EPA-600/3-76-090
August 1976
Ecological Research Series
SULFUR DIOXIDE PHOTOOXIDATION RATES AND
AEROSOL FORMATION MECHANISMS
A Smog Chamber Study
Environmental Sciences Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of'traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:
1 Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal
species, and materials. Problems are assessed for their long- and short-term
influences. Investigations include formation, transport, and pathway studies to
determine the fate of pollutants and their effects. This work provides the technical
basis for setting standards to minimize undesirable changes in living organisms
in the aquatic, terrestrial, and atmospheric environments.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/3-76-090
August 1976
SULFUR DIOXIDE PHOTOOXIDATION RATES AND
AEROSOL FORMATION MECHANISMS
A Smog Chamber Study
by
W.C. Kocmond
J.Y. Yang
Calspan Corporation
Buffalo, New York 14221
Contract No. 68-02-1231
Project Officer
Basil Dimitriades
Environmental Sciences Research Laboratory
Office of Research and Development
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
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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.
11
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ABSTRACT
The objective of this investigation was to obtain smog chamber data
pertaining to the oxidation of SCL into sulfate under simulated urban and rural
atmospheric conditions. Tasks were performed on various systems ranging from
HC + NOX + S02 to the clean air + SCL mix. Emphasis has been placed on the
rates of SCL photooxidation and on chemical characterization of aerosol products.
Results showed the rate of S02 oxidation to vary from less than 1% per hour for
the clean air + S02 system to about 2.7% per hour for the propylene + NOX + S02
system. Results were also interpreted to suggest that the major SCL oxidation
process is the reaction of SCL with OH radicals. Particulate matter, as
occurred in natural rural air, appeared to have no appreciable effect upon S02
photooxidation; nevertheless questions still remain on the role of natural
particulates.
iii
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CONTENTS
Abstract iii
Figures vi
Tables vii
1. INTRODUCTION 1
2. EXPERIMENTAL FACILITIES 2
3. THE S02-CLEAN AIR SYSTEM 4
3.1 Data Summary -- SO -Containing Systems 7
3.2 Comparison of Sulfate Analysis by the Barium
Perchlorate Method with EAA Data 12
3.3 S02 in the Presence of Natural Nuclei 15
4. PROPYLENE + NO AND PROPYLENE + NO + SO EXPERIMENTS 19
A. .X. Z*
5. THE INORGANIC SYSTEM - CO + NO + SO 26
X &
6. THE RURAL AIR + S02 SYSTEM 33
7. SUMMARY AND CONCLUSIONS 39
References 42
Appendix A Aerosol ง Chemistry Data for All Calspan Smog
Chamber Experiments 43
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FIGURES
Number Page
1 Aerosol Development in the S02 + Clean Air System 8
2 Chemistry Data for Propylene + NO System 21
A
3 Chemistry Data for Propylene + NO System 21
j\
4 Aerosol and Chemistry Data for Propylene + NO + S09 System... 22
A ฃ
5 Aerosol and Chemistry Data for Propylene + NO + S09 System... 23
A Cm
6 Aerosol and Chemistry Data for SO- + NOV System 29
ฃ A
7 Aerosol and Chemistry Data for S02 + NOX + 100 ppm CO System.. 30
8 Aerosol and Chemistry Data for S09 + NO + 400 ppm CO System.. 31
ฃ> A
9 Aerosol and Chemistry Data for Rural Air System Containing
Natural Particles 35
10 Aerosol and Chemistry Data for Rural Air (With Natural
Particles) + S02 System 36
11 Aerosol and Chemistry Data for Rural Air (Without Natural
Particles) + S02 System.. 37
vi
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TABLES
Number Page
I. Summary of "Clean Air" S02 Photooxidations 9
II. Aerosol Sample Sulfate and Ammonium Content 14
III. Comparison of Calspan and Battelle Analytical Results 17
IV. Summary of Chemistry Data from Propylene + NO and
Propylene + NOX + S02 Irradiations 20
V. Summary of Aerosol Data from Propylene + NOV and Propylene +
NOV + S09 Irradiations 20
A ฃ
VI. Summary of Chemistry Data from the Inorganic Test Series 27
VII. Summary of Aerosol Data from Inorganic Test Series 27
VIII. Aerosol Sample Sulfate and Ammonium Content 34
A-l. Log of Calspan Smog Chamber Experiments. 44
VII
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Section 1
INTRODUCTION
One of the principal concerns facing atmospheric scientists today
lies in our lack of basic knowledge of aerosol behavior in the polluted
atmosphere. Work has progressed in understanding aerosol formation mechanisms,
but few dependable models of aerosol development have emerged. Indeed, even
in the relatively simple SOp system, only the mechanics of aerosol behavior
are reasonably well understood. The actual mechanisms responsible for aero-
sol development, however, must still be determined.
The ubiquitous presence of S02 in the urban atmosphere makes it one
of the key pollutants requiring our research attention. While its presence
is known to be responsible for the production of significant sulfate-contain-
ing aerosol, the S02 photooxidation rate in the presence of various impurities
is not well established and needs to be known. Smog chamber data suggest an
S02 photooxidation rate in clean filtered air of a few tenths of a percent
per hour or less. In the presence of reactive hydrocarbons and oxides of
nitrogen, higher rates of up to a few percent per hour are frequently observed.
It has been the objective of this investigation to obtain chamber
irradiation data on various systems ranging from HC + NO + S09 to the clean
s\ ฃ
air + S02 mix. Emphasis has been placed on examining the rates of S02 photo-
oxidation in these systems and in chemically characterizing the aerosols which
are formed. Midway through this year's program aerosol collections and routine
sulfate analysis were initiated. Late in the period, nitrate and ammonia
analysis procedures were also performed. Discussions are presented of several
smog chamber systems that were tested. These include S02 + clean air (Section
3), propylene + NOX + S02 (Section 4), an inorganic system of CO + NOX + S02
(Section 5), and rural air t S02 (Section 6)., The rationale for choosing
these systems is also provided within the text. A summary and conclusions of
this year's findings is given in Section 7.
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Section 2
EXPERIMENTAL FACILITIES
The smog chamber used at Calspan (Kocmond et a!., 1973) consists
of a cylindrical chamber 30 feet (9.14 meters) in diameter and 30 feet
(9.14 meters) high enclosing a volume of 20,800 ft3 (590 m3). The 1.25 cm
thick chamber walls are coated with a specially- formulated fluoroepoxy-type
urethane which has surface energy and reactivity properties comparable to
those of FEP Teflon. Illumination within the chamber is provided by 28.6 kw
of fluorescent blacklight and sun lamps installed inside 24 lighting modules
and arranged in eight vertical channels attached to the wall of the chamber.
Each lighting module contains two 40-watt sun lamps, eight 85-watt high out-
put black lamps, and two 215-watt specially-produced black lamps. The light-
ing modules are covered with 0.5 cm Pyrex glass and are sealed from the cham-
ber working volume. Measured light intensity using the kjENOg] method
reported by Stedman & Niki is kd~0.35 min .
Chamber air is purified through a recirculation system consisting
of a series of absolute and activated charcoal filters. Nearly all gaseous
contaminants and parti cul ate matter can be removed from the chamber air in
about four to five hours of filtration. Filtered air generally contains no
measurable particles, less than 0.1 ppm NO , 0.2 ppmC non-methane HC, and no
X
measurable SO or ozone.
New this year is a chamber washdown system, a humidifier, and a
dehumidification system. The recirculating washdown system consists of a
stainless steel spray head which rotates on two axis and can wet all of the
chamber surfaces with distilled water or cleaning solution. Generally, the
procedure is to first wash the chamber surfaces with a 5% solution of a
laboratory glass cleaning agent followed by two or three rinsings with tap
water and two final rinsings with distilled water. Drying is accomplished
by fresh air flushing followed by air filtration. Chamber humidity can be
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increased by spraying distilled water into the chamber from a remotely-operated
spray nozzle near the chamber top. Nuclei which are introduced by the evapor-
ating spray droplets are removed by absolute particle filters during the air
filtration cycle. Chamber dehumidification when needed is accomplished by
passing the chamber air over refrigeration coils to remove excess water. The
system was designed and fabricated at Calspan and is capable of controlling
humidity down to about 20% RH.
Instrumentation used to monitor aerosol behavior and reactant con-
centrations within the chamber includes a Bendix Model 8002 chemiluminescent
ozone analyzer, Model 8101-B nitrogen oxides analyzer, Model 8300 total sulfur
analyzer, and the Model 8201 reactive hydrocarbon analyzer; a Hewlett-Packard
5750 gas chromatograph; a Thermo Systems Model 3030 Electrical Aerosol Analyzer
(EAA); an MRI Integrating Nephelometer; a Gardner Associates' small particle
detector; and a 6E condensation nucleus counter. A Meloy flame photometric
total sulfur analyzer on loan from the EPA was also used for most of the
experiments. More complete descriptions of the chamber and analytical instru-
mentation facilities are given in an earlier Calspan report (Kocmond et al.,
1973).
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Section 3
THE S02-CLEAN AIR SYSTEM
Major emphasis on the current phase of this program has been placed
on determining the S02 photooxidation rate (Rst^) i" clean as wel1 as con~
taminated atmospheres. Clean air + S02 irradiations are routinely performed
to establish chamber reactivity and to gauge the effect of previous experi-
ments on H2SCL aerosol formation. In the past, S02 photooxidation rates, as
determined from aerosol analyzer data, have been in the range of a few tenths
of a percent per hour in clean filtered air. The effect of certain pollutants,
especially reactive hydrocarbons, is to enhance R$o2 appreciably.
The production of aerosol from SCL photooxidation is generally attri-
butable to chemical conversion of S02 to S03 followed by rapid reactions with
normally-occurring atmospheric constituents, such as H20 and NH3, to form
condensable products. Under clean atmospheric conditions, therefore, sulfuric
acid formation from S02 may be expected to proceed via the following sequence
of reactions (A.M. Castleman, Jr., et al., 1975):
(1) Oxidation of S02 to S03
(2) Reaction of S03 with water to yield H2S04
(3) Clustering of H2S04 and water molecules to form pre-nucleation
embryos.
An understanding of the detailed mechanism of S02 conversion to S03 in the
ambient atmosphere is still lacking. Homogeneous photolysis of SCL via
O C,
solar radiation in the 2400-3400 A range would give an oxidation rate far
less than that normally observed even in the unpolluted atmosphere (J.P.
