EPA-600/3-76-001
January 1976
Ecological Research Series
DYNAMIC BEHAVIOR OF
VINYL CHLORIDE IN AQUATIC ECOSYSTEMS
Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Athens, Georgia 30601
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:
1. Environmental Health Effects Research
2, Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal
species, and materials. Problems are assessed for their long- and short-term
influences. Investigations include formation, transport, and pathway studies to
determine the fate of pollutants and their effects. This work provides the technical
basis for setting standards to minimize undesirable changes in living organisms
in the aquatic, terrestrial, and atmospheric environments.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/3-76-001
January 1976
DYNAMIC BEHAVIOR OF VINYL CHLORIDE
IN AQUATIC ECOSYSTEMS
by
James Hill IV, Heinz P. Kollig,
Doris P. Paris, N. Lee Wolfe,
and Richard G. Zepp
Environmental Research Laboratory
U.S. Environmental Protection Agency
Athens, Georgia 30601
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
ENVIRONMENTAL RESEARCH LABORATORY
ATHENS, GEORGIA 30601
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DISCLAIMER
This report has been reviewed by the Environmental
Research Laboratory, U.S. Environmental Protection Agency,
and approved for publication. Mention of trade names or
commercial products does not constitute endorsement or
recommendation for use.
11
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ABSTRACT
To evaluate the behavior of vinyl chloride in aquatic
ecosystems, best estimate and worst case Models of lake and
stream ecosystems were analyzed through the use of
mathematical simulation* The characteristics of the
chemical, biological, and physical transformations of vinyl
chloride indicated in the models were determined by
laboratory experimentation and extrapolation of reaction
data for similar compounds* These transformations included
oxidation, substitution, elimination, hydrolysis, and free
radical reactions; complexation; direct and indirect
photochemical reactions; microbial degradation and toxicity;
bacterial, algal, and fungal sorption; and volatilization*
Loss of vinyl chloride from the aquatic environment by
volatilization appeared to be the most significant process
in its distribution*
This report was submitted in fulfillment of ROAP 04AEM,
Tasks 005 and 009, and ROAP 03ACQ, Task 009, at the
Environmental Research Laboratory! Athens, Georgia* Work
was completed as of September 1975*
ill
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CONTENTS
I Conclusions and Recommendations 1
II Introduction 3
III System Analysis 7
Assumptions 9
Results and Discussion 16
IV Chemical Interactions 33
Materials and Methods 34
Results and Discussion 36
pH Studies 36
Oxidation Studies 36
Natural Waters 38
Complexation 38
V Photochemical Interactions 41
Materials and Methods 43
Results and Discussion 44
Direct Photolysis 44
Indirect Photolysis 45
VI Microbiological Interactions 48
Materials and Methods 48
Results and Discussion 51
Sorption to Microorganisms 51
Bacterial Degradation 52
Toxicity to Bacteria 53
VII Physical Interactions 54
Materials and Methods 55
Results and Discussion 55
VIII References 50
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FIGURES
1 Composite representation of the analysis 4
procedures
2 Initial conceptual model of vinyl chloride 5
interactions in an aquatic environment
3 Working conceptual model of vinyl chloride 8
interactions in an aquatic system
4 Best estimate model of vinyl chloride in the 10
aquatic environment
5 System model with worst case chemical and 11
biological transformation reaction rates
6 System model of vinyl chloride in stratified 12
lake with a simple idealized food web
7 Lake simulation with best estimate model 17
8 Stream simulation with best estimate model 18
9 Lake simulation of the model of Figure 5 19
10 Stream simulation of the model of Figure 5 20
11-14 Stratified lake simulation of the model in 21-24
Figure 6
15-18 Stratified lake model's response to pulse 26-29
input of vinyl chloride to epilimnion water
19-21 Stratified lake model's response to pulse 30-32
input of vinyl chloride to sediments
22 Vinyl chloride reaction vessel 35
23 Pathways for light induced decomposition of 42
vinyl chloride
24 Decomposition of vinyl chloride in water by 47
VI
-------
attack of free radicals generated by photolysis
(300 am) of hydrogen peroxide
25 Apparatus for vinyl chloride degradation and 49
toxicity studies
26 KVCM versus Kn a* *our mixing levels 58
VII
-------
TABLES
Mm.
1 Worst case model parameters 15
2 Order of magnitude estimates for half-lives 37
for vinyl chloride reactions
3 Equilibrium constants for some compounds 40
structurally related to vinyl chloride
4 Rate coefficients for oxygen and vinyl chloride 57
gas exchange at four mixing levels
Vlll
-------
ACKNOWLEDGEMENTS
The authors gratefully acknowledge the contributions of
their colleagues* John T. Barnettf David !.• Lewis* and Bill
ifaca* Helpful and constructive content vas received fron
Say R« Lassiter* James W. Falcot and George L. Baughnan*
The efforts of Shirley H. Hercules in editing and Anne
L* Warner and Carlyn B« Haley in typing are sincerely
apprec iat ed»
IX
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SECTION I
CONCLUSIONS AND RECOMMENDATIONS
A worst case system analysis of vinyl chloride behavior
in aquatic systems suggests that unrealistically high levels
of vinyl chloride inputs would be necessary to maintain
significant concentrations in these systems. However* given
extreme environmental conditions* aquatic sediments could
exhibit long-term storage of low levels of vinyl chloride*
Chemical degradation of vinyl chloride under pH*s*
reactant concentrations* and temperatures common to the
environment should not be significant* Neither auto-
oxidation nor degradation by free radicals is important in
most natural waters at low vinyl chloride concentrations*
Increased persistence of vinyl chloride due to complexation
with Ag* and Cu* should be minimal* Data are not available
for consideration of other metal species*
Experiments with distilled water* water from the efflu-
ent of a PVC plant* and two natural waters indicate that
photolysis of vinyl chloride is probably a slow process
under environmental conditions*
Vinyl chloride does not appear to be sorbed by
microorganisms* as indicated by laboratory experiments with
five mixed bacterial populations* three mixed fungal
populations* two axenic bacterial cultures* and one alga*
The five mixed bacterial populations did not degrade the
vinyl chloride to any detectable extent* Also* at vinyl
chloride concentrations up to 900 mg l~l» no toxic effects
on the bacterial cultures could be detected*
The rate of bulk exchange of gaseous vinyl chloride bet-
ween atmosphere and water is about twice that of oxygen*
Loss of vinyl chloride by volatilization from water is
therefore probably the most significant process in its
distribution*
The assumptions and consequently the conclusions of this
analysis may be invalid when vinyl chloride enters a re-
ceiving water as a component of a tar or sludge or when
large concentrations of surface active agents are present
with the vinyl chloride in water* Further study is neces-
sary for specific situations where these conditions exist*
-------
The reactions of vinyl chloride with chlorine and hypo-
chlorous acid should be studied under conditions that pre-
vail in the chlorination processes of municipal water treat-
ment plants* Alsot the reactions o± organics that may form
vinyl chloride under these conditions should be studied*
-------
SECTION II
INTRODUCTION
Vinyl chloride (CH2 = CHCl)f a colorless, highly flam-
mable gas, is used primarily in -the production of the resin,
polyvlnylchloride (PVC)* The PVC is then used in the manu-
facture of many synthetic plastics and rubbers* Vinyl
chloride monomer (VCM) is therefore present in many
manufacturing operations and, because water is used as a
medium in the polymerization reaction, it is also a possible
contaminant of waste water discharged from these plants*
In recent studies, chronic exposure to VCM has resulted
in liver injury to laboratory rats and rabbits* Also, some
workers in PVC plants have contracted angiosarcoma of the
liver (1)* Because of its possible harmful effects on
humans and other living organisms and the ubiquitous nature
of vinyl chloride in the manufacturing industry, the behav-
ior of VCM in aquatic ecosystems has come under critical
study*
/
The present study was undertaken to investigate the be-
