Another major concept utilized in these models is that components

can be represented as compartments equivalent to a well-stirred
chemical reactor in a processing plant. Definition of what

constitutes a compartment or component is part and parcel of the
process of bringing the conceptual model into specific focus with a
particular agent in a given segment or region of the environment. The
extent of correspondence between (a) the definition of a "compartment"
of the model, and (b) the characteristics of an environmental component
determines how well a given variable-form module represents reality.
Redefinition of compartments serves to make the model more sophisticated
or less complicated, as knowledge is gained about the component and its
functions.

The conceptual model for the transport of pesticides in the environment
has been devised from three units: atmospheric/terrestrial, freshwater
aquatic, and estuarine/marine. The nature of the presentations differ
somewhat as expected for diverse points of reference, but the basic
components and chemico-physical and biological flows are compellingly
similar. This report will attempt to synthesize these components and
processes further into an overall concept, then consider representations
for the three major areas.

10



x
ME SOSPHERE a) Why
é| ¢
X® oh
STRATOSPHERE —) #” Pig
b

[}

TROPOSPHERE x x

oN fae!
x F3 Fs 4

1|
B % Gases K | Wal)

Precipitation washout i

=
Fcllout Erosion

Wash-outy L———__——

Co-distillation

------------45

<

Figure 4A: ATMOSPHERE

31



SECTION V
THE ATMOSPHERIC/TERRESTRIAL MODEL

The model consists of a set of assumptions derived from experiment,
experience, and physical law that are set forth graphically to
illustrate the principal components ("compartments") of the system,
the means by which the chemical itself or the components bearing the
chemical being modeled move or change in the environment, and the
relationships between compartments vis-a-vis this movement. Also
enumerated and elucidated are the factors affecting these routes,
such as the characteristics of the chemical and compartment.

ASSUMPTIONS

1. Elements or components of the terrestrial environment considered
are confined in a geographic and geophysical sense to a local
environment consisting of "ATMOSPHERE," "SOIL and WATER," "FLORA,"
and "FAUNA."

2. These elements and their constituent aspects can be set forth
as compartments, representing chemical reactors.

3. The model is directly applicable only to the agent; its breakdown
products or metabolites are representable as parallel models following
identical conceptual functions of disposition.

4. The interrelationships of compartments and the movement of
chemicals can be represented by a chemical process flow sheet.
DEFINITIONS

1. ATMOSPHERE. The gaseous phase containing suspended aerosols and
particulates above the earth and its biota.

a. Troposphere. The portion of the atmosphere in direct contact
with soil, water, and the biota.

27




portions surrounded by a waxy cuticle. Materials can be deposited

on this latter surface by fallout or precipitation, by condensation,
or by reversible sorption. Some agents can pass on through into
plant tissue or may be broken down chemically or photolytically on
the surface. A portion may be washed off the leaves and added to the
SOILS compartment. Material bound to the foliage will subsequently
enter litter as decay occurs. An agent on the foliage may be
volatilized off or sorb onto air particulates.

In the Subsurface zone, material may be brought into the plant by
uptake of water or by sorbtion onto the root surface and subsequent
penetration of the cuticle. Some may "leak" out or be released to

the SOIL from the cuticle. Both the Aerial and Subsurface portions
of FLORA are subject to herbivorous feeding, moving material into

the Soil Organisms and other FAUNA, and an agent in either compartment
is subject to chemical or biochemical alteration. Once an agent is in
FLORA, it may be translocated to other tissues, including fruiting
bodies associated with either portion. Similar to animals, a given
species of herbivore may select only a limited tissue on which to
feed; all portions of a plant are seldom ingested by a single

creature at one time. Distribution within the plant of a given agent
would therefore have a very marked effect on the subsequent nature
and extent of movement of a chemical from FLORA to other major
compartments. All of these movements would be less complex in
photosynthetic microorganisms.

"Bound" agents, including material strongly sorbed (seemingly
irreversibly) and material covalently reacted (but bearing the active
groups intact) are difficult to define and determine. Some of the
"bound" residues may be released by extraction, when sorption is
reversed, or by chemical or enzymatic treatment, where the conjugating
bonds are cleaved. In both FLORA and FAUNA (including Soil Organisms)
materials considered metabolized or altered so as to leave the scheme
may re-enter a compartment as a result of such action.

36


SECTION III
INTRODUCTION

Literally millions of chemicals and combinations of chemicals are now
manufactured and isolated, formulated, used, and ultimately disposed
of in the environment. Management of the resources of regulatory
agencies, supporting scientific institutions and manufacturers of the
chemicals demands effective and reliable shortcuts in evaluating the
potential hazard involved in such chemicals. The purpose of this
conceptual model is to elucidate the disposition of an agent in the
environment to permit judicious collection and evaluation of data
that indicate the critical points in that disposition. From the
conceptual model one could develop a more explicit model for the
behavior and disposition of a specific chemical in a particular
environment--a model that includes realistic parameters and by
computer simulation provides realistic estimates of the concentration
of that chemical in space and time.

A number of models have been proposed for the movement of specific
agents or classes of chemicals in various environments. Some attempt
to represent the global distribution of agents; others relate to
smaller portions of the whole environment or to generalized segments
(e.g., within man). Highly significant contributions to this effort
are the works of BISCHOFF AND BROWN (1966), WOODWELL et al., (1967,
1971), HARRISON et al., (1970), NISBET AND SAROFIM (1972), KENAGA
(1972), LINDSTROM et al., (1974), and ELZY et al., (1974).

In setting forth this particular set of models encompassing the
atmospheric/terrestrial, freshwater aquatic, and estuarine/marine



SECTION IX
KEY LITERATURE SOURCES FOR PESTICIDE EFFECTS RESEARCH

GENERAL TEXTS - CHEMISTRY, MODELING AND BIOLOGY

ASHTON, F. M. and A. S. CROFTS, (1973). "Mode of Action of
Herbicides." John Wiley and Co., New York. 504 pp.

AUDUS, L. J. (1964). "The Physiology and Biochemistry of
Herbicides." Academic Press, London. 555 pp.

DeRUSSO, R. M., R. ROY and C, CLOSE. (1965). "State Variables for
Engineers." John Wiley & Sons, Inc., New York.

FEST, C. and K. J. SCHMIDT. (1973). “The Chemistry of
Organophosphorus Insecticides; Reactivity, Synthesis, Mode of
Action, Toxicology." Springer Verlag, Berlin; New York. 339 pp.

JACQUEZ, J. A. (1972). "Compartmental Analysis in Biology and
Medicine." Elsevier, New York. 237 pp.

KARNOPP, D. and R. C. ROSENSERG. (1968). "Analysis and Simulation
of Multiport Systems." Massachusetts Institute of Technology,
Cambridge, Mass. 221 pp.

KEARNY, P. C. and D. D. KAUFMAN. (1969). “Degradation of
Herbicides." M. Dekker, New York. 394 pp.

LUKENS, R. J. (1971). "Chemistry of Fungicidal Action." Springer
Verlag, New York 130 pp.

MEYER, J. H. (1971). "Aquatic Herbicides and Algaecides." Noyes
Data Corp., Park Ridge, N. J. 176 pp.

O'BRIEN, R. (1967). “Insecticides; Action and Metabolism."
Academic Press, New York. 332 pp.

SONDHEIMER, E, and J. B. SIMEONE. (1970). "Chemical Ecology."
Academic Press, New York. 336 pp.

63



In all of the preceding skeletal representations each storage
component may be divided into discrete physical, chemical, and
biological storage components with their associated transfers,

rate coefficients, and coupled subsystems (e.g., food web biological
uptake and storage with its associated growth, respiration, and
trophic dynamics). A typical expansion of the surface layer storage
component from the vertical representation of a lake in Figure 6 is
shown in Figure 9.

Inputs and outputs may be expanded in a manner similar to the
storage based upon their physical and chemical characteristics
(dissolved, particulate, or absorbed). Expansion of the storage
compartments may be necessitated by expansion of the hydraulic
input-output to the epilimnion (Figure 10) into three separate
inputs and outputs.

The storage labeled "Food Web" in Figure 9 is at the heart of most
problems concerning pesticides in the environment (MOORE, 1967). A
skeletal abstraction of a food web structure is shown in Figure 11
(compare to Figure 3). One method of allowing for the influence of
food web dynamics upon the pesticide storages and fluxes in the model
is to assume that the biomass levels in the aggregates representing
the food web are at a steady state. Under this assumption the
influence of the food web may be included in rate coefficients that
affect the flux of pesticide between storage components representing
pesticide concentration in the food web compartments. This is
exemplified in the compartment diagram for the linear, donor-
controlled model of DDT in the freshwater marsh of Figure 12.

Another method of allowing for the effects of the food web on
pesticide behavior is to couple the explicit representation of the
food web to the related pesticide storages. Thus, there will be two
storage components coupled together in a manner similar to that of

46


Irologic ‘Atmospheric Hydrologic
ets rr
N

| ‘ \

t i}
‘ 1 \

Atmospheri Amospher' raulic
inputcoutput Input-Output 2 input Output init uteut
; ; z ; :
littoral Zone = J- --- - —-— —_ 2 -------- -| Pelagic Zone
~<- x _—

4 ,

--—-—-——|
wa ---- 4

1 Tiyaro t
logic
[__ Suspension }x] Px{___settting | \ Parameters_) [7 Settling x] [X[_Suspension J

1
i : -_
1 1 I an) 1 1
1 1 1 t 1 ‘
! >| Fyerautie I
! ' Input-Output |
1
1 | [<_—____—__ i
I Benthic Zone '

Figure 7: Horizontal Representation of a Lake.


Figure A-5 (see Appendix) for each storage of pesticide in a biotic
component. The mathematical representation of this type of interaction
is presented by HARRISON et al., (1971).

Surface Concentration

7 of DDT 7 Concentration in Sunfish a Concentration in Carp

| | |

oe Concentration in Concentration in
rT Concentration in Tadpole tT] Bloodworm t Narrow-leaf Pon

ntration in
t Synended Matter <—| Concentration in Water |<—{ DDT Granules (Input)

!

Figure 12; Food Chain Model of DDT in a Freshwater
Marsh (from EBERHARDT et al., 1971).

Remembering that there is no best or correct representation, a
plausible general model for a pesticide in the aquatic environment
based upon the vertical skeletal structure is presented in Figure 13,
an example of the result of the process of expanding the diagrams

to include the system storages or processes that may be considered
important. The system processes included in Figure 13 are intended
to constitute a minimal set of parameters to be considered when
investigating the movement and impact of a pesticide in the aquatic
environment.

50



c. the hypothesized system structure, which includes the
influence of other process rates acting through the causal
topology; and

d. the time series of inputs to the system.

Analytical techniques for estimating the effects of individual processes

on the system behavior are summarized in Section I. The results provide
an analytical basis for reduction of complex system diagrams.

54



The first skeletal diagram in Figure 6 is intended for a dimictic
lake in which process dynamics are affected by the presence of a
strong thermocline. The division between epilimnion and hypolimnion
may allow for long-term storage and release from the sediments of
the reduced forms of some chemical species (HUTCHISON, 1957; O'MELIA,
1972). The surface layer is isolated as a storage component in this
vertical model because of the possibility of enrichment in heavy
metals and pesticides (DUCE et al., 1972) and the neuston food web.
The sediments are treated as a Separate storage unit because of
possible long-term storage (AHR, 1973), sorption-desorption process
rates (HUANG, 1971) and the benthic food web.

A similar vertical skeletal structure without the hypolimnion may be
used for a holomictic lake or a freshwater marsh. However, a shallow
lake or a marsh may be better represented by a horizontal structure
(SCHINDLER, 1974) as presented in Figure 7. Here the storage is
divided among aquatic communities, which have varying response times
and process rates.

The independent variable implied in both of these lake models is time.
However, either one may be used as a two-dimensional stream or river
model by choosing longitudinal distance (i.e., downstream) as the
independent variable and including hydraulic and morphologic effects
on settling and mixing.

Finally, the lotic system may be represented by a horizontal array
of vertical column structures (similar to that of Figure 6) with
longitudinal distance as the independent variable. The transfers
between columns represent the transverse mixing in the system
(HOLLEY and ABRAHAM, 1973). This concept is presented in the
diagram of Figure 8.

42



4. Frequency response analysis (CHILD and SHUGART, 1972;
WEBSTER et al., In Press) provides frequency-related
measures of system behavior. Both the referenced
papers and current studies indicate that the sampling
ratio (&) and the undamped natural frequency (,) are
well described by a second-order control system _
approximation of the system (KUO, 1962; DERUSSO et al.,
1965). When the system is overdamped (most ecosystems
appear to be so), then the undamped natural frequency
becomes a measure of the maximum required sampling
rate for system variables.

5. Component analysis (HILL, 1973) allows numerical
determination of a limited number of coefficient
values from the A matrix of the linear, donor-
controlled representation and the system transfer
function as determined from experimental input-
output data.

