PB81-213266
Behavior of DDI, Kepone, and Permethrin in
Sediment-Water Systems under Different
Oxidation-Reduction and pH Conditions
Louisiana State Univ., Baton Rouge
Prepared for
Environmental Research l,ab
Athens, GA
Jun 81
U.S. DEPARTMENT OF COMMERCE
National Technical Information Service
NT IS
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EPA 600/3-81-038
June 1981
BEHAVIOR OF DDT, KEPONE, AND PERMETHRIN.IN SEDIMENT-WATER
SYSTEMS UNDER DIFFERENT OXIDATION-REDUCTION AND pH CONDITIONS
by
Robert P. Gambrell
C.N. Reddy
Vicki Collard
Gloria Green
W.H. Patrick, Jr.
Laboratory for Wetland Soils and Sediments
Center for Wetland Resources
Louisiana State University
Baton Rouge, Louisiana 70803
Grant No. 908940
Project Officer
Harvey W. Holm
Environmental Systems Branch
Environmental Research Laboratory
Athens, Georgia 30613
ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
Athens, Georgia.30613
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NOTICE
TEIS DOCUMENT HAS BEEN REPRODUCED
FROM THE BEST COPY FURNISHED US BY
THE SPONSORING AGENCY. ALTHOUGH IT
IS RECOGNIZED TEAT CERTAIN PORTIONS
ARE ILLEGIBLE, IT IS BEING RELEASED
IN THE "INTEREST "OF MAKING AVAILABLE
AS MUCH INFORMATION AS POSSIBLE.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/3-81-038
2.
ORD Report
3. RECIPIENT'S ACCESSIOfeNO.
PB« 215266
4. TITLE AND SUBTITLE
Behavior of DDT, Kepone, and Permethrin in Sediment-
Water Systems under Different Oxidation-Reduction
and pH Conditions - ...
S. REPORT DATE
June 1981
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
R.P. Gambrell, C.N. Reddy, V. Collard, G. Green and
W.H. Patrick, Jr.
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Center for Wetland Resources
Louisiana State University
Baton Rouge LA 70803
10. PROGRAM ELEMENT NO.
ACUL1A
11. CONTRACT/GRANT NO.
804940
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Research LaboratoryAthens
Office of Research and Development
U.S. Environmental Protection Agency
Athens GA 30613
GA
13. TYPE OF REPORT AND PERIOD COVERED
Final, 10/76-7/79
14. SPONSORING AGENCY CODE
EPA/600/01
15. SUPPLEMENTARY NOTES
16. ABSTRACT
A study was conducted to determine the effects of pH and oxidation-reduction
(redox) conditions of soil and sediment-water systems on the persistence of three
insecticide compounds. Three pH levels, ranging from moderately acid to mildly alka-
line, were studied for each compound. Four redox potential levels (-150, 50, 250, and
450 mv) were studied ranging from strongly reduced (anaerobic) to well oxidized
(aerobic). The insecticide-substrate combinations included in the project were DDT in
a Mobile Bay (Mobile AL) sediment material, Kepone in the sediment material .of a trib-
utary of the James River (Hopewell VA), and Permethrin in an Olivier soil material
(Baton Rouge; LA). Sample aliquots were removed from the laboratory 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 (ppm) to near 0 ppm 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 combinations of imposed pH and redox potential condi-
tions. The recovery of Permethrin was affected by both pH and redox potential condi-
tions over 25-day incubations. Unlike DDT, Permethrin was lost more rapidly under
oxidizing conditions.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS c. COS AT I Field/Group
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
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DISCLAIMER
This report has been reviewed by the Environmental Research
Laboratory, U.S. Environmental Protection Agency, Athens, Georgia,
and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the U.S.
Environmental Protection Agency, nor does mention of trade names
or commercial products constitute endorsement or recommendation
for use.
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FOREWORD
Environmental protection efforts are increasingly directed
towards preventing adverse health and ecological effects associ-
ated, with specific compounds of natural or human origin. As part
of this Laboratory's research on the occurrence, movement, trans-
formation, impact, and control of environmental contaminants, the
Environmental Systems Branch studies complexes of environmental
processes that control the transport, transformation, degrada-
tion, and impact of pollutants or other materials in soil and
water and assesses environmental factors that affect water
quality.
Because of their widespread use in agriculture, synthetic
organic pesticides have been the subject of considerable research
to determine their their fate and transport in the environment,
particularly in well-drained agricultural soils. Additional
information is needed on the effects of physicochemical processes
on pesticides in sediment systems where their residues have a
potentially adverse effect. This, report ..examines the effects of
two important environmental parameters, redox potential and
hydrogen ion activity, on the-persistence of three pesticides
in soil and sediment-water systems.
David W. Duttweiler
Director
Environmental Research Laboratory
Athens, Georgia
111
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ABSTRACT
A study was conducted to determine the effects of pH and
oxidation-reduction conditions on the persistence of three
insecticide compounds in soil and sediment-water systems.
Continuously stirred suspensions spiked with the compounds were
maintained at precise pH and redox potential levels for incuba-
tions of several weeks. Three suspension pH levels were studied
ranging from moderately acid to weakly alkaline. Four redox
potential levels studied ranged from strongly reduced (anaerobic)
to well oxidized. Samples of the suspensions were removed
periodically, extracted, and analyzed by gas chromatography to
determine treatment effects on the concentration of the compounds
with time. DDT, a chlorinated hydrocarbon, was studied in a
Mobile Bay (Alabama) sediment material. Kepone, also a chlori-
nated hydrocarbon, was incubated with a sediment material
collected from Bailey's Creek, a tributary of the James River,
near Hopewell, Virginia. Permethrin, a chlorinated synthetic
pyrethroid, was studied in an Olivier silty clay loam soil
material from Baton Rouge, Louisiana.
The recovery of DDT decreased very rapidly under strongly
reducing (-150 mv) conditions. This is consistent with informa-
tion in the literature on DDT. The rate of loss decreased as
redox potential increased. The two most commonly reported
degradation products of DDT (DDD and DDE) were also measured. A
moderate increase in DDD was noted early in the incubation of
the strongly reduced treatment as DDT was rapidly being lost,
but then DDD levels also declined rapidly after most of the DDT
was removed.
There was little apparent effect of either pH or redox
potential on the levels of Kepone added to the James River
sediment material.
Both pH and redox potential affected the recovery of
Permethrin. Unlike DDT, oxidizing conditions appeared to
accelerate the loss of this compound from the soil system.
The results of this study suggest the physicochemical
conditions of soil and sediment water systems should be consid-
ered in evaluating the potential environmental impact of organic
pesticides. The persistence and fate of many of these compounds
may differ depending on the environmental compartment in which
IV
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the compounds become associated and the physicochemical condi-
tions of the various environmental compartments. For example,
this study suggests Permethrin residues in typical upland
agricultural soils may disappear much more quickly than residues
which become associated with anaerobic sediments after being
transported from a field by a runoff event.
This report was submitted in fulfillment of Grant No. 908940
by Louisiana State University under the sponsorship of the U.S.
Environmental Protection Agency. This report covers the period
26 October 1976 to 25 July 1979, and work was completed as of
25 July 1979.
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CONTENTS
Abstract iv
Figur.es vii
Tables . ix
Acknowledgment x
1. Introduction 1
,;.. 2. Conclusions 5
3. Recommendations 8
4. Literature Review 10
DDT 10
~ ~ Kepone .". ". .7 7" . . ". v ."". ~. . . . . "." . . "15
Permethrin ^ 17
5. Materials and Methods 21
Experimental microcosms . 21
Degradation studies 24
DDT 24
Kepone 27
Permethrin 29
6. Results and Discussion 31
DDT 31
Kepone 44
Permethrin 45
7. Auxiliary Studies 55
DDT degradation under aerobic, anaerobic,
and alternate aerobic/anaerobic
conditions 55
Adsorption of l^C-labelled DDT by
different components of sediment
particulates 57
Redox and pH effects on settling rate
and solid/liquid phase distribution of
14C-labelled DDT 60
Redox and pH effects on diffusion of DDT
and Kepone into sediment cores 61
References 65
Appendices 72
A. Development and testing of procedures/trouble
shooting/additional notes/quality assurance ... 72
B. Tables for DDT, Kepone, and Permethrin
degradation studies under controlled pH and
redox potential conditions 83
.-. vi
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FIGURES
Number
pH and redox potential control apparatus for
incubating pesticide-amended soil and sediment
suspensions 22
The effect of redox potential (Eh) on the recovery
of added DDT from Mobile Bay sediment suspension
during a 45-day incubation at pH 6.0 (amended
with 25 ppm DDT .initially) 32
The effect of redox potential (Eh) on the recovery
of added DDT from Mobile Bay sediment suspension
during a 45-day incubation at pH 7.0 (amended
with 40 ppm DDT initially) 33
The effect of redox potential (Eh) on the recovery
of added DDT from Mobile Bay sediment suspension
during a 45-day incubation at pH 8.0 (amended
with 25 ppm DDT initially) 34
The effect of redox potential (Eh) on the recovery
of ODD from a Mobile Bay sediment suspension
amended with DDT during a 45-day incubation at
pH 6.0 38
The effect of redox potential (Eh) on the recovery
of ODD from a Mobile Bay sediment suspension
amended with DDT during a 45-day incubation at
pH 7.0 39
The effect of redox potential (Eh) on the recovery
of ODD from a Mobile Bay sediment suspension
amended with DDT during a 45-day incubation at
pH 8.0 40
The effect of redox potential (Eh) on the recovery
of DDE from a Mobile Bay sediment suspension
amended with DDT during a 45-day incubation at
pH 6.0 41
VII
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Figures (cont'd)
Number Page
9 The effect of redox potential (Eh) on the recovery
of DDE from a Mobile Bay sediment suspension
amended with DDT during a 45-day incubation at
pH 7.0 42
10 The effect of redox potential (Eh) on the recovery
of DDE from a Mobile Bay sediment suspension
amended with DDT during a 45-day incubation at
pH 8.0 43
'11 The effect of redox potential (Eh) on the recovery
of added Kepone from James River sediment
suspension during a 51-day incubation at pH 5.0
(amended with 21 ppm Kepone initially) 45
12 The effect of redox potential (Eh) on the recovery
of added Kepone from James River sediment
suspension during a 52-day incubation at pH 7.0
(amended with 21 ppm Kepone initially) 46
13 The effect of redox potential (Eh) on the recovery
of added Kepone from James River sediment
suspension during a 70-day incubation at pH 8.0
(amended with 21 ppm Kepone initially) 47
14 The effect of redox potential (Eh) on the recovery
of added Permethrin from an Olivier soil
suspension during a 25-day incubation at pH 5.5
(amended with 15-17 ppm Permethrin initially) ... 50
15 The effect of redox potential (Eh) on the recovery
of added Permethrin from an Olivier soil
suspension during a 26-day incubation at pH 7.0
(amended with 15-17 ppm Permethrin initially) ... 51
16 The effect of redox potential (Eh) on the recovery
of added Permethrin from an Olivier soil
suspension during a 26-day incubation at pH 8.0
(amended with 15-17 ppm Permethrin initially) ... 52
Vlll
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TABLES
Number
Kepone levels in various environmental compartments
around Hopewell, Virginia, and critical concentra-
tions for selected fish species (41, 42, 43) .... 16
Toxicity of Pounce to several aquatic animals
(Jolly et al., 1978) 20
Recovery of Permethrin from an Olivier soil suspen-
soil incubated under continuous nitrogen or air
purging at pH 5.5 and pH 7.5 48
Effect of pH and oxidation levels on the relative
degradation of the cis and trans isomers of
Permethrin for selected sampling dates and redox
potential treatments 53
DDT, DDD, and DDE recovery from a DDT-amended Mobile
Bay sediment suspension incubated under, continuous
aerobic, anaerobic, and alternate aerobic-anaerobic
conditions for 3 months 56
The effect of initial DDT concentration and selective
removal of soluble salts, organic matter, and iron
oxides on water soluble and organic solvent
extractable DDT in Calcasieu River and Mobile Bay
sediment materials 59
The activity of 3:1 hexane:acetone extractable
l^C-labelled DDT with time in column settling
studies 62
14
The activity of water soluble C-labelled DDT with
time in column settling studies 62
Diffusion of DDT and Kepone from a sediment-water
interface into Mobile Bay sediment material
equilibrated under a range of pH and redox
potential conditions 64
IX
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ACKNOWLEDGMENTS
The authors wish to acknowledge Ms. Cheryl Hinton for
assisting in sample preparation and analysis and Ms." Rita
Strate for manuscript preparation. Appreciation is also
extended to a number of scientists associated with pesticide
laboratories mentioned elsewhere in the report for their help
during the study.
x
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SECTION 1
INTRODUCTION
Synthetic organic pesticides have been used extensively
for almost three decades for controlling nuisance weed, insect,
and microbial organisms. However, environmental problems some-
times arise 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 which may be
transported to sensitive ecosystems away from the point of
application.
Because of documented cases of environmental problems
associated with synthetic organic pesticide use, pest control
research has been directed to: 1) use of more selective and
less persistent materials, 2) use of non-chemical means of pest
control, 3) refinement of application equipment and methods, 4)
improved monitoring of pest populations and activity in fields
to permit.more judicious scheduling of pesticide applications,
and, 5) a combination of these procedures. Because of their
effectiveness and economic benefits, it is likely that synthetic
organic pesticides will continue to play a key role in most pest
control programs for the foreseeable future.
A substantial amount of environmentally related research
has been conducted with pesticides and especially 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. However, pesticide residues are subject to a wide range
of physicochemical conditions in the environment. Soon after
typical agricultural 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 condi-
tions at the point of application. For example, typical agricul-
tural soils exhibit a wide range in texture (from sandy to heavy
clay material), pH commonly ranges from 5 to 7.5, soils are non-
saline, and the organic carbon., content of the plow layer typically
ranges from a few tenths of a percent up to 2 percent. Compared
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to typical agricultural soils, sediments are characterized 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 as nitrogen and phosphorus, trace
metals, toxic metals, petroleum hydrocarbons, and certain pesti-
cides. For pesticides, these differences 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 information available on pH
and redox potential (oxidation-reduction conditions) effects on
adsorption and degradation for selected pesticide compounds to
document that these are important parameters to be considered in
understanding the environmental fate of many pesticides. How-
ever, there is need for much more work to be done under carefully
controlled pH and redox potential conditions to improve our
understanding of factors affecting the environmental persistence
and transport of pesticides. This is especially important since
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.
This research was conducted to determine the effects, of
physicochemical 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-bis-(p-chloro-
phenyl)-2, 2, 2-trichloroethane] 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. Additionally, since this was the first pesticide
research conducted in this laboratory, it was desirable to use a
compound for which much published information is available on
extraction, cleanup, and analysis techniques. For example, it
was believed that good and reproducible methods of sample
preparation and extraction would be available from the literature
such that these aspects of the study would present minimal
problems and our attention could focus on the planned experimental
parameters to be imposed on pesticide amended sediment-water
systems. In practice, there, were problems in most of the various
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procedural steps. An examination of the literature suggested
this might be the .case as there was considerable variability
in the reported optimum preparation and extraction procedures
for different soil and sediment materials. Also, most published
DDT work has involved soil materials. The Mobile Bay sediment
material used contains substantially more clay and-organics than
typical agricultural soils and can be expected to bind most
synthetic organics more tightly. There was also a wide range of
reported degradation times for DDT and its analogs. All of this
suggested that the particular environmental materials studied
play an important role in determining the suitability of the
various reported procedures and the environmental fate determined
from different studies. These points will be addressed in the
following review of the literature.
*: Kepone [decachloro octahydro-1, 3, 4-metheno-2H-cyclobuta-
[cd]pentalen-2-one] was included in these studies to determine
if its persistence in the environment is influenced by physico-
chemical conditions. The known environmental problems with this
compound are confined to the James River and connecting estuaries.
Since essentially nothing was known of factors affecting Kepone
persistence in soils and sediment-water systems, this compound
was included to determine if studies of physicochemical effects
on its persistence might suggest something about its fate in the
James River and perhaps suggest management practices which can
be used to minimize adverse environmental impacts.
The persistence of Permethrin, [3-phenoxybenzyl (+) cis-
trans-3-(2, 2-dichlorovinyl)-2, 2-dimethylcyclopropanecarboxylate]
a synthetic pyrethroid, was also studied under controlled physi-
cochemical conditions. The synthetic pyrethroids are a rela-
tively new class of insecticides which are highly effective
against target insects, exhibit low mammaliam toxicity, and are
far less persistent in the environment than many chlorinated
hydrocarbon insectides. The high susceptibility of larvae and
juvenile crustaceans to certain of these compounds and the
expected increasingly important role of the synthetic pyrethroids
in insect control programs suggest it is important to examine
factors affecting the persistence of these residues in the
environment.
Early in this work, it was apparent that published extrac-
tion procedures for recovering various pesticides from typical
agricultural soils were often not effective when applied to
typically fine textured, anaerobic sediments. Also, conventional
drying of anaerobic soil and sediment materials containing
relatively non-persistent pesticides which exhibit different
degradative rates, depending on physicochemical conditions, was
believed to introduce artifacts which affect results of degrada-
tion studies. A review of the literature revealed that almost
all of the published extraction procedures involved agricultural
soils. Thus an unplanned but important phase of this work was
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to develop and test sample processing procedures for fine
textured anaerobic soils and sediments which give satisfactory
and reproducible recoveries.
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SECTION 2
CONCLUSIONS
A study was conducted to determine the effects of pH and
oxidation-reduction conditions of soils and sediment-water
systems on the persistence of three insecticide compounds. Soil
or sediment materials amended with DDT, Kepone, and Permethrin
were incubated as suspensions under conditions of carefully
controlled pH and redox potential conditions in laboratory
microcosms.
The effects of physicochemical parameters on the persistence
and transformations of DDT were studied in a Mobile Bay sediment
material at pH 6.0, 7.0, and 8.0. The recovery of DDT from the
spiked Mobile Bay sediment material decreased very rapidly under
strongly reduced conditions (-150 mV) such that 90 percent could
not be recovered after as little as 5 days. This apparent rapid
degradation rate under strongly reducing conditions was somewhat
greater than reported in most published studies on the effects
of reducing conditions on DDT persistence.
