A continuos time dynamic control system of the "Level IV Fugacity Model" is presented and applied to selected organic chemicals in evaluative environments system. In order to illustrate the numerical solution by this model a discretization is used to calculate the fugacity, concentration and fugacity settling time for a set of three insecticides applied in a hypothetical three compartmental environmental system. The model employs the fugacity concept and treats three bulk compartments: air, water and bottom sediment. Input to the model consists of a description of the environmental, the physical-chemical and reaction properties of the chemical, and emission rates. Expressions in matrix form are included for emissions, advections, reactions, and inter-phase transference. An algorithm to determine the values of the fugacities, concentrations and fugacity settling time is given