Topological analysis can be used as an aid in evaluating the influence
of connectivity upon process rates in the system. Flow analysis can
provide a measure of steady-state distribution of flow through the
process pathways. A preliminary sensitivity analysis can determine
the effect of an error in parameter estimation upon storage levels
and hence upon flows. These three evaluations of process-system
interaction provide criteria for elimination of components that have
the least effect on system behavior, thus systematically reducing the
graphic representation. This results in information that may be used
as a first approximation in choosing measurement methods and sampling
rates for evaluation of system hypotheses.

MECHANISMS OF DISPOSITION

Much of the movement and fate of a given agent is dependent on the
rate and nature of certain mechanisms or processes which do not differ

14



play a progressively great role in the upper atmospheric compartments
and, conversely, chemical reaction (except for ozonolysis) would be
expected to be of Jess importance in those upper compartments.
Iteration of the basic Troposphere model through the upper atmospheric
compartments is easily accomplished.

Materials can enter or leave the atmospheric compartments by
reversible sorption, interacting especially with SOIL and FLORA
surfaces, or by volatilization/condensation from these surfaces.
Particulate matter would settle out onto surfaces or be washed out

by precipitation. Winds, mechanical action (such as abrasion),
various modes of direct introduction (application, emission sources),
and meteorologic aerosol formation in association with codistillation
would result in particulate aerosol introductions into the ATMOSPHERE.

FAUNA, and to a lesser extent FLORA, would be subject to ingestion of
portions of the tropospheric compartment by respiration, while sorption
would provide dermal exposure. Inhaled particles not trapped in lungs,
spiracles, etc., and particles or aerosols trapped on skin, hair, etc.,
and thereby subjected to grooming (e.g., fur licking), may be ingested
with mucous. Air is also present in soils, in equilibrium with the
soil surfaces re any component chemical; it likely plays little

role per se in exposure of Soil Organisms and is therefore ignored.
Depending on atmospheric mixing and soil movement, the exposure of
Soil Organisms may be qualitatively and quantitatively different than
the exposure of surface FAUNA via the air.

A schematic faunal subsystem (Figure 5) illustrates the probable
inputs and outputs of the several compartments in Figure 4B (compare
to Figure 3). Depending upon the food source, material from one or
more of the other major compartments may be ingested, exposing the
lumen tissue to the chemical in the food, air, or water. It may be
sorbed, broken down within the lumen, and/or passed out with the

32



SCHINDLER, J. (1974). Personal Communication.

TOMOVIC, R. and M. VAKOBRATOVIC. (1972). “General Sensitivity
Theory." Elsevier, New York.

ULANOWICZ, R. E. (1972). Mass and energy flow in closed ecosystems.
J. Theor. Biol. 34, 239.

WEBSTER, J. R., J. B. WAIDE and B. C, PATTEN. (In Press). Nutrient
cycling and ecosystem stability, In, "Mineral Cycling in
Southeast Ecosystems," F. Howell (ed). AEC Symposium Series.

WOODWELL, G. M., C. F. WURSTER, JR. and P. A. ISSACSON. (1967).
DDT residues in an East Coast estuary: A case of biological
concentration of persistent insecticide. Science 156, 821.

WOODWELL, G. M., P. P. CRAIG and H. A. JOHNSON. (1971). DOT in the
biosphere: Where does it go? Science 174, 1101.

62


CONTENTS

Page Page

ABSTRACT 2. wee ee ee ee ee ee ww ee ii
LIST OF FIGURES 2... 1... 224s, rr
ACKNOWLEDGEMENTS 2 2 6. ee ee ee ee ee ee vi
FOREWORD 2 2 oe ee ee ee vii
SECTIONS
I CONCLUSIONS © 2 ee ee ee et ee et ee 1
II RECOMMENDATIONS . 2. 2 1 eee ee ee ee ee eee 3
II] INTRODUCTION 22. ee cee ee ee ee ee ee ee 4
IV OVERALL CONCEPT OF THE MODEL .. 1.2... ee ee i
V THE ATMOSPHERIC/TERRESTRIAL MODEL. 2... 2.2 ee 27
VI THE FRESHWATER AQUATIC MODEL... 1.2.2. ee ee 40
VII THE ESTUARINE/MARINE MODEL . 2... 1. eee eee 55
VIII REFERENCES 2. eee ee eee ee ee see 59
IX KEY LITERATURE SOURCES FOR PESTICIDE

EFFECTS RESEARCH. 2 2 1 ee eee eee ee eee 63
APPENDIX. . 2. ee ee ee ene wee ewe ee 73

ili



U.S. Department of the Interior. Office of Water Resources
Research. Bibliography Series. Water Resources Scientific
Information Center, Washington, D. C. Examples: DDT in Water -
WRSIC 71-211; Dialdrin in Water - WRSIC 72-202; Aldrin and
Endrin in Water - WRSIC 72-203.

(1972). Water Quality Criteria. A Report of the Committee
on Water Quality Criteria. Environmental Studies Board.
National Academy of Sciences. National Academy of Engineering,
Washington, D.C.

(1971). Water Quality Criteria Data Book. Volume 3. Effects
of Chemicals on Aquatic Life. Water Pollution Control Research
Series 18050 GWV 05/71.

DYRSSEN, D. and D. JAGNER. (1972). "The Changing Chemistry of the
Oceans." Proceedings of the 20th Nobel Symposium, August 16-20,
1971, Goteborg, Sweden. Wiley-Interscience, New York. 365 pp.

EISLER, R. (1970a). Factors affecting pesticide-induced toxicity
in an estuarine fish. U.S. Bureau of Sport Fisheries and
Wildlife Technical Paper No. 45.

- (1970b). Acute toxicities of organochlorine and
organophosphorus insecticides to estuarine fishes. U.S. Bureau
of Sport Fisheries and Wildlife Technical Paper No. 46.

EPSTEIN, S. S. and M.S. LEGATOR. (1971). "The Mutagencity of
Pesticides." MIT Press, Cambridge, Mass.

GILLETT, J. W. (ed). (1970). "The Biological Impact of Pesticides
in the Environment." Environmental Health Sciences Series No. 1,
Oregon State University, Corvallis, Oregon.

HEATH, R. G., J. W. SPANN, E. F. HILL and J. F. KREITZER. (1972).
Comparative Dietary Toxicities of Pesticides to Birds. U.S.D.I.,
Fish and Wildlife Service, Bureau of Sport Fisheries and Wildlife.
Special Sci. Report-Wildlife No. 152. Washington, D.C.

KRAYBILL, H. G. (ed). (1969). Biological Effects of Pesticides
in Mammalian Systems. Ann. N. Y. Acad. Sci. 160.

PIMENTAL D. (1971). “Ecological Effects of Pesticides on Non-Target
Species." Executive Office of the President, Office of Science
and Technology. Washington, D.C.

ROSEN, A. A. and H. F. KRAYBILL (eds). (1966). "Organic Pesticides

in the Environment." Adv. in Chem, Series 60. American
Chemical Society, Washington, D.C.

65



REPORTS OF FEDERAL AGENCIES OF BROAD PROBLEMS

BALDWIN, I. L. (1962). Pest Control and Wildlife Relationships.
National Acad. Sci., National Res. Council.

JENSEN, J. H. (1965). Report of the Pesticide Residues Committee.
National Acad. Sci., National Res. Council.

(1969). Report of the Committee on Persistent
Pesticides. Div. of Biology and Agriculture, National Res.
Council to USDA.

MacLEOD, C. M. (1963). Use of Pesticides. President's Science
Advisory Comm.

MRAK, E. M. (1969). Report on the Secretary's Commission on
Pesticides and Their Relation to Environmental Health. To
U.S.D.H.E.W.

TECHNICAL DATA

ANON. (1972). Ecological Research Series. Office of Research and
Monitoring. U.S. Environmental Protection Agency, Washington,
D.C. Example: An Evaluation of DDT and Dieldrin in Lake
Michigan. EPA-R3-72-003, August.

(1969). Effects of Pesticides in Water. A Report of the
States. U.S. Environmental Protection Agency. Office of
Research and Development.

(1969). “Fish and Chemicals." A Symposium on Registration
and Clearance of Chemicals for Fish Culture and Fishery
Management. 99th Annual Meeting of the American Fisheries
Society, New Orleans, Louisiana. September 12, 1969.

- (1958-59). Handbook of Toxicology. National Acad. Sci.,
National Res. Council, Saunders, Philadelphia.

Vol. I. Acute Toxicities of Solids, Liquids, and Gases to
Laboratory Animals. W. S. Spector, ed.

Vol. III. Insecticides. W. 0. Negherbon, ed.

Vol. V. Fungicides. D. S. Dittmer, ed.

- (1972). Pesticide Study Series 2, 3, 5, 6, 7, 8, 9, and 10,
Environmental Protection Agency, Office of Water Programs.

64


Pesticide Biochemistry and Physiology. Academic Press.
New York (Monthly).

Pesticide Monitoring Journal. EPA, Washington, D.C. (Quarterly).

Residue Reviews. Springer Verlag (Irregular - several volumes
per year).

Science. Amer. Assoc. Adv. Sci. (Weekly).
Soil Science. Amer. Soc. Soil Science (Monthly).

Toxicology and Applied Pharmacology. Society of Toxicologists
(Monthly).

Transactions of the American Fisheries Society. Allen Press, Inc.
(Quarterly).

Water Pollution Control Federation Journal (Monthly).
Water Research (Monthly).

Weed Science. Amer. Weed Soc. (Bimonthly).
ABSTRACT SOURCES

Biological Abstracts (Semi-monthly).
Chemical Abstracts (Weekly).
Pesticide Abstracts (Monthly).
Sport Fishery Abstracts (Quarterly).
Water Pollution Abstracts (Monthly).

COMPUTER LITERATURE SEARCH DATA BASES

Medline (Biomedical) National Library of Medicine.
Toxline (Toxicology) National Library of Medicine.

WRSIC Water Resources Scientific Information Center

67



workers breathing or otherwise coming into contact with chemicals
present at relatively low concentrations for long periods of time

or at relatively high concentrations intermittently for short periods
of time. Direct or indirect application of chemicals to flora or
fauna can constitute a significant input for animals higher in the
food chain if residues of the chemical or its alteration products
are retained in the food.

Inadvertant and accidental release or even purposeful misuse or
abuse of various chemicals and chemical products can also be a
serious and significant direct source of agents to fauna. While some
such sources are moderated through the atmosphere, soil, water, or
flora, opportunities arise for direct inputs to fauna under some such
circumstances.

Soil_and Water

Many of the direct introductions of pesticides into the environment
are sources closely connected to the soil and water regions.
Application of pesticides and fertilizers by spraying a solution,
liquid suspension, or granular formulation are important inputs to
the soil surface, subsurface and the aquatic surfaces on both a local
and global scale. In addition to adventitious contamination by
accidental spills, other usages, and leakage from sources, a local
region becomes a source by dumping or discarding material or by
creation of sanitary landfills. Since the latter are generally of
greater scope, the subsequent infiltration by rainfall and movement
of surface or ground water can be major inputs throughout the soil,
as detailed by ELZY et al., (1974).

Once a chemical is introduced into the soil and/or water environments,

those compartments may continue to act as a reservoir for long periods
of time, leading to transfer of an agent to flora and fauna. Depending

25


SECTION IV
OVERALL CONCEPT OF THE MODEL

An explicit, overall conceptual model derived from the principles of
chemistry, physics, and biology and valid for all pesticides and
environments, would over-reach the bounds of current knowledge. For
practical translation into a quantitative model, the common threads
of these principles and of the constituents of the environmental
regions must be woven into a fabric or matrix of systems capable of
analysis. Practically, we are forced to examine experimentally
relatively.small regions which can be characterized and/or controlled,
or we must generalize these models by summation (see HARRISON et al.,
1970; WOODWELL et al., 1971). Iterative simulation of the models over
all environmental regions would require an unachievable data base, but
much can be learned about the whole even from the parts. These will
tell us where sampling and monitoring will be valid and helpful.
Attention could thus be focused on the processes and mechanisms
affording (and on these factors affecting) disposition.

PRELIMINARY SYSTEMS ANALYSIS FOR REDUCTION AND EXPERIMENTAL DESIGN

A diagrammatic representation of a system is usually of value to a
scientific investigation even if the potential applications of the
system representation are not realized. The trial-and-error expansion
and reduction of compartments forces the investigators explicitly to
acknowledge the boundaries and the level of definition of the system.

Deciding upon alternative representations of flow and control paths
promotes consideration of even the most remote possibilities. Finally,
many of the assumptions necessary to represent the system are explicit
in the diagram.

1



Sublimation from a Surface -

This might be regarded as a compartment with the barrier consisting of
the heat of vaporization of the component and is significant for the
outer portions of multi-layered chemical adsorbed or held on a

surface exposed to the atmosphere.

Ingestion (includes feeding, drinking, imbibing,
inhalation, pinocytosis, etc.) -

The mass of the compartment ingested moves into biota at rates highly
dependent on age, physiological and nutritional status, species,
season, temperature, availability of alternative foods or sources of
water, etc. Several physicochemical and biological processes may be
involved with the intimate uptake (absorption, facilitated or active
transport, etc.).

