EPA-600/3-76-017 .
February 1976 Ecological Research Series
PHOTOCHEMICAL 0X10ANTS IN THE
AMBIENT AIR OF THE UNITED STATES
Environmental Sciences Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
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2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to develop and
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environmental degradation from point and non-point sources of pollution. This
work provides the new or improved technology required for the control and
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EPA-600/3-76-017
February 1976
PHOTOCHEMICAL OXIDANTS IN THE AMBIENT
AIR OF THE UNITED STATES
BY
Basil Dimitriades
Environmental Sciences Research Laboratory
Research Triangle Park, North Carolina 27711
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
ENVIRONMENTAL SCIENCES RESEARCH LABORATORY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
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DISCLAIMER
This report has been reviewed by the Environmental Sciences
Research Laboratory, U.S. Environmental Protection Agency, and
approved for publication. Mention of trade names or commercial
products does not constitute endorsement or recommendation for
use.
n
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CONTENTS
Chapter Page
LIST OF FIGURES v
LIST OF TABLES viii
1. INTRODUCTION 1
References for Chapter 1 3
2. ATMOSPHERIC LEVELS AND VARIATION OF PHOTOCHEMICAL OXIDANTS 5
Introduction 5
Concentrations of Oxidants in Urban Atmospheres 5
Concentrations of Ozone in Urban Atmospheres 19
Concentrations of Peroxyacetyl Nitrate in Urban Atmospheres 21
Concentrations of Oxidants from Natural Sources 21
References for Chapter 2 24
3. CHEMISTRY OF OXIDANT FORMATION 27
Introduction 27
Mechanism of Oxidant Formation 27
Hydrocarbon Reactivity 34
Relationships Between Oxidant and Oxidant Precursors 43
References for Chapter 3 55
4. EFFECTS OF METEOROLOGICAL FACTORS ON OXIDANT FORMATION 59
Introduction 59
Effects of Sunlight 59
Effects of Temperature and Humidity 61
Transport Phenomena 61
Forecasting Techniques 63
References for Chapter 4 65
5. ADVERSE EFFECTS OF OXIDANTS 67
Toxicologic Effects . * 67
Epidemiological Appraisal of Oxidants 71
Correlation of Oxidant with Eye Irritation 73
Effects of Oxidants on Vegetation 77
Effects of Oxidants on Materials 79
References for Chapter 5 81
6. ATMOSPHERIC LEVELS AND VARIATION OF OXIDANT PRECURSORS AND RELATED
POLLUTANTS 83
Introduction 83
Concentrations of Hydrocarbons in Urban Atmospheres 83
Concentrations of Nitrogen Oxides in Urban Atmospheres 94
iii
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Chapter Page
Concentrations of Sulfur Oxides in Urban Atmospheres Ill
Concentrations of Aerosols in Urban Atmospheres 119
References for Chapter 6 124
7. EMISSIONS OF OXIDANT PRECURSORS 129
Introduction 129
Nationwide Emissions 129
South Coast Air Basin Emissions , 133
References for Chapter 7 137
8. RELATIONSHIPS BETWEEN AIR QUALITY AND EMISSIONS 139
Introduction 139
Rollback Models 139
Other Models and Methods 142
Calculation of Control Requirements 143
References for Chapter 8 145
9. NATIONAL AND REGIONAL POLICIES FOR ABATEMENT OF PHOTOCHEMICAL AIR
POLLUTION 147
History 147
Present Policies 148
References for Chapter 9 151
10. IMPLEMENTATION OF ABATEMENT POLICIES 153
Status of State Abatement Programs 153
Control of Hydrocarbons and Nitrogen Oxides from Mobile Sources 154
Control of Organic Emissions from Stationary Sources 157
Control of Nitrogen Oxides from Stationary Sources 160
Estimation of Emission Rates 162
References for Chapter 10 169
11. ECONOMIC CONSEQUENCES OF OXIDANT POLLUTION 173
Cost of Oxidant Effects 173
Direct Costs of Abatement 173
Impact of Abatement on Economy 180
References for Chapter 11 181
TECHNICAL REPORT DATA AND ABSTRACT 182
IV
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LIST OF FIGURES
Figure Page
2-1 Monthly Variation of Mean Hourly Oxidant Concentrations for Three
Selected Cities 11
2-2 Monthly Variation of Mean Daily Maximum 1-Hour Average Oxidant
Concentrations for Three Selected Cities 11
2-3 Diurnal Variation of Mean Hourly Average Oxidant Concentrations in
Los Angeles and St. Louis 12
2-4 Diurnal Variation of Mean Hourly Average Oxidant Concentrations in
Philadelphia, August 6-8, 1966 . . . . 12
2-5 South (California) Coast Air Basin 13
2-6 Annual and 3-Year Moving Averages of Daily Maximum 1-Hour Oxidant Con-
centrations in Los Angeles for July through September, 1963-1972 17
2-7 Annual and 3-Year Moving Averages of Daily Maximum 1-Hour Oxidant Con-
centrations in Azusa, Calif., for July through September, 1963-1972. ... 17
2-8 Annual and 3-Year Moving Averages of Daily Maximum 1-Hour Concentrations
in Riverside, Calif., for July through September, 1963-1972 17
2-9 Average of Daily Maximum 1-Hour Oxidant Concentrations for Months of
August in Azusa, Calif., 1957-1972 18
2-10 Distribution of Average of Daily Maximum 1-Hour Oxidant Concentrations
(pphm) in Los Angeles Basin During July through September, 1970-1972 ... 19
2-11 Diurnal Variation of Hourly Ozone Concentrations in Philadelphia and
Denver 20
2-12 Variation of Mean 1-Hour Average Oxidant and PAN Concentrations, by
Hour of Day, in Downtown Los Angeles, 1965 22
2-13 Variation of Mean 1-Hour Average Oxidant and PAN Concentrations, by
Hour of Day, at the University of California at Riverside, September
1966 23
2-14 Monthly Variation of Oxidant and PAN Concentrations at the University
of California at Riverside, June 1966-June 1967 23
3-1 Chemical Changes Occurring During Photoirradiation of Hydrocarbon-
Nitrogen Oxide-Air Systems 28
3-2 Flow Diagram for Propylene-Nitrogen Oxide-Ultraviolet Reaction System. . . 30
3-3 A Lumped Kinetic Mechanism for Photochemical Smog 31
3-4 Correlation of Solvent Reactivity Data from Battelle, SRI, and Shell
Studies 42
3-5 Maximum Daily 1-Hour-Average Oxidants as a Function of 6 to 9 A.M.
Averages of Nonmethane Hydrocarbons at CAMP Stations, June through
September, 1966 through 1968, Los Angeles, May through October 1967. ... 45
3-6 Maximum Daily 1-Hour-Average Oxidant Concentrations as a Function of
6 to 9 A.M. Averages of Total Nitrogen Oxides in Washington, D.C., June
through September, 1966 through 1968 46
3-7 Maximum Daily 1-Hour-Average Oxidant Concentrations as a Function of
6 to 9 A.M. Average Total Nitrogen Oxides in Philadelphia, June through
September, 1965 through 1968 46
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Page
3-8 Maximum Daily 1-Hour-Average Qxidant Concentrations as a Function of
6 to 9 A.M. Averages of Total Nitrogen Oxides in Denver, June through
September, 1965 through 1968 47
3-9 Upper Limit of Maximum Daily 1-Hour-Average Oxidant Concentrations,
Calculated Nonmethane Hydrocarbon Concentration of 1.5 ppm C, as a
Function of Average Total Nitrogen Oxides from 6 to 9 A.M. at Three
Los Angeles Stations, May through October 1967 48
3-10 Nonraethane Hydrocarbon-Oxidant Envelopes Superimposed on Maximum Daily
1-Hour-Average Oxidant Concentrations as a Function of 6 to 9 A.M.
Average of Total Nitrogen Oxides in Pasadena, California, May through
October 1967 49
3-11 Approximate Isopleths for Selected Upper-Limit Maximum Daily 1-Hour-
Average Oxidant Concentrations, as a Function of the 6 to 9 A.M.
Averages of Nonmethane Hydrocarbons and Total Nitrogen Oxides in
Philadelphia, Pa., Washington, D.C., and Demrer, Colo., June through
August, 1966 through 1968 50
3-12 Oxidant Isopleths from Laboratory Experiments Showing Effect of
Varying Initial Precursor Hydrocarbon (Propylene) and Nitric Oxide
Concentrations on Maximum Ozone Concentrations 51
3-13 Equal Response Lines Representing Combinations of Total Nonmethane
Hydrocarbon and Nitrogen Oxide Corresponding to Oxidant and Nitrogen
Dioxide Yields Equal to the National Air Quality Standards ... 54
3-14 Equal Response Lines Representing Combinations of Total Nonmethane
Hydrocarbon and Nitrogen Oxide Corresponding to Specific Levels of
Maximum Ozone Yields 55
4-1 Diurnal Variation of Mean 1-Hour-Average Oxidant Concentrations at
Selected California Sites, October 1965 62
4-2 Diurnal Variation of Mean 1-Hour-Average Carbon Monoxide Concentrations
at Selected California Sites, October 1965 62
5-1 Regression Curves Relating Eye Irritation and Simultaneous Oxidant
Concentrations from a Number of Stations in the Los Angeles Area 74
5-2 Variation of Mean Maximum Eye Irritation, as Judged by a Panel of
"Experts," with Maximum Oxidant Concentrations, Pasadena, August-
November, 1955 74
5-3 Relationship Between Oxidant Concentrations and Eye Discomfort in Los
Angeles, October 29 through November 25, 1962 75
5-4 Mean Index of Eye Irritation Versus Oxidant Concentration 76
6-1 Concentration Ratios for Nonmethane Hydrocarbons/Methane in Los Angeles
(213 Hours During October and November 1964) and Cincinnati (574 Hours
During September 1964), with 655 yg/m3 (1 ppm) Methane Deducted to
Correct for Estimated Background Biospheric Concentration 85
6-2 Nonmethane Hydrocarbons by Flame lonization Analyzer, Averaged by
Hour of Day over Several Months for Various Cities 89
6-3 Nonmethane Hydrocarbons by Flame lonization Analyzer Averaged by
Hour of Day for Three Los Angeles County Sites, October 1966 through
February 1967 90
6-4 Nonmethane Hydrocarbon Trends in Los Angeles, 1963-1972 94
6-5 Pollutant Trends for July, August, and September in Los Angeles,
1963-1972 95
VI
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Figure Page
6-6 Distribution of Total Hydrocarbon Concentrations in the South Coast Air
Basin. Average of Daily Maximum 1-Hour Concentrations (ppm C) During
July, August, and September, 1970-1972 96
6-7 Frequency Distribution of 3-Hour-Average Concentrations of Nitrogen
Oxides at Los Angeles CAMP Station, December I, 1963, to December 1,
1964 99
6-8 Monthly Average of Nitric Oxide Concentrations in Three Cities, 1969-
1972 99
6-9 Monthly Average of Nitrigen Dioxide Concentrations in Three Cities,
1969-1972 99
6-10 Average Daily 1-Hour Concentrations of Selected Pollutants in Los
Angeles, California, July 19, 1965 109
6-11 Diurnal Variation of Nitrogen Dioxide Concentrations at Sites in the
United States 110
6-12 Weekday and Weekend 1-Hour-Average Nitric Oxide Levels in Chicago,
Illinois, 1962-1964 110
6-13 Oxides of Nitrogen Trends in Los Angeles, 1963-1972, 6 to 9 A.M. and
Maximum One-Hour Average Concentrations 114
6-14 Distribution of Oxides of Nitrogen Concentrations in the South Coast Air
Basin. Average of Daily Maximum One-Hour Concentrations (pphm) During
July, August, and September, 1970-1972 114
6-15 Distribution of Nitrogen Dioxide Concentrations in the South Coast Air
Basin. Average of Daily Maximum One-Hour Concentrations (pphm) During
July, August, and September, 1970-1972 " 115
6-16 Diurnal Patterns of Sulfur Dioxide Concentrations (Conductimetric Data
Taken in Washington CAMP Station in 1968) 118
6-17 Seasonal Patterns of Sulfur Dioxide Concentrations (Monthly NASN Data
for 1964-1971) 118
6-18 Seasonal Patterns of Sulfate Concentrations (Monthly NASN Data for
1957-1970) 120
6-19 Long-Term Pattern of Sulfate Concentrations (Monthly NASN Data for
1957-1970) 120
7-1 Percentage of Emissions from Major Sources in the South Coast Air
Basin, 1970 135
9-1 Organization of the U.S. Environmental Protection Agency (June 1975) . . . 149
VI1
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LIST OF TABLES
Table Page
2-1 Summary of Maximum Oxidant Concentrations Recorded in Selected Cities,
1964-1967 7
2-2 Cumulative Frequency Distribution of Hourly Average Oxidant Concentration in
Selected Cities, 1964-1965 8
2-3 Summary of Total Oxidant Concentrations Recorded at Camp Sites, 1964-1972. . 9
2-4 Highest Monthly Mean of One-Hour Average Oxidant Concentrations Recorded
in Selected Cities, 1964-1965 10
2-5 Oxidant Trends in the South Coast Air Basin, 1963-1972, Three-Month Averages
of Daily Maximum One-Hour Oxidant Concentrations for July, August, and
September 15
2-6 Oxidant Trends in the South Coast Air Basin, 1963-1972, Annual Averages
of Daily Maximum One-Hour Oxidant Concentrations for All Days of the
Year 15
2-7 Oxidant Trends in the South Coast Air Basin, 1963-1972, Average of Three
Highest One-Hour Oxidant Concentrations for July, August, and September . . 16
2-8 Oxidant Trends in the South Coast Air Basin, 1963-1972, Number of Hours
with Oxidant Concentrations Equal to or Exceeding 20 pphm for July,
August, and September 16
3-1 Validation Values of Rate Constants and Their Comparison with the Recom-
mended Values of Investigations 32
3-2 Comparison of Reactivities of Different Types of Organics 36
3-3 Photochemical Reactivities of Hydrocarbons 40
T-4 Reactivities and Classification of Solvents 41
6-1 Some Hydrocarbons Indentified in Ambient Air 42
6-2 Mean of Daily Maximum Hourly Average Total Hydrocarbon Concentrations for
17 California Cities, 1968-1969 87
6-3 Frequency Distribution Data for 6 to 9 a.m. Nonmethane Hydrocarbon
Concentrations at Camp Sites, 1967-1972 88
6-4 Average Atmospheric Light Hydrocarbon Concentrations, by Hour, Los Angeles
and Azusa, September through November, 1967 91
6-5 Total Hydrocarbon Trends in the South Coast Air Basin, 1963-1972, Three-
Month Averages of Daily Maximum One-Hour Concentrations for July, August,
and September 92
6-6 Total Hydrocarbon Trends in the South Coast Air Basin, 1963-1972, Three-
Month Averages of 6 to 9 a.m. Daily Average Concentrations for July,
August, and September 92
6-7 Total Hydrocarbon Trends in the South Coast Air Basin, 1963-1972, Annual
Averages of Daily Maximum One-Hour Concentrations for All Days of the
Year 93
6-8 Frequency Distribution Data for 6 to 9 a.m. Nitric Oxide Concentrations
at CAMP Sites, 1962-1972 100
6-9 Frequency Distribution Data for 6 to 9 a.m. Nitrogen Dioxide Concentrations
at CAMP Sites, 1962-1972 102
viii
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Table Page
6-10 Nitric Oxide Concentration in California by Averaging Time and
Frequency, 1963-1967 104
6-11. Nitrogen Dioxide Concentration in California by Averaging Time and
Frequency, 1963-1967 106
6-12 Ambient Nitrogen Dioxide Concentrations in Various Cities in 1972 Measured
by Different Methods 108
6-13 Oxides of Nitrogen Trends in the South Coast Air Basin, 1963-1972, Three-
Month Averages of Daily Maximum One-Hour Concentrations for July, August,
and September Ill
6-14 Oxides of Nitrogen Trends in the South Coast Air Basin, 1963-1972, Three-
Month Averages of 6 to 9 a.m. Daily Average Concentrations for July,
August, and September Ill
6-15 Oxides of Nitrogen Trends in the South Coast Air Basin, 1963-1972, Annual
Averages of Daily Maximum One-Hour Concentrations for All Days of the
Year 112
6-16 Nitrogen Dioxide Trends in the South Coast Air Basin, 1963-1972, Three-
Month Averages of 6 to 9 a.m. Daily Average Concentrations for July,
August, and September 112
6-17 Nitrogen Dioxide Trends in the South Coast Air Basin, 1963-1972, Three-
Month Averages of Daily Maximum One-Hour Concentrations for July,
6-18
6-19
6-20
6-21
6-22
6-23
6-24
6-25
6-26
6-27
6-28
6-29
7-1
7-2
Nitrogen Dioxide Trends in the South Coast Air Basin, 1963-1972, Annual
Averages of Daily Maximum One-Hour Concentrations for All Days of the
Year
Variation of Oxidant and Precursor Concentrations Within the South Coast
Air Basin, July, August, and September, 1970-1972
Cumulative Distribution by Percent of Annual Average Sulfur Dioxide Con-
centrations, Urban Sites
Cumulative Distribution by Percent of Annual Average Sulfur Dioxide
Concentrations, Nonurban Sites
Maximum Concentrations of Sulfur Dioxide for Various Averaging Times at CAMP
Sites, 1962-1968
Cumulative Distribution by Percent of Annual Average Sulfate Concentrations,
Urban Sites
Cumulative Distribution by Percent of Annual Average Sulfate
Concentrations, Nonurban Sites
Suspended Particle Concentrations (Geometric Mean of Center City Station)
in Urban Area, 1961-1965
Distribution of Selected Cities by Population Class and Particle
Concentrations 1957-1967
Distribution of Selected Nonurban Monitoring Sites by Category of Urban
Proximity, 1957-1967
Quarterly and Annual Size Distribution of Particulate Matter Suspended
in Air, 1970
Concentration and Size of Particulate Chemical Constituents in Urban
Air
Estimates of Nationwide Hydrocarbon Emissions by Source Category, 1968 . .
Summary of Hydrocarbon Emissions from 22 Metropolitan Areas in the
United States, 1967-1968
113
115
116
116
117
119
119
121
122
122
123
124
130
131
IX
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Table
7-3
7-4
7-5
7-6
7-7
7-8
7-9
8-1
9-1
10-1
10-2
10-3
10-4
10-5
10-6
11-1
11-2
11-3
11-4
11-5
11-6
11-7
11-8
11-9
Percent of Total Area Hydrocarbon Emissions by Source Category, 22
Metropolitan Areas in United States, 1966
Estimates of Nationwide Nitrogen Oxide Emissions by Source Category,
1968
Percent of Total Area Nitrogen Oxide Emissions by Source Category,
22 Metropolitan Areas in the United States, 1966
South Coast Air Basin, Average Emissions of Contaminants into the
Atmosphere, 1970
South Coast Air Basin, Comparison of Stationary and Mobile Sources,
1970 »
South Coast Air Basin, Hydrocarbon and Nitrogen Oxide Emission Rates,
1960-1970
South Coast Air Basin, Projected Hydrocarbon and Nitrogen Oxide Emission
Rates, 1975-1980
Required Emission Reductions Based on Rollback Model with Various
Input Variables
National Air Quality Standards for Oxidant-Ozone, Nitrogen Dioxdie,
and Hydrocarbons
Hydrocarbon and Nitrogen Oxide Emission Standards for New Motor Vehicles
and Engines, 1973-1976
Sample Calculation of Gasoline Motor Vehicle Exhaust Emission Factors for
Hydrocarbons from Light-Duty Vehicles
Sample Calculation of Weighted Speed Adjustment Factor for Hydrocarbon Ex-
haust Emissions from Light-Duty Vehicles
Sample Calculation of Gasoline Motor Vehicle Crankcase and Evaporative
Emission Factors for Hydrocarbon from Light-Duty Vehicles
Emission Factors for Diesel Engines Emission Factor Rating: B
Emission Factors for Aircraft (Ib/engine - LTO cycle and kg/ engine - LTO
cycle) Emission Factor Rating: A «
Estimated Air Pollution Damage Costs in the United States, 1968
Estimated Air Pollution Damage Costs in the United States for 1968
and 1977 with No Pollution Control
Summary of the United States Air Pollution Damage Cost Ranges
for 1970
Federal Transaction Costs Associated with Air Pollution Abatement, 1972. .
Cost of Air Pollution Abatement
Annualized Unit Cost Increases for Light-Duty Vehicles
Annual! zed Unit Cost Increases for Heavy-Duty Trucks
Estimates of Annual (Cumulative) Unit Costs of Light-Duty Motor Vehicle
Hydrocarbon Emission Control
Estimated Cost Effects of the Clean Air Act for Fiscal Year 1971
Page
131
132
133
134
135
136
136
145
150
155
165
165
166
167
168
174
174
175
175
176
177
178
179
180
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PHOTOCHEMICAL OXIDANTS IN THE AMBIENT AIR
OF THE UNITED STATES
CHAPTER 1
INTRODUCTION
The photochemical oxidants problem has been known to exist in the United
States for more than 30 years. First manifestations of the problem occurred in
California and included accelerated deterioration of rubber products, damage to
vegetation, and eye irritation. Subsequent correlative observations suggested
certain adverse effects of photochemical oxidants upon human and animal health.
By 1947, the problem of oxidants and other photochemical pollutants, in general,
had such dimensions that one state (California) developed and enacted legislation
specifically addressed to this problem. While the problem is severest in the
southwest edge of California, high levels of oxidants are known to occur in every
major urban center in the United States and, through transport, in nonurban areas
also.
In this report, an effort is made to (1) present and analyze all evidence
attesting to the presence of a photochemical oxidants problem in the United States
and (2) present and assess the national effort to alleviate this problem. Be-
cause of the early appearance and the severity of this problem in the Los Angeles
basin of California, this basin's atmosphere was given by far most of the research
attention in the area of photochemical air pollution. For this reason, experiences
from the Los Angeles situation constitute the main basis of this report.
Most of the material used in this report was taken from existing reports
or documents such as the Air Quality Criteria reports for hydrocarbons, oxidants,
and nitrogen oxides " and the Control Technique documents for hydrocarbon and
4-6
nitrogen oxide emissions from mobile and stationary sources. Such documents
present information and viewpoints generated prior to 1970; however, some sections
of this report have been more recently updated.
The term "photochemical oxidants" is used by convention to define those
atmospheric pollutants that are photochemical reaction products and are capable
of oxidizing neutral iodide ions. Extensive research has unequivocally identified
several components of the photochemical oxidants mixture. Thus, ambient oxidants
are known to consist mainly of ozone, peroxyacetyl nitrate, and nitrogen dioxide
and are suspected to include also, in lesser amounts, other peroxyacyl nitrates,
1
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hydrogen peroxide, and alkyl hydroperoxides. An important distinction to be made
here is that the formation of nitrogen dioxide in ambient air clearly precedes the
formation of the other oxidants. For this reason, the relative levels of nitrogen
dioxide and of the aggregate of the other oxidants vary considerably during the
day, the nitrogen dioxide being invariably the dominant oxidant earlier in the
day. Because of this difference in variation pattern and the differences in effects
between nitrogen dioxide and the aggregate of the other oxidants, the nitrogen
dioxide pollution problem has been treated independently of the other photochemical
oxidants problem. Further, because of its predominance among the other non-nitro-
gen dioxide oxidants, ozone has been singled out and treated as the sole represen-
tative of such oxidants and has been given most of the research attention.
Today, photochemical air quality is defined in terms of concentrations of
ozone and nitrogen dioxide only. This should not be interpreted to suggest that
other photochemical pollutants are thought to be of less concern. Rather, it re-
flects (1) the fact that the ozone and nitrogen dioxide pollution problems are
more easily measured and, hence, more amenable to research than the eye irritation,
plant damage, and visibility reduction problems associated with the other pollutants,
and (2) the assumption that abatement of the ozone and nitrogen dioxide pollution
problems will in all probability alleviate the other photochemical pollution pro-
blems also.
The oxidants found in the lower levels of the earth's atmosphere have been
traced to both natural and anthropogenic sources. One natural source of oxidants
is the abundantly present ozone in the stratosphere, which can be transported into
the biosphere. ''Oxidants can also form naturally from electrical discharges in
the atmosphere as well as from atmospheric photochemical reactions involving naturally
emitted organic vapors and nitrogen oxides. Obviously, the levels of oxidants
resulting from the total of such uncontrollable sources must be known if assess-
ment of the anthropogenic sources is to be made reliably.
Oxidants from anthropogenic sources are products of atmospheric photochemical
reactions involving primary organic and inorganic pollutants and atmospheric oxygen.
More specifically, the oxidant formation process is initiated by the sunlight-in-
duced photolysis of nitrogen dioxide to nitric oxide and oxygen atoms (NO^NO + 0).
Resultant oxygen atoms react then both with atmospheric molecular oxygen to form
ozone and with organic pollutants to form other (nonozone) oxidizing species that
convert a considerable part of the nitric oxide back into nitrogen dioxide. The
net result of this photochemical activity is the accumulation of ozone (and other
oxidants) to concentration levels that depend on numerous factors, including local
meteorological conditions (sunlight intensity, air stagnation, temperature, etc.)
as well as the concentrations, makeup, and variation patterns of the primary pollu-
tants present. Such dependence of oxidant formation on numerous factors makes
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this pollution problem immensely complex; however, as discussed later, it also
has the fortunate consequence that it" offers several options to the abatement
effort.
REFERENCES FOR CHAPTER 1
1. Air Quality Criteria for Hydrocarbons. U.S. Department of Health, Education,
and Welfare, Public Health Service, National Air Pollution Control Administration.
Washington, D.C. NAPCA Publication No. AP-64. March 1970.
2. Air Quality Criteria for Photochemical Oxidants. U.S. Department of Health,
Education, and Welfare, Public Health Service, National Air Pollution Control
Administration. Washington, D.C. NAPCA Publication No. AP-63. March 1970.
3. Air Quality Criteria for Nitrogen Oxides. U.S. Department of Health, Education,
and Welfare, Public Health Service, National Air Pollution Control Administration.
Washington, D.C. NAPCA Publication No. AP-84. January 1971.
4. Control Techniques for Carbon Monoxide, Nitrogen Oxide, and Hydrocarbon Emissions
from Mobile Sources. U.S. Department of Health, Education, and Welfare, Public
Health Service, National Air Pollution Control Administration. Washington, D.C.
NAPCA Publication No. AP-66. March 1970.
5. Control Techniques for Nitrogen Oxide Emissions from Stationary Sources. U.S.
Department of Health, Education, and Welfare, Public Health Service, National Air
Pollution Control Administration. Washington, D.C. NAPCA Publication No. AP-67.
March 1970.
6. Control Techniques for Hydrocarbon and Organic Solvent Emissions from Stationary
Sources. U.S. Department of Health, Education, and Welfare, Public Health Service,
National Air Pollution Control Administration. Washington, D.C. NAPCA Publication
No. AP-68. March 1970.
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CHAPTER 2. ATMOSPHERIC LEVELS
AND VARIATION OF PHOTOCHEMICAL OXIDANTS
INTRODUCTION
Although buildup of photochemical oxidants (OX) occurs in nearly every urban
center in the United States, no pollutant episodes involving a sudden and massive
assault upon human health have been attributed to photochemical oxidants alone.
Accordingly, no case studies in which pollutants and their effects during oxidant
pollution episodes were comprehensively and systematically examined have been
reported. The case made for viewing the photochemical oxidants as an air pollution
problem has been based mainly on (1) observations of humans, animals, plants, and
materials in areas known to have high oxidant levels, and (2) results from studies
in which human subjects, animals, plants, and materials were deliberately exposed
to smoggy atmospheres or to synthetic mixtures containing oxidants. Therefore, in
order to present this case, it would be necessary and sufficient to present (1)
data on concentration and frequency of occurrence of photochemical oxidants, and
(2) evidence regarding the adverse effects of oxidants. Data on the occurrence of
oxidants are given in this chapter; evidence on effects of oxidants will be pre-
sented and discussed in Chapter 5.
CONCENTRATIONS OF OXIDANTS IN URBAN ATMOSPHERES
Analytical Methods
In the early 1950's, the Los Angeles County Air Pollution Control District
(LAAPCD) established the first air monitoring network in the United States (12
stations), using automatic instruments for continuous measurement of gaseous
pollutants. Network instrumentation included potassium iodide (KI) total oxidant
analyzers; ozone photometers were added in 1958. In 1961, the State of California
Department of Public Health organized a 16-station Statewide Cooperative Air Moni-
toring Network (SCAN). During 1961-1962, the Public Health Service of the U. S.
Department of Health, Education, and Welfare initiated its Continuous Air Moni-
toring Project (CAMP) by installing one CAMP station in each of the following
cities: Chicago, Philadelphia, Cincinnati, San Francisco, New Orleans, and
Washington (now located in Chicago, Philadelphia, Denver, Cincinnati, St. Louis,
and Washington).
Today, data on oxidants are obtained by various techniques in 195 permanent
monitoring stations operated by local, state, and Federal agencies. In addition,
several temporary stations are being used to obtain data needed for special studies.
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Oxidant has been measured with colorimetric analyzers using neutral-phosphate-
buffered 10 percent KI reagent (CAMP, LAAPCD) or 20 percent KI (SCAN). Such
analyzers respond not only to ozone (03), but also to nitrogen dioxide (N02), sulfur
dioxide (S02), peroxyacetyl nitrate (PAN), and other oxidants. The response to N02
is positive and equal to from 10 to 20 percent of that of 03, depending on the
specific analytical procedures used; the response to S02 is negative and equal
to that of 03. To eliminate the S02 interference, the CAMP analyzers were equipped
early in 1964 with chromium trioxide scrubbers, which remove the S02 from the sample
stream. Therefore, the CAMP oxidant data reported after 1963 were not affected by
S02 interference. Data reported from all stations, however, are affected by the
N02 interference.
To adjust the CAMP oxidant data for N02, the following equation is used
(all concentrations are expressed in parts per million):
Adjusted oxidant = OX - 0.2 N02 (2-1)
For analyzers equipped with the chromium trioxide scrubber, the data should be
additionally adjusted for the N02 that results from partial oxidation of nitric
oxide (NO) in the chromium trioxide column. Thus, total adjustment is:
Adjusted oxidant = OX - 0.2 N02 - 0.11 NO (2-2)
If the oxidant analyzer is not equipped with the chromium trioxide scrubber and the
concentration of S02 is known, then adjusted oxidant can be computed as follows:
Adjusted oxidant = OX - 0.2 N02 + S02 (2-3)
Such adjustedotherwise termed here "corrected"oxidant data represent
mainly 03 and to a lesser degree PAN and other oxidants commonly present in ambient
air.
Concentrat ions
Table 2-1 shows the maximum hourly average concentrations and peak concentra-
tions, as well as the number and percentage of days when the maximum hourly average
oxidant concentration exceeded 290, 200, and 100 micrograms per cubic meter (yg/m3)
(0.15, 0.10, and 0.05 ppm) for 12 monitoring sites.1 It is interesting to note that
peak concentrations in St. Louis reached 1670 pg/m3 (0.85 ppm). Such extraordinarily
high readings, however, usually occurred at night and were of short duration. It is
suspected that the high concentration in St. Louis resulted from emissions from a
large chemical complex near the monitor rather than an atmospheric photochemical
reaction.
The cumulative frequency distribution of hourly average concentrations for these
same 12 sites is presented in Table 2-2. Interpretation of the data in Table 2-2
must be made with caution. For example, on the basis of yearly average, a conclu-
sion that Los Angeles, San Diego, Denver, and Santa Barbara had similar oxidant
6
-------
Table 2-1. SUMMARY OF MAXIMUM OXIDANT CONCENTRATIONS
RECORDED IN SELECTED,CITIES, 1964-19671
City
Pasadena
Los Angeles
San Diego
Denver3
St. Louis
Philadelphia
Sacramento
Cincinnati
Santa Barbara
Washington, D.C.
San Francisco
Chicago
Total days
of available
data
728
730
623
285
582
556
711
613
723
577
647
530
Number and percent of total days
with maximum hourly average
>^ concentration specified
0.05 ppm
Days
546
540
440
226
362
233
443
319
510
313
185
269
Percent
75.0
74.0
70.6
79.3
62.2
41.9
62.3
52.0
70.5
54.2
28.6
50.8
0.10 ppm
Days
401
354
130
51
59
60
104
55
76
65
29
24
Percent
55.1
48.5
20.9
17.9
10.1
10.9
14.6
9.0
10.5
11.3
4.5
4.5
0.15 ppm
Days
299
220
35
14
14
13
16
10
11
7
6
0
Percent
41.1
30.1
5.6
4.9
2.4
2.3
2.3
1.6
1.5
1.2
0.9
0
Maximum
hourly
average,
ppm
0.46
0.58
0.38
0.25
0.35
0.21
0.26
0.26
0.25
0.21
0.18
0.13
Peak
concen-
tration,
ppm
0.67
0.65
0.46
0.31
0.85
0.25
0.45
0.32
0.28
0.24
0.22
0.19
Eleven months of data beginning February 1965.
problems might be reached. Yet examination of the data in Table 2-1 shows that the
peak concentration, the maximum hourly average, and the percentage of days with
elevated oxidant concentrations are in fact quite different for these four cities.
The principal reason for this apparent contradiction is associated with the nature
of oxidant formation. Because ozone, the major oxidant, is a photochemical product
and not a direct emission, the conditions necessary for its formation are restricted
to the hours of sunlight. During any single day, therefore, the time when oxidants
can be produced is restricted to a 6- to 8-hour period; at the most, this time
interval represents 35 percent of the 24-hour period. On this basis, 65 percent of
the cumulative hourly data in Table 2-2 represent values that are close to zero.'
As a result, the differences that exist between cities tend to disappear in the pro-
cess of averaging. Thus, the usefulness and meaning of the yearly averages presented
in Table 2-2 have serious limitations.
For similar reasons, the fact that yearly oxidant averages in urban areas
approach atmospheric ozone background concentrations has little or no significance.
These yearly values are low because 65 percent of the averaged values are necessarily
near zero, as previously indicated.
-------
Table 2-2. CUMULATIVE FREQUENCY DISTRIBUTION OF HOURLY
AVERAGE OXIDANT CONCENTRATIONS IN SELECTED CITIES,
1964-19651
(PPm)
City
Pasadena
Los Angeles
San Diego
Denver^
St. Louis
Philadelphia
Sacramento
Cincinnati
Santa Barbara
Washington, D.C.
San Francisco
Chicago
Percenti lea
1
0.26
0.22
0.14
0.12
0.11
0.14
0.12
0.10
0.10
0.10
0.07
0.08
2
0.23
0.18
0.12
0.10
0.09
0.11
0.10
0.08
0.09
0.09
0.06
0.08
5
0.18
0.14
0.10
0.08
0.07
0.08
0.08
0.07
0.08
0.07
0.05
0.06
10
0.12
0.10
0.08
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.04
0.05
30
0.04
0.04
0.04
0.04
0.04
0.03
0.04
0.04
0.04
0.03
0.03
0.03
50
0.02
0.02
0.03
0.03
0.03
0.02
0.02
0.02
0.03
0.02
0.02
0.02
70
0.01
0.01
0.02
0.02
0.02
0.02
0.01
0.02
0.02
0.01
0.01
0.01
90
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.02
0.01
0.01
0.01
1964-1965 :
yearly
average
0.042
0.036
0.036
0.036
0.031
0.026
0.030
0.030
0.036
0.029
0.019
0.028
Concentrations greater than or equal to specified value in indicated
percentage of samples.
Eleven months of data beginning February 1965.
Table 2-3 presents, on a. yearly basis, the maximum hourly average concentration
and the number of days during which the maximum hourly average exceeded specified
values for total oxidant at each of the CAMP sites from 1964 through 1972.2
Seasonal and Diurnal Variations
Seasonal and diurnal variations in oxidant concentrations result largely from
(1) variations in emissions of oxidant-forming pollutants, (2) variations in atmos-
pheric transport and dilution processes, and (3) variations in other atmospheric
variables involved in the photochemical formation of oxidant. Typically, each of
these factors varies significantly over periods as short as a few hours; the latter
two also vary significantly among the seasons. Considerable variations in observed
ambient oxidant concentrations, therefore, would be expected.
The highest monthly mean oxidant concentrations generally occur during the
period from late spring to early fall. Oxidant concentrations also exhibit a daily
variation. For urban centers, the maximum generally occurs around noon, the period
when shorter wavelength solar radiationwhich is photochemically importantreaches
the surface of the earth with greatest intensity. Table 2-4 presents oxidant con-
centrations recorded in selected cities during the month having the highest mean
8
-------
Table 2-3. SUMMARY OF TOTAL OXIDANT CONCENTRATIONS
RECORDED AT CAMP SITES, 1964-19722
City
Chicago
Cincinnati
Denver
Philadelphia
St. Louis
Washington, D.C.a
Year
1964
1965
1966
1967
1968
1969
1970
1971
1972
1964
1965
1966
1967
1968
1969
1970
1971
1972
1965
1966
1967
1968
1969
1970
1971
1972
1964
1965
1966
1967
1968
1969
1970
1971
1972
1964
1965
1966
1967
1968
1969
1970
1971
1972
1964
1965
1966
1967
1968
1969
1970
1971
1972
Days
of
valid
data
254
275
235
255
211
24
200
276
312
303
310 ,
208
228
86
48
7
221
257
285
298
166
151
108
141
184
209
269
266
315
282
140
92
112
260
47
253
329
292
289
163
95
96
294
203
293
284
325
322
217
71
167
299
179
Number of days with at
least 1 hourly average 3^
concentration specified
0.05 ppm
149
120
52
113
113
15
97
90
79
137
182
54
122
65
23
1
96
69
226
187
76
149
70
69
63
94
124
109
145
124
88
37
29
47
20
156
206
174
185
100
47
20
77
77
163
150
134
137
134
30
95
144
45
0.10 ppm
15
9
6
16
17
0
4
14
4
36
19
1
24
7
5
0
10
3
51
46
12
28
2
9
5
26
37
23
52
28
18
3
10
5
10
26
33
33
38
7
5
0
1
9
40
25
27
27
40
1
10
17
6
0.15 ppm
0
0
3
1
5
0
3
2
0
5
5
0
1
. 0
1
0
1
1
14
9
4
5
0
1
1
1
9
4
19
3
3
0
0
0
1
6
8
5
4
2
0
0
0
2
4
3
2
5
9
0
2
0
0
Maximum
hourly
average,
ppm
0.13
0.13
0.19
0.16
0.18
0.07
0.20
0.17
0.14
0.26
0.17
0.10
0.20
0.14
0.16
0.08
0.16
0.15
0.25
0.19
0.21
0.26
0.13
0.18
0.20
0.18
0.20
0.33
0.52
0.17
0.21
0.11
0.13
0.14
0.15
0.26
0.35
0.22
0.20
0.23
0.12
0.08
0.13
0.16
0.20
0.21
0.16
0.26
0.25
0.10
0.16
0.13
0.13
Site moved at end of 1968.
-------
Table 2-4. HIGHEST MONTHLY MEAN OF ONE-HOUR AVERAGE OXIDANT
CONCENTRATIONS RECORDED IN SELECTED CITIES,
1964-19651
City
Pasadena
Los Angeles
San Diego
Denver3
St. Louis
Philadelphia
Sacramento
Cincinnati
Santa Barbara
Washington
San Francisco
Chicago
Month having
highest mean
1-hour average
oxidant concentration
July
August
October
July3
May
July
June
July
May and September^
May
May
April
Monthly
mean of hourly
average concentrations,
ppm
0.075
0.056
0.050
0.050
0.042
0.054
0.040
0.048
0.042b
0.041
0.031
0.044
Monthly mean of
maximum daily
1-hour average
concentrations,
ppm
0.24
0.17
0.11
0.11
0.072
0.11
0.075
0.098
0.064 and 0.072
0.072
0.046
0.070
Eleven months of data beginning February 1965.
1964-1965 average for the months of May and September.
1-hour average concentration averaged for the years 1964 and 1965. For these months
the means of all hourly concentrations and the means of the maximum daily 1-hour
average concentrations are listed.
The seasonal variation of oxidant concentrations by month is illustrated in
Figures 2-1 and 2-2 for three of the stations. Figure 2-1 illustrates the mean by
month of all hourly average concentrations for Los Angeles, Denver, and Phoenix.
Figure 2-2 shows the mean by month of daily maximum 1-hour average concentrations
for the same cities. In these figures, the importance of solar radiation and tem-
peraturebeing higher outside the winter seasonis readily apparent. Note that
for Denver, the high values occur around midsummer. For Los Angeles, the high
values occur toward late summer and autumn, apparently reflecting, in part, lower
windspeeds and less cloudiness during these seasons. In addition, the character-
istics of atmospheric transport in Los Angeles are more favorable to a day-to-day
carryover of precursor pollutants in autumn than in midsummer, the result of the
greater balance between the sea and land breezes.
In Figure 2-3, the diurnal variation of mean 1-hour average oxidant concen-
trations are shown for Los Angeles and St. Louis. Selected for the Los Angeles
presentation is the calendar month (August) during which the highest monthly mean
10
-------
0.06
FEB. MAR. APR. MAY JUN. JUL. AUG. SEP. OCT. NOV. DEC
Figure 2-1. Monthly variation of mean hourly oxidant concentrations for three selected cities.1
0.20
L_._L _!._.. I
JAN. FEB. MAR. Al't?. MAY JUN. Jill. AlJi.. SEP. OCT. NOV. DEC.
Figure 2-2. Monthly variation of mean daily maximum 1-hour average oxidant concentrations for
three selected cities. 1
11
-------
average for the years 1964 and 1965 occurred; the St. Louis presentation illustrates
the calendar month (June) that had the highest monthly mean average in 1966. Figure
2-4 illustrates the diurnal variation of mean 1-hour average oxidant concentrations
for a 3-day period (August 6-8, 1966) in Philadelphia during which unusually high
concentrations of oxidants were'recorded. Although there are some differences, all
curves of Figures 2-3 and 2-4 show a distinct peak around noon. This peak results
largely from the interaction of diurnal variations in emissions, solar radiation
intensity, and atmospheric dilution.
0.16
0.30r-"
LOS ANGELES,
AUGUST 1964 AND 1965
I I I I I I I I I I I
LOCAL TIME
Figure 2-3. Diurnal variation of mean hourly
average oxidant concentrations in Los Angeles
and St. Lou is. 1
LOCAL TIME
Figure 2-4. Diurnal variation of mean hourly
average oxidant concentrations in Philadelphia,
August 6-8, 1966.1
Peak emissions occur with the morning rush-hour traffic, at a time when solar
radiation and dilution are weak. As the vehicle- related emissions drop off toward
BiJdmorning and midc'-iy, radiation intensity increases to a maximum around noon;
dilution increases japidly in the forenoon to reach a maximum around midafternoon.
As a result of these conditions and of the kinetics of the reaction system involved,
the diurnal variation of oxidant concentration typically shows a peak around noon.
The most complete data depicting oxidant trends in an urban center are those
taken in the Los Angeles basin.-'1 The basin, referred to as the South (California)
Coast Air Basin, consists of all of Orange and Ventura Counties and the most
populated portions of Los Angeles, Riverside, San Bernardino, and Santa Barbara
Counties (Figure 2-5). A series of mountain ranges separate the basin from other
uir basins. In Santa ...'.Lara County, the Santa Ynez fountains are the approximate
separation line. The clidLii of P'ouatains formed by the San Gabriel, San Bernardino,
San Gorgonio, and San Jacinto Mountains separates the basin- on the north and east
from the Southwest Desert Air Basin.
12
-------
SAN BERNARDINO
San BernardinoO
Rjyerside O
OSanta \
Ana \
''":":;X ORANGE S RIVERSIDE
PACIFIC OCEAN
Figure 2-5. South (California) Coast Air Basin.4
The basin has an area of approximately 8680 square miles and a population of
9.7 million. Although the basin contains 49 percent of the state's population, it
occupies only 6 percent of its area, and population density is 1120 people per
square mile. In 1970, there were over 6 million automobiles, trucks, and motor-
cycles registered in the South Coast Air Basin, an increase of 57 percent since
1960.
