EPA/600/4
85-038
FB35-212413
National Air Pollution
Background Network 1976-1984
Final Project Report
(U.S.) Environmental Monitoring Systems Lab.
Research Triangle Park, NC
May 8 5
jjiwimuiai
0.1 Dspertenst cJ Camert*
KsSsad Tecteacd Service
-------
PB85-212U13
EPA/600/4-85/038
May 1985
THE NATIONAL AIR POLLUTION BACKGROUND NETWORK
FINAL PROJECT REPORT
by
Gary F. Evans
Monitoring and Assessment Division
Environmental Monitoring Systems Laboratory
Project Officer
Barry E. Martin
Monitoring and Assessment Division
Environmental Monitoring Systems Laboratory
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
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TECHNICAL REPORT DATA
(Pteasr reed /»W-uctn>ns un rhe mene Ocjore comptennjtt
1 REPORT NO 2
EPA/600/4-85/038
3 RtCIPlENTS ACCSSStOfHO
PB8 5 2 1 2 k 1 3 /AS
4 title ano subtitle
The National Air Pollution Background Network
Final Project Report
5 REPORT DATE
M.-.V 19RS
6 PERFORMING ORGANIZATION CODE
MAD
/ AtiTHORtSl
Gary F• Evans
B PERFORMING ORGANIZATION REPORt NO
EMSL Draft No. 0913
B PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Monitoring Systems Laboratory
Office of Research and Development
U. S. Environmental Protection Agency
Research Triangle Park, NC 27711
10 PROGRAM ELEMENT NO
A9FF(E0301) Oxidants
11 CONTRACT/GRANT NO
1? SPONSORING AGENCY NAME AND ADDRESS
(same)
13 TYPE OF REPORT AND PERIOD COVE RED
Final Prnjprr Rspnrr ( |Q7f._«/,)
14 SPONSORING AGENCY CODE "
EPA/600/08
15 supplementary notes
16 abstract —
The U.S. Environmental Protection Agency, in cooperation with the U.S. Forest
Service, operated a network of ozone monitoring stations from 1976 through 19b3 in
selected National Forests within the continental U. S. The primary objective of
this project was to determine the level of ozone concentrations occurring in remote
areas, especially in relation to the National Ambient Air Quality Standard for
ozone. Secondary objectives Included the evaluation of regional differences, the
characterization of seasonal and diurnal patterns, and the assessment of long-term
trends for ozone concentrations in remote areas. Annual mean ozone concentrations
were found to vary from site-to-site and year-to-year within a range of 25 to 50
parts per billion (ppb). Hourly ozone concentrations in excess of 120 ppb, the
current level of the National Ambient Air Quality Standard, were occasionally
observed. Such events, however, were rate and generally confined to the spring and
summer months at sites in the eastern half of the U.S. and during the first half
of the study period. No such events were observed after 1960. Seasonal mean ozone
concentrations were greatest during tne spring months (April through June) and
diurnal maximums occurred most frequently during the early afternoon (1-3 p.m.).
While no statistical 1y significant trends were observed in mean ozone concentrations,
the frequency of exceedances of the National Aniblent Air Quality Standard decreased
over the course of the studv.
17 KEY WORDS ANO DOCUMENT ANALYSIS
1 DESCRIPTORS
b IDENTIFIERS/OPEN ENDED TERMS
C COS ATI 1 Icld/C'oup
Oz one
National forests
Chemiluml lescence
Oxidant!,
Remote Areas
Stratospher/Troposhpere
19 &ISTRIBUTION STATEMENT
Release to Public
IB SECURITY CLASS (Tttu Report)
Unclassifled
21 NO OF PAGES
20 SECURITY CLA£S (This pogfi
Unclassified
22 PRICE
CPA Form 2220 1 (9.711
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DISCLAIMER
This report has been reviewed by Che Environmental Monitoring Systems
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Mention of trade names of commercial products doe6 not consltute
endorsement or recommendation for use.
11
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FOREWORD
Measurement and monitoring research efforts are designed tc anticipate
potential environmental problems, to support regulatory actions by develop-
ing an in-depth understanding of the nature and processes that impact
health and the ecology, to provide innovative means of monitoring compliance
with regulations, and to evaluate the effectiveness of health and environ-
mental protection efforts through the monitoring of long-term trends. The
Environmental Monitoring Systems Laboratory, Research Triangle Park, North
Carolina, has the responsibility for assessment of environmental monitor-
ing technology and systems; implementation of agency-wide quality assurance
programs for air pollution measurement systems; and supplying technical sup-
port to oc^er groups in the Agency including the Office of Air, Noise, and
Radiation, the Office of Toxic Substances, and the Office of Enforcement.
The National Air Pollution Background Network was initiated at the
requept of the Office of Air Quality Planning and Standards. The project
was conducted jointly through an interagency agreement between the U.S.
Environmental Protection Agency and the Forest Service of the U.S. Depart-
ment of Agriculture. Results from the project are summarized in this
report. The data are available to all Interested researchers upon request
to the National Aeromeirlc Data Bank, Research Triangle Park, North Carolina.
Thomas R. Hauser
Director
Environmental Monitoring Systems Laboratory
Research Triangle Park, North Carolina
lit
-------
ABSTRACT
The U.S. Environmental Protection Agency, in cooperation with the U.S.
Forest Service, operated a retwork of ozone moritorirg stations from iy7b
through 1983 in selected Natioral Forests within the continental U. S. The
primary objective of this project was to determine the levei of ozone
concentrations occurrirg in recote areas, especially in relation to the
National Ambient Air Quality Standard for ozore. Secondary objectives
ircluded the evaluation of regional differences, the characterization of
seasoral ard diurnal patterns, and the assessment of long-term trends for
ozor.e concentrations in remote areas.
Annual mean ozore concentrations were found to vary from site-to-site
and year-to-year within a range cf 25 to 50 parts per billion (ppb). Hourly
ozone concentrations in. excess of 120 ppb, the current level of the National
Ambient Air Quality Standard, were occasionally observed. Such everts,
however, were rare and generally confined to the sprirg and summer mor.tns at
sites in the eastern half of the U.S. ard during the first half of the study
period. No such everts were observed after 1980. Seasonal mean ozone cor-
certratiors were greatest durirg the spring morths (April through Jure) ard
diurral maximums occurred most frequertly during the early afterroor. (1-3 p.m.).
