Characteristics of heavy metal element content and health risk assessment in groundwater in Zhaojue area, Sichuan Province, China

Groundwater serves as the primary drinking water source for residents in the Zhaojue area, located in the hinterland of the Daliang Mountains in Sichuan Province. This study investigated the spatial distribution, pollution characteristics, and health risks of 10 metal elements (As, Cd, Al, Mn, Hg, Co, Cu, Pb, Zn, Ni) through 48 groundwater sampling sites. Comprehensive analysis using single-factor and Nemerow composite pollution index evaluation methods, coupled with multivariate statistics and health risk models, revealed critical findings. The mean concentrations followed the order: Al > Mn > As > Cu > Zn > Hg > Cd > Pb > Ni > Co, with 1 site exceeding Al standards and 3 sites surpassing Hg limits. Spatial analysis showed elevated metal concentrations in eastern and central regions compared to western areas. Source apportionment identified three primary origins: Zn-Ni-Pb from industrial/agricultural/transportation activities (44.8% contribution), Co-Cu-Mn-Al from geological sources (22.2%), and Hg-As-Cd from mixed natural-anthropogenic sources (10.5%). While Nemerow indices indicated generally good water quality (89.58% of samples unpolluted), the health risk assessment revealed that children exhibited higher non-carcinogenic risks (HI: 0.41-3.36) compared to adults (HI: 0.16-1.33), with forty-four child samples exceeding the safety threshold (HI > 1). All child samples surpassed the incremental lifetime cancer risk (ILCR) threshold (1.0 × 10^-4), whereas only 20.8% of adult samples exceeded this limit. Arsenic was the main pollutant and ingestion was the main exposure pathway.These findings underscore significant carcinogenic risks in the studied area, necessitating urgent groundwater management interventions to mitigate health threats, particularly for vulnerable children.