ABSTRACT
The main use of an environmental model is the prediction of the behavior of a chemical in the environment. This knowledge is essential in the avoidance of disruptive effects to the ecosystem by new and existing chemicals. This chapter describes simple equilibrium models which help to elucidate the ultimate fate of the chemical by integrating the experimental data; determining the relative concentrations of the substance in various compartments of the environment; and assessing the degradative processes. The model provides information on behavior characteristics for compounds in the form of relative concentrations in each compartment, the importance of each reaction, and the overall persistence of the chemical. This information is useful in the initial screening and assessment of new chemicals. Expressing equilibrium in terms of fugacity separates the escaping tendency of the chemical from each phase and facilitates the calculation of the relative concentrations and amounts in each phase.
