EPA-450/3-75-036
March 1975
INVESTIGATION
OF RURAL OXIDANT LEVELS
AS RELATED
TO URBAN HYDROCARBON
CONTROL STRATEGIES
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
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EPA-450/3-75-036
INVESTIGATION
OF RURAL OXIDANT LEVELS
AS RELATED
TO URBAN HYDROCARBON
CONTROL STRATEGIES
by
Research Triangle Institute
Research Triangle Park, N. C. 27709
Contract No. 68-02-1386 Task 4
Program Element No. 2AC129
EPA Project Officer: Robert E. Neligan
Prepared for
ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, N. C. 27711
March 1975
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This report is issued by the Environmental Protection Agency to report
technical data of interest to a limited number of readers. Copies are
available free of charge to Federal employees, current contractors
and grantees, and nonprofit organizations - as supplies permit - from
the Air Pollution Technical Information Center, Environmental Protection
Agency, Research Triangle Park, North Carolina 27711; or, for a
fee, from the National Technical Information Service, 5285 Port Royal
Road, Springfield, Virginia 22161.
This report was furnished to the Environmental Protection Agency by
Research Triangle Institute, Research Triangle Park, N. C. , in fulfillment
of Contract No. 68-02-1386, Task 4. The contents of this report are repro-
duced herein as received from Research Triangle Institute. The opinions,
findings, and conclusions expressed are those of the author and not neces-
sarily those of the Environmental Protection Agency. Mention of company
or product names is not to be considered as an endorsement by the Environ-
mental Protection Agency.
Publication No. EPA-450/3-75-036
11
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ACKNOWLEDGMENTS
This project was conducted by the Research Triangle Institute,
Research Triangle Park, North Carolina, under Contract Number 68-02-1386
for the United States Environmental Protection Agency. The support of
this agency is gratefully acknowledged as is the advice and guidance of
the Project Officer, R. E. Neligan, and his staff.
Special acknowledgments are given to three branches of the U.S.
Environmental Protection Agency—the Monitoring Applications Laboratory of
the National Environmental Research Center, Las Vegas; the Chemistry and
Physics and the Quality Assurance and Environmental Monitoring Laboratories
of the National Environmental Research Center, Research Triangle Park. The
NERC, Las Vegas, provided the aircraft and pilots for the airborne monitor-
ing program. The Chemistry and Physics Laboratory, NERC-RTP, made available
their Mobile Laboratory for in-field gas chromatographic analysis of hydro-
carbons and related compounds. Recognition of the technical support of
Mr. W. A. Lonnemann and Mr. R. L. Seila is acknowledged as is the advice of
Dr. J. J. Bufalini and Laboratory Director, Dr. A. P. Altshuller. The
Quality Assurance and Environmental Monitoring Laboratory, NERC-RTP, operated
ozone analyzers in six cities located in the study area and supported the
quality assurance program. Recognition of the technical support of Mr. F. J.
Burmann, Mr. T. A. Hartlage, and Mr. J. C. Lang is acknowledged as is the
advice of Dr. T. R. Hauser and Laboratory Director, Dr. D. S. Shearer.
Work on this project was performed by staff members of the Engineering
Division and Environmental Studies Center of Research Triangle Institute
under the general direction of Mr. J. J. B. Worth, Group III Vice President.
Mr. Worth served as Laboratory Supervisor. Mr. C. E. Decker served as
Project Leader and was responsible for coordination of the program. Staff
members of Research Triangle Institute who contributed to the preparation
of this report are recognized and listed in alphabetical order: Dr. W. D.
Bach, Mr. C. E. Decker, Mr. W. C. Eaton, Mr. H. L. Hamilton, Mr. W. J. King,
Dr. L. A. Ripperton, Mr. J. B. Tommerdahl, Dr. F. M. Vukovich, Mr. J. H.
White, and Mr. J. J. B. Worth.
iii
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TABLE OF CONTENTS
ACKNOWLEDGMENTS . ill
LIST OF FIGURES viii
LIST OF TABLES xiv
Section
1.0 INTRODUCTION 1
2.0 STUDY PLAN 3
3.0 PROCEDURE 10
3.1 Ground Stations 10
3.1.1 Sampling Protocol 10
3.1.2 Site Locations/Description of Monitoring Stations 10
3.1.2.1 Wilmington, Ohio, (Wilmington Industrial 10
Air Park) Station
3.1.2.2 Wooster, Ohio, (Wayne County Airport) 13
Station
3.1.2.3 McConnelsville, Ohio, (Morgan County 16
Airport) Station
3.1.2.4 DuBois, Pennsylvania, (DuBois-Jefferson 19
Municipal Airport) Station
3.1.2.5 McHenry, Maryland, (Garrett County Airport 19
Station
3.1.3 Air Quality Measurements 19
3.1.3.1 Instrumentation 19
3.1.3.2 Instrument Calibration and Maintenance 21
3.1.4 Data Acquisition/Reduction 24
3.1.5 Data Validation and Quality Control 27
3.2 Aircraft Measurement Program 27
3.2.1 Aircraft Flight Protocol 27
3.2.2 Aircraft System Description 28
3.2.3 Systems Operation 33
3.2.4 Instrument Calibration/Altitude Effects/Data 34
Validation
3.2.4.1 Instrument Calibration 34
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TABLE OF CONTENTS (Continued)
Section
3.2.4.2 Altitude Effects on Instrumentation 35
3.2.4.3 Data Validation/Fly-by Comparisons/ 38
Ground Comparison Tests/Battelle Com-
parison Flight/Hydrocarbon Sample
Contamination Test
3.2.4.4 Comparison of RTI Solid Phase and Bendix 45
Gas Phase Ozone Analyzers
3.2.5 Data Acquisition/Reduction 45
4.0 PROGRAM SCHEDULE 50
4.1 Ground Station/Aircraft Measurement 50
Program Schedule
4.2 Quality Assurance Program 53
5.0 SUMMARY OF DATA AND STATISTICS 56
5.1 Summary Statistics 56
5.2 Diurnal Patterns 63
5.3 Summary of Climatic Conditions 72
6.0 INTERPRETATION OF RESULTS 77
6.1 Examination of Ozone and Hydrocarbon Data From 77
Aircraft Flights
6.1.1 Square Wave Flights 80
6.1.2 Double Box Flights 100
6.1.3 Eastern Flight of August 21, 1974 118
6.1.4 Vertical Profile Flights 121
6.1.5 Summary of Results 127
6.2 Examination of Ozone and Hydrocarbon Data From 129
Ground Stations
6.2.1 Characteristics of Rural and Urban Ozone 129
6.2.2 Ozone and Hydrocarbon Data from Ground Stations 139
6.3 Relationship Between High Ozone Episodes and 147
Synoptic Weather Conditions
6.3.1 Introduction 147
6.3.2 Correlation Between Pressure Systems and 150
High Ozone
vi
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TABLE OF CONTENTS (Continued)
Section
7.0
8.0
6.3.3 Case Studies
6.3.4 Discussion of Meteorological Analysis
6.4 Air Trajectories
6.5 Chemistry of Ozone Generation
6.6 Postulated Sequence for Ozone Generation and
Destruction in Rural Areas
CONCLUSIONS
REFERENCES
APPENDIXES
APPENDIX A:
APPENDIX B:
APPENDIX C:
APPENDIX D:
APPENDIX E:
APPENDIX F:
CALIBRATION SYSTEMS/PROCEDURE
PERFORMANCE CHARACTERISTICS AND OPERATIONAL
SUMMARIES FOR INSTRUMENTS
AIRCRAFT FLIGHT PLANS/DATA/METEOROLOGICAL SUMMARY
EVALUATION OF OZONE AND OXIDES OF NITROGEN
ANALYZERS AT REDUCED PRESSURE
OPERATIONAL PROCEDURES
TRAJECTORY ANALYSIS
155
167
172
177
184
189
191
193
vii
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LIST OF FIGURES
Figure Page
1 Location of fixed ground stations. 5
2 Square wave flight plan. 6
3 Double box flight plan. 8
4 Aerial view of Wilmington Industrial Air Park. 12
5 Aircraft, RTI, and EPA vans located on Parking Apron "C," 12
Wilmington Industrial Air Park.
6 Interior view of Environmental Monitoring Laboratory 13
showing some of the ambient air analyzers.
7 Interior view of Environmental Monitoring Laboratory 14
with data acquisition system in foreground.
8 Aerial view of Wooster, Ohio, (Wayne County Airport) site. 15
9 Exterior view of Wooster, Ohio, (Wayne County Airport) 15
station.
10 Interior view of Wooster, Ohio, (Wayne County Airport) 16
station.
11 Aerial view of McConnelsville, Ohio, (Morgan County Airport) 17
site.
12 Exterior view of McConnelsville, Ohio, (Morgan County 17
Airport) station.
13 Interior view of McConnelsville, Ohio, (Morgan County 18
Airport) station.
14 Diagram of DuBois-Jefferson Municipal Airport. 18
15 Diagram of Garrett County Airport. 20
16 Exterior view of McHenry, Maryland, (Garrett County Airport) 20
station.
17 Typical data printout. 26
18 Photograph of aircraft. 29
19 Air sampling probe used on C-45 aircraft. 30
2 Block diagram of aircraft instrumentation. 31
21 Air sample bag-filling system. 32
22 Compensation factor for adjustment of Bendix N0-N02-N0 36
analyzer data for effects of altitude.
23 Compensation factor for adjustment of RTI ozone analyzer 36
data for effects of altitude.
viii
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LIST OF FIGURES (Continued)
Figure Page
24 System used to calibrate analyzers while airborne. 37
25 Aircraft fly-by data. 39
26 Plot of data from ozone instrument in aircraft while on 40
ground and data from base station instrument.
27 Battelle comparison flight pattern. 42
28a Data from RTI/Battelle comparison flight. 43
28b Data from RTI/Battelle comparison flight. 44
29 Comparison data for RTI solid phase and Bendix gas phase 47
ozone analyzers.
30 Results of audits of ozone analyzers at stations during 54
period July 15-25, 1974, and August 15-21, 1974.
31 Mean diurnal ozone concentration at Wilmington, Wooster, 66
and McConnelsville, Ohio, from June 14-August 31, 1974.
32 Mean diurnal ozone concentration at Wilmington, Ohio; 67
DuBois, Pennsylvania; and McHenry, Maryland, from June 14-
August 31, 1974.
33 Mean diurnal ozone concentration for Canton, Cincinnati, 68
and Cleveland, Ohio, from June 14-August 31, 1974.
34 Mean diurnal ozone concentration for Columbus and Dayton, 69
Ohio; and Pittsburgh, Pennsylvania, from June 14-August 31,
1974.
35 Mean diurnal ozone concentration at McHenry (Garrett 70
County Airport) Station for 1972, 1973, and 1974.
36 Mean diurnal nitrogen dioxide concentration at Wilmington, 71
Wooster, McConnelsville, Ohio; DuBois, Pennsylvania; and
McHenry, Maryland, from June 14-August 31, 1974.
37 Mean diurnal concentration of total hydrocarbon, methane, 73
and carbon monoxide for Wilmington, Ohio, from June 14-
August 31, 1974.
38 Mean diurnal concentration of total hydrocarbon, methane, 74
and carbon monoxide for Wooster, Ohio, from June 14-
August 31, 1974.
39 Mean diurnal concentration of total hydrocarbon, methane, 75
and carbon monoxide for McConnelsville, Ohio, from June 14-
August 31, 1974.
40 Square wave flight pattern. 79
41 Double box flight pattern. 79
ix
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LIST OF FIGURES (Continued)
Figure Page
42 Square wave flight of June 27, 1974. 81
43 Ozone, acetylene, and isopentane concentrations upwind 84
. and downwind of Columbus—flight of June 27, 1974.
44 Square wave flight of July 16, 1974. 87
45 Ozone concentration versus distance and time along the 89
line of wind flow—flight of July 16, 1974.
46 Isopentane, acetylene, and carbon monoxide concentra- 91
tions upwind and downwind of Columbus—flight of
July 16, 1974.
47 Square wave flight of July 21, 1974. 93
48 Acetylene, isopentane, and carbon monoxide concentra- 95
tions upwind and downwind of Columbus—flight of
July 21, 1974.
49 Square wave flight of July 25, 1974. 97
50 Acetylene and isopentane concentrations upwind and 98
downwind of Columbus—flight of July 25, 1974.
51 Double box flight of July 6, 1974. 101
52 Double box flight of July 19, 1974. 104
53 Ozone concentrations along diagonal flight legs— 107
flight of July 9, 1974.
54 Suggested plume from Columbus: Flight of July 9, 1974. 110
55 Ozone concentrations at 762 m (2500 ft) msl downwind of 112
an urban area. Wind speed 3.6 m/sec (8 mph)—July 9, 1974.
56 Double box flight of July 13, 1974. 113
57 Eastern flight of August 21, 1974. 118
58 Vertical profile flights, Wilmington, Ohio, August 1, 1974. 122
59 Frequency distribution of times of maximum hourly ozone 130
concentration—rural stations.
f-, Frequency distribution of times of maximum hourly ozone 131
concentration—rural stations.
61 Frequency distribution of times of maximum hourly ozone 133
concentration—rural and urban stations.
62 Frequency distribution of times of minimum hourly ozone 135
concentrations for rural stations.
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LIST OF FIGURES (Continued)
Figure Page
63 Frequency distribution of times of minimum hourly ozone 136
concentrations for urban stations.
64 Comparison of frequency distributions of minimum hourly 138
ozone concentrations for rural and urban stations.
65 Variation of ozone and acetylene with time of day, Ohio 140
ground stations.
66 Acetylene and ozone variations, diurnal study, Wilmington, 141
Ohio, July 18, 1974.
67 Acetylene and ozone variations, diurnal study, Wilmington, 142
Ohio, July 23, 1974.
68 Acetylene and ozone variations, diurnal study, Wilmington, 143
Ohio, August 14, 1974.
69 "Maximum Effect" curve (Ground Station Data). 148
70 "Maximum Effect" curve (Aircraft Data). 149
71 The area average value of the maximum ozone concentration 151
(solid line) and the area average surface pressure (dashed
line) versus day of the month for the latter part of the
summer 1974.
72 The area average value of the maximum ozone concentration 152
(solid line) and the area average surface pressure (dashed
line) versus day of the month for the latter part of the
summer 1973.
73 Nine-point running average of the data presented in 153
figure 71.
74 Nine-point running average of the data presented in 154
figure 72.
75 The variation of the 8-hour average value (1200 to 156
2000 EOT) of ozone (yg/m3) for the period July 5-11, 1974,
in the eastern United States.
76 A) Surface pressure (mb with only tens and units digits 157
given) analysis (1700 EOT); B) Resultant winds; C) Mean
cloud cover (tenths) (0700 to 1900 EOT) for July 6, 1974.
Eight-hour average ozone values (yg/m3) (1200-2000 EDT)
indicated at each station.
77 A) Surface pressure (mb with only tens and units digits 159
given) analysis (1700 EDT); B) Resultant winds; C) Mean
cloud cover (tenths) (0700 to 1900 EDT) for July 8, 1974.
Eight-hour average ozone values (yg/m3) (1200-2000 EDT)
indicated at each station.
xi
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LIST OF FIGURES (Continued)
Figure
78 A) Surface pressure (mb with only tens and units digits 160
given) analysis (1700 EDT); B) Resultant winds; C) Mean
cloud cover (tenths) (0700 to 1900 EDT) for July 11, 1974.
Eight-hour average ozone values (yg/m3) (1200-2000 EDT)
indicated at each station.
79 The variation of the 8-hour average value (1200 to 161
2000 EDT) of ozone (yg/m3) for the period June 20-23, 1974
in the eastern United States.
80 A) Surface pressure (mb with only tens and units digits 162
given) analysis (1700 EDT); B) Resultant winds; C) Mean
cloud cover (tenths) (0700 to 1900 EDT) for July 22, 1974.
Eight-hour average ozone values (yg/m3) (1200-2000 EDT)
indicated at each station.
81 The variation of the 8-hour average value (1200 to 164
2000 EDT) of ozone (yg/m3) for the period August 25 to
September 5, 1973, in the eastern United States.
82 A) Surface pressure (mb with only tens and units digits 165
given) analysis (1700 EDT); B) Resultant winds; C) Mean
cloud cover (tenths) (0700 to 1900 EDT) for August 27,
1973. Eight-hour average ozone values (yg/m3) (1200-
2000 EDT) indicated at each station.
83 A) Surface pressure (mb with only tens and units digits 166
given) analysis (1700 EDT); B) Resultant winds; C) Mean
cloud cover (tenths) (0700 to 1900 EDT) for August 29,
1973. Eight-hour average ozone values (yg/m3) (1200-
2000 EDT) indicated at each station.
84 A) Surface pressure (mb with only tens and units digits 168
given) analysis (1700 EDT); B) Resultant winds; C) Mean
cloud cover (tenths) (0700 to 1900 EDT) for September 4,
1973. Eight-hour average ozone values (yg/m3) 1200-
2000 EDT) indicated at each station.
85 Average annual hydrocarbon emissions density, 1970 tons 171
mi~2. Source: National Emissions Data Summary.
86(a) Air parcel trajectories arriving at three locations for 174
the indicated 12-hour average ozone concentrations.
The triangle (A) indicates the 12, 24, 36 and 48-hour
positions of parcels arriving at 0000 GMT; the squares
(D) represent those parcels arriving at 1200 GMT.
xii
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LIST OF FIGURES (Continued)
Figure
86(b) Air parcel trajectories arriving at three locations for 175
the indicated 12-hour average ozone concentrations.
The triangle (A) indicates the 12, 24, 36 and 48-hour
positions of parcels arriving at 0000 GMT; the squares
O represent those parcels arriving at 1200 GMT.
86(c) Air parcel trajectories arriving at three locations for 176
the indicated 12-hour average ozone concentrations.
The triangle (A) indicates the 12, 24, 36 and 48-hour
positions of parcels arriving at 0000 GMT; the squares
O represent those parcels arriving at 1200 GMT.
87 Population density by counties: 1970. 185
88 Tracks of centers of anticyclones at sea level, August 186
1973.
xiii
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LIST OF TABLES
Table
1 Pollutants measured at monitoring stations 11
2 Calibration techniques 22
3 Results of statistical comparison of the RTI solid 46
phase instrument versus Bendix gas phase instrument
4 Program schedule 51
5 Listing of aircraft flights 52
6 Statistical summary of hourly ozone concentration 56
measurements by station (June 14-August 31, 1974)
7 Summary of ozone data above NAAQS by station (June 14- 57
August 31, 1974)
8 Statistical summary of hourly nitrogen dioxide concen- 57
tration measurements by station (June 14-August 31,
1974)
9 Statistical summary of hourly total hydrocarbon, methane 58
and carbon monoxide concentration measurements by
station (June 14-August 31, 1974)
10 Cumulative frequency distributions of hourly concentra- 60
tion of ozone by station (June 14-August 31, 1974)
11 Cumulative frequency distributions of hourly concentra- 61
tion of nitrogen dioxide by station (June 14-August 31,
1974)
12 Cumulative frequency distributions of hourly concentra- 62
tions of total hydrocarbon, methane, and carbon monoxide
by station (June 14-August 31, 1974)
13 Means of hourly concentrations of ozone for each hour of 64
day (June 14-August 31, 1974)
14 Means of hourly concentrations of nitrogen dioxide, total 65
hydrocarbon, methane, nonmethane hydrocarbon, and carbon
monoxide for each hour of day (June 14-August 31, 1974)
15 Comparison of low altitude resultant wind velocity at 76
selected locations by month
16 Abstract of hydrocarbon data: Square wave flight of 82
June 27, 1974
17 Abstract of hydrocarbon data: Square wave flight of 88
July 16, 1974
18 Abstract of hydrocarbon data: Square wave flight of 94
July 21, 1974
xiv
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LIST OF TABLES (Continued)
Table Page
19 Abstract of hydrocarbon data: Square wave flight of 99
July 25, 1974
20 Abstract of hydrocarbon data: Double box flight of 102
July 6, 1974
21 Abstract of hydrocarbon data: Double box flight of 105
July 9, 1974
22 Wind observations, July 9, 1974 108
23 Characteristics of ozone concentration distributions 109
by flight leg
24 Abstract of hydrocarbon data: Double box flight of 114
July 13, 1974
25 Abstract of hydrocarbon data: Eastern flight of 119
August 21, 1974
26 Abstract of hydrocarbon data: Vertical profile flight, 123
Wilmington, Ohio, August 1, 1974
27 Abstract of hydrocarbon data: Vertical profile flight, 124
Wooster and McConnelsville, Ohio, August 13, 1974
28 Abstract of hydrocarbon data: Vertical profile flight, 125
Wilmington, Ohio, August 15, 1974
29 Summary statistics for the daily maximum ozone concen- 132
tration for five rural and six urban stations
30 Summary statistics for the daily minimum ozone concen- 134
tration for five rural and six urban stations
31 Abstract of hydrocarbon data: Diurnal study, Wilmington, 144
Ohio, July 18, 1974
32 Abstract of hydrocarbon data: Diurnal study, Wilmington, 145
Ohio, July 23, 1974
33 Abstract of hydrocarbon data: Diurnal study, Wilmington, 146
Ohio, August 14, 1974
34 Concentrations of tropospheric ozone as given in more 179
recent and extensive studies. (From Junge, "Air Chemistry
and Radioactivity")J-/
35 Summary of simulated time-concentration profiles for 180
propylene-NO chemistry.3-*-^/
X
36 Summary of simulated time-concentration profiles for 181
propylene-NO chemistrya,b/
37 Jeffries'-Sickles' reaction mechanism 183
xv
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1.0 INTRODUCTION
Photochemical smog until recently has been generally considered an
urban phenomenon. Control strategies and implementation plans to achieve
the 1971 National Ambient Air Quality Standard (NAAQS) for photochemical
o
oxidants [160 yg/m (0.08 ppm) hourly average not to be exceeded more than
once per year] have mostly been focused on cities where the smog problem
has been identified.
In the late 1960's, ozone concentrations in rural areas in excess of
the generally accepted range for natural surface air (0.02-0.06 ppm,
average < 0.02 ppm)— were measured. As a specific example, reports of
damage to Christmas tree plantations in the area of Mount Storm, West
Virginia, and Garrett County, Maryland, led in 1970 to air pollution studies
21
and special oxidant measurements. Unexpectedly high oxidant— and high
ozone— concentrations were found at the above-mentioned locations. The
Environmental Protection Agency (EPA), in 1972, contracted with the Research
Triangle Institute (RTI) to conduct a study of atmospheric ozone in Garrett
4/
County, Maryland, and Preston County, West Virginia.— This 1972 study
confirmed the earlier reports of high ozone concentrations; approximately
11 percent of 1,043 hourly measurements made at the Garrett County, Mary-
land, Airport during the summer of 1972 exceeded the NAAQS (160 yg/m ).
Similar findings were obtained at satellite locations located around the
base stations 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 location developed
within particular air masses, which acquired and maintained their char-
acteristics over broad geographic regions.
In the summer of 1973, in order to further assess the areal extent of
the rural high ozone concentrations, the EPA contracted with RTI to estab-
lish a network of four monitoring sites for the measurement of ground-
level ozone concentrations and to carry out airborne measurements of ozone
with an instrumented twin-engine aircraft.
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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 was exceeded during 15 percent of 1,663 hours at
Lewisburg, West Virginia; 37 percent of 1,652 hours at McHenry, Maryland;
30 percent of 2,131 hours at Kane, Pennsylvania; and 20 percent of 1,785
hours at Coshocton, Ohio.—
In an effort to obtain information that would bear on the question of
whether control of hydrocarbon emissions in urban areas could cause an
abatement of the high rural ozone concentrations, the EPA funded the present
study, in which relationships were sought between the rural oxidant (ozone)
concentrations and ozone precursors—that is, hydrocarbons and oxides of
nitrogen.
Specifically, the study was to investigate the urban hydrocarbon-
"downwind" ozone relationship and, if possible, to obtain information that
would indicate whether hydrocarbons from one city could influence the ozone
concentration of another.
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2.0 STUDY PLAN
An Investigation into possible relationships between urban hydrocarbon
and rural oxidant concentrations was designed to determine changes in con-
centrations of specific atmospheric pollutants and classes of pollutants
during the passage of air over and downwind of an urban area. Perturbations
in ozone concentration should occur in air moving over the earth's surface
from rural to urban to rural to urban areas. Hence, it could be theorized
that generation of ozone downwind from the cities would be accompanied by
decreases in concentrations of the oxides of nitrogen and in the more
reactive hydrocarbons, both by dilution and by reaction.
2.1 Design of Study
In order to accomplish the objective set forth in section 2.0,
measurements of the concentration of ozone (0 ), oxides of nitrogen (NO ),
J X
and hydrocarbons (HC) of different reactivity uiust be obtained in air
flowing from an urban area. To determine the changes in concentrations and
in concentration ratios, measurements must be made at two or more points
downwind of the urban area. Unfortunately, optimum distances (or travel
times) for detecting the postulated concentration changes are not known. A
further complication in designing a measurement-station array is that the
normal day-to-day variations in wind direction preclude the selection of
a line that, with a high degree of confidence, can be assumed to represent
flow from the urban areas.
Additionally, in establishing the measurement protocol for achieving
the objective, provision must be made for assuring that useful data
are collected under each of several meteorological conditions. Pri-
marily, these meteorological conditions can be separated into those
providing a well-defined flow pattern and those representing stagnant
conditions characterized by low wind speed with variable direction.
Based on the above considerations, two modes of measurement were
employed: a network of five fixed, rural, ground-level stations and an
instrumented airplane flying specified patterns. These are discussed
in the following paragraphs.
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2.1.1 Ground-Level Stations
Since the basic problem is the occurrence of high ozone concen-
trations in rural air, a network of ground stations was established
in order to document occurrence of such concentrations during the obser-
vation program.
Central Ohio, specifically the city of Columbus, was selected as the
key area for investigation. Of all the areas in the Ohio Valley, the
vicinity of Columbus has the most uniform terrain, and synoptic wind flow
should be minimally affected by local topography. Finally and most im-
portant, persistent periods of ozone concentrations in excess of the National
Ambient Air Quality Standard (NAAQS) have been observed in rural air in
this region.
Figure 1 shows the selected locations of fixed ground stations for
the study. The station at McHenry, Maryland, provides continuity with
previous studies of ozone concentration in rural areas; data have been
collected at this site during the summers of 1972 and 1973. The other
eastern station is at DuBois, Pennsylvania, and the remaining three sta-
tions are located at Wilmington, Wooster, and McConnelsville, Ohio.
Wilmington was selected as the base station for the field measurement
program which extended from June 14 to August 31, 1974. Data from these
rural stations were supplemented by data from urban stations, which were
operated under the auspices of the Environmental Protection Agency. These
urban stations were located in Pittsburgh, Canton, Cleveland, Dayton,
Cincinnati, and Columbus; their geographical locations with respect to
the rural stations are shown in figure 1.
2.1.2 Airborne Measurements
Flight patterns were selected to provide for the collection of
data at several distances downwind from the urban area. Two flight pat-
terns were used. One of these (fig. 2) is a "square wave" pattern which
was flown on occasions when the advective transport was predictable (i.e.,
windspeeds equal to or greater than 7 knots) and could be expected to
persist over a 4- to 6-hour period. The pattern extends from 37 kilo-
meters upwind of the city, in order to provide background data, and up to
185 kilometers downwind of the city. A straight path flight returns over
the area covered to measure the changes with time in pollutant concen-
trations.
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0
Indianapolis
Cleveland
(Wooster)
Canton
Columbus
Dayton
(DuBois)
Pittsburgh
(McConnelsville) 1 ~~
(Wilmington)
(McHenry)
/
Cincinnati
rv
r v Louisville
CJ
V.
I Charleston
^
s
City Stations
(6)
Rural Sites
(5)
Figure 1. Location of fixed ground stations.
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COLUMBUS
Advective transport
(wind speed 2: 7 knots)
Figure 2. Square wave flight plan.
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The second flight pattern was in the shape of a double box (fig. 3).
This flight was used under stagnant air mass conditions (i.e., wind speed
less than 3 knots and wind direction undefined). As shown in the figure,
a diagonal path over the urban area is superimposed on a pattern of two
squares. The inner square has side lengths of 46 kilometers; the outer
has side lengths of 139 kilometers.
Comparison of concentration values obtained with the airplane instru-
ments with those at the base station was made by a low-level flight over
the ground station (approximate altitude of 15 meters) at the beginning
and the end of each flight pattern.
The double box flight patterns retained the same orientation for all
flights. The square wave pattern was oriented according to the predicted
wind directions, with the long leg downwind of the urban area.
Both square wave and double box flights were made at an altitude
midway between the surface and the top of the mixing layer. All flights
were planned for cloud-free conditions at flight level and between flight
level and the surface.
In addition to the patterned flights, certain other flights were
made: 1) an eastward flight into Pennsylvania to examine the areal
distribution of the ozone, 2) vertical profiles in the area of the base
station (morning, midday, and evening), and'3) a flight between the three
Ohio stations with vertical profiles at each station.
2.2 Analysis Procedure
The relationships between urban hydrocarbons and rural-area high
ozone concentrations were investigated through study of measurements of
concentrations of:
total hydrocarbon (THC)
methane (CH.)
4
ozone (0_)
nitrogen dioxide (NC- )
selected hydrocarbons, including acetylene.
Gas chromatographic analysis of selected hydrocarbons in grab samples was
provided by the Chemistry and Physics Laboratory of National Environmental
Research Center, Research Triangle Park, North Carolina.
-------
Cincinnati
Stagnation situation
(wind speed < 3 knots)
X
Figure 3. Double box flight plan.
-------
Values and ratios of concentrations of these pollution components were
examined, and comparisons were made upwind, over, and downwind of Columbus,
using data collected from the airplane flights. Ground station data were
used to verify the occurrence of rural high concentrations of ozone and to
determine concurrent concentrations of THC, CH,, and NO . Gas chromatograms
of grab samples from the three ground stations near Columbus were used to identify
hydrocarbon species for the identification of possible tracers (e.g., C~H )
indicating urban-generated pollution.
The rationale for the analysis is based on the assumption that the
NMHC/C^tL ratio should provide an indication of the contribution by the
city to the total nonmethane hydrocarbon input, and an indication of the
point at which the urban pollutant input no longer has an influence or
where its presence can no longer be detected. Gas chromatograms of the
individual organic compounds should show whether or not the city organics, as
a group of compounds, become indistinguishable from the hydrocarbon com-
pounds in the background air entering the city. Under ideal circumstances,
by comparing these ratios and concentrations obtained from the aircraft
and from the ground stations with the 0 readings, a sound judgement can
be made as to whether, and if so, to what degree, the hydrocarbons of the
city exert a detectable influence on 0 concentrations in the background
system.
-------
3.0 PROCEDURE
This section describes the protocol for the ground station network,
aircraft measurement program, and gas chromatographic field facility.
Site locations, instrumentation, calibration, maintenance, and data-
processing procedures employed in each of the above—mentioned areas are
described.
3.1 Ground Stations
3.1.1 Sampling Protocol
The field measurement program was designed to measure continuously
the ambient concentration of 0 , NO , THC, CH and NMHC by difference
at each of three manned stations in central Ohio, and 0 and NO at two
stations—one each in Pennsylvania and in Maryland. Availability of
specific hydrocarbon analyzers and the necessity of full-time field
operators restricted NMHC measurements to the three stations in central
Ohio. In addition to the five rural stations, the Quality Assurance and
Environmental Monitoring Laboratory of the Environmental Protection Agency
maintained and operated ozone analyzers at six city locations surrounding
the general study area. The six cities were Canton, Cincinnati, Cleve-
land, Columbus, and Dayton, Ohio, and Pittsburgh, Pennsylvania. Grab
samples were also collected daily at the three sites in central Ohio and
sent to the Wilmington site for subsequent analysis of individual hydro-
carbons by gas chromatography. Pollutants measured at each ground station
are listed in table 1.
3.1.2 Site Location/Description of Monitoring Stations
The principal criteria for the selection of a monitoring station
location were: 1) that the location be relatively free of natural and
manmade obstructions to air movement, 2) that it be removed from anthro-
pogenic sources of 0 precursors, and 3) that it be readily accessible by
aircraft in order to facilitate timely maintenance and routine calibra-
tion schedules. The locations selected met these criteria.
3.1.2.1 Wilmington, Ohio (Wilmington Industrial Air Park)
The Wilmington Industrial Air Park (formerly the Clinton County Air
Force Base) located 6 kilometers southeast of Wilmington, Ohio, served
as the base station for operations during the summer oxidant study.
Four vans (i.e., RTI base station, Environmental Protection Agency
10
-------
Table 1. Pollutants measured at monitoring stations
Station
Pollutants
Wilmington, Ohio
McConnelsville, Ohio
Wooster, Ohio
McHenry, Maryland
DuBois, Pennsylvania
Canton, Ohio
Cincinnati, Ohio
Cleveland, Ohio
Columbus, Ohio
Dayton, Ohio
Pittsburgh, Pennsylvania
0 , N02, THC,
03> N02, THC,
03, N02, THC,
N°
, HC by GC
t
, HC by GC
, HC by GC*
**
Base Station
**
Grab Samples
Chemistry and Physics Laboratory Van, RTI trailer, and Rutgers University
Van) and the Environmental Protection Agency Aircraft (C-45) were based
there. With the exception of the Rutgers University van, which was on site
for only 2 weeks in July, the facilities were operated at the base station
from the middle of June until the end of August. Figure 4 shows an aerial
view of the airfield and the surrounding terrain. Figure 5 is a photograph
showing the C-45 aircraft, the RTI Environmental Monitoring Laboratory, and
the EPA Chemistry and Physics Laboratory Van on location at Parking Apron
"C", Wilmington Industrial Air Park.
The elevation of the airfield is 403 meters above mean sea level arid
exposure is excellent from all directions. The airfield and hangars are
leased to Overseas National Airways, which maintains a maintenance facility
there. Overseas National Airways has jurisdiction over the airfield, and
traffic in and out averages approximately three flights per week.
The RTI Environmental Monitoring Laboratory was used as the base
station at Wilmington. It is a self-contained, 9.4-meter motorized vehicle,
custom-built for air quality monitoring. It is outfitted with the latest
complement of air quality monitoring instrumentation, a self-contained
11
-------
Figure 4. Aerial view of Wilmington Industrial Air Park.
Figure 5. Aircraft, RTI, and EPA vans located on
Parking Apron "C," Wilmington Industrial Air Park.
12
-------
calibration system for each pollutant analyzer, and a digital magnetic
tape recording system coupled to a minicomputer capable of online data
processing and printout of real-time air quality data in concentration
units and storage of the raw data on magnetic tape. The motorized van
has a self-contained motor-generator for generation of electrical power,
a controlled environment (heating and cooling), an a.c. voltage regulator,
a glass and Teflon manifold system for passage of air samples to the
monitors, a tower for mounting various meteorological sensors, and
storage space for compressed air and gas tanks:
Two interior views of the vehicle are shown in figures 6 and 7.
3.1.2.2 Wooster, Ohio (Wayne County Airport)^
The Wooster, Ohio, station was located at the Wayne County Airport,
approximately 10 kilometers northeast of Wooster, and is 346 meters
above mean sea level. Exposure is excellent from all directions.
Figure 8 is an aerial view of the county airfield and the surrounding
terrain.
Instrumentation and associated equipment were housed in an 2.4-by-
6-meter construction trailer modified to accommodate the ambient air
Figure 6. Interior view of Environmental Monitoring Laboratory
showing some of the ambient air analyzers.
13
-------
Figure 7. Interior view of Environmental Monitoring Laboratory
with data acquisition system in foreground.
quality analyzers and the data-acquisition and calibration systems (fig. 9).
Two air-conditioning units were installed on either end of the construction
trailer to control the interior temperature to approximately 22° + 2°C. An
interior view of the station is pictured in figure 10. Ozone, N0~, THC, and
CH, concentrations were recorded at this station. Also, grab samples were
collected twice daily—once in the morning and again in the evening. These
samples were forwarded daily to Wilmington by United Parcel Service for
subsequent analysis of individual hydrocarbons by gas chromatography. The
ambient air inlet was located at a point 3 meters above the roofline. An
all glass and Teflon inlet system with blower was used to aspirate sample air
through the manifold. Each analyzer sampled directly from the manifold.
14
-------
Figure 8. Aerial view of Wooster, Ohio,
(Wayne County Airport) site.
Figure 9. Ex-terior view of Wooster, Ohio,
(Wayne County Airport) station.
15
-------
Figure 10. Interior view of Wooster, Ohio,
(Wayne County Airport) station.
3.1.2.3 McConnelsville, Ohio (Morgan County Airport)
The McConnelsville, Ohio, station was located at the Morgan County
Airport situated approximately 40 kilometers southeast of Zanesville,
Ohio. The airport elevation is approximately 305 meters above mean sea
level, and the site has good exposure from all directions. Due to the
limited access to electric power at this site, a 2.4-by-6-meter con-
struction trailer was located adjacent to a small building, which served
as a terminal. An aerial view of the site with respect to the surrounding
terrain is shown in figure 11. An exterior view of the trailer located on
site is shown in figure 12. An interior view of the station is pictured
in figure 13. The measured pollutants and details of the sampling
station were identical to those at Wooster. Aircraft traffic into Morgan
County was mainly local, small-engine planes and averaged less than three
flights per week.
16
-------
Figure 11. Aerial view of McConnelsville, Ohio,
(Morgan County Airport) site.
Figure 12. Exterior view of McConnelsville, Ohio,
(Morgan County Airport) station.
17
-------
Figure 13. Interior view of McConnelsville, Ohio,
(Morgan County Airport) station.
Terminal
building
Air monitoring
station
Figure 14. Diagram of DuBois-Jefferson
Municipal Airport.
