furthest point
    out on the flight, point A, a sudden rise in S02 concentration and a sharp drop
    in ozone concentration were observed.   This observation was attributed to
    wind direction,  and the plume from the Portage des Sioux power plant (indica-
    ted in Figure 1,  just north of the city) intersected the flight path.   The
    power plant plume could be followed visibly to this general  area.
    
         The data in  Figure 2b from the cross section flight (CD) shows that the
    width of the urban plume looking at 0^ levels was about 20 km and had a skewed
    shape.   Evidence  for mixing of the urban plume with the power plant plume was
    not evident in the cross section data.   It is possible that the power plant
    plume was elevated above the flight altitude and did not descend to flight
    levels until it reached the vicinity of point A.
    
         The vertical profile through the urban plume (Figure 2c) shows that there
    were three temperature inversions over the area at the time of the flight,
    at about 400 m,  500 m and at 900 m.  The inversions did not have a strong
    effect on the pollutant profile with the exception that the NO levels showed
    
                                         262
    

    -------
       040-r
                                    -,-30
       000
           14 1
                 14 0    13 9    13 8
    
                  TIME.HOURS(CST)
                 OISTANCE(km)
    
    
                     2>
    
    
               AXIAL PATTERN
                                41
                                A
                                                - 010--
                                                  000
       147      MB      M9
    
          TIME.HOURS(CST)
    
    0      DISTANCE(km)      35
    C                     0
    
              2b
                                                  CROSS-SECTION  PATTERN
    Figure 2a.  Data, collected July  15,   Figure 2b.  Data, collected  July
       1975, from flight pattern AB           1975, from flight  pattern CD
                (Figure 1).                            (Figure 1).
                                                                               15,
    a drop below the lower  inversion.   The  pollutant profiles generally indicated
    a trend of decreasing concentrations  with  increasing altitude, with the excep-
    tion of S02 whose concentration was  too low to measure accurately.
    
    July 18, 1975 (Morning  and Afternoon)
    
         A steady wind from the southwest (see Table 1)  determined the flight
    pattern shown in Figure 1 for  this  date.   Two sets of flights were made, one
    in the morning and one  in the  afternoon.   The morning set of flights sought
                                          263
    

    -------
      1000-r
       750- -
       500- •
      250
            100
             03{PPM)
    140 000  DOS
    
        NOIPPM)
                              010
    020   030  040 002     002
    
       NOX|PPMI     S02IPPM)
                                                                                 300
    B SCAT(10 4M
     Figure 2c.  Pollution data collected July  15,  1975,  vertical  spiral  through
                           urban plume  (15:23-15:43  CST).
    
    data on the maximum NO concentration in the urban plume, and the afternoon
    set of flights sought data on the ozone maximum.
    
         The morning flight followed the patterns shown in Figure  1 as  EF  and GH.
    The data from these flight patterns and from a vertical spiral are  shown in
    Figures 3a, 3b, and 3c.  Maxima for NO and B    . occurred approximately  30  km
    downwind from point F; however, operator misjuagment  resulted  in the cross
    section of the plume being measured approximately 10  km downwind of where
    the morning NO maximum occurred.  By judging where sharp changes occur in
    pollution levels in Figures 3a and 3b, particularly B   . readings, it is
    possible to see that there is a parcel of air with higner primary pollutant
    levels within the urban plume that is approximately 44 km long and  15  km
    wide.  The existence of such a parcel could be explained by assuming that
    the city produces a large pulse of NO and particulate during the morning traf-
    fic rush, and that the parcel of air containing  these pollutants moves down-
    wind more or less intact.
    
         The morning vertical profile, Figure 3c, revealed a great deal of tempera-
    ture variability.  Two low-level inversions were present at approximately
    400-500 m and a series of inversions occurred above 750 m.  The pollutant
    profiles did not appear to be correlated to the  temperature profiles,  and  in
    general did not show a consistent pattern.
    
         Patterns FI and JK in Figure 1 were followed on  the afternoon  flight
    of July 18.  The data from these flights are plotted  in Figure 4a,  4b, and  4c.
    The ozone concentration in the urban plume reached a  maximum approximately
    50 km downwind of the starting point of the flight, point F.   At this  maximum,
    the ozone concentrations reached a level that was twice that seen in the
    morning flight at the positions of highest NO and B    . and was above  the
    federal standard of 0.08 ppm.  The maximum B    . occurred at the same  location
    as the maximum ozone readings; and the maximum B      level was approximately
    the same as seen in the morning flight.  The NO  IHB NO  maximum concentrations
    were about one-half to one-third lower than morning levels, and it  was no  longer
    possible to define distinct boundaries for the parcel of air which  was seen
                                          264
    

    -------
                                   -r 30
                                                                            -.30 Z
    _040T      V   X
                     94
                               9 2
                 TIME.HOURS(CST)
                  OISTANCE(km)        49
                                    E
    
                     3i
           1051    1050     1046    1042
    
                 TIMt HOURS(CST)
           0       DISTANCEIkm)        18
           H                        G
                                                               3b
               AXIAL PATTERN
         CROSS-SECTION  PATTERN
     Figure  3a.   Data,  collected the morn-
       ing of July  18,  1975,  from flight
             pattern  EF (Figure 1).
    Figure 3b.  Data, collected the morn-
      ing of July 18, 1975, from flight
            pattern GH (Figure 1).
                                         265
    

    -------
    z
    
    z
    UJ
    a
      1000 - -
    750 _.
      500 -.
      250
          000
               005
             03(PPM)
                     010
                         005
                            010
                          NO(PPM)
                                 H
    015 000    010
    
         NOX(PPM)
                                                 020
    20       30
      B SCATI10 4M ')
                                                                   200
        30 0
    TEMP(°C)
      Figure 3c.  Pollution data collected the morning of July 18,
                     spiral through urban plume (10:77-10:88 CST).
                                                                 1975, vertical
    during the morning flight.
    
         Comparing the maxima for individual pollutants can be misleading.   The
    pollutant burden can provide a better understanding of the quantities  of
    pollutants that have been produced.  For example, the maximum B    .  readings
    were about the same in the morning and afternoon flights; however,  the  volume
    of air in which these concentrations were distributed was much larger  in the
    afternoon, as indicated by the difference in plume widths shown  in  Figures  3b
    and 4b, and the difference in vertical profiles shown in Figures  3c and 4c.
    These differences indicate that there had in fact been a large production of
    particulate matter in the plume as it has moved away from the city.,  Similar
    consideration should be applied to the other pollutants in order  to get a
    proper picture of the plume impact on the surrounding rural  area.
    
         The vertical temperature profile through the plume during the  afternoon
    showed none of the temperature inversions present in the morning.   The  verti-
    cal pollutant profiles from the afternoon study were similar to  the morning
    profiles in that they revealed little in the way of a definable  pattern.
    
    August 3, 1975 (Afternoon)
    
         The wind on this date was from the north-northeast (Table 1)  and  the
    patterns shown in Figure 1 as LM and NO were flown during the early afternoon.
    The data are presented in Figures 5a, 5b, and 5c.  August 3  was  a Sunday, and
    this set of data provides a picture of the weekend urban plume which can be
    compared to the weekday plume characteristics in the other studies.  The maximum
    ozone concentrations in the plume (again levels above the federal  standard)
    were found 17 km downwind from the flight starting point, point  L.   As  seen
    in previous studies, the position of the maximum B   . readings  generally
    corresponds to the position of the maximum ozone ridings.   The  NO  readings on
                                         266
    

    -------
    006-r-
                                    -r*0
      070--
      050--
      400 -r
      36 0--
    < 320--
      28 0'
                                  T220
                                    - -20 0
                                    180  jr
                                        Q.
                                    - -16 0
      020 -r
              13 0     13 2      13 4
    
                TIME.HOURS(CST)
    
                 OISTANCE(km)
    
                     4a
                                 88
                                 I
                                                      020 T.
                                                    Z
    
                                                    t.  010
                                                      000 - •
                                                                                •^r 4 0
    
    
    
                                                                                      z
                                                                                      *
                                                                                -.30  o
                                                                                        U
                                                                                        C/l
                                                                                   --20  O
                                                    _ 060 -i-
                                                      050- -
                                                                                   -1-010
                                                                                         a.
                                                                                         o.
                                                                                   - - 005  o
                                                                                     000
                                                      34 OT
                                                      32 0--
                                                    = 300 +
                                                    4
                                                      28 0. .
                                                                                   --220
                                                                                   - -200
                                                                                   - -18 0
                                                                                     160
                                                      000
    14 0     13 9     13 8
    
       TIMt.HOURS(CST)
    
         DISTANCE(km)      37
                        J
            4b
             AXIAL  PATTERN
    
       Figure 4a.  Data,  collected  the
       afternoon of July  18, 1975,  from
        flight pattern  FI  (Figure 1).
                                                       CROSS-SECTION  PATTERN
    
                                               Figure  4b.   Data,  collected  the
                                               afternoon of July  18,1975, from
                                               flight  pattern JK  (Figure 1).
                                            267
    

    -------
      1000T-
      750- -
      500- -
          ObO
    100 000   006
         NOiPPM
                              010
    010        020 0?0 000  020   2 '
       NO),iPPMI    S02iPPM|
     30    3 b JO 0        30 0
    
    B-SC«T        IfMPl'C)
     Figure 4c.   Pollution data collected the afternoon of July 18, 1975, vertical
                     spiral through urban plume (14:27-14:45 CST).
    
    flight pattern LM were at the noise  level of the  instrument.   The  N0x  readings
    were somewhat elevated in the plume, and remarkably consistent throughout the
    entire flight.  The S02 readings -were elevated near the  farthest point  on the
    flight pattern, point M.  These high S02 levels are probably  clue to  the point
    sources along the Mississippi River  whose full impact  is better seen in the
    cross section flight pattern.
    
    
         The cross section of the plume  is extremely  interesting  in that it not
    only provides insight into the character of the urban  plume,  but also  insight
    into the effects of large point source plumes superimposed on the  urban plume.
    The data collected near point N (Figure 5b) show  high  SOg and N0x  readings.
    The most probable source of the 502  is the Portage des Sioux  power plant
    located north of the city and approximately 60 km from the point where  the
    measurements were made.  The Portage des Sioux plume could be observed  visually
    over the city approximately 30 km from the source heading toward the area
    where the measurements were made.  Further,, there are  no other point sources
    upwind capable of producing a plume  with the measured  concentrations and with
    a plume width of approximately 6-7 km (Figure 5b).  At the other end of this
    cross section flight pattern, point  0, high S02 levels were again  observed,
    as well as high B   ., and the highest ozone readings.   These high readings
    can be attributed to a number of point sources along the Mississippi River.
    The refinery complex at Wood River,  Illinois, the power  plant near Granite
    City, Illinois, and a brewery in St. Louis, Missouri,  were all  upwind  of point
    0.  All of the listed sources could  contribute to the  S02 arid particulate
    levels.  The refinery is a large source of hydrocarbons  and NO which  could
    have acted as precursors for the photochemical production of  ozone and  additional
    particulates.
    
         The vertical profile of the plume, Figure 5c, showed a temperature in-
    version layer at 850 m.  The inversion seemed to  have  little  effect  on  the
    pollutant profiles.  The pollutant levels remained fairly uniform  with  alti-
    tude.
                                          268
    

    -------
      000
      080-r-
      060--
                                   T 005
     :20.0- •
      too- -
                                    -- 20 0
    
                                   -.100
      015-,-
    f
      005- -
    
    
      000.
    13 6        13 5
     TIME.HOURS(CST)
    
    
      DISTANCE(km)
    
          5i
                                  134
                                   27
                                   M
              AXIAL PATTERN
     Figure  5a.   Data, collected August
      3,  1975,  from flight  pattern LM
                 (Figure 1).
                                                                             -i-30
                                                020 ...
      000
                                                         139
                 TIME HOURS(CST)
    
    
                  DISTANCE(km)
    
    
                      5b
    25
    0
         CROSS-SECTION  PATTERN
    Figure 5b.   Data, collected  August
     3,  1975,  from flight pattern  NO
                (Figure 1).
                                           269
    

    -------
      1000—
       055
            060
           03(PPM|
                 065
      005
    NO (PPM |
                                                010
    NOX(PPM)
      000
    S02(PPM)
                                                          HI-
    010 20
       B SCATIHI '
                                                                     3 0
    200   250
     TEMPfC)
         Figure 5c.  Pollution data collected August  3,  1975,  vertical  spiral
                        through urban plume  (14:65-14:97  CST).
    
    
    August 6, 1975 (Afternoon)
    
         Winds from the north-northeast caused pattern LP and  QR  to be  flown.
    The pattern with the plume, LP, showed that the maximum ozone concentration
    was 45 km downwind of the flight starting point (Figure 6a).  The highest
    B   .  values again occurred with the highest ozone levels.
     scat
    
         The cross section of the plume, pattern QR,  revealed  a well-defined
    urban plume with a width of about 30 km  (Figure 6b).  A slight depression  in
    ozone concentration was seen near point  R.  Correspondingly high concentrations
    of oxides of nitrogen occurred at the same location as the depression  in
    ozone.  The NO  were probably produced by a point source along the  Mississippi
    River.
    
         The vertical profile, Figure 6c, showed a low level temperature  inver-
    sion at 365 m.  A slight elevation in ozone and N0x concentration is  seen
    below the inversion but such a tendency  was not apparent for  the other pollu-
    tants.
    
                                       CONCLUSIONS
    
         This paper has reported the results of studies of the St. Louis  urban
    plume on four days during the summer of  1975.  Although the studies were
    done under a variety of meteorological conditions, several general  conclu-
    sions can be made.
    
         •    The St. Louis metropolitan area produces a well-defined urban plume
              that could be easily traced 100 km downwind of the  city.
    
         •    The St. Louis urban plume causes significant degradation  of the  air
              quality extending into rural areas downwind of the  city.  On July  15
              and 18 and August 3, 1975, maximum ozone readings in excess  of the
                                         270
    

    -------
      OOt T-
    s
    a.
    a.
      000--
                                    -.-30
                                   --20
      040
      240-,-'
      23 0--
                 -T-160
                                   --J40
      020-r
      010-
          128
    -I
           130
      TIME.HOURS(CST)
       DISTANCEIkm)
    
           6a
    
    AXIAL PATTERN
                                   13.2
                                  49
                                  P
                                                 100-1-
                                              • 0000- -*
                                                                 A
    
                                                                              -r 25 _-
                                                                              --20
                                                                                    I
                                                                                    a.
                                                                                    u
                                                                                    H-^
                                                                                    O.
                                      13 5      13 6      137
                                  Q      TIME HOURS(CST)     R
                                  0      DISTANCEikm)      33
    
                                               6b
    
                                 CROSS-SECTION PATTERN
      Figure 6a.  Data  collected August      Figure 6b.   Data collected August
       6,  1975, from flight pattern LP         6, 1975,  from flight pattern QR
                  (Figure  1).                               (Figure 1).
                                           271
    

    -------
    1000-r
    750- •
    500- -
    250.
         070   080
           03|PPM)
    005  000   005
      NQ(PPM)
    010    020    030 000       005
      NOX
    -------
              ozone and B   .  readings reached their highest values well downwind
              of the city^cat  ,
    
         •    Power plant plumes within the urban plume appeared to cause
              depletion of ozone in the area of impaction on the urban plume.
              The plume from the Portage des Sioux power plant was observed im-
              pacting within the St. Louis urban plume on two separate days, July
              15 and August 3, 1975.  Depletion of ozone was observed at distances
              up to 60 km from the power plant.
    
    DISCUSSION
    
         Davis et al. (1974) reported studies of the effects of power plants on
    ambient air quality in the Washington, D. C., area.  Depletion of ozone in
    plumes downwind of the power plants was found by Davis at distance <_ 24 km,
    and a net increase in ozone concentration relative to air surrounding the
    plume was found beyond 24 km.  The results reported in this work show de-
    pletion of ozone at 20 km from a power plant on July 15.  This agrees with
    Davis' work.  However, the data reported for August 3 revealed that the
    ozone depletion occurred to distances of 60 km, a significantly greater distance
    than reported by Davis.  The Portage des Sioux power plant investigated in
    this study burns only coal in a cyclo burner system which emits fairly high
    concentrations of NO.  The plant studied by Davis burned a fuel mixture of
    75% oil and 25% coal.  It is probable that the difference in combustion
    characteristics of these two plants could possibly explain the differences
    in effects of the power plant plumes.  The Portage des Sioux plant probably
    emits higher levels of NO than the plant studied by Davis and causes depletion
    effects of the plume to be seen for greater distances.
    
         White et al. (1976) reported results of measurements of ozone and light
    scattering aerosols in the St. Louis plume on one of the same days covered
    in this report.  The results and conclusions reported in this work are in
    essential agreement with those of White with one major exception.  White assumed
    that a quasi-Lagrangian interpretation could be made on the urban plume, and
    that transport and emission parameters changed so slowly that neighboring
    points in the plume could be reasonably compared.  Flux measurements were
    calculated based on this assumption.  It is felt that their assumption is  in
    error and validity of such flux calculations is open to question-  It is general-
    ly known from ground-based measurements that urban areas produce relatively
    high levels of pollutants during the morning and evening rush traffic periods.
    
         Demerjian et al. (1974) recently discussed this phenomenon in their review
    of photochemical smog formation.  The data in this report, collected during
    the morning of July 18, indicate that the St. Louis metropolitan area emitted
    a pulse of highly polluted air during the morning traffic period, as expected,
    and that this pulse was moving downwind within the plume.  Given that such a
    parcel of air existed within the plume, it cannot be assumed that adjacent
    points in the plume are comparable.  Quasi-Lagrangian assumptions cannot be
    made unless the size and position of such a parcel of air is carefully documented
    during the time period when the plume was studied.  White et al. made no such
    documentation.
                                         273
    

    -------
                                       REFERENCES
    
    Allen, P. W. 1973.   Regional  Air Pollution  Study  -  An  Overview.   Paper No.  73-21
         Proceedings of the 66th  Annual  Meeting, Air  Pollution  Control  Association.
    
    Davis, D. D., G. Smith, and 6.  Klauber,  1974.   Trace Gas  Analysis  of Power
         Plant Plumes via Aircraft  Measurement:  03,  NO ,  and SOa  Chemistry.
         Science 186, 733-736.
    
    Demerjian, K.,  J. Kerr, and J.  Cglvert.  1974.   The  Mechanism of  Photochemical
         Smog Formation.  Advances  in Environmental Science and Technology Vol.  4,
         1-262, John Wiley and  Sons, New York.
    
    EPA. 1975. Control  of Photochemical  Oxidants-Technical  Basis and Implications
         of Recent  Findings.   EPA-450/2-75-005.
    
    Hester, N., R.  Evans, C.  Fitzsimmons,  D.  Mage,  and  M.  Price 1975a.   Helicopter
         Platform Air Pollution Data, I.  The  RAPS  Program.   Paper  No.  75-40.4,
         Proceedings of the 68th  Annual  Meeting, Air  Pollution  Control  Association.
    
    Hester, N., R.  Evans, D.  Mage,  S. Pierett,  G.  Siple, and  J.  van  Ee.   1975b.
         Some Considerations  in Collecting Valid Data with  Airborne  Platforms.
         Proceedings, Speciality  Conference  on  Air Pollution  Measurement Accuracy
         as Relates to  Regulation Compliance, Speciality Conference, Air Pollution
         Control Association, New Orleans, Louisiana, October,  1975, pp 73-86.
    
    White, W., J. Anderson, D.  Blumenthal, R. Husar,  N. Gillani, S.  Fuller,
         W. Wilson.  1976.  Formation and  Transport of  Secondary Air Pollutants:
         Ozone and  Light Scattering Aerosols  in  St. Louis  Urban Plume.   Proceedings,
         171st National Meeting,  American  Chemical  Scoiety, New York,  New York.
         (In Press)
                                         274
    

    -------
                                                                               6-5
                                OZONE IN HAZY AIR MASSES
    
              R.  B. Husar, D. E. Patterson,  C.  C  .  Paley and N.  V.  Gillani*
    
    ABSTRACT
    
         A coie Atady o&  high ozone  conce,nttatiom>  in. a. synoptic tcale. hazy ait
    maf>& (blob] oval the.  e.a>>te.tn halfi  of,  the, U.S.  -it, te.potte.d.  The. data, bcue
    includes  (a) U.S. dJe.athe.t Smu.ce  Network &ot hoatly visibility obAdtvationt,
    (300 Atation*};  (b) the.  National Ax>  Scmpting Ne.twotk f,ot daily Aal&ate.  (60
    AtationA -in za&teAn U.S.);  and  (c)  the. SAR0AP data ba4e o^ EPA &on daily
    peafe ozone conce.nttation (90 Atationt -in -
    te.nce. and tsiantpofit o& a Aynopt^ic  Acate. hazy blob.  C onto at plotA oft ozone.
    alfto te.ve.al latge. ate.a6  u)ith e£eua,ted ozone le.ve.l&, uiho&e. locat-ion and spa-
    tial extent conAej>pond toaghly with tho&e. o& the. hazy btob&.  Long te.tm ob-
    &e.tvationA ofi  ozone, and  hazinu* at a tingle, station in St.  loud* 4now the.
    pte.vale.nce. ofi  high ozone. ie.veLt>  on hazy dayt.   Ba^ed on thi& ca&e. btudy, it
    i& not poAAible. to conclude. whethe.t Adl^ate. ^otmation it, enhanced by the.
             o^ e/euated  ozone  le.ve.1-^.
    
                                     INTRODUCTION
    
         In this paper, we report a  case  study of an episode of high ozone con-
    centrations in synoptic-scale hazy air masses over the eastern half of the
    United States.  In recent years, ozone concentrations well in excess of the
    ambient air quality standard (0.08 ppm)  have been observed in rural areas at
    distances of several  hundred kilometers  from known sources of ozone precur-
    sor gases (Coffey and Stasiuk, 1975).  Rural  ozone may be a product of at-
    mospheric reactions involving anthropogenic (White et al., 1976) as well as
    biogenic emissions, and  may also be due  to the  downward mixing of strato-
    spheric ozone.  The relative contributions of the various sources of rural
    ozone,  and the role of synoptic  meteorology,  are not quantitatively estab-
    lished.  High  rural ozone concentrations, however, have been observed most
    frequently inside large  slow-moving high pressure cells in midwestern and
    eastern U.S. (Ripperton  and Worth,  1973).
    
         The occurrence of large hazy  air masses  containing sulfate concentrations
    in excess of 20 yg/m3 have  also  been  reported recently (Hall et al., 1973;
    Husar et al., 1976).  The present  work was initiated to examine whether syn-
    optic scale hazy air  masses with high sulfate levels also contain high levels
    of ozone.   It was hoped  that certain  relationships could be found between
    ^Washington University,  St.  Louis,  Missouri.
    
                                         275
    

    -------
    these two noxious secondary pollutants which would shed some light on their
    origins.
    
         The method of analysis is based principally on inspection of contour
    plots of sulfates, ozone and ground visibility data over the eastern half
    of the U.S.  Air parcel trajectory analyses, surface wind data and local
    measurements of the pollutants in St.  Louis are also consulted.   The spatial
    and temporal density of the data base for national sulfate distribution is
    sparser than that for ozone.  However, hourly surface visibility observa-
    tions reported routinely from several  hundred weather stations have been
    used previously as an effective surrogate for sulfate data during air pol-
    lution episodes (Husar et al., 1976).
    
                              DATA BASE FOR THE ANALYSIS
    
         The following three sources of data have been utilized in this work.
    
    U.S. WEATHER SERVICE NETWORK FOR HOURLY OBSERVATIONS (SERVICE A)
    
         Values of ground level visual range and other weather parameters are
    recorded every hour at several hundred stations distributed over the U.S.
    The data from about 300 of these stations (Figure la) are available on mag-
    netic tapes supplied by the National Climatic Center, National Oceanic and
    Atmospheric Administration (NOAA).  The high spatial density of this net-
    work permits the meaningful use of computer contour plotting techniques.
    Using the visibility data, the spatial extent, the temporal evolution and
    the transport of hazy blobs* may be followed for several days by inspection
    of chronological visibility contour maps (Husar et al., 1976).  Noon visi-
    bilities were chosen to minimize the effect of early morning high humid-
    ities.   The noon relative humidity for inland stations  ranged between 50 and
    THE NATIONAL AIR SAMPLING NETWORK (EPA)  FOR SULFATE
    
         Hi-volume filter samples collected  over 24-hour periods by this network
    are routinely analyzed for sulfate.   The samples are collected every 12 days,
    simultaneously at all sampling locations.   For the present analysis, we were
    able to obtain sulfate data for about sixty NASN locations in the eastern
    half of the U.S.  The spatial distribution of these stations is shown in
    Figure Ib.  Isopleths of sulfate concentrations are plotted manually from
    the available data at 12-day intervals.
    
    
    THE SAROAD DATA BASE (EPA) FOR OZONE AND TOTAL OXIDANT
    
         Ozone and oxidant concentrations are recorded regularly at aerometric
    monitoring stations reporting to the U.S.  EPA.  Hourly average values are
    obtained from EPA's SAROAD data bank for 89 sites located in the eastern
    half of the U.S. (Figure Ic).  For each  station, the diurnal ozone pattern
    
    *In  the  context of this  report,  "blob"  is  used  synonymously with  "hazy air
    mass."
    
                                         276
    

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                   (a)                     (b)                 (c)
    
       Figure 1.  Geographical distribution and density of network stations:
                  (a) National Weather Service Network for visibility; (b) Na-
                  tional Air Sampling Network for sulfate; (c) EPA/SAROAD net-
                  work for ozone.
    
    was inspected and the daily peak concentration was chosen as the ozone level
    of the air mass.  Subsequently, contour plots were prepared for each day of
    the episode based on these peak observations.  Examples of data obtained by
    SAROAD stations are shown in Figure 6.   In the upper part of the figure, the
    hourly average ozone concentrations are shown at station No. 7 of the
    St. Louis city-county monitoring network.   The data exhibit the typical  di-
    urnal  pattern consisting of near-zero readings overnight and in the early
    morning, rising to a peak in the early afternoon followed by a drop in the
    evening hours.
    
         Although it is not clearly documented in the literature,  it is reason-
    able to assume that the low overnight concentrations are the direct conse-
    quence of physical and chemical removal processes that tend to scavenge
    ozone from the atmospheric surface layer.   It has been shown that the ozone
    concentration above the surface layer does not exhibit this diurnal pattern
    (Coffey and Stasiuk, 1975).  Coffey and Stasiuk (1975) also gave evidence
    that ozone measurements near the surface obtained during the convectively
    active noon hour are representative of the ozone concentrations in the air
    mass in the absence of positively or negatively interfering local sources.
    Thus,  the ozone concentration of the mixed layer air mass may be estimated
    from the envelope of the daily peak concentrations.
    
                                        RESULTS
    
         The relationship between ozone and haze is examined through a case
    study of a large hazy air mass that resided over the eastern U.S. for an
    estimated two weeks.   Successive contour maps of noon visibility (Figure 2)
    are plotted for every second day from June 25 through July 5,  1975.  Inspec-
    tion of the sequence of maps reveals that multi-state regions  are covered
    with a haze layer in which the noon visibility is less than 6  miles.   From
    long range trajectory calculations and surface wind information, it was
    determined that the air mass of June 25 within which the visibility was
    less than 6 miles was of maritime origin in the Gulf of Mexico.  This air
    mass had been transported in a northerly flow across Louisiana, Arkansas,
    
    
                                        277
    

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                                  JUNE 27, 1975
          JULY I, B75
        Figure 2.  Sequential contour plots of ground visibility at 1200 CST
                   (b  t = 3.92/visibility range).
    
    
    Illinois and Indiana.   Between June  25 and 27, a NNE trajectory prevailed
    in the southern states; but,  relative stagnation prevailed in the Great
    Lakes  region.  During  this stagnation, the air mass  became increasingly
    hazy.   Thereafter,  an  easterly flow  developed causing the hazy blob to  drift
    slowly westward,  passing over St.  Louis,  Missouri,  on June 28-29,  and con-
    tinuing across Missouri and Kansas (June  30), and then drifting into Iowa
    and Minnesota (July 1,2).
    
          The surface wind  pattern at  noon of  June 30 is shown in  Figure 3.
     Observe the  clockwise  circulation in  the  Great Lakes region.   By  July  3,
     the blob had circled over Lake Michigan continuing  its  residence  over  the
     high  pollutant emission  density regions of the northeast.   In  the next  two
     days,  however, a cold  Canadian front  advanced southward at a  relatively rapid
     pace,  sweeping the hazy  air  mass  ahead of it.   St.  Louis once  again experi-
     enced  substantially reduced  visibility on July 3-4  as the hazy air mass
     passed over  it.  By July 5,  visibility deteriorations to less  than 4 miles
     were  experienced in Atlanta,  Georgia, Birmingham, Alabama, and Tallahassee,
     Florida.   Air trajectory analysis confirmed  this southward motion of the  blob.
    
          During  the above  episode, sulfate data  were obtained arid  plotted  for
     June  23 and  July 5, 1975.  A  close  relationship  has been observed between
     the spatial  extent of  the hazy air  mass and  high sulfate concentrations as
     shown  in Figure 4.  On June  23, the blob  was located east of  Lake Erie
     where  sulfate concentrations  over 30  yg/m3 were  measured.   On  July 5,  both
     the haziness and high  sulfate levels  were reported  in the southeastern U. S.
     (Georgia and Alabama).   The  coincidence of hazy air masses and high sulfate
     concentrations on  these  two  days  confirms the utility of visibility obser-
     vations as a qualitative surrogate  for sulfates.
    
          Contour plots of  the daily maximum ozone concentrations  are  shown  in
    
    
                                         278
    

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                            JUN 38 
                       "/-
                       S.Y-
             , rr	
             ^  /  /,
       A  i
       y/ s
    
                                               "
      Figure 3.  Surface wind direction pattern at weather  stations  for 1200 CST
                 on June 30, 1975.
           JUNE 23, 1975  f \
                              JUNE 23, 1975
             \*
    
    SULFATE CCWC (ng/tn3)
    
    
     ^B 20 to 3O
     1771 10 to 20
                                                   JULY 5, 1975
                                                                      JULY 5, 1975
                                               EZ3 4 to 6
    
                                               IH 6 to 8
       Figure  4.   Comparison of contour plots of noon visibility and daily aver-
                  age  sulfate concentration for June 23 and July 5, 1975.
    
    
    Figure 5.  Inspection of  the corresponding  contour  plots  for ozone and
    visibility (Figures 5 and  2, respectively)  reveals  that the geographical
    location of high ozone  concentrations  roughly  corresponds to the  areas of
    low visibility (and high  sulfate).  As may  be  anticipated, however, the
    correlation with haziness  (low  visibility)  is  much  better for sulfate than
    for ozone.
    
         Contours of daily  maximum  ozone concentration  for June 25,  1975, show
    that an area of approximately 1000 square kilometers,  located halfway be-
    tween the Gulf of Mexico and the Great Lakes,  had ozone concentrations in
    excess of .08 ppm.  The air parcel trajectory  followed a  northerly course
    during that day.   It is worth noting that,  on  that  day, the haziness (Figure
    2) developed somewhat farther north (i.e. later  along  the trajectory) com-
    pared to the area of high  ozone levels.  The spatial extents of  ozone and
                                          279
    

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               JUNE 25
    
    
                                            i '..
                                             <-.  A
               JULY I
                                         JULY 3
                                                                    JULY 5
       OZONE CONC  (ppm)
    
       IB > 16
       • 12 to 16
       EZ2 .08 to 12
       CZI <08
    Figure 5.  Sequential contour plots of daily
                peak  ozone  concentration.
    haze areas roughly coincided on June 27 as the air mass stagnated.   During
    the following days of the episode, high ozone levels  (>0.08  ppm)  continued
    their presence in the same approximate region of the  U.S. where  the  haziness
    predominated.  As the hazy air mass moved to the south by July 5,  elevated
    ozone levels were comparatively suppressed immediately behind the  front,  but
    continued to be over .08 ppm farther to the north and west.
    
    
         The possible relationship between hazy air masses and high  ozone  con-
    centrations may also be studied by the analyses of long-term observations
    of visibility and ozone at fixed locations.  The lower part  of Figure  6
    shows the three-month variation of the extinction coefficient (bex^  =
    3.92/visual range).  The visibility data were recorded at a  St.  Louis  air-
    port.  The passage of the hazy blob observed previously over St.  Louis is
                                          280
    

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         25-
         20-
         15-
         10-
         05-
                                       OZONE
    ^~7Jfflllllfe  MtolMJI
                                 08
        150-
        .120-
        ~ 90-
        • 60-
         30 -}\
                   JUNE
                                         JULY
                                                              AUGUST
      Figure 6.  Comparison of long term observations of ozone and light extinc-
                tion coefficient, bext = 3.92/visibility, at an air monitoring
                station in St. Louis, Missouri.
    clearly shown by the two peaks  of  June  28-29 and July 3-4.  Comparison of
    peak ozone concentrations and visibility  data for June, July, and August
    1975 shows that ozone levels above the  standard roughly coincide with hazi-
    ness corresponding  to bexj- greater than 5.
    
                                      DISCUSSION
    
         The above data analysis provides  some  evidence  that  synoptic scale
    hazy air masses also contain elevated  ozone concentrations.  This evidence
    is based on only one case study,  and  is weaker  than  the observed corre-
    spondence between sulfate levels  and  haziness.  A possible  explanation for
    the simultaneous occurrence of  high ozone-haze-sulfate levels may be given
    on simple meteorological grounds:   in  stagnant  or slow-moving air masses,
    precursor gases for ozone and light-scattering  aerosol are  emitted and mix-
    ed, leading to an accumulation  of  these secondary pollutants due to the low
    ventilation coefficient.  It  is likely  that this mechanism  is the primary
    cause of synoptic scale air pollution  phenomena.  A  more  intriguing question
    is whether these two pollutants have  a  synergistic effect upon  each other's
    development.   Does  the presence of high ozone concentrations promote the
    oxidation of sulfur dioxide to  sulfate?
    
                                   ACKNOWLEDGEMENT
         This research  was  supported  by  the  U.S
    Environmental  Sciences  Research Laboratory,
    Carolina.  We  wish  to  express  our thanks  to
    the St.  Louis  County Health  Department.
    .  Environmental  Protection Agency,
     Research  Triangle Park, North
     W.E.  Wilson,  Jr., N. Turcu, and
                                     REFERENCES
    
     1.    Coffey,  P.E.  and  W.N.  Stasiuk.   Evidence  of Atmospheric Transport
          of Ozone into Urban  Areas.  Environmental  Science and Technology
          9(l):59-62,  Jan.  1975.
                                         281
    

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    2.   Hall, P.P. Jr., C.E.  Duchon,  I.E.  Lee and  R.R.  Hagan.   Long-Range
         Transport of Air Pollution:   A Case Study.   Monthly  Weather  Review
         101:404, Aug.  1970.
    
    3.   Husar, R.B., N.V.  Gillani,  J.D.  Husar,  C.C.  Paley  and  P.N. Turcu.
         Long-Range Transport  of Pollutants Observed  Through  Visibility
         Contour Maps,  Weather Maps  and Trajectory  Analysis.  Preprint, Third
         Symp. Atmos. Turb.,  Diff,  and Air  Quality, American  Metrological
         Society, Raleigh,  N.C., Oct.  1976.
    
    4.   Ripperton, L.A. and  J.J.B.  Worth.   Interstate  Oxone  Studies.   Second
         Joint Conf.  on Sensing of  Environmental  Pollutants,  Washington, D.C.,
         Dec.  1973.
                                        282
    

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               SESSION 7
     OZONE/OXIDANT TRANSPORT - II
    
      ChcuUunan:  A. P. Altshuller
    Environmental Protection Agency
                   283
    

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                                                                                 7-1
               THE  TRANSPORT OF PHOTOCHEMICAL SMOG ACROSS THE  SYDNEY  BASIN
    
                                 R.  Hyde and G. S. Hawke*
    
    ABSTRACT
    
         A cloAAifiication  ofi ozone,  tnaczA and AuA^ace. wind ne.condA  fan Sydney
    AhowA that high conce.ntnationA  can OCCUA -in both, moaning dnainage. filow and
    a&teAnoon Ae.abAe.e.ze.A.   SuA&ace.  wind tAajuctoAieJ* dusting the.  manning confainm
    the. importance,  ofi  cold ain drainage. in adve.cting ox.idant pAe.cuAAoAi> £nom
    inland AouAceA  towandA the. coaAt.   k^t&inoon tnaje.ctonieA  Ahow  that polluted
    aiA iA tnanAponte.d back inland  acnoAA the. baAin into a>ie.at> deA-ignatzd O4
          induAtsiiat and population growth ce.n&ie.&.
         Me.aAuAe.me.ntA  o^ the. ve.Atical AtAactuAe. o& Mind and tzmpeAotuAe. oveA
    Sydne.y indicate, that the. ^ofimation oft photoche,mical Amog  duAing  the. manning
    iA infi£ue.nce.d by thA&e. distinct £ayeAt> beJ.ow the. top o^ the. Au.bAide.nce.
    inveAAion.  JheJ>e.  conAiAt ofi a AhaJULow tocai dAainage.  fatow appAox.imateI.ij 100
    m de.e.p, which lateA meAg&A with a ne.gional drainage. ^Low  and  &oAm£  a weJUl-
    (noted tayeA 200-300 m  deep.   JkiA layeA iA capped by an inveAAion and main-
    tainA an appnoximateJly constant de.pth fan AaveAai houAA beJLow the. gAadie.nt
    Mind &tow.  OveA thit,  peAiod,  ozone. conce.ntAationA continue, to incAe.aAe. and
    only de.cAe.aAe. with the. onAival o& a Ae.abme.ze. on whe.n  AuAfiace. he.ati.ng dutAoyA
    the. capping inveAAion  allowing the. Qn.adie.nt wind to ne.ach the. gnoand.
    
                                       INTRODUCTION
    
         Sydney is located within a coastal basin at latitude 35°S on the east
    coast of Australia.  Details of the topography, given  in  Figure  1,  show the
    overall basin bounded  by a plateau 150 m high to the north and another in
    the south, with the Blue Mountains to the west.  Minor ridges, extending
    north from Campbelltown and northwest from Botany Bay, divide the region
    into the Hawkesbury Basin to the west, the Liverpool Basin to the southwest,
    and the Parramatta River Valley to the east.
    
         Unlike Los Angeles, Sydney does not experience semi-permanent maritime
    inversions, but comes  under the influence of subsidence inversions  associated
    with migratory anticyclones moving from west to east across Australia.  On
    some occasions, the passage of these high-pressure systems is blocked and
    they remain stationary over the Tasman Sea east of Sydney, causing  high oxidant
    *Macquarie  University,  North Ryde, N.S.W., Australia,  2113.
    
    
                                          285
    

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    286
    

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    episodes.  But in general each anticyclone causes high oxidant concentrations
    only on one or two days at a time.  During the oxidant season, from October
    1974 to April 1975, hourly-mean ozone concentrations exceeded 0.10 ppm in
    Sydney on approximately one day in six (Hyde & Hawke, 1976).
    
    
         The two dominant mesoscale wind systems affecting the Sydney region are,
    firstly, nocturnal and early-morning drainage flows and, secondly, afternoon
    seabreezes.  A preliminary examination of wind and temperature data, for
    some days when high oxidant concentrations were measured, indicated that ozone
    could occur in either the drainage flow or Seabreeze systems (Hawke and
    Iverach, 1974).  This was later confirmed by Hyde and Hawke (1976).
    
         This work is being continued as part of the contribution of Macquarie
    University to the Sydney Oxidant Study, a multi-disciplinary project investi-
    gating the formation of photochemical smog in the Sydney Basin, funded by the
    New South Wales State Pollution Control Commission.  Our present paper is
    divided into two parts; the first section presents a climatology of surface-
    wind trajectories within drainage flows and seabreezes on days with high oxidant
    concentrations and classifies variations in ozone concentrations throughout
    the day in terms of the meso-meteorological conditions.  The second part of
    the paper deals with the vertical structure of the atmosphere above Sydney
    and its relationship to concentrations of ozone during the morning.
    
    
                      SURFACE WINDFLOW AND CONCENTRATIONS OF OZONE
    
         In our earlier paper we showed that high concentrations of ozone occurred
    predominantly during the morning drainage flow.  However, some of the days
    studied in that paper had maximum concentrations of ozone occurring within
    or after the arrival of the afternoon Seabreeze.  The analysis has now been
    extended in order to determine the influence of meteorological conditions
    on the transport of oxidants and their precursors across the Sydney Basin.
    
    CLASSIFICATION OF OZONE CONCENTRATIONS
    
         The 69 days when hourly concentrations of ozone were at least 0.10 ppm
    between January 1974 and June 1975 have been divided into three main cate-
    gories according to the variations of ozone concentrations throughout the
    day.   Characteristics of the different categories are briefly described be-
    low and an example of each is given in Figure 2.
    
    Type Al  - morning increase in ozone concentrations terminated by the onset of
              the gradient wind at ground level.
    
    Type A2 - morning increase in ozone concentrations terminated by the arrival
              of the Seabreeze.
    
    Type B  - as for type Al  but followed by an abrupt increase in ozone concen-
              trations coinciding with the arrival  of the Seabreeze.
    
    Type C  - ozone concentrations continued to increase for up to two hours
              after the arrival  of the Seabreeze.
    
    
                                        287
    

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                                                          >3
                                                             KA.ft«.\cvC^L.\.£.
    Figure 2.  Variation  in ozone concentrations  during the day in  the Sydney Basin
                                   in four  categories.
                                          288
    

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         The frequency of occurrence of these different categories at the three
    monitoring stations in the Sydney region, given in Table 1, shows that maxi-
    mum ozone concentrations occur more frequently during the morning,  especially
    near the coast.  An explanation of meteorological  conditions associated with
    this type of ozone pattern is given in the next section.  Type C days occur
    relatively infrequently and have not yet been analyzed in detail.  However,
    Type B days do occur on a significant number of occasions, especially inland.
       TABLE 1.  NUMBER OF DAYS WHEN MAXIMUM OZONE CONCENTRATIONS WERE AT LEAST
    	0.10 PPM, IN FOUR CATEGORIES, FOR JAN. 1974 - JUNE 1975	
    
                                 LOCATION AND DISTANCE INLAND (KM)	
    TYPE
                Marrickville, 10
    Lidcombe,  21
    Wentworthville, 29
    Al
    A2
    B
    C
    TOTAL
    21
    16
    14
    5
    56
    8
    12
    18
    2
    40
    5
    13
    16
    2
    36
    
         The exact cause of high concentrations of ozone within afternoon sea-
    breezes has not yet been investigated but may be caused either by:
    
         •    a slowly moving seabreeze-front, with ozone forming within the sea-
              breeze circulation as a result of precursor emissions near the coast
              (Lyons and Olsson, 1973);
    
         •    air containing oxidant precursors moving out to sea in the morning
              drainage flow, undergoing photochemical reactions and then being
              advected back inland with the Seabreeze (Anlauf et al., 1975); or
    
         •    air advected from the Botany Bay region.
    
    SURFACE WIND TRAJECTORIES
    
         Although the above categorization of ozone concentration changes describe
    only conditions at the three fixed monitoring sites, surface-wind trajectories
    through these stations can be used to identify both source and receptor
    regions for photochemical smog in the Sydney Basin.  Surface-wind trajectories
    through both Marrickville and Lidcombe on the 69 days described in the preceding
    subsection were calculated using the method of Wendell (1972) as follows:
    
         (1)  backwards in time until midnight the previous day for hours when
              the ozone concentration reached at least 0.10 ppm before the onset
              of strong gradient winds or arrival of the afternoon Seabreeze, and
    
         (2)  forwards in time until midnight or until the trajectory moved outside
              the Sydney region for hours when ozone concentrations were at least
              0.10 ppm in the afternoon Seabreeze.
                                        289
    

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         The Sydney region was divided into 5 km grid squares  and the number of
    trajectories passing through each square was counted and converted into a
    percentage frequency of the total number of trajectories.   The results of
    this analysis for (1) and (2) above at Mam'ckville and Lidcombe are given
    in Figure 3.  The 5 per cent frequency category for trajectories backwards
    from Lidcombe has been omitted here because of the small number of trajectories
    involved.
    
         At the moment we do not know what proportion of pollutants within the
    morning drainage flow are subsequently incorporated into the overall sea-
    breeze circulation.  Angel! et al.  (1976) found that tetroons released within
    the morning drainage flow in the Los Angeles Basin were subsequently advected
    back inland with the afternoon Seabreeze.  Whether or not  a similar recircu-
    lation occurs in the Sydney basin is not yet known, and for this reason for-
    ward and backward trajectories in Figure 3 have been considered separately.
    
         This analysis of surface wind trajectories confirms that polluted air-
    masses arriving at both Marrickville and Lidcombe during the morning have
    been advected there by westerly drainage flow from source regions to the
    northwest.  The most common afternoon trajectory of polluted air within sea-
    breezes is towards the southwest of the Sydney Basin, including the Liver-
    pool-Campbell town region.  Unfortunately this region is designated as the
    major population growth centre for the next few decades (State Planning
    Authority of N.S.W., 1968, 1973).  Several papers which discuss the advect-
    ion of ozone across the Los Angeles basin show that the highest concentrations
    occur 50 km downwind of the major source regions within air advected inland
    with the afternoon Seabreeze (Hanna 1975, Tiao et al., 1975, Blurnenthal,
    1976).  The possible implications for Sydney are clear and illustrate the need
    to consider the incursion of photochemical smog when planning future growth
    centres.
    
                 VERTICAL STRUCTURE OF THE LOWER ATMOSPHERE OVER SYDNEY
    
         The other part of our work in the Sydney Oxidant Study concerns the
    vertical structure of wind and temperature on days with high concentrations
    of ozone.  This information is necessary  to explain variations in oxidant
    concentrations on different days and as meteorological input for photochemical
    smog models.
    
         Wind profiles are obtained using a recording single-theodolite pilot-
    balloon system developed by Hawke, and temperatures up to 300 m using a low-
    level tethersonde (Linacre 1976).  These systems have been developed because
    it is not possible to obtain a resolution of less than 300 m from routine
    six-hourly pilot-balloon ascents at Mascot and the nearest routine radiosonde
    stations are approximately 130 km away to the north and south of Sydney.
    