Kinetic Processes

Adsorption-Desorption Phenomena (phase-surface interactions) -

The principle parameters of this movement are the enthalpy of sorption
of the chemical and the activation energy of the surface. Hence the
structure and properties of the agent and the total surface chemistry
of the interface are critical. The nature and type of surface
(composition of soil, tissue of animal, type of particle) and the
surface area presented to the phase containing the "free" agent are
important. This process is regarded as being represented by a pair
of kinetic equations, the ratio of which rate constants is the measure
of the equilibrium attainable between the surface and the medium. The
residence time of the medium (rate of change in compartment contact),
if small in relation to the rates of these reactions, may limit
disposition. Where the rate of binding exceeds very greatly the rate

7



influence of the topological structure on system
behavior. Such information is useful in evaluating
alternative system structures and particularly in
determining the effects of reduction or aggregation
of components.

Flow analysis (HANNON, 1973) or input-output analysis
(LEONTIEF, 1966) is based upon the manipulation of the
A coefficent matrix in the linear, donor-control
approximation. Briefly, a matrix G is generated by

al (2)

Gs;

eB

1

in which each element (G; 5) is a relative measure of the
fraction of flow out of storage j that appears as input
to storage i under steady state conditions. This
information may be used to identify important processes
or flow paths in the system.

Sensitivity analysis (TOMOVIC and VUKOBRATOVIC, 1972;
PATTEN, 1973), may be used to evaluate the effect of a
perturbation, v(t), upon the storage levels in the system.
The measure of sensitivity, S, is useful in determining
which parameters have a prominent effect upon system
behavior. A linear approximation of S(t) is determined
from

dx,
t$) = (ae de) s(t) + (oat) wt) (3)

X; dA. Aig
where the terms in brackets are Jacobian matrices. With
a unit perturbation of each parameter, Ap the steady-
state values of S for each storage variable may be used
as a relative measure of system sensitivity to each
parameter.

13



on the time rate of change of the concentration of a chemical at a
site of localization, the compartment may act as a "sink" (where an
agent is effectively withheld from participation in the system) or

as a "reservoir" (where flows and transfer permit participation).

From the point of reference of a given species, a compartment may be
either a reservoir (and thus a "source" of an input) or a sink. A
breakdown product (such as DDE from DDT or methylmercury from mercury)
may arise in the soil and biota and subsequently appear broadly in the
environment, even though it was not manufactured or synthesized as
such. Thus, aS the ultimate repository of waste, unwanted materials,
and the products for which the chemicals were manufactured or prepared,
the SOIL and WATER have pervasive major inputs into other segments of
the environment.

26


A second major unifying thread of shared elements are the plants and
animals designated as "Biota" in Figure 1. The interfaces of the
physical environmental regions provide for considerable crossover of
an agent via the biota, yet explicit representation is difficult. The
phenomena of predation, migration, and vectorial transport (associated
with compartmental flows) are indicated in Figure 3. Similar to the
variable-form module of an environment, iteration of biological transfer
and storage modules provides extension and expansion of these routes
of disposition. Unlike interactions with the physical components of
the environment, however, the biocidal and physiologic activities of
pesticides can have pronounced direct and indirect effects on the
disposition of a given agent. Determination of such effects within
ecosystems would be vital to development of realistic simulation
models.

Chemicals are altered by both physical and biological systems in the
environment, so that site and rate of such change are highly significant
aspects of the disposition. Representing these changes in a single
model is difficult, especially when the agent (or its products) may
alter the rate of biotransformation. Where an agent is altered
chemically, we are assuming that the disposition of the product can

be considered to be into a model parallel to that of the parent
compound. The particulars of interaction may be describable for a
given relationship, so that defined systems can be set forth for a
specific chemical. In tracing the movements of an agent through this
conceptual model, the products of photolysis, chemical alteration, and
biotrans formation can be visualized as leaving the global array (Figure
2) and entering a similar point on a model for each product. There
might be many points interacting between the model of the parent agent
and models of products.



t

Mp

Concentration in
Biotic Component

J

Rate
Coefficient

(3
oO

i) !
'
; Coefficient
: ! ‘ ‘
1 4 ; !
Xx Uptake Rate fei +m Output Rate [Xx
ot oo
ot toe
typos
“3 trond “3
ol a
1] m4 4
ot 4
. tt ta
Growth Rate jt! | | ‘=| Death Rate
re ae |
i \ io | :
Rate \ rot ! Rat
Coefficient) | ot \ Coefficient
| oa ‘
Biomass
-7
Rat !
Coefficient -----m] Respiration |<
——_____—_—_—_—_—__—_——-
“3

Figure A-5:

Possible Coupling of Biomass (B) Subsystems

with Nutrient Concentration (Mb) Subsystems.

79



STICKEL, L. F. (1968). "“Organochlorine Pesticides in the
Environment." U.S.D.1., Fisheries and Wildlife Service, Bureau
of Sport Fisheries and Wildlife. Special Sci. Report-Wildlife
No. 119.

TUCKER, R. K. and D. C. CRABTREE, (1970). Handbook of Toxicity
of Pesticides to Wildlife. U.S.D.1., Fish and Wildlife
Service, Bureau of Sport Fisheries and Wildlife. Research
Publication No. 84, Washington, D.C.

WILKINSON, B. K., L. S. CORRILL and £. D. COPENHAVER. (1974).
"Environmental Transport of Chemicals Bibliography."

Oakridge National Laboratory (ORNL-E1S-74-68). 185 pp.

TECHNICAL JOURNALS AND PERIODICALS

Archives of Environmental Contamination and Toxicology. Springer
Verlag (Quarterly).

Bulletin of Environmental Contamination and Toxicology. Springer
Verlag (Monthly).

Comparative Biochemistry and Physiology. Pergammon (Monthly).
Environmental Science and Technology. American Chem. Soc. (Monthly).

Journal of Agricultural and Food Chemistry. American Chem. Soc.
(Bimonthly).

Journal of Fish Biology (Quarterly).

Journal of the Fisheries Board of Canada (Monthly).

Journal of the Water Pollution Control Federation (Quarterly).
Journal of Wildlife Management (Quarterly).

Limnology and Oceanography (Bimonthly).

Marine Pollution Bulletin (Monthly).

Nature (Weekly).

Pesticide Abstracts. EPA - Office of Pesticide Programs,
Washington D.C. (Monthly).

66


AS)





sanitary landfill, so that it would be a source having several inputs.
Other typical sources are shown in Table 2. For the purposes of models,
we then should consider the specific nature of sources providing inputs
into the environment.

Atmosphere

Considerable atmospheric input occurs upon application of the large
class of organic chemicals used as pesticides; i.e., insecticides,
fungicides, herbicides, and rodenticides. For example, DDT is

commonly applied by spraying a liquid suspension or solution by
aircraft or mobile ground equipment. WOODWELL et al., (1971) report
that in aerial applications of DDT to forests in the northeastern
United States 50 percent or less of the amount applied was deposited

in the forest. The rest was dispersed in the air either in the

gaseous form or as small droplets. While much of the airborne liquid
droplet fraction settles to the ground nearby, a significant amount
remains aloft, to become associated with other particles and distributed
in the environment at distances far from the point of initial application.

Table 2. SQURCES OF CHEMICALS FOR THE TERRESTRIAL ENVIRONMENT

Phase of

History of Chemical Examples

Preconsumption Manufacture, foud processing, mining,
refining

Distribution Application of chanical in pest control,
agriculture, or for public health purposes;
unintentional release resulting from the
use of products containing or made of
chemicals which are not totally confined
or immobilized; accidental spills in
transport or storage

Disposal Release of wastes in air or industrial and

domestic waste water; landfill operations;
incineration; dumping and discarding

23


ATMOSPHERE

morcame] [ orcame
PARTIC PARTIC:
uaTes Lares

cases

AEROSOLS:

|

MARINE ESTUARY-PELAGIC FRESH WATER

morcamtc| | orcanic
parnic | | partic:
uiares | | uvates

worcanic| | oRcanic worcanic] | orcame

[er] PARTIC. PARTIC: PARTIC. PaRTiC:
_ ucates | | ucares waves | | ucates

£

7 it isi

ESTUARY-LITTORAL, TERRA
woramc | | oncanic

morcanec | | orcante
partic | | rantic: partic || partic
wares | | uvares uures | | uates

8S

it u

ESTUARY-SEDIMENTS

morcante | | orcamc
partic. | | partic:
warer| | uates | | uates

Figure 15: Expanded, Iterated Basic Chemical Module for
Transport of Chemicals in Estuaries.

Open arrows indicate transport between modules via Run-off, River flow, Tidal
action, Turbulence, Fallout, and Atmospheric disturbances.

Biota-mediated Flux (overlay).
Solid arrows indicate unspecified migration, predation, life cycle-related
changes, and transport-dependent movement between food webs associated with
chemical modules representing environmental regions.



FORRESTER, J. W. (1971). “World Dynamics." Wright-Allen Press,
Cambridge, Mass. 142 pp.

HANNON, B. (1973). The structure of ecosystems. J. Theor. Biol.
41, 535.

HARRISON, H. L., O. L. LOUCKS, J. W. MITCHELL, D. F. PARKHURST,
C. R. TRACY, D. G. WATTS and V. J. YANNACONE, JR. (1970).
Systems studies of DDT transport. Science 170, 503.

HILL, J., IV (1973). Component Description and Analysis of
Environmental Systems. Masters Thesis. Utah State Univ.,
Logan, Utah. p. 94.

HOLLEY, E. R. and G. ABRAHAM. (1973). Field tests on transverse
mixing in rivers. J. Hydraulics Div. ASCE. HY12, 2313.

HUANG, J. (1971). Organic pesticides in the aquatic environment.
Water and Sewage Works. May, 139.

HUTCHISON, G. E. (1948). Circular causal systems in ecology.
Ann. N.Y. Acad. Sci. 50, 221.

HUTCHISON, G. E. (1957). "A Treatise on Limnology." John Wiley
and Sons, Inc., New York. p. 1015.

KENAGA, E. E. (1972). Guidelines for environmental study of
pesticides: determination of bioconcentration potential.
Res. Rev. 44, 73.

KARNOPP, D. and R. C. ROSENBERG. (1968). "Analysis and Simulation
of Multiport Systems." Massachusetts Institute of Technology.
Cambridge, Mass. p. 221.

Ku0, B. C. (1962). “Automatic Control Systems." Prentice-Hall.
Englewood Cliffs. N.J. p. 504.

LEONTIEF, W. W. (1966). “Input-Output Economics." Oxford
University Press, New York.

LINDSTROM, F. T., J. W. GILLETT and S. C. RODECAP. (1974).
Distribution of HEOD (dieldrin) in mammals: I. Preliminary
model. Arch. Environ. Contam. Toxicol. 2, 9.

MEADOWS, D. H., D. L. MEADOWS, J. RANDERS and W. H. BEHRENS, III.

(1972). "The Limits to Growth" Universe Books, New York.
p. 205,

60


METCALF, R. L., G. K. SANGHA and I. P. KAPOOR. (1971). Model
ecosystem for the evaluation of pesticide biodegradability
and ecological magnification. Environ. Sci. Technol. 5, 709.

MOORE, N. W. (1967). A synopsis of the pesticide problem, In
"Advances in Ecological Research," Volume 4, J. B. Cragg,
(ed). Academic Press, p. 75-128.

NISBET, I. C. T. and A. F. SAROFIM. (1972). Rates and routes
of transport of PCBs in the environment. Environ. Health
Perspect. 1, 21.

ODUM, E. P. (1971). “Fundamentals of Ecology." Saunders,
Philadelphia. p. 574.

ODUM, H. T. (1972). An energy circuit language for ecological
and social systems: Its physical basis, In "Systems Analysis
and Simulation in Ecology," Vol. II, B. C. Patten, (ed).
Academic Press. New York. p. 591.

O'MELIA, C. R. (1972). An approach to the modeling of lakes.
Hydrologie 34, 1.

PATTEN, B. C. (1971). A primer for ecological modeling and
simulation with analog and digital computers, In "Systems
Analysis and Simulation in Ecology," Vol. I. B. C. Patten
(ed). Academic Press, New York.

PATTEN, B. C. (1973). Need for an ecosystem perspective in
eutrophication modeling, In "Modeling the Eutrophication
Process," E. J. Middlebrooks, D. H. Falkenborg, and T. E.
Maloney (eds). Utah Water Research Laboratory, Logan Utah.
p. 227.

PATTEN, B. C., W. G. CALE, J. FINN AND R, BOSSERMAN, (In Press).
Propagation of cause in ecosystems, In "Systems Analysis and
Simulation in Ecology," Vol. IV, B. C. Patten (ed.).
Academic Press, New York.

QUINLAN, A. (1974). Personal Communication.

RANDERS, J. and D. L. MEADOWS. (1971). "System Simulation to
Test Environmental Policy: A Sample Study of DDT Movement
in the Environment." System Dynamics Group, Alfred P. Sloan
School of Management, Massachusetts Institute of Technology.
Cambridge, Mass. 52 pp.