During the period 1963-1972, continuous monitoring data were generated by 15
monitoring stations within a 2000-square-mile area within the Los Angeles basin
and outlined by the cities of San Bernardino, Azusa, Pasadena, Burbank, West Lot.
Angeles, Lennox, Long Beach, Anaheim, and Riverside. These abundant data are
extremely useful not only because they establish reliably the overall oxidant trend
in a large population center but also because they help to detect interactions among
pollution components in the urban center that cause local oxidant concentrations to
deviate from the centerwidc trend.
Four methods of data presentation are used here to show the trends of oxidant
within the Los Angeles basin:
13
-------
1. The average of daily maximum 1-hour concentrations during July, August, and
September (an average of 92 values each year).
2. The annual average of daily maximum 1-hour concentrations (an average of 365
values each year).
3. The average of the highest maximum 1-hour concentrations in July, August, and
September (an average of three values each year). This average represents
concentrations on the worst smog days.
4. The number of hours during July, August, and September when the concentrations
were equal to or greater than 20 parts per hundred million (pphm). The 20-
pphm level is indicative of high smog conditions and has been proposed as a
health effect "warning level."
The four types of data for each station, from 1963 through 1972, are shown in
Tables 2-5 through 2-8. Data for three stations--Azusa, Riverside, and Los
Angelesare discussed below. The data in Tables 2-5 through 2-8 can be used
similarly to show the trends at the other 12 stations.
Based on the data in Tables 2-5 through 2-7, the Azusa air monitoring station
recorded the highest oxidant concentrations of any of the stations during most of
the 10-year period. Riverside had the greatest increase, and Los Angeles is among
those cities whose concentrations have decreased markedly during recent years. The
oxidant trends in these three cities are illustrated in Figures 2-6, 2-7, and 2-8,
respectively. In these figures, the 3-month (July, August, and September) averages
of the maximum 1-hour concentrations are plotted for each year of the 10-year
period.
In each of the figures, the annual average of the maximum 1-hour concentration
during the smog months varies considerably from year to year. Some of the varia-
bility is attributed to the change of emission sources brought about by growth, or
by the effect of control programs, and some to changes of locations of the sources.
Much of the variability is attributed to meteorological factors. To reduce this
latter variability, 3-year moving averages were used as shown in the figures. Each
point is plotted at the midyear and represents the average of the July through
September maximum 1-hour concentrations during the 3 years. The value of 16 pphm in
1964 in Figure 2-6, for example, is the average during the July-September months of
1963, 1964, and 1965; the point represents the average of 276 measurements.
All of the methods show about the same trends. Perhaps because of the smaller
number of measurements, the trends of 3-year averages of the highest three values
are not as smooth as the trends of the other averages. It is interesting to observe
that all the figures show lower oxidant concentrations at Azusa and Riverside in
1968 than would be expected from the general trend. In the absence of any known
changes in emissions in 1968 to account for the decrease, the anomalous concen-
14
-------
Table 2-5. OXIDANT TRENDS IN THE SOUTH COAST AIR BASIN, 1963-1972, THREE-MONTH AVERAGES
OF DAILY MAXIMUM ONE-HOUR OXIDANT CONCENTRATIONS FOR JULY, AUGUST, AND SEPTEMBER3»3
(pphm)
Station
Anaheim
Azusa
Burbank
Corona
La Habra
Lennox
Long Beach
Los Angeles, Downtown
Pasadena
Pomona
Redlands
Reseda
Riverside
San Bernardino
West Los Angeles
1963
11.4
19.8
15.1
16.4
4.2
16.2
20.0
--
17.4
15.5
11.9
1964
9.6
24.2
15.6
25.6
7.3
15.7
21.9
" *~
21.2
12.2
10.3
1965
15.9
24.4
20.9
16.7
15.6
7.0
6.8
16.2
21.6
20.8
18.6
16.6
17.0
11.3
1966
14.1
25.8
17.0
13.8
13.3
7.0
7.8
17.3
22.2
21.4
19.6
18.6
17.0
11.6
1967
12.5
26.8
22.5
22.1
9.8(5
6.7
5.9
13.9
22.6
23.9
20.9
25.2
18.2
11.1
1968
11.9
21.9
19.0
16.2
?)n.o
6.9
4.6
14.3
22.3
20.8
17.2
18.0
19.5
15.2
11.2
1969
13.7
28.0
19.4
22.0
17.2
6.8
6.3
13.0
27.4
24.5
20.4
20.1
25.6
18.9
11.0
1970
10.7
28.8
18.5
20.8
10.0
6.2
6.0
13.2
25.7
23.5
20.1
17.4
25.6
23.1
10.1
1971
8.9
22.9
16.1
13.4
15.2
5.7
6.2
10.0
20.6
16.6
17.1
14.2
22.9
18.7
8.4
1972
8.7
18.1
13.2
13.3
3.4
4.0
11.4
17.1
14.6
13.6
12.1
22.2
14.8
7.1
Numbers in parentheses indicate number of months of missing data.
were not operating.
Dashes indicate stations
Table 2-6. OXIDANT TRENDS IN THE SOUTH COAST AIR BASIN, 1963-1972, ANNUAL AVERAGES
OF DAILY MAXIMUM ONE-HOUR OXIDANT CONCENTRATIONS FOR ALL DAYS OF THE YEAR3'3
(pphm)
Station
Anaheim
Azusa
Burbank
Corona
La Habra
Lennox
Long Beach
Los Angeles, Downtown
Pasadena
Pomona
Redlands
Reseda
Ri versi de
Son Bernardino
West Los Angeles
1963
8.0
13.2
8.9
1964
7.3
14.3
8.5
13.2(5)15.6
--
--
4.7
11.2
13.2
--
--
--
11.5
9.9
9.6
--
--
5.3
10.3
13.0
--
-_
--
13.1
9.9
8.0
1965
11.1
15.3
12.2
11.8
1966
10.1
16.1
11.5
9.8
11.9(1) 9.4
6.4(1) 6.2
5.6
11.7
13.7
5.8
12.0
13.9
16.0(5)13.9
.. | ._
13.0(2)13.0
10.9
9.5
9.3
11.3
11.0
9.0
1967
9.8
16.5
14.1
13.8
1968
8.6
14.2
12.4
12.7
8.1(3) 8.0
6.3
5.0
10.2
14.0
14.1
5.5
4.3
9.8
14.4
13.4
5.1(10} 10.0
13.3
14.4
10.7
9.8
10.9
12.5
9.8
8.6
1969
8.6
15.2
11.3
12.1
1970
7.6
16.0
10.9
12.3
9.6(1) 7.4
6.0
4.8
8.8
15.0
13.0
9.6
12.0
14.2
9.9
8.2
5.5
4.4
8.1
15.0
13.0
10.7
10.5
14.7
11.8
7.5
1971
6.3
13.1
9.3
9.5
9.1
5.1
4.7
7.0
12.0
9.1
9.1
9.0
13.7
10.0
6.3
1972
5.9
12.0
8.6
8.7
3.7
4.0
7.6
11.1
9.5
8.7
8.3
12.2
8.4
5.7
Numbers in parentheses indicate number of months of missing data.
were not operating.
Dashes indicate stations
15
-------
Table 2-7. OXIDANT TRENDS IN THE SOUTH COAST AIR BASIN, 1963-1972, AVERAGE OF THREE
HIGHEST ONE-HOUR OXIDANT CONCENTRATIONS FOR JULY, AUGUST, AND SEPTEMBER3»3
(pphm)
Station
Anaheim
Azusa
Gurbank
Corona
La Habra
Lennox
Long Beach
Los Angeles, Downtown
Pasadena
Pomona
Rcdlands
Reseda
Ri vers i de
San Bernardino
'.lest Los Armeies
1963
22.3
32.3
32.7
32.3
--
--
13.7
33.7
36.7
__
--
32.7
27.3
27.3
1964
20.0
38.7
30.7
46.0
--
--
16.0
33.3
36.0
__
--
--
39.3
31.3
19.3
1965
33.7
44.0
35.0
35.7
31.3
17.7
17.7
1966
30.3
41.7
28.0
29.7
26.3
16.3
18.3
29.3 ,36.0
36.7
37.7
--
30.0
30.0
34.3
22.7
39.0
37.3
__
32.3
35.7
34.3
24.0
1967
30.3
48.7
40.7
37.7
1968
27.3
38.0
36.7
38. 0
20.0(2)22.3
15.3
15.0
27.0
36.0
38.7
--
34.0
44! 3
28.7
24.7
21.3
17.0
37.0
42.0
41.7
33.7
32.3
50.0
27.3
?4.7
1969
33.3
44.7
33.0
40.0
39.0
14.0
14.3
25.0
43.7
43.3
35.0
33.7
43.7
31.3
22.7
1970
29.7
52.0
31.7
39.7
27.0
12.3
14.7
23.0
45.3
39.0
38.3
33.0
53.0
39.7
18.3
1971
27.3
40.3
27.3
27.0
35.7
16.3
17.3
19.7
39.7
33.0
31.3
26.0
43.3
30.0
17.0
1972
28.7
36.0
25.0
32.3
10.7
13.0
23.7
32.0
29.3
26.3
24.3
45.7
34.0
16.0
Numbers in parentheses indicate number of months of missing data.
were not operating.
Dashes indicate stations
Table 2-8. OXIDANT TRENDS IN THE SOUTH COAST AIR BASIN, 1963-1972, NUMBER OF HOURS WITH
OXIDANT CONCENTRATIONS EQUAL TO OR EXCEEDING 20 pphm FOR JULY, AUGUST, AND SEPTEMBERS'3
Station
Anaheim
Azusa
Burbank
Corona
La Habra
Lennox
Long Beach
Los Angeles, Downtown
Pasadena
Pomona
Redlands
Reseda
Riverside
San Bernardino
West Los Angeles
1963
31
108
56
__
--
6
45
167
__
__
--
77
60
37
1964
6
261
58
__
__
--
3
J
48
180
-_
--
--
174
69
5
1965
61
291
177
__
__
1
?_
60
205
186
--
117
107
109
15
1966
60
303
60
__
__
3
6
67
159
178
--
112
123
92
17
1967
28
326
206
__
1
0
0
31
212
251
--
193
301
123
10
1968
18
205
121
__
15
5
2
42
169
176
124
116
__
67
19
1969
37
318
135
__
65
0
1
18
313
242
202
167
--
119
8
1970
15
335
97
__
12
0
0
15
268
207
167
82
--
231
1
1971
12
196
52
24
62
1
1
3
121
77
96
16
202
119
2
1972
16
116
24
__
49
0
0
17
66
54
43
15
212
43
0
Dashes indicate stations were not operating or data were not reported.
16
-------
- 18
a:
2
IU
o
z
o
o
h-
2 12
X
O
10
1963
1964
1965
1966
1967 1968
YEAR
1969
1970
1971
1972
Figure 2-6. Annual and 3-year moving averages of daily maximum 1-hour oxidant concentrations
in Los Angeles for July through September, 1963 - 1972.3
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
YEAR
Figure 2-7. Annual and 3-year moving averages of daily maximum 1-hour oxidant concentrations
in Azusa, Calif., for July through September, 1963 - 1972.3
\ /ANNUAL AVERAGE
V
3-year MOVING AVERAGE
1963
1964
1965
1966
1967 1963
YEAR
1969
1970
1971
1972
Figure 2-8. Annual and 3-year moving averages of daily maximum 1-hour concentrations in Riverside,
Calif., for July through September, 1963-1972.3
17
-------
trations are attributed in part to masking effects from the varying weather condi-
tions.
The 3-year average method reduces, but may not completely remove, measurement
variability caused by meteorological factors. A further reduction of the effects
of meteorological variability can also be accomplished by adjusting the oxidant
concentration for variation in one or more meteorological parameters, if these
parameters are known. One parameter that is an important indicator of weather
conditions, and for which there were sufficient data available, is the temperature
aloft. Examination of such temperature-oxidant data for the Azusa area for the
month of August each year during the period 1957-1970 indicated that oxidant con-
centrations tended to increase approximately 1 pphm for each additional degree
Fahrenheit in the value of the monthly average maximum temperature. Evidently then,
a basis exists for adjusting the observed oxidant concentrations to remove some of
the variability that may be attributed to meteorological conditions. Such adjust-
ment results in lowering the oxidant concentrations for Augusts that were hotter
than normal and increasing the concentrations during cooler Augusts. These
adjusted concentrations are shown in Figure 2-9; a linear regression line is fitted
to the points for 1957 through 1970. The slope of this line and the distribution
of points around it lend considerable credence to the existence of an annual
increase of 0.64 pphm between 1957 and 1970. The adjusted concentrations for 1971
and 1972 are far below the regression line extrapolated through these years. The
abrupt departure from the long-term trend line is of such magnitude as to indicate
that the upward oxidant trend at Azusa may have terminated in 1970.
In contrast to Figure 2-7, which showed the 1968 average to be substantially
below the 3-year moving average line, Figure 2-9 shows that the adjusted 1968
32
30
o
I 26
z
111
Z 24
O
o
I221
X
0 20
©
POINTS NOT USED TO ESTABLISH
REGRESSION LINE
-©
18
1957
1960
1965
1970
1972
YEAR
Figure 2-9. Average of daily maximum 1-hour oxidant concentrations for months of August in
Azusa, Calif., 1957-1972.3 (Adjusted for temperature aloft.)
18
-------
concentration is above the regression line. This supports the premise that in Azusa
the low oxidant concentrations in 1968 were caused by weather; whereas the con-
centrations observed in 1970 and 1971 were not. In Riverside, the 1971-1972
temperature-adjusted concentrations were less than those for the previous 4 years,
but the differences did not meet the test for significance at the 5 percent level.
Thus, it is not certain whether the concentrations at Riverside peaked in 1070.
The basinwide pattern of oxidant concentrations is readily apparent when the 3-
year averages are plotted on a map, as in Figure 2-10. The averages of the maxi-
mum 1-hour concentrations in July, August, and September of the latest 3-year
period (1970-1972), are shown at each station, and isopleths were drawn for
the air basin. Oxidant concentrations are lowest in the southwest, increase
steadily toward the northeast, and reach a maximum in the Azusa-Riverside area,
Concentrations in Azusa and Riverside arc nearly five times higher than in the
coastal cities of Lennox and Long Beach.
\
RESEDA
-14.6
SAN BERNARDINO
20-
Figure 2-10. Distribution of average of daily maximum 1-hour oxidant concentrations (pphm)
in Los Angeles basin during July through September, 1970-1972.3
CONCENTRATIONS OF OZONE IN URBAN ATMOSPHERES
In one study, conducted by EPA in the summer of 1971, ambient air measurements
were made in several cities using a chemiluminescent detector that responds speci-
fically to ozone.^ Resultant data are summarized in Table 2-9.
Figure 2-11 shows the diurnal pattern of 1-hour average ozone concentrations
measured on 2 selected days at the Denver and Philadelphia CAMP sites. Because the
19
-------
Table 2-9. SUMMARY OF OZONE MEASUREMENTS IN VARIOUS CITIES, SUMMER 19715
State
Florida
Hawai i
Indiana
Iowa
Kansas
Kentucky
Louisiana
Minnesota
Nebraska
New Mexico
New York
North Carolina
Ohio
Oklahoma
Pennsylvania
Puerto Rico
Tennessee
Texas
Virginia
Wisconsin
City
Jacksonville
Mi ami
Tampa
Honolulu
Indianapolis
Des Moines
Wichita
Louisville
New Orleans
Minneapolis
Omaha
Albuquerque
Rochester
Charlotte
Cleveland
Columbus
Dayton
Toledo
Oklahoma City
Tulsa
Pittsburgh
San Juan
Memphis
Nashville
Austin
Corpus Christi
Dallas
El Paso
Houston
San Antonio
Norfolk
Richmond
Milwaukee
No. of
hourly
observations
2044
2092
1919
1388
2070
2141
2536
1836
2289
2025
2073
2209
2391
2097
1886
2214
2395
2342
1684
2113
2629
1177
1644
1713
2134
2263
2125
2775
2583
1919
1638
1353
2296
No. of times
standard
(0.08 ppm)
exceeded
6
0
0
0
74
17
4
74
58
1
1
8
no
38
23
112
168
156
32
18
105
0
34
13
14
59
38
6
48
55
9
33
64
Two
highest
levels
0.100 0.100
0.050 0.050
0.070 0.065
0.024 0.023
0.140 0.130
0.105 0.100
0.105 0.095
0.140 0.140
0.130 0.125
0.095 0.080
0.090 0.075
0.115 0.095
0.155 0.150
0.109 0.106
0.145 0.125
0.145 0.130
0.190 0.175
0.156 0.140
0.135 0.120
0.115 0.115
0.165 0.155
0.055 0.045
0.140 0.130
0.115 0.115
0.150 0.110
0.190 0.185
0.135 0.125
0.130 0.120
0.155 0.150
0.145 0.145
0.105 0.105
0.117 0.112
0.190 0.170
LOCAL TIME
Figure 2-11. Diurnal variation of hourly ozone concentrations in Philadelphia and Denver.2
20
-------
analytical method for ozone is relatively new, ambient ozone data accumulated thus
far are sketchy.
CONCENTRATIONS OF PEROXYACETYL NITRATE IN URBAN ATMOSPHERES
Peroxyacetyl nitrate concentrations were measured in Los Angeles using gas
chromatographic techniques with an electron-capture detector during September and
October 1965.6 Seven measurements per day were made for each of 16 weekdays in
September and 19 weekdays in October. The mean 1-hour-average concentrations of PAN
and oxidant by hour of day for these periods are shown in Figure 2-12.
Beginning in June 1966, measurements of PAN have been made on the campus of the
University of California at Riverside, also with the gas chromatograph and electron-
capture detector.1 Samples are usually collected once each hour between 6 a.m. and
5 p.m. In Figure 2-13, the mean 1-hour-average oxidant concentrations, as measured
with a Mast analyzer, and the mean 1-hour-average PAN concentrations are shown by
the hour of the day for the month of September 1966. The monthly mean hourly
oxidant and PAN concentrations and the monthly mean of the daily maximum hourly
average of 1 year's data are shown by month in Figure 2-14.
The comparison shown in Figure 2-14 is a good illustration of how specific
averaging processes affect results. The considerable variation;, in daily maximum
hourly concentrations as a function of time of year become much less obvious i f the
data include all hours. As stated previously, the latter dampening effect is the
result of including in the data those hours for which oxidant is necessarily at or
near zero. Because these near-zero hours account for approximately 65 percent of
the time of sampling, they have the effect of averaging-out the elevated daytin.e
values. Each method of averaging has its purpose, however, and subsequent inter-
pretations of the results require careful consideration.
In Figure 2-13, there are tvvo daily maxima for the oxidant and PAN concen-
trations. The PAN concentrations in Riverside arc an order of magnitude lower than
those in Los Angeles; the concentiaticns of oxidants are of the sai'ie order of mag-
nitude .
CONCENTRATIONS OF OXIDANTS FROM NATURAL SOURCES
Natural sources of the oxidants found in the lower atmosphere include electrical
discharges, stratospheric ozone, and atmospheric reactions of naturally emitted
organics and nitrogen oxides. Of these, the electrical discharge source is believed
to contribute only negligibly to biospheric ozone,
Stratospheric ozone, formed by the action of solar radiation upon oxygen at
altitudes between 15 and 37 kilometers can contaminate the lower atmospheric layers
through vertical transport. Although several theories are available to explain the
manner in which such transport occurs, it is generally believed thatwith the
21
-------
0.18
AVERAGES:
. __ .~ 19 WEEKDAYS, OCTOBER
!ir7~ 16 WEEKDAYS, SEPTEMBER
LOCAL TIME
Figure 2-12. Variation of mean 1-hour average oxidant and PAN concentrations, by hour of day,
in downtown Los Angeles, 1965.1
exception of a few, isolated instancesthe ozone concentrations transferred to
ground level do not exceed a few parts per hundred million.1
In efforts to obtain a measure of the total oxidant concentration from natural
sources, measurements were made in several nonurban locations. Results from such
early studies showed the oxidant in these areas to range mainly from less than 0.01
22
-------
-£ 0.14
g
< 0.«2
\-
Z
0.10
i r
OXIDANT
O
H
O.006 <
0 10 12
LOCAL TIME
Figure 2-13. Variation of mean 1-hour average
oxidant and PAN concentrations, by hour of
day, at the University of California at Riverside,
September 1966.1
E °-22r
0.
a- 0.20 L~
MONTHLY MEANS OF DAILY MAXIMUM
1-hour AVERAGE CONCENTRATIONS
- MONTHLY MEANS OF i-hour AVERAGE
CONCENTRATIONS
*OXIDANT BY MAST, CONTINUOUS
24 hours, PAN BY PANALY2ER,
SEQUENTIAL, 6 a.m. TO
4 OR 5 p.m. ONLY.
NOV. DEC. JAN. FEB. MAR. APR. MAY
MONTH
0
r-
<
o:
i-
z
UJ
u
z
0
u
t
z
<
Q
X
0
Z
<
1 L 1
s
0.1BCT
0.16
O.14
0.12
0.10
0.08<
0.06<
O.04<
O.02
o.oo
_
OXIDANT*
^-o cx>
r*- ^
/
^^~-V P/
^ ^.-^
^-^-*
JUN JUL. AUG.
I,
I966
Figure 2-14. Monthly variation of oxidant and PAN concentrations at the University of Califor-
nia at Riverside, June 1966-June 1967.1
to 0.04 ppm, with occasional readings as high as 0.07 ppm.1 More recent studies,
however, revealed frequent occurrence of oxidant concentrations exceeding the air
quality standard (0.08 ppm 03) in several rural areas in the continental United
States.7>8 These studies provided strong indications that a part of the oxidant
found in nonurban areas may result from transport of pollutants from urban areas.
Some clarifications must be made here in regard to the significance of these
concentrations of naturally formed oxidant. First, such concentrations are not
iiegligible; they may amount to as much as 50 percent or more of the level taken in
the United States to be the air quality standard for ozone (0.08 ppm 03). Second,
23
-------
although these concentrations occur in the absence of anthropogenic emissions, this
does not necessarily mean that in the presence of anthropogenic sources the observed
oxidant is simply the sum of the natural and the anthropogenic contributions. The
chemistry of oxidant formation from hydrocarbons and nitrogen oxides suggests that
the combination of natural and man-made emissions (hydrocarbons and nitrogen oxides)
can result in oxidant concentrations that can be either larger or smaller than the
sum of the concentrations caused by the two emission sources individually.
In conclusion then, the oxidant concentrations from natural sources, although
not unequivocally established, almost certainly are not negligible. Further,
assessment of the importance of these sources is not simple. The levels of oxidants
observed in areas free of human activities are not necessarily indicative of the
contribution of the natural sources to the oxidant observed in urban atmospheres.
REFERENCES FOR CHAPTER 2
1. Air Quality Criteria for Photochemical Oxidants. U. S. Department of Health,
Education, and Welfare, Public Health Service, National Air Pollution Control
Administration, Washington, D.C. NAPCA Publication No. AP-63. March 1970.
2. Data from National Air Sampling Networks, Continuous Air Monitoring Projects.
U. S. Environmental Protection Agency, Quality Assurance and Environmental
Monitoring Laboratory, Research Triangle Park, N.C. 1964-1973.
3. Kinosian, J. R. and S. Duckworth. Oxidant Trends in the South Coast Air Basin,
1963-1972. California Air Resources Board, Sacramento, Calif. April 1973.
4. California Emissions Inventory, 1970. California Air Resources Board, Sacra-
mento, Calif. July 1972.
5. Ambient Ozone Measurements, July through September 1971, National Aerometric
Data Bank. U. S. Environmental Protection Agency, Quality Assurance and
Environmental Monitoring Laboratory, Research Triangle Park, N. C.
6. Mayrsohn, H. and C. Brooks. The Analysis of PAN by Electron Capture Gas
Chromatography. California State Department of Public Health, Los Angeles,
California. (Presented at Western Regional Meeting of the Americal Chemical
Society. Los Angeles. November 18, 1965.)
7. Mount Storm, West Virginia-Gorman, Maryland, and Luke, Maryland-Keyser,
West Virginia, Air Pollution Abatement Activity. U. S. Environmental Pro-
tection Agency, Research Triangle Park, N. C. Publication No. APTD-0656.
April 1971.
8. Johnston, D. Investigation of High Ozone Concentrations in Vicinity of Garrett
County, Maryland, and Preston County, West Virginia. Final Report. Research
Triangle Institute, Research Triangle Park, N. C. Prepared for U. S. Environ-
24
-------
mental Protection Agency, Research Triangle Park, N. C., under Contract No.
68-02-0624. Publication No. EPA-R4-73-019. January 1973.
9. Title 42: Public Health; Part 410: National Primary and Secondary Ambient
Air Quality Standards. Federal Register. 36(84)=8186-8201, April 30, 1971
25
-------
CHAPTER 3. CHEMISTRY OF OXIDANT FORMATION
INTRODUCTION
When photochemical oxidants in air were identified as products of a photo-
chemical process involving primary air pollutants, it became apparent immediately
that the problem could not be abated by traditional methods of direct control. The
chemistry of this process had to be clearly understood before rational abatement
measures could be devised. Accordingly, in the ensuing years, numerous studies
of the oxidant chemistry were conducted witli the following specific objectives:
1. To identify the precursors of photochemical oxidants, that is, those
primary pollutants that participate as reactants in the oxidant-forming
process.
2. To determine the kinetics of the precursor reactions mainly for the
purpose of deducing the impact of precursor control upon oxidant
formation.
3. To determine the stoichiometry of the precursor reactions for the purpose
of more fully assessing the pollution problems caused by such precursors.
4. To elucidate in detail the oxidant-forming mechanism for the purpose of
providing theoreticalas distinct from empirical--input to the oxidant
abatement effort, and also for the purpsoe of relating oxidant formation to
other manifestations of photochemical pollution.
Several of these objectives have been achievedat least to a degree of completion
such that the information generated was sufficiently comprehensive and reliable to
permit development of a crude but promising oxidant abatement strategy. Because.
of their importance in the case made here regarding the photochemical oxidant
problem, these studies of the oxidant chemistry are presented and briefly discussed
in this report. The discussion is focused on those findings that are most noteworthy
and most relevant to a delineation of the photochemical oxidant problem.
MECHANISM OF OXIDANT FORMATION
The pioneering work of Haagen-Smit and his collaborators in 1952 first demon-
strated through laboratory experimentation that the photochemical oxidants present
in an urban atmosphere may indeed be products of atmospheric photochemical reactions
involving organic and inorganic (nitrogen oxides) pollutants. Since then numerous
studies of the oxidant formation phenomenon have been conducted,2-5 and a wealth of
information regarding the stoichiometry, kinetics, and mechamisms of these hydrocarbon
27
-------
(HC)-nitrogen oxide (NOX)-air-sunlight reactions in now available. The following
discussion summarizes the results of these studies and presents the chemical mechanism
that is presently thought to best explain the phenomenon of photochemical oxidant
formation.
All experimental research concerned with the mechanism of atmospheric oxidant
formation was conducted in the laboratory using experimental conditions that were
similar to, but not nearly as complex as, those prevailing in the real atmosphere.
Such simplifications of the natural systems had to be made in order to facilitate
research, but they also incurred penalty in terms of limitations on the validity of
the research findings. Thus, most mechanistic evidence obtained to date pertains
solely to the oxidant formation process occurring in the laboratory systems. The
extent to which this laboratory evidence is applicable to the real atmosphere is
not known with confidence and cannot be easily ascertained. The most that can be
said at this time is that all of the reaction steps known to occur in the experi-
mental reaction systems almost certainly occur in the real atmosphere also. The
converse, however, is not necessarily true; that is, unidentified reaction steps may
occur in the real atmosphere but not in the laboratory simulations.
The chemical changes that are observed to occur when a mixture of HC and NOX
pollutants is exposed to sunlight under conditions similar to those in atmosphere
are illustrated in Figure 3-1. The diagrams of Figure 3-1 depict the overall photo-
chemical process to consist of two distinct reaction stages occurring consecutively.
During the first stage, nitric oxide (NO) is converted into nitrogen dioxide (N02)
without any appreciable buildup of ozone (03) or other non-NIC^ oxidants. The second
IRRADIATION TIME
Figure 3-1. Chemical changes occurring during photoirradiation of hydrocarbon-nitrogen
oxide-air systems.
28
-------
stage starts when almost all the NO has been converted into N02 and is characterized
by rapid accumulation of 03 and other oxidant and nonoxidant type products. In the
absence of HC reactant, the overall process maintains the two-stage profile except
that the NO conversion process is now much slower, and the resultant 03 concentra-
tionsgiven adequate irradiationare much smaller.
Kinetic mechanism explaining the observations depicted in Figure 3-1 have been
postulated only in the last 10 years. The proposed mechanisms can be classified as
either "specific" (written for the photooxidation of a specific hydrocarbon) or
"lumped" (written for one or more species involving lumped reactants). The specific
mechanisms, such as the one shown in Figure 3-2 for propylene^ are as a rule more
complex and provide a more detailed and hence more informative picture. Because of
their complexity, however, specific mechanisms are nearly impossible to use in
practical applications, such as in developing mathematical models that predict
levels of oxidant in urban atmospheres based on levels of precursors. The diffi-
culty arises mainly from the extreme multiplicity of reaction steps needed to
describe the reactions of each of the numerous IIC reactants present in urban air.
This drawback in the specific mechanisms prompted the development of lumped mechan-
nisms--mechanisms that are less descriptive of the fundamental chemistry involved
but more useful in practical applications. An example of a lumped mechanism and its
associated rate constant data is given in Figure 3-3 and Table 3-1, respectively.?
By either of the mechanisms given in Figures 3-2 and 3-3, ozone formation in the
atmosphere appears to be the net result of the following main reactions:
UV
Xt<"\ a. \1f~\ (A f "7 -I ~s
(3-2)
(3-3)
(3-4)
(3-5)
(Where: ROX and R0y are organic and/or inorganic radicals that form only when organic
reactants are present in the system.) Through this mechanistic procedure, the NO pro-
duct from the photolysis of N02 reacts rapidly with and consumes 03 to regenerate the
photolyzed N02. Therefore, unless other processes convert the NO into N02, 03 is not
allowed to accumulate to important levels. However, other NO conversion processes
do exist--mainly, the reactions of NO with ROX and, to a much lesser degree, with
molecular oxygen (02). The reaction with ROX occurs only when photochemically
reactive organic reactants are present, and is sufficiently rapid to cause atmospheric
accumulation of 03 to as much as 1 part per million (ppm) or more. In the absence of
reactive organics, the only NO conversion process parallel to the Os-NO reaction is
29
1NU~|
0 +
03
ROY
A
2NO
light
^ m
02 »
+ NO
+ NO 1
+ o2 ,
INU T U
. o3
- N02 + 02
N02 + ROy
> 2N02
-------
8
+
CO
I
CJ
C
^J
"* ^
-L. CM
*x i
2 °
O co
O X
X O
*
o
CN
0
t °
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CO
I
0
CM 0
) O 0
i r CM
o
I
i
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(U
o
3
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T3
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D.
en
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tt
sr
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_Q>
g
s
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O *J
>- '«
c O
i g-
^1
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D
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lift!
0 1
? o o o cj
ro XIIX
O
CN
O
I
0
O
i=c
0
o
DC
t
0
o
I
o
I
+
+
o
o
U
cc
t
CO
0
cj
I
I O
^0 0
=00 0
CC DC
tt
x o
0 +
r- O
U I
?NX
I 0
+ +
0 0
0 0
DC CC
tt
I O
o +
CN 0
O I
I
CN
o
.
o "?
+ 1
§1
tt
s!
0 £
s
o
CN
I
CN
o
1
o
o =O
DC
t
I
o
_^_
0
S
o
+
*
I Reactions of organic
> free radicals with NO,
NO2, and O2
CN
O
Z
cj
I CN
0 + §
8=0 So
CC I CC
t
CN
o
z
o
o
1 1
o
o
cc
|
CN CN O
O O -»
+ z ±
0 ±
cc o
DC
o
cc
"- - o =0
8
-
O
z
c
o
n
'x
O
f^\
CM
O
I
O
O
^~
CN
O
I
"~~N
CN
O
0
CC
CN
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the reaction of NO with 02', this reaction, however, is relatively slow and does not
cause significant 03 accumulation.
In mathematical terms, the 03 buildup in the atmosphere is given by the equation:^
[N02]
[03] = kl (3-6)
3 [NO]
derived by applying the steady state hypothesis to chemical reaction-steps 3-1, 3-2,
and 3-3. In Equation 3-6, I designates light (sunlight) intensity, and k is a constant.
By this equation, any process that converts NO into N02such as the reaction of NO
with ROXtends to cause high [N02]/[NO] ratios, and hence high levels of 03 buildup.
The mechanistic picture described in the preceding paragraphs suggests at first
glance that any organic reactant that is capable of causing rapid conversion of NO
into N02 should also cause formation of high levels of 03. This, however, is only
partially true. In a generalized sense, 03 yield depends not only on the ability
of the organic reactant to oxidize the NO, but also on the tendency of the organic
reactant to react with and destroy 03 and on the nature and mechanistic role of the
products that result from the photooxidative degradation of the organic reactant.
Presently, the mechanism shown in Figure 3-2, although highly speculative
because it has not been validated yet over a wide range of reactant concentrations,
is believed to be reasonably valid and complete. However, it should be stressed
that this mechanism is limited in that it applies only to laboratory systems--
more specifically, to propylene-NOx-air mixtures that are photoirradiated in a
smog chamber. As mentioned previously, the mechanism of the oxidant-forming process
in a real atmosphere containing a multitude of reacting pollutants may include
reaction steps in addition to those listed in Figure 3-2. Such additional reac-
tions known or suspected to occur in the real atmosphere may include, for example,
photolysis of aldehydes, of ketones, and of lead halides and follow-up reactions of
the products from such photolyses. Additional photochemical reactions may also be
caused through energy transfer processes promoted by pollutants capable of absorbing
solar energy and of transferring such energy to nonabsorbing pollutants. Finally,
additional reactions of importance may occur on the surface of the aerosol particles
suspended in air. The question regarding the roles, if any, of all these reactions
in the oxidant-forming process that occurs in the real atmosphere is an open one.
Additional research must be done before answers are obtained.
HYDROCARBON REACTIVITY
From an air pollution standpoint, the photochemical reactivityor
"reactivity"--of an organic pollutant denotes the intrinsic ability of the pollutant
to participate in atmospheric chemical reactions that result in photochemical smog
34
-------
formation. The concept of hydrocarbon reactivity (the term "hydrocarbon" is meant
here to encompass all organic substances) was developed when laboratory research
showed that different organic substances, when exposed to atmospheric conditions, do
not react similarly. Specifically, when traces of an individual organic and NO in
air were irradiated with artificial sunlight, the resultant levels of smogin terms
of eye irritation, plant damage, visibility reduction, and material damagewere
found to vary widely with the chemical structure of the organic reactant. The same
laboratory studies also revealed that these smog manifestations, as a rule, were
accompanied by manifestations of chemical activity, such as disappearance of the
organic reactant, rapid conversion of NO into N02, and formation of products. As a
result of these studies, the concept of hydrocarbon reactivity has evolved to include
several reactivity types, each type corresponding to a specific chemical or biolog-
ical manifestation of photochemical smog. Hydrocarbon reactivity has been defined
and expressed in terms of the following;8
1. Rate of disappearance of organic reactant from irradiated organic-
NO-air mixtures.
2. Rate of conversion of NO into N02-
3. Yield of ozone or oxidant.
4. Yield of aldehydes and peroxyacyl nitrates.
5. Formation of aerosols.
6. Damage to plants.
7. Irritation of eyes.
The fact that organic substances differ greatly in reactivity is extremely
significant from a pollution control standpoint because it introduces the option of
selective control of organic emissions as an alternative to indiscriminate control.
In principle at least, this reactivity-based control is believed to be the superior
approach, and it is for this reason that considerable research effort has been
expended in obtaining reactivity data for organics and in exploring application of
such data in the development of control strategies. Such reactivity data presently
available, methods for obtaining them, and their application in control practices
are discussed next.
Because of the early recognition of hydrocarbon pollutants, a relative abundance
of reactivity data for HC is available. Data for nonhydrocarbon organics cover a
large variety of organic compounds but are not as comprehensive and reliable as
those for HC. Information, obtained through 1965, on several types of HC reactivity
was compiled and anlyzed by Altshuller^ and presented in terms of a reactivity
classification of hydrocarbons, as shown in Table 3-2. The Altshuller analysis is
an attempt to derive a single reactivity rating for each hydrocarbon that presumably
represents the composite of all reactivity types mainifested by that hydrocarbon.
This reactivity rating, which will be discussed later, has only limited validity,
35
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oxidant dosage, that is, the time-integrated concentration of oxidant. Such
reactivity data, however, are not satisfactory, mainly because they are extremely
sensitive to variations in smog chamber design and measurement conditions. The
problem is somewhat reduced by expressing reactivities of organics as measured in
one smog chamber in relation to the reactivity of a reference organic as measured in
the same chamber. A similar technique is the "reactivity scale" technique by which
the reference organic is chosen to be the most reactive organic known and is arbi-
trarily assigned a reactivity rating of 10 (or 100); thus, reactivities of organics
are expressed in terms of ratings ranging from 0 to 10 (or 100). In the present
case, the oxidant-reactivities of the organics tested in the aforementioned studies
are expressed in terms of the maximum oxidant concentration relative to the maximum
oxidant concentration for toluene. The principal reason for choosing toluene as
the reference organic is that toluene is a common test-organic in most of the
reactivity measurement programs reported. Such oxidant-reactivity data for various
hydrocarbon and nonhydrocarbon organics are given in summary form in Tables 3-3 and
3-4.
Reactivity data, such as those in Tables 3-3 and 3-4, are useful in that they
provide a degree of discrimination of the organic pollutants, based on the ability
of such pollutants to produce photochemical oxidant. These data, however, have
limitations. To illustrate the nature and magnitude of these limitations, it is
necessary that the intended use of the reactivity data first be considered.
As mentioned previously, the reactivity data are intended to provide a guide in
developing selective control strategies. Conceptually, such a strategy entails
reduction of each individual organic emission component to a degree commensurate
with the component's relative reactivity. In practice, selective control can be
implemented either by development of different emission rate standards for the
different organic emissions or by development of a reactivity standard for the
emission mixture. Either application introduces demands in terms of consistency,
interpretability, and abundance of reactivity data. Considering such applications
and their demands, the existing oxidant-reactivity data are deficient in three
respects.
First, the existing data are of limited internal consistency; that is, reac-
tivity data obtained in different laboratories (for the same organics) are not in
good agreement. The problem is probably caused by the diversity of smog chamber,
designs and reactivity measurement conditions used in the various laboratories.
Expressing the reactivity of each organic in relation to the reactivity of a
reference organic alleviates, but does not solve, the problem. The degree of agree-
ment among data from different laboratories is illustrated in Figure 3-4, in which
oxidant reactivities from the Battelle, Shell, and SRI studies are compared.
Reasonable correlation is indicated for the Battelle-Shell data, but correlation of
the Battelle-SRI data is poor.
39
-------
Table 3-3. PHOTOCHEMICAL REACTIVITIES OF HYDROCARBONS
Hydrocarbon
Methane
Ethane
Propane
n-butane
jvhexane
Iso-octane
n-nonane
Ethyl ene
Propylene
Butene-1
t-butene-2
cis-butene-2
2-me-butene-2
Hexene-1
Hexene-2
Tetra-me-ethylene
1 ,3-butadiene
Acetylene
Benzene
Toluene
Eth-benzene
n-prop-benzene
Iso-prop-benzene
n-but-benzene
Iso-but-benzene
sec-but-benzene
tert-but-benzene
.g-xylene
m-xylene
ji-xvlene
Mesitylene
Maximum cxidant-ozone, toluene equivalents3
BOM study! 3
_
-
_
0.08
0.10
0.13
-
1.55
2.00
1.87
1.99
2.08
2.14
1.70
1.73
-
2.51
-
0
1.00
0.92
0
0.79
-
-
-
-
1.49
-
1.37
1.73
GM studylO
_
-
.
0.53
0.57
0.63
-
0.93
1.80
1.57
1.47
1.47
1.63
1.37
_
2.00
1.60
-
0.17
1.00
0.70
0.70
0.63
0.80
0.57
0.87
0.43
1.07
1.30
0.87
1.53
Other studies4
0
0
0
-
-
-
0.4
1.9
1.2
1.2
_
-
-
1.2
-
-
2.0
0
_
1.0
-
-
-
_
_
_
-
-
1.3-2.0
_
2.3
Toluene reactivity in terms of maximum oxidant-ozone concen-
tration was: BOM: 0.355 ppm 03; GM: 0.30 ppm 03; other
studies: 0.36 to 0.50 ppm 03.
Second, the existing oxidant-reactivity data cannot be interpreted reliably in
terms of relative contributions of the various organic pollutants to the photo-
chemical oxidant observed in the real atmosphere. The problem here has two origins:
(1) the exact conditions in the real atmosphere cannot be reproduced in smog cham-
bers, (2) the existing reactivity data, which were obtained mostly from individual
compound tests, are not necessarily adequate for predicting reactivities of organic
pollutant mixtures such as those encountered in real atmospheres.
Third, the existing oxidant-reactivity data cover only those hydrocarbon and
nonhydrocarbon organics that have been identified thus far in the atmosphere and in
motor vehicle emissions. Many unidentified organic pollutants from diesel engines,
-------
Table 3-4. REACTIVITIES AND CLASSIFICATION OF SOLVENTS
Solvent
Paraffins (including
cycloparaffins)
Olefins
Aliphatic
Styrene
a-me-styrene
Aromatics
Benzene
prim-, sec- alky! benzenes
tert-alkyl benzenes
DiaTkyl -benzenes
Tri-,tetraalkyl benzenes
Ke tones
Acetone
rnalkyl ketones
Branched alkyl ketones
Cyclic ketones
Unsaturated ketones
Alcohols
prim-, sec-alky! alcohols
tert-alkyl alcohols
Diacetone alcohol
Ethers
Diethyl ether
Tetrahydrofuran
Ethyl cellosolves
Esters
prim-, sec-alky! acetates
tert-alkyl acetates
Cellosolve acetate
Phenyl acetate
me-benzoate
Amines
Ethyl amines
N-me-pyr roli done
N , N-dime-f ormami de
N , N-di me-acetarai ne
Halocarbons
Perhalogenated
Partially halogenated
paraffins
Partially halogenated
olefins
Nitroalkanes
2-nitropropane
Reactivity, toluene equivalents
Battell e14
Range
0.4-0.6
1.3-1.5
0.7
1.5
0
0.9-1.2
0.6
1.0
1.5
0
0.5-0.8
1.0-1.8
0.2
1.5-1.7
0.2
-
1.4
-
1.9
1.5
0.2
-
-
0
0
0.1-0.2
0.7
-
-
-
-
-
0.2
Avg.
0.5
1.4
0.7
1.5
0
1.0
0.6
1.0
1.5
0
0.65
1.4
0.2
1.6
0.2
-
1.4
-
1.9
1.5
0.2
-
-
0
0
0.15
0.7
-
-
-
-
-
0.2
SRI15
Range
0.9-0.9
-
-
-
-
1.0
:
-
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0.9
0.9-1.0
0.5
-
1.1-1.2
-
1.7
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1.9
0.7-1.4
-
1.1
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0.5-0.5
0.8
1.4
0.7
Avg.
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1.0
^
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0.9
0.95
0.5
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1.2
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1.7
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1.9
1.0
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1.1
-
-
-
-
-
-
0.5
0.8
1.4
0.7
Shell16
Range
0.8-1.0
1.8-3.1
-
-
0.2
1.0-1.2
0.5-0.5
1.3-1.7
3.2
0.1
0.9-1.4
1.3
0.5-0.6
-
0.6-1.45
0.3
-
2.5
1.4
-
0.8-1.0
0.5
-
-
-
-
-
0.2
0.95
-
-
-
-
Avg.
