EPA-600/3-77-001a
January 1977
Ecological Research Series
INTERNATIONAL CONFERENCE
ON PHOTOCHEMICAL OXIDANT
POLLUTION AND ITS CONTROL
I
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields
The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal
species, and materials. Problems are assessed for their long- and short-term
influences. Investigations include formation, transport, and pathway studies to
determine the fate of pollutants and their effects. This work provides the technical
basis for setting standards to minimize undesirable changes in living organisms
in the aquatic, terrestrial, and atmospheric environments.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/3-77-OOU
January 1977
INTERNATIONAL CONFERENCE
ON
PHOTOCHEMICAL OXIDANT POLLUTION
AND ITS CONTROL
Proceedings: Volume I
Hosted by the United States Environmental Protection Agency
September 12-17, 1976
Raleigh, North Carolina
Coordinated by the Triangle Universities
Consortium on Air Pollution
with the patronage of
Organization for Economic Cooperation and Development
Edited by
Basil Dimitriades
Environmental Sciences Research Laboratory
Research Triangle Park, N. C. 27711
Environmental Sciences Research Laboratory
Office of Research and Development
U. S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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DISCLAIMER
This report has been reviewed by the Environmental Sciences Research
Laboratory, U.S. Environmental Protection Agency, and approved for pub-
lication. Approval does not signify that the contents necessarily reflect
the views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
In general, the texts of the papers included in this report have been
reproduced in the form submitted by the authors.
Any papers included in the Program arid not included herein were not
submitted for publication.
11
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PREFACE
Since the late 1940's when the first studies of atmospheric pollution
began, photochemical smog has been evolving into a full-fledged problem with
an enormously strong and complex impact upon man's lifestyle. Smog is no
longer a subject of mainly academic interest. Its presence and consequences
are now fully felt by the layman and perhaps most painfully by the automobile
user. The use of automobiles is being restricted in the large urban centers
in the U. S., and even more restrictive measures including gasoline rationing
have been considered. The merits of the economic incentives traditionally
associated with industrial growth are now being seriously questioned, and
pressures grow stronger for a review and a more realistic appraisal of the
environmental, energy, and industrial growth priorities. Such a strong and
multifaceted impact of the photochemical pollution problem makes it imperative
that all judgment regarding the causes, occurrence, and solution or alleviation
of the problem be made responsibly and with the highest degree of confidence.
Thus, while it is extremely important that the health and welfare of the people
be protected, it is equally important to ascertain that such protection is
really achieved and that the health danger is not traded for other equally
bad or worse problems.
Intensive studies conducted in the past 3-4 years have resulted in an
abundance of suggestive evidence that in part supported and in part refuted
the earlier understanding, but did not resolve all existing issues. Thus, the
international scientific community is still divided on the issue of the justi-
fication of the 0.08-ppm ambient air quality standard for oxidant, one objection
arising from the questionable achievability of such a standard. A newly revived
issue of major importance pertains to the relative roles of the hydrocarbon
and nitrogen oxide precursors in the urban and rural oxidant formation processes.
The viewpoint of the U.S. Environmental Protection Agency supporting maximum
control of the hydrocarbon and limited control of the N0x emissions is challenged
in several Conference papers. More specific issues raised by the new evidence,
and debated in the Conference, are the achievability of the ambient oxidant
standard, the role of stratospheric ozone, the role of the natural ozone
precursors, the utility of current air quality simulation models, and the
significance of short- and long-range photochemical pollution transport.
Aside from the debate on the above issues, the Conference will gather and
bring into focus the latest developments in the areas of physical-chemical
research methodology, biological effects of oxidants, and emission control
methods. It was felt that inclusion of such widely diverse subject areas
would be essential for examining the balance, rationality, and effectiveness
of the entire oxidant control effort.
m
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The Conference Is expected to be extremely valuable to the U.S. Environ-
mental Protection Agency in that it will provide a forum for presenting the
Agency's evolving viewpoint on oxidant control strategies, and for sounding out
scientific receptivity to this viewpoint. The Conference is of value also to
the international community of scientists and government administrators in
that it will provide an opportunity for comparing the problems, experiences,
and control policies of one country with those of others. Considering the now
established international range of pollution transport, and the implications
of oxidant-related control upon international trade, such interaction among
countries is more than justified. For these reasons the organization of the
Conference was undertaken by the U.S. Environmental Protection Agency, with
the patronage of the Organization for Economic Cooperation and Development.
B. Dimitriades
IV
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CONTENTS
PREFACE Hi
ACKNOWLEDGMENT xv
SESSION 1 - ANALYTICAL METHODS FOR OXIDANTS AND 1
PRECURSORS - I
ChcuAman: K.H. Becker
1-1 METHODOLOGY FOR STANDARDIZATION OF ATMOSPHERIC 3
OZONE MEASUREMENTS
J.A. Hodgeson, E.E. Hughes, W.P. Schmidt, and
A.M. Bass
1-2 ULTRAVIOLET PHOTOMETER FOR OZONE CALIBRATION 13
A.M. Bass, A.E. Ledford, Jr., and J.K. Whittaker
1 -3 HYDROCARBON AND HALOCARBON MEASUREMENTS: 19
SAMPLING AND ANALYSIS PROCEDURES
R.B. Denyszyn, L.T. Hackworth, P.M. Grohse, and
D.E. Wagoner
SESSION 2 - ANALYTICAL METHODS FOR OXIDANTS AND 29
PRECURSORS - II
ChcUsunan: K.H. Becker
2-1 A NEW CHEMILUMINESCENT OLEFIN DETECTOR FOR 31
AMBIENT AIR
K.H. Becker, U. Schurath, and A. Wiese
2-2 GC-CHEMILUMINESCENCE METHOD FOR THE ANALYSIS OF 41
AMBIENT TERPENES
R.L. Seila
2-3 MEASUREMENTS OF SULFATE, INORGANIC GASEOUS NITRATE 51
AND OTHER CONSTITUENTS IN THE ATMOSPHERE
T. Okita
2-4 A PORTABLE INSTRUMENT FOR THE CALIBRATION OF OZONE 59
ANALYZERS BY OPTICAL ABSORPTION MEASUREMENTS
K.H. Becker, A. Heindrichs, and U. Schurath
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2-5 STATUS OF CALIBRATION METHODS FOR OZONE MONITORS 67
R.J. Paur, R.K. Stevens, and D.L. Flamm
SESSION 3 - SOURCES OF TROPOSPHERIC OZONE - I 73
ChjaAjma.ni R.A. Rasmussen
3-1 METEOROLOGICAL CONDITIONS CONDUCIVE TO HIGH LEVELS 75
OF OZONE
T.R. Karl and G.A. DeMarrais
3-2 OZONE IN RURAL AND URBAN AREAS OF NEW YORK STATE - ..., 89
PART I
P.Coffey, W. Stasiuk, and V. Mohnen
3-3 OZONE MEASUREMENT AND METEOROLOGICAL ANALYSIS OF 97
TROPOPAUSE FOLDING
V.A. Mohnen, A. Hogan, E. Danielsen, and P. Coffey
3-4 METEOROLOGICAL FACTORS CONTROLLING PHOTOCHEMICAL 109
POLLUTANTS IN SOUTHEASTERN NEW ENGLAND
R.A. Dobbins, J.L. Nolan, J.P. Qkolowicz, and
A.J. Gilbert
SESSION 4 - SOURCES OF TROPOSPHERIC OZONE - II ......................... 119
R.A. Rasmussen
4-1 AN ASSESSMENT OF THE CONTINENTAL LOWER TROPOSPHERIC .......... 121
OZONE BUDGET
R. Chatfield and R.A. Rasmussen
4-2 URBAN KINETIC CHEMISTRY UNDER ALTERED SOURCE CONDITIONS ..... 137
L.A. Farrow, I.E. Graedel , and T.A. Weber
4-4 THE EFFECT OF OZONE LAYERS ALOFT ON SURFACE '. . . . ............... 145
CONCENTRATIONS
T.N. Jerskey, T.B. Smith, and W.H. White
SESSION 5 - SOURCES OF TROPOSPHERIC OZONE - III ......................... 155
ChcuAman: R.A. Rasmussen
5-1 OZONE CONCENTRATIONS IN POWER PLANT PLUMES: .... .............. 157
COMPARISON OF MODELS AND SAMPLING DATA
T.W. Tesche, J.A. Ogren, and D.L. Blumenthal
5-2 OZONE AND NITROGEN OXIDES IN POWER PLANT PLUMES ............. 173
D. Hegg, P.V. Hobbs, L. Radke, and H. Harrison
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5-3 THE ANALYSIS OF GROUND-LEVEL OZONE DATA FROM 185
NEW JERSEY, NEW YORK, CONNECTICUT, AND MASSACHUSETTS:
DATA QUALITY ASSESSMENT AND TEMPORAL AND
GEOGRAPHICAL PROPERTIES
W.S. Cleveland, B. Kleiner, J.E. McRae, and R.E. Pasceri
5-4 CHEMICAL AND METEOROLOGICAL ANALYSIS OF THE MESOSCALE 197
VARIABILITY OF OZONE CONCENTRATIONS OVER A SIX-DAY
PERIOD
W.D. Bach, Jr., J.E. Sickles, II, R. Denyszyn, and
1W.C. Eaton
5-5 OZONE AND HYDROCARBON MEASUREMENTS IN RECENT OXIDANT 211
TRANSPORT STUDIES
W.A. Lonneman
SESSION 6 - OZONE/OXIDANT TRANSPORT - I 225
Chairman: A.P. Altshuller
6-1 TRANSPORT OF OZONE BY UPPER-LEVEL LAND BREEZE - AN 227
EXAMPLE OF A CITY'S POLLUTED WAKE UPWIND FROM ITS CENTER
E.K. Kauper and B.L. Niemann
6-2 OZONE FORMATION IN THE ST. LOUIS PLUME 237
W.H. White, D.L. Blumenthal, J.A. Anderson, R.B. Husar,
and W.E. Wilson, Jr.
6-3 LONG RANGE AIRBORNE MEASUREMENTS OF OZONE OFF THE 249
COAST OF THE NORTHEASTERN UNITED STATES
G.W. Siple, C.K. Fitzsimmons, K.F. Zeller, and
R.B. Evans
6-4 AIRBORNE MEASUREMENTS OF PRIMARY AND SECONDARY 259
POLLUTANT CONCENTRATIONS IN THE ST. LOUIS URBAN PLUME
N.E. Hester, R.B. Evans, F.G. Johnson, and
E.L. Martinez
6-5 OZONE IN HAZY AIR MASSES 275
R.B. Husar, D.E. Patterson, C.C. Paley and
N.V. Gillani
SESSION 7 - OZONE/OXIDANT TRANSPORT - II 283
Ckcuxman: A.P. Altshuller
7-1 THE TRANSPORT OF PHOTOCHEMICAL SMOG ACROSS THE 285
SYDNEY BASIN
R. Hyde and G.S. Hawke
7-2 OXIDANT LEVELS IN ALBERTA AIRSHEDS 299
H.S. Sandhu
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7-3 AN INVESTIGATION OF LONG-RANGE TRANSPORT OF 307
OZONE ACROSS THE MIDWESTERN AND EASTERN
UNITED STATES
G.T. Wolff, P.J. Lioy, G.D. Wright, R.E. Meyers,
and R.T. Cederwall
7-4 OXIDANT AND PRECURSOR TRANSPORT SIMULATION IN 319
THE RESEARCH TRIANGLE INSTITUTE SMOG CHAMBERS
J.E. Sickles, II, L.A. Ripperton, and W.C. Eaton
7-5 OZONE EPISODES ON THE SWEDISH WEST COAST 329
P. Grennfelt
SESSION 8 - IMPACT OF STRATOSPHERIC OZONE 339
Ckcusunan: R. Guicherit
8-1 OZONE OBSERVATIONS IN AND AROUND A MIDWESTERN 341
METROPOLITAN AREA.
G. Huffman, G. Haering, R. Bourke, P. Cook, and M. Sillars
8-2 A "TEXAS SIZE" OZONE EPISODE TRACKED TO ITS SOURCE 353
J.W. Hathorn, III and H.M. Walker
8-3 APPLICATION OF 1960's OZONE SOUNDING INFORMATION 381
TO 1970's SURFACE OZONE STUDIES
P.R. Sticksel
8-4 THE ROLE OF STRATOSPHERIC IMPORT ON TROPOSPHERIC 393
OZONE CONCENTRATIONS
E.R. Reiter
SESSION 9 - THEORIES ON RURAL OZONE/OXIDATES .......................... 411
B. Dimitn'ades
9-1 RESEARCH TRIANGLE INSTITUTE STUDIES OF HIGH OZONE ........... 413
CONCENTRATIONS IN NONURBAN AREAS
L.A. Ripperton, J.J.B. Worth, F.M. Vukovich,
and C.E. Decker
9-2 IMPORTANT FACTORS AFFECTING RURAL OZONE CONCENTRATION ....... 425
F.L. Ludwig, W.B. Johnson, R.E. Ruff, and
H.B. Singh
9-3 A MECHANISM ACCOUNTING FOR THE PRODUCTION OF OZONE IN ....... 439
RURAL POLLUTED ATMOSPHERES
M. Antell
9-4 NET OZONE FORMATION IN RURAL ATMOSPHERES .................... 451
T.Y. Chang and B. Weinstock
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9-5 THE KINETIC OZONE PHOTOCHEMISTRY OF NATURAL ................. 467
AND PERTURBED NONURBAN TROPOSPHERES
T.E. Graedel and D.L. Allara
SESSION 10 - PHYSIOLOGICAL EFFECTS OF OXIDANTS - I .................... 475
J. Knelson
10-1 ON THE RELATIONSHIP OF SUBJECTIVE SYMPTOMS TO ............... 477
PHOTOCHEMICAL OXIDANTS
I. Mizoguchi, K. Makino, S. Kudou and R. Mikami
10-2 EFFECTS OF OZONE PLUS MODERATE EXERCISE ON PULMONARY ........ 495
FUNCTION IN HEALTHY YOUNG MEN
B. Ketcham, S. Lassiter, E. Haak, and J.H. Knelson
10-3 EFFECTS OF OZONE AND NITROGEN DIOXIDE EXPOSURE OF ........... 505
RABBITS ON THE BINDING OF AUTOLOGOUS RED CELLS TO
ALVEOLAR MACROPHAGES
J.G. Hadley, D.E. Gardner, D.L. Coffin, and D.B. Menzel
10-4 RELATIONSHIPS BETWEEN NITROGEN DIOXIDE CONCENTRATION, ....... 513
TIME, AND LEVEL OF EFFECT USING AN ANIMAL INFECTIVITY
MODEL
D.E. Gardner, F.J. Miller, E.J. Blommer, and
D.L. Coffin
10-5 DEVELOPMENT OF OZONE TOLERANCE IN MAN ....................... 527
M. Hazucha, C. Parent, and D.V. Bates
SESSION 11 - PHYSIOLOGICAL EFFECTS OF OXIDANTS - II 543
Ckalfiman: J. Knelson
11-1 TOXIC INHALATION OF NITROGEN DIOXIDE IN CANINES 545
T.L. Guidotti and A.A. Liebow
11-2 THE EFFECT OF OZONE ON THE VISUAL EVOKED POTENTIAL 555
OF THE RAT SUPERIOR COLLICULUS AND VISUAL CORTEX
B.W. Berney, R.S. Dyer, and Z. Annau
11-3 HEALTH EFFECTS OF SHORT-TERM EXPOSURES TO N02-03 565
MIXTURES
E. Ehrlich, J.C. Findlay, J.D. Fenters, and
D.E. Gardner
11-4 BIOCHEMICAL INDICES OF NITROGEN DIOXIDE INTOXICATION 577
OF GUINEA PIGS FOLLOWING LOW LEVEL-LONG TERM EXPOSURE
B. Menzel, M.B. Abou-Donia, C.R. Roe, R. Ehrlich,
D.E. Gardner, and D.L. Coffin
IX
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11-5 BENEFIT EFFECTIVE OXIDANT CONTROL 589
R.A. Bradley, M. Dole, Jr., W. Schink, and S. Storelli
SESSION 12 - EFFECTS OF OXIDANTS ON VEGETATION - I 599
Chairman: W.W. Heck
12-1 OZONE INDUCED ALTERATIONS IN PLANT GROWTH AND 601
METABOLISM
D.T. Tingey
12-2 OXIDANT LEVELS ON REMOTE MOUNTAINOUS AREAS OF 611
SOUTHWESTERN VIRGINIA AND THEIR EFFECTS ON
NATIVE WHITE PINE (PINUS STROBUS L.)
E.M. Hayes, J.M. Skelly, and C.F. Croghan
12-3 THE EFFECTS OF OZONE ON PLANT-PARASIT1C NEMOTODES 621
AND CERTAIN PLANT MICROORGANISM INTERACTIONS
D.E. Weber
SESSION 13 - EFFECTS OF OXIDANTS ON VEGETATION - II 633
Chairman: W.W. Heck
13-1 GROWTH RESPONSE OF CONIFER SEEDLINGS TO LOW OZONE 635
CONCENTRATIONS
R.G. Wilhour and G.E. Neely
13-2 MACROSCOPIC RESPONSE OF THREE PLANT "SPECIES" TO 647
OZONE, PAN, OR OZONE + PAN
D.D. Davis and R.J. Kohut
13-3 RELATIVE SENSITIVITY OF EIGHTEEN HYBRID COMBINATIONS 655
OF PINUS TAEDA L. TO OZONE
L.W. Kress and J.M. Skelly
13-4 EFFECTS OF OZONE AND SULFUR DIOXIDE SINGLY AND IN 663
COMBINATION ON YIELD, QUALITY, AND N-FIXATION OF
ALFALFA
G.E. Neely, D.T. Tingey and R.G. Wilhour
SESSION 14 - REACTIVITY AND ITS USE IN OXIDANT-RELATED CONTROL 675
Chairman: J.G. Calvert
14-1 MULTIDAY IRRADIATION OF NOX ORGANIC MIXTURES 677
W.A. Glasson and P.H. Wendschuh
14-2 HYDROCARBON REACTIVITY AND THE ROLE OF HYDROCARBONS 687
OXIDES OF NITROGEN AND AGED SMOG IN THE PRODUCTION
OF PHOTOCHEMICAL OXIDANTS
J.N. Pitts, A.M. Winer, G.J. Doyle, K.R. Darnall and A.C. Lloyd
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14-3 APPLICATION OF REACTIVITY CRITERIA IN OXIDANT- 705
RELATED EMISSION CONTROL IN THE USA
B. Dimitriades and S.B. Joshi
14-4 PHOTOCHEMICAL REACTIVITY CLASSIFICATION OF 713
HYDROCARBONS AND OTHER ORGANIC COMPOUNDS
F.F. Farley
SESSION 15 - ATMOSPHERIC CHEMISTRY AND PHYSICS 727
Chairman: J.G. Calvert
15-1 DECOMPOSITION OF CHLORINATED HYDROCARBONS UNDER 729
SIMULATED ATMOSPHERIC CONDITIONS
F. Korte and H. Parlar
r
15-2 PHOTOOXIDATION OF THE TOLUENE-N02-02-N2 SYSTEM IN A 737
SMALL SMOG CHAMBER
H. Akimoto, M. Hoshino, G. Inoue, M. Okuda , and
N. Washida
15-3 THE CHEMISTRY OF NATURALLY EMITTED HYDROCARBONS 745
B.W. Gay, Jr. and R.R. Arnts
15-4 MEASUREMENT OF PHOTONS INVOLVED IN PHOTOCHEMICAL 753
OXIDANT FORMATION
D.H. Stedman, R.B. Harvey, and R.R. Dickerson
15-5 ACTIVE SOLAR FLUX AND PHOTOLYTIC RATE IN THE 763
TROPOSPHERE
J.T. Peterson, K.L. Demerjian, and K.L. Schere
SESSION 16 - MATHEMATICAL MODELS OF OZONE/OXIDANT AIR QUALITY - I .... 775
Chairman: K. Deme rj i a n
16-1 PHOTOCHEMICAL AIR QUALITY SIMULATION MODELLING: 777
CURRENT STATUS AND FUTURE PROSPECTS
K.L. Demerjian
16-2 THE SYSTEMS APPLICATIONS, INCORPORATED URBAN AIRSHED 795
MODEL: AN OVERVIEW OF RECENT DEVELOPMENTAL WORK
S.D. Reynolds
SESSION 17 - MATHEMATICAL MODELS OF OZONE/OXIDANT AIR QUALITY - II ... 803
Chairman: K. Demerjian
17-1 A SURVEY OF APPLICATIONS OF PHOTOCHEMICAL MODELS 805
J.E. Summerhays
XI
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17-2 TESTS OF THE DIFKIN PHOTOCHEMICAL DIFFUSION MODEL 817
USING LOS ANGELES REACTIVE POLLUTANT PROGRAM DATA
G.H. Taylor and A.Q. Eschenroeder
17-3 DEVELOPMENT OF A MARKET CHAIN MODEL FOR PHOTOCHEMICAL 827
OXIDANT PREDICTION
J.R. Martinez
17-4 A PRELIMINARY INVESTIGATION OF THE EFFECTIVENESS OF AIR .... 837
POLLUTION EMERGENCY PLANS
W.F. Dabberdt and H.B. Singh
SESSION 18 - OXIDANT-PRECURSOR RELATIONSHIPS AND THEIR INTERPRETATION . 849
IN TERMS OF OPTIMUM STRATEGY FOR OXIDANT CONTROL - I
ChcuAman: J.N. Pitts
18-1 A "J" RELATIONSHIP FOR TEXAS 851
H.M. Walker
18-2 AN ALTERNATIVE TO THE APPENDIX-J METHOD 871
FOR CALCULATING OXIDANT- AND N02- RELATED CONTROL
REQUIREMENTS
B. Dimitriades
18-3 COMBINED USE OF MODELING TECHNIQUES AND SMOG CHAMBER 881
DATA TO DERIVE OZONE-PRECURSOR RELATIONSHIPS
M.C. Dodge
18-4 OUTDOOR SMOG CHAMBER STUDIES: EFFECT OF DIURNAL 891
LIGHT DILUTION AND CONTINUOUS EMISSION ON OXIDANT
PRECURSOR RELATIONSHIPS
H.E. Jeffries, R. Kamens, D.L. Fox, and B. Dimitriades
18-5 USE OF TRAJECTORY ANALYSIS FOR DETERMINING EMPIRICAL 903
RELATIONSHIPS AMONG AMBIENT OZONE LEVELS AND METEOROLOGICAL
AND EMISSION VARIABLES
E.L. Meyer, Jr., W.D. Freas, III, J.E. Summerhays, and
P.L. Youngblood
SESSION 19 - OXIDANT-PRECURSOR RELATIONSHIPS AND THEIR 915
INTERPRETATION IN TERMS OF OPTIMUM STRATEGY FOR
OXIDANT CONTROL - II
CficuAman: E.L. Meyer
19-1 REPORT ON OXIDANTS AND THEIR PRECURSORS IN CANADA 917
L. Shenfeld
19-2 PRECURSOR CONCENTRATION AND OXIDANT FORMATION IN SYDNEY 927
G.H. Allen, K. Post, B.S. Haynes, and R.W. Bilger
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19-3 SMOG POTENTIAL OF AMBIENT AIR, SAMPLED AT DELFT ............ 943
NETHERLANDS: THE EFFECT OF INCREASING NOX CONCENTRATION
J. van Ham, and H. Nieboer
19-4 SUMMARY: A PRELIMINARY INVESTIGATION OF EXPECTED .......... 955
VISIBILITY IMPROVEMENTS IN THE LOS ANGELES BASIN FROM
OXIDANT PRECURSOR GASES AND PARTICULATE EMISSION CONTROLS
C.S. Burton, T.N. Jerskey, and S.D. Reynolds
SESSION 20 - CONTROL OF OXIDANT PRECURSOR EMISSIONS - I .............. 969
R.W. Bilger
20-1 TRAFFIC MANAGEMENT AS A MEANS OF OXIDANT PRECURSOR ......... 971
CONTROL FROM LOW-SPEED SATURATED TRAFFIC
R.B. Hamilton and H.C. Watson
20-3 CONTROL OF VEHICLE REFUELING EMISSIONS ..................... 989
A.M. Hochhauser and L.S. Bernstein
SESSION 21 - CONTROL OF OXIDANT PRECURSOR EMISSIONS - II 1001
Chainman: R.W. Bilger
21-1 NOX CONTROL TECHNOLOGY FOR STATIONARY SOURCES 1003
G.B. Martin and J.S. Bowen
21-2 EMISSION ESTIMATES OF N02 AND ORGANIC COMPOUNDS FROM 1015
COAL-FIRED BED COMBUSTION
P.E. Fennelly
21-3 EMISSIONS ASSESSMENT OF THE CHEMICALLY ACTIVE FLUID 1025
BED (CAFB) PROCESS
A.S. Werner, R.M. Bradway, D.F. Durocher, S.L. Rakes,
and R.M. Statnick
21-4 NOX CONTROL BY ABSORPTION 1035
G. Sakash
21-5 DEVELOPMENT OF A LOW EMISSIONS PROCESS FOR ETHYLENE 1039
DICHLORIDE PRODUCTION
W.S. Amato, B. Bandyopadhyay, B.E. Kurtz, and R.H. Fitch
SESSION 22 - AIR QUALITY AND EMISSION TRENDS 1051
Chcusuman: R.E. Neligan
22-1 THE IMPACT OF EMISSIONS CONTROL TECHNOLOGY ON 1053
PASSENGER CAR HYDROCARBON EMISSION RATES AND PATTERNS
F. Black
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22-2 CONTROL OF OXIDANTS IN SYDNEY 1069
D. Iverach and M.G. Mowle
22-3 OXIDANT AND PRECURSOR TRENDS IN THE METROPOLITAN ., 1077
LOS ANGELES REGION
J. Trijonis, T. Peng, G. McRae, and L. Lees
22-4 COMPARISON OF PAST AND PROJECTED TRENDS IN OXIDANT 1095
CONCENTRATIONS AND HYDROCARBON EMISSIONS
R.M. Angus, E.W. Finke, and J.H. Wilson
22-5 TRENDS IN AMBIENT LEVELS OF OXIDANT AND THEIR POSSIBLE 1103
UNDERLYING EXPLANATIONS
E.L. Martinez, N.C. Possiel, E.L. Meyer, L.G. Wayne,
K.W. Wilson, and C.L. Boyd
SESSION 23 - ON THE OZONE/OXIDANT CONTROL STRATEGY IN U.S 1113
CkcuJunan: A.B. Bromley
23-1 TRENDS IN PHOTOCHEMICAL OXIDANT CONTROL STRATEGY 1115
J. Padgett
23-2 PROBLEMS WITH CONVERTING STATE-OF-THE-ART PHOTOCHEMISTRY ... 1123
TO STATE LEVEL CONTROL STRATEGIES
W. Bonta and J. Paisie
23-3 OXIDANT CONTROL UNDER SECTION 110 OF THE CLEAN AIR ACT 1135
J.L. Pearson
23-4 OXIDANT CONTROL STRATEGY: RECENT DEVELOPMENTS 1143
B. Dimitriades
23-5 CONTROL REGULATIONS FOR STATIONARY SOURCES OF HYDROCARBONS . 1155
IN THE UNITED STATES
R.T. Walsh
PREPARED COMMENTS ON JAPANESE PHOTOCHEMICAL AIR QUALITY .... 1167
STANDARDS AND CONTROL STRATEGIES
Professor R. Kiyoura
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ACKNOWLEDGMENT
The assistance of the Conference Program Committee members in organizing
the technical program of the Conference is gratefully acknowledged. Program
Committee members were: Dr. A.P. Altshuller, EPA, USA (Chairman); Dr. K.H.
Becker, U. Bonn, Germany; Dr. R.W. Bilger, U. Sydney, Australia; Dr. J.C.
Calvert, Ohio State U., USA; Dr. B. Dimitriades, EPA, USA; Mr. M. Feldstein,
San Francisco, Calif., USA; Mr. D.R. Goodwin, EPA, USA; Dr. R. Guicherit,
IGTNO, Netherlands; Dr. A.B. Bromley, OECD, France; Dr. M. Hashimoto, Environ-
ment Agency, Japan; Dr. J. Knelson, EPA, USA; Mr. R.E. Neligan, EPA, USA;
Mr. J. Padgett, EPA, USA; Dr. J.M. Pitts, U. California, USA; Dr. R.A. Rasmussen,
Washington State U., USA; and Mr. J.O. Smith, EPA, USA.
Conference arrangements were made by the Triangle Universities Consortium
on Air Pollution, under the direction of Dr. Laurence Kornreich, through
Research Grant #800916-0451.
xv
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SESSION 1
ANALYTICAL METHODS FOR OXIDANTS AND PRECURSORS - I
K.H. Becker
University of Bonn
-------
1-1
METHODOLOGY FOR STANDARDIZATION OF
ATMOSPHERIC OZONE MEASUREMENTS
J. A. Hodgeson, E. E. Hughes, W. P. Schmidt, and A. M. Bass*
ABSTRACT
?neJLAjminany i.nto.n.c.ompaAi^on& have, be.e.n made, among 4eue/ut£ te.chyu.qau
-the. cati.bnati.on o^ atmoApheAi.c ozone, monitor. The^e pfioce.duAeA -include, the. 1
peAce.nt neuJAal bu^eAe-d potai>i>iwn todi.de. method; a modification o& thiA
method e.mptoyi.ng 0.1 motan. bofii.c aci.d fiatheA than the. ph.oAph.ate bu^eA; a 3-
mzteA dou.bie.-be.am u£tAavi.olet photome^eA; and gat> pha&e. tittettion. The. potai>-
.6.a(.i7i i.odi.de. tie.aQe.nt with bosiic add gave a mo tie, Atabie. coiofi de.ve.l.opme,nt and
much cJLo&eA agn.e.e.mant w+tk the. ultAavtotct me,ai>uA.m than that obtaine.d
wtth the. nuWwJL bu^eAe,d x.e.age.nt. Ozone, catibtiation data with the. 3-mzte.ti
photomete.1 agreed within 1 and 2 poAcent with gad phaAe. tittLOtion and vJLtxa.-
vi-oLoJi photometAic ozone. me.ai>uAe.me.nt{> x.e.&pe.ctiveJ.y made, at the. EnviAonme.ntat
Px.ote.ctA.on Agency faacltity in Re-ieaAeh Triangle, Vatik, Mo-^th Canotina.
INTRODUCTION
Atmospheric ozone (03) monitors have normally been calibrated against
manual idometric techniques. The Environmental Protection Agency (EPA) refer-
ence calibration procedure employs a 1 percent neutral buffered potassium
iodide (NBK1) reagent (1). The accuracy and reproducibility of iodmetric
calibration procedures have been the subject of controversy for several years.
In a recent example which received considerable publicity, 03 measurements in
the city of Los Angeles were discovered to be consistently biased 30 percent
lower than measurements in surrounding counties. Laboratory studies conclu-
sively demonstrated that the cause of the bias was the use of two different
iodometric calibration procedures (2). In data obtained earlier this year and
not given here, simultaneous measurements were made by NBKI with two sets of
samplers off a common manifold. One set of results obtained indicated higher
levels than the other by 30 percent. By interchanging reagents and components
the difference appeared to be attributable to an impinger effect.
Current activities of the National Bureau of Standards (NBS) have focused
on the establishment of definitive methodologies for the accurate measurement
of 03 in the subpart per million range for the purpose of calibrating constant
03 generators. Analytical techniques currently under study are the EPA refer-
*National Bureau of Standards, Washington, D.C.
-------
ence method which is a modified iodometric procedure suggested by Flamm (3).
The method employs boric acid (BA) rather than phosphate buffer to control pH.
It measures 03 by ultraviolet (UV) absorption with a 3-meter double-beam
photometer (4), and by gas phase titration (GPT) of 03 with known concentra-
tions of nitric oxide (NO) (5). In this paper preliminary results of compari-
sons of these various 03 calibration techniques are presented.
EXPERIMENTAL
Some exceptions were employed to the iodometric technique as described.
Midget impingers were employed rather than the illustrated Mae West-type
bubblers. We employed a calibrated wet test meter downstream of the impingers
to determine the integrated volume of air sampled. This approach gives more
accurate and reproducible measurements of sample volume and does not require
fine flow control devices. Finally, we measured the absorbance at a fixed
time of 5 minutes after ending sample collection, because of a slow color
development observed in the NBKI reagent.
The wet test meter was calibrated gravimetrically by metering a fixed
volume of air from a compressed air cylinder and measuring the weight loss of
the cylinder with a Voland Precision Balance, Model 1115-DN. As an additional
check during one of the experiments, the wet test meter measurement was com-
pared with the volume measured by means of a soap bubble meter connected to
the inlet of the sample probe. These measurements agreed within 1 percent.
The spectrophotometer employed was a Beckman Model DU with a Guilford
Model 222 digital absorbance readout attachment. Checks on the photometric
accuracy have been made with NBS optical glass filters which have certified
absorbance values at specified wavelengths, This instrument has been periodic-
ally calibrated over several years with standard iodine solutions and has
remained constant with an average calibration factor of 9.812 microliters of
03 per absorbance unit. This value corresponds to an absorption coefficient
at 352 nonometers (nm) for molecular iodine of 24,930 liters/mole-cm (log
base 10). It compares favorably with a value of 24,890 j^ 100 reported in
another study (6).
The 03 source was a variable photolytic generator (7). The clean air
source was an Aadco Model 737 pure air generator. The reagents employed for
the NBKI procedure were ACS reagent grade granular KI, potassium dihydrogen
phosphate (KH2P04) certified ACS grade, and anhydrous disodium hydrogen phos-
phate (Na2HP04) analytical reagent. The boric acid modified reagent also con-
tained 1 percent KI of the same grade and 0.1 molar boric acid ACS-CP grade.
The spectrophotometer calibration curve showed no evidence of a measurable
iodine demand for either of the reagents.
The primary UV photometer was a 3-meter double-beam instrument specific-
ally constructed at NBS for the purpose of 03 calibration in the subparts per
million (ppm) range (4). The other UV system was a commercially available
Dasibi Monitor Model 1003-AH. In work at NBS this instrument has been used
primarily as a secondary transfer standard. The iodometric measurements and
-------
the UV photometric measurements are currently measured in different labora-
tories at NBS. The Dasibi instrument was used as a transfer standard to re-
late 03 measurements obtained in different laboratories. The GPT apparatus
has been described previously (5).
RESULTS AND DISCUSSION
EVALUATION OF THE BORIC ACID -POTASSIUM IODIDE REAGENT
There has been considerable lack of interlaboratory reproducibility in
application of the NBKI technique (8, 9). Paur (10) has summarized a number
of recent studies in which the relationship of measurements by the NBKI
technique was compared to measurements of 03 by UV photometry or by GPT. The
ratio of measurements by NBKI to 03 measurements by either of these techniques
has varied over a range from 1.0 to 1.2. One particular problem with this
iodometric technique is the slow color development observed after the 03 is
collected. Variable results are thus obtained if the time of the absorbance
measurement is not controlled.
Flamm (3) has recently performed an evaluation of iodometric techniques.
He used different buffering systems and observed an absence of the slow color
development either in the absence of a buffering agent or with the addition of
0.1 molar boric acid. The addition of 0.1 molar boric acid stabilizes the pH
of the solution at approximately 5.3. With the boric acid-KI (BAKI) reagent,
Flamm observed 03 measurements which were 20% lower than those obtained with a
NBKI reagent. Measurements with boric acid reagent were in essential agreement
with a Dasibi 03 photometer, modified such that 03 measurements with GPT
measurements are obtained (10).
We made a reagent as described by Flamm and studied the variation in ab-
sorbance after sample collection for both this reagent and the neutral NBKI
reagent. The results of this study are shown in Figure 1. An 03 sample of
0.35 ppm was collected for 10 minutes. The initial time in Figure 1 corres-
ponds to the end of the sample collection. The color obtained with the BAKI
reagent is indeed stable and the initial absorbance at 4 minutes is approxi-
mately 22 percent lower than that obtained in the NBKI reagent. The slow
color development observed with the NBKI is apparently a result of a secondary
reaction which slowly releases iodine.
Based on the results shown in Figure 1, 03 measurements with the NBKI
reagent are approximately 22 percent higher than with the boric acid modifica-
tion, assuming that the absorption coefficient of iodine is the same in both
reagents. The absorption coefficients of iodine in both reagents were meas-
ured, and the values obtained agreed within 1 percent. We observed a slow
color development in the unexposed BAKI reagent (0.003 to 0.27 in a few days)
when the absorbance was measured against distilled water as a reference.
Therefore, in all our analyses the absorbance measurement was made against
unexposed reagent as a blank.
-------
OQ
O
CO
OQ
.155
.150
.145
.140
.135
.130
.125
.120
l__ J
[03] = 0.35 ppm
O NEUTRAL BUFFERED Kl REAGENT
x Kl REAGENT WITH 0.1 M
BORIC ACID
XXXX X
I
10
20
30
t, min
40
50
60
Figure 1. Absorbance versus time after sample collection.
COMPARATIVE OZONE MEASUREMENTS
We want to emphasize in the beginning that the comparative data obtained
thus far are limited in number and that some of the absolute results reported
here are preliminary in nature. However, in spite of the preliminary nature
of these data, we present what has been obtained so far and feel that some
interesting conclusions can be drawn therefrom.
-------
The method for making the comparative measurements between different lab-
oratories was to use the Dasibi instrument as a transfer standard. In this
role the instrument has performed remarkably well in that it has maintained
essentially the same calibration with respect to iodmetric measurements in the
same laboratory over the past two years.
In the first comparisons given below, the Dasibi instrument was calibrated
with both KI reagents. In these comparative data the Dasibi meter readings
were converted to UV photometric 03 concentrations by Equation 1. The physi-
cal path length (71 cm) of the Dasibi is assumed to be the same as the otpical
path length. Also, the gas temperature inside the optical cell is assumed to
be the same as the measured temperature adjacent to the cell in the instrument.
6
10 P T
where: k = 308.6 crrf atirf (log base e), the 253.7 nm 03 absorption
coefficient at 273 K and 1 atmosphere.
L = 71 cm, the physical path length
P0J0 - 1 atm and 273 K
I = Dasibi Span Factor
Al = Dasibi Meter Reading
By substituting the above values, Equation 2 reduces to
[03]
DAS
- Al)
(2)
where T is the temperature inside the optical cell in kelvins and P is the
barometric pressure in mm mercury (Hg). For all the data in Table 1, the
value used for T (313 K) was approximately the average temperature of the
optical cells with the instrument in continuous operation.
The comparative data obtained are given in Table 1. The two idometric
reagents were used sequentially at the same 03 concentration and in the same
sampling apparatus.
Ozone concentrations measured by the NBKI technique, [03]NBKI> and 03
concentrations measured by the boric acid version, [03]g/\Ki, were both fitted
to the 03 Dasibi measurements by linear regression analysis.
[03]NBKI = (1.35+0.01) [03]DAS - (0.0015+0.003)
(1.10+0.01) [03]DAS + (0.001 +0.003)
[031BAKI
(3)
(4)
An excellent fit was obtained in both cases with no observable deviation from
linearity over the range of concentrations measured. The zero intercepts are
negligible. The relation between the two iodometric techniques is:
7
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TABLE 1. CALIBRATION OF NBS-DASIBI BY IODOMETRIC METHODS
Date
8-19-76
8-20-76
8-28-76
8-31-76
L ^ DAS, ppm
.289
.1725
.4955
.094
.233
.378
.130
.256
.3415
.343
.462
.201
.136
.476
.043
.119
.220
.323
.413
.412
Neutral Buffered
Kl , ppm
.383
.227
.668
.128
.313
.513
.176
.345
.458
Boric Acid
KI, ppm
.308
.181
.540
.108
.263
.422
—
.285
.380
.379
.507
.225
.153
.520
.046
.132
.241
.354
.462
.461
[03]NBKI = (1.23 ±0.03) [03]BAKI (5)
Flamm (3) observed a value of 1.20 for the ratio of NB to BA node-metric
measurements.
On days intervening with those on which iodometric measurements were
made, the Dasibi was calibrated against the NBS 3-meter double beam photometer,
Multiple analyses were made at several concentrations and the averaged data
are presented in Table 2.
8
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TABLE 2. CALIBRATION OF DASIBI WITH NBS
3-METER PHOTOMETER
[03] DAS, ppm
.02531
.0989
.1695
.2999
.3578
.5192
.5193
.5238
1.0010
1.4813
[0,] UV, ppm
.02157
.1001
.1733
.3006
.3688
.5265
.5245
.5372
1.0275
1.5045
A linear regression analysis of these data yielded,
[03]uv = (1.020+0.004) C03]DAS - (0.001 +0.002) (6)
This fit also showed good linearity with a negligible intercept. By combining
Equation 6 with the previous results, the following relations were obtained:
[03]NBKI = (1.32+0.02) [03]uv (7)
[03]BAKI = (1.08+0.02) [03]uv - (8)
In order to obtain additional comparative data, the NBS Dasibi instrument
was transported to EPA's Research Triangle Park facility. Simultaneous 03
comparisons were made at the EPA Environmental Monitoring and Support Labora-
tory, where concurrent evaluations of the GPT method and a modified Dasibi
photometer (10) were being performed. The comparison was made on a single date
(8/24/76) using a common 03 sampling manifold. The 03 generator was cali-
brated at several fixed levels by GPT, and simultaneous measurements were made
at these same levels with the NBS Dasibi and the modified EPA Dasibi photom-
eter. The data obtained are given in Table 3.
The NBS Dasibi 03 readings in the first column were corrected to equi-
valent 03 measurements with the NBS 3-meter photometer by Equation 6. Analy-
sis of the data yielded
[03]QpT, EPA = (1.01 + 0.02) [03]uv, NBS + (0.011 + 0.003) (9)
[03]uy, EPA = (0.98 + 0.01) [03]uv, NBS + (0.003 + 0.001) (10)
The agreement obtained on the whole was excellent among the three 03 measure-
ments, considering the limited time and data available during this one-day
comparison.
-------
TABLE 3. OZONE COMPARATIVE MEASUREMENTS AT
EPA-RESEARCH TRIANGLE PARK
[03]DAS, NBS,ppm E03], NBS.ppm IM. EPA,ppm
0.053
0.125
0.203
0.285
0.371
0.456
0.619
0.061
0.142
0.223
0.309
0.390
0.481
— — —
0.056
0.127
0.205
0.290
0.374
0.459
0.620
SUMMARY AND CONCLUSIONS
The UV photometric measurements obtained at NBS agree within 1 and 2 per-
cent using GPT and UV photometric measurements respectively obtained at EPA-
Research Triangle Park. This is in accord with results obtained in other
works (6, 10, 11). Additional comparative data will be obtained to attempt to
reduce the small uncertainty remaining.
The 1 percent KI solution with 0.1 molar BA gives a stable color develop-
ment. Measurements with this reagent are in closer agreement with UV photo-
metric measurements than measurements obtained with the neutral phosphate
buffered system. The BA iodometric measurements obtained here were 22 percent
lower than measurements by NBKI and 8 percent higher than 03 measurements
obtained with the NBS 3-meter photometer.
We regard the absolute relations of either of the iodometric measurements
to the UV photometric measurements as preliminary at this point and intend to
obtain more data before reaching final conclusions. The iodometric measure-
ments in relation to UV contradict to some degree other data which have been
obtained. Flamm (3) and Paur (unpublished data) have observed closer agree-
ment between the boric acid iodometric measurements and UV photometry. The
NBKI results obtained were 35 percent higher than UV^which is outside of the
1.0-1.2 ratio range observed in other studies (10). An apparent impinger
effect in analyses obtained by the NBKI procedure was noted in the introduc-
tory remarks. The impinger set used to obtain the data above was the set
which apparently produced higher results. Impinger effects have been reported
previously (9). Whether the impinger design or materials in fact affects the
results, and whether an impinger effect applies to the BAKI reagent are ques-
tions to be answered by additional studies.
10
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ACKNOWLEDGEMENT
The authors are particularly grateful to Mike Beard of the Quality Assur-
ance Branch, Environmental Monitoring and Support Laboratory, EPA-Research
Triangle Park for the assistance he provided in the 03 comparisons by ultra-
violet photometry and gas phase titration.
DISCLAIMER
Certain commercial equipment, instruments, or materials are identified in
this paper in order to adequately specify the experimental procedure. In no
case does such identification imply recommendation or endorsement by the
National Bureau of Standards, nor does it imply that the material or equipment
identified is necessarily the best available for the purpose.
REFERENCES
1. Environmental Protection Agency, Federal Register^, No. 228,
22384 (November 25, 1971 ).
2. "Comparison of Oxidant Calibration Procedures," Final Report
of Ad Hoc Oxidant Measurement Committee, California Air
Resources Board, Sancramento, CA., 3 February 1975.
3. Daniel Flamm, preliminary report to the Environmental
Sciences Research Laboratory, Environmental Protection Agency,
Research Triangle Park, N.C., August 1976.
4. A. M. Bass, A. E. Ledford, Jr., and J. K. Whittaker, "Ultra-
violet Photometer for Ozone Calibration," preprint for
International Symposium on Photochemical Oxidant Pollution
and Its Control, Raleigh, N.C., 12-17 September 1976.
5. K. A. Rehme, B. E. Martin, and J. A. Hodgeson, "Tentative Method
for the Calibration of Nitric Oxide, Nitrogen Dioxide and Ozone
Analyzers by Gas Phase Titration," EPA Report No. R2-73-246, U. S.
Environmental Protection Agency, Office of Research and Develop-
ment, Washington, D.C. 20460.
6. J. A. Hodgeson, C. B. Bennett, H. L. Kelly, and B. A. Mitchell,
"Ozone Measurements by lodometry, Ultraviolet Photometry and
Gas-Phase Titration," publication preprint, submitted to
Analytical Chemistry, 1976.
7. J. A. Hodgeson, R. K. Stevens, and B. E. Martin, ISA Trans.
11, 161 (1972).
8. J. B. Clements, "Summary Report: Workshop on Ozone Measurements
by the Potassium Iodide Method," EPA-650-4-75-007, U. S. Environ-
11
-------
mental Protection Agency, Office of Research and Development,
Washington, D.C. 20460, February 1975.
H. C. McKee, R. E. Childers, and Van B. Parr, "Collaborative Study
of Reference Method for Measurement of Photochemical Oxidants in
the Atmosphere (Ozone-Ethylene Chemiluminescent Method), EPA-650/
4-75-016, U. S. Environmental Protection Agency, Office of Research
and Development, Washington, D.C. 20460, February 1975.
12
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1-2
ULTRAVIOLET PHOTOMETER FOR OZONE CALIBRATION
A. M. Bass, A. E. Ledford, Jr., and J. K. Whittaker*
ABSTRACT
In order to provide, a ^acitcty far photometric, ozone me.abu.re.me.nts, me have.
designed and constructed a do able.-beam photometer fan ozone. concentration^ in
the range 0.025 - 1.0 ppm. The. bampte path tength in tkL& instrument. U> app/tox-
ima.te.lij 300 cm. The -instrument, measures changes -in ozon.ize.d-a.iA bampte tranb-
oft mercury radiation at 253.7 nanometers where the pkoto-a.bbon.ptA.on
-section o{, ozone. ha-s been welt determined.
Radiation at wavelengths other than 253.7 nanometers ^rom the mercury tamp
Ls removed by passing the. Light through a narrow-band interference fitter. The
tight is cottimot.ed and passed through a beam sptitter whi.ch directs approxi-
mat.ety equat intensity beams through the tivo celts. Clean air falows through one
celt into the ozone generator and then the. ozonize.d air {^tows through the second
cett. The tight beams are recombined on the fiace o^ a photo multiplier tube used
in the photon counting mode. A rotating chopper atlows the two beams to be.
detected se.quentAal.ty so tliat the transmissions o^ the two cetls may be directty
indicate thai measurements may be made at the 0.05 ppm te.veL with a
~j& }Q% or better.
INTRODUCTION
Tests
preci.si.on
The oxidation of iodide to iodine by ozone (03), in a properly prepared
solution of potassium iodide (KI), is the basis for the reference method speci-
fied by the Environmental Protection Agency (EPA) for the calibration of atmos-
pheric monitors (1). Recent comparative measurements (2) of the specific
iodometric methods have raised serious doubts as to the accuracy and reproduci-
bility of iodometric calibration procedures. The report of the California Air
Resources Board recommended that oxidant analyzers in California should be
calibrated by an ultraviolet (UV) photometric method rather than by the ioda-
metric method (2). In May 1975 this recommendation was accepted for that
state's monitoring network. At the present time the EPA is considering two
candidate methods, gas phase titration (GPT) and UV photometry as replacements
for the 1% neutral-buffered potassium iodide (NBKI) procedure, the current
Federal Reference Method for calibration of pollutant monitors (1).
In order to provide a facility at NBS for the measurement of 03 concentra-
tions, independently of GPT based on a nitric oxide (NO) standard, an ultra-
'"National Bureau of Standards, Washington, DC
13
-------
violet photometer with the desired sensitivity for 03 measurements at ambient
concentrations was set up (3). The desired performance for the photometer was
capability for measurement of 03 concentrations over the range 0.05 ^ 1.0 parts
per million (ppm) with an accuracy of approximately 0.005 ppm over the entire
range.
EXPERIMENTAL
The photometric measurement method is based on the application and the
validity of the Beer-Lambert Law:
1=1 exp
-273 cPkl
~TT~"
10 T
(1)
where:
c is given in ppm (parts per million by volume).
k is 308.5 cnT^atnT1 (log base e), the ozone absorption coefficient (4)
at 253.7 nm, 273 K, and 1 atmosphere.
L is the path length, cm.
P is the total pressure, atm.
T is the temperature of the cell, °K.
I/I is the transmittance (Tr) of the sample.
The design of the photometer is based principally on the accuracy require-
ment, 10% at 0.05 ppm. The quantities k, L, P, T appearing in the equation are
all known or can be measured to within 1 or 2 percent. Thus the accuracy of the
concentration measurement is mainly determined by the accuracy of the trans-
mittance measurement. The error in the transmittance measurement may be ex-
pressed as
AC
C
ATr
Tr
1
(2)
It was estimated that the transmittance measurement could be made with a pre-
of about .0005 by using photon counting. For a concentration of
cision
0.05 ppm these conditions imply a transmittance of 0.995 which can be achieved
in an absorbing path of approximately 3 m.
The design that was selected for the photometer is shown in Figure 1. It
was decided that a double-beam arrangement would provide greater precision in
the measurement through elimination of the effect of variability of the UV
source. The cells of the photometer are made of 1-1/2" diameter pyrex pipe;
teflon gaskets are used to make vacuum-tight seals for the fused silica windows.
The light from a low pressure mercury discharge lamp is passed through a narrow-
band interference filter in order to isolate the 253.7 nanometers (nm) emission
line. The light is collimated by a fused silica lens and passed through a
partially-transmitting neutral density filter which serves as a beam splitter.
The two beams then pass through the two absorption cells. Adjustable aperturei
stops limit the diameter of the beams to ensure that there are no reflections
from inner walls of the cells. The light beams emerge from the cells and are
recombined on the face of a photomultiplier tube by another partially reflecting
filter.
14
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STOP
S A v P ' E CELL
MIRROR
Figure 1. Double beam ultraviolet photometer for measurement of
ozone concentrations.
The differential UV absorption method of photometry adopted for 03 con-
centration measurements requires the precise and accurate measurement of two
light intensities—one for each cell. Photon counting techniques for these
intensity measurements using a UV sensitive tube with excellent single photo-
electron resolution were used. If such a tube is cooled to about -20°C, the
dark count rate is a few counts per second. Utilizing high-speed electronics
and very precise timing methods it is possible to obtain accurate and statis-
tically well-characterized pulse counts corresponding to incident light in-
tensity on the photomultiplier. This method may be preferable to analog tech-
niques which are more subject to instability, drift, and uncertain amounts of
non-linearity.
The mercury vapor lamp is energized either by a 10 KHz square-wave power
oscillator or by a 60 Hz commercial power supply. Light passing through each
sample cell is alternately allowed to fall on the photomultiplier by means of a
light chopper. A chopper blade with a single hole is driven by a hysteresis
synchronous motor at a preselected rate (approximately 23 Hz) chosen to be
unrelated to any harmonic or subharmonic of the line frequency. Light emitting
diode-phototransistor pairs are used to sense the position of the hole in the
chopper; the signal from the phototransistor triggers a discriminator to start
the timing and counting cycle for each sample tube.
A logic system, triggered by the discriminators, controls the pulse count-
ers associated with each sample tube. In order to ensure precise counting time
as the photomultiplier is exposed to each tube, an electronic gate is used to
ensure that the photomultiplier is fully (and not merely partly) exposed to the
light beam passing through the sample.
The photomultiplier tube which must be selected for gain, low dark count
rate and, most importantly, negligible afterpulsing, detects the photons as they
15
-------
arrive. This type of tube, with outstandingly good single photon resolution, is
essential for this measurement.
The pulse output from the photomultiplier is amplified 100 times by direct-
coupled amplifiers and the pulses are detected by a high-speed pulse amplifitude
discriminator. Pulse counting is performed by convential 100 MHz pulse counters
and a rough guide of overall pulse rate is provided by a rate meter.
Counting time is determined by a preset counter which counts the revolu-
tions of the chopper blade past the light-emitting diode (LED) phototransistor
pairs. At the end of a counting interval, the results are printed out and the
sequence repeats.
House air, dried and filtered, flows through one cell (reference cell),
then into an 03 generator (5) from which ozonized air flows through the second
cell (sample cell). The measurement is made by comparing the ratio of the
signals transmitted by the two cells in the presence and in the absence of 03.
This procedure provides the transmittance (Tr = -j—), and the 03 concentration is
determined by application of the Beer-Lambert Law^ as discussed above. Since
the mercury lamp is viewed, nearly simultaneously, through both cells, fluc-
tuations in lamp intensity do not affect the measurement. Any impurities present
in the air stream are observed in both cells and do not interfere with 03
determination.
RESULTS
The performance of the photometer has been determined over the 03 con-
centration range 0.020 to 1.500 ppm. At each of the measured concentrations the
standard deviation was of the order of 0.005 ppm or less. A comparison of the
photometric measurements with those obtained by the iodometric and GPT methods
is presented at this Conference in the paper by J. A. Hodgeson, et al. (6).
REFERENCES
1. "Reference*Method for the Measurement of Photochemical Oxidants Corrected
for Interferences due to Nitrogen Oxides and Sulfur Dioxide," Federal
Register 36., 8195-8197 (30 April 1971).
2. (a) "Comparison of Oxidant Calibration Procedures," report of the Ad Hoc
Oxidant Measurement Committee of the California Air Resources Board,
Sacramento, CA (20 Feb. 1974).
(b) "Interagency Comparison of Iodometric Methods for Ozone Determina-
tion," W. B. DeMore, J. C. Romanovsky, M. Feldstein, W. J. Hamming,
and P. K. Mueller, in "Calibration in Air Monitoring," ASTM Special
Tech. Publ. 598, pp. 131-143 (Philadelphia, 1976).
3. J. B. Clements, "Summary Report: Workshop on Ozone Measurements by the
Potassium Iodide Method," EPA-650/4-75-007, U. S. Environmental Protection
Agency, Washington, D. C. 20460, February 1975, 36 pp.
16
-------
4. The value of k used in this work (308.5 cm^atnr1) is based on an evalua-
tion by R. Hampson and D. Garvin of measurements reported in the published
literature:
(a) Inn, E. C. Y. and Y. Tanaka, J. Opt. Soc. Am. 43_, 870 (1953).
(b) Hearn, A. 6., Proc. Phys. Soc. 78, 932 (1961).
(c) DeMore, W. B. and 0. Raper, J. Phys. Chem. 68, 412 (1964).
(d) Griggs, M., J. Chem. Phys. 49, 857 (1968).
(e) Simons, J. W., R. J. Paur, H. A. Webster and E. J. Bair, J. Chem.
Phys. 59, 1203 (1973).
(f) Becker, K. H., U. Schurath, and H. Seitz, Int. J. Chem. Kinet. 6., 725
(1974).
5. Hodgeson, J. A., R. K. Stevens, and B. E. Martin, ISA Trans. 11, 161
(1972).
6. Hodgeson, J. A., E. E. Hughes, and A. M. Bass, "Methodology for Standardi-
zation of Atmospheric Ozone Measurements," preprint for International
Symposium on Photochemical Oxidant Pollution and its Control, Raleigh, NC,
12-17 September 1976.
17
-------
1-3
HYDROCARBON AND HALOCARBON MEASUREMENTS:
SAMPLING AND ANALYSIS PROCEDURES
R. B. Denyszyn, L. T. Hackworth, P. M. Grohse, and D. E. Wagoner*
ABSTRACT
VaAinQ the. AummeA and ^ati o& 1975 appAox.imate.tij 3000 hydAocoAbon, 500
kaJLoc.aA.bon, and 100 het^eAocyctic anatyAeA weAe. peA^oAme,d -in the, atmoApheAic.
chemiAtAy taboAatoAy o& the. ReAe.aAch TAiangie. InAtitiite.. VuAing thu, peAiod
vaAiouA quality aon.tA.ol. pAoce.duAej> weAe. de.ve,£ope.d to e.vatu.ate. the. Aampting and
analytical method!, aAe.d to deteAmine. conce.ntAationA ofc vatiouA hydAocatbon and
hatocoAbon 4pecxe4 -in amb-lznt aiA cu> weJLt OA ui bmoQ c.hambeA bamptnA . TzAtA
u)eA£ poA^oAmid on: (a) the. Atab+jUty oft hydAOdOAbonA tn Jt^ton Aampting bag*;
(b) peAme.dtA.on ofa hydAoc.aAbon and hatocaAbonA -into TudtoA bag*; (c) the. Ata-
zeJio aJjt and btandoAd Aampte^> -in Te.diaA ba.g-4 beting t>hLppo,d batwuAe.d
to a btaA o{, 5% uiith 5 1 Ae.£ative. ktandaAd de.vtation.
M. conce.ntAation6 o^ >10 ppb, C2-C5~hydAocaAbon& me.OAaAe.me.nt!>,
21 AeJLattve. AtandaAd de.vtation can be. achte.ve.d.
The. Ae.latA.ve. AtandaAd de.vtation ofi FAe.on 11 me.aAuAe.me.ntt> at the.
Re^e.oAch TAiangle. InAtttute. aAe. pAe^entiy 31.
The. Atabtttty ofa both Ae.active. and LLnAe.ac.tive. hydAocoAbonA at the.
1-10 ppb conce.ntAation Aange. WOA e.valu.ate.d tn Te.dlaA bagA in the.
doAlz &OA a 1-we.e.k peAtod.
SeJLe.cte.d hydAocaAbonA and hetejiocycLic compounds
ceJLte,nt AtabJJLity in Te.^ton bagA in the. daAk.
9 Contamination o^ Te.dlaA bagA ^-itte.d ulith hydAocaAbon--(iAe.e. aiA U
viAtuaULy ne.Qtigi.bte. $OA hydAocoAbon and Aome. hatocoAbonA up to
& dayA.
INTRODUCTION
During the summer and fall of 1975 approximately 3000 hydrocarbon, 500
*Research Triangle Institute, Research Triangle Park, North Carolina.
19
-------
halocarbon, and 200 heterocyclic analyses were performed in the atmospheric
chemistry laboratory at Research Triangle Institute (RTI). Both ambient air and
smog chamber samples were included. In order to establish the credibility of
these analyses quality control (QC) procedures were developed that have estab-
lished the accuracy and precision of the procedures. These QC procedures have
also lead to improvement in the sampling arid analytical techniques.
Accuracy (bias) and precision (relative standard deviation) in hydrocarbon
measurements result from attention to four parts of the measurement procedures:
sampling analysis, instrument calibration, sample collection, and personnel
training. If optimum procedures are applied, gas samples containing hydrocar-
bons or halocarbons are stable enough to allow remote analysis; measurement
errors can be avoided; and a relative standard deviation of 2 percent is
possible in the 10-100 ppb concentration range. If any of the critical pro-
cedures are not followed, this precision is degraded.
ANALYSIS PROCEDURES
Analysis is performed with a modified gas chromatograph (GC), the selection
of which is of critical importance. A suitable GC must have detectors and
signal processing electronics with proven long-term stability and must be
sufficiently rugged to hold up under the rigors of continuous repetitive analysis,
It is advantageous that the GC have an interface for direct coupling to a data
processing computer. Additionally, the GC columns should be selected for low
bleed since ambient air analysis requires the maximum detectability. The
elution peaks should be well' separated in order to provide maximum information
from the analysis.
The specific GC employed for the hydrocarbon halocarbon analysis was the
Perkin-Elmer Model 900 with dual flame ionization detectors (FID) and two
electrometers. The controls were modified to allow independent operation of
the detectors so as to facilitate rapid adjustment for analyses that require
different flow rates and column temperatures. The valving system shown sche-
matically in Figure 1 was built to allow the introduction of cryogenically
trapped samples into the GC. Flexibility of the sample injection system is such
as to accommodate samples with both ppm and ppb concentrations. This flexi-
bility is achieved by replacing the secondary trap (liquid nitrogen trap) with a
sample loop. The GC electronics interfaces with a Hewlett Packard 3352B data
system.
Since hydrocarbon concentrations in ambient air are much too low for
detection with direct injection gas chromatography, sample concentration is
required. Concentration is usually accomplished for lower molecular weight
compounds with cryogenic traps although the choice of cryogen varies among
laboratories. The primary requirement of the concentration procedure is that it
be quantitative—recovery must closely approximate to 100 percent.
In order to avoid the condensation of oxygen that occurs in a liquid
nitrogen trap, liquid oxygen, which boils at a higher temperature than liquid
nitrogen was used in our traps. The collection efficiency of the liquid oxygen
traps was evaluated by testing them with ethylene and propane. When ethylene in
20
-------
Detei tor
,11 r i e • rid s
>nt
\
\
Figure 1. Valving for thermally controlled injection system.
air was passed through two traps in series, the first trap gave 4.0 ppb in
subsequent analysis while the second trap gave 0.3 ppb. This indicates a
collection efficiency of 93 percent for ethylene and, therefore, much better
efficiences for compounds with higher boiling temperatures. In a similar
experiment with propane, a collection efficiency of .greater than 99 percent was
obtained. Collection efficiences decreased at flow rates above 100 nrn/min and
with total sample volumes in excess of 500 mi as seen in Figure 2.
1OO -
90 -
80 -
70 -
60 -
50 .
100
250
500
750
1000
Figure 2. Dependence of collection efficiency on volume of sample.
This sample concentration and analysis system was quantitative for C2-C10
hydrocarbons when the above procedures were followed.
CALIBRATION
The accuracy and precision of the analytical step was determined with the
complex permeation tube system shown in Figure 3. In this system, carrier and
dilution air were catalytically cleaned of hydrocarbons and other pollutants
and mixed with accurate concentrations of dopant gases over broad concentration
ranges. Calibration gases were propylene and n-butane. Calibration was per-
formed using a 180 cm x 0.32 cm outside diameter (OD) column packed with 100-120
mesh n-octane Durapak maintained at 19°C with a helium flow of 20 m£/min. Each
concentration level was measured a minimum of four times.
21
-------
in
.
L,
Figure 3. Permeation tube calibration system.
In these tests, a precision of 5 percent was obtained in measuring con-
centrations. As may be seen in Figure 4, the relative standard deviation
appears to decrease with increasing concentration with a nearly linear depen-
dence. The relative bias of the measurements plotted in Figure 5 showed no such
dependence. The bias for propylene is positive and that for butane is negative;
the average deviation is +5 percent, respectively.
SAMPLE COLLECTION
Sample collection bags made of Teflon and Tedlar are commonly used in
atmospheric chemistry. Their purported attributes include ease of handling,
durability, chemical passivity, and low cost. Reported shortcomings include
fragility, permeability, and the outgassing of various photolytic compounds by
the polymeric materials of which the bags are made. Outgassing has been ob-
served at RTI and at other laboratories.
While compounds in the C2-C5 molecular weight range mixed with air are
stable in both Tedlar and Teflon bags, the more serious outgassing of Tedlar has
led us to use Teflon bags for samples containing high molecular weight hydro-
carbons, heterocyclics, and sulfur-containing compounds such as dimethyl sulfide
and thiophene.
Several interesting phenomena that could result in errors have been ob-
served in using Tedlar bags. Acetylene (in concentrations > 100 ppb) is ab-
sorbed by Tedlar and released when the bag is heated. If hydrocarbon mixtures
are blended in oxygen-nitrogen mixtures obtained by liquid boil off rather than
in catalytically cleaned air, the hydrocarbon concentration changes due to
permeation of the bag by oxygen in establishing partial pressure equilibrium
with the ambient air. Data indicating this activity are illustrated in Figure
6.
22
-------
o
+J
(O
O>
6 -
5
4 H
3
2
X Propylene
O Butane
10 20 30 40 50 60
Concentration Analyzed (ppb V/V)
Figure 4. Precision and its relationship to concentration.
10.
8'
O ro
i. >
4-
1-
O
6'
8.
10.
X Propylene
O Butane
in 20 30 40 50
Concentration Analyzed (ppb V/V)
Figure 5. Bias and its relationship to concentration.
60
23
-------
o>
c:
CU
CU
<_)
CO
s_
o
en
fO
CO
CU
c:
OJ
^
+->
CU
(_)
O
LD
O
(A/A)
24
-------
The stability without light of both reactive (trans-2-butene) and non-
reactive (acetylene) hydrocarbon mixtures in Tedlar bags was tested for a 1-
month interval. Filled Tedlar bags were stored in aluminum suitcases for
periods of up to 23 days. Initial hydrocarbon concentrations were 70 ppb; after
23 days, the concentrations of trans-2-butene and acetylene were 62 ppb and 56
ppb, respectively; losses were 11 percent and 20 percent. In a test using
acetylene and exposed to light, the data of Figure 7 were obtained. As shown,
the average deviation is 6 percent from the mean concentration. For the 12 ppb
sample used in this test, on the 5th, 6th, and 14th day the concentrations were
11.5, 11.0, and 14.0 ppb, respectively.
CoH^ Mean Concentration 11.5
>
^>
-Q
CL
CL
m.
12 •
1 0 .
8 -
6
1+
Average
o
• .
_i. _ _ --
Dash Lin
from Mea
0800 1600 2"+00 0800 1600
9/17/75 TIME 9/18/75
Figure 7. Stability of acetylene in Tedlar bags.
Additional stability tests were performed by exposing the sample bags to
the contaminated transportation environment such as associated with a field
collection program. Tedlar bags with control samples of hydrocarbon-free air
were shipped by United Parcel Service and air freight to various sampling
stations and then returned to the laboratory. Eight days of travel time lapsed.
Test results are given in Table 1. In this test the bags were exposed to var-
ious temperatures and unusually high concentrations of hydrocarbons in the
ambient air.
In contrast to hydrocarbons, halocarbon sampling is much more susceptible
to contamination. In normal laboratory air the concentration of Freon 11 is
several ppb so that even the fraction of a milliliter of laboratory air trapped
in a Swagelock fitting may invalidate data in a sample. The permeati
for 1,1,1-trichloroethane and tetrachloroethylene through Tedlar are much
high to use bags for sample collection. Stainless steel containers are
halocarbon sampling by many research groups but their high cost is prohibitive
for extensive sampling programs.
rates
too
used for
Aluminum sample containers (Altech Associates) appear to be excellent
containers for sampling and storing both hydrocarbon and halocarbon samples.
The results of a 1-month test of aluminum sample containers are given in Table
2. Both Freon 11 mixtures and undoped air were used. These aluminum cans have
been found to be usable with heterocyclic compounds such as furan but serious
wall interactions have been observed with sulfur compounds. The concentration
of thiophene, for example, decreased 29 percent in 4 days. However their low
25
-------
TABLE 1. STABILITY OF HYDROCARBON FREE AIR IN TEDLAR BAGS
Species
ethane/ethylene
propane
propylene
acetylene
n-butane
butene-1
isobutane
isopentane
cyclopentane
n-pentane
toluene
o-xylene
freon 11
cci4
trichloroethane
tetrac hi oroethyl ene
Bag
Concentration
ppb (V/V)
2.1
0.4
0.1
0.4
N.D.
N.D.
N.D.
N.D.
N.D.
0.0
1.2
0.6
13.5 ppt (V/V)
N.O.
0.3
<40.0
Cylinder Gas
Concentration
ppb (V/V)
2.1
0.4
0.1
0.5
N.D.
N.D.
N.D.
N.D.
N.D.
N.D.
1.1
0.8
N.D.
N.D.
N.D.
N.D.
N.D. = not detectable.
TABLE 2. FREON 11 IN ALUMINUM CANS
4-8-76
4-9-76
4-22-76
4-23-76
4-30-76
5-4-76
307 ppt
300
304
298
288
290
MEAN 298
S. OW 7.5
4.0
8.9
10.3
8.8
8.0
2.8
cost, convenience in use, and stability for most compounds indicate that alumi-
num cans are generally excellent for sample collection.
Teflon bags are also recommended for sample collection. Wall interactions
and permeation rates are low. However there is considerable variability in the
quality of the bags. Some give off compounds that are detected with the FID and
the electron capture detector. Because this outgassing varies with the batch,
and is usually less than with Tedlar, it is necessary to condition Teflon bags
with ozone and to analyze for background before being used for sampling. Table
3 gives data illustrating the excellent stability in the dark of various mix-
tures contained in Teflon bags.
PERSONNEL FACTORS
Training of personnel is important in operating a sampling program that is
26
-------
TABLE 3. STABILITY OF VARIOUS COMPOUNDS IN TEFLON BAGS
Net Loss After 3 Days
Dimethyl Sulfide 1%
Thiophene 5*
Dimethyl Disulfide 5%
Methyl Mercaptan 7%
Furan 14S
p-Xylene 14"J
Pyrrole 23"
to obtain accurate and precise data. This training must include familiarization
with GC and review of the various pitfalls that result in errors. Measurement
of trace quantities of various atmospheric contaminants requires much attention
to detail. Gas regulators with rubber diaphragms cannot deliver pure gases,
small leaks will result in errors. Personnel must learn to discern bad from
good data, and every phase of the measurement program must be given the required
attention.
CONCLUSIONS
Hydrocarbon and halocarbon measurements can be made accurately and pre-
cisely if proper attention is given to the analysis procedures, calibration,
sample collection, and personnel training. When this is done, C2-C5 hydro-
carbons at < 10 ppb concentrations can be measured with a bias of 5 percent and
a relative standard deviation of 5 percent. For concentrations above 10 ppb,
the bias is the same but the relative standard deviation improves to 2 percent.
Analysis of samples should be made within one week of collection and when
possible, on-site analysis is preferable.
27
-------
SESSION 2
ANALYTICAL METHODS FOR OXIDANTS AND PRECURSORS - II
K.H. Becker
University of Bonn
29
-------
2-1
A NEW CHEMILUMINESCENT OLEFIN DETECTOR
FOR AMBIENT AIR
K. H. Becker, U. Schurath, and A. Wiese*
ABSTRACT
\n tns&uwent faor continuous monitoring o& re.active. hydrocarbons -in
ambi.e.nt air -in the. parts putt bWiion concentration Aange. -is de.scribe.d. The.
new anal.yti.cal. method ts base.d upon the. chemilum-ine.sce.nt oUt^in — ozone, re-
action. The. chemilumine^ce.nt ole-i-in detectoA has been te.ste.d at ground le.ve.1
para-ULeJL to an automatic. Gas Chromatograph, aboard an airplane., and as a
detector adapted to a. gas chromato graphic column. Applications o& the. new
histAu.me.nt {,01 air pollution control are. discussed.
INTRODUCTION
In order to control photochemical oxidant precursors and their transport
over long distances, there is an urgent need for a simple technique capable of
measuring "reactive hydrocarbons" continuously, with high sensitivity, and
good time resolution. The term "reactive hydrocarbons" is generally applied
to the total amount of organic gaseous material, as measured by a Flame loni-
zation Detector (FID), less methane, which is considered unreactive in photo-
chemical smog. It might, however, be more appropriate to measure the reactiv-
ity of the hydrocarbons towards ozone (03) to obtain an indicator of their
smog forming potential. It has been shown in a number of field studies (1,2)
in urban areas with unspecified emission sources that ethylene and propene are
by far the most abundant unsaturated hydrocarbons which at the same time
represent the most reactive organics with respect to photo-oxidant formation.
Reactivity of organics is measured as rate constant times concentration. Sat-
urated hydrocarbons, although most present at higher concentrations are less
reactive. A suitable measure of the total olefin amount in ambient air may be
that of the intensity of the chemiluminescent reaction with 03, as measured in
a "reversed" chemiluminescent 03 analyzer which uses ozonized oxygen as re-
agent gas. The relative quantum yields of the most abundant olefins, ethylene
and propene, could also be a good "weighing" factor of their relative reactiv-
ity as smog precursors.
The paper describes a rather simple chemiluminescent olefin detector
which has been field tested as a continuous monitor of reactive hydrocarbons
in ambient air at ground level, in parallel with an automatic Gas Chromato-
graph (GC) (Siemens U 180). Another version of the detector has been success-
fully used for olefin measurements in plumes aboard an airplane up to an
*Institut fur Physikalische Chemie der Universitat Bonn, Bonn, Germany.
31
-------
altitude of 3000 meters. And the instrument was also adapted to a gas chroma-
tographic column for the selective detection of unsaturated hydrocarbons. A
similar technique has previously been used elsewhere (3). Part of the present
work has previously been published (4,5).
EXPERIMENTAL
The construction and principle of operation of the chemiluminescent
olefin detector are evident from the schematic diagram (Figure 1), which shows
the version used for airborne measurements. Ozonized oxygen from a silent
discharge ozonizer (2.5 liter/hour) and sample air (60 liter/hour) are drawn
into a mixing chamber (volume 230 ml) by a small diaphragm pump which is
protected against 03 by an activated charcoal filter. A chamber pressure of
400-500 torr was found satisfactory. The mixing chamber is mounted in front
of a photomultiplier tube (EMI-9635 QB) which, by its low quantum efficiency
above 600A, essentially eliminates interference by nitrogen oxide (NO) from
its chemiluminescent reaction with 03. The reaction chamber was drilled from
solid teflon contained in a light-tight metal cylinder. Teflon has the ad-
vantage of an extremely good optical reflectivity at short wavelengths,
thereby increasing the sensitivity of the detector.
The instrument was calibrated using a 425 liter evacuable glass cylinder
as mixing chamber. The container was filled with ambient or pure synthetic
air and spiked with the olefins by means of a precision gas syringe. Mixing
was achieved by a built-in teflon fan.
To increase the long term stability of the detector background signal
(photomultiplier dark current plus background chemiluminescence), the
photomultiplier and reaction chamber could be thermostat!zed. This procedure
was not necessary for shorter periods of operation, e.g., aboard an aircraft.
The sensitivity of the detector towards various olefins not only depends
on the relative quantum yields of the chemiluminescent reactions, but also on
the flow rate and total pressure in the chamber. Typical sensitivities, rela-
tive to ethylene taken as unity, were 2.5 for propene, 6.4 for trans-2-butene,
3.0 for cis-2-butene, and 4.4 for 1,3-butadiene.
To eliminate sensitivity changes due to relative humidity effects, an air
filter filled with Sicapent (phosphorus pentoxide on a solid support) was
found most satisfactory. The detector zero was checked at intervals by
switching a molecular sieve filter of suitable pore size to eliminate olefins.
RESULTS
Our prototype chemiluminescent olefin detector for air analysis at ground
level has been in continuous operation since May 1975. Maintenance amounts to
changing the Sicapent filter every 5 days, and the ozonizer oxygen supply tank
every 100 days.
32
-------
CM
O
Tr
1 -
1
1
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N -H O
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An 8 hour recording by the detector is compared with the ethylene concen-
tration as measured by a Siemens U 180 automatic GC (Figure 2). This GC per-
forms a complete analysis every 15 minutes, averaging over 10 minutes by a
preconcentration technique. The comparison shows a good correspondence be-
tween the detector output and the ethylene concentration which is by far the
most abundant olefin in ambient air. The continuous recording shows fine
structure of the concentration-time profile which is lost in the averaging
process of the GC analysis. Interpretation of the chemiluminescent detector
recordings is also much easier than would be an evaluation of the sometimes
confusing information contained in a complete GC analysis of the light hydro-
carbons every 15 minutes.
The high sensitivity and short time constant (about 3s) of the chemilumi-
nescent olefin detector make it a valuable tool for continuous airborne meas-
urements of reactive hydrocarbons. Figure 3 shows a recording obtained on a
first test flight in the Cologne-Bonn area. The flight level was changed after
passing over a lignite burning thermal power station from 4000 feet to 2600
feet (3800 to 2600 feet above ground). An extremely strong olefin signal
corresponding to a maximum of 700 ppb ethylene equivalents was obtained above
a petrochemical plant. It had been shown on a previous flight (6) under clear
weather conditions that the 03 concentration increased considerably above
average about 20 km downwind of the petrochemical plant, at a flight level of
2500 feet. The effect was less pronounced at lower and higher altitudes.
The performance of the instrument as a GC detector is shown in Figures 4,
5, and 6. In this mode the GC column outflow is blended with 60 liter/hour of
argon before analysis to reduce the residence time in the reaction chamber
which was run at atmospheric pressure. Figure 4 compares analyses of identi-
cal mixtures of alkanes and olefins in synthetic air (concentrations of the
order 50-100 ppm), as measured with a conventional FID, and with oTefin de-
tector. Peak-overlapping with alkanes is completely eliminated. Figure 5
shows the chemiluminescent detector response for car exhaust gas after separa-
tion on a GC column. Again, only the olefins are detected. Analysis of
ambient olefins by GC with the new detector requires pre-concentration. A
typical olefin analysis of ambient air is shown in Figure 6. It clearly
corroborates our previous statement that ethylene and propene are a good
measure of the total olefin content in ambient air under normal conditions.
CONCLUSIONS
It has been shown that unsaturated hydrocarbons can be measured continu-
ously in ambient air and in smog chamber experiments (7) with this inexpensive
rugged chemiluminescent detector. The output of the instrument is a useful
measure of the total olefin content of the atmosphere, with weighing factors
of 2.5 for propene, 6.4 for trans-2-butene, 3.0 for cis-2-butene, and 4.4 for
1,3-butadiene relative to ethylene as unity, taking account of the higher
photochemical reactivity of the higher olefins. One version of the detector
has been used successfully for airborne measurements of reactive hydrocarbons
above an industrialized area with distinct sources of olefins. The instrument
is also useful as a specific GC detector for unsaturated hydrocarbons which
need not be separated from alkanes.
35
-------
tO
t^
O)
Q)
c.
D
0)
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3
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-t->
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to
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co -i->
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cu
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36
-------
FID
c
o
-»-•
o
Q)
chemiluminescence
c detector
0>
Q.
O
C
o
-^-
o
CD
2 1 0
chart speed x 0,5
6543
time (min)
Figure 4. Chemiluminescent olefin analyzer as GC detector in comparison
with an FID: Analysis of a synthetic air sample (olefin con-
centration in the 50 - 100 ppm range).
37
-------
(f)
4-1
cd
M
4-)
•H
XI
o
°0
o
CO
t
o
in
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t
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(Nl
oventemperature
11,24 724
t
chartspeed x 0,33
0 [min]
Figure 5. GC analysis of car exhaust by the chemiluminescent olefin
detector.
38
-------
-p
•H
§
5 /» 3 2 1 0 [mini
Figure 6. GC analysis of a pre-concentrated air sample by the chemilumi-
nescent olefin detector.
39
-------
ACKNOWLEDGEMENT
This work was supported by the "Bundesminister des Innern" as part of
a program on photochemical air pollution control in the German Federal
Republic.
REFERENCES
1. H. H. Westberg, R. A. Rasmussen, and M. Holdren. Gas Chromato-
graphic Analysis of Ambient Air for Light Hydrocarbons Using a
Chemically Bounded Stationary Phase. Anal. Chem. 46:1852, 1974.
2. W. A. Lonneman, S. L. Kopczynski, P. E. Darley, and F. D. Sutter-
field. Hydrocarbon Composition of Urban Air Pollution. Env. Sci.
Technol. 8:229, 1974.
3. W. Bruening and F. J. M. Concha. Selective Detector for Gas
Chromatography Based on the Chemiluminescence of Ozone Reactions,
J. Chromatog. 112:253, 1975.
4. U. Schurath, A. Wiese, and K. H. Becker. Ein Chemilumineszen-
zanalysator fur ungesattigte Kohlenwasserstoffe in der Atmosphare.
Staub - Reinhalt. Luft, 1976, in press.
5. K. H. Becker, Ulrich Schurath, and Andreas Wiese. Gas Chromato-
graphic Detector for Olefins. Anal. Chem., 1976, in press.
6. W. Fricke and H. W. Georgii, private communication.
7. K. H. Becker, F. Bahe, W. Janek, J. Lobel, U. Schurath, W. W...Wendler,
and A. Wiese. Untersuchungen uber Smogbildung, insbesondere uber
die Ausbildung von Photooxidantien als Folge der Luftverunreinigungen
in der BRD. Annual Report 1975. University of Bonn, May 1976.
40
-------
2-2
GC-CHEMILUMINESCENCE METHOD FOR THE ANALYSIS OF AMBIENT TERRENES
R. L. Seil a*
ABSTRACT
A method {^on, the., quantitative. and qualitative. anaty^iA o^ ambient te.Ape.neJ>
•it, dej>cAibe.d and e.val.uate.d. Sampled o& ambient ait c.otie.cte.d on a t>oLid adbotb-
e.nt ate. de^otbe.d Into a cA.yoge.nlc. ttap fact In j e.ction Into a got, c.htomatogtaphic.
cotamn. k^teji Ae.pan.at.ion by the. column, the. Aampte. u> 6piit fiot £Jjnuitane.O(Li>
detection by ^lame. ionization and ozone, c.ke,mit(mine.t>c.e,nc.e.. The. chemitumineA-
ce.nce. dzte.ctot -it, a modi&ie.d comme.tc.ial. amb.ie.nt nittoge.yi ozidz-oicidzA oft
ge,n monitor, Re^ponAe. data fio-i a vasu.ety o& teA.pe.nic hydAocajibonA, and the.
o& &ome. ambient anaiy^e^ ate. ?ie.ponte.d.
INTRODUCTION
The contribution of natural hydrocarbons emitted from trees and other
vegetation to the formation of photochemical oxidants is a continuing subject of
debate and study. Rasmussen, et al . (1) report that monoterpenes and isoprene
are the major compounds released to the atmosphere from plants. The research of
Grimsrud et al. (2) indicate that terpenes are very reactive with short re-
sidence times in the atmosphere. These findings suggest that natural hydro-
carbons may be important precursors for the reactions which form 03 in rural
atmospheres .
In order to more fully understand the relationship between biomass and
rural 03 concentrations, varied and reliable analytical methods for the identi-
fication and quantisation of terpenes are desirable. Gas chromatography (GC)
with flame ionization detection (FID) has been the method used by most previous
investigators (1, 3, 4, 5, 6). The inherent problem with this method is that
the FID does not provide a definitive qualitative analysis, since it does not
enable identification of specific organic compounds (7). Experience in the
Environmental Protection Agency (EPA), Environmental Sciences Research Labora-
tory (ESRL) has been that the GC resolution of terpenes from the ever present
very dilute automobile exhaust in rural air is very difficult. This problem has
been overcome by the use of two detectors.
There is a problem of uncertainty concerning the results of detailed
hydrocarbon analyses of relatively clean rural air samples collected in Tedlar
bags due to contaminants from the polyvinyl fluoride film (11). Another problem
of using bags for sampling rural air for terpene analysis is that the ambient 03
in the bags reacts quickly with terpenes during the time interval between
*U. S. Environmental Protection Agency, Research Triangle Park, North Carolina.
41
-------
collection and analysis. For these reasons and the fact that the concentration
of large volumes of air is necessary for the analysis of low ambient terpene
concentrations, it was decided to assemble and test a GC method which would
employ a solid adsorbent for sampling large volumes and would simultaneously
measure the FID and chemiluminescent responses of these samples.
Ozone chemiluminescence measurement of olefins has been performed by
Quickert, et al. (8) who evaluated the direct response of a modified commercial
03 monitor to several selected olefins but not to terpenes. Mil born, et al. (9)
used the same instrument as a total olefin monitor for ambient measurements.
McClenny, et al. (10) measured the chemiluminescent response of various olefins
with 03 and demonstrated the feasibility for analysis of vinyl chloride and
related compounds by using a combination of GC and 03 chemiluminescence. A
commercial instrument manufacturer under contract to EPA has produced a proto-
type vinyl chloride analyzer using this method.
EXPERIMENTAL
INSTRUMENTATION
A schematic of the flame ionization-chemiluminescence chromatographic
system used for terpene analysis is provided in Figure 1. It consists basically
of two components—a Perkin Elmer 900 GC with FID and a Bendix Model 8101-B N0x
chemiluminescence analyzer.
TENAX DESORPTION UNIT
HELIUM
CARRIER
GAS
AIR
CHEMILUMINESCENT
ANALYZER
Figure 1. Schematic of FID-chemiluminescent gas chromatoqraph.
The NO analyzer used as a chemiluminescence detector was modified in
several respects. The photomultiplier tube was replaced with one from a Bendix
03 chemiluminescence analyzer. The red interference filter between the photo-
42
-------
multiplier tube and the reaction chamber was replaced with a transparent glass
window. The glass capillary which controls the flow of ambient air into the
reaction chamber at a rate of approximately 150 ml min"1 was replaced with one
identical to the one used to restrict the 03 flow into the reaction chamber to
20 ml min-1. This capillary gave a carrier gas inlet flow rate of 27 ml min"1.
The same pump which comes with the instrument was used to operate the reaction
chamber at a pressure of 50 Torr. The 03 air supply pressure switch used to
energize the 03 generator at 18 pounds per square inch gauge (psig) was adjusted
to allow operation at a pressure of 8 psig. A 35 liter tank was placed in the
vacuum line between the pump and the reaction chamber to act as a ballast.
The outputs from the FID amplifier and chemiluminescence analyzer were 1 mv
and 10 mv respectively and were connected to a strip chart recorder operated at
a chart speed of 1.27 cm min'1.
CHROMATOGRAPHIC CONDITIONS
The GC column employed was 120 cm x 2.36 mm inside diameter (ID) ss OPN/Porasil
C, 80/100 mesh (Waters Associates). The carrier gas was helium at a flow rate
of 50 ml min"1. The column and FID detector temperatures were 120°C and 160°C
respectively. After splitting, the carrier flow rate to the FID was 23 ml min"1
and the flow rate to the chemiluminescence detector was 27 ml min-1. The FID
air and hydrogen flows were 472 ml min"1 and 49 ml min"1 respectively. A cryo-
genic trap, consisting of 0.5 ml of Chromosorb 750 in a 27 cm x 2.36 mm ID
section of ss tubing, was used to trap the sample before injection onto the
column. Liquid oxygen was the cryogen. A Seiscor six port gas sampling valve
was used for flow diversions involved in sample trapping and injection. The
valve was placed in the GC oven with the column at a temperature of 120°C.
SAMPLING
Tenax GC (2,6 diphenyl-p-phenyleneoxide polymer, Alltech Associates) 60/80
mesh was the adsorbent used for collecting ambient samples. Stainless steel
tubes, 14 cm x 6.35 outside diameter (OD), containing 3.8 ml of Tenax and glass
wool plugs were the sampling cartridges. Before use the cartridges were con-
ditioned under helium flow at 350°C for at least 24 hours.
A Thomas pump connected to a two port manifold to which two Tenax cart-
ridges could be attached for duplicate sampling constituted the sampling ap-
paratus. The air flow rate was measured with a calibrated rotometer and ad-
justed as necessary when ambient samples were collected.
A special Tenax desorption unit was fabricated from a Perkin Elmer liquid
injection port. This design has been described by Bellar, et al. (12). The
exit of the desorption unit was connected to the sampling valve to which the
cryogenic trap was attached. The valve plumbing was reverse that of common GC
valve plumbing. In the valve off position, the carrier gas flows through the
cryogenic trap to the column. Only when the valve is actuated does helium from
the desorption unit flow through the cryogenic trap. This arrangement was used
to prevent contamination of the cryogenic trap from a Tenax cartridge in the
desorption unit. Samplers were desorbed at 250°C while purging the cartridge
43
-------
with helium at 47 ml mirr1 for 15 minutes.
CHEMICALS
Terpenes liquid samples were obtained from Glidden-Durkee, Aldrich and
Chemical Samples Company.
RESULTS AND DISCUSSION
Before the instrumentation was assembled, a preliminary experiment was
performed to determine if some terpenes would chemiluminesce when reacted with
03. This work was done using the apparatus as described by McClenny, et al.
(10). Bag samples of a-pinene, 3-pinene, myrcene, y-terpinene, and d-limonene
were sampled and did provide chemiluminescent response. This suggested that a
GC-chemiluminescence method for terpenes was feasible.
The chemiluminescent responses of selected terpenes were evaluated by
injecting masses varying from 0.08 yg to 1.08 yg into the FID-chemiluminescence
chromatograph. Samples were cryogenically trapped from bag standards prepared
by microliter syringe injections into nitrogen. This gave initial terpene
concentrations of 3 to 4 ppm. Lower bag concentrations were produced by with-
drawing and adding nitrogen to the bags. The FID analyses of the diluted bags
were used to calculate the terpene dilution concentrations by multiplying the
FID response times the terpene FID response factors obtained from the initial
known bag samples. Sample masses were also changed by varying the sample volume
between 8 and 100 ml.
Figure 2 is a graphical representation of the results of the response
study. The concentrations on the abscissa were calculated from the known
samples masses and a presumed total sample volume of 15 liters. The chemi-
luminescent response was determined by measuring peak area by the height times
width at half-height method. This area (mm2) response was divided by 100 to
give the relative response depicted by the ordinate of the graph. Most of the
curves are not straight lines. Myrcene and 3-pinene points appear to fall on a
straight line, while the other compounds show a slight decrease of sensitivity
with increasing concentration.
The chemiluminescence sensitivity varied considerably from compound to
compound as can be seen by the curves in Figure 2. Sensitivities were measured
by a linear regression calculation of the slope of the area response versus
concentration for the straight portion of the curves—generally at concentra-
tions below 5 ppb. The slopes were converted to the accepted sensitivity units
of millivolt second/yg (7). The minimum detectable masses were calculated by
dividing the minimum detectable area by the sensitivity for each compound. "The
minimum detectable area was the peak area for a recorder deflection of twice the
noise level. The noise level was 0.008 mv and the minimum detectable area was
30 mm2 or 0.57 mv • sec. The minimum detectable concentrations were calculated
from the known minimum detectable masses and an assumed sample volume of 15
liters. Table 1 summarizes the sensitivity and detectability results.
The sensitivity of chemiluminescent detection was improved considerably
(approximately 47 percent) by operating the chemiluminescent reaction chamber at
44
-------
70
0
a.
CONCENTRATION ppb CARBON
T r~ "~r r
0 10 20 30 40 SO 60 70 80
20 30 40 50 60 70 80 90 100 110 120
CONCENTRATION, ppb CARBON
Figure 2. Chemiluminescent response versus concentration* for selected
terpenes. (*A sample volume of 15 liters drawn through Tenax was assumed
for the concentration calculations.)
reduced (50 Torr) rather than ambient pressure.
Table 2 is a comparison of terpene relative chemiluminescence sensitivities
and their ozonolysis rates. There is a general positive correlation of in-
creased sensitivity with increased ozonolysis rate (2).
The efficiency of the Tenax cartridges was evaluated by two methods. A bag
of low concentration a-pinene, 3-pinene, d-limonene, and myrcene was prepared.
45
-------
TABLE 1. CHEMILUMINESCENCE SENSITIVITY, MINIMUM DETECTABLE
MASS AND CONCENTRATION FOR SELECTED TERRENES
*
Compound Sensitivity Minimum Detectable Minimum Detectable
Mass Cone.
Camphene
Myrcene
d-Limonene
y-Terpinene
a-Pinene
A3-Carene
B-Pinene
256.9
208.0
82.7
58.6
50.7
37.0
3.4
0.0022 yg
0.0027 yg
0.0069 yg
0.0097 yg
0.0112 yg
0.0153 pg
0.1665 yg
.03
.03
.08
0.11
0.13
0.18
1.97
*
Millivolt • second per microgram
Parts per billion. Concentrations based on 15 liter sample volume
TABLE 2. CHEMILUMINESCENCE RELATIVE SENSITIVITES AND RELATIVE
OZONOLYSIS RATE OF SELECTED TERRENES
Compound Relative Sensitivity Relative Ozonolysis Rate
Camphene
Myrcene
d-Limonene
Y-Terpinene
a-Pinene
A3-Carene
g-Pinene
5.1
4.1
1.6
1.2
1.0
0.73
0.067
--
8.6
4.4
1.9
1.0
0.83
0.25
A 25 liter sample was drawn through two Tenax cartridges in series. These
cartridges were analyzed. The analysis of a two liter cryogenic sample
directly from the bag provided a measurement of the actual bag concentrations.
