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 706/355-8400 ----------------------------------------------------------------------------- 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 that document the input data sets 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 authorities. EXAMS limnological data are composed of elements historically of interest to aquatic scientists world-wide, so generation of suitable environmental data sets 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. The complexity of the environmental description and the number of chemicals is fully user-controlled. This implementation allows for direct access file (UDB) storage of five interacting chemical compounds and 100 environmental segments; more complex configurations can be created and subsequently stored using EXAMS' write command. 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 includes file-transfer interfaces to the PRZM3 terrestrial model and the FGETS and BASS bio-accumulation models; it is a complete implementation of EXAMS in Fortran 95. -----------------------------------------------------------------------------