RELATING RECHARGE MECHANISMS TO CHEMICAL CHANGES IN AN UPDIP APPALACHIAN COAL MINE DISCHARGE: A CASE STUDY FROM LAMERT RUN, WEST VIRGINIA

Impaired drainage from active and abandoned mines degrades the water quality of receiving streams and aquifers. Coal mine drainage (CMD) has been studied for decades in Appalachia, but unknowns and uncertainties are still present, including the influence of mine hydrogeology on the outflow chemistry of above-drainage mines. To evaluate the influence of recharge type on above-drainage mine chemistry, samples were collected every two weeks at a CMD outflow treatment system from the Pittsburgh Coal seam in Harrison County, West Virginia. Samples were collected to measure geochemical changes taking place in the mine workings and along the flowpath of the passive treatment system.

Samples were divided into two groups based on the dominant type of recharge entering the mine during sample collection. Direct recharge dominated samples had lower concentrations of hydrolysable cations at the mine outflow, causing the discharge to be both net-acidic and net-alkaline during the study period. Total rare earth element concentrations at the outflow were positively correlated to Fe, Al, and Mn, and negatively correlated to pH and discharge. During both recharge regimes, Fe, Al, Mn, and rare earth elements were removed along the treatment system flowpath. Throughout the study period, 89% of dissolved inorganic carbon in the system was degassed to the atmosphere as CO₂.

This study demonstrates that varied recharge mechanisms can influence the CMD outflow chemistry, with implications in treatment system design, interpretation of routine chemical data, and extrapolation of CO₂ efflux from CMD outflows for large-scale carbon balance studies.