While r.o statistically significant trends were observed in mear ozone concen-
trations, the frequency of exceedarces of the National Ambient Air Quality
Standard decreased over the course of the study.
This report covers a period from January 1976 to December 1984 ar.d work
was completed as of February 1985.
iv
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CONTENTS
Page
Disclaimer ii
Foreward ill
Abstracr iv
List of Figures vi
List of Tables vll
1. Introduction 1
2. Conclusions 4
3. Background 5
A. Results and Discussion ..... 6
References 25
Appendix 27
v
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1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
FIGURES
Page
Location of NAPBN Monitoring Sites 2
Hourly Mean Qzor.e Concentration by Quarter-
Apache NK, AZ 9
Hourly Mean Ozor.e Concentration by Quarter-
Kisatchle NF, LA . . . . 10
Hourly Mean Ozor.e Concentration by Quarter-
Mark Twain NF, MO 11
Hourly Mean Ozone Concentration by Quarter-
Custer NF, MT ..... ....12
Hourly Mean Ozor.e Concentration by Quarter-
Croatar. NF, NC 13
Hourly Mean Ozone Concentration by Quarter-
Ochoco NF, OR 14
Hourly Mean Ozor.e Concentration by Quarter-
Creer. Mountair NF, VT 15
Hourly Mear. Ozone Concentration by Quarter—
Chequamegan NF, W1 16
Dally Mear and Maximum (>80ppb) Ozore Concentration -
Apache NF, AZ 17
Dally Mean and Maximum (>80ppb) Ozone Concentration -
Kisatchle NF, LA 18
Daily Mean and Maximum (>80ppb) Ozore Concentration -
Mark Twair NF, MO IV
Dally Mean ar.d Maximum (>80ppb) Ozor.e Concentration -
Custer NF, MT .20
Dally Mean ar.d Maximum (>80ppb) Ozone Concentration -
Croat an NF, NC 21
Daily Mean and Maximum (>80ppb) Ozor.e Concentration -
Ochoco NF, OR 22
Dally Mean and Maximum OBOppb) Ozone Concentration -
Greer. Mountain NF, VT 23
Dally Mean and Maximum (>H0ppb) Ozone Concentration -
Chequamegor. NF, W1 24
vi
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TABLES
Number Page
1 Description of NAPBN Monitoring Sites . 3
2 Annual Suauury Statistics for NAPBN Ozone (ppb) 7
A-l Cumulative Frequency Distribution Table of NAPBN Uzone (ppb)
Apache NF, AZ 27
A-2 Cumulative Frequency Distribution Table of NAPBN Ozone (ppb)
Klsatchic NF, LA 28
A-3 Cumulative Frequency Distribution Table of NAPBN Ozone (ppb)
Mark Twain NF, MO 29
A-4 Cumulative Frequency Distribution Table of NAPBN Ozone (ppb)
Custer NF, MT 30
A-5 Cumulative Frequency Distribution Table of NAPBN Ozone (ppb)
Croatan NF, NC ..... . *31
A-6 Cumulative Frequency Distribution Table of NAPBN Ozone (ppb)
Oclioco NF, OK 32
A-7 Cumulative Frequency Distribution Table of NAPBN Ozone (ppb)
Green Mountain NF, VT 33
A-b Cumulative Frequency Distribution Table of NAPBN Ozone (ppb)
Chequamegon NF, WI ..34
vii
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SECTION' 1
INTRODUCTION
In 1971, tiie National Ambient Air Quality Standard (NAAQb) for ozone was
established at an hourly average concentration not to exceed bo parts per
billion (ppb) more than once per year. At that tine, very few ozone measure-
Dents were available from rural and remote areas, arid ozone concentrations in
such areas were assumed to be generally low and inconsequential relative to
the stau^trd. Furthermore, ozone from background areas was thought to be
largely removed by chemical scavengers upon entry into an urban environment.
In the mid-1970's, the U.S. Environmental Protecticn Agency (EPA)
sponsored several field studies monitoring oione concentrations in rural
areasi't^i^ The monitoring was conducted during summer mo-iths in saall cities
3nd agricultural areas in the eastern half of the U.S. Results suggested that
rural areas experienced a greater range Ir. ozone concentration than had been
previously supposed and that ozone transported from rural to urban areas should
not always be disregarded.
In 1976, in response to these and other findings, EPA began to establish
a nationwide network of ozone monitoring stations located In remote areas.
Originally called the National Forest Ozone Study, this project was a joint
undertaking of EPA's Environmental Monitoring Systems Laboratory (EMbL), and
Office of Air Quality Planning and Standards (OAQPS), both located in Research
Triangle Park (RTP), North Carolina. The Forest Service of the U.S. Depart-
ment of Agriculture, working under an interagency agreement, participated in
the project by providing monitoring site locations within National Forest (NF)
areas and by performing routine operations at the monitoring stations.
The National Air Pollution Background Network (NAPBN) eventually con-
sisted of eight remote monitoring stations, each collecting continuous meas-
urements of ozone by the chemtluminescence technique. Each site was located
as far as was practical from any heavily used roadway and at least 1OU miles
froj any najor urban area. To ensure representative sampling, the sites were
located in open and relatively elevated areas for good exposure. An eftort
was made to distribute the sites across the continental U.S. to cover as many
regions of the country as possible. Site locations are shown in Figure 1,
and station descriptions ate provided in Table I. Earlier reports describing
the network and the early data were published in 197b4 and 1943.-*
The NAPBN was established to provide a reasonably long-term and contin-
uous record of ozone concentrations and patterns in areas well removed trom
anthropogenic sources of air pollution and to make these data available to
EPA and other interested researchers. The network was discontinued at the end
of 1983. All valid data are oa file and may be accessed through the National
Aerometric Data Bank (NADB), U.S. EPA, Mail Drop 14, Research Triangle Park,
North Carolina 27711.
