v>EPA
United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
ERA-45O/3-78-OJ3
April 1978
Air
Site Selection
for the Monitoring
of Photochemical
Air Pollutants
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This report is issued by the Environmental Protection Agency to report
technical data of interest to a limited number of readers. Gopies are
available free of charge to Federal employees, current contractors and
grantees, and nonprofit organizations - in limited quantities - from the
Library Services Office (MD-35), U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina 27711; or, for a fee, from the
National Technical Information Service, 5285 Port Royal Road, Sprinafield
Virginia 22161.
This report was furnished to the Environmental Protection Agency by
S.R.I. International, 333 Ravenswood Avenue, Menlo Park, CA 94025,
in fulfillment of Contract No. 68-02-2028. The contents of this report
are reproduced herein as received from S.R.I. International. The opinions,
findings, and conclusions expressed are those of the author and not
necessarily those of the Environmental Protection Agency. Mention of
company or product names is not to be considered as an endorsement
by the Environmental Protection Agency.
Publication No. EPA-450/3-78-013
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EPA-450/3-78-O13
SITE SELECTION
FOR THE MONITORING
OF PHOTOCHEMICAL AIR POLLUTANT!
by
F.L Ludvyig and E. Shelar
S.R.I. International
333 Ravenswood Avenue
Menlo Park, California 94025
Contract No. 68-02-2028
EPA Project Officer: E.L Martinez
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
; Office of Air, Noise, and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
April 1978
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• i-i.'.»i.'•.'.« -•'-X-:' '>,',>,'.-. i.i':^, ,'> .i.iffb !••
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PREFACE
The intent of this report is to provide a comprehensive and up to date technical resource
document to assist EPA, state and local air pollution control agencies, and other users in
developing better and more effective monitoring networks for the photochemical pollutants.
The information may be used by EPA in the future for developing more definitive guidelines
and criteria for such monitoring. However, this report in itself does not constitute the official
monitoring guideline of the Agency.
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v..,.^«.- «-.. ••l,-'
t ).- • ' • • 1
:; :,;-, :t ',„
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CONTENTS
ABSTRACT •• 1
PREFACE ii
LIST OF ILLUSTRATIONS vii
LIST OF TABLES '. ix
ACKNOWLEDGMENTS xi
1. SUMMARY •.....; 1
2. INTRODUCTION 7
2.1. Purpose 7
2.2. General Approach 7
3. IMPORTANT CHARACTERISTICS OF THE PHOTOCHEMICAL POLLUTANTS 9
3.1. Nonmethane Hydrocarbons 9
3.1.1. General 9
3.1.2. Sources of NMCH. 9
3.1.3. Reactions 9
3.2. Nitric Oxide and Nitrogen Dioxide , 9
3.2.1. General 9
3.2.2. Sources 13
3.2.3. Reactions 13
3.3. Photochemical Oxidants .....13
3.4. National Air Quality Standards .....16
4. MONITORING OBJECTIVES AND SITE TYPES 19
4.1. General 19
4.2. Important Principles for the Classification of Monitoring Objectives 19
4.3. Site Types to Meet the Monitoring Objectives 21
4.3.1. Site Types for Monitoring NMHC 21
4.3.2. Site Types for Monitoring NO 21
4.3.3. Site types for Monitoring NO2 21
4.3.4. Site Types for Monitoring OY 22
A
4.4. Summary of Monitoring Site Taxonomy for the Photochemical Pollutants..... 22
5. SELECTION OF MONITORING SITES FOR PHOTOCHEMICAL POLLUTANTS 25
5.1. General Principles of Site Selection ,...25
iii
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5.2. Site Selection Procedures 25
5.2.1. Nonmethane Hydrocarbons „ \ 25
5.2.1.1. General 25
5.2.1.2. Source-Oriented Monitors 29
5.2.1.3. Reactant-Oriented Monitors 38
5.2.2. Oxides of Nitrogen 38
5.2.2.1. General 38
S.2-.2.2. Source-Oriented Monitors ....41
5.2.2.3. "Neighborhood and Regional Scale Monitors 43
5.2.3. Oxidants 45
5.2.3.1. Regional Scale Monitors 45
5.2.3.2. Neighborhood Scale Monitors 49
6. RATIONALE FOR SITE SELECTION CRITERIA 51
6.1. Background 51
6.2. Identification of Conditions Conducive to High Pollutant Concentrations 51
6.2.1. Conditions Conducive to Photochemical Activity 51
6.2.2. Conditions Conducive to High Concentrations from Smokestack Emissions 52
6.3. Identification of General Areas Suitable for Monitoring.. 52
6.3.1. Nonmethane Hydrocarbons and Oxides of Nitrogen 52
6.3.1.1. General Considerations 52
6.3.1.2. Location of Areas of High Concentrations 57
6.3.2. Oxidants 69
6.3.2.1. General Considerations 69
6.3.2.2. The Transport of Ozone and the Location of Concentration Maxima 69
6.3.2.3. Destruction of Ozone by Urban NO Emissions T...83
6.4. Local Effects and the Selection of Specific Sites 86
6.4.1. Effects of Obstructions 86
6.4.2. Separation from Roadways...., 92
6.4.2.1. Nonmethane Hydrocarbons 92
6.4.2.2. Nitrogen Dioxide and Ozone 92
6.4.3. The Importance of Topographical Features 97
6.4.4. Height of Inlet 99
iv
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REFERENCES ••
APPENDIX A: BIBLIOGRAPHY
APPENDIX B: PROGRAM WINDROSE.
.101
.A-l
.B-l
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ILLUSTRATIONS
1. Schematic Diagram of Procedure for Selecting NMHC Monitoring Sites '.. 4
2. Schematic Diagram of Procedure for Selecting Neighborhood and Regional Scale Monitor-
ing Sites for NO and NO2 - - •*•••.
3. Schematic Diagram of Procedure for Selecting Oxidant Monitoring Sites
4. Atmospheric Nitrogen Dioxide Photolytic Cycle ll
5. Interaction of Hydrocarbons with the Atmospheric Nitrogen Dioxide Photolytic Cycle ...... 12
6. An Example of Diurnal Changes in the Concentrations of Selected Pollutants in Los ^
Angeles • • • • *
7. Relationship Among NOy and NMHC Concentrations and Potential Ozone Formation 18
8. Schematic Diagram of Procedure for Selecting NMHC Monitoring Sites 27
O Q
9. Example of Census Tracts •
10 Example of NEDS Point Source Emission Data • • •
32
11. Surface Wind Roses, July ..... •
12. Example of STAR Program Output- • • • • • •
13. Variations of Wind Speed with Height and Stability- •
14 Normalized Ground Level Concentrations from an Elevated Source for Slightly Unstable
... JO
Conditions
15. Normalized Ground Level Concentrations from an Elevated Source for Neutral Stability 37
16. St. Louis Wind Rose for Daytime Hours when the Temperature Exceeded 80 )F 39
17. Schematic Diagram of Procedure for Selecting Sites for Source Oriented NO and NO2
Monitoring
18. Schematic Diagram of Procedure for Selecting Neighborhood and Regional Scale Monitor-
ing Sites for NO and NO2 -
\9. Estimated Radius at Which NO and NO2 Concentrations Fall Below 7 ppb, as a Function r
of Metropolitan Population • • •
20. Estimated Areas Beyond Which NOX Concentrations are Likely to be Less than 7 ppb 47 .
21. Schematic Diagram of Procedure for Selecting Oxidant Monitoring Sites 48
22. Scattergram of Peak Hour Ozone Concentration Versus Air Temperature Along the Tra-
jectory for the Preceding 12 Hours •
23. An Example of a Weather Map and Distribution of Peak Hour Ozone (14 August 1974) 54
24. Annual Average and One Percentile Peak Hour NO2 and NOX Concentrations in the Los
Angeles Basin During 1975 • -. • • • •
25. Typical Air Flow Patterns in the Los Angeles Basin <• • •
26. Annual Average and One Percentile Peak Hour NO2 Concentrations in the San Francisco ^
Bay Area for 1975 *
27. Most Common Daytime Airflow Patterns in the San Francisco Bay Area 62
28. Annual Average NO2 Concentrations (ppb) in Southwestern Ohio 63
29. 24-Hour Average NO2 Concentration (ppb) in Southwestern Ohio, October 2, 1974 64
30. Weather Map and Ozone Distribution in the Eastern United States, October 2, 1974 65
31. Some Air Trajectories in the San Francisco Bay Area, July 2, 1970 , • 66
32. Variations of NO and NMHC Emissions, and NO2 and O, Concentrations along an Air
Trajectory Terminating in Livermore, California, July 2, 1970
vii
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33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
Variations of NO and NMHC Emissions, and NO2 and O3 Concentrations along an Air
Trajectory Passing through Richmond, California, July 2, 1970 .., „
Variations of NO and NMHC Emissions, and NO, and O, Concentrations Along the Tra-
jectory Shown, July 26, 1973
Variations of NO and NMHC Emissions and NO, and O, Concentrations Along the Tra-
jectory Shown, September 27, 1973
Variations of NO and NMHC Emissions and NO, and O, Concentrations Along the Tra-
jectory Shown, July 26, 1973
Percentage of Days (1970-1972) in the San Francisco Bay Area When One or More Hours
Equaled or Exceeded the Federal 1-Hour Average QX Standard of 0.08 ppm ,..
One-Percentile Peak-Hour Oxidant Concentrations in the Los Angeles Basin
Observed Maximum Daily Ozone Concentrations at Seven New England Sampling Sites .....
Vertical Cross Section of Ozone Concentration Over Western Connecticut and Long
Island, 1110-1220 EST, August 10, 1975 *
Vertical Cross Sections Over Connecticut, 1545-1715, August 10, 1975
Mean Diurnal Oxidant Profiles for Seven-Day Adverse Period (October 6-12, 1976) for
Upwind, Central Business District, and Downwind Sites at Fresno, California..............
Ozone Concentrations at About 300 m in the Houston Area, 1300-1600 (CST) October
8, 1973 'f
Ozone Concentrations at About 300 m in the Houston Area, 1300-1600 (CST), October
17, 1973 —
Ozone and NO, Concentration Patterns in the St. Louis Area During the Afternoon of
August 25, 1976
Ozone, NO and NO2 Concentrations in the St. Louis Area During the Afternoon of
October 1, 1976
Ozone, NOX and NO2 Concentrations in the St. Louis Area on October 2, 1976 88
Schematic Representation of the Airflow Around an Obstacle ., 91
Values of Cu/Q for Various Roadway/Receptor Separations and Wind/Roadway Angles;
Infinite Line Source
68
70
71
72
74
75
76
77
79
80
81
82
84
87
93
Maximum Roadway Contribution to Concentration at Different Distances ............. '. ... 94
Scattergram of the Product of NO and O3 Concentrations Versus NO, Concentration at 17
St. Louis Sites, October 1976, 1000 CST ...................... . ............. . ____ 9g
Change in Ozone Concentration for Different Amounts of Added NO ....... ........ ... 93
Average Diurnal Variations in Ozone Concentrations at Two Stations Near Rio Blanco,
Colorado ..............................................
100
viii
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TABLES
1.
2.
3.
4.
5.
6.
7.
8.
Summary of Important Characteristics of Monitoring Site Types.. 2
Nationwide Estimates of Hydrocarbon Emissions, 1975 10
Nationwide Estimates of Oxides of Nitrogen Emissions, 1975 . 14
National Air Quality Standards for the Photochemical Pollutants 17
Monitoring Objectives for NMHC, NO, NO2 and Ox ..................... .-Vv;<... 20
Monitoring Site Types for the Photochemical Pollutants 23
Monitoring Purposes and Site Types '. • • • 26
Example of a Statistical 'Wind Summary from the National Climatic Center (Asheville,
North Carolina) - • • • • • • 31
Tabulated Wind Statistics for Daytime Hours in St. Louis When Temperature Exceeded
80°F.
40
10. Monthly Frequency (1974) of Oxidant Standards Violations in Various Regions of the
Eastern U.S. - • • • • 55
Ik Winds Reported on Morning Weather Maps in Areas Where Peak-Hour Ozone Exceeded
80 ppb
56
ix
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ACKNOWLEDGEMENTS
The authors have been greatly assisted; by the comments and technical advice of many
persons, particularly Mssrs. E. L, Martinez, Neil Berg and Alan Hoffman of the Environmental
Protection Agency, and Ms. Joyce H. S. Kealbha of SRI International. We are also indebted to
Mrs. Linda Jones, Ms. Marilyn Fulsaas, Ms. Kathy Mabrey and Mr. Gary Parsons for their
contributions to the preparation of this report.
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1. SUMMARY
Pollution measurements are made for a wide variety of purposes, but attempts are seldom
made to link physical characteristics of a sampling location with the problem being addressed.
This may be because coherent scheme's have not been devised for classifying sites and relating
their characteristics to intended data use. A good site classification system is needed because
monitoring stations operating for many years, at the cost of thousands of dollars for equipment,
maintenance, and data processing, must be located where the data will satisfy the intended pur-
poses. The costs of poor siting proicedures go beyond the direct costs of establishing and
operating the stations. Data used to plan large-scale air quality control programs must be sound
if they are to warrant the economic and social impacts. Other data uses will have different
requirements and different consequences, but in most cases there will be considerable
justification for carefully matching monitoring sites with monitoring purposes.
The uses of air quality data can be broadly categorized as:
Air quality assessment
Development and evaluation of control plans
Enforcement of regulations
Research
Public health studies
Miscellaneous purposes.
Each category has its subcategories, but at no level of classification does this system
directly relate to physical factors. A site classification system that can be used to define an
appropriate set of physical characteristics for each site type must examine the uses of the data
in terms of the phy&c&l factors that influence the data. For example, different monitoring pur-
poses will have different levels of appropriate spatial smoothing. Sometimes it is necessary to
provide data representative of a neighborhood within the city; other uses require the represen-
tation of larger areas. Spatial representativeness provides a basis for classifying stations and
their uses. Furthermore, it has a physical basis that can help to define the required station
characteristics.
The measurement scales that are of greatest importance for the photochemical pollutants
are:
Urban to regional scale, to define multi-neighborhood or citywide conditions on'a scale
from several kilometers up to larger suburban or rural areas of reasonably homogene-
ous geography and extending for several tens of kilometers.
• Neighborhood scale, to define concentrations within some extended area of the city
that has relatively uniform land use; dimensions are of the order of a few kilometers.
Factors other than measurement scales have also been incorporated into the system for
classifying the monitoring purposes. For the photochemical pollutants, there are differences
related to the'pollutants' roles as reactants and products. For example, the air quality guide-
lines for NMHC emphasize their role as reactants, while the oxidant standards are differently
oriented. Ev|n though the scales of interest might be similar for air quality monitoring of
NMHC and 6 , the site selection processes will differ because of the intrinsic differences
between reactaa^ and products.
For any pollutant that has large individual sources, some monitoring is likely to be done.
to determine the impact of those sources on their surroundings. This source-oriented monitor-
ing can have different siting requirements from other, more general monitoring objectives. The
classification o| objectives and the corresponding site types should take the differences into
account. ^_t
This report describes a site classification system based on the considerations discussed
above. Table 1summarizes this system. The types of monitoring sites have been chosen to
meet the major Basses of monitoring data usage. Those classes were developed on the basis of
\
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Table 1
SUMMARY OF IMPORTANT CHARACTERISTICS
OF MONITORING SITE TYPES
General Site
Typo
Neighborhood
Neighborhood
Neighborhood
Neighborhood
Urban/
Regional
Subtype
Source-
Oriented
General
Important
Reactant
Area
Important
Product
Area
General
Represented
Small end of
Neighborhood
Neighborhood
a few
kilometers
Large end of
Neighborhood
Scale
Large end of
leighborhood
Scale
Urban/
Regional
Scale, tens
of kilometers
Applicable
Pollutants
NO,
N02
X
and
NMHC
NO,
N02
NMHC
and
0
NO,
N02
NMHC
°x>
N02
NO,
N02
NMHC
and
°x
General Location Description
In area most likely to be heavily
affected by emissions from the
be determined from simple Gaussian
models and climatological
summaries.
In an area of homogenous land
use, and sufficiently removed
from Individual sources and
sinks to be representative.
Areas subject to impact by
large point sources should be
avoided.
In areas where the emissions might
be expected to serve as react ants
to produce oxidants that would
impact on sensitive regions. Can-
didate sites will be upwind of
sensitive regions during photochem-
ically active meteorological condl-
:ions, e.g. temperatures above 80 F.
In areas of important Ox and N02
concentrations. Maximum Ox tends
to be about 5 to 7 hours travel
distance downwind (for photochemlc-
ally active meteorological condl-
:ions) of the upwind edge of 'the
city. If this distance falls with-
in the urban area, the maxima will
be found just outside the urbanized
area. Maximum NO- concentrations
tend to be displaced downwind of
maximum NOX emissions areas about
one or two hours travel distance.
ackground sites should be upwind
f the city, especially for photo-
lemically active meteorological
ondltions. Distances vary from
aout 30 km for regions with a
opulation of 200,000 to 140 km for
he largest urban areas. If the
ite will be upwind under the most
hotochemically active conditions,
le separations can be reduced.
general monitoring for purposes
ther than defining background
oncentrations need not be so
estrlctive.
Specific Site and Inlet Requirements
Inlet 3 to 15 m high and away from
vertical walls. Site should be .
by about twice the height of the
obstacle above the inlet. Separation
from highways should be;
Average Daily " , ,
Traffic Pollutant
(Vehicles) NMHC N0/N02
<1000 15 m 20 m
1,000-10,000 15-400 m 20-250 m
>10,000 >400 m >250 M
For defining typical population.
exposures, the site will be in a typica;
neighborhood in the central part of the
urban area. Maximum concentrations will
be found near maximum emissions for NO
and NMHC; for Ox maxima see product
catagorles. Inlet should be 3 to 15 m
high and away from vertical walls.
Separation from highways should be:
Average Daily
Traffic Pollutant
(Vehicles) Ox NMHC NO/NO2
<1000 20 m 15 m 20 m
1,000-10,000 20-250 m 15-400 m 20-250 m
>10,000 >250 m >400 m >250 m
Inlet heights and separation from
roadways should be the same as defined
above. Areas subject to the impact of
large individual sources sbvuld be
identified (see discussion for source-
oriented monitoring) and avoided.
Inlet heights, roadway separations,
distances from obstructions are the
same as discussed above.
nlet heights, roadway separations and
istances from obstructions are similar
o those given above.
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spatial representativity,.then subdivided according to the pollutant's role as a reactant or a pro-
duct. The system also considers whether the impact of a major source is of concern.
Most common monitoring purposes can be matched to .appropriate site typejs in Table 1,
but this is only a part of a system of site types and site selection procedures. The application of
the concept of spatial representivity to the selection of sampling sites generally depends on
finding a location that will not be unduly influenced by specific sources or sinks-except for
source-oriented monitoring. Sometimes, when human exposure is involved, relatively sensitive
areas may be sought. These might be areas with high population density, or many aged or
infirm people.
The site selection procedures and criteria for each of the pollutants have been summarized
in a set of flow diagrams. Figure 1 shows the requirements for selecting a site for monitoring
NMHC. The general locations are chosen to be representative of areas of major impact-either
of an individual source, or an area where the reactants are most apt to lead to high levels of
ozone impact. The specific recommendations for inlet locations that are shown have been
chosen to minimize extraneous or very localized influences.
A summary of the steps for selecting monitoring sites for NO and NO2 is shown in Figure
2. The minimum distance to roadways shown in the figure is based on an analysis that makes
use of the quasi-steady state relationship among O3, NO and NO2 concentrations and Gaussian
diffusion modeling. To some extent, the recommended setbacks represent a compromise
between the ideal of minimal interference and the practicality of limited space. The locations of
the general areas that are most suitable for monitoring are based on analysis of data from
several areas—Los Angeles, San Francisco, St. Louis, Houston, the Northeast U.S., and
southwest Ohio. Inlet locations were chosen to minimize extraneous influences.
Figure 3 summarizes the procedures for selection of oxidant monitoring sites. The gen-
eral locations are based on the scale of representativeness desired, i.e. neighborhood or
regional. As with NO , suggested guidance for locating the general areas that are suitable is
based on analysis of ozone data from five specific urban or interurban areas.
In summary, the guidance presented here will serve as a technical basis for selecting sites
that can be classified into a limited number of types. The standardization of physical charac-
teristics will ensure that comparison among sites of*the same type will not be clouded by pecu-
liarities in the siting. Use of the classification scheme does more than ensure compatibility of
data and allow reasonable comparisons among stations of the same type. It also provides a phy-
sical basis for the interpretation and application of those data. This should help to prevent
mismatches between what the data actually represent and what they are interpreted to
represent.
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ASSEMBLE GENERAL BACKGROUND INFORMATION,
FOR EXAMPLE:
• MAPS
• LAND USE
• EMISSIONS INVENTORIES
• POPULATION DENSITIES
• TRAFFIC DISTRIBUTION
• CLIMATOLOGICAL AND METEOROLOGICAL DATA
• EXISTING MONITORING DATA. IF ANY
IS A SOURCE ORIENTED OR A REACTANT
ORIENTED MONITORING SITE BEING CHOSEN?
SOURCE ORIENTED
COLLECT INFORMATION ABOUT
SOURCE, FOR EXAMPLE:
• EMISSION RATE
• STACK PARAMETERS
- DIMENSIONS
- EFFLUENT VELOCITY
AND TEMPERATURE
USE CLIMATOLOGICAL DATA AND
SIMPLE MATHEMATICAL MODELS
TO ESTIMATE AVERAGE CONCEN-
TRATIONS AND FREQUENCY OF
HIGH CONCENTRATIONS AT
LOCATIONS IN THE VICINITY
OF THE SOURCE
SELECT CANDIDATE AREAS NEAR
MAXIMUM AVERAGE CONCENTRA-
TIONS OR IN AREAS WITH MOST
FREQUENT HIGH CONCENTRATIONS
REACTANT ORIENTED
USE EMISSIONS INVENTORIES TO IDENTIFY
AREAS OF GREATEST EMISSION DENSITIES
TO IDENTIFY LARGE AREAS OF,
HIGH, UNIFORM CONCENTRATIONS
USE CLIMATOLOGICAL DATA TO IDENTIFY
AREAS MOST LIKELY TO PRODUCE HIGH O3
CONCENTRATIONS IN SENSITIVE AREAS
SELECT SPECIFIC SITES:
INLET HEIGHT, 3-15 m
MIMIMUM SEPARATIONS FROM ROADWAYS:
ADT< 1000, 15 m
ADT 1000 TO 10.000, 15-400 m
ADT > 10,000, 4OO m
FOR REACTANT ORIENTED MONITORS,
AVOID MAJOR POINT SOURCE EFFECTS
FIGURE 1 SCHEMATIC DIAGRAM OF PROCEDURE FOR SELECTING
NMHC MONITORING SITES
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PRODUCT ORIENTED
EMPHASIS WILL BE ON NO2
IS THE MONITORING TO
CHARACTERIZE THE
NEIGHBORHOOD SCALE
OR A LARGER SCALE?
REGIONAL SCALE
USE WIND DIRECTION
STATISTICS TO DETERMINE
DIRECTION WHICH IS
MOST OFTEN UPWIND
OF NEAREST URBAN AREA.
MAKE FINAL SITE SELECTION
INLET HEIGHT, 3-15m
MINIMUM DISTANCE TO
ROADWAYS:
ADT < 1000, 20 m
ADT 1000-10,000, 20-250 m
ADT > 10,000. > 250 m
AVOID POSSIBLE INFLUENCE
OF LARGE NOX SOURCES
ASSEMBLE BACKGROUND
INFORMATION
IS THE MONITORING TO
BE REACTANT ORIENTED
OR PRODUCT ORIENTED?
NEIGHBORHOOD SCALE
IDENTIFY AREAS OF
MAJOR NOX EMISSIONS
IDENTIFY MOST FREQUENT
WIND DIRECTIONS EMPHASIZ-
ING DIRECTIONS ASSOCIATED
WITH LOW WIND SPEEDS
IDENTIFY PROSPECTIVE SITING
AREAS DOWNWIND OF MAJOR
MOX EMISSIONS AREAS AND
NEAR THE EDGE OF THE
URBAN EMISSIONS REGION. FOR
HEALTH RELATED MONITOR-
ING, SOME EMPHASIS WILL BE
GIVEN TO POPULATED AREAS.
REACTANT ORIENTED;
-WILL MOST OFTEN BE
ON THE NEIGHBORHOOD
SCALE. EMPHASIS WILL
BE ON NO AND NOX
(NO+NO2)
USE MODELING TO ESTIMATE
REGIONS OF MAXIMUM
CONCENTRATIONS
IDENTIFY MOST FREQUENT
WIND DIRECTIONS DURING
PERIODS OF LIKELY
PHOTOCHEMICAL ACTIVITY.
