EFFECTS OF ACID MINE DRAINAGE ON AQUEOUS GEOCHEMISTRY OF BIG MINE RUN AND MAHANOY CREEK IN EAST-CENTRAL PENNSYLVANIA: A DOWNSTREAM EVALUATION

Geochemical alterations in water exposed to acid mine drainage (AMD) can degrade aquatic ecosystems and impair uses of downstream water. The Centralia Mine Drainage Tunnel, opened to drain a portion of an underground mine pool and improve the economic feasibility of coal mining in the Centralia, PA, region, now drains 3.3 million gallons of AMD into Big Mine Run stream. Big Mine Run flows into Mahanoy Creek, a tributary of the Susquehanna River. Acid mine drainage has low pH and elevated concentrations of dissolved sulfate, iron, aluminum, and other trace metals – due to the oxidation of pyrite and the dissolution of carbonate, oxide, and aluminosilicate minerals. Previous research, conducted by the USGS in 2001, measured pH values ranging from 4.0 – 8.4 and alkalinity values ranging from -11 to 108 ppm for Mahanoy Creek. This study is complimentary to the USGS study; pH, conductivity, major ions and trace metals were measured along a transect of Big Mine Run. Preliminary results indicate that the chemistry of Big Mine Run is fairly consistent along the stream length (pH = 3.8 to 3.7 and conductivity = 1114 to 1160 uS/cm). The major ion chemistry was dominated by sulfate and magnesium. Iron oxide-rich flocculent material, primarily composed of schwertmannite, ferrihydrite, and goethite, precipitates in low-flow zones of Big Mine Run and may contain precipitated heavy metals. Through seasonal sampling campaigns, this project will investigate how the aqueous geochemistry of Big Mine Run and Mahanoy Creek, a system that has not been studied since 2001, alter with an increase of distance from the targeted AMD source, the Centralia Mine Pool. Results will provide reference for apparent changes in aqueous geochemistry of Mahanoy Creek over the past 15 years.