Ecological Research Series
OXYGEN ISOTOPES IN ATMOSPHERIC
SULFATES, SULFUR DIOXIDE,
AND WATER VAPORS
Field Measurements, July 1975
Environmental Sciences Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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EPA-600/3-78-045
April 1978
OXYGEN ISOTOPES IN ATMOSPHERIC SULFATES, SULFUR
Field Measurements, July 1975
by
B. Holt, M. Bouchard, P. Cunningham, A. Engelkemeir,
E. Nielsen, S. Johnson, and R. Kumar
Argonne National Laboratory
Argonne, Illinois 60439
IAG-D6-F024
Project Officer
Jack L. Durham
Atmospheric Chemistry and Physics Division
Environmental Sciences Research Laboratory
Research Triangle Park, North Carolina 27711
ENVIRONMENTAL SCIENCES RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
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DISCLAIMER
This report has been reviewed by the Environmental Sciences Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. 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
Oxygen isotope ratios were determined for atmospheric samples of
sulfate aerosols, sulfur dioxide, and water vapor collected simultaneously
during a six-day period in July, 1975, at St. Louis, MO; Auburn, IL; and
Glasgow, IL. The collection sites were located about 100 km apart.
Concerted variations in isotopic and concentration results were found
for the three sites, demonstrating an apparent regional impact on the
quality and quantity of particulate sulfate in the atmosphere. At all
three sites, the oxygen-18 enrichments in suspended sulfates clearly varied
inversely with sulfate concentration. This variation suggests that sulfates
in cleaner air may have a different origin than sulfates in more polluted
air masses. Samples collected during a period of local thunderstorm
activity showed an abrupt increase in the oxygen-18 composition of particu-
late sulfate, but little effect on the isotopic composition of ambient
water vapor.
The lack of positive correlation between oxygen-18 variations in
aerosol sulfate and oxygen-18 variations in water vapor suggests that the
aerosol sulfate was not formed predominantly from the ambient water in the
air masses from which it was sampled.
This report was submitted in fulfillment of Interagency Agreement No.
EPA-IAG-D6-F024 by Argonne National Laboratory. This work covers the
period May 1976 to May 1977. The work was completed as of May 31, 1977.
iii
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CONTENTS
Abstract ill
Figures vi
Tables vii
1. Introduction 1
2. Conclusions 4
3. Recommendations 5
4. Experimental Procedures 6
Sample Collection 6
Sample Analysis 6
5. Results r~ 7
6. Discussion 20
Observations 20
Regionality 22
Meteorological Effects .... 22
Distinguishable Sulfates 22
Equilibration of S02 with Water Vapor . . 22
Origin of Aerosol Sulfate 23
References . 24
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FIGURES
Number Page
1 Location of sampling sites: St. Louis, MO; Auburn, IL; and
Glasgow, IL 3
18
2 0 enrichment in aerosol sulfate vs. sampling dates at the
three sites near St. Louis
18
3 0 enrichment in sulfate formed from SO gas at the three
sites 10
I Q
4 0 enrichment in water vapor vs. sampling dates at the three
sites 11
5 Aerosol sulfate collection rate at the three sites vs.
sampling dates 12
6 Collection rate of SO (expressed as SOp at the three sites
vs. sampling dates 13
18
7 Collection rate and 0 enrichment of aerosol sulfate and S0_-
derived sulfate at St. Louis, MO 14
18
8 Collection rate and 0 enrichment of aerosol sulfate and SO--
derived sulfate at Auburn, IL 15
18
9 Collection rate and 0 enrichment of aerosol sulfate and S0«-
derived sulfate at Glasgow, IL 16
18
10 0 enrichment vs. collection rate of aerosol sulfate collected
at St. Louis, MO 17
18
11 0 enrichment vs. collection rate of aerosol sulfate collected
at Auburn, IL 18
18
12 0 enrichment vs. collection rate of aerosol sulfate collected
at Glasgow, IL 19
vi
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TABLE
Number Page
1 Isotopic'and Concentration (Collection Rate) Data 8
vii
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SECTION 1
INTRODUCTION
The workability of various strategies for the control of sulfur dioxide
and sulfate levels in the environment depends to a large degree on the trans-
port and transformation of these materials in the atmosphere. Experimental
results obtained in the Chemical Engineering Division (CEN) at Argonne
National Laboratory (ANL) strongly suggest that measured oxygen isotope
ratios for sulfate oxygen can be used to help distinguish between the two
most likely mechanisms of sulfate formation in the atmosphere (1,2). Oxygen
isotope ratios are customarily reported in del units (%o) which are a
measure of deviation in parts per,thousand from Standard Mean Ocean Water
(SHOW). The concept of determining sulfate formation mechanisms from oxygen
isotope ratios is based on the following experimental observations:
1) The oxygen isotope ratios for atmospheric water (-15 to -25%o) and
air oxygen (+23%0) are significantly different.
