EPA-650/4-74-034
August 1974
Environmental Monitoring Series
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Research reports of the Office of Research and Development, Environmental Protection
Agency, have been grouped into five series. These five broad categories were estab-
lished 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:
I. Environmental Health Effects Research
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3. Ecological Research
4. Environmental Monitoring
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This report has been assigned to the ENVIRONMENTAL MONITORING series. This series
describes research conducted to develop new or improved methods and instrumentation
for the identification and quantification of environmental pollutants at the lowest con-
ceivable significant concentrations. It also includes studies to determine the ambient
concentrations of pollutants in the environment and/or the variance of pollutants as
a function of time or meteorological factors.
This report has been reviewed by the Office of Research and Development, EPA,
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endorsement or recommendation for use.
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EPA-650/4-74-034
PilSENCE OF SULFUR
by
David N. McNeils
National Environmental Research Center
Las Vegas, Nevada 89114
Program Element No. 21 AKB
ROAPNo738
EPA Project Officer: William E. Wilson
Chemistry and Physics Laboratory
National Environmental Research Center
Research Triangle Park, North Carolina 27711
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U.Si ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
August 1974
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DISTRIBUTION STATEMENT
This report is available to the public, for a nominal cost, through the
National Technical Information Service, 5285 Port Royal Road,
Springfield, Virginia 22151.
This report is a dissertation submitted to the faculty of the University of
North Carolina in partial fulfillment of the requirements for the degree
of Doctor of Philosophy in the Department of Environmental Sciences
and Engineering.
ii
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ABSTRACT
The loss of visibility in atmospheres laden with photochemical smog is largely
attributed to the presence of sulfate aerosols. This facet was thought to be the
most objectionable effect of the sulfate species and is reflected in the establish-
ment of the National Ambient Air Quality Standard for sulfur dioxide. Recent
reviews, however, have indicated that the adverse health effects appear more
strongly associated with suspended particulate sulfate than with the sulfur
dioxide.
The dark-phase reaction of olef in-ozone-sulfur dioxide was studied in an
attempt to elucidate the mechanism involved in the oxidative consumption of
the sulfur dioxide. The effect of several variables on the reaction stoichio-
metry and on the aerosol production was also investigated. These variables
included the reactant concentrations, the relative humidity, molecular oxygen
concentration and the olef in species although propylene was the primary olefin
studied.
The stoichiometry of the propylene-ozone reaction was found to be a smooth
function of the initial concentration ratio of these species. The olefin/ozone
consumption was 1 for a system in which the olefin was initially in excess
and 1 for a system having an initial ozone excess. The consumption ratio
was unaffected by the addition of sulfur dioxide or by varying the relative
humidity over the range of 20 to 38 percent.
Molecular oxygen had a significant effect on the reaction stoichiometry and
product formation in the propylene-ozone thermal reaction. The propylene/
ozone consumption ratio was lower in a system in which the molecular oxy-
gen concentration was reduced. Oxygen apparently also contributed to the
regeneration of ozone and the production of the hydroxyl radical species, both
of which interacted with the propylene and with products of the reaction.
A tentative mechanism has been proposed for the oxidative consumption of
sulfur dioxide in the propylene-ozone-sulfur dioxide system based on the
observations made during these studies. Secondary reactions are a distinc-
tive feature of this model which incorporated relatively few reactions to
explain the major characteristics of the systems studied.
Aerosol formation occurred in the dark reaction of propylene and ozone
although the particulate formed did not grow to a size which efficiently
scattered light. The addition of sulfur dioxide markedly enhanced both the
formation and subsequent growth of the aerosol. The same general patterns
of aerosol formation, growth and decay were observed throughout the series
of experiments over a broad range of initial conditions. These patterns are
consistent with a model which includes homogeneous nucleation, condensation
and coagulation processes.
iii
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An apparent equilibrium surface area was established for the aerosol when
the addition to the total surface area by condensation was equal to the loss
by coagulation. A strong correlation was found to exist between this equi-
librium surface area and the volumetric conversion rate. It was also
found that the correlation could be extended considerably in range to include
data from other experiments in which the aerosol was photochemically
generated. The establishment of the equilibrium surface area is due, there-
fore, to the physical processes rather than the chemical mechanism leading
to its formation.
IV
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Table of Contents
Page
List of Tables ,vii
List of Figures viii
I. Introduction 1
II. Review of Previous Work 7
A. Studies of the Olefin-Ozone System 7
B. Mechanism of the Olefin-Ozone Reaction 8
C. Reactions with Sulfur Dioxide 14
D. Aerosol Production in Hydrocarbon Systems 15
III. Theory of Aerosol Formation, Growth and Decay. 20
A. Nucleation 21
B. Condensation 26
C. Coagulation 29
IV. Experimental Arrangement and Procedures 34
A. Experimental Design and Arrangement 34
B. Experimental Apparatus 41
1. Reactor 41
2. Ozone Analysis 44
3. Ambient and Dew Point Temperatures Measurements 46
4. Sulfur Dioxide Analysis 47
5. Hydrocarbon Analysis 49
6. Infrared Spectroscopic Product Analysis 50
7. Sulfur Balance Determination 52
8. Light Scattering Measurements 53
9. Condensation Nuclei Count Determination 55
10. Sub-microscopic Aerosol Analysis 56
11. Optical Particle Analysis 61
C. Experimental Procedures 63
v
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V. Experimental Results and Discussion 71
A. Reactant Consumption Data and Reaction Stoichiometry 71
B. Product Analysis 94
C. Tentative Reaction Mechanism 111
D. Sulfate Analysis and Sulfur Mass Balance 114
E. Light Scattering Measurements 119
F. Aerosol Development 123
G. Aerosol Measurements by Single Particle Light
Scattering 158
VI. Conclusions and Recommendations 162
References 168
Appendices 175
1. Product Analysis by Fourier Transform Infrared
Spectroscopy. 175
2. Observed and Predicted Reactant Concentrations for
Gas Phase Experiments. 176
3. Aerosol Droplet Number, Surface Area, and Volume
Concentrations Distributions for Aerosol Experiments. 196
VI
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LIST OF TABLES
TABLE PAGE
2-1 Summary of Rate Constant Data 10
2-2 Relative Rate Constants 17
3-1 Coagulation Constants for Unequal Sized Particles 31
4-1 Permeability of Tedlar and Scotchpak to Gases and Vapors . 42
4-2 Data Table for Number, Surface Area and Volume Distribution 62
5-1 Summary of Experimental Conditions and Initial Reactant
Concentrations 72
5-2 Summary of Stoichiometric Data and Acetyaldehyde Production 75
5-3 Product Analysis by Fourier Transform Infrared Spectroscopy 105
5-4 Summary of Sulfuric Acid Analysis by X-ray Fluorescence
Spectroscopy and Liquid Chromatography 116
5-5 Volumetric Conversion Rate, Total Volume at 80 Minutes,
Mean Volume Diameter Growth Rate, Coagulation Constant
and Sulfur Dioxide Consumption at 80 Minutes for Aerosol
Experiments 138
5-6 Initial Sulfur Dioxide Reaction Rate and Oxidative Rate . . 141
5-7 Calculated Sulfur Dioxide Consumption based on the Observed
Volume Concentration 141
vn
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LIST OF FIGURES
FIGURE PAGE
4-1 Schematic of Experimental Arrangement 36
4-2 Laboratory Arrangement for Olefin-Ozone-Sulfur Dioxide
Studies ......... 38
4-3 Aerosol Measurement Instrumentation 39
4-4 Fourier Transform Infrared Spectrometer . 40
4-5 Variation of Relative Humidity with Time due to the
Permeation of Water Vapor 43
4-6 Schematic of Reactor Port Arrangement ........... 45
4-7 Schematic of the Electrical Aerosol Size Analyzer 58
4-8 Relationship Between Electrical Mobility and Particle Size
for Diffusion Charging where N = 1 x 10 (ions/cm )(sec) . 60
4-9 Calibration Data for Optical Aerosol Analyzer 64
4-10 Variation of Reactant Concentration with Time Due to Wall
Losses 69
5-1 Variation of Concentration with Time for Propylene-
Ozone-Sulfur Dioxide Reaction 78
5-2 Variation of Concentration with Time for Ethylene-Ozone-
Sulfur Dioxide Reaction 79
5-3 Stoichiometry of Olefin-Ozone Reaction versus Initial
Reactant Concentration Ratio 80
5-4 Concentration of Acetyaldehyde Produced versus Propylene
Reacted for Nine Propylene-Ozone Experiments 86
5-5 Sulfur Dioxide Consumption versus Propylene Reacted for
Different Initital Sulfur Dioxide Concentrations 88
5-6 Sulfur Dioxide Consumption versus Ozone Reacted for
Different Initial Sulfur Dioxide Concentrations 89
5-7 Variation of the Apparent Rate Constant with Time Due to
Secondary Reactions 92
viii
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LIST OF FIGURES (Continued)
FIGURE PAGE
5-8 Infrared Absorption Spectra of Reactor Contents - Runs 31
and 21 96
5-9 Infrared Spectra in Region of Carbon Monoxide Absorption -
Runs 31 and 21 97
5-10 Infrared Spectra in Region of Carbon Monoxide Absorption -
Runs 78 and 79 99
5-11 Infrared Spectra in Region of Carbon Monoxide Absorption -
Runs 81 and 82 100
5-12 Infrared Spectra in Region of Carbon Monoxide Absorption -
Runs 60 and 65 101
5-13 Infrared Absorption Spectra of Reactor Contents - Runs 28
and 29 104
5-14 Comparison of Results for Sulfuric Acid Analysis 118
5-15 Variation of the Scattering Coefficient, visual Range,
Surface Area Concentration and Sulfur Dioxide Concentration
with Time for a Propylene-Ozone-Sulfur Dioxide Experiment . 121
5-16 Variation of the Scattering Coefficient, Visual Range,
Surface Area Concentration and Sulfur Dioxide Concentration
with Time for an Ethylene-Ozone-Sulfur Dioxide Experiment . 122
5-17 Aerosol Particle Number, Surface Area and Volume Development
for a Propylene-Ozone Experiment 124
5-18 Total Volume, Number, Reciprocal of Number and Surface Area
Concentration versus Time for the Developing Sulfuric Acid
Aerosol - Run 101A 126
5-19 Total Volume, Number, Reciprocal of Number and Surface Area
Concentration versus Time for the Developing Sulfuric Acid
Aerosol - Run 101B 127
5-20 . Total Volume, Number, Reciprocal of Number and Surface Area
Concentration versus Time for the Developing Sulfuric Acid
Aerosol - Run 102 128
5-21 Total Volume, Number, Reciprocal of Number and Surface Area
Concentration versus Time for the Developing Sulfuric Acid
Aerosol - Run 103 129
IX
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LIST OF FIGURES (Continued)
FIGURES PAGE
5-22 Total Volume, Number, Reciprocal of Number and Surface
Area Concentration versus Time for the Developing Sulfuric
Acid Aerosol - Run 104 130
5-23 Total Volume, Number, Reciprocal of Number and Surface Area
Concentration versus Time for the Developing Sulfuric Acid
Aerosol - Run 105 131
5-24 Total Volume versus Sulfur Dioxide Consumption at T + 80
Minutes 143
5-25 Variation of the Equilibrium Surface Area with Volumetric
Conversion Rate 145
5-26 Initial Volumetric Conversion Rate versus Product of Initial
Propylene and Ozone Concentrations for Different Initial
Sulfur Dioxide Concentrations 147
5-27 . Development of the Volume Distribution with Time - Run 101A 148
5-28 Development of the Volume Distribution with Time - Run 101B 149
5-29 Development of the Volume Distribution with Time - Run 102 . 150
5-30 Development of the Volume Distribution with Time - Run 103 . 151
5-31 Development of the Volume Distribution with Time - Run 104 . 151
5-32 Development of the Volume Distribution with Time - Run 105 . 152
5-33 Variation of Volume Mean Diameter with Time for Six Aerosol
Experiments 154
5-34 Rate of Change in Mean Volume Diameter versus Volumetric
Conversion Rate 157
5-35 Variation of Aerosol Size Distribution with Time as Measured
with Optical Particle Size Analyzer - Run 31 159
5-36 Variation of Aerosol Size Distribution with Time as Measured
with Optical Particle Size Analyzer - Run 29 160
x
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AEROSOL FORMATION FROM GAS PHASE REACTIONS OF
OZONE AND OLEFIN IN THE PRESENCE OF SULFUR DIOXIDE
CHAPTER I
INTRODUCTION
A major source of the sulfur burden of our atmosphere results from
the combustion of solid and liquid fossil fuels. These fuels contain
significant quantities of sulfur as inorganic sulfides, sulfur contain-
ing organic compounds and some small fraction as sulfates. It is
estimated that sulfur dioxide accounts for upwards of 95% of the sulfur
released from the fuel combustion (Smith and Gruber, 1966).
There are several undesirable effects attributed to this contaminant
which include the degradation of materials, retardation of plant growth
and production, and of most importance, the difect impact on man's
health. In addition, literature reviews by Bufalini (1971) and Altshuller
and Bufalini (1971) provide many references citing the conversion of
sulfur dioxide to aqueous sulfuric acid droplets as one of the most basic
photochemical reactions. The exact physical and chemical mechanisms
which enter into this conversion are not adequately understood but the
resulting aerosol is known to contribute significantly to visibility
reduction. The scatter and absorption of visible radiation by gas
molecules and particulates are the causes of atmospheric visibility
reduction. Small particles (0.1 to 1 pm diameter) suspended in the
atmosphere are particularly effective in scattering visible light.
Until recently, this loss of visibility was thought to be the
most objectionable effect of the sulfate aerosol. The sulfur dioxide
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2
ambient air quality standards were based on judgemental decisions using
the best available data. A review of the standard using the Community
Health Environmental Surveillance System (CHESS) data indicated that
this standard has a defensible base. This same review, however, has
added a new facet to the problem, i.e., the fact that the adverse health
effects for certain health indicators, particularly asthma, appear
more strongly associated with suspended particulate sulfate than with
sulfur dioxide (Environmental Protection Agency, 1974). If new toxico-
logical data supports this finding then data collection and analysis
should be directed toward developing sulfate criteria. Of paramount
concern at the present is the complete lack of knowledge concerning
the relationship of sulfur dioxide to suspended sulfate levels. Addi-
tional information is also needed relative to the rate of conversion of
sulfur dioxide to sulfate. The standard will require another review
when these data are available particularly if they indicate that the
simple control of sulfur dioxide is not the most efficient way of
protecting man's health from exposure to sulfur compounds.
In the atmosphere sulfur dioxide is oxidized by either gas phase,
catalytic or photochemical processes. In irradiated olefin-oxides of
nitrogen systems decay of sulfur dioxide and formation of sulfuric acid
do not occur to any appreciable extent until most of the nitric oxide is
converted to nitrogen dioxide. Nitrogen trioxide is formed in the
reaction of ozone with nitrogen dioxide and the organic peroxides which
earlier reacted with the nitric oxide begin to accumulate. Reaction
with one of these oxidizing species rather than the direct photooxidation
of the sulfur dioxide probably accounts for most of the sulfate aerosol
generation. The oxidative interaction with the surfaces of aerosol
droplets or particles could also account in part for the decay of the
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sulfur dioxide. The significance of this mode would depend on the
reactant concentrations, the physical/chemical nature of the aerosol and
its surface area. The rate of this type of reaction may be limited by
the diffusion of sulfur dioxide to the active surfaces or by its diffu-
sion into and reactions throughout the aerosol material. The third
process, i.e., the photochemical reaction of sulfur dioxide when irra-
diated by sunlight, has perhaps been the most thoroughly invesitgated.
In particle-laden air, the oxidation can proceed by a number of paths
with the aerosol surface serving as a catalyst for chemical reactions
involving the photochemical products. In particle-free air, the oxida-
tion proceeds along fixed paths with components of the vapor phase. The
primary photochemical reaction involves the absorption of solar radia-
tion by the sulfur dioxide followed by reactions of the excited sulfur
dioxide molecules with molecular oxygen to form an intermediate sulfate
species. It is suggested that this intermediate then reacts with molec-
ular oxygen to the sulfur trioxide and ozone (Blacet, 1952).
These processes are, for the most part, poorly understood and become
considerably more complex when in the presence of other air pollutants.
In recent years, however, major advances in the knowledge of homogeneous
gas phase reactions have been accomplished although the factors governing
the gas to particle conversions remain largely unresolved and are only
briefly discussed in published reviews of the chemistry of air pollution.
Generally, aerosol production in gas phase reactions has been
monitored by condensation nuclei counters and integrating light scatter-
ing instruments. Both of these instruments provide evidence of the
presence of the aerosol but lack the ability to yield a quantitative
analysis of the mass or volumetric conversion rate or a size distribu-
tion of the aerosol produced. The condensation nuclei counter provides
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a count of the number of nuclei present per unit volume. The nuclei
are grown to a common size and their number concentration is sensed by
the attenuation of a light beam. The light scattering devices measure the
integrated scattering which changes as the size distribution, refractive
index and the concentration of the aerosol change over the span of the
measurement period.
Because of the inability of investigators to control or isolate
the various gaseous components or environmental factors leading to
aerosol production under field conditions, many of the studies designed
to investigate aerosol formation are conducted in chambers under con-
trolled environmental conditions. The photochemical systems studied
usually involve a hydrocarbon, nitric oxide, and sulfur dioxide. In
dark phase systems ozone is also introduced as a reactant.
A review of the literature indicates that the thermal reaction of
olefins and ozone in the presence of sulfur dioxide yields a sulfate
aerosol (Groblicki and Nebel, 1971 and Cox and Penkett, 1972). Recent
technological advances in both gas phase and aerosol measurement instru-
mentation now permits selected aspects of the olefin-ozone-sulfur dioxide
reaction with its attending aerosol production to be more thoroughly
investigated. The principal advances relative to the studies undertaken
are the flame photometric detection of total sulfur, the application of
the chemiluminesence reaction of ethylene and ozone to ozone analysis,
the development of the Fourier transform infrared spectrometer for gas
phase product analysis and the electrical mobility analyzer for the
in situ measurement of submicroscopic aerosols. Two new techniques
have also been applied to the sulfate analysis of filter samples. X-ray
fluoresence is being used to measure the total sulfur as well as other
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elements and compounds, and liquid chromatography is being used to
analyze for water soluble sulfates.
Data developed in these studies serve to develop a qualitative
understanding of the overall photochemical smog formation process as
well as to provide detailed quantitative input into newly developed
photochemical smog predictive models. Finally, these data, particularly
those dealing with mass or volumetric conversion rates, mechanism and
gas phase product yields, serve to provide the information necessary
to establish criteria which ultimately are used as the basis for stand-
ards for control.
Propylene was selected as the primary olefin to be studied because
it is a common atmospheric hydrocarbon, has moderate reactivity with
ozone and is a relatively simple molecule. Ethylene was also studied
but, like other first members in homologous series, is atypical. Neither
of these olefins produces organic aerosols in reaction with ozone.
The general aims of the research reported herein were to elucidate
selected aspects of the oxidative mechanism of sulfur dioxide and to
measure its mass conversion rate from the gaseous to the condensed state.
More specifically, the objectives of this research were:
1. to design a reaction vessel and sampling system which would
permit the study of selected dark phase reactions under controlled
conditions and reactant concentrations and which would yield reproducible
results.
2. to study the kinetics of the olefin-ozone-sulfur dioxide system
and to determine factors which influence the stoichiometry of the olefin-
ozone reaction and the formation of selected gas phase products.
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3. to assess and characterize the aerosol formed including measure-
ments of the size distribution, mass concentration, number concentration
and total light scattering both as a function of time and of system
component concentrations.
4. to infer from the aforementioned measurements the physical/
chemical mechanism leading to the formation and growth of the aerosol.
5. to advance a tentative mechanism for the oxidative consumption
of sulfur dioxide in the olefin-ozone-sulfur dioxide system based on
information contained in the literature and on the measurements reported
herein.
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CHAPTER II
REVIEW OF PREVIOUS WORK
A. Studies of the Olefin-Ozone System
The stoichiometry of the ethylene-ozone and the propylene-ozone
reactions were studied by Hanst et al. (1958). Within experimental
error they found a 1:1 ratio of olefin to ozone consumption. The initial
concentration ratios of the reactants in these studies were 1:1 for
ethylene and ozone and 3.36:1 for the propylene and ozone. Stedman
et al. (1973) reported similar results for various initial reactant con-
centrations where they show 1:1 stoichiometry by observation of equal
decrements of the reactants. Vbraski and Cvetanovic (1960) and Wei and
Cvetanovic (1963) studied this reactions at much higher concentrations
(20,000 ppm olefin and 4,000 ppm ozone) and found a quite different
result, i.e., the ratio of olefin to ozone consumed varied from 1.4 to
2.0 for the different olefins studied. This difference was attributed
(Hanst et al., 1958) to the possible further reaction of the zwitterions
formed in the initial olefin-ozone reaction with olefins at the high
concentrations. At lower concentrations, however, the zwitterion was
postulated to undergo unimolecular decomposition. One other study, i.e.,
that of Bufalini and Altshuller (1965), reports data for olefin-ozone
consumption ratios although propylene is not included. This ratio was
found to increase with increasing olefin concentration and level off
when the olefin concentration was in excess.
One other paramenter which has received cursory examination is the
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8
initial molecular oxygen concentration in the reactor. Oxygen can
participate in the reaction either as a scavenger of radicals or by
contributing to the formation of species which alter the consumption
ratio of the initial reactants. Cox and Penkett (1972) and Stedman et
al. (1973) report the independence of the olefin-ozone reaction from the
molecular oxygen concentration. In both cases, nitrogen was employed as
the diluent gas and in the Cox and Penkett study, the oxygen mole
fraction was estimated at 0.2%. Wei and Cvetanovic (1963), however,
found that in the absence of molecular oxygen the consumption ratio was
close to unity while in the presence of oxygen as previously reported,
this ratio increased to 1.4 - 2.0 depending on the olefin studied. The
departure from 1:1 stoichiometry was believed to be due to a secondary
attack on the olefin. An oxygen effect was also reported by Ripperton
et al. (1972) in their studies of the dark phase reaction of cyclohexene
and ozone. A decrease in aerosol formation was noted concurrent with a
decrease in the molecular oxygen content.
Cadle and Schadt (1952, 1953) studied the effect of varying the
reactor temperature and found no statistically significant change in the
bimolecular rate constant. The temperature was varied from 8 to 27°C
in the ozone and 1-hexene reaction and from 20 to 50°C in the ozone-
ethylene reaction.
B. Mechanism of the Olefin-Ozone Reaction
The rate constants for the reaction of ethylene and propylene, both
terminally bonded olefins, with ozone are fairly well known. The primary
step of the ozonalysis reaction most commonly cited is the Criegee
mechanism (1954, 1955) which leads to the formation of a stable carbonyl
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and a zwitterion as
0 + OL +1 RC+HOO~ + RCHO (1)
where R can be a hydrogen atom, an alkyl group or an alkyl group contain-
ing an alcohol functional group. This mechanism has been confirmed for
reactions in solution (Bailey, 1958 and Criegee, Blust and Zinke, 1954)
and as has been assumed by recent investigators to be operative in gas
phase reactions by analogy. The zwitterion species has never been re-
ported as being observed in the vapor phase. It was found to be a rela-
tively stable and long-lived species in the studies in solution. However,
in the gas phase, if this species has an appreciable lifetime, then there
should exist an observable difference in the rate of reactant consumption
and product formation. The observation of such a difference has only
been reported in one study, i.e., that of Cox and Penkett (1972) and was
interpreted as suggesting that an intermediate having an appreciable
lifetime is involved in at least one path to product formation.
Representative rate constants for this ozonalysis reaction and many
of those to follow are listed in Table 2-1 along with the appropriate
references.
For propylene, two modes of the mechanism are reported, one yield-
ing formaldehyde and an acetyl zwitterion and the other yielding acetyl-
aldehyde and the formyl zwitterion. The zwitterions are unstable
intermediates which can, according to Leighton (1961), react with an
aldehyde or ketone to form the ozonide (using the acetyl zwitterion as
the example)
R, CH, , R, ,0 CH_,
XV 3\ + - k2 !\ /\ / 3
C = O + .C 00 -» ^C C. (2)
«
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10
Table 2-1
Summary of Rate Constant Data
Rate Constant
11
14
15
16
17
18
19
20
21
22
23
24
25
26
-2
-3
4
Value
1.82 x 10
1.47 x 10
2.13 x 10
2.93 .
2.35 x
2.35 x
2.05 x
2.58 x 10
4.40 x 10
1.47 x 10
8.36 x 103
2.27
8.37 x 101
(2.93 - 29.3)xl04 "
1.57 x 10~4
Units
-1 . -1
ppm mm
-17
-3
-4
-2 . -1
ppm mm
ppm min
Reference
Garvin and Hampson, 1974
Stedman et al., 1970
Stuhl, 1973
Niki et al., 1972
Niki et al., 1972
Niki et al., 1972
Garvin and Hampson, 1974
Garvin and Hampson, 1974
Heicklen, 1973
Garvin and Hampson, 1974
Washida et al., 1973
Garvin and Hampson, 1974
Hampson et al., 1973
Garvin and Hampson, 1974
Hendry, 1974
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11
It can decompose,
CH3 k
\ + - 3
X 00 -» CH4 + C02 (3)
H .
4
-» CH OH + CO (4)
k5
-» CH2=C=0 + H20 (5)
k6
-* CH COOH (6)
k7
-» HCOOH (from formyl zwitterion) (7)
it can rearrange
CH, . 0
3\ + - k8 *
C 00 -» CH OC. (8)
H
k
.
TI
(9)
or it can dimerize
CHK /°~°\ XCH3
2 C 00 ^ C C (10)
' kio / \ / \
H H 0 O H
Three reactions with oxygen have also been proposed, the first two of
which are chain initiating steps
CH^ kll
C 00 +0 » 'OH + CH C00; (11)
H
CH3 k
\ + - 12
C OO +0 -» CH + CO + -HO (12)
H
CH3 k
X + - 13
C 00 4- 02 -> 03 + CH3CHO . (13)
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12
These latter reactions can potentially account for the apparent excess
in olefin consumption observed in some of the studies previously dis-
cussed. The ozone generated would simply react with additional olefin
while the formation of hydroxyl or hydroperoxy radicals is chain initi-
ating and can drive the system. This role of the hydroxyl radical was
discussed by Leighton (1961) and Weinstock (1971). Niki et al.. (1972)
proposed a hydroxyl radical chain mechanism for the propylene system
which included the reactions
k
OH + CH CH=CH -» CH CH - CH OH (14)
J ^ 3 £
k 00-
CH CH - CH OH + 0 + CH CH - CH OH (15)
J £ £ HO + CH (? (16)
K17 >P
OH + HCHO -> H20 + HC- (17)
Hydroxyl radicals react with hydrocarbons either by hydrogen atom abstrac-
tion or by addition. The propylene reaction also proceeds via and
addition to the double bond or by hydrogen abstraction resulting in the
radical formation. The aldehyde-hydroxyl radical reaction also yields
a free radical . As the acetyl , f ormyl and hydroxyl radicals are
chain carriers, the aldehyde products of the olefin-ozone reaction can
sustain chain reactions . The rate of the reaction of the aldehydes with
ozone, however, is negligible compared to propylene (Bufalini, 1974).
Carbon monoxide, another product of the ozone-olefin reaction will
also react with the hydroxyl radical (Baulch et al . , 1968)
k!8
OH + CO -* CO + H- (18)
k
H- + 0 + M -» M + -HO (19)
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13
The rate constant for the reaction of the hydroxyl radical with carbon
monoxide is about two orders of magnitude lower than for its reaction
with propylene or the two aldehydes. The reaction of carbon monoxide
with ozone is considerably slower (Pressman et al., 1970) with a
reported rate constant of < 5.9 x 10 ppm min
Other reactions have been reported as follows which involve the
reactants or principal products of the olefin-ozone reaction:
(20)
(21)
(22)
(23)
(24)
(25)
i i
k26 t?
HO + HCHO -» HO + HC- (26)
k27 /
H02 + CH3CHO -» H202 + CH3C- (27)
O'Neal and Blumstein (1973) proposed a new mechanism for the gas
phase olefin-ozone reaction involving biradical intermediates which react
by various modes. One mode of their mechanism includes the Criegee
split already discussed. The other major mode involves the ring opening
of the initial adduct into a species having two active sites, i.e.,
a biradical which can react in a variety of ways. These involve three
different intramolecular hydrogen abstractions and rearrangements of
the biradical intermediates.
CH O- + CO
HO + CO
HC- + 02
HO + 0,
2 3
OH + 0,
3
'OH + -H0_
2
~20
k
*21
!22
k
*23
k
24
k
*25
CH + CO
OH + CO
HO + CO
OH + 20,,
2
HO,, + 0,,
2 2
HO +0
2 2
-------
14
C. Reactions with Sulfur Dioxide
A biradical species was also proposed by an unnamed referee for the
mechanism used by Cox and Penkett (1972) in their ozone-olefin studies
conducted in the presence of sulfur dioxide. It was this biradical
or zwitterion species or an addition complex which was proposed by those
investigators as being the reactive intermediate responsible for the
oxidation of the sulfur dioxide. Likewise, Groblicki and Nebel (1971)
suggested the oxidizing species as being a reactive intermediate but
included an ozonide, an epoxide or a free radical as the potential
identity of that species.
Species which have been identified as capable of oxidizing the
sulfur dioxide are the hydroxyl radical, hydroperoxy radical and ozone.
The rate constants for the ozone and the hydroperoxy radical reactions are
quite slow relative to the rate constant with the hydroxyl radical and for
the three reactions are <2.93 x 10 (Davis et al., 1974), 1.32 (Payne
2 -1 -I
et al., 1973) and 5.58 x 10 (Wood et al., 1974) ppm min respectively.
Other radical species which may also be considered for their potential
as the oxidizing agent are the alkoxyl, peroxyakyl and the acetyl
radicals.
A three step mechanism has been proposed by Cox and Penkett (1972)
to describe this olefin-ozone-sulfur dioxide system. The scheme pre-
sented was independent of the nature of the intermediate species and of
other removal processes for this species in the system. Their mechanism
postulates the following steps:
kl
Olefin + Ozone -> Intermediate (I) + Aldehyde
I -* Wall, Decomposition, Reaction, etc.
I + SO ->3 SO + aldehyde
-------
15
The time rate of change in concentration of the intermediate species
[R ] can be expressed as
[RI]total = aV°l][°3] - k2 [I] - k3[l][S02] II-l
where a is the fraction of the ozone molecules reacting which lead to
the formation of the short-lived intermediate. They incorporated the
assumptions that the rate of formation of the intermediate species is
proportional to the initial rate of the olef in-ozone reaction and that a
pseudo steady state concentration of the intermediate species is
established, i.e., (dl/dt) =0. If follows then
*! [01] [03]
[I] = k2 + k3 [so2]
and
«k k [01] [0 ][SO ]
-RS0 - = k3[S°2][l] = k + V [SO]
_ _
03 1 f. . 2 _ i __ .