0.9
2.4
-
-
0.2
1.1
0.5
1.5
3,2
0.1
1.1
1.3
0.5
-
1.1
0.3
-
2.5
1.4
-
0.9
0.5
-
-
-
-
-
0.2
0.95
-
-
-
-
Class
III
V
III
V
I
IV
II
IV
V
I
III
IV
II
V
IV
I
V
V
V
V
III
II
IV
I
I
I
III
I
III
II
III
IV
II
-------
1 .O
i 1-6
UJ
< 1.4
O i 2
UJ '*
Ul
§ 1.0
o
(- 05
> 0.6
O
2 o-4
cc
il °-2
0.0
1 ' l _
I _
* *
__* _
BATTELLE -SRI
1
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
BATTELLE REACTIVITY, TOLUENE EQUIVALENTS
iii;
BATTELLE-SHELL
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
BATTELLE REACTIVITY, TOLUENE EQUIVALENTS
Figure 3-4. Correlation of solvent reactivity data from Battelle,14 SRI, 15 and Shel|16 studies.
refineries, etc., undoubtedly exist in the atmosphere. Such pollutants need to be
identified and their reactivities measured.
These imperfections of the presently available reactivity data, although real,
do not necessarily altogether prohibit the use of reactivity criteria in control
programs. Despite existing uncertainties, there is little doubt that organics such
as methane, ethane, propane, acetylene, and benzene are not significant oxidant
producers but that olefinic and polyalkyl benzene hydrocarbons are. Therefore, a
limited use of the reactivity concept in control strategies for organic emissions
is feasible.
As discussed in detail in Chapter 9, the present oxidant abatement strategy
in the United States consists of the following regulations and recommendations:
1. The national air quality standards for photochemical oxidants and for
nonmethane hydrocarbons (NMHC) promulgated by the Federal government.^
Unlike the oxidant standard, the NMHC standarda 6 to 9 a.m. average
concentration of 0.24 ppm C that is not to be exceeded more than once
per year--is not meant to be an air quality goal; rather, it is to serve
as a guide in devising implementation plans to achieve the oxidant
standard. Methane was exempted from this restriction upon hydrocarbons
mainly because of its low oxidant-forming potential.
2. The motor vehicle emission standards for total hydrocarbons promulgated by
the Federal government.20 Unlike the previous regulations, no hydrocarbon
was exempted from the standards for this sourcean obvious inconsistency.
3. The control guidelines for organic solvent emissions recommended by the
21
Federal government.
Under these guidelines, all organic solvents are
-------
assumed to be reactive except Cj to C$ n-paraffins, saturated halogenated
hydrocarbons, perchloroethylene, benzene, acetone, cyclohexanone, ethyl
acetate, diethylamine, isobutylacetate, isopropyl alcohol, methyl benzoate,
2-nitropropane, phenyl acetate, and triethylamine.
4. Control regulations for organic solvent emissions promulgated by individual
state governments. Some states adopted the Federal government recommen-
dations for exempt solvents; others adopted California Rule 66, which
assumes all solvents to be nonreactive except certain olefinic, aromatic,
and ketone-type organics. '
As suggested by these regulations, reactivity criteria were used in the formu-
lation of the present oxidant abatement strategy in the United States, but in a
somewhat inconsistent manner. Thus, the definitions of reactive (or of nonreactive)
organics used in California Rule 66 and in the Federal guidelines for State Imple-
mentation Plans are consistent neither with each other nor with the definitions used
in the motor vehicle emission standards and the air quality standards. This incon-
sistent use of the reactivity concept in present control practices is largely a
result of compromises made in the interest of rationality, responsiveness to specific
needs, and practicability of control regulations. The Federal government is now
taking a closer look at the significance of this inconsistency problem and some
corrective action may be taken.23
RELATIONSHIPS BETWEEN OXIDANT AND OXIDANT PRECURSORS
This section examines the functional relationships observed between photo-
chemical oxidant (OX) and two oxidant precursors, hydrocarbons (HC) and nitrogen
oxides (NOX). In the United States, these relationships have been used as the sole
basis for determining emissions control requirements for oxidant abatement. Because
of this use, and because of the enormous economic and social impact of such control,
these OX-HC-NOX relationships became an extremely controversial issue and were the
subject of numerous studies.
Early attempts to determine OX dependence on HC and NOX consisted of smog
chamber experimentation in which synthetic or automotive exhaust mixtures of HC and
NOX were photoirradiated under simulated atmospheric conditions. Results from those
studies could not be interpreted with confidence mainly because the smog chamber
methodology at the time was relatively crude and untested. More recently, the effort
to obtain improved data on the OX-HC-NOX relationships was expanded to include
application of three different research approaches: (1) ths aerometric data analysis
approach; (2) the smog chamber approach, using improved techniques; and (3) the
photochemical modeling approach. Presently, aerometric data analysis and smog cham-
ber tests are the only methods capable of yielding usable information on the
43
-------
OX-HC-NOX relationships; the photochemical modeling method is still in the develop-
mental stage.
Observational Model24,25
The basic assumption in the observational model is that early-morning HC and
NOX levels are indicators of the OX levels that will occur later in the day. Spe-
cifically, the 6 to 9 a.m. HC and NOX levels are compared with the daily 1-hour
maximum OX levels that normally occur between 10 a.m. and 2 p.m. Because formation
and accumulation of OX is influenced also by sunlight intensity, wind speed, and
other meteorological conditions, a specific ambient combination of HC and NOX will
not always result in a specific maximum OX level. Rather, it will result in a range
of maximum OX levels extending from zero (in days with total overcast, strong winds
causing rapid dispersion, etc.) to an upper limit (obtained during days of bright
sunshine, air stagnation, etc.). The level of this upper limit, obviously, will
depend only on the concentrations of the precursors. It is this upper limit that
the observational approach attempts to define.
The success of the observational approach depends critically on the number of
days for which pollutant measurements are available. Oxidant values for any given
combination of HC and NOX precursors can range from zero to the upper limit.
Because the upper limit is attained on only about 1 percent of the days in a year,
measurements for many days are needed in order to provide reasonable assurance that
an upper-limit point has actually been observed. The small number of data points
in the vicinity of the upper-limit line shown in Figure 3-5 for the relationship
between total nonmethane hydrocarbons (NMHC) and the maximum daily OX observed in
several cities illustrates this point. (In this figure and throughout the chapter,
hydrocarbons are measured in parts per million carbon, ppm C.) Because they are
limited in number, these upper limit points may not define the true upper-limit
oxidant line; more extensive observations would undoubtedly include still higher OX
concentrations. It seems reasonable to conclude, however, that the upper-limit
curve in Figure 3-5 is the most valid relationship available for the time period
prior to 1969.
Oxidant values below 140 yg/m3 (0.07 ppm) are omitted in Figure 3-5 because
several factors indicate these values may be subject to measurement errors; however,
the errors have no bearing on the upper-limit values. Likewise, the HC values below
200 ng/m3 (0.3 ppm) are not reportedeven though they may have a bearing on the
upper-limit OX level--because they are subject to even greater measurement error.26
The curve of Figure 3-5 can be used to predict the maximum 1-hour-average OX
concentration from a measured 6 to 9 a.m. average HC concentration. Likewise, the
minimal level of HC that will produce a given OX level can also be predicted. For
OX and HC levels below 0.1 ppm and 0.3 ppm C, respectively, numerical predictions
-------
0.30
0.25
0.20
APPROXIMATE UPPER-LIMIT
_ OBSERVED OXIDANT
^ j
z 0.15
g
x
o
LOS ANGELES
LOS ANGELES A
^WASHINGTONA A DENVtR
* LOS ANGELES
A A PHILADELPHIA
LOS ANGELES
A
PHILADELPHIA
PHILADELPHIA
WASHINGTON A >
_WASH,NG/TONA ApH|LADELp^
WASHINGTON AAA A / A A A A A
A A A A A
A VA*A A
WASHINGTON *j*AAtA AA A AA
0.10( ' &* A A A Af A
4*AA A AAA
A MA / A i A A A AA
0.05
A
A A
0.5
1.0 1.5
NONMETHANE HC, ppm C
2.0
2.5
Figure 3-5. Maximum daily 1-hour-average oxidants as a function of 6 to 9
a.m. averages of nonmethane hydrocarbons at CAMP stations, June through
September, 1966 through 1968, Los Angeles, May through October 1967.24
cannot be made. However, certain useful limitations can be defined; for example,
it can be seen that for the OX to be below 0.1 ppm, NMHC must be below 0.3 ppm C.
An observational approach similar to the one used to derive the OX-HC relation-
ship was used also in attempts to determine the dependence of OX on NOX. In this
case, the aerometric data analysis was guided by certain findings from smog chamber
studies: (1) only NO and N02 are precursors of OX and (2) although the N02-to-NO
ratio influences the rate of OX formation, it is the total NOX concentration that
determines the maximum OX concentration for given HC concentration and meteorological
conditions. Plots of daily maximum OX versus average 6 to 9 a.m. NOX concentrations
for three cities are shown in Figures 3-6 through 3-8.24 These plots show that OX
levels below 0.1 ppm are associated with NOX levels considerably below 0.1 ppm.
This complicates the problem of determining the OX-NOX relationship in the concen-
tration range of interest because the NOX data in this range suffer from consider-
able measurement error.
45
-------
O
X
0.20
0.15
0.10
0.05
APPROXIMATE UPPER-LIMIT OBSERVED OXIDANT
0.05
0.10
0.15
NO ppm
0.20
0.25
0.30
Figure 3-6. Maximum daily 1-hour-average oxidant concentrations as a function
of 6 to 9 a.m. averages of total nitrogen oxides in Washington, D.C., June through
September, 1966 through 1968.24
2
<
Q
0.35
0.30
0.25
0.20
0.15
0.10
0.05
APPROXIMATE UPPER-LIMIT
OBSERVED OXIOANT
0.05
0.10
0.15
N0x,ppm
0.20
0.25
0.30
Figure 3-7. Maximum daily 1-hour-average oxidant concentrations as a function
of 6 to 9 a.m. average total nitrogen oxides in Philadelphia, June through Sep-
tember, 1965 through 1968.24
46
-------
0.30
0.25
0.20
Q
X
o
0.1S
0.10
0.05
\ i i r
APPROXIMATE UPPER-LIMIT OBSERVED OXIDANT
4*s
I
0.05
0.10
0.15
0.20
0.25
NOX
Figure 3-8. Maximum daily 1-hour-average oxidant concentrations
as a function of 6 to 9 a.m. averages of total nitrogen oxides in Den-
ver, June through September, 1965 through 1968x4
If all data points are accepted as equally valid, a reference value of
200 mg/rn^ (0.10 ppm) OX would be associated with as little as 20 rag/m^ (0.01 ppm)
NOX. Because of the analytical uncertainties in the low concentration region, a
more rational approach is to locate an NOX level below which OX can be expected to
exceed the reference concentration, that is, 200 rag/m^ (0.10 ppm) OX, on 1 percent
of the days. Figures 3-6 through 3-8 show only seven occasions when the OX equalled
or exceeded 0.10 ppm and the NOX was less than 0.04 ppm. This frequency represents
about 1 percent of the combined data base.
Although the curves that define the maximum oxidant-forming potential in
Figures 3-5 through 3-8 were drawn to include all the data points, they were not
based on a statistical approach. The data were too limited in number to justify a
statistical analysis; however, strict adherence to the limits set by the few appli-
cable data points would associate an even lower value of NOX with 200 mg/m^ (0.10
ppm) OX. Current analytical uncertainties in the low-range measurements make such a
-------
conclusion unwise. From the relationships in Figures 3-6 through 3-8, it appears
that the 6 to 9 a.m. average NOX levels must be kept below 80 mg/m-* (0.04 ppm) in
order to prevent the maximum daily 1-hour OX concentration from reaching 200 mg/m^
(0.1 ppm) or more.
The reference concentration of 0.1 ppm OX used here was selected on the basis
of convenience; it is not the national air quality standard for oxidants (0.08 ppm)
adopted in the United States.
Data from three Los Angeles locations are shown in Figure 3-9^6 for a calcu-
lated NMHC level of 1.5 ppm C. At two of these stations, a 6 to 9 a.m. value of
0.04 ppm NOX, and a value of 0.05 ppm NOX at a third site, are associated with a
daily-maximum 1-hour-average OX concentration of 0.10 ppm. These Los Angeles
results are similar to those obtained in Washington, D.C., Philadelphia, and Denver.
0.30
X
o
0.25
0.20
0.15
0.10
0.05
UNIVERSITY
OF SOUTHERN
CALIFORNIA
MEDICAL
SCHOOL
0.05
0.10
0.15
NOX
\_
0.20
Figure 3-9. Upper limit of maximum daily 1-hour average oxi:
dant concentrations, calculated nonmethane hydrocarbon con-
centration of 1.5 ppm C, as a function of average total nitro-
gen oxides from 6 to 9 a.m. at three Los Angeles stations. May
through October 1967.26
-------
For these reasons, the NOX-OX relationship cited is considered the most
reasonable that can be made at this time. It should be noted that the relationship
states only that the 6 to 9 a.m. average NOX must be below 80 yg/m^ (0.04 ppm) to
prevent oxidant levels greater than 200 pg/m3 (0.1 ppm) from occurring more frequently
than 1 percent of the time later in the day. It does not attempt to specify the
exact NOY concentration. Whether this or an even more stringent limitation of NOX
is required can be assessed only after further observations have been made of
ambient atmospheres and the manner in which control of ambient HC concentration
affects ambient OX levels. Laboratory results indicate that I1C control, even in the
absence of NOK control, will definitely lead to reductions in ambient OX levels.
The preceding discussion dealt with the relationships of each individual
precursor to maximum OX Jcwli, without considering combined effects. An initial
attempt to explore the possible combined pollutant effects is shown in Figure 3-10
APPROXIMATE UPPER LIMIT
OBSERVED OXIDANTS
HYDROCARBON ENVELOPES
.i ppm C
- 2 0 ppm C
2 5 ppm C
J
NOX, ppm
Figure 3 10 fMonmethane hycirocarbon-oxidant envelopes superim-
posed on maximum daily 1-hour average oxidant concentrations as
d (unction of G to 9 a.m. average of total nitrogen oxides in Pasadena,
California, May through October 1967.24
-------
for Pasadena, California. In this figure, upper-limit OX-NMHC curves are super-
imposed on a graph to show the relationships of maximum OX levels to NOX concen-
trations for different NMHC concentrations. These relationships cannot be very
accurate, however, because of limitations in amount and comparability of data.
For example, the NMHC data used were not measured directly; rather, they were
calculated from total HC data, using established total HC-NMHC relationships.
Using the data available from CAMP stations, where NMHC is measured directly,
the OX-NMHC-NOX relationships appear to be as shown in Figure 3-11. Such relation-
27
ships again show qualitative agreement with laboratory simultations (Figure 3-12),
but they are of questionable accuracy because they are based on insufficient ambient
data.
z
o
CO
DC
<
(J
O
a:
Q
O
1.2
1.0
0.8
0.6
0.4
0.2
0.10
0.20
0.30
NOX, ppm
Figure 3-11. Approximate isopleths for selected upper-limit maximum
daily 1-hour-average oxidant concentrations, as a function the 6 to 9
a.m. averages of nonmethane hydrocarbons and total nitrogen oxides
in Philadelphia, Pa., Washington, D.C., and Denver, Colo., June
through August, 1966 through 1968.24
The difficulty in establishing the OX-HC-NO relationships from aerometric data
alone is understandable if the complexity of these relationships is recognized. Both
aerometric data analysis and smog chamber experimentation show clearly that,
although the OX varies monotonically with HC, its dependence on NOX shows a maximum.
Further, the OX-HC and OX-NOX relationships appear to be interdependent; that is,
50
-------
HI
Z
HI
>-
a-
a.
Figure 3-12. Oxidant isopleths from laboratory experiments showing effect of varying
initial precursor hydrocarbon (propylene) and nitric oxide concentrations on maximum
ozone concentrations.27
any relationship of one precursor to oxidant determines, to a degree, the relation-
ship of the other precursor to oxidant. Still another complication is introduced
by the apparent fact that the variations of HC and NOX in ambient air do not
parallel each other exactly. Thus, from Figure 3-10 it can be seen that each HC
level is associated with a wide range of NOX values and vice versa.
Because of the uncertainties of the OX-HC-NOX relationships derived from the
presently available aerometric data, the U.S. Environmental Protection Agency
(EPA) has judged that use of these relationships to estimate control requirements
for oxidant abatement cannot be made with confidence. Instead, EPA elected to use
the relatively more accurate OX-NMHC relationship depicted in Figure 3-5 as the
basis of the OX abatement strategy now in use in the United States.
51
-------
A more detailed discussion of the observational approach used to establish the
oxidant-oxidant precursor relationships can be found in Reference 24.
Critique of Observational Model
The OX-NMHC relationship (Figure 3-5) arrived at through use of the observa-
tional approach clearly is the result of a first effort to delineate the roles of
HC and NOX in OX formation and to provide bases for a rational OX abatement strategy.
This effort, although it has probably made the best use of the data available, did
not necessarily produce unequivocal results. Some of the limitations of the OX-NMHC
curve in Figure 3-5 obviously result from the inaccuracy and insufficiency of the
aerometric data available. Other limitations relate to the concept underlying the
observational model and become apparent only when the OX-NMHC curve is used to make
predictions. In view of the enormous importance of the applications intended for
this curve, its limitations--however unavoidable they may be at the present time--
must be fully defined, evaluated, and recognized.
The limitations caused by analytical inaccuracies have already been mentioned
in Chapter 2. Briefly, the main problems lie in the differential measurement of
NMHC and in the measurement of OX in the presence of relatively high levels of NOX
and S02. The analytical error in these measurements has a greater effect on the
data in the low concentration range. This is a serious limitation because it is
the low concentration data that define the air quality standard for NMHC, that is,
the NMHC concentration corresponding to the OX standard.
Insufficiency of data also incurs penalty in several respects. First, it does
not permit clear and reliable delineation of b.oth the HC and the NOX roles in OX
formation. Second, the shape of the OX-NMHC curve (Figure 3-5) is uncertain,
especially in the high concentration range. The magnitude of this latter error is
uncertain; however, its direction is known. Because the curve represents the
highest OX concentrations ever observed, it follows that the addition of new data
points can only raise the curve, resulting in a more linear character. Finally,
the insufficiency of data does not permit construction of separate curves for geo-
graphical locations with different climatologies. The use of a single OX-NMHC
curve to compute control requirements in different regions is obviously inappro-
priate.
Another persistently criticized limitation of the OX-NMHC curve in Figure
3-5 is that the curve appears to ignore the role of NOX in OX formation.28,29
Although this criticism is valid in principle, the magnitude of the limitation is a
complex function of several factors, and for this reason the role of NOX has often
been misunderstood.
It should be clear that, except for the uncertainties discussed in the preceding
paragraphs, the validity of the existing curve as a depiction of the OX-NMHC rela-
52
-------
tionship is not questioned. Validity questions arise only when this relationship is
used to predict the effect of HC control on ambient OX. Such predictions, in order
to be valid, require that the OX-NMHC relationship not change as a result of HC
control a requirement that clearly cannot be met because HC control will raise the
NOx-to-HC ratio in air, resulting in a different OX-NMHC relationship.
To better define this conceptual limitation of the OX-NMHC curve, consider its
most common application, which is to calculate from OX data alone the degree of HC
control required in order to achieve the OX standard. This calculation requires
knowledge of (1) the NMHC concentration corresponding to the presently observed OX
level, and (2) the NMHC concentration corresponding to the OX standard. Values for
both of these entities can be read off the OX-NMHC curve; however, only the former
is valid. The value of the NMHC concentration corresponding to the OX standard is
probably incorrect because it reflects the present NOx-to-HC ratio in air rather
than the higher ratio that will result from HC control. From smog chamber studies
of the OX-HC-NOX relationships, one may reasonably expect that, under the higher
NOx-to-HC ratio conditions of future atmospheres, the NMHC concentration corre-
sponding to 0.08 ppm of OX (the oxidant standard) will be greater than 0.24 ppm C.
Although it cannot be ascertained at this time, a drastically higher NMHC value is
not expected. This is because present plans call for control of both HC (to alle-
viate the OX problem) and NOX (to alleviate the N0£ problem). Therefore, a future
NO -to-HC ratio not drastically higher than the current one would be expected.
A final criticism of Figure 3-5 involves the number and siting of the monitors used
to collect the OX and NMHC data. The data were collected at one and the same monitoring
site located in the center of the city. The data, therefore, are indicative of the NMHC
levels but not of the OX levels because OX is expected to reach its maximum concentration
at some point downwind from the emission discharge point.
Smog Chamber Data
Unlike the atmospheric data analysis method, smog chambers provide a simple and
practical research tool for studying the HC and NO roles in OX formation. Because
experimental conditions in smog chambers can be controlled reliably and at will,
smog chamber experimentation is especially useful in studying the chemistry of the
OX formation process in detail. Thus, the individual as well as the interactive
effects of the precursors HC and NOX on OX formation can be delineated- -a feat
practically impossible to accomplish using aerometric data alone. The one and
critical drawback of the smog chamber method is the limitation in inherent
validity that prohibits use of the method for atmospheric predictions. Smog chamber
atmospheres are only crude simulations of real atmospheres and, as discussed earlier
in this chapter, it is not always possible to test the validity of smog chamber data
through comparison with atmospheric data. For these reasons, all early smog chamber
53
-------
findings regarding the OX-HC-NOX relationships were taken to reflect only qualita-
tively the relationships existing in the real atmosphere.27,30-33
In more recent studies, ' ' the question of comparability of the smog
chamber system with the real atmospheric system was given specific attention, and
as a result, the OX-HC-NOX relationships established from these chamber data are
believed to have relatively more quantitative validity. These more recent relation-
ships are depicted by the diagrams in Figures 3-13 and 3-14. These diagrams are
equal-response lines, each one being the locus of the (NMHC, NOX) points corre-
sponding to a certain fixed OX concentration. The shaded areas in Figure 3-13
represent those concentrations of the NMHC and NO reactants for which the
resultant maximum OX concentration is equal to or less than 0.08 ppm; line "def"
represents the NO standard corresponding to the California standard for N02 (1-
hour average N02 concentration not to exceed 0.35 ppm).
1.55
0.6
0.5 M«H-)
0.4
0.3
0.2
0.1
SLOPE
2.6
SLOPE <
70
V* I
l_b _~.~*.*-r-*;:rr;'t*.
2 3
NONMETHANE HC, ppm C
Figure 3-13. Equal response lines representing combinations of total nonmethane hydro-
carbon and nitrogen oxide corresponding to oxidant and nitrogen dioxide yields equal to
the national air quality standards.34
The utility of the information in Figure 3-13 is illustrated in the following
example in which a numerical air quality standard for NMHC is calculated using these
diagrams. Maximum 6 to 9 a.m. concentrations of NMHC and NOX during 1970 in the
United Statespresumed to be those observed in Los Angeles--have been reported to
29
be 8.4 ppm C and 1.4 ppm, respectively (point "g" in Figure 3-13). These concen-
trations obviously correspond to an OX concentration exceeding the standard. To
achieve the OX standard, the NMHC and NOX levels must be moved from their 1970
position (g) either vertically to below line "be" or in the direction leading to the
"bde" area. Considering the uncertainties regarding the slope of the "be" line
34
-------
4.0
6.0
8.0
10.0
NONMETHANE HC, ppm C
Figure 3-14. Equal response lines representing combinations of total nonmethane hydro-
carbon and nitrogen oxide corresponding to specific levels of maximum ozone yields.34
and the fact that the NOX levels below this line are too low to be achieved through
a reasonable control effort, it follows that the most rational control is in the
direction leading to point e (corresponding to 0.3 ppm NOX and 0.75 ppm C NMHC).
An additional factor to be considered here is the inadvertent variation of the NOX
concentration in the air above a city (Reference 24, Figure 4-7). To understand
the effect of this factor, the following facts must be understood: (1) the NC>2
standard imposes an upper limit to ambient NOX, but not a lower limit, and (2) as
illustrated in Figure 3-13, NOX levels below the "ab" line are associated with
above-standard OX levels. Because of these facts and because ambient NO levels--
24 x
corresponding to a constant HC levelvary by as much as +40 percent, it follows
that the NMHC must be controlled down to 0.20 to 0.25 ppm C in order to ensure
achievement of the OX standard even when the NOX level is unusually low relative to
NMHC.
REFERENCES FOR CHAPTER 3
1. Haagen-Smit, A.J. Chemistry and Physiology of Los Angeles Smog. Ind. Eng. Chem.,
44_:1342, 1952.
2. Leighton, P.A. Photochemistry of Air Pollution. New York, Academic Press, 1966.
3. Altshuller, A.P. and J.J. Bufalini. Photochemical Aspects of Air Pollution: A
Review. Photochem. Photobiol. 4:97, 1965.
55
-------
4. Altshuller, A.P. and J.J. Bufalini. Photochemical Aspects o£ Air Pollution: A
Review. Environ. Sci. Technol. 5_:39, 1971.
5. Seinfeld, J.H., T.A. Hecht, and P.M. Roth. Existing Needs in the Experimental
and Observational Study of Atmospheric Chemical Reactions. Systems Applications,
Inc. San Rafael, Calif. Prepared for U.S. Environmental Protection Agency,
Research Triangle Park, N.C., under Contract No. 68-02-0580. Report No. EPA-R4-
73-031. June 1970.
6. Demerjian, K.L., J.A. Kerr, and J.G. Calvert. The Mechanisms of Photochemical
Smog Formation. In: Proceedings of International Symposium on Air Pollution.
Union of Japanese Scientist and Engineers, Tokyo, Japan. 1972.
7. Demerjain, K. U.S. Environmental Protection Agency, Research Triangle Park, N.C.
Private communication to B. Dimitriades. October 14, 1974.
8. Altshuller, A.P. Reactivity of Organic Substances in Atmospheric Photooxidation
Reactions. Int. J. Air Water Pollut. 10_:713, 1966.
9. Altshuller, A.P. An Evaluation of Techniques for the Determination of the Photo-
chemical Reactivity of Organic Emissions. J. Air Pollut. Contr. Assoc. 16:257,
1966.
10. Heuss, J.M. and W.A. Glasson. Hydrocarbon Reactivity and Eye Irritation. Environ.
Sci. Technol. 2_:1109-1116, December 1968.
11. McReynolds, L.A., H.E. Alquist, and D.B. Wimmer. Hydrocarbon Emissions and Reac-
tivity as Functions of Fuel and Engine Variables. Transactions, Society of Auto-
motive Engineers. 74_:10-19, 1966. SAE Paper No. 650525.
12. Sturm, G.P., B. Dimitriadies, F.D. Sutterfield, and T.C. Wesson. Hydrocarbon
Reactivity Scales Derived from U.S. Bureau of Mines Smog Chamber. Bureau of
Mines, U.S. Department of the Interior, Washington, D.C. Report of Investigations
RI 8023. March 1975.
13. Dimitriadies, B. and T.C. Wesson. Reactivities of Exhaust Aldehydes. Bureau of
Mines, U.S. Department of the Interior, Washington, D.C. Report of Investigations
RI-7527. May 1971.
14. Levy, A. and S.E. Miller. Final Technical Report on the Role of Solvents in Photo-
chemical Smog Formation. National Paint, Varnish, and Lacquer Association, Wash-
ington, D.C. 1970.
15. Wilson, K.W. and G.J. Doyle. Investigation of Photochemical Reactivities of
Organic Solvents. Final Report. Stanford Research Institute, Irvine, Calif.
Contract No. CPA-22-69-1251. SRI Project PSU-8029. September 1970.
16. Laity, J.L., I.G. Burstain, and B.R. Appel. Photochemical Smog and the Atmos-
pheric Reactions of Solvents. Shell Oil Company. (Presented at National
American Chemical Society Meeting. Washington, D.C. September 1971.)
56
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17. Miller, D.F., A. Levy, and W.E. Wilson. A Study of Motor Fuel Composition
Effects on Aerosol Formation: Part II. Aerosol Reactivity Study of Hydro-
carbons. Battelle Laboratories, Columbus,.Ohio. Prepared for American Petro-
leum Institute, Washington, D.C. API Project EF-2. February 21, 1972.
18. Brunell, M.F., J.E. Dickinson, and W.J. Hamming. Effectiveness of Organic
Solvents in Photochemical Smog Formation. Los Angeles County Air Pollution
Control District, Los Angeles, Calif. 1966.
19. Title 42--Public Health; Part 410--National Primary and Secondary Ambient Air
Quality Standards. Federal Register. 36(84):8186-8201, April 30, 1971.
20. Title 40--Protection of the Environment; Part 85--Control of Air Pollution from
New Motor Vehicles and New Motor Vehicle Engines. Federal Register. 37(221):
24250-24320, November 15, 1972.
21. Title 42--Public Health; Part 420--Requirements for Preparation, Adoption and
Submittal of State Implementation Plans. Federal Register. 36(158):15502,
August 14, 1971.
22. Rule 66, Organic Solvents. In: Rules and Regulations of the Air Pollution
Control District, County of Los Angeles. Los Angeles County Air Pollution Con-
trol District, Los Angeles, Calif. November 1972.
23. Dimitriades, B. U.S. Environmental Protection Agency, Research Triangle Park,
N.C. Private communication to P.M. Covington, EPA Region IX, San Francisco,
Calif. August 31, 1975.
24. Air Quality Criteria for Nitrogen Oxides. Environmental Protection Agency, Air
Pollution Control Office, Washington, D.C. Publication No. AP-84. January 1971.
25. Schuck, E.A., A.P. Altshuller, and D.S. Barth. Relationships of Hydrocarbons to
Oxidants in Ambient Atmospheres. J. Air Pollut. Contr. Assoc. 20_: 297-302, May
1970.
26. Air Quality Criteria for Hydrocarbons. U.S. Department of Health, Education, and
Welfare, National Air Pollution Control Administration, Washington, D.C. Publica-
tion No. AP-64. March 1970.
27. Romanovsky, J.C., R.M. Ingels, and R.J. Gordon. Estimation of Smog Effects in
the Hydrocarbon-Nitric Oxide System. J. Air Pollut. Contr. Assoc. 17:454-459,
July 1967.
28. Hines, J.M., G.I. Nebel, and J.M. Colucci. National Air Quality Standards for
Automotive PollutantsA Critical Review. J. Air Pollut. Control Assoc. 21:535,
1971.
29. Hamming, W.J., R.L. Chass, J.E. Dickinson, and W.G. MacBeth. Motor Vehicle
Control and Air Quality: The Path to Clean Air for Los Angeles. Los Angeles
County Air Pollution Control District, Los Angeles, Calif. (Presented at National
57
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Air Pollution Control Association Meeting. Chicago. June 24-28, 1973. Paper
No. 73-73.)
30. Hamming, W. J. and J.E. Dickinson. Control of Photochemical Smog by Alteration
of Initial Reactant Ratio. J. Air Pollut. Cont. Assoc. 16^(6):317-323, June 1966.
31. Altshuller, A.P., S.L. Kopczynski, D. Wilson, W.A. Lonneman, and F.D. Sutterfield.
Photochemical Reactivities of Paraffinic Hydrocarbon-Nitrogen Oxide Mixtures Upon
Addition of Propylene or Toluene. J. Air Pollut. Contr. Assoc. 19(10):791-794,
October 1969.
32. Korth, M.W., A.H. Rose Jr., and R.C. Stahman. Effects of Hydrocarbon to Oxides
of Nitrogen Ratios on Irradiated Auto Exhaust. Part I. J. Air Pollut. Contr.
Assoc. 1£(5):168-174, May 1964.
33. Tuesday, C.S. The Atmospheric Photooxidation of trans-Butene-2 and Nitric Oxide.
Chemical Reactions in the Lower and Upper Atmosphere. New York, Interscience
Publishers, John Wiley and Sons, 1961. p. 15-49.
34. Dimitriades, B. On the Function of Hydrocarbons and Nitrogen Oxides in Photo-
chemical Smog Formation. U.S. Department of the Interior, Washington, D.C. Report
of Investigations RI 7433. September 1970. 37p.
35. Dimitriades, B. Effects of Hydrocarbon and Nitrogen Oxides on Photochemical Smog
Formation. Environ. Sci. Technol. 6:253, 1972.
58
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CHAPTER 4
EFFECTS OF METEOROLOGICAL FACTORS ON OXIDANT FORMATION
INTRODUCTION
In any given location, the atmospheric concentration of oxidant depends on
many factors. Some of these, such as the concentrations of nitrogen oxides and
hydrocarbons, and the reactivity of the hydrocarbons, have been mentioned earlier.
Other important factors are the size of the area, the meteorology, the topography,
the number and distribution of sources, and the rates of emissions.1'3 These latter
factors are important because they affect the distribution of pollution over a city.
The diurnal urban emission pattern of oxidant-forming pollutants is fairly
uniform from weekday to weekday. It is apparent, therefore, that variations in the
pattern of oxidant concentrations must be caused largely by meteorological factors.
Such factors include dilution (accomplished by the same process of atmospheric
turbulence and transport that affects other gaseous contaminants), sunlight
intensity, and temperature. Moreover, concentrations of oxidant upwind from an area
may be substantially different from concentrations downwind as a result of transport
phenomena.
Effects from some of these meteorological factors are discussed in the
following sections.
EFFECTS OF SUNLIGHT
All photochemical processes in ambient air start with absorption of sunlight
by pollutantsthose capable of absorbing such lightfollowed by dissociation into
reactive fragments. The most important of these light absorption-dissociation
processes involves nitrogen dioxide (NO).
Interaction of light with an NO molecule to form nitric oxide (NO) and an
oxygen (0) atom is a reaction between a photon and the N02 molecule. Thus, the rate
of N02 destruction, or of 0 atom formation, is directly proportional to the inten-
sity of light and the concentration of N02- Because ozone (03) forms from the
reaction of 0 atoms with molecular oxygen (02), it follows that 03 accumulation
depends strongly on light intensity.
The intensity and relative distribution of wavelengths of sunlight reaching the
earth's surface does not vary appreciably except in the presence of absorbing
species or light-scattering particles. Because polluted atmospheres contain variable
amounts of N02, and because the N0£ will absorb certain wavelengths of sunlight,
59
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some changes can occur in both the relative wavelength distribution and the intensity
of sunlight at a particular location. A reduction as high as 80 percent of intensity
o
near the region of 3250 angstroms (A) has been observed at the earth's surface during
an intense photochemical air pollution episode.^ Because most of the N(>2 had disap-
peared from the atmosphere at the time of the episode, it cannot have been respon-
sible for the observed decrease in light intensity. Rather, the reduction has been
generally attributed to the light-scattering effect of atmospheric aerosols formed
as a by-product of the photochemical interactions of reactive hydrocarbons, nitrogen
oxides, and sulfur dioxide.
Light intensity reductions of the magnitude observed would be expected to pro-
duce a substantial decrease in the rate of photochemical reactions. The actual
effect caused by aerosol diffusion is far more complex, however. As pointed out by
Leighton,5 the available light energy is a function of the mixing height of a given
polluted air mass. Within the upper half of the air mass, the available light
energy will tend to be the result of aerosol scattering, and this will be substan-
tially greater than that available from incident radiation alone. An opposite
effect is observed in the lower half of the air mass. Thus, the formation of photo-
chemical aerosols has the rather interesting effect of increasing the rate of photo-
chemical reactions in the upper half of the polluted air mass and, at the same time,
decreasing these rates in the lower half of the air mass. Thus, in areas where
visibility is often restricted, a less direct correlation between observed oxidant
concentrations and light intensity measured at ground level would be expected. The
total effect on oxidant levels of such intensity effects cannot be ascertained with-
out quantitative data on vertical mixing within a polluted air mass.
The variations in sunlight intensity that most affect development of oxidants
are those occurring as a function of time of day, time of year, and geographical
location. Maximum intensities prevail around noon, with duration times of near-
maximum intensities varying according to season and latitude. The amount of cloud
cover and the atmospheric accumulation of light-scattering and light-absorbing pollu-
tants are, of course, important factors.
Light intensity and duration control, to some extent, the amount of photo-
oxidized materials that can be formed. In the United States, the maximum noonday
intensity and the duration of nearly maximum light intensity do not vary appreciably
O
with latitude during the summer months. In the region of 3000 to 4000 A, the maxi-
mum total intensity is 2 x 10*6 photons per square centimeter per second (photons
cm" 2 sec~l), with the measurement remaining near this value for 4 to 6 hours. By
contrast, the winter values vary from 0.7 x 10*6 to 1.5 x lO1^ photons cm~2 sec~l,
depending on latitude; time near maximum light intensity in the winter is reduced to
2 to 4 hours.6 These times and intensities are important controlling factors in
determining the severity and duration of photochemical air pollution.
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EFFECTS OF TEMPERATURE AND HUMIDITY
The temperature of a polluted air mass determines the ground state energy of
all chemical species in the system. High temperatures increase ground state energy.
Because most chemical reactions require addition or subtraction of energy, a tem-
perature variation can also change the reaction rate.
Laboratory experiments'1 have shown that a 40 °F temperature rise increases the
rate of NO and hydrocarbon oxidation by a factor of 2. There is also evidence in
certain systems that a temperature increase of this magnitude results in a fourfold
increase in the rate of oxidant production." These substantial changes can affect
the concentrations of photochemical air pollution products in the atmosphere. (At
temperatures below 60 °F ambient levels of oxidant seldom exceed a few parts per
hundred million.)
Quantitative estimates of the effect of ambient temperature variations upon
these manifestations cannot be made at this time. The restrictive nature of the
laboratory experiments and the lack of knowledge concerning the variables and
reactions involved are two of the factors that prohibit other than qualitative
estimates.
The role of humidity in atmospheric reactions and specifically in the oxidant
formation process is also extremely complex because humidity may affect oxidant
formation both directly and Indirectly, liirect effectsnamely, acceleration of the
NO photooxidation and oxidant formation processes--were reported by Dimitriades;^
however, the magnitude of these effects has not been established. Humidity also
plays an important role in atmospheric aerosol formation; considering the possible
destruction of ozone on particulatu surfaces, it follows that humidity may also
indirectly affect oxidant accumulation.
TRANSPORT PHENOMENA
The transport of pollutants by wind in the Los Angeles basin has been the
subject of several studies.3>10-13 Most of the wind trajectories enter the basin
from the west; surface winds are predominately from the ocean to the land during
the spring, summer, and fall months.
To illustrate the eastward transport of oxidant, the diurnal variation of mean
hourly average concentrations during October 1965 in West Los Angeles, Los Angeles,
Azusa, and Riverside are shown in Figure 4-1.14 Data from the first three stations
are from the Los Angeles County Air Pollution Control District; data for the city
of Riverside are from the Riverside County Air Pollution Control District.
The station at West Los Angeles is about 10 miles west, and Azusa is about 20
miles east, of downtown Los Angeles. Riverside is about 30 miles east of Azusa.
61
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As shown, the time of the peak oxidant concentrations follows those in West Los
Angeles by about 1 hour in Los Angeles, 2 hours in Azusa, and 4 hours in River-
side.
Oxidant concentrations at Riverside exhibited a double peak. The first peak,
at about 11 a.m., is attributed to pollutants generated at or near Riverside; the
peak at 4 p.m. is attributed to pollutants transported from the large and more
densely populated Los Angeles metropolitan area.
As shown in Figure 4-2, the afternoon peak concentration of carbon monoxide in
Riverside is much smaller than the morning peak in Los Angeles. This suggests that
the polluted air mass was diluted as it moved eastward to Riverside. On the other
hand, the afternoon oxidant peak concentrations in Riverside were about as high as
the peak concentrations in Los Angeles. It is possible, therefore, that as the
polluted air mass moved eastward, the oxidants continued to be formed at a rate
about as great as the rate of dilution. It is also just as probable that the
second peak at Riverside represents oxidant contributions from local as well as
distant sources.
Z
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Figure 4-1. Diurnal variation of mean
1-hour average oxidant concentra-
tions at selected California sites, Octo-
ber 1965.14
i!<4.lj
20.0
16.0
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I I
;
-v^<
-
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Figure 4-2. Diurnal variation of mean
1-hour average carbon monoxide con-
centrations at selected California
sites, October 1965.14
62
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On the average, the direction of flow of surface wind and of pollutant
transport appear to coincide, but they are not the only meteorological factors
responsible for the transport of pollutants. Bell's appraisal of hour-by-hour
development of oxidant concentrations **" indicates that other mechanisms, such as
turbulence and downward motions created mechanically by airflow through mountain
gaps, were also responsible for pollutant transport.
On some days, as observed by Stephens,16 the polluted air mass from the Los
Angeles metropolitan area is defined by a sharp boundary that may not extend as far
as Riverside. The reason for this sharp boundary, Stephens postulates, is that the
temperature profile at the front of the air mass increased to the adiabatic lapse
rate resulting in rapid vertical ventilation.
The prevailing winds are not always westerly. Under some meteorological condi-
tions described by Bell, pollutants from Los Angeles have been transported out to
sea and then southward to Oceanside11 and even to San Diego, a distance of over 100
miles. Under other conditions, pollutants have been transported from the sea north-
ward to Ventura and Santa Barbara Counties.^»18
Preliminary data from a Statewide Cooperative Air Monitoring Network station
recently established by the State of California in Santa Cruz indicate that a
similar phenomenon may occur in the region of the San Francisco-Oakland metropolitan
area. Under certain conditions, pollutants from the metropolitan area are transported
out to sea and then brought back to shore by the local sea breeze to Santa Cruz, about
50 miles south. On these occasions, the hourly average oxidant concentrations have
been as high as from 240 to 350 micrograms per cubic meter (0.12 to 0.18 part per
million) in Santa Cruz. The very low concentrations of oxides of nitrogen and hydro-
carbons measured during these occasions again suggest substantial oxidant formation
in spite of high dilution.
FORECASTING TECHNIQUES
Efforts to forecast or estimate future oxidant concentrations have been made
for the last 20 years. Initially only the atmospheric dispersion conditions were
forecast, then the meteorological forecasts were combined with statistical analysis
of past air quality observations to empirically estimate future air quality. The
most recent development is the use of numerical models incorporating both meteoro-
logical and air quality parameters and processes. An additional simplification
that is being tested is the use of regression equations relating the input to the
output of each of the specific numerical models.
Air pollution potential forecasting techniques were first developed in the late
1950's and have been considerably improved over the years. The basic product of the
air pollution potential forecast is the prediction of the meteorological parameters
63
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that affect the transport and diffusion of pollutants. Initially, a stagnation
area, in which the conditions for high air pollution potential may develop, must be
defined and forecast to continue for at least 36 hours. Then the individual stations
within the stagnation area forecast the parameters affecting the pollution potential.
The meteorological criteria for a potential air pollution episode at a station are:
(1) the morning mixing height must be < 500 meters, (2) the morning transport wind
(mean wind within the mixing layer) speed must be < 4 meters per s-econd, (3) the
afternoon ventilation (product of the mixing height and transport wind speed) must
be < 6000 square meters per second, and (4) the afternoon transport wind must be
< 4 meters per second. Air pollution potential forecasts are made and air stagna-
tion advisories are issued regularly by the National Weather Service.
The Los Angeles County Air Pollution Control District uses a combination of
meteorological forecasts and past air quality statistics to predict the visibility,
eye irritation, and ozone maxima at several stations within the district. Detailed
32- to 36-hour forecasts are made of the meteorological parameters, which are then
combined with the ozone statistics. Forecasts of the inversion height, strength,
and slope over the Los Angeles basin; the winds over the basin; the maximum temper-
ature; and the cloud cover are prepared. This information is combined with the
seasonal variation in hours of sunshine, the monthly station maximum ozone averages,
the frequency distributions of monthly station daily maximum ozone values, and the
variability of average ozone values by day of the week and holidays. If the pre-
dicted ozone concentration equals or exceeds 50 parts per hundred million (pphm),
a smog alert is announced.
An evaluation of the Los Angeles data indicates a mean difference between pre-
dicted and observed ozone values from May to December of 4.8 pphm. The greatest
errors occured in September and October (within the smog seasonhigh ozone values)
with differences of 6.7 and 7.0 pphm, respectively. The least errors occurred in
December and January (within the relatively smog-free season) with differences of
2.2 and 2.5 pphm, respectively. The most accurate predictions were for the coastal
sections, with the error increasing inland.
Recently, numerical models combining the meteorological and photochemical
processes have been developed. They are based on the conservation equation. Some
are trajectory models and some are Eulerian or grid models. All are first generation
efforts and predict the oxidant levels within a factor of 2 or 3. Although the
models use observed or predicted meteorological data, the meteorological data are
part of the model input. Meteorological prediction models are not, presently, an
integral part of the photochemical air quality simulation models. To conserve
computer time and storage without affecting the physical assumptions of the model, a
linear piecewise regression technique is being evaluated to relate the input and out-
put of a specific model. The numerical modeling effort is in its infancy and much
remains to be done.