Several reasons for the rapid decrease in.DDT recovery were
considered. The "bound residue effect" (1) may be contributing
to the low recovery of DDT early in the incubations. The extent
of this process, if it is occurring, cannot be quantified, but
it appeared unlikely this phenomenon was a major factor only^
at -150 mV. Artifacts introduced during sample processing
(especially drying) were evaluated in the laboratory and even-
tually ruled out as a significant factor in the low initial
recovery of DDT under, strongly reducing conditions. Although
the levels of known degradation products measured did not
totally account for the loss in DDT, ODD levels were greatly
increased where DDT was disappearing rapidly at -150 mV providing
evidence that a substantial amount of DDT was actually degrading
within a matter of 1 to 3 days. It was concluded that DDT was
indeed degrading very rapidly under very strongly reduced
conditions in the Mobile Bay sediment material compared to
moderately reduced or oxidized 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 t9-.very rapid losses of DDT from
this material compared to most published degradation rates for
DDT. Another factor may be that the -150 mV potential included
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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 predominated. Only at 50 mV was there an
indication that a degradation product was accumulating in the
Mobile Bay sediment material. The small increase in DDD levels
noted with time was not equal to the rate of DDT loss indicating
DDD 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 degrades 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. 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.
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, accord-
ing to the literature, are highly sensitive to some synthetic
pyrethroids. Permethrin cannot be considered a persistent
pesticide compound compared to most chlorinated hydrocarbons.
However, its somewhat greater stability in reducing sediments
which may receive residues in runoff, and the potential for
adverse effects to organisms associated with sediment-water
systems make physicochemical effects on Permethrin degradation
an important environmental consideration.
The work with the three compounds included in this study
demonstrated that pH and oxidation-reduction conditions do
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affect the persistence of pesticide compounds and that different
compounds may respond differently to a given physicochemical
environment. In this study, the stability of one compound was
little affected by altered pH and oxidation conditions, another
was markedly affected by oxidation conditions, and the degrada-
tion of the third was strongly influenced by both pH and redox
potential conditions. ....--. ^. __~ _
A substantial amount of environmentally related research
has been conducted with pesticides and especially 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. However, pesticide residues are subject to a wide range
of physicochemical conditions in the environment. Soon after
typical agricultural applications, most residues become associ-
ated 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 condi-
tions at the point of application.
The ranges of physicochemical (pH and redox potential)
parameters studied are commonly encountered in soils, sediments,
and surface water which may receive pesticide residues. Also,
temporary flooding of soils or- certain dredged material disposal
methods can alter the physicochemical properties of contaminated
soils or sediments affecting the persistence and possibly the
mobility of pesticide residues. Information on the effects of
physicochemical conditions on the adsorption and degradation of
specific pesticides should contribute to improved predictive
capability on the transport and fate of pesticide residues in
various compartments of the environment.
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SECTION 3
RECOMMENDATIONS
The results of this study demonstrated that the physico-
chemical 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 environ-
mental 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 compartments which may receive residues, it is
important to understand the influence of physicochemical condi-
tions 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 poten-
tial for persistence and accumulation in anaerobic lake and
wetland sediment-water systems.
The following recommendations are made:
Elecause 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 compounds thought to be relatively persis-
tent, compounds known to be especially toxic, particularly to
non-target organisms, and compounds which 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 chemical 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 degradation in soils and
-" ':' 8 ~:
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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
which 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
physicochemical effects under more natural conditions to more
accurately reflect the rate of the processes under real world
conditions.
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. Thus
studies should be done to characterize the relationship of the
activity of microbial populations to the transformations observed
for synthetic organics under various physicochemical conditions.
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SECTION 4
LITERATURE REVIEW
A great deal of information has been published on the fate
of DDT in the environment and on methods of extraction and
analysis. There is considerably less information available on
Kepone and the synthetic pyrethroids. The following review of
literature will discuss these three classes of compounds
individually.
DDT
DDT [1, l-bis-(p-chlorophenyl)-2, 2, 2-trichloroethane]
and certain of its analogs have been used extensively in many
regions of the world for insect control beginning about 30 years
ago. Studies which indicated the biological accumulation and
environmental persistence of the DDT group of insecticides were
the first to conclusively establish that the widespread use of
certain synthetic pesticides can have serious environmental
consequences. Because of its long-term use and environmental
persistence, a substantial amount of information is available on
the fate of DDT in the environment as well as information on
methods of extraction and analysis.
DDT has been reported to volatilize rapidly from clean,
moving water (2) with a half life of only a few days. In
environmental water samples, the volatilization rate was
decreased by a factor of 2- to 3-fold (still relatively fast),
presumably due to 'the presence of suspended organic and in-
organic particulates. Others have also reported rapid volatil-
ization of chlorinated hydrocarbons from river water samples
equilibrated in the absence of sediments, and essentially no
volatilization into the atmosphere when water samples were
associated with sediments (3). This is indicative of the
strong partitioning of sparingly soluble, lipophilic chlorinated
hydrocarbons with the solid phase of soil- and sediment-water
systems. The effective scavenging of sediments for DDT group
compounds is well established in the literature (4). Similarly,
residues in soils are usually found in the surface horizons (5)
and do not significantly leach into deeper soil layers and
ground water. Organic matter content (6), and even the degree
of humification of organic matter (7), the content of fine clays
""'' 10 "'';.' .
-------
vs coarser material (8), the type of clay (9), and the presence .
of amorphous oxides of iron (6) are all thought to play important
roles in adsorbing pesticides. Pionke and Chesters (6) suggested
differences in structural composition of organics in reduced
sediments vs. oxidized systems would likely contribute to greater
adsorption by the reduced sediments in addition to the greater
adsorption due to the usual greater organic matter "content of
reduced sediments~relative to surrounding upland soils. "
Although certain of the known degradation products of DDT
have been used as the primary insecticide for some applications,
p, p'-DDT is by far the predominant compound of the DDT group
applied. More than a half dozen different degradation products
of the parent compound have been identified (10, 11), but the
primary degradation products reported in the literature are ODD
[1,. 1-bis-(p-chlorophenyl)-2, 2-dichloroethane] and DDE [1, 1-
bis-(p-chlorophenyl)-2, 2-dichloroethylene]. It has been pointed
out that commercially available p, p'-DDT applied contains some
o, p-DDT, (12). Thus this compound and its degradation analogs
have also been widely distributed in the environment, though in
substantially lower concentrations than the p, p'-DDT group.
It is well known that the DDT group of compounds is very
persistent in the environment with a "half-life" often reported
in terms of years and even longer than a decade in many systems.
However, there is a wide range in the reported persistence of
DDT and surprisingly short degradation times for some systems
have been reported. Some of the reported degradation times of
DDT include: 4-10 years in unflooded soils, 60-180 days in
flooded soils (review of literature by Sethunathan, [13]);
about 20 percent at 30°C in 140 days in soils in the presence of
water (14);.70 percent in 4 weeks in Crowley silt loam soil
incubated under argon, and 80 percent with 1 percent glucose
addition (Parr, Willis, and Smith, [15]); 50 percent loss of DDT
in 24 hours in oxygen deficient lake waters (16); about 65
percent loss of DDT after 4 weeks in anaerobic soil (17); 20
percent in 7 days in flooded Raber silt loam at 30°C (18); 3 years
in Oregon forest soils (19); and a half-life of 10 years in New
Brunswick forest soils (20). Thus various published reports
have indicated that the persistence of DDT may be more than 10
years in some natural systems and on the order of days for other
systems. It is apparent from the wide range in reported DDT
persistence in various natural systems that one or more environ-
mental factors associated with soils and sediment-water systems
must have marked direct and/or indirect effects on the degrada-
tion of DDT.
-------
Influence of Environmental Physicochemical Parameters on the
Fate of DDT
The degradation of DDT is temperature dependent. Gunzi and
Beard (14) reported a loss of about 20 percent at 30°C and 50
percent at 50°C in 140 days in the presence of water. In another
study, they reported a 20 percent removal in 7 days in a flooded
Raber silt loam at 30°C and 35 percent in 7 days at 40°C (18).
ODD and DDE are thought to be the predominant initial
degradation products of DDT in the environment and only a few
investigators (11, 21) have attempted to look beyond DDT, ODD,
and DDE when studying the environmental fate of the DDT group.
Although ODD and DDE are thought to be lost from most systems,
their degradation in soil has been very difficult to establish
(12). It is widely reported that ODD is the major product of
DDT degradation under anaerobic conditions and that DDE is the
chief degradative product formed under aerobic conditions.
The DDE formed from the degradation of DDT in aerobic soil
is resistant to further degradation (22). Metcalf et al. (23)
compared the environmental behavior of DDT, ODD, and DDE in a
model ecosystem. The DDE was found to be a highly persistent,
lipid-partitioning metabolite of DDT which accumulated in animal
tissues following the use of DDT. Their data also indicate that
ODD is also a lipid-partitioning compound, however, it is more
biodegradable than DDE. Toxicity of ODD is about one-tenth that
of DDT (24).
Factors affecting DDT degradative processes include the
amount and microbial availability of organic matter (energy
source), temperature, pH, oxidation-reduction conditions, kinds
and activity of microbial populations present, and certain
other factors such as the presence of electron transfer substances
like inorganic or organic iron forms. Many of these interacting
factors are affected by oxidation-reduction conditions. Thus
oxidation-reduction conditions should play a major role in the
environmental fate of DDT and a review of the literature shows
this to be the case.
Numerous investigators have shown that DDT is less persistent
in anaerobic than aerobic soils (15, 21, 25, 26, 27) and that
ODD is the principal degradation product in anaerobic or reduced
soils and sediments while DDE is the principal degradation
product in oxidized or aerobic systems (26). Farmer et al.
(26) suggested DDE is the more, hazardous of the two degradation
products (as confirmed by reports of DDE accumulation in birds,-
certain mammals, and marine organisms), and it has been suggested
that flooding should be considered where feasible as a management
practice to encourage the ODD degradation pathway (26). Guenzie
et al. (21) concluded that residues of DDT and other chlorinated
hydrocarbon insecticides can .be substantially reduced if the
"'" 12' i-;'-': .
-------
redox potential of field soils can be decreased to about 250 mV,
a mildly reduced condition. Guenzi et al. (21) also state the
available literature suggests that reduced soils and sediments
result in different degradative microbial populations and break-
down pathways as well as differences in adsorption of pesticides
to" sediments "and soils compared to oxidized or aerobic systems.
In a review of the literature, Sethunathan (13) reported
studies indicating a 4- to 10-year persistence of DDT in unflooded
soils while DDT disappeared from some flooded soils in 60 to 180
days. Although these data represent different studies and soil
materials, they are indicative of the role of oxidation-reduction
conditions in DDT degradation. Usually in soils with a readily
available energy source, flooding is the general treatment used
to obtain reducing or anaerobic conditions. It is interesting
to:note that Parr and Smith (15) noted a substantially greater
loss of DDT in unamended and organic matter amended Crowley silt
loam incubated under a nitrogen atmosphere at 1/3 bar moisture
(approximate moisture content of a field soil following gravity
drainage for 24 hours after saturation) than under flooded
conditions. Even in soils incubated anaerobically, the degrada-
tion of DDT will occur more readily when the system is amended
with an energy source. Of course, this enhances facultative and
obligate anaerobic microbial activity and subsequently results
in development of more strongly reduced conditions. Parr and
Smith (15) found that although glucose amendments increased DDT
loss from moist soil under a nitrogen atmosphere, alfalfa meal,
rice straw, and rice hulls were much more effective.
In studies with Aerobacter aerogenes, Plimmer et al. (28),
demonstrated the principal route of anaerobic microbial degrada-
tion was direct reductive dechlorination of DDT to ODD. They
also suggested that a large number of facultative and obligate
anaerobic bacteria can mediate this conversion under anaerobic
conditions, but not aerobic conditions.
The formation of DDE from DDT can be due to biological or
chemical dehydrochlorination, especially in alkaline environ-
ments. Guenzi and Beard (10) reported a comparison of DDE
formation in sterile and nonsterile soil material revealed that
84 percent of the conversions was the result of chemical degra-
dation at 30°C and the percentage was 91 at 60°C. In sterile
soil material, the DDE formation rate was similar in, submerged
soil and soil with a 1/3 bar moisture content. The transforma-
tion of DDT to DDE was believed to be catalyzed by certain
metals and minerals and they refer to studies where iron, iron
chlorides, aluminum chlorides, and iron oxides catalyze the
reaction at high temperatures (100°C to 130°C) in soils. Of
course, natural soil and sediment temperatures would not approach
these levels, but they point out that Lord (29) increased DDT
degradation by adding ferrous 'sulfate, ferric ammonium alum,
copper sulfate, and manganese sulfate to basic acetone solutions
' " ' 13 V.
-------
at 30°C. Again, an acetone solvent is not typical of soils and
sediments, but a role of metals in catalyzing the degradation of
DDT is suggested.
Guenzi and Beard (10) refer to the work of Nash (30) where
conversion of- DDT to DDE was. very -slow in a moist soil in the pH
range of 4 to 6.8, but increased rapidly as pH increased from
6.8 to 7.5. It was suggested that the DDT conversion to DDE was
principally a microbial process at lower pH, but probably a
chemical process at higher pH levels. Many microbes are reported
to possess the ability to transform DDT to DDE. The reaction is
said to be catalyzed by iron, enhanced under alkaline conditions,
and can be mediated by resistant insect strains (31).
Guenzi and Beard (10) concluded that conversion to DDE was
mostly a chemical process with some microbial contribution in
the systems studied. Water, temperature, and soil properties
affect the conversion. They suggest from their studies and the
literature that the transformation occurs at active sites which
may be iron oxides. Others have cited studies suggesting
that adding lime to increase pH, or adding aluminum or iron
oxides to the soil materials studied failed to enhance the
transformation of DDT to DDE and that microbial conversion is
the predominant process in moist soil while chemical processes
are most active in dry soils.
In a review of the literature, Sethunathan (13) cites work
of Gunzie et al. suggesting ODD formation occurs at about the
same redox potential at which nitrate becomes unstable in
soils. References were cited giving evidence that once formed,
ODD resisted further degradation. However, Castro and Yoshida
(32) were reported to have found that ODD was removed faster
from flooded than non-flooded soil, though the removal process
was slower than DDT loss.
Others also reported from a review of the literature that
ODD formed in flooded soils was more persistent than DDT and
that ODD appears relatively stable in lake sediments (16).
These people also cited studies in which 50 percent of the DDT
in oxygen deficient lake water was transformed to ODD in 24
hours, certainly one of the fastest conversions reported for
natural systems. Guenzi and Beard (10) reported that after 4
weeks of anaerobic incubation, 62 percent of the added DDT was
in the ODD form and only 34 percent of the original DDT re-
mained. Only traces of DDE were detected.
In a later study with a Raber silt loam material incubated
with DDT under flooded conditions, 80 percent of the applied DDT
was recovered unchanged after 7 days at 30°C, 12.3 percent as
ODD, and 0.8 percent as DDE for a total recovery of about 93
percent. Although they cite studies where ODD accumulations
14
-------
account for the loss in DDT, in this study, they found a rapid
degradation of DDT and a lack of an equivalent accumulation of
DDD.
Glass (33) has suggested an irreversible redox reaction for
the degradation of DDT under anaerobic conditions involving
electron transfer from reduced organic materials .through ferrous
iron ions. The role attributed to soil microorganisms was in
creating reducing conditions by depleting molecular oxygen
followed by facultative and obligate anaerobic organisms using
alternate electron acceptors (i.e., Fe3+, Mn4"1", NOp to produce
moderately to strongly reduced systems. The Fe+J ion gains an+_
electron from the metabolized organic substrate and becomes Fe
ion, an electron donor. The electron is then transferred to the
DDT molecule which exhibits a strong electron affinity because
.of'its chlorine atoms. In the process of electron capture, a
chloride ion is released and the parent molecule exists as a
free radical. This free radical abstracts a proton from a
proton donor and forms DDD. Wedemeyer (34) reported that DDT
dehydrochlorinated in the presence of reduced Fe(II)-cytochrome
oxidase. The work of Ecobichon and Saschenbrecker (35) showed
that the conversion of DDT to DDD would possibly result from the
action of reduced coenzymes, porphyrins, and other metallo-
proteins from plant tissue and micro-organisms which probably
degrade DDT by a chemical redox reaction rather than by an
enzymatic reaction. Kearney et al. (31) suggested the microbial
conversion of DDT to DDE is catalyzed by iron and enhanced with
increasing pH conditions.
KEPONE
Kepone is a caged chlorinated hydrocarbon (C, 24.48%; Cl,
72.26%; and 0, 3.26%) compound developed in the early 1950's and
introduced as a pesticide by Allied Chemical in 1958. It is a
white, crystalline, non-volatile solid reported to be insoluble
in water. It is very stable as it is unaffected by strong acids
and strong base (36).
It has been used as a fungicide and insecticide. It is
reported to be highly effective against ants, roaches, as well
as banana and potato insect pests, though its greatest use has
been for banana pest control in Central America (37). Interest
in the environmental impact of Kepone in the United States has
centered on one incident in which a Kepone production facility
discharged its toxic wastes through the Hopewell, Virginia
sewage treatment plant resulting in Kepone contamination of the
water, sediment, and biota of the James River as evidenced by
traces of Kepone found in fish and shellfish from this area (38,
39).
15
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Because Kepone has been demonstrated to be highly toxic and
highly bioaccumulative to many aquatic and benthic organisms
(40, 41), there is concern that a potentially serious Kepone
threat to aquatic organisms and possibly human consumers may
extend from the James River into the Chesapeake Bay. Because of
the environmental persistence of Kepone, the occurrence or
threat of adverse environmental impacts could continue for
years.
Table 1 gives levels of Kepone found in selected compart-
ments of the affected environment around Hopewell (42), and
levels reported to cause specific adverse^ effects on selected
species (41, 43).
TABLE 1. KEPONE LEVELS IN VARIOUS ENVIRONMENTAL COMPARTMENTS
AROUND HOPEWELL, VIRGINIA, AND CRITICAL CONCENTRATIONS FOR
SELECTED FISH SPECIES (41, 42, 43)
Environmental Compartment~Kepone Levels
James River water 0.1 to 4 ppb
fish and shellfish 0.1 to 20 ppm
Bailey's creek sediments 0.1 to 10 ppm
most samples in the
1-4 ppm range
Hopewell sewage sludge " 200-600 ppm
soil adjacent to Life Sciences 10,000-20,000 ppm
(Kepone production) plant
soil 3000 ft. east of plant 2-6 ppm
96-hr LCso for spot (Leiostomus 6.6 ppb in water
xanthurus), most sensitive of
several species treated (41)
Kepone concentration resulting 0.8 ppb in water
in morphological effects on
sheepshead minnows after 36
days exposure (43)
When this contamination event occurred, it was generally
known that Kepone was a persistent compound in the environment,
but relatively little was known about factors affecting its
environmental persistence or its release from contaminated soils
and sediments to more available forms. Various methods for
cleaning up Kepone contamination have been studied, such as
combustion (44), and in some cases implemented. In most cases,
effective cleanup procedures,have been limited to very localized
16 V. '
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situations such as disposal of waste from the production plant,
adjacent waste disposal facilities, sewage treatment facilities,
contaminated sludge, highly contaminated soils, and residences
in the area. One EPA report even mentions plans are being
developed and evaluated for dredging the James River (45).