"~ }-
If the two assumptions are valid, then a plot of this latter relation-
ship, i.e., Rn,/Ror.0 vs [SO ] would yield, via the intercept, the
fraction of ozone which reacts to form the oxidizing intermediate and
via the slope, the ratio of the second to third step rate constants. Cox
and Penkett presented such a graph for the olef ins studied (hexene,
2-methyl pentene, trans-2-butene, cis-2-butene and cis-2-pentene)
although only the initial rates and reactant concentrations were used.
D. Aerosol Production in Hydrocarbon Reactions
Prager et al. (1960), Wei and Cvetanovic (1963), Rasmussen (1964),
and Ripperton et al . (1972) all observed aerosol formation in the
reaction of certain hydrocarbons and ozone alone. Actually, only the
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16
olefins out of the group of hydrocarbon categories consisting of
olefins, paraffins, aromatics and aldehydes, react readily with ozone
in the gas phase. Table 2-2, developed by Niki et al. (1972), presents
relative rate constants for atomic oxygen and the hydroxyl radical as
well as for ozone in their reactions with the different hydrocarbon
classes.
Groblicki and Nebel (1971) likewise observed aerosol formation in
the dark phase reaction of various olefinic hydrocarbons and ozone. The
hydrocarbon concentration used in their studies was 4 ppm and the ozone
concentration was 0.6 ppm. A condensation nuclei count during these
studies showed that a-pinene, 1-heptene, 3-heptene and styrene produced
approximately 10 particles/cm when added to a chamber containing
ozone. Cyclopentene, propylene and 2,4,4-trimethyl-l-pentene with
ozone resulted in the formation of about 4 x 10 particles/cm while
the other hydrocarbons studied either produced less aerosol than the
propylene or none at all.
Very few studies of the olefin-ozone-sulfur dioxide thermal reaction
have been conducted which included an investigation of aerosol formation
factors. And, as previously indicated, aerosol measurement instrumenta-
tion was used to yield some integrated parameter on the aerosol such as
the light scattering coefficient, visibility reduction or total nuclei
count and not to provide a quantitative analysis of the aerosol produced.
Groblicki and Nebel (1971) used a Sinclair-Phoenix Smoke Photometer to
monitor the formation of a light scattering aerosol in their studies
which included sulfur dioxide as a reactant. They concluded that no
light scattering aerosol was formed unless propylene, ozone and sulfur
dioxide were all present and the amount of aerosol increases with the
-------
17
Table 2-2
Relative Rate Constants
Compound
Olefins
Propylene
Ethylene
Isobutene
Trans-2-Butene
2-Methyl-2-Butehe
Tetramethylethylene
Aromatics
Relative Rate Constants*
Benzene
Xylene
Aldehydes
Formaldehyde
Acetaldehyde
Proprionaldehyde
0
1.0
0.2
4.4
4.9
14
18
.007
0.05
.15
* .2
0,
3
1.0
0.3
1.7 * 2
2.8 ^ 36
2.4
3.9 ^ 62
<0.2
OH
1.0
0.1
2.5
4.2
7.1
8.6
SO. 05
1,1
0.9
0.9
1.8
Alkanes
n-Butane
.008
0.24
*Absolute Rate Constants (ppm min ) for Propylene
1.76 x 10'
0 OH
1.75 x 10"2 2.49 x 104
Source of Table: Niki et al. (1972).
-------
18
amount of ozone added to the system. They also concluded that the
sulfate aerosol formed was ammonium sulfate.
Cox and Penkett (1972) used a condensation nuclei counter to test
for the presence of aerosol during some of their experiments. The
major effort, however, relative to the aerosol analysis, consisted of
determining the mass of sulfur collected in bubblers containing hydrogen
peroxide and on membrane filters. Radiochemical techniques were used
to determine the mass of the S collected based on the amount of
radioactivity present after correcting for counter efficiency and
radioactive decay. A deionized water extraction of one filter yielded
a strongly acidic solution containing sulfate ions and it was concluded,
therefore, that the aerosol was sulfuric acid droplets.
The aerosol formation during the Cox and Penkett studies was
observed to follow second order kinetics. They also concluded that the
aerosol formation was not significantly affected by surface reactions.
This conclusion was based on the results of an experiment during which
an iron oxide aerosol was added to the reaction vessel increasing the
effective surface area by a factor of 2 to 3. The rate of ozone con-
sumption and the rate of the sulfate aerosol formation were not signifi-
cantly affected by the additional surface.
The role of water vapor concentration on aerosol formation in the
sulfur dioxide- ozone -cis-2-butene system was studied over a range of
relative humidities from about 10-78% and over a range of initial
sulfur dioxide concentrations (0.2 - 3.61 ppm). The aerosol formation
rate was observed to decrease with increasing relative humidity for all
of the sulfur dioxide concentrations studied. Wall losses for all of
the system components also increased but the decrease in the aerosol
formation rate was too large to be accounted for by this type of loss.
-------
19
Water vapor, it was concluded, inhibits the aerosol formation in the
olefin-ozone-sulfur dioxide reaction.
Clark (1972) conducted a comprehensive study of the formation and
growth of aerosols produced by the photooxidation of sulfur dioxide.
The advent of the recently developed Whitby Aerosol Analyzer permitted
for the first time, a study of the nucleation and growth of a forming
submicroscopic aerosol. This instrument was an earlier version of the
electrical mobility analyzer used in the study reported on in this paper
5
and has been described by Whitby and Clark (1966). A 625 ft" FEF
Teflon bag was used as the containment vessel and the ultraviolet
irradiation was provided by a cylindrical bank of fluorescent lamps.
The lamps used had about the same spectral energy distribution as sun-
light over the wavelength range of interest, i.e., 2900 to 3400 £ for
SO., photooxidation. Two important factors relative to the use of these
t.
lights are that they essentially provide full ultraviolet energy output
instantaneously and that they do not introduce excessive heat.into the
system.
The sulfur dioxide concentration ranged from 0.049 to 2.88 ppm
during these studies which yielded volumetric conversion rates of from
0.389 to 22.9 ym /cm -hr. The volume concentration was observed! to
increase non-linearly with time during the initial stages of the runs
which was attributed to a nucleation process. The increase in the
volume concentration was later characterized by a constant rate of con-
densation of material from the vapor to the condensed state. The calcu-
lated total surface area of the aerosol formed during these studies was
found to achieve an apparent equilibrium value which appeared to be a
function of the volumetric conversion rate.
-------
CHAPTER III
THEORY OF AEROSOL FORMATION, GROWTH AND DECAY
Aerosols can be divided into two major classifications according
to the mechanism? involved in their formation. Aerosols of large indi-
vidual particle size are primarily formed either by the communition or
nebulization of bulk materials into discrete particles small enough to
remain suspended in the gaseous medium. The much smaller aerosols are
formed by chemical reactions leading to polymerized species or by the
physical agglomeration of molecules leading from the vapor to the con-
densed phase. This formation mode is commonly referred to as "gas to
aerosol conversion1.
This report is concerned with only the second classification, i.e.,
the transformation to particulate material resulting from the phase
transition from the gas to the liquid state. The photooxidation of
sulfur dioxide and the oxidative consumption of sulfur dioxide in the
thermal reactions involving certain hydrocarbons and ozone are examples
of reactions that result in gas to aerosol conversions. The initial
step in the agglomeration process is the nucleation of molecules from
a supersaturated vapor. These nuclei may consist of clusters of the
condensable molecular species or foreign material (ions or particles)
of submicroscopic size. The growth of the newly formed embryos continues
by the diffusion of condensable material from the saturated vapor phase
directly onto the existing particulate surface. These processes
individually and in concert affect the time-dependent size distribution
-------
21
spectra of the aerosol. One other physical mechanism which influences
this distribution is coagulation. This process is an agglomerative
interaction which occurs if the concentration of the aerosol droplets
is sufficiently high.
A. Nucleation
Nucleation is the first step in one type of gas to liquid or solid
phase transition process. Homogeneous nucleation refers to the sponta-
neous formation of molecular aggregates or embryos resulting from the
random collisions of molecules in a supersaturated vapor. The nucleation
is termed heterogeneous if the condensation process occurs on a pre-
existing solid or liquid phase, i.e., foreign particles or charged ions.
Prerequisite to any self-nucleation is the establishment of a super-
saturated vapor in the gas volume. The supersaturated vapor develops
in chemical reactions between gaseous components only when the saturated
vapor pressure of the reaction products is less than the saturated vapor
pressure of the reactants.
The classical treatment of nucleation is included in works by a
number of authors including Amelin (1967) and Mason (1971) . The
experimental effort described in this paper involved a system which was
initially free of particles or ions. The treatment to follow, therefore,
is devoted to spontaneous homogeneous nucleation.
The embryos which rapidly form as a result of the statistical
fluctuations in the gaseous medium are also dissipated by evaporation
or breakup because of these same local thermal and density variations.
Only if the nuclei exceed some critical size (g*) will they survive
and continue to grow by condensation on the embryonic surfaces. The
free energy of the system is at its maximum value when the size of the
nuclei is g*.
-------
22
This variation of free energy in a supersaturated system with droplet
size can be plotted as
AG
g*
where AG is the incremental change in free energy and g is the number of
molecules in the aggregate. The supersaturated vapor is in a metastable
state with the chemical potential of the vapor being greater than that
of the condensed phase, i.e., y >y. . The embryos will develop only if
a b
they grow to a state where they are more stable than the vapor phase or
grow with a decrease in free energy to g>g*. In the case of heteromole-
cular homogeneous nucleation, a three dimensional plot is required to
accurately represent the change in free energy.
The total change in the free energy of a system upon the formation
of .an embryo of g molecules is described by the Gibbs free energy func-
tion for an isothermal, isobaric change as
AG = (y, - y )g + TT d2 0 (ili-l)
b a
where y = chemical potential/molecule in the vapor system
cl
y, = chemical potential/molecule in the condensed phase
b
d = diameter of the molecular aggregate
o = surface tension
The second term on the right is the surface free energy which goes from
zero to this value upon nucleation and is significant because of the
large surface to volume ratio for these small clusters.
-------
23
In order to form nuclei of size g*, dAG/dg must be at a maximum,
i.e., dAG/dg = 0. By differentiation of equation III-l this condition
is satisfied when
b a 3g
The critical free energy change is, therefore,
AG* = 1^ IJI-3
where d* = the diameter of the critical nucleus containing g* molecules.
An alternative expression relating the critical diameter for con-
tinued growth by condensation to the degree of saturation can be developed
from equation III-2 by expressing g in terms of the density and diameter
of the condensed molecular cluster and the difference in the chemical
potential of the vapor and the condensed phases in terms of the satura-
tion ratio (S) . This relationship was first developed by Kelvin (1870)
and can be expressed as
where M = molecular weight of the droplet
p = density of the droplet
R = universal gas constant
T = temperature .
S, the saturation ratio or degree of supersaturation is expressed by.
the equality
s m-£-m
where p = vapor pressure in the gas phase and
p (T) = saturated vapor pressure over a plane surface of the
liquid at the temperature T.
-------
24
The rate at which vapor molecules are impinging per unit area on
the embryonic surface is given by
B = n p (2?r M R T)"15 III-6
where n = Avogadro's number
and the rate of incorporation assuming an accommodation coefficient of
unity is simply the product of the impingement rate B and the surface
area. And finally, the rate of nucleation in embryos/cm -sec can be
expressed as
|^- = it d*2 B exp (-AGVkTJ III-7
at
where N = number concentration of embryos cm and
k = Boltzman's constant.
The preexponential term is a kinetic factor the expression of which
differs among various investigators (Becker and Doring, 1935; Reiss,
1950; Mason, 1971; and Mirabel and Katz, 1974).
From the foregoing discussion, it follows that homogeneous nuclea-
tion occurs in a gas volume only if S > S*, i.e., at some critical super-
saturation condition. The critical supersaturation condition is arbi-
trarily defined as that which will produce embryos capable of further
growth at the rate of one per unit volume per unit time. The vapor
supersaturation ratio is included in the exponential term in equation
III-7 and the rate of nucleation, therefore, increases sharply with the
degree of supersaturation.
The critical supersaturation required for spontaneous homogeneous
nucleation can be calculated from that equation by setting dN/dt = 1.
As vapor supersaturation increases it can also be seen from equation
III-4 that the embryo diameter decreases and from equation III-7 that
the number of embryos increases.
-------
25
One of the earlier works dealing with the kinetics of the sulfur
trioxide and water reaction was conducted by Goodeve et al. (1934).
The resultant product of this reaction, molecular hydrogen sulphate, was
observed to be in a state of supersaturation and condensed to produce
sulfuric acid molecular aggregates. They concluded from their reaction
velocity measurements that about one collision in one hundred results
in an association, and further, that the lack of a reaction in the
balance of the collisions was possibly due to an energy of activation,
a steric factor or the necessity of a third body collision to remove
the energy of association.
The self-nucleation rate for the sulfuric acid-water system was
theoretically treated by Doyle (1961). The rate of the transition was
characterized by a vector model developed by Reiss (1950) and adapted
for their study. The existence of a saddle point was assumed on the free
energy surface, and the rate of flow of embryos through this pass in the
energy barrier was used to approximate the rate of nucleation. The
nucleation rate was calculated and tabulated as a function of the partial
pressure of the sulfuric acid in the vapor phase for a system at 25°C and
50% relative humidity. These data indicate that self-nucleation becomes
-9
appreciable at sulfuric acid partial pressures of about 10 mm although,
according to Doyle, the rate is uncertain by three to four orders of
magnitude at this pressure. He attributed the source of the error to the
failure of the liquid droplet model at this supersaturation, uncertain-
ties in the acid partial pressure and uncertainties concerning the nature
of the dominant acid-bearing species at elevated humidities.
Limited theoretical studies of the rate of formation of critical
sized molecular clusters at relative humidities have recently been
conducted by Kiang et al. (1973) for the sulfuric acid-water system.
-------
26
Relative humidity is demonstrated to be a dominant factor in gas to
9
particle conversions. Their data indicates that only about 3 x 10
sulfuric acid molecules/cm are required to achieve a unit nucleation
rate (cm~ sec" ) in a system at 10% relative humidity. The errors
associated with this theoretical treatment relate to uncertainties in
the nucleation theory for small molecular aggregates.
B. Condensation
Growth of the molecular aggregates formed as a result of spontaneous
nucleation continues by two processes, condensation and thermal coagula-
tion. The initial growth of the newly formed droplet due to the direct
condensation of material from the vapor phase is rapid according to
classical theories relative to the early growth due to coagulation.
Homogeneous nucleation followed by surface condensation occurs, according
to equation II1-4 when the supersaturation in the gas volume exceeds
some critical value. Once an embryo exists, e.g., from the heteromole-
cular nucleation of sulfur trioxide and water, it becomes a soluble
nucleus upon which condensation can occur. The equilibrium vapor pressure
over this newly formed surface is lowered according to its composition and
concentration. Condensation will occur on this surface, therefore, at
a lower supersaturation level than required for the primary nucleation
or for condensation on an insoluble particle of the same size. When the
solution droplet is in equilibrium with its surrounding air,, its vapor
pressure must equal the partial pressure of the water vapor, and the
saturation ratio equals the relative humidity of the air.
An expression for the equilibrium water vapor pressure at the
surface of a droplet of solution is given by Mason (1971) as
. p" a1 M P M TTT 0
In * = r,_ - , ^m III-8
p p ' RdT p ' RT
-------
27
where p1 = equilibrium vapor pressure over the solution droplet
a1 = surface tension of the solution
M = molecular weight of water
p' = density of the solution
P = osmotic pressure of the solution.
Mason also gives an expression for the osmotic pressure for solutions
whose densities vary linearly with concentration as
* n
M n n2
where p = density of water
n = moles of solute
n_ = moles of water
i = factor which depends on the composition and the concentra-
tion of the solute.
The density of sulfuric acid solutions does not vary linearly with
concentration (Chemical Engineers Handbook, 1963) although over the
range of about 15 - 50% acid the relationship is nearly linear. The
combination of equations III-8 and III-9 yields two predictions relative
to the percent acid for the equilibrium system of sulfuric acid and water.
First, the percent acid decreases with increasing relative humidity for
a fixed particle size and secondly, the percent acid increases with
particle size for a constant relative humidity.
The rate of condensation on a droplet suspended in a gaseous medium
is expressed by the Maxwell equation (1890) corrected by Fuchs (1959)
for the influence of the droplet diameter as
dq 2ir D d M ,
* = (D - D )
dt R T C p PT
where q = quantity of vapor in the gas
-------
28
U = vapor diffusion coefficient
c, = a coefficient the value of which depends on the Knudsen number
p = equilibrium vapor pressure at the droplet temperature.
The influence of the Knudsen number on the rate of condensation can
perhaps be better understood by defining the characteristics of the trans-
fer process regimes. The Knudsen number (K ) itself is defined as the
ratio of the gas mean free path (1) to the particle radius, i.e.,
K = 21/d.
n
In the free molecule regime where d $ .01 ym and K -» °° the particles
n
behave as giant molecules and do not disrupt the random collisions of
the molecules of the medium. Transport properties for this regime may
be evaluated from the kinetic theory of gases.
The continuum regime includes large particles, i.e., d ;> 1 ym and
K -* 0. In this region, the transfer processes are adequately described
by the equations of continuum mechanics. The molecular structure of
the medium is not included in the description.
The region between these two extremes is referred to as the transi-
tion regime, i.e., where 0.01 < d < 1 lam and 13.2 > K > 0.132. Particles
in this size range disrupt the random motion of molecules in the medium,
and the molecular structure of the medium is still needed to describe
the system.
A comprehensive treatment of the transport processes and the transfer
equations for an isolated sphere in these three regimes is presented by
Hidy and Brock (1970). The condensation rate can, therefore, be
approximated through the use of the equations for the mass flux on the
surfaces of a spherical droplet.
As a droplet increases in size, the coefficient t decreases
-------
29
approaching unity for d » 1 and the Maxwell equation applies. Expressed
in terms of particle growth this equation becomes
dd 4 D M , . TTT -11
dT = iTTd (p - V ' II1-11
For smaller droplets the coefficient increases and varies according to
the accommodation coefficient which is sensitive to the molecular struc-
ture of the liquid.
If the nuclei exceeds the critical diameter (equation III-4) in
a supersaturated system, then it will continue to grow with a decrease
in the free energy. The transition would, according to theory, be rapid
and the droplet formed would grow without limit. In practical systems
which can be conceived, however, the supersaturation does not remain
constant as the embryos compete for the condensable vapor which is being
consumed at an increasing rate. The supersaturation, therefore, dimin-
ishes and the upper limit for the growth of the droplets is restricted.
C. Coagulation
Following the rapid growth of the newly formed nuclei by condensa-
tion, the continued growth of the particles or droplets will be dominated
by coagulation assuming that the number concentration remains above about
4 3
10 /cm . Coagulation is a coalescence of the nuclei due to the occurrence
of random collisions caused by the aerosol undergoing Brownian motion.
The theory predicting a second-order decay for the aerosol originated
with Smoluchowski (1917) who applied the diffusion equations to the
Brownian motion of hard non-interacting spheres thermally agitated in a
continuum. This aspect of aerosol stability has been extensively
treated by Fuchs (1964) and more recently by Hidy and Brock (1970) and
Husar (1971). The basic coagulation equation follows from a consideration
-------
30
of the number of collisions which occur per unit volume and time in an
aerosol due to diffusion and the number of particles is reduced by one
with each collision. The equation describing the decay of the number
concentration of equally sized aerosol particles is given as
^- = - K N2 111-12
dt
where N = the number concentration per unit volume cm and
K = the coagulation constant (cm sec ) which is given by
K = 4n d D (D here being the particle diffusion coefficient).
The value of K increases sharply as the system becomes more poly-
disperse and decreases as the particle size increases. The coagulation
constant for unequal size particles is given by Fuchs (1964) as
dl + d2 °1 + °2
K(d1,d2) = 4 it (-±-^-) (-±-2-) 0 111-13
where d + d = the diameter of the absorbing sphere in Fuchs1 model
D + D = the coefficient of relative diffusion for the two
particles
B = a correction factor necessary to account for the
concentration discontinuity which exists at the surface of the absorbing
sphere and is a function of the aerosol transfer process regime. Values
of K(d ,d ) are given in Table 3-1 from which it is evident that the
size distribution of the aerosol will rapidly become devoid of small
particles and the size of the larger particle is not significantly
affected by the interaction. Several more elaborate approaches than
the limiting sphere calculations of Fuchs have been performed including
those of Sahni (1966), Smirnov (1969) and Walter (1973). The results
have not significantly altered the values obtained from the
original work.
-------
Table 3-1
Coagulation Constants for unequal sized particles
K(dd) x 10~10 '
d]L(ym)
.002
:oo4
.01
.02
.04
.1
.2
.4
1
2
4
10
20
.002
4.5
7.5
30
90
300
1600
5000
13000
37000
77000
160000
400000
800000
.004
6
13
40
110
550
1400
4100
9500
20000
40000
100000
200000
.01
9
15
35
120
270
600
1600
3200
6600
16000
30000
.02
12
17
40
80
170
420
940
1700
4300
8500
.04
11
15
25
47
115
230
450
1100
2200
.1 .2 .4 1
7.2
8 5.2
11 5.3 4.0
24 9 4.7 3.4
45 16 7.1 3.7
90 30 12 5.2
220 72 28 10.3
430 140 54 19
2
3.2
3.4
5.6
9.6
10
20
3.0
3.7 3.0
5.5 3.3 3.0
Adapted from Fuchs, 1964
OJ
-------
32
One other phenomena affects the size distribution of the aging
aerosol, i.e., the sedimentation of the largest particles. The net
tendency of the interactions which occur in the aerosol including the
nucleation, condensation, coagulation and sedimentation is for the size
distribution to become self-preserving in time. A similarity theory to
describe the shape uniformity was originally presented by Friedlander
(1960) . Subsequently Clark and Whitby (1967) presented data from a
number of investigations properly normalized to demonstrate this self-
preservation. The data reported encompassed a wide range of experimental
conditions and suggest that a similarity spectrum forms in a matter
of hours for atmospheric aerosols originating from a number of different
sources and conditions. The similarity spectrum fit, however, was not
that predicted by the theory and at present there exists no direct
verification of the theory (Hidy and Brock, 1970).
Upon integration, equation 111-12 becomes
| - i. = Kt 111-14
o
where N = the initial particle concentration. The straight line
o
relationship between time and the reciprocal of the particle concentra-
tion dictated by this equation implies that K is invariant in time. The
value of K derived from this relationship has been the main experimental
fact reported by previous investigators in treating gas to particle
conversions. This limitation in quantitative aerosol analysis was pri*-
marily due to the lack of the sophisticated instrumentation necessary to
characterize the small particles generated by the binary homogeneous
nucleation process.
A term to account for the deposition of aerosol particles on the
walls or floor of an experimental chamber was added to equation 111-12
-------
33
by Langstroth and Gillespie (1947). The decrease in the number concen-
tration due to this 'wall loss1 is proportional to N, the concentration
at any time t and the change in concentration can be expressed as
- ^T = B N + KN2 111-15
dt
where 6 = the coefficient for wall loss. In a chamber which is not
mechanically stirred, deposition on the walls must be diffusive. The
small particles are transported near the wall by convective diffusion and
deposited on it by molecular diffusion through a stagnant air layer at
the containment surface. The thickness of this layer was reported by
Langstroth and Gillespie to 20 ym although the value varies considerably
among investigators. One of the more recent theoretical treatments was
performed by Van DeVate (1972) in which a thickness of 0.85 mm was
calculated for the stagnant air layer. The coefficient B, accounting for
the wall layer is given by Fuchs (1964) as
6 = H IU-16
where S = the surface area of the chamber
V = the chamber volume
§ = the thickness of the wall layer. Implicit in this expres-
sion for the wall loss constant is the bias of the wall for small
particles and the dependence of this term on the surface to volume ratio
of the chamber.
-------
CHAPTER IV
EXPERIMENTAL ARRANGEMENT AND PROCEDURES
A. Experimental Design and Arrangement
The experimental series discussed in this paper was designed to
provide insight into the oxidative consumption of the reactant-sulfur
dioxide and into the subsequent growth of the resultant aerosol. Initial
experiments were conducted on the propylene-ozone system for comparative
purposes and to establish a baseline for later studies conducted in the
presence of sulfur dioxide. Nitrogen was used as the diluent gas in
certain of these studies to test the role of molecular oxygen on the
reaction kinetics and on the reaction stoichiometry. Two levels of
relative humidity were also established in the reactor in an attempt
to determine the influence of that parameter on the gas-phase reaction.
These same parameters as well as the initial reactant concentrations
were varied in the studies which included sulfur dioxide. The propylene
and ozone were varied from conditions of olefin excess to ozone excess
and two levels of sulfur dioxide were used. Target concentrations of the
primary reactants, propylene, ozone and sulfur dioxide, were generally
as close to representative atmospheric levels as possible consistent
with the limitations imposed by the instrumentation used. This limita-
tion is most restrictive in the measurement of the time history for low
total reactant consumption. A few runs were made at elevated concentra-
tions to obtain a higher product yield thereby increasing the sensitivity
for the measurement of minor reaction products.
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35
A high concentration of carbon monoxide was added to two of olefin-
ozone-sulfur dioxide runs to make use of its capacity as a hydroxyl
radical scavenger in determining the participation of that species in
the reaction. Acetyaldehyde, which is reportedly formed as a result of
the propylene-ozone reaction, was investigated to determine its reactivity
in the presence of ozone or conversely its stability as a product of the
primary reaction.
A series of low reactant consumption runs were made wherein the
volumetric conversion rate was limited in order to follow more closely
the aerosol formation and growth.
Finally, a limited number of ethylene and ozone and ethylene-ozone-
sulfur dioxide experiments were conducted to determine similarities with
the propylene reactions and to observe the aerosol formation characteristics.
A schematic outlining the complete laboratory arrangement is shown
in Figure 4-1. The reaction containment vessel is shown at the top of
the figure while the reactant introduction system is shown on the right
side. This system includes the gas cylinders, the pressure and flow
regulation, ozonization and humidification. The diluent gas stream was
initially split twice with a metered fraction of the total flow passing
through the humidifier. Upon recombination there were two air streams
of similar properties, i.e., composition, flow, humidity and temperature.
Ozone was added to one of these inlet lines and the olefin and the sulfur
dioxide to the other thereby limiting the reactions to the confines of
the reactor.
The aerosol measuring instrumentation is shown directly below the
reactor where it was physically located. The positioning of these devices
was dictated by the requirement to minimize aerosol line losses.
-------
OZONE
GENERATOR
VENT
DEW POINT
HYGROMETER
REACTOR
AMBIENT,
AIR
SULFUR DIOXIDE
ANALYZER
OZONE
ANALYZER
GAS
CHROMATOGRAPH
OPTICAL AEROSOL
COUNTER
CONDENSATION
NUCLEI COUNTER
ROTAMETER
ELECTRICALLY ACTUATED
VALVE
CHARCOAL COLUMN
FILTER HOLDER
4
INJECTION
SEPTUM
MOBILITY
ANALYZER
FILTER
SAMPLES
INFRARED
SPECTROMETER
INTEGRATING
NEPHELOMETER
MAGNEHELIC
GAUGE
00
.
HUMIDIFIER
\
A
PROPYLENE
FIGURE 4-1 . SCHEMATIC OF EXPERIMENTAL ARRANGEMENT.
SULFUR
DIOXIDE
AIR OR
NITROGEN
-------
37
The gas-phase instrumentation is shown on the left along with the
dew point hygrometer. The volume of the reactor would not permit con-
tinuous sampling by all of the instrumentation shown although to eliminate
dynamic instabilities and to minimize the response time of the instrumen-
tation it was necessary to have all measurement devices in continuous
operation. The ambient air inlet shown at the upper left allows the
sulfur dioxide analyzer and the ozone analyzer to be switched to sample
the room air and the reactor intermittently. Similar arrangements were
made for the remainder of the instruments.
A photograph of the major portion of the instrumentation used
routinely during this study is shown as Figure 4-2. The reactor is
shown at the top center and the aerosol instrumentation directly below
except for the integrating nephelometer. This latter device, the
sampling section of which is oriented vertically, is located immediately
to the left of the reaction vessel. The reactant introduction system
can be seen in the background near the center of the picture. The gas
chromatograph is shown on the right and the sulfur dioxide and ozone
analyzers are to the left of the aerosol instrumentation table. At the
extreme left is a computer and display scope used for the processing of
data from the optical particle analyzer.
Figure 4-3 is a picture of the front panels of the condensation
nuclei counters, the optical particle analyzer and the electrical
mobility analyzer with its control module. Figure 4-4 is a picture of
the Fourier transform infrared spectrometer. The "folded path" cell
is in the background with the detectors, interferometer and recorder in
the foreground.
-------
FIGURE 4-2. LABORATORY ARRANGEMENT FOR OLEFIN-OZONE-SULFUR DIOXIDE STUDIES.
UJ
00
-------
FIGURE 4-3. AEROSOL MEASUREMENT INSTRUMENTATION.
Co
-------
40
FIGURE 4-4. FOURIER TRANSFORM INFRARED SPECTROMETER
-------
41
B. Experimental Apparatus
1. Reactor
The reaction bag was constructed of Dupont "Tedlar" PVF film
which was folded and then heat sealed along three sides. When inflated
the bag took on a pillowcase configuration. It was approximately 1.83m
in length and 0.94m in width and when fully inflated contained approxi-
mately 437 liters. The surface to volume ratio for the fully inflated
bag was 7.87m .
"Tedlar" was selected for the reactor because of its low reactivity
with the type of compounds encountered in these studies. The bag con-
figuration was employed because, in addition to its economy and sim-
plicity, the pressure in the system remains constant at ambient atmospheric
pressure as the volume is depleted by sampling. A dilution correction is
required when rigid walled containers are used and makeup air is added
to replace the sampled volume.
