EPA-660/3-74-024
DECEMBER 1974
                                                Ecological Research  Series

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                      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:

          1.   Environmental Health Effects Research
          2.   Environmental Protection  Technology
          3.   Ecological Research
          4.   Environmental Monitoring
          5.   Socioeconomic Environmental Studies

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.

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                                    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 1EA487
             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, U.S. Government Printing Office
          Washington, D.C. 20402 - Stock No. 5501-00973

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                             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.

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                             CONTENTS
                                                       Page Page
ABSTRACT	   ii
LIST OF FIGURES	   iv
ACKNOWLEDGEMENTS 	   vi
FOREWORD	   vii
SECTIONS
I    CONCLUSIONS 	   1
II   RECOMMENDATIONS 	   3
III  INTRODUCTION  	   4
IV   OVERALL CONCEPT OF THE MODEL	   11
V    THE ATMOSPHERIC/TERRESTRIAL MODEL 	   27
VI   THE FRESHWATER AQUATIC MODEL  	   40
VII  THE ESTUARINE/MARINE MODEL  	   55
VIII REFERENCES	   59
IX   KEY LITERATURE SOURCES FOR PESTICIDE
      EFFECTS RESEARCH 	   63
APPENDIX	   73

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                              FIGURES
No.                                                              Page
 1   Variable-Form Module:   Chemical                               5
 2   Global Array of Environmental  Regions                         7
 3   Food Web Module                                              9
 4   Diagram of the Atmospheric/Terrestrial  Model                  30
     4A   ATMOSPHERE                                              31
     4B   FAUNA                                                   34
     4C   FLORA                                                   37
     4D   SOIL and WATER                                          38
 5   Diagram of Fauna!  Subsystem Model                             33
 6   Vertical Representation of a Stratified Lake                  43
 7   Horizontal  Representation of a Lake                           44
 8   Horizontal  Array of Vertical Columns for
      Representation of Lotic Systems                              45
 9   Some of the Storages,  Processes, and Subsystems
      Associated with the Surface Layer Storage Compartment        47
10   An Expansion of the Hydrologic Input                          48
11   A Skeletal  Abstraction of a Food Web                          49
12   Food Chain Model of DDT in a Freshwater Marsh                 50
13   A Minimal Representation for a Pesticide
      in a Dimictic Lake                                          52-53
14   Simple Model of Transport in Estuaries                        56
15   Expanded, Iterated Basic Chemical Module for
      Transport of Chemicals in Estuaries                          57
     Biota-mediated Flux (overlay)                                 57
                                 IV

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                         FIGURES (Cont'd)
No.                                                              Page

A-l  Relationship Among Graphical  Representations                 74

A-2  Streeter-Phelps Oxygen-Deficient Model
      for a Stream                                                76

A-3  Vollenweider Lake Eutrophication Model                        76

A-4  Nutrient Model for Lake with  Biotic
      and Abiotic Storage                                         78

A-5  Possible Coupling of Biomass  (B) Subsystems
      with Nutrient Concentration  (Mb) Subsystems                 79

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                         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

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                             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.

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                             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 r§_ 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

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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 in a
rigorous scientific treatment of the  fate and effects of agents and
their alternatives  in pest control.

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                            SECTION II
                          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.

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                            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

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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).

WATER




ORGANIC

PANICULATE



INORGANIC

PARTICIPATE

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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,

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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.
         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.

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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
biotransformation 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.

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                                   TRANSPORT
                                   FLUX
             PRIMARY
            PRODUCERS
     PRIMARY
    CONSUMERS
              HIGHER
             CARNIVORES
SECONDARY
CONSUMERS
                           DECOMPOSERS
                            OMNIVORES
                            SCAVENGERS
                                   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.

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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

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                            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.
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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

          %  = 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

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     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.

2.   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  (5 is generated by

           G ^ A1                                   (2)

     in which each element (G. .)  is  a relative measure of the
                             1 J
     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.

