ANTHROPOGENIC NUTRIENT LOADING ON EPIGENIC KARST AQUIFER IN SOUTHEASTERN KENTUCKY

The proliferation of Confined Animal Feeding Operations (CAFOs) in karst terrains is a controversial issue. Although some studies have assessed the contamination risk of CAFOs in karst aquifers, little actual data have been published. This study looks at the loading of nutrients, including dissolved organic matter (DOM), nitrogen species (NH₃, NO₂, NO₃), and reactive phosphate (PO₄) from weekly samples collected May through August 2015 at Grayson-Gunnar Cave (GGC), an 11-km-long cave system in Southeastern Kentucky. Surveyed passages in GGC include two branches of an underground stream with strong connections to surface input—an epigenic karst aquifer. The south branch of this watershed includes low-density grazing and residential septic tanks. The north branch includes a poultry CAFO.

Weekly water samples were collected at the cave spring; three samples were also collected from each of the two branches of the cave stream. Analysis of NH₃, NO₂, NO₃, and PO₄ were conducted on these discrete samples using a HACH DR2800 spectrophotometer. Contemporaneous data form the cave stream were collected every 10 minutes using a YSI EXO2 sonde and include water level, temperature, physical chemistry, turbidity, total phycocyanin, and DOM.

From the discrete samples, nutrient flux and potential nutrient sources were computed using a mixing model. From the sonde data, we elucidate aquifer behavior during storm events by looking at key indicators of meteoric water input from sinking streams (e.g., conductivity, turbidity, and DOM) and conducting auto-correlation and cross-correlation analyses to assess the ‘lag’ times between input and output. Preliminary data from discrete samples reveal PO₄ and NO₂+NO₃ levels consistently above the recommended EPA concentration of 0.1 mg/L and 1.0 mg/L, respectively. The sonde data reveal twin peaks in water chemistry that consistently occur following precipitation events, likely the result of merging flowpaths from two sub-watersheds.