Comparison of the cryogenic analysis and Tenax analyses responses gave the Tenax
cartridge efficiency. A comparison of the responses of the front and back
cartridges by the fo™ul. (1 - . ) X 10CK .Iso produced
a trapping efficiency. The results of this experiment are presented in Table 3.
The fact that the Tenax adsorption efficiency for C10 terpenes is not
46
-------
TABLE 3. COMPARISON OF TENAX ADSORPTION EFFICIENCY
DETERMINED BY TWO METHODS FOR FOUR TERPENES OF VARYING SAMPLE SIZE
Compound Bag Concentration, Efficiency, Efficiency,
ppb Tenax Versus Front Cartridge
Cryogenic Versus Back
Analysis Cartridge
a-Pinene
g-Pinene
d-Limonene
Myrcene
.30
.59
.87
2.15
57%
63%
69%
33%
74%
70%
64%
28%
greater than 90 percent for a 25 liter volume is surprising and not what one
would expect from reviewing some of the literature on Tenax (13-18).
A high efficiency of desorption (> 95 percent) of Tenax adsorbents was
verified several times by trapping cryogenically a second consecutive 15 minute
sample from a cartridge. Comparison of the first desorption analysis with the
second indicated that practically all of the adsorbed species had been removed.
Chemiluminescence interference by aromatic hydrocarbons was evaluated by
analyzing automobile exhaust. There was no interference in the terpene re-
tention time region. This result agrees with the results of Hilborn, et al. (9)
and McClenny, et al. that aromatic compounds do not respond to ozone chemi-
luminescence (10).
The major source of error of this method arises from a sampling technique
which employs Tenax. The problems with Tenax are contamination and adsorption
efficiency.
Three types of blank analyses were performed to check Tenax background.
Cartridges were analyzed at the end of conditioning, after conditioning
and cooling, and after sampling prepurified nitrogen (Linde). The
analysis of a cartridge at the end of conditioning revealed zero back-
ground on both the FID and chemiluminescent responses at the amplifier
attenuations used for ambient analyses (FID-16X, Chemiluminescence -
2X). The cartridge was removed from the desorption unit and allowed to
cool for 15 minutes while continuing the helium purge flow. The subse-
quent chemiluminescent response revealed two small peaks, comparable in
magnitude to the minimum detectability. One peak retention time coin-
cided with that of A3-carene. The FID chromatogram revealed general
contamination, but again of a magnitude corresponding to minimum de-
tectable peaks. The 30 liter prepurified nitrogen sample displayed
general FID contamination of low magnitude. The chemiluminescent
response showed very small peaks at ct-pinene and myrcene and two small
47
-------
unknown peaks in the retention region of terpenes and three very signi-
ficant peaks at retention time zero to one minute. The two small un-
known peaks were major peaks in all the later ambient samples and were
confirmed to be Tenax artifacts by their absence from cryogenic concen-
tration analyses of two ambient bag samples.
The error due to the uncertainty of Tenax adsorption efficiency
under ambient sampling conditions is difficult to access and will be
more thoroughly investigated. The data of Table 3 indicate an effi-
ciency of 60 to 70 percent.
The reproducibility error expressed as percentage standard de-
viation was calculated from peak height measurements of four peaks from
eight duplicate ambient analyses. The average percent standard de-
viations were ± 20 percent and + 22 percent for the FID and chemilumi-
nescent responses respectively. The chemiluminescence and FID reproduci-
bility of the chromatograph without Tenax adsorption and desorption were
both ± 10 percent. The lack of any reproducibility difference between
the chemiluminescent and FID responses and the large reproducibility
discrepancy of the method with and without Tenax indicate that Tenax is
a large source of reproducibility error.
Ten duplicate day time ambient samples were collected and analyzed.
Six were from a small group of loblolly pines (Pinus taeda L.) behind
the EPA/RTP Environmental Research Center. The other four were from an
18 year old, rural, homogeneous stand of loblolly pine. The chemilumi-
nescence chromatograms of all of the samples showed only two peaks
corresponding to previously analyzed known terpenes. The two peaks were
a-pinene and myrcene, y-terpinene. Their concentrations were all less
than 2 ppb.
CONCLUSIONS
The method described herein has the advantage of simultaneous
measurement of FID and 03 chemiluminescent responses for GC samples.
This double measure provides for a more confident identification and quantit-
ation of terpenes in ambient air.
The disadvantage is that this method employs Tenax, which has been shown to
have adsorption efficiency and contamination problems, as a solid adsorbent for
concentrating ambient samples. If the use of Tenax proves to be too great a
problem, direct ambient cryogenic sampling of smaller volumes can be used as the
concentration technique.
ACKNOWLEDGEMENT
The author wishes to acknowledge the assistance of Dr. William McClenny of
the U.S. EPA Environmental Sciences Research Laboratory.
REFERENCES
1. Rasmussen, R.A. What Do the Hydrocarbons from Trees Contribute to Air
48
-------
Pollution? J. APCA, 22 (7): 537-543, 1972.
2. Grimsrud, E.P., Westberg, H.H., Rasmussen, R.A. Atmospheric Reactivity
of Monoterpene Hydrocarbons, N02 Photooxidation and Ozonolysis. In:
Proceedings of the Symposium on Chemical Kinetics Data for the Upper and
Lower Atmosphere, International Journal of Chemical Kinetics Symposium
No. 1, 1975. pp. 183-195.
3. Rasmussen, R.A., Werrt, F.W. Volatile Organic Material of Plant Origin in
the Atmosphere. Proc. Nat. Acad. Sci., 53: 215-220, 1964.
4. Rasmussen, R.A. Isoprene: Identified as a Forest-Type Emission to the
Atmosphere. Environ. Sci. Techno!., 4(8): 667-671, 1970.
5. Rasmussen, R.A., Holdren, M.W. Analyses of C5 to C10 Hydrocarbons in
Rural Atmospheres. APCA 65th Meeting, paper # 72-19, June, 1972.
6. Tyson, B.J., Dement, W.A., Mooney, H.A. Volatilisation of Terpenes from
Salvia Mellifera. Nature, 252 (5479): 119-120, 1974.
7. McNair, H.M., Bonelli, E.J. Basic Gas Chromatography. Varian Aerograph,
Walnut Creek, CA, 1969, pp. 118, 87-89.
8. Quickert, N., Findlay, W. J., Monkman, J.L. Modification of a Chem-
iluminescent Ozone Monitor for the Measurement of Gaseous Unsaturated
Hydrocarbons. The Science of the Total Environment 3(4): 323-328, 1975.
9. Hilborn, J.C., Findlay, W.J., Quickert, N. The Application of Chem-
iluminescence to the Measurement of Relative Hydrocarbons in Ambient
Air. In: Proceedings of the International Conference on Environmental
Sensing and Assessment, Las Vegas, Nevada, 1975, 24-2.
10. McClenny, W.A., Martin, B.E., Bumgardner, R.E., Stevens, R.K., O'Keeffe,
A.E. Detection of Vinyl Chloride and Related Compounds by a Gas Chroma-
tographic, Chemiluminescence Technique. Environ. Sci. Technol., 10(8):
810-813, 1976.
11. Seila, R.L., Lonneman, W.A., Meeks, S.A. Evaluation of Polyvinyl Fluoride
as a Container Material for Air Pollution Samples. J. Environ. Sci.
Health—Environ. Sci. Eng., All(2): 121-130, 1976.
12. Bellar, T.A., Lichtenberg, J.J. Determining Volatile Organics at Micro
gram-per-Litre Levels by Gas Chromatography. J. American Water Works
Assn., 66(12): 739-744, 1974.
13. Bertsch, W., Chang, R.C., Zlatkis, A. The Determination of Organic
Volatiles in Air Pollution Studies: Characterization of Profiles.
J. Chromatog. Sci., 12(4): 175-182, 1974.
14. Pellizzari, E.D., Development of Method for Carcinogenic Vapor Analysis
in Ambient Atmospheres. EPA-650/2-74-121, U.S. EPA, Research Triangle
Park, NC, 1974, 148 pp.
49
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15. Pellizzari, E.D., Development of Analytical Techniques for Measuring
Ambient Atmospheric Carcinogenic Vapors. EPA-600/2-75-076, U.S. EPA,
Research Triangle Park, NC, 1975, 187 pp.
16. Pellizzari, E.D., Bunch, J.E., Carpenter, B.H., Sawicki, E. Collection
and Analysis of Trace Organic Vapor Pollutants in Ambient Atmospheres,
Technique for Evaluating Concentration of Vapors by Sorbent Media.
Environ. Sci. Techno!. 9(6): 552-555, 1975.
17. Ibid, Thermal Desorption of Organic Vapors from Sorbent Media. Environ.
Sci. Technol. 9(6): 556-560, 1975.
18. Pellizzari, E.D., Bunch, O.E., Berkley, R.E., McRae, J. Determination
of Trace Hazardous Organic Vapor Pollutants in Ambient Atmospheres by
Gas Chromatograph/Mass Spectrometry/Computer. Anal. Chem. 48(6): 803-
806, 1976.
50
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2-3
MEASUREMENTS OF SULFATE, INORGANIC GASEOUS NITRATE
AND OTHER CONSTITUENTS IN THE ATMOSPHERE
T. Okita*
ABSTRACT
made. ofa Aiit&ate., gaA&ouA nit/tote. and otheA.
•in the. atmo&pk&ii -in Tokyo and W> Aiinnounding atea. GOA&OUA nWiata conce.n-
tsiationA weAe higheA. -in Aumm&i than in uiinteA and c.owieJLatz.d dtoboLy with tho&e.
Of) oxidantA. Sul^ata-to-Aul^usi dioxide, conc-antsiation fiatioA did not appeal to
dosuieJLcite. with oxMant c.onc.e.ntn.ationA, and thzy v&tizd uiith ti&tative. humidity.
INTRODUCTION
In photochemical air pollution various types of pollutants are produced,
including oxidants. They exert adverse effects on human health, plants, etc.
In this report, results from measurements of sulfate, inorganic gaseous
nitrate (probably nitric acid vapor) and other constituents, conducted in Tokyo
and its surrounding area, are presented and compared with measurements of
oxidants.
ANALYTICAL PROCEDURES
MEASUREMENT OF NITRATE
Ambient gaseous nitrate was measured by collecting it first on a Sodium
Chloride (NaCl )-impregnated filter from which it was subsequently extracted and
analysis was made for it. For preparation of the NaCl -impregnated filter, a
circular Toyo 51A cellulose filter 5 cm in diameter was soaked with a 5% aqueous
solution of NaCl, and was dried using an infrared lamp in a chamber free from
nitrogen dioxide (N02) and nitric acid gases. The filter was then stored in a
silica gel desiccator.
For ambient air sampling, either a Millipore FHLP Teflon filter or a Sumi-
tomo FP Teflon filter 47 mm in diameter along with an NaCl -impregnated filter
were placed in separate filter holders. They were connected in series, with the
FHLP filter upstream from the NaCl-impregnated filter. The inside walls of the
holders were coated with Teflon and the filter holders were heated by a 30-W
tape heater wound around the holder. The air was sampled through the filters at
*Department of Community Environmental Sciences, the Institute of Public Health,
Tokyo, Japan.
51
-------
a metered flow rate of about 20 1 mirr1. Participate and gaseous nitrates were
collected on the FHLP and Nad-impregnated filters, respectively.
For measurement, the gaseous nitrate collected on the Nad-impregnated
filter was extracted into 30 ml of hot water. Then 20 ml of the extract was
used for the nitrate measurement. The particulate nitrate collected on the FHLP
filter was ultrasonically extracted into 30 ml of warm water. In either case
the nitrate in solution was reduced to nitrite by hydrazine in alkaline solu-
tion. The resultant nitrite was determined by reacting it with Griess-Romijn
reagent (1) as modified by the technique as described in Ota et al. (2).
Efficiency of nitric acid collection on the Nad-impregnated filter was 90-
100% (mean efficiency 96.6%) for sampling flow rate of 20 1 min'1. Interference
from 0.1 ppm of N02 was equivalent to about 1 ygnr3 of nitrogen in the form of
nitrate ion (NOs). It was not enhanced by the presence of 03. Interferences
from peroxyacetylnitrate (PAN) and organic nitrates were negligible.
For particulate ammonium nitrate (deposited on the FHLP filter), ultrasonic
extraction of nitrate from the filter in warm water was the most efficient
extraction procedure, the efficiency being almost 100%. Loss of nitric acid
vapor on the FHLP filter was kept low (1-4%) by heating the filter holder with
a 30-W tape heater. Efficiency of particle collection by the FHLP filter has
been reported at 99.99%, even for the size corresponding to the penetration
maximum (3).
MEASUREMENT OF S02, N02, AND SULFATE (SOi;2)
Ambient S02 and N02 were measured using automated electric conductivity and
colorimetric (Saltzman) analyzers, respectively. Particulate sulfates were
collected on fiber glass filters and measured nephelometrically.
RESULTS
CORRELATIONS BETWEEN NITRATES, N02, AND OXIDANT CONCENTRATIONS
During 1973-1976, measurements of ambient gaseous and particulate nitrates
were conducted at the Institute of Public Health (IPH) and the Tokyo Metro-
politan Institute of Environmental Control (TMIEC), located, respectively, in
downtown Tokyo, and at Mt. Tsukuba (altitude 876 m) which lies about 80 km NNE
of downtown Tokyo (4).
Figure 1 shows the relationship of gaseous nitrate concentrations (measured
at the IPH between 10 a.m. and 5 p.m.) and daily maximum oxidant concentrations
measured at the Meguro Air Monitoring Station located about 3.5 km from the IPH
(during the period of July 25 to August 30, 1975). The data of Figure 1 indi-
cate that the concentration of gaseous nitrate increases with increasing oxidant
concentration. Such a correlation between gaseous nitrate and oxidant was also
found by our measurements in the summer of 1973 (4). Figure 2 shows the rela-
tionship between the concentrations of gaseous nitrate and N02 measured by the
sodium arsenite method (5). There was a tendency for high gaseous nitrate
concentrations to occur with high N02 concentrations in downtown Tokyo, but at
Mt. Tsukuba the gaseous nitrate concentrations were much higher than" were those
52
-------
of N02. As shown in Figure 3, there was no correlation between participate
nitrate and oxidant concentrations at the IPH site in the summer of 1975.
0.15
Q.
Q.
|0.10
•+-•
c
§
o
§0.05
"3
O
n
X
X
X K
X X
XX X
x x
X X
X
X
XX X
XXXX W
X XXX X
•x
30
o
'a
*-•
c
0)
XX X
«• .t) .
Gaseous NQjN Concentration /x.gm*
Figure 1. Relationship of gaseous
N03 concentration at the Institute
of Public Health versus daily maxi-
mum oxidant concentrations.
Q^Lj^Li- •; •••• . . :
°0 _ 2 A (
Gaseous NKjN Concentration fig m"1
Figure 2. Relationship between NO
and gaseous N0~ concentrations.
X IPH (July 25 - August 30, 1975)
t Mt. Tsukuba (June 25 - July 3, 1975)
Figure 4 shows the relationship between daily mean concentrations of
gaseous and particulate nitrates measured at the IPH and TMIEC sites in January
of 1976. Comparison of Figure 4 with Figures 1 and 3 indicates that, whereas
there was only a small seasonal change of the concentration of particulate
nitrate, the mean gaseous nitrate concentration in summer was about five times
that in winter in downtown Tokyo. To further study the seasonal variation of
gaseous nitrate concentration, additional measurements were made between October
13 and 17, 1975, at Mt. Tsukuba. These_measurements indicated that the mean N02
and both the gaseous and particulate N03 concentrations were 4.3, 0.4 and 1.5
ugnr3, respectively. Comparison of these results with those shown in Figure 2
reveals that the gaseous nitrate concentrations were much lower in autumn than
in early summer, whereas N02 showed an opposite pattern.
CORRELATIONS BETWEEN S0i;2/S02,
N0^/N02 AND OXIDANT CONCENTRATIONS
In the period June 25 to July 7, 1975 a survey of atmospheric constituents
was^conducted in a large area surrounding Tokyo (Figure 5). The data examined
and NOs1. Figure 6 indicates the day-
included measurements of SO?, NO
SO;2
to-day variation of daily mean values for S0^2-S/S02-S, N03-N/N02-N, oxidant
concentration and relative humidity at Kumagaya, Ichihara and Kawasaki. These
53
-------
0.15
E
Q.
a.
c
50.10
TJ
ll
1
c
o
50.05
XJ
&
n
X
X X
X X
xx x
X X
X X
X X
X
X X
X XXX X
X XXX X
X
246
Particulate NQjN Concentration
8
Figure 3. Relationship of participate HO^ concentration at
IPH versus daily maximum oxidant concentration.
cn
0
"oj
to*
u
5
u
z
in
o
rn fj
(5 U(
X
X
•»" "
..•»«
x«
ox o
o
0 °
o
.0
D 1 2
Particulate NO}N Concentration
Figure 4. Relationship between daily mean concentrations of
gaseous and particulate NOs on January 1-24, 1976.
X IPH
o Tokyo Metropolitan Institute of Environmental Control
54
-------
values show that SOi;2-S/S02-S correlates well with humidity rather than with
oxidant level. The N03-N/N02-N, on the other hand, shows some correlation with
oxidant level. The author found that nitric acid vapor is collected on glass
fiber filter and thus a portion of particulate nitrate comes from nitric acid
vapor in the atmosphere.
oKUMAGAYA
olGUSA
TOKYO ._„>
ol.PH.
.MT.TSUKUBA
Figure 5. Area surrounding Tokyo where survey of atmospheric
constituents was conducted June 25 - July 7, 1975.
REFERENCES
1. Mull in, J.B. and J. P. Riley. The spectrophotometric determination of
nitrate in natural waters, with particular reference to sea water. Analyt.
Chem. Acta 12, 1955. pp. 464-480.
2. Ota, T., R. Ishibashi and M. Osaki. Determination of nitrate ion using
hydrazine reduction technique. J. Japan Soc. Air Pollution 1, 1970. pp.
72 (in Japanese).
3. Liu, B.Y.H. and K. W. Lee. Efficiency of membrane and nucleopore filters
for submicrometer aerosols. Particle Technology Laboratory Publication No.
266, 1975.
4. Okita, T. and S. Morimoto. Measurement of nitric acid and particulate
nitrate in the atmosphere. Preprint of Autumnal Meeting of Met. Soc. of
Japan, 143, 1973 (in Japanese).
5. U. S. Environmental Protection Agency. Ambient air quality standards.
Reference method for determination of nitrogen dioxide. Federal Register
55
-------
38, 1973. pp. 15174-91.
6. Environment Agency of Japan, Study Committee of Contaminated Precipitation.
Report of Study of Contaminated Precipitation in 1975, 1976. (in Jap-
anese) .
o -
/I
M
40
30
1
3 20
1
O* 10
n
\
R-H- KUMAGAYA ' .
\fl}) I
i
/ •
/ \
f
90, ' '
\ { \
1 Rs / I
\\ '' \ "
-Xk^-'A >• •
A A- -
^^L O LI ^r ^i
-70 *xj /
1 1 1 1 1 1 1
016
014
012
to
en
Q10 &
*. N; "g
008 ^ I1
^ z
Q06 ^ ~
v-x 2
\
C/3 i rt
004 O
i
jy}
KUMAGAYA
- Ox
(pphm)
-8 ft R N
. t
' i
/ \
/ 1C l
'H -^Xx '
, t i i i i i
RN
X
•2.
010 2
o
u 1
0.08 '
<§
Q06 ^
\
004 O
M
1
2
0.02 if
V_-*
002 1* ° 25 26 30 1 2 3 7 °
^ JUNE JULY
n
25 26 30 1 2 3 7
JUNE JULY
40
^ 30
c/)
i 20
O
in
10
0
rioo o
R H '\
Rs / i
.(® .ICHIHARA / »
9°\ / \ -
\\ 1 R.H. \
' A ;'/^("
* NA7^ / * /I
N? ^^» • / i
. 70 S°2*-S
i i i i • it
an Rs
Q12
010
0.08
Q06
9
^ ,
Q04 3 zo
Z
I
002 O* 10
0 0
r
ICHIHARA
~0x
(pphm)'V
/ ^
/ X
•6//\^aN
/ / \ r> x
- 4 / / ^ — ^» i n ~
,:_. T-\
••~— «^**" ""*"^'»^>>>^
1 1 1 I 1 1 1
RN
0.10
0.08
0.06
Oj04
0.02
25 26 30 1 2 3 7
JUNE JULY
25 26 30 1 23 7
JUNE JULY
Figure 6. Day to day variations of Rc., R , oxidant concentration
and relative humidity--Kumagaya and Ichihara.
56
-------
Oo
3
C/l
20 -
10
o 0.4 6
VK
R.H.
^l KAWASAKI
' \\
\
-90 V
\ Rs
1 o
\ /\R.H.-
f /®T-*
\ J \ '
\ /s> 20
Z
1
d* 10
z
0 -u
KAWASAKI
' Ox
( pphm) 0
y \
"/X .^-"x "
yx^x\ c^*^* \
o \ N
\ ^^--o
LJ 1 1 ifl- —0^ 1 1
25 26 30 1 2 3 7
JUNE JULY
25 26 30 1 2 3 7
JUNE JULY
Figure 6. Day to day variations of R , R . oxidant concentration
and relative humidity--Kawasaki.
• 0.20
o.io
57
-------
2-4
A PORTABLE INSTRUMENT FOR THE CALIBRATION OF OZONE ANALYZERS
BY OPTICAL ABSORPTION MEASUREMENTS
K. H. Becker, A. Heindrichs, and U. Schurath*
ABSTRACT
An -inA&uunent ^on na.pi.d c&tibfiCLtionA o^ ozone, analyzes, oveA the. conc.e.n-
tsiation fianQe, 10 ppb to -ieve/io£ ppm u, deAcsubed. It tnctudeA a photoc.he.micj&t
ozone- 4ouA.ce. The. ozone. conce.ntMtA.on u* catcalate^d ^fiom the. optical, ab^o-tp-
tion o£ monochromatic 253.7 nanometer mediation, 06 me.cu>uAe.d -in a. tubuJLaSi ab-
boiption ceJUi. Due. to fvapid iej>pon&e., the. -in&tnwment pavticu£ci>i£y
i>iiLte.d fion. the. catibtt&tion o& c.hemitLwine.Ac.e.nt ozone. ayiaLyzeAb m£h bhoht tune.
INTRODUCTION
Ozone measurements in Europe indicated in 1973 that the ozone (03) con-
centration was frequently considerably higher than the natural background con-
centration of 20 to 40 ppb at ground level, and on some occasions exceeded
the 200 ppb level above which health effects are manifest (1). This releva-
tion initiated an international program for the investigation of the oxidant
situation in a number of European countries with the aim of recommending
control strategies. Since then the number of monitoring stations for 03 in
the German Federal Republic and other European countries was considerably
increased. Nearly all 03 analyzers in the stations are based on the chemilumi-
nescent reaction of 03 with ethylene which is particularly suited for continu-
ous monitoring. Such analyzers are not by principle absolute detectors and
must be calibrated. Furthermore, sensitivity changes must be anticipated
under continuous operating conditions. These changes cannot be totally elimi-
nated by re-calibrations with a built-in 03 generator which can lack stability.
In addition, 03 losses can occur in the sampling line and dust filter.
Calibrations of 03 analyzers are usually made by comparison with the
hydrogen iodide (HI) method. The stoichiometry of this wet chemical reaction,
at 03 concentrations below 500 ppb, is approximately the following (2,3):
03 + 2 I" + 2 H+ + I2 + H20 + 02 (1)
The procedure, apart from its well known error sources (4), has all the
disadvantages of an integrating method: the calibration is time consuming and
must be performed with an 03 source of highly constant output, whereas an ad-
vantage of chemiluminescent analyzers is, in particular, their short response
time.
*Institut fur Physikalische Chemie der Universitat Bonn, Bonn, Germany.
59
-------
This paper presents a reliable technique for the calibration of 03 anal-
yzers which eliminates the disadvantages of wet chemical methods. It measures
optical absorption by 03 using an ultraviolet means, a method frequently used
in laboratory experiments (5,6).
THE PRINCIPLE OF MEASUREMENT
The highest absorption coefficient of 03 in the Hartley band nearly
coincides with the wavelength 253.7 nanometers (nm) of the mercury resonance
line. The absorption obeys Beer's law, due to the continuous nature of the
absorption spectrum in this region. The recommended value of the absorption
coefficient at 253.7 nm is defined by Equation 2.
log10(I/I0) - k x p 273/T (2)
(T = temperature in K, x = absorption path in cm; p = ozone pressure in atmo-
spheres), is k = 133.9 atirr^crrr1 (7). This value obtains support from numer-
ous determinations (8) and agrees well with k = 134.5 atm-^cnr1 measured in
this laboratory (5). At an optical path length of 3 m and 20°C, 100 ppb 03
causes an intensity reduction of 0.89% relative to pure synthetic air. Weak
intensity reductions can be measured reliably at 253.7 nm, provided a low
pressure mercury lamp of sufficient stability is used. The suitable concen-
tration range of 10 to 500 ppb 03 can thus be covered.
EXPERIMENTAL
The experimental setup is shown schematically in Figure 1. Ozone is pro-
duced in synthetic air by means of a simple but efficient photochemical 03
generator with an elliptical reflector. The sampling gas then flows through
a light protected glass tube of 1500 mm length. Radiation from a low pressure
mercury lamp (Oriel type C-13-61) in a brass housing is collimated along the
axis of the tube through a metal capillary. The light is reflected at the far
end of the glass tube by a quartz triple prism which has the advantage over a
plane mirror that the angle of reflection is always 180°. Therefore no adjust-
ment of the prism is necessary, and the intensity of the reflected light is
nearly independent of the angle of incidence on the prism surface., The return-
ing light beam is deflected 90° by a plane mirror through a quartz window and
interference filter for 253.7 nm on the cathode of a photomu'ltiplier tube (EMI
9665 B). The light reaching the photomultiplier is better than 99.9% monochro-
matic since 95% of the lamp output is at 253.7 nm, and the interference filter
blocking ratio is 1:104. The effective absorption path is 3100 mm. All metal
parts exposed to the gas stream are teflon coated. The volume of the optical
cell including both the entrance and the exit chambers is 180 ml, giving a
residence time of 11 s at a typical flow rate of 1000 ml/min. Decay measure-
ments in the absorption cell at stopped flow resulted in a lifetime of 70
min., increasing to 100 min. after 1 hour exposure to ozonized air. The
systematic error due to heterogeneous decomposition of ozone in the cell is
therefore less than 0.3%.
60
-------
To determine 03 in the concentration range below 500 ppb, intensity
reductions below 4.35% must be measured. A well stabilized high voltage
supply for the photomultiplier tube, and a stable light source are therefore
needed. A selected low pressure mercury lamp of the above-mentioned type was
found adequate after a short period of conditioning, and at a constant line
voltage. Intensity changes below 5% are conveniently measured by compensating
95% of the voltage across the photomultiplier anode resistor at full intensity
IG with a battery. The remaining signal is amplified and displayed on a strip
chart recorder which is then deflected full scale at 5% optical absorption.
CALIBRATION OF A CHEMILUMINESCENT OZONE ANALYZER
A Bendix 03 analyzer, Model 8002, was calibrated in the 500 ppb range and
below. The coupling of the analyzer to the optical measuring cell is shown in
Figure 1. Both instruments were run with time constants of 1 s. The synthetic
air flow rate was 108 liter/hour. The calibration procedure is illustrated by
the strip chart recordings of the signals from both instruments in Figure 2.
Stepwise changes of the 03 concentration in the sampling gas were achieved by
shielding or unshielding part of the mercury lamp in the 03 generator. The
intensity I0 was checked in between the measurements by completely shielding
the mercury lamp in the generator. A drift of I0 could thus be taken into
account by linear interpolation. The calibration of the 03 analyzer, as de-
picted by the recordings in Figure 2, was completed within 11 minutes. Figure
3 shows the resulting plot of chemiluminescent analyzer signal versus the
optically measured 03 concentration, as calculated from the recordings by
means of Equation 2. The slope of the straight line gives the sensitivity of
that particular analyzer as 1.88 V per ppm 03, with a standard deviation of
+ 2.5%.
COMPARISON WITH THE POTASSIUM IODIDE (KI) METHOD
The potassium iodide (KI) method is widely considered an absolute method
for 03 measurements, since, under suitable conditions, the stoichiometry given
by Equation 1 is closely obeyed. In practice, however, the KI method often
leads to serious errors, as was shown recently on occasion of a monitoring
program in the U.S. (9). (One of the probable reasons for such errors is that
the sensitivity of chemiluminescent analyzers is reduced by a factor of nearly
2 when oxygen is used as test gas instead of synthetic or purefied air (10).)
The precision of the optical method for 03 determination depends, in principle,
only upon the reliability of the absorption coefficient at 253.7 nm used in
Equation 2. Determinations of the absorption coefficient are based on ele-
mentary physical measurements such as the length of the absorption path, the
pressure of 03, and the temperature. The relatively wide error limits of the
absorption coefficient, +_ 1.5%, are mainly due to the difficulties inherent in
the production and handling of pure 03. The 03 concentration is deduced from
the pressure increase after complete decomposition into molecular oxygen.
A direct comparison between optically measured 03 in synthetic air and
measurements by the KI method resulted in good agreement between the two
methods.
61
------- An error occurred while trying to OCR this image.
-------
-p
00.8
0)
N
^0.6
0)
OQ.4
N
o
O
0.2
tn
-H
100 200 300 400 ppb
ozone concentration
Figure 2. Calibration of a chemiluminescent ozone analyzer, (a) Absorp-
tion by ozone at 253.7 nm in the cell, (b) Corresponding signal of the
chemiluminescent ozone analyzer in series with the cell.
63
-------
CAP
e
ro
LT)
04
*
-M
C
O
•H
-P
C^
JH
O
w
4
3
2
1
O
S °-8
.6
c
O
N
O
C
Cn
-H
0.4
0.2
/•»*
2468
time (minutes)
10
Figure 3. Calibration curve, calculated from the recordings in Figure 2,
64
-------
ACKNOWLEDGEMENT
The authors express their thanks to J. Lobe! and A. Wiese for their valu-
able assistance. The 03 meter was developed as a part of a research programme
on photochemical smog formation in the German Federal Republic, supported by
the "Bundesministerium des Innern."
REFERENCES
1. Becker, K. H., and U. Schurath. Entsteht Photochemischer "Smog" in der
Bundesrepublik Deutschland? Umschau 73:310, 1973.
2. Leithe, W. Die Analyse der Luft und ihrer Verunreinigungen in der
freien Atmospha're und am Arbeitplatz. Wissenschaftliche Verlagsgesell-
schaft mbH, Stuttgart, 1968.
3. Methods of Air Sampling and Analysis. Published by American Public Health
Association, 1015 Eighteenth Street, N. W., Washington, D. C., 1972.
4. Perry, E. P., and D. H. Hern. Stoichiometry of ozone-iodine reaction:
Significance of iodate formation. Envir. Sci. Technol. 7:65 and 647, 1973.
5. Becker, K. H., U. Schurath, and H. Seitz. Ozone-Olefin Reactions in the
Gas Phase. 1. Rate Constants and Activation Energies. Int. J. Chem.
Kinet. VI:725-739, 1974.
6. Hames, P. Thesis, Technische Universitat Munchen/DECHEMA Institut
Frankfurt, 1975.
7. Hampson, R. F., Editor. Survey of photochemical and rate data for twenty-
eight reactions of interest in atmospheric chemistry. J. Phys. Chem.
Ref. Data 2:267-311, 1973.
8. Hudson, R. D. Critical review of ultraviolet photoabsorption cross
sections for molecules of astrophysical interest. Rev. Geophys. Space
Phys. 9:305, 1971.
9. Stephens, Edgar R., and Arthur M. Winer. The Oxidant Measurement
Discrepancy. California Air Environment 6(1), 1975/76.
10. Schurath, U., and W. Wendler. liber die Verwendbarkeit von ozonhaltigem
Sauerstoff zur Kalibrierung von Ozonanalysatoren. Staub-Reinhalt.
Luft 35 (9):329-310, 1975.
65
-------
2-5
STATUS OF CALIBRATION METHODS FOR OZONE MONITORS
R. J. Paur, R. K. Stevens, and D. L. Flamm*
ABSTRACT
The n neutral-bu^ered potaAAium i.odide federal Reference Method &or
calibrating ozone. monAton, kcu> been widety criticized ^or itA A&iong bttoad ab*ox.ption band £n the. 200-300
nanome.teA ie.Q4.on. The. go* pha^e. titnation te.c.hntqu.e. nztia.* on the. weJtt known
ie.acti.on o& n-l&iogen oxA.de. wtctfi ozone. Go* pfuue tAtAa&ion and ul&iav-ioJlLet
photometry yieJLd compa^ab£e sie.aZt& oveA an ozone, conce-ntsiation stange. ofi 0.05
to 0.7 ppm. Re.ce.ntty, undeA Environmental. Vnotz.ctA.on Agency t>pon*ouhip, a
modsifii.e.d potaAAium iodide, method ha* been developed. In ptieJLimjian.y 6tu.die.-i>,
the. new method appeau to be accurate and precise over the ozone concentration
fiange o$ 0.1 to 1.0 ppm.
INTRODUCTION
The Federal Reference Method for determining ozone (03) concentrations in
synthetic atmospheres used to calibrate 03 monitors is the U neutral-buffered
potassium iodide (1% NBKI) procedure as described in the Federal Register 36
(228): 22384-22397, November 25, 1971. This calibration method is based on
the spectrophotometric determination of iodine released from an NBKI absorbing
solution of 03.
The 1% NBKI method has been widely criticized for its inconsistent re-
sults. (See Figure 1.) In late 1973 it was discovered that state and local
agencies in the Los Angeles area were obtaining significantly different esti-
mates of 03 concentrations in that area. These differences were traced to
different KI calibration methods used by the various agencies. As a result of
those findings, some half dozen studies have been carried out since mid 1974
to determine the accuracy of various KI methods. The results of some of these
studies are summarized in Table 1.
*R. J. Paur, R. K. Stevens, Environmental Protection Agency, Research Triangle
Park, North Carolina.
D. L. Flamm, Texas A&M University, College Station, Texas.
67
-------
tn
I .20 -
1 . IE-
i—
0.
^1.12-
3
" 1 . 0B -
1 I .0H-
1.00-
0 . as -
c
r
CDMPRRI5QN DF Kl Nl
\
*'T
In
. a
M
4
'{ i
a 3~ m 3^ m 3-
n — — rvi
"^ •>» •** -s "* "«»
m 3- 3- 3- 3- 3-
TH EPT
*
4
j
m 3-
rvi
3- ui
.,,
m
Url
DflTE
Figure 1. Comparison of potassium iodide with gas phase titration.
Table 1 illustrates that the 1% NBKI method run under dry conditions
(i.e. the Federal Reference Calibration Method) gives results approximately
10% greater than ultraviolet (UM) photometry or gas phase titration (GPT). It
should be remembered that all of these studies were run under ideal conditions,
and that in normal usage the precision of the method may well be less than
that indicated by the Table.
In addition to the KI studies, the U.S. Environmental Protection Agency
(EPA) and other groups have examined several other methods for determining the
03 content of calibration atmospheres. Two of these methods, LIV photometry
and GPT, have been in use for some time and are generally considered to be
valid methods. A third method, 1% boric acid buffered potassium iodide (1%
BAKI) is new and is in the preliminary stages of evaluation.
ULTRAVIOLET PHOTOMETRY
Ozone lends itself to UV photometry due to its strong broad absorption
band in the 200 to 300 nanometer (nm) region. The peak of this band very
nearly coincides with the 254 nm radiation of low pressure mercury (Hg) dis-
charges. In spite of the high absorptivity of 03 at 254 nm (133.9 cm-1
atm s base 10), the UV photometer must have capability to resolve changes in
transmittance of less than 1 part in 104 if ozone concentrations to within 5
68
-------
TABLE 1. COMPARISON OF VARIOUS KI DETERMINATIONS WITH UV PHOTOMETRY OR GAS
PHASE TITRATION
Study
Baumgardner, et al
Baumgardner, et al
Baumgardner, et al
Baumgardner, Paur
Baumgardner, Paur
Baumgardner, Paur
Baumgardner, Paur
CARB, El Monte
Hodgeson
Beard
Smith
Hughes
KI Method
V/o NBKI
2% NBKI
2% NBKI
1% NBKI
1% NBKI
2% NBKI
2% NBKI
1% NBKI
2% NBKI
2% UBKI
V/o NBKI
1% NBKI
1% NBKI
1% NBKI
Reference
Method
GPT
GPT
GPT
GPT
GPT
GPT
GPT
UV
UV
UV
UV
GPT
GPT
GPT
Ratio0
1.01
1.04
0.61
1.05
1.12
1.13
1.18
1.25
1.29
0.96
1.11
1.08
1.11
1.0
KI
Reference
+ 0.04
+ 0.03
+ 0.04
+ .05
+ .07
+ .03
+ .05
a
a
a
+_ .01
+ .035
+ .02
b
03Conc.
Range, ppm
0.1 - 0.5
0.1 - 0.5
0.1 - 0.5
0.4
0.4
0.4
0.4
0.1 - 0.8
0.1 - 0.8
0.1 - 0.8
0.05-10.1
0.08- 0.8
0.2 - 0.4
0.2 - 0.4
Relative
Humidity
0
0
0
0
40-60%
0
40-60%
50%
50%
50%
0
0
0
0
a. These workers also report intercept data which indicates a constant
additive bias.
b. Variable depending on sampling time and color development time.
c. There is no absolute standard for ozone in the sub-part-per-million range.
Therefore, precision of calibration procedures is determined by the
reproducibility of measurements while the stability of the ozone
concentration is monitored by ambient air ozone monitors. The accuracy
of ozone calibration procedures at the sub-ppm level is estimated from
the degree of agreement between two or more procedures that are accurate
at ozone concentrations which can be monitored manometrically. UV
photometry and gas phase titration are methods of high precision; they
are accurate at high ozone concentrations; they agree well at sub-ppm
ozone concentrations so they are assumed to be accurate at low concen-
trations. For these reasons the results of most potassium iodide studies
are reported in terms of KI values relative to UV photometry or gas
phase titration values.
69
-------
ppb using a pathlength consistent with an easily portable instrument are to be
measured. At least one such photometer, which with minor modifications
appears to have the capacity for suitable accuracy, is commercially available.
GAS PHASE TITRATION
Gas phase titration techniques rely on the well known reaction of CL with
nitric oxide (NO):
nNO
(n - m)NO
The reaction can be monitored by determining either the amount of NO consumed
or the amount of nitrogen dioxide (N02) produced. Standard reference materials
(SRM) for NO are available from the National Bureau of Standards (NBS) in the
form of cylinders containing 50 to 100 ppm NO in nitrogen (N). A nitrogen
dioxide (N02) SRM is available in the form of a permeation tube. In addition
to NO and/or N02 standards of known accuracy, GPT methods generally require
accurate flow measurements to determine the degree of dilution of the standard
in the calibration system.
Figure 2 presents a typical comparison of 03 concentrations determined by
UV photometry and GPT. The slope of the curve is approximately unity and the
small scatter about the curve attests to the precision of both analyses.
Results similar to those in Figure 2 have been obtained in several laboratories
and are summarized in Table 2.
a:
LJ
LJl
a:
in
en
in
V.
31
CL
a.
^,
n
a
0.B--
0.7-
0.E-
0.S-
0.H-
0.3-
0.2-
0.1-
0.0
CDMPRRI5DN DF EPT RND UV
DZDNE DETERMINATIONS
SLOPE - I.003
- I
1 E/30/7S
2 7/0 I/7S
3 7/02/7S
H 7/03/7S
0.0 0.1 0.2 0.3 0.H 0.S 0.E 0.7 0 . B
D3/PPM/UV PHDTDMETER
Figure 2. Comparison of gas phase titration and UV ozone determination.
70
-------
TABLE 2. COMPARISON OF OZONE DETERMINATIONS BY GAS PHASE
TITRATION WITH UV PHOTOMETRY
Study
03 Con.
Range, ppm
Results
Paur*
DeMore
Hodgeson
Stedman
0.06 - 0.7
0 - 1
0 - 10
= 0 -009 ± -004) (°3)uv- (°-002 ± °-002)
(03)= (1.001 + .007) (03)uv- (0.005+0.003)
+ -02) (03)uv
- '02) (°3)uV
yv
QpT
GPT
(°3)
(Q3)GPT= d.o) (O3)
* Two separate 4-day studies using different NO standards and different
system flows.
BORIC ACID POTASSIUM IODIDE
The ]% boric acid potassium iodide (BAKI) method is similar to the 1%
NBKI method except for replacing the phosphate buffer with 0.1 M boric acid.
The results obtained from the BAKI method differ from the NBKI results in
several important aspects.
The NBKI method yields results some 10 percent greater than the BAKI
method at the 0.5 and 1.0 ppm levels. In studies conducted at Texas A&M Univ-
ersity, the BAKI results were in good (+_ 3 percent) agreement with a Dasibi 03
monitor set up to run as an absolute photometer. This Dasibi instrument was
later compared with an 03 calibration system at EPA headquarters in Research
Triangle Park, N.C. (EPA/RTP) and results agreed to within + 2 percent.
The color development of the NBKI method continues for some 15-30 minutes
or more after completion of sampling, and by the end of color development the
NBKI results may be more than 20% greater than the photometer results. In
contrast the BAKI color development appears to be stable by the time the
absorbing solution can be transferred to curvettes. The change in absorbance
in the NBKI method may be due to decomposition of an intermediate species
formed during sampling. A preliminary study of this phenomena indicates that
decomposition of hydrogen peroxide occurs at approximately the same rate as is
required to explain the time dependence of the absorbance.
The Texas A&M studies also indicate that the BAKI method yields the same
71
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results when using fritted bubblers as when using "midget impingers"; the NBKI
method has been criticized for yielding different results with different kinds
of absorber glassware.
A preliminary study of the BAKI method has been carried out in the EPA/RTP
laboratories to compare BAKI results with an 03 calibration system that utilizes
both GPT and UV photometry to provide a reliable estimate of the 03 concentra-
tion. For 50 data points (29 at ~500 ppb, (5 at ~250 ppb and 15 at ~120 ppb),
the average ratio of BAKI results to photometric results was 1,.016 with a
standard deviation for the ratio of 3 percent.
The new BAKI method is currently being examined with respect to its
stability under changes in relative humidity. Further studies will examine
the sensitivity of the method to impurities in the reagents. This last point
is of particular interest since the BAKI results were approximately 10% lower
than the photometric results at the 0.1 ppm level in the Texas A&M study; the
ratio of BAKI results to UV photometry results did not show any discernible
concentration dependence in the EPA/RTP results.
72
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SESSION 3
SOURCES OF TROPOSPHERIC OZONE - I
R.A. Rasmussen
Washington State University
73
-------
3-1
METEOROLOGICAL CONDITIONS CONDUCIVE TO HIGH LEVELS OF OZONE
T. R. Karl and G. A. DeMarrais*
ABSTRACT
AeJtome.t'Lic data aAe. c.onAtd&fie,d ^on. two tocationA: Los kngeJLeA and St.
louM>. NumesiouA AtudteJ* o& photochemical. oxA.da.nt, o{te.n catie.d Loi> AngeJLeJ,
-6mog, one. brought together to de.pi.ct the me.tz.osiologtc.al. e.^e.ctA on ozone, con-
ce,ntsiattonA. Re.ce.ntty obtaA,ne.d data fifiom the. Envvionme.ntal. P?iote.ction Agenct/'^
Regional kin. Pottu.tion Study OA.Q. Au.bje.cte,d to fm.QtieAbi.on anatyAeA to &oit oat
the. mzte.oMl.ogi.cal. vaJtiableA that asie. conducive, to high. te.ve.&> ofa AuAfaace
ozone..
INTRODUCTION
The ozone/oxidant problem, starting with a plant damage investigation (1),
has been studied for 30 years. The photochemical aspects were partially under-
stood a quarter-century ago (2). Beginning with specialized forecasts in 1952
and daily forecasts in 1953, the meteorologist was predicting when ozone con-
centrations [03] would be bothersome to people (3). By 1954, there was a
compendium on the meteorological aspects of the ozone problem in Los Angeles
(4) and a report on one of the largest field programs on the three dimensional
variation of oxidant and meteorology in the LA Basin (5). Space limitations
prevent the enumeration of all the field studies that have been conducted,
but the spatial coverage and results indicate that high [03] are a nationwide
affliction.
Observed levels of [03] are higher in California than in the rest of the
nation. The literature on the meteorological aspects of the ozone problem in
California, particularly in the LA Basin, is plentiful, but a composite pic-
ture does not exist. Such a picture, based on existing information, is pre-
sented in this paper and will be referred to as the Pipe-Mix Model.
A second major section of this report is an examination of various meteor-
ological variables related to [03] for a 25-station network in St. Louis (STL).
This data set was chosen for study because of the high quality and large quantity
of aerometric data within an urban and rural environment outside the LA area.
THE PIPE-MIX MODEL OF THE LOS ANGELES OXIDANT PROBLEM
A review of the literature indicated that an understanding of various
*Environmental Protection Agency, Research Triangle Park, North Carolina.
The authors are on assignment with EPA from the National Oceanic and Atmospheric
Administration, U.S. Department of Commerce.
75
-------
parts of the ozone problem in LA existed. There are two main meteorological
processes contributing directly to the problem—horizontal transport and vertical
mixing (abundant solar radiation away from the immediate coast is an everyday
phenomenon in the Basin in the summer, so its contribution to [03] does not
vary). The horizontal transport aspect has been called the "pipe reactor
effect" (6). Vertical mixing accounts for the mixing of air aloft with that
at the surface. The detailed descriptions and pictorial presentations that
follow are called the Pipe-Mix Model (July conditions are presented).
The basic elements in the Pipe Reactor Effect (Figure 1) are:
• The average wind speed in the Basin is 7 mph (7).
• Sunlight is of sufficient intensity to initiate photochemical reactions
early in the morning (8).
• Production exceeds destruction of ozone in this contaminated layer
during the period 2 to 7 hours after the photochemical reaction is
initiated (9). The time when the production first exceeds destruction
(in the summer) is around 8 a.m. (8).
• The daytime surface wind patterns are so persistent that the reactive
air mass moving downwind under the subsidence inversion can be
considered as moving in a pipe (6).
This pipe reactor effect means:
• Primary emissions in upstream locations result in problems further
down the pipe, and
• The resulting [03] are cumulative.
The basic elements in the Vertical Mixing Effect (Figure 2) are:
• There is a reservoir of ozone aloft that can be brought down by
vertical mixing. In 1954, ozone aloft was restricted to the volume
below the inversion base (5), but now the inversion is a major re-
servoir of ozone aloft (10, 11, 12).
• The reservoir extends from Coastal Ventura and Los Angeles County
to the mountains north and east of Los Angeles. Its presence to
the west and northwest of Los Angeles was shown by Lea (10). The
movement from Los Angeles to Coastal Ventura County was shown to
occur by Kauper and Niemann (13). Winds aloft data during night-
time hours for Santa Monica and Long Beach (14) show that this
movement is a frequent occurrence. During the day the movement
is in the opposite direction and the highest concentrations in the
Basin are generally over the eastern part (11, 12).
t [03] aloft remain relatively high throughout the night (10, 15, 16),
as there is very little ozone destruction aloft.
76
-------
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-------
• [03] aloft vary spatially and from day to day (10, 11, 12, 15).
The spatial variations are due to the various methods and places
through which the ozone gets into the layer aloft (10, 11, 17).
Prediction techniques based on historical data (18, 19, 20) show
that the highest ground level concentrations occur when the 500-mb
level (on the average, about 5.6 km above the surface) is relatively
high, is warm, and is marked by a weak pressure gradient. This
condition would likewise mean that the air aloft is stagnant (ozone
accumulates). Variations in rates of accumulation account for day-
to-day differences in concentrations aloft.
• Vertical mixing extends to much greater heights over the eastern
than over the western part of the Basin during the day (11, 12, 21).
Climatological data (7) for the Basin show the average diurnal
temperature ranges are 10° to 15°F in the western areas, whereas
they are 30° to 38°F in a very large part of the eastern section.
Surface-based inversions with negligible vertical mixing occur almost
every night where the range of temperatures is large and are relatively
infrequent in the west in July.
• Vertical mixing that gives a dilution benefit when it mixes surface
air with cleaner air aloft is a detriment when the concentrations
aloft are higher than those at the surface. In the western part>
of the Basin, because the increase in mixing height is small during
the day (22) and because the [03] in the affected volume aloft are
relatively low, the ground level concentrations are not increased
markedly in the typical situation (occasionally easterly winds
aloft move the higher concentrations to the west and vertical mixing
brings the high concentrations to the ground) (16). In the east,
where the daytime mixing occurs to greater heights and the [03] aloft
are relatively high, the ground level concentrations can be increased
markedly.
The combined parts of the pipe-mix model demonstrate the synergistic
effect of the two meteorological parameters, horizontal transport and vertical
mixing, in the observed levels of [03] in the area.
METEOROLOGICAL CONDITIONS RELATED TO OZONE CONCENTRATIONS IN ST. LOUIS
DATA
As part of the Environmental Protection Agency's (EPA) Regional Air
Pollution Study (RAPS) in St. Louis, a network of 25 Regional Air Monitoring
Stations (RAMS) continuously record aerometric data. Surface measurements
of [03], wind direction and speed, and global radiation (global radiation is
defined as the total of direct plus diffuse sky radiation received by a unit
horizontal surface), as well as the vertical temperature gradient near the
surface (5 to 30 meters), were derived from the RAMS network during the period
July 1, 1975 through September 15, 1975. The locations of the stations in
the network and their associated land use are shown in Figure 3.
79
-------
122
INDUSTRIAL. GENERALLY IS STORIES •
RESIDENTIAL, GENERALLY 2 STORIES
COMMERCIAL. > 10 STORIES
SINGLE FAMILY DWELLING 1 STORY
UNDEVELOPED OR AGRICULTURAL
AREA
118
•
123
01 23 45
MILES
0 1 2
10
KILOMETERS
124
•
Figure 3. Station locations and land use in the St. Louis area
(modified from Reference 23).
Additional data were acquired from the National Weather Service at Lam-
bert Airport, which is approximately 5 km northeast of Station 120. Synoptic
charts of various other meteorological variables, prepared by the National
Meteorological Center, were also employed.
In the RAMS network each station was visited at least twice weekly for
routine maintenance. The data from each station were checked by computer
programs (24) and by visual inspection to eliminate erroneous values.
RESULTS OF THE ANALYSIS
A stepwise regression technique was employed as a means of sorting out
the role played by various meteorological variables with regard to surface
80
-------
[03]. At each station ozone concentration was used as the dependent variable.
Table 1 lists all the variables subject to entry into the regression equations,
TABLE 1. VARIABLES SUBJECT TO ENTRY INTO THE REGRESSION EQUATION
[03]
TMAX
WS
AVERAGE OZONE CONCENTRATION (ppb) BETWEEN 1000
AND 1500 LOCAL DAYLIGHT TIME (LOT).
DAILY MAXIMUM TEMPERATURE AT LAMBERT AIRPORT (°C).
AVERAGE SURFACE WINDSPEED (m/sec) ACROSS THE RAMS
NETWORK BETWEEN 0800 AND 1500 LOT
SQUARE ROOT OF THE NUMBER OF DAYS SINCE THE LAST
MEASURABLE PRECIPITATION OCCURRED AT LAMBERT
AIRPORT
SQUARE ROOT OF 10 TIMES THE AVERAGE GLOBAL RADIA-
TION (lang/min) BETWEEN 0800 AND 1500 LOT DETERMINED
FROM STATIONS 103, 104, 107, 114, 118, AND 122.
SQUARE ROOT OF THE NUMBER OF DAYS SINCE THE LAST
COLD FRONT PASSED ST. LOUIS
HEIGHT OF THE 500 mb SURFACE (FEET ABOVE SEA LEVEL)
OVER ST. LOUIS AT 0700 LOT
24-HOUR CHANGE (FEET) IN THE HEIGHT OF THE 500-mb SUR-
FACE FROM THE PREVIOUS 0700 LOT OBSERVATION.
AT - TEMPERATURE (°C) AT 30 METERS MINUS THE TEMPERA-
TURE AT 5 METERS AVERAGED ACROSS STATIONS 109, 111,
AND 112 DURING THE PERIOD 1000 TO 1500 LOT.
YNRAIN -- REPRESENTS WHETHER OR NOT MEASURABLE PRECIPI-
TATION FELL BETWEEN 1000 AND 1500 LOT. THE VAR-
IABLE EQUALS 1 IF IT DID OCCUR AND 0 IF IT DID NOT
OCCUR.
WD - FRACTION OF TIME DURING THE PERIOD 0800 TO 1500 LOT
WHEN THE SURFACE WIND BLEW > 1 m/sec FROM THE EIGHT
SECTORS LISTED BELOW. WIND DIRECTION WAS DETERMINED
BY AVERAGING ALL 25 STATIONS.
VARIABLE
N
NE
E
SE
SECTOR (+22.5°)
360°
45°
90°
135°
VARIABLE
S
SW
W
NW
SECTOR (+22.5°)
180°
225°
270°
315°
CALM -- FRACTION OF TIME DURING THE PERIOD 0800 TO 1500 LOT
WHEN THE SURFACE WIND SPEED IN THE RAMS NETWORK
AVERAGED < 1 m/sec.
VORT500 -- AVERAGE VORTICITY (sec-1) AT 500 mb OVER ST. LOUIS BASED
ON THE 0700 AND 1900 LOT 500-mb VORTICITY CHARTS.
AVORT500 -- 12-HOUR CHANGE IN VORTICITY (sec'1) AT 500 mb BETWEEN
0700 AND 1900 LOT.
81
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Table 2 lists the importance of each variable at the various stations as
determined by their F ratios (25) in the final step of the regression technique.
The F ratio associated with each independent variable is a measure of the
additional variance explained by the variable not accounted for by the other
variables already in the regression equation. In this technique, F ratios were
computed for each variable and a step was made by the inclusion of a variable
with a significant F ratio or the deletion of a variable when its F ratio had
become insignificant due to the inclusion of other variables. The final step
occurred when the remaining variables (those without ranks in Table 2) had
F ratios that were statistically insignificant at the 1% significance level
(25). The signs (+ or -) in Table 2 on top of each ranked variable indicate
the sign of the coefficient in the final equation. For wind direction (WD)
the significant sector is listed above the rank along with its sign. At some
stations there are two significant wind directions. For these stations the rank
is listed for the more significant of the two. It should be noted that for the
three variables, global radiation (/RAD), the number of days since the last
frontal passage (/FRONT), and the number of days since the last measurable
precipitation occurred (/PRECIP), the square roots of the variables were_
found to be more effective predictors of average ozone concentrations [(L]
than linear predictors.
an approach. In general
and shortly after the passage of a front
to several days after their occurrence.
is not linearly correlated to [03] in STL
3-
There are sound physical reasons for this type of
meteorological conditions change rapidly during
or a significant rainfall, as opposed
One reason why the global radiation
is because often the most intense
global radiation occurs when dispersion is good, i.e., after a frontal passage.
TABLE 2. THE RELATIVE IMPORTANCE OF VARIOUS VARIABLES IN THE FINAL STEP OF
THE REGRESSION EQUATION
*%,
TMAX
WS
WD
^PRECIP
HT 500
^RAD
CALM
VORT 500
CFRONT
HT500
T
YN RAIN
1
a VORT 500
VARIANCE
EXPLAINED
BY RANKED
VARIABLES
SAMPLE
SIZE
101
1
4
-S
2
3
h •
59
53
102
1
2
3
64
69
103
1
2
S
4
3
5
80
"
104
1
3
2
5
4
1
77
50
105
4
3
2
5
1
6
'
75
57
106
4
2
"
1
3
65
61
107
1
2
-S
*NW
4
3
5
71
51
_
108
1
2
-S
rSW
4
3
5
1"
r
67
65
109
1
3
2
4
h
64
e,
110
1
3
-S
-SW
4
2
5
71
59
111
3
tNW
*W
4
1
2
5
t
69
56
112
4
-SW
6
1
>
2
5
3
84
41
113
3
5
+ SE
4
1
4
2
6
68
63
114
1
2
*SW
6
"
7
:
,
3
69
61
115
4
2
+SW
3
5
1
75
36
116
1
4
-S
2
3
67
43
117
1
3
2
5
4
65
48
118
+NE
-S
3
1
2
5
4
87
29
119
I 2
4
*NE
1
3
66
64
120
6
2
5
3
1
4
- -
88
37
122
4
2
1
~:
l.?3
I
-S
--
2
124
+ NW
2
125
6
3
(_ _
- +-—I
55 , 40
85 40 81
28 j 34 44
82
-------
It is immediately apparent that the importance of each variable can vary
considerably from station to station. Some of this variability can be attri-
buted to the fact that data were available at some stations and not others
on any given day. However, in general the maximum temperature (TMAX) and
the wind speed (WS) are the most important predictors of [03] in the RAMS
network. WS is important since it has the direct effect of diluting the
pollutant. Looking more closely at Table 2, it appears that WS is of less
importance as a predictor of [03] at rural stations. However, at these
stations the effects of dilution, low concentrations at high wind speeds, and
high concentrations at low wind speeds are combined with the effects of
advection from the city to give a non-linear relationship with [03].
There are several reasons for TMAX showing up as an important variable.
Laboratory results have shown that ozone production is temperature dependent
(26). However, the maximum temperature is a surrogate for various other
meteorological variables. The most obvious one in the summertime is global
radiation. There is a significant positive correlation between /RAD and TMAX.
The maximum temperature is also related to changes in air masses. For example,
a cold frontal passage with its good dispersion characteristics and cleaner
air is followed by several days with lower daily maximum temperatures. Addi-
tionally, lower maximum temperatures are observed with rain falling within
the tjme span between 1000 and 1500 LOT, which is the time span used to obtain
the [
-------
o
LL
LL
LLJ
O
CJ
CC
CC
O
O
SITE 102, NORTH (345°) OF DOWNTOWN
NE E SE S SW W NW CALM
N
NE
SE
SW
W
NW CALM
.5
.4
3
2
1
0
1
2
3
4
.5
.5
4
3
.2
1
0
.1
2
-3
4
-5
SITE 118, SOUTH (190°) OF DOWNTOWN
NE E SE S SW W NW
CALM
DISTANCE = 16km
I I I I
I
I
NE E SE S SW W NW CALM
SITE 121, NORTHWEST (335°) OF DOWNTOWN
ME E SE S SW W NW CALM
.b
A
.3
.2
.1
0
-.1
-.2
- 3
- 4
- 5
I I I
I I
N 55
DISTANCE = 27 km
.5
.4
3
2
.1
0
-.1
2
-3
-.4
-5
N
NE
W
NW CALM
: SE S SW
WIND DIRECTION
Figure 4. Correlation coefficients of the daily frequency distribution of
wind direction (WD) and calm (CALM) with ozone concentrations - shaded;
equally weighted average correlation coefficients derived from all 25
stations - unshaded. Distance is given from downtown St. Louis at Stations
102, 118, and 121.
84
-------
and /RAD". The height^ of the 500-mb surface HT500 serves much the same pur-
pose in explaining [03] as does TMAX. In fact, four out of five times when
HT500 ranked as the most significant variable in the regression equation,
TMAX did not even rank significantly as an important variable. It was somewhat
surprising to see /PRECIP rank high in significance so often. However, it
should be noted that /PRECIP shows a significant correlation with /RAD
(approximately 0.45). Upon further investigation of the results in Table 2,
the question arises of why the variable YNRAIN, which represents whether or
not measurable precipitation occurred (Table 1), ranked so few times as compared
to /PRECIP. YNRAIN is even more strongly correlated with /RAD" (approximately
-0.65) than is /PRECIP. In addition, both YNRAIN and /PRECIP are signifi-
cantly correlated with the same variables included in the regression analyses.
These results suggest that /PRECIP accounts for a process not accounted for
by YNRAIN. A plausible explanation for this is: summertime rainfall in STL
(which is mostly convective) inhibits ozone production during the daytime,
but in addition, after the rainfall, several days must pass before the return
of meteorological conditions that are conducive to high levels of ozone. The
variable /RAD, which is the driving mechanism for ozone production, frequently
takes a "back seat" to the various other meteorological variables. Many of
the reasons for this have already been cited. Primarily, the day-to-day var-
iance in the global radiation received at the surface is highly correlated
with other meteorological variables, TMAX, HT500, /PRECIP, YNRAIN, but in
addition, these variables also represent other meteorological factors that
influence [fi"3].
The remaining variables in Table 2 deserve brief comment. First, it
should be noted that sometimes the variable CALM, representing near calm
winds, was included in the regression equations even when WS was already in
the equation. Second, the stability_very close to the ground (AT) appears
to play a minor role in explaining [03] when other variables are used in
combination with this variable. Third, there is no apparent physical reason
for the sign of the vorticity at 500-mb (VORT500) at Stations 107, 118, and
125 to be positive. Lastly, at Station 112, when HT500 and AHT500 were both
in the same equation, the coefficient of AHT500 was negative. This indicates
a tendency for higher concentrations as the 500-mb ridge begins to break down.
CONCLUSIONS
Data has been analyzed from two metropolitan areas of differing climates.
In each area there was a dense network of high-quality data. The following
conclusions were reached from our analyses.
The proposed Pipe-Mix Model shows there are two meteorological processes,
horizontal transport and vertical mixing, contributing to the LA ozone problem.
The horizontal transport involves fairly well-known sources and photochemical
reactions, whereas the vertical mixing involves a source of "second-hand"
ozone that varies in concentration.
In the STL area, the combination of a few meteorological variables can
explain, on the average, about 70% of the day-to-day variance in average
ozone concentrations during hours of peak concentrations. Various combinations
of the following variables were effective in this regard: (a) the daily
85
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maximum temperature, (b) the wind speed, (c) the wind direction, (d) the
number of days since the last measurable precipitation occurred, (e) the
global radiation, and (f) the height of the 500-mb surface. Furthermore, it
was confirmed that the near-surface advection of ozone and/or its precursors
from the city does contribute to high ozone levels downwind of the city.
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Pollution Control District, California, 1974. 4 pp.
20. Air Resources Board (2). California Air Quality Data, October, November,
December 1974. Vol. VI, No. 4, Sacramento, California, 1974. 94 pp.
21. Lust, D. Semi-Annual Report on Operation of Environmental Meteorologi-
cal Support Unit in Los Angeles. Inter-Office Communication of National
Weather Service dated August 9, 1972.
22. Lust, D. Inversion Base Heights and Temperatures, Los Angeles Airport
and El Monte. Manuscript of Weather Service Forecast Office, Los Angeles,
California, 1976. 3 pp.
23. Auer, A.H. Metropolitan Land Use in the Metropolitan St. Louis Area.
Report No. AS116, Dept. of Atmospheric Science, Univ. of Wyoming, 1975.
30 pp.
24. Jurgens, R. B. and R. C. Rhodes. Quality Assurance and Data Validation
for the Regional Air Monitoring System of the St. Louis Regional Air
Pollution Study. In: Proceedings of the EPA's Conference on Environ-
mental Modeling and Simulation, Cincinnati, Ohio, 1976 (in press).
87
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25. Panofsky, H.A. and G. W. Brier. Some Applications of Statistics to
Meteorology. The Pennsylvania State University, University Park, Penn-
sylvania, 1958. 224 pp.
26. Alley, F.C. and L.A. Ripperton. The Effect of Temperature on Photo-
chemical Oxidant Production in a Bench Scale Reaction System. J. Air
Poll. Control Assoc., 11 (12): 562-565, 584, 1961.
27. Brooks, C.P. and N. Carruthers. Handbook of Statistical Methods in
Meteorology. Her Majesty's Stationary Office, London, 1953. pp. 210-241
88
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3-2
OZONE IN RURAL AND URBAN AREAS OF NEW YORK STATE
PART I
P. Coffey, W. Stasiuk, V. Mohnen*
ABSTRACT
Ozone, c.onc.e.ntA.ationA have. be.e,n mea^uA.e.d at nuJwJi and. uAban A-iteA -in
New Void State, ^on the, tat>t Ae.veA.al ye,au. MoAt o& the. ozone, fiound at
theAe, AiteJ> it, the, A£Au£t o& tang tiange. tAanApoAt pfioaeAAeA and not toc,at
photo ah em-inal. ge.neAation. Pe/iiodA o£ high ozone, conc.e.ntx.ationA oJio, Ae.gtonal.
i.n natuJie, and ajie, aAAociate,d wtth high pA&AAuAe. we.atheA. AyAtemA. The.
ox-ide. and pafittciitate. matteA pfiodu.c.e.d -In uAban oAeoi deA&ioi/A ozone, and
the^e. aSie.aA te.nd to e.x.pesu.e.nc.e. ^eweA hout& o& ozone. conc.e.ntSLatLonA
o& SO ppb than do the. Ausial atie.at>. Howe.veA., on occasion, ozone. appe,asu> to
be. ge,neAate,d -in the. usiban ptime. -In c,xce44 ofa the. psie.vattt.ng bac.kgfiou.nd ozone.
C-onc-e.ntA.ation&. The, magnitude, ofi the, con&itbtition ofi ozone. -60 ge,neAate,d to
the. ov&ioitt ozone. teveJLb -in the. aJji muA.e.
^6 both vanMibtn and
INTRODUCTION
Several years ago, the Division of Air Resources of the New York State
Department of Environmental Conservation and the Atmospheric Sciences Re-
search Center of the State University of New York initiated a continuing
study designed to investigate the sources of the ozone being found in New
York State and the northeastern United States.
Quite frequently, starting in late spring and continuing throughout
the summer, ozone concentrations in excess of the National Ambient Air
Quality Standard (80 ppb not to be exceeded more than one hour per year)
were being recorded at urban monitoring sites in New York State. While
these urban sites usually recorded ozone concentration patterns which
correspond to the classical diurnal cycle characteristic of local
photochemical generation and subsequent distruction, there was evidence
that the problem was more complex. Earlier studies by New York State (1)
in the mid-1960' s, using the cracking of rubber as an indicator of ozone,
indicated that ozone concentrations were higher in the rural areas than
in the urban areas. The results were reinforced' by Johnston (2) and
Richter (3) who, in the early 1970's, measured high concentrations of
ozone in rural Maryland and West Virginia, respectively.
*Bureau of Technical Services, Division of Air Resources, New York State
Department of Environmental Conservation, Albany, New York.
89
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STUDY DESIGN
The ozone study was designed to collect and analyze ozone data over a
large area from both stationary surface sites and instrumented aircraft. To
supplement existing urban monitors situated in the larger cities of New York
State, several sites were added.
The summit atmospheric physics laboratory at Whiteface Mountain (Eleva-
tion 4,980 feet) in the northern Adirondack Mountains of New York was chosen
to be a permanent site. This laboratory, operated by the Atmospheric Sciences
Research Center of the State University of New York, is situated in a very re-
mote area of the Northeast well over 100 miles from the nearest sizable urban
area. The elevation of the site, which is above the tree line, is sufficient
to place it above the summertime nocturnal inversion layer, yet low enough so
that it remains well within the daytime surface mixing layer.
A temporary rural elevated site was set up in a fire tower 40 feet above
the summit of Mount Utsayantha (elevation 3,200 feet) located in Delaware
County approximately 180 miles south of Whiteface Mountain. This site has
the same meteorological characteristics as the Whiteface site.
A third temporary rural site was operated in a remote conifer
forested valley area known as the "Pack Forest." This site (Elevation
800 feet) was approximately 55 miles south of Whiteface. Unlike the
other two rural sites, the Pack Forest location was typically under the
nocturnal inversion layer. The location of these rural sites and several
urban sites used during the study is shown in Figure 1.
OZONE STUDY SITES
IN
NEW YORK STATE
(N.YC.)
Figure 1. Locations of various sites in New York State.
90
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In addition to the above mentioned fixed location sites, instrumented
helicopter and airplane flights were made on both a local and long-range
basis.
RESULTS
The Whiteface station, because of its isolation from urban areas, pro-
duced ozone data which was unperturbed by local anthropogenic sources. The
monthly average ozone concentrations at this site for 1973 and part of 1974
are shown in Figure 2. The classical springtime rise is evident, as is the
fall and winter low. While not evident in this figure, the month of highest
ozone concentration is very dependent on year by year climate variations.
For example, while the 1973 highest average ozone concentrations were measured
for August, the highest month in 1974 was June. This coincided with a shift
in 1974 climatic conditions producing winter-like weather patterns over the
northeastern United States after June of that year.
701
60
SO
40
N 30-
O
20-
10-
JFMAMJJASONDJFMAM
1973 I 1974
Figure 2. Average monthly ozone concentrations recorded
at summit of Mount Whiteface.
EFFECT OF NOCTURNAL INVERSION
In Figure 3, ozone concentrations at the Whiteface site are compared
with those at the Pack Forest site from August 6, 1973 to August 17, 1973.
The Pack Forest valley site, which is under the nocturnal inversion, recorded
distinct diurnal variations in ozone concentration which look very much like
the classical case of local daytime photochemical ozone generation and subse-
quent nighttime destruction. However, the lack of local anthropogenic
sources and the existence of high concentrations of ozone above the nocturnal
91
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inversion layer as seen from the Whiteface data suggests a different mecha-
nism (4). That is, the ozone seen at both sites is generated elsewhere and
transported over long distances to these locations. The distinct diurnal
variation at the Pack Forest site is caused by local nighttime destruction of
ozone under the nocturnal inversion layer by reaction with gases such as ni-
tric oxide and terpenes, by contact with the surface and by reaction with par-
ti cul ate matter. The daytime breakup of the inversion layer allows ozone
replenishment from the ozone reservoir above this layer.
.16
.14
.12
I .06-1
i
04
.02
WHITEFACE
PACK FOREST
8/6/73
NOON
10
13
14
15
17
DAYS
Figure 3.
Ozone Concentrations at Whiteface and Pack l-orest
from August 6, 1973 to August 17, 1973.
That this mechanism is responsible for diurnal ozone fluctuations in
urban areas can also be demonstrated.
Approximately 25 miles to the south and east of the Pack Forest is loca-
ted the city of Glens Falls (population 18,500). Its ozone concentrations
are almost identical to those found at the Pack Forest site. The relation-
ship between these two sites is illustrated in Figure 4 on an hourly average
basis for the month of July, 1973. Note also on this figure the Whiteface
hourly average which exhibits a reverse diurnal. Evidently, the ozone con-
centration at Whiteface experiences a daytime minimum due to the influx of
ozone depleted air from under the nocturnal inversion. During the winter
months when the snow covered mountain summit is typically under the nocturnal
inversion, the summit ozone diurnal fluxuation is reversed as would be expec-
ted.
LONG RANGE TRANSPORT
That long range transport of ozone occurs on a massive scale is sugges-
ted by Figure 5. In this figure, continuous ozone data from the Whiteface
site for the first 17 days of August, 1973 is presented for comparison with
the rural Utsayantha site and the urban site of Syracuse, New York. The
missing ozone data is a result of malfunctions in the data transmission sys-
tem of the continuous air monitoring network. Despite a separation of 180
92
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HOURLY AVERAGES FOR JULY 73
WHITEFACE
PACK FOREST
GLENS FALLS
0 2 4 6 8 (0 12 14 (6 18 20 22 24
HOURS
Figure 4. Hourly ozone averages at Whiteface, Pack Forest
and Glens Falls sites for July, 1973.
t4-
.12-
.10
08-
.06
i
.WHITEFACE
SYRACUSE
,12
.10
.01
oc
.04-
02
0
WHITEFACE
UTSAYANTHA
12 Z
NOON
789
DAYS
IO II 12 13 14 15 16 17
Figure 5. Comparison of ozone concentration at Whiteface site with that at
Utsayantha and Syracuse sites for the first 17 days
of August, 1973.
93
-------
miles between the two rural stations (Utsayantha and Whiteface), the ozone
levels at both sites are nearly equal and exhibit the same variations.
Of perhaps more interest are the comparisons of the urban ozone concen-
trations at Syracuse with the rural concentrations at Whiteface. The typical
diurnal ozone pattern is seen in the urban areas with nighttime values
usually reduced to zero by reaction with nitric oxide. A close examination
of this figure shows that the urban daily maximum ozone values apparently
are high when non-urban ozone values are high and are low when non-urban
values are low. We have reported similar relationships for Whiteface,
Glens Falls and Montreal, Canada (5). This strengthens the hypothesis
that the urban ozone observed in New York State may be more the resultant
of a physical process of transport and mixing than of local photochemical
generation.
WEATHER
Episodes of high ozone concentrations are associated with high pressure
systems. Ozone concentrations rise as the center of the high moves south-
east of the area during which time the surface winds blow from the south-
west quadrant. Elevated sulfate concentrations are also associated with
these systems (5,6).
URBAN OZONE
It has been shown by Coffey and Stasiuk (7) that urban areas experience
fewer hours in excess of the 80 ppb ozone standard than do rural areas.
Figure 6 illustrates this point for the cities of New York, Mamaroneck,
Buffalo, Glens Falls and the rural sites at Whiteface and the Pack Forest.
Apparently, the destruction of ozone by nitric oxide tends to be greater
than the photochemical generation of ozone within the urban area.
URBAN OZONE PLUME
Figure 6 is interesting in that all the sites but one experience ozone
maximums of around 135 ppb. The site at Mamaroneck, however, experiences
several hours of ozone concentrations significantly higher. This site is
approximately 20 miles from New York City and typically downwind during an
ozone episode. An explanation of these high ozone concentrations is that on
occasion when reaching the Mamaroneck area, the urban plume from the New York
City area has depleted its nitric oxide content and has become a net producer
of ozone. This argument is reinforced by Figure 7 - an ozone concentration
isopleth of the northeastern area drawn from data supplied by 95 ozone report-
ing stations in the region. Several ozone plumes are evident as is the re-
gional nature of the ozone problem.
CONCLUSIONS
The diurnal fluctuations in ozone concentration observed at surface sites
is largely the resultant of local meteorological parameters and not local pho-
tochemical generation. Above the nocturnal inversion ozone a high concentra-
tion persists throughout the night and serves to replenish the surface ozone
94
-------
20-
(0
20
10
0
20
S 0
10
0
20
•
I
10
30
20
MAMARONECK
NEW YORK
BUFFALO
GLENS FALLS
PACK FOREST
WHITEFACE
80 90 I 0 110 120 <30 MO 150 ifcO <>0 180 190
OZONE ppb
Fiaure 6
9 '
Frequency distribution of ozone concentrations in excess of 80 ppb
from 7/1/73 to 8/22/73.
OZONE ISOPLETHS
6/23/75
Figure 7 3-4 P.M. ozone concentration isopleths of several northeastern
states for June 23, 1975.
95
-------
concentrations during the daylight hours.
The ozone problem is a regional one, episodic in nature associated with
high pressure systems.
Urban areas tend to have less ozone than do rural areas, however, ozone
plumes have been measured downwind of the larger urban areas. The relative
contribution of ozone generated in urban plumes to the overall ozone concen-
trations associated with high pressure systems is unknown. Similarly, the
relative contribution of ozone from the stratosphere and ozone produced from
naturally emitted precursors is also uncertain. Resolution of the reasons
for elevated ozone concentrations in these air masses is needed since the
levels are greater than the federal ambient air quality standard.
REFERENCES
(1) Statistical Analyses of Data from Effects Stations in New York State,
January-December, 1969. New York State Department of Environmental
Conservation, Report No. BAQS 24.
(2) Johnston, et.al., "Investigation of High Ozone Concentrations in the
Vicinity of Garrett County, Maryland and Preston County, West Virginia,1
Research Triangle Institute publication, January, 1973.
NTIS #PB-218540.
(3) Richter, H.G., "Special Ozone and Oxidant Measurements in Vicinity of
Mount Storm, West Virginia," Research Triangle Park, North Carolina,
Research Triangle Institute, October, 1970.
(4) Coffey, P.E., Stasiuk, W.N., "Evidence of Atmospheric Transport of
Ozone into Urban Areas," Environmental Science and Technology,
Volume 9, No. 1, p. 59. January, 1975.
(5) Stasiuk, W.N., Coffey, P.E. and McDermott, R.F., "Relationships
Between Suspended Sulfates and Ozone at a Non-Urban Site." Paper
No. 75-62.7 presented at 68th National Annual Meeting of the Air
Pollution Control Association, Boston, Massachusetts, June, 1975.
(6) Quickert, N., Wallworth, B. and L. Dubois, "Characterization of an
Episode with Elevated Ozone Concentrations."
(7) Coffey, P.E., Stasiuk, W.N., "Urban Ozone: Its Local and Extraregional
Components." Presented at the 79th National Annual Meeting of AICHe,
Houston, Texas, March, 1975.
96
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3-3
OZONE MEASUREMENT AND METEOROLOGICAL
ANALYSIS OF TROPOPAUSE FOLDING
V. A. Mohnen, A. Hogan, E. Danielsen, and P. Coffey*
ABSTRACT
Ozone me.aAusie.me.ntA made. at hOMQJioJL AuA&ace. AtationA in Mew Vofik and
Mat>AachiK>ettA i>how typical continental diusinal vacation; a moantaintop
(850 mb} station in the. same. fie.gion experienced veAy little. diuAnal
vafiiation. The, moataintop ozone, concentration atoat/4 exceeds that o& the,
AuA^ace. stations, and thib concentnation &ie.nd is predictable. by
met.e.otio ioQical analysis. The nesultA o& thus. nx.peJiimn.n&> indicate, that the.
ozone. souAce level Liu above. 850 mb. ftight e.xpeAijme,ntt> have.
that significant downward tAanApotit ofa ozone, fatiom the. ioweA
accompanies a tA.opo&pke.?iic faotd, and that thi& ozone.-e.n?iiche,d OAJI may n,e,ack
the. ^uut^ace. and/on remain in the. middle.
INTRODUCTION
Vertical profiles of ozone mixing ratio, averaged to remove the
fluctuations, are consistent with a net production in the upper stratosphere
and a net destruction at the earth's surface (1,2). From this results an
average background concentration for the "natural" ozone. Ozone concentra-
tions that far exceed this average, and that are not caused by a sudden
increase in downward transport, are caused by photochemical production of
ozone in the lower part of the troposphere from precursor gases of
anthropogenic origin. Downward transport of ozone from the stratosphere
to the troposphere occurs when the boundary between the stratosphere and
the troposphere deforms, becomes vertical in the core of the jet stream, and
then folds beneath the jet core. Danielsen (3) concluded after completing
several case studies of large-scale cyclogenesis that "tropopause folding"
was an integral part of cyclogenesis and that, therefore, the net seasonal
and annual transport of mass could be estimated by multiplying the mass
transport per cyclogenesis times the number of cyclogenetic events. This
estimate of 4.3 x 1020 gm:year -1 implied that a mass comparable to the
entire norther hemishperic stratosphere was exchanged in one year, the
outflow being from the lower stratosphere on the cyclonic side of the jets,
the inflow implied at higher elevation on the anticyclonic side of the
jets. Table 1 summarizes the current estimates on globally averaged ozone
*V.A. Mohnen and A. Hogan, State University of New York at Albany, Atmospheric
Sciences Research Center.
E. Danielsen, National Center for Atmospheric Research, Boulder, Colorado.
P. Coffey, New York State Department of Environmental Conservation, Albany,
New York.
97
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TABLE 1. SUMMARY
ESTIMATED STRATOSPHERIC OUTFLOW NORTHERN HEMISPHERE
(1959) 4 x 1020 gm/year
STRATOSPHERIC MASS
Ms = [4.5 + 0.5 cos |^ (t - lf|)] x 1020 gm
(1964) OUTFLOW DERIVED FROM Sr90 DEPOSITION IN 1960 + 1963
^ = [3.6 + 1.8 cos -^ (t - ^j|)] x 1020 gm/year
outflow
OZONE MASS MIXING RATIO IN LOWER STRATOSPHERE
XQ = [1.3 + 0.3 cos |^ (t - ^j|-)] x lO'6 gm/gm
ANNUAL OUTFLOW OF OZONE
4.7 x 1014 gm 03
5.8 x 1036 molecules
AVERAGE FLUX
7 x 1010 molecules cm"2 sec"1
PAETZOLD 1955 FABIAN + JUNGE 1970 REGENER 1957
4 x 1010 (4 - 7.6) x 1010 (12 - 16) x 1010
OZONE TRANSPORT IN SPRING 5 TIMES TRANSPORT IN FALL.
(Danielsen and Mohnen, 1976)
98
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fluxes (4).
Taba (5) reviewed the World Meteorological Organization Congress on
ozone observations, which concluded that in a major portion, daily and seasonal
variations in ozone concentrations were due to meteorological phenomena. More
recent reviews of the ozone literature (6-7) support this conclusion.
It is quite obvious that the average ozone concentration observed in
the planetary boundary layer is governed by more than one mechanism:
• Cyclogenetic events and subsequent further transport of
stratospheric air to the ground. (Depends on season and
geographic latitude as far as the jet stream is concerned,
and on atmospheric stability with regard to vertical transport.)
• Photochemical production within the planetary boundary layer
or in the lowest troposphere. (Depends on season, geographic
latitude, atmospheric stability and, most importantly, on the
concentration of anthropogenic precursor gases such as oxides of
nitrogen and reactive hydrocarbons.)
• Destruction on the earth's surface. (Depends strongly on the
type of surfaces. Values between 0.01 to 2 cm-s l have been
found for surface destruction rates; i.e., they can differ by a
factor as high as two hundred.)
It can be expected, therefore, that the average ozone concentration
differs from region to region. Background ozone measurements within the
planetary boundary layer for the purpose of establishing realistic air
quality standards must be made on a regional basis. The "region" is
defined by climatology, geographic latitude, topography, type of surface,
etc.
The Atmospheric Sciences Research Center (ASRC) and the New York State
Department of Environmental Conservation have collaborated in operating a
series of ozone observations in rural and urban New York State for several
years. Station descriptions can be found in Coffey and Stasiuk (8). This
analysis of ozone background concentration will be confined to the ASRC
Whiteface Mt. (4860 ft.) and Schenectady County Airport stations, the
Pittsfield, Mass, station operated by the Department of Public Health,
Commonwealth of Massachusetts, and the Albany-Rensselaer station operated
by the New York State Department of Environmental Conservation. The secular
variation of ozone (1974 data) for these four stations is presented in Figure
la.
The data are consistent with the classical concept of increased ozone
transport from the stratosphere to the troposphere during the spring
("springtime rise" of ozone). Further mixing down to the ground is enhanced
during the summer months, as indicated by the increase in afternoon mixing
height measured at the Albany Airport (Figure Ib).
A positive correlation between afternoon mixing height and ozone
concentration suggests ozone transport from aloft into the planetary boundary
layer. It is also interesting to note that the monthly averaged ozone
99
-------
40
Hi 3O
8:
^20
o
N
O
10
V/HITEFACE MTN.(~SOOO FEET) PITTS Ft ELD
SCHENECTADY RENSSELAER
Uj
^
O
s
UJ
to
UJ
O
4 5 6 7 8
MONTH 1974
1O II 12
Figure la. Secular variation of ozone.
18
16
O 14
* 12
LU
6
4
2
0
AFTERNOON
MORNING
to
G
3:
Uj
Cc
Uj
a:
i-
2:
O
§
/ 2 3 4 5 6 7 8 9 IO II 12
MONTH 1974
Figure Ib. Mixing height, Albany airport.
concentration for Whiteface Mt. (4860 ft. or 850 mb) was always highest
(except March 1974 for the Pittsfield station; however, March is not a
"photochemical" month) of all the stations. To further substantiate the
transport mechanism from aloft as the main source of ozone for this region
(versus the photochemical mechanism observed in other regions), we have
plotted the "normalized" ozone diurnal in Figure 2a for the four stations.
Also plotted in Figure 2b are the normalized diurnal variation of
(horizontal) windspeeds. Maximum wind speed results in maximum vertical
100
-------
w
32.2'
PPB
I
3
5
0^
N.
OJ
28.JJ
32J5\
9.7
42.9'
15.21
00
N
1574 ANNUAL ONE HOUR AVERAGES
Figure 2a. Normalized diurnal variation of ozone,
Whiteface Mtn. Rensselaer. Pittsfield.
W
W R P
28
— J
^
S
Cc
5
S
£
in
-------
Figure 3 shows the mean hourly ozone concentrations observed at
Whiteface Mt. and Schenectady County Airport during the period 21-31 July
1975. The 850 mb potential temperatures from the National Oceanic and
Atmospheric Administration radiosonde at Albany Airport are noted on the
same axis. This short data run is used to facilitate display of hourly
values; daily or twice daily means suppress some important short-term
trends in ozone concentration. Examination of Figure 3 shows an unmistakable
parallel in the trends in ozone concentration at Whiteface Mt. (altitude
<<850 mb) and in the 850 mb potential temperature reported for Albany, some
120 miles south of Whiteface Mt. At this level, an increase in air temperature
(and/or potential temperature) would be indicative of subsiding air. A
warming trend should then be accompanied by increasing ozone concentration,
and a cooling trend should be accompanied by steady, or decreasing, ozone
concentration. This is the general case for the Whiteface Mt., observations.
It is again obvious that the Schenectady ozone concentration appears to
approach, but never exceeds, the Whiteface Mt. ozone concentration. For the
northeastern region of New York State, we can therefore reiterate the importance
of meteorological mixing processes as the dominant parameter governing the
diurnal behavior of surface ozone concentrations.
We have further substantiated these findings through occasional airplane
flights (equipped with chemiluminescence ozone detectors) over New York State
to levels up to 12,000 ft. While the source of ozone observed at. the four
stations must be "uniformly" distributed at elevated levels (certainly above
the 850 mb level and therefore above the planetary boundary layer), we
cannot yet establish a link between ozone-rich stratospheric air mass
intrusions and high surface ozone concentrations.
However, the first large-scale experiments have been initiated in
collaboration with the National Center for Atmospheric Research (NCAR). Data
from three examples of tropopause folding have been collected and analyzed
that demonstrate the vertical ozone transport. The measurements were made
in Project DUSTORM during April 1975. Large scale cyclogenesis was predicted
and the NCAR aircraft first traversed the folded tropopause at 21,000 ft.,
flying perpendicular to the wind. After the limits of the zone were
determined, the plane turned back and reentered the zone. Three upwind-
downwind sampling flights were made—one near the warm boundary, one in
the center, and one near the cold boundary. Then the aircraft ascended to
25,000 ft. and this flight pattern was repeated. On the same day, an
observer traversed the same storm system on a commercial aircraft, making
ozone measurements at approximately 39,000-41,000 ft. Figure 4 shows the
vertical cross-sections along Electra and commercial airline flight paths
normal to folded tropopause and jet streams. Isotachs are drawn at
10 m-sec"1 intervals (solid lines). Folded tropopause (dashed lines) is
also indicated in Figure 4.
Figure 5 shows the locations of jet and Electra flight paths at 0000
GMT on the 26th and 27th of April 1975. Dashed line denotes trajectory of
ozone-rich air from 26th to 27th. Figure 6 shows the time profiles of
ozone number mixing ratio, wind speed, and temperature measured along commercial
flight path on 26 April 1975. Tropopause level (dashed line) is from
conventional tropopause analysis charts (provided to us by P. Falconer, NOAA).
102
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dW31 lOd
o
LU
CC
I—
LJ
O
ISI
O
QQ
51
O
LT
00
o
o
o
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00
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f\j
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00
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o
o
un
co
add OIlVd 9NIXIN fcO
103
-------
x- AIRLINE FLIGHT LEVEL
f 7!km
v FLIGHT LEVELS
= 6.4km
Figure 4. Vertical cross-sections along Electra and commercial airline flight
paths normal to folded tropopause and jet streams.
The preliminary evidence presented here from the Electra and commercial
flight data obtained during the operation of Project DUSTORM confirms the
concept of tropopause folding and the assumption that ozone-rich air is
transported into the troposphere with each major cyclonic development, and
that this ozone-rich air, although diluted by mixing with tropospheric air,
can reach the surface of the earth. The surface deposition pattern is
strongly asymmetrical due to the narrowness of the folded structure and
the strong deformations in the descending air. Some local regions may be
104
-------
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106
-------
8dd OI1VN 9NIXIN 3NOZO
QNIMZIdOH
107
-------
influenced by this ozone-rich layer for just two or three hours, others for
one or two days. More research is necessary to quantify the effects of this
ozone source on the surface ozone chemistry.
REFERENCES
1. Junge, C.E., "Global ozone budget and exchange between stratosphere
and troposphere." Tellus XIV, 363-377 (1962).
2. Fabian, P., "A theoretical investigation of tropospheric ozone and
stratospheric-tropospheric exchange processes." Pure and Appl.
Geophys., 106-108, 1027 (1973).
3. Reed, R.J. and E.F. Danielsen, "Fronts in the vicinity of the
tropopause." Arch.Meteor.Geophys.Biobl., SA, B11, 1-17 (1959).
4. Danielsen, E.F. and V.A. Mohnen, "Ozone measurements and meteorological
analysis of tropopause folding." International Symposium on Ozone,
Dresden (Aug. 1976).
5. Taba, H., "Ozone observations and their meteorological applications."
Technical Note No. 36, World Meteorological Organization, Geneva
(1961).
6. Vassy, A., "Atmospheric ozone." Advances in Geophysics, Vol. 11,
115-173. Academic Press, N.Y. (1965^
7. Reiter, E.R., Atmospheric Transport Processes. Part 2: Chemical Tracers.
AEC Div. of Technical Information (1971).
8. Coffey, P.E. and W.N. Stasiuk, "Evidence of tropospheric transport of
ozone into urban areas." Environmental Science and Technology,
Vol. 9, No. 1, p. 59 (Jan. 1975).
108
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3-4
METEOROLOGICAL FACTORS CONTROLLING PHOTOCHEMICAL POLLUTANTS IN
SOUTHEASTERN NEW ENGLAND
R. A. Dobbins, J. L. Nolan, J. P. Okolowicz, A. J. Gilbert*
ABSTRACT
The. ozom me.aAuSie.me.ntA in AouuthzaAteAn Ne.u) England fatiom May to Se,pte,m-
boji 1975 weAe. examined (&Ltk the. did oft data on ground le,vel. mutwiotogy,
not radiation, and nearby fi.adioi>ondej>. Ike, ozone. c.once,ntsiationA at -6euen
4-c£e/4 in tki& Ae,gion fluctuate, e.&Ae,ntially in unison 04 Mould OCC.UA. i
pollutant IMOA pfLimasiily tA.anApotite.d -into the, siagton. The, cle.afi-Me.atheA
diufinal cycle, normally &kowi> ve,iy low conce,nttation-& pfii.au to £untiit>e. and
the, daiJLy maximum oceans during late, a&tesinoon. OccaA-ional daily maximum
fLe,ading^> one, obAeAve,d to OC.CILI afate.fi &u.n&e,nt and
dtheA condition* aste, faavotiable,. A machaniAm Lb ofifieAnd in e-zplanatton ofa
the. diutnal cycle, that con&iAte,nt w-Lth the, ob£e.fivationA -^e,po^te,d by othe,-U.
INTRODUCTION
In this paper we examine the effect of transport and meteorological
conditions on photochemical air pollution in southeastern New England during the
period from May through September 1975. Ground level ozone (Oq) measurements
at seven sites in Massachusetts, Connecticut and Rhode Island (Figure 1),
along with the appropriate meteorological data, provide the basis for this
study. The sites represent small cities (Providence, Fall River) and rural
areas (Groton, Eastford, Scituate, Fairhaven, Medfield) on the northern
terminus of the northeast corridor. The ozone measurements at the sites
were made using the gas-phase chemiluminescence technique as prescribed by
the U.S. Environmental Protection Agency (EPA) (1), and the quality assurance
procedure was carried out for each instrument following the EPA guidelines
(2). This quality assurance program in Rhode Island included daily a zero
check, a single span point each week and a multipoint calibration once a
month. From 20 May 1975 through 14 November 1975 the EPA Region I labora-
tory conducted monthly audits of Massachusetts, Connecticut, and Rhode Island
sites including Eastford, Connecticut and Providence and Scituate, Rhode
Island. Dr. Thomas Spittler, reporting on the results of these audits,
concluded that the ozone data from the region was of good quality (3).
Continuous nitrogen dioxide (NO?) measurements were made in Providence using
*R. A. Dobbins, Brown University, Providence, Rhode Island.
J. L. Nolan, J. P. Okolowicz, State of Rhode Island, Department of Health,
Providence, Rhode Island.
A. J. Gilbert, New England Consortium for Environmental Protection, Providence,
Rhode Island.
109
-------
the Lyschkow modification of the Saltzman method. The instrument was zeroed
every day and standards were run once a month. Baseline drift was significant
but linearly corrected when reducing the data; therefore, the data is of good
quality.
1
2
3
4
5
6
7
Eastford
Groton
Scituate
Providence
Medfield
Fall River
Fairhaven
Figure 1. Location of Regional Ozone Monitoring Sites.
Our examination of the ozone readings was facilitated by the use of a
simple atmospheric total radiation meter. The device consisted of two flat
stainless disks with copper-constantan thermocouples mounted to measure their
temperature difference. One polished disk, which assumed air temperature,
was shaded by three horizontal aluminum wafers that formed a radiation shield.