An aluminized polyester bag (3M Company 'Scotchpak1) was constructed
and placed over the "Tedlar" bag to eliminate the transmission of
ultraviolet radiation and also to reduce the rate of permeation of gases
and vapors into or out of the reactor. A polyethylene tape was used to
seal the sections of this bag together. Permeation rates for several
gases and vapors are shown in Table 4-1 for the two materials in cm or
2
g/(100 cm )(24 hrs) per mil thickness. The permeation of water vapor
through the "Tedlar" was measured at a time when the relative humidity
in the laboratory was 54% and the ambient temperature was 27°C. Figure
4-5 shows the increase in the relative humidity with time which is
estimated at 57.4 mg HO/(100 cm )(24 hrs) per mil. The permeation of
water vapor was again measured but this time through both the "Tedlar"
and the 'Scotchpak1. Over the anticipated lifetime of the experiments
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42
Table 4-1
a b
Permeability of Tedlar and Scotchpak to Gases and Vapors
Tedlar
Gases
Oxygen
Nitrogen
Carbon Dioxide
Hydrogen
Vapors
Water
Ethyl Alcohol
Benzene
Acetic Acid
cm3/dOO cm2) (24 hrs) (mil) at 23.5°C
.50
.04
1.7
9.0
g/(100 cm2)(24 hrs)(mil) at 23.5°C
.50 (37.8 C, 90%RH)
.08
.22
.11
Scotchpak
Gases
Oxygen
Carbon Dioxide
Air
3 2
cm /(100 cm )(24 hrs)at 1 atmosphere
.05
.05
<.02
Vapors
Water
g/(100 cm )(24 hrs)
.003 (37.8°C, 95%RH)
Adapted from DuPont Company
Adapted from 3M Company
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43
50
40
30
20
10
12345
TIME (hours)
FIGURE 4-5. VARIATION OF RELATIVE HUMIDITY WITH TIME DUE TO THE
PERMEATION OF WATER VAPOR.
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44
to be conducted, one to two hours, no change in the relative humidity
could be detected within the resolution of the instrumentation used.
The reactor was supported horizontally on a lattice frame suspended
from the laboratory ceiling and about two meters above the floor. Air
was permitted to circulate freely about the outer bag. Seven Swagelok
0-Seal, V O.D. stainless steel (316) adapters were fitted to the bag
with threaded teflon blocks in the pattern shown in Figure 4-6. Addi-
tional thickness was provided at these points by the addition of a
layer of the polyethylene tape. Two of the ports were used to introduce
the reactants into the system and the other five were reserved for
sampling.
2. Ozone Analysis
A Meloy Laboratories, Incorporated, Model OA350 Ozone Analyzer
was used to monitor the ozone concentration in the reactor. The gas
sample and ethylene are delivered simultaneously to a mixing zone where
they react and produce chemiluminescence in the 430 pm region. This
light is photometrically detected and is directly proportional to the
ozone concentration. The photocurrent thus produced from this flameless.
reaction is converted to a voltage, amplified and then is available as
an analog signal and/or is displayed on a panel meter.
Oxidizing species other than ozone and reducing species which might
be expected to be encountered during this series of experiments do not
interfere with the analysis.
The instrument has six .operating ranges to cover the span of from
0 to 10 ppm and its minimum detectable sensitivity is 0.001 ppm.
Primary calibration of the analyzer was achieved by generating an
ozone atmosphere in the reactor, the concentration of which was determined
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45
.
I
~\
CD
5 ) 33 cm
1 OZONE AND DILUENT GAS INLET
2 MAGNEHLIC GAUGE, INTEGRATING NEPHELOMETER
3 VACUUM, ELECTRICAL MOBILITY ANALYZER, IR SPECTROMETER,
FILTER SAMPLES
4 OZONE AND SULFUR DIOXIDE ANALYZERS
5 DEW POINT HYGROMETER
6 OPTICAL PARTICLE ANALYZER, CONDENSATION NUCLEI COUNTER,
GAS CHROMATOGRAPH
FIGURE 4-6. SCHEMATIC OF REACTOR PORT ARRANGEMENT.
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46
using the Reference Method for the Measurement of Photochemical Oxidants
(Environmental Protection Agency, 1971) . The instrument was spanned on
the concentration value thus obtained. A three-way solenoid value was
installed, which when energized, closed the sample inlet port and allowed
ambient air to pass through a charcoal filter. This provided ozone free
air to the reaction chamber for a zero calibration.
The instrument also has an integral ozone generator (Pen-Ray ultra-
violet lamp) which provides a constant ozone source on demand to the
detector. This secondary calibration was used to monitor the stability
of the analyzer and to determine primary calibration requirements.
3. Ambient and Dew Point Temperature Measurements
A Cambridge Systems, Incorporated, Model 880 Dew Point Hygrometer
was used to sense the dew point temperature dynamically in the reactor and
was also used to monitor a remote Yellow Springs Instrument Company
Thermistor, Model 410X. The thermistor had a 3.4 second time constant,
an active element 5.1 cm in length and was used to sense the temperature
in the bag.
The hygrometer measures the dew point of a gas sample by presenting
a metal surface to the gas which will be at the temperature of the metal.
The surface is cooled to the dew point temperature of the gas being
sampled and condensation occurs. At the dew point temperature, an
equilibrium condition exists and the rate at which molecules leave the
surface water is equal to the rate at which water molecules enter the
surface water.
An optical system senses the presence of condensate on the metal
surface which is mirrored and an optical-thermal feedback system adjusts
and maintains the surface at the dew point temperature.
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47
The range of the hygrometer is -40°C to 50°C, its accuracy is ±1.1°C
and with this method being a primary measurement, no calibration is
required.
The relative humidity of the gas sample defined as the ratio of the
actual vapor pressure in the gas to the saturation vapor pressure with
respect to water at the prevailing dry bulb temperature can be calculated
as follows:
_ , .. , .... Saturation Vapor Pressure over water at Dew Point Temp.
Relative humidity =_ . * . . . . *-
Saturation Vapor Pressure over water at Ambient Temp.
The Smithsonian Meteorological Tables (list, 1958) were used to obtain the
appropriate saturation vapor pressure data.
4. Sulfur Dioxide Analysis
A Meloy Laboratories, Incorporated, Model SA 185-2 Flame
Photometric Detector Sulfur Analyzer was used to monitor the sulfur
dioxide concentration in the reactor. This instrument provides real
time analysis by monitoring the intensity of light emitted by sulfur as
it passes through a hydrogen rich flame. High detection sensitivity
is achieved by the geometrical arrangement of the burner block and the
photomultiplier tube and specificity by a narrow band pass (394 ym)
filter. Sulfur containing molecules are converted to an S species in
the hydrogen rich flame. The hydrogen and hydroxyl radicals which are
also produced in the flame react with the S to form activated S * as
follows:
OH + -H + S -» S * + HO
Radiation with a maximum intensity at 394 ym is emitted when this excited
S * species reverts to a lower energy state. The intensity of the light
-------
48
produced is directly proportional to a power slightly less than the
square of the sulfur concentration.
The range of the instrument is 0-1 ppm and its minimum detection
sensitivity is 0.005 ppm.
Calibration of the sulfur analyzer was achieved through the use of
a 2 cm long, Metronics Associates, Incorporated, Dynacal Permeation tube
(#2140) and a constant temperature (30°C) Meloy SO Gas Calibrator Model
CS-10. The use of permeation tubes to generate low concentrations of
gases has been described by O'Keeffe and Ortman (1966). The permeation
rate of the tube was calibrated gravimetrically over a period of 18 hours
using a Cahn Vacuum Electro Balance System Model R100 at 25°C as 558 pg/min.
The concentration of SO in ppm can be expressed as
/ N R 22.4 T 760
c (ppm) = ? IV-1
where R = permeation rate (yg/min)
F = Gas flow rate (ml/min)
M = molar gas volume at operating conditions
T = Temperature of the gas (°K) and
P = Pressure of the gas (mm Hg).
The change in permeation rate with temperature is given by (Meloy, 1972) :
T - T
log R2 = log R + 2950 2 l IV-2
2 1
The permeation rate, therefore, for this series of experiments was 812.4
ug/min at the 30°C operating temperature and the output concentration used
for spanning the sulfur analyzer was 0.365 ppm.
The instrument zero was achieved by passing air through an internal
charcoal column prior to its passage into the burner block.
-------
49
As this instrument is a total sulfur analyzer, a Millipore Mitex
(teflon) LSWP filter was added to the sample inlet to eliminate any
contribution from the sulfate aerosol.
A Lear Siegler, Incorporated, Model III Second Derivative Air
Analyzer was used to measure the sulfur dioxide concentration in the
reactor when nitrogen was used as the diluent gas. This instrument
measures the curvature or rate of change of the slope of intensity
with respect to wavelength for the absorption of ultraviolet radiation
at a prescribed wavelength. Its minimum detectable concentration for
sulfur dioxide is 10 ppb using the 6.3)1, 1m long, multipass cell. Its
relatively large volume and high sampling rate made extensive use of this
instrument impractical. The output signal from the ultraviolet photo-
multiplier tube was recorded on an integral component Honeywell Electronik
193.
5. Hydrocarbon Analysis
A Tracer, Incorporated, Model MT150 Gas Chromatograph was used
to monitor the concentration of the unreacted olefin and the product
acetyaldehyde in the reactor. A flame ionization detector measured the
difference in the ion current due to the combustion of the sample. Sample
was continuously drawn at 100 cm /min through a 5cm loop the contents of
which could be injected via an eight position pneumatic valve into the
chromatographic column. Poropak Q was used to pack the 2.75 m column
for the adsorption and desorption of the sample gases. This material.
provides good separation based on the vapor pressure of gases.and allows
for complete resolution of the peaks of interest. The column was operated
in an isothermal mode (85°C) and regenerated for 30 minutes at 230°C
(Intersociety Committee, 1972).
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50
An analysis, using a 200 cm sample injection and a silica gel
adsorption column, of the cylinder air used during the series of
experiments indicated the presence of methane, small amounts of ethane
and propane and trace levels of acetylene, n-butane, isobutane and
isopentane. None of these gases interfere with the analysis or react
with ozone or sulfur dioxide under the conditions of the experiment.
Calibration of the gas chromatograph was achieved by injecting
specified microliter quantities of pure olefin in the gas phase into a
51 I "Tedlar" bag along with carrier air. Calibration samples from this
bag were periodically injected into the chromatographic column correcting
for wall loss in the bag.
Operation of the column in the isothermal mode along with the semi-
continuous calibration allowed for the quantification of the gaseous
components by the measurement of peak heights which were recorded on a
Honeywell Incorporated Electronik - 193 chart recorder.
6. Infrared Spectroscopic Product Analysis
A Fourier Transform Infrared Spectrometer was used to measure
the product inventory in the reactor at a terminal point in some of the
experimental runs. This system consisted of two detectors operated at
liquid nitrogen temperature, a cell, a helium-neon laser for path align-
ment, a Nerst glower as a source of the infrared radiation, a Digilab
Incorporated, Model 496 scanning Michelson interferometer, a Data General
Nova 1200 dedicated computer for processing interferpgrams and spectra,
a teletype for user control and a Digilab Digital Plotter for plotting
the spectra. One of the detectors, indium antimonide, was used to scan
the frequency region 2000 cm to 3000 cm and the other, mercury-
cadmium-telluride, to scan the region 700 cm to 1200 cm . The glass
-------
51
cell was 2.5m long and with the mirrored surfaces on the ends, path
lengths of 140 and 160 m were used for the measurements. The operation
of a system of this type has been described in a recent article by Hanst,
et al., (1973).
In operation the cell was evacuated and then allowed to fill to
ambient atmospheric pressure by opening a valve connecting the cell with
the reactor. The infrared radiation from the Nernst glower entered the
interferometer where a scanning mirror projected a sine wave modulation
on each optical frequency passing through the cell to the detectors.
The superposition of the modulated frequencies reaching the detector
constitute the interferogram which is related to the spectrum through the
Fourier transform. A reference spectrum was taken before each experimental
run which consisted of the diluent gas humidified to match the water con-
tent of the run to follow. The digitized reference spectrum was stored
in the computer memory and was accessed after the sample was collected
in the cell. The ratio of the sample spectrum to the reference was
computed and plotted. The Lambert-Beer law was used to compute the con-
centrations from the equation
c ' TF- IV-3
where I = the intensity of the radiation at the particular wave number
for zero absorption
I = the absorption diminished intensity
k = the absorption coefficient
£. = the path length used and
C = the concentration to be determined.
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52
The absorption coefficients used in this study were obtained from
reference spectra of an extensive series of molecular species previously
studied at the National Environmental Research Center, Research Triangle
Park, North Carolina.
7. Sulfur Balance Determination
Two techniques were used to determine the total sulfur content
of the sulfate aerosol formed in the olefin-ozone-sulfur dioxide reaction.
The first of these involved the use of Dupont Instruments Model 820 Liquid
Chromatograph and a Technicon Corporation Auto Analyzer to determine the
concentration of water soluble sulfates. This method is the subject of
a technical report in preparation by Tejada (1974).
The aerosol was collected on Millipore Corporation, Fluoropore FGLP
(0.2 urn pore size) 37 mm diameter filters. The filter was extracted with
a 60/40 isopropyl alcohol (IPA)/water solution and the extract pumped
through a cation exchange resin (Dowex SOW - X2) to remove interferences.
The extract is then pumped through a column of solid barium chloranilate
where barium sulfate precipitates out. An equivalent amount of reddish
colored acid chloranilate ion is released and measured colorimetrically.
This method has a sensitivity better than 0.5 yg S0~/ml in 60% IPA.
Calibration of this method was accomplished by preparing solutions
of sulfuric acid in IPA/water to span the concentration range of the
samples being analyzed.
The second method made use of X-ray fluoresence techniques to
measure the total sulfur collected on the filters. A Lawrence Berkeley
Laboratory X-ray Fluoresence Spectrometer which incorporated a dedicated
Texas Instruments computer Model T1960A and used three secondary targets,
i.e., Ti, Mo, and Tb to optimize the sensitivity over the periodic
-------
53
table was used for this analysis. A Northern Scientific Corporation
1024 Channel ADC together with the computer served as a pulse height
analyzer conducting an energy sort of the X-ray pulses. The spectrometer
has been described in reports by Landis et al. (1970) and by Goulding
et al. (1972). The composition of the samples was determined by irradia-
ting them for 400 seconds with monochromatic X-rays and observing the
characteristic K and L X-rays. The secondary fluorescer, in this case,
Ti, was used to produce the near monochromatic X-ray source. The fluoro-
pore filter was selected for this analysis because of its low mass and
very low level of impurities (Dzubay and Stevens, 1973) in addition to
its high efficiency for collecting small particles. A standard Millipore
Corporation Field Monitor was used as the filter holder with the addition
of one extra retainer incorporated as a spacer in an attempt to insure a
uniform deposition distribution on the filter surface.
The analyzer was calibrated using evaporated foils of a number of
elements and compounds. The smooth calibration curve drawn through these
points was used to determine elements for which foils were not available.
Individual spectra of up to forty elements are stored in the computer
along with a spectrum from a blank filter. These spectra are compared
with the sample spectra using a stripping procedure in order to determine
the concentration of each element.
8. Light Scattering Measurements
A Meteorology Research, Incorporated, Model 1500 Integrating
Nephelometer was used to measure the light scattering coefficient (b )
SCcl£
as a function of time during the experimental runs. The design, operation
and calibration of this instrument have been described by Charlson et al.
(1969).
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54
The sampled gas is drawn into a cylindrical optical assembly with a
flash lamp mounted behind an opal glass screen on one side. A photo-
multipler tube is mounted in one end of the assembly to detect the
scattered light from the flash illuminated volume. A light trap and a
calibration mechanism are mounted on the opposite end. A reference photo-
tube is located in the illuminated volume. This volume is defined by
means of the physical arrangement which is such that the photomultiplier
tube is not visible from the flash lamp position. Light received at the
photomultiplier tube is due, therefore, to scatter from particulate
material in the illuminated volume. The reference phototube senses the
light directly from the .flash lamp and automatically eliminated the
effect of fluctuations in flash lamp output. Ultraviolet cutoff filters,
o
(-4100 A) are used with both phototubes to relate the instruments response
more nearly to the visible spectrum and to eliminate spurious radiation
in the ultraviolet region.
The effective wavelength of the nephelometer is 500 run for either
aerosols or particle-free gases. The human eye is most sensitive, however,
to radiation at 550 nm. Horvath and Noll (1968) have shown theoretically
and Alquist and Charlson (1969) have shown experimentally that the
measured scattering can be related to light scattered at the other wave-
length as b^ = 0.84 b^.
The normal sampling rate of this instrument is approximately 140 1pm
but because of the limited reactor volume the sampling rate was reduced
to approximately 300 cm /min. The nephelometer output is independent of
flow rate and a range of time constants and flash lamp rates are select-
able. For these studies a flash lamp rate of one per second and a ten
second time constant were used.
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55
Primary calibration of this instrument was achieved by sampling
Freon-12 and spanning the instrument on the tabulated light scattering
-4 -1
coefficient (3.6 x 10 m ) which was derived from the Rayleigh theory
based on its measured refractive index (Charlson et al., 1969). A
secondary calibration method is built into the instrument and consists
of a shutter arrangement on the end of the optical assembly opposite
the phototube. A white surface behind the shutter is illuminated via
a fiber optic light pipe and the light reflected has been optically cali-
brated against gases of known scattering coefficients.
There are two secondary meter scales with this instrument which do
not indicate the results of any measurement but rather relationships
that have extensive empirical support and some theoretical justification.
The visual range scale is based on the limiting contrast for daytime
visual determination of 0.02. The resulting relationship is
L (m) * ill = lil . IV-4
V b550 b500
The other scale, i.e., mass concentration, relates the mass of material
in a box one meter in cross section and of length L as
v
2
L x Mass =1.8 g/m . IV-5
(Charlson et al., 1969). The instrument panel meter displays the mass
concentration using the relationship between that parameter and the
light scattering coefficient which is indicated on the primary scale as
mass (yg/m3) = 3.8 x 10 b ^(m" ). IV-6
scat
Values for both of these secondary -scales were calculated from the b
SCcL u
measurements made during the experimental runs and are reported .herein.
9. Condensation Nuclei Count Determination
An Environmental One Corporation, Model Rich 100 Condensation
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56
Nuclei Counter was used to monitor the number concentration of particles
> 0.0025 pm diameter. The instrument operates on the principle of a
cloud chamber in which submicroscopic droplets grow to micrometer size
as a result of condensation of water from a supersaturated environment.
The sample air is diverted, at an approximate frequency of once per
second, to a humidifier and then to a cloud chamber where the volume is
rapidly expanded. The supersaturation achieved as a result of the
adiabatic expansion reaches in excess of 300%. A light beam is focused
on a solid state light sensitive element across the expansion chamber.
The beam is attenuated by the growing aerosol the extent of which is
proportional to the number concentration of the aerosol particles. At
the end of each cycle the chamber in pressurized and flushed out.
The concentration range of the counter is from 300 to 10 particles/
cm and has a linear response, as reported by the manufacturer, through
the 0-3x10 particles/cm range scale and a non-linear response on the
0-10 particles/cm scale. The response time of the instrument is five
seconds at 50 cm /sec.
Calibration by the manufacturer is based on the Pollack counter the
developmental history of which is given by Nolan (1972) .
10. Sub-microscopic Aerosol Analysis
A Thermo-Systems, Incorporated, Model 3030 Electrical Aerosol
Size Analyzer was used to measure with time the size distribution of the
growing sulfate aerosol in the 0.003 to 1 pm size range. The design,
operation and performance of a prototype of this instrument is described
in a paper by Liu et al. (1973) and is based on the principle of
"diffusion charging-mobility analysis" described by Whitby and Clark (1966)
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57
A flow schematic of the commercial model of the electrical mobility
analyzer is shown in Figure 4-7. The sample aerosol is introduced into
a charging region where it is exposed to unipolar positive ions produced
in a corona discharge. The charged aerosol then passes through the
mobility analyzer which consits of a precipitator, a high-efficiency
current collecting filter and an electrometer sensor. The collection
rod, to which a variable negative voltage is applied, is immersed in a
sheath of clean air surrounded by an annular cylinder of the aerosol.
Small particles with high electrical mobility are drawn to the collection
rod under an applied voltage and larger particles are collected on the
current collecting filter. The voltage on the rod is periodically
increased and particles of discrete size increments will be collected on
the rod with a concurrent decrease in the electrometer current. Particles
with a sufficiently high electrical mobility are collected on the rod
for a discrete voltage while those of lower mobility are sensed by the
electrometers. The cutoff mobility at which precipitation on the rod
occurs is given by:
ZP ' 27UL - IV-7
where Q = the total air flow
r = the inner electrode radius of the precipitator
r = the outer electrode radius of the precipitator
L = the length of the collecting rod and
V = the applied voltage.
The mobility distribution of the aerosol is thus measured from which the
size distribution is inferred. This inference is based on the electrical
mobility of the aerosol being a monotonically decreasing function of the
particle size. Whitby and Clark (1966) report that for analyzers in
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58
AEROSOL
FLOWMETER
AEROSOL!
IN ^
n
SHEATH
AIR IN
AEROSOL
FLOW
ADJUST
ABSOLUTE
FILTER
CHARGER
SHEATH
AIR
ANALYZER
SHEATH
AIR
J_
/CHARGER
TOTAL FLOW
ADJUST
VACUUM
SOURCE
TOTAL FLOW
FLOWMETER
ELECTROMETER
ASSEMBLY WITH
ABSOLUTE FILTER
FIGURE 4-7. SCHEMATIC OF THE ELECTRICAL AEROSOL SIZE
ANALYZER. [TAKEN FROM THERMO-SYSTEMS
INCORPORATED, 1974].
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59
which the conditions approximate diffusion charging this relationship
holds for particles up to approximately 1 ym in diameter.
Figure 4-8, adapted from the work of Bademosi (1971), shows the
relationship between the electrical mobility and the particle size for
diffusion charging for the conditions used in the design of this instru-
ment, i.e.,Nt=lx!0 (ions/cc)(sec). N is the positive ion con-
o o
centration in the charging region and t is the residence time in that
region. Up to approximately 0.02 ym, the mean charge on the particles
is one unit and, therefore, for this size and smaller particles, the
method provides an accurate sizing technique as the mobility Z is
P
related to the particle radius by the equation,
Z = 300 -^- (cm2/volt-sec) IV-8
p 6irrn
where e = the elementary charge unit is esu
C = the Cunningham Correction factor
n = the viscosity of the air and
r = the particle radius.
The mobility dependence decreases significantly with particle size
beginning at about 0.2 ym and is essentially zero for particles greater
than 1 ym in diameter. The definition of the upper end of the distribu-
tion curve has, therefore, a higher degree of uncertainty than, for
example, the region between 0.02 and 0.2 ym. Below 0.02 ym the distri-
bution of charges on the particles is either zero or one. The determina-
tion of the fraction of particles charged and the.diffusion loss becomes
increasingly more tenuous as the particle size decreases.
On this instrument the particle size interval from 0.0032 to 1.0 ym
has been divided into ten equal geometrical size intervals. The reported
-------
60
0.1
0.01
o
UJ
CM
O
0.001
0.0001
0.001
0.01
0.1
Dp(^m)
FIGURE 4-8. RELATIONSHIP BETWEEN ELECTRICAL MOBILITY AND
PARTICLE SIZE FOR DIFFUSION CHARGING WHERE
N0t = 1 x 10? (ions/cc)(sec). [ADAPTED FROM THE WORK
OFBADEMOSI, 1971].
-------
61
diameter for each interval is the geometric mean size. Table 4-2 shows
the computational sheet used to calculate the standard and the normalized
size distributions of count, surface area and volume. The calibration
constant AN/AI is calculated from the expression
77- = Q n e f f IV-9
AI s . p c p
where Q = the sample air flow
S
n = the mean particle charge
P
e = the elementary unit charge in coulombs and
f = the fraction of charged particles and
f = the number collected on the current collecting filter.
An absolute calibration of this instrument has not been accomplished
to date although an effort to determine the finite resolution of the
analyzer accounting for the charge distribution on the particles is
under study at the Particle Technology Laboratory, University of Minnesota.
11. Optical Particle Analysis
A Royco Instruments, Incorporated, Model 220 optical aerosol
counter was used to measure the size distribution of aerosol particles
from approximately 0.3 to 10 ym in diameter. The basic principle of
this instrument is that the light from a tungsten lamp is projected into
a viewing volume through which a dilute aerosol is passed, ideally with
only a single particle in the viewing volume at a time. The light
scattered at 90° from the focused beam is sensed by a photomultiplier
tube and converted to a voltage signal. The amount of light scattered
is related not only to the size of the particle but also to its shape,
absorbtivity, refractive index and orientation. For this study the shape
of the aerosol droplets are spherical and the absorbtivity and refractive
-------
Table 4-2. Data Table for Number, Surface Area and Volume Distribution'
Collector IxlO~12 AIxlO~12
AN
D Dpi AN/AI
.0032
.0056
.0100
.0178
.0316
.0562
.100
.178
.316
.562
1.000
.0042 1.102x10
.0075 3.596x10
.0133 1.069x10
.0237 3.062x10'
.0422 9.866x10
.0750 4.775x10
.133 2.356x10
.237 1.356x10
.422 7.781x10-
.750 4.461x10'
Voltage Amp.
20
Amp.
62
196
593
1220
2183
3515
5387
7152
8642
9647
AN AS AS
AlogD AN AlogD
ANx4 P ird ASx4 P
5.54(-5)
1.77(-4)
5.56(-4)
1.76(-3)
5.59(-3)
1.77(-2)
5.56(-2)
1.76(-1)
5.59(-l)
1.77
AV
AN
l/6rrd
3.88(-8)
2.2K-7)
1.23(-6)
6.97(-6)
3.93(-5)
2.2K-4)
1.23(-3)
6.97(-3)
3.93(-2)
AV
AlogD
AVx4 P
Taken from Thermo Systems Incorporated, 1974
N=
S=
V=
-------
63
index are fairly constant so that this counter can classify by size
as well as count the droplets.
The signal from the Royco was processed by a Nuclear Data, Incorpo-
rated, system consisting of a Particle Sizing Amplifier, a Model ND 560
Analog to Digital Converter and a ND 812 Computer. An ND 4410 Control
Function Module, an ND Tape Cassette, a teletypewriter and a Hewlett
Packard 1208 B Display Scope were used to manipulate, display and record
the distribution data.
Calibration of this instrument was accomplished by a number of
techniques. To compensate for degradation of the lamp, the counter is
equipped with a light pulse generator (mechanical chopper) to simulate
the passage of particles. The amplification is adjusted until the signal
reaches the calibration value. A zero check is made by placing a membrane
filter over the sample inlet. The prime calibration procedure consisted
of generating an aerosol of monodisperse latex spheres (refractive index
1.6) and sampling the suspended material with the optical aerosol analyzer.
The size of the spheres used were 0.3, 0.357, 0.481, 0.794 and 1.011 pm
and their corresponding peak channels were recorded with the multi-channel
analyzer. The calibration data for this system is shown in Figure 4-9.
C. Experimental Procedures
The reactor was flushed with diluent gas three times before each
run to sweep out unreacted and product species from previous experiments.
The bag was evacuated via a vacuum line to yield a maximum deflection on
the Dwyer magnehelic gauge, < - 0.5 inches of water. The reactor was
then filled with the diluent gas humidified to the same degree as for the
experiment which was to follow. The diluent gas was passed through a
-------
64
2.0
1.0
0.9
0.8
0.7
_ 0.6
1 0.5
a.
o
0.4
0.3
0.2
0.1
20
40
60 80
CHANNEL
100
120
FIGURE 4-9. CALIBRATION DATA FOR OPTICAL AEROSOL ANALYZER.
-------
65
charcoal column followed by a 142mm Millipore type AAWP filter (0.8 ym
mean pore size) prior to its introduction into the reactor to remove
contaminant aerosols and undesirable reactive gaseous species. The
diluent gases used in this experimental series were compressed air made
from a mixture of liquid oxygen and liquid nitrogen and compressed
nitrogen (High Purity Grade).
A complete set of background measurements was made with the total
instrument complement to confirm the essentially zero concentrations of
the reactive species and particulate material. The condensation nuclei
counter typically indicated a background nuclei count of about 400 con-
densation nuclei per cubic centimeter and its reported range is 300-10
en/cm . If during these background measurements, positive concentration
values (other than the en/cm level cited) were recorded, then the
flushing procedure was continued until a zero value was observed.
The propylene used for the reactor was a calibration mixture (Linde)
of 945 ppm in nitrogen while that used for the calibration of the gas
chromatograph was CP grade (>99.5%) and was introduced into the reactor
by being injected into the diluent gas stream from a gas tight syringe.
The sulfur dioxide was also in a calibration mixture, in this case from
Scott Research Laboratories, Incorporated and contained 89 ppm in nitrogen.
An Orec Model 03V1 OZONATOR was used to provide the desired ozone concen-
tration. Zero grade air was passed through a charcoal column and a Milli-
pore type AAWP filter before being exposed to the mercury vapor lamp in
the ozonizer. A Millipore type FALP (teflon) filter (lym mean pore size)
was used on the output of the ozone generator to remove any condensation
nuclei which might be photochemically generated by the ultraviolet lamp.
The carbon monoxide which was used for two of the runs was CP grade and
was injected into the diluent stream in the same manner as was the ethylene.
-------
66
The propylene, sulfur dioxide and the diluent gas were delivered
to the reactor at a constant rate and mixture ratio over a five minute
period. The humidification was provided as previously mentioned, byt
passing a metered portion of the diluent gas through bubblers containing
distilled water and immersed in a Forma Scientific Model 2800 Constant
Temperature Bath and Circulator. The ozone was fed into one of the two
diluent gas streams for a portion of the five minute period depending
on the concentration desired. Ozone was not, however, added during the
last thirty seconds of the filling time thereby permitting the other
reactants and diluent gas introduced during that terminal period to mix
thoroughly with the ozone. Electrically actuated solenoid values were
used to initiate and terminate the introduction of the gas phase com-
ponents into the reactor and this flow was controlled through Brooks
Instrument Division flowmeters and Parker-Hannefin needle valves. The
reactor was filled for each experiment to a positive pressure indication
on the magnehelic gauge, of 0.1" of water above ambient.
The total gas flow into the bag was about 90 1pm which was considered
adequate to insure uniform mixing of the reactants. The reactor was not
mechanically stirred during the experiments as the thermal gradients which
existed in and about the reactor were found to be adequate in maintaining
homogeneity among the gaseous species. Wilson et al. (1971) studied
the effect of stirring in a series of chamber experiments and noted a
decrease in the amount of aerosol with increased stirring rate. If the
stirring was sufficiently fast, the observation of light scattering
aerosol could be completely eliminated. The composition of the reactants
also influenced the effect noted with increased stirring. Cox and Penkett
(1972) observed a similar result in that when forced circulation was used
during their experiments, the effective rate of gaseous diffusion to
-------
67
their reactor walls was increased by a factor of about five. The effect
of stirring was not found to be a critical parameter on aerosol growth
in systems with initial low nuclei counts during studies conducted by
Kocmond et al. (1973). Aerosol decay by coagulation in the dark, however,
was noted to be significantly increased by stirring.