MAKE FINAL SITE SELECTION
INLET HEIGHT, 3-15 m
MINIMUM SEPARATION
FROM ROADWAYS:
ADT< 1000, 20m
ADT 1000-10,000, 20-250 m
ADT > 10,000. > 250 m
AVOID AREAS LIKELY
TO BE INFLUENCED BY
LARGE POINT SOURCES.
FIGURE 2 SCHEMATIC DIAGRAM OF PROCEDURE FOR SELECTING NEIGHBORHOOD
AND REGIONAL SCALE MON(ZORING SITES FOR NO AND NO2
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NEIGHBORHOOD
IS THE PURPOSE TO DEFINE
TYPICAL OR HIGHEST
CONCENTRATIONS ?
TYPICAL CITY
CONCENTRATIONS
SELECT REASONABLY
TYPICAL HOMOGENEOUS
NEIGHBORHOOD NEAR
GEOGRAPHICAL CENTER
OF REGION, BUT REMOVED
FROM INFLUENCE OF
MAJOR NOX SOURCES
SELECT SPECIFIC SITE.
AVOID LOW LYING AREAS.
AVOID INFLUENCE FROM
MAJOR NOX SOURCES. MINI-
MUM SEPARATIONS FROM
ROADWAYS
ADT < 1000, 20 m
ADT 1000-10,000, 20-250 m
ADT > 10,000, >250m
SHOULD BE IN AN OPEN
AREA WITH NO NEARBY
OBSTACLES. INLET SHOULD
BE AWAY FROM SURFACES
ANtf AT A HEIGHT OF
3 TO 15m
ASSEMBLE BACKGROUND INFORMATION:
MAPS
EMISSIONS INVENTORIES FOR NMHC AND NOX
CLIMATOLOGICAL DATA
EXISTING O3, NMHC AND ,NO2/NO DATA
IS THE MONITOR TO CHARACTERIZE
REGIONAL OR NEIGHBORHOOD CONDITIONS
HIGH CONCENTRATION AREAS
DETERMINE MOST FREQUENT
.WIND SPEED AND DIRECTION
FOR PERIODS OF IMPORTANT
PHOTOCHEMICAL ACTIVITY
USE EMISSIONS INVENTORIES TO
DEFINE EXTENT OF AREA OF IMPOR-
TANT NMHC AND NOX EMISSIONS
SELECT PROSPECTIVE MONITORING
AREA IN DIRECTION FROM CITY THAT
IS MOST FREQUENTLY DOWNWIND
DURING PERIODS OF PHOTOCHEMICAL
ACTIVITY. DISTANCE TO UPWIND
EDGE OF CITY SHOULD BE ABOUT
EQUAL TO THE DISTANCE TRAVELLED
BY AIR MOVING FOR 5 TO 7 HOURS
AT WIND SPEEDS PREVAILING DURING
PERIODS OF PHOTOCHEMICAL ACTI -
VITY. FOR HEALTH RELATED PURPOSES,
A MONITOR OUT OF THE MAJOR NO
EMISSIONS AREA, BUT IN A POPULATED
NEIGHBORHOOD IS DESIRABLE.
PROSPECTIVE AREAS SHOULD ALWAYS
BE OUTSIDE AREA OF MAJOR NOX
EMISSIONS
REGIONAL
DETERMINE MOST FREQUENT
WIND DIRECTION ASSOCIATED
WITH IMPORTANT
PHOTOCHEMICAL ACTIVITY
SELECT PROSPECTIVE MONITOR-
ING AREA UPWIND FOR
MOST FREQUENT DIRECTION
AND OUTSIDE AREA OF CITY
INFLUENCE-SEE FIGURE 19
SELECT SPECIFIC SITE. AVOID
VALLEYS; HILLTOP LOCATION
DESIRABLE. AVOID INFLUENCE
FROM NOX SOURCES. MINIMUM
SEPARATIONS FROM ROADWAYS:
ADT < 1000, 20 m
ADT 1000-10,000, 20-250 m
ADT > 10,000, > 250 m
INLET SHOULD BE WELL
REMOVED FROM OBSTACLES
AND AT A HEIGHT OF
3 TO 15m
FIGURE 3 SCHEMATIC DIAGRAM OF PROCEDURE FOR SELECTING OXIDANT MONITORING SITES
-------
2. INTRODUCTION
2.1. Purpose
As awareness of air pollution and its effects increases, so does the importance of measur-
ing the concentrations of the various air pollutants. Unrepresentative data may be misleading
and of less value than no data at all, even thbugh the cost of poor data will not differ much
from the cost of high quality data. It is not surprising that a proper methodology for the collec-
tion of air quality data should be of concern. This report focuses on the identification of suit-
able locations for .monitoring pollutants related to photochemical oxidant formation, i.e.:
Nonmethane hydrocarbons (NMHC)
Nitrogen dioxide (NO2)
Nitric oxide (NO)
Oxidants (Ov)
X.
2.2. General Approach
The establishment of siting criteria for monitoring stations starts by finding why the \pollu-
tants of interest are monitored. Siting criteria describe the proper physical location of a moni-
tor, so they are physically related to the reasons for monitoring. The second step toward
finding siting criteria for different monitoring purposes is to categorize the purposes according
to a physically based classification system. The final step is to review existing data and interpret
those data in such a way that specific siting criteria can be recommended.
This report reviews the reasons for monitoring pollutants, and then a physically based sys-
tem for classifying these reasons is described. The discussions of the siting criteria and their
derivation have been prefaced with a section that discusses pollutants of interest, their sources,
physical characteristics. Most of the data and analyses that led to the final siting recommenda-
tions are discussed in the last section of the report.
-------
-------
3. IMPORTANT CHARACTERISTICS OF THE PHOTOCHEMICAL POLLUTANTS
3.1. Nonmethane Hydrocarbons
3.1.1. General
The analysis of urban air for individual, nonmethane hydrocarbons (NMHC) has revealed
the presence of so many different compounds that it is very difficult to specify a set of charac-
teristics denning "hydrocarbons." However, the reference method for the determination of
hydrocarbons defines the hydrocarbons of interest to be those compounds that pass through a
filter with a porosity of 3 to 5/u,m and that cause a flame ionization detector to give a signal
(Lawrence Berkeley Laboratory~LBL, 1973). In addition to the many compounds involved,
another complication encountered when measuring hydrocarbons is the large amount of natural
methane present compared with the other hydrocarbon molecules. The methane concentration
is usually more than the concentration of the rest of the hydrocarbons combined, but methane
is not considered an important pollutant (Public Health Service—PHS, 1970a) because it does
not react appreciably to form harmful compounds. For most purposes, the hydrocarbons other
than methane are of interest, hence, the desire to measure "nonmethane hydrocarbons." The
most important characteristic of the NMHC, from an air pollution standpoint, is their ability to
enter into reactions with other compounds to produce secondary, harmful contaminants.
3.1.2. Sources of NMHC
Table 2 shows the nationwide estimates of hydrocarbon emissions for 1975. The table
shows highway vehicles to be very important sources of hydrocarbons. Organic solvent usage
and refining are other major sources of hydrocarbon emissions. These source types illustrate
the two major categories; mobile and stationary. Mobile sources are mainly comprised of gaso-
line powered vehicles with a small contribution from other types of vehicles, including aircraft
and diesel engines.
3.1.3. Reactions
A complete description of the complex reactions by which oxidants arise from the NMHC
is beyond the scope of this report, but a simplified summary can be given. The starting point is
nitrogen dioxide (N02), a product formed by the oxidation of nitric oxide (NO) which is>
formed during combustion. In the absence of hydrocarbons, NO2 is dissociated by sunlight to
produce NO and an oxygen atom. The oxygen atom combines with the atmospheric molecular
oxygen to produce ozone (O3) which then combines with the NO to produce NO2. Then, as
shown schematically in Figure 4, the process begins anew. Actually, the process is continuous
and there are equilibrium concentrations for each of the species. Photochemical oxidant con-
centrations are increased when the steady state of the NO2 photolytic cycle is disrupted by
NMHC that react with the NO to unbalance the cycle. Then ozone builds up to redress the bal-
ance. Figure 5 schemafically illustrates the role of hydrocarbons. Hydrocarbons also react with
atomic oxygen to produce oxidized compounds and free radicals which react with NO to further
change the photolytic equilibrium.
3.2. Nitric Oxide and Nitrogen Dioxide
3.2.1. General
Nitric Oxide (NO) is formed during the combustion of fossil fuels. Currently, there is no
evidence that NO is a health hazard at concentrations normally found in the atmosphere (EPA,
1971). Concern over the ambient levels of this gas and their relation to air quality arises
because NO is frequently oxidized to form nitrogen dioxide (NO2). Nitrogen dioxide is not
only toxic, it is also Wrosive and highly oxidizing. Small amounts of NO2, usually less than
0.5 percent, are formed directly during high temperature combustion. Some NO2, less than 10
percent, is formed by the direct oxidation of NO in the short interval between the ejection of
-------
Table 2
NATIONWIDE ESTIMATES OF HYDROCARBON
EMISSIONS, 1975
Source Category
Transportation
Highway
Non-Highway
Stationary Fuel Combustion
Electric Utilities
Other
Industrial Processes
Chemicals
Petroleum Refining
Metals
Other
Solid Waste
Miscellaneous
Forest Wildfires
Forest Managed Burning
Argricultural Burning
Coal Refuse Burning
Structural Fires
Organic Solvents
Oil and Gas Production
and Marketing
Total
Emissions
10 tons/year
11,7
10.0
1.7
1.4
0.1
1.3
3.5
1.6
0.9
0.2
0.8
Q.9
13.4
0.6
0.2
0.
0.
8
,1
,1
,1
,3
4.2
30.9
Percent of Total
37.9
32.4
5.5
4.5
0.3
4.2
11.3
5.2
2.9
0.6
2.6
2.9
43.4
1.9
0.6
0.2
0.2
0.1
26.8
13.6
100.0
Source: Hunt, et al, 1976
10
-------
NITROGEN
DIOXIDE
(N02)
SOURCE: PHS, 1970b
FIGURE 4. ATMOSPHERIC NITROGEN DIOXIDE PHOTOLYTIC CYCLE
11
-------
NITROGEN
DIOXIDE
(NO,)
SOURCE: PHS, 1970b
FIGURE 5. INTERACTION OF HYDROCARBONS WITH THE ATMOSPHERIC
NITROGEN DIOXIDE PHOTOLYTIC CYCLE
12
-------
>5O as an exhaust product and the time when it is diluted to concentrations below 1 ppm. Most
of the NO- found in the atmosphere results from the oxidation of NO to NO2 in the presence
of sunlight, ozone and hydrocarbons. The other oxides of nitrogen in the atmosphere have not
been considered because they are present only at very low concentrations or they are photo-
chemically nonreactive.
3.2.2. Sources
Table 3 shows the nationwide, anthropogenic emissions for NO . Stationary fuel combus-
tion accounted for over half of the total in 1975. Transportation is the other major source,
accounting for over 44 percent of the total amount emitted. Other minor contributors were
solid waste disposal and industrial processes.
3.2.3. Reactions
The participation of oxides of nitrogen in the photochemical process was illustrated
schematically in Figures 4 and 5. The example of diurnal changes of O3, NO and NO2 concen-
tration shown in Figure 6 also illustrates some of the photochemical phenomena. Before day-
light, on this particular day in Los Angeles, the concentrations of NO and NO2 remain rela-
tively constant. As urban activity increases from 6 to 8 a.m., the concentrations of the primary
pollutants, CO and NO, increase dramatically. Then, in response to increasing solar ultraviolet
radiation, the amount of NO2 increases as NO is converted to NO2. As the NO concentration
falls to very low levels (less than 0.1 ppm), photochemical oxidants begin to accumulate and
reach a peak about midday. The increase in automobile traffic in late afternoon and evening
caused an increase in the NO concentration. Even in the absence of sunlight, NO2 continues to
be formed from NO by ozone until the O3 supply is exhausted.
3.3. Photochemical Oxidants
Oxidants are defined as those atmospheric substances that will oxidize specified reagents;
potassium iodide is the most common of these reagents.
The most abundant of these oxidants
is O,. For this reason, the term oxidant and ozone are often used interchangeably. In general,
we do not distinguish between the two in this report. Ozone is not usually emitted directly into
the atmosphere, but is instead a secondary pollutant that is formed over a period of time from a
variety of atmospheric reactants. Ozone interacts with the environment more than any other
ambient pollutant. It reacts with other pollutants, with vegetation, with sampling probes, and it
is easily destroyecTby these reactions. Ozone's reaction with NO causes the amount of ozone
near highways to be much lower than that found nearby, away from the road.
As Figure 6 shov/s, the oxidant concentration is apt to reach a peak later than the concen-
trations of the hydrocarbons and oxides of nitrogen from which it is formed. Oxidant forma-
tion is affected by the intensity and duration of sunlight, temperature, and the emissions and
dilution processes affecting atmospheric concentrations of the other particpants in the photo-
chemical reactions. The relationship between the primary emissions of NO and NMHC and
the subsequent formation of atmospheric ozone is difficult to quantify. The slow formation and
the transport of secondary pollutants tend to produce large separations, spatially and temporally
between the major sources and the areas of high oxidant pollution.
There are a fevt primary sources of ozone, usually involving electrical discharge. In gen-
eral, these are not important contributors to observed urban concentrations, except in their
immediate vicinity. Ozone can also be brought to the surface from the stratosphere where it is
formed by photodjssociation of oxygen and recombination to ozone. Ozone accumulations have
been observed ffquently within inversion layers over urban and rural areas (Johnson and
Singh, 1975; Millet and Ahrens, 1970; Pitts, 1973). Convection can bring these elevated layers
to the surface.
13
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Table 3
NATIONWIDE ESTIMATES OF OXIDES OF NITROGEN
EMISSIONS, 1975
Source Category
10'
Emissions
tons/year
Percent of Total
Transportation 10.7
Highway 8.2
Non-Highway 2.5
Stationary Fuel Combustion 12.4
Electric Utilities 6.8
Other 5.6
Industrial Processes 0.7
Chemicals 0.3
Petroleum Refining 0.3
Mineral Products 0.1
Other <0.1
Solid Waste 0.2
Miscellaneous 0.2
Forest Wildfires 0.1
Forest Managed Burning <0.1
Agricultural Burning <0.1
Coal Refuse Burning 0.1
Structural Fires <0.1
Total 24.2
44.2
33.9
10.3
51.2
28.1
23.1
2.9
1.2
1.2
0.4
0.8
0.9
0.4
0.4
100.0
Source- Hunt, et al., 1976
14
-------
0.50
2400 0300 0600 0900 1200 1500 1800 2100 2400
TIME OF DAY
SOURCE: EPA, 1971
FIGURE 6. AN EXAMPLE OF DIURNAL CHANGES IN THE CONCENTRATIONS
OF SELECTED POLLUTANTS IN LOS ANGELES
15
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3.4. National Air Quality Standards
The air quality standards for the photochemical pollutants are summarized in Table 4.
The underlying motivation for all the primary standards is the protection of public health.
Ambient air standards for oxidants were chosen to keep the hourly level at less than 0.08 ppm
(Schuck et al., 1970) to provide a margin of safety.
Although NMHC at the usual ambient levels are not generally considered to constitute a
health hazard, some studies have shown that an average 6-9 a.m. concentration of 0.24 ppm of
NMHC can produce a maximum hourly average concentration of ozone of up to 0.1 ppm
(Schuck et al., 1970; Dimitriades, 1972). To keep oxidant levels below this value, guidelines
for NMHC were chosen to be a maximum of 0.24 ppm for the 6-9 a.m. average concentration,
not to be exceeded more than once each year. However, these guidelines are only applicable in
areas where the other precursors necessary to produce violations of the oxidant standard are
also present.
Recently, the joint effects on ozone production of the hydrocarbons and the oxides of
nitrogen have been considered in the formulation of urban ozone control strategies. Figure 7 is
a representation of the relationship among the initial concentrations of NO and NMHC and
the amounts of O3 that can be produced in the presence of sufficient sunlight. It is apparent
from Figure 7 that the NMHC guidelines could be exceeded in rural areas with very low NO
concentrations without resulting in oxidant violations. Thus, there is an implied caveat to the
measurement of NMHC for purposes of assessing whether oxidant standards are likely to be
violated, i.e., the presence of sufficient NO for photochemical production of ozone is assumed.
The primary and secondary standards for NO2 are 0.05 ppm, based on an annual arithmetic
average.
16
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TABLE 4
.. NATIONAL AIR QUALITY STANDARDS FOR THE PHOTOCHEMICAL POLLUTANTS
? ; - : ;' (Source: Fed. Reg., 1971) '
Pollutant
Photochemical
Oxidants
(corrected for
N02 and S02)
Hydrocarbons
(corrected for
methane)
.Nitrogen
Dioxide
Averaging
" Time
' 1 hour
3 hours
9-6 a.m.
Annual
Arithmetic.
Mean3
Primary
Standards
160 ug/m
(0.08 ppm). ,
160 Mg/m3
(0.24 ppm)
3 '
100 jug/m
(0.05 ppm)
Secondary
Standards^
Same as ,
. primary
standard
Same as
primary
standard
Samei as '
primary
standard
Federal Reference
Principle
Gas phase
chemi luminescence
Gas chromatography
— . flame ionizatior
detection.
Gas phase
chemiluminescence
a National standards other than those based on annual arithmetic means or
annual geometric means are not to be exceeded more than once per year.
b National Primary Standards: The levels of air quality necessary, with
an adequate margin of safety, to protect the public health. The hydrocarbon
standard is used only as a guide in devising implementation plans to achieve
oxidant standards.
c National Secondary Standards: The levels of air quality necessary to protect
the public welfare from any known or anticipated adverse effects to a pollutant.
-------
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18
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4. MONITORING OBJECTIVES AND SITE TYPES
4.1. General
Table 5 summarizes some of the common monitoring objectives. Each pollutant to which
a particular objective applies is marked by an "X" in an appropriate column. The monitoring
purposes listed in Table 5 are grouped into five general categories and one miscellaneous group.
The table shows that not all purposes apply to all pollutants. For example, toxic pollutants may
be monitored for purposes related to their effect on humans, while the nontoxic materials may
be monitored for other reasons. This section discusses factors that are important to the siting
of monitors for photochemical pollutants and to the development of a site classification system.
4.2. Important Principles for the Classification of Monitoring Objectives
Any site classification scheme should have a physical basis. A useful classifiction system
can be devised on the basis of the spatial area that is to be represented by the measurements.
This is a good example of a physical rationale for classification of monitoring purposes. The
secondary pollutants, particularly oxidant, require appreciable formation time. Hence, mixing
of reactants and products through large volumes of air will occur. This mixing reduces the
importance of monitoring small-scale spatial variability. The monitoring of small-scale variabil-
ity of the primary pollutants may sometimes be of only marginal importance also. For instance,
the reasons for monitoring NMHC are usually related to the role of hydrocarbons in the pro-
duction of oxidant. This role is accomplished only after a considerable elapsed time and large
scale mixing. Again, mixing tends to produce uniformity in the distribution of the products.
That uniformity in turn reduces the importance of measuring the small scale variability in the
distribution of the primary reactants.
There are several kinds of sources of primary pollutants. For some monitoring objectives,
the nature of the source will influence the desired characteristics of the monitoring site. Some
emissions are the product of numerous small individual sources. Other emissions may be pro-
duced in large quantities from a small number of localized sources. Furthermore, the localized
sources may be at ground level, or they may be elevated. Combinations of these source types
are quite common.
Finally, meteorological factors are important to the site selection process. For example,
when monitoring secondary pollutants, one must identify areas generally downwind of the pri-
mary pollutant sources during periods of strong oxidant formation. It will be important to con-
sider the winds, in combination with the length of time required for the oxidant to form, and
the locations of the major sources of the reactants. Meteorological factors also affect the selec-
tion of monitoring sites for primary pollutants, particularly when it is important to monitor the
impact of a single, large, elevated source. In such cases, the areas of maximum impact will be
governed by climatological factors. The frequency of occurrence of certain combinations of
wind speed, wind direction, and atmospheric stability will govern when and where the plume
from an elevated source of primary pollutants has its greatest ground level impact. Meteorolog-
ical factors are al|o important for the location of areas where secondary pollutants reach their
highest concentrations.
A site classification system should distinguish between source-oriented monitoring and
monitoring which is not directed toward the determination of the effects from large, individual
sources. Some distinction is necessary between the primary and the secondary pollutants; that
is, between reactants and products.
In summary, the following physical factors need to be considered in classifying monitoring
objectives and assi&rvvag site types:
1. Whether the effects of a single, large source are to be typified or excluded.
2. Atmospheric chemical reactions and whether the monitoring is supposed to provide
informatics about the reactants or the products.
19
-------
Table 5
MONITORING OBJECTIVES FOR NHMC, NO, NO,, AND 0
PURPOSE
AIR QUALITY ASSESSMENT
• Determine current air quality and trends
ENFORCEMENT OF REGULATIONS
• Determine compliance with Air Quality
Standards
- Federal primary
- State or local
• Provide data for preparation of
environmental impact statements
DEVELOPMENT AND EVALUATION OF CONTROL PLAN
• Evaluate results of control measures
- Local
- Larger area
RESEARCH - ORIENTATION
• Evaluate the contribution to observed
concentration of specific sources,
by type and location of emissions
- Natural
- Man-made ;
• Provide information on chemical reactions
involving the pollutants and their
reactivity
• Provide a basis for describing processes
that affect pollutant concentration
• Test monitoring equipment
PUBLIC HEALTH
• Determine long-term trends
• Provide a basis, for invoking short-term
or emergency control measures
MISCELLANEOUS
• Evaluate effects of exposure on humans
• Determine effects on plants, animals,
and materials
• Assess representatives of existing
monitoring sites
POLLUTANT
NHMC
X
X
X
X
X
X
X
X
X
X
X
X
X
NO
X
X
X
X
X
X
X
X
X
N02
X
X
X
X
X
X
X
X
X
X
X
X
X
X
°x
X
X
X
X
X
X
X
X
X
X
X
X
X
X
20
-------
3. The scale to be represented, especially:
- Neighborhood, and
- Urban to Regional.
The spatial scales of interest can be denned as follows.
Neighborhood- Measurements in this category would represent conditions throughout
some reasonably homogeneous urban subregion, with dimensions of a few kilometers. Homo-
geneity refers to pollutant concentrations. These kinds of stations would provide information
relating to health effectsjmd compliance with regulations because they will also represent condi-
tions in areas where people live and work. Neighborhood-scale data will provide valuable infor-
mation for developing, testing, and revising concepts and models that describe the
urban/regional concentration patterns. They will be useful to the understanding and definition
of processes that take hours to occur and hence involve considerable mixing and transport.
Urban to Regional: This scale of measurement would be used to typify concentrations
over 'very large portions of a metropolitan area and even larger rural areas with dimensions of
as much as hundreds of kilometers. Such, measurements would be useful for assessing trends
in city-wide air quality and the effectiveness of larger scale air pollution control strategies.
Measurements that represent a city-wide area will also serve as a valid basis for comparisons
among different cities. B
4.3. Site Types to Meet the Monitoring Objectives
When the monitoring objectives have been classified, site types can be identified that will
meet the important objectives. Most monitoring objectives for the photochemical pollutants
stress neighborhood and larger scales of representativeness. The importance of source-oriented
monitors, or reactant-versus-product oriented monitors, is different for each of the pollutants.
t
4.3.1, Site Types for Monitoring NMHC
The most important monitoring objectives for NMHC require specification of concentra-
tions on the urban-to-regional scale with due consideration given to the role of the NMHC in
the formation of oxidants. Other objectives refute neighborhood scale measurements to iden-
tify contributions of specific sources. The tafortant site types for NMHC would be
"urban/regional" and "neighborhood". Each of these has two subtypes. For the "neighborhood"
site, the subtypes are "general" and "source characterization." For the "urban/regional" sites,
important subtypes are "general" and "important reactant area".
4.3.2. Site Types for Monitorimg NO
The most important monitoring objectives for NO are the same as for NMHC, because
both are important to the formation of photochemical pollution, but are generally not con-
sidered toxic at ambient levels. The site types required to meet the most important objectives
of NO monitoring will be the same as thoseJorNMHC. This does not necessarily mean that
the individual sites would be collocated. For example, an "urban/regional site-important reac-
tant area" might be in a different place for NO than for NMHC because of differences in source
distributions.