    OBSERVATIONS ON APRIL 29, 1975
    
         During the 1975-76 oxidant season most of our wind and temperature
    profiles were obtained between sunrise and noon, in order to examine the
    influence of drainage and gradient wind flows on the morning increase of
    oxidant concentration.  One such set of observations was made on April 29,
    
                                         290
    

    -------An error occurred while trying to OCR this image.
    

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    1975, and shows stratification typical  of the  atmosphere  over Sydney during
    the morning on high oxidant days.   On that occasion,  simultaneous  wind and
    temperature profiles were obtained at least every  thirty  minutes between 0500
    and 1000 and are given in Figure 4.   Details of the  synoptic  situation, ozone
    concentrations at Lidcombe and Marrickville, and the  0900 radiosonde ascent
    from Williamtown (130 km to the north)  are given in  Figure 5.
    
    Macroscale Hind and Temperature Structure
    
         The synoptic map is typical of many high  oxidant days in Sydney, with a
    high pressure system centred over the Tasman Sea (Hawke and Iverach, 1974).
    At Williamtown the temperature profile  shows a well-defined structure below
    700 m with:
         •    a slightly stable layer between the surface and 250 m (a-b),
    
         •    a strong inversion layer between 250 m and 400 m (b-c),  and
    
         •    a weaker inversion layer between 400 m and 700 m (c-d).
    
         Wind profiles in Figure 4a have been divided into three periods  of time
    corresponding to changes in thermal  structure within the lower atmosphere.
    However certain features are common  to each set of measurements and are
    listed below:
    
         (1)  a surface layer approximately 200 m deep, with a wind speed of 2-3
              ms-1 from the north to northwest,
    
         (2)  a region of marked wind direction shear above the surface layer with
              a turning point at 250 m,  and
    
         (3)  a layer between 250 m and  700 m having a 6 ms"1 northerly wind and
              turning points in wind direction shear at 400 m and 700  m.
    
         Layer (1) above  has approximately the same height at layer a-b  in Figure
    5c and the turning points at 400 and 700 m in (3) occur at similar heights
    to points c and d.  These features describe the broadscale vertical structure
    and form part of the model  to be developed below.
    
    Mesoscale Wind and Temperature Structure
    
         On a smaller scale Figures 4a and 4b show that the low-level  wind and
    temperature structure on this day can be divided into three stages of develop-
    ment, as follows:
    
         (1)  Before sunrise (0635 a.m.) - during this period there was a strong
              surface inversion below 250 m with a westerly flow between  60 m and
              200 m, above a shallow northwesterly flow,
    
         (2)  0635 to 0845 a.m. - over this period the surface northwesterly layer
              heated up and formed a well-mixed layer approximately 100 m deep,
    
                                         292
    

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                                             3 oo
                                             loo
                                                                           l«
    Figure 4.  Wind and temperature profiles  at  Silverwater on April  29, 1975,
                                         293
    

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          (3)   0845  to  1000  a.m. - between 0845 and 0900 a.m. the depth of the well-
               mixed  surface  layer increased from 100 m to 200 m.  Subsequent wind
               and temperature profiles show this layer remaining 200 m deep until
               at least  1000.
     No  temperature profiles were made after 1000, but wind profiles at 1030
     and  1100 show that the region of wind shear at the top of the surface layer
     had  gone.  Surface wind records over the Sydney region on this day show a
     change in wind direction from northwesterly to northerly and increase in wind
     speed between 1030 and 1130, and correspond to the period when ozone concen-
     trations at Lidcombe and Marrickville started to decrease (Figure 5b).
    
     MODEL
    
     Vertical Structure
    
         The structure of wind and temperature profiles on April 29, 1975, (and
     many other similar observations over a wide range of gradient wind velocities
     obtained during the past two years) suggests that during the morning there can
     be three distinct layers over Sydney, below the top of the subsidence inver-
     sion.  These are shown schematically in Figure 6 where:
    
         •    'a1  is a local drainage flow down the Parramatta River valley,
              typically 80-150 m deep and contained by the region of high ground
              to the north of the river, and is a sub-layer of
    
         •    'b', a regional  drainage flow 200-300 m deep over the whole Sydney
              Basin.
    
         •    'c'  is the gradient wind flow below the top of the subsidence inversion.
    
    Time Development
    
         Before sunrise on a cloudless morning, drainage flow occurs within a
    ground-based inversion, caused partly by radiative cooling and partly by the
    advection of cold air from the Blue Mountains to the west.  After sunrise (at
    time ti in Figure 6), surface heating allows the local  drainage-flow to form a
    well-mixed layer underneath the still thermally-stable region.   Then at time
    t2 there is a  sudden increase in mixing depth, signifying the end of local
    drainage-flow  to form a well-mixed layer 200-300 m deep.   Dividing the drainage
    wind into local  and regional  flows can explain a characteristic feature of
    many wind profiles measured at Silverwater.  These show a surface layer about
    100 m deep suddenly doubling in depth sometime during the morning.   Obser-
    vations show that after this deepening the regional  drainage flow maintains
    a constant depth during subsequent surface heating and is separated from the
    gradient wind  above by a sharp inversion layer.   The gradient wind will
    reach the surface once surface heating has eroded this  inversion (at time t3).
    When this occurs, there is  usually an increase in mixing  depth  and a change
    in windspeed and wind direction.   This causes the sudden  reduction in ozone
    concentrations typical  of  type Al  days.
    
    
                                        294
    

    -------
    Figure 5.  April 29, 1975:   (a) Surface synoptic weather  map.   (b)  Concentrations
       of ozone at Lidcombe and  Marrickville.   (c)  0900  temperature  soundings  from
                         Williamtown, plotted  on  a  T-0 diagram.
             oC
                                               ClZftrcntuT
    
    
    
    
    
    
    
    
    *t
    
    
    \
    
    
    
    
    to? af (2t«,oOftu -wta,,4fcc.e F^.u
    /'
    
    •
    
    1
    
    -------
         Figure 6 also shows the Seabreeze onset at time t^,  separated from t3 by
    a period of time At which will  depend on both surface heating and the gradient-
    wind speed and direction.  At is an important variable, which equals zero if
    the Seabreeze arrives at a location before the breakdown  of regional drainage-
    flow.  Under these conditions the day would become type A2.
    
    
    Implications for the Formation of Oxidants in the Sydney  Basin
    
         The partition of drainage-flow into two types has important implications
    on the dispersion of oxidant precursors emitted into the  atmosphere during
    the morning.  Between sunrise and time t2, precursors emitted close to the
    ground are advected towards the east in the well-mixed local drainage-flow.
    At the same time, precursors emitted from higher chimneys will be carried
    downwind in a stable layer and not experience much lateral or vertical diffusion.
    On occasions when the gradient wind inhibits regional drainage-flow, these
    emissions from elevated sources are often advected in a direction different
    from that taken by the surface emissions.  After time t2, precursors from
    both surface and elevated sources undergo photochemical reactions within a
    well-mixed layer 200-300 m deep.  So subsequent concentrations of ozone
    during the morning largely depend on the time interval between t2 and t3.
    This time interval in turn depends on the strength of the inversion layer
    b-c in Figure 5c and would be influenced by the presence  of any cloud during
    the morning which can reduce the rate of surface heating  and so delay the
    breakdown of regional drainage flow.  Therefore, although the right synoptic
    conditions may be present, the concentrations of ozone on any particular
    day may be very sensitive to variations in the length of  time between the
    breakdown of the local drainage flow and the onset of either the gradient
    wind or afternoon Seabreeze.
    
                                       CONCLUSIONS
    
         The material presented in this paper is intended to  illustrate the im-
    portance of both horizontal transport and vertical structure of the lower
    atmosphere in the photochemical smog problem in Sydney.  A knowledge of the
    vertical structure of wind and temperatures is necessary  to identify the
    characteristic depths of layers which can inhibit the vertical diffusion of
    pollutants.  This information can then be used in the future for forecasting
    days with high concentrations of ozone and as meterologica'l input to photo-
    chemical smog models.  The horizontal transport of photochemical smog within
    mesoscale wind systems must be considered when planning future urban growth
    centres so as to avoid sitting them downwind of major oxidant source regions.
    
                                    ACKNOWLEDGEMENTS
    
         The authors are grateful to the State Pollution Control Commission
    for permission to publish ozone data appearing in this paper, to the Bureau
    of Meteorology for access to meteorological observations, and to Associate
    Professor E. T. Linacre for his comments during the preparation of the paper.
    Thanks are also due to Mrs. Campbell Gibson who typed the manuscript.
         This work was carried out under a grant from the State Pollution
    Control  Commission as part of the Sydney Oxidant Study.   The purchase and
    
                                         296
    

    -------
    maintenance of 3 anemometers in the Botany Bay region was  funded by a grant
    from the Botany Bay Project Committee.
    
                                       REFERENCES
    
    ANGELL, J. K., C. R. DICKSON, AND W. H. HOECKER.  Tetroon Trajectories in
    the Los Angeles Basin Defining the Source of Air Reaching San Bernadino-
    Riverside Area in Late Afternoon.  J. Appl. Met., 15:197-204, 1976.
    
    ANLAUF, K. G., M. A. LUSIS, H. A. WIEBE, AND R. D. S. STEVENS.  High Ozone
    Concentrations Measured in the Vicinity of Toronto, Canada.  Atmos. Environ.,
    9:1137-1139, 1975.
    
    BLUMENTHAL, D. L.  Distribution and Transport of Ozone in the South Coast
    Air Basin.  Calif. Air Environ., 6 (1):4-10, 1975.
    
    HANNA, S. R.  Modelling Smog Along the Los Angeles-Palm Springs Trajectory.
    N.O.A.A. Environ. Res. Lab., Atmos. Turbulence and Diffusion Lab., Contri-
    bution No. 75/4, 1975.
    
    HAWKE, G. S. AND D. IVERACH.  A Study of High Photochemical Pollution Days
    in Sydney, N.S.W.  Atmos.  Environ., 8:597-608.
    
    HYDE, R. AND G. S. HAWKE.   A Preliminary Analysis of the Influence of Meteor-
    ology on Ozone Levels in Sydney.  Smog '76 Conference, Clean Air Soc. of
    Aust. and N. Z., N.S. W. branch, Sydney, February 1976.
    
    LINACRE, E. T.  Low-Level  Temperature Soundings with a Radiosonde on a Tethered
    Balloon.  1976.  (in preparation)
    
    LYONS, W. A. AND L. E. OLSSON.  Detailed Mesometeorological Studies of Air
    Pollution Dispersion in the Chicago Lake Breeze.  Mon. Wea. Rev., 101:387-403,
    1973.
    
    STATE PLANNING AUTHORITY OF N. S. W.  Sydney Region:  Outline Plan 1970-2000
    A.D., March 1968.
    
    STATE PLANNING AUTHORITY OF N. S. W.  Population Projections for N. S. W.
    1971 to 2000,  November 1973.
    
    TIAO, G. C., G. E. P. BOX, AND W. J. HAMMING.  Analysis of Los Angeles Photo-
    chemical Smog  Data:  A Statistical  Overview.  J. Air Poll.  Control Assoc.
    25:260-268, 1975.
    
    WENDELL, L. L.  Mesoscale Wind Fields and Transport Estimates Determined from
    a Network of Wind Towers.   Mon. Wea. Rev.  100:565-578, 1972.
                                          297
    

    -------
                                                                                7-2
                           OXIDANT  LEVELS  IN  ALBERTA AIRSHEDS
    
                                       H. S. Sandhu*
    
    ABSTRACT
    
         Some. o£ the. oJot qaatity and me.te.oA.ologtcal data. gatkeA.e.d -in AtbeAta dat-
    ing tke. pabt tu)a ye.au ^on Delected da.y&  and time, ofi tke. ye.oA. u> fie.posite.d.
    CompafuAon be.tuie.e.n the. obteAvcd and calculated valaeA ofi ozone. hcu> A.e.ve,ale.d
    tke. odc.uAAe.nce. 0& pkotoc.ke.mlc.ai fie.actionf>.   PoAA-ible. AOUA.CZA con&iibuting to
    ozone. &oA.mation and tA.ant>poAt ate.  btu.e.&iy olit>coined.
    
                                       INTRODUCTION
    
         Most of the information available to date on photochemical oxidant
    pollution and its control is derived from the laboratory and field studies
    carried out in the United States  (1-3).   Over the years attempts have been
    made to apply this knowledge to northern  climates.   It has been argued that
    photochemical oxidants should not  pose a  pollution problem at higher latitudes
    because of reduced solar radiation and lower temperatures.  There is evi-
    dence now that these generalizations are  in  error (4,5).
    
         In Canada, no other cities of a size comparable to Edmonton (53° 34'N
    113° 35'W, elevation 676 m) and Calgary (51° 17'N 114°W, elevation 1080 m)
    with a population of about 500,000 each are  situated as far north.  The Pro-
    vince of Alberta, Figure 1, is  one of  the richest natural resource provinces
    in Canada.  Because of mankind's dependence  on energy, large resource develop-
    ments such as the recovery of oil  from Alberta Oil  Sands are taking place or
    will take place farther to the  north in the  coming years.  It is essential
    for environmental information to be gathered and analysed.  Predictions should
    be made at the extremes of the  meteorological conditions prevalent in the
    area instead of using conclusions  based on different climatic conditions.
    Some aspe'cts of photochemical air  pollution  in Alberta are briefly discussed
    in this paper.
    
                                 RESULTS AND  DISCUSSION
    
         Alberta Department of the  Environment expanded the monitoring network
    from one to three stations in each of  the two cities in 1974 and started
    using instruments that employ the  chemiluminescence method for detecting
    nitric oxide (NO), nitrogen dioxide (N02), and ozone (03), the flame ionisa-
    tion technique for detecting hydrocarbons (HC) and the infrared absorption
    *Alberta  Department  of the Environment, Edmonton, Canada.
    
    
                                          299
    

    -------
                               IZO
                                                  TMONTANA
                                                            110°
                           Figure  1.   The  Province  of  Alberta.
    
    
    method for carbon monoxide (CO).   Meteorological observations are made by
    Atmospheric Environment Service,  Environment Canada, employing standard
    instruments at various stations in Alberta.  Air monitoring reports for
    Edmonton and Calgary for the year 1974 have been published (6).
    
         Temperature and air pollutants recorded on a typical cold day in spring
    (sunny, 7.5 cm of snow) are given in Table 1.   Average wind speeds stayed
    around 16 km per hour (10 miles per hour).  Observed 03 values given in this
    table are a clear indication of its photochemical  production and transport
    at these latitudes under reduced  temperatures.   Rawinsonde observations recorded
    at an upper air sounding station  49 km outside  the city showed that the
    morning temperature inversion top was partially lifted by solar heating as the
    day progressed.  Steady-state concentrations of 03 were computed from the
    mechanism,
    
              N02  + sunlight  ->  NO + 0
    
              0   + 02 + M    ->  03 + M
    
              03  + NO        ->  02 + N02
    
    using theoretical  values of kl (clear sky approximation)  for these latitudes,
    
              k2 = 1.7 x 1013 (cm6 mole-2  sec'1) exp (+2100 (cal  mole-^/RT) (7)
                                         300
    

    -------
           TABLE  1.    TEMPERATURE AND AVERAGE AIR POLLUTANT CONCENTRATIONS
           MEASURED  AT THE  EDMONTON DOWNTOWN MONITORING STATION ON APRIL 1
                                         1975
       Variable     Hour   09     10     11     12    13    14    15    16    17
       Temp.              -16   -14   -13   -13   -11   - 9   - 8   - 8   - 8
       TO
    (PPhm)
    NO
    (pphm)
    °3
    (pphm)
    
    943433347
    
    255667765
    
    
    and
    
              k3 = 6.0 x 1011 (cm3 mole'1 sec'1) exp (-2460 (cal  mole'^/RT (8).
    
    These values are lower by a factor of two when compared to midday values of
    03 given in Table 1.  This discrepancy could be due to the combined effects
    of factors such as advection of background 03 increased albedo of the surface,
    production of 03 through other precursors or the production of 03 through
    heterogeneous reactions.  A preference for any one factor would be misleading
    at this time.  The observed peak value of 7 pphm is above the Alberta Standard
    and Canadian Objective (maximum desirable) which is 5 pphm.  Though rare, such
    situations could prevail up to three or four days at this time of the year
    depending on the intensity and dynamics of the air mass.
    
         During summer months in 1975, 03 levels above 5 pphm were recorded on
    almost all sunny days in Edmonton.  Levels observed on three  days during July
    1975 are given in Table 2.  Since non-urban 03 measurements are not available
    for this time period it is premature to interpret these data.
    
         Central Alberta, the area between Edmonton and Calgary,  is a region of
    high convective cloud activity and it experiences many thundershowers and
    hailstorms during summer months.  To date, no one has made measurements of
    surface 03 present in rural  areas during summer months.  A monitoring program
    is planned to observe non-urban 03 levels and estimate 03 produced through
    this natural phenomenon.
    
         To obtain information on the background levels of reactive pollutants
    at these northern latitudes, a three week monitoring study was carried out
    in Edmonton in September 1975.  A typical set of data is given in Table 3.
    
    
                                         301
    

    -------
            TABLE  2.   AVERAGE OZONE CONCENTRATIONS (PPHM) OBSERVED AT
            THE  EDMONTON DOWNTOWN MONITORING STATION DURING JULY 1975
    
    Day
    4
    24
    28
    Hour
    
    
    
    08 09 10
    1 3 10
    1 3 5
    666
    11
    7
    6
    7
    12 13 14 15
    10 11 16 9
    7778
    8 11 13 19
    16 17 18
    455
    667
    18 10 7
    19
    5
    10
    6
    
    TABLE 3. TEMPERATURE, WIND SPEED AND AVERAGE AIR POLLUTANT
    CONCENTRATIONS MEASURED AT THE EDMONTON DOWNTOWN MONITORING
    STATION ON SEPTEMBER 24, 1975*
    
    Hour
    07
    08
    09
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    Temp
    TO
    11
    12
    14
    18
    20
    22
    24
    23
    24
    24
    23
    23
    21
    18
    N02
    (ppnm)
    6 (2)
    6 (2)
    7 (2)
    6 (2)
    6 (2)
    5 (1)
    7 (1)
    7 (2)
    7 (2)
    9 (2)
    9 (2)
    11 (2)
    15 (3)
    15 (2)
    NO
    (pphm)
    40 (2)
    55 (2)
    16 (2)
    11 (1)
    6 (1)
    5 (1)
    6 (1)
    5 (1)
    5 (1)
    5 (1)
    5 (1)
    12 (2)
    24 (2)
    23 (3)
    (pp3m)
    0 (1)
    0 (1)
    0 (1)
    1 (2)
    3 (2)
    4 (3)
    4 (3)
    5 (3)
    5 (3)
    5 (3)
    4 (3)
    2 (2)
    0 (2)
    0 (2)
    Reactive
    Hydrocarbons
    (pptm)
    11
    24
    11
    6
    6
    6
    6
    6
    4
    5
    6
    7
    5
    6
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
               * The values in parenthesis are measured at Kavanagh, 45 km
    south of Edmonton city limits.
                                         302
    

    -------
    Average wind speed on this day was 6.5 km per hour "{4 miles per hour).  To
    the author's knowledge, background air pollutant levels shown in this table are
    the first reliable measurements outside a major urban center in Canada that is
    this far north.  During this period background 03 levels varied between 1-3 pphm
    on sunny days, peaking around midday.  The levels of reactive HC in Alberta
    cities are relatively small compared to those in other major cities at the
    present time.  The relationship of NO to 63 (Table 3) in the urban and non-
    urban air is quite interesting in that NO is the main molecule that reacts
    with urban 03.
    
         Meteorological and air quality data for the summer of 1976 is not avail-
    able yet in the reduced and manageable form.  However, monitored data for
    Edmonton, Calgary, and Medicine Hat (50° Ol'N, 110° 43'W, elevation 719 m) on
    July 25, 1976, are given in Tables 4 and 5.  July 25 was a typical hot summer
    day with more than 14 hours of sunshine.  The values of 03 recorded at Medicine
    Hat are typical background 03 values.  Residential monitoring stations in
    both Edmonton and Calgary recorded generally higher 03 concentrations as com-
    pared to downtown monitoring stations.  The hourly N02/N0 ratio around midday
    is higher in Calgary than in Edmonton, but 03 values are higher in Edmonton.
    A complete analysis will be carried out after all the data for 1976 becomes
    available.
    
    
                    TABLE 4.   SOME METEOROLOGICAL VARIABLES OBSERVED AT
                    THREE MONITORING STATIONS IN ALBERTA ON JULY 25, 1976
      Variable                    Edmonton         Calgary          Medicine Hat
    Sunshine (hours)
    Max. Temp. (°C)
    Max. Windspeed (km/hour)
    and Direction
    14.7
    26.7
    19
    Southwest
    15.2
    28.7
    20
    North
    14.3
    28.4
    
    -
      Precipitation (mm)              0               0                trace
                                     CONCLUSIONS
    
         Ozone is formed through photochemical reactions of air pollutants present
    in the major urban airsheds of Alberta.  Typical  background 03 concentrations
    are in the range 1-3 pphm.  Some observations suggest that the precursors for
    03 production are advected to the cities.  Oxidant/ozone concentrations are
    expected to stay below the provincial standard of 5 pphm in winter months,
    but will exceed the standard during summer months on sunny days.
    
                                  ACKNOWLEDGEMENTS
    
         The author thanks the Research Secretariat staff for helpful  discussions
    and the Air Quality Branch staff for the help in  acquiring the needed data.
    
    
                                         303
    

    -------
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    -------
                                 REFERENCES
    
    Altshuller, A. P. and J. Bufalini.   Photochemical  Aspects of Air Pollution:
    A Review.  Environ. Sci. Technol.  5:39,  1971.
    
    Pitts, J. N., Jr. and B. J. Finlayson.   Mechanisms of Photochemical  Air
    Pollution.  Angewandte Chemie.   14:1, 1975.
    
    Demerjian, K. L., J. A.  Kerr and J.  6.  Calvert.   The Mechanisms of
    Photochemical Smog Formation.  Adv.  Environ.  Sci.  Technol.  4:1, 1975.
    
    National Research Council  of Canada, Associate Committee on Scientific
    Criteria for Environmental Quality  Report NRCC No. 14096.  Photochemical
    Air Pollution:  Formation, Transport and Effects,  1975.   224 pp.  Also
    note other references in this report.
    
    Sandhu, H. S.  A Study of Photochemical  Air Pollutants in the Urban
    Airsheds of Edmonton and Calgary.   Alberta Environment,  Edmonton, 1975.
    155 pp.
    
    Annual Air Monitoring Reports for the Cities  of Edmonton and Calgary.
    Alberta Environment, 1974.  33 pp.  each.
    
    Johnston, H. S.   Gas Phase Reaction  Kinetics  of Neutral  Oxygen Species.
    National Bureau  of Standards Report  NSRDS 20,  1968.
    
    Clyne, M. A. A., B. A. Thrush and R. P.  Wayne.  Kinetics of the Chemi-
    luminiscent Reaction between Nitric  Oxide and  Ozone.  Trans.  Farad.
    Soc. 60:359, 1964.
                                   305
    

    -------
                                                                                 7-3
                     AN INVESTIGATION OF  LONG-RANGE TRANSPORT OF OZONE
                      ACROSS THE MIDWESTERN  AND  EASTERN UNITED STATES
    
         G.  T.  Wolff, P. J. Lioy, G. D. Wight, R.  E. Meyers, and R. T. Cederwall*
    
     ABSTRACT
          Long-siange. tnanApotit o& ozone. acAo&&  the. mtdweAteAn and e.a&teJin U. S.
         4.nveAtigate.d by anaiyz-ing dcuJty ozone.  -U,opte^th ma.pt> and. comparing them
    to  metwiotog-icat map4 and aJJi pa/icz-t &ia.j fan the, peju.od ApfcUL  12-
    23,  1976.   Thib peJiiod won, chaA.acteAize.d by the. px.eAe.nce. oft a tatiQe. hlgh-
    pfizAAutie. &yt>tem which pti.odu.ctd W4.deAptie.ad  violation* o$ the. ozone. t>tandatidi>
    OA  we££ e.d to
    produce the. dalty ozone, map-4.  Move.me.nt  o{ atie.af> ofa high ozone. c.once.ntA.atA.onA
    c.oM.e.Aponde.d to the. move.me.nt o& the. high psiUALLfie. £yt>te.m.  Actual,
    acAo44 the^>e. ane,aA ^ t>uppofite.d by &iaje.ctoiy anatyA^A.  VatiLy
    map4 weAe. ati>o pfio,pajiq.d and the.y Au@ge.At that aAeai OjJ tow
    ge.ne.siatty co4.ncA.de. w
    -------
    parcels had passed over industrialized and urban areas of the midwest, the
    authors suggested that the midwest could be a significant source region
    for the ozone entering the Corridor.   The data presented in this paper
    examine this hypothesis.   In addition, daily maps containing visibility
    isopleths are compared to the ozone isopleths.  Husar, and long et al.
    attempted to use visibility as tracers for sulfates (9,10).  The study
    reported in this paper employed this  technique in an attempt to track the
    movement of areas containing high concentrations of ozone.
    
                                       METHODOLOGY
    
         In September 1975, Connecticut hosted a meeting for state officials
    from EPA Regions I, II, III, and V on ozone transport and hydrocarbon  control
    strategies.   At this meeting, a task  force was established to gather,  dissem-
    inate, and analyze ozone  data from the monitoring networks of the partici-
    pating states.   The ozone data presented in this paper were obtained through
    the task force.
    
         Selection  of individual sites for inclusion in this analysis was  based
    on obtaining a  uniform geographical distribution and avoiding the presence
    of local interferring sources.  In some cases, it was impossible to satisfy
    the second criteria and local anomalies in ozone concentrations resulted.
    For most of the states near the East  Coast, this problem was eliminated by
    employing smoothing techniques.  In the western sections of the study  area,
    this was not possible because many of the sites are located in downtown urban
    areas.  As a result, the  ozone concentrations surrounding these areas  may
    actually be higher.  In addition, anomalies may occur due to calibration
    variations.   The task force, however, has established a quality assurance
    program to minimize these variations.
    
         Weather maps were obtained from  the National  Weather Service.   The air
    parcel trajectories were  developed at Brookhaven National Laboratories, and
    the method has  been discussed previously (8).
    
         Visibility isopleth  maps were developed from data obtained every  three
    hours by the National Weather Service.  Husar, in his analysis, used noon-
    time visibility readings  (9).  This approach resulted in local inconsisten-
    cies due to the occurrence of isolated storms and ground fog which produced
    visibilities not representative of the surrounding areas.  In an attempt to
    overcome these  difficulties, the isopleths presented here were based on the
    lowest recorded daily visibility in the absence of ground fog, precipitation,
    and a dew point depression of two degrees Fahrenheit or less,.  If these
    conditions persisted throughout the day at a particular site, the data were
    not used.
    
                                 RESULTS  AND DISCUSSION
    
         A high pressure system, which moved out of Canada on April 10 and 11,
    was centered over Lake Michigan on the morning of April 12 (Figure la).  On
    the afternoon of April 12, the first  ozone readings within the high pressure
    system in excess of the National Ambient Air Quality Standard (NAAQS=0.08
    ppm) were detected in Indiana and Ohio.  Ozone levels in excess of 0.06
    
                                         308
    

    -------
    ppm were generally confined to these two states also.
    
         By the morning of the 13th, the high was centered over the Ohio-West
    Virginia border (Figure Ib).  Ozone levels exceeding 0.06 ppm now extended
    from western Indiana eastward into New Jersey and areas exceeding 0.08 ppm
    were observed in Ohio and New Jersey.  This was in contrast to only one area
    being above the NAAQS on April 12 (Ohio).  Air parcel trajectories terminat-
    ing on April 13 indicate that the air over Ohio and Indiana on April  12 was
    advected to the East Coast of the Mid-Atlantic states by the afternoon and
    evening of April 13 (Figure 2b).
    
         From April 14 to April 16, the center of the high pressure system
    continued to move southeastward and by the morning of April 16, it was
    centered off the coast of North Carolina (Figures Ic-e).  The trajectories
    for the same period indicate that air parcels in the western Midwest
    (Illinois) were moving north-northeastward (Figures 2b-d).   During this
    time, the 0.06 ppm isopleth moved northward from northern Illinois on
    April 13 to northern Wisconsin on April  16.  The 0.08 ppm isopleth now
    extended in a band from Indiana to New Jersey.  Trajectories from the Ohio
    area during the same period exhibited a  more defined westerly component
    toward New Jersey.  As a result, by April 16, the 0.06 ppm and 0.08 ppm
    isopleths covered most of the northeast  from Maine to Virginia and
    Massachusetts to Virginia, respectively.
    
         On April 17 (Figures If and 2f), both the 0.06 ppm and the 0.08 ppm
    isopleths began to contract in the western Midwest as a cold front over
    western Illinois began to move eastward.  In the eastern sections, the
    trajectories on April  16 continued to move east-northeastward and, on
    April 17, the 0.06 ppm isopleth extended through northern New Hampshire.
    
         The pattern observed on April 17 changed little on April 18 (Figure
    Ig).  The cold front moved slowly eastward into Indiana.  Continued north-
    ward movement of the isopleths ceased, however, as a stationary east-west
    front prevented it from moving into northern Maine.  Trajectories from
    Richmond, Virginia, on April 17 and April 18 (Figures 2f-g) indicated that
    little horizontal  advection occurred over the Middle Atlantic States.  The
    same pattern persisted into April 19 as  the cold front moved into Ohio and
    contraction of the 0.06 ppm isopleth continued (Figures 1 and 2h).
    
         The eastward movement of the cold front across the northern part of the
    region greatly increased between April 18 and 19 (Figure Ih).  Over southern
    sections, the front was considerably slower and by the morning of April 20,
    it was oriented on a southwest-northeast plane from southern Indiana to
    southern Maine.  The northern edge of both of the isopleths generally
    corresponded with the position of the front.  Trajectories  on April 20
    (Figure 2h) further illustrate the air flow resulting from the frontal
    movement.
    
         Cyclogenesis on April 20 and 21 changed the flow patterns considerably
    by April 21 (Figure Ij).  As the low pressure system intensified over the
    Great Lakes, the predominantly westerly  flow across the East Coast shifted
    to a southeasterly flow.  This shift was demonstrated by the trajectories
    
    
                                         309
    

    -------
    la:  April  12
    Ic:  April  14
              le:  April 16
    Ib:  April  13
    Id:  April  15
          If: April  17
        Figure 1 a-f. The accumulation and transport of ozone, April 12-17.
                               310
    

    -------
    Ig:  April 18
    li:  April  20
    Ih:  April 19
    Ij :  April  21
                                           ^  0.06 ppm
    
    
    
                                           £.  0. 08 ppm
    Ik:  April  22
    
    
    
        Figure 1 g-k.  The accumulation and transport of ozone, April  18-22,
                                311
    

    -------
     2a: April  12
    2b:April
                                     1900
     2c:  April 14 (Chi.=0700)     2d:April  15  (Rich.=0700)
     2e:  April  16                     2f:  April  17
    Figure 2 a-f.  Backward air parcel trajectories for Chicago, Columbus, Boston,
    Richmond, and New York, April
       unless otherwise stated.
         position 12 hours ago.
     12-17.  All trajectories terminate at 1300 hours
     (Position key:  1 = position 6 hours ago, 2 =
    3 = position 18 hours
      24 hours ago.)
    
           312
         ago, and 4 = position
    

    -------
    2g:  April  18
    2h:  April 19
    2i:  April 20
    2j:   April  21
                            2k:  April 22
    Figure 2 g-k.  Backward air parcel trajectories for Chicago, Columbus,  Boston,
    Richmond, and New York, April 18-22.  All trajectories terminate at 1300 hours
       unless otherwise stated.  (Position key:   1 = position 6 hours ago, 2 =
              position 12 hours ago, 3 = position 18 hours ago, and 4 =
                             position 24 hours  ago.)
                                     313
    

    -------
    3a: April  12
    3b:  April  14
    3c:  April 16
    3d:  April 19
                                              KEY
    
                                               8-10 miles
                                           PSPI-*  7 miles
                                            8&i     mi .Let*
     3e:  April 21
       Figure 3 a-e.  Visibility recorded during the high ozone concentration
                          period of April 1976.
                                 314
    

    -------
    on April 21 while the trajectories on April 22 showed a pronounced southernly
    flow (Figures 2i and j).  This shift resulted in advection of the 0.06 ppm
    isopleth northward, but because of the cloud cover and precioitation
    associated with this flow, the 0.08 ppm isopleth remained confined to an
    area with partly sunny skies centered around New Jersey.
    
         On April 22, the low continued to move northeastward, while the cold
    front moved rapidly toward the Atlantic Ocean (Figure Ib).  The trailing
    edge of the 0.06 ppm isopleth is shown moving off the Coast.
         The visibilities for the same period are shown in Figures 3a-f.  There
    are considerable geographical similarities between the areas of low
    visibility and high ozone from April 12-19.  However, as the winds shifted
    on April 20 and 21 and the ozone levels decreased, the visibilities did not
    change substantially.  This was probably due to the moisture associated
    with the southeasterly flow.
    
                                       CONCLUSIONS
    
         The above analysis illustrates transport of photochemical air pollu-
    tion from the midwestern United States to the East Coast.   Trajectory
    analyses also suggest that transport of photochemical air pollution from
    the Southern states (south of Virginia and Kentucky) to the Mid-Atlantic
    States also occurred between April 17 and 19.
    
         The movements of the area of high ozone concentrations corresponded
    extremely well with the movements of the high pressure system as well as
    with the advance and retreat of frontal systems near the perimeter of the
    high pressure system.
    
         Visibility maps may be a valuable technique in tracing ozone transport
    under certain conditions.  A significant correspondence between the areas
    of high ozone and the areas of low visibility occurred during most of the
    study period.  Toward the end of the period, as the high pressure system
    weakened and moisture was advected into the area via an on-shore circu-
    lation, the relationship became less established.
    
         At the present time, daily ozone isopleth maps are being developed
    for the entire summer of 1976.  The techniques used in this report will
    be employed on this data.  Current efforts are also being undertaken to
    refine the selection and presentation of the visibility data.  In the
    present research we have only examined the daily maximum ozone concen-
    tration, subsequent studies will include analysis  of ozone during other
    time periods.  In addition, the possibility of stratospheric injection of
    ozone is being investigated by employing isentropic analysis (11).
    
    
                                     ACKNOWLEDGEMENTS
    
          The  authors  wish  to express  their gratitude  to  all of the  members
     of the  Moodus Data  Sharing  and  Analysis Committee for  providing the ozone
     data  used in this report.   The  authors also  thank Messrs.  Michael  Anderson,
    
                                         315
    

    -------
    James Oliver, William Simpson, Jerry Bujancius of the Connecticut Depart-
    ment of Environmental Protection, Richard Taylor of the New York State
    Department of Environmental  Control, and Konrad Wisniewski and William
    Edwards of the Interstate Sanitation Commission for their assistance in
    data collection and analysis.
    
                                     REFERENCES
    1.   Coffey, P.E. and W.N. Stasiuk, Jr.  Evidence of Atmospheric Transport
         of Ozone into Urban Areas.  Environmental Science and Technology.,
         9(l):59-62, 1975.
    
    2.   Wolff, G.T., W.N. Stasiuk, Jr., P.E. Coffey and R.E. Pasceri. Aerial
         Ozone Measurements over New Jersey, New York and Connecticut.  In:
         Proceedings of the 68th Annual Meeting of the Air Pollution Control
         Association, Boston, Mass., 1975.   paper 75-586.
    
    3.   Bach, Jr., W.D.  Investigation of Ozone and Ozone Precursor Concentra-
         tions at Non-Urban Locations in the Eastern U.S.  - Phase II:  Meteorolog-
         ical Analysis.  EPA-450/3-74-034-a, U.S. EPA, Research Triangle Park,
         N.C., 1975.  144 pp.
    
    4.   Wolff, G.T.  Preliminary  Investigation of the Photochemical Oxidant
         Problem in the N.J.-N.Y.-Conn. A.Q.C.R. Interstate Sanitation
         Commission N.Y., N.Y., 1974. 69 pp.
    
    5.   Rubin, R.A., L. Bruckman and J. Magyar.  Ozone Transport.  In:  Pro-
         ceedings of the 68th Annual Meeting of the Air Pollution Control
         Association, Boston, Mass., 1975.  paper 75-07.1.
    
    6.   Cleveland, W.S., B. Kleiner, J.E.  McRae and J.L.  Warner,  Photo-
         chemical Air Pollution:  Transport from the New York City Area
         into Connecticut and Massachusetts.  Science, 191:179-181, 1976.
    
    7.   Wolff, G.T., P.J. Lioy, G.D. Wight and R.E. Pasceri.  An Aerial
         Investigation of Photochemical Oxidants over the Eastern Mid-
         Atlantic States.  In:  Proceedings of EPA Symposium on Ozone
         Transport, Research Triangle Park, N.C., 1976(In Press).
    
    8.   Wolff, G.T., P.J. Lioy, R.E. Meyers, R.T. Cederwall, G.D.. Wight
         R.E. Pasceri and R.S. Taylor.  Anatomy of Two Ozone Transport Episodes
         in the Washington, D.C. to Boston, Mass. Corridor.  Presented at the
         10th Annual Meeting of the Mid-Atlantic Amer. Chem. Soc., Phil.,
         Pa., 1976  (also submitted for publication).
    
    9.   Husar, R.B., J.D. Husar, N.V. Gillani, S.B. Fuller, W.H. White, J.A.
         Anderson, W.M. Vaughan and W.E. Wilson, Jr.  Pollutant Flow Rate
         Measurements in Large Plumes:  Sulfur Budget in Power Plant and Area
         Source Plumes in the St. Louis Region..  Presented at the 172nd
         National Amer. Chem. Soc. Meeting, N.Y., 1976.
    
    
                                         316
    

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    10.    long,  E.Y.,  G.M.  Hidy,  T.F.  Lavery,  and F.  Berlander.   Regional  and
          Local  Aspects of Atmospheric Sulfate in the Northeast  Quadrant of
          the U.S.  In:   Reprints  3rd Symposium on Atmospheric Turbulence
          Diffusion and Air Quality, American  Meteorological  Society,  Raleigh,
          N.C.,  1976.
    
    11.    Danielson, E.F.  Transport and Diffusion of Stratospheric Radioactivity
          based on Synoptic Hemispheric Analyses of Potential Vorticity.  NYO-
          3317-3, Atomic Energy Commission, Washington, D.C., Nov.  1967.
                                         317
    

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                                                                                7-4
                       OXIDANT AND  PRECURSOR  TRANSPORT SIMULATION
                STUDIES IN THE RESEARCH TRIANGLE  INSTITUTE SMOG CHAMBERS
    
                  J. E. Sickles,  II,  L. A.  Ripperton,  and W.  C. Eaton*
    
    ABSTRACT
    
         Tke ge.neMition oft ozone,  undeA *lmalated  condition* o{, poU.ata.nt &ian*-
    pont wa* *tadie.* -in a *y*te.m  of, fiou/i,  11  cub^c meteA., oatdoon. *mog ckambeA*.
    CkambeA contraction wa* o$ 5 mil FEP  Te.{,lon   on an aluminum fitLame..  Simula-
    tion o-d tnan*poKt MO* accompll*ke.d by  iwiadiating fie,actant* fan tkA.e.e day*
    with *untight and by dilating the. content*  a$ tke. chamber*.  The. initial
    change. o& nonmetkane. kyd?ioc.aAbon wa*  1  to 10  pant* peA million c.anbon o& a
    AaAAogate. uAban miztuAz; tkz  initial nitsiogzn oxA.de.*' ckange wo* 0.10 to 1.0
    ppm.  Tkti, tLe*alte.d tn initial  nonme.tkane. kydtocatbon to OK*.doJ> ofi n^tA.oge.n
    natio* o{, 7 to 1Q.  W-itkoat tke. addition  oft A.e.actant* afat&i tke. initial ckaAge.,
    tke. *e.cond~ and tivuid-day c.ke.mtc.at *y*te.m*  -in tke ckambeA* generated ozone
    donce.n&iation6 gieateA than tke. National  Ambient AiA Qaality Standard fafi
    pkotocke.mlc.al oxldant.  Tke. analogy be.tMe.en tke. chemical bzhavlon. oft ckambeA.
    simulation* and nonu/iban high ozone.  (  >O.OS ppm} *y*te.m* me.a&asie.d In the. &le.ld
    i* good.
    
                                       INTRODUCTION
    
         The Research Triangle  Institute's outdoor smog chamber facility is shown
    in Figure 1.  The system is composed  of 4 outdoor chambers (each 27 cubic
    meters in volume) made of 5 mil FEP Teflon on aluminum frames.  Each chamber
    has its own air cleaning system to oxidize hydrocarbons (HC) and remove oxides
    of nitrogen (NO ).
    
         The study reported here  was conducted during July and August of 1975
    under Environmental Protection  Agency  sponsorship.  The purpose was to study
    the behavior of ozone (03) concentration  under simulated conditions of trans-
    port of oxidants and their precursors  downwind from urban environs.  To simu-
    late movement from the cities,  chemical pollutant systems were irradiated
    for multiple daylight periods and subjected to a period of dilution with clean
    air.  Data are reported for the three  24-hour dilution rates:  0.0% (i.e.,
    batch), 77.5%, and 95%.  After  24 hours of dilution, the chambers were operated
    in a batch mode with no additional dilution.
    
         Initial reactant charges were 1  to 10  parts per million carbon (ppmC)
    of a surrogate urban mixture  and 0.1  to 1.0 ppm of NO  of which 20% was nitro-
    gen dioxide (N02).  The nonmethane hydrocarbon (NMHC)xto NO  ratios were chosen
    to be from 7 to 20.                                         x
     *Research  Triangle Institute, Research Triangle Park,  North  Carolina.
    
                                           319
    

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                         Figure  1.  RTI Smog Chamber Facility.
    
                                       DISCUSSION
    
         The results of the study have been summarized in a series of tables similar
    to Table 1.   The first 4 columns  after the data and chamber number provide
    information  about the behavior of the system on the first day.  For this series
    of runs, the 24-hour dilution rate was 95% and it  was begun at the time of
    NO  crossover (at about 0830).  In chamber 1, the  NMHC charge was about 7
    ppmC and the NO  was about 1.0 ppm with a  ratio of 7.  Maximum 03 concentra-
    tion in Charnberxl was about 1.1  ppm the first day.  The next column indicates
    whether the  following data are from the second or  third day of irradiation.
    The N0x concentrations at sunrise were in  the parts per billion (ppb) range.
    The second-  and third-day NMHC/NOx ratios  were high; for the whole set of
    experiments  they ranged from 22 to over 250.  Gas  chromatographic analysis
    of the HC remaining on the second and third day showed a preponderance of
    alkanes and  aromatic compounds with alkenes virtually exhausted except for a
    few tens of  ppb of ethylene that  usually remained.
    
         The maximum 03 concentrations obtained on the second and third days were
    in most cases (in all cases in Table 1) above the  National Ambient Air Quali-
    ty Standard  (NAAQS) for photochemical oxidarit.  The net 03 concentrations
    generated (i.e., the difference between the morning minima and the afternoon
    maxima) were also almost always greater than the NAAQS despite extremely low
    NO  concentrations.
      X
    
         Table 2 represents another type of summary and analysis of the 03-genera-
    tive data from the second and third days of irradiation.  Both the NO  data
    and the NMHC/NOx ratios have been stratified by numerical range and tfie net
    03 concentrations associated with a particular combination have been listed
    in the appropriate cell.  Averages of individual cells, vertical  columns,
    and horizontal rows, are indicated.  Although not  presented, the  same treat-
                                          320
    

    -------An error occurred while trying to OCR this image.
    

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         TABLE 2.   NET OZONE GENERATED ON  SECOND AND  THIRD  DAYS  OF  IRRADIATION
               AS A FUNCTION OF OXIDES OF  NITROGEN  AND  NONMETHANE HYDRO-
                            CARBON/OXIDES  OF NITROGEN RATIO
    
    NMHC NOY
    NOX ppmC Range ppb 1-5 6-8
    Range ppm
    0-49
    
    
    .165
    50-99 .201 .201 *.124 .128
    avg. *.131 avg.
    
    
    
    
    
    .235
    100-199 *.152 .140 .263 .189
    *.217 avg. *.250 avg.
    *.153 *.105
    *.123 *.257
    *.054 *.068
    .163
    >200 .076 .147
    .206 avg.
    .172
    .173
    .129
    *.125
    Avg. .147 Avg. .149 Avg. .171
    
    9 - 14
    
    .195 .164
    .115 avq .
    *.182
    
    .312 .214
    .256 avq.
    .230
    .214
    *.190
    *.119
    *.177
    .123 .134
    .094 avq.
    .033
    *.285
    
    
    
    
    
    
    
    
    Avg. .180
    
    15
    
    .181
    .154
    
    
    .365
    .300
    .197
    .371
    *.344
    
    
    .150
    .135
    *.238
    *.228
    
    
    
    
    
    
    
    
    Avg.
    
    - 53
    
    .168
    avg.
    
    
    .315
    avg.
    
    
    
    
    
    .188
    avg.
    
