Tracing Carbon in Karst Environments in South-Central Kentucky to Identify Changes in Groundwater Dynamic Under Varying Land Uses

In karst landscapes, the source, transport, and fate of carbon is of interest for several reasons, including the determination of carbon storage and release, contaminant transport, geochemical evolution of karst aquifers, global carbon budgeting, and cave evolution. As water moves from the surface to subsurface through the atmosphere, soil, and bedrock of a karst system, carbon isotopes can be used to “fingerprint,” or track, carbon, as well as provide insight to the potential changes and storage of carbon over time. Over a ten-month period, weekly rainfall, soil water (using lysimeters at two different depths), surface well water (shallow and deep), as well as water samples from an interior cave waterfall, were collected from an established cave research site, Crumps Cave, in south-central Kentucky for studying agricultural influences on groundwater dynamics. Samples were filtered, preserved, and analyzed for δCDIC values. Additional geochemical data were collected for each sample in the form of pH, SpC, temperature, and discharge and the amount of precipitation was collected at 10-minute resolution. Beginning March 2016, sampling will begin in and around Mammoth Cave to broaden the regional scale of sampling the karst system under differing conditions. Samples will also be analyzed for δCDIC values. Sample sites will include up stream River Styx spring and downstream Echo River spring, Green River, and a sample in the cave to look at the carbon flux and relationships between the two springs as they flow into the Green River. Comparisons will be made between the Crumps and Mammoth Cave sites to determine changes based on hydrology and landuse in similar hydrogeologic settings, but with varying influences. This information can be combined with other geochemical and hydrologic data to determine the role of carbon in the processes taking place that impact cave formation, groundwater evolution, and contaminant transport (nutrients, etc.).