Research Product

A computer program was developed for modeling the fate of toxic chemicals that are discharged to natural water systems. The program permits the user to model the water and sediment transport in a natural water system and the movement and decay of chemicals discharged to that system. Either the equilibrium distribution of chemicals continually discharged to the system or the concentrations in the system as a function of time may be computed. From one to three types of solids may be considered. The reaction of the chemical and its transfer among phases are computed from specified characteristics of the chemical and environmental parameters of the system. The processes considered include photolysis, hydrolysis, biodegradation, volatilization and adsorption. Adsorption to the solids types included in the model is described as a local equilibrium process defined by a partition coefficient and the local solids concentration. All other processes are defined in terms of reaction rates. WASTOX does not explicitly specify each of the transport processes that may affect the chemical or solids. Transport is considered either as an advective process defined by a flow or a mixing process defined by a dispersion or exchange. Specification of separate transport processes is made by the user by defining up to nine sets of flows and dispersions (termed fields). Each field is applied to either dissolved chemical or adsorbed chemical and solids, or both. For example, dispersion within the stationary sediment is limited to dissolved chemical; therefore a field of dispersions would be specified by the user and applied only to this component. The use of such a non-specific transport structure permits construction of models consistent with the understanding of the particular natural water system and the question being addressed. WASTOX is sufficiently general to be applied to all types of natural water systems. It has been successfully applied to the James River Estuary, the Great Lakes, and the U.S. Environmental Protection Agency (EPA) experimental stream channels at Monticello, Minnesota.