Friend et al., 1973). The actual rate of S02 photooxidation must therefore
occur as a synergistic effect due to the presence of other trace reactive
contaminants in the atmosphere. A number of different reaction schemes of
S02 oxidation by free radical and active oxygen intermediates have been sug-
gested to account for the observed ambient monitoring data. A summation of
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the current understanding of the chemical kinetic schemes providing a reason-
able account of atmospheric SOp photooxidation is given by Calvert and McQuigg
(1975).
It is generally agreed that, even in the relatively unpolluted atmos-
phere, OH radicals may be generated by naturally-occurring photochemical pro-
cesses giving rise to concentrations of the order of 106 cm"3. The reaction
of OH radicals with S02 is considered to be a key process contributing to
atmospheric S02 oxidation. Ozone and HOp radicals are present at higher con-
centrations but contribute to SOp oxidation to a lesser extent because of the
considerably slower specific reaction rates. The specific rate constants for
S02 reactions with alky! oxyl and alkyl peroxyl radicals are not available as
experimental estimates. These reactive intermediates would, however, be rela-
tively unimportant in the unpolluted atmosphere. In the hydrocarbon and NO
X
polluted atmosphere, the alkyl oxyl and alkyl peroxyl radicals may contribute
to the overall S02 oxidation process to a more significant extent. Another
important factor in the polluted atmosphere lies in the possibility of a
synergistic effect of ozone and olefins on SOp oxidation. Such a possibility
has been suggested by Cox and Penkett (1971, 1972). According to Calvert and
McQuigg (1975), a diradical -OCHpO- species may be generated from ozone-olefin
reactions, and it may serve as an effective reaction intermediate for SOp oxi-
dation.
Reviews of the general mechanisms of the physical aspects of aerosol
formation, growth, and decay in the SOp-clean air system can be found in Clark
(1972) and Kocmond et al. (1975). Briefly, however, three main mechanisms
govern aerosol behavior in these systems: nucleation, condensation, and coag-
ulation. Initially, after the lights are turned on, homogeneous nucleation
of the newly-formed condensable product species occurs to form new particles
in the supersaturated vapor mixture. Once formed, the particles continue to
grow through condensation of the vapors and new product molecules onto their
surfaces. The rate of condensation depends primarily on the degree of super-
saturation, the diffusion coefficient, and the size of the particle itself.
Although condensation does not affect the particle concentration, it does
-------
result in increased particle surface and volume concentrations. The third
process, coagulation, refers to the collision and striking of particles with
one another. Here, the rate of coagulation is proportional to the square
of the particle number. Coagulation leads to a decrease in particle number
and surface concentration but does not affect the volume concentration.
For the SCL + clean air system, we have stated that the rate of
aerosol volume production approaches a constant value and that a plot of
\
volume against time yields a straight line (Clark, 1972; Kocmond et al.,
1975) over a reasonably long period of time. The reasoning was that the
rate of oxidation of S02 to S03 was equal to the rate of removal of S03 to
form sulfuric acid droplets. The rate of production of H^O^ aerosol, cor-
rected for molecular weight change and water concentration, would therefore
equal the rate of photooxidation of S02 which is constant during the linear
growth phase of the experiments. Under these conditions, the slope of the
straight line volume growth curve can be related directly to the rate of
photooxidation of S02 according to:
d[S02] dv ^1
" dt dt X p x - x MW2
where p is the density of the H2S04 droplet, P_ is the weight fraction of
H2S04 in the drop, MW^ is the molecular weight of S02, and MW2 is the molecu-
lar weight of H2S04>
The above equation is true if one assumes that (1) all of the SO,
formed combines with water to form HgSO, droplets; (2) the sulfuric acid
droplets are in equilibrium with the water vapor in the gas phase; and (3)
the droplets are represented by a pure HgSO^ solution. For a clean, contami-
nation-free system, these assumptions appear valid; however, in the presence
of even small amounts of particulates, reactive hydrocarbons or nitrogen
oxide species, large deviations from linearity can be expected with attendant
accelerated aerosol growth. In addition to homogeneous gas-phase reactions
involving the reactive intermediates generated from trace contaminants,
-------
heterogeneous paths may also contribute to accelerated S02 oxidation and
aerosol growth. The Calspan chamber with its relatively small surface to
volume ratio is especially suited to studies of heterogeneous reaction effects,
as well as the mechanics of aerosol growth and decay in the atmosphere.
Experiments have therefore been directed toward the aerosol characterization
and formation rate data relevant to the interpretation of atmospheric S02
photooxidation. The photooxidation rates reported here are based mainly on
interpolations of the EAA aerosol data. The initial and max rates are cal-
culated respectively from the data over an initial low growth period and a
relatively short interval of active aerosol development. The photooxidation
rates so computed must be regarded as excessively high whenever non-sulfate
aerosols are also being produced.
3.1 Data Summary -- SOp-Containing Systems
Careful examination of aerosol data from S02 + clean air experiments
performed during the past year shows that in most cases there is a slight
upward curvature in the volume growth during the late stage or about the
second half of each experiment. A typical example of this behavior is shown
in Figure 1. Here the volumetric growth curve rises slowly during the first
30 minutes or so and then increases rapidly thereafter. As noted in our pre-
vious discussion, this would suggest a role of trace contaminants in the air.
According to Calvert and McQuigg (1975), contributions to SCL photooxidation
by HOp-SOp and OH-S02 reactions would reach maximum values after about 30
minutes in the slightly polluted air. As the S02 + clean air irradiation
proceeds, reactive intermediates build up within the chamber (depending on
the background levels of NO and contamination of chamber surfaces) and the
X
photooxidation rate of S02 increases. Because of the upward curvature noted
in most S02 + clean air experiments, three rates of S02 photooxidation are
computed from the EAA dataone during the initial 30 to 45 minutes of the
experiment, one during the maximum aerosol growth period of the experiment,
and an average value computed for the full length of the experiment. Data
for all S02 + clean air experiments performed during the past year are sum-
marized in Table I. The table shows the experiment number, date, S02
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00
J20 ISO
TIft (MIN)
300
Figure 1 AEROSOL DEVELOPMENT IN THE SO2 + CLEAN AIR SYSTEM
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Table I.
SUMMARY OF "CLEAN AIR" S02 PHOTOOXIDATIONS
Run
No.
1
2
3,4
5
6
7
8
9
10-17
18
19-23
23B
24
25
26
27-29
30
32
33-36
37
38
39
40
41
42-44
45
46-48
49
50
51-53
54
Date
10/11/74
10/14/74
Clean Air
10/16/74
10/16/74
10/17/74
10/17/74
10/18/74
Propylene
2/11/75
Propylene
4/04/75
4/04/75
4/06/75
4/07/75
Inorganic
4/12/75
4/17/75
Inorganic
6/16/75
6/20/75
6/20/75
6/23/75
6/24/75
Rural Air
7/2/75
Rural Air
7/17/75
8/25/75
Fi 1 tered
8/29/75
S02 Cone.
ppm
0.28
0.30
Irradiations
0.25
0.25
0.37
0.31
0.36
+ NOX Irradiations
0.42
+ NOX + S02 Irradiations
-- AUTO EXHAUST
0.26
0.38
0.53
0.50
Test Series
0.96
0.54
Test Series
0.68
1.00
0.76
0.70
0.60
Irradiations
0.58
Irradiations
0.55
0.54
Rural Air + S02
0.50
RH
%
46
30
__
48
42
39
39
41
30
Irradiation
Dark Rx Time
Yes
Yes
CLEAN CHAMBER
Yes-Large
Yes
Yes
Small
No
No
min
180
120
120
90
90
120
60
210
EXPERIMENTSTHEN CLEAN CHAMBER ~
35
38
34
45
22
25
55
63
30
35
41
40
65
61
50
Yes -Large
Yes-Large
Yes -Large
Yes-Large
Small
Small
Small
Small
No
No
No
No
No
No
No
75
90
90
120
60
90
60
60
240
330
240
420
90
90
RSO
2(initial)
% hr
RSO,
2(max)
-1
1.0
2.0
1.3
0.8
0.4
0.
0.
.2
.5
0.2
11.1
3.4
2.8
3.7
0.6
0.5
1.4
0.5
0.7
0.4
0.4
0.5
0.5
0.2
0.1
% hr
3.6
5.0
2.6
1.7
0.9
0.2
0.7
-1
3.0
9.7
3.0
2.8
3.7
0.9
1.2
4.6
1.7
3.4
3.8
2.7
2.1
1.4
1.6
0.9
S02(ave)
% hr"1
1.7
4.4
1.9
1.1
0.9
0.2
0.6
1.4
8.5
3.3
2.5
3.2
0.9
1.0
3.0
1.7
1.6
2.1
2.1
1.2
0.7
1.1
0.5
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concentration at the beginning of the experiment, relative humidity, presence
or absence of a dark reaction, irradiation time, and the computed SCk photooxi-
dation rates as described above. Aerosol and chemistry data for these experi-
ments are provided in Appendix A.
Observed variations in the specific S02 oxidation rate appear to be
rather insensitive to limited changes in some of the common experimental vari-
ables, such as relative humidity, S02 concentration or chamber size. On the
other.hand, the history of chamber conditioning arising from preceding experi-
ments does seem to have an influence on the results in that somewhat higher
rates are usually observed after first completing experiments using auto
exhaust or reactive hydrocarbons in the presence of NO. What appears to be
A
a positive indicator of a reactive S02 system is the presence of a dark reac-
tion after admitting S02 into the chamber. Some of these effects can be seen
from the dark reaction data shown in Table I.
The first two experiments of the entire test series were conducted
after having just completed several auto exhaust irradiations on another
EPA program (Contract No. 68-02-0698). In both tests, there was a large dark
reaction prior to irradiation as well as enhanced S02 photooxidation. After
cleaning and rinsing the chamber with distilled water, two clean air irradia-
tions were performed to test for background reactions. In both instances, no
appreciable particle formation was observed.
Experiments 5-9 were repetitive S02 irradiations in clean air.
Here, as in previous instances, a conditioning effect was noted in that each
successive irradiation produced a slightly lower SO,, photooxidation rate.
The conditioning effect was also manifested in the form of a decreasing dark
reaction after each successive S02 experiment. It is likely that the condi-
tioning process results in the destruction or other losses of contaminants
within the chamber, which would presumably result in a lessening of the S0?
oxidation rate. Desorption of HONO (MONO j^ป HO + NO) from chamber surfaces
may, for example, occur to a lesser extent with each successive irradiation.
10
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On the other hand, after performing several HC-NO experiments, renewed forma-
A
tion of MONO may result in substantial contamination of chamber surfaces
requiring additional conditioning to achieve low R$o2- If t'ie cnam')er sur"
faces are badly contaminated, a large number of S02 conditioning tests may
be required before any appreciable reduction in Rcn is observed.
bU2
The second series of experiments seem to bear out this assessment.
