GEOCHEMISTRY OF MINE POOL DISCHARGES IN THE PITTSBURGH COAL BASIN

Seventy-two mine water discharges from flooded underground mines of the Pittsburgh coal bed were sampled for chemistry during 2012. Statistical techniques including correlation, principal component analysis (PCA), and cluster analysis (CA) were utilized to evaluate geochemical relationships.

The distributions of most solute concentrations are non-parametric. Strong correlations were observed between constituents of pyrite and carbonate dissolution (Fe, SO₄, Ca, Mg) as well as Na, Sr, and K. Several waters with high scores on PC1 are moderately saline with average concentrations of Na (1199 mg/L), Cl (350 mg/L), Br (1.69 mg/L), and Sr (4.13 mg/L). Waters with highly negative scores on PC2 are acidic with maximum concentrations of Fe³⁺ (35.3mg/L) and Al (23.3 mg/L) and discharge from shallow mines along the eastern margin of the coal subcrop. Waters with highly positive scores on PC2 are alkaline waters from deep, fully flooded mines with pH (6.3) and alkalinity (876 mg/L). PC3 has high scores primarily due to elevated Ba.

Pittsburgh coal bed waters display, on average, SO4 (923 mg/L), Na (267 mg/L), alkalinity (226 mg/L as CaCO3), Ca (245 mg/L), Cl (100 mg/L), and Fe (45 mg/L) with traces of brine constituents. Diagnostic variations in concentrations of Ba, Br, Sr, Cl, and Al reveal spatial trends and partitioning into six clusters.