2) The rate of oxygen exchange between sulfates and water is extremely
low.
3) Sulfates formed in the laboratory by dissolution of SO- in water
and subsequent oxidation by air to sulfate appear to consistently yield
sulfate comprising three oxygens resulting from isotopic equilibration be-
tween SO and water before oxidation and one oxygen originally associated
with the oxygen in air (3).
4) Sulfate formed in the laboratory by oxidation of S0« to SO- and
subsequent dissolution in water to form sulfate yields a sulfate enriched
18
in 0 compared with that produced as described in item 3 above.
Thus, sulfates formed by different mechanisms from the same SO-, water,
and air apparently can differ significantly in oxygen isotope ratio. As
18
noted, the 0 enrichment of atmospheric water and oxygen are significantly
-------
different so that they can be easily distinguished; moreover, once formed,
sulfate does not undergo oxygen exchange so that the formation mechanism is
permanently reflected in the sulfate oxygen isotope ratio. To examine the
formation mechanism of sulfate, it is, in principle, only necessary to sample
simultaneously the sulfate, sulfur dioxide, and water vapor present in a
given air mass and to measure the oxygen isotope ratios for each substance.
1 ft
Because of natural fractionation processes, the 0 enrichment of atmospheric
water is seasonally variable. As determined by analytical results on 24-hour
samples that were collected on 3 consecutive days each month for 16 months at
18
Argonne, the variations in the 0 enrichment of particulate sulfate did not
18
follow the observed seasonal variations in the 0 of ambient water vapor (3).
It might be assumed, however, that if atmospheric sulfate aerosols are sec-
ondary particles formed by hydrolysis of SCL, either before or after oxida-
18
tion, the 0 enrichment of the sulfate should have a seasonal quality that
is proportional to the number of water oxygen atoms incorporated into the
sulfate molecule.
This report gives the oxygen isotope results obtained on 12-hour diurnal
samples of aerosol sulfate, sulfur dioxide, and water vapor which were col-
lected simultaneously at Auburn and Glasgow, IL, and on 24-hour samples col-
lected simultaneously at St. Louis, MO, July 21-28, 1975. The purpose of the
experiment was to test for correlation of the isotopic quality of aerosol
sulfate with that of water vapor in sequential samples collected over a
period of 6 days, and to see whether changes in isotopic quality were re-
lated to local or regional effects. The three sampling stations, Fig. 1,
were located about 100 km apart. The St. Louis station was on the campus
of Washington University; the Auburn and Glasgow stations were in rural areas.
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o
ROCKFORD
CHICAGO
O
ARGONNE
ILLINOIS
ST LOUIS
Figure 1. Location of sampling sites: St. Louis, MO; Auburn, IL; and
Glasgow, IL
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SECTION 2
CONCLUSIONS
Some of the more significant conclusions from the experimental results
described in this report are presented below.
1) The concerted variations in concentrations and in isotopic qualities
of atmospheric sulfate and sulfur dioxide at the three sampling sites indi-
cate that sulfur pollution was distinctly regional in nature.
2) Meteorological conditions had a marked effect on the isotopic
quality and concentration of atmospheric sulfates.
3) The variations in oxygen isotope ratio of aerosol sulfate did not
correlate well with that of ambient water vapor, indicating that, within the
air masses under observation, the aerosol sulfate had an insignificant con-
tribution of oxygen from the ambient atmospheric water.
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SECTION 3
RECOMMENDATIONS
The results and observations of this report suggest that the following
projects need to be carried out:
1) Repeat the reported experiment on atmospheric sulfates and water
vapor by sampling simultaneously at three sites, over a period of two weeks
or more, preferably under a set of weather conditions different from that of
the reported experiment. The results would be valuable for confirming or
modifying the conclusions drawn from the reported experiment.