However, 'reports released later indicate cleanup of the contami-
nated James River by dredging "... may not be technically feasible
or financially possible..." as dredging costs could approach $1
billion and require the equivalent of 120 dredging years to
accomplish (46). Safe disposal of the contaminated dredged
sediments would be substantial additional problems. "
Although it is known or generally accepted that Kepone is
very persistent in the environment, there has been little if
any research on how various properties of soils or sediment-
wa;ter systems may affect the degradation and mobility of Kepone.
There is some evidence for degradation products of Kepone (36,
47), however, the identity of residual Kepone decomposition
products in the environment have not been determined as far as
we know.
Kepone was included in this study to determine if the
physicochemical parameters of pH and oxidation-reduction condi-
tions affect its environmental fate as has been found for many
other pesticides. Although management practices based on physi-
cochemical effects on the environmental fate of Kepone are not
being contemplated at this time, it was anticipated studies of
this type might provide some information useful for predicting
the impact or persistence of Kepone contamination in certain ,
environmental compartments.
PERMETHRIN
The development of resistance to conventional insecticides
by the cotton bollworm (Heliothis zea Boddie) and the removal of
remaining partially effective insectices such as DDT from general
agricultural use has created a great deal of interest in the
development of new insecticides that combine effective bollworm
control with minimum adverse environmental effects. In England,
recent developments in pyrethroid chemistry have resulted in the
synthesis of relatively stable compounds with high toxicity to
the cotton bollworm (48). This is a new class of compounds
having great potential for insect control and is replacing the
old class of natural pyrethrins which are manufactured from
certain plant extracts. These synthetic pyr.ethroids are being
used on an experimental basis and show such outstanding promise
that there is little doubt they will be used throughout the
Southern cotton growing areas if and when they receive final EPA
clearance.
17
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Natural pyrethins comprise the oldest class of organic
insecticides known and have a long history of use. However,
very little is known about the persistence or microbial degrada-
tion of natural or synthetic pyrethroids in soils (12).
The. first class of synthetic .pyrethroids which demonstrated
characteristically high activity against insects and low mam-
malian toxicity as well as greatly increased stability were
described by Elliott et al. (49, 50). These synthetic pyre-
throids are more photostable than many of the common organophos-
phates and carbonates and are more insecticidally active by at
least one order of magnitude. Many of these compounds were
synthesized during 1973-1977. Because of their outstanding
effectiveness against many insects, these compounds will likely
be introduced commercially to replace or compliment many exist-
ing products used for a variety of insect pests.
Synthetic pyrethroids include: 1) Allethrin; 2) Bio-
allethrin; 3) S-bioallethrin; 4) Tetramethrin;. 5) Resmethrin;
6) Bioresmethrin; 7) Cismethrin; 8) Phenothrin; 9) Permethrin;
10) Cypermethrin, and 11) Fenvalerate. Various other synthetic
pyrethroids which have been tested but which have not been
designated by common names include: 1) FMC 33297 (3-phenoxy-
benzyl (+)-3-(2, 2-dichlorovinyl)-2-2-dimethylcyclopropane
carboxylate); 2) Shell WL 41706 (a-cyano-3-phenoxybenzyl-2, 2,
3, 3-tetramethylcyclo-propane carboxylate); 3) Shell WL 43775
(ct-cyano-3-phenoxybenzyl-2- (4-chlorophenyl)-3-methyl-l-butyrate) ;
4) RU 11679; 5) RU 15525, and-others (51, 52).
All these synthetic pyrethroids are lipophilic compounds,
almost insoluble in .water. In these respects they resemble the
chlorinated hydrocarbons. They are- high boiling viscous liquids
and most exhibit low vapour pressure (53).
These pyrethroids were found to be 3 to 8 times more toxic
to fish and insects at low temperature (15°C) compared to high
temperature (32°C) (51, 54). No other work has been reported on
the kinetics of their degradation under various temperature
regimes.
Very little has been reported on the behavior of pyrethroids
in soil. Their physical properties would suggest relatively low
mobility in soil. Their low vapour pressure suggests that their
vapour diffusion in soil air space will not be significant (55).
Their highly lipophilic character with octanol-water coefficients
greater than 10^ (56) suggests that synthetic pyrethroids would
be strongly adsorbed in most soils and thus not leached readily
from the point of application or deposition (57). Significant
amounts of these compounds are likely to enter surface waters
only by direct application or by sediment transport from treated
soils and not by diffusion or leaching.
is --.:
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Very little is known of the metabolism of pyrethroids in
soil. Kaufman et al. (58) recently reported that Permethrin is
extensively degraded by soil microorganisms within 4 weeks by
ester cleavage and oxidation, eventually to carbon dioxide.
Pyrethroid esters with a-cyano groups have been reported to be
relatively more stable (59).. .. - - .
To date, work on the behavior of some of these synthetic
pyrethroids in soils has been reported only by Roberts and
Standen (60). They studied the degradation of cypermethrin and
geometric isomers of NRDC 160 (cis-) and NRDC 159(trans-) in
three soils varying in texture. The rate of degradation was
most rapid on sandy clay and sandy loam soils compared to a fine
textured soil. The major degradation route in all soils was
hydrolysis of the ester linkage leading to formation of 3-
.phenoxybenzoic acid and 3-(2, 2-dichlorovinyl)-2, 2-dimethyl-
cyclopropane carboxylic acid. A minor degradative route was
ring-hydroxylation to give an a-cyano-3-(4-hydroxyphenoxy)
benzyl ester, followed by hydrolysis of the ester bond. Under
waterlogged conditions, the rate of hydrolysis of cypermethrin
on sandy loam soil was slower than under aerobic conditions, and
3-phenoxybenzoic acid accumulated in the anaerobic soil. This
finding suggests the possibility of greater buildup of synthetic
pyrethroids in wetlands than in upland soils. Their study
indicates that oxidation-reduction conditions (redox potential)
of soil systems have a major effect on the degradation of
synthetic pyrethroids. Because redox potential and pH are
inversely related in many soil's, and because ester hydrolysis
reactions are influenced by the degree of acidity or alkalinity,
pH should also have an effect on the degradation of pyrethroids.
Synthetic pyrethroids have been reputed to be very toxic to
fish. The lipophilic nature of these pyrethroids indicates that
'they will be strongly absorbed/adsorbed by the gills of fish
'even from very low concentrations in water. Mauck et al. (54)
"reported toxicity of natural pyrethrins and synthetic pyrethroids
to fish. Miyamoto (61) gave preliminary data on the toxicity of
optical and geometrical isomers of phenothrin, permethrin,
resmethrin, and tetramethrin. Their data indicate that pyre-
throids were far more toxic to killifish than organophosphates
and carbonates (62).
Jolly et al. (63) reported the acute toxicity of, a pyrethroid
(Pounce) to aquatic animals. Results of their study are given
in Table 2. Crawfish were most sensitive to Pounce since they
are phylogenetically close to insects. Even a concentration of
less than half of one part per billion killed more than 50% of
the population in 96 hours. The high degree of toxicity of
Pounce to crawfish is in the same range as most toxic organo-
chlorine insecticides such as DDT, Endrin, and Toxaphene.
Pounce is now being used in limited quantities under an experi-
mental label.
' ' 19
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TABLE 2. TOXICITY OF POUNCE TO SEVERAL AQUATIC ANIMALS
(JOLLY ET AL., 1978) .
Concentration
Mean weight Total length (ppb) required
oj-ici-Aca
Crawfish, newly
(grams)
0.05
- (millimeters.)
8-12
UU JS.J.J.J. JW6
in 96 hours
0.39
hatched
Crawfish, juvenile
Channel catfish
Bass
Mosquitofish
Bullfrog tadpoles
0.50
0.02
1.14
0.25
0.01
20-30
14-17
45-55
15-25
6-8
0.62
1.10
8.50
15.00
7,033.00
In Louisiana and other coastal states in the United States,
much of the land used for agriculture is in close proximity to
lakes, streams and ponds that support aquatic animal populations
which are of great .commercial-importance. The transport and
persistence of pyrethroids in sediment-water systems are of
particular concern because of the demonstrated toxicity to some
benthic species. Benthic species potentially affected may be
commercially important species or lower members of predominantely
aquatic food chains. The crawfish industry is very important to
Louisiana and other coastal states. In Louisiana, the annual
value of pond-raised crawfish has been estimated to be $10
million.
20
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SECTION 5
MATERIALS AND METHODS
EXPERIMENTAL MICROCOSMS
Pesticide-amended soil and sediment suspensions were
incubated under controlled pH and redox potential conditions
using the microcosm shown in Figure 1. Suspensions were main-
tained in the 2-liter, 3-necked, flat-bottomed flasks by con-
tinuous stirring of the soil- or sediment-water mixture using a
motor-driven magnetic stirrer. Flexible polyvinyl chloride
(Tygon) tubing was placed over the 2-inch (5.08 cm) teflon-
coated magnetic stirring bar in the flask to prevent abrasive
wear to the stirring bar. Each flask was equipped with a combi-
nation pH electrode for measuring pH, two platinum electrodes
for monitoring redox potential, a thermometer, a serum cap for
adjusting pH or extracting samples, separate inlet tubes for air
and nitrogen, and an outlet tube, the end of which was submerged
in a water trap to prevent gaseous oxygen diffusion into the
flask.
All suspensions were maintained at 28°C + 1°. Thin card-
board or asbestos sheets were placed between the flask and the
stirring motor as required to control heat transfer from the
stirrer motor.
The two bright platinum electrodes positioned in the
sediment suspension were connected to a millivolt/pH meter
(Beckman Zeromatic, SS-3) for redox potential monitoring and
control. A saturated calomel reference electrode was connected
to the suspension with a saturated potassium chloride-agar salt
bridge. This laboratory-made reference electrode system was
more satisfactory than a commercial calomel reference electrode
since our experience has shown the solution contact (junction)
on many reference electrodes tend to clog with time when immersed
in highly colloidal materials. This contributed to excessive
junction potentials resulting in error to the redox potential
measurement. The recorder output of the millivolt/pH meter was
connected to a meter relay (General Electric Type 196) which
switched on an aquarium-type air pump whenever the redox
potential dropped below the preset level for each incubation
flask. Slow oxidation of the suspension during the aeration
21
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Calomel
half cell
Millivolt
meter
to '
Magnetic
stirrer
Meter
relay
Air pump
-Air
N,
1. pH electrode
2. Platinum electrodes
3. Salt bridge
4. Gas outlet
5. Serum cap
6. Air inlet
7. N2 inlet
a Thermometer
9. Stirring bar
Figure 1. pK and Redox Potential Control Apparatus for Incubating
Pesticide-Amended Soil and- Sediment Suspensions.
-------
cycle was achieved by metering the air flow to about 1 to 4
ml/minute. When the redox potential again reached the preset
potential, the meter relay would automatically switch off the
air pump.
; " Oxygen-free nitrogen gas was continuously supplied to the
j suspension at a rate of about 5 ml/minute through a separate gas
I inlet. This nitrogen gas was effective in: 1) removing air
] contamination from possible small leaks in the system, 2) pre-
] venting an accumulation of gaseous decomposition products such
I as carbon dioxide or possibly hydrogen sulfide which might
I affect microbial activity, and, 3) purging excess oxygen from
| the system at the end of the aeration cycle.
\ In the absence of oxygen, soils and sediments with suffi-
j cient organic matter content to support appreciable microbial
1 activity tend to become more reducing. Thus the oxidation-
! reduction levels of a soil or sediment water system can be
controlled over a wide redox potential range by regulating the
addition of air to the system. Using the microcosms as described
above permits redox potential control to within 5 to 10 milli-
volts of the desired potential.
Suspension pH was checked once or twice daily and adjusted
to the proper level as required using a syringe to add IN hydro-
chloric acid or IN sodium hydroxide through the serum cap
-': located in the center rubber stopper. The combination pH/
1 reference electrodes used (Beckman Model 39504) required infre-
; quent recalibration since the reference electrode portion,
; equipped with an annular ceramic reference junction, was less
I affected by a gradual changing junction potential due to clogging
;.i by colloidal particulates.
| All soil and sediment materials were batched when initially
j received and then separated into smaller, glass or plastic-lined
.j metal containers for storage at 4°C in their natural moist or
1 saturated conditions until needed in laboratory incubation
.'; ' studies. Each small storage container was thoroughly mixed on a
j roller-mixer immediately prior to weighing out into the incuba-
;: tion flasks. Sufficient water was added to adjust the solids to
' solution ratio to the desired level (300 grams soil or sediment
solids, on an oven dry basis, plus 1500 grams of water), and
i stirring was then begun for the preliminary incubation. The
i preliminary incubation consisted of gradually adjusting both pH
and redox potential conditions of the suspension in each vessel
to preselected levels. Stored soil materials required this
' preincubation to obtain reducing conditions while sediments had
; to be oxidized from their initially reduced condition. Thus
; before pesticide amendments, all of the four suspensions had
.'. achieved preselected redox potential levels ranging from
strongly reduced to well oxidized. Seven to 10 days were
'' 23' "'";: . .
-------
confirmed by extracting the aqueous phases of a spiked sediment-
water suspension and measuring the solution phase DDT. This
amount was negligible compared to DDT levels extracted from the
sediment phase. Thus in our laboratory studies, physicochemical
effects on degradation could be determined by considering the
change in DDT levels associated with the solid or sediment
phase. Therefore, the solution phase was separated by centrifu-
gation and discarded and only the solid phase was extracted for
DDT, ODD and DDE.
The following procedure was used to extract DDT, ODD and
DDE from reduced sediment-water suspension samples in this
study. Background information on the use of this procedure is
presented under the heading of Development and Testing of
Procedures (page 72). Oxidized samples were processed similarly
except that after centrifugation, the sediment material was
dried in a forced draft oven at 35°C.
DDT extraction steps1. Thaw sample. 2. Centrifuge
thawed sediment-water mixture in the glass storage bottle at
approximately 1,000 RCF for 15 minutes. An 0.5 g NaCl amendment
was mixed into the sample to enhance flocculation of solids
during the centrifugation step where necessary. The resulting
aqueous supernatant phase was clear. 3. Discard water phase.
4. Add 15 ml acetone, cover with aluminum foil, and seal
bottle with screw cap. 5. Use shaker for 2 minutes to disperse
sediment phase in acetone. 6._ Centrifuge at about 1,000 RCF
for 10 minutes. 7. Decant acetone layer and save as this
contains some DDT. 8. Repeat steps 4-7 using a new aluminum
foil cover. 9. Evaporate acetone residue in sediment under a
stream of compressed nitrogen for about an hour. 10. Grind
.sediment to a fine powder using porcelain mortar and pestle.
11. Weigh and label Soxhlet extraction thimbles, weigh into
thimbles 3-5 grams of the dry, ground sediment and determine the
exact sample weight. 12. Place thimble into a clean and dry
Soxhlet extraction apparatus, connect to a boiling flask contain-
ing 3 to 5 glass beads and 130 ml of a 3:1 hexane:acetone mixture
and 1 ml of 0.01 percent Nujol solution in hexane. Attach
condenser to top of Soxhlet apparatus. Be sure all joints are
tight. A drop or two of Nujol will seal the occasional ground
glass joint connections found to have slow leaks. 13. Extract
for 12 hours with individual heating elements adjusted for about
6 cycles per hour. 14. After extraction is complete, siphon
over as much solvent into the boiling flask as possible by
tipping extractor. 15. Place the thimble in a glass funnel in
top of Soxhlet extractor and let thimble drain completely.
Rinse thimble and funnel with acetone. 16". Siphon over the
remaining solvent and acetone rinse into the boiling flask and
rinse extractor twice with acetone. 17. Pour the solvent/
pesticide mixture through a funnel equipped with a glass bead
trap into a clean 250 ml separatory funnel. Rinse the boiling
flask and bead-trap funnel with acetone into the separatory
25
-------
funnel. 18. Add the acetone rinses from the sediment drying
steps into the separatory funnel. 19. Add 50 ml of NaCl-
saturated water to the separatory funnel, shake for two minutes
venting often, and permit layers to separate. 20. Drain off
the bottom water layer (the salt prevents an emulsion from
forming, and the water removes the acetone which shpuld not be
run through an electron capture detector). 21. Add 50 ml of
distilled water, shake for 2 minutes venting often, let separate,
then drain off excess water. 22. Repeat step 21 twice more.
Separation of aqueous phase may require more time after each
addition of water. 23. Set up a clean 200 ml volumetric flask
to receive the eluant from a filter funnel filled with sodium
sulfate washed with hexane for each sample. 24. Pour contents
of separatory funnel through the sodium sulfate and rinse
separatory funnel and sodium sulfate funnel twice with hexane.
25., Make 200 ml volumetric to volume with hexane and mix well.
This is the "concentrated" sample. 26. Where dilution was
necessary, 2 ml of the "concentrated" sample was made to volume
with hexane in a 25 ml calibrated, screw-capped test tube and
mixed. 27. For some reduced samples where sulfur caused
problems with the GC analysis, a 12 gauge copper wire pretreated
with 4N HNO, was added to the sample tube to remove this inter-
ference. 28. Inject 5 y£ of sample into the gas chromatograph.
DDT, ODD, and DDE were analyzed on a Perkin-Elmer Model
3920 B gas chromatograph equipped with a Ni-63 electron capture
detector, P-E Model 023 dual pen recorder, and a P-E Model M-l
Intergrator. Typical instrument operating parameters are given
below for DDT.
Column: glass, 6 foot length, 1/4-irich diameter, 10
percent OV-1 on Chromosorb W, 80/100 mesh
Flow Rate: 70 ml/minute
Carrier Gas: Zero grade nitrogen (Matheson)
Injector Temperature: 240°C
Column Temperature: 220°C
Interface Temperature: 250°C
Detector Temperature: 275°C
DDT, ODD, and DDE standard materials were Analytical
Reference Standards obtained from the Health Effects Research
Laboratory, U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina.
Sample concentration was determined by comparing sample
peak height with standard peak height (considering signal
attenuation differences) or by comparing peak areas of samples
and standards when the intergrator was used. With the instrumen-
tation described, it was determined the signal was linear with
changes in concentration up to and including an attenuation
setting of 512. Samples which/went off the recorder chart at an
26
-------
attenuation of 512 were diluted and run again. This linear
range was also found to apply to Kepone and Permethrin as well.
Kepone
Sediment Material
~~ Studies "of Kepone persistence under controlled physico-
chemical- conditions- were-conducted- using-a-sediment-material-
taken from a mud flat/marsh grass area adjacent to Bailey's
Creek near Hopewell, Virginia. This is part of the area
affected by Kepone contamination from the Life Science Kepone
manufacturing plant located in Hopewell. Although not inundated
at the time samples were obtained, it was apparent the sampling
area adjacent to Bailey's Creek was subject to periodic flooding
and that the sample material was deposited by sedimentation.