The second disk was painted with flat black paint to achieve a high emissivity
and was located on the top wafer so as to command a clear view of the sky.
The temperature difference between the disks was controlled by both radiation
and convection; therefore, the thermocouple output has no quantitative signi-
ficance. Nevertheless, the record does provide excellent qualitative differ-
entiation among the following types of atmospheric radiation histories: (a)
strong insolation as indicated by a noontime deflection of about +15°C with a
moderate turbulent noise component; (b) zero net
neutral stability; and (c) a negative deflection
of outgoing radiation from the earth's surface.
found to correlate perfectly with the occurrence
or low level inversion as revealed by radiosonde
Massachusetts.
radiation flux leading to
of 2.5 to 4.0°C indicative
The negative readings were
of either a surface-based
observations at Chatham,
Air parcel trajectories for the 500 meter level were calculated using the
computer program developed by Heffter and Taylor (4). This program used
observed winds to calculate the prior position at six-hour intervals of an
air parcel located over Providence at a specified time. The winds used in
the calculation apply to the 300 to 700 meter altitude band that is typical
of the middle level of the daytime convective boundary layer in our region.
The observed wind vector at a point on the surface or above the surface is
assumed constant for six-hour time periods, and the parcel wind vector at
each three-hour period is found by interpolation from all wind vectors observed
110
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within 300 nautical miles. The individual wind observations are weighted in
accordance with their distance and upwind/downwind locations from the time-
dependent position of the specified air mass. The assumption of stepwise
steadiness may not be suitable if, for example, a time-dependent pressure field
is present or a frontal system traverses the region. The procedure involving
weighting factors for the interpolation procedure is not known to have been
tested. Therefore, we consider the trajectories to be estimates and, in this
study, we applied two additional criteria. The estimated trajectory was
considered valid only if (a) the number of available observed winds was greater
than five and (b) the estimated trajectory was consistent with the surface
wind observed at the National Weather Service at Warwick, Rhode Island.
OBSERVATIONS
The graph of the daily average ozone concentrations for five of the seven
sites during the month of June 1975 (Figure 2) demonstrates the strong corre-
lation of ozone concentrations throughout the region. This situation suggests
that ozone concentrations in southeastern New England are, in large part, the
result of advection into the region. On a daily basis, the transport mechanism
results in ozone peaks occurring at approximately the same time and magnitude
"hroughout the region, especially on days having high sustained wind speeds.
Air parcel trajectories were examined for those days having a daily ozone
concentration greater than .055 ppm at Providence. The trajectories in
Figure 3 have arrival times closely corresponding to the occurrence of the
ozone peak at Providence. The trajectories indicate that 90 percent of the
air flows in question arrive from the southwest quadrant traveling northeast.
In examining the air flows from the southwest, we find that 60 percent of these
trajectories are generated by relatively large Bermuda highs. The remaining
40 percent of the southwest flows are generated by more complex weather systems,
such as approaching cold fronts and/or low pressure systems situated to the
north of the New England region. The northeasterly air flow indicated in Figure 3
is actually the reversal of air flowing from the southwest through the region.
The arrival of a "back door" cold front (from the northeast) results in this
air, with a high 03 concentration, being transported towards the southwest,
again passing through the region. This may be an example of the inability of
the trajectory model to deal with such discontinuities. In tracing the air
flows back 48 hours prior to their arrival at Providence, we find that 73 percent
of the trajectories lie along the "Northeast Corridor." These trajectories
correspond to the occurrence of the highest concentrations of 03 in the south-
eastern New England region during the period under study.
To demonstrate the variation of ozone increase in the morning hours, the
0300-0500 EST ozone average was plotted versus the 0800-1000 EST average at
both Providence and Scituate for selected conditions. The 0300-0500 period
was chosen to represent the ozone value just prior to sunrise, and the 0800-1000
interval was believed to be too early for any significant local ozone production.
These data were plotted for mornings following low level or surface-based
inversion (chosen with both radiosonde and radiometer data) and for mornings
following cloudy nights (selected with climatological and radiometer data)
for both Providence and Scituate. A least mean squares line was then fit to
111
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.10-.
.08"
.06
.Oh"
.0?
KLY to SYMBOLS
Providence
— Scituate
H+H Groton
+ + -«• Fall River
Eastford
PPM
DATE
7<
10
?0
Figure 2. Daily 03 averages, June 1975.
each set of data in Figure 4, with the slope of each line representing the
average ratio of the pre-sunrise to post-sunrise 03 reading. After sunrise
there was very little change in 03 concentration at either Scituate or Provi-
dence under the cloudy night condition. However, when radiation inversions
were present prior to sunrise, the post-sunrise 63 concentration at Scituate
increased by a factor of three and at Providence by a factor of ten.
In figures 5a and 5b we have graphed several pollutant concentrations
(hourly averages) on the same chart as the radiometer temperature difference.
Figure 5a illustrates several features that are typical of a clear sky diurnal
ozone cycle in our region. Ozone builds up during the first clear day to
a level of 0.035 ppm and falls to zero soon after sunset. During the second
sunny day the peak ozone reading of 0.055 ppm occurs at 1400-1500 hours EST
and again decreases sharply after sunset. In Figure 5b the radiometer indicates
a partly cloudy day, and the peak 03 reading of 0.12 ppm at noon is followed
by a long period during which the reading is 0.05 ppm. This level persists
until midnight during the night, when the radiometer shows no temperature
112
-------
£"/:> - o >co
Ai,Y to 6YM3CL3
• o Trajectory
endpoint
^ 1^-hour interval
position
— Estimated
trajectory
-/?oo
Figure 3. Air parcel trajectories daytime 03 peaks, May - September 1975,
difference; the sky is therefore overcast. After midnight the ozone reading
drops to 0.015 ppm and does not increase after sunrise, when cloudiness remains
high. These 03 concentration cycles are typical of clear and cloudy weather
in our region. Note that in Figure 5b the N02 concentration remains low and
does not decrease when the 03 readings increase dramatically during the first
partly cloudy day.
Table I is a list of seven dates on which ozone peaks occurred during the
nighttime hours. In each case the daytime concentrations were significantly
lower than the standard while the peak nighttime value was over or near the
standard. A comparison of the trajectories (Figure 6)
showed that on each occasion the trajectory originated
the southeastern New England region was cloudy all day
seems to indicate that the ozone was formed in the sunny area and combined
with clouds as it was advected into southeastern New England. This weather
condition was commonly associated with the approach of a cold front to our
region, but other more complex weather systems produced similar results. As
was the case for the daytime peaks, the majority (85 percent) of the wind
flows on these nights were from the southwest quadrant. Additionally, 70
percent of the trajectories were found to lie along the eastern seaboard.
with the weather maps
in a clear area while
and evening. This
113
-------
.Oil 5-
.030'
X
Scituate - after cloudy night (O)
.01')-
* -—-"^
Scituate - after inversion (-J-)
~A +
Providence - after inversion (•)
' ^^ -™
,0is
.030
.oV,
I
.0 0
1
.07'
Figure 4. Average 03 concentrations, ppm. Providence arid Scituate
pre- vs. post-sunrise.
DISCUSSION
The formation of ozone in the atmosphere over Los Angeles has been recently
discussed by Calvert (5), who shows that the rate controlling reactions
involve: (a) the photolysis (Kj of N02 to form 0 and nitric oxide (NO) which
is followed by the rapid formation of 03, arid (b) the recombination (K3) of
03 and NO to form N02 and 02. Thus, Calvert shows that, within a given air
parcel, the relationship for the concentration ratio is given by
[03] [NO]
(1)
between the hours of 0900 and 1400 local time. The increasing solar inten-
sity during the daylight hours causes 03 to reach peak levels in the after-
noon hours because, in part, the radiation-dependent K: is then a maximum.
We find many cases where there is a similarity between the 03 diurnal cycle
in our region and the Los Angeles Basin, suggesting that the above reaction
sequence describes our 03 concentrations. However, the basic mechanics that
caused the diurnal 03 in southeastern New England are entirely different.
These mechanisms must also be consistent with the previous observations:
the nearly coincident daily Q3 averages at five locations as shown in Figure 2;
the occurrence of nighttime high levels of 03 only under conditions of cloud-
iness; and finally, the occurrence of increasing daytime levels of 03 under
clear skies when the N02 concentrations are negligible.
114
-------
O O
*
; !
,
i
i i
! '
c
i
i
t I
i J
'•?
r1
r1!
\
o>
E
<1)
f •*-•
0.
1 k O)
, — 1
}f
r
\
r
t/5
< T3
CO
+J
to
3
CD
13
in
en
3
<
cu
o
o
S-
OJ
fO
QJ
-o
3
o
u
(O
o
O)
S-
115
-------
TABLE 1. CLOUDY NIGHTS WITH 03 PEAKS: TIME AND MAGNITUDE OF PEAKS (ppm)
Prov. Scit. Grtn. F.R. Estfd. Fhvn. Med.
May
12-13
June
3-4
June
29-30
July
4-5
Aug.
13-14
Aug.
21-22
Sept.
11-12
0200
.059
2300
.074
2300
.054
0000
.113
0000
.093
0000
.098
2000
.108
No
Data
2300
.054
0000
.049
2300
.088
2200
.093
2200
.084
No
Data
2200
.070
0100
.070
0200
.070
No
Night
2000
.140
2200
.130
No
Data
2100
.071
2300
.079
2200
.057
0100
.121
0000
.094
1900
.099
2000
.124
No
Data
2000
.045
0000
.061
No
Data
2000
.115
2300
.100
2100
.125
Mo
Data
Mo
Data
No
Data
No
Data
0100
. 1 35
1900
.125
1900
.103
No
Data
No
Data
No
Data
No
Data
0000
.095
0000
.100
2100
.138
Based on these observations, we conclude that long distance transport
is the major source of 03 observed in our region. We further hypothesize
that the depletion of ozone by reaction on the earth's surface with substances
that are readily oxidized is an important factor that influences its concen-
tration in the surface layer. These effects are the dominant factors that
control ozone levels in our area and that account for a diurnal cycle that is
strongly dependent upon the atmospheric stability. Some common sequences
that we observe that are explained by this hypothesis are the following:
(a) Clear Night Condition—Following a clear day, high concentrations of
ozone may be advected into our region. During a cloudless night, strong out-
going radiation results in the formation of a nocturnal surface layer that
is of depth equal to about 100 meters (6, 7). Within this confined layer,
the ozone is reduced to marginally detectable levels by surface depletion
reactions. Presumably high levels of ozone exist above the surface layer
and then escape detection by the monitoring devices whose intake ducts are
typically ten meters above the surface. Rural versus urban readings do
differ because traffic-generated NO may be injected at ground level into the
stable nocturnal surface layer by early morning traffic; thus urban 03 readings
will be generally lower than rural readings. Within two-three hours after
sunrise, the nocturnal inversion is dispersed by solar heating of the earth's
surface. Morning ozone readings rapidly increase when the 03 above the dis-
integrating inversion is allowed to reach the ground through a fumigation
process; (b) Cloudy Night Condition—A heavy layer of cloudiness present
116
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KEY to SYMBOLS
O Trajectory
endpoint
^ 12-hour interval
position
S//3-/?oo
Figure 6. Air parcel trajectories nighttime 03 peaks May - September 1975.
during nighttime hours results in a neutral atmosphere boundary layer whose
typical height is 500-1000 meters. If the cloudiness follows a clear day,
the 03 levels at the surface can be high because of advection from sources
outside our region. The 03 concentration is totally controlled by the levels
resulting from advection. Surface depletion reactions play a minor role because
mixing from aloft is unimpeded by any stable layer near the surface. These
two sequences are illustrated by the pre-sunrise/post-sunrise 03 ratios in
Figure 4 and by the correlation between the radiometer output and 03 concen-
trations shown in Figure 5.
SUMMARY
We conclude that the ozone concentrations in southeastern New England
result primarily from the transport of this pollutant into this region from
distant sources. A study of air mass trajectories indicates that the ozone
usually is transported from the southwest direction. The 03 violations occur
even when the morning N02 levels are low, suggesting that the local photolytic
effect does not contribute to the 03 peak.
We propose that under clear skies, surface depletion reactions occurring
within the nocturnal inversion layer cause the low 03 readings that are observed
prior to sunrise. After sunrise, when the inversion is broken up by solar
heating, the 03 existing aloft is allowed to fumigate the surface, causing
a rapid increase in ozone concentrations. Nighttime high levels of ozone
directly reflect the influence of long distance transport under conditions
when the cloudiness prevents the formation of a nocturnal inversion, and the
117
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unimpeded mixing diminishes the relative importance of the surface depletion
reaction.
This proposed mechanism involving surface depletion reactions is con-
sistent with the observations of others. It may explain why Calvert found
Equation 1 invalid during the early morning hours in the Los Angeles Basin
and why he and others have observed 03 concentrations increasing with alti-
tude in the early morning hours under clear skies. The surface depletion
reaction mechanism combined with transport is also consistent with the rural
03 readings at Wilmington, Ohio, reported by Lonneman et al. (8); these read-
ings increased dramatically during morning hours without a significant decrease
of the very low level of N02 that was observed.
ACKNOWLEDGEMENTS
The authors wish to acknowledge the assistance of Larry Niemeyer and Dale
Coventry of the U. S. Environmental Protection Agency, Research Triangle Park,
North Carolina, in running the air parcel trajectories model; Marvin Rosen-
stein, U. S. Environmental Protection Agency, Region I, for providing the
radiosonde data; and Arnold Leriche, U. S. Environmental Protection Agency,
Region I, for the air quality data. Financial support was supplied by the
New England Consortium for Environmental Protection for A. J. Gilbert and
J. P. Okolowicz.
REFERENCES
1. Appendix D, "National Primary and Secondary Ambient Air (Juality Stand-
ards," Federal Register, Vol. 36, No. 84, Part II, Friday, April 30, 1971.
2. EPA-R4-73-028c, Guidelines for Development of a Quality Assurance Pro-
gram (Photochemical Oxidants), June 1973.
3. Spittler, T. M., "Report on Ozone Field Audits for 1975 Summer Ozone
Study," N. E. Region APCA Monthly, Hartford, Conn., April 1976.
4. Heffter, J. L. and Taylor, A. D., "A Regional-Continental Scale Transport
Diffusion and Deposition Model," NOAA Technical Memorandum, ERL ARL-50,
June 1975.
5. Calvert, J. G., "The Theory of Ozone Generation in the Los Angeles
Atmosphere," Environmental Science and Technology, Vol. 10, 1976, p. 248.
6. Yamada, T. and Mellor, G., "A Simulation of the Wangara Atmospheric
Boundary Layer Data," Journal of Atmospheric Sciences, Vol. 32, 2309,
1975.
7. Shaw, N. A., "Acoustic Sounding of the Atmosphere," Ph.D. Thesis, Uni-
versity of Melbourne, Australia, 1971.
8. Lonneman, Buffalini & Seila, "PAN and Oxidant Measurements in Ambient
Atmospheres," Environmental Science and Technology, Vol. 10, 1976,
p. 374.
118
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SESSION 4
SOURCES OF TROPOSPHERIC OZONE - II
Ckcuxman: R.A. Rasmussen
Washington State University
119
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4-1
AN ASSESSMENT OF THE
CONTINENTAL LOWER TROPOSPHERIC OZONE BUDGET
R. Chat-field and R. A. Rasmussen*
ABSTRACT
Severai di^erent regime* oft photoc.hem-if>try and transport are nece**ary
to ducAA.be. the. di^erent pattern* o& dinmai ozone. variation ob*erved hi
rurai area* 0f) eastern North America. One chemicai regime may govern ozone.
concentrati.on &or day* then, within hour*, -Lt may be. dispiaced by another
regime a* precursor concentration*, atmo*pheric n\4.XA.n.Q, and AadLcution dkange.
because o& wind* and we.atheA. The^,e. n.e.g-ime.-i> inc.lu.de.: (a) expo^uAe o& the.
OAA'A 4uA)$ace layeA to &iopot>pheAA.c background ozone.; (b) duoM> to produce. e.nhanc.e.d oxi-dant le.ve.lA outi>i.de. any indi.vi.duaf.
urban pJtume..
Thue. re.gime^> are. iLtw&tratcd Mith cat>e. -t>tudi.e^> 4 ejected 04 arc.kejtype.ts
many day* o& inte.n&i.\>e. Aampting -in the. midweAt and northe.at>t o{, the. Unite.d
State.*. V-Uti.nct patteAnA ofa ozone, be.havi.or are. i.ntnrpre.te.d ut>i.ng faliioro-
carbon and hydrocarbon me.a&ure.me.ntA . . VeJiaJJ,e.d gad -chromato graphic anaty-dis
i.ndivi.duai hydrocarbon* ducri.be. oxi-dant pre.cur*or JLe.ve.lA. ftuoro carbon
me.aAure.mentt> describe, direct urban contami.natA.on and the. de.gre.e. o& accumula
tion o{, anthropoge.ni.c e.miAi>i,ont> on a re.gi.onai
The. tropo*pheri-c background appe.art> to be. about BQ% greateA than pre.-
reported and there, is e.vi.de.nc.e. {on e.a&t-wut at, weJLi a* north-touth
o{, the. me.an background aero** the. contine-nt. Thue. condu*-ion*
^rom a re.anaiy*i^, o^ the. e.xte.n*i.ve. ozone. *ounding program* o& the.
We present a briefi as*e**ment of, the deveiopments -in other descri.pt-
Of) the rurai ozone budget over the iast *i.x year* and *ugge*t dir.ecti.on*
future, more detailed modeiing nLinhi-k
INTRODUCTION
In 1970, the ozone budget of the nonurban troposphere seemed about to be
expressed with reasonable numerical precision. Fabian and Junge in that year
*Washington State University, Pullman, Washington.
121
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described a simple model, applicable outside urban areas, based on production
of ozone in the stratosphere and on destruction at the earth's surface. On
the basis of this model, all that seemed necessary to predict human exposure
was better quantitation of boundary layer micrometeorology and surface reac-
tivity. However, since 1970, a quantitative description of ozone concentra-
tions, reactions, and fluxes has become much less definite—the ozone budget
over and outside of the population centers of the mid-latitudes of the U.S.
appears to be much less understood. Certain realizations have produced this
indefiniteness:
• The long distance transport of oxidant pollution in urban and in-
dustrial plumes has been documented. For example, the work of
Cleveland et al. (1976), Westberg (1976), and Spicer (1976) suggests
that the plume of the New York City area may determine oxidant expo-
sure in Boston, nearly 300 km distant.
• Measurements of high rural oxidant levels, outside the boundaries of
distinct urban plumes, have repeatedly been reported. These levels
have been described in terms of smog-like chemistry acting on regional
accumulations of oxidant precursors (Robinson and Rasmussen, 1976;
Ripperton, et al., 1974) or in terms of ozone of stratospheric origin
(Coffey and Stasiuk, 1976).
t Levy (1971) has suggested that natural atmospheric processes produce
radicals from methane oxidation even in clean-environments. The de-
tails of this chemistry are still not adequately modeled; but, it is
recognized that the process can produce or destroy ozone faster than
transport to the earth's surface can destroy ozone (Crutzen, 1974).
Chameides and Walker (1973, 1976) have suggested that this chemistry
may produce much of the ozone of the troposphere.
• The prevalence of significant levels of non-methane hydrocarbons and
other trace gases in rural areas has been demonstrated (Rasmussen, et
al., 1976). It is not yet clear to what extent these gases may be
responsible for modulating the surface ozone budget. Some compounds
reduce ozone; others probably participate in free-radical chemistry
processes that produce ozone.
t Our understanding of the natural range in the level of background
tropospheric concentrations of ozone based on older methods of meas-
urement has been questioned by the use of more accurate surface and
airborne instruments. Chatfield and Harrison (1976c) have suggested
that mid-tropospheric background ozone levels may be as much as 60%
higher than estimated 1970.
This paper describes both the certainties and uncertainties of the tropo-
spheric ozone budget. The following section sketches the photochemical and
meteorological conditions affecting ozone transport and chemistry. Then
observations characterizing mid- and lower-tropospheric ozone levels, which
are free from boundary layer complexities, are presented. Three case studies
of surface ozone variation with concurrent levels of hydrocarbon species and
transport patterns are included. These case studies illustrate the alternate
122
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importance of (a) vertical mixing of tropospheric air, (b) natural photochemi-
cal processes in the boundary layer, and (c) enhanced photochemical production
of ozone due to anthropogenic emissions outside the boundaries of urban plumes.
OZONE CHEMISTRY AND TRANSPORT
In order to understand the variability of the concentrations of ozone
observed near the earth's surface, we must appreciate the physical and chemi-
cal processes that govern its concentration in the boundary layer and the
troposphere as a whole. Humans and plants, both sensitive to anomalously high
ozone concentrations, have always lived within a few meters of the earth's
surface. For this reason, our exposure to ozone has been within a very thin
region of the atmosphere—the boundary layer. This layer is the region where
ozone behavior is the most complex. Within the boundary layer (often consid-
ered equivalent to the "mixed layer") the chemistry and transport behavior of
ozone is quite distinct from the rest of the troposphere.
First, within the limits of the boundary layer there are large sinks for
atmospheric ozone. For three decades it has been apparent that the earth's
surfaces, whether or not covered by vegetation, reduce ozone readily at vari-
ous rates. Summaries of the importance of this sink may be found in Galbally
(1974) and in Fabian and Junge (1970). The ocean's surface has much less
ability to destroy ozone; its rate of destruction is still not well estimated
(Regener, 1973). More recently, it has become apparent that trace gases
emitted from natural biogenic sources and man's activities also effectively
reduce ozone close to their surface sources. On the other hand, some of these
gases, the hydrocarbons and nitrogen oxides, participate in reactions that
resemble smog chemistry in great dilution. Many hydrocarbons, like isoprene,
are measureable only within the earth's boundary layer, apparently indicating
that they oxidize before they can travel far vertically. Others, like methane,
appear to be distributed rather evenly throughout the troposphere (Ehhalt,
1972). Currently, the significance to the ozone budget of the photochemical
reactions of these hydrocarbons is subject to considerable uncertainty. Levy
(1972) and Crutzen (1974) have suggested that the oxidation of methane in the
unpolluted lower atmosphere could contribute to or could destroy significant
amounts of ozone. Chameides and Walker (1973) have taken the stronger posi-
tion that photochemical oxidation of methane supplies the major source of
tropospheric ozone. The ozone produced in their photochemical model dominates
over transport and vertical diffusion in controlling ozone concentrations in
the surface layer of the atmosphere (1976). Crutzen's (1974) description of
the relevant reaction chains points out that various small changes in reaction
rate coefficients and other model parameters change the destruction rate
significantly and even allow for a net sink for ozone. Other hydrocarbons in
addition to methane oxidize by means of radical-propagated reactions which may
produce and/or destroy ozone via similar reaction pathways. While non-methane
hydrocarbons are 3 to 4 orders of magnitude less concentrated in the boundary
layer than methane, most of them are 2 to 4 orders of magnitude more reactive
(Pitts, et al., 1976). The net result is that these species may contribute as
significantly as methane to ozone formation. Graedel et al. (1976) have in-
cluded isoprene and a-pinene in one reaction scheme; more ozone was generated
from these hydrocarbons than from methane.
123
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Three results of recent work stand out: (a) Chemical reactions produce
or destroy ozone in the troposphere, (b) The variability of meteorology (sun-
light, temperature, vertical mixing, and water vapor) and source strengths of
precursors (hydrocarbons and nitrogen oxides) may vary so to allow both net
production and destruction at different times, (c) Ozone-modulating chemistry
is most active within the boundary layer; the boundary layer and the lower
troposphere should be modeled as separate but interacting systems.
BACKGROUND TROPOSPHERIC OZONE
Systematic data on the variability of the ozone concentrations represent-
ative of the atmosphere above the boundary layer (90% of the troposphere) and
away from densely populated areas are scarce. The data available until re-
cently was incidental information obtained from programs designed to character-
ize surface ozone levels in urban air with little attention given to the ozone
levels above the boundary layer. The ozone data available for mid-troposphere
profiles was also peripheral since most of it came from ozone sounding programs
designed to characterize stratospheric ozone. However, the latter programs
provide an acceptable random sample of varying ozone levels characteristic of
different weather situations and geographical locations obtained with instru-
ments whose measurements are readily comparable.
Hering and Borden (1964a, 1964b, 1965, 1967) reported an extensive series
of ozone soundings of the troposphere and stratosphere launched from 1963 to
1965. However they cautioned that errors in their method could be quite
significant for the tropospheric portions of the soundings. Continuation of
that ozone sounding program from 1966 to mid-1969 demonstrates the nature of
one of these errors. Earlier ozone measurements used instruments based on the
chemiluminescent reaction of ozone with rhodamine dye (CL instruments). The
later ozonesonde studies used a Mast-type buffered KI electrochemical method
(EC instruments). An analysis comparing the standardization of the instruments
as well as the statistics of the ozone concentrations obtained from each type
of instrument suggested that the EC instruments give more reproducible (pre-
cise) estimates of the tropospheric ozone. The better data obtained by the EC
instruments in the second phase of the ozonesonde program are not very well
known. This is unfortunate since the second data set apparently provides more
information about the true variation of ozone in the mid-troposphere than does
the first, larger data set. Chatfield and Harrison (1967c) reported that
these EC instrument estimates may be more accurate estimates of free-
tropospheric ozone. If Chatfield and Harrison's analysis of the two data sets
is correct, estimates of tropospheric ozone based on Hering and Borden's
earlier work should be raised by 50 to 60 percent.
Vertical profiles of ozone for the six stations that launched EC-type
ozonesondes from 1966 to 1969 are shown in Figure 1. The ozone concentration
profiles are the means of numerous soundings measuring the ozone above the
stations named. The stations extended from the Canal Zone at 9°N to Goose Bay
at 53.5°N. All of the stations are located within a few degrees longitude of
the 75th meridian which passes through the East Coast of North America. The
data analyzed are for the summer season. Consequently, the tropopause, above
which ozone increases dramatically, is high, i.e., at Goose Bay, 9 km and, for
124
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the tropical stations, over 14 km. For the three stations north of 30°N, the
ozone profiles are nearly vertical. This constancy of ozone concentration
suggests either that there is little net diffusive transport in the vertical
or that the baroclinic eddies which produce the diffusive transport in
mid-latitudes are not well modeled by K-theory. The vertical variation in the
southern latitudes is a seasonal feature: in March for example, ozone is con-
stant or decreases with height at these same stations. Transport by Hadley-
cell motions and eddy motions described by Newell (1969) seems to be the most
reasonable explanation.
CANAL G.TURK KENNEDY WALLOPS BEDFORD GOOSE BAY
9.0 N
21.5 N
28.5N
37.5 N
42.5N
53.3N
0 20 40 20 40 20 40 20 40 20 40
40
120
OZONE MIXING RATIO, ppb
Figure 1. Averaged soundings of ozone concentration (in ppbv) above the
listed stations. Electrochemical sondes launched during the summer seasons
of the years 1966 through 1969 contributed to these means. The data for the
lowest kilometer are not well estimated.
Figure 2 shows tropospheric ozone in a way that compares north-south
variations among stations. The data used to generate this figure used EC
ozonesonde reports for the layer 2 to 3 km above the earth's surface. The
lower layers of the atmosphere are made more complex by boundary layer, local
chemistry and transport features. Bedford, Massachusetts, 42.5°N, and Wallops
Island, Virginia, 37.7°N, probably have additional complexities derived from
large anthropogenic oxidant and S02 sources upwind (S02, for example, produced
low instrument readings).
Certain aspects of Figure 2 argue persuasively that the stratosphere is
the predominant origin of free-tropospheric ozone in the mid-latitudes. The
left wall of Figure 2 shows a maximum ozone value at about 35°N in the month
of January. As the year progresses, this maximum retreats northward to about
43°N, where it stays from March until September, and then advances to a lower
latitude through the end of the year. The movement of this ridge of highest
ozone values corresponds well to the retreat and advance of the mean position
of the lower-tropospheric position of the polar front. It is this frontal
region to which Danielsen's (1970) description of stratospheric injections
into the troposphere applies. The value of the summer ozone maximum is also
125
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t, month
Figure 2. Time-latitude cross-section of ozone (ppbv) measured between 2
and 3 km by sondes launched from the stations listed in Figure 1. These
stations lie within a north-south band running through the Eastern U.S.
reasonable in that only in the spring is the lower stratosphere in the mid-
latitudes replenished with ozone from the tropical upper stratosphere. Injec-
tions from the stratospheric reservoir are also most likely to occur in the
highly contorted tropospheric westerlies that are characteristic: of spring
weather.
Latitudinal variation is likely to be the most important type of varia-
tion, given the tendency of the winds to blow zonally. However, in Figure 3,
contours of tropospheric ozone in the mid-troposphere, between 3 and 7 km, are
drawn for all the stations reporting CL ozonesonde observations. The con-
toured ozone concentrations of ozone depicted have been raised by a factor of
approximately 1.6 so as to agree with the results of the EC sonde data. The
data seem to suggest an east-west variation in annual mean ozone. The chemi-
cal and dynamical explanations have been discussed by Chatfield and Harrison,
(1967d).
TROPOSPHERIC BACKGROUND AS SAMPLED BY GROUND STATIONS
The deleterious effects of high ozone are most important near the ground;
but, the complex chemistry and transport occurring within the boundary layer
make ozone levels difficult to study. Aircraft and balloon soundings allow
more extensive characterization of ozone formation and movement within this
mixed layer, and have been quite useful in the past few years. However,
another way to reduce the complexity of ozone behavior near the surface is
intensive—that is frequent-measurement of ozone, hydrocarbon, and oxidant
precursors, as well as tracers that give information about the origin of the
126
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ozone sampled. For example, fluorocarbon tracers clearly identify the extent
to which ozone may have had an urban origin.
CONTOURS OF OZONE ppb at 3 to 7 km
Figure 3. Continental ozone background. Isopleths of ozone concentration
(ppbv) derived from chemiluminescent ozonesonde ascents above the nine
stations marked*. These isopleths are drawn for annual mean ozone; various
seasons may exhibit somewhat different ozone climatology.
One such period during which a surface site was apparently exposed to
clean tropospheric air is shown in Figure 4. The data were obtained at a farm
site near Elkton crossroads in southwestern Missouri, just northwest of the
Ozark Mountains. The fluorocarbon-11 (F-ll) trace at the top of the figure is
representative of uncontaminated urban emissions. Indeed, 115 ppt of F-ll was
the minimum observable background level for surface air at that time period
and altitude. As the radiation trace at the bottom of the figure shows, con-
ditions were generally overcasted. The movement of warm Gulf air into the
area during the afternoon resulted in showers in the early evening. One
squall line thunderstorm (not associated with a deep 500-mb though) passed
over the area at about 2200 CDT on the 25th. Intense stirring of clean middle
tropospheric air to the surface occurred for the F-ll trace dipped to 105 ppt.
The lack of any significant change in ozone level suggests that the ozone con-
centration overhead was similar to the concentration at the surface. The
vertical ozone profiles shown in Figure 1 for stations north of 30°N latitude
also suggest that the overhead ozone level does not normally change dramatic-
ally with altitude during the summer season. Total non-methane hydrocarbons
also decreased during this period from 50 to 30 yg nf3.
The ozone trace contained between August 25-26, 1976, is a typical
pattern for windy, low-radiation situations in rural areas. The general ozone
level varied irregularly between 30 and 47 ppb, and there was little indica-
127
-------
200
I 175
i 150
o
UJ
cr
Lx
125
100
8/25
'8/26
200
50
-,95
00 _
45
50 J20
HOURS
Figure 4. Variation in ozone, hydrocarbon, and fluorocarbon levels observed
during stormy weather near Elkton crossroads in southwestern Missouri.
tion of a diurnal cycle.
How do these surface concentrations compare to the tropospheric ozone
background illustrated in Figure 2? The latitude of Elkton, Missouri, is
closest to Wallops Island, Virginia (37.5°N). The mid-tropospheric ozone con-
centration observed with the Wallops ozonesondes reported approximately 55 ppb
of ozone in August and 50 ppb in September. Since Elkton is 17° west of
Wallops Island, the evidence summarized in Figure 3 suggests that we should
subtract approximately 5 ppb. In short, the agreement between sounding data
and remote site data is consistent with the interpretation that, the surface
ozone observed at Elkton under windy, low radiation conditions is primarily
derived from overhead replenishment of the ozone in the troposphere.
Such agreement is partly accidental since the standard deviation of the
tropospheric ozone background at one location and season is 0.2 to 0.3 of the
mean, as measured by the EC ozonesondes. The variability includes the range
of true climatic variability of ozone as well as instrumental variability of
the ozone data analyzed by Chatfield and Harrison (1967d). The variation on
the ozone levels from the climatology of the lower atmosphere suggested by
Figure 2 may persist for weeks, as observations at the same site in successive
years indicate. That is to say, ozone displays "weather" just as do rain and
temperature. Perhaps the most variation occurs in the spring, when the pre-
valence of blocking highs and cut-off lows create weather patterns which are
conducive to stratospheric injections of ozone into the troposphere (Danielsen
1976). In certain cases, it appears that stratospheric injections followed by
strong cumulonimbus downdrafts can produce hour-long periods when surface
ozone concentrations are observed at levels of hundreds of ppb (Lamb, 1976)
128
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and shorter periods when ozone can approach 600 ppb (Attmannspacher and
Hartsmannsgruber, 1973). Davis and Jensen (1976) have recently summarized
practical techniques for forecasting high ozone levels.
NATURAL PHOTOCHEMICAL OZONE IN THE BOUNDARY LAYER
The significance of the photochemical production of ozone within the
lower troposphere has been a point of controversy in recent years (Chameides
and Walker 1973, 1976; Chameides and Stedman, 1975; Fabian, 1974). Presuma-
bly, there is a greater likelihood of significant photochemistry occurring in
the boundary layer with its higher concentrations of oxidant precursors
than in the free troposphere. The evidence for significant photochemis-
try occurring in the mixed layer outside urban plumes in situations of
relatively clean environments has been poorly documented.
Several days after the storms that characterized the August 25-27 weather
at Elkton, Missouri, passed, the weather became sunny and the air relatively
clean as shown in Figure 5. On the 30th, a weak cold front passed through the
area in the early morning hours without bringing rain, although a few clouds
persisted. Fluorocarbon levels gradually increased from 115 ppt in the after-
noon although they remained below 125 ppt until midnight. Ozone showed a
typical diurnal variation for clear weather with a broad maximum in the middle
and late afternoon. The peak ozone hourly values reached 56 ppb, an increase
of 28 ppb from that morning at 0900 CDT, which was about the time of the
frontal passage.
200
a 175
150
o
u
k.
125
100
0,
200
8/30
• FREONS
° H C (TRAILER)
QHC (WOODS)
• OZONE
A RADIATION
12
16 20
50
95
00
45
50 J20
E
o>
a.
Figure 5. Fair weather diurnal variation pattern of ozone levels contrasted
with hydrocarbon and fluorocarbon levels observed near Elkton, Missouri. The
afternoon maximum in ozone may be due to local photochemistry.
129
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The hydrocarbon composition of the atmosphere was consistent with unpol-
luted rural air with 30 to 50 yg m 3. Total non-methane hydrocarbons (exclu-
ding oxygenated species) were usually about 50 yg m 3 in the afternoon. A
typical afternoon sample was composed of about 10 yg m"3 of natural gas
alkanes, 2.5 yg m~3 aromatics, 2.0 yg m 3 i-butane and n-pentane, 7.3 yg m~3
of isoprene, and 6.5 yg m 3 of four_unknown but prevalent hydrocarbons of
apparently rural origin and 20 yg m 3 of other hydrocarbons, about half of
which were statistically associated with rural unknown hydrocarbons. These
identifications were made on the basis of gas chromatographic separations
described in Rasmussen, Chatfield, and Holdren (1976). In summary, the hydro-
carbon composition of the atmosphere was dominated by rural hydrocarbons with
very dilute traces of some anthropogenic hydrocarbons.
The levels of hydrocarbons present were sufficient to produce the 28 ppb
ozone increase observed during the day. Since it is theoretically possible to
produce from each oxidized atom of carbon 3 or 4 radicals, and hence 3 or 4
ozone molecules, the 7.3 yg m~3 of photochemically reactive isoprene could
produce 28 ppb of ozone if it were to react completely. In addition, isoprene
reacts so much more rapidly with hydroxide radicals than does methane that, at
the concentrations observed, it creates almost twice as many radicals as
methane (Pitts, et al., 1976). In reality, there are many reactions that de-
stroy ozone and the necessary radical precursors. Also the flux of ozone into
or out of the boundary layer, both with the free atmosphere and with the
ground, are unquantified parameters affecting the resultant ozone concentra-
tions. Only intricate photochemical modeling will be able to balance all of
these effects.
While atmospheric chemistry processes within clean continental air can
plausibly produce ozone, one of the authors has argued elsewhere that many
pieces of evidence that seem to confirm photochemistry also confirm transport
arguments (Chatfield and Harrison 1976a). Solar radiation, for example,
governs meteorological processes (such as convective mixing) as well as photo-
chemical rates. Conclusive observational evidence for photochemical ozone
formation in rural atmosphere remains to be presented.
REGIONAL OXIDANT PHOTOCHEMISTRY
Perhaps the most problematic portion of the current understanding of the
lower tropospheric continental ozone budget is assessing the extent to which
urban and industrial hydrocarbon precursors may increase oxidant production on
regional or sub-continental scales. Recently there has been considerable
attention given to oxidant production in urban and industrial plumes. These
studies show very clearly marked pollutant episodes occurring outside cities.
Other contributors to this conference have described in greater detail the
theoretical and observational features of these urban plumes. However, there
is a larger problem of regional air pollution episodes. Our measurements at
Elkton, a site specifically chosen to represent clean air in the far Midwest,
suggest that the air within the boundary layer even at this very rural site is
almost never entirely free of anthropogenic emissions.
Often, rural air is so well mixed horizontally that the plumes of small
130
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to modest size (10,000 to 70,000 population) cities can not be distinguished
50 km downwind. Husar, et al. (1976) has noted the regional accumulation of
visibility-degrading aerosol into regional "blobs" shifted by synoptic winds.
Currently, such aerosol-haze is believed to be due to secondary heterogeneous
photochemical reactions involving either hydrocarbons or sulfates, or both.
Our example of apparent regional air pollution episode comes from ground
station studies conducted near Glasgow, Illinois, 104 km NNW of the St. Louis
Gateway arch in July 1975. The studies at this site were conducted just prior
to the Elkton studies.
The meteorology and trace chemistry conditions leading to this episode
are shown in Figure 6. Both the time variation of the F-ll concentrations and
total non-methane hydrocarbon (TNMHC) levels at the Glasgow site are shown.
The correlation for F-ll spikes—indicators of urban plumes-and TNMHC spikes is
very good, though not perfect. The line drawn at 115 ppt represents the mini-
mum F-ll concentrations observed as Glasgow, Illinois, or Elkton, Missouri.
The passage of urban air with higher levels of F-ll extend upward from this
background level as spikes. Besides the minimum background representative
of the cleanest air, there is a daily background suggested by the minimum
concentrations attained each day when the site was most nearly free of
urban plumes.
250
200-
150-
250
ACCUMULATION
OVER
BACKGROUND
15
Figure 6. Regional accumulation of fluorocarbon-11 and non-methane hydrocar-
bon sampled on a farm 110 km north of St. Louis during the first two weeks of
August 1975. The fluorocarbons spike to high levels when plumes of urban air
are sampled; hydrocarbons show a similar behavior. There is also a gradual
increase in minimum daily fluorocarbon concentrations from August 3 to August
13. On these dates, new high-pressure systems entered the area.
131
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A subtle but important feature of the data gathered at Glasgow is the
slow increase in this general level of the daily F-ll background from 117 ppt
on August 2 to 130 ppt on August 12, and the subsequent more rapid decline to
118 ppt on August 13. The rise was not due to instrumental drift. Instead
the rise in the F-ll background represents the accumulation of emissions in
the air over the Midwest during this period. Of course, our site at Glasgow
never sampled the same air parcel twice; but, the Eulerian description of the
site portrays fluorocarbon buildup in a manner fairly representative of air
parcels moving within a stagnant southward-drifting high-pressure system. The
last frontal passage bringing in new air from the northwest was on August 2.
During the following time lapse the air mass drifted from the industrial
Midwest into the Glasgow site where it peaked August 12-14.
Somewhat similar accumulative behavior is evident for the TNMHC loading
of the atmosphere shown in Figure 2, despite the greater variability that is
evident for these reactive substances. It is likely that nitrogen oxides also
increased during this period, but the Washington State University trailer did
not measure them.
Figure 7 shows in detail the ozone, F-ll, and TNMHC variations observed
on August 12. About midnight, the St. Louis plume passed over the station
according to the evidence of the surface winds and the F-ll readings monitored
at the trailer site. The surface winds then swung south to the west-southwest
from 0300 CDT until 1500 CDT; during this period it would have been nearly im-
possible for the site to be exposed to the St. Louis plume. By 1600 CDT, the
wind turned again to flow from the south, and within 4 hours the sampling sta-
tion was again directly exposed to St. Louis air. At 2000 CDT the plume-
generated oxidant rose to over 100 ppb and then dropped quickly.
The interim period of west-southwest winds shows ozone behavior equally
as interesting as the 100 ppb spike. During the interim period ozone reached
90 ppb for one hour, and remained at a level of over 85 ppb for 5 hours out-
side any identifiable urban plume.
The hydrocarbon chemistry of this day shows a mixture of anthropogenic
and natural emissions. TNMHC averaged around 80 yg m~3. Gas chromatographic
analysis of the ambient air samples taken in the afternoon show about 17.4 yg
m"3 natural gas hydrocarbons, 6.4 yg m~3 of aromatics, 4.4 yg nf3 of automotive
fuel vapors (e.g. pentane, octane), 4.3 yg m-3 of automotive exhaust emissions
(ethylene, propene, n-butane), 6.8 yg m~3 of isoprene, 10.0 yg m~3 of unknown
compounds of suspected rural origin, and 29.0 yg nr3 of other compounds.
Not all of the days during this interim period showed such high ozone
levels outside of the plume episodes. The previous day showed only 60 ppb of
ozone at maximum in conjunction with 60 yg m"3 of hydrocarbons. Ozone levels
might have risen further, but in the early afternoon clouds cut off the solar
radiation, and ozone began to decline immediately. Also there were differ-
ences in the hydrocarbon concentration which may have affected oxidant pro-
duction; i.e., there were lower concentrations of isoprene, and other rural
unknown compounds, and natural gas alkanes. Other reports of elevated ozone
distributions in the Eartern United States suggest the possibility of region-
wide production of oxidant. One particularly interesting set of ozone meas-
132
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250
225
200
1 8/12
REGIONAL AIR
POLLUTION EPISODE
1 8/13
1 FREONS
• HC
' OZONE
. RADIATION
150
200
Figure 7. Elevated ozone levels related to regional accumulations of oxidant
precursors by August 12 in Glasgow, Illinois. The F-ll spikes at 0 and 20
influx of urban air from St. Louis with accompanying increased
Between these spikes, F-ll remains at levels significantly above
CDT indicate
ozone levels
the minimum background value of 115 ppt. It is suspected that similarly ele-
vated levels of hydrocarbons and oxides of nitrogen may have produced the
high midday ozone.
urements was made at 500 m above the ground between Canton, Ohio, and the
Black Hills of South Dakota in the summer of 1974. The observed ozone con-
centration dropped from 70 ppb over the rural areas of Ohio early in the
morning to 40 ppb over the rural Great Plains late in the evening on the same
day. This measurement suggests a substantial east-west gradient in ozone, but
other considerations prevent our accepting this gradient as representative of
regional photochemistry acting solely on anthropogenic or natural emissions.
The 70 ppb measurement was made early in the morning, and there is no data or
estimate of the level to which it could have risen in the afternoon. Photo-
chemical considerations would allow even larger ozone gradients due to anthro-
pogenic emissions producing more ozone to add to the 70 ppb value. However,
the distance scale is also a synoptic distance scale, so that ozone differences
might be attributed to different ozone "weather": that is, the ozone gradient
may reflect mid-tropospheric ozone variations or other weather effects rather
than differing surface emissions. For these reasons it is important that
measurements on this larger synoptic scale be repeated.
CONCLUSIONS
Substantial uncertainties exist in quantifying the significance of the
133
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different sources of ozone or contributions of ozone precursors in the lower
tropospheric ozone budget over continents. There is a clear need to model
both transport and chemistry in the lowest few kilometers of the atmosphere.
Both chemical and meteorological parameters for models on this scale are rela-
tively uncertian. It appears that separate and interrelated models should be
constructed for:
(1) The boundary layer. Emissions and photochemistry of non-methane
hydrocarbons allow ozone levels to change significantly within a day,
but other important precursor transport processes may occur over sev-
eral days.
(2) The "free" lower troposphere. The interaction between local photo-
chemistry and synoptic-scale transport must be qualified.
Verbal models of ozone variation near the surface may allow for different
regimes of transport-dominated and photochemistry-dominated patterns of ozone
concentration gradients or distributions to develop. In summary they are:
(1) Clean, strongly mixed troposphere. Ground level ozone from 15 to 70
ppb determined by the ozone concentration of mid-troposphere. This
mid-tropospheric concentration may be summarized by latitude and
season, as in Figure 3, but it is a "climatology" of ozone subject to
ozone "weather."
(2) Clean, diurnally mixed troposphere. Both photochemistry and diurnal
boundary-layer mixing give adequate descriptions of the ozone be-
havior. Models should incorporate both parameters quantitatively.
(3) Urban plumes. Individual urban plumes frequently modify ozone con-
centrations in the lowest kilometer of the troposphere of the Eastern
United States. Large plumes may travel 200 to 300 km before losing
their character. Their composition produces variations in the ozone
pattern different than rural air; however, additions of rural hydro-
carbons like isoprene may rekindle ozone production particularly in
older plumes.
(4) Regional oxidant production. The trailing portions of slowly migra-
tory high pressure systems accumulate ozone and oxidant precursors
not attributable to a single urban area. There is a need for models
of the photochemistry of these situations. The relationship of area
wide production of oxidants with the development of photochemical
aerosol-haze patterns described as "blobs" through the Midwest needs
better study.
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Rasmussen, R. A., R. B. Chatfield, and M. Holdren. 1976a. Hydrocarbon Levels
Observed in a Midwest Rural Open-Forested Area. Report being submitted
to the Coordinating Research Council. Contract No. CAPRAC-11.
Rasmussen, R. A., R. B. Chatfield, and M. Holdren. 1976b. Hydrocarbon and
Oxidant Chemistries Observed at a Site near St. Louis. Report being sub-
mitted to the Environmental Protection Agency. Contract; No. 68-02-2254.
Regener, V. H. 1974. Destruction of Atmospheric Ozone at the Ocean Surface.
Arch. Met Geoph. Biokl. 23(Ser. A):131-135.
Ripperton, L. A., J. B. Tommerdahl, and J. J. B. Worth. 1974. Proceedings of
the Annual Meeting of the APCA, Denver, Colorado, June 9-13, 1974.
Robinson, E., and R. A. Rasmussen. March 1976. Identification of Natural and
Anthropogenic Rural Ozone for Control Purposes. Proceedings of the
Specialty Conference on Ozone/Oxidants - Interactions with the Total En-
vironment. APCA.
Spicer, Chester W. 1976. Ozone and Hydrocarbon Measurements by Batelle.
Proceedings of the Northeast Oxidant Transport Symposium held at Research
Triangle Park, North Carolina on January 20-21, 1976.
Westberg, H. H. 1976. Ozone and Hydrocarbon Measurements by W.S.U. Proceed-
ings of the Northeast Oxidant Transport Symposium held at Research Tri-
angle Park, North Carolina on January 20-21, 1976.
Westberg, H. H., K. J. Allwine, and D. Elias. March 1976. Vertical Ozone
Distribution above Several Urban and Adjacent Areas across the U. S.
Proceedings of the Specialty Conference on Ozone/Oxidants - Interactions
with the Total Environment. APCA.
136
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4-2
URBAN KINETIC CHEMISTRY
UNDER ALTERED SOURCE CONDITIONS
L. A. Farrow, T. E. Graedel, and T. A. Weber*
ABSTRACT
The. e.iie.ct oft alteAe.d Aoufi.ce. generation rates on ozone, conce.ntratA.onA in
northern New 3e.ue.ij has been as&es&e.d by a. /setx.e-6 oft de.tcuiie.d photoch2.mic.aJL
coitcuLati-onA. The. Sunday E^e.ct, -in (Mk4.dk me.asure.d Sunday ozone, concentra-
tion!, in ceAtain u/iban aA.e.as are. AimiJLar to those, occurring on wotikdays de.-
Apite. marke.dl.y di6fie.re.nt mo ton. ve.hicte. emissions, is succe.ssfiutty Ae.produ.ced.
The. concept ofi functional. oxyge.n gioupA iA introduced and a^ed to i>kow that
the. Sunday e.^e.ct sieAuJLtb ^ofun the. tight balance, between ozone pftodu.ctA.on
through ni&iic oxA.de. photo dissociation and oxygen &cave.nging by nitric otu.de,,
faswm the. a.dve.ctian o£ ozone, ^fiom. £e^4 uA.ban a/tea^, and {,fiom the. incofiponation
o& i,imitaA. quantities ofa ozone. pre.e.XASting above, the. morning mxjced layeA.
INTRODUCTION
The chemical generation and destruction of ozone in the urban troposphere
is known to be inextricably connected with the atmospheric chemistry of hydro-
carbons (HC) and oxides of nitrogen (NOX). Despite this connection, however,
ambient air quality data (Paskind and Kinosian, 1974) and smog chamber studies
(Dimitriades, 1975) have not shown a simple relationship between ozone and its
precursors. An example of the complexity of the problem is the Sunday Effect
(the only altered source condition for which substantial quantities of air
quality data are available), in which Sunday ozone concentrations in certain
urban areas are similar to those occurring on workdays despite markedly dif-
ferent motor vehicle emissions (Bruntz, et a!., 1974; Cleveland, et al.,
1974).
This paper presents the results of detailed chemical kinetic computations
representing workdays and Sundays in Hudson County, New Jersey. The computa-
tional techniques are applied to the Sunday Effect, which is shown to be a
consequence of the chemistry and meteorology of the urban troposphere.
COMPUTATIONAL FORMULATION
Calculation of the diurnal chemical concentrations in the urban tropo-
sphere is based on a chemistry of 143 reactions in 76 species. Extensive
*Bell Laboratories, Murray Hill, New Jersey.
137
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descriptions of the chemistry of oxides of nitrogen, hydrocarbons, and sulfur
compounds are included in the reaction set, as is a representation of the •
heterogeneous interactions between gas phase radicals and the atmospheric
aerosol. This chemical formulation is described in detail by Graedel, et al.,
(1976) (hereafter termed "Paper I"). As has been discussed previously (Paper
I), no chemical set can be considered a complete representation of tropospheric
photochemistry. The excellent agreement with data that results, however,
indicates that our formulation, at the very least, captures the essential
processes which control that chemistry.
The computational architecture that is utilized is based on a 3x1 matrix
of geographical areas, in which each matrix element is rectangularized trans-
formation of the dimensions of a county; those represented are (from west to
east), Morris County, New Jersey, Essex County, New Jersey, and Hudson County,
New Jersey. Since available emission inventories for the region are compiled
on a county-wide basis, each of the counties is treated as a "reaction volume"
with source terms corresponding to the emission data. Emissions attributable
to mobile sources are varied in accordance with local traffic density functions
and those for power plants in accordance with energy generation patterns.
Other emissions are regarded as constant with time. For computations with
varied source conditions, all sources are multiplied by the same reduction or
enhancement factor; diurnal emission patterns are preserved.
The flow of gases from one matrix element to the next is controlled by
the local wind velocity and direction. In the computations presented here, we
utilize an average diurnal wind flow pattern derived from measurements at
Newark Airport (Essex County) on summer days, of normal convective mixing. The
variations in mixing height are specified by a function derived from lidar
measurements of the atmospheric aerosol. The chemical species within each
reaction volume are assumed to be fully mixed.
Several differences exist between the workday and Sunday computations.
The most important is the marked difference in motor vehicle emissions and
power generation functions for Hudson County. Atmospheric aerosol concen-
trations are lower on Sundays and, perhaps as a result, the solar radiation at
ground level is somewhat higher (Cleveland et al., 1974). In addition to its
meteorological effects, the change in aerosol concentration reduces the hetero-
geneous interactions which have important effects on tropospheric chemistry
(Farrow, et al., 1975; Graedel, et al., 1975). The increased solar radiation
increases the rate of the photosensitive reactions included in the chemical
set.
RESULTS OF SUNDAY EFFECT CALCULATIONS
Computations of the kinetic chemistry of the urban troposphere have been
performed for Morris, Essex, and Hudson Counties, New Jersey, for both work-
days and Sundays. The workday computations have been described in detail in
Paper I, and the agreement with a wide variety of air quality data for Hudson
County (across the Hudson River from Manhattan) have been judged to be good.
For the Sunday computation, there are insufficient days with appropriate
characteristics (i.e. full sun, summer, westerly wind direction, wind speed
138
-------
within the central 50% of all values) to permit a direct comparison between
data and computational results. It is possible, however, to make general com-
parisons with less stringently stratified data. Figure la shows the computed
diurnal ozone (03) concentrations for workdays and Sundays. The Sunday com-
putation reproduces two important characteristics of the Sunday ozone data
illustrated by Bruntz, et al, (1974): the virtual equivalence of the after-
noon ozone peak, and the higher ozone values on Sunday morning. The ozone
computations show higher Sunday evening values not reflected in the data; this
discrepancy may be a result of inadequate representation of the heavy traffic
flow from New Jersey shore points to the metropolitan area that occurs on
summer Sunday evenings.
The reduction in the ozone precursors nitric oxide (NO) and nitrogen
dioxide (N02) on Sundays is snown in Figures Ib and Ic. Similar reductions
occur in air quality data (Cleveland, et al., 1974), and are representative of
concomitant reductions in other species such as carbon monoxide (CO) and
nonmethane hydrocarbons.
The results can be succinctly summarized: The computations have suc-
ceeded in reproducing the ozone Sunday Effect, while simultaneously demon-
strating the reduction in primary emittants known to occur on Sunday.
FUNCTIONAL GROUP ANALYSIS
The Sunday Effect is intriguing because of its defiance of the intui-
tively anticipated precursor-product relationship between ozone-producing
species and ozone itself. Having duplicated the Sunday Effect computation-
ally, we then proceeded to deduce a unifying analytical technique that not
only demonstrates why the Sunday Effect occurs, but offers potential insight
into a wide variety of other atmospheric chemical regimes. The initial step
is to divide the oxygen-containing species into groups on the basis of the
function of the incorporated oxygen in photochemical reactions. Four groups
are distinguished: fixed oxygen (0), accessible oxygen (aO), dissociative
oxygen (60), and odd oxygen (oO).
The chemical species assigned to each group depend on the chemical detail
of the analysis. In this study, odd oxygen includes 0(3P) (indicated through-
out as 0), 0(1D), and 03. Dissociative oxygen includes those species that
photodissociate to produce odd oxygen; N02 and nitrous oxide (N20) comprise
the 60 subgroup in this study. Accessible oxygen species are those that can
donate an oxygen atom to permit the formation of 60 in a single reaction step;
in our study this group comprises nine R02 radicals, nitric acid (HN03), H02,
nitrogen pentaoxide (N205), and N03.
N02 ^ NO + 0
N20 ^ N2 + 0( D).
(We note that recent experimental results indicate that N20 photodissociation
does not occur in the lower troposphere [Stedman, et al., 1976]. The effect
139
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o
102
OJ
0.
0.
K)'
SUNDAY
K) I 1 1 . I 1 1 1 1 1 L__L__L__J
0 2 4 f 6 8 10 12 14 16 16 f 20 22 t4
MR OF DAY
Figure 1. Computed diurnal concentration patterns for workdays and
Sundays in Hudson County, New Jersey.
140
-------
of its inclusion in the calculation at rates previously thought to be correct
has negligible effect on any of the results discussed herein.) Tfie triple
letter designations in Figure 2 are group transition rates that are not the
result of gas phase chemistry. Rates SMx represent the sums of all source
emission and meteorological rates contributing to changes in the group
concentration (note that rates SMx may be either positive or negative), and
rates ARx represent group concentration changes because of heterogeneous
reactions with atmospheric aerosols (Paper I). No triple letter rates are
indicated in Figure 2 for cf>0, since oxygen (02) dominates the <|>0 concentration
and is negligibly affected by SMF or ARF processes; since we neglect hetero-
geneous processes for N02 and N20, rate ARD does not exist.
S,M AR
t,
S,M AR
ARO
Figure 2. The functional oxygen group diagram. The symbol S refers to
emissions sources. M to meteorological sources and sinks, and
AR to removal by aerosol incorporation.
The relative magnitudes of the group transition rates are very different.
Figure 3 presents functional group diagrams for workday and Sunday at 12 a.m.
Several features are immediately apparent. The first is that the dominant
rates are DO and OD, and that they balance to better than 1% for both calcula-
tions. Secondly, the net rates for group transition from 4>0 to 50 are clearly
positive. Finally, while the magnitudes of the bypass group transition rates
are less than those along the central "backbone" of the diagram, they are of
potential significance in view of the net rates along the backbone. The same
consideration applies to the SMx rates. (For this problem, sources furnish
only fixed oxygen; the SMx rates are thus solely meteorological.) Aerosol
effects are small relative to the other group transition rates. A general
decrease in nearly all the rates is evident when comparing Sunday with work-
days. This decrease results from the decreased emissions of NO, the building
block compound that carries the oxygen from group to group, and of reactive
hydrocarbons, the precursors of the radicals responsible for most of the group
transitions. Despite the decreased rates, the strong feedback among the
141
-------
13 48
183
t
<*>
I
390 p 360 m 13178 ^
0 „ 117 a° . 129 S° .13113
2
69
14
85
1
40
|
c
11
>0
i
i
k
i
WORKDAY, 12 A.M.
7 48
103 0
SUNDAY, 12 A.M.
Figure 3. Functional oxygen group diagram at 12 a.m. for workdays and
Sundays, Hudson County, New Jersey.
142
-------
reactive atmospheric compounds enables the overall chemistry to retain its
basic weekday structure.
It can be seen from Figure 3 that the group transition rates DO and OD,
although markedly larger on workdays, have a similar net rate, which represents
the close balance between
N02 ^ NO + 0
NO + 03 -> N02 + 02.
The SMO rate is the largest of those remaining and is virtually identical
weekdays and Sundays. This term represents not only the ozone advected into
Hudson County from the less urban areas upwind, but also that which enters the
"reaction volume" as the rising height incorporates preexisting "fossil" ozone
(Ripperton, 1974) from above. This incorporation was shown in Paper I to be
consistent with air quality data, and provides a vital carryover buffer against
the day-to-day perturbations of ozone precursors.
The early morning excess in ozone concentrations on Sundays reflects the
ozone reductions that occur when rush hour NO emissions enhance the rate of
ozone scavenging by NO. These reductions, combined with the slightly higher
solar flux levels present on Sundays, produce a somewhat higher value net rate
of ozone production on Sunday mornings than on workday mornings. A further
factor inhibiting net ozone production on workdays is the increased rate of
the ozone scavenging reaction
N02-» + 03 •* N03 + 02
caused by the higher N02 concentrations. The inhibitory factors are eventu-
ally overcome by the workday presence of 60 (i.e. N02 + N20); the result is
virtual equality of resulting peak ozone.
CONCLUSIONS
Functional group analysis of oxygen in the troposphere has demonstrated
that the Sunday effect in urban areas results from the tight balance between
ozone production through N02 photodissociation and ozone scavenging by NO,
from the advection of ozone from less urban areas, and from the incorporation
of similar quantities of ozone preexisting above the morning mixed layer. The
higher levels of N02 on workdays increase the rates of the NO-N02-03 shuttle
reactions, but do not significantly alter the similar behavior of odd oxygen
on workdays and Sundays. The increased levels of NOX on workdays have other
consequences, however. The advective transport of NOX is enhanced relative to
Sundays (as seen in the increased group transition rate SMD), with a concomit-
ant expansion of the downwind impact of the urban area. In addition, the
rates of secondary reactions are higher on workdays, resulting in higher con-
centrations of organic and inorganic nitrates and concomitant increases in the
potential of the atmosphere to cause lachrymation.
143
-------
The success of the calculations and analysis performed thus far in deriv-
ing results consistent with field data for two cases of differing source con-
ditions suggests further studies on the changes in ozone concentrations as
anthropogenic emissions are varied over reasonable limits. Such work is now
proceeding and will be reported subsequently.
REFERENCES
Bruntz, S. M., W. S. Cleveland, T. E. Graedel, B. Kleiner, and J. L. Warner.
Ozone Concentrations in New Jersey and New York: Statistical Association with
Related Variables. Science, 186, 257-259, 1974.
Cleveland, W. S., T. E. Graedel, B. Kleiner, and J. L. Warner. Sunday and
Workday Behavior of Photochemical Air Pollutants in New Jersey and New York.
Science, 186, 1037-1038, 1974.
Dimitriades, B. Chamber Studies, Scientific Seminar on Automotive Pollutants.
EPA-600/9-75-003, Environmental Protection Agency, Washington, D.C., 1975.
Farrow, L. A., T. E. Graedel, and T. A. Weber. The Effect of Aerosols on the
Free Radical Chemistry of the Lower Atmosphere. Removal of Trace Contaminants
from the Air. ACS Symposium Series, 17, 17-27, 1975.
Graedel, T. E., L. A. Farrow, and T. A. Weber. Kinetic Studies of the Photo-
chemistry of the Urban Troposphere. Atmospheric Environment (in press), 1976
Graedel, T. E., L. A. Farrow, and T. A. Weber. The Influence of Aerosols on
the Chemistry of the Troposphere. Int. J. Chem. Kinetics Symp., 1, 581-594,
1975.
Paskind, J., and J. R. Kinosian. Hydrocarbon, Oxides of Nitrogen, and Oxidant
Pollutant Relationships in the Atmosphere over California Cities. Paper
presented at 67th Annual Meeting, Air Pollution Control Association, Denver,
Colorado, June 9, 1974.
Ripperton, L. A., Eastern United States High Ozone Concentration: Chemical
Aspects. Clean Air. 4, (16), 79-82, 1974.
Stedman, D. H., R. J. Cicerone, W. L. Chameides, and R. B. Harvey. Absence
of N20 Photolysis in the Troposphere. J. Geophys. Res., 81, 2003-2004, 1976.
144
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4-4
THE EFFECT OF OZONE LAYERS ALOFT ON SURFACE CONCENTRATIONS
T. N. Jerskey, T. B. Smith, S. L. Marsh, and W. H. White
ABSTRACT
Pottutant layeAA alo&t in the. Lot hnge,ieJ> Boi-m M&te, hound to
a vcwiity o^ me.c.haniAmt> ind.udi.ng heating ofc mountain AtopeA, conveAgence zone.4,
and plumed &x,om Atationafiy AouSLC.eA. Aged pottutantA te,nd to acc.umul.ate. ato^t
atong fioothittb during the, late, afiteJinoon. UndeA. Stagnant itiind condition* thue,
layeAA o& ozone, and otheA product* o^ photoc.hejntc.al. Ae,actiont> may Ae,matn hi the.
an.ua and c.on&iibtit£. to high ^uA^ace ozone, conaen.fruttuM.6 atong tha ^oothittt, on
the. Bottoming day. Examination o& the, c.he,m.i&tA.y o^ ?ie.e.ntA.ainme,nt AuggeJitA that
thu inteA.me,diate, ptioductA o^ photoc.he,mi.c,at fi^ac^tion^ [t>u,c,h a& ni&iouA actd and
alde.hyde^>] c.an ac,c.eJL&iat& the. tiate. o& ozone, ^oftmation. Thi& e,ntAjatnme.nt pfioc,&
may c.ontsU.but.(i AubAtantialiy to the, gsiound-l.e,ve,l. ozone, c.onc.e.n&iation undeA
e,piAode. condition^.
INTRODUCTION
This paper presents evidence that, under the stagnant wind conditions that
characterize episode periods, ozone layers aloft can account for a substantial
portion of the surface ozone concentrations in the Los Angeles Basin. The data
analyzed were obtained during the Three-Dimensional Gradient Study (Blumenthal
et a!., 1974). Below we discuss possible mechanisms for the formation of
pollutant layers aloft and analyze their possible effects on surface concentrations
SOURCES OF LAYERS ALOFT
An examination of a large number of layers aloft indicates that the fol-
lowing mechanisms may be responsible for their formation in the Los Angeles
Basin: (a) convergence of the windfields, (b) flow up heated mountain slopes,
(c) undercutting by the sea breeze, (d) plumes from stationary sources, and (e)
formation of a radiative inversion. With the exception of the first two me-
chanisms, the layers formed are near the surface and can be incorporated readily
into the mixed layer on the following day. When layers aloft form by conver-
gence of the windfields, the pollutants are often carried far above the in-
version base and generally have a low probability of becoming entrained on the
following day. Also, layers formed by upslope flow often are carried far above
the base of the inversion; but, because of the heating occurring on the mountain
slopes on the following day, these layers can be entrained and affect surface
concentrations along the foothills.
*Jerskey, Systems Applications, Inc., San Rafael, California.
Smith, Marsh, and White, Meteorology Research, Inc., Altadena, California.
145
-------
Pollutants carried into elevated layers during the afternoon are subject to
transport by the prevailing winds at those levels during the night. Depending
on wind direction and speed, the pollutants in the layers aloft may be carried
inland over the desert and diffused, may be carried toward the coastal areas, or
may remain in the foothill areas until the next morning. The worst pollution
episode conditions are associated with the lack of transport of the layers aloft
away from the foothill areas. Under these conditions, the material aloft
remains undiluted and is available for entrapment into the mixed layer on the
following day.
IMPACT OF LAYERS ALOFT ON SURFACE CONCENTRATIONS
The object of this phase of our analysis was to determine the impact of
the layers of pollutants aloft on concentrations within the mixed layer as the
inversion rises to entrain the material aloft. In our approach we assumed that
all the material aloft in the morning profile up to the midday inversion height
was entrained.
For the eight days on which a sufficient overlap existed between the
morning and midday measurement locations, we tabulated coefficients for the
correlation between the mass of entrained pollutants and the change of the
pollutant mass loadings between the morning and midday flights. The correlation
coefficients varied considerably over the eight days. Furthermore a high
correlation coefficient did not appear to be related to the quantity of pol-
lutant entrained from aloft or the pollutant concentration on a particular day.
Upon closer inspection of the data, we found that the entrained ozone did appear
to be correlated with the difference between the mass loading in the morning and
at midday. A similar conclusion could not be drawn for aerosol mass or carbon
monoxide, even when the change in mass loading was modified to account for
emissions into the air parcel. Instead of considering the mass entrained at
individual locations, the average mass entrained for the entire basin can be
calculated. By averaging the difference between the morning and midday loading
over the basin, one can minimize the variation of measurements from location to
location. Furthermore, averaging over all the measurements minimizes the effect
of advection, particularly for a secondary pollutant like ozone, whose spatial
variations in concentration are relatively small compared with those of primary
pollutants. The mean values of the entrained ozone mass loading arid the dif-
ference between the morning and midday mass loadings for the eight days studied
are plotted in Figure 1. The correlation coefficient for the eight days was
0.78.
Because of the relative location of Cable and Rial to and the routes flown
by the aircraft, the time delay between measurements made at the two locations
(typically 90 minutes) was approximately the time required for an air parcel to
be advected between them. For this portion of the data set we again calculated
the mass entrained from aloft (using the vertical ozone distribution at the
beginning of the trajectory measured at Cable) and the change of the mass
loading in the mixed layer calculated for Cable and Rial to. Morning and midday
trajectories between Cable and Rialto were available for eight days in 1973.
Afternoon trajectories were not considered since the depth of the mixed layer
generally decreased along the trajectory during this time period. By comparing
the change in the ozone mass loading with the ozone entrained from aloft (see
146
-------
220
200
180
1*160
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V)
a,
120
100
80
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40
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1
l
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l
0
10 20 30
40 50 60 70
Ozone Entrained--mg m
80 90
-2
100 110 120
Figure 1. The change in ozone mass loading as a function of
the mass of ozone entrained from the mixed layer.
Figure 2) we confirmed the observation that high ozone concentrations at Rialto
are correlated with high ozone concentrations aloft.
Further evidence that the layers aloft have an impact on the concentration
of ozone in the mixed layer is provided by an analysis of the surface concen-
trations for July 25, 1973, a day when ozone concentrations reached a level of
0.5 ppm at Upland (near Cable). Figure 3 shows the vertical sounding at Cable
at about 0830 Pacific Daylight Time (PDT) on July 25. Substantial ozone con-
centrations were found aloft, peaking at over 0.2 ppm at a height of 2100 feet
mean sea level (msl). The sounding also shows a rapid decrease in b
scat
above 1800 ft msl, indicating a very shallow surface mixing layer. Figure 4a
shows the surface ozone concentrations from the California Air Resources Board
(ARB) pollution network for the period from 0900-1000 PDT on July 25. Peak
values of 0.15 ppm in the basin occurred in the Upland area but generally high
values existed along the entire foothill area from San Bernardino (SBD) to
147
-------
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160
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A MIDDAY TRAJECTORY
7/18
7/25
A
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20 40 60 80 100 120 140
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Entrained Ozone--mg m c
160 180 200
Figure 2. The change in ozone mass loading along the trajectory from
Cable to Rialto as a function of the ozone entrained.
Burbank (BUR). By 1200-1300 PDT (Figure 4b) the ozone concentrations along the
foothills had increased at a time when the mixed layer at Cable had increased to
2500 ft msl, incorporating much of the pollutants aloft. At this time there was
also evidence of new ozone production in the central Los Angeles area (CAP).
Subsequently these new ozone concentrations were carried northeastward to the
foothill area and mixed with the existing high ozone concentrations to produce
levels as high as 0.5 ppm at Upland during the hours from 1600 to 1700 PDT.
These data suggest that the high ozone concentrations observed along the
foothills were influenced by the downward mixing of pollutants from aloft as
surface heating caused the inversion base to rise and entrain these materials.
Although ozone is mixed downward into the mixed layer, we believe that the
intermediate products (such as aldehydes and nitrous acid) of the photochemical
reactions are responsible for the high ozone concentrations observed along the
148
-------
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LEGEND
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Ozone
Temperature
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76-002
Figure 3. Vertical sounding at Cable Airport (Upland),
July 25, 1973 (0830 PDT)
foothills. The effect of these intermediate products on the ozone formation
rate is illustrated by the numerical simulation of a smog chamber experiment
using the Hecht et al. (1974) kinetic mechanism (see Figure 5). In Case 1 (see
Table 1) the simulation was performed without any initial ozone or aldehyde
concentration. Case 2, with the initial ozone concentration at 0.42 ppm, showed
little change in the final ozone concentration. However, when the aldehydes
were carried over (Case 3), the ozone production rate was accelerated initially,
leading to higher ozone concentrations at early times. The photolysis of
aldehydes produces radicals that react with nitri oxide to give nitrogen dioxide
(N02). Thus these intermediate products accelerate the formation of ozone by
increasing the concentration of N02.
SUMMARY AND CONCLUSIONS
Layers of ozone aloft can be formed by one of several mechanisms. Once
these layers are formed the impact they have on surface concentrations on the
following day depends on the strength and direction of the winds aloft. Under
stagnant conditions the layers can remain overnight where they were formed. On
the following day surface heating causes these layers to be entrained into the
mixed layer, where they can contribute a substantial fraction of the ozone
concentration on that day. Hence, a knowledge of the winds aloft can serve as a
forecasting tool for prediction episode conditions.
149
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TABLE 1. INITIAL POLLUTANT CONCENTRATIONS (IN PPM)
FOR THE RESULTS SHOWN IN FIGURE 5
Pollutant
Case 1
Case 2
Case 3
NO
N02
PAN
Ozone
Propylene
Formaldehyde
Acetaldehyde
Propionaldehyde
0.94
0.13
0
0
1.04
0.02
0
0
0.94
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0
0.42
1.04
0.02
0
0
0.94
0.13
0
0
1.06
0.25
0.17
0.03
These results suggest that air quality simulation models must take into
account the three-dimensional structure of pollutant concentrations in order to
predict episode conditions.
ACKNOWLEDGMENTS
This study was carried out under the support of the California Air Re-
sources Board (ARE) as part of a study to examine the data from the Three-
Dimensional Gradient Study. Mr. Gary Palo and Mr. C. L. Bennett of the ARB
served as contract monitors and contributed significant inputs in regard to the
ARB problems and interests in the study.
REFERENCES
Blumenthal, D. L., et al. Three Dimensional Pollutant Gradient Study. 1972-
1973 Program. MRI 74 FR-1262, ARB-631 and ARB-2-1245, 1974. Meteorology
Research, Incorporated, Altadena, California.
Hecht, T. A., J. H. Seinfeld, and M. C. Dodge. Further Development of a
Generalized Kinetic Mechanism for Photochemical Smog, Environ. Sci.
nol. , Vol. 8, p. 327.
Tech-
153
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SESSION 5
SOURCES OF TROPOSPHERIC OZONE - III
R.A. Rasmussen
Washington State University
155
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5-1
OZONE CONCENTRATIONS IN POWER PLANT PLUMES:
COMPARISON OF MODELS AND SAMPLING DATA
T. W. Tesche, J. A. Ogren, and D. L. Blumenthal*
ABSTRACT
F/te£d measurements and modi-Ling studies have, been carried out to investi-
gate reports that ozone, may be generated -in plumes farom large power plants -in
concentrations exceeding amb-ient levels. Analyst o{ aerometric data firom
three Western poweA plants consistently revealed ozone depletion w/ctn/en the
p£ume /en the. vicinity o& the. stack and a gx.adu.aJL -increase /en ozone. concentra-
tion to approximately background levels fiasi dom.u),ind. Wo ozone. ge,ne.siation wa&
ob4eA.ued -in the. p£ume-4 Atu.die.d. Exte.nt»ive. mode.1. vaLida£ion Atudie.* with the.
Re.active, Plume. Mode£ we^ie peA|$oAmed. CompastU>on o^ mode.1. psie.dictionA and mea-
-iu/ied plume. c.onc.e,n&ia£ion-{> -indicatzd that the. mode.1. AJ> a aie^a£ tool. ^on. Atudy-
/tng AeacXtue p£ume-6. To deteAm/cne whetne-A tne mode£ coa£d be a6ed to ievea£
conditions ^on. which ozone, might be generated /en plwn&>, hypothetical. Ace.nasiio&
.involving di^eAant. ambi&nt hydrocarbon i.nv weAe. i.nveA£igate.d. for vary
high hydrocarbon concentrations (6 ppm as methane.} the. model does predict net
ozone formation ok approximately 6-12 percent aboue background levels. The
Limitations and implications ofa this result are discussed.
INTRODUCTION
The possibility of ozone formation above ambient concentrations in power
plant plumes has recently been raised by several investigators (1,2). To
better understand the factors affecting the behavior of ozone in power plant
plumes, the Electric Power Research Institute (EPRI) contracted with Meteoro-
olgy Research, Inc., (MRI) and Systems Applications, Inc., (SAI) to perform at
three Western United States power plants to determine the behavior of ozone in
the plumes, and to support a validation study of the Reactive Plume Model (RPM),
originally developed to study reactive power plant plumes under various envir-
onmental conditions. Because the results of the EPRI study are presented in
greater detail elsewhere (3,4), only the essential findings are reviewed here.
The primary emphasis of this paper concerns the modeling results obtained with
RPM.
*T. W. Tesche, Systems Applications, Inc., San Rafael, California. J. A. Ogren
and D. L. Blumenthal, Meteorology Research, Inc., Altadena, California.
157
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FIELD MEASUREMENT PROGRAM
Airborne plume sampling was conducted in August and October 1975, primar-
ily with the MRI Cessna 206, which was instrumented to measure and record con-
tinuously ozone (03), nitric oxide (NO), nitrogen oxides (NOX), sulfur dioxide
(S02), light scattering coefficient, condensation nuclei, temperature, dew
point, turbulence, pressure (altitude), and position. Sulfate aerosol and
hydrocarbon (HC) samples were obtained for later chemical analysis. Support-
ing ground-based measurements included winds aloft (using pibals) and ultra-
violet solar radiation. In addition, a Douglas B-23 (operated by the Univer-
sity of Washington), instrumented similarly to the Cessna 206, was used to
collect supplemental plume data during part of the program.
Aerometric measurements were made at the following power plants: Four
Corners, Farmington, New Mexico (coal-fired, dry environment); Cunningham,
Hobbs, New Mexico (gas-fired, dry environment); and Wilkes, Longview, Texas
(gas-fired, humid environment). Data from coal-and oil-fired plants in humid
environments were also analyzed along with the data from the plants listed
above to provide a comprehensive basis for studying the behavior of ozone in
power plant plumes. In all of the cases studied, ozone depletion within the
plume occurred near the plant, followed by a gradual increase to background
levels as ambient air was entrained in the plume.
A typical ozone profile is shown in Figure 1. The plume is readily iden-
tified by the elevated S02 concentrations. High values of NO., NOX, and bscat
were also associated with the plume. Ozone concentrations in the plume were
well below background levels. Depletion of ozone relative to background was
observed wherever the plume was distinguishable from background concentrations,
although the deficit was very small at far downwind distances. Another example
of plume concentration data is presented in Figure 2. This plume isopleth
characterization is based on ozone measurements at five altitudes. The plume
contained high NO and NOX concentrations, and a pronounced ozone deficit. How-
ever, an ozone layer with high concentrations was observed above the plume.
Analysis of the data collected on this day revealed that the ozone layer was
not associated with the plume, and was probably caused by the advection and
aging of pollutants emitted upwind of the sampling area. Clearly, without
supporting measurements upwind of the plant, and well outside of the plume, it
would be possible to misinterpret some of the ozone profiles used to create
Figure 2 as evidence of ozone formation on the edges of the plume.
MATHEMATICAL MODELING OF POWER PLANT PLUMES
Recently, the California Air Resources Board sponsored the development of
a package of three numerical models to characterize both the physical and
chemical transformations of power plant plumes (5). One of these - the Reac-
tive Plume Model (RPM) -was an integral part of the EPRI study.
THE REACTIVE PLUME MODEL (RPM)
RPM was developed to study the complexities of plume photochemistry in
detail; transport and dispersion are treated in a less rigorous fashion. The
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model employs a refined version of the lumped-hydrocarbon, Hecht-Seinfeld-
Dodge photochemical mechanism (6). For generality, the kinetic mechanism has
been augmented with a set of provisional sulfur oxidation reactions in order to
simulate the environment of power plant plumes contain sulfur emissions. The
model is based upon a mass balance for pollutant species involved in plume
photochemistry. Within a Lagrangian air parcel moving downwind, photochemical
reactions are modeled by accounting for:
• The mass of a given pollutant emitted from the stack - initial
conditions
• The mass of a given pollutant entrained from the ambient air as the
plume expands - boundary conditions
• The mass of a given pollutant created or destroyed due to reactions
within the air parcel - chemical reactions.
Plume dilution is prescribed in RPM either from measurement or theory. Esti-
mates of dilution rates can be based on measured plume widths and mixing depths;
alternatively, the model can compute the dilution of pollutants by a Gaussian
formula using dispersion coefficients estimated from either the standard
Pasquill-Gifford method (7), the modified Bowne scheme (8), or a recent method
based upon similarity theory (5). The speed at which the parcel is transported
downwind is specified from wind measurements aloft via pibal records. Reliance
is placed upon aircraft measurements to determine the pollutant concentrations
as close to the stack as possible (the initial conditions) and to record the
temporal and spatial variation in background pollutant concentrations (boundary
conditions). Finally, average concentrations of pollutants measured by air-
craft within the plume are used for comparison with model predictions.
RPM VALIDATION STUDIES
One objective of the EPRI program was to provide a data base suitable for
determining RPM's accuracy in simulating the behavior of reactive power plant
plumes. Consequently, a large number (sixteen) of model verification studies
were carried out with the EPRI field data. One set of comparisons between
predictions and measurements is presented here.
On August 28, 1975, the Four Corners plume was sampled by the MRI aircraft.
At distances of 5, 21, 60, and 87 km downwind of the plant, the plume was
characterized with horizontal traverses at three different altitudes and with
vertical spirals. Concentrations of S02 in the Four Corners plume were identi-
fiable at all four sampling distances. Maximum S02 concentrations within the
core of the plume exceeded 1 ppm at 5 km and declined with increasing distance
from the plant, falling to 0.04 ppm at 87 km. The observed S02 concentrations
outside the plume were 0.01 ppm or less.
Ozone concentrations outside the plume were in the 0.04 to 0.05 ppm range,
increasing slightly with the increase in solar insolation during the morning.
While ozone concentrations within the plume were depressed relative to those
161
-------
outside at all distances, the absolute ozone concentrations in the plume in-
creased with distance downwind, from a minimum of 0.01 ppm or less at 5 km to
0.04 ppm at 87 km. Background reactive HC levels were estimated to be 0.027
ppm by volume (approximate 0.16 ppm as methane). The mean wind speed ranged
from 1.2 to 5.0 meters per second.
The RPM simulation for this day was carried out for a distance of 100 km
from the stack. Predicted NO, N02, 03 and S02 concentrations, designated by
the symbol "0", are presented in Figures 3 through 6. Background and plume
measurements, designated by "B" and "M" respectively, are also plotted in the
figures. Nitric oxide predictions (Figure 3) exhibit excellent agreement with
the data. After approximately 24 km, NO levels in the plume are depressed to
approximately background levels. In addition, N02 predictions (Figure 4) are
also in good agreement with the data. On the other hand, ozone predictions
exceed measured values by approximately 30 percent far downwind of the stack.
As may be seen in Figure 5, the measured concentrations increase gradually; at
84 km the measured plume ozone is just slightly less than the background. In
Figure 6 very good agreement exists between predicted and measured S02 con-
centrations over a relatively wide range of values.
Based on the RPM validation studies conducted to date, it is possible to
make a preliminary assessment of the model's validity and utility. RPM is
capable of predicting the dilution of conservative pollutants and tracer
material quite well. For reactive primary pollutants such as NO and S02, pre-
dictions are generally in good agreement with measurements. Model predictions
of secondary pollutants such as N02 and 03 are strongly influenced by the con-
centrations of reactive HC in the ambient atmosphere. There appears to be a
tendency for the model to overpredict N02 and 03 concentrations when high
background HC concentrations are present. However, at present, it is not
clear whether there are factors involved in the N02 and 03 overpredictions
other than high HC estimates. From RPM simulations for which the assumed HC
concentrations are believed to be reasonably accurate, we estimate that the
accuracy of the Model for 03 predictions at large downwind distances is within
+_ 25 percent. In general, the overall predictive capability of the model
appears to be commensurate with the ability of present sampling methods (9) to
characterize the unsteady nature of power plant plumes.
OZONE FORMATION IN POWER PLANT PLUMES
To determine if RPM is capable of identifying conditions for which ozone
in excess of background concentrations may be formed in plumes, two basic
simulations were carried out. First, the photochemical model CHEMK was used
to predict initial background concentration variations throughout the day.*
Then, with the predicted background concentrations as inputs, RPM was exercised
to study how the predicted plume ozone levels varied relative to the predicted
*Due to numerical instabilities in the integration algorithm, it is not possi-
ble to conduct a "background simulation" with RPM. Instead, another model,
CHEMK, incorporating the same kinetic reaction steps as RPM, was used to sim-
ulate the temporal changes in the background pollutant concentration (10).
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background. If the plume concentrations exceed background levels, this would
suggest that the model is simulating a condition for which ozone generation in
the physical environment might occur.
Two hypothetical scenarios involving different ambient HC concentrations
were investigated. In one case HC was approximately 6.0 ppm as methane; in
the other HC was reduced to 0.6 ppm as methane. Initial conditions similar
to what might be expected in an urban air atmoshpere were chosen for the
simulations. Dispersion characteristics and initial pollutant concentrations
were chosen to be identical to those observed for the Four Corners Plume on
August 28, 1975. Wind speeds varied between 1.2 and 5.0 meters per second.
The following simulations were carried out for both scenarios:
• Using the CHEMK photochemical model, the initial ambient concentra-
tions reacted for 6 hours leading to a predicted variation in back-
ground concentrations.
• RPM was exercised using as inputs the time-varying background con-
centrations of NO, N02, 03, olefins, paraffins, aldehydes, aromatics,
and S02 predicted by CHEMK.
Results of the simulations are presented in Figures 7 and 8. The curves in
the figures give the background ozone concentrations predicted by CHEMK and
the plume ozone concentrations predicted by RPM using computed CHEMK back-
grounds for NO, N02, 03, S02, and the four lumped HC groups - olefins, alde-
hydes, aromatics, and paraffins. In Figure 7, the low HC case, predicted
plume ozone concentrations exceed predicted background levels by about 0.005
to 0.010 ppm between simulation times of 60 and 180 minutes. Before and after
this period the plume is observed to have an ozone deficit relative to the
background. On the other hand, the case of highly reactive HC backgrounds
(Figure 8) is associated with an ozone bulge of 0.030 ppm (approximately 12
percent above background) occurring midway through the simulation. In fact,
with the exception of the ozone deficit occurring in the first 20 minutes of
the simulation, the plume ozone levels exceed predicted ambient levels by
0.015 to 0.030 ppm (6 to 12 percent above ambient) throughout the simulation.
Thus, for the initial and background conditions used in the high HC background
example, RPM predicts net ozone generation in the plume relative to the pre-
dicted background ozone level given by CHEMK.
From this case study it appears that for ambient reactive HC concentra-
tion levels on the order of 6.0 ppm as methane, RPM predicts plume ozone con-
centrations approximately 6 to 12 percent higher than the predicted background
concentrations derived from a smog chamber photochemical model. While this
result suggests that for high background HC conditions the models do predict
slight ozone formation, the results of this case study are too limited to con-
firm or refute an ozone formation hypothesis in the real environment because
important phenomena that affect background and plume pollutant concentrations
(e.g., emissions from other sources, surface pollutant removal processes) were
not included in the simulations. One way to include these phenomena and
perhaps to derive a more general result would be to use a more sophisticated
photochemical model that treats plume and background reactions simultaneously,
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and accounts for source emissions and pollutant removal processes.
CONCLUSIONS
From the results of field studies, data analysis and a review of the
literature, we conclude that formation of ozone in power plant plumes above
ambient concentrations is not a common occurrence if it occurs at all. In
all of the plumes studied during the EPRI program the ozone observed in the
plume can be explained by entrainment of ambient ozone and ozone precursors.
It appears that for certain special conditions RPM does predict plume
ozone concentrations slightly in excess (6 to 12 percent) of background levels.
These conditions involve the entrainment of high ambient reactive HC concen-
trations (6.0 ppm as methane). However, the computer simulations yielding
this result are only the first step in examining the ozone formation hypothesis.
In attempting to determine the contribution of a given power plant to
regional ozone concentrations, one should examine the plume and the plant site
for conditions that may be conducive to ozone formation. These include a
major HC source in the immediate vicinity of the plant or high HC emissions
from the plant itself. If conditions potentially conducive to ozone formation
in the plume are encountered, models capable of predicting photochemical re-
actions may be of value in assessing the situation.
ACKNOWLEDGEMENTS
The authors express their sincere thanks to the many individuals who con-
tributed to various aspects of this program, particularly Dr. W. H. White and
Mr. J. Anderson (MRI) and Drs. M. K. Liu, G. Z. Whitten, and P. M. Roth, and
Mr. M. A. Yocke (SAI). This study was supported by the Electric Power Research
Institute under Contract No. RP-572, under the direction of Mr. Charles
Hakkarinen.
REFERENCES
1. Davis, D. D. , G. Smith, and G. Kletuber, Trace Gas Analysis of Power Plant
3.
Plumes Via Aircraft Measurement:
186, 1974, pp. 733-736.
0~, NO , S0? Chemistry, Science, Vol
cs
Buffi ngton, P. D. and E. A. Bartczak, Ozone: Chemical Action and Reaction
in the Lower Level Transport Winds, Presented at the 68th Annual Meeting
of the Air Pollution Control Association, Boston, Massachusetts, June
1975.
Ogren, J. A., D. L. Blumenthal, and W. H. White, Study of Ozone Formation
in Power Plant Plumes, Presented at the Ozone/Oxidants: Interactions
with the Total Environment meeting, Air Pollution Control Association II-
5 Committee, Dallas, Texas, March 10-12, 1976.
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4. Determination of the Feasibility'of Ozone Formation in Power Plant
Plumes, Report to the Electric Power Research Institute prepared by
Systems Applications, Inc., and Meteorology Research, Inc., contract
No. RP-572, May 1976.
5. Liu, M. K., D. Durran, P. Mundkur, M. Yocke, and J. Ames, The Chemistry,
Dispersion, and Transport of Air Pollutants Emitted from Fossil Fuel
Power Plants in California: Data Analysis and Emission Impact Model,
Report EF76-18 to the California Air Resources Board by Systems Applica-
tions, Inc. San Rafael, California, May 1976.
6. Meet, T. A., J. H. Seinfeld, M. C. Dodge, Further Development of a
Generalized Kinetic Mechanism for Photochemical Smog, Environ. Sci. Tech.
Vol. 8, 1974, pp. 237-339.
7. Slade, D. H., ed., Meteorology and Atomic Energy 1968, U.S. Atomic Energy
Commission Publication TID-24190, 1968.
8. Bowne, N. E., Diffusion Rates, Journal of the Air Pollution Control
Association, Vol. 24, No. 9, September 1974.
9. Tesche, T. W., G. Z. Whitten, M. A. Yocke, M. K. Liu, Theoretical Numeri-
cal, and Physical Techniques for Characterizing Power Plant Plumes.
Report EC-144 to the Electric Power Research Institute by Systems Appli-
cations, Inc., San Rafael, California, October 1975.
10. Whitten, G. Z., Rate Constant Evaluations Using a New Computer Modeling
Scheme, Paper presented at the 167th National Meeting of the American
Chemical Society, April 1974.
171
-------
5-2
ABSTRACT
OZONE AND NITROGEN OXIDES IN POWER PLANT PLUMES
D. Hegg, P. V. Hobbs, L. F. Radke, and H. Harrison*
aAe. pAe.Aente.d o& aiAboAne. me.at>uAme.nti> taken -in the. plumed o& two
coal- and two gaA-faiAe-d pow w>eAe made. o& the, conce.ntAo
tion o^ nitAi.c oxA.de., ni\tAoge.n dioxide., ozone, and Aul&uA dioxA.de., tempe.AatuAe.,
Ae.lative. humidity, and ultAav-iolet Aadtation. Ozone, conce.ntAati.onA exceeding
thote. ofa the. AuAAounding ambient aiA we.Ae. not &ound in thcAe. plumes, which
we.Ae. obAeAve.d out to diAtanceA o^ 90 km (4 houAA tAave.1 time.} ^Aom- the. AtockA.
AnalyAiA o& the. plume. che.miAtn.y &ugge.At!> that, oveA dLbtanzeA and time. i,c.aleA
within which. plwneA one. di^eAentiable. fitiom background (the. vie.ati-{si.eX.d} , the.
che.m&iy JJ* Qe.neMUULy contftolZe.d by the. ^utfe-6 at which the. plumes m/tx
the. ambtent CUA. natheA. than by chejnicoit ki.netA.cJ,. Con&e.que.ntty , on the&e.
-6ca£e4, the. iate.t> o& conveAAton oft nitric oxide, to nitAOQen dioxide, i
and the nitAoge.n dio xi.de. /nitAi.c oxi.de. nation aAe. malt (the. highest fiatio
me.a£(Lfie.d WOA 4.3}. ThiA analy&i^ con&iAte.nt with the. absence o{, ob&eAv-
able. ozone. ge.neAation i.n the. ne.aji- ^i.eJLd^ ofi the. poweA plant plumes Atudie.d.
INTRODUCTION
The possibility of ozone (03) formation, perhaps in excess of federal
standards, in the near field plumes (the distance over which the plume is dif-
ferentiable from the background) of fossil --fueled power plants has been sug-
gested by the observations of Davis et al. (1974) at the Morgantown, Maryland,
coal-fired power plant. However, in other studies, ozone at concentrations
above the ambient background levels has not been detected in power plant plumes
(Teshe et al . , 1976).
In this paper we present the results of field studies of the plumes from
two coal and two gas-fired power plants. The two coal-fired plants were the
Pacific Power and Light Plant at Centralia, Washington, and the Four Corners
Plant at Farmington, New Mexico. The gas-fired plants were the Cunningham
Plant at Hobbs, New Mexico, and the Wilkes Plant at Longview Texas. Airborne
measurements were made of the concentrations of nitric oxide (NO), nitrogen
dioxide (N02), QS, and sulfur dioxide (S02), temperature, relative humidity,
ultra-violet radiation, and condensation nucleus concentrations. Data were
collected in thirty flights over an S-month period and parameters needed to
specify the nitrogen oxides (N0x)-ozone chemistry of the plumes were derived.