4.3.3. Site Types for Monitoring NO2
Objectives that require neighborhood scale measurements are common in monitoring NO2
because of the pollutant's toxicity. There are four possible subtypes:
r
21
-------
General
Source characterization
Important reactant area
Important product area
Urban/regional site types are also considered important for NO2 monitoring.
4.3.4. Site Types for Monitoring Ox
Many of the most important oxidant monitoring objectives are related to its status as a
product in the photochemical process and most require measurements that represent the larger
scale features of O distribution. Therefore, the appropriate sites should be located so that the
product nature of the pollutant is emphasized.
4.4. Summary of Monitoring Site Taxonomy for the Photochemical Pollutants
Table 6 summarizes a suggested set of site types that should meet nearly all the important
monitoring objectives,. In subsequent sections, the requirements for locating sites of the sug-
gested types will be explored. The site classifications shown in Table 6 were derived to meet
the important requirements of photochemical pollutant monitoring. The classification scheme is
related to similar approaches that have been applied before to the problem of deriving site types
for carbon monoxide monitoring (e.g., Ott, 1975; Ludwig and Kealoha, 1975), sulfur dioxide
monitoring (Ball and Anderson, 1977), and for particulate sampling (Ludwig, Kealoha, and
Shelar, 1977). This provides a common basis for site selection that leads to similar monitoring
site types for the different pollutants so that integrated, multipurpose monitoring will often be
feasible.
22
-------
Table 6
MONITORING SITE TYPES FOR THE
PHOTOCHEMICAL POLLUTANTS
General Site
Type
Neighborhood
Neighborhood
Urban/regional
Urban/regional
Urban/regional
Traffic
effects
Subclass
Source -
oriented
General
Important
reactant
area
Important
product
area
General
Street canyon
or traffic
corridor
Scale to be
Represented
Smaller end of
the neighbor-
hood scale,
1-2 km
Neighborhood
Urban /Regional
tens of km.
Urban/Regional
Urban/Regional
Middle, on
the scale of
streets
Other Important
Factors
Areas where measure-
ments will identify
contributions of
specific sources
Areas, where measure-
ments will be
dominated by single
sources are to be
avoided
Areas where reactants
are expected to con-
tribute importantly
to photochemical air
quality especially in
sensitive receptor
areas
Areas where important
photochemical pollu-
tant products are
expected to occur
Areas where measure-
ments are representa-
tive of whole region
without regard to its
importance in larger
scale photochemical
processes
Must be a large
traffic source of
NO nearby
|
Photochemical
Pollutants to
which most
applicable
NO,, NMHC, NO
-
N02 , NMHC , Ox
NO
NO, NMHC, N02
Ox, N02
NO, N02, NMHC,
°x
NO, N02, Ox
Remarks
Similar to source
oriented site, but
not as restrictive
Composite of
neighborhood
observations
Similar to other
urban/regional
sites, but not so
restrictive . ,
Specifically to
assess the impacts
of reactions among ;
NO, N02, and Ox
i
23
-------
-------
5. SELECTION OF MONITORING SITES FOR PHOTOCHEMICAL POLLUTANTS
5.1. General Principles of Site Selection
The selection of a specific monitoring site requires four major steps:
1. identify the purpose to be served by the monitoring
2. Identify the monitoring site type(s) that will best serve the purpose
3. Identify the general locations where the monitoring sites should be placed
4. Identify specific monitoring sites.
The major categories of monitoring purpose have been listed and that list includes most of
the possible outcomes of Step 1 above.
Step 2 can be accomplished by the use of Table 7, which is a matrix of the monitoring
purposes enumerated earlier and the station types given in Table 6. The combinations of mon-
itoring purpose and site type that apply to the different pollutants are indicated in Table 7.
This table is designed to serve as a guide to matching purpose with appropriate site type.
The most important principle in the selection of specific sites is that the effects from indi-
vidual sources, other than those of interest in source-oriented monitoring, should be minimal.
The concept of representativity implies homogeneity. The regions of strong gradients need to
be identified and avoided. In general, the undesirable areas are likely to be associated with
strong individual sources or sinks, so the problem becomes one of locating the important
sources or sinks and assessing their effects on the surroundings. The importance of a source or
sink depends on the scale to be represented and on the concentrations prevailing in the region
of interest. In rural areas with low pollutant concentrations, a certain source or sink may distort
conditions appreciably, but that same source or sink in a city neighborhood might go virtually
unnoticed because of the generally higher concentrations and the greater density of similar
sources and sinks.
5.2. Site Selection Procedures
The following discussions of site selection have been kept specific. The justification for
the recommendations are given in Section 6 of this report.
5.2.1. Nonmethane Hydrocarbons
5.2.1.1. General
Figure 8 presents the step-by-step procedure for selecting nonmethane hydrocarbon mon-
itoring sites. The selection of monitoring sites begins with the assembly of the necessary back-
ground information. The first box of the flow chart in Figure 8 gives examples of information
that is valuable in the site selection process. Maps and aerial photographs of the region provide
information concerning the location of streets, commercial areas, and the nature of the regional
topography. If an emissions inventory has not already been compiled for the region, it will
probably be necessary to compile one. The Environmental Protection Agency (1974) has
prepared a guide for assembling emissions inventories. The methodology for calculating air
pollutant emissions factors has been'described in detail in another EPA (1975) document. This
latter document is subject to frequent revisions and the issuance of supplements and addenda.
The user should use the most recent methodologies.
Population densities are important because they identify regions of great public exposure
and the distribution of population density in an area approximates the distributed source emis-
sions. If one knows the total emissions in the region arising from, say, space heating, then it is
reasonable to distribute these emissions according to the distribution of population. Population
and housing data are available for the census tracts within 241 Standard Metropolitan Statistical
Areas (SMSA). Figure 9 from one of these Bureau of the Census (1972) documents shows
the size of some tracts. In general, tracts are smaller in areas of dense population than in less
25
-------
Table 7
MONITORING PURPOSES AND SITE TYPES
* Purpose
1. Determine compliance
with Air Quality
Standards
Federal Primary
State and Local
2. Provide data for
preparation of
environmental impact
statements
3. Evaluate the contribution
to observed concentration
of specific sources, by
type and location of
emissions
Natural
Man-made
—
4. Provide information on
chemical reactions
involving the pollutants
and their reactivity
5. Provide a basis for des-
cribing processes that
affect pollutant concen-
tration
6. Teat monitoring equipment
7. Evaluate results of
control measures
Local
Larger
8. Determine long-term trends
9. Provide a basis for
invoicing short— term or
eaergency control measures
10. Evaluate effects of human
exposure to the pollutants
11. Determine effects on plants
animals, and materials
12. Assess representativeness
of existing monitoring
sites
Site Types
Urban/Regional
Important
Reactant
NMHC, NO
NMHC, NO,
2
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2
NMHC, NO, NO
NMHC, NO, N02
NO NMHC
i
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Product
0
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x
NO , 0
£. K
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x 2
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NO , 0
NO,, 0X
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0 2
x
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2 x
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NO,, 0 , NMHC
2' x
NO,, 0
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NO,, 0
2 x
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2 x'
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Source
NO,
NO?
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2
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2
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N02, 0
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2 x
26
-------
ASSEMBLE GENERAL BACKGROUND INFORMATION,
FOR EXAMPLE:
• MAPS
• LAND USE
• EMISSIONS INVENTORIES
• POPULATION DENSITIES
• TRAFFIC DISTRIBUTION
• CLIMATOLOGICAL AND METEOROLOGICAL DATA
• EXISTING MONITORING DATA, IF ANY
IS A SOURCE ORIENTED OR A REACTANT
ORIENTED MONITORING SITE BEING CHOSEN?
SOURCE ORIENTED
COLLECT INFORMATION ABOUT
SOURCE, FOR EXAMPLE:
• EMISSION RATE
• STACK PARAMETERS
- DIMENSIONS
- EFFLUENT VELOCITY
AND TEMPERATURE
USE CLIMATOLOGICAL DATA AND
SIMPLE MATHEMATICAL MODELS
TO ESTIMATE AVERAGE CONCEN-
TRATIONS AND FREQUENCY OF
HIGH CONCENTRATIONS AT
LOCATIONS IN THE VICINITY
OF THE SOURCE
SELECT CANDIDATE AREAS NEAR
MAXIMUM AVERAGE CONCENTRA-
TIONS OR IN AREAS WITH MOST
FREQUENT HIGH CONCENTRATIONS
REACTANT ORIENTED
USE EMISSIONS INVENTORIES TO IDENTIFY
AREAS OF GREATEST EMISSION DENSITIES
USE SIMULATION MODELS TO IDENTIFY LARGE
AREAS OF HIGH, UNIFORM CONCENTRATIONS
USE CLIMATOLOGICAL DATA TO IDENTIFY
AREAS MOST LIKELY TO PRODUCE HIGH O3
CONCENTRATIONS IN SENSITIVE AREAS
(SEE TEXT)
SELECT SPECIFIC SITES:
INLET HEIGHT, 3-15 m
MIMIMUM SEPARATIONS FROM ROADWAYS:
ADT< 1000, 15 m
ADT 1000-10,000, 15-400 tn
ADT > 10,000, >400 m
FOR REACTANT ORIENTED MONITORS,
AVOID MAJOR POINT SOURCE EFFECTS
FIGURE 8 SCHEMATIC DIAGRAM OF PROCEDURE FOR SELECTING
NMHC MONITORING SITES
27
-------
CD
x:
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28
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densely populated areas. The Office of Air Quality Planning and Standards of EPA has
prepared computer programs that will apportion area source emissions from the National Emis-
sions Data Systems (NEDS; see e.g., Bosch, 1975) into gridded areas according to population.
Valuable information concerning major point sources in the area are also available from NEDS.
Figure 10 gives an example of point source emission information from NEDS.
Traffic data are useful as bases for an emissions inventory, especially if they can be con-
verted into emissions estimates for different grid squares within the region of interest. A com-
puter program is available for converting traffic data from the Federal Highway Administration
or other sources into a gridded inventory for the pollutants, carbon monoxide, oxides of nitro-
gen, and nonmethane hydrocarbons. This program (Ludwig et al., 1977) can also be used to
calculate concentrations arising from traffic emissions for specified weather conditions and times
of day.
Climatological and meteorological data are essential to the proper selection of monitoring
sites. One kind of climatological summary that is of particular use is the frequency distribution
of wind speed and direction. This information comes either as a tabulated joint frequency dis-
tribution like that shown in Table 8 (an example of material that is available from the National
Climatic Center in Asheville, North Carolina) or as a wind rose, another form in which the
same kind of information is often presented. Examples of wind roses are shown in Figure 11
from the National Climatic Atlas (National Oceanic and Atmospheric Administration, 1968).
More specific summaries might be useful for selecting reactant-oriented monitoring sites.
Appendix B to this report contains a simple computer program that can be used with data from
the National Climatic Center to determine the joint frequencies of wind speed and direction
during periods of high temperatures. The stratification of the data on the basis of temperature
is justified because ths photochemical reactions tend to be more pronounced during such
periods.
Finally, the site selection process should use any existing monitoring data or special stu-
dies that are available for the region of interest. If a body of data exists from reasonably well
located monitoring stations, then those data will be more useful than modeling for determining
the locations of areas of maximum concentrations within the region. Special studies can also
provide useful information concerning the variability of concentrations in time and space. Spe-
cial studies often focus on important kinds of air pollution events and will provide useful gui-
dance for the location of monitors that will characterize similar events in the future.
Ludwig and Kealoha (1975) in their report on the selection of sites for carbon monoxide
monitoring presented several appendices to help identify sources of information that are useful
to the site selection process.
After the background material has been assembled, a decision must be made regarding
whether or not the monitor is to be the.source-oriented or the reactant-oriented type. The two
branches in the flow chart in Figure 8 show the procedures for the selection of these two
different types of sites.
5.2.1.2. Source-Oriented Monitors
In general, source-oriented monitoring of NMHC is less important than reactant-oriented
monitoring, but there will be occasions when the effects and impacts of a specific hydrocarbon
source are of interest. A discussion of the identification of areas important to source-oriented
monitoring can also be useful for identifying areas that should be avoided in locating other
types of monitors.
Figure 8 shows that source characteristics are important in selecting source-oriented sites.
It would be wise to check NEDS information independently to ensure that there have not been
changes in the operating characteristics of the source and that the information in NEDS has
been properly archived. The next step is to combine the source information with climatological
information to identify areas of greatest impact. Source-oriented monitoring applies to large
point sources, generally elevated. The impact of such an elevated point source can be defined
in different ways.
29
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Table 8
EXAMPLE OF A STATISTICAL WIND SUMMARY FROM THE
NATIONAL CLIMATIC CENTER
(Asheville, North Carolina)
PERCENTAGE FREQUENCIES
OF WIND DIRECTION AND SPEED:
OHKTK3M
N
NNE
NE
ENE
p
ESE
SE
SSE
S
'ssw
'sw
wsw
w
WNW
iNW
!NNW
iCALM
ITOTAL
HOURLY OBSERVATIONS OF WIND SPEED
ilN MILES PER HOUR>
0 • 3
4-
4-
4-
4-
4-
+
4-
1
4.7 ft . 12 • 13 . IS
i ; 2 ; i
1
1
1
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+ 1
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4-
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19 • 24 , JS . 31
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SPEED
11.4
10.5
11.7
11.4
9- n
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8.6
8.9
11.0
13.3
14.4
15.5
17.3
15.3
14.6
13.1
12.0
1?.5
Source: National Climatic Center
Asheville, N. C.
31
-------
I I S I -x| __' . I 3 *
32
-------
A model of some sort will provide a mechanism by which the source characteristics and
the climatological information can be combined to define areas of important impact. Several
simple computerized models are available for determining the areas of maximum average
impact, from a point source. These models include the Climatological Dispersion Model (Busse
and Zimmerman, 1973) and the model presented by Ludwig, Kealoha, and Shelar (1977). Esti-
mates can also be made without -using a computer. The greatest long-term impact is likely to be
associated with the most frequent combinations of wind direction, speed, and atmospheric sta-
bility. These joint frequencies can be obtained from the National Climatic Center from the out-
put of their STAR computer program. An example of the STAR program output is shown in
Figure 12.
The direction from the source to the receptor site will be the downwind direction for the
most frequent combination of stability, wind speed, and wind direction. The best distance at
which to locate the monitoring site can be estimated by calculating the plume rise for the stabil-
ity and wind speed of concern. The wind speed at the top of the stack is likely to differ from
that measured at ground height, typically 10 meters. Beals (1971) has given information that
can be used to correct the wind speed observed near ground level to that at stack height; the
required corrections are summarized in Figure 13 . Briggs (1969) gives equations for determin-
ing plume rise. Once the height of the plume is known for the most common combination of
stability, wind'Speed, and wind direction, then the distance to the area of maximum concentra-
tion for that case can be estimated from graphs like those given by Turner (1969). Figures 14
and 15 are two of Turner's graphs. The ordinate in these graphs represents concentration nor-
malized for emission rate, Q, and wind speed, u.
The location of the maximum concentration is of great importance to the site selection
problem, but its absolute magnitude is of less importance. Figures 14 and 15 show that the
concentration rises rapidly with distance to a maximum and then falls gradually beyond the
maximum. The location of the site should probably be somewhat beyond the distance where
the maximum concentration is predicted. This allows some margin for error by putting the
monitor in a region of relatively small gradients rather than near the strong gradients toward
the source from the maximum.
The highest short-term concentration from an elevated source is most likely to occur at
ground level under extremely unstable conditions, such unstable conditions are unlikely to
occur during the 6:00 - 9:00 a.m. period specified as being of interest in the air quality guide-
lines, because surface heating in the early morning is insufficient to produce strong instability.
Therefore, the slightly unstable and moderately unstable conditions which are possible during
this time period are more important. The wind directions and wind speeds occurring most fre-
quently with slightly unstable and moderately unstable conditions can be determined from the
output of the STAR program. The effective plume rise should be calculated for the most fre-
quent wind speeds. Figure 14 can be used as a basis for locating the distance from the source
to the region of maximum NMHC concentrations under slightly unstable conditions. The
direction for the best monitoring site will be the most frequent direction occurring during
slightly unstable conditions. If several directions commonly occur under such atmospheric sta-
bility conditions, then it may be necessary to Have more than one site.
Since the purpose for locating source-oriented monitoring sites is to determine the impact
of a specific source, it will generally be necessary to have another site nearby to characterize the
"background" conditions in the area. A reactant-oriented site located in a direction from the
source that is opposite that of the source-oriented site will serve the purpose. An effort should
also be made to avoid locating the source-oriented site in an area that is impacted by other
major point sources. If this cannot be done, then measurements of wind speed and direction at
the sampling site will be essential so that it will be possible to determine when the source of
interest is affecting on the monitor. Wind speed and direction measurements will allow the data
to be interpreted so that the impacts of different major sources can be differentiated.
33
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600
1.0
1.5 2.0 2.5 3.0
WIND INCREASE FACTOR
- 150
4.0 5.0
SA-1567-9
FIGURE 13 VARIATIONS OF WIND SPEED WITH HEIGHT AND
STABILITY
35
-------
10"
DISTANCE
km
Source: Turner, 1969
FIGURE 14 NORMALIZED GROUND LEVEL CONCENTRATIONS FROM AN ELEVATED
SOURCE FOR SLIGHTLY UNSTABLE CONDITIONS
36
-------
minimum pin
iiiiiiiiiUimiimiiiiiiiiiiiiliiunmiiiiiiiH
100
DISTANCE - km
Source: Turner, 1969
FIGURE 15 NORMALIZED GROUND LEVEL CONCENTRATIONS FROM AN ELEVATED
SOURCE FOR NEUTRAL STABILITY
37
-------
After the general area for the source-oriented monitor has been identified, it is necessary
to select a specific location within that area. The inlet should be about 3 to 15 meters in height
and well removed from ground-level sources such as roadways or large space heating or process
emissions of hydrocarbons. Specific siting requirements are discussed further in the next sec-
tion.
5.2.1.3. Reactant-Oriented Monitors
The right-hand branch of the flow chart in Figure 8 shows the steps necessary to select
reactant-oriented NMHC monitoring sites. The first step is to use the emissions inventories to
identify areas where emission densities are greatest. This may be sufficient, but it is preferable
to take the next step and use the simulation model in combination with the emissions inventory
and climatological information, to estimate the concentration distribution throughout the area.
The Climatological Dispersion Model (Busse and Zimmerman, 1973) is well suited for this pur-
pose. The candidate areas for locating the monitoring sites will be found in those areas where
high concentrations are expected. The best areas will be relatively large and have reasonably
uniform concentration throughout.
It is reasonable to select areas for monitoring NMHC that are most likely to be associated
with high oxidant concentrations in sensitive areas. The first step in finding where such areas
are located is the identification of those meteorological conditions most likely to associated with
the production of large concentrations of oxidants. The approach taken here is to derive wind
statistics for those hours when high temperatures prevail. Figure 16 and Table 9 are examples
of the output that can be derived from the computer program in Appendix B. The wind direc-
tions associated with light winds and high temperatures define the critical travel directions for
the measured hydrocarbons. In general, the oxidant concentrations will begin to build up
within a few tens of kilometers downwind of the sources. Each of the areas determined to be
subject to relatively high hydrocarbon concentrations should be examined to see if it lies
upwind of any particularly sensitive areas. Those high hydrocarbon areas that are upwind of
sensitive areas during conditions likely to produce high oxidant values are the best places for
NMHC monitors.
The monitoring site should be well removed from local sources. Figure 8 specifies
minimum separations between the monitor and roadways with different levels of average daily
traffic (ADT). The site should be well away from other major ground level sources of hydro-
carbons, e.g. gasoline stations, dry cleaners, surface coating operations, refineries, or petro-
chemical complexes. No exact minimum separation can be specified for these kinds of sources,
but the discussions in Section 6 of this report should provide the reader with sufficient under-
standing so that the minimum separation can be calculated for a specific source.
The inlet at the monitoring site should be placed between about 3 and 15 meters above
ground level and about a meter above the support surface. It should be separated from any
surrounding obstacles by about twice the height of the obstacle above the inlet.
5.1.2. Oxides of Nitrogen
5.2.2.1. General
NO is not a criteria pollutant. However, the role of NO in the formation and destruction
of ozone is too important to be ignored. Also, NO is the pollutant initially emitted from most
of the sources of concern. The importance of NO demands that the siting requirements for
monitoring it be considered, but the major emphasis still remains on the criteria pollutant, NO,.
In the following sections procedures are given for siting NO2 monitors for general purposes, for
reactant-oriented purposes, and for product-oriented purposes. General monitoring has been
considered to be that which would be used to characterize population exposure. Product-
oriented monitoring is similar, but the emphasis on NO2's role as a product leads to the selec-
tion of locations in high concentration areas. Finally, reactant-oriented monitoring of NO and
NO2 concentrations has objectives similar to those discussed above in connection with
reactant-oriented hydrocarbon monitoring.
38
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LEGEND & NOTES
1. Wind speed (mps)
/•gy-2 3-4 5-6 7-8 9-10 >IOmps
3. Inner circle area of rose is
proportional to frequency (%) of
calm conditions (1 mps or less)
2. Frequency scale (%)
0 5 10
15
1
4. Angle of wind rose linas reflect
direction from which wind is
blowing
N
I
W
FIGURE 16 ST.LOUIS WIND ROSE FOR DAYTIME HOURS WHEN THE
TEMPERATURE EXCEEDED 80°F.
Data represent observations from 1 January 1960 through 31
December 1974.
39
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5.2.2.2. Source-Oriented Monitors
Figure 17 is a flow chart presenting the steps necessary to the selection of an appropriate
monitoring site that can be used for assessing the impact of large sources of oxides of nitrogen.
The similarities with that part of Figure 8 that deals with source-oriented hydrocarbon monitor-
ing are obvious. The process begins with the acquisition of the background information includ-
ing the characteristics of the source that is being studied. The source strengths and the stack
parameters are of primary importance. These data, along with climatological data, particularly
the output of the STAR program, will be required to determine where concentration maxima
are most likely to be found. If there are existing monitoring data for NO and NO2 in the area,
then they should be used in the selection process. Maps and emissions inventories are
required to identify susceptible neighborhoods and other sources of NO that might interfere
with the measurements.
The NAAQS are concerned with annual mean concentrations of NO2, so the emphasis in
site selection will be in finding those areas where long-term averages are apt to be the highest.
However, it appears that a short term standard may be adopted in the future, so that possibility
must also be considered. A simple model like that given by Ludwig, Kealoha and Shelar
(1977) or the COM (Busse and Zimmerman, 1973) or Turner's (1969) workbook should serve
to define such areas. Such models are likely to overestimate the concentrations of NO- that
will be observed because they deal with total oxides of nitrogen rather than the single com-
pound NO2. Nevertheless, it is expected that the maximum NO2 concentrations will occur in
approximately the same locations as the maximum NO concentrations. The best course would
be to locate the site somewhat beyond the expected point of maximum NO to allow somewhat
more time for the formation of NO2.
If one is selecting a site to determine whether the annual standard is violated, then "max-
imum" refers to long-term average concentrations. If the monitoring is done to assess compli-
ance with a short-term standard such as EPA may adopt and some states already have (e.g.,
California has an one-hour standard of 250 ppb), then the most likely areas for the occurrence
of violations of this standard should be identified. In general, short term maxima occur with
more unstable atmospheric conditions and are closer to the source. For example, a comparison
of Figures 14 and 15 shows that for any given stack height, the ground level concentrations will
be greater, and closer to the stack, for the. unstable conditions (Figure 14) than for the neutral
conditions (Figure 15).
Once the general areas for the site have been selected, a more specific site must be
located. It should be near the area of anticipated maximum NO2 influence, but removed from
interferences so that its measurements will accurately characterize the influence of the source
being studied. The site should be away from heavy traffic. The flow chart (Figure 17) recom-
mends minimum separation distances from streets and roadways with different levels of average
daily traffic (ADT). It is not certain, but buildings, trees, and other obstacles may scavenge
NO2. .To avoid this kind of interference, the monitor should be away from such obstacles.
Two or three times the height of the obstacle above the monitor is recommended. For similar
reasons, a probe inlet along a vertical wall is undesirable because air moving along that wall
may be subject to removal mechanisms.
Air from a fairly tall, large point source will be reasonably well mixed by the time it
reaches ground level. Therefore, vertical gradients are not apt to be large in the first few
meters above the ground and a wide range of probe heights will be acceptable; 3 to 15 meters
is suggested. If the height of the source under study is comparable to this height, then the gra-
dients may be large and any monitoring that is done to assess compliance wih the NAAQS or to
evaluate health effects should be done nearer to the breathing zone, i.e. about 3 meters.
