Prioritization of ground water contaminants and sources

The objective of this research was to identify chemical, physical, bacteriological, 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. Adverse health effects were based on carcinogenic potency, toxicity, hazardous chemical priorities and drinking water standards. Application of the methodology for wellhead protection areas, (WHPAs) revealed that approximately 200 different contaminants have been detected in the nation's public ground water supplies. The seven chemical constituents with the highest priority were arsenic, chromium, cadmium, carbon tetrachloride, chloroform, 1,1-dichloroethylene, and ethylene dibromide. Other contaminants of concern were trichloroethylene, nitrates, barium, 1,1,1-trichloroethane, benzene, tetrachloroethylene, selenium, lead, toluene, mercury, gross alpha radiation, methylene chloride, coliform bacteria, metolachlor, metribuzin, 1,1,2,2-tetrachloroethane, dibromochloroethane, 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 highest priority including agricultural activities, hazardous waste sites, landfills, industrial operations, septic tank systems, oil and gas field activities, urban land use, and underground storage tanks.