Origin and Scope of Hexavalent Chromium in North Carolina Groundwater

Abstract

Potential groundwater contamination from coal ash ponds is a current public health concern in North Carolina. One of the suspected contaminants is chromium, particularly the toxic hexavalent chromium form. A recent study on chromium in groundwater from the Piedmont Aquifers of NC finds that chromium is more prevalent than previously thought due to geogenic sources from water-rock interactions in naturally enriched ultramafic rock formations. To expand on the prior work, this project generates a dataset of domestic, community, and monitoring wells across the mountain, Piedmont, and coastal regions of NC to investigate the scope and origin of hexavalent chromium in groundwater. Geospatial and statistical analyses show increasing hexavalent and total chromium concentrations as aquifer lithology characterization by mafic material increases non-mafic formations to major mafic formations. Correlation tests show a strong, positive correlation between hexavalent and total chromium concentrations in groundwater. These new results support previous findings and provide additional evidence that hexavalent chromium is the predominant species of total dissolved chromium, and that groundwater in aquifers with lithology containing mafic constituents will have elevated levels of chromium when compared to aquifers in non-mafic lithology.