Dissolved Pesticides in Weekly Water Samples from the NAWQA Regional Stream Quality Assessments (2013-2017)

Dissolved pesticides were measured in weekly water samples from 482 wadeable streams in five regions of the United States during 2013-2017, as part of the U.S. Geological Survey's (USGS) Regional Stream Quality Assessment (RSQA). One study was conducted each year, starting with the Midwest (2013), followed by the Southeast Piedmont (2014), Pacific Northwest (2015), Northeast (2016), and Central California Coast (2017). Within each region, 77-100 streams were sampled over 6-14 weeks, followed by ecological surveys of fish, invertebrate and fish communities. The first study (Midwest) is an agricultural-gradient study, where the majority of sites were located along a gradient from undeveloped to 100% agricultural land within the watershed, and a smaller number of sites were sampled to represent urban and mixed land uses within the region. The last four studies were urban-gradient studies, where the majority of sites were located along a gradient from undeveloped to highly urbanized, and a smaller number of sites were sampled to represent agricultural and mixed land uses characteristic of the region. Weekly water samples were analyzed for 225 pesticide compounds by direct aqueous injection liquid chromatography with tandem mass spectrometry (LC-MS/MS) at the USGS National Water Quality Laboratory (NWQL) in Denver, CO. Potential for pesticides to cause aquatic toxicity in the sampled streams was predicted by comparing measured dissolved pesticide concentrations with aquatic-life benchmarks, the Pesticide Toxicity Index, and species sensitivity distributions. This Data Release is issued in support of future publications by the RSQA Project, and it provides sampling site locations, pesticide analyte information, summaries of quality-control data, and concentration data for pesticide compounds in environmental weekly water samples.