GEOCHEMICAL ENVIRONMENT OF THE STIRLING MINE AND BIG MINE RUN DISCHARGES IN THE WESTERN MIDDLE ANTHRACITE FIELD, PENNSYLVANIA

Stirling Discharge and Big Mine Run are both located in the Western Middle Anthracite field of Pennsylvania. Both discharges smell of sulfur and rocks in the streams are coated with yellow/orange precipitates (yellow boy). Samples were collected from several stations along each discharge on October 18, 2006, with six replicates per station. Three replicates were acidified and all were transported back to the lab on ice. Sediments were collected at selected stations for analysis using a Scanning Electron Microscope with Energy Dispersive X-ray Spectrometer (EDS). The physical parameters pH, dissolved oxygen (DO), Oxidation Reduction Potential (ORP), conductivity, and flow rate were measured in situ. Alkalinity, acidity, dissolved sulfate, and dissolved metals (Fe, Mn, Pb) were measured in the laboratory. Stirling discharge is hypoxic (DO ~ 1.0 mg/L) with a pH near neutral (~6.0). On the day of the study it had an average flow rate of ~0.36 m/s, mean temperature of 13.7 °C, ORP of 890.3 mV, and conductivity of 393.5 µS. Big Mine Run is oxic (DO ~ 7.2 mg/L) with an acidic pH (~4.5). Average flow rate on the day of sampling was ~0.42 m/s and mean temperature was 12.8 °C, ORP was 525.0 mV, and conductivity was 193.0 µS. SEM images of the yellow boy precipitate for both streams featured small round structures typical of the types formed by many of the iron oxidizing micro-organisms. Twisted stalks indicative of Gallionella, one iron precipitating micro-organism, were found only at Stirling Discharge. Precipitates from all stations analyzed with EDS contained C, O, Fe, Si, and Al.