18
-------
3.1.2.4 DuBois, Pennsylvania (DuBols-Jefferson Municipal Airport)
The DuBois, Pennsylvania, station was located at the DuBois-Jefferson
Municipal Airport 13 kilometers northwest of DuBois, Pennsylvania. The
site is 554 meters above mean sea level and is well ventilated. An aerial
view of the site with respect to the surrounding terrain is shown in
figure 14. Instrumentation and associated equipment to measure 0., and
NO- concentrations were housed in a 2.4-by-4.6-meter construction trailer,
similar to the trailer shown in figure 12 and parked approximately 183
meters away from, but parallel to the runway. An air-sampling inlet system
identical to that used at the previously mentioned stations was used to
bring sample air to each analyzer. The DuBois station was not a manned
station, but was checked daily by an employee of the airport.
3.1.2.5 McHenry, Maryland (Garrett County Airport)
The McHenry, Maryland, station was located at the Garrett County
Airport, approximately 884 meters above mean sea level. The airport com-
plex consists of 762-meter paved landing strip, an apron, hangars, and a
•
terminal building. The airport is mainly used by small, private aircraft.
Figure 15 is a diagram of the airport which shows the location of
the air-monitoring station. An exterior view of the station is shown in
figure 16. Ozone and N0? concentrations were measured at this site. The
air quality analyzers, strip-chart recorders, and data-acquisition system
were located in a small workroom at the east end of the hangar. The
interior environment of the station was controlled by an 18,000 Btu
heating/cooling system. The ambient air inlet system and operation of the
analyzers at this unmanned station were identical to those at the DuBois
station.
3.1.3 Air Quality Measurements
3.1.3.1 Ins trumentation
Ambient ozone concentrations were measured at all stations (i.e.,
rural, urban) using the Bendix Model 8002 chemiluminescent ozone analyzer
or equivalent. The principle of operation of this instrument is based on
the gas-phase chemiluminescent reaction between ethylene and ozone. The
reliability, stability, specificity, and precision of the ozone measure-
ments by this technique have been demonstrated and adequately described
in the literature— .
19
-------
I Hangar
Workroom
(location of instrument)
:\
762m runway
Apron
Parking
area
n
Gas
pumps
50 100 150
J Terminal
/ building
/
Meters
Figure 15. Diagram of Garrett County Airport.
Figure 16. Exterior view of McHenry, Maryland,
(Garrett County Airport) station.
20
-------
Nitrogen dioxide concentrations were measured at all stations using
the Bendix Model 8101-B NO-NO -N09 analyzer. The principle of operation
X £,
of this instrument is based on the gas-phase chemiluminescent reaction
between NO and 0~. The measurement of N02 concentration by this instru-
ment requires that NO- be reduced to NO prior to the reaction with 0.,.
The sum of the NO measurement plus that produced by reducing N0~ to NO
is the nitrogen oxide (NO ) concentration. Subtraction of the previous
X.
NO measurement from the NO measurement gives the N0? concentration.
X ^
Nonmethane hydrocarbon (NMHC) concentrations were measured at three
stations (i.e., Wilmington, Wooster, McConnelsville) using the Beckman
6800 air quality chromatograph. The Beckman 6800 air quality chromato-
graph utilizes an automatic gas chromatographic-flame ionization detector
(GC-FID) to measure THC and CH, in ambient air. The NMHC concentration of the
ambient sample is computed by subtraction of CH, from the THC measurement.
Detailed hydrocarbon analyses of grab samples collected during air-
craft flights and at manned ground stations in Ohio were obtained by the
Chemistry and Physics Laboratory of the Environmental Protection Agency
using a Perkin-Elmer Model 900 chromatograph system. The system consisted
of two Perkin-Elmer Model 900 chromatographs with a PEP-1 data-reduction
system. Three columns were employed for the analysis of selected hydro-
carbon fractions: 1) a 2.4-m x 0.15 cm i.d. silica gel at 30°C (C^-C,
aliphatics), 2) a 91.4-m x 0.15 cm i.d. dibutylmaleate open tubular column
at 0°C (C^-Cg aliphatics), and 3) a 91.4-m x 0.15 cm i.d. open tubular
column coated with m-bis-m-phenoxyphenoxy benzene at 70°C (C,-C-n aromatics).
— — o ID
The analytical and sampling techniques system employed here has been
well documented in the literature.—
3.1.3.2 Instrument Calibration and Maintenance
Dynamic calibration techniques were used to calibrate each analyzer
at 2-week intervals during the 75-day period of field operations and are
outlined in table 2. Data obtained from the calibrations were used to
provide updated transfer equations for converting voltage outputs to
o
pollutant concentrations in physical units (yg/m ).
21
-------
Table 2. Calibration techniques
Pollutant Calibration technique
Ozone Ultraviolet ozone generator referenced
to the neutral-buffered potassium iodide
method (Federal Reference Method)
Nitric oxide/nitrogen dioxide Gas phase titration technique
Hydrocarbons (THC, CH.) Standard calibration gas certified as
to CH. and THC content
4
Selected hydrocarbons Mixtures prepared from pure hydrocarbons
Brief descriptions of the calibration techniques cited in table 2
follow:
1. Ozone—Ultraviolet ozone generator referenced to the neutral-
buffered potassium iodide (KI) method.
Dynamic calibration of the ozone analyzers was accomplished by
use of an ultraviolet ozone generator. The ozone source consists of a
shielded 20.3-cm mercury vapor lamp which irradiates a 1.6-cm quartz tube
through which clean (compressed) air flows at 5 £/min. Variable ozone
concentrations over the measurement range can be generated by variable
shielding of the lamp envelope. Although the ultraviolet ozone generator
had been shown to be quite stable and reproducible, the neutral buffered
KI method was used as the reference method.
2. Nijrric oxide/nitrogen dioxide—Gas phase titration technique.
The gas phase titration technique developed by Hodgeson and
associates at the Environmental Protection Agency was used for dynamic
calibration of the chemiluminescent NO-NO -N0~ analyzers. The technique
X ^
is based on the application of the rapid gas phase reaction between nitric
oxide and ozone to produce a stoichiometric quantity of nitrogen dioxide.
3
Nitric oxide (61 mg/m ) in nitrogen (contained in pressurized cylinders)
is diluted with zero air to provide NO concentrations in the range 20 to
3
940 yg/m and used to calibrate the NO and NO channels. Nitrogen
X.
dioxide concentrations are produced by quantitative reaction of NO with
ozone. Primary calibration of the concentration of NO in nitrogen was
achieved by titration of an NO concentration of 1.2 mg/m with successive
22
-------
3
concentrations of ozone (0 to 1.6 mg/m ) generated by an ozone generator
referenced to the neutral-buffered KI method. The NO concentration of
each cylinder was determined prior to going to the field, once per month
in the field, and at the conclusion of the study.
3. Methane calibration gas.
Calibration of the hydrocarbon analyzers was accomplished using
mixtures of stable gases prepared to exact concentrations in pressurized
cylinders. Mixtures of methane in air purchased from Scott Research
Laboratory with a certificate of analysis as to the methane and total
hydrocarbon concentrations were used for all calibrations.
4. Selected hydrocarbons.
Hydrocarbon standards used to calibrate the Perkin-Elmer gas
chromatograph were prepared at regular intervals using a dilution tech-
nique of pure compounds (i.e., 99.9 percent pure hydrocarbons) with
hydrocarbon-free air. Concentration mixtures in the parts-per-billion
to parts-per-million range were prepared using up to 50 compounds in the
C~ to C Q hydrocarbon range. Response factors were calculated by the
computer system for subsequent use in the analysis routine. Comparison
of the peak height, retention times, and area for hydrocarbons in standard
mixtures were used to identify and quantify the various hydrocarbons
collected in the grab samples.
A detailed discussion of the calibration methods and procedures
utilized during this program is given in appendix A.
Routine maintenance of the automated instruments was performed by the
operators at the three manned stations in Ohio. Maintenance of the
instruments at the DuBois and McHenry stations took place during the
regularly scheduled biweekly calibration trips. A complete record of
operational status (i.e., operational, repairs, maintenance, calibration,
1 -.operative, etc.) was maintained for each analyzer throughout the duration
f the measurements program at each station. This information was
necessary for quality control and for use in the data validation process.
When failures occurred, the instrument was brought back on line in
the most expedient manner (i.e., by substitution and/or repair). Periods
of failure and reasons are summarized in appendix B, "Performance
Characteristics and Operational Summaries for Instruments."
23
-------
3.1.4 Data Acquisition/Reduction
Ozone, NCL, THC, and CH, concentration data at each station were
recorded in analog form on strip-chart recorders and in digital form on
magnetic tape recorders. The strip-chart recorders were used for backup
data in case of failure of the magnetic tape unit and also as a real-time
record for assessment of the operational status of each analyzer. Primary
data storage was on magnetic tape.
Due to the unavailability of five identical data acquisition systems
and to other time constraints, three different systems were used to record
data at the five rural stations. Metrodata DL-630 data loggers were used
at the McConnelsville and Wooster stations; Westinghouse Pulse-0-Matic
recording systems were used at DuBois and McHenry; and a Hewlett-Packard
2015H data-acquisition system and HP-2100A computer were used at the
Wilmington station. A brief description of each data-acquisition system
is presented in the following paragraphs.
The Metrodata Model DL-630 data system used at Wooster and McConnels-
ville, Ohio, is a complete data-acquisition system capable of recording up
to 40 channels of analog data plus a time code, station identification, and
manual data entry on magnetic tape. Commands are locally selectable via
front-panel, lighted push buttons. Channel selection allows the observation
of the existing signal on any channel on the front panel, three-digit
display in essentially real-time. The scan rate is 40 channels/second and
data are recorded on magnetic tape at 5-minute intervals.
The Westinghouse Pulse-0-Matic magnetic tape data acquisition system
used to record data at DuBois, Pennsylvania, and McHenry, Maryland, inte-
grates the signal from the air quality analyzer for a 15-minute interval
and provides a true 15-minute average. A battery backup unit is included
in the recorder to preserve the time information on magnetic tape in the
event of a power failure.
The Hewlett-Packard data system used at the Wilmington station con-
sists basically of a digital magnetic tape data acquisition system and an
HP-2100 computer. The signals from the respective analyzers are scanned
at 5-minute intervals. These sampled voltages are digitized and recorded
on the magnetic tape in computer-compatible format; in addition, the
24
-------
scanned data are introduced into the minicomputer where the appropriate
transfer functions are applied to each of the analyzer signals and the
resulting values in concentration units are printed out. Five-minute data
are accumulated, and at the end of each hour a summary, which includes the
5-minute data plus the hourly average, is printed out for immediate use.
Field data recorded on magnetic tape from the Metrodata, Westinghouse,
and Hewlett-Packard data-acquisition systems were returned to Research
Triangle Institute for processing on a weekly and/or biweekly basis. The
data manipulation required to recover the data stored on a magnetic tape
consisted of two phases:
1. Translation of the tape to a form compatible with
available data-processing equipment, and
2. Processing the data on a computer to obtain concen-
3
trations in Mg/m .
The end result was a hard-copy printout, which was then available for
inspection and validation. This printout consists of the date, station
identification, hourly average of 5- or 15-minute readings, and 24-hour
3
average concentrations in ug/m for each pollutant.
In order to obtain a printout of data that contained all the infor-
mation, certain supplementary data had to be supplied to the computer.
These data included times when the instruments were inoperative or not
functioning properly and linear best-fit equations relating the voltage
output of the instrument to the concentration of the pollutant being
measured. The times for instruments being inoperative came from operator
logs, calibration log sheets, quality control charts, examination of pre-
liminary computer runs, and strip charts. The equations were derived from
data obtained during calibration—the known input gas concentrations and
the resulting voltage output from the instrument. A regression analysis
was performed on these points to obtain a best-fit equation characterizing
he instrument's response. The printout produced by the computer then
3
contained the data in yg/m . If data were absent or invalid, the number
99999.9 and a code letter were inserted to indicate the reason for loss of
data. A sample page of printout is shown in figure 17.
25
-------
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3.1.5 Data Validation and Quality Control
In order to achieve and maintain a high level of confidence in air
quality data, it is essential to monitor routinely critical instrument
parameters and to maintain appropriate records. Quality control was
initiated for the summer oxidant study by verification of calibration pro-
cedures, standards, and operating procedures, performing dynamic calibra-
tions at specified intervals; maintaining adequate records; and thoroughly
training operators.
Calibration data, as well as daily zero and span information when
available, were examined for excessive zero and span drift. If zero drift
exceeded + 1 percent of full scale per 24-hour period, the data of the
preceding 24-hour period were of questionable validity. Span drift was
determined from multipoint calibration data every 2 weeks. Span drift
exceeding + 3 percent per 2 weeks was usually associated with instrument
malfunction, and the data were deleted.
To verify data-recorder accuracy, a constant voltage data input
standard was recorded every 5 minutes (or 15 minutes) in conjunction with
the air quality data. It was not necessary to invalidate any ambient air
quality data resulting from analog-to-digital conversion errors.
At the completion of each computer program set, the processed data
were compared with strip-chart data for randomly selected periods. A
typical check included comparison of computer-processed data and strip-
chart data for six selected 1-hour averages per day. The recorded data on
strip charts were also edited for signs of equipment malfunctions, exces-
sive pollutant levels, or unusual diurnal patterns.
3. 2 Aircraft Measurement Program
3.2.1 Aircraft Flight Protocol
The two basic flight patterns flown during the field measurement pro-
gram were described in section 2.1.2, "Airborne Measurements." In addition
to these basic patterns, vertical profile flights and one eastern wide area
flight were flown. An RTI meteorologist at the base station provided the
RTI field manager with all meteorological information necessary to make
27
-------
decisions regarding when to fly and the type of aircraft mission to be
flown. His secondary duties included preflight planning, accompanying the
actual mission as an airborne observer, and finally assimilating and
summarizing the mission data into a useful format.
To perform the primary duty, the field meteorologist kept abreast of
the general synoptic weather situation through information provided by
local news media, supplementing this with real-time surface data obtained
from the Operation Section of Overseas National Airways located at
Wilmington Industrial Air Park. The primary criterion for a mission was
the condition of relatively clear skies at or below the flight level. When
such conditions were forecast for the following day, the RTI field manager
and the EPA flight crew were alerted. At 0845 the morning of the projected
mission, the meteorologist telephoned the National Weather Service Upper Air
Station at Dayton and obtained data for the lower 500 millibars from their
morning radiosonde flight. From the Dayton sounding, the meteorologist com-
puted the stability and forecast the depth of thermal mixing and the heights of
cloud layers that might form later in the day. Using this information
and the vertical wind profile, the decision was then made to fly either a
double box or a square wave, providing all other flight conditions such
as adequate VFR visibility and no severe weather forecast for the mission
area still prevailed. The sounding was also used to select a flight
altitude in the mixing layer but below any clouds that might form. In the
case of the square wave, wind direction at flight altitude determined the
orientation of the pattern.
Vertical ascents were occasionally flown when the meteorologist noted
some interesting features in the temperature profile, such as a subsidence
inversion. The long eastern wide area flight had only one meteorological
criterion, that of stagnant high pressure. Flight altitude was a function
of topography, and the pattern was determined by navigational criteria.
3.2.2 Aircraft System Description
Instrumentation for the measurement of ozone, oxides of nitrogen, and
temperature and equipment for the collection of grab samples were installed
aboard a C-45H aircraft, provided by the National Environmental Research
Center at Las Vegas, Nevada. The C-45 aircraft (fig. 18) with a full load
28
-------
Figure 18. Photograph of aircraft.
of fuel has a capacity for 340 kg of instrumentation and a crew of four—
pilot, copilot, meteorological observer, and instrument operator. Under
si
these conditions, the C-45 has an average cruising speed of 130 knots, a
climb rate of 152 m/min, and a flight range of approximately 5 hours.
Navigation equipment includes two VOR units with DME, and ADF, and a flux-
gate compass.
The air intake system used on the C-45 is illustrated in figure 19
and consisted of a 5-cm i.d. aluminum probe permanently mounted on the
underside of the aircraft nose approximately 1 meter forward of any point
on the plane. The probe was lined with 2.5-cm i.d. Teflon tubing to mini-
mize reaction of air pollutants with the manifold wall.
The other end of the Teflon tube extended inside the aircraft cabin.
Two 0.635-cm i.d. Teflon tubes and a temperature-sensing thermister were
inserted well into the 2.5-cm i.d. Teflon tube. One of the 0.635-cm i.d.
Teflon lines was connected to a glass sample manifold from which the 0~
and N0x analyzers sampled. Ram pressure created by air rushing through
29
-------
To instruments
Temperature
instrument
Aircraft body
To bag
sample
pump
(For hydrocarbon analysis)
0.635-cm i.d.
Teflon tube
Air temperature
sensor
Glass
tubing
insert
2.5-cm i.d.
Teflon
tubing
Inlet
Spacers
(aluminum &
plexiglass)
Am
Figure 19. Air-sampling probe used on C-45 aircraft.
the 2.5-cm i.d. tube forced a steady flow of sample air into the cabin mani-
fold. The pressure in the manifold was essentially that of the unpressurized
aircraft cabin, which prevented the pressurization of the instrument
sample inlets. The other 0.635-cm i.d. Teflon line was connected to a
stainless steel diaphragm pump used to fill sample bags. The air sample
inlet system was designed for a minimum of sample contamination by
emissions from the aircraft itself. Ram pressure caused an airflow through
the Teflon tube providing sufficient flushing to keep gases within the
aircraft cabin from diffusing into the tube and contaminating the air
sample stream. Tests were conducted to insure that contamination from
the interior of the aircraft was not getting into the sample manifold.
A block diagram of the instrumentation installed in the C-45 is shown
in figure 20 and included an RTI solid-phase ozone analyzer, a Bendix
30
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•To Tedlar bags
Output
signal
Switchin
network
Strip chart
recorders
NO-
NO,
Temp
Selectible
input
Figure 20. Block diagram of aircraft instrumentation.
N0-N09-N0 analyzer, a Yellow Springs temperature sensor, an air sample
^ X
pump, five strip-chart recorders, and a 2kW-Nova inverter. All instrumen-
tation was shock mounted with Areoflex twisted steel rope shock mounts.
The ozone analyzer used in the aircraft is a solid-phase chemilumi-
nescent instrument built by RTI. It is a self-contained instrument
requiring no external pressurized gas supplies of any kind. The analyzer
operates in a cyclic mode with a calibration signal response and a measure
cycle response output once during each 2-minute cycle. The performance
fi Q /
characteristics of the analyzer have been described in the literature.—'—
The Bendix 8101-B chemiluminescent analyzer was used in the aircraft
to monitor oxides of nitrogen. Support equipment on board for this instru-
ment included a compressed oxygen cylinder and a two-stage diaphragm vacuum
pump. The sample inlet for the instrument was from the same manifold as
the ozone analyzer.
31
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To sample inlet
on aircraft
ass wool
packed in S.S. tube
0.635-cm Teflon
tubing, flexible
SS metal
bellows
pump
Quick
disconnect
connector
set
20 liter
Tedlar bag
Figure 21. Air sample bag-filling system.
The system used for collecting grab samples is shown in figure 21.
The system consists of a stainless steel metal bellows pump with a manga-
nese dioxide catalytic converter on the input to convert any ozone to
oxygen. The output of the pump was connected to a 20-liter Tedlar bag
with Teflon lines using stainless steel, quick-disconnect fittings.
Temperature changes in the sample airstream were monitored by the
temperature section of a Yellow Springs Instrument Company Model 91 hygro-
meter. The temperature sensor, a small 0.635-cm diameter bead, was located
just inside the sample inlet downstream from the points where the bag
sample and ozone-oxides of nitrogen samples were drawn off.
The principal means of data acquisition aboard the aircraft were
five strip-chart recorders, Hewlett Packard/Mosely Model 680 units,
mounted in an instrument rack along with switching networks that allowed
the monitoring of each of the inputs on a digital voltmeter or the applica-
tion of a zero voltage to the recorders for a zero adjustment without
disconnecting any cables.
The power for each of the instruments was supplied by a 2-kW Nova
inverter powered by the aircraft 28-volt d.c. electrical system. The
inverter was a well-regulated unit with current limiting for overload
failure protection.
32
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3.2.3 System Operation
Procedures for the operation of the aircraft instruments were
established and documented early in the program so that data could be
taken under uniform conditions in the event of a change of operators.
Also, operating from predetermined procedures insured more consistent
operation with the same operator.
Operational procedures for the aircraft are broken down into four
categories: 1) preflight, 2) inflight, 3) routine calibration, and 4)
ground operation. The procedures for each area are listed step-by-step
in appendix E. The general objectives accomplished by the procedures are
described in the following paragraphs.
1. Preflight.
Preflight checks were made in order to insure that all instru-
ments were working and set to the proper range and mode of operation.
Also, the strip-chart recorders were checked for operation. The manifold
was checked to insure that the instruments were connected properly.
These procedures were set to insure that valid data collection began as
soon after takeoff as possible and that minimum data were missed due to
instruments being improperly set.
2. Inflight.
The primary function of the instrument operator was to annotate
the strip charts with time and to observe the instruments for symptoms of
erratic or abnormal operation. The meteorological observer operated the
bag sample apparatus and made pertinent observations of weather conditions
and aircraft location.
3. Routine calibration.
Routine calibrations were conducted on each of the gas analyzers
in the aircraft each day for which a flight was planned. Calibrations were
conducted against the instruments in the van which were considered as
"secondary field standards." The aircraft calibration was accomplished
in two steps: 1) calibration of a portable calibration unit and 2)
calibration of the analyzers using the portable calibration unit. The
procedures involved are discussed in section 3.2.4.1.
33
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4. Ground operation.
The instruments aboard the aircraft were operated continuously
during the summer study. Immediately after landing and taxiing to the air-
craft tie-down position, a 117-volt a.c. source was connected to the instru-
mentation before the aircraft engines were shut down. Prior to takeoff, at
least one engine was started, bringing a generator into operation before
ground power was disconnected from the aircraft instrumentation system.
Since the aircraft sampling probe system was designed only for operation
during flight, an alternative means was needed for supplying sample air to
the instruments while on the ground. This was accomplished by connecting
0.635-cm Teflon lines to the Instrument inlet. Each Teflon line extended
through the cockpit window and was supported approximately 1 meter
above the aircraft. Concentration values of nitrogen dioxide and ozone
could then be read from the instruments in the aircraft and compared to
those values being measured in the base station.
3.2.4 Instrument Calibration/Altitude Effects/Data Validation
3.2.4.1 Instrument Calibration
All gas analyzers were calibrated immediately before each flight.
The gas analyzers in the RTI van were of the same type as those
used in the aircraft and were considered secondary standards for the
aircraft calibrations. Specifically, the output concentration of a
portable calibration unit capable of generating 03, NO, and NC>2 was deter-
mined by connecting it to the analyzers in the base station and observing
their response. The portable unit was then carried to the aircraft and
operated under the same conditions (flow rates, pressures, line voltage,
etc.) as in the base station. The aircraft instruments were connected to
the portable calibration unit, and either the span was adjusted to its
proper setting (in the case of the Bendix NO-N02~NOx analyzer), or the
internal calibration level was determined (in the case of the RTI ozone
monitor). Zero determinations for the NC>2 instrument were carried out by
connecting a clean-up system to the sample input of the analyzer. No zero
adjustment was necessary on the ozone analyzer by virtue of the way the
output is computed. The temperature-measuring instrument aboard the
34
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aircraft did not require frequent calibration due to its inherent stability.
It was calibrated at the beginning and end of the program and twice between.
The calibration consisted of a two-point calibration, one at 0°C determined
by an ice bath and one at ambient temperature as measured by a lab-type
mercury thermometer.
3.2.4.2 Altitude Effects on Instrumentation
The environmental test chamber facility at NERC, Las Vegas, was used
to determine the effects of change in altitude on instrument responses prior
to their use in the aircraft measurement program. This facility consisted
of a sealable chamber approximately 71 cm x 81 cm x 152 cm high. Temper-
ature, dew point, and pressure could be set by control units external to
the chamber and could be varied during the test.
A series of tests was run on three instruments, the RTI ozone monitor,
a Bendix ozone analyzer, and a Bendix NO-NCL-NO analyzer. Each instrument
£• X
was placed in the chamber and calibrated. Then a constant concentration of
the gas being measured by the instrument was input to the instrument through
a port in the side of the chamber. The calibration gas was input to the
instrument through a glass manifold open to the inside of the chamber to
insure that the pressure on the sample inlet was the same as the chamber
pressure. The chamber then was depressurized in increments to the pressure
equivalent of 3,658-meter altitude (and beyond in some tests) while the
response of the instrument was being monitored on two strip-chart recorders.
Results of multiple runs of this test were processed to produce a curve for
each instrument. From this curve the percentage decline in instrument
response at a given altitude was determined. Curves for the two instru-
ments used in the aircraft are included in figures 22 and 23. A detailed
description of the test is included in appendix D.
In addition to the tests run in the chamber, tests of instrument
behavior were performed on the ozone instrument while airborne. A standard
calibration system using an ultraviolet ozone source and rotameter was used
aboard the aircraft with a modification on the output. A restriction was
placed on the output, along with a vent controlled by a valve (see fig.
24). By closing the valve, the calibration system could be pressurized.
35
-------
0)
CO
c
4-1 O
O CU
en
rH 0)
cu u
o
O T3
^1 a)
CX N
•H -H
O rH
(U 03
ff! 6
1-J
O
C
1.9 r
1.8 '
1.7 -
1.6 -
1.5
1.4
1.3 '
1.2 -
1.1 -
1.0
Figure 22.
6 8 10
Altitude (1000 feet)
Compensation factor for adjustment of Bendix NO-NO^-NO
analyzer data for effects of altitude.
1.6 r
-------
Needle valve
Used to adjust system
pressure
Calibration
system
Compressed
Air
Mass
flow
meter
Vent
Section of 0.32 OD Teflon
Altimeter
I 1
To instruments
Figure 24. System used to calibrate analyzers while airborne.
An altimeter was connected to the system so that the pressure could be
adjusted to the same level as it was on the ground. The flow out the vent
was monitored and the length of the 0.32-cm Teflon restriction adjusted so
that the flow out the vent did not exceed 1 &/min (at standard con-
ditions). This insured that sufficient calibration gas flowed through the
manifold to keep it flushed and not contaminated with cabin air.
Proper operation of the instruments was verified at the different
altitudes by measuring flow rate in flight. Sample flow rates were
monitored for the instruments during the tests on the aircraft at the
various altitudes. During routine flights, sample flow rates were checked
periodically to insure that the operating conditions were unchanged. This
insured that the results obtained during the altitude tests were still
valid (including the correction curves).
The results of these inflight calibration and operational verifi-
cation tests were in agreement with the tests run in the fixed chamber.
Repeatedly it was shown that the response of the instrument declined
linearly with ambient pressure.
37
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3.2.4.3 Data Validation
Various steps were taken to insure the validity of the data other
than those which were a part of the quality assurance program. These
included: 1) low altitude passes above the base station with all instru-
mentation in operation, 2) comparison of readings in the aircraft while on
the ground to those in the adjacent base station, 3) airborne comparison
of readings in the EPA aircraft with readings in another aircraft inde-
pendently instrumented and operated, and 4) hydrocarbon air sample contami-
nation tests. Data were also obtained during the program to demonstrate
the comparability of the RTI solid phase and Bendix gas phase chemilumi-
nescent ozone analyzers.
Fly-by Comparisons
Fly-bys were conducted by flying the aircraft over Wilmington Indus-
trial Air Park at an altitude between 15 and 30 meters above the terrain.
Generally, the aircraft approached the field from the end opposite the
base station (approach from the northeast) and flew over the taxiway
parallel to the runway. Flying in this manner, the aircraft could safely
achieve a lower altitude and hold it longer than flying from another direc-
tion over grass or wooded terrain. The time for the aircraft to fly from
the end of the runway to the base station took approximately 30 seconds,
which gave the instrument some time to stabilize before a reading was
taken.
A plot of the results is included in figure 25. Here the readings
taken from the airborne RTI instrument are plotted on the ordinate against
the fixed base station 5-minute instantaneous sample readings taken
closest in time plotted on the abscissa. Perfect agreement between the
two instruments would be indicated by a plot in which all points fell on a
line passing through the origin and inclined at an angle of 45°. The
departure of the instrument behavior from this ideal is not unexpected.
During the early hours of the day at a time when many of these passes were
made, a homogeneous concentration of ozone due to mixing had not been
achieved. This was borne out by observing the strip-chart trace in the
aircraft during the measure cycle. It was frequently quite erratic, indi-
cating variations in the concentration of ozone at different points
surrounding the base station.
38
-------
200
C
O
•H
4-1
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cu
to
13
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i-i
3
CO
ca
a)
e
o
N
o
lOOh
i I .__..<. i p __^j i
100 200
300
Ozone measured in aircraft
Figure 25. Aircraft fly-by data.
Ground Comparison Tests
Ground comparison tests were also used to check the aircraft
measurement systems. These tests consisted of comparisons between the
base station and aircraft instrumentation, while the aircraft was parked
adjacent to the base station. The sampling ports for the aircraft and
base station were located approximately 20 meters apart, at a height of
4 and 7 meters, respectively, above the ground. Figure 26 shows a plot
of the aircraft and base station ozone concentration measurements during
a selected time interval.
39
-------
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Battelle Comparison Flight
A third means of insuring data validity was to determine the
comparability between two similar aircraft measurements systems operating
in the same environment. This test was conducted in conjunction with
Battelle Memorial Research Institute. Battelle operated a Cessna 173
aircraft outfitted with a REM gas phase chemiluminescent ozone analyzer
and ram-pressure bag-filling system. Due to the differences in cruising
speed of the two aircraft, a formation flight could not be flown. The
triangular pattern shown in figure 27 was flown twice by both aircraft
with the EPA C-45 aircraft preceding the Battelle Cessna aircraft. A plot
of comparable ozone data obtained during this flight is presented in
figure 28. Ozone concentrations are plotted versus location along the
flight path; consequently, there was a time difference between data
obtained at the same point. The time difference varied with position on
the flight plan.
The plot shows good agreement between the RTI instrument and the REM
instrument over the duration of the flight path, the differences being
typically less than 10 percent.
Hydrocarbon Sample Contamination Test
Another system test was conducted to verify the integrity of the
sample inlet system. On the first flight, the gas chromatographic analysis
of the bag samples indicated a high concentration of gasoline vapors.
The logical deduction was that air from the interior of the aircraft was
being drawn into the sample along with the ambient air. The sample inlet
was modified to produce the system described and illustrated earlier
(fig. 19). During a planned test flight, the contents of a lecture bottle
of a known hydrocarbon were released continuously in the cabin during the
collection of a bag sample. This bag was analyzed and the concentration
of the known hydrocarbon observed and compared to ambient concentrations
measured earlier during the flight. The test indicated that no detect-
able amount of cabin air containing the high concentration of the released
hydrocarbon was evident in the bag sample. Since the sample inlet for the
hydrocarbon bag sample was approximately 15-cm downstream from the ozone-
oxides of nitrogen sample inlet, it was assumed that the ozone-oxides of
nitrogen sample was uncontaminated as well.
41
-------
Dayton OMNI
Dayton
Ohio
Richmond
OMNI
Montgomery
County
OMNI
Wilmington
(Base station)
h-
16.1 km
Figure 27. Battelle comparison flight pattern.
42
-------
Montgomery Co. OMNI
Battelle 15:55
•BTI-EPA 15:46
Battelle
o RTI/EPA
400
300
Richmond OMNI
Battelle 15:40
RTI-EPA 15:34
Dayton OMNI
Battelle 15:27
RTI-EPA 15:22
Montgomery Co.
Battelle 15:13
RTI-EPA 15:11
200
100
OZONE CONCENTRATION (ug/mJ)
Figure 28a. Data from RTI/Battellc comparison flight.
43
-------
Battella 16:50
KTI-EPA 16:30
Montgomery Co. OMNI
Battelle
o RTI/EPA
Richmond OMNI
Dayton OMNI
Montgonery Co. OMNI
Battelle 16:40
RTI-EPA 16:22
Battelle 16:23
RTI-EPA 16:09
Battelle 16:09
RTI-EPA 15:58
Battelle 15:55
RTI-EPA 15:46
I
400
Figure 28b.
300 200 100 0
OZONE CONCENTRATION (ug/»3)
Data from RTI/Battelle comparison flight.
44
-------
A test for bag permeation was carried out by storing bags of zero air
in the aircraft for long periods of time and reanalyzing them to see if
any hydrocarbons permeated the bags; none was found.
3.2.4.4 Comparison of RTI Solid Phase and Bendix Gas Phase Ozone
Analyzers
Tests were conducted to demonstrate the comparability of the RTI solid
phase and Bendix gas phase chemiluminescent analyzers. These tests were
conducted in the RTI Mobile Monitoring Laboratory with the two instruments
located side by side. Both instruments were connected to the same sampling
manifold through which ambient air was being aspirated. The output of each
was sampled once every 5 minutes, 24 hours per day, and recorded on mag-
netic tape. The RTI ozone monitor used for this test had a set of three
sample and hold modules and electrical analog subtraction and division
circuitry, which carried out the function of comparing the measure signal
level with the known internal calibrate. This removed the requirement for
manually reducing the data as was done for the aircraft data (see section
3.2.5 for the procedure that was followed to accomplish this). Data
recorded on the magnetic tape were processed by computer and printed out
in concentration units (micrograms per cubic meter).
Tests were run on these instruments on two occasions: once in the
spring of 1974 (April 17, 18, 19 and May 2, 3) and again in late summer
1974 (August 9-September 1) , yielding ample data for comparative analysis.
A statistical analysis was performed on the data (spring and summer)
to evaluate numerically the similarity of the readings. Results of this
analysis are shown in table 3. The data were also graphed for the summer
period and are presented in figure 29. The periods used for the statis-
tical analysis are indicated on the graph. These data substantiate that
the two instruments are comparable.
3.2.5 Data Acquisition/Reduction
The aircraft data-acquisition system used consisted of five Hewlett-
Packard/Mosely 680 electric-writing, strip-chart recorders rack-mounted in
a single unit. Also included in the unit was switching circuitry, which
allowed the input of the recorders to be shorted without shorting each
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instrument output. This facilitated the zero adjustment check of the
recorders by allowing this operation to be carried out with a single switch.
A digital voltmeter (DVM) was included for checking the instrument levels
(and therefore checking the operation of the strip-chart recorders by
checking the correctness of the deflection). The DVM could be switched to
any instrument output with no movement of test leads.
Since there were up to five individual records represented—concen-
trations of CL, NO, N09, NO and temperature—some means had to be utilized
J ^ X
to correlate the five with each other and with the corresponding ground-
level measurements. The zero adjust switch was used for this purpose.
Each time a significant point was crossed in the flight pattern, the switch
was activated causing all recorders to trace simultaneously to zero and
return to normal leaving a distinguishable mark. The time of the event was
marked on the ozone recorder to the nearest minute. The operator maintained
a separate log of the times and the event which occurred. Since all
recorders were run at the same chart speed, 20.3 cm/hr, the strip charts
could be laid side by side and the time and location corresponding to any
event determined.
The processing of the aircraft data was completely a manual operation.
First, the strip charts were annotated with location information to deter-
mine which portions of the record contained data to be interpreted and
which data were not valid (because of changing altitude, for example).
Next, the trace deflection was measured for each strip chart and the
appropriate scale applied to determine the represented concentration. The
ozone data presented a somewhat special case, as both the measure cycle
and calibrate cycle deflections are measured in terms of distance from the
base line determined by trace during the purge cycle. The ozone concen-
tration was computed from the following formula:
03 Cone (yg/m3) = C^X |
where M is the measured deflection above base line of the strip chart
during measure cycle.
48
-------
C is the measured deflection above the base line of the
strip-chart trace during calibration.
C_, is the concentration of the internal calibration unit
Gen
determined during on-ground calibration.
X is the factor determined from the graphs giving response
variation of the instrument with altitude.
After the data were converted to micrograms per cubic meter, they
were placed on a map illustrating the flight path at the point correspond-
ing to its origin. The flight path was drawn during the post flight
debriefing of the pilot and copilot and using notes made by the
meteorological observer. The data were then put on the map by observing
where the particular data point fell on the strip chart in relation to
noted significant events in the flight path (turns, prominent landmarks,
etc.) and placing it on the pertinent portion of the flight path at a
proportionate distance between the two nearest significant features. The
times of all turns were placed on the maps as an aid to those who analyze
the data. Oxides of nitrogen data were omitted, since they were generally
below the detectable limits of the instrument.
Examples of selected aircraft flight paths with corresponding ozone
data and positions for hydrocarbon grab samples are presented in Section 6.0,
"Interpretation of Results." Data from all flights are presented in
appendix C.
49
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4.0 PROGRAM SCHEDULE
Details on the program schedule and the sequence of events that
occurred during the period May 1, 1974, to August 31, 1974, are presented
in this section. The overall program schedule as originally projected at
the beginning of the program and presented in the "Work Plan" for Contract
68-02-1386, Task 4, is shown in table 4. Subsequent discussions related
to the sequence of events that occurred in the ground station and air-
craft measurement programs are presented in section 4.1, "Ground Station
and Aircraft Measurement Program Schedule." Section 4.2 presents a brief
discussion of the sequence of events that occurred during the "Quality
Assurance Program," implemented in order to document and to insure the
quality and validity of the data collected during this study.
4.1 Ground Station/Aircraft Measurement Program Schedule
The schedule presented in table 4 for each task was met with respect
to acquisition/checkout/preparation of equipment for ground stations; site
selection; preparation/installation/checkout of equipment in aircraft;
installation of stations, analyzers, and equipment at designated sites;
and calibration of all analyzers. Each of the five rural stations was
set up, calibrated, and brought on line in a consecutive, orderly manner.