Experiments 10-17 and 19-23 were performed as part of the chamber intercom-
parison test series involving propylene + NO and propylene + NO + S09
X X c
irradiations. Following these experiments, a number of auto exhaust irradia-
tions were performed. In spite of cleaning and rinsing the chamber surfaces
after these tests, the next several S02 + clean air irradiations produced
large dark reactions and much higher than usual S02 photooxidation rates.
In fact, the rates observed in this particular test series (23B-26) were the
highest ever observed at Calspan for S02 + clean air irradiations.
Following the above experiments, an inorganic test series was per-
formed (experiments 27-29 and 33-36) in which various amounts of CO was intro-
duced into the NO + S09 system. Different levels of carbon monoxide ranging
/\ Cm
from background concentrations of less than 10 ppb to 400 ppm were irradiated
in the presence of SO, + NO in an effort to evaluate the possible effects of
ฃ /\
CO on RSO?' (The significance of these experiments is discussed in more detail
in Section 5.) It is worth noting that for this series of tests, as well as
the subsequent S0? + clean air experiments (experiments 30 and 32 and 37-41),
R$02 (initial) was at significantly lower values. On the other hand, R$02(ave)
still was relatively high suggesting that surface contamination or reactive
intermediate production or both were not completely eliminated. Note also
that the amount of dark reaction in the later tests was much lower indicating
a less reactive system.
The final series of experiments involving rural air + S02 irradia-
tions with and without natural nuclei was designed to test for accelerative
effects of natural nuclei on the heterogeneous oxidation of SO,,. Interposed
11
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between the rural air tests, SOp + clean air irradiations were performed.
The experiments, numbers 45, 49, 50 and 54, show a distinct chamber condition-
ing effect in terms of reduced value of the initial, maximum, and average R$02'
Since only rural background levels of hydrocarbon and NOV (less than 0.2 ppm
A
non-methane HC and <0.02 NOV) were used in this test series, no significant
A
contamination of the chamber air or its surfaces occurred between the S02 +
clean air irradiations. This is further evidenced by the fact that no appre-
ciable dark reaction was observed after introducing S02 into the chamber for
any of the last few experiments. The range of S02 photooxidation rates in
experiments 45, 49, 50 and 54 may be taken as typical of the Calspan chamber
after conditioning, i.e., from a few tenths of a percent per hour to slightly
greater than 1% hr .
3.2 Comparison of Sulfate Analysis by the Barium Perchlorate Method
with EM Data
Midway through this year's program, an effort was made to develop
microanalytical capabilities for direct determination of sulfate content of
the aerosol using the barium perchlorate titration method (Fielder and Morgan,
1960). Determinations of R$o2 could then be made and compared with apparent
photooxidation rates as computed from EAA data. For several of the experi-
ments, analytical results were checked by independent analysis of filter
samples at Battelle. Ammonium analysis was also provided by Battelle for
several of the runs and by Calspan for the last few experiments of the entire
test series. In this section, results of some of the experiments are pre-
sented and compared with EAA data where possible.
Analysis Procedure
In the initial series of sulfate aerosol analyses, samples were col-
lected with a two-inch diameter Gelman inline filter holder, with the total air
3
volume for each sample about 1 m . Prewashed Tissuquartz filters were used to
minimize the possibility of on-filter oxidation of S02- The sulfate content
for each aliquot filter sample was only slightly greater than the detectability
12
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limity of the barium perchlorate titration technique. Consequently, the ana-
lytical results were found to be unsatisfactory, both with respect to compari-
son with EAA data and from comparison of Calspan and Battelle results.
For the later experiments, a 142 mm diameter Gelman inline filter
holder was used to acquire aerosol samples. This permitted the sampling of
air volumes in the range of 7 m3 to 15 m3 within convenient sampling periods.
For experiments 39 on, one-half of each filter sample was delivered to Battelle
for analysis. The remaining half of each sample was analyzed at Calspan accord-
ing to the following method.
Each filter sample was digested over low heat for about an hour in
20 ml of distilled water. The sample was filtered, adjusted to alkaline pH
with two drops of 0.02 N NaOH and then reduced to 10 ml by evaporation over
low heat. Forty ml isopropanol was added to each sample to make up a 4:1
isopropanol-water solution of 50 ml total volume. The sulfate content in
each sample was determined by titration with 0.0048 N barium perchlorate to
the thorin indicator end point. Ammonium analysis was performed by digestion
of the filter sample in distilled water with the addition of two drops of
0.05 N HpSO,. The resulting solution was filtered and concentrated to 10 ml
by evaporation over slow heat. Analysis of the solution was then performed
with a gas-sensing ammonium ion specific electrode.
Analysis results for a number of experiments are summarized in
Table II. The table shows the experimental conditions, initial S02 concen-
tration, sulfate content of the collected aerosol, computed S02 oxidation
rate, initial and maximum S02 oxidation rate as determined from EAA data,
NH4+ content and stoichiometric NH4+ to sulfate ratio.
It may be noted from the data in Table II that the results tend to
agree best with the "initial" S02 photooxidation rates as determined from the
EAA data. In this respect, the data are in good agreement for the S02 + clean
air and SO- + NO + CO systems. The apparent lack of agreement between the
L, X
-------
Table II. AEROSOL SAMPLE SULFATE AND AMMONIUM CONTENT
Run No. & Initial
Conditions S02 Cone. ,
ppm
31
33
34
36
39
40
41
42
43
44
45
46
47
48
51
52
53
so2 +
so2 +
so2 +
so2 +
so2 +
so2 +
so2 +
Rural
Rural
Rural
S02 H-
so2 +
so2 +
so2 +
so2 +
so2 +
SOo +
NOX +
N0y +
A
N0y +
A
NOX +
clean
clean
clean
air
air
air
clean
rural
rural
rural
100 ppmCO
100 ppmCO
400 ppmCO
400 ppmCO
air
air
air
air
air
air
air
filtered rural air
filtered rural air
filtered rural air
0.60
0.56
0.46
0.45
0.76
0.70
0.60
<0.01
<0.01
<0.01
0.58
0.52
0.48
0.52
0.65
0.50
0.54
Sul fate
Content
yg/rn3
--
12.2
27.8
13.0
44.0
46.9
46.4
.53
.67
4.9
39.3
35.2
25.2
23.6
25.5
49.3
22.8
S02 Ox.
Rate,
%/hr
0.2
0.5
0.2
0.5
0.5
'0.6
0
0.4
0.5
0.4
0.3
0.3
0.7
0.3
Rs02(initial)
EAA Data
%/hr
0.3
0.4
0.5
0.3
0.7
0.4
0.4
0
0.5
2.0
1.2
1.0
1.9 4-
0.8
1.1
Rso?(niax)
EAA^Data
%/hr
0.9
1.0
1.1
1.2
3.4
3.8
2.7
.-_
-
0
2.1
2.3 4-
1.6 i
1.4 i
(Dark Rx)
1.1
1.2
RsQ?(ave) NH4 Stoichiometric
EAA^Data Content NH4+ - Sul fate
%/hr uq/m3 Ratio
0
0
0
0
1
2
2
1.
0.
0.
1.
1.
0.
0.
.6
.6
.8
.8
.6
.1
.1
__
8.1
2 13.9
8 17.2
8 ,17.7
1 15.7
1 16.5
9 15.4
7 13.1
_
...
...
...
...
4.4
0.9
1.3
1.9
1.8
1.7
0.8
1.5
-------
sulfate analysis and R$02(max) and R$02(ave) for these systems suggests the
presence of background contaminants which led to the formation of impurity
aerosols other than sulfate. Under these conditions, the assumption that
all aerosol formed is H2$04 is obviously not valid. Indeed, the rather appre-
ciable amounts of NH^in the samples lead to uncertainties in the interpreta-
tion of data obtained with the electrical aerosol analyzer during the later
stages of the experiments. The EAA data can be interpreted to give the instan-
taneous S02 oxidation rates only when the aerosol composition, including the
content of water of hydration, is well established. Aerosol loss, especially
during the late stages of the experiment period, is difficult to avoid and
therefore directly affects the results. It would appear from these data that
initially nearly all of the aerosol formed is H2S04 and that later into the
experiment substantial contributions to aerosol development occur from impuri-
ties within the air or from contaminated chamber surfaces or both.
3.3 S09 in the Presence of Natural Nuclei
Evidence of initial catalytic effects on aerosol growth can be seen
from the data summaries for experiments 46 through 53. In experiments 46, 47
and 48, unfiltered rural air containing natural nuclei was irradiated in the
presence of SO^. In almost every instance, the computed S02 oxidation rate
based on sulfate determinations was much lower than that determined from the
EAA data assuming acid aerosol. Apparently under these conditions, background
impurities, as well as natural nuclei in the rural air, were sufficient to
produce appreciable initial aerosol growth beyond that due to S02 photooxida-
tion alone. In assuming that all of the aerosol formed was H2S04, the EAA
estimation of R$o2 was obviously too high. After a relatively short time,
the aerosol grew beyond the detection limits of the EAA and the apparent
S02 oxidation rate decreases. Although we have followed the usual procedure
of evaluating the EAA data in terms of ^(initial)' Rsฐ2(max)' and RS02(ave),
an obvious point of inflection in aerosol growth does not exist for the S02 +
rural air irradiation rate data.
15
-------
The data for experiments 51 through 53 show similar trends. Here,
rural air was introduced into the chamber followed by absolute filtering to
remove natural particles. No charcoal filtering of the air was attempted.
After irradiating the sample for three hours, aerosol samples were collected
for comparisons with EAA data. As before, R$o2 based on the aerosol analyzer
output was substantially higher than that determined from sulfate analysis.
In these experiments, even after absolute filtering of the air, the presence
of natural background levels of non-methane hydrocarbons, NOX and 03 were
apparently sufficient to produce enhanced aerosol growth during the early
stages of the experiments. The computation of a large S02 oxidation rate
based solely on HpSO, aerosol was therefore erroneously high, since aerosol
sufficient to produce enhanced aerosol growth during the early stages of
the experiments. The computation of a large SCL oxidation rate based solely
on H2SO^ aerosol was therefore erroneously high, since aerosol composition
was of mixed origin. The data indicate that the S02 photooxidation rate as
computed from aerosol sulfate content falls within the range of 0.3 to 0.5
percent per hour regardless of whether the S02 is irradiated in natural rural
air, with only the natural particulates removed or with cleaning through both
absolute and charcoal filters. Initial aerosol production is enhanced some-
what over the S02 + clean air system, but after several hours of irradiation
the S02 + clean air and S02 + rural air samples give comparable results in
terms of aerosol development.