; ' Sediment samples were shoveled into plastic-lined, 5-gallon
paint buckets, sealed, and shipped to Baton Rouge by commercial
bus. This material was moist, but not water saturated. In the -
lab, the sediment material was composited,-spread -thinly, and
large pieces of roots and other undecomposed plant material
removed by hand. The composited samples were mixed and returned
to the original 5-gallon container and stored in a moist condi-
tion at 4°C until used in incubation studies. This material
contained approximately 2 wg/g Kepone as collected and is desig-
nated as James River sediment material elsewhere in this report.
Amending Sediment Suspensions--
James River sediment material which was incubated as a
suspension at selected pH and redox potential conditions was
amended with a solid Kepone spiking material. This material was
prepared by grinding 37.5 mg of Kepone (99% purity, pesticide
standard grade material from Applied Science Laboratories, Inc.)
with 30 grams of a silty loam soil which had been combusted at
900°C to destroy organic matter. Five grams of this Kepone-
amended soil material containing 6.25 mg Kepone was added to
each suspension (containing 300 g sediment solids) as an aqueous
slurry (20 ml H-0) to give a spiking level of about 21 yg/g.
Kepone Extraction and Analysis
As described for the DDT studies, it was determined that
essentially all of the Kepone in the incubated suspensions was
associated with the solid phase. Therefore, the aqueous sample
phase was separated and discarded.
Although apparent degradation products of Kepone have
recently been observed on gas chromatograms (47), during the
time of this study, the identity of possible Kepone degradation
products was unknown and thus no standards were available for
identification and quantification of degradation products (36).
-: '27
-------
Thus this study looked only at levels of Kepone vs. time in the
controlled incubations as a measure of physicochemical effects
on the persistence of Kepone.
The following procedure was used to extract Kepone from the
sediment-water samples for the Kepone data, reported in this
study.
Kepone extraction steps1. Thaw sample. 2. Add 0.5
grams of NaCl and mix with sample to enhance flocculation of
solids during centrifugation. 3. Centrifuge the sediment-water
mixture in the glass storage bottle at approximately 1,800 RCF
for 45 minutes and discard the water layer. 4. Add 15 ml of
acetone, then seal the bottle with an aluminum foil-lined screw
cap. 5. Disperse sediment-acetone mixture for 2 minutes on a
mechanical shaker. 6. Centrifuge at approximately 1,800 RCF
for 15 minutes, decant, and save the acetone extract as it
contains some Kepone. 7. Repeat steps 4-6 using a new aluminum
foil liner if necessary. 8. Dry the sediment (evaporate the
acetone) under a stream of compressed nitrogen for about 1 hour.
9. Grind the sediment material to a fine powder. 10. Label
and weigh Soxhlet extraction thimbles, weigh into labelled
thimbles 3-5 grams of the dry, ground sediment material, and
determine exact sediment weight. 11. Place thimbles into a
clean, dry Soxhlet extraction apparatus, connect to a boiling
flask containing several glass beads and 130 ml of a 1:1 benzene-
methanol mixture, and attach condenser to top of Soxhlet
apparatus. Be sure all ground" glass connections are tight. 12.
Extract for 12 hours with heating units adjusted for about 6
cycles per hour. 13. After extraction is complete, siphon over
as much solvent into the boiling flask as' possible by tipping
extractor. 14. Place the thimble in a glass funnel positioned
in the top of the Soxhlet extractor and let the thimble drain
completely. Rinse thimble and funnel with acetone. 15. Siphon
over the remaining solvent and acetone rinse into the boiling
flask and rinse extractor twice with acetone. 16. Pour the
solvent/pesticide mixture through a funnel equipped with a glass
bead trap into a clean 250 ml separatory funnel. Rinse the
boiling flask and bead trap funnel with acetone into the separa-
tory funnel. 17. Add the acetone rinses from the sediment
drying steps into the separatory funnel. 18. Add 50 ml of
NaCl-saturated water to the separatory funnel, shake for two
minutes venting often, and permit the layers to separate. 19.
Drain off the bottom water layer. 20. Add 50 ml of distilled
water, shake for 2 minutes venting often, let layers separate,
then drain off the excess water. 21. Repeat step 20 twice
more. 22. Set up a clean 250 ml volumetric flask with a filter
funnel filled with sodium sulfate for each sample. 23. Dilute
as necessary to bring concentration within linear range of the
gas chromatograph's electron capture detector.
28
-------
Kepone was analyzed on the same gas chromatograph with the
same operating paramters as described for DDT except that a 6-
foot glass column with a 1/4-inch diameter packed with 1.5
percent OV-1, 1.95 percent QF-1 on 80/100 mesh Chromosorb W was
used.
Kepone standard material was Analytical Reference Standards
obtained from the Health Effects Research Laboratory, U. S.
Environmental Protection Agency, Research Triangle Park, North
Carolina. Kepone standards were made in a 95 percent benzene, 5
percent methanol solution.
Permethrin
Soil Material
The effects of controlled pH and oxidation-reduction
conditions on the degradation of Permethrin were studied using
aqueous suspensions of an Olivier silty clay loam soil obtained
from the Louisiana State University Agricultural Experiment
Station Burden Research Center in Baton Rouge. The soil material
was obtained at field moisture conditions, air dried, ground,
and stored in a dry state at ambient temperatures until needed
for pesticide degradation studies.
Amending Soil Suspensions
Aqueous suspensions of the Olivier soil material were
amended with Permethrin dissolved in acetone. The Permethrin
material for the controlled pH-redox potential studies was
obtained from Applied Science Laboratories. The pesticide
material for a preliminary Permethrin study was obtained from
Dr. Sammy Smith of the USDA Soil and Water Pollution Laboratory,
Baton Rouge, Louisiana, who had research material from the FMC
Corporation, developer of the compound. The purity of the FMC
Corporation material was reported to be 94.5 percent. The
compound was reported to consist of cis and trans isomers
comprising 38.8 and 61.2 percent of the total material respec-
tively. The soil suspensions were amended with Permethrin
dissolved in acetone. The initial spiking level was 15 to 17
ug/g oven dry soil solids.
Permethrin Extraction and Analysis
The procedure which gave the best and most reproducible
recovery for our experimental materials were similar'to those
described previously for DDT with the following exceptions:
A 60:40 hexane:acetone solution was used with an 8-hour
Soxhlet extraction. The GC oven temperature was 200°C, and a
6-foot, 1/4-inch diameter glass column packed with 5 percent SP-
2330 on Chromosorb W was used. This column permits separation
of the cis and trans isomers.
29
-------
A preliminary study was conducted with Permethrin at two
pH levels (5.5 and 7.5) under conditions of continuous nitrogen
purging (to simulate anaerobic or reducing conditions) and
continuous air purging (to simulate aerobic or oxidizing soil
conditions).
30
-------
SECTION 6
RESULTS AND DISCUSSION
DDT
DDT-amended Mobile Bay sediment material was incubated at
three pH levels ranging from mildly acid to mildly alkaline
(6.0, 7.0, and 8.0) and four redox potential levels ranging from
strongly reduced to well oxidized (-150, 50, 250, and 450 mv) to
determine the effects of these physicochemical conditions on the
levels of DDT and its two predominate degradation products, ODD
and DDE, with time. The effects of pH on recovery of DDT from
the amended sediment material were negligible at each of the
four redox potential levels studied. However, redox potential '
treatments greatly affected the recovery of DDT.
Under well oxidized and weakly oxidized (+450 and +250 mv)
conditions for all three pH levels studied, the recovery of DDT
decreased to about two thirds _of initial levels during the first
two weeks of the incubation (Figures 2-4). After two weeks
until the end of the incubations at about 45 days, DDT recovery
remained essentially unchanged or perhaps decreased slightly.
DDT recovery decreased at a gradual and almost uniform rate
during the entire incubation under moderately reduced (+50 mv)
conditions such that only about one-third of the initial levels
was recovered at pH 6.0 and 7.0 and about one-fourth initial
levels recovered at pH 8.0 after 45 days.
Under strongly reducing conditions (-150 mv) , DDT recovery
decreased to about 10 percent of spiking levels within 2 to 5
days after which recovery approached zero for the duration of
the incubation.
Although numerous studies have reported more rapid degrada-
tion of DDT under reducing soil conditions compared to well-
drained, oxidized soils, this apparent rapid degradation
(greater than 90 percent in a few days) at -150 mv warrents
additional discussion. We were able to find only one other
published report of comparable DDT degradation rates in the
literature, 50 percent loss in 24 hours in oxygen deficient lake
waters, (16). Most published reports indicate equivalent levels
of degradation in terms of a few weeks to a few months rather
31
-------
20-
a
O
o
10
10
Eha-150 nW
20
20
30
40
3Q
TIME (days)
Ehs SOmV
Eh B 450 mV
50
Figure 2. The Effect of Redox Potential (Eh) on the Recovery of Added DDT from Mobile
Bay Sediment Suspension During a 45-Day Incubation at pH 6.0 (amended with 25 ppm
DDT initially).
-------
: eo
50
4O
3O-
2O
-10
IE
a
; a.
u
: . O
v
Ul
U) 60
]-. ' \ so
40-
30
20
10'
Eh=-150mV 6Q
SO
40
3O
2O-
* 10
A
* A * A
1O 20 30 40 SO
\
Eh>2SOmV ' 6Q
A
SO
*°
30
i
1 A i *
20-
A »
1O
Eh=50mV .
,
A
A
A
A
A *
A A
A
10 20 3*0 40 ' 50
Eh=450mV
1
A *
A
A
. " *
* A
A
i i
i *
A
A
1O 2O 30 4O 50 ,g 2Q 3'Q 40 go
TIME (days)
Figure 3. The Effect of Redox Potential (Eh) on the Recovery of Added DDT from Mobile
Bay Sediment Suspension During a 45-Day Incubation at pH 7.0 (amended with 40 ppm
DDT initially).
-------
30
20
10-
i
a
a
CONC.
30-
20
10
EhB-ISOmV 3Q
20
1O-
t » t 1 1 1
10 2O 30 40 SO
I
Eh-250mV 3Q
1 /
*
2O
* ft
* i »
» i
10
-
Eh=5OmV
4
*
A
*
A
A
*
» *
t
10 20 3O 40 SO
6h=4SOmV
» « ,
A
* A *
' ' ' «',
1
,..- ,, ,. | | ,..,-.., ..*.,-..- | , ,.,. 1
10
40 50
TIME (days)
1O
2O
30
40
SO
Figure 4. The Effect of Redox Potential (Eh) on the Recovery of Added DDT from Mobile
Bay Sediment Suspension During a 45-Day Incubation at pH 8.0 (amended with 25 ppm
DDT initially).
-------
than days. Thus we suspected experimental artifacts when first
confronted with the apparent rapid degradation rates at -150 mv.
There are several possible explanations to explain the initial
low recovery of DDT under strongly reduced conditions: 1)
drying artifacts, 2) the "bound residue effect", 3) volatiliza-
tion in the continuous stream of nitrogen which purged the
system, 4) adsorption on the glass walls of the flasks, tubing,
electrodes,- or the teflon coated magnetic"stirring bar'inserted
in a short length of tygon tubing, and 5) unusually rapid degra-
dation of DDT in the strongly reduced Mobile Bay sediment
materials in this study. These points will be considered below.
To dry the sediment samples before Soxhlet extraction, we
had previously determined that drying in the original glass
storage bottles in a forced draft oven at 35 to 40°C for 2 or 3
days was satisfactory for both moderately reduced and well
oxidized samples. Higher temperatures, which would effect more
rapid drying, were not considered as this would have probably
enhanced DDT volatilization as the sediment samples dried. The
low recovery at -150 mv initially suggested- to us that drying
strongly reduced samples under air at elevated temperatures for
2 or 3 days may have contributed to enhanced degradation during
drying. Because of this potential artifact, another technique
was developed in which strongly reduced sediment samples could
be dried in about 2 hours (see Development and Testing of
Procedures, page 74). Incubations at -150 mv were repeated
using the new drying technique, but this did not change the
apparent degradation rates.
At this point, it is appropriate to mention the. "bound
residue effect" reported for parathion (1) and the possibility
this phenomena is contributing to the apparent rapid degradation
of DDT in this study. The bound residue effect refers to
evidence that some proportion of the total amount of a compound,
such as a pesticide, may be adsorbed so firmly to soil solids
(mineral + organic) that it cannot be removed by the extraction
procedures used to determine residues. Thus a lack of recovery
or a decrease in recovery of a particular compound with time
which is normally attributed to degradation may in part be due
to "irreversible" adsorption. In carbon-14 studies, the propor-
tion of added, labeled carbon recovered as C02 clearly indicates
degradation. However, even in radiotracer studies, if all of
the compound is not recovered as C02 and by solvent extraction,
it is difficult to confirm whether the remaining label is
associated with the parent molecule as a bound residue or as
various degradation compounds. It is interesting to note that
at 250 and 450 mv there was some decrease in DDT recovery during
the first two weeks after which little further reduction
occurred. Perhaps the "bound residue effect" contributed to
this initial apparent loss in DDT. With parathion, this effect
was reported to be twice as pronounced under flooded (anaerobic).
conditions compared to nonflooded conditions (1). However, even
. ,-: 35" ;,:'>
-------
where C-14 labelled compounds are used as mentioned above, it is
not possible to establish whether the bound residue represents
the parent compound or some degradation product. Thus the
possibility that the parent DDT molecule became less susceptible
to extraction procedures with time cannot be ignored, though the
actual significance of "the bound residue effect" in this study
cannot be determined. If, as for "the reported parathion study,-
anaerobic- conditions-only doubled the-"bound-residue - effect"
over aerobic conditions, this process would not come close to
explaining the large recovery differences observed between -150
mv and higher redox potentials.
The possibility of volatilization from the system was ruled
out as no DDT was recovered when an organic solvent used in
place of water in the air trap (page 22) was extracted for DDT.
The possibility that some adsorption occurred on the
surfaces of the incubation vessel and its components cannot be
ruled out as no effort was made to test for this. However, it
seems unlikely that this would account for the observed treatment
differences with DDT and, as will be evident from Figures 11,
12, and 13, adsorption to surfaces of the laboratory microcosms
could not have occurred to a significant extent in the Kepone
studies.
The fifth possibility is that the added DDT was indeed
degraded within a few days at -150 mv. The chemical and
microbial properties of the Mobile Bay sediment material at
-150 mv are likely very different from most soil and sediment
materials examined in DDT degradation studies, even those
studies in which flooded or reduced conditions were imposed. In
terms of texture (44 percent clay, 32 percent silt) and organic
carbon content (1.8 percent), this material is not untypical of
many soil and sediment materials. However, its sulfide content
at -150 mv was above 400 ppm, potentially reactive iron (that
quantity extracted by relatively mild chemical extractants)
exceeded 37,000 yg/g and soluble iron levels at -150 mv were 3
and 330 yg/g oven dry solids (8:1 water:soil ratio) at pH 8.0
and 6.5 respectively (64). These properties and possibly others
make the Mobile Bay sediment material different from most soils
used for DDT studies.
Glass (33) concluded that the iron redox system in reduced
soils is involved with DDT degradation and that redox systems
other than iron may also contribute to DDT reduction by electron
transfer processes. A relationship between ferrous iron levels
and DDT degradation was established. In the work of Glass (33),
the experimental combination of soils and treatments giving most
rapid DDT degradation resulted in recovery of only 6 percent of
initial DDT levels after 28 days. Although extraction procedures
for iron differed somewhat from, those used by Glass, we have
previously shown that soluble 'and exchangeable (method similar
' ' ' -: '36."1. .
-------
to Glass's "soluble" iron) ferrous iron levels in Mobile Bay
sediment material under a range of pH and oxidation-reduction
conditions equaled or far exceeded iron levels in the reduced
soil materials studied by Glass (33, 64). Thus the chemical
properties of the Mobile Bay material may be more conducive to
rapid DDT degradation than most materials studied and reported
in the literature.
An obvious avenue to explore whether degradation accounted
for the rapid loss in DDT is to examine the levels of known DDT
degradation products at -150 mv, and especially levels of DDD as
this compound is reported to be the predominant, first stage
decomposition, product under reducing conditions.
Although DDD levels extracted were not sufficient to account
for the rapid disappearance of DDT during the first few days,
DDD levels in the -150 mv treatment were 3 to 8 ppm during the
first few days dt all 3 pH levels compared to about 0.5 ppm for
the two most oxidized treatments. Thus there is firm evidence
that at least some DDT did degrade-very rapidly under strongly
reduced conditions, though a mass balance was not found. It is
possible that some of the DDD rapidly formed was also subject to
rapid degradatipn, or, that under strongly reducing conditions
in Mobile Bay material, another intermediate was involved in DDT
degradation.
DDD levels gradually decreased from elevated initial levels
(due to DDT degradation) to 2 -to 3 ppm after about 45 days in
the -150 mv treatments (Figures 5-7). DDD levels at 50 mv were
fairly constant during the incubations, though a slight tendency
to increase was noted at most pH treatments. At 250 and 450 mv
which represent poorly oxidized and well oxidized conditions,
DDD levels were consistently around 0.5 ppm for the duration of
the incubation.
DDE is reported to be the predominant degradation product
of DDT under oxidized conditions. DDE levels ranged from
essentially zero to around 1 ppm at all pH-redox potential
combinations (Figures 8-10). Surprisingly, based on the litera-
ture, the -150 and 50 mv treatments (strongly and moderately
reducing) exhibited higher DDE levels than the better oxidizing
treatments. Though DDD production was greater than DDE pro-
duction under the reduced treatments, it is apparent some DDE
was produced under anoxic conditions during the rapid loss of
DDT in the Mobile Bay sediment material. Because of the more
rapid DDT degradation under reducing conditions, the DDE
accumulated to slightly greater levels than in the better
oxidized treatments where DDT was relatively stable.
In summary, DDT recovery from a spiked Mobile Bay sediment
material decreased very rapidlyunder strongly reducing condi- .
tipns such_that greater_than 901 percent could ..not be recovered
-------
u>
00
h = -150mV
E
a
a.
6
z-7
O-
o
6-
Eh = 250 mV
Eh= SOmV
Eh= 45O mV
50
TIME (days)
50
to
Figure 5. The Effect of Redox Potential (Eh) on the Recovery of ODD from Mobile Bay
Sediment Suspension Amended with DDT During a 45-Day Incubation at pH 6.0.
-------
IS,
o.
a
O
z
o
Eh= -ISOmV
7.5-
7.5
2.5
Eh =280mV
20
I
SO
Eh= 50 mV
20
Eh= 450 mV
50
TIME (days)
Figure 6. The Effect of Redox Potential (Eh) on the Recovery of ODD from a Mobile Bay
Sediment Suspension Amended with DDT During a 45-Day Incubation at pH 7.0.