The six urban stations were set up, calibrated, and brought on line by the
Environmental Protection Agency during the week of June 10-15, 1974. The
field measurement program began at all stations on or before June 15, 1974.
The aircraft was ferried to Wilmington on schedule and subsequently prepared
for routine aircraft flights, as dictated by meteorological conditions and
the program plan. During the ensuing 75-day measurement program, dynamic
calibrations were performed on each analyzer on a biweekly basis. Travel
delays, instrument failures, and quality control/assurance procedures
altered the schedule somewhat. Data acquisition continued through the end
of August 1974.
50
-------
Table 4. Program schedule
Date
Task
May 6, 1974
June
July
August
September
October
7
10
11
15-17
18
6
7-10
3-14
12-14
15
15
1
3-8
17-22
1-6
15-21
27-31
31
1-5
15-31
1-31
15-31
November 1-30
31
December 15
31
January 31, 1975
Start program/begin equipment acquisition.
Begin preparation of comprehensive program plan.
Receive government furnished equipment.
Begin checkout of analyzers, recorders, etc.
Select sites for ground stations.
C-45 aircraft ferried to RDU/begin installation and
checkout of systems.
Submit comprehensive program plan.
Transport equipment from RTI to ground stations.
Aircraft system test flights from RDU.
Install, checkout, and calibrate equipment at monitor-
ing stations.
Begin field measurements at five rural stations.
Begin field measurements at six urban stations (EPA).
Begin data reduction and analysis.
Calibrate analyzers at each station.
Calibrate analyzers at each station.
Calibrate analyzers at each station.
Calibrate analyzers at each station.
Calibrate analyzers at each station.
Terminate field measurement program.
Disassemble equipment and monitoring sites and trans-
port to Research Triangle Park. Return aircraft to
NERC, Las Vegas.
Continue data processing/reduction/begin statistical
analysis of data.
Complete data processing/validate data.
Continue statistical analysis of data/begin prepara-
tion of draft final report.
Complete data analysis/draft of final report.
Submit draft of final report for EPA review.
Begin finalizing report.
Receive EPA review of final report.
Submit final report.
51
-------
During the 75-day field measurement program, a total of 19 aircraft
flights were flown in support of ground-station measurements. These flights
were flown under varying meteorological conditions and included square wave
patterns, double box patterns, vertical profiles, calibration and instrument
checkout flights, and an eastern wide-area flight. A listing of all flights
is presented in table 5. A complete description of all flights with flight
tracks, data, and meteorological summary is presented in appendix C.
* »...,
Table 5. Listing of aircraft flights
Date
20 June
25 June
27 June
4 July
6 July
9 July
13 July
16 July
17 July
21 July
25 July
1 August
1 August
1 August
1 August
9 August
13 August
15 August
21 August
Type of flight
Square Wave
Vertical Profile
Square Wave
Square Wave
Double Box
Double Box
Double Box
Square Wave
Vertical Profile
Square Wave
Square Wave
Vertical Profile
Vertical Profile
Vertical Profile
Vertical Profile
Batelle Comparison Flight
Vertical Over Morgan and
Wayne County
Vertical Profile
Eastern Flight
Time
1126—1245
0754—0934
1131—1340
1148—1256
1245—1719
1026—1449
1100—1518
1130—1403
1155—1321
1158—1434
1308—1622
0704—0810
0823—0913
1320—1414
1656—1822
1502—1631
1024—1406
1053—1218
0939—1632
Flight altitude
(meters)
610
to 3658
762
762
762
762
762
914
to 2590
975
762
to 2438
to 1829
to 3658
to 3658
610
762 to 2286
to 366
1219
52
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4.2 Quality Assurance Program
A quality assurance program was conducted as a separate task under
Contract 68-02-1386 (Task 8) in order to assure, assess, and document the
validity of the air quality measurements for the Summer 1974 Oxidant Study.
Specific components of the quality assurance program included the following:
(1) implementation of quality control procedures consisting of biweekly
multipoint calibrations, daily zero and span checks, special operational
checks, setting of action limits on checks and calibration; (2) certifica-
tion of RTI and EPA calibration teams by the primary reference laboratory
(i.e., Measurements Standardization Branch of National Environmental
Research Center, Research Triangle Park) prior to beginning the field
measurement program; and (3) onsite quality performance audits of the ozone,
nitrogen dioxide, and hydrocarbon analyzers by a quality assurance team.
The audit team utilized the same dynamic calibration techniques and appara-
tus as did the RTI and EPA calibration teams to provide reference samples
to the ozone, nitrogen dioxide, and hydrocarbon analyzers. These calibra-
tion techniques and apparatus are described in appendix A.
During July and August 1974, four audits were performed at each
of the rural and urban stations. Control charts were prepared, and
the results for two of the audits are shown in figure 30. The ordinate of
figure 30 is the percent difference in the analyzer response and the refer-
3
ence concentration, which was 196 yg/m (0.1 ppm). The results of both
-I'idits shown in figure 30 indicate that the analyzer responses at all sta-
tions were within +_ 20 percent of the reference value. Twenty percent at
3
196 yg/m is the reproducibility of the method at the 95 percent level, as
found in a collaborative test conducted by the Environmental Protection
9/
Agency.— Analyzer responses to the audit concentrations of nitrogen
dioxide at the five rural stations were within + 20 percent or better of
the reference value. Audits of the hydrocarbon analyzers at Wilmington,
rkCcr-nelsville, and Wooster indicated that in all cases methane was measured
to within 13 percent of the assayed value and total hydrocarbon measured
as methane to within 21 percent or better. Audit of the EPA Perkin-Elmer
model 900 gas chromatograph system at Wilmington indicated measurements of
better than 15 percent for all compounds contained in the audit hydrocar-
bons samples.
53
-------
+20 -
Inpui
M I-1
O Ui
Audit level 196 Mg/m (0.1 PPM1*
lesponse-Inpu
i i
H-> I-1 1 -1
<-n O l-n O I.
x*\
-20 -
1
1 1 1 1 1 II
Wilmington Dayton McConnelsville DuBois McHenry
Cincinnati Columbus Cleveland Pittsburgh
AUDIT OF 0 ANALYZERS BY RTI AND EPA CALIBRATION TEAMS (JULY 15-25)
+20
Audit level 196 yg/m (0.1 PPM)
McHenry DuBois Canton McConnelsville Dayton Aircraft
Pittsburgh Cleveland Wooster Columbus Wilmington Cincinnati
AUDIT OF 03 ANALYZERS BY RTI AUDIT TEAM (AUGUST 15-21)
Figure 30. Results of audits of ozone analyzers at
stations during period July 15-25, 1974,
and August 15-21, 1974.
54
-------
The results of the quality assurance/audit program have demonstrated
that the air-quality measurements obtained during the Summer 1974 Oxidant
Study are valid and that the performance audit results represent realistic
estimates of the accuracy and precision of these measurements for the
concentration levels audited. The details of the Quality Assurance Program
are documented in the final report for Contract 68-02-1386, Task 8, "Quality
Assurance Program Relative to Summer 1974 Oxidant Study."—
55
-------
5.0 SUMMARY OF DATA AND STATISTICS
The results of the field measurement program are presented in this
section and include summary statistics, diurnal pollutant-concentration
patterns, and a meteorological summary for June, July, and August 1974.
Ozone and hydrocarbon data from three diurnal studies at Wilmington,
hydrocarbon analyses of grab samples at Wilmington, Wooster, and McConnels-
ville, and concentrations of ozone and hydrocarbons, and pertinent ratios
of compounds in grab samples collected during aircraft flights are not
presented here, but are summarized in section 6.0 in order to facilitate
discussion and interpretation of these results.
5.1 Summary Statistics
Mean hourly ozone concentrations, standard deviations, and case counts
by station are shown in table 6, and ozone data above the NAAQS for photo-
chemical oxidant are summarized in table 7. Statistical data for nitrogen
dioxide and total hydrocarbon, methane, and carbon monoxide concentrations
by station are presented in tables 8 and 9, respectively.
Table 6. Statistical summary of hourly ozone
concentration measurements by station
June 14-August 31, 1974
Station
Wilmington, Ohio
McConnelsville, Ohio
Wooster, Ohio
McHenry, Maryland
DuBois, Pennsylvania
Canton, Ohio*
Cincinnati, Ohio*
Cleveland, Ohio*
Columbus, Ohio*
Dayton, Ohio*
Pittsburgh, Pennsylvania*
Mean hourly
concentration
(yg/m3)
103
102
94
113
112
71
49
62
65
71
56
Standard
deviation
(yg/m3)
55
48
59
45
63
56
54
48
64
56
56
Case count
1751
1801
1878
2011
1667
1829
1548
1652
1935
1576
1622
*Urban stations
56
-------
Table 7. Summary of ozone data
above NAAQS by station
(June 14-August 31, 1974).
Station
Maximum
hourly average
concentration
(yg/m3)
Days
exceeding
percentile standard
(yg/m3)
Hours Hours
above above
standard standard
(number) (%)
Wilmington, Ohio*
McConnelsville, Ohio*
Wooster, Ohio*
McHenry, Maryland*
DuBois, Pennsylvania*
Canton, Ohio**
Cincinnati, Ohio**
Cleveland, Ohio**
Columbus, Ohio**
Dayton, Ohio**
Pittsburgh, Pennsyl-
vania**
370
330
330
330
400
280
360
270
340
260
300
260
240
260
270
310
230
220
200
220
220
230
58
56
55
43
54
44
20
26
27
35
37
259
239
262
262
341
148
54
51
113
114
106
14.9
13.3
14.0
13.0
20.5
8.0
3.5
3.0
5.8
7.2
6.5
*Rural stations
**Urban stations
—Based on data available from each station
Table 8. Statistical summary of hourly
nitrogen dioxide concentration
measurements by station
(June 14-August 31, 1974).
Station
Wilmington, Ohio
McConnelsville, Ohio
Wooster, Ohio
McHenry, Maryland
DuBois, Pennsylvania
Mean hourly
concentration
(yg/m3)
13
12
13
11
19
Standard
deviation
(Ug/m3)
24
34
15
6
9
Case count
1741
1775
1889
2017
1971
57
-------
Table 9. Statistical summary of hourly
total hydrocarbon, methane, and
carbon monoxide concentration
measurements by station
(June 14-August 31, 1974).
Station
Wilmington, Ohio
McConnelsville, Ohio
Wooster, Ohio
Parameter
THC
CH4
CO
NMHC*
THC
CH4
CO
NMHC*
THC
CH4
CO
NMHC*
Mean hourly
concentration
(yg/m3)
1180
1120
330
60
1260
1040
230
220
1360
1170
200
190
Standard
deviation
(yg/m3)
300
310
460
130
380
90
300
340
200
Case count
831
811
980
754
707
244
849
831
793
NMHC = THC - CH,
The mean hourly concentrations for ozone at the rural stations ranged
3 3
from 94 to 113 yg/m , as opposed to a range of 49 to 71 yg/m at the urban
stations. The standard deviations for all stations, both rural and urban,
were, however, similar in magnitude (see table 6). Maximum hourly ozone
concentrations were 370 yg/m at Wilmington, 330 y-g/m at McConnelsville,
330 yg/m3 at Wooster, Ohio; 330 yg/m3 at McHenry, Maryland; 400 yg/m3 at
33 3
DuBois, Pennsylvania; 280 yg/m at Canton, 360 yg/m at Cincinnati, 270 yg/m
33 T
at Cleveland, 340 yg/m at Columbus, 260 yg/m at Dayton, Ohio; and 300 yg/m
at Pittsburgh, Pennsylvania.
The data summarized in table 7 show that the NAAQS for photochemical
3
oxidants (160 yg/m ) was exceeded during approximately 15, 13, 14, 13, and
21 percent of the hours at the rural stations (i.e., Wilmington, McConnels-
ville, Wooster, Ohio; McHenry, Maryland, and DuBois, Pennsylvania) and
approximately 8, 4, 3, 6, 7, and 7 percent of the hours at the urban
stations (i.e., Canton, Cincinnati, Cleveland, Columbus, Dayton, Ohio; and
58
-------
Pittsburgh, Pennsylvania), respectively. These data also show that the
NAAQS for photochemical oxidant was exceeded approximately twice as
frequently at rural stations as at urban stations, both in terms of percent
of days and percent of hours.
The mean hourly concentrations of nitrogen dioxide at the five rural
3
stations ranged from 11 to 19 yg/m and was slightly above the detect-
3
ability level of the measurement method (= 10 yg/m ). Maximum hourly
3 3
nitrogen dioxide concentrations were 90 yg/m at Wilmington; 70 yg/m at
3 3
McConnelsville; 90 yg/m at Wooster, Ohio; 60 yg/m at McHenry, Maryland;
3
and 70 yg/m at DuBois, Pennsylvania. The mean hourly concentrations for
nonmethane hydrocarbon (THC-CH.) were approximately 60 yg/m at Wilmington,
3 3
220 yg/m at McConnelsville, and 190 yg/m at Wooster for the measurement
3
period. Maximum hourly nonmethane hydrocarbon concentrations were 120 yg/m
3 3
at Wilmington; 280 yg/m at McConnelsville; and 280 yg/m at Wooster. Mean
3
hourly carbon monoxide concentrations ranged from approximately 200 yg/m
3
at Wooster and McConnelsville to 325 yg/m at Wilmington. Maximum hourly
3 3
carbon monoxide concentrations were 480 yg/m at Wilmington; 270 yg/m at
3
McConnelsville; and 260 yg/m at Wooster.
The data presented in tables 8 and 9 were used to compute the
nonmethane hydrocarbon (NMHC = THC-CH,)/N09 ratio (ppm carbon/ppm N09) at
4 £. £-
each station. The ratios of NMHC/NO~ for the measurement period are:
1. Wilmington, Ohio: 13*,
2. McConnelsville, Ohio: 53*,
3. Wooster, Ohio: 42*.
The low ratio found at Wilmington, Ohio, (13) is more nearly characteristic of
urban ratios, while the higher ratios at McConnelsville and Wooster, Ohio,
are representative of what would be expected in rural environments.
Cumulative frequency distributions for hourly ozone concentrations by
station are presented for the entire period in table 10. Cumulative
frequency distributions for hourly nitrogen dioxide concentrations are
presented in table 11. Cumulative frequency distributions of hourly total
hydrocarbon, methane, and carbon monoxide concentrations are presented in
table 12.
_
Molar Ratios = ppm C/ppm N0«
59
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5.2 Diurnal Patterns
Mean ozone concentrations for each hour of the day by station for
the period June 14 through August 31, 1974, are shown in table 13. Mean
nitrogen dioxide, total hydrocarbon, methane, nonmethane hydrocarbon, and
carbon monoxide concentrations for each hour of the day by station are
presented in table 14. Mean diurnal curves for ozone are shown for rural
and urban stations in figures 31-34. Figures 31 and 32 present the mean
diurnal curves for Wilmington, McConnelsville, Wooster, and Wilmington,
McHenry, and DuBois, respectively. Mean diurnal ozone curves for the
cities of Canton, Cincinnati, and Cleveland are presented in figure 33
and for the cities of Columbus, Dayton, and Pittsburgh in figure 34.
The mean diurnal ozone curves for the rural and urban stations show the
same general pattern; however, several differences can be noted as
follows:
1. Mean hourly ozone concentrations for rural stations range
from approximately 40 yg/m during early morning hours to
140-160 pg/m in the afternoon, while for urban stations,
3 3
the mean ranges from 15-25 yg/m to 100-125 yg/m .
2. Mean hourly ozone concentrations tend to peak later in the
afternoon at rural sites (see table 13). This observation
is further discussed in section 6.2.
3. The overall range or spread of mean ozone concentrations for
both rural and urban stations from low to high was approxi-
o
mately the same (i.e., 100-125 yg/m ) during this period of
time.
Figure 35 contrasts the mean diurnal ozone concentration curves for 1972,
1973, and 1974 at McHenry, Maryland. Figure 35 shows that the 1972 and
1974 diurnal curves are almost identical, while the 1973 concentrations
are somewhat higher. The difference between the 1972, 1974 curves and the
1973 curve can be attributed to differences in meteorological conditions.
Mean diurnal curves for nitrogen dioxide concentration for each
station are presented in figure 36. Mean diurnal concentrations for
total hydrocarbon, methane, and carbon monoxide are presented in
63
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figures 37-39. The shaded area between the total hydrocarbon and methane
curves represents the mean hourly nonmethane hydrocarbon concentration,
as determined by subtracting the CH, measurement from the THC measurement
of the Beckman 6800 THC, CH^, CO analyzer.
Mean hourly nitrogen dioxide concentrations from all five rural
stations ranged from approximately 5-25 yg/m . A majority of these measure-
ments were at or below the generally accepted minimum detectable level of
o
10 yg/m for the measurement method. Mean hourly total hydrocarbon and
methane measurements at two stations in Ohio did not exhibit much varia-
bility or diurnal pattern (i.e., Wilmington and McConnelsville). A diurnal
variation was apparent at Wooster. Nonme thane hydrocarbon (THC-CH.) concen-
3
trations were low (> 80 vg/m ) at Wilmington and higher at McConnelsville
3
and Wooster (i.e., 100-230 yg/m ). A consistent diurnal pattern was not
evident. Carbon monoxide concentrations were variable at Wilmington,
ranging from a low of 270 to a high of 500 yg/m , peaked at 1700 at Wooster,
and were uniformly consistent at McConnelsville. These concentration values
are higher at all stations than the geochemical background, which is
3
considered to be on the order of 80-140 yg/m .
5.3 Summary of Climatic Conditions
During the last 2 weeks of June, temperatures over the study area
averaged 6 degrees below normal with a cold period during the last week
(6-8°F below normal). Precipitation, a total of 5.08-7.62 cm , occurred
during the last week, as a broad low-pressure trough covered the whole area.
The resultant wind vectors at 915 m for this period at Dayton, Pittsburgh,
and Huntington also indicate the cyclonic curvature associated with the
trough aloft (table 15).
July of 1974 was unusually dry. Dayton, Ohio, received only 14 percent
of its normal monthly rainfall of 8.99 cm. Throughout the study area,
precipitation ranged from 2.54-7.62 cm below normal for the month. Sunshine
was relatively abundant, -65 percent of maximum possible for the month.
Mean monthly temperature departures from the 30-year mean of -1°F to +1°F
were recorded, which is well within normal variability. The resultant winds
at 915 m were predominantly westerly with lower speeds (~2.8 m/sec) than
72
-------
I500r
1000 1200 1400 1600
1800 2000 2200 2400 0200 0400 0600
Hour of day (EDT)
0800
Figure 37. Mean diurnal concentration of total hydrocarbon,
methane, and carbon monoxide for Wilmington, Ohio,
from June 14-August 31, 1974.
73
-------
E
6C
c
o
•H
a
e
o
o
o
u
U
U
EC
H
1200-
900-
600
300
x THC
Q CH4
• CO
0
0800 1000 1200 WOO 1600 1800 2000 2200 3*00 0200 0400 0600
Hour of day (EOT)
Figure 38. Mean diurnal concentration of total hydrocarbon,
methane, and carbon monoxide for Wooster, Ohio,
from June 14-August 31, 1974.
74
-------
,B
00
CO
c
o
(B
t-i
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0)
a
c
o
o
o
u
PC
u
u
PC
H
6&00 1000 1200 1400 1600 1800 2000 2200 2400 0200 0400 0600 0800
Hour of day (EOT)
Figure 39. Mean diurnal concentration of total hydrocarbon,
methane, and carbon monoxide for McConnelsville, Ohio,
from June 14-August 31, 1974.
75
-------
Table 15. Comparison of low-altitude resultant wind
velocity at selected locations by months
Month
June
July
August
Year
1974*
1973
1972
1974*
1973
1972
1974*
1973
1972
Location
Pittsburgh
233/3.1**
260/6.3
280/6.3
284/3.3
270/4.7
270/4.3
207/3.7
280/3.3
260/4.2
Dayton
288/2.5
250/6.9
290/5.0
265/2.5
280/3.7
270/4.9
241/3.0
280/2.9
270/4.3
Huntington
249/4.9
250/5.7
280/5.0
276/2.7
280/4.6
270/4.6
235/2.8
280/2.9
280/5.4
**
The 1974 data computed from incomplete sets of teletype reports of the
915 meters wind vector. The 1972 and 1973 data are taken from Clima-
tological Data, National Summary, for the 900 mb surface (~1,050 m).
Wind direction (deg)/wind speed (m/sec).
in the previous 2 years. This suggests that low-pressure systems passed
north of the area, moving primarily west to east. The monthly mean 700 mb
(~ 3 km) charts substantiate that type of flow.
In August, precipitation returned to the area, with 1.5 times normal
monthly rainfall at most stations. Resultant winds at Pittsburgh at
915 m showed a major shift toward southerly flow. Surface weather maps
suggest high pressure was common along the eastern seaboard, giving a flow
of air into the study area from the east. The air flow at 500 mb shows a
persistent long wave trough which slowly regressed across the area, but
with frequent, minor disturbances moving through. Potential temperature
time sections from the ground to 5 km, at Dayton and at Pittsburgh show no
major disturbances in the vertical structure of the atmosphere during August.
In general, departures from long-term averages for various climatic
variables occurred in one portion of the study period and were compensated
for in other portions. Over the period, the weather conditions approximated
a "normal" summer.
76
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6.0 EXAMINATION AND INTERPRETATION OF RESULTS
The data obtained during this study can be divided into three
sections: measurements at rural ground stations, data from six suburban
locations, and data from aircraft flights. Results obtained in each of
these areas have been analyzed both as individual sets and in relation to
each other. An attempt has been made to develop a comprehensive pattern
of relationship between ozone concentrations over rural areas and urban
sources of ozone precursors. In reviewing the analyses that follow, one
must keep in mind that the "parcel" of air which has been sampled does
not represent a closed system. That particular parcel has had a unique
history involving injection of contaminants from anthropogenic and natural
sources at unknown rates and quantities, and mixing with adjacent parcels,
each having its own unique history. Throughout the life of the parcel,
reactions producing and destroying ozone are continually in progress.
Each concentration measurement made during this study involved some
averaging in time, space, or both. As a consequence, extreme variations
in concentrations adjacent in time or space, for the most part, are elimi-
nated. However, since the distribution of contaminant concentrations is
not likely to be smooth function, there was the possibility of sampling
a uniquely high or low concentration.
6.1 Examination and Interpretation of Ozone and Hydrocarbon Data from
Aircraft Flights
The rationale for the two types of survey flights, square wave and
double box patterns, is given in section 2. The square wave pattern
was flown on a clear day when orderly wind speed and wind direction were
predicted to last for a period of hours. The pattern was flown starting
upwind and continuing downwind of Columbus. On days of disorganized, low
wind speed and stagnant conditions, the double box pattern was flown
around the airspace of Columbus.
In order to aid in the understanding of the discussion of the airborne
studies, an outline of the flight patterns and a discussion of their features
is given below.
77
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Figure 40 illustrates the square wave pattern. In this example, the
wind at flight altitude is from the east. The plane departs from the
base station at Wilmington and flies to a point upwind (i.e., to the east)
of Columbus. The plane enters the flight pattern by flying the first
crosswind "leg;" spoken of as "leg-1" in the discussion. Additional cross-
wind flights are spoken of as "leg-2," "leg-3," etc.
Figure 41 illustrates the double box pattern. This type of flight
always originated at the Wilmington base station. After a portion of the
diagonal towards the northeast is flown, the inner box of the pattern is
traversed. The sides of the inner and outer box are considered as flight
legs and numbered sequentially counterclockwise with the northern side
of the inner box assigned as leg 1, the western side of the inner box as
leg 2, etc., and the northern side of the outer box as leg 5, the western
side of the outer box as leg 6, etc.
Individual ozone readings and areas where hydrocarbon bag samples
are collected are entered on drawings of the flight patterns. It is
suggested that frequent reference be made to these drawings while one
reads the discussion and interpretation of aircraft data.
Various flight conditions and meteorological summaries are given in
appendix C. Concentrations of ground station's pollutants are summarized
in tables and graphs in section 5 and in full form in the computer print-
outs which were supplied to the project monitor.
The rationale for choosing the data (primary and derived) given in
tables in this section were the following. Ozone was presented for comparison
with hydrocarbon data. Acetylene was chosen as a key compound in the inter-
pretation of the hydrocarbon data because it is recognized as the best index
compound for exhaust from the internal combustion engine. As far as is
known, acetylene has no natural sources. Furthermore, acetylene is one of
the most inert of all hydrocarbons in an atmospheric photochemical system.
Very little is known about the relative abundance of other hydrocarbons in
nature, and one cannot, from an examination of the literature, choose with
much certainty a compound other than acetylene as an index of anthropogenic
hydrocarbon emissions. Even butane and alkylated benzenes have natural
origins in vegetation and soil and would be expected in natural crude-oil
seepage. Since acetylene does not react appreciably on the time scale
78
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N
Wind Direction
VC
00
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00
0)
-ct
00
01
CO
00
0)
CM
00
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rH
00
Q) M
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Leg 5
00
01
Leg 7
Figure 41. Double box flight pattern.
79
-------
involved, other substances were compared to it to separate decreases caused
by dilution from the changes caused by chemical reaction.
The measured concentrations presented for acetylene and other hydro-
carbons were in the parts per billion (as carbon) range, and it is recognized
that there is a real problem in analysis at these concentrations. At such
low concentration, a small absolute error can result in a very large relative
error. Although any given value may be in error, it is felt that the
analyses taken as a whole furnish an emerging picture of the process of
ozone generation in rural air.
Although not much is known on natural sources for acetaldehyde, the
acetaldehyde/acetylene ratio was computed and tabulated. In a smog system,
acetaldehyde should be generated more rapidly than it is destroyed.
Carbon monoxide, like acetylene, should not react appreciably on the
time scales involved. Since CO is generated by all combustion sources and
acetylene only by oxidation and cracking in the automobile engine, a com-
parison of the two should be informative. It should be kept in mind that
CO also has natural sources. Isobutylene/isobutane and propylene/propane
ratios were expected to provide an index of the degree of reaction the
hydrocarbons had undergone in the ozone-generative processes. Ethylbenzene
was chosen to be compared with acetylene because it is a representative
aromatic compound and is less likely to be a sample contaminant than toluene
or benzene. The propylene/acetylene ratio was also chosen to be an index
of oxidation by ozone and photochemical processes.
6.1.1 Square Wave Flights
Five separate square wave patterns were flown during the course of
this study. Four of these are examined in detail below.
1. Square Wave Flight of Saturday, June 27, 1974
This flight began upwind of Columbus and continued to Cincinnati.
The somewhat irregular flight path is shown in figure 42. Hydrocarbon data
and ratios are given in table 16.
Diurnal Variation of Ozone Concentration
There is little apparent diurnal ozone change at flight level. The
average ozone concentration for the first crosswind leg was 101 yg/m ;
3
for the last crosswind leg, 113 yg/m .
80
-------
\ ll;0t
FLIGHT DATE: June 27. 1974
PATTERN: Square Wave
TRUE AIRSPEED: 277.8 km/h (150 knots) MISSION ALTITUDE: 762.0 m (2,500 ft)
above msl
LOW LEVEL WINDS: Sfc
609 m (2,000')
914 m (3,000')
1219 m (4,000')
DATA: Ozone Concentration in Ug/m
Time in EOT
Hydrocarbon Sample Positions
Denoted by i i
070°/5.14 m/s (10 knots)
080V8.74 m/s (17 knots)
065V8.23 m/s (16 knots)
055V7.72 m/s (15 knots)
Low Level Winds Obtained From National
Weather Service
Upper Air Station
Dayton, Ohio-0800 EOT
Figure 42. Square wave flight of June 27, 1974.
81
-------
Table 16. Abstract of hydrocarbon data: Square wave flight of June 27, 1974.
Category
Ozone, yg/nH
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide /acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
Sample number
(Time of sample collections-EDT)
1
(1139)
96.
1.4
4.7
0.27
193.
0.5
0.2
0.4
0.9
2
(1153)
103.
2.5
1.2
0.28
112.
0.3
0.1
0.5
0.3
3
(1209)
101.
2.3
2.6
0.32
139.
0.2
0.1
0.6
0.4
4
(1224)
112.
1.8
4.9
0.27
150.
0.2
0.2
0.8
0.5
Ozone, yg/m^
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
5
(1242)
104.
1.7
3.9
0.26
153.
0.4
0.2
0.8
0.5
6
(1255)
117.
2.5
1.8
0.25
100.
0.3
0.2
0.7
0.3
7
(1309)
110.
2.1
2.5
0.32
152.
0.3
0.2
0.2
0.4
8
(1335)
103.
1.1
6.9
0.24
218.
0.2
0.1
0.3
0.5
82
-------
Variation of Ozone Concentrations Upwind, Over, Downwind of the City
Average ozone concentrations for the eight, crosswind legs of the flight
were 99, 98, 102, 102, 110, 107, 116, and 113 yg/m . The ozone variation
from the first through the fourth crosswind legs was slight. About 56 km
(50 nm) downwind of the center of Columbus, on the fifth crosswind leg,
there was a noticeable increase in average ozone concentration. This could
indicate a necessary incubation time for occurrence of maximized ozone for-
mation in that parcel of air. An estimate of the time of origin of that air
parcel from the center of Columbus was computed as follows. If a constant
wind speed of 8 m/sec (15 knots) is assumed, approximately two hours would
have passed since the air now in the area of leg 5 left the center of
Columbus. Subtracting two hours from the time of collection, 1224, gives
1024 as the estimated of the time the air parcel was over Columbus. In the
3
seventh leg, the average ozone concentration increased to 116 yg/m in air
parcel, which was estimated to have left the center of Columbus around 0900.
That time may well have corresponded to the time of increased human activity
in Columbus on this Saturday morning. Air in that parcel would be expected
to contain higher concentrations of city-emitted hydrocarbons than adjacent
samples, and, in fact, it did.
Other Ozone Variations
In figure 42, there appears to be a gradient in ozone concentration
(from higher to lower) crosswind from east to west. The average ozone
3
concentration on the western side of the pattern is 119 yg/m ; on the
3
eastern side, 100 yg/m . The presence of this gradient was due, in part
3
to the higher ozone concentrations, up to 140 yg/m , observed west
of Wilmington and northeast of Cincinnati. Several other ozone concentra-
tions depict a hot spot of ozone in that vicinity and suggest the presence
nf an urban plume; however, no specific source for the plume can be deduced
from the available data.
Variation of Hydrocarbon Concentrations and Ratios
Concentrations of two hydrocarbons versus distance from the city
are shown in figure 43. The figure shows the presence of hydrocarbons
from the city in samples one, two, and three. Two miles upwind of the city
center (sample one) both acetylene and isopentane concentrations were lower
83
-------
140
•>
6
"ti 120
8 110
o
N
O
100
90
a
a
-------
than they were in samples two and three which were collected immediately
downwind of the city. That ozone concentration does not increase notice-
ably immediately downwind of the city can be explained in two ways. (1) The
concentration of ozone entering the city from upwind is initially depressed
or quenched by nitric oxide and other ozone-reactive compounds being
emitted from the city. (2) Due to the city's influence on the chemical
composition of the air mass, a certain induction period is required for
ozone formation to again "peak," thus an increase is observed at a later
time, that is, further downwind. This time period would be dependent on
solar irradiation and movement of the air.
The hydrocarbon concentration (as shown by acetylene and isopentane)
began to fall off in the samples taken on the fourth, fifth, and sixth
legs. But on the seventh leg, the concentration of both acetylene and
isopentane increased. This rise was more or less coincident with the in-
crease in ozone, showing a relationship between ozone, hydrocarbons, the
time of the air parcel's emission from the city (e.g., in the morning
during presumed maximum human activity), and distance from the city.
The data show a preexisting level of both ozone and hydrocarbons
upwind of the city. Of course, injection of ozone-precursor materials
from both natural and anthropogenic sources into the air before it entered
the city was constantly occurring.
Comparison of Aircraft Data with Ground-Station Data
The ground station at Wilmington, Ohio, was directly below the line
of flight followed on June 27, 1974. The parcel of air that gave the
enhanced ozone and hydrocarbon readings on the seventh leg of the flight
is estimated to have been near Wilmington around 40 minutes earlier,
that is 1215 EOT. On the ground, the ozone concentration was very constant
3 3
from 1000 until 1200, increasing only 2 yg/m (from 76 to 78 yg/m ). In
3 3
the internal 1200-1215, the ozone concentration rose by 12 yg/m to 89 yg/m .
Ozone concentration continued to increase and peaked at a concentration
3 3
of 143 yg/m at 1645. It is tenuous, however, to associate the 12-yg/m
rise in ozone concentration with the passage of the high hydrocarbon-content
air parcel over Wilmington. The hydrocarbon-carbon monoxide analyzer was
off-line at Wilmington on this day so no comparison of these pollutants
could be made with the aircraft data.
85
-------
At the ground station in Columbus, the ozone concentration was
approximately 4 yg/m for the hour ending at 0500. The hourly average
from 1100 to 1200 was missing from the data. The peak hourly average
3
concentration for the day was 157 yg/m for the period 1800-1900.
2. Square Wave Flight of Tuesday, July 16, 1974
The orientation of the transport wind during this flight gave
another opportunity to examine the possibility of one city's influence upon
the ozone concentration of another. Ozone concentrations at several Ohio
ground stations on July 16 were low when compared to those of other July
days. The flight track is shown in figure 44. Hydrocarbon data are sum-
marized in table 17.
Diurnal Variation of Ozone Concentration
To assess the concentration trend with time, data along the straight,
return flight path were compared with data from approximately the same
space along the flight legs of the square wave pattern. Thus, in the
portion of the flight path over Dayton only the value along the return
3 3
flight leg, 189 yg/m , was compared with the value 188 yg/m , measured
on the crosswind leg of the square wave. At the next intersection of
3 3
flight paths, 177 yg/m was compared to an earlier 156 yg/m , and so forth.
A statistical test applied to these two data sets showed that one was not
significantly different from the other. There was, however, a slight ten-
dency toward higher concentrations with the passage of time.
Variation of Ozone Concentrations Upwind, Over, and Downwind of the City
The data were next statistically examined for trends with distance
and time from the Columbus urban area. For this analysis data from each "tooth"
of the square wave was considered as a data set. (A "tooth" consists of one
downwind leg and two crosswind legs.) Each set contains data points common
with the preceding set. However, when tested at the 0.05 level, data of
the first set were found to be significantly different from the other sets.
Average values for each data set are plotted versus distance from the
center of Columbus in figure 45. These indicate a consistent increase in
ozone downwind of the city.
Other Ozone Variations
Differences in ozone concentrations north and south of the center
86
-------
40'30'
CLINTON
CO. AFB
FLIGHT DATE: July 16, 1974
TRUE AIRSPEED: 250.0 km/h (135 knots)
LOW LEVEL WINDS: Sfc
609 m (2,000')
914 m (3,000')
1219 m (4,000')
DATA: Ozone Concentration in yg/m
Time In EOT
Hydrocarbon Sample Positions
Denoted by j .
PATTERN: Square Wave
MISSION ALTITUDE: 914.4 m (3,000 ft)
above msl
060°/1.54 m/s (3 knots)
080V5.14 m/s (10 knots)
060°/3.60 m/s (7 knots)
015°/4.12 m/s (8 knots)
Low Level Winds Obtained From
National Weather Service
Upper Air Station
Dayton, Ohio-0800 EDT
Figure 44. Square wave flight of July 16, 1974.
87
-------
Table 17. Abstract of hydrocarbon data: Square wave flight of
July 16, 1974
Category
Ozone, yg/m
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
Sample number (time of sample collection-EDT)
1
(1149)
133
2.1
2.8
0.28
133.
0.5
0.2
0.4
1.2
2
(1207)
134
2.9
1.9
0.36
124.
0.4
0.2
0.3
0.7
3
(1222)
145
1.7
7.1
0.30
177.
0.4
0.1
0.3
0.4
4
(1254)
148
1.8
3.1
0.34
189.
0.3
0.2
0.8
0.6
5
(1254)
175
0.40
0.3
2
Ozone, pg/m
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
6
(1310)
188
3.1
1.7
0.44
142.
0.3
0.3
0.2
0.6
7
(1327)
189
3.5
2.1
0.45
129.
0.4
0.4
0.3
0.7
8
(1337)
145
1.9
2.2
0.28
147.
0.4
0.2
0.3
0.8
9
(1349)
155
1.4
3.9
0.24
171.
0.6
0.2
7.7
0.6
88
-------
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line of the flight were small. Center line concentrations upwind and up to
about 40 km downwind of the city were higher than along the corresponding
edges, but then decreased slightly further downwind. Nearer, but upwind
of Dayton, the centerline concentrations increased more rapidly than the
edge concentrations.
Variation of Hydrocarbon Concentrations and Ratios
Hydrocarbon samples 2, 6, 7, and 9 were taken over the urban areas
of Columbus and Dayton. Except for a sample 9, the samples collected
over urban areas had a higher acetylene concentration than those collected
over "rural" areas.
When concentrations of the gases isopentane, acetylene, and carbon
monoxide are plotted versus distance from the center of Columbus (figure 46),
in each case the concentration in sample 2 was higher than in sample 1.
With increasing distance from the city, the concentrations gradually de-
creased until, about 56 km (30 run) downwind, the concentrations approached
those observed in the air 19 km (10 nm) upwind of Columbus. The fifth
sample (taken on crosswind leg 6) has an elevated value of isopentane
and carbon monoxide. The acetylene concentration is missing due to analyti-
cal problems. If the wind direction and speed stayed constant at 073° and
3.6 m/sec (7 knots), the parcel of air at leg 6 would have been in the
Columbus metropolitan area around 0646. This roughly corresponds to the
time of early morning traffic buildup, and so these elevated hydrocarbon
concentrations downwind could be due to this Tuesday morning traffic.
