Date of Award
Master of Science (MS)
Nitrate pollution is a major environment problem facing many agriculturally intensive areas around the world. In the midwestern USA, upstream tributaries to the Mississippi River via the Mackinaw and Illinois rivers, local excess nitrate can create problems with the safety of drinking water. In central Illinois, lakes, which are regulated and designated for use as municipal water supply, can periodically exceed EPA drinking water criteria for nitrogen. Lake Bloomington of the Money Creek watershed is the primary source of water for the City of Bloomington, whereas Evergreen Lake of the Six Mile Creek watershed serves as auxiliary supply. Both watersheds are dominated by row crop agriculture, primarily corn and soybean, with the main differences being Lake Bloomington has permanent residencies along the lakeshore that all function on septic waste systems. In this study, we collected 29 low-flow condition samples, taking necessary field parameters, analyzing ion concentrations, and analyzing the samples for δ15N and δ18O of nitrate. The combination of field parameters, ion data, and isotope ratios allows us to attempt identification of contributors of nitrate in this system and make deductions about the evolution of nitrate spatially. Results of this study suggest that contributions may indeed be from manure and septic waste and that denitrification processes were, at least for Evergreen Lake, occurring at the time of sampling. KEYWORDS: nitrate, isotopes, denitrification, septic waste
Andrews, William, "Identifying Unknown Sources of Nitrate in Two Central Illinois Watersheds" (2021). Theses and Dissertations. 1426.