    
    
    
    
    
    
    
    
    
    .241
    
       Indicates 3rd-Day Values
         A term, fossil 03, has been coined to denote 03 generated in urban en-
    virons which is transported over unspecified distances downwind.   To investi-
    gate this phenomena, the decay of 03 in spent, non-03-generating  systems was
    examined from both chamber and field studies.   Nighttime half-lives of 03 were
    calculated for non-dilution chamber operation  and are presented in Table 3.
    Maximum 03 levels of the previous day are shown and half-lives assuming first
                                         322
    

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                                                        O AVERAGE 0, MAXIMA
                                                        • AVERAGE 0,  MINIMA
                                                  O     OAVERAGE AO,
                                K>      20      30      40
    
                                   OXIDES OF NITR06EN,   ppb
                                                               SO
    Figure  2.   Average  maxima,  minima, and  A03 concentrations as  a function of
                N0x concentrations  at sunrise on the  second and  third days  of
                irradiation.
                     .60i
                     .801-
                     .40
                     .30
                     .201
                      .101-
    O AVERAGE 0, MAXIMA
    • AVERAGE 0, MINIMA
    D AVERAGE  AOj
                              0.60       1.00      1.50     2.00
    
                                            NMHC. ppm
                                                              2.50
                                                                      3.00
     Figure  3.  Average  maxima,  minima,  and AQ3 concentrations  as a function of
                 nonmethane hydrocarbon concentrations  on the  second and  third
                 days  of irradiation.
                                            323
    

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    0.40 -
                                                      O AVERAGE  0,  MAXIMA
                                                      • AVERAGE  AO,
                                        100      160      200      250
                                        NMHC/NOX   , ppmC/ ppm
                                                            900
    Figure  4.  Average maxima  andA03 as  a function  of nonmethane  hydrocarbon  to
                oxides of nitrogen ratio.
                 W
                 \2
              E OB
              Q.
              O.
                04
                0.2
                0.0
       • August 13 - Batch 01 Dilution
                  03 Minimum  0.53 ppm
                  03 Maximum  0.72 ppm
                  A03       0.20 ppm
       A August 9 - 77% Dilution
                  03 Minimum  0.10 ppm
                  03 Maximum  0.40 ppm
                  A03       0.30 ppm
    I July ?•"- - 95% Dilution
            03 Minimum 0.02 ppm
                                                              03 Maximum
                                                              A03
                     0.?9 ppm
                     0.26 ppm
                                                        A A
                  -  I  I   I  I* I*I«I«UI*I  I   I
                                            I
                     0800 0400 OtOO 0800  WOO  ItOO  1400  1600 1800 2000  2tOO  2400
                                          TIME  ( HOURS - EOT)
     Figure 5.   Ozone  profiles over  second-day irradiations for same  initial
                  conditions and different dilutions  in Chamber  1.
                                             324
    

    -------
    order decay were calculated using the 0200 and 0500 hours concentrations.
    The table shows the 0200 hours concentrations and the calculated half-lives.
    The tabulated half-lives have been corrected for dark-phase clean chamber 03
    decay.  Of the values calculated, 17 are below 20 hours, 5 are below 60 hours,
    and two are rather large, 265 and 450 hours.  Data from two field studies may
    be used to obtain rough estimates of the dark phase 03 half-life.  A series of
    vertical 03 concentration profiles taken with an aircraft on August 1, 1974,
    at Wilmington, Ohio, are shown in Figure 6.  If it is assumed that the profile
    at 0700 on August 2 was the same as that at 0700 on August 1, then an assumed
    first-order decay from 1700 August 1 to 0700 August 2 suggests an 03 half-
    life of 29.5 hours.  Ozone measurements collected aloft (from 1800 June 8,
    1976, to 0200 June 9, 1976) during the second flight of the DaVinci balloon.
    suggest a half-life of 16 to 34 hours.
                                  0.09     0.075      0.10
                                         05. ppm
    0.126
                 Figure 6.   Vertical  ozone soundings, August 1, 1974,
                                   Wilmington,  Ohio.
    
    
         With half-lives of 20 to 30 hours, the amount of 03 left over on the
    following morning can provide a high minimum on which to build a high maximum
    for the first day.  With half-lives of 20 to 30 hours, however, a parcel of
    fossil 03 cannot maintain high concentrations for more than a day or two without
    augmenting synthesis.
    
         Figures 7, 8, and 9 may be employed to compare field measurements with
    second- and third-day smog chamber data.  Figure 7 depicts diurnal curves
    drawn from hourly 03 averages at three Ohio stations in the summer of 1974.
    The maxima are between 0.07 and 0.08 ppm, indicating that many of the indi-
                                         325
    

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              TABLE 3.  DARK PHASE OZONE HALF-LIVES IN SMOG CHAMBER RUNS
    
    Date
    July 24
    July 30
    August 6
    August 10
    August 13
    August 14
    Experimental Chamber Max [03] Previous [03] at:
    Type Number Day ppm 0200 ppm
    Dilution
    95% *
    Initiated at
    1700
    Dilution
    95% Initi-
    ated at NOX
    Crossover
    Dilution 77%
    Initiated at
    NOX Cross-
    over
    Dilution 77%
    Initiated at
    NOX Cross-
    over
    Batch
    
    
    
    Batch
    
    
    
    1
    2
    3
    4
    1
    2
    3
    4
    1
    2
    3
    4
    1
    2
    3
    4
    1
    2
    3
    4
    1
    2
    3
    4
    0.185
    0.138
    0.119
    0.089
    0.286
    0.212
    0.214
    0.175
    0.479
    0.366
    0.350
    0.214
    0.400
    0.293
    0.288
    0.179
    1.378
    0.886
    0.997
    0.549
    0.724
    0.525
    0.786
    0.336
    0.066
    0.048
    0.038
    0.025
    0.102
    0.085
    0.076
    0.083
    0.311
    0.243
    0.213
    0.109
    0.218
    0.175
    0.150
    0.109
    0.776
    0.561
    0.567
    0.415
    0.422
    0.333
    0.352
    0.252
    Half-Life
    (t1/2) hrs
    4.3
    3.6
    11.6
    13.3
    6.4
    6.2
    7.4
    7.8
    14.9
    11.6
    10.0
    7.1
    16.6
    14.2
    19.2
    14.2
    33.5
    42.9
    50.3
    265.4
    119.9
    27.2
    54.5
    449.6
    
      *Mechanical dilution had been terminated prior to the time periods chosen
       for half-life calculations.
    vidual concentrations making up the hourly averages were over the NAA^S.  The
    time of maxima at these rural  stations was shifted more toward sundown than
    that typically observed in an  urban atmosphere.   Also the slope of the build-
    up side of the diurnal rural 03 curve is steeper than the 03-destructive side.
    Generally, this is not the case in urban atmospheres where freshly emitted
    pollutants (e.g. auto exhaust  in evening rushhour traffic) act as 03-destructive
    agents and cause the sharp drop on the destructive side of the diurnal urban
    03 profile.
                                         326
    

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                0.0* r
                                                     • MCCONNELSVILLE
                                                     o WOOSTER
                                                     • WILMINGTON
                0.00
                  OTOO  OMO  1100  IMO  1600  1700  l»00  tlOO  £300  0100  OSOO 050O OTOO
                                     TIME  (HOURS -EST)
    
      Figure 7.   Mean diurnal 03  concentration at  Wilmington,  Wooster,  and
                McConnelsville, Ohio,  from  June 14-August 31,  1974.
    t
    9
    'I'ri'rrri'i'i'i'i'i'rrrri'i'i'i'i'i'i' TiTT'i'i'i'i'iTi'i'i'i'i'i'i'i'iTi'i'i1 , n
    ' 7/21 il IU • HO. Oil. HOW «M 7/25 tl 951 • HO. OR EWf.0 TOO
    - ° ° ° " o « *
    - • X *
    I *li|l||l||l,l1illHlillrt1ill-1i|ldlal*Cli'1ilillJl«l«lilll •lOl«l(llJli(ll!l«l»llllBllllfllellll«lOl«1«1«lBlfll<1lll fl'rtC
    1 1 2 3 1 5 * 1 • 9ltlllfli~m$ltl7lfl92f2l22~23~ f 1 2 3~ 1 5 ( 7 • f Itl Mllfli 15 1* iflt H202I [2223 I 1 2
    lilt OF DKY
    I'l'I'I'ITI'I'I'I'I'I'ITI'I'I'I'I'I'l1-
    7/» fl
    >«i
    -------
         Concentration profiles for the previously discussed (Table 1)  July 28-
    30 three-day run are presented in Figure 8.   In this run, there was a 95%
    dilution of the system in 24 hours starting  at the time of NO  crossover.
    The NO   became virtually undetectable,  and  the second- and tnS>d-day maximum
    03 andxnet 03 concentrations were in excess  of the NAAQS.  Note also that
    the 03-destructive side of the second-day 03 profile is less steep  than that
    typically observed for urban air.
    
         Figure 9 depicts the hourly averages of N0x from the field obtained at
    the same time and in the same areas as the 03 data in Figure 7.  The N0x
    concentrations ranged from about 2 to 12 ppb.  Smog chamber second- and third-
    day values were 1 to 53 ppb.  Calculated from average data, the NMHC/NO  ratios
    ranged from 27 to over 300 for field data and ranged from 22 to over 256 for
    second- and third-day smog chamber data.
    
         Chamber data of the second and third day are remarkably similar to field
    data.   In making comparisons between field data and chamber data the follow-
    ing caveats should be observed.  No additional reactants were added to the
    chambers after the first day, whereas there  is continuous addition  of reac-
    tants  to the ambient air.  The so-called "dirty chamber effect" was also ob-
    served in the chamber.  Direct comparisons and control  strategy decisions based
    on these data are therefore difficult.
    
                                       CONCLUSIONS
    
         In partially spent simulated urban  photochemical systems, 03 was gener-
    ated in concentrations above the NAAQS with  low concentrations (ppb) of NO
    and high NMHC/NO  ratios.                                                 x
                    X
         The smog chamber data also suggest that the role of fossil 03 is to
    provide a high minimum upon which to build a high maximum on the next day.
    The fossil 03, unaugmented by subsequent synthesis, probably cannot provide
    concentrations over the NAAQS for more than a day or two.
    
         The smog chamber data indicate that the dilution effect (i.e., more efficient
    03 generation per molecule of N0x with dilution) is an important process in
    delivering high 03 atmospheres.
    
         The atmospheric chemical problems in general and the high rural 03 problem
    in particular will yield to a three-faceted approach:  field measurements,
    experimentation in smog chambers, and mathematical modeling.  Each single
    facet has its limitations but iterative studies using the combined approach
    should yield useful information and solutions to current problems of atmos-
    pheric chemistry.
                                         328
    

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                                                                                 7-5
                        OZONE EPISODES ON THE SWEDISH WEST COAST
    
                                      P.  Greenfelt*
    
    ABSTRACT
    
          Ozone. me£tt>iL>iejme,nti>  nave been postfaorwed. -in Gothe.nbusig on the. S>we,dit>k
    c.oaf>t Atnce. 1972.   On ^nveJiaJi occcw-toni e.veAy t>u.mmeA 4.ncAe.ai>e.d lnvoJU,  o& ozone
    WQAQ.  ob-ieAved.   The. highest finc.ond.iid 1-houA mean uicu, 110 ppb.  The.  high  ozone.
    £eve£6  co4.ncA.dejd hi tune. with incAeaA e.d c.onc.e.ntfLation{> o& paSLticJLe,-bosine. t>uJL-
    phuA  both in. and. outbade. Goth&nbuAg  and o& Aoot outA4.de. Gothe.nbuA.g .  Ttuij zctoiy
             Ahowe.d that moAt o{, th&>e. zplAodu weAe. aA&o(u.ate.d with ttian&pofit o&
                                      INTRODUCTION
    
           Long-distance transport of air pollutants over western  Europe has been the
     object of extensive research in these countries since  around  1970.   This work
     has  been  focussed mainly on sulphur compounds and their  role  in  the acidification
     of lakes, running waters and soil.  The study of other essential  air pollutants
     such as heavy metals, chlorinated hydrocarbons and nitrogen oxides  has  been very
     limited.   However, as regards photochemical oxidants a few  reports  of investiga-
     tions are available (1,2).  This paper presents results  of  measurements of ozone
     and  associated parameters performed on the Swedish west  coast.
    
                            OZONE MEASUREMENTS IN GOTHENBURG
    
          Continuous  ozone measurements according to the chemiluminescent ozone-
     ethylene  method  have been carried out in Gothenburg on the  Swedish  west coast
     since January 1972.   Gothenburg is a highly industrialized  city  (e.g. two oil
     refineries),  with a population of half a million.  Initially, the purpose of
     the  measurements was to investigate the possible occurrence of locally  produced
     photochemical  ozone.   Once the results were obtained,  the measurements  were
     extended  to  include long-range transport of oxidants and their precursors.
    
         -Only two months after the measurements were started, on  the  16th of March,
     the  ozone level  in Gothenburg rose to above 90 ppb (Figure  1).  Although higher
     peaks have been  observed later, this one was remarkable  because  it  occurred so
     early in  the  year.  March is considered to be a winter month  in  Sweden; the
     monthly mean  temperature in Gothenburg is +0.7°C.  The meteorological conditions
     and  the concentration of other pollutants on this day  are shown  in  Table 1.  The
     data clearly  indicate that this ozone peak could not be  associated  with any
     natural sources.   This is particularly obvious from the  concentrations  of soot
     and  particle-borne sulphur as well as from the visibility data.
    ^Swedish  Water and Air Pollution Research Laboratory  (IVL),  Gothenburg,  Sweden.
    
                                          329
    

    -------
                           100
                         a.
                         o.
                         o
                         N
                         O  40
                            20
                                 72-03-16
                             00  03 06  09 12  15  18  21   24
                                           TIME
            Figure 1.  Ozone concentrations in Gothenburg, 16 March 1972,
           TABLE 1.  METEOROLOGICAL CONDITIONS AND CONCENTRATION OF AIR
                     POLLUTANTS IN GOTHENBURG ON 16 MARCH 1972
          Wind direction
          Wind velocity
          Temperature
          Relative humidity
          Visibility
          Overcast
    
          Ozone
          S02
          Soot (OECD-method)
    at 13.00 hrs
     max. 1-hour
          Particle-borne sulphur
              (X-ray fluorescence)
                                     daily mean
                       SSE
                      3 m/s
                      7 km (4 miles)
                       No
    180 yg/m3
    114 yg/m3
     57 yg/m3
     40 yg/m3
         In the following months (March-August) of 1972, several similar peaks in
    ozone concentration above the natural  background level  were observed.  These
    occurred mostly in the afternoons and early evening hours.  However, peaks were
    observed also at other hours of the day, e.g. early morning.  For this period,
    1-hour concentrations above 80 ppb occurred on a total  of 16 days; the highest
                                         330
    

    -------
    value recorded was 110 ppb.  In subsequent summers  (1973-76) similar ozone epi-
    sodes were not as numerous as in 1972, and on no occasion did the ozone level
    exceed 110 ppb within Gothenburg.
    
         The episodes have been evaluated on the basis of meteorological conditions
    and the concentration of other pollutants.  The meteorological conditions during
    days with high ozone levels showed large variations.  For example, the daily
    maximum temperatures during episodes in 1972 and 9173 ranged from +11.5°C to
    31.5 C.  The wind velocity also varied considerably  (episodes could occur at
    wind velocities of up to 13 m/s), whereas there was  a clear pattern with resnect
    to wind direction:  During nearly all episodes winds were blowing from the sec-
    tor SE-W.  Mostly low or moderate values for visibility were recorded.  All
    meteorological observations were made at Torslanda Airport, 10 km west of Gothen-
    burn (Figure 2).
                            TORSLANDA
                            (METEORO
                            LOGICAL
                            PARAMETERS )
                            (O3,NOX,PART.
                            SOOT)
                                              GOTHENBURG
    CENTRAL
    GBG (SOOT
    SO2,PART.S,
    03)
    
        N
                                                    1O KM
       Figure  2.   Location of  sampling  stations  for  air  pollution monitoring  and
                               meteorological measurements
         Sulphur dioxide, soot and particle-borne sulphur are measured in Gothenburg
    in a routine network.  To determine the origin of the ozone episodes observed in
    Gothenburg, comparisons were made between daily mean concentrations of these
    pollutants and peak ozone concentrations.  Correlation coefficients were calcu-
    lated for each month with more than 10 comparable data in the periods March-
    August 1972 and 1973.  No significant covariations for sulphur dioxide and soot
    were found, but a clear positive relationship was observed for particle-borne
    sulphur.   The correlation coefficients between daily maximum 1-hour ozone mean
    values and daily mean values of particle-borne sulphur were in the range of
    0.30-0.80 in nine out of ten months (Table 2).  As examples of the covariations,
    plots from August 1972 and 1973 are shown in Figure 3.
                                         331
    

    -------
    TABLE 2.  CORRELATION BETWEEN DAILY  MAXIMUM 1-HOUR  CONCENTRATIONS  OF  OZONE  IN
    GOTHENBURG (GBG) AND SOOT,  PARTICLE-BORNE  SULPHUR.IN  GOTHENBURG  AND RORVIK.
    MARCH - AUGUST 1972 AND 1973.
    
    
    
    1972
    
    
    
    
    1973
    
    
    
    
    Ozone vs. Ozone vs.
    soot soot
    Gbg Rb'rvik
    r n r n
    March 0.31 22 0.13 24
    May -0.21 27 -0.17 27
    June 0.04 22 0.68 26
    July 0.36 25 0.43 28
    Aug. 0.01 17 0.48 17
    April -0.23 13 0.30 13
    May 0.50 31 0.50 31
    June 0.28 30 0.34 30
    July 0.08 31 0.42 28
    Aug. 0.25 26 0.51 26
    Ozone vs. Ozone vs.
    part. S part, S
    Gbg Rdrvik
    r n r n
    0.48 22 0.38 24
    -0.15 27 0.01 27
    0.30 23 0.69 24
    0.65 25 0.60 28
    0.80 17 0.30 13
    0.50 13 0.67 13
    0.63 31 0.51 31
    0.62 30 0.54 30
    0.31 31 0.31 31
    0.65 26 0.63 26
    
    
    - 25-
    2
    ^-20-
    £ 15-
    X
    Q.
    - 10-
    (0
    5-
    0'
    I
    
    
    AUG 1972 .
    * R = 0,80
    .
    
    *
    i
    
    ) 20 40 60 80 100
    OZONE (PPB)
    
    AUG 1973
    • — 25' •
    " R • 0,65
    0 20- • *
    £ 15.-
    X *
    Q! , * 9
    5 •*•• *•
    0 1*1 1 4 1
    0 20 40 6*0 8O 100
    OZONE (PPB)
    Figure 3.  Daily mean concentration of particle-borne sulphur in Gothenburg
                         plotted against maximum 1-hour concentration of ozone
                      in Gothenburg for the months of August 1972 and 1973
    
                                        332
    

    -------
                            LONG-RANGE  TRANSPORT  OF  OZONE
    
          From other measurements on the Swedish  west coast it is  known  that the
    concentration of particle-borne sulphur within Gothenburg is mostly  a product
    of long-range transported sulphur.   The daily ozone peak concentrations  in
    Gothenburg were therefore compared  to the concentrations of soot and particle^-
    borne sulphur samples at a non-urban coastal  station (Rorvik)  about  40 km south
    of Gothenburg (Figure 2).  This station is primarily used for  long-range trans-
    port studies.  Soot and particle-borne sulphur have proven to  be very useful
    tracers for long-range transport of air pollutants.  Positive  correlations  for
    particle-borne sulphur and for soot were observed at this station (Table 2).
    These results indicated that the observed ozone episodes were  not associated
    with pollutants produced in Gothenburg, but were a result of long-range  trans-
    ported pollutants.   To confirm this, 48-hour  trajectories were calculated for
    the days with high  ozone concentrations in 1972 and 1973 (3).   It was found
    that in 28 out of 33 cases, the air masses came from the sector E-S-W, having
    passed over heavily industrialized  areas in Great Britain or on the  Continent.
    As an example, the  trajectory for March 1972  is plotted in Figure 4.
                                    16 MARCH,1972
                   Figure 4.   48-hour trajectory for 16  March  1972.
          Comparisons were also made between daily maximum concentration of ozone
    and particle-borne strong acid measured according to Brosset (4).   However,
    acid has not as yet been measured on a routine basis comparable to ozone moni-
    toring and no statistical evaluation is therefore possible.   Nevertheless,  an
    examination of the data will  show that most of the strong acid  episodes are
    associated with ozone peaks (Table 3).
    
         In the summer of 1975 ozone measurements were also performed  at the non-
    urban station (Rorvik).  There, high ozone levels were observed on several  oc-
    casions..  The 1-hour ozone concentration exceeded 120 ppb on 11 days in that
    period; the maximum hourly concentration was 210 ppb.
    
         There was mostly a close covariation between the ozone levels observed in
                                         333
    

    -------
       TABLE 3.  COMPARISON  BETWEEN  CONCENTRATION  OF  STRONG ACID ON PARTICLES
       SAMPLED AT RORVIK AND MAXIMUM OZONE  CONCENTRATIONS DURING THE FIVE MOST
       ACID EPISODES IN THE  SUMMER OF 1975
    
    
    
    
    May
    
    Aug
    
    
    
    
    
    19
    29
    . 5
    7
    29
    H+
    n mole/m3
    Rb'rvik
    225
    62
    77
    21
    56
    NH4+/H+
    mole/mole
    Rorvik
    2.8
    2.4
    1.3
    2.8
    3.6
    03
    ppb
    Gothenburg
    66
    45
    54
    84
    47
    03
    ppb
    Rorvik
    76
    75
    130
    151
    -
    
    Rorvik and Gothenburg.  However, for most of  the  time,  the  level  was higher at
    Rorvik.   This indicates that there is no local contribution to the ozone level
    in Gothenburg.  Instead, other pollutants emitted  locally partly  destroy the
    incoming ozone.  Figures 5 and 6 give examples of  ozone episodes.
           — 100-
           01
             80
    
             20
               00 03  06  09  12  15   18  21  24  03  06  09  12   15  18  21  24
    
                        75-06-18           TIME            75-06-19
               00 03  06 09  12  15  18  21  24  03  06  09  12   15  18  21  24
    
                       75-06-20           TIME            75-06-21
     Figure  5.   Ozone  concentration in Gothenburg and Rorvik, June 18-21,  1975.
    
                                         334
    

    -------
            -
            00
            UJ
    140
    
    120
    
    100
    
     80
           N
                                                          A—,
           A
                                *. >V\
                           AXv     V
    ,rv
               00  03  06  09  12  15  18  21  24  03  06  00  12   15  18 21
    
                        75-08-06            TIME            75-08-07
                                                 24
                00  03 06  09  12   15  18  21  24 03  06 09  12  15  18  21  24
                        75-08-08            TIME       75-08-09
    
       Figure  6.  Ozone  concentration  in Gothenburg and  Rorvik,  August 6-9,  1975.
    
    
         In a further investigation of the cause of the ozone episodes, continuous
    measurements of nitrogen oxides were carried out during the summer of 1975 at
    Rorvik.  The levels of nitrogen monoxide as well as nitrogen dioxide were in
    the range of 1-10 ppb.  Despite the small variations in concentration, positive
    relationships could be seen between the early morning concentrations of nitro-
    gen oxides and maximum ozone levels.  Figure 7 is an example of  the variation
    pattern.
    
                                      DISCUSSION
    
         From our measurement data as well as from those collected in other countries
    in western Europe, it is clear that several ozone episodes occur  every summer
    over large areas in Europe.  The impact of these episodes is not  known and no
    investigations have as yet been carried out in Sweden to clarify  this.  It is
    very likely that these ozone peaks cause damage to vegetation, but no such ef-
    fects have as yet been observed.  One reason for this may be that plant injuries
    on the Swedish west coast are often assumed to be caused by sea  spray.
    
         As regards effects on human health, complaints about photochemical smoq
    were made on one occasion (28 May 1973) in Gothenburg to the local Board of
    Health.  The highest concentration of ozone in Gothenburg that day was 80 opb.
    No data from areas outside the city are available.  This episode  was associated
    wtth very high concentrations of an aerosol consisting  of sulphuric acid and
    ammonium sulphate (5,6).
                                          335
    

    -------
                                                                         21  24
    Figure 7.   Variations  in  concentrations  of ozone  and  nitrogen  oxides  at  Rorvik,
                            2 July 2975  and  6  August  1975.
    
    
         One question that arises when studying the simultaneous occurrence of high
    ozone levels and high concentrations of acid sulphate aerosols is:  Does ozone
    play any role in the oxidation of sulphur dioxide in the lonq-range transported
    air masses?  The question is very justified considering the correlations observed
    between ozone and sulphate.  In winter,  the sulphate in the frequent episodes
    resulting from long-range transported pollutants is formed through catalytic
    oxidation.  In summer, this process is less likely because of, among other things,
    low relative humidities.  The summer aerosols also differ from the winter aero-
    sols in several other respects, e.g. size distribution and acidity.  These dif-
    ferences indicate that sulphates are formed by different mechanisms and that
    ozone or oxidants are compounds that might play a role in sulphate formation.
    
         It is well known that the reaction between ozone and sulphur dioxide in
    the gas phase is a very  slow reaction and of minor importance for the oxidation
    of sulphur dioxide.  However, according to pxperiments by Penkett, oxidation by
    ozone in the liquid phase might be possible (7).   The acid aerosols normally occur-
    ring in connection with  ozone episodes contain a water phase even at rather low
    relative humidities.  Research on this reaction mechanism is in progress.
    
    
                                      REFERENCES
    
    1.  Cox, R. A., A. E. J.  Eggleton, R. G.  Derwent, J. E. Lovelock, and D. H. Pack.
        Long Range Transport of Photochemical Ozone in North-Western  Europe.  Nature,
        225  (5504):  118-121,  1975.
    
    2.  Grennfelt, P.  Measurements of Ozone  in Gothenburg, January 1972 - August
        1973 and Studies of  Co-Variations Between Ozone and Other Air Pollutants.
        Internal publication B221, Swedish Water and Air Pollution Research Labora-
        tory  (IVL), Gothenburg, January 1975.
                                          336
    

    -------
    3.  Henrikson, A.  B.   An Investigation of the Accuracy in Numerical  Computations
        of Horizontal  Trajectories in the Atmosphere Meteorologi, 27.   Swedish Mete-
        orological and Hydrological  Institute, Stockholm, 1971.
    
    4.  Askne, C., and C.  Brosset.  Determination of Strong Acid in Precipitation,
        Lake Water and Air-Borne Matter.   Atm. Environ.  6:  695-696,  1972.
    
    5.  Brosset, C., K.  Andreasson,  and M. Perm.   The Nature and Possible Origin of
        Acid Particles Observed at the Swedish West Coast.  Internal  publication
        B189, Swedish  Water and Air  Pollution Research Laboratory (IVL), Gothenburg,
        1974.
    
    6.  Brosset, C.  Acid  Particulate Air Pollutants in Sweden.   Internal publication
        B 222, Swedish Water and Air Pollution Research  Laboratory (IVL), Gothenburq,
        1975.
    
    7.  Penkett, S.  A.  Oxidation of S02  and Other Atmospheric  Gases  by Ozone in
        Aqueous Solution.   Nature Physical Science, 240  (101):   105-106, 1972.
                                         337
    

    -------
             SESSION 8
    IMPACT OF STRATOSPHERIC OZONE
    
      ChcuAmam   R.  Guicherit
        IGTNO, Netherlands
                339
    

    -------
                                                                                   8-1
              OZONE OBSERVATIONS  IN  AND AROUND A MIDWESTERN  METROPOLITAN AREA
    
          G.  D. Huffman, G. W.  Haering, R. C. Bourke, P.  P.  Cook, M. P. Sillars*
    
     ABSTRACT
          A -ia/r/cei o£ ground le.\>eJi and attitude, me.aAuA.ewe.ntA  o^ ozone, have. be.e.n
     c.aAAA,e.d oat -in the. lndLa.na.poLU>  o/ieo. faiom 1974 to  7976.   The. majox, x.&>uLt!>
     o&  the. ground ItveJi ttudiu  ate.  ie.v-ie.we.d and eA.   In addition, an e.xte.n£-ive. AeAieA o& aLtlta.de.
     AuA.ve.yA o^ ozone, have, been  conducted .   Typical A.uuLtA  ofa both hoA^zontal
     and v&itic.al flight path* one. pA.e^>e,nte,d.  Again the^e. n.eAmLtt, one. de^cJvibe.d
     In  teAm& o& long lange. c.onve.c£Lon,  tiVibuLtnt mLitLng,  photoc.he.mLc.aL Qe.neAatLo\
     and t>t>iatopheJu.c. tnan&poJit.   The. dLveJiA-Lty ofa the. teAt x.eAuJLtb Indicates
     that undeA gLve.n me^te-o^oiog-Lcal  condition* any one. on motie. oft the. above, pno-
     ce44£4 may OC.CUA,  In AummaSLy, ozone. ge.neAation and tA.ant>pofct Ln an uJtban
     e.nvinonme.nt AJ> e.'xJJim&Ly c.ompLe.K, and additional data L& fie.quin.e.d pniofi to
     an  Ln-de.pth understanding o& the, phe.nome.na i.nvolve.d.  Suc.h an undeJiAtand-
     -ing would the.n hope.fiulty Le.ad to an e. ft Active. c.ontA.ol AtnatiLay,
    
                                        INTRODUCTION
    
          The Environmental Protection Agency (EPA) issued regulations in 1971  (1)
     stating that oxidant levels  were to be maintained  at  values less than 0.08
     ppm.   This was predicated upon oxidant levels of 0.01 to 0.05 ppm in rural
     areas (2) and the presumption that values exceeding these levels were genera-
     ted in urban centers.
    
          In actuality, the oxidant level existing at a given location is the re-
     sult of a complex interaction between meteorological, transport and genera-
     tion (or destruction) processes  and can be described—to first order accuracy
     --by the following relations (3, 4, 5):
          3lJ.
          U1fl.  =0                                                    [2]
    
    
          8T'     '                =  kT'                                 [3]
    *G. D. Huffman,  G.  W.  Haering, Indianapolis  Center for Advanced  Research
    (ICFAR) and Purdue  University School of  Science, Indianapolis,  Indiana.
     R. C. Bourke,  P.  P.  Cook, Indianapolis  Center for Advanced  Research and
    Detroit Diesel  Allison Division, General  Motors, Detroit, Michigan.
     M. P. Sillars,  CWS,  Inc., Flint, Michigan.
    
                                           341
    

    -------
                 J
                               JJ-
                                  .J
                                         »jj
                                                   exp  (-1
                                                                   C4]
    where Cartesian tensor notation has been used with 1 and 2 denoting the hori-
    zontal coordinates and 3 the vertical direction.  A repeated subscript indi-
    cates a summation while ,i  indicates differentiation.   T1  and P1  represent
    the deviation from the adiabatic temperature and pressure conditions^ with the
              temperature, and  concentration divided into a time mean, I)., T1 , and
                                   i.e., u., t, and c^ '.   The fluid properties
                                   v-the kinematic viscosity,  k-the thermal con-
                                   constant, and a-the mass diffuslvity.  g repre-
                                   S. .  the Kronecker delta and F    the frequency
    vejocity
    C^  , and instantaneous value,
    are denoted by p -the density,
    ductivity, R-the°universal gas
    sents the gravitational force,
    OCTIOJ one y i ay i oa L. I una I  iuii~c, u .  . uie IMUNfcJLKer Ufc! I Id ClMU t     UHG TTeqUB
    factor and Ev ;  the activation energy of the (i)-th chemical  species, with  ,
    denoting time.  Equations [1] through [4] represent the conservation of mo-
    mentum, energy,  and mass for a turbulent medium.  These relations are for-
    mally indeterminate since the Reynolds averaging procedure has introduced
    
    the unknowns u.u,, tu". and cllV, which describe the turbulent diffusion
    processes.  Attempts are currently being made to solve these equations (3);
    however, they are of value even in this form since they show that the concen-
    tration at a point is due to convection, turbulent transport, viscous trans-
    port, and generation or destruction.   There is a strong interaction between
    concentration, temperature, velocity and the chemical  reactions themselves.
    Note that the terrain and external transport features  enter the process
    through the boundary conditions.   This balance is shown schematically in
    Figure 1.
         TRANSPORT IN
                            BOUNDARY CONDITIONS APPLIED
                              ALONG EXTERNAL SURFACES
    TRANSPORT OUT
                                                                      TIME RATE
                                                                      OF CHANGE
            Figure 1.  Processes Represented by the Transport Equations.
    
                                         342
    

    -------
         With this phenomenological description of the oxidant generation transport
    process in mind, the Indianapolis Center for Advanced Research (ICFAR) in
    conjunction with the City of Indianapolis, State of Indiana, Environmental
    Protection Agency-Region V (in 1974), and a consortium of local businesses
    instituted a continuing study of ozone levels in and around Indianapolis.
    This paper will summarize the major findings of three years of ground level
    and altitude measurements and attempt to interpret the results in terms of
    the previously described phenomena.
    
                                GROUND LEVEL MEASUREMENTS
    
         The ground level measurements were initiated in June of 1974 using six
    monitoring stations.  Their location relative to Indianapolis and Marion
    County is shown in Figure 2.   These locations have been used throughout the
    three years of the study with some minor changes.  All data was taken according
    to EPA guidelines (6) with the data quality assurance tasks performed in 1974
    by EPA contractors (7) and by the Indiana Air Pollution Control Division in
    subsequent years.
    
         While ground level measurements do not in general reveal substantial
    insight into the ozone generation/transport mechanisms, they do serve to define
    the magnitude of the problem and can be used to estimate the contribution of
    various processes to over-all oxidant levels.  In this context, the following
    results were obtained from both the 1974 (8) and 1975 (9) studies.
         A unique relative ordering existed between the sites in ozone concen-
    tration, which did not change significantly with wind direction.   This im-
    plies that wave-like ozone excursions that have been noted in the Los Angeles
    Basin (10) do not occur in Indianapolis.   The substantial terrain differences
    may account for this.
    
         A high degree of correlation existed in the daily profile or time rate
    of change of ozone measured at each site with no decrease in this correlation
    with increasing distance.  This is illustrated in Figure 3.  This result in
    conjunction with the lack of correlation between site ordering and wind direc-
    tion indicates that horizontal is much smaller than vertical mixing.   Further-
    more, the time rate of change of concentration is in balance with vertical
    diffusion processes and the generation (destruction) term.  This  is indicative
    of elevated, remote natural or anthropogenic sources.  This may be due to
    photochemical generation at the surface, stratospheric ozone (11, 12), and/or
    a cyclic vertical ozone or ozone precursor transport process (10).
    
         Ozone levels in the incoming air at upwind rural background  sites often
    exceeded the federal standard.  This is illustrative of long range transport
    of ozone and/or ozone precursors (13, 14, 15).
    
         No statistically significant differences were found for daily average
    ozone concentrations between weekends and weekdays; however, the  percentage
    of weekend violations of the hourly standard was higher than for  weekdays.
    Moreover, traffic density in the area of each site showed a negative rela-
    tionship with the relative ordering of sites on measured levels,  i.e., inner
    city, high traffic density sites showed low ozone levels while upwind and
    downwind, low traffic density sites showed higher ozone levels.  This suggests
    
                                         343
    

    -------
    increased turbulence and scavenging towards the center of the city  (16,  17).
         Measured ozone levels had a strong positive correlation with tempera-
    ture and solar radiation.  This is,also a commonly noted effect and  is  due  to
    enhanced reaction rates_through Fu; exp (-E1 YRT) and increased turbulent
    mixing as a result of gT'6. /T .
                                              too
                                                           10    15    ao
                                                         lntonH«Dlitanc« ml
                                                                            28
                                            Figure  3.   Intersite  Distance Robust
                                                  Correlation Coefficient.
                               Jutonon Counly
          Figure  2.   Monitoring  Sites.
         In addition to the ozone measurements, some nitrogen dioxide  (N02)  and
    non-methane hydrocarbons (NMHC) measurements have been  carried  out.   The rela-
    tionship between the maximum daily ozone concentration  and  the  6:00-9:00 a.m.
    N02 and NMHC is shown in Figures 4 and 5.  This indicates a  low correlation,
    i.e., approximately 0.35, in both cases.  While this  cannot  be  interpreted as
    non-correlated in an absolute sense, it does indicate a weak direct  relationship,
       OJDr
                                                        MO-MO UK NO, CoKOTMUoi, M*
                                                                             o.wo
    
    Figure 4.  Maximum Ozone and Morning   Figure  5.  Maximum Ozone and Reactive
         N02 Concentrations - 1975.         Hydrocarbon Concentrations - 1975.
    
    
                                ALTITUDE  MEASUREMENTS
    
       Since the velocity,  temperature, and  concentration  fields are inherently
    
                                        344
    

    -------
    three-dimensional and  time-dependent  in  nature,  a series of altitude measure-
    ments has been carried out  in  conjunction with the previously discussed
    ground level measurements  (7,  8,  9,  12).
    with a fixed wing aircraft,  an AID  and a
    for altitude effects  following reference
    ture measurements.  Three  separate  types
    ducted:  vertical spirals  above a ground
    hundred feet to approximately  30,000 ft.
    line to county line (see Figure 2)  from
      All experiments have been conducted
     Dasibi ozone monitors—corrected
     12--and a thermistor for tempera-
     of aircraft flights have been con-
     station from altitudes of a few
    ; horizontal traverses from county
    2000 to 15,000 ft.; and, long range
    horizontal traverses  from  state  line  to state line at a series of altitudes.
    
         Some typical  results  for  the  vertical  spiral  flights are shown in
    Figures 6 through  12.   Figures 6 through 8  show a  discontinuous and/or inter-
    mittent behavior.  These spikes  do not indicate a  smooth ozone profile but
    rather irregularly shaped  "lumps." Mechanisms must be in existence to main-
    tain this structure since  diffusive processes would, over a period of time,
    normally yield a fairly uniform  distribution.
    
                                                11000
                                                mooo
                           M»: 8-25-74
                           Tim*: 8:46am.
                           Wind: WSW~15mph
                                                 8000
                                                 MOO
                                                 4000
                                                 2000
                  002   OJM   ooe
                 OxofM Concentration, ppffl
                                 QOB
                                                                       8-23-'74
                                                                    Tkiw: 2:30 pun.
                                                                    Wind: WNW^Mmph
                                                          jQround
                                                   oi—^r    .
        Figure 6.   Ozone  Concentration
         and Altitude  -  Indianapolis.
          '0   0.10   OJO   030   040   O90
                feonCaneMMtan, ppm
    
    
       Figure 7.  Ozone Concentration
        and Altitude - Indianapolis.
         Figures 9 through 11 demonstrate  a  more  uniform distribution typical of
    a well mixed layer.  Note that  Figures 9 and  12  approach a high ozone concen-
    tration at the higher altitudes.  This is  consistent with an elevated source.
    Figure 12 also shows two distinct strata of high ozone at
    along with a low ground level concentration.   This  may be
                      lower altitudes
                      due to ground level
    generation and transportation aloft  and/or transportation downward from a high
    level source with ground  level  scavenging.
         The processes that occur within  the  atmospheric surface layer are of
    particular importance and show  somewhat different behavior than those aloft.
    A series of these measurements  is  shown in  Figure 13 for both summer and af-
    ternoon conditions.  Although the  concentration  gradients are quite different
                                          345
    

    -------
    near the ground, they approach the same value aloft.   Similar  results  are re-
    ported in reference 18.  This particular set of  values  is  indicative of a
    "blanket" of ozone covering the entire area during  the  measurement period.
    Both afternoon curves indicate a well mixed layer with  nearly  uniform concen-
    tration.  However, the night between the two afternoons  indicates  a low ground
    level concentration with values aloft approaching those  of the afternoons.
    This phenomenon could be caused by an ozone reservoir  blanketing  the area
    with continual scavenging at the surface.  At night, when  no photochemical
    processes are present and vertical transport is  limited  by the inversion,
    the surface ozone is destroyed.  However,  in the afternoon, with  enhanced
    vertical transport and photochemical processes,  the surface concentration
    approaches that of the blanket.
                           12,000
                           10,000
                            8000
                            600°
                            4OOO
                            2000
    Date: 8-23-'74
    Tim*: 2:00pjn
    Wind:
                                              Uv*
                                    005 *   0.10     0.15
                                     Ozone Concentration, ppm
                                                        020
             Figure 8.  Ozone  Concentration  and Altitude - Indianapolis.
         Horizontal flights at a series  of  altitudes  were  also
    Figure 14 shows that there are significant  departures  from
    of ozone concentration with the principal demarcation
    ft.  This sharp delineation often occurs on  days  with
    (Figures 9 and 12).
                   carried out.
                   uniform stratification
              located  at  about 4000
              high  ozone  concentration
         Cross-country flights generally  indicate  constant or slowly varying ozone
    values with distance from  Indianapolis  at  constant  altitudes.   Figure 15 shows
    a typical result and corresponds to conditions  in Figure  13.   The origin of the
    deep spikes is unknown—they were  not generally present.   The  "steady" ozone
    values were observed to extend  upwind and  laterally to approximately 70 miles--
    the extent of the flight.  Figure  16  shows  results  obtained from another cross-
    country flight.  Again reasonably  uniform  ozone values occur  for the length
    of the traverse—approximately  300 miles.   This condition corresponds to the
    vertical traverse of Figure 11.
                                         346
    

    -------
     30,000
     20,000
     10,000
                                               30,000
           Ground
                                  8- 28- '75
                              Tinw: 5:00pm
                                    2QPOO
                                    10jOOO
    iL**^ __^
    ~oos     oS>
                                015
    0.20
                                                                         :  3-6-'76
                                                                      Tlnw: 4:OO pm
                              Uv*
    005
    OJO
    0.15
    0.20
                Oxon* Concentration, ppm
      Figure 9.  Ozone concentration
            and altitude - 1975.
                                               Ozone Concentration, ppm
                                     Figure  10.   Ozone  concentration
                                          and  altitude  -  1976.
                                   30#00r
    30000
    2QDOO
                            6-9- '76
                            7^30 pan
    1QQOO
                                             r
                                             I
                                             i
                                               10^000
               O06    OflO^  OI5   Q20
             Ozon«Conc«itration, ppm
      Figure 11.   Ozone  concentration
           and altitude  -  1976.
                                                           Date: 9-2-"7S
                                                           Tim*: 7:00pm
                                        0              OJO             020
                                               Ozoo* Concentration, ppm
                                     Figure  12.   Ozone-altitude data
                                       over  Northwest Indianapolis.
                                          347
    

    -------
      1400
      12OO
      1000
     £ 800
      600
      400
      200
       i: 7-17- '75
    Tlrm: 4:OOpm
    Date
    Tinw: 3:00pm
    
    Dite:7-17-'75
    Tbiw:5.-00ant
                             Tmpwatura °F.
                            70 75 80 85 90
                                         15,000
    7-W-75
     3=00 pm
                0.06     OX)    0.15
    
                Ozone Concentration, ppm
                                 0.20
                                                10,000
                                                 5,000
                                                           <03
                                                                         -.03
                                                                   .03     >.03
      30
    West
                                                           20
    10    0    10
    
    from City Canter
                                                 20
                                                 East
    Figure  13.   Ozone concentration and     Figure 14.   Ozone concentration over
    altitude,  25-hr,  period,  Indianapolis.  Indianapolis,  7-29-75,  5:00-8:00 p.m.
                                              Numbers on  plot denote  lines of con-
                                              stant ozone concentration.
           J04
           • .08
        . Date 7-17-*75
          TbNK 440am
          AltHudK900n
                      Flitf* Direction
                           Dtnciton
                             10
                                                  30     40      80
                                                                         80
                                      from Center of City
    
      Figure  15.   Ozone Concentration and Temperature Upwind  of Indianapolis  at
                                   900 Feet Altitude.
                                           348
    

    -------
                                                   Wind Dhwctton
                                                   Ftiffit DtaKtton
             .08
                                                                      §7
       >: 8-9-'7«
    Tim*: 5:30 pm
    Altttud*: 1500ft
                                                ^JTwnpwvlim
                                             *r  A •'••
                                                   '•
                                                                A
    •0
    
    7»
              wo 130 100 *> »o 40  20  o  ao 40  eo  ao 100 «o MO no no
                    M«k«4feA^^6                            QtfM^ft^M^AA_^_^^»
                ^   iiomupBi                            wwwnw^^*"™""^^
                           ^•JJ	f-, i, - »fc - /*^—J^» stf ^^lAAAtM^ta
                           MilM rrani tiM vwmr 01 HMMNMPOMI
    
          Figure 16.   Ozone Concentration and Temperature Near Indianapolis.
    
    
         Even though many different ozone profiles are encountered, a few general
    characteristics can be noted.  First, ozone levels do not change appreciably
    over long distances at constant altitude both upwind and laterally as long
    as no frontal activity is encountered.  Secondly, ground level concentrations
    change in a diurnal pattern—mornings usually having lower values with  high
    values in the afternoon.  Ozone levels at altitudes of a few thousand feet
    tend to remain reasonably constant diurnally--barring gross meteorological
    changes.  Afternoon ozone concentrations have similar values both at the
    surface and aloft.  This may be due  to scavenging of ozone at the surface
    during the night and morning hours and then afternoon surface increases result-
    ing from both photochemical processes and enhanced vertical mixing.  Finally,
    ozone concentrations at altitudes of 25,000 ft. are often quite high indica-
    ting potential ozone transport from  the stratosphere.
    
                             UPPER AIR METEOROLOGICAL STUDY
    
         In an effort to isolate meteorological transport of ozone-rich air from
    the more conventional sources due to photochemical formation and surface ad-
    vection, a meteorological study (19) was conducted of a high ozone incidence
    that occurred on February 24, 25, and 26, 1976.  During this time period both
    Dayton and Indianapol-is measured ozone levels exceeding the current standards.
    A study of area and national surface maps indicated that advection and/or
    long range transport from an adjacent urban center to Indianapolis or Dayton
    was unlikely.
    
         To explore other possible causes, a series of vertical cross-sections
    were plotted extending from the surface to 50,000 ft.  The cross-sections
    originated at International Falls, Minn. (INL) and followed an irregular path
    through Green Bay, Wis. (GRB),  Dayton, Ohio (DAY), Huntington, W. Ma. (HTS)
                                          349
    

    -------
    and Greensboro, N.  C.  (6SO).   For both dates,  the wind aloft and the location
    of the tropopause were plotted (see Figures  17 and 18).   These figures show
    a low-level jet located immediately below the  break in the tropopause.  If
    the high-speed jet is  an ozone rich wind stream originating near the tropo-
    pause break and gradually descending,  winter occurrences of high ground level
    ozone concentrations could be more easily explained.   While this phenomena is
    unlikely during the summer months it may well  explain unusual  occurrences
    during the late fall,  winter and spring.
                                                                  DAY  HTS
                                                                            GSO
       INL
                 Qfe
                                              INL
                                                        ORB
      Figure 17.  Vertical cross-section
         of Atmosphere over Midwest -
              February 29, 1976.
    Figure 18.   Vertical  cross-section
       of Atmosphere over Midwest -
            February 25,  1976.
                                       CONCLUSIONS
    
         The diversity of the test data indicates that meteorological, transport,
    and photochemical processes all could be important contributors to ground and
    altitude ozone levels.  Under a given set of conditions, one process may
    dominate or all three processes may make equal contributions.  As a result,
    it is difficult to draw general conclusions.  Categorization of ozone pro-
    files according to atmospheric stability might prove useful—unfortunately a
    broad enough data base is not yet available for this purpose.
    