Hydrocarbon samples 6 and 7 were taken over the Dayton area and contain
the highest acetylene concentrations observed. The ozone concentrations at
Dayton were also the highest observed. Since the acetylene concentration
over Dayton was almost twice the value of sample 4 (whose concentration is
assumed to be due in part to Columbus), it seems that Dayton's higher acety-
lene concentration (over that of sample 4) was due to emissions in and
near Dayton itself.
Comparison of Aircraft Data with Ground Station Data
The overall ozone concentration measured aloft during the flight
was higher than that reported by any of the ground stations of Cincinnati,
Dayton, Columbus, or Wilmington.
90
-------
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20 30 40 50 60 70 80 90 100 120
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Distance, from City Center, Kilometers
Figure 46.
1 2 3 485
Hydrocarbon Sample Number
Isopentane, acetylene, and carbon monoxide concentrations
upwind and downwind of Columbus. Flight of July 16, 1974.
91
-------
3. Square Wave Flight of Sunday, July 21, 1974
This was the only square wave flight made on a Sunday. During
the flight, ground level ozone concentrations in Columbus were less than
3 3
140 yg/m all day. Ozone concentrations at Wilmington were about 110 yg/m
3 3
at 1200 but increased to over 160 yg/m by 1400 and exceeded 200 yg/m at
1800 EOT. Ozone concentrations at rural locations in Ohio showed similar
behavior. The flight track is shown in figure 47. Hydrocarbon data are
summarized in table 18.
Diurnal Variation of Ozone Concentration
Comparison of ozone concentrations near intersecting points of the
flight path shows that there was little diurnal variation at points over
"rural" areas. However, at the point of intersection just downwind of
3
the city, an increase of 40 yg/m ozone was noted during a 2-hour time
period.
Variation of Ozone Concentrations Upwind, Over, and Downwind of the City
The average ozone concentration increased for each successive cross-
wind leg downwind of Columbus. Ozone values recorded on the outer edges
of the flight pattern also showed a steady increase with both time and
increasing distance downwind of the city.
Variation of Hydrocarbon Concentrations and Ratios
When the concentrations for the gases, acetylene, isopentane, and
carbon monoxide are plotted in figure 48 versus distance from the city
for samples 1, 2, 3, 4, 5, and 6 (crosswind legs 2, 3, 4, 5, 6, and 7,
respectively), a definite increase in concentration of each was noted as
the plane flew into the Columbus area. Then, as samples were collected
farther and farther downwind, steadily lower concentrations were observed.
No "bulge" in hydrocarbon concentrations occurred downwind, as was seen
in other square wave flights. It should be noted that this flight occurred
on Sunday, a day without typical workday traffic patterns. Beyond about 74 km
(40 run) these pollutants were found to be at about the same concentrations
as they were upwind of the city.
92
-------
12:29
183 183 2"Jl91 206 179
13.50 / 189 193
FLIGHT DATE: July 21, 197A
TRUE AIRSPEED: 259.3 kzn/h (140 knoti.)
LOW LEVEL WINDS: Sfc
609 m (2,000')
914 m (3,000')
1219 m (4,000')
DATA: Ozone Concentration in pg/m'
Tljne In EDT
Hydrocarbon Sample Positions
Denoted !.y i i
P.UTERN: -^uare Vave
•.L'^iOS ALTI'.uBE: 975.36 m (3,200 ft)
above msl
O30'"/3.09 m/s (6 knots)
060V6.17 n/s (12 knots)
055-/4.12 n/s (8 -x,ots)
0"',-" 'l.oC m/s (7 knots)
Lou Level Winds Obtained From
National Weather Service
Upper Air Station
Dayton, Ohio-0800 EDT
Figure 47. Square wave flight of July 21, 1974.
93
-------
Table 18. Abstract of hydrocarbon data: Square wave flight of
July 21, 1974
Catetory
2
Ozone, pg/m
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
Sample number (time of sample collection-EDT)
1
(1222)
180
1.4
1.6
0.24
171.
0.3
0.3
0.0
0.8
2
(1235)
183
2.8
1.3
0.37
132.
0.3
0.4
0.1
0.5
3
(1251)
188
2.2
1.6
0.30
136.
0.4
0.0
4
(1306)
194
1.8
2.8
0.28
156.
0.6
0.6
0.1
1.3
5
(1321)
195
1.8
1.3
0.26
144.
0.3
0.3
0.1
0.6
3
Ozone, yg/m
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/ propane
E thy Ibenzene /acetylene
Propylene/acetylene
6
(1337)
206
1.4
1.6
0.23
164.
0.6
0.4
0.7
7
(1359)
197
1.5
1.9
0.23
153.
0.3
0.3
0.5
8
(1410)
208
1.8
1.5
0.26
144.
0.3
0.4
0.1
0.9
9
(1419)
216
2.8
1.0
0.33
118.
0.3
0.8
0.2
1.0
94
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Hydrocarbon Sample Number
Figure 48. Acetylene, isopentane, and carbon monoxide concentrations
upwind and downwind of Columbus. Flight of July 21, 1974.
95
-------
4. Square Wave Flight of Thursday, July 25, 1974
Navigational difficulties were encountered during this flight.
Thus, the flight track is very irregular. The flight track is shown in
figure 49. Hydrocarbon concentrations and ratios are given in table 19.
Diurnal Variation of Ozone Concentration
There appeared to be little diurnal variation of ozone based on
a comparison of average concentration taken upwind of the city of Columbus
3 3
at the beginning (185 yg/m ) and end of the flight (180 yg/m ).
Variation of Ozone Concentrations Upwind, Over, and Downwind of the City
A comparison of average ozone concentrations on cross legs 3 through 6
shows an increase in ozone concentrations downwind of Columbus with a
gradual decrease until at about 74 km (40 run) downwind, concentrations were
similar to those on the upwind legs.
Based primarily on nine, high data points to the northwest of Columbus,
a sharply defined downwind plume containing high concentrations of ozone
(^ 296 yg/m ) is indicated. The plume axis lies (approximately) along the
278 degrees radial from Columbus, suggesting a transport wind from 98
degrees east of north. The plume seemed to be about 37 km (20 nm) wide
with higher concentrations on the southeast edge (ozone concentrations at
least 25 percent higher than elsewhere along the flight path). Surface
wind peaks were small and from a northeast to east-southeast direction.
Because of the irregular flight plan and misorientation with the apparent
transport wind, further evidence of a city plume did not appear in the
ozone data.
Variation of Hydrocarbon Concentrations and Ratios
Acetylene and isopentane concentrations for samples collected upwind
and downwind of Columbus are shown in figure 50. Acetylene did increase down-
wind of the city, peaking in sample 4, 52 km (28 nm) from the city's center.
It then fell off slowly until at 122 km (66 nm) downwind its concentration
was about the same as the upwind concentration. Isopentane behaved in
almost the reverse manner, being lower at the point at which acetylene
peaked and much higher 122 km (66 nm) downwind in sample 6. Sample 6 was
collected in the vicinity of Lima, and this city's influence, especially a
96
-------
FLIGHT DATE: July 25. 1974 PATTERN: Square Wave
TRUE AIRSPEED: 259.3 km/h (140 knots) MISSION ALTITUDE: 762.0 meters (2,500 ft)
LOW LEVEL WINDS: Sfc
609 m (2,000')
914 m (3.0001)
1219 m (4,000')
DATA: Ozone Concentration in ug/m
Time in EOT
Hydrocarbon Sample Positions
Denoted by . .
above msl
070V2.57 m/s (5 knota)
135V3.60 m/8 (7 knots)
130V4.12 m/s (8 knots)
110°/4.12 m/s (8 knots)
Low Level Winds From
National Weather Service
Upper Air Station
Dayton, Qhlo-0800 EDT
Figure 49. Square wave flight of July 25, 1974.
97
-------
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Table 19. Abstract of hydrocarbon data: Square wave
flight of July 25, 1974.
Category
3
Ozone, yg/m
Acetylene , ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
Sample number (time of sample collect ion- EDT)
1
(1329)
197
1.8
2.0
0.22
112.
0.3
0.1
<0.1
0.3
2
(1340)
206
2.6
1.7
0.28
108.
0.1
0.2
0.1
0.4
3
(1405)
217
2.3
1.5
0.27
117.
0.3
0.5
0.1
0.7
4
(1420)
211
2.7
1.8
0.26
96.
0.3
0.3
0.4
5
(1449)
186
2.4
1.5
0.25
104.
0.4
0.1
0.6
2
Ozone, yg/m
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
>~>T-O •• ' -^/acetylene
6
(1509)
177
2.0
1.6
0.25
125.
0.3
0.6
0.1
2.8
7
(1542)
190
1.4
2.2
0.26
186.
0.5
0.3
1.1
8
(1557)
191
1.7
2.8
0.23
164.
0.5
0.3
0.8
9
(1610)
175
1.2
1.7
0.22
183.
0.7
0.2
0.9
99
-------
tank storage area, could have been present here. The very large concen-
tration of isopentane in sample 5 tends to substantiate this observation.
Comparison of Aircraft Data with Ground Station Data
This flight passed over none of the rural ground stations. The wind
at 750 m (2500 ft msl) was generally from the direction of the McConnelsville
station. Examination of the diurnal curves for Columbus and McConnelsville
show that the rural station attained higher ozone concentrations than the
city station (170 vs 147 Ug/m at peak hourly average). The ozone concen-
trations measured by the aircraft instrument were higher on the average
than either the city or the rural station. The low pass check of the air-
brone ozone instrument showed it was reading from 15 to 19 percent higher
than the Wilmington ground station instrument. The close check kept on
calibration of instruments leads us to believe that this was a real
difference.
6.1.2 Double Box Flights
The rationale for the use of the double box flight pattern has been
presented in section 2 of this report. Three double box flights were
examined for variations of ozone concentration in the areas of the city,
the inner box, and the outer box. Also, the hydrocarbon samples were
compared with one another and related to the average ozone concentration
in the area where they were collected. When appropriate, meteorological
conditions for the area are presented and pollutant behavior at the ground
stations is discussed.
1. Double Box Flight of Saturday, July 6, 1974
The flight track is shown in figure 51. Hydrocarbon concentrations
and ratios are given in table 20. Unfortunately, the hydrocarbon samples
and their analyses are incomplete. The aircraft passed into and out of
an area of haze several times; thus the meteorological summary in appendix
C, figure C-5, should be examined. The distribution of temperature at
flight level did not indicate a frontal zone aloft as the strong turning
of the wind between 610 m (2000 ft) and 915 m (3000 ft) suggested. The
air trajectories at 915 m (3000 ft) (see appendix F) for this time period
showed a northwesterly flow into the area with a change toward easterly
100
-------
(6)
160
VJ
159 1J8
167 165 169 167 1J6 176
1.66 176
1JI5 1IJ9 174 173 1B1
16:32
FLIGHT DATE: July 6, 1974
TRUE AIRSPEED: 277.8 tan/h (150 knots)
LOW LEVEL WINDS: Sfc
609 m (2,000')
914 m (3,000')
1219 in (4,000')
DATA: Ozone Concentration in Mg/m
Tine In EOT
Hydrocarbon Sample Positions
Denoted by | (
PATTERN: Double Box
MISSION ALTITUDE: 762.0 m (2,500 ft)
above msl
080°/2.57 m/s (5 knots)
130V3.60 m/s (7 knots)
215°/2.06 m/s (4 knots)
290°/2.06 m/s (4 knots)
Low Level Winds From
National Weather Service
Upper Air Station
Dayton, Ohio-0800 EDT
Figure 51. Double box flight of July 6, 1974.
101
-------
Table 20. Abstract of hydrocarbon data: Double box
flight of July 6, 1974.
Sample number
(Time of sample collection-EDT)
12345
Category
3
Ozone, yg/m *****
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
678
(1430)
173 * *
3.9
1.4
0.4
0.5
0.1
0.4
9 10
(1615)
185 *
1.4
5.5
0.4
0.1
0.6
0.7
*
No data—analytical problem.
102
-------
as the surface high-pressure system moved eastward. Surface winds at
Dayton, Columbus, and Akron were northeast to easterly throughout most
of the day. The 1300 EDT weather observation at Dayton showed that the
visibility decreased from 13 km (8 miles) at 1000 to 8 km (5 miles)
at 1300, and to 5 km (3 miles) by 1600. At the Columbus airport the
visibility was never less than 13 km (8 miles) after 1000. At Akron and
Cleveland, the visibility was essentially unlimited. The three hourly
weather reports from Cincinnati Airport showed that visibility never ex-
ceeded 5 km (3 miles) after sunrise.
From the available data, no meteorological cause of the strong visi-
bility gradient can be determined.
Diurnal Variation of Ozone Concentration
At most of the common locations in the flight plan the ozone concen-
trations were nearly identical. The principal exception is the return
diagonal leg from Columbus to Wilmington, where concentrations increased
•j
over previous values by from 30 to 100 yg/m . These variations were
most evident in the vicinity of the city.
Variation of Ozone Concentrations in Space
To the north of an east-west line approximately through Columbus,
the average ozone concentrations were substantially less (200 yg/m on
3 33
leg 2 and 173 yg/m on leg 6) than the 252 yg/m on leg 5 and 286 yg/m
on leg 8. On legs 1, 7, 9, 3, 5, and 10, a sharp (>_ 30 yg/m ) decrease
of ozone occurred in the span of 4 minutes (18 km, 10 nm), as the aircraft
moved from hazy to clear air. The change of visibility correlated with
an increase of ozone concentration, suggesting that the haze (as well as
the ozone) was of photochemical origin.
2. Double Box Flight of Tuesday, July 9, 1974
The flight pattern and measured ozone concentrations for the flight
of July 9, 1974, are shown in figure 52. Hydrocarbon data are presented in
table 21. On this day a broad area of high pressure covered the south-
central and southeastern sections of the United State. A weak cold front
lying on an east-west line through the Lake Superior region separated
this high-pressure system from another high situated over the Hudson's
Bay area of Canada.
103
-------
261 255 271 265 265 267 253 252 254 255 252
CLINTON
CO. APB
252 256 251 \
13:29\
(8)
FLIGHT DATE: ' July 9, 1974
PATTERN: Double Box
TRUE AIRSPEED: 277.8 kra/h (150 knots) MISSION ALTITUDE: 762.0 m (2,500 ft)
above msl
LOW LEVEL WINDS: Sfc
609 m (2,000')
914 m (3,000')
1219 m (4,000')
DATA: Ozone Concentration ug/m
Time In EOT
Hydrocarbon Sample Positions
Denoted by I I
215°/2.06 m/s (4 knots)
250V4.63 m/s (9 knots)
270°/3.09 m/s (6 knots)
285°/2.57 m/s (5 knots)
Lou Level Winds From
National Weather Service
Upper Air Station
Dayton, Ohlo-0800 EDT
Figure 52. Double box flight of July 9, 1974.
104
-------
Table 21. Abstract of hydrocarbon data: Double box flight of July 9, 1974.
Category
Ozone, Vg/m^
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
Sample number
(Time of sample collection-EDT)
I
(1046)
240
3.8
3.1
0.30
79.
0.6
0.3
0.3
0.5
2
(1059)
235
2.3
2.4
0.27
117.
0.2
0.2
0.4
0.4
3
(1113)
238
2.1
3.5
0.27
129.
0.5
0.1
0.1
0.2
4
(1124)
237
1.9
9.3
0.28
147.
0.4
0.2
0.1
0.6
5
(1133)
336
8.9
0.9
0.67
75.
0.5
0.3
0.2
0.4
o
Ozone, pg/m
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
i r opylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
6
(1206)
253
1.8
17.6
0.25
139.
0.4
0.1
0.3
0.3
7
(1239)
245
1.7
2.9
0.26
153.
0.4
0.2
0.2
0.5
8
(1310)
239
1.9
3.3
0.22
116.
0.5
0.1
0.1
0.3
9
(1344)
323
3.5
1.7
0.38
109.
0.6
0.1
0.1
0.3
10
(1423)
263
3.5
2.2
0.32
91.
0.3
0.1
0.3
0.2
105
-------
Wind conditions over the Columbus area are given in table 22. In
general the wind direction veered with height and remained within the
2.5 to 5 m/sec (5 to 10 mph) speed range. It is of interest to note that
the surface wind at Columbus backed from 250° at the beginning of the
flight to approximately 130° at the end of the flight period. The
increase in wind speed to 7.5 m/sec (15 mph) during mid-afternoon can be
considered to remove this flight from the "stagnating high pressure
system" category. However, this speed increase may have been transitory
and local as is suggested by the measured speeds of 5 m/sec (10 mph) or
less shown in both the 0800 and 2000 EDT upper wind observations at Dayton,
Ohio. The backing of the wind with time in both the upper wind and surface
observations was probably associated with the development of a trough of
low pressure over the southern Appalachians during this period and the
development of a ridge of high pressure east of Columbus.
Diurnal Variation of Ozone Concentration
The ozone concentration measurements from this flight were first
examined for evidence of a time trend in the data to determine if a
correction should be applied to negate the effect of the normal afternoon
increase in ozone concentrations usually found in surface-level measure-
ments. Figure 53 shows a comparison of the ozone concentrations measured
on the flights along the diagonal of the double box pattern from southwest
to northeast from 1026 EDT to 1154 EDT* and from northeast to southwest
from 1402 EDT to 1449 EDT. No time trend of increasing ozone is evident
in the data shown in figure 53, although there is a separation of at least
two hours between the measurements making up the data pairs. The diver-
gence of the data points at the southwestern end of the flight can probably
be associated with altitude changes during ascent and descent from and to
the base station at Wilmington. Based on this analysis, the measured ozone
concentrations were used without correction for a trend with time.
This flight was interrupted to fly the pattern of the inner box and, conse-
quently, took longer to complete than did the uninterrupted return flight.
See flight pattern, appendix C, flight C-6.
106
-------
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107
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108
-------
Other Ozone Variations
The ozone concentrations on the eight legs of the flight (each
side of each box pattern being considered a flight leg) were examined
to determine if there were recognizable differences in the fields of ozone
concentrations from which these sets of samples had been drawn. The
results are summarized in table 23. For convenience, the legs of the flight
have been numbered sequentially counterclockwise, starting with the northern
side of the inner box as number 1 and the northern side of the outer box
as number 5.
Several features stand out in the statistics given in table 23. Ex-
cluding leg 4 (inner box) and leg 8 (outer box), the average concentrations
of ozone around the inner box are on the order of 10 percent less than
around the outer box, and the average deviations from those average concen-
trations are about twice as large around the outer box. The extreme devia-
tion from the average concentration in each case is positive, that is, a
higher-than-average concentration.
The average concentrations along flight legs 4 and 8 differ from the
average concentrations on the other three legs of their boxes by about 20
and 6 percent, respectively.
When the ozone concentration measurements are plotted in their appro-
priate geographic relationship (figure 54) it appears that there is a
Table 23. Characteristics of ozone concentration
distributions by flight leg - July 9, 1974
Flight
Leg
1
/_
3
4
5
6
7
8
No. of
Obs.
6
6
4
5
16
17
15
16
Average
Concentration
(yg/m3)
232
244
243
287
263
264
263
278
Av . Dev .
from Average
2.7
10.5
9.8
39.2
8.7
21.0
19.0
20.0
No.
4
2
1
3
7
5
8
12
of Dev.
2
4
3
2
9
12
7
4
Max.
(Ug/nf
4
19
20
75
28
85
66
72
Dev.
5
14
10
46
11
28
43
27
109
-------
261 1SS Ml 145 245 147 IS! JS2 154 255 JS2
110 227 233 "* 23* 21*
CLIKTOH
CO. A'B
FLIGHT DATE: July 9. 1974
TRUE AIRSPEED: 277.8 krn/h (150 knots)
LOW LEVEL WINDS: Sfc
609 n (2,000')
914 n (3,000')
1219 m (4,000')
DATA: Ozone Concentration yg/n
Time in EDT
Hydrocarbon Sample Positions
Denoted by
PATTERN: Double Box
MISSION ALTITUDE: 762.0 n (2,500 ft)
above msl
215V2.06 m/s (4 knots)
250°/4.63 m/s (9 knots)
270V3.09 m/s (6 knots)
285V2.57 m/s (5 knots)
Low Level Winds From
National Weather Service
Upper Air Station
Dayton, Ohio-0800 EDT
Figure 54. Suggested plume from Columbus: flight of July 9, 1974.
110
-------
correlation between the high values of ozone concentrations observed
3
on legs 4 and 8. An area of ozone concentration greater than 300 yg/m
can be depicted as shown by the hatched area in the figure. Considering
the west to southwesterly winds at flight level, this area of high ozone
concentration can be construed as an ozone plume emanating from Columbus.
The hydrocarbon data, as exemplified by the acetylene concentrations,
correlate well with these observations. The two inner-city acetylene
concentrations were 3.8 and 3.5 ppbc. To the east the concentration or
the inner leg of the pattern was 8.9 ppbc; the concentration on the outer
box was 3.5 ppbc. Concentrations on the north, west, and south legs of
both inner and outer boxes ranged from 1.7 to 2.3 ppbc. There is also
3
an ozone concentration value of 349 yg/m along the last quarter of leg 6
3
and several measurements of concentrations sliehtly in excess of 300 yg/m
in the vicinity of the turn from leg 6 to leg 7. These high concentrations
of ozone cannot be attributed to Columbus. However, Dayton is approximately
3
32 km almost due west of the measurement of 349 yg/m ozone, and Cincinnati
is southwest of Columbus, practically along an extension of the diagonal
flight path through the boxes, and approximately 59 km from the > 300 yg/m
measurements. If this association of ozone concentrations with urbanized
areas has validity, a conditions such as shown schematically in figure 55
might arise at flight level (762 m, 2500 ft, MSL) with a windspeed of
3.6 m/sec (8 mph).
3. Double Box Flight of July 13, 1974
On July 13, 1974, the double box flight pattern originated at 1100
at Wilmington, Ohio. The flight ended at 1518 EDT. The flight altitude
762 m (2500 feet) MSL; the true air speed was 69 m/sec (135 knots). Winds,
as measured by the Dayton RAOB station were:
SFC 130° 2 m/sec (4 kt)
600 m (2000 ft) 205° 3 m/sec (6 kt)
900 m (3000 ft) 145° 1 m/sec (2 kt)
1200 m (4000 ft) 075° 1 m/sec (2 kt)
Ten hydrocarbon bag samples were collected during the flight. Ozone
was measured continually. The flight track is shown in figure 56. Hydro-
carbon concentrations and ratios are summarized in table 24.
Ill
-------
400
350
^300
60
e
o
•H
4-1
cd
H
4J
C
0250
o
01
d
o
N
O
200
50
10
20 30 40 50 60
Downwind Distance, Kilometers
70
80
90
Figure 55.
Travel Time, Hours
Ozone concentrations at 762 m (2500 ft) msl downwind
of an urban area. Curve has been synthesized from the
highest ozone concentrations attributed to Columbus, Dayton
and Cincinnati in the discussion of the flight of July 9,
1974. Windspeed, 3.6 m/sec (8 mph) .
112
-------
(6)
12:27
241 2*1 /14:33
239 241 252 248 236 144 236 244
CLINTON
CO AFB
FLIGHT DATE: July 13. 1974
PATTERN: Double Box
TRUE AIRSPEED: 250.0 km/h (135 knots) MISSION ALTITUDE: 762.0 m (2,500 ft)
above msl
LOW LEVEL MINDS: Sfc
609 m (2,000')
914 m (3,000')
1210 m (4,000')
DATA: Ozone Concentration In Mg/m
Time In EOT
Hydrocarbon Sample Positions
Denoted by | |
130°/2.06 m/s (4 knots)
205V3.09 m/s (6 knots)
145°/1.03 m/s (2 knots)
075°/1.03 m/s (2 knots)
Low Level Winds From
National Weather Service
Upper Air Station
Dayton, Ohio-0800 EDT
Figure 56. Double box flight of July 13, 1974.
113
-------
Table 24. Abstract of hydrocarbon data: Double box flight of July 13, 1974.
Category
o
Ozone, yg/m
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide/ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
Sample number
(Time of sample collection-EDT)
1
(1118)
231
2.8.
2.4
0.24
86.
0.4
0.1
-
0.4
2
(1132)
230
2.3
2.7
0.21
91.
0.5
0.2
-
0.4
3
(1144)
230
1.7
3.2
0.23
135.
0.4
0.2
~0.4
0.6
4
(1156)
220
2.5
2.5
0.28
112.
0.4
0.1
0.2
0.4
5
(1205)
255
6.4
1.3
0.49
77.
0.3
0.1
0.2
0.3
Ozone, yg/m
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide/ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
6
(1239)
237
1.7
2.9
0.23
135.
0.2
0.2
~0.5
0.7
7
(1311)
273
3.1
2.5
0.34
110.
0.3
0.1
0.2
0.3
8
(1343)
235
1.9
2.5
0.24
126.
0.3
0.2
0.3
0.5
9
(1414)
251
2.4
2.0
0.24
100.
0.3
0.2
0.7
0.8
10
(1454)
263
2.5
3.7
0.30
120.
0.3
>0.5
>0.1
1.3
114
-------
Diurnal Variation of Ozone Concentration
There appears to be little diurnal variation along the flight path
during this time frame. This statement is based on the small change
in the average ozone concentration (231 yg/m ) for the initial diagonal
extending from Wilmington to the northeast as compared to the concentration
3
(242 yg/m ) on the same diagonal on the home-bound leg at the end of the
flight, which ended 3 hours after completion of the first diagonal.
There does, however, seem to be a significant diurnal change in the
ozone concentrations (along a portion of the same diagonals) taken over
Columbus. The three values recorded earlier in the day (around 1118)
3 3
averages 231 yg/m ; later in the day (around 1454) the average was 263 pg/m .
This would be expected behavior for a somewhat stagnant air mass above a
city; in other words, it reflects the more dramatic diurnal behavior of an
air mass above the city as compared to the 7o2 m (2500 ft) level variations
throughout the general area of the double box pattern.
Variation of Ozone Concentrations; Inner Box Versus Outer Box
The overall average of the ozone concentration along the four sides
3
of the inner box is 234 yg/m . The corresponding average for the outer
3
box is 244 yg/m . This result suggests that the inner box is more under
the city's influence than is the outer box. However, the difference between
o
the ozone average of inner and outer box is only 10 yg/m .
Other Variations in Ozone Concentrations
There were two ozone "hot spots" in two of the box sides. One was
on the eastern leg of the inner box where, over at least a 9 km (5 nm)
3
path, the ozone concentration was greater than 272 yg/m . The second was on
•".he western leg of the outer box where the ozone concentration averaged
3
274 yg/m over a 37 km path. Both these high ozone spots occurred during
'• "• pa?:t of the flight track where hydrocarbon samples were being collected.
The hydrocarbon content of the bags is discussed below. The inner-box
ozone "hot spot" probably can be attributed to Columbus while that in the
outer box probably reflects precursor injection from upwind (i.e., from
somewhere other than Columbus.
Comparison of Various Hydrocarbon Concentrations and Ratios with Ozone
Concentrations
Hydrocarbon samples 1 and 10 were taken over the city of Columbus,
115
-------
approximately 3.5 hours apart. During this span of time, the average ozone
3
concentration over the city increased from 231 to 263 Ug/m .
The acetylene concentrations were about the same in the two samples,
2.8 and 2.5 ppbc. However, there was some doubt of the validity of the
acetylene concentration in the analysis. The carbon monoxide concentration
3 3
was 344 yg/m in sample 1 and 366 pg/m in sample 10. Each of the hydro-
carbons n-butane, isopentane, and n-pentane (which were analyzed on a
different chromatographic column and whose concentrations are considered
valid) show an increase with time when samples 1 and 10 are compared. A
similar increase is noted for each of the oxygenated compounds, acetaldehyde,
propionaldehyde, and acetone. An increase also occurred in the unsaturated
compounds, isobutylene.
All these increases could be expected to occur in the air over a city
while stagnant-air conditions were prevalent. The hydrocarbon concentra-
tions would build due to emissions and to evaporative processes; the oxygenated
compounds would increase due to oxidation of hydrocarbons both by combustion
and in atmospheric photochemical processes.
Average concentrations for gases in the four samples of the inner box
were 7.7 ppbc for isopentane, 3.2 ppbc for acetylene, 9.2 ppbc for n-butane,
3.4 ppbc for n-pentane, and 1.4 ppbc for isobutylene. The highest concen-
tration in each case occurred in sample 5, which incidentally was obtained
in the area of high ozone discussed earlier. The corresponding averages
for the four samples of the outer box were 4.8 ppbc for isopentane, 2.3 ppbc
for acetylene, 6.1 ppbc for n-butane, 2.5 ppbc for n-pentane, and 0.75 ppbc
for isobutylene. In each case, the average concentration was lower than
that of the inner box. Also, the highest concentration in each case occurred
in sample 7, again a sample taken in a high ozone area.
The average concentrations for gases in the four samples of the inner box
for the oxygenated compounds acetaldehyde, propionaldehyde, and acetone were
6.6, 2.6, and 6.9 ppbc, respectively. The highest concentration for each
occurred in sample 5. The average concentrations for the same oxygenated
compounds in the outer box were 5.6, 2.6, and 12.2 ppbc. The highest con-
centration for each occurred in sample 7. The concentrations of oxygenated
compounds were about the same in the inner and outer boxes for acetaldehyde
and propionaldehyde; acetone was much higher in the outer box.
116
-------
The similarity in concentrations for the oxygenated compounds suggests
that their presence away from the city is dependent on injection of hydro-
carbons from the city followed by photooxidation. The direct emissions of
these compounds from sources in the countryside surrounding the city cannot
at this time be ruled out, nor can the possibility that there was an appre-
ciable "residue" of compounds from a prior day's emission from Columbus.
6.1.3 Eastern Flight of August 21, 1974
The purpose of this flight was to examine variations in ozone concentra-
tion over a widespread area under stagnant-air conditions. The aircraft
departed from Wilmington at 0949. The flight was flown at 1200 m (4000 ft)
msl at a true air speed of 69 m/sec (135 knots). The 1200 m (4000 ft)
winds at 0700 measured at the Dayton RAOB Station were from the south-
east at 2.6-5.1 m/sec (5-10 knots). The total time of the mission was 6
hours. Eight hydrocarbon bag samples were collected in the areas indicated
on the flight track shown in figure 57. Hydrocarbon concentrations and
ratios are summarized in table 25. The flight path was planned so that a
large area could be surveyed for ozone while allowing the plane to pass
over each of the ground stations.
Diurnal Variation of Ozone Concentration
It is difficult to establish whether diurnal variation occurred during
this flight since only at two points did the flight pattern pass through
the same airspace. At one of these crossover points, the later ozone con-
centration was 6 yg/m higher than the earlier concentration (239 versus
233). At the other crossover point, the later ozone concentration was
3
21 yg/m lower than the earlier value (247 versus 268). If the average con-
c. .tration for the flight from Wilmington to McConnelsville (Wayne County
Airport) is compared with the corresponding portion of the return flight
(about 32 km further north), an increase of 36 yg/m ozone is seen. These
flight portions were flown about 5 hours apart. Whether this finding could
support the idea of significant diurnal variation is questionable.
High Ozone Concentrations During the Flight
An area existed near McConnelsvilee (Morgan County Airport) where five
consecutive ozone measurements averaged 262 yg/m . The average for the
117
-------
CLINTON
09:49 CO. tra 16="
17*1*5
10 N. Mi.-
FLIGHT DATE: August 21. 1974
TRUE AIRSPEED: 250 kn/h (135 knots)
LOU LEVEL WINDS: Sfc
609 m (2000')
914 m (3000')
1219 m (4000')
DATA: Ozone Concentration in Mg/«
Tlo« In EDT
Hydrocarbon Sanple Positions
Denoted by i i
PATTERN: Eastern Stagnation Ground
Station Interlock
MISSION ALTITUDE: 1219 III (4000 ft)
above Ml
140V2.06 »/9 (4 knots)
145V5.66 ml a (11 knots)
130V6.69 «/s (13 knots)
140V6.69 •/« (13 knots)
Low Level Ulnds Fron
National Weather Service
Upper Air Station
Dayton, ohlo-0800 EDT
Figure 57. Eastern flight of August 21, 1974.
118
-------
Table 25. Abstract of hydrocarbon data: eastern flight of
August 21, 1974
Category
3
Ozone, pg/m
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
Sample number (time of sample collection-EDT)
1
(1010)
204.
1.7
2.
-
-
0.4
0.5
0.1
0.6
2
(1056)
233.
1.9
1.
-
-
0.2
0.2
0.2
0.4
3
(1147)
298.
2.8
1.
-
-
0.5
0.7
0.3
1.1
4
(1207)
215.
1.8
2.7
-
-
0.4
0.8
0.1
1.2
Ozone, yg/m
Acetylene, ppbc
Aceta ' ^ehyde/acetylene
Carbon monoxide, ppm
.ft'-- , ,,:onoxide/acetylene
•^ atyiene/isobutane
Propylene/propane
Ethylbenzene/acetylene
•'T ovlene/acetylene
5
(1304)
258.
2.8
1.
-
-
0.5
0.7
0.3
1.1
6
(1500)
342.
6.9
0.9
-
-
0.2
0.3
0.4
0.3
7
(1530)
292.
2.8
1.
-
-
0.3
0.2
0.3
0.4
8
(1600)
193.
1.3
2.
-
-
0.6
1.0
0.3
2.
119
-------
five consecutive preceeding measurements was only 180 yg/m . In the
flight log it was noted that the area was particularly hazy, and several
industrial plumes (power plants and others) could be clearly observed,
and the odor of one (a pulp mill) was detected. It is possible that the
ozone enhancement could have been caused by photochemistry involving
effluents from these sources. The ground-station ozone concentration at
3
the same time (1015-1030) however, was only 45 yg/m . Evidently, some
stratification of ozone generative-ability existed.
A second "hot spot" occurred on the flight track leaving the Wayne
County Airport over the city of Dover, Ohio. The average for four ozone
3
measurements here was 393 yg/m . The four preceding points averaged only
259 yg/m3.
A third high ozone area was located just south of the DuBois-Jefferson
3
County Airport. The last two measurements before landing averages 359 yg/m .
3
The preceding five measurements averaged only 290 yg/m . Concentration of
3
ozone at the ground station was approaching 310 yg/m at this time. In
fact, DuBois had the highest diurnal peak for all stations, rural or urban,
measured that day.
Another elevation in ozone concentration occurred as the plane passed
northwest of Pittsburgh, about 50 km (30 run) downwind of the city. It is
significant that winds were from the southeast that day. A peak concentra-
3
tion of 405 yg/m was observed. The influence of the Pittsburgh city "plume"
is probable here. The hydrocarbon sample taken near this point also showed
elevated values of acetylene, other hydrocarbons, and carbon monoxide, again
pointing to the influence of the city.
Comparison of Aircraft Data with Ground Station Data
3
In general, ozone concentrations were high (i.e., >180 yg/m ) at all
ground stations during the portion of the day between 1600-1800.
At Wilmington, the average hourly ozone concentration from 0900-1000 was
3
76 yg/m when the airplane departed. The ozone concentrations at 1220 m
3
(4000 ft) msl ranged from 160-170 yg/m as the plane departed.
On the return flight, about 6 hours later, ozone concentration near
3
Wilmington averaged 183 yg/m in the 1500-1600 hour; ground concentration
3
averaged about 205 yg/m . Ozone concentrations at Wilmington reached a
high of 209 yg/m that day in the 1500 hour.
120
-------
Near the Wayne County Airport (Wooster) ozone concentrations averaged
about 140 yg/m in the 1100-1200 hour. The corresponding ground concentra-
tion during the same time frame was approximately 110 yg/m . The high for
3
the day at Wooster was 233 yg/m , occurring in the 1800 hour.
Near Garrett County, Maryland, ozone concentrations averaged 157 yg/m
during the 1200-1300 hour; ground concentrations were about 155 yg/m . The
3
high concentration for the day was about 189 yg/m and occurred during the
1800 hour.
Near the DuBois-Jefferson County Airport, the ozone concentrations just
3
before the aircraft landed averaged 379 yg/m . The ground concentration
3 3
was about 310 yg/m . The high for the day was 329 yg/m , which was the
highest concentration recorded at any of the ground stations, rural or
urban, for that day.
Pittsburgh and Columbus had peak ozone concentrations of about 188 and
3
176 yg/m for the hours ending at 1600 and 1900, respectively.
6.1.4 Vertical Flights
Vertical flights were made on June 25, July 17, August 1, and
August 15 over Wilmington and, on August 13, over Wooster and McConnelsville.
Flight tracks and ozone data for these vertical flights are presented in
figures in appendix C. Ozone data for the vertical flights flown on August
1, 1974, are presented in figure 58. Hydrocarbon concentrations and ratios
for vertical flights where grab samples were collected are summarized in
tables 26, 27, and 28.
The vertical profiles were all flown in the morning, except for the
"noon" and "evening" flights on August 1, 1974. On the latter two flights,
no hydrocarbon bag samples were collected.
In the mornings, in all cases, the ozone concentration aloft was higher
:>!-n the ground-station concentration and increased with altitude and usually
.Tf,p.2ared to peak somewhere between 610 m (2000 ft) and 1830 m (6000 ft).
At still higher elevations, the concentrations decreased. This is inter-
preted as being due to destruction of ozone in the nocturnal radiation
layer, preservation of ozone (with only slight destruction) in the remnant
of the previous day's mixing layer above the radiation inversion, and lower
concentrations still further aloft. The ozone at these highest altitudes
121
-------
CM
OO
SB c/1
O
-m
CN
o
.o
o
.""I
O
.o
c
o
HJ
(-1
4-1
c
-------
Table 26. Abstract of hydrocarbon data: vertical profile flight
Wilmington, Ohio, August 1, 1974
Category
2
Ozone, yg/m
Acetylene , ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
Sampling altitude (meters) (Time-EDT)
Ground
0845-
(0900 am)
30.
3.8
1.4
0.28
74.
0.4
0.3
0.2
0.4
Ground
1210-
(1315 pm)
110.
