This research was initiated to develop environmental exposure assessment procedures that can be used to predict the pathways of potentially harmful chemicals in freshwater environments. The approach is based on three premises: (1) the overall rate of disappearance of a chemical from the aquatic environment is controlled only by the dominant transformation and transport processes, (2) these processes can be studied independently in the laboratory, and (3) the laboratory data can be extrapolated to environmental conditions. Laboratory procedures have been developed for measuring the rates of volatilization, photolysis, oxidation, hydrolysis, and biotransformation as well as the sorption partition coefficients on natural sediments and on a mixture of four bacteria. Two models have been used to extrapolate the laboratory results to the environment. The one-compartment model assumes that the aquatic system is a single well-mixed reactor from which chemicals are transformed, degraded, and/or transported. It can be used to analyze acute discharges such as spills and to establish priorities for in-depth laboratory studies. The nine-compartment computer model is used to study the effect of transport and transformation processes studied in the laboratory on the distribution of a chemical in ponds, streams, and eutrophic and oligotrophic lakes. Part II of this report describes the application of these procedures to environmental assessment to the distribution and fate of eleven organic compounds.

"Prepared for Environmental Research Lab, Athens, Ga."--Cover. "October 1977." "1NE625"--Technical report data. "EPA/600/01"--Technical report data. Includes bibliographical references.