1
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Chequamegon
Croatan
Figure 1. Location of NAPRN Monitoring Sites
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TABLE 1. DLSCR1PT10N OF NAPBN MONITORING SITt-S
National
Forest
Apache
State
Elevation
Above MSL
AZ 2500 M
Latitude/
Long 1tude
3 3 c 4 5' OO" N /
109°00'00"U
Start Krid
Date Date
SAROAU
COL) c.
9/16/7y 12/3 1/Bi 0300SOl10AUM
Klsatchle
LA
65 M
310 J 0'00"N/
92#2B'20"W
5/26/7b 9/30/82 191490101A08
Mark Twain MO
2 30 M
37°2B'00"N/
90°11'00"W
12/18/78 12/31/B3 2b295000lAU8
Custer
HT
1250 M
4 5°14'00"N/
106°15'00"W
6/23/7b U/22/B3 27o3lOlOlAOb
Croatan
NC
13 M
34° 59'05"N/
77*11'24"W
3/13/76 12/31/B3 34094 5101 A'Jti
Octioco
OK
1350 M
44o13'30"N/
119°<.2'25"W
10/04/79 12/05/83 38W2011 1AU-
Creen
Mountain
VT
390 M
43° 56'O0"N/
73°02'00"W
10/24/76 9/2b/82 4702o5lOlAU8
Chequamegon Wl 440 M
4 5°12'00"N/
90°3 7 *00"W
8/10/78 9/30K2 5104900O1AOS
3
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SECTION 2
CONCLUSIONS
• Although exceedances of Che original level (80 ppb) and the revised
level (120 ppb) of the NAAQS for ozone were occasionally observed at the
NAPBN remote monitoring stations, the latter were rare occurrences and
observed only during spring and early summer months and at sites in the
eastern half of the U.S.
• The frequency of exceedances of the 60 ppb level was less than 5 percent
of valid hours for all site years, and no exceedances of the 120 ppb
level were observed after 1980.
• Annual mean ozore concentrations fell within a range of 25 to 50 ppb
with sites In the western U.S. recording higher mean levels, but lower
variances than those in the east.
• Diurnal maximum hourly ozone concentrations occurred most frequently in
the early afternoon (1 co 3 p.m.), and the maximum quarterly mean occur-
red In the spring (April through June).
• Although statistical tests for trend revealed no significant increases
or decreases in mean ozone concentrations, there were decreases in the
frequency of exceedances of the NAAQS level(s) during thj course of the
study.
4
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SECTION 3
BACKGROUND
That some natural background level of ozone exists in the lower tropo-
sphere, which is primarily attributable to the exchange of air between the
troposphere and the ozone-rich stratosphere, is commonly accepted. Various
researchers have postulated what this concentration level might be in the
absence of other sources, and how it might vary in time and space. Keiter,^
for example, has estimated that annual mean troposphenc ozone concentrations
of stratospheric origin range from 19 to 29 ppb. Mohnen^ has concluded that a
range of annual mean concentrations of 22 to 35 ppb constitutes a representa-
tive tropospheric level for ozone of stratospheric origin at mid-latitude
locations. Seasonal mean concentrations as high as 50 ppb in the boundary
layer are believed by Singh, et al,' to be the result of stratospheric ozone
mixing into the lower levels of the troposphere. The peak in w.an ozone
concentrations at remote rural areas has been observed during the spring and
early summer,*1 when stratospheric ozone concentrations over mid-latitudes of
the Northern Hemisphere are at a seasonal maximum.^
The mechanisms that Inject stratospneric ozone into the troposphere,
Including tropospheric folding (TF) events (associated w_th large-scale
atmospheric disturbances) and the mean meridional circulation, have been
studied by Uanielsen,^ itenielson and Mohnen,'! Reiter,^ and Viezee, et al.^3
Although there is stil. considerable debate on the relative contribution of
the two mechanisms, Singh, et al,' estimates that TF events are responsible
for the largest portion of air exchanged between the stratosphere and tropo-
sphere. According to Mohnen,^ stratosphere-troposphere interchange processes
may cause as many as 0.9% of hourly comentration values at ground level to
exceed 80 ppb ozone. Although the actual occurrence of stratospheric intru-
sions reaching the ground has been suggested,^ measurements aloft by Viezee,
et al,^ during intrusions associated with TF events, indicate that the channel
of ozone rich air emanating from the stratosphere becones horizontal at about
4300 m. Cases of stratospheric air being transported directly to near ground
levels are considered rare,? and are not likely to be responsible for wide-
spread high ozone episodes. The impact of TF events or other exchange mecha-
nisms is probably greatest during the late winter and spring since the strong
upper level eddies associated with TF events are relatively frequent and most
intense in the United States during this season, and the concentration of
ozone in the stratosphere is near the annual maximum.
The occurrence of high ozone events during the mid and late summer, how-
ever, may not be as closely tied to the stratospheric pool of ozone. In rural
eastern U.S. areas, extensive studies'^, 1 7,18 have been conducted to inves-
tigate the concentration levels and probable sources of ozone during this sea-
son. The highest ozone levels during the summer months are.generally believed
to arise from photochemical reactions of anthropogenic emissions which reach
rural areas through the direct impact of urban ozone plumes and/or through
long-range (multlday) transport of ozone vitnln the lower troposphere.
5
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SECTION 4
RESULTS AND DISCUSSION
The National Air Pollution Background Network (NAPriN) became fully
operational in late 1979 with the establishment of the eighth and final air
monitoring station which was located within the Ochoco National Forest in
Oregon. At each sice, U.S. Forest Service personnel visited the monitoring
station once per week to perform routine operation and maintenance procedures
and to cut and label strip charts. These charts were nailed to EMSL/RTP
where they wore reduced to hourly average values which were keypunched and
entered into EPA's mainframe computer. After validation, including statisti-
cal procedures to test for outliers, the data were entered into EPA's SAKOAL
data storage system. Site visits were made quarterly by either EPA or con-
tractor personnel to audit and calibrate each ozone analyzer. Calibration
was performed using a certified UV photometer.