         Even though the phenomena cannot be described in concise terms, results
    indicate that for the Indianapolis area wave-like migrations of ozone and/or
    ozone precursors are not a major contributor to ground level concentrations.
    Furthermore, vertical mixing seems to dominate other processes with either a
    surface or elevated source supplying the ozone.  During a winter period,
                                         350
    

    -------
    stratospheric sources have been identified.   This is not necessarily the pre-
    dominant contributor in the summer with ozone and/or ozone precursors,  ver-
    tical transport and re-entrainment coupled with photochemical  generation
    equally likely!  All in all, ozone generation and transport in an urban en-
    vironment is extremely complex and additional data is required before an
    in-depth understanding of the phenomena involved can be reached.   Such  an
    understanding would then hopefully lead to an effective control  strategy.
    
                                       REFERENCES
    
    1.   "Requirements for Preparation, Adoption and Submittal of Implementation
         Plans," Federal Register, 36_, August 1971, p. 15486.
    
    2.   "Air Quality Criteria for Photochemical Oxidants," National  Air Pollution
         Control Association, Durham, N. C., March 1970, p. 4-3.
    
    3.   Bradshaw, P.  An Introduction to Turbulence and its Measurements,  Per-
         gammon Press, Oxford, England, 1971.
    
    4.   Lumley, J. L. and H. A. Panofsky.  The  Structure of Atmospheric Turbulence
         Interscience Publishers, New York, N. Y.  1964.
    
    5.   Beer, J. M. and N. A. Chigier.  Combustion Aerodynamics,  John Wiley and
         Sons, Inc., New York, N. Y.  1972.
    
    6.   Guidelines for Development of a Quality Assurance Program,  Reference
         Method for Measurement of Photochemical Oxidants, EPA Monitoring Series
         No. EPA-R4-73-028c, June 1973, Office of Research and Monitoring,  U. S.
         Environmental Protection Agency, Washington, D. C.
    
    7.   Waltz, E. W. and D. Raichart.  "Indianapolis 1974 Summer Ozone Study -
         Data Documentation Report,"  Indianapolis Center for Advanced Research,
         April 1975.
    
    8.   Lovelace, D. E., et al.  "Indianapolis  1974 Summer Ozone Study,"  The
         Indianapolis Center for Advanced Research, February 1975.
    
    9.   Haering, G. W.  "Interim Air Quality Report,"  Indianapolis  Center for
         Advanced Research, March 1976.
    
    10.  Blumenthal, D. L.  and W. H.  White.  "The Stability and Long  Range  Trans-
         port of Ozone or Ozone Precursors," Paper No. 75-07.4, Air  Pollution
         Control Association, Boston, Mass., June 1975.
    
    11.  Sticksel, P. R.  "The Stratosphere as a Source  of Surface Ozone,"  Paper
         No. 75-07.6, Air Pollution Control Association, Boston,  Mass., June 1975.
    
    12.  Cook, P.  P.  and R.  C. Bourke.   "Correction of Ozone-Altitude Data  and
         Stratospheric-Source Implications," Air Pollution Control Association
         Journal, June 1976.
    
    13.  Wolff, G. T., et al.   "Aerial  Ozone Measurements over New Jersey,  New
    
    
                                         351
    

    -------
         York and Connecticut,"  Paper  No.  75-58.6, Air  Pollution  Control Associa-
         tion, Boston,  Mass.,  June  1975.
    
    14.   Rabino, R.  A.  "Ozone  Transport,"  Paper  No.  75-07.1, Air  Pollution  Control
         Association,  Boston,  Mass., June  1975.
    
    15.   Price, J.  H.,  et al.   "Estimation of  Minimum Achievable  Oxiclant Levels
         by Trajectory Analysis:   Implications for Oxiclant  Control,"  Paper  No.
         75-07.2, Air  Pollution  Control  Association, Boston, Mass,,, June 1975.
    
    16.   Cleveland,  W.  S., et  al.   "Sunday and Workday  Variations in  Photochemical
         Air Pollutants in New Jersey  and  New  York," Science,  Vol.  186, pg.  1037,
         1974.                                                     ~~
    
    17.   Levitt, S.  B.  and Chock,  D. P.   "Weekday-Weekend Pollutant and Meteoro-
         logical Studies of the  Los Angeles Basin,"  Paper No.  75-51.1, Air  Pol-
         lution Control Association, Boston, Mass.,  June 1975.
    
    18.   "Control of Photochemical  Oxidants -  Technical Basis  and Implications  of
         Recent Findings," U.  S.  EPA.   Research  Triangle Park,  North  Carolina,
         July 15, 1975.
                                         352
    

    -------
                                                                                 8-2
                    A "TEXAS SIZE" OZONE EPISODE TRACKED TO ITS SOURCE
    
                            J.  W.  Hathorn III and H. M. Walker*
    
     ABSTRACT
                  September 25 and Octoben. 1, 1975, a wide*pn.ead  ozone. (03j
     episode  occuAAed -in Texa*.   TAack* ofa mojiitoAing data  &OA the. peAiod August
     10 to  OctobeA 31  cleanly *how evidence ofi thi* epi*ode completely acAo**
     the *tate.   In addition,  evidence i* o^eAed that mo*t in*tance*  ofa  high
     0$ at  all *ite* an.e Aelated to wide*pAead episode*.
    
         The. ^Aeqaent,  Aegional ozone. episode* expenienced in the  Ea*ten.n
     United State*  vertical ozone
     have -6/iown that thefie *&  -incAea^ed ozone concentrations within the
     layeA.  and cuM.ently~ accepted fisiontal model* Indicate that thi& ozone Lt,
     probably oft  &tA.ato-{>pheJvic
         An analy*-if>  o&  the Apace and time continuity o£ a fitiont'* low-level
    -f,tA.u.ctuJie demonAtSLOte*  that the stable layen oven, the region experiencing
    an ozone episode  waf> actually the lemnant o^ a. cold fifiont that had pushed
    through i,QMVwJL day* eantien.   The stable lay en. d-i* appealed and n.eappean.ed
    at *even.al station*  indicating that it wo* losing It* Identity a* Jit di*-
    *lpated.  Any ain. within the *table layen. would have been mixed in the low-
    en. &iopo*phen.e.   Since  thu> * table lay en, i* the n.emnant o& a cold fanont,
    It* lncn.ea*ed ozone  content could have caa*ed an/on. "*eeded" an ozone
    epi*ode.
    
         S,tnato*phenA.c ozone accompanying the &n.ontal *y*tem oft Septemben. 24 I*
    believed to have  Initiated the photochemical oxidation *eqaence broadly
    acn.o** the *tate.  Thi* *equ.ence buitt to epi*odic levels, which peaked
    dunging the peniod di*cu**ed.
    
                                       INTRODUCTION
    
         The frequent occurrence of regional  ozone (03) episodes in the eastern
    United States suggests  that their cause is related to repetitive meteoro-
    logical patterns.
    
          This paper  seeks  to analyze such patterns and develop a more detailed
    understanding of  the regional  episode.  The subject of this study is the
    *J. W. Hathorn III, Applied Meteorology,  Inc.,  Houston, Texas,
     H. M. Walker, Monsanto Co., Texas  City,  Texas.
                                          353
    

    -------
    week-long episode occurring in Texas between September 25 and October 1, 1975.
    
         This was plainly a major episode that extended to practically all of
    the monitoring sites of the state network.
    
         Figure 1 presents time plots of daily ozone peaks for the 2 1/2
    month period beginning on August 20th.   Part 1A depicts patterns for
    Houston, Aldine, Texas City, and El  Paso, which are shown with the one-week
    period under discussion being outlined.   As a result of this work, another
    widespread episode was noted during  the  period September 14-17, 1975.  This
    episode is also outlined.  Both of these episodes are sharply defined at
    all sites.
    
         Figure 1-C extends the analysis to  Corpus Christi, Orange, and Fort
    Worth and adds high quantity data sets  from two non-urban Texas sites.  The
    Port O'Connor data was obtained courtesy of DuPont and the Athens data (by
    Radian Corporation) was obtained courtesy of Texas Utilities.  Again, all
    tracks show the effect of both episodes, although, in the case of the rural
    Athens sites, three of the four effects  are manifest as maxima in the data
    actually peaking below the 0.08 ppm ambient air standard.
    
         Figure 1-B shows tracks for Clute,  Sari Antonio, Dallas, Austin,
    Nederland, and the other El Paso site.   All sites but Austin reacted to
    the September 14-17 episode, and all but El Paso (Campbell) to the
    September 25 through October 1 episode.   The latter observation was un-
    expected in view of the sharp episode effect displayed by the other El
    Paso monitor during that period.
    
         Figure 1-D depicts Houston sites operated by the Houston City Air
    Pollution Control Department and adds a  track for Lake Charles, Louisiana,
    obtained courtesy of the Louisiana Air  Control Commission.  The Houston
    sites strongly evidenced the episodes.   The Lake Charles track shows slight
    evidence of the two episodes.
    
         Considering all four sections of Figure 1 together, one sees the
    persistence of these two episodes that  covered the state.  Closer inspection
    of all tracks suggests that additional  episodes could have been defined for
    the periods August 21-23, October 6-7,  and October 29-30.  These would also
    have had relatively wide coverage.  In  fact, for the entire 73-day period
    one might well conclude that most periods of high ozone at alj sites
    occurred as manifestations of broad  ozone episodes.
    
         Figure 2 presents time patterns of  ozone for a number of the sites
    hour-by-hour during the episode.  The strong diurnal pattern Is clearly
    evident in the cities with the highest  emissions of various sorts.  Thus,
    the Houston sites have the highest peaks and the greatest number of hours
    of essentially zero ozone each night.  Conversely, rural Athens barely
    reached the National Ambient Air Standard (NAAS) during the episode but ex-
    hibited little diurnal variation and has relatively high ozone levels through-
    out the night many nights.  Port O'Connor has a pattern similar to Athens
    with occasional reversion to a more  urban-type pattern.  El Paso's pattern
    is surprisingly similar to that of Houston.  Texas City's is characterized
    
    
                                         354
    

    -------
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    by many high nighttime hours -- probably indicative of winds  directly off
    the Gulf.   This was somewhat unexpected since Texas City in general  has
    relatively high levels of both hydrocarbons and ozone.
    
         Since  it  is more than 750 airline miles from El Paso to Orange, the
    event of September 25 to October 1 was truly of synoptic proportion -- far
    beyond the  scale of any local pollution situation.
    
         Previous  data suggests that ozone episodes that cover large regions
    recur with  a typical set of characteristics as follows:
    
         1.  High  ozone concentrations will persist for several days.
    
         2.  Both  rural and urban monitoring stations throughout the region,
             whether upwind or downwind of urban or industrial areas,  will
             experience the episode.
    
         3.  Concentrations of other contaminants will not necessarily be high.
    
         4.  Ozone concentrations rise sharply after sunrise and decrease
             sharply in the evening.
    
         5.  Usually, the wind is from the southern quadrant and there is a
             large subtropical anticyclone (i.e., high pressure area)  located
             east  to northeast of the region experiencing the episode; (i.e.,
             the event is "on the backside of a HIGH.")
    
         6.  The frequency of occurrences is high (e.g., in Texas, more than
             three times in some months).
    
         The data  of Figures 1 and 2 confirm that the episode under study
    possessed most of these characteristics.  Additional monitoring information
    revealed that  characteristic #3 was apparently applicable; the concentrations
    of other contaminants were not uniformly nor especially high.  Item #6,  the
    weather characteristics will now be discussed in detail.
    
    SYNOPTIC WEATHER SITUATION FOR THE SEVEN-DAY EPISODE
    
         The synoptic weather situation leading up to the seven-day ozone episode
    began with a cold front passing through Texas between September 18 and 20.
    Figure 3 presents the surface weather map  for September 20,  1975, for 7:00
    a.m. EST, and also shows the locations of two vertical cross-sections (A-A1
    and B-B', heavy dashed lines) to be discussed later.
    
         The cold front merges with Hurricane Eloise on the afternoon  of
    September 22,  in the central Gulf of Mexico (Figure 4) and became  stationary
    along the Atlantic Coast of the United States until September 28,  while
    the remnants of the hurricane moved up the coast toward Nova  Scotia (Figures
    5 through 7).
    
         On September 26 (Figure 6), a high pressure area following the cold
    front moved into the central United States (Missouri) and then drifted
    
    
                                         359
    

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     slowly  east-northeastward  until  on  October  1  (Figure 8)  it was  located  in
     the  Atlantic  Ocean.   During  the  seven-day period  from September 25  through
     October 1 ,  Texas was  located on  "the  backside of  this HIGH" and experienced
     generally southerly flow.  These were  the seven days during which the ozone
     episode occurred.
    
         Those  familiar with synoptic weather patterns recognize this sequence
    of events (except for Hurricane  Eloise) as rather typical.
    
    THREE-DIMENSIONAL STRUCTURE OF THE ATMOSPHERE FOR THE EPISODE
    
         To understand how an ozone  episode in Texas beginning on September 25
    was caused  by stratospheric ozone, the three-dimensional  structure of the
    cold front  in both space and time (beginning on September 20)  must be
    examined.   Vertical cross-sections perpendicular to the front at its
    steepest point (Section A-A1  in  Figure 3)  and parallel  to the front (Section
    B-B'  in Figure 3) describe the front's three-dimensional  structure during
    the early development stage.   A time series  of vertical  temperature pro-
    files show  the transition continuity from the development stage to the
    dissipation stage.   Then, another vertical  cross-section  shows the structure
    of the front in its dissipation stage.
    
         A vertical cross-section from International  Falls,  Minnesota, to
    Pittsburgh, Pennsylvania (see Section A-A1  in Figure 3)  is presented in
    Figure 9.   The cold front intersects the surface near Pittsburgh,  passes
    over Flint, Michigan, and Green Bay, Wisconsin, before  it intersects the
    tropopause  in central  Wisconsin.   The cold front is undergoing rapid
    development indicated by potential  temperatures within  the lower frontal
    layer (dashed lines indicate constant potential  temperature,  i.e., isentropes)
    not yet equalling those at the tropopause  over International  Falls.   (There
    is another  stable layer over Pittsburgh, Flint, and Green Bay that can be
    identified  as the remnants of another cold front that had pushed through
    the area several  days earlier.)  The cold  front is moving rapidly (about
    9 miles per hour) eastward.
    
         Another cross  section (B-B'  on Figure 3) through Green  Bay that
    essentially parallels  the cold front until  it intersects  the  ground just
    south of Longview,  Texas is shown in Figure  10.   The frontal  remnant that
    was also noted in Figure 9 can be identified in Figure  10 as  well.
    
         These cross-sectional  analyses (Figures 9 and 10)  indicate that fronts
    are continuous layers  that can cover large areas.   In addition, the layer
    itself can  persist  in  time.  To illustrate persistence,  a time-series of
    vertical temperature profiles measured at  Longview, Texas, from September
    19 through September 28 are presented in Figure 11.  The  cold front passed
    Longview on the afternoon of September 19  and is identified  as a shaded area
    on all  subsequent profiles.  Between September 22  and 23, the front
    decreased in altitude  from 8,700  feet to 5,800 feet (conserving its original
    potential temperature) and remained at about that  altitude throughout the
    seven-day episode.
    
    
         The temperature profiles for September 23 through  28 have the "typical"
    
                                         367
    

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    appearance of those when air is subsiding over a stable layer.   This is
    consistent with the circulation patterns aloft over Texas for this period.
    
         Having now demonstrated that the cold front that passed through Texas
    between September 19 and 21 actually remained over the area as  a stable
    layer through September 28, a cross-sectional analysis (Figure  12) indicates
    that the layer covered not just Texas but the entire central United States.
    (The cross-section is identified as C-C1 on Figure 6.)  The cold front-
    stable layer can be identified over Longview, Texas, but not over Lake
    Charles, Louisiana, on September 26.  This indicates that the atmosphere
    over Lake Charles has become well mixed and has destroyed the stable layer.
    Any air that was previously in the stable layer is now mixed throughout
    the lower troposphere.
    
         Two days later the stable layer reappeared at Lake Charles but
    disappeared over Del  Rio, Texas (Figure not included).  This sporatic
    disappearance (i.e.,  mixing) and reappearance of a "frontal remnant-stable
    layer" is a typical occurrence on the "backside of a HIGH."  There, the
    trailing edge of the  cold front is losing its identity as other meteorological
    phenomena begin to dominate.  The speed with which the cold front-stable
    layer loses its identity depends on the speed of motion of the  High pressure
    area.   A slowly drifting HIGH may result in several  disappearances and
    reappearances of the  layer.
    
                 STRUCTURE OF A FRONT AND ASSOCIATED OZONE MEASUREMENTS
    
    FRONTAL MODEL
    
         The three-dimensional  structure of a front has been modeled by Reed
    and Daniel sen, 1959,  by analyzing the discontinuities in the temperature
    and wind fields at the frontal  and tropopause surfaces.  Their  model, after
    which the analysis in Figure 9 is patterned, describes the front as a
    layer of air whose upper and lower surfaces are tied to the tropopause
    ahead of and behind the front, respectively.  Air within the frontal layer
    can actually have the same potential temperature (i.e., be on the same
    isentropic  surface) as air in the stratosphere.
    
    Vertical  Motion Within the Frontal Layer
    
         More recently, Shapiro, 1969, examined the detailed vertical motions
    in the upper frontal  zone using a high-resolution numerical technique.  He
    has shown that there  can be downward motion of air of up to 0.15 meters
    per second  within the upper frontal  zone.  This downward moving air would
    conserve its potential temperature (i.e., flow along an isentropic surface)
    as it moved down in the frontal layer.   Since it is stratospheric in
    origin, it  contains high concentrations of ozone.
    
    Observations of Ozone Within the Frontal Layer
    
         Vertical  profiles of ozone have been measured by several research
    programs.  Figure 13  presents one such  profile measured by the  Air Force
    Cambridge Research Laboratory's (AFCRL) ozone program on May 7, 1963,
    
    
                                         372
    

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    7:12 a.m. EST, at Tallahassee Florida.  This profile shows that as the
    ozonesonde (instrument package) ascended through a frontal layer at an
    altitude of about 8 km, there was an increase in ozone.  Other profiles
    at Tallahassee and at other stations (Hering and Bordon, 1964, 1965, and
    1967; and Carney, 1976) have indicated similarly that sometimes there are
    increased concentrations of ozone within frontal layers.  This is probably
    stratospheric ozone being transported down an isentropic surface within
    the frontal layer.
                                      OTONAQIAM
             FRONTAL
             LAYER
    Figure 13.   Vertical  ozone profile (ozonagram)  for Tallahassee, Florida, for
      May 7, 1963, 7:12 a.m.  EST indicating that there was  an increase of ozone
          concentrations  measured by the ozonesonde as it ascended through
                                  a  frontal  layer.
    
         While being transported down the inside of the front, the ozone will
    move with the general circulation at each level and will persist until,
    either  destroyed by precipitation, washout, etc., or mixed into the lower
    tropospheric air.  The general circulation over the backside of a HIGH has
    the required anticyclonic subsidence to mix the air within the "dissipating"
    frontal layer to the surface.
    
    A Perspective Sketch of the Frontal Structure
    
         To summarize  the structure, a sketch of the three-dimensional
    perspective of the frontal surfaces (Figure 14) shows that they are
    essentially topological surfaces that connect the tropopause  (a surface)
    to the  earth's surface.  Gridlines on the front's surface are sketched to
    show that the front at the trailing edge (left-hand side) has flattened
    and is  almost horizontal.  In addition, a section of these gridlines on
                                         374
    

    -------
     the  leading and trailing edges of  the  front  are  omitted  to  show the thick-
     ness of the innerfrontal layer and to  show the tendency  for stratospheric
     air  to flow downward within  the  layer.  A jet stream maximum is indicated
     at about 200 millibars  (mb)  over the leading edge  of the front  and  a low-
     level anticyclonic subsidence is indicated at the  trailing  edge.
                                                                 JET STREAM
                                                          LEADING EDGE OF THE
                                                          COtO FRONT
                       STATIONARY PORTION OF
                       THE FRONT
    Figure 14.  Artist's sketch of the structure of a cold front.  Grid  lines  on  the
     frontal  surface are broken to show the thickness of the frontal  layer  near the
    leading and trailing edges.  The tendency for stratospheric air to flow downward
      within the frontal layer is indicated.  Also, the dissipation of the  frontal
          layer near the trailing edge is indicated as well as the anticyclonic
                               subsidence near that edge.
    
    
     ROUTINE EVENTS LEADING TO AN EPISODE
    
          The sequence of events leading up to the regional ozone episode is:
    
          1.   Ozone-rich stratospheric air begins to flow down inside the
              developing frontal layer at the upper levels.
    
          2.   Several days later, ozone from the upper rear portion of the  front
              has moved (a) down within the frontal layer, and (b) around to a
              position near the trailing edge.
    
          3.   As the trailing edge dissipates and the air within the  front
              mixes in the lower troposphere, ozone is transported to the
              earth's surface.
          The meteorological analysis  has  provided  a  clearly feasible mechanism
     for bringing stratospheric ozone  to the  surface  of  the  earth  in  Texas.   The
     quantities involved are not definable  by this  analysis.   However, reasonable
    
                                           375
    

    -------
    assumptions suggest that this injected ozone may amount to an appreciable
    part of, perhaps even a majority of, the ozone found at unpolluted rural
    sites.  However, in urban areas it could hardly contribute more than a
    small portion of the total ozone burden.
    
         Another phenomenon is believed to operate and exert a major influence.
    This is initiation or triggering.   It is suggested that stratospheric ozone
    played the role of a free-radical  oxidation initiator and triggered a
    gradual buildup of photochemical oxidation processes, which culminated in
    the episodic ozone levels of September 25 through October 1.
    
         For the benefit of those unfamiliar with the details of chemical
    oxidation processes, let me comment that it Is well  known that hydrocarbon
    oxidation reactions employing oxygen proceed by free-radical sequences.
    However, an initial source of such radicals is required to initiate the
    process.
    
         A dramatic example of the importance of initiation can be cited from
    one of Monsanto's commercial experiences.  In the commercial production
    of cumene hydroperoxide, which is  the first step in Monsanto's synthesis
    of phenol, cumene is oxidized with air.   This reaction is initiated by
    providing an initial level of a percent  or so of cumene hydroperoxide in the
    oxidation mixture.   Thermal fragmentation of a portion of this initiator
    provides enough radicals to get the process going.  It is exceedingly
    difficult to initiate the process  if no  peroxide is present.  When Monsanto
    started up its plant in 1962, no oxidation occurred, even after 16 hours
    of bubbling air through hot cumene.  When one pint of a dilute cumene
    hydroperoxide solution was added to a 21,000 gallon reactor, the reaction
    started briskly in less than three minutes.  The applicable sequence of
    free-radical initiation and propagation  steps is illustrated in Figure 15.
    
         It is believed that initiation of this type provides the chemical path
    by which stratospheric ozone can initiate an ozone episode,on a scale as
    broad as the entire state of Texas.
    
         Significant levels of stratospheric ozone, though well  below the NAAS,
    may become widely dispersed in the lower troposphere.  This ozone can, by
    reaction with olefins, create ozonides that are unstable and cleave yielding
    diradicals.  These diradicals can  propagate hydrocarbon oxidation sequences
    of the type shown in Figure 15.  Figure  16 illustrates part of this process.
    
         Radicals from the hydrocarbon ozidation process can oxidize nitric
    oxide (NO) interferring with the nitrogen-dioxide photolytic cycle, causing
    a buildup of ozone (Figure 17).  Note that the process of Figure 17 is
    conservative of free-radicals, allowing  it to continue and to oxidize more
    and more NO.  Every molecule of NO oxidized is, of course, equivalent
    potentially to creating one more molecule of ozone.
    
         Critics of this suggestion will, no doubt, point out that the nitrogen
    dioxide photolytic cycle is capable of providing many oxygen atoms that
    might act as initiators for the oxidation of hydrocarbons.  This may or may
                                         376
    

    -------
        INITIATION:
    
              R-O-O-H     	»-     R •  + H-0 •
    
    
      PROPAGATION:
    
           R-H + H-0 •     	+-     H20 + R •
    
           R .  + 02       	^     R-0-0 •
    
        R-0-0  • + R-H      	•*     R-O-O-H  +  R •
    
    
                 ETC,
                                         R « CgH5C (CH3)
    
     Figure 15.  Free-radical  initiation  and  propagation,
    CH3 - CH = CH9   +   0,    	*     CH,  - C     C-H
                                                  IJ  ir  H
    
                   CH20   +   CH3  -
                                       0
         Figure 16.   Hydrocarbon oxidation sequences,
    
    
                             377
    

    -------
                      R-CH2-0-0 • + N-0   	*•    R-CH2-0 •  + NO
                               R-CH20 •   	•*    R • + CH20
                               R • + (L   	*-    R-0-0
                         R-0-0 ' + N-0    	*-    R-0 • + N02
                                   ETC,
    
    
      Figure 17.   Oxidation of Nitric Oxide, Nitrogen Dioxide photolytic cycle.
    
    not be so.  Oxygen atoms and various hydrocarbon free-radicals do not have
    the same energetic properties and ability to transfer with all moieties.
    Therefore, initiation of oxidation chain process in the manner suggested
    may be favored.
    
          A factor favoring stratospheric ozone being the initiator is that it
     will  be well  mixed into many thousands of feet of the lower troposphere.
     Each  day, as  mixing begins, a fresh infusion downward can provide a source
     of make-up free-radical initiator to keep photochemical  activity building.
    
          Some confirmation of this view is obtained in the fact that it is
     now being observed in aerial plume studies (7, 8) that ozone concentration
     in downwind plumes seems to be closely related to upwind ozone concentrations
     feeding into  the urban photochemical process.
    
          It should also be noted that stratospheric ozone is not the only possible
     source of such initiation.   Transported ozone  and carryover ozone frequently
     observed in bands near the inversion level can act similarly.  As suggested,
     ozonides, hydroperoxodes, and perhaps even peroxyacetylnitrate (PAN) can
     act as sources of free-radicals and carry the  initiation process over from
     one day to the next.
    
          There is certainly a great need to provide a chemical  explanation for
     the broad scale ozone episode.  Pollution, as  a direct cause, is ruled out
     because of its invariability, the distances involved, and the involvement
     of unpolluted sites.  Air stagnation is an unlikely cause because of the
     lack  of an accompanying sharp or consistent buildup in other pollutants
     and because the rapid development in high ozone peaks frequently occurs
     before sufficient time has elapsed to permit such a buildup.
    
          It is believed that the phenomenon discussed occurs primarily in
     continental  polar air masses and involves their associated fronts.  We
     believe that  it occurs most often in the fall  of the year in central
     United States but may be associated with intrusions in other seasons.
                                         378
    

    -------
         While we regret that we cannot offer unequivocal proof that the
    synoptic-scale ozone episode is triggered by an injection of stratospheric
    ozone, we believe that strong evidence exists that this may be the case.
    Future research efforts, particularly aerial studies, should make an effort
    to seriously test this thesis.
    
                                         SUMMARY
    
         The frequent, regional ozone episodes experienced in the eastern United
    States are probably caused, in part, by the transport of ozone-rich
    stratospheric air to the earth's surface.  Numerous vertical ozone profiles
    have shown that there is increased ozone concentrations within the frontal
    layer, and currently-accepted frontal models indicate that this ozone is
    probably of stratospheric origin.
    
         An analysis of the space and time continuity of a front's low-level
    structure demonstrates that the stable layer over the region experiencing
    an ozone episode was actually the remnant of a cold front that had pushed
    through several  days earlier.  The stable layer disappeared and reappeared
    at several stations indicating that it was losing its identity as it
    dissipated.   Any air within the stable layer would have been mixed in the
    lower troposphere.   Since this stable layer is the remnant of a cold front,
    its increased ozone content could have caused and/or "seeded" an ozone
    episode.
    
                                    ACKNOWLEDGEMENTS
    
         The kind cooperation of the staffs of the Texas Air Control Board, the
    Houston Air  Pollution Control Department, the Louisiana Air Control
    Commission,  the  DuPont Company, Texas Utilities, and Radian Corporation in
    providing data is  greatly appreciated.
    
    
                                     REFERENCES
    
    1.   Carney, Thomas A.,  1976.  Vertical  Distributions of Ozone  as Evidence
         of the Role of Stratospheric Transport  in  the  Spatial and  Temporal
         Distribution of Tropospheric Ozone.   In:   Proceedings of the Ozone/
         Oxidants, Interactions with the Total  Environment, Specialty Con-
         ference, Dallas, Texas, March 10-12,  1976.   P.  234.   (Thomas A.
         Carney, Tennessee Depart of Public  Health, Division of Air  Pollution
         Control, C2-220 Cordell Hull Building,  Nashville, Tennessee 37219.)
    
    2.   Hering, W.S. and T  R. Borden, Jr.,  1964.   Ozonesonde  observations  over
         North America, Vol. 2.  Environmental  Research  Paper  No.   38.   Report
         AFCRL-64-30  (II),  Air  Force Cambridge  Research Laboratories.
    
    3.   Hering, W.  S. and T. R. Borden, Jr.,  1965.   Ozonesonde observations
         over North America, Vol. 3.  Environmental Research Paper  No.   133.
         Report AFCRL-64-30  (III), Air Force Cambridge  Research Laboratories.
    
    4.   Hering, W.S. and T. R.  Borden,  Jr., 1967.  Ozonesonde observations
    
    
                                         379
    

    -------
         over North America,  Vol.  4.   Environmental  Research  Paper  No.   Z79.
         Report AFCRL-64-30 (IV),  Air  Force  Cambridge  Research Laboratories.
    
    5.   Reed, R.  J.  and E.  F.  Danielsen,  1959:   Fronts  in  the vicinity  of  the
         tropopause.   Arch.  Meteoro. Geophy.  Bioklim., All, 1-17.
    
    6.   Shapiro,  Melvyn A.   On the  Scale  of Atmospheric  Motions within  Middle-
         Tropospheric Frontal  Zones.   NCAR Cooperative Thesis No. 18,  Florida
         State University and Laboratory of  Atmospheric  Science, NCAR, 1969.
    
    7-   Dr.  Max Shauck, Baylor University,  private  communication.
    
    8-   White, Blumenthal,  et al.,  Meteorological Research,  Inc.,  Paper to be
         presented at the International Conference on  Photochemical Oxidant and
         Its  Control, September 12-17,  1976,  Raleigh,  N.  C.
                                       380
    

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                                                                                8-3
                          APPLICATION OF 1960'S OZONE SOUNDING
                       INFORMATION TO 1970'S SURFACE OZONE STUDIES
    
                                     P. R. Sticksel*
    
    ABSTRACT
    
         It has been purported tkat high ozone. levels In the lower troposphere
    OSLO., at least partially, the. result o^ ozone. transport firom the stratosphere
    downward along stable layers.  A limited -investigation oft this hypothesis was
    conducted using ozone measurements made -in the. lower troposphere In  1963
    and 1974 and the data {,rom the. North American upper ait soundings o& tempera-
    ture and wind.  Three-dimensional Isentropic trajectories traced backward
    firom the lower troposphere failed to confirm the hypothesis o^ continuous
    downward transport along stable Lagers.  However, a sloping stable layer ex-
    tending ^rom coast to coast ac/io-4-i the United States was Identifi-ied  &or the
    May, 1963, case, and AoundinQ-b -into this layer at three widely-separated sta-
    tions revealed higher-than-average ozone concentrations uiithin the layer.
    
                                      INTRODUCTION
    
         This is a report on the testing of a hypothesis--that episodes  of high
    surface ozone concentrations are at least partially the result of transport
    of stratospheric ozone  downward along  stable layers.  These stable layers are
    hypothesized to (a) originate at breaks in the tropopause at higher  latitudes,
    (b) follow surfaces of  constant potential temperature downward, and  (c) ter-
    minate within inversion layers near the surface.  The basis for this hypothesis
    is observations of ozone maxima appearing at various levels in the troposphere
    during the upper atmosphere ozone sounding programs conducted in the 1960's.
    Kroening and Ney (1) identified "rivers" of high ozone concentrations exiting
    from the stratosphere at tropopause breaks and entering the upper troposphere.
    
         In a recent paper, Sticksel (2) showed one example of a vertical cross
    section through the atmosphere from Florida to Greenland on which there was a
    sloping stable layer.   The surface synoptic chart is Figure 1, and the cross
    section with the sloping layer is Figure 2.  This stable layer (between the
    potential temperatures  of 310°K and 315°K) appeared in many upper atmospheric
    soundings along the eastern coast of the Northern Hemisphere on May  15, 1963,
    at 1200 Greenwich Meridian Time (GMT).  Ozone soundings at Tallahassee,
    Florida; Bedford, Massachusetts; and Churchill, Manitoba, all displayed ozone
    peaks along this surface of constant potential temperature (isentropic surface)
    (Figures 3a, 3d, 3e).   At Thule, Greenland this isentropic surface was within
    *Battelle Columbus Laboratories, Columbus, Ohio.
    
                                         381
    

    -------
            Figure 1.  Surface synoptic map for 1200 GMT on May 15, 1963.
                              (Weatherwise, August, 1963)
    
    the stratosphere after passing through a break in the tropopause north of
    Churchill.
         Sticksel (2) also noted that high  concentrations  of lower tropospheric
    ozone appearing on the Northern Hemisphere soundings  of the 1960's  followed a
    seasonal progression and recession from low latitudes  to high latitudes and
    back again during the spring-summer-fan  period.   This movement corresponds
    to the seasonal progression and recession of the  tropopause break poleward and
    equatorward.
    
         This evidence for the transport of ozone between  the stratosphere and
    surface is circumstantial.  Proof of a  continuous trajectory downward and a
    description of the mechanism of descent are required.   If downward  trans-
    port along a stable isentropic layer can  be demonstrated, the horizontal
    extent of this movement should be determined.
    
                                 ISENTROPIC TRAJECTORIES
    
         The approach chosen for this investigation of possible stratosphere-
    to-surface transport was to study the pressure and wind patterns on isen-
    tropic surfaces.  Pressure data for constructing  the  isentropic charts were
    obtained from the temperature-pressure  soundings  of the United States and
    Canadian rawinsonde networks.   Wind speeds and directions were interpolated
    from the wind observations made during  these same soundings.
         Since
    thesis was
    one of the pieces
    the May 15, 1963,
    of evidence for the stratosphere-to-surface hypo-
    cross section, this date was chosen for the
    isentropic analysis.   Work was done with both  the 9=310°K and the 9-315°K
    surfaces.  The 310°K surface intersected the Tallahassee sounding at 650 mil-
    libars (mb).   This was the top of the ozone layer that extended from the ground
    to about four kilometers at this station (Figure 3a).   Above this layer of
    high ozone there was a shallow layer in which  ozone concentration dropped off
                                         382
    

    -------
                                                                         O) H-
                                                                        .c s:
                                                                        +-> CD
    
                                                                        -C: O
                                                                         C7>O
                                                                         ^ CM
                                                                         O •—
                                                                         S-
                                                                        J^  5-
                                                                        4->  O
                                                                           C(-
                                                                         OJ
    
                                                                         rj T3
                                                                        4->  C
                                                                         (O  to
    
                                                                         CD 'c
                                                                         Q.  O)
                                                                         £  OJ
                                                                         O)  S-
                                                                        4-> CD
           O)
           QJ
    
           cn
           
           c:
           0) O)
          -(-> +->
           o o
          Q_ C
              O)
              T3
    
          n to
          us ai
          CTl C
    on  fO     i —
    CO  O.  «*
    o  E LO >,
          i— >
              » ai
           (O 3C
                                                                        J- (O
                                                                        OH-
                                                                        n3 a)
                                                                        O O)
                                                                        S-
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                                                                               c   .
                                                                           -t-J  Q  C
                                                                            CO
    (SJDq!||iiu)3anSS3Hd
    
                           383
    

    -------
    slightly and then a two-kilometer layer of concentrations equal  to those in
    the surface layer.  This upper layer is intersected by the 315°K isentropic
    surface.  Both these surfaces were high enough so that they did  not intersect
    the ground even in the mountainous portions of southwestern United States.
    
         Since all processes in the free atmosphere tend to be largely adiabatic
    as long as there is no condensation, air particles should remain on the same
    isentropic surface unless saturation occurs (3).   Other nonadiabatic atmos-
    pheric processes include radiational heating and cooling, evaporation, and
    convective activity (4).
    
         Indications of the direction of vertical  motion were obtained from the
    relationship between wind directions and isobars  on the isentropic charts.
    Winds blowing toward higher pressure were evidence of descending motion.
    Generally air parcels moving from north to south  on an isentropic: surface in
    the Northern Hemisphere are descending toward  lower altitudes.   Some caution
    must be taken in these vertical motion determinations because the isentropic
    surface itself may also be moving.  Thus, these rules are reliable only when
    movements are strong.  If this is the case, the forward motion  of the air
    relative to the surface is guaranteed (5).
    
         Keeping these limitations of isentropic analysis in mind,  an additional
    step was taken to determine the origins of the ozone-rich air.   Trajectories
    were traced backward along the isentropic surfaces in 12-hour segments from
    one standard radiosonde launch time to the preceding launch time.  These
    trajectories were graphically computed from the streamlines on  the surfaces
    following the method given by Saucier (6).  Trajectories, once  constructed,
    should be viewed as surrounded by a region of  uncertainty expanding with
    distance from the origin of the trajectory.  In the case of the  three-dimensional
    isentropic trajectories, the region of uncertainty can be visualized as cone-
    like.   The base of the cone-like volume is an  ellipse rather than a circle.
    
    
                                         RESULTS
    
    MAY 15, 1963
    
         Figure 4 portrays the isentropic surface  for 1200 Greenwich Meridian
    Time (GMT) on May 15, 1963.  The surface has a depression (region of high
    pressure) over the Texas panhandle and a dome  (region of low pressure) center-
    ed over northeastern Wyoming.  The intersection of the 9=315°K  surface with
    the tropopause occurs along a line running across Canada from the southwest
    to the northeast.
    
         Streamline patterns on the surface generally follow the isobars.  There
    is an anticyclonic divergence center on the Louisiana-Mississippi border.
    Some ascending motion is apparent in the western United States  and some de-
    scending motion in the eastern United States.   There is no strong descending
    motion from the Canadian area of the tropopause southward into  the central
    or eastern United States.
    
         The strongest winds on the surface would  represent the greatest relative
    
                                         384
    

    -------
      (A)  TALLAHASSEE,FLORIDA
    200|-
             t:
           ,0L  - —.V>-  .  !
            0    50     TOO    150    200
                   PARTIAl PRESSURE Of OZONE
                              250   300   -60    60
                                                                     	"1200
                                                   40    -20
                                                    1E MPERAlORE
                                                                   "00
                                                                  £- —  -^ 500
                                                                    	
                                                                  20    40
    2°r)'
              (B) ALBUQUERQUE,NEW MEXICO
    
                 :-    (  -   •     t    -t   ,  1  !  '=
      \
             PARTIAL PRESSURE OF OZONE l^mb'
       (C) FT. COLLINS, COLOR ADO
     R
     E
     S
     S
     u
     R
    E
    
    (mb)
            ...
          50    100    150    200   250   300   -80
             PARTIAL PRESSURE OF O7ONE '^mb
       (D) BEDFORD, MASSACHUSETTS
                                                                       ^200
                                                                       I500
                                              -60   -40
                                                        -20
                                                   TEMPERATURE
                                                                   1
                                                                   0
                                                                  i'CI
                                                                  20    40
                                                                     -—-^200
                                                    1EMPEBATU8F   (XI
                                             -60   -40    -20    0     20    40
                                                                       ^200
               100    150    2OO
    
             PARTIAL PRESSURE OF OZONE
       (E) CHURCHILL, MANITOBA
    
          —-	_       __.  -    _
          50    100    150    200   250   300
    
             PARTIAL PRESSURE OF OZONE U^b)
                                                    -60    -40    -20    0 „   20    40
                                                          TEMPERATURE   l'O
     Figure 3.   Ozonesonde soundings for 1200 GMT on May 15, 1963.
                   (Hering and Borden, Vol. 2, 1965)
                                  385
    

    -------
    FIGURE 4. PRESSURES (MB) AND DIRECTIONAL STREAMLINES OF THE 315 K
            ISENTROPIC SURFACE FOR 1200 C1MT ON MAY 15, 1963  SHADED
            AREA DENOTES WIND SPEEDS GREATER THAN bO KNOTS.  HEAVY
            DASHED LINES ENCLOSE PORTION OF THE SURFACE WHICH IS IN
            THE STRATOSPHERE
                             386
    

    -------
    motion of the air to the surface and consequently the areas  of most pronounced
    vertical motion.  These wind maxima indicate strongest ascent over Kansas and
    Missouri with strongest descent occurring between Indiana and Virginia.
    
         Isentropic trajectories were computed to determine whether the ozone-
    rich air that appeared along this surface at Tallahassee, Bedford, and
    Churchill could be traced backward in the direction of the tropopause.  The
    results of these computations are displayed in Figure 5.  The air that arrived
    above Tallahassee on May 15 (Trajectory No. 1) was above the Houston, Texas,
    region 48 hours earlier.  This trajectory resembles the flow one would expect
    around the north side of the high pressure area located in the Gulf of Mexico.
    The motion along this trajectory was generally upward.
    
         The Bedford trajectory (No. 2) followed a different path and indicated
    descent for the air parcel  as it traveled southward from northern Canada to
    Massachusetts.  However, it should be stated that none of the temperature
    soundings along this trajectory had a stable layer encompassing the isentropic
    surface.
    
         Trajectory No.  3 from Churchill backward displayed not descending move-
    ment, but rather small ascending motion.  The position of the air parcel
    24 hours earlier was over northern British Columbia at a height that would
    have been within the stratosphere on May 15.  However, on May 14, this loca-
    tion was still within the troposphere.
    
         Although one must take into account the pitfalls accompanying the compu-
    tation of isentropic trajectories, the ones described here should be represen-
    tative of the true flow.  One can conclude from these results that the high
    ozone concentrations observed at 9=315°K on the May 15 soundings did not
    arrive there by direct transport from the stratosphere along a stable layer.
    In fact the ozone at the three stations probably came from three different
    source areas, even though their final potential temperatures were identical.
    
    
    DAYTON, OHIO--1974
    
         Calculation of an  isentropic trajectory for the  period of a recent  oxidant
    study in Ohio provided some additional insight on the hypothesis of descending
    ozone parcels.  On August 7, 1974, at 0000 GMT (8 p.m. EOT) a vertical ozone
    sounding made by an airplane over Dayton, Ohio, measured ozone concentrations
    of over 160 yg/m3 in the layer between the surface and  1500 meters (7).  The
    isentropic trajectory traced backward from this point and time is shown  as
    trajectory No. 4 in Figure 5.  This trajectory was calculated for the 9=300°K
    surfaces.  It terminated at 825 mb at Dayton, which was approximately 1800
    meters above the ground and within the layer of high  atmospheric ozone concen-
    tration.  Forty-eight hours earlier this air was over central Wisconsin  at
    775 mb (an altitude of about 2300 meters), thus indicating descending motion.
    On the morning of August 6 (1200 GMT) the 300°K surface was within a strong
    inversion layer.  At the other 12-hour checkpoints along its journey the air
    parcel was within a layer that was slightly stable.
    
         It is significant to compare the isentropic trajectory (solid line) with
    
                                         387
    

    -------
                                                                    695
                                                                    5-15     650
                                                                    OOZ  , 5-15-63
                                                                              I2Z
    FIGURE 5  ISENTROPIC TRAJECTORIES PLOTTED BACKWARD IN 12-HOUR
             PORTIONS FROM POINT OF TERMINATION  PRESSURES AT THE
             12-HOUR POINTS ARE GIVEN IN MILLIBARS
             NO 1  TERMINATION POINT = TALLAHASSEE ON MAY 15, 1963, AT
             1200 GMT (9 = 310 K).
             NO 2  TERMINATION POINT = BEDFORD ON MAY 15, 1963, AT
             1200 GMT (8 = 315 K)
             NO. 3  TERMINATION POINT = CHURCHILL ON MAY 15, 1963, at
             1200 GMT (6 = 315 K).
             NO 4.  TERMINATION POINT = DAYTON, OHIO ON AUGUST 7, 1974
             AT, 0000 GMT (9 = 300 K)  DASHED LINE IS THE 3000 FEET MSL
             TRAJECTORY COMPUTED BY THE RESEARCH  TRIANGLE  INSTITUTE
             (1975) FOR THE SAME TIME.
                                 388
    

    -------
     a  trajectory  at  3000  feet  (dashed  line) originating at Wilmington, Ohio,
     (20  miles  southeast of  Dayton)  computed by the Research Triangle Institute (8)
     for  their  concurrent  oxidant  study.  The path and endpoints for the 36-hour
     extent  of  the  RTI  constant level trajectory are quite similar to those of the
     three-dimensional  isentropic  trajectory.
    
     Additional  Comment on the  May,  1963, Case
    
          A  prediction  of  the paths  of  the May 15, 1963, isentropic trajectories
     could have  been  obtained from the  500 mb chart for that date (Figure 6).  The
     path of the Tallahassee air parcel was dictated by the HIGH covering the
     southern United  States.  Control of the Bedford trajectory was exerted by the
     trough  in  the  northeast, while  the relatively straight isentropic trajectory
     from Churchill resembles the  500-mb contour pattern in that region.
          Figure 6.   North American 500 mb chart for 1200 GMT on May 15, 1963.
                   Shaded portions enclose areas for which the 9=315 K
                           surface was within a stable layer.
         Another interesting observation related to the 315°K isentropic surface
    is depicted in Figure 6.  The shaded areas enclose all the stations for which
    the 1200 GMT soundings on May 15 had a stable or slightly stable layer en-
    compassing some portion of the interval  between 310°K and 320°K.  This aerial
    representation shows a discontinuity in  the stable surface occurring along a
    broad area near the U.S.-Canadian border.   Any stratospheric ozone that
    reached the troposphere south of this discontinuity must not have proceeded
    along a direct trajectory.  However, the pervasiveness of the stable layer
    over most of the United States suggests  that there may have been an extensive
    layer of ozone related to the HIGH in Mexico.  Closer inspection of the
                                         389
    

    -------
    soundings at Tallahassee,  Albuquerque,  New  Mexico  and  Ft.  Collins,  Colorado
    (Figure 3) verifies that there  was  a  deep layer  of ozone  above  each station.
    The layer at Tallahassee contains  two maxima—about 450 mb to  550 mb and  600  mb
    to the surface.   At Albuquerque the ozone layer  extends from 500 rnb to  the
    surface with a peak at 550 mb.   At  Ft.  Collins there is an above-average  ozone
    layer between 400 and 550  mb.   Thus,  the original  hypothesis is supported in
    part.  There may likely be a large  layer of ozone  sloping upward from low to
    high latitudes.   The ozone in  this  layer is so extensive  that  its source  is
    not anthropogenic.   However, by turbulent mixing it can supply  ozone to the
    surface layer, which supplements the  man-created oxidants there.  It is sug-
    gested that the  stratosphere was the  original source of this pervasive  ozone
    layer and that it was associated with the subtropical  HIGH.  The mechanism
    of transfer downward is still  to be determined.
    
