Identifying Vadose-Surface Interaction Using Dripwater Chemistry from Diamond Caverns, KY

Spatial and temporal variations in the chemistry of cave dripwaters collected from Diamond Caverns, KY were studied using samples collected approximately every 3 weeks for 13 months. Samples were collected from fifteen sites extending approximately 0.5 miles from the mouth of the cave along, or adjacent to, the tourist trail through the cave. The majority of drips came off the end of a speleothem, and drip length varied from inches to feet. During collection, CO2 levels, temperature, rate of flow (drips/minute), and time were recorded at each site. Water samples accumulated in fixed positions below drips until a minimum of 300 mL was collected. After collection, samples were titrated for alkalinity, and 50 mL of each sample was preserved for analysis. All samples were analyzed at the ERTL facility at the University of Kentucky, using OES-ICP-MS. The suite of elements analyzed included Ca, Mg, K, Na, Ba, Sr, Mn, Fe, Ni, Co, Cu, Si, Al, and Zn. Goals for the project included establishing a base composition for dripwaters from the Caverns, identifying outlier compositions, and comparing these data to both external (above-ground) and cave interior environmental variables. Spatial parameters included CO2 levels and electrical conductivity, potential groundwater flow paths, and external environmental conditions (e.g. proximity to paved and agricultural areas). A detailed cave survey facilitated the comparison of surface features to sampled sites below. Temporal parameters included seasonal fluctuations (e.g. precipitation, temperature) and the impacts of seasonal tourism on the cave environment. Certain elemental abundances (e.g. Cu, Cr, Zn, Fe, Al, Na) were correlated to surface sources of anthropogenic contamination, while elemental ratios (e.g. Ca/Mg and Ca/Sr) were used to predict which sites were direct conduits to the surface, and which had more complicated vadose zone plumbing. Geochemical variations were compared to meteorological parameters at nearby Mammoth Cave National Park.