Comparisons of the Calspan and Battelle sulfate and, where available,
NH. analyses are shown in Table III. The data as shown are in substantial
agreement and give added confidence to the reliability of the analytical tech-
niques. In order to minimize the effect of background contaminants, each of
the quartz filters were individually washed with water distilled over perman-
ganate and then recompressed and dried. This may have resulted in inhomogenei-
ties in porosity, as well as aerosol particulate distribution over the filter.
It is, therefore, not surprising to find up to 30% difference in analytical
results for some of the samples.
16
-------
Table 111. COMPARISON OF CALSPAN AND BATTELLE ANALYTICAL RESULTS
Run No.
39,
40
41
42
43
S-138
S-140
Origin
Calspan
Calspan
Calspan
Calspan
Calspan
BatteH e
BatteH e
Calspan Analyses
ter
Battelle Analyses
153
246
162
2.8
4.7
1712
728
yg/filter
156
350
97
< 10
< 10
1230
590
NH4
yg/filter
96
144
66
< 2
20
220
120
17
-------
It is worth noting that the ammonium content for each of the filter
samples analyzed fell within a narrow range of 96 to 146 yg per filter.
Although inadvertent contamination of the filters must be considered, a more
reasonable explanation is that the aerosol sulfate was generated from trace
amounts of NH~ in the chamber air. For the S09 photooxidation experiments,
+ 33
the NH^ content of the aerosol samples ranged from 8.1 yg/m to 19.1 yg/m .
A residual MM- concentration in the chamber air of about 0.04 ppm would
+
account for the aerosol ammonium measured. The fact that the observed NH^ /
S0^~ stoichiometric ratio was greater at low sulfate concentrations tends to
support the contention that the background chamber NH-, content is the respon-
o
sible factor for the observed aerosol NHป stoichiometry. At the rather low
background NhL concentration conditions, NH, would be incorporated mainly
by neutralization subsequent to an initial formation of sulfuric acid aerosol.
In the absence of heterogeneous mechanisms, this low level NH3 contamination
is not expected to affect significantly the S02 photooxidation rates.
18
-------
Section 4
PROPYLENE + NOV AND PROPYLENE + NOV + S00 EXPERIMENTS
A X i.
This year, several propylene + NO and propylene + NOV + SO,, experi-
A At
ments were performed as part of a smog chamber intercomparison test series.
The propylene + NO system has been subjected to data evaluation by extensive
A
computer modeling of kinetic data in the past and offers a good opportunity
for comparing chamber performance with model predictions. Summaries of the
chemistry and aerosol data for these experiments and two corresponding Bat-
telle experiments are given in Tables IV and V. In Table IV, the run number
and date, reactant concentrations, and times to ozone and N02 maximum values
are shown. Table V summarizes the maximum number concentration for each sys-
tem, the initial volumetric production rate [dv/dt]S02, the computed initial
S0ฃ oxidation rate as determined from EAA data, and the maximum aerosol pro-
duction rate [dv/dt]max, achieved during the course of the experiments.
Chemistry data for the propylene + NO system and chemistry and aerosol data
A
for propylene + NO + SO, tests in which the same initial reactant concen-
X ฃ
trations were used are plotted in Figures 2-5 (i.e., run numbers 15, 16 and
22, 23).
From the data in Table IV, it can be seen that for an initial con-
centration of 3.0 ppmC propylene and 0.50 NOV (runs 15, 16, 22, and 23), the
A
time to ozone peak is about 180 to 190 minutes, and the time to N02 max is
about 120 minutes. The Battelle data is similar, but the time to [N02]max is
somewhat shorter. Maximum ozone concentrations are between -550 and .705 ppm
for the Calspan runs and about .420 ppm for the Battelle tests. Variations in
the initial reactant concentrations resulted in appreciable differences in the
ozone (max), as well as in the times to 03 and N02 maxima. The addition of
S0? to the propylene + NO system did not affect the chemical behavior in
any significant manner. A somewhat reduced [03]max yield in the presence
of S0? may be inferred from the Calspan data, but a definitive conclusion
to this effect cannot be made.
19
-------
Table IV.
SUMMARY OF CHEMISTRY DATA FROM PROPYLENE + NO,, AND PROPYLENE + NO + SO, IRRADIATIONS
Run
No. Date System
11 10/21/74 Propylene + NO
A
14 12/27/74
15 12/31/74
16 1/03/75
Battelle - 114 "
17 1/16/75 Propylene + N0y + SO,
A C>
21 2/14/75
22 2/16/75
23 2/17/75
Battelle - 197
SUMMARY OF AEROSOL DATA FROM
Run
No . Date System
11 10/21/74 Propylene + NOX
14 12/27/74
15 12/31/74
16 1/03/75
Battelle - 114
17 1/16/75 Propylene + NOV + SO,
A L.
21 2/14/75
22 2/16/75
23 2/17/75
Battelle - 197 "
Propylene i 2i
ppmC ppm ppm
3.0 0.46 .13
3.0 0.60 .05
3.0 0.46 .04
3.0 0.45 .05
2.9 0.42 .10
3.5 0.48 .05
2.6 0.48 .04
3.1 0.46 .03
3.1 0.47 .05
3.2 0.39 .10
Table V.
PROPYLENE + NO AND PROPYLENE
A
[ ]
max 2
cm pm /cc-hr
2.6 x 105
1.0 x 105
1.4 x 105
1.2 x 105
>107 18.1
4.0 x 106 3.2
>107 5.3
>107 4.7
9.5 x 105 23.0
i line u
Eฐ3-'max ^S^ma)
ppm mm
.760 140
.790 235
.705 180
.685 190
.420 190
.605 135
.555 225
.555 180
.565 180
.430 160
+ NO + SO, IRRADIATIONS
A ฃ
R
S02(initial)
% hr"1
...
0.7
0.3
0.4
0.4
0.7
> i i me i
("nift i
, L'"*oJm
min
85
150
110
120
85
95
165
120
120
60
rdV-l
[dt]max
v\n /cc-hr
6.1
--
>1500
466
392
361
77
20
-------
! ON 05 \ \ } I pirnSt *~ซL svsra j "I i I I I I
j j 4 h | 4. J i ,_. j J 4 + 4. .J. I j. i i
! Etjlffi} 51, BW i i OEHISTW DATA i i I | | j i
|Tf j i \ [-] I I I i i i i i i +
|j j1 1 | ; j.j. _..__, ] I] i | i
60 120
TINE (KIN)
Figure 2 CHEMISTRY DATA FOR PROPYLENE + NOX SYSTEM
o-o
60 120
Tilt (MIN)
Figure 3 CHEMISTRY DATA FOR PROPYLENE + NOX SYSTEM
21
-------
PIOTIEHE + Sp2 + NOx SVSTB1
JBOSOLMTA [
60 120
TIfE (KIN)
J0
Tilt (MM)
Figure 4 AEROSOL AND CHEMISTRY DATA FOR PROPYLENE + NOX + SO2 SYSTEM
22
-------
B^EPjS] 1 1 nrซW^ttsSir T V T r r-
Nwwi iMBW1 T !~! r~i-ป s -i i-4.-;?..slrH'. i i i j i
[-T^-~Ri i 1 1. ป i .W080LWA | j ] t "~T~
sM-U-l Mi 'T I ! ! ! i ! i I i t
, t .jT ! I i i i i i ! !
H-4-4 ...J L i ! 11 I i 1~t ft t M f~.
!___[ i ! I | | 1 i i |"H t i- f j i i | | I i |
i n
~i-ij
-t t
I
t 4~~4~
\ i j 4
''.', t i ' t
iSl I i ! I !~T~T~T~t~
JUST ! i r-ft-
s
1*5
j |l|U
i i s
-4
-t-H
w
JRUNffilA'1 F"7
0.5
f" "T"1 j ! I f-! rT\ i 1 1 i
t f I i I i ! 1 1 1-4 1 i 1
i ! [ t r ; f I I i i ! I I
ซ> 120
Tilt (HIM)
6 AEROSOL AND CHEM.STRV DATA f OR PROPYLENE + NO
)c +
23
-------
By contrast, large differences were noted in aerosol behavior of
the propylene + NO system after adding SO,. The most obvious differences
A L*
observed were in the peak number concentration and maximum volumetric growth
rate of the aerosol. The data in Table V show that the maximum particle
concentration was generally more than two orders of magnitude greater for
the propylene + NO system with added SO,. A malfunction of the aerosol
A ฃ
analyzer during experiments 14-16 prevented the acquisition of aerosol data
for these experiments. In experiment 11, the [dv/dt]max for the propylene +
NOV system in the absence of SO, was found to be 6.1 un^/cc-hr"1. An apparent
A C*
syriergistic effect seems to occur wtth the addition of SOg in that the maximum
volumetric growth rate is greater for the mixed system than for the individual
rates of propylene + NOV and SO, combined. Note that [dv/dt]max for
X ฃ.
experiments 17-23 in which there was added SO, produced volumetric growth
3 1
rates which ranged from 361 to >1500 ym /cc-hr . Before the onset of rapid
0~ formation, the volumetric growth rate was more like that of the SO, + clean
31
air system alone (i.e., a few mm /cc-hr ). The computed R$0o for the first
1^
30 minutes of experiments 17-23 was between 0.3 and 0.7% hr .
Some of these features can be seen from the aerosol data plotted
in Figures 4 and 5 (experiments 22 and 23) for the propylene + NOX + SO,
system. After admitting SO, and irradiating the sample, there was an expected
7-1
rise in particle concentration to values in excess of 10 cc . The volume
concentration during the first 60 to 90 minutes was very low because of the
small size of the nuclei, generally less than 0.04 pm in diameter.
The beginning of the second stage of aerosol growth occurred at
about the time that the NO was oxidized out of the system and rapid 03 for-
mation took place. At this point (about 110 minutes), there was a seemingly
explosive growth of the aerosol in terms of both surface and volume concen-
trations. Nearly all of the growth was in the form of additional condensation
on existing particles since the particle concentration did not increase during
this period. By contrast, in the propylene + NO system, only a modest
A
increase in particle number occurred after NO oxidation was complete. Some
aerosol growth occurs, but it is small compared to that observed for the
system with added SO,.
24
-------
At Battelle, kinetic treatment of the data indicates that during the
induction period (when the N0/N02 ratio >1), oxidation of S02 to aerosol can be
attributed entirely to the S02 + OH reaction. Oxidation of S02 is relatively
slow during this period because of the competition for OH exhibited by propy-
lene and NOX. Estimates suggest that only 1-2 percent of the OH during this
period is available to react with S02. It may also be inferred for this in-
terval that the rate of S02 oxidation by H02 and R02 is at least two orders
of magnitude slower than the rate of NO oxidation by these intermediates.