Supplemental measurements will be valuable to the interpretation of the air quality data
collected at the stations. ~ In source-oriented monitoring, anemometers will provide information
that allows the analyst to" determine when emissions from the stack have impinged on the
41
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ASSEMBLE BACKGROUND INFORMATION,
FOR EXAMPLE:
• SOURCE NOX EMISSION RATE
• STACK PARAMETERS
— DIMENSIONS
— EFFLUENT VELOCITY AND TEMPERATURE
• CL1MATOLOGICAL DATA
• MAPS
• INVENTORY OF OTHER EMISSIONS IN AREA
• EXISTING MONITORING DATA, IF ANY
USE CLIMATOLOGICAL DATA AND SIMPLE
MATHEMATICAL MODELS TO DETERMINE AREAS
OF HIGH NOX CONCENTRATIONS
SELECT SPECIFIC SITE:
INLET HEIGHT, 3-15 m
MINIMUM SEPARATIONS FROM ROADWAY SOURCES
ADT < 1000, 20 m
ADT=1000 TO 10,000, 20 m-250 m
ADT > 10,000, > 250 m
SEPARATED FROM NEARBY OBSTACLES BY TWICE
THE HEIGHT OF THE OBSTACLE ABOVE THE
INLET
FIGURE 17 SCHEMATIC DIAGRAM OF PROCEDURE FOR SELECTING SITES
FOR SOURCE ORIENTED NO AND NO2 MONITORING
42
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monitoring site. Records of the stack operation, particularly as they affect the emissions, can
also be used to evaluate the impact of that particular source on its surroundings.
5.2.2.3. Neighborhood and Regional Scale Monitors
Figure 18 shows procedures to select sites for neighborhood and regional scale NO moni-
toring. As always, the process begins with the acquisition of background information. Then it
must be decided whether the emphasis of the monitoring will be on oxides of nitrogen as a pro-
duct, primarily NO2, or as total oxides of nitrogen serving as reactants in the photochemical
process. If the concern is for oxides of nitrogen in their role as reactants, then the site selec-
tion process is similar to that suggested for hydrocarbon monitors. A simple diffusion model
can be Used to identify neighborhoods where maximum NOX concentrations are to be expected,
especially during those seasons when photochemical activity is likely to be at its greatest. If
modeling cannot be done, then the next best approach is to identify those neighborhoods with
maximum NOX emissions. The high concentration areas can be examined to see if populated
areas or areas that might be susceptible to harmful effects from photochemical pollution are
found downwind. "Downwind" refers to wind directions that are most frequent during weather
conditions conducive to photochemical activity. It has been found. (Meyer, et al., 1976;
Ludwig, Reiter, et al., 1977) that the factor most associated with h%h ozone concentrations,
and hence greatest photochemical activity, is air temperature. Therefore, a wind rose based on
those hours with high temperatures should serve to identify the most likely wind directions dur-
ing periods of photochemical pollutant formation. Figure 16 presents an example of such a
wind rose derived from hourly wind observations when the temperature exceeded 80°F in St.
Louis, Missouri. Other temperatures could be chosen. It appears that photochemical ozone
formation becomes most important above about 20°C (68°F).
As Figure 18 shows, the final site selection for neighborhood scale monitoring of NO and
NO2 concentrations will find a location where local NO sources have minimal influence on the
observation. The identification of areas where there will be high concentrations from a point
source has already been discussed. Figure 18 suggests minimum separations between the moni-
tor and nearby roadways (as a function of average daily traffic) to keep the influence of traffic
sources at a minimum. The recommended inlet height is in the range from 3 to 15 meters. If
the site is properly chosen so that the data collected there will represent neighborhood condi-
tions, then the oxides of nitrogen should be reasonably well mixed and the height of the inlet
will not be very critical.
When the interest is in NO,,, as it will be for monitoring related to health effects or the
NAAQS, then the site should be "product-oriented . There are two scales of measurement that
are of interest, neighborhood and regional. Selecting neighborhood scale, product-oriented
monitoring sites for NO2 begins in the same way as the procedure for selecting reactant-
oriented sites. Areas of major NO emissions are identified and the most frequent wind direc-
tions for periods of photochemicaiactivity are defined. Then, prospective siting areas will be
chosen downwind of the major source areas. Observations suggest (see Section 6) that NO2
concentrations are likely to fall off rather rapidly outside the urbanized area. Therefore, the
best locations for characterizing high NO2 concentrations will be within the city. For long term
'average concentrations, the maxima tend to be displaced downwind of the major source areas.
The displacement is the distance traveled by the air in an hour or two under normal wind con-
ditions. This will usually be a few kilometers. The highest one-hour average concentrations of
NO2 tend to be very close to the areas of greatest NO emissions. Thus, a site to ascertain
compliance with a short term standard would be located in an area of maximum emissions. In
both cases, monitoring for short or long term standards, residential neighborhoods will be most
important, because the assessment of compliance with air quality standards relates to public
health.
For either short or long term monitoring, the measurements should be representative of a
reasonably large, neighborhood-sized area. Therefore, the location must be away from NO
sources, either major point sources or traffic sources. An inlet height of 3 to 15 meters is
43
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PRODUCT ORIENTED
EMPHASIS WILL BE ON NO2
IS THE MONITORING TO
CHARACTERIZE THE
NEIGHBORHOOD SCALE
OR A LARGER SCALE?
REGIONAL SCALE
USE WIND DIRECTION
STATISTICS TO DETERMINE
DIRECTION WHICH IS
MOST OFTEN UPWIND
OF NEAREST URBAN AREA.
USE FIG. 19 TO ESTIMATE
MINIMUM DISTANCE
BETWEEN SITING AREA
AND URBAN AREA
MAKE FINAL SITE SELECTION
.INLET HEIGHT, 3-15 m
MINIMUM DISTANCE TO
ROADWAYS:
ADT < 1000, 20 m
ADT 1000-10,000, 20-250 m
ADT > 10,000, >250 m
AVOID POSSIBLE INFLUENCE
OF LARGE NOX SOURCES
ASSEMBLE BACKGROUND
INFORMATION
IS THE MONITORING TO
BE REACTANT ORIENTED
OR PRODUCT ORIENTED?
NEIGHBORHOOD SCALE
IDENTIFY AREAS OF
MAJOR NOX EMISSIONS
IDENTIFY MOST FREQUENT
WIND DIRECTIONS EMPHASIZ-
ING DIRECTIONS ASSOCIATED
WITH LOW WIND SPEEDS
IDENTIFY PROSPECTIVE SITING
AREAS DOWNWIND OF MAJOR
NO EMISSIONS AREAS AND
NEAR THE EDGE OF THE
URBAN EMISSIONS REGION. FOR
HEALTH RELATED MONITOR
ING, SOME EMPHASIS WILL BE
GIVEN TO POPULATED AREAS.
REACTANT ORIENTED;
WILL MOST OFTEN BE
ON THE NEIGHBORHOOD
SCALE. EMPHASIS WILL
BE ON TOTAL OXIDES
OF NITROGEN
USE MODELING TO ESTIMATE
REGIONS OF MAXIMUM
NOV CONCENTRATIONS
IDENTIFY MOST FREQUENT
WIND DIRECTIONS DURING
PERIODS OF LIKELY
PHOTOCHEMICAL ACTIVITY.
MAKE FINAL SITE SELECTION
INLET HEIGHT, 3-15 m
MINIMUM SEPARATION
FROM ROADWAYS:
ADT < 1000, 20 m
ADT 1000-10,000, 20-250 m
ADT > 10,000, > 250 m
AVOID AREAS LIKELY
TO BE INFLUENCED BY
LARGE POINT SOURCES.
FIGURE 18 SCHEMATIC DIAGRAM OF PROCEDURE FOR.SELECTING NEIGHBORHOOD
AND REGIONAL SCALE MONITORING SITES FOR NO AND NO2
44
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desirable and it should not be along a vertical wall where destructive processes might affect the
measurements. Wherever possible the site should be away from obstructions. The rule of
thumb mentioned earlier, i.e. separation from an obstruction by a distance of two times the
obstruction heights above the monitor, applies to both the reactant- and product-oriented,
neighborhood scale NOX and NO2 monitoring sites.
The procedure for selecting regional scale monitoring sites has been placed in the
product-oriented branch of the flow chart in Figure 18. This is because most of the sources of
NO are in the urban areas. Regional monitoring will measure the concentrations of NO and
NO2 after they have been modified by chemical reactions in the atmosphere and have become
"products". There is some ambiguity in this approach; there is evidence (e.g. Singh, Ludwig
and Johnson, 1977) that when oxides of nitrogen are present in remote regions, they can ini-
tiate oxidant-forming reactions. However, in regional scale monitoring of NO and NO2, the
distinction between product and reactant makes little difference to the site selection process.
Inasmuch as the monitoring purpose for this kind of site will usually be served best by a
site that has only minimal urban influence, the best areas will be those which are least fre-
quently downwind of an area of strong emissions. A wind rose applicable to the region will be
used to determine which direction is most frequent. Figure 19 shows the distance at which the
Office of Air Quality Planning and Standards (OAQPS, 1977) has estimated urban influences on
NO concentrations fall to about 7 ppb. The value 7 ppb was chosen to be slightly above the
limits of detection of current instrumentation. Figure 20 (from OAQPS, 1977) provides a con-
venient representation of those areas within which regional monitoring of NO2 is probably
above "background" concentrations.
After the general areas for the regional scale monitoring have been identified, the specific
site will be chosen to minimize influences of NO sources. It is important to avoid the
influence of large point sources such as power plants that might be located in rural areas. The
methodology for identifying areas of major point source impact (already discussed) can be used
to identify areas to be avoided. Wind monitoring at the site could identify instances of point
source impact.
Inlet heights of 3 to 15 meters are recommended for the reasons discussed in connection
wHh neighborhood monitoring sites. A monitoring site should be removed from obstacles.
The separation should be greater than required for neighborhood monitoring sites because the
influences of obstacles should be reduced to especially low levels, commensurate with the lower
levels of NO concentrations in the nonurban areas. The inlet for a regional monitor should be
at least a meter or two above the instrument shelter and should not be located so that it pro-
trudes from a wall of that shelter.
5.2.3. Oxidants
Two types of neighborhood scale monitoring sites are considered. One will be used to
characterize typical concentrations in the urban region and the other to measure maximum, or
near-maximum, concentrations in the region. A regional site for typical concentrations in the
area surrounding the city is also discussed. Figure 21 summarizes the procedure for selecting
the important kinds of sites. It reemphasizes the importance of collecting background informa-
tion before site selection precedes.
5.2.3.1. Regional Scale Monitors
After the background information has been assembled, the next step in selecting a
regional scale monitor is to determine what direction is most associated with those meteorologi-
cal conditions that are conducive to photochemical formation of ozone. As noted before, tem-
perature serves as a good indicator of the propensity for ozone formation. Prospective areas for
regional scale background monitoring of ozone would be found in a direction that is upwind of
the urban area for those winds which are frequently associated with high temperatures. For
example, Figure 16 shows that winds from directions between south-southeast and west are
common in St. Louis when temperatures exceed 80°F so the best areas for regional background
45
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4000
3500
3000
S 2500
z
o
p
2000
Q
UJ
N
CO
§ 1500
1000
500
200
For urban areas with populations
greater than 4 million, radius of
influence is about 140 km
20
40
60
80
100
120
140
ESTIMATED RADIUS (km) WHERE NOX < 7 ppb
Source:'OAQPS, 1977
FIGURE 19 ESTIMATED RADIUS AT WHICH NO AND NO2 CONCENTRATIONS FALL
BELOW 7 ppb, AS A FUNCTION OF METROPOLITAN POPULATION
46
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47
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NEIGHBORHOOD
IS THi PURPOSE TO DEFINE
TYPICAL OR HIGHEST
CONCENTRATIONS ?
TYPICAL CITY
CONCENTRATIONS
SELECT REASONABLY
TYPICAL HOMOGENEOUS
NEIGHBORHOOD NEAR
GEOGRAPHICAL CENTER
OF REGION. BUT REMOVED
FROM INFLUENCE OF
MAJOR NOX SOURCES
SELECT SPECIFIC SITE.
AVOID LOW LYIN'o AREAS.
.AVOID INFLUENCE FROM
MAJOR NOX SOURCES. MINI-
MUM SEPARATIONS FROM
ROAD-WAYS
ADT < 1000, 20m
ADT- 1000-10,000, 20-250 m
ADT > 10,000, >260m
SHOULD BE IN AN OPEN
AREA WITH NO NEARBY
OBSTACLES. INLET SHOULD
BE AWAY FROM SURFACES
AND AT A HEIGHT OF
3 TO 15m
ASSEMBLE BACKGROUND INFORMATION:
• MAPS
• EMISSIONS INVENTORIES FOR NMHC AND NOX
• CLIMATOLOGICAL DATA
• EXISTING 03, NMHC AND NO2/NO DATA
IS THE MONITOR TO CHARACTERIZE
REGIONAL OR NEIGHBORHOOD CONDITIONS ?
REGIONAL
HIGH CONCENTRATION AREAS
DETERMINE MOST FREQUENT
WIND SPEED AND DIRECTION
FOR PERIODS OF IMPORTANT
PHOTOCHEMICAL ACTIVITY
USE EMISSIONS INVENTORIES TO
DEFINE EXTENT OF AREA OF IMPOR-
TANT NMHC AND NOX EMISSIONS ,
SELECT PROSPECTIVE MONITORING
AREA IN DIRECTION FROM CITY THAT
IS MOST FREQUENTLY DOWNWIND
DURING PERIODS OF PHOTOCHEMICAL
ACTIVITY. DISTANCE TO UPWIND
EDGE OF CITY SHOULD BE ABOUT
EQUAL TO THE DISTANCE TRAVELLED
BY AIR MOVING FOR 5 TO 7 HOURS
AT WIND SPEEDS PREVAILING DURING
PERIODS OF PHOTOCHEMICAL ACTI -
VITY. FOR HEALTH RELATED PURPOSES,
A MONITOR OUT OF THE MAJOR NO
EMISSIONS AREA, BUT IN A POPULATED
NEIGHBORHOOD IS DESIRABLE.
PROSPECTIVE AREAS SHOULD ALWAYS
BE OUTSIDE AREA OF MAJOR NOX
EMISSIONS
DETERMINE MOST FREQUENT
WIND DIRECTION ASSOCIATED
WITH IMPORTANT
PHOTOCHEMICAL ACTIVITY
SELECT PROSPECTIVE MONITOR-
ING AREA UPWIND FOR
MOST FREQUENT DIRECTION
AND OUTSIDE AREA OF CITY
INFLUENCE-SEE FIGURE 19
SELECT SPECIFIC SITE. AVOID
VALLEYS; HILLTOP LOCATION
DESIRABLE. AVOID INFLUENCE
FROM NOX SOURCES. MINIMUM
SEPARATIONS FROM ROADWAYS:
ADT < 1000, 20m
ADT-1000 TO 10,000, 20-250 m
ADT > 10,000, > 250 m
INLET SHOULD BE WELL
REMOVED FROM OBSTACLES
AND AT A HEIGHT OF
3 TO 15 m
FIGURE „ THEMATIC DIAGRAM OF PROCEDURE FOR SELECTING OXIDANT MONITOHING SITES
-------
monitoring would be to the southwest of St. Louis. The regional background monitor should
be as far from any urban area as possible, preferably outside the areas of urban influence as
denned in Figures 19 and 20.
The monitoring site should not be in a low-lying area, because such areas are much more
likely to be subject to destructive processes at the surface during times of pronounced atmos-
pheric stability. A location on top of a small hill will minimize the effects of the surface des-
tructive processes, and hence will be desirable. Avoidance of NO sources is particularly impor-
tant for this kind of site. The identification of those areas around a large point source of NO
where NO interference is probable has been discussed already. Traffic sources of NO should
not be nearby. Figure 21 provides minimum suggested separations between the monitor and
roadways. It is important to separate the monitor from obstructions. If the monitor is located
atop a small hill or knoll, it will minimize destructive effects of trees or other nearby obstacles.
Even atop a hill the monitor should be no closer to any obstruction than about twice the height
of the obstruction above the monitor. It is important when monitoring ozone to have the inlet
away from vertical surfaces, because ozone is easily destroyed by contact with surfaces.
An inlet height of about 3 to 15 meters is desirable. Concentrations measured near the
upper end of this range are probably more representative of background concentrations in the
lower troposphere, but a compromise must be struck between the sampling of these more
representative concentrations and the possible destruction of ozone during passage through a
long inlet tube.
5.2.3.2. Neighborhood Scale Monitoring Sites
There are two monitoring alternatives in a neighborhood scale site. The desire may be to
monitor the highest oxidant concentrations within the urban area or to characterize oxidant
concentrations that are typical of the population exposure. In the latter case, as shown in Fig-
ure 21, prospective sites will be in reasonably homogeneous neighborhoods within the urban-
ized area. The neighborhoods considered should be away from the influence of major NO
sources. In general, this would eliminate siting in heavily industrial neighborhoods, although
there are conceivable instances when the characterization of ozone concentrations in such
neighborhoods would be of interest. The specific site within a neighborhood should meet the
criteria noted in Figure 21.
Figure 21 also shows how to select areas where the highest oxidant concentrations are to
=be found. It will not be possible to identify the point of maximum ozone concentration with
absolute certainty, but it is possible to make qualitative estimates of the best places to locate
monitoring sites. The best strategy is probably to recognize the difficulty in identifying a single
site that will measure the area's highest concentrations and locate several stations in likely
places. Once the decision has been made to locate a site near the highest concentrations in the
area, it is then necessary to determine the most frequent wind speeds and directions for periods
that are conducive to photochemical formation of oxidants. Existing monitoring data can be
used to identify specific days when high ozone concentrations were observed and these days can
be examined to determine the characteristic wind patterns. If there are no historical oxidant
data, air temperature will provide a reasonable measure of the potential for photochemical pro-
duction of ozone. Another possibility is to use wind data for the season and hours when ozone
concentrations are apt to be the highest. Since high ozone concentrations are most likely to
occur in the summer months or early fall, the monthly wind rose maps in the Climatic Atlas
(National Oceanic and Atmospheric Administration, 1968) would tell the user the most fre-
quent wind directions during the oxidant season. The monthly wind rose is not as good as his-
torical oxidant data or a high temperature wind rose because it does not provide information
concerning wind speed during oxidant episodes. Also, the monthly wind rose will include night-
time hours and days when ozone formation was low. The monthly wind rose should be used as
a last resort.
Emissions inventories define the limits of the area within which most of the NOX and
NMHC emissions take place. Alternatively, the outer bounds of the urban areas defined on
49
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conventional topographic or street maps can be used, because the edges need not be denned
very precisely. Photochemical formation of ozone takes place over a long period of time
(hours) so that mixing will obscure the effects of any fine scale details in the emissions field.
The areas where maximum oxidant is most likely will.be outside the regiqn of major NO
emissions, but within the radii of influence defined by OAQPS and shown in Figure 20. The
oxidant maxima are apt to be found in the downwind direction so the area that must be con-
sidered is an angular segment of perhaps 45° that extends from the edge of the city to as far as
150 km from the city center. The area that has to be considered can be reduced further by
recognizing that concentrations of precursors will continue to increase as the air passes over the
source region. Once the air moves beyond the source region, dilution will reduce concentra-
tions of the precursors and ozone formed from them. As long as ozone production is rapid
enough to offset dilution, the concentration will continue to rise. By mid- to late-afternoon the
ozone production will no longer be able to offset dilution and destruction processes. This sug-
gests that one might determine where the pollutants from the morning rush hour are at mid-
afternoon; that would be a likely location for high ozone concentrations. The air leaving the
upwind (for photochemically favorable meteorological conditions) side of the city during the
morning rush hour will accumulate more precursor pollutants during its history than the air
which was on the downwind side of the city at the same time, hence the suggestion that the 5
to 7 hour travel distance recommended in Figure 21 be measured from the upwind side of the
city.
Under light wind conditions, e.g. 10 km h"1, such as might accompany high ozone concen-
trations, the distance would be about 50 to 70 km from the upwind edge of the city. For an
ordinary, symmetric city with a diameter of 50 km, the promising monitoring areas are about 25
to 45 km from the center of the city. If air leaving the upwind side of the city during the
morning rush hour is still within the emissions area during mid-afternoon, then it will still be
under the influence of NO emissions which reduce observed ozone concentrations. In an
extensive metropolitan area, the most likely locations for maximum ozone concentrations will
be several kilometers beyond the downwind edge of the city. In very extensive metropolitan
areas there may be relatively unpopulated "islands" within the widespread sea of NO emissions;
such islands would be candidate areas for high ozone concentrations. However, choosing unpo-
pulated islands or more rural areas beyond the fringes of the metropolitan area deemphasizes
the importance of health effects. Some subjective decisions will have to be made about the
importance of monitoring the maximum ozone concentrations wherever they may occur versus
the monitoring of the maximum ozone concentrations to which appreciable portions of the
population are exposed.
The minimum separations given in Figure 21 will reduce the effects of ozone destruction
at the surface or by NO emissions. The monitor should be away from obstacles and the inlet
should be away from vertical surfaces. An inlet height of 3 to 15 meters is suitable. In the
case of oxidant monitoring, it is very important to avoid low lying areas. Monitoring on a slight
rise or knoll has some advantage in helping to reduce ozone destruction by surrounding sur-
faces, especially during the late afternoon or evening hours. However, the importance of
minimizing these destructive effects may have to be weighed against a desire to monitor condi-
tions typical of those to which the population is exposed.
50
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6. RATIONALE FOR SITE SELECTION CRITERIA
6.1. Background
The following three problem areas must be addressed during the siting process:
1. A simple method must be devised to identify the meteorological conditions that are
conducive to photochemical activity.
2. A method must be devised to identify the regions where:
concentrations are near their maximum and where concentrations are typical of the
region of interest
concentrations of reactants can be measured that are important in subsequent photo-
chemical processes
public exposure to a criteria pollutant will be significant.
3. The specific characteristics of a monitoring site that will minimize local, non-
representative effects have to be determined.
This section describes the reasons for the recommendations given in the preceding sec-
tion. It attempts to solve the problems listed above. Each of the three major problem areas are
addressed separately.
6.2. Identification of Conditions Conducive to High Pollutant Concentrations
6.2.1. Conditions Conducive to Photochemical Activity
The essential ingredients for the photochemical formation of high concentrations of ozone
are:
* an accumulation of precursor emissions
* sunshine
* relatively little ozone removal.
The last item, relatively weak removal of ozone, depends more on location than xm
meteorological factors and will be discussed later.
Ozone data provide the best means of identifying the meteorological conditions during
past high ozone incidents, and hence the characteristic wind patterns that prevail during high
ozone days. If there are no ozone data, another approach must be taken to identify meteoro-
logical conditions likely to accompany high ozone concentrations. A practical approach must
use common meteorological data collected at airports and archived by the National Climatic
Center in Asheville, North Carolina. Meyer et al. (1976) compared ozone concentrations
observed during afternoons1 with conditions that the air had been exposed to along its trajec-
tory. The highest correlations were between ozone and air temperature during the last three
hours before arriving at the observing site. They-fqund correlation coefficients that ranged
from 0.37 to 0.71. The overall correlation, for all six sites and all 372 trajectories, was 0.52.
The temperature-ozone correlations found for urban sites were very similar to those found for
rural sites.
Ludwig, Reiter, et al. (1977), using a method of analysis similar to that used by Meyer et
al. (1976), obtained similar results. All their sites were rural2. The correlations between ozone
and temperature were based on 30 cases for each site and ranged from 0.57 to 0.81. The tem-
peratures used were the average of those observed during the last 12 hours of the trajectory.
The correlation for the combined data was 0.54. Price (1976), using only cases when the ozone
1 Stations used were Indianapolis, Indiana; Houston, Texas; Boston, Massachusetts; Poinette, Wisconsin;
McConnelsville, Ohio; and Dubois, Pennsylvania. The data were from the months of July and August 1974.
2 The stations used were McHenry, Maryland; Queeny, Missouri; Wooster, Ohio; and Yellowstone Lake,
Wisconsin.
51
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concentration exceeded ISO ppb, obtained a correlation of 0.27 between ozone concentration
and temperature (at the same hour and location). Presumably the correlation would have been
higher if the sample had included instances of lower ozone concentrations. No other variable
seems to provide as good a description of ozone concentration as temperature.