Annual summary statistics for the ozone data collected at each NAPdK
site are shown in Table 2. Statistics tabulated include the annual percent
data (the number of valid hourly ozone values divided by the number of poss-
ible hours expressed as a percentage), mean, standard deviation, 50th percen-
tile (or median), 95th percentile, maximum hourly value, and the percentage
of valid hours with ozone concentrations greater than both BO and 120 parts
per billion (ppb). More complete frequency distributions by calendar quarter
are included in the Appendix.
EPA established in 1971 the first National Ambient Air Quality Standard^
for photochemical oxidants (primarily ozone) at a 1-hour average of tJO ppb
which was not to be exceeded more than once in any given year. In 1979, EPA
promulgated a revised standard^ which stated that the expected number of
days per calendar year with daily maximum ozone concentrations exceeding 120
ppb must be less than or equal to one. This new standard differs from the
original in several Important ways, including the specific designation of
ozone, the emphasis on the daily maximum concentration, and the statistical
interpretation of "expected exceedances."22 The most obvious difference,
however, is the change in the level of the standard from 80 to 120 ppb.
As may be seen in Table 2, exceedances of the 80 ppb level did occur
during most years at the five NAPBN sites located in the eastern half of the
U.S., but in all cases the frequency of such exceedances was less than 5
percent of valid hours. At four of these sites (tCisatchle, Mark Twain,
Croatan, and Green Mountain), exceedances of the 120 ppb level were observed.
These instances, however, were quite rare (<0.25-4 of valid hours) and were
confined to the first half of the study period (1976 through I960). Techni-
cally, therefore, trie NAPilN sites have been in compliance with the current
ozone standard since 1980.
6
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TABLE 2.
ANNUAL SUMMARY STATISTICS FOR NAPBN OZONC (ppb)
Tear
X Cata
Hean
Stdjfev
50-Xlle
95-111*
Ku
I >80
X> 120
Arliona
1979
27.7
49.3
9.8
50
65
BO
0
0
1960
95.6
47.4
13.0
45
70
90
0.3
0
Apache NF
1981
94.7
35.3
7.4
35
50
65
0
0
1962
91.1
41.2
9.2
40
55
75
0
0
1983
69.6
37.9
9.0
35
55
70
0
0
Loulalana
1976
39.4
31.5
21.4
30
70
125
2.6
0.03
1977
74.J
33.7
23.5
30
60
135
4.4
0.08
Kisatchle NF
1978
*7.7
37.9
21.0
35
75
12S
2.8
0.07
1979
79.6
26.B
14.7
25
55
100
0.1
0
1930
50.7
27.7
16.1
25
60
105
0.3
0
19S1
30.7
30.1
16.7
30
60
95
0.3
0
1982
41.7
28.3
16.8
25
60
90
0.2
0
Hlaiourl
1978
6.1
23.7
•"9.8
J5
40
SO
0
0
1979
95.6
39.3
16.2
35
75
125
2.4
0.01
Hnk Niln
19 SO
53.9
45.4
20. a
45
BO
155
4.5
0.08
NF
1981
69.6
31.7
14.3
JO
55
115
0.4
0
1982
96.9
37.5
16.3
35
65
95
0.5
0
1983
92.7
38.5
18.3
35
70
110
1.8
0
Montana
1977
66.8
40.2
11.1
40
60
60
0
0
1978
51.8
41 .o
6.9
40
55
75
0
0
Custer NF
1979
71.6
3*.2
9.9
35
50
70
0
0
1980
86.5
36.8
11.9
35
55
70
0
0
19B1
72.6
30.1
9.0
30
45
70
0
0
1*82
66.7
30.7
6.4
30
45
55
0
0
198}
90.9
35.2
9.0
35
50
65
0
0
North
1978
49.1
33.2
18.B
30
65
105
0.3
0
Carolina
1979
94.3
27.8
16.6
25
60
85
0.1
0
Croatan NF
1980
67.6
28.5
16.9
25
65
150
0.9
0.07
1981
84.2
27.4
15.4
25
55
90
0.1
0
198:
81.0
25.2
15.6
25
55
95
0.2
0
198]
89.6
25.2
16.1
25
55
65
O.l
0
Oregon
1979
23.9
29.2
6.7
30
40
50
0
0
1980
66.5
38.5
9.3
40
55
60
0
0
Ochoco NF
19BI
88.7
31.2
7.6
30
45
75
0
0
1982
69.0
34.1
8.0
35
50
65
0
0
1963
83.2
34.4
7.5
35
50
60
0
0
Veraoac
1976
12.1
29.3
i:.s
30
45
60
0
0
19)7
74.0
37 .b
21.5
35
75
145
4.6
0.23
Creeo HC. NF
1978
41.9
29.0
17.9
25
65
105
1.4
0
1979
73.3
31.6
16.6
30
65
105
1.0
0
1980
97.9
32.3
17.5
30
65
115
1.5
0
1981
83.7
2B.5
14.4
30
55
105
0.2
0
1982
59.5
28.5
16.4
>0
55
100
0.5
0
Wlaconaln
1978
27.2
32.7
13.0
30
60
100
0.1
0
1979
87.7
35.2
14.6
35
60
ItC
$•!
0
ChcquaiMgon
1980
72.2
38.8
19.3
35
75
115
2.7
0
NF
1981
92.6
33.1
12.3
30
55
60
0
0
1982
69.2
35.7
11.7
35
55
90
0.1
0
7
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It is interesting to note that, with the exception of the Apache NF in
Arizona, the annual mean ozone values at NAPBN sites fall within a range of
25 to AO ppb. Remembering that Mohnen^ has estimated that, in the absence of
anthropogenic sources, annual mean tropospheric ozone concentrations of strat-
ospneric origin would range from 22 to 35 ppb, it would appear that most (about
902) of the ozone observed at the remote NAPBN sites may be of stratospheric
origin. The higher annual mean values observed at the Apache Station may be
due to the elevation (2500 meters) of that site which was by far the highest
in the network. It has been reported that ozone of stratospheric origin in-
creases in concentration with increasing altitude above mean sea level.^
While the sites in the western half of the U.S. (Apache, Custer, and
Ochoco) tended to record slightly higher annual mean values (presumably due
to relative differences in elevation), they showed much less variation (as
measured by the standard deviation) and, with the exception of the Apache
site in 1980, no exceedances of even the 80 ppb level.