havior of vinyl chloride in aquatic systems under conditions
simulating large inputs of VCM from industrial sources* The
study involved the use of a conceptual model of vinyl
chloride interactions in aquatic systems; physical,
chemical, and biological experiments with vinyl chloride;
mathematical models; and system analysis* The relationships
among the various facets of the study are represented in the
diagram in Figure 1*
The physical, chemical, and biological interactions of
vinyl chloride with the components of aquatic systems deter-
mine the behavior of vinyl chloride in the system* The
individual interactions can be characterized quantitatively
by laboratory experimentation and the behavior of VCM within
an aquatic system can be approximated by simulation of a
system model* An initial conceptual model of the
interactions of vinyl chloride in an aquatic environment,
developed as described by Gillett et al* (2) is represented
by the compartment diagram in Figure 2* In the diagram the
boxes represent storage of vinyl chloride or its reaction
products and the arrows represent transport or
transformation processes*
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Conceptual Models of
Vinyl Chloride Interactions
in Aquatic Ecosystems
Model Structure
Mathematical Models of
Vinyl Chloride Behavior
I
Simulation
System Analysis of
Mathematical Models
Quantitative
Interactions
Qualitative
Interactions
Model Parameters
Chemical, Biological, and
Physical Experiments
Mechanistic Behavior
Holistic Behavior
Results and Conclusions
Figure !• Composite representation of the analysis
procedures*
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Elimination Reaction
Products
Hydrolysis Reaction
Products
INPUT
Free Radical
Reaction Products
Vinyl Chloride in Atmosphere
Vinyl Chloride in Water
Vinyl Chloride
Sorbed on Participates
Vinyl Chloride
in Sediments
OUTPUT
Direct Photochemical
Reaction Products
Indirect Photochemical
Reaction Products
Microbial Degradation
Products
Vinyl Chloride in Food
Web Organisms
Figure 2. Initial conceptual model of vinyl chloride
interactions in an a
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A system analysis based upon the conceptual model was
used to estimate the behavior of vinyl chloride In aquatic
systems under both typical ("best estimate") and extreme
("worst case") conditions* The rates of the various
possible transport and transformation processes were
determined in the laboratory*
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SECTION III
SYSTEM ANALYSIS
For the purposes of the present study the behavior of
vinyl chloride in an aquatic system may be assumed to be a
function of four aspects of the system:
• the components of the system with which vinyl chlo-
ride may associate or react (£.*&•* water, organisms)
other chemical species);
• the interactions or coupling pathways among these
components;
• the characteristics of the interactions (£,*£*, magni-
tude* rate, saturation); and
• the rates of vinyl chloride inputs to the system*
The conceptual model of Figure 2 was used to organize
the. facts and assumptions into an initial system hypothesis
as described by Gillett et al* (2). This model represents
the components and interaction pathways considered to be
important in a study of vinyl chloride in an aquatic system*
This initial conceptual model was transformed to the
conceptual model of Figure 3 through consideration of pre-
liminary studies of vinyl chloride (3), available data on
vinyl chloride and analogous compounds, and constraints on
the scope of the investigation,as defined by the nature of
the problem*
The working conceptual model (Figure 3) indicated the
need for quantitative characterization of the chemical, bio-
logical, and physical interactions between the components*
The transport process dynamics have been evaluated in pub-
lished descriptions of the behavior of the transport media
(£•£*, particle, fluid, and trophic dynamics)* The
transformation process dynamics were evaluated by chemical,
biological, and physical experimentation*
The qualitative conceptual model (Figure 3) and the
associated quantitative interaction descriptions can be
logically reduced or expanded to provide a hierarchy of
system models* These system models can be represented
mathematically and evaluated by simulation to provide
descriptions of vinyl chloride behavior at various levels of
abstraction or generality*
-------
Products
Free Radical Reaction
Products
Direct Photochemical
Reaction Products
Indirect Photochemical
Reaction Products
Microbial Degradation
Products
Coordination Complexes
INPUT
Vinyl Chloride
in Atmosphere
Elimination Reaction
Products
Hydrolysis Reaction
1-
1
OUTPUT
Surface Active Agents
Vinyl Chloride in Water
Vinyl Chloride
Sorbed on Particulates
Sediments
Vinyl Chloride
in Bacteria
Vinyl Chloride in Algae
I
Vinyl Chloride
in Filter Feeders
I
Vinyl Chloride
1
ide in
ts
\
in Predators
Vinyl Chloride in
Danthif* FpPflPr^
Figure 3* Working conceptual model of vinyl chloride
interactions in an aquatic system*
-------
The quantitative aspects of the possible behavior of
vinyl chloride in aquatic systems may be approximated by
simulation and analysis of a system model of a sample lake
and stream* The conclusions resulting from these
hypothesesf howeverf are only as good as the assumptions
made in their formulation* These assumptions may be changed
to Incorporate new information or to apply the analysis to a
particular aquatic system*
ASSUMPTIONS
The most significant assumption in this type of analysis
is the model itself* The choices of components and their
couplings represent a mixture of logical analysis, physical
intuition, and personal biases* These choices affect the
parameters, inputs, outputs, and responses of the model*
A best estimate approximation of the behavior of vinyl
chloride in a sample lake or stream was obtained assuming
the most reasonable estimates of the rates of transformation
processes as determined from laboratory results*
Experiments indicated that rates for all processes except
volatilization are essentially zero (Section IV, V, VI, and
VII)* This assumption results in the simplified model of
Figure 4*
To evaluate the boundaries of possible vinyl chloride
behavior, two additional system models were derived
describing extreme behavior at two levels of resolution* In
these worst case analyses, all chemical and biological
transformation processes were assumed to proceed at a rate
that is Just below the level of measurement in the
experimental procedures used for their determination*
Conditions in the aquatic environment (£.*£*• turbulence,
stratification, sediment scouring) were assumed to be at the
extreme of the environmentally realistic range that would
cause worst case system responses* The system models of
Figures 5 and 6 were analyzed subject to these worst case
assumptions*
A set of linear, first-order ordinary differential
equations was assumed to be a reasonable mathematical appro-
ximation of the dynamic behavior of vinyl chloride in the
hypothesized structures* This is Justified by recourse to
the theory of linearization about an operating path (4) and
assumes that vinyl chloride input represents a small system
perturbation*
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Vinyl Chloride
in Atmosphere
T
a
1,2
INPUT.
Vinyl Chloride
in Water
OUTPUT
Figure 4« Best estimate model of vinyl chloride in the
aquatic environment*
10
-------
Vinyl Chloride
in Atmosphere
INPUT
Vinyl Chloride
in Water
1
a3,2
OUTPUT
Chemical and Biological
Reaction Products in Water
OUTPUT
Figure 5. System model with worst case chemical and
biological transformation reaction rates*
11
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"8.3
I
"3
Chemical and Biological
Reaction Products in Water
Chemical and Biological
Reaction Products in Water
Vinyl Chloride
in Atmosphere
1
Vinyl Chloride in
Benthic Organisms
Vinyl Chloride in
Filter Feeding Organsims
Vinyl Chloride in
Filter Feeding Organisms
1
"9.1
'10.6
Vinyl Chloride in
Predator Organisms
a10.9
"10.7
Vinyl Chloride in
Omnivorous Organsims
fls.9
«5.7
Figure 6. System model o± vinyl chloride in stratified
lake with a simple idealized food web*
12
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The system diagrams of Figures 4 through 6 therefore
were directly translated to a set of equations that can be
written in vector form as
• » AX + BU (1)
at
where the x^ represent the variable quantities stored in the
boxes; the a^^ represent the rate coefficients for transfer
from box J to box i; and the u.. represent the inputs to box
i.