Sampling was initiated immediately after the reaction vessel was
full and was generally intermittent. The electronics portion of the
instrumentation was kept operating while the pneumatic system was off in
some cases and cycled to sample room air in others. These measures were
necessitated because of the limited total volume in the reactor and the
large sampling volume demands of the instruments. The experiments were
designed to last until one of the principal reactants, i.e., the olefin
or ozone had been consumed by > 90%.
A Westronics, Incorporated, Model MllE Multipoint Recorder was used
to record the ambient temperature and the output of the ozone and sulfur
dioxide analyzers, the condensation nuclei counter, the integrating
nephelometer, and the dew point hygrometer. The output of the flame
ionization detector in the gas chromatograph was recorded on the Honeywell
Electronik 193 Strip Chart Recorder. The Royco optical particle data
was stored in the memory of the Nuclear Data ND 812 computer system and
printed out on a teletypewriter. The data output from the electrical
mobility analyzer was manually recorded. The analog output from the
various instruments was digitized and recorded along with the other
digital data on computer cards for subsequent data manipulation.
A series of measurements was performed to determine the loss of the
reactants in the containment vessel. Propylene, ozone and sulfur dioxide,
were introduced into the reactor individually along with the diluent gas
and their concentration monitored over an extended period of time. The
-------
68
loss of the reactant species could be a function of molecular diffusion
to and reactions with the reactor walls and/or reactions with species
not purged from the bag after previous runs or introduced with the
species under study.
The observed loss for these three species was apparently the result
of a first order reaction, with the species irreversibly lost to the walls
of the reactor. Figure 4-10 shows the linear relationship resulting
from a plot of the logarithm of concentration versus time for the three
species for typical decay measurement runs. The slopes of the lines
are the rate constants for the wall loss reaction as predicted from the
following equations :
= -k[A] IV-10
where A = some hypothetical species and
k = the velocity constant.
The equation simply states that the rate of the wall loss reaction is
directly proportional to the concentration of the reactant present. By
integration the equation becomes :
In [A] = -kt + constant IV-11
from which the value of k can be obtained. Reaction rates are also
often reported in terms of the half life of the species in the system.
For the first order reaction the half life is related to the rate constant
by
t>» = ^p.. iv-12
The rate constants and half lifes measured for the three species in
the reaction containment vessel were as follows:
-------
69
10
9
8
7
6
5
_ 2
ex
O
I-
oc.
y 0.9
o 0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
z r
I -
kw-2.35x10-4 min-1
kw = 9.7 x 10-4 min-1
S02
kw = 1.52 x 10-4 min-1
3
t (hrs)
FIGURE 4-10. VARIATION OF REACTANT CONCENTRATION WITH
TIME DUE TO WALL LOSSES.
-------
70
Propylene Ozone Sulfur Dioxide
-4 -1 -4 -1 -4 -1
Rate Constant (k) 2.35x10 min 9.7x10 min 1.52x10 min
Half Life (t>5) 49.1 hrs. 11.9 hrs. 76.0 hrs.
The data from several experiments were corrected for these different
rates of loss due to wall deposition although the net result was insigni-
ficant and is not included in this report.
-------
CHAPTER V
Experimental Results and Discussion
The experimental results obtained during this study generally relate
to two separate yet interrelated scientific fields. The first few sec-
tions of this chapter deal with the analysis of gas phase reactants and
products while the later sections are concerned with the gas to particle
conversion process and the growth of the newly-formed aerosol. The inter-
relationships are made clear throughout the treatment to follow. Extensive
use-has been made of tables and figures in supplementing the discussion
of the experimental results.
A tabulation of the gas phase products observed by the Fourier
Transform Infrared Spectrometer for eleven runs is included in the
Appendix as is the listing of the observed and predicted values of the
reactant concentrations as a function of time for the basic series of
nineteen gas phase experiments. The droplet number, surface area and
volume concentration distributions at several different times are also
tabulated in the Appendix for a series of six aerosol experiments.
A. Reactant Consumption Data and Reaction Stoichiometry
Several series of olefin-ozone-sulfur dioxide experiments were con-
ducted to obtain information relative to the Stoichiometry of the olefin-
ozone reaction, the influence of sulfur dioxide on the reaction, the
role of molecular oxygen and the effect of varying the relative humidity
on the system. A summary of the initial conditions for one series of
nineteen experiments is shown in Table 5-1. Sixteen of these runs
-------
Table 5-1. Summary of Experimental Conditions and
Initial Reactant Concentrations
Propylene
ton
91
92
93
94
21
31
25
26
27
86
87
88
89
90
T(°C)
24
24
24
25
27
28
24
25
25
24
26
23
26
25
RH (%)
26
39
23
37
19
19
22
22
22
23
20
25
21
21
Olefin
(ppm)
2.580
3.012
2.753
2.930
8.125
8.555
1.878
3.547
3.461
.922
1.112
3.281
3.318
2.739
Ozone
(ppm)
1.660
1.651
2.573
2.683
2.882
2.714
2.377
1.080
.983
1.969
2.056
.274
.295
1.970
Sulfur Dioxide
(ppm)
0
0
0
0
0
.5250
.5827
.6206
.1939
.2010
.6507
.2075
.6373
.5803
Olefin/O:
1.554
1.824
1.070
1.092
2.819
3.153
.790
3.284
3.522
.468
.541
12.00
11.26
1.390
-------
Table 5-1. Continued
Propylene
:un
98
95
T(°C)
25
25
RH (%)
23
20
Olefin
(ppm)
2.825
3.025
Ozone
(ppm)
2.025
1.813
Sulfur Dioxide
(ppm)
.2039
.5582
Olef in/O
1.395
1.669
Ethylene
97
28
29
26
27
28
22
22
20
3.112
11.85
12.50
2.102
3.807
3.617
.5884
0
.5294
1.480
3.113
3.456
U)
-------
74
included propylene as the olefin species while the other three involved
ethylene. The observed temperature with one standard deviation for the
propylene runs was 25.1 ± 1.9°C while the measured relative humidity
was 21.8 ± 2.0% for low water vapor concentration runs and 38.0 ± 1.9%
for the higher level runs. The initial concentration of propylene ranged
from about 0.9 to 8.6 ppm for this series and for ozone the range was
from about 0.3 to 2.8 ppm. The initial sulfur dioxide concentration was
in general, at one of three levels, 0.0, 0.2, or 0.6 ppm. The ratio of
the initial concentrations of the two principal reactants typically
ranged from about 0.5 to 3.5 with this initial olefin-ozone concentration
ratio being about 12 for two of the runs.
The amount of the reactants consumed in this series of experiments
is summarized in Table 5-2. Also shown is the percentage of one of the
principal reactants which was consumed at the point at which the time
averaged stoichiometric change was measured. This percentage generally
referred to the quantity of ozone reacted as the olefin was usually in
excess. Ozone was in excess, however, for runs 86 and 87 and the per-
centage refers to the amount of the propylene consumed. The amount of
sulfur dioxide reacted ranged from about 0.02 to 0.2 ppm in this series.
Only acetyaldehyde, of the stable aldehyde products formed in the olefin-
ozone reaction, could be measured with the gas chromatographic arrange-
ment used. This species, which is formed in the reaction of ozone with
propylene, was followed in time for several of the experiments and the
concentration value attained near the end of the run is included in
Table 5-2. Due to the longer time required for the acetyaldehyde to
elute from the gas chromatographic column and because of the lower
sensitivity for its measurement, it was not followed on every experiment.
-------
Table 5-2. Summary of Stoichiometric Data and
Acetyaldehyde Production
Propylene
lun
91
92
93
94
21
31
25
26
27
86
87
88
89
90
AOL
(ppm)
1.811
1.957
1.852
1.975
3.917
3.934
1.630
1.498
1.468
.817
.954
.501
.539
1.999
A03
(ppm)
1.463
1.499
2.315
2.415
2.610
2.468
1.702
.978
.889
1.050
1.109
.249
.270
1.757
AS02
(ppm)
0
0
0
0
0
.174
.180
.141
.058
.078
.151
.022
.052
.205
AOL/AO
1.238
1.306
.800
.818
1.501
1.594
.958
1.532
1.651
.778
.860
2.011
1.996
1.138
Reacted
.88
.91
.90
.90
.90
.91
.72
.92
.90
.88*
.86*
.91
.92
.89
CH CHO
(ppm)
n.m.
n.m.
n.m.
n.m.
1.65
1.80
.73
.45
.58
n.m.
.48
n.m.
n .m.
.82
-J
en
-------
Table 5-2. Continued
Propylene
:un
98
95
97
28
29
AOL
(ppm)
2.084
1.721
1.265
4.557
4.964
A03
(ppm)
1.805
1.633
Ethylene
.980
3.039
2.876
ASO
(ppm)
.102
.165
.183
0
.299
AOL/AO
1.155
1.054
1.291
1.500
1.726
% 0
Reacted
.89
.90
.47
.80
.80
CH CHO
(ppm)
.84
.79
n.m. not measured
* % OL Reacted
-------
77
Acetyaldehyde is not a product of the reaction of ozone with ethylene
and would not, therefore, be expected to be present in those runs.
The variation of concentration with time for a typical propylene-
ozone-sulfur dioxide run is shown in Figure 5-1. The near 1:1 stoichio-
metric consumption for the two principal reactants is readily apparent in
the near constant difference in their concentrations with time for this
experiment. The consumption of the sulfur dioxide is markedly slower
than it is for the other two reactants. The acetyaldehyde production is
also shown and as it does not appear to follow linearly the loss of the
propylene, the process leading to its appearance is more complex than
if it were formed in a single bimolecular reaction.
The reaction involving propylene can be contrasted with a run in
which ethylene was the olefin reacted with the ozone. The variation of
the concentration for the reactants in the ethylene experiment is shown
in Figure 5-2. The initial concentrations for this run were about the
same as they were for the propylene experiment and although the same
trends in consumption are observed, the reaction proceeds much more slowly.
The data listed in Tables 5-1 and 5-2 were used to plot the varia-
tion in the apparent stoichiometry of the olefin-ozone reaction with the
initial reactant concentration ratio (Figure 5-3). There are a total of
thirteen data points plotted which represent ozone-propylene reactions
conducted in air. The line drawn through the points appears to satisfy
these data and was fixed by eye. Ten of these thirteen experiments were
conducted in the presence of sulfur dioxide. The presence of the sulfur
dioxide had no apparent effect on the stoichiometry of the primary reaction
as all of the data closely follow a smooth curve. This result indicates
that the oxidative consumption of the sulfur dioxide is due to a reactive
product of the propylene-ozone reaction rather than to a primary reactant
-------
10
FIGURE 5-1. VARIATION OF CONCENTRATION WITH TIME FOR
PROPYLENE-OZONE-SULFUR DIOXIDE REACTION.
03
-------
o
I
<:
oc.
\-
LU
O
o
o
VO
FIGURE 5-2. VARIATION OF CONCENTRATION WITH TIME FOR ETHYLENE-
OZONE-SULFUR DIOXIDE REACTION.
-------
2.2
2.0
1.8
1.6
1.4
^^
< 1.2
1.0
0.8
0.6
CO
-*L.
oPROPYLENE-OZONE
oETHYLENE-OZONE
APROPYLENE-OZONE IN NITROGEN
PROPYLENE-OZONE WITH CARBON MONOXIDE
1
4 5
8
10 11 12
OL\
03/
FIGURE 5-3. STOICHIOMETRY OF OLEFIN-OZONE REACTION VERSUS
INITIAL REACTANT CONCENTRATION RATIO.
03
o
-------
81
such as ozone. This conclusion was fully substantiated through an
experiment in which ozone and sulfur dioxide were the only reactants. The
consumption of those species in this experiment was slow enough so as
not to be distinguished from losses attributable to wall effects.
The nature of the reactive product of the olefin-ozone reaction
which results in the consumption of the sulfur dioxide has been studied
by Cox and Penkett (1972). Evidence that this product is a short-lived
intermediate of the primary reaction was derived from experiments in
which the sulfur dioxide was introduced at different times after the
initiation of the olefin-ozone reaction. When the sulfur dioxide was
added after the ozone had sufficient time to react with the olefin, the
aerosol formation was barely perceptible, whereas when the sulfur dioxide
was initially present or added shortly after the run began, the aerosol
formation was significant.
The data shown in Figure 5-3 indicate that the reaction is compli-
cated by secondary reactions. The apparent stoichiometry of the reaction
is decidedly affected by the initial concentration ratio. In general,
a system which initially has propylene in excess results in a consumption
ratio of the propylene to ozone greater than one while in a system
which initially has an ozone excess condition the value of this ratio
is less than one. These results are in general agreement with those
reported by Wei and Cvetanovic (1963) for experiments conducted at much
higher reactant concentrations. Several olefins including propylene
were studied by those investigators and the consumption ratio was found
to vary from 1.4-2.0 for the different olefins in the high olefin excess
system. Bufalini and Altshuller (1965) also studied a series of olefins
but in concentrations much closer to values used in this study and
observed a similar trend. Preliminary results from two current studies
-------
82
in progress elsewhere are also in good qualitative agreement with those
reported herein. One of these, directed by Williamson (1974) , makes use
of high initial reactant concentrations and is projected to include
propylene. Initial results for the ethylene system indicate a consump-
tion ratio of less than one for the ozone rich system and equal to or
greater than one for the ethylene rich system. The other investigation
is being conducted by Niki (1974) and makes use of propylene concentra-
tions ranging from 2.0 to 5.8 ppm and ozone concentrations from about
1.4 to 8.3 ppm. The stoichiometry which they have observed for these
propylene .studies ranges from 0.9:1 to 1.4:1. For the study reported
herein, the consumption ratio varies over the range of experimental con-
ditions used from about 0.8 to 2.0 and it appears to approach this latter
value as a limit. When a condition of initial ozone excess exists, these
data would support a postulate that either ozone is interacting with pro-
ducts of the primary olefin-ozone reaction or that propylene is being
produced. Similarly for a system which is initially rich in propylene
these data could support a postulate that propylene interacts with a
reactive product of the initial reaction and/or that ozone is being pro-
duced as a result of a secondary reaction. A reaction that could result
in the production of ozone is shown as reaction 13, Chapter II, as postu-
lated by Bufalini and Altshuller (1965) and involves an interaction of
the reactive intermediate with molecular oxygen.
The three ethylene-ozone-sulfur dioxide experiments are also included
in Figure 5-3. These data follow the same general trend as do the data
from the propylene system and the slightly increased scatter is believed
due to the method of olefin introduction into the reactor. The propylene
was metered into the system at a constant rate for the entire reactor
filling period while the ethylene was injected via a septum into the
-------
83
diluent gas stream. It appears that the sulfur dioxide is oxidized by
a reactive product of the primary reaction in the ethylene system in
analogy to the oxidative process in the propylene system.
The molecular oxygen concentration was sharply reduced for several
runs in an attempt to determine whether oxygen has a role in the reaction.
The results of four of these experiments in which nitrogen was used as
the diluent gas are recorded on Figure 5-3. An obvious reduction in the
propylene to ozone consumption ratio occurred indicating that molecular
oxygen plays a significant role in modifying the consumption of one or
both of the primary reactants. This result runs contrary to that reported
recently by Cox and Penkett (1972) and Stedman et al. (1973) . Those
investigators concluded as a result of their studies that molecular
oxygen does not affect the stoichiometry of the primary olefin-ozone
reaction.
Wei and Cvetanovic (1963) studied the reaction of high concentrations
of several olefins including propylene with ozone in the gas phase both
in the presence and in the absence of molecular oxygen and found a lower
consumption ratio in the absence of the oxygen. Data collected in the
current study by Niki (1974) led him to the conclusion that oxygen has a
pronounced effect on the olefin-ozone system.
The observation of this molecular oxygen effect has led to the
postulate that a secondary attack on the propylene is occurring in this
reaction. As the consumption ratio changes in the presence or absence
of molecular oxygen, a secondary attack on the olefin by the reactive
intermediate can be eliminated as being responsible for the stoichiometric
change. Other reactions which could account for the oxygen effect and
the deviation from 1:1 stoichiometry are those which involve an interaction
of the intermediate species and molecular oxygen, e.g., reactions 11-13
-------
84
in Chapter II-B. The products are the hydroxyl and the peroxyacetyl
radicals, the methyl radical, carbon dioxide and the hydroperoxy radical,
and ozone and acetylaldehyde for the three reactions respectively. Each
of these reactions, therefore, results in the production of a species
capable of further interacting with the olefin in a chain propagating
reaction. The three species formed also react with carbon monoxide
although the rate constant for the reaction of the hydroxyl radical with
carbon monoxide is approximately 10 times greater than the reaction
with the hydroperoxy radical and about 10 greater than the reaction of
carbon monoxide .with ozone. The addition of an appropriate concentration
of carbon monoxide to serve as a scavenger in the system should, therefore,
provide a convenient method of testing for the formation and presence of
the hydroxyl radical. As the hydroxyl radical would also react with the
olefin and sulfur dioxide in the system in addition to any aldehydes
formed and other minor products of the olefin reaction, a sufficient
carbon monoxide concentration was needed to affect the overall reaction
stoichiometry significantly. In other words, it was desired to cause
the loss of the hydroxyl radical, if present, to be greater in its
reaction with carbon monoxide than its total loss in all of its other
possible reactions. This can be expressed in functional form as
k18 [-OH][CO] > [-OH]
-------
85.
Two experiments in which 458 ppm of carbon monoxide was added to the
propylene-ozone-sulfur dioxide system were conducted and the stoichiometric
results are included in Figure 5-3. These results substantiate the postu-
late relative to the formation of the hydroxyl radical in this reaction
and its subsequent secondary attack on the olefin species.
One final result included graphically in Figure 5-3 is the lack of
an effect of a change in the relative humidity on the olefin-ozone
reaction over the range studied. The propylene runs included one experi-
ment conducted in air and two in nitrogen for which the relative
humidity was elevated to about 38 percent. Cox and Penkett (1972)
observed a water vapor concentration effect on the sulfur dioxide con-
sumption with a decrease in the sulfur dioxide oxidation rate occurring
with increasing relative humidity. The data from two runs in the study
reported herein showed a slight but similar trend. The consumption of
sulfur dioxide in run 60, which was conducted in an atmosphere at 20
percent relative humidity, was 0.071 ppm/ppm of ozone consumed while
for run 65 conducted at a relative humidity of 36 percent, this ratio
was 0.066 ppm/ppm of ozone consumed. The products of these two experi-
ments as measured with the infrared spectrometer do not reflect an effect
due to the variation in the relative humidity.
The acetyaldehyde concentration produced in several of the experiments
was plotted against the amount of propylene reacted (Figure 5-4). Each
of the data points represents a separate run. The measurements of both
the olefin and the aldehyde were made at the same time, late in the
experiments. The line drawn was determined by fitting the data to a
linear function by the method of least squares. The slope of the regres-
sion line forced through the origin is 0.44 which also indicates the
mean yield of acetyaldehyde in these reactions. The data included are
-------
86
1.8
1.6
1.4
1.2
o 1.0
01
o
ce
^0.8
0.6
0.4
0.2
AOL(ppm)
FIGURE 5-4. CONCENTRATION OF ACETYALDEHYDE PRODUCED VERSUS
PROPYLENE REACTED FOR NINE PROPYLENE-OZONE
EXPERIMENTS.
-------
87
from experiments conducted in the presence of sulfur dioxide, the oxida-
tive step of which purportedly produces acetyaldehyde. The contribution
from that step amounted to approximately thirteen percent according to
data from runs 30 and 21 reported in the product analysis table in the
Appendix. Making an adjustment for the contribution from the sulfur
dioxide oxidation reaction the modified production of 0.38 ppm of acety-
aldehyde per ppm of propylene reacted is in close agreement with the
results reported by Scott et al. (1957) and Wei and Cvetanovic (1963).
A relationship between the consumption of the sulfur dioxide and
one or both of the primary reactants was also sought. . Using the data
from runs in which the initial olefin to ozone concentration ratio was
equal to or greater than one, the plots shown in Figures 5-5 and 5-6 were
developed. By including the initial sulfur dioxide concentration in the
plot, it can be seen from Figure 5-5 that an apparent linear relationship
can be established between the formation of the sulfur species and the
olefin reacted. These lines were constructed by fitting the data by the
method of least squares and forcing the regression line through the origin.
The sulfur dioxide concentrations employed in this analysis with one stand-
ard deviation were 0.605 ± 0.028 and 0.202 ± 0.007 ppm. The data plotted
in Figure 5-6 demonstrate the non-linearity of the relationship between
the amounts of ozone consumed and the sulfur dioxide produced. These
data further enforce the postulate concerning the identity of the oxidiz-
ing species for the sulfur dioxide as being a reactive product of the
propylene reaction.
The data plotted in Figure 5-3 and previously discussed show that
the stoichiometry of the propylene-ozone reaction for these experiments
was generally other than 1:1. As the reactant consumption ratio dropped
when the partial pressure of the molecular oxygen was reduced, it was
-------
88
0.24
0.20
o
<
0.12
0.08
0.04
0.4
0.6
=0.605 ±0.028 ppm
=0.202 ±0.007 ppm
0.8
1.2
1.6
2.0
2.4
AOL(ppm)
FIGURE 5-5. SULFUR DIOXIDE CONSUMPTION VERSUS PROPYLENE REACTED FOR
DIFFERENT INITIAL SULFUR DIOXIDE CONCENTRATIONS.
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89
[S0£]o= 0.605 ±0.028 ppn
= 0.202+0.007 ppm
0.4
1.2 1.6
A 03 (ppm)
2.4
FIGURE 5-6. SULFUR DIOXIDE CONSUMPTION VERSUS OZONE REACTED FOR
DIFFERENT INITIAL SULFUR DIOXIDE CONCENTRATIONS.
-------
90
speculated that ozone and/or the hydroxyl radical were being produced
in the reaction of a product of the ozone-propylene reaction with oxygen.
The reduction of the reactant consumption ratio when the carbon monoxide
was added enforced the speculation relative to the formation of the
hydroxyl radical which was subsequently scavenged by the carbon monoxide.
These measurements do not, however, demonostrate whether the change in
stoichiometry with the changing propylene/ozone initial condition is due
to the production of propylene, enhanced consumption of ozone or to an
interaction of these species with reaction products. To investigate
further the reaction mechanism with regard to the stoichiometry, the
R R
variation of the functions , 1 , , and , -i rn i with time was noted.
If the only reactions involving these species were with each other then
R = R and the plots of the rate over reactant product versus time
OL 03
would yield a straight line of zero slope, and the value of the function
would be equal to the second order rate constant. If, however, a plot
of one of the functions initially displays a negative slope, then that
species is being produced in the reaction according to
. _
[OL] [03] l 2 [OL] [03]
where [A] [B] = product of the concentration of reactants A and B lead-
ing to the ozone production and
k = rate constant of the hypothetical bimolecular reaction.
Conversely, if a plot of one of the functions were to display a positive
slope initially then that species is being consumed by another process as
v v_3
[OL][03] - *1 *2 [03]
The variation of these two functions with time for run 98 is shown
-------
91
in Figure 5-7. The resultant curves are typical for the series of
experiments conducted in that the R function, i.e., the function which
OL
includes R , increases with time to some maximum and then decreases to
OL
a value that is approximately equal to that of the R function. The
function which includes R also increases with time but at a much
slower rate and without the peak typical of the other curve. The values
of the functions at the reported zero time are approximately equal and
represent the rate constant for the propylene ozone-reaction.
Some mention is warranted, at this point, on how the derivatives of
the reactant concentrations with respect to time were estimated. The
first five data points were fitted to a second order polynomial from
which the value of the third point and its derivative were estimated.
The first observed data point was then dropped and the sixth added to
establish a new set of five data points to be fitted. This operation
was continued through the total set of data collected and was performed
using a computer program of the Statistical Analysis System (SAS) (Service,
1972) . Values required which were beyond the range of the observed data
were estimated by extrapolation. This latter feature was implemented
repeatedly during this study to obtain the concentration and rate at
the zero time.
One additional factor affecting the absolute accuracy of the initial
R-T and R values is the fact that the primary reaction actually commenced
ULi (Jo
at a time prior to the zero time reported on these plots. The reported
zero time, as previously indicated, was taken as the time at which the
reaction vessel became full.
Data of the type reported in Figure 5-7 provide a measure of the
second order rate constant for the propylene-ozone reaction and yield
semi-quantitative information on the reaction stoichiometry. The reaction
-------
92
FIGURE 5-7. VARIATION OF THE APPARENT RATE CONSTANT WITH TIME
DUE TO SECONDARY REACTIONS.
-------
93
which involves R is observed in the figure to increase with time suggest-
ing that ozone is being consumed by a product of the principal reaction.
The postulated generation of ozone by a secondary reaction, e.g., the
reaction of the unstable intermediate with molecular oxygen, is either
nonexistent or is completely masked by the enhanced ozone consumption.
The product or products responsible for the additional loss of ozone are
unidentified at this time but are known not to include the products
measured and reported later in this paper. The rate of reaction of
ozone with the aldehydes and carbon monoxide is too slow to be of signi-
ficance while the yield of the other products is too low to influence
the disappearance of the ozone. The slowness of the acetyaldehyde-ozone
reaction relative to that of propylene with ozone was confirmed by con-
ducting one experiment with acetyaldehyde and ozone as the sole reactants.
The rate of loss of the ozone in the system with the aldehyde was such
that over the lifetime of a typical experiment in this series it could
not be distinguished from the first order loss of the ozone to the walls
of the reactor. An equation of the form of V-3 may itself be symbolic
with the second term representing several reactions.
The other curve in Figure 5-7 indicates that propylene is also
being subjected to a secondary reaction. The postulate concerning the
formation of the hydroxyl radical in a reaction involving the interme-
diate species and molecular oxygen can be used to explain that curve.
As the hydroxyl radical is formed and reacts with propylene the function
plotted rises to its maximum value. Formaldehyde and acetyaldehyde are
produced in the propylene-ozone reaction and eventually compete for the
_j^
hydroxyl radical causing the function f -, r -. to diminish to some
IOLJ LO3J
equilibrium value.
-------
94
The value of k based on the propylene rate data for run 98 was
1.46 x 10 ppm min and based on the ozone rate data was 1.39 x 10
ppm min~ . The mean and one standard deviation for k computed from
the thirteen runs conducted in air and based on the rate of change in the
ozone concentration was 1.40 ± .38 (x 10 ppm min ). For these runs,
-RQL -RQ3
the function , ,» , was generally equal to or greater than , ,.- -.
while for the runs conducted in the reduced oxygen atmosphere this
relationship was reversed. This trend indicates that the relative rate
of olefin involvement in secondary reactions had diminished with the
oxygen depletion.
The initial olefin/ozone concentration ratio was 12 for run 88 and,
therefore, the ozone would be expected to behave in a pseudo first order
rate. The initial concentration of the ozone was 0.27 ppm and the R
function was essentially constant displaying only a slight increase over
the period of the experiment. The first order rate constant for run 88
-2 -1 -1
based on ozone was 1.34 x 10 ppm min
B. Product Analysis
An inventory of the products formed in the gas phase reactions of
propylene with ozone, propylene-ozone-sulfur dioxide, ethylene with
ozone and ethylene-ozone-sulfur dioxide was conducted by studying the
infrared absorption spectrum of the gaseous components in the reactor at
a time when approximately 90% of the ozone had been reacted (80% for
the ethylene runs). The volume of the glass sample cell was about 60
liters and long infrared absorption path lengths were achieved by
'folding1 the beam with mirrors placed near the ends of the cell. The
operation of the Fourier Transform Infrared Spectrometer is described in
Chapter IV-B,6. Before each experimental run, a reference or background
-------
95
spectrum of the properly humidified diluent gas was obtained and the
sample spectrum from the run was subsequently ratioed against this
background measurement. The ratio recording technique eliminates many
of the interferences which may otherwise obscure the regions of interest
and increases the detectability limits for the system.
Ratio recordings for three spectral regions, 700-1200 cm" , 2000-2300
cm and 2600-3000 cm , are shown in Figure 5-8 for runs 21 and 31. The
infrared absorption path length for both of these measurements was 160 m
through air at one atmosphere which contained the products of the
propylene-ozone and the propylene-ozone-sulfur dioxide runs respectively.
Spectral regions which include strong water and carbon dioxide absorption
bands were excluded from these measurements because of the significant
interference which they cause on quantitative product analysis. The con-
centrations of the identified product compounds calculated from the
spectrum which appears at the top of Figure 5-8 are 0.94 ppm carbon-
monoxide, 3.44 ppm formaldehyde, 1.59 ppm acetyaldehyde and a trace
amount of formic acid. The regions of primary propylene, formaldehyde
and acetyaldehyde absorption are marked with a range bar and the prominent
absorption peak(s) used in the calculation are identified. The lower
spectrum in Figure 5-8 is for the experiment (run 21) conducted without
any sulfur dioxide. The product concentrations calculated from this
spectrum are 0.93 ppm for carbon monoxide, 3.21 ppm for formaldehyde,
1.49 ppm for acetyaldehyde, 0.2 ppm for ketene and again a trace of
formic acid was observed.
A ratio plot with scale expansion of the region from 2000-2300 cm
for the two experimental runs is shown in Figure 5-9. The scale expansion
technique tends to make the absorption lines more obvious without increas-
ing the background noise. The upper spectrum shows the carbon monoxide
-------
2200 2300 2600
2700
2VD 9000
FIGURE 5-8. INFRARED ABSORPTION SPECTRA OF REACTOR CONTENTS.
-------
97
RATIO WITH rj
SCALE EXPANSION'*
'I- I
KETENE
JRUN 21
-C3H6 + 03
RAT 10 WITH
SCALE EXPANSION;
2000cm"1 2100 2200 2300
FIGURE 5-9. INFRARED SPECTRA IN REGION OF CARBON MONOXIDE ABSORPTION.
-------
98
continuum for the run conducted in the presence of sulfur dioxide while
the lower plot shows a ketene spectrum superimposed on the carbon monoxide
continuum for the run which did not include sulfur dioxide. The ketene
is identified by the double indentation on the carbon monoxide continuum
with the right lobe characteristically being slightly deeper and broader.
The appearance of ketene as a product of the propylene-ozone reaction
has been previously reported (Scott et al., 1957) and has been postulated
to result from the disassociation of the acetyl form of the zwitterion
species (Leighton 1961) as shown by reaction 5 in Chapter II-B. The
dramatic disappearance of the ketene spectrum in the presence of sulfur
dioxide indicates that the reaction rate of the oxidizing species with
the sulfur dioxide is much faster than is the rate of the decomposition
reaction.
