| Abstract |
MEXAMS, the Metals Exposure Analysis Modeling System, provides an enhanced capability for assessing the impact of priority pollutant metals on aquatic systems. It allows the user to consider the complex chemistry affecting the behavior of metals in conjunction with the transport processes that affect their migration and fate. This is accomplished by linking MINTEQ, a geochemical model, with EXAMS, an aquatic exposure assessment model. MINTEQ is a thermodynamic equilibrium model that computes aqueous speciation, adsorption and precipitation/dissolution of solid phases. It has a well-documented thermodynamic data base that contains equilibrium constants and other accessory data for seven priority pollutant metals: arsenic, cadmium, copper, lead, nickel, silver and zinc. The model was developed by combining the best features of two other existing geochemical models MINEQL and WATEQ3. EXAMS is designed for the rapid evaluation of synthetic organic pollutants. Given the characteristics of a pollutant and an aquatic system, EXAMS computes steady-state pollutant concentrations (exposure), the distribution of the pollutant in the system (fate), and the time required for effective purification of the system (persistence). Its linkage to MINTEQ required several modifications. To facilitate the use of MEXAMS, a user interactive program was developed. This program queries the user to obtain water quality data for MINTEQ, then controls the operation of MINTEQ and EXAMS, passing simulation results back and forth between the models. |