-------
7-
6-
j .
4
3-
2-
E 1-
Q.
a
u
!'
6
5
4-
3-
2 -
1
7 -
I
Eh=-150mV
8-
. '
4-
, S | 3-
2 -
1
10 2*0 3*0 4*0 60
1 7-
Eh = 250mV 6_
S-
4-
3-
2-
. y 1
Eh= 50 mV
(
: ,
»
1O 2O 3O 40 SO
Eh= 45OmV
i
1 B B S f I § t
1O 20 3~0 40 SO |'j 2O 3'0 4*0 50
TIME (days)
Figure 7. The Effect of Redox Potential (Eh) on the Recovery of DDD from a Mobile Bay
Sediment Suspension Amended with DDT During a 45-Day Incubation at. pH 8.0.
-------
E
a
a
O
.o
Ehs-tSOmV
1.5
05-
30
Eh325OmV
Eho SO mV
20
1.5
0.5-
Eh" 45OmV
60
TIME (days)
20
30
40
80
Figure 8. The Effect of Redox Potential (Eh) on the Recovery of DDE from a Mobile Bay
Sediment Suspension Amended with DDT During a 45-Day Incubation at pH 6.0.
-------
1.5-
1.0-
0.5-
"i
a
a.
O
z
o
o-
1.5-
1.0-
0.5-
Eha-150mV
1.5'
1.0-
0*
* . ' '
10 20 30 4*0 50
1
Eh=250mV 1g
1.0-
0*
9
10 2O 30 40 50
TIME (days
Eh=50mV
t
*
»
.
10 20 30 40 50
i
Eh = 45OmV
i
*
; , » i
1O 2O 3O 40 50
) ;
Figure 9. The Effect of Redox Potential (Eh) on the Recovery of DDE from a Mobile Bay
Sediment Suspension Amended with DDT During a 45-Day Incubation at pH 7.0.
-------
Eh= -16OmV
Eh- 9OIBV
1.0A
' 0.5
i i
i o
. Z
O
! ' 1.5-
t
Eh = 25OmV
50
TIME (days)
Eh»45O mV
~~4O '. ?0
« « |
SO
Figure 10. The Effect of Redox Potential (Eh) on the Recovery of DDE from a Mobile Bay
Sediment Suspension Amended with DDT During a 45-Day Incubation at pH 8.0.
-------
after as little as 5 days. The evidence indicates this loss is
due to a considerable extent to rapid DDT degradation. A less
rapid loss (two-thirds in about 45 days) was noted at 50 mv
(moderately reduced conditions) while DDT appeared fairly stable
under better oxidized conditions after an unexplained decrease
of about,one third of initial levels during the first two weeks.
Where DDT loss was rapid under reduced conditions,"both ODD and
DDE -levels- increased-with'"DDD~production~predominating. ~~
Only at 50 mv was there an indication that a degradation
product was accumulating. However, the very slight increase in
ODD levels noted with time was not equal to the rate of DDT loss
from these treatments. Thus it is believed ODD levels would
begin to decline within another month or so when it appeared DDT
loss would essentially be complete at moderately reduced
conditions.
KEPONE
Figure 11 indicates the effect of redox potential on the
levels of Kepone in James River sediment suspensions incubated
at pH 5.0 for 51 days. At redox potentials of -150, +50, and
+250 mv (strongly reduced to weakly oxidized), initial Kepone
recovery was 17 to 18 yg/g while initial recovery was 15 to 16
yg/g at 250 mv (well oxidized). .During the 51 day incubation,
there appeared to be a very gradual decline in Kepone levels to
about 12 to 13 yg/g in all treatments except for the Day 51 -150
mv data which increased, possibly due to experimental variability.
Figure 12 indicates Kepone levels in James River sediment
suspensions incubated at pH 7.0 for 52 days. During the initial
few days, 16 to 22 yg/g Kepone was recovered from all redox
potential treatments (most of these data were clustered around
20 yg/g). There is some scatter in the data, but these data
suggest little if any Kepone degradation at any redox potential
level during the 52 day incubation. As observed for pH 5.0,
there is no evidence that oxidation-reduction levels have any
effect on Kepone degradation.
Figure 13 gives the effect of redox potential on Kepone
levels in James River sediment suspensions incubated at pH 8.0.
For unknown reasons, considerable variability was noted between
sampling dates and between subsamples, especially at-450 and 250
mv. After 70 days, Kepone recovery had decreased from near 20
yg/g to 10 yg/g at all redox potential levels. Since there is a
substantial decrease in Kepone levels for only the last sampling
date at pH 8.0 (which was about two weeks beyond any other
sampling date at any pH), we are not sure if this represents
some experimental variability or the beginning of degradation
after a lag phase of about 2 months. A gradual decline was
'. :: 44'. 'I:''., . ' '
-------
30
20
10
?
a
a
o
Z
o
u
3O
20
1O
Ehs-ISOmV 30
20
.: . .
. i *
« *
' . . . ,
10-
1O 20 3O 4O SO |
Eh«250mV 30
2O
«-t: :
. t . .
It
10
Eh= 50 mV
" i i .
' .
« .
1O 2O 3O 4O SO
Eh=45OroV
: : -
' : : t
i
i
10 20 3O 4O SO 10 2O 3O 4O SO
TIME (days)
Figure 11. The Effect of Redox Potential (Eh) on the Recovery of Added Kepone from
James River Sediment Suspension During a 51-Day Incubation at pH 5.0 (amended with
21 ppm Kepone initially).
-------
30
2O
1O
a
0.
-0
0 .
o
30
2O
10
Eh=-150roV
3O
' ' : . . . : ' ' '
* * . ,
* * *
: .
10
1O 2O 30 4O SO
1
Eh = 250mV 3(>
A
»
» * * *
> . « . . - , i
i
10
10 20 3O 40 50
EhsSOtnV
A i
.. t : t : . -
^* * * t
A
10 20 3O 4O 5O
Eh = 450mV
*
*: t : * : : . * i . !
» * » »
A
A
10 20 30 4O 5O
TIME (days)
Figure 12. The Effect of Redox Potential (Eh) on the Recovery of Added Kepone from
James River Sediment Suspension During a 52-Day Incubation at pH 7.0 (amended with
21 ppm Kepone initially).
-------
-J '
30
20
10
1
a
6
z
o.
o
'30
2O
10
Eh'-tSOmV . '
*.*:**
* *
*
* «>
20 30 40 SO 60 TO
1
Eh»2SOmV 3Q
*
* *
** * * * :
*
to
*
Eh. BO nV
* I
******
*
*
20 3O 40 8O SO ' Vo
EH.4001BV
*
*. * : * * :
*
20 3O 40 50 60 10
TIME (d«»l)
20 30 40 60 BO JO
Figure 13. The Effect of Redox Potential (Eh) on the Recovery of Added Kepone from
James River Sediment Suspension During a 70-Day Incubation at PH 8.0 (amended with
21 ppm Kepone initially).
-------
noted for the two most reducing (-150 mv and 50 mv) sediment
materials whereas the decline, if real, was more abrupt in the
better oxidized suspensions. As found at pH 5.0 and pH 7.0,
there is no clear indication that oxidation-reduction conditions
affected Kepone degradation at pH 8.0. However, the data
suggests that Kepone degradation may be enhanced somewhat at pH
8.0 relative to pH 7.0 and 5^0 and-that this loss may occur only
after a -considerable- lag - period-.
PERMETHRIN
A preliminary study conducted on the effects of controlled
pH and oxidation conditions indicated substantial effects of
both parameters on the persistence of Permethrin in the Olivier
silty clay loam. After obtaining oxidized and reduced condi-
tions by continuous air or nitrogen purging for several days,
the pH of the suspensions was adjusted to 5.5 and 7.5 and
several additional days of equilibration permitted before the
samples were spiked with 17.8 yg/g Permethrin. -Immediately
after spiking, approximately 14 to 15 yg/g Permethrin was
recovered from all treatments (Table 3). At 5 days, Permethrin
TABLE 3. RECOVERY OF PERMETHRIN FROM AN OLIVIER SOIL
SUSPENSION INCUBATED UNDER CONTINUOUS NITROGEN OR AIR
PURGING AT pH_ 5.5 and pH 7.5
pH 5.5 i ~~pH 7.5
Day Nitrogen Air Nitrogen Air
Permethrin, yg/g
5
17
20
12.5
12.5
12.5
2.0
0.1
0.3
7.7
6.1
6.1
6.9
3.3
3.1
disappearance appeared to be a function of both pH and oxidation
levels. These trends continued until the experiment'was termi-
nated at 20 days. At 20 days, Permethrin had essentially
disappeared under oxidized conditions at pH 5.5 while under
reducing conditions levels only decreased to around 12 yg/g..
Both oxidation levels at pH 7.5 resulted in intermediate degra-
dation rates. Approximately 6.0 ppm were recovered under
reducing conditions and 3.0 ppm were recovered under oxidizing
conditions at 20 days. .'
-------
Unlike Kepone persistence which showed little response to
either pH or oxidation-reduction conditions, or DDT which
responded primarily to oxidation levels, this preliminary study
indicated Permethrin persistence was substantially affected by
both pH and oxidation-reduction conditions.
~;'" Another 'study with Permethrin" was conducted using four
controlled--redox- potentiallevels -(-150,- +50r"+250y -and- +450-mv)
and 3 pH levels (5.5, 7.0, and 8.0). These data are presented
in Figures 14-16.
Again it is apparent that both pH and redox potential
influenced the loss of Permethrin from these systems. Under
well oxidized conditions (+450 mv) Permethrin had essentially
disappeared (less than 0.5 ppm) at all pH levels after 19 days.
Under strongly reducing conditions, approximately one third was
lost from the pH 5.5 treatment while about two thirds of initial
levels were lost at pH 8.0 after 26 days. In this study thei*e
was a tendency for Permethrin to degrade more quickly with
increasing pH under both oxidizing and reducing- conditions. -
The data in Figures 14-16 include the total Permethrin
content of the samples (the sum of the cis and trans isomers).
Because a gas chromatography column was selected which would
separate the cis and trans isomers, it was possible to look at
the effects of pH and redox potential on the degradation of the
individual isomers. Table 4 indicates the percentage of total
Permethrin in the trans isomer. for two sampling dates under
strongly reducing (-150 mv) and well oxidized (+450 mv) condi-
tions. This information could be calculated for every sample in
this study, but the information in Table 4 summarizes the
important physicochemical effects noted. Day 1 (Day 2 for pH 8)
was selected to give the ratio near the beginning of the incuba-
tion. Day 15 (Day 14 for pH 7.0) was selected for inclusion in
this table because this was the last sampling date.before
Permethrin levels decreased to very low levels in the oxidized
treatments.
From Table 4 it is apparent that both pH and oxidation have"
substantial effects on the relative degradation of the cis and
trans isomers. Increasing pH (from 7 to 8) and increasing
oxidation conditions favored the loss of the trans isomer
relative to the cis. There was relatively little change in the
ratio under reduced conditions at pH 5.5 and 7.0 during the
first 15 days.
The results of this study confirm what is already known
about Permethrin in that long-term accumulation of residues will
not pose an environmental threat. However, this study does
indicate that physicochemical conditions of the environmental
compartment receiving residues,can have a substantial effect on,
the_persistence of Permethrin during the course of a few weeks
'' ' ''.: -49- '::-- ' .. - - '
-------
tn-
o
30
20-
1.
1
ji
u
z
o
0
.' SO
20
to-
Ehe-19OmV 30-
20
1 * * : * .
* A
* A 10
A
10 20 3O
'1
Eh»2SOmV 30
20
t
t
t
10-
i »
1
EhiSOmV
l
4
:
10 20 30 i
Eh=450mV i
i
' '
A '
A * ' '
i
10 2'0 30 10 20 ( 30 :
TIME (days)
,1
Figure 14. The Effect of Redox Potential (Eh) on the Recovery of Added Permethrin from
an Olivier Soil Suspension During a 25-Day Incubation at pH 5.5 (amended with 15-17
: ppm Permethrin initially) .
-------
. -. jbbui beri-.:.;. . .=
en
H
t
'
Tdrjx:
. -
JK
1 1
'/*
' i
f
i
i
1
i.-
! ,
! [
O
3
3O
2O
to
30
2O
to
;TA,:..£ 3 .; . gr, - - . . . _.,.:. ....
Eh* -ISO mV ' . .. :. ' JO
20
10 30. . 20
8 * . '
*** * '*
* * * * * i *
* * * *
1O'
10 2O 3O
Eh»2SOmV '' 3O-
- - 1
^SOO^fl ^ . 30
- 30
+ ^-~~ J , -o .,
* . *"* ."'/. -:i '.
^k ' ^ . ' 1O^
0
o
o
10
* * 10 . 30 30
" : « * '. ''* .
, * . » .«
8 i i
tO 20 30
Eh*450mV
* i t<> SO ' 30
* * 0
W 0 0
.8 o g ,
1 ***!* !
20
TIME (
-------
i 30
Ul
EhB-UOmV
I ' t
Elw 280 mV
20
TIME (days)
.30
Figure 16. The Effect of Redox Potential (Eh) on the Recovery of Added Permethrin from
an Olivier Soil Suspension During-a 26-Day Incubation at pH 8.0 (amended with 15-17
; ppm Permethrin initially). . j 1 ;
-------
"TABLE"*. "EFFECT "OF piTAND'OXIDATION LEVEL'S " ON THE~ RELATIVE
DEGRADATION .OF THE CIS, AND TRANS ISOMERS'OF-PERMETHRIN FOR
SELECTED SAMPLING DATES AND. R^DOX-''f>CifENTIAI.:-TREATMENTS '<
' ' '''"' ' ' '.''' '"' ' " ' "i" "'"'''' *'"' '*'' ';- ; * -, ' ' '
Day 1 of IncubationDay 15 of Incubation
(Day 2 for pH 8) (Day 14' for pH'Y/O)
pH
5.5
-150 mv -'.+450 mv ;
, ':';'. ,;,".' 64 ,'2'J ' ;'; ' 62. 6
''"'. ;' '+' oib*. ' "''' +i i. 5 ''
.' .^- -iso^my;' -tt"
.
he.ight^cig^ L^r
1 ''6'4\ 3'^ ' ?>~t 'it
"'"iX ,'."^' ' .QJp7 OR,'. .? !;
. +450 my ^ .
' - ' . . . M
an!s,!i,. "~ ~~r
?J 24v:4: :" ;
7.0
8i'°
65.7 J
+ 0.3
61.6
+ 0.1
'" : "62.4 ' --1 '
;;; v:o.r .
1 56.6 '
+ 0.1
''.^6J^J'«-.; V2o;-a^ /%
<-50'.0'I -. --J ---14i'»l
+ 0.0 + 3.2
Mean of two subsamples (extraction of two separate soil samples
from the same experimental incubation vessel).
'Standard deviation.
to a few months. Strongly reducing conditions characteristic of
sediments will enhance the persistence of Permethrin. This is
similar to results for Cypermethrin, another synthetic pyrethroid,
which has been found to degrade more quickly under aerobic
conditions than waterlogged conditions in a sandy loam soil (60).
Our results also correspond with one study of Permethrin in
which approximately 60 percent of the 14C activity of labelled
Permethrin in an oxidized Hagerstown silty clay loam was trapped
as 14C02 vs. 1 percent from the anaerobically incubated soil.
In the system used by Kaufman et al., (65) it was not determined
if more of the 14C activity from degradation products might have
been present in the aqueous phase. In our studies, both the
water and soil were extracted for the parent compound and it is
demonstrated conclusively that Permethrin is degraded more
rapidly under oxidized conditions.
Considering the documented high toxicity of certain
synthetic pyrethroids to a number of aquatic and benthic
organisms (63), it should be kept in mind that the strongly
reduced environs of many sensitive benthic species favors some
increase in the persistence of residues which may adversely
affect these populations should residues be transported from
adjacent fields in surface runoff. On the other hand, residues
in upland soils will degrade more quickly. Thus the length of
..->" '53-:;:.:'..
-------
time between Permethrin application and a significant runoff
event will strongly influence the potential for adverse environ-
mental effects of Permethrin residues in wetlands or sediment-
water systems.
The FMC Corporation (66) found the cis isomer present in
higher concentrations in treated cotton plot soil than the trans
isomervIt-was suggested-either~the~cis-isomer was~more persis-
tent or that this isomer was more easily removed from treated
cotton leaf surfaces and transported to the soil. Surface
runoff samples also contained a higher proportion of the applied
cis than trans isomer and again it was suggested either greater
persistence or mobility of the cis isomer accounted for these
differences. Our work suggests that soil oxidation conditions
probably contributed to enhanced degradation of the trans isomer
as. cotton is usually grown in well oxidized soils.
. v-- 54 ;;->
-------
SECTION 7
AUXILIARY STUDIES
DDT DEGRADATION UNDER AEROBIC, ANAEROBIC, AND ALTERNATE AEROBIC/
CONDITIONS
Materials and Methods
Mobile Bay sediment material was preincubated as suspensions
under continuous air purging or nitrogen purging for a 2-week
period to obtain oxidizing and reduced suspensions. After two
weeks, four equal 1800 gram aliquots (200 grams oven dry solids
plus 1600 grams water) of the reduced material were spiked with
DDT at a level of 26.6 u g/g (oven dry solids basis). Two of
these suspensions were incubated under continuous nitrogen
purging and two were incubated under alternate nitrogen/air
purging (two week cycles) for 3 months. At the same time, two
spiked, continuously aerobic suspensions were set up. Thus each
of the three treatments was replicated. After 3 months, the
aqueous phase was separated by centrifugation and filtration and
analyzed for the DDT, ODD, and DDE according to published
methods (67). DDT and its metabolites were extracted from the
sediment phase and analyzed using methods described elsewhere in
this report.
Results and Discussion
Loss of DDT from the solid sediment phase was greatest and
almost complete under continuous reduced conditions (Table 5).
Continuous oxidizing conditions resulted in the highest levels
of residual DDT (approximately 4.3 pg/g). The alternating
aerobic-anaerobic treatment gave intermediate levels (approxi-
mately 1.1 yg/g). As expected, ODD levels were greatest in the
anaerobic treatment. ODD was not detected in the aerobic
suspensions and was present in intermediate amounts in the
suspension solids subject to alternate aerobic/anaerobic condi-
tions. DDE levels were very similar in all three treatments,
with the aerobic treatment containing the largest quantity by a
small margin and the continuous anaerobic treatment the smallest
quantity of DDE after 3 months. Given 88-92 percent recovery
from samples extracted immediately after spiking, this study
suggests either a significant "bound residue effect" or that
most of the DDT (as well as ODD and DDE assuming these are the
55
-------
TABLE 5. DDT, ODD, AND DDE RECOVERY FROM A DOT-AMENDED
MOBILE BAY SEDIMENT SUSPENSION INCUBATED UNDER CONTINUOUS
AEROBIC, ANAEROBIC, AND ALTERNATE AEROBIC-ANAEROBIC
CONDITIONS FOR 3 MONTHS
"Sediment
Oxidation-Reduction
Conditions
Aerobic
Anaerobic
Alternate Aerobic-
Anaerobic
4
0
1
Levels
.32'
.09
.13
DDT
+
± °
+ 0
, yg/g oven dry solids
Compound
0.05t
.02 0.