The data consisted primarily of ambient and plume 03 concentrations, plume
*University of Washington, Seattle, Washington.
173
-------
center-line and plume average N02/N0 ratios, plume center-line and plume average
NO to NO conversion rates, and the correlations of N02/N0 with NO across the
plume. We conclude that at the spatial resolution of our measurements (? 150
m) the NOX-03 chemistry is commonly controlled by the rate of mixing of a plume
with the ambient air, rather than by kinetic rate constants. Consequently,
the macroscopic conversion rate of NO to N02 is slow and the N02/N0 ratios re-
main too low to permit ozone generation in the near-field plume. A full account
of the work summarized in this paper, including all field data, has been given
by Hegg et al. (1976).
INSTRUMENTATION
The University of Washington's (U.W.) B-23 aircraft was used for most of
the sampling, but some data were gathered by a Cessna 206 operated by Meteor-
ology Research, Inc. (Ogren et al., 1976). In addition to an extensive set
of meteorological and aerosol sizing instruments (Hobbs et al., 1976), the
U.W. sampling aircraft also carried a Meloy 160-2A sulfur analyzer, a Monitor
Labs 8440 chemiluminescent NOX analyzer, a Monitor Labs 8410A ozone analyzer
and an Eppley untrviolet radiometer. The sulfur analyzer was periodically
calibrated against a Meloy CS10-2 calibration source (permeation tube), and
the NOX and ozone analyzers were calibrated against a Monitor Labs 8500 cali-
bration source (which was ultimately calibrated against gas-phase titration
for NO and against buffered potassium iodide for ozone).
A
FIELD RESULTS AND ANALYSIS
Ozone concentrations higher than in the surrounding ambient air were
never observed in the power plant plumes that we studied. We did observe
three episodes (on October 10, 11, and 13, 1975) of very high 03 levels (^120
ppb) in the plume of the Wilkes plant at Longview, but detailed analysis (Hegg
et al., 1976) of the background 03 field, including its vertical structure,
revealed that the high concentrations in the plume on these occasions were
caused by the advection of high ambient blobs of 03 into the plume,
The amount of 03 that can exist in photochemical steady-state with a
given quantity of NOX is directly related to the ratio of N02/N0 (Steadman
and Jackson, 1974). For a system of either NOX p"ius hydrocarbons (HC), or
NOX plus HC plus S02, it has been shown experimentally that 03 generation
will not occur to any appreciable extent until the N02/N0 ratio rises to
about 10 (Kocmond et al., 1975). Therefore, the ratios of N02/N0 in power
plant plumes give an indication of the near-field ozone generating capability.
Since the NOX emitted from power plants is mostly NO, the conversion rate of
NO to N02 is also an important parameter.
In the above discussion, we have tacitly assumed that the plumes are close
to photochemical steady-state. This, at first glance, appears to be plausible
because the fast rate constants of the NOX-03 system result in a very short
relaxation time to steady-states, about 1 minute at typical plume concentra-
tions of NO (0.050 ppm and 03 (0.015 ppm) for typical temperatures and UV
radiation levels. Indeed, the NOX-03 system has been shown to be in
174
-------
photochemical steady-state for well-mixed ambient air (Steadman and Jackson,
1974). However, a diffusing plume may not be in macroscopic photochemical
equilibrium because diffusive mixing times over the spatial scale of the
plume may be short compared to the chemical relaxation times. Indeed, over
a small enough spatial scale, the mixing times do become short compared to
chemical relaxation times. The relative size of this sub-scale to the plume
mixing scale determines the extent to which a plume is macroscopically in
a steady-state. We must therefore consider this problem in more detail.
A plume of NO , initially mostly NO, interacting with ambient air con-
taining 0 (or anyxother species of comparable reactivity with NO) may be
viewed as a bimolecular reaction, with initially unmixed reactants, in a
turbulent fluid. This problem has been treated theoretically with some success;
also, some laboratory results are available (O'Brian, 1974; Hill, 1976).
Assuming that the bimolecular reaction is fast compared to mixing times over
the scale of the plume (for NO + 03 ->N02 + 02, Tn : 1 minute for typical NO
3
concentrations near 0.05 ppm), the reactant species become spatially segre-
gated with the reaction occurring entirely within a relatively narrow reaction
zone between the two spatial regions. Figure 1 illustrates this view of the
plume. The width of the reaction zone is essentially the spatial sub-scale
over which the mixing time is comparable to the chemical relaxation time. The
well known ozone deficits associated with power plant plumes are, in fact,
manifestations of spatial segregation of reactant species. Figure 2 shows an
example of this effect which suggests that the width of the reaction zone is
indeed small compared to the plume radius. Thus, over the spatial scale of
the plume, the mixing time is long compared to the chemical relaxation time
and most of the volume of a plume should be in local photochemical steady-
state.
The time required to mix the initially separated reactants (NO and 03)
over the whole plume is longer than that required for reactions between NO and
03 to take place in the sub-scale. Therefore, the macroscopic rate of reaction
is controlled by the rate of mixing of the plume with the ambient air, rather
than by the kinetic rate constant for the reaction. The plume chemistry is
therefore diffusion controlled.
Evidence for the diffusive control of the plume chemistry can be obtained
by considering the spatial distribution of the N02/N0 ratio in the plume.
Since N02 is the product of the reaction of NO and 03, the ratio of N02/N0
should be highest at the reaction zone; for a biomolecular diffusion-controlled
reaction, this zone should be located at the edge of the plume between the
regions of high NO and 03 (Figure Ib). Assuming this to be the case, the
ratio of N02/N0 should then be negatively correlated with the total concen-
tration of NO (which we employed as a plume tracer and assumed to be con-
served in the plume).
Table 1 shows the results of a correlation analysis of N02/N0 with NOX
in the power plant plumes we have investigated. In fourteen out of eighteen
cases there was a negative correlation between N02/N0 and NOX indicating that
the plumes were indeed generally diffusion controlled. However, on three
occasions there were significant positive correlations between N02/N0 and NOX,
175
-------
5000
„ 2500
(a) Nitric oxide
I KM
(a)
200
100
(b) Ozone
I KM
(b)
Figure 1. Diagrams for a bimolecular
reaction in a turbulent plume: (a)
shows a cross-sectional view of the
plume. The reaction zone is an
annul us of area A and width LR. The
interior of the plume, where the
concentration of NO is high, has area
B. Area C is the exterior region of
ozone. E is a mixing turbulent eddy
of velocity VV and scale A. (b) shows
concentrations of the gases across
section (a).
which indicates that in some situations the
controlled. This is not surprising in view
scales for atmospheric mixing,, and it is to
gradients of NOx become small over both the
and the macroscale of the plume.
Figure 2. Profiles of nitric oxide
and ozone across the plume of the
Four Corners coal-fired power plant
on 16 October 1975. The range was
1 km downwind from the stack and
the altitude was 1950 m.
plume chemistry may be chemically
of the variability in the time
be expected when concentration
spatial scale of the measurements
The degree to which the plumes are in chemical steady state may
sidered in terms of the three fast reactions:
be con-
NO + hv
NO + 0
(1)
0 + 02 +
0
M
(2)
k,
NO + 03 —-*-* N02 + 02 (3)
where the k's are rate constants and ka = 8.0 x TO"3 (x < 400 nm), k2 = 1.1 x
176
-------
TABLE 1. CORRELATION OF N02/N0 WITH NOX IN POWER PLANT PLUMES
Date
6/16/75
M
n
7/29/75
ii
8/20/75
n
10/10/75
M
10/11/75
ii
10/17/75
n
M
n
10/30/75
10/31/75
II
Power Plant *™*°
Centralia* 0.8
1.6
4.8
0.8
1.6
0.2
3.2
Longview t 5.0
3.0
3.0
10
Farmington* 20
40
70
10
Centralia* 8.0
2.4
5.6
Correlation
Coefficient
(Vxy)
-0.75
-0.92
-0.94
-0.87
-0.90
-0.57
-0.51
+0.98
+0.10
-0.76
+0.99
-0.91
-0.91
-0.54
+0.80
-0.74
-0.80
-0.69
Significance
Level (%)
> 90
> 90
> 98
> 95
> 99
> 75
> 50
98
< 50
> 90
99
> 90
> 95
> 50
80
> 80
80
> 80
Data Source
Hegg et al .
(1976)
M
M
n
n
M
n
M
Ogren et al .
(1976)
M
n
Hegg et al .
(1976)
n
M
Ogren et al .
(1976)
Hegg et al .
(1976)
M
II
* Coal-fired
T Gas-fired
177
-------
10-3U exp(500/T), and k3 = 1.7 x 1CT12 exp(-1310/T) (Crutzen, 1974). If the
system is in the photostationary state, then:
H = (N02) ka/k3(NO)(03) = 1 (4)
(Steadman and Jackson, 1974). Because values for all of the parameters in
Equation (4) can be determined from our airborne measurements, departures of
the measured ty from unity are indicators of departure from chemical steady
state at the spatial scales of the measurements. Moreover, departures of ^
from unity are explicable in terms of the relative size of the reaction ozone
compared to the size of the plume.
Before displaying these departures, however, we wish to consider the de-
pendence of \i> on the width of the reaction zone (expressed in terms of the
ratio of the time scale of the chemical kinetics to the time scale of plume
mixing). Consider a simple bimolecular reaction:
A + B ^> C . (5)
where k is the chemical rate constant. Then,
(jy\ 0_n
dt \* 8 r*
where Kr is an eddy diffusion coefficient along the radius of a cylindrical
plume, and the bars indicate the effect of correlated concentration fluctua-
tions. If the effect of correlated concentration fluctuations on the chemical
kinetics is negligible for fast chemistry, Equation 6 can be approximated as:
<±A = M _5
•df - TD - XC
where T. is the kinetic time scale and T is a diffusive time scale defined
by: C D
K 32A = K A = V TTA , .
rW?~ r FT- Yr2T 2 ' I8j
v TD
Tn is a time scale characteristic of the mixinq over some sub-scale (LD) of the
U K
plume, T is the turbuieni time scale over the spatial scale R (Figure la) and
V is the turbulent velocity fluctuation. The value of B is given by;
Tl (9)
D
Integrating (7) over the chemical time scale:
178
-------
ln/= 0^- 1 (10)
Ho TD
and
A = AQ exp{g TC/TD + 1} . (11)
Hence,
$ = a _I = a exp{_3 T /, + 1} (12)
K3 AB L u
Values of ^ and tp/Tn from our field data are listed in Table 2. The
value of TC was determined from the formula of Steadman and Jackson (1974),
namely:
T - (\s + ic fNi~n + k (r\ \\~ (~\i\
T p — IK'K —^INUyrls—^Ugyj V ' ^ /
The value of TD was approximated as:
TD = R/2V£ (14)
where R is the radius of the plume, VE - 0.4 If and U is the mean wind velocity
(Pasquill, 1974). The data in Table 2 were fitted to Equation 12 and a and e
determined as regression coefficients. The values were found to be stable
with values of: a = 0.2 +_ 0.03 and 3 - 4 +. 1. The multiple correlation coef-
ficient of the regression was found equal to 0.61. We conclude that observed
departures from the photostationary state can indeed be explained by the rela-
tive size of a plume reaction zone and that the plume chemistry is, in fact,
diffusion controlled.
If the plume chemistry is diffusion controlled, the net conversion rate
of NO to N02 will be considerably slower than that inferred from chemical
kinetics. Furthermore, the value of the ratio N02/N0 should, and does, remain
low. Conversion rates of NO to N02 were calculated for the plume centerline
and for the plume as a whole using the formula
(N02). + y(NO). (N02)f
1 . , . 1 = T f-\Z\
(1 - Y) (N0)i (N0)f (^>
where y "is the fraction of NO converted to N02 and the subscripts i and f
refer to the initial and final times, respectively, that the concentrations
were measured. (Note that Equation 15 assumes that NOX is conserved.) Meas-
ured values for the 50% conversion times of NO to N02 are shown in Table 3.
The 50% NO to N02 conversion times for the centerline of the plume are plotted
in Figure 3, where it can be seen that the conversion rate decreases approxi-
mately inversely as the square of the travel time from the stack; this result
is consistent with our previous conclusion that the plume chemistry is diffu-
sion controlled.
Ratios of N02/N0 measured during this study are quite low (Tables 4 and
179
-------
TABLE 2. VALUES OF TC/TD AND CORRESPONDING VALUES OF
Date Power Plant
TC/TD
^ (obsen/ed) (ca]cuiated)
10/17/75
n
10/31/75
n
10/11/75
II
10/31/75
10/30/75
10/16/75
n
10/30/75
Farming ton
n
Central ia
II
Longview
n
Central ia
n
Farmington
n
Central ia
20
40
2.4
5.6
3
10
21
0.8
17
30
18
0.034
0.002
1.17
0.44
0.17
0.18
0.39
0.88
0.005
0.010
0.45
2
3
1
1
13
16
1
,860
,718
429
,215
721
648
,200
358
,700
,300
,144
6
9
9
9
7
7
9
10
5
5
10
0.60
0.64
0.13
0.14
0.13
0.12
0.17
0.15
0.54
0.37
0.18
+_ 0,
+ 0.
+ 0..
± °-
± °-
+ 0.
± °-
+ 0.
± °-
+ 0.
1 °-
19
11
05
03
02
02
05
03
06
05
03
0
0
0
0
0
0
0
0
0
0
0
.47
.43
.01
.12
.30
.29
.14
.03
.52
.51
.12
TABLE 3. TIMES REQUIRED FOR 50% OF NO TO BE CONVFRTED
TO N02 IN POWER PLANT PLUMES
Date
6/16/75
n
7/29/75
8/20/75
10/11/75
10/17/75
10/31/75
11/4/75
11/5/75
Power Plant
Central ia
n
n
M
Longview
Farmington
Central ia
n
n
Travel Time
(min)
5.0
14
23
30
18
96
7.9
14
2.3
50% Conversion
Time Along
Center line (min)
5.9 -
7.6
Indeterminate
n
366 -
24 -
119 -
11.6 -
29 -
2 -
1002
53
160
120
320
3.4
Average 50%
Conversion Time
for Plume (min)
3.6 - 4.3
Indeterminate
n
ii
48 - 82
93 - 126
Indeterminate
—
3.3 - 16.7
180
-------
1000
0)
~ 100
o
o
8?
fc 10
-------
TABLE 4. N02/N0 RATIOS ALONG THE CENTERLINE OF THE PLUME FROM THE
CENTRALIA COAL POWER PLANT ON 30 OCTOBER 1975
Range
(km)
0.8
8.0
17.6
22.4
38.4
Travel Time
(min)
1.4
14
22
39
65
NO
(ppm)
0.42
0.099
0.065
0.055
0.039
N02/N0
0.33
1.3
1.9
4.3*
2.6
*Highest ratio observed in study.
TABLE 5. PLUME AVERAGE N02/N0 RATIOS WITH CORRESPONDING TRAVEL TIMES
FOR VARIOUS FLIGHTS AT THE CENTRALIA COAL POWER PLANT
Date
7/29/75
II
6/16/75
II
II
8/20/75
II
11/5/75
M
Travel Time
(min)
15
30
3.3
6.7
20
3.5
60
1.5
3
NOX
(ppm)
0.13
0.07
0.27
0.11
1.05
0.38
0.06
0.07
0.05
N02/N0
0.25 + 0.03
0.27 + 0.05
0.24 + 0.02
1.14 + 0.07
1 . 08 + 0.14
0.27 + 0.01
0.26 + Q.03
0.47 + 0.07
0.70 + 0.10
would be inferred from chemical kinetics. The highest value of N02/N0 was
4.3, which is consistent with our observation that ozone was not generated in
the power plant plumes that we studied.
ACKNOWLEDGEMENTS
This research was supported by contracts RP572-3-1 and RP330-1 from the
Electric Power Research Institute.
REFERENCES
1. Crutzen, P. J. 1974. Photochemical Reactions Initiated By and Influencing
Ozone in Unpolluted Tropospheric Air. Tellus. 26: 47-56.
182
-------
2. Davis, D. D., G. Smith and G. Klauber 1974. Trace gas analysis of Power
Plant Plumes via Aircraft Measurement. Science. 186: 733-735.
3. Hegg, D. A., P. V. Hobbs and L. F. Radke 1976. Reactions of Nitrogen
Oxides, Ozone and Sulfur in Power Plant Plumes. Final Report Under
Contract RP 572-3-1 And Interim Report Under Contract RP 330-1 prepared
for the Electric Power Research Institute, 3412 Hill view Avenue, Palo
Alto, California 94304.
4. Hill, J. C. 1976. Homogeneous Turbulent Mixing with Chemical Reaction.
Ann. Rev. Fluid Mech. 8: 135-161.
5. Hobbs, P. V., L. F. Radke and E. E. Hindman II 1976. An Integrated Air-
borne Particle-Measuring Facility and Its Preliminary Use in Atmospheric
Aerosol Studies. J. Aerosol Sci. 7: 195-211.
6. Kocmond, W.C., D.B. Kittelson, J.Y. Young and K.L. Demerjian, 1975.
Study of Aerosol Formation in Photochemical Air Pollution. EPA Report
No. 65013-75-007.
7. O'Brian, E. E. 1974, Turbulent Diffusion of Rapidly Reacting Chemical
Species. Adv. in Geoph. 18b: 341-348.
8. Ogren, J. A., S. A. Muller, M. E. Thistlewaite, J. A. McDonald, W. R.
Kiruth, M. E. Drehsen, J. A. Nuebuck and S. B. Bristow 1976. Data Volume,
Determination of the Feasibility of Ozone Formation in Power Plant Plumes.
Meteorology Research Inc. Report MRI 76-FR-1388.
9. Pasquill, F. 1974. Atmospheric Diffusion. 2nd Ed., Halstad Press, New
York.
10. Steadman, D. H. and J. 0. Jackson. 1974. The Photostationary State in
Photochemical Smog. Paper presented at CODATA Chemical Kinetics Meeting,
Detroit, Michigan.
11. Tesche, K. W., G. Z. Whitten, M. A. Yoche and M. K. Liu. 1976. Theoretical
Numerical and Physical Techniques for the Characterization of Power Plant
Plumes. Electric Power Research Institute, Topical Rpt. EC-144.
133
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5-3
THE ANALYSIS OF GROUND-LEVEL OZONE DATA FROM NEW JERSEY,
NEW YORK, CONNECTICUT, AND MASSACHUSETTS: DATA
QUALITY ASSESSMENT AND TEMPORAL AND
GEOGRAPHICAL PROPERTIES
W. S. Cleveland, B. Kleiner, J. E. McRae,
and R. E. Pasceri*
ABSTRACT
Hourly, ground-level ozone, measurements firom 47 suites in eastern New
Vork, northern Went Jersey, Conne.dtic.uut, and Massachusetts firom May 7, 1974
to September SO, 1974, are analyzed, (/arious techniques fior assessing data
quality and uniform calibration show the. data to be OjJ high retiabiJLitiy {,or
yielding i.n^ormati,on on the. ozone. problem in the. fio.Qi.on. Statistical analyses
show that ni.ghttane concentration*, negative, to those ducting the. day, are
highest in MaAAachuA&ttA. The. i»Lt diA&vibuution ofi daMLy maxAjnum conce.ntn.a-
tion (Vie. hi.ghut i.n the. Stmfiosid-Gie.e.nwi.ch ie.gi.on o& Aouth Connecticut and
ne.xt hi.ghut -in a ie.gi.on to the. e.aAt and notithe.aAt oft Sta.m&otLd-Gsie.e.nW'ich.
Jkue. n.vJtt&, together with otheA anaJLyAeA, demonstrate, that photochemical.
aiA potation sizAuutting fiiom primary e.miAi>i,on& in the. Wew Vork City metro-
politan area. JU> transported by prevailing Minds on a 300 km northeast trajec-
tory through Connecticut as &ar as northeastern Massachusetts.
INTRODUCTION
This paper presents an analysis of ambient ground-level ozone measure-
ments from a region of the northeastern United States covering eastern New
York, northern New Jersey, Connecticut, and Massachusetts. The data consist
of hourly averages from May 1, 1974, to September 30, 1974, at 41 sites.
Their quality and uniform calibration assessed, their diurnal behavior is
analyzed, and the geographical variation in concentrations over the region is
described.
The ozone data, gathered at monitoring site locations shown in Table 1
and Figure 1, were provided by the following agencies: New Jersey sites — New
Jersey Department of Environmental Protection; New York sites (except Yonkers)
— New York State Department of Environmental Conservation; Yonkers — Boyce
Thompson Institute; Connecticut sites — Connecticut Department of Environ-
mental Protection; Massachusetts sites — Massachusetts Department of Public
Health.
*W. S. Cleveland, B. Kleiner, J. E. McRae, J. L. Warner, Bell Laboratories,
Murray Hill, New Jersey. R. E. Pasceri, New Jersey Department of Environ-
mental Protection, Trenton, New Jersey.
185
-------
TABLE 1. SUMMARY OF OZONE DATA AT 41 SITES IN THE NORTHEASTERN UNITED STATES
FOR 1974. ALL OZONE CONCENTRATIONS ARE IN PPB.
Column Description
1 Site name
2 State (J = New Jersey, Y = New York, C = Connecticut, and M =
Massachusetts).
3 Site letter (the site letter together with the state allows
identification of the location in Figure 1).
4 Maximum hourly reading from May to September with suspect values
shown by a *.
5 Number of days from May to September with valid daily maxima (i.e.,
maximum hourly concentration from 0800 to 2400 EST).
6 Median of the daily maxima for June to August.
7 Upper quartile of daily maxima for June to August (one site omitted)
8 Ratio of upper quartile of readings at 1500 hours EST from May 15
to August 15 to upper quartile of readings at 0100 hours EST from
May 15 to August 15.
Name
Asbury Park
Somerville
Chester
Bayonne
Elizabeth
Newark
Welfare Island
Yonkers
Eisenhower Park
Babylon
Mamaroneck
Greenwich
Stamford Farms
Stamford Trailer
Bridgeport
Danbury
New Haven
Waterbury
Morris
Deep River
Middletown
New Britain
Groton
Hartford
Windsor
Eastford
Springfield
State Code Maximum Days Median Quartile Ratio
J
J
J
J
J
J
Y
Y
Y
Y
Y
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
M
A
S
C
B
E
N
W
Y
E
B
M
G
S
D
N
W
M
d
m
n
g
H
W
E
S
176
196
170
208*
98
140
185
132
154
207*
165
270
250
240
250
270
302
252
225
202
365
240
244
306
234
197
108
(conti
121
114
90
122
95
125
115
148
48
109
120
133
63
136
137
89
94
76
90
57
105
119
110
135
103
56
131
nued)
59
58
90
80
50
47
81
56
55
72
62
100
97
91
80
81
76
75
85
94
80
82
74
68
60
85
34
82
81
110
100
64
63
102
80
111
89
140
145
134
116
120
127
112
99
117
122
124
113
103
82
96
48
2.2
5.5
1.7
4.8
4.7
5.6
5.3
3.4
4.5
3.5
8.3
3.7
3.1
5.6
4.1
4.8
3.7
5.1
2.9
2.6
3.1
2.5
2.7
2.9
4.8
2.7
1.9
186
-------
TABLE 1. (continued)
Name
State Code Maximum Days Median Quartile Ra ti o
Worchester
Fitchburg
Fall River
Lowel 1
Quincy
Boston
Cambridge
Waltham
Medford
Kingston
Pittsfield
Rensselaer
Schenectady
Glens Falls
M
M
M
M
M
M
M
M
M
Y
M
Y
Y
Y
W
F
f
L
Q
B
C
w
M
K
P
R
S
G
250
174
214
145
173
136
130
116*
166
159
166
128
128
127
— . . M .-_
128
136
94
135
102
84
95
92
76
123
109
106
116
115
66
65
73
63
62
36
54
42
52
64
65
60
56
64
86
87
109
86
79
56
74
59
79
91
84
78
72
84
1.8
2.1
1.5
2.5
2.0
2.0
1.9
2.4
3.1
3.0
2.2
2.9
2.4
2.5
Figure 1. Site letters in column 3 of Table 1 are shown at site locations
187
-------
With the exception of the Boyce Thompson Institute unit, all monitors
were of the gas phase, ozone-ethylene type. Some of the commercial types used
(Bendix, REM) have been recently examined by Clark, et al., who also briefly
reviewed the development history of the ozone-ethylene detector (1). Field
tests of various ozone and oxidant analyzers have been reported by Stevens,
et al. (2,3). The cooperating agencies have found that the various commer-
cial brands of analyzers are equivalent with regard to the accuracy needed for
air monitoring networks. Boyce Thompson Institute employed the colorimetric
method for oxidants determination with a dichromate scrubber to avoid sulfur
dioxide interference (4).
Each monitoring agency, operating independently, utilized a variety of
analyzers, field calibration techniques and schedules. Generally, however,
all field calibrations were referred to the federal reference method utilizing
the reaction of oxidants with neutral, buffered potassium iodide (5). In
addition, the Connecticut, New Jersey, and New York agencies participated with
their EPA Region II laboratory in a joint ozone calibration on June 21, 1974
(6). Previously, on June 14-17, the EPA laboratory had calibrated their
Bendix 016059 calibrator at the National Bureau of Standards, Washington, D.
C., which utilized the federal reference method. Efforts toward standardizing
ozone calibration techniques have been reported by Hodgeson, et al (7).
DATA QUALITY AND CALIBRATION
No detailed investigation of ambient air quality data can omit the impor-
tant consideration of data quality (8). A number of nonstatistical considera-
tions make it plausible that the data are of high quality. The first is the
reliability and relative ease of maintenance of the chemiluminescent monitors
(3). The second is the high frequency of site visits by agency personnel and
the data review programs carried out by all agencies. Third, the uniformity
of calibration was greatly enhanced among the New Jersey, New York, and Con-
necticut agencies by the joint calibration program of June 21, 1974, described
in the introduction. While such considerations inspire confidence in the
data, it is still desirable to use statistical methodology for further veri-
fication. In this section the particular techniques that have been used in
assessing the ozone data are described.
Bad data, particularly if caused by transmission errors, often have
little regard for the measurement scale. Thus, the first step in our data
quality assessment was to calculate the largest hourly reading at each site
and inspect the data for a time interval containing the maximum. In a number
of cases, transmission errors were detected; in a few cases, correctly trans-
mitted numbers were discarded as unlikely because of a lack of validation from
other sites. In three cases, suspicion was raised but there was no proof of
bad data. These values were retained with the notation that something might
be wrong. A typical example was recorded in Waltham, Massachusetts, on August
7, 1974; 24-hourly values in ppb starting at 0100 hours EST were 0, 10, 20,
10, 20, 30, 40, 50, 50, 100, 120, 100, 80, 70, 40, 40, 50, 40, 40, 40, 30, 30,
20, 10. The readings were not terribly unusual; but, in comparison with
measurements for the day at other sites, were atypical. At other sites, there
was relatively little photochemical activity measured; the highest reading
being 70 at Cambridge.
188
-------
Table 1 lists the maxima for the 41 sites to show the highest concentra-
tions of ozone in the region. The three suspect values are indicated. For
these sites, the second highest readings in ppb are 167 (Bayonne), 112 (Wal-
tham), and 201 (Babylon).
If the data at a particular site contains an undue amount of measurement
noise, then it is to be expected that the variation of the measurements
through time will not correspond well with those at other sites. For each
day, the maximum of the hourly averages from 0800 to 2400 was calculated for
each site. Correlation coefficients, with 5% trimming at points along the two
principal components, between all pairs of sites were computed for the square
roots of these daily maxima (9). The trimming is a statistical device which
prevents a small fraction of the data having an undue influence on the corre-
lations, which are meant to summarize the general behavior. The sample distri-
bution of the square roots is approximated well by a normal probability plots
for each of the 41 sites (10). Although in a few cases, such as Bridgeport,
the square root maxima are skewed to the right, the square roots provide a
more satisfactory plot than logs or the untransformed data.
Since distance between sites must be taken into account in assessing the
levels of the correlations, correlations between all pairs of sites are
plotted against inter-site distances in Figure 2. Moving statistics have been
superimposed on the plot to summarize the behavior of the plotted points. The
middle curve summarizes the middle of the distribution of correlations given
distance, the upper curve summarizes the upper tail of the distribution, and
the lower curve summarizes the lower tail. The correlations tend to be quite
large for small distances, and, as has previously been observed, tend to
decrease with increasing distance (11). The only site with unusually low
values, given distance to other sites, is Asbury Park. In fact, all correla-
tions below 0.2 involve this site. A careful study of the Asbury Park data
led to the conclusion that the site location, and not data quality, was
responsible for the low values. This conclusion is discussed further in the
final section of this paper.
One of the most elusive questions for statistical methodology to investi-
gate is thart of uniform calibration, particularly between different agencies.
Respite the joint calibration described earlier, it was desirable to use the
data to conduct further checks. The distributions of daily maxima at pairs of
sites were compared by an empirical quantile-quantile (EQQ) plot (12, 13).
This analysis was complicated, however, because even if two sites are located
within a few miles of one another and even if calibration is exactly the same,
the two sites do not have to have the same ozone concentrations, since local
primary emissions can substantially influence ozone levels (14). However, the
philosophy invoked is that if there is a major discrepancy between two close
sites for which an explanation cannot be found, then the calibration is
questioned.
To eliminate distortions due to missing data, the distributions of daily
maxima at two sites were compared only for days when both sites have all daily
maxima. X-j, for i = l,...,n, is the ordered daily maxima (Xi is the smallest,
X2 is the next smallest, etc.) from one site, and Yi the ordered maxima for
the second site. The EQQ method of comparing the ozone levels at the two
189
-------
08
06 •
C
O
L.
i,
O
0.4 •
02 •
0 0
000 O
100
300
Figure 2.
200
Distance - km
Correlations of square root daily maximum ozone concentrations
between all pairs of the 41 sites are plotted against the dis-
tances between sites. Moving statistics have been superimposed
to summarize the information on the plot.
400
sites consists of plotting Y-j versus X-j. If the plotted points lie near the
line Y=X, the two distributions are nearly the same. These plots were made
for a large number of pairs of nearby sites and only one major discrepancy was
found. Figure 3 shows the EQQ plot for Mamaroneck, maintained by the New York
State Department of Environmental Conservation, and Stamford Trailer, which is
24 km from Mamaroneck and is maintained by the Connecticut Department of
Environmental Protection. The points on the EQQ plot lie well below the line
Y=X, indicating that Stamford has considerably higher ozone levels. The
result in the next section that ozone measurements in the region are highest
in Connecticut carries with it important conclusions about the nature of the
190
-------
photochemical air pollution problem in the region. It is, therefore, import-
ant to investigate further whether the recorded Connecticut concentrations are
too high as a result of faulty calibration.
An important factor for consideration is that Mamaroneck is in the vicin-
ity of strong automobile emissions of nitric oxide, which would tend to reduce
the ozone concentrations (14). An example of the effect of these emissions
is, as shown in the next section, that Mamaroneck has the lowest nighttime
ozone concentrations of the 41 sites. In order to compare the Connecticut
data in other ways, EQQ plots have been made in Figure 3 comparing Fall River,
Massachusetts, with Groton, Connecticut; and Babylon, New York, with Bridgeport,
Connecticut. Groton, located in eastern Connecticut appears to agree quite
well with Fall River. Babylon, like many of the Connecticut sites, lies in a
region where prevailing winds reach after crossing the center of the New York
City metropolitan area and has ozone concentration distributions much like
Z 140
>
s
50 100 150 200
Stamford Trailer
100 140
Groton
220
c
c
O BO-
X
<0
m
80 120
Bridgeport
40 80 120 160
Stamford Trailer
Figure 3. Empirical quartile-quartile plots of daily maximum ozone con-
centrations (ppb) for four pairs of sites.
191
-------
that of many of the Connecticut sites. Levels in Babylon agree quite well
with those in most of Connecticut, and are only slightly lower overall than
the levels in the Stamford-Greenwich region, which, as will be shown, are the
highest in the state of Connecticut. For example, the EQQ plot in Figure 3
comparing Babylon and Bridgeport shows the two sites to have very similar
distributions. The fourth EQQ plot in Figure 3 compares the distributions of
daily maxima at Bayonne, New Jersey, and Stamford Trailer for all days from
May to September when the resultant wind direction at 1000 and 1300 hours EST
at La Guardia Airport is between 0° and 180°. The two sites have very similar
concentration distributions for such days which lends credence to uniform
calibration between new Jersey and Connecticut.
A final verification for the Connecticut data comes from an aircraft
flight on August 1, 1974, in which ozone was measured over the state of
Connecticut (15). The aircraft measurements gave no indication of Connecticut
ground station measurements being too high. For example, at 1606 hours EST
the aircraft 1000 ft. over Bridgeport was measuring 135 ppb while the ground
station average from 1600-1700 hours EST was 110 ppb.
DIURNAL VARIATION OF OZONE CONCENTRATIONS
The diurnal variation at each of the 41 sites was studied by calculating
and plotting the upper quartiles for each hour of the day from May 15 to
September 15. One noticeable feature was the reduction in the amount of
diurnal variation in the upper quartiles at the Massachusetts sites. In Table
1 the ratios of the upper quartiles at 1500 divided by the upper quartiles at
0100 are given. The ratio tends to decrease with increasing distance from the
New York City metropolitan region. In particular, the Massachusetts values
appear to be the lowest. One site, Mamaroneck, has an unusually large ratio,
caused, presumably, by local sources of primary emissions which appear to
reduce the ozone levels overall, but which have a particularly strong influ-
ence on nighttime levels. Mamaroneck has the lowest upper quartile at 0100
for all 41 sites.
GEOGRAPHICAL VARIATION OF OZONE CONCENTRATIONS
A detailed comparison of the 41 ozone concentration distributions at the
sites would be easier if there were not missing values. Missing data can lead
to distortion in the comparison of distributions unless special care is taken.
To illustrate this, consider two nearby sites with nearly the same ozone con-
centration distributions. Suppose the first has all data from May through
September; but, for the second, the data is missing for the first two weeks in
May when the maxima are at their lowest for the season. Then a comparison of
all data at site one with all data at site two would leave the false impres-
sion that site two has a higher ozone distribution. In a previous section,
each comparison of distributions to check calibration involved only two sites.
But in this section, the goal is to compare the 41 distributions simultane-
ously. The number of days with no missing data at all sites is extremely
small, so it is necessary to compare distributions of values over different
sets of days. Thus a statistical technique was developed to determine which
192
-------
aspects of the daily maxima at each site were reliable for all sites, except
for the upper quartile at Eisenhower Park. Thus these values, given in Table
1, are regarded as valid for comparing the dependence of ozone levels on
geographical location. One result, somewhat unexpected before this analysis
was carried out, is that Eastford and Deep River, despite having only about
one month of data, are usable in the geographical comparison. However, it was
found that the largest reading at each site could not be used for comparing
ozone concentration distributions at different sites.
Analysis of the data revealed that the ozone levels taper off at the
beginning and end of the May to September period. Since data at a site tends
to be missing in stretches of several days, rather than isolated days, and
since a number of sites have missing data for large stretches of days at the
beginning and end of the season, it makes comparison of distributions even
more difficult if the whole period May-September is included. For this reason
only the months June-August were used in computing the medians and upper
quartiles.
In Figure 4 the upper quartiles are plotted against geographical location.
The region of highest ozone concentrations is in the Greenwich-Stamford region
of southwestern Connecticut, while the next highest are in a belt which spreads
out from there to the east and northeast. The five sites with the lowest
upper quartiles and medians are Boston, Waltham, Springfield, Newark, and
Elizabeth.
Figure 4. Upper quartiles of daily maximum ozone concentrations from June
to August at each site are plotted against geographical locations,
The values are coded by numbers: 0=79 ppb or less; 1=80-99 ppb;
2=100-114 ppb; 3=115-129 ppb; 4=130 ppb or more.
193
-------
SUMMARY
Hourly average, ground-level ozone measurements from 41 sites in eastern
New York, northern New Jersey, Connecticut, and Massachusetts for the time
period May 1, 1974, to September 30, 1974, have been analyzed. The quality
and uniform calibration of the data were assessed by several statistical
procedures. In a few cases short stretches of data were invalidated, A
discrepancy between the Mamaroneck and Stamford Trailer sites, which brought
the uniformity of calibration between New York and Connecticut into question,
was resolved by the conclusion that local primary emissions were reducing the
ozone concentrations in Mamaroneck substantially. The general conclusion is
that the ozone data are of high quality and reliable for examining the problem
of ozone pollution.
An analysis of diurnal behavior revealed that diurnal variation tends to
decrease (i.e. nighttime values are closer to daytime values) with increasing
distance from the New York City metropolitan region. Nighttime values, rela-
tive to the daytime values, were particularly high in Massachusetts.
An analysis of the geographical variation in ozone concentrations showed
that the lowest concentrations are in Boston, Waltham, Springfield, Newark,
and Elizabeth. All five sites are located next to high traffic density
arteries, and therefore have large emissions of nitric oxide that reduce the
ozone levels. Since this depression of the levels drastically reduces the
information content in data from such areas, it is recommended that future
placement of ozone monitors not be immediately adjacent to high traffic den-
sity roadways.
The highest ozone concentrations are in the Stamford-Greenwich region of
Connecticut while the next highest are in a region to the east and northeast
of Stamford-Greenwich.
CONCLUSIONS
This paper and other publications directly dealing with transport of
photochemical air pollution provides strong evidence that photochemical air
pollution resulting from primary emissions in the New York City metropolitan
area is transported by prevailing winds on a 300 km northeast trajectory
through Connecticut and as far as northeastern Massachusetts (16,17). This
occurrence accounts for southwestern Connecticut having the highest ozone
concentrations in the region. Thus, it would appear that, similar to the Los
Angeles Basin, the chemistry of ozone production is such that areas downwind
of strong precursor emissions have the highest ozone concentrations (18,19).
The phenomenon of transport provides the explanation for the low correla-
tion of ozone daily maxima at Asbury Park with those at other sites. Asbury
Park is the only site which is both south to southeast of the New York City
metropolitan area and in a region which is downwind of the area on a signifi-
cant number of days. Thus Asbury Park has its highest ozone concentrations
when the wind is from the northwest and north, while the majority of other
sites, which lie to the east and northeast, have their highest ozone concen-
194
-------
trations when the wind is from the west and southwest.
Transport also provides the explanation for the high nighttime ozone
concentrations in Massachusetts relative to those during the day. The distance
between the New York City metropolitan area and eastern Massachusetts is such
that the effects of transport, in the form of high ozone concentrations, often
occur in eastern Massachusetts during the time period from 1900 to 2400 hours.
REFERENCES
1. Clark, T. A., R. E. Baumgardner, R. K. Stevens, and K. J. Krost. Evalua-
tion of New Ozone Monitoring Instruments by Measuring in Non-Urban Atmos-
pheres. Instrumentation for Monitoring Air Quality. ASTM STP 555.
American Society for Testing and Materials, Philadelphia, Pennsylvania,
1974.
2. Stevens, R. K., J. A. Hodgeson, L. F. Ballard, and C. E. Decker. Ratio
of Sulfur Dioxide to Total Gaseous Sulfur Compounds and Ozone to Total
Oxidants in the Los Angeles Atmosphere - An Instrument Evaluation Study.
Determination of Air Quality, G. Mamantov and W. 0. Shults, eds., Plenum
Publishing Co., New York, 1972.
3. Stevens, R. K., T. A. Clark, C. E. Decker, and L. F. Ballard.
Field Performance Characteristics of Advanced Monitors for Oxides of
Nitrogen, Ozone, Sulfur Dioxide, Carbon Monoxide, Methane, and Nonmethane
Hydrocarbons. APCA Meeting, Miami, Florida, June 1972.
4. Jacobson, J. S. and G. D. Salottolo. Photochemical Oxidants in the New
York-New Jersey Metropolitan Area. Atmos. Env. 9, 1975, pp. 321-322.
5. U. S. Environmental Protection Agency. National Primary and Secondary
Air Quality Standards, Federal Register 36, 1971, pp. 8186-8201.
6. Brown, R. M., G. Wolff, and J. A. Spatola. Results of the Cooperative
Ozone Calibration. Environmental Protection Agency Region II, Edison,
New Jersey, July 21, 1974.
7. Hodgeson, J. A., R. K. Stevens, and B. E. Martin. A Stable Ozone Source
Applicable as a Secondary Standard for Calibration of Atmospheric Moni-
tors. ISA Transactions, II, No. 2, 1972, pp. 161-167.
8. Nehls, G. J. and G. G. Akland. Procedures for Handling Aerometric Data.
J. Air. Poll. Control Assoc., 23, 1973, pp. 180-184.
9. Gnanadesikan, R., and J. R. Kettenring. Robust Estimates, Residuals, and
Outlier Detection with Multiresponse Data. Biometrics, 28, 1972, pp. 81-
124.
10. Kempthorne, 0. and L. Folks. Probability, Statistics, and Data Analysis.
Iowa State University Press, 1971, pp. 220-221.
195
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11. Bruntz, S. M. , W. S. Cleveland, T. E. Graedel, B. Kleiner, and J. L.
Warner. Ozone Concentrations in New Jersey and New York: Statistical
Association with Related Variables. Science 186, October 18, 1974, pp.
257-259.
12. Wilk, M. B. and R. Gnanadesikan. Probability Plotting Methods for the
Analysis of Data. Biometrika, 55, 1968. pp. 1-17.
13. Cleveland, W. S., T. E. Graedel, B. Kleiner, and J. L. Warner. Sunday
and Workday Variations in Photochemical Air Pollutants in New Jersey and
New York. Science, 186, December 13, 1974. pp. 1037-1038.
14. Graedel, T. E., and L. A. Farrow. Ozone: Involvement in Atmospheric
Chemistry and Meteorology. Ozone Chemistry and Technology. Franklin
Institute Research Laboratories, Philadelphia, 1975.
15. Wolff, G., W. Stasiuk, P. Coffey, and R. Pasceri. Aerial Ozone Measure-
ments Over New Jersey, New York, and Connecticut, presented at APCA
Annual Meeting, Boston, 1975.
16. Cleveland, W. S., B. Kleiner, J. E. McRae, and J. L. Warner. Photo-
chemical Air Pollution: Transport from the New York City Area into
Connecticut and Massachusetts. Science, 19, 1976. pp. 179-181.
17. Cleveland, W. S., B. Kleiner, J. E. McRae, and J. L. Warner. The
Analysis of Ground-Level Ozone Data from New Jersey, New York, Connecti-
cut, and Massachusetts: Transport from the New York City Metropolitan
Area. Proceedings of the Fourth symposium on Statistics and the Environ-
ment. American Statistical Association, Washington, D. C., 1976.
18. Altshuller, A. P. Evaluation of Oxidant Results at CAMP Sites in the
United States. J. Air. Pollut. Control Assoc., 25, 1975. pp. 19-24.
19. Tiao, G. C., G. E. P. Box, and W. J. Hamming. Analysis of Los Angeles
Photochemical Smog Data: A Statistical Overview. J. Air.. Pollut.
Control Assoc., 25, 1975. pp. 260-268.
196
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5-4
CHEMICAL AND METEOROLOGICAL ANALYSIS OF THE
MESOSCALE VARIABILITY OF OZONE CONCENTRATIONS
OVER A SIX- DAY PERIOD
W. D. Bach, Jr., J. E. Sickles, II, R. Denyszyn and W. C. Eaton
ABSTRACT
The. Reieat.cn Tfu.angie. InAtttate. conducted low aititu.de. aiACAa^t
oveA e.aAt Texai, mo At ofa LoulAtana, and adjacent ofie.aA Ofj the. Guifi o^ Mexico
to ^investigate. the. aAe.ai e.xte.nt oft htgh ozone. conce.ntAationA . Ozone, concen-
tAa£ionA wete con£tnuou6£i/ me.aAuAe.d aJLong the. ^Light pathA and at ground Ata-
tionA at CofipuA ChfuAti, Pofit O'Connor, huAtin, Houston, and Vont AAthuA,
Je.~x.aA and at Ve.HiddQ.n-, LouiAtana.
On Octobe.fi 19, 7975, a htgh p^e44uAe Ay&tejm developed oue^ the. a/^ea and
motion, began to de.ve.lop a Atabl.e. iaye.fi o^ oJji ato{t. Ozone, concen-
-in exce.6-6 o^ HO yg/m3 wete ^oand oueA e.&t>t Texai and ove/i u}ute.x.n
Ai the. ptieA&uAe. AyAtejm deue^oped and moved ea4^wow.d the. ne.x.t day,
the. highest ozone, wai meaiu/ied oveji weAteJin LoiuAtana. Ozone. conce.ntn.ationA
above 760 yg/m3 at 300 meteAi, oveA. the. 6u£^ o^ Mexico and inland, bat
to 110 yg/m3 above the. stable, iaye.fi. Ozone. me.at>(Vte,me.ntt> at the.
gtiound monttofving ioc.at4.onA ag/teed wtth the. tA.e.ndt> o^ the. oJjibonno, me.aAuAe.me.ntt>,
paAc.eJL iAaj e.ctoAie^ aAAivtng at ground AtationA OA at
potntA aiong the. ^tight ttacki, weAe. computed to de.AcAi.bo. the. hotiizontai motion
Of) the. atmoApheAic. boundoAy iaye.fi. Ttme.-aitUude. CAOAA Ae.ctionA o& pote.ntiai
te.mpeAatuAe. at Lake. ChauJLuA, LomiA-iana, 4/iowed a dynamic. atmoApheAic boundary
iayeA.
The. occuM.e.nce.A 0(J htgh ozone. conce.ntAationA and ozone. gfiadie.ntA wtthtn
thiA ep-c6ode weAe. examined conAtdeAtng the. ozone. pfi&cuAAofi ejn^AtonA and the.
mete.oAoiog4.cai Actuation. Ozone. pfie.cuAf,ofi ejru.AAi.onA -in the. Atudy afie.a and
timite.d ve.ntHation aAe. pfiimaAiZy fie.ApoMi.bie. fiofi maintaining the. high ozone.
conce.ntAationA untii cie.ane.fi aiA -iA tAanApoAte.d -into the. ne.Qi.on.
»
INTRODUCTION
Until about ten years ago, ozone (03), a principal constituent of photo-
chemical smog, was thought to occur in high concentrations only in urban areas
where the precursor materials — hydrocarbons (HC) and oxides of nitrogen (NOX)
— were abundant in automotive exhaust. Nonurban ozone concentrations typically
ranged from 40 to 120 yg/m3, below the present National Ambient Air Quality
*Research Triangle Institute, Research Triangle Park, North Carolina.
197
-------
Standard (NAAQS) of 160 yg/tn3 (1). Recent measurements have shown that ozone
concentrations frequently exceed the NAAQS at numerous nonurban locations in
different parts of the United States (2-5). In most instances, the evidence
indicates that horizontal transport of ozone and the in situ generation/destruc-
tion cycle of ozone are primary contributors to the high concentrations.
Hydrocarbon emission densitites in several counties along the northern
Gulf Coast are in the 95th to 98th percentile of all counties in the United
States, due in large to the petrochemical industry of the area (6), The abund-
ance of hydrocarbons in the atmosphere suggests that generation of photochemi-
cal oxidants may be a problem in and downwind of the urban industrial centers.
In studies conducted by the Texas Air Control Board (7-9), hourly ozone
concentrations greater than 160 yg/m3 were measured in nonurban areas of east
and southeast Texas and along the coast of the Gulf of Mexico, High ozone con-
centrations were found upwind of urban areas, in onshore flow from the Gulf of
Mexico, and in pine forests a hundred miles or more from the principal hydro-
carbon emissions areas. Neither the spatial extent of the region of high ozone
concentration nor the sources of high ozone concentrations were determined.
In response to the Environmental Protection Agency's interest in develop-
ing strategies to control urban oxidants including ozone, the Research Triangle
Institute conducted a field program of surface and airborne measurements to
investigate and document the occurrences and the area! extent of regions of
high ozone concentration in the northern Gulf Coast area of Texas and Louisiana.
The program began June 25 and continued through October 31, 1975.
This analysis considers one episode of high ozone concentration at the
ground and aloft that shows a strong dependence of the observed ozone concen-
trations upon slowly changing meteorological conditions. Some of the measured
concentrations are not identified with urban precursors and may represent a
natural event, further complicating the problems of oxidant control.
DATA ACQUISITION AND ANALYSES
fe
GROUND STATION MEASUREMENTS
RTI established a base station at the Beauregard Parrish Airport, DeRidder,
Louisiana, a nonurban location 50 miles north of Lake Charles. Ozone, oxides
of nitrogen, sulfur dioxide, and total suspended particulate (TSP) were contin-
uously monitored. Grab samples were taken for later analysis of selected
hydrocarbon and halocarbon species. The Texas Air Control Board provided
hourly ozone data measured at their Nederland (Port Arthur-Beaumont), Houston
(Aldine), Austin, and Corpus Christi, Texas locations. These locations are
generally considered more urban-industrial than nonurban since they are near
large hydrocarbon emission areas (Figure 1). Ozone measurements at Port
O'Connor, Texas, were provided by the DuPont Company. All of these locations
were routinely audited by EPA and RTI as a part of an independent quality
assurance program.
198
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•^
I
AUSTIN
\ • '~-ft r \
DeRIDOjER ^;,., :;j; ^ »_A
HOUSTON .
-.T^----^-s xu
'NEDERLAND ^^'"-o "-jC1
PORT O'CONNOR
', ,-;'-j^fCORPUS CHRISTI
| > 10
vl >ioo
HYDROCARBON EMISSION DENSITY
(tons / mi2 / yr )
Figure 1. Hydrocarbon emission density by county.
AIRCRAFT MEASUREMENTS
RTI operated a twin engine aircraft from the DeRidder base station. The
ozone, oxides of nitrogen, air temperature, and dewpoint temperature were con-
tinuously monitored and the data digitized at 30-second intervals. Similar
measurements were made aboard the EPA B-26 research aircraft. These aircraft
provided spatial coverage unavailable from any other source.
Flight plans were designed to investigate specific problems of the Gulf
Coast area, including a pair of area! survey flights. The survey flights were
conducted on successive days when similar meteorological conditions were expec-
ted. Additional flights were designed during the field program to investigate
specific situations that developed or were indicated by meteorological condi-
tions or air quality data. Flight protocols called for a low pass over the
DeRidder ground station after takeoff and again before landing to cross-check
the aircraft and ground-based measurements. When directed, the aircraft were
used to obtain vertical profile data in 1000 to 2000 feet vertical increments
during both ascent and descent over a given location.
199
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AIR PARCEL TRAJECTORIES ANALYSES
Approximate trajectories were computed for air parcels arriving at selected
positions along the flight track when the aircraft was in the vicinity. Those
computations used 12-hourly wind data from the regular rawinsonde network, aver-
aged vertically over the lowest 2 km of the atmosphere. Parcel displacements
were integrated at 2-hour intervals over a 48-hour period to give the trajec-
tories.
CROSS SECTION ANALYSES
Time-altitude cross sections of potential temperature, 9, and the southerly
wind component, v, were developed for the Lake Charles rawinsonde location,
which is typical of the conditions in the coastal area during the period. Po-
tential temperature is conserved in adiabatic processes, and it is a good indi-
cator of atmospheric changes. Descending e-isopleths with increasing time
indicate descending motion and/or advection of cooler air. Furthermore, as the
vertical gradient of e increases, atmospheric stability increases, and the
vertical mass transfer is inhibited.
FLIGHT ANALYSES
Altitude corrections were applied to airborne ozone measurements in accor-
dance with test results in the EPA-Las Vegas Environmental Test Chamber. The
corrected ozone data showed excellent continuity of trends at 2-minute inter-
vals, so the concentrations at 10-minute intervals along the flight track were
plotted. Concentrations of oxides of nitrogen were seldom above the detectabil-
ity of the chemiluminescent instruments, so those numerical data were of little
value.
CASE STUDY
OVERVIEW
On October 16, a tropical storm moved inland about 150 miles east of De
Ridder. Over the next two days a ridge of high pressure moved southeastward
causing clearing skies, cooler temperatures, and a northwesterly flow of air.
By the evening of October 18, the ridge had expanded and covered much of the
coastal area. The atmosphere at Lake Charles was well-mixed to approximately
1.7 km (Figure 2). Above that, a large-scale subsiding motion associated with
the ridge had begun to develop a stable layer. An anticyclonic circulation
pattern of a high pressure system began to develop on the morning of October
19. The subsidence continued, lowering the mixing height and inversion layer
to 1.0 km on the morning of October 21. Thereafter, the subsidence diminished
and wanner air returned with a southerly flow. The stable layer began to rise,
but its intensity did not diminish until the afternoon of October 22. By the
morning of October 23, the stable layer was effectively broken and vertical
mixing was no longer confined. This sequence of events is typical of transient
anticyclonic systems.
During this period the maximum afternoon hourly ozone concentrations were
generally high at urban and nonurban locations until the high pressure ridge or
center passed eastward (Table 1). Thereafter, the afternoon ozone concentrations
200
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20 21 22
DATE, OCTOBER 1975
23 24
Figure 2. Time-altitude cross section of potential temperature at Lake Charles,
Louisiana. Temperature inversion is stippled.
TABLE 1. MAXIMUM AFTERNOON OZONE CONCENTRATIONS (yg/rrT)
Location
Corpus Christi
Port 0' Connor
Austin
Houston
Nederland
DeRidder
18
112
106
128
M*
M
109
19
224
151
154
M
M
122
20
140
133
156
136
156
256
October
21
112
98
124
138
182
210
22
88
76
108
90
120
76
23
64
22
88
84
78
22
24
50
30
62
64
60
30
''Missing Data
were perceptably lower as the onshore, well-mixed flow developed and prevailed.
An eastward migration of higher ozone concentrations with the pressure system
is also apparent.
The concentrations measured at Corpus Christi and Port O'Connor on October
19» at Austin on October 19 and 20, and at DeRidder on October 20 and 21, are
among the highest recorded at those locations during the study period.
201
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OCTOBER 19
On the morning of October 19, a weak high pressure center developed within
the ridge in southeastern Texas and western Louisiana. The western half of
a 2-day survey flight was initiated to investigate the gradient of ozone which
might occur with the predominently northerly flow of air. By mid-afternoon,
the high pressure center was located to the south-southeast of Lake Charles,
but the pressure gradient was weak.
Air flow in the mixed layer had been northerly and was turning westerly
during the day (Figure 3). The predominance of a northerly flow even in a
developing anticyclone indicates an unusual situation. Anticyclonically-curved
trajectories are expected with the transient high pressure system. These tra-
jectories had cyclonic curvature, suggesting that the high pressure system was
being formed and had only recently begun to establish its influence in the flow
regime.
Figure 3.
Ozone concentrations along flight track
maximum of hourly ozone concentrations
trajectories with 12-hour positions (
pressure isobars ( - ) for October 19, 1975,
), the daily
), air parcel
), and surface
The flight began at 1000 CDT, proceeded clockwise around the rectangular
pattern at 650 m (^2000 ft MSL) before returning to DeRidder at 1700 CDT. All
measurements were made within the well-mixed boundary layer, capped by the in-
version layer.
202
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Ozone concentrations measured during the eastern half of the flight were
of the order of 130 yg/m3, while in the western half, concentrations were most-
ly at or above the NAAQS. Cleraly, the western half of the flight shows an
area-type distribution rather than a plume-type distribution of ozone developing
from a localized source of precursors.
The substantial decrease of ozone from the northwest to the northeast cor-
ner of the flight does not seem related to hydrocarbon source areas along those
trajectories. The air arriving in the northwestern corner had a path roughly
over the Oklahoma City area 24 to 36 hours before the aircraft reached this
point. The air arriving in the northeastern corner passed over the Tulsa,
Oklahoma, area, also an oil refining area, 24 hours before. On the southbound
leg of the flight, the aircraft apparently passed through a narrow plume south-
west of the Shreveport, Louisiana, area and measured ozone concentrations as
high as 169 yg/m3 for a brief period.
Upon return to DeRidder, the ozone concentrations and their gradients
were quite similar to those measured upon departure 7 hours previously. This
suggests that the ozone existed in a quasi-steady state in the afternoon bound-
ary layer. The higher ozone concentration of east Texas are not associated
with specific ozone precursor source regions. The urban-industrial regions
make no discernable contribution to those concentrations.
OCTOBER 20
By the afternoon of October 20, the high pressure center had moved to a
position just north of Mobile, Alabama. Central pressures increased to 1023 mb
as the circulation system developed. A high pressure ridge extended southeast-
ward from the high center to the south of the flight area. For the previous
24 hours, southerly winds were reported at all of the ground monitoring stations.
Further away from the high pressure center more air movement had occurred at
Austin and Houston than at DeRidder and Nederland.
Of the ground stations, only DeRidder (256 yg/m3) showed ozone concentra-
tions above NAAQS. Surface trajectories showed that air arriving at DeRidder
in the late afternoon had been in transit from the Nederland area for the past
24 hours. Concentrations measured at DeRidder were among the highest encountered.
The eastern portion of the area survey blocks was flown at 650 m (^2000
feet) counterclockwise along the path (Figure 4). The subsidence inversion
covered the Gulf Coastal plain from southern Texas to central Alabama. Conse-
quently, vertical motion probably was restricted to 1.5 km (^5000 feet) or
less but above flight level. The area coverage was reduced from the previous
day for operational reasons.
Ozone concentrations near 160 yg/m3 were encountered on all legs of the
flight and were persistent in the northern, western, and southern portions of
the flight. Again, eastern portions of the flight were lower than the other
portions, but were higher by about 30 yg/m3 than on the previous day. Concen-
trations and concentration gradients over 4-hour intervals at DeRidder were
continuous.
203
-------
Figure 4. Ozone concentrations along flight track (
maximum of hourly ozone concentrations ( (_} ),
trajectories with 12-hour positions (—& ),
pressure isobars ( ) for October 20, 1975.
), the daily
air parcel
and surface
High ozone concentrations persisted during the period of north and westerly
flow across areas of low emission densities. The influence of precursor emis-
sion areas is not apparent. Since flights remained below the subsidence inver-
sion, downward transport of ozone into the boundary layer is unlikely. The air
parcels arriving in the northeastern corner of the flight suggests an increase
of concentration with time. Twenty-four hours previously the parcel was near
the Arkansas-Louisiana border, roughly in the area where ozone concentrations
on the order of 110 pg/m were sampled^ At flight altitude 24 hours later,
concentration on the order of 145 ug/m were encountered. Air parcels arriv-
ing in the northwestern corner on this evening came from areas of east Texas
where ozone concentrations were about equaj to the NAAQS. Upon arrival, these
concentrations increased to about 190 yg/m , an increase of 30 yg/m .
In the southwestern corner of the flight path, the trajectory shows flow
across Nederland to the sample point where it had remained nearly stagnant for
about 12 hours. Ozone concentrations at flight level were just below the NAAQS
but were the lowest measured during this part of the flight.
The pattern of high ozone in the western part of the flight and lower in
the eastern part persisted. Concentrations were generally higher throughout
the flight. The ground stations near the flight area indicate increasing ozone
concentrations while Corpus Christi and Port O'Connor indicate a reduction in
the maximum concentration as onshore flow returned there.
204
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OCTOBER 21
On October 21, the high pressure center had proceeded further eastward
leaving only a ridge line with a northeastward axis. The air had begun to flow
northward. The mixing depth of Lake Charles rose from 1.2 km in the morning to
1.45 km in the afternoon. The potential temperature associated with the mixing
depth, however, did not change, suggesting that overall ascent of the air was
occurring. Measurements of high ozone concentrations on the previous day at
DeRidder, and the high concentrations already observed in the afternoon indi-
cated that a flight was necessary. The RTI aircraft left Lake Charles for
Nederland then went 160 km south out over the Gulf of Mexico before returning
to Lake Charles via Nederland and DeRidder, where a vertical profile was flown
(Figure 5).
Figure 5. Ozone concentrations along flight track (.
.), the daily
maximum of hourly ozone concentrations ( {_} ), air parcel
trajectories with 12-hour positions ( & ), and surface
pressure isobars ( -) for October 21, 1975.
Ozone concentrations exceeded the NAAQS throughout the flight except at
the southern tip of the flight, where ozone briefly decreased by about 20 yg/m3.
The over-water flight was made along the axis of the wind into Nederland out-
bound at 100 m and returning at 425 m (^1400 feet). Trajectories suggest that
advection of air having lower ozone concentrations into the Nederland area
might have been expected within about 12 hours. The ground level concentration
in Nederland decreased over the next 12 hours; but probably more in response
to local nocturnal ozone destruction than in advection. On the following day,
205
-------
the maximum ozone concentration was 62 pg/m3 lower, indicating a change of air
mass characteristics.
Trajectories also indicate that the air reaching Nederlarid had been carried
out to sea, approximately 24 hours before a reversal of wind initiated a return
flow into the Nederland area. Though initially it might appear that the high
ozone concentrations were associated with air flow from the Gulf of Mexico, the
trajectories analysis clearly shows that the air is only returning after having
passed over land-based sources of ozone and ozone precursors.
In the vertical profile to approximatly 3 km at DeRidder (Figure 6),, ozone
concentrations increased with altitude to 1.2 km. Above 1.6 km, ozone concen-
trations decreased and remained constant, thereafter, to the top of the sound-
ing. The ambient temperature decreased with altitude to 1.6 km. Over the next
300 m, the temperature was isothermal and the dewpoint temperature decreased by
11.2°C. During descent, ozone concentrations remained below "110 yg/m3 above
1.5 km. In the next 300 m of descent, ozone doubled to 216 ug/m3 and slowly
decreased to 178 pg/m3 in the lowest 300 m of the air. The aircraft tempera-
tures agree closely with the late afternoon soundings taken at Lake Charles.
On the return trip from DeRidder to Lake Charles, ozone concentrations also
remained above the NAAQS between 300 and 600 m above the ground.
Temper a Lure , ( '(')
0 5 H) 1 r> 1'')
I I I I
D Temp.
O Ozone
I I 1 I
10
01
T3
3
40 80 120 ^160 200 240
Ozone,
Figure 6. Vertical profiles of ozone and temperature at DeRidder at 1900 CDT
October 21, 1975.
On this day, trajectories arriving at Houston and Austin showed a well-
developed southerly flow, having been on the side of the high pressure system
206
-------
for a longer time. Afternoon concentrations in the Houston area were 137
a fairly low value for that station, and concentrations at Austin had decreased
to 124 pg/m3 from 159 ug/m3 on the previous day.
OCTOBER 22
By the afternoon of October 22, the influence of the high pressure ridge
had weakened through the area. The pressure gradient had increased and a
strong onshore flow had developed through all levels of the atmosphere. Ozone
concentrations between 99 and 122 pg/m3 were measured during the EPA aircraft
flight with no particular pattern to the concentrations measured (Figure 7).
Ground level ozone concentrations at the four stations were comparable to those
measured aloft indicating a relatively uniform distribution of ozone in the on-
shore flow.
Figure 7. Ozone concentrations along flight track
the daily
..,..._. _____ v ,
maximum of hourly ozone concentrations ( \_/ ), air parcel
trajectories with 12-hour positions ( — & - ), and surface
pressure isobars ( - ) for October 22, 1975.
The air parcel trajectories indicate a long fetch over water preceded by
turning from a northeasterly flow into a southeasterly to southerly flow. The
ozone concentrations were slightly higher than background concentrations. The
turning of the trajectories from a northeastern into a southerly flow suggests
that the air might have had an earlier origin over the Gulf Coast region.
207
-------
Mixing depth increased to about 1.8 km in the morning. By afternoon the stable
layer had risen to 2.2 km; but, the afternoon mixing depth reached only about
1.8 km. Warm air associated with the increased onshore flow left a relatively
unstable column of air within the mixed layer. The ventilation of the near
coastal area had increased substantially and ozone concentrations decreased.
OCTOBER 23, 24
For the next two days, October 23 and 24, strong onshore winds persisted
exceeding 10 m/s through most of the first 2 km. The lowest maximum ozone con-
centrations reported during the measurement program occurred at Nederland and
Houston. The increased wind speeds reduced the local residence time of injec-
ted ozone precursors, increased the turbulence of the atmosphere giving better
dispersion, and probably inhibited development of the oxidant potential on the
Texas Gulf Coast.
Ozone concentrations between 68 and 93 ug/m3 were measured during an EPA
flight on October 24 (Figure 8. These values were consistent with concentra-
tions found onshore at ground measurement stations. The strong southerly flow
at this time gave no indication of having had any recent history over any con-
tinental areas.
Figure 8. Ozone concentrations along flight track (-
-), the daily
— —...... — _._..-, ...-,.._ „. — ^\~
maximum of hourly ozone concentrations ( \_/ ), air parcel
trajectories with 12-hour positions ( £ ), and surface
pressure isobars ( ) for October 22, 1975.
208
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CONCLUSIONS
The single episode of high, nonurban ozone clearly demonstrates that ozone
concentrations exceed the NAAQS and persist for several days over a large
(^50,000 mi2) area that has a low precursor emission and does not have an
identifiable source region. That area apparently expands with increased con-
centrations and moves with the high pressure cell where vertical mixing is
inhibited and horizontal transport is limited.
The local changes of ozone concentrations in the northern Gulf Coast area
are strongly affected by transient high pressure systems and the history of
the arriving air.
These findings are consistent with findings of other investigations that
lead to the concept of a spent photochemical system developing in a slow-moving
high pressure cell. Therefore, in at least one case, the same concept applies
to the northern Gulf Coast area.
ACKNOWLEDGEMENTS
This research was performed under Contract No. 68-02-2048 with the Office
of Air Quality Planning and Standards, Environmental Protection Agency, Research
Triangle Park, North Carolina.
DISCLAMER
The opinions expressed herein are those of the authors and are not neces-
sarily those of the sponsoring agency.
REFERENCES
1. Federal Register, National Primary and Secondary Ambient Air Quality
Standards, April 30, 1971.
2. Research Triangle Institute, Investigation of Ozone and Ozone Precursor
Concentrations at Nonurban Locations in the Eastern United States, Phase I,
EPA-450/3-74-034, May 1974.
3. Stasiuk, W. N. and P. E. Coffey, Rural and Urban Ozone Relationships in
New York State, JAPCA, 24, 564-568, 1974.
4. Research Triangle Institute. Investigation of Rural Oxidant Levels as
Related to Urban Hydrocarbon Control Strategies, EPA-450/3-74-035, March,
1975.
5. Muller, P. R., M. H. McCutchan, H. P. Milligan, Oxidant Air Pollution in
the Central Valley, Sierra Nevada Foothills and Mineral King Valley of
California, Atmos. Environ., 6:603-633, 1972.
209
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6. Personal Communication from Dr. E. L. Meyer, OAQPS, Environmental Protec-
tion Agency.
7. Texas Air Control Board, Yellow Pine Study, 1975.
8. Johnson, D. J., Texas Ambient Air Quality Continuous Monitoring Network,
Texas Air Control Board, Air Quality Evaluation Division, 1973.
9. Wallis, R., J. H. Price, G. K. Tannahill, and J. P. Grise, Ozone Concen-
trations in Rural and Industrial-Urban Cities in Texas, Texas Air Control
Board, Air Quality Evaluation Division, 1975.
210
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5-5
OZONE AND HYDROCARBON MEASUREMENTS IN RECENT OXIDANT TRANSPORT STUDIES
W. A. Lonneman*
ABSTRACT
In Ae.ce.nt yeou, ^-ieJid Atudie.* weAe. undertaken to investigate, ozone- and
ozone.-pAe.cuAt,oA tnanApoAt. In thus. AtudieA &l&> weAe colle.cte.d and ana-
lyzed &OA kydAoc.aA.bon concentration. The. analytical AeAultA indicate, tkat
AuAal ambie.nt aiA dowwiind o& uAban centeAA con&iAtA laAgel.y ofa diluted uAban
mix., with lo&A 0& the. moAe. Ae.acti.ve. hydAocaAbon components. HydAocaAbon and
nitAogen oxA.de.* analyses at Wilmington, Ohi.o, indicate, that high ozone. concen-
tAation* OAC pAobably due. to tAantpoAt pAocei>i>ei> and aAe not tke. AeAu£t o&
local photochemical ^oAmoution.
INTRODUCTION
In recent years field studies were conducted to investigate the extent of
ozone (03) and 03-precursor transport downwind of urban areas. These studies
were designed to provide better assessment of the oxidant transport problem
and to furnish a data base for planning future oxidant control strategies.
The study sites were located near large industrial and highly populated areas
since the anthropogenic origin of high levels of tropospheric 03 is expected
to be the most significant and the only controllable source.
In 1974, EPA and EPA contractors conducted a study in Ohio. A network of
ground sampling sites for 03 was established, principally in Ohio but also in
neighboring states. Some of these sites, mainly those operated by RTI, were
equipped with other instrumentation for more detailed pollutant analysis.
These other activities included the collection of bag samples for subsequent
analyses of detailed hydrocarbons (HC) by the Environmental Sciences Research
Laboratory (ESRL) mobile labs. An aircraft was used to follow urban plumes
downwind of several metropolitan areas. In addition to 03 and temperature
measurements, the aircraft collected Tedlar bag samples for detailed HC anal-
ysis. Clinton County airport, an abandoned U. S. Air Force base, near Wil-
mington, Ohio, was used as the base station for these studies. The airport
had very little air traffic and was ideally situated to sample urban plumes
originating from nearby Dayton, Cincinnati, and Columbus. The EPA-ESRL
mobile laboratory which was located at this site, measured continuous diurnal
profiles of several pollutants. In addition, gas chromatographic analysis
of the collected air sample bags was performed for detailed HC composition.
*U.S. Environmental Protection Agency, Research Triangle Park, North Carolina.
211
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In 1975, a similar field study was conducted in the northeast. This
study was undertaken in order to explain the high nighttime 03 concentrations
observed at several sampling sites throughout EPA Region I. The northeast
area, including New York and New Jersey, represents the most highly populated
and industrialized section of the United States. Needless to say, this area
provides a critical testing ground for transport phenomena arid constitutes the
extreme test of present oxidant control strategy. The sampling network in-
cluded several 03 sampling sites located throughout EPA Region I. EPA con-
tractors installed and operated additional sampling sites, at Battelle facil-
ities located in Simsbury, Connecticut, and Washington State University
located in Groton, Connecticut. The ESRL-EPA laboratory was located south of
Boston, Massachusetts. In addition to these ground station laboratories,
three aircraft were used to provide more extensive coverage of 03 and HC
precursor concentration, including the transport of urban plumes over the
Atlantic.
Detailed reports of the 1974 study are presently available as EPA reports
(1, 2). Reports of the 1975 study should be completed in the near future.
The purpose of this paper is to present some results from these studies.
EXPERIMENTAL
The instruments employed in the ESRL mobile laboratory are listed in
Table I. Calibration procedures were used frequently to ensure the quality of
the data collected. Also for quality control, the calibration of the 03
monitors was checked on a day-to-day basis, often by an audit team.
TABLE 1. MOBILE LABORATORY INSTRUMENT ARRAY
Pollutant/detection objective
Instrument
Nitrogen oxides
Total hydrocarbon, methane,
carbon monoxide
Total sulfur
Ozone
PAN
Freon-11, carbon tetrachloride
Visibility
UV-Visible radiation
Wind speed and direction
Temperature and relative humidity
TECO 14B
Beckman 6800
Meloy SA-120
Bendix model 8000
G.C.-Electron capture
G.C.-Electron capture
MRI-Integrating Nepholometer
Eppley radiometer
Bendix Aerovane system
Hydrothermograph
The gas chromatographic procedures for detailed HC analysis are published
elsewhere (3). A modification of the published cryogenic trapping procedure
was used to concentrate larger air volumes and is graphically illustrated in
Figure 1.
212
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VALVE OPERATION
VALVE NORMAL
VALVE ENERGIZED
AIR SAMPLE IN
VALVE B
GCCOLUMN
TRAP
2.5 LITER
TANK
WALLACE-TIERNAN
PRESSURE GUAGE
Figure 1. Trapping system.
For HC trapping we used the dual valve system illustrated in Figure 1.
The vacuum gauge is a 0-200 torr Wallace-Tiernan gauge. Valve A is connected
to a high-speed rotary vacuum pump and is opened to evacuate the 2.5-liter
tank to 10-torr pressure (about a 30-second operation). At this point, valve
A is closed. A bag sample is connected to port No. 1 of valve V^ The trap
is immersed in liquid 02. Valve B is opened, and sample from the bag is
pulled through the system at a rate of about 150 cm3/min. When the pressure
setting on the vacuum gauge reaches 20 torrs, valve VT is energized, routing
the air sample into the trap. Samples are collected over a pressure differ-
ential of 20-170 torrs. This calculates to be (150/750) (2500 C) or about 500
C of air sample. Therefore, when the pressure on the gauge reaches 170 torrs,
valve MI is deenergized. To inject the sample, the cyrogen is removed, and
valve V2 is energized. As illustrated in Figure 1, the trapped contents are
front flushed onto the column; however, the trap can be easily modified to
back flush the trapped contents onto the G.C. column.
RESULTS AND DISCUSSION
The location in Wilmington, Ohio, proposed to be an ideal rural sampling
site, since it is surrounded by three major metropolitan areas. The site is
downwind of a major city regardless of wind direction. The ground-level HC
concentration of Wilmington was determined by collecting 30-minute-to-one-hour
integrated bag samples during morning, afternoon, and evening periods. On
occasion, 24-hour diurnal studies were conducted for a more complete investi-
gation of HC compositional and concentration variations. This task involved
the use of an automated bag sampler to collect 12 2-hour integrated samples.
213
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A comparison of HC between urban and downwind rural areas involves the
use of frequency plots of sample concentration versus the number of sample
observations. Unfortunately, during these studies, ground-level urban samples
were not collected in Cincinnati, Dayton, or Columbus; however, the HC concen-
tration at these sites is expected to be similar to other urban sites sampled
in previous studies. Frequency plots for Wilmington and for several urban
areas previously studied are given in Figure 2.
80
70
60
a.
<
C/3
50
O 40
I-
o 30
oc
tu
a.
20
10
0 50 I50
5100
6100
600 900 1200 1500 1800 2100 3100 4100
SUM OF NON METHANE HYDROCARBON, ppb C
Figure 2. Distribution of the sum of nonmethane hydrocarbons at various sampling
sites during the 600-900 a.m. time period.
If plots were available for these Ohio cities, they would probably be
similar to that shown for the St. Louis SLU profile, since the size of the St.
Louis metropolitan area is comparable to these Ohio cities. The profiles for
Wilmington and St. Louis SLU are similar except for an approximate 5-6 fold
dilution. A similar dilution factor may be observed by comparing average
acetylene concentration between the two sampling sites.
The percentage value given in parenthesis in Figure 2 for each sampling
site represents an estimate of total nonmethane HC as vehicular tailpipe emis-
sions. This estimation was established from an average total nonmethane
hydrocarbon/acetylene (TNMHC/C2H2) factor of 15.5, determined from previous
tunnel or roadway samples collected in New York, St. Louis, Denver, and
Boston. The value of 15.5 was calculated by averaging published factors of
13.9 for New York tunnels (3) and 15.0 for St. Louis roadways (4), with
unpublished values of 16.0 for Denver roadways and 17.0 for ESostori tunnel
samples. The percentage calculation involved the ratio of the estimated
vehicular emissions (average C2H2 X 15.5) to the average of the observed TNMHC.
The difference between the percentage of vehicular emission and 100 represents
HC from other urban HC sources, such as gasoline evaporative, spillage emis-
sion and industrial contribution.
214
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No new or unidentified HC peaks, except those resulting from bag out-
gassing, were observed on our G.C. systems during the analysis of bag samples
collected during the study. Naturally emitted HC, such as the Cio terpenes,
are resolved on our G.C. systems; however, none of these compounds were ever
observed, at least at the sensitivity of our instruments (1 ppbC). The frequency
distribution plots for these sampling sites were established from as few as 25
sample points and may not be exactly representative; however, a large sample
size would probably not significantly change the dimensions of these curves.
The analysis of bag samples collected at McConnelsville (another sampling
site operated by RTI during the 1974 Midwest study, located 100 miles east and
somewhat north of Wilmington) resulted in a distribution of TNMHC similar to
that observed at Wilmington. Typically, the average TNMHC concentrations were
higher during the morning hours than during the late afternoon sampling
periods. These results are given in Figure 3. This dilution effect between
morning and afternoon samples was observed in every urban area previously
studied and is likely to be the result of improved vertical mixing resulting
from surface heating during afternoon hours.
30
25
WILMINGTON.OHIO
20
c/3
LU
0.
<
15
cc
UJ
CO
5
z
10
MORNING SAMPLES
700-900
EVENING SAMPLES
1700-1900
McCONNELSVILLE.OHIO
100 200 300 0 100 200
TOTAL NON METHANE HYDROCARBON CONCFNTRATION ppbC
300
Figure 3. Sum of nonmethane hydrocarbon versus number of samples for two
ground sites used in the 1974 Midwest Oxidant Transport Study.
215
-------
The composition of HC in samples collected at Wilmington and RcConnels-
ville, as well as at other ground sites, and in aircraft samples collected
downwind of urban areas generally indicated reduced olevin and aromatic con-
tent. Figure 4 illustrates this for total olefin content for a diurnal study
of the Wilmington site on July 18, 1974. The dashed line in the figure repre-
sents the average olefin content of the TNMHC concentration for 42 samples of
less than 10 ppbC C2H2 concentration observed at St. Louis, Denver, and New
York sampling sites. At each sample period, the sample bag collected at
Wilmington during the diurnal study showed lower olefin content. The graph
also illustrates reduced olefinic content during afternoon, undoubtedly the
result of photochemical activity.
A different illustration of olefin loss is shown in Figure 5. In this
figure, the estimated percent of olefin reacted was plotted, versus time. The
percent of olefin reacted was determined by ratioing the observed sum of
olefin concentration in the sample to the estimated original olefin concen-
tration. The estimated original olefin concentration was determined by a cal-
culation similar to one described earlier for vehicular TNMHC that uses C2H2
concentration and an averaged olefin/C2H2 factor of 3.4 obtained from tunnel
and roadway samples. This calculation indicates that as much as 70 percent of
the original olefin concentration has reacted by the late afternoon.
Similar observations, differing in magnitude, were made for other diurnal
studies conducted at Wilmington. The results shown in Figures 2, 4, and 5
suggest that the ambient air sampled in Wilmington was a diluted urban HC mix,
with associated photochemical loss of the more reactive compounds during the
transport process.
It was stated earlier that low araomatic content of the TNMHC was also
observed in Wilmington samples. The G.C. elution of these aromatic compounds
was interfered with by unknown peaks later identified as outgassing compon-
ents from Tedlar bag surfaces. These interfering peaks present serious
problems for the accurate measurement of aromatic content and is an area we
are presently investigating in our laboratories by evaluating alternate air
sample containers. These unknown peaks were not included in any of the TNMHC
summations. Acetaldehyde and acetone also were peaks identified as outgassing
from Tedlar bag surfaces. It is likely that both acetone and acetaldehyde are
both components of these rural ambient atmospheres; however, quantitative
evaluation of these ambient levels is impossible because of this inconsistant
outgassing contribution.
Ozone concentrations at Wilmington often exceeded the National Air Quality
Standard of 80 ppb during the late afternoon and evening hours. The late
evening levels of ozone suggests transport; however, th,e possibility that
morning levels of TNMHC and nitrogen oxices (NOX) at Wilmington are responsi-
ble for afternoon 03 concentrations was investigated. Figure 6 shows a plot
of morning concentrations of TNMHC and NOX. The solid line in the figure
represents the 0.08 ppm 03 isopleth, determined by computer simulation of an
atmospheric model developed by Dodge (5). The model is based on a mixture of
n-butane-propylene-NOx. The 0.08 ppm isopleth was determined from the worst
possible case of limited vertical mixing and no horizontal transport.
216
-------
QC
<
<
x
o
I—
u.
o
DC
L1J
a.
20
18
16
14
12
10
8
6
4
2
— URBAN AVERAGE FOR 42 SAMPLES AT 10 ppb ACETYLENE OR LESS —
0000 0200 0400 0600 0800 1000 1200 1400 1600
TIME OF DAY
1800
2000 2200 2400
Figure 4. Diurnal variation of average olefinic fraction of total nonmethane
hydrocarbon, Wilmington, Ohio, July 18, 1974.
a
UJ
o
4
0000 0200 0400 0600 0800 1000 1200 1400 1600 1800 2000 2200 2400
TIME OF DAY
Figure 5. Diurnal variation of the fraction of olefins reacted, Wilmington,
Ohio, July 18, 1974.
217
-------
30
28
26
24
22
20
.Q
g 18
x
i 16
14
12
10
8
6
4
20 40 60 80 100 120
1 NMHC, ppb
140
160
180
200
Figure 6. Wilmington, Ohio, 1974 sum of nonmethane hydrocarbon versus
NOX (600-900 a.m.).
Of the 16 data pairs available for the month of August, only two pairs
fell on the right-hand side of the 0.08 ppm 03 isopleths, meaning that these
HC and NOX levels were capable of producing 03 at or above 0.08 ppm. Ozone
maximums observed on these days are shown in Table 2.
TABLE 2. OZONE MAXIMUMS FOR AUGUST, 1974, DAYS WHERE MORNING NMHC
AND NOX CONCENTRATIONS ARE KNOWN IN WILMINGTON, OHIO-
DATE
5
6
8
X 9
10
14
16
OZONE MAXIMUM, ppb
63
66
63
73
70
77
85
DATE
19
20
21
24
25
27
X28
OXONE MAXIMUM, ppb
69
93
90
94
93
96
45
218
-------
The dates of the two data points falling on the right-hand side of the
0.08 ppm isopleth were August 9 and 28. On these two days, the 03 standard
was not exceeded. On 7 of the other 14 days, however, the Os standard was
either approached or exceeded. These results suggest that local HC and NOX
levels do not account for all local 03 observed and that a considerable
portion of this 03 is transported from upwind sources.
Other indications of the urban influence on downwind 03 air quality are
shown in Figures 7 and 8. These figures were constructed from aircraft
flights upwind and downwind of Columbus. Figure 8 represents a square wave
plume flight by RTI downwind of Columbus on July 21, 1974. The acetylene
profile was established from bag samples collected along perpendicular paths
to the urban plume. The ozone profile was drawn by averaging continuous 03
concentrations measured along these paths. This figure, demonstrates, in
effect, a net 15 to 20 yg/m3 increase in 03 as far as 40 miles downwind of
Columbus.
Figure 8 represents a double-box type pattern as flown on July 9, 1974,
during very stable atmospheric conditions. The solid line was constructed
from C2H2 measurements of bag samples collected parallel to wind direction.
The dotted line represents C2H2 profile constructed from C2H2 measurements of
bag samples collected at locations perpendicular to the wind direction. On
this day, the downwind urban effect on 03 air quality is even more signi-
ficant.
Results from the 1975 northeast study also show the effect of transported
03 and 03 precursors. The purpose of this study was not to investigate the
transport of 03 from urban to rural sites, but to study the transport of 03
and its precursors from one urban area into other urban areas. In general,
the study was concerned with the implementation of an effective transportation
control plan designed to lower the 03 concentration when the 03 levels were
already high upwind of the urban areas. A complete analysis of the data is
not presently available. The ESRL mobile laboratory was located on Chicka-
tawbut Hill, 10 miles south of Boston. Typical profiles of 03 and other
pollutants at the site are shown in Figure 9. Ozone transport is evident by
the observation of increasingly high 03 concentrations during nighttime hours.
The evidence for urban origin of this 03 is a corresponding increase in the
concentrations of C2H2 and peroxyacetylnitrate (PAN). Similar results were
observed on other days.
Aircraft measurements of 03 and precursor concentrations were made over
the eastern coastal regions of Massachusetts. Often, an urban plume contain-
ing high levels of 03 was followed hundreds of miles out over the Atlantic
Ocean. In an effort to investigate urban tracer relationships, C2H2 and
corresponding 03 data were assembled for comparison. On the basis of an
analysis of samples collected over the Atlantic during late afternoons and
evenings, there appeared to be a linear relationship between these two pollut-
ants. Linear regression equations were determined for the data of three
flights and for all the data points collected during these flights. The
results are recorded in Table 3.
219
-------
3.0
0
I
llf
2
UJ
5f2.0
LU
3
1.0
0
,-•
1 1 1 1 1
, ^.
•' ^"-->. OZONE
— ., —
~" T NET INCREASE 15-20 M9/m3
OZONE STANDARD
x-'
_/'
n
COI
1
.u
MB
-1
vx
v
^
X«-^ ACETYLENE ~
WIND DIRECTION * v-^^
71
"1 1 1 1 1 1
200
ISOn
a.
Ul
z
o
N
100 °
50
n
10
10
20
30 40 50
DISTANCE, miles »
Figure 7. Air flight of 7/21/74, traverse pattern over Columbus, Ohio
Figure 8. Air flight of 7/9/74, box pattern over Columbus, Ohio.
220
-------
o
I-
cc
o
o
cc
3
o
120
110
100
90
80
70
60
50
40
30
20
10
JULY 18 JULY 19
WIND SPEED: 7 mph 11 mph
WIND DIRECTION: 240° 240°
S^«t»y ~
—t—.-^..
1.5
1.0
0.5
o
u
o
u
DC
UJ
4
CC
e
0100 0600 1200
JULY 18, 1975
1800 2400 0600 1200 1800
TIME OF DAY JULY 19, 1975
2400
Figure 9. Diurnal hourly concentrations of Oa, CO, acetylene, and
visibility, Chikatawbut, July 18 and 19, 1975.
TABLE 3. CORRELATION OF OZONE VERSUS ACETYLENE OFR EPA-LV AIRCRAFT SAMPLES
BOSTON OXIDANT STUDY, 1975
Sample
Period
August 14
August 20
August 27
All samples
Observations
7
7
6
66
P
0.91
0.95
0.94
0.85
Slope
19.6
15.9
14.6
19.4
Intercept
46.1
38.1
32.0
31.0
Os Range
ppb
53-186
40-69
58-99
29-186
C2H2
Range,
ppbC
1.0-7.1
0.3-1.5
1.6-2.6
0.2-7.1
The correlation coefficients between 03 and C2H2 for these data sets are
quite high, suggesting a significant relationship. The comparison of slope
and intercept for the data sets is quite interesting. A bold interpretation
of these results would suggest that the variation of the slope values for
these data sets may be the result of variable chemical physical and chemical
parameters such as initial concentration of HC and NOX, HC/NOX ratios, ambient
temperature, and sunlight intensity.
On the other hand, the intercept could represent background 03 when the
C2H2 concentration is zero; or, in other words, the vehicular contribution is
absent. The 03 concentration represented by the intercept could be due to
natural and industrial sources of HC and NOX. Caution must be exercised when
221
-------
making such interpretation. However, the values for the intercepts interest-
ingly compare to background measurements of 30 ppb of ozone made over Maine on
August 28, 1976.
In recent months, we have commenced a study of natural HC emissions at a
forested area west of Durham, North Carolina. The vegetation at the site con-
sists primarily of loblolly pine and has been used to perform micrometeoro-
logical measurements to estimate mass and energy balance. The purpose of our
sampling program is to determine the composition of natural HC emissions.
In preliminary studies to determine detailed HC composition, 03 bag
samples were collected at various vertical heights below, within, and above
the tree canopy. Additional samples were collected at ground level, upwind
and downwind of this forested area. In some bag samples a~ and g-pinene at
times myrcene and A-carene were observed, most frequently in samples collected
within or below the tree canopy. In these studies, a maximum of 87 ppbC a-
pinene, 19 ppbC 3-pinene, 3.3 myrcene, and 4.8 ppbC A-carene were observed at
ground level, suggesting that perhaps pine needle litter was the principal
source.. Concurrent 03 measurements indicated a 40 ppb 03 level above the tree
canopy and 30 ppb 03 within or below the canopy. The reduced level of 03 in
the canopy suggests 03 removal by either surface deposition or terpene-
ozonolysis mechanisms. Samples collected upwind and downwind of the forested
area showed no difference in 03 concentration and only trace levels of terpene
compounds in downwind samples. These studies also suggested that terpene
emissions and ambient temperature were directly related.
More recently, simultaneous diurnal studies for HC and 03 were performed
at two vertical heights, one within and one above the tree canopy. The
results of these studies are not presently available. Ultimately, we plan to
determine vertical fluxes of these terpene hydrocarbons in an effort to evalu-
ate emission strength.
CONCLUSIONS
Field studies conducted in recent years to investigate rural 03 have
indicated that the high levels of 03 are of anthrophogenic origin, transported
from upwind sources. The HC composition at rural Wilmington, Ohio, was simi-
lar to the HC composition at urban sampling sites. In fact the HC sampled in
these rural areas appeared to be a diluted urban HC mix depleted to some
extent of the reactive olefinic hydrocarbons. This loss of olefinic HC was
probably the result of photochemical degradation.
Acetylene and corresponding 03 measurements showed significant correla-
tion in aircraft sampling programs of urban plumes over ocean bodies during
the 1975 Northeast Study.
REFERENCES
1. Investigation of Rural Oxidant Levels as Related to Urban Hydrocarbon
Control Strategies, U. S. Environmental Protection Agency, Publication
EPA-450/3-75-036, 1975.
222
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2. Transport of Oxidant Beyond Urban Areas, U. S. Environmental Protection
Agency, Publication EPA-600/3-76-018, 1976.
3. Lonneman, W. A., S. L. Kopczynski, P. E. Dorley, and F. D. Sutterfield,
Environ. Sci. Technol. 8, 229, 1974.
4. Kopczynski, S. L. , W. A. Lonneman, T. Winfield, and R. Seila, J. Air Poll
Control Assoc., 25, 255 (1975).
5. Dodge, M. Combined Use of Modeling Techniques and Smog Chamber Data to
Derive Ozone-Precursors Relationships, these proceedings.
223
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SESSION 6
OZONE/OX I DANT TRANSPORT - I
A. P. Altshuller
Environmental Protection Agency
225
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6-1
TRANSPORT OF OZONE BY UPPER-LEVEL LAND BREEZE -
AN EXAMPLE OF A CITY'S POLLUTED WAKE UPWIND FROM ITS CENTER
E. K. Kauper and B. L. Niemann*
ABSTRACT
Of) alficAa^t i>oundlnQ& avid tsiaveAAeA, meoAuSLtng ozone, and the. at-
tempeAatuAe. A-tAuctuAe. between the. C-oaAtai. po>itA.ont> ofa Lot> knaeJLeA and
(/e.ntuAa County to the. nonthwut weAe. made. duA-ing the. AummeA oft 7975. W-tmii
alofit weAe. .t>Ajnultane.ouAl.y obtained, and the. movemznt o& uppeA te.\)eJL ozone.
layeAA weAe. de.ducte.d by mean-5 o{, tAaje.c£oAy anaiyt>eA ubtng thAe.e.-houAty A&ie.am-
Line. chasitA. The. uppeA £e.veJL {^tow, Ln the. JLayeAA containing the. ozone, maxima,
4.ndie,ate,d that the. ozone, wcw brought oveJt the. Ve.ntuA.a County coaAt&ne. fiiom
the. Loi> Ange£e6 Bat>in, euen though AuA^ace. wind SLe.posit£, AJ>, Mould t>how that no Lo& Angetu c.onne.c.*tion WOA tnvolve.d.
INTRODUCTION
Questions regarding the origin of high ozone values in areas of southern
California assumed to be upwind of the Los Angeles Metropolitan area have long
, been asked (1). Answere, using surface wind flow maps, indicate that such occur-
rences either were due to local sources in the Ventura County area northwest of
Los Angeles, or came from off the Pacific Ocean (2). A second path, that
through the San Franando Valley to the interior valleys of Ventura County, has
also been postulated.
Recently, more detailed analyses of ozone episode cases in Ventura County
have suggested the importance of ozone transport aloft and subsequent fumiga-
tion to the ground as a causative mechanism (3). However, these analyses have
been seriously hampered by lack of wind, temperature and ozone profiles in
Ventura County and air mass trajectories of high ozone concentration parcels
aloft leaving the Los Angeles area.
To document the three-dimensional situation off the southern California
coast, the California Air Resources Board funded a study of the over-water
transport of ozone in 1975 from which the data used for this paper were
derived (4).
GEOGRAPHICAL AND METEOROLOGICAL SETTING
The project area of concern involved the coastal portion of southern Cali-
fornia, between West Los Angeles - Santa Monica and the Ventura County coast-
line to the north and west of the Los Angeles Basin.
*E. K. Kauper, Metro Monitoring Services, Covina, California.
B. L. Niemann, Teknekron Inc., Berkeley, California.
227
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Flights were conducted during the summer of 1975 under what would be con-
sidered typical summer conditions. A marine layer, usually capped by a stratus
cloud deck, was present during all operations. The height of the inversion and
its strength varied during the study, with high inversions the rule during the
June 2-4 study period, moderately low inversions during the period of July 10-11,
followed by a period with a deepening marine layer, July 14-18.
EQUIPMENT
The airborne sampling was conducted from a Piper PA28-140, with the tem-
perature and ozone sampling intake located on the left side of the fuselage,
away from the engine
exhaust outlet.