64
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REFERENCES FOR CHAPTER 4
1. Schuck, E.A., J.N. Pitts, and J.K. Swan. Relationships between Certain Meteoro-
logical Factors and Photochemical Smog. Int. J. Air Water Pollut. 10:689-711,
1966.
2. Smith, M.E. The Concentrations and Residence Times of Pollutants in the Atmo-
sphere. In: Chemical Reactions in the Lower and Upper Atmosphere. New York,
Interscience Publishers, 1961. p. 155-166.
3. Neiburger, M. What Factors Determine the Optimum Size Area for an Air Pollution
Control Program. In: Proceedings of the 3rd National Conference on Air Pollu-
tion, December 12-14, 1966. U.S. Department of Health, Education, and Welfare.
Washington, D.C. PHS Publication No. 1649. 1967. p. 442-449.
4. Stair, R. The Spectral Radiant Energy from the Sun through Varying Degrees of
Smog at Los Angeles. In: Proceedings 3rd National Air Pollution Symposium.
Pasadena, Stanford Research Institute, 1955.
5. Leighton, P.A. Photochemistry of Air Pollution. New York, Academic Press, 1961.
300 p.
6. Bufalini, J.J. and A.P. Altshuller. Synergistic Effects in the Photooxidation of
Mixed Hydrocarbons. Environ. Sci. Technol. 1_: 133-138, February 1967.
7. Bufalini, J.J. and A.P. Altshuller. The Effect of Temperature on Photochemical
Smog Reactions. Int. J. Air Water Pollut. 7_(8):769-771, October 1963.
8. Alley, F.C. and L.A. Ripperton. The Effect of Temperature on Photochemical Oxidant
Production in a Bench Scale Reaction System. J. Air Pollut. Contr. Ass. 11(19):581-
584, December 1961.
9. Dimitriades, B. Methodology in Air Pollution Studies Using Irradiation Chambers.
J. Air Pollut. Contr. Ass. 1^:460-466, 1967.
10. Neiburger, M. and J.G. Edinger. Summary Report on Meteorology of the Los Angeles
Basin with Particular Respect to the "Smog" Problem. Vol. 1. Air Pollution
Foundation. Los Angeles, Calif. Report Number 1. April 1954. 54 p.
11. Neiburger, M., N.A. Renzetti, and R. Tice. Wind Trajectory Studies of the Move-
ment of Polluted Air in the Los Angeles Basin. Vol. 2. Air Pollution Foundation.
Los Angeles, Calif. Report Number 13. April 1956. 74 p.
12. Stasiuk, W.N. and P.E. Coffey. Rural and Urban Ozone Relationships in New York
State. J. Air Pollut. Contr. Ass. 2£(6):564-568, June 1974.
13. Drivas, P.J. and F.S. Shair. A Tracer Study of Pollutant Transport and Dispersion
in Los Angeles Area. Atmos. Environ. 8^:1155-1164, 1974.
14 _ Air Quality Criteria for Photochemical Oxidants. U.S. Department of Health,
Education, and Welfare, Public Health Service, National Air Pollution Control
Administration, Washington, D.C. NAPCA Publication No. AP-63. March 1970.
65
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15. Bell, G.B. A Study of Pollution Transport Due to Surface Winds in Los Angeles,
Orange, Riverside and San Bernardino Counties. California Department of Public
Health. Berkeley, Calif. December 1959.
16. Stephens, E.R. Temperature Inversions and the Trapping of Air Pollutants.
Weatherwise. 18/4):172-175, August 1965.
17. Meteorological Conditions during Oxidant Episodes in Coastal San Diego County in
October and November, 1959. California Department of Public Health. Berkeley,
Calif. May 22, 1960.
18. Faith, W.L., G.S. Taylor, and H.W. Linnard. Air Pollution in Ventura County.
California Department of Public Health. Berkeley, Calif. June 1966.
66
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CHAPTER 5
ADVERSE EFFECTS OF OXIDANTS
TQXICOLOGIC EFFECTS
The photochemical process produces a number of irritating or toxic chemicals.
However, of interest here are only those that are likely to be toxic at or near
concentrations found in polluted ambient air. Photochemical oxidants such as
ozone, nitrogen dioxide, and peroxyacyl nitrates are gases that exert their toxic
influence through exposure by inhalation. If present in sufficient concentrations,
these gases are capable of causing death. At sublethal concentrations, they pro-
duce more occult but nonetheless health-impairing physiologic malfunctions or
anatomic lesions.
Numerous studies of the toxicologic effects of oxidants have been conducted.
A detailed review of the data and conclusions from these studies can be found
elsewhere. A summarized discussion of these findings is presented in the follow-
ing sections.
Effects of Ozone
#-
Data from early studies on laboratory animals indicated that death from
pulmonary edema and inflammation occurred after exposure to ozone concentrations
of 29,400 to 58,000 micrograms per cubic meter (yg/m )or 15 to 30 parts per
million (ppm)and above for several hours and that pulmonary edema as measured
by wet weight to dry weight ratios could be produced by exposures on the order
of 1960 to 3920 iJg/ro^ (1 to 2 ppm) for 3 hours in small rodents. Data reviewed
here indicate that evidence of transudation of blood protein into the lung (as
measured by recovery of labelled albumin in pulmonary lavage fluid) occurs after
exposures to as little as 490 yg/m (0.25 ppm) for a few hours. Cells are quickly
damaged and cast off. Regeneration of the same or different cell types is apparent
as early as 24 hours after exposure. This is probably not a specific lesion, but
is indicative of the presence of a noxious influence at this anatomical level.
There is a turnover of cells in the terminal portion of the bronchioles and
proximal alveoli, which produces a characteristic lesion consisting of enlarged
cuboidal cells (hyperplastic Type II pulmonary epithelium).
A tentative mathematical model for ozone uptake in the respiratory tract of
man predicts that the peak dose would occur in the small, but nonterminal, bron-
chioles (16 to 20th segment of Weible) whose constriction might be expected to
67
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lead to decrements in closing capacity measurements. It is of interest in this
connection that concomitant exposure to sulfur dioxide and ozone in man causes
exaggerated decrements in various pulmonary flow rate responses. However, such
response might be predicted from a two-stage action, i.e., proximal airway reflex
response for sulfur dioxide and probably ozone plus a second more distal airway
direct tissue response for ozone. There appear to be some differences of opinion
regarding the segmental level of the most severe airway response on the basis of
pathologic anatomy in investigations conducted in laboratory animals: some in-
vestigators claim that the most sensitive tissue is in the terminal bronchioles
and proximal alveolar epithlium; whereas, others think the higher airway is more
sensitive. It is now known, however, that there is fairly diffuse damage through-
out the pulmonary portion of the airway. Thus, the mathematical model mentioned
above might not necessarily be completely accurate at this tentative stage since
allowance for velocity of the bolus of gas at various segmented levels and other
factors may need to be adjusted according to more precise pulmonary airway mor-
phometry and experimental observations yet to be made.
As previously mentioned, fibrosis and emphysema are features of exposure
to ozone of longer duration, either continuously or intermittently. The role
of the epithelial lesion in the genesis of structural modification of the lung
is unclear at this time. It may only reflect, for instance, a sequential cycle
of epithelial injury and replacement; or, on the other hand, it may be inter-
twined in some manner with the fibrotic and other changes important in the genesis
of emphysema. It is tempting to speculate that the emphysema might be secondary
to two independent factors that might act in concert, namely, (1) partial
obstruction of the distal airway by the maturation and contraction of the
fiborplastic lesions in this region and (2) loss of tone and stretching of
the preexisting collagenous pulmonary framework due to chemical alteration of
the collagen molecule. Microscopic observations support the fibrosis of the
distal airway. A report of the effect of ozone (and nitrogen dioxide) in the
denaturation of collagen molecules has been discussed in Reference 1. Increased
rigidity occurred principally at edemagenic exposures of ozone and presumably
is associated with increased tissue pressure due to fluid or to dilution of
the surface-active material by edema fluid. Diminished recoil or elasticity
demonstrated by pressure-volume curves employing both air and saline, on the
other hand, as noted with repeated exposures to low levels of ozone for 30
days, suggest diminished contractile force of the lung. Furthermore, the ani-
mals tested showed gross pulmonary overdistention and a noticeable but, accord-
ing to the investigators, non-statistically significant reduction in number of
alveoli.
68
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It is possible that such changes herald the onset of pulmonary emphysema,
which develops at a later stage than elevated expiratory flow resistance.
Furthermore, a nonreflex component may be involved. It is possible that the
suspected nonreflex component is constriction of the lower airway in response
to the direct ozone injury at this segmental level. The recent studies on
human volunteers in which closing capacities were studied suggests that this
level in the bronchiolar tree contributes significantly to physiologic alte-
rations in human beings and that ozone acts reflexively by stimulating centers
in the nasopharynx, thus causing constriction of the larger airways, and non-
reflexively by direct chemical action in the terminal portions of the airways.
An interesting feature of acute health response of human beings to ozone
exposure has been the apparent augmentation of effects when persons at risk
in oxidant episodes indulged in sports. This has shown up in post hoc analysis
studies of performance records of high school athletes, and in systematically
conducted clinical observations of school children in Japan. A common feature
has been that subjects exercising actively suffer higher risk. The observa-
tions that human volunteers suffer more decrement in pulmonary physiologic
parameters, more mortality due to pulmonary edema, and more susceptibility to
pulmonary infection when the subjects exercised during exposure to ozone
tend to lend credence to these reports. It would appear fairly reasonable
to suppose that the exercise factor produces an increased dose by virtue of
increased minute volume. Another factor, however, mouth breathing during
strenuous exercise, may be peculiarly important in human exposure; uptake
experiments conducted in anesthetized dogs suggest that a change from nose to
mouth breathing would double the ozone dose delivered to the deeper airways.
While a change from nose to mouth breathing is undoubtedly important in man,
this mechanism is not normally resorted to in exercised rodents in which mouth
breathing is abnormal. Nonetheless, Stokinger reports a several-fold diminu-
tion in the concentration of ozone required to kill rats exposed while ex-
ercising. Gardner et al. note an increment in mortality from bacterial
infection after ozone exposure of mice while continuously walking.
There appears to be no question that exposure of mice to ozone and syn-
thetic smog at concentrations well below those seen in polluted ambient air
enhances mortality from infections. There is, however, a natural reluctance
to relate such findings directly to human beings without substantiating evidence
in a variety of species. Thus far, in limited studies, considerably higher
concentrations of pollutants have been required to effectively show mortality
differences in other animals. There is evidence that this may be related to
the natural resistance of the animal species to the particular infectious
agent rather than to a basic difference in its reactivity to the system. The
important point for the successful operation of this system as presently used
69
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in animals is the availability of a microorganism that is capable of invading
the lung with the subsequent production of mortality. The pollutant then
enhances the mortality by depressing the bacterial defense mechanism.
In the application of this model to the human subject through epidemic-
logical studies, it would appear essential to seek associations between oxi-
dant episodes and the establishment of deep lung infection by such pathogens
as Diplococci pneumonia or Klebsiells pneumonia. Such studies have not yet
been seriously undertaken.
Effects of Peroxyacetyl Nitrate
Data on the lethality of peroxyacetyl nitrate (PAN) are sparse, but those
that are available suggests that it is less lethal to mice than ozone, about
the same as nitrogen dioxide, and more lethal than sulfur dioxide.
Campbell et al. exposed mice to high concentrations of PAN, 480 to 700
yg/m (97 to 145 ppm) as measured at the chamber outlet, for 2 hours at 27°C.
The studies demonstrated that the majority.of mice exposed to 540 yg/m (110 ppm)
or more of PAN died within a month. It was observed that mice exposed to high-
er concentrations died earlier than those exposed to lower concentrations.
Median lethal exposures characteristically produced a delayed mortality pattern,
with most deaths occurring in the second and third week after exposure. Mor-
tality was greater among older mice than younger mice, and it was greater at
higher temperatures. It was not influenced appreciably by changes in relative
humidity.
Experiments carried out on humans have suggested that exposure to PAN
o
results in increased oxygen uptake during exercise. Smith has carried out
a group of studies on male college students averaging 21 years of age. The
subjects were exposed to 1485 yg/m' (0.3 ppm) PAN by breathing through the
mouth (nose clamps were used) for 5 minutes while at rest, and then the subjects
were engaged immediately in 5 minutes of exercise on a bicycle ergotometer.
Both air containing PAN and air free of PAN were used without the knowledge of
the subjects. Since the pollutant has no characteristic smell or taste, it
was considered that the experiment was carried out in a "blind" fashion. It
was noted that there was a statistically significant increase in oxygen uptake
during exercise, without any change at rest. Expiration velocity was reduced
after exercise. The changes could possibly be a reflection of an increase in
the work of breathing due to an increase in airway resistance. Because the
report of this work does not adequately describe the experimental design or
the statistical analysis, these results merit replication before conclusive
statements can be made.
In conclusion, the data obtained so far on the effects of PAN on animals
70
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and man are too incomplete to enable conclusions to be drawn regarding any
effect of this pollutant at ambient concentrations.
EPIDEMIOLOGICAL APPRAISAL OF OXIDANTS
The possibility that photochemical air pollution could be a major health
hazard has been of growing concern. A number of systematic studies have been
conducted in an attempt to determine if an association exists between episodes
of high oxidant pollution and general mortality, acute illness, aggravation of
chronic respiratory disease, impairment of performance, or untoward symptoms
such as eye irritation. A detailed review of the data and conclusions from
these studies can be found elsewhere. A brief summary of these findings follows.
Epidemiologic studies have been conducted to determine the relationship
of photochemical air pollution with mortality, hospital admissions, aggravation
of respiratory disease, impairment of human performance, irritation of the
respiratory tract, and eye irritation. The effects of prolonged oxidant ex-
posure on mortality, morbidity, ventilatory function, and community satisfaction
have also been studied.
No convincing relationship was observed between short-term variations in
photochemical oxidants and daily mortality or hospital admissions, although
there was a suggestion that mortality could be related to oxidant levels.
A study of 137 patients with asthma demonstrated significantly more asthma
attacks on days when maximal hourly photochemical oxidant concentrations ex-
ceeded 430 yg/m (0.25 ppm).
Chronic respiratory disease patients who were removed from an ambient
atmosphere of elevated oxidant concentrations to a room from which pollutants
were filtered have shown improvement in ventilatory function. In two other
studies, no significant association was found between variations in ambient
oxidant levels and changes in respiratory symptoms or function in patients
with chronic respiratory disease.
The team performance of high school cross-country track runners was im-
paired on days of elevated oxidant concentrations measured 1 hour before the
commencement of each race; hourly oxidant concentrations ranged from 60 to
590 yg/m (0.03 to 0.3 ppm). The threshold for this effect has subsequently been
estimated at about 235 yg/m" (0.12 ppm). These findings may possibly be
related to a pulmonary irritation effect similar to that shown to occur at
higher levels of exposure but at lower levels of exertion. Significantly more
automobile accidents have also occurred on days of high oxidant concentrations.
A study of student nurses in Los Angeles has demonstrated a threshold for
increased cough and chest discomfort at daily maximum hourly average oxidant
3
concentrations between 500 and 600 yg/m (0.25 and 0.30 ppm). This same study
71
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also indicated a threshold for increased eye discomfort on days with maximum
hourly average oxidant concentrations at about 300 pg/m (0.15 ppm), These
results are consistent with those from other studies that have shown that eye
3
irritation appears to increase when oxidant concentrations exceed 200 yg/m
(0.10 ppm).
Eye irritation, at times accompanied by nasal irritation, was the most
frequently reported nuisance effect of air pollution in California. A post-
ulated explanation for the relationship between ambient oxidant levels and
eye irritation is that the level of oxidant is a measure of the photochemical
activity that produced the eye irritants. The relationship between oxidants
and eye irritation is discussed in more detail later in this chapter.
Lung cancer mortality rates were similar among California residents
studied in both high- and low-oxidant-pollution areas. A relationship between
noncancerous chronic respiratory disease mortality and long-term photochemical
oxidant exposure has been suggested in an isolated study in which other im-
portant variables were not analyzed. Factors other than oxidant exposure
could well have accounted for these observations, and considerable documentation
from other epidemiologic studies is required to substantiate these findings.
Several surveys have also reported a higher incidence of both chronic respira-
tory disease symptoms and other respiratory symptoms, including asthma and
nose and throat complaints, among residents of Los Angeles than among residents
of other areas of California.
A significantly larger proportion of Los Angeles residents have been
subjectively bothered by air pollution than have residents of the San Francisco
Bay area and the rest of the state. A larger proportion of residents who were
bothered by air pollution have considered moving or have moved from Los Angeles
than have residents of other areas of California. One-third of the physicians
sampled in the Los Angeles area had advised one or more of their patients to
leave the area for health reasons, and nearly one-third of the physicians had
themselves considered moving from Los Angeles because of air pollution.
In conclusion, from the information presently available, it appears that
epidemiologic evidence on the health effects of photochemical oxidant pollution
is inadequate. Consistent results for some effects, obtained by various in-
vestigators under varying conditions of exposure, are lacking. The few demon-
strated associations between oxidant exposure and health effects, such as asthma,
pulmonary function, or athletic performance, are inadequate to establish with
confidence minimum threshold levels for each effect.
Reported studies suggest, however, that photochemical oxidants are po-
tentially hazardous environmental contaminants. Subjects with chronic res-
72
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piratory disease seem to be those most threatened by such exposure, but vir-
tually all segments of the population may experience eye irritation at levels
of oxidants frequently present in the ambient air. Hazards to normal respira-
tory function, optimum athletic performance, and safe automobile driving have
also been suggested. An association, although not necessarily a cause-effect
relationship, has been shown to exist between ambient levels of photochemical
oxidants and eye irritation. Since one of the objectives of air pollution
control is to promote good health and minimize exposures to potentially haz-
ardous pollutants, the information provided by reported studies cannot be dis-
counted.
CORRELATION OF OXIDANT WITH EYE IRRITATION
Several studies have been conducted in Los Angeles to determine the occasions
and the types of pollutants responsible for eye irritation and their relation-
ship, if any, to oxidant pollution. The first set of studies was conducted
Q
by the Air Pollution Foundation in 1954.
During the first period of the study, observers were asked on Tuesdays
and Fridays to report eye irritation. This later was changed to just those
days for which eye-irritating levels of pollution were predicted. In general,
the observers were office and factory workers; one of the panels consisted
of a group of staff members of the California Institute of Technology. The
eye irritation data were compared with instantaneous values of oxidant concen-
trations as measured by potassium iodide analyzer. The resultant data are
shown in Figures 5-1 and 5-2. The "expert" panel (experienced scientists)
and the other panel did not significantly differ in the correlations of eye
irritation with oxidants, carbon monoxide, particulates, and aldehydes. During
the second period, August through November of 1955, similar panels observed
eye irritation effects during each day of the work week. In this study, maxi-
mum oxidant concentrations were compared with reported eye irritation effects.
The data from these studies demonstrate increasing eye irritation with
increasing concentrations of oxidant pollution over the range of instantaneous
values from 100 to 880 yg/m (0.05 to 0.45 ppm), although no clearly demar-
cated threshold level for this effect is apparent (see Figure 5-1).
Other studies on eye irritation have been performed, including one in
which a panel of employees of the Los Angeles County Air Pollution Control
District was questioned during the period 1955-1958. A group of environ-
mental sanitation workers in the San Francisco Bay area was also studied
during the same period. Neither of these panels reported anything other than
a tendency to experience increasing occurrence of eye irritation with in-
creasing oxidant levels. As in all such studies, some individuals reported
eye irritation even when no oxidant was present.
73
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40
30
o;
UJ 20
or
O
U
i/>
O
10
Di
o;
LU
>-
IU
s /«
STATION 3
-.- STATION 4E
STATION 4L
STATION 5
STATION 8
ALL STATIONS
10 20 30
OXIDANT CONCENTRATION, pphm
50
Figure 5-1. Regression curves relating eye irritation and simultaneous oxidant concentrations from
a number of stations in the Los Angeles area. 10
10
20 30 40 SO 60 70
MAXIMUM OXIDANT CONCENTRATION, pphm
80
Figure 5-2. Variation of mean maximum eye irritation, as judged by a panel of "experts," with
maximum oxidant concentrations, Pasadena, August- November, 1955.10
7H
-------
12
Hammer et al. reported on respiratory and eye symptoms among two groups
of student nurses studied during a 24-day period from October 29 through No-
vember 25, 1962, in Santa Barbara and Los Angeles. Data plotted in Figure 5-3
again show a relationship between increasing eye irritation and maximum daily
photochemical oxidant concentrations over the range of 200 to 800 ug/m (0.10
to 0.55 ppm).
40
H- 30
o:
O
u.
Z 20
O
U
\st
5 10
DAILY MEAN FREQUENCY OF SYMPTOM _
DAILY MAXIMUM OXIDANT LEVEL
29 31 2 4 6 8 10 12 14 16 18 20 22 24
J.. MOV.
0.50
0.40
0.30
0.20 <
Q
0.10
Figure 5-3. Relationship between oxidant concentrations and eye discomfort .in Los Angeles,
October 29 through November 25, 1962.10
A study was conducted to evaluate the sensory effectiveness of air-
filter media for removing eye irritants from polluted air in downtown
Los Angeles. A statistically significant correlation between eye irrita-
tion and oxidant concentrations was found to occur in nonfiltered room air.
The scatter diagram of results (Figure 5-4) suggests an eye irritation thres-
hold as the concentration of oxidants exceeds 200 yg/m (0.10 ppm). The index
of eye irritation for the study groups increased progressively as oxidant
concentrations exceeded the 200 yg/m (0.10 ppm) level.
Oxidant measurements at levels likely to be associated with eye irrita-
tion have been reported for a number of cities outside California. Circum-
stantial evidence of increased eye irritation has been reported in Washing-
ton, D. C., Denver, New York City, and St. Louis. An epidemiologic study
of eye irritation was carried out by McCarroll et al. on a population living
in midtown Manhattan. In October 1963, substantial increases occurred in the
frequency of new reports of eye irritation (increasing from about 2 to nearly
5 percent of the population). Oxidant measurements, made at some distance
away, had increased during the period under study. Unfortunately, clear
conclusions from these data cannot be drawn; there were high levels of sulfur
oxide pollution, of particulate pollution, and of carbon monoxide. It is
75
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quite possible that eye irritation symptoms in New York City result from
mixed pollution of both the oxidizing and reducing type.
18
16
14
O
C 12
o:
HI
uj
u_
O
X
UJ
O
z
z
UJ
10
MODERATE" IRRITATION
"BARELY NOTICEABLE" IRRITATION
-." !-."" ' "..
0 5 10 15 2O 25 3O 35 t
OXIDANT CONCENTRATION, pphm
Figure 5-4. Mean index of eye irritation versus oxidant concentration. 10
It should be noted here that when interpreting implied relationships
associating eye irritation and ambient oxidant levels, care must be exercised
in conclusions regarding cause and effect. Experimental studies have shown
that ozone, the principal contributor to ambient oxidant levels, is not an
eye irritant. Peroxyacyl nitrates have been shown to be powerful eye irri-
tants; even more irritating is peroxybenzoyl nitrate. Formaldehyde and
acrolein, also products of the photochemical system, have been shown to pro-
duce eye irritation. A postulated explanation for the relationship between
ambient oxidant levels and eye irritation is that "oxidant" is a measure
of the photochemical activity that produces the aforementioned eye irritants.
76
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EFFECTS OF OXIDANTS
Introduction
Injury to vegetation was one of the earliest manifestations of photo-
chemical air pollution. A peculiar type of injury to leafy vegetables,
ornamentals, and field crops, characterized by banding, silvering, and stip-
pling of the leaves, was first investigated in the United States by Middleton
et al. Plant injury of this kind has since spread to widely separated areas
of the world, with increasing severity and with associated economic losses
to both farmers and nurserymen.
Three specific phytotoxic materials have been isolated from the photo-
chemical complex: ozone, nitrogen dioxide, and the peroxyacyl nitrates. The
latter homologous series of compounds includes peroxyacetyl nitrate (PAN),
peroxypropionyl nitrate (PPN), peroxybutyryl nitrate (PEN), and peroxyisobu-
tyryl nitrate (P. BN). Preliminary work has shown that PPN is several times
as toxic to vegetation as PAN while PEN and P. BN are more toxic than PPN.
& iso
Since PAN is the only member of the series that has received much study, and
since PPN and PEN, though usually present in the ambient air, are normally
below detectable limits, discussion will be restricted to the effects of PAN.
The presentation of the quantitative effects of ozone and PAN has to be
limited to laboratory and controlled field exposures since, under ambient
conditions, the effects of these compounds cannot be easily differentiated.
The term "oxidant" will be used when discussing the toxic materials to which
the plants are exposed under ambient conditions. Research has shown that
additional phytotoxicants may be present in the photochemical complex. Syner-
gistic effects between the toxicants discussed and other atmospheric con-
taminants may also produce injury to sensitive plant species. On the basis
of available information, ozone is the most important phytotoxicant of the
photochemical complex.
A detailed review of the studies conducted in the United States and
the resultant evidence can be found elsewhere. Following is a brief summary
of the findings.
Review of Information on Effects
Acute symptoms are generally characteristic of a specific pollutant
while chronic injury patterns are not. Injury to leaves by ozone is ident-
ified as a stippling or flecking. Such injury has occurred experimentally
in the most sensitive species after exposure to 60 pg/m (0.03 ppm) ozone
for 8 hours. Injury will occur in shorter time periods when low levels of
sulfur dioxide are present. PAN-produced injury is characterized by an
under-surface glazing or bronzing of the leaf. Such injury has occurred
77
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experimentally in the most sensitive species after exposure to 50 pg/m (0.01
ppm) PAN for 5 hours. Leaf injury has occurred in certain sensitive species
after a 4-hour exposure to 100 yg/m (0.05 ppm) of total oxidant.
There are a number of factors affecting the response of vegetation to
photochemical air pollutants. Variability in response is known to exist
between species of a given genus and between varieties within a given species.
Sensitive plants can be useful biological indicators of photochemical air
pollution. Varietal variations have been most extensively studied with
tobacco, and a sensitive tobacco strain, Bel-W3, has been isolated arid de-
veloped as a monitor for studying the extent, severity, and frequency of
ambient oxidant.
The influence of light intensity on the sensitivity of plants during
growth appears to depend on the phytotoxicant. Plants are more sensitive
to ozone when grown under low light intensities. Reported findings are in
general agreement that sensitivity of greenhouse-grown plants to oxidants
increases with temperature from 4.4° to 32.7°C (40° to 100°F). However, there
is some indication that this positive correlation may result from the over-
riding influence of light intensity on sensitivity.
The effects of humidity on the sensitivity of plants has not been well
documented. General trends indicate that plants grown and/or exposed under
high humidities are more sensitive than those grown at low humidities. Though
there has been little research in this direction, there are indications that
soil factors influence the sensitivity of plants to phytotoxic air pollutants.
Plants grown under drought conditions are less susceptible than those grown
under moist conditions. Studies indicate that plants appear to be more sen-
sitive when they are grown in soil having low total fertility.
The age of the leaf under exposure is important in determining its
sensitivity to air pollutants. There is some evidence that oxidant or ozone
injury may be reduced by pretreatment with the toxicant.
Identification of an injury to a plant as being caused by air pollution
is an arduous undertaking. Even when the markings on the leaves of a plant
can be identified with an air pollutant, it is often quite difficult to
evaluate these markings in terms of their effect on the intact plant. Further
difficulty arises in trying to evaluate the economic impact of air pollution
damage to the plant.
The interrelations of time and concentration, or dose, as they affect
injury to plants, are essential to air quality criteria. There are, however,
only scant data relating concentrations and length of photochemical oxidant
exposure to chronic injury and effects on reduction of plant growth, yield,
78
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or quality. There is also a dearth of information relating acute injury to
concentrations and duration of exposure to PAN or mixtures of photochemical
oxidants. A larger body of information exists on the acute effects of ozone,
but even in this instance, the information is far from complete.
Bacteriostatic and bacteriocidal properties of photochemical oxidants
in general have been demonstrated. The growth suppression of microorganisms
by ozone is a well-known phenomenon, although ozone concentrations for this
activity are undesirable from a human standpoint. The bacteriocidal activity
of ozone varies with its concentration, the relative humidity, and the species
of bacteria.
Hydrocarbons were first recognized as phytotoxic air pollutants about
the turn of the century as a result of complaints of injury to greenhouse
plants from illuminating gas. Ethylene was shown to be the injurious com-
ponent. Renewed interest in hydrocarbons, and ethylene in particular,
occurred in the mid-1950's when ethylene was found to be one of the primary
pollutants in the photochemical reaction complex. Research on several un-
saturated and saturated hydrocarbons proved that only ethylene had adverse
effects at known ambient concentrations. It is noteworthy that the activity
of acetylene and propylene resemble more closely that of ethylene than do
other similar gases, but 60 to 500 times the concentration is needed for com-
parable effects.
In the absence of any other symptom, the principal effect of ethylene is
to inhibit growth of plants. Unfortunately, this effect does not characterize
ethylene because other pollutants at sublethal dosages, as well as some diseases
and environmental factors, may also inhibit growth.
Epinasty of leaves and abscission of leaves, flower buds, and flowers
are somewhat more typical of the effects of ethylene, but the same effects
may be associated with nutritional imbalance, disease, or early senescence.
Perhaps the most characteristic effects are the dry sepal wilt of orchids
and the closing of carnation flowers. Injury to sensitive plants has been
3
reported after exposure to ethylene concentrations of 1.15 to 575 yg/m (0.001
to 0.5 ppm) for an 8- to 24-hour period.
Economic loss has not been widely documented except among flower growers
in California, where damage to orchids and carnations has been assessed at
about $800,000 annually. More research needs to be done on economic losses
sustained in field and greenhouse crops from long exposures to very low con-
centrations of ethylene.
EFFECTS OF OXIDANTS ON MATERIALS
/
Studies have focussed mainly on the effects of ozone and nitrogen dioxide
79
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~on materials. A detailed discussion of the symptoms and mechanism of ozone
and nitrogen dioxide attack on materials can be found elsewhere. The follow-
ing paragraphs summarize the information relative to the effects of ozone on
materials presented in Reference 1.
Ozone is a major factor in the overall deterioration of a number of
different types of organic materials. In fact, certain specific organic com-
pounds are more sensitive to ozone attack than humans or animals. The magni-
tude of damage is difficult to assess in some cases because naturally occurring
ozone is a component of weathering, and weathering itself is a major cause of
materials deterioration. Nevertheless, researchers have shown that atmospheric
ozone resulting from the activities of man has been responsible for accelerating
the deterioration of several classes of materials.
Although the total extent of ozone-associated damage to materials is not
known, ozone may very well be a major contributor to the weathering of materials.
Ozone is an extremely active compound, and generally, any organic material is
incompatible with concentrated ozone. Many organic polymers are subject to
chemical alteration from exposure to very small concentrations of ozone, in-
cluding atmospheric concentrations. This sensitivity usually increases with
the number of double bonds in the chemical structure of the polymer.
The most widely used generic groups of elastomers are highly sensitive
to attack by atmospheric ozone. These groups include natural rubber and
synthetic polymers of styrene-butadiene, polybutadiene, and polyisoprene.
Atmospheric ozone will not attack vulnerable elastomers exposed in a relaxed
state (no stress) even for long periods of time. However, cracks easily dev-
elop on exposure to atmospheres containing 20 to 40 yg/m (0.01 to 0.02 ppm)
ozone if vulnerable elastomers are under a tensile stress of as little as 2
or 3 percent. Unfortunately, elastomeric products are normally used in a
stressed state. Other factors that determine the rate,of ozone attack on
elastomers are the type and formulation of the elastomeric material, concen-
tration of atmospheric ozone, period of exposure, rate of diffusion of ozone
to the elastomer surface, and temperature.
Researchers have developed antiozonant additives that are capable of
protecting elastomers from ozone attack. Antiozonants, however, are expensive
and sometimes migrate to the surface of elastomeric products, where they may
be removed during usage. Oils, gasoline, and other chemicals may extract
antiozonants from elastomers and thus decrease the resistance to ozone attack.
Researchers have conducted laboratory exposures of textiles to ozone.
Apparently only cotton is affected. Considering the above-normal exposure con-
centrations and the limited end-use life of most cotton products, the magnitude
of deterioration by ozone is minimal.
80
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Some important textile dyes, however, are susceptible to fading during
exposure to ozone. Certain blue disperse dyes used on acetate and polyester/
cotton fabrics and nylon carpets have been particularly troublesome. Laboratory
exposures have shown that ozone concentrations as low as 100 ng/m (O.OS ppm)
are capable of producing visible fading. To prevent or mitigate fading by ozone,
the textile industry can select combinations of fabrics, resistant dyes, and
inhibitors, but these increase the cost of finished products.
Laboratory exposures of different types of paint have shown some damage with
exposure to ozone at 1960 yg/m (1.0 ppm), but essentially no statistically de-
tectable damage when exposed to concentrations of 196 ug/m (0.1 ppm). Oil-based
house paint was most susceptible. Field exposures in Los Angeles (high smog
pollution) also produced considerably more damage to some paints (especially the
oil -based house paint) than was observed at a rural control exposure site.
A recent atmospheric corrosion study indicates that the presence of oxi-
dants (mainly ozone) inhibits the corrosion rates of several types of common
steels. Increasing oxidant concentrations correlate with decreasing corrosion
rates, even when atmospheric sulfur dioxide is present.
REFERENCES FOR. CHAPT1IL5 __ ______ _ _. ________ , _____________
1. Air Quality Criteria for Photochemical Oxidants and Related Hydrocarbons.
NATO Committee on the Challenges of Modern Society. Report No. N. 29.
February 1974.
2. Wayne, W.S., P.P. Wehrle, and R.E. Carroll. Oxidant Air Pollution and
Athletic Performance. J. Amer. Med. Assoc. 199_(12) :901-904, 1967.
3. Proceedings of the First Japan/0. S. Conference on Photochemical Air
Pollution, Tokyo, June 1973.-
4. Gardner, D.E., T.R. Lewis, S.M. Alpert, D.J. Hurst, and D.L. Coffin.
The Role of Tolerance in Pulmonary Defense Mechanisms. Arch. Envi-
ron. Health. _25_: 432-438, December 1972.
5. Gardner, D.E., J.W. Illing, and D.L. Coffin. Enhancement of Effect
of Exposure to 03 and N02 by Exercise. U.S. Environmental Protection
Agency, Research Triangle Park, N.C. (presented at the Society of
Toxicology, Washington, D.C. March 10-14, 1974.)
6. Stokinger, H.E. Ozone Toxicology: A Review of Research and Indus-
trial Experience, 1954-1964. Arch. Environ. Health. 10:719-731,
1965.
7. Campbell, K.I,, G.L. Clarke, L.O. Emile, and R.L. Olata. The Atmos-
pheric Contaminant Peroxyacetyl Nitrate; Acute Inhalation Toxicity
in Mice. Arch. Environ. Health. JL5_:739-744, December 1967.
8. Smith, L.E. Peroxyacetyl Nitrate Inhalation. Arch. Environ. Health.
10_:161-164, February 1965.
9. Renzetti, N.A. and V. Gobran. Studies of Eye Irritation Due to Los
Angeles Smog 1954-1956. Air Pollution Foundation. San Marino, Calif.
July 1957.
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10. Air Quality Criteria for Photochemical Oxidants. U.S. Department of
Health, Education, and Welfare, Public Health Service, National Air
Pollution Control Administration. Washington, D.C. NAPCA Publica-
tion No. AP-86. March 1970.
11. Goldsmith, J.R. and M. Deane. Outdoor Workers in the United States
and Europe. The Millbank Memorial Fund Quarterly. 45:107-116,
1965.
12. Hammer, D.I., B. Portnoy, P.M. Massey, W.S. Wayne, T. Oelsner, and
P.P. Wehrle. Los Angeles Pollution and Respiratory Symptoms;
Relationship During a Selected 28-day Period. Arch. Environ.
Health. 10^:475-480, March 1965.
13. Richardson, N.A. and W.C. Middleton. Evaluation of Filers for
Removing Irritants from Polluted Air. University of California,
Department of Engineering. Los Angeles, Calif. Report Number
57-43. June 1957.
14. McCarroll, J.R., E.J. Cassell, W. Ingram, and D. Wolter. Health
and the Urban Environment; Air Pollution and Family Illness:
I. Design for Study. Arch. Environ. Health. 1.0_:357-363, Febru-
ary 1965.
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CHAPTER 6
ATMOSPHERIC LEVELS AND VARIATION OF OXIDANT
PRECURSORS AND RELATED POLLUTANTS
INTRODUCTION
It has been established unequivocally that the oxidants found in urban at-
mospheres are secondary pollutants and that the primary pollutants that act as
oxidant precursors are the hydrocarbons and the nitrogen oxides, i.e., nitric
oxide and nitrogen dioxide (NO and N0_). To be more accurate, not all atmospheric
hydrocarbons are capable of producing oxidants--methane being the most important
exception--and there are nonhydrocarbon organics also (e.g. aldehydes) that are
capable of forming oxidant. However, as a first approximation, the term "hydro-
carbons," or better yet "nonmethane hydrocarbons," adequately describes the
organic component of the oxidant precursor mixture in the atmosphere.
Because of this reactant-product relationship between oxidant and the oxi-
dant precursors, any oxidant abatement strategy must rely exclusively on modi-
fication of the atmospheric concentrations of the precursors. For this reason,
knowledge of the concentrations of oxidant precursors and of the oxidant-oxidant
precursor association in the ambient air is essential. Such information has
been obtained in the United States and is presented here. Data on concentrations
and concentration variation patterns for the oxidant precursors are presented and
discussed in this chapter. The subject of the quantitative relationships be-
tween oxidant and oxidant precursors, being extremely complex and somewhat con-
troversial, is treated rigorously in a separate chapter. Data on ambient sulfur
oxides and aerosol are also included in this chapter, mainly for the purpose of
providing a more complete picture of the pollutants that may have a role in the
oxidant formation process.
CONCENTRATIONS OF HYDROCARBONS IN URBAN ATMOSPHERES
Analytical Methods
The data available on atmospheric concentrations of hydrocarbons were
obtained primarily by three analytical methods: flame ionization detection (FID),
gas chromatography (GC) coupled with FID, and infrared spectrophotometry applied
either in a scanning or the nondispersive mode. Mass spectrometry, colorimetry,
and coulometry were also used but to a much lesser extent.
The FID instruments respond to organic compounds with an intensity that
is approximately in proportion to the number of carbon atoms bound to carbon
or hydrogen. Carbon atoms bound to oxygen,' nitrogen, or halogens cause reduced
83
-------
or no response. Since the FID response per carbon atom is not exactly the same
from compound to compound, FID measurement results are usually expressed in
terms of parts per million of the calibration gas used. For example, a measure-
ment result of 10 ppm-methane (or 10 ppm C) means that the analyzed sample caused
a response equal to that caused by 10 parts per million of methane. Thus, for
samples with substantially different hydrocarbon compositions, the FID readings
may not accurately reflect differences in total hydrocarbon concentration among
the samples.
FID has been used in conjunction with subtractive columns to make measure-
ments upon fractionated hydrocarbon mixtures. Thus, to measure the methane and
total nonmethane hydrocarbon levels in air, the U.S. Environmental Protection
Agency's Continuous Air Monitoring Program (CAMP) stations used FID and a carbon
column that could selectively remove all nonmethane hydrocarbons from a sample.
Similar techniques were also used in some special studies to collectively measure
the following hydrocarbon groups: (1) olefins and acetylenes; (2) aromatics
except benzene; and (3) the other hydrocarbons in the sample, including benzene.
Such fractionations and associated measurements upon the ambient hydrocarbon
mixture are extremely useful for reasons that are discussed in more detail in
the next section. Briefly stated here, the reason is that such fractionations
provide simple and practical means of excluding hydrocarbons that do not con-
tribute appreciably to photochemical oxidant from the hydrocarbon measurement.
The most noteworthy application of such a technique is in the monitoring of
total nonmethane hydrocarbon. Considering the predominately natural origin,
high relative levels, and extremely low reactivity of methane, measurement of
nonmethane hydrocarbons provides a much more accurate measure of the controllable
organic precursors of oxidant than measurement of total hydrocarbon.
Gas chromatography coupled with FID was used to obtain whatever data are
presently available on the detailed composition of atmospheric hydrocarbons.
Unfortunately, the amount of these extremely useful data obtained thus far is
very limited, mainly because of the high demands of the chromatographic method
in time, skill, and expense.
Nature and Concentrations of Hydrocarbons in Urban Atmospheres
Although on occasions all other hydrocarbon concentrations drop to un-
measurably low levels, methane does not. Numerous measurements1 suggest a
worldwide minimum methane concentration of about 0.8 to 1.0 mg/m (1.2 to 1.5
ppm). In inhabited areas, methane levels are often much higher; values of 4
mg/m" (6 ppm) or more have been observed.
Ratios of nonmethane hydrocarbons (as carbon) to methane have been esti-
2
mated for urban areas, after subtracting the background levels of methane.
-------
The nonmethane to methane hydrocarbon ratios for several weeks averaged 0.6
in Cincinnati, Ohio, and 1.9 in Los Angeles, California, although methane values
were similar (Figure 6-1) . The higher Los Angeles ratios are probably caused
by greater traffic density, solvent losses, and natural gas emissions in that
area.
2.0
1.0
0.6
0.5
<- 01
Z Z
UJ <
z t-
O UJ
U f 0.3
o
0.15
LOS ANGELES
12
12
LOCAL TIME
Figure 6-1. Concentration ratios for
nonmethane hydrocarbons/methane
in Los Angeles (213 hours during
October and November 1964) and
Cincinnati (574 hours during Sep-
tember 1964), with 655 /ug/m3 (1
ppm) methane deducted to correct
for estimated background biospher-
ic concentration.2
Table 6-1 lists the individual hydrocarbons detected in samples of urban
air by gas chromatographic analysis in several investigations. Of the 56
compounds detected, 17 were alkanes, 23 were alkenes (including two alkadienes),
2 were alkynes, 10 were aromatics, 3 were cycloalkanes, and 1 was a cycloalkene.
The length of this list is limited only by the sensitivity of the analytical
methods, and it is certain that many additional hydrocarbon compounds are actually
present in urban air. Especially at the higher carbon numbers, the chromatographic
data become so complex that their interpretation in terms of individual compounds
may be highly uncertain. The listing in Table 6-1 of compounds with carbon
numbers of 7 and higher must be considered as only a partial list.
All the hydrocarbons above carbon number 4 listed in Table 6-1 are found
in gasoline. These and the lower alkenes and acetylenes are also found in
automobile exhaust gases. The lower alkanes (methane, ethane, and propane)
occur in only small amounts in auto exhaust gases, but are ordinary constituents
of natural gas. Stephens and Burleson have reported that the hydrocarbon com-
position of Los Angeles air resembled that of auto exhaust gases with an addition
85
-------
Table 6-1. SOME HYDROCARBONS IDENTIFIED IN AMBIENT AIR3'5
Carbon
number
Compound
Carbon
number
Compound
1
2
Methane
Ethane
Ethylene
Acetylene
Propane
Propylene
Propadiene
Methyl acetylene
Butane
Isobutane
1-butene
cis-2-butene
trans-2-butene
Isobutene
1,3-butadiene
Pentane
Isopentane
1-pentene
cis-2-pentene
trans-2-pentene
2-methyl-1-butene
2-methyl-2-butene
3-methyl-1-butene
2-methyl-l,3-butadiene
Cyclopentane
Cyclopentene
10
Hexane
2-methylpentane
3-methylpentane
2,2-dimethy!butane
2,3-dimethylbutane
cis-2-hexene
trans-2-hexene
cis-3-hexene
trans-3-hexene
2-methyl-1-pentene
4-methyl-1-pentene
4-methyl-2-pentene
Benzene
Cyclohexane
Methylcyclopentane
2-methylhexane
3-methylhexane
2,3-dimethylpentane
2,4-dimethyl pentane
Toluene
2,2,4-trimethylpentane
p_-xylene
m_-xylene
p-xylene
rn-ethyl to! uene
p_-ethyl toluene
1,2,4-trimethylbenzene
1,3,5-trimethylbenzene
sec-butyl benzene
of natural gas and gasoline vapor. However, samples taken in industrial areas
and from near the smoke plume from a brush fire have shown distinctive differences
in composition, which should reasonably be attributed to these particular recognized
sources.