Ozone data from each site were stratified Dy quarter and averaged by
hour-of-day to evaluate seasonal and diurnal cyclical behavior. These diur-
nal plots by quarter appear for each of the NAPBN sites in Figures I through
9. At 'he Apache NF site in Arizona, depicted in Figure 2, very little
diurnal structure is apparent in the data. This flat pattern is suggestive
of very good atmospheric mixing and/or an absence of locally produced or
transported ozone from photochemical production. Some seasonality is appar-
ent in the data with the second quarter (April through June) clearly exhibit-
ing the maximum mean ozone concentration. This observation is in accord with
the fact that stratospheric ozone concentrations over midlatitudes of the
Northern Hemisphere are at a seasonal maximum during the spring and early
summer months. The remaining sites exhibit varying degrees of diurnality and
seasonality, with both patterns being more pronounced at the sites in the
eastern half of the U.S. Generally, maximum hourly means are seen to occur in
the early afternoon i1-1 p.m.) and the pattern of elevated springtime quar-
terly means prevails. In no case, however, do the cyclical patterns at these
remote sites resemble the well-known ozone patterns for urban locations.
Concentrations there are typically negligible during the evening and early
morning hours, build to a sharp peak at midday, and exhibit a seasonal maxi-
mum during the summer quarter (often termed the "photochemical season").
The daily mean ozone concentration was plotted for the duration of the
project at each site (Figures 10 through 17). Also shown in trie plots is
each daily maximum that exceeded the 80 ppb level, the level of the original
NAAIJS for ozone. It is again clear from these plots that a seasonal pattern
exists in remote ozone concentrations, with the maximum occurring in the
spring quarter. Greater variation in ozone concentrat.ons occurs at sites in
the eastern half of the U.S., and exceedances of the 80 ppb ozone level occur-
red primarily at these sites. Statistical trend analysis was applied to the
mean ozone values at each site, and in no case was there evidence of either
an increasing or decreasing systematic pattern. However, it is clear from
Figures 10 through 14 that, with the possible exception of the Mark Twain
site (Figure 12), the frequency of e?evated ozone episodes (hourly ozone
concentrations > 80 ppb) decreased over the duration of the study period. It
should be noted that although many urban sites were affected by an ozone
calibration change in 1979, such was not the case for the NAPBN sites jhere
the calibration technique was consistent throughout the study period.
B
-------
80-
70*
601
50
P 40
P
B
30
20"
10"
0 2 4 6 8 10 12 14 16 18 20 22 24
HOUR LOCAL TIRE
LEGEND: QUARTER » » » 1 DDOg o-o--» 3 *-+¦ -A 4
OVERALL AVERAGE(PPB) 39.3 49.4 40.2 36.8
~ 0 0 0 ft ^ "? ~ —jr ~-a
A-~Cr--ti—A—A - "a—ft- - "~"
Figure 2. Hourly Mean 0zo"? Concentration by Quarter -
Apache NF, AZ
-------
80-
70"
60:
50:
P 40i
p
B
301
20-
10"
0"
rrr
2
LEGENDl QUARTER
OVERALL AVERACE(PPB)
I I I I I I I
6 8 10 12 14 16 18 20 22 24
HOUR LOCAL TIME
m » | £ O—-©--<~ 3 Ar-A--A 4 .
32.3 38.6 27.9 26.4
Figure 3. Hourly Mean Ozone Concentration by Quarter -
Klsatchle NF, LA
-------
80"
70""
60"
50-
P 40:
P
B
30 "j
20-
101
0
O..
JO*'*
&
"" O-fi n" '
us
° "O- «
* A —tx - -ft" "
'I I I I I
'I
0 2
LEGEND: QUARTER
OVERALL AVERAGE
8 10 12 14 16 18 20 22 24
HOUR LOCAL TIME
» m » j Q -D 2 O—O- 3 fr -A- -A ^
31.1 47.3 43.2 28.4
Figure 4. Hourly Mean Ozone Concentration hy Quarter -
Hark Twain NF, MO
-------
80-
70-
60
50-J
P 40
P
B
301
20:
10
0"
t^-ti—£---a--a—a. .
4--*
I
0 2 4
LEGEND: QUARTER
OVERALL AVERACE(PPB)
T
T
T
I"
8 10 12 14 16
HOUR LOCAL TIME
• * » I d-d -d g o—o--^ 3
34.9 (1.1 38.8
18 20 22 24
6"A"A 4
28.0
Fiqure 5. Hourly Mean Ozone Concentration hy Quarter -
Custer NF, MT
-------
80"
70"
60'
50"
P 40"
P
B
301
20-
10"
0-
•° n
a...
T
a
I*
6 8 10 12 14 16 18 20
HOUR LOCAL TIME
» »
-------
80"
70-
eo-
5C-
P 40-
P
B
30~j
20-:
10
0-
, -ft - -ft:.-
A - -ft- - -&—A- -~£± - •
—A- - a-" A"*
"T"
2
T*
4
T"
16
"V
6
8 10 12 14
HOUR LOCAL TM£
LEGEND: QUARTER
OVERALL AVERAGE(PPB)
-*-~ 1
32.9
D D-D 2
37.3
18 20 22 24
6- -A--A 4
29.4
38.0
F1qure 7. Hourly Mean Ozone Concentration by Quarter -
Ochoco NF, OR
-------
80-
U»
76"
60"
50-
P 40^
P
B
301
20"
10-
01
.-~"•¦D-D-q
ft Q
T»TT
0
2
i
4
LEGENDt QUARTER
OVERALL AVERACE(PPB)
'I" I
8 10 12 14 16
HOUR LOCAL TIDE
»¦ ¦» 1 D D g
18 20
22
"T
24
32.3
40.5
28.0
6- -A- -A 4
25.4
Ffqure 8. Hourly Mean Ozone Concentration by Quarter -
Green Mountain NFf VT
-------
80-
70-
60"
50"
P 40"
P
B
30"
20-
10-
A - -it - a— A-
0~
T"
2
rrjT
4
"I I I
8 10 12 14 16
HOUR LOCAL TIME
— 1
"¦¦i"rFr
18
o—o--<~ 3
32.9
0
LEGEND: QUARTER
OVERALL AVERACE(PPB)
35.9
DD U 2
(6.8
20 22 24
6--A--A 4
26.4
Floure 9. Hourly Mean Ozone Concentration *^y Quarter -
Cf.eouanpnon MF, WI
-------
K5-:
iee-
75~
p
p
B
50i
25"
197E 1979 198C ISC 1
YEAR
P
P
E
19B1
YEAR
0«kT MtMJW C
Figure 10. Dally Mean and Maximum (>80ppb) Ozone Concentration -
Apache Af, AZ
17
-------
p
p
B
125"
iee
75-
50"
25-1
• •
11J 'ft
197S
P
P
B
125"
1CC"
?5
50 -
25"
e-i
1977
1978
YEAR
1979
19E0
M
19E0
OAJ-* maxujw (>BOOPB> •
Figure 11.