The sampling line, of 0.6 cm teflon, was kept short (1.2 m) to reduce the
possibility of ozone loss due to wall effects. The ozone monitor was a Dasibi
1003AH, factory modified to provide reading update every 13 seconds, recorded
on a Hewlett-Packard 680M strip chart recorder.
The ozone sensor, together with the recording system, was calibrated by
the California Air Resources Board at its El Monte, California, facility.
Winds aloft were measured by means of optical tracking, using theodolites,
of 30 gram pilot balloons. The balloons were inflated to a standard free-lift
condition which gave a rate of rise averaging 600 ft/min (3 mps) from the sur-
face to 5000 ft (1.5 km).
OPERATIONS
The aircraft followed the flight path shown in Figure 1, starting from
Santa Monica Airport (SMO), climbing to 5000 ft (1525 m) and then descending
for a touch-and-go landing at Ventura County Airport, Oxnard (OXR). The return
trip to SMO was generally along the coast during good weather (VFR conditions);
but when cloud cover required instrument flight, the path was along an inland
route shown in Figure 1.
These flights were performed every three hours during the day, with one
flight near midnight to monitor the nighttime conditions.
An aircraft observer recorded temperature and altitude information during
the climbing and descending phases of the flights, with ozone being recorded
continuously throughout the flight.
With the Dasibi instrument obtaining a reading every 13 seconds, the sam-
pling rate in horizontal flight, corresponding to the aircraft's cruising
speed of 120 mph, was one sample every 0.4 miles (0.6 km). During climb and
descent, the rate of altitude change was 300 feet per minute, giving an ozone
reading at 65 ft (20 m) intervals.
Winds aloft were measured at three locations, Los Angeles International
Airport (LAX), Point Dume (DUM), and OXR, and were scheduled on the same time
basis as the aircraft flights.
228
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C3-S
CL
03
c:
O
(O
o
o
-M
i/i
TD
CD
•T-"
CH
-<->
M-
ro
s-
o
S-
O)
S-
229
-------
RESULTS
The data obtained by the aircraft and the wind observation stations were
plotted as vertical soundings, and placed on vertical cross-sections covering
the route from Santa Monica to Oxnard. Figure 2 presents soundings of tempera-
ture and ozone at these two locations for a specific time. There is some ques-
tion regarding the ozone values as recorded between 1000 and 2000 ft over SMO;
but the other data points appear to be valid.
Cross sectional analysis of these data indicates that layers of ozone-rich
air exist aloft over the coastal route between the Los Angeles Basin and the
Ventura County area. These layers are mainly found just above the base of the
main subsidence inversion, but also can be located within the stable layer of
the inversion itself, as seen in Figure 2.
Trajectory analysis was carried out, using the winds aloft data from the
pilot balloon network, plus winds aloft data taken by the Navy at Point Mugu
(NTD). Wind flow streamline maps for the various altitudes with the maximum
ozone were used in this work. Figure 3 represents the trajectory of the air
parcel found over Oxnard with a concentration of 0.45 ppm at 900 ft. (0.3 km)
when the ozone maximum over Santa Monica was 0.31 ppm, at a similar height.
For comparison, the trajectory taken by a surface air parcel arriving at
OXR at the same time as the upper air parcel is also shown in Figure 3. Its
track into the coast at OXR from the west is characteristic of trajectories
derived from the surface wind reports.
To provide some sort of climatology of upper air flow, trajectories of air
containing the maximum ozone aloft over Oxnard were constructed daily for the
1200 PDT time period. Nine such trajectories were prepared, five of which
followed a track along the coast between Santa Monica Bay and the Ventura
coastline, similar to that shown in Figure 3. Three others were located along
a San Fernando Valley - Thousand Oaks path, while only one could not be traced
into the Los Angeles source region.
Inspection of the conditions associated with the individual trajectories
indicates that the over-water trajectory from Los Angeles is more likely when
the marine layer is shallow. The trajectories which indicated movement into
Ventura County from the San Fernando Valley were associated with the deeper
marine layer conditions.
A similar climatological approach to the ozone concentrations aloft,
averaged for the project period, is shown in Figure 4. The ozone values in-
crease aloft during the day over both SMO and OXR, but stay near 0.10 ppm
during the night, rather than decreasing to near zero as is the case for sur-
face measurements.
The most frequent winds aloft are shown in Figure 5, again for the project
period. It is evident that the easterly winds dominate the flow, especially at
levels aloft above the surface. For example at 1200 PDT, while the westerly
sea breeze is blowing in the layer between the surface and 1000 ft at LAX and
OXR, the flow aloft is easterly. At Point Dume (DUM), midway between the Los
230
-------
CO
Q .2 .4 .6 .8
70 BO
TEMP ("F)
90
OXR
Figure 2a. Temperature and ozone sounding (OXR), July 10, 1975, 1500 PDT.
231
-------
30
b
o
0)
•O
3
20
10
0 .2 -4 .6 .8 1.0 70
03 (PPM)
SMO
80
TEMP (°F)
90
Figure 2b. Temperature and ozone sounding (SMO), July 10, 1975, 1500 PDT,
232
-------
f "™** ^
Q
a.
o •
" O
10 JT
O) C>O
CO O
o a>
CD S-
•r- I—
jz:
O)
^: o
4-> re
•i- <4-
3: S-
a: oo
X *"• ^*
o
OJ
(O
-
cn-
s —
s- o
as o
o
O Q-
S- O
O LT>
+J 1—
(J
C1J ^
•"-3 LO
O)
5-
Z3
CD
233
-------
.25
O.
O.
O
O
O
O
09
O
N
O
.20
.15
.10
.05
v'%.
06
09 12 15 18
23
HOUR (PDT)
Figure 4. Average maximum ozone above inversion base, July 9-18, 1975.
234
-------
t-
3000
2000
1000
sfc.
3000
- 2000
co
1000
(1107) Easterly 1106(1410) 2204(1410)
/
Westerly
(1108)
1405 0904(1406) 2204(2206) 2206
1106(0904) 1104 2205(1406) 2510(2706) . 2512
3602(3605) 2202(1805) 2205(2710) 2706(2710) 2706
06
09
12
15
18
sfc.
3000
_ 2000
_i
CO
1000
sfc.
06
09
12
15
18
06
09
12 15 18
HOUR (PDT)
2202
/
Easterly
0908
\
2904
2702
\
\
(a)
23
• 1107 / 2705 2505
Easterly
Westerly
2903 2703
1109 1107 1106" 2711 2505
I
3102 1402 1403 2709 2908
• i ii • |
\
\
m
*
\
1112
Easterly
0904
0906
1102
1
23
23
(b)
/
• 1409 2207
•
Easterly 1
• 1106 1404 / 2208
•
• 1105 1106 2208 2210
*
1604 0603 I 2711 2510
i t f i i
2905
( 1
2208
1 1
Westerly
2515
2710
-•
KEY:
Wind Direction
(10's of degs.)
•
Wind Speed, mph
2204
2704
i i
(c)
Figure 5. Most frequent winds aloft, June-July 1975; (a) OXR, NTD in ():
(b) DUM; (c) LAX.
235
-------
Angeles coastline and Ventura area, the westerly winds are not noted until well
after 1200 PDT, even at the surface.
Conditions shown in Figure 5 reinforce the idea that ozone layers aloft
can easily be transported from the east (from Los Angeles) to the Ventura
County coast.
CONCLUSIONS
On the basis of a three-dimensional study of wind flow and ozone between
the coastal portion of Los Angeles and Ventura County to the northwest, it is
concluded that ozone rich layers exist aloft, and may be tracked as entities
over the length of the study area.
The most persistent ozone layer was found just above the base of the subsi-
dence inversion characteristic of the southern California summer season.
Trajectories of air containing the ozone aloft indicated a prior history
over the Los Angeles Basin. (Surface wind-derived trajectories, on the other
hand, give the impression that such a transport did not occur.)
The persistence of the ozone layers aloft, and the upper flow indicating
transport from the Los Angeles area during what is considered normal summer
conditions, leads to the conclusion that such is the common situation, and that
the reported high ozone values at surface locations in Ventura County may well
be the result of the surfacing of the aged photochemical pollution cloud from
Los Angeles.
REFERENCES
1. Tubbs, D. Photochemical Oxidant Air Pollution in Ventura County,
2nd edition, 1965-1974, Report by the Ventura County Air Pollution
Control District, 1975, 115 pp.
2. Chaplin, A.S. and R.R. Russell. A Report on the Impact of the Proposed
Camarillo Airport on the Air Quality of the Oxnard Plain, Environmental
Systems Div. Litton Systems, Inc., Camarillo, CA., 1970, p. 3.9.
3. Sklarew, R.C., and A.S. Chaplin. Analysis of Formation of High Ozone
Concentrations in Ventura County, Report by the Environmental Systems
Division, Xonies Corporation, to Ventura County Air Pollution Control
District, 1975, 54 pp.
4. Kauper, E.K. and B.L. Niemann. Los Angeles to Ventura Overwater Ozone
Transport Study, Report to California Air Resources Board, Sacramento,
CA, #ARB4-1126, 1975.
236
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6-2
OZONE FORMATION IN THE ST. LOUIS URBAN PLUME
W.H. White, D.L. Blumenthal, J.A. Anderson, R.B. Husar and
W.E. Wilson, Jr.*
ABSTRACT
The. pottutant e.mLf>Atont> ofa me.tAopoLitan St. LOUAJ> can cau/ie.
ofa the, Fe.deAat Ambte.nt Standard faoti ozone. 160 km oft mono, downultnd. The.
appaAe.nt ozone. yteJLd ofa the. eAtimate.d hydAoc.aA.bon e.m.L&A cJLoAe. to the. the.osLe.tLc.aJL Atotc-htomztsitc. uppeA Urn-it.
c.oncJLuAtonA aAe. dnawn ^ftom d^taiie.d obAe.sivationA ofi the. St. Lou/a usiban
ptume. made, by tAime.nte.d aJAcAa^t dusting the. AummeAi, ofa 1973, 1974, and 1975.
INTRODUCTION
Metropolitan St. Louis is a major urban-industrial center, encompass-
ing coal-fired power plants with a combined capacity of 4600 megawatts (mw),
oil refineries with a combined capacity of 4.4 x 105 barrels/day, various
other industry, and a population of about two million. It is surrounded by
flat, predominantly agricultural terrain, the nearest neighboring city of
50,000 or more people being 135 km distant. Due to its isolation, the impact
of St. Louis on ambient air quality is relatively easy to determine; air that
has been modified by the aggregate emissions of the metropolitan area forms
a 30-50 km-wide urban plume downwind. The Fate of Atmospheric Pollutants
Study (FAPS) showed that the aerosol burden of this plume is often identifi-
able 80 to 120 km from the city (1, 2, 3, 4).
As part of Project Midwest Interstate Sulfur Transformation and Trans-
port (MISTT), pilot balloons and instrumented aircraft were used during the
summers of 1973, 1974, and 1975 to quantify the three-dimensional flow of
aerosols and trace gases in the St. Louis urban plume (5). The primary sampl-
ing platform for the program was the MRI Cessna 206 (6). In addition to
extensive aerosol and meteorological instrumentation, this single-engine
plane carried continuous monitors for ozone (03) (chemiluminescence), nitric
oxide (NO) and nitrogen oxides (NO ) (chemiluminescence), and sulfur dioxide
(S02) (electrochemical). The flight pattern of the sampling aircraft was
designed to characterize cross wind sections of the plume at discrete distances
downwind of the city, and was established with the aid of an instrumented
*W.H. White, D.L. Blumenthal, J.A. Anderson, Meteorology Research, Inc.,
Altadena, California.
R. B. Husar, Washington University, St. Louis, Missouri.
W. E. Wilson, Jr., U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina.
237
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scout aircraft operated by Washington University (7). Airborne operations
were supported with half-hourly observations of winds aloft obtained by mobile
pilot balloon units operating in the sampling area.
The use of a highly-mobile fixed-wing aircraft as the primary sampling
platform led to an improved understanding of pollutant transport and disper-
sion at scales of 100 km or more. In addition, the design of the experiment
made possible the study of transformations undergone by pollutants in the
atmosphere at dilutions and time scales which are difficult to simulate in
the laboratory. The formation of aerosols and loss of sulfur dioxide in the
St. Louis urban plume are discussed elsewhere (7, 8). In this paper, we will
present some results on the formation and transport of ozone, and discuss
their implications for a control policy.
RESULTS
A plume of ozone concentrations well above background levels was en-
countered directly downwind of St. Louis on most sampling days. Ozone con-
centrations within this plume often exceeded 0.2 ppm, and concentrations in
excess of 0.3 ppm were recorded. Net production of 03 and/or nitrogen dioxide
(N02) was often apparent less than 15 km downwind of major hydrocarbon (HC)
sources near Wood River (chemical industry) and downtown St. Louis (motor
vehicles). Figure 1 shows profiles of ozone and oxidant (03 + N02) concen-
trations measured immediately downwind of the metropolitan area under dif-
ferent wind regimes.
The geometry of the urban plume strongly depended on the prevailing wind
direction. Under northwesterly or southeasterly conditions, parallel plumes
from Wood River and St. Louis could be distinguished in traverses immediately
downwind of the metropolitan area. The combined initial width of the two
plumes was about 50 km. Under southwesterly or northeasterly flow, the two
plumes tended to overlap and merge into one. The highest ozone concentra-
tions were measured under these conditions, when the individual plumes rein-
forced each other. On two days in 1975, the wind held steady from the south-
west all day long and the combined urban plume was mapped from St. Louis out
to distances greater than 150 km.
Figure 2 shows ozone and aerosol light-scattering coefficient (b .)
profiles recorded by the sampling aircraft during selected cross-wind tra-
verses downwind of St. Louis on July 18, 1975. Each traverse path was flown
at three different altitudes, starting just, downwind of St. Louis at 0900
Central Daylight Time (CDT) and finishing near Decatur, Illinois, at 1900 CDT.
These horizontal traverses, together with vertical soundings such as that
shown in Figure 3, documented a broad, shallow pollutant plume extending from
St. Louis out past Decatur, 170 km to the northeast. Outside the plume, ozone
concentrations were fairly uniform and generally below the 0.08 ppm Federal
Ambient Standard. Within the plume, ozone concentrations exceeded the Feder-
al Ambient Standard even at 160 km from the St. Louis Arch. At this distance,
where concentrations outside the plume were 0.07 ppm or less, concentrations
in the center of the plume remained as high as 0.12 ppm.
The July 18 plume was mapped under hazy skies, with some scattered thunder-
238
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Figure 1. Horizontal profiles of ozone and oxidant concentrations downwind
of metropolitan St. Louis under four different wind regimes. Pro-
files were recorded during traverses along profile baselines at
the following altitudes and times: (clockwise from top) 610 m MSL,
1145-1152 CDT, 12 August 1974; 455 m MSL, 0933-0952 CDT, 30
July 1974; 760 m MSL 1451-1512 CDT, 28 July 1975; 455 m MSL, 1027-
1048 CDT, 15 August 1974. Arrows show average winds measured in
mixing layer during sampling period; their lengths equal distance
covered in one hour at average wind speed.
239
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CHAMPA IGNN
fv^-^j' URUANA
>,/-u xi^.;
MISSOURI / II I.INOIS
0 50
KILOMCTTRS
A POWER PLANT
• REFINERY
Figure 2. Selected horizontal profiles of ozone concentration and light-
scattering coefficient (b ,) downwind of St. Louis on 18 July
1975. Profiles were recoruea during traverses along profile base-
lines at the following altitudes and times: (starting near city)
455 m MSL, 0849-0907 CDT; 455 m MSL, 1157-1220 CDT; 610 m MSL,
1348-1410 CDT; 760 m MSL, 1631-1656 CDT; 760 m MSL, 1804-1834 CDT.
Spiral indicates location of vertical sounding shown in Figure 3.
showers appearing toward evening. The depth of the mixed layer, which was 0.3
km at 0900 CDT, increased rapidly during the morning, and exceeded 1.0 km by
early afternoon. The continuing presence of a low pressure trough over the
western plains produced strong southwesterly flow over the Missouri and upper
Mississippi valleys, which was documented in the sampling area by a total of
36 pilot balloon observations carried out as part of Project MISTT. The mean
transport vector (1) lay between 230° and 243 during the middle of the day,
at speeds of 20-36 km/hr. At these speeds, among the highest encountered
during the program, emissions from the city would have aged roughly 5-7 hours
by the time they were sampled in the farthest passes.
The general direction of the airflow was corroborated by the alignment
of power plant plumes in successive traverses. All of the major (greater
than 1,000 mw capacity) power plants lying in and immediately upwind of the
240
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; bSCAT
0 0 I
0 I 2
TEMPERATURE (C)
TEMPERATURE
V
02
4
15
ppm
lO-'m
20
OZONE
l> Cf «T
180 210 240 270 DIRECTION
SPEED tm/s) 6 8 10
Figure 3. Vertical profiles of ozone concentration, (bscaj-), temperature,
and wind, measured in late morning on 18 July 1975. Profiles of
ozone, bsca£, and temperature were recorded during spiral descent
over Mt. Olive, Illinois (identified by spiral in Figure 2), 1130-
1143 CDT. Straight line with temperature profile shows dry adia-
batic lapse rate. Wind profiles were derived from pilot balloon
released from Sorento, Illinois, 15 km from Mt. Olive, at 1200 CDT.
TEMPERATURE
0
0 I 2
TEMPERATURE (C)
IBO 210 240 2/0 DIRECTION
SPtfU (m/sl 6 8 10
Figure 4. Vertical profiles measured in early afternoon on 11 August 1975.
Profiles of ozone, bscat, and temperature were recorded during spiral
descent over Butler, Illinois (identified by spiral in Figure 5),
1329-1343 CDT. Wind profiles were derived from pilot balloon
released from Taylorville, Illinois, 40 km northeast of Mt. Olive,
at 1330 CDT.
241
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area are noted in Figure 2. The plumes from some of these plants can be
identified in Figure 2 by their ozone deficits, which result from the scav-
enging of the ambient ozone by plume NO (9). The Coffeen plant, 85 km WNW
of St. Louis, is the only major downwind pollutant source known to the authors
which lies within the July 18 urban plume.
Figure 5 shows selected ozone and b . profiles recorded on August 11,
1975. Sampling began upwind of St. Louis at 0800 CDT and continued downwind
of the city until a line of thunderstorms moved into the sampling area at about
1600 CDT. At this time, the sampling aircraft had just completed a set of
passes 145 km from the Gateway Arch, and the scout aircraft, which was not
instrumented for ozone, had identified the aerosol plume 100 km further down-
wind. In all sampling passes downwind of the city, ozone concentrations
outside the urban plume were below the 0.08 ppm Federal Ambient Standard, while
concentrations within the plume were substantially above. Near Hillsboro,
Illinois, 85 km from St. Louis, the ozone concentration reached 0.2 ppm in
the middle of the day.
Skies on August 11 were partly cloudy., with scattered cirrus present
during the morning and early afternoon. The mixing depth was about 0.3 km
at 1000 CDT and reached 1.4 km by 1330 CDT (Figure 4). A weak low in western
Nebraska triggered southwesterly flow in the lower atmosphere, at speeds
somewhat below those of July 18. The mean transport vector lay between 221°
and 243° during the middle of the day, at speeds in the range 16-30 km/hr.
At these wind speeds, the sampling aircraft was progressing downwind at
roughly the same rate as the air.
A distinctive feature of the MISTT program was the characterization
of pollutant concentrations and winds over complete cross-sections of the
urban plume. From the measurements at a given cross-section, the horizontal
mass flow rate of a pollutant across that cross-section can be calculated
directly:
FLOW RATE = u(x,z) (C(x,y,z) - C(x,z)) dy dz,
J A J 0
where x is distance downwind, y,z are cross-wind and vertical coordinates,
u is wind speed (from pilot balloon observations), C is pollutant concentra-
tion (from aircraft measurements), and C is average pollutant concentra-
tion outside the plume (from aircraft measurements). Figure 6 shows ozone
flow rates from three different days, plotted against distance downwind of
the city. The quantities plotted are the flow rates of ozone in excess of
background, and thus represent the specific contribution of metropolitan St.
Louis to atmospheric loadings.
The measurements for Figure 6 were not, in general, made in the Lagran-
gian mode. Moreover, the measureme-ts at less than 50 km from the city were
all made in the morning, while the measurements at greater distances were
all made in the afternoon. It is, therefore, difficult to distinguish be-
tween the contributions of solar elevation and atmospheric residence time
to the increase in the ozone flow rate over the first 100 km. Nevertheless,
it is of interest that the flow rates at 50 km or more from the city cluster
in the range 95-125 T/hr. These numbers may be taken as a rough estimate
242
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OZONF
CHAMPAIGN
A FJOWF:R PLANT
• REFINERY
KH.OME1EHS
76-407
Figure 5. Selected horizontal profiles of ozone concentration and b
downwind of St. Louis on 11 August 1975. Profiles were riSBfded
during traverses of profile baselines at the following altitudes
and times: (starting upwind of city) 455 m MSL, 0744-0758 CDT;
425 m MSL, 1019-1036 CDT; 610 m MSL, 1245-1310 CDT; 760 m MSL,
1442-1508 CDT. Spiral indicates location of vertical sounding
shown in Figure 4.
for the rate at which ozone was formed in the atmosphere from the emissions
of metropolitan St. Louis.
DISCUSSION
The St. Louis urban plume was mapped on a total of eight days during
the July 15-August 15, 1975, MISTT experiment, and ozone was a conspicuous
indicator of the plume during this period. Daytime ozone concentrations
within the plume generally exceeded the 0.08 ppm Federal Ambient Standard,
even on the most distant sampling runs. Peak concentrations in the plume
were typically twice those in the unmodified background air, and surpassed
0.15 ppm on most sampling days. (It should be noted that the object of Pro-
243
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ject MISTT was not to develop a climatology of the urban plume, but to mea-
sure it in detail under conditions favorable for doing so, and sampling days
were chosen according to this criterion.) Earlier measurements by FAPS
had also found excess ozone in the St. Louis urban plume on two days in
April, 1973 (3).
While upwind sources undoubtedly contribute to regional backgrounds at
St. Louis, they clearly do not account for the excess concentrations of the
urban plume, which were consistently found downwind of the city regardless
of the wind regime. On the two days discussed in detail in this paper, the
nearest upwind city of any size was Springfield, Missouri, over 300 km from
St. Louis with only about 100,000 people. Nor is a stratospheric origin for
the excess ozone any more likely; this would not explain the restriction of
high concentrations to the mixed layer, and their alignment with the wind.
Moreover, Figures 2 and 5 show that the excess ozone in the plume is associated
with light-scattering aerosols, which would not be expected in a clean airmass
subducted from the stratosphere. The excess ozone concentrations downwind
of St. Louis must be attributed directly to the emissions of the metropolitan
area.
The most obvious policy implication of the MISTT data is that ozone
control strategies must, to be effective, be formulated on a regional scale.
The 1975 experiment documented, in air 160 km from St. Louis, violations of
the Federal Ambient Standard for ozone which were traceable to emissions from
the metropolitan area. Between 125 and 160 km downwind there was no signifi-
cant decay in the flow rate of ozone and no significant increase in the cross-
wind and vertical dimensions of the urban plume, so that violations of the
standard probably extended much farther out. None of the ground-level ozone
monitors operated by the State of Illinois were situated in the path of the
observed ozone plume, so that the airborne measurements can be compared with
the standard network measurements only in the background air, where they were
consistent (10). Aircraft soundings in the plume (Figures 3 and 4) showed
ozone concentrations to be quite uniform through the mixed layer, however,
and it is probable that the high plume concentrations encountered aloft were
experienced near the surface as well.
The elevated ozone concentrations within the St. Louis urban plume were
superimposed on background ozone levels which were themselves substantially
above those associated with clean air (11). On most sampling days, midday
ozone levels outside the urban plume lay in the range 0.07-0.12 ppm. It is
clear that if the emissions of St. Louis can contribute to the ozone back-
grounds of cities far downwind, then much of the ozone background of St. Louis
itself may not be natural, but instead due to cities and industry far upwind
of St. Louis. There is some evidence that the composition of the upwind back-
ground strongly affects the chemistry of the downwind plume. For example,
unusually high (for St. Louis) peak ozone concentrations were observed on
July 28, 1975, a day of unusually high (for St. Louis) ozone backgrounds
(Figure 1).
The annual emissions of non-methane HC in metropolitan St. Louis are
estimated at about 1.6 x 105 tonnes (10, 12, 13). This corresponds to an
average of 18-36 tons/hr, depending on whether emissions are spread out through
245
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the day or concentrated in the daylight hours. H. M. Walker has pointed out
that if these figures are accurate then the formation of 120 tons/hr of ozone
in the St. Louis urban plume corresponds to a yield of one to two parts (by
volume) ozone for each part (by volume as C) emitted HC (13). This would be a
much higher yield than is typically found in smog chamber studies (14).
Possible explanations for the high apparent yield would include enhanced pro-
duction at low concentrations in the absence of wall losses, and the partici-
pation of incompletely-reacted HC products contributed by the background air.
Hydrocarbon measurements taken during the recently-completed 1976 MISTT experi-
ment may help to resolve this point.
Whatever its origin, the high apparent ozone yield of HC in the St. Louis
urban plume carries important implications for photochemical simulation models.
If most of the ozone produced in the plume is attributable to free radicals
and unreactive HC advected into the city from upwind sources, then the compo-
sition of the background air is a critical input to a simulation model. This
means that successful simulation on the mesoscale is dependent, via initial
and boundary conditions, on successful simulation on the synoptic scale.
Alternatively, if most of the ozone produced in the plume is attributable
simply to the efficient utilization of HC emitted in metropolitan St. Louis,
then the ozone yield of these HC is near the theoretical stoichiometric upper
limit of two to one (15) or four to one (13). This means that the chain
lengths of the reactions involving the more reactive HC species are determined
primarily by the size of the initial HC molecule, and not by a competition
between chain-propagating and chain-terminating reactions as in present lumped
kinetic photochemical models (16).
ACKNOWLEDGEMENT
This research was supported by the U.S. Environmental Protection Agency,
Environmental Sciences Research Laboratory, Aerosol Research Branch.
REFERENCES
1. Haagenson, P. L. and A. L. Morris. J. of Applied Meteorology 13:901,
1974.
2. Stampfer, J. F. and J. A. Anderson. Atmospheric Environment, 9:301,
1975.
3. Breeding, R. J. , P. L. Haagenson, J. A. Anderson, J. P. Lodge, Jr.
and J. F. Stampfer, Jr. J. of Applied Meteorology 14:204, 1975.
4. Breeding, R. J., H. B. Klonis, J. P. Lodge, Jr., J. B. Pate, D. C.
Sheesley, T. R. Englert and D. R. Sears. Atmospheric Environment
10:181, 1976.
5. Wilson, Jr., W. E., R. J. Charlson, R. B. Husar, K. T. Whitby, and
D. L. Blumenthal. Proc. 69th Annual Meeting Air Pollution Control
Assoc., Paper #76-30-06, June 1976.
246
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6. White, W. H., J. A. Anderson, W. R. Knuth, D. L. Blumenthal , J. C.
Hsiung and R. B. Husar. Final Report to LJ.S.E.P.A. on contract number
68-02-1919 by Meteorology Research, Inc., Altadena, California, 1976.
7. Husar, R. B., J. D. Husar, N. V. Gillani, S. B. Fuller, W. H. White,
W. M. Vaughan and W. E. Wilson, Jr. Proc. of the Div. Environmental
Chemistry, 171st National ACS Meeting, New York, April 1976.
8. White, W. H., J. A. Anderson, D. L. Blumenthal, R. B. Husar, N. V.
Gillani, J. D. Husar and W. E. Wilson, Jr. Science, 1976 (in Dress).
9. Ogren, J. A., D. L. Blumenthal, W. H. White, T. W. Tesche and M. K.
Liu. Proc. Int'l. Conf. on Photochemical Oxidants and its Control,
Raleigh, North Carolina, 1976. ( in press)
10. Illinois E.P.A. 1976.
11. Blumenthal, D. L., T. B. Smith, W. H. White, S. L. Marsh, D. S. Ensor,
R. B. Husar, P. S. McMurry, S. L. Heisler and P. Owens. Final Report
to California Air Resources Board on contract number ARB 2-1245 by
Meteorology Research, Inc., Altadena, California, 1974.
12. U.S.E.P.A. 1976.
13. Walker, H. M. Proc. of the Conf. on Ozone/Oxidants, Air Pollution
Control Assoc., Dallas, March 1976.
14. Wilson, W. E., Jr., D. F. Miller, A. Levy and R. K. Stone. J. Air
Pollution Control Assoc. 23:949, 1973.
15. Klauber, G. M., Ph.D. thesis, Johns Hopkins University, 1975
16. Hecht, T. A., J. H. Seinfeld and M. C. Dodge, Environmental Science
and Technology 8:327, 1974.
247
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6-3
LONG RANGE AIRBORNE MEASUREMENTS OF OZONE OFF THE
COAST OF THE NORTHEASTERN UNITED STATES
G. W. Siple, C. K. Fitzsimmons, K. F. Zeller, and R. B. Evans*
ABSTRACT
The. Envpont -in the. noitntQ.n.vi Unite.d States tn. the.
•iuinmeA ofi 7975. An 4.nl>tA.me.nte.d ouAcA&fit w)o6 o6e.d to meo6u/ie ozone and nitsvic.
Q->u.de., and to take, bag AampleA, among otheA paJiam&teAA. kvi tfia^e.ctox.y anal-
y&oA indicate, that the. oJin. mo44 c.onta4.ning kigh ozone. c.onc.e.ntA.ationt> monJJ:otie.d
ove.fi the. kttant-lc. Ocean 250 ItULometeAA e.a!>t oft Wew Vo^tk C^ty pa64ecf oveA that
metA.opotitan an.e.a on the. mox.nJ.ng o& the. day the. mea
-------
INSTRUMENTATION
A field team from the U.S. Environmental Protection Agency's Environmen-
tal Monitoring and Support Laboratory at Las Vegas, Nevada, (EMSL-LV) partic-
ipated in the^NOTS gathering extensive air quality data with the Long Range
Air Monitoring Aircraft (LORAMA) during August of 1975. The aircraft, a
Monarch B-26, was modified to operate as an air monitoring platform. The in-
strumentation on board the aircraft is listed in Table 1. Oxidant, measured
as ozone (Os), was monitored during each flight by a gas-phase chemilumines-
cent Bendix 8002, an instrument which has proven reliable and precise for
field data collection. Nitric oxide (NO) was measured with a TECO 14B single-
channel gas-phase chemiluminescent analyzer, modified for high sensitivity
and low noise. This particular instrument is designed to reliably measure
NOX in the range of 5 parts per billion (ppb) fullscale; but, this instrument
Was not used to monitor total NOx or nitrogen dioxide (N02) at any time dur-
ing the study. Other data routinely collected included coefficient of light
scattering (b$cat), outside ambient temperature, dewpoint temperature, alti-
tude, and navigational position. Bag samples were taken at strategic points
on most flights for subsequent HC analysis by gas chromatography.
There are several important considerations with regard to air pollution
data collected by means of an airborne platform. However, these are discussed
in the literature (Hester et al., 1976) and are not specified here. It should
be mentioned that detailed quality control procedures were an integral part of
the field work; instrument calibration was performed on all instruments before
and after each day's flights, checking both zero and one span level. During
flight, periodic zero input checks were made. These calibration data, along
with altitude correction factors derived from environmental chamber tests
(Siple et al., 1976), were used to process the data into useable engineering
units.
TABLE I. LORAMA INSTRUMENTATION
Parameter
Outside Ambient Temperature
Dewpoint Temperature
Particulate Light Scattering
Altitude
Location
Hydrocarbons
Method/Instrument
°3
NO
Chemi luminescence/Bendix 8002
Chemi luminescence/TECO 14B modified
for low noise/high sensitivity
Integrated circuit/LX5700
Hygrometer/Cambridge 13F-C3
Integrating nephelometer/MRI 1550
Integrated circuit/LX 3702A
Digital DME/Collins DME-40
Bag Samples (Tedlar)
250
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MONITORING STRATEGY
The report of Cleveland et al. (1976), based on ground-level ozone data,
seems to strongly indicate the reality of the pollutant transport phenomenon
in the northeastern U.S. However, one might generally expect micro- and meso-
scale geographical, meteorological, and anthropogenic irregularities within
the study path to adversely affect conclusions concerning broad area phenomena
such as pollutant transport over terrestrial areas. In contrast, air quality
monitoring over oceanic areas offers unique opportunities for experimental
design and data interpretation; the relatively smooth ocean surface provides
simplified conditions for the study of pollutant dispersion. The ocean is
not recognized as a significant source of, or a sink for, photochemical oxi-
dant activity. Although complex interactions between oxidant and the ocean
surface probably do occur, the exact nature of such interactions is not
we!1-defined.
Without such knowledge, and for the sake of simplicity, it can be assumed
that transport and dispersion of oxidant and oxidant precursors by meteoro-
logical means are primarily responsible for the ambient pollutant concentra-
tions over marine areas. Under these simplified conditions, the fate of pol-
lutants originating in littoral areas can be described confidently.
This report examines ozone data collected by the LORAMA over portions of
the Atlantic Ocean off the northeastern seaboard. Perhaps the most signifi-
cant flight was #9, performed on the afternoon of August 14, between 1430 and
1745 Eastern Daylight Time (EOT).
RESULTS AND DISCUSSION
Figure 1 shows the flight path for flight #9, which departed the Naval
Air Station at South Weymouth (NZW) at about 1430 EOT on August 14. The
flight turned south, to begin a spiral over Vineyard Bay, between the Eliz-
abeth Islands and Martha's Vineyard. Figure 1 shows instantaneous ozone con-
centrations in ppb every two minutes, as a function of position, time, and
altitude.
Figure 2 presents the vertical profiles of all data parameters measured
continuously; the spiral began at 2135 meters above mean sea level (m MSL)
and descended to 60 m MSL. One can notice two shallow temperature inver-
sions; the base of the higher one is at approximately 1525 m MSL, the base
of the lower is at approximately 1220 m MSL. The ozone profile, the humid-
ity profile, and the light scattering coefficient profile indicate distinct
patterns related to these inversions. However, one can note the rapid in-
crease in ozone between 200 m MSL and 60 m MSL. This increase would not
appear to be related to a trapped polluted layer since the temperature pro-
file indicates a near adiabatic lapse rate at these lower altitudes. Sim-
ilar measurements on numerous other flights over the ocean corroborate this
observation. This might signify that the air within the mixing layer over
the ocean is not necessarily well-mixed. Unfortunately, the TECO 14B was
251
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24)
94{'30m}
j_7+7 (1310m |>
(1452)72 'A
Figure 1. Flight #9 (August 14, 1975): Flight pattern and ozone
distribution map.
252
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SEA
LEVEL
SEA
LEVEL
0 20 40 60 80 100120140160180200
CONCENTRATION, ppb
-30 -20 -10 0 10 20
TEMPERATURE,°C
30 40
SEA
LEVEL
SEA
LEVEL
0 10 20 30 40 50 60 70 80 90 100
RELATIVE HUMIDITY. %
01 23456789
SCATTERING COEFFICIENT, lO
10
Figure 2. Flight #9 (August 14, 1975): Vertical profiles of parameters
for spiral #1.
253
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non-operational on this particular day so there is little indication as to
the NO precursor values at this point.
At the completion of the spiral, the aircraft flew over Martha's Vine-
yard then headed southward again at an altitude of 335 m MSL. The ozone
concentration continued to increase at this altitude and, at a point about
130 km south of Martha's Vineyard, the aircraft turned east. The ozone val-
ues continued to rise for a short distance, peaking at 214 ppb, then de-
creasing again. Bag samples taken in this area showed relatively high con-
centrations of acetylene (Environmental Protection Agency, 1976). The air-
craft traveled about 110 km in an easterly direction, then turned northward.
The ozone concentration continued to decrease, although there were several
minor maxima and minima along the way. After passing the northern point of
Cape Cod, the aircraft turned west, climbed to 490 m MSL and made a large
circuit of eastern Massachusetts and the ocean just to the east of Boston,
returning to NZW at about 1745 EOT.
The ozone concentrations in the northern circuit (50 ppb to 80 ppb)
were lower than in the southern circuit (100 ppb to 200 ppb). In terms of
ozone concentration, the air monitored in the southern circuit would appear
to have a different history than that monitored in the northern circuit.
If the spiral data taken near the beginning of the flight is a good indi-
cator of the vertical profiles throughout the flight path (i.e., consider-
ing the time difference during the flight), the altitude difference between
the two circuits is of little consequence.
Figure 3 illustrates a trajectory analysis calculated backwards in
time from the coordinates of the southwest corner of flight #9 (bull's-
eye). This is the area where the highest ozone concentrations were re-
corded. The aircraft was in this locality at approximately 1530 EOT.
Three individual trajectories are represented on the figure by the letters
A, C, and D. (These trajectories were prepared using the USAF ETAC tra-
jectory program.) The letter C represents the trajectory of an air mass
between the altitudes of 300 m above ground level (AGL) and 600 m AGL,
terminating at the bull's-eye at 0700 EOT on August 14. The letter D rep-
resents the trajectory of an air mass between the same altitudes terminat-
ing at the bull's-eye at 1300 EOT. Finally, the letter A represents the
trajectory of an air mass between the same altitudes terminating at the
bull's-eye at 1900 EOT. The numbers associated with these letters indicate
the number of 6-hour periods backward in a given trajectory.
It should be noted before any further analysis is forthcoming that any
such trajectory is not solely definitive; there is necessarily an error mar-
gin which brackets the calculated path, compounding the error the further
the trajectory recedes in time from the starting point. The program which
generates these positions attempts to provide macroscale behavior based on a
collection of widespread microscale observations.
Nonetheless, one can say that, in general, the air arriving at the
bull's-eye portion of the flight path before and after flight #9 was from
the northwest through west-northwest. The indicated trajectories C and A
pass over southern New York state and northern New Jersey; all trajectories
pass over portions of Long Island.
254
-------
Figure 3. Computer trajectories for air parcel between 300 m AGL and
600 m AGL for August 14, 1975: A terminates at © at
1900 EOT; C terminates at © at 0700 EOT; D terminates
at © at 1300 EOT.
ISOfEDT
0500EDT
Figure 4. Hand-drawn trajectories for
air parcels at surface level
by time and space, terminat-
ing at 1600 EOT August 14,
1975.
Figure 5. Hand-drawn trajectories for
air parcels at 305 m AGL,
terminating at 1600 EOT
August 14, 1975.
255
-------
Figures 4 through 7 were prepared by hand by our staff meteorologist
and represent a best judgment air trajectory analysis. The basis for these
trajectories is the extensive pibal and radiosonde data collected during the
NOTS. The trajectories in Figure 4, at surface level, indicate generally
westerly flow from early in the morning until late afternoon. Figure 5, at
305 m AGL, shows air flow generally from the west-southwest through west-
northwest. The trajectories in Figure 5, at 610 m AGL, show a more north-
westerly component for the air at this altitude. These figures appear to
offer a rationale for the divergence of measured ozone concentrations in the
different sectors of the flight. These air masses appear to have passed over
land areas with different precursor emission potential; e.g., New York City
vs. upstate Connecticut.
Figure 7 is a combination of the surface trajectory of Figure 4 and the
305 m AGL trajectory of Figure 5. Figure 7 represents a backward trajectory
from points on the flight pattern, suggesting the ground area swept by the
column of air from the surface to 305 m AGL from 0800 EOT to 1600 EOT. Al-
though this is a subjective analysis neglecting vertical motion and based
only on limited data, it can be concluded that a sizeable percentage of the
air arriving at these points at 1600 EOT came from somewhere in the shaded
areas between the surface and 305 m AGL.
160()EDT
1600EDT
Figure 6. Hand-drawn trajectories for air parcels at 610 m AGL, terminating
at 1600 EOT August 14, 1975.
These subjective trajectories compare favorably with the computer-
generated trajectories, and are consistent with the hypothesis that the high
ozone air was influenced by urban sources of ozone and ozone precursors (e.g.,
New York City, Newark), while the low ozone air was influenced by more rural
sources of these air contaminants (e.g., upstate New York). The paucity of
wind data over marine areas and the inherent errors of trajectory analysis
limit definitive conclusions regarding ozone and ozone precursor transport.
256
-------
With due regard for these limitations and the assumption of non-interaction
of the ozone-ocean interface, the present analysis indicates that elevated
ozone values were measured 250 km downwind of the New York City area.
1400MJ
"SLURf^CE
6IJIOEDT
Figure 7.
0800EDT 1100EDT
SURFACE SURFACE1400EDT
SURFACE
Combination of surface and 305 m AGL trajectories showing ground
area swept by air arriving at the bull's-eye at 1600 EOT
August 14, 1975.
CONCLUSIONS
Ozone data collected from an airborne platform over a wide area off the
northeastern seaboard on August 14, 1975, show two basic regimes: high ozone
(>0.08 ppm) in the southern sector of the area, low ozone (<0.08 ppm) in the
northern sector. Vertical profile information suggests that ozone may not be
well-mixed throughout the mixing depth over the ocean. Two separately-
generated air parcel trajectories imply that the high ozone air measured in
the southern flight sector passed over highly urbanized areas of New York and
New Jersey on the morning of August 14, whereas the low ozone air measured in
the northern flight sector was over rural areas of southern New England on
the same morning. This suggests that ozone and/or ozone precursors have been
transported at least 250 km downwind from a large source area.
Transport of air parcels over land surfaces will undoubtedly have a
greater dispersive effect on air concentrations of air parcel constituents
than transport over marine surfaces. However, under suitable meteorological
conditions, transport winds could clearly carry an air parcel from the New
York Metropolitan area as far as the Boston Metropolitan area, the oxidant
burden of which exceeds the National Ambient Air Quality Standard.
257
-------
REFERENCES
Blumenthal, D.L., W.H. White, R.L. Peace, arid T.B. Smith. Determination
of the Feasibility of the Long-Range Transport of Ozone or Ozone Precursors.
Meteorology Research, Inc. Prepared for the U.S. Environmental Protection
Agency, EPA-450/3-74-061, November 1974.
Cleveland, W.S., B. Kleiner, J.E. McRae, and J.L. Warner. Photochemical
Air Pollution: Transport from the New York City Area into Connecticut
and Massachusetts. Science, 191:179-181, 1976.
Environmental Protection Agency, Northeast Oxidant Transport Symposium,
Research Triangle Park, North Carolina, January 20-21, 1976 (to be published)
Hester, N.E., R.B. Evans, D.T. Mage, J.L. Pierett, G. W. Siple, and J. J.
van Ee. Some Considerations in Collecting Valid Data with Airborne Platforms.
Proceedings of Specialty Conference on Air Pollution Measurement Accuracy
as It Relates to Regulation Compliance, Air Pollution Control Association,
Pittsburgh, 1976.
Siple, G.W., C.K. Fitzsimmons, J.J. van Ee, and K. F. Zeller. Air Quality
Data for the Northeast Oxidant Transport Study, 1975: Final Data Report.
U.S. Environmental Protection Agency (to be published).
258
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6-4
AIRBORNE MEASUREMENTS OF PRIMARY AND SECONDARY POLLUTANT
CONCENTRATIONS IN THE ST. LOUIS URBAN PLUME
N. E. Hester, R. B. Evans, F. G. Johnson, and E. L. Martinez*
ABSTRACT
4.nAtnume.nte.d mth aiA pollution monttoAf, we.fie. uAtd to
acteAize. the. uAban plume. o^ mzttopo titan St. Loui6, t4l^^ouAi. Maximum oxi-
dant and paAticulate. c.onc.e.ntsiationt> we.fie. fiound we.lt downwtnd o{ the. cJ
and. ove.fi nuAat aAe.at>. The. maxima fan both ozone, and poAtic.ut.ate. weAe.
fiound to coincide.. A paAc.e.1 ofi aiA, c.hoAacteAU,ttc. ofi a peAiod oft htgh e.mit>-
AionA due. to moaning fiu^k houA tAa^-ic., wai> di^c.oveAe.d within the. uAban plume..
PoweA plant plume.* AupeAimpoAe.d on the. uAban plume. weAe. fiound to de.c.tie.a?>e.
the. c.once.ntfLation ofi ozone. i.n the. uAban plume, fan du>tancu a& Qtiz-at a* 60
k-ilometeAt, .
INTRODUCTION
Several studies during the last 5 years have shown ozone (Os) concentra-
tions that exceeded the federal standards in rural areas. A recent study
by the United States Environmental Protection Agency of the phenomena concluded
that these high ozone values could not be attributed to natural sources (EPA,
1975). The high ozone levels seemed to be related to a combination of local
man-made sources and the transport of ozone and ozone precursors into rural
areas from upwind urban areas.
As part of the Regional Air Pollution Study (RAPS) personnel from the
Environmental Monitoring and Support Laboratory, Las Vegas, Nevada, made a
number of flights with instrumented helicopters to measure ozone and related
parameters in the St. Louis, Missouri, urban plume during the summer of 1975
(Allen 1973). These measurements were requested by the EPA Office of Air
Quality Planning and Standards to aid in developing better criteria for the
siting of monitoring stations for the reactive pollutants nitrogen oxides
(N0x, i.e., NO, N02) and ozone. In this report, the results of five flights
made during July and August are discussed. Further flights in this program
were conducted during the summer of 1976; however, the data have not yet been
analyzed.
*N.E. Hester, R.B. Evans, F.G. Johnson, U.S. Environmental Protection Agency,
Las Vegas, Nevada 89114.
E. L. Martinez, U.S. Environmental Protection Agency, Research Triangle Park,
North Carolina 27711. (On assignment from National Oceanic and Atmospheric
Administration, U. S. Department of Commerce.)
259
-------
A close examination of the data from the 1975 flights provides insight
into the chemical transformations which occur in urban plumes, and reveals
the contribution of the city to the pollution problems of the surrounding
rural areas.
EXPERIMENTAL
INSTRUMENTATION AND TECHNIQUE
The helicopters used in this study were instrumented to measure ozone
(03), nitric oxide (NO), total oxides of nitrogen (N0x), sulfur dioxide (S02),
temperature, dewpoint, particulate light scattering, pressure altitude, air
speed, compass heading, and navigational position. A more detailed descrip-
tion of the helicopters' capabilities, limitations, and instrumentation, and
a description of the data collection and processing techniques have been pub-
lished previously (Hester et al., 1975a, 1975b).
The wind data used in this study were obtained from four stations which
were operated continually by RAPS during the time the helicopter flights
were made. Wind measurements were taken by pilot balloons at approximately
one-hour intervals. The locations of these four stations, indicated as
Pibal 141, 142, 143, and 144, are plotted on the map shown in Figure 1. The
wind data reported in Table 1 represent the mean and standard deviation of
the speed and direction readings taken between 0600 and 1800 Central Standard
Time (CST) at all four pibal stations on the days of the experiments.
TABLE 1. MEAN WIND SPEED AND DIRECTION BY DATE
Wind Speed Direction
Date Altitude (MSL) (Mean 1 Std. Dev.) (Mean 1 Std. Dev.)
July 15, 1976 200M 5.7 MPS +_2.3 198° + 36
250M 5.9 MPS +_ 2.5 200 £ 37
3COM 5.8 MPS +_ 2.6 205 + 40
350M 5.7 MPS +_ 2.7 208 £ 43
July 18, 1975 200M 8.0 MPS + 3.3 229 +_ 21
250M 8.6 MPS +_ 3.7 231 + 18
300M 9.2 MPS +_ 4.1 232 £ 16
350M 10.0 MPS +4.7 232 £ 15
August 3, 1975 200M 5.9 MPS +_ 2.3 10 +_ 16
250M 6.0 MPS + 2.2 12 + 16
300M 6.3 MPS ^2.3 12 £ 16
350M 6.5 MPS ^ 2.5 12 £ 16
August 6, 1975 200M 7.0 MPS +_ 2.9 30 + 18
250M 7.1 MPS + 2.8 31 £ 17
300M 7.1 MPS + 2.8 31 ^17
350M 6.9 MPS + 2.9 32 + 17
260
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H
WEMTZVILLE
RAMS 5TOY
108
GRANITE CITY f COLLINSVILLE
POWER PLANT
PIBAL
PIBAL 144
PETROLEUM REFINERY COMPLEX
EDWARDSVILLE
AST ST LOUIS
CHEMICAL REFINERY
BREWERY SCOTT AIR FORCE BASE
BELLEVILLE
PIBAL 143
SCALE IN KILOMETERS
Figure 1. St. Louis map with aircraft flight patterns superimposed.
Flight patterns for each experiment were planned based on the most recent
forecast of wind speed and direction coupled with the most recent pibal measure-
ments from one or more of the four pibal stations. The point chosen to begin
each day's sampling flight was, by best estimate, along the center!ine of the
urban plume, and near the outer edge of the metropolitan area. The first leg
of each flight proceeded with the wind away from the city at an
305 m (1,000 feet) mean sea level (MSL). Ground elevations in
altitude of
the St. Louis
area are typically 120 to 180 m MSL. The helicopter maintained a constant
air speed of 111 kilometers per hour (60 knots). A maximum was sought in
261
-------
pollutant concentration as the aircraft proceeded. On morning flights, the
maximum in NO concentration was sought, and on afternoon flights, the maximum
in ozone concentration was sought. The first leg of each flight proceeded
past the point of the pollutant maximum until pollutant levels had ceased to
fall sharply. At this point, a 180° turn was made. In some flights, where
it was desired to better define the plume, the return leg proceeded all the way
back to the starting point. However, most of the flights returned directly
to the point of maximum pollutant concentration along the flight path, and then
proceeded to fly a cross section of the urban plume.
The cross sections were determined by flying flight legs at 90° to the wind
direction at 305 m MSL until the outer boundaries of the plume were defined. In
some cases, the cross section revealed that the estimates of the position of the
plume center!ine had been somewhat in error, and higher pollution levels were
found.
After the cross section was completed, the aircraft returned to the
position of the maximum ozone or NO concentration and performed a vertical
distribution of pollutants.
RESULTS BY DATE
July 15. 1975 (Afternoon)
On this date, the wind was steady from the south (see Table 1) and the
flight patterns shown on Figure 1 as AB and CD were flown. The data from
these flight patterns and from the vertical spiral are shown in Figures 2a,
2b, and 2c.
The data in Figure 2a from the flight down the plume axis, AB, revealed
that the maximum ozone concentration (approximately 0.14 ppm) was 25 km downwind
of B, the point closest to the city (approximately 40 km downwind of center
of the city). The ozone maximum corresponds with the maximum light scattering
coefficient (B .) reading, and with NO and S02 levels that were so low that
they were at the noise level of the instruments. Near the furthest point
out on the flight, point A, a sudden rise in S02 concentration and a sharp drop
in ozone concentration were observed. This observation was attributed to
wind direction, and the plume from the Portage des Sioux power plant (indica-
ted in Figure 1, just north of the city) intersected the flight path. The
power plant plume could be followed visibly to this general area.
The data in Figure 2b from the cross section flight (CD) shows that the
width of the urban plume looking at 0^ levels was about 20 km and had a skewed
shape. Evidence for mixing of the urban plume with the power plant plume was
not evident in the cross section data. It is possible that the power plant
plume was elevated above the flight altitude and did not descend to flight
levels until it reached the vicinity of point A.
The vertical profile through the urban plume (Figure 2c) shows that there
were three temperature inversions over the area at the time of the flight,
at about 400 m, 500 m and at 900 m. The inversions did not have a strong
effect on the pollutant profile with the exception that the NO levels showed
262
-------
040-r
-,-30
000
14 1
14 0 13 9 13 8
TIME.HOURS(CST)
OISTANCE(km)
2>
AXIAL PATTERN
41
A
- 010--
000
147 MB M9
TIME.HOURS(CST)
0 DISTANCE(km) 35
C 0
2b
CROSS-SECTION PATTERN
Figure 2a. Data, collected July 15, Figure 2b. Data, collected July
1975, from flight pattern AB 1975, from flight pattern CD
(Figure 1). (Figure 1).
15,
a drop below the lower inversion. The pollutant profiles generally indicated
a trend of decreasing concentrations with increasing altitude, with the excep-
tion of S02 whose concentration was too low to measure accurately.
July 18, 1975 (Morning and Afternoon)
A steady wind from the southwest (see Table 1) determined the flight
pattern shown in Figure 1 for this date. Two sets of flights were made, one
in the morning and one in the afternoon. The morning set of flights sought
263
-------
1000-r
750- -
500- •
250
100
03{PPM)
140 000 DOS
NOIPPM)
010
020 030 040 002 002
NOX|PPMI S02IPPM)
300
B SCAT(10 4M
Figure 2c. Pollution data collected July 15, 1975, vertical spiral through
urban plume (15:23-15:43 CST).
data on the maximum NO concentration in the urban plume, and the afternoon
set of flights sought data on the ozone maximum.
The morning flight followed the patterns shown in Figure 1 as EF and GH.
The data from these flight patterns and from a vertical spiral are shown in
Figures 3a, 3b, and 3c. Maxima for NO and B . occurred approximately 30 km
downwind from point F; however, operator misjuagment resulted in the cross
section of the plume being measured approximately 10 km downwind of where
the morning NO maximum occurred. By judging where sharp changes occur in
pollution levels in Figures 3a and 3b, particularly B . readings, it is
possible to see that there is a parcel of air with higner primary pollutant
levels within the urban plume that is approximately 44 km long and 15 km
wide. The existence of such a parcel could be explained by assuming that
the city produces a large pulse of NO and particulate during the morning traf-
fic rush, and that the parcel of air containing these pollutants moves down-
wind more or less intact.
The morning vertical profile, Figure 3c, revealed a great deal of tempera-
ture variability. Two low-level inversions were present at approximately
400-500 m and a series of inversions occurred above 750 m. The pollutant
profiles did not appear to be correlated to the temperature profiles, and in
general did not show a consistent pattern.
Patterns FI and JK in Figure 1 were followed on the afternoon flight
of July 18. The data from these flights are plotted in Figure 4a, 4b, and 4c.
The ozone concentration in the urban plume reached a maximum approximately
50 km downwind of the starting point of the flight, point F. At this maximum,
the ozone concentrations reached a level that was twice that seen in the
morning flight at the positions of highest NO and B . and was above the
federal standard of 0.08 ppm. The maximum B . occurred at the same location
as the maximum ozone readings; and the maximum B level was approximately
the same as seen in the morning flight. The NO IHB NO maximum concentrations
were about one-half to one-third lower than morning levels, and it was no longer
possible to define distinct boundaries for the parcel of air which was seen
264
-------
-r 30
-.30 Z
_040T V X
94
9 2
TIME.HOURS(CST)
OISTANCE(km) 49
E
3i
1051 1050 1046 1042
TIMt HOURS(CST)
0 DISTANCEIkm) 18
H G
3b
AXIAL PATTERN
CROSS-SECTION PATTERN
Figure 3a. Data, collected the morn-
ing of July 18, 1975, from flight
pattern EF (Figure 1).
Figure 3b. Data, collected the morn-
ing of July 18, 1975, from flight
pattern GH (Figure 1).
265
-------
z
z
UJ
a
1000 - -
750 _.
500 -.
250
000
005
03(PPM)
010
005
010
NO(PPM)
H
015 000 010
NOX(PPM)
020
20 30
B SCATI10 4M ')
200
30 0
TEMP(°C)
Figure 3c. Pollution data collected the morning of July 18,
spiral through urban plume (10:77-10:88 CST).
1975, vertical
during the morning flight.
Comparing the maxima for individual pollutants can be misleading. The
pollutant burden can provide a better understanding of the quantities of
pollutants that have been produced. For example, the maximum B . readings
were about the same in the morning and afternoon flights; however, the volume
of air in which these concentrations were distributed was much larger in the
afternoon, as indicated by the difference in plume widths shown in Figures 3b
and 4b, and the difference in vertical profiles shown in Figures 3c and 4c.
These differences indicate that there had in fact been a large production of
particulate matter in the plume as it has moved away from the city., Similar
consideration should be applied to the other pollutants in order to get a
proper picture of the plume impact on the surrounding rural area.
The vertical temperature profile through the plume during the afternoon
showed none of the temperature inversions present in the morning. The verti-
cal pollutant profiles from the afternoon study were similar to the morning
profiles in that they revealed little in the way of a definable pattern.
August 3, 1975 (Afternoon)
The wind on this date was from the north-northeast (Table 1) and the
patterns shown in Figure 1 as LM and NO were flown during the early afternoon.
The data are presented in Figures 5a, 5b, and 5c. August 3 was a Sunday, and
this set of data provides a picture of the weekend urban plume which can be
compared to the weekday plume characteristics in the other studies. The maximum
ozone concentrations in the plume (again levels above the federal standard)
were found 17 km downwind from the flight starting point, point L. As seen
in previous studies, the position of the maximum B . readings generally
corresponds to the position of the maximum ozone ridings. The NO readings on
266
-------
006-r-
-r*0
070--
050--
400 -r
36 0--
< 320--
28 0'
T220
- -20 0
180 jr
Q.
- -16 0
020 -r
13 0 13 2 13 4
TIME.HOURS(CST)
OISTANCE(km)
4a
88
I
020 T.
Z
t. 010
000 - •
•^r 4 0
z
*
-.30 o
U
C/l
--20 O
_ 060 -i-
050- -
-1-010
a.
o.
- - 005 o
000
34 OT
32 0--
= 300 +
4
28 0. .
--220
- -200
- -18 0
160
000
14 0 13 9 13 8
TIMt.HOURS(CST)
DISTANCE(km) 37
J
4b
AXIAL PATTERN
Figure 4a. Data, collected the
afternoon of July 18, 1975, from
flight pattern FI (Figure 1).
CROSS-SECTION PATTERN
Figure 4b. Data, collected the
afternoon of July 18,1975, from
flight pattern JK (Figure 1).
267
-------
1000T-
750- -
500- -
ObO
100 000 006
NOiPPM
010
010 020 0?0 000 020 2 '
NO),iPPMI S02iPPM|
30 3 b JO 0 30 0
B-SC«T IfMPl'C)
Figure 4c. Pollution data collected the afternoon of July 18, 1975, vertical
spiral through urban plume (14:27-14:45 CST).
flight pattern LM were at the noise level of the instrument. The N0x readings
were somewhat elevated in the plume, and remarkably consistent throughout the
entire flight. The S02 readings -were elevated near the farthest point on the
flight pattern, point M. These high S02 levels are probably clue to the point
sources along the Mississippi River whose full impact is better seen in the
cross section flight pattern.
The cross section of the plume is extremely interesting in that it not
only provides insight into the character of the urban plume, but also insight
into the effects of large point source plumes superimposed on the urban plume.
The data collected near point N (Figure 5b) show high SOg and N0x readings.
The most probable source of the 502 is the Portage des Sioux power plant
located north of the city and approximately 60 km from the point where the
measurements were made. The Portage des Sioux plume could be observed visually
over the city approximately 30 km from the source heading toward the area
where the measurements were made. Further,, there are no other point sources
upwind capable of producing a plume with the measured concentrations and with
a plume width of approximately 6-7 km (Figure 5b). At the other end of this
cross section flight pattern, point 0, high S02 levels were again observed,
as well as high B ., and the highest ozone readings. These high readings
can be attributed to a number of point sources along the Mississippi River.
The refinery complex at Wood River, Illinois, the power plant near Granite
City, Illinois, and a brewery in St. Louis, Missouri, were all upwind of point
0. All of the listed sources could contribute to the S02 arid particulate
levels. The refinery is a large source of hydrocarbons and NO which could
have acted as precursors for the photochemical production of ozone and additional
particulates.
The vertical profile of the plume, Figure 5c, showed a temperature in-
version layer at 850 m. The inversion seemed to have little effect on the
pollutant profiles. The pollutant levels remained fairly uniform with alti-
tude.
268
-------
000
080-r-
060--
T 005
:20.0- •
too- -
-- 20 0
-.100
015-,-
f
005- -
000.
13 6 13 5
TIME.HOURS(CST)
DISTANCE(km)
5i
134
27
M
AXIAL PATTERN
Figure 5a. Data, collected August
3, 1975, from flight pattern LM
(Figure 1).
-i-30
020 ...
000
139
TIME HOURS(CST)
DISTANCE(km)
5b
25
0
CROSS-SECTION PATTERN
Figure 5b. Data, collected August
3, 1975, from flight pattern NO
(Figure 1).
269
-------
1000—
055
060
03(PPM|
065
005
NO (PPM |
010
NOX(PPM)
000
S02(PPM)
HI-
010 20
B SCATIHI '
3 0
200 250
TEMPfC)
Figure 5c. Pollution data collected August 3, 1975, vertical spiral
through urban plume (14:65-14:97 CST).
August 6, 1975 (Afternoon)
Winds from the north-northeast caused pattern LP and QR to be flown.
The pattern with the plume, LP, showed that the maximum ozone concentration
was 45 km downwind of the flight starting point (Figure 6a). The highest
B . values again occurred with the highest ozone levels.
scat
The cross section of the plume, pattern QR, revealed a well-defined
urban plume with a width of about 30 km (Figure 6b). A slight depression in
ozone concentration was seen near point R. Correspondingly high concentrations
of oxides of nitrogen occurred at the same location as the depression in
ozone. The NO were probably produced by a point source along the Mississippi
River.
The vertical profile, Figure 6c, showed a low level temperature inver-
sion at 365 m. A slight elevation in ozone and N0x concentration is seen
below the inversion but such a tendency was not apparent for the other pollu-
tants.
CONCLUSIONS
This paper has reported the results of studies of the St. Louis urban
plume on four days during the summer of 1975. Although the studies were
done under a variety of meteorological conditions, several general conclu-
sions can be made.
• The St. Louis metropolitan area produces a well-defined urban plume
that could be easily traced 100 km downwind of the city.
• The St. Louis urban plume causes significant degradation of the air
quality extending into rural areas downwind of the city. On July 15
and 18 and August 3, 1975, maximum ozone readings in excess of the
270
-------
OOt T-
s
a.
a.
000--
-.-30
--20
040
240-,-'
23 0--
-T-160
--J40
020-r
010-
128
-I
130
TIME.HOURS(CST)
DISTANCEIkm)
6a
AXIAL PATTERN
13.2
49
P
100-1-
• 0000- -*
A
-r 25 _-
--20
I
a.
u
H-^
O.
13 5 13 6 137
Q TIME HOURS(CST) R
0 DISTANCEikm) 33
6b
CROSS-SECTION PATTERN
Figure 6a. Data collected August Figure 6b. Data collected August
6, 1975, from flight pattern LP 6, 1975, from flight pattern QR
(Figure 1). (Figure 1).
271
-------
1000-r
750- •
500- -
250.
070 080
03|PPM)
005 000 005
NQ(PPM)
010 020 030 000 005
NOX
-------
ozone and B . readings reached their highest values well downwind
of the city^cat ,
• Power plant plumes within the urban plume appeared to cause
depletion of ozone in the area of impaction on the urban plume.
The plume from the Portage des Sioux power plant was observed im-
pacting within the St. Louis urban plume on two separate days, July
15 and August 3, 1975. Depletion of ozone was observed at distances
up to 60 km from the power plant.
DISCUSSION
Davis et al. (1974) reported studies of the effects of power plants on
ambient air quality in the Washington, D. C., area. Depletion of ozone in
plumes downwind of the power plants was found by Davis at distance <_ 24 km,
and a net increase in ozone concentration relative to air surrounding the
plume was found beyond 24 km. The results reported in this work show de-
pletion of ozone at 20 km from a power plant on July 15. This agrees with
Davis' work. However, the data reported for August 3 revealed that the
ozone depletion occurred to distances of 60 km, a significantly greater distance
than reported by Davis. The Portage des Sioux power plant investigated in
this study burns only coal in a cyclo burner system which emits fairly high
concentrations of NO. The plant studied by Davis burned a fuel mixture of
75% oil and 25% coal. It is probable that the difference in combustion
characteristics of these two plants could possibly explain the differences
in effects of the power plant plumes. The Portage des Sioux plant probably
emits higher levels of NO than the plant studied by Davis and causes depletion
effects of the plume to be seen for greater distances.
White et al. (1976) reported results of measurements of ozone and light
scattering aerosols in the St. Louis plume on one of the same days covered
in this report. The results and conclusions reported in this work are in
essential agreement with those of White with one major exception. White assumed
that a quasi-Lagrangian interpretation could be made on the urban plume, and
that transport and emission parameters changed so slowly that neighboring
points in the plume could be reasonably compared. Flux measurements were
calculated based on this assumption. It is felt that their assumption is in
error and validity of such flux calculations is open to question- It is general-
ly known from ground-based measurements that urban areas produce relatively
high levels of pollutants during the morning and evening rush traffic periods.
Demerjian et al. (1974) recently discussed this phenomenon in their review
of photochemical smog formation. The data in this report, collected during
the morning of July 18, indicate that the St. Louis metropolitan area emitted
a pulse of highly polluted air during the morning traffic period, as expected,
and that this pulse was moving downwind within the plume. Given that such a
parcel of air existed within the plume, it cannot be assumed that adjacent
points in the plume are comparable. Quasi-Lagrangian assumptions cannot be
made unless the size and position of such a parcel of air is carefully documented
during the time period when the plume was studied. White et al. made no such
documentation.
273
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REFERENCES
Allen, P. W. 1973. Regional Air Pollution Study - An Overview. Paper No. 73-21
Proceedings of the 66th Annual Meeting, Air Pollution Control Association.
Davis, D. D., G. Smith, and 6. Klauber, 1974. Trace Gas Analysis of Power
Plant Plumes via Aircraft Measurement: 03, NO , and SOa Chemistry.
Science 186, 733-736.
Demerjian, K., J. Kerr, and J. Cglvert. 1974. The Mechanism of Photochemical
Smog Formation. Advances in Environmental Science and Technology Vol. 4,
1-262, John Wiley and Sons, New York.
EPA. 1975. Control of Photochemical Oxidants-Technical Basis and Implications
of Recent Findings. EPA-450/2-75-005.
Hester, N., R. Evans, C. Fitzsimmons, D. Mage, and M. Price 1975a. Helicopter
Platform Air Pollution Data, I. The RAPS Program. Paper No. 75-40.4,
Proceedings of the 68th Annual Meeting, Air Pollution Control Association.
Hester, N., R. Evans, D. Mage, S. Pierett, G. Siple, and J. van Ee. 1975b.
Some Considerations in Collecting Valid Data with Airborne Platforms.
Proceedings, Speciality Conference on Air Pollution Measurement Accuracy
as Relates to Regulation Compliance, Speciality Conference, Air Pollution
Control Association, New Orleans, Louisiana, October, 1975, pp 73-86.
White, W., J. Anderson, D. Blumenthal, R. Husar, N. Gillani, S. Fuller,
W. Wilson. 1976. Formation and Transport of Secondary Air Pollutants:
Ozone and Light Scattering Aerosols in St. Louis Urban Plume. Proceedings,
171st National Meeting, American Chemical Scoiety, New York, New York.
(In Press)
274
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6-5
OZONE IN HAZY AIR MASSES
R. B. Husar, D. E. Patterson, C. C . Paley and N. V. Gillani*
ABSTRACT
A coie Atady o& high ozone conce,nttatiom> in. a. synoptic tcale. hazy ait
maf>& (blob] oval the. e.a>>te.tn halfi of, the, U.S. -it, te.potte.d. The. data, bcue
includes (a) U.S. dJe.athe.t Smu.ce Network &ot hoatly visibility obAdtvationt,
(300 Atation*}; (b) the. National Ax> Scmpting Ne.twotk f,ot daily Aal&ate. (60
AtationA -in za&teAn U.S.); and (c) the. SAR0AP data ba4e o^ EPA &on daily
peafe ozone conce.nttation (90 Atationt -in -
te.nce. and tsiantpofit o& a Aynopt^ic Acate. hazy blob. C onto at plotA oft ozone.
alfto te.ve.al latge. ate.a6 u)ith e£eua,ted ozone le.ve.l&, uiho&e. locat-ion and spa-
tial extent conAej>pond toaghly with tho&e. o& the. hazy btob&. Long te.tm ob-
&e.tvationA ofi ozone, and hazinu* at a tingle, station in St. loud* 4now the.
pte.vale.nce. ofi high ozone. ie.veLt> on hazy dayt. Ba^ed on thi& ca&e. btudy, it
i& not poAAible. to conclude. whethe.t Adl^ate. ^otmation it, enhanced by the.
o^ e/euated ozone le.ve.1-^.
INTRODUCTION
In this paper, we report a case study of an episode of high ozone con-
centrations in synoptic-scale hazy air masses over the eastern half of the
United States. In recent years, ozone concentrations well in excess of the
ambient air quality standard (0.08 ppm) have been observed in rural areas at
distances of several hundred kilometers from known sources of ozone precur-
sor gases (Coffey and Stasiuk, 1975). Rural ozone may be a product of at-
mospheric reactions involving anthropogenic (White et al., 1976) as well as
biogenic emissions, and may also be due to the downward mixing of strato-
spheric ozone. The relative contributions of the various sources of rural
ozone, and the role of synoptic meteorology, are not quantitatively estab-
lished. High rural ozone concentrations, however, have been observed most
frequently inside large slow-moving high pressure cells in midwestern and
eastern U.S. (Ripperton and Worth, 1973).
The occurrence of large hazy air masses containing sulfate concentrations
in excess of 20 yg/m3 have also been reported recently (Hall et al., 1973;
Husar et al., 1976). The present work was initiated to examine whether syn-
optic scale hazy air masses with high sulfate levels also contain high levels
of ozone. It was hoped that certain relationships could be found between
^Washington University, St. Louis, Missouri.
275
-------
these two noxious secondary pollutants which would shed some light on their
origins.
The method of analysis is based principally on inspection of contour
plots of sulfates, ozone and ground visibility data over the eastern half
of the U.S. Air parcel trajectory analyses, surface wind data and local
measurements of the pollutants in St. Louis are also consulted. The spatial
and temporal density of the data base for national sulfate distribution is
sparser than that for ozone. However, hourly surface visibility observa-
tions reported routinely from several hundred weather stations have been
used previously as an effective surrogate for sulfate data during air pol-
lution episodes (Husar et al., 1976).
DATA BASE FOR THE ANALYSIS
The following three sources of data have been utilized in this work.
U.S. WEATHER SERVICE NETWORK FOR HOURLY OBSERVATIONS (SERVICE A)
Values of ground level visual range and other weather parameters are
recorded every hour at several hundred stations distributed over the U.S.
The data from about 300 of these stations (Figure la) are available on mag-
netic tapes supplied by the National Climatic Center, National Oceanic and
Atmospheric Administration (NOAA). The high spatial density of this net-
work permits the meaningful use of computer contour plotting techniques.
Using the visibility data, the spatial extent, the temporal evolution and
the transport of hazy blobs* may be followed for several days by inspection
of chronological visibility contour maps (Husar et al., 1976). Noon visi-
bilities were chosen to minimize the effect of early morning high humid-
ities. The noon relative humidity for inland stations ranged between 50 and
THE NATIONAL AIR SAMPLING NETWORK (EPA) FOR SULFATE
Hi-volume filter samples collected over 24-hour periods by this network
are routinely analyzed for sulfate. The samples are collected every 12 days,
simultaneously at all sampling locations. For the present analysis, we were
able to obtain sulfate data for about sixty NASN locations in the eastern
half of the U.S. The spatial distribution of these stations is shown in
Figure Ib. Isopleths of sulfate concentrations are plotted manually from
the available data at 12-day intervals.
THE SAROAD DATA BASE (EPA) FOR OZONE AND TOTAL OXIDANT
Ozone and oxidant concentrations are recorded regularly at aerometric
monitoring stations reporting to the U.S. EPA. Hourly average values are
obtained from EPA's SAROAD data bank for 89 sites located in the eastern
half of the U.S. (Figure Ic). For each station, the diurnal ozone pattern
*In the context of this report, "blob" is used synonymously with "hazy air
mass."
276
-------
(a) (b) (c)
Figure 1. Geographical distribution and density of network stations:
(a) National Weather Service Network for visibility; (b) Na-
tional Air Sampling Network for sulfate; (c) EPA/SAROAD net-
work for ozone.
was inspected and the daily peak concentration was chosen as the ozone level
of the air mass. Subsequently, contour plots were prepared for each day of
the episode based on these peak observations. Examples of data obtained by
SAROAD stations are shown in Figure 6. In the upper part of the figure, the
hourly average ozone concentrations are shown at station No. 7 of the
St. Louis city-county monitoring network. The data exhibit the typical di-
urnal pattern consisting of near-zero readings overnight and in the early
morning, rising to a peak in the early afternoon followed by a drop in the
evening hours.
Although it is not clearly documented in the literature, it is reason-
able to assume that the low overnight concentrations are the direct conse-
quence of physical and chemical removal processes that tend to scavenge
ozone from the atmospheric surface layer. It has been shown that the ozone
concentration above the surface layer does not exhibit this diurnal pattern
(Coffey and Stasiuk, 1975). Coffey and Stasiuk (1975) also gave evidence
that ozone measurements near the surface obtained during the convectively
active noon hour are representative of the ozone concentrations in the air
mass in the absence of positively or negatively interfering local sources.
Thus, the ozone concentration of the mixed layer air mass may be estimated
from the envelope of the daily peak concentrations.
RESULTS
The relationship between ozone and haze is examined through a case
study of a large hazy air mass that resided over the eastern U.S. for an
estimated two weeks. Successive contour maps of noon visibility (Figure 2)
are plotted for every second day from June 25 through July 5, 1975. Inspec-
tion of the sequence of maps reveals that multi-state regions are covered
with a haze layer in which the noon visibility is less than 6 miles. From
long range trajectory calculations and surface wind information, it was
determined that the air mass of June 25 within which the visibility was
less than 6 miles was of maritime origin in the Gulf of Mexico. This air
mass had been transported in a northerly flow across Louisiana, Arkansas,
277
-------
JUNE 27, 1975
JULY I, B75
Figure 2. Sequential contour plots of ground visibility at 1200 CST
(b t = 3.92/visibility range).
Illinois and Indiana. Between June 25 and 27, a NNE trajectory prevailed
in the southern states; but, relative stagnation prevailed in the Great
Lakes region. During this stagnation, the air mass became increasingly
hazy. Thereafter, an easterly flow developed causing the hazy blob to drift
slowly westward, passing over St. Louis, Missouri, on June 28-29, and con-
tinuing across Missouri and Kansas (June 30), and then drifting into Iowa
and Minnesota (July 1,2).
The surface wind pattern at noon of June 30 is shown in Figure 3.
Observe the clockwise circulation in the Great Lakes region. By July 3,
the blob had circled over Lake Michigan continuing its residence over the
high pollutant emission density regions of the northeast. In the next two
days, however, a cold Canadian front advanced southward at a relatively rapid
pace, sweeping the hazy air mass ahead of it. St. Louis once again experi-
enced substantially reduced visibility on July 3-4 as the hazy air mass
passed over it. By July 5, visibility deteriorations to less than 4 miles
were experienced in Atlanta, Georgia, Birmingham, Alabama, and Tallahassee,
Florida. Air trajectory analysis confirmed this southward motion of the blob.
During the above episode, sulfate data were obtained arid plotted for
June 23 and July 5, 1975. A close relationship has been observed between
the spatial extent of the hazy air mass and high sulfate concentrations as
shown in Figure 4. On June 23, the blob was located east of Lake Erie
where sulfate concentrations over 30 yg/m3 were measured. On July 5, both
the haziness and high sulfate levels were reported in the southeastern U. S.
(Georgia and Alabama). The coincidence of hazy air masses and high sulfate
concentrations on these two days confirms the utility of visibility obser-
vations as a qualitative surrogate for sulfates.
Contour plots of the daily maximum ozone concentrations are shown in
278
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JUN 38
"/-
S.Y-
, rr
^ / /,
A i
y/ s
"
Figure 3. Surface wind direction pattern at weather stations for 1200 CST
on June 30, 1975.
JUNE 23, 1975 f \
JUNE 23, 1975
\*
SULFATE CCWC (ng/tn3)
^B 20 to 3O
1771 10 to 20
JULY 5, 1975
JULY 5, 1975
EZ3 4 to 6
IH 6 to 8
Figure 4. Comparison of contour plots of noon visibility and daily aver-
age sulfate concentration for June 23 and July 5, 1975.
Figure 5. Inspection of the corresponding contour plots for ozone and
visibility (Figures 5 and 2, respectively) reveals that the geographical
location of high ozone concentrations roughly corresponds to the areas of
low visibility (and high sulfate). As may be anticipated, however, the
correlation with haziness (low visibility) is much better for sulfate than
for ozone.
Contours of daily maximum ozone concentration for June 25, 1975, show
that an area of approximately 1000 square kilometers, located halfway be-
tween the Gulf of Mexico and the Great Lakes, had ozone concentrations in
excess of .08 ppm. The air parcel trajectory followed a northerly course
during that day. It is worth noting that, on that day, the haziness (Figure
2) developed somewhat farther north (i.e. later along the trajectory) com-
pared to the area of high ozone levels. The spatial extents of ozone and
279
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JUNE 25
i '..
<-. A
JULY I
JULY 3
JULY 5
OZONE CONC (ppm)
IB > 16
• 12 to 16
EZ2 .08 to 12
CZI <08
Figure 5. Sequential contour plots of daily
peak ozone concentration.
haze areas roughly coincided on June 27 as the air mass stagnated. During
the following days of the episode, high ozone levels (>0.08 ppm) continued
their presence in the same approximate region of the U.S. where the haziness
predominated. As the hazy air mass moved to the south by July 5, elevated
ozone levels were comparatively suppressed immediately behind the front, but
continued to be over .08 ppm farther to the north and west.
The possible relationship between hazy air masses and high ozone con-
centrations may also be studied by the analyses of long-term observations
of visibility and ozone at fixed locations. The lower part of Figure 6
shows the three-month variation of the extinction coefficient (bex^ =
3.92/visual range). The visibility data were recorded at a St. Louis air-
port. The passage of the hazy blob observed previously over St. Louis is
280
-------
25-
20-
15-
10-
05-
OZONE
^~7Jfflllllfe MtolMJI
08
150-
.120-
~ 90-
• 60-
30 -}\
JUNE
JULY
AUGUST
Figure 6. Comparison of long term observations of ozone and light extinc-
tion coefficient, bext = 3.92/visibility, at an air monitoring
station in St. Louis, Missouri.
clearly shown by the two peaks of June 28-29 and July 3-4. Comparison of
peak ozone concentrations and visibility data for June, July, and August
1975 shows that ozone levels above the standard roughly coincide with hazi-
ness corresponding to bexj- greater than 5.
DISCUSSION
The above data analysis provides some evidence that synoptic scale
hazy air masses also contain elevated ozone concentrations. This evidence
is based on only one case study, and is weaker than the observed corre-
spondence between sulfate levels and haziness. A possible explanation for
the simultaneous occurrence of high ozone-haze-sulfate levels may be given
on simple meteorological grounds: in stagnant or slow-moving air masses,
precursor gases for ozone and light-scattering aerosol are emitted and mix-
ed, leading to an accumulation of these secondary pollutants due to the low
ventilation coefficient. It is likely that this mechanism is the primary
cause of synoptic scale air pollution phenomena. A more intriguing question
is whether these two pollutants have a synergistic effect upon each other's
development. Does the presence of high ozone concentrations promote the
oxidation of sulfur dioxide to sulfate?
ACKNOWLEDGEMENT
This research was supported by the U.S
Environmental Sciences Research Laboratory,
Carolina. We wish to express our thanks to
the St. Louis County Health Department.
. Environmental Protection Agency,
Research Triangle Park, North
W.E. Wilson, Jr., N. Turcu, and
REFERENCES
1. Coffey, P.E. and W.N. Stasiuk. Evidence of Atmospheric Transport
of Ozone into Urban Areas. Environmental Science and Technology
9(l):59-62, Jan. 1975.
281
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2. Hall, P.P. Jr., C.E. Duchon, I.E. Lee and R.R. Hagan. Long-Range
Transport of Air Pollution: A Case Study. Monthly Weather Review
101:404, Aug. 1970.
3. Husar, R.B., N.V. Gillani, J.D. Husar, C.C. Paley and P.N. Turcu.
Long-Range Transport of Pollutants Observed Through Visibility
Contour Maps, Weather Maps and Trajectory Analysis. Preprint, Third
Symp. Atmos. Turb., Diff, and Air Quality, American Metrological
Society, Raleigh, N.C., Oct. 1976.
4. Ripperton, L.A. and J.J.B. Worth. Interstate Oxone Studies. Second
Joint Conf. on Sensing of Environmental Pollutants, Washington, D.C.,
Dec. 1973.
282
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SESSION 7
OZONE/OXIDANT TRANSPORT - II
ChcuUunan: A. P. Altshuller
Environmental Protection Agency
283
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7-1
THE TRANSPORT OF PHOTOCHEMICAL SMOG ACROSS THE SYDNEY BASIN
R. Hyde and G. S. Hawke*
ABSTRACT
A cloAAifiication ofi ozone, tnaczA and AuA^ace. wind ne.condA fan Sydney
AhowA that high conce.ntnationA can OCCUA -in both, moaning dnainage. filow and
a&teAnoon Ae.abAe.e.ze.A. SuA&ace. wind tAajuctoAieJ* dusting the. manning confainm
the. importance, ofi cold ain drainage. in adve.cting ox.idant pAe.cuAAoAi> £nom
inland AouAceA towandA the. coaAt. k^t&inoon tnaje.ctonieA Ahow that polluted
aiA iA tnanAponte.d back inland acnoAA the. baAin into a>ie.at> deA-ignatzd O4
induAtsiiat and population growth ce.n&ie.&.
Me.aAuAe.me.ntA o^ the. ve.Atical AtAactuAe. o& Mind and tzmpeAotuAe. oveA
Sydne.y indicate, that the. ^ofimation oft photoche,mical Amog duAing the. manning
iA infi£ue.nce.d by thA&e. distinct £ayeAt> beJ.ow the. top o^ the. Au.bAide.nce.
inveAAion. JheJ>e. conAiAt ofi a AhaJULow tocai dAainage. fatow appAox.imateI.ij 100
m de.e.p, which lateA meAg&A with a ne.gional drainage. ^Low and &oAm£ a weJUl-
(noted tayeA 200-300 m deep. JkiA layeA iA capped by an inveAAion and main-
tainA an appnoximateJly constant de.pth fan AaveAai houAA beJLow the. gAadie.nt
Mind &tow. OveA thit, peAiod, ozone. conce.ntAationA continue, to incAe.aAe. and
only de.cAe.aAe. with the. onAival o& a Ae.abme.ze. on whe.n AuAfiace. he.ati.ng dutAoyA
the. capping inveAAion allowing the. Qn.adie.nt wind to ne.ach the. gnoand.
INTRODUCTION
Sydney is located within a coastal basin at latitude 35°S on the east
coast of Australia. Details of the topography, given in Figure 1, show the
overall basin bounded by a plateau 150 m high to the north and another in
the south, with the Blue Mountains to the west. Minor ridges, extending
north from Campbelltown and northwest from Botany Bay, divide the region
into the Hawkesbury Basin to the west, the Liverpool Basin to the southwest,
and the Parramatta River Valley to the east.
Unlike Los Angeles, Sydney does not experience semi-permanent maritime
inversions, but comes under the influence of subsidence inversions associated
with migratory anticyclones moving from west to east across Australia. On
some occasions, the passage of these high-pressure systems is blocked and
they remain stationary over the Tasman Sea east of Sydney, causing high oxidant
*Macquarie University, North Ryde, N.S.W., Australia, 2113.
285
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286
-------
episodes. But in general each anticyclone causes high oxidant concentrations
only on one or two days at a time. During the oxidant season, from October
1974 to April 1975, hourly-mean ozone concentrations exceeded 0.10 ppm in
Sydney on approximately one day in six (Hyde & Hawke, 1976).
The two dominant mesoscale wind systems affecting the Sydney region are,
firstly, nocturnal and early-morning drainage flows and, secondly, afternoon
seabreezes. A preliminary examination of wind and temperature data, for
some days when high oxidant concentrations were measured, indicated that ozone
could occur in either the drainage flow or Seabreeze systems (Hawke and
Iverach, 1974). This was later confirmed by Hyde and Hawke (1976).
This work is being continued as part of the contribution of Macquarie
University to the Sydney Oxidant Study, a multi-disciplinary project investi-
gating the formation of photochemical smog in the Sydney Basin, funded by the
New South Wales State Pollution Control Commission. Our present paper is
divided into two parts; the first section presents a climatology of surface-
wind trajectories within drainage flows and seabreezes on days with high oxidant
concentrations and classifies variations in ozone concentrations throughout
the day in terms of the meso-meteorological conditions. The second part of
the paper deals with the vertical structure of the atmosphere above Sydney
and its relationship to concentrations of ozone during the morning.
SURFACE WINDFLOW AND CONCENTRATIONS OF OZONE
In our earlier paper we showed that high concentrations of ozone occurred
predominantly during the morning drainage flow. However, some of the days
studied in that paper had maximum concentrations of ozone occurring within
or after the arrival of the afternoon Seabreeze. The analysis has now been
extended in order to determine the influence of meteorological conditions
on the transport of oxidants and their precursors across the Sydney Basin.
CLASSIFICATION OF OZONE CONCENTRATIONS
The 69 days when hourly concentrations of ozone were at least 0.10 ppm
between January 1974 and June 1975 have been divided into three main cate-
gories according to the variations of ozone concentrations throughout the
day. Characteristics of the different categories are briefly described be-
low and an example of each is given in Figure 2.
Type Al - morning increase in ozone concentrations terminated by the onset of
the gradient wind at ground level.
Type A2 - morning increase in ozone concentrations terminated by the arrival
of the Seabreeze.
Type B - as for type Al but followed by an abrupt increase in ozone concen-
trations coinciding with the arrival of the Seabreeze.
Type C - ozone concentrations continued to increase for up to two hours
after the arrival of the Seabreeze.
287
-------
>3
KA.ft«.\cvC^L.\.£.
Figure 2. Variation in ozone concentrations during the day in the Sydney Basin
in four categories.
288
-------
The frequency of occurrence of these different categories at the three
monitoring stations in the Sydney region, given in Table 1, shows that maxi-
mum ozone concentrations occur more frequently during the morning, especially
near the coast. An explanation of meteorological conditions associated with
this type of ozone pattern is given in the next section. Type C days occur
relatively infrequently and have not yet been analyzed in detail. However,
Type B days do occur on a significant number of occasions, especially inland.
TABLE 1. NUMBER OF DAYS WHEN MAXIMUM OZONE CONCENTRATIONS WERE AT LEAST
0.10 PPM, IN FOUR CATEGORIES, FOR JAN. 1974 - JUNE 1975
LOCATION AND DISTANCE INLAND (KM)
TYPE
Marrickville, 10
Lidcombe, 21
Wentworthville, 29
Al
A2
B
C
TOTAL
21
16
14
5
56
8
12
18
2
40
5
13
16
2
36
The exact cause of high concentrations of ozone within afternoon sea-
breezes has not yet been investigated but may be caused either by:
• a slowly moving seabreeze-front, with ozone forming within the sea-
breeze circulation as a result of precursor emissions near the coast
(Lyons and Olsson, 1973);
• air containing oxidant precursors moving out to sea in the morning
drainage flow, undergoing photochemical reactions and then being
advected back inland with the Seabreeze (Anlauf et al., 1975); or
• air advected from the Botany Bay region.
SURFACE WIND TRAJECTORIES
Although the above categorization of ozone concentration changes describe
only conditions at the three fixed monitoring sites, surface-wind trajectories
through these stations can be used to identify both source and receptor
regions for photochemical smog in the Sydney Basin. Surface-wind trajectories
through both Marrickville and Lidcombe on the 69 days described in the preceding
subsection were calculated using the method of Wendell (1972) as follows:
(1) backwards in time until midnight the previous day for hours when
the ozone concentration reached at least 0.10 ppm before the onset
of strong gradient winds or arrival of the afternoon Seabreeze, and
(2) forwards in time until midnight or until the trajectory moved outside
the Sydney region for hours when ozone concentrations were at least
0.10 ppm in the afternoon Seabreeze.
289
-------
The Sydney region was divided into 5 km grid squares and the number of
trajectories passing through each square was counted and converted into a
percentage frequency of the total number of trajectories. The results of
this analysis for (1) and (2) above at Mam'ckville and Lidcombe are given
in Figure 3. The 5 per cent frequency category for trajectories backwards
from Lidcombe has been omitted here because of the small number of trajectories
involved.
At the moment we do not know what proportion of pollutants within the
morning drainage flow are subsequently incorporated into the overall sea-
breeze circulation. Angel! et al. (1976) found that tetroons released within
the morning drainage flow in the Los Angeles Basin were subsequently advected
back inland with the afternoon Seabreeze. Whether or not a similar recircu-
lation occurs in the Sydney basin is not yet known, and for this reason for-
ward and backward trajectories in Figure 3 have been considered separately.
This analysis of surface wind trajectories confirms that polluted air-
masses arriving at both Marrickville and Lidcombe during the morning have
been advected there by westerly drainage flow from source regions to the
northwest. The most common afternoon trajectory of polluted air within sea-
breezes is towards the southwest of the Sydney Basin, including the Liver-
pool-Campbell town region. Unfortunately this region is designated as the
major population growth centre for the next few decades (State Planning
Authority of N.S.W., 1968, 1973). Several papers which discuss the advect-
ion of ozone across the Los Angeles basin show that the highest concentrations
occur 50 km downwind of the major source regions within air advected inland
with the afternoon Seabreeze (Hanna 1975, Tiao et al., 1975, Blurnenthal,
1976). The possible implications for Sydney are clear and illustrate the need
to consider the incursion of photochemical smog when planning future growth
centres.
VERTICAL STRUCTURE OF THE LOWER ATMOSPHERE OVER SYDNEY
The other part of our work in the Sydney Oxidant Study concerns the
vertical structure of wind and temperature on days with high concentrations
of ozone. This information is necessary to explain variations in oxidant
concentrations on different days and as meteorological input for photochemical
smog models.
Wind profiles are obtained using a recording single-theodolite pilot-
balloon system developed by Hawke, and temperatures up to 300 m using a low-
level tethersonde (Linacre 1976). These systems have been developed because
it is not possible to obtain a resolution of less than 300 m from routine
six-hourly pilot-balloon ascents at Mascot and the nearest routine radiosonde
stations are approximately 130 km away to the north and south of Sydney.
OBSERVATIONS ON APRIL 29, 1975
During the 1975-76 oxidant season most of our wind and temperature
profiles were obtained between sunrise and noon, in order to examine the
influence of drainage and gradient wind flows on the morning increase of
oxidant concentration. One such set of observations was made on April 29,
290
------- An error occurred while trying to OCR this image.
-------
1975, and shows stratification typical of the atmosphere over Sydney during
the morning on high oxidant days. On that occasion, simultaneous wind and
temperature profiles were obtained at least every thirty minutes between 0500
and 1000 and are given in Figure 4. Details of the synoptic situation, ozone
concentrations at Lidcombe and Marrickville, and the 0900 radiosonde ascent
from Williamtown (130 km to the north) are given in Figure 5.
Macroscale Hind and Temperature Structure
The synoptic map is typical of many high oxidant days in Sydney, with a
high pressure system centred over the Tasman Sea (Hawke and Iverach, 1974).
At Williamtown the temperature profile shows a well-defined structure below
700 m with:
• a slightly stable layer between the surface and 250 m (a-b),
• a strong inversion layer between 250 m and 400 m (b-c), and
• a weaker inversion layer between 400 m and 700 m (c-d).
Wind profiles in Figure 4a have been divided into three periods of time
corresponding to changes in thermal structure within the lower atmosphere.
However certain features are common to each set of measurements and are
listed below:
(1) a surface layer approximately 200 m deep, with a wind speed of 2-3
ms-1 from the north to northwest,
(2) a region of marked wind direction shear above the surface layer with
a turning point at 250 m, and
(3) a layer between 250 m and 700 m having a 6 ms"1 northerly wind and
turning points in wind direction shear at 400 m and 700 m.
Layer (1) above has approximately the same height at layer a-b in Figure
5c and the turning points at 400 and 700 m in (3) occur at similar heights
to points c and d. These features describe the broadscale vertical structure
and form part of the model to be developed below.
Mesoscale Wind and Temperature Structure
On a smaller scale Figures 4a and 4b show that the low-level wind and
temperature structure on this day can be divided into three stages of develop-
ment, as follows:
(1) Before sunrise (0635 a.m.) - during this period there was a strong
surface inversion below 250 m with a westerly flow between 60 m and
200 m, above a shallow northwesterly flow,
(2) 0635 to 0845 a.m. - over this period the surface northwesterly layer
heated up and formed a well-mixed layer approximately 100 m deep,
292
-------
3 oo
loo
l«
Figure 4. Wind and temperature profiles at Silverwater on April 29, 1975,
293
-------
(3) 0845 to 1000 a.m. - between 0845 and 0900 a.m. the depth of the well-
mixed surface layer increased from 100 m to 200 m. Subsequent wind
and temperature profiles show this layer remaining 200 m deep until
at least 1000.