6]



oz

Table I, FACTORS AFFECTING PISPOSITION OF CHEMICALS IN THE ENVIRONMENT

Mechanism, Pathway,
‘or Process

Properties of Agent

Properties of Environmental
Component

Environmental Control

Convective mass
transport; Inter-
particle diffusion

Co-distillation;
volatilization/
Condensation

Intra-particle
diffusion

Ingestion

Adsorption/desorption

General-association with
compartmental component

Size, diffusion coeffi-
cient in media; vapor
pressure, latent heat of
vaporization; interaction
with media; intra-
molecular interactions

Size, diffusion coefficient
in particle, chemical
gradient

General-association with
compartmental component

Structure, enthalpy of
sorption (mono-layered);
enthalpy of fusion
(mu ti~layered)

Vectorial flux; degree
of saturation of immobile
matrix by movement

Water evaporation rate,
surface area, interaction
with agent, dearee of soil
moisture, extent of satura-
tion of air

Structure (micro), dearee
of water saturation,
alterations of structure
by temperature, pH, ionic
strenath

Nutritional value to
feeder, attractiveness
(chemical or physical),
availability of alternative
foods, dearee of competi-
tion with other feeders,
nutrietional and physiologic
status of feeder

Macro- and microstructure,
surface area, activation
energy of surface

Physical (water or air
flow, soil movement) ;
temperature and gross
energy distribution

Temperature, energy flux

Temperature, pH, humid-
ity or soil moisture

General-biological
structure of ecosystem,
physical conditions
affecting rate or choice
of foods (temperature,
season, light)

Temperature, humidity or
soi] moisture, pH



Department of Entomology, School of Life Sciences, University of
I1linois, Urbana-Champaign, Illinois 61801.

Oregon State University, Corvallis, Oregon 97331.

Department of Entomology, Fisheries, and Wildlife, University of
Minnesota, St. Paul, Minnesota 55101.

Cornel] Pesticide Residue Laboratory, Cornell University, Ithaca,
New York 14850.

Trace Level Research Institute, Purdue University, Lafayette,
Indiana 47907.

Department of Environmental Health, University of Cincinnati College
of Medicine, Cincinnati, Ohio 45219.

Biological Sciences Library, University of New Hampshire, Kendall
Hall, Durham, New Hampshire 03824.

College of Agriculture and Environmental Science, Rutgers--the State
University, New Brunswick, New Jersey 08903.

Institute of Biological Sciences, School of Agriculture and Life
Sciences, North Carolina State University, Box 5306, Raleigh,
North Carolina 27607.

Rhode Island Agricultural Experiment Station, University of Rhode
Island, 113 Woodward Hall, Kingston, Rhode Island 02881.

University of California, Berkeley, Department of Entomology and
Parasitology, Berkeley, California 94720.

University of California, Davis, Department of Environmental
Toxicology, Davis, California 95616.

University of California, Riverside, Department of Entomology,
Riverside, California 92502.

Louisiana Cooperative Wildlife Research Unit. Louisiana State
University, Baton Rouge, Louisiana 70803.

Massachusetts Cooperative Wildlife Research Unit. University of
Massachusetts, Amherst, Massachusetts 01003.

South Carolina Community Pesticide Study. Medical University of

South Carolina, 80 Barre Street, Charleston, South Carolina
29401.

71



Now

A-1
An2

A-3
A-4

FIGURES (Cont'd)

Relationship Among Graphical Representations

Streeter-Phelps Oxygen-Deficient Model
for a Stream

Vollenweider Lake Eutrophication Model

Nutrient Model for Lake with Biotic
and Abiotic Storage

Possible Coupling of Biomass (B) Subsystems
with Nutrient Concentration (Mb) Subsystems

78

79



Pw hr

on nn

10
1
12
13

14
15

FIGURES

Variable-Form Module: Chemical

Global Array of Environmental Regions

Food Web Module

Diagram of the Atmospheric/Terrestrial Model
4A ATMOSPHERE

4B FAUNA

4C FLORA

4D SOIL and WATER

Diagram of Faunal Subsystem Model

Vertical Representation of a Stratified Lake
Horizontal Representation of a Lake

Horizontal Array of Vertical Columns for
Representation of Lotic Systems

Some of the Storages, Processes, and Subsystems
Associated with the Surface Layer Storage Compartment

An Expansion of the Hydrologic Input
A Skeletal Abstraction of a Food Web
Food Chain Model of DDT in a Freshwater Marsh

A ttinimal Representation for a Pesticide
in a Dimictic Lake

Simple Model of Transport in Estuaries

Expanded, Iterated Basic Chemical Module for
Transport of Chemicals in Estuaries

Biota-mediated Flux (overlay)

45

47
48
49
50

52-53
56

57
57


TRANSPORT
FLUX

PRIMARY
CONSUMERS

MIGRATION PREDATION

SECONDARY
CONSUMERS

NZ

CHEMICAL DECOMPOSERS

MODULE

LE

LIFE
CYCLE
CHANGES

Figure 3: Food web module.
Solid arrows indicate intra-web flux by predation and
feeding; open arrows indicate other transport and transfer
within the food web or between food webs of different regions
or zones.


FOREWORD

This report is a product of the Environmental Protection Agency's
Substitute Chemicals Research Program, which seeks chemical
alternatives to certain pesticides. The report provides an overall
view of these chemicals regarding their pathways through and possible
effects on the environment. Since the substitute chemicals to be
investigated may exhibit properties similar to conventional pesticides,
such as bio-concentration and bio-degradation, this program was
initiated to study the environmental routes and rates of transport,
metabolic fate, and sinks for a variety of these substances.

Many chemicals, including the substitute chemicals, move throughout
all of the environment, and their total impact cannot be evaluated

by a research program dealing with only one part of the environment.
Experiments designed to provide data for regulatory function must
include as many parts of the environment as possible. For this
reason, the whole ecosystem approach has been adopted in this program.

We have thus presented an overall] conceptual scheme from which
scientists, administrators, management executives, and other
interested persons with a concern for pesticide-related problems
can obtain an overview.

vii



PeCANICAL nePOKi WALA .
(Please read lustructions on the reverse before completing)

TR PORT NO, 2 Is, RECIPIENT'S AGGESSION NO. ;

QTITLE AND SUBTITLE Is. REPORT DATE |
A Conceptual Model for the Movement of Pesticides November 1, 1974 :
through the Environment: A Contribution of the EPA 6. PERFORMING ORGANIZATION CODE
Alternative Chemicals Program

7 AUTHORIS) la. PERFORMING ORGANIZATION REPORT NO.

James W, Gillett, James Hill IV, Alfred W. Jarvinen
and W. Peter Schoor

9, PERFORMING ORG \NIZATION NAME AND ADDRESS 70, PROGRAM ELEMENT NO.
National Ecological Research Laboratory 1EA487
Environmental Protection Agency 11. CONTRACT/GRANT NO.

Corvallis, Oregon 97330

12. SPONSORING AGENCY NAME AND ADDRESS: 13, TYPE OF REPORT AND PERIOD COVERED

Final
Same 14, SPONSORING AGENCY CODE

76, SUPPLEMENTARY NOTES

16. ABSTRACT This report presents a conceptual model of the movement and disposition of
pesticides in the environment. A multi-media model is built up from simple modules
representing basic processes and components of air, soil, and water. More specific
models are exposited for the atmospheric/terrestrial, freshwater aquatic, and
estuaring/marine environments. Through iterative operations of expansion and
systematic reduction of the components and processes these models of segments of the
environment can be joined to provide a holistic view of the disposition of a chemical
and its attendant effects. Ultimately systems analysis and mathematical simulation
techniques can be employed to evaluate the fate of a specific chemical in a par-
ticular environment. The conceptual model is thus a first step in organizing facts,
assumptions, and hypotheses into a graphic and logical arm capable of exploitation
in further experimentation of pesticide disposition and effects. While rejecting
formulation of a model with global validity, the authors emphasize the commonalities
of the basic processes and components in the various environments. Thus, a multi~
media approach to disposition studies is made explicit even in the absence of a
single all-media global model.

17. KEY WORDS AND DOCUMENT ANALYSIS

a DESCRIPTORS >. 1DENTIFIERS/OPEN ENDED TERMS |c. COSATI Field/Group
Air Pollution Systems Analysis Alternative Chemicals 1201
Conceptual Model Water Pollution Program 0611

Ecology Laboratory Microcosms 0606
Environmental Biology Simulated Ecosystems

Hazardous Materials
Mathematical Model

Pesticides
18. DISTRIBUTION STATEMENT 19. SECURITY CLASS (This Report) 21, NO. OF PAGES
UNCLASSIFIED
20. SECURITY CLASS (This page] 22, PRICE
UNCLASSIFIED

EPA Form 2220-1 (9-73)
¥ U.S. GOVERNMENT PRINTING OFFICE: 1974—697-650/65 REGION 10


APPENDIX
GRAPHIC REPRESENTATION OF PESTICIDES IN AQUATIC SYSTEMS

In approaching any problem, an investigator must first form a
mental image or conceptual model of the system. This conceptual
model usually is not well defined and varies considerably from one
investigator to another. With the complex problems associated with
environmental systems, solving and/or communicating the conceptual
model requires translation into the nonempirical language of
mathematics or symbolic logic.

Since direct translation of the conceptual model into mathematical
representation is awkward and difficult, the initial description is
best formulated into a graphic symbolism. The nature of the graphic
description is dependent upon the investigator's conceptualization of
the processes, the degree of resolution required, and data that are
available or that can be measured from experiments with the system.
The graphical representation is the heart of systematic experimental
design because the applicability of the ensuing analysis is limited
by the ability of the investigator to represent his conceptual model
of the system processes in graphic form. There is no best or correct
graphical representation of a system. They differ only in the degree
of realism and utility.

Graphical representations can be improved by iteration. After
application of analytical techniques, any unusual or unexpected
storage levels or flow rates may require modification of the
components or connectivity of the original graphical representation.
The nature of the iterative interactions among the graphical
representation, the mathematical model, and data acquisition is
presented in Figure A-1.

73



system may vary considerably depending upon application and resources
available for evaluating the hypothesis. While there appears to be
no upper limit to the resolution of a model, the lower limit (a single
storage component) is demonstrated for a stream and a lake in the
following examples (Figures A-2 and A-3) from O'MELIA (1972). The
low level of resolution in these examples does not necessarily imply
that there is a better representation for a particular application.
© © |
an 1
KL xX

Input Rate | [output Rate

c .
H ,
o

,
D Oxygen Deficit
a

_ TKiL—KeD where D = oxygen deficit, L = BOD remaining,
K, = deoxygenation coefficient, and
Kz = reaeration coefficient.

Figure A-2: Streeter-Phelps Oxygen Deficit Model for a Stream..

z

=
zo
©

3
--ol2L-

5

=

o|

we

ees 3 ae
2
=

O-

0)

Me
Nutrient Concentration

= + ~(0 +q)M, where M., = concentration of nutrient,
J = flux of M to lake,
9 = sedimentation coefficient,

= flow coetticient, and Z = mean lake depth,

Me =
a Zz

Figure A-3: Vollenweider Lake Eutrophication Model.

76


in character or principle between the various compartments. Explicit
in this dependency are (a) the physical, chemical, and biological
principles of behavior of the chemical and environmental component and
(b) the organization of the constituents as described in the diagram.

It is convenient to divide these processes into two major groups:
transport processes, where the agent is moved vectorially in
association with an environmental component or by mass flow and
diffusion; and kinetic processes, where the movement can be described
by kinetic rate constants related more specifically and pointedly to
the agent. When considering distributions of a chemical with respect
to time, these diverse processes may play significant roles in
determining whether a given disposition is flow-limited (by transport
processes), compartmentalized (by kinetic processes), or some
combination of both. The reference time frame, not specified for

the conceptual model, is a highly significant parameter vital in
translating the conceptual model to realistic simulations. Similarly,
the spacial reference point (volume, location) has purposely been left
vague to permit the general case to be stated with the understanding
that specification of spacial and geographic localization will be
carried out in translation and elaboration of the modules (Figures 1
and 3) into models.

Examples of transport processes can be seen in dispositions primarily
dependent on stream flow, surface-to-ground water flow (leaching),
blood circulation, xylem transport, and precipitation from air.
Kinetic process-dependent dispositions may involve high or practically
irreversible sorption or binding, differential rates of sorption or
desorption between compartments of a major subsystem, or differential
chemical alteration. The following are offered as the principle
processes limiting or affording disposition of an agent in the
environment. More than one process may be occurring simultaneous ly
along the same route, so that the factors controlling the process
determine the proportion going by a particular pathway, which in turn
may alter that of another route.

15


EPA-660/3-74-024
DECEMBER 1974

Ecological Research Series



One manner of increasing the resolution of a model is to divide a
single storage component into sub-units, which may have differing
rates of input or output for the stored variable. For example, the
nutrient concentration in the lake (Mw) from Figure A-3 may be divided
between abiotic storage (Ma) and biotic storage (Mb) with the result
shown in Figure A-4. If the output rate (from sedimentation and flow)
of the nutrient stored in the biotic component differs from that of
the nutrient stored in the abiotic component, then the mean residence
time is changed and the dynamic behavior of the nutrient output may
be changed considerably from the single storage representation.

Another means of increasing the resolution of the representation is
to include a time-varying parameter instead of the mean value of an
exogenous variable that controls a rate of flow for an endogenous
variable. Thus, instead of a mean lake depth (Z), a time varying
Jake depth [Z(t)] could be incorporated in the model.