.13 0.
ODD
0
58 + 0.03
38 + 0.13
0.
0.
0.
DDE
10 + C
08 + C
10 + C
).01
).. 00
).01
Dissolved Levels, yg/fc
Aerobic
Anaerobic
Alternate Aerobic-
Anaerobic
0
0
0
.58
.08
.33
+ 0
± °
+ 0
.32
.11
.23
nde
nd
nd
0.
0.
0.
05 + C
19 + C
14 + C
).02
).01
J.15
Initially spiked with 26.6 yg/g DDT
T
Mean of replicated treatments
''Standard deviation
ENot detected
primary initial degradation products of DDT) were degraded to
other unknown compounds during the 3 month incubation. Thus as
DDT is removed from these Mobile Bay suspensions, there is not
an equivalent accumulation of the two primary degradative
compounds.
The dissolved DDT in the aqueous phase after 3 months is
also indicated in Table 5. No dissolved ODD could be detected.
Dissolved DDT and DDE levels in the three treatments were very
low and exhibited greater experimental error compared to quanti-
ties extracted from the sediment phase. The relative quantities
of dissolved DDT and DDE were, as expected, similar to sediment
extractable levels.
The results of this preliminary study are in general agree-
ment with literature findings in that anaerobic conditions are
.''' 56 '"
-------
conducive to most rapid loss of DDT while favoring ODD formation
over DDE. Aerobic conditions resulted in the slowest loss of
DDT and favored DDE formation over DDD. In this particular
study, there were less differences in levels of the three
compounds due to imposed oxidation-reduction conditions at
the end of 90 days than expected from the literature. Alternate
anaerobic/aerobic conditions resulted in concentrations between
those found for continuous aerobic or anaerobic treatments.
This small study was initiated with the hypothesis that frequent
changes in redox potential may be accompanied by rapid DDT
degradation due to associated transformations between ferrous
iron and ferric oxyhydroxides. Iron in soils and sediments has
been implicated in mediating electron transfer processes involved
with DDT degradation (33). Although the abundance of potentially
reactive iron in the Mobile Bay sediment material relative to
most soils used for DDT degradation studies may have enhanced
degradation, frequent chemical transformations of the iron
between oxidized and reduced forms were not associated with
enhanced degradation over physicochemical conditions in which
the iron was not undergoing redox transformations.
ADSORPTION OF 14C-LABELLED DDT BY DIFFERENT COMPONENTS OF
SEDIMENT PARTICULATES
Materials and Methods
Two sediments were used in this study. A sediment material
was collected from the Calcasieu River ship channel near the
1-210 bridge in Lake Charles, Louisiana. The Mobile Bay sediment
material was the same used for DDT sediment degradation studies.
The effects of selective removal of different components on
adsorption of "C-labelled DDT were studied for both sediments.
The sediments were first washed several times to remove
soluble salts and soluble low molecular weight organic molecules.
A portion of this material was equilibrated with labelled DDT
and the remainder treated with 30% hydrogen peroxide on a hot
plate to remove the insoluble organic matter which is an impor-
tant adsorptive component of sediments and soils. After the
organic matter was destroyed, residual sediment-solids were
washed several times with deionized water to remove excess
hydrogen,peroxide, soluble salts and free acid left .from the
hydrogen peroxide and a portion used for the labelled DDT
adsorption studies.
The remainder of the sediment material treated to remove
soluble salts and organic matter was subjected to sodium
dithionate-sodium citrate-sodium bicarbonate treatments as
described by Jackson (68) to remove iron oxyhydroxides. Original
57
-------
untreated sediment material was used to compare the adsorption
of C-labelled DDT of the whole sediment with the treated
sediment materials.
Duplicate 10 gram portions of air dry, pretreated sediments
were placed in 40 ml centrifuge tubes containing 20 ml of ^-^C-
labelled (0.05 uCi/ml) DDT solution (0.1 ppm and 1.00 ppm). The
contents of the centrifuge tubes were shaken on a horizontal box
shaker for 2 hours, centrifuged, and the clear supernatant
solution was removed and stored for "C counting by liquid
scintillation.
The residual sediment in the centrifuge tubes was extracted
with 20 ml of hexane-acetone (3:1) for two hours, centrifuged,
and the supernatant solution was removed for liquid scintillation
counting. The results are expressed as percent of added ^C
measured in solution and extracted by the hexane-acetone extrac-
tant. It was assumed that measured ^4C represented the added
parent compound.
Results and Discussion
14
Table 6 shows the percent of added C-labelled DDT
recovered in solution and extracted by the hexane-acetone mixture
in Calcasieu River and Mobile Bay sediments. Almost all of the
added ^C-labelled DDT was adsorbed oh sediment solids in both
the sediment materials. DDT levels in solution was little
affected by soluble salts removal. Recovery in solution did
increase somewhat (from about 0.6 percent to just over 1 percent)
where organic matter was removed, but further treatment to
remove ferric oxyhydroxides had no apparent influence on soluble,
labelled DDT in these sediment materials.
14
The hexane-acetone extractable C-labelled DDT was sig-
nificantly affected by the treatments to remove sediment
components in.both sediment materials. The hexane-acetone
extractable C-DDT increased from 27 to around 45 percent and
21 to around 70 percent, respectively at 0.1 ppm and 1.0 ppm
addition levels after the organic matter was removed in the
Calcasieu River sediment. This indicates organic matter is
playing an important role on the adsorption of DDT in this
material. It appears that soluble salts and iron oxyhydroxides
are not affecting the adsorption as their removal did not
significantly change the hexane-acetone extractable l^c-labelled
DDT in the Calcasieu River sediment material. The Mobile Bay
sediment material appeared to respond differently depending on
initial DDT concentration. The hexane-acetone extractable DDT
increased with the removal of both soluble salts and organic
matter from about 41 percent to 61 and 76 percent, respectively.
At 1.0 ppm initial DDT concentration, there was an apparent
decrease in solvent extractable DDT as adsorptive components
were removed. The hexane-acetone extractable DDT was different
58
-------
Ul
TABLE 6 . THE EFFECT OF INITIAL DDT CONCENTRATION AND SELECTIVE REMOVAL OF SOLUBLE SALTS, ORGANIC
MATTER. AND IRON OXIDES ON HATER SOLUBLE AND ORGANIC SO..VENT EXTRACTABLE DDT IN CALCASIEU RIVER
_AMP-_HpflILE_ BAY SEDIMENT HATEFUALS
0.1 |ig DDT/g oven dry solids
Componei
< EXTRACTABLE
> water soluble 0-6*I
tO.06*
Soluble
0.58
to. 01
26.3
nts Removed in
Organic Iron
0.98 0.95
46,
.7 43.2
1.0 |ig DDT/g oven dry solids
Soluble Organic
0.62 0.60 1.10
21.2 20.7 73. H
Mobile Bay Sediment Material
0.1 i:g DDT/g oven dry solids
Components Remove
Iron
labelled
1.08
tO. 02
66.6
Soluble
0.65 0.62
+0.01 +0.01
41.3 60.9
1.0 ug
Organic Iron
1.17 1.
^0.00 +0.
75.6 65.
14 0.67
04 t^O.OO
,1 37.6
DDT/g oven dry solids
Extraction
Soluble Organic
0.59 : 1.36
to. 03 . tO. 06
27.6 29.8
* 0.2 V 5.2
Iron
oxides
1.33
+ 0.00
31.5
* 0.2
Mean quantity from extraction of duplicate subsaraples
Standard deviation
-------
in Calcasieu River and Mobile Bay sediment materials indicating
the role of indigenous physical and chemical characteristics on
the adsorption of DDT. The hexane-acetone extractable DDT in
Calcasieu River sediment was less than found for Mobile Bay
sediment material at 0.1 ppm, and at 1.0 ppm, the results were
inconclusive." In general, the-results suggest that among
several components of sediments, organic matter appears to play
a major role on the adsorption of DDT.
REDOX AND pH EFFECTS ON SETTLING RATE AND SOLID/LIQUID PHASE
DISTRIBUTION OF 14C-LABELLED DDT
Materials and Methods
': The Mobile Bay sediment was incubated under reducing and
oxidizing conditions at three pH (5.0, 6.5, and 8.0) levels for
3 months. The sediment was kept in suspension by continuous
stirring. Nitrogen gas was bubbled through the suspensions to
maintain reducing conditions. Oxygen gas was used to maintain
oxidizing conditions. The pH of the sediment suspensions was
controlled by adding either dilute hydrochloric acid or sodium
hydroxide as necessary.
At the end of the 3-month incubation period, 300 ml of the
preincubated sediment suspension was transferred to graduated
cylinders containing 700 ml of distilled water. The pH of the
distilled water in the graduated cylinder had been adjusted to
correspond to the pH of the sediment suspensions.
One ml of the 14C-labelled DDT (activity of 8.33 yCi/ml)
was added to each of the graduated cylinders. All the sus-
pensions were mixed thoroughly and allowed to settle. Sus-
pension samples were withdrawn at 0.25, 0.5, 1, 2, 4, 8, 16, and
24 hours at the 700 ml level. (The cylinders were uniform with
respect to height and diameter. Ten ml of the suspension was
transferred to 40 ml centrifuge tubes containing 0.5 ml of NaCl
solution (a flocculating agent). The suspensions were centri-
fuged for 15 minutes at about 1,000 RCF. The clear supernatant
solution was transferred to glass vials. Addition of sodium
chloride to aid in flocculation of suspended colloids and subse-
quent centrifugation was done( instead of centrifugation and
filtration because of the possibility the 0.45 y membrane filters
may retain some of the dissolved, labelled DDT by adsorption.
After removing the water .fraction, the residual sediment in the
centrifuge tube was shaken for 30 minutes with 10 ml of a
^hexane-acetone mixture (3:1), centrifuged, and this supernatant
extract transferred to glass vials. This fraction was called
total although it is acknowledged labelled DDT recovery may not
have been quantitative.
60
-------
The sample solution was transferred to glass scintillation
vials containing. 15 ml of Aquaspl scintillating liquid." The C
activity was determined by counting Beta radia'tion;* . i
Results and Discussion
The suspension which was equilibrating under pH 8.0
oxidizing conditions was lost one night just a few days before
this study was scheduled to be concluded due to abrasion from
the magnetic stirrer bar and the sediment.mineral phase which
caused a hole to form in the bottom of the glass incubation
flask.
14
Solvent-extractable, C-labelled DDT thoroughly mixed with
a Mobile Bay sediment-water mixture settled beneath the arbitrary
sampling point (700 ml level on graduated cylinders) most rapidly
under moderately acid (pH 5.0), reducing conditions during the
24 hour settling study (Table 7). Reducing, pH 8.0 conditions
resulted in the maximum total levels (approximately 10 times pH
5.0, reducing, levels) of labelled DDT at this sampling depth.
Mildly alkaline conditions likely favored greater dispersion of
colloidal materials which reduced flocculation and contributed
to greater total levels in the upper part of the column relative
to the more acid treatments. Soluble levels also were slightly
greater under pH 8.0, reducing condition's' (Table 8)'. If "the
increase in soluble levels with increasing pH is real, it is
likely due to: 1) an equilibrium with the greater total levels
or 2) the effects of increasing pH on increasing the concentra-
tion of soluble humic acids which may complex with DDT. r. n
Because of interactions imposed between physicochemical,
treatments, time, particle size distribution, equilibrium,
between solid and soluble forms, the loss of the pH 8.0 oxidizing
treatment, and some experimental error, the results of this
study were difficult to evaluate. There was some suggestion
that under reducing conditions for the Mobile Bay sediment,
moderately acid conditions would tend to effect more rapid
removal of soluble and especially suspended particulate DDT
forms from a quiescent water column than near neutral or
slightly alkaline pH conditions.
REDOX AND pH EFFECTS ON DIFFUSION OF DDT AND KEPONE .INTO
SEDIMENT CORES
Materials and Methods
A quantity of Mobile Bay sediment was added to six 4-liter
Erlenraeyer flasks containing deionized water at a solid:solution
ratio of 1:4. The sediment material was incubated under three
different pH (5, 6.5 and 8.0) and two different redox conditions
61
-------
TABLE 7. THE ACTIVITY OF 3:1 HEXANE:ACETONE EXTRACTABLE
14C-LABELLED: DDT. WITH TIME IN COLUMN SETTLING STUDIES
Settling
time , hours
0.25
0.5
1
2
4
:*' 8
16
24
Reduced Sediment
pH 5.0
7,480
6,127
7,007
2,128
1,207
119
77
64
pH 6.5
counts
8,010
6,591
7,244
7,112
6,816
5,870
1,957
353
pH 8.0
per minute/10
12,620
13,080
8,961
6,116
3,911
1,624
1,023
652
Oxidized Sediment
pH 5.0 pH
7,449 . 4,
6,650 2,
6,280 2,
797
700
295
298
105
6.5
928
903
898
388
298
130
175
102
TABLE 8. THE ACTIVITY OF WATER SOLUBLE 14C-LABELLED
DDT WITH TIME IN COLUMN SETTLING STUDIES
Settling
time, hours
0.25
0.5
1
2
4
8
16
24
Reduced Sediment
pH 5.0
113
89
64
68
43
29
23
24
pH 6.
counts
447
380
221
127
95
90
193
80
5 pH 8.0
per minute/ 10
430
312
483
385
127
91
93
94
Oxidized Sediment
pH 5.0 pH
ml sample -
1137
276
226
99
55
55
57
65
6.5
iae
123
199
69
37
32
70
48
62
-------
for 90 days so that both the chemical and biological systems
reach equilibrium.
At the end of the 3-month incubation period, moisture
contents of the sediment suspensions were determined. Then, a
calculated quantity of the incubated sediment suspensions was
transferred to glass cylinders which were sealed at the bottom.
The sediment suspensions were allowed to settle for two days.
Approximately 500 grams of sediment material (oven dry solids)
were present in each cylinder.
A coarse textured soil was combusted at 1000°C and spiked
at a level of 1,000 wg/g DDT and Kepone. Five grams of this
spiked soil was added to the flood water in each cylinder, and
allowed to settle to the sediment water interface. The cylinders
containing the sediments spiked with DDT and Kepone were kept in
a dark room at 27°C for six months. The flood water lost by
evaporation was replaced frequently with deionized water.
At the end of the 6-month incubation period, the sediment
in the glass cylinder was frozen and sectioned at 1-cm inter-
vals. The sediment in each section was dried in draft oven at
40°C, and analyzed for DDT and Kepone which diffused from the
surface into deeper layers.
The pH 8.0, oxidizing suspension was lost just before the
90-day equilibration period ended as discussed elsewhere. The
pH 5.0, reduced Kepone column "was broken.
Results and Discussion
Table 9 gives DDT and Kepone levels vs depth in the column
diffusion studies. No clear treatment effects were apparent and
sampling problems made critical evaluation of this data of
dubious value. The initial horizon of each core consisted of a
thin layer of 0.5 to about 1.2 cm thick which was poorly con-
solidated compared to lower horizons. In the initially reduced
cores, this poorly consolidated layer was approximately the same
thickness as the surface oxidized sediment layer as indicated by
the light brown color of this surface horizon. An attempt was
made to keep the thickness of subsequent horizons a uniform 1.5
cm, though this may have varied slightly. Because of possible
problems in obtaining uniform depth increments in each column,
these data are presented with no interpretation or conclusions
attempted.
63
-------
TABLE 9. DIFFUSION OF DDT AND KEPONE FROM A SEDIMENT-WATER
INTERFACE INTO MOBILE BAY SEDIMENT MATERIAL EQUILIBRATED
UNDER A RANGE OF pH AND REDOX POTENTIAL CONDITIONS
Horizon
I1
2
3
<* 4
5
DDT
Reducing
pH 5.0 pH 6.5
902 1260
26.8 1.3
1.70 0.12
0.22 0.10
0.17 0.05
» vg/g oven dry
pH 8.0
450
2.4
0.50
0.57
0.11
Kepone, pg/g
Horizon
1
2
3
4
5
Reducing
pH 5.0 pH 6.5
f 182
35.6
1.65
0.21
0.02
pH 8.0
364
. 57.9
5.96
0.06
0.04
pH 5
590
33.
0.
11
11
oven dry
pH 5
209
42.
0.
0.
11
solids
Oxidizing
.0 pH 6.5 pH 8.0
619 t
5 4.6
25 0.08
0.06
H
solids
Oxidizing
.0 pH 6.5 pH 8.0
207 t
0 70.6
89 1.15
02 0.05
H
'Sediment suspension lost during preincubation
«
Lost sample
*Core column broke
64
-------
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71
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APPENDIX A
DEVELOPMENT AND TESTING OF PROCEDURES/TROUBLE
SHOOTING/ADDITIONAL NOTES/QUALITY ASSURANCE
INTRODUCTION
The previous sections of this report represent work
conducted to meet research objectives. A considerable amount of
additional work was performed in testing and developing proce-
dures, trouble shooting, and repeating studies with which there
were problems. This section will briefly discuss some of this
work. The objectives of this section are to: 1) present
information and procedures which may be useful to others ini-
tiating pesticide research in sediment-water systems, 2) present
findings of studies to determine the recovery efficiency of
extraction methods used for the primary degradation experiments,
and 3) provide additional information on the conduct of this
project, such as the need to repeat some work and substantially
modify procedures on some studies.
TESTING OF EXTRACTION METHODS
DDT :
.In addition to surveying the literature for extraction
methods for DDT, four local and regional laboratories conducting
pesticide monitoring or research were visited to obtain informa-
tion on methodology. These were: Feed and Fertilizer Labora-
tory, Louisiana State University campus; laboratory of the
Louisiana Wildlife and Fisheries Commission, Division of Water
Pollution Control, Louisiana State University campus; USDA Soil
and Water Pollution Laboratory, Baton Rouge, Louisiana; and the
Pesticides Monitoring Laboratory, U.S. EPA. Bay St. Louis,
Mississippi.
Initial experience with the commonly used method of shaking
soil or sediment samples with appropriate organic solvents to
extract DDT was not satisfactory with the Mobile Bay sediment
material. It was soon apparent that good and reproducible
recovery of DDT from fine textured, anaerobic sediments was more
difficult to achieve than from' typical agricultural soils. A
12-hour Soxhlet extraction using 3:1 hexane-acetone gave
72 \: .
