EPA-600/3-78-017
January 1978
Environmental Monitoring Series
FATE OF HALOGENATED COMPOUNDS
IN THE ATMOSPHERE
Interim Report -1977
Environmental Monitoring ar
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL MONITORING series.
This series describes research conducted to develop new or improved methods
and instrumentation for the identification and quantification of environmental
pollutants at the lowest conceivably significant concentrations. It also includes
studies to determine the ambient concentrations of pollutants in the environment
and/or the variance of pollutants as a function of time or meteorological factors.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/3-78-017
January 1978
FATE OF HALOGENATED COMPOUNDS IN THE ATMOSPHERE
Interim Report -- 1977
by
Hanwant B. Singh
L.J. Salas
H. Shiegeishi
A.H. Smith
Stanford Research Institute
Menlo Park, California 94025
Grant No. 8038020
Project Officer
John Spence
Atmospheric Chemistry and Physics Division
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, N.C. 27711
ENVIRONMENTAL SCIENCES RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, N.C. 27711
-------
DISCLAIMER
This report has been reviewed by the Environmental Sciences Research
Laboratory, U. S. Environmental Protection Agency and approved for
publication. Approval does not signify that the contents necessarily
reflect the views and policies of the U. S. Environmental Protection
Agency, nor does mention of trade names or commercial products constitute
endorsement or recommendation for use.
ii
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ABSTRACT
The second year involved air monitoring at five sites that include urban,
non-urban and marine. In situ analysis was performed for a total of 31
chemical species, nineteen were halogenated compounds, five were nitrogen
containing species, and the remaining seven included hydrocarbon, CO, and CL.
Data suggest that the northern hemisphere troposphere contains 2906 ppt of
chlorine atoms. The chlorine contribution of fluorocarbons is 33% of the
total while that due exclusively to chlorocarbons is 77%. The natural chlorine
contribution due solely to CH^Cl is 25% of the total organic chlorine burden.
The burden of halocarbons in the troposphere is increasing when compared to
the background data collected exactly a year ago,
Based on the budget and distribution of methyl chloroform and its em-
issions inventory, a two-box model was used to develop the conclusion that
average tropospheric hydroxyl radical (HO) concentration was about 4.1x10
HO/ml. This is significantly lower than the hitherto accepted HO concentra-
tions in the troposphere. It was further found that there maybe significant
gradients in the northern and southern hemispheric HO concentrations.
This report was submitted in fulfillment of Grant Number R 8038020-2 by
Stanford Research Institute under the sponsorship of the U.S. Environmental
Protection Agency. This report covers the period 21 July 1976 to 21 July
1977.
iii
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CONTENTS
Abstract ,,, , iii
Figures ,,,,, , ,., ,,,.,,,,, vi
Tables , vii
1. Introduction ,,, 1
Overview.,..,.. 1
Overal 1 ob j ectives , 1
2. Conclusions ,.,., < i., 2
3. Summary , , ,.,,,,, 3
4. Second Year (Phase I) Progress 8
5. Data Analysis , 23
Background concentrations of measured trace
constituents 23
Urban-nonurban pollutant relationships ,,,. 31
Limited ocean water analysis for ^0 ,,.,,, ,,, 36
Preliminary testing for the presence of chloroacetyl
chlorides ,,,., 37
6. Halocarbon Lifetimes and Their Global Balance ,,,,,,,,. 40
Halocarbon lifetimes ,.,.,,,,,,,,, 40
Estimation of HO radical abundance in the northern and
southern hemispheres , .,...,., 44
Results and discussion , , ..,,.,.,,, 48
7. Halocarbons and ^0 Standards Intercomparison ,,,, 52
8. Future Plans ,,,, 53
REFERENCES 54
LIST OF PUBLICATION 56
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. FIGURES
Number Page
1 Location of Monitoring Sites 10
2 Halocarbons in the Ambient Air at Menlo Park 13
3 Separation of CH3Cl, CH-Br, and CH I Along with Other
Halocarbons 14
4 Separation of CH Cl, CH2C12 Alon§ with Several Other
Halocarbons 15
5 Phosgene Separation from the Ambient Air 16
6 Chromatogram Showing SF, and N00 Separation from Ambient
Air 6. . . ? 17
7 PAN and PPN Separation from Ambient Air Using a
Coulometric EC-GC 18
8 F114, F21, and CH Br Separation from Ambient Air 19
9 Ethylene Dibromide and C0C1, Separation from Ambient Air. . 20
i D
10 Chromatogram Showing Light Hydrocarbon Analysis 21
11 Average Long-Term N^O Variabilities in the Troposphere. . . 27
12 Atmospheric CO Concentrations at a Clean Marine Site
(Latitude 38.9°N) 28
13 Atmospheric CH4 Concentrations at a Clean Marine Site
(Latitude 38.9°N) 29
14 Atmospheric C^A^ Concentrations at a Clean Marine Site
(Latitude 38.9°N) 30
15 Identical CCloF and CCl^ Behavior as an Indicator of a
Common Urban Source in the Eastern United States 34
16 NO Profile in the Pacific Ocean 37
17 CC1, Loss in Ambient Air When Passed Through a Column of
Water 30
18 Global Emissions of Methyl Chloroform 46
19 Methyl Chloroform Residence Times in the Northern and
Southern Hemispheres 49
VI
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TABLES
Number
1 Background Concentrations of Measured Trace Constituents
in the Northern Hemisphere
2 Atmospheric Growth Rates of Important Halocarbons ..... 5
3 Atmospheric Residence Times of Important Halocarbons. „ . . 5
4 Chemical and Meteorological Parameters Measured ...... 7
5 Aerometric Instrumentation in SRI Environmental Mobile
Laboratory ......................... 12
6 Northern Hemispheric Background Concentrations (ppt) of
Trace Constituents .................... . 24
7 Urban-Nonurban Pollutant Relationships ........... 32
8 Halocarbons, SFg, and ^0 in the Lower Troposphere ..... 42
9 Halocarbon Residence Times and Average Hydroxyl Radical
Concentrations ....................... ^3
10 Residence Times of Important Halocarbons .......... 44
11 Residence Times of CH^CCl. and the HO Abundance, in the
N.H. and S.H ..... . . ................. 50
12 Analysis and Intercomparisons of an Identical Air Sample
by SRI and WSU ....................... 52
vii
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INTRODUCTION
OVERVIEW
In this study, we attempt to characterize the concentrations, vari-
abilities and distributions of a large number of halocarbons, hydrocarbons
and other atmospheric trace constituents, which have a bearing on tropo-
spheric/stratospheric chemistry. Many halocarbons stable in the tropo-
sphere (CC1 F ) are suspect as precursors of stratospheric ozone,
x y
destroying chlorine atoms while others are known for their toxicity and
carcinogenicity. It is therefore essential that the urban-nonurban
distributions of these species be determined.
The scope of the study in the second year was expanded to include a
limited number of hydrocarbons, since it was felt that some of the non-
methane hydrocarbons may play an important role in the stratospheric
chemistry of ozone. In addition, important tropospheric constituents
that play an important role in the troposphere were included.
OVERALL OBJECTIVES
The overall objectives of this project are:
• To determine the distribution, atmospheric loading, sources,
and sinks of halogenated compounds, selected photochemical
pollutants, and natural trace constituents that have a
possible stratospheric impact.
• To use halocarbons to understand complex atmospheric transport
phenomena having a bearing on pollution control strategies.
• To use halocarbons as reactive tracers to understand natural
tropospheric chemistry.
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CONCLUSIONS
It is found that the atmosphere is contaminated with a large number
of pollutants that disperse quite rapidly. While these pollutants are a
source of great concern because of their ability to destroy stratospheric
ozone, they also provide opportunities to better understand the natural
atmosphere. The atmospheric burdens of species such as fluorocarbons
(Fll and F12) are increasing at a rate comparable with their emissions.
The atmospheric residence times calculated in this report lend credence
to the contention that the stratosphere may be the only important sink
for these species. Other chemical constituents such as methyl chloroform
(and fluorocarbons 22) are scavenged at a slower rate than earlier believed
and are also a source of great concern and cannot be allowed to be emitted
at ever-increasing rates. A qualitative case for the control of carbon
monoxide which reduces the scavenging ability of the atmosphere, can also
be made.
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SUMMARY
The second year results involved air monitoring at five urban and non-
urban stations with the help of an instrumented environmental mobile laborato-
ry. The monitoring stations included urban, remote marine, remote continental,
high altitude and intermediate locations. In situ analysis was performed for
a total of 31 chemical species and six meteorological parameters. Of the 31
chemical species sought, 19 were halogenated compounds, five were nitrbgen
containing species, and the remaining seven included hydrocarbons. CO and 0,,
Meteorological parameters measured were wind speed, wind directionf rel-
ative humidity, temperature, pressure and solar flux, The northern hemispheric
background concentrations of the chemical species as measured at Point Arena.
California (marine environment, cleanest site monitored it 38,57°Nr«123,440W) in
May 1977 are given in Table 1,
Table 1 data also suggest that the troposphere (northern hemisphere), con-
tains 2906 ppt of chlorine atoms, The chlorine contribution of fluorocarbons
is 33% of the total while that due exclusively to chlorocarbons is 77%, The
natural chlorine contribution due solely to CH-C1 is 25% of the total organic
chlorine burden.
The burden of halocarbons in the troposphere is increasing, When com-
pared to background data collected exactly a year ago (Singh et al,, 1977) the
following growth patterns are observed for the important halocarbons (see
Table 2).
Atmospheric residence times of a number of important halocarbons have
been calculated based on our measurements and the test available emissions
data. These are summarized in Table 3,
The residence times of Fluorocarbon 12 and 11? as calculated from our
data, are compatible with earlier assertions of no significant tropospheric
sinks. The residence times of more reactive halocarbons were found to be
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Table 1
BACKGROUND CONCENTRATIONS OF MEASURED TRACE CONSTITUENTS
IN THE NORTHERN HEMISPHERE
(Marine Environment)
Compound
Average" Concentration
(PPt)
Fluorocarbon-12
Fluorocarbon-11
Fluorocarbon-22
Fluorocarbon-21*
Fluorocarbon 113
Fluorocarbon 114
Sulfur hexafluoride
Carbon tetrachloride
Chloroform
Methylene chloride
Methyl chloride
Methyl iodide
Methyl bromide
Hexachloroethane
Methyl chloroform
Dibromoethane *
Tetrachloroethylene
Trichloroethylene
Phosgene
Nitrous oxide
Nitric oxides
Nitrogen dioxide
Peroxyacetyl nitrate (PAN)*
Peroxypropionyl nitrate (PPN)§
Ozone
Carbon monoxide
Total nonmethane hydrocarbons
Methane
Acetylene
Ethane
Propane**
220.5 (19.8)tt
126.5 (12.4)
20-30
5.0 (1.9)
22.6 (4.8)
11.9 (5.2)
0.27 (0.03)
123.6 (8.3)
19.9 (5.1)
44.8 (21.5)
733.3 (134.1)
4.8 (2.9)
20.1 (4.2)
6.8 (1.4)
110.7 (18.1)
5.4 (1.0)
33.4 (4.6)
11.5 (1.0)
15.4 (4.2)
314.9 X 10
<5 X 103
<5 X 103
110.1 (55.3)
40.2 (16.5)
35 X 10J (5 X
119 X 103 (14
(11.5
X 103)
103)
1479 X 103 (19 X 103)
<400
1932.6 (324.0)
433.8 (163.7)
Not quantifiable.