Finally, the rate controlling flow and storage may be explicitly
included in the representation and the two resulting subsystems can
be realistically coupled (HARRISON et al., 1970). This is
demonstrated in Figure A-5 for the biotic component of the lake
model in Figure A-4. These expansions of the diagrams may continue
until the point of diminishing returns is reached with respect to
either application or resources.

77



fed

Lod

Wind, abrasion, mechanical)

Volatilization

Erosion

=> To

—

Ie --------»

<a TF ir
| SOIL SURFACE
- -f]-- --4-9) [surrace
WATER TNORGANTC [ oncanie
e-— CULATES| }é - - PARTI-
Xa ("free") CULATES
o : Pe. xe x—e
ih Wash- off NS
% >} x Surface Surface
| US eer
OS “8 Decay

Tillage, geophysical, biological

y SUBSURFACE

x

|

GROUND Surface Surface
Kk imbibing WATER INORGANIC ‘ORGANIC
PARTI- PARTI
("free") [&- 7) | curates fe-— CULATES K Decay
Leakage xTMo x

Qu. ne ee

SOIL

I" -- > ORGANISMS

DM

AQUATIC

To

|_—_» Aquatic

Figure 4D. SOIL and WATER



systems and by quantifying interactions of components, mathematical
simulation can direct critical experiments to verify hypotheses of
disposition and effect. The conceptual model is the first step ina
rigorous scientific treatment of the fate and effects of agents and
their alternatives in pest control.


SECTION I
CONCLUSIONS

Pesticides are applied to the ecosystem of the pest and not to the

pest alone. An ecosystem by definition is a causally closed system

in which each process is influenced by overall system structure. The
concept of the ecosystem represented simply in thought or language is

of little operational use until translated into more functional diagrams.
Each of the many forms of system diagrams has strengths and weaknesses
depending upon their application. An iterative process of expansion

and systematic reduction of components to achieve an optimal balance
between resolution and effort can be employed to join various segments
of the environment.

Placing the pesticide problem in the control diagram format forces the
investigator explicitly to define and delimit a complex hypothesis.
Further, systems analysis and simulation techniques may be applied to
mathematical approximation of the hypothesis stated in the control
diagram. When applied to a preliminary system diagram, these analyses
allow systematic reduction to a less complex form. As a preliminary to
an experimental study, these techniques can provide answers to many
questions concerning the variables to be measured, the accuracy required
of the measurement, and the frequency of sampling. Thus, these methods
of modeling and techniques of analysis enable investigators to develop
models for the behavior of a specific pesticide in a specific ecosystem
yielding an approach to optimum information re resource expenditure.

Ultimately, mathematical modeling and analysis could precede
introduction of chemical which might be potentially hazardous in the
environment. By identifying those properties of the agent and the



In a typical mathematical representation, which may be derived from
the system diagram, each of the storage blocks accounts for one of a
set of simultaneous differential equations. Also, each of the valve
symbols accounts for a rate term in the set of equations. In addition,
the coefficients or parameters in circles (many of which are omitted
from Figure 13 for the sake of visual simplicity, e.g., pH, temperature,
and Eh) appear as rate modifying coefficients in the equations. Each
of these coefficients must be estimated from the literature or
determined by a set of measurements on the system. Thus even the
minimal set of variables of Figure 13 results in a complicated set of
mathematical equations and requires a large data base for evaluation.

This complex representation can be reduced by aggregation of the
least important variables for a particular pesticide and ecosystem.
The inclination to eliminate the least important variables is usually
intuitively focused either on very rapid processes, "which cannot be
rate limiting," or conversely on very slow processes, "which cannot
transport or transform much matter or energy," depending upon the
investigator's objectives. The possible dangers in using these bases
for eliminating variables lies in the synergistic behavior of causally
closed environmental systems .*

The effect of an individual process on system behavior is dependent
upon four levels of system interactions. These are
a. the rate coefficients and parameters for the process itself;
b. the hypothesized topology for the system interactions as
presented in the system diagram;

*An ecosystem is a completely connected system (COMMONER, 1971) that
is closed in the control sense (HUTCHISON, 1948; PATTEN, 1973). A
closed control system or feedback system may exhibit “emergent
properties" (CANNON, 1967) or “synergistic effects" (ODUM, 1971)
that are dependent upon system structure or total system properties
(BERTALANFFY, 1968). These properties can affect the influence of
a specific process upon system behavior.

51



fecal matter, which then passes on to the SOIL or as food for other
FAUNA. The portion absorbed may be distributed throughout the

organisms to other tissues, which may alter the agent's structure

to more easily excreted products, store the agent (for later release
or for ingestion by a predator species), or provide for the agent's

excretion.

=: Respiration:

Ingestion

Ingestion

(see FAUNAL subsyion) )

f

HIGHER
CARNIVORES, |

(see FAUNAL subsysteny )

7

PRIMARY

CARNIVORES <
(see FAUNAL ae,

if

Death
J
Drinking

Excretion

Bathing

HERBIVoRS
Tngestion TT eee FAUNAL, i ae,

r

ft Decay

AP Le

7.

Figure 4B: FAUNA

34

From
AQUATIC


Graphical Representation
Alternative Hypotheses
Qualitative
Mathematical Model Data Aquisition
’ Analysis <: Experiment
Quantitative Constraints

Figure A-1: Relationship Among Graphical Representations,
The Mathematical Model and Data Acquisition
(from QUINLAN, 1974).

Circuit diagrams (CLOSE, 1963) compartment diagrams (ODUM, 1971),
block diagrams (KUO, 1962) signal flow graphs (KUO, 1962), bond
graphs (KARNOPP and ROSENBERG, 1968), energy circuit language (ODUM,
1962), and Forrester diagrams (FORRESTER, 1971; MEADOWS et al., 1972)
are all examples of graphical representations of systems. Each has
advantages and disadvantages depending upon the nature of the system
to be described.

Bond graphs are excellent symbolic representations for

environmental systems in which energy flow is of primary concern

and in which complementary variables (a potential and a related flux)
may be defined. Compartment diagrams are useful representations of

74


and environmental components. Table 1 summarizes these to indicate
those factors which should be known or determined in making judgments
as to the probable disposition of the chemical. Obviously, all
properties play some role in that disposition in the complex, real
world. As modeling proceeds from the conceptual level to mathematical
simulation, these values become the critical inputs, especially as the
disposition is related over time.

SOURCES OF CHEMICALS RELEASED INTO THE ENVIRONMENT

Each of the major compartments of the model can receive direct input
of certain chemicals as a result of the action of man. These inputs
are derived from "sources," which can be defined as the places and
activities leading to the release of a particular agent. A source
may result in a variety of inputs into major compartments and
subcompartments, and more than one source may have very similar input
into a model of pesticide behavior. For example, if methoxychlor were
sprayed on a forest in a diesel oi] medium, this application ("source"
would have inputs into the atmosphere (both gases and aerosols), on to
the cuticular or dermal surfaces of biota, and on to the surfaces of
soil and water. A source may be deliberate, accidental, or
adventitous, but the inputs have been handled uniformly in the models.

The sources can be grouped generally according to the major compartments
to which inputs are directed and according to the time frame in the
history of a particular agent that it may enter a model from a source.
The latter might be divided into preconsumption (synthesis and
manufacture), distribution (transport, storage, consumption, application,
or use), and disposal (dumping, release). A chemical plant might serve
as a source of atmospheric release of a pesticide during manufacture,

a site of accidental spills during storage and transportation, and

then have to dispose of waste materials containing the agent in

22


settling and fallout, and precipitation (including material washed

off of plant surfaces). Excretion, exfoliation, and decay of animal
tissues and defoliation, withering, litterfall, and subsequent decay
of plant materials add to the routes of entry. Material can leave

the Soil Surface by erosion (wind, water, or mechanical), by
volatilization, by photochemical and chemical alteration, and by
ingestion by Soil Organisms and other FAUNA. Some material is lost
from the Surface by tillage, mechanical mixing (geophysical or
biological), and "leaching." The movement of Surface water into the
Ground water takes with it solubilized and reversibly sorbed materials.
Within the Surface compartment, much as in the case of the Troposphere,
materials can be bound to the surfaces of particulates. Surface
waters can become contaminated by a Ground water-source containing an
agent, which would then be distributed in the Soil Surface.

In the Subsurface zone, material can enter from the Soil Surface, be
brought into the zone by Soil Organisms or FLORA (through translocation,
leakage, and root decay), and can leave by routes noted earlier--
sorption into FLORA and Soil Organisms (and to a lesser extent, other
FAUNA), ingestion by Soil Organisms and FAUNA, and through the Ground
water into FLORA and out into other waters (streams, lakes, estuaries-~
labeled AQUATIC). In actual cases, it would be necessary to
characterize each soil horizon by iteration of interconnected
Subsurface models.

39


}
i

Tz

Table 1 (cont)

Mechanism, Pathway,
or Process

Properties of Agent

Properties of Environmental
Component

Environmental Control

Chemical reaction
phenomena

Biological alteration
(activation, degrada-
tion, conjugation)

Structure (reactive
groups); eneray of
activation, free energy of
reaction, nature of
mechanism

Structure (reactive
groups), eneray of
activation, free energy
of reaction, nature of
reaction mechanism,
binding constant to
enzymes acting on it

Structure (catalytic
sites), energy of
activation, reactive
sites, dearee of coupling
to other systems providing
reactants or removing
products

Genetic capacity for
eliciting appropriate
enzyme, nature of enzyme,
species status (physio-
logical, nutritional,
psychological), sens
tivity to agent (inhibi-
tion, synergism, toxi-
city), degree of coupling
to other systems providing
reactants or removing pro-
ducts, presence or absence
of cofactors

Temperature, humidity or
soil moisture, pH nature
and quantity of light

Temperature, pH, humidity
or soil moisture, biologi-
cal structure of eco-
system, previous chemical
history





ACKNOWLEDGEMENTS

The authors gratefully and most humbly acknowledge the contributions

of their colleagues Ray R. Lassiter and Edward J. Rykiel, Jr. (SERL);
Patrick W. Borthwick, Marlin E. Tagatz, and Gerald J. Walsh (GBERL);
and Eugene Elzy, F. T. Lindstrom, Marvin L. Montgomery, and Rizanul
Haque (Environmental Health Sciences Center, Oregon State University,
Corvallis, Oregon). Helpful and constructive comment was received

from N. R. Glass and A. S. Lefohn (NERL), J. Eaton (NWQL), T. W. Duke
(GBERL), and D. W. Duttweiler, W. M. Sanders, and G. L. Baughman (SERL).
Timely preparation would not have been possible without the dedicated
assistance of Program Support Center (NERC-Corvallis).

vi


The system diagram is a complex, qualitative hypothesis which must be
tested by experiment. The hypothesis cannot be realistically tested
in the graphical form of the conceptual models given so far (Figures

1 and 2). A more exact representation of the relationship between
storages and flow rates is needed. The many possible mathematical
forms for these relationships may be classified as linear or nonlinear
and as recipient-controlled, donor-controlled, or mixed.

The linear, donor-controlled form (PATTEN, 1971) is probably the most
elementary (CHILD and SHUGART, 1972). It can be represented mathe-
matically as

dX _
a AX + BZ (1)
in which X is a storage level vector, dX/dt is a flow rate vector, Z

is an input vector, and A and B are coefficient matrices.

Donor-control implies that flow rate depends only upon the storage
level from which the flow originates. Although this assumption may be
unrealistic, the use of a linear, donor-control approximation of the
system representation appears to be justified for these preliminary
analyses. Often, linear approximations are less sensitive to parameter
estimation errors than nonlinear representations. Also several
expedient techniques of analysis may be applied to the linear,
donor-control approximations. The following analysis techniques can
yield alternative statements of the system diagram hypothesis that

can be interpreted in terms of reduction and experimental design.

1. Topological analysis is currently being developed by
a group of Dr. B. C. Patten's graduate students at the
University of Georgia (PATTEN et al., In Press). This
technique is intended to allow determination of the

12


environmental systems when mass or energy storage and their rates

of exchange are of interest but complementary variables are not
explicitly defined (ULANOWITZ, 1972). Signal flow graphs and
associated control system analysis techniques are valuable when
feedback control properties of the system are of primary concern.
Forrester diagrams may be used in the general case to represent
interactions, transformations, and transports of mass or energy
without recourse to specific component equations or other constraints
upon the system variables.

A Forrester diagram can be used to present a conceptual model of the
transport and transformation of pesticides in the aquatic environment.
From this presentation a reduced or working model in compartment form
may be derived for a specific pesticide and specific ecosystem. The
compartment diagram should include the mathematical form of the
interactions and can provide a basis for preliminary system analysis
as an aid to experimental design.

Forrester Diagrams

In Forrester diagrams of dynamic systems, six symbols are commonly
used.

A solid line represents a directed pathway for transfer
of matter or energy.

A dashed line represents a directed pathway for control
or information transfer.

The cloud symbol represents a source or sink (input or
output) outside the defined system boundaries.

A rectangle indicates storage of matter or energy.

The valve symbol indicates rates along the associated
pathway.