The typical or sample lake is assumed to be 10* m2 and
10 m deep* It has a residence time of 10 days and strati-
fies in summer with a metalimnion 0*5 m wide centered at a
5—meter depth* It is completely mixed above and below the
thermocline when stratified and completely mixed otherwise*
The typical or sample stream parameters were derived from
Tsivoglou and Wallace's (5) data on the Chattahoochee and
Jackson rivers*
For the best estimate modelt equation (1) reduces to
dx
L = a x + u (2)
dt »,2 2 i
The rate coefficient value, e-i ,21 of the best estimate model
of the lake is a bulk gas exchange coefficient between water
and atmosphere of 0*436 day"1 (6t Section VII of this
report)• The input was set at 1 mg I'1 vinyl chloride in
the influent water as a reference value*
The gas exchange coefficient* a1)2t in the best estimate
stream model is 0.96 clay"1 (5, Section VI of this report),
and the input is again 1 mg I'1 vinyl chloride*
13
-------
The worst case model was analyzed using values for a^j
listed in Table 1. It should be noted that these are
extreae values and would not be expected to apply in a
typical lake or stream* The values for each of the
coefficients were chosen as described*
• a-i ,2 — as discussed for best estimate model.
• a3 2 and an 4 — represent the combined effects of
the hypothesized chemical and biological reaction
pathways for vinyl chloride in water* Values were
determined either by assuming that the reaction
occurred at a rate immediately below the level of
detection or by extrapolating laboratory conditions
to their extreme analog in the aquatic environment*
• a* 2 and a2 « — are the results of an approximation
for eddy current transport across a thermocline,
which was extrapolated to the hypothetical lake
morphology (7)*
• a6,2» *7,4t and aa s —— were based upon the fraction
of the lower trophic level biomass assumed to be
assimilated per year (8)*
* &9,6t *9,7t and a.9 s ~~ were based on the trophic
level assumption used for a6 2t a? 4» and as s and
the assumption of an evenly distributed food
preference•
* aio,6» aio,7? and ato a ~~~ were based on the trophic
level assumption used for a« zi a7 *t and a8 s and an
evenly distributed food preference*
* as,6f as,7t as, a» and a.s,9 ~~~ were based upon an
average 10—day turnover time and a population loss of
90% of ingested material averaged over a year (8 )•
* as»* ~~~ assumes an average settling rate for particu—
lates of 0*1 cm sec"1 (7) and diffusion-limited
transport in unmixed interstitial waters with an
effective surface fraction of 0*38 for several sizes
of closely—packed spheres* The diffusion coefficient
for vinyl chloride was estimated from the diffusion
coefficient for oxygen and the ratio of gas exchange
coefficients (9)*
• a*, s ~~ assumes diffusion limited transport and no
scouring of sediments*
The sorption of vinyl chloride onto particulates was
assumed to be reversible and very fast so that an
equilibrium with a K =10 (see Section VI) was maintained.
The concentration of organic particulates was taken as
constant (.!.•£• t input = output) at 1*66 rag I'1 (7)*
14
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Table 1. WORST CASE MODEL PARAMETERS
Svmbql
.Interactions
Value <
ai,2
a3,2
an,*
a*,2
a6,2
as, s
, 61 a9, 7
a
aio, 6*
as, 6* as, 7
as, 8 ! as^ 9
as, 4
a*,s
Ji*
Volatilization of vinyl
chloride
Chemical and biological
degradation
Chemical and biological
degradation
Transport across theraocline
Transport across thermocline
Uptake by filter feeding
organisms
Uptake by filter feeding
organisms
Uptake by benthic organisms
Uptake by predator
Uptake by omnivore
Turnover rate of organisms
Water to sediment transport
Sediment to water transport
Loss from compartment
Input to water
Input to water
0.436
0.115
0.115
0.0178
0.0178
0.000292
0.000292
0.000292
9.73 (10~s)
7.3 (10~5)
0.1
0.107 (10~2)
3.45 (10"*)
I
•j aJi
1 ppm
15
-------
Complexation of vinyl chloride with silver or copper was
assumed to be negligible since typical Cu+ and Ag* concen-
trations in aquatic systems are less than 30 rag m 3f as much
as 80% of which is adsorbed onto organic colloids (7). In
addition* complexation would probably be very rapid and
reversible* Finally, the concentration o± vinyl chloride in
the air above the water was assumed to be maintained at
essentially zero by surface replacement*
RESULTS AND DISCUSSION
The concentration of vinyl chloride in the water and the
cumulative loss to the air for the best estimate model
(Figure 4) of the sample lake are shown in Figure 7* These
results are for a vinyl chloride input of 1 mg I"1 and a
fractional input of 10% of the total water volume* A
similar result for a volume of water in the sample stream as
it travels downstream is indicated in Figure 8* These
results indicate that with a volume input of 10% water per
day containing 1 mg l~l vinyl chloride, the concentration of
vinyl chloride in the sample stream and lake would be less
than 0*2 mg I"1.
If the chemical and biological reaction pathways with
worst case rates are added to the preceding examples (Figure
5), the resultant distribution of vinyl chloride is as
indicated in Figures 9 and 10* It should be noted that in
this worst case no losses of degradation products other than
washout or dilution are postulated* Even so* the
degradation products reach a steady—state concentration
below 0.3 mg I"1.
The behavior of vinyl chloride in the worst case model
of Figure 6, which represents a stratified lake with a
simplistic food web, is indicated in the graphs of Figures
11 through 14* The results are self-explanatory except for
the concentrations in sediments and benthic organisms* The
assumptions of diffusion—limited exchange between water and
unmixed lower sediment layers and of lack of scour dictate a
relatively long half—life for vinyl chloride in the
sediment—benthic organism-predator—orainivore cycle ( tu = 3
yr )• With these assumptions the vinyl chloride
concentration in the sediment approaches a steady—state
value of 0*358 mg I'1 in about 15 years* The vinyl chloride
in benthic organisms reaches a steady—state value of 0*013
mg l~* in the same time period while the concentrations in
other organisms are less*
16
-------
0.662
0.331 -
Vinyl Chloride in Water
Vinyl Chloride in Air
TIME, days
Figure 7« Lake simulation with best estimate model*
17
-------
Vinyl Chloride in Water
Vinyl Chloride in Air
0.896
0.448
o
5
TIME, days
/
10
Figure 8. Stream simulation with best estimate model.
18
-------
Vinyl Chloride in Water
Vinyl Chloride
Degradation Products
0.274
25
TIME, days
50
Figure 9. Lake simulation of the model of Figure 5.
19
-------
Vinyl Chloride in Water
Vinyl Chloride
Degradation Products
9.68
S
X
o
__l
25
TIME, days
50
Figure 10. Stream simulation of the model of Figure 5.
20
-------
Vinyl Chloride in Epilimnion
• — Vinyl Chloride Degradation
Products in Epilimnion
Vinyl Chloride in Sediments
0.176
*>
UJ
o
I
o
•z.
0.0879
0
100
TIME, days
200
Figure 11• Stratified lake simulation of the model in
Figure 6.
21
-------
Vinyl Chloride in Hypolimnion
Vinyl Chloride Degradation
Products in Hypolimnion
13.50
V \
0
25
TIME, days
5(
Figure 12. Stratified lake simulation of the model in
F i gure 6•
22
-------
Vinyl Chloride in Filter
Feeding Organisms
(Hypolimnion)
Vinyl Chloride in
Predator Organisms
Vinyl Chloride in
Omnivorous Organisms
0
25
TIME, days
Figure 13* Stratified lake simulation of the model in
Figure 6«
23
-------
Vinyl Chloride in Filter
Feeding Organisms
(Epilimnion)
Vinyl Chloride in
Benthic Organisms
6.59
O
i—I
X
2 3.29
g
n:
o
0
25
TIME, days
50
Figure 14. Stratified lake simulation of the model in
Figure 6.
