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United States
Environmental Protection
Agency
Environmental Research
Laboratory
Athens GA 30613
Research and Development
EPA-600/S3-81-038 July 1981
Project Summary
Behavior of DDT, Kepone, and
Permethrin in Sediment-Water
Systems Under Different
Oxidation-Reduction and
pH Conditions
Robert P. Gambrell, C. N. Reddy, Vicki Collard, Gloria Green, and
W. H. Patrick, Jr.
A study was conducted to deter-
mine the effects of pH and oxidation-
reduction (redox) conditions of soil
and sediment-water systems on the
persistence of three insecticide com-
pounds. Three pH levels, ranging from
moderately acidic to mildly alkaline,
were studied for each compound.
Four redox potentials (-150, 50, 250,
and 450 mv) ranging from strongly
reduced (anaerobic) to well oxidized
(aerobic) were studied. The
insecticide-substrate combinations
included in the project were DDT in a
Mobile Bay (Mobile, Alabama)
sediment material, Kepone in the sedi-
ment material of a tributary of the
James River (Hopewell, Virginia) and
Permethrin in an Olivier soil material
(Baton Rouge, Louisiana). Sample ali-
quots were removed from the labora-
tory microcosms to determine the
recovery of the added compounds
with time. A substantial redox
potential effect was noted for DDT
where recovery decreased from the
spiking level of around 25 parts per
million to less than 10 percent of the
spiking level within a few days at -150
mv (strongly reduced condition). A
less rapid loss of DDT was noted at 50
mv (moderately reduced condition).
but the pesticide appeared stable
under better oxidized conditions
during the 45-day incubations. The
levels of Kepone recovered did not
change appreciably during 56 days of
incubation under any of the
combination of imposed pH and redox
potential conditions. The recovery of
Permethrin was affected by both pH
and redox potential conditions over
25-day incubations. Unlike DDT,
Permethrin was lost more rapidly
under oxidizing conditions. Increasing
pH enhanced the loss of .this
compound over the range of redox
potential levels studied.
Information of the effects of
physicochemical conditions on the
persistence of pesticide residues such
as demonstrated in this project should
enable better prediction of the fate
and potential impacts of residues in
various environmental compart-
ments.
This Project Summary was develop-
ed by EPA's Environmental Research
Laboratory, Athens, GA, to announce
key findings of the research project
that is fully documented in a separate
report of the same title (see Project
Report ordering information at back).
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Introduction
Synthetic organic pesticides have
been used extensively for almost three
decades for controlling nuisance
weeds, insects, and microbial
organisms. Environmental problems
sometimes arise, however, when non-
target organisms are adversely affected
either as a direct result of pesticide
application or waste disposal, or as a
result of pesticide residues that may be
transported to sensitive ecosystems
away from the point of application.
A substantial amount of environ-
mentally related research has been
conducted with pesticides, and espe-
cially insecticides, such that much is
known about their fate and mobility
under certain environmental conditions.
Most environmental studies on fate and
transport have focused on well-drained
agricultural soils. Pesticide residues,
however, are subject to a wide range of
physicochemical conditions in the
environment. Soon after typical agricul-
tural applications, most residues
become associated with medium
textured, well-oxidized, near neutral pH
soils. Subsequently, these residues may
be transported in dissolved or adsorbed
forms to surface waters and sediments
of streams, rivers, lakes, or estuaries
where the physical and chemical
properties (physicochemical) as well as
biological populations of the receiving
environment are very different from the
conditions at the point of application.
For example, typical agricultural soils
exhibit a wide range in texture (from
sandy to heavy clay material), pH
commonly ranges from 5 to 7.5, soils
are nonsaline, and the organic carbon
content of the plow layer typically
ranges from a few tenths of a percent up
to 2 percent. Compared to typical agri-
cultural soils, sediments are character-
ized by finer texture (greater clay
content), a narrower pH range (6.5 to
7.5), greater organic carbon content,
moderate to strongly reducing (anoxic)
conditions, and, depending on coastal
proximity, sediments may have a higher
salinity. These conditions have been
shown to markedly affect the chemical
mobility and biological availability of
nutrients such nitrogen and
phosphorus, trace metals, toxic metals,
petroleum hydrocarbons, and certain
pesticides. For pesticides, these dif-
ferences are thought to affect the
adsorptive capacity of the solid phase
for pesticides and the chemical and
especially microbial processes affecting
pesticide degradation.
There is sufficient published informa-
tion available on pH and redox potential
effects on adsorptioin and degradation
for selected pesticide compounds to
document that these are important
parameters to be considered in under-
standing the environmental fate of
many pesticides. There is need for much
more work to be done under carefully
controlled pH and redox potential condi-
tions, however, to improve understand-
ing of factors affecting the environ-
mental persistence and transport of
pesticides. This is especially important
as little is known of the physicochemical
effects on the fate of most pesticide
residues in some ecosystems, such as
sediment-water systems, where
residues have the greatest potential for
biological accumulation and
subsequent adverse effects. Such
information should lead to development
of improved predictive capability on the
transport and fate of pesticide residues
in various compartments of the
environment.