-------
recoveries consistently between 90 and 95 percent on Mobile Bay
sediment suspensions which had been incubated under weakly
reduced to well oxidized conditions. Recovery from spiked,
strongly reduced samples were not as good and tended to be less
;. reproducible. The reasons for this difficulty were not readily
apparent. At first it was believed that drying of anaerobic wet
sediment samples in a draft oven at 35-40°C for 1 to 3 days may
have contributed-a drying-artifact and alternate- sample drying
procedures were developed (see Acetone Drying of Wet Sediment
Samples, page 74). However, results using alternate drying
methods and reevaluation of the data suggested any apparent
improvement in DDT recovery from strongly reduced sediments was
probably more a function of how quickly the spiked test suspen-
sions were extracted rather than any improvement resulting from
modified drying procedures. It was not possible to quantify the
recovery efficiency for DDT from the strongly reduced Mobile Bay
sediment suspensions because, as discussed elsewhere in this
report, there was evidence that some of the DDT degraded very
rapidly under strongly reduced conditions in addition to any
other processes which may have affected extractable DDT levels.
Kepone
Recovery of Kepone from James River sediment material was
initially tested using the same extraction method applied to
Mobile Bay sediments for DDT as well as two other solvent
systems (Table A-l).
When routine extraction and analysis of Kepone samples from
the controlled pH-redox potential studies were begun, it was soon
apparent that Kepone extraction efficiency was poorly reproduc-
ible. At this time we became aware of a 1977 publication by
Moseman et al. (69) on Kepone methodology in which the benzene-
methanol solvent system was found to give good recovery of
Kepone and to aid in obtaining reproducible electron capture
1 response compared to other extracting solvents. These procedures
] were tested on Kepone-amended James River sediment suspensions
1 and were found to give fair to good recovery and good reproduc-
I ibility. Subsequently, we switched to the benzene-methanol
i procedure and repeated earlier studies done with hexane-acetone.
Permethrin
This laboratory's experience with DDT and Kepone indicated
good and reproducible pesticide extraction from fine grained,
anaerobic sediments was more difficult than extraction from
typical aerobic agricultural soils for which most published
extraction methods have been used. Therefore, a thorough study
of various extraction procedures was conducted on both oxidized
and reduced soil amended with Permethrin before initiating
experimental incubations under.controlled pH and oxidation-
reduction conditions.
-------
TABLE A-l. KEPONE RECOVERY FROM AMENDED JAMES RIVER
SEDIMENT SUSPENSIONS1"
Solvent System
1:1 hexane-acetone
1:5 methylenechloride-
hexane
Suspension Treatment
Drying Procedure Oxidized Reduced
:-_---.. Recovery., ,%..--
35°C, draft oven 20 10
35°C, draft oven
20
10
3 : 1 hexane-acetone
3 ;.;1 hexane-acetone
35°C, draft oven
acetone
72
72
14
100
12-hour Soxhlet extraction
U
see Acetone Drying "of Wet Sediment Samples
A summary of the methods tested for extracting Permethrin
from wet soil samples is given below. The excess water ini-
tially present in the sample was removed by centrifugation,
extracted, and analyzed for Permethrin. It was found that
essentially all of the Permethrin added to the soil-water
mixtures was partitioned with the solid phase as essentially no
Permethrin was measured in the aqueous phase.
Permethrin recovery by the various extraction methods
tested are given in Table A-2 for both oxidized and reduced soil
samples. The 1.5:1 hexane-acetone solvent system with 8-hour
Soxhlet extraction method was selected and used for all
Permethrin work (see Table A-3).
ACETONE DRYING OF WET SEDIMENT SAMPLES
During initial DDT degradation studies, recovery of DDT
from strongly reduced sediment samples was well below levels
added to the suspensions, even after only a few hours to one day
following DDT amendments. Elevated levels of degradation
products were: also apparent only a few hours to 1 day into the
incubation. At the time, these rapidly occurring- transformations
of DDT were interpreted as changes occurring during the drying
step for the strongly reduced samples which appeared as treatment
effects.
-------
TABLE A-2. SUMMARY OF METHODS TESTED FOR EXTRACTING
PERMETHRIN FROM OXIDIZED AND REDUCED SOIL SUSPENSIONS
I: Acetone Drying Method - . . .
A. 4-hour Soxhlet extraction
1. 1:1 hexane-acetone
2. 1:2 hexane-methanol
B. 12-hour Soxhlet extraction
1. 1:1 hexane-acetone
2. 1:2 hexane-methanol
H
C. 8-hour Soxhlet extraction.
1. 1.5:1 hexane-acetone
II. Oven Drying (40°C for 48 hours)
A. 4-hbur Soxhlet extraction
1. 1:1 hexane-acetone
2. 100% hexane
B. 12-hour Soxhlet extraction
1. 1:1 hexane-acetone
2. 100% hexane
III.' Shaking Moist Samples with Extracting Solvent
A. Methanol extraction*
B. 1:1 hexane-acetone extraction'
See Acetone Drying of Wet Sediment Samples
Permethrin method used by U.S.D.A. Soil and Water Pollution
Laboratory, Baton Rouge, Louisiana
*Two grams soil + 5 grams ix'aCl shaken for 30 minutes with
9:1 methanol-water mixture. Mixture was filtered, extracted
three times with methylene chloride, the methylene chloride
concentrated on hot plate, 100 ml hexane added, and solvent
system again concentrated on hot plate to 50 ml, then dried
by eluting through
ETwo grams soil + 5 grams NaCl shaken with 100 ml of 1:1
hexane-acetone for 30 minutes, filtered, acetone extracted
with water and hexane solution dried with NaSO^
,:' 15
-------
TABLE A-3. PERMETHRIN RECOVERY FROM SPIKED OXIDIZED AND
REDUCED SOIL SUSPENSIONS BY VARIOUS EXTRACTION-METHODS
Extraction Method
acetone dry, 4-hr Soxhlet, 1:1
hexane-acetone
acetone, 4-hr Soxhlet, 1:2 hexane-
methanol
acetone dry, 12-hr Soxhlet, 1:1
hexane-acetone
acetone dry, 12-hr Soxhlet, 1:2
hexane-methanol
acetone dry, 8-hr Soxhlet, 1.5:1
hexane-acetone
oven dry, 4-hr Soxhlet, 1:1
hexane-acetone
oven dry, 4-hr Soxhlet, 100%
hexane
oven dry, 12-hr Soxhlet, 1:1
hexane-acetone
oven dry, 12-hr Soxhlet, 100%
hexane
methanol extraction of moist
soil by shaking
1:1 hexane-acetone extraction of
. . . . Recovery,
Oxidized
78
67
76
95
90
66
88
58
71
64
79
r %
Reduced
58
60
82
89
90
76
63
61
75
74
74
moist soil by shaking
76" ;:.";.>
-------
The original procedure used for reduced samples had been to
remove excess water from the sediment-water mixtures by centrifu-
gation and then dry the wet sediment samples at 35°C in a forced
draft oven. This temperature range was found to give good
recovery from oxidized sediment samples whereas higher oven
temperatures -resulted in poor DDT recovery, presumably due to
volatilization losses. However, the low drying temperature
necessitated 1 to 4 days in the oven, depending on sample size.
It was believed the exposure of strongly reduced sediments to
oxidized conditions near the optimum temperatures for most
microbial activity may have favored an enhanced rate of chemical
degradation or mixed anaerobic-aerobic microbial activity which
was not typical of sediment-water systems.
Although Browman (70) reported successful extraction of wet
. (moisture remaining after pouring off excess water) sediments by
shaking with organic solvents, preliminary studies indicated
shaking was not a satisfactory method for our samples. Soxhlet
extraction of wet sediments was also not satisfactory. Thus
sediment drying seemed an essential step.
A number of different drying techniques were examined
including freeze drying. The most satisfactory technique was to
centrifuge the sediment-water mixtures and decant the super-
natent water as before, then remove the residual moisture by
shaking the solids with acetone twice, evaporating residual
acetone under a nitrogen stream, and combining the DDT extracted
during the acetone drying step" with the solvent mixture from the
Soxhlet extraction of the solid phase. The samples can be dried
in less than 2 hours using this procedure. This method was
tested on reduced sediment suspensions and recovery approached
80 percent vs greater than 90 percent for oxidized samples.
Surprisingly, extracted levels of DDT in the most strongly
reduced samples at each pH was again found to be far below
spiking levels within a very short time. The apparent high
recovery efficiency of the extraction procedure using acetone
.drying and the continued low DDT/high ODD levels in the early
portion of the experimental incubations under controlled physico-
chemical conditions probably resulted from sampling and extrac-
tion of the acetone drying test samples about 1 hour after
spiking which gave less time for microbial or chemical decomposi-
tion in the reduced suspension.
REMOVAL OP SULFUR INTERFERENCE FROM SOLVENT EXTRACTS OF STRONGLY
REDUCED SOIL AND SEDIMENT SAMPLES
Organic solvent extraction of certain strongly reduced
soils and sediments will solubilize sufficient sulfur to
contaminate the column and/or electron capture detector for a
77
-------
.-in-
considerable period of time masking pesticide peaks. Many of
the reduced Mobile Bay sediment extracts required treatment to
remove sulfur. This was done by treating bare, 12 gauge copper
wire with 4N HN03 to remove oxide coatings and immersing the
surface active wire in the sample test tubes for about 30
minutes with occasional swirling. " More than one treatment was
sometimes necessary to remove the sulfur. This method was a
modification of a published procedure (67). A small quantity of
elemental mercury can be added to the sample as an alternate way
of removing sulfur interference.
A PROBLEM WITH ERRATIC RESPONSE OF GAS CHROMATOGRAPH TO KEPONE
SAMPLES AND STANDARDS
Kepone was being analyzed with a 1.5 percent OV-1, 1.95
percent QF-1 column connected to an electron capture detector.
For the first few months of Kepone analyses, the instrument
response (peak height or peak area) was reproducible to within 4
percent and usually within 2 percent on repeated injections of
the same sample or standard.
Over a very short period of time, the response became
erratic and varied from 20 to as much as 40 percent on repeated
sample or standard injections. The instrument electronics were
determined to be stable. The usual cleanup procedures of re-
placing the silanized glass wool packing at the beginning of the
column and solvent rinsing plus high temperature "baking out" of
the injector and interface tubing did not alleviate the problem.
It was noted that where standards containing both Aldrin and
Kepone were injected repeatedly, the Aldrin response was very
reproducible and the Kepone response was not.
This erratic response to Kepone was confirmed on two other
electron capture instruments at the USDA Soil and Water Pollution
Control Laboratory in Baton Rouge. Thus the problem appeared
peculiar to Kepone. A telephone conversation with personnel of
the USDA Plant Protection Laboratory at Gulfport Mississippi who
were experienced with Kepone analysis revealed that this is not
an uncommon problem with Kepone. This lab often derivatized the
Kepone in samples to overcome poor gas chromatography performance
for Kepone.
While getting set up to do the same with our Kepone samples,
it was learned that, by mistake, someone had ammended the sediment
suspensions used for one short term auxiliary Kepone study with
100 ug/g levels of Zn, Cu, Cd, and Pb.
It seemed plausible that the hot benzene-methanol extract
was removing a portion of these.metals which accumulated as a
solid residue in the glass liner of the injector. These residual
metal deposits may have catalyzed some Kepone decomposition
' ' '" 78 '"
-------
within the injector resulting in a highly variable response.
The glass injector liners were cleaned by repeated rinsing with
4N nitric acid (a common method of removing metal contamination
from glassware). This treatment was successful in restoring the
gas chromatograph to give a stable and reproducible response to
Kepone.
It is possible that solvent extraction of indigenous metals
from soils and sediments would eventually cause the same problem
with Kepone in many instruments.
After this incident, the glass injector liners were
periodically acid cleaned and no further problems developed with
the Kepone analyses.
REPEATED STUDIES
DDT
Because we initially believed the DDT sample processing
methods for strongly reduced sediments were contributing to
drying artifacts, new drying methods were implemented (see
Acetone Drying for Wet Sediment Samples, page 74) and incubations
were repeated for the -150 and 50 mv treatments at all three pH
levels using a somewhat greater sampling frequency. The repeated
data are presented in this report due to the greater sampling
frequency and less apparent experimental error at pH 6.0. This
accounts for the different sampling dates on oxidized and
reduced treatments.
. The repeated work showed the low initial recovery of DDT
from strongly reduced samples was apparently not a drying
artifact as discussed elsewhere in this report. In most cases
the data from repeated studies was very similar to the original
data.
Kepone
A Kepone incubation at pH 6.5 was completed using a hexane-
acetone extractant and samples were stored. Another incubation
at pH 8.0 was in progress before a problem with extracting
methods was detected. Extraction and analyses for Kepone were
stopped until the procedure was changed giving good and repro-
ducible Kepone recovery. Thus the pH 8.0 study data begins on
sampling day 16 where a benzene-methanol extraction procedure
was implemented. The data for pH 6.5 using hexane-acetone was
not included in this report. Instead, this study was repeated
at pH 7.0 using the benzene-methanol procedure.
79
-------
QUALITY ASSURANCE
The number of sample processing steps for each pesticide
analysis in this study was large (page 25, 28, and 29). Many
of these steps were necessary to remove the water from the
suspension aliquots taken for samples. This is in contrast to
most residue "analysis procedures which start with an air-dried ~
soil.-~ The-large-number-of-steps introduces-considerable oppor- -
tunity for experimental error to creep into the methodology.
For most of the analyses for pesticide recovery under
controlled physicochemical conditions, duplicate sample aliquots
were withdrawn, and were processed and analyzed by gas chroma-
tography separately. These duplicate analyses are indicated in
Figures 3, 4, 6, 7, 9, 10, 11, 12, 13, 14, 15, and 16 where two
data points are given for each sampling date. The precision of
the extraction procedure as indicated by the closeness of
duplicate values on separate sample aliquots appeared very good
in most cases.
Accuracy is indicated by comparing recovery levels at the
first sampling date in an incubation with the spiking levels
presented in the legend for each of Figures 2-16. With a few
exceptions which are apparent in the figures, the ability to
recover spiking levels was satisfactory. The low initial
recoveries of DDT under strongly reducing conditions (-150 mv)
was believed due to rapid degradation, and this is examined more
thoroughly in the DDT discussions.
Replication refers to data obtained from individual experi- -
mental units. The duplicate values discussed above to illustrate
the precision of the sample processing procedure represent sub-
sampling, not replication. The degradation studies under con-
trolled pH and redox potentials (Figures 2-16) were subsampled,
but not replicated. It was believed our experimental objectives,
with the time and equipment available, would best be served by
having a larger number of treatments (where treatments were
different levels of a continuous variable) with a large number
of samples taken with time. However, the question of reproduc-
ibility of experimental results (treatment effects) needs to be
addressed. The repeated studies done with DDT under reduced
conditions do approximate replication. Recall that many of the
incubations of DDT at -150 and 50 mv were repeated at a later
date using a different sample drying procedure. As reported
elsewhere, it was eventually concluded that the method of drying
did not account for the rapid decrease in DDT levels at -150 mv.
Thus the repeated studies represent samples taken at different
times from different microcosms incubated under the same imposed
physicochemical conditions. Figure A-l illustrates the recovery .
of DDT with time at pH 8.0 and +50 mv from two different
incubations. A redox potential, of 50 mv was selected for
80'
-------
25 -
20 -
E
a
p
§10-
5 -
0 = repeated sediment incubation
(samples processed using acetone
drying procedure)
X = original sediment incubation
(samples dried at 35°C in forced
draft oven)
i i \ i i i
10 15 20 25 30 35
TIME (days)
40
45
Figure A-l: DDT Recovery with Time from Two Mobile Bay Sediment Suspensions Incubated at
pH 8.0 and +50 mv.
-------
comparisons because at this potential there was a moderate
decrease in recovery throughout the incubation. Other than
some scatter seen in data points during the first few days of
the original incubation, DDT levels and changes in DDT levels
were very similar from the two microcosms. This is an indication
that the microcosms do replicate reasonably well. -
82
-------
APPENDIX B. TABLES FOR DDT, KEPONE, AND PERMETHRIN
DEGRADATION STUDIES UNDER CONTROLLED pH AND
REDOX POTENTIAL CONDITIONS
:: 83 <:'
-------
TABLE B-l. THE EFFECT OF REDOX POTENTIAL ON THE RECOVERY
OF ADDED DDT DURING A 45-DAY INCUBATION OF MOBILE BAY
SEDIMENT SUSPENSION" AT nH
Incubation
Period, days
0
1
2
3
4
5
7
9
10
11
13
15'
18
20
21
24
25
30
32
35
37
40
42
45
Redox Potential, mv
-150
22. Of
6.6
1.3
0.8
0.4
0.6
0.4
0.2
0.4
0.5
0.3
0.7
1.7
0.6
0.2
0.0
0.1
50 250
DDT,
24
21
20
19
22
20
21
12
14
"17
16
10
.11
11
14
10
yg/g oven dry sold
H 11
.2 21.5
.9
.8
.6 23.3
.3
.6 17.5
.3
20.4
6
.2
.9 16.2
9
16.9
.4
.8
14.0
17.0
.3
13.1
.4
18,5
.4 14.0
450
i A e*
24.0
24.0
17.4
22.7
19.9
16.7
13.1
'14.8
16.0
12.2
17.0
16.0
Quantity from extraction of single sample
11
Lost Sample/missing value
84"
-------
TABLE B-2.
THE EFFECT OF REDOX POTENTIAL ON
i
THE RECOVERY
OF ADDED DDT DURING A 45-DAY INCUBATION OF MOBILE BAY
SEDIMENT SUSPENSION AT OH 7.0
«.j
±ncuoadon
. Period,, days
0
1
4
5
;'" 7
9
11
12
13
18
19
21
22
24
27
.28
. 32
36
37
41
42
45
Redox
-150 50
* 34.8'
10.3 27.4
5.1 23.2
2.6 30.8
1.7 26.5
f 29.4
3.1 27.1
0.8 19.3
0.1 14.8
+ +
1 1
t t
. .. 0.1 8.3
.0.0 9.5
f 10.2
* . 7.6
0.0 f
Potential
250
oven dry
25.9*
54.6
+ 2.7
22.8
+ 0.6
25.2
+ 0.9
18.4
+ 4.0
^~
21.7
+ 1.3
22.4
+ 0.0
t
t
17.0
. + 0.7 .
, mv
"450
40.8^
+ 5.0*
38.1
+ 6.4
27.0
+ 2.5
28.6
+ 1.2
15.0
.+ 1.4 :
"* '
22.6
+ 0.4
23.0
+ 0.9
20.6
+ 0.2
20.6*
Lost sample/missing value
Quantity from extraction of single sample
'Lost one subsample
Mean quantity from extraction of duplicate subsamples
'standard deviation ...
