Exposure Analysis Modeling System (EXAMS): User Manual and System Documentation

摘要

The Exposure Analysis Modeling System (EXAMS) was designed for rapid evaluation of the behavior of synthetic organic chemicals in aquatic ecosystems. From the chemistry of a compound and the relevant transport and physical/chemical characteristics of the ecosystem, EXAMS computes: (1) Exposure: the ultimate (steady-state) expected environmental concentrations (EECs) resulting from a specified pattern of (long-term, time-invariant) chemical loadings, (2) Fate: the distribution of the chemical in the system and the fraction of the loadings consumed by each transport and transformation process, and (3) Persistence: the time required for effective purification of the system (via export/transformation processes) once the chemical loadings cease. EXAMS combines loadings, transport, and transformations into a set of differential equations using the law of conservation of mass as an accounting principal. This law accounts for all of the chemical mass entering and leaving a system as the algebraic sum of external loadings, transport processes that export the compound from the system, and transformation processes that convert the parent compound to daughter products.