                                       CONCLUSIONS
    
         From the results of this limited investigation the  following  conclusions
    were drawn:
    
         (1)  "Rivers" (inversion layers) of  ozone extending  from  a tropopause
              break to the surface are not  a  reliable  explanation  for  all high
              surface ozone concentrations.  Further investigation may  show that
              there is transport downward along slightly stable layers  in some
              cases.  In any event, the sharp  ozone  peaks observed in  the upper
              troposphere do not isentropically descend unaltered  to  the surface
              where they produce ozone maxima.
    
         (2)  Layers of ozone extensive enough  and deep enough to  rule  out anthro-
              pogenic sources were observed in  the  lower troposphere  associated
              with a large subtropical  HIGH at  500 mb.  This  suggests  another
              descent mechanism associated  with the  development of synoptic scale
              systems.
    
         (3)  Predictions of isentropic trajectory paths can  be made  from the
              contours on isobaric surfaces where those surfaces  are  near the same
              pressure as the origin of the isentropic trajectory.   Movement  along
              contours from higher to lower latitudes  will indicate descent.
              Movement from west to east  will  indicate little movement  in the
              vertical direction.
    
                                       REFERENCES
    
    1.   Kroening, J. L. and E. P.  Ney, Atmospheric  Ozone, J. Geoph.  Res., 67:
         1867-1875, 1962.
    
    2.   Sticksel, P. R., Occurrence and  Movement of Tropospheric  Ozone Maxima,
         In:  Proceedings Ozone/Oxidant Interactions with the Total Environment
         Specialty Conference, Southwest  Section Air Pollution Control  Association,
         Dallas, Texas, 1976,  pp.  252-267.
    
    3.   Byers, H. R., General Meteorology, 3rd Edition, McGraw-Hill  Book Company,
         New York, New York, 1959,  p.  146.
    
                                         390
    

    -------
    4.   Oliver, V.  J., and M.  B.  Oliver,  "Construction  and Use  of Isentropic
         Charts," in Handbook of Meteorology,  F.  A.  Berry,  E.  Bollay,  and  N. R.
         Beers, eds., McGraw-Hill  Book Company,  New  York,  New  York,  1945,  pp.  848-56.
    
    5.   Saucier, W. J., Principles of Meteorological  Analysis,  The  University
         of Chicago  Press, Chicago, Illinois,  1955,  p.  255.
    
    6.   Ibid., p. 313.
    
    7.   Spicer, C.  W., J. L. Gemma, D.  W.  Joseph,  P.  R.  Sticksel, and G.  F. Ward,
         "The Transport of Oxidant Beyond  Urban  Areas,"  Report by  the  Battelle
         Columbus Laboratories  to  the U.S.  EPA,  EPA-600/3-76-018,  U.S.  Environmental
         Protection  Agency, Research Triangle  Park,  N.C.,  February,  1976,  p. 189.
    
    8.   The Research Triangle  Institute,  Investigation  of Rural Oxidant Levels
         as Related  to Urban Hydrocarbon Control  Strategies.   EPA-450/3-75-036,
         U.S. Environmental Protection Agency, Research  Triangle Park,  N.  C.,
         March, 1975.
                                         391
    

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                                                                                 8-4
          THE  ROLE  OF  STRATOSPHERIC IMPORT ON TROPOSPHERIC  OZONE  CONCENTRATIONS
    
                                       E. R. Reiter*
    
    ABSTRACT
         The. e.££e.ctA  o£ &tfiat.o-f>pke.fiic ozone, impotitb into  the. loweA. &iopo£phe.sie.
    one. t>tu.die.d thtiouqh analogy to radioactive. fallout:,  ^nom ozone.&onde. meoiuAe-
    mewXi and  ^fiom  houAly ozone me.aAuA.me.nti> at  lug^pitze.,  Germany (3000 m above.
    mean &e.a le.ve.1  (M.S.L. ) ) .   It -i& bkown that the, max.-ima.rn allowable. houAly con-
    ce.ntsiation o^ 74.7 ppb  ofi  ozone. (0^}  -if, exceeded by &u.ch impontA  on appfiox.-i-
    mateJLy 0.1 pe.nce.vit o^ the.  day* -in the. cycJLoge,ne.tic.al£y  active. K.e.Qi.onA o^ mid-
    dle. latsitLideA.  The. i>tn.atoi,pke.tic CAAC-uJLation patte.fin that ptLOvideA the. ozone.
              in the.  toweA  i>tAatot>phe,ne. appe.au to play a significant fioLe. in
          that provide. 0-$ c.once.ntfiationA  in the. lowe.fi tnopo&pheAe. two to thAe.e.
          in exce44 o& the.  maximum allowable, liveJL &e.t by EPA.
    
                                       INTRODUCTION
    
         The present  federal standards of ozone  (OQ) concentrations not to be
    exceeded for longer than one hour are 160 yg/irr (= 74.7 ppb,  or 0.1238 yg/g).
    This value is transgressed relatively frequently even in rural  areas away from
    known pollution sources  (for references see Singh et  a!.,  1975).   The question
    arises to what extent stratospheric 03 transported into the lower troposphere
    could lead to ambient ozone concentrations that either  exceed the federal
    maximum level or  produce such a high  background level that even a modest
    industrial and/or photochemical contribution could push the concentration
    values over the "allowable" maximum.
    
         To answer this question we have  taken several approaches.
    
    STRATOSPHERIC RESIDENCE  TIMES OF AIR  MASSES
    
         Using data on the  mean meridional circulation published by J. F. Luis in
    CIAP Monograph 1  (Reiter et al . , 1975), together with case studies on eddy
    transport and tropopause height adjustments  (Renter,  1975a),  the  annual mass
    budget of the northern  hemisphere stratosphere given  in Table 1 was derived.
    
         Observed residence  times of nuclear debris in the  stratosphere agree
    very well with these estimates.
    
         From satellite data Lovill (1972) estimated the  average  global value of
    total ozone to be 303.3  Dobson units  (or mini-atmospheric-centimeters at
    *Colorado State University,  Fort Collins, Colorado.
    
    
                                          393
    

    -------
             TABLE  1.  MASS BUDGET OF THE STRATOSPHERE (IN PERCENT OF THE
                   MASS  EQUIVALENT TO ONE HEMISPHERIC STRATOSPHERE)
      Seasonal adjustments of tropopause level                   10%
      Mean meridional circulation                                43%
      Stratospheric exchange between hemispheres                 16%
      Large-scale eddies (jet streams)                           20%
      Small-scale eddies (thunderstorms)                     n eg1iqib1e
    
                                                                 89%
     normal  temperature  and pressure).  The total weight of the ozone column,
     therefore,  is 6.495 x lO'^g/cm2, or 1.6565 x 109 tons in one hemisphere.   If,
     according to Table  1, 73% of the air in the stratosphere is exchanged with
     the  troposphere each year (the 16 percent of interhemispheric exchange within
     the  stratosphere cannot be counted here), 1.2 x 109 tons of ozone should be
     affected by this transport in each hemisphere.
    
         Regener and Aldaz (1969) determined the vertical flux of ozone to be
     1.3  x 109 tons per year over the whole globe.  A somewhat smal'er flux of
     0.804 x 109 tons per year over the globe was determined by Junge (1962, 1963;
     Fabian  and Junge, 1970).  Comparing these values with the above number for
     hemispheric transport, we arrive at the conclusion that only about half of
     the  stratospheric ozone is available for transport into the troposphere.  The
     ozone in the middle and upper stratosphere (above 15 to 20 km) is still photo-
     chemical^ active and subject to dissociation.  (See Reiter et al., 1975, for
     data and references.)  Therefore only ozone in the 1 ower stratosphe re can be
     considered as a potential source of tropospheric ozone.           ~~
    
                              OZONE AND RADIOACTIVE FALLOUT
    
         Detailed data on radioactive fallout during the early 1960's are avail-
    able from the U.S.  Public Health  Service  Radiation Surveillance network.
    Excessive fallout' concentrations  in dry air at the ground usually could be
    ascribed to the import of tropospheric air into the stratosphere (for typical
    case studies see Reiter,  1972).   Radioactive  debris concentration measure-
    ments in the stratosphere are also available  for this  time period from Pro-
    ject Stardust.   We have  attempted to correlate stratospheric Strontium90
    (Sr90)  concentrations (Seitz  et al. ,  1968)  with 03 to  arrive at Sr90/03 ratios,
    For May-August 1963 we obtained an average ratio of 500 in the lower strato-
    sphere  of the northern hemisphere (Figure 1), with Sr  given in dpm/1000 SCF
    (standard cubic feet) and 03  given in yg/g.   A correction has to be applied
    to this  ratio,  because the Sr90 data of May-August were actually compared
    with ozone concentrations of  March-April.   Using the relationship
                                         0
                                           exp(-t/T)
    (where N is the extrapolated Sr90/03 ratio for March-April; N  is the value
    of this ratio at t = 0; T is the e-folding residence time of §r90 in the
    
                                         394
    

    -------
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    -------
     stratosphere, i.e., 14 months) we arrive at a correction factor of 1.24 for
     t = -3 months.  Thus the representative Sr90/03 ratio in the lower strato-
     sphere for March-April 1963 was assumed to be 620.  This value, together with
     others, is shown in Figure 2.  The straight line in this diagram predicts the
     Sr90/03 ratio under the assumptions that the stratospheric 03 concentration
     remains invariant and the the Sr90 concentration is subject to an e-folding
     time of 14 months.
    
         The Sr90/03 ratios of 250 to 300 derived from measurements of September-
     November 1964 do not fit this straight line.  We have to take into account,
     however, that ozone concentrations in the lower stratosphere are only half as
     high in fall than in spring  (D'utsch, 1971).  Therefore, to project the Sr90/03
     ratio measured in fall to 03 concentrations as they would prevail during
     spring, the ratios of 250 to 300 would have to be reduced by a factor of 2
     (dashed "box" in Figure 2) (Reiter, 1975b).
    
         We can now proceed to estimate 03 concentrations at ground level, that
     should have been encountered with surface radioactive fallout of stratospheric
     origin.  Since in spring and summer of 1963 the bulk of radioactive fallout
     was due to the US and USSR test series of megaton devices conducted during
     1962, we can estimate the contribution of Sr90 to the total radioactivity
     measured at ground level in 1963 to be of the order of 1% (Reiter, 1975b).
     By spring of 1964 the Sr90 contribution was of the order of 2%.  A surface
     fallout value of 5 p C/m3 observed in summer of 1963, therefore, should have
     contained approximately 0.05p C/m3 of strontium, or 3.145 dpm/1000 SCF of
     Sr90.  With a Sr90/03 ratio of 620 in the appropriate units the ozone concen-
     tration in this surface air should have been 0.0051 yg/g.  With the same
     ratio of 620 the Federal maximum value of 03 of 74.7 ppb would correspond to
     a Sr90 activity of 76.76 dpm/1000 SCF, or at least 7676 dpm/1000 SCF of total
     radioactivity.  This amounts to 122 p C/m3.
    
         Figure 3 shows the average fallout over the U.S. Public Health Service
     Radiation Surveillance network during 1963.  Discounting the high concentra-
     tions over Nevada, which most likely were due to local sources, we can con-
     clude that the "natural" average background of stratospheric 03 at the ground
     should be of the order of 3 to 5 percent of the federal hourly maximum value.
     Slightly higher values prevail in the lee of the Rocky Mountains, where
     Chinook winds provide a rapid mechanism of transport of stratospheric air
     towards the ground.
    
         The maximum fallout encountered during 1963 is shown in Figure 4.  We
     should emphasize that these are 24-hour average values.  Nevertheless they
     come within about 20 percent of the hourly allowable maximum value of equiva-
     lent ozone concentrations (Reiter, 19755).
    
                                 OZONESONDE MEASUREMENTS
    
         We should expect that "instantaneous"  measurements of 03 concentrations
    will  off and on reach considerably higher values than indicated by 24-hour
    average values,  especially if rapid transport processes from the stratosphere
    are involved,  with little mixing in the upper troposphere.   To investigate
    this  possibility we  reviewed 1477 ozonesonde observations between December
    
                                          396
    

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    398
    

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    1962 and December  1965 (Hering, 1964; Heririg and Borden, 1964:, 1965a,b, 1967)
    Table 2 shows a frequency distribution of maximum 03 mixing ratios (yg/g)
    below the 800-mb level (for the stations Albuquerque, New Mexico, and Ft.
    Collins, Colorado, below 750 millibars (mb)).  The layer below this level
    was assumed  to be  characteristic of the planetary boundary layer  (PEL).   In
    approximately 2 percent of the soundings the hourly allowable maximum of
    74.7 ppb or  0.1238 yg/g had been exceeded.
    
         Of the 31  cases  with  excessive  03 concentrations  in the  PBL,  only three
    (i.e.,  0.2% of the  total  sample)  qualified as possible stratospheric  air
    intrusions:   Goose  Bay,  Canada, 5-2-1963,  0.15 yg/g;  Tallahassee,  Florida,
    8-14-1963,  0.19  yg/g; and  Seattle, Washington, 4-15-1964,  0.16 yg/g.   All
    other  cases  (listed in Table  3) had  to be  suspect of tropospheric  sources
    (Reiter, 1976a).   Figures  5  and 6 show isentropic trajectories constructed
    backwards in time  for the cases of Goose Bay  and Tallahassee.  The case of
    March 24, 1964, in which an ozonesonde intercepted high 03 concentrations
    (ca. 3.5 yg/g) above the 500-mb level over Albuquerque, New Mexico, was not
    considered in the  above statistics,  because  these excessive concentrations
    were encountered outside the PBL.
    
         Since the ozonesondes intercepted layers with high 03 concentrations
    away from the earth's surface we have to expect that these concentrations
    will be reduced by turbulent mixing processes within the PBL.  Even though
    almost  undiluted parcels of air can reach the ground on occasions when such
    layers  are "tapped" by strong  turbulence, the one-hour  averaging process
    inherent in the maximum allowable value of 74.7 ppb will reduce these in-
    stantaneous  "spikes" considerably.  In analogy we could consider the peak
    gusts versus the one-hour average wind speed.
    
                                HOURLY OZONE OBSERVATIONS
    
         Up to this  point we considered  daily average and instantaneous 03 con-
    centrations,  neither of which is strictly comparable to hourly ozone  concen-
    trations.   We were  fortunate to receive hourly ozone data for 529 days, taken
    at Zugspitze, Germany (3000  m above  M.S.L.)  from August 1973  to February,
    1976.   These  data were kindly supplied by Drs. Reinhold Reiter and H.  0.
    Kantor of the Institut fuer  atmosphaerische  Umweltforschung at Gannisch-
    Partenkirchen,  Germany.
    
         In Figure 7 we have plotted a joint frequency distribution of hourly
    maximum 03  concentrations  in excess  of the daily mean values  (ppb) by classes
    of 2 ppb,  and daily mean values by classes of 5 ppb.   The maximum allowable
    value  of 74.7 ppb would be exceeded  to the right of the shaded line in this
    diagram.  The "normal" scatter of observation points is produced partly by
    instrument  noise,  but mostly -- with above-average ozone concentrations -- by
    turbulent mixing processes acting upon stratospheric air intrusions.
    
         Two observations depart significantly from the "normal"  scatter  of
    observation points.  Table 4 gives  the hourly 03 concentrations which  yielded
    the two points  of excessive  maximum  concentrations in Figure  7.  Since the
    allowable  maximum value  of 74.7 ppb  was exceeded during 9 consecutive  hours
    (by as  much as  a factor of 2.64)  we  should count this episode as only  one day
    
                                        400
    

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                                                              401
    

    -------
    402
    

    -------
    Figure 6.   Composit 6-hour trajectory segments  from  August  11,  1963,  18  GMT
     to August 14,  12 GMT.   Pressures  in  millibars  are indicated  next  to  dots
                   corresponding  to  synoptic  observation times.
                                        403
    

    -------
    ppb (MAX HOURLY
    
     50 r
             ;DAILY MEAN)
                                                           120.40 141.16
                                                             I   I
     10 •
    2      2
       0
       Figure
     12    32    39    61    95   117   75    62    21    85                529
       10        20        30        40         50        60 ppb DAILY MEAN
    f.   Difference  between  maximum  hourly ozone  concentrations  (ppb)  and
        daily mean  concentrations as  a  function  of daily mean concentra-
        tions,  observed  at  Zugspitze  (3000 m  above M.S.L.)  between  August
        1973 and February 1976.  The  frequency distribution by  5-ppb  classes
        of the  daily mean and  2-ppb classes of hourly  maximum minus daily
        mean is given by the numbers  in the diagram.   The dashed line
        indicates the limits of  the present data  distribution.   To  the
        right of the shaded line the  federal  maximum value  of 74.7
        would be exceeded.   Dots indicate the mean values of (max.
        daily mean)  in each class of  daily mean  values.   The solid
        gives an approximate best fit to  these dots.   The cross marks the
        mean value  of both  distributions, that of (max.  hourly  - daily
        mean) and that of the  daily mean  values.   The  dashed-dotted line
        approximates the position of  the  mode values in  each class  of
        daily mean  concentrations.  Note  that two observations  fall out-
        side the plotted distribution.
                                404
                                                                             ppb
                                                                             hourly
                                                                             line
    

    -------
     TABLE  3.   OZONE  CONCENTRATIONS  IN THE  PLANETARY BOUNDARY LAYER EXCEEDING
                        FEDERAL  STANDARDS,  ARRANGED BY DATE
    
    Episode No.
    ]
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    Date
    5-2-63
    5-15-63
    6-26-63
    7-3-63
    8-7-63
    8-14-63
    9-11-63
    9-11-63
    9-18-63
    1-20-64
    4-8-64
    4-15-64
    4-17-64
    4-20-64
    4-20-64
    7-1-64
    7-1-64
    7-15-64
    7-15-64
    8-26-64
    • 9-23-64
    1-22-65
    7-14-65
    10-6-65
    10-7-65
    10-8-65
    10-13-65
    11-3-65
    11-10-65
    12-1-65
    12-1-65
    Maximum 03 (yg/q)
    0.15
    0.13
    0.19
    0.17
    0.15
    0.19
    0.17
    0.17
    0.15
    0.17
    0.18
    0.16
    0.20
    0.13
    0.16
    0.13
    0.13
    0.17
    0.15
    0.19
    0.13
    0.15
    0.16
    0.19
    0.24
    0.24
    0.13
    0.14
    0.25
    0.14
    0.14
    Station
    Goose Bay
    Tal lahassee
    Bedford
    Bedford
    Bedford
    Tal lahassee
    Tallahassee
    Seattle
    Tal lahassee
    Bedford
    Seattle
    Seattle
    Seattle
    Tallahassee
    Seattle
    Albuquerque
    Bedford
    Bedford
    Goose Bay
    Bedford
    Tallahassee
    Tallahassee
    Bedford
    Pt. Muqu
    Pt. Muqu
    Pt. Muqu
    Pt. Muqu
    Pt. Mugu
    Pt. Muqu
    Pt. Muqu
    Tallahassee
    
    ther than two
    0.2 percent
    (as plotted in
    of the total san
    Figure 7). This one day would
    iple of days -- in correspondenc
    then correspond
    :e to our obser-
    to
    vations over the U.S.  (Reiter, 1976b).
    
         Even though we have not yet carried out an isentropic trajectory analy-
    sis for this case, we  are convinced that we are facsd with a massive strato-
    spheric air intrusion  because:  (a) Cosmogenic beryllium7 (Be7)  concentrations
    rose significantly during that period (Table 5);  (b)  a cold front,  associated
                                         405
    

    -------
    with a strong northwesterly jet stream,  passed before  the  rise  in  03  concen-
    trations.
         TABLE 4.   HOURLY  OZONE  CONCENTRATIONS  (ppb), ZUGSPITZE  (GERMANY)
                             ON  JANUARY  8 AND 9,  1975
    
    January 8
    Time
    (hr.)
    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    ppb
    
    25.82
    27 .'28
    27.94
    30.08
    31.30
    30.93
    28.07
    27.37
    26.91
    27.69
    37.78
    47.88
    Time
    (hr.)
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    ppb
    
    42.88
    50.81
    62.21
    52.92
    52.06
    54.83
    57.03
    62.80
    79.85
    114.10
    157.74
    197.55
    Time
    (hr.)
    1
    2
    3
    4
    5
    6
    7
    3
    9
    10
    11
    12
    January 9
    ppb
    
    158.89
    170.36
    171.44
    159.78
    81.33
    28.50
    25.33
    27.79
    30.31
    30.71
    31.43
    31.82
    Time
    (hr.)
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    ppb
    
    32.12
    32.22
    25.61
    25.18
    24.88
    22.37
    22.39
    19.84
    19.10
    17.92
    16.89
    17.17
       TABLE 5.   THE DAILY  AVERAGE  Be7  CONCENTRATIONS  MEASURED  AT  ZUGSPITZE
    
    7 January 1975
    8 January 1975
    9 January 1975
    10 January 1975
    11 January 1975
    12 January 1975
    1 .33 pc/m3
    4.99 pc/ms
    10.35 pc/ms
    13.79 pc/m3
    11.17 pc/ma
    11 .66 pc/ms
    13 January 1975
    14 January 1975
    15 January 1975
    16 January 1975
    17 January 1975
    18 January 1975
    14.60 pc/ms
    11 .84 pc/ms
    15.29 pc/ma
    7.10 pc/ms
    5.71 pc/ms
    2.98 pc/ms
    
         Peculiar about this event are the excessive values of hourly 03 concen-
    trations.  Rises in Be7 concentrations and jet stream-associated stratospheric
    air intrusions were also involved in the statistical distribution shown in
                                         406
    

    -------
    Figure 7 without exceeding the maximum allowable hourly 03 concentration value
    (Reiter, 1976b).  The answer to this puzzle is given in Figure 8, showing
    the 100-mb surface of January 7, 1975, 00 GMT.  The center of gravity of the
    stratospheric polar vortex, according to this map, lies over Europe in a
    rather anomalous position.  It began to establish itself in this position
    on January 6.  Sinking motions in the middle and lower stratosphere to the
    rear of the European trough helped to establish a low-stratospheric ozone
    reservoir with well above average concentration values.  This reservoir was
    tapped by a typical stratospheric extrusion process.
    
         We are convinced, therefore, that the departure of the two data points
    with excessive 03 maxima in Figure 7 from the rest of the statistical distri-
    bution is not so much due to the peculiar absence of mixing in the tropo-
    sphere, but to an anomalous behavior of the stratospheric circulation and to
    the establishment of an excessively strong ozone reservoir in the lower
    stratosphere.
    
         We still will have to allow for the fact that the 03 concentrations
    described above were measured at an elevation of 3000 m above M.S.L., i.e.
    above the normal height of the PBL.  Mixing processes within the PEL should
    reduce these concentrations considerably, perhaps by as much as a factor of
    two.
    
                                       CONCLUSIONS
    
         The foregoing discussion shows that the maximum allowable hourly 03
    concentration of 74.7 ppb can be exceeded on occasion in the cyclogenetically
    active regions of middle latitudes, and especially under favorable trough
    positions in the stratospheric vortex.  Such excessive concentrations in
    these regions have a probability of approximately 0.2 percent, measured in
    days of observations on an annual basis.
    
         It is also apparent that natural background levels of stratospheric
    ozone in the lower troposphere can fluctuate considerably, and can reach 20%,
    perhaps 50% of the maximum allowable hourly level considerably more often
    (see Figure 7).  Relatively small additions of anthropogenic 03, under such
    conditions, will  lead to ambient 03 concentrations above 74.7 ppb.
    
                                    ACKNOWLEDGEMENTS
    
         The research reported in this paper was supported by an Environmental
    Protection Agency grant to Stanford Research Institute.
    
                                       REFERENCES
    
    Dutsch, H.U., 1971:  Photochemistry of atmospheric ozone.  Advances in Geo-
         physics. 15, 219-322.                                 ~           ~~
    
    Fabian, P.  and C.E. Junge, 1970:   Global rate of ozone destruction at the
         earth's surface.   Arch.  Meteor.  Geoph.  Bioklim., Ser. A, 19(2), 161-172.
                                         407
    

    -------
    408
    

    -------
    Hering, W.S., 1964:  Ozonesonde observations over North America,  Vol.  1.
         Report AFCRL-64-30(I),  pp. 1-512, Air Force Cambridge Research Labora-
         tories.
    
    	, and T.R. Borden, Jr., 1964:   Ozonesonde observations over  North Ameri-
         ca, Vol. 2.  Report AFCRL-64-30(II),  Air Force Cambridge Research Lab-
         oratories.
    
    	_, and T.R. Borden, Jr., 1965a:   Ozonesonde observations over North Ameri-
         ca, Vol. 3.  Report AFCRL-64-30(III), Air Force Cambridge Research Lab-
         oratories.
    
          , and T.R. Borden, Jr., 1965b:   Mean distribution of ozone density over
    ~~North America, 1963-1964.  Report AFCRL-65-913, Air Force Cambridge
         Research Laboratories.
    
    	__, and T.R. Borden, Jr., 1967:   Ozonesonde observations over North America,
         Vol. 4.  Report AFCRL-64-30(IV), Air Force Cambridge Research Labora-
         tories .
    
    Junge, C.E., 1962:  Global ozone budget and exchange between stratosphere and
         troposphere.  Tellus, 14(4), 363-377.
    
         , 1963:  Studies of global exchange processes in the atmosphere by
         natural and artificial tracers.  J. Geophys. Res., 68(13), 3849-3856.
    
    Lovill, J.E., 1972:  The global distribution of total ozone as determined by
         the NIMBUS III Satellite Infrared Interferometer Spectrometer.  Colorado
         State University, Ft. Collins, Colorado, Ph.D. Dissertation, 72 pp.
    
    Regener, V.H. and L. Aldaz, 1969:  Turbulent transport near the ground as
         determined from measurements of the ozone flux and the ozone gradient.
         J. Geophys. Res., 74(28), 6935-6942.
    
    Reiter, E.R., 1972:  Atmospheric transport processes, Part 3:  Hydrodynamic
         tracers.  U.S. Atomic Energy Commission, TID-25731, 212 pp.
    
         , 1975a:  Stratospheric-tropospheric exchange processes.  Reviews of
         Geophysics and Space Physics, 13(4), 459-474.
    
         , 1975b:  The transport of radioactive debris and ozone from the strato-
         sphere to the ground.  Report to Stanford Research Institute, 22 November
         1975, 36 pp.
    
         , 1976a:  Ozone concentrations in the lower troposphere as revealed by
         ozonesonde observations.  Report to Stanford Research Institute, 24 March
         1976, 106 pp.
    
         , 1976b:  Lower-tropospheric ozone in excess of Federal maximum value.
         Report to Stanford Research Institute, 28 June 1976, 39 pp.
    
    	, E. Bauer and S.C. Coroniti, 1975:  The natural stratosphere 1974.  CIAP
         Monograph No. 1, U.S. Department of Transportation.
    
                                        409
    

    -------
    Seitz, H., B.  Davidson, J.P.  Friend  and  H.  W.  Feely,  1968:   Final  report  on
         Project Streak.   Numerical  models of  transport,  diffusion  and fallout of
         stratospheric material.   Isotopes,  Inc.,  Westwood,  New  Jersey,  Report No.
         NYO-3654-4, 97 pp.
    
    Singh, H.B., W.B.  Johnson and E.R. Reiter,  1975:   The relation  of  oxidant
         levels to meteorochemical  processes:   A review of available research
         results and monitoring data.  Stanford Research  Institute:  Interim
         Report, SRI Project 4432,  119 pp.
                                       410
    

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                SESSION 9
    THEORIES ON RURAL OZONE/OXIDATES
                :  B. Dimitriades
     Environmental Protection Agency
                    411
    

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                                                                                  9-1
                     RESEARCH  TRIANGLE INSTITUTE STUDIES  OF  HIGH OZONE
                             CONCENTRATIONS IN NONURBAN AREAS
    
           L. A.  Ripperton,  J.  J.  B.  Worth, F. M. Vukovich,  and C.  E. Decker*
    ABSTRACT
    
          The. ReieoAcn T/u.pont>ouhip oft the, Environmental. Pfiote,cti.on
    Age.nct/ to heJLp cnoAac.ie'u.ze the, pnenomcnen ofi high HoJwJi ozone, conce.n&iationA .
    The. moAt txignifi-ic-ant n.e^>ult& o& theJse, ptiogfiamA -include the, ^ottowtng:   (a)
    Ai high  pneA&uAe, Ay*te,mA move, acAo&i,  the.  U.  S. faom dJe^t to Ea&t,  high ozone,
    c,onc.e.ntsiationA -in a. high ptiUbuAe, &yt>te,m  aAe. fiound in an aAea o/J  a.ppnoyjjmctte,ty
    60,000 t>q.  mi. and cine, aA£oCsicute.d with  incAe.ci&ing population de,nA-itij;  (6)
    the, high ozone. c,onc.e,ntnation& we/Le,  ^oand  to  OCC.UA on tka tA.aiting  bide, o^  the.
    high  pneA&uAe, AyAte.m; (a) thzofi&ticat Atudiu indicate,d that din  in the, lead-
    ing edge o& a high ptLU&uAe. t>y&te.m  had  been  in the. high pieJ>&uA.e,  t>y&te,m a.
    day on. te^&,  wheJte,a^ the, ait on the, t>utiiing Aide, ofa the. high pfie^AuAe, £yte.m
    had been ^ne^ie two to &
    -------
     in  the understanding of the chemistry of ozone generation in nonurban atmos-
     pheres is the paucity of oxides of nitrogen (NO ) found there.  Most of the
     NO  measurements that have been made in the rural field studies have been in
     the noise level of the instrumentation available, around 0.005 ppm.   Neverthe-
     less, on second and third days of continuous smog chamber runs at RTI, N0x
     concentrations of this level have produced ozone concentrations in excessxof
     the NAAQS (7).
    
         In the summers of 1970 (1), 1972 (2), 1973 (3), 1974 (4), 1975 (8), and
     1976 (9), Research Triangle Institute (RTI) conducted field studies, under
     Environmental Protection Agency (EPA) sponsorship, that have helped characterize
     the phenomenon of high nonurban concentrations of ozone.
    
         Some investigators have data indicating massive intrusion of stratospheric
     ozone into the troposphere, but the bulk of evidence obtained by RTI in these
     investigations favors the generation of ozone from anthropogenic precursors
     and the transport of this ozone and its precursors from a few miles to a few
     hundred miles in the lower levels of the troposphere.  The following technical
     report describes the findings of the six previous summer studies conducted
     by RTI and subsequent conclusions drawn from these data.
    
                                      FIELD STUDIES
    
         In 1970, in response to an air pollution incident at and near Mt. Storm,
     West Virginia, RTI measured ozone concentrations of several  hours duration
     that exceeded 0.1 ppm using a chemiluminescent (Rhodamine B) instrument (1).
     In the summer of 1972, RTI conducted a study of atmospheric ozone near Mt.
     Storm in Garrett County, Maryland, and Preston County, West Virginia.  The
     1972 study confirmed the earlier reports of high ozone concentrations; approxi-
     mately 11 percent of 1,043 hourly measurements made at the Garrett County,
     Maryland Airport during the summer of 1972 exceeded the NAAQS.  Similar find-
     ings were obtained at satellite locations around the base station at a radius
     of approximately 19 kilometers.  Analysis of synoptic meteorological data,
     as well as an examination of ozone wind roses for the Garrett County Maryland
     Airport led to a hypothesis that the high ozone concentrations at this loca-
     tion developed within particular air masses that acquired and maintained their
     characteristics over broad geographic regions (2).
    
         In the  summer of 1973, in order to further assess the aerial  extent of
    high rural  ozone concentrations, RTI established a network of four monitoring
    sites  for the measurement of ground-level  ozone concentrations and conducted
    airborne  measurements of ozone with an instrumented twin-engine aircraft.
    These  four sites were located at or near McHenry, Maryland (Garrett  County);
    Kane,  Pennsylvania;  Coshocton, Ohio; and Lewisburg, West Virginia.   This
    study  confirmed the  hypothesis that the high rural  ozone concentrations
    extended  over a considerable area.   For the summer and early fall  of 1973,
    the NAAQS for photochemical oxidants was exceeded during 15  percent  of 1,663
    hours  at  Lewisburg;  37 percent of 1,652 hours at McHenry; 30 percent of 2,131
    hours  at  Kane; and 20 percent of 1,785 hours at Coshocton (3).
    
         In 1974, a study was conducted in Ohio to investigate the relationship
    between high rural  oxidant levels and urban hydrocarbon control  strategies.
    
    
                                         414
    

    -------
    All data obtained in the 1974 study showed strong evidence for the involve-
    ment of anthropogenic precursors and urban effluvia in the generation of the
    high ozone concentrations in rural  areas.   As a result of these investigations
    it was postulated that the high concentrations of ozone (produced by photo-
    chemical processes) found in nonurban portions of the area studied are pri-
    marily an air mass characteristic and will occur when a slow-moving high
    atmospheric pressure system passes  over the region (4).
    
         In 1975, RTI conducted a study for EPA to further investigate the re-
    lationship between high ozone concentration and high pressure systems and
    to determine the change in the concentration of ozone in the center of a
    high pressure system, as the system moves  from an area of low population
    density to an area of high population density.  Ozone, nitrogen oxides, and
    hydrocarbon data were collected at  ground  stations located in Bradford,
    Pennsylvania, Lewisburg, West Virginia, Creston, Iowa, and Wolf Point, Montana,
    and from an instrumented aircraft flying specified flight patterns.  High
    ozone concentrations and the frequency of  exceeding the NAAQS were found to
    be associated with high population  density and high pressure (8).
    
          In 1976, RTI  under EPA sponsorship participated  in the flight of DaVinci
    II, an  Energy Research Development Administration  (ERDA) sponsored manned
    balloon-borne experiment conducted in the St. Louis area during early June.
    Ozone and meteorological variables were monitored  from a Lagrangian frame
    of reference over  a twenty-four hour period.  Data obtained from the balloon
    and on  the ground  indicate that high ozone concentrations (>0.13 ppm) were
    transported  aloft  undiminished  for several hundreds of miles  from  an  urban
    area  (9).
    
          For various reasons the characterization of high ozone systems in dif-
    ferent  parts of the country may be different.   In  this paper, RTI  presents a
    summary of its findings and discusses suppositions with regard to  high ozone
    concentrations in  nonurban areas and the relationship between high ozone and
    high  pressure systems, in particular high pressure systems that originate in
    Canada  and the Northern Plans and sweep the area south of the Great Lakes
    and into the Atlantic Ocean.
    
                                   RESULTS OF STUDIES
    
         Observational data and theoretical considerations have indicated the
    following behavior of the diurnal maximum ozone concentrations in  rural
    regions in the midwest and eastern portions of the United States as a high
    pressure system moves through the region (Figure 1).  When the leading edge
    of a high pressure system passes through a rural region, the diurnal maximum
    ozone concentration generally begins to lower in value, and a relative minimum
    value usually occurs before the center of the high pressure system reaches
    the sampling station.  A relative maximum value of the diurnal maximum ozone
    concentration is found on the back side of the high pressure system.  It has
    been hypothesized that this distribution is related to the residence time of
    air in  the high pressure system.  Generally, the residence time is larger on
    the back side of that system (Figure 2).  This allows time for air parcels
    to obtain large or critical concentration  of ozone precursors, time for the
    generation of ozone from much less  active  precursors, and time for the accu-
    
    
                                         415
    

    -------
              3750
    3125
          Distance fkm")
    
    2500       1875      1250
    625
          200 —
      s   150 —
          100 —
           50-
                              BRADFORD
                       	 CRESTON     Hi§h Pressure
                       	 WOLF POINT     Center
               654
                Bradford § Wolf Point
               4          3
                 Creston
                            I
                            1
    
                          Days
      Figure  1.  The temporal and spatial variations of the diurnal maximum ozone
          concentrations through a moving high pressure system based on the
           1975 data at Wolf Point, Montana; Creston, Iowa; and Bradford,
                                    Pennsylvania.
    
    mulation of ozone.   Because of the difficulty of measuring low concentrations
    of N0x and other precursors, this  hypothesis  has not been substantiated.   It
    is suggested that the low concentration of N0x that apparently exist in
    rural boundary layers is a result  of rapid gas phase chemical  reactions.
    
         In the summer of 1975, the ozone concentration at Wolf Point,  Montana,
    which was the western-most station in the 1975 array and in the Northern
    Plains never exceeded the NAAQS.   Furthermore, Figure 1  shows  that  the diurnal
    maximum ozone concentration did not behave similarly to that found  for sta-
    tions further east; that is, the  ozone concentration on the back side of
    the high was not a relative maximum.  When the high pressure system reached
    Creston, Iowa, low concentrations  of ozone were found on the eastern portion
    of the high pressure system and high concentrations on the back part of that
    system.   This distributional characteristic of ozone in high pressure systems
    was most highly developed when the system reached Bradford, Pennsylvania (4).
    
         There are two or three mechanisms that may be responsible for  high ozone
                                         416
    

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                                                -1
                                            10 ms
                                                  -1
    Figure 2.   Hypothetical  distribution of air parcel  residence time (days)
             in a circular high pressure system versus  system speed.
                                       417
    

    -------
    concentrations in rural regions associated with high pressure systems.   One
    mechanism is synthesis.  Another is vertical  transport.   And still  another
    is horizontal transport.  Theory and trajectory analyses suggest that within
    a high pressure system it is quite possible for air, although it moves  slowly
    and without strong directional influence, to  travel  400  miles within a  24-
    hour period.  Data from the DaVinci II experiment have suggested that air
    reaching ozone concentrations of 0.13 to 0.14 ppm by late afternoon over
    the city of St. Louis was transported almost  undiminished 150 miles across
    the State of Illinois into Indiana (Figure 3).   The  ozone concentrations in
    the air aloft remained at essentially the same  concentrations; whereas, the
    air at the ground that was being monitored by a mobile van that kept the
    balloon in sight, behaved in the usual surface  diurnal fashion and  reached
    lower values at night.  At the beginning of the next daylight period, the
    ozone concentration began to rise.  This mechanism is believed to behave
    in the following manner.
    
         In the rural region, air is mixed during the day through great depths.
    Throughout the mixing depth, the ozone concentration is  generally homogenous.
    At night, when the nocturnal inversion is produced near the ground., the
    ozone concentration near the surface is reduced by gas phase destruction and
    by contact with the surface of the earth.  The  nocturnal inversion  will
    prevent destructive agents from being injected  into  the  layer above.  There-
    fore, the ozone concentration in this layer will remain  undepleted  and will
    maintain itself overnight as is suggested by  the data shown in Figure 3.
    Thus, a diurnal variation of ozone will be found in  the  surface layer whereas
    little or no diurnal variation will be found  in the  layer above the nocturnal
    inversion.
    
         After sunrise two processes occur that cause that cause the increase in
    ozone near the surface.  Solar and sensible heating  erode the nocturnal inver-
    sion allowing air containing higher concentrations of ozone aloft to be mixed
    to the surface.  Furthermore, the air in the  surface layer has accumulated
    large concentrations of ozone precursors that will eventually be used to
    synthesize ozone.  Data are not yet available from the DaVinci II experiment
    to test this hypothesis with calculations.
    
         Many have attributed high ozone concentrations  in rural regions to the
    near surface transport of so-called fossil ozone.  In general, the  half-life
    of ozone at night as indicated by RTI smog chamber studies and by observed
    data (Table 1) would be around 20 to 30 hours.   This would not allow fossil
    ozone to be responsible for the high concentrations  found in rural  areas for
    more than two days without synthesis to maintain these concentrations.
    
         It can be seen in Figure 4, which represents a  series of flights made in
    1974 at Wilmington, Ohio, that the ozone concentration increased with time
    through a layer from the surface, 1000 ft. mean sea  level (MSL) to  approximate-
    ly the 6000 foot level (MSL).  Computations made using these data and available
    meteorological data during the same period indicated that approximately 50
    percent of the increase of ozone at the lower level  and  in the period 0704
    Central Daylight Time (CDT) to 1320 CDT, could  be explained by vertical mix-
    ing.   However, vertical mixing accounts for only 10  percent of the  increase
    between 1320 and 1656 CDT.  At 1656 CDT, the  vertical gradient is reversed
    
    
                                          418
    

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                                                              419
    

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                        TABLE 1.   DARK PHASE OZONE  HALF  LIFE*
    
    Station
    Bradford, Pennsylvania
    Creston, Iowa
    Wolf Point, Montana
    Half-life
    Mean (hrs)
    13.1
    20. 4
    15.4
    Std. Dev.
    (percent)
    15.2
    28.5
    15.9
    Range
    2.8-75.9
    3.4-180.9
    3.6-70.7
    Case Count
    65
    60
    61
    
    *Half life was calculated using  ozone  data  from  the  1975  Summer  Oxidant
     Study from 0200 to 0500, assuming  a first  order decay  rate.
                                 1754 1414
                 0704'
                     HYDROCARBON
                       SAMPLE
                     (MORNING)
                                             1320
                          1656
                         100
    150
    200
                                                    -3,
    250
                                12
    
    
                                11
    
    
                                10
    
    
                                 9
    
    
                                 8
    
    
                                 7
                                                                   00
                                                                    o
                           OZONE CONCENTRATION (uG/M  )
        Figure 4.   Ozone profile flight,  Wilmington,  Ohio,  August 1,  1974.
    
    
                                        420
    

    -------
    such that the lower level Is supplying ozone to the upper levels.   This sug-
    gested that, in this latter case, since vertical mixing could not account
    for a major portion of the increase in ozone in the lower boundary layer,
    most of the increase from morning till late afternoon is due to synthesis.
    
         That synthesis plays a part in producing high concentration of ozone in
    rural areas can be seen by the fact that in many cases rural sites exhibit a
    higher concentrations of ozone than do nearby urban sites (Table 2 and 3).
    The data in Figure 3 have suggested that synthesis accounted for most of the
    increase in ozone at lower levels.  It has also been discussed that in the
    northern part of the United States, the high ozone that is associated with
    high pressure is found on the back side of an eastward moving high pressure
    system.  This is thought to be due to the fact that as the system moves, air
    in the front part of the high pressure system has spent insufficient time in
    that system to accumulate ozone precursors and to be exposed to unimpeded
    solar radiation.  On the back side of the high pressure system, we find air
    that has spent two to six days in that system.  This air has had plenty of
    time to accumulate ozone precursors and has undergone many diurnal ozone
    cycles.
    
         As the high pressure system moves east, population density increases and
    consequently the potential for greater emissions of hydrocarbons and NO .  The
    polluted air from the cities injected into the system as it moves eastward
    will permit the generation of ozone.   As has been shown in smog chamber
    work, an aged system with low concentrations of NO  will generate high concen-
    trations of ozone (greater than the NAAQS).  The most active of the organic
    precursors, olefins, are also those that are most reactive in destroying
    ozone.  These are reacted rapidly and the less reactive precursors are pre-
    served to react later.  The less reactive precursors can generate high ozone
    concentrations given enough time, and they do not destroy ozone very rapidly.
    The more aged the system the more favorable the conditions for retaining
    ozone that it generates.
    
         As a result of the reported studies, the following hypothesis has been
    established for high ozone in the rural boundary layers in midwestern and
    eastern portions of the United States.  Air parcels in high pressure systems
    moving from Canada across the Northern Great Plains pick up very little in
    the way of ozone precursors from the  plains.  What precursors are injected
    into the system are natural in oYigin because there are relatively few anthro-
    pogenic sources in this region. * As the high pressure system moves further
    eastward across a line arbitrarily drawn from Fargo, North Dakota to Dallas,
    Texas, the population, according to the 1970 density map, increases quite
    rapidly from about ten people per square miles to 103 people per square
    mile.  The accumulation of ozone precursors should increase considerably to
    the east of this line due to the increased potential for anthropogenic in-
    jection.  It is doubtful that the rural population itself can contribute
    enough material to generate the ozone.  However, the cities should produce
    enough precursor material to begin to generate large concentrations of ozone.
         Results of these research programs imply that the control of hydrocarbons
    in any individual city will reduce, but not necessarily prevent, the occur-
    rence of high rural ozone concentrations in excess of the NAAQS at any given
    rural site.  The implication is that the release of hydrocarbons and oxides
    
                                         421
    

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           TABLE 2.  SUMMARY OF OZONE DATA FOR 1973  AND  1974  OXIDANT  STUDIES
    
    Station
    McHenry, MD
    Kane, PA
    Coshocton, OH
    Lewisburg, WV
    Wilmington, OH
    McConnelsville,
    OH
    Wooster, OH
    McHenry, MD
    DuBois, PA
    Canton, OH
    Cincinnati , OH
    Cleveland, OH
    Columbus, OH
    Dayton, OH
    Pittsburgh, PA
    Year
    1973
    1973
    1973
    1973
    1974
    1974
    1974
    1974
    1974
    1974
    1974
    1974
    1974
    1974
    1974
    Type of
    Station
    Rural
    Rural
    Rural
    Rural
    Rural
    Rural
    Rural
    Rural
    Rural
    Urban
    Urban
    Urban
    Urban
    Urban
    Urban
    Average 03
    (ppm)
    0.074
    0.065
    0.056
    0.052
    0.052
    0.057
    0.047
    0.057
    0.056
    0.035
    0.025
    0.031
    0.033
    0.035
    0.028
    No. Hours
    > 0.08 ppm
    600
    639
    357
    249
    259
    262
    262
    262
    341
    148
    54
    51
    113
    114
    106
    Mo.
    Hours
    1622
    2131
    1785
    1663
    1751
    2011
    1878
    2011
    1667
    1829
    1548
    1652
    1935
    1576
    1622
    Hours
    > 0.08
    ppm (%)
    37.0
    30.0
    20.0
    15.0
    14.9
    13.0
    14.0
    13.0
    20.5
    8.0
    3.5
    3.0
    5.8
    7.2
    6.5
    
    of nitrogen from anthropogenic or biogenic sources, located in both urban
    or rural areas, all combine to generate appreciable quantities of ozone over
    widespread regions.
    