2) Repeat the experiment, sampling upwind and downwind of a well-
defined, substantial source of S0_, such as an isolated industrial emitter.
The results would be expected to reflect the influence of the localized
strong source of S0_.
3) Perform oxygen isotope analyses on samples of sulfur oxides taken
directly from the emission stacks of typical power plants arid refineries.
Compare the isotopic results on such primary (freshly emitted) oxides of
sulfur to those of ambient oxides simultaneously sampled in a region several
kilometers downwind. If the isotopic quality of the ambient sulfates in the
selected region are found to differ isotopically from that of the primary
sulfates of the strong emitter, it might be concluded that ambient sulfates
are made up predominantly of secondary particles.
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SECTION 4
EXPERIMENTAL PROCEDURES
SAMPLE COLLECTION
Particulate sulfate samples and ambient sulfur dioxide samples were col-
lected simultaneously in a filter pack, mounted in a hi-vol air sampler [sul-
fates on a top, 20 x 25 cm (8 x 10 in.), glass-fiber filter and the SO on a
bottom, K.CO_-glycerol-treated, cellulose fiber filter]. Ambient water vapor
was concurrently sampled by drawing a stream of air through a cold trap
(-80°C) located near the hi-vol air sampler. Consecutive sets of samples of
sulfates, SO^, and water vapor were collected each day at about 2 meters
(6 feet) or more above ground level.
SAMPLE ANALYSIS
Sulfur dioxide samples collected on K9CO -glycerol filters were air-
oxidized to sulfate. These and the particulate sulfate samples were con-
verted quantitatively to BaSO, by conventional methods. Each BaSO, sample
was filtered into a porous graphite cup in which the oxygen was converted to
18
C0? by high-temperature, high-voltage techniques (4). The 0 analysis of
the C0? was made on a high-precision isotope-ratio mass spectrometer (Model
NAA-RM57 of Nuclide Corporation, State College, PA, with modified electronic
circuits and gas-inlet system (5).
Water samples were converted quantitatively to H« and CO by reaction
with hot graphite. The hydrogen was discarded through a palladium membrane
and the CO was disproportionated to carbon and C0? by high-voltage discharge
for subsequent mass spectrometric analysis of the CO^ (4).
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SECTION 5
RESULTS
Measurements of oxygen isotope ratios are reported for aerosol sulfates,
the sulfates resulting from collection and air oxidation of atmospheric S0_
on K-CO -glycerol-treated paper filters, and water-vapor samples. Concentra-
tion data, presented in the form of collection rates (ymole/hr, assuming that
the three hi-vol air samplers were each operated at a constant air flow rate
throughout the sampling period), are reported for aerosol sulfates and sul-
fates resulting from SCL collection.
Isotopic and concentration data are given in Table 1 and in Figs. 2
through 12. Figures 2-4 show intersite comparisons of the isotopic results
for particulate sulfate, sulfate formed by SO- collected on the alkaline
filters, and ambient water vapor. Figures 5 and 6 show intersite comparisons
of concentration results (expressed in terms of collection rate) for particu-
late sulfate and sulfate formed by SO- collection. Figures 7-9 give all the
sulfur results obtained at each of the three sites, and Figs. 10-12 show the
variations in isotopic results with concentration (collection rate) of aerosol
sulfate at each site. (In the figures showing sampling dates, each numbered
tick represents the beginning of the indicated day, -i.e., midnight.)