No temperature profiles were made after 1000, but wind profiles at 1030
and 1100 show that the region of wind shear at the top of the surface layer
had gone. Surface wind records over the Sydney region on this day show a
change in wind direction from northwesterly to northerly and increase in wind
speed between 1030 and 1130, and correspond to the period when ozone concen-
trations at Lidcombe and Marrickville started to decrease (Figure 5b).
MODEL
Vertical Structure
The structure of wind and temperature profiles on April 29, 1975, (and
many other similar observations over a wide range of gradient wind velocities
obtained during the past two years) suggests that during the morning there can
be three distinct layers over Sydney, below the top of the subsidence inver-
sion. These are shown schematically in Figure 6 where:
• 'a1 is a local drainage flow down the Parramatta River valley,
typically 80-150 m deep and contained by the region of high ground
to the north of the river, and is a sub-layer of
• 'b', a regional drainage flow 200-300 m deep over the whole Sydney
Basin.
• 'c' is the gradient wind flow below the top of the subsidence inversion.
Time Development
Before sunrise on a cloudless morning, drainage flow occurs within a
ground-based inversion, caused partly by radiative cooling and partly by the
advection of cold air from the Blue Mountains to the west. After sunrise (at
time ti in Figure 6), surface heating allows the local drainage-flow to form a
well-mixed layer underneath the still thermally-stable region. Then at time
t2 there is a sudden increase in mixing depth, signifying the end of local
drainage-flow to form a well-mixed layer 200-300 m deep. Dividing the drainage
wind into local and regional flows can explain a characteristic feature of
many wind profiles measured at Silverwater. These show a surface layer about
100 m deep suddenly doubling in depth sometime during the morning. Obser-
vations show that after this deepening the regional drainage flow maintains
a constant depth during subsequent surface heating and is separated from the
gradient wind above by a sharp inversion layer. The gradient wind will
reach the surface once surface heating has eroded this inversion (at time t3).
When this occurs, there is usually an increase in mixing depth and a change
in windspeed and wind direction. This causes the sudden reduction in ozone
concentrations typical of type Al days.
294
-------
Figure 5. April 29, 1975: (a) Surface synoptic weather map. (b) Concentrations
of ozone at Lidcombe and Marrickville. (c) 0900 temperature soundings from
Williamtown, plotted on a T-0 diagram.
oC
ClZftrcntuT
*t
\
to? af (2t«,oOftu -wta,,4fcc.e F^.u
/'
•
1
-------
Figure 6 also shows the Seabreeze onset at time t^, separated from t3 by
a period of time At which will depend on both surface heating and the gradient-
wind speed and direction. At is an important variable, which equals zero if
the Seabreeze arrives at a location before the breakdown of regional drainage-
flow. Under these conditions the day would become type A2.
Implications for the Formation of Oxidants in the Sydney Basin
The partition of drainage-flow into two types has important implications
on the dispersion of oxidant precursors emitted into the atmosphere during
the morning. Between sunrise and time t2, precursors emitted close to the
ground are advected towards the east in the well-mixed local drainage-flow.
At the same time, precursors emitted from higher chimneys will be carried
downwind in a stable layer and not experience much lateral or vertical diffusion.
On occasions when the gradient wind inhibits regional drainage-flow, these
emissions from elevated sources are often advected in a direction different
from that taken by the surface emissions. After time t2, precursors from
both surface and elevated sources undergo photochemical reactions within a
well-mixed layer 200-300 m deep. So subsequent concentrations of ozone
during the morning largely depend on the time interval between t2 and t3.
This time interval in turn depends on the strength of the inversion layer
b-c in Figure 5c and would be influenced by the presence of any cloud during
the morning which can reduce the rate of surface heating and so delay the
breakdown of regional drainage flow. Therefore, although the right synoptic
conditions may be present, the concentrations of ozone on any particular
day may be very sensitive to variations in the length of time between the
breakdown of the local drainage flow and the onset of either the gradient
wind or afternoon Seabreeze.
CONCLUSIONS
The material presented in this paper is intended to illustrate the im-
portance of both horizontal transport and vertical structure of the lower
atmosphere in the photochemical smog problem in Sydney. A knowledge of the
vertical structure of wind and temperatures is necessary to identify the
characteristic depths of layers which can inhibit the vertical diffusion of
pollutants. This information can then be used in the future for forecasting
days with high concentrations of ozone and as meterologica'l input to photo-
chemical smog models. The horizontal transport of photochemical smog within
mesoscale wind systems must be considered when planning future urban growth
centres so as to avoid sitting them downwind of major oxidant source regions.
ACKNOWLEDGEMENTS
The authors are grateful to the State Pollution Control Commission
for permission to publish ozone data appearing in this paper, to the Bureau
of Meteorology for access to meteorological observations, and to Associate
Professor E. T. Linacre for his comments during the preparation of the paper.
Thanks are also due to Mrs. Campbell Gibson who typed the manuscript.
This work was carried out under a grant from the State Pollution
Control Commission as part of the Sydney Oxidant Study. The purchase and
296
-------
maintenance of 3 anemometers in the Botany Bay region was funded by a grant
from the Botany Bay Project Committee.
REFERENCES
ANGELL, J. K., C. R. DICKSON, AND W. H. HOECKER. Tetroon Trajectories in
the Los Angeles Basin Defining the Source of Air Reaching San Bernadino-
Riverside Area in Late Afternoon. J. Appl. Met., 15:197-204, 1976.
ANLAUF, K. G., M. A. LUSIS, H. A. WIEBE, AND R. D. S. STEVENS. High Ozone
Concentrations Measured in the Vicinity of Toronto, Canada. Atmos. Environ.,
9:1137-1139, 1975.
BLUMENTHAL, D. L. Distribution and Transport of Ozone in the South Coast
Air Basin. Calif. Air Environ., 6 (1):4-10, 1975.
HANNA, S. R. Modelling Smog Along the Los Angeles-Palm Springs Trajectory.
N.O.A.A. Environ. Res. Lab., Atmos. Turbulence and Diffusion Lab., Contri-
bution No. 75/4, 1975.
HAWKE, G. S. AND D. IVERACH. A Study of High Photochemical Pollution Days
in Sydney, N.S.W. Atmos. Environ., 8:597-608.
HYDE, R. AND G. S. HAWKE. A Preliminary Analysis of the Influence of Meteor-
ology on Ozone Levels in Sydney. Smog '76 Conference, Clean Air Soc. of
Aust. and N. Z., N.S. W. branch, Sydney, February 1976.
LINACRE, E. T. Low-Level Temperature Soundings with a Radiosonde on a Tethered
Balloon. 1976. (in preparation)
LYONS, W. A. AND L. E. OLSSON. Detailed Mesometeorological Studies of Air
Pollution Dispersion in the Chicago Lake Breeze. Mon. Wea. Rev., 101:387-403,
1973.
STATE PLANNING AUTHORITY OF N. S. W. Sydney Region: Outline Plan 1970-2000
A.D., March 1968.
STATE PLANNING AUTHORITY OF N. S. W. Population Projections for N. S. W.
1971 to 2000, November 1973.
TIAO, G. C., G. E. P. BOX, AND W. J. HAMMING. Analysis of Los Angeles Photo-
chemical Smog Data: A Statistical Overview. J. Air Poll. Control Assoc.
25:260-268, 1975.
WENDELL, L. L. Mesoscale Wind Fields and Transport Estimates Determined from
a Network of Wind Towers. Mon. Wea. Rev. 100:565-578, 1972.
297
-------
7-2
OXIDANT LEVELS IN ALBERTA AIRSHEDS
H. S. Sandhu*
ABSTRACT
Some. o£ the. oJot qaatity and me.te.oA.ologtcal data. gatkeA.e.d -in AtbeAta dat-
ing tke. pabt tu)a ye.au ^on Delected da.y& and time, ofi tke. ye.oA. u> fie.posite.d.
CompafuAon be.tuie.e.n the. obteAvcd and calculated valaeA ofi ozone. hcu> A.e.ve,ale.d
tke. odc.uAAe.nce. 0& pkotoc.ke.mlc.ai fie.actionf>. PoAA-ible. AOUA.CZA con&iibuting to
ozone. &oA.mation and tA.ant>poAt ate. btu.e.&iy olit>coined.
INTRODUCTION
Most of the information available to date on photochemical oxidant
pollution and its control is derived from the laboratory and field studies
carried out in the United States (1-3). Over the years attempts have been
made to apply this knowledge to northern climates. It has been argued that
photochemical oxidants should not pose a pollution problem at higher latitudes
because of reduced solar radiation and lower temperatures. There is evi-
dence now that these generalizations are in error (4,5).
In Canada, no other cities of a size comparable to Edmonton (53° 34'N
113° 35'W, elevation 676 m) and Calgary (51° 17'N 114°W, elevation 1080 m)
with a population of about 500,000 each are situated as far north. The Pro-
vince of Alberta, Figure 1, is one of the richest natural resource provinces
in Canada. Because of mankind's dependence on energy, large resource develop-
ments such as the recovery of oil from Alberta Oil Sands are taking place or
will take place farther to the north in the coming years. It is essential
for environmental information to be gathered and analysed. Predictions should
be made at the extremes of the meteorological conditions prevalent in the
area instead of using conclusions based on different climatic conditions.
Some aspe'cts of photochemical air pollution in Alberta are briefly discussed
in this paper.
RESULTS AND DISCUSSION
Alberta Department of the Environment expanded the monitoring network
from one to three stations in each of the two cities in 1974 and started
using instruments that employ the chemiluminescence method for detecting
nitric oxide (NO), nitrogen dioxide (N02), and ozone (03), the flame ionisa-
tion technique for detecting hydrocarbons (HC) and the infrared absorption
*Alberta Department of the Environment, Edmonton, Canada.
299
-------
IZO
TMONTANA
110°
Figure 1. The Province of Alberta.
method for carbon monoxide (CO). Meteorological observations are made by
Atmospheric Environment Service, Environment Canada, employing standard
instruments at various stations in Alberta. Air monitoring reports for
Edmonton and Calgary for the year 1974 have been published (6).
Temperature and air pollutants recorded on a typical cold day in spring
(sunny, 7.5 cm of snow) are given in Table 1. Average wind speeds stayed
around 16 km per hour (10 miles per hour). Observed 03 values given in this
table are a clear indication of its photochemical production and transport
at these latitudes under reduced temperatures. Rawinsonde observations recorded
at an upper air sounding station 49 km outside the city showed that the
morning temperature inversion top was partially lifted by solar heating as the
day progressed. Steady-state concentrations of 03 were computed from the
mechanism,
N02 + sunlight -> NO + 0
0 + 02 + M -> 03 + M
03 + NO -> 02 + N02
using theoretical values of kl (clear sky approximation) for these latitudes,
k2 = 1.7 x 1013 (cm6 mole-2 sec'1) exp (+2100 (cal mole-^/RT) (7)
300
-------
TABLE 1. TEMPERATURE AND AVERAGE AIR POLLUTANT CONCENTRATIONS
MEASURED AT THE EDMONTON DOWNTOWN MONITORING STATION ON APRIL 1
1975
Variable Hour 09 10 11 12 13 14 15 16 17
Temp. -16 -14 -13 -13 -11 - 9 - 8 - 8 - 8
TO
(PPhm)
NO
(pphm)
°3
(pphm)
943433347
255667765
and
k3 = 6.0 x 1011 (cm3 mole'1 sec'1) exp (-2460 (cal mole'^/RT (8).
These values are lower by a factor of two when compared to midday values of
03 given in Table 1. This discrepancy could be due to the combined effects
of factors such as advection of background 03 increased albedo of the surface,
production of 03 through other precursors or the production of 03 through
heterogeneous reactions. A preference for any one factor would be misleading
at this time. The observed peak value of 7 pphm is above the Alberta Standard
and Canadian Objective (maximum desirable) which is 5 pphm. Though rare, such
situations could prevail up to three or four days at this time of the year
depending on the intensity and dynamics of the air mass.
During summer months in 1975, 03 levels above 5 pphm were recorded on
almost all sunny days in Edmonton. Levels observed on three days during July
1975 are given in Table 2. Since non-urban 03 measurements are not available
for this time period it is premature to interpret these data.
Central Alberta, the area between Edmonton and Calgary, is a region of
high convective cloud activity and it experiences many thundershowers and
hailstorms during summer months. To date, no one has made measurements of
surface 03 present in rural areas during summer months. A monitoring program
is planned to observe non-urban 03 levels and estimate 03 produced through
this natural phenomenon.
To obtain information on the background levels of reactive pollutants
at these northern latitudes, a three week monitoring study was carried out
in Edmonton in September 1975. A typical set of data is given in Table 3.
301
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TABLE 2. AVERAGE OZONE CONCENTRATIONS (PPHM) OBSERVED AT
THE EDMONTON DOWNTOWN MONITORING STATION DURING JULY 1975
Day
4
24
28
Hour
08 09 10
1 3 10
1 3 5
666
11
7
6
7
12 13 14 15
10 11 16 9
7778
8 11 13 19
16 17 18
455
667
18 10 7
19
5
10
6
TABLE 3. TEMPERATURE, WIND SPEED AND AVERAGE AIR POLLUTANT
CONCENTRATIONS MEASURED AT THE EDMONTON DOWNTOWN MONITORING
STATION ON SEPTEMBER 24, 1975*
Hour
07
08
09
10
11
12
13
14
15
16
17
18
19
20
Temp
TO
11
12
14
18
20
22
24
23
24
24
23
23
21
18
N02
(ppnm)
6 (2)
6 (2)
7 (2)
6 (2)
6 (2)
5 (1)
7 (1)
7 (2)
7 (2)
9 (2)
9 (2)
11 (2)
15 (3)
15 (2)
NO
(pphm)
40 (2)
55 (2)
16 (2)
11 (1)
6 (1)
5 (1)
6 (1)
5 (1)
5 (1)
5 (1)
5 (1)
12 (2)
24 (2)
23 (3)
(pp3m)
0 (1)
0 (1)
0 (1)
1 (2)
3 (2)
4 (3)
4 (3)
5 (3)
5 (3)
5 (3)
4 (3)
2 (2)
0 (2)
0 (2)
Reactive
Hydrocarbons
(pptm)
11
24
11
6
6
6
6
6
4
5
6
7
5
6
* The values in parenthesis are measured at Kavanagh, 45 km
south of Edmonton city limits.
302
-------
Average wind speed on this day was 6.5 km per hour "{4 miles per hour). To
the author's knowledge, background air pollutant levels shown in this table are
the first reliable measurements outside a major urban center in Canada that is
this far north. During this period background 03 levels varied between 1-3 pphm
on sunny days, peaking around midday. The levels of reactive HC in Alberta
cities are relatively small compared to those in other major cities at the
present time. The relationship of NO to 63 (Table 3) in the urban and non-
urban air is quite interesting in that NO is the main molecule that reacts
with urban 03.
Meteorological and air quality data for the summer of 1976 is not avail-
able yet in the reduced and manageable form. However, monitored data for
Edmonton, Calgary, and Medicine Hat (50° Ol'N, 110° 43'W, elevation 719 m) on
July 25, 1976, are given in Tables 4 and 5. July 25 was a typical hot summer
day with more than 14 hours of sunshine. The values of 03 recorded at Medicine
Hat are typical background 03 values. Residential monitoring stations in
both Edmonton and Calgary recorded generally higher 03 concentrations as com-
pared to downtown monitoring stations. The hourly N02/N0 ratio around midday
is higher in Calgary than in Edmonton, but 03 values are higher in Edmonton.
A complete analysis will be carried out after all the data for 1976 becomes
available.
TABLE 4. SOME METEOROLOGICAL VARIABLES OBSERVED AT
THREE MONITORING STATIONS IN ALBERTA ON JULY 25, 1976
Variable Edmonton Calgary Medicine Hat
Sunshine (hours)
Max. Temp. (°C)
Max. Windspeed (km/hour)
and Direction
14.7
26.7
19
Southwest
15.2
28.7
20
North
14.3
28.4
-
Precipitation (mm) 0 0 trace
CONCLUSIONS
Ozone is formed through photochemical reactions of air pollutants present
in the major urban airsheds of Alberta. Typical background 03 concentrations
are in the range 1-3 pphm. Some observations suggest that the precursors for
03 production are advected to the cities. Oxidant/ozone concentrations are
expected to stay below the provincial standard of 5 pphm in winter months,
but will exceed the standard during summer months on sunny days.
ACKNOWLEDGEMENTS
The author thanks the Research Secretariat staff for helpful discussions
and the Air Quality Branch staff for the help in acquiring the needed data.
303
-------
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REFERENCES
Altshuller, A. P. and J. Bufalini. Photochemical Aspects of Air Pollution:
A Review. Environ. Sci. Technol. 5:39, 1971.
Pitts, J. N., Jr. and B. J. Finlayson. Mechanisms of Photochemical Air
Pollution. Angewandte Chemie. 14:1, 1975.
Demerjian, K. L., J. A. Kerr and J. 6. Calvert. The Mechanisms of
Photochemical Smog Formation. Adv. Environ. Sci. Technol. 4:1, 1975.
National Research Council of Canada, Associate Committee on Scientific
Criteria for Environmental Quality Report NRCC No. 14096. Photochemical
Air Pollution: Formation, Transport and Effects, 1975. 224 pp. Also
note other references in this report.
Sandhu, H. S. A Study of Photochemical Air Pollutants in the Urban
Airsheds of Edmonton and Calgary. Alberta Environment, Edmonton, 1975.
155 pp.
Annual Air Monitoring Reports for the Cities of Edmonton and Calgary.
Alberta Environment, 1974. 33 pp. each.
Johnston, H. S. Gas Phase Reaction Kinetics of Neutral Oxygen Species.
National Bureau of Standards Report NSRDS 20, 1968.
Clyne, M. A. A., B. A. Thrush and R. P. Wayne. Kinetics of the Chemi-
luminiscent Reaction between Nitric Oxide and Ozone. Trans. Farad.
Soc. 60:359, 1964.
305
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7-3
AN INVESTIGATION OF LONG-RANGE TRANSPORT OF OZONE
ACROSS THE MIDWESTERN AND EASTERN UNITED STATES
G. T. Wolff, P. J. Lioy, G. D. Wight, R. E. Meyers, and R. T. Cederwall*
ABSTRACT
Long-siange. tnanApotit o& ozone. acAo&& the. mtdweAteAn and e.a&teJin U. S.
4.nveAtigate.d by anaiyz-ing dcuJty ozone. -U,opte^th ma.pt> and. comparing them
to metwiotog-icat map4 and aJJi pa/icz-t &ia.j fan the, peju.od ApfcUL 12-
23, 1976. Thib peJiiod won, chaA.acteAize.d by the. px.eAe.nce. oft a tatiQe. hlgh-
pfizAAutie. &yt>tem which pti.odu.ctd W4.deAptie.ad violation* o$ the. ozone. t>tandatidi>
OA we££ e.d to
produce the. dalty ozone, map-4. Move.me.nt o{ atie.af> ofa high ozone. c.once.ntA.atA.onA
c.oM.e.Aponde.d to the. move.me.nt o& the. high psiUALLfie. £yt>te.m. Actual,
acAo44 the^>e. ane,aA ^ t>uppofite.d by &iaje.ctoiy anatyA^A. VatiLy
map4 weAe. ati>o pfio,pajiq.d and the.y Au@ge.At that aAeai OjJ tow
ge.ne.siatty co4.ncA.de. w
-------
parcels had passed over industrialized and urban areas of the midwest, the
authors suggested that the midwest could be a significant source region
for the ozone entering the Corridor. The data presented in this paper
examine this hypothesis. In addition, daily maps containing visibility
isopleths are compared to the ozone isopleths. Husar, and long et al.
attempted to use visibility as tracers for sulfates (9,10). The study
reported in this paper employed this technique in an attempt to track the
movement of areas containing high concentrations of ozone.
METHODOLOGY
In September 1975, Connecticut hosted a meeting for state officials
from EPA Regions I, II, III, and V on ozone transport and hydrocarbon control
strategies. At this meeting, a task force was established to gather, dissem-
inate, and analyze ozone data from the monitoring networks of the partici-
pating states. The ozone data presented in this paper were obtained through
the task force.
Selection of individual sites for inclusion in this analysis was based
on obtaining a uniform geographical distribution and avoiding the presence
of local interferring sources. In some cases, it was impossible to satisfy
the second criteria and local anomalies in ozone concentrations resulted.
For most of the states near the East Coast, this problem was eliminated by
employing smoothing techniques. In the western sections of the study area,
this was not possible because many of the sites are located in downtown urban
areas. As a result, the ozone concentrations surrounding these areas may
actually be higher. In addition, anomalies may occur due to calibration
variations. The task force, however, has established a quality assurance
program to minimize these variations.
Weather maps were obtained from the National Weather Service. The air
parcel trajectories were developed at Brookhaven National Laboratories, and
the method has been discussed previously (8).
Visibility isopleth maps were developed from data obtained every three
hours by the National Weather Service. Husar, in his analysis, used noon-
time visibility readings (9). This approach resulted in local inconsisten-
cies due to the occurrence of isolated storms and ground fog which produced
visibilities not representative of the surrounding areas. In an attempt to
overcome these difficulties, the isopleths presented here were based on the
lowest recorded daily visibility in the absence of ground fog, precipitation,
and a dew point depression of two degrees Fahrenheit or less,. If these
conditions persisted throughout the day at a particular site, the data were
not used.
RESULTS AND DISCUSSION
A high pressure system, which moved out of Canada on April 10 and 11,
was centered over Lake Michigan on the morning of April 12 (Figure la). On
the afternoon of April 12, the first ozone readings within the high pressure
system in excess of the National Ambient Air Quality Standard (NAAQS=0.08
ppm) were detected in Indiana and Ohio. Ozone levels in excess of 0.06
308
-------
ppm were generally confined to these two states also.
By the morning of the 13th, the high was centered over the Ohio-West
Virginia border (Figure Ib). Ozone levels exceeding 0.06 ppm now extended
from western Indiana eastward into New Jersey and areas exceeding 0.08 ppm
were observed in Ohio and New Jersey. This was in contrast to only one area
being above the NAAQS on April 12 (Ohio). Air parcel trajectories terminat-
ing on April 13 indicate that the air over Ohio and Indiana on April 12 was
advected to the East Coast of the Mid-Atlantic states by the afternoon and
evening of April 13 (Figure 2b).
From April 14 to April 16, the center of the high pressure system
continued to move southeastward and by the morning of April 16, it was
centered off the coast of North Carolina (Figures Ic-e). The trajectories
for the same period indicate that air parcels in the western Midwest
(Illinois) were moving north-northeastward (Figures 2b-d). During this
time, the 0.06 ppm isopleth moved northward from northern Illinois on
April 13 to northern Wisconsin on April 16. The 0.08 ppm isopleth now
extended in a band from Indiana to New Jersey. Trajectories from the Ohio
area during the same period exhibited a more defined westerly component
toward New Jersey. As a result, by April 16, the 0.06 ppm and 0.08 ppm
isopleths covered most of the northeast from Maine to Virginia and
Massachusetts to Virginia, respectively.
On April 17 (Figures If and 2f), both the 0.06 ppm and the 0.08 ppm
isopleths began to contract in the western Midwest as a cold front over
western Illinois began to move eastward. In the eastern sections, the
trajectories on April 16 continued to move east-northeastward and, on
April 17, the 0.06 ppm isopleth extended through northern New Hampshire.
The pattern observed on April 17 changed little on April 18 (Figure
Ig). The cold front moved slowly eastward into Indiana. Continued north-
ward movement of the isopleths ceased, however, as a stationary east-west
front prevented it from moving into northern Maine. Trajectories from
Richmond, Virginia, on April 17 and April 18 (Figures 2f-g) indicated that
little horizontal advection occurred over the Middle Atlantic States. The
same pattern persisted into April 19 as the cold front moved into Ohio and
contraction of the 0.06 ppm isopleth continued (Figures 1 and 2h).
The eastward movement of the cold front across the northern part of the
region greatly increased between April 18 and 19 (Figure Ih). Over southern
sections, the front was considerably slower and by the morning of April 20,
it was oriented on a southwest-northeast plane from southern Indiana to
southern Maine. The northern edge of both of the isopleths generally
corresponded with the position of the front. Trajectories on April 20
(Figure 2h) further illustrate the air flow resulting from the frontal
movement.
Cyclogenesis on April 20 and 21 changed the flow patterns considerably
by April 21 (Figure Ij). As the low pressure system intensified over the
Great Lakes, the predominantly westerly flow across the East Coast shifted
to a southeasterly flow. This shift was demonstrated by the trajectories
309
-------
la: April 12
Ic: April 14
le: April 16
Ib: April 13
Id: April 15
If: April 17
Figure 1 a-f. The accumulation and transport of ozone, April 12-17.
310
-------
Ig: April 18
li: April 20
Ih: April 19
Ij : April 21
^ 0.06 ppm
£. 0. 08 ppm
Ik: April 22
Figure 1 g-k. The accumulation and transport of ozone, April 18-22,
311
-------
2a: April 12
2b:April
1900
2c: April 14 (Chi.=0700) 2d:April 15 (Rich.=0700)
2e: April 16 2f: April 17
Figure 2 a-f. Backward air parcel trajectories for Chicago, Columbus, Boston,
Richmond, and New York, April
unless otherwise stated.
position 12 hours ago.
12-17. All trajectories terminate at 1300 hours
(Position key: 1 = position 6 hours ago, 2 =
3 = position 18 hours
24 hours ago.)
312
ago, and 4 = position
-------
2g: April 18
2h: April 19
2i: April 20
2j: April 21
2k: April 22
Figure 2 g-k. Backward air parcel trajectories for Chicago, Columbus, Boston,
Richmond, and New York, April 18-22. All trajectories terminate at 1300 hours
unless otherwise stated. (Position key: 1 = position 6 hours ago, 2 =
position 12 hours ago, 3 = position 18 hours ago, and 4 =
position 24 hours ago.)
313
-------
3a: April 12
3b: April 14
3c: April 16
3d: April 19
KEY
8-10 miles
PSPI-* 7 miles
8&i mi .Let*
3e: April 21
Figure 3 a-e. Visibility recorded during the high ozone concentration
period of April 1976.
314
-------
on April 21 while the trajectories on April 22 showed a pronounced southernly
flow (Figures 2i and j). This shift resulted in advection of the 0.06 ppm
isopleth northward, but because of the cloud cover and precioitation
associated with this flow, the 0.08 ppm isopleth remained confined to an
area with partly sunny skies centered around New Jersey.
On April 22, the low continued to move northeastward, while the cold
front moved rapidly toward the Atlantic Ocean (Figure Ib). The trailing
edge of the 0.06 ppm isopleth is shown moving off the Coast.
The visibilities for the same period are shown in Figures 3a-f. There
are considerable geographical similarities between the areas of low
visibility and high ozone from April 12-19. However, as the winds shifted
on April 20 and 21 and the ozone levels decreased, the visibilities did not
change substantially. This was probably due to the moisture associated
with the southeasterly flow.
CONCLUSIONS
The above analysis illustrates transport of photochemical air pollu-
tion from the midwestern United States to the East Coast. Trajectory
analyses also suggest that transport of photochemical air pollution from
the Southern states (south of Virginia and Kentucky) to the Mid-Atlantic
States also occurred between April 17 and 19.
The movements of the area of high ozone concentrations corresponded
extremely well with the movements of the high pressure system as well as
with the advance and retreat of frontal systems near the perimeter of the
high pressure system.
Visibility maps may be a valuable technique in tracing ozone transport
under certain conditions. A significant correspondence between the areas
of high ozone and the areas of low visibility occurred during most of the
study period. Toward the end of the period, as the high pressure system
weakened and moisture was advected into the area via an on-shore circu-
lation, the relationship became less established.
At the present time, daily ozone isopleth maps are being developed
for the entire summer of 1976. The techniques used in this report will
be employed on this data. Current efforts are also being undertaken to
refine the selection and presentation of the visibility data. In the
present research we have only examined the daily maximum ozone concen-
tration, subsequent studies will include analysis of ozone during other
time periods. In addition, the possibility of stratospheric injection of
ozone is being investigated by employing isentropic analysis (11).
ACKNOWLEDGEMENTS
The authors wish to express their gratitude to all of the members
of the Moodus Data Sharing and Analysis Committee for providing the ozone
data used in this report. The authors also thank Messrs. Michael Anderson,
315
-------
James Oliver, William Simpson, Jerry Bujancius of the Connecticut Depart-
ment of Environmental Protection, Richard Taylor of the New York State
Department of Environmental Control, and Konrad Wisniewski and William
Edwards of the Interstate Sanitation Commission for their assistance in
data collection and analysis.
REFERENCES
1. Coffey, P.E. and W.N. Stasiuk, Jr. Evidence of Atmospheric Transport
of Ozone into Urban Areas. Environmental Science and Technology.,
9(l):59-62, 1975.
2. Wolff, G.T., W.N. Stasiuk, Jr., P.E. Coffey and R.E. Pasceri. Aerial
Ozone Measurements over New Jersey, New York and Connecticut. In:
Proceedings of the 68th Annual Meeting of the Air Pollution Control
Association, Boston, Mass., 1975. paper 75-586.
3. Bach, Jr., W.D. Investigation of Ozone and Ozone Precursor Concentra-
tions at Non-Urban Locations in the Eastern U.S. - Phase II: Meteorolog-
ical Analysis. EPA-450/3-74-034-a, U.S. EPA, Research Triangle Park,
N.C., 1975. 144 pp.
4. Wolff, G.T. Preliminary Investigation of the Photochemical Oxidant
Problem in the N.J.-N.Y.-Conn. A.Q.C.R. Interstate Sanitation
Commission N.Y., N.Y., 1974. 69 pp.
5. Rubin, R.A., L. Bruckman and J. Magyar. Ozone Transport. In: Pro-
ceedings of the 68th Annual Meeting of the Air Pollution Control
Association, Boston, Mass., 1975. paper 75-07.1.
6. Cleveland, W.S., B. Kleiner, J.E. McRae and J.L. Warner, Photo-
chemical Air Pollution: Transport from the New York City Area
into Connecticut and Massachusetts. Science, 191:179-181, 1976.
7. Wolff, G.T., P.J. Lioy, G.D. Wight and R.E. Pasceri. An Aerial
Investigation of Photochemical Oxidants over the Eastern Mid-
Atlantic States. In: Proceedings of EPA Symposium on Ozone
Transport, Research Triangle Park, N.C., 1976(In Press).
8. Wolff, G.T., P.J. Lioy, R.E. Meyers, R.T. Cederwall, G.D.. Wight
R.E. Pasceri and R.S. Taylor. Anatomy of Two Ozone Transport Episodes
in the Washington, D.C. to Boston, Mass. Corridor. Presented at the
10th Annual Meeting of the Mid-Atlantic Amer. Chem. Soc., Phil.,
Pa., 1976 (also submitted for publication).
9. Husar, R.B., J.D. Husar, N.V. Gillani, S.B. Fuller, W.H. White, J.A.
Anderson, W.M. Vaughan and W.E. Wilson, Jr. Pollutant Flow Rate
Measurements in Large Plumes: Sulfur Budget in Power Plant and Area
Source Plumes in the St. Louis Region.. Presented at the 172nd
National Amer. Chem. Soc. Meeting, N.Y., 1976.
316
-------
10. long, E.Y., G.M. Hidy, T.F. Lavery, and F. Berlander. Regional and
Local Aspects of Atmospheric Sulfate in the Northeast Quadrant of
the U.S. In: Reprints 3rd Symposium on Atmospheric Turbulence
Diffusion and Air Quality, American Meteorological Society, Raleigh,
N.C., 1976.
11. Danielson, E.F. Transport and Diffusion of Stratospheric Radioactivity
based on Synoptic Hemispheric Analyses of Potential Vorticity. NYO-
3317-3, Atomic Energy Commission, Washington, D.C., Nov. 1967.
317
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7-4
OXIDANT AND PRECURSOR TRANSPORT SIMULATION
STUDIES IN THE RESEARCH TRIANGLE INSTITUTE SMOG CHAMBERS
J. E. Sickles, II, L. A. Ripperton, and W. C. Eaton*
ABSTRACT
Tke ge.neMition oft ozone, undeA *lmalated condition* o{, poU.ata.nt &ian*-
pont wa* *tadie.* -in a *y*te.m of, fiou/i, 11 cub^c meteA., oatdoon. *mog ckambeA*.
CkambeA contraction wa* o$ 5 mil FEP Te.{,lon on an aluminum fitLame.. Simula-
tion o-d tnan*poKt MO* accompll*ke.d by iwiadiating fie,actant* fan tkA.e.e day*
with *untight and by dilating the. content* a$ tke. chamber*. The. initial
change. o& nonmetkane. kyd?ioc.aAbon wa* 1 to 10 pant* peA million c.anbon o& a
AaAAogate. uAban miztuAz; tkz initial nitsiogzn oxA.de.*' ckange wo* 0.10 to 1.0
ppm. Tkti, tLe*alte.d tn initial nonme.tkane. kydtocatbon to OK*.doJ> ofi n^tA.oge.n
natio* o{, 7 to 1Q. W-itkoat tke. addition oft A.e.actant* afat&i tke. initial ckaAge.,
tke. *e.cond~ and tivuid-day c.ke.mtc.at *y*te.m* -in tke ckambeA* generated ozone
donce.n&iation6 gieateA than tke. National Ambient AiA Qaality Standard fafi
pkotocke.mlc.al oxldant. Tke. analogy be.tMe.en tke. chemical bzhavlon. oft ckambeA.
simulation* and nonu/iban high ozone. ( >O.OS ppm} *y*te.m* me.a&asie.d In the. &le.ld
i* good.
INTRODUCTION
The Research Triangle Institute's outdoor smog chamber facility is shown
in Figure 1. The system is composed of 4 outdoor chambers (each 27 cubic
meters in volume) made of 5 mil FEP Teflon on aluminum frames. Each chamber
has its own air cleaning system to oxidize hydrocarbons (HC) and remove oxides
of nitrogen (NO ).
The study reported here was conducted during July and August of 1975
under Environmental Protection Agency sponsorship. The purpose was to study
the behavior of ozone (03) concentration under simulated conditions of trans-
port of oxidants and their precursors downwind from urban environs. To simu-
late movement from the cities, chemical pollutant systems were irradiated
for multiple daylight periods and subjected to a period of dilution with clean
air. Data are reported for the three 24-hour dilution rates: 0.0% (i.e.,
batch), 77.5%, and 95%. After 24 hours of dilution, the chambers were operated
in a batch mode with no additional dilution.
Initial reactant charges were 1 to 10 parts per million carbon (ppmC)
of a surrogate urban mixture and 0.1 to 1.0 ppm of NO of which 20% was nitro-
gen dioxide (N02). The nonmethane hydrocarbon (NMHC)xto NO ratios were chosen
to be from 7 to 20. x
*Research Triangle Institute, Research Triangle Park, North Carolina.
319
-------
Figure 1. RTI Smog Chamber Facility.
DISCUSSION
The results of the study have been summarized in a series of tables similar
to Table 1. The first 4 columns after the data and chamber number provide
information about the behavior of the system on the first day. For this series
of runs, the 24-hour dilution rate was 95% and it was begun at the time of
NO crossover (at about 0830). In chamber 1, the NMHC charge was about 7
ppmC and the NO was about 1.0 ppm with a ratio of 7. Maximum 03 concentra-
tion in Charnberxl was about 1.1 ppm the first day. The next column indicates
whether the following data are from the second or third day of irradiation.
The N0x concentrations at sunrise were in the parts per billion (ppb) range.
The second- and third-day NMHC/NOx ratios were high; for the whole set of
experiments they ranged from 22 to over 250. Gas chromatographic analysis
of the HC remaining on the second and third day showed a preponderance of
alkanes and aromatic compounds with alkenes virtually exhausted except for a
few tens of ppb of ethylene that usually remained.
The maximum 03 concentrations obtained on the second and third days were
in most cases (in all cases in Table 1) above the National Ambient Air Quali-
ty Standard (NAAQS) for photochemical oxidarit. The net 03 concentrations
generated (i.e., the difference between the morning minima and the afternoon
maxima) were also almost always greater than the NAAQS despite extremely low
NO concentrations.
X
Table 2 represents another type of summary and analysis of the 03-genera-
tive data from the second and third days of irradiation. Both the NO data
and the NMHC/NOx ratios have been stratified by numerical range and tfie net
03 concentrations associated with a particular combination have been listed
in the appropriate cell. Averages of individual cells, vertical columns,
and horizontal rows, are indicated. Although not presented, the same treat-
320
------- An error occurred while trying to OCR this image.
-------
TABLE 2. NET OZONE GENERATED ON SECOND AND THIRD DAYS OF IRRADIATION
AS A FUNCTION OF OXIDES OF NITROGEN AND NONMETHANE HYDRO-
CARBON/OXIDES OF NITROGEN RATIO
NMHC NOY
NOX ppmC Range ppb 1-5 6-8
Range ppm
0-49
.165
50-99 .201 .201 *.124 .128
avg. *.131 avg.
.235
100-199 *.152 .140 .263 .189
*.217 avg. *.250 avg.
*.153 *.105
*.123 *.257
*.054 *.068
.163
>200 .076 .147
.206 avg.
.172
.173
.129
*.125
Avg. .147 Avg. .149 Avg. .171
9 - 14
.195 .164
.115 avq .
*.182
.312 .214
.256 avq.
.230
.214
*.190
*.119
*.177
.123 .134
.094 avq.
.033
*.285
Avg. .180
15
.181
.154
.365
.300
.197
.371
*.344
.150
.135
*.238
*.228
Avg.
- 53
.168
avg.
.315
avg.
.188
avg.
.241
Indicates 3rd-Day Values
A term, fossil 03, has been coined to denote 03 generated in urban en-
virons which is transported over unspecified distances downwind. To investi-
gate this phenomena, the decay of 03 in spent, non-03-generating systems was
examined from both chamber and field studies. Nighttime half-lives of 03 were
calculated for non-dilution chamber operation and are presented in Table 3.
Maximum 03 levels of the previous day are shown and half-lives assuming first
322
-------
O AVERAGE 0, MAXIMA
• AVERAGE 0, MINIMA
O OAVERAGE AO,
K> 20 30 40
OXIDES OF NITR06EN, ppb
SO
Figure 2. Average maxima, minima, and A03 concentrations as a function of
N0x concentrations at sunrise on the second and third days of
irradiation.
.60i
.801-
.40
.30
.201
.101-
O AVERAGE 0, MAXIMA
• AVERAGE 0, MINIMA
D AVERAGE AOj
0.60 1.00 1.50 2.00
NMHC. ppm
2.50
3.00
Figure 3. Average maxima, minima, and AQ3 concentrations as a function of
nonmethane hydrocarbon concentrations on the second and third
days of irradiation.
323
-------
0.40 -
O AVERAGE 0, MAXIMA
• AVERAGE AO,
100 160 200 250
NMHC/NOX , ppmC/ ppm
900
Figure 4. Average maxima andA03 as a function of nonmethane hydrocarbon to
oxides of nitrogen ratio.
W
\2
E OB
Q.
O.
04
0.2
0.0
• August 13 - Batch 01 Dilution
03 Minimum 0.53 ppm
03 Maximum 0.72 ppm
A03 0.20 ppm
A August 9 - 77% Dilution
03 Minimum 0.10 ppm
03 Maximum 0.40 ppm
A03 0.30 ppm
I July ?•"- - 95% Dilution
03 Minimum 0.02 ppm
03 Maximum
A03
0.?9 ppm
0.26 ppm
A A
- I I I I* I*I«I«UI*I I I
I
0800 0400 OtOO 0800 WOO ItOO 1400 1600 1800 2000 2tOO 2400
TIME ( HOURS - EOT)
Figure 5. Ozone profiles over second-day irradiations for same initial
conditions and different dilutions in Chamber 1.
324
-------
order decay were calculated using the 0200 and 0500 hours concentrations.
The table shows the 0200 hours concentrations and the calculated half-lives.
The tabulated half-lives have been corrected for dark-phase clean chamber 03
decay. Of the values calculated, 17 are below 20 hours, 5 are below 60 hours,
and two are rather large, 265 and 450 hours. Data from two field studies may
be used to obtain rough estimates of the dark phase 03 half-life. A series of
vertical 03 concentration profiles taken with an aircraft on August 1, 1974,
at Wilmington, Ohio, are shown in Figure 6. If it is assumed that the profile
at 0700 on August 2 was the same as that at 0700 on August 1, then an assumed
first-order decay from 1700 August 1 to 0700 August 2 suggests an 03 half-
life of 29.5 hours. Ozone measurements collected aloft (from 1800 June 8,
1976, to 0200 June 9, 1976) during the second flight of the DaVinci balloon.
suggest a half-life of 16 to 34 hours.
0.09 0.075 0.10
05. ppm
0.126
Figure 6. Vertical ozone soundings, August 1, 1974,
Wilmington, Ohio.
With half-lives of 20 to 30 hours, the amount of 03 left over on the
following morning can provide a high minimum on which to build a high maximum
for the first day. With half-lives of 20 to 30 hours, however, a parcel of
fossil 03 cannot maintain high concentrations for more than a day or two without
augmenting synthesis.
Figures 7, 8, and 9 may be employed to compare field measurements with
second- and third-day smog chamber data. Figure 7 depicts diurnal curves
drawn from hourly 03 averages at three Ohio stations in the summer of 1974.
The maxima are between 0.07 and 0.08 ppm, indicating that many of the indi-
325
-------
TABLE 3. DARK PHASE OZONE HALF-LIVES IN SMOG CHAMBER RUNS
Date
July 24
July 30
August 6
August 10
August 13
August 14
Experimental Chamber Max [03] Previous [03] at:
Type Number Day ppm 0200 ppm
Dilution
95% *
Initiated at
1700
Dilution
95% Initi-
ated at NOX
Crossover
Dilution 77%
Initiated at
NOX Cross-
over
Dilution 77%
Initiated at
NOX Cross-
over
Batch
Batch
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
0.185
0.138
0.119
0.089
0.286
0.212
0.214
0.175
0.479
0.366
0.350
0.214
0.400
0.293
0.288
0.179
1.378
0.886
0.997
0.549
0.724
0.525
0.786
0.336
0.066
0.048
0.038
0.025
0.102
0.085
0.076
0.083
0.311
0.243
0.213
0.109
0.218
0.175
0.150
0.109
0.776
0.561
0.567
0.415
0.422
0.333
0.352
0.252
Half-Life
(t1/2) hrs
4.3
3.6
11.6
13.3
6.4
6.2
7.4
7.8
14.9
11.6
10.0
7.1
16.6
14.2
19.2
14.2
33.5
42.9
50.3
265.4
119.9
27.2
54.5
449.6
*Mechanical dilution had been terminated prior to the time periods chosen
for half-life calculations.
vidual concentrations making up the hourly averages were over the NAA^S. The
time of maxima at these rural stations was shifted more toward sundown than
that typically observed in an urban atmosphere. Also the slope of the build-
up side of the diurnal rural 03 curve is steeper than the 03-destructive side.
Generally, this is not the case in urban atmospheres where freshly emitted
pollutants (e.g. auto exhaust in evening rushhour traffic) act as 03-destructive
agents and cause the sharp drop on the destructive side of the diurnal urban
03 profile.
326
-------
0.0* r
• MCCONNELSVILLE
o WOOSTER
• WILMINGTON
0.00
OTOO OMO 1100 IMO 1600 1700 l»00 tlOO £300 0100 OSOO 050O OTOO
TIME (HOURS -EST)
Figure 7. Mean diurnal 03 concentration at Wilmington, Wooster, and
McConnelsville, Ohio, from June 14-August 31, 1974.
t
9
'I'ri'rrri'i'i'i'i'i'rrrri'i'i'i'i'i'i' TiTT'i'i'i'i'iTi'i'i'i'i'i'i'i'iTi'i'i1 , n
' 7/21 il IU • HO. Oil. HOW «M 7/25 tl 951 • HO. OR EWf.0 TOO
- ° ° ° " o « *
- • X *
I *li|l||l||l,l1illHlillrt1ill-1i|ldlal*Cli'1ilillJl«l«lilll •lOl«l(llJli(ll!l«l»llllBllllfllellll«lOl«1«1«lBlfll<1lll fl'rtC
1 1 2 3 1 5 * 1 • 9ltlllfli~m$ltl7lfl92f2l22~23~ f 1 2 3~ 1 5 ( 7 • f Itl Mllfli 15 1* iflt H202I [2223 I 1 2
lilt OF DKY
I'l'I'I'ITI'I'I'I'I'I'ITI'I'I'I'I'I'l1-
7/» fl
>«i
-------
Concentration profiles for the previously discussed (Table 1) July 28-
30 three-day run are presented in Figure 8. In this run, there was a 95%
dilution of the system in 24 hours starting at the time of NO crossover.
The NO became virtually undetectable, and the second- and tnS>d-day maximum
03 andxnet 03 concentrations were in excess of the NAAQS. Note also that
the 03-destructive side of the second-day 03 profile is less steep than that
typically observed for urban air.
Figure 9 depicts the hourly averages of N0x from the field obtained at
the same time and in the same areas as the 03 data in Figure 7. The N0x
concentrations ranged from about 2 to 12 ppb. Smog chamber second- and third-
day values were 1 to 53 ppb. Calculated from average data, the NMHC/NO ratios
ranged from 27 to over 300 for field data and ranged from 22 to over 256 for
second- and third-day smog chamber data.
Chamber data of the second and third day are remarkably similar to field
data. In making comparisons between field data and chamber data the follow-
ing caveats should be observed. No additional reactants were added to the
chambers after the first day, whereas there is continuous addition of reac-
tants to the ambient air. The so-called "dirty chamber effect" was also ob-
served in the chamber. Direct comparisons and control strategy decisions based
on these data are therefore difficult.
CONCLUSIONS
In partially spent simulated urban photochemical systems, 03 was gener-
ated in concentrations above the NAAQS with low concentrations (ppb) of NO
and high NMHC/NO ratios. x
X
The smog chamber data also suggest that the role of fossil 03 is to
provide a high minimum upon which to build a high maximum on the next day.
The fossil 03, unaugmented by subsequent synthesis, probably cannot provide
concentrations over the NAAQS for more than a day or two.
The smog chamber data indicate that the dilution effect (i.e., more efficient
03 generation per molecule of N0x with dilution) is an important process in
delivering high 03 atmospheres.
The atmospheric chemical problems in general and the high rural 03 problem
in particular will yield to a three-faceted approach: field measurements,
experimentation in smog chambers, and mathematical modeling. Each single
facet has its limitations but iterative studies using the combined approach
should yield useful information and solutions to current problems of atmos-
pheric chemistry.
328
-------
7-5
OZONE EPISODES ON THE SWEDISH WEST COAST
P. Greenfelt*
ABSTRACT
Ozone. me£tt>iL>iejme,nti> nave been postfaorwed. -in Gothe.nbusig on the. S>we,dit>k
c.oaf>t Atnce. 1972. On ^nveJiaJi occcw-toni e.veAy t>u.mmeA 4.ncAe.ai>e.d lnvoJU, o& ozone
WQAQ. ob-ieAved. The. highest finc.ond.iid 1-houA mean uicu, 110 ppb. The. high ozone.
£eve£6 co4.ncA.dejd hi tune. with incAeaA e.d c.onc.e.ntfLation{> o& paSLticJLe,-bosine. t>uJL-
phuA both in. and. outbade. Goth&nbuAg and o& Aoot outA4.de. Gothe.nbuA.g . Ttuij zctoiy
Ahowe.d that moAt o{, th&>e. zplAodu weAe. aA&o(u.ate.d with ttian&pofit o&
INTRODUCTION
Long-distance transport of air pollutants over western Europe has been the
object of extensive research in these countries since around 1970. This work
has been focussed mainly on sulphur compounds and their role in the acidification
of lakes, running waters and soil. The study of other essential air pollutants
such as heavy metals, chlorinated hydrocarbons and nitrogen oxides has been very
limited. However, as regards photochemical oxidants a few reports of investiga-
tions are available (1,2). This paper presents results of measurements of ozone
and associated parameters performed on the Swedish west coast.
OZONE MEASUREMENTS IN GOTHENBURG
Continuous ozone measurements according to the chemiluminescent ozone-
ethylene method have been carried out in Gothenburg on the Swedish west coast
since January 1972. Gothenburg is a highly industrialized city (e.g. two oil
refineries), with a population of half a million. Initially, the purpose of
the measurements was to investigate the possible occurrence of locally produced
photochemical ozone. Once the results were obtained, the measurements were
extended to include long-range transport of oxidants and their precursors.
-Only two months after the measurements were started, on the 16th of March,
the ozone level in Gothenburg rose to above 90 ppb (Figure 1). Although higher
peaks have been observed later, this one was remarkable because it occurred so
early in the year. March is considered to be a winter month in Sweden; the
monthly mean temperature in Gothenburg is +0.7°C. The meteorological conditions
and the concentration of other pollutants on this day are shown in Table 1. The
data clearly indicate that this ozone peak could not be associated with any
natural sources. This is particularly obvious from the concentrations of soot
and particle-borne sulphur as well as from the visibility data.
^Swedish Water and Air Pollution Research Laboratory (IVL), Gothenburg, Sweden.
329
-------
100
a.
o.
o
N
O 40
20
72-03-16
00 03 06 09 12 15 18 21 24
TIME
Figure 1. Ozone concentrations in Gothenburg, 16 March 1972,
TABLE 1. METEOROLOGICAL CONDITIONS AND CONCENTRATION OF AIR
POLLUTANTS IN GOTHENBURG ON 16 MARCH 1972
Wind direction
Wind velocity
Temperature
Relative humidity
Visibility
Overcast
Ozone
S02
Soot (OECD-method)
at 13.00 hrs
max. 1-hour
Particle-borne sulphur
(X-ray fluorescence)
daily mean
SSE
3 m/s
7 km (4 miles)
No
180 yg/m3
114 yg/m3
57 yg/m3
40 yg/m3
In the following months (March-August) of 1972, several similar peaks in
ozone concentration above the natural background level were observed. These
occurred mostly in the afternoons and early evening hours. However, peaks were
observed also at other hours of the day, e.g. early morning. For this period,
1-hour concentrations above 80 ppb occurred on a total of 16 days; the highest
330
-------
value recorded was 110 ppb. In subsequent summers (1973-76) similar ozone epi-
sodes were not as numerous as in 1972, and on no occasion did the ozone level
exceed 110 ppb within Gothenburg.
The episodes have been evaluated on the basis of meteorological conditions
and the concentration of other pollutants. The meteorological conditions during
days with high ozone levels showed large variations. For example, the daily
maximum temperatures during episodes in 1972 and 9173 ranged from +11.5°C to
31.5 C. The wind velocity also varied considerably (episodes could occur at
wind velocities of up to 13 m/s), whereas there was a clear pattern with resnect
to wind direction: During nearly all episodes winds were blowing from the sec-
tor SE-W. Mostly low or moderate values for visibility were recorded. All
meteorological observations were made at Torslanda Airport, 10 km west of Gothen-
burn (Figure 2).
TORSLANDA
(METEORO
LOGICAL
PARAMETERS )
(O3,NOX,PART.
SOOT)
GOTHENBURG
CENTRAL
GBG (SOOT
SO2,PART.S,
03)
N
1O KM
Figure 2. Location of sampling stations for air pollution monitoring and
meteorological measurements
Sulphur dioxide, soot and particle-borne sulphur are measured in Gothenburg
in a routine network. To determine the origin of the ozone episodes observed in
Gothenburg, comparisons were made between daily mean concentrations of these
pollutants and peak ozone concentrations. Correlation coefficients were calcu-
lated for each month with more than 10 comparable data in the periods March-
August 1972 and 1973. No significant covariations for sulphur dioxide and soot
were found, but a clear positive relationship was observed for particle-borne
sulphur. The correlation coefficients between daily maximum 1-hour ozone mean
values and daily mean values of particle-borne sulphur were in the range of
0.30-0.80 in nine out of ten months (Table 2). As examples of the covariations,
plots from August 1972 and 1973 are shown in Figure 3.
331
-------
TABLE 2. CORRELATION BETWEEN DAILY MAXIMUM 1-HOUR CONCENTRATIONS OF OZONE IN
GOTHENBURG (GBG) AND SOOT, PARTICLE-BORNE SULPHUR.IN GOTHENBURG AND RORVIK.
MARCH - AUGUST 1972 AND 1973.
1972
1973
Ozone vs. Ozone vs.
soot soot
Gbg Rb'rvik
r n r n
March 0.31 22 0.13 24
May -0.21 27 -0.17 27
June 0.04 22 0.68 26
July 0.36 25 0.43 28
Aug. 0.01 17 0.48 17
April -0.23 13 0.30 13
May 0.50 31 0.50 31
June 0.28 30 0.34 30
July 0.08 31 0.42 28
Aug. 0.25 26 0.51 26
Ozone vs. Ozone vs.
part. S part, S
Gbg Rdrvik
r n r n
0.48 22 0.38 24
-0.15 27 0.01 27
0.30 23 0.69 24
0.65 25 0.60 28
0.80 17 0.30 13
0.50 13 0.67 13
0.63 31 0.51 31
0.62 30 0.54 30
0.31 31 0.31 31
0.65 26 0.63 26
- 25-
2
^-20-
£ 15-
X
Q.
- 10-
(0
5-
0'
I
AUG 1972 .
* R = 0,80
.
*
i
) 20 40 60 80 100
OZONE (PPB)
AUG 1973
• — 25' •
" R • 0,65
0 20- • *
£ 15.-
X *
Q! , * 9
5 •*•• *•
0 1*1 1 4 1
0 20 40 6*0 8O 100
OZONE (PPB)
Figure 3. Daily mean concentration of particle-borne sulphur in Gothenburg
plotted against maximum 1-hour concentration of ozone
in Gothenburg for the months of August 1972 and 1973
332
-------
LONG-RANGE TRANSPORT OF OZONE
From other measurements on the Swedish west coast it is known that the
concentration of particle-borne sulphur within Gothenburg is mostly a product
of long-range transported sulphur. The daily ozone peak concentrations in
Gothenburg were therefore compared to the concentrations of soot and particle^-
borne sulphur samples at a non-urban coastal station (Rorvik) about 40 km south
of Gothenburg (Figure 2). This station is primarily used for long-range trans-
port studies. Soot and particle-borne sulphur have proven to be very useful
tracers for long-range transport of air pollutants. Positive correlations for
particle-borne sulphur and for soot were observed at this station (Table 2).
These results indicated that the observed ozone episodes were not associated
with pollutants produced in Gothenburg, but were a result of long-range trans-
ported pollutants. To confirm this, 48-hour trajectories were calculated for
the days with high ozone concentrations in 1972 and 1973 (3). It was found
that in 28 out of 33 cases, the air masses came from the sector E-S-W, having
passed over heavily industrialized areas in Great Britain or on the Continent.
As an example, the trajectory for March 1972 is plotted in Figure 4.
16 MARCH,1972
Figure 4. 48-hour trajectory for 16 March 1972.
Comparisons were also made between daily maximum concentration of ozone
and particle-borne strong acid measured according to Brosset (4). However,
acid has not as yet been measured on a routine basis comparable to ozone moni-
toring and no statistical evaluation is therefore possible. Nevertheless, an
examination of the data will show that most of the strong acid episodes are
associated with ozone peaks (Table 3).
In the summer of 1975 ozone measurements were also performed at the non-
urban station (Rorvik). There, high ozone levels were observed on several oc-
casions.. The 1-hour ozone concentration exceeded 120 ppb on 11 days in that
period; the maximum hourly concentration was 210 ppb.
There was mostly a close covariation between the ozone levels observed in
333
-------
TABLE 3. COMPARISON BETWEEN CONCENTRATION OF STRONG ACID ON PARTICLES
SAMPLED AT RORVIK AND MAXIMUM OZONE CONCENTRATIONS DURING THE FIVE MOST
ACID EPISODES IN THE SUMMER OF 1975
May
Aug
19
29
. 5
7
29
H+
n mole/m3
Rb'rvik
225
62
77
21
56
NH4+/H+
mole/mole
Rorvik
2.8
2.4
1.3
2.8
3.6
03
ppb
Gothenburg
66
45
54
84
47
03
ppb
Rorvik
76
75
130
151
-
Rorvik and Gothenburg. However, for most of the time, the level was higher at
Rorvik. This indicates that there is no local contribution to the ozone level
in Gothenburg. Instead, other pollutants emitted locally partly destroy the
incoming ozone. Figures 5 and 6 give examples of ozone episodes.
— 100-
01
80
20
00 03 06 09 12 15 18 21 24 03 06 09 12 15 18 21 24
75-06-18 TIME 75-06-19
00 03 06 09 12 15 18 21 24 03 06 09 12 15 18 21 24
75-06-20 TIME 75-06-21
Figure 5. Ozone concentration in Gothenburg and Rorvik, June 18-21, 1975.
334
-------
-
00
UJ
140
120
100
80
N
A—,
A
*. >V\
AXv V
,rv
00 03 06 09 12 15 18 21 24 03 06 00 12 15 18 21
75-08-06 TIME 75-08-07
24
00 03 06 09 12 15 18 21 24 03 06 09 12 15 18 21 24
75-08-08 TIME 75-08-09
Figure 6. Ozone concentration in Gothenburg and Rorvik, August 6-9, 1975.
In a further investigation of the cause of the ozone episodes, continuous
measurements of nitrogen oxides were carried out during the summer of 1975 at
Rorvik. The levels of nitrogen monoxide as well as nitrogen dioxide were in
the range of 1-10 ppb. Despite the small variations in concentration, positive
relationships could be seen between the early morning concentrations of nitro-
gen oxides and maximum ozone levels. Figure 7 is an example of the variation
pattern.
DISCUSSION
From our measurement data as well as from those collected in other countries
in western Europe, it is clear that several ozone episodes occur every summer
over large areas in Europe. The impact of these episodes is not known and no
investigations have as yet been carried out in Sweden to clarify this. It is
very likely that these ozone peaks cause damage to vegetation, but no such ef-
fects have as yet been observed. One reason for this may be that plant injuries
on the Swedish west coast are often assumed to be caused by sea spray.
As regards effects on human health, complaints about photochemical smoq
were made on one occasion (28 May 1973) in Gothenburg to the local Board of
Health. The highest concentration of ozone in Gothenburg that day was 80 opb.
No data from areas outside the city are available. This episode was associated
wtth very high concentrations of an aerosol consisting of sulphuric acid and
ammonium sulphate (5,6).
335
-------
21 24
Figure 7. Variations in concentrations of ozone and nitrogen oxides at Rorvik,
2 July 2975 and 6 August 1975.
One question that arises when studying the simultaneous occurrence of high
ozone levels and high concentrations of acid sulphate aerosols is: Does ozone
play any role in the oxidation of sulphur dioxide in the lonq-range transported
air masses? The question is very justified considering the correlations observed
between ozone and sulphate. In winter, the sulphate in the frequent episodes
resulting from long-range transported pollutants is formed through catalytic
oxidation. In summer, this process is less likely because of, among other things,
low relative humidities. The summer aerosols also differ from the winter aero-
sols in several other respects, e.g. size distribution and acidity. These dif-
ferences indicate that sulphates are formed by different mechanisms and that
ozone or oxidants are compounds that might play a role in sulphate formation.
It is well known that the reaction between ozone and sulphur dioxide in
the gas phase is a very slow reaction and of minor importance for the oxidation
of sulphur dioxide. However, according to pxperiments by Penkett, oxidation by
ozone in the liquid phase might be possible (7). The acid aerosols normally occur-
ring in connection with ozone episodes contain a water phase even at rather low
relative humidities. Research on this reaction mechanism is in progress.
REFERENCES
1. Cox, R. A., A. E. J. Eggleton, R. G. Derwent, J. E. Lovelock, and D. H. Pack.
Long Range Transport of Photochemical Ozone in North-Western Europe. Nature,
225 (5504): 118-121, 1975.
2. Grennfelt, P. Measurements of Ozone in Gothenburg, January 1972 - August
1973 and Studies of Co-Variations Between Ozone and Other Air Pollutants.
Internal publication B221, Swedish Water and Air Pollution Research Labora-
tory (IVL), Gothenburg, January 1975.
336
-------
3. Henrikson, A. B. An Investigation of the Accuracy in Numerical Computations
of Horizontal Trajectories in the Atmosphere Meteorologi, 27. Swedish Mete-
orological and Hydrological Institute, Stockholm, 1971.
4. Askne, C., and C. Brosset. Determination of Strong Acid in Precipitation,
Lake Water and Air-Borne Matter. Atm. Environ. 6: 695-696, 1972.
5. Brosset, C., K. Andreasson, and M. Perm. The Nature and Possible Origin of
Acid Particles Observed at the Swedish West Coast. Internal publication
B189, Swedish Water and Air Pollution Research Laboratory (IVL), Gothenburg,
1974.
6. Brosset, C. Acid Particulate Air Pollutants in Sweden. Internal publication
B 222, Swedish Water and Air Pollution Research Laboratory (IVL), Gothenburq,
1975.
7. Penkett, S. A. Oxidation of S02 and Other Atmospheric Gases by Ozone in
Aqueous Solution. Nature Physical Science, 240 (101): 105-106, 1972.
337
-------
SESSION 8
IMPACT OF STRATOSPHERIC OZONE
ChcuAmam R. Guicherit
IGTNO, Netherlands
339
-------
8-1
OZONE OBSERVATIONS IN AND AROUND A MIDWESTERN METROPOLITAN AREA
G. D. Huffman, G. W. Haering, R. C. Bourke, P. P. Cook, M. P. Sillars*
ABSTRACT
A -ia/r/cei o£ ground le.\>eJi and attitude, me.aAuA.ewe.ntA o^ ozone, have. be.e.n
c.aAAA,e.d oat -in the. lndLa.na.poLU> o/ieo. faiom 1974 to 7976. The. majox, x.&>uLt!>
o& the. ground ItveJi ttudiu ate. ie.v-ie.we.d and eA. In addition, an e.xte.n£-ive. AeAieA o& aLtlta.de.
AuA.ve.yA o^ ozone, have, been conducted . Typical A.uuLtA ofa both hoA^zontal
and v&itic.al flight path* one. pA.e^>e,nte,d. Again the^e. n.eAmLtt, one. de^cJvibe.d
In teAm& o& long lange. c.onve.c£Lon, tiVibuLtnt mLitLng, photoc.he.mLc.aL Qe.neAatLo\
and t>t>iatopheJu.c. tnan&poJit. The. dLveJiA-Lty ofa the. teAt x.eAuJLtb Indicates
that undeA gLve.n me^te-o^oiog-Lcal condition* any one. on motie. oft the. above, pno-
ce44£4 may OC.CUA, In AummaSLy, ozone. ge.neAation and tA.ant>pofct Ln an uJtban
e.nvinonme.nt AJ> e.'xJJim&Ly c.ompLe.K, and additional data L& fie.quin.e.d pniofi to
an Ln-de.pth understanding o& the, phe.nome.na i.nvolve.d. Suc.h an undeJiAtand-
-ing would the.n hope.fiulty Le.ad to an e. ft Active. c.ontA.ol AtnatiLay,
INTRODUCTION
The Environmental Protection Agency (EPA) issued regulations in 1971 (1)
stating that oxidant levels were to be maintained at values less than 0.08
ppm. This was predicated upon oxidant levels of 0.01 to 0.05 ppm in rural
areas (2) and the presumption that values exceeding these levels were genera-
ted in urban centers.
In actuality, the oxidant level existing at a given location is the re-
sult of a complex interaction between meteorological, transport and genera-
tion (or destruction) processes and can be described—to first order accuracy
--by the following relations (3, 4, 5):
3lJ.
U1fl. =0 [2]
8T' ' = kT' [3]
*G. D. Huffman, G. W. Haering, Indianapolis Center for Advanced Research
(ICFAR) and Purdue University School of Science, Indianapolis, Indiana.
R. C. Bourke, P. P. Cook, Indianapolis Center for Advanced Research and
Detroit Diesel Allison Division, General Motors, Detroit, Michigan.
M. P. Sillars, CWS, Inc., Flint, Michigan.
341
-------
J
JJ-
.J
»jj
exp (-1
C4]
where Cartesian tensor notation has been used with 1 and 2 denoting the hori-
zontal coordinates and 3 the vertical direction. A repeated subscript indi-
cates a summation while ,i indicates differentiation. T1 and P1 represent
the deviation from the adiabatic temperature and pressure conditions^ with the
temperature, and concentration divided into a time mean, I)., T1 , and
i.e., u., t, and c^ '. The fluid properties
v-the kinematic viscosity, k-the thermal con-
constant, and a-the mass diffuslvity. g repre-
S. . the Kronecker delta and F the frequency
vejocity
C^ , and instantaneous value,
are denoted by p -the density,
ductivity, R-the°universal gas
sents the gravitational force,
OCTIOJ one y i ay i oa L. I una I iuii~c, u . . uie IMUNfcJLKer Ufc! I Id ClMU t UHG TTeqUB
factor and Ev ; the activation energy of the (i)-th chemical species, with ,
denoting time. Equations [1] through [4] represent the conservation of mo-
mentum, energy, and mass for a turbulent medium. These relations are for-
mally indeterminate since the Reynolds averaging procedure has introduced
the unknowns u.u,, tu". and cllV, which describe the turbulent diffusion
processes. Attempts are currently being made to solve these equations (3);
however, they are of value even in this form since they show that the concen-
tration at a point is due to convection, turbulent transport, viscous trans-
port, and generation or destruction. There is a strong interaction between
concentration, temperature, velocity and the chemical reactions themselves.
Note that the terrain and external transport features enter the process
through the boundary conditions. This balance is shown schematically in
Figure 1.
TRANSPORT IN
BOUNDARY CONDITIONS APPLIED
ALONG EXTERNAL SURFACES
TRANSPORT OUT
TIME RATE
OF CHANGE
Figure 1. Processes Represented by the Transport Equations.
342
-------
With this phenomenological description of the oxidant generation transport
process in mind, the Indianapolis Center for Advanced Research (ICFAR) in
conjunction with the City of Indianapolis, State of Indiana, Environmental
Protection Agency-Region V (in 1974), and a consortium of local businesses
instituted a continuing study of ozone levels in and around Indianapolis.
This paper will summarize the major findings of three years of ground level
and altitude measurements and attempt to interpret the results in terms of
the previously described phenomena.
GROUND LEVEL MEASUREMENTS
The ground level measurements were initiated in June of 1974 using six
monitoring stations. Their location relative to Indianapolis and Marion
County is shown in Figure 2. These locations have been used throughout the
three years of the study with some minor changes. All data was taken according
to EPA guidelines (6) with the data quality assurance tasks performed in 1974
by EPA contractors (7) and by the Indiana Air Pollution Control Division in
subsequent years.
While ground level measurements do not in general reveal substantial
insight into the ozone generation/transport mechanisms, they do serve to define
the magnitude of the problem and can be used to estimate the contribution of
various processes to over-all oxidant levels. In this context, the following
results were obtained from both the 1974 (8) and 1975 (9) studies.
A unique relative ordering existed between the sites in ozone concen-
tration, which did not change significantly with wind direction. This im-
plies that wave-like ozone excursions that have been noted in the Los Angeles
Basin (10) do not occur in Indianapolis. The substantial terrain differences
may account for this.
A high degree of correlation existed in the daily profile or time rate
of change of ozone measured at each site with no decrease in this correlation
with increasing distance. This is illustrated in Figure 3. This result in
conjunction with the lack of correlation between site ordering and wind direc-
tion indicates that horizontal is much smaller than vertical mixing. Further-
more, the time rate of change of concentration is in balance with vertical
diffusion processes and the generation (destruction) term. This is indicative
of elevated, remote natural or anthropogenic sources. This may be due to
photochemical generation at the surface, stratospheric ozone (11, 12), and/or
a cyclic vertical ozone or ozone precursor transport process (10).
Ozone levels in the incoming air at upwind rural background sites often
exceeded the federal standard. This is illustrative of long range transport
of ozone and/or ozone precursors (13, 14, 15).
No statistically significant differences were found for daily average
ozone concentrations between weekends and weekdays; however, the percentage
of weekend violations of the hourly standard was higher than for weekdays.
Moreover, traffic density in the area of each site showed a negative rela-
tionship with the relative ordering of sites on measured levels, i.e., inner
city, high traffic density sites showed low ozone levels while upwind and
downwind, low traffic density sites showed higher ozone levels. This suggests
343
-------
increased turbulence and scavenging towards the center of the city (16, 17).
Measured ozone levels had a strong positive correlation with tempera-
ture and solar radiation. This is,also a commonly noted effect and is due to
enhanced reaction rates_through Fu; exp (-E1 YRT) and increased turbulent
mixing as a result of gT'6. /T .
too
10 15 ao
lntonH«Dlitanc« ml
28
Figure 3. Intersite Distance Robust
Correlation Coefficient.
Jutonon Counly
Figure 2. Monitoring Sites.
In addition to the ozone measurements, some nitrogen dioxide (N02) and
non-methane hydrocarbons (NMHC) measurements have been carried out. The rela-
tionship between the maximum daily ozone concentration and the 6:00-9:00 a.m.
N02 and NMHC is shown in Figures 4 and 5. This indicates a low correlation,
i.e., approximately 0.35, in both cases. While this cannot be interpreted as
non-correlated in an absolute sense, it does indicate a weak direct relationship,
OJDr
MO-MO UK NO, CoKOTMUoi, M*
o.wo
Figure 4. Maximum Ozone and Morning Figure 5. Maximum Ozone and Reactive
N02 Concentrations - 1975. Hydrocarbon Concentrations - 1975.
ALTITUDE MEASUREMENTS
Since the velocity, temperature, and concentration fields are inherently
344
-------
three-dimensional and time-dependent in nature, a series of altitude measure-
ments has been carried out in conjunction with the previously discussed
ground level measurements (7, 8, 9, 12).
with a fixed wing aircraft, an AID and a
for altitude effects following reference
ture measurements. Three separate types
ducted: vertical spirals above a ground
hundred feet to approximately 30,000 ft.
line to county line (see Figure 2) from
All experiments have been conducted
Dasibi ozone monitors—corrected
12--and a thermistor for tempera-
of aircraft flights have been con-
station from altitudes of a few
; horizontal traverses from county
2000 to 15,000 ft.; and, long range
horizontal traverses from state line to state line at a series of altitudes.
Some typical results for the vertical spiral flights are shown in
Figures 6 through 12. Figures 6 through 8 show a discontinuous and/or inter-
mittent behavior. These spikes do not indicate a smooth ozone profile but
rather irregularly shaped "lumps." Mechanisms must be in existence to main-
tain this structure since diffusive processes would, over a period of time,
normally yield a fairly uniform distribution.
11000
mooo
M»: 8-25-74
Tim*: 8:46am.
Wind: WSW~15mph
8000
MOO
4000
2000
002 OJM ooe
OxofM Concentration, ppffl
QOB
8-23-'74
Tkiw: 2:30 pun.
Wind: WNW^Mmph
jQround
oi—^r .
Figure 6. Ozone Concentration
and Altitude - Indianapolis.
'0 0.10 OJO 030 040 O90
feonCaneMMtan, ppm
Figure 7. Ozone Concentration
and Altitude - Indianapolis.
Figures 9 through 11 demonstrate a more uniform distribution typical of
a well mixed layer. Note that Figures 9 and 12 approach a high ozone concen-
tration at the higher altitudes. This is consistent with an elevated source.
Figure 12 also shows two distinct strata of high ozone at
along with a low ground level concentration. This may be
lower altitudes
due to ground level
generation and transportation aloft and/or transportation downward from a high
level source with ground level scavenging.
The processes that occur within the atmospheric surface layer are of
particular importance and show somewhat different behavior than those aloft.
A series of these measurements is shown in Figure 13 for both summer and af-
ternoon conditions. Although the concentration gradients are quite different
345
-------
near the ground, they approach the same value aloft. Similar results are re-
ported in reference 18. This particular set of values is indicative of a
"blanket" of ozone covering the entire area during the measurement period.
Both afternoon curves indicate a well mixed layer with nearly uniform concen-
tration. However, the night between the two afternoons indicates a low ground
level concentration with values aloft approaching those of the afternoons.
This phenomenon could be caused by an ozone reservoir blanketing the area
with continual scavenging at the surface. At night, when no photochemical
processes are present and vertical transport is limited by the inversion,
the surface ozone is destroyed. However, in the afternoon, with enhanced
vertical transport and photochemical processes, the surface concentration
approaches that of the blanket.
12,000
10,000
8000
600°
4OOO
2000
Date: 8-23-'74
Tim*: 2:00pjn
Wind:
Uv*
005 * 0.10 0.15
Ozone Concentration, ppm
020
Figure 8. Ozone Concentration and Altitude - Indianapolis.
Horizontal flights at a series of altitudes were also
Figure 14 shows that there are significant departures from
of ozone concentration with the principal demarcation
ft. This sharp delineation often occurs on days with
(Figures 9 and 12).
carried out.
uniform stratification
located at about 4000
high ozone concentration
Cross-country flights generally indicate constant or slowly varying ozone
values with distance from Indianapolis at constant altitudes. Figure 15 shows
a typical result and corresponds to conditions in Figure 13. The origin of the
deep spikes is unknown—they were not generally present. The "steady" ozone
values were observed to extend upwind and laterally to approximately 70 miles--
the extent of the flight. Figure 16 shows results obtained from another cross-
country flight. Again reasonably uniform ozone values occur for the length
of the traverse—approximately 300 miles. This condition corresponds to the
vertical traverse of Figure 11.
346
-------
30,000
20,000
10,000
30,000
Ground
8- 28- '75
Tinw: 5:00pm
2QPOO
10jOOO
iL**^ __^
~oos oS>
015
0.20
: 3-6-'76
Tlnw: 4:OO pm
Uv*
005
OJO
0.15
0.20
Oxon* Concentration, ppm
Figure 9. Ozone concentration
and altitude - 1975.
Ozone Concentration, ppm
Figure 10. Ozone concentration
and altitude - 1976.
30#00r
30000
2QDOO
6-9- '76
7^30 pan
1QQOO
r
I
i
10^000
O06 OflO^ OI5 Q20
Ozon«Conc«itration, ppm
Figure 11. Ozone concentration
and altitude - 1976.
Date: 9-2-"7S
Tim*: 7:00pm
0 OJO 020
Ozoo* Concentration, ppm
Figure 12. Ozone-altitude data
over Northwest Indianapolis.
347
-------
1400
12OO
1000
£ 800
600
400
200
i: 7-17- '75
Tlrm: 4:OOpm
Date
Tinw: 3:00pm
Dite:7-17-'75
Tbiw:5.-00ant
Tmpwatura °F.
70 75 80 85 90
15,000
7-W-75
3=00 pm
0.06 OX) 0.15
Ozone Concentration, ppm
0.20
10,000
5,000
<03
-.03
.03 >.03
30
West
20
10 0 10
from City Canter
20
East
Figure 13. Ozone concentration and Figure 14. Ozone concentration over
altitude, 25-hr, period, Indianapolis. Indianapolis, 7-29-75, 5:00-8:00 p.m.
Numbers on plot denote lines of con-
stant ozone concentration.
J04
• .08
. Date 7-17-*75
TbNK 440am
AltHudK900n
Flitf* Direction
Dtnciton
10
30 40 80
80
from Center of City
Figure 15. Ozone Concentration and Temperature Upwind of Indianapolis at
900 Feet Altitude.
348
-------
Wind Dhwctton
Ftiffit DtaKtton
.08
§7
>: 8-9-'7«
Tim*: 5:30 pm
Altttud*: 1500ft
^JTwnpwvlim
*r A •'••
'•
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Figure 16. Ozone Concentration and Temperature Near Indianapolis.
Even though many different ozone profiles are encountered, a few general
characteristics can be noted. First, ozone levels do not change appreciably
over long distances at constant altitude both upwind and laterally as long
as no frontal activity is encountered. Secondly, ground level concentrations
change in a diurnal pattern—mornings usually having lower values with high
values in the afternoon. Ozone levels at altitudes of a few thousand feet
tend to remain reasonably constant diurnally--barring gross meteorological
changes. Afternoon ozone concentrations have similar values both at the
surface and aloft. This may be due to scavenging of ozone at the surface
during the night and morning hours and then afternoon surface increases result-
ing from both photochemical processes and enhanced vertical mixing. Finally,
ozone concentrations at altitudes of 25,000 ft. are often quite high indica-
ting potential ozone transport from the stratosphere.
UPPER AIR METEOROLOGICAL STUDY
In an effort to isolate meteorological transport of ozone-rich air from
the more conventional sources due to photochemical formation and surface ad-
vection, a meteorological study (19) was conducted of a high ozone incidence
that occurred on February 24, 25, and 26, 1976. During this time period both
Dayton and Indianapol-is measured ozone levels exceeding the current standards.
A study of area and national surface maps indicated that advection and/or
long range transport from an adjacent urban center to Indianapolis or Dayton
was unlikely.
To explore other possible causes, a series of vertical cross-sections
were plotted extending from the surface to 50,000 ft. The cross-sections
originated at International Falls, Minn. (INL) and followed an irregular path
through Green Bay, Wis. (GRB), Dayton, Ohio (DAY), Huntington, W. Ma. (HTS)
349
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and Greensboro, N. C. (6SO). For both dates, the wind aloft and the location
of the tropopause were plotted (see Figures 17 and 18). These figures show
a low-level jet located immediately below the break in the tropopause. If
the high-speed jet is an ozone rich wind stream originating near the tropo-
pause break and gradually descending, winter occurrences of high ground level
ozone concentrations could be more easily explained. While this phenomena is
unlikely during the summer months it may well explain unusual occurrences
during the late fall, winter and spring.
DAY HTS
GSO
INL
Qfe
INL
ORB
Figure 17. Vertical cross-section
of Atmosphere over Midwest -
February 29, 1976.
Figure 18. Vertical cross-section
of Atmosphere over Midwest -
February 25, 1976.
CONCLUSIONS
The diversity of the test data indicates that meteorological, transport,
and photochemical processes all could be important contributors to ground and
altitude ozone levels. Under a given set of conditions, one process may
dominate or all three processes may make equal contributions. As a result,
it is difficult to draw general conclusions. Categorization of ozone pro-
files according to atmospheric stability might prove useful—unfortunately a
broad enough data base is not yet available for this purpose.
Even though the phenomena cannot be described in concise terms, results
indicate that for the Indianapolis area wave-like migrations of ozone and/or
ozone precursors are not a major contributor to ground level concentrations.
Furthermore, vertical mixing seems to dominate other processes with either a
surface or elevated source supplying the ozone. During a winter period,
350
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stratospheric sources have been identified. This is not necessarily the pre-
dominant contributor in the summer with ozone and/or ozone precursors, ver-
tical transport and re-entrainment coupled with photochemical generation
equally likely! All in all, ozone generation and transport in an urban en-
vironment is extremely complex and additional data is required before an
in-depth understanding of the phenomena involved can be reached. Such an
understanding would then hopefully lead to an effective control strategy.
REFERENCES
1. "Requirements for Preparation, Adoption and Submittal of Implementation
Plans," Federal Register, 36_, August 1971, p. 15486.
2. "Air Quality Criteria for Photochemical Oxidants," National Air Pollution
Control Association, Durham, N. C., March 1970, p. 4-3.
3. Bradshaw, P. An Introduction to Turbulence and its Measurements, Per-
gammon Press, Oxford, England, 1971.
4. Lumley, J. L. and H. A. Panofsky. The Structure of Atmospheric Turbulence
Interscience Publishers, New York, N. Y. 1964.
5. Beer, J. M. and N. A. Chigier. Combustion Aerodynamics, John Wiley and
Sons, Inc., New York, N. Y. 1972.
6. Guidelines for Development of a Quality Assurance Program, Reference
Method for Measurement of Photochemical Oxidants, EPA Monitoring Series
No. EPA-R4-73-028c, June 1973, Office of Research and Monitoring, U. S.
Environmental Protection Agency, Washington, D. C.
7. Waltz, E. W. and D. Raichart. "Indianapolis 1974 Summer Ozone Study -
Data Documentation Report," Indianapolis Center for Advanced Research,
April 1975.
8. Lovelace, D. E., et al. "Indianapolis 1974 Summer Ozone Study," The
Indianapolis Center for Advanced Research, February 1975.
9. Haering, G. W. "Interim Air Quality Report," Indianapolis Center for
Advanced Research, March 1976.
10. Blumenthal, D. L. and W. H. White. "The Stability and Long Range Trans-
port of Ozone or Ozone Precursors," Paper No. 75-07.4, Air Pollution
Control Association, Boston, Mass., June 1975.
11. Sticksel, P. R. "The Stratosphere as a Source of Surface Ozone," Paper
No. 75-07.6, Air Pollution Control Association, Boston, Mass., June 1975.
12. Cook, P. P. and R. C. Bourke. "Correction of Ozone-Altitude Data and
Stratospheric-Source Implications," Air Pollution Control Association
Journal, June 1976.
13. Wolff, G. T., et al. "Aerial Ozone Measurements over New Jersey, New
351
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York and Connecticut," Paper No. 75-58.6, Air Pollution Control Associa-
tion, Boston, Mass., June 1975.
14. Rabino, R. A. "Ozone Transport," Paper No. 75-07.1, Air Pollution Control
Association, Boston, Mass., June 1975.
15. Price, J. H., et al. "Estimation of Minimum Achievable Oxiclant Levels
by Trajectory Analysis: Implications for Oxiclant Control," Paper No.
75-07.2, Air Pollution Control Association, Boston, Mass,,, June 1975.
16. Cleveland, W. S., et al. "Sunday and Workday Variations in Photochemical
Air Pollutants in New Jersey and New York," Science, Vol. 186, pg. 1037,
1974. ~~
17. Levitt, S. B. and Chock, D. P. "Weekday-Weekend Pollutant and Meteoro-
logical Studies of the Los Angeles Basin," Paper No. 75-51.1, Air Pol-
lution Control Association, Boston, Mass., June 1975.
18. "Control of Photochemical Oxidants - Technical Basis and Implications of
Recent Findings," U. S. EPA. Research Triangle Park, North Carolina,
July 15, 1975.
352
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8-2
A "TEXAS SIZE" OZONE EPISODE TRACKED TO ITS SOURCE
J. W. Hathorn III and H. M. Walker*
ABSTRACT
September 25 and Octoben. 1, 1975, a wide*pn.ead ozone. (03j
episode occuAAed -in Texa*. TAack* ofa mojiitoAing data &OA the. peAiod August
10 to OctobeA 31 cleanly *how evidence ofi thi* epi*ode completely acAo**
the *tate. In addition, evidence i* o^eAed that mo*t in*tance* ofa high
0$ at all *ite* an.e Aelated to wide*pAead episode*.
The. ^Aeqaent, Aegional ozone. episode* expenienced in the Ea*ten.n
United State* vertical ozone
have -6/iown that thefie *& -incAea^ed ozone concentrations within the
layeA. and cuM.ently~ accepted fisiontal model* Indicate that thi& ozone Lt,
probably oft &tA.ato-{>pheJvic
An analy*-if> o& the Apace and time continuity o£ a fitiont'* low-level
-f,tA.u.ctuJie demonAtSLOte* that the stable layen oven, the region experiencing
an ozone episode waf> actually the lemnant o^ a. cold fifiont that had pushed
through i,QMVwJL day* eantien. The stable lay en. d-i* appealed and n.eappean.ed
at *even.al station* indicating that it wo* losing It* Identity a* Jit di*-
*lpated. Any ain. within the *table layen. would have been mixed in the low-
en. &iopo*phen.e. Since thu> * table lay en, i* the n.emnant o& a cold fanont,
It* lncn.ea*ed ozone content could have caa*ed an/on. "*eeded" an ozone
epi*ode.
S,tnato*phenA.c ozone accompanying the &n.ontal *y*tem oft Septemben. 24 I*
believed to have Initiated the photochemical oxidation *eqaence broadly
acn.o** the *tate. Thi* *equ.ence buitt to epi*odic levels, which peaked
dunging the peniod di*cu**ed.
INTRODUCTION
The frequent occurrence of regional ozone (03) episodes in the eastern
United States suggests that their cause is related to repetitive meteoro-
logical patterns.
This paper seeks to analyze such patterns and develop a more detailed
understanding of the regional episode. The subject of this study is the
*J. W. Hathorn III, Applied Meteorology, Inc., Houston, Texas,
H. M. Walker, Monsanto Co., Texas City, Texas.
353
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week-long episode occurring in Texas between September 25 and October 1, 1975.
This was plainly a major episode that extended to practically all of
the monitoring sites of the state network.
Figure 1 presents time plots of daily ozone peaks for the 2 1/2
month period beginning on August 20th. Part 1A depicts patterns for
Houston, Aldine, Texas City, and El Paso, which are shown with the one-week
period under discussion being outlined. As a result of this work, another
widespread episode was noted during the period September 14-17, 1975. This
episode is also outlined. Both of these episodes are sharply defined at
all sites.
Figure 1-C extends the analysis to Corpus Christi, Orange, and Fort
Worth and adds high quantity data sets from two non-urban Texas sites. The
Port O'Connor data was obtained courtesy of DuPont and the Athens data (by
Radian Corporation) was obtained courtesy of Texas Utilities. Again, all
tracks show the effect of both episodes, although, in the case of the rural
Athens sites, three of the four effects are manifest as maxima in the data
actually peaking below the 0.08 ppm ambient air standard.
Figure 1-B shows tracks for Clute, Sari Antonio, Dallas, Austin,
Nederland, and the other El Paso site. All sites but Austin reacted to
the September 14-17 episode, and all but El Paso (Campbell) to the
September 25 through October 1 episode. The latter observation was un-
expected in view of the sharp episode effect displayed by the other El
Paso monitor during that period.
Figure 1-D depicts Houston sites operated by the Houston City Air
Pollution Control Department and adds a track for Lake Charles, Louisiana,
obtained courtesy of the Louisiana Air Control Commission. The Houston
sites strongly evidenced the episodes. The Lake Charles track shows slight
evidence of the two episodes.
Considering all four sections of Figure 1 together, one sees the
persistence of these two episodes that covered the state. Closer inspection
of all tracks suggests that additional episodes could have been defined for
the periods August 21-23, October 6-7, and October 29-30. These would also
have had relatively wide coverage. In fact, for the entire 73-day period
one might well conclude that most periods of high ozone at alj sites
occurred as manifestations of broad ozone episodes.
Figure 2 presents time patterns of ozone for a number of the sites
hour-by-hour during the episode. The strong diurnal pattern Is clearly
evident in the cities with the highest emissions of various sorts. Thus,
the Houston sites have the highest peaks and the greatest number of hours
of essentially zero ozone each night. Conversely, rural Athens barely
reached the National Ambient Air Standard (NAAS) during the episode but ex-
hibited little diurnal variation and has relatively high ozone levels through-
out the night many nights. Port O'Connor has a pattern similar to Athens
with occasional reversion to a more urban-type pattern. El Paso's pattern
is surprisingly similar to that of Houston. Texas City's is characterized
354
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by many high nighttime hours -- probably indicative of winds directly off
the Gulf. This was somewhat unexpected since Texas City in general has
relatively high levels of both hydrocarbons and ozone.
Since it is more than 750 airline miles from El Paso to Orange, the
event of September 25 to October 1 was truly of synoptic proportion -- far
beyond the scale of any local pollution situation.
Previous data suggests that ozone episodes that cover large regions
recur with a typical set of characteristics as follows:
1. High ozone concentrations will persist for several days.
2. Both rural and urban monitoring stations throughout the region,
whether upwind or downwind of urban or industrial areas, will
experience the episode.
3. Concentrations of other contaminants will not necessarily be high.
4. Ozone concentrations rise sharply after sunrise and decrease
sharply in the evening.
5. Usually, the wind is from the southern quadrant and there is a
large subtropical anticyclone (i.e., high pressure area) located
east to northeast of the region experiencing the episode; (i.e.,
the event is "on the backside of a HIGH.")
6. The frequency of occurrences is high (e.g., in Texas, more than
three times in some months).
The data of Figures 1 and 2 confirm that the episode under study
possessed most of these characteristics. Additional monitoring information
revealed that characteristic #3 was apparently applicable; the concentrations
of other contaminants were not uniformly nor especially high. Item #6, the
weather characteristics will now be discussed in detail.
SYNOPTIC WEATHER SITUATION FOR THE SEVEN-DAY EPISODE
The synoptic weather situation leading up to the seven-day ozone episode
began with a cold front passing through Texas between September 18 and 20.
Figure 3 presents the surface weather map for September 20, 1975, for 7:00
a.m. EST, and also shows the locations of two vertical cross-sections (A-A1
and B-B', heavy dashed lines) to be discussed later.
The cold front merges with Hurricane Eloise on the afternoon of
September 22, in the central Gulf of Mexico (Figure 4) and became stationary
along the Atlantic Coast of the United States until September 28, while
the remnants of the hurricane moved up the coast toward Nova Scotia (Figures
5 through 7).
On September 26 (Figure 6), a high pressure area following the cold
front moved into the central United States (Missouri) and then drifted
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slowly east-northeastward until on October 1 (Figure 8) it was located in
the Atlantic Ocean. During the seven-day period from September 25 through
October 1 , Texas was located on "the backside of this HIGH" and experienced
generally southerly flow. These were the seven days during which the ozone
episode occurred.
Those familiar with synoptic weather patterns recognize this sequence
of events (except for Hurricane Eloise) as rather typical.
THREE-DIMENSIONAL STRUCTURE OF THE ATMOSPHERE FOR THE EPISODE
To understand how an ozone episode in Texas beginning on September 25
was caused by stratospheric ozone, the three-dimensional structure of the
cold front in both space and time (beginning on September 20) must be
examined. Vertical cross-sections perpendicular to the front at its
steepest point (Section A-A1 in Figure 3) and parallel to the front (Section
B-B' in Figure 3) describe the front's three-dimensional structure during
the early development stage. A time series of vertical temperature pro-
files show the transition continuity from the development stage to the
dissipation stage. Then, another vertical cross-section shows the structure
of the front in its dissipation stage.
A vertical cross-section from International Falls, Minnesota, to
Pittsburgh, Pennsylvania (see Section A-A1 in Figure 3) is presented in
Figure 9. The cold front intersects the surface near Pittsburgh, passes
over Flint, Michigan, and Green Bay, Wisconsin, before it intersects the
tropopause in central Wisconsin. The cold front is undergoing rapid
development indicated by potential temperatures within the lower frontal
layer (dashed lines indicate constant potential temperature, i.e., isentropes)
not yet equalling those at the tropopause over International Falls. (There
is another stable layer over Pittsburgh, Flint, and Green Bay that can be
identified as the remnants of another cold front that had pushed through
the area several days earlier.) The cold front is moving rapidly (about
9 miles per hour) eastward.
Another cross section (B-B' on Figure 3) through Green Bay that
essentially parallels the cold front until it intersects the ground just
south of Longview, Texas is shown in Figure 10. The frontal remnant that
was also noted in Figure 9 can be identified in Figure 10 as well.
These cross-sectional analyses (Figures 9 and 10) indicate that fronts
are continuous layers that can cover large areas. In addition, the layer
itself can persist in time. To illustrate persistence, a time-series of
vertical temperature profiles measured at Longview, Texas, from September
19 through September 28 are presented in Figure 11. The cold front passed
Longview on the afternoon of September 19 and is identified as a shaded area
on all subsequent profiles. Between September 22 and 23, the front
decreased in altitude from 8,700 feet to 5,800 feet (conserving its original
potential temperature) and remained at about that altitude throughout the
seven-day episode.
The temperature profiles for September 23 through 28 have the "typical"
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appearance of those when air is subsiding over a stable layer. This is
consistent with the circulation patterns aloft over Texas for this period.
Having now demonstrated that the cold front that passed through Texas
between September 19 and 21 actually remained over the area as a stable
layer through September 28, a cross-sectional analysis (Figure 12) indicates
that the layer covered not just Texas but the entire central United States.
(The cross-section is identified as C-C1 on Figure 6.) The cold front-
stable layer can be identified over Longview, Texas, but not over Lake
Charles, Louisiana, on September 26. This indicates that the atmosphere
over Lake Charles has become well mixed and has destroyed the stable layer.
Any air that was previously in the stable layer is now mixed throughout
the lower troposphere.
Two days later the stable layer reappeared at Lake Charles but
disappeared over Del Rio, Texas (Figure not included). This sporatic
disappearance (i.e., mixing) and reappearance of a "frontal remnant-stable
layer" is a typical occurrence on the "backside of a HIGH." There, the
trailing edge of the cold front is losing its identity as other meteorological
phenomena begin to dominate. The speed with which the cold front-stable
layer loses its identity depends on the speed of motion of the High pressure
area. A slowly drifting HIGH may result in several disappearances and
reappearances of the layer.
STRUCTURE OF A FRONT AND ASSOCIATED OZONE MEASUREMENTS
FRONTAL MODEL
The three-dimensional structure of a front has been modeled by Reed
and Daniel sen, 1959, by analyzing the discontinuities in the temperature
and wind fields at the frontal and tropopause surfaces. Their model, after
which the analysis in Figure 9 is patterned, describes the front as a
layer of air whose upper and lower surfaces are tied to the tropopause
ahead of and behind the front, respectively. Air within the frontal layer
can actually have the same potential temperature (i.e., be on the same
isentropic surface) as air in the stratosphere.
