GEOCHEMISTRY OF FOUR ACID MINE DRAINAGE SITES IN THE MIDDLE ANTHRACITE REGION OF EASTERN PENNSYLVANIA

This study is part of a larger project to characterize the different iron-precipitating microbes at four acid mine drainage (AMD) sites within the middle anthracite field in eastern Pennsylvania. Although the sample sites are geographically close to one another, each discharge is fed by a different mine pool. It is anticipated that the differing geochemistry associated with each pool and associated discharge will give rise to different populations of microbes. Samples were taken from Big Mine Run (BMR) near Ashland, PA, which is fed by discharge from the Centralia pool via the Centralia Tunnel; Sterling Discharge (SD) near Shamokin, PA, fed by discharge from the Henry Clay/Sterling pool; and the Scarlift Site 15 (SL) AMD treatment system (one sample above the system and one below) near Ranshaw, PA, constructed to treat drainage from the Corbin Mine Pool. Scarlift Site 15 has a gravity fed vertical flow wetland (VFW) treatment system designed to remove iron, aluminum, and sulfate from the AMD. Measurements of pH, dissolved oxygen (DO), oxidation-reduction potential (ORP), and conductivity were collected in situ at each site, and samples collected for analysis of alkalinity and acidity immediately upon return to the lab, where subsamples were preserved for later analysis of selected metals, simple cations, and anions. Results indicated that each site was geochemically unique. A comparison of results between the SL1 and SL2 sites showed that the levels of dissolved aluminum and iron were reduced while the pH and alkalinity of the water moving through the VFW system increased, indicating that the treatment facility is working. The BMR sample had the lowest pH of 4.38 and highest DO. That sample was taken not at the tunnel exit but near the road after the water cascaded over the rocky streambed, allowing for extensive aeration. Although iron concentrations were relatively low at BMR when compared to the other sites, BMR had the highest concentrations of dissolved Al, Mn, Ni and Zn. The SD and SL1 samples had roughly comparable amounts of dissolved metals; although SD had a higher pH of 6.12, whereas SL1 had a pH of 4.46. Genetic material has been extracted from sediment samples collected at each site and the DNA sequenced, providing percentages of different species of microbes in each sample. Microbial population analysis is underway.