24
-------
A diagnostic input consisting of a pulse o± vinyl chlo-
ride can produce a characteristic response for each compon-
ent* This response is a very concise way of demonstrating
the behavior predicted by the system hypothesis* The total
response to a pulse input contains all the information
necessary to characterize the system (10)* Figures 15
through 17 show the component responses to a pulse input of
1 mg I"1 vinyl chloride to the epilimnion waters for the
model of Figure 6* In Figure 18, the beginning of the slow
loss of vinyl chloride from the sediments can be seen after
about 60 days*
The results of a pulse input of 1 mg I"1 vinyl chloride
to the sediments are shown in Figures 19 through 21* The
slow but continuous loss of vinyl chloride from the
sediments is evident* This loss occurs to the air (rate - 7
x 10"6 mg l~l day"1 ) and to downstream waters (rate = 3.9 x
10~* mg I"1 day"1 ).
All of the results assume steady—state levels of biomass
components and particulates and do not include any low level
toxic effects or biomagnification (i»e», selective retention
of vinyl chloride )• From the results of these model
simulations it appears that vinyl chloride should not remain
in an ao;uatic ecosystem under most natural conditions*
25
-------
Vinyl Chloride in
Epilimnion Water
Vinyl Chloride Reaction
Products in Epilimnion
Water
1.0
3 0.5
31
O
_i
25
TIME, days
50
Figure 15« Stratified lake model's response to pulse input
of vinyl chloride to epilimnion water.
26
-------
Vinyl Chloride in Filter Feeding
Organisms (Hypolimnion)
Vinyl Chloride in Benthic
Organisms
Vinyl Chloride in Predator
Organisms
Vinyl Chloride in Omnivorous
Organisms
25
TIME, days
Figure 16* Stratified lake model's response to pulse input
of vinyl chloride to epilimnion water*
27
-------
Vinyl Chloride in Hypolimnion
Water
Vinyl Chloride in Sediments
Vinyl Chloride Reaction
Products in Hypolimnion
Water
Vinyl Chloride in Filter
Feeding Organisms
(Epilimnion)
25
TIME, days
50
Figure 17. Stratified lake model*s response to pulse input
of vinyl chloride to epllimnion water*
28
-------
Vinyl Chloride in Sediments
(Extended Time Scale)
50
TIME, days
100
Figure 18* Stratified: lake model's response to pulse Input
o~f vinyl chloride to epiliranlon water*
29
-------
Vinyl Chloride in Sediments
1.000
0
50
TIME, days
100
Figure 19* Stratified lake model's response to pulse input
of vinyl chloride to sediments*
30
-------
Vinyl Chloride in Hypolimnion
Water
Vinyl Chloride in Benthic
Organisms
Vinyl Chloride in Filter
Feeding Organisms
(Hypolimnion)
c.ou
CT>
s
X
LU
21.43
o
o
1
^J
0
s"~ 1 ""
/
/
/
_ / _
/
/
/
i
) 50 10
TIME, days
Figure 20. Stratified lake model's response to pulse input
of vinyl chloride to sediments.
31
-------
Vinyl Chloride in Eplimnion
Water
——— Vinyl Chloride in Atmosphere
1O.V
ir\ "
O
X
LU
|8.43
3
•^P»
j_
o
0
(
1 /
•//
/
/
^^m J
/
/
,
^ 1
) 50 10
TIME, days
Figure 21* Stratified lake model's response to pulse input
of vinyl chloride to sediments*
32
-------
SECTION IV
CHEMICAL INTERACTIONS
No reference to studies of the degradation of vinyl
chloride in water could be found in the literature.
However* considerable data are available concerning the
chemistry of vinyl chloride and related compounds that can
be extrapolated to reaction conditions anticipated in the
environment. Evidence supporting such extrapolations was
obtained in a few preliminary experiments*
Four pathways were postulated as potential mechanisms
for chemical degradation or alteration of vinyl chloride in
the environment: substitution (ll)t elimination (12),
addition (13), and oxidation (14).
In nucleophilic substitution, the chloride ion is
displaced by a nucleophilic species (Nu) (11). Reactive
nucleophiles common to the aquatic environment are amines,
thiols, water, and hydroxide ion. The reaction can be
either first or second order depending on the specific
mechanism.
The most probable elimination reaction in the
environment is one in which hydrogen chloride is eliminated
from vinyl chloride in the presence of base, producing
acetylene (12 )• This is a second—order reaction and the
rate is dependent upon the concentrations of both vinyl
chloride and base. The most significant base present in
natural water would be hydroxide ion:
H H
\ = CX Base HC=CH +
/ \
H Cl
The addition reaction most likely to occur to vinyl
chloride in the aquatic environment is the addition of water
across the carbon-carbon double bond, catalyzed by acid
(13).
33
-------
H H
\ X H+
C = C —2—>
X \ H20
H CI
H OH
I I
H-C-C-H
I I
H Cl
0
II
CH -C-H
This reaction is second order with its rate dependent upon
concentrations of both vinyl chloride and acid*
Based on kinetic studies in mixed systems, only a few
oxidative processes are potentially important for vinyl
chloride in the environment (14)* Autooxidation (with
molecular oxygen) (16) is a possibility; but since its rate
is dependent upon the rate of homolytic cleavage of the
strong carbon—hydrogen bond, the rate of oxidation of vinyl
chloride would be slow*
Free radicals are anticipated to react with the carbon-
carbon double bond (14), resulting in oxidation* However,
since literature data are not available to evaluate the role
of free radicals in natural waters, extrapolation of
laboratory data to natural waters is tenuous*
The reactivity of vinyl chloride was studied, and known
structure—reactivity relationships and activation parameters
were used to evaluate the significance of the above pathways
for vinyl chloride disappearance in the environment*
MATERIALS AND METHODS
Vinyl chloride was obtained from Matheson Chemical
Company and used as received* Distilled water was used in
all experiments except for natural water studies* The
Oconee River water sample was obtained in Athens, Georgia,
and filtered through a 0.22-y filter prior to use ( pH 6*1)*
The Okefenokee Swamp water sample was obtained at Kingfisher
Landing, Okefenokee Swamp, Georgia, and was used as obtained
(pH 4*2)* Hydrogen peroxide was purchased from Baker
Chemical Company*
A special reaction vessel (Figure 22) designed to
eliminate volatilization, was made for these studies*
34
-------
SEPTUM
TEFLON STOPCOCK
INSIDE DIAMETER 6 MM
VOLUME APPROX. 2.9 ML
Figure 22* Vinyl chloride reaction vessel*
35
-------
The vessel was filled to the top with water and 20 ml of
vinyl chloride was added* The filled vessel was placed in a
constant temperature bath (+ 2°C ) and removed at recorded
intervals for analysis* The concentration of vinyl chloride
at each time interval was determined by comparison of glc
peak heights using a vinyl chloride-carbon tetrachloride
standard solution* Experimental error was determined to be
± 10%.
Glc analysis was carried out on a Tracor Microtech 220
Gas Chromatograph fitted with a 3 m x 0*63 cm column packed
with 0.4% Carbowax 1500 on Carbopack; injection, column, and
detector temperatures were 210°C, 40°C, and 210°C,
respectively*
RESULTS AND DISCUSSION
oH Studies
In reaction mixtures at pH 3*0 (HCl), 7.0. and 11.0
(NaOH) at 85°C, no reaction could be detected after 27
hours. Extrapolation of data, assuming hydrolysis,
elimination, addition* or substitution mechanisms, indicates
that these reactions would have half—lives on the order of
years.
Literature information was used to estimate half—lives
for several possible reactions of vinyl chloride under
environmental reaction conditions (Table 2)* The estimated
half—lives were in good agreement with our experimental
data* In view of these half—lives, any contribution to the
disappearance of vinyl chloride by chemical degradation via
these pathways normally would not be significant since other
processes are faster.