1981
19B2
19S3
VEftR
Dally Mean and Maximum (*80ppb) Ozone Concentration -
Klsatchte NF, LA
18
-------
125"
100T
P
P
6
75"
50-
25"
—
197E
u
1979
1980
—r
1931
VEAR
P
P
6
125"
100"
75"
56*
25"
e-l
• •
• «e
• • •
$|ypi
1931
0*1-> MAXIWUU fBOPPfl) •
1982
1983
19S-1
YEAR
Figure 12. Dally Mean and Maximum (>80ppb) Ozone Concentration -
Mark Twain NF, MO
19
-------
125 7
iee-
p
p
B
75-
S0"
85
0"d
19??
1978
1979
VEA«?
1980
1981
las-
ted
75-
p
p
B
se-
25
1981
(Mk.T MAXIMUM (»bo®P6) •
1982
19S3
YEAR
I9S4
Figure 13. Dally Mean and Maximum (>80ppb) Ozone Concentration
Custer NF, MT
20
-------
125"
iee-
p
p
B
75"!
ser
25"
e-d
ft
1978
P
P
B
125"
100"
75"
50
251
0"j
»
1979
1980
1981
YEAR
•D
O
ift
4
1981
0*1» MMMWUW (>(0**B)*
1982
19B3
19S*
YEAR
Figure 14. Dally Mean and Maximum (>80pph) Ozone Concentration -
Croatan N?, NC
?1
-------
1B5-
iee
p
p
8
75"
50"
85"
ed
1978
1979
125
100-
75
P
P
B
50
zs-
6-d
1981
(VU.1 UAJ-IHUU (••OPPB; •
1982
198C
YEAR
1983
YEAR
1921
19E4
Figure 15. Dally Mean and Maximum (>80ppb) Ozone Concentration
Ochoco Nf, OR
22
-------
ie5-
•• »
e •
1976
e-i
1977
1978
YEAR
* i #
198*
• * <
i&se
Ct«kY wjl uju t~e>^a) •
—i I
1981
198c
1953
YEAR
Figure 16. Dally Mean and Maxlmun (>80ppb) Ozone Concentration
Green Mountain NF, VT
23
-------
125"
s
a
V rp.ra
1979
1980
YEAR
1931
e-d
?!
T—
1981
i—
1983
VEAR
l9f 3
oaj. * tMKiwjv pespps; *
Figure 17. Daily Mean and Maximum (>80ppb) Ozone Concentration -
ChequameQon NF, WI
24
-------
REFERENCES
1. Research Triangle Institute. Investigation of Ozone and Ozone Precursor
Concentrations at Nonurban Locations In the Eastern U.S. EPA 450/3-74-
034A, U.S. Environmental Protection Agency, Research Triangle Park,
North Carolina, 1974.
2. Research Triangle Institute. Formation and Transport of Oxidants Along
the Gulf Ccast and In the Northern U.S. EPA-450/3-76-033, U.S. Environ-
mental Protection Agency, Research Triangle Park, North Carolina, 1976.
3. Research Triangle Institute. Investigation of Rural Oxidant Levels as
Related to Urban Hydrocarbon Control Strategies. EPA-45/3-75-036, U.S.
Environmental Protecton Agency, Research Triangle Park, North Carolina,
1975.
4. Martinez, E.L., T.A. Hartlage, N.C. Posslel, and B.E. Martin. A National
Network to Assess Long-term Patterns of Rural Ozone. Proceedings of
71st Annual Meeting of the Air Pollution Control Association, APCA,
1978.
5. Evans, G.F., P.L. Flnkelsteln, B.E. Martin, and N.C. Posslel. Ozone
Measurements from a Network of Remote Sites. J. Air Pollution Control
Association 33(4), 1983.
6. Relter, E.R., and V.A. Mohnen. The Issue of Stratospheric Ozone
Instrusion. In: Proceedings of International Conference on Photochemi-
cal Oxidant Pollution and its Control, Vol. I. EPA-600/3-77-00la,
U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina, 1977.
7. Singh, H.B., U. Vieze, W.B. Johnson, and F.L. Ludwig. The Impact of
Stratospheric Ozone on Tropospherlc Air Quality. JAPCA 30(9), 1980.
8. Singh, H.B., F.L Ludwig, and W.B. Johnson. Ozone In Clear and Remote
Atmospheres: Concentrations and Variabilities. Final Report, 1977.
9. Pittock, A.B. Ozone Climatology, Trends and the Monitoring Problem.
In: Proceedings of the International Conference on Structure, Composi-
tion and General Circulation of the Upper Atmosphere and Possible
Anthropogenic Perturbations, 1:455-466, 1974.
10. Danlelson, E.K. Stratospheric-Troposphere Exchange Based on Radioac-
tivity, Ozone and Potential Vortlclty. J Atmos. Sci., 25:502, 1968.
11. Danlelson, E.K., and V.A. Mohnen. Project Duststorm Report: Ozone
Transport, In-*ltu Measurements, and Meteorological Analyses of Tropo-
pause Folding. J. Geophys. Res. 82:5867, 1977.