Whether fluorocarbon 21 is a true atmospheric constituent
or an experimental artifact still remains unresolved.
Dibromoethane was above 4 ppt only 3970 of the time.
§
tt
PAN and PPN data are reported from the Reese River Site
(No. 10) which was a clean Continental Site. No PAN and
PPN data at Point Arena (Site 11) were obtained because
of instrument breakdown.
Propane was above 250 ppt only 157o of the time.
Standard deviation.
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Table 2
ATMOSPHERIC GROWTH RATES OF IMPORTANT HALOCARBONS
Compounds
Percent Increase in Tropospheric
Budget over a One-Year Period
(May 1976-May 1977)
Fluorocarbon-12
Fluorocarbon-11
Carbon tetrachloride
Methyl chloroform
9
11
9
12
Table 3
ATMOSPHERIC RESIDENCE TIMES
OF IMPORTANT HALOCARBONS
Compounds
Fluorocarbon 12
Fluorocarbon 11
Methyl chloroform
Chloroform
Tetrachloroethylene
Residence Time
(years)
50.0
36.0
8.0
1.7
0.4
inconsistent with all prior estimates. These were significantly longer
than believed.
Based on the budget and distribution of methyl chloroform and its
emissions inventory, a two-box model was used to develop the conclusion
that average tropospheric hydroxyl radical (HO) concentration was about
4 X 105 HO/ml. This is significantly lower than the hitherto accepted HO
concentrations in the troposphere. It was further found that there may
be significant gradients in the northern and southern hemispheric HO
concentrations. Within the limit of uncertainties, the average HO levels
in the northern and southern hemispheres are defined by the following
equations:
5
-------
(HO) + (HO) _ 5
b'H- . SLi. = (HO).,. . = 4.1 X 1(T HO/ml (1)
2 Globe
(HO) „
^^ = 1.6 to 3.0 . (2)
-------
indicate constant background with extremely small spatial and temporal varia-
tions .
The next phase of the second year research effort (Phase II) is planned
currently to determine the global inventories of the pollutants of interest
with special emphasis on the southern hemispheric burdens and the north/south
distribution of trace constituents.
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SECOND YEAR (PHASE I) PROGRESS
In this section we report progress accomplished subsequent to the
first year research effort. The first year progress report has already
been summarized (Singh et al., 1976). The following steps were involved:
• An SRI mobile laboratory was equipped and readied to
measure a large number of air quality and meteorological
parameters. These are listed in Table 4. A total of
19 halogenated and 12 nonhalogenated chemical species,
along with important meteorological parameters, were
measured. The inclusion of hydrocarbon analysis was
prompted by our determinations of low HO levels in the
troposphere and the possibility that the role of HCs
in stratospheric chemistry may not be limited to CH*.
• A total of five short-term monitoring studies with the
help of the mobile laboratory were completed (Sites 7-
11) Figure 1 shows the exact locations of these sites
as well as the monitoring period. The locations were
selected to be:
- Clean marine
- Clean continental
- Clean high altitude
- Urban contaminated.
The monitoring period spans through winter to early summer (May 1977).
Sites 9 and 10 are clean air sites roughly 200 km and 500 km away from
the nearest marine source, respectively. Both of these sites are moun-
tain peak sites at elevations of 2379 m and 1982 m (MSL), respectively.
Site 11 is a clean marine air surface site while Site 8 is an urban
surface site (Riverside) in the south coast air basin. Site 7 at Mill
Valley is an elevated marine site (762 m MSL) that can be strongly
affected by urban transport from San Francisco.
• Site monitoring had the following features:
- All field monitoring was conducted on a 24-hour
daily schedule. Actual monitoring periods are shown
in Figure 1.
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Table 4
CHEMICAL AND METEOROLOGICAL PARAMETERS MEASURED
Halogenated
Species
CC12F2(F12)
CC13F(F11)
CHC1F2(F22)
CHC12F(F21)
CC1F2CC12F(F113)
CC1F2CC1F2(F114)
SF6
cci4
CHC13
CH2C12
CH3C1
CH3Br
cci3cci3
3 3
CH2BrCH2Br
cci2cci2
CHC1CHC12
coci2
Nitrogen
Species
N20
NO
N02
PANt
. PPN1"
Hydrocarbons
and Others
°3
CO
TNMHC*
C2H2
C2H6
C3H8
Meteorological
Parameters
Wind speed
Wind direction
Relative humidity
Solar flux
Temperature
Pressure
TNMHC = Total hydrocarbons -
f
II II
PAN = CH3COON02; PPN = CH3CH2COON02
-------
Lj • OREGON
I f""™ |«eoc »u,
A > \
n^i !
r~ ^ «r^ • • . J 1
/ c' 'l" / P :
f \ /
SITE
7
8
LOCATION
Monitoring Period
MILL VALLEY
Jan 12-27 1977
RIVERSIDE
Apr 25-May 3, 1977
May 5-12, 1977
LAT.
37° 59'
33° 54'
LONG.
122° 39'
117° 23'
ELEV.
meters
762
249
2379
REESE RIVER
May 14-19, 1977
38<> 59*
38° 57'
117° 28'
123° 44'
1982
PT. ARENA
May 24-29, 1977
FIGURE 1 LOCATION OF MONITORING SITES
10
-------
- THC, CH^, CO, NOX, and 03 were continuously monitored
at all sites.
- Meteorological parameters (Table 4) were continuously
monitored at all sites.
- Synoptic meteorological information was acquired
separately.
Table 5 shows the instrumentation in the SRI mobile
laboratory. A stainless steel manifold was used to
collect all air samples from a fixed elevation of 4 m
above the ground.
Extensive cryogenic concentrations of air samples were
required at liquid oxygen temperatures to measure all
hydrocarbons (except City), F114, CI^Br, CH2C12, C2Clg,
CH2BrCH2Br, C2HC13, and SFg. The collection volumes were
generally less than 300 ml of air. As a general rule
200 ml of air were preconcentrated. In many cases cryo-
genically preconcentrated GC injections also provided data
for species which could also be measured directly. Cryo-
genic concentrations were in stainless steel traps packed
with glass wool. Materials were desorbed by rapidly heat-
ing the trap to 100°C for about 30 sees. In all cases a set
procedure was followed for the cryogenic injections.
Figures 2-10 show chromatograms of all species listed in
Table 4 for which gas chromatographic analysis was used.
Calibrations for halocarbons, hydrocarbons, PAN, PPN,
N20 and SF6 were performed using permeation tubes, gas
phase coulometry, and multiple dilutions as necessary.
In addition, long term secondary standards were main-
tained and exchanged with other laboratories for inter-
comparisons. Several secondary standards were kept on
board to ascertain the stability of instruments. In
the case of PAN and PPN analysis, only gas phase
coulometry was used and the data must be considered
somewhat preliminary until the confirmations of the
reliability of absolute PAN and PPN determinations
using coulometry can be made. In the meanwhile, the
data on PAN and PPN do look reasonable.
Calibrations for THC, CO, and CHA were conducted on
board at least twice a day. N02 calibrations were con-
ducted using a permeation tube as primary standard. Stan-
dard secondary mixtures of NO and N©2 were used in the
field; 03 primary calibrations were performed using the
neutral buffer KI method and then monitored with the
Bendix 03 calibrator.
11
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Table 5
AEROMETRIC INSTRUMENTATION IN SRI
ENVIRONMENTAL MOBILE LABORATORY
Component Measured
Instrumentation
Halocarbons, SFg, and
CO, CH4, THC
NO/NO* (N02 by difference)
-*
D3
Solar flux
Wind speed, wind direction,
temperature, pressure, and
relative humidity
Data systems
Two Perkin Elmer 3920 GCs equipped
with a total of four frequency-
modulated EC detectors
A coulometric EC detector with two
detectors in series
Beckman 6800 Air Quality GC
Bendix Model 8101-B chemilumines-
cence analyzer
Bendix Model 8002 chemiluminescence
analyzer
Eppley UV pyranometer
Standard meteorological equipment
Auto Lab System IV for the two
Perkin Elmer GCs
Digitem tape system for all other
parameters
A Teflon manifold was used for NO/NOX and Oj analysis; for all
other measurements, a stainless steel manifold was used.
-------
i i : ; I : :
! i ... :. ... i . !
FIGURE 2 HALOCARBONS IN THE AMBIENT AIR AT MENLO PARK
-------
FIGURE 3 SEPARATION OF CH3CI, CH3Br, AND CH3I ALONG WITH OTHER
HALOCARBONS
-------
Ul
FIGURE 4 SEPARATION OF CH3CI, CH2CI2 ALONG WITH SEVERAL OTHER HALOCARBONS
-------
! I IHI
Flurocwbon 11
Retention Time 6.9 nun
p - 0.40
Sample Size 13.0 mU
(Menlo Park, California Air)
lonization Efficiency,
ECD2 Signal
ECD1 Signal «_
Phosgene
Retention Time "• 5.1
p = 0.65
7.0 6.0 5.0
TIME — minutes
SA-4487-1
FIGURE 5 PHOSGENE SEPARATION FROM
THE AMBIENT AIR
16
-------
5.0 ml WR
MENUO PARK
II 15 13 H 1 1 5" 2
TIMECMIN;
FIGURE 6 CHROMATOGRAM SHOWING SF6 AND N2O SEPARATION FROM AMBIENT AIR
17
-------
WATER
5 ml SAMPLE
FROM U.C. RIVERSIDE
MAY 2, 1977
COULMETRIC EC-GC
EC2
SA-4487-2
FIGURE 7 PAN AND PPN SEPARATION FROM AMBIENT AIR USING A
COULOMETRIC EC-GC
18
-------
F11I
F12T
CHgCI
200 ml SAMPLE
FROM MILL VALLEY
JANUARY 27, 1977
F21
CH3Br
nun
SA-4487-3
FIGURE 8 F114, F21 AND CH3Br SEPARATION FROM AMBIENT AIR
19
-------
CH2BrCH2Br
100 ml AIR INJECTION
U.C. RIVERSIDE
(Sample collected from
a conjested parking lot)
98
94
90 26
TIME (min)
22
18
FIGURE 9 ETHYLENE DIBROMIDE AND C2CI6 SEPARATION FROM AMBIENT AIR
20
-------
100 ml AIR INJECTION
U.C. RIVERSIDE
APRIL 29, 1977
C,H
2"4
FIGURE 10 CHROMATOGRAM SHOWING LIGHT HYDROCARBON ANALYSIS
21
-------
A stainless steel manifold was used for all pollutant
measurements except those for NO, NOX, and 0^, for which
a Teflon manifold was used. Stainless steel sampling
loops were used for all GC injections. Concentrating
procedures were developed and used successfully for am-
bient measurement. All GC-EC data were fed to an Auto
Lab IV electronic data processor. All non-GC-EC data
were fed to a Digitem tape data system.
