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Paper No. 218-12
Presentation Time: 9:00 AM-6:30 PM
TRACING CARBON IN KARST ENVIRONMENTS TO INVESTIGATE THE GEOCHEMICAL EVOLUTION PROCESSES OF KARST AQUIFERS
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 changes in karst processes (evolution of caves). 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 in south-central Kentucky for studying groundwater dynamics and agricultural impacts. Samples were filtered, preserved, and analyzed for δ13CDIC values. Additional geochemical data were collected for each sample in the form of pH, SpC, and temperature and discharge and amount of precipitation were collected at 10-minute resolution. These data were analyzed to establish the sources of carbon and its movement through the epikarst groundwater system over varying seasons and during storm events, which helped to determine the major sources of carbon (soil, rock, etc.) and its flux through the karst system to aid in quantifying the contributions from different fractions. 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.) that are influenced by carbon. From these data, additional information will be gleaned on how carbon removed through the carbonate rock dissolution process can be quantified and sourced to provide a better accounting of large-scale carbon dynamics.