3.   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               dX.

                        S(t)  +  [^I]  V(t)       (3)
                 d Xi            d
     where the terms  in brackets  are  Jacobian matrices.  With
     a unit perturbation of each  parameter, A. ., the steady-
     state values of  S^ for each storage  variable may be used
     as a relative measure of system  sensitivity to each
     parameter.

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     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 (o> ) 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

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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 simultaneously
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.
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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-distill ation -

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.
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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, pinocy tosis, 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 (jihase- surf ace 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 tine 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
                                  17

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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 v/ater, 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
                                   18

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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

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                                       Table I.  FACTORS AFFECTING DISPOSITION 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-disti 1 lation;
  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
  (multi-layered)
Vectorial flux; degree
  of saturation of immobile
  matrix by movement
l-iater evaporation rate,
  surface area, interaction
  with aaent, degree of soil
  moisture, extent of satura-
  tion of air
Structure (micro), degree
  of water saturation,
  alterations of structure
  by temperature, pH, ionic
  strength

Nutritional  value to
  feeder, attractiveness
  (chemical  or physical),
  availability of alternative
  foods, degree 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
  soil  moisture,  pH

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                                                                   Table I  (cont)
Mechanism, Pathway,
    or Process
Chemical reaction
  phenomena
Biological alteration
  (activation, degrada-
  tion, conjugation)
Properties of Agent
Structure (reactive
  groups);  energy  of
  activation,  free energy  of
  reaction, nature of
  mechani sm
Structure (reactive
  groups),  energy  of
  activation,  free energy
  of reaction,  nature  of
  reaction  mechanism,
  binding constant to
  enzymes acting on  it
Properties of Environmental
        Component
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), sensi-
  tivity to aaent (inhibi-
  tion, synergism, toxi-
  city), degree of coupling
  to other systems providing
  reactants or removing pro-
  ducts, presence or absence
  of cofactors
Environmental Control
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

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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 oil 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

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   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.   SOURCES OF  CHEMICALS FOR THE TERRESTRIAL ENVIRONMENT
     Phase of
History of Chemical                           Examples

Preconsumption              Manufacture, food processing, mining,
                            refining
Distribution                Application of chemical 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

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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

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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 Mater

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

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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 HATER have pervasive  major inputs into other segments of
the environment.
                                  26

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                             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

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          (1)  Suspended participates.  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 (1-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.   Mjm.  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.   Soi1-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 separated into two regions containing the same components.

-------
     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

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OJ
o
                  LEGEND:

                   Mass compartnwital transftr


                   Chemical movamtnt  	


                   Rwirslbl* sorptlon  4- —	


                   Photolysis        Q O


                   Chemical (x) or (M)

                       biological brtakdown
                                                                                                         >To

                                                                                                          AQUATIC
                            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.

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        ME SO SPHERE
                        ''
          mi
      STRATOSPHERE
GASES

            AEROSOLS
            Surface
rt
                            ^

                            C
                            ^ 0
           SUSPENDED

           ARTICULATES
       Precipitation  washout
4Tl
                       Fell out


                     Wash-out*
                              7^v~
                                b
                  Erosion
                             Co-distillation
    Figure 4A:  ATMOSPHERE
             31

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play a progressively great  role  in  the  upper atmospheric compartments
and, conversely,  chemical  reaction  (except for ozonolysis) would be
expected to be of less  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 jre_  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 fauna! 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

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FOOD (From PLANTS,
FAUNA, SOILS, and
SOIL ORGANISMS)
                                To  other^FAUNA
                                Blood   (Hemolymphr
                                                   x,m
                                     i.    .1
                                      bound
1
                                Lumen
                                Gut
 WATER
(SOILS;
AQUATIC
                          •iT   Hair
                                Feathers
*
j^""*x,m
^~*x,m

ve organs
Kidney) ^~**>m

Dermus
s
doderm ^^~*x,m

^^^^
Jtory organs ^^^"*"*>n^

**~ ^x.m

tissues and organs
le, nervous system,
adipose)

uctive tissues


e-

t-

e
e-


<

«-

f

J






^•M


*

if









o
"«)
V
o>
c
	





Inhc










^





lie










-»
AT




itior




                                           Offspring
                                            (fetus, eggs)
         Figure 5:   Diagram of Faunal  Subsystem Model.
   (Based on BISCHOFF and BROWN,  1966).   Arrows indicate
   flows or transfers of agent and/or  compartment mass.
                                 33