Some total hydrocarbon concentration data for California are given in
Table 6-2. Since interest here is only in the oxidant-forming potential of hydro-
carbons, the data in Table 6-2 are of limited utility for two reasons: first,
because they include methane, which is not an oxidant precursor; and second,
because they represent hydrocarbon concentrations observed at an unspecified time
of the day. Insofar as oxidant formation is concerned, hydrocarbon data mainly
of interest are only those for the reactivethat is, oxidant-forminghydrocar-
bons, and for the concentrations of such hydrocarbons during the morning hours,
e.g., 6 to 9 a.m. only. After 9 a.m., hydrocarbon concentrations are generally
86
-------
Table 6-2. MEAN OF DAILY MAXIMUM HOURLY AVERAGE TOTAL HYDROCARBON CONCENTRATIONS
FOR 17 CALIFORNIA CITIES, 1968-19697
(ppmC)
City
San Francisco Bay Area
Ri chtnond
San Rafael
San Francisco
Redwood City
San Jose
Central Valley
Fresno
Bakersfield
Sacramento
Stockton
Central Coast
Salinas
Monterey
Southern California
Los Angeles (downtown)
Azusa
Anaheim
Riverside
San Bernardino
San Diego
1968
June
5
4
5
N.A.
4
3
7
4
3
3
3
4
4
4
5
4
3
July
6
4
4
12
4
3
7
4
4
2
2
5
4
5
5
5
N.A.
Aug.
4
5 .
N.A^
14
4
3
8
5
4
3
3
4
5
5
7
5
4
Sept.
6
6
5
163
6
4
10a
5
5
3
3
5
5
6
6
63
5
Oct.
ga
13a
7a
13
8a
63
10a
103
6a
3
43
6
63
8
7
63
7
Nov.
8
10
6
11
83
5
9
7
4
4a
43
73
5
10a
7
63
7
Dec.
93
9
6
9
7
5
103
7
5
43
43
73
5
10a
8
63
ga
1969
Jan.
8
6
5
7
7
4
7
6
4
3
43
6
4
7
7
5
7
Feb.
8
6
5
6
5
4
8
5
3
3
43
4
4
7
93
I.A.
6
Mar.
7
8
5
7
6
5
7
7
5
3
3
5
5
7
8
63
6
Apr.
6
6
5
5
6
3
6
4
4
2
3
4
5
5
4
5
5
May
4
6
4
5
5
3
6
4
4
I.A.
3
3
5
3
4
4
3
3Highest mean concentration for 12-month period.
&N.A. = not available.
smaller and participate to a. lesser extent in the oxidant-forming process. Also,
hydrocarbon concentrations during the summer and early fall months are of relatively
greater interest because it is during these months that atmospheric oxidant reaches
its highest concentration levels in the year.
Frequency distribution data for 6 to 9 a.m. nonmethane hydrocarbon concen-
trations in various cities are given in Table 6-3. It should be noted that non-
methane hydrocarbon concentration is determined as difference between a total
hydrocarbon measurement and a methane measurement. Therefore, the analytical
error attendant to the nonmethane hydrocarbon determination is relatively large,
suggesting that measurements of concentrations below 0.1 ppm C are unreliable.
Seasonal and Diurnal Variation
Data available have not been analyzed yet for seasonal variations in non-
methane hydrocarbon levels. In 14 of the 17 California cities included in
Table 6-2, the highest hydrocarbon concentrations occurred in October or
November. Such consistency is presumably a consequence of the generally
similar meteorological conditions along the California coast. Cities else-
where would be expected to show other patterns, dependent on their particular
meteorology.
87
-------
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88
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Figures 6-2 and 6-3 show diurnal patterns for nonmethane hydrocarbons in
8 9
several cities, averaged over several months. ' In most of these, the maximum
concentrations at 6 to 8 a.m. are mainly due to the morning commuter traffic
rush. The morning peak is clearest in Denver and Los Angeles, where the auto-
mobile is especially important as a means of transportation. However, even
within a large metropolitan area, there may be considerable variation. Figure 6-3
shows average diurnal patterns for norimethane hydrocarbons at three locations
in Los Angeles County. There are considerable differences among the three
patterns, although the morning maxima are still evident in all. Table 6-4
gives diurnal patterns for the f* to C. hydrocarbons and isopentane, showing
the hour-by-hour variations as averaged over several weeks in the Los Angeles
smog season. All species listed reach a maximum in the morning, then decline
through the midday.
"S
(MAY THROUGH AUGUST AND OCTOBER, 1968)
L J L J L J L I I I
E
H- 1.0
§ 0.5
o:
<
u
g °
Q
i 1.0
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Tr
ST. LOUIS
(MAY THROUGH JULY, SEPTEMBER, AND OCTOBER, 1968)
J I J I i J i I I J
DENVER
(JANUARY THROUGH MARCH, MAY, SEPTEMBER, AND OCTOBER, 1968)
L J 1 I L.. _ 1 I I I I
"T " T~ T
1 WASHINGTON,
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'JANUARY
0 ' '
12
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I
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I
THROUGH APRIL AND AUGUST illROUGH OCTOBER, 1968)
| | |
6 1
;
I
2 6 12
LOCAL TIME
Figure 6-2. Nonmethane hydrocarbons by flame icnization analyzer, averaged
by hour of day over several months for various cities.8
89
-------
3.0
2.0
1.0
WEST LOS ANGELES
3.0
V)
O
to
cc
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X
LLJ
z
<
H
1.0
0
2.0
LOS ANGELES
1.0
12
6
a.m.
12
6
p.m.
12
LOCAL TIME
H
Figure 6-3. Nonmethane hydrocarbons by flame ionization analyzer averaged by hour of
day for three Los Angeles County sites, October 1966 through February 1967.9
Hydrocarbon Trends
As with the oxidant trends, the hydrocarbon trends discussed here are
those observed in the Los Angeles air basin, for which the atmospheric data
available are abundant. Such data consist of total hydrocarbon measurements
90
-------
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and were taken from 11 monitoring stations operated during most of the period
1963-1972. The data are presented in Tables 6-5 through 6-7, using the following
presentation forms:
1. The average of maximum hourly- concentrations during July, August, and
September (an average of 92 values each year).
2. The average concentrations from 6 to 9 a.m. during July, August, and
September (an average of 276 one-hour values each year).
3. The annual average of maximum hourly concentrations (an average of 365
values each year).
Table 6-5. TOTAL HYDROCARBON TRENDS IN THE SOUTH COAST AIR BASIN, 1963-1972,
THREE-MONTH AVERAGES OF DAILY MAXIMUM ONE-HOUR CONCENTRATIONS
FOR JULY, AUGUST, AND SEPTEMBERS'11
(ppm C)
Station
Anaheim
Azusa
Burbank
Lennox
Long Beach
Los Angeles, Downtown
Pasadena
Pomona
Reseda
Riverside
San Bernardino
1963
4.9
6.4
5.6
6.3
__
--
__
--
1964
6.9(2)
4.5
4.9
--
5.9
4.4
--
--
6.3(2)
--
1965
5.7
--
--
5.6,
6.9(1)
,;_
--
--
6.0
5.3
1966
6.1
--
__
6.0
6.0
--
--
5.9
5.8
1967
4.8
3.8(2)
--
._
__
4.6
4.4
--
--
5.2
5.2
1968
5.0
4.7
--
..
__
4.5
4.9
--
4.7
5.2
1969
5.0
5.9
--
_.
__
4.8
3.9
_-
--
5.3
5.3
1970
5.3
7.8
6.1
5.8
__
5.0
3.2
4.1
5.4
5.6
5.4
1971
6.1
5.9
5.9
4.5
__
4.8
4.2
3.5
4.2
4.6
4.8
1972
6.6
5.5
5.2
4.8
4.6
4.5
3.5
4.4
4.2
4.7
Numbers in parentheses indicate number of months of missing data. Dashes indicate stations were
not operating or data were not reported.
Table 6-6. TOTAL HYDROCARBON TRENDS IN THE SOUTH COAST AIR BASIN, 1963-1972, THREE-
MONTH AVERAGES OF 6 TO 9 a.m. DAILY AVERAGE CONCENTRATIONS
FOR JULY, AUGUST, AND SEPTEMBERa.il
(ppm C)
Station
Anaheim
Azusa
Burbank
Lennox
Long Beach
Los Angeles, Downtown
Pasadena
Pomona
Reseda
Riverside
San Bernardino
1963
--
3.8
5.0
--
4.4
5.6
--
1964
4.9(2)
3.3
4.2
--
4.5
3.7
--
--
--
5.2(2)
--
1965
4.1
--
--
4.3
5.7
--
--
--
4.5
4.5
1966
4.2
--
--
--
4.5
5.4
--
--
--
4.9
4.8
1967
3.8
--
--
--
--
4.2
3.7
--
--
4.3
4.5
1968
3.5
3.4
--
_-
--
3.9
4.1
--
--
3.9
4.3
1969
4.0
4.4
--
--
3.9
3.0
--
--
4.6
4.4
1970
3.9
5.1
5.0
4.3
--
4.4
2.5
3.4
3.8
4.2
4.8
1971
5.1
4.2
5.0
3.2
--
4.4
3.5
3.0
3.6
3.9
4.0
1972
4.6
4.0
4.2
3.2
--
4.1
3.5
3.0
3.6
2.9
4.0'
Numbers in parentheses indicate number of months of missing data. Dashes indicate stations were
not operating or data were not reported.
92
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Nonmethane hydrocarbon data computed from the total hydrocarbon data using
established relations between total and nonmethane hydrocarbon for the Los Angeles
atmosphere.are depicted in Figure 6-4. Figure 6-5 shows trends of the 6 to 9 a.m.
nonmethane hydrocarbon in Los Angeles, along with corresponding trends of the 6 to
9 a.m. nitrogen oxides and the maximum hourly oxidant. Figure 6-6 shows distribu-
tion of total hydrocarbon concentrations in the Los Angeles air basin.
MAX-HOUR AVERAGES - ALL DAYS OF YEAR
O MAX-HOUR AVERAGES - JULY, AUG., SEPT.
O 6 TO 9 a.m. AVERAGES - JULY, AUG., SEPT.
1963
1971
1972
Figure 6-4. Nonmethane hydrocarbon trends in Los Angeles, 1963-1972.1
CONCENTRATIONS OF NITROGEN OXIDES IN URBAN ATMOSPHERES
The nitrogen oxides of interest here are nitric oxide (NO) and nitrogen
dioxide (NO,), the mixture of which is commonly referred to as "NO ." While NO
£. A
is clearly a precursor of photochemical oxidant, NO- is considered to be both an
oxidant and a precursor of oxidants. Because of this "precursor" nature of NO.
and the similarity of the analytical methods for NO and NO,,, the information on
ambient NO- concentrations is presented in this chapter, dealing with the oxi-
dant precursors, rather than in Chapter 2, which dealt with oxidants.
Analytical Methods
In air monitoring practices thus far, both NO and NO- have been measured
colorimetrically, the NO requiring an intermediate step of oxidation into N0_.
Because of uncertainties and the somewhat controversial nature of the analytical
methods for NO , these methods are discussed here in some detail.
X.
The colorimetric Griess-Saltzman method is the most suitable manual method
12,13
The method
3
generally applicable to the measurement of NO- in the atmosphere
can be used to determire concentrations of N0~ in the air from 40 to 1500 mg/m
(0.02 to 0.80 ppm). Ordinarily, interferences are not a serious problem, although
high ratios of sulfur dioxide to nitrogen dioxide (about 30:1) can cause bleaching
-------
10
NNUAL AVERAGE
THREE-YEAR MOVING AVERAGE
1.0
1963 64
71
72
YEAR
Figure 6-5. Pollutant trends for July, August, and September in Los Angeles, 1963-1972.11
and give misleadingly low values.^ Interference from other oxides of nitrogen
are negligible at concentrations found in polluted air. Peroxyacetyl nitrate
CPAN) can give a response of up to 35 percent of an equivalent molar concentration
of NC>2, but in ordinary ambient air, PAN concentrations are too low to cause sig-
95
-------
Figure 6-6. Distribution of total hydrocarbon concentrations in the South Coast Air Basin. 11
Average of daily maximum 1-hour concentrations (ppm C) during July, August, and September,
1970-1972.
nificant error.-'-2 More recent data suggest that ozone also, at high ozone to N02
ratios, may cause a negative inteference.^
In the original method, Saltzman used solutions of sodium nitrite as
calibration standards. He reported that, under laboratory conditions, 0.72
mole of nitrite produces the same color as 1 mole of N0_ gas and incorporated
this factor into his calculations. In recent years, this stoichiometric factor
has been the source of considerable controversy. Values ranging from 0.5 to 1.00
11~\-7-7 'y ^
have been reported, ~ and one recent study reconfirmed Saltzman's original
findings. The method can be standardized by using an accurately determined con-
centration of NO. gas, thus eliminating the stoichiometric factor from the cal-
culations .
The NO is generally determined by oxidizing it to N0_, measuring the resultant
N07, and converting measurement results to NO concentrations. For the NO oxi-
24 25
dation step, the oxidizers used are aqueous or solid potassium permangenate and
O ft 7 Q
dichromate or chromium trioxide in various formulations, all of which have
somewhat uncertain lifetimes at peak efficiency. In addition, the dichromate
and chromium trioxide preparations are extremely sensitive to high humidity.
2g
More recently developed promising methods are the ones by Hartkamp and by
Forwerg and Creselius.
96
-------
It is generally believed that ambient NO concentrations are underestimated
as a result of the poor conversion efficiency, a factor that should be kept in
mind when studying NO data. Additional error may also be introduced depending
on whether the NO measurement is done in series or in parallel with the N02
measurement, as explained next.
In the series mode, which some workers prefer, the sample air passes through
an N09 analyzer for removal and measurement of NO,,, then through an oxidizer
31 32
where NO is converted to N0_, and finally through a second N0_ analyzer. '
The response from the second N0? analyzer is a measure of the NO in the sample
air. However, up to 14 percent of the N0? may be converted to NO in the first
analyzer. Therefore, it is better to remove the N07 by a special absorber, such
33
as triethanolamine on firebrick. Even in this case, up to a few percent of
the N0_ may be converted to NO depending on the humidity and the age of the absorber.
The parallel mode requires two separate analyses: in one, sample air
is analyzed for N0_; and in another, sample air is analyzed for total NO . In
the latter analysis, the sample is passed through an oxidizing scrubber to con-
vert NO to N0_. Problems here are the uncertain efficiency of the scrubber as
well as some retention of N0~ in the scrubber.
The Griess-Saltzman method for N02 measurement cannot be used successfully
when the delay between sample collection and color measurement is more than 4 to
6 hours or when sampling periods of longer than 1 hour are required. In such
situations, the Jacobs-Hochheiser method has been preferred. With this method,
sampling periods can be as long as 24 hours, and samples can be collected in the
field and analyzed in a control laboratory with a delay of 2 weeks or more, if
necessary. The method, however, has been found recently to have some serious
drawbacks. New, soon to be published, studies have shown the Jacobs-Hochheiser
method to suffer from N02 collection efficiency problems that cause erroneously
high results for low NO- levels and low results for high N02 levels. Also, the
method suffers from error due to positive interference from NO. Considerable
improvement of the NO- collection efficiency was achieved by adding small amounts
of sodium arsenite to the Jacobs-Hochheiser collection reagent.
Other recent developments have resulted in considerably improved methods
for NO measurement. For example, use of permeation tubes now permits much more
"Z A
re^able calibration of the N02 measurement methods. Also, new, highly promising,
chemjluminescence methods have been developed for measurement of NO, and, in-
directly, of NO- also. ' ' Introduction of these new methods into U.S.
monitoring networks was scheduled for completion by the end of 1974.
Concentrations
The majority of available continuous air quality data for nitrogen oxides
are less than 15 years old. In 1956, the Los Angeles County Air Pollution Control
97
-------
District (LAAPCD) began monitoring NO and NO,, continuously. In 1961, the Cali-
fornia State Department of Public Health organized the Statewide Cooperative Air
Monitoring Network (SCAN), which, since 1968, has been operating 27 monitoring
stations in California. Data on ambient NO have been obtained also by the
x
Federal government through its Continuous Air Monitoring Program (CAMP) and the
National Air Surveillance Networks (NASN). The data obtained in the SCAN and
CAMP stations were by the continuous Griess-Saltzman method; NASN used the in-
tegrated Jacobs-Hochheiser method. These two analytical methods do not agree
well; therefore, the respective data should be compared and interpreted carefully.
Tables 6-8 and 6-9 show frequency distribution data for 6 to 9 a.m. concen-
trations of NO and NO, measured at the CAMP stations. Data for 1963-1967 from
selected cities in the California SCAN and LAAPCD networks are given in Tables 6-10
and 6-11. Table 6-12 includes data from various cities, showing N0_ levels by
the Jacobs-Hochheiser method, by the "arsenite" version of the Jacobs-Hochheiser
procedure, and by the recently developed chemiluminescence method.
The data given in the Tables 6-10 and 6-11 should be analyzed with care.
It should be noted, for example, that these data, as given, do not show seasonal
and diurnal effects and therefore cannot be directly associated with the oxi-
dant levels observed in the respective locations. Since the interest here is
on the role of NO in the oxidant formation process, the most useful data are those
for NO from 6 to 9 a.m., because these data represent the NO concentrations
A A
that are assumed to cause the oxidant formed later in the day. Also, more
pertinent data are those for NO concentrations during the summer and the early
fall months when the oxidant levels are highest. In view of the large seasonal
and diurnal variations in NO (see next section), a more appropriate compilation
of ambient NO concentration data would emphasize data for 6 to 9 a.m. and for
summer and early fal1.
Seasonal and Diurnal Variations
Seasonal variation of ambient NO is illustrated in Figure 6-7, where
A
frequency distribution data were plotted separately for each of the four seasons
in 1964. The plots show the lowest NO levels to occur during the summer months
and the highest during winter. Such variation is probably caused by increased
accumulation of NO during the winter months, when early-morning temperature
inversions (resulting in air stagnation) are more intense, and NO emissions
from power generation and heating sources are increased.
Nitric oxide displays a more marked seasonal variation than N0_ does.
38
This can be seen when Figures 6-8 and 6-9 are compared. For NO, as for most
primary contaminants, higher mean values are observed during late fall and
through the winter months, when there is less overall atmospheric mixing and
generally less ultraviolet energy available for forming secondary products. The
98
-------
o
z
1.0
0.8
0.6
0.4
0.2
0.1
0.08
0.06
0.04
0.02
0.01 0.1 0.5 1 5 10 50
% OF TIME CONCENTRATION IS EXCEEDED
90
Figure 6-7. Frequency distribution of 3-hour-average concentrations
of nitrogen oxides at Los Angeles CAMP Station, December 1, 1963,
to December 1, 1964.
120
120
O WASHINGTON. D.C
AST. LOUIS, MO.
oDENVER,COLO.
O WASHINGTON, D.C.
AST. LOUIS, MO.
ODENVER.COLO.
TIME, month
TIME, month
Figure 6-8. Monthly average of nitric oxiide con- Figure 6-9. Monthly average of nitrogen dioxide
centrations in three cities, 1969-1972.38 concentrations in three cities, 1969-1972.38
pattern for NO- (Figure 6-9) is less distinct and shows less variation from
month to month.
The diurnal variations of NO and NO- in Los Angeles, California, on July 19,
1965, are shown in Figure 6-10 along with the variations of carbon monoxide (CO)
99
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103
-------
Table 6-10. NITRIC OXIDE CONCENTRATION* IN CALIFORNIA BY AVERAGING TIME
AND FREQUENCY, 1963-1967
(ppm)
Place, site No. ,
averaging
time
Anaheim-176
1 hr
8 hr
1 day
1 mo
1 yr
Bakersfield-201
1 hr
8 hr
1 day
1 mo
1 yr
Fresno-226
1 hr
8 hr
1 day
1 mo
1 yr
Oakland-327
1 hr
8 hr
1 day
1 mo
1 yr
Port Chicago-429
1 hr
8 hr
1 day
1 mo
1 yr
Richmond-428
1 hr
8 hr
1 day
1 mo
1 yr
Riverside-126
1 hr
8 hr
1 day
1 rno
1 yr
Sacramento-276
1 hr
8 hr
1 day
1 mo
1 yr
Maximum for year
63
0.29
0.18
0.11
0.05
0.02
0.34
0.20
0.12
0.05
0.87
0.49
0.21
0.03
0.01
0.93
0.57
0.33
0.02
1.08
0.60
0.35
0.14
0.04
64
0.30
0.19
0.09
0.04
0.47
0.22
0.15
0.06
0.02
0.93
0.60
0.35
0.14
0.07
1.10
0.59
0.28
0.11
1.08
0.53
0.26
0.09
0.04
65
0.70
0.29
0.17
0.05
0.52
0.25
0.14
0.03
0.02
0.66
0.34
0.26
0.11
0.05
0.57
0.36
0.24
0.10
0.04
0.97
0.62
0.28
0.10
0.03
66
0.40
0.24
0.15
0.04
0.02
0.44
0.27
0.16
0.07
0.02
0.54
0.24
0.12
0.04
0.68
0.34
0.26
0.13
0.05
0.14
0.07
0.06
0.02
0.01
0.74
0.45
0.20
0.07
0.43
0.26
0.20
0.08
0.04
0.75
0.49
0.23
0.07
0.04
67
0.66
0.41
0.18
0.07
0.04
0.56
0.36
0.22
0.09
0.04
0.59
0.30
0.14
0.05
0.02
0.91
0.52
0.30
0.11
0.05
0.24
0.12
0.07
0.02
0.01
0.58
0.35
0.21
0.08
0.04
0.52
0.26
0.20
0.08
0.04
0.90
0.58
0.33
0.07
0.03
Percentile
0.01
0.62
0.55
0.72
0.92
0.18
0.74
0.74
0.97
0.1
0.40
0.28
0.40
0.28
0.41
0.26
0.70
0.55
0.13
0.10
0.49
0.35
0.47
0.38
0.70
0.54
1
0.22
0.18
0.12
0.25
0.18
0.14
0.22
0.16
0.11
0.41
0.32
0.26
0.08
0.06
0.05
0.27
0.23
0.18
0.29
0.21
0.18
0.37
0.29
0.22
10
0.07
0.07
0.06
0.06
0.09
0.08
0.07
0.06
0.04
0.04
0.04
0.04
0.15
0.14
0.13
0.11
0.03
0.03
0.02
0.02
0.10
0.10
0.09
0.08
0.11
0.10
0.09
0.08
0.09
0.09
0.09
0.07
30
0.03
0.03
0.03
0.04
0.03
0.03
0.03
0.04
0.01
0.01
0.01
0.02
0.05
0.05
0.06
0.07
0.01
0.01
0.01
0.01
0.04
0.05
0.05
0.07
0.04
0.04
0.05
0.05
0.03
0.03
0.04
0.05
50
0.01
0.02
0.02
0.02
0.02
0.01
0.02
0.02
0.02
0.04
0.00
0.00
0.00
0.01
0.02
0.02
0.03
0.03
0.04
0.05
0.00
0.01
0.01
0.01
0.01
0.02
0.02
0.03
0.04
0.04
0.02
0.02
0.03
0.03
0.04
0.02
0.02
0.02
0.03
0.04
70
0.00
0.01
0.01
0.02
0.00
0.00
0.01
0.02
0.00
0.00
0.00
0.00
0.01
0.01
0.02
0.02
0.00
0.00
0.00
0.01
0.01
0.01
0.01
0.02
0.01
0.01
0.01
0.03
0.00
0.01
0.01
0.01
90
0.00
0.00
0.00
0.01
0.00
0.00
0.00
0.01
0.00
0.00
0.00
0.00
0.00
0.00
0.01
0.02
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.01
0.00
0.00
0.00
0.01
0.00
0.00
0.00
0.01
104
-------
Table 6-10 (continued).
NITRIC OXIDE CONCENTRATION3 IN CALIFORNIA BY AVERAGING TIME
AND FREQUENCY, 1963-1967
(ppm)
Place, site No.,
averaging
time
Salinas-536
1 hr
8 hr
1 day
1 mo
1 yr
San Bernardino-151
1 hr
8 hr
1 day
1 mo
1 yr
San Diego-101
1 hr
8 hr
1 day
1 mo
1 yr
San Diego-106
1 hr
8 hr
1 day
1 mo
1 yr
San Diego-108
1 hr
8 hr
1 day
1 mo
1 yr
San Jose-376
1 hr
8 hr
1 day
1 mo
1 yr
Santa Barbara-351
1 hr
8 hr
1 day
1 mo
1 yr
Stockton-252
1 hr
8 hr
1 day
1 mo
1 yr
Maximum for year
63
0.25
0.12
0.06
0.03
0.01
0.74
0.45
0.24
0.14
0.04
0.75
0.48
0.26
0.17
0.38
0.18
0.14
0.04
64
0.25
0.12
0.06
0.02
1.10
0.63
0.21
0.08
0.02
0.40
0.26
0.12
0.05
0.02'
0.60
0.46
0.27
0.14
0.38
0.19
0.10
0.04
0.50
0.29
0.15
0.06
0.03
65
0.34
0.16
0.10
0.04
0.90
0.43
0.23
0.09
0.03
0.56
0.22
0.12
0.04
0.01
0.39
0.22
0.17
0.12
0.72
0.45
0.21
0.11
0.03
0.48
0.33
0.23
0.11
0.03
66
0.45
0.21
0.10
0.04
0.50
0.26
0.20
0.07
1.20
0.42
0.26
0.12
0.05
0.34
0.15
0.08
0.52
0.18
0.14
0.07
0.03
0.42
0.25
0.15
0.57
0.29
0.18
0.10
0.87
0.50
0.26
0.11
0.03
67
0.29
0.15
0.07
0.03
0.01
0.36
0.15
0.11
0.05
0.03
0.80
0.34
0.22
0.10
0.04
0.60
0.29
0.16
0.08
0.03
0.68
0.38
0.21
0.08
0.04
0.36
0.16
0.09
0.02
0.01
Percenti le
0.01
0.45
0.47
1.00
0.40
0.60
0.68
0.68
0.68
0.1
0.24
0.20
0.32
0.25
0.65
0.42
0.31 .
0.22
0.40
0.25
0.54
0.46
0.51
0.40
0.47
0.39
1
0.15
0.10
0.06
0.15
0.12
0.09
0.38
0.26
0.20
0.21
0.13
0.10
0.20
0.16
0.12
0.37
0.29
0.25
0.32
0.22
0.18
0.27
0.23
0.19
10
0.05
0.04
0.04
0.03
0.05
0.05
0.05
0.04
0.10
0.10
0.10
0.09
0.05
0.06
0.05
0.05
0.07
0.07
0.06
0.05
0.17
0.15
0.15
0.12
0.07
0.07
0.08
0.06
0.08
0.07
0.07
0.06
30
0.01
0.02
0.02
0.02
0.02
0.02
0.03
0.03
0.02
0.03
0.04
0.05
0.00
0.01
0.02
0.02
0.03
0.03
0.03
0.03
0.07
0.08
0.08
0.08
0.01
0.02
0.02
0.03
0.02
0.02
0.03
0.03
50
0.00
0.01
0.01
0.01
0.01
0.01
0.01
0.02
0.02
0.03
0.01
0.01
0.01
0.02
0.04
0.00
0.00
0.00
0.00
0.02
0.01
0.02
0.02
0.02
0.03
0.03
0.04
0.04
0.07
0.04
0.01
0.01
0.01
0.01
0.03
0.01
0.01
0.01
0.02
0.03
70
0.00
0.00
0.00
0.01
0.00
0.01
0.01
0.01
0.00
0.00
0.00
0.01
0.00
0.00
0.00
0.00
0.00
0.01
0.01
0.02
0.01
0.02
0.02
0.02
0.00
0.00
0.00
0.01
0.00
0.00
0.01
0.01
90
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.01
0.01
0.02
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Determined by continuous Griess-Saltzman method.
Concentrations greater than or equal to specified value in indicated percentage of samples.
105
-------
Table 6-11. NITROGEN DIOXIDE CONCENTRATION3 IN CALIFORNIA BY AVERAGING
TIME AND FREQUENCY, 1963-1967
(ppm)
Place, site Mo. ,
averaging
time
Anaheim-176
1 hr
8 hr
1 day
1 mo
1 yr
Bakersfield-201
1 hr
8 hr
1 day
1 mo
1 yr
Fresno-226
1 hr
8 hr
1 day
1 mo
1 yr
Oakland-327
1 hr
8 hr
1 day
1 mo
1 yr
Port Chicago-429
1 hr
8 hr
1 day
1 mo
1 yr
Richmond-428
1 hr
8 hr
1 day
1 mo
1 yr
Ri verside-126
1 hr
8 hr
1 day
1 mo
1 yr
Sacramento-276
1 hr
8 hr
1 day
1 mo
1 yr
Sal inas-536
1 hr
8 hr
1 day
1 mo
1 yr
Maximum for year
63
0.20
0.15
0.11
0.06
0.03
0.17
0.10
0.07
0.03
r
0.10
0.08
0.05
0.03
0.02
0.28
0.19
0.10
0.05
0.03
0.27
0.18
0.14
0.06
0.29
0.17
0.13
0.07
0.04
64
0.22
0.13
0.11
0.04
0.17
0.10
0.08
0.04
0.02
0.41
0.25
0.16
0.05
0.03
0.56
0.26
0.19
0.05
0.04
0.32
0.21
0.13
0.07
0.04
65
0.23
0.16
0.13
0.05
0.25
0.18
0.11
0.04
0.02
0.23
0.15
0.10
0.06
0.03
0.49
0.31
0.25
0.08
0.05
0.30
0.20
0.13
0.07
0.04
66
0.27
0.15
0.12
0.05
0.04
0.15
0.10
0.08
0.04
0.03
0.14
0.11
0.06
0.04
0.03
0.29
0.18
0.13
0.05
0.03
0.17
0.09
0.07
0.03
0.03
0.14
0.08
0.07
0.03
0.25
0.18
0.13
0.05
0.04
0.27
0.21
0.15
0.05
0.03
0.11
0.07
0.05
0.03
67
0.27
0.19
0.13
0.07
0.04
0.19
0.14
0.09
0.05
0.04
0.17
0.12
0.07
0.05
0.03
0.33
0.23
0.15
0.06
0.04
0.14
0.07
0.06
0.04
0.03
0.21
0.14
0.10
0.05
0.03
0.31
0.23
0.17
0.05
0.04
0.30
0.20
0.13
0.05
0.04
0.10
0.08
0.05
0.02
0.02
Percenti'le
0.01
0.25
0.19
0.22
0.33
0.15
0.21
0.49
0.30
0.11
0.1
0.21
0.18
0.14
0.13
0.14
0.13
0.23
0.20
0.11
0.09
0.15
0.10
0.32
0.29
0.22
0.19
0.09
0.07
1
0.15
0.13
0.10
0.10
0.09
0.08
0.09
0.08
0,06
0.14
0.13
0.10
0.08
0.07
0.06
0.10
0.08
0.07
0.18
0.15
0.14
0.14
0.12
0.11
0.06
0.05
0.04
10
0.07
0.07
0.06
0.06
0.06
0.06
0.05
0.04
0.04
0.04
0.04
0.03
0.07
0.06
0.06
0.05
0.04
0.04
0.04
0.03
0.06
0.06
0.05
0.05
0.09
0.08
0.07
0.05
0.07
0.06
0.06
0.05
0.03
0.03
0.03
0.02
30
0.05
0.04
0.04
0.05
0.04
0.04
0.04
0.04
0.03
0.03
0.03
0.03
0.04
0.04
0.04
0.04
0.03
0.03
0.03
0.03
0.04
0.04
0.04
0.04
0.05
0.05
0.05
0.05
0.04
0.04
0.04
0.04
0.02
0.02
0.02
0.02
50
0.03
0.03
0.03
0.04
0.04
0.03
0.03
0.03
0.03
0.04
0.02
0.02
0.02
0.02
0.02
0.03
0.03
0.03
0.03
0.03
0.02
0.02
0.02
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.04
0.04
0.04
0.04
0.03
0.03
0.03
0.03
0.04
0.02
0.02
0.02
0.02
0.02
70
0.02
0.02
0.02
0.03
0.02
0.02
0.03
0.03
0.01
0.01
0.02
0.02
0.02
0.02
0.02
0.03
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.03
0.02
0.02
0.03
0.04
0.02
0.02
0.02
0.03
0.01
0.01
0.01
0.02
90
0.01
0.01
0.01
0.02
0.01
0.01
0.02
0.03
0.01
0.01
0.01
0.02
0.01
0.01
0.02
0.02
0.01
0.01
0.01
0.02
0.01
0.01
0.02
0.02
0.01
0.01
0.02
0.03
0.01
0.01
0.02
0.02
0.01
0.01
0.01
0.01
106
-------
Table 6-11 (continued).
NITROGEN DIOXIDE CONCENTRATION3 IN CALIFORNIA BY AVERAGING
TIME AND FREQUENCY, 1963-1967
(ppm)
Place, site No. ,
averaging
time
San Bernadino-151
1 hr
8 hr
1 day
1 mo
1 yr
San Diego-101
1 hr
8 hr
1 day
1 mo
1 yr
San Diego-106
1 hr
8 hr
1 day
1 P10
1 yr
San Diego-108
1 hr
8 hr
1 day
1 mo
1 yr
San Jose-376
1 hr
8 hr
1 day
1 mo
1 yr
Santa Barbara-351
1 hr
8 hr
1 day
1 mo
1 yr
Santa Cruz-841
1 hr
8 hr
1 day
1 mo
1 yr
Stockton-252
1 hr
8 hr
1 day
1 RIO
1 yr
Maximum for year
63
0.14
0.12
0.06
0.03
0.01
0.33
0.18
0.12
0.06
0.03
0.30
0.19
0.13
0.07
0.13
0.08
0.06
0.02
64
0.06
0.03
0.02
0.35
0.15
0.09
0.06
0.02
0.20
0.11
0.09
0.05
0.01
0.39
0.31
0.18
0.07
0.05
0.18
0.12
0.09
0.03
0.02
0.22
0.15
0.08
0.05
0.03
65
0.11
0.07
0.05
0.03
0.52
0.22
0.12
0.04
0.02
0.17
0.09
0.05
0.02
0.01
0.23
0.16
0.12
0.07
0.31
0.13
0.08
0.04
0.03
0.12
0.14
0.11
0.07
0.03
0.02
66
0.25
0.14
0.11
0.06
0.04
0.40
0.19
0.12
0.06
0.03
0.15
0.11
0.07
0.37
0.25
0.14
0.06
0.03
0.27
0.20
0.16
0.06
0.04
0.13
0.08
0.06
0.03
0.09
0.07
0.04
0.02
0.16
0.11
0.07
0.03
0.02
67
0.22
0.17
0.13
0.07
0.05
0.34
0.17
0.08
0.03
0.02
0.21
0.13
0.08
0.04
0.02
0.27
0.18
0.12
0.07
0.04
0.06
0.04
0.02
0.02
0.18
0.10
0.06
0.03
0.02
0.01
0.23
0.35
0.17
0.35
0.34
0.28
0.12
0.20
0.1
0.19
0.16
0.22
0.18
0.14
0.11
0.25
0.18
0.29
0.24
0.14
0.12
0.08
0.06
0.16
0.12
Percent! leb
1
0.13
0.12
0.10
0.12
0.11
0.09
0.10
0.09
0.07
0.13
0.12
0.10
0.18
0.16
0.13
0.08
0.07
0.07
0.06
0.05
0.04
0.09
0.07
0.06
10
0.07
0.06
0.06
0.05
0.06
0.06
0.05
0.04
0.04
0.04
0.03
0.02
0.06
0.15
0.05
0.05
0.09
0.09
0.08
0.07
0.05
0.05
0.04
0.03
0.03
0.03
0.03
0.02
0.04
0.04
0.04
0.03
30
0.04
0.04
0.04
0.04
0.03
0.03
0.03
0.03
0.01
0.01
0.01
0.02
0.03
0.03
0.03
0.03
0.05
0.05
0.05
0.05
0.03
0.03
0.03
0.03
0.02
0.02
0.02
0.02
0.02
0.03
0.03
0.02
50
0.02
0.02
0.03
0.03
0.04
0.01
0.02
0.02
0.02
0.02
0.00
0.00
0.00
0.01
0.01
0.02
0.02
0.02
0.02
0.03
0.04
0.04
0.04
0.04
0.04
0.02
0.02
0.02
0.03
0.03
0.01
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
70
0.01
0.01
0.01
0.01
0.00
0.01
0.01
0.01
0.00
0.00
0.00
0.00
0.01
0.01
0.02
0.02
0.03
0.03
0.03
0.04
0.02
0.02
0.02
0.02
0.01
0.01
0.01
0.02
0.01
0.01
0.02
0.02
90
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.01
0.00
0.00
0.00
0.00
0.00
0.00
0.01
0.01
0.01
0.02
0.02
0.03
0.01
0.01
0.01
0.02
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
Determined by continuous Griess-Saltzrnan method.
Concentrations greater than or equal to specified value in indicated percentage of samples.
107
-------
Table 6-12. AMBIENT NITROGEN DIOXIDE CONCENTRATIONS IN VARIOUS
CITIES IN 1972 MEASURED BY DIFFERENT METHODS
(arithmetic average for period of operation)
City
Los Angeles, Cal .
Chicago, 111.
Salt Lake City, Utah
Denver, Colo.
New York-New Jersey
Baltimore, Md.
Washington, D.C.
San Jose, Cal .a
Louisville, Ky.
Springfield, Mass.
Phoenix, Ariz.
Atlanta, Ga.
Detroit, Mich.
St. Louis, Mo.a
Pittsburgh, Pa.
Dallas, Texas
Columbus, Ohio
Memphis, Tenn.
Houston, Texas
San Diego, Cal .
Dayton, Ohio
Indianapolis, Ind.
Omaha, Neb.
Lancaster, Pa.
Grand Rapids, Mich.
Richmond, Va.
Canton, Ohio
Miami , Fla.
Tampa, Fla.
Toledo, Ohio
Reading, Pa.
Rochester, N. Y.
Seattle, Wash.
Providence, R. I.
Philadelphia, Pa.
Corpus Christi , Texas
Cincinnati , Ohio
Buffalo, N. Y.
Dubuque, Iowa
Worcester, Mass.
Chattanooga, Tenn.
Boston, Mass.
Milwaukee, Wis.
Johnstown, Pa.
N02 concentration, ng/m3
Jacobs-
Hochheiser
252
238
159
106
182
159
146
193
184
125
159
183
180
123
177
145
149
148
137
136
158
107
113
132
127
171
126
120
156
139
158
98
134
98
197
85
156
76
70
120
125
132
124
__
Arsenite
182
117
62
42
100
96
88
85
87
82
80
80
80
79
78
76
68
64
64
63
64
61
60
60
59
58
57
55
56
54
52
48
47
45
83
43
73
32
30
71
53
74
76
25
Chemi lu-
minescence
118
121
114
no
65
64
64
84
68
73
69
62
60
58
64
47
52
31
66
76
53
56
30
36
44
37
53
53
52
38
60
26
51
--
84
43
61
49
23
38
--
64
aCommon site for all instruments.
108
-------
0.50
LOCAL TIME
Figure 6-10. Average daily 1-hour concentrations of selected pollutants in Los Angeles, California,
July 19, 1965.39
39
and ozone (0,). This concentration profile graphically depicts the NO peak
J
and the associated lag in NO- peak as the NO is converted. It also illustrates
the subsequent increase in 0, concentration. The data in Figure 6-10 do not show
O
the generalized increase in evening NO levels due to the late afternoon peak
X
automotive traffic. On this particular day, evening dispersion factors apparently
prevented any substantial buildup of the NO . It should be pointed out that Los
A
Angeles, however, is a unique city because of the tremendous influence of auto-
mobile emissions; other cities would not necessarily exhibit the same characteris-
tics. Figure 6-11 shows diurnal variations in NO- concentration in several other
. . 38
cities.
The hours at which the peak concentrations of NO usually occur either
X
coincide with, or take place shortly after, the hours of peak automotive traffic.
The diurnal pattern, therefore, shows little day-to-day variation except for
weekends and holidays, when traffic differs from weekday patterns. The diurnal
variations of NO on weekdays, Saturdays, and Sundays are shown for the Chicago
40
CAMP station in Figure 6-12. The Sunday peak concentrations of NO at 8 a.m. are
about one-third of the weekday peak concentrations. On some weekends, some
locations have peak NO concentrations equal to weekday peak values, but the
peaks occur 1 to 3 hours later. Furthermore, weekend NO concentrations in certain
recreational areas often exceed weekday values.
109
-------
100
90
80
"e 70
1
c
-------
Table 6-13. OXIDES OF NITROGEN TRENDS IN THE SOUTH COAST AIR BASIN, 1963-1972,
THREE-MONTH AVERAGES OF DAILY MAXIMUM ONE-HOUR CONCENTRATIONS
FOR JULY, AUGUST, AND SEPTEMBER*.11
(pphm)
Station
Anaheim
Azusa
Burbank
LaHabra
Lennox
Long Beach
Los Angeles, Downtown
Pasadena
Pomona
Redlands
Reseda
Riverside
San Bernardino
West Los Angeles
1963
6.0
10.7
17.3
__
__
14.1
25.0
15.1
4.9
16.4
1964
7.4
12.9
18.0
_
--
14.5
20.8
14.6
--
._
15.2
1.9
15.5
1965
7.2
10.8
23.6
8.7
24.8
17.8
24.9
15.2
18.0
16.9
12.8
7.7
20.1
1966
14.8
12.4
20.7
11.7
25.2
17.6
27.8
17.5
18.4
__
16.2
17.6
10.9
19.7
1967
13.2
13.0
22.6
12.6(2)
29.1
24.7
21.4
17.1
19.4
18.0
13.2
16.5
15.8
1968
18.3
13.6
33.1
13.6
30.8
27.1
23.2
18.2
25.3
8.1
23.3
13.1
25.3
1969^
16.7
13.4
33.4
14.6
23.4
26.9
21.0
24.0
26.7
7.5
21.3
--
12.4
21.0
1970
12.9
19.3
30.0
8.9
37.0
31.2
33.8
25.0
32.7
12.1
27.7
--
14.7
28.7
1971
17.5
19.0
33.7
17.0
32.0
16.7
32.2
17.7
28.9
13.1
23.3
_
25.5
1972
14.6
16.2
30.5
14.5
27.1
22.8
27.8
20.6
25.4
11.8
23.5
11.9
12.8
18.2
Numbers in parentheses indicate number of months of missing data.
or data were not reported.
Dashes indicate stations were not ooeratinq
Table 6-14. OXIDES OF NITROGEN TRENDS IN THE SOUTH COAST AIR BASIN, 1963-1972,
THREE-MONTH AVERAGES OF 6 TO 9 a.m. DAILY AVERAGE CONCENTRATIONS
FOR JULY, AUGUST, AND SEPTEMBERS."H
(pphm)
Station
Anaheim
Azusa
Burbank
LaHabra
Lennox
Long Beach
Los Angeles, Downtown
Pasadena
Pomona
Redlands
Reseda
Riverside
San Bernardino
Uest Los Angeles
1963
3.5
7.8
13.3
__
-_
9.5
19.9
10.1
--
_
-.
