Chemical and isotopic data for a study of seasonality of nitrate sources and isotopic composition in the Upper Illinois River, 2004-2008

This data release contains chemical and isotopic data used in an investigation of nitrate sources and transport in the Upper Illinois River basin. Samples (total = 445) include river water from the Upper Illinois River and its major tributaries plus urban wastewater and agricultural groundwater. Data include concentrations of nitrate, chloride, and sulfate; isotope ratios of N and O in nitrate; and isotope ratios of H and O in water.