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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 [[[
\
<
r/
                                       MAN
                                             M,X
                               (see FAUNAL subsystem)
                                      HIGHER
                                    CARNIVORES   .
                                              M,X«
                               (see FAUNAL subsystem)
                                        1
        PRIMARY
       CARNIVORES
               M,X
(see FAUNAL subsystem)
         Ingestion
                      /-
                                                     c
         HERBIVORES ^^
                 M,X
•vKsee FAUNAL. subsystem)
                                               mP
                                             Decoy
                                      From
                                      AQUATIC
                          Figure 4B:   FAUNA
                                    34

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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 SOIj. and WATER compartments (Figure 4D).   Initially on the
Soi1 Surface subcompartment, these materials become part of the
organic participates 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 propose 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

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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

-------
    y*^  \±l
    X   .  I   , ^ ^^
- - ^«  o
                *~\
                X,M|
                   4
                                        Co-distillation
                               Wash
     l
                                out
                                          ^Volatilization
                               Cuti
    FOLIAG6
Trans- ^
 location
                  ROOTS
                     Cuticle
            cle
                                      FRUITING
                                     -   BODY
                                             X,M
             FRUITING"
            ~~   BODY
            "~*  X,M
                      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 HATER (Figure 4D) .  Material can enter this  compartment
directly at the Surface by sorption from the ATMOSPHERE,  condensation,
                              37

-------
    I: A
I  \
Wind, abrasion, mechanical)
   ±3
                                                     Tillage, geophysical,biological
                                —v T°
                                     >AQUATIC
                               Figure 4D.   SOIL  and WATER

-------
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

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                            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

-------
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.
                                  41

-------
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

-------
  AtmosphericN
  Parameters
            Atmospheric Input
            Atmospheric
            Parameters
 Output to
Atmosphere
t * '
' X
y ,'~


Surface Layer
1 V
/ \

                                                           Rate
                                                         Coefficient
                          [X| Vertical Mixing
                              Epilimnion
                                Diffusion
                             Hypolimnion
               Sedimentation
                                           Solubilization
r /
/ /
/ /
x /


Sediments
\ ^
\ ^
\
\
\
 Figure  6:   Vertical  Representation of  a  Stratified Lake.
Solid  line - pathway  of transfer of matter or energy;  dashed
Tine - 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 - coefficients and  parameters
affecting flow rates.   (Similar for Figures 6-13.)

-------
                                                               V
                                                           Amospheric
                                                           Input-Output
Pelagic Zone
1
l
1
1
1
1







|   Suspension   |X]   1X1    Settling    |   V^ParameWs^x'  |    Settling    |Xl   LXI   Suspension   |
               Figure 7:  Horizontal  Representation of  a Lake.

-------
cn
                                                                                       Hydraulic
                                                                             — ~ — V Parameters
Morpholigic ^_ — — -^
Parameters J— ~~ ~~
            Figure  8:   Horizontal Array  of Vertical  Columns  for Representation of Lotic Systems.