25
-------
12. Relter, E.R. The Role of Stratospheric Import on Tropospheric Ozone
Concentrations. In: Proceedings of International Conference on Photo-
chemical Oxidant Pollution and its Control, Vol. I, EPA-60j/3-77001a,
U.S. Environmental Protection Agency, Research Triangle Park., North
Carolina, pp. 393-410.
13. Viezce, U., W.B. Johnson, and H.B. Singh. Airborne Measurements of
Stratospheric Ozone Intrusions into the Troposphere over the United
States. Prepared for CRC, Project No. CAPA-15-76(1-72). Final Report,
1979.
14. Lamb, R.G. A Case Study of Stratospheric Ozone Affecting Ground-Level
Oxidant Concentrations. J. Appl. Meteorol. 16(8), 1977.
15. Cleveland, W.S., B. Kleiner, J.E. McRae, and J.L. Warner. Photochemical
Air Pollution: Transport from the New York. City Area Into Connecticut
and Massachusetts. Science 191:179-181, 1976.
16. Wight, G.O., G.T. Wolff, P.J. Lioy, R.E. Meyers, and R-T. Cedervall.
Formation and Transport of Ozone on the Northeast Quadrant of the United
States. Air Quality Meteorology and Atmospheric Ozone, ASTM STP 653,
A.K. Morris and R.C. Barras, eds., pp. 445-457, ASTM, 1978.
17. Allard, D., M. Chan, C. Marlla, and E. Stephens. Philadelphia Oxidant
Data Enhancement Study - Aralysis and Interpretation of Measured Data.
EPA-450/4-81-011, U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina, 1981.
18. Chang, T.Y., and B. Weinstock. Net Ozone Formation in Rural Atmospheres.
In: Proceedings of International Conference on Photochemical Oxidant
Pollution and its Control, Vol. I, EPA-600/3-77-001a, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina, pp. 451-458,
1977.
19. Martinez, J.R., and H.B. Singh. Survey of the Role of N0X in Nonurban
Ozone Formation. EPA-450/4-79-035, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina, 1979.
20. National Primary and Secondary Ambient Air Quality Standards. Federal
Register 36:8186. April 30, 1971.
21. National Primary and Secondary Ambient Air Quality Standards. Federal
Register 44:8202. February 8, 1979.
22. Curran, T.C. and W.M. Cox. Data Analysis Procedures for the Ozone NAAQS
Statistical Format. JAPCA 29(5), 1979.
23. Johnson, W.B. and W. Viezee. Stratospheric Ozone in the Lower Tropo-
sphere. Atmos. Environ. 15, 1981.
26
-------
APPENDIX
TABLE A-l. CiwUtiva Fraquancy Distribution Tobl« of N»PBN Oiont 0«t* tPPBl
APACHE.*/ MATXOIUl FOREST
II
10/
50/
60/
90/:
95-;
99/
N«an
Std.
Y«»r
QUARTER
79
US
40
60
65
TO
75
60
56
12
2059
35
50
55
60
60
65
46
9
eo
1994
15
*5
55
ES
55
60
46
0
2150
50
60
65
70
75
60
59
10
2092
30
50
60
65
70
75
49
14
2129
30
35
40
40
45
45
35
5
01
2C30
30
35
40
45
45
50
35
7
1960
35
*5
SO
50
55
60
43
7
2108
25
35
35
40
40
4S
32
6
2200
25
30
35
35
40
45
32
5
62
1917
30
35
<•5
50
55
55
38
6
ie:s
<•0
50
55
60
65
65
SO
6
2152
30
40
45
SO
! 5
60
40
9
2063
30
<•0
45
45
50
50
36
7
01
164b
35
40
40
45
45
50
38
4
202 7
35
45
55
55
60
65
45
9
2055
25
35
45
50
50
60
37
9
2125
25
35
35
40
40
45
321 6
27
-------
TABLE A-2. Ciaaulativ* Frequency Oi%tr ibut ior» Table of NAPBN Ozon* Data (PPO)
KI5ATCHIE.L4 MATIOIUl FOPtSI
M
10/
50/
60/
90/
95/
99/
Me»r»
Std
Tsar
CJIRIEB
341
10
SB
59
70
74
62
40
21
76
961
i:
i:
56
66
64
100
37
24
2K6
5
25
40
52
64
91
26
19
77
479
25
40
60
60
ns
100
45
20
1660
20
50
75
90
95
no
S3
25
213S
S
20
<.5
ss
65
eo
26
20
2206
5
20
35
45
£0
75
25
15
7ft
171b
25
45
60
70
60
95
4S
16
<.es
25
50
70
60
90
116
5?
22
245
10
30
<•9
55
55
60
30
16
1726
10
25
<•0
55
6S
65
26
16
79
1991
IS
30
35
45
50
60
26
12
2001
10
30
40
50
55
65
29
15
1409
5
20
40
50
55
60
25
lb
1590
10
20
35
45
50
70
24
14
BO
1997
10
25
35
45
50
65
26
14
IS
35
50
55
65
60
35
16
660
10
30
45
60
75
60
31
19
1269
10
25
40
50
60
60
26
17
ei
761
15
30
40
45
55
65
30
13
1140
10
30
50
55
60
60
31
16
770
10
25
45
55
65
60
30
16
tt
910
10
25
35
45
50
65
26
12
1670
10
30
50
55
65
76
33
16
990
$
20
35
45
50
60
22
16
79
s
25
40
SO
55
55
27
16
28
-------
TABLE A"3* CuBulilivt frtqutncy Distribution Tiblc of NAPBN Oxont 0«t« IPPB)
MARK TUAlH.nO NATIONAL FCatST
N
10/
50/
60/
90/
95/
97/
He»n
Std
Y«»r
CHARTER
76
4
536
IS
25
35
35
40
45
26
10
79
1
215:
IS
35
45
50
ss
70
34
13
2
217}
30
SO
65
75
60
o?
