                                                           File: ABSTRACT.TXT


                         EXAMS Model System Abstract

               Center for Exposure Assessment Modeling (CEAM)
     National Exposure Research Laboratory - Ecosystems Research Division
                  Office of Research and Development (ORD)
               U.S. Environmental Protection Agency (U.S. EPA)
                          960 College Station Road
                         Athens, Georgia 30605-2700

                                706/546-3549



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                                  Summary

The Exposure Analysis Modeling System, first published in 1982
(EPA-600/3-82-023), provides interactive computer software for formulating
aquatic ecosystem Models and rapidly evaluating the fate, transport, and
exposure concentrations of synthetic organic chemicals--pesticides,
industrial materials, and leachates from disposal sites.  Exams contains an
integrated Database Management System (dbms) specifically designed for
storage and management of project databases required by the software.  User
interaction is provided by a full-featured Command Line Interface (cli),
context-sensitive help menus, an on-line data dictionary and cli users'
guide, and plotting capabilities for review of output data.  Exams provides
20 output tables which document the input datasets and provide integrated
results summaries for aid in ecological risk assessments.

Exams' core is a set of process modules that link fundamental chemical
properties to the limnological parameters that control the kinetics of fate
and transport in aquatic systems.  The chemical properties are measurable by
conventional laboratory methods; most are required under various regulatory
authority.  When run under the EPA's GEMS or pcGEMS systems, Exams accepts
direct output from qsar software. Exams limnological data are composed of
elements historically of interest to aquatic scientists world-wide, so
generation of suitable environmental datasets can generally be accomplished
with minimal project-specific field investigations.

Exams provides facilities for long-term (steady-state) analysis of chronic
chemical discharges, initial-value approaches for study of short-term
chemical releases, and full kinetic simulations that allow for monthly
variation in mean climatological parameters and alteration of chemical
loadings on daily time scales.  Exams has been written in generalized
(N-dimensional) form in its implementation of algorithms for representing
spatial detail and chemical degradation pathways.  This DOS implementation
allows for study of five simultaneous chemical compounds and 100
environmental segments; other configurations can be created through special
arrangement with the author.

Exams provides analyses of

     Exposure: the expected (96-hour acute, 21-day and long-term chronic)
     environmental concentrations of synthetic chemicals and their
     transformation products,

     Fate: the spatial distribution of chemicals in the aquatic ecosystem,
     and the relative importance of each transformation and transport process
     (important in establishing the acceptable uncertainty in chemical
     laboratory data), and

     Persistence: the time required for natural purification of the ecosystem
     (via export and degradation processes) once chemical releases end.

Exams 2.96 includes file-transfer interfaces to the PRZM terrestrial model
and the FGETS bioaccumulation model.

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