A dynamic fate and transport multimedia environmental model was developed and applied to assess the release of five priority contaminants in the Passaic River Watershed, including: napthalene, toluene, trichloroethylene, 1-1-1 trichloroethane and xylene. The model uses the current releases of contaminants as well as cross-boundary advection to determine the fate and environmental distribution of these chemicals in the watershed. The model was developed using a dynamic fugacity approach in order to allow for scenario analysis such as source reductions and no-action alternatives. This modeling effort is expected to achieve a comprehensive assessment of contaminants not only in the proximity of their release but on the scale of the entire watershed, or even larger areas.

This new modeling approach is based on the partition of chemicals between homogeneous and adjacent compartments (i.e. water, air, soil, sediment and vegetation) in order to determine their final distribution in the environment. The effect of spatial resolution on model prediction was addressed in this study by comparing the modeling results of Passaic River Watershed as one environmental unit versus considering the watershed as several sub-watershed units. Other points addressed in the present model include: the determination of the likelihood and the required time for environmental contamination to reach steady state and the consistency of the intermedia transfer rates 'in estimating actual environmental processes. As part of the model development, the linking of the multimedia model to the available Geographical Information System (GIS) database was  successfully demonstrated. A procedure was developed for deriving relevant data that can be used for other environmental applications. This mode of data manipulation identified the need for recording available and future data in a manner and units useful for multimedia modeling applications. This consistency in data representation would ultimately result in wider use of multimedia models and for their validation.

The current unsteady state Level IV fugacity model was successfully validated using the widely referenced ChemCAN model. Applications of this model to the watershed environment provided more information on the fate of contaminants, thus allowing for better decisions in controlling their releases. The inclusion of spatial resolution was found to improve the results of the multimedia models by several orders of magnitude, especially for high molecular weight non-volatile organic contaminants. Furthermore, considering the soil compartment as three separate and distinct layers was found to significantly improve the estimation of the contaminants distribution as a function of depth. Finally, it was observed that the organic contaminants used in the multimedia model displayed different behavior in their distribution and Intermedia mass transfer rates based on their physical and chemical properties. Non-volatile contaminants like naphthalene show a preferential distribution in the soil layers irrespective of their point of release and as a result they may persist in the environment for long period, especially if the degradation rate in that compartment is low. Volatile contaminants such as toluene tend to move more freely and distribute evenly, between the different environmental compartments and as a result they do no persist in the environment for long period of time.