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TABLE I. ISOTOPIC AND CONCENTRATION (COLLECTION RATE) DATA
Location
St. Louis
Auburn
Glasgow
Sampling Date
July 1975
Start
(hr/day)
19:30/21
10:15/23
11:40/24
7:45/25
15:00/26
13:20/27
15:45/28
7:00/22
16:45/22
5:25/23
16:45/23
6:00/24
17:15/24
5:25/25
16:30/25
5:00/26
16:30/26
5:10/27
16:30/27
10:00/22
18:45/22
8:00/23
18:40/23
8:00/24
19:15/24
7:25/25
18:55/25
7:10/26
18:30/26
7:00/27
18:30/27
Stop
(hr/day)
10:10/23
11:35/24
7:35/25
15:00/26
13:15/27
15:30/28
8:00/29
16:30/22
5:15/23
16:40/23
5:45/24
17:10/24
5:10/25
16:25/25
5:00/26
16:30/26
5:10/27
16:30/27
5:00/28
18:30/22
7:40/23
18:40/23
8:00/24
19:10/24
7:15/25
18:30/25
6:55/26
18:30/26
7:00/27
18:30/27
6:30/28
Sulfate Aerosol
Collection
Rate
(ymol/hr)
4.3
1.7
2.2
8.6
10.4
8.7
9.0
6.4
8.9
9.5
2.1
3.7
3.2
7.4
6.0
5.8
6.7
8.5
6.1
8.1
7.8
5.3
2.7
3.7
2.5
4.4
3.7
7.7
8.8
6.1
4.8
18o
(%0>
7.3
14.2
7.9
5.3
3.4
7.6
7.5
9.2
2.6
7.1
15.0
10.5
7.8
3.8
6.1
2.9
3.5
7.4
8.5
1.6
7.1
11.8
19.8
12.6
15.1
8.5
14.1
5.7
6.9
12.9
15.3
Sulfate from SO
on K2C03 Filter
Collection
Rates
(vimol/hr)
19.7
15.0
1.4
37.7
33.8
39.1
23.5
72.2
5.5
17.7
7.5
2.2
1.8
9.0
7.7
9.2
4.7
8.5
3.1
15.0
2.5
12.4
1.3
3.0
0.7
3.2
0.6
18.5
14.0
3.1
1.6
18o
(%„)
10.2
11.6
5.2
13.1
10.5
13.8
12.1
10.3
12.1
12.4
13.7
15.1
12.8
10.5
11.4
11.1
8.4
8.8
11.9
8.8
9.9
12.5
16.7
6.1
42 (d)
6.7
32. 4 (d)
13.4
13.5
3.5
17.9
Water
Vapor
18o
(%o)
-7.5
-6.0
-10.1
(a)
(a)
(a)
(a)
-2.8(b)
-5.0
-7.2
-8.4
-9.1
-7.5
-10.1
(c)
-10.1
4.6(b)
-9.9
-9.4
-0.4(b)
-6.6
-8.0
-7.6
-10.9
-8.3
-11.2
-10.9
-13.0
-6.5
L2.0(b)
-8.6
(a)
(b)
(c)
(d)
Sample was not collected.
Sample was damaged by partial evaporation during storage.
Sample was lost.
Sample was too small to obtain a reliable mass spectrometric analysis.
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24-
22-
20-
18
16-
8 14-
O
oo
10-
8-
6-
2-
Low Pressure Frontal System
P Glasgow
Auburn
£ ASt Louis
21 22 23 24 25 26 27 28 29 30 31
July 1975
18
Figure 2. 0 enrichment in aerosol sulfate vs. sampling dates at the
three sites near St. Louis
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8
O
oo
24-
22-
20-
18
16
14
12
10
8
6
4
2
0
9 Glasgow
A St. Louis
o
Auburn
21 22 23 24 25 26 27 28 29 30 31
July 1975
18,
Figure 3. 0 enrichment in sulfate formed from SC>2 gas at the three sites
10
-------
8
<0
14
12
10
8
6
4
2
0
-2-
-4-
-6-
-8-
-10-
-12-
-14
/ vo Glasgow
Auburn
i i i
2122232425262728293031
July 1975
18
Figure 4. 0 enrichment in water vapor vs. sampling dates at the three sites
11
-------
13-
13
w u
10
o>
l-H
O
I
»v
-------
-------
«o
18-
16-
14 -
13-
10-
8-
6-
4 -
2-
0-
40-
36-
O 28-
5 24'
U 20-
ce ie-
o
B
12-
8-
J 4-
O
^ 0
SUIiPATE AEROSOL
SULFATE FORMED FROM SO.