-------
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

-------
1 Atmospheric Settling}^
                                  	'
                               1X1    Settling
                  1,
                  Washout   1X1

                          t
                         Inorganic Particulates
               /Meteorological^
                 Atmospheric
Solar Input Rate [XJ
                 Available Solar Energy
»     i
                    t
                      i
                                                                                        I	*'
                                                                                        j [Precipitation Loading(X]
Hydraulic Output [X]  [XI Hydraulic Loading |
                                                                                                                  *

[XI  Gas ExchanjT"!
                                                           I'
                                                                  Concentration in Surface Layer
                                                                         ot water
                                                       Adsorption  ""fcxj
                                                     Concentration on
                                                       Particulates
                                                                Photochemical
                                                                 Degradation
                                                            M
                                                                                        [Sortition and I n|e$1ion[^X^
                                                                                   [XI Decomposition  |
                                 *   i
                            [XI  Transmission Coefficient
                                                                              Surface Food Web

                                                                            Organic Particulates
                                                                                               [)Q  Biodegradation
                     Figure 9:   Some of  the Storages,  Processes,  and Subsystems
                                    Associated  with  the  Surface  Layer Storage Compartment.

-------
CO
                     Solubilization/
                            Precipitation
               [\/\ Hydrologic Input of
               |/l\l Pesticide Particles
                       Pesticide Particles
                                                      Hydrologic Input of
                                                      Dissolved Pesticide
Direct Chemical Oxidation
and Microbial Degradation
                                     Adsorbed on
                                  Suspended Particles
                                         Figure  10:   An Expansion  of the  Hydrologic  Input.

-------
                                                          Respiration

D



_ 	 — ,
, i
i i

N
I!




A
Sorption | j
i
i




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

-------
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).
r
r
r
Surface Concentration
of DDT
,

Concentration in Tadpole
i

Concentration in
Suspended Matter
r
^

Concentration in Sunfish


Concentration in
Bloodworm
\
/
Concentration in Water
9
*

Concentration in Carp

Concentration in
Narrow-leaf Pondweed

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

-------
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

-------
cn
ro
                                                                                                                                                                                        	1  COMCCMTOAYiOKj   I     '
                                                                                                                                                                                            I    1M  S*C«M40     L	

                                                                                                                                                                                        - —L   COMVOMKH5     I     I

-------
en
CO
                 Figure 13:   A Minimal  Representation  for a Pesticide in a Dimictic Lake.

-------
     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

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                            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

-------
             SOURCE
                                      PHYSICAL FORM
                                                                  RESERVOIR
                                                                                                  LOSS
cn
cr>
                          Figure  14:   Simple Model of Transport  in  Estuaries.

-------
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

-------

-------
?
V—

ATMOSPHERE
GASES
INORGANIC ORGANIC
PARTIC PARTIC
ULATES ULATES



MARINE

WATER


INORGANIC
PARTIC
ULATES

ORGANIC
PARTIC
ULATES

Ol
1 BIOTA 1
V_y
en
00
                                               ESTUARY-PELAGIC
                                                              ^—x

FRESH

WATER


WATER
INORGANIC
PARTlC-
ULATES

ORGANIC
PARTIC-
ULATES

( BIOTA 1
                                                                        AA
                                                                        W
ESTUA
WATER

^Y-LITTORAL
INORGANIC
PARTIC
ULATES
ORGANIC
PARTIC-
ULATES

^\
( BIOTA ]
v_y
o
ESTUAI
WATER

1Y-SEDIMENTS
INORGANIC
PARTIC-
ULATES
ORGANIC
PARTIC
ULATES

I BIOTA j








INORGANIC
PARTIC






ORGANIC
PARTIC


                                                                                                  vv
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.

