Contaminants in Appalachian Water Resources Generated by Non-acid-forming Coal-Mining Materials

This chapter summarizes environmental processes causing elevated total dissolved solids (TDS) and associated trace elements in streams influenced by mining in non-acid-forming geologic strata, discusses the spatial distribution of mining impacts on water quality, and describes the contaminants’ biological effects. Appalachian coal mining affects water quality by enabling accelerated mineral weathering and consequent release of dissolved elements; such effects are evident during and after mining. In non-acid-forming geologic systems where calcium-bearing minerals neutralize the acidity produced by pyrite oxidation, mineral weathering results in circumneutral pH or alkaline waters with elevated concentrations of calcium, magnesium, sulfate, and bicarbonate, which are the dominant major ions in Appalachia’s surface-mining-influenced streams. The TDS concentration in streams is proportional to specific conductance (SC), which can be measured in the field. Many mining-influenced streams have SCs >500 µS cm−1 and often exceed 2000 µS cm−1, while streams in unmined forested areas generally have SCs <100 µS cm−1, which is characteristic of natural background conditions. Aquatic macroinvertebrates of pollution-sensitive taxa are adversely affected in streams with elevated SCs. Although many metals may be present at levels below aquatic toxicity thresholds, other elements, especially selenium, impact aquatic organisms through bioaccumulation and consequent toxic effects.