Si
17
J
2021
20
40
55
65
60
110
43
19
4
2025
IS
25
40
45
SS
70
29
14
SO
1
1474
10
30
40
45
50
60
27
13
2
2174
35
55
70
60
65
95
SS
17
1
64 b
30
50
70
60
65
100
53
19
4
226
20
45
56
65
75
97
44
16
61
1
16)6
20
30
40
50
SS
65
32
12
2
2030
20
35
45
55
SS
66
37
14
1
2092
15
30
40
SO
60
60
31
16
4
2092
10
25
35
40
55
70
27
14
62
1
2079
15
\S
40
45
50
60
12
2
21 IS
30
45
60
65
70
60
47
14
)
21 36
25
45
55
65
70
65
44
16
4
2162
10
25
35
45
55
70
27
14
as
1
2143
10
30
40
45
SO
60
29
13
2
ieo2
30
45
60
65
75
90
46
IS
]
2053
30
50
65
75
65
97
51
16
4
2119
10
30
40
SO
60
75
30
16
29
-------
TABLc A-A* Cuailitivt Frequency Distribution Table of NaPBH Oronm Oata IPPB)
CUSU&.MT NATlO»U«to fC^CST
N
10/.
SO/.
00/
90/C
0
SO
50
55
60
40
9
3
980
25
40
SO
55
55
55
39
10
79
1
60
10
IS
2S
25
30
30
17
7
2
2029
30
40
45
50
55
60
4C
9
3
2110
30
40
50
50
55
60
41
0
2057
20
30
ss
35
40
45
29
7
SO
1
2159
2S
3S
*0
4S
50
55
35
2
107)
3S
4S
ss
55
60
70
46
to
S
1959
25
40
so
55
60
65
40
12
%
17b 5
IS
2S
30
35
35
40
25
7
01
1
m;
IS
30
35
*0
40
SS
20
9
2
u«
2S
3S
<.0
45
50
55
37
0
J
I7«
2S
3S
*0
45
45
SO
35
7
4
2ieo
IS
2S
30
30
30
35
2d
f.
02
t
1*16
20
30
3S
40
40
45
29
6
2
1279
2S
<•0
«S
50
50
55
30
0
1
7ta
20
IS
<•0
*5
45
51
33
9
<>
2 109
20
30
30
35
35
40
27
6
0]
1
16^9
25
33
35
35
40
11
30
6
2
2166
30
<¦0
*5
50
50
55
39
0
1
21<>t
30
<>0
SO
50
55
60
40
9
*
1767
20
30
3S
40
40
40
30
7
30
-------
TABLK A-5. Cwltliv* Frequency 0>»trihution Ttbl* of NAPBN Ocona Data IPPBI
CPOtTAII.f.C NATICMI routsi
U
10/
so/.
eo/
oo/ 1 is/
99/
re»r*
Std
T«»r
QUAQ1C 9
517
?0
45
5S
es
70
65
*1
17
76
1*10
IS
45
6 f
65
70
75
1S
st>s
s
T5
SO
60
70
75
30
ro
loll
5
:o
30
<•0
40
55
22
ii
7»
?H5
10
30
40
45
55
65
30
it
1 TSn
16
35
SO
60
60
70
3<»
17
2007
5
:s
«.s
ss
60
75
2?
ia
J061
i
IS
30
*0
so
65
20
IS
SO
:oi-
10
70
30
3S
40
SO
21
ii
ro<.6
20
*5
60
70
eo
100
21
1614
5
to
40
SS
eo
75
26
ta
1"»50
5
ro
10
35
40
55
20
i:
SI
1076
10
rs
IS
*5
so
60
??
12
I67J
1%
35
so
SS
65
75
SS
17
1541
i
rs
«s
SO
60
70
zt
17
tieo
s
;o
10
40
4 It
•5
13
M
I90o
10
?s
IS
45
so
55
27
13
20J<.
10
30
«s
55
60
eo
11
16
i io:
5
iS
*0
SO
55
60
2a
16
I05S
\
IS
;s
30
35
45
17
11
a>
:ot.:
10
:s
<•0
45
50
6 '
17
1*
7170
s
10
45
SS
60
70
11
16
l<>68
s
20
40
so
60
7S
ZS
16
0
io
10
15
37
SO
10
IZ
31
-------
TABLE A-6. Cumulative Frequency Distribution Table of NAPBN Ozone Data IPPB>
OCHOCO.OR NATIONAL FOREST
N
10/.
50/
80/
90/
95/
99/
flcan
Sid.
Year
QUARTER
79
4
2096
20
30
35
40
40
45
29
7
BO
1
1555
30
40
45
45
50
50
33
6
2
2115
30
40
50
50
55
55
40
6
3
2079
JO
45
50
55
60
70
43
II
4
200/
25
35
35
40
45
50
32
7
SI
1
1673
20
30
35
35
40
40
30
6
2
1692
20
35
40
40
45
50
32
8
3
1679
25
35
45
45
50
55
36
6
4
2124
20
30
30
30
3i
35
27
<•
62
I
1779
30
35
35
40
40
45
33
2
2069
30
40
45
50
55
55
39
6
3
1905
25
35
45
45
50
55
35
9
4
1960
20
30
30
35
35
35
28
5
ej
I
2029
25
35
35
40
40
40
3:
5
2
1785
30
35
45
45
50
55
37
7
3
2098
25
35
45
50
50
55
37
9
4
1376
25
30
35
40
40
45
30
6
32
-------
TAB1.E A-7 . Cwulitiv* Fr»qu«rtcy Distribution Table of NIPON Ozona Data (PPBI
GREEN HT..VT NATIO'l&l FORtM
N
10/
50/
60/.
94/
95X
99Z
11c an
Std.
Year
QUARTER
76
-------
TAA1 P A u CunuUtiva frtquewy Distribution Tobl« of HA PPM Oxont Ditt (PPB)
1 A£ L£» A-O. CHEOUAMCGOH.gi NATIO'tiL F0PE5T
N
10/
50/
BO/.
90/
95/
99/
He - n
Std.
Tear
QUARTER
78
1
1 IS<*
20
35
50
60
65
77
37
16
4
1225
20
30
35
35
40
55
29
a
79
1
1665
25
35
*5
55
60
70
36
it
S
2027
30
------- |