Vertical Motion Within the Frontal Layer
More recently, Shapiro, 1969, examined the detailed vertical motions
in the upper frontal zone using a high-resolution numerical technique. He
has shown that there can be downward motion of air of up to 0.15 meters
per second within the upper frontal zone. This downward moving air would
conserve its potential temperature (i.e., flow along an isentropic surface)
as it moved down in the frontal layer. Since it is stratospheric in
origin, it contains high concentrations of ozone.
Observations of Ozone Within the Frontal Layer
Vertical profiles of ozone have been measured by several research
programs. Figure 13 presents one such profile measured by the Air Force
Cambridge Research Laboratory's (AFCRL) ozone program on May 7, 1963,
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7:12 a.m. EST, at Tallahassee Florida. This profile shows that as the
ozonesonde (instrument package) ascended through a frontal layer at an
altitude of about 8 km, there was an increase in ozone. Other profiles
at Tallahassee and at other stations (Hering and Bordon, 1964, 1965, and
1967; and Carney, 1976) have indicated similarly that sometimes there are
increased concentrations of ozone within frontal layers. This is probably
stratospheric ozone being transported down an isentropic surface within
the frontal layer.
OTONAQIAM
FRONTAL
LAYER
Figure 13. Vertical ozone profile (ozonagram) for Tallahassee, Florida, for
May 7, 1963, 7:12 a.m. EST indicating that there was an increase of ozone
concentrations measured by the ozonesonde as it ascended through
a frontal layer.
While being transported down the inside of the front, the ozone will
move with the general circulation at each level and will persist until,
either destroyed by precipitation, washout, etc., or mixed into the lower
tropospheric air. The general circulation over the backside of a HIGH has
the required anticyclonic subsidence to mix the air within the "dissipating"
frontal layer to the surface.
A Perspective Sketch of the Frontal Structure
To summarize the structure, a sketch of the three-dimensional
perspective of the frontal surfaces (Figure 14) shows that they are
essentially topological surfaces that connect the tropopause (a surface)
to the earth's surface. Gridlines on the front's surface are sketched to
show that the front at the trailing edge (left-hand side) has flattened
and is almost horizontal. In addition, a section of these gridlines on
374
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the leading and trailing edges of the front are omitted to show the thick-
ness of the innerfrontal layer and to show the tendency for stratospheric
air to flow downward within the layer. A jet stream maximum is indicated
at about 200 millibars (mb) over the leading edge of the front and a low-
level anticyclonic subsidence is indicated at the trailing edge.
JET STREAM
LEADING EDGE OF THE
COtO FRONT
STATIONARY PORTION OF
THE FRONT
Figure 14. Artist's sketch of the structure of a cold front. Grid lines on the
frontal surface are broken to show the thickness of the frontal layer near the
leading and trailing edges. The tendency for stratospheric air to flow downward
within the frontal layer is indicated. Also, the dissipation of the frontal
layer near the trailing edge is indicated as well as the anticyclonic
subsidence near that edge.
ROUTINE EVENTS LEADING TO AN EPISODE
The sequence of events leading up to the regional ozone episode is:
1. Ozone-rich stratospheric air begins to flow down inside the
developing frontal layer at the upper levels.
2. Several days later, ozone from the upper rear portion of the front
has moved (a) down within the frontal layer, and (b) around to a
position near the trailing edge.
3. As the trailing edge dissipates and the air within the front
mixes in the lower troposphere, ozone is transported to the
earth's surface.
The meteorological analysis has provided a clearly feasible mechanism
for bringing stratospheric ozone to the surface of the earth in Texas. The
quantities involved are not definable by this analysis. However, reasonable
375
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assumptions suggest that this injected ozone may amount to an appreciable
part of, perhaps even a majority of, the ozone found at unpolluted rural
sites. However, in urban areas it could hardly contribute more than a
small portion of the total ozone burden.
Another phenomenon is believed to operate and exert a major influence.
This is initiation or triggering. It is suggested that stratospheric ozone
played the role of a free-radical oxidation initiator and triggered a
gradual buildup of photochemical oxidation processes, which culminated in
the episodic ozone levels of September 25 through October 1.
For the benefit of those unfamiliar with the details of chemical
oxidation processes, let me comment that it Is well known that hydrocarbon
oxidation reactions employing oxygen proceed by free-radical sequences.
However, an initial source of such radicals is required to initiate the
process.
A dramatic example of the importance of initiation can be cited from
one of Monsanto's commercial experiences. In the commercial production
of cumene hydroperoxide, which is the first step in Monsanto's synthesis
of phenol, cumene is oxidized with air. This reaction is initiated by
providing an initial level of a percent or so of cumene hydroperoxide in the
oxidation mixture. Thermal fragmentation of a portion of this initiator
provides enough radicals to get the process going. It is exceedingly
difficult to initiate the process if no peroxide is present. When Monsanto
started up its plant in 1962, no oxidation occurred, even after 16 hours
of bubbling air through hot cumene. When one pint of a dilute cumene
hydroperoxide solution was added to a 21,000 gallon reactor, the reaction
started briskly in less than three minutes. The applicable sequence of
free-radical initiation and propagation steps is illustrated in Figure 15.
It is believed that initiation of this type provides the chemical path
by which stratospheric ozone can initiate an ozone episode,on a scale as
broad as the entire state of Texas.
Significant levels of stratospheric ozone, though well below the NAAS,
may become widely dispersed in the lower troposphere. This ozone can, by
reaction with olefins, create ozonides that are unstable and cleave yielding
diradicals. These diradicals can propagate hydrocarbon oxidation sequences
of the type shown in Figure 15. Figure 16 illustrates part of this process.
Radicals from the hydrocarbon ozidation process can oxidize nitric
oxide (NO) interferring with the nitrogen-dioxide photolytic cycle, causing
a buildup of ozone (Figure 17). Note that the process of Figure 17 is
conservative of free-radicals, allowing it to continue and to oxidize more
and more NO. Every molecule of NO oxidized is, of course, equivalent
potentially to creating one more molecule of ozone.
Critics of this suggestion will, no doubt, point out that the nitrogen
dioxide photolytic cycle is capable of providing many oxygen atoms that
might act as initiators for the oxidation of hydrocarbons. This may or may
376
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INITIATION:
R-O-O-H »- R • + H-0 •
PROPAGATION:
R-H + H-0 • +- H20 + R •
R . + 02 ^ R-0-0 •
R-0-0 • + R-H •* R-O-O-H + R •
ETC,
R « CgH5C (CH3)
Figure 15. Free-radical initiation and propagation,
CH3 - CH = CH9 + 0, * CH, - C C-H
IJ ir H
CH20 + CH3 -
0
Figure 16. Hydrocarbon oxidation sequences,
377
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R-CH2-0-0 • + N-0 *• R-CH2-0 • + NO
R-CH20 • •* R • + CH20
R • + (L *- R-0-0
R-0-0 ' + N-0 *- R-0 • + N02
ETC,
Figure 17. Oxidation of Nitric Oxide, Nitrogen Dioxide photolytic cycle.
not be so. Oxygen atoms and various hydrocarbon free-radicals do not have
the same energetic properties and ability to transfer with all moieties.
Therefore, initiation of oxidation chain process in the manner suggested
may be favored.
A factor favoring stratospheric ozone being the initiator is that it
will be well mixed into many thousands of feet of the lower troposphere.
Each day, as mixing begins, a fresh infusion downward can provide a source
of make-up free-radical initiator to keep photochemical activity building.
Some confirmation of this view is obtained in the fact that it is
now being observed in aerial plume studies (7, 8) that ozone concentration
in downwind plumes seems to be closely related to upwind ozone concentrations
feeding into the urban photochemical process.
It should also be noted that stratospheric ozone is not the only possible
source of such initiation. Transported ozone and carryover ozone frequently
observed in bands near the inversion level can act similarly. As suggested,
ozonides, hydroperoxodes, and perhaps even peroxyacetylnitrate (PAN) can
act as sources of free-radicals and carry the initiation process over from
one day to the next.
There is certainly a great need to provide a chemical explanation for
the broad scale ozone episode. Pollution, as a direct cause, is ruled out
because of its invariability, the distances involved, and the involvement
of unpolluted sites. Air stagnation is an unlikely cause because of the
lack of an accompanying sharp or consistent buildup in other pollutants
and because the rapid development in high ozone peaks frequently occurs
before sufficient time has elapsed to permit such a buildup.
It is believed that the phenomenon discussed occurs primarily in
continental polar air masses and involves their associated fronts. We
believe that it occurs most often in the fall of the year in central
United States but may be associated with intrusions in other seasons.
378
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While we regret that we cannot offer unequivocal proof that the
synoptic-scale ozone episode is triggered by an injection of stratospheric
ozone, we believe that strong evidence exists that this may be the case.
Future research efforts, particularly aerial studies, should make an effort
to seriously test this thesis.
SUMMARY
The frequent, regional ozone episodes experienced in the eastern United
States are probably caused, in part, by the transport of ozone-rich
stratospheric air to the earth's surface. Numerous vertical ozone profiles
have shown that there is increased ozone concentrations within the frontal
layer, and currently-accepted frontal models indicate that this ozone is
probably of stratospheric origin.
An analysis of the space and time continuity of a front's low-level
structure demonstrates that the stable layer over the region experiencing
an ozone episode was actually the remnant of a cold front that had pushed
through several days earlier. The stable layer disappeared and reappeared
at several stations indicating that it was losing its identity as it
dissipated. Any air within the stable layer would have been mixed in the
lower troposphere. Since this stable layer is the remnant of a cold front,
its increased ozone content could have caused and/or "seeded" an ozone
episode.
ACKNOWLEDGEMENTS
The kind cooperation of the staffs of the Texas Air Control Board, the
Houston Air Pollution Control Department, the Louisiana Air Control
Commission, the DuPont Company, Texas Utilities, and Radian Corporation in
providing data is greatly appreciated.
REFERENCES
1. Carney, Thomas A., 1976. Vertical Distributions of Ozone as Evidence
of the Role of Stratospheric Transport in the Spatial and Temporal
Distribution of Tropospheric Ozone. In: Proceedings of the Ozone/
Oxidants, Interactions with the Total Environment, Specialty Con-
ference, Dallas, Texas, March 10-12, 1976. P. 234. (Thomas A.
Carney, Tennessee Depart of Public Health, Division of Air Pollution
Control, C2-220 Cordell Hull Building, Nashville, Tennessee 37219.)
2. Hering, W.S. and T R. Borden, Jr., 1964. Ozonesonde observations over
North America, Vol. 2. Environmental Research Paper No. 38. Report
AFCRL-64-30 (II), Air Force Cambridge Research Laboratories.
3. Hering, W. S. and T. R. Borden, Jr., 1965. Ozonesonde observations
over North America, Vol. 3. Environmental Research Paper No. 133.
Report AFCRL-64-30 (III), Air Force Cambridge Research Laboratories.
4. Hering, W.S. and T. R. Borden, Jr., 1967. Ozonesonde observations
379
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over North America, Vol. 4. Environmental Research Paper No. Z79.
Report AFCRL-64-30 (IV), Air Force Cambridge Research Laboratories.
5. Reed, R. J. and E. F. Danielsen, 1959: Fronts in the vicinity of the
tropopause. Arch. Meteoro. Geophy. Bioklim., All, 1-17.
6. Shapiro, Melvyn A. On the Scale of Atmospheric Motions within Middle-
Tropospheric Frontal Zones. NCAR Cooperative Thesis No. 18, Florida
State University and Laboratory of Atmospheric Science, NCAR, 1969.
7- Dr. Max Shauck, Baylor University, private communication.
8- White, Blumenthal, et al., Meteorological Research, Inc., Paper to be
presented at the International Conference on Photochemical Oxidant and
Its Control, September 12-17, 1976, Raleigh, N. C.
380
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8-3
APPLICATION OF 1960'S OZONE SOUNDING
INFORMATION TO 1970'S SURFACE OZONE STUDIES
P. R. Sticksel*
ABSTRACT
It has been purported tkat high ozone. levels In the lower troposphere
OSLO., at least partially, the. result o^ ozone. transport firom the stratosphere
downward along stable layers. A limited -investigation oft this hypothesis was
conducted using ozone measurements made -in the. lower troposphere In 1963
and 1974 and the data {,rom the. North American upper ait soundings o& tempera-
ture and wind. Three-dimensional Isentropic trajectories traced backward
firom the lower troposphere failed to confirm the hypothesis o^ continuous
downward transport along stable Lagers. However, a sloping stable layer ex-
tending ^rom coast to coast ac/io-4-i the United States was Identifi-ied &or the
May, 1963, case, and AoundinQ-b -into this layer at three widely-separated sta-
tions revealed higher-than-average ozone concentrations uiithin the layer.
INTRODUCTION
This is a report on the testing of a hypothesis--that episodes of high
surface ozone concentrations are at least partially the result of transport
of stratospheric ozone downward along stable layers. These stable layers are
hypothesized to (a) originate at breaks in the tropopause at higher latitudes,
(b) follow surfaces of constant potential temperature downward, and (c) ter-
minate within inversion layers near the surface. The basis for this hypothesis
is observations of ozone maxima appearing at various levels in the troposphere
during the upper atmosphere ozone sounding programs conducted in the 1960's.
Kroening and Ney (1) identified "rivers" of high ozone concentrations exiting
from the stratosphere at tropopause breaks and entering the upper troposphere.
In a recent paper, Sticksel (2) showed one example of a vertical cross
section through the atmosphere from Florida to Greenland on which there was a
sloping stable layer. The surface synoptic chart is Figure 1, and the cross
section with the sloping layer is Figure 2. This stable layer (between the
potential temperatures of 310°K and 315°K) appeared in many upper atmospheric
soundings along the eastern coast of the Northern Hemisphere on May 15, 1963,
at 1200 Greenwich Meridian Time (GMT). Ozone soundings at Tallahassee,
Florida; Bedford, Massachusetts; and Churchill, Manitoba, all displayed ozone
peaks along this surface of constant potential temperature (isentropic surface)
(Figures 3a, 3d, 3e). At Thule, Greenland this isentropic surface was within
*Battelle Columbus Laboratories, Columbus, Ohio.
381
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Figure 1. Surface synoptic map for 1200 GMT on May 15, 1963.
(Weatherwise, August, 1963)
the stratosphere after passing through a break in the tropopause north of
Churchill.
Sticksel (2) also noted that high concentrations of lower tropospheric
ozone appearing on the Northern Hemisphere soundings of the 1960's followed a
seasonal progression and recession from low latitudes to high latitudes and
back again during the spring-summer-fan period. This movement corresponds
to the seasonal progression and recession of the tropopause break poleward and
equatorward.
This evidence for the transport of ozone between the stratosphere and
surface is circumstantial. Proof of a continuous trajectory downward and a
description of the mechanism of descent are required. If downward trans-
port along a stable isentropic layer can be demonstrated, the horizontal
extent of this movement should be determined.
ISENTROPIC TRAJECTORIES
The approach chosen for this investigation of possible stratosphere-
to-surface transport was to study the pressure and wind patterns on isen-
tropic surfaces. Pressure data for constructing the isentropic charts were
obtained from the temperature-pressure soundings of the United States and
Canadian rawinsonde networks. Wind speeds and directions were interpolated
from the wind observations made during these same soundings.
Since
thesis was
one of the pieces
the May 15, 1963,
of evidence for the stratosphere-to-surface hypo-
cross section, this date was chosen for the
isentropic analysis. Work was done with both the 9=310°K and the 9-315°K
surfaces. The 310°K surface intersected the Tallahassee sounding at 650 mil-
libars (mb). This was the top of the ozone layer that extended from the ground
to about four kilometers at this station (Figure 3a). Above this layer of
high ozone there was a shallow layer in which ozone concentration dropped off
382
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O) H-
.c s:
+-> CD
-C: O
C7>O
^ CM
O •—
S-
J^ 5-
4-> O
C(-
OJ
rj T3
4-> C
(O to
CD 'c
Q. O)
£ OJ
O) S-
4-> CD
O)
QJ
cn
c:
0) O)
-(-> +->
o o
Q_ C
O)
T3
n to
us ai
CTl C
on fO i —
CO O. «*
o E LO >,
i— >
» ai
(O 3C
J- (O
OH-
n3 a)
O O)
S-
Q)
c .
-t-J Q C
CO
(SJDq!||iiu)3anSS3Hd
383
-------
slightly and then a two-kilometer layer of concentrations equal to those in
the surface layer. This upper layer is intersected by the 315°K isentropic
surface. Both these surfaces were high enough so that they did not intersect
the ground even in the mountainous portions of southwestern United States.
Since all processes in the free atmosphere tend to be largely adiabatic
as long as there is no condensation, air particles should remain on the same
isentropic surface unless saturation occurs (3). Other nonadiabatic atmos-
pheric processes include radiational heating and cooling, evaporation, and
convective activity (4).
Indications of the direction of vertical motion were obtained from the
relationship between wind directions and isobars on the isentropic charts.
Winds blowing toward higher pressure were evidence of descending motion.
Generally air parcels moving from north to south on an isentropic: surface in
the Northern Hemisphere are descending toward lower altitudes. Some caution
must be taken in these vertical motion determinations because the isentropic
surface itself may also be moving. Thus, these rules are reliable only when
movements are strong. If this is the case, the forward motion of the air
relative to the surface is guaranteed (5).
Keeping these limitations of isentropic analysis in mind, an additional
step was taken to determine the origins of the ozone-rich air. Trajectories
were traced backward along the isentropic surfaces in 12-hour segments from
one standard radiosonde launch time to the preceding launch time. These
trajectories were graphically computed from the streamlines on the surfaces
following the method given by Saucier (6). Trajectories, once constructed,
should be viewed as surrounded by a region of uncertainty expanding with
distance from the origin of the trajectory. In the case of the three-dimensional
isentropic trajectories, the region of uncertainty can be visualized as cone-
like. The base of the cone-like volume is an ellipse rather than a circle.
RESULTS
MAY 15, 1963
Figure 4 portrays the isentropic surface for 1200 Greenwich Meridian
Time (GMT) on May 15, 1963. The surface has a depression (region of high
pressure) over the Texas panhandle and a dome (region of low pressure) center-
ed over northeastern Wyoming. The intersection of the 9=315°K surface with
the tropopause occurs along a line running across Canada from the southwest
to the northeast.
Streamline patterns on the surface generally follow the isobars. There
is an anticyclonic divergence center on the Louisiana-Mississippi border.
Some ascending motion is apparent in the western United States and some de-
scending motion in the eastern United States. There is no strong descending
motion from the Canadian area of the tropopause southward into the central
or eastern United States.
The strongest winds on the surface would represent the greatest relative
384
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(A) TALLAHASSEE,FLORIDA
200|-
t:
,0L - —.V>- . !
0 50 TOO 150 200
PARTIAl PRESSURE Of OZONE
250 300 -60 60
"1200
40 -20
1E MPERAlORE
"00
£- — -^ 500
20 40
2°r)'
(B) ALBUQUERQUE,NEW MEXICO
:- ( - • t -t , 1 ! '=
\
PARTIAL PRESSURE OF OZONE l^mb'
(C) FT. COLLINS, COLOR ADO
R
E
S
S
u
R
E
(mb)
...
50 100 150 200 250 300 -80
PARTIAL PRESSURE OF O7ONE '^mb
(D) BEDFORD, MASSACHUSETTS
^200
I500
-60 -40
-20
TEMPERATURE
1
0
i'CI
20 40
-—-^200
1EMPEBATU8F (XI
-60 -40 -20 0 20 40
^200
100 150 2OO
PARTIAL PRESSURE OF OZONE
(E) CHURCHILL, MANITOBA
—- _ __. - _
50 100 150 200 250 300
PARTIAL PRESSURE OF OZONE U^b)
-60 -40 -20 0 „ 20 40
TEMPERATURE l'O
Figure 3. Ozonesonde soundings for 1200 GMT on May 15, 1963.
(Hering and Borden, Vol. 2, 1965)
385
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FIGURE 4. PRESSURES (MB) AND DIRECTIONAL STREAMLINES OF THE 315 K
ISENTROPIC SURFACE FOR 1200 C1MT ON MAY 15, 1963 SHADED
AREA DENOTES WIND SPEEDS GREATER THAN bO KNOTS. HEAVY
DASHED LINES ENCLOSE PORTION OF THE SURFACE WHICH IS IN
THE STRATOSPHERE
386
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motion of the air to the surface and consequently the areas of most pronounced
vertical motion. These wind maxima indicate strongest ascent over Kansas and
Missouri with strongest descent occurring between Indiana and Virginia.
Isentropic trajectories were computed to determine whether the ozone-
rich air that appeared along this surface at Tallahassee, Bedford, and
Churchill could be traced backward in the direction of the tropopause. The
results of these computations are displayed in Figure 5. The air that arrived
above Tallahassee on May 15 (Trajectory No. 1) was above the Houston, Texas,
region 48 hours earlier. This trajectory resembles the flow one would expect
around the north side of the high pressure area located in the Gulf of Mexico.
The motion along this trajectory was generally upward.
The Bedford trajectory (No. 2) followed a different path and indicated
descent for the air parcel as it traveled southward from northern Canada to
Massachusetts. However, it should be stated that none of the temperature
soundings along this trajectory had a stable layer encompassing the isentropic
surface.
Trajectory No. 3 from Churchill backward displayed not descending move-
ment, but rather small ascending motion. The position of the air parcel
24 hours earlier was over northern British Columbia at a height that would
have been within the stratosphere on May 15. However, on May 14, this loca-
tion was still within the troposphere.
Although one must take into account the pitfalls accompanying the compu-
tation of isentropic trajectories, the ones described here should be represen-
tative of the true flow. One can conclude from these results that the high
ozone concentrations observed at 9=315°K on the May 15 soundings did not
arrive there by direct transport from the stratosphere along a stable layer.
In fact the ozone at the three stations probably came from three different
source areas, even though their final potential temperatures were identical.
DAYTON, OHIO--1974
Calculation of an isentropic trajectory for the period of a recent oxidant
study in Ohio provided some additional insight on the hypothesis of descending
ozone parcels. On August 7, 1974, at 0000 GMT (8 p.m. EOT) a vertical ozone
sounding made by an airplane over Dayton, Ohio, measured ozone concentrations
of over 160 yg/m3 in the layer between the surface and 1500 meters (7). The
isentropic trajectory traced backward from this point and time is shown as
trajectory No. 4 in Figure 5. This trajectory was calculated for the 9=300°K
surfaces. It terminated at 825 mb at Dayton, which was approximately 1800
meters above the ground and within the layer of high atmospheric ozone concen-
tration. Forty-eight hours earlier this air was over central Wisconsin at
775 mb (an altitude of about 2300 meters), thus indicating descending motion.
On the morning of August 6 (1200 GMT) the 300°K surface was within a strong
inversion layer. At the other 12-hour checkpoints along its journey the air
parcel was within a layer that was slightly stable.
It is significant to compare the isentropic trajectory (solid line) with
387
-------
695
5-15 650
OOZ , 5-15-63
I2Z
FIGURE 5 ISENTROPIC TRAJECTORIES PLOTTED BACKWARD IN 12-HOUR
PORTIONS FROM POINT OF TERMINATION PRESSURES AT THE
12-HOUR POINTS ARE GIVEN IN MILLIBARS
NO 1 TERMINATION POINT = TALLAHASSEE ON MAY 15, 1963, AT
1200 GMT (9 = 310 K).
NO 2 TERMINATION POINT = BEDFORD ON MAY 15, 1963, AT
1200 GMT (8 = 315 K)
NO. 3 TERMINATION POINT = CHURCHILL ON MAY 15, 1963, at
1200 GMT (6 = 315 K).
NO 4. TERMINATION POINT = DAYTON, OHIO ON AUGUST 7, 1974
AT, 0000 GMT (9 = 300 K) DASHED LINE IS THE 3000 FEET MSL
TRAJECTORY COMPUTED BY THE RESEARCH TRIANGLE INSTITUTE
(1975) FOR THE SAME TIME.
388
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a trajectory at 3000 feet (dashed line) originating at Wilmington, Ohio,
(20 miles southeast of Dayton) computed by the Research Triangle Institute (8)
for their concurrent oxidant study. The path and endpoints for the 36-hour
extent of the RTI constant level trajectory are quite similar to those of the
three-dimensional isentropic trajectory.
Additional Comment on the May, 1963, Case
A prediction of the paths of the May 15, 1963, isentropic trajectories
could have been obtained from the 500 mb chart for that date (Figure 6). The
path of the Tallahassee air parcel was dictated by the HIGH covering the
southern United States. Control of the Bedford trajectory was exerted by the
trough in the northeast, while the relatively straight isentropic trajectory
from Churchill resembles the 500-mb contour pattern in that region.
Figure 6. North American 500 mb chart for 1200 GMT on May 15, 1963.
Shaded portions enclose areas for which the 9=315 K
surface was within a stable layer.
Another interesting observation related to the 315°K isentropic surface
is depicted in Figure 6. The shaded areas enclose all the stations for which
the 1200 GMT soundings on May 15 had a stable or slightly stable layer en-
compassing some portion of the interval between 310°K and 320°K. This aerial
representation shows a discontinuity in the stable surface occurring along a
broad area near the U.S.-Canadian border. Any stratospheric ozone that
reached the troposphere south of this discontinuity must not have proceeded
along a direct trajectory. However, the pervasiveness of the stable layer
over most of the United States suggests that there may have been an extensive
layer of ozone related to the HIGH in Mexico. Closer inspection of the
389
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soundings at Tallahassee, Albuquerque, New Mexico and Ft. Collins, Colorado
(Figure 3) verifies that there was a deep layer of ozone above each station.
The layer at Tallahassee contains two maxima—about 450 mb to 550 mb and 600 mb
to the surface. At Albuquerque the ozone layer extends from 500 rnb to the
surface with a peak at 550 mb. At Ft. Collins there is an above-average ozone
layer between 400 and 550 mb. Thus, the original hypothesis is supported in
part. There may likely be a large layer of ozone sloping upward from low to
high latitudes. The ozone in this layer is so extensive that its source is
not anthropogenic. However, by turbulent mixing it can supply ozone to the
surface layer, which supplements the man-created oxidants there. It is sug-
gested that the stratosphere was the original source of this pervasive ozone
layer and that it was associated with the subtropical HIGH. The mechanism
of transfer downward is still to be determined.
CONCLUSIONS
From the results of this limited investigation the following conclusions
were drawn:
(1) "Rivers" (inversion layers) of ozone extending from a tropopause
break to the surface are not a reliable explanation for all high
surface ozone concentrations. Further investigation may show that
there is transport downward along slightly stable layers in some
cases. In any event, the sharp ozone peaks observed in the upper
troposphere do not isentropically descend unaltered to the surface
where they produce ozone maxima.
(2) Layers of ozone extensive enough and deep enough to rule out anthro-
pogenic sources were observed in the lower troposphere associated
with a large subtropical HIGH at 500 mb. This suggests another
descent mechanism associated with the development of synoptic scale
systems.
(3) Predictions of isentropic trajectory paths can be made from the
contours on isobaric surfaces where those surfaces are near the same
pressure as the origin of the isentropic trajectory. Movement along
contours from higher to lower latitudes will indicate descent.
Movement from west to east will indicate little movement in the
vertical direction.
REFERENCES
1. Kroening, J. L. and E. P. Ney, Atmospheric Ozone, J. Geoph. Res., 67:
1867-1875, 1962.
2. Sticksel, P. R., Occurrence and Movement of Tropospheric Ozone Maxima,
In: Proceedings Ozone/Oxidant Interactions with the Total Environment
Specialty Conference, Southwest Section Air Pollution Control Association,
Dallas, Texas, 1976, pp. 252-267.
3. Byers, H. R., General Meteorology, 3rd Edition, McGraw-Hill Book Company,
New York, New York, 1959, p. 146.
390
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4. Oliver, V. J., and M. B. Oliver, "Construction and Use of Isentropic
Charts," in Handbook of Meteorology, F. A. Berry, E. Bollay, and N. R.
Beers, eds., McGraw-Hill Book Company, New York, New York, 1945, pp. 848-56.
5. Saucier, W. J., Principles of Meteorological Analysis, The University
of Chicago Press, Chicago, Illinois, 1955, p. 255.
6. Ibid., p. 313.
7. Spicer, C. W., J. L. Gemma, D. W. Joseph, P. R. Sticksel, and G. F. Ward,
"The Transport of Oxidant Beyond Urban Areas," Report by the Battelle
Columbus Laboratories to the U.S. EPA, EPA-600/3-76-018, U.S. Environmental
Protection Agency, Research Triangle Park, N.C., February, 1976, p. 189.
8. The Research Triangle Institute, Investigation of Rural Oxidant Levels
as Related to Urban Hydrocarbon Control Strategies. EPA-450/3-75-036,
U.S. Environmental Protection Agency, Research Triangle Park, N. C.,
March, 1975.
391
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8-4
THE ROLE OF STRATOSPHERIC IMPORT ON TROPOSPHERIC OZONE CONCENTRATIONS
E. R. Reiter*
ABSTRACT
The. e.££e.ctA o£ &tfiat.o-f>pke.fiic ozone, impotitb into the. loweA. &iopo£phe.sie.
one. t>tu.die.d thtiouqh analogy to radioactive. fallout:, ^nom ozone.&onde. meoiuAe-
mewXi and ^fiom houAly ozone me.aAuA.me.nti> at lug^pitze., Germany (3000 m above.
mean &e.a le.ve.1 (M.S.L. ) ) . It -i& bkown that the, max.-ima.rn allowable. houAly con-
ce.ntsiation o^ 74.7 ppb ofi ozone. (0^} -if, exceeded by &u.ch impontA on appfiox.-i-
mateJLy 0.1 pe.nce.vit o^ the. day* -in the. cycJLoge,ne.tic.al£y active. K.e.Qi.onA o^ mid-
dle. latsitLideA. The. i>tn.atoi,pke.tic CAAC-uJLation patte.fin that ptLOvideA the. ozone.
in the. toweA i>tAatot>phe,ne. appe.au to play a significant fioLe. in
that provide. 0-$ c.once.ntfiationA in the. lowe.fi tnopo&pheAe. two to thAe.e.
in exce44 o& the. maximum allowable, liveJL &e.t by EPA.
INTRODUCTION
The present federal standards of ozone (OQ) concentrations not to be
exceeded for longer than one hour are 160 yg/irr (= 74.7 ppb, or 0.1238 yg/g).
This value is transgressed relatively frequently even in rural areas away from
known pollution sources (for references see Singh et a!., 1975). The question
arises to what extent stratospheric 03 transported into the lower troposphere
could lead to ambient ozone concentrations that either exceed the federal
maximum level or produce such a high background level that even a modest
industrial and/or photochemical contribution could push the concentration
values over the "allowable" maximum.
To answer this question we have taken several approaches.
STRATOSPHERIC RESIDENCE TIMES OF AIR MASSES
Using data on the mean meridional circulation published by J. F. Luis in
CIAP Monograph 1 (Reiter et al . , 1975), together with case studies on eddy
transport and tropopause height adjustments (Renter, 1975a), the annual mass
budget of the northern hemisphere stratosphere given in Table 1 was derived.
Observed residence times of nuclear debris in the stratosphere agree
very well with these estimates.
From satellite data Lovill (1972) estimated the average global value of
total ozone to be 303.3 Dobson units (or mini-atmospheric-centimeters at
*Colorado State University, Fort Collins, Colorado.
393
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TABLE 1. MASS BUDGET OF THE STRATOSPHERE (IN PERCENT OF THE
MASS EQUIVALENT TO ONE HEMISPHERIC STRATOSPHERE)
Seasonal adjustments of tropopause level 10%
Mean meridional circulation 43%
Stratospheric exchange between hemispheres 16%
Large-scale eddies (jet streams) 20%
Small-scale eddies (thunderstorms) n eg1iqib1e
89%
normal temperature and pressure). The total weight of the ozone column,
therefore, is 6.495 x lO'^g/cm2, or 1.6565 x 109 tons in one hemisphere. If,
according to Table 1, 73% of the air in the stratosphere is exchanged with
the troposphere each year (the 16 percent of interhemispheric exchange within
the stratosphere cannot be counted here), 1.2 x 109 tons of ozone should be
affected by this transport in each hemisphere.
Regener and Aldaz (1969) determined the vertical flux of ozone to be
1.3 x 109 tons per year over the whole globe. A somewhat smal'er flux of
0.804 x 109 tons per year over the globe was determined by Junge (1962, 1963;
Fabian and Junge, 1970). Comparing these values with the above number for
hemispheric transport, we arrive at the conclusion that only about half of
the stratospheric ozone is available for transport into the troposphere. The
ozone in the middle and upper stratosphere (above 15 to 20 km) is still photo-
chemical^ active and subject to dissociation. (See Reiter et al., 1975, for
data and references.) Therefore only ozone in the 1 ower stratosphe re can be
considered as a potential source of tropospheric ozone. ~~
OZONE AND RADIOACTIVE FALLOUT
Detailed data on radioactive fallout during the early 1960's are avail-
able from the U.S. Public Health Service Radiation Surveillance network.
Excessive fallout' concentrations in dry air at the ground usually could be
ascribed to the import of tropospheric air into the stratosphere (for typical
case studies see Reiter, 1972). Radioactive debris concentration measure-
ments in the stratosphere are also available for this time period from Pro-
ject Stardust. We have attempted to correlate stratospheric Strontium90
(Sr90) concentrations (Seitz et al. , 1968) with 03 to arrive at Sr90/03 ratios,
For May-August 1963 we obtained an average ratio of 500 in the lower strato-
sphere of the northern hemisphere (Figure 1), with Sr given in dpm/1000 SCF
(standard cubic feet) and 03 given in yg/g. A correction has to be applied
to this ratio, because the Sr90 data of May-August were actually compared
with ozone concentrations of March-April. Using the relationship
0
exp(-t/T)
(where N is the extrapolated Sr90/03 ratio for March-April; N is the value
of this ratio at t = 0; T is the e-folding residence time of §r90 in the
394
-------
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+-> 0)
' — -
O 3 LJ_
CO =t O
- -- I OO
>,
r- ro
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JDCTi -i—
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C CO C
O •!-
N -O r—
o c
ro
C
ro ^ —
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en
3.
-------
stratosphere, i.e., 14 months) we arrive at a correction factor of 1.24 for
t = -3 months. Thus the representative Sr90/03 ratio in the lower strato-
sphere for March-April 1963 was assumed to be 620. This value, together with
others, is shown in Figure 2. The straight line in this diagram predicts the
Sr90/03 ratio under the assumptions that the stratospheric 03 concentration
remains invariant and the the Sr90 concentration is subject to an e-folding
time of 14 months.
The Sr90/03 ratios of 250 to 300 derived from measurements of September-
November 1964 do not fit this straight line. We have to take into account,
however, that ozone concentrations in the lower stratosphere are only half as
high in fall than in spring (D'utsch, 1971). Therefore, to project the Sr90/03
ratio measured in fall to 03 concentrations as they would prevail during
spring, the ratios of 250 to 300 would have to be reduced by a factor of 2
(dashed "box" in Figure 2) (Reiter, 1975b).
We can now proceed to estimate 03 concentrations at ground level, that
should have been encountered with surface radioactive fallout of stratospheric
origin. Since in spring and summer of 1963 the bulk of radioactive fallout
was due to the US and USSR test series of megaton devices conducted during
1962, we can estimate the contribution of Sr90 to the total radioactivity
measured at ground level in 1963 to be of the order of 1% (Reiter, 1975b).
By spring of 1964 the Sr90 contribution was of the order of 2%. A surface
fallout value of 5 p C/m3 observed in summer of 1963, therefore, should have
contained approximately 0.05p C/m3 of strontium, or 3.145 dpm/1000 SCF of
Sr90. With a Sr90/03 ratio of 620 in the appropriate units the ozone concen-
tration in this surface air should have been 0.0051 yg/g. With the same
ratio of 620 the Federal maximum value of 03 of 74.7 ppb would correspond to
a Sr90 activity of 76.76 dpm/1000 SCF, or at least 7676 dpm/1000 SCF of total
radioactivity. This amounts to 122 p C/m3.
Figure 3 shows the average fallout over the U.S. Public Health Service
Radiation Surveillance network during 1963. Discounting the high concentra-
tions over Nevada, which most likely were due to local sources, we can con-
clude that the "natural" average background of stratospheric 03 at the ground
should be of the order of 3 to 5 percent of the federal hourly maximum value.
Slightly higher values prevail in the lee of the Rocky Mountains, where
Chinook winds provide a rapid mechanism of transport of stratospheric air
towards the ground.
The maximum fallout encountered during 1963 is shown in Figure 4. We
should emphasize that these are 24-hour average values. Nevertheless they
come within about 20 percent of the hourly allowable maximum value of equiva-
lent ozone concentrations (Reiter, 19755).
OZONESONDE MEASUREMENTS
We should expect that "instantaneous" measurements of 03 concentrations
will off and on reach considerably higher values than indicated by 24-hour
average values, especially if rapid transport processes from the stratosphere
are involved, with little mixing in the upper troposphere. To investigate
this possibility we reviewed 1477 ozonesonde observations between December
396
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1962 and December 1965 (Hering, 1964; Heririg and Borden, 1964:, 1965a,b, 1967)
Table 2 shows a frequency distribution of maximum 03 mixing ratios (yg/g)
below the 800-mb level (for the stations Albuquerque, New Mexico, and Ft.
Collins, Colorado, below 750 millibars (mb)). The layer below this level
was assumed to be characteristic of the planetary boundary layer (PEL). In
approximately 2 percent of the soundings the hourly allowable maximum of
74.7 ppb or 0.1238 yg/g had been exceeded.
Of the 31 cases with excessive 03 concentrations in the PBL, only three
(i.e., 0.2% of the total sample) qualified as possible stratospheric air
intrusions: Goose Bay, Canada, 5-2-1963, 0.15 yg/g; Tallahassee, Florida,
8-14-1963, 0.19 yg/g; and Seattle, Washington, 4-15-1964, 0.16 yg/g. All
other cases (listed in Table 3) had to be suspect of tropospheric sources
(Reiter, 1976a). Figures 5 and 6 show isentropic trajectories constructed
backwards in time for the cases of Goose Bay and Tallahassee. The case of
March 24, 1964, in which an ozonesonde intercepted high 03 concentrations
(ca. 3.5 yg/g) above the 500-mb level over Albuquerque, New Mexico, was not
considered in the above statistics, because these excessive concentrations
were encountered outside the PBL.
Since the ozonesondes intercepted layers with high 03 concentrations
away from the earth's surface we have to expect that these concentrations
will be reduced by turbulent mixing processes within the PBL. Even though
almost undiluted parcels of air can reach the ground on occasions when such
layers are "tapped" by strong turbulence, the one-hour averaging process
inherent in the maximum allowable value of 74.7 ppb will reduce these in-
stantaneous "spikes" considerably. In analogy we could consider the peak
gusts versus the one-hour average wind speed.
HOURLY OZONE OBSERVATIONS
Up to this point we considered daily average and instantaneous 03 con-
centrations, neither of which is strictly comparable to hourly ozone concen-
trations. We were fortunate to receive hourly ozone data for 529 days, taken
at Zugspitze, Germany (3000 m above M.S.L.) from August 1973 to February,
1976. These data were kindly supplied by Drs. Reinhold Reiter and H. 0.
Kantor of the Institut fuer atmosphaerische Umweltforschung at Gannisch-
Partenkirchen, Germany.
In Figure 7 we have plotted a joint frequency distribution of hourly
maximum 03 concentrations in excess of the daily mean values (ppb) by classes
of 2 ppb, and daily mean values by classes of 5 ppb. The maximum allowable
value of 74.7 ppb would be exceeded to the right of the shaded line in this
diagram. The "normal" scatter of observation points is produced partly by
instrument noise, but mostly -- with above-average ozone concentrations -- by
turbulent mixing processes acting upon stratospheric air intrusions.
Two observations depart significantly from the "normal" scatter of
observation points. Table 4 gives the hourly 03 concentrations which yielded
the two points of excessive maximum concentrations in Figure 7. Since the
allowable maximum value of 74.7 ppb was exceeded during 9 consecutive hours
(by as much as a factor of 2.64) we should count this episode as only one day
400
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401
-------
402
-------
Figure 6. Composit 6-hour trajectory segments from August 11, 1963, 18 GMT
to August 14, 12 GMT. Pressures in millibars are indicated next to dots
corresponding to synoptic observation times.
403
-------
ppb (MAX HOURLY
50 r
;DAILY MEAN)
120.40 141.16
I I
10 •
2 2
0
Figure
12 32 39 61 95 117 75 62 21 85 529
10 20 30 40 50 60 ppb DAILY MEAN
f. Difference between maximum hourly ozone concentrations (ppb) and
daily mean concentrations as a function of daily mean concentra-
tions, observed at Zugspitze (3000 m above M.S.L.) between August
1973 and February 1976. The frequency distribution by 5-ppb classes
of the daily mean and 2-ppb classes of hourly maximum minus daily
mean is given by the numbers in the diagram. The dashed line
indicates the limits of the present data distribution. To the
right of the shaded line the federal maximum value of 74.7
would be exceeded. Dots indicate the mean values of (max.
daily mean) in each class of daily mean values. The solid
gives an approximate best fit to these dots. The cross marks the
mean value of both distributions, that of (max. hourly - daily
mean) and that of the daily mean values. The dashed-dotted line
approximates the position of the mode values in each class of
daily mean concentrations. Note that two observations fall out-
side the plotted distribution.
404
ppb
hourly
line
-------
TABLE 3. OZONE CONCENTRATIONS IN THE PLANETARY BOUNDARY LAYER EXCEEDING
FEDERAL STANDARDS, ARRANGED BY DATE
Episode No.
]
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Date
5-2-63
5-15-63
6-26-63
7-3-63
8-7-63
8-14-63
9-11-63
9-11-63
9-18-63
1-20-64
4-8-64
4-15-64
4-17-64
4-20-64
4-20-64
7-1-64
7-1-64
7-15-64
7-15-64
8-26-64
• 9-23-64
1-22-65
7-14-65
10-6-65
10-7-65
10-8-65
10-13-65
11-3-65
11-10-65
12-1-65
12-1-65
Maximum 03 (yg/q)
0.15
0.13
0.19
0.17
0.15
0.19
0.17
0.17
0.15
0.17
0.18
0.16
0.20
0.13
0.16
0.13
0.13
0.17
0.15
0.19
0.13
0.15
0.16
0.19
0.24
0.24
0.13
0.14
0.25
0.14
0.14
Station
Goose Bay
Tal lahassee
Bedford
Bedford
Bedford
Tal lahassee
Tallahassee
Seattle
Tal lahassee
Bedford
Seattle
Seattle
Seattle
Tallahassee
Seattle
Albuquerque
Bedford
Bedford
Goose Bay
Bedford
Tallahassee
Tallahassee
Bedford
Pt. Muqu
Pt. Muqu
Pt. Muqu
Pt. Muqu
Pt. Mugu
Pt. Muqu
Pt. Muqu
Tallahassee
ther than two
0.2 percent
(as plotted in
of the total san
Figure 7). This one day would
iple of days -- in correspondenc
then correspond
:e to our obser-
to
vations over the U.S. (Reiter, 1976b).
Even though we have not yet carried out an isentropic trajectory analy-
sis for this case, we are convinced that we are facsd with a massive strato-
spheric air intrusion because: (a) Cosmogenic beryllium7 (Be7) concentrations
rose significantly during that period (Table 5); (b) a cold front, associated
405
-------
with a strong northwesterly jet stream, passed before the rise in 03 concen-
trations.
TABLE 4. HOURLY OZONE CONCENTRATIONS (ppb), ZUGSPITZE (GERMANY)
ON JANUARY 8 AND 9, 1975
January 8
Time
(hr.)
1
2
3
4
5
6
7
8
9
10
11
12
ppb
25.82
27 .'28
27.94
30.08
31.30
30.93
28.07
27.37
26.91
27.69
37.78
47.88
Time
(hr.)
13
14
15
16
17
18
19
20
21
22
23
24
ppb
42.88
50.81
62.21
52.92
52.06
54.83
57.03
62.80
79.85
114.10
157.74
197.55
Time
(hr.)
1
2
3
4
5
6
7
3
9
10
11
12
January 9
ppb
158.89
170.36
171.44
159.78
81.33
28.50
25.33
27.79
30.31
30.71
31.43
31.82
Time
(hr.)
13
14
15
16
17
18
19
20
21
22
23
24
ppb
32.12
32.22
25.61
25.18
24.88
22.37
22.39
19.84
19.10
17.92
16.89
17.17
TABLE 5. THE DAILY AVERAGE Be7 CONCENTRATIONS MEASURED AT ZUGSPITZE
7 January 1975
8 January 1975
9 January 1975
10 January 1975
11 January 1975
12 January 1975
1 .33 pc/m3
4.99 pc/ms
10.35 pc/ms
13.79 pc/m3
11.17 pc/ma
11 .66 pc/ms
13 January 1975
14 January 1975
15 January 1975
16 January 1975
17 January 1975
18 January 1975
14.60 pc/ms
11 .84 pc/ms
15.29 pc/ma
7.10 pc/ms
5.71 pc/ms
2.98 pc/ms
Peculiar about this event are the excessive values of hourly 03 concen-
trations. Rises in Be7 concentrations and jet stream-associated stratospheric
air intrusions were also involved in the statistical distribution shown in
406
-------
Figure 7 without exceeding the maximum allowable hourly 03 concentration value
(Reiter, 1976b). The answer to this puzzle is given in Figure 8, showing
the 100-mb surface of January 7, 1975, 00 GMT. The center of gravity of the
stratospheric polar vortex, according to this map, lies over Europe in a
rather anomalous position. It began to establish itself in this position
on January 6. Sinking motions in the middle and lower stratosphere to the
rear of the European trough helped to establish a low-stratospheric ozone
reservoir with well above average concentration values. This reservoir was
tapped by a typical stratospheric extrusion process.
We are convinced, therefore, that the departure of the two data points
with excessive 03 maxima in Figure 7 from the rest of the statistical distri-
bution is not so much due to the peculiar absence of mixing in the tropo-
sphere, but to an anomalous behavior of the stratospheric circulation and to
the establishment of an excessively strong ozone reservoir in the lower
stratosphere.
We still will have to allow for the fact that the 03 concentrations
described above were measured at an elevation of 3000 m above M.S.L., i.e.
above the normal height of the PBL. Mixing processes within the PEL should
reduce these concentrations considerably, perhaps by as much as a factor of
two.
CONCLUSIONS
The foregoing discussion shows that the maximum allowable hourly 03
concentration of 74.7 ppb can be exceeded on occasion in the cyclogenetically
active regions of middle latitudes, and especially under favorable trough
positions in the stratospheric vortex. Such excessive concentrations in
these regions have a probability of approximately 0.2 percent, measured in
days of observations on an annual basis.
It is also apparent that natural background levels of stratospheric
ozone in the lower troposphere can fluctuate considerably, and can reach 20%,
perhaps 50% of the maximum allowable hourly level considerably more often
(see Figure 7). Relatively small additions of anthropogenic 03, under such
conditions, will lead to ambient 03 concentrations above 74.7 ppb.
ACKNOWLEDGEMENTS
The research reported in this paper was supported by an Environmental
Protection Agency grant to Stanford Research Institute.
REFERENCES
Dutsch, H.U., 1971: Photochemistry of atmospheric ozone. Advances in Geo-
physics. 15, 219-322. ~ ~~
Fabian, P. and C.E. Junge, 1970: Global rate of ozone destruction at the
earth's surface. Arch. Meteor. Geoph. Bioklim., Ser. A, 19(2), 161-172.
407
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408
-------
Hering, W.S., 1964: Ozonesonde observations over North America, Vol. 1.
Report AFCRL-64-30(I), pp. 1-512, Air Force Cambridge Research Labora-
tories.
, and T.R. Borden, Jr., 1964: Ozonesonde observations over North Ameri-
ca, Vol. 2. Report AFCRL-64-30(II), Air Force Cambridge Research Lab-
oratories.
_, and T.R. Borden, Jr., 1965a: Ozonesonde observations over North Ameri-
ca, Vol. 3. Report AFCRL-64-30(III), Air Force Cambridge Research Lab-
oratories.
, and T.R. Borden, Jr., 1965b: Mean distribution of ozone density over
~~North America, 1963-1964. Report AFCRL-65-913, Air Force Cambridge
Research Laboratories.
__, and T.R. Borden, Jr., 1967: Ozonesonde observations over North America,
Vol. 4. Report AFCRL-64-30(IV), Air Force Cambridge Research Labora-
tories .
Junge, C.E., 1962: Global ozone budget and exchange between stratosphere and
troposphere. Tellus, 14(4), 363-377.
, 1963: Studies of global exchange processes in the atmosphere by
natural and artificial tracers. J. Geophys. Res., 68(13), 3849-3856.
Lovill, J.E., 1972: The global distribution of total ozone as determined by
the NIMBUS III Satellite Infrared Interferometer Spectrometer. Colorado
State University, Ft. Collins, Colorado, Ph.D. Dissertation, 72 pp.
Regener, V.H. and L. Aldaz, 1969: Turbulent transport near the ground as
determined from measurements of the ozone flux and the ozone gradient.
J. Geophys. Res., 74(28), 6935-6942.
Reiter, E.R., 1972: Atmospheric transport processes, Part 3: Hydrodynamic
tracers. U.S. Atomic Energy Commission, TID-25731, 212 pp.
, 1975a: Stratospheric-tropospheric exchange processes. Reviews of
Geophysics and Space Physics, 13(4), 459-474.
, 1975b: The transport of radioactive debris and ozone from the strato-
sphere to the ground. Report to Stanford Research Institute, 22 November
1975, 36 pp.
, 1976a: Ozone concentrations in the lower troposphere as revealed by
ozonesonde observations. Report to Stanford Research Institute, 24 March
1976, 106 pp.
, 1976b: Lower-tropospheric ozone in excess of Federal maximum value.
Report to Stanford Research Institute, 28 June 1976, 39 pp.
, E. Bauer and S.C. Coroniti, 1975: The natural stratosphere 1974. CIAP
Monograph No. 1, U.S. Department of Transportation.
409
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Seitz, H., B. Davidson, J.P. Friend and H. W. Feely, 1968: Final report on
Project Streak. Numerical models of transport, diffusion and fallout of
stratospheric material. Isotopes, Inc., Westwood, New Jersey, Report No.
NYO-3654-4, 97 pp.
Singh, H.B., W.B. Johnson and E.R. Reiter, 1975: The relation of oxidant
levels to meteorochemical processes: A review of available research
results and monitoring data. Stanford Research Institute: Interim
Report, SRI Project 4432, 119 pp.
410
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SESSION 9
THEORIES ON RURAL OZONE/OXIDATES
: B. Dimitriades
Environmental Protection Agency
411
-------
9-1
RESEARCH TRIANGLE INSTITUTE STUDIES OF HIGH OZONE
CONCENTRATIONS IN NONURBAN AREAS
L. A. Ripperton, J. J. B. Worth, F. M. Vukovich, and C. E. Decker*
ABSTRACT
The. ReieoAcn T/u.pont>ouhip oft the, Environmental. Pfiote,cti.on
Age.nct/ to heJLp cnoAac.ie'u.ze the, pnenomcnen ofi high HoJwJi ozone, conce.n&iationA .
The. moAt txignifi-ic-ant n.e^>ult& o& theJse, ptiogfiamA -include the, ^ottowtng: (a)
Ai high pneA&uAe, Ay*te,mA move, acAo&i, the. U. S. faom dJe^t to Ea&t, high ozone,
c,onc.e.ntsiationA -in a. high ptiUbuAe, &yt>te,m aAe. fiound in an aAea o/J a.ppnoyjjmctte,ty
60,000 t>q. mi. and cine, aA£oCsicute.d with incAe.ci&ing population de,nA-itij; (6)
the, high ozone. c,onc.e,ntnation& we/Le, ^oand to OCC.UA on tka tA.aiting bide, o^ the.
high pneA&uAe, AyAte.m; (a) thzofi&ticat Atudiu indicate,d that din in the, lead-
ing edge o& a high ptLU&uAe. t>y&te.m had been in the. high pieJ>&uA.e, t>y&te,m a.
day on. te^&, wheJte,a^ the, ait on the, t>utiiing Aide, ofa the. high pfie^AuAe, £yte.m
had been ^ne^ie two to &
-------
in the understanding of the chemistry of ozone generation in nonurban atmos-
pheres is the paucity of oxides of nitrogen (NO ) found there. Most of the
NO measurements that have been made in the rural field studies have been in
the noise level of the instrumentation available, around 0.005 ppm. Neverthe-
less, on second and third days of continuous smog chamber runs at RTI, N0x
concentrations of this level have produced ozone concentrations in excessxof
the NAAQS (7).
In the summers of 1970 (1), 1972 (2), 1973 (3), 1974 (4), 1975 (8), and
1976 (9), Research Triangle Institute (RTI) conducted field studies, under
Environmental Protection Agency (EPA) sponsorship, that have helped characterize
the phenomenon of high nonurban concentrations of ozone.
Some investigators have data indicating massive intrusion of stratospheric
ozone into the troposphere, but the bulk of evidence obtained by RTI in these
investigations favors the generation of ozone from anthropogenic precursors
and the transport of this ozone and its precursors from a few miles to a few
hundred miles in the lower levels of the troposphere. The following technical
report describes the findings of the six previous summer studies conducted
by RTI and subsequent conclusions drawn from these data.
FIELD STUDIES
In 1970, in response to an air pollution incident at and near Mt. Storm,
West Virginia, RTI measured ozone concentrations of several hours duration
that exceeded 0.1 ppm using a chemiluminescent (Rhodamine B) instrument (1).
In the summer of 1972, RTI conducted a study of atmospheric ozone near Mt.
Storm in Garrett County, Maryland, and Preston County, West Virginia. The
1972 study confirmed the earlier reports of high ozone concentrations; approxi-
mately 11 percent of 1,043 hourly measurements made at the Garrett County,
Maryland Airport during the summer of 1972 exceeded the NAAQS. Similar find-
ings were obtained at satellite locations around the base station at a radius
of approximately 19 kilometers. Analysis of synoptic meteorological data,
as well as an examination of ozone wind roses for the Garrett County Maryland
Airport led to a hypothesis that the high ozone concentrations at this loca-
tion developed within particular air masses that acquired and maintained their
characteristics over broad geographic regions (2).
In the summer of 1973, in order to further assess the aerial extent of
high rural ozone concentrations, RTI established a network of four monitoring
sites for the measurement of ground-level ozone concentrations and conducted
airborne measurements of ozone with an instrumented twin-engine aircraft.
These four sites were located at or near McHenry, Maryland (Garrett County);
Kane, Pennsylvania; Coshocton, Ohio; and Lewisburg, West Virginia. This
study confirmed the hypothesis that the high rural ozone concentrations
extended over a considerable area. For the summer and early fall of 1973,
the NAAQS for photochemical oxidants was exceeded during 15 percent of 1,663
hours at Lewisburg; 37 percent of 1,652 hours at McHenry; 30 percent of 2,131
hours at Kane; and 20 percent of 1,785 hours at Coshocton (3).
In 1974, a study was conducted in Ohio to investigate the relationship
between high rural oxidant levels and urban hydrocarbon control strategies.
414
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All data obtained in the 1974 study showed strong evidence for the involve-
ment of anthropogenic precursors and urban effluvia in the generation of the
high ozone concentrations in rural areas. As a result of these investigations
it was postulated that the high concentrations of ozone (produced by photo-
chemical processes) found in nonurban portions of the area studied are pri-
marily an air mass characteristic and will occur when a slow-moving high
atmospheric pressure system passes over the region (4).
In 1975, RTI conducted a study for EPA to further investigate the re-
lationship between high ozone concentration and high pressure systems and
to determine the change in the concentration of ozone in the center of a
high pressure system, as the system moves from an area of low population
density to an area of high population density. Ozone, nitrogen oxides, and
hydrocarbon data were collected at ground stations located in Bradford,
Pennsylvania, Lewisburg, West Virginia, Creston, Iowa, and Wolf Point, Montana,
and from an instrumented aircraft flying specified flight patterns. High
ozone concentrations and the frequency of exceeding the NAAQS were found to
be associated with high population density and high pressure (8).
In 1976, RTI under EPA sponsorship participated in the flight of DaVinci
II, an Energy Research Development Administration (ERDA) sponsored manned
balloon-borne experiment conducted in the St. Louis area during early June.
Ozone and meteorological variables were monitored from a Lagrangian frame
of reference over a twenty-four hour period. Data obtained from the balloon
and on the ground indicate that high ozone concentrations (>0.13 ppm) were
transported aloft undiminished for several hundreds of miles from an urban
area (9).
For various reasons the characterization of high ozone systems in dif-
ferent parts of the country may be different. In this paper, RTI presents a
summary of its findings and discusses suppositions with regard to high ozone
concentrations in nonurban areas and the relationship between high ozone and
high pressure systems, in particular high pressure systems that originate in
Canada and the Northern Plans and sweep the area south of the Great Lakes
and into the Atlantic Ocean.
RESULTS OF STUDIES
Observational data and theoretical considerations have indicated the
following behavior of the diurnal maximum ozone concentrations in rural
regions in the midwest and eastern portions of the United States as a high
pressure system moves through the region (Figure 1). When the leading edge
of a high pressure system passes through a rural region, the diurnal maximum
ozone concentration generally begins to lower in value, and a relative minimum
value usually occurs before the center of the high pressure system reaches
the sampling station. A relative maximum value of the diurnal maximum ozone
concentration is found on the back side of the high pressure system. It has
been hypothesized that this distribution is related to the residence time of
air in the high pressure system. Generally, the residence time is larger on
the back side of that system (Figure 2). This allows time for air parcels
to obtain large or critical concentration of ozone precursors, time for the
generation of ozone from much less active precursors, and time for the accu-
415
-------
3750
3125
Distance fkm")
2500 1875 1250
625
200 —
s 150 —
100 —
50-
BRADFORD
CRESTON Hi§h Pressure
WOLF POINT Center
654
Bradford § Wolf Point
4 3
Creston
I
1
Days
Figure 1. The temporal and spatial variations of the diurnal maximum ozone
concentrations through a moving high pressure system based on the
1975 data at Wolf Point, Montana; Creston, Iowa; and Bradford,
Pennsylvania.
mulation of ozone. Because of the difficulty of measuring low concentrations
of N0x and other precursors, this hypothesis has not been substantiated. It
is suggested that the low concentration of N0x that apparently exist in
rural boundary layers is a result of rapid gas phase chemical reactions.
In the summer of 1975, the ozone concentration at Wolf Point, Montana,
which was the western-most station in the 1975 array and in the Northern
Plains never exceeded the NAAQS. Furthermore, Figure 1 shows that the diurnal
maximum ozone concentration did not behave similarly to that found for sta-
tions further east; that is, the ozone concentration on the back side of
the high was not a relative maximum. When the high pressure system reached
Creston, Iowa, low concentrations of ozone were found on the eastern portion
of the high pressure system and high concentrations on the back part of that
system. This distributional characteristic of ozone in high pressure systems
was most highly developed when the system reached Bradford, Pennsylvania (4).
There are two or three mechanisms that may be responsible for high ozone
416
-------
-1
10 ms
-1
Figure 2. Hypothetical distribution of air parcel residence time (days)
in a circular high pressure system versus system speed.
417
-------
concentrations in rural regions associated with high pressure systems. One
mechanism is synthesis. Another is vertical transport. And still another
is horizontal transport. Theory and trajectory analyses suggest that within
a high pressure system it is quite possible for air, although it moves slowly
and without strong directional influence, to travel 400 miles within a 24-
hour period. Data from the DaVinci II experiment have suggested that air
reaching ozone concentrations of 0.13 to 0.14 ppm by late afternoon over
the city of St. Louis was transported almost undiminished 150 miles across
the State of Illinois into Indiana (Figure 3). The ozone concentrations in
the air aloft remained at essentially the same concentrations; whereas, the
air at the ground that was being monitored by a mobile van that kept the
balloon in sight, behaved in the usual surface diurnal fashion and reached
lower values at night. At the beginning of the next daylight period, the
ozone concentration began to rise. This mechanism is believed to behave
in the following manner.
In the rural region, air is mixed during the day through great depths.
Throughout the mixing depth, the ozone concentration is generally homogenous.
At night, when the nocturnal inversion is produced near the ground., the
ozone concentration near the surface is reduced by gas phase destruction and
by contact with the surface of the earth. The nocturnal inversion will
prevent destructive agents from being injected into the layer above. There-
fore, the ozone concentration in this layer will remain undepleted and will
maintain itself overnight as is suggested by the data shown in Figure 3.
Thus, a diurnal variation of ozone will be found in the surface layer whereas
little or no diurnal variation will be found in the layer above the nocturnal
inversion.
After sunrise two processes occur that cause that cause the increase in
ozone near the surface. Solar and sensible heating erode the nocturnal inver-
sion allowing air containing higher concentrations of ozone aloft to be mixed
to the surface. Furthermore, the air in the surface layer has accumulated
large concentrations of ozone precursors that will eventually be used to
synthesize ozone. Data are not yet available from the DaVinci II experiment
to test this hypothesis with calculations.
Many have attributed high ozone concentrations in rural regions to the
near surface transport of so-called fossil ozone. In general, the half-life
of ozone at night as indicated by RTI smog chamber studies and by observed
data (Table 1) would be around 20 to 30 hours. This would not allow fossil
ozone to be responsible for the high concentrations found in rural areas for
more than two days without synthesis to maintain these concentrations.
It can be seen in Figure 4, which represents a series of flights made in
1974 at Wilmington, Ohio, that the ozone concentration increased with time
through a layer from the surface, 1000 ft. mean sea level (MSL) to approximate-
ly the 6000 foot level (MSL). Computations made using these data and available
meteorological data during the same period indicated that approximately 50
percent of the increase of ozone at the lower level and in the period 0704
Central Daylight Time (CDT) to 1320 CDT, could be explained by vertical mix-
ing. However, vertical mixing accounts for only 10 percent of the increase
between 1320 and 1656 CDT. At 1656 CDT, the vertical gradient is reversed
418
-------
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419
-------
TABLE 1. DARK PHASE OZONE HALF LIFE*
Station
Bradford, Pennsylvania
Creston, Iowa
Wolf Point, Montana
Half-life
Mean (hrs)
13.1
20. 4
15.4
Std. Dev.
(percent)
15.2
28.5
15.9
Range
2.8-75.9
3.4-180.9
3.6-70.7
Case Count
65
60
61
*Half life was calculated using ozone data from the 1975 Summer Oxidant
Study from 0200 to 0500, assuming a first order decay rate.
1754 1414
0704'
HYDROCARBON
SAMPLE
(MORNING)
1320
1656
100
150
200
-3,
250
12
11
10
9
8
7
00
o
OZONE CONCENTRATION (uG/M )
Figure 4. Ozone profile flight, Wilmington, Ohio, August 1, 1974.
420
-------
such that the lower level Is supplying ozone to the upper levels. This sug-
gested that, in this latter case, since vertical mixing could not account
for a major portion of the increase in ozone in the lower boundary layer,
most of the increase from morning till late afternoon is due to synthesis.
That synthesis plays a part in producing high concentration of ozone in
rural areas can be seen by the fact that in many cases rural sites exhibit a
higher concentrations of ozone than do nearby urban sites (Table 2 and 3).
The data in Figure 3 have suggested that synthesis accounted for most of the
increase in ozone at lower levels. It has also been discussed that in the
northern part of the United States, the high ozone that is associated with
high pressure is found on the back side of an eastward moving high pressure
system. This is thought to be due to the fact that as the system moves, air
in the front part of the high pressure system has spent insufficient time in
that system to accumulate ozone precursors and to be exposed to unimpeded
solar radiation. On the back side of the high pressure system, we find air
that has spent two to six days in that system. This air has had plenty of
time to accumulate ozone precursors and has undergone many diurnal ozone
cycles.
As the high pressure system moves east, population density increases and
consequently the potential for greater emissions of hydrocarbons and NO . The
polluted air from the cities injected into the system as it moves eastward
will permit the generation of ozone. As has been shown in smog chamber
work, an aged system with low concentrations of NO will generate high concen-
trations of ozone (greater than the NAAQS). The most active of the organic
precursors, olefins, are also those that are most reactive in destroying
ozone. These are reacted rapidly and the less reactive precursors are pre-
served to react later. The less reactive precursors can generate high ozone
concentrations given enough time, and they do not destroy ozone very rapidly.
The more aged the system the more favorable the conditions for retaining
ozone that it generates.
As a result of the reported studies, the following hypothesis has been
established for high ozone in the rural boundary layers in midwestern and
eastern portions of the United States. Air parcels in high pressure systems
moving from Canada across the Northern Great Plains pick up very little in
the way of ozone precursors from the plains. What precursors are injected
into the system are natural in oYigin because there are relatively few anthro-
pogenic sources in this region. * As the high pressure system moves further
eastward across a line arbitrarily drawn from Fargo, North Dakota to Dallas,
Texas, the population, according to the 1970 density map, increases quite
rapidly from about ten people per square miles to 103 people per square
mile. The accumulation of ozone precursors should increase considerably to
the east of this line due to the increased potential for anthropogenic in-
jection. It is doubtful that the rural population itself can contribute
enough material to generate the ozone. However, the cities should produce
enough precursor material to begin to generate large concentrations of ozone.
Results of these research programs imply that the control of hydrocarbons
in any individual city will reduce, but not necessarily prevent, the occur-
rence of high rural ozone concentrations in excess of the NAAQS at any given
rural site. The implication is that the release of hydrocarbons and oxides
421
-------
TABLE 2. SUMMARY OF OZONE DATA FOR 1973 AND 1974 OXIDANT STUDIES
Station
McHenry, MD
Kane, PA
Coshocton, OH
Lewisburg, WV
Wilmington, OH
McConnelsville,
OH
Wooster, OH
McHenry, MD
DuBois, PA
Canton, OH
Cincinnati , OH
Cleveland, OH
Columbus, OH
Dayton, OH
Pittsburgh, PA
Year
1973
1973
1973
1973
1974
1974
1974
1974
1974
1974
1974
1974
1974
1974
1974
Type of
Station
Rural
Rural
Rural
Rural
Rural
Rural
Rural
Rural
Rural
Urban
Urban
Urban
Urban
Urban
Urban
Average 03
(ppm)
0.074
0.065
0.056
0.052
0.052
0.057
0.047
0.057
0.056
0.035
0.025
0.031
0.033
0.035
0.028
No. Hours
> 0.08 ppm
600
639
357
249
259
262
262
262
341
148
54
51
113
114
106
Mo.
Hours
1622
2131
1785
1663
1751
2011
1878
2011
1667
1829
1548
1652
1935
1576
1622
Hours
> 0.08
ppm (%)
37.0
30.0
20.0
15.0
14.9
13.0
14.0
13.0
20.5
8.0
3.5
3.0
5.8
7.2
6.5
of nitrogen from anthropogenic or biogenic sources, located in both urban
or rural areas, all combine to generate appreciable quantities of ozone over
widespread regions.
By the time the high pressure system reached Kansas City, cities have
provided sufficient precursors for generation of a high concentration of
ozone. Once the ozone system has been generated, anthropogenic effluents
provide enough fuel for the process to continue. The denser the population
becomes, the greater the amount of precursor material released and the higher
the potential for producing large concentrations of ozone becomes. As the so-
called city plume moves out, widens and is then added to the material injected
from the rural regions and from smaller cities, ozone will be generated in
concentration greater than the NAAQS. Eventually, the urban plumes, although
they may be undetectable by other means, will have overlapped in such a way
that they produced an areawide ozone phenomena.
422
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TABLE 3. SUMMARY OF OZONE DATA FOR 1975 OXIDANT STUDY
Station
Bradford, PA
Lewis burg, WV
Creston, IA
Wolf Point, MT
DeRidder, LA
Pittsburgh, PA
Columbus, OH
Poynette, WI
Cedar Rapids,
IA
Des Moines, IA
Omaha, NB
Nederland, TX
Port O'Connor,
TX
Austin, TX
Houston, TX
Year
1975
1975
1975
1975
1975
1975
1975
1975
1975
1975
1975
1975
1975
1975
1975
Type of
Station
Rural
Rural
Rural
Rural
Rural
Urban
Urban
Rural
Urban
Urban
Urban
Urban
Rural
Urban
Urban
Average
03 (ppm)
0.040
0.038
0.035
0.028
0.030
0.030
0.022
0.038
0.025
0.036
0.035
0.027
0.027
0.025
0.026
No. hours
^0.08 ppm
100
59
17
0
38
227
43
126
6
124
64
138
99
19
141
No.
Hours
2332
2386
2117
2160
2994
2841
2885
2663
2781
2528
1787
2714
2912
2504
2104
Hours
> 0.08
ppm (%}
4.3
2.5
0.8
0.0
1.3
8.0
1.5
4.7
0.2
4.9
3.6
5.1
3.4
0.8
6.7
CONCLUSIONS
Some of the most significant conclusions of the RTI Summer Studies are
the following. As high pressure systems moves across the United States,
high ozone concentrations found in that system are associated with high popula-
tion density. The data indicate that high concentrations of ozone observed at
rural locations are generated in the lower troposphere. The air on the back
side of an eastward-moving high pressure system experiences longer residence
time than air in the leading edge of that system. Generally, high ozone is
found on the back side of high pressure systems.
An areawide system (a radius of 225 miles or more) of high ozone
concentrations can exist in which most features suggestive of a precursor
origin have been smoothed out. However, a short range urban influence on both
hydrocarbon and ozone concentration can be observed. The evidence indicates
an observable urban influence extending as far as 150 miles downwind of the
city.
423
-------
Transport of fossil ozone can occur for several hundred miles. The
delivery of high concentrations of ozone to rural sites depends on both the
movement of so-called fossil ozone and the synthesis of fresh ozone from
systems containing low concentrations of N0x and hydrocarbons that are mainly
alkanes and aromatics.
REFERENCES
1. Richter, H. G. Special Ozone and Oxidant Measurement in the Vicinity
of Mt. Storm, West Virginia. Research Triangle Institute. Task
Report, Task No. 3. NAPCA Contract No. 70-147, 1975.
2. Research Triangle Institute. Investigation of High Ozone Concentration
in the Vicinity of Garrett County, Maryland, and Preston County, West
Virginia. Issued as Environmental Protection Agency Report No. EPA-R4-
73-019.
3. Research Triangle Institute. Investigation of Ozone and Ozone Precursor
Concentrations at Non-Urban Locations in the Eastern United States,
Phase I. Issued as Environmental Protection Agency Report No. EPA-450/
3-74-034, May 1974.
4. Research Triangle Institute. Investigation of Rural Oxidant Levels as
Related to Urban Hydrocarbon Control Strategies. Issued as Environmental
Protection Agency Report No. EPA-450/3-75-035, March 1975.
5. Stasiuk, W. N. and P. E. Coffey. Rural and Urban Ozone Relationships
in New York State, J.A.P.C.A., 24, 1974. pp. 564-568.
6. Junge, C. E. Air Chemistry and Radioactivity. Academic Press, New
York, 1963. pp. 37-59.
7. Research Triangle Institute. Oxidant Precursor Relations Under Pollutant
Transport Conditions. Final Report. Environmental Protection Agency
Contract 68-02-1296, May 1976.
8. Research Triangle Institute. Study of the Formation and Transport of
Ambient Oxidants in the Western Gulf Coast and Northcentral and North-
east Regions of the United States. Final Report. Environmental Protection
Agency Contract No. 68-02-2048, August 1976.
9. Research Triangle Institute. Ambient Monitoring Aloft of Ozone and
Precursors in the Vicinity of and Downwind of a City. Interim Report.
Environmental Protection Agency Contract No. 68-02-2391, July 1976.
424
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9-2
IMPORTANT FACTORS AFFECTING RURAL
OZONE CONCENTRATION
F.L. Ludwig, W.B. Johnson, R.E. Ruff and H.B. Singh"
ABSTRACT
Statistical anatyAeA o^ 120 aiA tAaje.ctoAi.eA aAAi.vi.ng at fiouA di{,fieAe.nt
AuAol ozone. monJ.tofu.ng AiteA in the, e,aAteAn Unite.d States have, been uAe.d
to ide-ntifiy the. emiAAionA and mete.oAo logical condition that OAe. mo&t
cloAely Atu.die.d by companding the. long&-AeoXe spatial diAtAi-bationA o&
maxAmum-houA ozone. conce.ntiati.onA with co?ifieApon.di.n.g we.atheA patteAnA.
The. average aifi tempeAatuAe. doling the. laAt 12 houAA ofi the. tAaje.ctoAy
MU the. beAt tingle. deAcAi.pton ofa ozone. conczntsiationA; ozideA o& nitsioge.n
emiA4i.onA weA-e. Ai.gni^i.cantiy coAAeJLate.d with ozone, but hydAocajtbon. miAAtonA
wiete not. The. tAaje.ctoAy analyteA alf>o Akowe.d that ozone, conce.ntAati.onA
above, BO ppb weAe. mo&t fiAe.que.ntly at>-t>ociate.d with light AouthweAt wind* and
the. absence ofi pAe.cipitation. The. coAA.eAponding vJe.atheA patte/inA aAe, the,
waAm aiA Ai.de. ofi fiAontA and the. weAteAn paAtA ofa anticyclones. In ge.neAal,
the. ttudieA showed violation* ofi ox.i.dant AtandaAdA to ex-tencf oveA aAe,af, laAgeA
than the. typical aiA qualify contAol Ae.Qi.on, AuggeAting the. ne.ce.t>t>ity o&
Ae.viAi.onA i.n the. pAeAe.nt contAol philo&ophieA.
INTRODUCTION
The adoption of ambient air quality standards (AQS) brings with it
some corollary concepts. The first of these is the air quality control
plan. This is a concert of actions that will ensure that air quality will
not violate the established standards. In practice, these control plans
have been formulated for limited geographical regions under the assumption
that the consequences of control measures—and conversely, of uncontrolled
emissions—are quite limited in area.
Figure 1 shows the air quality control regions (AQCR) into which the
eastern United States has been divided. Observations of high ozone concen-
trations in rural areas have raised the possibility that the consequences
of pollutant emissions might be much more widespread than originally assumed
when AQCRs were defined. Figure 2 shows the distribution of maximum-hour
ozone concentrations in the eastern United States for May 22 1974. The
shaded areas show where the federal standard of 80 ppb was exceeded. It is
^Stanford Research Institute, Menlo Park, California.
425
-------
immediately apparent that the AQS are exceeded over areas that are much
larger than the typical air quality control region. There are at least two
possibilities for the widespread occurrence of high ozone levels:
• There are large-scale natural processes producing high ozone
concentrations.
• The effects of man-made emissions are much more pervasive than
originally thought.
Figure 1. Federal Air Quality Control Regions
426
-------
60 80
.80 !t
40
22
80 ',220 ®0 60
Figure 2. Distribution of maximum-hour 03 concentrations
for the eastern United States for 22 May 1974.
Both these possibilities have important consequences in the formulation
and execution of emission control policies. This paper summarizes recent
studies of the importance to the above explanations (Ludwig et al , 1976),
with emphasis on the second explanation. This paper addresses two facets
of the problem:
• The effects of meteorological conditions and emissions
within the mixing layer on subsequent formation of ozone.
• The relationships between large-scale ozone patterns and
synoptic weather features.
427
-------
METHODS
A statistical approach was used to determine what tropospheric factors
are important to ozone formation in rural areas. Four rural monitoring sites
were chosen for study:
• McHenry, Maryland
• Queeny, Missouri
• Wooster, Ohio
• Yellowstone Lake, Wisconsin.
Thirty cases were chosen for analysis from the data collected at each
of these stations during the summer of 1974. The emphasis was placed
on cases with high ozone (03) readings. Fifteen cases were chosen for
each site from among the days whose high-hour 63 concentration was in
the upper 20 percentile of the 1975 summer high-hour observations for
that site. The remaining 15 cases for each site were split between
days when the 03 concentrations were among the bottom 20 percentile
and days with near-median maximum hourly concentrations.
Once the 120 cases had been chosen, air trajectories were calculated
by applying Heffter and Taylor's (1975) methods to the available rawin-
sonde and pilot balloon data. The resulting trajectories were then used
to determine the air's history during the 60 hours preceding the observation.
The air trajectories were plotted on maps provided by the Environmental Pro-
tection Agency (EPA) that show average annual emission densities of oxides
of nitrogen (NOX) and nonmethane hydrocarbons (NMHC) for each U.S. county.
From these the emissions encountered were estimated for different segments
of the trajectory; the average emission rates were corrected to account
for the time of day and diurnal emission cycles.
The trajectories were also plotted on three-hour weather maps* to
determine the weather prevailing at different times. The weather infor-
mation was used to estimate the following factors suspected to be important
to the production of ozone:
• Temperature
• Relative humidity
• Dewpoint
• Insolation
• Precipitation
*National Weather Service Synoptic Analyses are available from
the National Climatic Center, Asheville, North Carolina.
428
-------
• Atmospheric stability.
Temperature and dewpoint can be estimated directly from the weather maps
and they can be used to derive relative humidity. Other factors have to
be derived indirectly. The occurrence of precipitation, its type (e.g.,
rain, drizzle, and so forth) and a subjective classification of its charac-
ter and intensity (e.g., continuous moderate, intermittent light, and so
forth) are shown on the weather maps. The subjective classifications were
assigned numbers approximately proportional to precipitation rates, based
on the guidance provided to U.S. Air Force weather observers (U.S. Air
Force, 1957). Insolation strength was estimated from cloud cover and solar
elevation using a method described by Ludwig and Dabberdt (1972). Stability
classification was based on Ludwig and Dabberdt's (1972) modification of
Pasquill's (.1961) methodology.
Using the Storage and Retrieval of Aerometric Data (SAROAD) data base,
the large-scale distribution of maximun-hour ozone concentrations were
determined for all 365 days of 1974. Smoothing techniques were used to
suppress small-scale variability such as might be found within, and in the
immediate vicinity, of cities. The smoothing also suppresses the effects
of anomalous or erroneous readings. The maximum hourly average ozone concen-
trations were determined for each day and for each site. All the measure-
ments taken in a single city were averaged and used as a single measurement
representative of the entire city. The available observations were then
used to interpolate for grid points, which served as the basis for subsequent
isopleth analysis. The Oo isopleths were then compared with the weather map
for the same day (National Oceanic and Atmospheric Administration, 1974).
The comparisons were subjective, but were guided by the results of the tra-
jectory studies.
RESULTS
Once the average meteorological factors and emissions were deter-
mined for 12-hour segments of each of the 120 trajectories, linear
correlations between the ozone concentrations and each of the meteoro-
logical and emissions indexes were calculated. In some cases there
were important relationships that were not reflected in the linear
correlation coefficients. For instance, linear correlation between 03
concentration and precipitation is not particularly high, but there is
an important relationship, as should be evident from the scatter diagram
in Figure 3. In this diagram, the joint occurrences of ozone concentra-
tions and precipitations index values are marked by the asterisks; if
more than one case had approximately the same values, then the number
of cases is shown instead of an asterisk. As noted earlier, the pre-
cipitation that occurred along the trajectory during the 12 hours be-
fore the observation generally prevents ozone concentrations from rising
above 80 ppb. This probably arises from a combination of factors,
such as washout of ozone or its precursors, and the concurrent limited
sunshine and lower temperatures that are not conducive to ozone forma-
tion.
429
-------
o
"
O
N
O
\
MAXIMUM O, CONCENTRATION
O 4. 7. 11. 15. 19. 22. 26. 10. 13. 17.
4x AVERAGE PRECIPITATION INDEX DURING LAST TWELVE HOURS
Figure 3. Scatter diagram of ozone concentration versus precipitation
index during last 12 hours of trajectory.
Temperature was found to have the greatest linear correlation with
observed ozone concentrations. Average temperature along the trajectory
during the 12 hours preceeding the observation is especially important,
with a linear correlation of 0.54. If temperature is used in a regression
equation to describe ozone concentrations, the addition of other meteorolo-
gical variables will not improve the specification very much, but inclusion
of the NOX emissions does help, raising the correlation to about 0.6. The
hydrocarbon (HC) emissions are not significantly correlated with ozone con-
centration.
Several linear regression equations were formed using temperature and
two emissions indexes (e.g., NOX and HC during the last 12 hours of the
trajectory, NOX during the last 12 hours and during the preceding day) and
NOX and HC emissions throughout the preceding days weighted to emphasize
the more recent emissions. There is little to choose among the different
combinations; all achieved linear correlations with 03 of about 0.6 and
standard errors of estimate around 47 ppb.
However, it was apparent from scatterframs of observed ozone versus
the values calculated from the regression that ozone concentrations greater
than about 80 ppb had a different, and stronger, relationship with the
predictors than do the lower concentrations. For this reason, separate
regression equations were derived for those cases where the observed
03 was less than 80 ppb and for those cases with higher values. Figure 4
illustrates the results of two such "piecewise" regressions. In
430
-------
both cases, the temperature and emissions during the last 12 hours
of the trajectory were used to predict the cases with C>3< 80 ppb.
The same variables were used in Figure 4a to predict the higher o
ozone values; for Figure 4b the temperature was replaced with
measures of insolation during the preceding 24 hours. The two-
part regressions achieve correlations of about 0.8 between observed
and estimated ozone concentrations and standard errors of about
35 ppb.
The fact that ozone concentrations can be so well predicted by
emissions and meterological conditions to which the air was exposed
during the preceding 12 hours does not ensure that events at earlier
times are not influential. This is particularly true for air tem-
perature and isolation. If we track the same air for several days,
the temperatures and sunshine conditions will tend to be much the
same from day to day and the values for one day would serve nearly
as well in a linear regression equation as those from the next. The
large spatial variability of emissions causes these indexes to be
generally independent from one time period to the next. Thus, the
fact that NOX emissions along the air trajectory 24 to 36 hours
earlier are significantly correlated with the observed ozone concen-
trations suggests that the influence of such emissions may presist
for a considerable period of time.
For those cases where 03 concentrations exceeded 80 ppb, the
air had generally been within about 450 km of the observing site
12 hours earlier, and within 1150 km 36 hours before. Taken in
conjunction with the data that indicate that some influence may
presist for 36 hours or more, this suggests that the influence of
emissions can be quite widespread.
When ozone concentrations were above 80 ppb, the air had come
more often from a direction between south and west than from any of
the other quadrants. Thus, when we have relatively high concentra-
tions of ozone in rural areas, the causes for those concentrations
are most likely to have occurred during the preceding day or so, and
within about 1000 km to the southwest. Obviously, this is not an
infalliable generation, but it does provide some guidance that might
be useful in the formulation of control strategies. Furthermore,
some justification for the generalization is found in the compari-
sons of large-scale distributions of maximum hourly ozone concen-
trations in the eastern United States with the concurrent synoptic
weather patterns.
The findings of the trajectory studies have their counterparts
in the interpretation of the larger scale ozone patterns. The pre-
ferred wind directions, the warm temperatures, and the sunny conditions
associated with high ozone concentrations are characteristic of
certain kinds of meteorological situation, and we might expect to find
most areas of high ozone in connection with these meteorological
conditions. Similarly, emissions in combination with wind speed
and direction influences might be expected to produce some preferred
geographical areas for high ozone concentration.
431
-------
(a) ESTIMATED
O ?*•>.
1 ""
w
o
§ '"•
o
w
?•: 10.
o
o
Q 10"'
w
W
a
o
a
P.
2;
O
H 211.
f5
W
u
O 17T-
u
o
N
O
Q
W
t/3
ca
o
o
u
(o/ ESTIMATED FROM TEMPERATURE
Am INSOLATION
EMISSIONS
P6. 10*.
UO. 159. 177. 195.
Ce , OZONE CONCENTRATION ESTIMATED WITH REGRESSION EQUATION— ppb
Figure 4. Estimated versus observed Oa for two regression expressions.
432
-------
The expected grographical and meteorological relationships
have been found. The following geographical areas accounted for
nearly all of the 1974 cases where 03 exceeded 80 ppb:
• New England
• The area southwest of Lakes Erie and Ontario
• The areas south and southwest of Lake Michigan
• The Washington-Philadelphia Corridor
• The St. Louis-Ohio River Valley area
• The Texas-Louisiana Gulf Coast
• The Florida Peninsula
• The western parts of Oklahoma, Kansas, and Nebraska.
All but the last two regions are clearly identified with regions of
major anthropogenic emissions. The Florida Peninsula appears to be
an area where the frequent occurrence of meteorological conditions
favorable to ozone production is more important than the emissions.
As yet we have not found a satisfactory explanation for the fre-
quent high ozone concentrations in the western parts of Oklahoma,
Kansas, and Nebraska. If the data are all valid, then the following
possibilities have to be considered: long-range transport of pre-
cursors from Texas, agricultural sources of NOX, stratospheric ozone
brought to the surface by the lee waves of the Rocky Mountains or by
frequent cyclogenesis in the area. Figure 5 shows an example of
ozone distribution in the eastern United States, with areas of high
ozone concentration in several of the regions mentioned above.
The trajectory analyses showed that high ozone concentrations
were more likely with warm temperatures, profuse sunshine, and light
southwesterly winds. These conditions are associated with the warm
air side of weather fronts and the western parts of anticyclones
(.high-pressure areas). Studies of stratospheric intrusion (e.g.
Ludwig et al, 1976) indicate that this phenomenon is most likely be-
hind strong cold fronts, in areas of cyclogenesis, and in the lee
waves of large mountain ranges. It has also been found (Ludwig et al. ,
1976) that squall lines can be sites of stratospheric intrusion.
Figure 6 is a schematic representation of the weather patterns that
are most likely to be associated with high ozone concentrations in
the eastern United States. Figure 7 is an example of the weather
patterns and the corresponding distribution of maximum-hour ozone
oxidant concentrations in the eastern United States. Figure 7 is an
example of the weather patterns and the corresponding distribution
of maximum-hour ozone oxidant concentrations in the eastern United
States were associated with one of the expected synoptic patterns,
especially those involving warm air and light southerly or westerly
433
-------
Figure 5. Example of Ch distribution in the eastern United States
on 14 June 1974.
winds-
APPLICATIONS
Some of the findings discussed above have been arrived at by
different means elsewhere. The relationships with high pressure
areas have been noted before (Environmental Protection Agency, 1975)
and long-range transport has been demonstrated in several case
434
-------
Figure 6. Schematic diagram showing parts of weather systems
favorable for high ground level concentrations of ozone.
studies (Coffey and Stasiuk, 1975; Cleveland et al., 1975; Lyons and
Cole, 1976; and Martinez and Meyer, 1976). The question arises, how
can results of the kind reported here be applied to the problem of
control strategy development?
The synoptic weather patterns that are associated with high
ozone concentrations seem to be sufficiently well-defined that they
can be used to defind spheres of influence for major anthropogenic
source areas. In general, the regions influenced by a source will
tend to be toward its northeast, but there are likely to be differences
from one region of the country to another, because the orientation of
the ozone-associated weather features will be different in different
regions. The distance that a source's influence extends downwind
could be estimated from trajectory analyses for specific weather
situations of the kind known to be associated with high ozone concen-
trations. It appears that the influence of a source is not likely
to last much longer than about 36 hours, and hence the distance
traveled during such a period should define the outer limits of
influence. The trajectory studies reported here, the dimensions of
the high-ozone areas in the synoptic analyses and the results of other
studies (Martinez and Meyers, 1976) all indicate that the areas of
435
-------
I
^§c^.^"^v m
—~f WTCA^y - 3&' '-^K> <& : Vr
• - ' 'S x?« V,-3i«P -*t ' 1
»A efc«?^-'«" ?>%^: '-i«- • \
^iX^W^-^
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iHvl
'yoci? rJ
f^;ri ^ rf'^ \? ^
;5" ^. !.L..v >8Vt ^
I ""> 0| >vU)'Sl
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a
o
HH
H
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^
O
o
si
o
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OJ
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Ol r—
03 O)
S- -M
O) OO
(J
E -O
O
CD
436
-------
influence of major sources have dimensions of more than a hundred
kilometers. This is larger than most of the air quality control
regions shown in Figure 1. Perhaps larger regions are more appropriate
to the oxidant control problem and revisions should be considered.
ACKNOWLEDGMENTS
The support of the Environmental Protection Agency, Office of
Air Quality Planning and Standards, under Contract No. 68-02-2084 is
gratefully acknowledged. We have found the comments and other assist-
ance of the Project Officer, Mr. Phillip Youngblood, to be most
helpful.
Mr. Dale Coventry of EPA and Mr. R. Hows of Research Triangle
Institute have provided much useful data, as has the staff of the
National Climatic Center.
At SRI the following people have provided invaluable assistance:
E. Shelar, R.L. Mancuso, J.H.S. Kealoha, A.H. Smith, R. Trudeau,
P.B. Simmon, and L.J. Salas.
REFERENCES
Bruntz, S.M., W.S. Cleveland, B. Kleiner and J. L. Warner, 1974: The
Dependence of Ambient Ozone on Solar Radiation, Wind, Temperature and
Mixing Height. Proc. Symp. Atmos. Diff. and Air Poll., Santa Barbara,
Calif. (Sept. 9-13), Amer. Met. Soc., pp.125-128.
Cleveland. W.S., B. Kleiner, J.E. McRae and J.L. Warner, 1975: The Analysis
of Ground-level Ozone Data from New Jersey, New York, Connecticut and
Massachusetts: Transport from the New York City Metropolitan Area.
Undesignated Report, Bell Laboratories, Murray Hill, N.J., 63 pp.
Coffey, P. E. and W. N. Stasiuk, 1975: Evidence of Atmospheric Transport
of Ozone into Urban Areas, Environ. Sci. and Tech., 9, 59-62.
Environmental Protection Agency, 1975: Control of Photochemical Oxidant--
Technical Basis and Implications of Recent Findings. EPA Report
450/2-75-005, 37 pp.
Heffter, J.L. and A.D. Taylor, 1975: A Regional Continental Scale Transport,
Diffusion and Deposition Model, Part I: Trajectory Model, Nat. Ocean.
and Atmos. Admin. Tech. Memo. ERL ARC-50, pp. 1-16.
Ludwig, F.L., E. Reiter, E. Shelar, R.L. Mancuso, W.B. Johnson and P.B. Simmon,
1976: Meteorochemical Influence on Rural Ozone Concentrations, Final
Report EPA Contract 68-02-2084, Stanford Research Institute, Menlo Park,
California, Draft Submitted September 1976.
437
-------
Lyons, W.A. and H.S. Cole, 1976: Photochemical Oxidant Transport: Mesoscale
Lake Breeze and Synoptic-Scale Aspects. J. Appl. Meteorol. 15, 733-743.
Martinez, E. L. and E.L. Meyer, 1976: Urban-nonurban Ozone Gradients and
their Significance, Presented at Air Poll. Cont. Assoc. Spec. Conf. on
Ozone/Oxidants: Interactions with the total Environment, Dallas, Texas,
March 12, 1976.
Pasquill, F., 1961: The Estimation of the Dispersion of Windborne Material,
Meteorol. Mag. (London), 90, 33-49.
U.S. Air Force, 1957: On-the Job Training Program No. JP 25251, Weather
Observer, Chapter 5.
438
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9-3
A MECHANISM ACCOUNTING FOR
THE PRODUCTION OF OZONE IN RURAL POLLUTED ATMOSPHERES
M. Antell*
ABSTRACT
In tku> ne.pofit a ktnztic. model ofi nvJwJi &mog u> juAtifi-ie-d and
The. modeJL Ae.tA ozone. (0^} , nonme.thane. hydn.oc.an.bon (MMHC), and nitsioge.n dA.oxA.da
(N02) at me.at,uA.e.d £eve£i. It oAAwmeA that the. only organic Ape.CA.eJ, pnej>e.nt
Ln 4ucA -imogi one. "nonA.e.acA~A.ve." hydAoc.an.bonA and pn.odu.ctA o& photo -oxidation
o{\ nonn-e.a(itive.A. The. concentration oft the. panjtAjaMLy ox.
a&Aime.d to be. at a le.ve.1 de.^-Lne.d by thiuA photoche.mic.at ptLOdu.c.tJ.on and de.-
£tnu.c,tA.on. At me.aAuA.e.d le.ve.tt> o& NOz and WMHC, ozone, production Ji& pie.dicte,d
to be. taJiQe. e.noagh to account ^on. ozone. £e.ve2A note.d A.n tLusiat &mog&. The.
ttate. Of) nut ozone, psiodac^ion pfie.dicte.d AA .0126 ppm/kfi, aldehyde, and ke.tone.
ie.ve2A p^.e.dic.te.d one. .010 ppm and .0093 ppm n.e.&pe.c.tive.iy kofl a Ay&tem Con-
taining .007 ppm W02, .06 ppm 03, and .02 ppm pentana.
INTRODUCTION
The purpose of this paper is to present a rough model of the mechanism
of ozone production in polluted rural atmosphe'res. By indicating which reac-
tions are of major import, it simplifies the task of developing sophisticated
predictive models for smog production in very low concentration systems. The
model presented is a simplified mathematical description of the production of
ozone by an oxides of nitrogen-alkane system, at equilibrium with its products
under average daytime insolation. Oxides of nitrogen (N0x), alkane, and ozone
(03) are varied in this model about levels measured in rural ozone-producing
atmospheres. Solutions are reached for the concentration of intermediate smog
products and of the net ozone production rate of such a system.