31 22 23 24 25 26 27 28 39
JULY 1975
21 22 23 24 25 26 27
28 29
JULY 1975
18
Figure 7. Collection rate and 0 enrichment of aerosol sulfate and SO,
derived sulfate at St. Louis, MO
14
-------
18-
16-
14 -
12-
2°
«o
6-
4 -
2-
0-
SULFATE AEROSOL
SULFATE FORMED FROM SO,
OT se-
ll
I--I
U
o:
z
o
Cd
J
O
40-
24 -
8-
--I—> 1—• [—•—| r—i . 1 . 1 • 1—
212223242526272829
JULY 1975
21 22 33 24 25 26 27 28 29
JULY 1975
18
Figure 8. Collection rate and 0 enrichment
derived sulfate at Auburn, IL
of aerosol sulfate and
15
-------
22-
»:
16-
16-
l4 -
SULFATE AEROSOL
SULFATE FORMED FROM S02
00°
8-
6-
4 -
2-
0-
22-
20-
V 1B-
t/i 1
a; le-j
° u -I
a ,J
* 8-)
1 H
£ 41
21 22 23 24 25 26 27 28 29
JULY 1975
21 22 23 24 25 26 27 28 29
JULY 1975
18
Figure 9. Collection rate and 0 enrichment of aerosol sulfate and S0r
derived sulfate at Glasgow, IL
16
-------
8
oo
20-
18-
16-
14-
12-
8-
6-
4-
2-
0
D
n
01 23456789 10 11 12
Collection Rate (yumole SO^/Hr)
18
Figure 10. 0 enrichment vs. collection rate of aerosol sulfate collected
at St. Louis, MO
17
-------
8
oo
20-
18-
16-
14-
12-
o 10 J
8-
6-
4-
2-
0
D
D
D
D
D
D
D
D
D
D
01 23456789 10 11 12
Collection Rate (/xmole
18
Figure 11. 0 enrichment vs. collection rate of aerosol sulfate collected
at Auburn, IL
18
-------
20-
18-
16-
14-
12-
O
00
8-
6-
4 -
2-
0
D
D
D
D
D
I I
I ' I
01 234567
Collection Rate
89 10 11 12
So|~/Hr)
18
Figure 12. 0 enrichment vs. collection rate of aerosol sulfate collected
at Glasgow, IL
19
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SECTION 6
DISCUSSION
OBSERVATIONS
The following observations may be made from the results plotted in the
figures.
18
1) Figure 2 shows that the values for 6 0 in aerosol sulfate peaked
at about the same time at the three sites. Maxima occurred at all three
sites on about July 23; minima occurred on about July 26.
2) Figure 5 shows that on these same dates, July 23 and 26, corre-
sponding but inverse peaking in concentration (collection rate of aerosol
sulfate) occurred at all three sites.
3) The concerted peaking for the three sites (Figs. 2 and 5) corre-
sponded to the time of movement of weather fronts across the region that in-
cludes the three sites. A low-pressure barometric cell moved in an easterly
direction across the region on July 23 and was accompanied by thunderstorms.
Less prominent barometric pressure changes also occurred about July 26.
18
4) Figure 3 shows that variations in 6 0 for sulfates formed by
collection of atmospheric S0~ on alkaline filters were roughly concerted
at the three sites, although not necessarily equal in magnitude. The varia-
tions appeared to be most prominent on the days of unsettled weather condi-
tions (July 23-24, 26-27). The validity of these results will be discussed
later.
5) Figure 6 shows that the concentrations of S0_ (expressed as collec-
tion rate) apparently dropped to near zero at all three sites immediately
after the low pressure cell, accompanied by thunderstorms, passed over the
region on July 23-24. (The unusually high value for the Auburn sample on
20
-------
July 22 coincided with a northeast wind, blowing from the direction of a
large power plant in Springfield, IL.)
18
6) In Fig. 4, a general downward trend in the 0 content of water
vapor is evident for the three sites during the first 3 to 4 days of sampling.
The local thunderstorm that occurred on about July 23-24, accompanied by
abrupt reductions in concentrations of sulfates and SO- and corresponding
18
increases in the 0 del values of sulfates, apparently had very little
effect on the isotopic content of the atmospheric water vapor.
18
The 12-hour overnight samples of water vapor were often higher in 6 0
than the associated 12-hour day samples. This may have been caused by a
higher contribution of ground water to ambient water vapor, through evapora-
tion from soil and evapotranspiration from plants, at night when air movement
was generally at a minimum. This was a ground-level sampling problem, its
effects probably being most prominent in the overnight sample at Glasgow on
July 26-27.