In environments like municipal water chlorination
facilities, however, high concentrations of chlorine would
exist* Based on the reactivity of carbon—carbon double
bonds with chlorine and hypohalous acid, under such
conditions vinyl chloride may be converted to more highly
chlorinated compounds*
Oxidation Studies
The reactivity of vinyl chloride with molecular oxygen
was also investigated. Experiments were carried out at 20
36
-------
Table 2. ORDER OF MAGNITUDE ESTIMATES FOR HALF-LIVES
FOR VINYL CHLORIDE REACTIONS
Reactior^
Elimination3
Substitution1*
Addition0
Additiond
Addition6
Hydrolvsis
Li terature data
Temp*
C °C»
95.53
130
25
25
25
120
Reactant
Methoxide
C2H5S-
H2O
C12
HOCl
H7O
Maximum rate
constant M * sec~*
10~7
10~9
10~*
10~*
10~2
No RX
Estimated t,
at *
25°C8
<10 yr
<10 yr
<1 yr
140 hr
1000 hr
<10 vr
^Reference 17t methanol solvent, 10 3M methoxide.
Reference 18, reaction of 1— chloropropene in ethanol at 1 x 10~~3M
thiol.
f*
Reference 19, acid catalyzed hydration at pH 3.
Reference 20, 1,3,3—trichloropropene in aqueous acetic acid——1 mg I"1
chlorine*
eReference 21, hypohalous acid addition to allyl alcohol at pH 4*5
1 mg I"1 hypohalous acid*
Reference 15*
&Calculated assuming pseudo first—order kinetics*
-------
mg I * vinyl chloride in water saturated with molecular
oxygen at elevated temperatures* After 12 hours at 85°C, no
degradation of the vinyl chloride could be detected* At
temperatures and oxygen concentrations in natural waters,
therefore* vinyl chloride will not be degraded by molecular
oxygen at a significant rate*
As anticipated* at elevated temperatures vinyl chloride
was degraded by hydrogen peroxide* At 85°C hydrogen
peroxide decomposes to give hydroxy radicals (HO*), which
react with vinyl chloride* With 1 x 10~2 M hydrogen
peroxide and 1 x 10~* M vinyl chloride, the reaction obeys
zero-order kinetics, indicating that decomposition of
hydrogen peroxide is the rate—determining step*
The significance of this reaction pathway is difficult
to assess because no data are available concerning the
concentration and species of free radicals in natural
waters* These experiments do indicate that if reactive
radicals were present in natural waters at significant
concentrations, they may potentially degrade vinyl chloride*
Natural Waters
Vinyl chloride was shown to be chemically stable in two
natural water samples* No degradation could be detected in
Oconee River water (pH 6*1) and Okefenokee Swamp water (pH
4*2) after 41 hours at room temperature and at 85°C*
Assuming the pathways previously discussed, extrapolation of
the elevated temperature data to environmental conditions
would indicate a minimum half—life of at least one year*
Although only two representative water samples were
employed, the results obtained are in agreement with
behavior predicted based on known chemical reactivity of
vinyl chloride*
Comolexation
To study the effect of complexatlon with metal ions on
the persistence of vinyl chloride in water, three important
points should be considered:
• How strong are the complexes?
• What are the concentrations of the metal species?
• What are the concentrations of the competing ligands?
38
-------
A survey o± the literature did not disclose any equilibrium
constants for the formation of coordinate complexes between
vinyl chloride and metal ions* However* data for the
formation of complexes between structurally related olefinic
compounds and Ag+ and Cu+ (Table 3) indicate that electron-
withdrawing groups attached to the double—bonded carbon atom
of the olefin decrease the equilibrium constant* Assuming a
concentration of 10 mg I"1 for the silver—ethylene complex*
equilibrium calculations show the complex to be greater than
99% dissociated* Similarly* the cuprous—/9—chloro—allyl
alcohol complex at 6*2 mg l~* is also greater than 99%
dissociated* The effect of other ligands common to the
aquatic environmentt which would be competing for the metal
ions* are neglected in these calculations* Thus we conclude
that at low metal ion and vinyl chloride ion concentrations*
complexatlon by these metal ions is not important*
39
-------
Table 3. EQUILIBRIUM CONSTANTS FOR SOME COMPOUNDS
STRUCTURALLY RELATED TO VINYL CHLORIDE3
Olefin (L)
Ethylene
Trans— dichlo roet hylene
Cis— dichloroethylene
Allyl alcohol
Allyl alcohol
ft— chloroallyl alcohol
Metal CM)
Ag+
Ag+
Ag+
Ag+
Cu*
Cu*
I OB k
1.93b
-0.509C
-0.796C
1.15d
4.72e
1.34e
where L = number of Uganda present«
^Reference 22*
cReference 23*
^Reference 24*
eReferencc 25.
40
-------
SECTION V
PHOTOCHEMICAL INTERACTIONS
Several possible mechanisms exist for the decomposition
of vinyl chloride by light (Figure 23). Mechanism I, direct
photolysis* involves direct absorption of light by vinyl
chloride followed by reaction from its excited state (VCM)*.
Several studies have indicated that vinyl chloride in the
vapor phase decomposes when irradiated with very short
wavelength ultraviolet light « 200 nm) (20f 27, 28). The
primary reaction processes are homolysis of the carbon-
chlorine bond yielding a chlorine atom and elimination of
molecular HCl. Twisting around the double bond* an
undetectable reaction* may also occur.
Mechanism II* photosensitized reaction via energy
transfer* involves absorption of light by a triplet
sensitizer followed by energy transfer to vinyl chloride to
form its first excited triplet state* (VCM)*. Studies by
Bellas e_t al» (29)* for example* indicated that photolysis
of vinyl chloride can be sensitized in the vapor phase by
mercury atoms. The authors concluded that in this case* the
primary photochemical process for triplet VCM in the vapor
phase involved elimination of molecular HCl. However*
homolysis of the carbon—chlorine bond could not be ruled out
by their data. In solution* the major photoreaction for
triplet chlorinated olefins was found to involve twisting
around the double bond (30).
Mechanism III* which we have called chemical
sens!tization, involves direct chemical reaction between
sensitizer and olefin. Such reactions are known to occur in
the condensed phase with simple olefins and electronically
excited ketones (31).
Mechanism IV* free radical decomposition and
polymerization of VCM initiated by photochemical homolysis
of a species like a peroxide* is also a possible pathway.
Examples of the light-initiated polymerization of vinyl
monomers are discussed by Walling (32). Url and co-workers
found that polymerization of vinyl monomers can be
"photosensitized" by chlorophyll (33) and by iron complexes
(34, 35). The "photosensitization" in these cases clearly
did not Involve energy transfer* but rather the generation
of free radicals followed by polymerization (Mechanism IV).
41
-------
Mechanism I. Direct Photolysis
VCM ^.(VCM)*
(VCM)* -* products
Mechanism II. Photosensitized Reaction (Energy Transfer)
S ^1S*
1S* -*3S*
3S* + VCM -»S + 3(VCM)"
3(VCM>* -» products
Mechanism III. Chemical Sensitization
S* + VCM -» products
Mechanism IV. Light-initiated Free Radical Decomposition
A-B ^i-A* + B'
A' + VCM -»ACH2CHC!'
