Organic wastewater contaminants in the upper Chattahoochee River Basin, Georgia, 1999–2002

Abstract

The U.S. Geological Survey recently de-veloped a laboratory method designed to analyze organic wastewater contaminants (OWCs) typically found in do-mestic and industrial wastewater. As part of five differ-ent studies conducted from 1999 through 2002, 74 water samples were collected at 26 sites in the upper Chatta-hoochee River Basin and analyzed for OWCs. In gen-eral, the number of OWCs detected and the concentra-tions of OWCs measured at various site types decreased from effluent samples, to stream samples collected dur-ing wet-weather conditions, to stream samples collected during baseflow conditions, to drinking-water samples. Although few of the OWCs measured have drinking-water standards or other human or ecological health crite-ria, there were 3 exceedences of the maximum contami-nant level for the insecticide diazinon and 12 exceedences of aquatic-life criteria for the insecticides diazinon, car-baryl, and chlorpyrifos. The total concentration of 13 po-tential endocrine disruptors measured as part of the OWC method exceeded 1 microgram per liter in most samples collected from treated effluent and from tributary streams during wet-weather conditions. Little is known, however, about the potential health effects to humans or aquatic organisms exposed to low levels of most of these chemi-cals, or more importantly, to mixtures of these chemicals. Several patterns in the number and relative concen-trations of OWCs detected among the various site types indicate the potential to use OWCs to identify the likely presence or absence of wastewater in specific samples or sites at various flow conditions. For example, detec-tion frequencies and relative concentrations of some OWCs, such as several plasticizers and (or) fire retar-dants and detergent metabolites, at various sites and flow conditions may help locate sources of wastewater to streams upstream from sampling locations.