Project
This research was conducted to
determine the effects of physicochemi-
cal conditions on the persistence of
three pesticides in soil and sediment-
water systems. Soil and sediment
suspensions were incubated at selected
pH and redox potential levels which
include the range commonly found in
these systems.
Three insecticides were studied. DDT
[1,1 -/?/s-(p-chlorophenyl)-2,2,2-trichlo-
ethane] was included because it is still'
widely distributed in the environment
though its use has been eliminated or
greatly restricted in recent years. Also,
there is considerable published
information for DDT on different
degradative pathways and products
dependent upon oxidation conditions. A
Mobile Bay (Mobile, Alabama) sediment
material was used in the laboratory
microcosms for DDT studies.
Kepone [decachloro octahydro-1,3,4-
metheno-2H-cyclobuta [ccflpentalen-2-
one] was included in these studies
using a sediment material from a
tributary of the James River (Bailey's
Creek, Hopewell, Virginia) to determine
whether its persistence in the environ-
ment is influenced by physicochemical
conditions. The known environmental
problems with this compound are
confined to the James River area.
Because essentially nothing was known
of factors affecting Kepone persistence
in soils and sediment-water systems,
this compound was included to dei
mine whether studies of physi
chemical effects on its persistei
might suggest something about its f
in the James River and perhaps sugg
management practices that could
used to minimize adverse envin
mental impacts.
The persistence of Permethrin,
phenoxybenzyl (±) cis-trans-3-(2
dichlorovinyl-2,2-dimethylcyclopropar
carboxylate] a synthetic pyrethrc
was also studied under control
physicochemical conditions using
Olivier soil material (Baton Rou
Louisiana). The synthetic pyrethro
are a relatively new class of insecticic
that are highly effective against tan
insects, exhibit low mammalian toxic
and are far less persistent in t
environment than many chlorinat
hydrocarbon insecticides. The- hi
susceptibility of larvae and juven
crustaceans to certain of these coi
pounds and the expected increasing
important role of the synthe!
pyrethroids in insect control prograr
suggest it is important to examii
factors affecting the persistence
these residues in the environment.
Conclusions
The effects of oxidation-reductic
conditions on the persistence and tran
formations of DDT were studied in
Mobile Bay sediment material at pH 6.
7.0, and 8.0. The recovery of DDT fro
the spiked Mobile Bay sedimei
material decreased very rapidly undi
strongly reduced conditions (-1 50 m
such that 90 percent could not t
recovered after as little as 5 days. Th
apparent rapid degradation rate und<
strongly reducing conditions was som<
what greater than reported in mo:
published studies on the effects <
reducing conditions on DDT persistenci
Various explanations for the rapi
decrease in DDT recovery were cor
sidered, including experimental art
facts. Although the levels of measure
degradation products (ODD and DDE
measured did not totally account for th
loss in DDT, ODD levels were greatl
increased where DDT was disappearin
rapidly at -150 mv providing evidenc
that a substantial amount of DDT wa
actually degrading within a matter of
to 3 days. It was concluded that DD
was indeed degrading very rapidl
under very strongly reduced condition:
in the Mobile Bay sediment materia
compared to moderately reduced 0
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jxidized conditions. It is probable the
chemical properties and possibly the
microbial activity of the strongly
reduced Mobile Bay sediment material
are very different from most soils and
sediments used for DDT studies and
that these differences contribute to very
rapid losses of DDT from this material
compared to most published degrada-
tion rates for DDT. Another factor may
be that the -150 mv potential included
in this study was a more intense
reducing condition than is achieved in
other studies of DDT degradation in
flooded soils or soils equilibrated in the
absence of air.
A less rapid loss was noted at 50 mv
(moderately reduced conditions) while
DDT appeared fairly stable under better
oxidized conditions. Where recovery of
DDT decreased rapidly (strongly
reduced conditions) both ODD and DDE
levels were elevated, but ODD predomi-
nated. Only at 50 mv was there any
indication that a degradation product
was accumulating in the Mobile Bay
sediment material. The small increase
in ODD levels noted with time was not
equal to the rate of DDT loss, indicating
that ODD was also not stable where
conditions were conducive to rapid DDT
degradation.
The results of these DDT studies were
in general agreement with other
published reports on the environmental
fate of DDT with the possible exception
that DDT may degrade more rapidly
under strongly reduced conditions in
Mobile Bay sediment material than in
most anaerobic soils and sediments.