         By the time the high pressure system reached Kansas City, cities have
    provided sufficient precursors for generation of a high concentration of
    ozone.  Once the ozone system has been generated, anthropogenic effluents
    provide enough fuel for the process to continue.  The denser the population
    becomes, the greater the amount of precursor material released and the higher
    the potential for producing large concentrations of ozone becomes.  As the so-
    called city plume moves out, widens and is then added to the material injected
    from the rural regions and from smaller cities, ozone will  be generated in
    concentration greater than the NAAQS.   Eventually, the urban plumes, although
    they may be undetectable by other means, will have overlapped in such a way
    that they produced an areawide ozone phenomena.
                                         422
    

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                 TABLE 3.   SUMMARY OF  OZONE  DATA  FOR  1975  OXIDANT STUDY
    
    Station
    Bradford, PA
    Lewis burg, WV
    Creston, IA
    Wolf Point, MT
    DeRidder, LA
    Pittsburgh, PA
    Columbus, OH
    Poynette, WI
    Cedar Rapids,
    IA
    Des Moines, IA
    Omaha, NB
    Nederland, TX
    Port O'Connor,
    TX
    Austin, TX
    Houston, TX
    Year
    1975
    1975
    1975
    1975
    1975
    1975
    1975
    1975
    1975
    1975
    1975
    1975
    1975
    
    1975
    1975
    Type of
    Station
    Rural
    Rural
    Rural
    Rural
    Rural
    Urban
    Urban
    Rural
    Urban
    Urban
    Urban
    Urban
    Rural
    
    Urban
    Urban
    Average
    03 (ppm)
    0.040
    0.038
    0.035
    0.028
    0.030
    0.030
    0.022
    0.038
    0.025
    0.036
    0.035
    0.027
    0.027
    
    0.025
    0.026
    No. hours
    ^0.08 ppm
    100
    59
    17
    0
    38
    227
    43
    126
    6
    124
    64
    138
    99
    
    19
    141
    No.
    Hours
    2332
    2386
    2117
    2160
    2994
    2841
    2885
    2663
    2781
    2528
    1787
    2714
    2912
    
    2504
    2104
    Hours
    > 0.08
    ppm (%}
    4.3
    2.5
    0.8
    0.0
    1.3
    8.0
    1.5
    4.7
    0.2
    4.9
    3.6
    5.1
    3.4
    
    0.8
    6.7
    
                                       CONCLUSIONS
    
         Some of the most significant conclusions of the RTI Summer Studies are
    the following.   As high pressure systems moves across the United States,
    high ozone concentrations found in that system are associated with high popula-
    tion density.   The data indicate that high concentrations of ozone observed at
    rural locations are generated in the lower troposphere.   The air on the back
    side of an eastward-moving high pressure system experiences longer residence
    time than air in the leading edge of that system.   Generally, high ozone is
    found on the back side of high pressure systems.
    
              An areawide system (a radius of 225 miles or more) of high ozone
    concentrations  can exist in which most features suggestive of a precursor
    origin have been smoothed out.   However, a short range urban influence on both
    hydrocarbon and ozone concentration can be observed.  The evidence indicates
    an observable urban influence extending as far as  150 miles downwind of the
    city.
                                         423
    

    -------
         Transport of fossil  ozone can occur for several  hundred miles.   The
    delivery of high concentrations of ozone to rural  sites depends on both the
    movement of so-called fossil  ozone and the synthesis  of fresh ozone from
    systems containing low concentrations of N0x and hydrocarbons that are mainly
    alkanes and aromatics.
    
                                      REFERENCES
    
    1.   Richter, H. G.  Special Ozone and Oxidant Measurement  in  the Vicinity
         of Mt. Storm, West Virginia.  Research Triangle Institute.  Task
         Report, Task No.  3.  NAPCA Contract No. 70-147,  1975.
    
    2.   Research Triangle Institute.  Investigation of High Ozone Concentration
         in the Vicinity of Garrett County, Maryland, and  Preston  County,  West
         Virginia.   Issued as Environmental Protection Agency Report No. EPA-R4-
         73-019.
    
    3.   Research Triangle Institute.  Investigation of Ozone and  Ozone Precursor
         Concentrations at Non-Urban Locations  in the Eastern United States,
         Phase I.   Issued as Environmental Protection Agency Report No. EPA-450/
         3-74-034, May 1974.
    
    4.   Research Triangle Institute.  Investigation of Rural Oxidant Levels as
         Related to  Urban Hydrocarbon Control Strategies.  Issued  as Environmental
         Protection Agency Report No. EPA-450/3-75-035, March 1975.
    
    5.   Stasiuk, W. N. and P. E. Coffey.  Rural and Urban Ozone Relationships
         in New York State, J.A.P.C.A., 24, 1974.  pp. 564-568.
    
    6.   Junge, C. E.  Air Chemistry and Radioactivity.  Academic  Press, New
         York, 1963.  pp. 37-59.
    
    7.   Research Triangle Institute.  Oxidant Precursor Relations Under Pollutant
         Transport Conditions.  Final Report.  Environmental Protection Agency
         Contract 68-02-1296, May 1976.
    
    8.   Research Triangle Institute.  Study of the Formation and  Transport of
         Ambient Oxidants in the Western Gulf Coast and Northcentral and North-
         east Regions of the United States.  Final Report.  Environmental  Protection
         Agency Contract No. 68-02-2048, August 1976.
    
    9.   Research Triangle Institute.  Ambient Monitoring Aloft of Ozone and
         Precursors  in the Vicinity of and Downwind of a City.  Interim Report.
         Environmental Protection Agency Contract No. 68-02-2391,  July 1976.
                                        424
    

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                                                                                 9-2
                           IMPORTANT FACTORS AFFECTING RURAL
    
                               OZONE CONCENTRATION
    
    
               F.L.  Ludwig, W.B. Johnson, R.E.  Ruff  and  H.B.  Singh"
    ABSTRACT
         Statistical anatyAeA o^ 120 aiA tAaje.ctoAi.eA  aAAi.vi.ng at fiouA di{,fieAe.nt
    AuAol  ozone. monJ.tofu.ng AiteA in the, e,aAteAn  Unite.d States have, been uAe.d
    to ide-ntifiy the. emiAAionA and mete.oAo logical condition  that OAe. mo&t
    cloAely Atu.die.d by companding the. long&-AeoXe spatial diAtAi-bationA o&
    maxAmum-houA ozone. conce.ntiati.onA with co?ifieApon.di.n.g we.atheA patteAnA.
    The. average aifi tempeAatuAe. doling the. laAt  12  houAA ofi  the. tAaje.ctoAy
    MU the. beAt tingle. deAcAi.pton ofa ozone. conczntsiationA;  ozideA o& nitsioge.n
    emiA4i.onA  weA-e. Ai.gni^i.cantiy coAAeJLate.d with ozone, but hydAocajtbon. miAAtonA
    wiete not.   The. tAaje.ctoAy analyteA alf>o Akowe.d  that ozone, conce.ntAati.onA
    above,  BO ppb weAe. mo&t fiAe.que.ntly at>-t>ociate.d with  light AouthweAt wind* and
    the. absence ofi pAe.cipitation.  The. coAA.eAponding vJe.atheA patte/inA aAe, the,
    waAm aiA Ai.de. ofi fiAontA and the. weAteAn paAtA ofa anticyclones.  In ge.neAal,
    the. ttudieA showed violation* ofi ox.i.dant AtandaAdA to ex-tencf oveA aAe,af, laAgeA
    than the. typical aiA qualify contAol Ae.Qi.on,  AuggeAting  the. ne.ce.t>t>ity o&
    Ae.viAi.onA  i.n the. pAeAe.nt contAol philo&ophieA.
    
    
                                  INTRODUCTION
    
         The adoption of ambient air quality standards (AQS) brings with it
    some corollary concepts.  The first of these is the air quality control
    plan.   This is a concert of actions that will ensure that air quality will
    not violate the established standards.  In practice, these control plans
    have been  formulated for limited geographical regions under the assumption
    that the consequences of control measures—and  conversely, of uncontrolled
    emissions—are quite limited in area.
    
         Figure 1  shows the air quality control  regions (AQCR) into which the
    eastern United States has been divided.  Observations of high ozone concen-
    trations in rural areas have raised the possibility  that the consequences
    of pollutant emissions might be much more widespread than originally assumed
    when AQCRs were defined.  Figure 2 shows the distribution of maximum-hour
    ozone  concentrations in the eastern United States  for May 22 1974.  The
    shaded areas show where the federal standard of 80 ppb was exceeded.  It is
    ^Stanford Research  Institute,  Menlo Park, California.
    
                                          425
    

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    immediately apparent that the AQS  are  exceeded  over  areas  that  are  much
    larger than the typical  air quality  control  region.   There are  at least  two
    possibilities for the widespread occurrence  of  high  ozone  levels:
    
         •     There are  large-scale natural  processes producing high ozone
              concentrations.
    
         •     The effects of  man-made  emissions  are much  more  pervasive than
              originally thought.
                    Figure  1.   Federal Air  Quality  Control  Regions
    
                                         426
    

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                                           60   80
    .80   !t
                                                                   40
                                                                22
               80 ',220 ®0 60
              Figure  2.   Distribution of maximum-hour 03 concentrations
                         for  the eastern United States for 22 May 1974.
    Both these possibilities  have  important consequences in the formulation
    and execution of emission control  policies.  This paper summarizes recent
    studies of the importance to the  above explanations (Ludwig et al , 1976),
    with emphasis on the second explanation.  This paper addresses two facets
    of the problem:
    
         •    The effects of  meteorological conditions and emissions
              within the mixing layer on subsequent formation of ozone.
    
         •    The relationships between large-scale ozone patterns and
              synoptic  weather features.
                                        427
    

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                                    METHODS
    
          A  statistical approach was used to determine what tropospheric factors
     are  important  to ozone formation in rural areas.  Four rural monitoring sites
     were chosen  for study:
    
          •    McHenry, Maryland
    
          •    Queeny, Missouri
    
          •    Wooster, Ohio
    
          •    Yellowstone Lake, Wisconsin.
    
     Thirty  cases were chosen for analysis from the data collected at each
     of these stations during the summer of 1974.   The emphasis was placed
     on cases with  high ozone (03) readings.  Fifteen cases were chosen for
     each site from among the days whose high-hour 63 concentration was in
     the  upper 20 percentile of the 1975 summer high-hour observations for
     that site.   The remaining 15 cases for each site were split between
     days when the  03 concentrations were among the bottom 20 percentile
     and  days with  near-median maximum hourly concentrations.
    
          Once the  120 cases had been chosen, air trajectories were calculated
     by applying  Heffter  and Taylor's (1975) methods to the available rawin-
     sonde and pilot balloon data.  The resulting trajectories were then used
     to determine the air's history during the 60 hours preceding the observation.
     The  air trajectories were plotted on maps provided by the Environmental Pro-
     tection Agency (EPA) that show average annual emission densities of oxides
     of nitrogen  (NOX) and nonmethane hydrocarbons (NMHC) for each U.S. county.
     From these  the emissions encountered were estimated for different segments
     of the  trajectory; the average emission rates were corrected to account
     for  the time of day  and diurnal emission cycles.
    
          The trajectories were also plotted on three-hour weather maps* to
     determine the  weather prevailing at different times.  The weather infor-
     mation  was  used to estimate the following factors suspected to be important
     to the  production of ozone:
    
          •    Temperature
    
          •    Relative humidity
    
          •    Dewpoint
    
          •    Insolation
    
          •    Precipitation
    *National  Weather Service Synoptic Analyses are available from
     the National Climatic Center, Asheville, North Carolina.
    
                                         428
    

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         •    Atmospheric stability.
    
    Temperature and dewpoint can be estimated directly from the weather maps
    and they can be used to derive relative humidity.  Other factors have to
    be derived indirectly.  The occurrence of precipitation, its type (e.g.,
    rain, drizzle, and so forth) and a subjective classification of its charac-
    ter and intensity (e.g., continuous moderate, intermittent light, and so
    forth) are shown on the weather maps.  The subjective classifications were
    assigned  numbers approximately proportional to precipitation rates, based
    on the guidance provided to U.S. Air Force weather observers (U.S.  Air
    Force, 1957).  Insolation strength was estimated from cloud cover and solar
    elevation using a method described by Ludwig and Dabberdt (1972).  Stability
    classification was based on Ludwig and Dabberdt's (1972) modification of
    Pasquill's (.1961) methodology.
    
         Using the Storage and Retrieval  of Aerometric Data (SAROAD) data base,
    the large-scale distribution of maximun-hour ozone concentrations were
    determined for all  365 days of  1974.   Smoothing techniques were used to
    suppress small-scale variability such as might be found within, and in the
    immediate vicinity,  of cities.   The smoothing also suppresses the effects
    of anomalous or erroneous readings.  The maximum hourly average ozone concen-
    trations were determined for each day and for each site.  All the measure-
    ments taken in a single city were averaged and used as a single measurement
    representative of the entire city.   The available observations were then
    used to interpolate  for grid points,  which served as the basis for  subsequent
    isopleth analysis.   The Oo isopleths  were then compared with the weather map
    for the same day (National  Oceanic and Atmospheric Administration,  1974).
    The comparisons were subjective, but  were guided by the results of  the tra-
    jectory studies.
                                    RESULTS
    
         Once the average meteorological  factors and emissions were deter-
    mined for 12-hour segments of each of the 120 trajectories, linear
    correlations between the ozone concentrations and each of the meteoro-
    logical  and emissions indexes were calculated.   In some cases there
    were important relationships that were not reflected in the linear
    correlation coefficients.   For instance, linear correlation between 03
    concentration and precipitation is not particularly high, but there is
    an important relationship, as should be evident from the scatter diagram
    in Figure 3.  In this diagram, the joint occurrences of ozone concentra-
    tions and precipitations index values are marked by the asterisks; if
    more than one case had approximately the same values, then the number
    of cases is shown instead of an asterisk.  As noted earlier, the pre-
    cipitation that occurred along the trajectory during the 12 hours be-
    fore the observation generally prevents ozone concentrations from rising
    above 80 ppb.  This probably arises from a combination of factors,
    such as  washout of ozone or its precursors, and the concurrent limited
    sunshine and lower temperatures that are not conducive to ozone forma-
    tion.
    
    
                                         429
    

    -------
      o
      "
      O
      N
      O
    
               \
                   MAXIMUM O, CONCENTRATION
            O     4.      7.     11.     15.     19.     22.     26.     10.     13.     17.
                         4x AVERAGE PRECIPITATION INDEX  DURING LAST TWELVE HOURS
    
       Figure 3.  Scatter diagram of ozone concentration versus precipitation
                  index during last 12 hours of trajectory.
    
         Temperature was found to have the greatest linear correlation with
    observed ozone concentrations.  Average temperature along the trajectory
    during the 12 hours preceeding the observation  is especially important,
    with a linear correlation of 0.54.  If temperature is used in a regression
    equation to describe ozone concentrations, the  addition of other meteorolo-
    gical variables will not improve the specification very much, but  inclusion
    of the NOX emissions does help, raising the correlation to about 0.6.  The
    hydrocarbon (HC) emissions are not significantly correlated with ozone con-
    centration.
    
         Several linear regression equations were formed using temperature and
    two emissions indexes  (e.g., NOX and HC during  the last 12 hours of  the
    trajectory, NOX during the last 12 hours and during the preceding  day) and
    NOX and HC emissions throughout the preceding days weighted to emphasize
    the more recent emissions.  There is little to  choose among the different
    combinations; all achieved linear correlations  with 03 of about 0.6  and
    standard errors of estimate around 47 ppb.
    
         However, it was apparent from scatterframs of observed ozone  versus
    the values calculated from the regression  that  ozone concentrations  greater
    than about 80 ppb had a different, and stronger, relationship with the
    predictors than do the lower concentrations.  For this reason, separate
    regression equations were derived for those cases where the observed
    03 was less than 80 ppb and for those cases with higher values.  Figure 4
    illustrates the results of two such "piecewise" regressions.   In
                                        430
    

    -------
    both cases, the temperature and emissions during the last 12 hours
    of the trajectory were used to predict the cases with C>3< 80 ppb.
    The same variables were used in Figure 4a to predict the higher o
    ozone values; for Figure 4b the temperature was  replaced with
    measures of insolation during the preceding 24 hours.   The two-
    part regressions achieve correlations of about 0.8 between observed
    and estimated ozone concentrations and standard  errors  of about
    35 ppb.
    
         The fact that ozone concentrations can be so well  predicted by
    emissions and meterological conditions to which  the air was exposed
    during the preceding 12 hours does not ensure that events at earlier
    times are not influential.   This is particularly true for air tem-
    perature and isolation.  If we track the same air for several days,
    the temperatures and sunshine conditions will tend to be much the
    same from day to day and the values for one day  would serve nearly
    as well  in a linear regression equation as those from the next.  The
    large spatial variability of emissions causes these indexes to be
    generally independent from one time period to the next.  Thus, the
    fact that NOX emissions along the air trajectory 24 to  36 hours
    earlier are significantly correlated with the observed  ozone concen-
    trations suggests that the influence of such emissions  may presist
    for a considerable period of time.
    
         For those cases where 03 concentrations exceeded 80 ppb, the
    air had generally been within about 450 km of the observing site
    12 hours earlier, and within 1150 km 36 hours before.  Taken in
    conjunction with the data that indicate that some influence may
    presist for 36 hours or more, this suggests that the influence of
    emissions can be quite widespread.
    
         When ozone  concentrations were above  80 ppb, the  air had  come
    more often from  a direction  between south  and west  than from  any  of
    the other quadrants.   Thus,  when  we have  relatively high  concentra-
    tions of ozone  in rural areas, the causes  for those concentrations
    are most likely  to  have occurred  during  the  preceding  day or  so,  and
    within about 1000 km  to the  southwest.   Obviously,  this  is  not  an
    infalliable  generation, but  it does provide  some guidance that  might
    be  useful in the formulation of  control  strategies.  Furthermore,
    some justification  for the generalization  is found  in  the compari-
    sons of  large-scale distributions  of maximum hourly ozone concen-
    trations in  the  eastern United States  with  the  concurrent synoptic
    weather  patterns.
    
          The findings of the trajectory studies have their counterparts
     in the interpretation of the larger scale ozone patterns.  The pre-
     ferred wind directions,  the warm temperatures,  and the sunny conditions
     associated with high ozone concentrations are characteristic of
     certain kinds  of meteorological  situation, and  we might expect to find
     most areas  of  high ozone in connection with these meteorological
     conditions.   Similarly,  emissions in combination with  wind speed
     and direction  influences might be expected to produce  some preferred
     geographical areas for high ozone concentration.
    
    
                                    431
    

    -------
                      (a)  ESTIMATED
            O  ?*•>.
    
    
    
    
            1  ""
            w
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            w
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    EMISSIONS
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                                                         UO.    159.    177.    195.
              Ce , OZONE  CONCENTRATION ESTIMATED WITH REGRESSION EQUATION—  ppb
    
    
    
    
    Figure  4.  Estimated  versus  observed  Oa for  two regression  expressions.
    
    
    
                                           432
    

    -------
         The expected grographical  and meteorological  relationships
    have been found.  The following geographical  areas accounted for
    nearly all of the 1974 cases where 03 exceeded 80  ppb:
    
         •    New England
    
         •    The area southwest  of Lakes Erie and Ontario
    
         •    The areas south and southwest of Lake Michigan
    
         •    The Washington-Philadelphia Corridor
    
         •    The St. Louis-Ohio River Valley area
    
         •    The Texas-Louisiana Gulf Coast
    
         •    The Florida Peninsula
    
         •    The western parts of Oklahoma, Kansas, and Nebraska.
    
    All but the last two regions are clearly identified with regions of
    major anthropogenic emissions.   The Florida Peninsula appears to be
    an area where the frequent occurrence of meteorological conditions
    favorable to ozone production is more important than the emissions.
    As yet we have not found a satisfactory explanation for the fre-
    quent high ozone concentrations in the western parts of Oklahoma,
    Kansas, and Nebraska.  If the data are all valid,  then  the following
    possibilities have to be considered:   long-range transport of pre-
    cursors from Texas, agricultural sources of NOX, stratospheric ozone
    brought to the surface by the lee waves of the Rocky Mountains or by
    frequent cyclogenesis in the area.  Figure 5 shows an example of
    ozone distribution in the eastern United States, with areas of high
    ozone concentration in several  of the regions mentioned above.
    
         The trajectory analyses showed that high ozone concentrations
    were more likely with warm temperatures, profuse sunshine, and light
    southwesterly winds.  These conditions are associated with the warm
    air side of weather fronts and the western parts of anticyclones
    (.high-pressure areas).  Studies of stratospheric intrusion (e.g.
    Ludwig et al, 1976) indicate that this phenomenon  is most likely be-
    hind strong cold fronts, in areas of cyclogenesis, and  in the lee
    waves of large mountain ranges.  It has also been  found (Ludwig et al. ,
    1976)  that squall lines can be sites of stratospheric  intrusion.
    Figure 6 is a schematic representation of the weather patterns that
    are most likely to be associated with high ozone concentrations in
    the eastern United States.  Figure 7 is an example of the weather
    patterns and the corresponding distribution of maximum-hour ozone
    oxidant concentrations in the eastern United States.  Figure 7 is an
    example of the weather patterns and the corresponding distribution
    of maximum-hour ozone oxidant concentrations in the eastern United
    States were associated with one of the expected synoptic patterns,
    especially those involving warm air and light southerly or westerly
    
                                     433
    

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       Figure 5.  Example of Ch distribution in the eastern United States
                  on 14 June 1974.
    winds-
                                  APPLICATIONS
          Some of  the findings discussed above have been arrived at by
     different means elsewhere.  The relationships with high pressure
     areas  have  been noted before  (Environmental Protection Agency, 1975)
     and  long-range transport has  been demonstrated in several case
                                       434
    

    -------
     Figure 6.  Schematic diagram showing parts of weather systems
                favorable for high ground level concentrations of ozone.
    
    studies (Coffey and Stasiuk, 1975; Cleveland et al.,  1975;  Lyons and
    Cole, 1976; and Martinez and Meyer, 1976).   The question  arises, how
    can results of the kind reported  here be applied to  the problem of
    control strategy development?
    
         The synoptic weather patterns that  are associated with high
    ozone concentrations seem to be  sufficiently well-defined that they
    can be used to defind spheres of  influence  for major  anthropogenic
    source areas.   In general, the regions influenced by  a source will
    tend to be toward its northeast,  but there  are likely to  be differences
    from one region of the country to another,  because  the orientation of
    the ozone-associated weather features will  be different in  different
    regions.  The  distance that a source's influence extends  downwind
    could be estimated from trajectory analyses for specific  weather
    situations of  the kind known to  be associated with  high ozone concen-
    trations.   It  appears that the influence of a source  is not likely
    to last much longer than about 36 hours, and hence  the distance
    traveled during such a period should define the outer limits of
    influence.  The trajectory studies reported here, the dimensions of
    the high-ozone areas in the synoptic analyses and the results of other
    studies (Martinez and Meyers, 1976) all  indicate that the areas of
                                     435
    

    -------
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                  436
    

    -------
       influence of major sources have dimensions of more than a hundred
       kilometers.   This is larger than most of the air quality control
       regions shown in Figure 1.  Perhaps larger regions are more appropriate
       to the oxidant control  problem and revisions should be considered.
                                   ACKNOWLEDGMENTS
    
            The support of the Environmental  Protection Agency, Office of
       Air Quality Planning and Standards, under Contract No.  68-02-2084 is
       gratefully acknowledged.  We have found the comments and other assist-
       ance of the Project Officer, Mr.  Phillip Youngblood, to be most
       helpful.
    
            Mr.  Dale Coventry of EPA and Mr.  R. Hows of Research Triangle
       Institute have provided much useful data, as has the staff of the
       National  Climatic Center.
    
            At SRI the following people  have  provided invaluable assistance:
       E.  Shelar, R.L. Mancuso, J.H.S.  Kealoha, A.H. Smith, R. Trudeau,
       P.B. Simmon, and L.J.  Salas.
                                       REFERENCES
    
    Bruntz, S.M., W.S.  Cleveland, B.  Kleiner and J.  L.  Warner, 1974:   The
         Dependence of Ambient Ozone on Solar Radiation, Wind, Temperature and
         Mixing Height.  Proc. Symp.  Atmos.  Diff. and Air Poll.,  Santa Barbara,
         Calif.  (Sept. 9-13), Amer.  Met.  Soc., pp.125-128.
    
    Cleveland.  W.S., B. Kleiner,  J.E.  McRae  and J.L.  Warner, 1975:   The Analysis
         of Ground-level  Ozone Data from New Jersey,  New York, Connecticut and
         Massachusetts:  Transport from the  New York  City Metropolitan Area.
         Undesignated Report, Bell Laboratories, Murray Hill, N.J., 63 pp.
    
    Coffey, P.  E. and W.  N.  Stasiuk,  1975:   Evidence  of Atmospheric Transport
         of Ozone into Urban Areas, Environ.  Sci. and Tech., 9, 59-62.
    
    Environmental Protection Agency,  1975:   Control  of Photochemical  Oxidant--
         Technical  Basis  and Implications  of Recent  Findings.  EPA Report
         450/2-75-005,  37 pp.
    
    Heffter,  J.L. and A.D.  Taylor, 1975:   A  Regional  Continental  Scale Transport,
         Diffusion  and Deposition Model,  Part I:  Trajectory Model, Nat.  Ocean.
         and  Atmos.  Admin.  Tech.  Memo.  ERL ARC-50, pp.  1-16.
    
    Ludwig, F.L., E. Reiter, E.  Shelar, R.L.  Mancuso, W.B.  Johnson  and P.B.  Simmon,
         1976:   Meteorochemical  Influence  on Rural Ozone Concentrations,  Final
         Report EPA Contract 68-02-2084,  Stanford Research Institute,  Menlo  Park,
         California, Draft  Submitted  September 1976.
                                        437
    

    -------
    Lyons, W.A. and H.S.  Cole, 1976:   Photochemical  Oxidant Transport:  Mesoscale
         Lake Breeze and Synoptic-Scale Aspects.   J.  Appl.  Meteorol.  15, 733-743.
    
    Martinez, E.  L. and E.L.  Meyer,  1976:   Urban-nonurban  Ozone Gradients and
         their Significance,  Presented at  Air Poll.  Cont.  Assoc.  Spec. Conf. on
         Ozone/Oxidants:   Interactions with the total  Environment, Dallas, Texas,
         March 12, 1976.
    
    Pasquill, F.,  1961:  The  Estimation of the Dispersion  of Windborne Material,
         Meteorol. Mag. (London),  90,  33-49.
    
    U.S.  Air Force, 1957:   On-the  Job  Training Program No.  JP 25251,  Weather
         Observer, Chapter 5.
                                        438
    

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                                                                                  9-3
                                A MECHANISM ACCOUNTING FOR
                   THE  PRODUCTION OF OZONE IN  RURAL  POLLUTED ATMOSPHERES
    
                                        M. Antell*
    
    ABSTRACT
         In tku> ne.pofit a ktnztic. model ofi nvJwJi &mog u> juAtifi-ie-d and
    The. modeJL Ae.tA  ozone. (0^} ,  nonme.thane. hydn.oc.an.bon (MMHC), and nitsioge.n  dA.oxA.da
    (N02) at me.at,uA.e.d  £eve£i.   It oAAwmeA that the.  only organic Ape.CA.eJ, pnej>e.nt
    Ln 4ucA -imogi one.  "nonA.e.acA~A.ve." hydAoc.an.bonA and pn.odu.ctA o& photo -oxidation
    o{\ nonn-e.a(itive.A.   The. concentration oft the. panjtAjaMLy ox.
    a&Aime.d to  be. at a le.ve.1 de.^-Lne.d by thiuA photoche.mic.at ptLOdu.c.tJ.on and  de.-
    £tnu.c,tA.on.   At me.aAuA.e.d le.ve.tt>  o& NOz and WMHC,  ozone,  production Ji& pie.dicte,d
    to be. taJiQe. e.noagh to account ^on. ozone. £e.ve2A  note.d A.n tLusiat &mog&.  The.
    ttate. Of) nut ozone,  psiodac^ion pfie.dicte.d AA .0126 ppm/kfi, aldehyde, and ke.tone.
    ie.ve2A p^.e.dic.te.d one. .010  ppm and .0093 ppm n.e.&pe.c.tive.iy kofl a Ay&tem Con-
    taining .007 ppm W02,  .06  ppm 03, and .02 ppm pentana.
    
                                       INTRODUCTION
    
         The purpose of this  paper is to present a  rough model of the mechanism
    of ozone production in polluted rural atmosphe'res.  By indicating which reac-
    tions are of major import,  it simplifies  the task of developing sophisticated
    predictive models  for smog production in  very  low concentration systems.   The
    model presented is a simplified mathematical description of the production  of
    ozone by an oxides of nitrogen-alkane system, at equilibrium with its products
    under average daytime insolation.  Oxides of nitrogen (N0x), alkane, and ozone
    (03) are varied in this model about levels measured in rural ozone-producing
    atmospheres.  Solutions are reached for the concentration of intermediate  smog
    products and of the net ozone production  rate of such a system.
    
                                     THESIS AND METHOD
    
         The following line of reasoning was  used  to develop and justify this
    simplified steady-state model of the rural ozone-producing atmosphere.
    
    BASIC ASSUMPTIONS
    
         It appears that air masses generating ozone over the rural southeastern
    United States may  reflect  a pollution injection received more than  a day earlier,
    perhaps over the industrial Midwest areas.  The fact that these air masses
    are aged argued for modeling on the assumption  that they are well mixed with
    *U.S. Environmental  Protection Agency, Washington, D. C.
    
                                          439
    

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    respect to ozone precursors.
    
         Reactive organic species injected into an air mass a day or more prior
    to its arrival over rural areas will be completely removed by ongoing active
    photochemistry.  The bulk of alkanes so injected will remain unreacted.
    
         The only reactive organic species remaining are those such as alde-
    hydes and ketones that are replenished by the reaction of alkanes.  In other
    words, pollutants injected into an air mass passing over densely populated
    areas undergo olefin photochemistry to leave alkanes and partially oxidized
    organics.  If this reactive-depleted air mass then passes over areas of low
    emission density, it undergoes alkane photochemistry.  During this phase,
    partially oxidized organic species promote the alkane photochemistry, which
    in turn maintains the concentration of partially oxidized species.  This
    argument is the basis of an assumption that the rural ozone-producing atmos-
    phere is characterized by a steady-state concentration of reactive species
    maintained and defined by a concentration of alkanes.  The alkane species
    can be shown to be removed slowly enough to justify assuming its concentra-
    tion to be invariant.
    
    ASSUMED CONCENTRATIONS
    
         We assume levels of anthropogenic pollutants in the range of those
    observed in rural ozone-producing air.  These are:
    
         •    Ozone = .06 ppm (US EPA 1975)
    
         •    Nitrogen dioxide = .07 ppm (RTI 1974)
    
         t    Nitric oxide = .0019 based on assumption of photostationary concen-
              tration of 03 and NO  at an average daily insolation (Jeffries et
              al., 1976)
    
         •    Nonmethane organic FID (flame ionization detection) response (which
              includes hydrocarbons and several other organic species) has been
              measured in these smogs at .2 ppm C (RTI 1974).  We conservatively
              set nonmethane hydrocarbon (NMHC) equal to .1 ppm C, or 1/2 of FID
              response.
    
         •    The concentration of other species - carbonyls, radicals - is poorly
              known.   These concentrations are solved within the model.
    
         For ease of analysis, in this model all hydrocarbon is assumed to be
    pentane, and all  reactive intermediates are assumed to be those produced in
    pentane photo-oxidation.
    
    KINETIC MODEL
    
         Also, to simplify calculation, the qualitative lumped kinetic mechanism
    of Hecht et al. (1974) is used to set pertinent reactions and reaction rates.
    In this mechanism compounds within the classes alkane, ketone, aldehyde, etc.
    are each treated as  having equivalent reaction rates and products.  Further-
    
    
                                         440
    

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    more, where several reactions follow an initiating reaction with high effi-
    ciency, these several are lumped together and treated as a single reaction
    of rate equal to initial reaction.
    
         When the rate constants from Hecht et al.  (1974) are used, the system
    is not highly ozone-productive.   In particular, using the given concentra-
    tions of hydrocarbon, ozone, and NO ,  radical chains are terminated by per-
    oxyacetyl nitrate (PAN) formation.  The critical  parameters creating this
    effect are the relative rates of reaction of peroxyacyl  radical with NO vs.
    with N02.  If instead of Hecht et al.'s (1974)  evaluation of these contents,
    we utilize those of Niki et al.  (1972), radical chains are lengthened con-
    siderably.  Those rate constants applicable to peroxyacyl radical suggested
    by Niki et al. (1972) are utilized in  this paper.   To this author, this as-
    sumption is not unwarranted.  The reaction rates  suggested by Niki et al.
    (1972) preclude any significant PAN formation in  irradiated hydrocarbon-NOx
    systems prior to the point that N02»NO.  In contrast, rates suggested by
    Hecht et al.  (1974) imply significant  PAN formation even when N02 = NO.
    Initial stages in NO-alkane smog chamber runs present a system in which NO,
    N02, and presumably peroxyacyl radical  are present.  However, these systems
    do not generate significant PAN until  late in runs when NO is suppressed by
    net 03 production (Altshuller, et al.,  1969; Bufalini, et al., 1970).
    
         The reactions, reaction rates, and overall reaction mechanism are listed
    in Tables 1,  2, and 3.  The model attempts to maintain simplicity.  It is
    noted that only a few reactions are of primary importance in the description
    of OH-H02 cycle mediated, alkane photo-oxidation.   A number of reactions of
    secondary import are excluded in this  analysis.  Their exclusion is justified
    as they are relatively inefficient mechanisms for radical removal, or pro-
    duction, or recycling in the rural polluted atmosphere.   We define "inefficient1
    competing reactions as those which react at rates  less than, and generally
    much less than, 15% of the reactions modeled.  Inefficient reactions include,
    for example,  the reaction of hydroxyl  radical (OH) with carbon monoxide (CO)
    and methane (CH^), a variety of radical combination reactions, and production
    of OH by nitrous acid (HN02), nitric acid (HN03),  or 03 photolysis, or by
    reaction of 03P (triplet atomic oxygen) with hydrocarbons.
    
    MATHEMATICAL  DESCRIPTION OF MODEL
    
         The steady-state model is amenable to a mathematical description.
    Production rates of OH,H02 ,  ketone, and  aldehyde  are set  equal  to  their de-
    struction  according to  the  reactions,  reaction constants,  and  reaction
    chains of Tables 1, 2, and 3.  A tabulation of this mathematical description
    is seen in Table 4.  It is noted that  a "C" factor is included to allow for
    variation of  relative reaction rates of peroxyacyl radical with NO and N02.
    "C" is the fractional  percentage of peroxyacyl  radicals converted to PAN.
    Aldehyde photolysis or reaction with OH is assumed to be only 1/3 effective
    for destruction of aldehyde.  Two-thirds of the time aldehyde reactions will
    lead to production of the one carbon less aldehyde analogue which is "seen"
    in this model  as no change at all.
    
         In fact,  we have assumed the aldehyde to be  1/3 propanal, 1/3 ethanal,
    and 1/3 methanal.   This assumption is  reasonably  close to the proportion of
    
    
                                         441
    

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         .02-
      •c
         .01 -1
       .001  -
                                     •^ Takeup  NOX  (XIO)
                 A
                /  \
    \Production 0-»
      \            3
        »
        N
          *
           X
             %
              \
               X
                  *x
    NO=.OOI9ppm
    03=.06 ppm
    Pentane=.002ppm
    kj =.37/min.
    C = fraction  of peroxyacyl
        radicals  reacting with
        N02
                    .1
            Figure  1.  Effect of assumption of several  rates of peroxyacyl
                          reaction  with N02 versus with  NO.
    
    aldehyde species that might be expected to be generated from pentane under-
    going photo-oxidation.  In any case, the system is  not very sensitive to
    perturbation  of this assumption.
    
    
    BOUNDARY CONDITIONS
    
         According  to the above discussion, alkane  hydrocarbon is consumed slowly
    enough  to be  considered a  pseudo-conservative species.  Any solution of the
    system  of equations defined in this report, for which hydrocarbon take-up
    is greater than 1/2 of the assumed hydrocarbon  concentration, violates the
    model's assumptions.
    
         NO  is a different case.  It is consumed effectively during transport
    
                                       442
    

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                      TABLE  I.   REACTIONS  IN A RURAL ATMOSPHERE
    (Groups of reactions are headed by the rate determining reactions. We
    later model on the reasonable assumption that the net reaction following a
    rate determining reaction occurs at the rate set by the initial reaction.)
    1.
    2.
    3.
    4 1
    4 i i
    4 i 1 1
    4iv.
    4v.
    N02 UV^ NO + 0
    0 + 02 	 ^ 03
    03 + NO 	 > N02 + 02
    RCHO UV> R- + CHO
    R- + 02 > ROO-
    ROO- + NO 	 . RO- + N02
    RO- + 02 	 H02 + R'CHO
    •CHO + 02 . CO + H02
     *NET 4 RCHO + 302+NO
    
    
    
    **5i.    RCHO + OH
                                       R'CHO  +  CO  +  N02  +  2H02
    
    
    
                                       RC  - 0
             RC
                0
                  0
                    + NO
    5iii.  RC^,
    
    
    
    5iv.   RC^  + 02
    
    
    
    5v.    ROO- + NO
    
    
    
    5vi.   RO- + 02
    
    
    
    NET 5 RCHO + OH + 202 + 2NO
    
    
    
    6.     H02 + NO
    
    
    
    7.     H02 + H02
    
    
    
    8.     OH + N02
    
    
    
    9i.    RCH2R + OH + 02
    
    
    
               }'+ NO
     RCQJ.   + N02
    
    
    
     ROO-  + C02
    
    
    
    tRO-  + N02
    
    
    
     R'CHO + H02
    
    
    
    ,R'CHO + 2N02
    
    
    
     N02  + OH
    
    
    
     H202  + 02
                                                       C02 + H02
                                    (continued)
    
    
    
    
                                        443
    

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                                 TABLE 1.  (continued)
                      0
                    '2
            H 1V
    NET 9 RCH2R + OH + 202 + NO
    
    lOi.   RiC*^R2
    
    lOii.  RiC^° + 02
    
    lOiii. RTC^  + NO
    
    lOiv.  F
    
    10v.   F.
    
    lOvi.  ROO-  + NO
    
    lOvii. RO-  + 02
    
    NET 10 RiCtiL + 502 + 3NO
                                     UV
            H02
    
            N02
    
           i- R2'
                                                      HO?
                  and R2- + 02
     R!-  + C02
    
     ROO-
    
     RO-  + N02
    
    ,R'CHO f H02
    
     Rl  CHO + R'2  CHO + 2H02
                                                                   3N02
       Hi.   R1'CH2C:50R2 + OH
    llii. R
    11 iii. R
    11 iv. R
    ***NET 11 R
    .iL«nU Ko • Uo *v K i U n L« K o
    11C°°'HC °R2 + NO + 02 	 >Rict^ + R2ct§0. + N02
    :2C:"'g0.+ NO + 02 	 >R2'CHO + H02 + N02
    :1CH2C"""°R2 + 302 + 2NO + OH 	 vRi'CHO + R2 ' CHO + H02 + C02 + 2N02
    
      *R'  = alkyl radical  of one less carbon than R.
    
     **Note that the effect of reaction 5iib Rc5n + NOp     v RC ?nN02 would be:
                                               UO*      	#    00  /-
    
       NET 5b RCHO + OH + 02 + N02 	^ PAN
    
       (reaction 10 and 11  are affected analogously).
    
    ***Reaction 11 is poorly characterized (NAQCAC 1976).
    so the main source of N0x in rural smog must be jn-situ emissions,  largely
    from mobile sources.
    
         It need not be contradictory for the model to allow for a significant
    continual replenishment of N0x and insignificant replenishment of organics
    from local automotive emissions.  This is because the ratio of NO,  to  organics
                                         444
    

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      TABLE 2.  RATE CONSTANTS OF REACTIONS IN TABLE 1 IN PPM-"1 MIN'1 EXCEPT
                                     AS NOTED
    1.
    2.
    3.
    4.
    5.
    6.
    7.
    8.
    9.
    10.
    11.
    N00
    L.
    0 + 00
    00 + NO
    RCHO 	
    RCHO + OH
    H00 + NO
    L.
    H00 + H00
    L. C.
    OH + N00
    L.
    RCH2R + OH +
    RC*2 UV
    RCH2C~° + OH
    v NO + 0
    — > °3
    } N00 + 00
    re. L.
    	 > R' + *CHO
    _» «c°
    _^ N09 + OH
    — * H2°2
    
    n Rr-°°-
    U0 x KLS.R
    c. ~ 	 " f ^l\
    . Rc'Hc:2
    t \\
    kl =
    k3 •
    k4 =
    k5 =
    k6 '
    k7 '
    k8 '
    kio =
    kll '
    .37/min
    2 x lO'4
    20.8
    2.5 y. 10-3/min
    2.3 ^ 104
    7 x 102
    5.3 x 103
    1.5 x 104
    3.8 x 103
    8.2 x 10"4/min
    3.8 x 103
    TABLE 3.  REACTION PATHWAYS OCCURRING IN THE RURAL POLLUTED ATMOSPHERE
           PATHWAYS LABELED BY REACTION GROUPS DISCUSSED IN TABLE 1
              RCHO and
                0
              RC R
    ^--.^  4,5,9,10,11
    
    4,10   X
           00-)
         RCHR
                         alkane
                               N0
                                    RCH200-
                                                  NO
                                 N02
    
                          4,5,9,10,11
                   'NO
                                       445
    

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     TABLE 4.  SIMULTANEOUS STEADY STATE EQUATIONS DESCRIBING RURAL POLLUTED AIR
    
    
     1.   Production  ketone  =  destruction  ketone
    
         (OH)  (HC)  3.8 x  103  =  [8.2 x  10^ +  (OH)  (3.8 x 103)] Ke
    
     2.   Production  aldehyde  =  destruction aldehyde
    
         Ke  (2-C) 8.2  x TO'4  +  (2-C) (Ke) (OH) 3.8 x TO3 =
    
         [(.33  + C)  (OH)  2.3  x  10^ + (.33) 2.5 x 1Q-3] Al
    
     3.   Production  OH =  destruction OH
    
         (H02)  (NO)  700 =
    
         (OH)  (He)  5 x 103  +  (OH)  (Al) 2.3 x  10^ + (OH)  (Ke)  3.8 x  1Q3 +
    
         (OH)  (N02)  1.5 x 104
    
     4.   Production  H02 = destruction  H02
    
         (2-c)  (Ke)  (16.4 x 1(H) + 2(A1) 2.5 x 10-3 + (OH)  (He) 3.8 x 103
    
         + (OH) (Ke) (1-c)  3.8  x 103 + (OH)  (Al)  (1-c) 2.3  x 10^ -
    
         2 (H02)2 5.3  x 103 + (H02)  (NO)  (700)
    
    
         where: He  =  hydrocarbon
                Al  =  aldehyde
                Ke  =  ketone
                c   =  fraction  of  peroxyacyl  radicals reacting with NO?
    mass emissions from (post 1969) automobiles is less than one (1), while
    optimum ozone production (particularly in alkane systems) is achieved at NO
    to hydrocarbon mass concentrations of 1:5 or greater.   However, a boundary
    condition for NO  replenishment is set by this argument.
    
         Replenishment of N0x and hydrocarbon is from the  same automotive source.
    Given that the organic content of rural  smog is a phenomenon of transport,
    then in-situ precursor replenishment should not be the major contribution
    (perhaps less than 20%} to organic concentrations.  Therefore,  the maximum
    uptake and replenishment of N0x per day  as mass concentration allowable under
    these boundary conditions is equal to 20% x mass of concentration of organics
    in rural smog x ratio of emissions of NO  to organics.  This term is equal to
    .02 ppm N0x replenishment per day allowable maximum.   Solutions of the equa-
    tions proposed in this report for several concentrations of ozone, hydrocarbon,
    and NO  are assayed against the above boundary conditions for hydrocarbon and
    NO  takeup.
    
                                         446
    

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                                          RESULTS
    
         The effect of mathematically assuming a variety of rates  of  reaction of
    peroxyacyl radical with  N02  and  NO on ozone production is seen  in  Figure 1.
    03 = .06 ppm, N02 =  .007 ppm,  and hydrocarbon = .02 ppm pentane.   C  =  .05
    corresponds closely  to the  ratio of reactions used by Niki et  al.  (1971);
    C = .3 corresponds to that  used  by Hecht et al. (1974); C =  .8  corresponds
    to that used by Dimerjian (1974).
    
