Quantitative source apportionment deciphering hydrogeological and anthropogenic contributions to selenium enrichment...

To clarify the mechanisms of selenium (Se) enrichment and/or contamination in groundwater under combined hydrogeological and anthropogenic influences, a representative catchment (Handan, central North China) was selected to systematically explore the factors controlling groundwater Se concentrations. The results revealed a moderate enrichment level (0.078-19.61 μg/L) and significant spatial heterogeneity of Se. The Durov diagram and self-organizing map (SOM) indicated that the hydrochemical facies, reflected by major ions, exerted a limited effect on the Se enrichment. Leveraging the principal component analysis-absolute principal component score-multiple linear regression (PCA-APCS-MLR) model, we quantitatively identified the contributions of six potential sources of Se in the groundwater. The oxidative dissolution of Se-bearing pyrite was the primary contributor (38.08 %), followed by heavy industrial contamination (23.21 %), surface water infiltration (ca. 22.14 %), and hydrogeochemical processes (13.43 %). Agricultural non-point source input (2.63 %) and rural domestic sewage-related pollution (0.51 %) were minor sources. Additionally, the presence of SO₄^2-, Cl^-, and NO₃^- promoted Se enrichment through competitive adsorption. Our findings, grounded in quantitative source apportionment, offer a scientific framework and conceptual insights for developing precise strategies to manage Se in groundwater under complex hydrogeological and anthropogenic influences, supporting both pollution mitigation and resource utilization.