CONCENTRATIONS OF ORGANIC CARBON AND NITROGEN OF UNSATURATED CLASTIC SEDIMENTS FROM BUTLER CAVE, VIRGINIA USA

The distribution and concentration of natural organic matter, and its control in the fate and transport of organic contaminants, has been largely ignored in karst aquifers. Clastic cave sediments, poorly studied in comparison with cave waters, biota and chemical precipitates, can store organic matter and play a critical role in long-term contaminant behaviors. Organic chemicals have the potential to sorb on to natural organic matter in sediments. Increasing amounts of total organic carbon (TOC) in sediments can lead to more sorption of organic contaminants resulting in storage and retardation of contaminants in the aquifer. To understand how organic contaminants interact with cave sediments, a robust knowledge of the TOC content of these sediments must be obtained. In this study, core and grab samples of sediment were collected from unsaturated areas of Butler Cave, VA, USA (a cave typical of the Valley and Ridge karst of the eastern USA) and analyzed for total carbon, organic carbon, and total nitrogen concentrations. These samples were taken from different depositional facies in the cave system that have been previously described and mapped. The few previous studies that do describe TOC of cave sediments report TOC wt% of clastic cave sediments from 0.0001 – 1, higher than the TOC wt % reported for non-karst sediments (< ~0.01). Preliminary analyses of these data resulted in similar concentrations of TOC wt% of other cave sediments.