22
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DATA ANALYSIS
Experiments at all sites went satisfactorily and no insurmountable
problems were encountered. The most difficult conditions were encountered
at Badger Pass (Site 9) where we were caught in a snow storm. The higher
standard deviations at Badger Pass are probably a reflection of the un-
favorable weather conditions. Point Arena (Site 11) was found to be the
cleanest site with consistent winds from the west-northwest. Riverside
(Site 8) was representative of the urban site monitored by us. Because
of our decision to monitor on a 24-hour daily basis, a vast amount of data
was collected. Although all of the data have been treated statistically,
our interpretation of the data is by no means complete. Nevertheless, we
can provide a summary of preliminary observations. More detailed analysis
and interpretations will appear in future reports and publications.
BACKGROUND CONCENTRATIONS OF MEASURED TRACE CONSTITUENTS
Table 6 shows a summary of data on the background concentrations of
19 halogenated and 11 nonhalogenated atmospheric trace constituents. The
corresponding standard deviations are also shown. These are based on
monitoring at Site 11, which was the cleanest site monitored. The winds
were consistently from W-NW and the data is representative of background
conditions. Table 6 also lists the background concentrations reported by
us in May 1976 for comparison purposes.
Consistent with our earlier observations, all halocarbons (except
CH^BrCH-Br) were found to be ubiquitous and could be measured within the
sensitivities of our measurements 1007o of the time. CH_BrCH_Br was
detectable above 4 ppt at least 39% of the time. It is expected that the
true background of concentration of CH9BrCH~Br is probably less than
4 ppt.
Seven fluorinated species (F12, Fll, F22, F21, F113, F114, and SF,)
D
were sought and measured during the field programs. F12, Fll, F113, F114,
23
-------
Table 6
NORTHERN HEMISPHERIC BACKGROUND CONCENTRATIONS (ppt) OF TRACE CONSTITUENTS
May 1976--Badger Pass May 1977--Point Arena
Compounds j(Lat. 37.40°N, LonR. 119.39°W) • (lat. 38.57°N, LonR. 123.44°W)
Fluorocarbon-12 (F12) 203.5** (18.5) ^ '
Fll
F22
F21
F113
F114
SF6 .
CCl^
CHC13
CH Cl
^ ^
CH Cl
CH I
CH Br
C2C16
CH CC13
CH BrCH Br
C2CI4
C2HCL3
COCl
^
N20
NO
NO
PAN
PHN
°3
CO
CH4
C2H2
C2H6
C3H8
I 115.6
i
i
I
14.2
1 19.9
i
0.24
; 113.9
'. 17,1
,
713.0
9.2
4.7
,
98.8
--
30.7
15.6
21.7
311.6 X 10
< 5,000
- 5,000
--
--
3
53 x 10
..
3
1,412 X 10
--
:
(5.0) \
i
(4.9)
(3.4)
(0.04) :
(6.5)
(2.7)
'(51.1)
(4.6)
(2.6)
(9.7)
(10.5)
(2.5)
(5.2)
3 3
(18.2 X 10 )
3
(12 x 10 )
•5
(103 x 10 ) !
220.5
126.5
20 -
5.0
22.6
11.9
0.27
123.6
19.9
44.8
733.3
4.8
20.1
6.8
110.7
5.4
33.4
11.5
15.4
314.9
100.1
40.2
35 x
119 X
1,479 X
1,932.6
433.8
(19.8)
(12.4)
*
30 i
(1.9)
(4.8)
(5.2)
(0.03)
(8.3)
(5.1)
(21.5)
(134.1)
(2.9)
(4.2)
(1.4)
(18.1)
(1.0)
(4.6)
(1.0)
(4.2)
3 3
x 10 (11.5 x 10 )
< 5,000
< 5,000
(55.3)*
(16.5)*
3 3
10 (5 X 10 )
103 (14 X 103)
•j 3
10 (19 X 10 )
< 400
(324.0)
fi
(163.7)
No to: Concentrations of species such as CH-jCljC^Br are higher because of the marine
environment of Point Arena.
Vr
Not quantifiable.
i
Measurable only 397, of the times above 4 ppt.
I'AN and I'I'N concentrations are taken from Reese River (Site 10), a clean continental
site.
0'illu WJK only detectable 15% of the times above 250 ppt.
tt.
1 *7
Average concentration in parts per trillion (10 v/v)
quantity inside the parenthesis is the standard deviation.
24
-------
and SF, background concentrations of 221, 127, 23, 12, and 0.3 ppt,
b
respectively, are compatible with reported measurements by other investi-
gators and our own earlier measurements. The ratio of F12/F11 of 1.74 com-
pares well with a ratio of 1.76 reported earlier (Singh et al., 1976).
The F113 concentration of 23 ppt is consistent with the concentration of
20 ppt and 21 ppt reported by Singh et al. (1976) and Dagmar et al. (1976)
one year ago. Both F114 and SF, levels are generally compatible with the
b
limited data available in literature. F21 could be measured all the time.
It still remains uncertain, however, whether F21 is an experimental
artifact or a true atmospheric constituent. F22 was observed but could
not be quantified because of its poor electron capture response. A crude
extrapolation will place its background concentration within 20 to 30 ppt.
Background concentrations of CGI,, CHC1_, CH.C1-, CH-C1 are measured
to be 124, 20, 45, and 733, respectively. Once again, these concentra-
tions are reasonable and not in disagreement with reported data. CH9C19
background of 45 ppt is being reported by us for the first time and com-
parative data is not available. Cox (1975), however, did report a CH-Cl.
concentration of 35 (±19) in 1974.
Concentration gradients of CH-C1, CHC13, CH»I and CH»Br between the
marine and the continental environment were observed. Consistent with
our earlier observations it still appears that CH.C1, CH_I, and CH_Br
find a major source in the ocean. This may also be true for CHC1_. How-
ever, most coastal areas are contaminated with CHC1,. and a clear marine
source relationship for CHC1, cannot be established at this time.
C^Cl, has been measured for the first time in the ambient background
atmosphere and is found to be a ubiquitous component. A background con-
centration of 7 ppt is observed. C0C1, is not manufactured in the United
/ b
States, but about 500 tons a year are imported from Europe. Most of the
C~Clft is released to the atmosphere eventually. It is also produced as an
impurity during the manufacture of C-Cl,. It is likely that C_C1,
abundance is a matter of long-time accumulation in the atmosphere. Natural
sources of C0C1, may also exist. Additionally, chlorination of C0C1. can
/ D 2. q.
produce C2C16 *n t*ie absence of excess oxygen. C-C1, has been identified
25
-------
in drinking water which has undergone chlorination. It is likely that
stratosphere would be a major removal mechanism for C0C1£. Tropospheric
/ o
sinks are expected to be unimportant. We note here that C^Cl levels in
Riverside (Site 8) were found to be significantly higher and a primary or
a secondary urban source is indicated.
C..C1, and C.HCl,. were measured at 33 and 12 ppt, respectively.
C?HC1_ background concentration of 12 ppt is somewhat lower than the 16 ppt
reported earlier by us. However, in previous instances C-HC1- was measur-
able at a frequency of less than 100%. Thus the latest concentration of
12 ppt for C^HCl,. reflects an improvement in the sensitivity of our
measurements.
Phosgene is expected to be a photo-oxidation product of chloro-
ethylenes (Singh, 1976) and was measured at a background concentration of
16 ppt.
NO was found to be distributed quite uniformly and was present at an
average concentration of about 315 ppb. Figure 11 shows a plot of the
average NO concentrations measured by us at several locations, based on
short-term field measurements. It is clear from Figure 11 that no sig-
nificant differences in N~0 levels over a period of 19 months can be
deciphered. Thus N20 levels are found to be relatively uniform in both
space and time.
Oxides of nitrogen (NO, NO-) were present at levels below the detec-
tion limit of our chemiluminescent instrumentation. It is safe to assume
that these levels are below 5 ppb.
PAN and PPN were not measured at Point Arena because of instrument
breakdown. However, at Reese River, a relatively clean continental site,
concentrations of 110 ppt and 40 ppt for PAN and PPN were measured. These
should be representative of the background conditions. Since PAN and PPN
are photochemical products, significant seasonal variations can be expected.
Ozone was measured at a nearly constant concentration of 35 ppb.
Maximum 1-h concentration did not exceed 46 ppb. The background of ozone
at the surface is expected to show a significant seasonal and diurnal
variation as suggested by Singh et al. (1977b).
26
-------
350
340
330
320
310
3
a
~ 300
O
CM
290
280
270
260
250
I I ». I I I I
NOV DEC JAN FEB MAR APR MAY JUN JULY DEC JAN FEB MAR APR MAY JUN
(1976) (1977)
SA-4487-6
FIGURE 11 AVERAGE LONG-TERM N20 VARIABILITIES IN THE TROPOSHERE
Carbon monoxide was measured at a nearly constant level of 119 ppb.
This pacific marine air background concentration is identical to the CO
levels of 117 ppb measured by Linnenbom et al. (1973) in 1970-1971. This
implies that the background of CO has undergone no change at least since
1970. Figure 12 shows the relatively uniform background of CO at Site 11.
Methane was measured at a nearly constant level of 1480 ppb. This
value is in good agreement with several other measurements although lower
than the average 1600-ppb level reported by Heidt and Pallock (1976). No
significant variations in the CH, concentration were observed (Figure 13).