Figure 22 is a scattergram from Ludwig, Reiter, et al. (1977); joint occurrences of ozone
concentration and average temperature are marked by the asterisks. Where there were more
than one occurrence of the same combination of temperature and concentration, the number of
occurrences are plotted. The scattergram shows that in only two instances (of 120) did the
ozone concentration exceed the federal standard when the average temperature along the trajec-
tory during the preceding 12 hours remained below 70°F. There were only 13 cases when the
average temperature exceeded 75°F and ozone remained below the standard.
Seasonal variations in ozone concentration,also provide an approach to the determination
of meteorological conditions conducive to ozone formation. Ludwig, Simmon, et al. (1977)
prepared analyses of ozone concentrations in the eastern United States like that shown in Fig-
ure 23 for every day of the year 1974.. These analyses reveal those meteorological conditions
that accompany high ozone concentrations at different locations in the eastern United States.
The frequencies of ozone standard violations in different parts of the United States for each
month of the year are given in Table 10. The table shows that high ozone concentrations are
most frequent in the months of June, July and August. In some areas, more than two-thirds of
the days experienced violations of the federal ozone standard during the summer months so the
monthly wind roses for these locations should provide reasonable estimates of the wind direc-
tion associated with high ozone concentrations. The oxidant standard was violated at one or
more locations in the Los Angeles Basin for every day of July and August, 1975 (California Air
Resources Board, 1975). In the San Francisco Bay Area, about one-third of the days showed
violations somewhere in the area and in the San Joaquin Valley, the figure was over 80%.
Table 11 (from Ludwig, Reiter, et al., 1977) provides another means for identifying winds
that accompany high ozone concentrations. Light winds are frequent companions to high
ozone concentrations. This is consistent with other work (e.g. Price, 1976; Meyer et al., 1976)
that found high ozone concentration associated with weak pressure gradients and light winds.
Table 11 shows that southerly winds are frequently associated with high ozone concentrations in
several of the areas. :
6.2.2. Conditions Conducive to High Concentrations from Smokestack Emissions
In general, atmospheric instability mixes pollutants emitted from elevated stacks to the
ground before much dilution takes place and hence leads to high ground level concentrations;
however, this type of atmospheric behavior is usually short lived and the resulting concentra-
tions are short-term. Long-term average ground level concentratipns arising from stack emis-
sions are more likely to have the location of their maxima determined by those combinations of
meteorological conditions that are most frequent. The neutral stability class (see for example
Gilford, 1961) can occur at any hour of the;day, unlike the stable and unstable categories.
Therefore, the neutral class is the most commonly occurring stability. The most commonly
occurring combination of wind speed and wind direction for the neutral stability category will
often determine where the maximum long term average concentrations will occur at ground
level.
6.3. Identification of General Areas Suitable for Monitoring
6.3.1. Nonmethane Hydrocarbons and Oxides of Nitrogen
6.3.1.1. General Considerations
Ludwig and Kealoha (1975) have shown that most of the concentration of an inert pollu-
tant whose sources are near ground level come from sources within a few kilometers of the
52
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Table 10
MONTHLY FREQUENCY (1974) OF OXIDANT STANDARDS VIOLATIONS
IN VARIOUS REGIONS OF THE EASTERN U.S.
Florida
Peninsula
Texas -Louis iana
Gulf Coast
New England
Western Oklahoma,
Kansas, Nebraska
SE of Lakes Erie
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Table 11
WINDS REPORTED ON MORNING WEATHER MAP IN AREAS
WHERE PEAK-HOUR OZONE EXCEEDED 80 ppb
(No. of days from June through August)
Region
Florida Peninsula
Texas -Louis iana
Gulf Coast
New York-New
England
Western Oklahoma,
Kansas, Nebraska
SE of Lakes Erie
and Ontario
Washington -Phil-
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S or SW shore of
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Ohio River Valley
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56
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monitor. This fact underlies the suggestion that, the general areas for reactant oriented moni-
toring be chosen on the basis of emissions inventories. Concentrations in areas of typical emis-
sions will tend to be characteristic of the region as a whole. Figure 24b shows the distribution
of average NOX concentrations in the Los Angeles Basin for the year 1975; Figure 24d shows
the distribution of the 1 percentile values of daily peak hour NOX concentrations. This latter
representation shows the concentrations which were exceeded on only 3-4 days during the year.
In both instances there is an area of high concentrations that corresponds roughly to the most
populated part of the basin. The high values observed at the Lennox site in the southwest part
of the basin may be the result of that site's proximity to several major roadways and the Los
Angeles International Airport (see for example Perkins, 1973). The figures support the
assumption that the concentrations are distributed roughly hi accordance with the emissions dis-
tribution.
The displacements of concentration relative to emissions can be related to transport by
winds. Figure 25 shows typical afternoon and early morning air flow patterns in the Los
Angeles Basin (Los Angeles Air Pollution Control District, 1974). The NOX patterns are dis-
tended to the east and to the northwest, more or less along the streamlines shown in Figure
25a. The air flow patterns shown in the figure are much the same in summer and winter, but
with differences in strength. In the summer, the afternoon wind speeds typically reach 7 or 8
m s"1; in the winter about 5 m s"1. The nighttime pattern shown in Figure 25b has stronger
winds in winter, 2 to 5 m s"1, than in the summer, 2 to 3 m s"1. When monitoring products,
consideration must be given to the delay that takes place between the emission of the reactants
and the formation of the products. This delay will separate the location of the maximum pro-
duct concentration from the location of the maximum reactant emissions. In the case of
ozone, the separation may be quite large. In the case of NO2, the time that it takes to form
from the originally emitted NO can be quite short if local ozone concentrations are high or
longer if ozone concentrations are low.
6.3.1.2. Location of Areas of High Concentrations
It is apparent from the above discussion that there are three different conditions that lead
to high NO2 concentrations. The first of these causes high NO2 concentrations in the vicinity
of an area of strong NO emissions when ozone concentrations are high and winds are nearly
stagnant. The second condition occurs when ozone concentrations are high (so that rapid
transformation occurs from NO to NO2 before much dilution occurs) and the winds are appreci-
able so that the NO2 maximum is displaced downwind slightly from the NO emissions. The
third condition leading to high NO2 concentrations would be stagnation with little ozone
present. The emitted NO could accumulate for long periods of time and gradually undergo the
oxidation to NO2. In this case, the NO2 maximum would be found near the area of major
emissions.
Under all three conditions, the separation between maximum concentration and max-
imum emission will be small. When the air is nearly stagnant the products cannot travel far
from the emissions regardless of the speed of the reaction. When large amounts of ozone are
present, the reactions proceed quickly so that NO2 is formed before the air has had time to
move very far from the sources. Figure 24a illustrates this effect. The distribution of average
NO2 concentrations is shown for the year 1975 in the Los Angeles Basin. It is evident that the
maximum average NO2 concentrations tend be displaced from the center of the city in the
direction of the afternoon streamlines. This suggests that the location of average daily max-
imum NO2 concentrations is usually displaced somewhat from the major source areas. How-
ever, Figure 24c shows the distribution of the one percentile daily maximum concentrations
and they are nearly centered on the downtown Los Angeles area. This suggests that stagnation
or the rapid transformation of NO 'u NO2 are quite important in producing very high
concentrations of NO2, but less so in determining the location of average concentrations.
57
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There is evidence of similar behavior in the San Francisco Bay area, although the density
of NO2 and NO data is not entirely adequate to document the effect. Figure 26 shows the
1975 average N&2 concentrations and the 1975 one percentile peak hour NO2 values. The
highest concentrations occur in the populated areas around the edge of the Bay. The fact that
the San Francisco concentrations are somewhat less and the San Jose concentrations are some-
what more than in the other populated areas around the Bay is probably a reflection of the
differences in wind speeds, or ventilation, at these sites. San Francisco is subject to strong
winds blowing through the Golden Gate while San Jose tends to have lighter winds than some
of the other locations. Furthermore, as the typical flow patterns in Figure 27 indicate, pollu-
tion emitted elsewhere in the Bay area is transported to San Jose and provides an elevated back-
ground concentration to which local contributions are added. Differences between the average
NOj concentrations for 1975 and the one percentile peak hour concentration values are not as
evident as they are in the Los Angeles example. The Bay Area average concentrations and high
percentile concentrations both are confined to the high emissions areas, with some distortion of
the patterns along the typical streamlines.
Figure 28 shows the annual average NO2 concentrations in southwest Ohio. The prevail-
ing wind in this area is from the southwest (National Oceanic and Atmospheric Administration,
1968). The wind effects are evident in the figure; the concentrations increase rapidly as the city
of Dayton is approached from the southwest and the patterns are distended to the northeast,
downwind of the city. The pattern supports the observation that maximum long-term average
NO2 concentrations tend to be displaced in the downwind direction from areas of maximum
emissions. Probably not all of the distortion in the pattern in Figure 28 is due to the wind; at
least part may be the result of emissions in the vicinity of Wright-Patterson Air Force Base.
The distributions of 24-hour average NO2 concentrations in southwestern Ohio were
analyzed for 12 different days in 1974. In general, when the concentrations were relatively low,
the patterns tended to be elongated in the direction of the wind. Of the days examined, the
highest concentrations occurred on October 2, shown in Figure 29. The weather map and the
ozone distribution for this day in the eastern United States are shown in Figure 30. The high
pressure area to the west of Ohio moved eastward over Ohio on the following day. The near
stagnation conditions associated with the high pressure area allowed NO emissions to accumu-
late and caused the widespread high NO2 concentrations shown in Figure 29.
Up to this point the discussion has focused on the distribution of NO and NO2 in space.
There are other approaches to the interpretation of the data. A volume of air can be followed
and the changes in concentration of various pollutants with time within that volume can be
related to the emissions entering the volume. This approach has been applied in the San Fran-
cisco Bay Area. Figure 31 shows 20 of the 31 trajectories, based on surface winds, that were
used for the analyses. The numbers at the end of the trajectories indicate the time of arrival at
that point. The points along the trajectories show the location at one hour intervals. Ludwig
and Kealoha (1974) describe the methods used in developing the analyses. Concentrations of
oxidant and NO2 along the trajectory were determined from isopleth analyses of the hourly
values observed at the various monitoring locations in the area. The trajectories end at the
time of maximum concentration at their terminous. In only one of the 31 trajectories studied
did the maximum NO2 and oxidant concentrations occur at the same time. In the remaining
cases the oxidant concentration reached its peak 1 to 6 hours after the NO2 concentration. The
typical time lag was about 2 to 3 hours showing that the NO2 maxima are upwind of the oxidant
maxima.
The trajectory analyses also showed that the changes in NO2 concentrations generally
lagged behind changes in NO emission rates by periods of about 2 hours or less. Figures 32
and 33 provide two examples of this behavior. The figures show the changes in concentration
of N02 and ozone near ground level as the air moved along the path shown in the upper half of
the figure. The changes in the emissions of NO and hydrocarbons are also shown. The units
of the emissions are meters per minute. These seemingly anomolous units for emissions are
60
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SOURCE: Smalloy 1957
FIGURE 27 MOST COMMON DAYTIME AIRFLOW PATTERNS IN THE SAN FRANCISCO BAY AREA
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FIGURE 31 SOME AIR TRAJECTORIES IN THE SAN FRANCISCO BAY AREA, JULY 2, 1970
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convenient for some modeling purposes. They can be interpreted as follows--if the emissions
for one minute are introduced into the atmosphere at the surface without mixing, their depth
would be that shown in the graph. Remembering that one g-mole occupies about 23 liters, the
units can be interpreted in terms of g-mol m'2 min'1--ohe mole m'2 min"1 equals about 23000
.
''.: The above results suggest that during the day, NO2 maxima are found downwind of major
emissions sources at distances typically travelled by the air in one or two hours. Since the tra-
jectories cover only daytime conditions with significant ozone buildup, the. results are not to be
generalized too much. The results do suggest that even under conditions that are favorable for
the conversion of NO emissions to NO2 concentrations, the conversion can require a few
Hours, which can translate into important spatial separations.
6.3.2. Oxidants.
6.3.2.1. General Considerations
It was stated earlier that maximum oxidant concentrations should be found about 5 to 7
hours travel time downwind (for conditions most conducive to oxidant formation) of the
upwind edge of the metropolitan area. If the region identified in this way is within the area of
major emissions, then the likely places for high ozone concentration will be just beyond the
downwind edge of the major emissions area. The assumptions underlying the suggestion are as
follows: ;
maximum oxidant concentrations are most likely to accompany large accumulations of
precursor emissions.
Large accumulations of precursor emissions are most likely in air that travels across the
entire emitting region, especially during the morning rush hour.
- Maximum oxidant concentrations are reached in the early to middle afternoon, after the
morning rush hour emissions have been traveling 5 to 7 hours. ,
Emissions of NO within the metropolitan area will destroy ozone near ground level and
keep the concentrations below their maxima. .
The recommendations for selecting areas of probable oxidant maxima are applicable to
relatively large urban areas. For small areas, lateral mixing of clean air into the urban "plume"
is apt to reduce both precursor and oxidant concentrations so that maximum oxidant concentra-
tions will occur closer to the city than predicted. In large sprawling metropolitan areas there
, may be "islands" of low NO emissions; 'these islands may then be the locations of maximum
oxidant concentration, rather than the downwind edge of the metropolitan area.
The following sections present evidence to support the recommendations. Examples of
ozone maxima in several geographical areas are presented. Finally, evidence of ozone destruc-
tion by urban NO emissions is given.
; I - '• ..
6.3.2.2. The Transport of Ozone and the Location of Concentration Maxima
Figure 34 shows the buildup of ozone and NO2 concentrations in a parcel of air that was
over San Francisco during the morning rush hour. The figure shows very high hydrocarbon
and NO emissions between 6 and 8 A.M. (PST) and lower emissions during the rest of the tra-
jectory. The NO2 concentrations rose to their maximum by about 1100. Oxidant levels
remained quite low until about that time and then they rose to their peak concentrations at
around 1400. Two more examples are given in Figures 35 and 36. In the first of these, the
emissions were relatively high between 0600 and 0800 A.M. and then fell as in the preceding
example. However, they rose again and remained high, rising sharply during the last half hour
of the trajectory. The increased emissions near the end of the trajectory tended to truncate the
increasing ozone concentrations. In the example shown in Figure 36, emissions were relatively
high throughout, rising to a peak at the next-to-last hour (1400) and then falling. Oxidant con-
centrations continued to rise from early morning through the early to middle afternoon. A rise
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in oxidant concentration occurred when the major precursor emissions were confined mostly to
the early part of the trajectory (Figure 34) and also for cases when precursor emissions were
strong throughout the course of the air movement (Figures 35 and 36).
The trajectory analyses confirm that ozone concentrations tend to increase with time until
early- to mid-afternoon and that the highest concentrations are likely to be found 5 to 7 hours
downwind of the major emissions centers; the time interval represents the time between the
morning rush hour emissions and early afternoon. The NO emissions within the city tend to
retard the buildup of ozone so that in very, large regions, such as the San Francisco Bay Area or
the Los Angeles Basin, we would expect to find the ozone maxima just beyond the areas of
major NO emissions. Figure 37 shows the frequency of oxidant standards violations in the Bay
Area. It is clear from this figure that the most frequent violations occur at the southern and
eastern edges of the metropolitan area, as expected. To the northeast, the maximum frequency
of .violations occurs well beyond the city, towards Sacramento. This may reflect the generally
higher wind speeds through the Delta area and into the Central Valley. These higher wind
speeds will carry the precursors beyond the urban area before maximum formation of oxidants
occurs.
Figure 38 shows the 1-percentile peak-hour oxidant readings for the Los Angeles area for
1975. The maxima are along the downwind edge of the city. There is also a ridge of high
values extending to the east-southeast, probably reflecting the general transport of air from the
Los Angeles Basin out into the desert regions. Figure 38 shows that the maximum ozone con-
centrations may occur near the downwind edge of a large metropolitan area, but important
effects from that metropolitan area may extend well beyond the area of maximum concentra-
tion. This is observed in other areas as well as Los Angeles. The effects of the New York
Metropolitan area on surrounding areas have been studied by Cleveland et al. (1975). They
compared maximum daily ozone concentrations measured during the summer of 1974 at
numerous New England monitoring sites with the wind directions during the same day and
showed that the highest ozone concentrations occurred with wind directions from New York.
Even Boston^ nearly 300 km from New York, showed the effect. They only considered days
with well defined wind directions and temperatures above 70°F at Hartford, Connecticut.
Ludwig and Shelar (1977) also examined the distribution of ozone concentrations in the
New England area. Figure 39, shows the observed maximum hour average ozone concentra-
tions at seven sites during the period from July 15 to August 31, 1975. The sites are arranged
from bottom to top in order of increasing distance from New York City—ranging from
Bridgeport at about 80 km to Boston at about 300 km. An asterisk represents one observation;
a numeral represents multiple cases. Weekend values are plotted above the weekday values.
The tendency toward decreasing ozone concentrations with increasing distance from New York
is apparent. The Spearman rank correlation (Langley, 1970) between the upper decile ozone
concentrations and the distance from New York shows a negative correlation, significant at the
3 percent level. Upper decile values were chosen because the effect should be greatest for the
high ozone cases.
Ludwig and Shelar (1977) examined the data from the Northeast Oxidant Study (Siple et
al., 1976; Spicer, et al., 1976; Washington State University, 1976; Wolff et al., 1975) and found
evidence of ozone "plumes" from urban areas. Figure 40 shows the distribution ozone concen-
trations on August 10, 1975. This was a day of weak pressure gradients with light winds in the
southern New England area. The observed pressure gradients should have caused general sur-
face airflow from west or west-southwest. The winds at 850 mb (approximately 1500 m alti-
tude) shifted during the day from west-northwest to west-southwest. Thus, the pollutants from
the urban areas should have traveled east or east-northeast during the day. As Figure 40
shows, concentrations exceeded 150 ppb along the south coast of Connecticut. Although the
lack of data from eastern Long Island prevents confirmation, it appears that the highest concen-
tration probably occurred over Long Island or Long Island Sound. The hours during which the
highest values were observed along the Connecticut coast were in the early afternoon, around
1300 or 1400 EST. Figure 40 shows the ozone distribution in a vertical plane, along a line that
73
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122°
-39°
37l-
FIGURE 37 PERCENTAGE OF DAYS (1970 - 1972) IN THE SAN FRANCISCO BAY AREA
WHEN ONE OR MORE HOURS EQUALED OR EXCEEDED THE FEDERAL
1-HOUR AVERAGE Ox STANDARD OF 0.08 ppm
74
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\k
LONG ~~ ^^— ^ GREAT
ISLAND BRIDGEPORT WARREN HARRINGTON
1200 1220 EST
!D
0)
01
M-J
6000
5000
4000
3000
2000
1000
0
03 CONTOURS IN ppb
100
140
FIGURE 40 VERTICAL CROSS SECTION OF OZONE CONCENTRATION OVER
WESTERN CONNECTICUT AND LONG ISLAND, 1110-1220 EST,
AUGUST 10, 1975
77
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is nearly north-south. The analysis shows that above Bridgeport, Connecticut the highest con-
centrations were at an altitude of about 300 m. This elevated plume may have been the result
of the difference in chemical reactions between ground level and more elevated layers. At
ground level the ozone-producing reactions are partially offset by competing ozone-destroying
reactions. In particular, NO released near ground level will quickly combine with the ozone.
Eventually the NO2 produced by this reaction results in increased ozone, but on the shorter
term, the net result is a reduction in ozone concentrations near ground level.
Figure 41 shows two cross sections later, the same day. It also shows the streamlines for
the 850 mb winds at 1900 EST. The cross sections are based on data collected between 1545
and 1715 EST. These analyses show an elevated ozone layer above Bridgeport, Connecticut,
where concentrations, exceeded 180 ppb. Over western Long Island Sound they exceeded 140
ppb. If the 850 mb streamlines represent the air motions affecting the ozone transport around
this time, then the air that passed over Bridgeport also passed over Groton. If that were the
case, the two cross sections indicate a decline in the ozone concentrations from values above
180 ppb to about 125 ppb. At the south end of the cross section, just south of the east end of
Long Island, there were very high concentrations aloft—in excess of 230 ppb. The air reaching
this area had passed over the Newark and Jersey City regions of New Jersey, then over the
south tip of Manhattan and the Queens-Brooklyn areas. The high ozone concentrations aloft
seejtn very likely to have had their genesis in emissions from those upstream regions.
The cross sections shown in Figures 40 and 41, and numerous others, suggest that the
ozone producing processes proceed through a rather deep layer above the city. At the lower
levels ozone may be destroyed by NO and other processes at the surface, but once the plume
passes beyond the edge of the city, mixing processes bring high concentrations down to the sur-
face from aloft. This appears to account for the fact that the high ozone concentrations, at least
in very large urban areas, occur at ground level very near the downwind edge of the city.
Beyond that point lateral spreading and vertical mixing in combination with destruction at the
surface offset the reduced production rates.
Other examples of the buildup of ozone downwind of cities are available. The California
Air Resources Board (ARB, 1977) found, in a study conducted at Fresno, California during
episode-level days, that there were higher ozone values on the downwind edge of the city than
in air entering the city. Figure 42 shows their results as plots of the mean diurnal oxidant con-
centrations taken at the upwind edge, central business district, and downwind edge of Fresno.
The results show the gradient between upwind and downwind stations was most pronounced
during the early afternoon hours.
Westberg and Rasmussen (1973) measured ozone concentrations at about 300 m altitude
in the vicinity of Houston. Figures 43 and 44 give examples when ozone concentrations were
relatively high. The general wind direction is shown in the figures and the flight paths are indi-
cated by the hatched lines. Observed ozone concentrations, in ppb, are indicated at various
locations along the flight paths. These concentrations were used as the basis for the isopleth
analyses shown in the figures. The increase in ozone concentrations across the city from the
upwind to the downwind edge and beyond is apparent in both figures. The location of the max-
imum concentrations occurs between about 60 and 80 km downwind of the upwind edge of the
Houston area.
Martinez and Bach (1977) described ozone plumes downwind of smaller Texas source
areas, specifically the petrochemical complexes near Nederland and Port Arthur. In the case
that they studied, the maximum concentrations occurred about 75 km downwind of the source
area. At the wind speeds prevailing during the period of observation this represented about 3-
1/2 hours transport time. This is somewhat less than the 5 to 7 hours discussed earlier. How-
.ever, the time of the observation (1400 to 1800 local time) and the relatively small source areas
may have contributed to the maximum concentration occurring closer to the source than would
be the case for larger cities in the early afternoon.
The data collected by the 25 station St. Louis monitoring network of EPA's Regional Air
Pollution Study (RAPS) provide a good source of information for determining the location of
78
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12 +
10 +
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Source: California Air Resources Board, 1977
' ' ' '
FIGURE 42 MEAN DIURNAL OXIDANT PROFILES FOR SEVEN-DAY ADVERSE
PERIOD (OCTOBER 6-12, 1976) FOR UPWIND, CENTRAL BUSINESS
DISTRICT, AND DOWNWIND SITES AT FRESNO, CALIFORNIA
80
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40 30
DISTANCE FROM HOUSTON (MILES)
20 10 N 10 20 30
30-
20-
eo-
FIGURE 43 OZONE CONCENTRATIONS AT ABOUT 300 M IN THE HOUSTON AREA,
1300-1600 (CST) OCTOBER 8, 1973
81
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50
DISTANCE FROM HOUSTON (MILES)
20 10 N 10 20
160^140 100 ppb
60-,
FIGURE 44 OZONE CONCENTRATIONS AT ABOUT 300 m IN THE HOUSTON AREA,
1300-1600 (CST) OCTOBER 17, 1973
82
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oxidant maxima and the effects of NO emissions in a city. Objective analyses of ozone and
NO, concentration distributions were prepared by computer for the afternoon hours of 13 days
in 1976. The days were chosen because at least one of the monitoring stations observed ozone
concentrations of twice the standard, i.e. 160 ppb. Examples of these analyses are given in Fig-
ure 45 . The objective analysis procedure begins by interpolating concentration values for a
regularly spaced set of 361 grid points. These grid point values, obtained from the 25 irregu-
larly spaced monitoring sites, then provide the framework for generating computer isopleths of
pollutant concentration. The interpolation scheme uses the first-degree, least-squares fit of a
polynomial surface to the data from the 5 nearest observing stations, weighted inversely with
distance (Endlich and Mancuso, 1968; Mancuso and Endlich, 1973). The objective analyses
smooth the data somewhat. This is desirable for our purposes, where we are attempting to
locate general features of the distributions of the pollutants. The winds are represented in the
figures by vectors pointing in the direction in which the wind is blowing and centered on the
monitoring site. The length of a wind vector is proportional to the wind speed and shows the
distance that would be traveled in one hour at that speed. The winds show considerable varia-
tion in time and space. The ozone maximum occurred in the downwind direction in 9 of the 13
cases. In those 9 cases, the distance from the upwind edge of the city to the ozone maximum
varied from about 4 to 7 times the distance corresponding to one hour's air movement for the
typical noon wind. The maximum concentrations generally occurred in the early- to mid-
afternoon. In one instance the maximum ozone concentration appeared to be upwind of the
city, at least for the wind directions at the time of that maximum. However, there had been
considerable variation in wind direction through the day, so that the maximum may not have
been truly upwind.