--
2.9
12.1
1964
5.0
9.3
14.5
._
-_
10.1
17.1
10.1
--
»_
__
13.8
0.9
11.1
1965
4.2
7.6
17.5
__
19.5
12.7
20.4
10.4
14.1
_-
11.5
9.2
5.4
14.3
1966
8.0
8.7
15.3
__
19.4
13.5
22.7
12.2
12.1
__
11.2
14.0
7.9
14.0
1967
7.9
9.5
18.0
5.1(2)
22.5
17.1
16.8
12.1
14.3
__
13.3
10.7
12.6
12.5
1968
10.2
9.4
26.5
7.0
24.1
18.1
18.5
11.8
17.5
4.2
15.5
--
9.6
18.8
1969
10.6
10.2
27.8
9.8
19.0
18.3
17.0
15.7
20.4
4.5
15.2
--
9.4
16.0
1970
8.2
15.4
25.1
5.3
25.9
23.4
27.5
16.5
24.4
7.6
19.9
--
12.7
21.4
1971
11.1
14.3
27.5
10.0
24.0
10.5
27.1
11.1
20.3
8.2
17.7
--
__
20.3
1972
9.8
12.3
23.5
9.8
19.7
16.4
21.9
13.3
18.4
7.5
15.5
8.5
8.9
14.2
Numbers in parentheses indicate number of months of missing data. Dashes indicate stations were not operating
or data were not reported.
to the basinwide averages. Perhaps the most significant implication of these
results is that delineation of the oxidant-hydrocarbon-NOx relationships from
atmospheric data alone is not easy. The most serious problem undoubtedly is
the interfering effects from the varying meteorological conditions.
CONCENTRATIONS OF SULFUR OXIDES IN URBAN ATMOSPHERES
The sole purpose of including data on the atmospheric concentrations of
sulfur oxides in this chapter is to present a more complete picture of the
pollutants that may have a role in the oxidant formation process. Laboratory
studies suggested that sulfur dioxide (SO-) may either enhance or inhibit oxi-
dant formation depending on the hydrocarbon reactant used. Field studies,
however, were inconclusive, leaving the question of the S0_ role in oxidant
111
-------
Table 6-15. OXIDES OF NITROGEN TRENDS IN THE SOUTH COAST AIR BASIN, 1963-1972, ANNUAL
AVERAGES OF DAILY MAXIMUM ONE-HOUR CONCENTRATIONS FOR ALL DAYS OF THE YEARa.ll
(pphm)
Station
Anaheim
Azusa
Burbank
LaHabra
Lennox
Long Beach
Los Angeles, Downtown
Pasadena
Pomona
Redlands
Reseda
Riverside
San Bernardino
West Los Angeles
1963
10.7
12.6
31.0
_.
-_
30.5
36.8
24.7
_.
__
-_
5.7
31.1
1964
11 l^3)
12'. 5
27.7
,.
.-
33.1
29.7
23.8
_, _
_
23.5^
3.3(3)
29.1
1965
13.50)
10.7(2)
33.3
17.90)
36.7(1)
27.9
34.1
21.0,
22.3(5)
20.5(2)
19.2
9.7(8)
31.6
1966
13.3(2)
12.5
32.1
17.2
40.8
28.0
37.8
22.8
23.8
._
25.3, .
17. 90)
14.l(z)
29. '3
1967
19.1
13.5
36.7
16.4(3)
51.5
33.4
36.4
25.9
28.9
..
27.5
17.3
16.2
30.5
1968
28.5
14.7
45.8
22.2
46.3
37.5
37.1
26.7
32.5
9.4(3)
30. 0/-,,,
31.5(11)
13.2
34.0
1969
25.8
13.4
42.0
16 lO)
44^3
34.8
35.2
28.2
31.5
7.3(3)
27.2
11.5(3)
32.4
1970
22.4
17,9
43.0
14.4
50.8
38.7
40.7
33.2
35.8
11.9
5 301 ':
14>>
36.7
1971
25.0
19.2
42.8
22.0
51.1
32.3
44.6
28.0
35.3
16.9
6.9(9)
16.9(7)
36.6
1972
26.0
18.6
40.5
24.1
50.0
36.2
39.1
30.7
33.6
17.2
35.6
16.6
15.1
32.0
aNumbers in parentheses indicate number of months of missing data. Dashes indicate stations were not operating
or data were not reported.
Table 6-16. NITROGEN DIOXIDE TRENDS IN THE SOUTH COAST AIR BASIN, 1963-1972,
THREE-MONTH AVERAGES OF 6 TO 9 a.m. DAILY AVERAGE CONCENTRATIONS
FOR JULY, AUGUST, AND SEPTEMBER*J1
(pphm)
Station
Anaheim
Azusa
Burbank
LaHabra
Lennox
Long Beach
Los Angeles, Downtown
Pasadena
Pomona
Redlands
Reseda
Riverside
San Bernardino
West Los Angeles
1963
2.3
4.4
5.8
3.7
7.7
5.8
--
9.2
1.6
5.7
1964
3.2
6.4
6.8
--
4.7
8.7
6.6
--
_ _
--
7.6
0.2
5.9
1965
3.2
5.5
8.7
- _
7.2
5.7
9.5
6.5
8.2
__
7.0
5.9
3.6
7.8
1966
6.1
6.4
7.7
6.1
4.4
10.7
7.3
7.6
-_
6.8
8.0
5.0
7.2
1967
4.0(4)
6.7
10.9
8.6
7.7
7.1
7.3
7.8
_ -
8.4
7.1
7.4
8.5
1968
4.0
6.4
12.6
4.1
7.6
7.8
5.9
7.5
8.5
2.3
8.5
4.7
7.5
1969
6.1
7.0
13.4
6.4
8.0
7.5
4.8
10.0
10.3
2.5
9.5
6.8
9.9
1970
4.7
8.8
11.7
3.2
8.7
9.6
10.2
10.8
11.3
5.2
11.8
7.4
9.6
1971
5.3
8.0
12.8
5.6
7.8
4.7
10.8
7.2
10.2
6.0
9.5
8.2
8.2
9.8
1972
4.1
7.1
9.7
5.3
6.3
7.2
9.5
7.5
8.5
4.4
7-9(1)
4.5V '
5.9
6.5
a Numbers in parentheses indicate number of months of missing data.
Dashes indicate stations were not operating or data were not reported.
formation open. In addition to SCL, sulfates also are present in the atmosphere
as a result of photooxidation of SO,,. Sulfates occur in the form of constituents
of the aerosol suspended in the air, and relate to the photochemical oxidant in
that they are products of the same photooxidation process that results in oxi-
dant formation. Thus, factors that tend to enhance oxidant formation also tend
to enhance oxidation of SO- to sulfate.
112
-------
Table 6-17. NITROGEN DIOXIDE TRENDS IN THE SOUTH COAST AIR BASIN, 1963-1972,
THREE-MONTH AVERAGES OF DAILY-MAXIMUM ONE-HOUR CONCENTRATIONS
FOR JULY, AUGUST, AND SEPTEMBER9'11
(pphm)
Station
Anaheim
Azusa
Burbank
LaHabra
Lennox
Long Beach
Los Angeles, Downtown
Pasadena
Pomona
Redlands
Reseda
Riverside
San Bernardino
West Los Angeles
1963
4.6
7.1
10.5
9.0
12.2
9.6
11.6
3.1
8.6
1964
5.7
9.6
12.3
9.5
13.7
10.3
9.6
0.9
8.7
1965
5.1
8.2
13.7
6.0
11.1
10.5
15.6
10.4
11.1
9.8
9.0
5.2
12.5
1966
9.8
9.5
12.1
8.2
10.2
9.1
17.4
10.9
11.3
10.3
10.1
7.0
11.2
1967
7.2
10.0
16.1
6.8(2)
14.1
15.2
12.2
10.9
11.4
12.3
9.5
11.1
10.0
1968
8.5
10.7
19.5
10.0
12.7
16.0
11.1
11.8
12.6
4.7
12.9
7.0
14.8
1969
10.3
10.5
22.6
10.4
11.8
16.6
10.2
16.7
14.6
4.8
14.0
13.6
10.0
11.8
1970
8.2
13.0
19.0
6.5
14.0
17.3
16.3
18.2
15.8
8.2
16.8
9.0
10.7
13.9
1971
9.1
11.6
21.1
9.8
12.0
11.5
17.6
12.7
13.4
9.4
13.6
10.8
11.9
13.9
1972
6.8
10.7
14.7
8.5
8.8
12.3
14.6
11.8
11.6
7.3
12.2
6.1
8.7
9.3
a Numbers in parentheses indicate number of months of missing data.
Dashes indicate stations were not operating or data were not reported.
Table 6-18. NITROGEN DIOXIDE TRENDS IN THE SOUTH COAST AIR BASIN, 1963-1972, ANNUAL
AVERAGES OF DAILY MAXIMUM ONE-HOUR CONCENTRATIONS FOR ALL DAYS OF THE
(pphm)
Station
Anaheim
Azusa
Burbank
LaHabra
Lennox
Long Beach
Los Angeles, Downtown
Pasadena
Pomona
Redlands
Reseda
Riverside
San Bernardino
West Los Angeles
1963 1 1964
6.0
8.3
10.9
6.1(3)
8.8
10.5
_
|
11 .5
13.0
10.0
--
_
10.3(6)
3.1
10.4
11.3
11.7
10.9
8.9(D
0.8(3)
10.3
1965
6. 3/_,
7.9(2)
12.8
7.7(1)
12!l(l)
10.8
14.6
10.7,
11.3(5)
9.2(2)
9.8
5.2^)
13.5
1966
7.9(2)
9.3
13.3
8.8
11.7
11.5
15.8
10.6
10.8
10.5
7.7(D
7.7
12.3
1967
8.6(D
9.4
16.2
7.4(3)
15.9
14.1
13.5
11.8
11.8
11.8
8.6
9.1
12.2
1968
10.8
9.2
19.1
10,1
14.4
16.3
13.1
12.5
13.3
4.8(3)
1 1 9
s^11)
6.4
14.5
1969
9.2
9.3
16.8
8.l(D
12.0
14.3
11.3
14.0
12.8
3.6<3)
1 n p
I \J , O / ry \
7.40)
12.1
1970
8.9
11.2
16.3
5.9
13.3
14.7
14.4
16.9
14.0
6.4
12.7
7.9
9.0(4)
13.2
1971
9.5
11.6
16.6
9.4
13.2
12.4
17.1
14.2
12.7
8.3
g'o(i)
9.1
14.6
1972
8.2
11.6
14.0
9.5
11.9
13.4
14.6
13.5
12.5
7.5
12.9
5.7
8.4
12.4
Numbers in parentheses indicate number of months of missing data. Dashes indicate stations were not operating
or data were not reported.
Concentrations of sulfur oxides have been measured by several different
methods, e.g., conductimetric, colorimetric, coulometric, etc. To date, the
methods have not been evaluated adequately, and, therefore, the respective
measurement results may not be directly comparable. Nevertheless, for the
113
-------
o
z
MAX-HOUR AVERAGES-ALL DAYS OF YEAR
O MAX-HOUR AVERAGES - JULY, AUG., SEPT.
O &-9a.m. AVERAGES-JULY, AUG., SEPT.
10
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
YEAR
Figure 6-13. Oxides of nitrogen trends in Los Angeles, 1963-1972, 6 to 9 a.m. and maximum
one-hour average concentrations. 11
LOS ANGELES
SAN BERNARDINO
LOS ANGELES
WEST
L.A. 24.1
Figure 6-14. Distribution of oxides of nitrogen concentrations in the South Coast Air Basin. Average
of daily maximum one-hour concentrations (pphm) during July, August, and September, 1970-1972.11
-------
Figure 6-15. Distribution of nitrogen dioxide concentrations in the South Coast Air Basin. Average
of daily maximum one-hour concentrations (pphm) during July, August, and September, 1970-1972.1
Table 6-19. VARIATION OF OXIDANT AND PRECURSOR
CONCENTRATIONS WITHIN THE SOUTH COAST AIR BASIN,
JULY, AUGUST, AND SEPTEMBER, 1970-1972
Average concentration
Station
Los Angeles
Anaheim
Azusa
San Bernardino
Basinwide average
NOX,
pphm
31.3
15.0
18.2
13.8
22.3
N02,
pphm
16.2
8.0
11.8
10.4
12.1
HC,
ppm C
4.8
6.0
6.4
5.0
5.0
Ox,
ppm
11.5
9.4
23.3
18.9
14.8
purposes of this report, the data presented in this chapter are sufficiently
informative.
The most extensive body of SO- concentration data has been obtained by the
National Air Surveillance Network (NASN), a network of over 200 stations operated
cooperatively by the Federal government and local health and air pollution
agencies. The NASN data represent SCL concentrations in 24-hour integrated
samples taken in downtown or center city areas only and analyzed by the West-
Gaeke method. Data for nonurban atmospheres are very few. Tables 6-20 and
6-21 present the distributions of ambient SCL concentrations for urban and
115
-------
Table 6-20. CUMULATIVE DISTRIBUTION BY PERCENT OF ANNUAL
AVERAGE SULFUR DIOXIDE CONCENTRATIONS, URBAN SITES
Year
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
Number of
stations
33
26
33
34
45
47
98
109
97
71
Percent of concentrations
<20
yg/m3
36.4
15.3
12.2
29.4
24.5
21.3
34.7
39.5
54.6
66.2
<40
yg/m3
60.6
30.7
45.5
44.1
48.9
48.9
64.3
73.5
84.5
90.1
<60
yg/m3
69.7
49.9
57.6
64.6
62.2
68.1
76.5
86.4
91.7
98.5
<80
yg/m3
72.7
57.5
69.7
76.4
73.3
74.5
86.7
94.7
96.9
100.0
<100
yg/m3
84.8
76.7
100.0
100.0
77.7
100.0
94.8
97.4
100.0
Table 6-21. CUMULATIVE DISTRIBUTION BY PERCENT OF ANNUAL
AVERAGE SULFUR DIOXIDE CONCENTRATIONS, NONURBAN SITES
Year
1968
1969
1970
1971
Number of
stations
5
6
3
9
Percent of concentrations
-------
Table 6-22. MAXIMUM CONCENTRATIONS OF SULFUR DIOXIDE FOR VARIOUS
AVERAGING TIMES AT CAMP SITES, 1962-1968
(ppm)
City, averaging time
1962
1963
1964
1965
1966
1967
1968
Chicago, IL:
1 hour
24 hours
1 month
1 year
Cincinnati, OH:
V hour
24 hours
1 month
1 year
Denver, CO:
1 hour
24 hours
1 month
1 year
Philadelphia, PA:
1 hour
24 hours
1 month
1 year
St. Louis^ MO:
1 hour
24 hours
1 month
1 year
Washington, D. C:
1 hour
24 hours
1 month
1 year
0.86
0.36
0.18
0.10
0.46
0.11
0.04
0.03
1.03
0.35
0.13
0.09
0.38
0.18
0.10
0.05
1.69
0.71
0.33
0.14
0.48
0.11
0.06
0.03
0.85
0.46
0.12
0.06
0.48
0.25
0.11
0.05
1.12
0.79
0.35
0.18
0.57
0.18
0.06
0.84
0.43
0.15
0.09
0.73
0.26
0.08
0.06
0.62
0.22
0.09
0.04
1.14
0.55
0.27
0.13
0.56
0.15
0.06
0.03
0.36
0.06
0.03
0.02
0.94
0.36
0.13
0.08
0.96
0.19
0.06
0.05
0.35
0.20
0.08
0.05
0.98
0.48
0.27
0.09
0.42
0.14
0.05
0.03
0.26
0.05
0.02
0.01
0.72
0.35
0.12
0.09
0.84
0.18
0.06
0.04
0.45
0.25
0.10
0.04
i.n
0.65
0.32
0.12
0.38
0.07
0.03
0.02
0.17
0.02
0.01
0.77
0.33
0.15
0.10
0.55
0.21
0.05
0.03
0.37
0.15
0.07
0.86
0.51
0.27
0.12
0.38
0.08
0.03
0.02
0.24
0.05
0.03
0.01
0.88
0.36
0.16
0.08
0.68
0.16
0.05
0.03
0.41
0.18
0.10
0.04
also reflect variations in meteorology and power use. Thus, an analysis of 12
years of New York data showed that ambient S09 concentrations are inversely
42
proportional to temperature.
Sulfate data have been collected nationwide since 1957 by NASN.
Such data consisted of measurements of sulfate (sulfuric acid and soluble sul-
fates) in suspended particulate matter collected from 24-hour integrated samples.
The analytical method involves collection of aerosol from the air sample, water
extraction of collected aerosol, and analysis of .extract for sulfate by the
methylthymol blue method. Tables 6-23 and 6-24 present the urban and nonurban
distributions of annual sulfate averages. Figures 6-18 and 6-19 depict seasonal
and long-term variations in ambient sulfate. Since the only data available are
for 24-hour integrated samples, diurnal variations of sulfates are not known.
117
-------
0.18
0.15
0.00
LOCAL TIME
Figure 6-16. Diurnal patterns of sulfur dioxide concentrations (conductimetric data taken in
Washington CAMP station in 1968).
300
200
O
w
100
1964
1965
1966
1967 1968
YEAR
1969
1970
1971
Figure 6-17. Seasonal patterns of sulfur dioxide concentrations (monthly NASN data for
1964-1971).
43
A few data on ambient levels of sulfuric acid were reported by Thomas.
Using an automatic instrument (conductivity) to simultaneously measure SCL and
sulfuric acid, Thomas found sulfuric acid levels in Los Angeles and El Segundo,
California, to range from 6.4 to 50.4 yg/m , and to constitute 2.3 to 13.4 per-
cent of the S02 level.
118
-------
Table 6-23. CUMULATIVE DISTRIBUTION BY PERCENT OF ANNUAL
AVERAGE SULFATE CONCENTRATIONS, URBAN SITES
Year
1957
1958
1960
1961
1962
1963
1964
1965
1966
1967
1968
1970
Number of
stations
33
48
61
68
79
90
100
119
99
121
146
164
Percent of concentrations
<5.0
yg/mj
17
6
13
12
16
12
23
12
21
25
21
9
<10.0
vig/m3
57
54
38
32
52
54
66
50
53
60
60
53
<15.Q
ug/mj
87
77
72
72
81
81
84
78
84
87
85
84
<20.Q
yg/m3
93
98
93
91
96
96
95
97
98
97
96
95
<25.0
pg/m3
97
100
TOO
97
97
98
97
99
99
98
99
98
<30.0
yg/m3
100
100
100
100
100
100
100
100
100
100
100
100
Table 6-24. CUMULATIVE DISTRIBUTION BY PERCENT OF ANNUAL
AVERAGE SULFATE CONCENTRATIONS, NONURBAN SITES
Year
1965
1966
1967
1968
1970
Number of
stations
25
27
26
25
25
Percent, of concentrations
<5.03
pg/rn
40
48
50
48
36
00.0
ug/m3
88
96
92
88
87
<15.Q
pg/m
100
100
100
100
TOO
CONCENTRATIONS OF AEROSOLS IN URBAN ATMOSPHERES
As in the case of sulfur oxides, information on aerosol levels in urban
atmospheres is included in this report only because atmospheric aerosol formation
is related to oxidant formation in at least two respects. First, aerosol
influences the overall oxidant formation (and/or destruction) process by pro-
moting those reaction steps that occur on surfaces. Second, a part of the par-
ticulate material suspended in urban atmospheres is known to consist of products
of the same photochemical activity that results in oxidant formation.
Most data on ambient aerosol concentrations come from the National Air
Surveillance Network (NASN) and consist of total suspended particulate measure-
44 45
ments by the high-volume sampler method. ' Sizes of particles in collected
119
-------
LU
<
25
20
15
10
1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970
YEAR
Figure 6-18. Seasonal patterns of sulfate concentrations (monthly NASN data for 1957-1970).
25<
20
E
"a 15
=i
2 10
URBAN
I I
1957 1958 1959 1960 1961 T962 1963 1964 1965 1966 1967 1968 1969 1970
YEAR
Figure 6-19. Long-term pattern of sulfate concentrations (monthly NASN data for 1957-1970).
samples range from a fraction of a micrometer to 100 micrometers. The NASN
data generally relate to samples taken in the center-city commercial district.
This portion of the community will generally not show annual average concentrations
as high as those found in various industrial areas; however, they are among the
higher area concentrations in a community. Annual concentrations in nearby
suburban residential areas generally will be about one-half of those found in
center-city areas.
A summary of data for several cities is given in Table 6-25. Concentrations
of benzene-soluble organic particles are included as a measure of the organic
particulate matter in the total sample. Table 6-26 shows the relation of
population class of urban areas to particle concentration for the period 1958-1967,
while Table 6-27 shows the frequency distribution of particle concentration in
nonurban areas for the same period.
Whatever data are currently available on size distribution in suspended
particles were for the most part obtained by the NASN Cascade Impactor Network.
120
-------
Table 6-25. SUSPENDED PARTICLE CONCENTRATIONS (GEOMETRIC MEAN OF CENTER
__________ CITY STATION) IN URBAN AREAS. 1961-1965
Standard metropolitan statistical area
Chattanooga
Chicago-Gary-Hammond-East Chicago
Philadelphia
St. Louis
Canton
Pittsburgh
Indianapolis
Wilmington
Louisvil le
Youngstown
Denver
Los Angeles-Long Beach
Detroit
Baltimore
Birmingham
Kansas City
York
flew York-Jersey City-Newark-Passaic-Patterson-Clifton
Akron
Boston
Cleveland
Cincinnati
Milwaukee
Grand Rapids
Nashvil le
Syracuse
Buffalo
Reading
Dayton
Allentown-Bethlehem-Easton
Columbus
Memphis
Portland (Oreg.)
Providence
Lancaster
San Jose
Toledo
Hartford
Washington
Rochester
Utica-Rome
Houston
Dallas
Atlanta
Richmond
"Jew Haven
Wichita
Bridgeport
Flint
Fort Worth
New Orleans
Worcester
Al bany-Schenectady-Troy
Minneapolis-St. Paul
San Diego
San Francisco-Oakland
Seattle
Springfield-Holyoke
Greensboro-High Point
Miami
Total
suspended particles
ng/m
180
177
170
163
165
163
158
154
152
148
147
145.5
143
141
141
140
140
135
134
134
134
133
133
131
128
127
126
126
123
120.5
113
113
108
108
108
105
105
104
104
103
102
101
99
98
98
97
96
93
93
93
93
93
91.5
90
89
80
77
70
60
58
Rank
1
2
3
4
5
6
7
8
9
10
11
12
13
14.5
14.5
16.5
16.5
18
20
20
20
22.5
22.5
24
25
26
27.5
27.5
29
30
31.5
31.5
34
34
34
36.5
36.5
38.5
38.5
40
41
42
43
44.5
44.5
46
47
50
50
50
50
50
53
54
55
56
57
58
59
60
Benzene-sol uble
organic particles
ug/m
14.5
9.5
10.7
12.8
12.7
10.7
12.6
10.2
9.6
10.5
11.7
15.5
8.4
11.0
10.9
8.9
8.1
10.1
8.3
11.7
8.3
8.8
7.4
7.2
11.9
9.3
6.0
8.8
7.5
6.8
7.5
7.6
9.5
17.7
6.8
14.0
5.6
7.1
9.4
6.1
7.0
6.8
8.8
7.8
8.3
7.3
5.2
7.2
5.3
7.8
9.7
8.2
6.6
6.5
8.5
8.0
8.3
7.0
6.3
5.7
Rank
2
19.5
12.5
4
5
12.5
6
15
18
14
8.5
1
28
10
11
23
34
16
30.5
8.5
30.5
25
42
44.5
7
23
56
25
40.5
50
40.5
39
19.5
38
50
3
58
46
21
55
47
50
25
36.5
30.5
43
60
44.5
59
36.5
17
33
52
53
27
35
30.5
47.5
54
57
121
-------
Table 6-26. DISTRIBUTION OF SELECTED CITIES BY POPULATION CLASS
AND PARTICLE CONCENTRATION, 1957-1967
Population class
0.7-1 million
400,000-700,000
100,000-400,000
50,000-100,000
25,000-50,000
10,000-25,000
<10,000
Total urban
Number of cities with indicated 3
average particle concentration (ug/m )
<40
--
--
--
--
--
--
1
1
40
to
59
--
--
3
2
5
7
5
22
60
to
79
1
--
7
20
24
18
7
77
80
to
99
--
4
30
28
12
19
15
108
100
to
119
2
5
24
16
12
9
11
79
120
to
139
_-
6
17
12
10 -
5
2
52
140
to
159
1
O
4
1
12
6
2
2
1
31
160
to
179
i
1
3
5
1
3
2
16
180
to
199
i
__
1
2
1
2
1
--
8
>200
_-
1
3
3
--
--
7
Total
cities
in table
n
5
7
18
99
93
71
64
44
401
Total
cities
in U.S. A
0
3
7
19
100
180
--
5453a
--
--
Incorporated and unincorporated areas with population over 2500.
Table 6-27. DISTRIBUTION OF SELECTED
URBAN MONITORING SITES BY CATEGORY
OF URBAN PROXIMITY, 1957-1967
Category
Near urban3
Intermediate
Remote
Total
nonurban
Number of cities with indicated
average parti cle3
concentration (pg/tn )
<20
__
4
4
20-39
1
5
5
11
40-59
3
6
--
9
60-79
1
__
--
1
Total
5
11
9
25
Near urban-although located in unsettled areas, pollutant levels
at these stations clearly indicate influence from nearby urban
areas. All of these stations are located near the northeast
coast "population corridor."
""intermediate-distant from large urban centers, some agricultural
activity, pollutant levels suggest that some influence from
human activity is possible.
"Remote-minimum of human activity, negligible agriculture, sites
are frequently in state or national forest preserve or park
areas.
122
-------
Table 6-28 presents a summary of the 1970 data at six cities on a quarterly and
annual basis. Table 6-29 presents a summary of data on occurrence of various
46-49
chemical constituents in particles suspended in urban air.
Table 6-28. QUARTERLY AND ANNUAL SIZE DISTRIBUTION
OF PARTICULATE MATTER SUSPENDED IN AIR, 1970
City
Chicago
Cincinnati
Denver
Philadelphia
St. Louis
Washington, D.C.
Quarter
1
2
3
4
Year
1
2
3
4
Year
1
2
3
4
Year
1
2
3
4
Year
1
2
3
4
Year
1
2
3
4
Year
Number of
samples
4
6
7
4
21
1
6
7
4
18
4
5
7
5
21
2
6
7
5
20
5
5
9
3
22
5
6
6
6
23
Average
concentration,
yg/m3
97.8
82.4
98.3
63.0
86.5
61.9
77.5
88.9
48.6
74.3
51.4
51.4
59.1
80.7
59.7
60.4
50.9
66.1
56.8
58.5
81.2
73.7
76.5
44.5
73.1
53.0
55.3
73.5
41.1
56.3
Average
MMD?
ptn
2.31
0.51
0.62
0.66
0.76
0.37
0.54
0.77
1,01
0.70
0.41
0.19
0.34
1.02
0.40
0.31
0.26
0.62
0.55
0.47
0.97
0.53
0.89
1.02
0.83
0.47
0.26
0.51
0.73
0.46
Average
geometric
standard
deviation
10.41
8.16
5.88
8.00
8.18
5.71
6.47
5.15
4.32
5.49
7.99
10.22
9.50
10.65
10.50
6.02
11.21
3.91
6.34
5.65
6.61
10.33
5.69
5.34
6.80
5.98
8.80
3.95
4.11
5.22
Average mass of
parti cul ate, %
<1 urn
37
63
61
58
55
72
63
57
50
59
67
76
69
50
65
74
71
64
63
67
51
61
53
50
54
67
73
69
59
68
<2 MM
48
74
75
71
68
84
76
72
68
74
78
85
79
62
75
85
80
81
76
80
65
72
68
66
68
79
83
84
76
81
a Mass median diameter.
Particle concentrations in air have both diurnal and annual (seasonal)
cycles, which for most cities are generally predictable in shape. A city with
cold winters will experience a seasonal maximum in midwinter as a result of
increased fuel use for space heating. A daily maximum in the morning, probably
between 6 and 8 a.m., usually relates to a combination of meteorological factors
and an increase in strength of sources of particulates, including automobile
traffic.
123
-------
Table 6-29. CONCENTRATION AND SIZE OF PARTICIPATE CHEMICAL
CONSTITUENTS IN URBAN AIR43-46
Component
Fe
Pb
Zn
Cu
Ni
Mn
V
Cd
Ba
Cr
Sn
Mg
so42-
N03"
Cl
NH4+
P042~
Organic
(pentane sol . )
Concentration, ug/m3
0.6 - 1.8
0.59 - 3.2
0.1 - 1.7
0.08 - 0.4
0.04 - 0.11
0.02 - 0.17
0.06 - 0.14
0 - 0.08
0 - 0.09
0.28 - 0.31
0 - 0.09
0.42 - 7.21
1.9 - 13.1
2.96 - 11.7
2.5 - 3.54
4.0 - 9.5
0.22 - 0.31
3.2 - 17.6
HMD, a pm
2.2 - 3.57
0.25 - 1.43
0.58 - 1.79
0.87 - 2.78
0.83 - 1.67
1.34 -' 3.04
0.35 - 1.25
1.54 - 3.1
1.95 - 2.26
1.5 - 1.9
0.93 - 1.53
4.5 - 7.2
0.1 - 0.66
0.23 - 0.59
0.3 - 0.86
0.35 - 0.53
3.7 - 3.9
0.07 - 0.31
Particles
12 - 35
59 - 74
14 - 72
16-61
28 - 55
13-40
41 - 72
22 - 28
2p - 31
45 - 74
28 - 55
17 - 23
65 - 85
55 - 62
55 - 63
65 - 82
18
58 - 98
a Mass median diameter.
In cities where photochemical pollution predominates, the maximum in con-
centration of particles in the range from 0.1 to 1 micrometer may come around
noon, after the sun has had an opportunity to cause photochemical reaction.
Under these conditions, the highest concentration of particles below 0.1
micrometer will come earlier, and there may be no clear trend for larger
particles.
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i.
2.
3.
Altshuller, A.P. Non-Methane Hydrocarbon Air Quality Measurements.
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Altshuller, A.P., G.C. Ortman, and B.E. Saltzman. Continuous Monitor-
ing of Methane and Other Hydrocarbons in Urban Atmospheres. J. Air Pol-
lut. Contr. Assoc. 16_:87-9l, February 1966.
Stephens, E.R. and F. R. Burleson. Distribution of Light Hydrocarbons
in Ambient Air. University of California at Riverside, Calif. (Pre-
sented at 62nd Annual Meeting of the Air Pollution Control Association.
New York. June 22-26, 1969.)
124
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4. Neligan, R.E. Hydrocarbons in the Los Angeles Atmosphere. Arch. En-
viron. Health. S:581-591, December 1962.
5. Altshuller, A.P., S.L. Kopczynski, W.A. Lonneman, and F.D. Sutterfield.
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Environ. Sci. Technol. 4.:503-506, 1970.
6. A Study of Low Visibilities in the Los Angeles Basin, 1950-1961. Los
Angeles County Air Pollution Control District. Los Angeles, Calif. Air
Quality Report No. 53. 1964.
7. California Air Quality Data, 1968-1969. California Air Resources Board.
Sacramento, Calif.
8. 1962-1967 Summary of Monthly Means and Maximums of Pollutant Concentra-
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Networks. U.S. Department of Health, Education, and Welfare, National
Air Pollution Control Agency. Publication No. APTD 69-1. April 1969.
9. Laboratory Data, 1966-1967. Los Angeles County Air Pollution Control
District. Los Angeles, California.
10. C2-C5 Hydrocarbons in the Los Angeles Atmosphere. Environ. Sci. Tech-
nol. 2_: 1117-1120, December 1968.
11. Hydrocarbon, Oxides of Nitrogen, and Oxidant Trends in the South Coast
Air Basin, 1963-1972. California Air Resources Board. Sacramento,
Calif. 1974.
12. Tentative Method of Analysis for Nitrogen Dioxide Content of the
Atmosphere. In: Methods of Air Sampling and Analysis. American
Public Health Association. Washington, D.C. 1972. p. 329-336.
13. Nitrogen Content of the Atmosphere, Method D 1607-69. In: 1971
Annual Book of ASTM Standards. Water, Atmospheric Analysis, Part
23. Philadelphia, American Society for Testing and Materials,
1971. p. 381-386.
14. Stevens, R.K. et al. Instrumentation for the Measurement of N02-
In: Proceedings of 1973 ASTM Conference, Boulder, Colo., August
1973. American Society for Testing and Materials. Philadelphia,
Pa. 1974.
15. Stratman, H. and M. Buck. Messung von Stickstoffdioxid in der
Atmosphere. Air Water Pollut. 1£: 313-326, May 1966,
16.^ Buck M. and H. Stratmann. The Joint and Separate Determination
of Nitrogen Monoxide and Nitrogen Dioxide in the Atmosphere.
Staub. _27:11-15, June 1967.
17. Huygen, I.C. Reaction of Nitrogen Dioxide with Griess Type Rea-
gents. Anal. Chem. £2:407-409, March 1970.
18. Gill, W.E. Determination of NO and N02 in Air. Amer. Ind. Hygiene
Assoc. J. 21_(1) :87-96, February 1960.
19. Kooiker, R.H., L.M. Schuman, and Y.K. Chan. Nitrogen Dioxide
Poisoning. Arch. Environ. Health. 7_(1): 13-32, July 1963.
20. Saltzman, B.E. and A.F. Wartburg, Jr. Precision Flow Dilution
System for Standard Low Concentrations of Nitrogen Dioxide. Anal.
Chem. 3^:1261-1264, September 1965.
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21. Shaw, J.T. The Measurement of Nitrogen Dioxide in Air. Atmos.
Environ. l_(2):81-85, March 1967.
22. Scaringelli, P.P., E. Rosenberg, and K.A. Rehme. Comparison of
Permeation Devices and Nitrite Ion as Standards in the Colorimetric
Determination of Nitrogen Dioxide. Environ. Sci. Technol.
4_(ll):924-929, 1970.
23. Tentative Method for Determination of Nitrogen Dioxide in the
Atmosphere (24-Hour Sampling Method). Standardization Advisory
Committee, National Air Pollution Control Administration. Anal.
Chem. 3£: 426-428, 1958.
24. Thomas, M.D., J.A. MacLeod, R.C. Robbins, R.C. Goettelman, and
R.W. Eldridge. Automatic Apparatus for Determination of Nitric
Oxide and Nitrogen Dioxide in the Atmosphere. Anal. Chem. 28:
1810-1816, December 1956.
25. Calhoun, J.D. and C.R. Brooks. A Solid Oxidant for Oxides of
Nitrogen Analyzer. California State Department of Public Health,
Berkeley, Calif. (Presented at Seventh Conference on Methods in
Air Pollution. Los Angeles. January 1965.)
26. Ripley, D.L., J.M. Clingenpeel, and R.W. llurn. Continuous
Determination of Nitrogen Oxides in Air and Exhaust Gases. Air
Water Pollut. 8^:455-463, 1964.
27. Wilson, D. and S.L. Kopczynski. Laboratory Experiences in
Analysis of Nitric Oxide with "Dichromate" Paper. J. Air Pollut.
Contr. Assoc. 1_8:160-161, March 1968.
28. Jones, E.E., L.E. Pierce, and P.K. Mueller. Evaluation of a Solid
Oxidant System. Jacksonville University, Jacksonville, Fla.
(Presented at Seventh Conference on Methods in Air Pollution
Studies. Los Angeles. January 25, 1965.)
29. Hartkamp, 11.V. Untersuchunger uebcr die Oxydation und die
Messung von Stickstoffmonoxide in Kleinen Konzentrationen [Inves-
tigation of Oxidation and Measurement of Nitric Oxide in Low Con-
centrations]. Schriftreihe der Landesanstalt fuer Immissions
und Bodennutzungsschuts des Landes Nordrhein-Westfalen. Essen,
West Germany. Number 18, p. 55-74, 1970.
30. Forwerg, W. and H.J. Crecelius. Zur Bestimmung des Stickstoff-
monoxides in atmosphaerischer Luft [Determination of Nitric Oxide
in Atmospheric Air]. Staub. 28^:514-516, 1968.
31. Mueller, P.K. and Y. Tokiwa. Series vs. Parallel Continuous
Analysis for NO, N02, and NOX. California State Department of
Public Health, Berkeley, Calif. (Presented at Eighth Converence on
Methods in Air Pollution and Industrial Hygiene Studies. Oakland,
Calif. February 1967.)
32. Mueller, P.K., et al. Series vs. Parallel Continuous Analysis
for NO, N02 and NOX; II, Laboratory Data. California State
Department of Public Health, Berkeley, Calif. (Presented at
Ninth Conference on Methods in Air Pollution and Industrial
Hygiene Studies. Pasadena, Calif. 1968.)
33. Levaggi, D.A., W. Siu., M. Feldstein., and E. Kothny. Quantita-
tive Separation of Nitric Oxide from Nitrogen Dioxide at Atmos-
pheric Concentration Ranges. Environ. Sci. Technol. 6^:250-252,
March 1972.
126
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34. O'Keeffe, A.E. and G.C. Ortman. Primary Standards for Trace
Gas Analysis. Anal. Chem. 38_: 760-763, 1966.
35. Fontijn, A., A.J. Sabadell, and R.J. Ronco. Homogeneous Chem-
ilumenescent Measurement of Nitric Oxide with Ozone. Anal. Chem,
£2:575-579, May 1970.
36. Guicherit, R. Indirect Determination of Nitrogen Oxides by a
Chemiluminescence Technique. Atmos. Environ. 6_:807-814, 1972.
37. Stevens, R.K., P.E. Paules, and R.J. Bambeck. Field Performance
Characteristics of Advanced Monitors for NOX, 03, S02, CO, CH4, and
Non-methane HC. Environmental Data Corp. of Monsovia, Calif. (Paper
No. 72-71. Presented at Air Pollution Control Association Meeting,
Miami, Fla., June 1972.)
38. CAMP Data. National Aerornetric Data Bank. U.S. Environmental
Protection Agency, Research Triangle Park, N.C.
39. Comprehensive Technical Report on All Atmospheric Contaminants
Associated with Photochemical Air Pollution. System Development
Corporation, Santa Monica, Calif. Report No. TM-(L)-4411/002/01.
June 1970.
40. The Automobile and Air Pollution: A Program for Progress, Part
II. U.S. Department of Commerce. Washington, D.C. December
1967.
41. Wilson, W.E., A. Levy, and D.B. Wimmer. The Effect of S02 on
Formation of Oxidant. J. Air Pollut. Contr. Assoc. 22:311,
1972.
42. Blade, E. and E. Ferrand. Sulfur Dioxide Air Pollution in New
York City: Statistical Analysis of Twelve Years. J. Air Pollut.
Contr. Assoc. 1_9:873, 1969.
43. Thomas, M.D. Sulfur Dioxide, Sulfuric Acid Aerosol, and Visi-
bility in Los Angeles. J. Air Water Pollut. 6^:443, 1962.
44. Air Quality Data, 1964-1965. U.S. Department of Health, Educa-
tion, and Welfare, Division of Air Pollution. Cincinnati, Ohio.
1966. p. 1-2.
45. Air Pollution Measurement of the National Air Sampling Network,
1957-1961. U.S. Department of Health, Education, and Welfare,
Division of Air Pollution. Cincinnati, Ohio. 1962. p.6-8.
46. Deposition and Retention Models for Internal Dosimetry of the
Human Respiratory Tract. Task Group on Lung Dynamics for Com-
mittee II of the International Radiological Protection Commis-
sion, Chairman, P.E. Morrow. Health Physics. 1_2:173-207, 1966.
47. Cadle, R.D. Particle Size. New York, Reinhold, 1965. 390 p.
48. Drinker, P. and T.F. Hatch. Industrial Dust, Hygenic Signifi-
cance, Measurement and Control (2nd Ed.). New York, McGraw-
Hill, 1954. 401 p.
49. Washington, D.C. Metropolitan Area Air Pollution Abatement
Activity. U.S. Department of Health, Education, and Welfare,
National Center for Air Pollution Control. Cincinnati, Ohio.
1967.
127
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CHAPTER 7. EMISSIONS OF OXIDANT PRECURSORS
INTRODUCTION
Hydrocarbons and nitrogen oxides are emitted to the atmosphere from both
natural and man-made sources, the natural contribution being the major one.
Natural hydrocarbon emissions arise mostly from biological processes, from trees,
and from localized sources such as geothermal areas, petroleum and natural gas
fields, coal fields, and natural forest fires. Worldwide emission rates for natural
methane and for volatile terpenes and isoprene, for which measurements have been
made, have been estimated to be 3 x 10^ tons per year and 4.4 x 108 tons per year,
respectively. Natural sources of nitrogen oxides are mostly biological processes,
and worldwide emissions are approximately 5 x 10^ tons per year.
Of the anthropogenic sources, combustion of fuels is by far the most important
source of hydrocarbon and nitrogen oxide emissions. Additionally, hydrocarbon and
nonhydrocarbon organic emissions also arise from the use of such organics as process
raw materials.
From a pollution control standpoint, the distinction made between natural and
man-made sources and the use of annual emission rates are not entirely satisfactory.
Thus, anthropogenic emissions such as from leaking fuel lines, home appliances,
etc., cannot be subjected to systematic control because of their "accidental"
nature; therefore, from a control standpoint, such emissions are considered to be
"natural." To generalize, classification of sources and emissions into "control-
lable" and "uncontrollable" may be more appropriate than the distinction now in use.
Also, emission rate data reflecting annual or even daily averages are inadequate in
that they mask diurnal variations in emission rate. Considering that only the
morning to noon emissions are of main photochemical consequence, it is evident that
ignoring the diurnal variation in emission rate does not permit equitable assessment
of the various emission sources.
The comments made in the preceding paragraph are merely discussion points.
The following sections in this report deal with the anthropogenic emissions only,
and the emission rate data are presented as they are available, that is, mostly
daily and yearly averages.
NATIONWIDE EMISSIONS.
Hydrocarbons
Hydrocarbon emission sources generally are treated in terms of mobile and
stationary sources because of the differing control strategies required for each in
terms of engineering, technological, economic, and legal factors that must be taken
129
-------
into account. Total nationwide emissions of hydrocarbons and related organic com'
pounds for the year 1968 are estimated to be 32 x 106 tons. Table 7-1 shows the
distribution of this total by major source categories, including percent of relative
contribution. Motor vehicles (49 percent), industrial processes (14 percent), and
solvent usage (10 percent) constitute by far the most significant sources. Accord-
ing to Mason et al., who reported similar information for the year 1966, approximately
63 percent of the total hydrocarbon emission arises from urban areas.
Table 7-1. ESTIMATES OF NATIONWIDE HYDROCARBON EMISSIONS
BY SOURCE CATEGORY, 19681'3
Source
Transportation
Motor vehicles
Gasol ine
Diesel
Aircraft
Railroads
Vessels
Nonhighway use, motor fuels
Fuel combustionstationary
Coal
Fuel oil
Natural gas
Wood
Industrial processes
Solid waste disposal
Miscellaneous
Forest fires
Structural fires
Coal refuse
Organic solvent evaporation
Gasoline marketing
Agricultural burning
Total
Emissions
106 tons/yr
16.6
0.7
4.6
1.6
8.5
32.0
15.6
0.3
0.3
0.1
0.3
0.2
0.1
-b
0.4
2.2
0.1
0.2
3.1
1.2
1.7
15.2
0.4
Percent of total
emissions
51.9
2.2
14.4
5.0
26.5
100.0
48.7
1.0
1.0
0.2
1.0
0.7
0.3
__b
1.2
6.9
0.2
0.6
9.7
3.8
5.3
47.5
1.2
aThese emission estimates are subject to revision as more refined information
becomes available.
Negligible.
Hydrocarbon emission estimates have been made for 22 major metropolitan areas
in the United States.1 Table 7-2 shows this information for each of the available
areas. Perhaps of greater significance are the data given in Table 7-3, compiled
from the study by Mason et al.2 The most significant finding was that while trans-
portation sources accounted for a higher proportion of total hydrocarbon emissions
in these metropolitan areas than in the nation as a whole, the range was extremely
wide: 37 to 99 percent.
130
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Table 7-2. SUMMARY OF HYDROCARBON EMISSIONS FROM
22 METROPOLITAN AREAS IN THE UNITED STATES,
1967-19681
Location3
Los Angeles
Philadelphia
San Francisco
Detroit
Washington, D.C.
