Water Resources Research Act Program

Details for Project ID KY_2023_Erhardt

Understanding nitrate pollution sources during flooding events in Kentucky

Institute: Kentucky
Year Established: 2023 Start Date: 2023-09-01 End Date: 2024-08-31
Total Federal Funds: $20,000 Total Non-Federal Funds: $20,000

Principal Investigators: Andrea Erhardt

Project Summary: This project will use geochemical tools to isolate the role of flooding events on nitrate contamination in Kentucky. Multiple watersheds across the state are identified as priorities for nutrient reduction. Nitrate pollution is predominantly from fertilizer application to farm fields, though some nitrate pollution may originate directly from rainfall. Understanding these different sources will aid in identifying the highest-priority regions for nutrient management. This study will investigate nitrate pollution at two sites, one in the Inner Bluegrass and one in Eastern Kentucky. These sites differ in their presumed contribution from fertilizer-sourced nitrate, allowing us to test isotope tools for source identification. The tool we’re using for this source distinction is isotope ratios of the nitrogen and oxygen in nitrate. Each element can be present in different masses, i.e. oxygen with a mass of 16 or a mass of 18. Stable isotope geochemistry uses the differences between how each of these masses behaves in chemical reactions to trace different sources and are reported as a ratio of the two different masses. Since nitrate from fertilizer and nitrate in precipitation have different isotope ratios, the total isotope value can tell us how much each source contributed to the system. In this study, we hope to use new isotope techniques to better constrain the nitrate sources in regions with both high and low fertilizer contributions. We hope to understand how large flooding events transport nitrate and which source dominates during a range of flow conditions.