7) Figure 7 indicates that while the oxygen del values for aerosol
sulfate in St. Louis varied inversely with the concentration parameter
(correlation coefficient = -0.750, Fig. 10), the del values for the sulfates
formed from collected SO- apparently varied directly with the S0_-concentra-
tion parameter (correlation coefficient = 0.837). (Note the relative magni-
tudes of the collection rates of particulate sulfate and S0_.)
18
8) Figure 8 shows an inverse 6 0-concentration relationship for
sulfate aerosol in Auburn (correlation coefficient = -0.639, Fig. 11), but
18
no significant correlation (correlation coefficient = -0.248) in the 6 0-
concentration relationship for SO .
18
9) Figure 9 indicates that for Glasgow the 6 0-concentration relation-
ships are inverse for sulfate aerosol (correlation coefficient = -0.841,
Fig. 12) and only very weakly so for SO™ (correlation coefficient = -0.320).
These observations give substantial support to postulates that (1) the
fluctuations in concentration and isotopic quality of aerosol sulfate were
regional phenomena; (2) both local and continental meteorological changes
had important effects on the quality and concentration of atmospheric sulfate
21
-------
within the region; and (3) the aerosol sulfate was not necessarily formed
from the water that was carried by the air masses from which it was collected.
REGIONALITY
The regional character of the variations of both the isotopic quality
and the concentrations of atmospheric sulfates and S00 is shown by the con-
certed peaking of these parameters at St. Louis, Auburn, and Glasgow (Figs.
2-6). If the origin of the pollutants at Auburn and Glasgow had been pri-
marily the urban plume of St. Louis, the effect of a time lag should have
been evident in the results. Likewise, local sources of sulfur pollution
near either Auburn or Glasgow would not have produced the observed concerted
pattern for all three sites.
METEOROLOGICAL EFFECTS
The apparent marked effects of local weather, on July 23 and 24, and
of continental air movements, on July 26 and 27, demonstrate the impact that
meteorological changes can have on atmospheric sulfur, apart from possible
coincidental variations in emissions and/or transformations.
DISTINGUISHABLE SULFATES
18
The pronounced negative correlation between 6 0 and concentration of
sulfate aerosols at all three sites, in connection with local weather dis-
turbances (Figs. 2, 5, 7-12), suggests that as sulfate was removed from the
atmosphere, the residual sulfate had a different isotopic character. Iso-
topic fractionation of oxygen in sulfates caused by partial removal is un-
likely, however, because sulfate is relatively inert to isotopic exchange
with water in which it is dissolved. A possible explanation for the negative
correlation is that the sulfate contained in the air, after the thunderstorm
disturbance, was transported trom higher altitudes by turbulent mixing. The
high-altitude sulfate may have had a different origin (possibly a different
mechanism of formation) from that of the low-altitude sulfate.
EQUILIBRATION OF SOO WITH WATER VAPOR
On comparison of the data in Figs. 3 and 4, it might appear that the
lack of positive changes in SO. (monitored as sulfate on the alkaline filt
and water vapor at Auburn and Glasgow suggests a lack of perceptible
22
-------
equilibration of oxygen isotopes between the SO. and atmospheric water in
the air masses from which they were collected, although SO might be expected
to approach isotopic equilibrium with water in the atmosphere in a manner
similar to the CO--H 0 system (6).
The validity of the herein reported isotopic data for SCL has been
placed in considerable doubt, however, by subsequently performed, but yet
18
unreported, experimental results obtained on blends of SCL of various 0
enrichments. The results of these later experiments indicate that isotopic
exchange between the moist reagents on the K»(XL-glycerol-treated filters
and the collected SCL, prior to oxidation to sulfate, can seriously impair
the isotopic fingerprint of the S0_. For this reason, the reported S0? re-
sults are probably not applicable to the determination of equilibration be-
tween SCL and water in the atmosphere.
ORIGIN OF AEROSOL SULFATE
If significant portions of the aerosol sulfate collected and analyzed
in this experiment had been formed by S02-water reactions (either before or
after oxidation of the sulfur) in the air masses from which they were col-
lected, a component of the isotope variations in the aerosol sulfate might
be expected to track that of the water vapor with an amplitude of at least
one-fourth that of the water vapor. The apparent lack of positive correla-
tion between the isotope variations in aerosol sulfate and water vapor at
both Auburn and Glasgow suggests that the aerosol sulfate was not formed
predominantly from the water in the air masses from which it was sampled.
