Pollution characteristics, pollution sources and driving factors of hexavalent chromium in groundwater: A case study in Xianyang region, China.

Hexavalent chromium (Cr(VI)) is a recognized carcinogen that poses significant risks to public health. The Xianyang area in China is characterized by groundwater Cr(VI) pollution. In this study, a coupled framework was developed by incorporating hydrochemical method, geo-statistical analysis, correlation analysis, principal component analysis (PCA), positive matrix factorization (PMF) and the geo-detector model to identify pollution characteristics, pollution sources and associated driving factor of Cr(VI) in groundwater. The results indicate that groundwater is primarily characterized by HCO-Ca·Mg and HCO-Na types, while high Cr(VI) samples are mainly associated with SO·Cl-Na and HCO-Na types. Cr(VI) concentrations are higher in unconfined groundwater (average: 48.7 μg/L) than in confined groundwater (average: 40.9 μg/L). Multivariate statistical analysis indicates that Cr(VI) primarily originates from rock weathering and anthropogenic inputs. The geo-detector analysis further suggests that natural factors contribute 83.2% to the high Cr(VI) in unconfined groundwater, with pH (26%) and mean annual precipitation (22.7%) being the key environmental variables influencing the spatial variability of Cr(VI). The Cr(VI) pollution is influenced by dual-factor combinations, with the combinations between mean annual precipitation and pH (0.378), as well as Eh and pH (0.373), being the most significant factors affecting Cr(VI) distribution. The geo-detector analysis also reveals the contribution of traffic-related factors and industrial activities to Cr(VI) contamination. The study results improve the understanding of Cr(VI) pollution characteristics in the region and provide a reliable framework for identifying the sources and drivers of high-risk pollutants.