0.9
3.2
0.17
189.
1.0
0.5
1.2
0.2
609.6 m
(0715 am)
179.
1.4
1.1
0.22
157.
0.1
0.3
0.2
0.4
2
Ozone, pg/m
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propyiene/propane
Ethylbenzene/acetylene
•if ylene/acetylene
1219.2 m
(0730 am)
183.
1.4
1.7
0.23
164.
0.1
0.2
0.1
0.3
2438.4 m
(0745 am)
128.
0.4
5.0
0.17
425.
0.1
0.5
0.3
1.3
2438.4 m
(0750 am)
-
0.4
6.3
0.19
475.
2.3
0.6
0.3
1.5
123
-------
Table 27. Abstract of hydrocarbon data: vertical profile flight
Wooster and McConnelsville, Ohio, August 13, 1974
Category
Ozone, pg/m
Acetylene, ppbc
Acetaldehyde/ acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
Sampling altitude (meters) (Time-EDT)
Wooster
Ground
(-1130 am)
142.
2.2
1.6
0.4
168.
2.2
0.2
0.4
0.6
762 m
(1157 am)
151.
1.5
3.3
-
-
>0.2
0.9
0.3
0.5
1524 m
(1146 am)
125.
0.3
11.3
-
-
0.4
0.1
0.7
1.0
2286 m
(1135 am)
121.
0.2
16.5
-
-
0.5
0.2
1.0
0.2
McConnelsville
3
Ozone, yg/m
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
Ground
(-1230 pm)
149.
2.0
1.5
0.3
160.
0.2
0.1
0.3
0.5
762 m
(1313 pm)
153.
1.6
2.0
-
-
>0.1
0.1
0.1
0.5
1524 m
(1303 pm)
121.
0.6
3.0
-
-
0.7
0.1
0.3
1.0
2286 m
(1252 pm)
111.
0.4
6.5
-
-
3.5
0.5
-
4.3
124
-------
Table 28. Abstract of hydrocarbon data: vertical profile flight
Wilmington, Ohio, August 15, 1974
Category
3
Ozone, pg/m
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
Sampling altitude (meters) (Time-EDT)
Ground
(-1130 am)
117.
2.7
1.1
0.58
215.
0.1
0.1
0.4
0.2
610 m
(1056 am)
160.
2.7
1.2
0.59
219.
0.1
0.1
1.3
0.2
1220 m
(1121 am)
186.
1.7
2.3
0.31
182.
0.3
0.2
0.2
0.4
1830 m
(1134 am)
124.
3.4
0.7
0.80
235.
0.2
0.7
0.2
0.1
2
Ozone, pg/m
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propy . ene/propane
Ethylbenzene/acetylene
• rr. '-yleie /acetylene
2490 m
(1158 am)
109.
0.2
16.
0.14
700.
0.5
0.4
0.5
3.5
3050 m
(1208 am)
70.
0.2
11.
0.13
650.
4.3
0.8
0.
10.
3660 m
(1220 pm)
90.
>0.1
>11.
0.14
>1400.
-
1.9
1.0
21.
125
-------
was probably due to some movement of ozone upward from the mixing layer
into air which probably had no ozone synthesis or, at best, a minimal
generation.
The series of three vertical flights made on August 1 (figure 58)
indicate some photochemical ozone generation by the time of the "noon"
samples. By the time of the "evening" samples, the ozone concentration
at the ground had equalled or slightly exceeded the samples taken at
610 m (2000 ft) to 1220 m (4000 ft) and all concentrations measured at
or below 1220 m (4000 ft) were higher than the morning concentrations.
The hydrocarbon analyses show a general although not universal
tendency for acetylene to decrease with increasing altitude. At some
point aloft, however, the acetylene concentrations dropped precipitously,
as for example at 2440 m (8000 ft) on August 5 and August 15 over Wilmington,
and 1525 m (5000 ft) over Wooster and McConnelsville on August 13. The
acetaldehyde/acetylene and the propylene/acetylene ratios increased many
fold at the same time. Supposedly, however, the acetylene is less reac-
tive in atmospheric oxidation than other organics which are diluted along
with acetylene, so that the hydrocarbon/acetylene ratio should furnish a
measure of the extent of selective oxidation of the hydrocarbon. That the
acetaldehyde/acetylene ratio aloft was several-fold larger than at lower
levels (this was observed on all vertical flights) could be interpreted in
one of two ways, if one considers acetylene as unreactive.
1. A longer time was available in the air aloft for conversion of
hydrocarbons to aldehydes (or a faster rate of conversion occurred) than
at lower elevations.
2. The air aloft, in which the acetaldehyde/acetylene ratios were
startlingly greater than at lower elevations, had a completely different
history from the air beneath it in terms of injection of pollutants.
A rational explanation for the increased propylene/acetylene ratio
is not easily perceived unless the air aloft had a different history of
pollutant injection from the air near the ground. Propylene should be
destroyed more rapidly than acetylene, and its generation in the atmosphere
from other organic compounds seems kinetically and mechanistically improb-
able. The propylene/acetylene phenomenon was observed on all vertical
flights except the August 13 flight over Wooster.
126
-------
6.1.5 Summary of Results Relating to Aircraft Flight
In making conclusions about the aircraft data, it is instructive to
refer again to several tables and figures. Table 18 and figure 47 repre-
sent the square wave flight of July 21, 1974. The isobutylene/isobutane
ratio should decrease steadily in a reaction chamber, even if it is being
physically diluted. The same is true of the isopropylene/propane ratios.
In the case of this flight, the C ratio and the CL ratio were both 0.3 up-
wind of Columbus. Over Columbus the C, ratio was also 0.3, and the C« ratio
was 0.4. In hydrocarbon sample 4 taken downvind of Columbus, both ratios
were 0.6, indicating, at least, the injection of some olefins. The two
samples taken over Dayton had C ratios of 0.6 and 0.3 and C ratios of 0.4
and 0.3. Sample 8 was taken at approximately the same point in space as
sample 4. The ratios here were: sample 4, C,; 0.6, C_; 0.6; and sample 8,
C^; 0.3, C~; 0.4. The time differential between samples 4 and 8 was about
1 hour (1306-1410). The C» ratio comparison for samples 2 and 9 (which
are also comparable specially) was as follows: the isobutylene/isobutane
ratio was 0.3 in sample 9 and 0.4 in sample 2. If there is a pattern in
this, it is not one which would be consistent with the idea of a slug of
pollution drifting, like a smog chamber without walls, downwind from Columbus.
Pollution from the ground is assumed to be constantly mixed upward. Carbon
monoxide concentrations behave as if the substance had been injected in
the air over Columbus and was slowly diluted as the air drifted downwind.
The sequence of carbon monoxide values were: upwind 0.24 ppm, over Columbus
0.37 (at 1235) and 0.33 (at 1419) then 0.30, 0.28, 0.26, 0.23, and 0.23
ppm. As the flight got further downwind from Columbus, the same kind of
sequence can be seen in the acetylene concentration of the various samples.
Although there is clearly a region-wide (radius of 200 km [125 miles]
• nore) systea of high ozone concentration, a strong inference can be made
; the prod' "Ion of perturbations on the system (itself nonhomogeneous)
by the cities in the form of "hot spots." A good example of the latter
was found on the August 21 flight (fig. 57), which shows concentrations
of ozone to the northwest of Pittsburgh (approximately 50 km (30 miles)
downwind) ranging from 302 to 405 yg/m with all adjacent readings on the
3
flight path below 300 yg/m and values approximately 40 km (25 miles) upwind
127
-------
of Pittsburgh with values ranging from about 150 to 280 yg/m . The acety-
lene concentration measured downwind of Pittsburgh was 6.9 ppbc as compared
with a range of 1.3 to 2.8 ppbc in the rest of the flight samples.
On the double box flight of July 9 (figure 52 and table 21), the
urban influence of Columbus is seen to extend at least 70 km (44 miles)
to the east. This can be seen in both the hydrocarbon analyses and in the
ozone concentrations. In the two samples taken over the city, acetylene
concentrations are 3.8 and 3.5 ppbc, the concentrations north of the city
(inner-box value first, then outer-box value) were 2.3 and 1.8; on the
west they were 2.1 and 1.7; on the south they were 1.9 and 1.9; on the
east the inner box concentration was 8.9 and the outer box 3.5 ppbc. The
fact that the acetylene concentration of the eastern part of the inner
box was greater than the over-the-city concentrations could be either a
peculiarity of the plume distribution or representative of an earlier
hour of greater urban activity. The same phenomenon can be observed when
the ozone concentrations and the carbon monoxide concentrations in various
parts of the flight pattern were compared. This latter case (i.e., the
Columbus double box pattern) is clear cut, but the Pittsburgh influence
(at about 50 km) inferred from the data of August 21 may have been due
to some source other than Pittsburgh although no such source has been
positively identified.
In figure 48, data for acetylene, isopentane, and carbon monoxide from
the flight on Sunday, July 21, are plotted versus distance downwind of Columbus.
In air measured downwind of Columbus, the elevation over concentrations
measured upwind continued for about 69 km (43 miles) for acetylene, about
48 km (30 miles) for isopentane, and about 69 km (43 miles) for carbon
monoxide. The concentration increased over the city. It varied somewhat
downwind but remained elevated over the upwind concentration.
The overall patterns of hydrocarbon and ozone concentrations, though con-
siderably irregular, suggests a trend toward an increase aloft over or slightly
downwind of the city, followed at a further distance by a return to the
background concentration plus, at times, a slight increment.
The data indicate an extent of urban influence which is detectable
and assignable to a specific city if that city is about 80 km (50 miles)
or less distant from the sampling point.
128
-------
The nitric oxide and nitrogen dioxide concentrations aloft, except
in rare cases, were undetectable with the instrument used. This instru-
ment had been checked as to its proper operation at reduced pressures and
was calibrated before each flight. Much smaller increases of ozone con-
centrations with increased time of solar irradiation, in spacially compar-
able samples, were measured aloft than either in the cities or at the non-
urban surface stations. This plus the evidence from the vertical flights
indicates that the diurnal curve of ozone concentrations above the radia-
tion inversion layer is much shallower than that at the surface. The
possibility exists that, at times, diurnal ozone trends aloft may be un-
detectable. The existance of a diurnal ozone trend aloft would be controlled
by three things: the residue aloft of oxides of nitrogen and hydrocarbons
left from the previous day, mixing of ozone precursors aloft and the mixing
upward of ozone generated from fresh precursors emitted at the surface.
6.2 Interpretation of Ozone and Hydrocarbon Data from Ground Stations
6.2.1 Characteristics of Rural and Urban Ozone
Figures 59 and 60 show charts of the frequency distribution of the
hour of occurrence of the daily maximum ozone concentration at each of the
five rural and six urban stations during the summer of 1974. The chart in
the lower righthand corner of each figure is the combined frequency dis-
tribution for the rural or urban stations. One station (Cincinnati) has
been omitted from the set of combined urban station data because of the
small number of observations.
Summary statistics for the daily maximum ozone concentration at each
of the 11 stations are given in table 29. It is interesting to note that
among the rural stations, only McHenry did not have a mean daily maximum
ozone concentration value above the NAAQS. This is an unexpected result
since McHenry, during the previous summer period of observation (1973), had
ozone concentrations higher than those found at other stations in the area
covered by the present study. None of the urban stations had mean daily
maximum concentrations above the NAAQS. The lowest maximum daily ozone
concentrations at all the rural stations were considerably higher than the
corresponding concentrations at the urban stations.
129
-------
10.
Wilmington
55 Days
15., McConnelsville
56 Days
10
5-
(56 12
18
24
15
10
0 »
DuBois
56 Days
15 i
10
0
06
Wooster
57 Days
06
12
12
18 24
18
24
McHenry
J6 12 18
Hour - EOT
24
50 - Combined Data
281 Days
40
30
20
10 •
0
06 12 18
Hour - EOT
Figure 59. Frequency distribution of time of maximum hourly
ozone concentrations at rural stations.
24
130
-------
15,
10-
Cincinnati
42 Days
otL
06
12
18
0 06
12
15^
10-
Columbus
56 Days
0 0'6 12
15i
CO
>,
w
n
Canton
57 Days
10-
>
Hi
06 12
Hour - EOT
24
24
18 24
18 7k
10
5-
Cleveland
54 Days
El
06
12
18
24
15 1
10-
5-
0
Pittsburgh
55 Days
$
W
f
'"'>,'
« .•» '
:~™-'i
''#«• '
r S«R
9 EH 1..-. ...' 1 ^ Da
06
12
18
24
50,
Combined Data, Excluding
Cincinnati
275 Days
06 12 18
Hour - EOT
Figure 60. Frequency distribution of time of maximum hourly
ozone concentrations at urban stations.
131
-------
Table 29. Summary statistics for the daily maximum ozone
concentration for five rural and six urban stations.
The statistics are given in yg/m
STATION
Statistic
Mean
Std. Dev.
Minimum
Maximum
No. of Days
RURAL
c
o
4->
60
c
•a
r-H
•H
s
187
54
89
370
55
>
al
O
151
44
49
260
53
CO
3
jz
9
rH
O
CJ
158
67
39
340
56
c
o
.u
£
3
C_)
158
51
20
280
47
-o
c
a)
t-(
01
>
01
iH
U
135
51
39
270
54
45
60
V-i
J3
CO
4J
•p
•H
PL,
149
56
39
308
55
Returning to the charts in figures 59 and 60, it is apparent that
the individual station frequency distributions are not smooth functions,
although for the most part, similar characteristics are displayed by
both the rural and urban data. When the combined data charts for each
of the two categories are compared, the similarity in the characteristics
is more obvious. Both distributions are bimodal with the primary peak
occurring in the late afternoon (not unexpectedly) and the secondary peak
occurring in the hour after midnight. The most frequent times of
occurrence of the ozone maximum concentrations in the two combined
data sets show a difference of three hours; the rural maximum most
frequently occurs during the hour between 1700 and 1800 EDT while
the urban maximum occurs between 1400 and 1500 EDT. The greater
number of occurrences of daily maximum ozone concentrations at the rural
stations during the hour immediately following midnight may not be signifi-
cant. Almost half of the occurrences in this hour at the rural stations
are accounted for by McHenry data. This station may be unique among the
group because of its hilltop location and the consequent potential (but
not proven) advection of higher ozone concentrations from aloft as a result
of nocturnal, katabatic wind flow.
132
-------
Four Rural Stations
224 Days
Five Urban Stations
06 12 18
Hour - EOT
24
20
10
0 06 12 18
Hour - EDT
Figure 61. Comparison of frequency distribution of time
of hourly maximum ozone for rural and urban
stations.
If, on the basis of the above discussion, the McHenry data are elimi-
nated, the frequencies of occurrence of the time of hourly maximum ozone
concentrations for rural and urban stations compare as shown in figure 61.
The general characteristics of the rural distribution have not changed.
The maximum hourly ozone concentration is still indicated as being most
frequently measured during the hour between 1700 and 1800 EDT at the
rural stations, and the bimodal distribution is still apparent.
In summary, the data indicate that the maximum hourly ozone concen-
tration usually occurs in both urban and rural areas between the hours
of 1200 and 2000 EDT. The maximum hourly ozone concentration is lower
in urban areas than in rural areas and occurs about three hours earlier.
These features perhaps are related. If some "process" in the urban area,
such as increased release of nitric oxide from afternoon automobile
133
-------
traffic, operates to counteract the increase in ozone anticipated as a
result of photochemical reactions, the maximum concentration obtained would
be lower and would occur earlier in time, relative to events in the absence
of that "process." The process might involve an increase in emissions of
nitric oxide associated with increases in traffic at a time in the day
when ultraviolet irradiation is also declining. A similar effect of nitric
oxide would not be prevalent in rural areas.
Since the pattern of the time variation of ozone concentration on a
daily basis is determined not only by the maximum concentration values,
but also by the minimum daily values, similar frequency distributions for
the time of occurrence of the minimums are presented in figures 62 and 63.
Again, data for the five rural and the six urban stations are shown
individually but in the combined data sets Cincinnati (urban) has been
omitted because of the shorter period of record.
Summary statistics for the distribution of daily minimum ozone
concentrations at each of the 11 stations are given in table 30.
Table 30. Summary statistics for the daily minimum ozone
concentration for five rural and six urban stations
(Except for the number of days, the statistics are given in pg/m .)
STATION
Statistic
Mean
Std. Dev.
Minimum
Maximum
No. of Days
RURAL
c
o
4-1
00
c
3
•H
f
41
24
1
11
56
-------
30,
Wilmington
56 Days
30-
20-
10.
06
McConnelsville
60 Days
18 24
0
06
30^ Wooster
61 Days
20-
10-
30-
tT)
0 20
10-
a
McHenry
61 Days
12 18
12
24
18
24
ffl
06 12 18
Hour - EOT
24
30
20 -
10
0 &
DuBois
58 Days
06 12 18 24
70-
60-
50-
40-
30-
20-
10-
n
f
'^
/
*" '
/
Combined Data
296 Days
f*
1 __ J
06 12 18
Hour - EOT
24
Figure 62. Frequency distributions of times of hourly
minimum ozone concentrations for rural stations.
135
-------
JU ^
20-
10-
0
(
30-
20-
10-
0
c
30,
20.
10.
0
(
30,
20.
10-
0
0
m Cincinnati JU"
1 46 Days
I 20-
10-
S mm _Ji\ |-i
Cleveland
58 Days
1
1 i jfjL nF^I
D 0*6 12 18 2*4 0 0*6 1*2 18 24
Dayton * 30
57 Days
20
1 F*, 1(>
I, PL
v;i- J ^ j
Pittsburgh
59 Days
;
UjiJl, ..-^
) 0*6 12 18 24 0 06 12 18 24
Columbus 80*
60 Days
70.
1
? rCl 60.
) 06 1*2 18 24 5°"
Canton 40"
61 Days
30-
I Flq 20"
!aJIL n« J3
06 12 18 24
Hour - EOT
>« Combined Data, Excluding
Cincinnati
; 295 Days
rr
V
i n
HJ^i fi
fe: 1
.IX .. .*..!». n« r^
06 12 18
Hour - EOT
Figure 63. Frequency distributions of times of hourly
minimum ozone concentrations for rural stations.
24
136
-------
The higher mean minimum concentrations of ozone at the rural stations,
compared to the urban stations, coupled with the fact that most (2/3) of
the rural stations during this period did not experience a single 1-hour
period of no measurable concentration of ozone, suggest that the ozone-
destruction mechanisms in the rural areas are less active, or less effec-
tive, than in the urban areas. This may be accounted for, perhaps, by a
greater abundance of nitrogen oxides from combustion sources in the urban
air.
From the frequency distributions given in figures 62 and 63, and in
particular from the combined data for the urban stations and for the rural
stations (figure 64), certain common features are apparent. Both data
sets have essentially bimodal frequency distributions, with peaks in the
hours immediately following sunrise (0600 to 0900 EDT) and in the hours
near midnight. A striking difference is evident, however, in the high
number of occurrences of the daily minimum value of ozone concentration at
the urban stations during the hour immediately following midnight EDT.
At all urban stations the minimum value of ozone concentration occurred
most frequently during this hour. In the absence of other data, this
could be explained as a result of the occurrence of trends of increasing
values of ozone concentration lasting over several-day periods—for example,
during the first several days of the influence of high-pressure systems.
Under such circumstances, assuming the upward trend of values was persis-
tent, the first hour of each day would have the minimum ozone concentration
for that day. However, since a similar high frequency of occurrence of the
minimum during this hour did not occur at the rural stations, explanation
of the basis of a trend of increasing concentrations is not tenable.
The occurrence of this peak in frequency of occurrence most likely is
due to the procedure used in summarizing the data when the same minimum
value of ozone concentration occurred during more than one hour during a
day. This procedure called for crediting the earliest of the multiple
hours with the event. In the case of urban data, the frequent occurrence
of the limiting value of zero for ozone concentration precluded a time
distribution of the minimum and increased the apparent frequency of
occurrence during the first hour of the day.
137
-------
70
60-
50
o 40.
« 30
"B
55
20.
10
Four Rural Stations 70
235 Days
60
50
40
30
'', '#< '*•*
• T "31_
l.\.-'...'..*.?vl._- P^l
06 12 18
06 12
Hour - EDT
24
Five Urban Stations
295 Days
0 06 12 18
Hour - EDT
24
Figure 64. Comparison of frequency distributions of time
of hourly minimum ozone concentrations for
rural and urban stations.
138
-------
6.2.2 Ozone and Hydrocarbon Data at Ground Stations
Examination of figures 31 and 32 shows that the diurnal ozone trends
at the ground-based rural sites are well defined. The lowest hourly
concentrations occurred usually in the 0800-0900 period. The concentration
peaked around the 1700-1900 period and then exhibited an overall decrease
throughout the night. Minima to maxima differentials on days of high ozone
o
were of the order of 100 yg/m or greater.
Three studies were made at Wilmington to examine diurnal variations of
hydrocarbon concentrations. Times for collection of the other samples
taken during the summer were separable into three periods—morning, noon,
and evening. A comparison of the morning (0600-1000), noon (1000-1400),
and evening (1400-1800) concentrations of acetylene and ozone from
Wilmington, McConnelsville, and Wooster is presented in figure 65. The ozone
concentrations were progressively larger as tne day went on, whereas the
acetylene concentrations were at a low in the noon samples. Acetylene
concentrations in the evening samples were higher than the noon samples,
indicating a fresh input of hydrocarbons. The low for acetylene at noon was
probably related to two factors, a decrease in automobile traffic (over
morning and evening), and a greater dilution due to mixing.
Diurnal Studies
Acetylene concentrations from three diurnal studies at Wilmington
are plotted in figures 66, 67, and 68 along with the simultaneous ozone
concentrations. Hydrocarbon concentrations and ratios from the diurnal
studies are presented in tables 31, 32, and 33. The three sets of data
seem to have come from three different systems or populations. The ozone
and acetylene concentrations correlate directly on July 18 and inversely
on July 23.
The July 23 case (fig. 67) can be explained in almost classical
terms: high hydrocarbon, low ozone at the time of maximum traffic, maximum
ozone, minimum hydrocarbon, slightly after midday (a function of photo-
chemistry and traffic patterns), and a decay of ozone concentrations and a
buildup of hydrocarbons in the nocturnal radiation inversion layer. There
was an influx of acetylene in the 1400 to 1600 sample inferred to be the
influence of noon-time auto traffic at some point upwind. The 1400 to 1600
139
-------
180
160-
WO-
120-
B
§ KXH-
g 80r-
o
o 601-
40
20
0
O WILMINGTON
D WOOSTER
a McCONNELSVILLE
MOO/BOO
a
a.
a)
c
a)
OJ
a
\
\
0600
yiooo
I000/I400
Time Segment
Figure 65. Variation of ozone and acetylene with time
of day, Ohio ground stations.
140
-------
I0r 400r
OL
300-
to
^200
KDO
Ozone
———Acetylene
L.J
i
L !
____
020406
08 K) 12 14 16
Hour of Day (EOT)
18 20 22 24
Figure 66. Acetylene and ozone variations. Diurnal
study, Wilmington, Ohio, July 18, 1974.
141
-------
10
9
u
400,-
— Ozone
• — Acetylene
02 04
08 10 \Z f4 K 1820 22 24
Hour of Day (EDT)
Figure 67. Acetylene and ozone variations. Diurnal
study, Wilmington, Ohio, July 23, 1974.
142
-------
10
9
8
1
6
•
4
2
2
\
0
r 400
.
300
-
'1
«200
•
100
n
-
— — Ozone
- — -— Acetylene
.
H"1 -n
1 T j
•— - r~"~T
i i i i i i i i i i i
02 04 06 08 10 12 14 16 18 20 22 24
Hour of Day (EDT)
Figure 68. Acetylene and ozone variations. Diurnal
study, Wilmington, Ohio, August 14, 1974.
143
-------
Table 31. Abstract of hydrocarbon data: Diurnal study
Wilmington, Ohio, July 18, 1974
Category
0
Ozone, pg/m
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
Acetaldehyde, ppbc
Acetone, ppbc
Ozone, yg/nH
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
Acetaldehyde, ppbc
Acetone, ppbc
Time of sample collection (EDT)
0-2
132.
1.7
.1
.17
100.
.4
.2
1.1
.4
2.0
4.5
2-4
137.
2.1
.9
.18
86.
.4
.1
.3
.2
1.8
5.0
4-6
138.
1.4
2.1
.20
143.
.0
.1
.3
.4
2.9
1.7
6-8
98.
1.8
2.2
.20
111.
.5
.1
.2
.3
3.9
6.9
8-10
106.
2.8
1.0
.35
125.
.5
.5
.3
1.2
2.9
4.5
10-12
169.
1.9
.7
.31
163.
.3
.1
.2
.4
1.3
3.0
12-14
240.
4.9
.8
.42
86.
.4
.1
.1
.1
3.8
6.4
14-15
368.
8.1
.8
.68
84.
.0
.1
.1
.1
6.7
19.2
15-16
369.
6.0
1.3
.57
95.
.1
.0
.1
.1
7.5
20.7
16-17
312.
9.2
.8
.59
64.
.4
.2
.1
.1
7.3
11.1
17-18
285.
4.3
1.6
.38
88.
.1
.1
.1
.1
7.0
9.3
18-20
266.
4.8
1.1
.43
90.
.1
.1
.1
.1
5.1
11.4
20-22
218.
3.2
1.3
.34
106.
.2
.0
.1
.2
4.1
6.7
22-24
193.
3.5
1.2
' .34
97.
.2
.1
.1
.2
4.3
6.0
144
-------
Table 32. Abstract of hydrocarbon data: Diurnal study
Wilmington, Ohio, July 23, 1974
Category
Ozone, Vg/m^
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/
acetylene
Isobutylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
Acetaldehyde, ppbc
Acetone, ppbc
2
Ozone, Ug/m
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/
acetylene
Isolmtylene/isobutane
Propylene/propane
Ethylbenzene/acetylene
Propylene/acetylene
Acetaldehyde, ppbc
Acetone, ppbc
Time of sample collection (EDT)
0-2
101.
2.1
2.0
.29
138.
.3
.1
>-5
.5
4.2
4.7
2-4
76.
2.4
1.8
.29
121.
.2
.1
.1
.5
4.2
9.7
4-6
56.
2.7
1.6
.28
104.
.2
.1
.2
.5
4.3
19.7
6-8
38.
6.8
.7
.45
66.
.3
.1
.3
.4
4.5
11.5
8-10
42.
6.0
.7
.44
73.
.3
.2
.2
.4
4.4
10.2
10-12
113.
4.3
.8
.34
79.
.2
.1
.4
.3
3.5
8.0
12-14
168.
2.3
1.1
-
-
.2
.1
>.2
.2
2.6
6.9
14-16
160.
4.4
1.0
.43
98.
.2
.1
.2
.2
4.6
9.2
16-18
163.
2.9
2.7
.63
217.
.2
.1
.6
.3
7.8
-
18-20
142.
3.0
1.8
.40
133.
.2
.2
.7
.6.
5.4
4.9
20-22
115.
3.8
1.3
.38
100.
.4
.2
.2
.6
5.1
8.6
22-24
91.
4.8
2.7
.40
83.
.3 '
.2
.2
.4
12.8
12.5
145
-------
Table 33. Abstract of hydrocarbon data: Diurnal study
Wilmington, Ohio, August 14, 1974
Category
o
Ozone, yg/mj
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene /propane
E thy Ibenzene/ acetylene
Propylene/acetylene
Acetaldehyde
Acetone
3
Ozone, yg/m
Acetylene, ppbc
Acetaldehyde/acetylene
Carbon monoxide, ppm
Carbon monoxide/acetylene
Isobutylene/isobutane
Propylene /propane
Ethy Ibenzene /acetylene
Propylene/acetylene
Acetaldehyde
Acetone
Time of sample collection (EDT)
0-2
55.
1.0
2.1
.13
130.
.36
.2
.9
.7
2.1
3.1
2-4
39.
.9
1.8
.13
144.
.3
.2
.4
.8
1.6
2.3
4-6
29.
.6
2.7
.13
217.
.3
.2
.7
1.2
1.6
".0
6-8
24.
1.2
1.2
.14
117.
.3
.3
.4
.5
1.4
2.4
8-10
39.
.7
3.3
.16
229.
.3
.1
.4
.4
2.3
1.0
10-12
86.
1.3
2.2
.22
169.
.3
.1
.6
.3
2.9
2.0
12-14
113.
1.2
1.5
.18
150.
.2
0
.3
0
1.8
4.4
14-16
131.
1.5
1.4
.21
140.
.2
.1
.3
.3
2.1
6.3
16-18
144.
1.1
2.1
.21
191.
.4
.2
.3
.5
2.3
7.5
18-20
142.
0.8
2.7
.25
313.
.4
.2
.6
.6
2.2
4.1
20-22
105.
2.7
1.0
.31
115.
.5
.4
.3
.4
2.8
5.0
22-24
91.
3.1
0.8
.43
139.
.3
.2
.4
.4
2.5
2.2
146
-------
ozone concentration seems to have been prevented from reaching a potentially
higher concentration due to injection of oxides of nitrogen into the air at
the same time as the hydrocarbons. The July 18 case presents almost a
complete reversal of the acetylene/ozone relationship as was depicted in
the July 23 case. The unsatisfactory and tentative conclusion here is that
vagaries of meteorology and transport must be evoked to explain this case.
In the August 14 case (fig. 68) the acetylene concentrations were low and
were virtually constant from 0000 to 2000 and the ozone showed a diurnal
curve typical of others taken at this station.
The relationship of the hydrocarbons concentration to ozone concentra-
tion in this study can best be shown by figures 69 and 70- These figures
should be considered as proof of the important involvement of anthropo-
genic pollution in the generation of the high ozone concentrations. High
ozone concentrations were associated with relatively high acetylene
concentration. If acetylene is only an anthropogenic and if some of the
high ozone had been generated from natural precursors only, some of the
high ozone concentrations should have occurred at the low end of the
acetylene concentration. This should be a telling relationship for
determining the participation of city air in the generation of rural ozone.
6.3 Relationship Between High Ozone Episodes and Synoptic Weather Conditions
6.3.1 Introduction
Recently, the literature has contained a number of studies in which
3
the presence of high ozone (ozone concentrations greater than 160 yg/m )
has been observed in rural boundary layers—* * . Miller et al.— have
attributed the high ozone concentrations found in rural areas to the for-
mation of ozone by anthropogenic precursors such as hydrocarbons and
nitrogen oxides emitted from urban regions and transported to rural regions.
12/
However, Stasiuk and Coffey^— have questioned this mechanism, but suggested
13/
no alternative. Bruntz et al.— have shown that the concentration of
ozone is correlated to solar radiation and to wind speed. They have shown
that the concentrations are lower with low levels of solar radiation
(suggesting synthesis as the source of the high ozone) and also with high
wind speeds.
147
-------
_ %•
^^ - •
I
I
I
00
Q.
CD tt
UJ
TP
to ^
UJ
_J
h-
* g
10
CVJ
O
o
o
10
ro
o
o
ro
o
10
CVJ
O
IO
CM
o
o
O
10
(fl
Q
O
tfl
4->
CO
•o
c
o
o
4-1
O
U-l
w
e
e
CTv
VO
s,
•rl
'3NOZO
148
-------
in
ro
-------
Data collected by RTI in the summers of 1973 and 1974 have indicated
that systemic increases of the ozone concentration over large areas often
occur during this period. The data were collected by RTI in the eastern
part of the United States at various stations placed in rural regions.
This portion of the report summarizes some initial studies on the nature
of the large-scale meteorological conditions at the surface when systemic,
high ozone concentrations were found.
6.3.2 Correlation Between Pressure Systems and High Ozone
Figures 71 and 72 summarize the correlation found between high ozone
concentrations and synoptic pressure systems. The ozone data presented
in the graphs for each day represent the area average value of the maximum
1-hour average ozone concentrations observed at each station. The area
average was constructed by averaging over all stations. The area averaged
maximum concentration is employed in order to remove local anomalies which
may exist at a given time and given station, and to demonstrate the
systematic nature of the increases and decreases in ozone over a fairly
large area (the maximum distance between stations was 480 kilometers).
The pressure for each day is the area average station pressure for the
region of interest.
These data indicate that high ozone concentrations are found when
a high-pressure system exists in the region. The correlation is not
one-to-one with respect to pressure; i.e., the highest pressure does not
correlate with the highest ozone concentration and the lowest pressure
does not correlate with the lowest ozone concentration. This is primarily
due to the fact that pressure in itself does not affect ozone synthesis or
the vertical mixing of ozone, which are the only mechanisms for increasing
the ozone, nor does pressure affect the destruction of ozone. In terms of
high ozone, it appears that high-pressure systems provide those environ-
mental conditions that allow the production of high ozone.
Figures 73 and 74 show the result of computing a nine-point running
mean using the same data employed to construct figures 71 and 72. The
effect of computing running means is to filter out short-period synoptic
fluctuations, leaving only the long-period trends. It is noted from
150
-------
ABE4 AVERAGE SURFACE PRESSURE
(millibars)
CO
o
oo
o\
1/1
g
CM
o
(N
3
•-3
8
o
o
O
o
o
m
(Em/8rt)
aw)zo aovHaAV vsrav
r^
-------
0)
AREA AVERAGE SURFACE PRESSURE
(millibars)
(£m/8rt)
3NOZO 33VH3AV V3HV
152
-------
AREA AVERAGE SURFACE PRESSURE
(millibars)
IT)
CO
o
oo
o o
vO CM
CM CM
CM
60
O
CO
O
CM
C
3
O
oo
O
O
1^
0)
bO
•H
•a
0)
•u
C
0)
03
0)
01
60
tfl
DO
C
•H
O
cx
0)
•H
ro
00
•H
3NOZO 30VH3AV V3HV
153
-------
AREA AVERAGE SURFACE PRESSURE
(millibars)
(eui/3rl)
3NOZO 30VH3AV V3HV
154
-------
these figures that periods of extermely high ozone are generally
associated with periods of higher pressure, and low ozone with lower
pressure. Generally, the lowest ozone concentration is found after the
minimum pressure, which may be interpreted to mean that the lowest ozone
concentrations occur after frontal passage when the leading edge of a
high-pressure system is moving into the area. During time periods shown
in the two figures, the area average maximum ozone concentration was
3
greater than 160 yg/m , a greater percentage of the time than below that
value.
6.3.3 Case Studies
The following represents a summary of three cases in which a high-
pressure system moved into the area under study accompanied by a
simultaneous increase in the concentration of ozone. Figure 75 presents
the variation of average ozone concentration (average ozone concentration
for the period 1200 EOT to 2000 EDT) for the period July 5-11, 1974. The
stations represented are Wilmington, Ohio; McConnelsville, Ohio; Wooster,
Ohio; DuBois, Pennsylvania; and McHenry, Maryland. The data indicate
that after July 5, all stations experienced periods in which the ozone
3
concentration exceeded 160 yg/m . The largest 8-hour average concentra-
3
tion, 282 yg/m , was found at McHenry on July 8.
On July 4, a high-pressure system was found to the northwest of the
study area and was moving southeastward into the Ohio, Pennsylvania,
Virginia, and West Virginia region. The center of the high-pressure
system was found in the northeastern part of Ohio on July 6, approximately
where the largest ozone concentration was reported (Wooster) (fig. 76a).
The average ozone concentration exceeded 160 yg/m at three of the stations.
The surface winds on this date were small in magnitude (less than or equal
to 3 m/s) over the area, and the surface flow was disorganized in the
eastern portions of the United States (fig. 76b). During the daylight
period, clouds obscured all stations where ozone was being measured, but
Wooster had the minimum cloud cover of all these stations (fig. 76c).
Skies were clear in south central Michigan, northeastern Indiana, and
northwestern Ohio.
155
-------
300-,
ao
a
C
o
c
01
y
§
N
O
-------
£l..'.«X^-7r '
Figure 76. a) Surface pressure (mb with only tens and units digits given)
analysis (1700 EDT); b) resultant winds; c) mean cloud cover
(tenths) (0700 to 1900 EDT) for July 6, 1974. Eight-hour
average ozone values (pg/m3) (1200-2000 EDT) indicated at each
station.
157
-------
The high-pressure system continued to drift slowly eastward, and on
July 8, the center was in the western part of Pennsylvania (fig. 77a).
The largest 8-hour average ozone concentration on that date was also found
in this region; and all stations for which an average ozone concentration
o
could be computed had concentrations larger than 160 yg/m . Again, the
surface winds were generally weak over the area, and the surface flow was
disorganized (fig. 77b). Clouds were evident at all ozone-reporting
stations, and the amounts were 0.4 or less (fig. 77c).
The high-pressure system continued to move eastward as a front
approached the region of interest. After the front passed all the stations
in the area, the average concentration of ozone decreased markedly (fig.
78a). The average surface wind speed in the region was in excess of 10 mph,
and an organized flow at the surface from the northeast characterized the
region of interest (fig. 78b). All but one of the ozone stations
(Wilmington) were in a region where the average daylight cloudiness was
less than 0.4 (fig. 78c).
Figure 79 presents the average ozone variation (same 8-hour averages
as before) for the period July 20-23, 1974, during which a high-pressure
system moved into the area of interest. In this case, data from
Wilmington, Ohio; DuBois, Pennsylvania; McHenry, Maryland; and McConnels-
ville and Wooster, Ohio were available. The data indicate a systematic
increase of ozone at all stations, and the largest ozone concentrations
were observed on July 22.
A high-pressure center was found to the north northwest of the region
of interest on July 20. Unlike the previous case, the high center moved
rapidly. On July 22, the highest 8-hour average ozone concentration was
located at a station nearest to the center of high pressure, which was
found off the northeast coast at 1700 EDT (fig. 80a). All stations but
•i
one had an 8-hour average ozone concentration exceeding 160 yg/m . The
surface winds over the area on July 22 were generally weak (less than or
equal to 3.0 m/s), but the surface flow was organized, having a direction
from the southeast (fig. 80b). Clouds were found at each station report-
ing ozone concentrations with the station reporting the highest average
ozone concentrations having the same amount of cloudiness as the station
reporting the lowest average concentrations (* 0.7 cloud cover) (fig. 80c).