Ratio plots, with scale expansion of the spectral region which
includes ketene, for two additional propylene-ozone experiments conducted
in air at one atmosphere are shown in Figure 5-10. The relative humidity
in the reactor was approximately 19% for run 78 and 33% for run 79. The
presence of ketene in both of these runs and at approximately the same
concentration is readily apparent. Nitrogen was used as the diluent gas
for the product spectra shown in Figure 5-11. Run 81 was conducted in an
atmosphere at 36% relative humidity while the relative humidity for run
82 was about 20%. The formation of ketene in those runs in an atmosphere
with a sharply depleted molecular oxygen content is also apparent. Ratio
plots of two more runs conducted in the presence of sulfur dioxide are
shown in Figure 5-12 for which the relative humidity was 20 and 36%
respectively. There is no ketene observable in these product absorption
spectra nor in that of run 31 previously discussed.
Ratio recordings of the three spectral regions, 700-1200 cm ,
-------
SCALE EXPANS [ON
RATIO WITH
SCALE EXPANSION
99
2000cm"1 2100 2200 2300
FIGURE 5-10. INFRARED SPECTRA IN REGION OF CARBON MONOXIDE ABSORPTION,
-------
100
RAT 10 WITH
SCALt EXPANSION
RATIO WITH
SCALE EXPANSION
2000cm'1 2100 2200 2300
FIGURE 5-11. INFRARED SPECTRA IN REGION OF CARBON MONOXIDE ABSORPTION
-------
101
I;: {RUN 60
RATIO WITH
SCALE EXPANSION i
RUN 65
C3H6 + 03 + S02
LOWRH
RATIO WITH
SCALE EXPANSION
2000cm
2100
2300
FIGURE 5-12. INFRARED SPECTRA IN REGION OF CARBON MONOXIDE ABSORPTION
-------
103
2000-2300 cm and 2600-3000 cm for two ethylene-ozone reactions are
shown in Figure 5-13. Sulfur dioxide was included as a reactant in run
29 recorded in the lower spectrum. The products observed from these
reactions are carbon monoxide, formyaldehyde, and in .the case of Run 28
(without sulfur dioxide), a trace of formic acid. For Run 29, a quanti-
fiable amount of formic acid was observed at approximately 1130 cm
The results of the product identification and measurement for all
of the experiments analyzed by the Fourier transform spectroscopic method
are listed in the Appendix. The concentration values tabulated are in
parts per million (ppm) and were calculated by applying the Lambert-Beer
equation to the absorption spectra as discussed in Chapter IV-B,6. A
more detailed product evaluation is contained in Table 5-3 for eight of
these runs. The run identification number, the relative humidity and
the product concentration expressed as ppm product per ppm of ozone
reacted are tabulated. The error term noted below each product species
is based on the confidence with which the absorption coefficients used
in the measurements are known and does not relate to the measurement
itself. The absorption coefficient for ketene was not measured due to
difficulties encountered in the quantitative isolation of pure ketene
for calibration purposes. The value used for this species is, therefore,
a best estimate (Gay, 1974) and the error term is believed to be realistic.
An evaluation of data in Table 5-3 shows that the production of
carbon monoxide is unaffected by the addition of sulfur dioxide to the
system. Analogous to the formation of ketene from the decomposition of
the acetyl form of the intermediate species, carbon monoxide and water
were speculated as forming from the decomposition of the formyl form
of that species. For this analogy to hold, a higher concentration of
carbon monoxide would be expected in the absence of sulfur dioxide. This
-------
CO
. RATIO PLOT
1000
2000
2100
2300 HOD
2100
MOO
FIGURE 5-13. INFRARED ABSORPTION SPECTRA OF REACTOR CONTENTS.
-------
Table 5-3
Product Analysis by Fourier Transform Infrared Spectroscopy
Propylene - Ozone Reaction
Run
60
(with S02)
65
(with S02)
31
(with S02)
21
(without SO2)
81
(without SO -in
82
(without SO -in
Ethylene - Ozone
29
(with S02)
RH CO* HCHO* CH CHO*
% (± 0.02) (± 0.03) (±0.1)
20 0.34 1.34 0.68
36 0.35 1.32 0.76
19 0.36 1.32 0.61
19 0.36 1.24 0.58
36 0.18 0.56 0.32
N2)
20 0.23 0.51 0.30
V
Reaction
20 0.38 1.42 0
CH CO* HCOOH*
(± 0.03) (± 0.07)
0 Trace
0 Trace
0 Trace
0 . 08 Trace
0.08 0
0.06 0
0 0.07
28
(without SO )
22
0.28
1.38
Trace
*ppm/ppm ozone consumed
o
en
-------
106
was not observed in these experiments as the production of carbon monoxide
appeared constant relative to the rate of ozone consumption. Both forms
of the intermediate species are operative in oxidizing the sulfur dioxide
as evidenced by the formation of light scattering aerosols in both the
ethylene and propylene systems (data follows in Section E). The formation
of the carbon monoxide observed may still be via that decomposition reac-
tion but direct evidence is lacking. Reaction 4, Chapter II-B indicates
that carbon monoxide and methyl alcohol could be formed by another decom-
position reaction. No methyl or other alcohol was observed in these
analyses and, therefore, reaction 4 is apparently not operational or
has a minor role in generating the carbon monoxide.
Formic acid was observed in each of the experiments conducted in the
oxygen enriched system and is postulated to result from a recombination
of the hydroxyl and the peroxyformyl radicals.
For the purpose of discussion, a mechanism is adopted which is
similar to the three step mechanism proposed by Cox and Penkett (1972)
in that the olefin-ozone reaction produces a reactive intermediate which
subsequently can decompose, rearrange, or react with other than the two
primary reactants and which is the oxidizing species for sulfur dioxide.
The new mechanism does not, however, exclude additional reactions parti-
cularly those which involve a secondary attack on the principal reactants.
Based on this mechanism, one should observe a higher production of
formaldehyde in the ozone-ethylene reaction conducted in the presence of
sulfur dioxide while in the absence of sulfur dioxide, production of formic
acid and carbon monoxide should be higher. These features were not
observed in the reactions with ethylene, and in fact the tendency,
although slight, was in the opposite direction.
An increase in both formaldehyde and acetyaldehyde production was
-------
107
also expected for reactions of propylene and ozone occurring in the
presence of sulfur dioxide. The data listed in Table 5-3 demonstrates
this feature in the case of formaldehyde but it is not well defined in
the case of acetyaldehyde. A number of calculations were made to sub-
stantiate the increase in aldehyde yield consistent with the sulfur
dioxide oxidative step in the mechanism producing the products sulfur
trioxide and stable aldehyde. The nine propylene runs listed in the
Appendix were used to determine the formation ratio of the two aldehyde
species. The observed mean of the ratio of formaldehyde to acetyaldehyde
with one standard deviation for the nine experiments was 1.85 ± 0.20.
This finding tends to confirm the increase in the acetyaldehyde product-
tion concurrent with that of the formaldehyde. The ratio of the formal-
dehyde concentration to that of carbon monoxide was also calculated for
the seven runs conducted in an oxygenated atmosphere. Pour of the runs
were conducted without any sulfur dioxide in the system and for these
the mean ratio was calculated as 3.17 ± 0.26. In the other three
experiments which included sulfur dioxide, the mean ratio was 3.80 ± 0.16.
A t-test shows these mean ratios to be significantly different at the 95%
level. As the carbon monoxide concentration apparently remains constant,
the difference in the mean ratio values is due to a change in the form-
aldehyde concentration. This result supports the finding of increased
formaldehyde, or more generally, aldehyde production in the propylene-
ozone thermal reaction when conducted in the presence of sulfur dioxide.
The competition for the reactive intermediate was affirmed by noting
that a gain in carbon for run 21 was 0.40 ppm accounted for in the species
ketene while the corresponding loss relative to run 31 was 0.43 ppm carbon
accounted for in the two aldehyde species. Although the initial reactant
concentrations were not precisely the same, it is also interesting to note
-------
108
that 0.20 ppm sulfur dioxide was consumed in run 31 while 0.17 ppm ketene
was formed in run 21. To determine whether this indication establishes
a real relationship between the two species would require further experi-
mentation.
A product analysis of the two propylene-ozone experiments conducted
in a reduced oxygen atmosphere and listed in the table in the Appendix
indicates that no formic acid was formed. This finding refutes the mecha-
nistic step shown as reaction 7 in Chapter II-B, in which the acid results
from the decomposition of the formyl form of the intermediate species.
An oxygen enriched atmosphere is required for the production of the formic
acid as it is for the formation of the hydroxyl radical. The other
species which was formed with the hydroxyl radical from one of the pro-
posed interactions of the reactive intermediate with molecular oxygen is
the peroxyformyl radical. It is speculated that a recombination of these
two radical species could result in the formation of the formic acid
according to
Hc'dO- + -OH -*- O + HCOOH (28)
The species shown, however, is also known to be very unstable and rapidly
decomposes as
p
HCOO- » CO + 'HO (22)
A decomposition reaction of this form can also account for the essentially
constant production per ppm of ozone consumed of carbon monoxide in the
oxygen enriched system. The occurrence of such a reaction in this system
is reinforced by the observation that the carbon monoxide was lower in
the oxygen deprived atmosphere.
One further observation noted from these two experiments which made
use of nitrogen as the diluent gas is the marked reduction in the produc-
-------
109
tion of both aldehyde species compared to the runs conducted in air. The
production of formaldehyde for these two runs averaged about 0.54 ppm/ppm
of ozone reacted and for the acetyaldehyde was 0.31 ppm/ppm of ozone
consumed. This result can be accounted for by another reaction of the
intermediate species with oxygen resulting in the formation of ozone and
aldehyde, reaction 13, Chapter II-B, for example. It is also significant
to note that this reaction would contribute a major fraction of the
aldehyde formed.
Ammonia was not observed as a product or a contaminant in these
experimental runs.
Scott et al. (1957) also observed formaldehyde, acetyaldehyde, carbon
monoxide and ketene in the reaction of propylene with ozone. In addition,
they reported values for carbon dioxide and water and an upper limit for
acid production. The initial concentration for each of the two reactants
used in their experiments was 32 ppm. The results described herein are in
good qualitative agreement with their findings. Vrbaski and Cvetanovic
(1960) also conducted an extensive product analysis of the propylene-
ozone reaction although at considerably higher reactant concentrations.
Carbon monoxide and formaldehyde were not included in their analyses
performed by gas-liquid chromatography. Products reported were acetyalde-
hyde, propionaldehyde, acetone, methyl alcohol, carbon dioxide and formic
acid. The yield reported for formic acid (0.34 ppm/ppm of ozone consumed)
was considerably higher than observed in this study or in the study of
Scott et al. (1957). The values reported for propionaldehyde and acetone
were very low being 0.003 and 0.008 ppm/ppm of ozone consumed respectively
while that for the alcohol was 0.033 ppm/ppm ozone reacted.
Although there is some variation in product formation among the
different investigations, there is general agreement relative to the
-------
110
formation of aldehydes as a major product of the olefin-ozone reactions.
These species result from the attack on and the rupture of the double
bond by ozone and the addition of an oxygen atom onto one of the fragments.
Through this mechanism and as observed in this study ethylene produces
formaldehyde and the propylene yields acetyaldehyde and formaldehyde.
There is also general agreement that carbon monoxide and carbon dioxide
are among the major products although carbon dioxide was not measured in
this study. Alterations in the product inventory and yield due to the
presence of the sulfur dioxide are not reported elsewhere.
It was not possible during these experiments to identify quantita-
tively all of the minor products formed during the reactions. Some of
the products were below the detection limits of the instrumentation while
the characteristic absorption spectra of others appears in the region of
major products and were completely masked. Carbon dioxide was not quanti-
tated as there existed a short free air path in the experimental arrange-
ment between the cell and the detector. Despite these limitations, it
was still of interest to calculate a material balance on carbon, i.e., to
calculate the ratio of the concentration of carbon atoms found in the
identified products to the concentration of carbon atoms in the reacted
olefin. This ratio was 62.5% for run 31 which included sulfur dioxide
and 66.6% for run 21 which included only the propylene and ozone. The
ethylene reactions yielded a carbon balance of 56.3% for run 29 with
sulfur dioxide and 54.7% for run 28 which did not contain the sulfur
species. Assurance that this difference was not due to equipment failure
was obtained by comparing the results of the olefin and acetyaldehyde
measurements made by the Fourier transform infrared spectrometer and the
gas chromatograph. The four measurements of propylene and acetyaldehyde
-------
Ill
agreed to approximately ten percent and the two measurements of ethylene
agreed to within three percent.
C. Tentative Reaction Mechanism
To summarize the evidence presented in the previous sections, the
following scheme provides the salient features of a mechanism for the
propylene-ozone-sulfur dioxide system which is consistent with the data
observed in these experiments. The initial steps of the tentative mecha-
nism are those which directly influence the concentration of either the
sulfur dioxide or the species responsible for its oxidative consumption.
The final steps in the mechanism are presented to account for other pro-
ducts observed in the various experiments conducted.
One scheme which is generally accepted for the ozonalysis reaction
is the Criegee mechanism in which the reactive intermediates are the
zwitterions. The structure and reactivity of these species are considered
in popular practice to be biradical in character (Calvert, 1973). It is
proposed that these reactive intermediates are responsible for the oxida-
tion of the sulfur dioxide in the system. The products of the initial
reaction are stable aldehydes and the active biradical species according
to the equations
03 + CH3-CH=CH2 -> HCHO + CUCKOO- (1)
* CH CHO + HCHOO- (la)
The intermediate can only interact with the olefin, molecular oxygen and
the sulfur dioxide. The finding that the stoichiometry of the reaction
is affected by the presence of oxygen indicates that the intermediates
are not directly involved in a secondary attack on the olefin. Inter-
actions of the intermediate with molecular oxygen occur as follows:
-------
112
0
RCHOO' + 0 -* -OH + RCOO- (11)
RCHOO- + 0 * 0 + RCHO (13)
A secondary attack on the olefin by species other than ozone generated
in the system has been demonstrated and through the calculated addition
of a prescribed amount of carbon monoxide, the agent responsible for the
secondary attack was tentatively identified as the hydroxyl radical. A
reduction in the aldehyde yield observed in experiments conducted in a
reduced oxygen atmosphere indicates that reaction 13 is also active in
the system. This ozone production is apparently offset by the increasing
participation of ozone in reactions involving unidentified products of the
primary reaction.
An apparent decomposition reaction of the acetyl form of the biradical
intermediate was noted in the propylene-ozone interactions and resulted
in the production of ketene according to the reaction
CH CHOO- -» CH =C=0 + HO . (5)
The rate of this reaction must be slow since the ketene was not observed
in systems which included sulfur dioxide as a reactant. This result
along with a materials balance analysis enforced the identification of
the intermediate as the species which oxidized the sulfur dioxide parti-
cularly as none of the other species under consideration form ketene.
The hydroxyl radical was involved in a secondary attack on the olefin
species. The rate constant for these reactions is approximately one
hundred times greater than is the rate constant for the hydroxyl radical-
sulfur dioxide reaction thus eliminating that species from consideration
as the oxidizing agent. The propylene-hydroxyl radical reaction is itself
chain propagating:
-------
113
*OH + CH -CH=CH -* CH CH-CH OH . (14)
J * J &
The final step in the proposed mechanism is the oxidative consumption of
the sulfur dioxide by.the reactive biradical species:
RCHOO- + SO -» SO + RCHO . (29)
Other potentially oxidizing species for the sulfur dioxide have been
eliminated in the preceding sections.
The mechanistic steps which follow next are advanced to account for
other products observed by the infrared spectroscopic analysis.
An oxygen effect was observed in the production of formic acid thereby
eliminating the decomposition of the formyl form of the intermediate as
being responsible for its formation. It is speculated, however, that a
reaction between the hydroxyl and the peroxyformyl radicals will produce
the acid observed:
0
OH + HCOO- -> 0 + HCOOH . (28)
The formation of carbon monoxide from another decomposition of the
formyl form of the biradical species in analogy with the formation of
ketene from the decomposition of the acetyl form was not observed. There
was an oxygen effect noted in the formation of the carbon monoxide and in
contrast to the ketene, the presence of sulfur dioxide did not affect
the observed concentration. The peroxyformyl radical requires an enriched
oxygen atmosphere for its formation in this mechanism (reaction 13), is
known to be highly unstable and on decomposition can account for the
carbon monoxide as follows:
O
HCOO- -> CO + HO . (22)
-------
114
The hydroxyl radical formed in the oxygen enriched system reacts
with the aldehyde species with about the same rate constant as with the
olefin. This reaction leads to the formation of formyl and acetyl radicals
which in the presence of oxygen become an additional source of peroxy-
formyl and peroxyacetyl radicals:
0
OH + RCHO -» HO + RC- (16)
9. ?
RC- + °2 * RC'°°* <3°)
The notable difference between the foregoing mechanism and the three-
step mechanism employed by Cox and Penkett (1972) is the relatively large
involvement of secondary reactions shown above. The deviation from 1:1
stoichiometry results from a secondary consumption of the olefin and
secondary reactions between ozone and other products of the olefin-ozone-
sulfur dioxide system. The observed oxygen effect in these studies which
affected the stoichiometry and the yield of the various products indicates
that in an oxygen deprived system, the consumption of ozone by product
species becomes more significant relative to the olefin consumption. In
an oxygen enriched system, however, additional ozone is regenerated as
are the radical species.
D. Sulfate Analysis and Sulfur Mass Balance
Several samples, collected on Millipore Corporation Fluoropore
filters, were studied in an attempt to perform a sulfur balance on the
propylene-ozone-sulfur dioxide reaction and also to confirm the conver-
sion of the sulfur dioxide to a sulfate aerosol. The filters were 37 mm
in diameter and had a mean pore size of 0.2 ym. X-ray fluorescence spectro-
scopy, for a total sulfur measurement, and liquid chromatography, for
measurement of water soluble sulfates, were used to estimate the sulfuric
-------
115
acid mist loading on tha filter. Both techniques were employed as they
are still under development as methods for use on atuiospheric samples of
mixed components. Also, a test for consistency was desired particularly
on this aerosol which is expected to contain only SO (HO) .
J b ii
A summary of the analytical results from both methods is shown in
Table 5-4. The total volume sampled, the calculated WEISS concentration
of the sulfuric acid aerosol in \ig/mJ. the equivalent concentration of
sulfur dioxide in ppm and the measured amount of sulfur dioxide consumed
are tabulated. Using the liquid chromatographic results as a basis the
sulfur balance for the five samples analyzed by that method indicate
that recoveries of from 77 to 100 percent were achieved. The two
samples for which the recovery was essentially 100S ware collected near
the end of the first hour of the experiments while tb.& other three samples
were collected approximately one half hour later into the run. The
fraction of the sulfur unaccounted for by the filter analysis is believed
to have been lost to the system by diffusion to and obsorbance on the
reactor walls. The extensive sampling requirements for runs 16, 24 and
32 coupled with the late period in the run for the filter sampling, i.e.,
after the ozone had been depleted by 90%, left the bag nearly empty and
the surface to volume ratio increased accordingly thereby enhancing the
potential for diffusive losses.
As no ammonia was observed in the samples analyzed by the Fourier
transform infrared spectrometer it was assumed that the total sulfate
aerosol loading on the filters was due to sulfuric acid. It also follows
from the high sulfur recoveries observed from the X-ray fluoreraence spectro-
scopic and liquid chromatographic analyses that the dominant if not the
only conversion for the sulfur dioxide is via an oxiclative process result-
ing in the formation of the acid aerosol.
-------
Table 5-4
Summary of Sulfuric Acid Analysis by X-ray Fluoresence
Spectroscopy and Liquid Chromatography
Sample
16
24
32
60
65
Sample
16
24
32
60
65
... 2
ng (s)/cm
1348
596
1071
4149
3417
Vig(S)/ml
1.97
3.85
3.32
2.50
ug(s)
10.84
4.79
8.61
33.37
27.48
vg(so^)
29.3
9.85
19.3
99.6
75.0
X-ray Analysis
3
1147
853
1237
1289
1061
Liquid Chromatography
H2S04,M/*3,
1033
585
922
1282
966
SO (ppm)
.187
.139
.202
.210
.173
SO2 (ppm)
.168
.095
.150
.209
.57
Measured
ASO2 (ppm)
.202
.124
.187
.205
.158
% Recovery
83
77
80
100
99
-------
117
The results of the liquid chromatographic analysis were used as a
basis as the system was calibrated with sulfuric acid during the same
time period in which the samples were analyzed. Calibration samples were
prepared by adding .1 N sulfuric acid aqueous stock solution to isopropy1
alchohol in the prescribed volumetric ratio and taking aliquots to yield
standards in the range of 0.5-5 yg (SO.)/ml (a span that encompassed the
samples collected). The plot of peal; height for these standards vs con-
centration was non-linear in these low concentrations as was expected
from solubilities and kinetics considerations (Tejada, 1974) .
Analysis of samples by X-ray fluorescence spectroscopy for elements
lighter than potassium (A=39) is hindered by the self-absorption (of the
low energy characteristic X-rays) within the filter mutrix or by the
aerosol loading (Dzubay & Stevens, 1974). The correction for self-absorp-
tion for particles < 2 ym, however, is small and the data to follow
demonstrates that aerosol generated in the gas phase reaction of propylene-
ozone sulfur dioxide consisted largely of sub-microscopic droplets. A
ratio plot of the results of the total mass of sulfuric acid collected
on the filter as estimated by the X-ray fluorescence and the liquid
chromatographic technique is shown as Figure 5-14. The unit ratio is
based on the acceptance of the results of the wet chemical analysis as
a reference. Also, shown on this figure is the mass of the acid measured
by the two methods.
Although the data are limited an initial evaluation of these results
led to a postulate explaining the high results obtained by the X-ray
fluorescence technique for low total mass loadings, X-ray fluorescence
spectroscopic analysis under ideal conditions examines an area about 25 mm
in diameter on the filter. The ratio of the examined to the total filter
area of the 37 mm diameter filters used was about 0.45, and the sample
-------
118
SAMPLE
24
32
60
65
X-RAY
FLUORESCENCE
14.68
26.37
102.18
84.16
LIQUID
CHROMATOGRAPHY
10.06
19,65
101.68
76.56
RATIO
1.46
1.34
1.00
1.10
>
Q_
"* i
cr 2
O
c
-------
119
was assumed to be uniformly deposited over the total surface. Precautions
were taken to facilitate the collection of a uniformly distributed sample
on the filter by adding an extra spacer ring to the in-line filter holder
to allow the captive aerosol more time to disperse laterally prior to
entrapment. The data suggest, however, that the aerosol was preferentially
loaded on the central portion of the filter first. For heavier loadings,
the deposition became more uniformly distributed as the increasing pres-
sure drop at the center made collection on the outer portion more favor-
able. The data further suggest that for a total mass loading of >100 yg
of sulfuric acid and with the sampling arrangement and flow rate employed
the results were comparable. This postulate was later substantiated by
2
separately analyzing the central 1.98 cm and the balance of filter sample
number 16 by the liquid chromatographic technique. The mass loading per
unit area was found to be 1.7 times higher over the. central portion of the
filter than over the outer ring.
E. Light Scattering Measurements.
An integrating nephelometer was used to measure the light scattering
coefficient of the aerosol formed in the gas to particle conversion.
Scatter from particulate material over an angle from about 8.5 to 168.8°
was measured by this device.
According to this instrument, no light scattering aerosol was formed
in reactions which did not include sulfur dioxide.' In addition, no light
scattering aerosol was observed over the lifetime 'of the experiment, in
the reaction of ozone with sulfur dioxide.
The meteorological range or local visual distance was estimated from
the measurement of the scattering coefficient according to equation IV-4
adjusted for the wavelength used by the eye in sunlight. These data are
-------
120
reported for two representative experiments in Figures 5-15 and 5-16.
Included in these figures is a plot of sulfur dioxide consumption with
time and a plot of the variation in the total surface area with time as
measured with the Electrical Aerosol Size Analyzer. The final stage of
the latter curve is affected by the rapid growth of the acid aerosol out
of the measurement range of this instrument. The important feature for
the discussion and comparison to follow is related, however, to the
initial rate of growth to the achievement of some apparent stable total
surface area.
Figure 5-15 contains plots of these data for a propylene-ozone-sulfur
dioxide reaction. The initial rate of sulfur dioxide consumption is the
highest for the run and is responsible for the rapid establishment of a
large total surface area due almost exclusively to a nucleation process.
Although the total surface area is large, the newly formed embryos are
too small at early times to scatter light efficiently. As the experiment
progressed, however, the aerosol particles grew by nucleation, condensa-
tion and coagulation becoming increasingly more efficient in scattering
light. The mean surface area diameter for this run was estimated at 15,
30 and 60 minutes as 0.22, 0.26 and 0.30 urn respectively. These mean
surface area diameter estimates are affected by the growth of the aerosol
out of the range of the analyzer and are, as a result, slightly smaller
than would be expected. Concurrent with the increase in the scattering
coefficient is a decrease in the visual distance which, at eight minutes
into the run, was almost 16 kilometers (km) and which diminished to about
2 km within forty-five minutes.
Figure 5-16 contains plots for the ethylene-ozone-sulfur dioxide
system which are similar to those shown in Figure 5-15. The ethylene-
ozone reaction has been shown previously to be slower than the propylene-
-------
121
10
20
30
40
f (min)
FIGURE 5-15. VARIATION OF THE SCATTERING COEFFICIENT, VISUAL
RANGE, SURFACE AREA CONCENTRATION AND SULFUR
DIOXIDE CONCENTRATION WITH Till/IE FOR A PROPYLENE-
OZONE-SULFUR DIOXIDE EXPERIMENT.
-------
122
co
o
t (min)
FIGURE 5-16. VARIATION OF THE SCATTERING COEFFICIENT, VISUAL
RANGE, SURFACE AREA CONCENTRATION AND SULFUR
DIOXIDE CONCENTRATION WITH TIME FOR AN ETHYLENE-
OZONE-SULFUR DIOXIDE EXPERIMENT.
-------
123
ozone reaction and the sulfur dioxide consumption is likewise slower. The
rate of establishment of surface area is reduced compared to the propylene
system and the stable total surface area level is also lower. The scatter-
ing coefficient measurement shows that the rise of this function is appre-
ciably slower than in the propylene system although the mean surface
diameter of the particles is essentially identical for the two systems at
the times measured. The estimated diametar at 15, 30, and 60 minutes was
0.22, 0.25 and 0.31 urn respectively. This result indicates that although
the nucleation process is more limited, the growth of the acid aerosol
in the two systems follows the same pattern. The degradation of the
visual distance with time liJcewise displays the relative slowness of the
ethylene system. Visibility, which v/as reduced to about 16 km at eight
minutes in the propylene system was essentially unlimited and at the end.
of forty-five minutes was greater than 6 km compared to 2 kin in the pro-
pylene system.
F. Aerosol Development
The propylene-ozone reaction was monitored to determine if a nuclea-
tion process was active in this system and to follow the growth of any
aerosol formed. A condensation nuclei counter was used to measure the
total number concentration as a function of tims while the electrical
mobility analyzer was used to obtain an estimate of the total surface
area and volume concentrations. These data, for a typical olefin-ozone
reaction, are shown in Figure 5-17. An induction period lasting almost
five minutes occurred prior to the initiation of the nucleation process.
Once started, however, the nucleation proceeded rapidly reaching a peak
concentration of approximately 95,000/cm at fifteen minutes into the run.
Although the nucleation process continued, the peak and subsequent decay
-------
124
100
80
60
CSI
co
40
o
CO
20
I
RUN 91
10
20
30
40
50
60
70
t (min)
FIGURE 5-17. AEROSOL PARTICLE NUMBER, SURFACE AREA AND VOLUME
DEVELOPMENT FOR A PROPYLENE-OZONE EXPERIMENT.
-------
125
of the number concentration indicated that a transient equilibrium was
attained between the two processes and which was followed by a period of
increasing domination by the coagulation process. The curves drawn
through these concentration data and those to follow were fitted by eye.
The total volume concentration was observed to increase linearly for
almost thirty minutes and then remain essentially constant for the dura-
tion of the experiment. The conservation of the total volume is consistent
with a system under the control of pure Brownian coagulation with no new
material being added to the aerosol volume.
The total surface area concentration initially increased rapidly due
to the large surface to volume ratio of the newly formed embryos. Conden-
sable material was limited in this system and at an early stage of the
aerosol's development, the coagulation process dominated causing the
total surface area concentration to diminish.
There was no significant aerosol growth observed in the propylene-
ozone system and the count mean diameter of the aorosol at sixty minutes
was estimated by the electrical mobility analyzer as 0.018 ym. There
were no particles > 0.042 pm observed nor was any light scattering aerosol
registered on the integrating nephelometer.
Figures 5-18 through 5-23 show the total volume, surface area and
number concentrations for a series of six aerosol experiments which in-
cluded sulfur dioxide as a reactant. The growth of the aerosol formed
in these reactions was limited by design to remain essentially within the
range of the electrical mobility analyzer. Wall losses evident at higher
reactant concentrations were eliminated as were inaccuracies associated
with coupling of size distribution data from different measurement devices.
The initial reactant concentrations were also varied for these experiments
to obtain a range of sulfur dioxide consumption values. Ona other variable
-------
126
500
CO ICO
E E
400
300
200
E
o
CO
100
10 20 30 40 50 60
t (min)
RUN 101 A
70
11
CM
10
CO
CO
X
CO
7
6
5
4
CO
o
3 o
tI
X
Ha
2
1
80
FIGURE 5-18. TOTAL VOLUME, NUMBER, RECIPROCAL OF NUMBER AND
SURFACE AREA CONCENTRATION VERSUS TIME FOR THE
DEVELOPING SULFURIC ACID AEROSOL.
-------
127
FIGURE 5-19. TOTAL VOLUME, NUMBER, RECIPROCAL OF NUMBER AND
SURFACE AREA CONCENTRATION VERSUS TIME FOR THE
DEVELOPING SULFURIC ACID AEROSOL.
-------
128
FIGURE 5-20. TOTAL VOLUME, NUMBER, RECIPROCAL OF NUMBER AND
SURFACE AREA CONCENTRATION VERSUS TIME FOR THE
DEVELOPING SULFURIC ACID AEROSOL.
-------
129
FIGURE 5-21. TOTAL VOLUME, NUMBER, RECIPROCAL OF NUMBER AND
SURFACE AREA CONCENTRATION VERSUS TIME FOR
THE DEVELOPING SULFURIC ACID AEROSOL.
-------
130
10 20 30 40 50 60 70 80 90
t (min)
FIGURE 5-22. TOTAL VOLUME, NUMBER, RECIPROCAL OF NUMBER AND
SURFACE AREA CONCENTRATION VERSUS TIME FOR THE
DEVELOPING SULFURIC ACID AEROSOL.
