A NATIONAL RECONNAISSANCE OF PHARMACEUTICALS AND OTHER ORGANIC WASTEWATER CONTAMINANTS IN GROUNDWATER

As part of the continued effort to collect baseline information on the environmental occurrence of pharmaceuticals and other organic wastewater contaminants (OWCs) in the Nation’s water resources, the U.S. Geological Survey’s Toxic Substances Hydrology Program collected samples from a network of 47 groundwater sites across 18 states in 2000. These samples were analyzed for 83 OWCs using three research methods developed by the U.S. Geological Survey. Site selection focused on areas suspected to be susceptible to contamination from either animal or human wastewaters (i.e. down gradient of a landfill, unsewered residential development, or animal feedlot). Thus, sites sampled were not necessarily used as a source of drinking water but provide a variety of geohydrologic environments and are associated with potential sources of OWCs. The network consisted of 42 wells, 3 springs, and 2 sumps. The 42 wells have varied uses: observation, domestic and municipal supply, and irrigation. Wells depths ranged from 2.4 to 310.9 meters, with a median well depth of 19.2 meters. The 2 sumps are part of a seepage monitoring system where drainage water is collected from buried perimeter tile lines surrounding earthen basins containing livestock waste. OWCs were detected in approximately 98% of the sites sampled, with 46 of the 83 OWCs being found at least once. The results of this study document that many OWCs have sufficient persistence and mobility to be transported to groundwater in detectable quantities. Future research will be needed to identify those factors that are most important in determining the occurrence and concentrations of OWCs in groundwater.