Finally, the circle represents coefficients and
parameters that affect flow rates.

The degree of resolution or complexity of the Forrester diagram of a

75



' Cam am — |
' '
rt
1 : 1 L
Primary Producers = [ ~AL First Consumers

----74 ~ «

! ‘

=

R Death and
Excretion

& 5) Death and
a Excretion

ima ~~ - - -|

mee

SS | CS ay
| /_ | oe
B lr
sate) E . sae]
' | : Injestion || 1
H A £ ' ‘ \
~~ g bey
Particulate Organic Matter SZ Second Consumers

sae) i] YX foeath and Excretion] ron
oP i a)

\ Ingestion ry =
Comme py | Ey
| =| Decomposers

Figure 11: A Skeletal Abstraction of a Food Web.
49


College of Forest Resources. University of Washington, Seattle,
Washington 98105.

SOME PRIVATE CORPORATIONS HAVE PERFORMED
PESTICIDE RESEARCH AS RELATED TO AQUATIC LIFE

Bionomics, Inc., P.0. Box 135, Main Street, Wareham, Massachusetts
02571.

Industrial Bio-Test Laboratories, Inc., 1810 Frontage Road,
Northbrook, Illinois 60062.

Envirogenics Company, Division of Aerojet-General Corporation,
El Monte, California 91734.

Union Carbide Corporation, Tarrytown Technical Center, Tarrytown,
New York 10591.

Lakeside Laboratories, 1707 East North Ave., Milwaukee, Wisconsin
53201.

Syracuse University Research Corporation, Merrill Lane, University
Heights, Syracuse, New York 13210.

72


Soo 00

ys4y 1
a

Concentration in

fy Abiotic Component

| __Uptake Rate nM \ ese
way , |

1
! ' Rate
' \\ Coefficient
Rate ! Mo \
Coefficient | & - Concentration in —-4 @)
‘ Biotic Component 7
t

| Output Rate
Mean Level of DN
Biotic Component A
63
ae,

Figure A-4: Nutrient Model for Lake with
Biotic and Abiotic Storage.

reece

78


Technical Publications Office POSTAGE AND FEES PAID
ENVIRONMENTAL PROTECTION AGENCY ENVIRONMENTAL PROTECTION AGENCY > a

National Environmental Research Center EPA-335
200 S.W. 35th Street Special Fourth-Class Rate
Book

Corvallis, Oregon 97330

Official Business

TED ST y;
~» "es

R. Feder, (PS)
ORD-ED-TH |
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P.O. Box 1159
Cincinnati, Ohio 45201

If your address is incorrect, please change on the above label;
tear off; and return to the above address.

If you do not desire to continue receiving this technical report
series, CHECK HERE (C] ; tear off label, and return it to the
above address.



9S

SOURCE PHYSICAL FORM RESERVOIR Loss
—S = ee —
VAPOR
BIOLOGICAL
DEGRADATION
AIR NEW
PARTICULATE 4
pissouveo INTERSTITIAL,
WATER MQ
RESIDENT MIGRATING
SUSPENDED BIOTA ANIMALS
PARTICULATE
WATER) (SEDIMENT)
FRESH ‘SED!
TIDAL
DISSOLVED FLUSHING
INFLOWING SUSPENDED bh
WATER PARTICULATES Parmioutates P|
‘SUSPENDED 7] DEEP
PARTICULATE SEDIMENTS
SALINE
DISSOLVED CHEMICAL,
DEGRADATION
PARTICULATE
DIRECT
INPUT TERRESTRIAL
BIRDS AND
DISSOLVED MAMMALS

Figure 14:

Simple Model of Transport in Estuaries.



a. Surface. The top portion of the soil, capable of interacting
with the air directly.

(1) Surface water. The result of precipitation, ground
water springs, etc., but distinct from streams, ponds,
lakes, etc. (parts of the AQUATIC model); includes "free"
water associated with soils and all solutes.

(2) Organic particulates. Colloidal materials in suspension
including organic matter and decaying material derived from
biota.

(3) Inorganic particulates. Inorganic soil structural
materials (clay, silicates, minerals, etc.) and those
insoluble materials of non-biological origin.

b. Subsurface. Similar to (4-a) but containing the ground
water.and associated soil water. Actually there exists a
series of parallel plates or zones through the soil profile
which will differ in composition, environmental condition, etc.
The subsurface region indicated in this model is considered to
be all that below the immediate surface in contact with the
atmosphere.

PATHWAYS

The foregoing compartments are displayed in Figure 4. A compound
introduced into the ATMOSPHERE (Figure 4A) may be in the vapor phase,
as an aerosol, or in the form of a large particle. Chemicals in the
vapor phase would be expected to adsorb reversibly to the surface of
aerosols and other particulates, where the potential for alteration by
chemical or photolytic means (due to catalytic sites thereon) is much
greater than in the vapor phase. The particles might condense or break
down, and chemicals would be redistributed. A chemical on the surface
of a particle or aerosol could absorb reversibly into the particle,
where photolysis would be very much less likely. All of these
interactions would be taking place in the Mesosphere and Stratosphere
as well as the Troposphere, which are mixed by diffusive and
meterological conditions and events. Photolysis would be expected to

29



SIE Science Information Exchange. Smithsonian Institution,
Washington, D.C.

NTI Search U.S. Department of Commerce.

ISI Institute for Scientific Information.

FEDERAL AND STATE RESEARCH LABORATORIES WHERE
BOTH DATA AND INTERPRETATION OF DATA IS AVAILABLE

National Water Quality Laboratory. Pesticide Research Team.
Mr. John G. Eaton, Coordinator. Duluth, Minnesota 55804.

Fish Control Laboratory, U.S. Bureau of Sport Fisheries and Wildlife,
P.0. Box 862, LaCrosse, Wisconsin 54601.

Fish-Pesticide Research Laboratory, Bureau of Sport Fisheries and
Wildlife, Route 1, Columbia, Missouri 65201.

Radiation and Metabolism Laboratory, U.S. Department of Agriculture,
Fargo, North Dakota 58102.

Gulf Breeze Environmental Research Laboratory, Sabine Island, Gulf
Breeze, Florida 32561.

Newtown Fish Toxicology Station, U.S. Environmental Protection Agency,
3411 Church Street, Cincinnati, Ohio 45244.

Southeast Environmental Research Laboratory, U.S. Environmental
Protection Agency, College Station Road, Athens, Georgia 30601.

Perrine Primate Laboratory, Wenatchee Research Section, U.S.
Environmental Protection Agency, P.0. Box 73, Wenatchee,
Washington 98801.

U.S. Environmental Protection Agency Laboratory, Region 10, 15345 N.E.
36th Street, Redmond, Washington 98052.

Office of Pesticide Programs, Criteria and Evaluation Division, U.S.
Environmental Protection Agency, Washington, D.C. 20250.

Gulf Coast Water Supply Laboratory, U.S. Environmental Protection
Agency, P.O. Box 158, Dauphin Island, Alabama 36528.

Idaho Fish and Game Department, P.0. Box 25, Boise, Idaho 83707.

68


0g

Respiration

aN

wesosenene »; % | ove eanas wero KI
AU :

HIGHER
CARNIVORES i

[ee FAUNAL subeysten)

if

PRIMARY
CARNIVORES:

a)
ic

ial
ma wy)

svrarosenene S11 Py
é

Thageaton

RHA

&
|ivee FAUNAL Ei
eon 1
— seaae ES Erevn
x * Ir
: Th at satrkee i aouarie
b ee bi-- --4 {> SURFACE I
ten, cs Hany || See Fe] sou
awh LL nonat 1) P| RSE | OSE fe -- 4 oncamons
“ad oe arse | € Vy sat
LEGEND: Counc !
‘Mass comportmentel tanster, ——"y x) Tome noo ey SS |
Chante! mevenant = ————> ams |
evarubo septon Tee eeeees
Pratt -
toni! or
siongee! tataon LY _—

fN Cm 2
Figure 4: Diagram of the Atmospheric/Terrestrial Model.

Flow and transfer functions are indicated by the legend. Focus on segments or
major compartments of the model is provided by expanded views in Figures 4A-D.



St

—s |
J.

Atmospheric
Unput-Output__ fy
\

\

‘Atmospheric
Parameters

fraulic
w inpet Output

I

Littoral Column

Littoral Column Pelagic Column

Figure 8: Horizontal Array of Vertical Columns for Representation of Lotic Systems.



of desorption, the material may appear to be irreversibly bound.
Where these rates are both substantially slower than the rate of
media movement, the surface interaction will characterize the
disposition, Moisture level, pH, and temperature, as they affect
the chemical and the surface, will play major roles in this
phenomenon.

Chemical Transformation -

The non-biological alteration of a chemical introduced into any part
of the environment is dependent on the moisture, pH, and temperature
of that environment, on the nature of reactive groups on the agent,
and on the presence of catalytic sites (on particles, etc.). The
nature and intensity of illumination additionally determines
photochemical reactions. At very high temperatures (pyrolysis) both
physical and chemical structure may be broken down to yield material
in the vapor state. In biota, soils, and water, and to a much less
extent in air, cation and anion exchange capacity coupled with
eletrolyte levels determines ionic interactions which may alter the
structure or availability of a chemical, such as by the formation of
insoluble complexes. In some instances the chemical reaction phenomena
are closely associated with adsorption-desorption processes, related
nonlinearly to the extent of coverage by, say, soil or air moisture
of the catalytic binding site where the reaction might be hydrolysis.
To the extent that the media are suitable for reaction or provide a
necessary reactant (e.g., ozone) these processes can appear to be
compartmentalized in rate of disposition.

Biological Alteration (includes activation,
degradation and conjugation) -

These processes are assumed to be catalyzed by enzymes, although
similar or identical chemical or photochemical reactions may be taking


8b

Hydrologic
Parameters

i

Hydrologic Input of
Dissolved Pesticide

K

and

Microbial Degradation

prccccccccene —

Solubitization/
Precipitation}

| Hydrotogic Input of
| Pesticide Particles

i)
Hydrologic '
Parameters |
1
i)
i
i
\
|
i
I
1
i]
j
l

——___———_—_——

!

Pesticide Particles

!

Dissolved in Water

t Direct Chemical Oxidation

Sorption / Desorption

‘Metabolic
Degradation

pe

~
\
\
s Biomass
sams)
7 Oe
7

‘
\
i]
\
1
\
|
1
i
\
i}
\
\
i)
\

Hydrologic
Parameters
7
I
| CS
i
1
Hydrologic Input of |
Adsorbed Pesticide

'

Adsorbed on
Suspended Particles

Food Web Storages

Figure 10:

An Expansion of the Hydrologic Input.



The following definitions apply to Figure 15 only:

Run-off: Any transport from land adjacent to an estuary,
including drainage not covered by river flow, such as non-
specific drainage from swamps.

Tidal action: Any transport mediated by tidal flushing and
tidal currents.

Biota-mediated flux: Any transport of organisms from one
domain (sea coast, ocean, and fresh water) to another, such
as in the case where a predator leaves its domain to feed in
another domain, possibly itself becoming prey, or contamination
through excretions (feces, urine, and regurgitated pellets).
Emigration and immigration are also included.

River flow: Any transport mediated by a river or rivulet.
This includes adsorbed as well as non-adsorbed materials.
Atmospheric disturbances: 1) Any transport caused by
unusually high tides due to strong winds. 2) Any transport
caused by agitation of the sediment or shore/bank by
abnormally strong wave action or currents due to strong winds.
Turbulence: Any transport due to abnormal mixing caused by
eddies (underwater storms).

Tides and Currents: Any transport due to normal tides and
currents.

Fall-out: Any transport via the atmosphere.

57


ABSTRACT

This report presents a conceptual model of the movement and disposition
of pesticides in the environment. A multi-media model is built up from
simple modules representing basic processes and components of air, soil,
and water. More specific models are exposited for the atmospheric/
terrestrial, freshwater aquatic, and estuarine/marine environments.
Through iterative operations of expansion and systematic reduction of
the components and processes these models of segments of the environment
can be joined to provide a holistic view of the disposition of a
chemical and its attendant effects. Ultimately systems analysis and
mathematical simulation techniques can be employed to evaluate the

fate of a specific chemical in a particular environment. The conceptual
model is thus a first step in organizing facts, assumptions, and
hypotheses into a graphic and logical array capable of exploitation in
further experimentation of pesticide disposition and effects.

While rejecting formulation of a model with global validity, the authors
emphasize the commonalities of the basic processes and components in
the various environments. Thus, a multi-media approach to disposition
studies is made explicit even in the absence of a single, all-media
global model.

This report was submitted in fulfillment of Project Element 1EA487,
ROAP 21BCL, Task No. 10 by the National Ecological Research Laboratory
under the sponsorship of the Environmental Protection Agency. Work
was completed as of September 1974.


