During 2001, 76 water samples were collected upstream and downstream of select towns and cities in Iowa during high-, normal-, and low-flow conditions to determine the contribution of urban centers to concentrations of emerging contaminants in streams under varying flow conditions. The towns ranged in population from about 2,000 to 200,000. Overall, one or more targeted contaminants were detected in 98.7% of the samples collected, with 62 of the 105 compounds being found. The most frequently detected compounds were metolachlor (pesticide), cholesterol (plant and animal sterol), caffeine (stimulant), b -sitosterol (plant sterol), and 1,7-dimethylxanthine (caffeine degradate). The number of contaminants detected decreased as streamflow increased from low- (51 compounds detected) to normal- (28) to high-flow (24) conditions. Antibiotics and other prescription drugs were only frequently detected during low-flow conditions. During low-flow conditions, 15 compounds (out of the 23) and ten compound groups (out of 11) detected in more than 10% of the streams sampled had significantly greater concentrations in samples collected downstream than in those collected upstream of the urban centers. Conversely, no significant differences in the concentrations were found during high-flow conditions. Thus, the urban contribution of emerging contaminants to streams became progressively muted as streamflow increased. This research was conducted in collaboration with the Iowa Geological Survey. See http://ia.water.usgs.gov/owcs/home.html for more information on the sampling sites.
Kolpin, D.W., Skopec, M., Meyer, M.T., Furlong, E.T., and Zaugg, S.D., 2004, Urban contribution of pharmaceuticals and other organic wastewater contaminants to streams during differing flow conditions: Science of the Total Environment, v. 328, no. 1-3, p. 119-130.
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