-------
                           SECTION VIII

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BERTALANFFY, L.  VON.  (1963).   "General  Systems  Theory."   George
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BISCHOFF, K. B.  and  R.  G. BROWN.   (1966).   Drug  distribution  in
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CANNON, R. H.  (1967).   "Dynamics  of Physical  Streams."   McGraw-Hill,
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CHILD, G. I. and H.  H.  SHUGART, JR.   (1972).   Frequency  response
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CLOSE, C. M.  (1963).  "Notes on the Analysis  of Linear  Circuits."
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COMMONER, B.  (1971).  "The Closing  Circle."   Alfred A.  Knopf, Inc.,
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DeRUSSO, R. M.,  R.  ROY  and C.  CLOSE.   (1965).  "State  Variables for
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DUCE, R. A., J.  G.  QUINN, C.  E. OLNEY, S. R. PIOTROWICZ,  B. J. RAY
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EBERHARDT, L. L., R. L.  MEEKS and  T.  J.  PETERLE.   (1971).   Food chain
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ELZY, E., F. T.  LINDSTROM,  L.  BOERSMA, R. SWEET  and P. WICKS.  (1974).
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FORRESTER, J.  11.   (1971).   "World Dynamics."  Wright-Allen  Press,
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HANNON, B.  (1973).   The structure of ecosystems.   J. Theor.  Biol.
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HARRISON, H. L.,  0.  L.  LOUCKS,  J. W.  MITCHELL,  D.  F.  PARKHURST,
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HILL, J., IV  (1973).   Component Description  and Analysis of
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HOLLEY, E. R.  and G.  ABRAHAM.  (1973).   Field tests on  transverse
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HUANG, J.  (1971).  Organic pesticides  in the aquatic environment.
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HUTCHISON, G.  E.   (1948).   Circular causal  systems  in ecology.
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HUTCHISON, G.  E.   (1957).   "A Treatise on Limnology."   John Wiley
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KENAGA, E. E.   (1972).   Guidelines for environmental  study  of
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KARNOPP, D. and R.  C. ROSENBERG.   (1968).   "Analysis  and Simulation
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KUO, B. C.  (1962).   "Automatic Control  Systems."   Prentice-Hall.
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LEONTIEF, W. W.  (1966).  "Input-Output Economics."  Oxford
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LINDSTROM, F.  T., J.  W.  GILLETT and S.  C. RODECAP.  (1974).
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MEADOWS, D. H., D.  L. MEADOWS,  J. RANDERS and W. H. BEHRENS,  III.
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                                  60

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METCALF, R. L., G. K. SANGHA and I.  P.  KAPOOR.   (1971).   Model
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MOORE, N. W.  (1967).  A synopsis of the pesticide problem, Jji
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NISBET, I.  C. T.  and A. F.  SAROFIM.   (1972).   Rates and  routes
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ODUM, E. P.  (1971).  "Fundamentals  of  Ecology."   Saunders,
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ODUM, H. T.  (1972).  An energy circuit language for ecological
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O'MELIA, C. R.  (1972).  An approach to the modeling of  lakes.
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PATTEN, B.  C.  (1971).  A primer for ecological modeling  and
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PATTEN, B.  C.  (1973).  Need for an  ecosystem perspective in
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     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, Jj]^ "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.
                                   61

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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  Ted). 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).  DDT in the
     biosphere:  Where does it go?   Science 174, 1101.
                                   62

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                            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. ROSENBERG.   (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

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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

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	.  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

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STICKEL, L. F.  (1968).  "Organochlorine Pesticides in the
     Environment."  U.S.D.I., 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.I.,  Fish and Wildlife
     Service, Bureau of Sport Fisheries and Wildlife.  Research
     Publication No. 84, Washington, D.C.

WILKINSON, B. K., L. S. CORRILL and E.  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

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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 lexicologists
     (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

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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.O. 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.O. 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.O.  Box 25, Boise,  Idaho 83707.
                                 68

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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.O.  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.O. 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

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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.O. 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  8°225..


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  80521.

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

Department of Fisheries and Wildlife, Michigan  State University,  East
     Lansing, Michigan  48823.
                                   70

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

Oregon State University, Corvallis, Oregon   97331.

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

Cornell 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

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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.O. 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

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                             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-l.

                                  73

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                         Graphical Representation
                          Alternative Hypotheses
                               Qualitative
     Mathematical Model
Data Aquisition
          Analysis
        Quantitative
  Experiment
  Constraints
     Figure A-l:   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

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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

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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.

