OCCURRENCE OF ANTIBIOTIC RESIDUALS AND OTHER ORGANIC WASTEWATER COMPOUNDS IN SELECTED STREAMS IN NORTHERN ARKANSAS, 2004

The recent release of reports describing the occurrence of antibiotics and other organic wastewater compounds (OWCs) in streams, including many compounds of emerging environmental concern, has prompted numerous investigations into these emerging contaminants throughout the Nation. These environmentally active compounds are produced widely for the human health and commercial sector, animal agriculture, and veterinary medicine. A study was completed in 2004 by the U.S. Geological Survey, in cooperation with the University of Arkansas and the U.S. Department of Agriculture, to determine the occurrence of antibiotics and other OWCs in selected northern Arkansas streams. Samples were collected in March and April 2004 from 17 stream sites located upstream and downstream from selected wastewater-treatment plant (WWTP) discharges in northwestern Arkansas and at one site considered relatively undeveloped in north-central Arkansas. One site upstream and two sites downstream from the WWTP discharge on Mud Creek were resampled in August 2004. All of the stream sites, except for Spavinaw Creek near Maysville, had detectable concentrations of at least one of the targeted OWCs. In general, a substantially greater number of OWCs was detected at sites located downstream from WWTP discharges. The mean number of detections in sites upstream from WWTP discharges (including the relatively undeveloped site) was 3, while the mean number of detections at sites downstream from WWTP discharges was 13. During the two sampling periods, 42 of the 108 compounds targeted were detected in collected water-quality samples. Only eight of the detected compounds had concentrations greater than 1 microgram per liter and most of the other detected compounds had estimated concentrations that were less than the laboratory reporting limits. The most frequently detected compounds included caffeine, phenol, para-cresol, and acetyl hexamethyl tetrahydro naphthalene.