About the time of 03 appearance, there is a rapid rise in the rate
of S02 oxidation. It has not been determined, however, whether the accelerated
rate of S02 oxidation is due to an increase in OH, R02, and H02 radicals, or
to the appearance of other reactive intermediates resulting from propylene +
Oo reactions.
Although sulfate analyses had not started at Calspan when these
experiments were performed, more recent determinations show that the average
S00 photooxidation rate during the overall irradiation period in the propy-
^ _i
lene + NOV + SOP system is approximately 2.7% hr . For Battelle run #107,
A b
the maximum rate is about 2.3%/hr which is in accord with the Calspan data.
(Recall that R$OO is typically about one percent per hour for the S02 + clean
air system.) Since the accelerated production of aerosol during the second
growth stage amounts to an equivalent S02 photooxidation rate of up to 30% hr~ ,
most of the aerosol which is produced must be organic in nature. Additional
determinations of sulfate concentration in the HC-NO -S02 system are planned
both at Calspan and Battelle in an effort to establish the conditions of
maximum S02 photooxidation rate and to assess in more detail the chemical
nature of aerosol composition.
.25
-------
Section 5
THE INORGANIC SYSTEM - CO + NOX + S02
One of the questions regarding the rate of S02 photooxidation
involves the contributions of the HO and H02 radicals to the overall oxida-
tion process. Theoretically, if contaminants leading to the formation of
OH are important, then one should be able to study the effects of OH scaveng-
ing on R$OO by irradiating an inorganic system such as CO + NOX + S02. It
is postulated that the added CO would scavenge OH radicals in competition
with S02 and thus inhibit the oxidation of S02- The higher the CO level the
lower would be the expected oxidation rate of S02. In the postulated compe-
titive process for OH radicals, the following reactions involving OH and H02
are expected to be important:
HO + CO -> C02 + H (1)
H + 02 + M -> H02 + M (2)
H02 + NO * HO + N02 (3)
S02 + OH(M) + HS03 -ป Products (4)
At low concentrations of CO, the S02 + OH reaction would be a rate controlling
process for OH consumption. As the concentration of CO is increased, reaction
(1) would become dominant.
In an effort to determine the effects of increasing the level of CO
on R$02> several experiments were performed in the Calspan chamber using
various levels of CO ranging from background concentrations to about 400 ppm.
The NO and N02 concentrations were kept at approximately 0.5 ppm and 0.05 ppm
respectively. The average temperature for the tests was ~80ฐF and the rela-
tive humidity was kept as close as possible to 50%. Chemistry and aerosol
data for these experiments are summarized in Tables VI and VII.
26
-------
Run
No.
27
28
29
31
33
34
36
Table VI.
SUMMARY OF CHEMISTRY DATA FROM THE
Date System C0i
4/08/75 S02 +
4/09/75 S02 +
4/10/75 S02 +
4/14/75 S09 +
C
4/18/75 S02 +
4/22/75 S02 +
4/29/75 S02 +
*
Background level of CO;
N0x +
NOX +
NOX +
NOY +
X
N0x +
NOX +
NOY +
X
b (CO)
b (CO)
b (CO)
CO
CO
CO
CO
ppm
b*
b
b
100
100
430
410
INORGANIC TEST SERIES
NO. N021 S02-
ppm
0.52
0.51
0.46
0.43
0.42
0.46
0.62
ppm
0.
0.
0.
0.
0.
0.
0.
05
05
04
03
03
04
06
ppm
0
0
0
0
0
0
0
.55
.72
.56
.60
.56
.44
.48
3 max
ppm
.002
.002
.002
.046
.031
.520
.267
t
t
+
t
generally <1 ppm
Run
No. Date
27
4/08/75
28 4/09/75
29
31
33
34
36
*
S
4/10/75
4/14/75
4/18/75
4/22/75
4/29/75
Table VII.
SUMMARY OF AEROSOL DATA FROM INORGANIC TEST SERIES
System Nmax Smax* S02(i) S02(max)
S02 H
so2 ^
S02 H
S02 H
S02 H
S02 H
S02 H
hNOx
h NOX
hNOx
hNOx
h N0x
LNOx
-N0x
/ \ = maximum surface
(max;
+ b
+ b
+ b
+ CO
+ CO
+ CO
+ CO
area
cc'1
(CO) >107
(CO) >107
-i
(CO) >10X
>107
7
>10X
>107
7
>107
of aerosol
ym /cc %
3.2xl03
3.4xl03
2.9xlOJ
3
2.6xlOJ
2.9xl03
3
3.2xlOJ
produced during
hr"1
0.6
0.4
0.5
0.3
0.4
0.5
0.3
% hr
1.
0.
1.
0.
1.
1.
1.
-1
1
9
6
9
0
1
2
S02(ave)
% hr"1
0
0
1
0
0
0
0
.8
.8
.0
.6
.6
.8
.8
experiment.
27
-------
The data show that in the Calspan chamber neither the initial nor
the maximum S02 photooxidation rate is affected by changes in the CO concen-
tration up to 400 ppm when there is appreciable NO in the system. There are,
A
however, changes which occur with respect to the chemistry. As the CO level
is increased, there is a noticeably more rapid oxidation of NO to NO,, together
with an increase in the amount of ozone formed. Representative illustrations
of chemistry and aerosol data for each of three CO levels (background, 100 ppm
and 400 ppm) are shown in Figures 6, 7, and 8.
The figures show that aerosol behavior is nearly identical for the
three CO levels tested. The principal difference in the tests was in the
larger dark reaction in the experiments involving high concentrations of CO.
(Dark reactions could be minimized by introducing the CO into the chamber
through a charcoal + A1203 scrubber to remove metal carbonyl contaminants.)
As shown for each test, there is an immediate rise in particle concentration
after turning on the lights. The maximum number always exceeded the upper
limit (10 particles/cc) of the Gardner small particle detector at this stage
of this experiment. After periods of time ranging from less than 10 minutes
to about an hour, the concentration of particles decreased to a level within
the range of the particle detector. Meanwhile, the aerosol surface and volume
concentrations increase slowly at first and then at a slightly more rapid rate.
For these experiments the range of initial S02 oxidation rates was between
0.3 and 0.6% hr" or approximately the same as that measured for the S02 +
clean air system. The average S02 oxidation rate, R$o2/ \, as measured
with the aerosol analyzer was in the range of 0.6 to 1.0 hr"1, which is
somewhat lower than in the S02 + clean air system. No changes are evidenced
in the aerosol data as a function of the increasing CO concentration. The
maximum particle concentration, Nm. and the maximum aerosol surface con-
HldX
centration, $max, is approximately the same for all seven experiments.
This series of experiments was conducted in the absence of any hydro-
carbon additives. The fate of OH and H02 radicals within the reaction system
was largely governed by the presence of NO and N02 as shown by Reaction (3).
28
-------
1
,
-a t
1975 !, ! i i j j \ i j AEROSOL DATA j i
r tjt i t i i-~*-j i } | | t
4f<1H
------ 12
10 i
i r i i ix ! i I
: ! ; i ; J; : -r -}.
| | | | i X i | r j
j f-j i--*/!- : i i i
i : i i ' : i ; i j
i i i / | : '. ;;>
ItfOTTlT'
"60 ' '""iffl""' 180
TDt (MIN)
..'. -r -t
........
ao
"0 i
j S02 + m SYSTEM i I ; i i ! i I i
180
Tilt (HIN)
300
Figure 6 AEROSOL AND CHEMISTRY DATA FOR SO2 + NOX SYSTEM
29
-------
T ^^^.} y y f
a 1 k t |. j : (....,..; .4 ,...ฃ.* -\ t t f j I i
rtLllBS ! i ! ! i Mi i i ซHSOLMm i i i i i
-+--4 f lT-1 ! t ! \f -t ! 7 i 1 1 i i 1 t
3h3
f t~-
: i
.fi
--f r i- r>"4 if i !"
'ป i ! I I !
TIffi (MIN)
flPRJLl
.7
,j
I I i ! i i I $Cb + IKL + CD SYSTEM
* f i i ; - - -+ *.-.,-..
,B(5 M ! j i ! I
i I 1 I i i ซ-00ป100pmf i
(MIN)
Figure 7 AEROSOL AND CHEMISTRY DATA FOR SO2 + NOX + 100 PPM CO SYSTEM
30
-------
120 180
TlfE (MIN)
120 ISO
TIfE (MIN)
300
Figure 8 AEROSOL AND CHEMISTRY DATA FOR S02 + NOX + 400 PPM CO SYSTEM
31
-------
The observed data showing a lack of effect of added CO up to 400 ppm is
therefore consistent with the expectation that the rate of Reaction (7) is
small in comparison to the reverse rate of Reaction (3). The results of the
above experiments are not conclusive, since sulfate analysis from aerosol
collections were only in agreement with the initial rate of SOg oxidation in
the clean air + S02 experiments. As mentioned previously, it is possible that
the final rate of S02 oxidation as determined from the EAA may be erroneously
high due to the contributions to aerosol growth from reactions other than those
involving sulfate. If this is the case, the RCn may actually be even
S02(ave)
lower than that shown. Additional experiments are needed to resolve this
question.
32
-------
Section 6
THE RURAL AIR + S02 SYSTEM
A few experiments were performed to examine possible catalytic
effects of natural nuclei in rural air on the S02 oxidation rate. These
tests were preliminary in nature and are still under way so that only a
brief discussion of results will be presented here. Some results have
already been presented in Section 3 as part of the comparison of sulfate
analysis procedures using the EAA data and the barium perchlorate method.
Chemistry and aerosol data for the rural air, rural air + S02>
and filtered rural air (free of particles only) + S02 systems are shown in
Table VIII. The table shows the run number and conditions, initial S02
concentration, sulfate content, R$o? as determined from sulfate analysis,
^ .j.
the maximum aerosol surface concentration, and the NH. content of the aero-
sol samples. In our previous discussion, we stated that the S02 photooxida-
tion rate as computed from aerosol sulfate data was found to fall within
the range of 0.3 to 0.5 percent per hour regardless of whether the S02 was
irradiated in natural rural air, with only the natural particles removed,
or with cleaning through absolute plus charcoal filtering of air. Initial
aerosol growth was found to be somewhat enhanced over the S02 + clean air
system, but for the most part aerosol development was similar for both systems.
Three classes of rural air experiments were performed. They are
summarized in Table VIII and illustrated in Figures 9, 10, and 11. The first
experiment set, numbers 42, 43 and 44, involves irradiations of rural air
alone with no other added contaminants. Data from these experiments provide
a baseline against which the rural air + S02 experiments can be compared.