158
-------
r
r>/«
B
Figure 77. a) Surface pressure (mb with only tens and units digits given)
analysis (1700 EOT); b) resultant winds; c) mean cloud cover
(tenths) (0700 to 1900 EOT) for July 8, 1974. tight-hour
average ozone values (yg/m3) (1200-2000 EDT) indicated at each
station.
159
-------
Figure 78. a) Surface pressure (rab with only tens and units digits given)
analysis (1700 EDT); b) resultant winds; c) mean cloud cover
(tenths) (0700 to 1900 EDT) for July 11, 1974. Eight-hour
average ozone values (yg/m3) (1200-2000 EDT) indicated at each
station. 160
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300 -,
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McHenry, Md.
McConnelsville, Ohio
Wooster, Ohio
DuBois, Pa.
Wilmington, Ohio
I
20
I I
21 22
Time (days)
I
23
July 1974
Figure 79. The variation of the 8-hour average value
(1200 to 2000 EOT) of ozone (ug/m3) for the period
July 20-23, 1974, in the eastern United States.
161
-------
Figure 80. a) Surface pressure (mb with only tens and units digits given)
analysis (1700 EOT); b) resultant winds; c) mean cloud cover
(tenths) (0700 to 1900 EOT) for July 22, 1974. Eight-hour
average ozone values (yg/nr5) (1200-2000 EOT) indicated at each
station.
-------
A cold front approached the region of interest on July 22 and was
located through eastern Ohio on July 23. The average ozone concentration
was lower at all stations on July 23 than on July 22 when cyclonic flow
and overcast skies prevailed over the region of interest.
The highest concentrations of ozone encountered during the two
summer periods in which ozone was observed occurred during the period
August 25 to September 5, 1973. The 8-hour average ozone concentration
o
(fig. 81) were greater than 160 yg/m at all stations (McHenry, Maryland;
Kane, Pennsylvania; Coshocton, Ohio; and Lewisburg, West Virginia) from
the beginning to the end of the period. The largest single 1-hour average
3
ozone concentration occurred at McHenry on August 28 and was 366 yg/m ,
which is almost equal to the 8-hour average ozone concentration on the
3
same day and at the same station (350 yg/m ).
During the period, a high-pressure system moved from the northeast.
The center of the high was in West Virginia on August 26 and drifted into
Kentucky on August 27 (fig. 82a). On August 27, the highest 8-hour average
ozone concentration (350 yg/m ) was found at Coshocton. Lewisburg,
however, which was closer to the center of the high-pressure system, had
o
the smallest concentration reported (193 yg/m ), but it too exceeded
3
160 yg/m . The surface winds in Maryland, western, south central
Pennsylvania, West Virginia, and southeastern Ohio were weak, and the
surface flow was disorganized; whereas, north of that region, strong
surface winds and organized flow from the southwest were found (fig. 82b).
Kane had 0.8 cloud cover, but 0.1 to 0.2 cloud cover characterized the
remainder of the stations observing ozone (fig. 82c).
The high-pressure center moved northward into Indiana and western Ohio
on August 28, then moved eastward and was located in eastern Ohio and
western Pennsylvania on August 29 (fig. 83a). McHenry had the highest
3
8-hour average value of ozone (307 yg/m ), and Coshocton, the lowest
(181 yg/m ). Again, both maximum and minimum values exceeded 160 yg/m .
The surface wind speeds were weak in the region of interest, and the
surface flow was disorganized (fig. 83b). All stations had cloud cover.
Kane and McHenry had the least cloud cover (« 0.2), and Coshocton had the
most (= 0.6) (fig. 83c).
163
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Figure 82. a) Surface pressure (mb with only tens and units digits given)
analysis (1700 EDT); b) resultant winds; c) mean cloud cover
(tenths) (0700 to 1900 EDT) for August 27, 1973. Eight-hour
average ozone values (yg/m3) (1200-2000 EDT) indicated at each
station. 165
-------
B
•
r. .£.. -'--• f
Figure 83. a) Surface pressure (mb with only tens and units digits given)
analysis (1700 EDT); b) resultant winds; c) Mean cloud cover
(tenths) (0700 to 1900 EDT) for August 29, 1973. Eight-hour
average ozone values (yg/m^) (1200-2000 EDT) indicated at each
station.
166
-------
The center of high pressure continued to move eastward slowly
and was found over McHenry on September 4 (fig. 84a) . McHenry was
also the station that experienced the highest value of the eight-
hour average ozone concentration. Again, all reporting stations had
3
eight-hour average values greater than 160 Ug/m . The surface wind
speeds were small over the area and the surface flow disorganized
(fig. 84b). Less than 0.4 cloud cover was found over all stations
with the exception of Lewisburg (fig. 84c). Lewisburg had more than
0.8 cloud cover, but yet had an eight-hour average ozone concentration
3
of 190 Ug/m which was the lowest value reported on that day.
A rapid-moving cold front passed through the region of interest
on September 5, and a new high-pressure center moved into the region
from the northwest. The eight-hour average ozone concentrations
3
were less than 160 yg/m on September 6, but surpassed that value
when the high-pressure center moved in from the northwest. It was
not until a rather slow-moving low-pressure system began to move
into the region on September 9 that the eight-hour average ozone
3
concentrations remained below 160 yg/m for more than 1 day.
6.3.4 Discussion of Meteorological Analysis
The preceding analysis is based on the data collected in the
summers of 1973 and 1974 and may be subject to varied interpretation.
The most plausible explanation resulting from this analysis is
presented in the following discussion.
High pressure systems appear to provide appropriate environmen-
tal conditions for the production of high concentrations of ozone
(greater than the NAAQS) over large areas (at least the order of 1.8
x 10 square kilometers). The highest ozone concentrations were
found at observing stations near centers of the high pressure.
These central areas were characterized by weak winds, disorganized
flow, and relatively clear skies. Some cloud cover was present in
each of the cases studied, but complete overcast conditions did
167
-------
Figure 84. a) Surface pressure (mb with only tens and units digits given)
analysis (1700 EOT); b) resultant winds; c) mean cloud cover
(tenths) (0700 to 1900 EOT) for September 4, 1973. Eight-hour
average ozone values (yg/m3) (1200-2000 EDT) indicated at each
station.
-------
not occur when there were high ozone concentrations. Furthermore,
it appears that the amount of cloudiness, other than complete
overcast, does not have a marked influence on the production of ozone.
To some degree, the maximum ozone concentration appears to be af-
fected by the length of time high pressure center remains in a parti-
cular region; the longer the high pressure center persists, the
higher the concentrations of ozone.
The lowest ozone concentrations were found after frontal
passages. The eight-hour average ozone concentration for the 1200
3
to 2000 EDT period fell below 160 yg/m only after the passage of
a frontal system and its associated trough of low pressure. While
the ozone concentration reached a minimum, following the passage
of the trough, it did not always fall below the NAAQS.
As discussed earlier, mechanisms that can increase ozone con-
centrations in the surface layer are synthesis—given the required
precursors and solar radiation—and vertical mixing—under conditions
such that the ozone concentration increases with height in the mixing
layer. In the weak, disorganized flow and clear skies associated
with the central areas of high pressure system conditions are
appropriate for the development of strong, surface-based, radiation
induced, nocturnal thermal inversions. In such inversion layers
gas phase reactions and contact with vegetation and other objects
on the earth's surface cause ozone destruction. By morning the
ozone concentration near ground level is considerably lower than
existed during the preceding evening hours, and the concentration
increases with height. After sunrise heating of the earth's surface
takes place and the radiation inversion is replaced by a thermally
unstable layer. Within this unstable layer, convective circulation
will mix the higher concentrations of ozone from aloft with the
lower concentrations near the surface, effectively increasing the
near-surface concentration of ozone relative to the minimum value
that occurred near sunrise. This process is illustrated by the
ozone concentration profiles shown in figure 58. On the particular
169
-------
day illustrated, mixing could have accounted for approximately
50 percent of the increase of ozone concentration near the sur-
face from early morning until late afternoon. An increase of
ozone concentration from this process alone cannot produce concen-
trations at the surface as high as was experienced during the
preceding day because some of the ozone in the mixed layer was
destroyed during the intervening night. Day-to-day increases in
ozone concentration can be accounted for only by synthesis.
There is no doubt that photochemical reactions can produce
ozone in high concentrations in the relatively cloud-free regions
of high pressure systems if there are appropriate concentrations of
ozone precursors. The required precursors for ozone synthesis
may be of natural or anthropogenic origin. Sources of both types
of precursors are abundant in the region of the study; natural
precursors from the vegetation and anthropogenic precursors from
urban, industrial, and vehicular activities (figure 85). The dis-
tribution of these precursors in a high pressure system could be
expected to be relatively uniform after a period of a few days
except in the vicinity of well defined source areas such as urban-
industrial centers. Since precursors of ozone are also destruc-
tive agents, injections from such well defined source areas initially
may cause reductions in ozone concentrations, producing inhomo-
genieties in the overall ozone concentration. In the central
region of a high pressure system the lack of organized wind flow
produces thorough mixing, and abundant solar radiation makes con-
ditions ideal for the production of high ozone concentrations.
These conditions are repeated on a day-to-day basis so the central
region of the high pressure system (the region of highest pressure)
will usually have the highest concentrations of ozone. This pro-
cess does not require the transport of the center of highest
ozone concentration per se. The characteristics of the air mass
170
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association with the unique conditions in the center of the high
pressure system will produce, on a daily basis, the highest
ozone concentrations.
At present, data are inadequate to permit postulation of the
relative contributions of anthropogenic and natural precursors to
the high concentrations measured in high pressure systems over
the study area. Estimation of the relative contributions may be
possible if a high pressure system can be studied from its source
region into an area of higher emission rates of anthropogenic pre-
cursors.
6.4 Air Trajectories
Trajectories were numerically computed for air parcels arriving
over the Garrett County, DuBois, McConnelsville, and Wilmington
locations at 900 m (3000 ft MSL) at each 0000 and 1200 GMT from
June 16 to September 1, 1974. Winds at 900 m (3000 ft) were
extracted from the teletype data transmissions for the 16 rawin-
sonde stations within and surrounding the study area and were used
as the basic input data for the numerical computations.
Trajectories were computed for the forty eight-hour period prior
to the air mass's arrival in two-hour increments, based on spatially
weighted (inverse distance) horizontal displacements, linearly
interpolated in time. The plotted trajectories for each day are
given in appendix F.
Twelve-hour average ozone concentrations were computed for each
of the five ozone monitoring locations for the period six hours
before to six hours after 0000 GMT or 1200 GMT (1400 to 0200 EOT
and 0200 to 1400 EDT). The central times are the same as the tra-
jectory arrival times. The dates and times of the high ozone concen-
trations—when the twelve-hour average ozone concentration exceeded
the upper decile concentration—were noted for Garrett County,
McConnelsville, and DuBois. Trajectories for air arriving at each
172
-------
station associated with high ozone were plotted. Similarly low
ozone—for data in the lowest decile concentrations—trajectories
were plotted for each of the three stations. The trajectories
for high and low ozone concentrations are shown in figures 86a, 86b,
and 86c.
The ozone trajectories at Garrett County arrive from the west
southwest through northeast at a slow speed, especially during the
last twelve hours of the trajectory. Although most trajectories
cross east central Ohio and northern West Virginia during that time,
the earlier positions (24 to 48 hours before arrival) of the trajec-
tories do not suggest a preferred source region for high ozone at Garrett
County. Low ozone concentrations, although infrequent, are obviously
associated with rather rapidly-moving air. No directional preference
for low ozone trajectories is apparent.
Previous studies have shown upper decile ozone concentrations
at Garrett County are associated with trajectories crossing the lower
Michigan, northern Ohio area, or moving northeastward parallel to
the ridgelines of the Appalachian Mountains of West Virginia, but
not from east central Ohio as shown in 1974. Part of the reason for
the difference may lie in preferred wind directions of the seasons
resulting from different pressure patterns and pressure system move-
ments.
At DuBois, the high ozone concentration is associated with air
moving primarily from the west across Ohio, which arrives during
the day or night. Wind speeds are generally higher than those noted
at Garrett County. At other times the trajectories crossing much
of the same areas, including the Ohio River Valley and the southern
side of the Great Lakes, are associated with low ozone concentrations,
probably because they move faster. These trajectories show no particu-
lar preference of arrival time.
In speed, direction, and area coverage, the high ozone trajectories
arriving at DuBois are quite like those which arrived at Kane,
Pennsylvania, during the 1973 study. The low ozone trajectories which
arrived at Kane had a much more northwesterly origin, but moved at
speeds comparable to low ozone trajectories arriving at DuBois.
173
-------
-45"
S9«-
168
Garrett County
62
Figure 86a. Air parcel trajectories arriving at three locations for
the indicated 12-hour average ozone concentrations. The
triangles (A) indicate the 12, 24, 36 and 48-hour posi-
tions of parcels arriving at 0000 GMT; the squares (O)
represent those parcels arriving at 1200 GMT.
174
-------
/" 75.
>_ 200 yg/rn
DuBois
48
Figure 86b. Air parcel trajectories arriving at three locations for the
indicated 12-hour average ozone concentrations. The
triangles (A) indicate the 21, 24, 36 and 48-hour positions
of parcels arriving at 0000 GMT; the squares (o) represent
those parcels arriving at 1200 GMT.
175
-------
> 168
McConnelsville
0 < 45
Figure 86c. Air parcel trajectories arriving at three locations for the
indicated 12-hour average ozone concentrations. The
triangles (A) indicate the 12, 24, 36 and 48-hour positions
of parcels arriving at 0000 GMT; the squares (O) represent
those parcels arriving at 1200 GMT.
176
-------
The trajectories associated with high ozone concentrations at the
McConnelsville site show a unique arrival pattern: all arrive from
locations east through south to west-southwest of the site. The trajec-
tories have origins (48-hour positions) in the north through east and into
the west, but none come from the northwest, across central Ohio. Although
some high ozone trajectories indicate rapid movement, the last 12-hour
movements are slower. All of these trajectories arrive at 0000 GMT. That
the low ozone trajectories arrived at 1200 GMT is a reflection of the strong
diurnal range of ozone at McConnelsville. As in other cases, the speeds
are greater, yet the air appears to have moved along the Ohio River Valley
or from the northeast. Neither path is free of industrial or population
centers.
The high and low ozone trajectories computed for McConnelsville in
1974 bear no resemblance to similar trajectories computed in 1973 for
Coshocton, Ohio, which is 72 km (45 mi.) to the north.
The strong diurnal character of high or low ozone at McConnelsville
as well as the diurnal average of ozone (fig. 31) suggest that nocturnal
radiative inversions effectively limit the vertical mixing of ozone and
its destructive agents, thus allowing the destruction of ozone near the
ground.
That the high and low ozone trajectories arriving at DuBois often-
times follow the same course suggests that the path taken by the air does
not have a substantial impact upon the ozone concentrations. The year-to-
year variability of the areas associated with high or low ozone concentra-
tion further supports this idea.
The speed of movement of the air, especially in the 12 hours prior
to arrival, did seem inversely related to the ozone concentration. If
the recent movement was slow, conditions are stagnant; the ozone concen-
tration was higher than in other cases where recent air movement was
faster.
6.5 Chemistry of Ozone Generation
The evidence indicates that high ozone concentrations observed in
rural areas probably did not just originate in the cities and drift,
unaffected, downstream. The most telling argument for this is that the
177
-------
maximum ozone and average concentrations measured in the large cities of the
study area were lower than those measured at the rural sampling sites.
If drift of urban ozone alone were responsible for the high rural concentra-
tions, urban concentrations would be equal to or higher than rural concen-
trations. Therefore, some of the ozone measured at the rural sites was
generated as the air moved from the cities to and beyond the sampling sites.
Data taken before the mid-1960's indicate no such elevated concentrations
of ozone in rural areas as have been observed in this study. Reference
is here made to the ozone section of Junge's "Air Chemistry and Radio-
activity";— also see table 34, reproduced from Junge, which summarizes
data from a number of observers. Regener's study at O'Neil, Nebraska,
in the summer of 1953 is particularly pertinent (average ozone, 60 Vg/m ,
range 30-100 Ug/m ). RTI-UNC investigations from 1964 to 1967 in the mountains,
and piedmont of North Carolina and at sea did not encounter the high non-urban
phenomenon as it existed in the Ohio Valley in the summer of 1974. The
point of these results (Regener, Junge and RTI-UNC) with regard to the high
_3
non-urban 0 concentrations is that no high (> 160 yg/m ) concentrations
were observed previously in a number of kinds of natural environments. Earlier
investigators did not observe the high concentrations of ozone now being
measured. The argument that this increase in rural ozone is an artifact
of change in instrumentation (KI to chemiluminescent) cannot be supported,
because compounds known to interfere with the KI method (i.e., SO and
H-S) do not occur in sufficient concentrations in most of the truly remote
areas. The data presented in figure 58 are the best argument for the
occurance of 0» synthesis in the atmosphere's boundary layer.
It is improbable that any different types of reactions are occurring
to cause generation of the ozone at rural sites that do not also occur
in the urban air. Natural precursors should also enter into these reac-
tions. The major difference between hypothetically natural air and the
urban-rural mixture lies in its past history. At one time part of the
mixture possessed higher concentrations of ozone precursors than those
which were measured at the rural site. The possible importance of this
is that the urban portion of the mixture would have contributed greater con-
centrations of stable intermediates which are capable of generating hydroxyl
and hydroperoxyl radicals.
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181
-------
Kopczynski et al—found that dilution of his initial reactants (in
this case, aldehydes and NO ) reduced the net ozone concentrations obtained
by a lesser percentage than the initial reactants. Reasoning by analogy
one can postulate that the chemical intermediate behave similarly. Computer
simulations shown in tables 35 and 36 suggest also that dilution of the
ozone precursors is accompanied by a smaller net percentage decrease in
concentrations of ozone and or some of the secondary pollutants such as
aldehydes. These computer simulations are based on the set of reaction
mechanisms compiled by Jeffries and Sickles— (see table 37). Computer
simulation suggests also that the stable intermediates left from a previous
run with simulated urban concentration plus low concentrations of hydrocarbon
and N0? can generate greater concentrations of ozone than the sum of each
system ran separately.
Although there are many pathways of *OH generation the photolysis of
aldehydes offers one of the most productive in terms of each molecule's
involvement.
Hydroxyl Radical Formation
1. CH 0 + hV 1- H- + HCO
H + 0- —* HOO*
HCO + 02 >• CO + HOO*
HOO* + NO »• NO + • OH
2. RCHO + hV >• R* + HCO
R + 02 •• R02
RO + NO >• NO + RO*
HCO + 0 >- CO + HOO*
HOO' + NO »• NO + • OH
Further Peroxy Radical Formation
RH + • OH >• R* + H20
R- + 0 »• ROO*
182
-------
Table 37. Jeffries'-Sickles' reaction mechanism3
Reaction
hv + N02
hv + HN02
hV + H202
hV + CH 0
hV + CH 0
hV + RCHO
hV + RCHO
hv + 0
NO + 03
0 + N02
°3 + N02
NO + NO
N03 + N02
N2°5
N2°5
NO + NO
OH + N02
OH + NO
OH + CO
OH + H202
OH + H02
H02 + NO
H02 + 03
H02 + H02
OH + CH20
H02 + CH.,0
OH + RCHO
HO + RCHO
0 + C,H,
J 0
H00 + CJT.
/ JO
OH + C,H,
J 0
= NO + 0
= OH + NO
= 2 OH
= CO
= H02 + CO
= ROO + H02
= CO
= °3
= N02
= NO
= N03
= N02
= N205
- N02 + N03
- 2 HN03
= 2 HNO
= HN03
= HN02
-H02
-H02
=
= OH + N0_
= OH
= H2°2
= H02 + CO
= H202 + CO + H02
= RC03
= RC03 + H202
= R'OO + H02 + CO
= RH04 + RCHO
= R'OO + CH 0
Reaction Rate Constant
0.40
0.133
2.2
4.4
8.0
3.5
1.75
4.16
2.4
1.34
4.59
1.28
5.58
1.55
5.0
3.2
6.5
1.2
2.5
1.2
1.2
2.0
4.5
5.3
2.1
2.1
2.2
1.1
5.3
1.1
1.25
E-4*
E-3
E-4
E-4
E-5
E 6
E 1
E 4
E-2
E 4
E 3
E 1
E-6
E-5
E 3
E 4
E 2
E 3
E 4
E 2
E 0
E 3
E 4
E-2
E 4
E-2
E 3
E 0
E 4
*a
This mechanism is continuously being revised and refined.
*
E - Exponential
183
-------
Ozone Formation
N02 + hv —>• NO + 0
° + °2 ^ °3
03 + NO >• N02 + 02
ROO* + NO —»- N02 + RO- (one 0- preserved)
Although other processes may enter into the generation of the ozone
concentrations observed at the rural sampling sites, the process postulated
here must account for a considerable portion.
The hypothesis is that the high ozone concentrations observed in the
rural areas are formed by the same reactions which generate ozone in the
city. In the rural areas where measurements have been made, the ozone
precursors, hydrocarbons and oxides of nitrogen, are most likely a mixture
of material from anthropogenic-urban, anthropogenic-rural, and natural
sources. The ozone is formed in transit to or in situ at the rural sampling
sites. One contribution of the city air is to provide a slightly higher
concentration of ozone precursors, but the major contribution of the urban
air is to provide the stable intermediate which will provide enough *OH
radicals upon solar irradiation to drive the NO + ROO* reaction at a rate
in the neighborhood of 1.5 pphm hr or greater.
6.6 Postulated Sequence for Ozone Generation and Destruction in Rural Areas
Figure 87 is a population map of the United States, and figure 88 shows
the typical movement of typical northern United States' high-pressure centers
which travel from sparsely populated areas into the more densely populated
areas and on out to sea. (These samples are for August 1973.) A relation-
ship between high-pressure and high ozone concentration has been shown in
section 6.3.
In a postulated sequence of events, a high-pressure system moves into
the more populated area holding anthropogenic pollutants in a relatively
small volume of air and causing all trace gases with an origin at the sur-
face to accumulate. The influence of a single urban area on the lower layer
of the air mass is one of producing a perturbation on and adding an increment
to the region-wide pollution system, but this increment loses the identity
184
-------
Sourct: U3. Munm* of tttt Coma. Cmrat of PopuUUo* w
Koiulnf: 1970. United SUU» Sumnuiy.
Figure 87. Population density by counties: 1970.
185
-------
of Anticyclowt el S*o L«v»1, Augoii 1973
Doit i»dKBt« tM*rvMi
•! 740 • *. B 8 T. ^igwr* •%•*• arctt tn^KMn 4*w. fifwn below.
pMttM« *f IUIIMIWT CMMW fw pm*d
iU to i4«»tir»*4 far 34 b*ura
to •••r«ot »ilhb«r
•• DMli*d IIIM in u*ck
Figure 88. Tracks of centers of anticyclones at sea level, August 1973.
186
-------
of its specific source within 48 to 80 km (30 to 50 miles). In other words,
all the air over a very large area becomes polluted to the degree that ozone
concentrations in excess of the National Ambient Air Qualtiy Standard (NAAQS)
can be generated in sunlight.
As polluted air moves into the area of a sampling station in the after-
noon, the ozone concentration is relatively constant throughout the mixing
layer. As the sun goes down, photochemical activity drops to zero, and a
radiation inversion begins to be established. Ozone is not being generated.
In the lowest centimeter of air nearest the ground ozone is being destroyed
at a possible rate of ~25 percent hr . The effect of this process at any
distance aloft depends on meteorological factors. Near the ground, for
example, the level of the sample inlet ozone is being destroyed by nitric
oxide. These two processes are probably the main ones for destroying ozone
in the destructive phase of the diurnal cycle The ozone-depleted air and
the ozone-destructive gases diffuse slowly within the radiation inversion and
none or very little diffuses above the radiation inversion layer. In the air
above the radiation layer, the ozone-destructive materials are near depletion
because of the previous day's photochemical primary and secondary activity.
Ozone is depleted to a much lesser extent above the radiation layer than
at the surface of the ground. Thus, a reservoir of air is maintained at
some elevation above the surface in which ozone is at a substantially higher
concentration than at the ground. Also, ozone-reactive material is held
close to the surface during the time of the radiation inversion.
The morning solar irradiation has two functions in the sequence of
events. It warms the surface of the earth and erodes the radiation in-
version from the ground up. This mixes air containing higher ozone con-
centrations downward and carries the accumulated nocturnal emissions of
ozone precursors aloft. The second function of the solar irradiation is
to initiate photochemical processes. Photochemical generation of ozone
proceeds more rapidly near the ground, but due to mixing, the ozone con-
centration is essentially constant throughout the extended mixing layer
by evening.
Computer simulation supports the hypothesis that the concentrations
of hydrocarbons and oxides of nitrogen observed may not alone be responsible
187
-------
for the generation of ozone concentrations measured but that an accumu-
lation of stable intermediates produced in the ozone-generative processes
upwind will amplify ozone generation from the hydrocarbons and oxides of
nitrogen present. Computer simulation also supports the idea that high
ozone concentrations (above the NAAQS) can be generated by a mixture of
primary precursors (oxides of nitrogen and hydrocarbons) and stable inter-
mediates at concentrations which would not permit such high ozone generation
from either the primary precursors alone or the stable intermediates alone.
The trajectory analyses show that the air in which high ozone concen-
trations occur at the sampling sites has, in 48 hours, come from a few
tens to a few hundreds of kilometers away. The sequence of effects, as
described above, suggests that diurnal changes in ozone at the ground
depend on local processes. The continual generation of high ozone in a
sequence of days, as hypothesized above, depends both on transported
pollutants as well as hydrocarbons and oxides of nitrogen from local sources.
Our knowledge of the atmospheric behavior of so-called stable inter-
mediates (e.g., RCHO, CH-0, lUO , HONO) is slight. Whatever their concen-
tration, it seems likely, if the hypothetical sequence of ozone generation
and destruction outlined above is correct, that the stable intermediates
are destroyed at or near the surface. In that case, the air above the
radiation inversion acts as a reservoir of higher concentrations of the
intermediates.
188
-------
7.0 CONCLUSIONS
The following observations and conclusions are based on data collected
in the study of high rural concentrations of ozone in 1974 in the eastern
United States.
1. The NAAQS for photochemical oxidants was exceeded approxi-
mately twice as frequently at the rural stations as at
the urban stations. Mean diurnal ozone concentration curves
for the rural and urban stations were similar, varying
mainly in magnitude of hourly ozone concentration and time
of maxima. Nocturnal concentrations of ozone were on the
average three to five times higher at the rural sites
relative to the urban sites.
2. Nitrogen dioxide concentrations observed at the rural
stations were at or near the minimum detectable level for
3
the measurement method (i.e., approximately 10 yg/m ).
3. There were periods (at times 5 days or more) during which
the near surface concentration of ozone equaled or exceeded
3
the NAAQS of 160 ug/m (0.08 ppm) hourly average over large
areas (2.3 x 10 square kilometers or more). That anthropo-
genic air pollution was present in this air was demonstrated
by the presence of acetylene in all hydrocarbon samples and
the presence in a preponderance of samples of carbon monoxide
in concentrations 2 to 6 times the usually quoted geochemical
background of 91-137 Mg/m3 (0.08 to 0.12 ppm).
4. An area-wide system [radius -240 kilometers (150 miles) or
more] of high ozone concentration can exist in which most
features suggestive of precursor origin have been smoothed
out, but a short-range urban influence on both hydrocarbon
and ozone concentrations can be observed. The evidence
indicated an observable urban influence extending on the order
of 48 to 80 kilometers (30 to 50 miles) downwind of a city.
189
-------
5. When the central region of a synoptic high pressure system—
a region characterized by relatively clear skies and weak,
disorganized flow near the surface—moved into the region of
interest, high concentrations of ozone, as averaged over
all simultaneous cases, were reported at all stations. In
this respect, high concentrations of ozone are defined as "
o
concentrations in excess of 160 yg/m for 8 hours each day.
This condition persisted as long as the high pressure center
remained in the immediate vicinity.
6. Pertinent data from the 1974 summer study show that the high
concentrations of ozone observed at rural sites were gener-
ated in the lower troposphere.
7. The observed high ozone concentrations cannot be explained in
terms of air flow from a specific point source or a single
urban-industrial area source. In other words, no specific
trajectory could be uniformly associated with the arrival of
air containing either high or low concentrations of ozone at
any of the rural sites.
8. The results of this research provide substantial support for
transport of ozone precursors from urban areas to the
rural stations under appropriate meteorological conditions.
During transport and in the presence of sunlight, ozone is
synthesized.
9. The results of this research program imply that the control
of hydrocarbon in any individual city will reduce but not neces-
sarily prevent the occurrence of high rural ozone concentrations in
excess of the NAAQS, at any given rural site. The impli-
cation is that the release of hydrocarbons and oxides of
nitrogen from anthropogenic or biogenic sources, located in
either an urban or rural area, all combine to generate appre-
ciable quantities of ozone over wide areas.
190
-------
8.0 REFERENCES
1. Junge, C. E. , Air Chemistry and Radioactivity, Intern. Geophys.
Ser., 4-, New York, Academic Press. (1963).
2. "Mount Storm, West Virginia-Gorman, Maryland, and Luke, Maryland-
Keyser, West Virginia, Air Pollution Abatement Activity",
Air Pollution Control Office Publ. No. APTD-0656, Research
Triangle Park, N.C., Environmental Protection Agency, April
(1971).
3. Richter, H. G. , "Special Ozone and Oxidant Measurements in Vicinity
of Mount Storm, West Virginia", Final Report, Research Triangle
Institute, October (1970).
4. "Investigation of High Ozone Concentration in the Vicinity of
Garrett County, Maryland, Maryland and Preston County, West
Virginia", Research Triangle Park, N.C., Research Triangle
Institute, January (1973). (Also issued as Environmental
Protection Agency Report No. EPA-R4-73-019).
5. "Investigation of Ozone and Ozone Precursor Concentrations at
Nonurban Locations in the Eastern United States", Research
Triangle Park, N.C., Research Triangle Institute, May (1974)
(Also issued as Environmental Protection Agency Report No.
EPA-450/3-74-034).
6. Decker, C. E., T. M. Royal, and J. B. Tommerdahl, "Field Evaluation
of New Air Pollution Monitoring Systems", Final Report.
Research Triangle Institute, Contract CPA-70-101, Environmental
Protection Agency, June (1972).
7. Lonneman, W. A., S. L. Kopczynski, P. E. Darly, and F. D. Sutterfield,
"Hydrocarbon Composition of Urban Air Pollution", Environ. Sci.
Technol. , _8, 229-236 (1974).
8. Decker, C. E., T. M. Royal, and J. B. Tommerdahl, "Development and
Testing of an Air Monitoring System", Final Report. Research
Triangle Institute, Contract 68-02-1011, Environmental Protection
Agency, December (1973).
9. McKee, H. C., "Collaborative Testing of Methods to Measure Air Pollu-
tants-Ill Chemiluminescent Method for Ozone". Presented at
67th Annual Meeting of Air Pollution Control Association, Denver,
Colorado, June 9-13, 1974.
10. Smith, F. S., T. M. Royal, and C. E. Decker, "Quality Assurance Program
Relative to Summer 1974 Oxidant Study"t Final Report. Research
Triangle Institute, Contract BOA-68-02-1386, Task 8, Environmental
Protection Agency, February (1975).
191
-------
11. Miller, P. R., M. H. McCutchon, and H. D. Milligan, "Oxidant
Air Pollution in the Central Valley, Sierra Nevada Foothills,
and Mineral King Valley of California", Atmos. Environ., ^,
623 (1972).
12. Stasiuk, W. N. and P. E. Coffey, "Rural and Urban Ozone Relation-
ships in New York State", JAPCA. 24_, 564-568 (1974).
13. 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, 257-258 (1974).
14. Bering, W. S., and T. R. Borden, Jr., "Ozonesonde Observations
over North America", Vols, 2, 3, 4, Air Force Cambridge Research
Laboratories, Office of Aerospace Research, U.S.A.F. Clearing
House, Department of Commerce, Washington, B.C. (1964, 1965,
1967).
15. Kopczynski, S. L., A. P. Altshuller, and F. D. Sutterfield, "Photo-
chemical Reactivities of Aldehyde-Nitric Oxide Systems",
Environ. Sci. Technol., 8, 909-918 (1974).
16. Jeffries, H. E. and J. E. Sickles, "Mechanism for Ozone Generation",
Personal Communication, January (1975). (Reproduced as table
37.)
192
-------
APPENDIX A
CALIBRATION SYSTEMS/PROCEDURES
193
-------
APPENDIX A
CALIBRATION SYSTEMS/PROCEDURES
Dynamic calibration procedures were used to calibrate all analyzers
used during the field measurement period. Biweekly calibrations were per-
formed on each instrument using the procedures described below.
A-l. General
Because the five stations were at elevations above mean sea level,
adjustments to the data were necessary to reduce values to reference con-
dition of 25°C (298K) and 760 mmHg. Adjustments to volume measurements
were made using the following equation:
V x
298
760 t + 273
where
V = volume of air at reference conditions, liters,
K
V = volume of air at sampling conditions, liters,
P = barometric pressure at sampling conditions, mmHg, and
t = temperature at sampling conditions, °C.
Table A-l summarizes the sampling conditions assumed for each site.
Table A-l. Altitude-pressure relationship for sampling sites
Altitude above
mean sea level
Station
Wilmington , Ohio
McConnelsville ,
Ohio
Wooster, Ohio
McHenry, Md.
DuBois, Pa.
meters
402. 5
305
346
885
554
feet
1,321
1,000
1,136
2,900
1.817
Foom
temperature,
°C
25 ± 2°
25 ± 2°
25 ± 2°
25 ± 2°
25 ± 3°
Baro-
metric
pressure
mmHg
723.4
732.0
731.0
682.5
710.4
Volume of 1 liter at
reference conditions
(25°C, 760 mmHg)-
liters
0.95
0.96
0.96
0.90
0.94
Derived from table p. 9-4, Handbook of Air Pollution, PHS Publication No.
999-AP-44, "Barometric Pressure at Various Altitudes."
195
-------
The same adjusted volume was used each time a calibration was per-
formed. A basic step-wise procedure was employed for dynamic calibration
of all air quality analyzers as follows:
1. Verify operational status of each analyzer prior to beginning
calibration.
2. Connect instrument inlet line or instrument calibration inlet
line, as the case may be, to the manifold of the calibration
apparatus or, for hydrocarbon instruments, directly to cylin-
ders containing calibration gas.
3. Allow instrument to sample zero air (i.e., air minus the pol-
lutant of concern) for a period of time sufficient to establish
a valid zero output. Average the instrument output for zero
input concentration for at least 15 minutes. Record voltage
and/or chart readings as dictated by the type of data acqui-
sition system used.
4. Introduce a pollutant calibration concentration equal to
approximately 80 percent of the operating range and adjust
the span of instrument as required upon initial setup of the
instruments. This adjustment is normally required only upon
initial setup of an instrument or if excessive span drift
occurred during the evaluation period. Omit step 4, except
on initial setup of analyzer.
5. Introduce successive pollutant calibration concentrations of
10, 20, 40, 60, and 80 percent of the operating range of the
instrument being calibrated. Allow sufficient time to estab-
lish a valid instrument output for each calibration concentra-
tion, and average the instrument output for that input cali-
bration concentration for at least 15 minutes. Record the
voltage and/or chart reading for that calibration point and
proceed to the next higher calibration concentration and repeat
the sequence of events.
6. Return the instrument inlet line to the ambient air sampling
manifold and compute a transfer equation, which relates
196
-------
pollutant concentration Input to instrument voltage output,
for each instrument.
7. Document thoroughly all parameters required to complete the
calibration record sheet designed for each analyzer.
A-2. Ozone Analyzers
A dynamic calibration system producing ozone by ultraviolet irradia-
A-l/
tion of oxygen was used to calibrate the gas phase chemiluminescent
ozone analyzers. The ozone generator consisted of a shielded mercury
lamp (20.3 cm in length) which irradiated clean compressed air flowing
through a quartz tube (1.5 cm in diameter). By varying the length of
the lamp exposed to the air and the total flow of compressed air (usually
set at 5.0 1/min), ozone concentrations from zero to approximately 1 ppm
(1960 yg/m3) were produced.
A portable calibration unit consisting of a regulated power supply,
zero air source, calibrated rotameter, ozone generator, mass flowmeter
for nitric oxide mixtures, and a glass manifold with sampling ports was
assembled. This unit was transported from site to site for calibration
of each ozone (as well as nitrogen dioxide) analyzer. A schematic dia-
gram of the ozone calibration system is shown in figure A-l.
In order to obtain a reference measure of the ozone output of the
A-2/
calibration unit, the neutral-buffered KI analysis method was used
for each calibration point. A diagram of the calibration system is
shown in figure A-l. The analyzer and the bubbler train sampled simul-
taneously from the glass manifold. A diagram of the KI sampling train
and apparatus used to calibrate the sample flow rate is shown in figure
A-2.
A-3. Nitrogen Oxides Analyzer
A-3/
The NO-NCL-NO analyzer was calibrated by gas phase titration.
•^ X
The technique makes use of the rapid gas phase reaction between NO and
0 to produce a stoichiometric quantity of NO . A schematic diagram
showing components of the parts of the calibration size then is presented
in figure A-3.
197
-------
Pen-ray
lamp
Adjustable sleeve
\
J
Collar
^
Quartz tube
Needle
valve
Flow controller
Silica gel
Molecular sieve
Charcoal
Cylinder
air
Vent
Figure A-l. Ozone calibration system.