Among the various C~ hydrocarbons sought, C-H, was found to be the
most prevalent. A background concentration of 1930 ppb was measured at
Point Arena. Figure 14 shows the atmospheric variabilities of C_H, during
the monitoring period at Point Arena (Site 11). The sources of C2H6 are
not well known. Our best estimates suggest that if HO is the major
27
-------
500
400
.o
a
a
300
o
o
200
100
May 1977
I
20
40 60 80
NUMBER OF HOURS
100
120
FIGURE 12 ATMOSPHERIC CO CONCENTRATIONS AT A CLEAN MARINE SITE
(LATITUDE 38.9°N)
removal process for C0H£ in the atmosphere, its ground level flux must
/ b
be of the order of 5 to 10 million tons a year. Similar calculations
for CH. suggest a ground level flux of 200-400 million tons a year. We
believe that even though the concentration of C0H, in the atmosphere is
o 2 6
about 10 times lower than CH, concentration, a distinct possibility
exists that C-H,. plays an important role in the stratospheric chemistry.
This is because the C0H, + Cl rate constant is about 10 times faster
e. o
than the CH, + Cl rate constant.
Hitherto, all hydrocarbons other than CH, have been considered to
play an unimportant role in the stratosphere. It is suggested that C0H,
i o
ought to be considered in the stratospheric models. The sources and
sinks of C-H, are still uncertain. However, our preliminary analysis of
28
-------
5000
4000
J 3000
2000
1000
May 1977
J.
20
40 60 80
NUMBER OF HOURS
100
120
FIGURE 13
ATMOSPHERIC CH4 CONCENTRATION AT A CLEAN MARINE SITE
(LATITUDE 38.9°N)
emissions data from mobile sources suggests that mobile sources contribute
no more than 2Q70 of the atmospheric C0H,. Natural gas would be perhaps
/ o
the most significant source of atmospheric C0H£. Other natural sources
2. o
of C-H, may exist also.
/ b
Acetylene and propane were also identifiable in the remote atmospheres,
but these background concentrations were too low to quantify. It is ex-
pected that the true background concentrations of C0H_ and C_H0 are lower
Z / jo
than 400 ppt and 250 ppt, respectively. While C0H0 was measured at
j o
434 ppt at Point Arena, at least 85% of the time C_H0 was below our
j o
detectability limit of 250 ppt.
29
-------
5000
4000
3000
Q
a
ID
M
o
2000
1000
May 1977
*»ti •%'•: -
I
I
20
40 60 60
TIME — hours
100
120
FIGURE 14 ATMOSPHERIC C2H6 CONCENTRATIONS AT A CLEAN MARINE SITE
(LATITUDE 38.9°N)
The chlorine content of the northern hemispheric troposphere can be
calculated to be 2906 ppt. The contributions due to fluorocarbons and
chlorocarbons (nonf luorinated) were found to be 337o and 77% respectively.
The natural chlorine contribution due to CH-C1 alone was found to be about
257». These proportions do not differ significantly from the 1976 pro-
portions.
The northern hemisphere background of F12, Fll, CH CC1- and CC1,
increased at a yearly rate of 9, 11, 12, and 9 percent, respectively.
While emissions of F12 and Fll have been changing in the United States,
the growth rates do seem reasonable. The increase of 12% for CH.,CC1, is
somewhat lower than expected, while the 9% increase for CC1, is higher
than expected.
30
-------
URBAN-NONURBAN POLLUTANT RELATIONSHIPS
Sites 7 through 11 were monitored both from the viewpoint of obtaining
geochemical background levels, and also for generating urban-nonurban
relationships. The carcinogenicity and toxicity of many halocarbons
necessitate the determination of these relationships. Additionally,
urban data is a good indicator of the anthropogenic source of several
pollutants. These sources may be either primary or secondary.
Table 7 shows these relationships and provides a summary of data
obtained during the five field studies. We emphasize that the reliability
of Badger Pass (Site 9) may have been influenced by the very unfavorable
weather conditions caused by snowstorms. Table 7 shows the minimum,
maximum, and average concentration of pollutants at all sites. In addi-
tion, the standard derivations, number of data points, and the frequency
of detection are provided. Site 11 (Point Arena) was the cleanest
site monitored and should be most representative of background conditions.
Site 10 (Reese River) was a relatively clean continental site and Site 8
(Riverside) is most representative of an urban environment.
Table 7 contains a great deal of data that is self-explanatory.
While we defer more detailed discussions of the urban-nonurban relation-
ships for future reports and publications, a few quick observations can
be made:
• Maximum concentrations of F12 and Fll in urban areas remained
below 4 ppb. The average concentration of F12 and Fll were
less than five times their background levels.
• F21 was nearly always identified. Whether it is a true
atmospheric constituent, or an experimental artifact, could
not be conclusively established. At no time did the con-
centration of F21 exceed 23 ppt (Site 8); the average
concentrations did not exceed 10 ppt.
• Fll3 and F114 could be measured at their maximum concentra-
tions of 2.5 and 1.1 ppb, respectively. A clear urban source
for F113 and F114 was indicated.
• The average concentration of SFg did not exceed 1 ppt at
any of the sites monitored. At the urban site (Site 8),
however, levels as high as 9 ppt were encountered.
31
-------
URBAN-NOKl'RBAN POLLUTANT RKLATIONSHIPS
(Concentra tions of Attnosphcr ic Trace Const! tuents)
Compounds
(Concentration Units)
CCL.F, (ppt)
2 Z
CCl F (ppt)
CHCIF, (ppt)
2
CHCl.F (ppt)
CCl FCC1F2 (ppt)
CC1F CCIF (ppt)
SF (ppt)
CCL^ (ppt)
CHCl, (ppt)
J
[ CH2«2 (Pft)
CH Cl (ppt)
CH 1 (ppt)
CHjBr (ppt)
i
j C Cl (ppt)
1 * **
CH CCl (ppt) :
;
1
CH.BrCII Br (ppC)
2 2
Mill Valley , UC Riverside Badger Pass : Reese River
Site 7 Silo 8 ; Site 9 ! Site 10
Max* 672.7 ."C* 121 | Max 2,870.0 N 69 iMax 476.1 N 55 Max 337.9 N 45
Mir. 214.1 f 1.0
Av* 329.8 (106.0)'
Max 325.4 N 141
Mtn 198.2 £ 1.0 Min 191.8 f 1.0
Av 503.9 (401.0) ;Av 266.2 (29.3)
Max 3,300.0 N 93 Max 338.1 N 79
Min 132.0 f 1.0 Min 122.1 £ 1.0
Av 186.9 (32.2)
Av 505.5 (494.7)
Max 30 N Max N
Min 20 £ Min -- f
Av
Av
Max N 1 Max 22.9 N 48
Min -- £ Hin 4.3 £ 1.0
Av
Av 9.3 (2.9)
Max 180.7 N 261 ! Max 1,144.0 N 43
.Min 13.0 £ 1.0 Min 19.7 £ 1.0
Av 40.8 (27.3) j Av 98.9 (166.0)
Max 21.1 N 15 ' Max 212.3 N 17
Min 8.9 f 1.0 | Min 6.4 f 1.0
Av 13.7 (4.0) ! Av 52.7 (56.2)
Max 0.46 N 7
Min 0.36 £ 1.0
Av 0.39 (0.03)
Max 8.5 N 74
Min 0.3 I 1.0
Av 0.9 (1.4)
Mix 185.8 y 153 Max 199.1 H 8
Min 101.8 f 1.0
Min 79.6 E 1.0
Av 149.0 (41.6)
Max N
Min -- £
Av
Max 12.4 N 45
Mtn 0.3 £ 1.0
Av 8.1 (2.8)
Max 255.0 K 120
Min 13.1 £ 1.0
Av 26.5 (23.2)
Max 15.2 N 14
Hin 3.1 f t.O
Av 8.5 (3.5)
Max 1.60 N 44
Min 0.19 f 1.0
Av 0.40 (0.39)
Min 185.7 f 1.0
Av 239.4 (32.7)
Max 233.5 N 34
Min 117.6 £ 1.0
Av 144.7 (19.0)
Max N
Min -- £
Av
Max 11.3 N 49
Min 0.5 f 1.0
Av 8.5 (2.1)
Max 59.8 N 79
Min 4.2 f 1.0
Av 19.0 (7.1)
Max 15.4 N 28
Min 3.0 £ 1.0
Av 9.4 (4.1)
Max 0.55 N 33
Mtn 0.26 f 1.0
Av 0.32 (0.06)
Max 226.4 N 58 Max 191.1 N 79
Min 98.8 f 1.0 Min 86.6 f 1.0 Min 91.7 £ 1.0
Av 131.9 (11.2) Av 144.3 (30.5) i Av 124.5 (31.0) Av 126.3 (18.8)
j '
Max 36.3 N 66 ; Max 310.0 N 12 IMax 38.2 N 36
Max 19.1 N 29
Min 4.4 f 1.0 Min 24.0 £ 1.0 Min 2.4 £ 1.0 Min 5.9 f 1.0
Av 25.5(5.3) Av 67.0(73.9) Av 15.6(8.1) j Av 12.7(4.1)
Max 86.6 N 14 Max 473.4 N 20 ,Max 126.0 N 48 j Max 98.7 N 24
Min 38.0 f 1.0
Min 33.1 f l.OlMin 8.8 £ l.OlMin 14.7 £ 1.0
Av 54.6 (14.5) Av 110.6 (94.4) i Av 44.5 (25.0) j Av 51.5 (21.6)
Max 1,319.5 N 136
Min 391.5 f 1.0
Max 3,811.0 N 46 'Max 1,522.1 N 33
Min 566.1 f 1.0'Min 313.1 f 1.0
Av 730.3 (191.4) Av 1,487.5 (731.8) Av 724.9 (261.2)
Max 23.0 N 3'.' Max 25.7 N 36 .Max < 1 N 40
Min 0.3 f 1.0