As shown in Figure 9, no appreciable aerosol development occurs in the "simple"
rural air system. In the absence of S02, only modest increases are noted in
aerosol number, surface and volume concentrations after the lights are turned
on. Some small sulfate content was measured in the aerosol sample (-0.5 ug/m ,
33
-------
Table VIII. AEROSOL SAMPLE SULFATE AND AMMONIUM CONTENT
CO
Run No. & Initial
Conditions S02 Cone.,
DDin
42
43
44
46
47
48
51
52
53
Rural
Rural
Rural
so2 +
so2 +
so2 +
so2 +
so2 +
so, +
air
air (filtered)
air (filtered)
rural air
rural air
rural air
filtered rural air
filtered rural air
filtered rural air
<0
<0
<0
0
0
0
0
0
0
.01
.01
.01
.52
.48
.52
.65
.50
.54
Sul fate
Content
.53
.67
4.9
35.2
25.2
23.6
25.5
49.3
22.8
S02 Ox.
Rate,
% hr
0
0
0
0.5
0.4
0.3
0.3
0.7
0.3
RSO?^
ERA
%
0
0
0
2.
1.
1.
1.
0.
1.
Data
hr
0
2
0
9 4-
8
1
EAA Data
% hr
0
0
0
2.3 +
1.6 +
1.4 +
(Dark Rx)
1.1
1.2
NH4
Content
ug/m3
0
0
8.1
17.2
17.7
15.7
16.5
15.4
13.1
S(max)
urn /cc
500
100
190
3400
3200
3700
3400
2500
2600
-------
JRJIJK2J I j 1
KpgiHijrr:
I i i ! i :
Ii ; f i f
ปi i t ! I !
[ I i i i I
43"i t i i [ -
S ' : i i
S t i- i - -r '
in i "^ ; ; ! :
agj..2-|5...4....,-t i i
4-1-1 i ; f-
(ซ*. Ail? WITH wiiricu[s ' i I F
t i -T--r i i !-
4 * f
~j -f \ 4 j i \- -i ; ;
-I f i i I I i \ I * 4
i | | : j I j : i
-i \ | [ \ * -f t i * f
I ! i i i i i I f j |
! i i ; ; i | j | :
i iStHFACE
*
:
--7&f--
ml y>
oU! j(j
-9JI-25-
-3D-&
-" 20i B <
!
i
-Bf-5"
-; ' r
360
TIME CHIN)
ii+,.,...-.,.
\JUdS,\BK\ I i
300
Tilt (MIN)
Figure 9 AEROSOL AND CHEMISTRY DATA FOR RURAL AIR SYSTEM CONTAINING
NATURAL PARTICLES
35
-------
16
-if
(MN>
HHBWWTAi i i
1 i !
' '
60 120
T!^E (HIM)
500
Figure 10 AEROSOL AND CHEMISTRY DATA FOR RURAL AIR (WITH NATURAL
PARTICLES) +SO2 SYSTEM
36
-------
--+ I !"~ /-} f i~~
: | 1 ./ : : ,
-354 t t i-
-180
-120
Tilt (MIN)
lllki_l 1 j I i 1 1
:
!
r- i
i--4 i i
jnuMi^fi u\i ฑJT,J \;;',
' : t ; i f ; f
__i_4_l_4 i J.....4
_^_
-j | I } i f t t
-I I \ } t H f
i :::;:::
-i '. i i t f : i -
! I : ! ! i i !
..+ 4. + +
\"\ ! i ! I I i i i i i
i I i i i j. i . j. ; i
,+.,..,.t t ^ : i
i T i : : i : : i i
ao
Tilt (MM)
Figure 11 AEROSOL AND CHEMISTRY DATA FOR RURAL AIR (WITHOUT NATURAL
PARTICLES) +S02 SYSTEM
37
-------
i O
Table VIII) and also NH, (~8 yg/m ); however, these concentrations are con-
sidered normal for a relatively contamination-free environment.
In experiments 46, 47 and 48, S02 was added to unfiltered rural air
and irradiated for several hours. In these experiments substantial aerosol
growth in excess of either the S02 + clean air or the rural air system was
observed. The newly formed aerosol is not pure H2$04, however, since results
of the sulfate analysis indicate an S00 oxidation rate of 0.3 to 0.5% hr~ .
ฃ -I
This is substantially below the 1.0 to 2.0% hr (as determined from EAA
analysis) which would be necessary to account for all the aerosol that is
produced. An example of this type of system is shown in Figure 10. The
figure shows typical features of aerosol development for photochemical sys-
tems involving S02. The principal difference between this and most other
systems is the more rapid aerosol volume and surface development during the
first 60 minutes or so of the experiment. In most S02 + clean air experiments,
there is a slow initial aerosol growth followed by somewhat accelerated rates
after the first 30 minutes of irradiation. On the other hand, in the rural
air + S02 experiments, there was a slight decrease in aerosol volume late in
the experiment, presumably because aerosol growth had proceeded beyond the
detection range of the EAA, resulting in an "apparent" aerosol loss.
In the final test series of the rural air experiments, S02 was
introduced into the chamber after first removing all natural particles from
the system. In this sense, the system was similar to the S02 + clean air
system except that natural rural background levels of NO , HC and ozone were
A
present in the chamber air. Aerosol and chemistry data from this type of
system is illustrated in Figure 11. In this test series, R$02 as determined
from sulfate analysis was not affected to any large extent by the presence
of natural background impurities. Although initial aerosol surface and
volume growth is slightly higher in this system than for S02 + clean air
alone, the differences are not large and are not considered significant.
38
-------
Section 7
SUMMARY AND CONCLUSIONS
Over 54 experiments were performed during the past year to gather
smog chamber irradiation data on various systems ranging from S02 in clean
air to CO + NOX + S02 experiments and rural air + S02 irradiations. From
an analysis of the aerosol and chemistry data generated in these systems,
the following conclusions can be made:
(1) The average S02 photooxidation rate in the Calspan chamber is
approximately 1.0% hr'1 in clean filtered air. Sulfate determinations from
aerosol analysis by the barium perchlorate method were in good agreement with
EAA data during the initial phases of aerosol development. Determinations of
RS02 from E^A data were generally higher during the later stages of the experi-
ment.
(2) In the presence of hydrocarbon contamination (in this case,
propylene), higher rates of S00 oxidation are observed. Recent data points
-1
to an average R$o2 in *he propylene + NOX + S02 system of about 2.7% hr .
(3) Apparent synergistic effects occur with the addition of S02
to the propylene + NOV system in that the maximum volumetric growth rate of
A
aerosol is greater for the mixed system than the sum of rates for propylene +
NO and SO, alone. Abundant production of aerosol during the maximum growth
A ฃ
phase may be attributed in part to the formation of non-sulfate particulates
probably organic in nature.
(4) Using concentration of 3.0 ppmC propylene, 0.50 NOX, and a
light intensity of k.-[N02]~0.35 min"1, the time to ozone peak is about 180
minutes, and the time to N02 maximum is about 120 minutes in the Calspan
chamber. Although maximum ozone yields appeared somewhat lower for the S02
39
-------
containing system, overall chemistry data for the propylene + NO system with
/^
or without the addition of S02 were basically similar.*
(5) Experiments using an inorganic test system of CO + NOX + S02
shows no appreciable difference in RSO? as a function of CO concentration
when there is excess NO present. Amounts of CO ranging from <10 ppm to
/\
400 ppm were used in the tests. In recent irradiations using S02 clean air,
it has been observed that the addition of CO (60 ppm) appreciably lowers
the S02 photooxidation rate. These observations are consistent with the
presumed mechanism that the OH-S02 reaction is mainly responsible for S02
photooxidation. A competitive OH radical scavenging by added CO via
As shown by data in Table IV, the time to [00I u is very sensitive to the
j iTIclX
initial [HC]/[N01 ratio, while the [0,]m3X/ achieved during irradiation is
x j max
dependent on the initial [NO ]. In experiments with comparable [NO L at
X A I
about 0.5 ppm, a somewhat lower [00]m=v associated with the presence of S00
o max c
is consistently observed. The difference in [0,]m, values in the presence
ซ5 max
or absence of S02 is less than about 20 percent. In kinetic simulation
assessments by Niki, Daby and Weinstock (1972) and by Calvert and McQuigg
(1975), it has been suggested that a competitive OH radical removal by reac-
tions with CO would result in a lowering of alkylperoxy and acylperoxy radi-
cal formation from OH radical reactions with aldehydes and alkenes. This
would give rise to slower NO to N02 conversion with a consequent lowering
of the 0^ yield. By analogy, one may expect the presence of SO* to exert a
similar effect as indicated by our data in Table IV. On the other hand,
the production of significantly higher aerosol yields in the S02-containing
systems or just the later dates of irradiation experiments may have entailed
a slightly lower light intensity in these latter cases. This would account
for a lower [0 .,],.. without significantly affecting other aspects of chemical
o RluX
changes. In view of these uncertainties and the fact that a corresponding
decrease in [O.,]mav/ was not observed in the Battelle data, definitive con-
<3 max
elusions regarding possible S02 effects on the HC-NOx-air irradiation systems
would be unwarranted.
40
-------
OH + CO * H + C02
H + 02 + M -> H02 + M
would give rise to a reduced RSQ2. In the presence of comparatively high NO,
however, OH radical is regenerated by
H02 + NO -> OH + N02
Thus, R$o2 is unaffected by the addition of CO to the NOX + S02 + air reaction
system. The conversion of NO to N02 would, however, be accelerated by the
addition of CO.
(6) Results of experiments using particle-free and unfiltered rural
air + S02 suggest that the photooxidation rate of SOp is not affected appre-
ciably by the presence of background levels of natural nuclei. On the other
hand, aerosol growth, especially during the early stages of the rural air +
SOp experiments, is substantially greater than that due to S02 photooxidation
alone. Other reactions besides those involving sulfate production are probably
involved in overall aerosol production. It is recommended that additional
experiments be performed to determine the effects of natural and artificial
nuclei on the photooxidation rates of S02- Special attention in future experi-
ments must be given to aerosol composition analysis in order to assess the role
of key constituents on aerosol formation processes.
41
-------
REFERENCES
Calvert, J.6. and McQuigg, R.D., Int. J. Chemical Kinetics, Symposium No. 1,
113 (1975).
Castleman, A.W., Jr., Davis, R.E., Munkelwitz, H.R., Tang, I.N., and Wood,
W.P., Int. J. Chem. Kinetics, Symposium No. 1, 629 (1975).
Clark, W.E., Ph.D. thesis, University of Minnesota, Measurement of Aerosol
Produced by the Photooxidation of SCL in Air, 1972.