-------
131
10
20 30
40 50 60
t (min)
70
80
FIGURE 5-23. TOTAL VOLUME, NUMBER, RECIPROCAL OF NUMBER AND
SURFACE AREA CONCENTRATION VERSUS TIME FOR
THE DEVELOPING SULFURIC ACID AEROSOL.
-------
132
is displayed on these plots, that being the reciprocal of the number con-
centration which is related to the coagulation constant by equation 111-14.
The general patterns in the formation and growth of the aerosol observed
in this series of runs appeared similar for each run over the range of
experimental conditions employed.
The process by which the acid aerosol was formed and developed in
i
this system is postulated to include the three mechanisms of nucleation,
condensation and coagulation. Initially, for a brief instant, the vapor
phase mixture was free of all nuclei. Homogeneous nucleation then occurred
spontaneously due to the diffusional or effusional aggregation of mole-
cules in the supersaturated system. Supersaturation in this system is
postulated to have been primarily achieved as a result of the gas phase
reaction leading to the production of species of sufficiently low
volatility which allowed the critical saturation to be exceeded. The
surface free energy was critical to the stability of these newly formed
embryos because of their small size.
The solution droplets formed persisted and grew by condensation
because the supersaturation exceeded that required by equation III-8. The
size of the nuclei apparently exceeded the critical diameter required by
the Kelvin equation (III-4) and the supersaturation was maintained result-
ing in the continued growth of the droplets with a decrease in the free
energy. Eventually the supersaturation diminished due to a depletion of
the reactants in the gas phase and the subsequent reduction in the pro-
duction of acid vapor. The vapor was extracted faster than it was being
produced and a practical limit was reached.
The coagulation process in this system immediately followed the
commencement of the nucleation phase because of the rapid buildup in the
number concentration and the Brownian collisions which followed. The
-------
133
rate of coagulation eventually became equal to the nucleation rate and
the maximum number of nuclei was observed. The nucleation rate was
finally surpassed and eventually the decay typical to a pure coagulation
process was noted.
The number concentration was observed to be decaying at the start of
the experiments indicating that the build up of the aerosol by nucleation
was very rapid and was near completion at the recorded zero time or was
at least dominated completely by the coagulation process. Ozone was
added to the reactor late in the charging period of five minutes and was
not added in the final thirty seconds for any of these aerosol runs. In
an attempt to monitor the nucleation process, the condensation nuclei
count was recorded through the reactor charging period for runs 104 and
105. In these two cases the ozone was added to the reactor, already
partially charged with sulfur dioxide, propylene and air, for thirty
seconds commencing at 3.75 minutes into the filling period. Prior to
the addition of the ozone, the observed nuclei count was approximately
400/cm . The initiation of the homogeneous nucleation process was
essentially instantaneous with the maximum concentration of 940,000/cm
attained approximately thirty seconds before the recorded zero time. Here
also, the maximum concentration of nuclei corresponded to a transient
equilibrium condition during which the rate of addition of particles to
the system by nucleation was equal to the loss by coagulation.
The relationship between the number concentration data and the coagu-
lation constant predicts that the reciprocal of the number concentration
should increase linearly with time for a system in which coagulation is
the only removal process. The slope of the line formed as a result of
this relationship is numerically equal to the average coagulation constant
of the polydisperse aerosol system. The plots of the reciprocal number
-------
134
concentration in Figures 5-18 through 5-23 show that after some initial
period, a linear relationship was established. Wall or sedimentation
losses would have been demonstrated by an increasing slope of this curve
commencing at the time of occurrence. It was expected that should this
phenomena occur, as it did in some of the higher concentration experiments,
it would happen late in the run when the surface to volume ratio of the
reactor has increased significantly.
The higher value of the coagulation constant noted for the first
several minutes of the runs can be accounted for by the relatively large
difference between the diameter of the newly formed embryos and the mean
diameter of the growing aerosol. According to the theory of coagulation,
for particles of unequal sizes, the coagulation constant increases rapidly
with an increasing diameter ratio (Table III-l and equation 111-13).
The total surface area concentration for the six runs was observed
to rise rapidly commencing prior to the recorded zero time. The large
number of nuclei formed as a result of the gas to particle conversion
coupled with the large surface to volume ratio for the small particles
was responsible for this initial increase in surface area. As the
aerosol growth continued, condensation tended to increase while coagula-
tion reduced the total surface area observed until an apparent equilibrium
condition between these processes was established. . The surface area
function remained essentially constant until the condensable material in
the system diminished and the growth process was dominated by coagulation.
The increase in the total volume concentration proceeded at an
appreciably slower rate than did the surface area concentration, again
because of the small volume and relatively large surface area of the
nuclei. The initial rise in the total volume was due to nucleation and at
some later time, when sufficient surface area had been established, to
-------
135
condensation. When the condensation process ceased due to the depletion
of the vapor phase the total volume concentration was conserved as there
were no system losses such as to the reactor walls. The slight decline
noted in the total volume concentration curve for run 104 was due to the
growth of the aerosol, or more specifically to some of the aerosol particles
exceeding the range of the electrical mobility analyzer. Losses to the
walls were contraindicated as the reciprocal number concentration curve
was linear through this period consistent with a pure coagulation process.
At any time in the developmental history of the aerosol produced in
the thermal reaction of propylene, ozone and sulfur dioxide, the relative
contribution of each of the three processes varys. The expression for
the rate of generation of particles in a particular class of the size
distribution per unit volume for the simultaneous occurrence of nuclea-
tion, condensation and coagulation takes the form (according to Hidy and
Brock, 1970 and Brock 1974):
' = h I b(v ,v') n(v )n(v') dv1 - n(v,t) / bn(v')dv'
3t b C C b
V
coagulation
V-4
condensation nucleation
where n = concentration of species in number per unit volume
b - collision parameter for Brownian motion in the free molecule
regime
v = volume of particular class of molecular aggregate
Y = rate of condensation
YN = rate of generation of particles in the class by nucleation.
The rate of change in the mass concentration of the sulfuric acid (S) ,
which is coupled to the equation for the rate of generation, takes the
-------
136
functional form
9[H SO ] . » ~
3* = k3(J[l][S02] - | Y(v,s)n(v,t)dv - £ v?N(v,s)dv V-5
assuming that k [l][SO ] equals the rate of formation of the acid species
due to the thermal reaction. And, if a pseudo-steady state is proposed
for the acid concentration then
00 00
k3Q [I][S02] = I fndv + { v?Ndv V-6
Owing to the form of the nucleation term, nucleation will take place only
at high acid concentrations but condensation, once an aerosol phase has
been established, will occur at a much lower supersaturation.
Once an aerosol has been formed it is difficult to distinguish
between continued nucleation and condensation relative to their respective
contribution to the aerosol mass. Small nuclei attach to the established
aerosol surface in much the same manner and according to laws of the same
form as do the condensing molecules. For example, one variable measured
during this study was the change in the mean volume diameter with time.
The governing rate equation based on condensation is . ° = «'S , ,
' ' n dt molecules
while for the attachment of nuclei the expression is , ° = «"S , ..
dt nuclei
The equations are of the same form differing in the constants «' or «".
For a constant mass of acid in molecular form and a constant acid mass as
d Dpv
nuclei, c would also be constant as was observed in the initial period
of growth in these experiments. This could occur when the rate of produc-
tion of the acid is constant which, according to the initial linearity
of the volumetric conversion rate, was the case for this series of
experiments.
An empirical result of computer simulation studies performed by
-------
137
Brock (1974) indicates that for a system involving only the nucleation
and coagulation processes, the reciprocal number concentration curve is
markedly curved during the early stages of aerosol development in agreement
with observations made during the studies reported herein. In contrast,
the results of a simulation involving only the condensation and coagulation
processes indicate that the reciprocal number concentration increases
linearly with time. These empirically determined results can be used for
the six aerosol experiments to distinguish between the nucleation and con-
densation processes from the reciprocal number concentration curves. The
nucleation process appears to persist for a longer period in systems with
a lower sulfur dioxide consumption and a lower total surface area (run
103 for example) while for runs in which the loss of sulfur dioxide is
greater, the surface and volume increase more rapidly at the expense of
the supersaturation level. As the acid vapor drops below the critical
saturation in these high sulfur dioxide consumption runs (runs 104 and
105 for example) condensation commences earlier and at a lower super-
saturation state than required by nucleation.
The volumetric conversion rate, total volume at 80 minutes, volume
mean diameter growth rate, coagulation constant and the sulfur dioxide
consumption through the first 80 minutes, all calculated from the data
shown in Figures 5-18 through 5-23, are listed in Table 5-5.
The relative humidity was approximately the same during each of
these aerosol experiments. The volumetric conversion rate was calculated
for the period during which this function was constant, i.e., for at
least the first twenty minutes of the run. The values listed for the
volume and the sulfur dioxide consumption reflect measurements made when
the experiments were eighty minutes old and when the volume accumulation
was becoming stabilized. The coagulation constant was calculated from the
-------
Table 5-5.
Volumetric Conversion Rate, Total Volume at 80 minutes, Mean Volume
Diameter Growth Rate, Coagulation Constant and Sulfur Dioxide
Consumption at 80 minutes for Aerosol Experiments
d5
Run
101A
101B
102
103
104
105
RH (%)
19
19
18
20
20
18
dv . urn
cm hr
217
182
139
89
437
483
-^
iirn
cm
158
150
86
61
235
290
\M*k*
pv ,ym
~dtT (hr)
.391
.340
.295
.258
.655
.671
KxlO 9
1
1
1
1
1
1
/ 3 -1*
(cm sec )
.26
.44
.49
.61
.27
.28
ASO (p
11
10
8
4.
17.
21.
Pi
5
5
5
LJ
CO
-------
139
linear portion of the curve of the reciprocal of the number concentration
versus time. The rate of change in the mean volume diameter related to
the initial period of each run for which this function was apparently
constant.
The mean coagulation constant with one standard deviation calculated
from the reciprocal number concentration curves for these runs was 1.39 ±
-9 3
0.14 (x 10 cm /sec). The mean, count mean diameter calculated from the
data for the six runs which appears in the Appendix with one standard
deviation was 0.064 ± 0.014 ym. According to Fuchs (1964), the coagula-
tion constant for equal sized particles having diameters between 0.04 and
-9 -9 3 /
0.1 um would be in the range of 0.72 x 10 to 1.10 x 10 cm /sec (Table
IIT1). The agreement between the theoretically predicted and the meas-
ured values is very high particularly when the polydispersity is considered.
The count mean diameters of the distributions indicate that the
particles are larger than the molecules in the suspending gas. In this
system in which the Knudsen number is greater than 13.2, i.e., the free
molecule regime, the kinetic theory of gases may be applied to aerosol
coagulation. This implies that the particles are behaving like giant
molecules mixed in the gas in such a way that they merely constitute
just another component of the multicomponent gas phase system.
For these low level runs, the total amount of sulfur dioxide reacted
was small and the reaction rate was slow. The volumetric conversion rate
was essentially constant during at least the first twenty minutes of these
runs as evidenced by the total volume concentration curves on Figures 5-18
through 5-23. Based on the initial, near linear consumption of the sulfur
dioxide, an estimate of the consumption rate of that species during the
initial period where the volumetric conversion rate was constant could
be calculated. In the performance of this calculation it was assumed that
-------
140
the sulfur dioxide consumption was directly proportional to the formation
of the sulfur trioxide during this period, that the sulfuric acid to
water ratio in the particles was constant and that equilibrium existed
between the vapor and the condensed phase of the aqueous sulfuric acid.
Bray (1970) generated tabulations of the relative humidity and the water
vapor pressure over aqueous solutions of sulfuric acid as a function of
the temperature and density at the equilibrium condition. The tabulation
also included a correlation of the percent acid and the density of the
aqueous sulfuric acid solution as reported in the Chemical Engineers
Handbook (1963) .
The following expression relates the oxidation rate of the sulfur
dioxide with the volumetric conversion rate of the aqueous sulfuric acid
solution through the percent acid and the solution density data:
dfS02] dtVSO,(H,0) 1 MSO,
= iti_ fp £ V-7
dt
where f = the mole fraction of sulfuric acid in the aqueous solution
at the temperature and relative humidity of the system
p = density of the solution and
M = molecular weight of the species.
Using the average temperature of 27°C, average relative humidity of 19
percent for the six aerosol runs and data from Bray's tabulation (density =
1.477 g/cm ; percent acid = 58.43), the initial reaction rate of the sulfur
dioxide was calculated. Dividing this result by the initial sulfur dioxide
concentration yields the oxidation rate by the reactive species in this
dark reaction. The results of these computations are listed in Table 5-6.
The mean oxidation rate with one standard deviation calculated from
these data is 0.360 ± .096 percent/hour which is in good agreement with
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141
nun
101A
101B
102
103
104
105
dt IFF"1 HI
7.80 x 10"4
6.54
4.97
3.17
. 15.67
17.36
Table 5-6. Initial Sulfur Dioxide Reaction Rate and Oxidative Rate.
"X J "1) Oxidative
0.414
0.299
0.229
0.476
0.435
0.307
Table 5-7. Calculated Sulfur Dioxide Consumption based on the Observed
Volume Concentration.
ASO Calculated
Run ASO_ Calculated (ppm) 7 :
2 ee ASO Observed
2.0
2.1
1.5
1.8
I.-9
1.9
101A
101B
102
103
104
105
0.022
0.021
0.012
0.008
0.033
0.041
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142
the observations of Cox and Penkett (1971) who reported an oxidation
rate of 0.4 percent per hour for sulfur dioxide in their studies.
It was also of interest to determine whether the total volume con-
centration of aerosol measured at eight minutes into the run correlated
with the sulfur dioxide consumption using the density, percent acid, and
equilibrium conditions assumed in the previous calculations. The sulfur
dioxide concentration was calculated, which according to the assumptions
would be responsible for the volume observed. The calculated sulfur
dioxide concentration was then compared to the amount reacted. The
results of this analysis are reported in Table 5-7. The mean ratio of
the calculated to the observed sulfur dioxide consumption based on these
data is 1.9 ± 0.2 indicating that the volume concentration measured was
somewhat greater than can be accounted for by this type of computation.
There are a number of factors which could possibly account for this dif-
ference including an inaccuracy in the original assumptions of constant
acid to water ratio in the volume and equilibrium between the vapor and
the condensed phase of the aqueous sulfuric acid. It is believed, however,
that this error more probably stems from the lack of an absolute calibra-
tion on the aerosol measuring instrument.
The observed volume and the sulfur dioxide consumption data, both
at eighty minutes into the run, were plotted for the six aerosol experi-
ments (Figure 5-24). The line was fit through the origin by a least
squares regression analysis and a slope of approximately 13.5 was obtained.
These data demonstrate the linearity of the relationship existing between
these two parameters and as predicted by equation V-7.
The data displayed in Figures 5-18 through 5-23 show that the total
surface area concentration grows quite rapidly to some apparent equilibrium
level where it remains essentially constant for a significant period of
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143
300
200
CO
4^
ro
100
8 12 16
AS02(ppb)
20
24
FIGURE 5-24. TOTAL VOLUME VERSUS SULFUR DIOXIDE CONSUMPTION
ATT+80 MINUTES,
-------
144
time. The total volume concentration of the aerosol can be seen to be
increasing linearly to and in some cases beyond the time at which the
equilibrium surface area is established. This indicates that the equili-
brium condition is established as a result of the gain of surface area
due to condensation and nucleation being offset by the loss due .to
coagulation. The equilibrium condition is destroyed when the reactants
have largely been consumed, the degree of supersaturation diminished and
new surface area is not being formed. The coagulation process continues
and the total surface area is thereby reduced.
Clark (1972) noted, for his experiments dealing with the photooxida-
tion of sulfur dioxide, a strong correlation between the equilibrium sur-
face area and the volumetric conversion rate. A linear relationship was
demonstrated in a log-log plot of the two parameters. This correlation
was tested for the series of six aerosol experiments under discussion
the results of which are shown in Figure 5-25. The line shown is fit
to the six data points by the method of least squares regression analysis.
The equation which best fits these data is given as
dv
log S0 = 0.583 log (^-) + 0.239 (V-8)
E at
for which a correlation coefficient of 0.9933 was obtained.
Also plotted on this figure are the data from Clark's experiments
as well as some data from sulfur dioxide photooxidation studies conducted
by the University of Minnesota and by Calspan Corporation. Although it
is generally considered a tenuous operation to extend a regression line
beyond the limits of the data it was successfully done through more than
two log decrements with these data. It is immediately apparent that all
of the data plotted could be fit to a single regression line with a high
correlation coefficient. Of note in this observation is the fact that
-------
104
CO
o
103
10?
I I I I Mill
OMcNELIS EXPERIMENTS
D CLARK (1972)
A CALSPAN (KOCMOND ET AL, 1973)
UNIV. OF MINNESOTA LARGE BAG (KOCMOND ET AL., 1973)
UNIV. OF MINNESOTA SMALL BAG (KOCMOND ET AL., 1973)
LILIJI II II
0.1 0.2 0.3 0.4 0.6 0.8 1
2 34 6 8 10 20 30 40 60 80100 200 300500
dV , ,
(unr/cnH-hr)
at
tn
FIGURE 5-25. VARIATION OF THE EQUILIBRIUM SURFACE AREA WITH VOLUMETRIC CONVERSION RATE.
-------
146
the data plotted for which the volumetric conversion rate < 30 ym /cm -hr
are from experiments involving the photooxidation of sulfur dioxide while
those with the volumetric conversion rate > 80 ym /cm -hr are from a thermal
reaction involving olefin-ozone-sulfur dioxide. The tendency toward the
equilibrium surface area is controlled, therefore, by the physical processes
of nucleation, condensation and coagulation rather than the particular
chemical reaction leading to the gas to particle conversion.
The volumetric conversion rate measured for the initial period of the
aerosol growth is plotted in Figure 5-26 against the product of the initial
ozone and propylene concentrations for two different initial concentrations
of sulfur dioxide. Included in this plot are eight of the experiments
discussed earlier in this report for which both the reactant concentra-
tion data and the volumetric conversion rates were available and which
involved higher reactant concentrations. The data point closest to the
origin represents run 104 of the aerosol series. The curves shown are the
least squares regression lines fit to the data and forced through the
origin. The volumetric conversion rate for the higher concentration runs
AV
was estimated from over the first few minutes of the reactions only.
These data indicate that for a given sulfur dioxide concentration, the
aerosol formation follows second order kinetics with respect to the olefin
and ozone concentrations. These data also indicate a predictive capability
for the volumetric conversion rate which, for the low concentration runs,
was observed to remain constant for a prolonged period.
The volume distribution of the aerosol was followed in time for the
six runs. The distributions plotted at selected time intervals for these
runs are shown in Figures 5-27 through 5-32. Depending on the time at
which the distributions were measured they were influenced to a different
degree by one or more of the three processes: nucleation, condensation
-------
147
300
CO
200
CO
o.
100
0.204 ±0.010 ppm
123456
ffOLj [03])0 (ppm2)
FIGURE 5-26. INITIAL VOLUMETRIC CONVERSION RATE VERSUS PRODUCT OF
INITIAL PROPYLENE AND OZONE CONCENTRATIONS FOR
DIFFERENT INITIAL SULFUR DIOXIDE CONCENTRATIONS.
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148
300
200
00
o
100
0.013 0.024 0.042 0.075 0.133 0.237 0.422 0.750
Dp (yLtm)
FIGURE 5-27. DEVELOPMENT OF THE VOLUME DISTRIBUTION WITH TIME.
-------
149
0.013 0.024 0.042 0.075 0.133 0.237 0.422 0.750
Dp(/im)
FIGURE 5-28. DEVELOPMENT OF THE VOLUME DISTRIBUTION WITH TIME.
-------
150
Dp
FIGURE 5-29. DEVELOPMENT OF THE VOLUME DISTRIBUTION WITH TIME.
-------
200
a
oo
151
RUN 103
45MIN
MIN
T+ 5 WIN
0.013 0.024 0.042 0.075 0.133 0.237 0.422 0.750
Dp
FIGURE 5-30. DEVELOPMENT OF THE VOLUME DISTRIBUTION WITH TIME
00
o
100
0.013 0.024 0.042 0.075 0.133 0.237 0.422 0.750
Dp (/.tm)
FIGURE 5-31. DEVELOPMENT OF THE VOLUME DISTRIBUTION WITH TIME.
-------
152
0.013 0.024 0.042 0.075 0.133 0.237 0.422 0.750
FIGURE 5-32. DEVELOPMENT OF THE VOLUME DISTRIBUTION WITH TIME.
-------
153
dV
and coagulation. The frequency parameter used in these plots, ,
°9 P
presents the distribution in such a manner that the area under the curve
in a given size range is proportional to the volume in that range.
There are several notable features in these developmental volume
distributions which were similar for each of the experiments. Most
obvious is the shift in the distributions to larger mean diameters with
time. The rate of change appears, however, to decrease at later times
and the mean volume diameter appears to be approaching some limit. The
increase in the total volume i's also readily apparent, particularly in
runs in which the sulfur dioxide consumption was highest.
Although in the logrithimic display of these data, it appeared
that the distributions were becoming narrower, in fact the spread increased
over a larger range of particle diameters. The count distribution data
(included in the Appendix) also reflect the increasing polydispersity
with time. From theoretical considerations, the tendency for the size
distribution, due to droplet growth by diffusion of vapor, i.e., conden-
sation, is to become narrower. The increasing polydispersity in this
system, therefore, must have been due to the formation of.larger particles
by collisions and coalesence of smaller ones, also theoretically predicted.
The tail of the distribution curves for measurements made late in the runs
show that for the runs in which the amount of sulfur dioxide reacted was
high, there was some few particles which outgrew the range of the electrical
mobility analyzer.
The volume mean diameters of the growing aerosol were calculated for
each of the runs at several different times out to beyond eighty minutes
in most cases. These data are plotted in Figure 5-33 and show that the
rate of change in the volume mean diameter is apparently constant for
-------
154
I O
RUN 104
RUN 101B
FIGURE 5-33. VARIATION OF VOLUME MEAN DIAMETER WITH
TIME FOR SIX AEROSOL EXPERIMENTS.
-------
155
the initial period of at least twenty minutes. The slopes of the linear
portion of these curves are listed in Table 5-5 and range from 0.258 pm/hr
for run 103 to 0.671 ym/hr for run 105. The higher rates correspond to the
runs in which the largest amount of sulfur dioxide was reacted. The mean
volume diameters for each of the runs tended to reach some upper limit
of development which for the conditions of these experiments appeared to
be about 0.25 to 0.30 ym.
The curves plotted in Figure 5-33 also indicate two distinct growth
regimes which are more obvious on the curves having the higher initial
rate of change in the mean volume diameter. The knee of these curves
corresponds in time to the point at which the reciprocal number concentra-
tion curves became linear (Figures 5-18 through 5-23). The coagulation
process essentially commences in these systems concurrently with the
initiation of the gas phase reaction because of the very rapid increase
in the number concentration of nucleated droplets and continues through-
out the experimental period. The nucleation process, however, occurs
initially when the supersaturation exceeds some critical value and recedes
when either the supersaturation drops too low to support the process or
when sufficient surface area is formed and the condensation process com-
petes for the material in the vapor phase. It is suggested for these
curves, that the initial linear increase in the volume mean diameter is
due to a coupling of the nucleation and the coagulation processes while
the later and slower increase is due to condensation and coagulation.
The relative sharpness of the knee depends on the accumulative effect of
the speed with which the critical surface area in the system develops and
with which the acid in the vapor phase is depleted by condensation. The
net result of this additive effect is a sharp decline in.and termination
of the homogeneous nucleation process.
-------
156
The constant rate of change observed initially in the volume mean
diameter was found to be linearly related to the volumetric conversion rate
measured for each of the aerosol experiments through the logarithms of the
two functions. These data are plotted in Figure 5-34 and the line shown
is fit by the method of least squares regression analysis. The equation
which best fits this data is given by
dD
Io9 (~^) = 0.6102 log (^) - 1.8172
at at
for which a correlation coefficient of 0.9880 was obtained.
The results of these aerosol characterization studies could have an
immediate application in the generation of sulfuric acid mist of known
physical properties for controlled laboratory animal exposures. The data
displayed in Figure 5-26 indicate that the volumetric conversion rate of
condensable material from the vapor to the aerosol phase is predictable
from a knowledge of the initial reactant concentrations. And, for a
given initial concentration of sulfur dioxide, the aerosol formation
follows a second order rate law with respect to the two primary reactants,
propylene and ozone. The curve drawn in Figure 5-34 shows that the rate
of change in the mean volume diameter is also predictable based on the
volumetric conversion rate. Finally, the curves previously discussed and
displayed in Figure 5-33 show that some limit on the development of the
mean volume diameter occurs in practical systems and is likewise predict-
able. For the conditions of these experiments a limit of 0.25 to 0.30 urn
was imposed on the growth of the mean volume diameter.
Although it is believed that aerosols having other mean volume dia-
meters could be generated through this mechanism, the mean volume diameter
observed in these studies is of particular interest. Previous studies,
summarized by Lewis et al. (1972), made use of aerosols of 0.8, 2.5 and
-------
157
ft
1.0
0.9
0.8
0.7
0.6
0.5
.0.4
i
0.3
0.2
0.1
5x101
0.6102
102
5x102
103
dv
dt
FIGURE 5-34. RATE OF CHANGE IN MEAN VOLUME DIAMETER VERSUS
VOLUMETRIC CONVERSION RATE.
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158
7.0 vim mass median diameters (mmd) to measure the effect of sulfuric acid
mist on the pulmonary function of guinea pigs. Few particles of the
largest size penetrate beyond the nasal-pharangeal region where they can
cause an obstruction in the larger airways. The two smaller sizes can
penetrate the lower regions of the respiratory system and interact with
the smooth muscle lining around the terminal and other small bronchioles.
It is this smooth muscle which contracts to produce in humans the symptoms
of asthma, the physiological response most strongly associated with
suspended particulate sulfate (Environmental Protection Agency, 1974).
An acid aerosol with a mass mean diameter of the size generated during
the aerosol studies discussed in this dissertation (approximately 0.3 ym)
has not been used in exposure studies. It is suggested that these smaller
particles would penetrate the alveoli, the division of the pulmonary
region of the lung which has no smooth muscle and as a result, a different
physiological or histopathological response may be observed.
G. Aerosol Measurements by Single Particle Light Scattering.
The aerosol generated in the series of the experiments just discussed
was limited in growth by controlling the initial reactant concentrations.
That series led to the development of an internally consistent mechanism
to describe the relative contribution of the different processes leading
to the production and growth of the acid aerosol. The aerosol produced
in the higher reactant concentration experiments was also monitored with
an optical aerosol analyzer. The results of these measurements for typical
experimental runs are shown in Figures 5-35 and 5-36 for a propylene-ozone-
sulfur dioxide system and for a ethylene-ozone-sulfur dioxide system
respectively. The general trends displayed for the two different olefins
are similar with the production of the light scattering aerosol occurring
-------
159
RUN 31
03 - S02
20 40 60 80 100 120 140 160 180 200 220 240
CHANNEL
FIGURE 5-35. VARIATION OF AEROSOL SIZE DISTRIBUTION WITH TIME AS
MEASURED WITH OPTICAL PARTICLE SIZE ANALYZER,
-------
160
3000
RUN 29
C2H4 03 - S02
20 40 60 80 100 120 140 160 180 200 220 240
CHANNEL
FIGURE 5-36. VARIATION OF AEROSOL SIZE DISTRIBUTION WITH TIME AS
MEASURED WITH OPTICAL PARTICLE SIZE ANALYZER.
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161
earlier and at a faster rate in the propylene system. The fact that
ethylene produces a similar aerosol is itself of note supporting the basic
features of the gas phase mechanism postulated earlier. Principal features
of these aerosol size distributions are the first peak which occurs at
about 0.38 pm, the saddle at approximately 0.76 ym and the second peak at
channel 140 for which the diameter is 1.35 ym. Although the aerosol
outgrew the range of the electrical mobility analyzer, the measurement
by that instrument indicated a somewhat lower mean size for the first
peak. More important, however, is the existence of the second peak
which occurred in each of the higher concentration runs. It is speculated
that this secondary peak and the saddle point occur as a result of the
enhanced coagulation among particles of unequal sizes. This mechanism
would account for the peak becoming more pronounced at the expense of
the smaller particle sizes through the saddle point of the combined
distribution for these systems of higher reactant consumption. More
significant in the observation of the second peak is the fact that
although only a relative few droplets grow to this larger size they can
account for an appreciable fraction of the total aerosol mass.
-------
CHAPTER VI
CONCLUSIONS AND RECOMMENDATIONS
As a result of the measurements made during these experiments and
reported on in this dissertation, the mechanism leading to the oxidative
consumption of sulfur dioxide is better understood. In addition, the
mechanism leading to the production, growth and decay of a sulfuric acid
aerosol from the thermal gas phase reaction has been explained in terms
of the basic processes of nucleation, condensation and coagulation.
Finally, the coupling of the gas phase and the aerosol information pro-
vides a unique set of data with which to evaluate atmospheric and photo-
chemical smog chamber results. The principal conclusions reached as a
result of these studies follow in a summarized format.
1. The reactor vessel and sampling system designed and assembled
for these experiments were found to perform satisfactorily in the study
of selected dark phase reactions and in the measurement of specific gas
and condensed phase products. A reactor having a larger volume is sug-
gested for use in any additional studies of the type conducted to allow
for more nearly continuous sampling with all of the instrumentation.
2. Wall effects did not affect the results or the conclusions of
this study significantly. The losses of the individual reactants were
measured and found not to affect the stoichiometric results. The sulfur
mass balance and the aerosol reciprocal number concentration measurements
indicate that a measurable loss of sulfur to the walls occurred only at
the terminus of the runs when the surface to volume ratio of the reactor
became excessively large. The lower recovery of total carbon evaluated
-------
163
near the end of the runs was believed due to the carbon content of
unmeasured products.
3. The stoichiometry of the propylene-ozone reaction was found to
be a smooth function of the initial concentration ratio of these species.
The olefin/ozone consumption was > 1 for a system in which the olefin was
initially in excess and < 1 for a system having an initial ozone excess.
The consumption ratio was unaffected by the addition of sulfur dioxide
to the reactor or by varying the relative humidity over the range of 20
to 38 percent.
4. Molecular oxygen had a significant effect on the reaction stoichi-
ometry and product formation in the propylene-ozone thermal reaction. The
propylene/ozone consumption ratio was lower in a system in which the molec-
ular oxygen concentration was reduced. Oxygen also contributed to the
regeneration of ozone and the production of the hydroxyl radical species,
both of which interacted with the propylene and with products of the reac-
tion. Although the formation of the hydroxyl radical had been postulated,
these experiments provided the first direct evidence for its participation
and its role.
