ANTHROPOGENIC NUTRIENT TRANSFER WITHIN AN EPIGENIC KARST AQUIFER IN SOUTH-CENTRAL KENTUCKY

The recent proliferation of Confined Animal Feeding Operations (CAFOs) on karst landscapes has been controversial. In epigenic karst aquifers that have strong hydrological connections with meteoric recharge from the surface, scientific understanding of nutrient transfer patterns is still limited. In this study, we monitored major ions, nutrients, and physical data were at major karst spring in south-central Kentucky over a period of 9 months in 2015. This research comprises two objectives: 1) to assess the connectivity between point sources of anthropogenic contamination (e.g., septic systems and CAFOs) and underground stream, and 2) to determine fate and travel time of nutrients within the cave system.

This study combines the analysis of long-term physical data (including precipitation, spring discharge, water temperature, and specific conductivity) with an analysis of nutrient dynamics (dissolved organic matter, total phycocyanin) at the scale of storm events. A second focus is the concentrations and daily loads of nutrients (nitrogen species and phosphate) and dissolved organic carbon (DOC), and specific UV absorption (SUVA) from discrete sampling during summer 2015. Nutrient concentrations are elevated as expected. Nitrate exceeds established background concentrations of 2 mg/L and was more dilute during storm events. Phosphate exceeds the EPA recommendation of 0.1 mg/L with higher concentrations during storms due to the mobilization of sediment substrates. Dissolved organic carbon (DOC) concentrations spiked during storm events and, combined with values of SUVA, suggest the rapid transfer of organic matter from the surface with limited degradation, a hypothesis supported by cross-correlation analysis between precipitation and of spring conductivity data which infers that surface inputs are transferred within the aquifer in 2 to 5 hours.