RECONSTRUCTED IMPACTS OF ACID MINE DRAINAGE ON AN INDIANA LAKE USING DIATOM AND GEOCHEMICAL SEDIMENT RECORDS

The primary goal of this research was to analyze the effects of acid mine drainage on Green Valley Mine Pond from the sediment archives by using diatom fossil and geochemical tools to reconstruct the lake’s history records. The Green Valley Coal Mine near Terre Haute, Indiana was active from 1948-1963. John A. Scott Lake was dammed to create a tailing pond for the mining operations. Upon closure of the mine, the Indiana Department of Natural Resources conducted reclamation projects to convert the site into a public recreational area. The USGS Divisions of Reclamation published a report in 2011 stating that acid mine drainage (AMD) is still seeping into the lakes from the previous mining activity. To analyze AMD effects, two sediment cores were taken from the Green Valley site; one core, measuring 37 centimeters, from deeper water in the central part of the lake basin, and another, measuring 39 cm, collected in shallower water near where AMD seeps into the lake. The sediment cores were sub-sampled at a 0.5-cm resolution to analyze diatom assemblages, phosphorus concentrations, and metal concentrations. Diatom and geochemical data together indicate a significant change occurring in the lake environment in the upper third of the core. In this interval, the dominant planktonic diatom species, Aulacoseira ambigua, shifts to Stephanodiscus minutulus. Simultaneously the most substantial phosphorus phase buried in the sediment (mineral-detrital) shifts to Fe-bound phosphorus. These changes likely signify a response driven by addition of AMD. The AMD modified the availability and cycling of nutrients, leading to eutrophication of the modern lake system.