ACH2CHCr + VCM -* polymer
ACH2CHCr + O2 -* ACH2CHCI02*
ACH2CHCI02' + VCM -» polyperoxides
ACH2CHCI' + B' -*ACH2CHCIB
2ACH2CHCI* -^ACH=CHCI + ACH2CH2CI
2ACH2CHCI' -^(ACH2CHCI42
Figure 23* Pathways for light induced decomposition of
vinyl chloride*
42
-------
The photodegradation of vinyl chloride was studied to
determine whether the above processes are possible in the
aquatic environment, and whether their ratest it they occur,
are sufficiently high to compete with other processes*
MATERIALS AND METHODS
Vinyl chloride gas from Matheson Company was used
without further purification. Laboratory distilled water
was redistilled from basic permanganate immediately prior to
use*
Natural waters were obtained from the Oconee River in
Athensf Georgia, and the Okefenokee Swamp (Big Water Lake)
in South Georgia* Commercial humic acid was obtained from
Aldrich Chemical Company*
Stock solutions of vinyl chloride were prepared in small
bombs equipped with gas-tight Teflon stopcocks* Aliquants
of VCM in gas—tight syringes were added to the bombs that
were completely filled with known volumes of carbon
tetrachloride; the gas rapidly dissolved into the CCl* •
Aqueous solutions were prepared following the same
procedures; the concentration in water was then measured
exactly by comparison to the CCl« stock solutions* Analyses
for VCM were performed by gas—liquid chromatography on a 2 m
x 0*32 cm glass column packed with 0*4% Carbowax 1500 on
Carbopack A* The column was cured by heating at 200°C for
48 hours with slow purging by nitrogen*
Glc analyses were performed on a Tracor MT—220
Chromatograph using a flame detector* Photolysis studies
were conducted on a rotating turntable apparatus, described
in detail by Moses, Liu, and Monroe (36). A 450-watt high-
pressure mercury lamp was the light source* The ultraviolet
spectrum of VCM in water was obtained with a Perkin-Elmer
602 Digital Spectrophotometer using a specially constructed
quartz cell equipped with a gas-tight Teflon stopcock. All
photolysis studies were carried out in reaction cells
equipped with gas-tight Teflon stopcocks. Controls
established that no leakage of VCM occurred from these cells
over a period of at least two weeks.
Kinetic studies were generally carried out at VCM
concentrations of 10 to 20 mg l"1. The light from the
mercury lamp was filtered through a 3 mm-thick Pyrex sleeve
(cutoff at 300 nm) for most of the studies. Singlet oxygen
43
-------
studies were conducted using 1.00 x 10~* M methylene blue as
sensitizer and 578 nm monochromatic light* Acetone
sensitization studies employed 10% (by volume) acetone in
water and 313 nm light. Filter solutions (1.0 cm thick)
were as follows: 573 nm - 50 g cupric chloride (hydrated),
150 g anhydrous calcium chloride, and 150 g potassium
dichromate in 500 ml distilled water slightly acidified by
hydrochloric acid; 313 nm - 0.001 M potassium chromate in 3%
aqueous potassium carbonate, and 3 nm—thick Pyrex sleeve.
The actinometer for the acetone sensitized photolysis was a
solution of 0.05 M benzophenone and 0.100 M cis-1,3-
pentadiene in benzene (37).
RESULTS AND DISCUSSION
Direct Photolysis
The rate of direct photolysis of a pollutant is
proportional to the degree of overlap between the electronic
absorption spectrum of pollutant: and the spectrum of light
source, vinyl chloride and sunlight, respectively, for the
present study. Atmospheric ozone prevents essentially all
sunlight of wavelengths below 295 nm from reaching the
earth's surface. Vinyl chloride, in the vapor phase,
however, does not absorb above 220 nm (28), and our studies
show that in water it does not absorb above 218 nm. The
longer wavelength singlet—triplet transitions of simple
ethylene derivatives that occur at wavelengths > 295 nm are
highly forbidden and thus have extremely low extinction
coefficients (38).
The lack of overlap between vinyl chloride absorption
and sunlight radiation spectra indicates that direct
photolysis of vinyl chloride would be very slow in the
aquatic environment. To confirm this experimentally, we
exposed solutions of vinyl chloride (10 mg l~*) in pure
water to filtered (> 300 nm) light from a mercury lamp. No
photolysis occurred over a 90—hour period. The integrated
intensity of the 300—370 nm light in our photochemical
apparatus was found to be about eight times more intense
than midday—June sunlight (lat. 34°N) in the same spectral
region.
44
-------
Indirect Photolysis
Although direct photolysis (Mechanism I) is immeasurably
slowt the literature indicates that the light-induced
transformations of vinyl chloride could occur through
indirect pathways (Mechanisms II-IV). For example*
substances found dissolved in certain natural waters were
found to greatly accelerate the photodecomposition of some
pesticides (39, 40). Photolysis experiments were therefore
conducted in natural waters and in distilled water
containing model photosensitizers that absorb light of
wavelengths > 300 run.
Vinyl chloride was not readily degraded by singlet
oxygen* an excited form of oxygen generated by methylene
blue photosensitization. However* in the presence of
acetone* a high-energy triplet sensitizer* or hydrogen
peroxide* a free radical source* VCM decomposed rapidly when
irradiated with ultraviolet light* The disappearance
quantum yield (313 nm ) for the acetone—sensitized reaction
(3*0 x 10~2 M VCM) was 0.75. A colorless precipitate formed
during photolysis* but it was not identified.
Since the major photochemical process for triplet 1*2—
dichloroethylene and other mono—olefins involves
isomerization (30)* twisting about its carbon—carbon bond
would be expected to be the primary process for triplet VCM.
Other studies have indicated that reaction between triplet
ketones and olefins ( 41 ) to form oxetanes is not
particularly efficient. Therefore the high disappearance
quantum yield for the acetone—sens!tized photolysis of VCM
was surprising. The photolysis may involve inefficient
homolysls of the carbon-chlorine bond of triplet VCM*
followed by free-radical polymerization of VCM* i.e.* most
of the VCM would be consumed by secondary thermal reactions.
The importance of photosensitization via energy transfer
for the disappearance of VCM in the environment is difficult
to predict. Such sensitization occurs efficiently only when
the triplet state energy of the sensitizer equals or exceeds
that of the acceptor, i.e., VCM. Since the triplet state
energies of mono-olefins are very high (78-82 kcal mole"1)
(38), only high energy sensitizers such as acetone (triplet
energy 80 kcal mole"1 ) are effective. Unfortunately, little
is known about the concentrations and distribution of high-
energy sensitizers in the aquatic environment. The matter
is further complicated by the fact that competing energy
acceptors such as dissolved oxygen are also present in the
aquatic environment.
45
-------
The high susceptibility of VCM to free radical attack in
water was demonstrated by its rapid disappearance in the
presence o£ hydroxy free radicals generated by photoysis of
hydrogen peroxide (Figure 24)• Since PVC plant effluents
are likely to contain small amounts of peroxides, such as
peroxydisulfate (32), that are used in the polymerization
process* sunlight—induced decomposition of VCM was
considered as a possible pathway for its disappearance from
PVC plant effluent water*
Howevert using the same apparatus employed in the
present direct photolysis studies, Thruston (3) found that
VCM photolyzed very slowly (half-life 40 hours) in PVC plant
effluent* When exposed to sunlight* it photolyzed even
slower* Very little reaction was detected after 25 hours of
exposure*
Our natural water studies were carried out in unfiltered
waters collected from the Oconee River, a moderately
polluted river in Athens, Georgia, and from the Okefenokee
Swamp, an unpolluted water that is highly colored by
dissolved humlc materials* In both natural waters, and in
water containing 20 mg I"1 commercial "humlc acid" (a
derivative of decayed plants), no decomposition of VCM (10
mg l~*) occurred during a 20—hour irradiation period*
46
-------
100
o
I 80
60
o
>
o 40
e
Q_
20
I
1 2
TIME, hrs
Figure 24» Decomposition of vinyl chloride in water by
attack of free radicals generated by photolysis
(300 nm) of hydrogen peroxide.