198
-------
To vacuum
pump
Manometer
Absorbers
Figure A-2. KI sampling train and apparatus for calibration
of flow rate under operational conditions.
199
-------
Calibration system
Pen-ray Adjustable sleeve ..
, v „ , , Mass flowmeter
lamp \ Collar ,_ ... 3 , . .
\ \. x- (0-50 cm-'/min)
\i
X ^
"n* *n*
K,
s
\_
_/
Quartz tub
Capillary / ^
(pFlo
£sil
E&Mol
TCha
BO
Cylinder
air
S'
wmeter
ica gel
ecular sieve
rcoal
V
S \ NO/J
&^ (100 F
eaction
chamber
>pm)
N ftixing
bulb Manifolc
LC^S£
ent
Figure A-3. Gas phase titration system.
200
-------
After the preliminary zero and span checks, the first step in the
final calibration is the introduction of zero air into the analyzer.
After 10 minutes, a zero reading is taken on the NO, NO-, and NO channels.
£m X
Before transporting the NO calibration gas cylinders to the field,
the NO concentration of the contained calibration gases was verified
A-3/
using the technique of Hodgeson and associates. The procedure con-
sisted of titrating an NO concentration of 1.0 ppm with successive con-
centrations of ozone (0-0.8 ppm) produced by an ozone generator refer-
enced to the neutral-buffered KI procedure. The resultant NO detector
outputs, after stabilization at each titration points (i.e., 0.0, 0.1,
0.2, ... 0.8 ppm ozone added), were plotted as concentration ppm (y-axis)
versus 0_ concentration added, ppm (x-axis). A straight line drawn
through the linear portion of the titration curve was extrapolated to the
x-axis. The concentration of the x-axis intercept, C', was the 0_ con-
centration equivalent to the initial diluted NO concentration. An example
of a typical gas phase titration curve is presented in figure A-4. The
cylinder NO concentration was then calculated as follows:
where
CNn = cylinder NO concentration, ppm
F = measured NO flow, ml/min,
C' = equivalence point 0-, concentration, ppm, and
F = total clean air flow, ml/min.
The NO portion of the analyzer was calibrated by dynamic flow dilu-
tion of the cylinder gas. This was accomplished by metering the NO from
the cylinder through a calibrated mass flowmeter and then into the dilu-
tion system of the ozone generator. To calibrate the NO- portion of the
analyzer, a constant NO concentration of approximately 940 yg/m3 (0.5 ppm)
was produced by dilution. Ozone was added in increments from the generator.
Decrements observed on the spanned NO detector are then equivalent to the
NO- concentration produced by the 0, source. Since the NO- produced was
equivalent to 0. consumed, the calibrated 0 source served as a calibrated
NO- source when NO was present in excess. After adequate time (~10 min)
201
-------
a
a
o
a
C
o
o
i
0.1 02 03 0.4 05 0.6 0.7 Ofl 0.9
0., Concentration (ppm) (0_ generator)
1.0
Figure A-4. Gas-phase titration of NO with 0~.
202
-------
for stabilization at each point, the mV output of each channel was re-
corded.
The N0? concentration was deduced from the decrease of the NO signal,
and a calibration curve relating N0« concentration and analyzer mV output
was constructed.
A-4. Hydrocarbon Analyzer
Calibration of hydrocarbon instruments was accomplished utilizing
standard calibration gases certified by the supplier. For this study
cylinders of methane in air were obtained from Scott Research Laboratories.
Several concentrations ranging from 0 to 10 ppm of CH, were used for cali-
bration purposes. In the absence of acceptable cylinders of zero air (i.e.,
CH, < 0.10 ppm) an alternate procedure utilizing electronic zeroing was
used in lieu of dynamic zero. The following concentrations of methane in
air were used to calibrate the hydrocarbon anlyzers:
Supplier Cylinder #
Certification by
manufacturer (± 2%)
CHA* CO
Scott Research Laboratories
Laboratories A
*THC
B
C
as CH, = CH, concentration for cylinders A,
8 . 5 ppm
8 . 4 ppm
8.1 ppm
B, C.
21 . 4 ppm
23.2 ppm
24.4 ppm
203
-------
REFERENCES
A-l. J. A. Hodgeson, R. K. Stevens, and B. E. Martin. "A Stable Ozone
Source Applicable as a Secondary Standard for Calibration of
Atmospheric Monitors." Air Quality Instrumentation. Vol. 1,
John Scales, ed., 149-150, ISA, Pittsburgh, Pa., 1972.
A-2. 40 CFR 50, Appendix D.
A-3. J. A. Hodgeson, R. E. Baumgardner, B. E. Martin, and K. A. Rehme.
"Stoichiometry and Neutral lodometric Procedure for Ozone by
Gas-Phase Titration with Nitric Oxide." Anal. Chem. 4^3. 1123-
1126, 1971.
204
-------
APPENDIX P
PERFORMANCE CHARACTERISTICS AND
OPERATIONAL SUMMARIES FOR INSTRUMENTS
205
-------
APPENDIX B
PERFORMANCE CHARACTERISTICS AND
OPERATIONAL SUMMARIES FOR INSTRUMENTS
B-l. Instrument Performance Characteristics.
Minimum detectable concentrations, ranges, and precisions for the
air quality monitoring instruments used in this study are summarized in
table B-l.
B-2. Operational Summaries for Instruments by Station.
Operational data are summarized for each analyzer by station during
this study in table B-2. For this program, operational time is divided
into the following categories:
(1) Percent operational time, and
(2) Percent downtime.
Percent operational time includes all categories or operational status
other than downtime, which includes routine maintenance, awaiting repair,
or repair. The data presented in table B-2 include percent operational
time—which is synonymous with percent valid data—percent downtime, and
number and nature of failures. It should also be noted that, for this
study, Research Triangle Institute engineers and technicians were respon-
sible for maintenance and repair of all analyzers, except the Beckman
Model 6800 THC, CH,, CO analyzers. Beckman, under separate contract to
the Chemistry and Physics Laboratory of Environmental Protection Agency,
supplied three Model 6800 chromatographs with calibration gases, etc.,
and was responsible for maintenance and/or repair of the Beckman analyzers.
Included in the service contract were labor, parts, routine maintenance/
calibration at 2-week intervals, and 24-hour turnaround on service for
instrument failure.
207
-------
Table B-l. Instrument performance characteristics
Minimum
detectable Range
concentration
Precision
(% of indicated
Instrument
Parameter yg/m3 ppm yg/nr ppm concentration)
Bendix Model 8002
Chemiluminescent Ozone
Analyzer
RTI Solid Phase
Chemiluminescent Ozone
Analyzer
4.0 0.002 0-392 0-0.2
4.0 0.002 0-392 0-0.2
Bendix Model 8101-B
Chemiluminescent NO, NOX N02 9.4 0.005 0-940 0-0.5
NO-NOX-N02 Analyzer
Beckman Model
6800 THC, CH4, THC, CH4> CO 30.0 0.050 0-3270 0-5.0
CO Analyzer
Perkin-Elmer Selected
Model 900 Gas Hydrocarbons sub-ppb
Chromatograph
ppb-ppm
+ 2%
+ 2%
+ 2%
1%
208
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209
-------
APPENDIX C
AIRCRAFT FLIGHT PLANS/DATA/
METEOROLOGICAL SUMMARY FOR EACH FLIGHT
211
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-------
40"30'-
-10 N. Mi.
12:10
CLINTON
CO. AFB
FLIGHT DATE: June 20. 1974
PATTERN: Square Wave
TRUE AIRSPEED: 277.8 km/h (150 knots) MISSION ALTITUDE: 609.6 m (2.000 ft)
above mal
LOW LEVEL WINDS: Sfc
609 m (2,000')
914 m (3.0001)
1219 • (4.000')
DATA: Ozone Concentration in ug/n
Tine in EOT
215/2.57 n/s (5 knots)
270°/9.26 «/• (18 knots)
300°/9.77 «/• (19 knots)
290°/10.29 m/s (20 knots)
Figure C-l. Partial square wave flight on June 20, 1974.
214
-------
Flight Data - June 20, 1974
Square Wave
Time
1105
1126
1136
1141
1151
1156
1206
Leg 0 * NO * £»*•
J £• \ \s )
Base 133
130
127
134
135
132
1 124 17 26.7
126
127
125
133
2 137 17 26.1
126
3 129 17 26.1
127
134
134
128
4 134 17 26.6
132
134
5 137 34 26.4
138
134
135
130
6 130 34 26.4
128
Time Leg 0 * NO,* T.^'
J £m 1 \J )
1211 7 130 34 26.4
132
156
149
138
1221 8 149 17 26.7
150
148
9 149 17 26.7
152
1231 10 153
153
157
166
171
171
165
153
1245 11 153
154
149
145
157
157
149
160
168
157
149
145
157
- Nitric oxide below detectable limit.
* 3
Concentration in yg/m .
METEOROLOGICAL SUMMARY FOR FLIGHT
High pressure centered over northern Alabama produced moderately strong
westerly flow through Ohio. Winds at the 2000 foot msl flight level
were 280° at 20 knots. Flight level visibility was generally less than
5 miles.
-------
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216
-------
Flight Data - June 25, 1975
Vertical Profile - Wilmington, Ohio
Time
0803
0811
0817
0823
0831
0837
0845
0853
0901
0909
0918
Altitude
(Meters)
610
1220
1830
2440
3050
3660
3050
2440
1830
1220
610
Oo
(yg/m3)
57
76
76
79
80
81
80
82
102
76
80
Temp.
12.5
7.7
3.0
- 1.1
- 5.5
- 5.5
- 0.5
3.0
8.4
12.9
15.0
NO/NO,
(yg/m3)
0)
t-i
JD
a
4J
o
0)
0)
Tl
o
i-H
OJ
#
217
-------
":" / »» »' 117 UN
FLIGHT DATE: June 27. 1974
TRUE AIRSPEED: 277.8 k»/h (ISO knots)
LOW LEVEL WINDS: Sfc
609 • (2,000')
914 • (3,000')
1219 • (4,000')
DATA: Ozone Concentration In Ug/«
Tine in EOT
Hydrocarbon Saaple Pod clone
Denoted by | |
PATTERN: Square Wave
MISSION ALTITUDE: 762.0 • (2,500 ft)
above Bel
070* /5.14 m/« (10 knots)
080*78.74 •/* (17 knots)
065V8.23 •/> (16 knots)
055V7.72 •/« (IS knots)
Low Level Winds Frost
National Weather Service
Upper Air Station
Dayton, Ohlo-0800 EOT
Figure C-3. Partial square-wave flight on June 27, 1974.
218
-------
Flight Data - June 27, 1974
Square Wave
Time
1121
1131
1136
1146
1150
1202
1207
1217
1222
Leg
Base
1
2
3
4
5
6
7
8
0 * Temp.
3 CO
138 15.8
138
135
127
127
123 15.9
133
133 16.1
125
125
135
141
150 16.8
149
146 16.2
145
137
133
129
133
135 16.2
137
133 16.3
127
137
141
143
147 16.3
150
150
151 16.7
149
157
146
134
Time Leg OB*
1232 9 9 129
138
137
1239 10 135
131
139
147
166
1249 11 158
163
1252 12 168
174
150
145
139
1302 13 123
135
1307 14 126
131
141
170
188
1317 15 173
174
161
1322 16 158
168
RETURN 161
150
151
146
143
134
135
?£•
16.6
16.3
17.4
17.3
17.3
16.7
- Nitrogen dioxide and nitric oxide below detectable limit
219
* 3
Concentration in jag/m .
-------
METEOROLOGICAL SUMMARY FOR FLIGHT OF JUNE 27, 1974
A high pressure center over Quebec produced a northeasterly flow over
Ohio. Winds at the 2500 foot msl flight level were 060° at 15 knots.
There was scattered cumulus at 3000 feet msl. Good WR visibility was
maintained throughout the mission with good thermal mixing to 9000 feet msl.
220
-------
40*30'
12:56
Clinton
X Co- A"
39° 30'
83°
FLIGHT DATE: July It, 1974
PATTERN: Square Wave
TRUE AIRSPEED: 240.8 Itn/h (130 knot*) MISSION ALTITUDE: 762.0 a (2,500 ft)
LOU LEVEL WINDS : Sfc
609 m (2,000')
914 • (3,000')
1219 n (4,000')
DATA: Ozone Concentration In ug/g
TlM In EOT
above msl
220°/3.60 m/8 (7 knots)
225°/13.9 n/s (27 knots)
240°/15.4 m/s (30 knots)
245°/14.9 m/s (29 knots)
Figure C-4. Partial square-wave flight on July 4, 1974.
221
-------
Flight Data - July 4, 1974
Square Wave
Time
1208
1220
1226
n * Temp.
Leg 03 (OG)
Base 212 26.3
234
234
250
254
1 236 26.5
245
255
2 254 26.3
252
250
238
229
221
Ti. Leg 03* *£•
1238 3 229 26.3
231
238
237
1245 4 237
235
235
252
256
1257 ABORT
- Nitrogen dioxide and nitric oxide below detectable limits
* / 3
Concentration in pg/m .
METEOROLOGICAL SUMMARY FOR FLIGHT
Strong low level southwesterly flow predominated with winds at the 2500 foot
msl flight level being 235° at 28 knots. Scattered cumulus formed at
3500 feet msl below which it was moderately hazy. Thermal mixing in the
afternoon extended through a layer up to 8500 feet msl.
222
-------
1
(6)
VL-
ip ip tp i]
, M ».,..,.. * ... ,-
»»:«
FLIOIT DATE I July 6. 197*
TRUE AIRSPEED: 277.8 k»/h (1JO knot*)
LOU LEVEL VnXDS: Sfc
609 • (2,000'}
9U • (3.000')
1219 • (4.000')
DATA: Oxon* Conc*ot ration la Ug/m
TIM to EOT
Hydrocarbon
D«not«d by
Poaltlona
PATTERN: Doubl* Box
MISS10B ALTITUDE: 762.0 • <2,500 ft)
above m*l
080V2.57 */• (5 knot.)
130V3.60 •/» (7 knot*)
21SV2.06 •/• (4 knots)
290*/2.M •/• (4 knot*)
Low Uval Wind. Fro*
National Waatnar S«rvlca
Opp«r Air Station
Dayton, Ohlo-0800 EOT
Figure C-5. Double-box flight of July 6, 1974.
223
-------
Flight Data - July 6, 1974
Double-Box
Time
1245
1317
1327
1343
1351
. n * Temp.
Leg 03 (.JJ
Base 247 23.0
253
237
229
226
237
247
255
286
249
248
239
229
210
198
198
1 196 22.3
197
203
202
204
2 214 22.5
219
223
243
261
276
257
246
3 253 23.5
248
244
264
4 241 22.5
241
207
204
n» u. o,* »g-
1403 4A 189 21.8
204
184
155
158
164
173
1418 5 181 23.7
173
174
189
185
178
166
176
167
169
•165
167
158
159
160
1447 6 176 24.7
187
197
221
206
213
218
223
254
281
245
250
244
250
272
263
- Nitrogen dioxide and nitric oxide below detectable limits.
* 3
Concentration in yg/m .
224
-------
Flight Data - July 6, 1974
Double-Box (Continued)
Tin* Leg O/ *«*•
1525 7 254 25.5
258
268
264
285
282
289
299
304
297
310
283
277
281
301
289
295
305
1601 8 314 24.4
285
277
285
265
239
254
227
197
198
177
165
178
197
185
219
H. Leg 03* £*•
1632 9 202 25.0
192
185
159
157
174
215
194
210
209
243
283
341
384
374
316
274
273
266
255
262
279
281
1719 END 26.8
- Nitrogen dioxide and nitric oxide below detectable limits.
* 3
Concentration in yg/m .
225
-------
METEOROLOGICAL SUMMARY FOR FLIGHT OF JULY 6, 1974
A high pressure center over lake Erie sitting behind a dissipating
stationary front over the Ohio River Valley divided the mission area in
half along an east-west line through Columbus. The northern sector was
clear with unlimited visibility. Visibility in the southern sector was
sometimes less than a mile due to heavy haze. The transition area be-
tween these two sectors was less than ten miles across. Winds up through
the 2500 foot msl flight altitude were light and veering in direction.
Thermal mixing was indicated up to 8000 feet msl.
226
-------
rLIGHT DATE: July 9. 1974
TRUE AIRSPEED: 277.8 Wh (ISO knots)
LOW LEVEL WINDS: Sfc
609 • (2.000')
914 • (3,000*)
1219 • (4,000*)
DATA: Otonc Concentration Mg/a
T!M ID EOT
Hydrocarbon Staple Positions
Denoted bjr i 1
PATTERN: Double Box
MISSION ALTITUDE: 762.0 • (2,500 ft)
above •*!
215*72.06 ml* (4 knots)
250V4.63 •/. (9 knots)
270V3.09 •/• (6 knots)
285*72.57 m/t (5 knots)
Low Level Hinds From
National Heather Service
Upper Air Station
Dayton. Ohio-O800 EOT
Figure C-6. Double-box flight on July 9, 1974.
227
-------
Flight Data - July 9, 1974
Double-Box
Time
°
°
1027
Base
1057
1110
1121
1130
193
193
231
234
256
270
253
266
246
234
241
244
220
234
236
234
236
234
233
227
230
230
233
240
241
256
263
263
241
233
236
241
268
362
310
254
26.4
1141
4A
1154
26.3
26.4
1227
26.5
256
249
243
246
243
241
268
291
287
266
257
252
255
254
252
253
267
265
265
271
255
261
260
261
257
246
260
245
236
247
240
247
274
349
286
247
272
315
26.8
27.5
27.4
- Nitrogen dioxide and nitric oxide below detectable limits.
* 3
Concentration in ng/m .
228
-------
Flight Data - July 9, 1974
Double-Box (Continued)
Time Leg 0,* f°r\
J \ *•»/
1259 7 329 27.5
318
260
255
238
244
252
220
257
267
273
268
252
256
251
1329 8 265 27.7
269
261
273
268
285
340
350
297
265
251
272
259
264
270
258
Time Leg 0^*
1402 9 265
266
276
262
247
250
247
244
247
264
255
253
282
303
262
277
269
282
259
270
274
299
315
296
1449 END
<°C)*
28.0
28.4
- Nitrogen dioxide and nitric oxide below detectable limits.
* 3
Concentration in yg/m .
METEOROLOGICAL SUMMARY FOR FLIGHT
This was the third day of stagnant high pressure with the center now
located over southeastern Kentucky producing a light generally westerly
flow over the mission area. Visibility at 2500 feet msl was 2 to 4 miles
throughout the flight. Cumulus formed at 3000 feet msl with thermal
mixing occurring to 9300 feet msl.
229
-------
2» 228 __ 233 22> 22
FLIGHT DATE: July 13. 1974
TRUE AIRSPEED: 250.0 lun/h (135 knots)
LOW LEVEL WINDS: Sfc
609 m (2,000')
914 m (3,000')
1210 B (4,000')
DATA: Ozone Concentration In Mg/m
Time In EOT
Hydrocarbon Sample Positions
Denoted by ^ |
PATTERN: Double Box
MISSION ALTITUDE: 762.0 m (2,500 ft)
above msl
130V2.06 m/s (4 knots)
205V3.09 »/s (6 knots)
145V1.03 m/s (2 knots)
075VI.03 t«/s (2 knots)
Low Level Winds From
National Weather Service
Upper Air Station
Dayton, Ohio-0800 EDT
Figure C-7. Double box flight on July 13, 1974.
230
-------
Flight Data - July 13, 1974
Double-Box
Time
1100
1130
1142
1154
Leg 03*
Base 225
224
229
227
222
228
233
231
234
236
224
229
235
225
1 229
228
233
228
229
219
2 223
227
234
230
237
232
3 223
223
213
225
233
Time Leg 03*
1203 4 231
272
280
237
240
1214 4A 247
236
233
236
232
231
237
1227 5 241
241
241
235
229
229
232
236
244
236
248
252
241
239
Time Leg 0^*
1259 6 236
237
239
236
236
240
268
271
281
272
280
259
252
248
249
252
1331 7 239
237
241
239
225
231
232
233
241
231
242
211
222
251
264
- Nitrogen dioxide and nitric oxide below detectable limits.
* 3
Concentration in pg/m .
231
-------
Flight Data - July 13, 1974
Square Wave
Time Leg (>3* Time Leg 03*
1402 8 257 1433 9 258
251 228
245 226
256 238
249 217
241 241
259 237
256 238
249 243
239 251
238 261
235 261
234 267
242 243
242 235
263 224
245
239
249
239
238
241
1518 END
- Nitrogen dioxide and nitric oxide below detectable limits.
* 3
Concentration in yg/m .
METEOROLOGICAL SUMMARY FOR FLIGHT
A high center over the Ohio Valley produced light winds which backed
from southeasterly at the surface to northwesterly at around 15,000
feet msl. Good thermal mixing was experience to about 6500 feet msl.
Visibility ranged from five to twenty miles throughout the mission
with few cumulus.
232
-------
Ill JU
, V« 12
12) 121 T 12t 122 12)
\ CLINTON
co. »r«
FLIGHT DATE: July 16. 1974
TRUE AIRSPEED: 250.0 km/h (135 knots)
LOW LEVEL WINDS: Sfc
609 m (2,000')
914 m (3,000')
1219 • (4,000')
DATA: Ozone Concentration in ug/n
Time In EOT
Hydrocarbon Sample Position*
Denoted by
PATTERN: Square Wave
MISSION ALTITUDE: 914.4 m (3,000 ft)
above mal
060"/I.54 m/s (3 knots)
080V5.14 m/s (10 knots)
060V3.60 m/s (7 knots)
015V4.12 m/s (8 knots)
Low Level Winds From
National Weather Service
Upper Air Station
Dayton, Ohlo-0800 EOT
Figure C-8. Square-wave flight on July 16, 1974.
233
-------
Flight Data - July 16, 1974
Square Wave
Time Leg
1131 Base
1142 1
1147 2
1159 3
1205 4
1213 5
1220 6
.. * Temp. _.
0, f0r\ Time Leg
J ^ \j J
126 19.4 1233 7
123
128
126
122 1237 8
123
126 19.6
116
1247 9
120 19.8
116
128
133 1251 10
137
126
132
131 19.7
132 1302 11
136 20.0
129
134 1308 12
132
137
137 20.0
149 1316 13
146
132 20.5
147 1321 14
146
144
140
134
"3*
132
139
142
152
139
151
151
147
149
149
149
156
175
159
152
166
161
156
157
156
188
176
166
168
171
181
rS'
19.9
20.4
20.7
20.8
21.3
21.0
21.4
21.8
- Nitrogen dioxide and nitric oxide below detectable limits.
A ^
Concentration in yg/m .
234
-------
Flight Data - July 16, 1974
Square-Wave (Continued)
Time Leg 0* J"*' Time Leg 0 * J**'
J V ^*/ -5 ^ O/
1325 RETURN 227 21.0
211
189
189
182
177
156
147
139
146
152
152
157
154
154
151
146
144
146
1403 END 20.8
- Nitrogen dioxide and nitric oxide below detectable limits.
* / 3
Concentration in yg/m .
METEOROLOGICAL SUMMARY FOR FLIGHT
A generally northerly flow persisted over the Ohio area with the 3000 foot
msl mission altitude winds being 060° at 7 knots. A subsidence inversion
capped the thermal mixing layer at 8800 feet msl and extended up to
11,100 feet msl with very dry air above the base of the inversion. Visi-
bility was generally about 3 miles, but got down to one mile over Dayton.
235
-------
U
05
o o»
CM O
ro r">
o
O
in
CM
U1
CM
CM
5 § 8
CM CM CM
(d
OS
W
PH
•st
r-l
r^
iH
>>
t-l
3
O
4-1
C
1
ES
0)
u-i
O
o.
cfl
O
•H
H
fe
|
W
w
H
3
/
/
/
1
O
O
in
CM
/°-^
O
o
o
00
1
/) o
*
^JQ tf"
O
O
o
^
1
1
o
o
o
CM
o
o
0
vO
1
0
8
m
1
I
o
o
m
,— i
0
8
i
i
o
o
o
r-l
O
0
o
1
o
0
o
CM
1
o
O ON
CM |
u
0)
C-T 3
°e bo
o _ ^
m "^
Z
0
o
o
I s
rH
o
in
(1SW aAoqe
236
-------
Flight Data - July 17, 1974
Vertical Profile - Wilmington, Ohio
Time
1155
1203
1211
1220
1227
1236
1244
1254
1303
1312
Altitude (meters)
1220
1372
1525
1678
1830
1983
2135
2288
2440
2593
_ * Temp.
°3 (°C)
183 18.5
204
203
192
192
203
175 16.2
166
192
161 15.3
161
153
156 15.2
160
154
159 15.1
142
132
165 15.8
148
121
145
151 15.5
130
128
153 15.3
151
138
138
111 14.0
114
118
114
- Nitrogen dioxide and nitric oxide below detectable limits
* / 3
Concentration in yg/m .
237
-------
METEOROLOGICAL SUMMARY FOR FLIGHT OF JULY 17, 1974
In attempting a vertical profile of a subsidence inversion, we encountered
a very stable, basically isothermal layer instead between 5500 feet msl and
8800 feet msl. There was a high pressure center northeast of Pittsburgh.
Winds in the stable layer were light northwesterly.
238
-------
13:29
\ Hi}}
>c
FLIGHT DATE: July 21. 197»
TRUE AIRSPEED: 259.3 ka/h (140 knots)
LOW LEVEL WINDS: Sfc
609. • (2,000')
914 • (3,000')
1219 a (4,000')
DATA: Ozone Concentration in pg/n
Tla* In EOT
Hydrocarbon Staple Position*
Denoted by | |
PATTERN: Square Wave
MISSION ALTITUDE: 975.36 a (3,200 ft)
above aal
0300/3.09 a/a (6 knots)
060V6.17 B/S (12 knots)
055V4.12 a/s (8 knots)
025V3.60 B/S (7 knots)
Low Level Winds Froa
National Weather Service
Upper Air Station
Dayton, Ohlo-0800 EOT
Figure C-10. Square-wave flight on July 21, 1974.
239
-------
Flight Data - July 21, 1974
Square Wave
Time
1158
1212
1216
1229
1234
1245
1249
1259
1304
Leg
Base
1
2
3
4
5
6
7
8
0 * Temp.
°3 (°C)
177 21.8
181
175
166
157
151
136
147 17.3
155
162 18.0
174
179
183
191
191
187 19.0
187
187 18.5
189
189
183
176
176
172 18.3
176
183 18.5
183
191
206
179
185 18.7
198
202 19.0
200
191
193
189
191
Time Leg 03*
1315 9 187
185
1319 10 191
191
189
200
206
1330 11 212
210
214
1335 12 212
212
202
202
198
1346 13 200
191
1350 14 189
193
193
195
1357 RETURN 200
198
198
196
198
204
206
206
213
219
219
226
226
191
192
188
187
179
183
1434 END
Temp.
(°C)
18.3
18.8
19.4
19.8
19.8
19.0
20.5
20.5
- Nitrogen dioxide and nitric oxide below detectable limit.
* / 3
Concentration in yg/m .
240
-------
METEOROLOGICAL SUMMARY FOR FLIGHT OF JULY 21, 1974
An inversion aloft at 3500 feet msl was burned off by the time of the
flight with thermal mixing indicated to 7600 feet msl. Winds at the
3200 foot msl flight altitude were 050° at 8 knots. Visibility ranged
from 7 miles over Columbus to over 20 miles downwind of the city.
241
-------
FLIGHT DATE: July 25. 1974
TRUE AIRSPEED: 259.3 ka/h (140 knots)
LOW LEVEL WINDS: Sfc
609 • (2,000')
914 • (3,000')
1219 m (4,000')
DATA: Ozone Concentration In Ug/»
Tine In EOT
Hydrocarbon Saaple ftsltlona
Denoted by i |
PATTERN: Square Wave
MISSION ALTITUDE: 762.0 meter* (2,500 ft)
above «sl
070V2.57 n/s (5 knots)
135V3.60 •/. (7 knots)
130V4.12 •/. (8 knots)
110-Ik.12 ml* (8 knots)
Low Level Winds Fron
National Weather Service
Upper Air Station
Dayton, Ohlo-0800 EOT
Figure C-ll. Square-wave flight on July 25, 1974.
242
-------
Flight Data - July 25, 1974
Square Wave
Time
1308
1318
1327
1338
1348
1401
1403
1414
Leg 03*
Base 195
191
188
186
196
177
1 156
187
187
187
2 190
194
196
197
194
205
3 210
210
206
208
208
4 254
267
244
217
207
207
5 200
204
6 202
212
209
231
249
7 296
253
Temp.
(°C)
21.5
22.0
22.0
21.5
22.5
22.7
22.7
22.5
22.0
22.5
22.5
23.0
23.0
23.0
Time Leg 03*
1418 8 244
233
204
196
1427 9 191
1429 10 196
199
201
201
207
1438 11 206
201
204
202
1446 12 197
197
197
172
181
174
177
1500 13 175
172
173
1507 14 173
173
178
181
179
189
1519 15 194
196
199
216
210
Temp.
(*C)
22.5
22.5
23.0
23.0
22.3
22.5
23.0
23.0
23.1
22.5
22.5
22.5
22.5
23.0
22.0
22.0
22.2
23.5
- Nitrogen dioxide and nitric oxide below detectable limit.
* 3
Concentration in yg/m .
243
-------
Flight Data - July 25, 1974
Square Wave (Continued)
Time
Leg
Temp.
Time
Leg
Temp.
1528 16
1536 17
(return
by
Pattern)
208 23.5
204 22.4
204 23.0
191
199
221
235 23.9
217
183
169
172
169 24.9
168
170
171
1536 17 188
(Cont'd) 196
190
187
178
172
178
179
168
179
181
188
1622 185
23.0
22.0
21.0
20.0
22.0
24.0
25.0
- Nitrogen dioxide and nitric oxide below detectable limit.
* 3
Concentration in pg/m .
METEOROLOGICAL SUMMARY FOR FLIGHT
On this day, the Ohio Valley was between fronts with generally easterly
flow near the surface. Visibility ranged from 2 to 5 miles with
moderate turbulence. Thermal mixing occurred to 7000 feet msl with
cumulus forming at 3500 feet msl.
244
-------
w
w
Q
W r^
O O
vO
-------
Flight Data - August 1, 1974
Vertical Profile - Wilmington, Ohio
Tin«-;
07 04''
\4
07 Q6;
0712
0718
0726
0744
0803
0810
Altitude (meters)
305
610
915
1220
1830
2440
915
Low Pass
"3*
80
179
168
183
186
128
179
109
Temp.
23
21
18
12
11
20
- Nitrogen dioxide and nitric oxide below detectable limits
* 3
Concentration in yg/m .
METEOROLOGICAL SUMMARY FOR FLIGHT
High pressure centered over eastern West Virginia produced southwesterly
flow through Ohio. By afternoon, good thermal mixing was experienced to
the base of a shallow inversion between 8200 feet msl and 9000 feet msl.
By 1900, the inversion had burned off.
246
-------
§
S
Cd
CJ
00
00
O
00
O
oo
O
ON
o
CM
09
0)
iH
•H
y-i
O
h
a.
03
O
0)
H
W
u
u
H
O
O
O
vO
O
O
O
O
I 00
O
vD
3
00
•H
O
O
O
N
O
O
ITl
O
O
O
10
oo
O
O
m
247
-------
Flight Data - August 1, 1974
Vertical Profile - Wilmington, Ohio
Time
0844
0850
0900
0910
0913
Altitude (meters)
Low Pass
915
1830
919
Low Pass
*
°3
88
175
171
174
100
Temp.
(°C)
22
12
21
- Nitrogen dioxide and nitric oxide below detectable limits.
* 3
Concentration in yg/m .
METEOROLOGICAL SUMMARY FOR FLIGHT
High pressure centered over eastern West Virginia produced southwesterly
flow through Ohio. By afternoon, good thermal mixing was experienced to
the base of a shallow inversion between 8200 feet msl and 9000 feet msl.
By 1900, the inversion had burned off.
248
-------
g
H
1
CO
W
a
CM
•*
o
m
sr
vD
O
I 5
w
O
in
CO
ao
•»
co
CM
-*
CO
CO
CO
cs
CO
CM
CO
o
CM
w
«
3
H
$
CTi
ca
00
o
u
60
C
•H
S
4-1
O
a.
a
•H
(1)
s
O
§
in
CM
i
T
§
(isw
249
399.0 aaruinv
s«
"• §
tsl
o o
-a-
o
o
m
u
oo
-------
Flight Data - August 1, 1974
Tine
1320
1327
1335
1340
1346
1352
1402
1410
1418.
1432
1446
1455
1502
1508
1515
1516
Altitude (meters)
Low Pass
610
915
1220
1525
1830
2440
3050
3660
3050
2440
1830
1220
915
610
Low Pass
"a*
189
195
193
218
189
196
158
139
153
118
158
217
208
214
204
190
Temp.
(°c)
26
22
19
16
13
9
7
9
9
13.5
19.5
23
26
- Nitrogen dioxide and nitric oxide below detectable limits.
* 3
Concentration in ug/m .
METEOROLOGICAL SUMMARY FOR FLIGHT
High pressure centered over eastern West Virginia produced southwesterly
flow through Ohio. By afternoon, good thermal mixing was experienced to
the base of a shallow inversion between 8200 feet msl and 9000 feet msl.
By 1900, the inversion had burned off.
250
-------
(N
CM
vO
o
c
o
4J
00
c
O
O
8
o
o
(1SW
§
o
I
§
IA
o -
O 00
-------
Flight Data - August 1, 1974
Vertical Profile - Wilmington, Ohio
Time
1656
1705
1710
1718
1724
1739
1746
1753
1758
1802
1805
1812
1816
Altitude (meters)
Low Pass
610
915
1220
1830
2450
3050
3630
3050
2450
1830
1220
Low Pass
*
°3
245
245
222
236
192
153
164
143
165
163
233
219
247
Temp.
(°C)
27
24
21
15
12
7
4
18.8
- Nitrogen dioxide and nitric oxide below detectable limits.
* 3
Concentration in yg/m .
METEOROLOGICAL SUMMARY FOR FLIGHT
High pressure centered over eastern West Virginia produced southwesterly
flow through Ohio. By afternoon, good thermal mixing was experienced to
the base of a shallow inversion between 8200 feet msl and 9000 feet msl.
By 1900, the inversion had burned off.
252
-------
39°30
CLINTON
CO. AFB
84°30
FLIGHT DATE: August 9. 1974
TRUE AIRSPEED: 240.8 km/h (130 knots)
LOW TFVEL WINDS: Sfc
609 m (2,000')
914 m (3,000')
1219 m (4,000')
DATA: Ozone Concentration in ug/m .
Time in EDT
PATTERN: EPA-RTI/Batelle Comparison Flight
MISSION ALTITUDE:
609.6 m (2,000 ft)
above msl
220 /2.06 m/s (4 knots)
285°/3.60 m/s (7 knots)
295°/3.09 m/s (6 knots)
295°/2.57 m/s (5 knots)
Low Level Winds From National Weather Service
Upper Air Station, Dayton, Ohio-0800 EDT
Figure OI6a. EPA-RTI/Battelle comparison flight on August 9, 1974.
253
-------
39°30
84° 30
CLINTON
CO. AFB
FLIGHT DATE: August 9. 1974
TRUE AIRSPEED: 240.8 km/h (130 knots)
LOW LEVEL WINDS: Sfc
609 tn (2,000')
914 m (3,000')
1219 tn (4,000')
DATA: Ozone Concentration in ug/m
Time in EDT
PATTERN: EPA-RTI/Batelle Comparison Flight
MISSION ALTITUDE: 609.6 m (2,000 ft)
above msl
220°/2.06 m/s (4 knots)
285°/3.60 m/s (7 knots)
295°/3.09 m/s (6 knots)
295°/2.57 m/s (5 knots)
Low Level Winds From National Weather Service
Upper Air Station, Dayton, Ohio-0800 EDT
Figure C-16b. EPA-RTI/Battelle comparison flight on August 9, 1974.
254
-------
Flight Data - August 9, 1974
EPA-RTI/Batelle Comparison Flight
Time
1503
1511
1529
1534
1546
Leg
Wilmington to
Montgomery County
Montgomery County to
Dayton
Dayton to
Richmond
Richmond to
Montgomery County
(over Montgomery Co.)
Montgomery County to
Dayton
(over Dayton)
n * Temp.
°3 (°C)
194 27
187
198
off scale
274 27
287
241
224
212
192
193 27
194
193
204
206
195
199 27
214
211
207
275
250 26
296 27
274
235
214
201
189
- Nitrogen dioxide and nitric oxide below detectable limits.
* 3
Concentration in yg/m .
255
-------
Flight Data - August 9, 1974
EPA-RTI/Batelle Comparison Flight (Continued)
Time
1558
1609
1622
1634
1640
Leg
Dayton to
Richmond
Richmond to
Montgomery County
(over Montgomery Co.)
Montgomery County to
Wilmington
Low Pass
Wilmington
o * Temp.
°3 cc)
194 27
191
191
194
204
202 27
212
212
212 26
222
326
253 26
206
193
186
191
187
141
- Nitrogen dioxide and nitric oxide below detectable limits.
* 3
Concentration in ug/m .
METEOROLOGICAL SUMMARY FOR FLIGHT
There was a dissipating cold front north of the Dayton area. Surface
winds were light and generally easterly at the time of the mission.
Visibility was around 7 miles.
