United States
Environmental Protection
Agency
Environmental Research
Laboratory
Athens GA 30613
Research and Development
EPA-600/S3-82-093 Feb. 1983
SERA Project Summary
Community Structure, Nutrient
Dynamics, and the
Degradation of Diethyl
Phthalate in Aquatic
Laboratory Microcosms
T. L Hall, J. A. Hamala, P. F. Hendrix, H. P. Kollig, J. A. Krewer, L. C. Langner,
and W. R. Payne, Jr.
An investigation was conducted of
the environmental fate of diethyl phthal-
ate (DEP) in the continuous-flow
channel microcosms housed in the U.S.
Environmental Protection Agency's
(EPA) Environmental Research Labora-
tory, Athens, GA. The microcosms were
designed to enable testing of the Ex-
posure Analysis Modeling System
(EXAMS), a theoretical-type predictive
model for the determination of the fate
of toxic compounds in freshwater sys-
tems. The objectives of the investiga-
tions were to determine (1) whether a
definable stable state could be achieved
in which to test the model, (2) the
effects of different nutrient treatments
on ecosystem structure and function
and on the fate of DEP. and (3) the
degree of similarity between replicate
microcosms.
Aufwuchs assemblages in the micro-
cosms reached fairly stable levels of
biomass, metabolic activity, and similar
species composition within two or three
months after inoculation. Communities
receiving direct nutrient inputs appeared
to stabilize first, followed by down-
stream communities.
A highly significant relationship be-
tween phosphorus inputs and aufwuchs
chlorophyll a was established, sugges-
ting that the relatively stable input
concentrations of inorganic nutrients
into any given compartment were
among the primary factors controlling
maximum development of aufwuchs.
Replicate microcosms were statisti-
cally indistinguishable with respect to
nutrient concentrations for most of the
experimental period. Compartments
receiving direct inputs of inorganic
nutrients had the most consistent repli-
cability. Although non-taxonomic com-
munity structure was generally similar
in replicate compartments, some dif-
ferences were observed in relative
species abundance.
Sorption, volatilization; and photoly-
sis were insignificant processes in the
fate of DEP. Alkaline hydrolysis at pH
10 showed only a slight effect. Microbial
degradation was the dominant process.
First-order degradation rates were all
within an order of magnitude, even
though there were significant differ-
ences in both chemical environments
and biological communities.
This Project Summary was developed
by EPA's Environmental Research Lab-
oratory, Athens, GA. to announce key
findings of the research project that is
fully documented in a separate report of
the same title (see Project Report order-
ing information at back).
Introduction
The fate of toxic compounds in aquatic
ecosystems is influenced by a number of
biotic and abiotic factors. Experimental
analysis of such factors in laboratory
ecosystems provides one means of de-
riving information for use in predictive
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models of environmental fate of toxic
compounds. For this purpose, it is im-
portant that experimental systems meet
the assumptions of the model and the
requirements of the parameterization
procedure. This report presents the re-
sults of an experimental study of the fate
of the plasticizer, diethyl phthalate (DEP),
in a set of continuous-flow microcosms
subjected to a range of nutrient enrich-
ment levels. Primary emphasis is on the
degree to which the experimental systems
fulfilled the parameterization require-
ments of the Exposure Analysis Modeling
System (EXAMS). Those requirements
are that (1) physical, chemical, and biolog-
ical processes that influence the envi-
ronmental fate of a compound be at
steady state during the time interval under
study; (2) manipulation of chemical inputs
into the microcosms creates a set of
different environments in which to study
the fate of the compound; and (3) identi-
cally manipulated microcosms behave as
statistically indistinguishable replicates.
These requirements are addressed in
terms of several physical, chemical, and
biological variables that were measured
routinely throughout the experiment.
Materials and Methods
The experimental system consisted of a
19.5-m-long, 46-cm-wide, 51-cm-deep
"U-shaped" Plexiglas flume lined with
Teflon film. The flume was divided into
two independent channels, each subdi-
vided into eight 250-liter compartments
equipped with outlet weirs such that the
effluent from an upstream compartment
constituted the influent for the next one
downstream. Uniform mixing in each
compartment was accomplished by the
use of Teflon-covered Plexiglas paddle-
wheels suspended longitudinally in each
compartment and adjusted to a rotation
speed of 2.0 rpm. The system was based
in an environmental chamber that pro-
vided control of temperature (21 °C), water
flow (500 I/day), relative humidity (50%),
and light (2000 fc of fluorescent light on a
12-h light/dark cycle).
The first two compartments in each
channel were not treated with nutrients
or biotic inoculum to allowfor the study of
alkaline hydrolysis, uv photolysis, sorp-
tion and volatilization under abiotic condi-
tions. The remaining six downstream
compartments in each channel were
inoculated from local ponds and streams,
and nutrient chemicals were continuously
added to selected compartments to create
gradients of nutrient enrichment.
A concentrated solution DEP was added
through an all glass, constant-head sys-
tem at 2.0 ml/min to achieve a final
concentration of approximately 194 /ug/l
when diluted with the incoming water.
The DEP input was moved consecutively
from one replicate pair of compartments
to the next on a weekly basis to allow for
the study of DEP degradation under
conditions existing in each individual pair.
Water samples were collected for anal-
ysis weekly from each compartment. Dis-
solved nutrients (nitrate, nitrite, ammonia,
Kjeldahl nitrogen, total phosphorus, and
orthophosphorus) were analyzed on glass
fiber filtered aliquots in a Technicon
Autoanalyzer. Total and dissolved organic
carbon were analyzed in a Beckman TOC
analyzer. DEP was extracted in iso-octane
and analyzed by electron capture in a gas-
liquid chromatograph. Dissolved oxygen
and pH were measured with electronic
meters in situ; these values were used to
estimate community metabolic activity.
Biological analyses (algal and bacterial
enumeration, total ATP concentration,
chlorophyll a content, ash-free dry weight,
DEP concentration, and total organic
carbon) were performed on samples
collected weekly from artificial substrates
attached to the sides of the compart-
ments. Chlorophyll a, ATP, and bacterial
numbers were also measured in water
column samples.
Results and Conclusions
1. Aufwuchs communities appeared to
reach a definable steady state within
two to three months of inoculation,
based on available data for taxonomic
and non-taxonomic community struc-
ture (relative abundance of algal
species, similarity indices, chloro-
phyll a, ash-free dry weight, ATP, and
total organic carbon) and community
metabolic activity (relative changes
in dissolved oxygen and pH). Also,
based on metabolic activity estimates,
communities receiving direct nutrient
inputs appeared to stabilize first, fol-
lowed by downstream communities.
2. A significant linear regression
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T. L Hall, J. A. Hamala, P. F. Hendrix. J. A. Krewer. andL C. Langnerare with The
Bionetics Corporation; the EPA authors H. P. Kollig (also the EPA Project
Officer, see below) and W. R. Payne, Jr., are with the Environmental Research
Laboratory, Athens, GA 30613.
The complete report, entitled "Community Structure, Nutrient Dynamics, and the
Degradation of Diethyl Phthalate in Aquatic Laboratory Microcosms," (Order
No. PB83-136 341; Cost: $ 14.50, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Research Laboratory
U.S. Environmental Protection Agency
College Station Road
Athens, GA 30613
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
4BtNCY
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