5. Acetyaldehyde, formaldehyde, carbon monoxide, ketene and formic
acid were observed products of the propylene-ozone reaction. The concen-
trations of acetyaldehyde, formaldehyde and carbon monoxide were affected
by the molecular oxygen concentration. Ketene was apparently unaffected
by the availability of oxygen while the production of formic acid depended
on its presence. Ketene was not observed in any of the reactions involving
sulfur dioxide as a reactant indicating that its rate of formation is
significantly slower than the rate of the bimolecular reaction between
sulfur dioxide and the intermediate species.
6. The mechanism which follows has been advanced in this dissertation
-------
164
for the oxidative consumption of sulfur dioxide in the propylene-ozone-
sulfur dioxide system and which is consistent both internally and with the
data observed in this study. Secondary reactions are a distinctive
feature of this model which incorporates relatively few reactions to
explain the major characteristics of the system studied. The rate con-
stant for the propylene ozonalysis step of the mechanism was estimated
to be 1.40 ± 0.39 (x 10 ppm min ). The steps of the proposed
mechanism are as follows:
0 + CH -CH=CH * HCHO + CH CHOO- (1)
«j
-------
165
patterns are consistent with a model which includes homogeneous nucleation,
condensation and coagulation. Nucleation commenced in the system which
included sulfur dioxide almost immediately upon initiation of the gas
phase reaction. Coagulation of the newly formed embryos and the growing
droplets commenced within seconds and persisted throughout the experi-
mental period. Condensation began with the establishment of a stable
aerosol phase and soon replaced nucleation as the primary gas to particle
conversion process.
9. An apparent equilibrium surface area was established for the
aerosol when the addition to the total surface area by condensation was
equal to the loss by coagulation. A strong correlation was found to exist
between this equilibrium surface area and the volumetric conversion rate.
It was also found that the correlation could be extended considerably in
range to include data from experiments conducted elsewhere in which the
aerosol was photochemically generated. The establishment of the equili-
brium surface area is due, therefore, to the physical processes rather
than the chemical mechanism leading to its formation.
10. The volume distributions were observed to shift to larger sized
droplets with time. An upper limit for droplet growth was noted and
was attributed to the depletion of the reactant concentrations, of the
concentration of the sulfuric acid in the vapor phase and of the number
concentration of the aerosol droplets. The initial rate of change in the
mean volume diameter was found to be highly correlated with the volumetric
conversion rate according to a power function relationship.
11. Finally, the apparent dependence of the volumetric conversion
rate on the initial reactant concentrations and of the rate of change of
the mean volume diameter on the volumetric conversion rate provide a pre-
dictive capability potentially useful in the generation of a sulfuric
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166
acid aerosol of known physical properties for controlled laboratory
animal experimentation.
It is recommended that additional research be conducted to measure
or to obtain through appropriate mathematical models the sulfur dioxide
oxidation rate. The reaction scheme advanced in this dissertation with
its mechanism for ozone regeneration and hydroxyl radical production could
be tested in existing kinetic models comparing the results with the con-
centration profiles observed in this study.
Experimentation along the lines conducted in this study should also
be continued to include other olefinic compounds. The structure and
reactivity of the intermediate species and the reaction products would
vary depending on the unsaturated hydrocarbon investigated. Tetramethyl-
ethylene, for example, would yield acetone as an initial product in lieu
of the aldehydes. The hydroxyl radical reaction with the acetone is
expected to be significantly slower than its reaction with the aldehydes
and the product inventory and primary reaction stoichiometry would be
affected. The products of the secondary reaction between the olefin and
the hydroxyl radical require identification as do the products of the
decomposition reactions of the hydroxyl radical-olefin adducts. The
products of these composite reactions could be followed in time with a
system like the Fourier Transform Infrared Spectrometer and the concen-
tration profiles evaluated to determine the relative potential of the
various olefins in photochemical smog development.
The hydroxyl radical is, perhaps, the most important oxidizing species
in photochemical smog particularly in the early stages before the ozone
concentration develops. Although the initial reaction of the hydroxyl
radical with saturated and unsaturated hydrocarbons is established, its
mode of reaction with aromatics is speculative. Experimental evidence is
-------
167
needed to fix the exact mechanism of that reaction. Specification of the
oxidation mechanism for sulfur dioxide in reactions involving the hydroxyl
radical with olefins, parraffins and aromatic hydrocarbons is also needed.
These reactions potentially contribute to the development of secondary
aerosols in the ambient atmosphere which are largely responsible for the
aggravation of respiratory ailments and reduced visibility associated with
photochemical smog.
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-------
170
Friedlander, S.K., "Similarity Considerations for the Particle-Size
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-------
171
Husar, R.B., "Coagulation of Knudsen Aerosols," Ph.D. Thesis, University
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-------
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-------
174
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-------
Appendix 1: Product Analysis by Fourier Transform Infrared Spectroscopy
Run RH (%) CO (ppm) HCHO (ppm) CH CHO (ppm) CH2CO (ppm) HCOOH (ppm)
28 C2H4 + 03 22 .84 4.14 0 0 Trace
29 C«,H,, + O., + SO., 20 1.09 4.06 0 0 .19
21
79
81
82
:3»6 + °3
:3H6 + °3
:3H6 + o3 + so2
:3H6 + °3
;3H6 + °3
:3H6 +. 03 + so2
:,H, + o, + so.,
36 3 2
3H6 + °3 in N2
:3H6 + 03 in N2
19
19
19
19
33
20
36
36
20
175
.93
.94
.56
.70
.71
.79
.73
.87
2
3
3
1
2
2
2
2
1
.12
.21
.44
.77
.27
.82
.97
.23
.94
1
1
1
1
1
1
1
1
.25
.49
.59
.99
.36
.43
.70
.30
.12
. 18 Trace
.20 Trace
0 Trace
.32 Trace
. 34 Trace
0 Trace
0 Trace
.32 0
.22 0
01
-------
176
Appendix 2: Observed and Smoothed Reactant Concentrations
for Gas Phase Experiments.
Smoothed data are listed through the first half
of the 'OBS1 sequence followed by the observed
concentration values. The time derivatives of
the concentration values are indicated by the
1DOT' notation.
-------
OBS
1
2
3
4
5
6
7
8
9
10
11
12
13
15
16
17
IB
19
20
21
22
23
24
TIME
0.0
1.5
3.0
4.5
6.0
9.5
14.5
20.5
26.5
35.0
43.5
52.0
0.0
1.5
3.0
4.5
6.0
9.5
14.5
20.5
26.5
35.0
43.5
52.0
HC
8.12507
7.662u5
7.23351
6.83947
6.47991
5.77509
5.16662
4.73827
4.46861
4.20761
4.06259
4.04746
7.70000
6.77300
5.79800
5.10900
4.77300
4.45400
4.20200
4.09200
4.03400
HCOOT
-.320182
-.297188
-.274194
-.251199
-.228205
-.174552
-.111191
-.067231
-.040845
-.024701
-.009421
.005861
RUN It
03
2.88215
2.54341
2.23673
1.96211
1.72000
1.32i55
0.95053
0.66120
0.45569
0.27253
0.15747
0.12115
2.55000
2.21000
2.COOOO
1.70000
1.28000
0.95500
0.66200
0.44700
0.27300
O.X7200
0.11400
21.
03DOT
-.236510
-.215139
-.193769
-.172398
-.149031
-.iOSiBO
-.066193
-.043283
-.030780
-.018168
-.008905
.000358
S02
0
0
0
0
0
0
0
0
0
0
0
0
S02DOT
0
0
0
0
0
0
0
0
0
0
0
0
FLAG
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
OLX03
23.4177
19.4878
16.1794
13.4198
11.1454
7.6320
4.9110
3.1329
2.0363
1.1467
0.6397
0.4903
-------
_.RUN_»_25.__
OBS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
3<»
35
36
TIME
0.0
1.5
3.0
4.5
6.0
7.5
n.o
20.0
2R.O
3P.O
47.0
57.0
66.0
75.0.
«3.0
91.0
100.0
109.0
0.0
1.5
3.0
4.5
6.0
7.5
13.0
20.0
28.0
38.0
47.0
57.0
66.0
75.0
83.0
91.0
100.0
109.0
HC
.87786
.78501
.69609
.61109
.53001
.45285
1.20348
0.96989
0.79430
0.63495
0.53740
0.45650
0.40226
0.35848
0.33503
0.31216
0.28179
0.24754
1.87600
1.53900
1.18700
0.97500
0.78800
0.64000
0.53*00
0.45900
0.40300
0.35700
0.33300
0.31800
0.27700
0.24900
HCOOT
-.0632034
-.0605892
-.0579751
-.0553610
-.0527469
-.0501327
-.0405476
-.0301656
-.0203730
-.0139678
-.0100405
-.0073793
-.0054750
-.0039788
-.0034759
-.0031598
-.0035897
-.0040197
03
2.37699
2.26547
2.16267
?. 06858
1.99261
1.92047
1.70577
1.50335
1.3?309
1.15703
1.06069
0.98858
0.92370
0.85641
0.80746
0.76169
0.71554
0.67506
2.27000
2.15000
2.08000
1.98000
1.70000
1.50000
1.33000
1.15000
1.06000
0.99600
0.92000
0.85700
. 0.80700
0.76300
0.71500
03DOT
-.0772514
-.0714405
-.0656295
-.0598186
-.0496536
-.0465367
-.0360289
-.0272264
-.0201304
-.0139203 .
-.0102874
-.0077714
-.0071519
-.0067102
-.0060014
-.0054422
-.0048130
-.0041839
SO 2
.582743
.574805
.567062
.559513
.552157
.544996
.518966
.494454
.475969
,463097_
.454454
. .446463
.439819
.43?438
.424536
.417090
.409335
..402307
.566000
.561000
.552000
.520000
.493000
.476000
.461000
.455000
.446000
.440000
.433000
.424000
.417000 _
.410000
.4Q?000
S0200T FLAC
-.00535633
-.00522694
-.00509755
-.00496815
-.00483876
-.00470937
-.00418712
-.00306539
-.00204479
-.00124745
-.00093915
-.00080307
-.00083868
-.00088?37
-.00090368
-.00090212
-.00082131
-.00074049
(
(
(
<
(
(
(
(
(
(
(
(
(
(
(
(
(
(
> OLX03
4.46365
4.04389
3.66808
3.33?67
3.04871
2.79015
2.05286
1.45809
1.05093
0.73466
0.57002
0.45129
0.37157
0.30700
0.27053
0.23777
0.20163
0.16711
3
J
)
J
)
)
)
)
)
J
)
)
)
)
)
) -
) w
)
-------
DBS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
IB
19
20
21
22
23
24
25
26
27
28
29
30
31
32
TIME
0.0
1.5
3.0
6.0
10.0
17.0
24.0
32.0
39.0
47.0
55.0
64.0
71.0
80.0
91.0
0.0
1.5
3.0
4.5
6.0
10.0
17.0
24.0
32.0
39.0
47.0
55.0
64.0
71.0
80.0
91.0
HC
3.54659
3.42474
3.30908
3.19961
3.39634
2.85124
2.52829
2.39025
2.28256
2.20528
2.13821
2.08635
2.34329
2.01263
1.99044
1.9U425
3.46000
2.76800
2.54200
2.40900
2.25600
2.23200
2.12800
2.07900
2.06VOO
2.00000
1.98000
1.99000
HCDOT
-.0833005
-.0791711
-.0750416
-.0709122
-.0667827
-.0557708
-.0365000
-.0191743
-.0133804
-.0104328
-.0068144
-.0364363
-.0045340
-.0033217
-.0016095
.0004831
R
03
1.07984
0.98602
0.89997
0.82167
0.75113
0.61791
0.47074
0.36625
0.28003
0.22113
0.16859
0.13032
0.10151
0.08298
0.06345
0.04652
0.98000
0.91800
0.72900
0.61300
0.46900
0.36700
0.28000
0.22200
0.16800
0. 13000
0.13200
0.08400
0.06200
0.04700
UN * 26.
03DOT
-.0651314
-.0599585
-.0547357
-.0496128
-.0444400
-.0320097
-.0185722
-.3135722
-.0099257
-.0077414
-.0057763 .
-.0042370
-.0030956
-.0024547
-.0018860
-.0011908
502
.620152
.610093
.600614
.591718
.583402
.565275
.539787
.521412
.508221
.500380
.491768
.484739
.479418
.475815
.471807
.467689
.602000
.593000
.583000
.565000
.540000
.521000
.503000
.501000
.492000
.484000
.480000
.476000
.471000
.468000
S02D3T
-.00690340
-.00651270
-.00612500
-.03573731
-.00534961
-.33411949
-.00315637
-.00225174
-.00153991
-.00118088
-.00093265
-.00076722
-.00060213
-.00047723
-.00041340
-.00033539
FLAG
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
3
0
0
0
0
3
0
0
0
0
0
0
3
0
0
0
OLX03
3.82976
3.37638
2.97806
2.62902
2.32575
1.76182
1.19018
0.87544
3.63919
0.48765
0.36047
0.27189
0.20792
0.16700
0.12S28
0.09231
-------
RUN # 27.
DBS TIME
1 O.C
2 1.5
3 3.0
4 4. 5
5 6.0
6 7.5
7 13.0
0 19. U
9 25. C
10 3i.O
U 39.0
12 44.0
13 49.0
14 58. u
15 68. C
16 76.0
17 84.0
18 93.0
19 101.0
20 C.O
21 1.5
22 3.0
23 4. 5
24 6.0
25 7.5
26 1J.O
27 19.0
28 25.0
29 21.C
30 39.0
21 44.0
32 4S.O
33 58.0
34 68.0
35 76.0
36 84.0
37 7j 7}
Co
O
-------
1
OBS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
2'J
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
TIKE
0.0
1.5
3.0
6.0
11.5
17. C
22.5
27.5
32.5
37.5
42.5
47.5
52.5
57.5
65.0
7C.O
75. C
80.0
85.0
95.0
J.C
1.5
3iO
6.0
11.5
17.0
22.5
27.5
32.5
37.5
42.5
47.5
52.5
57.5
65.0
70.0
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80. C
85. C
95.0
HC
11.8498
11.6368
11.4344
11.0613
10.5001
1C.C644
9.6343
9.2907
9.0227
8.8315
8.5778
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11 .8500
11.4500
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10.0500
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3.80672
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2.37533
2.18218
1.99914
1 .82686
1.66971
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3.57000
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2. 63COO
2.37000
2.19000
2.00COO
1.82000
1.68COO
1.53000
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28.
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FLAG
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
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0
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0
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0
0
0
0
0
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OLX03
45.1090
42.7947
40.6282
36.7111
30. 8629
26.5032
22.8845
20.2740
18.0577
16.1340
14.3225
12.8955
11. 6654
10.6035
9.1937
8.5224
7.9038
7.1968
6.6042
5.5957
1 »
oo
-------
DBS
1
2
3
4
5
6
7
8
9
13
11
12
13
14
15
16
17
13
19
20
21
22
23
24
25
26
27
28
29
30
31
32
TIME
2.5
5. C
10.0
15.0
20.0
25.0
30.0
35. C
40.0
45.0
53.5
58.5
£4. C
77.5
87.0
C.O
2.5
5.0
10. 0
15.0
20.0
25.0
30.0
35.0
40.0
45. C
S3. 5
53.5
64. C
77.5
87.0
hC
12.5020
11.8036
11 .2398
10.7103
10.2431
9. 8461
9.5693
9. J521
9. 0576
8.8549
8.6362
8.3576
8.1707
8. 04 30
7.7354
7.5384
12. 68CC
11.5400
11.2000
10.72CO
10.2500
9.8200
S.5760
9 .3590
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8. /620
8.7350
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8 .2200
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3.61723
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1.94086
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1.61748
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0.36160
0.74162
3.42000
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2.38000
2- 15000
1.94000
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1
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1
1
0
0
0
0
0
0
o
0
0
0
0
0
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0
0
0
ni *m
45-???*,
40.4635
^A. 5136
31.2625
76.R904
23.3832
70.5740
18.1512
15.9413
14.3226
12.7659
10.5284
9.37B9
8.5398
6.6648
5.5907
-------
RUM * 31.
OBS
1
2
3
4
5
6
7
8
9
10
11
12
13
15
16
17
18
19
20
21
22
23
24
TIME
0.0
1.5
3.0
4.5
5.5
10.5
18.5
24. 0
32.0
37.5
46.0
55.0
0.0
1.5
3.0
4.5
5.5
10.5
18.5
24. 0
32.0
37.5
46.0
55.0
HC
8.55502
8.05260
7.58708
7.15846
6.89321
5.81298
5.08467
4.83663
4.62060
4.52596
4.43847
4.45258
8.62200
6.77000
5.81200
5.06200
4.87700
4.6230U
4. 502 JO
4.47800
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03
2.71353
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0.60891
0.41815
0.24538
0.17306
0.09287
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2.38000
2.07000
1.81000
1.65000
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0.61900
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S02
524980
482373
452138
430607
429385
397888
368151
358121
351134
347638
341452
335170
526000
480000
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342000
335000
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1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
OLX03
23.
19.
15.
12.
11.
6.
3.
2.
1.
0.
0.
3.
2143
1445
7476
9425
4881
4974
0961
0224
1338
7833
4122
3070
-------
RUN ft 86.
UbS
TIKE
HCCJT
U3DUT
SO 2
SG2DOT
FLAG
CLXC3
1
2
j
4
c
e
1C
11
12
13
Is
It
lo
17
le
2C
22
23
24
26
2b
3u
31
33
3s
Ji
Jo
27
Jd
0.0
1.5
s . 5
6 .0
11. C
l7 .u
23.0
2S.C
37. C
47.0
Sf.C
o5 .c
73. C
81. o
S7.C
C'.C
l.L
1.5
3.C
c.G
1 l.L
17. c
23. C
2S. C
37.o
J7.C
65.0
73. C
o 1 .C
69. C
S7.C
11S.L
.921666
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ibuiJSc
4s J t' 13
. _>c t i;ic
. Jo looo
IloIuJJ
.15SC.1S
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.7iCCCC
.5150CC
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3 / 1 u 0 0
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RUN « 87.
CBS TIME
1 0.0
2 1.5
3 3.0
4 4.5
5 8.0
6 16.0
7 24.0
8 32.0
9 41.0
10 50.0
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15 93.0
16 0.0
17 i.5
18 3.0
19 4.5
20 8.0
21 16. U
22 24.0
23 32.0
24 41.0
25 50.0
26 59.0
27 67.0
28 76.0
29 35. J
30 S3.0
HC
1.1116C
1.07261
1.03446
0.99716
0.9134J
C. 7392C
0.57677
0.47589
0. 39184
0.32611
0.27222
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0.20769
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0.15748
1.101CO
0.937CO
0.732CO
0.57500
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1
1
1
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1
1
0
0
0
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0
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0
0
0
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0
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OLX03
2.28510
2.12B72
1.98496
1.85307
1.60010
1. 15830
0.83342
0.64668
0.49950
0.38964
0.30788
0.25905
0.21462
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0.14911
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CD
cn
-------
K
OBS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
TIME
0.0
1.5
3.0
4.5
6.0
7.0
13.0
22.0
29.0
36.0
45.0
53.0
61.0
69.0
77.0
83.0
0.0
1.5
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4.5
6.0
7.0
13.0
22.0
29.0
36.0
45.0
53.0
61.0
69.0
77.0
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3.28134
3.23994
3.20084
3.16405
3.12957
3.10786
2.99912
2.93428
2.87909
2.84561
2.81450
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3.30600
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OLX03
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-------
RUN # 89.
OBS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
IS
16
17
18
19
20
21
22
23
24
25
26
TIME
0.0
1.5
3.0
4.5
7.0
13.0
19.0
26.0
34.0
44.0
52.0
63.0
74.0
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1.5
3.0
4.5
7.0
13.0
19.0
26.0
34.0
44.0
52.0
63.0
74.0
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2.98867
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0
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OLX03
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-------
J?U N_JL 9 0.
OBS
1
2
3
4
5
6
7
8
9
10
11
12
13
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
35
36
TIME
o.o
1.5
3.0
4.5
15.0
23.0
27.0
31.0
39.0
47.0
55.0
69.0
7«.0
Sfl.O
95.0
103.0
111.0
0.0
1.5
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15.0
23.0
27.0
31.0
39.0
47.0
55.0
69.0
78.0
88.0
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103.0
111.0
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1.87000
1.78000
1.70000
1.51000
1.25000
1.02000
0.91400
0.81700
0.69900
0.60900
0.53800
0.42400
0.36600
0.31300
0.28300
0.23700
0.21600^
0300T
-.0672579
-.0634219
-.0595859
-.0557499
-.0*64426
-.0351251
-.0273047
-.0232000
-.0204154
-.0141097
-.0108605
-.0089872
-.0070730
-.0059651
-.0052988
-.0046182
-.0040686
-.0035191
S02
.580315
.570500
.561140
.552235
.533223
.50P065
.479342
.471RA6
.465237
.454214
.444872
.436136
.420877
.411129
.399639
.391147
.382920
.375522
.559000
.555000
.533000
.50?000
.480000
.47?000
.465000
.454000
.445000
.436000
.421000
.411000
.400000
.391000
.3fl?000
..376000
S02DOT
-.00669454
-.00639150
-.00608846
-.00578542
-.00507832
-.00379175
-.00234598
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-.00110370
-.00109513
-.00113158
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-.00097653
-.00087282
FLAG
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
OLX03
5.39619
4.91569
4.48035
4.08697
3.33507
2.27197
1.56700
1.30392
1.11488
0.84845
0.67708
0.55108
0.39002
0.31725
0.25607
0.21846
0.18470
0.15777
oo
oo
-------
RUN « 91.
DBS
1
2
3
i*
1
6
7
8
9
10
11
12
13
l
-------
RUN #92.
UBS
1
2
3
5
6
7
b
9
10
11
12
13
14
15
lo
17
18
19
20
21
22
23
24
25
2c
27
20
29
30
31
32
33
34
TIME
0.0
1.5
3.0
6.0
11.0
17. u
19.9
24.0
30.0
39.0
53.0
60.0
6U.C
77.0
86.0
94. C
108. C
0.0
1.5
3.0
6.0
11.0
17.0
19.9
2
-------
RUN » 93.
OBS TIPE
1 U.O
2 1.5
3 3.0
4 6.0
5 b.C
6 14.2
7 16 .0
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9 32.0
1C 41. t
11 49.0
12 58.0
13 67. C
14 76.0
15 . 86.0
It 94. U
17 112.0
Id C.C
IS 1.5
20 3.0
21 6.C
22 8.C
23 14.2
24 It.C
25 24.0
26 32.0
27 il.O
28 49.0
29 sa.o
30 o7.(.
31 76. C
32 66. C
33 St.C
3t 112.0
HC
2.753CO
2.663Q5
2. g 7 5-59
2.vl051
2.3066J
2.C1704
1.94220
1.65715
1.-6415
1.31642
1.2C939
1.14/73
I.C7674
1.C1874
0.9676U
0.93a97
0.90064
2.7*600
. 2.329CO
1.917CO
l.t71CO
1 .45800
1.3C200
1.16700
l.L70tO
l.COiCC
C.942CO
HCDOT
-.C6C925C
-.0590031
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-.0532375
-.050o75C
-.C427313
-. 0^.04250
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-.0032751
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03
2.57259
2.42836
2.29375
2.05338
1.93120
1. 53751
1.54181
1.25198
1.03362
0.84093
0.72247
0.61362
0.51900
0.44773
C. 37565
0.32065
0.25754
2.42000
2.31000
2.04000
1 .92000
1.53000
1.26000
1.C300C
O.U4200
0.717CC
0.61500
0.44400
0.33300
C.2560C
03DOT S02 S02DOT
-.C993578
-.0929463
-.0865347
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-.0052832
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0
0
0
0
0
0
C
0
0
C
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
- o""
0
0
FLAG
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
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0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
CLXC3
7.08235
6.46686
5.90869
4.94971
4.45451
3.20206
2.99451
2.07471
1.51338
I. 10702
0.87374
0.70427
0.55883
0.45612
0.36351
0.30794
0.23200
H^
-------
FUN
94.
OBS 1 I^t
1 0.0
2 1.5
3 3.0
4 5.0
5 11. C
o 12 .0
7 17.0
8 24. C
9 32 .u
1C 41. C
11 -,'J.U
12 57.0
13 71.0
Is 79.0
15 87. C
lo 94.0
17 " 102. u
10 C.C
19 1 .t
20 3.C
21 5.C
22 11. 0
23 12. C
2-. 17. o
25 24.0
2t> 32.0
27 41.0
28 -,9.0
29 57.C
30 71.0
31 79.0
32 ti/.C
33 94.0
34 IC2.C
HC
2.S2957
<:. 61015
2.55138
2.11/32
1 .b75t3
1.3J7JO
1 .2 Jc.,03
i . i -j 7 1 1,
1 . 01.028
1 .00705
C.97^79
0.9550;-
2.570CC
2.12500
1.9C800
1 .'to 6 JO
1 .24500
1 .15000
C.9UCOO
0.95SOO
HCDJT 03
-.0813174 2.08281
-.0779099 2.52o69
-.L 7<. 5025 2.38047
-.U69-jf.92 2.20094
-.0^6329^ 1.79184
-.0^«-J57U 1.732^-1
-.'02^234 U21V52
-.021J206 0.99821
-.Ul4jft70 0.82002
-.0119761 C. 09432
-.GJ90542 0.59111
-.0062152 O.s5375
-.0045929 0.39237
-.0015511 0.30230
.OOC0713 0.2o799
2.5400C
2.37000
2.19000
1.78000
1.49000
1.2100C
1.00000
O.U2300
O.C92CO
0.59100
0.45500
0.39200
0.34100
0.30200
U3D'JT
-.107338
-.1007UO
-.094171
-.0853oO
-.OoJo9o
-. 058176
-.046-590
-.C25269
-.018362
-. 014026
-.012051
-.007217
-.UO5950
-. 004893
-.003o84
SO 2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
SO 2 DOT
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
FLAG
I
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
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0
0
r.'LX03
7.U5949
7.10037
t.-1738
5.e.l544
3.H9280
3.*6tlJ6
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I. J9636
O.Uf 620
0.68401
(i. *7.^157
0. 39r-13
0.33235
0.29050
0.25394
i
. _ is
-------
KUN # 95.
08S
1
2
3
5
6
7
a
10
11
12
14
15
lo
17
18
20
21
22
23
24
25
26
27
20
29
30
TIME
0.0
1.5
J.O
b.d
9.0
16.0
40.0
4b.O
56.0
64.0
72.0
80.0
86.2
0.0
1.5
3.0
4.5
6.U
9.0
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24.0
40.0
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3,
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2.
2.
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02490
93108
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37562
33550
31134
30361
02«tOO
52400
154QO
92100
59300
42000
36100
33oOO
31000
HCDOT
-.0635928
-.0615022
-.0594115
-.0573209
-.0541152
-.0510489
-.0412V25
-.0304795
-.0159087
-.0110915
-.0061819
-.OOoJl37
-.0040172
-.0020207
-.0004734
1
1
1
1
1
1
1
0
0
o
0
0
0
0
0
1
1
1
1
1
0
0
0
0
0
0
0
c
*
*
*
*
*
03
81263
71052
61396
52294
39415
20979
01tS2
79480
51492
42433
35126
29291
245H6
20522
18002
71000
61000
53000
28000
01000
79000
52100
42oOO
35100
29300
24oOO
20500
leooo
P3DOT
-.0699221
-.0662244
-.0625267
-.0588291
-.0531593
-.0477266
-.0357746
-.0252097
-.0140306
-.0109594
-.0085375
-.0068375
-.0055 3<: 1
-.0044754
-.0036550
S02
.558233
.550147
.542290
.534661
.523406
.512349
.485605
.460639
.429429
.420580
.416343
.410486
.404343
.397914
.392736
.549000
.543000
.536000
.512000
.484000
.462000
.428000
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.416000
.411000
.404000
.398000
S0203T FLAG OLXOS
-.00546656 1
-.00531432 1
-.00516208
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-.0008 21 '+3
-.00084911 1
5.48302
I 5.01367
4.58427
4.19241
3.65922
3.23609
2.22696
1.53140
0.82120
0.63171
0.49835
0.40294
0.32754
0.26911
0.23467
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-------
RUN # 97.
UdS
1
<:
3
4
5
6
/
0
9
10
11
12
1 j
1*
16
17
Id
19
20
21
22
23
24
25
67
2.t>99f2
2.52573
2.4122S
2.32294
C 0 C
2.1 /UOO
2. 144CC
HCDOT
-.0750C11
-.0626476
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-.0142708
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C3
2.152"26
2.06753
2.03436
2.00274
1.97268
l.V2.t02
I.db3t8
1.82963
1.79353
1. 76975
1. 74839
1. 70574
1.63103
1.55542
1.52U75
1.5Cc60
1.44159
1.41457
1. 39098
1.3C327
i. 31336
1.2B-.98
1.24979
1.22762
1.21360
1. 194b6
1.17343
I. 14914
1.122CO
2.00000
1.98000
1.92000
1.U2JCO
1.71000
1.63000
~l.r£OCO~~
1.50000
1.42000
03 DOT
-.0236669
-.0226331
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-,OOV729tt
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S02
' ".568442
.581254
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. 521997
.508731
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.44975*
.446410
.441629
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.429909
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. itf.ono
S02DOT
-".00^95912"
-.00462497
-.00429182
-.00395867
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FLAG
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
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0
-Q-
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
OLX03
6.54282
6.22117
5.94915
5.72' 51
5.54518
5.39344
5.21136
4. 93666
4.78903
4.6^855
4.54*78
4.30824
3.93452
3.M315
3.49777
3.4005^
3. 13232
3.U3869
2.9*663
2.B?907
2.6B751
2.60290
2.49474
2.^2883
2.36757
2.32741
2.276*5
2. 16682
2.07233
i i
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£*.
-------
LES lift
I C.C
2 1.3
3 3.C
4 <«.3
5 o.C
o 13. C
7 21.0
-------
196
Appendix 3: Aerosol Droplet Number, Surface Area, and Volume
Concentrations Distributions for Aerosol Experiments.
DP Geometric Mean Diameter
AMP Electrometer Current Sensed
DIFFERENCE Current Difference
DX dx
d log D
P
DX ,
r dx
x d log D
-------
101A
OP
.0042
.0075
.0133
.0237
.0422
.0750
.1330
.2370
.4220
.7500
AMP
0.0
9.2800
9.1700
8.5900
4.6900
0.8140
0.0360
0.0
0.0
0.0
0.0
5
DIFFERENCE
0.0
0.396E 06
0.620E 06
0.119E 07
0.3B2E 06
0.371E 05
0.84BE 03
0.0
0.0
0.0
ON
0.
1582248.
2480079.
4776716.