         The solution for the concentration of ketone, aldehyde, H02,  OH,  and
    net 03 production per hour  at  these concentrations, at C =  .1,  are respec-
    tively .936 x 10-2,  .101  x  10'1, .684 x 10~4, .198 x lO'6, and  .126  x  10'1
    ppm.   The effect of  variation  of hydrocarbon and N02, and of ozone,  on ozone
    production are shown in  Figures  2 and 3.
            .010
            .001
                                      Dotted line indicates violation of I\IOX takeup assumption
                          Pentane = .01 ppm
                                Ratio of constants of peroxyacyl
                                reaction with NC>2 versus with NO is equal to 1:33.
                                         ozone
                            .06 ppm
                            ,37/mm
                         Pentane = .005 ppm
                       .01
    .02
    .03
    (ppm)
     Figure 2.   Effect  of  variation of initial concentrations  of pentane and NO
                         of ozone production and NO  takeup.
                                          447
    

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             E
             CL
             Q.
                 .02
    .01
    NOX Takeup (x10)
                    Boundary Condition For
                      NOX Takeup
                                             NO?
                                              h"
                                            Pentane
                                            .007ppm
                                            .37/min
                                            .02 ppm
        63 Production
                                            Ratio of rate constants of
                                            peroxyacyl radical reaction with
                                            N02 versus with NO is equal to 1:33.
                           0.1
                      0.2
    
                    03 in ppm
       Figure 3.   Effect of  level  of  ozone  on  ozone  production  and NO  takeup.
                                  DISCUSSION OF RESULTS
    
         Variation of the ratio of reaction of peroxyacyl  radical with  NO and
    N02 (Figure 1) is shown to strongly affect potential ozone  formation  in  an
    alkane-NO  system.  The effect of variation of NO  and hydrocarbon  is expected.
    Their ratio, as well as absolute concentrations, strongly control net pro-
    duction of ozone.  At measured levels of precursors, ozone  production in rural
    smog systems is both N0x and hydrocarbon concentration dependent.   N0x  takeup
    as a percentage of NO  concentration is significant so the  system can only
    maintain ozone production over several hours by continued replenishment  of
    NO .  The model presented here is realistic only for systems  containing  ozone,
    hydrocarbon, and nitrogen oxides at close to measured  levels.  At conditions
    tending to create faster generation of ozone, the N0x  is taken up very quickly.
    Maintenance of levels of NO  and organics in such systems would  imply local
    sources of pollution contributing more of these ozone  precursors than are
    contributed by long range transport.  Such a condition violates  several  of
    the explicit assumptions of the model.  In particular, local  pollution sources
    of such magnitude would likely emit sufficient quantities of  olefin to suppress
    alkane photo-oxidation.
    
                                       CONCLUSIONS
    
         The modeled production of 03 from an alkane-NO  system is shown  to  be
    highly dependent on the relative rates of reaction of  peroxyacyl radical with
    N02 versus with NO.  If those rates are near the extreme of rates reported  in
    the literature, such systems can account for the amounts of ozone presently
    found in the rural east coast of the United States.
    
         The mathematical model here presented also suggests the  presence in
    rural polluted air of significant quantities (roughly  .02 ppm) of carbonyl
    compounds.  If such concentrations were observed, they would  tend to  support
    the theory that rural ozone in the U.S. is generally a phenomenon created by
    widespread, human generated, hydrocarbon and nitrogen  oxide pollution.
                                         448
    

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          TABLE 5.   ALGORITHMS FOR SOLUTION OF NET PRODUCTION OF OZONE PER
         HOUR, AND THE NET TAKEUP OF HYDROCARBON AND NITROGEN OXIDE PER HOUR
     Net Os production per hour* -
    
     60 [(H02) (NO) (700) + (Ke) (2-c) 8.2 x 10^ + 3.8 x 103 (Ke) (OH) (2-c) +
    
     2 AL 2.5 x 10'3 + (Al) (OH) (1-c) 2.3 x 104]
    
    
     Takeup of hydrocarbon per hour =
    
     60 [ 3.8 x 103 (OH)  (He)  ]
    
     Takeup of nitrogen dioxide per hour**  =
    
     60 [ OH (1.5 x 10^)  (N02) + (C) Ke 8.2 x TO'4 + (C)  (Ke) (OH) 3.8 x TO3
    
                              + (C) (Al)  (OH) 2.3 x
     * 03  production rate = rate of oxidation of NO by H02  + rate of oxidation
                             of NO by ROD-  and related species
    
             takeup rate = rate of production of HN03  + rate of production of
                           PAN
                                    REFERENCES
    
    Altshuller, A. P., S.L. Kopczynsk, D. Wilson, W. Lonneman, and F.D.
         Sutterfield.  Photochemical Reactivities of N-Butane and other
         Paraffinic Hydrocarbon, 1969.   Journal Air Pollution Control
         Association  19:787.
    
    Bufalini, J. J., B. W. Gay, and S.  L. Kopczynsk.  1970.  Oxidation of
         N-Butane by Photolysis of NO.   Environmental  Science and
         Technology.  4:333-338.
    
    Dimerjian, K. L., J.  A. Kerr,  and J. G.  Calvert.  1974.  The Mechanism
         of Photochemical  Smog Formation.  Advances in Environmental Science
         and Technology.   4:1-262.
    
    Hecht,  T. A., J. H. Seinfeld,  and M. C.  Dodge.   1974.  Further Develop-
         ment of Generalized Kinetic Mechanism for  Photochemical Smog.
         Environmental  Science and Technology.  8:327-338.
    
    Jeffries, H. E. , J. E. Sickles II,  L. A.  Ripperton.   1976.   Ozone Transport
         Phenomena Observed and Simulated.   Paper 14.3 - Annual  APCA Convention.
    
    National Air Quality Criteria  Advisory Committee.   1976.   Final  Report.
    
                                         449
    

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    Niki, H.,  E.  E.  Daby,  and B.  Weinstock.   1972.   Mechanisms of Smog Reactions.
         Advances in Chemistry Series - Ozone and Smog Reactions.  New York.
    
    Research  Triangle Institute.   1974.  Investigation of Ozone Precursor
         Concentrations at Non-Urban Locations in the Eastern United States.
    
    U.  S. Enviornmental  Protection Agency.   1975.  Control  of Photochemical
         Oxidants -  Technical  Basis and Implications of Recent Findings.   35 p.
                                        450
    

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                                                                                 9-4
                       NET  OZONE FORMATION IN RURAL ATMOSPHERES
    
                             T.Y.  Chang and B. Weinstock*
    ABSTRACT
         A photochemical model was  used to explain ozone.  (03)  formation with
    aikane/oxides  o&  nitrogen (NO*)  mix.tun.es -in smog dkambe.fi  experiments design-
    ed to simulate rural conditions.  In oftde.fi to ^it the smog  ch.ambe.fi data,  tke
    model had to  be. modified to -include, an hydrozyl  (HO) radical source and
    he.te.noQe.ne.oa.&  wail reactions.   The. unmodified model was applied to predict
    the. e^ect on  rural  G>3  ie.ve.it>  o£ less reactive. hydrocarbons  (HC-6),  which afie
    le^t ove.n {^rom ulban emissions  and dikpe.ue.d into fiuAal OAZOA .  ffiom thii,
    analy&iti, it is concluded that the. ie.^tove.fi utiban HCi make.  Little,  contribu-
    tion e.ithe.fi to the. ae.ne.tiation  o& e.le.vate.d fiuAal ozone, le.ve.ls on. to the. in-
    cfie.at,e. of, elevated levels already pfiesent.  It ik suggested instead that the
    majcfi causes oft elevated tiufial 03 levels afie the tfianspofvt  o^  high 03 con-
    cent>iations generated in ufiban afieas and additional. 03 produced by Reactions
    015 {^fiesh HC and WOX  emissions  ^fiom local fuifial souJice?,, both natural and man-
    made.  Data ^fiom  the 1974 Midwest study afie {}0und to be in  agreement with the
    lattefi suggestion.   Eased on these findings, a method if>  proposed  to cofUiect
    hydfiocafibon fieactivity  scales  ^on. tke e^ect ofi dilution  that  occurs in the
    atmosphere.  The  analysis in this study is in disagreement  with the justifi-
    cation presented  faon the new Environmental Protection Agency Policy State-
    ment that severe  control ofi all hydrocarbons, without fiegard to reactivity,
    will be necessary to reduce elevated rural C>3 levels.
    
                                     INTRODUCTION
         The observation  of  elevated ozone (03) concentrations  in  rural  areas  has
    become a matter of much  interest in recent years.  It has been  suggested that
    less reactive hydrocarbon  (HC)  emissions from urban areas may  contribute im-
    portantly to this phenomenon.   These HCs, which are leftover after  a single
    day of solar irradiation,  are  expected to be transported to rural areas,
    where they can react  further on succeeding days and thereby contribute  sig-
    nificantly, as some suggest, to the elevation of rural ozone concentrations.
    Their effect would be most pronounced under meteorological  conditions,  such
    as a high pressure system,  when pollutants are not ventilated  rapidly to the
    global atmosphere and are  circulated over wide areas for many  days.   New smog
    chamber experiments have been  made to simulate this behavior.   In these ex-
    *Ford Motor  Company,  Dearborn, Michigan.
    
                                          451
    

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    periments, very long irradiation times and much higher initial hydrocarbon/
    oxides of nitrogen (HC/NOX) ratios were used compared with those used in
    earlier experiments to simulate urban photochemistry.  It was found that many
    HCs, previously found to be unreactive in urban simulations, produced signifi-
    cant concentration of ozone under the new conditions (1).  These results
    appeared to support the above concept.  Citing this as a basis, the Environ-
    mental Protection Agency (EPA) issued a Policy Statement (2) in which it was
    stated that HC reactivity no longer was essential  to HC control strategy and
    that all HC emissions would be regulated in the future, without regard to
    their photochemical reactivity.  It was advised that the previous strategy of
    the replacement of more reactive HCs by less reactive ones as a means of oxi-
    dant abatement, such as in Los Angeles Air Pollution Control District (LAAPCD)
    Rule 66(3), should be regarded now only as an interim measure and that future
    planning should consider complete HC control regardless of reactivity.
    
         The objectives of this paper are to examine the validity of this new
    concept and of the use of smog chamber data as a simple representation of
    atmospheric behavior.  In a recent paper (4), we have considered these
    questions with respect to methane and found that methane, on balance, will
    diminish elevated rural ozone levels contrary to the conclusions of a recent
    publication (5).   Methane is so unreactive compared with other HCs, however,
    that generalizations cannot be drawn from its behavior.  The methodology
    developed in that study (4) was modified for this  paper to include higher
    alkanes and the behavior of the modified systems is taken as a prototype for
    the reactions of less reactive HCs.   First, the modified photochemical model
    is used to explain the new smog chamber data.  The model is applied next to
    evaluate the contribution of less reactive h'Cs to  elevated rural ozone levels.
    The relevance of these findings to abatement strategy for elevated rural ozone
    levels is discussed next.  Finally, some suggestions are made for a revised
    HC reactivity scale.
    
                                 PHOTOCHEMICAL MODEL
         The reference photochemical  model  used in this study is a modified ver-
    sion of a model used previously in a study of the methane-carbon monoxide-
    nitrogen oxides (CH^-CO-NOx) system (4).   A list of reactions and rate co-
    efficients is given in Appendix A.  Reactions of alkanes with oxygen (0)
    and hydroxyl  radicals (HO) and reactions  involving radicals produced from
    alkane-0 and  alkane-HO reactions  are added to the previous model.  All
    types of alkyl  groups are lumped  together and represented by R.  A parameter,
    3, is introduced
    
                 RO + 02 = BRCHO + (l-B)HCHO  + H0?               R46)
    
    to represent  the fraction of total aldehydes produced that are not formalde-
    hyde.  The values of 3 are assumed to be  0, 1/2, 2/3, and 3/4 for methane,
    ethane, propane, and butane, respectively.  The reaction,
    
                 H02 + N02 = HONO + 0?,                          R30)
                                         452
    

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     also is  added  to  the  present  model  and  a  larger  value  for  removal  rate  for
     nitric acid  (HN03)  [R57]  is used.   Rain-out  removal  for  hydrogen  peroxide
     (H202) and alkyl  hydroperoxide  (HOOR)  is  deleted.  The photodissociation
     coefficients,  R2  through  RIO, are  assumed to be  proportional  to the  photo-
     dissociation coefficient  for  nitrogen  dioxide (N02), kj.
    
          The model  used here  incorporates the main features of the models of Niki
     et  al. (6), Hecht et  al.  (7), Demerjian et al. (8), and Pitts et  al. (9).
     Major uncertainties in  photochemical models  have been  discussed by Hecht et
     al.  (10), Durbin et al. (11), and  Pitts et al. (9).  The set of photochemical
     rate  equations  is strongly nonlinear.  Therefore, absolute predictions  of the
     photochemical model are somewhat uncertain.   Relative  trends of the  photo-
     chemical behavior, however, are believed  to  be predicted by the model with
     good  reliability.
    
                          ANALYSIS OF  NEW SMOG CHAMBER DATA
    
    
          As mentioned before, the new  EPA smog chamber experiments (1) were de-
     signed to simulate rural  atmospheric conditions.   High initial HC/NOX ratios,
     8:1,  were used  compared with ratios of 2-3:1  used to simulate urban  condi-
     tions in earlier experiments.   Longer irradiation times also were used  to
     simulate carry-over of urban emissions to rural areas.   Data for  the propane/
     NOX system, run 194,  (1)  are given  in Table  1.  In a simulation with the un-
     modified photochemical model,  less  than 2 pphm 03 was  predicted after 430
     min,  much less  than the observed maximum  value of 11  pphm.   This disagreement
     was not unexpected.  Propane,  like  alkanes in general,  should produce HO radi-
     cals  very slowly in these experiments, with  the consequence that there  should
     be a  very long  induction  period before the 03 concentration builds up.   The
     much  more rapid production of 03 seen in  the actual experiment is a  conse-
     quence of a substantial HO background common to all laboratory experiments
     (12).
    
         An  attempt to fit the experimental  behavior  was  made in  simulation  1  by
     the addition  of a constant HO  source of 3 x  10'4  ppm  min"1  to the model.  This
    approach  also has been used by Pitts et al.  (9).   In  addition, an 03 removal
    term, k55 = 1  x 10~3 min'1, was  introduced to simulate  the  03 removal at the
    walls that is characteristic of smog chambers.  A reasonable  prediction  of the
    experimentally  observed N02 maximum and of the time to  reach  this maximum is
    obtained.  An 03 maximum still is  not observed, however,  and  the 430 min.  03
    concentration predicted is much  higher now than 11  pphm.
    
         A different approach  to produce an HO background was used in simulation
    2.  The  rate  constant, k20, for  the reaction,
    
                   NO + N09 +  H20  =  2  HONO                       R20)
                                         453
    

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             TABLE 1.   EPA DATA AND SIMULATION  RESULTS  FOR  PROPANE - N0xa
    
    Maximum NO 2
    
    
    EPA Run
    No. 194
    Sim. lc
    Sim. 2d
    Sim. 3e
    Sim. 4f
    Time
    (min)
    55
    
    80
    105
    65
    70
    Cone.
    (ppb)
    130
    
    147
    142
    132
    132
    Maximum 03
    Time Cone. HC
    (min) (pphm) (ppm)
    225 11.0 3.18
    
    3.24
    3.35
    305 14.5 3.40
    250 12.6 3.38
    At 430
    N02
    (ppb)
    95 b
    
    80
    110
    11
    16
    min
    NO
    (PPb)
    <1.0
    
    2.9
    5.4
    1.0
    1.8
    
    03
    (pphm)
    7.6
    
    33
    26
    14
    11
    
     a  k^  = 0.33 min'1,  kdiiution  =  2.2  x  10~4 min-1,  k34 =  22 ppnH min-1,
    
        k_5 = 3200 ppm"1  min'1,  (H20)  =1 x  104 ppm;  initial concentrations:
    
        (HC) = 4.0 ppm,  (NO)  =  180  ppb,  (N02) = 20 ppb,  (Os)  = 0 pphm.
    
     b  (NOX) - (NO).
    
     c  k55 = 1 x 10~3 min'1, constant HO source = 3 x  10~4 ppm/min.
    
     d  k9n = 1.9 x 10"5  ppm'2  min'1,  k91 =  1.8 ppm'1 min'1,  kr-r = 1 x 10'3 min'1.
         c\J                           c.\                     DO
    
     e  add k-,g = 1.5 x  10~   ppm"   min"  .,  to d
    
                                      -3     -1
     f  same as e except,  k^c =  3 x 10   min  .
    was arbitrarily increased from 1.9 x 10~n to 1.9 x 10~5 ppm'2 min'1.  The
    rate of the back reaction, k21, was increased from 1.8 x 10~5 to 1.8 ppm'1
    min'1.  By this adjustment, the concentration of HONO is built up quickly and
    this provides rapid HO source because nitrous acid (HONO) produces HO by
    photodissociation.   This approach has been used independently by Sickles(13).
    Although the rate constant for the homogeneous formation of HONO by R20 is
    known to be slow (14,15), the heterogeneous rate on the walls is probably
    very much faster in smog chambers.  The predicted 03 is in better agreement
    than in simulation  1, but is still too high; an 03 maximum still is not ob-
    served, and the time for the N02 maximum changes in the wrong direction.
    For simulation 3, the rate constant, kI9, for the homogeneous reaction,
    
                   N205 + H20 = 2HN03,                           R19)
    
    was increased from  1.5 x 10'5 used in simulation 2 to 1.5 x 10~3 ppm'1
    min'1 to represent  the heterogeneous reaction that is likely to be of more
                                         454
    

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     importance  in  smog  chambers.  With this modification, an 03 maximum now  is
     predicted and  the agreement with  the experimental observations is notice-
     ably improved.   In  simulation 4,  the effect of  increasing the 03 decay rate,
     k55, from 1  x  10~3  to  3  x  10~3 min'1 was calculated and this improved the
     agreement with  the  experimental data further.   Similar situations have been
     made for data  obtained with the ethane/NOx system.  The same qualitative
     behavior for the model adjustments were observed and the quantitative agree-
     ment with the  experimental data was again satisfactory.
    
          Model  calculations  also were compared with the 03 maxima observed in
     similar experiments that have been reported by  Heuss (16).  Using the same
     parameters  as  in simulation 4, the model predicted 03 maxima of 7.8, 14, and
     15  pphm compared with  the  experimental values of 8, 13, and 20 pphm for
     ethane, propane, and butane, respectively.
    
          These  simulations give insight into the importance of the HO background
     and  of heterogeneous reactions to 03 formation  in smog chamber experiments.
     The  agreement of the model predictions with the experimental data alterna-
     tively gives a measure of  confidence of the reliability of the model for
     predictions  of atmospheric behavior for alkane/NOx mixtures.
                     SIMULATED RURAL ATMOSPHERIC PHOTOCHEMISTRY
         Calculations with the unmodified photochemical model, i.e., without the
    changes made to take account of the idiosyncrasies of smog chambers, have
    been made to simulate rural atmospheric photochemistry.  Steady state calcu-
    lations were made at first to investigate the variation of the steady state
    03 with a variety of fixed HC and NOX concentrations.  For each fixed HC
    concentration the predicted 03 concentration goes through a maximum as the
    fixed NOX concentration is varied.  As the fixed HC concentration is
    increased, the NOX concentration corresponding to the 03 maximum also in-
    creases, as does the 03 maximum.  From these steady-state calculations, it
    can be concluded that atmospheric 03 concentrations are affected not only by
    the absolute concentration of both HC and NOX, but also by the HC/NOX ratio.
    
         Time-dependent photochemical model calculations were made next.  In the
    first set of calculations, the concentrations of HC and NOX were kept con-
    stant, and the daily buildup of 03 was predicted.  These calculations were
    made to determine the sensitivity and time dependence of 03 formation to the
    NOX concentration and characteristic time of 03 buildup.  Some of the results
    are given in Table 2.  The initial 03 concentration was taken to be 4 pphm;
    that of propane to be 0.1 ppm (0.3 ppmC).  The NOX concentration was taken
    as a variable since reliable rural NOX data are not available because of in-
    terferences in the measuring techniques that give rise to spuriously high N02
    values.   The photodissociation coefficient for N02 in min"1 used was:
    
              ki  = 0.66 e-3-8/cosX,  cosX>0
                                                                 (1)
              k: = 0,               cosX<0.
    
    
                                        455
    

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          TABLE 2.   DAILY  MAXIMUM  03  IN PPHM: (HC) AND  (NOX) KEPT CONSTANT*
    
    
                      Day     (NOX)=0.1 ppb     1 ppb     10 ppb
    
                       1           4.0           4.4        10
    
                       3           3.3           5.6        15
    
                       5           2.9           7.0        18
    
                       7           2.7           8.2        19
    
                      10           2.7           9.5        21
    
                      13           2.7          10.2        22
    
    
     (propane)  =0.1  ppm,  (CH4) =  2 ppm, (CO) =0.2 ppm, (H20) = 2 x 1C)4 ppm
     and  (NOX)  =0.1,  1, 10 are kept constant.
    
     Initial  (63) =  4  pphm
    
    
     a.   The  NO was  initially pure N09.
               X                      c
    
    
    The angle of inclination of the sun,  X, is  approximated  by,
    
              X = Tr(H/12 -1),                                    (2)
    
    where H is the hour of day.   The  values of  kj  given by Equation  (1)  give a
    good approximation of measured values  of Iq  by Sickles (13).
    
         The amount of 03 formed  is seen  to be  sensitive to  the  NOX  concentration.
    When (NOX) = 0.1 ppb,  the daily maximum 03  decays  from 4 to  2.7  pphm.   When
    (NOX) = 1 ppb,  the time for the 03  concentration  to double from  4 to 8 pphm
    is about a week, and the 03 concentration approaches an  asymptotic value of
    about 10 pphm.   When (NOX)  =  10 ppb,  the doubling  time of the  initial  03 con-
    centration is about one day and the  asymptotic maximum 03 is  a little  above
    22 pphm.   These calculations  show that reliable measurements  of  N02  and a more
    quantitative understanding  of NOX chemistry  are critical  for  a better  under-
    standing of rural 03.
    
         The next set of time-dependent  calculations were  made to  simulate the
    effect of less  reactive,  "leftover"  hydrocarbons  in an urban  plume on  several
    ambient rural  03 concentrations,  ranging from  0-20 pphm.   The  reactants were
    given various initial  concentrations  that were allowed to decay  continuously
    during the two days.   Further details  of the  calculations and  the results are
    given in Table  3.  Propane, which can  be considered as a prototype for less
    reactive, "leftover"  hydrocarbons,  was set  at  an  initial  concentration of 0.1
                                         456
    

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     ppm (0.3 ppmC).   This concentration is much higher than the concentrations
     observed for the less reactive hydrocarbons in the 1974 Midwest study (17).
     The NOX was taken to be pure N02 initially at a concentration of 10 ppb.
     This concentration is at the upper limit of the N02 concentrations observed
     in the 1974 Midwest study (17), which generally ranged from 5-10 ppb.   As
     mentioned before, the N02 measurements are probably too high, so that 10  ppb
     N02 should be significantly higher than rural  N02  levels.   The reason for the
     choice of these  hydrocarbon and N02 concentrations was to  represent extreme
     rural  concentrations that would favor formation of elevated ozone levels.
    
    
            TABLE 3.   DAILY MAXIMUM 03: (HC) AND (NOX)  ALLOWED TO DECAY
                     Initial     Initial 03     Maximum 03 (pphm)
                     Propane       (pphm)       1st day   2nd day
    
                       0.1            0           4.1       4.3
    
                       0.1            4           7.4    Decreasing
    
                       0.1           10          11.4      11.2
    
                       0.1           15          15.3    Decreasing
    
                       0.1           20       Decreasing Decreasing
    
     Initial concentrations at 0600:   (CH4) = 2 ppm, (CO) = 0.2 ppm,
     (N02) = 10 ppb, (H20) = 2 x 104 ppm.
         These calculations snow a number of interesting characteristics of rural
    ozone behavior.  The 03 maxima on the second day are, except for one case,
    lower than those on the first day.  This is a consequence of the rapid decay
    of NOX during the first day.  In general, it can be concluded that the rela-
    tive residence time of NOX is much shorter than that of propane under these
    simulated rural conditions.  When the initial 03 concentrations are 0 and 4
    pphm, they build up to 4.1 and 7.4 pphm, respectively, in the first day.
    When the initial 03 concentrations are 10 and 15 pphm, relatively little
    change in concentration occurs in the first day.  When the initial 03 concen-
    tration is 20 pphm, this concentration decreases continuously during the
    first day.  From these calculations, it appears highly unlikely that less
    reactive, "leftover" hydrocarbons would generate elevated rural 03 levels.
    At the concentrations that these HCs and NOX are likely to be present in
    rural atmospheres, these HCs could contribute to the lowering of already
    existing elevated rural 03 levels.  In the following discussion, a more
    probable explanation of the elevated rural 03 levels is offered.
                                         457
    

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                                     DISCUSSION
          It  is reasonable to assume that the high ozone concentrations generated
     in  urban areas are transported into rural areas, particularly under meteoro-
     logical  conditions that retard their dispersion into the global atmosphere.
     This  will result in an elevation of the rural ozone levels above the natural
     background ozone concentration.  The longer that the adverse meteorological
     conditions persist, the greater the effect will be, and the greater the size
     of  the area affected.  The degree to which the elevated rural ozone concen-
     trations are further increased, sustained, or diminished by further photo-
     chemistry in the rural areas on succeeding days depends on the concentrations
     of  both  HCs and NCL that are present there.  The preceding analysis strongly
     suggests that the less reactive, "leftover" HCs of the urban plume will not
     contribute importantly to sustaining or increasing the elevated rural ozone
     levels.  (Unreacted NOX from urban areas, where it is present in excess, will
     also  be  transported to rural areas and contribute to ozone formation there,
     but this aspect of the problem will not be discussed here because of the lack
     of  reliable rural N02 data.)  A more likely explanation for the persistence
     and increase of elevated rural 03 levels is the reactions of new HC  (and NOX)
     emissions in the rural areas from local sources, both natural and man-made.
     The relative amounts of natural and man-made sources of rural HCs and NOx  is
     an  unresolved question, which will not be discussed further here.
    
         The  relative  importance of "leftover"  HCs  compared  to  fresh  HC  emissions
    in rural  photochemistry  can  be  deduced  from detailed  measurements  of rural  HC
    compositions.   If  the  "leftover"  HCs  from urban areas  are  present in signifi-
    cant concentrations,  this  should  be  evidenced  by an  accumulation  of  less re-
    active species  compared  to more reactive  ones  in the  rural  atmosphere.   This
    is because  the  more  reactive species  are  removed much  faster than  the less  re-
    active ones.  This  effect  is similar  to a  separation  of  more volatile species
    from less volatile  ones  by fractional  distillation.   Detailed  HC  compositions
    have been measured  in  the  1974  Midwest  study  (18).   There  is little  evidence
    of such fractionation  in all  of these  data,  both in  samples  taken  at the
    ground and  aloft.   Thus  it would  be  plausible  to conclude  that,  for  the area
    studied and  for the  conditions  that  existed during  the  study,  the  atmospheric
    HCs  observed  were  representative,  in  the  main,  of local  emission  sources.
    
         Some very  interesting  data were taken on August 1,  1974, in  this Midwest
    study.  Ozone measurements were reported,  as,  shown  in Figure 1 , at a variety
    of elevations for  0704-0741, 1320-1414, and 1656-1754 hours (Figure  58, page
    122 in reference 17).   Concurrent nonmethane HC (NMHC)  measurements  were made
    at the ground and  aloft  at  0704-0741  and  at the ground at  1210-1315.  The
    early morning profile supports  the conclusion of the preceding paragraph.
    The NMHC concentrations  of 105  and 113 ppbC at the  ground  and at  2000 ft.,
    respectively, represent  the  sum of the "leftover" NMHC and the new NMHC
    emissions,  which are trapped by the  early morning ground inversion.   The
    concentration of 58 ppbC  at  4000 ft.  is the "leftover"  NMHC concentration in
    the mixing  layer,  which  is  being augmented by leakage from the ground inver-
    sion layer and  diminished  by leakage  into the inversion  layer.   The  35 ppbC
                                         458
    

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    at 8000 ft. is the "leftover"  NMHC in the inversion layer, which  is  being
    augmented by leakage from the  mixing layer and diminished by leakage into
    the global atmosphere.   At 1210-1315 hours, the ground inversion  probably
    has burned away, and the NMHC  concentration at the ground is 89 ppbC,  which
    is intermediate between  the  ground and mixing layer values observed  in the
    early morning.
                                    1754  1414
                         Hydrocarbon
                            Sample
                          (Morning)
                              5          7.5         10.
                               Ozone  Concentration ( pphm )
    Figure 1.   Ozone profile, Wilmington, Ohio, August 1,  1974  (17) TNMHC:  2000
               ft., 113 ppbC; 4000 ft, 58 ppbC; 8000 ft.,  35  ppbC  at 0704-0741
               hours; ground, 105 ppbC at 0745-9000 hrs;  ground, 89 ppbC at
               12-1315 hrs.
                                        459
    

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         The ozone profiles are most revealing.   The concentrations in the ground
    inversion layer in the early morning decrease markedly with decreasing alti-
    tude because of ground destruction of 03.   (The lines drawn in Figure 1  simply
    connect individual measurement points.)  The concentrations in the mixing
    layer are relatively constant with altitude  at about 9 pphm.   This would be
    representative of an initially elevated 03 level as analyzed in Table 3.  The
    one point measured in the inversion layer is at about 7.5 pphm 03.  At noon,
    when the ground inversion has burned away, the 03 concentrations in the  mix-
    ing layer are constant with altitude at about 10 pphm, which is above the
    early morning 9 pphm value.  The 03 concentrations in the inversion layer are
    seen to be constant with altitude and unchanged from the early morning value.
    The evening measurements show the same trenc.  The concentration in the  mix-
    ing layer has increased further to about 12  pphm, while that in the inversion
    layer is still at 7.5 pphm.
    
         These data thus illustrate the explanation that is offered here for the
    elevated rural 03 levels.  The increase in the elevated 03 concentration in
    the mixing layer is a consequence of reactions of fresh HCs (and NOX) emitted
    into the mixing layer.   It is likely that the "leftover" HCs there play  only
    a minor role in augmenting this increase.   There is no change in the elevated
    03 concentration in the inversion layer, because little fresh HCs are added
    there and it has mainly "leftover" HCs to react.
    
                                     CONCLUSIONS
         The preceding analysis and discussion disagrees with the conclusions in
    the new EPA Policy Statement (2).   The extreme control  of all HC emissions
    regardless of reactivity that is stated there to be necessary in order to
    resolve the rural  03 problem is shown here to have a questionable basis.   We
    conclude here instead that the present control strategy,  based on reducing 03
    levels in urban areas, will also be effective in reducing rural  03 levels.
    HC reactivity scales relevant to urban 03 will be considered next.
    
         In urban areas, the conversion of NO to N02 plays  an important role  in
    the time-dependent smog chemistry.   (In rural areas, by contrast, the NO
    emissions are rapidly converted to  N02 because of the excess 03 present.)  It
    has been pointed out that the N0-N02 conversion is driven largely by HO chain
    reactions, and a reactivity scale  based on HO-hydrocarbon rate constants  gives
    a representation of this (6).  Pitts et al.  recently have published a detailed
    study of this concept (19).  Reactivity scales based on smog cnamber data
    (20) are equivalent to this (6).
    
         The N0-N02 conversion is only  the first stage of 03  production in urban
    areas as has been  pointed out before (6).  In the later stages of the reac-
    tion, the N02 is rapidly consumed  and the 03 concentration builds up.  An
    HO reactivity scale does not give  an adequate representation of these later
    stages of the reaction.  In addition, HO reactivity scales do not take into
    account the dilution of the reactants by dispersion.  As  a consequence, we
    believe that HO reactivity scales  overpredict the reactivity of less reactive
    hydrocarbons compared with more reactive hydrocarbons.
    
                                         460
    

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          To  take  account of  the  later  stages of  the reaction  in the reactivity
     scale, a factor  should be  introduced to express the effectiveness of differ-
     ent  HCs  in  producing a net increase of radical species present.  This would
     also improve  the  reactivity  scale  for the first stage of  the reaction.  Our
     understanding  of  the detailed chemical mechanism is not good enough at this
     time to  make  a reliable  estimate of this factor.  Qualitatively, we know  that
     olefins  are very  effective in producing radical species because they often
     produce  two new ones for each one  they consume.  Alkanes, on the other hand,
     more commonly  break even in  this respect, producing a single new radical  for
     each one consumed.  The  failure to include this net radical production con-
     cept in  the reactivity scale, then, qualitatively underpredicts the reac-
     tivity of more reactive  species and overpredicts the reactivity of less re-
     active species.
    
          Another  factor should be introduced into the reactivity scale to take
     atmospheric dilution of  smog precursors into account.  It is proposed that
     this  could  be  approximated by multiplying the HO rate constant for each HC
     by a  fraction, which would represent the fraction of emissions of that HC
     which are consumed in the  urban area in a single day.  For very reactive  HCs,
     this  fraction  would be unity.  For very unreactive HCs, this fraction would
     be close  to zero.  This  procedure  is suggested by the findings in this paper
     that  leftover  HCs from urban areas contribute only marginally to subsequent
     03 formation.  Such a procedure would, in part, remove the overprediction of
     the  reactivity of less reactive HCs in the reactivity scales based on HO  re-
     activity  or equivalently based on  smog chamber data.
    
         An  important corollary to these  conclusions  is  worth  mentioning.   In
    the last  few years,  catalysts have  been  used to meet the  HC emission  standards
    for motor vehicles.   One concomitant  effect of the  use of  catalysts  is  to
    reduce the photochemical  reactivity of the  HC emissions  (21).   Therefore, the
    reduced  HC emissions  of catalyst-equipped vehicles  should  have  a  much  more
    beneficial effect on  urban  03 reduction  than was  expected  without taking  this
    change of reactivity  into account.
                                    ACKNOWLEDGMENT
    
    
          The  authors  would  like  to  express  appreciation  to Hiromi  Niki  for many
     helpful discussions.
                                         461
    

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                                     REFERENCES
    
    1.  Dimitriades, B. and S. B. Joshi.   Application of Reactivity Criteria in
        Oxidant-Related Emission Control  in U.S.A.   In:  Proceedings of this Con-
        ference.
    
    2.  "Policy Statement on Use of the Concept of Photochemical  Reactivity of
        Organic Compounds in State Implementation Plans for Oxidant Control,"
        U. S. EPA, January 29, 1976.
    
    3.  Los Angeles Air Pollution Control  District, Rule 66.
    
    4.  Weinstock, B. and T. Y. Chang.   Methane and Nonurban Ozone.  Presented at
        the 69th Annual Meeting of the  Air Pollution Control Association, Portland,
        Oregon, June, 1976.
    
    5.  Chameides, W. and D. H. Stedman.   Ozone Formation from NOX in Clean Air.
        Environ. Sci. Technol. 10: 150-153 (1976).
    
    6.  Niki, H.,  E. E. Daby and B.  Weinstock.   Mechanisms of Smog Reactions.
        Advanc. Chem. 113: 16-57, 1972.
    
    7.  Hecht, T.  A., J.  H.  Seinfeld and M.  C.  Dodge.   Further Development of Gen-
        eralized Kinetic  Mechanism for  Photochemical  Smog.  Environ. Sci. Technol.
        8:  327-339, 1974.
    
    8.  Demerjian, K. L.,  J. A. Kerr  and J.  G.  Calvert.  The Mechanism of Photo-
        chemical Smog Formation.   Adv.  Environ. Sci.  Technol.  4:  1-262, 1964.
    
    9.  Pitts, Jr., J.  N., G.  J.  Doyle, A.  C.  Lloyd and A. M.  Winer.  Chemical
        Transformations in Photochemical Smog  and their Applications to Air
        Pollution  Control  Strategies.   NSF-RANN Grant AEN 73-02904 A02, Second
        Annual Report,  October 1, 1974  - September  30, 1975.  University of
        California Statewide Air Pollution Research Center,  Riverside, Calif.
    
    10.   Hecht T.  A., M.-K.  Liu and  D.  C.  Whitney.   Mathematical  Simulation of
         Smog Chamber Photochemical  Experiments.   EPA-650/4-74-040. U. S.  En-
         vironmental Protection Agency, Washington, D.C.   20460,  1974-
    
    11.   Durbin, P. A., T. A.  Hecht  and G.  Z.  Whitten.  Mathematical Modeling
         of Simulated Photochemical  Smog.   EPA-650/4-75-026, U. S.  Environ-
         mental  Protection Agency, Washington,  D. C.,  1975.
    
    12.   Niki, H.  and B.  Weinstock.   Recent Advances  in Smog Chemistry, EPA
         Scientific Seminar  on Automotive  Pollutants,  EPA-600/9-75-003, U.  S.
         Environmental  Protection Agency,  Washington,  D.C.,  February, 1975.
                                        462
    

    -------
    13.  Sickles, II., J. E.  Ozone-Precursor Relationships of Nitrogen Dioxide,
         Isopentane, and Sunlight Under Selected Conditions.   Ph.D.  Thesis,
         University of North Carolina, Chaoel Hill, N.C., 1976.
    
    14.  Chan, W. H., R. J. Nordstrom, J. G. Calvert and J. H. Shaw.  Kinetic
         Study of HONO Formation and Decay Reactions in Gaseous Mixtures of
         HONO, NO, N02, H20, and N2>  Environ. Sci. Techno!.  10: 674-682, 1976.
    
    15.  Kaiser, E.  W. and C. H. Wu. (To be published.)
    
    16.  Heuss, J. M.  Photochemical Reactivity of Mixtures Simulating Present
         and Expected Future Concentrations in the Los Angeles Atmosphere.   Pre-
         sented at the 68th Annual  Meeting of Air Pollution Control  Association,
         #75-16.1, Boston, Mass., June, 1975.
    
    17.  Research Triangle Institute.   Investigation of Rural  Oxidant Levels as
         Related to  Urban Hydrocarbon  Control Strategies.  EPA-450/3-75-036,
         U. S. Environmental Protection Agency, Research Triangle Park, N.C.,
         1975.
    
    18.  Detailed HC Analyses referred to in (17); available  from W. A. Lonneman,
         U. S. EPA.
    
    19.  Darnall, Karen R., A.  C. Lloyd, A. M. Weiner and J.  N. Pitts, Jr.   Re-
         activity Scale for Atmospheric Hydrocarbons Based on  Reaction with Hy-
         droxyl Radical.   Environ.  Sci. Techno!.  10: 692-696,  1976.
    
    20.  Proceedings of the Solvent Reactivity Conference.  U. S. Environmental
         Protection  Agency, Research Triangle Park, N.C., EPA-650/3-74-010,
         November, 1974.
    
    21.  Powers, T.  F.  The Oxidant Formation Potential of Emissions from Cata-
         lyst Equipped Vehicles.  In:   Proceedings of Specialty Conference  on
         Ozone-Oxidants-Interactions with the Total  Environment.  APCA Southwest
         Section, March 1976, pp. 189-200.
                                        463
    

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                    APPENDIX
    
    
    
    List of Reactions and Rate Coefficients
    
    
    
    
    
        Reactions	      Rate Coefficient (Kj)*
    Rl)
    R2)
    R3)
    R4)
    R5)
    R6)
    R7)
    R8)
    R9)
    RIO)
    Rll)
    R12)
    R13)
    R14)
    R15)
    R16)
    R17)
    R18)
    R19)
    R20)
    R21)
    R22)
    R23)
    R24)
    R25)
    R26)
    R27)
    R28)
    (conti
    N02 + HV = NO + 0
    HONO + HV - HO + NO
    HOOH + HV - HO + HO
    ROOH + HV = RO + HO
    RC03H + HV = R02 + HO
    03 + HV = OD + 02
    HCHO + HV = H02 + H02 + CO
    HCHO + HV - CO
    RCHO + HV = R02 + H02 + CO
    RN02 + HV - RO + NO
    OD + M = 0 + M
    OD + H20 = HO + HO
    0 + 02 + M = 03 + M
    0, + NO = N09 + 09
    0 L- L.
    0, + N09 = NO, + 09
    O L, O L-
    NO + N03 = N02 + N02
    N09 + NO- = N00C
    2 3 25
    N2°5 = N02 + N03
    N^Oj- + H?0 = NH07 + HNO,
    L- 0 C. O O
    NO + N02 + H20 = HONO + HONO
    HONO + HONO = NO + N02 + H20
    NONO + HN03 = N02 + N0? + H^O
    N02 + N02 + H20 = HONO + HN03
    NO + HO - HONO
    N02 + HO = HN03
    CO + HO = H02
    HN00 + HO = N00 + H00
    2 22
    HNO, + HO = N00 + H00
    3 32
    nued)
    kl
    6.8E-2k]
    3.5E-3k]
    3.5E-3k]
    3.5E-3k1
    3.5E-3k]
    4.7E-3k]
    1.1E-2k1
    1.2E-3k]
    3.5E-3k]
    4.7E+4
    3.1E+5
    2.1E-5
    2.5E+1
    4.8E-2
    1.5E+4
    4.4E+3
    1.4E+1
    1.5E-6
    1.9E-11
    1.8E-5
    2.2E-2
    8.7E-9
    1.2E+4
    1.5E+4
    2.1E+2
    3.1E+3
    1.9E+2
    
                     464
    

    -------
    APPENDIX
    
    R29)
    R30)
    R31)
    R32)
    R33)
    R34)
    R35)
    R36)
    R37)
    R38)
    R39)
    R40)
    R41)
    R42)
    R43)
    R44)
    R45)
    R46)
    R47)
    R48)
    R49)
    R50)
    R51)
    R52)
    R53)
    R54)
    R55)
    R56)
    R57)
    (continued)
    Reactions
    NO + H02 = N02 + HO
    N02 + H02 = HN02 + 02
    H02+ HO - H20 + 02
    03 + H02 = HO + 02 + 02
    03 + HO = H02 + 02
    HC2 + 0 = R02 + HO
    HC2 + HO - R02 + H£0
    CH4 + HO - R02 + H20
    HCHO + HO = H02 + CO + H20
    RCHO + HO = RC03 + H20
    HOOH + HO = H02 + H20
    ROOH + HO = R02 + H20
    RC03H + HO = RC03 + H20
    NO + R02 = N02 + RO
    NO + RCO- - NOp + ROp
    O L- C-
    N02 + RC03 = PAN
    PAN = N03 + R02
    RO + 02 = 8RCHO + (1-8) HCHO + H02
    RO + NO = RN02
    RO + N00 = RN00
    2 3
    H02 + H02 = HOOH + 02
    H02 + R02 = ROOH + 02
    R02 + R0? = RO + RO + 02
    HOp + RCOo = RCO^H + Op
    c~ O O C,
    ROp + RCO,, = R0p + RO + Op
    L. O L. C.
    DPH 4- orn — DO 4. on
    Kl/U~ T KUU-} •" KU/-J * KUo
    O 3 L— L-
    °3 =
    RN03 =
    HN03 =
    
    Rate Coefficient (Kj)*
    7.0E+2
    3.5E+1
    1.5E+5
    2.2E+1
    8.3E+1
    k34
    k35
    1.1E+1
    2.1E+4
    2.1E+4
    1.2E+3
    1.2E3
    1.2E+3
    7.0E+2
    1.5E+3
    3.5E+1
    3.0E-3
    4.4E-3
    1.2E+2
    1.1 E+2
    4.9E+3
    4.9E+3
    4.9E+2
    4.9E+3
    4.9E+2
    4.9E+2
    0
    1 .OE-4
    5.0E-4
    * in ppm-min units
    
    
    
    
                                    465
    

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                                                                                 9-5
                      THE  KINETIC OZONE PHOTOCHEMISTRY  OF  NATURAL
                           AND PERTURBED NONURBAN TROPOSPHERES
    
                             T.  E. Graedel and D. L. Allara*
    ABSTRACT
         The, diu/inal kineJic. photoc.he.m-U>tny o& natural and peAtuJibud nonurban
    &wpo?>pheAeA  hat, been fie.pfiej>e.nte.d by a. computation u&ing ewiAAionA and fie.dc.-
    tionb o^ teApe,neA,  ammonia,  hydAoge.n Aulfi-ide,, and  otheA on.ga.nic. and inorganic.
    Ape.ci.eA.  Ike. computational HQJ>uJtM> faon, the. unperturbed caAe. a'te. Ai.multane.ouAly
    coni>iAte.nt with nonusiban obAeJivationA o^  monoteA.pe.neA,  meJ.ha.ne., ozone., oy^ide^
    o^ nitiogun,  hydtoge,n ^at^-idn, ammonia, AL&&UA  dioxide.,  acetone., and total
    nonmeJhane. hydsiocatibom,,  ^oft nitric oxJ.de., hydfioge.n AuZfiide., and ammonia
    ewJ>&*ion rioter  adjuAte.d to g-cve ofa^eAued c.onc.e.n&LationA.  Substantial amount!*
    ofa ozone.  (^32 ppb  peafe)  can be pfioduc.e.d in fiemote.  ane.a tnopo&pneAeA by photo-
    che.mic.al pfioc.e^i>i&.   The. ponte.d  faom un.ban aAe.a6)  at the. ^ofimation oft ofiganic. and inorganic
    nittate. compound*;  the. ozone, peafe c.onc,tntnation, how&veA,  dec^eaie^ to ^29 ppb.
                                      INTRODUCTION
    
         The chemistry  of natural  tropospheres is  regarded  as potentially signif-
    icant to interactive  ozone chemistry, the atmospheric carbon monoxide budget,
    and natural  sulfate and  acid rain production among  other issues.  Despite
    the importance of these  issues, the chemical processes  remain largely unex-
    plored and the emission  rates  of the reactants poorly defined.
    
         In this paper  we present  the results of calculations representing the natural
    and perturbed nonurban troposphere, particularly  as they apply to the chemistry
    and resulting concentrations of ozone in nonurban areas.   The calculations
    show that some ozone  formation occurs naturally by  photochemical processes
    on non-anthropogenic  emissions, but that the addition of anthropogenic nitric
    oxide has only minimal  effect  on remote area ozone  concentrations.
    
                     GASEOUS EMISSIONS INTO NATURAL TROPOSPHERES
    
         A large number of gaseous species are emitted  from natural  sources;
    those whose  emissions have been quantitatively assessed are listed in Table 1.
    Many of the  emission  rates are based on observed  global  concentrations and
    * Bell Laboratories,  Murray Hill, New Jersey.
    
                                          467
    

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     estimated  atmospheric  residence  times;  in these cases the emission rate quoted
     is  that  needed  to  provide  a  balance between known or estimated source and
     removal  rates.   The  emission  estimates  are therefore sensitive to errors in
     the estimated residence  time  and  in the global concentration assessment and
     should,  in general,  be regarded  as "order-of-magnitude"(ll)  numbers only fur-
     ther limitation  is that  natural  emissions processes are not  the same in
     all  geographical locations.   (Terpene emission rates based on data from forests
     obviously  could  not  be expected  to apply to desert areas, for example.)
     Although some of the emission mechanisms postulated or identified differ under
     different  conditions of  terrain  and vegetation, it is premature to do more
     than to  simulate an  average  natural area in this study.  The results must thus
     be  regarded  as  "bulk-averaged chemistry,"  rather than as being strictly appli-
     cable to any particular  geographic location.
                  TABLE 1.  NATURAL EMISSION RATES OF ATMOSPHERIC GASES
       Molecule
       CH,,
    
       H2S
       NO
    Initial  Emission*
      Rate Estimate
    
      1.30xlO-n
    
      1.87xlO-10
    
    
      2.31xlO'm
      1.00x10
                            -11
      Reference
    
    Ehhalt, 1,974
    
    Kellogg, et
    al., 1972
    
    Robinson and
    Robbins, 1970
    
    Robinson and
    Robbins, 1970
    Final  Emission*
      Rate Chosen	
    
      1.52xlC)-13@
    
      1.87X1C)-11
    
    
      l.lSxlO-11
    
    
      l.OOxlO-11
    Isoprene
    a-Pinene
    1.84x10-12t§
    1.84xlO-§
    Rasmussen, 1972
    Rasmussen, 1972
    1.84xlO~lc
    1.84xlO-10
    
       * Units are g cm"2 sec"1.
    
       t These rates are diurnally varied in accordance with the patterns
         illustrated in Paper I.
    
