ELEMENTAL COMPOSITION OF SPECIFIC CONDUCTANCE ASSOCIATED WITH LAND USE AND GEOLOGY IN CENTRAL APPALACHIA

Previous water quality studies conducted in central Appalachia revealed elevated specific conductance (SpC) and pH across the mountainous headwaters, regardless of the underlying geology. In many cases, waters draining clastic rocks and coal-mines are alkaline rather than acidic, especially below valley fills of crushed overburden where calcareous minerals have dissolved and neutralized acidity produced by pyrite oxidation. The goals of this study were to characterize the geochemical composition and concentration of dissolved ions contributing to the SpC and pH of surface water and groundwater sources in the Clinch and Powell River basins, and to correlate these data with land use and geology. We predicted that areas downstream of resource extraction (particularly mining) would show anomalous levels of trace metals versus the undisturbed headwaters where source water geology would dominate. Geographical data and mining permit information were collected from ArcGIS-based maps available through the VA Department of Mines, Minerals, and Energy’s websites and the U.S. Geological Survey’s Streamer program. The 19 clastic and 18 carbonate sites selected through the geographical analysis included springs, streams, valley fills, limestone quarries, national forest, pastureland, and a sawmill Brownfields site. Clastic bedrock sites were underlain by coal-bearing Pennsylvanian-aged sandstones and shales, and carbonate bedrock sites drained lower Cambrian- to middle Ordovician-aged limestones and dolomites.

We visited each site once-to-twice during the Fall (2020) and Winter (2021) field seasons, and collected duplicate samples for metals analysis along with SpC, pH, and temperature measurements. Water samples were filtered to 0.45 µm, transported on ice, and acidified in the lab (< pH 2.0 with 1:1 HNO₃) prior to analysis by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Our results showed that streams draining coal mine-influenced sites had significantly higher concentrations of salinity consisting of sodium, magnesium, and calcium, but that some carbonate sites exhibited comparably high concentrations of sodium and strontium, and significantly higher levels of barium.