1529624.
148598.
3393.
0.
0.
0.
N
2630164.00
OS
0.0
280.06
1378.92
8407.02
8550.60
2630.18
188.63
0.0
0.0
0.0
s
5358.85
0V
0.0
0.3SO
3.050
33.294
60.114
32.840
4.173
0.0
0.0
0.0
V
33.46
~HDN7Nf
0.0
a. 6516
0.9429
1.8161
0.5816
0.0565
0.0313
0.0
' 0.0
0.0
OS/5-
0.0
"0.0523
0.2573
1.5688
1.5956
0.4908
0.0352
0.0
0.0
0.0
OV/V
0.0
0.0105
0.0912
0.9952
1.7969
0.9816
0.1247
O.D
0.0
0.0
-------
10
DP
.0042
.0075
.0133
.0237"
.0*22
.0750
.1330
.2370
.4220
.7500
I1A
' AMP
0.0
0.0
6.9500
6.8500
6.1900
2.8600
0.6510
0.0700
0.0020
0.0
0.0
15
DIFFERENCE
"0.0
0.0
0.107E 06
0.202E 06 '-
0.329E 06
0.105E 06
0.137E 05
0.922E 03
0.156E 02
0.0 ' " "
ON "
0.
0.
427602.
808368.
1314151.
421919.
54753.
3688.
62. "
0.
"N "
757635.25
" " os
0.0
O.D
237.75
1422.73
7346.10
7467.96
3344.29
.... .... 649>14
34.80
0.0
5
5050.69
ov --
0.0
o.o
- 0.526
5.634
51.646
93.244
67.347
~*- 25.708
2.446
0.0
V
61.64
DN/N
0.0
o.o -
0.5644
1.0670
1.7345
0.5569
-" 0.0723
0.0049
0.0001
0.0
OS/S
0.0
0.0
0.0471
0.2817
1.4545
1.4786
0.6027
0.1285
0.0069 '
0.0
DV/V
0.0
0. 3
0.0085
0.3914
0.8379 " '
1.5128
1.0926
0.4171
0.0397
0.0
VO
00
-------
101A
OP
.0042
.0075
.0133
.0237
.0422
.0750
.1330
.2370
.4220
.7500
AMP
0.0
0.0
5.5800
5.5200
5.4700
4.6400
1.9390
0.3240
0.0720
0.0210
45
DIFFERENCE
0.0
0.0
0.641E 05
0.1 53E 05
0.819E 05
0.129E 06
0.380E 05
0.342E 04
0.397E 03
0.669E 02
ON
0.
0.
256562.
61240.
327551.
515891.
152197.
13668.
1587.
268.
OS
0.0
0.0
142.65
107.78
1831.01
9131.27
8*62.18
2405.65
887.31
473.76
DV
0.0
0.0
0.316
0.427
12.873
~114.012 "~"
187.203
95.269
62.382
58.885
-OWN" * -
0.0
0.0
0.7722
0.1843
' 0.9859
1.5528
0.4581
0.0411
0.0048
0.0308
DS/S
0.0
0.0
0.0243
0.0184
0.3124
1.5581
1.4440
0.4105
0.1514
0.0808
DV/V
0.0
0.0
Q.3024
0.0032
0.0969
0.8583
1.4092
0.7172
0.4696
0.4433
0.0060
N
332240.50
S
5860.40
V
132.84
ID
-------
101A 75
DP AMP DIFFERENCE
.0042 0.0 0.0
.0075 4.7500 0.180E 06
.0133 4.7000 0. 107E 05
.0237 4.6900 0.612E 04
.0422 4.6700 0.138E 05
.0750 4.5300 0.965E 05
.1330 2.5100 0.47BE 05
.2370 0.4800 0.525E 04
.4220 0.0930 0.521E 03
.7500 0.0260 O.S03E 02
0.0080
ON OS DV DN/N DS/S OV/V
0. 0.0 0.0 0.0 0.0 0.0
719203. 127.30 0.159 1.9947 0.0216 3.0010
42761. 23.78 0.053 0.1186 0.0041 0.0003
24497. 43.11 0.171 0.0679 0.0074 0.0011
55249. ~ 308.84 2.171 0.1532 0.0528 0.0140
385820. " 6829.01 " 85.266 1.0701 1.1675 0.5483
191307. 10636.67 235.308 0.5306 1.8184 1.5131
20991. ~ 3694.39 146.306 0.0582 0.6316 0.9408
2085. 1165.69 81.953 0.0358 0.1993 0.5270
321. 568.51 70.662 0.0009 0.0972 0.4544
N S V
360558.00 5849.32 155. 51
t\j
0
0
-------
1018
DP
.0042
.0075
.0133
.0237
.0422
.0750
.1330
.2370
.4220
.7500
AMP
0.0
7.0300
6.9100
5.9000
1.B700
0.1550
0.0
0.0
0.0
0.0
0.0
5
DIFFERENCE
0.0
0.432E 06
0.108E 07
0.123E 07
0.169E 06
0.740E 04
0.0
0.0
0.0
0.0
DN
o.
1726078.
4318760.
4935940.
676807.
29605.
0.
0.
0.
0.
N
2921797.00
OS
0.0
305.52
2401.23
8687.25
3783.35
524.01
0.0
0.0
0.0
0.0
s
3925.34
0V
0.0
0.381
5.312
34.403
26.599
6.543
0.0
0.0
0.0
0.0
V
18.31
DN/N
0.0
0.5908
1.4781
1.6894
0.2316
0.0101
0.0
0.0
D.O
0.0
" "DS/S"
0.0
0.0778
0.6117
2.2131
0.9638
0.1335
0.0
0.0
0.0
0.0
DV/V
O.O
0.0208
0.2901
1.8790
1.4527
0.3573
O.D
0.0
0.0
0.0
-------
1018
DP
.0042
.0075
.0133
.0237
-.0422
.0750
.1330
.2370
.4220
.7500
' " ftHP
0.0
6.3100
6.2900 ~
6.2500
5.5200
2.4600
0.5220
0.0520
0.0
0.0
0.0
16
DIFFERENCE
0.0
0.719E 05
0.428E 05
0.224E 06
0.302E 06
" 0.925E 05
0.1 HE 05
0.705E 03
0.0
0.0
ON
0.
287673;
171040.'
894105.
~ 1207598.
370158.
44293.
2820. "
0. '" "
0.
N
744421.00
DS
0.0
-50.92 - -
95.10
15/3.62
6750.47
6551.79
Z4&Z.68
496.40
0.0
O.D
S
4495.24
- 'DV
O.D
0.064
0.210
6.Z3Z
47.459
81.805
!>4.<>BU
19.659
0.0
0.0
"v
52.48
'DN/N
0.0
0.3864
0.2296
1.2011
1.6222
0.4972
0.0595
"0.0038
~o.o -
0.0
DS/S
0.0
0.0113
0.0212
0.3501
1.5017 ~
1.4575
0.5478
0.1104
0.0
0.0
DV/V
0.0
0.0012
0.0040
0.1188
0.9044
1.5589 '
1.0382
0.3746
O.D
0.0
-------
101B
OP
0042
0075
0133
0237
0422
0750
1330
2370
4220
7500
40
AMP DIFFERENCE
0
5
5
5
5
4
1
0
0
0
0
.0
.3900
.3700
.3400
.3200
.3000
.5840
.2700
.0590.
.0150
.0030
0.0
0.719E
0.321E
0.612E
0.101E
0.130E
0.310E
0.286E
0. 342E
0.535E
05 ""
05
04
06
06
05
04
03
02
ON
0.
267673.
128283.
24495.
402533.
518756.
123831.
11445.
1369.
214.
N
374649.25
OS
0.0
50.92
71.33
43.11
2250.16
9181.97
6885.02
2014.26
765.53
379.01
5
5410.32
0V
0.0
0.064 '"
0.158
0.171
15.820
114.645
152.312
79.769
53.820
47.108
V
115.97
ON/N
0.0
0.7678
0.3424
0.0654
1.0744
1.3846
0.3305
0.0305
0.0037
0.0306
DS/S
0.0
0.0094
0.0132
O.OOBO
0.4159
1.6971
1.2726
0.3723
0.1415
0.3701
OV7V"
0.0
o.ooo*
0.0014
0.0015
0.1364
0.9886
1.3134
0.6879
9.4641
0.4062
-------
1018
OP
.0042
.0075
.0133
.0237
.0422
.0750
.1330
.2370
.4223
.7500
AMP
0.0
4.5600
4.5400
4.5100
" 4.4900
4.3300
2.4700
0.4920
0.0910
0.0240
0.0090
75
" DIFFERENCE
0.0
0.719E
0.321E
0.612E
0.158E
" 0.888E
0.466E
0.544E
0.521E
0.669E
05
05
04
05
05
05
04
03
02
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0.
287673.
128283.
24495.
63142.
355260.
186407.
21750. "-
; ' 2085.
268.
N
267J4U.50
OS
0.
50.
71.
43.
352.
6288.
0
92
33
11
97 ~
10
10364. 2O
3828.
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473.
s
5659
04
68
76
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DV
0.0
0.064
0.158
0.171
2.481
78.512
229.280
* 151. 5 99
81.952
SB.BBb
V
150.78
" DNXN
0.0
1.0761
0.4798
0.0916
0.2362
1.3289
0.6973
" 0.0814
0.0078'
O.oOlO
OS/S
0.
0.
' 0.
"0.
0.
1.
1.
0.
0.
0.
0
0090
0126
0076
0624
1111
8313
6764
2060
0837
DV/V
0.0
0.0034
0.0010
0.0011
0.0165
0.5207
1.52D7
1.0055
0.5435
0.3905
-------
102
OP
.0042
.0075
.0133
.0237
.0422
.0750
.1330
.2370
.4220
.7500
" AMP
0.0
6.9900
6.8400
5.3000
1.5500
0.0100
0.0
0.0
0.0
0.0
0.0
5
DIFFERENCE ON DS DV DN/N DS/S DV/V
0.0 0. 0.0 0.0 0.0 0.0 0.0
0.539E 06 2157608. 381.90 0.477 0.6189 0.0982 0.0294
0.165E 07 6585036. 3661.28 8.100 1.8388 0.9413 0.4992
0.115E 07 4593000. 8083.68 32.013 1.3174 2.0783 1.9732
0.152E 06 607745. 3397.29 23.884 0.1743 0.8735 1.4722
0.477E 03 1910. 33.81 0.422 0.0005 0.0087 0.025.0
0.0 0. 0.0 0.0 0.0 0.0 0.0
0.0 0. 0.0 0.0 0.0 0.0 0.0
0.0 0. 0.0 0.0 0.0 0.0 O.O
0.0 0. 0.0 0.0 0.0 O.O 0.0
N S V
3486324.00 3889.49 16.22
to
o
en
-------
102
OP
.0042
.0075
.0133
.0237
.0422
.0750
.1330
.2370
.4220
.7500
" AMP"
~0~.0~
5.9700
5.9400
5.9200 "
5.1500
2.1100
D.3600"
0.0
0.0
0.0
0.0 "
16
DIFFERENCE
"' 0.0
0.108E 06
0.214E 05
0.236E 06
0.300E 06
0.836E 05
0.848E 04
0.0
0.0
0.0
DN " " *
0.
431516. '
"" 85522.
943095.
" 1199705.
334250;
33926.
0.
0.
0.
N
757003.25
OS
0.3
76.38
" 47.55
1659.85
6706.35 "
5916.22
18B6. 31
0.0
0.0
O.O
s
4073.16
- ov-
0.0
0.095
0.105
6.573
47.148 '
73.869
41.729
0.0
0.0
0.0
V" ' '
42.38
ON/N
0.0
0.5703
0.1130
1.2458
1.5848
0.4415
0.0448
0.0
0.0"
0.0
DS/S
0.0
0.0188
0.0117
0.4075
1.6465
1.4525
0.4631
0.0
- o.o "
0.0
OV/V
0.0
0.0023
0.0025 "
0.1551
1.1125
1.7430
0.9846
0.0
0.0
0.0
-------
102
OP AMP
.0042 0.0
.0075 4.6800
.0133 4.6500
.0237 4.6300
.0422 4.5900
.0750 3.7200
.1330 1.3400
.2370 0.1400
.4220 0.0
.7500 0.0
0.0
45
DIFFERENCE ON OS
0.0 0. 0.0
0.108E 06 431516. 76.38
0.214E 05 85522. 47.55
0.122E OS 48992. 86.23
0.858E 05 343337. 1919.25
0.114E 06 454580. 8046.06
0.283E 05 113088. 6287.68
0.190E 04 7594. 1336.47
0.0 0. 0.0
0.0 0. 0.0
N S
371156.50 4449.91
DV
0.0
0.095
0.105
0.341
13.493
100.462
139.098
52.927
0.0
0.0
V
76.63
DN/N
0.0
1. 1626"
0.2304
0.1320
0.9250 "
" 1.2248
0.3047
0.0205
0.0
0.0
DS'/S"
0.0
0.0172
0.0107 "
0.0194
0.4313
1.8081
1.4130
0.3003
0.0
0.0
OV/V
0.0
0.0012
0.0014
0.0045
0.1761
1.3110
1.8152
0.6907
0.0
0.0
NJ
r-»
-------
102
OP AMP
.00*2 0.0
.0075 3.9000
.0133 3.8100
.0237 3.0000
.0422 3.7900
.0750 3.4900
.1330 1.7400
.2370 0.2400
.4220 0.0
.7500 0.0
0.0
75
DIFFERENCE ON OS DV ON/N OS/S DV/V
0.0 0. 0.0 0.0 0.0 0.0 0.0
0.324E 06 1294562. 229.14 0.286 2.6466 0.0539 0.0033
0.107E 05 42761. 23.78 0.053 0.0874 0.0056 0.0006
0.306E 04 12247. 21.55 0.085 0.0250 0.0051 O.OOlb
0.296E 05 118392. "661.81' 4.653 0.2420 0.1557 0.0542
0.836E 05 334250. 5916.22 73.869 0.6833 1.3918 0.8601
0.353E 05 141360. 7859.61 173.873 0.2890 1.8490 2.0244
0.325E 04 13018. 2291.10 90.733 0.0266 0.5390 1.0564
0.0 0. 0.0 0.0 0.0 0.0 0.0 " "
0.0 0. O.O 0.0 0.0 0.0 0.0
N 5 V
489146.75 4250.80 85.89
o
oo
-------
103
DP
.0042
.0075
.Oi33
.0237
.0422
.0750
.1330
.2370
.4220
.7500
AMP 1
0.0
5.4500
5.3900
3.5400
0.7070
0.0080
0.0
0.0
0.0
0.0
" 0.0'
5
HFFERENCE
0.0
0.216E 06
0.198E 07
0.867E 06
0.690E 05
0.382E 03
"0.0
0.0
0.0
0.0
DN
0.
863046.
7910596.
3469857.
275853.
1528.
0.
0.
0.
0.
" N
os
0.0
152.76
" 4398.29
6106.95
1542.02
27.05
0.0
0.0
0.0
0.0
5
ov
0.0
0.191
9.730
24.185
10.841
0.338
0.0
0.0
0.0
0.0
V
~tm/N '
0.0
T>.275T~
2.527T
1.1085
0.0881
"0.0005
0.0
0.0
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0.0
DS/S
0.0
"" 0.0500
1.4389
1.9978
0.5045
0.0088
0.0
0.0
0.0
0.0
OV/V
0.0
0.0168
0.8595
2.13*3
0.9576
0.0298
O.D
0.0
0.0 '
0.0
3056.76
11.32
K)
to
-------
103
OP
.0042
.0075
.0133
.0237
" .0422
.0750
.1330
.2370
.4220
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0.0
0.0
4.4100
4.3700
3.2000
1.0750
0.1470
0.0
0.0
0.0" "
0.0
15
DIFFERENCE
0.0
0.0
0.428E 05
0.358E 06
0.210E 06
0.443E 05
0.346E 04 """"
0.0
0.0
o.o
oft'
0.
o.
171040.
1433016.
838610.
177248.
13853.
0.
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o.
*
658441. 25
DS
0.0
0.0
95.10 "
2522.11
4687.83 "'
--- 3137.29
770.24
0.0
0.0
0.0
s - --
ZB03.14
DV
0.0
0.0
0.210
9.988
32.957
" 39.172
17.040
0.0
0.0
0.0
-y -
24.84
" ON/N
0.0
o.o
0.2598
1.2736
0.2692
0.0213
0.0
0.0
0.0
os/s
0.0
0.0 "
0.0339
0.8997
1.6723
1.1192
0.2749
0.0
0.0
0.0
DV/V
0.0
0.0
0.0085
0.4021
1.3267
1.5769
0.6859
0.0
0.0
0.0
-------
103
OP
.00*2
.0075
.0133
.0237
.0422
.0750
.1330
.2370
.4220
.7500
45
AMP DIFFERENCE
0.0
3.5000
3.4400
3.4200
3.3000
2.2800"
0.7000
0.1100
0.0170
0.0
0.0
0.0
0.216E 06
0.214E 05
0.3676 05
0.101E 06
0.754E 05
0.139E 05
0.1 26E 04
0.132E 03
0.0
ON
0.
863046.
85522.
146976.
402533.
301780.
55602.
5044.
529.
0.
N
465257.00
OS
0.
152.
47.
25B.
2250.
5341.
3091.
887.
295.
0.
S
3081
0
76
55
68
16
50
45
80
77
0
.41
DV
0.0
0.191
0.105
1.024
15.820
66.693
68.390
35.159
20.794
0.0
V
52.04
-OKI7S- -
0.
l'
0.
0.
0.
0.
0.
0.
0.
0.
0
8550 "
1838
3159
8652 "
6486
1195
0108
0011 -
0
DS/S
0.0
0.0496
0.0154
0.0839
0.7302
1.7335
1.0033
0.2881
0.0960
0.0
DV/V
0.
o ;
0.
t).
0.
1.
1.
0.
0.
0.
0
0037
0020
0197
3040
2815
3141
6756
3995
0
-------
103
OP
.0042
.0075
.0133
.0237
'.0422'
.0750
.1330
.2370
.4220
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AMP
0.0
0.0
2.7000
2.6900
"" 2.6800
2.2400
0.8970
0.1500
' 0.0270
0.0030
0.0
75
" OIFFEREF
0.0
0.0
0.107E
0.306E
0.434E
'" 0.641E
0.1 76E
0.167E
0.187E
0.134E
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05
04
05
05
05
04
03
02
ON
0.
o-
42761.
12248.
173641;-
256513.
70397.
6672.
747.
54.
N
140758.13
OS
0.
DV
0
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23.
21.
970.
4540.
3914.
1174.
417.
94.
S
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78
56
66
28
09
19
56
75
.21
0
0
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0
..... 6
56
86
46
29
11
V
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.500
.356
.777
59.47
rON/N '
o.o
0.0
0.3038 "
0.0870
1.2336
1.8224
0.5001
0.0474
0.0053
0.0004
OS/S
0.0
0.0
0.0085
0.0077
0.3480
1.6278
1.4033
0.4210
0.1497
0.0340
OV/V
0.0
0.0
0.0009
0.0014
0.1148
0.9533 ~ ~
1.4560
0.7819
0.4936
0.1980
-------
104
OP
.0042
.0075
.0133
.0237
.0422
.0750
.1330
.2370
.4220
.7500
AMP
0.0
10.1700
10.1000
9.9200
6.7500
1.9490
0.2410
0.0020
0.0
0.0
0.0
5
DIFFERENCE ON
0.0
0.252E 06
0.192E 06
0.971E 06
0.474E 06
0.816E 05
0.563E 04
0.271E 02
"0.0 " ""
0.0
0.
1006876.
769661.
3882614.
1894666.
326228.
22523.
108.
0.
0.
N
1975673.00
DS
0.0
178.22
427.94
6833.40
10591.18
5774.23
1252.30
19.09
0.0
0.0
S
6269.09
DV
0.0
0.223
0.947
27.062
74.460
72.096
27.704
0.756
0.0
0.0
V
50.81
DN/N
0.0
0.5096
0.3896
1.9652
0.9590
0.1651
0.0114
0.0001
0.0
0.0
DS/S
0.0
0.0284
0.0683 "
1.0900
1.6B94
0.9211
0.1998
0.0030
--Q-.0
0.0
DV/V
0.0
0.3044
0.0186
0.5326
1.4654
1.4189
0.5452
0.0149
0.0
0.0
-------
10'
OP
.0042
.0075
.0133
.0237
.0422
.0750
.1330
.2370
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it
AMP
0.0
0.0
9.0800
8. 8900
8.6200
5.5600
1.5400
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0.0460
0.0050
o.o
15
"DIFFERENCE
0.0
0.0
0.203E 06
0.827E 05
0.302E 06
0.192E 06
0.302E Ob
0.286E 04
"' 0.319E 03 "
0.223E 02
ON
0.
0.
812442.
330695.
1207598.
767820.
120910.
11445.
1276.
89.
N
813068.00
DS
0.0
0.0
"*51.7Z"
582.02
6750.47
13590.41
6722.59
2014.26
713.33
157.92
S
7745.68
- - ovr
0.0
0.0
0.999
2.305
47.459
169.688
148.719
" 79.769
50,150
19.628
V
129.68
ON/N
0.0
0.0
0.9992
0.4067
1.4852
0.9443
0. 1487
0.0141
0.0016
0.0001
DS/S
0.0
0.0
0.0583
0.0751
0.8715
1.7546
0.8679
~ " ' 0.2600
0.0921"
0.0204
OV/V
0.0
0.0
0.0077
0.0178
0.3660
1.3085
1.1468
0.6151
0.3867
0.1514
-------
104
OP
.0042
.0075
.0133
.0237
.0*22
.0750
.1330
.2370
.*220
.7500
AMP
0.0
0.0
6.9200
6.9100
6.9000
6.5*00
3.6700
0.7650
0.1520
0.0*80
0.0200
45
DIFFERENCE
0.0
0.0
0.107E 05
0.306E 04
0.355E 05
0. 137E 06
0.684E 05
0.831E 0*
0.809E 03
0.125E 03
ON
0.
0.
42757.
12248.
142070.
548170.
273767.
33249.
3237.
500.
N
263999.00
OS
0.0
0.0
23.77
21.56
794.17
9702.61
15221.44
5851.84
1809.42
884.35
S
8577.29
DV
0.0
0.0
0.053
0.085
5.583
121.146
336.733
231.746
127.210
109.919
V
233.12
DN7tf -
0.0
0.0 ~
0.1620
0.0464
0.5381
2.0764 '
1.0370
0.1259
0.0123
0.0019
"DS/S
0.0
"0.0 "
0.0028" "
0.0025
0.0926
1.1312 "
1.7746
0.6822
0.2110
0.1031
DV/V ~
0.0
0.0
0.0002
0.0004
0.0240
0.5197
1.4445
0.99*1
0.5*57
O.*715
-------
104
OP
.0042
.0075
.0133
.0237
.0422
.0750
.1330
.2370
.4220
.7500
AMP "
0.0
5.8200
"' 5.7600
5.7500
5.7300
5.6200
3.8500
0.8820
0.1550
0.0400
0.0150
75
OIFFEREI
0.0
0.216E
0.107E
0.612E
0. 109E
0.845E
0.699E
0.986E
0.895E
0.112E
YCE
06
05
04 -
05
05
05 '
04
03
03
- ON '
o.
863046.
42757.
24497.
43410.
338070.
279704.
39432.
3579i"
446.
N
OS
0
_...- -152
23
43
242
5983
15551
6940
2000
789
5
.0
.76
.77
.66
.84
.55
.11
.80
.60
DV
0.0
0.191
0.053
0.171
1.706
74.713
344.036
"274.844
140.665
98.142
v
01
0
2
0
0
0
o
0
o
0
N/N
.0
.1115
.1046 "
.0599
.1062 "
.8271
.6843
.0965
.0088
.0011
-
os/s
0.0
0.0193
0.0030
0.0054
0.0306
0.7544
1.9606
0.8749
0.2522
0.0995
OV/V
0.0
0.0008
0.0002
0.3097
0.0073
0.3198
1.4726
1.1764
"0.6021
0.4201
-------
105
DP
.0042
.0075
.0133
.0237
.0422
.0750
.1330
.2370
.4220
.7500
" AMP ' "
0.0
10.4800
10.4700
10.0700
6.3600
1.6150
0.1570
0.0
0.0
0.0
5
DIFFERENCE
0.0
0.360E 05
0.428E 06
0.114E 07
0.468E 06
0.696E 05
0.370E 04
0.0
" 0.0
0.0
ON
0.
143843.
1710398.
4544008.
1872566.
278478.
14796.
0.
0.
0.
OS
0.0
25.46
950.98
7997.45
10467.64
4929.05
822.64
0.0
0.0
0.0
0V
0.0
0.032
2.104
31.672
73.592
61.544
18.199
0.0
O.D
0.0
DN/N
0.0
0.0672
0.7989
2.1224
0.8746
0.1301
0.0069
D.O
D.O
0.0
DS/S
0.0
0.0040
0.1510
1.2698
" " 1.6620
0.7826
0.1306
0.0
0.0
0.0
OV/V
0.0
0.0007
0.0450
0.6770
1.5730
1.3154
0.3890
0.0
0.0
0.0
0.0
N
2141021.00
s
6298.30
V
46.79
-------
105
DP
.0042
.0075
.0133
.0237
.0422
.0750
.1330
.2370
.4220
.7500
AMP
"(T.O
0.0
8.7800
8.5800
8.4200
5.4600
"1.6300
0.2790
0.05*0
~ 0.0080
0.0
15
DIFFERENCE
0.0
0.0
0.214E
0.490E
0.292E
0.183E
0.318E
0.305E
0.358E
0.357E
06
05
06
06
05
04
03
02
ON
0.
0.
855199.
195969.
1168134.
731530.
127318.
12204."
1432.
143.
N
DS
0.0
ovo"
475.49
344.91
" 6529.87
12948.07
7378.89
2147.90
800.32
252.67
S
DV
0.0
0.0
1.052
1.366
45.908
'" 161.668
156.601
85.062
56.266
31.405
V
'" ON/N
0
o
1
0
1
" 0
0
o
0
0
.0
.0
.1064
.2535
.5112
.9464
.1647
.0158
.0019
.0002
OS/S
0.0
o.o
0.0622
0.0451
0.8542
1.6938
0.9260
0.2810
0.1047
0.0331
OV/V
0.
0.
0.
0
0
0078
0.0131
0.3405
1.1990 ~
1.
0.
0.
1615
6309
4173
0.2329
772981.00
7644.53
134.83
-------
105 45
OP AMP DIFFERENCE DN OS
.0042 0.0 0.0 0. 0.0
.0075 0.0 0.0 0. 0.0
.0133 7.2000 0.118E 06 470363. 261.52
.0237 7.0900 0.612E 04 24495. 43.11
.0422 7.U700 0.345E 05 138124. 772.11
.0750 6.7200 0.146E 06 582550. 10311.13
.1330 3.6700 0.696E 05 278479. 15483.43
.2370 0.7150 0.782E 04 31296. 5508.18
.4220 0.1380 0.786E 03 3144. 1757.23
.7500 0.0370 0.937E 02 375. 663.26
0.0160
N 5
382206.00 8699.99
0V DN/N DS/S OV/V
0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0
0.579 1.2307 0.0301 0.0026
O.ltl 0.0641 0.0050 0.0008
5.428 0.3614 0.0887 0.0241
128.744 1.5242 1.1852 0.5712
342.529 0.7286 1.7797 1.5197
218.136 0.0819 0.6331 0.9678
123.540 0.0082 0.2020 0.5481
82.439 0.0010 0.0762 0.3658
V
225o39
to
t>
O
-------
105
OP AMP
.0042 0.0
.0075 5.6700
.Oi33 5.6400
.0237 5.6000
.0422 5.5900
.0750 5.4700
.1330 4.3400
.2370 1.2930
.4220 0.2610
.7500 0.0690
0.0250
75
DIFFERENCE ON OS 0V DN/N DS/S OV/V " "" "
0.0 0. 0.0 0.0 0.0 0.0 0.9
0.108E 06 431516. '" 76.38 0.095 1.4057 0.0088 0.0003 »
0.428E 05 171040." " ~ 95.10'"" 0.210 0.5572 0.0109 0.0007
0.306E 04 12248. 21.56 O.085 0.0399 0.0025 0.0003
0.118E 05 47357. 264.72 ~ "' ~ 1.861 0.1543 0.0304 0.0062 '"
0.540E 05 215830. 3820.19 "" "47.698 0.7031 0.4388 0.1589
0.718E 05 287149. 15965.50 353.193 0.9354 1.8338 1.1769
0.140E 05 55976. 9851.70 390.150 0.1823 1.1316 1.2996
0.149E 04 5976. ~ 3340.48 " 234.849 0.0195 0.3637 0.7823
0.196E 03 785. 1389.69 172.730 0.0026 0.1596 O.S753
N S V - -
306968.75 8706.32 300.22
. ' ro
NJ
o-
-------
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EPA Form 2220-1 (9-73) (Reverie)
-------
INSTRUCTIONS
1. REPORT NUMBER
Insert the EPA report number as it appears on the cover of the publication.
2. LEAVE BLANK
3. RECIPIENTS ACCESSION NUMBER
Reserved for use by each report recipient.
4. TITLE AND SUBTITLE
Title should indicate clearly and briefly the subject coverage of the report, and be displayed prominently. Set subtitle, if used, in smaller
type or otherwise subordinate it to main title. When a report is prepared in more than one volume, repeat the primary title, add volume
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5. REPORT DATE
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6. PERFORMING ORGANIZATION CODE
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7. AUTHOR(S)
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15. SUPPLEMENTARY NOTES
Enter information not included elsewhere but useful, such as: Prepared in cooperation with, Translation of, Presented at conference of,
To be published in, Supersedes, Supplements, etc. . ' . '
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Include a brief (200 words or less) factual summary of the most significant information contained in the report. If .the report contains a
significant bibliography or literature survey, mention it here. . .
17. KEY WORDS AND DOCUMENT ANALYSIS , '
(a) DESCRIPTORS - Select from the Thesaurus of Engineering and Scientific Terms the proper authorized terms that identify the major
concept of the research and are sufficiently specific and precise to be used as index entries for cataloging.
(b) IDENTIFIERS AND OPEN-'
ended terms written
ND OPEN-ENDED TERMS - Use identifiers for project names, code names, equipment designators, etc. Use open-
in descriptor form for those subjects for which no descriptor exists.
(c) COSATI FIELD GROUP - Field and group assignments are to be taken from the 1965 COSATI Subject Category List. Since the ma-
jority of documents are multidisciplinary in nature, the Primary Field/Group assignment(s) will be specific discipline, area of human
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22. PRICE
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EPA Form 2220-1 (9-73) (Reverse)
------- |