       § Total terpene emissions assumed to be equally divided between
         isoprene and a-pinene.
    
       @ This is the amount needed to balance CH^ loss by reaction with
         HO in the fully mixed planetary boundary layer of average depth
         1 km.  Diffusion loss of CH^ to the stratosphere is not included
         in these computations.
         Detailed discussions of the bases for and uncertainties in these emission
    rates are presented by Graedel  and Allara (1976, referred to as "Paper I").
                                         468
    

    -------
                     CHEMICAL REACTIONS IN NONURBAN TROPOSPHERES
    
         The inorganic compounds present in urban and natural atmospheres are
    similar, as are the chemical reactions describing their interactions.  For
    0-H-N chemistry, we utilize a set of 40 reactions identical to those of Groups
    1 and 2 of Graedel, et al.   (1976, referred to as "Paper II").  The sulfur
    chemistry of Paper II treated only oxidized sulfur compounds.  We have there-
    fore devised an appropriate reaction set for reduced sulfur, which is given
    in Paper I.  The combined reaction set for compounds of sulfur totals 37 reactions.
    The chemistry of ammonia is also the subject of a newly devised reaction set,
    described in detail in Paper I.
    
         A significant difference between the difference between the chemistry of
    urban and natural tropospheres is the composition of the complex organic
    compounds.   Urban atmospheres contain a variety of species derived chiefly
    from automotive emissions,   petroleum processing and handling, and evaporated
    paint solvents.  Remote area organics are largely derived from botanically
    emitted terpenes.  In each  case eventual chemical breakdown of the long carbon
    chains produces simple products such as the aliphatic aldehydes.  We have devised
    chemically reasonable reaction chains for ^-pinene and isoprene in the presence
    of common atmospheric species.  Examples of these chains are shown on Figures
    1 and 2; full descriptions  are given in Paper I.
    
         The total chemical reaction set, including both organic and inorganic pro-
    cesses, contains 333 reactions involving 207 distinct chemical species.
    
                              METEOROLOGICAL INFLUENCES
    
         The effects of meteorological variables upon the concentrations of
    chemical species in the atmosphere are substantial, and very complex tech-
    niques are sometimes utilized for the treatment of meteorological parameters.
    For studies that attempt to elucidate chemical mechanisms rather than detailed
    spatial  structure, however, it appears sufficient to use somewhat simplified
    descriptions of the operational meteorology.  Following the computational
    techniques  of Paper II, therefore, we define the diurnally varying reaction
    volume by the mixing depth  pattern specified therein and also use the diurnal
    variation in solar photon flux described.   For the natural troposphere calcula-
    tion we impose the further  requirement of spatial homogeneity of emissions and
    terrain within the diurnal  wind fetch; this allows advection to be neglected.
    Within the  reaction volume   thus defined, all chemical  species are regarded
    as fully mixed, i.e.,  the concentrations of all  species are spatially constant
    within the  volume.  The assumption of full  mixing on a molecular scale appears
    to be relatively accurate during days of normal  convective turbulence; near-
    uniform vertical  concentrations of many chemical species have been measured at
    such times  by airborne instruments (e.g.,  Blumenthal and White, 1975).  Such
    an assumption is less  valid during the stable nighttime hours, however, and
    we anticipate that our computation more accurately represents the physical
    mixing conditions that are  present in the daytime troposphere.
    
                                       RESULTS
    
    
         The computed diurnal  variations of a  number of species in the unperturbed
    
                                         469
    

    -------
                          HO,
                         H02,
                          OR
                         CH362
                   02
                            1)02
                            2) HO, NO
    
                            3) CLEAVAGE
                                         CHO
                           l)02
                           2) HO, NO
    
                      CHO 3) CLEAVAGE
         1)02
        2) HO, NO
        3)CLEAVAGE
    CH2CHO
    
    
    CHOC (CH3)CH CHO
    PRODUCTS INCLUDING
          HCHO, CHO
    
    PRODUCTS INCLUDING
       CH3CH=CH2,CO
    Figure  1.  Schematic display of the chemical  reaction sequence for  hydrogen
    abstraction from a-pinene.  The dots indicate the location of the unpaired
    electron bond; the dotted  line shows the bond that cleaves on the subsequent
    rearrangement or disproportionation.  The end products of the chain are relatively
    simple  free radicals or stable molecules that participate in common atmospheric
    reactions.  Some of the most significant of the products are indicated, but
    the chemical balance present in the actual  equations is not necessarily reflected.
    
    
    nonurban troposphere are illustrated in Figure 3.  The comparison of these
    results with the sparse quantities of field data are discussed in detail in
    Paper I; the concentrations calculated agree to within a factor of  ^3 for nearly
    all species that have been measured in natural atmospheres and included in our
    study:  nitrogen oxides (NOX), ammonia (NHs), hydrogen sulfide (H2S), sulfur
    dioxide (SCh). formaldehyde (HCHO), carbon monoxide  (CO), methand  (CHu),
                                       470
    

    -------
                                                                   02
                                                                    CHO
    Figure 2. Schematic display of the chemical  reaction sequences for ozone attack
    on a-pinene.
    
    isoprene, a-pinene, acetone, and total nonmethane hydrocarbons.  This is partic-
    ularly satisfactory since formaldehyde and acetone are chemical products
    and thus validate the general chemical  treatment as well as the emission and
    meteorological aspects of the computation.
    
         The exception to the good agreement discussed above is ozone, whose con-
    centration  is generally measured at <_ 60 ppb in nonurban areas, rather than the
    32 ppb computed here.  The ubiquitous presence of ozone in the mid-troposphere is
    well known, however, and the incorporation of this ozone into the expanding
    morning mixed layer is probable.  This process (termed the incorporation of
    "fossil" ozone by Ripperton, 1974) is thus  expected to increase the ozone
    concentrations in the lower troposphere.  We are incorporating this effect
    into calculations now in progress and will report the results separately.
    The combined effects of local photochemistry and fossil ozone injection may
    be thought  of as producing the natural ozone background in vegetated areas
    subject to  normal stratospheric-tropospheric mixing processes.
    
          A final  consideration of interest is the effect of transported anthropo-
    genic emissions on nonurban chemistry.   Since remote areas have abundant sources
    of hydrocarbons and meagre sources of oxides of nitrogen,  transport of the latter
    is more likely to influence the natural  chemical  cycles.   To assess this effect,
    we add to the natural  nitric oxide (NO)  source strength an amount sufficient to
    maintain a daily NOX concentration of ^20 ppb (shown by Robinson (1976)  to be
    indicative of the transport of urban  air into nonurban regions).  The response
    of the remot^ area ozone balance to this new source strength is rather small;
    the diurnal  peak value decreasing from 32 ppb to 29 ppb.   Similar results
                                          471
    

    -------
        5-2
        (T
    
        UJ
        O
    o
    
    Q
      -3
    
    
    
      -4
    
    
    
      -5
      -i
    f> _g
    
    
    Q-3
    fe
    
    -------
    of stimuli.  The natural sources, together with photochemical and thermochemical
    processes, produce a rich spectrum of chemical reactions and generate moderate
    amounts of ozone.  This photochemically produced ozone, together with any
    preexisting ozone in the nonurban troposphere, combine to form a naturally-
    produced ozone background.  This natural background can be affected to some
    degree by the transport-generated injection of anthropogenic contaminants, but
    calculations representing the injection of NO show such perturbations to be
    minimal.
    
                                      REFERENCES
    
    Blumenthal, D.  L.,   and W. H.  White,  The stability and long range transport
    of ozone  or ozone precursors,  paper presented at 68th Annual  Meeting, Air
    Pollution Cont.  Assoc., Boston,  June  16, 1975.
    
    Ehhalt, D.  H.,  The  atmospheric cycle  of methane, Tellus, 26_,  58-70, 1974.
    
    Graedel,  T. E.,  L.  A.  Farrow,  and T.  A.  Weber, Kinetic studies of the photo-
    chemistry of the urban troposphere, Atmospheric Environment,  (in press),
    1976, Paper II).
    
    Graedel,  T. E.,  and D. L.  Allara, The kinetic photochemistry of natural  tro-
    pospheres,  submitted for publication, 1976, (Paper I).
    
    Kellogg,  W. W.,  R.  D.  Cadle, E.  R.  Allen,  A.  L. Lazrus, and E.  A.  Martell,
    The sulfur cycle, Science, 175,  587-596, 1972.
    
    Rasmussen,  R.  A., What do  the  hydrocarbons from trees contribute  to air pol-
    lution?,  J. Air  Pollution  Contr.  Assoc., 22^, 537-543, 1972.
    
    Rasmussen,  R.  A., Recent field studies,  in Scient.  Sem. on Automotive Pollutants,
    EPA-600/9-75-003, Environmental  Protection Agency,  Washington, D. C., 1975.
    
    Ripperton,  L.  A., Eastern  United States  high ozone concentrations:   chemical
    aspects,  Clean  Air,  £ (16),  79-82,  1974.
    
    Robinson, E.,   and  R.  C. Robbins, Gaseous  nitrogen compound pollutants from
    urban and natural sources, J.  Air Pollution Contr.  Assoc., 20, 303-306,  1970.
    
    Robinson, E.,  and R.  A.  Rasmussen,  Identification of natural  and anthropogenic
    rural ozone for  control  purposes, Proc.  Specialty Conf. on Ozone/Oxidants-
    Interactions with the  Total  Environment, Pittsburgh:  Air Pollution  Contr. Assoc.
    3-13, 1976.
                                         473
    

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                 SESSION 10
    PHYSIOLOGICAL EFFECTS OF OXIDANTS - I
    
            Ckcuxman:   J. Knelson
       Environmental  Protection Agency
                     475
    

    -------
                                                                                10-1
            ON  THE  RELATIONSHIP OF SUBJECTIVE SYMPTOMS TO  PHOTOCHEMICAL OXIDANT
    
                     I.  Mizoguchi, K. Makino, S. Kudou, and  R.  Mikami*
    
    ABSTRACT
    
         The. daily incidences ofi acute subjective symptoms  -in  515  Atu.de.nt!> ofa a.
    JO.YIA.OH  high school  Mere recorded fan a 6]-day period  and were  analysed in
    relation to environmental factors,  especially prevalence ofi  photochemical.
    oxA-dants.  Sample, and multiple. correlation analyses and maJLti-vaniate analysis
    were used  to investigate, the. relationship between environmental factors and
    the. symptoms.   In addition,  incidences oft symptoms connected with predisposi-
    tions,  such as allergy,  asthma,  and ositho&tatic dyt>fie.QuJtaution,  weAe. compa?ie,d
    u.ndeA. di^e.fie.nt ox^idant le.v&L*>.   Eye. iAA^utation, throat iwiLtation, t>hofctneJ>A
    o& bnnatk, and ke.adaa.he. cofifie.iate.d Aigni&icantty  {p<0.001} to  ozone..   Thtioat
    iAAJjtjation, cough,  and phte.gm coM.eJLate.d £-ignifiicantl.y  to  £u£fiuA dioxA.de.,
    too.  Humidity Ahowe.d significant negative. cowieJ&ition  to  cough,  tethafigy,
    phie.gm, thsioat itfutation, and shortness ofi bfieath.   Studies on the. muJLtipte.
    cofin.eHatA.on coe.^icie,nt^ &howe.d highly significant coM.e.£ations bntu)e.e.n difi-
    ^ojtojit  pOAAA ofi e.nviA.onme.ntai fiactotis including ozidants and se.veA.at symptoms.
    The. result oft  a pfiincipat component anatysis suggests that tkete one. associa-
    tions between  oxA.dant,  suJL^uA. dioxA.de, suspended poftticutate matte*, and eye
    imitation, hoasiAeness,  sonc thsioat, headache, and so on.  The incidences o{^
    the symptoms wcne. compared wtth ne^eAence to the predispositions o& the stu-
    dents.  A  significant increase in the incidence ofa cough Mas observed in asthma
    Qfioup;  the otitnostatic dysnegutation group showed appreciable  increases in
    the incidence  oft headache and lethargy in the days in which  oxidant levels
    exceeded 0.15  ppm.
    
                                       INTRODUCTION
    
         During the summer many residents in metropolitan Tokyo  and the Tokaido
    megalopolitan  areas manifest symptoms caused by photochemical  oxidants.  This
    has become of  considerable social concern in recent years.   Hausknecht (1)
    reported that  changes in chronic conditions related to  oxidants and other
    weather factors were noted by eye complaints, asthma, and  nose and throat
    complaints.  In Japan similar reports (2, 3, 4) were  recently  published in
    journals and governmental reports.   In our country, the deleterious effects
    of photochemical oxidants first attracted public attention when the shocking
    *I. Mizoguchi, K. Makino,  Tokyo  Metropolitan Research Laboratory  of Public
    Health, Tokyo, Japan.
     S. Kudou, R. Mikami, School  of  Medicine, University of Tokyo,  Tokyo,  Japan.
    
                                          477
    

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    episode at the Rissho Girls High School  took place on July 18,  1970.   Scores
    of girls playing handball on their campus suffered eye and throat irritation,
    and shortness of breath.  More than 10 of them had trouble in breathing and
    temporary clouding of consciousness and were admitted to a neighboring hospi-
    tal.  Attacks like the Rissho High School episode have occurred a few times
    every year since then.  The oxidant level in Tokyo is gradually rising.  It
    is a most important problem for us to reveal the extent of actual effects of
    photochemical oxidants on health and to encourage control.
    
         Since 1974 we have been conducting investigations on the relationship
    between multiple variables including subjective symptoms, photochemical oxi-
    dants, other air pollutants, meteorological  factors,  and clinical signs in
    students of a junior high school located in  southeastern Tokyo  (ca 12 km
    away from the center).  In our investigation period,  maximum oxidant  concen-
    tration was 0.23 ppm, and clinical examinations were  carried out under 0.17
    ppm oxidant level.  The values of respiratory function tests were not dif-
    ferent from control values.  The only signs  we found  were decreases in lysozyme
    activities and in the pH of tears (5).   Analyzing the daily incidences of
    subjective symptoms related to environmental conditions presented several
    interesting clues, however.
                                  MATERIALS AND METHOD
    
    POPULATION AND SUBJECTIVE SYMPTOMS
    
         The study population was composed of students of a public junior high
    school located in a southeastern area of Tokyo.   Almost all  students of this
    school live within 1.5 km from the school.   Five hundred fifteen students
    recorded 17 symptoms every day from May 20th to  July 19th,  in 1974..   These
    symptoms previously recorded in health diaries are shown in  Table 1.  The time
    and place in which each student became aware of  symptoms were recorded.   Sub-
    jective symptoms used were those which occurred  from 8 am to 5 pm.   Daily
    incidences of the symptoms are indicated by percentages of all 515 students.
    Frequencies of several symptoms and daily maximum oxidant and sulfur dioxide
    concentrations are shown in Figure 1.   Stars at  the top of Figure 1  indicate
    the days when maximum oxidant concentrations exceeded 0.15 ppm.   It  will  be
    noticed that oxidant peaks correspond with  peaks of frequencies  of most
    symptoms.  Such crude data were subjected to statistical procedures.
    
         In order to examine incidences of the  acute symptoms with reference  to
    the predispositions of the students, three  subgroups were picked out of all
    515 students according to questionnaires (Table  2):   allergy, asthma, and
    orthostatic deregulation (O.D.).   In Japan, O.D.  is a present important  pro-
    blem in the field of school health administration.   Although the concept  has
    not been established completely, it seems that  its entity is something dif-
    ferent from postural hypotension.   The criteria  we used is shown in  Table 3
    (6).  The number of students in each group were:  Allergy group - 74, Asthma
    group = 20, O.D. group = 47; some overlapped each other.
                                         478
    

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                                 TABLE 1.  HEALTH DIARY
    Check
    the proper space
    if you had symptoms below
    Date
            May 20
             Mon.
    May 21
    Tues.
    May 23
     Wed.
    1.   Eye irritation
    2.   Redness of conjunctiva
    3.   Watering of eyes
    4.   Blurred vision
    5.   Cough
    6.   Phlegm
    7.   Sneeze
    8.   Shortness of breath
    9.   Hoarseness
    10.  Sore throat
    11.  Dizziness
    12.  Headache
    13.  Nausea
    14.  Numbness of extremities
    15.  Lethargy
    16.  Abdominal pain
    17.  Diarrhea
    Time when you had
    the symptoms
                am
                pm
        am
        pm
        am
        pm
    Place where you had
    symptoms:
    1.  Indoors    2.   Playground
    3.  Outdoors   4.   Outside school
    Duration
               mm
               hrs
                                                                   mm
                                                                   hrs
                   mm
                   hrs
    Treatment (Ex: washing,
       gargling, etc.)
    Check if absent from school
    Reason for your absence
                                         479
    

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                                                                    1112
                                                                      Temp
                                                                    20compl3ints
         Figure  1.   Correspondence of  daily  changes  in  subjective  symptoms
                          with  oxidant  concentrations.
    AIR POLLUTION AND METEOROLOGICAL DATA
    
         Oxidants, other air pollutants, and meteorological factors were measured
    every hour throughout this investigation period at a sampling room set up in
    the studied school.  (Air pollutants and their measurement methods are shown
    in Table 4.)  Meteorological  factors obtained were temperature, relative
    humidity, wind speed, solar radiation, ultraviolet radiation, and visibility.
    Discomfort Index was calculated from temperature and humidity.  Minimum values
    were used for humidity and visibility; maximum values of the other environ-
    mental variables were used.
                                        480
    

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                         TABLE 2.   RATIOS OF YES TO ALL STUDENTS
    QUESTIONNAIRES
    1.    Having nausea
    2.    Liable to be tired
    3.    Liable to get carsick
    4.    Frequently having headaches
    5.    Frequently having sleep disturbances
    6.    Liable to feel ill under difficult circumstances
    7.    Liable to be irritated
    8.    Liable not to feel refreshed in the morning
    9.    Liable to feel dizzy
    10.  Having urticaria
    11.  Liable to be pale
    12.  Frequently having eczema
    13.  Having asthma attacks
    14.  Liable to feel ill in a long erect posture
    15.  Liable to palpitate or be short of breath after light exercise
    16.  Having loss of appetite
    24
    22
    19
    18
    14
    13
    12
    11
    10
     9
     6
     5
     4
     3
     3
     3
           TABLE 3.   CRITERIA FOR GROUPING OF ORTHOSTATIC DYSREGULATION GROUP
    
    Major Symptoms
    3
    or 2
    or 1
    Major Symptoms:
    Minor Symptoms:
    
    
    
    Nos.
    Nos.
    Minor Symptoms
    + 0
    + 1
    + 3
    6, 8, 9, 14, and 15 )
    2, 3, 4, 11, and 16 J
    
    
    
    
    From Questionnaire in
    Table 2
                                         481
    

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                        TABLE 4.  MEASURED ENVIRONMENTAL FACTORS
                           Item
                Method
      Air pollutants
    0
     X
    03
    S02
    
    NO
    
    N02
    
    HC(total)
    
    CO
    
    Aerosol
    
    SPM
    
    SOi,
    
    N03
    
    Aldehyde
    (total)
    Neutral Potassium Iodide
    Chemiluminescence
    Conductimetric
    Saltzman
    
    Saltzman
    Flame ionization
    
    Infrared absorption
    Light scattering
    High volume air sampler*
    Spectrometric*
    Spectrometric*
    
    3-Methyl-2-Benzothi azolone hydrazone*
      One hour averaged for air pollutants
     *Four hours averaged
      Meteorological
      Factors
      Reading taken every hour
                Temperature
                Relative humidity
                Discomfort Index
                                                               Calculated
                                  STATISTICAL ANALYSIS
    SIMPLE CORRELATION ANALYSIS
         To study the relationship between the symptoms and environmental  factors,
    simple correlation analysis was first adopted.   Two variables were used:  one
    was daily incidences of each symptom, the other was daily maximum value of
    each environmental factor for 61  successive days.
    
    MULTIPLE CORRELATION ANALYSIS
    
         Multiple correlation analysis was performed with three variables:  one
    of the symptoms and a pair of environmental factors.
                                         482
    

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    PRINCIPAL COMPONENT ANALYSIS
    
         Principal component analysis is a mathematical and statistical method
    that has been used to derive principal components which represent a number
    of different variables.  Variables of 17 symptoms and 14 environmental factors
    are analyzed.  Principal components represent the degree of overlap or simi-
    larity among these variables as measured by correlation coefficients.   Another
    interpretation is that principal components are synthetical characteristics
    that give weight to each variable and combine these variables primarily.
    Generally principal components are selected until the sum of ratios of the
    variances will exceed 60 per cent of the total variance.  The ratio of 60
    per cent is regarded to interpret most significant characteristics of the
    variables.  The list of variables is contained in Table 7.
    
                                         RESULTS
    
    SIMPLE CORRELATION COEFFICIENTS
    
         Figure 2 shows some typical variation of simple correlation coeffi-
    cients between representative environmental pollutants  and the symptoms.
    Exceedingly high correlation coefficients were noted between oxidant  and
    eye irritation, sore throat, shortness of breath, headache, and blurred
    vision.  The  simple correlation  pattern of ozone with variation of the
    symptoms, is  noticed to be  similar  to that of oxidant.  Sulfur dioxide and
    suspended particulate matter were revealed to have fairly  high coefficient
    values to some symptoms such as  sore throat, cough, phlegm, lethargy, and
    blurred vision.  There are  extremely high negative correlation coefficients
    between humidity and sore throat, cough, phlegm, lethargy, and sneezing.
    Besides there are  significant  (p<0.01) correlation between solar radiation
    and lethargy  as well as between  pollution index  (Pindex)  (8) and several
    symptoms.  Table 5 is the list of all symptoms and environmental factors
    between which there are significant  (p<0.001 and p<0.01)  correlation  coef-
    ficients (0.001 or 0.01 of  significance level, used t-test, express extremely
    close associations).  From  mutual comparisons of values of the coefficients,
    the values of oxidant give  us a  large evaluation of contribution to occurrence
    of the symptoms.   Wind speed and visibility have no significant correlation
    coefficients  in spite of our expectation.  The expectation came from  obser-
    vation of weather  in the days when many students complained of mucous mem-
    brane irritations  and respiratory symptoms.
    
    
    MULTIPLE CORRELATION COEFFICIENTS
    
         F-test was used to examine the significance of multiple correlation
    coefficients.   Figure 3 shows  that multiple correlation coefficients  of sub-
    jective symptoms will  change according to the pairs of air pollutants.  Char-
    acteristic results of these  analyses are significant from p<0.005 coefficients
    among  several  symptoms  and pairs of environmental factors such  as ox-S04, ox-
    Aldehyde,  and ox-N03.   Sulfate, nitrate, and aldehyde have no significant
    simple correlation coefficients to any symptoms, but their pairs, which include
                                         483
    

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                        0.8   0.6   0.4   0.2
    -0.2
                          c.c.
                             p 0.001 p.0.01
                                            X
                          Hum .f\)
     p 0.01
                                               /N02
    
          -Eye Irritation
    
          .Shortness of
          Breath
    
          -Sore Throat
    
          -Headache
    
    
          -Blurred Vision
    
    
          •Watering of
                  Eyes
    
          -Cough
    
          -Dizziness
    
          -Hoarseness
    
    
          -Phleghi
    
    
          -Lethargy
    
          -Sneeze
    
          -Abdominal-pain
    
    
          -Diarrhea
    
          .Numbness of
          Extrimities
    
          •Nausea
    
          Redness of
          "Conjunctiva
                   Figure 2.  Changes  in simple  correlation  coefficients
                      between each  environmental  factor and  symptoms.
    oxidant,  S02, or suspended participate matter  (SPM), have appreciably  high
    values with  several symptoms such as  eye irritation, shortness  of breath,
    sore throat, headache,  blurred vision, watering  of eyes, cough, dizziness,
    hoarseness,  phlegm, and lethargy.   If we adopt p<0.01 as the  significant  level,
    there are too many correlation coefficients to list in this  limited space.
    For this  reason, we adopted a severe  significant level  (p<0.005).   In  spite
    of this  severe level,  29 combinations are listed in Table 6.
                                            484
    

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       TABLE 5.  EACH SYMPTOM AND ENVIRONMENTAL FACTOR BETWEEN WHICH THERE WAS A
                      SIGNIFICANT SIMPLE CORRELATION COEFFICIENT
           Symptoms
            Environmental Factors
      p 0.001                     p 0.01
    Eye irritation
    
    Shortness of breath
    Sore throat
    
    Headache
    Blurred vision
    
    Eye watering
    Cough
    Vertigo
    Ox, 03, S02
    
    Ox, 03, Hum(-)
    0 , Hum(-), 03
    S02, SPM
    S02, Ox
    0
    Hum(-), S02, SPM
    Pindex, Hum(-),
    SPM, N03, Aid.
    S02, Pindex, SPM
    Pindex
    
    03, Hum(-), Pindex, N03
    Hum(-), S02, 03, SPM,
    Pindex
    Hum(-), Pindex
    Oy, 03, Pindex
    Pindex, 0 , S02, 03,
    Aid., Hum(-), SPM, N03
    Hoarseness
    Phlegm
    Lethargy
    Sneeze
    Abdominal pain
    Diarrhea
    Numbness of extremities
    Nausea
    Redness of conjunctiva
    Hum(-)
    Hum(-), S02
    Hum(-)
    Hum(-)
    —
    —
    —
    —
    —
    Pindex, S02, 03, 0 , SPM
    X
    SPM, Ox, 03, Pindex
    SPM, S02, Ox
    S02, SPM, 03, 0
    X
    SPM, S02, Hum(-)
    —
    Hum(-), SPM
    SPM, Hum(-)
    —
    
    PRINCIPAL COMPONENTS
         Three major principal  components were produced,  which  altogether accounted
    for 63 per cent of the total  variance of the data.   These three  principal  com-
    ponents can be considered to  have independent interpretation  to  each  other
    and are shown in Table 7.
                                         485
    

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                                    0.6   0.4
    0.2
    n-c-cp
    cv
    O
    I/}
    |
    X
    o
    \
    \
    \
    \
    
    /
    z:/
    3*
    3
    °\
    \
    ^
    
    
    
    
    
    
    
    
    
    
    
    
    
    ^
    \
    //
    ^
    \
    ,\
    fcl\
    \ \ .
    \-o
    ff
    '"/i
    / 1
    1
    \
    V
    V\
    II
    8V
    inl 1
    ik \
    °\\ \-
    \ \XP
    \ I 1
    1
    \l[
    '• r
    •^ V
    
    
    
    f
    *
    t
    i
    v^
    
    
    
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    V
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    \ / '
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    ""-V \
    \S:\
    
    
    -Eye Irritation
    ^Shortness of
    "Breath
    •Sore Throat
    
    
    •Headache
    
    
    •Blurred Vision
    •Watering of
    Eyes
    •Cough
    
    "Dizziness
    
    •Hoarseness
    
    •Phlegm
    
    •Lethargy
    •Sneeze
    
    •Abdominal Pain
    •Diarrhea
    
    Numbness of
    "Extrimities
    
    -Nausea
    
    .Redness of
    Conjunctiva
           Figure 3.  Changes in multiple correlation coefficients between each
                            environmental factor and symptoms.
    FIRST PRINCIPAL COMPONENT
    
         The factor that has high loadings of variables is associated with res-
    piratory symptoms such as sore throat and cough.   Headache, eye irritation,
    hoarseness, blurred vision, shortness of breath,  and phlegm follow.  Thus,
    this principal component is associated with irritation of mucous membranes as
    well as respiratory symptoms.  High loadings of headache, lethargy and
    dizziness suggest an association of this component with other systemic symptoms
    to some extent.  In addition, oxidant, ozone, and sulfur dioxide have high
                                         486
    

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                                            1.0
                                         CO.
                                           0.5'
                  •HUM
      .-i.n
                        -0.5
                           2ND PC
                           AEROSOL
                                               HC
                                                   S04
                                           NO*
                                                      • AID*
                                                'NO
                                              HEADACHE
                                    SHORTNESS OF BREATH
                                     WATERING OF EYES
                              DIARRHEA*   SORF THROAT
    
                                              0.5 .
                  OX
                   •
                 .SOe
                  •03
    
                  EYE IRRITATION
                 .»  .'     1,0
                                    MBDOMINAL TAIN
                                     TEMP
                   REDNESS ot CONJUNCTIVA*
                                                                  BLURRED VISION-;
                                                                        HOARSENESS
                                                                                    1ST PC
                                                                       SNEEZE  *
                                                                  NAUSEA.   PHLEGM
                                                NUMBNESS OF EXTRIMITIES*
                                                                      LETHARGY*
                                                                                  .COUGH
                                          -0.5H
            Figure 4.
                      -l.OJ
    Distribution of the  1st  principal
                 principal  components.
    components vs  the 2nd
    loadings, and  it is recognized  that oxidant affects symptoms mentioned above.
    The first principal component is  considered to be  a factor associated with
    "Photochemical  Air Pollution."
                                             487
    

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          TABLE 6.   EACH SYMPTOM AND  ENVIRONMENTAL FACTORS-COMPLEX BETWEEN  WHICH
                 THERE  WAS A SIGNIFICANT  MULTIPLE CORRELATION COEFFICIENT
           Symptoms
              Environmental Factors
                     p 0.001
         Eye  Irritation
    
    
         Shortness  of Breath
    
    
         Sore  Throat
    
    
         Cough
    
         Hoarseness
    
         Phlegm
    0 -S02, 0-S04, 0 -Aid.,  0  -Temp., 0 -SPM,
    0*-N03.   xxx
    
    Ox-S04, 0  -Aid., 0 -S02,  0  -Temp., 0 -N03,
    0 -SPM.   xxx
     X
    0 -SCV, 0  -SPM, 0 -S02, 0 -Temp., 0 -Aid.,
    S6VSPM, Clx-N03.
    
    S02-SPM, Ox-SPM, SPM-S04.
    
    S02-SPM, Ox-SPM, SPM-SO^, SPM-N03, SPM-Ald.
    
    S02-SPM, S02-S0v
                                  10
              15
           20
                                                                  25
    30?
    Eye
    Irritation
    
    Sore
    Throat
    Shortness
    of Breath
    Cough
    
    
    Headache
    
    Watering
    of Eyes
    
    Sneeze
    
    
    Phlegm
    
    
    Hoarseness
    
    
    Lethargy
                          All  Students
                                     Dick Lines: Average
                          Allergy Group
                                     Thin Lines: Incidences
                                      of 7, June, '74.
    	 O.D. Group
    
    
     * P ,0.05   ** P--0.01 (  Chi-square Test )
             Figure 5.  Changes  in subjective  symptoms related  to  oxidant
       concentration and subgroups.   On June  7,  1974, oxidant  concentration  in
                               Tokyo rose above  0.23 ppm.
                                           488
    

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               TABLE 7.   THE RELATIONSHIP AMONG SYMPTOMS,  AIR POLLUTANTS,
                  AND WEATHER FACTORS BY PRINCIPAL COMPONENTS ANALYSIS
    
    
    Air
    Variables
    Pollutants &
    1st PC
    
    2nd PC
    
    3rd PC
    
    Weather Factors
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    0
    03
    S02
    SOh
    NO
    N02
    N03
    CO
    Dust
    SPM
    Aldehyde
    HC
    Temperature
    Humidity
    0.740
    0.717
    0.691
    0.187
    0.016
    0.013
    0.425
    -0.104
    0.024
    0.618
    0.404
    0.006
    0.310
    -0.706
    0.368
    0.249
    0.309
    0.752
    0.476
    0.872
    0.783
    0.555
    0.900
    -0.025
    0.748
    0.848
    -0.060
    -0.267
    -0.386
    -0.402
    -0.002
    -0.151
    -0.221
    0.176
    -0.029
    0.604
    0.143
    -0.075
    -0.047
    0.227
    -0.632
    0.255
    Symptoms
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    Eye Irritation
    Redness of Conjuctiva
    Watering of Eyes
    Blurred Vision
    Cough
    Phlegm
    Sneeze
    Shortness of Breath
    Hoarseness
    Vertigo
    Sore Throat
    Headache
    Nausea
    Numbness of Extremities
    Lethargy
    Abdominal Pain
    Diarrhea
    0.813
    0.288
    0.722
    0.792
    0.879
    0 . 780
    0.726
    0.789
    0.799
    0.881
    0.726
    0.816
    0.607
    0.510
    0.740
    0.534
    0.268
    0.086
    -0.164
    0.031
    -0.087
    -0.176
    -0.197
    -0.181
    -0.017
    -0.095
    -0.078
    0.004
    -0.020
    -0.284
    -0.315
    -0.361
    -0.036
    0.180
    -0.281
    -0.411
    -0.199
    0.021
    0.232
    0.302
    0.452
    -0.371
    0.280
    -0.125
    0.175
    0.136
    0.444
    0.144
    0.234
    0.376
    0.169
    
    SECOND PRINCIPAL COMPONENT
    
         Aerosol, nitrogen dioxide,  hydrocarbon,  nitrate,  sulfur dioxide,  aldehyde,
    and carbon monoxide have high loadings successively.   These variables  are the
    first air pollutants.   The second principal  component  must be related  to "High
    Air Pollution."
                                         489
    

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    THIRD PRINCIPAL COMPONENT
    
         Loadings of variables are less remarkable in this component, but this
    fact could be said to relate to "Temperature and Carbon Monoxide."
    
         The variances of the first and second principal components account for 54
    per cent of the total variance.  The third accounts for only nine per cent
    and it does not have the features of factors that have high loadings.  Other
    principal components have less per cent of variance than the third.  In
    Figure 5, a scattering graph is drawn whose axes are first and second princi-
    pal components.  It shows that factors associated with photochemical oxidants
    are partial to right side and make a group, and that other factors distribute
    at random.
    
    CONCERNING PREDISPOSITIONS
    
         Figure 5 and Table 8 show changes in incidences of the symptoms both
    concerned with subgroups and also related to oxidant concentrations.  The Chi-
    square test was carried out to examine differences between all  days average
    incidences of all students and two subgroups:  allergy and O.D. groups.  In
    the allergy group, days averaged incidences of cough, phlegm, headache and
    dizziness were significantly (p<0.05) higher than those of all  students.  On
    the other hand, the O.D. group had significantly (p<0.01 or p<0.05) higher
    average incidences of most symptoms (indicated by single and double stars in
    column 4 of Table 8).  The O.D. group seems to be a characteristic group;
    the O.D. students have a considerable number of complaints and have weak
    adaptability to changes in ambient conditions.  In other words, they are most
    sensitive to the environment.  The asthma group consists of too few examples
    to examine the differences; therefore we do not mention this group in this
    chapter.
    
         Differences of the incidences which related to oxidant concentrations
    were tested separately in three different oxidant concentrations.  The oxidant
    concentration was studied through all 75 days of the period.  During the pe-
    riod, oxidant concentrations rose above 0.15 ppm during 5 days.  It exceeded
    0.23 ppm on June 7, 1974.  A significant increase in the incidences in oxi-
    dant conditions is indicated by single (p<0.05) and double (p<0.01) stars
    in the 2nd, 3rd, 5th, 6th, 8th and 9th columns of Table 8 as well as in
    Figure 6.  Figure 5 represents comparisons of incidences under varying oxidant
    levels.
    
         In general, eye complaints,  respiratory symptoms such as cough and short-
    ness of breath and headache increase in the high oxidant conditions.  While
    extremely significant increases of cough and phlegm are observed in the asthma
    group, the O.D.  group shows characteristic increases of headache.
                                         490
    

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                                       DISCUSSION
    
         In this investigation period,  weather in Tokyo was  somewhat unusual.
    In June and early in July, wet and  rainy days continue every year,  in the  so
    called Tsuyu season, but in 1974, Tsuyu season persisted until  late in July
    and temperatures were lower than in more normal  years.  For this reason occur-
    rences of photochemical  smog in Tokyo were fewer and milder to  some extent;
    therefore,  signs except  lysozymic activity and pH in tears  may  not  have been
    found under this condition.
    
         The searches for acute effects of air pollution through some respiratory
    function test (9, 10) and through the comparisons of frequencies and severities
    of attacks in asthma patients have  been reported (11).  These reports are
    excellent but do not focus on photochemical  oxidant and  leave something to
    analyse statistically.
    
         There were some reports (12, 13) dealing with the effects  of photochemical
    oxidant in which absenteeism and performance were used as parameters.  Our
    study revealed that daily incidence of the symptoms correlated  and  associated
    closely with daily maximum oxidant  concentration, as shown in this  paper.
    It can be said that the  subjective  symptom is a more sensitive  parameter.
    
         Several problems remain, however, on the collection of daily frequencies
    of subjective symptoms  related to photochemical  oxidants.  The  first is eval-
    uation for the bias occurring through the mental states  of the  students.  If
    official smog warning information is given to a studied  school, it  is inevit-
    able that mental situations and responses to the questionnaires in  health
    diaries will change.  We checked this bias by comparing  frequencies of the
    symptoms with and without delivery  of warning information at similar oxidant
    conditions.  Results were not significantly different.  However, more precise
    checking is required to  evaluate this factor.
    
         The second problem  is a limit  by which the students checked only symptoms
    recorded previously in  health diaries.  Acute effects of photochemical oxidant
    and other air pollutants may be more multifarious.  The  blank of free answer
    was not adopted in health diaries because of possible student reluctance to
    write.  This might miss, however, other responses of the students to ambient
    conditions.
    
         Means of delivery  of health diaries is the third problem.   From our
    experience, daily delivery and collection of diaries provoked more  responses
    than at long intervals.   In this investigation they were carried out monthly,
    and this interval may avoid excess  responses.  On the other hand, maintenance
    of constant concern of  students was difficult.
    
         It was reported (14) that most students who suffered from severe symptoms
    had allergic predisposition in the  Rissho High School episode and other similar
    incidents.  This research could not make a clear connection between allergic
    predisposition and severe symptoms.  For the study concerning predisposition,
    more than 1500 samples  are required because more than 50 at least are
    necessary as the population of a subgroup for statistical analysis  in such a
    study period.
    
                                         492
    

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         There are interactions and relations of photochemical  oxidants to other
    air pollutants and weather conditions.   Simple correlation  analysis between
    these factors measured in this school to each other was carried out and reported
    (15).  Its one point was that there were significant correlations between
    oxidants, ozone, sulfur dioxide, and suspended particulate  matter.   Our results
    from comparison of coefficient levels show, however, that oxidants  contribute
    manifestly to occurrences of the specific symptoms.
    
         Visibility and wind speed did not show significant correlation with any
    symptoms.  However, short visibilities and slow wind speeds were pointed out
    on the days when many subjective symptoms were reported.   This discrepancy
    comes from the fact that shortening of visibility is caused by smog and rain,
    and that slow wind speed not always bring about elevation of oxidant concen-
    tration.   In a few cases of days when oxidant concentration exceeded 0.15 or
    0.20 ppm, there were unusually scarce complaints of subjective symptoms.
    This problem requires more and different approaches.  One of them is classi-
    fication of air pollutants and weather conditions that vary in the  day when
    many students complained of specific subjective symptoms.
    
                                       REFERENCES
    
    1.   Hausknecht, R.  Air Pollution:  Effects reported by  California Residents.
         Publ. California State Dept.  Public Health, California, 1969.
    
    2.   Shimizu, T., and Y. Tsunetoshi, et al.  Classified Subjective  Symptoms
         of Junior High School Students Affected with Photochemical Air Pollution.
         J. of Japan Society of Air Pollution, 9(4); 734-741, 1975.
    
    3.   Makino, K., and I.  Mizoguchi.  Symptoms caused by Photochemical Smog.
         Japanese J. of Public Health, 22(8):421-430, 1975.
    
    4.   Sekizawa, N., et al.   Effects of Tokyo Smog on Health.  Annual Report
         of Tokyo Metropolitan Res.  Institute for Environmental Protection, 5:206-
         227, 1974.
    
    5.   Shimizu, K., et al.  Effect of Photochemical Smog on the Human Eye -
         Epidemiological, Biochemical, Opthalmological, and Experimental Studies.
         J. of Clinical Opthalmology,  30(4);407-418, 1976.
    
    6.   Ichihashi, Y., and  M. Okuni,  ed.  Orthostatic  Dysregulation.   Chugai
         Med. Co. Ltd., Tokyo, 1974.
    
    7.   Okuno, T., H. Kume, T. Haga,  and T. Yoshizawa.  Multivariate Analysis.
         Nikkagiren Publ. Co.  Ltd.,  Tokyo,  1975.
    
    8.   Babcock, L. R.  A Combined  Pollution Index for Measurement of  Total Air
         Pollution.  JAPCA,  20(10):653-659, 1970.
                                         493
    

    -------
    9.   Toyama, T.  Air Pollution and Its Health Effects  in Japan.   Arch  Environ
         Health, 8:161-173, 1964.
    
    10.  Mcmillan, R. S., et al.   Effects of Oxidant Air Pollution on Peak
         Expiratory Flow Rates in  Los Angeles School Children.   Arch  Environ
         Health, 18:941-949, 1969.
    
    11.  Ishizaki,  T.,  et al.   Clinical  Study of  the Effect  of Air Pollution  upon
         Asthmatic  Patients.   J. of  Japan Society of Air Pollution, 7(1):7-12,
         1972.
    
    12.  Wayne,  W.  S.   Oxidant Air Pollution  and  Athletic.Performance.   JAMA,
         199:901-904,  1967.
    
    13.  Walborg, S. W., et al.  Oxidant  Air  Pollution and  School Absenteeism.
         Arch Environ Health,  19:315-322,  1969.
    
    14.  Mikami, R., and S.  Kudo.  Clinical  Examination  of Students Affected  from
         Photochemical  Smog.   J. of  Japanese  Clinical Medicine,  31:2039-2044,
         1973.
    
    15.  Mikami, R., et al.   Survey  Report on Health Effect  of Photochemical  Air
         Pollution, 1974, Tokyo B-Team.   Bureau of Air Quality Control,  Japan
         Environmental  Protection  Agency.  Tokyo.  1975.
                                        494
    

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                                                                                 10-2
                      EFFECTS OF OZONE PLUS  MODERATE EXERCISE ON
                        PULMONARY FUNCTION  IN  HEALTHY YOUNG MEN
    
                 B.  Ketcham, S.  Lassiter, E. Haak,  and J.  H. Knelson*
    
    
    ABSTRACT
                 healthy non-smoking mate subjects weAe exposed to 0.6 ppm ozone.
        1 houAS  in an enviAonmental chambeA.   Back Au.bje.ct was seated at nest ex-
    c.s.pt {,OA two IB-minute exetcx-42. peAiods  on. a. b^cyc-le eA.gome.te.si.  Ike. ezeAcise
    was sufficient to approximately double the. Aest-ing heaAt note,.  Subject* weAe
    asked to Aepofct any symptoms that occuJiAed daAing the. couASe ofi the. chambeA
    exposures and daity theAea&teA {,OA the. ^otlow-up peAiod.  Pulmonary function
    studies included spiAometAy, maximum e.x.piAatoiy falow-voiunne. cujwej,,  and body
    pttthy&mographic me.aAuA.e.me.nt o{, airway tie-AiAtance. and lung uo£ume4.   Change.*
    i.n pulmonary function afiteA 1 and 2 housi*  o& ozone. uieAe. compa>ie.d to valuer
    obtained at  the, tame, timu during a contAol 2-houA expo^uAe. to cie.an aiA.
    MoAt Aubje.ctt> e.xpo*e.d to ozone. complaMie.d  ofa cough, Aub&teAnal che^t pain,
    AhoAtn&AA ofa bAe.ath,  and a de.cAe.a*e.d ability to maxJjnaULy intpiAe..   A faew Aub-
    je.ct6 continued with symptom *e.veAa£ houAA post e.x.posuAe..  h&teA  1  houA o&
    ozone,, maxMnal mi.de.x.piAatofiy &low Aote.  (MMFR),  minute, volume.* (1/25  and 1/50),
    peak e.x.pt may be. the. most K.eJMibJte. and sensitive, -indicator
    oft the. adveASe. e^eati o& ozone, on lung  function.   Eve.n though conS-ideAable.
    
    -------
         The present oxidant alert level is 0..6 ppm maximum 1-hour concentration.
    This level approximates peak smog episode levels found within the Los Angeles
    basin.  This study was designed:   (a) to better define the adverse health
    effects of short-term exposures to 0.6 pprn ozone utilizing a homogeneous group
    of human volunteers carefully selected to minimize intersubject variability
    and, (b) confirm earlier studies  reporting impaired pulmonary function at
    these levels (7).
    
    
                                MATERIALS AND METHODS
    
         Twenty healthy non-smoking male volunteers between the ages of 19 and 27
    participated in this experiment.   The mean anthropometric data for the group
    was:  age, 22.7 years; weight, 73.4 kg; height, 180.1 cm.   Normal healthy male
    subjects were selected by screening all candidates with a Minnesota Multi-
    phasic Personality Inventory (MMPI), a complete medical history, a physical
    examination, and a complete blood cell count.   Suitable subjects were candi-
    dates who were within normal limits on all screening tests.  After obtaining
    informed consent to participate voluntarily in the study,  final  selection of
    the subjects was determined by an adequate performance in  a chamber training
    session.  Subjects were paid for  the time of their participation at the rate
    of four dollars per hour.   None of the subjects had a history of allergic,
    respiratory, or cardiac illness.
    
         All exposures and the pulmonary function  testing were conducted in a con-
    trolled environmental chamber (8'x8'x8') constructed of 1/2-inch plexiglass
    (8).  Ozone was generated from pure oxygen using an OREC ozone generator and
    was injected into the chamber air-supply duct  at a low pressure point.  The
    air-ozone mixture was dispersed into the chamber through a perforated grill in
    the chamber ceili