United States
Environmental Protection
Agency
Environmental Research
Laboratory
Corvallis OR 97333
Research and Development
EPA-600/S3-83-079 Mar. 1984
&EPA Project Summary
Ecosystem Responses to
Alternative Pesticides in the
Terrestrial Environment
Eric Goodman, Matt Zabik, Jeffrey J. Jenkins,
Robert M. Kon, and Renate M. Snider
A conceptual model was developed
to describe aspects of the fate and
effects of a pesticide in an orchard
ecosystem. In order to refine, parameter-
ize, and test a mathematical model
based upon this conceptual model, a
program of field and laboratory experi-
ments was undertaken. The environmen-
tal behavior of azinphosmethyl was
studied in a Michigan apple orchard
watershed to gather data for the model
on initial distribution within the orchard,
vertical movement of the pesticide
under the influence of rainfall, loss from
the orchard with runoff, and the effects
of the pesticide on several invertebrate
populations. The estimated proportion
of a low-volume application initially
distributed within the orchard averaged
.624 (standard deviation of .149) over
three seasons (1976-1978). Examination
of residues reaching each layer showed
the majority of the dislodgeable residues
were distributed to the trees and grass-
broadleaves. The litter-moss and soil
contained residue levels roughly ten
times lower than tree leaf residues.
Runoff studies indicated loss, via this
route, of less than 1 % azinphosmethyl
residues present in the orchard. The
generalized model developed, entitled
the Pesticide Orchard Ecosystem Model
(POEM), includes as a special case the
model for the azinphosmethyl applica-
tions under the conditions of this field
study. POEM also includes facilities for
altering parameters to describe effects
of other formulations, other pesticides,
other application procedures and/or
other field conditions.
This Project Summary was developed
by EPA's Environmental Research
Laboratory, Corvallis, OR, to announce
key findings of the research project that
is fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
The work presented in the full report is
one portion of an effort to characterize the
dynamics and effects of an example
compound in the terrestrial environment,
utilizing primarily field measurements
and the methodology of systems modeling
and simulation. Data collection, model
refinement, and revised experimental
design were done iteratively, yielding a
model that is parameterizable and data
that are relevant to the problem being
attacked.
The study of pesticide dynamics through
in situ field studies is difficult due to the
lack of natural or planned experiments
(inability to control much of the variance,
i.e., climatic conditions) and the relatively
high levels of error associated with field
data. Modeling techniques were employed
to aid in the understanding of the
necessarily large amount of field data
needed to construct a "meaningful"
picture of the pesticide's fate.
Description
The field experimental program used to
investigate the distribution, attenuation
arid movement of the organophosphate
insecticide azinphosmethyl, 0,0-dimethyl-
5-(4-oxo-1,2,3, benzotriazin-3(4H)-ylmethyl)
phosphorodithioate (Guthion ), in a
Michigan apple orchard is given in
Chapter I. The compound was followed
from its spray application through the
orchard vegetation/litter/soil environment
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and into aquatic systems. The form of the
model describing azinphosmethyl move-
ment and attenuation, as well as data
handling procedures and the derived
rates, is presented in Chapter II. Obser-
vations were made concurrently within
the same orchard to examine the effects
of azinphosmethyl on several ground-
dwelling invertebrates, including detailed
studies of the isopod Trachelipusrathkei.
Field and laboratory data collected on 7".
rathkei were used to develop a model
describing its ecobiology and temporally-
distributed pesticide-induced mortality.
The output of the fate model described in
Chapter II was used to determine the
time-course of azinphosmethyl exposure.
In Chapter III the field experimental
program used to determine azinphos-
methyl airborne residues is presented. A
multi-component kinetic model used in
the assessment of the contribution of air-
borne loss to theoverall attenuation of de-
posit residues is also described.
In Chapter IV, movement and attenuation
of azinphosmethyl are examined as a
function of environmental conditions. A
computer simulation is described which
allows the user to predict the fate and
effects of azinphosmethyl on several
types of organisms.
Chapter V describes the results of the
field sampling program for invertebrates
in the orchard plots, providing information
on the effects of azinphosmethyl spraying
(additional material on the isopod 7".
rathkei is found in Chapter IX). Chapter VI
contains the results of a laboratory
assessment of the toxicity of azinphos-
methyl and diazinon to various invertebrates.
Chapter VII briefly describes the models
developed for spiders, earthworms, and
springtails. Chapter VIII presents a
detailed description of the ecobiology of
the isopod Trachelipus rathkei, while
Chapter IX describes the effects of the
azinphosmethyl spray program on the 7".
rathkei field population. Chapter X pre-
sents the model for T. rathkei, including
both its general life cycle and its response
to pesticide exposure.
Appendix A documents the data analysis
procedures employed locally at Michigan
State University to parameterize the
model. Appendix B is the users' guide for
the Pesticide Orchard Ecosystem Model
(POEM) described in this report.
Recommendations
(1) Further work to refine, parameterize,
and test the components of the POEM
model, or similar models, for other
pesticides and other conditions should be
undertaken. In many cases, the current
forms are derived based on sparse data in
the literature. While predictions based on
these forms may be informative and
useful in some contexts, they are not
likely to be very accurate for predicting
actual fate and impacts of pesticides until
they have been carefully refined based on
currently non-existent data. Nevertheless,
the present model may be helpful,
because it allows the user to determine
the implications of various sets of
assumptions about pesticide dynamics
and effects.
(2) Work on models for the long-term
effects of pesticide exposure on populations
of invertebrates should be continued.
While this study includes a reasonable
model for effects of azinphosmethyl on
isopods and less refined models for
collembola, earthworms, and spiders, the
methodology should be extended and
refined through application to other
pesticides and organisms.
(3) The model presented here does not
provide an overall indicator of the
ecosystem-level impact of a pesticide in a
particular situation. While impacts on
individual populations are likely to be key
components of any sound measure of
overall impact, the importance and role of
each population in the ecosystem must
also be defined and incorporated in the
measure. Research aimed at identifying
key populations and modeling their
functions should be undertaken. The
search for integrating measures or
indicators of ecosystem stress or damage
for terrestrial systems should be broadened
and intensified.
Eric Goodman, Matt Zabik, Jeffrey J. Jenkins, Robert M. Kon, and Renate M.
Snider are with Michigan State University, East Lansing, Ml.
Jay D. Gile is the EPA Project Officer (see below).
The complete report consists of two parts, entitled "Ecosystem Responses to
Alternative Pesticides in the Terrestrial Environment:"
"A System Approach," (Order No. PB 84-162 726; Cost: $25.00)
"POEM Source Program, Sample Data, Sample Runs (Magnetic Tape,"
(Order No. PB 84-162 734; Cost: $790.00)
The above report and magnetic tape will be available only from: (cost subject to
change)
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
Corvallis, OR 97333
if U.S. GOVERNMENT PRINTING OFFICE; 1984 — 759-015/7626
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
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