the physical pathways of contamination. MST methods provided information on whether the source was likely of human or nonhuman origin only; however, MST did not provide information on the pathways of contamination.

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Situated in two major physiographic provinces, the Appalachian Plateaus and the Central Lowland, the basin includes varied topographic and geomorphic features that affect the hydrology. As of 1990, the basin was inhabited by approximately 10.4 million people. Lake effect has a large influence on the temperature and precipitation of the basin, especially along the leeward southeast shore of Lake Erie. Mean annual precipitation generally increases from west to east, ranging from 31.8 inches at Detroit, Mich., to 43.8 inches at Erie, Pa. The rocks that underlie the Lake Erie-Lake St. Clair Basin range in age from Cambrian through Pennsylvanian, but only Silurian through Pennsylvanian rocks are part of the shallow groundwater flow system. The position of the basin on the edge of the Michigan and Appalachian Basins is responsible for the large range in geologic time of the exposed rocks. Rock types range from shales, siltstones, and mudstones to coarse-grained sandstones and conglomerates. Carbonate rocks consisting of limestones, dolomites, and calcareous shales also underlie the basin. All the basin is overlain by Pleistocene deposits till, fine-grained stratified sediments, and coarse-grained stratified sediments most of Wisconsinan age. A system of buried river valleys filled with various lacustrine, alluvial, and coarse glacial deposits is present in the basin. The soils of the Lake Erie-Lake St. Clair Basin consist of two dominant soil orders: Alfisols and Inceptisols. Four other soil orders in the basin (Mollisols, Histisols, Entisols, and Spodosols) are of minor significance, making up less than 8 percent of the total area. The estimated water use for the Lake Erie-Lake St. Clair Basin for 1990 was 10,649 Mgal/d (million gallons per day). Power generation accounted for about 77 percent of total water withdrawals for the basin, whereas agriculture accounted for the least water-use withdrawals, at an estimated 38 Mgal/d. About 98 percent of the total water used in the basin was drawn from surface water; the remaining 2 percent was from ground water. Agricultural and urban land are the predominant land covers in the basin. Agriculture makes up approximately 74.7 percent of the total basin area; urban land use accounts for 11.2 percent; forested areas constitute 10.5 percent; and water, wetlands, rangeland, and barren land constitute less than 4.0 percent. The eight principal streams in the basin are the Clinton, Huron, and Raisin Rivers in Michigan, the Maumee, Sandusky, Cuyahoga, and Grand Rivers in Ohio, and Cattaraugus Creek in New York. The Maumee River, the largest stream in the basin, drains 6,609 mi2 and discharges just under 24 percent of the streamflow from the basin into Lake Erie. Combined, the eight principal streams discharge approximately 54 percent of the surface water from the basin to the Lake Erie system per year. Average runoff increases from west to east in the basin. The glacial and recent deposits comprise the unconsolidated aquifers and confining units within the basin. Yields of wells comp...

The occurrence of antibiotics in surface water and groundwater in urban basins has become a topic of increasing interest in recent years. Little is known about the occurrence, fate, or transport of these compounds and the possible health effects in humans and aquatic life. The U.S. Geological Survey, in cooperation with the City of Columbus, Division of Power and Water, did a study to provide a synoptic view of the occurrence of antibiotics in source and finished waters in the upper Scioto River Basin. Water samples were collected seasonally-winter (December 2005), spring (May 2006), summer (August 2006) and fall (October 2006)-at five surface-water sites, one groundwater site, and three water-treatment plants (WTPs). Within the upper Scioto River Basin, sampling at each WTP involved two sampling sites: a source-water intake site and a finished-water site. One or more antibiotics were detected at 11 of the 12 sampling sites. Of the 49 targeted antibiotic compounds, 12 (24 percent) were detected at least one time for a total of 61 detections overall. These compounds were azithromycin, tylosin, erythromycin-H 2 O, erythromycin, roxithromycin, ciprofloxacin, ofloxacin, sulfamethazine, sulfamethoxazole, iso-chlorotetracycline, lincomycin, and trimethoprim. Detection results were at low levels, with an overall median of 0.014 µg/L. Hap Cremean WTP had the fewest detections, with two source-water detections of sulfamethoxazole and azithromycin and no detections in the finished water. Of the total of 61 detections, 31 were in the winter sample run. Sulfamethoxazale and azithromycin detections represent 41 percent of all antibiotic detections. Azithromycin was detected only in the winter sample. Some antibiotics, such as those in the quinoline and tetracycline families, dissipate more quickly in warm water, which may explain why they were detected in the cool months (winter, spring, and fall) and not in the summer. Antibiotic data collected during this study were compared to antibiotic data collected in previous national, regional, and local studies. Many of the same antibiotic compounds detected in the upper Scioto River Basin also were detected in those investigations. Antibiotic group Tetracyclines Sulfonamides and quinolones Macrolides and beta lactams Human-therapy treatment types Atypical pneumonia syndromes Urinary-tract infections Respiratory infections Community-acquired pneumonia Chlamydial infections Respiratory infections Community-acquired pneumonia Strep throat Rickettsial infections Rocky Mountain spotted fever Chronic bronchitis Laryngitis Typhus Gastrointestinal infections Gastroenteritis Sinusitis Q fever Diarrhea Meningitis Lyme disease Bone and skin infections Osteomyelitis Skin infections Impetigo Ehrlichiosis Staph infections Erysipelas Acne Venereal diseases Chlamydial infections Cellulitis Rosacea Middle-ear infections Animal-husbandry treatment types Growth promotion Bacterial infections Growth promotion Disease prevention

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