Using Chemical Fingerprinting to Analyze Stormwater Runoff Patterns in McClure's Bog, North Carolina

Abby Sgan, Jeff Wilcox

asgan@unca.edu

ENVIRONMENTAL STUDIES

McClure’s Bog, a Southern Appalachian wetland located in Henderson County, North Carolina, has undergone extensive hydrologic remediation efforts since the mid-1990s. McClure’s is located downstream from a livestock farm, a source of runoff and excess nutrients that threatens fragile populations of federally protected pitcher plants. To combat this, engineers rerouted runoff around the bog’s central area and constructed three water retention cells that serve to collect rerouted runoff during major storm events. This project compared chemical signatures, or “fingerprints”, of agricultural runoff to signatures of well and pond water samples in order to analyze patterns of runoff movement throughout the bog. We used ion chromatography to identify major ion concentrations (sodium, potassium, magnesium, calcium, chloride, nitrate, and sulfate), and used alkalinity titrations to determine bicarbonate concentrations. These chemical markers were analyzed in eighteen water samples collected from twelve sampling locations across three dates from late 2023 to early 2024. The samples were compared to previous water samples dating back to 2014. We found that runoff exhibited a distinct chemical signature that expresses lower sodium and potassium concentrations than groundwater, and higher magnesium than both precipitation and groundwater. Using these signatures, we identified when and where runoff contaminants affected bog water quality. We concluded that runoff is still infiltrating some groundwater-fed areas despite rerouting, although areas with pitcher plants did not appear to be affected by runoff. Investigation into other sources that could be affecting observed chemical signatures is still needed, however, and could be completed through further study.

May-14-2024