Multimedia Environmental Models

Abstract

In this introductory paper it is suggested that multimedia mass balance models can play a valuable role in improving our understanding of the behavior of chemicals in the environment. They can provide a rational basis for chemical management by linking emission rates to prevailing environmental concentrations and identifying such issues of concern as tendency to bioaccumulate, persistence for excessive times, and the potential to undertake intermedia transport. Four principles are outlined: the need for iterative modeling starting with simple models and progressing toward more complexity with fidelity to real conditions; the value of evaluative models as a means of focusing attention on how the chemicals’ properties translate into fate; the need for more validation of these models by comparing observations with simulations; and finally, the value of the fugacity concept as a means of expressing multimedia partitioning, transport, and transformation more simply. These principles are demonstrated by a case study in which a variety of models is applied to assess the fate and transport of hexachlorobenzene in evaluative, regional, and aquatic environments. This example demonstrates that multimedia models can provide a comprehensive, quantitative picture of how specific chemicals behave in the environment, thus contributing to conditions engineered such that the beneficial uses of chemicals can be enjoyed sustainably and without risk of adverse effects on humans or the ecosystem.