-------
TABLE B-3. THE EFFECT OF REDOX POTENTIAL ON THE RECOVERY
OF ADDED-DDT DURING A 45-DAY INCUBATION OF MOBILE BAY
SEDIMENT SUSPENSION AT pH 8.0
Period, days
0
1
4
7
15
20
25
30
35
40
45
-150
+0.011
2.4
+0.1
1.0
+0.0
0.0
+0.0
0.4
+0.0
0.2
+0.0
*
0.0
+0.0
. *
0.0
+0.0
o.oe
Redox Pote
50
/
DDT , yg/g oven
23.4
t
*
15.8
+ 0.1
13.5
+ 0.0
11.6
+ 0.9
10.1
+ 0.0
7.5
+ 0.0
8.2
+ 0.0
8.2
+ 0.4
4.7
+ 0.1
;ntial, mv
250
, ...
27.2
+ 0.0
23.2
+ 0.0
17.7
+ 0.1
18.0
+ 0.1
15.2
+ 1.3
15.8
+ 0.2
13.6
+ 0.1
16.0
+ 0.3
13.7
+ 0.6
450
25.4
+ 0.8
25.8
+ 0.6
17.2
+ 1.1
16.6
+ 1.2
15.8
+ 0.2
17.8
+ 0,2
15.3
+ 0.4
16.3
+ 0.6
14.2
+ 0.3
Mean quantity from extraction of duplicate subsamples
Standard deviation
*Lost sample/missing value
eLost one subsample
-------
TABLE B-4. THE EFFECT OF REDOX POTENTIAL ON THE RECOVERY
OF ODD DURING A 45-DAY INCUBATION OF MOBILE BAY SEDIMENT
SUSPENSION AT pH 6.0
Incubation
Period,, days
0
1
2
. 3
4
5
7
9
10
11
13
15.
18
20
21
24
25
30
32
35
37
40 ..
42
45
-150
1.37f
5.93
6.70
6.60
4.75
6.17
5.42
5.50
4.80
4.50
4.42
4.55
3.55
2.55
2.22 .
2.45
2.37
Redox P
50
-
- ODD, yg/g
it
0.67
0.57
0.47
1.05
0.65
0.75
0.75
1.03
0.73
-0.83
0.87
1.35
0.70
0.69
0.69
1.00
otential,
250
oven dry
0.57
0.73
0.57
U
0.55
1.00
0.45
0.52
0.69
' 0.79
0.61
0.61
mv
450
j
0.63
0.67
0.73
0.87
0.47
0.37
0.27
0.50
1.00
0.67
0.61
0.46
Quantity from extraction of single sample
Lost sample/missing value
'..'. 87' *;',,*
-------
TABLE B-5. THE EFFECT OF REDOX POTENTIAL ON THE RECOVERY
OF ODD DURING A 45-DAY INCUBATION OF MOBILE BAY SEDIMENT
finfiPRMSTOM &T nH
Incubation
Period,, days
0
1
4
5
7
9
11
12
13
18
19
21
22
24
27
28
32
36
37
41
42
. 45
-150
t
1.86
8.07
5.07
4.60
1.10
1.78
1.27
1.32
2.29
2.99
' 2.07
2.22
2.37
- 2.14
2.37
Redox
50
ODD, yg/g
l.Ol1
0.98
0.94
1.10
1.25
0.16
1.14
1.16
0.15
_
1.45
.2.14
1.07
. 1.30
1.30
1.16
1.38
Potential
250
ovsn Qjry
0.70J;
+0.31
0.30
+0.04
0.34
+0.01
0.33
+0.07
0.28
+0.04
, mv
450
j
0.38
+0.09
0.45
+0.13
0.24
+0.02
0.27
+0.00
0.24 . .
+0.02
Lost sample/missing value
Quantity from extraction of single sample
*Mean quantity from extraction of duplicate subsamples
eStandard deviation
-------
TABLE B-6. THE EFFECT OF REDOX POTENTIAL ON THE RECOVERY
OF ODD DURING A 45-DAY INCUBATION OF MOBILE BAY SEDIMENT
SUSPENSION AT pH 8.0 :
Redox Potential, mv
Period,, days -150 50 250 450
0
1
4
7
15
20
25
30
35
40
45
7.62!
+0.24*
^~
6.28
+0.23
6.41
+0 . 06
6.91
+0.10
5.24
+0.13
4.26
+0.13
3.66
+0.15
4.64
+0.06
2.90
+0.06
3.06
+0.11
2.96
+0.03
)DD, pg/g oven dry sol
0.71
+0.15
"" A
T
f
1.56
+0.05
1.28
+0.08
- 1.41
+0.03
1.94
+0.91
2.04 '
+0.02
1.46
+0.02
1.88
+0.06
2.07
+0.35
0.64
+0.02
~ ±
T
t
0.59
+0.00
0.80
+0.32
0.64
+0.02
0.62
+0.01
0.61
+0.-03
0.64
+0.03
0.92
+0.04
0.68
+0.16
0.56
+0.09
~ *
T
1=
0.45
+0.04
0.56
+0.07
0.54
+0.07
0.48
+0.12
0.44
+0.02
. 0.41
+0 . 04
0.40
+0 . 04
0.37
+0.07
Mean quantity from extraction of duplicate subsamples
*Lost sample/missing value
Standard deviation
..-.; 89 <-,.-
-------
TABLE B-7. THE EFFECT OF REDOX POTENTIAL ON THE RECOVERY
OF DDE DURING A 45-DAY INCUBATION OF MOBILE BAY SEDIMENT
SUSPENSION AT PH 6.0
Period, days
0
1
2
3
4
5
7
9
10
11
13
15
18
20
21
24
25
30
32
35
37
40
42
45
' -150
0.25f
0.95
0.95
0.95
0.87
0.75
0.83
0.65
0.70
0.63
0.67
0.45
0.35
0.35
0.34
11
0.32
Redox Potential, mv
50 250
/ j
DDE, pg/g oven dry solids
f 0.27
11 0.25
0.12
0.12
0.12
0.15
0.15 0.17
0.15
0.17 .
0.12
0.15
" 0.17 ; 0.17
0.20
0.12
0.12
0.17
0.15
0.07
11
0.24
0.63
450
0.30
0.32
0.12
0.20
0.15
0.13
0.12
0.17
Quantity from extraction of single sample
Lost sample/missing value .
9Q -=>
-------
TABLE B-8. THE EFFECT OF REDOX POTENTIAL ON THE RECOVERY
OF DDE DURING A 45-DAY INCUBATION OF MOBILE BAY SEDIMENT
SUSPENSION AT oH 7.0
:
Incubation
Period, days
0
1
4
5
7
9
II
12
13
18
19
21
22
24
27
28
32
36
37
41
42 -
45
-150
t
0.34
0.92
0.81
0.75
0.68
0.68
0.54
0.21
0.38
0.36
0.63
0.37
0.39
. 0.36
0.38
Redox
50
/
DDE / vg/g
0.4511
0.39
0.37
0.32
0.09
0.41
0.18
0.20
-
0.99
6.84
0.70
. 0.81
0.74
0.71
0.83
Potential
250
.
oven dry
o.osf
+0.12
0.00
+0.00
'0.06
+0.01
0.08
+0.01
0.06
+0.04
, mv
450
0.11
+0.08
0.04
+0.01
0.08
+0.01
0.12
+0.01
0.08 .
+0.01
Lost sample/missing value
Quantity from extraction of a single sample
'Mean quantity from extraction of duplicate subsamples
Standard deviation
91
-------
TABLE B-9. THE EFFECT OF REDOX POTENTIAL ON THE RECOVERY
OF DDE DURING A 45-DAY INCUBATION OF MOBILE BAY SEDIMENT
SUSPENSION AT PH 8.Q
Incubation
Period, days
0
1
4
7
15
20
25
30
35
40
45
-150
f
+0.02*
e
0.96
+0.01
0.94
+0.04
0.69
+0.06
0.58
+0.02
0.56
+0.04
0.54'
+0.02
0.38
+0.12
0.54
+0.01
0.44
+0.02
Redox ]
50
.
DDE, pg/g
0.18*
e
e
0.34
+0.00
0.28
+0.03
0.30
+0.04
e
0.38
+0.01
e
0.31
+0.01
0.34*
Potential, mv
250
oven dry solios
0.26
+0.04
e
: e
0.27
. +0.01
0.33
+0.05
0.29
+0.03
0.30
+0.01
0.37
+0.00
0.37
+0.05
0.38
+0.02
0.39* .
450
0.34
+0.07
e
e
0.19
+0.01
0.29
+0.00
0.27
+0.02
0.27
+0.01
0.26
+ 0.02
0.30
+0.07
0.28
+0.01
0.34*
Mean quantity from extraction of duplicate subsamples
Lost one subsample
TStandard deviation
Lost sample/missing value
.;: 92' '.:.%
-------
TABLE B-10. THE EFFECT OF REDOX POTENTIAL ON THE RECOVERY
OF ADDED KEPONE DURING A 51-DAY INCUBATION OF JAMES RIVER
SEDIMENT SUSPENSION AT pH 5.0
Incubation
Period,, days
0
1
2
4
6
9
12
15
18
24
27
35
45
Redox Potential,
-150
17.6
+ 0.8
16.8
+ 0.6
18.0
+ 0.8
14.3
+ 0.3
15.2
+ 2.4
15.5
+ 0.2
14.9
+ 3.8
15.0
+ 0.2
13.9
+ 0.8
13.2
+ 0.5
17.3
+ 0.2
12.2
50
Kepone, ug/g
! 18.6
11 + 0.2
17.8
+ 0.7
20.6
+ 3.0
17.4
+ 0.1
16.1
+ 0:1
17.9
+ 0.2
17.3
+ 2.6
16.4
- + 0.3
11.7
± i-7
14.1
. + 1.3
15.7
+ 0.0
t t
13. 6e
+ 0.1
. 51
. 17.7
E 12.6
± 0.6
250
oven dry
17.8
+ 0.5
17.7
+ 0.2
16.5
+ 2.4
15.6
+ 0.4
18.2
+ 0.5
15.8
+ 1.2
16.8
+ 0.8
13.0
+ 0.8
13.4
+ 0.4
13.3
+ 0.9
16.2
+ 1.4
16.1
+ 0.8
13.6
+ 0.9
mv
450
14.7
+ 0.5
15.5
+ 0.1
16.0
+ 0.7
14.8
+ 0.4
13.7
+ 1.3
15.6
+ 1.6
13.4
+ 1.6
12.3
+ 0.8
12.8
+ 0.9
9.7
+ 0.0
16.4
+ 0.2
f t
13. 9E
12.4
+ 0.4
Mean quantity from extraction of duplicate subsamples
Standard deviation
'Lost sample/missing value
£ '
Lost one subsample
93
-------
TABLE B-ll. THE EFFECT OF REDOX POTENTIAL ON THE RECOVERY
OF ADDED KEPONE DURING A 52-DAY INCUBATION OF JAMES RIVER
SEDIMENT SUSPENSION AT pH 7.0
Incubation
Period,, days
0
1
2
4
6
9
15
18
21
24
27
30
35
40 .
45
52
Redox Potential,
-150
19.7
+ 0.5
22.1
+ 0.0
16.7
+ 1.4
21.0
+ 0.0
18.5
+ 1.8
20.9
+ 1.2
17.1
+ 2.7
18.9
+ 0.5
18.7
+ 0.9
15.7
+ 0.7
16.6
+ 1.4
16.0
+ 1.6
19.3
+ 0.9
19.3
+ 4.7
20.6
+ 0.4
18.9
± 3-7
50
Kepone, yg/g
I 20.0
11 +0.5
18.0
+ 0.7
18.6
+ 0.0
16.4
+ 1.7
17.3
+ 0.5
20.1
+ 1.8
16.8
+ 0.0
_ 18.2
+ 0.4
18.9
+ 0.8
15.9
+ 0.2
14.7
+ 0.4
14.0
+ 1.7
19.8
+ 0.2
20.5
+ 2.1
19.7
+ 0.1
22.4
+ 0.3
250
oven dry
17.3
+ 3.6
19.6
+ 1.1
20.3
+ 1.1
20.7
+ 2.4
20.1
+ 0.6
17.3
+ 0.4
18.2
. + 1.4
20.3
+ 1.8
18.9
+ 0.8
16.1
+ 0.5
18.4
+ 0.4
19.8
+ 0.8
21.2
+ 0.2
20.8
+ 5.2
18.2
+ 0.2
22.1
+ 1.3
mv
450
17.6
+ 0.8
17.9
+ 5.0
20.6
+ 1.6
19.0
+ 0.4
18.6
+ 0.7
19.9
+ 4.8
19.9
+ 0.6
. 19.5
+ 1.5
19.4
+ 0.9
16.5
+ 0.3
16.7
+ 2.0
19.6
19.0
+ 2.0
13.6
+ 3.7
17.0
+ 0.6
19.8
+ 2.5
Mean quantity from extractions of duplicate subsamples
Standard deviation
« 94'
-------
TABLE B-12. THE EFFECT OF REDOX POTENTIAL ON THE RECOVERY
OF ADDED KEPONE DURING A 70-DAY INCUBATION- OF JAMES RIVER
SEDIMENT SUSPENSION AT pH 8.0
Incubation
Period,, days
16
19
24
30
37
.42
49
56
70
Redox Potential,
-150
t
+ 1.2fl
17.8
+ 2.1
21.6
-I- 0.4
21.4
+ 1.5
21.7
+ 0.6
21.0
+ 0.8
17.3
+ 0.4
18.2
+ 0.1
10.5
50
pone, yg/g
20.4
+ 1.1
17.5
+ 0.7
23.0
+ 4.0
19.9
+ 0.5
19.7
+ 1.9
18.5
+ 0.6
14.1
+ 1.4
15.8
+ 0.4
9.3
+ 0.5
250
oven dry
20.0
+ 5.8
17.8
+ 1.7
19.4
+ 5.3
17.2
+ 0.1
22.3
+ 2.0
18.2
+ 3.1
16.4
+ 1.5
21.0
+ 2.4
10.1
+ 2.2
mv
450
. .
20.3
+ 2.2
16.8
+ 0.3
18.4
+ 0.3
17.3
+ 1.8
19.8
+ 3.8
20.9
+ 4.0
18.7*
19.5
+ 1.2 .
9.5
+ 0.8
Mean quantity from extraction of duplicate subsamples
Standard deviation
*Lost one subsample
-------
TABLEB-13. THE EFFECT OF REDOX POTENTIAL ON THE RECOVERY
OF ADDED PERMETHRIN DURING A 25-DAY INCUBATION OF
OLIVIER SOIL SUSPENSION AT pH 5.5
Incubation
Period,, days
Redox Potential, mv
-150
50
Permethrin, yg/g
1
4
6
11
15
18
25
+
14. e;
+ 0.31'
15.3
+ 0.8
14 . 7
+ 0.3
12.7
+ 1.0
12.2
± 1-3
14.6
+ 0.9
11.4
+ 2.5
12.0
+ 0.5
12. 3*
-
12.6
± 1-1
11.6
+ 0.7
11.8
+ 0.6
13.0
+ 0.1
11.7
+ 1.3
250
oven dry
15.4
+ 0.3
14.2
+ 0 . 3
11.5
+ 0.2
7.6
+ 0.6
5.8
+ 0.1
8.0
+ 0.1
4.2
+ 0.1
450
solids
8.4
+ 0.4
10.9
+_ 0.2
7.7
+ 2.8
6.2
+ 0.0
2.3
+ 0.1
0.2
+ 0.0
0.2
+ 0.1
Mean quantity from extraction of duplicate subsamples
Standard deviation
*Lost one subsample
96
-------
TABLE B-14. THE EFFECT OF REDOX POTENTIAL ON THE RECOVERY
OF ADDED PERMETHRIN DURING A 26-DAY INCUBATION OF
OLIVIER SOIL SUSPENSION AT pH 7. 0
Redox Potential, mv
Period, days
1
2
3
5
8
12
14
19
21
23
26
-150
50
Permethrin, ug/g
8.7* 16.0
+ 1.8T + 2.5
10.4
+ 1.1
9.7
+ 0.6
7.2
t 1'3
6.0
+ 0.3
8.2
+ '2.4
8.2
+ 0.1
7.8
+ 0.0
7.5
+ 1.1
11.1
+ 1.5
8.0
+ 0.1
14.0
+ 1.4
10.7
+ 0.3
10.7
+ 1.6
6.811
9.6
+ 0.6
9.4
+ 0.6
6.9
+ 2.6
6.4
+ 1.3
11.4
+ 0.8
6.8
+ 1.9
250
oven dry
13. 9*
12.4
+ 0.8
11.2
+ 0.1.
9.4
+ 1.1
11.6f
5.5
+ 3.0
8.0
+ 0.5
5.3
+ 2.6
4.6
+ 3.1
2.8
+ 2.5
1.8
.+ 0.1
450
solids
14.2
+ 0.2
12.2
+ 1.9
11.8
+ 0.0
9.6
+ 1.7
7.3
+ 0.4
4.1
+ 0.5
3.2
+ 0.4
0.9
+ 0.2
0.9
+ 0.0
0.6
+ 0.1
0.4
+ 0.0
Mean quantity from extraction of duplicate subsamples
Lost one subsample
^Standard deviation
.:" 97' ^.-
-------
TABLE B-15. THE EFFECT OF REDOX POTENTIAL ON THE RECOVERY
OF ADDED PERMETHRIN DURING A 26-DAY INCUBATION OF
. . OLIVIER SOIL SUSPENSION AT PH 8 . 0
; Redox Potential, mv
Incubation '
Period,, days -150 50 250 450
0
2
5
12
15
19
23
26
Permethrin, yg/g oven dry solids
24. Of 17. 4f 22. 7f 17. 4f
11.6?
+ 0.3T
9.1
+ 0.6
5.4
+ 1.0
6.0
+ 0.7
6.9
+ 0.2
6.0
+ 0.3
6.1
+ 0.4
14.1
+ 1.1
8.2
+ 0.2
6.5
+ 2.8
7.4
- + 1.8
5.2
+ 0.1
6.1
+ 1.5
5.6
+ 1.0
10.7
+ 0.4
5.8
± 1-1
1.7
+ 0.3
1.5
+ 0.9
0.4
+ 0.1
0.3
+ 0.0
0.3
+ 0.0
12.6
+ 0.1
8.2
+ 0.2
3.8
+ 0.4
2.1
+ 0.1
0.4
+ 0.0
0.2
+ 0.0
0.3
+ 0.0
Lost one subsample
Mean quantity from extractionof duplicate subsamples
'Standard deviation
98
------- |