Cox, R.A. and Penkett, S.A., J. Chem. Soc. Faraday Trans., I, 6j3, 1735 (1972).
Cox, R.A. and Penkett, S.A., Nature, 229, 486 (1971).
Fielder, R.S. and Morgan, H., Anal. Chim. Acta, 23_, 538 (1960).
Friend, J.P., Leifer, R., and Trichon, M., J. Atmospheric Sci., 30_, 465 (1973).
Kocmond, W.C., Kittelson, D.B., Yang, J.Y., and Demerjian, K.L., Study of
Aerosol Formation in Photochemical Air Pollution, Calspan Corporation
Report No. NA-5365-M-2, 1975.
Kocmond, W.C., Kittelson, D.B., Yang, J.Y., and Demerjian, K.L., Determination
of the Formation Mechanisms and Composition of Photochemical Aerosols,
First Annual Summary Report, Calspan Report No. NA-5365-M-2, 1973.
Niki, H., Daby, E.E., and Weinstock, "Mechanism of Smog Reactions" in "Photo-
chemical Smog and Ozone Reactions," Advances in Chemistry Series
No. 113, American Chemical Society, Washington, D.C., 1972, pp. 35.
Stedman, D.H. and Niki, H., Env. Sci. Tech., 7_, 735 (1973).
42
-------
APPENDIX A
AEROSOL & CHEMISTRY DATA FOR ALL CALSPAN SMOG CHAMBER EXPERIMENTS
43
-------
Table A-l. LOG OF CALSPAN SMOG CHAMBER EXPERIMENTS
Run
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23A
Date
10/11/74
10/14/74
10/14/74
10/15/74
10/16/74
10/16/74
10/17/74
10/17/74
10/18/74
10/18/74
10/21/74
11/14/74
11/18/74
12/27/74
12/31/74
1/03/75
1/16/75
2/11/75
2/12/75
2/13/75 1
2/14/75
2/16/75 1
2/17/75 1
System
so,
so2
Filtered Air
Filtered Air
SO 2
so2
so2
so2
so2
Propylene + NO
Propylene + NO
Propylene + NO
Propylene + NO
Propylene + NO
Propylene + NO
Propylene + NO
Propylene+N0+S02
so2
Propylene+N0+S02
Propylene+N0+S02
Propylene+N0+S02
Propylene+N0+S02
Propylene+N0+S09
Comment
Rsฐ2(i) S02(max)
% hr"1 % hr"1
ABORT - NO Instrument
failure
1.0
2.9
Partial lights - chamber
not cleaned
Partial lights - chamber
not cleaned
Background check
Wash chamber - background
check
Conditioning test
Conditioning test
Conditioning test
Conditioning test
Conditioning test
Chamber intercomparison
Test Series - Exp. 10-23
Begin using HC analyzer
0.7
Begin aerosol collections 0.2
ABORT - M0ฅ Instrument
failure x
0.3
0.4
0.4
3.6
5.0
3.0
>15%*
>28%*
>27%*
% hr"
1.7
4.4
1.3
0.8
0.5
0.2
0.5
2.6
1.7
1.2
0.2
0.7
1.9
1.1
0.9
0.2
0.6
As determined from EAA data. Aerosol undoubtedly contains organic species.
44
-------
Run
No.
23B
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
Date
4/04/75
4/04/75
4/06/75
4/07/75
4/08/75
4/09/75
4/10/75
4/12/75
4/14/75
4/17/75
4/18/75
4/22/75
4/28/75
4/29/75
6/16/75
6/20/75
6/20/75
6/23/75
6/24/75
6/25/75
6/26/75
6/30/75
7/02/75
7/08/75
System
SO,
so
so
so
,S09+NO +b (CO)
ฃ X
S02+NOx+b (CO)
+b
so
S09+N0 +b (CO)
A
S0
S0
S0
S0
S0
CO
S0
NOX + CO
NOV + CO
A
NOX + CO
NOX + CO
47
7/09/75
so2
S02
so2
so2
Rural Air
Filtered Air
Filtered Air
so2
Rural Air + S02
Rural Air + S02
Comment
Wash chamber - condi-
tioning experiment
Conditioning experiment
Conditioning experiment
Conditioning experiment
- S02 calibration
Inorganic test series -
experiments 27-36
Background check
100 ppm CO
Background check
100 ppm CO
400 ppm - Lg. dark
reaction
ABORT - Lg. dark
reaction
410 ppm CO
Conditioning experiment
kd = 0.31
Conditioning experiment
Conditioning experiment
Conditioning experiment
Conditioning experiment
Irradiation of particle'
free rural air
Background check
Background check
Conditioning experiment
With natural particles
dark reaction
With natural particles 1.2 1.6
S02(il
% hr"1
11.1
3.4
2.8
3.7
0.6
0.4
0.5
0.6
0.3
0.5
0.4
0.5
0.3
1.4
0.5
0.7
0.4
0.4
^
0.5
- 2.0
S02(max)
% hr"1
9.7
3.9
2.8
3.7
1.1
0.9
1.6
0.9
0.9
1.2
1.0
1.1
1.2
4.6
1.7
3.4
2.7
2.7
2.1
2.3 i
S02(ave)
% hr"1
8.5
3.3
2.5
3.2
0.8
0.8
1.0
0.6
0.6
1.0
0.8
0.8
0.8
3.0
1.7
1.6
2.1
2.1
1.2
0.8
0.8
45
-------
Run
No.
48
49
50
51
52
53
54
Date
7/10/75
7/17/75
8/25/75
8/26/75
8/27/75
8/28/75
8/29/75
System
Rural Air + SO,
SOo
Comment
Rsฐ2(i) Rsฐ2(max) S02(ave)
so2
Particle-Free
Rural Air + SO
Particle-Free
Rural Air + SO,
Particle-Free
Rural Air + SO,
2
% hr
-1
With natural particles 1.0
Aerosol analyzer 0.5
calibration
Background check 0.2
Absolute filtered 1.9
only -
Absolute filtered 0.8
only
Absolute filtered 1.1
only
Background check 0.1
% hr"1
1.4 4-
1-4
1.6
1.1
1.2
0.9
% hr
1.1
0.7
1.1
0.9
0.7
0.5
-1
46
-------
RUN #1 - AEROSOL DATA FOR S02 SYSTEM
tf
jjpjffl.
i
iA-
! i .1 HO. i i j i i i i ! [ l._
0 0 60 ]20 BO
THE Own)
RUN #2 - AEROSOL DATA FOR S02 SYSTEM
....i i '; 4 4 4 -t- 1 1- *"
"eo * w So
TIfE (MN)
47
-------
RUNS #5 & #6 - AEROSOL DATA FOR S02 SYSTEM
SO^SVSTEN ,
t ....................... n ....... f ...... i ...... '
...... \ ....... i ....... i ....... i ....... ..... tt
i ...... i ....... i ...... i ...... i ....... i ...... ] ...... i ..... j ....... i
OCTOER 1
"60 ' ' 120 ' ' 0"
TIfE (HIM)
I"*!* ] i
iOCnJERtf. iN
Jfif f-ff--
i I : :
MHซh
RUNS #7 & #8 - AEROSOL DATA FOR S02 SYSTEM
S&2 SYSTEM
.ID7., i flEHDSpL.MTrA
M i i i i i i ; mta I
"til I |-
12^-24 t"~f-
i ' j i i i i ! i j : j
-|4-f \ f '; f \ 4 4- 4- }
Tiff (MIN)
48
-------
RUN #9 - AEROSOL DATA FOR S0ฃ SYSTEM
60 120
TINE (MIN)
RUN #10 - CHEMISTRY DATA FOR PROPYLENE + NO SYSTEM
i i i irumtCTiM rari \\l\ill\
49
-------
RUN #11 - AEROSOL DATA FOR PROPYLENE + NOV SYSTEM.
/\
"'"T "'I""1 - "**7 J
RLNซ1 I ;
OCJQBER 21, 5971'
T
-60
360
RUN #11 - CHEMISTRY DATA FOR PROPYLENE + NO SYSTEM
, ,
Tilt (MIH)
50
-------
RUN #12 - CHEMISTRY DATA FOR PROPYLENE + NO SYSTEM
THE (HIM)
RUN #13 - CHEMISTRY DATA FOR PROPYLENE + NO SYSTEM
(MIN)
51
-------
RUN #14 - CHEMISTRY DATA FOR PROPYLENE + NO SYSTEM
RUN #15 - CHEMISTRY DATA FOR PROPYLENE + NOV SYSTEM
A
TIfE (TON)
52
-------
RUN #16 - CHEMISTRY DATA FOR PROPYLENE + NOV SYSTEM
A
0L 0L
120
TIIE (HIM)
53
-------
RUN #17 - AEROSOL DATA FOR PROPYLENE + NOX + S02 SYSTEM
RUN #17 - CHEMISTRY DATA FOR PROPYLENE + NOX + S02 SYSTEM
54
-------
RUN #18 - AEROSOL DATA FOR S00 SYSTEM
Tilt (MIN)
55
-------
RUN #21 - AEROSOL DATA FOR PROPYLENE + NOV + SO- SYSTEM
A
IT* * T
Tilt (MM)
RUN #21 - CHEMISTRY DATA FOR PROPYLENE + NOX + S02 SYSTEM
IRK ? 211
.i-ซj[j4''4t it t t1""
I _i i i J. j j_! !!Nปw_..4,
i : ! : i i j i I i i
ซp^THi^il^"sysiiT~'| T [" f~T 1 T T~]
t+ t-.-.tt r i}- f+|fi-|
OBsnBlปTA ! i i __
56
-------
RUN #22 - AEROSOL DATA FOR PROPYLENE + SO, + NO SYSTEM
t A
^
.5
ฃ
II
""1 I" I It i I -i- ! [-MJ !!-; i I ! ! i 1
-1 ! t t t f i im I i i I ! l 1 i i
ป| I I I i ) I ! [ f 44 | i j 1-4 J^ I | j....
I j I f { i f- 1 1 i -li 1 i ..L-^h...] i i { ]
\ \ i -. i | \
~in\ | }-
I i L.
i i I
121 i f
.sn
21 1 1
H# N^ PRDPS02
5UWCE
......
"If I | f f j | |
I | i j j f"jฅ-| i ! ! I I i i
"i I i6
-4 1--]
-! 1 ] 5
44 j ,
... H: ;.. I I j4, j. \---A
V \ l\
:m
-i 4 u
-60
Tilt (MIN)
120
180
-!0
RUN #22 - CHEMISTRY DATA FOR PROPYLENE + S02 + NOX SYSTEM
"w'ifzi ....... i ....... I ....... i ...... ! piftyiENE +'si^'i'Nd^svs:tBi' "I I""1"]'" [ I ...... I"'"] ....... 1 ..... 1 ...... 1 ....... 1 ....... [ ...... I
~~ ...... ....... ....... ....... OSS " ' ....... ....... ....... ....... " ...... T ..... ....... ......