47
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SECTION VI
MICROBIOLOGICAL INTERACTIONS
In natural watersf the interactions of vinyl chloride
with living organisms must also be considered as a possible
mechanism for disappearance of the compound* Two possible
pathways were considered—-—sorption to microorganisms and
degradation by bacteria* The toxicity of the vinyl chloride
to bacteria was also investigated*
MATERIALS AND METHODS
Five mixed bacterial populationst three mixed fungal
populationst and two single organism cultures C Bacilluq
subtilis. and Flavobacterjum harriaonii) were isolated from
natural aquatic systems in and near Athensf Georgia* An
alga* ChioreIIa ovrenoidoaa• was obtained from the Starr
Collection* University of Indiana* Bloomington, Indiana*
A saturated solution of vinyl chloride was prepared by
bubbling the gas into sterile distilled water for one hour*
Vinyl chloride solutions for the bacterial degradation and
toxicity studies were prepared by aseptically diluting the
saturated solution to varying extents with a solution of
nutrient broth that was diluted 1:20, 1:40, 1:80, or 1:100
in basal salts medium (42)* The pH of the medium was 6*9*
For the sorption studies, the saturated VCM solution was
diluted with distilled water*
Analyses for VCM were done by direct gas-liquid
chromatography ( glc) using a Tracor MT-220 Chromatograph
equipped with dual flame ionization detectors* Peak areas
were obtained using a Varian Aerograph Model 477 integrator*
VCM amounts were determined by comparison of glc peak areas
from the experimental solutions with those from VCM gas
standards in air prepared by MG Scientific Company* VCM
eluted in approximately two minutes as a single, sharp
symmetrical peak from a 1*5 meter Porapak Q (Waters
Associates, Inc.) column (4 mm ID) at an oven temperature of
125°C, an injection port temperature of 215°C, and a carrier
gas (nitrogen) flow rate of 90 ml/min*
For the degradation and toxicity studies, 250—ml flasks
with side arms and screw caps, as illustrated in Figure 25,
48
-------
HOLE
SCREW CAP
RUBBER SEPTUM
enzsna "^TEFLON FILM LINER
Figure 25. Apparatus for vinyl chloride degradation and
toxicity studies*
49
-------
were used* The VCM stock solution was introduced by syringe
through the hole in the screw top into flasks containing
dilute nutrient broth and bacteria* Samples for glc
analysis were removed in the same manner* The Teflon liner
covering the top was sealed with cellulose tape immediately
after the syringe was removed*
The side-arm tube was designed to fit the Klett-
Summerson photoelectric colorimeter in which turbidity of
the culture was measured using a blue filter (425 nm)* This
allowed growth to be monitored without opening the flasks*
Each isolated bacterial population was inoculated into
two flasks containing 1:20 nutrient broth* The saturated
VCM solution was added to one of the cultures to give a
final concentration of 20 mg VCM per liter* The other
culture, the control, received no VCM* Each series of
cultures included a flask containing medium and VCM but no
organisms* The cultures were incubated at 21°C on a
gyratory shaker under an exhaust hood*
After one week the resultant populations were
transferred to a 1:20 nutrient broth solution containing 40
mg I"1 VCM* Weekly transfers were made for a period of five
weeks* decreasing the nutrient broth concentration and
increasing the VCM concentration until nutrient broth was
diluted 1:80 and VCM concentration was 120 mg l"1. After
five weeks, bacteria for degradation studies were harvested
from the 1:80 nutrient broth containing 120 mg I'1 VCM,
washed three times, and transferred to basal salts medium
containing 54 mg l~l VCM as the only carbon source* Inocula
from the same series of flasks were used to continue the
toxicity studies* The concentration of nutrient broth was
decreased to a ratio of 1 part nutrient broth to 100 parts
basal salts medium and the concentration of the vinyl
chloride was increased at each 48-hour transfer until the
VCM concentration was 900 mg l~*.
Bacteria used in sorption studies were grown in 1:10
nutrient broth for 24 hours, harvested, and washed three
times* Enough bacteria were transferred to 5—ml graduated
centrifuge tubes with ground glass stoppers to give
approximately 5 g dry weight of bacteria per liter of water*
-^
Fungi from three field sites were isolated on Rose
Bengal (Difco) plates and maintained on Saboraud*s 'medium
(Difco) slants* Inocula for fungi were suspensions prepared
by agitating 10 ml of sterile water in a plate containing
the sporulating fungi* The suspension was introduced into
50
-------
medium containing 6.0 g glucose per liter. Medium was
decanted and enough fungi were transferred to 5-ral graduated
centrifuge tubes with ground glass stoppers to give
approximately 5 g dry weight of fungi per liter of water.
Chlorella ovrenoidosft was grown in Bensen-Fuller medium
containing 0.1% Hutner's trace element solution and
incubated on a shaker at 15°C under 170 ft-c of continuous
light. Cultures were centrifuged, washed three timest and
transferred to 5-ml graduated centrifuge tubes with ground
glass stoppers for sorption studies to give approximately 4
S dry weight of algae per liter of water. To eliminate
corrections for volatilization of VCM to the air above the
solution* tubes were filled to the top and all data were
compared with data from control tubes (containing no
organisms).
To determine dry weights of algae and bacteria used in
sorption studies* cultures were centrifuged and the
organisms were washed three times. The organisms were
quantitatively transferred to tared beakers and dried to a
constant weight at 90°C. Fungi were separated from test
cultures for dry weight determinations by filtering* first
through tared pre—filters* then through tared 0.22 micron
Nucleopore filters* and by drying to a constant weight at
90 °C.
RESULTS AND DISCUSSION
Sortition o-t Vinvl Chloride to Microorganisms
In systems in which sorption is linear Cvery low solute
concentrations), the simple distribution coefficient
may be used to describe the extent of sorption of a compound
to microorganisms
K, - 2£E (3)
d ce
where c = concentration (mg/mg) of solute in solution at
equilibrium
51
-------
x = amount (mg) of material s orbed per mg of
solution
-------
containing only basal salts and 54 mg l~» VCM without an
additional carbon source. These cultures were monitored
daily for one week. No degradation was detected at any time
in any of the cultures.
Byington and Liebman (43) have shown that
trichloroethylene was transformed to chloral hydrate by rat,
rabbitt and dog liver microsomes in a reaction requiring
NADPH and oxygen. Based on the structures of the compounds
and the requirement of NADPH, alcohol dehydrogenase may be
the active enzyme. If so, degradation of VCM by bacteria
could be possible via the following pathway:
H H H H Alcohol H H HO
V/ _* H-C-C-C1 Pehydrogenase > H_£ _ ^ __* H-C-C-H
/ \ V/ NADPH H' ' '
H Cl 0 flAU^ti, ti cl QH cl
If the bacteria were capable of degrading VCM by this
pathway, a system in which oxygen was not a limiting factor
would be needed. The closed flask systems described earlier
could limit the oxygen in the system. Therefore, six one-
liter flasks containg the five bacterial populations in 1:40
nutrient broth and an uninoculated control were bubbled with
0.1% VCM in air for 96 hours and monitored for possible
products by glc analysis at low column temperature using
FID. No degradation products were detected in any of the
cultures.
Toxicitv of Vinyl Chloride to Bacteria
The toxicity of VCM to five actively growing bacterial
populations was tested. Testing could not be done at VCM
concentrations up to its solubility in water (1700 mg I"1)
because of the difficulty in supplying the bacteria with
sufficient oxygen for growth above a VCM concentration of
900 mg I""1. Because even at 900 mg I"1 VCM the oxygen
concentration was low, a low nutrient broth concentration
was used also (1:100) to insure that any differences in
growth would be due to the presence of VCM rather than
insufficient oxygen. No difference could be detected
between bacterial growth in cultures and in test cultures
containing up to 900 mg l"1 VCM. The VCM was therefore not
toxic to bacteria at these concentrations.