Boston
Pittsburgh
St. Louis
Hartford
Dallas
Seattle
Houston
Milwaukee
Cincinnati
Buffalo
Kansas City
Providence
Indianapolis
San Antonio
Dayton
Louisville
Birmingham
Population
7,100,000
5,500,000
4,500,000
4,090,000
2,700,000
2,700,000
2,520,000
2,410,000
2,290,000
2,187,000
2,010,000
2,000,000
1,730,000
1,660,000
1,300,000
1,230,000
1,200,000
1,050,000
982,000
880,000
840,000
750,000
Area,
mi 2
41,000
4,590
7,000
2,680
2,270
1,280
3,050
4,500
2,650
8,000
15,000
7,800
2,630
2,620
1,470
3,200
1,000
3,080
7,320
2,310
1,390
1,120
Emissions,
103 tons/yr
1,270
470
790
480
310
87
95
330
120
143
170
292
83
55
130
230
54
74
71
64
46
64
Defined on the basis of Standard Metropolitan Statis-
tical Areas; these may include substantial areas that
are rural in nature and thus of low population density.
Table 7-3. PERCENT OF TOTAL AREA HYDROCARBON
EMISSIONS BY SOURCE CATEGORY,
22 METROPOLITAN AREAS IN UNITED STATES, 19662
Source category
Transportation
Motor vehicles
Fuel combustion
Power plants
Industrial
Domestic
Process losses
Refuse disposal
Percent of total area emissions
Average
70.2
66.9
2.8
0.1
2.2
0.5
19.9
7.1
Range
37-99a
0-18
1-63
0.4-26
More recent estimates indicate that the maximum
percent of total area hydrocarbon emissions in the
transportation category is somewhat less than 99.
131
-------
Nitrogen Oxides
The distribution of nitrogen oxide (NOX) emissions by major source categories
is indicated in Table 7-4.3 Fuel combustion is the major cause of technology-
associated emissions. In 1968 coal, oil, natural gas, and motor-vehicle fuel com-
bustion accounted for over 18 of an estimated 20.6 million tons of man-made NOX in
the United States. Of the 10 million tons generated by stationary combustion sour-
ces, power plans emitted 4 million tons; industries, 4.8 million tons; and home and
office heating plants, the remaining 1.2 million tons. Natural-gas-burning sources
made the largest contribution of any fuel in the stationary source group. An esti-
mated 8 million tons was emitted from transportation sources, 7 million tons of
which was from motor vehicles. Industrial processes, solid waste disposal, and
other miscellaneous sources accounted for about 2.5 million tons of NOX.
Table 7-4. ESTIMATES OF NATIONWIDE NITROGEN OXIDE
EMISSIONS BY SOURCE CATEGORY, 19683
Emissions
Source category
Transportation
Motor vehicles
Gasoline
Diesel
Ai rcraf ta
Railroads
Vessels
Nonhighway
Fuel combustion in
stationary sources
Coal
Fuel oil
Natural gasc
Wood
Industrial
Solid waste disposal
Miscellaneous
Forest fires
Structural fires
Coal refuse
Agricultural
Total
106 tons/year
8.1
10.0
0.2
0.6
1.7
20.6
7.2
Nb
0.4
0.2
0.3
4.0
1.0
4.8
0.2
1.2
N
0.2
0.3
6.6
0.6
Percent of total emissions
39.3
48.5
1.0
2.9
8.3
10Q.O
34.9
N
1.9
1.0
1.5
19.4
4.8
23.3
1.0
5.8
N
1.0
1.5
32.0
2.9
Emissions below 3000 feet.
N-not reported. Estimated less than 0.05 x 106 tons/year.
°Includes LPG and kerosene.
Relatively small quantities of NOX are emitted from noncombustion industrial
processes, mainly the manufacturing and use of nitric acid.1* Even though total
132
-------
quantities may be small, high concentrations of NOX can be emitted from some of
these chemical processes. Electroplating, engraving, welding, metal cleaning, and
explosive detonation can also be responsible for industrial NOX emissions. The
same is true with regard to the manufacture and use of liquid-NC^-based rocket
propellants.
NOX emissions from 22 cities are summarized by source category in Table 7-5.
Table 7-5. PERCENT OF TOTAL AREA NITROGEN OXIDE EMISSIONS
BY SOURCE CATEGORY, 22 METROPOLITAN AREAS IN THE UNITED STATES, 19662
Source category
Transportation
Motor vehicles
Other
Fuel combustion in
stationary sources
Power plants
Industrial
Domestic
Process losses
Refuse disposal
Percent of total area emissions
Average
42.6
36.3
6.3
50.7
23.0
23.8
3.9
5.2
1.5
Range
23-74
10-79
1-21
0.1-5.8
Over 50 percent of the total NOX emissions occur in highly populated areas; 60
percent of stationary source emissions and 45 percent of motor-vehicle emissions
'occur in urban areas.^
SOUTH COAST AIR BASIN EMISSIONS
Detailed emission inventory data are available for the Los Angeles, California,
air basin. The estimated average emission of contaminants into the atmosphere of
the South Coast Air Basin is shown in Table 7-6. Total emissions in 1970 were 16,640
tons per day, including 3200 tons of organic gases, 235 tons of particulates, 1570
tons of nitrogen oxides, 315 tons of sulfur dioxide, and 11,300 tons of carbon
monoxide.
A comparison of the emissions derived from stationary and mobile sources is
shown in Table 7-7 and in Figure 7-1. The stationary sources were responsible for
over 80 percent of the sulfur dioxide and more than 50 percent of all particulate
emitted. Mobile sources emitted 71 percent of the organic gases and 77 percent of
the nitrogen oxides.
133
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Table 7-6. SOUTH COAST AIR BASIN, AVERAGE EMISSIONS OF CONTAMINANTS
INTO THE ATMOSPHERE, 1970^
(tons per day)
Emission source
Stationary
Petroleum
Production
Refining
Marketing
Subtotal
Organic solvent users
Surface coating
Dry cleaning
Degreasing
Other
Subtotal
Chemical
Metallurgical
Mineral
Incineration
Open burning (dumps)
Open burning (backyard)
Incinerators
Other
Subtotal
Combustion of fuels
Steam power plants
Other industrial
Domestic and commerical
Subtotal
Agri cul ture
Debris burning
Orchard heaters
Agricultural product processing plants
Subtotal
Total, stationary sources
Mobile
Motor vehicles
Gasoline powered
Exhaust
Blowby
Evaporation
Diesel powered
Subtotal
Ai rcraft
Jet driven
Piston driven
Subtotal
Ships and railroads
Total , mobi le sources
Grand total
Organic gases by
reactivity
High
,
5.0
68.1
73.1
49.2
6.1
22.6
32.9
110
Low
114
40.0
79.5
234
201
26.1
82.6
140
450
Total
114
45.0
148
307
250
32.2
105
173
560
: i.o i.o
Parti-
culate
matter
0.4
5.0
5.4
15.0
6.0
21.0
0.5
21.3
26.5
i 1 |
0.2 2.0 2.2
1.2 13.0 14.2
1.2 1.2
0.5 4.3 4.8
1.9 20.5 22.4
0.2
0.1
0.2
0.5
0.9
6.8
6.7
0.2
13.7
7.1
5.0
8.9 0.5
9.8 12.6
195 732
1200
51.3
306
1560
21.7
11.3
33.0
1590
1790
401
16.9
154
51.7
7.0
6.8
0.4
14.2
8.0
5.0
9.4
22.4
927
1600
68.2
460
51.7
623 2180
36.6
16.3
52.9
5.4
681
1410
58.3
27.6
85.9
5.4
2270
3200
0.7
4.7
1.2
10.2
T6.8
7.8
9.8
9.8
27.4
4.6
3.8
0.9
9.3
128
62.4
16.8
79.2
23.8
0.2
24.0
3.6
107
235
Oxides of
nitrogen
27.9
22.0
11.0
60.9
0.2
3.0
5.5
0.3
2.3
1.2
2.4
6.2
135
88.8
60.1
284
0.5
0.5
360
951
229
1180
13.1
7.3
20.4
6.2
1210
1570
Sulfur
dioxide
5.5
50.0
55.5
1.0
1.0
115.0
32.9
0.8
0.1
0.2
0.3
40.9
9.5
0.6
51.0
1.6
1.6
258
34.9
16.8
51.7
3.0
1.0
4.0
1.1
'56.9
315
Carbon
monoxide
5.0
5.0
3.0
4.0
34.4
1.3
30.0
69.7
1.1 -
0.4
1.5
24.1
24.1
103
10,800
218
11,000
44.1
155
199
9.2
11,200
11,300
134
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Table 7-7. SOUTH COAST AIR BASIN, COMPARISON OF STATIONARY
AND MOBILE SOURCES, 19705
(tons per day)
Source
Stationary
Mobile
Total
Stationary
Mobile
Total
organic
gases
927
2,270
3,200
29%
71%
Parti cu late
matter
128
107
235
54%
46%
Nitrogen
oxides
360
1,210
1,570
23%
77%
Sulfur
dioxide
258
56.9
315
82%
18%
Carbon
monoxide
103
11,200
11,300
1%
99%
Total
emissions
1,780
14,800
16,600
11%
89%
ORGANIC GASES
3200 tons/day
THER
PETROLEUM
INDUSTRY
ORGANIC SOLVENT
USERS
NITROGEN OXIDES
1570 tons/day
ITHER
COMBUSTION
OF FUELS
CARBON MONOXIDE
11300 tons/day
Figure 7-1. Percentage of emissions from major sources in the South Coast Air Basin,1970.5
Emissions trends in the United States are illustrated by those developed for
the South Coast Air Basin. Tables 7-8 and 7-9 show such trends using emission data
for 1960, 1965, 1970, and projected emissions for 1975 and 1980 also.
135
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Table 7-8. SOUTH COAST AIR BASIN, HYDROCARBON AND
NITROGEN OXIDE EMISSION RATES, 1960-19705'3
Source
Combustion
Mobile
Air transport
Road transport
Railways and
navigation
Stationary
Power stations
Industrial combustion
Domestic and commer-
cial heating
Waste incineration
Industrial
Petroleum refining0
Chemical
Mineral
Metal urgical
Miscellaneous
Forest fires and
open burning
Surface coating,
painting, etc.
Service stations
Dry cleaning
Organic uses
Emission rate, tons/day
Hydrocarbons
1960
19
2853
--
1
V20
J
~J
321
50
--
310
__d
35
206
1965
40
2410
1
")
(20
\
--
283
80
--
411
__d
40
256
1970b
86(33)
2180(1560)
5(0)
7(0.2)
7(0.1)
0.4(0.2)
1(0)
159(5)
--
HO)
--
250(49)
148(68)
32(6)
173(33)
Oxides of nitrogen
1960
8
830
--
255
5
,6
1
5
J
--
--
1965
16
697
1
1
V425
\
J 1
60
1
13
3
--
--
--
--
1970
20
1180
6
135
89
60
1
f1
1
9
\
6
--
--
aThe emission inventory on which this table is based^ indicates the amount
of fuel or the scale of operation for the sources listed.
Numbers in parentheses indicate rates of "reactive" emission.
clncluding evaporation losses in storage.
Included in "Petroleum refining" emissions.
Table 7-9. SOUTH COAST AIR BASIN, PROJECTED HYDROCARBON
AND NITROGEN OXIDE EMISSION RATES, 1975-19805
Emission rate, tons/day
Pollutant and
source
Hydrocarbons
Mobile
Stationary
Oxides of nitrogen
Mobile
Stationary
1975
Uncontrolled13
1690
210
1290
385
Controlled0
335
140
535
357
1980a
Uncontrolled^
1850
225
1410
420
Controlled0
200
149
320
392
Projected 1980 hydrocarbon emission data are for "reactive" organic emissions,
Assuming that no new abatement technology is applied.
"Assuming that appropriate abatement technology is applied.
136
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REFERENCES FOR CHAPTER 7
1. National Air Pollution Control Administration, Reference Book of Nationwide
Emissions. U.S. Department of Health, Education, and Welfare, National Air
Pollution Control Administration. Durham, N.C.
2. Mason, D.V., G. Ozolins, and C.B. Morita. Sources and Air Pollutant Emission
Patterns in Major Metropolitan Areas. (Presented at the 62nd Annual Meeting
of the Air Pollution Control Association. New York. June 22-26, 1969.
Paper 69-101.)
3. Nationwide Inventory of Air Pollutant Emissions, 1968. U.S. Department of
Health, Education, and Welfare, National Air Pollution Control Administration.
Raleigh, N.C. Publication No. AP-73. August 1970. p. 14-16,
4, Atmospheric Emissions from Nitric Acid Manufacturing Processes. Manufacturing
Chemists' Association and U.S. Department of Health, Education, and Welfare.
Cincinnati, Ohio. Public Health Service Publication No. 99-AP-27. 1966.
5. California Emission Inventory, 1970. California Air Resources Board,
Sacramento, California. July 1972.
137
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CHAPTER 8
RELATIONSHIPS BETWEEN AIR QUALITY AND EMISSIONS
INTRODUCTION
Air pollution legislation in the United States requires that numerical standards
for ambient air quality be set and that, for achievement of these standards, appropriate
emission control strategies be developed and implemented. Development of such control
strategies, in turn, requires that the air quality be numerically defined as a function
of emission rate. In the case of primary pollutants, e.g., carbon monoxide, the
relationship between ambient concentration of pollutant and respective emission rate
is controlled solely by the pollutant dispersion process. In the case of secondary
pollutants such as the photochemical oxidants, the oxidant concentration-emission
rate relationships are controlled not only by the dispersion of the hydrocarbon and
nitrogen oxide emissions, but also by the atmospheric reactions of these oxidant
precursors to produce oxidant.
In either case, the process of translating emission rates into air quality levels
is an extremely complex one and cannot be quantified easily; that is, absolute levels
of air quality cannot be calculated simply from emission rate, meteorology, and reac-
tion rate data. This problem makes it extremely difficult to evaluate the degree
of degradation of air quality caused in a source-free area as a result of initiation
of human activity. However, most control practices to date have dealt with situations
in urban areas, where specific interest has been in the degree of air quality improve-
ment or degradation associated with application of a control measure or with expansion
of human activity. In such control practices, fortunately, the problem is simplified
to that of relating changes in air quality to changes in emission rate.
Relating changes in air quality to changes in emission rates for the purpose
of developing numerical control strategies requires use of a model, that is, a premise
that describes the physical and/or chemical mechanisms by which emissions affect
air quality. Several types of models of varying complexity and inherent accuracy
have been conceived and considered. Such models and their application in development
of control strategies are discussed next.
ROLLBACK MODELS
A simple and intuitively obvious air pollution model is the one commonly referred
to as "simple rollback."1 This model assumes that the concentration of any stable
pollutant in the air above an area is equal to the-background concentration of that
pollutant plus a fraction of the total emission rate of that pollutant in the area.
Mathematically, the simple rollback model is described by Equation 8-1:
139
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Ci = B + ke (8-1)
where: C^ = ambient concentration of a specific pollutant at the i1 point
B = background concentration of pollutant at the i point
k = proportionality factor depending on meteorology, location of
sources relative to i point, and the other factors that influence
the source-receptor interaction at the i point
e = total emission rate from all sources in area.
Because of the difficulties in obtaining numerical values for k, Equation 8-1 was
modified to relate changes in air quality (C±~) to changes in emission rate (e) .
Such modification led to Equation 8-2:
(GF) (PAQ)-(DAQ) + (B)[1-(GF)]
(GF) [(PAQ)-(B)]
where: R = degree of emission rate reduction required in order to change
air quality from the (PAQ) to the (DAQ) level
(GF) = growth factor, signifying the maximum potential for increase of
emitter density
(PAQ) = present air quality, taken to be equal to the maximum observed
level of the pollutant of concern in the atmosphere
(DAQ) = desired air quality, that is, the air quality standard
(B) = background level of pollutant, not subject to growth or control
Equation 8-2 appeared too complex, so it was simplified by setting (B) [l-(GF) ]=0
and (GF) [(PAQ)-(B)]=(GF) (PAQ)-(B), resulting in Equation 8-3, which has been used
in the United States to calculate control requirements.
R = (GF) (PAQ) - (DAQ)
(GF) (PAQ) - (B) (8-3)
Application of this formula is straightforward in the cases of primary pollutants.
In the cases of a secondary pollutant such as ozone, reduction of ambient ozone levels
obviously can be achieved only through control of the ozone precursors. It is also
obvious that in order to calculate such control needs, it is necessary that (PAQ),
(B) , and (DAQ) of Equation 8-3 be known for the ozone precursors rather than for
ozone. Of these, (B) and (PAQ) can be obtained through direct measurement of the
background and total levels of ozone precursors. The "desired" level, however, of
the ozone precursors (DAQ), that is, the precursor level corresponding to the air
quality standard for ozone, obviously, is not measurable. Knowledge of the (DAQ)
value requires that the dependence of ozone on its precursors be known quantitatively.
Such dependence has been estimated, although not unequivocally; it was derived through
analysis of atmospheric data as was discussed in Chapter 3. Specifically, it was
found that for the oxidant concentration to be below 0.1 part per million (ppm) , the
nonmethane hydrocarbon concentration must be below 0.3 ppm carbon no single numerical
value could be justified. By extending this conclusion, it follows that for the
140
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oxidant to be below the standard of 0.08 ppm, the nonmethane hydrocarbon concentration
must be below 0.24 ppm C. This last value has been used as the value for (DAQ) in
Equation 8-3 to compute hydrocarbon control requirements for achievement of the oxidant
standard.
The method outlined in the preceding paragraphs is the result of a first effort
to relate air quality to emissions. As such, it has inadequacies, some of which
were unavoidable because they represented the least damaging alternative among those
available, and others that were merely uncertainties resulting from lack of specific
backup evidence. On the basis of the comments and criticism voiced thus far, it
appears that the most controversial parts of this early method are the method's "simple
rollback" model and the technique for translating air quality in terms of ozone into
air quality in terms of ozone precursors. For this reason, these two points of the
method are examined critically.
The simple rollback model's premise that the concentration of man-made contaminants
in air is proportional to the rate at which these contaminants are emitted in the
air (Equation 8-1) is a rational one. Further, application of this model requires
relatively little input data. For example, using this model, a usable relationship
between air quality and emissions can be obtained without need for meteorological
data. This combination of rationality and simplicity is what precipitated the choice
of this model for use in the first efforts to relate air quality to emissions.
One inadequacy of the simple rollback model is that the model's validity cannot
be verified experimentally. Such verification would require uniform reduction of
emissions from all types of sources in a region--a situation that almost never occurs.
Also, the model is questionable in the cases of those pollutants that are consumed
or produced as a result of atmospheric reactions; in such cases, Equation 8-1 cannot
be valid unless these reactions are of first order with respect to the pollutant.
Application of this model also requires that we know the maximum concentration
that each pollutant can attain presently, since this maximum concentration is taken
to be the measure of the air quality level (PAQ) corresponding to the present emission
rate. Further, it is assumed that this maximum concentration is equal to the maximum
observed concentration--an assumption that may not be sound since there may not be
an air quality measuring station at the point of the highest pollutant concentration.
Finally, the simple rollback model is of limited usefulness because it treats
the total of emission sources in a region as a single emitter. Thus, the model cannot
predict the individual effects on air quality of emitters of different types (e.g.,
mobile and stationary). This limitation becomes evident in the cases where technologi-
cal considerations dictate that control requirements be defined separately for different
emitter types.
141
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OTHER MODELS AND METHODS
The limitations of the simple rollback model and its applications have pushed
air pollution workers to devise and use other models that were either simplified
or extended versions of the simple rollback. Some of these models are mentioned
briefly.
The "proportional model" is similar to the simple rollback except that it assumes
additionally that the oxidant concentration in an area is directly proportional to
the reactive hydrocarbon emission rate in that area. Thus, by this model, the hydrocarbon
concentration does not necessarily need to be reduced down to 0.24 ppm C in order
to ensure achievement of the oxidant standard; rather, the reactive hydrocarbon concen-
tration needs to be reduced to a degree equal to the degree of oxidant reduction
needed in order to achieve the oxidant standard.
The "variable source rollback" model is an extension of the simple rollback
and is described by Equation 8-4:
Ci = B + k.. Y ci (8-4)
1 ij *-> 3 ^ J
where j designates the type of emission source, and k.. is assumed to be the same
for all source types. This model distinguishes the various types of emission sources
and their contributions to C., and permits calculation of control requirements separately
for each source type.
Under circumstances such that the k.. cannot be assumed to be the same for all
source types, Equation 8-4 becomes Equation 8-5:
Ci = B + 5"" k. . e. (8-5)
1 <-> ij j ^
and describes a model which, in principle, is more accuratebut also more complex--
than the model described by Equation 8-4.
These more advanced air pollution models can make more detailed predictions than the
simple rollback, which makes it possible to test their assumptions against experimental
data. Thus, they allow one to predict the spatial distribution of various concentra-
tions of pollutants on a given day, or for some long time period, which is not possible
by simple rollback. These computed distributions can then be compared with measured
air quality, and the models modified to obtain superior agreement. In addition,
they can make short-term predictions for specific meteorological conditions, which
can be compared with observed values. Because these more advanced models have this
testing potential, they are being widely studied and tested. However, they also
require vast data inputs of emission rates, traffic patterns, local meteorology,
and topography. These requirements, thus far, have prohibited use of these models
with advantage over the simpler rollback models.
The technique for translating air quality in terms of oxidant into air quality
in terms of oxidant precursors also has problems. This technique is based on the
142
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use of the oxidant-hydrocarbon relationship (Figure 3-5) derived from aerometric
data and, as discussed in Chapter 3, this relationship suffers from serious uncertaint
ties. Thus, it is questionable whether the value 0.24 ppm C is an appropriate one
to use for (DAQ) in Equation 8-3. It has been suggested that the oxidant-hydrocarbon
relationship and a hydrocarbon standard consistent with the oxidant standard be derived
from smog-chamber data (see Chapter 3). In view of the limitations of the aerometric
data, the smog chamber method, despite its own shortcomings, is now being given serious
consideration.
CALCULATION OF CONTROL REQUIREMENTS
The 1970 Amendments of the Clean Air Act directed the U.S. Environmental Protection
Agency (EPA) to conduct a national program of research, regulation, and enforcement
activities directed to prevent and control air pollution. The program includes genera-
tion of scientific evidence that could be used by the Federal and state governments
as basis for development of emission control regulations. In pursuing these objectives,
EPA developed techniques for estimating emission control requirements for achievement
of the national air quality standard for oxidants. Specifically, EPA developed techni-
ques for deriving numerical standards for motor vehicle emissions-'- and for calculating
regional requirements for hydrocarbon emission control.2
The simplest method for deriving numerical emission standards is the one based
on use of the rollback model, and more specifically, on Equation 8-3. Use of this
equation requires that (1) a year be specified as the reference or "present" year,
(2) a "target" year be specified, that is, the future year in which the air quality
standard is expected to be achieved, and (3) numerical values be provided for (PAQ),
(DAQ), (GF), (B), and emission rate for the reference year. The factor (PAQ) designates
the highest pollutant concentration observed during the reference year. The growth
factor (GF) is defined so that the product (GF) (PAQ) represents the highest pollutant
concentration that would be expected to occur in the target year if no controls were
to be applied.
To illustrate these calculations, Equation 8-3 is used to derive a numerical
hydrocarbon emission standard for 1975 model year automobiles. For the purpose of
comparing such a standard with the one legislated by the U.S. Congress, the same
reference year will be used in these calculations as used by the Congress, i.e.,
1970. Since 10 years are needed after 1975 to phase out the uncontrolled autos,
it follows that the target year should be 1985. Numerical values for the various
entries in Equation 8-3 are as follows.
By one estimate, the growth factor (GF) for the period 1970-1985 is 1.76. This
value was based on a noncompounded growth rate of automobile population of 5.1 percent
per year. The (PAQ), that is, the highest concentration of nonmethane hydrocarbon
observed during 1970, is somewhat uncertain. It almost certainly occurred in the Los
Angeles air basin; however, most of the Los Angeles data available are for total rather
143
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than nonmethane hydrocarbons. Based mainly on measurements conducted by EPA in Los
Angeles, the highest nonmethane hydrocarbon concentration during 1970 is estimated to
be 8 ppm C. The background nonmethane hydrocarbon concentration is taken to be 0.1
ppm C. Finally, the (DAQ), that is, the air quality standard for nonmethane hydrocar-
bon, has been determined by EPA to be 0.24 ppm C (see Chapter 3).
Using these numerical values, the degree of hydrocarbon emission control required
is calculated, using Equation 8-3, to be 99 percent. This indicates need for much
more drastic control of hydrocarbon emissions than the 90 percent control legislated by
Congress. It must be stressed, however, that the above calculations provide only first
estimates and, in some respects, they are almost certain to be inaccurate. Some open
questions regarding these calculations are as follows.
The value used for the growth factor is at issue for a number of reasons. First,
use of noncompounded rather than compounded growth data is probably incorrect. Second,
it is questionable whether growth in terms of increase of automobile population affects
the maximum hydrocarbon concentration as much as it has been assumed in the preceding
calculations. It is logical that the center points of a city, where the maximum hydro-
carbon concentration is likely to occur, would eventually get saturated with traffic
and that further growth would raise pollutant levels in the suburbs rather than in the
downtown areas. Finally, growth in the suburbs cannot be entirely without consequence.
One may expect, for example, that suburbs located upwind from the center of the city may
contribute to the pollutant buildup occurring in the downtown areas. All these effects
point to a true (GF) value that lies somewhere between 1.0 and an upper limit value
somewhat higher than 1.76.
The (PAQ) value used is also uncertain. This value is intended to represent the
highest concentration in Los Angeles in 1970, and it is questionable whether the data
available include this concentration. The data were limited to those taken during
1970, and were available only for the smog season of that year. Because of these
limitations and because there is some uncertainty whether the sampling sites are
properly situated, the (PAQ) value (0.8 ppm C) may be somewhat inaccurate.
The (B) value (0.1 ppm C) may be erroneously low. Background or uncontrollable
levels of nonmethane hydrocarbons in Los Angeles may be as high as 0.6 ppm C--in which
case no control could ever achieve the 0.24-ppm C standard.
Finally, the (DAQ) value (0.24 ppm C) is also subject to uncertainties as discussed
in Chapter 3. For example, if emission control will result in considerably higher
nitrogen oxide to hydrocarbon ratios in the future, as it is now expected, then a
higher nonmethane hydrocarbon concentration (e.g., 0.5 ppm C) may still be sufficiently
low to ensure achievement of the oxidant standard.
For the purpose of illustrating the effects of all these uncertainties on the
calculated control requirements, such requirements were calculated using different
144
-------
sets of numerical data; results, including those obtained in the preceding calculations,
are presented in Table 8-1.
Table 8-1. REQUIRED EMISSION REDUCTIONS BASED ON ROLLBACK MODEL
WITH VARIOUS INPUT VARIABLES
Growth
factor
(GF)
1.76
1.5
1.0
1.5
Present air
quality (PAQ),
ppm C
8.0
8.0
6.0
6.0
Desired air
quality (DAQ),
ppm C
0.24
0.5
0.5
0.75
Background
(B),
ppm C
0.1
0.1
0.1
0.1
Required
reduction (R),
percent
99.0
96.6
93.2
92.7
These control requirements are more stringent than those imposed by the 1970
Amendments of the Clean Air Act. Further, if hydrocarbon emissions of nonautomotive
origin cannot be controlled effectively, or if the concentration of uncontrollable
(background) nonmethane hydrocarbons exceeds 0.1 ppm C, then control requirements
for the automotive emissions should be even more stringent.
Numerical emission standards can be derived by applying the control requirement
figures calculated in the preceding paragraph to the emission rate values for 1970.
These values are 34.0, 4.1, and 4.0 grams per mile for carbon monoxide, hydrocarbons,
and nitrogen oxides, respectively, resulting in a numerical standard for hydrocarbon
emissions ranging from 0.04 to 0.3 gram per mile.
Compared with the calculation of national emission standards, the EPA-recommended
method for calculating regional control requirements for hydrocarbon emissions is
much simpler. Specifically, based on the oxidant-hydrocarbon relationship depicted
in Figure 3-5, EPA has constructed a curve that relates the highest, oxidant concentration
observed during the reference year to the degree of nonmethane hydrocarbon concentration
reduction required in order to ensure achievement of the oxidant standard. The resultant
figure then, assuming zero levels of background oxidant and nonmethane hydrocarbon,
is taken to be the degree of nonmethane hydrocarbon emission control required for
the region under consideration. Obviously, the accuracy of these calculations depends
on the accuracy of the curve in Figure 3-5 and on the validity of the 0.24-ppm C
value that has been taken to represent the nonmethane hydrocarbon concentration cor-
responding to 0.08 ppm of oxidant. Both the curve in Figure 3-5 and the 0.24-ppm C
value are of limited validity, as discussed in detail in Chapter 3.
REFERENCES FOR CHAPTER 8
]. Earth, D.S. Federal Motor Vehicle Emission Goals for CO, HC, and NOX Based
on Desired Air Quality Levels. J. Air Pollut. Contr. Assoc. 20^:519, 1970.
2. Federal Register. Vol. 36, p. 15486-15506, Aug. 14, 1971.
145
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CHAPTER 9
NATIONAL AND REGIONAL POLICIES FOR ABATEMENT
OF PHOTOCHEMICAL AIR POLLUTION
HISTORY
In 1963, the U.S. Congress introduced and enacted Public Law 88-206, known
as the Clean Air Act of 1963, outlining the Federal government's program for
preventing and controlling air pollution in the United States. The Act emphasized
a regional approach to air pollution control, and its implementation was ass'gned
to the U.S. Department of Health, Education, and Welfare. In ensuing years, the
Act was amended three times, in 1965, 1966, and 1970, resulting in considerable
expansion of State and local control programs and strengthening abatement activ-
ities on the Federal level. Further, implementation of the Clean Air Act has
become and remains the responsibility of the U.S. Environmental Protection Agency
(EPA) and the Agency's Administrator, who reports directly to the President of
the United States.
The control of motor vehicle emissions was initiated in the State of Cali-
fornia in 1959 with the adoption of standards to control exhaust hydrocarbons
and carbon monoxide. This was supplemented in 1960 with standards to control
emissions resulting from crankcase blowby. The early California standards were
goals requiring the demonstration of feasible technology before the establish-
ment of implementation deadlines. Such scheduling was contingent upon the
availability and certification of devices, systems, or modifications that would
enable motor vehicles to meet the standards. In 1963, California adopted diesel
smoke standards; however, as with the previous standards, there-was no immediate
implementation schedule. As a result of the certification of appropriate de-
vices and systems, California required a first level of crankcase emission con-
trol effective with the 1963 models, improved crankcase emission control for
1964, and control of exhaust hydrocarbons and carbon monoxide in 1966.
The 1965 Amendments to the Federal Clean Air Act gave the Secretary of
the Department of Health, Education, and Welfare the authority to control emissions
from motor vehicles. Accordingly, on March 30, 1966, the initial Federal motor
vehicle emission standards were adopted to become applicable with the 1968
models. The standards and procedures were similar to those that had been em-
ployed by California and required some control of exhaust hydrocarbons and
carbon monoxide from light-duty vehicles and 100 percent control of crankcase
emissions from gasoline-fueled cars, buses, and trucks. The term light-duty
vehicle refers to self-propelled vehicles designed for street or highway use,
147
-------
weighing less than 6000 pounds fully loaded, and carrying no more than 12 pass-
engers. Thus, the vehicle population is divided into two groups, light- and
heavy-duty, which generally correspond to cars as opposed to buses and trucks.
On June 4, 1968, revised Federal standards that required more stringent
control of hydrocarbons and carbon monoxide from light-duty vehicles, of evap-
orative emissions from the fuel tanks and carburetors of light-duty vehicles,
and of exhaust hydrocarbon and carbon monoxide emissions from gasoline-fueled
engines for heavy-duty vehicles were published. The fuel evaporative emission
standards became fully effective with model-year 1971. The other standards
applied to 1970 model-year vehicles and engines. Thus, with the introduction of
1970 models, the industry had reduced hydrocarbon emissions by almost three-
quarters and carbon monoxide emissions by about two-thirds.
On November 10, 1970, standards were published applicable to 1972 model
light- and heavy-duty vehicles and heavy-duty engines. The significant modi-
fication in these standards pertained to the method of evaluating the exhaust
hydrocarbon and carbon monoxide emissions from light-duty vehicles. Improved
methods of test operation, exhaust sampling, and gas analysis had been developed
so that emission measurements would be more representative of actual discharges
from in-use vehicles. On November 15, 1972, standards were published applicable
to 1973, 1974, 1975, and 1976 light-duty vehicles and engines.
PRESENT POLICIES
The Clean Air Act in its present form authorizes EPA to carry on a national
program of air pollution research and control activities. This program" in-
cludes research on air pollution effects, research and development of control
technology, control program support activities, financial and technical assistance
to state and local agencies, development of air quality and emission standards,
air pollution monitoring, and other activities related to these aims. The or-
ganizational structure of EPA, shown in Figure 9-1, reflects the Agency's specific
responsibility areas.
Presently adopted pollution abatement policies are centered around a re-
gional approach to air pollution control with emphasis on effort at the state
and local government levels. EPA is responsible for establishing and sustaining
a national research and development effort both within the Agency and extra-
murally through grant, contract, and cooperative activities. The Agency, under
the Clean Air Act provisions, develops and issues air quality criteria for spe-
cific air pollutants that are known to result from man-made sources and are judged
to have an adverse effect on public health and welfare. Such criteria documents
must accurately reflect the latest scientific knowledge pertaining to the effects
of such pollutants and to factors that might alter such effects.
148
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Following the issuance of criteria, EPA develops air quality standards
(Table 9-1)l and promulgates regulations calling for implementation of such stan-
dards. Thus, each state is required to submit an acceptable plan that provides
for implementation, maintenance, and enforcement of the air quality standards
within the state. In the event that a state fails to submit an acceptable plan,
EPA develops and promulgates such a plan. Implementation plans must also pro-
vide for the establishment of an air quality surveillance system meeting speci-
fied minimum requirements.
Table 9-1. NATIONAL AIR QUALITY STANDARDS
FOR OXIDANT-OZONE, NITROGEN DIOXIDE, AND HYDROCARBONS
1
Pollutant
Oxidant-ozone,
Ppm
Nitrogen di-
oxide, ppm
Nonmethane
hydrocarbons,
ppm C
Averaging
time
1 hour
1 hour
1 year
3 hours
California
0.10a
0.25b
-
Federal
0.08C
0.05d
0.246
One-hour average oxidant-ozone concentration must
not exceed 0.10 ppm (based on health effects).
One-hour average nitrogen dioxide concentration
must not exceed 0.25 ppm (based on coloration).
C0ne-hour average oxidant-ozone concentration must
not exceed 0.08 ppm more than once per year (based
on health effects).
Annual mean nitrogen dioxide concentration must not
exceed 0.05 ppm (based on health effects).
p
The average 6 to 9 a.m. nonmethane hydrocarbon con-
centration should not exceed 0.24 ppm C more than
once per year. Achievement of this standard is not
obligatory; it is offered merely as a quide to
development of oxidant-ozone reduction strategies.
(Based on role of NMHC in oxidant formation.)
EPA also develops emission standards for mobile and stationary sources.
Unlike the stationary source standards, mobile source emission standards are
subject to specific restrictions spelled out in the Clean Air Act. Thus, the
hydrocarbon and carbon monoxide standards for 1975 and later and the nitrogen
oxides standard for 1976 and later light-duty vehicles and engines must be such
that they will require at least 90 percent reduction of the emission rates of
the 1970 (for hydrocarbon and carbon monoxide) or 1971 (for nitrogen oxides)
vehicles and engines. Finally, while EPA retains ultimate authority over regu-
lations pertaining to emissions from new automobiles and aircraft and to fuel
150
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specifications, any state or political subdivision thereof may adopt or enforce
standards and/or control requirements more stringent than those prescribed by
EPA.
REFERENCE FOR CHAPTER 9
1. Title 42--Public Health, Part 410--National Primary and Secondary Ambient Air
Quality Standards. Federal Register. 36(84):8186-8201, April 30, 1971.
151
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CHAPTER 10
IMPLEMENTATION OF ABATEMENT POLICIES
STATUS OF STATE ABATEMENT PROGRAMS
Under the provisions of the Clean Air Act, as amended in 1970, States were
required to submit plans to the U.S. Environmental Protection Agency (EPA) that
would implement the national ambient air quality standards promulgated by EPA
on April 30, 1971. On August 14, 1971, EPA promulgated guidelines for prepa-
, . 2
ration and submission of the State Implementation Plans (SIPs). By May 30, 1972,
EPA was required by the Act to approve or disapprove the SIPs, or portions thereof.
By July 30, 1972, EPA was required to promulgate any portions of SIPs not yet
approved.
On May 31, 1972, EPA published in the Federal Register the formal approval
3
and/or disapproval of the SIPs. Of the 55 SIPs (50 states plus American Samoa,
Puerto Rico, Guam, the Virgin Islands, and the District of Columbia), only 14
were totally approved. The 41 remaining SIPs were disapproved in part because
of the absence of, or deficiency in, one or more essential regulatory portions.
In these cases, the EPA was required to propose and promulgate substitute regu-
lations .
On June 14, July 27, and September 22, 1972, the EPA proposed regulations
to correct the regulatory deficiencies of the SIPs. As of November 15, 1972,
13 states had corrected these deficiencies, thereby negating the need for the
EPA to promulgate regulations for those states. Thus, as of December 31, 1972,
there were 24 states for which EPA promulgation was not necessary.
After holding public hearings and reviewing comments, EPA promulgated regu-
lations for 7 states on September 22, 1972, and for 7 additional states on
October 28, 1972. Action on the remaining 14 states for which EPA promulgation
is required is held in abeyance pending completion of hearings and review of
public comments. If any of these states correct the regulatory deficiencies
of their SIPs, EPA promulgation will be obviated. Also, EPA promulgation would
be revoked for the aforementioned 14 states if necessary regulations were adopted
by the states.
In those cases where controls on new automobiles and of new stationary
sources are not expected to be sufficient for achievment of the oxidant standard,
it is required that the statesor EPA if the states fail to comply--submit plans
for transportation controls aiming at reduction of emissions by placing controls
on older vehicles, by inspection-maintenance, and/or by reducing vehicle miles
153
-------
traveled. Such plans were to be submitted (for 38 regions) by April 15, 1973.
The status of these transportation control plans may change due to matters now
in litigation and other factors.
There have been several major impediments to the promulgation of SIPs and
achievement of air quality standards. One such problem was the confusion caused
by the discovery of inaccuracy in the nitrogen oxide measurement technique.
Another such consideration is the Sierra Club suit against the EPA on the issue
of nondegradation of air quality. By alleging that the Administrator violated
the intent of Congress in his method of approving SIPs, the Sierra Club brings
to issue policies on growth and development that may cause deterioration in air
quality in areas where the national air quality standards are not exceeded. As
a result of this suit, additional litigation and legislation are expected on
this issue.
CONTROL OF HYDROCARBONS AND NITROGEN OXIDES FROM MOBILE SOURCES
EPA has been assigned responsibility for a number of programs and activi-
ties designed to abate pollution emanating from motor vehicles. Regulations
establishing emission standards, testing procedures, and enforcement practices
have been developed and promulgated to guide future actions. Table 10-1 lists
mobile source emissions standards promulgated by EPA up to and through 1973.
Staff and contract personnel from the National Academy of Sciences are assessing
the technological feasibility of attaining the 1975 and 1976 standards established
in the legislation. EPA is expanding its capability to monitor industry pro-
gress, which is focussed upon optimization of carburetion and on add-on devices
to clean up the internal combustion engine. Demonstration programs have been
initiated concerning the feasibility of low-emission vehicles powered by con-
ventional internal combustion engines. EPA is also directing a research and
development program for low-emission power sources including the automotive
gas turbine, the steam engine, electric drives, the free-piston engine, the
Stirling engine, and the stratified-charge engine.
Federal authority for the control of vehicular emissions ends with the sale
of new vehicles. States are encouraged to take action to ensure the continued
operation and efficiency of emission control systems and other automotive systems
that affect emissions. Reduced effectiveness of control systems after they leave
the manufacturer may be due to a number of causes, including gross malfunction,
improper adjustment, and deliberate removal or tampering.
A state may determine that its air quality in certain areas is such that
a state control program for vehicle emissions is necessary to augment the degree
of control provided by the Federal standards for new cars sold since 1968. Options
available to the states, such as inspection and maintenance programs, may reduce
carbon monoxide and hydrocarbon exhaust emissions.
154
-------
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Other methods are available to check crankcase control devices, and these
may be considered in addition to exhaust inspection. Recent model-year vehicles
are equipped with evaporative control systems. Inspection and maintenance of
these may be desirable, but little information on possible programs is currently
available.
States must select methods for reducing vehicular emissions for both the
control of existing air pollution and the prevention of future air pollution.
Many practical difficulties may arise in implementing a statewide inspection
and a maintenance system, but experience now being obtained by several states
should be of assistance.
Five programs of the Coordinating Research Council, which are concerned
with surveillance, maintenance, and inspection, are of particular significance
here. These are Cooperative Air Pollution Engineering (CAPE) Projects 14
through 18.
Although it has been shown that various inspection and maintenance programs
can reduce emissions of carbon monoxide and hydrocarbons, additional data are
needed to demonstrate the cost and cost-effectiveness of such programs in practice.
In addition to inspection and maintenance of vehicles, other actions that
may assist in reducing emissions from motor vehicles include the following:
1. Substitution of public transportation, in part, for the private auto-
mobile in urban areas.
2. Application of exhaust emission control devices to pre-1968 (preexhaust-
controlled) light-duty vehicles.
3. Planning of freeways and traffic control systems to minimize stop-and-
go driving arid thus reduce emissions.
States must also consider long-range planning with respect to vehicle emissions.
Some options of this type are listed below:
1. Planning for emergency actions to reduce vehicular emissions during
periods when unfavorable weather conditions create an air pollution
emergency.
2. Planning for governmental certification of maintenance and inspection
personnel to protect the public from mechanics who inadvertently cause
an increase in vehicular emissions through maladjustment or improper
maintenance of engine components.
As an aid in estimating the quantity of vehicle emissions in a certain region,
a procedure developed by the Federal government is available for use by states
or communities. It requires only information concerning vehicle registrations
or vehicle miles to arrive at estimated emissions.
156
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CONTROL OF ORGANIC EMISSIONS FROM STATIONARY SOURCES
The Federal responsibility in the effort to control stationary source emissions
is limited to approving or disapproving SIPs, issuing new source performance
standards, that is, emission standards for new and significantly modified point
sources, and issuing standards for hazardous pollutants. One group of new
source performance standards for five industrial source categories were promul-
gated in 1971 (Group I in list below) and were revised in 1973. Standards for
a second group of sources (Group II) were proposed in 1973. Groups I and II of
the stationary sources considered thus far are listed below:
Group I: Fossil-fuel-fired steam generators
Municipal incinerators
Cement plants
Nitric acid plants
Sulfuric acid plants
Group II: Petroleum .refineries
Secondary lead smelters
Iron and steel mills
Sewage treatment plants
Asphalt concrete plants
Bras? and bronze ingot production plants
Storage vessels for petroleum liquids
Hazardous pollutants are also essentially a stationary source problem. Asbestos,
beryllium, and mercury have been identified as hazardous pollutants and regu-
lations were promulgated for such pollutants.
Of the state control activities, the most notable one is the development
and adoption of Rule 66 in the County of Los Angeles, California, for control
of organic solvent emissions .^ The Rule classifies organics into photochemically
reactive and nonreactive ones and imposes upper limits to allowable emission
rates. The rest of the states have either adopted Rule 66 in its entirity or
developed similar alternatives.
Methods used to control organic emissions are (1) substitution of materials,
(2) operational or process changes, and (3) use of control equipment. Substitu-
tion of photochemically less reactive materials for reactive ones is used in
cases where the organic emissions cannot be collected or incinerated by practical
means. Such is the case, for example, with the organic solvent emissions from
painting of buildings and structures. Control devices are classified into four
categories based on the following control principles: incineration, adsorption,
absorption, and condensation. Control methods used in some industrial pro-
cesses are described in the following paragraphs.
157
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Petroleum Refining
Evaporation losses during storage are minimized by the use of floating-roof
tanks, pressure tanks, and vapor conservation or recovery systems. Hydrocarbons
from catalyst regenerators can be controlled by waste-heat boilers. Leakage from
valves, pumps, and compressors can be reduced by systematic maintenance of
connections and seals. Waste-water separators can be controlled by enclosing
the separator tanks. Vapor recovery systems or smokeless flares are utilized
to control hydrocarbon vapors from blowdown systems. Stripping gases from acid
treating, doctor treating, and caustic treating and air-blowing effluents can
be controlled by incineration.