Av 6.7 (6.5)
Min 1.0 f 1.0. Min < 1 f 0.0
Av 10.4 (5.9) |Av < I
Max 1,136.0 N 50
Min 402.0 £ 1.0
Av 692.5 (177.6)
Max < 1 N 34
Min < 1 f 0.0
Av < 1
Point Arena
Site 11
Max 272.2 N 47
Min 179.8 f 1.0
Av 220.4 (19.8)
Max 201.5 N 73
Min 98.5 f 1.0
Av 126.5 (12.4)
Max N
Min -- £
Av
Max 8.3 N 42
Mtn 0.4 £ 1.0
Av 5.0 (1.9)
Max 41.7 K 34
Min 14.2 £ 1.0
Av 22.6 (4.8)
Max 22.6 N 41
Min 3.3 £ 1.0
Av 11.9 (5.2)
Max 0.34 N 32
Min 0.16 £ 1.0
Av 0.27 (0.04)
Max 142.6 N 72
Min 106.0 f 1.0
Av 123.6 (8.3)
Max 41.8 N 58
Min 8.2 f 1.0
Av 20.0 (5.1)
Max 102.4 N 39
Mtn 16.0 £ 1.0
Av 44.8 (21.5)
Max 1,212.8 N 39
Min 497.7 f 1.0
Av 733.4 (134.1)
Max 16.1 N 42
Min 2.1 f 1.0
Av 4.8 (2.9)
Max 33.6 N 14 Max 176.6 N 26 |Max 29.5 N 40 | Max 10.1 N 34 ' Max 32.1 N 35
Min 14.8 f 1.0
Av 23.8 (6.0)
Min 7.4 £ l.OlMin 2.5 £ 1.01 Min 2.4 f l.Oi Min 11.4 f 1.0
Av 45.5 (39.8) !AV 7.9 (6.1) '. Av 5.2 (1.7) Av 20.1 (4.2)
i
Max 12.0 N 22 Max 33.9 N 8 .Max 10.6 N 13 Max 7.9 N 14 Max 8.6 N 28
Min i.O f 1.0
Av 5.9 (1.6)
Max 894.6 N 109
Min 107.1 f 1.0
Av 312.6 (129.0)
Min 5.3 f 1.0= Kin 1.9 £ 1.0 Min 4.2 f 1.0 Min 3.2 f 1.01
Av 17.3 (9.8) -AV 6.2 (3.1) Av 5.4 (0.9) Av 6.8 (1.4)
Max 3,012.0 X 40 :Hax 341.6 N 51
Min 282.4 f l.OjMln 130.3 f 1.0
Max 177.7 N 26 Max 150.3 N 36
Min 84.1 f 1.0 Min 82.6 f 1.0
Av 834.4 (360.3) :A» 229.2 (56.0) . Av 142.5 (21.9) Av 110.7 (18.0)
Max 22.8 K 11 ; Max 92.5 K 24 !Max <4 N 13 • Max <4 N Max 6.5 N 28
Hin 5.2 f 1.0
Av 10.5 (4.7)
Min 4.3 f l.OiMtn <4 f O.OlMin <4 f Min 4.0 £0.39
Av 23.1 (13.6)
Av < 4 Av < 4 Av 5.4 (0.7)
-------
Table 7 (Concluded)
Compound s
I (Concentration Units)
c Cl (ppt) :M»
• 2 4 Min
Av •
C.KCl, (ppO ' Max
23 ' Min
Av
COCl. (ppt) i Max
| Mln
j Av
NO (ppb)
250 N -Max 10,103.0 N 14 1 Max
250 f Min 3,173.0 f 1.0 1 Min
250 ! Av 5,951.1 (1,679.5) Av
(10"12 v/v); ppb - parts per billion (10~9 v/v) ; ppa «
Badger fa3S
Site 9
39.3
22.2
28.5 (4.6)
15.7
10.4
12.5 (1.3)
19.8
7.8
13.1 (4.0)
487.3
265.8
315.3 (39.7)
2.8
0
1.2 (0.9)
..
238.0
47.6
139.0 (63.0)
98.0
24.5
57.2 (23.3)
54.1
36.8
46.4 (3.0)
--
..
900.0
101.0
323.0 (170.2)
7,581.0
1,197.0
2,990.5 (1,152.
6,992.0
< 250
488.4 (1,215.
;
N 63
£ 1.0
N 20
f 1.0
N 11
I 1.0
N 31
f 1.0
Max
Min
Av
Max
Min
Av
Max
Mln
Av
Max
Min
Av
N 153 Max
f 0.32 j Min
N 7
f 1.0
N 9
f 1.0
N 153
£ 1.0
N 92
f 0.41
N 92
f 1.0
2)
N 92
f 0.33
5)
Av
Max
Hln
Av
Max
Min
Av
Max
Min
Av
Max
Min
Av
Max
Min
Av
Max
Min
Av
Max
Min
Av
Max
Hin
Av
Max
Min
Av
Reese River
Site 10
38.8
22.4
31.8 (3.1)
16.0
6.4
11.9 (2.4)
27.6
2.4
13.7 (7.3)
358.7
263.3
306.2 (22.3)
8.0
0
2.5 (1.5)
1.2
0
0.5 (0.3)
262.5
24.5
110. 1 (55.3)
87.5
17.5
40.2 (16.5)
55.6
10.3
38.3 (9.7)
328.0
108.0
147.8 (28.0)
2,020.0
1,446.7
1,656.3 (157.3)
< 400
- 400
< 400
4,257.9
929.1
2,259.6 (506.6)
1,140.0
< 250
295.1 (175.6)
N 48
£ 1.0
N 23
f 1.0
N 28
f 1.0
N 33
£ 1.0
H 96
f 0.86
N 96
f 0.40
N 56
f 1.0
N 41
f 1.0
N 96
f 1.0
N 88
f 1.0
N 88
f 1.0
N 73
£ 0.0
N 73
f 1.0
N 73
f 0.40
Max
Min
Av
Max
Mln
Av
Max
Min
Av
Max
Mln
Av
Max
Mln
Av
Max
Mln
Av
Max
Mln
Av
Max
Mln
Av
Max
Mln
Av
Max
Mln
Av
Max
Mln
Av
Max
Mln
Av
Max
Min
Av
Max
Min
Av
Point Arena
Site 11
47.8
18.0
33.4 (4.8)
12.4
10.1
11.5 (0.6)
23.7
9.2
15.5 (4.3)
337.9
297.3
314.8 (11.5)
5.5
0
2.2 (1.6)
15.3
1.5
3.8 (2.2)
--
45.3
20.8
34.9 (5.3)
144.0
89.3
118.8 (13.8)
1,513.3
1,440.0
1,479.2 (19.1)
< 400
< 400
< 400
2,503.5
1,368.0
1,923.7 (324.0)
714.4
< 250
433.8 (163.7)
N
f
N
f
N
f
N
f
N
f
N
£
N
£
N
f
N
£
S
£
N
£
N
£
H
f
N
f
53
1.0
15
1.0
21
1.0
31
1.0
117
0.35
117
1.0
115
1.0
114
1.0
115
1.0
87
0.0
87
1.0
87
0.15
parts per million (10* v/v).
OJ
Maxiauna concentration.
Minimua concentration.
Average concentration.
Standard deviation.
A*
Nuxber of data points or number of hours for continuous Instrumentation (NO,
'Frequency of detection.
> CO,
-------
Values of CC1, at Mill Valley (Site 7, downwind of San
Francisco) and Riverside (Site 8) were found to be higher
than at the clean background locations. This is consistent
with our earlier view that CCl^ is predominantly an
anthropogenic pollutant and is still emitted in relatively
significant quantities (Singh et al., 1976, Altshuller,
1976). Figure 15 clearly shows CCl^ levels increasing
with corresponding Fll levels based on the data taken by
EPA in the northeast. Thus, the urban sources of CCl^
are not limited to any special geographical regions. The
maximum concentration of CCl^ as measured by us did not
exceed 0.3 ppb.
800
JULY 18 Fll
•— JULY 18 CCI4
-— JULY 31 Fll
-— JULY 31 CCU
100
15 17 19 21 23
FIGURE 15 IDENTICAL CCI3F AND CCI4 BEHAVIOR AS AN INDICATOR OF A COMMON
URBAN SOURCE IN THE EASTERN UNITED STATES
Concentrations of CHC1.J and Ct^C^ did not exceed 0.5 ppb.
It seems CH^Cl finds significant usage, and at Site 8,
CH3C1 levels were found to be about twice the background
levels.
CH^I has probably no anthropogenic sources, but CHUBr
levels up to 0.2 ppb indicate urban contamination. This
is consistent with our first year findings when CHoBr
levels up to 210 ppt were measured in Los Angeles. The
-------
average value of 46 ppt at Riverside can be compared with a
concentration of 108 ppt measured by us in Los Angeles
(Singh et al., 1976).
^2^1^ levels did not exceed 45 ppt at any of the sites
monitored. The average concentration at Riverside, however,
was about three times the background levels and an urban
source is suggested.
is a commonly used degreasing solvent and its con-
centration always remained below 3.1 ppb. Its average
concentration of 0.8 ppb at Riverside is about eight times
its background levels.
• CH2BrCH2Br was measured at concentrations not exceeding 0.1
ppb. The average urban concentration at Site 8, however,
was about five times the expected background concentrations.
This is consistent with an urban source of
which is known to be automobiles.
• C_C1, and C-HClo did not exceed concentrations of 2.5 and
0.5 ppb, respectively. The average urban levels of C,2^L
and 02^3, however, were 30 and 22 times the background
levels, respectively.
• Phosgene at levels somewhat higher than 0.1 ppb was
measured. The urban levels (Site 8) were a factor of 3
higher than the background concentrations. The average
COClo concentrations at Riverside of 47 ppt was higher than
the 1976 average value of 32 ppt measured in Los Angeles.
This is probably because of the downwind nature of Site 8,
which permits additional photooxidation of chloroethylene
precursors.
• While ^2° was found to be distributed quite uniformly, urban
levels as high as 1.6 ppm were measured. This is at variance
with our earlier observations in Los Angeles where no sig-
nificant N£O intrusions were observed. Contamination from
sources in the immediate vicinity is indicated.
• NO and N0~ levels did not exceed 87 p.pb and 61 ppb, respec-
tively (Site 8).
• PAN and PPN levels did not exceed 6 ppb and 2 ppb, respec-
tively. The average PAN/PPN ratio in Riverside was found
to be about 5. In cleaner atmospheres, this ratio is
reduced to about 2.5.
• Oo levels did not exceed 125 ppb at any location monitored.
At relatively clean locations the maximum 1-hour, On valve
was between 45 and 55 ppb. These levels suggest geographic
uniformity of Oo levels in clean atmospheres.
• CO levels up to 2.6 ppm (hourly average) were measured at
Site 8.
35
-------
C2H2, C2H£, and 03113 maximum concentrations of 2.0 ppm,
9 ppb, 15 ppb, and 10 ppb, respectively, were measured. CH^
levels in Riverside at least for some time dipped to 1.1 ppm,
which is below the background level. No instrumental problems
could be found. It is likely that a plume with CH, concentra-
tions lower than the background passed over the area.