The example shown in Figure 45 has the ozone maximum located in about the place
where it might have been expected on the basis of the high temperature wind rose for St.
Louis, given in Figure 16. This was not always the case. Comparably high concentrations were
found to the north, closer to the city and to the northeast. On one or two occasions, somewhat
lower ozone maxima were observed to the west of the city. On one occasion, to be discussed
later, higher concentrations were observed south of St. Louis. These exceptions to the rule do
not necessarily invalidate it, but they do suggest that a single monitor to locate the maximum
ozone concentrations is likely to be inadequate. Nevertheless, a station located according to the
rules given here would have observed concentrations near the maxima on many of those days
when the highest oxidant concentrations occurred.
6.3.2.3. Destruction of Ozone by Urban NO Emissions
Figure 45 illustrates the tendency for lower ozone concentrations to occur over the city.
At 1400 and 1600, there was a trough in the ozone concentration distribution over St. Louis,
while there was an increase toward the downwind direction, especially at 1400. On the other
hand, NO2 concentrations were highest near the downwind edge of the city for most of the
afternoon.
October 1 and 2, 1976, provide better examples of the destruction of ozone over the city.
Figure 46 shows the NO, NO-,, and ozone concentrations in the St. Louis vicinity for the after-
noon and early evening hours of October 1, a day of very light winds. Precursors and the
resulting ozone tended to accumulate near the city. At noon, virtually all of the NOX was
present as NO,; the figure shows no NO concentrations exceeded 2 pphm. The concentrations
of NO, were at a maximum over the city. The maximum ozone concentrations were observed
just outside the city to the northwest. For the next four hours the NO concentration remained
low while the NO2 and ozone patterns drifted very slowly toward the southeast. By 1800 the air
motion had reversed itself, carrying the NO2 and ozone accumulations back toward the city.
The NO concentrations rose sharply in the late afternoon and early evening in response to the
afternoon rush hour. The effect of the city was dramatically apparent at 1800. While NO and
NO, had their maxima nearly centered over the city, there is a deep minimum in the ozone
field over the city where it was generally less than 2 pphm. Just to the south, outside the city,
concentrations in excess of 20 pphm were observed. To the northeast, also outside the city,
83
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OZONE (pphm)
NO2 (pphm)
1200
CST
1400
? \
IS 16
1600
10 I:
(L//+ +
:// /
. \
22 I
A_
FIGURE 45 OZONE AND NO2 CONCENTRATION PATTERNS IN THE ST. LOUIS
AREA DURING THE AFTERNOON OF AUGUST 25, 1976
84
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concentrations in excess of the federal standard were found. Obviously, the monitoring of
maximum ozone concentrations will require a station outside the major urban emissions area.
Figure 47 shows that the NO concentrations remained very high over the city, throughout
the night. The concentrations of NO2 also remained high and were ^centered over the major
emissions area. Ozone concentrations at ground level were less than 2 -pphrn throughout most
of the area during the early morning hours. The accumulated NO remained in the area until
after sunrise. As shown in Figure 47 the NO concentrations had dropped to about 12 pphm by
0800 on this Saturday morning. By. 1000 (not shown in the figure), they were below 2 pphm,
where they remained throughout most of the day. Between 0800 and 1400 the winds were light
and variable but tended toward the northeast, carrying precursors with them. At 1400, the
maximum ozone concentrations were northeast of the city. Between 1400 and 1600 the light
winds tended to reverse themselves and carry the ozone back toward the city. The result was a
pattern similar to that observed the preceding afternoon. At 1800 the ozone concentrations
over the city itself were generally less than 2 pphm while those north and south of the city
reached 10 to 12 pphm. Again, the bite taken out of the ozone pattern by the NO emissions
provides considerable support to the recommendation that maximum ozone concentrations not
be sought within the urban area itself. .
6.4. Local Effects and the Selection of Specific Sites
The major types of site for the photochemical pollutants are supposed to represent large
areas. This means that the site should be selected so that it is in an area of small gradients and
that the readings are not affected by small changes in the location of the station. This criterion
will be met if the site is such that no single source contributes disproportionately to the read-
ings obtained there, but rather that the readings represent the sum of many small contributions
from"numerous individual sources. In the case of the photochemical pollutants, sinks can be as
important as sources. Wherever possible, we have tried to quantify the effect of sources and
sinks so that we could choose .some acceptable effect and then specify the conditions under
which that level would not be exceeded. If the reader disagrees with our choice of acceptable
level of influence, another can be chosen and the same methods applied to revise the siting cri-
teria accordingly.
6.4.1. Effects of Obstructions
The effects of obstructions and nearby surfaces may not be very important for hydrocar-
bon monitoring, but it is known that ozone, and perhaps the oxides of nitrogen, can be des-
troyed on contact with surfaces. It is important that sampling be done at a location where the
air has had as little contact with nearby surfaces as possible. Figure 48 is a schematic represen-
tation of airflow around a sharp edged building based on the work of Halitsky (1961), Briggs
(1973), and Gifford (1973). The figure shows that air in the cavity zone will make considerable
contact with the building. Air outside the cavity zone will have passed over the building with
minimal contact. It is assumed that the flow around other obstructions is similar to that shown
in Figure 48. According to Briggs (1973), the cavity zone extends to roughly 1-1/2 building
heights downwind of the building. Using this as a guide, we have recommended that the
sampler be separated from any obstruction by at least twice the height of the obstruction above
the inlet. Figure 48 also illustrates why it has been recommended that inlets along the side of a
building be avoided. There is airflow up the side of the building which has considerable contact
with the building and presents a substantial possibility for destruction of a fragile pollutant.
The inlet for sampling must extend above the roof of the building to avoid the compli-
cated airflow within the cavity zone. If the building housing the instruments is rather small, say
about 2 meters high, then an extension of the inlet above the roof by a distance of about 1-1/2
meters should be sufficient. For taller buildings it may not be possible to avoid the cavity zone
on top of the building without using an inlet line that is so long that it will introduce pollutant
losses of its own. If sampling from the top of a tall building cannot be avoided, then the wisest
course will be to place the inlet toward the upwind side of the building. Upwind again refers to
the wind direction for the most important photochemical conditions.
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CAVITY ZONE
SA-3400-1
FIGURE 48 SCHEMATIC REPRESENTATION OF THE AIRFLOW AROUND AN OBSTACLE
91
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6.4.2. Separation from Roadways - ,„,*, .. ,„„„,.,„, ..... ...... . . ,„
Streets and roadways are important sources of possible interference with the measurement
of pollutants. In the case of NMHC and total .oxides of nitrogen, they can be considered as
simple sources and their contributions can be evaluated' by father straightforward means. In the
case of NO2 and ozone, the effects are more complicated. Ozone will be removed by the NO
emitted along roadways and hence the roadway will act as a sink. At the same time, that the NO
is reacting to remove ozone, it is also being transformed into NO2. In the following sections
the magnitude of the effects are estimated and related to the separation between roadways and
monitors.
f. • .
6.4.2.1. Nonmethane Hydrocarbons
Figure 49, from Dabberdt and Sandys (1976), shows the concentration normalized for
wind speed and emission-Tate, at different distances from a roadway, for different wind direc-
tions relative to that roadway. The figure was obtained by assuming an infinitely long section of
roadway and calculating the concentrations using, the HIWAY computer model (Zimmerman
and Thompson, 1975). The figure shows that there is a maximum concentration at each dis-
tance for rather small angles between the winr? and the roadway. Those maximum concentra-
tions can be combined with estimates of emission rate along the road and a minimum wind
speed to estimate the maximum concentrations likely to occur at a given distance from the
road. The slightly stable condition represented in Figure 49 will provide fairly conservative
(i.e. high) estimates of the roadway contribution.
Figure 50 was derived from Figure 49 and it shows the maximum concentrations to be
expected at different distances from a roadway for three different average daily traffic (ADT)
loadings. The figure was prepared assuming aim s^ wind speed (u), and emission rates (Q)
of 4 "g mi'1 for oxides of nitrogen and NMHC. Peak hour traffic was used to derive the figure;
it was assumed that peak hour traffic was equal to 10% of the ADT. It can be seen from Figure
50 that the maximum contribution from roadways can be kept below about 8 pphm, or about a
third of the 24 pphm standard, if the separations shown in Figure 8 are adhered to. If the
NMHC monitor were collocated with an NO/NO2 monitor, and the minimum setbacks specified
for those pollutants were followed, then according to Figure 50, the traffic contribution to
observed NMHC concentrations would only be increased to 9 or 10 pphm at worst. If attention
is paid to the direction of the roadway .relative to common wind directions, the effect of the
road can be further reduced.
6.4.2.2. Nitrogen Dioxide and Ozone
During the daytime there is a tendency for the concentrations of ozone, NO, and NO2 to
be in an equilibrium described by the following equation (see e.g., Calvert, 1976):
where the brackets indicate concentrations of the enclosed species and the constants, kl, k3,
refer respectively to the reactions rates of: (1) the photolytic decomposition of NO2 into atomic
oxygen and NO; and (2) the reaction of ozone with NO to form NO2 and molecular oxygen.
This equilibrium takes a minute or two to be established, so shorter term measurements in the
vicinity of NO sources will not usually satisfy the equation. However, the equilibrium provides
a good description over longer averaging periods. Figure 51 is a scatter diagram of the product
of [NO] and [O31 versus [NO21 at RAPS stations in St. Louis for hour averaged observations
(0900-1000 CST, on October 1, 1976). .The slope of the line of best fit is an estimate of the
ratio of kj/k3 for the hour. The slope is 6.96 pphm; the intercept is 0.50 pphm2~very nearly
92
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1.0
10
FIGURE 49
20 30 40 50 60 70 £1090100
ROADWAY/RECEPTOR SEPARATION — m
SOURCE: Dabberdt and Sandys, 1976
VALUES OFCu/Q (10-3m-1) FOR VARIOUS ROADWAY/RECEPTOR
SEPARATIONS AND WIND/ROADWAY ANGLES; INFINITE LINE SOURCE
93
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1000
100 —
ASSUMPTIONS: 1. PEAK-HOUR TRAFFIC EQUAL
10% OF ADT
2. SLIGHTLY STABLE ATMOSPHERE
3. INITIAL VERTICAL DISPERSION
EQUAL TO 1.5 m
4. EMISSION RATE EQUAL TO 4 g mile'1
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DISTANCE FROM HIGHWAY - m
FIGURE 50 MAXIMUM ROADWAY CONTRIBUTION TO CONCENTRATION AT
DIFFERENT DISTANCES
94
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zero. The correlation is better than 0.98. Assuming that k1 is constant throughout the area, an
assumption which implies uniform insolation over , the area, the validity of the equilibrium
assumption for hour-average data seems well established. Hours other than that shown in Fig-
ure 51 were tested with generally similar results; however, when NO concentratidns were too
low to be measured reliably, then the slope-and the ratio kj/k3-could not be determined very
well.
The equilibrium relationship provides a valuable tool for estimating the impact of NO
sources on ozone and NO2 concentrations during the daytime. If we also assume that any
increase in NO2 (ANO2) in the vicinity of an NO source is caused by the reaction of NO with
O3, then
A[03] -- A[M>2]
Finally, it can be assumed that all the NO introduced by a source will appear as either NO or
NO2 when equilibrium is established. For the shorter term effects occurring near an NO
source, the more complicated reactions leading to other nitrogen containing compounds are not
important.
The original, or upwind, state is described by the steady-state equation
[03]
, (N02]
[NO]
= C
[NOX] - [NO]
[NO]
where C = kj/k3 and tNOxl = [NO] + [NO21. The new condition after the introduction of
NO and the reestablishment of the steady state are:
.[N02]
2' new
[NO],
A[M?2]
[NO]
- A[M?2]
The net changes in lO3l and [NO21, i.e. A [O31 and A[NO21 are numerically equal, but of oppo-
site sign. This is because we have assumed that the new NO2 all comes from the oxidation of
NO by O3. The changes in O3 and NO2 concentration are of interest in assessing the effects on
the ambient concentrations of the NO added from the roadway. The following definition can
then be used:
Substituting from Equation (5) into Equation (4) and rearranging gives
X2 + {[03] + &[NOX] + [NO] + C}x + A[M?J.[03] = 0
6
Equation (6) is a simple quadratic equation that can be solved for X, i.e. the change in
ozone and NO2 concentrations. It requires knowledge of the amount of NO added--A [NOxl-of
95
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the original conditions—[O31, .[NO], and [NO21— and of the current value of kl so that C •«•=
kj/kg can be evaluated. In this model, the oxides of nitrogen are conservative, so relatively
simple methods can be used to assess the contribution of the roadway at various locations.
Once the change in NOX concentration, A [NO ], caused by the roadway is evaluated, for exam-
ple from Figure 50, then the effects on ozone and NO2 concentration can also be estimated.
The model discussed above assumes that the quasi-steady state condition prevails. The
reactions occur relatively quickly, but not so quickly that the steady state condition will always
be a valid assumption. However, the model is still useful for the purposes of evaluating road-
way effects on ozone and NO2 concentrations, because it provides a relatively conservative esti-
mate. The estimates provided by the model will generally be greater than the actual changes in
NO2 and ozone when the adjustment to the steady state condition is not complete.
Equation (6) .was solved and graphed for three values of initial ozone concentration, rang-
ing from 80 to 240 ppbfand four values of initial NO concentrations, 1, 30, 60 and 100 ppb.
Three values of kj/k3 were also considered. Figure 52 shows the results for two values of
kj/kj, 0.5 and 2. The change in ambient ozone concentration is plotted versus the change in
NO concentration when the NOV is added as NO.
A A ,
It is apparent from Figure 52 that when ambient NO concentrations are very low, the
introduction of large amounts of NOX will remove nearly all the ambient ozone, and cause a
corresponding increase in NO2 concentrations. For higher ambient NO concentrations, the
removal of ozone by added NO is still very pronounced, but not so large as when initial NO
concentrations are low. For nearly all the conditions, the reduction in ozone concentration is
approximately equal, numerically, to the amount of added NO when the added NO amounts
to less than about 50 ppb.
The fact that atmospheric ozone depletion (and NO2 augmentation) are approximately
equal to the added NOX concentrations, when the added NO is less than about 50 ppb, allows
Figure 50 to be used to estimate the setback that will be required in order to keep changes in
ozone caused by roadway emissions below an arbitrary level. Singh et al. (1977) have indicated
that ozone concentrations in remote locations are generally in the range from about 20 to 60
ppb. Using this as a guide, the effect of a street should probably be kept below about 40 to 50
ppb. The figure shows that under the worst conditions, the effects of a single street can be kept
below about 40 to 50 ppb if we are about 20 meters removed from small streets with an ADT
of about 1000 and about 250 m from a larger street with ADT of 10,000. However, the large
freeways with ADT of about 50,000 should be 4 km away if their effects on ozone
concentration are to be less than about 40-50 ppb. A requirement for such a large separation
between a monitor and a major roadway is impractical, but may not really be necessary, because
the ozone concentrations of greatest interest (peak-hour concentrations) are most likely to
occur in the early-to-mid-afternoon. During those hours the traffic on the roadway is less than
the 10% of ADT that was assumed in the preparation of Figure 50. Therefore, the influences
of the roadway would be correspondingly less and the required separations could be reduced to
a kilometer or two. The general areas in which the ozone monitors are to be located will usu-
ally be "outside the major urban region, where streets are likely to have lower traffic volumes
and be more widely spaced, Therefore, the requirements for ratherlarge separations between
an ozone monitor and nearby streets and highways will not be as stringent as they would be for
locating a monitor within a heavily populated region. Furthermore, the analyses of ozone con-
centrations in the heavily populated areas suggest that the heavy NO emissions throughout
those areas will already have reduced ozone concentrations to very low levels and thus have
placed a limit on the possible effects of any nearby NO sources.
6.4.3. The Importance of Topographical Features
It was recommended that an ozone monitor not be placed in a valley but that a location
on a knoll was preferable. This recommendation arises because of the destruction of ozone, that
takes place at the surface. In a valley cold air drainage and stable conditions, especially at
97
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tvight, will cause air to remain relatively stagnant and without vertical mixing. Under such con-
ditions the destructive processes at the surface will quickly deplete any ozone that is present
and the monitor will measure values that are less than is typical of the lower troposphere.
Singh et al. (1977) have analyzed data from remote locations and found that the destructive
processes at the surface are appreciable even when there are no NO sources nearby. Figure 53,
from their report, shows an example of this effect. That figure shows the average ozone con-
centration for different hours of the day at two locations in Colorado. These stations are
separated by less than 5 kilometers but station C-20 is in a valley about 200 meters below sta-
tion C-23. During the daytime, when vertical mixing is generally good, the two stations show
essentially the same average ozone concentrations However, at night when vertical mixing is
generally poor,1 the destructive processes in the valley reduce concentrations by about 10 to 15
ppb below those at the mountain station.
6.4.4. Height of Inlet
It is recommended that inlets for ozone, NO2, and NMHC monitoring be placed within a
limited range of height, 3 to 15 m. The height range should be limited in order to allow com-
parisons of data collected at different stations to be made in such a way that data differences
represent differences in the general pollutant concentration, rather than the effects of local
sources and vertical gradients. To a large extent, practical considerations dictate that a fairly
wide range of inlet heights be allowed in order to accomodate the special situations that will
inevitably be encountered. The monitoring of the photochemical pollutants will not generally
be concerned with local effects. All the siting criteria have been designed to provide measures
of rather large, well mixed air volumes. The long periods of time required for the formation of
ozone ensures that it will be reasonably homogeneous, so long as the setback recommendations
are observed and local sinks are avoided. The hydrocarbon and NO measurements are also
supposed to represent reasonably well mixed air masses so that vertical gradients should be
small as long as local sources are avoided. Nevertheless, the two ends of the range, 3 meters
and 15 meters, may serve somewhat different purposes. When the major objective of the mon-
itoring is related to public health, then the 3 meter height is preferred over the 15 meter height
because it is closer to the breathing level. Three meters is about as low as one can get and still
avoid vandalism of the inlet. Lower heights are also likely to present obstacles to pedestrians.
The upper end of the recommended height range, 15 meters, will provide samples that are
more nearly representative of the well mixed air volume. An inlet of 15 meters should be rea-
sonably well removed from the destructive processes at the surface. A higher inlet is also less
apt to be influenced by local traffic sources.
99
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REFERENCES
•».
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102
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Appendix A
BIBLIOGRAPHY
A literature review during the early phases of this project provided a collection of papers
and reports on topics related to the measurement and distribution of the concentrations of the
photochemical pollutants. The bibliography compiled during that literature review has been
arranged alphabetically and is given on the following pages.
A-l
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-------
BIBLIOGRAPHY
Achinger, W. C., and R. T. Shigehara, 1968: A Guide for Selected
Sampling Methods for Different Source Conditions, JAPCA,
18(9), pp. 606-609.
Akland, G. G., 1972: Design of Sampling Schedules, JAPCA, 22(4),
pp. 264-266.
Altshuller, A. P., 1966: An Evaluation of Techniques for the
Determination of the Photochemical Reactivity of Organic
Emissions, JAPCA. 16(5), pp. 257-260.
Altshuller, A. P., 1975: Evaluation of Oxidant Results at Camp
Sites in the United States, JAPCA, 25(1), pp. 19-24.
/
Altshuller, A. P., and J. J. Bufaline, 1971: Photochemical Aspects
of Air Pollution - A Review, Enc. Sci. Tech., 5(1), pp. 39-64.
Altshuller, A. P., W. A. Lonneman, and S. L. Kopczynski, 1973: Non-
Methane Hydrocarbon Air Quality Measurements, JAPCA, 23(7),
pp. 597-599.
Altshuller, A. P.,. G, C. Ortman, B. E. Saltzman, and R. E. Neliman,
1966: Continuing Monitoring of Methane and Other Hydrocarbons in
Urban Atmospheres, JAPCA, 16(2), pp. 87-91.
Amdur, M. 0., and Discussions by J. W* Clayton, Jr., 1969: Toxicologic
Appraisal of Particulate Matter, Oxides of Sulfur, and Sulfuric
Acid, JAPCA, 19(9), pp. 638-646.
Aschbacher, P. W., 1973: Air Pollution Research Needs:Livestock Production
Systems, JAPGA. 23(4), pp. 267-272.
Babcock, L. R., Jr., 1970: A Combined Pollution Index for Measurement of
Total'Air Pollution, JAPCA, 20(10), pp. 653-659.
Babcock, L. R. and N. L. Nagda, 1973: Cost Effectiveness of Emission
Control, JAPCA, 23(3), pp. 173-179.
Bayley, E., and A. Dockerty, 1972: Traffic Pollution of Urban Environ-
ments, J. Royal. Soc. Health, 92(1), pp. 6-11.
Beaton, J. L., J. B. Skog, tad E. C. Shirley, 1972: Traffic Information
Requirements for Estimates of Highway Impact on Air Quality,
Materials & Research. Department Air Quality Control Manual, Division
of Highways, State of California, 29 pp.
A-3
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Beaton, J. L., J. B. Skog, and E. C. Shirley, 1972: A Method for
Analyzing and Reporting Highway Impact on Air Quality, Materials
& Research Department Air Quality Manual, Division of Highways,
State of California, 30 pp.
Beaton, J. L., J. B. Skog, and A. J. Ranzieri, 1972: Motor Vehicle
Emission Factors for Estimates of Highway Impact on Air Quality,
Materials & Research Department Air Quality Manual, Division of
Highways, State of California, 58 pp.
Beaton, J. L., J. B. Skog, E. C. Shirley, and A. J. Ranzieri, 1972:
Meteorology and Its Influence on the Dispersion of Pollutants
from Highway Line Sources, Materials & Research Department Air
Quality Manual, Division of Highways, State of California, 159 pp.
Beaton, J. L., J. B. Skog, E. C. Shirley, and A. J. Ranzieri, 1972:
Mathematical Approach to Estimating Highway Impact on Air Quality,
Materials & Research Department Air Quality Manual, Division of
Highways, State of California, 65 pp.
Beaton, J. L., J. B. Skog, E. C, Shirley, and A. J. Ranzieri, 1972:
Mathematical Approach to Estimating Highway Impact on Air
Quality, Appendix, Materials & Research Department Air Quality
Manual, Division of Highways, State of California, 107 pp.
Beaton, J. L., J. B. Skog, E. C. Shirley and A. J. Ranzieri, 1972:
Analysis of Ambient Air Quality for Highway Projects, Materials
& Research Department Air Quality Manual, Division of Highways,
State of California, 105 pp.
Benarie, M. M., Letter to the Editor - The Effect of the Sample Variance
on the Field Evaluation of Air Pollution Monitoring Instruments,
Atm. Env., vol. 8, pp. 1203-1204.
Benedict, H. M., C. J. Miller, and J. S. Smith, 1973: Assessment of-
Economic Impact of Air Pollutants on Vegetation in the United States
1969 and 1971. Final Report,CRC Contract CAPA 2-69(1-71), National
Air Pollution Control Administration Contract CPA 70-16, Stanford
Research Institute, Menlo Park, California, 96 pp.
Benson, F. B., W. C. Nelson, V. A. Newill, J. E. Thompson, M. Terabe,
S. Oomichi, and M. Nagata, 1970: Relationships Between Air Quality
Measurement Methods in Japan and the United States - II - Suspended
Particular Matter, Atm. Env.. vol. 4, pp. 409-415.
Berry, B. J. L., et al, 1974: Land Use, Urban Form and Environmental
Quality, Dept. of Geography, U. of Chicago, for the Office of Res.
and Development, Environmental Protection Agency, 442 pp.
A-4
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Bisselle, C. A., S. H. Lubore, and R. P. Pikul, 1972: National
Environmental Indices: Air Quality and Outdoor Recreation, The
Mitre Corporation, McLean, Va., for the Council on Environmental
Quality, Washington, D. C., 262 pp.
Blomquist, E. T., 1966: Federal Activity in Developing Air Quality
Criteria, JAPCA, 16(10), pp. 530-531.
Breitenbach, E. P., and M. Shelef, 1973: Development of a Method for
the Analysis of .NO and NH by NO-Measuring Instruments, JAPCA.
23(2), pp. 128-131.