53
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SECTION VII
PHYSICAL INTERACTIONS
The conceptual model for vinyl chloride behavior in
aquatic systems suggests that volatilization may be an
important process in determining the distribution of the
compound* A preliminary study of the stability of vinyl
chloride in water (3) indicates that the loss of vinyl
chloride from water through volatilization is relatively
rapid* Gas exchange experiments were therefore undertaken
to provide data for determination of the specific rate of
volatilization of vinyl chloride from water*
The specific rate of gas exchange (K) at an interface
between water and atmosphere is a function of properties (P)
of the gas molecules (e»g*t diffusivity, molecular
diameter)* and the turbulence (T) in the watert
K - f(P.T) (4)
If the specific rates are determined from concentrations
measured for two gases (denoted 1 and 2) simultaneouslyf the
common parametert turbulencef can be eliminated from the
functional relationship
K.
f(P.T)
for constant properties PI and PZ» This ratio (equation 5)
of specific rates is not significantly affected by
temperature changes between 10°C and 30°C» by the level of
turbulencet by the direction of gas transfer) or by the
presence of dissolved solids (9)* In the gas exchange
experiments) the specific rate of vinyl chloride loss was
determined relative to and concurrently with the specific
54
-------
rate of oxygen reaeration to eliminate the need for
measurement of turbulence and to relate vinyl chloride
volatilization to available environmental determinations of
oxygen reaeration*
For comparison, the ratio of specific rates was also
calculated using estimates of molecular diameter.
MATERIALS AND METHODS
Nitrogen-sparged, deionized water (900 ml) and saturated
vinyl chloride solution (10 ml) were added to each of four
beakers in an exhaust hood* The contents of beakers 1, 2,
3, and 4 were stirred to create vortices with depths of 0
(quiescent), 1*5 cm, 5 cm, and 10 cm, respectively* Oxygen
and vinyl chloride concentrations were measured every 10
minutes for 180 minutes using a dissolved—oxygen meter and a
gas chromatograph* Six replications of these experiments
were performed*
RESULTS AND DISCUSSION
The gas exchange dynamics at the interface were
represented as a first—order approach to equilibrium using
the equation
= K(C-C) (6)
where C = gas concentration
t = time
K = specific rate
C = saturation concentration
s
The concentrations of oxygen and vinyl chloride for each
beaker in each replicate were used to determine the sums of
squares for the best least squares fit to the logarithmic
form of the solution to equation 6. The corrected sums of
squares for all beakers stirred alike were pooled to
55
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estimate the specific rates tor each of the four levels of
mixing* These specific rates are presented in Table 4 with
their 95% confidence intervals* A linear regression of
on KQ resulted in the equation
KVCM
giving a constant ratio of
2.30 + 0.31 (8)
at a 95% level of confidence* The constant ratio line and
ratios at each mixing level are graphed in Figure 26*
The ratio of gas exchange coefficients may also be
estimated as the reciprocal of the ratio of molecular
diameters (9)* Two different values for the vinyl chloride
diameter may be obtained depending upon the method by which
it is calculated* The diameter calculated using a critical
volume of 168*9 ml mole'1 (44) in the van der Waals equation
is 3*55 A* Assuming a molecular diameter for oxygen of 2*95
At the resulting ratios of gas exchange coefficients using
the two different diameters are
0.83 and 0.87 (9)
respectively*
The experimentally determined estimate of the ratio of
gas exchange coefficients (K /K ) indicates that the
VCM 02
56
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Table 4. RATE COEFFICIENTS FOR OXYGEN AND VINYL CHLORIDE
GAS EXCHANGE AT FOUR MIXING LEVELS
Vortex
depth
f emJ
0
1.5
5.0
10.0
•3.54( 10~3 )±2.28( 10""* )
•1.24( 10~2 )±1.4S( 10""3)
-3.85( 10~2)±1.16< 10~2)
•8.03(10~2 )±3.86(10~2)
-3.03C 10~3 )±2.74( 10~* )
10~2)±1.22( 10~3)
10~2)±1.06( 10~3)
10~» )±7.88(10~2)
57
-------
-0.729
-1750
-0.0803
-0.0419
min
-0.00354
'1
Figure 26. K versus K at four mixing levels.
58
-------
specific rate of exchange of vinyl chloride gas between
water and air is about twice that of oxygen*
59
-------
REFERENCES
1. U. S. Environmental Protection Agency. Vinyl Chloride
Monitoring Near the B. F. Goodrich Chemical Company in
Louisvillet Kentucky. Surveillance and Analysis
Division* Athens» Georgia. June 1974. 45p.
2. Glllett, J. W., J. Hill, IV, A. W. Jarvinen, and W. P.
Schoor. A Conceptual Model for the Movement of
Pesticides Through the Environment. National
Environmental Research Center, Corvallis, Oregon. EPA—
660/2-74-024. December, 1974. 80p.
3. Thruston, A. D., Jr. and A. W. Garrison. Stability of
Vinyl Chloride Monomer in Water. Internal Report,
Southeast Environmental Research Laboratory, Athens,
Georgia. 1974. 2p.
4. Director, S. W. and 8. A. Rohrer. Introduction to
System Theory. New York, McGraw Hill, Inc., 1972.
441p.
5. Tsivoglou, E. C. and J. K. Wallace. Characterization of
Stream Reaeration Capacity. Georgia Institute of
Technology. Office of Research and Monitoring,
Washington, D. C. EPA-R3-72-012. October, 1972* 315p.
6. Baca, R. G«, M. W. Lorenzen, R. D* Mudd, and L. V.
Kimmel. A Generalized Water Quality Model for Eutrophic
Lakes and Reservoirs. Pacific Northwest Laboratories.
Richland, Washington. 211B01602. Office of Research
and Monitoring, U. S. Environmental Protection Agency.
August, 1974. 140p.
7. Hutchinson, G. E. A Treatise on Limnology. Volume I.
New York, John Wiley and Sons, Inc., 1957. 1015p.
8. Russell—Hunter, W. D. Aquatic Productivity. Toronto,
Collier Macmillan, 1970. 305p.
9. Tsivoglou, E. C. Tracer Measurement of Stream
Reaeration. Georgia Institute of Technology.
Washington, D. C* Water Pollution Control
Administration. June, 1967. 86p.
60
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10* Martens* H. R. and D* R. Allen* Introduction to Systems
Theory* Columbus, Ohio, Charles E. Merrill Books, Inc.,
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11. Giorgio Modena* Accounts Chem* Res* 4:73, 1971.
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New York, American Elsevler Scientific Publishing Co.,
Inc., 1973. p. 163.
13. Bolton, R. In: Comprehensive Chemical Kinetics, Volume
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42. Payne* W. J. and V. E. Feisal. Appl. Microblol.
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63
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/3-76-001
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
DYNAMIC BEHAVIOR OF VINYL CHLORIDE IN AQUATIC
ECOSYSTEMS
5. REPORT DATE
January 1976 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
James Hill IV, Heinz P. Kollig, Doris F
N. Lee Wolfe, and Richard G. Zepp
8. PERFORMING ORGANIZATION REPORT NO
Paris
9. PERFORMING ORG-\NIZATION NAME AND ADDRESS
Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Athens, Georgia 30601
10. PROGRAM ELEMENT NO. 1BA023
~AP 04AEM;Task 005,RQAP 03ACO,
task 009
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Same as above
13. TYPE OF REPORT AND PERIOD COVERED
Task Milestone Rept. FY75
14. SPONSORING AGENCY CODE
EPA-ORD
15. SUPPLEMENTARY NOTES
16. ABSTRACT
To evaluate the behavior of vinyl chloride in aquatic ecosystems,
best estimate and worst case models of lake and stream ecosystems were
analyzed through the use of mathematical simulation. The characteristic
of the chemical, biological, and physical transformations of vinyl
chloride indicated in the models were determined by laboratory experi-
mentation and extrapolation of reaction data for similar compounds.
These transformations included oxidation, substitution, elimination,
hydrolysis, and free radical reactions; complexation; direct and
indirect photochemical reactions; microbial degradation and toxicity;
bacterial, algal, and fungal sorption; and volatilization. Loss of
vinyl chloride from the aquatic environment by volatilization appeared
to be the most significant process in its distribution.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Systems analysis
Vinyl chloride
Chemical degradation
Biodegradation
Aquatic environment
12A
6F
8H
8. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
21. NO. OF PAGES
74
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
64
U.S. GOVERNMENT PRINTING OFFICE: 1976-657-695/5363 Region No. 5-11
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