Gasoline Distribution Systems
Vapors emitted during the loading of gasoline tank trucks can be collected
and delivered to a vapor disposal system. The collection system consists of a
tight-fitting hatch and a vapor delivery line. For top-loading tanks, the vapor
delivery line is an annular space around the gasoline delivery line. For bottom-
loading tanks, the vapor line is a separate line connected at the top of the
tank. Vapors can be delivered to a gas-blanketed vapor holder and used as fuel
in boilers and heaters where the load rack is adjacent to the refinery. For
storage and loading facilities at other locations, packaged vapor recovery units
have been developed in which the vapors are compressed and reabsorbed in gasoline.
Chemical Planets
The principal raw materials for synthetic organic products are derived
mostly from petroleum and to a lesser extent from the by-products of the coking
of coal. These materials are processed through the following types of conversions:
alkylation, hydrogenation, dehydrogenation, dehydration, esterification, halo-
genation and dehalogenation, oxidation, nitration, and polymerization. Waste
gases from processing units can be collected and delivered to a burner, to a
gas holder, or into a fuel header system. Waste gases from units producing
chlorinated hydrocarbons can be processed to recover by-product hydrochloric
acid. Direct-flame and catalytic afterburners are used to eliminate organic
vapors and mists from many off-gases.
Paint, Lacquer, and Varnish Manufacture
Emissions from paint and lacquer manufacture occur during mixing, grinding,
and thinning operations. Varnish ingredients must be "cooked" to promote such
reactions as depolymerization, esterification, isomeriration, melting, and
bodying. Emissions contain fatty acids, aldehydes, acrolein, glycerol, acetic
acid, formic acid, and complex residues of thermal decomposition. Control systems
consist of condensers, scrubbers, and afterburners.
158
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Rubber and Plastic Products Manufacture
Emissions from rubber product manufacture occur during heat plastic!zation,
chemical plasticization, and vulcanization. Control techniques include carbon
adsorption, direct-flame and catalytic incineration, and reformulation to non-
photochemical ly reactive materials. In plastic products manufacture, emissions
can occur from curing ovens, particularly when dioctyl phthalate is used as a
plasticiser. Such mists can be controlled with high-energy scrubbers or with
afterburners.
Surface Coating Applications
Emissions of hydrocarbons f*om the application of paint, varnish, and simi-
lar coatings are due to the evaporation of the solvents, diluents, and thinners.
Where controls are required, reformulation with nonphotochemically reactive sol-
vents is a method of control Afterburners have been used to control emissions
from paint bake ovens. These ovens can sometimes be redesigned to reduce the
volume of gases to be handled, effecting considerable savings. Heat recovery
systems can lower operating costs by reducing fuel requirements.
Degreasing Operations
Most vapor-phase degreasers use chlorinated hydrocarbon solvents, prin-
cipally trichlorethylene. Less photochemically reactive 1,1,1-trichloroethane
(methyl chloroform) and perchloroethylene can be substituted. Activated-carbon
adsorbers can be used to control emissions in some applications. Solvent emissions
can be minimi zee by elimination of drafts, good drainage of work items, controlled
speed of work entering and leaving work zone, and covering of lank whenever
possible.
Dry Cleaning
Dry cleaning is done by two processes: those using petroleum solvents and
those using perchloroethylene or other halogenated solvents. In plants using
perchloroethylene, vapor is recovered by water-cooled condensers, which may be
followed by activated-carbon adsorbers. The value of the solvent makes recovery
economically feasible. Plants using petroleum solvents can be controlled, if
necessary, by using solvents reformulated to be nonphotochemically reactive.
Control by activated carbon may be feasible.
Stationary Fuel Combustion
Hydrocarbons may be emitted if combustion is not complete. When properly
designed and operated, stationary fuel combustion equipment is not a serious
source of organic emissions.
159
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Metallurgical Coke Plants
The hydrocarbons from the coking of coal are collected to recover by-
products. Emissions occur during charging operations and from improperly fitting
doors and other leaks. Emissions during charging can be reduced by steam-jet
aspirators in the collection pipes. Self-sealing doors and good maintenance pro-
grams can reduce' emissions.
Sewage Treatment Plants
Primary sewage plants emit hydrocarbons from the screening and grit chambers
and from the settling, tanks. Activated-sludge plants emit gas from the aeration
tanks. Trickling filter plants emit organic gas from the filters, the clarifiers,
and the sludge-digestion tanks. Control of emissions can be accomplished by
covering or enclosing the various treating units and oxidizing or combusting
the effluent gases.
Waste Disposal
Burning of waste materials can cause emissions of hydrocarbons. Open
burning and inefficient incinerators are the predominant sources of such emissions.
Control can be achieved by using multiple-chamber incinerators, by disposing of
the waste in sanitary landfills, or by recycling.
Miscellaneous Operations
Emissions from deep fat fryers and coffee roasters can be controlled by
afterburners. Fish cookers can be controlled by condensers. Evaporators of
liquids from fish processing can be controlled by condensers and scrubbers and
fish meal driers by scrubbing with chlorinated water. Noncondensible gases from
charcoal manufacturing can be burned.
CONTROL OF NITROGEN OXIDES FROM STATIONARY SOURCES
Regulatory measures regarding nitrogen oxide (NO ) emissions from stationary
sources are limited to the Federal new source performance standards discussed
in the preceeding section of this report and to state regulations as required for
implementation of the air quality standard for nitrogen dioxide (NO,). Commer-
cially demonstrated control techniques used in the United States with varying
degrees of success are described in the following paragraphs.8
Combustion Modification
Two-stage combustion in oil- and gas-fired boilers has reduced NO emissions
X
from power plant boilers by 30 to 50 percent. Low-excess-air operation has
reduced NO emissions from oil- and gas-fired power plant boilers by 30 to 60
Jv
percent, depending upon the percentage of excess air, the design of the boiler,
160
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and the type of firing. Tangential firing can produce reductions in NOX of up
to 50 percent compared with front-fired or opposed-fired furnaces.
A modified two-stage combustion technique combined with low-excess-air
firing has reduced the stack-gas NO concentration emitted by two 750-megawatt
gas-fired power-plant boilers from 1500 to 175 parts per million (ppm) . Nominal
costs with no decrease in generating capacity were reported by the company.
Emissions of NO from gas turbine engines is currently a major problem.
Since standards are in the process of being determined for NO levels from tur-
A
bines, there is considerable effort being expended to define the emissions picture
for these sources. The major control method in use at the present time is steam
or water injection into the corobustor section of the turbine. Since this method
requires ultrapure water, its applicability is seriously limited and a major
effort is underway by the turbine industry to develop dry control methods. These
dry methods generally involve hardware modification in the area of the combustor.
The combustors are redesigned to incorporate staged combustion effects and in-
ternal combustion gas recirculation for NO reductions.
X
Diesel engine emissions have been under considerable study by the automo-
tive industry and many of the control techniques for mobile sources also apply
to stationary sources. The precombustion chamber concept, developed many years
ago to control peak engine pressures, has been found to be a very effective NO
X
control device. Essentially this concept is a staged combustion process: a
rich fuel mixture is ignited in a separate chamber and then forced into the cylinder
along with additional air to complete combustion. Other methods for reduction of
NO in stationary diesels arc: reduced fuel injection rate, increased retardation
X
of timing water injection, exhaust gas recirculation, and lower compression ratio.
Most of the current work with piston engines is directed at mobile sources,
but stationary engine work is in planning based on results from automotive stu-
dies .
All of the above approaches are based on considerations of chemical equi-
librium and reaction rate. They involve reduction of peak gas temperatures,
trends away from oxidizing and toward reducing atmospheres, and changes in the
time-temperature history of the combustion gases. These approaches are all
commercially demonstrated for large oil- and gas-fired boilers, but are yet to
be demonstrated for large coal-fired boilers.
Changes_ in_Fuel or Energy Source
Generation of electricity through the use of nuclear energy is projected
to grow in the future. Essentially no NO is emitted since this source of
X
energy does not depend on the combustion of fossil fuels. In 1968, 12 billion
kilowatt-hours of electric power generated from nuclear energy was reported in
the United States; optimistic sources project 3000 billion kilowatt-hours by 1990.
161
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Waste Disposal Technique
Substitution of sanitary landfills for open burning has proved to be a
commercially demonstrated control technique in certain areas of the country.
Chemical Sources
Nitrogen oxides from chemical sources may be decolorized by catalytic re-
duction using fuels such as natural gas or hydrogen. Such reactions are exother-
mic and much heat is generated. Because of practical considerations, such as
catalyst life and the temperature limitations of structural materials, only the
process of decolorization by reduction to NO has been uniformly successful.
Catalytic reduction of NCL to NO is not a true control technique; it merely
decolorizes the stack gas. Stack velocities and normal atmospheric turbulence
contribute to rapid dilution, with increasingly slow rates of oxidation of NO by
air. Photochemical reactions in the atmosphere can, however, oxidize these
small NO concentrations to N0?.
Other Techniques
Other control techniques that have had limited commercial success or of only
speculative nature include energy substitution, source relocation, catalytic
reduction of NO to nitrogen, caustic scrubbing, incineration of NO to nitrogen,
steam and water injection, flue-gas recirculation, stack-gas treatment, and
adsorption on molecular sieves.
ESTIMATION OF EMISSION RATES
For an accurate air pollution survey, whether for a single source or for
a metropolitan area, pollutant emissions must be identified by type and quantity.
This determination--together with meteorological air quality and effects sampling
programs--fulfi11s the requirements for local, state, and Federal air pollution
control activities.
Ideally, the determination of emission rates should include analysis of
emission effluents from all sources of interest, but this is impractical when
an air pollution survey must cover a large area containing thousands of sources.
For this reason, emission rates are estimated using emission factors, that is,
emission rates per unit of source magnitude. Such emission factors have been
determined for all sources of significance in the United States and are used
here to illustrate the computational procedure used to estimate emission rates
for single sources or for a region.
Regional Vehicular Emissions
The basic method for predicting total motor vehicle emissions is to multiply
emission factors, modified to represent on-the-road emission rates, by the vehicle
miles of travel (VMT). The National Air Pollution Control Administration (an
162
-------
EPA predec.esor agency) used a similar simplified approach for estimating nation-
wide vehicle emissions. Two types of vehicle operating conditions were assumed,
urban and rural. All urban travel was assumed to be at an average speed of 25
miles per hour beginning from a "cold start"; i.e., the vehicle was assumed not
to have been driven prior to beginning travel at the urban driving speed. All
rural travel was assumed to be at an average speed of 45 miles per hour, beginning
from a "hot start." In this case, the vehicle was assumed to have been operated
before being driven at the rural speed. The emission factors were then adjusted
for these average speeds. A further seasonal adjustment was made. No correction
was made for altitude. The national miles of travel for passenger cars, trucks, and
buses were taken from Highway Statistics. The future projections of national
vehicle miles of travel were estimated from the "medium" projections presented
in Resources in America's Future. It should be noted that forecasts made prior
12
to the 1970 census assumed a higher growth rate than is now occurring. The
total VMT were divided into passenger car and truck miles and further into rural
and urban driving, according to the assumed weighting. The national emissions
for each pollutant were then obtained by multiplying these vehicle miles traveled
by the appropriate emission factor.
Subsequently, a method that modified this approach on a regional basis was
developed from appropriate emission factors and the motor vehicle population and
13
driving pattern for the particular region. ' Total vehicle travel is determined
from regional transportation studies, local traffic surveys, U.S. Department of
Transportation data, and Federal Highway Administration publications. " The
statistics available from Highway Statistics1 include, by state, miles of public
roads and streets, average daily traffic loads, number and type of vehicles
registered, and estimated motor vehicle (passenger and truck) travel by highway
system. Also included are motor fuel consumption and speed trends by roadway
type and vehicle type. Highway Statistics assumed that since the total emissions
from all gasoline-powered motor vehicles in a region is a function of the vehicle
emission factors, the vehicle miles traveled in the region, and the percent
travel that is urban or rural, a proportional relationship could be made to ob-
tain regional emissions from the average national emissions. This assumption
is valid if the regional vehicle mix of ages, types, makes, and deterioration
rates, as well as the percentages of road types, average speeds, and miles of
travel, are the same as the national average. The following equations are used
to obtain regional emission estimates:
TE = UH + RE
UL = CIJF) CWT) fa) fk)
RP. = (RF) (VMT) (1-a) (k)
163
-------
where:
TE = Total emission of a pollutant, tons/year
UF = Urban emission of a pollutant, tons/year
RE = Rural emission of a pollutant, tons/year
UF = Urban emission factor, g/mi
VMT = Vehicle miles of travel
a = fraction of travel that is urban
k = 1.1023 x 10" ton/g (conversion factor)
RF = Rural emission factor, g/mi
The emission factors (for both cars and trucks) needed for the calculation
are presented for each pollutant (hydrocarbons, carbon monoxide, and oxides of
nitrogen) by year and by urban and rural driving. The VMT and the fraction of
urban travel are to be obtained from local traffic studies. (Vehicle miles
of travel and projections for future years for most cities are available as a
result of the Federal Aid Highway Act of 1962, which required cities with pop-
ulations over 50,000 to initiate transportation studies in order to qualify for
Federal aid for road construction.)
This simplified method can be updated by using the latest emission factors
given in Reference 18. A sample calculation for a metropolitan area is shown in
Tables 10-2 to 10-4. Adjustment of the emission factor for the speeds of the road-
way type, with the miles of the roadway type, vehicle type (light-duty or heavy-
duty), and the respective vehicle miles traveled would provide an even more accurate
calculation of emissions.
The accuracy of the gasoline-powered motor vehicle emissions prediction is
not only dependent on the emission factors, it is also very sensitive to traffic
data (vehicle type and age reix, miles of roadway type, average speed) that are
best developed by local traffic surveys. IVhere air quality levels are developed
by a proportional or rollback model, data must be obtained on at least a country-
19
wide basis. The use of a dispersion model requires that the data be developed
19
on a grid basis. " The grid size is dependent on the sophistication of the cal-
culation; grid cells down to 1 square mile or 1 square kilometer are often used.
20
The Chicago area transportation study used traffic zones in the study area
that varied from 0.25 square mile in the central business district to 36 square
miles in the outlying areas. A study of Washington, D.C., divided the metro-
politan area into 48 irregular subareas that were smaller in the central business
district than in the suburbs. This unique approach to the evaluation of trans-
portation alternatives provided a method for estimating emissions from transpor-
tation data without trip distribution and traffic assignment models. The method
makes use of vehicle trip forecasts along with highway network information to
estimate future travel, the speeds at which this travel will occur, and the
emission levels produced.
164
-------
Table 10-2. SAMPLE CALCULATION OF GASOLINE MOTOR VEHICLE
EXHAUST EMISSION FACTORS FOR HYDROCARBONS
FROM LIGHT-DUTY VEHICLES
Model
year
1971
1970
1969
1968
1967
1966
1965
1964
1963
1962
1961
1960
1959
1958
Total
ci
2.9
3.6
4.4
4.5
8.8
8.8
8.8
8.8
8.8
8.8
8.8
8.8
8.8
8.8
di
1.00
1.05
1.16
1.21
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
m,"
0.013
0.075
0.174
0.135
0.103
0.115
0.097
0.083
0.060
0.059
0.027
0.017
0.010
0.032
si
0.79
0.79
0.79
0.79
0.79
0.79
0.79
0.79
0.79
0.79
0.79
0.79
0.79
0.79
c-jd-jtn-jS-j
0.03
0.22
0.70
0.58
0.72
0.80
0.67
0.58
0.42
0.41
0.19
0.12
0.07
0.22
5.85
See Reference 13 for sample calculation.
Table 10-3. SAMPLE CALCULATION OF WEIGHTED SPEED
ADJUSTMENT FACTOR FOR HYDROCARBON EXHAUST
EMISSIONS FROM LIGHT-DUTY VEHICLES
Average speed (j),a
miles/hour
Total
20
30
40
50
60
^
0.40
0.15
0.20
0.15
0.10
VJ
1.00
0.77
0.69
0.54
0.48
fJVJ
0.40
0.12
0.14
0.08
0.05
0.79
Speeds used were determined arbitrarily for pur-
poses of this sample calculation.
"'Determined arbitrarily.
165
-------
Table 10-4. SAMPLE CALCULATION OF GASOLINE
MOTOR VEHICLE CRANKCASE AND EVAPORATIVE
EMISSION FACTORS FOR HYDROCARBON
FROM LIGHT-DUTY VEHICLES
Model year
1971
1970
1969
1968
1967
1966
1965
1964
1963
1962
1961
1960
1959
1958
Total
hi
0.5
3.0
3.0
3.0
3.8
3.8
3.8
3.8
3.8
7.1
7.1
7.1
7.1
7.1
mi
0.013
0.075
0.174
0.135
0.103
0.115
0.097
0.083
0.060
0.059
0.027
0.017
0.010
0.032
himi
0.01
0.22
0.52
0.40
0.39
0.44
0.37
0.32
0.23
0.42
0.19
0.12
0.07
0.23
3.9
23
EPA's Guide for Compiling a Comprehensive Emission Inventory*'" provides
detailed procedures for preparing stationary and mobile source emission inven-
tories. The section on gasoline-powered motor vehicles is particularly useful.
Although this approach requires automatic data processing equipment, it will
produce a uniform format that allows ready comparison with other regions and that
is compatible with stationary source data now being accumulated. This approach
is recommended because of its relationship to El'A's National Environmental Emissions
Data System. If the Guide is used, the gasoline-powered vehicle emission factors
in Reference 1 should be used until Compilation of Air Pollutant Emission Factors'
is revised to include them. Tables 10-5 and 10-6 present emission factors for
diesel engine and aircraft emissions.
Where a detailed transportation emissions inventory, air quality data, and
the necessary technical expertise are all available, rather sophisticated eval-
uations of transportation control and highway system alternatives are possible.
24
Such an approach was developed by the Argonne National Laboratory.
Hydrocarbon Emissions from Stationary Sources
Hydrocarbon emissions from stationary sources are estimated using emission
factors. Because such emission factors may at times be based on limited or vari-
166
-------
Table 10-5. EMISSION FACTORS FOR DIESEL ENGINES
a,23
EMISSION FACTOR RATING: B
Pollutant
Particulates
Oxides of sulfur
(SOX as S02)b
Carbon monoxide
Hydrocarbons
Oxides of nitrogen
(NOX as N02)
Aldehydes (as HCHO)
Organic acids
Heavy-duty truck and bus
engines
lb/103 gal.
13
27
225
37
370
3
3
kg/103 liters
1.56
3.24
27.0
4.44
44.4
0.36
0.36
Locomotives
lb/103 gal.
25
65
70
50
75
4
7
kg/103 liters
3
7.8
8.4
6.0
9.0
0.48
0.84
Data presented in this table are based on weighting factors applied to actual
tests conducted at various load and idle conditions with an average gross
vehicle weight of 30 tons (27.2 metric tons)and fuel consumption of 5.0 mi/gal.
(2.2 km/liter).
DData for trucks and buses based on average sulfur content of 0.20 percent, and
for locomotives, on average sulfur content of 0.5 percent.
able data, emission factors should he used with caution unless the data upon
which the factor is based have been studied or reviewed.
Reference 2.3 is a compilation of available emission factors for hydrocarbons
and other pollutants from various types of sources. These emission rates are
for uncontrolled sources unless otherwise noted. An example of how emission
factors are used is given below:
Petroleum refiner)', fluid catalytic cracking unit:
Given: Fluid catalytic cracking unit with 10,000 barrels per day of fresh
feed; operates 350 days per year and has no carbon monoxide boiler.
Find: Annual hydrocarbon emissions.
Hydrocarbon emission factor (from Reference 23): 220 pounds per
1000 barrels of feed.
(10,000 bbl/day) (220 lb/1000 bbl) (350 day/year)
= 770,000 Ib HC/year
Nitrogen Oxide Emissions from Stationary Sources
As in the case of hydrocarbon emissions, nitrogen oxide emissions are also
estimated using emission factors. However, unlike the hydrocarbon case, develop-
ment of accurate NO emission factors is very difficult because of the complex nature
of NO formation from combustion processes.
167
-------
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There is no convenient way of anticipating the approximate amount of NO
A.
pollutants formed from a given amount of fuel, as there is for the oxides of sul-
fur (SO ). The formation of SO is directly related to the concentration of
X X
sulfur in the fuel. On the other hand, NO can be formed in substantial concen-
X
trations of several hundred parts per million or more with no chemically bound
nitrogen in the fuel.
The amount of NO. emitted depends upon equipment design, a complex set of
combustion conditions, and operating variables such as installation size, type of
burner, cooling surface area, firing rate, and air/fuel ratio. Consequently, the
determination of accurate emission factors that represent average or typical
emissions from each class of equipmeTit involves a complicated sampling procedure,
which requires the selection of representative operating conditions.
Reference 23 is a compilation of average emission factors for NO and other
pollutants from various types of sources. These emission rates represent uncon-
trolled sources unless otherwise noted. For an operation in which control equip-
ment is utilized, the emission rate given for an uncontrolled source must be
multiplied by one minus the percent efficiency of the equipment, expressed in
hundredths.
An example of how to use emission factors is given below:
Given: Power plant burns 50 million gallons of fuel oil per year.
Find: Annual NO emissions.
x
NO emission factor (from Reference 23): 105 pounds per 1000 gallons
of fuel.
(50,000,000 gal./year)(105 lb/1000 gal.) - 5,250,000 Ib NO /year
REFERENCES FOR CHAPTER 10
1. Title 42--Public Health; Part 410--National Primary and Secondary Ambient Air
Quality Standards. Federal Register. 36_(84) : 8186-8201, April 30, 1971.
2. Federal Register. Aug. 14, 1971.
3. Title 40--Protection of Environment. Federal Register. 37_(221):24250, Nov. 15,
1972.
4. Title 40--Protection of Environment. Federal Register. ,38_(161) : July 2, 1973.
5. Title 40--Protection of Environment. Federal Register. _38(126):17682, Aug. 21,
1973.
6. Rule 66, Organic Solvents. In: Rules and Regulations of the Air Pollution Control
District, County of Los Angeles. Los Angeles County Air Pollution Control District.
Los Angeles, Calif. Nov. 1972.
169
-------
7. Control Techniques for Hydrocarbon and Organic Solvent Emissions from Stationary
Sources. U.S. Department of Health, Education, and Welfare, Public Health
Service. Washington, D.C. Publication No. AP-68. March 1970.
8. Control Techniques for Nitrogen Oxide Emissions from Stationary Sources. U.S.
Department of Health, Education, and Welfare, Public Health Service. Washing-
ton, D.C. Publication No. AP-67. March 1970.
9. Goodman, K. , J. Kurtzweg, and N. Cernansky. Determination of Air Pollution
Emissions from Gasoline-Powered Motor Vehicles. U.S. Department of Health,
Education, and Welfare, National Air Pollution Control Administration. Durham,
N.C. April 1970. 21 p.
10. Highway Statistics, 1970. U.S. Department of Transportation, Federal Highway
Administration. Washington, D.C. 1970. p. 199.
11. Landsberg, H.H. et al. Resources in America's Future. Resources of the
Future, Inc. Baltimore, John Hopkins Press, 1963.
12. 1970 Census of Population, General Population Characteristics. U.S. Depart-
ment of Commerce, Bureau of the Census. Washington, D.C. PC(1)-B Series.
1970.
13. Kurtzweg, J.A. and D.W. Weig. Determining Air Pollutant Emissions from Trans-
portation Systems. In: Proceedings of Annual Meeting of the Association for
Computing Machinery. New York, N.Y. October 24, 1969. p. 22
14. Strate, II.E. Nationwide Personal Transportation StudyAnnual Miles of Auto-
mobile Travel. U.S. Department of Transportation, Federal Highway Administra-
tion. Washington, D.C. Report No. 2. April 1972. p. 14.
15. Nationwide Personal Transportation Study, Automobile Occupancy. U.S. Depart-
ment of Transportation, Federal Highway Administration. Washington, D.C.
Report No. 1. April 1972.
16. Guidelines for Consideration of Economic, Social and Environmental Effects
(PPM 20-8 Modification). U.S. Department of Transportation, Washington, D.C.
17. Cernansky, N.P. and K. Goodman. Estimating Motor Vehicle Emissions on a
Regional Basis. U.S. Department of Health, Education and Welfare, National
Air Pollution Control Agency. Durham, N.C. 1970.
18. Kircher, D.S. and D.P. Armstrong. An Interim Report on Motor Vehicle Emission
Estimation. U.S. Environmental Protection Agency, Office of Air and Water Pro-
grams. Research Triangle Park, N. C. Publication No. EPA-4SO/2-73-003. October
1973.
19. Projected Motor Vehicle Emissions, Appendix I. Federal Register.
36(228) :22412, November 25, 1971.
170
-------
20. Croke, E.J., K.G. Croke, R.E. Wendell, and J.E. Norco. The Role of Trans-
portation Demand Models in the Projection of Future Urban and Regional Air
Quality. Argonne National Laboratory, Center for Environmental Studies.
In: Proceedings of International Congress of Transportation Conferences.
Washington, D.C. May 31-June 2, 1972.
21. Berwager, D.S. and G.V. Wickstrom. Estimating Auto Emissions of Alter-
native Transportation Systems. Metropolitan Washington Council of Governments.
Washington, D.C. Report No. DOT-05-2004. April 1972. p. 76.
22. Guide for Compiling a Comprehensive Emission Inventory. U.S. Environmental
Protection Agency, Office of Air Programs. Research Triangle Park, N.C.
Publication No. APTD-1135. June 1972. p. 5-15 to 5-19.
23. Compilation of Air Pollutant Emission Factors (Revised). U.S. Environ-
mental Protection Agency, Office of Air Programs. Research Triangle Park,
N.C. Publication No. AP-42. April 1973.
24. The Development of a Methodology to Evaluate Alternative Transportation.
Argonne National Laboratory, Center for Environmental Studies. Argonne,
Illinois. Publication No. 7221A. April 1972. p. 44-63.
171
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CHAPTER 11
ECONOMIC CONSEQUENCES OF OXIDANT POLLUTION
COST OF OXIDANT EFFECTS
Total costs of air pollution effects consist of "damage" costs and "avoidance"
costs. Damage costs are those resulting directly from exposure to pollutants and
include the tangible costs of medical and hospital care, costs of loss of work
due to pollution-caused illness, costs of damage and/or repair of damage to
materials and vegetation, and costs associated with destruction of ecosystems.
Intangible costsnot easily given a dollar xralue--include those arising from
psychological disturbances caused by the damage effects as well as by loss of
aesthetic, recreational, and other environmental amenities. Avoidance costs are
those caused by actions taken to avoid pollution, e.g., migration into less polluted
areas. Such costs are also difficult to be given a dollar value as they are
usually caused by more than one reason.
One national estimate of total air pollution damage costs, reported by the
Council of Environmental Quality (CEQ), is summarized in Tables 11-1 and 11-2.
Such estimates are by no means complete or reliable; for example, they do not
include health damage directly caused by automobile pollutants and include only
one measure 01" the intangible costs of air pollution. Further, they disagree
with other estimate^. For example, Rabcock and Nagda reported a cost figure as
high a? $20 billion compared to CHQ's $10 billion. More recent estimates of the
d«i, ago cc i>t is associated with individual pollutants are summarized in Tab In 1 ] - 3
and total as much as $8." billion; the oxidant contribution estimate ranges from
$0.5 billior to $1,5 billion.
In conclusion, EPA's best estimate of total air pollution damage cost for
1970 is $12.3 billion. EPA's best estimate of the oxidant contribution is $1.1
b111i on .
DIRECT COSTS OF ABATEMENT
Ideall), this chapter should deal with the cost of implementing oxidant
abatement policies. However, while some abatement actions are addressed directly
and wholly to the photochemical oxidant problem, complete disassoclation of this
problem and related abatement from the other air pollution problems is extremely
difficult. For this reason, the following discussion will deal first with the
better established abatement cost for air pollution in its totality; estimates
of the oxidant-related contribution will then be discussed.
Costs of implementing abatement policies consist of "transaction" costs and
"abatement" costs, and are borne partly by the public sector (Federal, state, and
173
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Table 11-1. ESTIMATED AIR POLLUTION DAMAGE
COSTS IN THE UNITED STATES, 1968
Type of cost
Annual cost,
billions of dollars
Damage costs
Materials damage
Damage to crops
Cleaning of soiled materials
Damage to human health
Damage to animal health
Reduced property values
Other
Avoidance costs
Total
4.8a
O.lb
__c
6.id
c
5.2
__c
c
16.2
Includes damage to 50 materials thought most susceptible
to air pollution deterioration.
b
Includes direct visible effects.
c
Not estimated.
Includes estimates on treatment and prevention costs for
illnesses caused by air pollution plus income lost due
to morbidity and early mortality.
Table 11-2. ESTIMATED AIR POLLUTION9 DAMAGE COSTS IFI THE UNITED STATES
FOR 1968 AND 1977 WITH NO POLLUTION CONTROL
Damage class
Healtn
Residential property
Materials and vegetation
Total
Annual cost of damage,
bi llions of dollars
1968b
6.1
5.2
4.9
16.2
1977C
9.3
8.0
7.6
24.9
b
Including oxidant, nitrogen dioxide,carbon monoxide, sulfur dioxide,
and particulate matter.
In 1968 dollars.
:In 1970 dollars.
174
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Table 11-3. SUMMARY OF THE UNITED STATES AIR POLLUTION
DAMAGE COST RANGES FOR 1970
Damage
effect
Health
Materials
Plants
Animals
Property
values
Soiling
Visibi 1 i ty
Total
Damage cost range, millions of dollars
Participate
matter
8-41
169-767
10
1-3
300-1765
519-2077
0
1007-4663
Sulfur
dioxide
1-4
215-972
4
0
126-745
0
0
346-1725
Nitrogen
dioxide
0-1
52-236
2
0
47-275
0
0
101-514
Oxidants
44-221
254-791
116
4-11
67-399
0
0
483-1538
Carbon
monoxide
9-44
30-134
0
0-2
19-114
0
0
58-294
Total
62-311
720-2900
132
3-16
559-3298
519-2077
0
1995-8734
local government!, and parilv by the private sector (industry'1,. Transaction costs-
borne mainly by the puMic sector cons i st of costs oi research, development,
planning, monitoring, arid enforcement needed to achieve environmental peals ard
standards. Abatement costs home almost entirely by the p?'ivatc sector arc
by definition those of emission reduction. It should he noteu, however, t! at
since airy f.-ioir.^iou reduction activity has una\oidublf i:ide effects fe.g., effects
on productivity, product quality, by-product revenue, etc.) of economic Jirpact,
the true cost of such actii.it>' cannot ho £ivui a dolla* value Kith any confidence.
For this reason, abatement costs, as estimated, can rnlv have a pross nature.
Table 11--4 includes data on estimated transaction v.osts to the i-Vdc.ral govern-
ment for 19~2. It should K noted that these costs do not include those bcrne
by state and local Government and hv the private sectoi, Ore estimate of the cost
borne by the state and local ^overiui'ent for 19^2 is ^56.3 mill ion,'' thus bringing
the transaction costs tot;il to $522 inilJion.
Table 11-4. FEDERAL TRANSACTION COSTS
ASSOCIATED WITH AIR POLLUTION ABATEMENT, 19721
Type of cost
T
Cost, millions
of dollars
Research and development
Planning
Monitoring and surveillance
Administration, standard
setting, enforcement
Other
Total
136.5
2.2
29.0
82.0
15.0
264.9
175
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Table 11-5 includes data on abatement costs for 1971 and, as projected, for
1981. The projection data reflect not only population and human activity growth,
but also planned additional controls to achieve an additional improvement of air
quality,
Table 11-5. COST OF AIR POLLUTION ARATEMENT3'1
Cost type
Public
Private
Mobile sources3
Stationary sources
Total
Annual cost, billions of 1972 dollars
1971
0.2
1.2
0.7
2.1
1981
1.2
10.5
5.7
17.4
Cumulative
1972-1981
8.4
58.8
38.4
105.6
Excluding heavy-duty vehicles.
Based on the data in Tables 11-4 and 11-5, the total annual direct cost of
implementing air pollution abatement policies in the United States amounts to
$2.4 billion for 1972 and to $4.0 billion, approximately, for 1973.
Of this total cost for abatement, only a fraction is due to oxidant-related
control. Calculation of this fraction is based on certain facts and assumptions.
One fact is that oxidant abatement is pursued through unilateral control of hydro-
carbon emissions. Therefore, only the cost of hydrocarbon control needs to be
considered here. To calculate cost of hydrocarbon control, the approximateon--
a reasonable one--is made that all controllable hydrocarbon emissions are discharged
from mobile sources, from storage tanks and catalyst regenerators of refineries,
and from solvent evaporation. Cost estimates for control of such emissions are
as follows.
No reliable estimate of the annual transaction cost of hydrocarbon control
has been made; such cost must be a fraction of the $322 million estimated to be
the transaction costs for all emissions.
Annual cost of control of motor vehicle emission has been estimated to be
$1.0 billion for 1972, $1.9 billion for 1973, and $8.4 billion for 1977.5 These
costs include only those directly resulting from Federal requirements; costs
from state activities are not included. Further, these costs are--at least for
the early years in the decade of the 70's--mainly for control of carbon monoxide
and hydrocarbons and only to a lesser degree for nitrogen oxide control. One way
of calculating the hydrocarbon control cost portion is based on use of hardware
cost data reported by the National Academy of Science, Committee on Motor Vehicle
176
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Emissions. From such data it can be estimated that the cumulative cost of hydro-
carbon control hardware and maintenance for 1972 model-year autos is approxi-
mately 44 percent of the total control hardware and maintenance cost; analogous
percentage figures for 1973 and 1977 models are 64 and 35 percent, respectively.
Further, from data on fuel economy loss due to control, it is estimated that,
for the 1972 models, 50 percent of such loss is caused by the hydrocarbon controls;
analogous percentage figures for the 1973 and 1977 models are 38 and 67 percent,
respectively. From these estimates it can be deduced that the cost of the motor
vehicle hydrocarbon emission control is roughly $0.5 billion for 1972, and $1.1
billion for 1973.
Control costs for hydrocarbon emissions from refineries--more specifically,
from catalyst regenerators and storage tanks--have been estimated to amount to
roughly 20 percent of the total refinery emission control cost, that is, $J4.6
million per year.
No reliable estimates for solvent emission control cost are available.
Based on these figures, the total hydrocarbon control cost is at least
50.5 billion for 1972, and $1.1 billion for 1973.
Estimates of annual control cost per unit are given in Tables 11-6 and 11-7
for light-duty vehicles and heavy trucks, respectively. Such costs include only
operating and maintenance costs and range, within the period 1968-1977, from $6.1
to $64.7 for light-duty vehicles, and from 0 to $422 for heavy-duty diesel engines,
("Corresponding costs of operating a typical $3470 automobile total $2060 for the
first year, and $1470 for the second. A typical heavy-duty diesel truck costs
approximately $20,000.) Total cost of control hardware3 brings the annual control
cost to $67 for 1972.
Table 11-6. AiMUALIZED UNIT COST INCREASES FOR LIGHT-DUTY VEHICLES'
(dollars)
::^
Model vear
'%.",
Increased
fuel us 3
"Id" ntenance 6. 10
Mji ntenance
offsets
Total annual 16.10
irerati'i'i i
1969
fi. 10
1970 1971 f 1972
15.90 15.90
6.10 , 12.70 , 12.70
6.10 i £.10 i 28.60 L'f.'.CO
1973
21 .50
1C.. 60
37.00
1974
21.50
15.60
17.00
1975 i 1976
40.60
40.60
:o.ioa
-36. 30
54.40
60.40"
h
-36 . 30
r ^ " 0
1977
^0.60
6'i.4Cd
-36. 30U
64.70
01
>' 1 U:rt afiv.- i fcr 19/b-'7 ,';y,'
Offsets for reduced renuirenents for nresent type tune-uos and exhaust systen "iai ntenance
177
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Table 11-7. ANNUALIZED UNIT COST INCREASES FOR HEAVY-DUTY TRUCKS-
(dollars)
Cost
type
Gasoline engines
Increased fuel usea
Maintenance
Total operating and
maintenance
penalties
Annualized control,
investment costs
Total annual i zed
cost increase
Diesel engines
Increased fuel usec
Annualized control,
investment costs '
Total annual i zed
cost increase
Model year
1968-69
None
None
None
None
None
None
None
None
1970-72
1.80
1.80
1973
9.90
9.90
8.20
18.10
None
None
None
1974
9.90
9.90
8.20
18.10
None
None
None
1975
68.40
31.70
100.10
48.40
148.50
222.00
200.00
422.00
1976
68.40
31.70
100.10
48.40
148.50
222.00
200.00
422.00
1977
68.40
31.70
100.10
48.40
148.50
222.00
200.00
422.00
aBased on average of 1380 gal. of fuel per year as baseline, fuel at 33<£/gal.
Based on 5-year engina life, annualized straight-line basis.
cBased on average of 10,660 gal. of fuel per year as baseline, fuel at 26ii/gal.
Total increase in emission cont.ro] hardware price from an uncontrolled 1968
automobile to a 1976 dual-catalyst system (needed to meet the 1977 model-year
standards') controlled automobile has been calculated by the National Acadeir.y of
Sciences to he $373 per automobile; EPA predicts $327.50; industry estimates
range from $298 to $428/1 Operating and maintenance costs (Tables 11-6 and 11-7)
raise this per unit cost by another $260.
The per unit costs reported here are fcr control of carbon monoxide, hydrocar-
bon, and nitrogen oxide emissions. The cost of the hydrocarbon control alone can
be calculated, as mentioned earlier, based on the control hardware cost data
reported by the National Academy of Science/ and on maintenance and fuel cost
data reported by FiPA (see Table 11-6). In these calculations, hardware needed
for hydrocarbon control was differentiated from hardware needed for carbon monoxide
and nitrogen oxide control, and total hardware and maintenance costs were broken
down accordingly. Also, fuel economy loss due to hydrocarbon controls was taken
to be SO percent of the loss due to all controls for the 1971-1972 models, 58
percent for the 1973-1974 models, and 67 percent for the 1975 models (before the
1-year extension of the emission standards was granted). Based on these data
and assumptions, the annual cumulative pcr-auto costs of hydrocarbon emission
control in the United States were estimated and are given in Table 11-8.
178
-------
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179
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IMPACT OF ABATEMENT ON ECONOMY
The desirable and intended impact of control is to reduce pollution costs.
Such tradeoffs between damage costs and abatement costs are illustrated by the
data of Table 11-9, which summarizes the original estimates of costs associated
with implementing the Clean Air Act of 1970. Based on the incomplete data
available, total damage costs of air pollution in 1977 with no controls are
expected to be about $25 billion. With controls, damages are estimated at $11
billion, and abatement costs are $12 billion, resulting thus in savings of $2
billion. From the data of Table 11-9, it appears that mobile source emission con-
trols are not cost effective. This tradeoff estimate, however, is inaccurate since
the damage costs do not include many of the damages resulting from the primary auto
emissions (carbon monoxide, nitrogen oxides, and hydrocarbons).
Table 11-9. ESTIMATED COST EFFECTS OF THE CLEAN AIR ACT
FOR FISCAL YEAR 19771
(billions of 1970 dollars)
Emission source
Mobile
Stationary fuel
consumption
Industrial orocesses
Miscel laneous
Total
Damage costs
Without
controls
2.2a
12.8
7.0
2.3
24.3
With
controls
1.2a
3.4
3.7
2.3
,10.6
Control costs
8.4
2.5
1.2
0
12.1
Health damage costs from carbon monoxide, nitrogen oxide, and
hydrocarbon emissions are not included due to lack of data.
Beyond the initial cost effect of air pollution abatement are the secondary
impacts that spread into other sectors of the economy. Such impacts have both
negative and positive effects. Thus, abatement costs raise the prices of pollu-
tion-causing articles and services, thus reducing sales of such articles and
servicesa negative effect. On the positive side, the demand for pollution
abatement equipment induces new investment and higher employment, thus creating
higher income and more spending, The Council on Environmental Quality, the
Environmental Protection Agency, and the Commerce Department have made several
attempt? to quantify these impacts of pollution control throughout the entire
economy. First results showed that the overall impact on the economy was minor.
Another impact of control is on energy consumption. The emission control
methods presently used by the U.S. automobile manufacturers have caused an increase
in fuel consumption of 7 to 15 percent. However, it is not certain whether present
180
-------
fuel penalties will continue with emission control technology now being developed
for future use.
Finally, it is expected that the emission standards and control actions will
have an impact on the balance of international trade. Initial studies indicated
a maximum negative impact on U.S. net exports between $2 billion and $3 billion
during the peak years of 1975 and 1976. However, these projections are clearly
overestimated because the economic model used made no allowances for foreign
pollution abatement regulations. Other estimates indicate the U.S. net exports
to rise slightly in spite of increased pollution control costs. Overall, the
information available is not sufficiently complete to permit a reliable estimation
of pollution abatement effects on international trade.
REFERENCES FOR CHAPTER 11
1. Environmental Quality1973. The fourth annual report of the Council
of Environmental Quality, Washington, D.C. Sept. 1973.
2. Babcock, L.R., Jr. and N.L. Nagda. Cost Effectiveness of Emission
Control. J. Air Pollut. Contr. Assoc. 2_3(3):173, March 1973.
3. The Social and Economic Costs and Benefits of Compliance with the Auto
Emission Standards Established by the Clean Air Amendments. An interim report
prepared for the Committee in Public Works, U.S. Senate, by National Academy of
Sciences, Washington, D.C. Serial No. 93-16. Dec. 1973.
4. T.E. Waddell. The Economic Damages of Air Pollution. U.S. Environmental
Protection Agency, Research Triangle Park, N.C. (In press, 1974.}
5. The Economics of Clean Air. Annual Report of the Administrator of the
U.S. Environmental Protection Agency to the U.S. Congress, Washington, D.C.
March 1972.
6. The Economic Impact of Pollution Control upon the General Economy: A
Continuation of Previous Work. Chase Econometric Associates, Inc. October 1972.
(Unpublished report prepared for the U.S. Environmental Protection Agency, Research
Triangle Park, N.C.)
7. d'Arge, R.C. and A.V. Kneese. Environmental Quality and International
Trade. University of California. Riverside, Calif. June 1972.
181
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-600/3-76-017
3. RECIPIENT'S ACCESSION-NO.
4 TITLE AND SUBTITLE
Photochemical Oxidants in the Ambient Air of the
United States
5 REPORT DATE- .
February 1976
6. PERFORMING ORGANIZATION CODE
/ AUTHORiS)
Dr. Basil Dimitriades
8. PERFORMING ORGANIZATION REPORT NO.
9 PtRPORMING ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Research and Development
Environmental Sciences Research Laboratory
Research Triangle Park, N. C. 27711
12. SPONSORING AGENCY NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
1A1008
11. CONTRACT/GRANT NO.
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA-ORD
15 SUPPLEMENTARY NOTES
16. ABSTRACT
The problem of photochemical oxidants in the ambient air of the United States is
examined with respect to its nature, magnitude, and present day control. Concentra-
tion levels of ozone, nitrogen dioxide, peroxyacetyl nitrate, and other photochemi-
cally formed pollutants are surveyed, and their effects on human health, vegetation,
and materials, as well as their economic impacts, are discussed. Oxidant precursors,
hydrocarbons, and nitrogen oxides are reviewed with regard to ambient concentrations
and emission rates and in terms of chemical reactions that produce oxidants. Oxidant
control efforts are discussed with specific emphasis placed on scientific approaches,
emission control methods, costs of control, and control legislation.
17.
a.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
*Reviews
Air Pollution
Oxidizers
*0zone
^'Concentration (composition)
*Chemical reactions
b. IDENTIFIERS/OPEN ENDED TERMS
United States
COSATI Field/Group
05B
13B
11G
07B
07D
13 DISTRIBUTION STATEMENT
Available to public through National
Technical Information Service, Springfield
Virginia 22161
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
192
20. SECURITY CLASS (Thispagel
' UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
182
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