Contrasting Contaminant Occurrence in Urban and Agricultural Streams in the Midwestern and Southeastern United States

Abstract:

Streams in urban and agricultural settings are known to have many anthropogenic chemical stressors; however, there are important differences in the occurrence of pesticides, metals, legacy contaminants, combustion byproducts, and contaminants of emerging concern between the two settings. In 2013 and 2014, the U.S. Geological Survey characterized water-quality stressors and ecological conditions in 100 streams in the Midwestern U.S. and 115 streams in the southeastern U.S., respectively. Water samples were collected weekly for 10-12 weeks during spring and early summer. Habitat, sediment chemistry, and ecological communities were sampled once at the end of the water-sampling period. Water and(or) sediment samples were analyzed for pesticides, nutrients, wastewater indicator compounds, polycyclic aromatic hydrocarbons, halogenated compounds, metals, volatile organic compounds, and pharmaceuticals. The spatial and temporal distribution of detected compounds and health-based-benchmark-normalized summations of compound mixtures indicate important differences between agricultural and urban settings. In general, urban streams are affected by more complex chemical mixtures than agricultural streams. Although higher herbicide and nutrient concentrations generally are found in agricultural settings, the more frequent occurrence of insecticides, hydrocarbons, halogenated compounds, and metals in urban settings indicates higher potential toxicity in urban streams than in agricultural streams. The effects of these complex mixtures and other stressors are being evaluated in relation to stream ecological communities at the regional scale.