LIMITED OCEAN WATER ANALYSIS FOR N20
Ocean water samples from depths of 0, 50, 100, 150, 200, 250, and
300 m were obtained from the north Pacific. These samples were collected
by the U.S. Coast Guard and analyzed at SRI for N?0. A total of 28 samples
were analyzed from two locations (41035'N-125055'W and 45057'N-125025'W).
The corresponding water temperature was also available. The water samples
were analyzed at 22°C and the N_0 concentrations were corrected then for
temperature.
Figure 16 clearly shows the ocean denitrification zone below 100 m
where N~0 is synthesized, and an average saturation approaching 325% was
observed. The surface water supersaturation between these latitudes
(42-46°N) was about 227«. Using a simplified film diffusion model and an
average N_0 atmospheric concentration of 300 ppb, an average flux of
-12 2
0.326 X 10 g/cm -s can be calculated. This compares favorably with
-12 2
estimates of Hahn of 0.22 - 0.47 X 10 g/cm -s in the Pacific. Our
flux estimate, if extended globally, results in an average N,0 flux of
12
37 X 10 g/year from the marine sources.
It is possible to estimate the N«0 lifetime from this marine source
12
alone. A flux of 37 X 10 g/year and a uniform steady state N?0 con-
centration of 300 ppb correspond to a 62-year lifetime. Should addi-
tional sources of N^O exist, the calculated lifetime will be lower than
62 years.
Additional data will be obtained during subsequent months of the
second year effort to define the source capacity of the ocean for N_0
and some chlorinated species (e.g., CH-C1) more accurately.
36
-------
100
150
PERCENT SATURATION*
200 250 300
350
400
50
100
150
a.
HI
a
200
250
300
T
T
T
T
AVERAGE
SATURATION
•Percent Saturation is the NjO Concentration in sea water
relative to the N2O Concentration that is in equilibrium with
an atmospheric N-O Concentration of 300 ppb at the water
sample temperature.
x a
A RUN 1
• RUN 2
D RUN 3
X RUN 4
28 October 1976
(41° 35'N - 125°55'W)
29 October 1976
(45° 35'N - 125°55'W)
O X -
I I I I
I I I I
A
I I
0.2
0.4
0.6
0.8
1.0
1.2
N2O CONCENTRATION IN SEA WATER —
1.4 1.6
SA-4487-7
FIGURE 16 N20 PROFILE IN THE PACIFIC OCEAN
PRELIMINARY TESTING FOR THE PRESENCE OF CHLOROACETYL CHLORIDES
The two major products of the photochemical oxidation of chloroeth-
ylenes are likely to be phosgene and chloroacetyl chlorides. While the
former has been measured (Singh, 1976), methods for the measurement of
low levels of chloroacetyl chlorides are not available currently. An
indirect method therefore was employed to test for the existence of tri-
chlororoacetyl chloride in the atmosphere. The method was based on two
fundamental observations:
37
-------
• A gas chromatographic column packing (DC-200) catalytically
decomposed CC1-COC1 to CC1, .
• CC1 COC1 is extremely soluble in water.
Thus an experiment was devised in which ambient air was passed continuously
through a column of water and the air was analyzed for CC1, at the inlet
and the outlet of the water column. The difference in the CC1, concen-
• ' 4
trations would be representative of the CC^COCl concentration in the
atmosphere. Figure 17 shows the results of these preliminary experiments.
1.0
0.9
R 0.8
0.7
0.6
I I
t
R = Ratio of the CCI4 response in ambient air at the
outlet and inlet of a water column.
• Reese River (Site 10)
• U.C. - Riverside (Site 8)
Effect of Relative humidity <0.5%
I
100 200
AIR FLOW — time (mini
I
300 400
SA-4487-8
FIGURE 17 CCI4 LOSS IN AMBIENT AIR WHEN PASSED THROUGH A COLUMN OF WATER
38
-------
It was found that indeed the air emerging from the water column (100 ml of
water; air flow rate = 250 ml/min) was deficient in CC1,. This could mean
two things:
• CC1/ itself is lost to water and therefore may find a sink
in rain-out processes.
• There are trichloroacetyl chlorides present in the air.
The fact that a greater loss of CC14 is observed at Riverside (Site 8)
than at the cleaner Reese River location (Site 10) would tend to support
the presence of CC1-COC1 at least in the urban environs. Indeed, both
of the above possibilities may be true. Additional experiments are
required to further refine these preliminary observations.
39
-------
HALOCARBON LIFETIMES AND THEIR GLOBAL BALANCE
HALOCARBON LIFETIMES
Data were analyzed primarily to determine the lifetimes of halocarbons
and to relate them to laboratory and modeling studies. In order to accom-
plish this, a tropospheric budget model was developed. The rate of in-
crease of the pollutant mass in the atmosphere is given by
dM M
J_ ,. f -^ i.
where M. is the accumulative mass in the troposphere of component i,
f.(t) is input as a function of time of component i, and T. is the e-fold
lifetime of component i. When t = 0, M. = 0. (Note: The year 1920 is
taken to be t = 0.)
The pattern of emissions for most halocarbons is best described by
an exponential growth function. This choice is not arbitrary and is
confirmed by emissions data:
fi(t) = a± exp(b.,t) (4)
A\A J^
- = a. expfb.t) - ~ (5)
: i \ i / T
dt
The above equation is easily solved,
Vi
M = =—=-
i - - -
\
Amount present in the
atmosphere at time tf M.
i -i\
i Amount actually added
up to time
added ftf
ci fl
J n
(t)
40*
-------
From Equations (4), (6), and (7), one can derive
b.T. exp(b.tf) - exp(-tf/Ti)
i b.T. + 1 exp
For all compounds of interest here, exp (b.tf) » 1 and
exp{-
« 1
Simplifying and rearranging equation (8),
Equation (9) is always valid even if the atmosphere is significantly
unmixed. The prime reason for deriving this budget model is that the
fractional conversion of a first-order reaction is independent of initial
concentrations, and therefore Equation (9) is independent of the mixing
processes. This is an important consideration in the development of this
model. For species such as CH«CC1_, it implies the use of a seasonally
averaged HO concentration. For inert reactants such as Fll (F stands for
f luorocarbon) , it implies an overall empirical first-order loss and is not
representative of a given mechanistic scheme. Equation (9) gives almost
identical results for Fll when verified against the 1-D model of Rowland
and Molina (1976). Table 8 shows the northern hemispheric background
concentrations measured by us and the interhemispheric gradients as
obtained from available data. Table 9 shows the detailed calculations
of atmospheric residence times of several species.
The residence times of F12 and Fll (Table 10) are consistent with
models that suggest no or insignificant tropospheric sinks. The longer
lifetimes of tropospherically reactive species are inconsistent with the
existing knowledge of atmospheric chemistry. Our conservative analysis of
atmospheric halocarbon data shows that average HO concentrations must be
2 to 6 X 10 HO/ml instead of the accepted range of 10 to 30 X 10 HO/ml.
These lower HO values tend to resolve the apparent discrepancies in the
biospheric budgets and distribution of chlorinated hydrocarbons and CO.
41
-------
Table 8
HALOCARBONS, SF6> and N2
IN THE LOWER TROPOSPHERE
Compounds
CC12F2(F12)
CC13F(F11)
**
CHC12F(F21)
CC12FCC1F2(F113)
SF6
CC14
CHC13
CH3C1
CH3I
CH3Br
CH3CC13
CC12CC12
CHC1CC12
COC12
N20
Major
Sources
A
A
A
A
A
A
A
N
N
N
A
A
A
SA
N
Average Northern
Hemispheric Background
Concentrations ,*
ppt (I0'12v/v)
Monitoring Period
5/12/T6 - 5/17/76
203. 5f (18.5)*
115.6 (5.0)
lit. 2 (It. 9)
19.9 (3.»0
0.2k (0.01+)
113.9 (6.5)
17.1 (2.7)
713.0 (51.1)
9.2 (U.6)
U.7 (2.6)
98.8 (9.7)
30.7 (10.5)
15.6 (2.5)
21.7 (5.2)
311.6 x 103
(18.0 x 103)
Ratio of Average
Southern and
Northern Hemispheric
Concentrations^
0.89
0.89
—
—
—
0.95
<0.1l'
—
—
—
0.1+2
—
0.10
—
1.00
N = Natural, A = Anthropogenic, SA = Secondary Anthropogenic
"Site Location: lat 37°39', long 119°UO'; elevation 2360 m
t
Mean of all data points collected
Standard deviation
From Cox et al. (1976) and Rasmussen et al. (1976); also see text
Preliminary data
42
-------
Table 9
HALOCARBON RESIDENCE TIMES AND AVERAGE
HYDROXYL RADICAL CONCENTRATIONS
F12
Fll
CH3CC13**
**
CHC13
(Years-1)
0.1230
0.1350
0.1050
0.1211*
0 0970
Emissions
up to May 1976
in Million Tons
(ppt)*
1*.6 (222)
3.1 (131)
3.7 (162)
1.1 (52)
11 7 (1*10)
Measured
Atmospheric
(ppt)
3.9 ± 0.35* (192 ± 17.1*)
2.5 ± 0.11 (109 ± k-7)
1.5 ± Q.15 (70 ± 6.9)
0.2 ± 0.03 (9 ± I.1*)
0 5 + 0 17 (16 +55)
Fraction
•i - -i
0.86 ± 0.08
0.63 ± 0.03
0.1*3 ± G.Ol*
0.17 ± 0.03
0 0^ + n C1
Residence
Time
?i ± ATi
(Years)
50 ± 33
36 : ?
7.2 ± 1.2
Hate Constants vith H0,k265
(265°K)
Davis (1976) Kaufman (1976)
—
5.31 x io"15 1.25 x 10"11*
c.27 x io~lu 9.25 x 10"11*
HO
/, .c molecule s\
I1" =1 j
—
5.1(±0.9) ' - 3.3(±0.c) "
* •'
3.o(±o.")T - z.oUo.s)'
ppt is calculated by uniformly distributing the emissions in tr.e troposphere
^
standard deviation
from rate constants determined by Eavis (frcn Chang and Wuebble, l?7c)
from rate constants determined by Kaufman (unpublished data, 19"t)
while emissions data for CH3CC13 is quite accurate, CHClj emissions may be in dispute
-------
Table 10
RESIDENCE TIMES OF IMPORTANT HALOCARBONS
Compounds
Residence Times
(years)
Fluorocarbon-12 (CC1 Fj
Fluorocarbon-11 (CC1 F)
Methyl chloroform (CH CC1 )
Chloroform (CHC13)
Tetrachloroethylene (C2C1.)
