CO2 AND INORGANIC CARBON FLUXES FROM MINE WATERS IN WEST VIRGINIA AND PENNSYLVANIA

Historic coal mining in West Virginia and Pennsylvania has resulted in metal and acidity contamination in streams of both states. Depending on the associated geologic strata, the discharge chemistry varies widely. If carbonate units are present, the mine may discharge dissolved inorganic carbon (DIC) in the form of CO₂ and HCO₃^-. Previous studies have quantified the flux of CO₂ and determined that degassing is an important part of the remediation process by increasing the pH and causing metal precipitation. In this project, we quantify the DIC discharge from six different abandoned coal mines. The objective of this study is to determine the variations in flux of CO₂ and DIC spatially and temporally. They were selected to provide a range of geologic settings and CO₂ concentrations. CO₂ is measured with an Anton Paar CarboQC carbonation meter; DIC concentrations are determined by adding a citric acid buffer to the solution and then measuring CO₂ concentration, pH, and temperature. Coincident data are collected for pH, temperature, specific conductivity, and discharge. Preliminary data from April-July 2017 document a pH range from 2.8 to 6.5, specific conductivity from 646 to 2,257 µS/cm, and discharge from 0.22 to 5.7 L/s. Measured concentrations of CO₂ range from <0.001 g-C/L to 0.04 g-C/L; total DIC concentrations range from <0.05 g-C/L to 6.5 g-C/L. The maximum CO₂ flux was 84 kg-C/d and the maximum DIC flux was 293 kg-C/d. Based on these preliminary results, the variation in flux is controlled by changes in discharge more than by changes in CO₂ concentration. The CO₂ concentrations and fluxes are comparable to other values reported for regional mine sites.