Bullock, J., and W. M. Lewis, 1968: The Influence of Traffic on
Atmospheric Pollution., Atmospheric Environment, vol. 2, pp. 517-534.
Calvert, S., 1971: Air Pollution Research Problems (TR-1 Research
Committee Survey Report No. 1.), JAPCA. 21(11), pp. 694-701.
Charlson, R. J., N. C. Ahlquist, H. Selvidge, and P. B. MacCready, Jr.,
1969: Monitoring of Atmospheric Aerosol Parameters with the
Integrating Nephelometer, JAPCA. 19(12), pp. 937-942.
Clifton, M., D. Kerridge, W. Moulds, J. Pemberton, and J. K. Donoghue,
1959: The Reliability of Air Pollution Measurements in Relation
to the Siting of Instruments, Int. J. Air Poll., vol. 2, pp. 188-197.
Cole, A. F., and M. Katz, 1966: Summer Ozone Concentrations on Southern
Ontario in Relation to Photochemical Aspects and Vegetation Damage,
JAPCA. 16(4), pp. 201-206.
Collis, R. T. H. (Team Leader), et. al., 1972: Regional Air Pollution
Study: A Prospectus--Part II-'-Research Plan, SRI Final Report, 278 pp.
Copley, Charles M. Jr., Division of Air Pollution Control, City of St. Louis,
Missouri and D,, A. Pecsok, Air Pollution Control, St. Louis, Missouri,
St. Louis Air Monitoring Network, 63rd Annual Meeting - APCA, St.
Louis, Mo.
Corn, M., R. W. Dunlap, L. A. Goldmuntz, and L. H. Rogers, 1975: Photochemical
Oxidants: Sources, Sinks and Strategies, JAPCA, 25(1), pp. 16-18.
Corning Laboratories, Inc., Procedure for Constructing a Sample Station
Network, Corning Laboratories, Inc. (formerly Doerfer Labs), Cedar
Falls, Iowa.
Dabberdt, W. F., and R. C. Sandys, and P. A. Buder, 1974: A Population
Exposure Index for Assessment of Air Quality Impact, SRI Project 3364,
Final Report, 43 pp.
A-5
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Dabberdt, W. F., R. C. Sandys, and P. A. Buder, 1974: Assessment of the
Air Quality Impact of Indirect Sources,. SRI Project 2947, Final
Report, 97 pp.
Daily, J. W., 1971: Los Angeles Gasoline Modification: Its.Potential
as an Air Pollution Control Measure, JAPCA. 21(2), pp. 76-80.
deKoning, H. W., and Z. Jegier, 1968: A Study of the Effects of Ozone
and Sulfur Dioxide on the Photosyntheses and Respiration of Euglena
Gracilis, Atmospheric Environment, vol. 2, pp. 321-326.
deKoning, H. W., and Z. Jegier, 1968: Short Communication - Quantitative
Relation Between Ozone Concentration and Reduction of Photosynthesis
of Euglene Gracilis, Atmospheric Environment, vol. 2, pp. 615-616.
Derham, R. L., G. Peterson, R. H. Sabersky, and F. H. Shair, 1974: On the
Relation Between the Indoor and Outdoor Concentrations of Nitrogen
Oxide's, •JAPCA, 24(2), pp. 158-161.
Derivent, R. G. and H. N. M. Stewart, 1973: Review Paper - Air Pollution
from the Oxides of Nitrogen in the United Kingdom, Atm. Env., vol. 7,
pp. 385-401.
t ;
Dimitriades, B., 1967: Determination of Nitrogen Oxides in Auto Exhaust,
JAPCA, 17(4), pp. 238-243.
Dittrich, T. R., and C. R. Cothern, 1971: Analysis of Trace Metal Parti-
culates in Atmospheric Samples Using X-Ray Fluorescence, JAPCA, 21(11),
pp. 716-719.
Drivas, P. J., and F. H. Shair, Probing the Air Flow within the Wake Down-
wind of a Building by Means of a Tracer Technique, Atm. Env., vol. 8,
pp. 1165-1175.
Drivas, P. J., and F. H. Shair, Dispersion of an Instantaneous Cross-Wind
Line Source of Tracer Released from an Urban Highway, Atm. Env.. vol. 8,
pp. 475-485.
Dugger, W. M. Jr., Jane Koukol, and R. L. Palmer,.1966: Physiological and
Biochemical Effects of Atmospheric Oxidants on Plant, JAPCO, 16(9),
pp. 467-471.
Elkus, B. E., and K. R. Wilson, .Air Basin Pollution Response Function:
The Weekend Effect, Dept. of Chem., U.C. San Diego, La Jolla, Ca.
Submitted to Science.
Environmental Instrumentation Group, Lawrence Berkeley Laboratory, Berkeley,
Calif., 1973: Instrumentation for Environmental Monitoring. NSF Grant
No. AG-271.
A-6
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Environmental Protection Agency, 1973: The National Air Quality
Program: Air Quality and Emissions Trends, Annual Report, Vol.
II, 350 pp.
Environmental Protection Agency, 1973: Monitoring and Air Quality
Trends Report, 1972 , EPA-450/1-73-004, Monitoring and Data
Analysis Division, Durham, N. Carolina, 218 pp.
EPA Announces Partial Results of Collaborative Test Measurements Program,
1974: JAPCA. 24(8), pp. 783.
Environmental Protection Agency sets National Air Quality Standards
for Sulfur Oxides, Particulate Matter, Carbon Monoxide, Photo-
chemical Oxidants, Nitrogen Oxides, and Hydrocarbons, JAPCA.
21(6), pp. 352-353.
Epstein, S. S., 1969: Introduction to Special Report on Toxicologic
and Epidemiologic Bases for Air Quality Criteria, JAPCA, 19(9),
pp. 629-630.
Eschenroeder, A. Q., G. W. Deleny, and R. J. Wakl, 1973: Field Pro-
gram Designs for Verifying Photochemical Diffusion Models. EPA-
R4-73-012, vol. C, APCA No. CR-3-273.
Everett, M. D., 1974: Roadside Air Pollution Hazards in Recreational
Land Use Planning, J. Am. Inst. of Planners. 40(2), pp. 83-89.
Fair, D. H., 1972: SAROAD Station Coding Manual, NACPA Pub. No.
APTD-0907, 140 pp.
Fara, G. M., A. Pagano, and G. Ziglio, 1973: Investigation of Pollution
from Motorized Traffic in the City of Milan, Minerva Medica, 64(5),
EPA Translation TR-265-74, pp. 254-271.
Fensterstock, J. C., J. A. Kurtzweg, and G. Ozolins, 1971: Reduction of
Air Pollution Potential Through Environmental Planning, JAPCA. 21(7),
pp. 395-399.
Gatz, D. F., 1975: Relative Contributions of Different Sources of Urban
Aerosols: Application of a New Estimation Method to Multiple Sites
in Chicago, Atm. Env.. vol. 9, pp. 1-18.
Georgii, H. W., E. Busch, and E. Weber, 1967: Investigation of the
Temporal and Spatial Distribution of the Immission Concentration
of Carbon Monoxide in Frankfurt/Main, Report No. 11 of the Institute
for Meteorology and Geophysics of the University of Frankfurt/Main
(Translation No. 0477, NAPCA).
A-7
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Gitchell, A., R. Simonaitis, and J. Heicklen, 1974: The Inhibition
of Photochemical Smog—1. Inhibition by Phenol, Benzaldehyde,
and Aniline, JAPCA, 24(4), pp. 357-361.
Glasson, W. A., and C. S. Tuesday, 1970: Hydrocarbon Reactivity and
the Kinetics of the Atmospheric Photooxidation of Nitric Oxide,
JAPCA, 20(4), pp. 239-243.
Gloria, H. R., G. Bradburn, R. F. Reinisch, J. N. Pitts, Jr., J. V.
Behar, and L. Zafonte, 1974: Airborne Survey of Major Air Basins
in California, JAPCA. 24(7), pp. 645-652.
Goetz, A., and R. Pueschel, 1967: Basic Mechanisms of Photochemical
Aerosol Formation, Atm. Env.. vol. 1, pp. 287-306.
Goldsmith, J. R. and J. A. Nadel, 1969: Experimental Exposure of
Human Subjects to Ozone, JAPCA. 19(5), pp. 329-330.
Greene, N. E., and J. H. Shaw, 1972: The Identification of Atmos-
pheric Nitric Oxide by a Spectroscopic Span, JAPCA, 22(6), pp.
468-470.
Hall, H. J., H. I. Fuller, and A. C. Stern, 1970: Foreign Profiles
in Air Pollution Control Activities: Special Sources of
Information, JAPCA, 20(11), pp. 753-755.
Hamburg, F. C., 1971: Some Basic Considerations in the Design of an
Air Pollution Monitoring System, JAPCA. 21(10), pp. 609-613.
Hamming, W. J., and R. D. MacPhee, 1967:* Relationship of Nitrogen
Oxides in Auto Exhausts to Eye Irritation—Further Results of
Chamber Studies, Atm. Env.. vol. 1, pp. 577-584.
Haskell, E. H., 1974: Land Use and the Environment: Public Policy
Issues, Environment Reporter. Monograph 20, 5(28), 32 pp.
Hawke, G. S., and D. Iverach, 1974: A Study of High Photochemical
Pollution Days.in Sydney, N.S.W., Atm. Env.. vol. 8, pp. 597-608.
Heck, W. W., 0. C. Taylor, and H. E. Heggestad, 1973: Air Pollution
Research Needs: Herbaceous and Ornamental Plants and Agriculturally
Generated Pollutants, JAPCA. 23(4), pp. 357-266.
Heggestad, J. E., 1969: Consideration of Air Quality Standards for
Vegetation with Respect to Ozone, JAPCA. 19(6), pp. 424-426.
Heitner, K. L., and J. E. Krier, 1974: An Approach to Air Quality
Management Standards, JAPCA. 24(11), pp. 1039-1043.
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Heller, A. N., J. J. Schueneman, and J. D. Williams, 1966: The Air
Resource Management Concept, JAPCA, 16(6), pp. 307-309.
Herrick, R. A., 1971: TR-2 Air Pollution Measurements Committee Looks
at EPA's Proposed Test Methods, JAPCA, 21(10), pp. 652-653.
Hill, A. C., 1971: Vegetation: A Sink for Atmospheric Pollutants,
JAPCA, 21(6), pp. 341-346.
Hill, C. A., S. Hill, C. Lamb, and T. W. Barrett, 1974: Sensitivity
of Native Desert Vegetation to SO and. to SO and NO Combined,
JAPCA, 24(2), pp. 153-157.
Hilborn, J., 1974: Atmospheric Sample Pumps -- A Possible Source of
Error in Total Hydrocarbon, Methane, and Carbon Monoxide Measure-
ment, JAPCA. 24(10), pp. 983-984.
Holzworth,. G. C., 1969: Large-Scale Weather Influences on Community
Air Pollution Potential in the United States, JAPCA, 19(4), pp.
248-254.
Iwasaki, K., S. Fukuoka, and T. Ohira, 1971: On the Results of
Continuous Measurements of Automobile Exhaust Gas in the Vicinity
of the Ushigome Yanagicho Intersection, Tokyoto Kogai Kenkysha
Kempo, vol. 2, pp. 62-67, EPA Translation TR-278-74.
Jaffe, L. S., 1967: Effects of Photochemical Air Pollution on Vegeta-
tion with Relation to Air Quality Requirements, JAPCA. 17(1),
pp. 38-42.
Johnson, W. B., Jr., 1969: Lidar Applications in Air Pollution
Research and Control, JAPCA, 19(3), pp. 176-180.
Kahn, H. D., 1973: Distribution of Air Pollutants (Note on),
JAPCA. 23(11), pp. 973.
Kamens, R. M. and A. C; Stern, 1973: Methane in Air Quality and
Automobile Exhaust Emission Standards, JAPCA. 23(7), pp. 592-596.
Kauper, Erwin K.,and Charlotte J. Hopper, 1965: The Utilization of
Optimum Meteorological Conditions for the Reduction of Los
Angeles Automotive Pollution, JAPCA. 15(5), pp. 210-213.
Kinosian, J. R., and D. Simeroth, 1973: The Distribution of CO and
Ox Concentrations in Urban Areas, Calif. Air Resources Board,
Div. of Technical Services.
Knox, J. B., 1974: Numerical Modeling of the Transport Diffusion and
Deposition of Pollutants for Regions and Extended Scales, JAPGO.
24(7), pp. 660-664.
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Knox, J. B., and R. Lange, 1974: Surface Air Pollutant Concentration
Frequency Distributions: Implications for Urban Modeling, JAPCA,
24(1), pp. 48-53.
Kopczynski, S. L., W. A. Lonneman,. T. Winfield, and R. Seila, 1975:
Gaseous Pollutants in St. Louis and Other Cities, JAPCA. 25(3),
pp. 251-255.
Kurtzweg, C. L., and J. A. Kurtzweg, 1973: Urban Planning and Air
Pollution Control: A Review of Selected Recent Research, Am.
Inst. of Planners J.. 39(2), pp. 82-92.
Kurtzweg, J. A., and D. W. Weig, 1969: 'Determining Air Pollution
Emissions from Transportation Systems, presented at: The
Applications of Computers to the Problems of an Urban Society,
New York, N.Y., U.S. Dept. ^f Health, Education and Welfare,
National Air Pollution Control Administration, Durham, North
Carolina.
Lamb, R. G., 1968: An Air Pollution Model at Los Angeles, A Master's
Thesis No. 2749, University of California, Los Angeles, Calif. 104 pp.
Lamb, R. G., and M. Neiburger, 1971: An Interim Version of a Generalized
Urban Air Pollution Model, Atm. Env.. vol. 5, pp. 239-264.
Larsen, R. I., 1969: A New Mathematical Model of Air Pollutant
Concentration, Averaging Time, and Frequency, JAPCA, 19(1), pp. 24-30.
Larsen, R. I., 1970: Relating Air Pollutant Effects to Concentration
and Control, JAPCA, 20(4), pp. 214-225.
Larsen, R. I., 1974: An Air Quality Data Analysis System for Inter-
relating Effects, Standards, and Needed Source Reductions--Part 2,
JAPCA, 24(6), pp. 551-558.
Larsen, R. I., C. E. Zimmer, D. A. Lynn, and K. G. Blemel, 1967: Analyz-
ing Air Pollutant Concentration and Dosage Data, JAPCA. 17(2),
pp. 85-93.
Leavitt, J. M., F. Pooler, Jr., and R. C. Wanta, 1957: Design and
Interim Meteorological Evaluation of a Community Network for
Meteorological and Air Quality Measurements, JAPCA, 7(3), pp. 211-215.
Leone, I. A., and E. Brennan, 1969: The Importance of Moisture in Ozone
Phytotoxicity, Atm. Env.. vol. 3, pp. 399-406.
Levaggi, D. A., W. Siu, and M. Feldstein, 1973: A New Method for Measur-
ing Average 24-Hour Nitrogen Dioxide Concentrations in the Atmosphere,
JAPCA. 23(1), pp. 30-33.
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Lillie, R. , 1972: Air Pollutants .Affecting the Performance of Domestic
Animals, A Literature Review, USDA Ag. Res. Service, Agriculture
Handbook No. 380.
Lord, H. C., D. W. Egan, F. L. Johnson, and L. D. .Mclntosh, 1974: Measure-
ment of Exhaust Emissions in Piston and Diesel Engines by Dispersive
Spectroscopy, .JAPCA, 24(2), pp. 136-139. . >
Ludwig, F. L., W. B. Johnson, and R. E. Inmat^ 1975: Air Quality Impact
Study for a Proposed Highway Widening Near Ojai^ Part 2: Projected
Impact, Final Report, California Dept. of Transportation Contract
J-7292, Stanford Research Institute, Menlo Park, California, in
preparation.
Ludwig, F. L., and J. H. S. Kealoha, 1974: Present and Prospective
San Francisco Bay Area Air Quality, Final Report for Wallace,
McHargj Roberts and Todd and the Metropolitan Transportation
Commission, Stanford Research Institute, Menlo Park, California, 110 pp.
Lutmer, R. F., K. A. Busch,, and P. L. DeLong, 1967: Effect of Nitric
Oxide, Nitrogen Dioxide^ or Ozone on Blood Carboxyhemoglobin
Concentration During Low-Level Carbon Monoxide Exposures, Atm. Env.,
vol. 1, pp. 45-48.
Lynn, D. A., and T. B. McMullen, 1966: Air Pollution in Six Major U.S.
Cities as Measured by the Continuous Air Monitoring Program, JAPCA,
16(4), pp. 186-190. • :. .......
Mage, D. T., J. Noghrey, 1972: True Atmospheric Pollutant Levels by Use
of Transfer Function for an Analyzer System, JAPCA. 22(2), pp. 115-118.
Mahoney, J. R., 1972: Fundamentals of Air Pollution Analysis for the
Planner, source unknown, typed manuscript, pp. 1-8.
Marchesani, V. J., T. Towers,'and H. C. Wohlers, 1970: Monor Sources
of Air Pollutant Emissions, JAPCA. 20(1) pp. 19-22.
Marcus, A. H., 1973: Air Pollutant Averaging Times: Notes on a
Statistical Model, Atm. Eriv.. vol. 7, pp. 265-270.
Martinez, J. R., R. A. Nordsieck, and A. Q. Eschenroder, 1973: Morning
Vehicle-Start Effects on Photochemical Smog, Env. Sci. Tech 7(10)
pp. 917-923. ~ " '
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Mason, D. V., G. Ozolins, and C. B. Morita, 1969: Sources and Air
Pollutant Emission Patterns in Major Metropolitan Areas, APCA #69-101,
Annual Meeting APCA, New York, N. Y.
Maynard, J. B., and W. N. Sanders, 1969: Determination of the Detailed
Hydrocarbon Composition and Potential Atmospheric Reactivity of
Full-Range Motor Gasolines, JAPCA, 19(7), pp. 505-510.
McCarroll, J., 1967: Measurements of Morbidity and Mortality Related to
Air Pollution, JAPCA, 17(4), pp. 203-209.
McCormick, R. A., 1971: Air Pollution in the Locality of Buildings, Phil.
Trans. Roy. Soc. Land. A., pp. 515-526.
McGuire, T., and K. E. Noll, 1971: Relationship Between Concentrations
of Atmospheric Pollutants and Averaging Time, Atm. Env., vol. 5, pp.
291-298.
McHugh, E. W., 1967: The Effect of Rapid Transit on San Francisco Bay
Air Quality, JAPCA, 17(5), pp. 277-279.
McKee, H. C., R. E. Childers, 0. Saenz, Jr., T. W. Stanley, and J. H.
Margeson, 1972: Collaborative Testing of Methods to Measure Air
Pollutants: I. The High-Volume Method for Suspended Particulate
Matter, JAPCA, 22(5), pp..342-347.
Megonnell, W. H., and S. Smith Griswold, 1966: Federal Air Pollution
Prevention and Abatement Responsibilities and Operations, JAPCA,
16(10), pp. 526-529.
Milford, S. N., G. C. McCoyd, L. Aronowitz, J. H. Scanlon, and C. Simon,
1971: Developing a Practical Dispersion Model for an Air Quality
Region, JAPCA, 21(9), pp. 549-554.
Miller, P. R., M. H. McCutchan, and H. P. Milligan, 1972: Oxidant Air
Pollution in the Central Valley, Sierra Nevada Foothills, and
Mineral King Valley of California, Atm. Env., vol. 6, pp. 623-633.
Moore, G. E., M. Katz, and W. B. Drowley, 1966: Polynuclear Aromatic
Hydrocarbons in Urban Atmospheres in Ontario, JAPCA. 16(9), pp.
492-497.
Morgan, J. B., and C. Golden, and E. C. Tabor, 1967: New and Improved
Procedures for Gas Sampling and Analysis in the National Air Sampl-
ing Network, JAPCA, 17(5), pp. 300-304.
Mosher, J. C., W. G. MacBeth, M. J. Leonard, T. P. Mullins, and
M. F. Brunelle, 1970: The Distribution of Contaminants in
the Los Angeles Basin Resulting from Atmospheric Reactions
and Transport, JAPCA, 20(1), pp. 35-42.
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Mueller, P. K. , M. Hitchcock, and Discussion by R. C. Wands, 1969:
Air Quality Criteria—lexicological Appraisal for Oxidants,
Nitrogen Oxides, and Hydrocarbons, JAPGA. 19(9), pp. 670-678.
Munn, R. E.., and B. Bolin, 1971: Review Paper - Global Air Pollu-
tion - Meteorological Aspects, Atm. Env., vol. 5, pp. 363-402.
Munn, R. E., and I. M. Stewart, 1967: The Use of Meteorological
Towers in Urban Air Pollution Programs, JAPCA, 17(2), pp. 98-101.
Nader, J. S., 1973: Developments in Sampling and Analysis Instrument-
ation for Stationary Sources, JAPCA, 23(7), pp. 587-591.
National Air Pollution Control Administration, 1968: Report for
Consultation on the Washington, D. C., National Capital Interstate
Air Quality Control Region, U. S. Dept. of HEW.
National Air Pollution Control Administration, 1968: Report for
Consultation on the Metropolitan Los Angeles Air Quality Control
Region, U.S. Dept. of HEW.
National Air Pollution Control Administration, 1968: Report for
Consultation on the Metropolitan Boston Intrastate Air Quality
Control Region, U.S. Dept. of HEW.
National Air Pollution Control Administration, 1968: Report for
Consultation.on the San Francisco Bay Area Quality Control Region,
U.S. Dept. of HEW.
National Air Pollution Control Administration, 1969: Report for
Consultation on the Metropolitan Pittsburgh City Intrastate Air
Quality Control Region, U.S. Dept. of HEW.
National Air Pollution Control Administration, 1969: Report for
Consultation on'the Greater Metropolitan Cleveland Intrastate
Air Quality Control Region, U.S. Dept. of HEW.
National Air Pollution Control Administration, 1969: Report for
Consultation on the Metropolitan Kansas City Intrastate Air
Quality Control Region, U.S. Dept. of HEW.
National Air Pollution Control Administration, 1969: Report for
Consultation on the Metropolitan Baltimore Intrastate Air Quality
Control Region, U.S. Dept. of HEW.
National Air Pollution Control Administration, 1969: Report for
Consultation on the Hartford-Springfield Interstate Air Quality
Control Region (Connecticut-Massachusetts), U.S. Dept. of HEW.
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Nelson, C. J., C. M. Shy, T. English, C. R. Sharp, R. Andleman, L. Truppi,
and J. VanBruggen, 1973: Family Surveys of Irritation Systems During
Accute Air Pollution Exposures -.- 1970 Summer and 1971 Spring Studies
JAPCA. 23(2), pp. 81-90.
Neustadter, H. E., .and S. M. .Sidik, 1974: On Evaluating Compliance with
Air Pollution Levels "Not,to,be Exceeded .More Than Once a Year",
JAPCA. 24(6), pp. 559-563. _"
Ninomiya, J. S., and A. Golovoy,.1969: Effects of Air-Fuel Ratio on
Composition of Hydrocarbon Exhaust from Toluene, Toluene-n-Heptane
Mixture and Iso-octane, JAPCA, 19(5), pp. 342-346.
Nicholson, S. H., 1975: A Pollution Model for Street Level Air, Atm. Env
vol. 9, pp. 19-31. ,
NATO Committee on the Challenges of Modern Society, 1974: Control
Techniques for Hydrocarbon and Organic Solvent Emissions from
Stationary Sources, Pub 1. No. N. 19. .-.- ,
NATO Committee on the Challenges of Modern Society, 1974: Control
Techniques for Nitrogen Oxide Emissions from Stationary Sources,
Publ. No. N.20, '.',-''"•
NATO Committee on the Challenges of Modern Society, 1974: Air Quality
Criteria for Photochemical Oxidants and Related Hydrocarbons,
Publ. No. N. 29.
Oshima, R. J., 1974: A Viable System of Biological Indicators for
Monitoring Air Pollutants, JAPCA, 24(6), pp. 576-578.
Ott, W. R., 1974: Need for Adequate Monitoring Siting Criteria,
Manuscript, 6 pp. ,.''••
Ott, W. R., 1975: Development of Criteria for Siting Air Monitoring
, Stations, (draft) to be presented at the 68th Annual Meeting of
the APCA, Boston, Mass.
Ott, W., and R. Eliassen, 1973: A Survey Technique for Determining the
Representativeness.of Urban Air Monitoring Stations With Respect
to Carbon Monoxide, JAPO), 23(8), pp. 685-690,
Ott, W. R., and D. Mage, 1972: The Representativeness of Urban Air
Monitoring Stations With Respect to CO, Proceedings of the Second
Annual Environmental Engineering and Sciences Conf., Louisville,
Kentucky, pp.. 379-394.