256
-------
FLIGHT DATE: August 13. 1974
TRUE AIRSPEED: 250.0 ka/h (13} knot*)
LOU LEVEL WINDS: Sfc
609 • (2,000')
91« • (3,000')
1219 • (4,000')
DATA: Oiotie Concentration in Wg/»
Time la EOT
PATTERN: Ohio Ground Station Interlock
MISSION ALTITUDE: 762.0 a (2,500 ft)
above msl
205V2.57 •/« (5 knot*)
255V8.74 «/« (17 knots)
270°/8.74 la/s (17 knots)
270V8.23 */• (16 knots)
Low Uv«l Winds Fro» (Utlonml Huthcr Service
Upper Air Station, Deyton, Ohio-0800 EOT
Figure C-17a. Ohio ground station interlock flight on August 13, 1974.
257
-------
o
W
W
O
CM
u-l
CM
fl
o
SB
u
en
<:
CM
m
CM
•a-
CM
o
CM o
CM v>
g
w
CO
3
0)
C
c
o
u
o
S
O
M
cx
cd
u
«
<-> e
60
Zl
w
z
O
O
o
CM
o
o
§
o
o
o
(1SK
258
-------
B
r-
in
CM
CM
o
CM o
w
W
sf
r~
a.
co
00
CO
o
o
t-l
(X
W
§
O
§
m
I
o
s?
CN
j
u
§
O
CM
1
§
in
S ^
\*>
w
o o
-t O
dsw
-------
Flight Data - August 13, 1974
Vertical Profile - Wooster and McConnelsville
Time Event
1025 Wilmington to Wooster
(792 meters)
1117
Vertical Profile at Wooster
1122 Low Pass
22S8 meters
1525 meters
752 meters
1206 Wooster to McConnelsville
(792 meters)
* Temp.
U3 (°C)
111 23
102
125
144
125
151
125
142
131
132
121
134
114
136 23.7
120
118
126
130
127
130
134
132
137
142
145
134
142 26.4
122 15.4
125 21
152 25
141
149
154
139
139
147
139
131
98
- Nitrogen dioxide and nitric oxide below detectable limits.
260
* 3
Concentration in yg/m .
-------
Flight Data - August 13, 1974
Vertical Profile - Wooster and McConnelsville (Continued)
Time
1206
1238
Event
Wooster to McConnelsville
(792 meters)
(Continued)
0 * Temp.
3 (°C)
131
146 23.8
167
167
165
157
154
Vertical Profile at McConnelsville
1141 Low Pass 26.3
1157 (2288 meters)
1206 (1525 meters)
1219 (762 meters)
1223 McConnelsville to Wilmington
(762 meters)
1306
117
120
136
155
157
165
166
167
176
154
137
140
146
159
155
154
143
136
135
142
142
155
151
151
149
14.5
19.2
24.4
25.6
- Nitrogen dioxide and nitric oxide below detectable limits.
* i 3
Concentration in vg/m .
261
-------
METEOROLOGICAL SUMMARY FOR FLIGHT OF AUGUST 13, 1974
High pressure over West Virginia produced generally westerly low level
flow over Ohio. There was a high overcast with relatively good visi-
bility and thermal mixing through a fairly shallow layer to 4000 feet msl.
262
-------
m
ts
00
•-(
(M
§
(M
vD
in
O
in
O
_ in
Ox
3g I
B J
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M
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Flight Data - August 15, 1974
Vertical Profile - Wilmington
Time
1053
1117
1130
1153
1201
1215
1228
Altitude (meters)
Low Pass
• 610
1220
1830
2440
3050
3660
*
°3
117
160
186
124
109
70
90
- Nitrogen dioxide and nitric oxide below detectable limits.
* / 3
Concentration in yg/m .
METEOROLOGICAL SUMMARY FOR FLIGHT
Ohio was experiencing a light northerly flow. Good thermal mixing
occurred to 7500 feet msl with visibility about 5 miles due to haze.
Few cumulus formed at 4000 feet msl.
264
-------
cunw
11:13
7 HAKE
j/ «. AP
\11:27
-UUi/
FLIGHT DATE: Amuat 21. H7<
TUIt AIRSPEED: 250 ba/h (135 toon)
UM LEVEL WINDS s Sic
605 > (2,000')
»U > (3,000')
12H . (4,000')
DATA: Oio« Calcntratlon In U«/«
tlmt if EOT
iy4rocarboa
Dnat*d by
PATTERN: Ea«t«rn StagiKttoii Ground
Station Interlock
MISSION ALTITUDE: 1219 • (4000 ft)
above ••!
UOV!.0» •/• (4 knot.)
U5V5.M •/• (11 knot.)
130*/«.M •/• (13 knot.)
UOV6.M «/f (13 knot.)
Lo> Uv.l Wlndi Pro*
htloMl Uuttar S«rvlc«
Dppir Air Station
Daytoo, Ohlo-0600 IDT
Figure C-19.
Eastern flight of August 21, 1974.
265
-------
Flight Data - August 21, 1974
Time Event
0949 Wilmington
to
McConnelsville
(1220 meters)
1029
1044 McConnelsville
to
Wooster
(1220 meters)
1113
1127 Wooster
to
Garrett Co.
°3*
170
161
169
169
167
163
165
161
163
173
171
204
191
199
171
171
169
241
251
256
258
256
262
233
231
223
231
233
180
180
176
164
139
141
183
195
241
254
348
379
403
393
399
268
Temp.
20.7
19.8
19.7
20.3
20.2
20.3
20.0
20.5
20.0
20.6
19.9
20.5
*
Time Event 0- Temp.
1150 Wooster 298 19.5
to 201
Garrett Co. 121
(Cont'd) 237
186
192
258
363 20.7
330
235
215
166 19.9
137
135
137
130
131 20.4
130
144
148
148
139
1235 152 18.9
1242 Garrett Co. 161 19.6
to 176 19.0
DuBois 164
148
152
160
181
213
272
252
270 21.0
282
258
237
272
288
274
296
318 20.9
353
1322 365 21.3
- Nitrogen dioxide and nitric oxide below detectable limits.
* 3
Concentration in yg/m .
266
-------
Flight Data - August 21, 1974 (Continued)
Time Event 03 (°c?"
1431 DuBois 314 22.1
to 274
Wilmington 314
295
278
250
255
302
314
342
335 21.1
318
352
354
405
342 21.7
333
333
299
276
286
270
253 20.9
247
270
Time Event 03* *f*P"
(1431) DuBois 290
to 301
Wilmington 289
(Cont'd) 297
284
292
239
249
232
219
209
230
264
251
209
208
253
241
253
253 21.2
199
190
183
188
188
- Nitrogen dioxide and nitric oxide below detectable limits.
* 3
Concentration in ug/m .
METEOROLOGICAL SUMMARY FOR FLIGHT
A high pressure center had been moving steadily eastward through the mission
area for three days and was now centered over southern New England. However,
relatively high pressure, light surface winds and poor visibility still pre-
vailed in our area of operations. Flow was generally from the southeast. A
shallow subsidence inversion at 12,000 feet msl was not penetrated during the
mission which was flown at 4000 feet msl. Thermal mixing was through a deep
layer to 9500 feet msl. A layer of altocumulus covered the southern half of
the mission area from Wilmington to Garrett County during the morning but had
either moved south or dissipated by late afternoon. There was a field of
building cumulus over western Pennsylvania during the afternoon with bases
around 6000 feet msl. Visibility varied throughout the mission ranging from
as little as 2 miles to as much as 20 miles.
267
-------
APPENDIX D
OZONE AND OXIDES OF NITROGEN ANALYZER EVALUATION
AT REDUCED PRESSURE
269
-------
APPENDIX D
OZONE AND OXIDES OF NITROGEN ANALYZER EVALUATION
AT REDUCED PRESSURE
D-l Introduction and Summary
A series of tests were conducted in an altitude chamber at the
National Environmental Research Center at Las Vegas, Nevada. The
purpose of these tests was to determine the characteristic behavior
of a Bendix NO-NO2~NO analyzer, a Bendix 0- analyzer, and an RTI
solid phase chemiluminescent 0., meter to changing altitude, as in un-
pressurized aircraft. Two of these instruments were subsequent!-' used
in the aircraft measurement program for the Summer 1974 Oxidant Study.
The instruments were placed in the chamber and calibrated at
ambient pressure. The chamber was then sealed and partially evacuated
simulating a higher altitude environment. Calibration gases were
generated externally from a calibration system operating at a constant
ambient pressure, and drawn into the chamber to the gas analyzer inputs,
to insure constant calibration levels with changing pressure. Tests
were run over the range of pressures corresponding to ground level to an
altitude of approximately 5,000 meters (18,000 feet). Test results
demonstrated that all instruments responded in a repeatable manner to varia-
tions in pressure. Typically the output of the instrument dropped nearly
in proportion to the density of the air sample. From these data, graphs
were constructed whereby a single correction factor could be determined
for each instrument at an altitude. The effects of altitude on the instru-
ment then could be compensated for by multiplying by that correction factor.
To Insure that the results of these tests were applicable over an
extended period of time to the specific instruments tested, checks were
made on Instruments during flight. Flow rate checks were made periodically
on the instruments to insure that the flow dynamics of the instruments did
not change with time, for this would affect the behavior of the instrument
with varying altitude. Also, as a check, in-flight calibrations were per-
formed twice on the instruments during the 3-month project. Results of
these showed the same response for varying pressure as was determined during
the chamber tests. However, more critical logistical problems existed in
the aircraft for these tests making them significantly more difficult to
perform accurately in the air than in a test chamber (for example, the problem
271
-------
of producing known ozone concentration while the ozone generator pressure
varies and the problem of carrying extra gas cylinders in an aircraft
already loaded to capacity).
D-2 Test Set-up
The 0» and NO-NCL-NO analyzers were mounted inside a Weber Pressure
Chamber, Model WF-27-40 + 200 HV. A schematic diagram of the chamber
is shown in figure D-l, illustrating the chamber controls, support gases
and signal lines to the analyzers and the sample manifold system. The
glass sample manifold was mounted inside the chamber, with the downstream
end exhausted into the chamber. Teflon tubing was used to connect the
sample inlet of each instrument to the manifold. Oxygen and ethylene
gases were conveyed to the instruments inside the chamber, through
.318 cm i.d. s.s. tubing passed through .635 cm o.d. bulkhead Swagelok con-
nectors. The s.s. tube to Swagelok fitting seal was completed with a
2.54 cm o.d. sleeve of .318 cm i.d., .635 cm o.d. Teflon tube as shown in
figure D-2. The ethylene exhausted from the ozone analyzer was vented in-
to the chamber after being passed through a catalytic converter.
A descriptive diagram of the calibration system is shown in figure
D-3. The apparatus consists of a clean air source, compressed cylinder
of nitric oxide in nitrogen, regulating valves, flow meters, an ozone generator,
and mixing flasks.
D-3 Calibration Gases
2
Ozone concentrations in yg/m for various ozone generator sleeve settings
were determined using the Neutral-Buffered Potassium Iodide Method de-
scribed in the April 30, 1971 Edition of the Federal Register.
Nitric oxide span concentrations were obtained by diluting pressurized
NO in nitrogen with zero air. Nitrogen dioxide span concentrations were
generated by the gas phase titration technique, where the gas phase reaction
between NO and 0- was assumed to produce a stochiometric quantity of N02:
NO + 0 —>• N0 + 0 (1)
272
-------
VENT
SPAN I CAPILLARY
CONCENTRATION^ [{RESTRICTION
FROM GAL.
SYSTEM
INST.
SIGNAL
OUTPUTS
THERMISTOR
TEMPERATURE
PROBE
MANIFOLD
CHAMBER
TEFLON FILTER
CHAMBER
CONTROL
110 VAC
TO CHAMBER
VACUUM SYSTEM
Figure D-l. Schematic diagram of test set-up In pressure chamber.
273
-------
CHAMBER WALL
SIGNAL CABLE
FROM
INSTRUMENTS
GASES
TO INSTRUMENTS
EPOXY
5.08 cm (2") o.d. GALVANIZED PIPE CAP
"0" RING SEAL
0.635 cm (V) °-d- TEFLON
0.368 cm (1/8") o.d. TEFLON
OR STAINLESS STEEL TUBING
5WAGELOK BULKHEAD CONNECTOR
Figure D-2. Seal around stainless steel/Teflon tubing which
supplies gases to instrument in test chamber.
274
-------
PEN RAY LAMP
LAMP
TRANS FORMEB
p v
h*
« REGULATED 110 VAC
= « ' 1
CAPILLARY
RESTRICTION
FLOWMETER
SILICA GEL
MOLECULAR
SIEVE AND
CHARCOAL
t
ADJUSTABLE
SLEEVE
I
T
J WATER
MANOMETER
QUAm
REACTION
FLASK
HASTINGS
MASS FLC
(0-50 ml/min)
NO
VENT
,t
CAPILLARY
RESTRICTION
TO MANIFOLD
Figure D-3. Ozone generator/gas phase titration system
for calibration of 0- and NO-NO analyzers.
•J X
275
-------
Provided an excess of NO is maintained, the relationship between NO, 0~,
and the concentration of NO., in ppm, produced, is determined as follows:
FNO
where
C , C = Calibration system concentration of NO or NO- in ppm
C_-.T = Cylinder NO concentration, ppm
Ol Li
F - = NO flow rate, cc/min
F_ = Total flow through the system, zero air + NO, cc/min
C =" 0- concentration, ppm
°3
The NO concentration supplied by the manufacturer for the pressurized
cylinder of NO used in this test, was referenced to equivalent ozone
concentrations added during titration. A straight line was drawn through
the linear portion of the titration curve and extrapolated to the axis of
the curve representing the ozone concentration. The concentration
-* termined by the intercept was considered the 0_ concentration equivalent
to the initial diluted NO concentration. The cylinder NO concentration
was then determined from the following formula:
CYL
276
-------
where parameters not previously defined are:
C' » concentration of NO in cylinder as determined
CYL
from gas titration procedure
C' * initial NO concentration from titration system with
no 0» generated, determined from the equivalence point
of the 0- concentration.
Actual values obtained in the titration run during this study
were:
= 0.865 ppm
F = 46 cc/min
F - 5046 cc/min
Substituting in equation (4) yields
r- a 5046 x 0.865 ppm
CCYL 46 = 94.9 ppm
The concentration of cylinder NO determined by the titration method
agreed to within 10% of the concentration reported by the manufacturer.
The discrepancy may in part be due to the age and prior cylinder use,
which were not known at the time of this test.
D-4 Test Procedure
The units under test were calibrated several times during the
study at ambient conditions of temperature and pressure (25 C and 708
mm Hg). These calibrations were conducted by administering the zero
air and span concentrations directly to the sample manifold through the
removable by-pass shown in figure D-l. The pressure differential between
the manifold and ambient conditions during these tests was determined to
be less than 0.6 cm of water. Subsequent calibrations were conducted with
the chamber controlled at 25 C and at various simulated altitudes above
ambient. During the reduced pressure tests, the sample manifold was
maintained at chamber pressure by placing a capillary restriction upstream
from the manifold and leaving the downstream end of the manifold open
277
-------
ended into the chamber (refer to fig. D-4). The sample was drawn
into the chamber because the chamber was at a vacuum relative to the
calibration system which was at ambient. The length of the teflon capil-
lary was adjusted so that the flow drawn into the chamber was 2.5 to 4 i/
min. The remainder of the 5 Jl/min by the calibration system was
vented into the room through an unrestricting vent to maintain a constant
ambient pressure within the calibration system. This, in effect, provides
for a known concentration of the calibration gas (0_, NO, or N0» in this
case) to be made available to the instrument at the pressure of interest
based on measurements or calibration procedures conducted at ambient
pressure. Figure D-4 illustrates the typical pressure and flow condi-
tions during a reduced pressure test with the chamber controlled at a
simulated altitude of 3048 meters (10,000 feet).
It was observed that the instruments adjusted much more rapidly
to changes in pressure than did the entire system (instrument and
calibration system) to changes in concentration. Therefore, these
tests consisted of setting the system up for a single calibration gas
level input and varying the pressure stepwise over the range being tested.
Runs were repeated using the same input concentration levels on different
days to determine repeatability. Also, different input concentrations
were used to check linearity of the analyzers over the pressure range
of interest.
D-5 Results of Tests
Bendiy NO-NQ^-NO.. Analyzer
L. X
The response of the chemiluminescent NO-NO--NO analyzer to two
different constant concentration levels of NO under varying environmental
pressure is shown in figure D-5. The data appears to be very repeatable
with no more scatter than found when the instrument is operated under normal
laboratory conditions.
A graph showing the percentage correction necessary to convert
readings taken at any altitude up to 5500 meters (18,000 feet) to the
actual concentration is shown in figure D-6. This graph was used for
determining the correction factors for adjusting the data taken at various
278
-------
CALIBRATION
UNIT
5 1/min
t
^ 3.5 1/min
1.5 meters of 3.2 mm o.d.
Teflon
0.6 cm H20
Differential
from Ambient
•* 1.5 1/min
1 1
To Instruments
Chamber
179 mm Hg
Differential
from Ambient
Figure D-4. Typical pressure and flow conditions for
chamber setting at simulated altitude of
3048 meters (10k feet).
279
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ALTITUDE
Figure D-6. Correction factor for Bendix NOX analyzer to com-
pensate for changes in altitude. (To use,
divide reading obtained from instrument by
number read from graph for the altitude needed.)
281
-------
altitudes to a common altitude for comparison. Note that the approxi-
mate linearity of this curve is derived by plotting instrument response
with altitude on the ordinate instead of pressure.
During these tests the volumetric ratio of NO to air as expressed
in ppm is held constant. At conditions of sea level and 25°C, 1 ppm of
NO is 1225 yg/m . At altitudes above sea level this figure drops pro-
portionally with the density of air. It follows then that for each ppm
3*
input the actual concentration*in yg/m is 1225 at a pressure of 760
mm Hg and drops linearly to zero at 0 mm Hg. Therefore for a concentra-
3
tion of 0.555 ppm of NO the mass per volume would be 681 yg/m at sea level
and drop linearly to zero at 0 mm Hg. This type of response, the ideal mass
per volume response, is shown in figure D-7 along with the actual re-
sponse of the instrument to 0.555 ppm input. The two appear to track
reasonably over the range of pressure 760 to 500 mm Hg with less than
10% error. This would be expected since the output of the instrument is
directly proportional to the amount of light given off by a reaction of
ozone and NO. Consequently, all operating conditions being equal, the
instrument response should be directly proportional to the amount of
mass of NO being sampled by the instrument. Hence it is expected that
the output would fall off nearly linearly.
There is, however, an additional variable and that is the variation
in sample flow rate in the instrument. If the instrument response is
proportional to the mass of NO entering the sample inlet, then the re-
sponse drop-off due to decreasing pressure would be further compounded by
any accompanying decrease in volumetric flow. Variations in volumetric
flow rate with changing pressure were determined experimentally both in
the test chamber and in the aircraft. Attempts at mathematically pre-
dicting the response of the instrument based on the assumption that
**
instrument response depended solely on the mass of sample air being
drawn through yielded a significant difference between the predicted and
* 3
The use of yg/m here should not be taken as a cubic meter at standard
conditions. Here the m-* refers to a cubic meter at the pressure of the
sample.
**
Mass of air as it varied with air density and flow rate.
282
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283
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measured response. The difference (error) was actually greater than
the difference computed for the case discussed in the preceding para-
graph where the assumption was that the instrument response varied only
with changes in sample flow due to changing ambient pressure with no
compensation for varying sample volumetric flow rate. Curve C in
Figure D-7 illustrates the predicted instrument response with compensa-
tion made for changes in volumetric flow and air density.
A possible reason for this is variations in pressure in the
reaction chamber where the ozone and NO react. In the tests reported
here, no means were included for controlling the reaction chamber pressure
in the instrument or even accurately measuring it. A small vacuum gauge
indicated that the actual chamber pressure did change a small amount but
no significant quantitative data were taken. A more meaningful test of
the NO detection technique would result from controlling the actual
reaction chamber pressure. However, the tests performed here more closely
simulate actual operating conditions where the instrument and its vacuum
pump are placed aboard an aircraft and no attempt is made to control the
reaction chamber pressure, or volumetric flow rate. It should be noted
that the change in volumetric flow rate with altitude was found to be
quite repeatable and was checked on each flight at the altitude(s) of
interest.
Analyzer response to calibrated span concentrations of N0« are
illustrated in figure D-8. The measurement of NO. with a chemiluminescent
analyzer involves the same processes as the measurement of NO with only
one difference — the conversion of NO- to NO by means of a catalytic
converter. Therefore, to analyze the NO- response, the data were examined
to see how the response to NO- compared to the response to NO. To do
this the ratio of NO- to NO response was computed for various pressures
for one input concentration (.555 ppm NO and .316 ppm NO-). Figure D-9
shows the ratio for different ambient pressure conditions. The data
indicates a trend toward lower converter efficiencies at lower absolute
pressures (higher altitudes); however the variation on all runs was less
than 8% up to 4572 meters or 15,000 feet (down to 429 mm Hg). At altitudes
of 12,000 feet or less the average decrease in efficiency appeared to be
approximately 3-5%. Therefore, the same correction factors for
NO data were used with N02 data for compensation of altitude effects.
284
-------
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Bendix Ozone Analyzer
The response of the gas phase chemiluminescent ozone analyzer to
span concentrations for various environmental pressures is shown in
figure D-10.
Daily measurements were normalized to an initial reading of unity
at ambient pressure conditions in the laboratory. Then the results of
all runs were plotted on the same graph. This graph, shown in figure
D-ll, shows a decrease in response almost directly with the density of
the sample air. (Sample air density is the broken line of the same
graph.) The graph also shows repeatability of the instrument response;
however, verification of the altitude factors by means of an inflight
calibration is recommended at frequent intervals during airborne measure-
ment programs.
RTI Ozone Monitor
The RTI solid phase chemiluminescent ozone monitor uses a rhodamine-B
disk for sensing ozone. Since the disk response is dependent on the recent
history of the disk, a fixed level calibration ozone generator was built
into the unit and is energized periodically. The standard cycle in the
instrument tested consists of four parts, each of 30 seconds duration:
(1) purge with clean air, (2) sample from ambient (measure cycle),
(3) purge again, and (4) calibration gas from internal ozone generator
(calibrate cycle). The measured concentration is then computed from the
ratio of the disk response to ozone in ambient air to its response to the
ozone calibration concentration. Therefore, the instrument response with
altitude is solely dependent on the behavior of the internal ozone
generator with altitude.
The RTI instrument was tested at a different time than the other two
instruments, but the same test setup and equipment were used. A constant
concentration of ozone was generated external to the pressure chamber and
applied to the instrument input. The instrument response to this input
(measure response) and the response to the internal generator were
recorded. The measure response alone indicates the response of this
disk under the varying pressure and pressure-induced flow conditions. The
disk response does not significantly affect the accuracy of the instrument
287
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288
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since the measured concentration is always determined from the ratio of
the sample response to calibration response. Consequently, the measure
response data are not plotted here.
Since measure response is the response to an externally generated
concentration of ozone, the behavior of the internal generator may be
determined for varying pressure conditions by computing the ratio of
calibration response to measure response. The total instrument response,
however, is the ratio of measure response to calibration response and is,
therefore, the reciprocal of the above function. Consequently, this
ratio, normalized to 1.0 at ambient conditions, is shown in figure D-12.
The response of the RTI instrument falls off with increasing pressure
as did the other instruments tested. This decrease in response is due to
an increase in the ppm output of the ozone generator at higher altitudes
(lower pressures) produced by at least two separate mechanisms:
(1) reduced volumetric flow rate through generator due to lower vacuum
pump efficiency at higher altitudes, and (2) reduced pressure between the
ultraviolet light source and the quartz tube containing the air to be
exposed to the light for ozone generation (lower pressure means fewer
ozone molecules which absorb ultraviolet light). Still another source of
variation of ozone output from the generator is the change in pressure
within the quartz chamber where the clean air sample is irradiated with
UV to produce ozone. The overall instrument response curve (fig. D-12)
was used for compensation of values obtained in the aircraft for altitude
effects. This is accomplished by reading the value corresponding to the
altitude of Interest from the graph and dividing it into the reading
obtained from the instrument.
The instrument performed in a repeatable manner during all tests.
All the mechanisms assumed to cause variation in performance with pressure
were relatively time invariant (i.e., not changing with age and condition
of ...he instrument) except flow rates. To prevent an unnoticed change in
the vacuum pump efficiency at higher altitudes from changing the altitude
response characteristics and causing erroneous data to be recorded, flow
rates were monitored by means of a soap bubble flow meter during the tests
and later during the data flights.
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APPENDIX E
OPERATIONAL PROCEDURES FOR AIRCRAFT INSTRUMENTATION
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/fflMHX F
OPERATIONAL PROCEDURES FOR AIRCRAFT INSTRUMENTATION
E-l. General
The specific operational procedures for the aircraft instrumenta-
tion are listed below. An introductory paragraph describing generally
what each sequence of operations is designed to accomplish is given prior
to each checklist. Procedures are included for:
1. Preflight Checklist,
2. Ozone Analyzer Calibration:
Ozone Generator Verification (Calibration Unit),
Ozone Instrument Calibration,
3. NO-NO.-NO Analyzer Calibration,
<£ A
NO-NO,, Source Verification (Calibration Unit),
N0-N09-N0 Instrument Calibration.
£ X
E-2. Preflight Checklist for Aircraft Operation
1. Conduct required calibrations and ambient air checks.
2. Connect glass manifold to line coining from sample port in
lower right front of cabin and connect both ozone and NO instruments
A
to manifold.
3. Check instruments for proper mode of operation.
Ozone Instrument
a. Lamp current—9 ma. Setting about 90.
b. Mode control—sample 1.
c. Rotameter—about 2.
d. Shutter—open.
~7
e- Sensitivity—10 ,. . , , ....
adjust to give output of about 1/4
f _ c . . , to 1/2 of full scale.
f. F.b. output—4.
g. Time constant norm OK calibrate signal.
h. Zero adjust—set to zero,
i. High voltage setting—990V,
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NO Meter
x
a. Set oxygen pressure to 20.
b. Check cylinder pressure for reading of 25 on output
gauge.
c. Check ozone generator light—should be ON.
d. Check valve switch—should be NO-NO -NO .
xx
e. Check mode switch—should be on ambient.
f. Set all PPM range switches to O.S.
g. Turn pump and power switches ON.
Recorder Panel
a. Set top switch on control panel to zero full counter-
clockwise .
b. Turn all recorders on.
c. Set range on top A recorders to 0-IV; on bottom recorder
to 0-10 mV.
d. Set zero adjust for 10 percent scale.
e. Set all chart speeds to 8 in/hr.
f. Put pens down.
g. Turn DVM on and set range for 2 VDC.
Power Panel
a. Switch 1 should be set for ground power.
b. Priority 1 and 2 power—ON. Lights should be ON.
c. Timer pump OFF—center pos.
Manifold
a. Check placement of 2 Teflon tubes and temperature sensor.
They should be at least 15.24 cm inside Teflon pipe air
inlet. Make sure they are secure.
Temperature Gauge
a. Function switch should be an ambient and meter should
read approximate cabin temperature.
E-3. Ozone Analyzer Calibration
The ozone analyzer calibration will be checked before each flight
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by injecting a known concentration of ozone into the sample manifold
from a one-point generator. This will establish the behavior of the
instrument on the ground. Results of experimental tests at the begin-
ning of the program and at approximately its midpoint will be used to
determine the instrument behavioral variations with altitude and, there-
fore, what corrections must be made in the data taken at different
altitudes.
1. Verification of Ozone Generator (External)
The base station ozone analyzer shall be used to routinely
determine the concentration output of the portable system used to gener-
ate ozone construction in the aircraft. The ozone instrument then is
in effect a transfer standard used to calibrate the calibration box from
a standard ozone generator whose output has been referenced to the
neutral-buffered KI method.
The ozone generator is a dual pen-ray lamp unit with adjustable
sleeves covering the lamps. The setup procedure for operating the unit
is as follows:
a. Connect to 110 VAC outlet.
b. Switch ON and adjust lamp current to 15 ma. Allow to
stabilize overnight.
c. Connect air supply from breathing quality air cylinder
to air inlet.
d. Close pressure adjust valve.
e. Adjust air valve for a flow indication on the large rota-
meter of 6.7 (TOB).
f. Set sleeves to first marked setting.
g. Connect sample manifold to glass ball joint on front of
instrument and connect ozone analyzer to first opening
in manifold.
h. Allow enough time for analyzer to stabilize, indicated
by constant trace on strip-chart recorders or constant
output concentration levels by station minicomputer.
i. Read generator output on teletype.
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2. Routine Calibration of Ozone Analyser in Aircraft
Immediately before every flight, the portable calibration
unit shall be used to calibrate the aircraft ozone analyzer. Additional
verification of ozone analyzer performance and aircraft manifold system
checks can be accomplished by comparison of aircraft ambient readings
with base station readings while on the ground and during a low pass
at the beginning and end of each flight.
The procedure for calibrating the analyzer is as follows:
a. Set up calibration system and connect to aircraft
analyzer as described in steps 1-8 under verification
of ozone generator.
b. Note the height of the instrument responses to the
internal calibration unit and the external calibration
unit. Responses are measured from the baseline deter-
mined during the purge cycle to the average response
after the instrument has stabilized during each phase
of the cycle. Illustration of measurement procedures
is given in section 3.2.4.1.
c. Compute the magnitude of the internal calibration level
from the following formula:
r m c —
int gen M
where
C, is the ozone concentration output by the internal
calibration unit.
C is the ozone concentration output by the portable
calibration unit.
M is the instrument response while in the measure phase
of its cycle.
C is the instrument response while in the calibrate
phase of its cycle.
d. Return the instrument to ambient air by connecting it to
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the sample inlet brought in from above the aircraft
through the window.
Allow the instrument to stabilize and note readings and
time. Compute concentration from formula
C = C
amb int C
where
C , is the measure ozone level in the ambient air.
omb
Readings may be compared with base station readings to
verify operation of instruments.
f. After the aircraft is airborne long enough to insure
operation of all instrumentation, the aircraft will fly
a low-pass flight over the base station as low as safely
possible. The ozone instrument should be in the measure
mode as the pass is made. The time is marked on the
strip-chart recorder, and the value computed for later
comparison.
g. After flight, connect instrument sample input to top
of flowmeter and measure sample flow rate. Compare
with data from previous runs.
E-4. Nitrogen Oxides Analyzer Calibration
The known concentration of NO for instrument calibration is derived
by a dilution of NO from a known calibration gas cylinder with air.
Although, by careful flow measurement and control, the resulting con-
centration may be computed, checks may be made using the base station
NO analyzer to check for any calibration system (or analyzer) malfunctions.
Such a cheese should be carried out every 2 weeks as soon as possible after
base-station calibration.
1. Verification of NO Calibration Unit
X
The NO. calibration unit produces a known quantity of NO by
X
diluting a known NO calibration gas to a concentration within the range
of normal atmospheric values. The ozone generator used for calibrating
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the ozone analyzer is Included in the equipment to allow production of
N02 from NO for calibration of that channel of the analyzer. The per-
formance of the calibration unit may be checked by connecting it to the
instrument in the base station as soon as possible after a calibration
of the station. This should verify its operation. In order to accomplish
this, the following steps will be carried out:
a. Set up the calibration unit as described in steps 1
through 7 under "Verification of Ozone Generator
(External)."
b. Connect the calibration gas to the NO inlet on the cali-
bration system. .Close the NO valve.
c. Connect a vacuum pump to the fitting on the regulator
and pump it down. Close the cylinder valve and repeat
the process several times.
d. Adjust the NO valve for a reading of 4.5 (top of ball)
on the small rotameter. This represents a flow of
28.2 cc/min at the Clinton County elevation.
e. Set the ozone generator sleeves to their first notch.
f. Connect NO analyzer to manifold on output of cal unit
and allow time for instrument stabilization. Instrument
should have the following readings:
for NO
C..n - C x 1880
N02 gen
for N02
CNO " (CNOx"Cgen) x 1220
where
CN~ is the calibration system output for NO in ppm,
C is the ozone output of the generator in ppm,
C is the calibration system output for N0~ in ppm,
riUn ^
C is the concentration of the calibration gas. After
x dilution by a factor of 28.2/5028.2.
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g. If readings do not compare, check operation of instrument,
calibration of the NO cylinder, or flow of gases in
calibration unit.
2. Routine Calibration of NO Analyzer
On the days on which a flight is to be run, a zero and span
calibration shall be performed on the NO analyzer before takeoff. First,
X
the zero module is connected to the instrument, and the zero adjust poten-
tiometers are adjusted for zero output. Next, the one-point cal unit is
connected to the analyzer, and the span controls are set.
The specific instructions for calibrating the units are as follows:
a. Make sure the NO analyzer and the calibration unit lamp
have been running for a day continuously prior to start-
ing the calibration. Check ojygen supply and vacuum
pump for operation. Set scale on 0-0.5 ppm for NO,
NO , and NO .
£* X
b. Plug in zero module and turn unit on.
c. Disconnect NO analyzer from manifold and connect to
X
zero module. Allow instrument to stabilize.
d. Connect a Digital Voltmeter to the NO position and
insure that the short jumpers from the control panel are
connected to the DVM.
e. Adjust the NO zero adjust potentiometers until a reading
of zero is obtained on the DVM.
f. Repeat steps 4 and 5 for the NO and NO channels.
g. Disconnect the zero module from the NO analyzer and
connect the analyzer to the calibration unit through a
manifold.
h. Set up the cal unit as done in the verification of its
operation. Set the ozone generator sleeves to the first
notch and allow everything to stabilize.
i. Compute the concentrations of NO, NO- and NO from
^ X
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ii 28.2
N0x 5028.2 * cyl/
So * C'NO ~ CGEN
CN02 * CGEN
where all concentrations are in PPM and
C is the concentration of cal gas from the cylinder
after dilution with air,
C is the concentration of NO output,
C is the concentration of N0? output,
Cn_XT is the output concentration of the ozone generator,
C is the concentration of the NO calibration gas
cylinder.
j . From these concentrations compute the expected response
of the instrument and set the span potentiometers to
obtain that response.
k. Reconnect the manifold to a sample lower and the NO
X
analyzer to it. Then compare readings of ambient levels
with those recorded in the base station.
It Disconnect NO cylinder from cal unit and allow unit to
run to an hour with ozone lamp ON to flush system out.
m. After flight has been completed, connect top of bubble
flowmeter to sample inlet and measure flow while on
ground. Record value and check for any change since
past runs.
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APPENDIX F
AIR PARCEL TRAJECTORIES
303
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AIR PARCEL TRAJECTORIES
3000 FEET MSL
June 18 to September 1, 1974
for Air Arriving at
Garrett County, Maryland
DuBois, Pennsylvania
Morgan County, Ohio
Wilmington, Ohio
Twelve-hour positions prior to arrival are indicated by a
triangle (A) for those air parcels arriving at 0000 GMT and
by a square O for those arriving at 1200 GMT.
An overlay is provided to help identify locations.
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TECHNICAL REPORT DATA
(Please read Instructions on the icvcrsc before completing)
\. REPORT NO.
EPA-450/3-75-036
4. TITLt AND SUBTITLE
Investigation of Rural Oxidant Levels As Related to
Urban Hydrocarbon Control Strategies
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
March 1975
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Research Triangle Institute
Research Triangle Park,
North Carolina 27709
10. PROGRAM ELEMENT NO.
2AC129
11. CONTRACT/GRANT NO.
68-02-1386
Task 4
12. SPONSORING AGENCY NAME AND ADDRESS
Monitoring and Data Analysis Division
Office of Air Quality Planning and Standards
Environmental Protection Agency
Research Triangle Park, N.C. 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final - June 1974 to Feb.'75
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
From June 14 to August 31, 1974, a study was conducted in the Ohio Valley area to investigate high rural
oxidant concentrations above the NAAQS and their possible relationship to urban hydrocarbons. Data regard-
Ing the oxidant, nitrogen dioxide, and hydrocarbon relationships were obtained by sampling from a network
consisting of five rural and six urban ground stations and an instrumented aircraft. Gases sampled were 03,
NOx, THC, CH4, and selected hydrocarbons. Gas chromatograms of grab samples collected at three rural ground
stations near Columbus and during aircraft flights were used to identify hydrocarbon species and possible
tracers (e.g., C2H2) indicative of urban-generated pollution.
The NAAQS for photochemical oxidants (160 gg/m3 hourly average) was exceeded twice as frequently at rural
as at urban stations, with the frequency of occurrence for rural stations ranging from 10 to 20 percent of
the total hourly concentration during the measurement program. Area-wide systems of high ozone concentrations
were observed where the urban influence on both hydrocarbon and ozone concentrations extended from 40 to 80
kilometers (30 to 50 miles) downwind of Columbus. High ozone concentrations (* 160 pg/m3 for eight hours)
were observed at all stations when the central region of a synoptic high pressure system moved into the
region and persisted as long as the high pressure center remained in the immediate vicinity. No specific air
trajectory could be uniformly associated with the arrival of air containing either high or low concentrations
of ozone at any of the rural sites. The results of the field measurement program provide substantial support
for transport of ozone precursors from urban areas to rural stations under appropriate meteorological condi-
tions. These results also imply that the control of hydrocarbon in any individual city will not necessarily
prevent the occurrence of high rural ozone concentrations in excess of the NAAQS at any given nonurban site.
The implication is that the release of hydrocarbons and oxides of nitrogen from anthropogenic or biogonic
sources, located in either an urban or rural areaV all combine to generate appreciable quantities of ozone
over wide areas.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Photochemical Air pollutants-formation and
transport. Ambient ozone levels--rural and
urban. Precursors of ambient ozone—hydro-
carbons, nitrogen dioxide. National Ambien'
Air Quality Standards for ozone.
b.lDENTIFIERS/OPEN ENDED TERMS
Atmospheric ozone levels
Ozone formation and tran
port related to weather
conditions
COSATI Held/Group
Atmospheric
Photochemistry
Air Pollution
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (This Report)
None
21. NO. OF PAGES
359
20. SECURITY CLASS (This page)
None
22. PRICE
EPA Form 2220-1 (9-73)
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