Abstract

Karst aquifers are highly susceptible to contamination because of the connection with surface water.  Nitrate contamination is common; with most karst aquifers exhibiting some degree of impact.  Horn Hollow Valley (HHV) in Carter County Kentucky is a karst aquifer system that appears to be minimally impacted by nitrate and chloride contamination.  Sampling of the HHV area was conducted from June 2005 to November 2006.  Nitrate as nitrogen (NO₃-N) concentrations were between 0.13 to 1.54 mg/L; chloride concentrations ranged from 1.43 to 66.3 mg/L.  Impact from anthropogenic sources are observed at 1 mg/L for NO₃-N and 13 mg/L for chloride.  Sources of nitrate are primarily soil organic matter and mineralized fertilizers.  In addition to mineralized fertilizers, chloride appears to be contributed from road salts.  Compared to waters from three other systems: the Mammoth Cave area, the southwestern Illinois sinkhole plain, and the Missouri Ozarks-Salem Plateau; waters from HHV exhibited lower concentrations of both NO₃-Nand chloride.  Waters from Mammoth Cave and the Missouri Ozarks tended to have higher NO₃-N concentrations and similar chloride concentrations.  Waters from southwestern Illinois had higher NO₃-N concentrations and chloride concentrations.  Overall, the karst aquifer of HHV appears to be a relatively pristine system, with minor human impacts.

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