50.0 ± 33.0
36.0 ± 8.0
7.2 ± 1.2
1.7 ± 0.4
0.4 ± 0.1
ESTIMATION OF HO RADICAL ABUNDANCE IN THE NORTHERN
AND SOUTHERN HEMISPHERES
In the previous section we determined the average atmospheric residence
times of several halocarbons. In this section, we shall concentrate on
the global budget and hemispheric distribution of CH_CC1~ to determine the
HO abundance in the northern hemisphere (N.H.) and the southern hemisphere
(S.H.).
The uniqueness of CH_CC13 as an indicator of HO abundance stems from
two major considerations:
• Sources are entirely man-made and reliable emissions data
are available.
• Reaction with HO is the major removal mechanism and the
rate constant is accurately known (NASA, 1977), rela-
tively fast, and not strongly dependent on temperature
[k = 3.5 X 1012 exp (-1562/T) ml/mol/s]; and CH3CC13 is
easy to measure and a relatively reliable global data
base is available.
The average N.H. concentration of CH-CCl., has been measured by
several investigators (Singh et al., 1977; Cronn et al., 1976; Lovelock,
1977).
May 19
tion of 91 ppt based on the lower 50% of the data. Cronn has conducted
Singh has reported an average lower tropospheric concentration in
-12
May 1976 of 99 ppt (10 v/v) based on all of the data and a concentra-
44
-------
aircraft measurements at several altitudes within the troposphere and
reported an average tropospheric concentration of 95 ppt. A 5% to 10?0
vertical concentration gradient at the surface and near tropopause alti-
tudes was also observed. Lovelock has reported a N.H. concentration of
about 90 ppt in early 1976. Thus, the N.H. CH-CCl- background concentra-
tion ranges from 89 to 90 ppt in May 1976. Because of some vertical
gradients, the true background of CH.,CC1 is probably closer to 90 ppt.
In our present calculations, a lower and upper range of 89 and 99 ppt were
considered. Subsequent calculations will be based on a N.H. background
concentration of 89 ppt, unless otherwise stated. We may add that the
case for reduced HO levels, as well as for a larger HO gradient between
the N.H. and the S.H., is made even more strongly if one considers the
upper limit of the background concentration (99 ppt in May 1976). The
use of 89 ppt (lower limit), in our opinion, is both more reliable and
also conservative.
The S.H. data are limited but a north/south concentration ratio of
1.43 has been reported by Rasmussen (1976) from S.H. data collected in
New Zealand and at the South Pole. This is at variance with the data
reported by Lovelock (1977), who reports a north/south ratio of about 2.
Because of the consistent use of internal standards and reliable inter-
calibrations with our data, we believe that Rasmussen's data for the southern
hemisphere are probably reliable. Also, we find that the growth of atmo-
spheric C^CCl^, as reported by Lovelock, is more rapid than the emissions
data would allow. Hence we shall consider the data reported by Rasmussen
for the present study but add that a larger ratio, as reported by Lovelock,
only enhances the HO differences between the two hemispheres. The cal-
culations reported here are therefore kept conservative by considering
a north/south ratio of 1.43 to 1.53.
The growth of CH_CC1« emissions has been nearly exponential since at
least 1957. Figure 18 shows the most recent global emission inventory
of CH-CC1., since 1951 (private communication of J. Plonka--Dow Chemicals).
The growth prior to 1957 does not fit the prescribed exponential pattern,
but the errors due to this deviation are minimal since both simulated and
actual emissions prior to 1957 are less than 3% of the total emissions.
45
-------
103
UO
0.1
CH3CCB3 WORLDWIDE EMISSIONS
GROWTH RATE, b = 0.166/YEAR
SIMULATE EMISSION RATE (103 TONS/YER),
E = 1.391 EXP [0.166 (YEAR - 1940)]
1950
1955
1960
1965
1970
1975
1980
FIGURE 18 GLOBAL EMISSIONS OF METHYL CHLOROFORM
The line in Figure 18 shows an exponential growth rate (b) of 0.166/yr.
The emissions up to May 1976 add up to 3.0 million tons of CH-jCCl-j
released. The simulated growth rate (thousand tons/year) can be described
as 1.391 exp[0.166 (year-1940) ] .
If N and S are the cumulative masses and T and T are the residence
n s
times (years) of CH.,CC13 in the N.H. and the S.H. , respectively, then
-------
dN ,_, N (N - S) ,.-.
— = a.exp(bt) - — - *— ^ - L (10)
n e
4i _S_ x (N - S)
dt = " T + T
s e
where T is the interhemispheric exchange rate and the function a.exp(bt)
e
represents the time-varying emissions of CH-CC1., in the N.H. The S.H.
CH-CCl., emissions are not included in Equation (11) because they are
expected to be less than 5% of N.H. emission. Assuming N = S = 0 at t = 0,
Equations (10) and (11) can be easily solved to give
(12)
.,„ +*
and
amount of CH-CC1- present
R = = b
cumulative CH-CC1, emissions
4 *!)
where D = I/[T (b - Qf)(b - P) ] and a and P are roots of the equation
v nT TTITTTTTT
\ e s n/ en es ns
The average global residence time T is defined as
3.
, . [1 + (N/S)]
T =
a l/T + l/ (N/S)
The interhemispheric exchange rate (T ) is known from past tracer
and meteorological studies. Using a number of tracers, L. Machta from
NOAA (personal communication) concludes that the most reliable estimate
for T is 14 to 17 months, with 14 months as perhaps the optimum choice.
This is also consistent with the fluorocarbon-11 (Fll) data of Krey
(Committee on Aeronautical and Space Sciences, 1976) taken in 1974, a
time when Fll emissions had not been perturbed significantly. From
Krey's Fll measurements, N/S = 1.20, and knowing b = 0.14/yr (1969-1974),
and T = 30 to 75 years for Fll (Singh, 1977; NAS, 1976), Equation (12)
S
can be used to calculate T [= (N/S - l)/(b + 1/T ) ] of about 14 to 16
6 S
47
-------
months. Rasmussen's 1976 data show N/S tor Fll of 1.13, but it is not
possible to calculate T because perturbation in Fll emissions had
cJ
already taken place. If one considers that these perturbations resulted
in a reduction of Fll emissions (lower b), then a value of 14-16 months
for T is not in disagreement with this Fll data. For the present calcu-
lations, Machta's estimates for T of 14-17 months will be used and 14
months will be considered the optimum T value. While 17 months is
probably the accepted upper limit for T , values somewhat lower than 14
months have also been suggested. Newell et al. (1969) has calculated a
T of 11 months from exclusively meteorological considerations. This
estimate may be low because Hadley cells may return to the original
hemisphere without accomplishing complete mixing with the other hemisphere.
Additionally, we wish to add that the HO gradient would be even larger
for lower values of T . Thus a range of 14-17 months of T is both
e e
reliable and conservative.
RESULTS AND DISCUSSION
Given the known values of N/S, R, T , and b, we can use Equations
(12), (13), and (15) to calculate T , T , and T . The results are
s n. 3.
plotted in Figure 19, which clearly shows that T is quite insensitive to
cl
all parameters under consideration. Using the lower and upper bounds of
measurements (99 and 89 ppt in the N.H., respectively), we calculate an
average residence time of eight and 10 years, respectively. We believe
eight years is the most reliable estimate of the average global CH,CC1_
residence time. Reasonable projections for future release rates of
CH-CCl,, and a T of eight years lead to a steady state stratospheric 0«
3 3 3L j
destruction that is about 2070 as large as those resulting from continuous
release of Fll and F12 at the 1973 rate (private communication of
J. McConnel--York University).
As is also clear from Figure 19, for all cases under consideration
T > T . The variation in calculated values of T and T . however, is
n s n s '
sensitive to both the N/S ratio and T . For the optimum case of
N/S = 1.43, Te = 14 months, we get Tn = 15 years and Tg = 5 years. Larger
48
-------
I I I
TO = INTERHEMISPHERIC EXCHANGE RATE
re (months)
36
34
32
30
28
26
24
CH3CC63 RESIDENCE TIME IN THE N.H.
CH3CCfi3 RESIDENCE TIME IN THE S.H.
GLOBAL AVERAGE RESIDENCE TIME OF
CH3CC63
1.43
1.45
1.47
1.49
1.51
N/S-
15
16
17
ra (upper limit)
ra (lower and
optimum limit)
TB (months)
I 17
fTs 16
" 15
14
1.53
FIGURE 19 METHYL CHLOROFORM RESIDENCE TIMES IN
THE NORTHERN AND SOUTHERN HEMISPHERES
49
-------
N/S ratios result in a much larger difference between T and T . Similarly
« n s
the upper limits of our tropospheric budget show a much larger difference
in T and T , and values of T less than 14 months accomplish the same.
n s' e
The 17-month upper limit of T brings about a closer agreement, in which
T = 1.3 T . For T > 20 months, which is unrealistic, no clear-cut case
n s e
of T > T can be made.
n s
Thus, while uncertainties remain and the present calculations cannot
be considered as final, nevertheless a strong case for T > T can be
IT S
made. Using the rate constant of CH_CC1~ + HO reaction at the weighted
average tropospheric temperature of 265°K (k = 9.64 x 10~" ml/mol/s),
we can calculate the HO burden from CCCl residence times. For the
optimum conditions (N/S = 1.43), the results are shown in Table 11. Thus
-T-uum C
we find that a global average HO (HO) concentration of about 4 X 10 HO/ml
Table 11
RESIDENCE TIMES OF CH3CC13 AND THE HO
ABUNDANCE, IN THE N.H. AND S.H.
(months)
14
15
16
(years)
15.0
12.2
10.4
(years)
5.0
5.6
6.4
(years)
8.3
8.3
8.3
HO/ml X 105
N.H.
2.1
2.6
3.1
S.H.
6.3
5.6
5.0
/N.H. + S.H.\
AvA 2 )
4.2
4.1
4.1
is consistent with the observational data. Table 11 also shows that for
reasonable estimates of T (14-16 months),
(HO)
+ (HO)
- = (HO) = 4.1 X
HO/ml
(16)
50
-------
(HO)
_ &'tt- = 1.6 to 3 (17)
(HO)N.H.