©
1

»
<] Input Rate |
t
i
©


1
©
1
1
*
| Output Rate [>
/
/
/
Deficit

  Figure  A-2:
   ^ = KiL - K>D    where D = oxygen deficit, L = BOO remaining,
   dt
                   K, = deoxygenation coefficient, and
                   K? = reaeration coefficient.
Streeter-Phelps  Oxygen Deficit Model  for a Stream.
                              t
                               *
                       [XI   Input Rate   |     |   Output Rale

                                              ©
                                     M.
                                Nutrient Concentration
                       =  - _(o +
                               VL where M» = concentration of nutrient,
                                     J = flux of M to lake,
                                     o = sedimentation coefficient,
                                     q = flow coefficient, and Z = mean lake depth.
        Figure A-3:   Vollenweider Lake Eutrophication  Model
                                     76

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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
lake 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

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  +
                                  ©0
                                     I      I
                                   A	I
   [X|    Input Rate     |     r +~\    Output Rate    |X]

^
L r ~ ~
i
Concentration in
Abiotic Component


       Uptake Rate

    *
   Rate
Coefficient

                            Excretion Rate   |
                                        *
L _
Concentration in
Biotic Component
      Mean Level of
     Biotic Component
                     [XI   Output Rate    |
                      I                 *
         Figure A-4:  Nutrient Model for Lake with
                     Biotic and Abiotic Storage.
                           78

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                             f
                      Concentration in
                      Biotic Component
           Rate
        Coefficient
            t
    I
   [V|   Uptake Rate    [•*- n   T-»-[   Output Rate   |X|
   [XI   Growth Rate
            T
           Rate
        Coefficient
        Rate
    Coefficient
        t
   Death Rate
4      T
       Rate
    Coefficient
                             B
                         Biomass
                       	»|   Respiration    [X]
Figure A-5:   Possible  Coupling of Biomass  (B) Subsystems
            with Nutrient Concentration (Mb) Subsystems,

                           79

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                                             .A4-/OK I
                            (I'lcase read Instructions on the reverse before completing)
i. m PORT NO.
                             2.
                                                           3. RECIPIENT'S ACCESSION-NO.
4. TITLfc AND SUBTITLE
 A Conceptual Model for the Movement  of Pesticides
 through  the Environment:  A Contribution of the EPA
 Alternative Chemicals Program
                                    5. REPORT DATE
                                      November  1,  1974
                                    6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
 James W. Gillett,  James Hill IV, Alfred W.  Jarvinen
 and W. Peter  Schoor
                                                           8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORG '\NIZATION NAME AND ADDRESS
 National  Ecological Research Laboratory
 Environmental  Protection Agency
 Corvallis, Oregon  97330
                                    10. PROGRAM ELEMENT NO.
                                          1EA487
                                    11. CONTRACT/GRANT NO.
                                                                                          -V1
 1?. SPONSORING AGENCY NAME AND ADDRESS

 Same
                                    13. TYPE OF REPORT AND PERIOD COVERED i!
                                    	Final	I
                                                           14. SPONSORING AGENCY CODE
 16. 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.
a.
                                KEY WORDS AND DOCUMENT ANALYSIS
                  DESCRIPTORS
                                              b.lDENTIFIERS/OPEN ENDED TERMS
                                                 c.  COSATI Field/Group
Air  Pollution
Conceptual Model
Ecology
Environmental Biology
Hazardous Materials
Mathematical Model
Pesticides
Systems Analysis
Water Pollution
Alternative  Chemicals
  Program
Laboratory Microcosms
Simulated Ecosystems
1201
0611
0606
19. DISTRIBUTION STATEMENT
                                              19. SECURITY CLASS (This Report)
                                              	UNCLASSIFIED
                                                 21. NO. OF PAGES
                                              20. SECURITY CLASS (Thispage)

                                                   TWPT.ASSTT?Tl?n
                                                 22. PRICE
EPA form 1220-1 (8-73)
                            U.S. GOVERNMENT PRINTING OFFICE: 1974-697-650/65. REGION 10

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