- 4- J J --; * ! - - i -| '.- , --- - \ '' 4 ""f t" "I" '' '
i i I ; ' i i i i i i i ! r i i j : i i i i i
0,2^0.11 f I i t t
: ; : : ' f
i i ! i t t t : i r
80 120
Tiff (MIN)
I | | } | [ 4 4 f f i i I0-6
! i I i i ; i i i j 1 i i
i i i I i f f- j i
1 j ! ! ! : j !__J0
2W
57
-------
RUN #23A - AEROSOL DATA FOR PROPYLENE + NOX + S02 SYSTEM
f ! |l PRGPYIBC + NOx + SO? SVSm
60 120
TWE (MIN)
RUN #23A - CHEMISTRY DATA FOR PROPYLENE + NO
+ S02
SYSTEM
: i
t -
L-
i
4
4-
4-
1-
i
i
[-.
4
I-
--. y
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1
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1.2
0.6
60 ]2B
WE. (MIN)
180
210
L.
58
-------
RUN #23B & #24 - AEROSOL DATA FOR S02 SYSTEM
16
120
1 iQ
RUN #25 & #26 - AEROSOL DATA FOR S02 SYSTEM
120
AID 907
59
-------
RUN #28 - AEROSOL DATA FOR
S02 + NOX SYSTEM
! ' i
/i i i !
-9~* \ 4 t
-60
RUN #28 - CHEMISTRY DATA FOR S02 + NOX SYSTEM
(MIN)
60
-------
RUN #29 - AEROSOL DATA FOR S0? + NO SYSTEM
Cn yv
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--16 i If
30-
-1H *
!
" 2Dr-]fl *
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ID f
-li 4
120 M
Tilt (MM)
So ""so
RUN #29 - CHEMISTRY DATA FOR S0 + NO SYSTEM
+ | -- - < ', : : : r " "
300
360
61
-------
RUN #30 - AEROSOL DATA FOR S02 SYSTEM
ii Q
62
-------
RUN #31 - AEROSOL DATA FOR SO- + NO- + CO SYSTEM
G* A
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60 120 MO wi
TIfE (HIM)
RUN #31 - CHEMISTRY DATA FOR S09 + NOV + CO SYSTEM
C. X
TIfE (MIN)
63
-------
RUN #32 - AEROSOL DATA FOR S02 CONDITIONING EXPERIMENT
f
3
1,
s
X
1
0
RUN #32
4
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Tilt (HIM)
12
10
8
6
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2
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RUN #32A - AEROSOL DATA S02 CONDITIONING EXPERIMENT
RlซiB2A
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-3
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i VOLUME
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0 60
TIME (NIN)
64
-------
RUN #33 - AEROSOL DATA FOR S0? + CO + NO SYSTEM
^- A
-60
120
Tilt (MM)
~'' 0
RUN #33 - CHEMISTRY DATA FOR S02 + CO + NOX SYSTEM
60
120 180
Tilt (WIN)
65
-------
RUN #34 - AEROSOL
DATA FOR S02 + NOX + CO SYSTEM
ADD'L SO,
ifee~
0 -60 0 60
RUN #34 - CHEMISTRY DATA FOR S02 + NOX + CO SYSTEM
[/HO}. 2Z, 135 j | ] jronsriWDATA ! .
p-+1 1 I I I I
300
Tilt (HIM)
66
-------
RUN #36 - AEROSOL DATA FOR SO- + NO + CO SYSTEM
ฃ X
ro f ]
123 180
THE (MIN)
RUN #36 - CHEMISTRY DATA FOR S02 + NOX + CO SYSTEM
. T -,
f', 1 1 :
...J i i i i i i
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120 MO
Tilt (MIN)
67
-------
RUNS #37 & #38 - AEROSOL DATA FOR S02 SYSTEM
I
11
12
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:
60 12D ISO
TIfE (MIN)
RUN #39 - AEROSOL DATA FOR S02 SYSTEM
12) 180
TIfE (MIN)
2MO
910
68
-------
RUN #40 - AEROSOL DATA FOR S02 SYSTEM
i t t i" T ^'fir^ "$"
180 20
Tilt (CIIN)
RUN #41 - AEROSOL DATA FOR S02 SYSTEM
BCEOLfoTA: i i
+ t -t-8B f-W-i
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120
180 ZO 300
TJIt (MIN)
350
69
-------
RUN #42 - AEROSOL DATA FOR RURAL AIR WITH PARTICLES SYSTEM
,_,
1 !
4--
11 -
]2 -J-
-i t t I-
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--
+ t
78+
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6
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A ' ' A ' ' 2ft 300~
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360
RUN #42 - CHEMISTRY DATA FOR RURAL AIR WITHOUT PARTICLES SYSTEM
60 129
TIFEtaN)
180
2W ' 510
70
-------
ป| I i \ i ;ป
i ' ' : ': ''
RUN #43 - AEROSOL DATA FOR RURAL AIR WITHOUT PARTICLES SYSTEM
RURAL AIR WlHoilT PARTICLES' I I I I I ] ] [ 1 1
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Tilt (ran)
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ป-t-
RUN #44 - AEROSOL DATA FOR RURAL AIR WITHOUT PARTICLES SYSTEM
w'w M 1 1 M
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J3-I--J
TIffi (WN)
71
-------
RUN #45 - AEROSOL DATA FOR S02 SYSTEM
-W -20 0
Iffl
Tilt (MIN)
72
-------
RUN #46 - AEROSOL DATA FOR RURAL AIR WITH PARTICLES * S02 SYSTEM
13)
240
500 3EO
THE CHIN)
RUN #46 - CHEMISTRY DATA FOR RURAL AIR WITH PARTICLES + S02 SYSTEM
-80
SflWT
UgflS
-40 -20 ""d
"60 120
Tilt (MIN)
73
-------
RUN #47 - AEROSOL DATA FOR RURAL AIR WITH PARTICLES + S02 SYSTEM
tf...
-80 -40
120 180
THE (MIN)
RUN #47 - CHEMISTRY DATA FOR RURAL AIR WITH PARTICLES + S02 SYSTEM
_^L*
-80 -W -20 0
^TIEta)^
74
-------
RUN #48 -
AEROSOL DATA FOR RURAL WITH PARTICLES + S02 SYSTEM
f ....... j ...... 4 ....... ? ...... 4 ...... 4 ...... i ...... I ..... i ....... i ....... I ....... ....... ....... _____
SUSME i i
j I i i i i I !--4-ffii-3B-i
i i ' ฃ: \ i^
-------
RUNS #49 & #50 - AEROSOL DATA FOR S02 SYSTEM
ID7
(WIN)
Tilt (WIN)
76
-------
RUN #51 - AEROSOL DATA FOR FILTERED RURAL AIR + S02 SYSTEM
Tn 1 if"! 1 iiW
i _ i i i i ! i / i : ' i !
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RUN #51 - CHEMISTRY DATA FOR FILTERED RURAL AIR + S02 SYSTEM
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i FIIJIHBJ RUR*L All) +
4T--
I WA
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7r+-
i ;
i_.-~i
; i
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U-
i&i
-t-
4',.\44 t 4"
Tilt (MIN)
77
-------
RUN #52 - AEROSOL DATA FOR FILTERED RURAL AIR + S02 SYSTEM
TIME (HIM)
RUN #52 - CHEMISTRY DATA FOR FILTERED RURAL AIR +
S02 SYSTEM
-180 -120
"ซ " * 0 60
Tilt (MIN)
120
Ml
78
-------
RUN #53 - AEROSOL DATA FOR FILTERED RURAL AIR + S00 SYSTEM
'""*--'.isk I ! ; ! '""
-MO
RUN i?53 - CHEMISTRY DATA FOR FILTERED RURAL AIR + S02 SYSTEM
lffljS4_4_4 i ; ' i i FiupipuAiB.^ ] j | j i i u..i i
iAuajsra, MB I ! I ! ! I ! tKrtfenwinmAi j ! ! ! i ! ! ! I 1
i 4- f * '- r - f" f ""t" "'* ; ! ! ' ' r t f t t t f
-i i ; > : -v + + + *
' - '
0 60
TOE (MN)
79
-------
RUN #54 - AEROSOL DATA FOR S02 SYSTEM
tf
.1
60 120
TIHE (MIN)
80
-------
... TECHNICAL REPORT DATA
(Please read Instructions on the reverse before ci
EPA-600/3-76-090
. RECIPIENT'S ACCESSION-NO.
fLE
SULFUR DIOXIDE PHOTOOXIDATION RATES AND AEROSOL
FORMATION MECHANISMS
A Smog Chamber Study
. REPORT DATE
August 1976
. PERFORMING ORGANIZATION CODE
W,C. Kocmond
J.Y. Yang
^PERFORMING ORGANIZATION REPORT NO.
NA-5365-M-3
NG ORGANIZATION NAME AND ADDRESS
Calspan Corporation
Buffalo, NY 14221
0. PROGRAM ELEMENT NO.
1AA008
1. CONTRACT/GRANT NO.
68-02-1231
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Sciences Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, N.C. 27711
3. TYPE OF REPORT AND PERIOD COVERED
inal
4. SPONSORING AGENCY CODE
PA-ORD
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The objective of this investigation was to obtain smog chamber data pertaining
to the oxidation of S02 into sulfate under simulated urban and rural atmospheric
conditions. Tasks were performed on various systems ranging from HC + NO + S0? to
the clean air + S02 mix. Emphasis has been placed on the rates of S02 photooxiaation
and on chemical characterization of aerosol products. Results showed the rate of S0_
oxidation to vary from less than 1% per hour for the clean air + SO- system to about
2.7% per hour for the propylene + NO + SO,, system. Results were also interpreted to
suggest that the major SO oxidationxprocess is the reaction of S02 with OH radicals.
Particulate matter, as occurredin natural rural air, appeared to have no appreciable
effect upon SO- photooxidation; nevertheless questions still remain on the role of
natural particulates.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
COSATI Field/Group
*Air pollution
*Suflur dioxide
*AerosoIs
Nitrogen oxides
Hydrocarbons
*Sulfates
*Photochemical reactions
*0xidation reduction
reactions
*Reaction kinetics
Test Chambers
13B
07B
07D
07C
07E
14B
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
. _
EPA Form 2220-1 (9-73)
19. SECURU
89
22. PRICE
UNCLASSIFIED
81
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