Although some differences in the N.H. and S.H. levels of HO are to
be expected because of natural differences in water vapor, ozone, and
particulate concentrations, a much larger difference can be attributed,
at least in part, to CO (a principal sink for HO), whose levels are three
times higher in the N.H. when compared with the S.H. (Seiler, 1974). The
HO asymmetries based on an analysis of the atmospheric abundance of
CH_CC1« are also in agreement with the present CH,—CO —H_ balance in the
troposphere (Crutzen and Fishman, 1977). If the additional CO in the N.H.
is because of man-made sources predominantly, as the current data seem to
suggest, continued release of CO has and will further reduce the HO levels,
thereby depleting the scavenging ability of the atmosphere. A switch to
fossil fuels in coming years is likely to cause more severe depletions in
the HO abundance. These HO losses will not only allow a larger strato-
spheric input of anthropogenic halocarbons and hydrocarbons but may
already have altered the stratospheric chemistry by permitting increased
intrusion of natural tropospheric species such as CH, and CH-C1. In
addition, continuous exponential growth of CH_CC1 at its present rates
is likely to be a cause of concern because of potential effects on the
stratospheric ozone. The effect may be further escalated in the future
as more and more nations substitute CH_CC1« to replace declining usage
of C_HC1_ and to some extent C Cl, (for toxicity and health reasons),
thereby causing extraordinary increases in CH-CC1., emissions.
51
-------
HALOCARBONS AND N_0 STANDARDS INTERCOMPARISON
Because halocarbons are relatively new pollutants present at very
low concentrations, the generation of primary standards is a difficult
and tedious task. At the same time, the needs are such that an extremely
high degree of accuracy is required. There are no agreed-upon sources
of primary standards. To test the uncertainties in measurements, identical
samples of air of unknown composition were analyzed by SRI and Washington
State University (WSU) independently. The results of this intercomparison
are shown in Table 12 and indicate reasonable agreement.
Table 12
ANALYSIS AND INTERCOMPARISON OF AN
IDENTICAL AIR SAMPLE BY SRI AND WSU
Compound
N20
F12
Fll
CH3CC13
cci4
Concentration (ppt)
SRI
312 x 103
224
124
106
122
WSU
329 x 103
250
150
104
150
52
-------
FUTURE PLANS
A great deal of field data was collected during Phase I of the
second year research effort. While the data has been processed, the
analysis is by no means complete. Additional analysis will appear in
subsequent reports and publications. In the immediate future, however,
the emphasis is shifting to a global monitoring program for the halocarbon
and hydrocarbon trace constituents. Four trips into the southern hemi-
sphere are planned. In three of the trips, samples will be collected at
several selected locations between 60°N and 60°S and analyzed at SRI.
Specially treated stainless steel and glass containers of one-liter size
will be used to collect air at 25 psi. Clean metal bellows pumps will be
used for pressurization. The fourth trip to the southern hemisphere will
be an oceanographic cruise from San Francisco to New Zeland. Air and ocean
water analysis will be conducted in situ during this cruise. Limited air
samples from the South Pole will be complemented with these data.
The main objective of the Phase II effort of the second year research
will be to understand interhemispheric variations and to collect more
extensive southern hemispheric data.
53
-------
REFERENCES
Altshuller, A. P., "Average Tropospheric Concentration of Carbontetra-
chloride Based on Industrial Production, Usage, and Emissions,"
Env. Science Tech.. Vol. 10, pp. 596-598 (1976).
Chang, J. S., and D. J. Wuebbles, "A Theoretical Model of Global Tropo-
spheric OH Distribution," Proceedings of the Nonurban Tropospheric
Composition Symposium, Hollywood, Florida, November 10-12, 1976.
Committee on Aeronautical and Space Sciences, Chlorofluorocarbon Effects
and Regulations, Hearing Before the U.S. Senate Subcommittee on the
Upper Atmosphere, 1976.
Cox, R. A., et al., "Photochemical Oxidation of Halocarbons in the
Troposphere," Atmospheric Environment, Vol. 10, pp. 305-308 (1976).
Cronn, D.A., et al., Measurement of Tropospheric Halocarbons by Gas
Chromatography-Mass Spectrometry, Washington State University,
Interim Report Submitted to EPA, Grant R-0804033, 1976.
Crutzen, P. J., and J. Fishman, "Average Concentration of OH in the
Northern Hemisphere Troposphere, and the Budgets of CH^, CO, and
H2," Geophvs. Res. Lett., in press, 1977.
Heidt, L.E., and W. H. Pallock, "Measurements of N20, CH^, H2, CO and
C02 in the Nonurban Troposphere," Proceedings of the Nonurban
Tropospheric Composition Symposium, Hollywood, Florida, November
10-12, 1976.
Lovelock, J. E., "Methyl Chloroform in the Troposphere as an Indicator
of OH Radical Abundance," Nature. 267, p. 32, 1977.
Linnebom, V. J., J. W. Swinnerton, and R. A. LaMontagne, "The Ocean as a
Source of Atmospheric Carbon Monoxide." JGR. Vol. 78, pp. 5333-5340
(1973).
NAS: Halocarbons, Effects on Stratospheric Ozone, Panel on Atmospheric
Chemistry, National Academy of Sciences, Washington, D.C., 1976.
NASA, Chlorofluoromethane Assessment Workshop Report, NASA Goddard Space
Flight Center, March 1977.
Newell, R. j et al., "Interhemispheric Mass Exchange from Meteorological
and Trace Substance Observations," Tellus. Vol. 21, pp. 641-647,
1969.
54
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Rasmussen, R. A., et al., "Trip Report on the Cruise of the Alpha Helix
Research Vessel," Washington State University, Pullman, Washington,
1976.
Rasmussen, R. A., Status of Washington State University's Interhemispheric
Halocarbon and Nitrous Oxide Measurements, JPL Publication 77-12,
International Problems Related to the Stratospheric, September 15-17,
1976.
Rowland, F. S., and M. J. Moliva, "Estimated Future Atmospheric Concen-
trations of CCl^ (Fluorocarbon-11) for Various Hypothetical Tropo-
spheric Removal Rates," J. Phys. Chem., Vol. 80, pp. 2049-2056
(1976).
Seiler, W., "The Cycle of Atmospheric CO," Tellus, Vol. 26, pp. 116-135,
1974.
Singh, H. B., et al., "Atmospheric Carbontetrachloride: Another Man-Made
Pollutant." Science. Vol. 192, pp. 1231-1234, 1976b.
Singh, H. B., et al., Atmospheric Fates of Halogenated Compounds—First
Year Summary Report, SRI Project 4487, Grant EPA-8038021, pp. 35,
1976a.
Singh, H. B., "Phosgene in the Ambient Air," Nature. Vol. 264, pp. 428-429,
1976.
Singh, H. B., "Atmospheric Halocarbons: Evidence in Favor of Reduced
Average Hydroxyl Radical Concentration in the Troposphere,"
Geophys. Res. Lett.. Vol. 4, pp. 101-104, 1977.
Singh, H. B., et al., "Urban-Nonurban Relationships of Halocarbons, SFg,
N20, and Other Atmospheric Trace Constituents," Atm. Env., in press
(1977a).
Singh, H. D., F. L. Ludwig, and W. B. Johnson, "Ozone in Clean Remote
Atmospheres: Concentrations and Variabilities," Final Report, SRI
Project 5661, Contract CAPA 15-76, SRI International (1977b).
Sze, N. D., "Anthropogenic CO Emissions: Implications for the Atmospheric
CO-OH-CH4 Cycle," Science. Vol. 195, pp. 673-675, 1977.
55
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LIST OF PUBLICATIONS
The following is a list of papers accepted for publication based
on the research efforts of the first year and portions of the second year:
• "Atmospheric Carbon Tetrachloride: Another Man-Made
Pollutant," Science. Vol. 192, p. 1231 (1976).
• "Phosgene in the Ambient Air," Nature. Vol. 264, p. 428
(1976).
"Generation of Accurate Halocarbon Primary Standards from
Permeation Tubes," Env. Sci. and Tech. . Vol. 11, p. 511
(1977).
••Distribution, Sources and Sinks of Atmospheric Halogenated
Compounds," J. Air Pollution Control Assoc., Vol. 27,
p. 332 (1977).
"Atmospheric Halocarbons: Evidence in Favor of Reduced
Average Hydroxyl Radical Concentrations in the Tropo-
sphere," Geophys. Res. Letters. Vol. 4, p. 101 (1977).
"Urban-Nonurban Relationships of Halocarbons, SFg,
and Other Atmospheric Trace Constituents," Atm. Env.,
in press (September 1977).
"Preliminary Estimation of Average Tropospheric HO
Concentrations in the Northern and Southern Hemispheres,"
Geophys. Res. Letters, in press (1977).
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/3-78-017
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
FATE OF HALOGENATED COMPOUNDS IN THE ATMOSPHERE
Interim Report -- 1977
5. REPORT DATE
January 1978
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Hanwant B. Singh, L.J. Salas, H, Shiegeishi, and
A.H. Smith
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Stanford Research Institute
Menlo Park, California 94025
10. PROGRAM ELEMENT NO.
1AA605 AI-02 CFY-771
11. CONTRACT/GRANT NO.
8038020
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Sciences Research Laboratory - RTP, NC
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Interim 7/76-7/77
14. SPONSORING AGENCY CODE
EPA/600/09
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The second year results involved air monitoring at five urban and nonurban
stations with the help of an instrumented environmental mobile laboratory. The
monitoring stations included urban, remote marine, remote continental, high
altitude and intermediate locations. In situ analysis was performed for a total
of 31 chemical species and six meteorological parameters. Of the 31 chemical species
sought, 19 were halogenated compounds, five were nitrogen containing species, and
the remaining seven included hydrocarbons, CO, and Oj,
Data suggest that the troposphere (northern hemisphere) contains 2906 ppt of
chlorine atoms. The chlorine contribution of fluorocarbons is 33% of the total
while that due exclusively to chlorocarbons is 77%. The natural chlorine con-
tribution due solely to CH^Cl is 25% of the total organic chlorine burden. The
burden of halocarbons in the troposphere is increasing when compared to background
data collected exactly a year ago.
Based on the budget and distribution of methyl chloroform and its emissions
inventory, a two-box model was used to develop the conclusion that average tropo-
spheric hydroxyl radical (OH) concentration was about 4 x 10^ HO/ml. This is
significantly lower than the hitherto accepted OH concentrations in the troposphere.
It was further found that there may be significant gradients in the northern and
southern hemispheric HO concentrations.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
* Air pollution
* Halohydrocarbons
* Chemical analysis
Troposphere
13B
07C
07D
04A
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
21. NO. OF PAGES
65
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
57
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