Co-distillation

“Nf ee ee —

Cutilcle
FOLIAGE FRUITING
X,M Trans < BODY
--|> ocation > cou
<+- al XM
+
—+> le — .
ROOTS SRO oDY
> XM K_
wd JS

Cuticle

Figure 4C: FLORA

The most complex and probably most significant compartment in the
disposition of an agent entering the terrestrial environment is that
of SOILS and WATER (Figure 4D). Material can enter this compartment
directly at the Surface by sorption from the ATMOSPHERE, condensation,

37


In the higher vertebrates this process is complicated by functions
such as the enterohepatic cycle (gut + liver + bile + intestinal
lumen). In higher animals material may be lost through the skin,
hair, or feathers. As noted earlier, these tissues also receive
exposure from the ATMOSPHERE (and some instances SOIL). Some agents
may be altered externally and some may not penetrate the dermal
barrier. Unabsorbed material could volatilize or be adsorbed by
atmospheric particles. Except for exhalation of unadsorbed material,
pulmonary losses of chemicals taken into animals by other routes
appear negligible.

Agents are also distributed to reproductive tissues, which can
constitute a major outlet of chemical for the exposed animal. In
female mammals this release can continue on through parturition into
lactation. The route to offspring may be of great significance, since
the young of many species serve as food for higher trophic levels.

Another major loss route, in addition to excretion, is the death and
decay of tissues and organisms, leading to the entry of the material
into the SOIL and WATER compartments (Figure 4D). Initially on the
Soil Surface subcompartment, these materials become part of the
organic particulates and later free water of that compartment, but
are transferred by mechanical, geophysical, and biological action

into the Subsurface compartment. Soil Organisms then ingest these
particles, and one could prepose an elementary version of the scheme
in Figure 5 for disposition of the chemical in those organisms.
Additionally some Soil Organisms may be purged of some chemicals by
reversible sorption of materials in the gut lumen onto the out-going
soil particles.

The other major biological compartment is that of FLORA (Figure 4C),
represented as a generalized model with both Subsurface and Aerial

35


SECTION VIII
REFERENCES

AHR, W. M. (1973). Long lived pollutants in sediments from the
Laguna Atacosa National Wildlife Refuge, Texas. Geol. Soc.
Amer. Bull. 84, 2511.

BERTALANFFY, L. VON. (1963). “General Systems Theory." George
Braziller, Inc., New York. p. 289.

BISCHOFF, K. B. and R. G. BROWN. (1966). Drug distribution in
mammals. Chem. Eng. Prog. Symp. Ser. A 66, 32.

CANNON, R. H. (1967). "Dynamics of Physical Streams." McGraw-Hill,
New York. p. 1093.

CHILD, G. I. and H. H. SHUGART, JR. (1972). Frequency response
analysis of magnesium cycling in a tropical forest ecosystem,
In "Systems Analysis and Simulation in Ecology," Vol. II,

B. C. Patten (ed). Academic Press, New York. p. 592.

CLOSE, C. M. (1963). "Notes on the Analysis of Linear Circuits."
Rensselaer Polytechnic Institute, Troy, N. Y. p. 123.

COMMONER, B. (1971). "The Closing Circle." Alfred A. Knopf, Inc.,
New York. p. 326.

DeRUSSO, R. M., R. ROY and C. CLOSE. (1965). "State Variables for
Engineers." John Wiley and Sons, Inc., flew York.

DUCE, R. A., J. G. QUINN, C. E. OLNEY, S. R. PIOTROWICZ, B. J. RAY
and T. L. WADE. (1972). Enrichment of heavy metals and organic
compounds in the surface microlayer of Narragansett Bay, Rhode
Island. Science 176, 161.

EBERHARDT, L. L., R. L. MEEKS and T. J. PETERLE. (1971). Food chain
model for DDT kinetics in a freshwater marsh. Nature 230, 60.

ELZY, E., F. T. LINDSTROM, L. BOERSMA, R. SWEET and P. WICKS. (1974).
Analysis of the movement of hazardous chemicals in and froma
landfill site via a simple vertical-horizontal routing model.
Oregon State Agricultural Experiment Station Special Report No.
414, Oregon State University, Corvallis, OR 97331. 110 pp.

59



environments, this report has established limits of validity and
relevance focused locally rather than globally. The utility of the
conceptual model rests in its conversion and evolution into an explicit
mathematical statement capable of evaluation as a hypothesis. Current
and near-future capabilities for extrinsic control of environments will
limit such testing to laboratory microcosms, such as those of METCALF
et al., (1971), and to small external sites, both characterizable as
limited within the concepts of the model. Extension of the model
conceptually in space and time can be made to the extent that the
elements of the models can be grouped, subsected or interconnected.

Figure 1: Variable-form Module: chemical.
A chemical may exist "free" or "bound" in one of the states
shown, all of which can interact within a region (inside box)
or interact with adjacent modules of other environments
(indicated by arrows).

ORGANIC (WORGANIC
PARTICULATE) | PARTICULATE

WATER



lb

T

|

i}
roa
i}

1

Water Column

: ()

“oncentration \tmosph
In wees Concentration

i i
H Tiydrolagic

Coefficient _/ |
1 i By
1
1

Equitibrium
Levels and
Rate Coetficie

C

/

{
t
i)
1
amma [

t t 1 j
4 Dx recitation top] <a \ t
[atmospheric settting PX] Cl wastor TX] ' ‘ [Hydrautte output Px] Hydraulic Loading } Dx{as Exchange]
Uh | ice
\ | :
---+ Concentration in Surtace L
Inorganic Particulates i oncente awaer. ace Layer
F 7 H H '
[_Aeanton TX t
' ' \ ' [Sorbtion and Injestion} x] j
1
an n
4 1 | Dx{Beomoniton “J 1) DL Bitesrataion ]
Concentration on I 1
H Particulates 1 ‘ \
\ i 1
| ! Photochemical u u !
j-j-- —---~---- | oc
Available Solar Energy | Degradation | Surtace Food Web
i
y Organic Particulates
yo
t
ii ES
E® De iiminisiontaioen J ~~ ~ - =~ = ST ------ !
Ca)
Figure 9: Some of the Storages, Processes, and Subsystems

Associated with the Surface Layer Storage Compartment,



eg

‘

EER] 7
PEE] Gs
{ N

Figure 13:

A Minimal Representation for a Pesticide in a Dimictic Lake.



because the rates of change are so slow or so fast as to lie outside
apparent rate-limiting processes, or because events do not appear to
affect disposition or effects of pesticides directly.

ATMOSPHERE

UPPER
on FLOWS » »

T T
t J
LOWER MARINE — > maritiMe <9 CONTINENTAL
<
<m az] 4 a> Sm
S< al | oa ee
rp cm p= PP
Be ro] }as 2%
at) es] leo Fo
a c= cz _D
cp 43] jor ND
x Bl 12m Ba
%o 3| |R2 Zo
22 sLlTMs o2
22 2 $
2
T
OCEAN ESTUARY STREAM LAKE
KK FLow FLOW
PELAGIC LITTORAL PELAGIC PELAGIC PELAGIC
aed TOAL ~~ =
FLUX See
“Sy?
m z
@ 3 LITTORAL | m
a 2 g
g FA 3
| & cat
8 | 45 °
zie
= -
2
4
a
BENTHOS \ J
<SE GROUND
SHOR AND SURFACE TERRA
ETIO1 WATERS
sepments a2

Figure 2: Global array of environmental regions.
Modules can be arrayed as representing environmental regions
interacting by flow (open arrows) or other transport and
transfer phenomena (solid arrows) so as to represent global
disposition.



EPA-660/3-74-024
DECEMBER 1974

A CONCEPTUAL MODEL FOR THE MOVEMENT
OF PESTICIDES THROUGH THE ENVIRONMENT:

A contribution of the EPA
Alternative Chemicals Program

By

James W. Gillett
James Hill IV
Alfred W. Jarvinen
W. Peter Schoor

National Ecological Research Laboratory
Gulf Breeze Environmental Research Laboratory
National Water Quality Laboratory
Southeast Environmental Research Laboratory
National Environmental Research Center
Corvallis, Oregon 97330

Project Element 1£A487
ROAP 21BCL, Task 03

NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330

For sale by the Superintendent of Documents, US. Government Printing Of
Washington, D.C. 20402 - Stock No. 5501-00973 somes



(1) Suspended particulates. Solid matter, including
certain microscopic biota, suspended in the atmosphere.
Each particle has a surface subcompartment.

(2) Aerosols. Microscopic matter (solid or liquid)
dispersed in the atmosphere, each with a surface
subcompartment.

(3) Gases. The gases and vapor-phase components of
the atmosphere.

b. Stratosphere. A compartment above the troposphere and
beluw the mesosphere having components as in (1-a), but not
interacting directly with the earth and its biota.

c. .Mesosphere. A compartment below the mesopause and
ionosphere and above the stratosphere having compartments
as in (l-a and b), but not interacting directly with the

earth except through the troposphere and stratosphere.

2. FAUNA. Biota excluding plants and microorganisms (except
protozoans) and including not only the terrestrial surface species
but also those living predominantly in the atmosphere and in the soil.

a. Man. Human beings representable by a subsystem of several
compartments based on anatomical and physiological characteristics.

b. Higher carnivores. Those creatures feeding on primary
carnivores (and perhaps in some instances on forms lower in
the food web).

c. Primary carnivores. Those species feeding predominantly
on herbivores and (to a lesser extent) primary producers.

d. Herbivores. Those species feeding on primary producers,
usually plants and related microorganisms.

e. Soil-organisms. Those primary producers dwelling
predominantly in soil and the scavengers of the plant and
animal matter constituting the organic matter of soils.

3. FLORA. The biota including largely the photosynthetic primary
producers « consumed by man, herbivores, and soil organisms. Generally

the plant is represented as having a subsurface portion (consisting of
subcompartments for the root tissues and potential storage or fruiting

bodies) and a surface portion (consisting of foliage and fruiting body),
all surrounded by a cuticular compartment.

4. SOILS AND WATER. In addition to soil organisms (2-e), this
compartment is is separated into two regions containing the same components.



Fish Control Laboratory, U.S. Bureau of Sport Fisheries and Wildlife,
Route 1, Box 9, Warm Springs, Georgia 31830.

Southeastern Fish Cultural Research Laboratory, U.S. Bureau of Sport
Fisheries and Wildlife, Marion, Alabama 36756.

U.S. Environmental Protection Agency, Pesticide Monitoring Laboratory,
Bay St. Louis, Mississippi 29520.

Great Lakes Fishery Laboratory, Bureau of Commercial Fisheries, Fish
and Wildlife Service, U.S. Department of the Interior, Ann Arbor,
Michigan 48107.

Wisconsin Department of Natural Resources, P.0. Box 450, Madison,
Wisconsin 53701.

Agricultural Research Service Laboratories (U.S. Department of
Agriculture) Regional.
(Studies on nuisance aquatic insecticides, herbicides, etc.)

Department of Defense, Naval Ship Research and Development, Center,
Annapolis, Maryland 21402.
(Anti-Fouling Agents)

National Agricultural Library, U.S. Department of Agriculture,
Beltsville, Maryland 20705.

Alaska Department of Environmental Conservation, Pouch 0, Juneau,
Alaska 99801.

Conservation Library Center, Denver Public Library, 1357 Broadway,
Denver, Colorado 80283.

Division of Pesticide Community Studies, Office of Pesticide Programs,
Environmental Protection Agency, 4770 Buford Highway, Chamblee,
Georgia 30341.

Gulf South Research Institute, P.0. Box 1177, New Lberia, Louisiana
70560.

Fish Control Laboratory, U.S. Bureau of Sport Fisheries and Wildlife,
Route 1, Box 9, Warm Springs, Georgia 31830.

Fish Farming Experimental Station, U.S. Bureau of Sport Fisheries and
Wildlife, Box 860, Stuttgart, Arkansas 72160.

69



Transport Processes

Convective Mass Transport ("leaching," "drift") -

This physical process operates in all environments, in both the
gaseous and liquid phases, usually along the direction of mass flux.
In SOILS it would depend strongly on the degree of soil saturation,
in the ATMOSPHERE on the micrometeorological air flows, and in the
AQUATIC environment on hydrodynamics.

Inter-particle Diffusion (linear, eddy, etc.) -

This process operates where chemical gradients or local turbulence
exist. Viscous solvent drag effects (included in the commonly used
term "dispersion coefficient") also operate.

Intra-particle Diffusion (absorption/de-absorption) -

Fickian chemical gradients act as driving forces causing chemical
mass to enter and diffuse into or out of particulate matter itself.
The structure of the particle, its degree of internal saturation with
water, the size and diffusivity of the chemical, and the chemical's
structure are important factors. Included in this category would be
"exclusion-type" processes, where pore size of inorganic particulates
may be large under one set of environmental conditions (pH, degree of
saturation), permitting entry of chemical to sites unexposed under
other conditions, and the subsequent trapping or binding of the agent
therein when the conditions change.

Co-distillation -

Volatilization in association with water evaporation takes place at

the soil/air and water/air interfaces and is highly dependent on the
temperature, degree of soil moisture or amount of water surface exposed,
and the chemical vapor pressure.