The persistence of added Kepone was
studied in James River sediment
materials incubated at three pH (5.0,
7.0, and 8.0) levels and four redox
potential levels (-150, 50, 250, and 450
mv). There was no clear indication that
redox potential had any effect on
Kepone recovery with time, though a
very gradual reduction in Kepone
recovery was noted at all redox levels at
pH 8.0 in the stirred suspensions.
The persistence of Permethrin, a
synthetic pyrethroid, was studied in an
Olivier soil suspension amended with
this compound under a range of redox
potential conditions at pH 5.5, 7.0, and
8.0. Both pH and redox potential
strongly influenced the degradation of
this compound. UnliKe DDT, Permethrin
was lost more rapidly under oxidizing
conditions. Increasing pH enhanced this
loss under both moderately reduced
(+50 mv) and weakly oxidized (+250 mv)
conditions. In well oxidized
suspensions, Permethrin recovery
decreased from the approximately 17
ppm spiking level to less than 0.5 ppm in
about 3 weeks. Under strongly reducing
conditions, recovery of the added
Permethrin ranged from near spiking
levels to around 1/3 of spiking levels
(depending on pH) during the 26-day
incubations.
The results of this study indicate
Permethrin is more persistent under
reducing conditions typical of
sediments that are a habitat for many
important benthic organisms, which,
according to the literature, are highly
sensitive to some synthetic pyrethroids.
Permethrin cannot be considered a per-
sistent pesticide compared to most
chlorinated hydrocarbons. However, its
somewhat greater stability in reducing
sediments that may receive residues in
runoff, and the potential for adverse
effects to organisms associated with
sediment-water systems, make physi-
cochemical effects on Permethrin
degradation an important environ-
mental consideration.
The results of this study demon-
strated that the physicochemical
conditions of the soil and sediment-
water systems studied (pH and redox
potential) substantially influenced the
environmental chemistry of two of three
synthetic organic pesticides included in
this project. The results of this study and
the very limited information available
from the literature indicate that the
persistence, degradation pathways and
products, and the mobility of many or
most synthetic organics may be affected
by the physicochemical characteristics
of the environmental compartments
with which these residues become
associated. Because of the apparent
important effects of physicochemical
conditions on the environmental
chemistry of synthetic organics, and the
wide range in these properties found in
the various environmental compart-
ments that may receive residues, it is
important to understand the influence
of physicochemical conditions on the
environmental chemistry of pesticides
before an accurate assessment can be
made of the fate and potential impact of
pesticide residues in all affected areas
of the environment. For example,
biometer flask studies of a compound
such as Permethrin in a typical aerobic
soil may not indicate the potential for
persistence and accumulation in
anaerobic lake and wetland sediment-
water systems where there is consider-
able potential for adverse impacts on
benthic organisms.
Recommendations
Because of probable physicochemical
influences on the environmental
chemistry of most pesticides, additional
work should be done to characterize
these effects for existing compounds \
where this information is lacking. Of
particular importance are those com-
pounds thought to be relatively persis-
tent, compounds known to be especially
toxic, particularly to non-target
organisms, and comounds that are
released into the environment in
relatively large quantities. The non-
volatile organics of the EPA priority
pollutant list should be considered as
prime candidates for studies of this type.
As part of the information the chemi-
cal industry is required to furnish
when applying for registration to label
and market a new pesticide product,
testing should be done to determine
persistence and pathways of degrada-
tion in soils and sediments under a
range of physicochemical conditions.
Also, the information should be
obtained for a number of typical soils
and sediments under their indigenous
physicochemical conditions that should
include a wide range of these properties.
Though the laboratory suspension
studies of the type conducted in this
project should accurately indicate the
effects of physicochemical conditions
on the environmental chemistry of the
compounds studied, there is a need to
systematically examine physicochemi-
cal effects under more natural condi-
tions to more accurately reflect the rate
of the processes.
The activity of microbial populations,
either directly or indirectly, plays a
major role in the fate of pesticide
residues in the environment as well as
in regulating the physicochemical
conditions of the various environmental
compartments. Studies should be done
to characterize the relationship of the
activity of microbial populations to the
transformations observed for synthetic
organics under various physicochemi-
cal conditions.
ft US GOVERNMENT PRINTING OFFICE. 1M1 -757-012/7194
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R. P. Cambrel/, C. N. Reddy, V. Collard, G. Green, and W. H. Patrick. Jr. are with
Louisiana State University, Baton Rouge, LA 70803.
Harvey W. Holm is the EPA Project Officer (see below).
The complete report, entitled "Behavior of DDT, Kepone, and Permethrin in
Sediment-Water Systems Under Different Oxidation-Reduction and pH
Conditions," (Order No. PB 81-213 266; Cost: $11.00, subject to change/ will
be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Research Laboratory
U.S. Environmental Protection Agency
College Station Road
Athens, GA 30613
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
. PS 0000329
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