PRIORITIZATION OF GROUND-WATER CONTAMINANTS AND SOURCES

The objective of this research was to identify chemical, physical, bac teriological, and viral contaminants, and their sources, which present the greatest health threat in public ground water supplies in the USA ; and to classify (prioritize) such contaminants and relative to their health concerns. The developed contaminant prioritization methodology was based on frequency of occurrence and adverse health effects. Adve rse health effects were based on carcinogenic potency, toxicity, hazar dous chemical priorities and drinking water standards. Application of the methodology for wellhead protection areas, (WHPAs) revealed that a pproximately 200 different contaminants have been detected in the nati on's public ground water supplies. The seven chemical constituents wit h the highest priority were arsenic, chromium, cadmium, carbon tetrach loride, chloroform, 1,1-dichloroethylene, and ethylene dibromide. Othe r contaminants of concern were trichloroethylene, nitrates, barium, 1, 1,1-trichloroethane, benzene, tetrachloroethylene, selenium, lead, tol uene, mercury, gross alpha radiation, methylene chloride, coliform bac teria, metolachlor, metribuzin, 1,1,2,2-tetrachloroethane, dibromochlo roethane, simazine, radium-266, and toxaphene. The contaminant source prioritization methodology was also based on frequency of occurrence. Over 30 categories of sources were evaluated, with the eight with high est priority including agricultural activities, hazardous waste sites, landfills, industrial operations, septic tank systems, oil and gas fi eld activities, urban land use, and underground storage tanks.