Supporting Data: Complex Mixtures of Pesticides in Midwest U.S. Streams Indicated by POCIS Time-Integrating Samplers

The Midwest United States is an intensely agricultural region where pesticides in streams pose risks to aquatic biota, but temporal variability in pesticide concentrations makes characterization of their exposure to organisms challenging. To compensate for the effects of temporal variability, we deployed polar organic chemical integrative samplers (POCIS) in 100 small streams across the Midwest for about 5 weeks during summer 2013 and analyzed the extracts for 227 pesticide compounds. Analysis of water samples collected weekly for pesticides during POCIS deployment allowed for comparison of POCIS results with periodic water-sampling results. The median number of pesticides detected in POCIS extracts was 62, and 141 compounds were detected at least once, indicating a high level of pesticide contamination of streams in the region. Sixty-five of the 141 compounds detected were pesticide degradates. Mean water concentrations estimated using published POCIS sampling rates strongly correlated with means of water concentrations measured weekly, however, the POCIS-estimated concentrations generally were lower than the measured water concentrations. Summed herbicide concentrations (units of ng/POCIS) were greater at agricultural sites than at urban sites and summed concentrations of insecticides and fungicides were greater at the urban sites. Consistent with these differences, summed concentrations of herbicides correlate to percent cultivated crops in the watersheds and those of insecticides and fungicides correlate to percent urban land use. With the exception of malathion concentrations at nine sites, POCIS-estimated water concentrations were lower than aquatic-life benchmarks. The POCIS provide an alternative approach to traditional water sampling for characterizing chronic exposure to pesticides in streams across the Midwest region.
This data release provides tables presenting a) deployment-time-normalized concentrations of pesticides in POCIS extracts, and b) estimated water concentrations for 52 pesticides based on; concentrations in POCIS extracts, chemical-specific sampling rates, and mean concentrations in water samples collected during POCIS deployment.