Spatial and temporal patterns of trace metal distribution and ecological risk in a coal-mined central appalachian watershed, USA.

This study examines the spatial distribution of trace metals in the Levisa Fork River and its primary tributaries across Buchanan County, Virginia, and Pike County, Kentucky, USA, where extensive historical and ongoing coal mining may influence watershed geochemistry and environmental health. To evaluate potential exposure pathways, we analyzed 31 surface sediment samples, 2 sediment cores, 33 surface water samples, and 1 groundwater sample for As, Al, Cr, Cd, Cu, Fe, Li, Mg, Mn, Ni, Pb, and Zn using ICP-OES. Analytical calibration produced R2 values of 0.998 to 1.000 for all elements, indicating high analytical reliability. Environmental DNA (eDNA) water sampling was also used to assess aquatic biodiversity.Surface water trace metal concentrations were generally low to moderate, whereas the single groundwater sample showed elevated concentrations of As (5.44 µg/L), Mn (1,319.23 µg/L), and Pb (11.31 µg/L). Mn levels were in exceedance of the USEPA (United States Environmental Protection Agency) 2004 lifetime health advisory while Pb levels were in exceedance of USEPA MCL drinking water criteria. These findings warrant further investigation to determine potential risk for residents relying on well water. Sediment concentrations often exceeded USEPA Regional Screen Levels (RSL) especially with regard to As, Cd, Li and Mn. Sediment analyses showed widespread enrichment across all measured elements, with enrichment factors ranging from 1.85 to 48.37. Spatial analyses identified enrichment hotspots for As, Cd, Cu, Mg, Ni, and Zn at downstream meander point bars and near Grundy, Virginia. Although only one site exceeded the Potential Ecological Risk Index (PERI) threshold of 150 for total ecological risk, Cd (22.39-148.41) and As (24.05-94.62) frequently exceeded the moderate risk of 80, warranting continued monitoring. eDNA results indicated spatial variation in aquatic biodiversity, including salamander indicator species and two species of conservation concern in Virginia. Together, these findings suggest that anthropogenic redistribution of trace metals is occurring within the watershed. Future investigations should determine if this redistribution is contributing to elevated environmental and public health risk within the watershed.