THESIS AND METHOD
The following line of reasoning was used to develop and justify this
simplified steady-state model of the rural ozone-producing atmosphere.
BASIC ASSUMPTIONS
It appears that air masses generating ozone over the rural southeastern
United States may reflect a pollution injection received more than a day earlier,
perhaps over the industrial Midwest areas. The fact that these air masses
are aged argued for modeling on the assumption that they are well mixed with
*U.S. Environmental Protection Agency, Washington, D. C.
439
-------
respect to ozone precursors.
Reactive organic species injected into an air mass a day or more prior
to its arrival over rural areas will be completely removed by ongoing active
photochemistry. The bulk of alkanes so injected will remain unreacted.
The only reactive organic species remaining are those such as alde-
hydes and ketones that are replenished by the reaction of alkanes. In other
words, pollutants injected into an air mass passing over densely populated
areas undergo olefin photochemistry to leave alkanes and partially oxidized
organics. If this reactive-depleted air mass then passes over areas of low
emission density, it undergoes alkane photochemistry. During this phase,
partially oxidized organic species promote the alkane photochemistry, which
in turn maintains the concentration of partially oxidized species. This
argument is the basis of an assumption that the rural ozone-producing atmos-
phere is characterized by a steady-state concentration of reactive species
maintained and defined by a concentration of alkanes. The alkane species
can be shown to be removed slowly enough to justify assuming its concentra-
tion to be invariant.
ASSUMED CONCENTRATIONS
We assume levels of anthropogenic pollutants in the range of those
observed in rural ozone-producing air. These are:
• Ozone = .06 ppm (US EPA 1975)
• Nitrogen dioxide = .07 ppm (RTI 1974)
t Nitric oxide = .0019 based on assumption of photostationary concen-
tration of 03 and NO at an average daily insolation (Jeffries et
al., 1976)
• Nonmethane organic FID (flame ionization detection) response (which
includes hydrocarbons and several other organic species) has been
measured in these smogs at .2 ppm C (RTI 1974). We conservatively
set nonmethane hydrocarbon (NMHC) equal to .1 ppm C, or 1/2 of FID
response.
• The concentration of other species - carbonyls, radicals - is poorly
known. These concentrations are solved within the model.
For ease of analysis, in this model all hydrocarbon is assumed to be
pentane, and all reactive intermediates are assumed to be those produced in
pentane photo-oxidation.
KINETIC MODEL
Also, to simplify calculation, the qualitative lumped kinetic mechanism
of Hecht et al. (1974) is used to set pertinent reactions and reaction rates.
In this mechanism compounds within the classes alkane, ketone, aldehyde, etc.
are each treated as having equivalent reaction rates and products. Further-
440
-------
more, where several reactions follow an initiating reaction with high effi-
ciency, these several are lumped together and treated as a single reaction
of rate equal to initial reaction.
When the rate constants from Hecht et al. (1974) are used, the system
is not highly ozone-productive. In particular, using the given concentra-
tions of hydrocarbon, ozone, and NO , radical chains are terminated by per-
oxyacetyl nitrate (PAN) formation. The critical parameters creating this
effect are the relative rates of reaction of peroxyacyl radical with NO vs.
with N02. If instead of Hecht et al.'s (1974) evaluation of these contents,
we utilize those of Niki et al. (1972), radical chains are lengthened con-
siderably. Those rate constants applicable to peroxyacyl radical suggested
by Niki et al. (1972) are utilized in this paper. To this author, this as-
sumption is not unwarranted. The reaction rates suggested by Niki et al.
(1972) preclude any significant PAN formation in irradiated hydrocarbon-NOx
systems prior to the point that N02»NO. In contrast, rates suggested by
Hecht et al. (1974) imply significant PAN formation even when N02 = NO.
Initial stages in NO-alkane smog chamber runs present a system in which NO,
N02, and presumably peroxyacyl radical are present. However, these systems
do not generate significant PAN until late in runs when NO is suppressed by
net 03 production (Altshuller, et al., 1969; Bufalini, et al., 1970).
The reactions, reaction rates, and overall reaction mechanism are listed
in Tables 1, 2, and 3. The model attempts to maintain simplicity. It is
noted that only a few reactions are of primary importance in the description
of OH-H02 cycle mediated, alkane photo-oxidation. A number of reactions of
secondary import are excluded in this analysis. Their exclusion is justified
as they are relatively inefficient mechanisms for radical removal, or pro-
duction, or recycling in the rural polluted atmosphere. We define "inefficient1
competing reactions as those which react at rates less than, and generally
much less than, 15% of the reactions modeled. Inefficient reactions include,
for example, the reaction of hydroxyl radical (OH) with carbon monoxide (CO)
and methane (CH^), a variety of radical combination reactions, and production
of OH by nitrous acid (HN02), nitric acid (HN03), or 03 photolysis, or by
reaction of 03P (triplet atomic oxygen) with hydrocarbons.
MATHEMATICAL DESCRIPTION OF MODEL
The steady-state model is amenable to a mathematical description.
Production rates of OH,H02 , ketone, and aldehyde are set equal to their de-
struction according to the reactions, reaction constants, and reaction
chains of Tables 1, 2, and 3. A tabulation of this mathematical description
is seen in Table 4. It is noted that a "C" factor is included to allow for
variation of relative reaction rates of peroxyacyl radical with NO and N02.
"C" is the fractional percentage of peroxyacyl radicals converted to PAN.
Aldehyde photolysis or reaction with OH is assumed to be only 1/3 effective
for destruction of aldehyde. Two-thirds of the time aldehyde reactions will
lead to production of the one carbon less aldehyde analogue which is "seen"
in this model as no change at all.
In fact, we have assumed the aldehyde to be 1/3 propanal, 1/3 ethanal,
and 1/3 methanal. This assumption is reasonably close to the proportion of
441
-------
.02-
•c
.01 -1
.001 -
•^ Takeup NOX (XIO)
A
/ \
\Production 0-»
\ 3
»
N
*
X
%
\
X
*x
NO=.OOI9ppm
03=.06 ppm
Pentane=.002ppm
kj =.37/min.
C = fraction of peroxyacyl
radicals reacting with
N02
.1
Figure 1. Effect of assumption of several rates of peroxyacyl
reaction with N02 versus with NO.
aldehyde species that might be expected to be generated from pentane under-
going photo-oxidation. In any case, the system is not very sensitive to
perturbation of this assumption.
BOUNDARY CONDITIONS
According to the above discussion, alkane hydrocarbon is consumed slowly
enough to be considered a pseudo-conservative species. Any solution of the
system of equations defined in this report, for which hydrocarbon take-up
is greater than 1/2 of the assumed hydrocarbon concentration, violates the
model's assumptions.
NO is a different case. It is consumed effectively during transport
442
-------
TABLE I. REACTIONS IN A RURAL ATMOSPHERE
(Groups of reactions are headed by the rate determining reactions. We
later model on the reasonable assumption that the net reaction following a
rate determining reaction occurs at the rate set by the initial reaction.)
1.
2.
3.
4 1
4 i i
4 i 1 1
4iv.
4v.
N02 UV^ NO + 0
0 + 02 ^ 03
03 + NO > N02 + 02
RCHO UV> R- + CHO
R- + 02 > ROO-
ROO- + NO . RO- + N02
RO- + 02 H02 + R'CHO
•CHO + 02 . CO + H02
*NET 4 RCHO + 302+NO
**5i. RCHO + OH
R'CHO + CO + N02 + 2H02
RC - 0
RC
0
0
+ NO
5iii. RC^,
5iv. RC^ + 02
5v. ROO- + NO
5vi. RO- + 02
NET 5 RCHO + OH + 202 + 2NO
6. H02 + NO
7. H02 + H02
8. OH + N02
9i. RCH2R + OH + 02
}'+ NO
RCQJ. + N02
ROO- + C02
tRO- + N02
R'CHO + H02
,R'CHO + 2N02
N02 + OH
H202 + 02
C02 + H02
(continued)
443
-------
TABLE 1. (continued)
0
'2
H 1V
NET 9 RCH2R + OH + 202 + NO
lOi. RiC*^R2
lOii. RiC^° + 02
lOiii. RTC^ + NO
lOiv. F
10v. F.
lOvi. ROO- + NO
lOvii. RO- + 02
NET 10 RiCtiL + 502 + 3NO
UV
H02
N02
i- R2'
HO?
and R2- + 02
R!- + C02
ROO-
RO- + N02
,R'CHO f H02
Rl CHO + R'2 CHO + 2H02
3N02
Hi. R1'CH2C:50R2 + OH
llii. R
11 iii. R
11 iv. R
***NET 11 R
.iL«nU Ko • Uo *v K i U n L« K o
11C°°'HC °R2 + NO + 02 >Rict^ + R2ct§0. + N02
:2C:"'g0.+ NO + 02 >R2'CHO + H02 + N02
:1CH2C"""°R2 + 302 + 2NO + OH vRi'CHO + R2 ' CHO + H02 + C02 + 2N02
*R' = alkyl radical of one less carbon than R.
**Note that the effect of reaction 5iib Rc5n + NOp v RC ?nN02 would be:
UO* # 00 /-
NET 5b RCHO + OH + 02 + N02 ^ PAN
(reaction 10 and 11 are affected analogously).
***Reaction 11 is poorly characterized (NAQCAC 1976).
so the main source of N0x in rural smog must be jn-situ emissions, largely
from mobile sources.
It need not be contradictory for the model to allow for a significant
continual replenishment of N0x and insignificant replenishment of organics
from local automotive emissions. This is because the ratio of NO, to organics
444
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TABLE 2. RATE CONSTANTS OF REACTIONS IN TABLE 1 IN PPM-"1 MIN'1 EXCEPT
AS NOTED
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
N00
L.
0 + 00
00 + NO
RCHO
RCHO + OH
H00 + NO
L.
H00 + H00
L. C.
OH + N00
L.
RCH2R + OH +
RC*2 UV
RCH2C~° + OH
v NO + 0
— > °3
} N00 + 00
re. L.
> R' + *CHO
_» «c°
_^ N09 + OH
— * H2°2
n Rr-°°-
U0 x KLS.R
c. ~ " f ^l\
. Rc'Hc:2
t \\
kl =
k3 •
k4 =
k5 =
k6 '
k7 '
k8 '
kio =
kll '
.37/min
2 x lO'4
20.8
2.5 y. 10-3/min
2.3 ^ 104
7 x 102
5.3 x 103
1.5 x 104
3.8 x 103
8.2 x 10"4/min
3.8 x 103
TABLE 3. REACTION PATHWAYS OCCURRING IN THE RURAL POLLUTED ATMOSPHERE
PATHWAYS LABELED BY REACTION GROUPS DISCUSSED IN TABLE 1
RCHO and
0
RC R
^--.^ 4,5,9,10,11
4,10 X
00-)
RCHR
alkane
N0
RCH200-
NO
N02
4,5,9,10,11
'NO
445
-------
TABLE 4. SIMULTANEOUS STEADY STATE EQUATIONS DESCRIBING RURAL POLLUTED AIR
1. Production ketone = destruction ketone
(OH) (HC) 3.8 x 103 = [8.2 x 10^ + (OH) (3.8 x 103)] Ke
2. Production aldehyde = destruction aldehyde
Ke (2-C) 8.2 x TO'4 + (2-C) (Ke) (OH) 3.8 x TO3 =
[(.33 + C) (OH) 2.3 x 10^ + (.33) 2.5 x 1Q-3] Al
3. Production OH = destruction OH
(H02) (NO) 700 =
(OH) (He) 5 x 103 + (OH) (Al) 2.3 x 10^ + (OH) (Ke) 3.8 x 1Q3 +
(OH) (N02) 1.5 x 104
4. Production H02 = destruction H02
(2-c) (Ke) (16.4 x 1(H) + 2(A1) 2.5 x 10-3 + (OH) (He) 3.8 x 103
+ (OH) (Ke) (1-c) 3.8 x 103 + (OH) (Al) (1-c) 2.3 x 10^ -
2 (H02)2 5.3 x 103 + (H02) (NO) (700)
where: He = hydrocarbon
Al = aldehyde
Ke = ketone
c = fraction of peroxyacyl radicals reacting with NO?
mass emissions from (post 1969) automobiles is less than one (1), while
optimum ozone production (particularly in alkane systems) is achieved at NO
to hydrocarbon mass concentrations of 1:5 or greater. However, a boundary
condition for NO replenishment is set by this argument.
Replenishment of N0x and hydrocarbon is from the same automotive source.
Given that the organic content of rural smog is a phenomenon of transport,
then in-situ precursor replenishment should not be the major contribution
(perhaps less than 20%} to organic concentrations. Therefore, the maximum
uptake and replenishment of N0x per day as mass concentration allowable under
these boundary conditions is equal to 20% x mass of concentration of organics
in rural smog x ratio of emissions of NO to organics. This term is equal to
.02 ppm N0x replenishment per day allowable maximum. Solutions of the equa-
tions proposed in this report for several concentrations of ozone, hydrocarbon,
and NO are assayed against the above boundary conditions for hydrocarbon and
NO takeup.
446
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RESULTS
The effect of mathematically assuming a variety of rates of reaction of
peroxyacyl radical with N02 and NO on ozone production is seen in Figure 1.
03 = .06 ppm, N02 = .007 ppm, and hydrocarbon = .02 ppm pentane. C = .05
corresponds closely to the ratio of reactions used by Niki et al. (1971);
C = .3 corresponds to that used by Hecht et al. (1974); C = .8 corresponds
to that used by Dimerjian (1974).
The solution for the concentration of ketone, aldehyde, H02, OH, and
net 03 production per hour at these concentrations, at C = .1, are respec-
tively .936 x 10-2, .101 x 10'1, .684 x 10~4, .198 x lO'6, and .126 x 10'1
ppm. The effect of variation of hydrocarbon and N02, and of ozone, on ozone
production are shown in Figures 2 and 3.
.010
.001
Dotted line indicates violation of I\IOX takeup assumption
Pentane = .01 ppm
Ratio of constants of peroxyacyl
reaction with NC>2 versus with NO is equal to 1:33.
ozone
.06 ppm
,37/mm
Pentane = .005 ppm
.01
.02
.03
(ppm)
Figure 2. Effect of variation of initial concentrations of pentane and NO
of ozone production and NO takeup.
447
-------
E
CL
Q.
.02
.01
NOX Takeup (x10)
Boundary Condition For
NOX Takeup
NO?
h"
Pentane
.007ppm
.37/min
.02 ppm
63 Production
Ratio of rate constants of
peroxyacyl radical reaction with
N02 versus with NO is equal to 1:33.
0.1
0.2
03 in ppm
Figure 3. Effect of level of ozone on ozone production and NO takeup.
DISCUSSION OF RESULTS
Variation of the ratio of reaction of peroxyacyl radical with NO and
N02 (Figure 1) is shown to strongly affect potential ozone formation in an
alkane-NO system. The effect of variation of NO and hydrocarbon is expected.
Their ratio, as well as absolute concentrations, strongly control net pro-
duction of ozone. At measured levels of precursors, ozone production in rural
smog systems is both N0x and hydrocarbon concentration dependent. N0x takeup
as a percentage of NO concentration is significant so the system can only
maintain ozone production over several hours by continued replenishment of
NO . The model presented here is realistic only for systems containing ozone,
hydrocarbon, and nitrogen oxides at close to measured levels. At conditions
tending to create faster generation of ozone, the N0x is taken up very quickly.
Maintenance of levels of NO and organics in such systems would imply local
sources of pollution contributing more of these ozone precursors than are
contributed by long range transport. Such a condition violates several of
the explicit assumptions of the model. In particular, local pollution sources
of such magnitude would likely emit sufficient quantities of olefin to suppress
alkane photo-oxidation.
CONCLUSIONS
The modeled production of 03 from an alkane-NO system is shown to be
highly dependent on the relative rates of reaction of peroxyacyl radical with
N02 versus with NO. If those rates are near the extreme of rates reported in
the literature, such systems can account for the amounts of ozone presently
found in the rural east coast of the United States.
The mathematical model here presented also suggests the presence in
rural polluted air of significant quantities (roughly .02 ppm) of carbonyl
compounds. If such concentrations were observed, they would tend to support
the theory that rural ozone in the U.S. is generally a phenomenon created by
widespread, human generated, hydrocarbon and nitrogen oxide pollution.
448
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TABLE 5. ALGORITHMS FOR SOLUTION OF NET PRODUCTION OF OZONE PER
HOUR, AND THE NET TAKEUP OF HYDROCARBON AND NITROGEN OXIDE PER HOUR
Net Os production per hour* -
60 [(H02) (NO) (700) + (Ke) (2-c) 8.2 x 10^ + 3.8 x 103 (Ke) (OH) (2-c) +
2 AL 2.5 x 10'3 + (Al) (OH) (1-c) 2.3 x 104]
Takeup of hydrocarbon per hour =
60 [ 3.8 x 103 (OH) (He) ]
Takeup of nitrogen dioxide per hour** =
60 [ OH (1.5 x 10^) (N02) + (C) Ke 8.2 x TO'4 + (C) (Ke) (OH) 3.8 x TO3
+ (C) (Al) (OH) 2.3 x
* 03 production rate = rate of oxidation of NO by H02 + rate of oxidation
of NO by ROD- and related species
takeup rate = rate of production of HN03 + rate of production of
PAN
REFERENCES
Altshuller, A. P., S.L. Kopczynsk, D. Wilson, W. Lonneman, and F.D.
Sutterfield. Photochemical Reactivities of N-Butane and other
Paraffinic Hydrocarbon, 1969. Journal Air Pollution Control
Association 19:787.
Bufalini, J. J., B. W. Gay, and S. L. Kopczynsk. 1970. Oxidation of
N-Butane by Photolysis of NO. Environmental Science and
Technology. 4:333-338.
Dimerjian, K. L., J. A. Kerr, and J. G. Calvert. 1974. The Mechanism
of Photochemical Smog Formation. Advances in Environmental Science
and Technology. 4:1-262.
Hecht, T. A., J. H. Seinfeld, and M. C. Dodge. 1974. Further Develop-
ment of Generalized Kinetic Mechanism for Photochemical Smog.
Environmental Science and Technology. 8:327-338.
Jeffries, H. E. , J. E. Sickles II, L. A. Ripperton. 1976. Ozone Transport
Phenomena Observed and Simulated. Paper 14.3 - Annual APCA Convention.
National Air Quality Criteria Advisory Committee. 1976. Final Report.
449
-------
Niki, H., E. E. Daby, and B. Weinstock. 1972. Mechanisms of Smog Reactions.
Advances in Chemistry Series - Ozone and Smog Reactions. New York.
Research Triangle Institute. 1974. Investigation of Ozone Precursor
Concentrations at Non-Urban Locations in the Eastern United States.
U. S. Enviornmental Protection Agency. 1975. Control of Photochemical
Oxidants - Technical Basis and Implications of Recent Findings. 35 p.
450
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9-4
NET OZONE FORMATION IN RURAL ATMOSPHERES
T.Y. Chang and B. Weinstock*
ABSTRACT
A photochemical model was used to explain ozone. (03) formation with
aikane/oxides o& nitrogen (NO*) mix.tun.es -in smog dkambe.fi experiments design-
ed to simulate rural conditions. In oftde.fi to ^it the smog ch.ambe.fi data, tke
model had to be. modified to -include, an hydrozyl (HO) radical source and
he.te.noQe.ne.oa.& wail reactions. The. unmodified model was applied to predict
the. e^ect on rural G>3 ie.ve.it> o£ less reactive. hydrocarbons (HC-6), which afie
le^t ove.n {^rom ulban emissions and dikpe.ue.d into fiuAal OAZOA . ffiom thii,
analy&iti, it is concluded that the. ie.^tove.fi utiban HCi make. Little, contribu-
tion e.ithe.fi to the. ae.ne.tiation o& e.le.vate.d fiuAal ozone, le.ve.ls on. to the. in-
cfie.at,e. of, elevated levels already pfiesent. It ik suggested instead that the
majcfi causes oft elevated tiufial 03 levels afie the tfianspofvt o^ high 03 con-
cent>iations generated in ufiban afieas and additional. 03 produced by Reactions
015 {^fiesh HC and WOX emissions ^fiom local fuifial souJice?,, both natural and man-
made. Data ^fiom the 1974 Midwest study afie {}0und to be in agreement with the
lattefi suggestion. Eased on these findings, a method if> proposed to cofUiect
hydfiocafibon fieactivity scales ^on. tke e^ect ofi dilution that occurs in the
atmosphere. The analysis in this study is in disagreement with the justifi-
cation presented faon the new Environmental Protection Agency Policy State-
ment that severe control ofi all hydrocarbons, without fiegard to reactivity,
will be necessary to reduce elevated rural C>3 levels.
INTRODUCTION
The observation of elevated ozone (03) concentrations in rural areas has
become a matter of much interest in recent years. It has been suggested that
less reactive hydrocarbon (HC) emissions from urban areas may contribute im-
portantly to this phenomenon. These HCs, which are leftover after a single
day of solar irradiation, are expected to be transported to rural areas,
where they can react further on succeeding days and thereby contribute sig-
nificantly, as some suggest, to the elevation of rural ozone concentrations.
Their effect would be most pronounced under meteorological conditions, such
as a high pressure system, when pollutants are not ventilated rapidly to the
global atmosphere and are circulated over wide areas for many days. New smog
chamber experiments have been made to simulate this behavior. In these ex-
*Ford Motor Company, Dearborn, Michigan.
451
-------
periments, very long irradiation times and much higher initial hydrocarbon/
oxides of nitrogen (HC/NOX) ratios were used compared with those used in
earlier experiments to simulate urban photochemistry. It was found that many
HCs, previously found to be unreactive in urban simulations, produced signifi-
cant concentration of ozone under the new conditions (1). These results
appeared to support the above concept. Citing this as a basis, the Environ-
mental Protection Agency (EPA) issued a Policy Statement (2) in which it was
stated that HC reactivity no longer was essential to HC control strategy and
that all HC emissions would be regulated in the future, without regard to
their photochemical reactivity. It was advised that the previous strategy of
the replacement of more reactive HCs by less reactive ones as a means of oxi-
dant abatement, such as in Los Angeles Air Pollution Control District (LAAPCD)
Rule 66(3), should be regarded now only as an interim measure and that future
planning should consider complete HC control regardless of reactivity.
The objectives of this paper are to examine the validity of this new
concept and of the use of smog chamber data as a simple representation of
atmospheric behavior. In a recent paper (4), we have considered these
questions with respect to methane and found that methane, on balance, will
diminish elevated rural ozone levels contrary to the conclusions of a recent
publication (5). Methane is so unreactive compared with other HCs, however,
that generalizations cannot be drawn from its behavior. The methodology
developed in that study (4) was modified for this paper to include higher
alkanes and the behavior of the modified systems is taken as a prototype for
the reactions of less reactive HCs. First, the modified photochemical model
is used to explain the new smog chamber data. The model is applied next to
evaluate the contribution of less reactive h'Cs to elevated rural ozone levels.
The relevance of these findings to abatement strategy for elevated rural ozone
levels is discussed next. Finally, some suggestions are made for a revised
HC reactivity scale.
PHOTOCHEMICAL MODEL
The reference photochemical model used in this study is a modified ver-
sion of a model used previously in a study of the methane-carbon monoxide-
nitrogen oxides (CH^-CO-NOx) system (4). A list of reactions and rate co-
efficients is given in Appendix A. Reactions of alkanes with oxygen (0)
and hydroxyl radicals (HO) and reactions involving radicals produced from
alkane-0 and alkane-HO reactions are added to the previous model. All
types of alkyl groups are lumped together and represented by R. A parameter,
3, is introduced
RO + 02 = BRCHO + (l-B)HCHO + H0? R46)
to represent the fraction of total aldehydes produced that are not formalde-
hyde. The values of 3 are assumed to be 0, 1/2, 2/3, and 3/4 for methane,
ethane, propane, and butane, respectively. The reaction,
H02 + N02 = HONO + 0?, R30)
452
-------
also is added to the present model and a larger value for removal rate for
nitric acid (HN03) [R57] is used. Rain-out removal for hydrogen peroxide
(H202) and alkyl hydroperoxide (HOOR) is deleted. The photodissociation
coefficients, R2 through RIO, are assumed to be proportional to the photo-
dissociation coefficient for nitrogen dioxide (N02), kj.
The model used here incorporates the main features of the models of Niki
et al. (6), Hecht et al. (7), Demerjian et al. (8), and Pitts et al. (9).
Major uncertainties in photochemical models have been discussed by Hecht et
al. (10), Durbin et al. (11), and Pitts et al. (9). The set of photochemical
rate equations is strongly nonlinear. Therefore, absolute predictions of the
photochemical model are somewhat uncertain. Relative trends of the photo-
chemical behavior, however, are believed to be predicted by the model with
good reliability.
ANALYSIS OF NEW SMOG CHAMBER DATA
As mentioned before, the new EPA smog chamber experiments (1) were de-
signed to simulate rural atmospheric conditions. High initial HC/NOX ratios,
8:1, were used compared with ratios of 2-3:1 used to simulate urban condi-
tions in earlier experiments. Longer irradiation times also were used to
simulate carry-over of urban emissions to rural areas. Data for the propane/
NOX system, run 194, (1) are given in Table 1. In a simulation with the un-
modified photochemical model, less than 2 pphm 03 was predicted after 430
min, much less than the observed maximum value of 11 pphm. This disagreement
was not unexpected. Propane, like alkanes in general, should produce HO radi-
cals very slowly in these experiments, with the consequence that there should
be a very long induction period before the 03 concentration builds up. The
much more rapid production of 03 seen in the actual experiment is a conse-
quence of a substantial HO background common to all laboratory experiments
(12).
An attempt to fit the experimental behavior was made in simulation 1 by
the addition of a constant HO source of 3 x 10'4 ppm min"1 to the model. This
approach also has been used by Pitts et al. (9). In addition, an 03 removal
term, k55 = 1 x 10~3 min'1, was introduced to simulate the 03 removal at the
walls that is characteristic of smog chambers. A reasonable prediction of the
experimentally observed N02 maximum and of the time to reach this maximum is
obtained. An 03 maximum still is not observed, however, and the 430 min. 03
concentration predicted is much higher now than 11 pphm.
A different approach to produce an HO background was used in simulation
2. The rate constant, k20, for the reaction,
NO + N09 + H20 = 2 HONO R20)
453
-------
TABLE 1. EPA DATA AND SIMULATION RESULTS FOR PROPANE - N0xa
Maximum NO 2
EPA Run
No. 194
Sim. lc
Sim. 2d
Sim. 3e
Sim. 4f
Time
(min)
55
80
105
65
70
Cone.
(ppb)
130
147
142
132
132
Maximum 03
Time Cone. HC
(min) (pphm) (ppm)
225 11.0 3.18
3.24
3.35
305 14.5 3.40
250 12.6 3.38
At 430
N02
(ppb)
95 b
80
110
11
16
min
NO
(PPb)
<1.0
2.9
5.4
1.0
1.8
03
(pphm)
7.6
33
26
14
11
a k^ = 0.33 min'1, kdiiution = 2.2 x 10~4 min-1, k34 = 22 ppnH min-1,
k_5 = 3200 ppm"1 min'1, (H20) =1 x 104 ppm; initial concentrations:
(HC) = 4.0 ppm, (NO) = 180 ppb, (N02) = 20 ppb, (Os) = 0 pphm.
b (NOX) - (NO).
c k55 = 1 x 10~3 min'1, constant HO source = 3 x 10~4 ppm/min.
d k9n = 1.9 x 10"5 ppm'2 min'1, k91 = 1.8 ppm'1 min'1, kr-r = 1 x 10'3 min'1.
c\J c.\ DO
e add k-,g = 1.5 x 10~ ppm" min" ., to d
-3 -1
f same as e except, k^c = 3 x 10 min .
was arbitrarily increased from 1.9 x 10~n to 1.9 x 10~5 ppm'2 min'1. The
rate of the back reaction, k21, was increased from 1.8 x 10~5 to 1.8 ppm'1
min'1. By this adjustment, the concentration of HONO is built up quickly and
this provides rapid HO source because nitrous acid (HONO) produces HO by
photodissociation. This approach has been used independently by Sickles(13).
Although the rate constant for the homogeneous formation of HONO by R20 is
known to be slow (14,15), the heterogeneous rate on the walls is probably
very much faster in smog chambers. The predicted 03 is in better agreement
than in simulation 1, but is still too high; an 03 maximum still is not ob-
served, and the time for the N02 maximum changes in the wrong direction.
For simulation 3, the rate constant, kI9, for the homogeneous reaction,
N205 + H20 = 2HN03, R19)
was increased from 1.5 x 10'5 used in simulation 2 to 1.5 x 10~3 ppm'1
min'1 to represent the heterogeneous reaction that is likely to be of more
454
-------
importance in smog chambers. With this modification, an 03 maximum now is
predicted and the agreement with the experimental observations is notice-
ably improved. In simulation 4, the effect of increasing the 03 decay rate,
k55, from 1 x 10~3 to 3 x 10~3 min'1 was calculated and this improved the
agreement with the experimental data further. Similar situations have been
made for data obtained with the ethane/NOx system. The same qualitative
behavior for the model adjustments were observed and the quantitative agree-
ment with the experimental data was again satisfactory.
Model calculations also were compared with the 03 maxima observed in
similar experiments that have been reported by Heuss (16). Using the same
parameters as in simulation 4, the model predicted 03 maxima of 7.8, 14, and
15 pphm compared with the experimental values of 8, 13, and 20 pphm for
ethane, propane, and butane, respectively.
These simulations give insight into the importance of the HO background
and of heterogeneous reactions to 03 formation in smog chamber experiments.
The agreement of the model predictions with the experimental data alterna-
tively gives a measure of confidence of the reliability of the model for
predictions of atmospheric behavior for alkane/NOx mixtures.
SIMULATED RURAL ATMOSPHERIC PHOTOCHEMISTRY
Calculations with the unmodified photochemical model, i.e., without the
changes made to take account of the idiosyncrasies of smog chambers, have
been made to simulate rural atmospheric photochemistry. Steady state calcu-
lations were made at first to investigate the variation of the steady state
03 with a variety of fixed HC and NOX concentrations. For each fixed HC
concentration the predicted 03 concentration goes through a maximum as the
fixed NOX concentration is varied. As the fixed HC concentration is
increased, the NOX concentration corresponding to the 03 maximum also in-
creases, as does the 03 maximum. From these steady-state calculations, it
can be concluded that atmospheric 03 concentrations are affected not only by
the absolute concentration of both HC and NOX, but also by the HC/NOX ratio.
Time-dependent photochemical model calculations were made next. In the
first set of calculations, the concentrations of HC and NOX were kept con-
stant, and the daily buildup of 03 was predicted. These calculations were
made to determine the sensitivity and time dependence of 03 formation to the
NOX concentration and characteristic time of 03 buildup. Some of the results
are given in Table 2. The initial 03 concentration was taken to be 4 pphm;
that of propane to be 0.1 ppm (0.3 ppmC). The NOX concentration was taken
as a variable since reliable rural NOX data are not available because of in-
terferences in the measuring techniques that give rise to spuriously high N02
values. The photodissociation coefficient for N02 in min"1 used was:
ki = 0.66 e-3-8/cosX, cosX>0
(1)
k: = 0, cosX<0.
455
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TABLE 2. DAILY MAXIMUM 03 IN PPHM: (HC) AND (NOX) KEPT CONSTANT*
Day (NOX)=0.1 ppb 1 ppb 10 ppb
1 4.0 4.4 10
3 3.3 5.6 15
5 2.9 7.0 18
7 2.7 8.2 19
10 2.7 9.5 21
13 2.7 10.2 22
(propane) =0.1 ppm, (CH4) = 2 ppm, (CO) =0.2 ppm, (H20) = 2 x 1C)4 ppm
and (NOX) =0.1, 1, 10 are kept constant.
Initial (63) = 4 pphm
a. The NO was initially pure N09.
X c
The angle of inclination of the sun, X, is approximated by,
X = Tr(H/12 -1), (2)
where H is the hour of day. The values of kj given by Equation (1) give a
good approximation of measured values of Iq by Sickles (13).
The amount of 03 formed is seen to be sensitive to the NOX concentration.
When (NOX) = 0.1 ppb, the daily maximum 03 decays from 4 to 2.7 pphm. When
(NOX) = 1 ppb, the time for the 03 concentration to double from 4 to 8 pphm
is about a week, and the 03 concentration approaches an asymptotic value of
about 10 pphm. When (NOX) = 10 ppb, the doubling time of the initial 03 con-
centration is about one day and the asymptotic maximum 03 is a little above
22 pphm. These calculations show that reliable measurements of N02 and a more
quantitative understanding of NOX chemistry are critical for a better under-
standing of rural 03.
The next set of time-dependent calculations were made to simulate the
effect of less reactive, "leftover" hydrocarbons in an urban plume on several
ambient rural 03 concentrations, ranging from 0-20 pphm. The reactants were
given various initial concentrations that were allowed to decay continuously
during the two days. Further details of the calculations and the results are
given in Table 3. Propane, which can be considered as a prototype for less
reactive, "leftover" hydrocarbons, was set at an initial concentration of 0.1
456
-------
ppm (0.3 ppmC). This concentration is much higher than the concentrations
observed for the less reactive hydrocarbons in the 1974 Midwest study (17).
The NOX was taken to be pure N02 initially at a concentration of 10 ppb.
This concentration is at the upper limit of the N02 concentrations observed
in the 1974 Midwest study (17), which generally ranged from 5-10 ppb. As
mentioned before, the N02 measurements are probably too high, so that 10 ppb
N02 should be significantly higher than rural N02 levels. The reason for the
choice of these hydrocarbon and N02 concentrations was to represent extreme
rural concentrations that would favor formation of elevated ozone levels.
TABLE 3. DAILY MAXIMUM 03: (HC) AND (NOX) ALLOWED TO DECAY
Initial Initial 03 Maximum 03 (pphm)
Propane (pphm) 1st day 2nd day
0.1 0 4.1 4.3
0.1 4 7.4 Decreasing
0.1 10 11.4 11.2
0.1 15 15.3 Decreasing
0.1 20 Decreasing Decreasing
Initial concentrations at 0600: (CH4) = 2 ppm, (CO) = 0.2 ppm,
(N02) = 10 ppb, (H20) = 2 x 104 ppm.
These calculations snow a number of interesting characteristics of rural
ozone behavior. The 03 maxima on the second day are, except for one case,
lower than those on the first day. This is a consequence of the rapid decay
of NOX during the first day. In general, it can be concluded that the rela-
tive residence time of NOX is much shorter than that of propane under these
simulated rural conditions. When the initial 03 concentrations are 0 and 4
pphm, they build up to 4.1 and 7.4 pphm, respectively, in the first day.
When the initial 03 concentrations are 10 and 15 pphm, relatively little
change in concentration occurs in the first day. When the initial 03 concen-
tration is 20 pphm, this concentration decreases continuously during the
first day. From these calculations, it appears highly unlikely that less
reactive, "leftover" hydrocarbons would generate elevated rural 03 levels.
At the concentrations that these HCs and NOX are likely to be present in
rural atmospheres, these HCs could contribute to the lowering of already
existing elevated rural 03 levels. In the following discussion, a more
probable explanation of the elevated rural 03 levels is offered.
457
-------
DISCUSSION
It is reasonable to assume that the high ozone concentrations generated
in urban areas are transported into rural areas, particularly under meteoro-
logical conditions that retard their dispersion into the global atmosphere.
This will result in an elevation of the rural ozone levels above the natural
background ozone concentration. The longer that the adverse meteorological
conditions persist, the greater the effect will be, and the greater the size
of the area affected. The degree to which the elevated rural ozone concen-
trations are further increased, sustained, or diminished by further photo-
chemistry in the rural areas on succeeding days depends on the concentrations
of both HCs and NCL that are present there. The preceding analysis strongly
suggests that the less reactive, "leftover" HCs of the urban plume will not
contribute importantly to sustaining or increasing the elevated rural ozone
levels. (Unreacted NOX from urban areas, where it is present in excess, will
also be transported to rural areas and contribute to ozone formation there,
but this aspect of the problem will not be discussed here because of the lack
of reliable rural N02 data.) A more likely explanation for the persistence
and increase of elevated rural 03 levels is the reactions of new HC (and NOX)
emissions in the rural areas from local sources, both natural and man-made.
The relative amounts of natural and man-made sources of rural HCs and NOx is
an unresolved question, which will not be discussed further here.
The relative importance of "leftover" HCs compared to fresh HC emissions
in rural photochemistry can be deduced from detailed measurements of rural HC
compositions. If the "leftover" HCs from urban areas are present in signifi-
cant concentrations, this should be evidenced by an accumulation of less re-
active species compared to more reactive ones in the rural atmosphere. This
is because the more reactive species are removed much faster than the less re-
active ones. This effect is similar to a separation of more volatile species
from less volatile ones by fractional distillation. Detailed HC compositions
have been measured in the 1974 Midwest study (18). There is little evidence
of such fractionation in all of these data, both in samples taken at the
ground and aloft. Thus it would be plausible to conclude that, for the area
studied and for the conditions that existed during the study, the atmospheric
HCs observed were representative, in the main, of local emission sources.
Some very interesting data were taken on August 1, 1974, in this Midwest
study. Ozone measurements were reported, as, shown in Figure 1 , at a variety
of elevations for 0704-0741, 1320-1414, and 1656-1754 hours (Figure 58, page
122 in reference 17). Concurrent nonmethane HC (NMHC) measurements were made
at the ground and aloft at 0704-0741 and at the ground at 1210-1315. The
early morning profile supports the conclusion of the preceding paragraph.
The NMHC concentrations of 105 and 113 ppbC at the ground and at 2000 ft.,
respectively, represent the sum of the "leftover" NMHC and the new NMHC
emissions, which are trapped by the early morning ground inversion. The
concentration of 58 ppbC at 4000 ft. is the "leftover" NMHC concentration in
the mixing layer, which is being augmented by leakage from the ground inver-
sion layer and diminished by leakage into the inversion layer. The 35 ppbC
458
-------
at 8000 ft. is the "leftover" NMHC in the inversion layer, which is being
augmented by leakage from the mixing layer and diminished by leakage into
the global atmosphere. At 1210-1315 hours, the ground inversion probably
has burned away, and the NMHC concentration at the ground is 89 ppbC, which
is intermediate between the ground and mixing layer values observed in the
early morning.
1754 1414
Hydrocarbon
Sample
(Morning)
5 7.5 10.
Ozone Concentration ( pphm )
Figure 1. Ozone profile, Wilmington, Ohio, August 1, 1974 (17) TNMHC: 2000
ft., 113 ppbC; 4000 ft, 58 ppbC; 8000 ft., 35 ppbC at 0704-0741
hours; ground, 105 ppbC at 0745-9000 hrs; ground, 89 ppbC at
12-1315 hrs.
459
-------
The ozone profiles are most revealing. The concentrations in the ground
inversion layer in the early morning decrease markedly with decreasing alti-
tude because of ground destruction of 03. (The lines drawn in Figure 1 simply
connect individual measurement points.) The concentrations in the mixing
layer are relatively constant with altitude at about 9 pphm. This would be
representative of an initially elevated 03 level as analyzed in Table 3. The
one point measured in the inversion layer is at about 7.5 pphm 03. At noon,
when the ground inversion has burned away, the 03 concentrations in the mix-
ing layer are constant with altitude at about 10 pphm, which is above the
early morning 9 pphm value. The 03 concentrations in the inversion layer are
seen to be constant with altitude and unchanged from the early morning value.
The evening measurements show the same trenc. The concentration in the mix-
ing layer has increased further to about 12 pphm, while that in the inversion
layer is still at 7.5 pphm.
These data thus illustrate the explanation that is offered here for the
elevated rural 03 levels. The increase in the elevated 03 concentration in
the mixing layer is a consequence of reactions of fresh HCs (and NOX) emitted
into the mixing layer. It is likely that the "leftover" HCs there play only
a minor role in augmenting this increase. There is no change in the elevated
03 concentration in the inversion layer, because little fresh HCs are added
there and it has mainly "leftover" HCs to react.
CONCLUSIONS
The preceding analysis and discussion disagrees with the conclusions in
the new EPA Policy Statement (2). The extreme control of all HC emissions
regardless of reactivity that is stated there to be necessary in order to
resolve the rural 03 problem is shown here to have a questionable basis. We
conclude here instead that the present control strategy, based on reducing 03
levels in urban areas, will also be effective in reducing rural 03 levels.
HC reactivity scales relevant to urban 03 will be considered next.
In urban areas, the conversion of NO to N02 plays an important role in
the time-dependent smog chemistry. (In rural areas, by contrast, the NO
emissions are rapidly converted to N02 because of the excess 03 present.) It
has been pointed out that the N0-N02 conversion is driven largely by HO chain
reactions, and a reactivity scale based on HO-hydrocarbon rate constants gives
a representation of this (6). Pitts et al. recently have published a detailed
study of this concept (19). Reactivity scales based on smog cnamber data
(20) are equivalent to this (6).
The N0-N02 conversion is only the first stage of 03 production in urban
areas as has been pointed out before (6). In the later stages of the reac-
tion, the N02 is rapidly consumed and the 03 concentration builds up. An
HO reactivity scale does not give an adequate representation of these later
stages of the reaction. In addition, HO reactivity scales do not take into
account the dilution of the reactants by dispersion. As a consequence, we
believe that HO reactivity scales overpredict the reactivity of less reactive
hydrocarbons compared with more reactive hydrocarbons.
460
-------
To take account of the later stages of the reaction in the reactivity
scale, a factor should be introduced to express the effectiveness of differ-
ent HCs in producing a net increase of radical species present. This would
also improve the reactivity scale for the first stage of the reaction. Our
understanding of the detailed chemical mechanism is not good enough at this
time to make a reliable estimate of this factor. Qualitatively, we know that
olefins are very effective in producing radical species because they often
produce two new ones for each one they consume. Alkanes, on the other hand,
more commonly break even in this respect, producing a single new radical for
each one consumed. The failure to include this net radical production con-
cept in the reactivity scale, then, qualitatively underpredicts the reac-
tivity of more reactive species and overpredicts the reactivity of less re-
active species.
Another factor should be introduced into the reactivity scale to take
atmospheric dilution of smog precursors into account. It is proposed that
this could be approximated by multiplying the HO rate constant for each HC
by a fraction, which would represent the fraction of emissions of that HC
which are consumed in the urban area in a single day. For very reactive HCs,
this fraction would be unity. For very unreactive HCs, this fraction would
be close to zero. This procedure is suggested by the findings in this paper
that leftover HCs from urban areas contribute only marginally to subsequent
03 formation. Such a procedure would, in part, remove the overprediction of
the reactivity of less reactive HCs in the reactivity scales based on HO re-
activity or equivalently based on smog chamber data.
An important corollary to these conclusions is worth mentioning. In
the last few years, catalysts have been used to meet the HC emission standards
for motor vehicles. One concomitant effect of the use of catalysts is to
reduce the photochemical reactivity of the HC emissions (21). Therefore, the
reduced HC emissions of catalyst-equipped vehicles should have a much more
beneficial effect on urban 03 reduction than was expected without taking this
change of reactivity into account.
ACKNOWLEDGMENT
The authors would like to express appreciation to Hiromi Niki for many
helpful discussions.
461
-------
REFERENCES
1. Dimitriades, B. and S. B. Joshi. Application of Reactivity Criteria in
Oxidant-Related Emission Control in U.S.A. In: Proceedings of this Con-
ference.
2. "Policy Statement on Use of the Concept of Photochemical Reactivity of
Organic Compounds in State Implementation Plans for Oxidant Control,"
U. S. EPA, January 29, 1976.
3. Los Angeles Air Pollution Control District, Rule 66.
4. Weinstock, B. and T. Y. Chang. Methane and Nonurban Ozone. Presented at
the 69th Annual Meeting of the Air Pollution Control Association, Portland,
Oregon, June, 1976.
5. Chameides, W. and D. H. Stedman. Ozone Formation from NOX in Clean Air.
Environ. Sci. Technol. 10: 150-153 (1976).
6. Niki, H., E. E. Daby and B. Weinstock. Mechanisms of Smog Reactions.
Advanc. Chem. 113: 16-57, 1972.
7. Hecht, T. A., J. H. Seinfeld and M. C. Dodge. Further Development of Gen-
eralized Kinetic Mechanism for Photochemical Smog. Environ. Sci. Technol.
8: 327-339, 1974.
8. Demerjian, K. L., J. A. Kerr and J. G. Calvert. The Mechanism of Photo-
chemical Smog Formation. Adv. Environ. Sci. Technol. 4: 1-262, 1964.
9. Pitts, Jr., J. N., G. J. Doyle, A. C. Lloyd and A. M. Winer. Chemical
Transformations in Photochemical Smog and their Applications to Air
Pollution Control Strategies. NSF-RANN Grant AEN 73-02904 A02, Second
Annual Report, October 1, 1974 - September 30, 1975. University of
California Statewide Air Pollution Research Center, Riverside, Calif.
10. Hecht T. A., M.-K. Liu and D. C. Whitney. Mathematical Simulation of
Smog Chamber Photochemical Experiments. EPA-650/4-74-040. U. S. En-
vironmental Protection Agency, Washington, D.C. 20460, 1974-
11. Durbin, P. A., T. A. Hecht and G. Z. Whitten. Mathematical Modeling
of Simulated Photochemical Smog. EPA-650/4-75-026, U. S. Environ-
mental Protection Agency, Washington, D. C., 1975.
12. Niki, H. and B. Weinstock. Recent Advances in Smog Chemistry, EPA
Scientific Seminar on Automotive Pollutants, EPA-600/9-75-003, U. S.
Environmental Protection Agency, Washington, D.C., February, 1975.
462
-------
13. Sickles, II., J. E. Ozone-Precursor Relationships of Nitrogen Dioxide,
Isopentane, and Sunlight Under Selected Conditions. Ph.D. Thesis,
University of North Carolina, Chaoel Hill, N.C., 1976.
14. Chan, W. H., R. J. Nordstrom, J. G. Calvert and J. H. Shaw. Kinetic
Study of HONO Formation and Decay Reactions in Gaseous Mixtures of
HONO, NO, N02, H20, and N2> Environ. Sci. Techno!. 10: 674-682, 1976.
15. Kaiser, E. W. and C. H. Wu. (To be published.)
16. Heuss, J. M. Photochemical Reactivity of Mixtures Simulating Present
and Expected Future Concentrations in the Los Angeles Atmosphere. Pre-
sented at the 68th Annual Meeting of Air Pollution Control Association,
#75-16.1, Boston, Mass., June, 1975.
17. Research Triangle Institute. Investigation of Rural Oxidant Levels as
Related to Urban Hydrocarbon Control Strategies. EPA-450/3-75-036,
U. S. Environmental Protection Agency, Research Triangle Park, N.C.,
1975.
18. Detailed HC Analyses referred to in (17); available from W. A. Lonneman,
U. S. EPA.
19. Darnall, Karen R., A. C. Lloyd, A. M. Weiner and J. N. Pitts, Jr. Re-
activity Scale for Atmospheric Hydrocarbons Based on Reaction with Hy-
droxyl Radical. Environ. Sci. Techno!. 10: 692-696, 1976.
20. Proceedings of the Solvent Reactivity Conference. U. S. Environmental
Protection Agency, Research Triangle Park, N.C., EPA-650/3-74-010,
November, 1974.
21. Powers, T. F. The Oxidant Formation Potential of Emissions from Cata-
lyst Equipped Vehicles. In: Proceedings of Specialty Conference on
Ozone-Oxidants-Interactions with the Total Environment. APCA Southwest
Section, March 1976, pp. 189-200.
463
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APPENDIX
List of Reactions and Rate Coefficients
Reactions Rate Coefficient (Kj)*
Rl)
R2)
R3)
R4)
R5)
R6)
R7)
R8)
R9)
RIO)
Rll)
R12)
R13)
R14)
R15)
R16)
R17)
R18)
R19)
R20)
R21)
R22)
R23)
R24)
R25)
R26)
R27)
R28)
(conti
N02 + HV = NO + 0
HONO + HV - HO + NO
HOOH + HV - HO + HO
ROOH + HV = RO + HO
RC03H + HV = R02 + HO
03 + HV = OD + 02
HCHO + HV = H02 + H02 + CO
HCHO + HV - CO
RCHO + HV = R02 + H02 + CO
RN02 + HV - RO + NO
OD + M = 0 + M
OD + H20 = HO + HO
0 + 02 + M = 03 + M
0, + NO = N09 + 09
0 L- L.
0, + N09 = NO, + 09
O L, O L-
NO + N03 = N02 + N02
N09 + NO- = N00C
2 3 25
N2°5 = N02 + N03
N^Oj- + H?0 = NH07 + HNO,
L- 0 C. O O
NO + N02 + H20 = HONO + HONO
HONO + HONO = NO + N02 + H20
NONO + HN03 = N02 + N0? + H^O
N02 + N02 + H20 = HONO + HN03
NO + HO - HONO
N02 + HO = HN03
CO + HO = H02
HN00 + HO = N00 + H00
2 22
HNO, + HO = N00 + H00
3 32
nued)
kl
6.8E-2k]
3.5E-3k]
3.5E-3k]
3.5E-3k1
3.5E-3k]
4.7E-3k]
1.1E-2k1
1.2E-3k]
3.5E-3k]
4.7E+4
3.1E+5
2.1E-5
2.5E+1
4.8E-2
1.5E+4
4.4E+3
1.4E+1
1.5E-6
1.9E-11
1.8E-5
2.2E-2
8.7E-9
1.2E+4
1.5E+4
2.1E+2
3.1E+3
1.9E+2
464
-------
APPENDIX
R29)
R30)
R31)
R32)
R33)
R34)
R35)
R36)
R37)
R38)
R39)
R40)
R41)
R42)
R43)
R44)
R45)
R46)
R47)
R48)
R49)
R50)
R51)
R52)
R53)
R54)
R55)
R56)
R57)
(continued)
Reactions
NO + H02 = N02 + HO
N02 + H02 = HN02 + 02
H02+ HO - H20 + 02
03 + H02 = HO + 02 + 02
03 + HO = H02 + 02
HC2 + 0 = R02 + HO
HC2 + HO - R02 + H£0
CH4 + HO - R02 + H20
HCHO + HO = H02 + CO + H20
RCHO + HO = RC03 + H20
HOOH + HO = H02 + H20
ROOH + HO = R02 + H20
RC03H + HO = RC03 + H20
NO + R02 = N02 + RO
NO + RCO- - NOp + ROp
O L- C-
N02 + RC03 = PAN
PAN = N03 + R02
RO + 02 = 8RCHO + (1-8) HCHO + H02
RO + NO = RN02
RO + N00 = RN00
2 3
H02 + H02 = HOOH + 02
H02 + R02 = ROOH + 02
R02 + R0? = RO + RO + 02
HOp + RCOo = RCO^H + Op
c~ O O C,
ROp + RCO,, = R0p + RO + Op
L. O L. C.
DPH 4- orn — DO 4. on
Kl/U~ T KUU-} •" KU/-J * KUo
O 3 L— L-
°3 =
RN03 =
HN03 =
Rate Coefficient (Kj)*
7.0E+2
3.5E+1
1.5E+5
2.2E+1
8.3E+1
k34
k35
1.1E+1
2.1E+4
2.1E+4
1.2E+3
1.2E3
1.2E+3
7.0E+2
1.5E+3
3.5E+1
3.0E-3
4.4E-3
1.2E+2
1.1 E+2
4.9E+3
4.9E+3
4.9E+2
4.9E+3
4.9E+2
4.9E+2
0
1 .OE-4
5.0E-4
* in ppm-min units
465
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9-5
THE KINETIC OZONE PHOTOCHEMISTRY OF NATURAL
AND PERTURBED NONURBAN TROPOSPHERES
T. E. Graedel and D. L. Allara*
ABSTRACT
The, diu/inal kineJic. photoc.he.m-U>tny o& natural and peAtuJibud nonurban
&wpo?>pheAeA hat, been fie.pfiej>e.nte.d by a. computation u&ing ewiAAionA and fie.dc.-
tionb o^ teApe,neA, ammonia, hydAoge.n Aulfi-ide,, and otheA on.ga.nic. and inorganic.
Ape.ci.eA. Ike. computational HQJ>uJtM> faon, the. unperturbed caAe. a'te. Ai.multane.ouAly
coni>iAte.nt with nonusiban obAeJivationA o^ monoteA.pe.neA, meJ.ha.ne., ozone., oy^ide^
o^ nitiogun, hydtoge,n ^at^-idn, ammonia, AL&&UA dioxide., acetone., and total
nonmeJhane. hydsiocatibom,, ^oft nitric oxJ.de., hydfioge.n AuZfiide., and ammonia
ewJ>&*ion rioter adjuAte.d to g-cve ofa^eAued c.onc.e.n&LationA. Substantial amount!*
ofa ozone. (^32 ppb peafe) can be pfioduc.e.d in fiemote. ane.a tnopo&pneAeA by photo-
che.mic.al pfioc.e^i>i&. The. ponte.d faom un.ban aAe.a6) at the. ^ofimation oft ofiganic. and inorganic
nittate. compound*; the. ozone, peafe c.onc,tntnation, how&veA, dec^eaie^ to ^29 ppb.
INTRODUCTION
The chemistry of natural tropospheres is regarded as potentially signif-
icant to interactive ozone chemistry, the atmospheric carbon monoxide budget,
and natural sulfate and acid rain production among other issues. Despite
the importance of these issues, the chemical processes remain largely unex-
plored and the emission rates of the reactants poorly defined.
In this paper we present the results of calculations representing the natural
and perturbed nonurban troposphere, particularly as they apply to the chemistry
and resulting concentrations of ozone in nonurban areas. The calculations
show that some ozone formation occurs naturally by photochemical processes
on non-anthropogenic emissions, but that the addition of anthropogenic nitric
oxide has only minimal effect on remote area ozone concentrations.
GASEOUS EMISSIONS INTO NATURAL TROPOSPHERES
A large number of gaseous species are emitted from natural sources;
those whose emissions have been quantitatively assessed are listed in Table 1.
Many of the emission rates are based on observed global concentrations and
* Bell Laboratories, Murray Hill, New Jersey.
467
-------
estimated atmospheric residence times; in these cases the emission rate quoted
is that needed to provide a balance between known or estimated source and
removal rates. The emission estimates are therefore sensitive to errors in
the estimated residence time and in the global concentration assessment and
should, in general, be regarded as "order-of-magnitude"(ll) numbers only fur-
ther limitation is that natural emissions processes are not the same in
all geographical locations. (Terpene emission rates based on data from forests
obviously could not be expected to apply to desert areas, for example.)
Although some of the emission mechanisms postulated or identified differ under
different conditions of terrain and vegetation, it is premature to do more
than to simulate an average natural area in this study. The results must thus
be regarded as "bulk-averaged chemistry," rather than as being strictly appli-
cable to any particular geographic location.
TABLE 1. NATURAL EMISSION RATES OF ATMOSPHERIC GASES
Molecule
CH,,
H2S
NO
Initial Emission*
Rate Estimate
1.30xlO-n
1.87xlO-10
2.31xlO'm
1.00x10
-11
Reference
Ehhalt, 1,974
Kellogg, et
al., 1972
Robinson and
Robbins, 1970
Robinson and
Robbins, 1970
Final Emission*
Rate Chosen
1.52xlC)-13@
1.87X1C)-11
l.lSxlO-11
l.OOxlO-11
Isoprene
a-Pinene
1.84x10-12t§
1.84xlO-§
Rasmussen, 1972
Rasmussen, 1972
1.84xlO~lc
1.84xlO-10
* Units are g cm"2 sec"1.
t These rates are diurnally varied in accordance with the patterns
illustrated in Paper I.
§ Total terpene emissions assumed to be equally divided between
isoprene and a-pinene.
@ This is the amount needed to balance CH^ loss by reaction with
HO in the fully mixed planetary boundary layer of average depth
1 km. Diffusion loss of CH^ to the stratosphere is not included
in these computations.
Detailed discussions of the bases for and uncertainties in these emission
rates are presented by Graedel and Allara (1976, referred to as "Paper I").
468
-------
CHEMICAL REACTIONS IN NONURBAN TROPOSPHERES
The inorganic compounds present in urban and natural atmospheres are
similar, as are the chemical reactions describing their interactions. For
0-H-N chemistry, we utilize a set of 40 reactions identical to those of Groups
1 and 2 of Graedel, et al. (1976, referred to as "Paper II"). The sulfur
chemistry of Paper II treated only oxidized sulfur compounds. We have there-
fore devised an appropriate reaction set for reduced sulfur, which is given
in Paper I. The combined reaction set for compounds of sulfur totals 37 reactions.
The chemistry of ammonia is also the subject of a newly devised reaction set,
described in detail in Paper I.
A significant difference between the difference between the chemistry of
urban and natural tropospheres is the composition of the complex organic
compounds. Urban atmospheres contain a variety of species derived chiefly
from automotive emissions, petroleum processing and handling, and evaporated
paint solvents. Remote area organics are largely derived from botanically
emitted terpenes. In each case eventual chemical breakdown of the long carbon
chains produces simple products such as the aliphatic aldehydes. We have devised
chemically reasonable reaction chains for ^-pinene and isoprene in the presence
of common atmospheric species. Examples of these chains are shown on Figures
1 and 2; full descriptions are given in Paper I.
The total chemical reaction set, including both organic and inorganic pro-
cesses, contains 333 reactions involving 207 distinct chemical species.
METEOROLOGICAL INFLUENCES
The effects of meteorological variables upon the concentrations of
chemical species in the atmosphere are substantial, and very complex tech-
niques are sometimes utilized for the treatment of meteorological parameters.
For studies that attempt to elucidate chemical mechanisms rather than detailed
spatial structure, however, it appears sufficient to use somewhat simplified
descriptions of the operational meteorology. Following the computational
techniques of Paper II, therefore, we define the diurnally varying reaction
volume by the mixing depth pattern specified therein and also use the diurnal
variation in solar photon flux described. For the natural troposphere calcula-
tion we impose the further requirement of spatial homogeneity of emissions and
terrain within the diurnal wind fetch; this allows advection to be neglected.
Within the reaction volume thus defined, all chemical species are regarded
as fully mixed, i.e., the concentrations of all species are spatially constant
within the volume. The assumption of full mixing on a molecular scale appears
to be relatively accurate during days of normal convective turbulence; near-
uniform vertical concentrations of many chemical species have been measured at
such times by airborne instruments (e.g., Blumenthal and White, 1975). Such
an assumption is less valid during the stable nighttime hours, however, and
we anticipate that our computation more accurately represents the physical
mixing conditions that are present in the daytime troposphere.
RESULTS
The computed diurnal variations of a number of species in the unperturbed
469
-------
HO,
H02,
OR
CH362
02
1)02
2) HO, NO
3) CLEAVAGE
CHO
l)02
2) HO, NO
CHO 3) CLEAVAGE
1)02
2) HO, NO
3)CLEAVAGE
CH2CHO
CHOC (CH3)CH CHO
PRODUCTS INCLUDING
HCHO, CHO
PRODUCTS INCLUDING
CH3CH=CH2,CO
Figure 1. Schematic display of the chemical reaction sequence for hydrogen
abstraction from a-pinene. The dots indicate the location of the unpaired
electron bond; the dotted line shows the bond that cleaves on the subsequent
rearrangement or disproportionation. The end products of the chain are relatively
simple free radicals or stable molecules that participate in common atmospheric
reactions. Some of the most significant of the products are indicated, but
the chemical balance present in the actual equations is not necessarily reflected.
nonurban troposphere are illustrated in Figure 3. The comparison of these
results with the sparse quantities of field data are discussed in detail in
Paper I; the concentrations calculated agree to within a factor of ^3 for nearly
all species that have been measured in natural atmospheres and included in our
study: nitrogen oxides (NOX), ammonia (NHs), hydrogen sulfide (H2S), sulfur
dioxide (SCh). formaldehyde (HCHO), carbon monoxide (CO), methand (CHu),
470
-------
02
CHO
Figure 2. Schematic display of the chemical reaction sequences for ozone attack
on a-pinene.
isoprene, a-pinene, acetone, and total nonmethane hydrocarbons. This is partic-
ularly satisfactory since formaldehyde and acetone are chemical products
and thus validate the general chemical treatment as well as the emission and
meteorological aspects of the computation.
The exception to the good agreement discussed above is ozone, whose con-
centration is generally measured at <_ 60 ppb in nonurban areas, rather than the
32 ppb computed here. The ubiquitous presence of ozone in the mid-troposphere is
well known, however, and the incorporation of this ozone into the expanding
morning mixed layer is probable. This process (termed the incorporation of
"fossil" ozone by Ripperton, 1974) is thus expected to increase the ozone
concentrations in the lower troposphere. We are incorporating this effect
into calculations now in progress and will report the results separately.
The combined effects of local photochemistry and fossil ozone injection may
be thought of as producing the natural ozone background in vegetated areas
subject to normal stratospheric-tropospheric mixing processes.
A final consideration of interest is the effect of transported anthropo-
genic emissions on nonurban chemistry. Since remote areas have abundant sources
of hydrocarbons and meagre sources of oxides of nitrogen, transport of the latter
is more likely to influence the natural chemical cycles. To assess this effect,
we add to the natural nitric oxide (NO) source strength an amount sufficient to
maintain a daily NOX concentration of ^20 ppb (shown by Robinson (1976) to be
indicative of the transport of urban air into nonurban regions). The response
of the remot^ area ozone balance to this new source strength is rather small;
the diurnal peak value decreasing from 32 ppb to 29 ppb. Similar results
471
-------
5-2
(T
UJ
O
o
Q
-3
-4
-5
-i
f> _g
Q-3
fe
-------
of stimuli. The natural sources, together with photochemical and thermochemical
processes, produce a rich spectrum of chemical reactions and generate moderate
amounts of ozone. This photochemically produced ozone, together with any
preexisting ozone in the nonurban troposphere, combine to form a naturally-
produced ozone background. This natural background can be affected to some
degree by the transport-generated injection of anthropogenic contaminants, but
calculations representing the injection of NO show such perturbations to be
minimal.
REFERENCES
Blumenthal, D. L., and W. H. White, The stability and long range transport
of ozone or ozone precursors, paper presented at 68th Annual Meeting, Air
Pollution Cont. Assoc., Boston, June 16, 1975.
Ehhalt, D. H., The atmospheric cycle of methane, Tellus, 26_, 58-70, 1974.
Graedel, T. E., L. A. Farrow, and T. A. Weber, Kinetic studies of the photo-
chemistry of the urban troposphere, Atmospheric Environment, (in press),
1976, Paper II).
Graedel, T. E., and D. L. Allara, The kinetic photochemistry of natural tro-
pospheres, submitted for publication, 1976, (Paper I).
Kellogg, W. W., R. D. Cadle, E. R. Allen, A. L. Lazrus, and E. A. Martell,
The sulfur cycle, Science, 175, 587-596, 1972.
Rasmussen, R. A., What do the hydrocarbons from trees contribute to air pol-
lution?, J. Air Pollution Contr. Assoc., 22^, 537-543, 1972.
Rasmussen, R. A., Recent field studies, in Scient. Sem. on Automotive Pollutants,
EPA-600/9-75-003, Environmental Protection Agency, Washington, D. C., 1975.
Ripperton, L. A., Eastern United States high ozone concentrations: chemical
aspects, Clean Air, £ (16), 79-82, 1974.
Robinson, E., and R. C. Robbins, Gaseous nitrogen compound pollutants from
urban and natural sources, J. Air Pollution Contr. Assoc., 20, 303-306, 1970.
Robinson, E., and R. A. Rasmussen, Identification of natural and anthropogenic
rural ozone for control purposes, Proc. Specialty Conf. on Ozone/Oxidants-
Interactions with the Total Environment, Pittsburgh: Air Pollution Contr. Assoc.
3-13, 1976.
473
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SESSION 10
PHYSIOLOGICAL EFFECTS OF OXIDANTS - I
Ckcuxman: J. Knelson
Environmental Protection Agency
475
-------
10-1
ON THE RELATIONSHIP OF SUBJECTIVE SYMPTOMS TO PHOTOCHEMICAL OXIDANT
I. Mizoguchi, K. Makino, S. Kudou, and R. Mikami*
ABSTRACT
The. daily incidences ofi acute subjective symptoms -in 515 Atu.de.nt!> ofa a.
JO.YIA.OH high school Mere recorded fan a 6]-day period and were analysed in
relation to environmental factors, especially prevalence ofi photochemical.
oxA-dants. Sample, and multiple. correlation analyses and maJLti-vaniate analysis
were used to investigate, the. relationship between environmental factors and
the. symptoms. In addition, incidences oft symptoms connected with predisposi-
tions, such as allergy, asthma, and ositho&tatic dyt>fie.QuJtaution, weAe. compa?ie,d
u.ndeA. di^e.fie.nt ox^idant le.v&L*>. Eye. iAA^utation, throat iwiLtation, t>hofctneJ>A
o& bnnatk, and ke.adaa.he. cofifie.iate.d Aigni&icantty {p<0.001} to ozone.. Thtioat
iAAJjtjation, cough, and phte.gm coM.eJLate.d £-ignifiicantl.y to £u£fiuA dioxA.de.,
too. Humidity Ahowe.d significant negative. cowieJ&ition to cough, tethafigy,
phie.gm, thsioat itfutation, and shortness ofi bfieath. Studies on the. muJLtipte.
cofin.eHatA.on coe.^icie,nt^ &howe.d highly significant coM.e.£ations bntu)e.e.n difi-
^ojtojit pOAAA ofi e.nviA.onme.ntai fiactotis including ozidants and se.veA.at symptoms.
The. result oft a pfiincipat component anatysis suggests that tkete one. associa-
tions between oxA.dant, suJL^uA. dioxA.de, suspended poftticutate matte*, and eye
imitation, hoasiAeness, sonc thsioat, headache, and so on. The incidences o{^
the symptoms wcne. compared wtth ne^eAence to the predispositions o& the stu-
dents. A significant increase in the incidence ofa cough Mas observed in asthma
Qfioup; the otitnostatic dysnegutation group showed appreciable increases in
the incidence oft headache and lethargy in the days in which oxidant levels
exceeded 0.15 ppm.
INTRODUCTION
During the summer many residents in metropolitan Tokyo and the Tokaido
megalopolitan areas manifest symptoms caused by photochemical oxidants. This
has become of considerable social concern in recent years. Hausknecht (1)
reported that changes in chronic conditions related to oxidants and other
weather factors were noted by eye complaints, asthma, and nose and throat
complaints. In Japan similar reports (2, 3, 4) were recently published in
journals and governmental reports. In our country, the deleterious effects
of photochemical oxidants first attracted public attention when the shocking
*I. Mizoguchi, K. Makino, Tokyo Metropolitan Research Laboratory of Public
Health, Tokyo, Japan.
S. Kudou, R. Mikami, School of Medicine, University of Tokyo, Tokyo, Japan.
477
-------
episode at the Rissho Girls High School took place on July 18, 1970. Scores
of girls playing handball on their campus suffered eye and throat irritation,
and shortness of breath. More than 10 of them had trouble in breathing and
temporary clouding of consciousness and were admitted to a neighboring hospi-
tal. Attacks like the Rissho High School episode have occurred a few times
every year since then. The oxidant level in Tokyo is gradually rising. It
is a most important problem for us to reveal the extent of actual effects of
photochemical oxidants on health and to encourage control.
Since 1974 we have been conducting investigations on the relationship
between multiple variables including subjective symptoms, photochemical oxi-
dants, other air pollutants, meteorological factors, and clinical signs in
students of a junior high school located in southeastern Tokyo (ca 12 km
away from the center). In our investigation period, maximum oxidant concen-
tration was 0.23 ppm, and clinical examinations were carried out under 0.17
ppm oxidant level. The values of respiratory function tests were not dif-
ferent from control values. The only signs we found were decreases in lysozyme
activities and in the pH of tears (5). Analyzing the daily incidences of
subjective symptoms related to environmental conditions presented several
interesting clues, however.
MATERIALS AND METHOD
POPULATION AND SUBJECTIVE SYMPTOMS
The study population was composed of students of a public junior high
school located in a southeastern area of Tokyo. Almost all students of this
school live within 1.5 km from the school. Five hundred fifteen students
recorded 17 symptoms every day from May 20th to July 19th, in 1974.. These
symptoms previously recorded in health diaries are shown in Table 1. The time
and place in which each student became aware of symptoms were recorded. Sub-
jective symptoms used were those which occurred from 8 am to 5 pm. Daily
incidences of the symptoms are indicated by percentages of all 515 students.
Frequencies of several symptoms and daily maximum oxidant and sulfur dioxide
concentrations are shown in Figure 1. Stars at the top of Figure 1 indicate
the days when maximum oxidant concentrations exceeded 0.15 ppm. It will be
noticed that oxidant peaks correspond with peaks of frequencies of most
symptoms. Such crude data were subjected to statistical procedures.
In order to examine incidences of the acute symptoms with reference to
the predispositions of the students, three subgroups were picked out of all
515 students according to questionnaires (Table 2): allergy, asthma, and
orthostatic deregulation (O.D.). In Japan, O.D. is a present important pro-
blem in the field of school health administration. Although the concept has
not been established completely, it seems that its entity is something dif-
ferent from postural hypotension. The criteria we used is shown in Table 3
(6). The number of students in each group were: Allergy group - 74, Asthma
group = 20, O.D. group = 47; some overlapped each other.
478
-------
TABLE 1. HEALTH DIARY
Check
the proper space
if you had symptoms below
Date
May 20
Mon.
May 21
Tues.
May 23
Wed.
1. Eye irritation
2. Redness of conjunctiva
3. Watering of eyes
4. Blurred vision
5. Cough
6. Phlegm
7. Sneeze
8. Shortness of breath
9. Hoarseness
10. Sore throat
11. Dizziness
12. Headache
13. Nausea
14. Numbness of extremities
15. Lethargy
16. Abdominal pain
17. Diarrhea
Time when you had
the symptoms
am
pm
am
pm
am
pm
Place where you had
symptoms:
1. Indoors 2. Playground
3. Outdoors 4. Outside school
Duration
mm
hrs
mm
hrs
mm
hrs
Treatment (Ex: washing,
gargling, etc.)
Check if absent from school
Reason for your absence
479
-------
1112
Temp
20compl3ints
Figure 1. Correspondence of daily changes in subjective symptoms
with oxidant concentrations.
AIR POLLUTION AND METEOROLOGICAL DATA
Oxidants, other air pollutants, and meteorological factors were measured
every hour throughout this investigation period at a sampling room set up in
the studied school. (Air pollutants and their measurement methods are shown
in Table 4.) Meteorological factors obtained were temperature, relative
humidity, wind speed, solar radiation, ultraviolet radiation, and visibility.
Discomfort Index was calculated from temperature and humidity. Minimum values
were used for humidity and visibility; maximum values of the other environ-
mental variables were used.
480
-------
TABLE 2. RATIOS OF YES TO ALL STUDENTS
QUESTIONNAIRES
1. Having nausea
2. Liable to be tired
3. Liable to get carsick
4. Frequently having headaches
5. Frequently having sleep disturbances
6. Liable to feel ill under difficult circumstances
7. Liable to be irritated
8. Liable not to feel refreshed in the morning
9. Liable to feel dizzy
10. Having urticaria
11. Liable to be pale
12. Frequently having eczema
13. Having asthma attacks
14. Liable to feel ill in a long erect posture
15. Liable to palpitate or be short of breath after light exercise
16. Having loss of appetite
24
22
19
18
14
13
12
11
10
9
6
5
4
3
3
3
TABLE 3. CRITERIA FOR GROUPING OF ORTHOSTATIC DYSREGULATION GROUP
Major Symptoms
3
or 2
or 1
Major Symptoms:
Minor Symptoms:
Nos.
Nos.
Minor Symptoms
+ 0
+ 1
+ 3
6, 8, 9, 14, and 15 )
2, 3, 4, 11, and 16 J
From Questionnaire in
Table 2
481
-------
TABLE 4. MEASURED ENVIRONMENTAL FACTORS
Item
Method
Air pollutants
0
X
03
S02
NO
N02
HC(total)
CO
Aerosol
SPM
SOi,
N03
Aldehyde
(total)
Neutral Potassium Iodide
Chemiluminescence
Conductimetric
Saltzman
Saltzman
Flame ionization
Infrared absorption
Light scattering
High volume air sampler*
Spectrometric*
Spectrometric*
3-Methyl-2-Benzothi azolone hydrazone*
One hour averaged for air pollutants
*Four hours averaged
Meteorological
Factors
Reading taken every hour
Temperature
Relative humidity
Discomfort Index
Calculated
STATISTICAL ANALYSIS
SIMPLE CORRELATION ANALYSIS
To study the relationship between the symptoms and environmental factors,
simple correlation analysis was first adopted. Two variables were used: one
was daily incidences of each symptom, the other was daily maximum value of
each environmental factor for 61 successive days.
MULTIPLE CORRELATION ANALYSIS
Multiple correlation analysis was performed with three variables: one
of the symptoms and a pair of environmental factors.
482
-------
PRINCIPAL COMPONENT ANALYSIS
Principal component analysis is a mathematical and statistical method
that has been used to derive principal components which represent a number
of different variables. Variables of 17 symptoms and 14 environmental factors
are analyzed. Principal components represent the degree of overlap or simi-
larity among these variables as measured by correlation coefficients. Another
interpretation is that principal components are synthetical characteristics
that give weight to each variable and combine these variables primarily.
Generally principal components are selected until the sum of ratios of the
variances will exceed 60 per cent of the total variance. The ratio of 60
per cent is regarded to interpret most significant characteristics of the
variables. The list of variables is contained in Table 7.
RESULTS
SIMPLE CORRELATION COEFFICIENTS
Figure 2 shows some typical variation of simple correlation coeffi-
cients between representative environmental pollutants and the symptoms.
Exceedingly high correlation coefficients were noted between oxidant and
eye irritation, sore throat, shortness of breath, headache, and blurred
vision. The simple correlation pattern of ozone with variation of the
symptoms, is noticed to be similar to that of oxidant. Sulfur dioxide and
suspended particulate matter were revealed to have fairly high coefficient
values to some symptoms such as sore throat, cough, phlegm, lethargy, and
blurred vision. There are extremely high negative correlation coefficients
between humidity and sore throat, cough, phlegm, lethargy, and sneezing.
Besides there are significant (p<0.01) correlation between solar radiation
and lethargy as well as between pollution index (Pindex) (8) and several
symptoms. Table 5 is the list of all symptoms and environmental factors
between which there are significant (p<0.001 and p<0.01) correlation coef-
ficients (0.001 or 0.01 of significance level, used t-test, express extremely
close associations). From mutual comparisons of values of the coefficients,
the values of oxidant give us a large evaluation of contribution to occurrence
of the symptoms. Wind speed and visibility have no significant correlation
coefficients in spite of our expectation. The expectation came from obser-
vation of weather in the days when many students complained of mucous mem-
brane irritations and respiratory symptoms.
MULTIPLE CORRELATION COEFFICIENTS
F-test was used to examine the significance of multiple correlation
coefficients. Figure 3 shows that multiple correlation coefficients of sub-
jective symptoms will change according to the pairs of air pollutants. Char-
acteristic results of these analyses are significant from p<0.005 coefficients
among several symptoms and pairs of environmental factors such as ox-S04, ox-
Aldehyde, and ox-N03. Sulfate, nitrate, and aldehyde have no significant
simple correlation coefficients to any symptoms, but their pairs, which include
483
-------
0.8 0.6 0.4 0.2
-0.2
c.c.
p 0.001 p.0.01
X
Hum .f\)
p 0.01
/N02
-Eye Irritation
.Shortness of
Breath
-Sore Throat
-Headache
-Blurred Vision
•Watering of
Eyes
-Cough
-Dizziness
-Hoarseness
-Phleghi
-Lethargy
-Sneeze
-Abdominal-pain
-Diarrhea
.Numbness of
Extrimities
•Nausea
Redness of
"Conjunctiva
Figure 2. Changes in simple correlation coefficients
between each environmental factor and symptoms.
oxidant, S02, or suspended participate matter (SPM), have appreciably high
values with several symptoms such as eye irritation, shortness of breath,
sore throat, headache, blurred vision, watering of eyes, cough, dizziness,
hoarseness, phlegm, and lethargy. If we adopt p<0.01 as the significant level,
there are too many correlation coefficients to list in this limited space.
For this reason, we adopted a severe significant level (p<0.005). In spite
of this severe level, 29 combinations are listed in Table 6.
484
-------
TABLE 5. EACH SYMPTOM AND ENVIRONMENTAL FACTOR BETWEEN WHICH THERE WAS A
SIGNIFICANT SIMPLE CORRELATION COEFFICIENT
Symptoms
Environmental Factors
p 0.001 p 0.01
Eye irritation
Shortness of breath
Sore throat
Headache
Blurred vision
Eye watering
Cough
Vertigo
Ox, 03, S02
Ox, 03, Hum(-)
0 , Hum(-), 03
S02, SPM
S02, Ox
0
Hum(-), S02, SPM
Pindex, Hum(-),
SPM, N03, Aid.
S02, Pindex, SPM
Pindex
03, Hum(-), Pindex, N03
Hum(-), S02, 03, SPM,
Pindex
Hum(-), Pindex
Oy, 03, Pindex
Pindex, 0 , S02, 03,
Aid., Hum(-), SPM, N03
Hoarseness
Phlegm
Lethargy
Sneeze
Abdominal pain
Diarrhea
Numbness of extremities
Nausea
Redness of conjunctiva
Hum(-)
Hum(-), S02
Hum(-)
Hum(-)
—
—
—
—
—
Pindex, S02, 03, 0 , SPM
X
SPM, Ox, 03, Pindex
SPM, S02, Ox
S02, SPM, 03, 0
X
SPM, S02, Hum(-)
—
Hum(-), SPM
SPM, Hum(-)
—
PRINCIPAL COMPONENTS
Three major principal components were produced, which altogether accounted
for 63 per cent of the total variance of the data. These three principal com-
ponents can be considered to have independent interpretation to each other
and are shown in Table 7.
485
-------
0.6 0.4
0.2
n-c-cp
cv
O
I/}
|
X
o
\
\
\
\
/
z:/
3*
3
°\
\
^
^
\
//
^
\
,\
fcl\
\ \ .
\-o
ff
'"/i
/ 1
1
\
V
V\
II
8V
inl 1
ik \
°\\ \-
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1
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vA
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\S:\
-Eye Irritation
^Shortness of
"Breath
•Sore Throat
•Headache
•Blurred Vision
•Watering of
Eyes
•Cough
"Dizziness
•Hoarseness
•Phlegm
•Lethargy
•Sneeze
•Abdominal Pain
•Diarrhea
Numbness of
"Extrimities
-Nausea
.Redness of
Conjunctiva
Figure 3. Changes in multiple correlation coefficients between each
environmental factor and symptoms.
FIRST PRINCIPAL COMPONENT
The factor that has high loadings of variables is associated with res-
piratory symptoms such as sore throat and cough. Headache, eye irritation,
hoarseness, blurred vision, shortness of breath, and phlegm follow. Thus,
this principal component is associated with irritation of mucous membranes as
well as respiratory symptoms. High loadings of headache, lethargy and
dizziness suggest an association of this component with other systemic symptoms
to some extent. In addition, oxidant, ozone, and sulfur dioxide have high
486
-------
1.0
CO.
0.5'
•HUM
.-i.n
-0.5
2ND PC
AEROSOL
HC
S04
NO*
• AID*
'NO
HEADACHE
SHORTNESS OF BREATH
WATERING OF EYES
DIARRHEA* SORF THROAT
0.5 .
OX
•
.SOe
•03
EYE IRRITATION
.» .' 1,0
MBDOMINAL TAIN
TEMP
REDNESS ot CONJUNCTIVA*
BLURRED VISION-;
HOARSENESS
1ST PC
SNEEZE *
NAUSEA. PHLEGM
NUMBNESS OF EXTRIMITIES*
LETHARGY*
.COUGH
-0.5H
Figure 4.
-l.OJ
Distribution of the 1st principal
principal components.
components vs the 2nd
loadings, and it is recognized that oxidant affects symptoms mentioned above.
The first principal component is considered to be a factor associated with
"Photochemical Air Pollution."
487
-------
TABLE 6. EACH SYMPTOM AND ENVIRONMENTAL FACTORS-COMPLEX BETWEEN WHICH
THERE WAS A SIGNIFICANT MULTIPLE CORRELATION COEFFICIENT
Symptoms
Environmental Factors
p 0.001
Eye Irritation
Shortness of Breath
Sore Throat
Cough
Hoarseness
Phlegm
0 -S02, 0-S04, 0 -Aid., 0 -Temp., 0 -SPM,
0*-N03. xxx
Ox-S04, 0 -Aid., 0 -S02, 0 -Temp., 0 -N03,
0 -SPM. xxx
X
0 -SCV, 0 -SPM, 0 -S02, 0 -Temp., 0 -Aid.,
S6VSPM, Clx-N03.
S02-SPM, Ox-SPM, SPM-S04.
S02-SPM, Ox-SPM, SPM-SO^, SPM-N03, SPM-Ald.
S02-SPM, S02-S0v
10
15
20
25
30?
Eye
Irritation
Sore
Throat
Shortness
of Breath
Cough
Headache
Watering
of Eyes
Sneeze
Phlegm
Hoarseness
Lethargy
All Students
Dick Lines: Average
Allergy Group
Thin Lines: Incidences
of 7, June, '74.
O.D. Group
* P ,0.05 ** P--0.01 ( Chi-square Test )
Figure 5. Changes in subjective symptoms related to oxidant
concentration and subgroups. On June 7, 1974, oxidant concentration in
Tokyo rose above 0.23 ppm.
488
-------
TABLE 7. THE RELATIONSHIP AMONG SYMPTOMS, AIR POLLUTANTS,
AND WEATHER FACTORS BY PRINCIPAL COMPONENTS ANALYSIS
Air
Variables
Pollutants &
1st PC
2nd PC
3rd PC
Weather Factors
0
03
S02
SOh
NO
N02
N03
CO
Dust
SPM
Aldehyde
HC
Temperature
Humidity
0.740
0.717
0.691
0.187
0.016
0.013
0.425
-0.104
0.024
0.618
0.404
0.006
0.310
-0.706
0.368
0.249
0.309
0.752
0.476
0.872
0.783
0.555
0.900
-0.025
0.748
0.848
-0.060
-0.267
-0.386
-0.402
-0.002
-0.151
-0.221
0.176
-0.029
0.604
0.143
-0.075
-0.047
0.227
-0.632
0.255
Symptoms
Eye Irritation
Redness of Conjuctiva
Watering of Eyes
Blurred Vision
Cough
Phlegm
Sneeze
Shortness of Breath
Hoarseness
Vertigo
Sore Throat
Headache
Nausea
Numbness of Extremities
Lethargy
Abdominal Pain
Diarrhea
0.813
0.288
0.722
0.792
0.879
0 . 780
0.726
0.789
0.799
0.881
0.726
0.816
0.607
0.510
0.740
0.534
0.268
0.086
-0.164
0.031
-0.087
-0.176
-0.197
-0.181
-0.017
-0.095
-0.078
0.004
-0.020
-0.284
-0.315
-0.361
-0.036
0.180
-0.281
-0.411
-0.199
0.021
0.232
0.302
0.452
-0.371
0.280
-0.125
0.175
0.136
0.444
0.144
0.234
0.376
0.169
SECOND PRINCIPAL COMPONENT
Aerosol, nitrogen dioxide, hydrocarbon, nitrate, sulfur dioxide, aldehyde,
and carbon monoxide have high loadings successively. These variables are the
first air pollutants. The second principal component must be related to "High
Air Pollution."
489
-------
THIRD PRINCIPAL COMPONENT
Loadings of variables are less remarkable in this component, but this
fact could be said to relate to "Temperature and Carbon Monoxide."
The variances of the first and second principal components account for 54
per cent of the total variance. The third accounts for only nine per cent
and it does not have the features of factors that have high loadings. Other
principal components have less per cent of variance than the third. In
Figure 5, a scattering graph is drawn whose axes are first and second princi-
pal components. It shows that factors associated with photochemical oxidants
are partial to right side and make a group, and that other factors distribute
at random.
CONCERNING PREDISPOSITIONS
Figure 5 and Table 8 show changes in incidences of the symptoms both
concerned with subgroups and also related to oxidant concentrations. The Chi-
square test was carried out to examine differences between all days average
incidences of all students and two subgroups: allergy and O.D. groups. In
the allergy group, days averaged incidences of cough, phlegm, headache and
dizziness were significantly (p<0.05) higher than those of all students. On
the other hand, the O.D. group had significantly (p<0.01 or p<0.05) higher
average incidences of most symptoms (indicated by single and double stars in
column 4 of Table 8). The O.D. group seems to be a characteristic group;
the O.D. students have a considerable number of complaints and have weak
adaptability to changes in ambient conditions. In other words, they are most
sensitive to the environment. The asthma group consists of too few examples
to examine the differences; therefore we do not mention this group in this
chapter.
Differences of the incidences which related to oxidant concentrations
were tested separately in three different oxidant concentrations. The oxidant
concentration was studied through all 75 days of the period. During the pe-
riod, oxidant concentrations rose above 0.15 ppm during 5 days. It exceeded
0.23 ppm on June 7, 1974. A significant increase in the incidences in oxi-
dant conditions is indicated by single (p<0.05) and double (p<0.01) stars
in the 2nd, 3rd, 5th, 6th, 8th and 9th columns of Table 8 as well as in
Figure 6. Figure 5 represents comparisons of incidences under varying oxidant
levels.
In general, eye complaints, respiratory symptoms such as cough and short-
ness of breath and headache increase in the high oxidant conditions. While
extremely significant increases of cough and phlegm are observed in the asthma
group, the O.D. group shows characteristic increases of headache.
490
-------
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DISCUSSION
In this investigation period, weather in Tokyo was somewhat unusual.
In June and early in July, wet and rainy days continue every year, in the so
called Tsuyu season, but in 1974, Tsuyu season persisted until late in July
and temperatures were lower than in more normal years. For this reason occur-
rences of photochemical smog in Tokyo were fewer and milder to some extent;
therefore, signs except lysozymic activity and pH in tears may not have been
found under this condition.
The searches for acute effects of air pollution through some respiratory
function test (9, 10) and through the comparisons of frequencies and severities
of attacks in asthma patients have been reported (11). These reports are
excellent but do not focus on photochemical oxidant and leave something to
analyse statistically.
There were some reports (12, 13) dealing with the effects of photochemical
oxidant in which absenteeism and performance were used as parameters. Our
study revealed that daily incidence of the symptoms correlated and associated
closely with daily maximum oxidant concentration, as shown in this paper.
It can be said that the subjective symptom is a more sensitive parameter.
Several problems remain, however, on the collection of daily frequencies
of subjective symptoms related to photochemical oxidants. The first is eval-
uation for the bias occurring through the mental states of the students. If
official smog warning information is given to a studied school, it is inevit-
able that mental situations and responses to the questionnaires in health
diaries will change. We checked this bias by comparing frequencies of the
symptoms with and without delivery of warning information at similar oxidant
conditions. Results were not significantly different. However, more precise
checking is required to evaluate this factor.
The second problem is a limit by which the students checked only symptoms
recorded previously in health diaries. Acute effects of photochemical oxidant
and other air pollutants may be more multifarious. The blank of free answer
was not adopted in health diaries because of possible student reluctance to
write. This might miss, however, other responses of the students to ambient
conditions.
Means of delivery of health diaries is the third problem. From our
experience, daily delivery and collection of diaries provoked more responses
than at long intervals. In this investigation they were carried out monthly,
and this interval may avoid excess responses. On the other hand, maintenance
of constant concern of students was difficult.
It was reported (14) that most students who suffered from severe symptoms
had allergic predisposition in the Rissho High School episode and other similar
incidents. This research could not make a clear connection between allergic
predisposition and severe symptoms. For the study concerning predisposition,
more than 1500 samples are required because more than 50 at least are
necessary as the population of a subgroup for statistical analysis in such a
study period.
492
-------
There are interactions and relations of photochemical oxidants to other
air pollutants and weather conditions. Simple correlation analysis between
these factors measured in this school to each other was carried out and reported
(15). Its one point was that there were significant correlations between
oxidants, ozone, sulfur dioxide, and suspended particulate matter. Our results
from comparison of coefficient levels show, however, that oxidants contribute
manifestly to occurrences of the specific symptoms.
Visibility and wind speed did not show significant correlation with any
symptoms. However, short visibilities and slow wind speeds were pointed out
on the days when many subjective symptoms were reported. This discrepancy
comes from the fact that shortening of visibility is caused by smog and rain,
and that slow wind speed not always bring about elevation of oxidant concen-
tration. In a few cases of days when oxidant concentration exceeded 0.15 or
0.20 ppm, there were unusually scarce complaints of subjective symptoms.
This problem requires more and different approaches. One of them is classi-
fication of air pollutants and weather conditions that vary in the day when
many students complained of specific subjective symptoms.
REFERENCES
1. Hausknecht, R. Air Pollution: Effects reported by California Residents.
Publ. California State Dept. Public Health, California, 1969.
2. Shimizu, T., and Y. Tsunetoshi, et al. Classified Subjective Symptoms
of Junior High School Students Affected with Photochemical Air Pollution.
J. of Japan Society of Air Pollution, 9(4); 734-741, 1975.
3. Makino, K., and I. Mizoguchi. Symptoms caused by Photochemical Smog.
Japanese J. of Public Health, 22(8):421-430, 1975.
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494
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10-2
EFFECTS OF OZONE PLUS MODERATE EXERCISE ON
PULMONARY FUNCTION IN HEALTHY YOUNG MEN
B. Ketcham, S. Lassiter, E. Haak, and J. H. Knelson*
ABSTRACT
healthy non-smoking mate subjects weAe exposed to 0.6 ppm ozone.
1 houAS in an enviAonmental chambeA. Back Au.bje.ct was seated at nest ex-
c.s.pt {,OA two IB-minute exetcx-42. peAiods on. a. b^cyc-le eA.gome.te.si. Ike. ezeAcise
was sufficient to approximately double the. Aest-ing heaAt note,. Subject* weAe
asked to Aepofct any symptoms that occuJiAed daAing the. couASe ofi the. chambeA
exposures and daity theAea&teA {,OA the. ^otlow-up peAiod. Pulmonary function
studies included spiAometAy, maximum e.x.piAatoiy falow-voiunne. cujwej,, and body
pttthy&mographic me.aAuA.e.me.nt o{, airway tie-AiAtance. and lung uo£ume4. Change.*
i.n pulmonary function afiteA 1 and 2 housi* o& ozone. uieAe. compa>ie.d to valuer
obtained at the, tame, timu during a contAol 2-houA expo^uAe. to cie.an aiA.
MoAt Aubje.ctt> e.xpo*e.d to ozone. complaMie.d ofa cough, Aub&teAnal che^t pain,
AhoAtn&AA ofa bAe.ath, and a de.cAe.a*e.d ability to maxJjnaULy intpiAe.. A faew Aub-
je.ct6 continued with symptom *e.veAa£ houAA post e.x.posuAe.. h&teA 1 houA o&
ozone,, maxMnal mi.de.x.piAatofiy &low Aote. (MMFR), minute, volume.* (1/25 and 1/50),
peak e.x.pt may be. the. most K.eJMibJte. and sensitive, -indicator
oft the. adveASe. e^eati o& ozone, on lung function. Eve.n though conS-ideAable.
-------
The present oxidant alert level is 0..6 ppm maximum 1-hour concentration.
This level approximates peak smog episode levels found within the Los Angeles
basin. This study was designed: (a) to better define the adverse health
effects of short-term exposures to 0.6 pprn ozone utilizing a homogeneous group
of human volunteers carefully selected to minimize intersubject variability
and, (b) confirm earlier studies reporting impaired pulmonary function at
these levels (7).
MATERIALS AND METHODS
Twenty healthy non-smoking male volunteers between the ages of 19 and 27
participated in this experiment. The mean anthropometric data for the group
was: age, 22.7 years; weight, 73.4 kg; height, 180.1 cm. Normal healthy male
subjects were selected by screening all candidates with a Minnesota Multi-
phasic Personality Inventory (MMPI), a complete medical history, a physical
examination, and a complete blood cell count. Suitable subjects were candi-
dates who were within normal limits on all screening tests. After obtaining
informed consent to participate voluntarily in the study, final selection of
the subjects was determined by an adequate performance in a chamber training
session. Subjects were paid for the time of their participation at the rate
of four dollars per hour. None of the subjects had a history of allergic,
respiratory, or cardiac illness.
All exposures and the pulmonary function testing were conducted in a con-
trolled environmental chamber (8'x8'x8') constructed of 1/2-inch plexiglass
(8). Ozone was generated from pure oxygen using an OREC ozone generator and
was injected into the chamber air-supply duct at a low pressure point. The
air-ozone mixture was dispersed into the chamber through a perforated grill in
the chamber ceili |