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Ott, W. R. , and D. T. Mage, 1974: Trend Assessment o£ Air Quality-
Over Large Physical Areas by Random Sampling, presented at the
4th Annual Environmental Engineering and Science Conference,
Kentucky, pg. 19.
Ott, W. R., and D. T. Mage, 1974: A Method of Simulating the True
Human Exposure of Critical Population Groups to Air Pollutants,
presented at Int. Symp.: Recent Advances in the Assessment of
the Health Effects of Environmental Pollution, Paris, 11 pp.
Pack, M. R., and D. F. Adams, 1966: Problems of Relating Atmospheric
Analyses to Effect of Air Pollution on Agriculture, JAPCA. 16(4),
pp. 219-223.
Parker, W. R., and N. A. Huey, 1967: Multi-purpose Sequential Samplers,
JAPCA; 17(6), pp. 388-391.
Pedace, E. A., E. B. Sansone, 1972: The Relationship Between "Soiling
Index" and Suspended Particulate Matter Concentrations, JAPCA. 22(5),
pp. 348-351.
Perkins, N. M., 1973: Do Air Monitoring Station Data Represent the
Surrounding Community Exposure? Int. J. Biometeorology. vol. 17,
pp. 23-28.
Peterson, C. M., 1968: Measuring and Relating Atmospheric Pollution to
Meteorological Parameters, JAPCA. 18(10), pp. 654-656.
Pierrard, J. M., and Discussion by J. P. Lodge, Jr. and P. W. West, 1969:
Environmental Appraisal—Particulate Matter, Oxides of Sulfur, and
Sulfuric Acid, JAPCA. 19(9), pp. 632-637.
Pitts, J. N., Jr., and Discussion by R. D. Cadle, 1969: Environmental
Appraisal: Oxidants, Hydrocarbons, and Oxides of Nitrogen, JAPCA,
19(9), pp. 658-669.
Pooler, F., Jr., 1974: Network Requirements for the St. Louis Regional
Air Pollution Study, JAPCA. 24(3), pp. 228-231.
Public Damage Countermeasures Branch, Automotive Public Damage Subcommittee,
1971: A Survey of Environmental Pollution by Automotive Exhaust
Gases, Report No. 1, Pollution by GO, PDCB, Construction Division,
Nerima District, Tokyo, 51 pp.
Rasmussen, R. A.,. 1972: What Do the Hydrocarbons from Trees
Contribute to Air Pollution? JAPCA. 22(7), pp. 537-543.
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Reynolds, S. D., M. Lii, T. A. Hecht, P. M. Roth, and H. Seinfeld,
1974: Mathematical Modeling of Photochemical Air Pollution -
III. Evaluation of the Model, Atnu_Env., vol. 8, pp. 563-596.
Rich, S., and N. C. Turner, 1972: Importance of Moisture on
Stomatal Behavior of Plants Subjected to Ozone, JAPCA. 22(9),
pp. 718-721. ,-•
Ripperton, L. A., L. Kornreich, and J. J. B. Worth, 1970: Nitrogen
Dioxide in Non-Urban Air, JAPCA. 20(9), pp. 589-592.
Ripperton, L. A., and D. Lillian, 1971: The Effect of Water Vapor
on Ozone Synthesis in the Photo-Oxidation of Alpha-Pinene,
JAPCA. 21(10), pp. 629-635.
Robinson, E., and R. C. Robbins, 1957: Sources, Abundance, and Fate
of Gaseous Pollutants, Prep, for Amer. Petroleum Inst. Final
Report, Project PR-6755, Stanford Research Institute, Menlo
Park, California.
Robinson, E., and R. C. Robbins, 1970: Gaseous Nitrogen Compound
Pollutants from Urban and Natural Sources, JAPCA. 20(5),
pp. 303-306.
Romanovsky, J. C., R. M. Ingels, and R. J. Gordon, 1967: Estimation
of Smog Effects in the Hydrocarbon-Nitric Oxide System, JAPCA.
17(7), pp. 454-459.
Roth, P. M., P. J. W. Roberts, M. Liu, S. D. Reynolds, and J. H.
Seinfeld, 1974: Mathematical Modeling of Photochemical Air
Pollution - II. A Model and Inventory of Pollutant Emissions,
Atm. Env.. vol. 8, pp. 97-130.
Rubin, E. S., 1974: The Influence of Annual Meteorological Variations
on Regional ^Air Pollution Modeling: A Case Study of Allegheny
County, Pennsylvania,. JAPCA. 24(4), pp. 349-356.
Rust Engineering Co., The, and Applied Science Division, Litton
Industries, 1967: A Proposal for a System Engineering Study
of Metropolitan Air Pollution Control, JAPCA. 17(2), pp. 98-101.
Rydell, C. P., and G. Schwarz, 1968: Air Pollution and the Shape
of Urban Areas, J. Am. Inst. of Planners, pp. 50-51.
Salo, A. E., W. L. Oaks, amd D. R. MacPhee, 1975: Measuring the
Organic Carbon Content of Source Emissions for Air Pollution
Control, JAPCAg 25(4), pp. 390-393.
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Saltzman, B. E., 1968: Standardization of Methods for Measurement
of Air Pollutants, JAPCA.. 18(5), pp. 326-329.
Saltzman, B. E., 1970: Significance of Sampling Time in Air Monitor-
ing, JAPCA. 20(10), pp. 660-665.
Saltzman, B. E., 1972: Simplified Methods for Statistical Interpretation
of Monitoring Data, JAPCA, 22(2), pp. 90-95.
, Sandberg, J. S., and R, H. Thuillier, 1970: Oxidant Levels Over San
Francisco Bay and Adjacent Land Stations, JAPCA. 20(9), pp. 599-602.
Sandberg, J. S., R. Thuillier, and M. Feldstein, 1971: A Study of the
Oxidant Concentration Trends in the San Francisco Bay Area, JAPCA,
21(3), pp. 118-121.
Sandys, R. C., P. A. Buder, and W. F. Dabberdt, 1975: ISMAP--A Traffic
Emissions/Dispersion Mode for Mbbile Polluting Sources, User's
Manual, prepared for the California Business Properties, Inc.,
Hawthorne, California, Stanford Research Institute, Menlo Park,
California, in preparation.
Sauter, G. D., and W. R. Ott, 1974: A Computer Program for Projections
of Vehicular Pollutant Emissions in Urban Areas, JAPCA, 24(1),
pp. 54-59.
Savas, E. S., 1967: Computers in Urban Air Pollution Control Systems,
Socio-Economics Planning Sciences, 1(2), pp. 157-183.
Sawyer, R. F., 1970: Reducing Jet Pollution Before It Becomes Serious,
Astronautics and Aeronautics, pp. 62-67.
Schimmel, H., and L. Greenburg, 1972: A Study of the Relation of
Pollution to Mortality, New York City, 1963-1968, JAPCA, 22(8),
pp. 607-616. '
Schnelle, K. B., Jr., and R. D. Neeley, 1972: Transient and Frequency
Response of Air Quality Monitors. JAPCA, 22(7), pp. 551-555.
Schuck, E. L., A. P. Altshuller, D. S. Earth, and G. B. Morgan, 1970:
Relationship of Hydrocarbons to Oxidents in Ambient Atmospheres,
JAPCA. 20(5) pp. 297-302.
Schuck, E. A., and E. R. Stephens, and R. R. Schrock, 1966: Rate Constant
Ratios During Nitrogen Dioxide Photolysis, JAPCA, 16(12), pp. 695-696.
Schulze, R. H., 1973: 'The Economics of Environmental Quality Measure-
ment, JAPCA. 23(8), pp. 671-675.
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Searle, V. C., 1969: Technical Information Resources in the Air
Pollution Field, JAPCA, 19(3), pp. 137-141.
Seinfeld, J. H., 1972: Optimal Location of Pollutant Monitoring
Stations in an Air Shed, Atm. Env.. vol. 6, pp. 847-858.'
Seki, T., H. Hoshikawa, M. Suzuki, and T. Sugano, Air Pollution
at the Street Level Due to Automobile Exhaust in Sendai City,
(Report No. 5), EPA Translation TR-283-74, Sendaishi Eisei
Ken Kyshoho, pp. 210-216.
Senate Document No. 92, 1968: Progress in the Prevention and Control
of Air Pollution, 90th Congress, pg. 85.
Severs, R. K., 1975: Simultaneous Total Oxidant and Chemiluminescent
Ozone Measurements in Ambient Air, JAPCA. 25(4), pp. 394-396.
Shaw, J. T., 1967: The Measurement of Nitrogen Dioxide in the Air,
Atm.- Env., vol. 1, pp. 81-85.
Sheehy, J. P., W. C. Achinger, and R. A. Simon, 1969: Handbook of
Air Pollution, PHS Publ. No. 999-Ad-44, 231 pp.
Sinclair, D., 1967: A New Photometer for Aerosol Particle Size
Analysis, JAPCA. 17(2) pp. 105-108.
Sklarew, R. C., A. J. Fabrick, and J. E. Prager, 1972: Mathematical
Modeling of Photochemical Smog Using the PICK Method, JAPCA.
22(11), pp. 865-869.
Smil, V., 1975: Energy and Air Pollution: USA 1970-2020, JAPCA
25(3), pp. 233-236.
Smith, P. E., 1973: The Effects of Some Air Pollutants and Meteorological
Conditions on Airborne Algae and Protozoa, JAPCA. 23(10), pp. 876-880,
Souka, A., R. Marek, and L. Gnan, 1975: A New Approach to Roof Monitor
Particulate Sampling, JAPCA. 25(4), pp. 397-398.
South Coast Air Basin Coordinating Council, Air Monitoring Site
Criteria, Air Monitoring Committee, Tec. Advisory Committee, 10 pp.
Speizer, F. E., and Discussion by I. J. Selikoff, 1969: An Epidemiological
Appraisal of the Effects of Ambient Air*or Health: Particulates
and Oxides of Sulfur, JAPCA. 19(9), pp. 647-656.
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Spindt, R. S., 1967: Computer Analysis of the California Cycle,
JAPCA. 17(3), pp.. 166-167.
Stanford Research Institute, 1972: Regional Air Pollution Study:
A Prospectus, Part Ill-Research Facility, Final Report EPA
Contract 68-02-0207. Stanford Research Institute, Menlo Park,
California, 167 pp» : -,s; •/ -
•• . :• . - . - ' .• • J. :
Stanley, W. J., 1968: Air Resource Management in the City of Chicago,
Pollution Incident Control Plan, APCA, No. 68-56, presented at
61st Annual Meeting of APCA, St. Paul, Minn.
Stedman, D. H., E. E. Daby, F. Stuhl, and H.Niki, 1972: Analysis of
Ozone and Nitric Oxide by a Chemiluminescent Method in Laboratory
and Atmospheric Studies of Photochemical Smog, JAPCA, 22(4) pp. 260-263.
Stephens, E. R., 1969: Chemistry of Atmosphere Oxidants, JAPCA,
19(3), pp. 181-185. •.••-,'•.•."
Stephens, E. R., 1975: Chemistry and Meteorology in an Air Pollution
Episode. JAPCA, 25(5), pp. 521-524.'
Stephens, E. R., and F. R. Burleson, 1967: Analysis of the Atmosphere
for Light Hydrocarbons, JAPCA, 17(3), pp. 147-153.
Stephens, E. R., and F. R. Burleson, 1969: Distribution of Light
Hydrocarbons in Ambient Air, JAPCA, 19(12), pp. 929-936.
Stephens, E. R., and M. A. Price, 1969: Atmospheric Pjotochemical
Reactions in a Tube Flow Reactor, Atm. Env.. vol. 3, pp. 573-582.
' ' - • - ..' ^ • • '_-"' '- -(:•'-
Stern, A. C., 1973: Strengthening the Clean Air Act,fJAPCA, 23(12),
pp. 1019-1022.
Stuart, D. G., 1968: Planning for: Pedestrians4 J; Am. Inst. of
Planners, pp. 37-41.
Sweet, A. H., B. J. Steigerwald, and J. H. Ludwig, 1968: The Need
for a Pollution-Free Vehicle, National Center for Air Pollution
Control, JAPCA. 18(2).
TA-8 Meteorological Committee (APCA), 1968: Annotated.Bibliography
for Air Pollution Meteorology, JAPCA, 18(7), pp. 449-453.
TA-8 Meteorological Committee (APCA):, 1969: Note .oh the Design and
Location of'Air Sampling Devices, JAPCA. 19(10), p. 802.
A-19.
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Thompson, C. R., E. G. Hensel,and G. Kats, 1973: Outdoor-Indoor
Level of Six Air Pollutants, JAPCA. 23(10), pp. 881-886.
Tiao, G. C., G. E. P. Box, and W. J. Hamming, 1975: Analysis of
Los Angeles Photochemical Smog Data: A Statistical Overview,
JAPCA, 25(3), pp. 260-268.
Tokyo Metropolitan Government, Environmental Pollution Dept.,
Regulation Section, 1973: Results of Environmental Survey
of the Vicinity of the Itsukaichi Kaidoguchi Intersection
in Suginami Ward, EPA Translation TR-280-74.
TR-2 Air Pollution Measurements Committee, 1967:- Recommended
Standard Method for Atmospheric Sampling of Fine Particulate
Matter by Filter Media - High Volume Sampler, JAPCA, 17(1),
pp. 17-25.
Trorap and Sargent (Editors), 1964: A Survey of Human Biometeorology,
Tec. Note No. 65, WMO-No. 160.TP.78, Geneva, Switzerland, 109 pp.
U.S. Environmental Protection Agency, 1971: Air Quality Criteria
for Nitrogen Oxides, NAPCA Publ. No. AP-84.
U.S. Environmental Protection Agency, 1971: Air Quality Considerations
in Transportation and Urban Planning - A Five Year Program,
USEPA Publ. No. EPA-CPA 70-100.
U.S. Environmental Protection Agency, 1971: Guides for Short Term
Exposures of the Public to Air Pollutants. I. Guide for Oxides
of Nitrogen, USEPA Publ. No. 199-903.
U.S. Environmental Protection Agency, 1972: Transportation Controls
to Reduce Motor Vehicle Emissions in Salt Lake City, Utah, APTD Rep.
No. 1445.
U.S. Environmental Protection Agency, 1973: Cost of Air Pollution Damage
A Status Report, NAPCA Publ. No. AP-85.
U.S. Environemtnal Protection Agency, 1973: Investigation of High Ozone
Concentration in the Vicinity of Garrett County, Maryland and
Preston County, West Virginia, EPA-R4-73-019.
U.S. Public Health Service, 1966: Air Pollution - A National Sample,
USPHS Publ. No. 1562.
U.S. Public Health Service, 1968: A Compilation of Selected Air
Pollution Emission Control Regulations and Ordinances, USPHS Publ.
No. 999-AP-43.
A-20
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TJ.S. Public Health Service, 1970: Air Quality Criteria for Photo-
chemical Oxidants, NAPCA Publ. No. AP-63
U.S. Public Health Service, 1970: Air Quality Criteria for Hydro-
carbons, NAPCA Publ. No. AP-64.
U.S. Public Health Service, 1970: Air Pollution Injury to
Vegetation, NAPCA Publ.. No. AP-71.
U.S. Public Health Service, 1970: Nitrogen Oxides - An Annotated
Bibliography, NAPCA Publ. No. AP-72.
U.S. Public Health Service, 1970: Hydrocarbons and Air Pollution:
An Annotated Bibliography, Part I and Part II, NAPCA Publ. No.
AP-75.
Walthter, E. G., 1972: A Rating of the Major Air Pollutants and
Their Sources by Effect, JAPCA. 25(5), pp. 352-355.
Warner, P. 0., and L. Stevens, 1973: Revaluation of the "Chatta-
nooga School Children Study" in the Light of Other Contemporary
Governmental Studies: The Possible Impact of these Findings on
the Present NOn Air Quality Standard, JAPCA, 23(9), pp. 769-772.
2
Watanabe, H., and T. Nakadoi, 1966: Fluorophotometric Determination
of Trace Amounts of Atmospheric Ozone, JAPCA, 16(11), pp. 614-617.
Wayne, L. G., 1967: Eye Irritation as a Biological Indicator of
Photochemical Reactions in the Atmosphere, Atm. Env., vol. 1,
pp. 97-104.
Weedfall, R. 0., and B. Linsky, 1969: A Mesoclimatological Classi-
fication System for Air Pollution Engineers, JAPCA. 19(7),
pp. 511-513.
Weisman, B., D. H. Matheson, and M. Hirt, 1969: Air Pollution
Survey for Hamilton, Ontario, Atm. Env., vol. 3, pp. 11-23.
Wendell, R. E., J. E. Norco, and. K. G. Croke, 1973: Emission
Prediction and Control Strategy: Evaluation of Pollution from
Transportation Systems, JAPCA. 23(2), pp. 91-97.
Williams, J. D., J. R. Farmer., R. B. Stephenson, G. G. Evans, and
R. B. Dalton, 1968: Air Pollutant Emissions Related to Land Area-
A Basis for a Preventive Air Pollution Control Program,
NAPCA Publ. No. APTD-68-11.
A-21
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Willis, B. H., and J. R. Mahoney, 1972; Planning for Air Quality,
(Typed Manuscript — Paper Presented at Confer-In), Environ-
mental Research and Technology, Inc., Mass. 16 pp.
Wilson, W. E., Jr., E. L. Merryman, A. Levy, and H. R. Taliaferro,
1971: Aerosol Formation in Photochemical Smog: I. Effect of
Stirring, JAPCA. 21(3), pp. 128-132.
Wright, G. W., and Discussion by R. M. Albrecht, 1969: An Appraisal
of Epidemiological Data Concerning the Effect of Oxidants,
Nitrogen Dioxide and Hydrocarbons Upon Human Populations, JAPCA.
19(9), pp. 679-682.
Wronski, W., E. W. Anderson, A. E. Berry, A. P. Bernhart, arid H. A.
Belyea, 1966: Air Pollution Considerations in Planning and
Zoning of a Large, Rapidly Growing Municiplaity, JAPCA. 16(3),
pp. 157-158.
Yamada, V. M., 1970: Current Practices in Siting and Physical Design of
Continuous Air Monitoring Stations, JAPCA. 20(4), pp. 209-213.
A-22
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Appendix B
Program WINDROSE
Program WINDROSE calculates the frequency distribution of wind direction and speed
from standard National Climatic Center surface observation data. The program includes only
those winds which accompany temperatures above 80°F (26.7°C) and occur during the daylight
hours (0600 to 2000 LST).
WINDROSE was written for a CDC computer, but with a few modifications it can be
compatible for use with other machines. The program will read WBAN/WMO hourly surface
observations from tapes prepared by the National Climatic Center,. In addition to the data
tape, the only other user supplied input is a card indicating the year/month/day start and stop
dates of the data to be processed. The card format is 2F7.0.
B-l
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-------
TRACE
CDC 670O FTN V3.0-JS5F QPT-Q
C
c
C
c
c
c
c
2
3
4
5
6
7
8
<5
10
11
12
13
14
15
16
18
C
C
C
PROGRAM WNDRCSE (INPUT.OUTPUT»TAPE1.TAPt2)
WIND ROSE'PROGRAV - - - CALCULATES FREQUENCY DISTRIBUTION LiF WIND
SPEED VS WIND DIRECTIUNo PROGRAM WILL READ WBAN/WM'J HOURLY
SURFACE OUSERVATICN CARD IMAGE TAPES PREPARED dY THE NATIONAL
CLIMATIC CENTER, NOAA. USER MUST ENTER STAHT AND STOP DATES OF
DATA THAT IS TO BE. PROCESSED.
DIMENSION DAT(80).CAT(17,7),CLASS(6).ICLASC12). WNDIK< 17)
DIMENSION WSWD( 16.6)»NOC< 16}
DIMENSION TOTSPD(7),TOTDIR(17)
DATA { WNDJR=4HCALN-. 3HNNE.3H NE.3HENE,3H E ,3HESfc:,3H SE.3HSSE.3H S
2.3HSSW.3H S*.3HWSW,JH W 83HWNta,3H NVn. 3MNNW , 3H N )
DATA {ICLAS=1 , 2 , 2 , 3 » 3 » 4 , 4 , 5 , 5 , O . 6 ,7)
DATA (CLASS= 7H1.0-2•0,7H3•0-4.0,7H5•0-6.0,7H7.0-3•O•
1883.0-10.0,8H.GT.I 1 .0 )
FORMAT (1HI.25X*«IKO ROSES FOR ST. LOUIS FOR DU.SING *Fb.O* TQ*FS.O
FORMAT (/IH s*tCF. NO. =*I4)
FORMAT (/IH e*P.E. NO. =*I4)
FORMAT (/IN ,*REC. NO. =*I4>
FORMAT (2F7.0)
FORMAT <5X.FC.O»F2.0 )
FORMAT (8X,F2.0,F2«0«4X,A1,F2.0)
FORMAT (// ,30X*FREGUENCIES OF OCCURRENCES*//IH
1*6A10.3X*TOTAL*/)
FORMAT (IH ,2XA4,9X,7(F8.l.2X))
FORMAT (8A10)
FORMAT (IH ,8A10)
FORMAT (// ,30X*PtRCENTAG£ fJP OCCURRENCES*//IH * *DI RECT/C ATEGORY
l*6Ai0.3X,*TOTAL*/>
FORMAT
FORMAT (IH ,1€I5)
FORMAT (/IH ,*NC. CF CALM CBSERVAT IONS:*F7.I/)
FORMAT(/1X,*CCLUMN TOTAL*3X,7(F8.1.2X))
CALL MEMSETX (0 .0 .CAT.119) S NO8S = 0
READ START AND STOP DATES TC UE PROCESSED - FORMAT IS 2F7.0
READ 5.UDATE.EDATE
PRINT 1.8DATE.EDATE
, *D I RECT/CATtGORY
C
C
C
READ SURFACE OOS TAPE - WRITTEN FOR COC COMPUTER
100 BUFFER IN I 1
IF
110 NF=NF+1
PRINT 2,NF
GO TO 200
120 NP=NP+1
PRINT 3»NP
130 NR=NR*1
LEN=LENGTH(1)
CO 180 I=1»LEN
0) COATC1),DAT<80))
130,110.120
B~3
-------
WNDROSE
TRACE
CDC 6700 FTN V3.O-36SF OPT =
C
C
C
140
150
C
C
C
C
C
C
DECODE <13,6,OAT GO TO 150
TT=100.+TT
GO TO 150
TT=-TT
CONTINUE
CHECK FCR TEMPERATURE LESS THAN 80 DEG F
IF(TT.LT.80.) GO TC 180
CONVERT KIND SPEED UNITS
CAT( IWD, IC)=CAT{ IWD.IO + 1 .0 $ NOBS=NOfciS+l
CONTINUE
GO TC IOC
PRINT StCLASS
DO 201 I=2tl7
TOT=0.0
DO 202 L=2.7
TOT=CAT(ItL)+TCT
CONTINUE
TOTDIR(I)=TOT
CONTINUE
ATOT=0.
DO 203 L=2.7
TOT=0.0
DO 204 1=2,17
TOT=TOT+CAT
-------
WNDROSE
TRACE
CDC 6700-FTN V3.0-355F OPT-0 77/6
C
c
C
220
205
206
230
PRINT 16.CAT(1,1)
COMPUTE THE PERCENTAGE OF OCCURRENCES AT EACH DIRECTION
WIND SPEED CLASS. - .
DO 220 IW=2,17 ...
DO 220 IC=2,7 O: . J .,••-•
WS*D( IW-1 , IC-1 )=CAT( IW, IC)*100.0/NOBS '>
IF CCAT(JW, 1CJ.GT.0.0) NOC{IW-1 ) = 1C-1
CONTINUE
CALMA=CAT(1 . 1 )*100«0/NOBS
PRINT12.CUASS
DO 205 1 = 2,17 .,
TOTDIR(I)=TOTDIRC I )/NOBS*100.
DO 206 1=2,7
TOTSPD
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-450/3-78-013
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Site Selection for the Monitoring of Photochemical
Air Pollutants
5. REPORT DATE
April, 1978
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
F.L. Ludwig, and E. Shelar
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Stanford Research Institute
Menlo Park, CA 94025
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-02-2028
12. SPONSORING AGENCY NAME AND ADDRESS
OAQPS
Monitoring & Data Analysis Division
Research Triangle Park, N.C. 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final '
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16, ABSTRACT
Abstract enclosed within document.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS [c! COSATI Field/Group
8. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (ThisReport)'
Unclassified
21. NO. OF PAGES
126
2O. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-t (9-73)
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