23
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REFERENCES
18
1. Cunningham, P. T. and B. D. Holt. 0 Analysis in the Study of Atmo-
spheric Sulfate Aerosols. In: Chemical Engineering Division Environ-
mental Chemistry Annual Report, July 1974-June 1975, ANL-75-51,
Argonne National Laboratory, Argonne, IL, 1975. 19-43 pp.
2. Holt, B. D., A. G. Engelkemeir, S. A. Johnson and P. T. Cunningham.
Oxygen Isotopy in the Formation of Sulfate Aerosols. In: Proceedings
of the Second International Conference on Stable Isotopes, Oak Brook,
IL, 1975. ERDA, CONF-751027, 1976. 683-692 pp.
3. Holt, B. D., P. T. Cunningham and A. G. Engelkemeir. Application of
Oxygen-18 Analysis to the Study of Atmospheric Sulfate Formation.
International Conference on Stable Isotopes, Lower Hutt, New Zealand,
1976. N. Z. Dept. Sci. Ind. Res. Bulletin (in press).
4. Holt, B. D. Preparation of Carbon Dioxide from Sulfates, Sulfur
Dioxide, Air, and Water for Determination of Oxygen Isotope Ratio.
Anal. Chem., 49:1664-1667, 1977.
5. Holt, B. D. Determination of Stable Sulfur Isotope Ratios in the
Environment. Prog, in Nuclear Energy, Anal. Chem., Vol. 12, pp. 11-26.
Pergamon Press, 1975.
6. Bottinga, Y. and H. Craig. Oxygen Isotope Fractionation between C0_
and Water, and the Isotopic Composition of Marine Atmospheric CO^.
Earth and Planet. Sci. Let., 5:285-295, 1969.
24
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TECHNICAL REPORT DATA
I'Please read Instructions on the reverse before completing]
REPORT NO.
EPA-600/3-78-045
3. RECIPIENT'S ACCESSION»NO.
TITLE AND SUBTITLE
OXYGEN ISOTOPES IN ATMOSPHERIC SULFATES, SULFUR
DIOXIDE, AND WATER VAPORS
Field Measurements, July 1975
5. REPORT DATE
April 1978
6. PERFORMING ORGANIZATION CODE
AUTHOR(S)
B. Holt, M. Bouchard, P. Cunningham, A Kengelkemeir,
E. Nielsen, S. Johnson, and R. Kumar
8. PERFORMING ORGANIZATION REPORT NO.
PERFORMING ORGANIZATION NAME AND ADDRESS
Argonne National Laboratory
9700 South Cass Avenue
Argonne, Illinois 60439
10. PROGRAM ELEMENT NO.
1AA603 AH-01 (FY77)
11. CONTRACT/GRANT NO.
IAG-D6-F024
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Sciences Research Laboratory - RTF, NC
Office of Research and Development
U.S. Environmental Protection Agency
13. TYPE OF REPORT AND PERIOD COVERED
Final 5/76 - 5/77
14. SPONSORING AGENCY CODE
EPA/600/09
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Oxygen isotope ratios were determined for atmospheric samples of sulfate
aerosols, sulfur dioxide, and water vapor collected simultaneously during a six-day
period in July, 1975, at St. Louis, MO; Auburn, IL; and Glasgow, IL. The collec-
tion sites were located about 100 km apart.
Concerted variations in isotopic and concentration results were found for the
three sites, demonstrating an apparent regional impact on the quality and quantity
of particulate sulfate in the atmosphere. At all three sites, the oxygen-18
enrichments in suspended sulfates clearly varied inversely with sulfate concen-
tration. This variation suggests that sulfates in cleaner air may have a different
origin than sulfates in more polluted air masses. Samples collected during a
period of local thunderstorm activity showed an abrupt increase in the oxygen-18
composition of particulate sulfate, but little effect on the isotopic composition
of ambient water vapor.
The lack of positive correlation between oxygen-18 variations in aerosol
sulfate and oxygen-18 variations in water vapor suggests that the aerosol sulfate
was not formed predominantly from the ambient water in the air masses from which it
Mac sampled.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
*Air pollution
*Sulfur dioxide
*Sulfates
*Water vapor
*0xygen isotopes
Chemical analysis
St. Louis, MO
Auburn, IL
Glasgow, IL
13B
07B
07D
18B
13. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
31
20. SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
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