16



RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development,

U.S. Environmental Protection Agency, have been grouped into
five series. These five broad categories were established to
facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in
related fields. The five series are:

Environmental Health Effects Research
Environmental Protection Technology
Ecological Research

Environmental Monitoring
Socioeconomic Environmental Studies

OAPwWwN—

This report has been assigned to the ECOLOGICAL RESEARCH STUDIES
series. This series describes research on the effects of pollution

on humans, plant and animal species, and materials. Problems

are assessed for their long- and short-term influences. Investigations
include formation, transport, and pathway studies to determine

the fate of pollutants and their effects. This work provides

the technical basis for setting standards to minimize undesirable
changes in living organisms in the aquatic, terrestrial and atmospheric
environments.

This report has been reviewed by the National Environmental

Research Center--Corvallis, and approved for publication. Mention
of trade names or commercial products does not constitute endorsement
or recommendation for use.




SECTION VI
THE FRESHWATER AQUATIC MODEL

This section develops a systematic approach to an optimal
representation of the behavior of pesticides in aquatic environments.
A quantitative discussion of processes and parameters important to
the fate and transport of pesticides-in-general is futile because of
the diverse chemical and physical properties of pesticides. This is
further complicated by the need to specify chemical, biological, and
physical characteristics of the aquatic ecosystem. Therefore, a
qualitative approach to studying and modeling the fate and transport
of pesticides in aquatic ecosystems is discussed.

There has been a shift in many areas of science toward studies of
wider scope. This has been brought about partly by increased
emphasis on "the environment" and partly by wider knowledge of the
techniques of system studies. According to MOORE (1967) the emphasis
in pesticide studies has shifted from

Pesticide + Pest
to
Pesticide + Ecosystem

Past pesticide research resulted in few system studies and fewer
mathematical analyses of such studies.

One area of system studies is that of microcosm or partial system
studies (METCALF et al., 1971). These studies emphasize a particular
short food chain largely as an index for comparison of various studies.
Their quantitative applicability to real-world ecosystem is therefore
limited. Nevertheless, they provide the basis of a large portion of
our comprehension of the behavior of pesticides in the environment.

40



The chemical input may be in the gaseous state or adsorbed onto
particulates released into the atmosphere. Accidental discharge
resulting from explosions, containment vessel failure, human error,
or other accidents involving vehicles or devices for transporting
chemicals can cause major problems in a local geographic area, but
are probably minor when considered on a global scale.

Chemical input into the atmosphere through routine use of products
made of chemicals not totally immobilized, either intentially or
unintentionally, is of major concern. For their model, NISBET and
SAROFIM (1972) had to estimate the amount of PCBs lost to the
atmosphere by evaporation of hydraulic fluids, lubricants,
dielectric: fluids used in transformers, and various plastics which
are manufactured using PCBs.

Flora

Except for the direct application of plant growth regulators and
chemicals used in pest control and for other agricultural purposes,
sources are generally separated from flora by atmosphere, soil, and
water of the environment. With direct application, input may occur
on the foliage and/or fruiting body; alternatively, soil or water
applications are sources of indirect inputs.

Fauna

As with flora, few sources directly input into these compartments.
Medical and veterinary application of drugs and medicines, cosmetic
and hygienic dermal applications, and consumption of food and non-
food items constitute typical types of deliberate exposure from
sources. In occupational use and, to a lesser extent, the general
public, exposure can occur by direct inhalation of vapors or
absorption through the skin. Hence, concern has been evidenced for

24


To omen FAUNA

FOOD (From PLANTS,
FAUNA, SOILS, and 4.1 Blood (Hemolymph)® 4, Ly
SOIL ORGANISMS) iv “pound”
I 7 AF
at umen  g@g=*x,m
TV Gut ge xm iq
Digestive organs §
WATER : s
(Liver, Kidney) *x,m KH a4
(SOILS, wer, Meney 3
AQUATIC: £
= Hair -L LJ
qT 7, Feathers Dermus |e - >
Iv Endoderm gf >TMTM jet ATMOS
he
Ai Respiratory organs ow K-
SOILS Ty Comme Inhalation

Other tissues and organs
(muscle, bone, nervous system,
adipose)

Reproductive tissues

Offspring
(fetus, eggs)

Figure 5:

Diagram of Faunal Subsystem Model.
(Based on BISCHOFF and BROWN, 1966).
flows or transfers of agent and/or compartment mass.

33

Arrows indicate




place at the same time (at reduced rates) in the same compartment or
others. The great increase in rate of the enzyme-catalyzed reaction
provides opportunity for compartmental differentiation of disposition.
These reactions are highly dependent on species, status (physiological,
nutritional, and previous chemical history), and route of exposure.
They may: provide for an agent becoming more or less biologically
active; for binding or conjugation in a form more or less available
to other organisms, compartments, etc., without altering the potential
biological activity; or for the covalent interaction of the agent with
an enzyme, thus altering the capacity of the system subsequently to
carry out alterations at the same rate (inhibition).

The biological effects of an agent are difficult to separate from
disposition, inasmuch as one potential effect is to alter disposition
routes and/or rates. Known pesticide-induced enzymatic reactions in
both vertebrates and invertebrates include oxidation-reduction,
hydrolysis, conjugation, and carbon-carbon bond cleavage. The enzyme
activities induced may represent de novo synthesis of theretofore
unexpressed genomes (microbial) or amplification of the rate of genome
expression (higher animals). Biochemical alteration of environmental
contaminants and agents can be viewed as a function of the expression
of genetic material in coordination with the ability of the environment
and the biological species to provide for synthesis of enzyme and
cofactors to support the reactions. Changes in the course of this
expression may be one of the biological effects interacting strongly
on the disposition of a particular chemical.

Factors Affecting Disposition

As noted in the foregoing discussion of mechanisms, the disposition of
chemicals in the environment is governed by physicochemical, physical,
and biologic processes which can be related to properties of the chemical

19




SECTION IT
RECOMMENDATIONS

The conceptual model necessarily will benefit from criticism,
experimentation, and utilization in research. The process of
improving and updating the conceptual relationships should be
a continuing function of this program.

Analysis of the disposition of pesticides in particular segments of
the environment and of the effects accompanying their distribution and
fate should employ the conceptual models in developing more explicit
hypotheses and as an operational framework. Research in laboratory
microcosm and in field validation of laboratory studies of processes,
effects, etc., should be correlated through appropriate models derived
from this conceptual base.

In relation to the Substitute Pesticides Program, this conceptual

model should be employed in referencing the probable disposition of an
alternative chemical to that of the de-registered or suspect agent that
the substitute might replace.



SECTION VII
THE ESTUARINE/MARINE MODEL

The considerations incorporated in the freshwater aquatic model
continue in relevance and validity into the estuarine/marine system,
which can be viewed as specialized iterations of the general model
(Figures 1 and 3). The relationship to the terrestrial and
freshwater systems have been alluded to earlier (Figure 2). Thus,
it is sufficient here to outline the significant differences and
inter-relationships applicable to these regions of the environment.

The physical state of a compound in a system depends on its relation
with the other components of the system, a behavior which can ideally
be described by distribution constants when at equilibrium. For
instance, the pharmaco-dynamic action of many drugs depends on their
relative ability to bind to different sites. In such a fashion, the
bloodstream may act as a reservoir permitting slow release of a drug
to assure its long-term action. This ability to bind substances can
occur anywhere. The toxicity of a pollutant must thus be evaluated
in terms of the physical state(s) in which it shows toxicity and not
merely by its observed concentration. With regard to availability to
a carnivore, a pollutant adsorbed to detritus may be as unavailable
as that adsorbed to a grain of sand.

Figure 14 is a schematic diagram of flow of a chemical through an
estuary. It should be pointed out strongly that the estuarine system
is exceedingly complex and any simulation will require time and caution.

Figure 15 is a representation of functional interactions at the
interfaces between the estuary and other indicated ecosystems. The
arrows indicate possible flux of chemicals without regard to form and
origin. Interactions in the estuary are treated in a more precise
conceptual fashion in Figure 14.

55


National Agricultural Chemicals Association, 1155 15th St. NW,
Washington, D.C. 20005.

Division of Biology and Agriculture, National Research Council, 2101
Constitution Ave. NW, Washington, D.C. 20418.

New Hampshire Pesticides Control Board, State House Annex, Room 201,
Concord, New Hampshire 03301.

New York State Department of Environmental Conservation, 50 Wolf Rd.,
Albany, New York 12201.

Patuxent Wildlife Research Center. Laurel, Maryland 20810.

Toxicological Research Laboratory. Veterinary Sciences Research
Division. Agricultural Research Service, USDA, P.0. Box 311,
Kerrville, Texas 78028.

Community Study Pesticide Project. Idaho Department of Health,
Statehouse, Boise, Idaho 83707.

Division of Wildlife Services. Bureau of Sport Fisheries and
Wildlife. U.S. Department of the Interior, 1717 H Street NW,
Washington, D.C. 20240.

Denver Wildlife Research Center. U.S. Bureau of Sport Fisheries and
Wildlife, Building 16, Federal Center, Denver, Colorado 80225. com FLOR

COLLEGES AND UNIVERSITIES ASSOCIATED WITH
PESTICIDE RESEARCH OR PESTICIDE INFORMATION

Water Resources Research Institute, 314 Nuclear Science Center,
Auburn University, Auburn, Alabama 36830.

Lake Ontario Environmental Laboratory, College at Oswego, State
University of New York, Oswego, New York 13126.

Colorado State University, Fort Collins, Colorado 980521.

Department of Zoology, Mississippi State University, Mississippi
State, Mississippi 39762.

Department of Fisheries and Wildlife, Michigan State University, East
Lansing, Michigan 48823.

70



Global model studies are important in setting an overall framework
within which smaller system studies may be placed. RANDERS and
MEADOWS (1971) studied the movement of DDT in the environment, and
WOODWELL et al., (1971) made a similar study. An important
conclusion of both these papers was that the DDT concentration in
food chain organisms would continue to increase long after the rate
of application was decreased or terminated. This conclusion was
based on computer simulation studies and comparative analyses.

Smaller system studies of greater detail bring us closer to
interactions at the ecological level. Analyses of pesticide
transformations and transports at the ecological level may make use
of both ecological theory and various applications of systems theory.
For example, EBERHARDT et al., (1971) applied system simulation to a
field study as an aid in interpreting the data.

The above examples deal with specific pesticides in relatively
defined ecosystems and are not generally applicable to a description
of fate and transport. The presentation that follows is applicable
to pesticides and aquatic ecosystems in general but can also be used
as a Starting point for any specific pesticide and system.

SKELETAL DIAGRAMS FOR A PESTICIDE IN THE AQUATIC ENVIRONMENT*

The most effective aggregation of storage components and rate
processes varies as attention is turned from one aquatic regime to
another. Even within the range of lentic systems, the diagrammatic
representation for a deep dimictic lake would be inappropriate when
used for a freshwater marsh. For this reason, several basic frameworks
or skeletal models without detailed process embellishment are presented
for different aquatic environments.

*See Appendix for detailed background.

4]



‘Atmospheric
Parameters 7~ ~

\

Atmospheric Input

su

vL

‘Atmospheric
77 \ Parameters
Output to
etree
\
lL

Ces)
ind-turbulence)

sz
J

L Epilimnion
7
7 7 3
/ 1 =
f i z
5 2 Hydrologic
[setting Dx titusion E = - Cara
' 3
‘ =
! =
Hypolimnion <_< i 2
a s
/
: |
DX] Solubilization

Sediments.

Figure 6:

Vertical Representation of a Stratified Lake.

Solid line - pathway of transfer of matter or energy; dashed
ine - control pathway of information transfer; cloud symbol -
sink or source external to system boundaries; rectangle -

storage of matter or energy; valve symbol - rate-controlling
parameter or force; and circle ~ coe

affecting flow rates.

Tcients and parameters
(Similar for Figures 6-13.)


The regional models can be considered as amplified aspects of a basic
variable-form module (Figure 1) within which a chemical may exist in

a "free" or "bound" form. Since any chemical may be used as a pesticide,
a term describing its function, the fate and movement of any agent (and
effects consequent to that disposition) can be described and displayed
without regard to that extrinsic function. Thus, the model should
serve not only for pesticidal chemicals, but also for other natural

and man-made agents that are being evaluated. The subcompartments of
modules may exist in varying proportions and with diverse relationships
in different environments. Specification and elaboration of this basic
chemical module are employed to relate it more specifically to a region
or zone within the environment, and interrelating and interfacing such
subsystems generates models of broader relevance. Subsequently,
iteration of models can occur longitudinally (to represent stream flow,
geographical or climatic regions, or atmospheric processes), vertically
(to represent water depths, soil horizons, or meteorologic events), or
horizontally (to represent distances from interfaces) to develop
multi-media models.

At the interfaces of the regions explicit representation becomes most
difficult. Although the models exposited cannot be viewed as globally
valid, the iteration and conjunction of subsystems generate a global
array (Figure 2) that serves conceptually as an overall model. As
shown in Figure 2, some elements are "shared" in a more or less
regular manner through seasonal, circadian, or shorter cycles and in
an irregular manner through meteorologic and geologic changes. The
tidelands, flood plains, and marshes are not fully represented by
either aquatic or terrestrial models exposited herein, but both
provide sufficient elements for subsequent elaboration as knowledge
of the physical structure, physicochemical relationships, and
alteration rates of these interfaces is improved. These interactions
cannot be ignored simply because the mean flux appears to be zero,