Source Identification and Health Risks of Heavy Metals in Huixian Karst Wetland Sediments: A Multi-Model Approach

Huixian Wetland faces severe heavy metal contamination (particularly Hg and Cd) from industrial, agricultural, and aquaculture activities, yet the widely-used USEPA health risk assessment model fails to capture the long-term bioaccumulation effects critical to understanding ecological risks in this karst wetland ecosystem. This study investigates the influence of anthropogenic activities on heavy metal contamination and bioaccumulation processes in sediments at Huixian Karst Wetland, Guilin, China. we collected 18 sediment points (58 sediment samples) and analyzed the contents of seven heavy metals (As, Hg, Cu, Cr, Ni, Pb, and Zn). Results revealed that the average concentrations of As, Hg, Cu, Cr, Ni, Pb, and Zn were 2.10, 1.54, 1.47, 1.92, 1.94, 2.22, and 3.15 times higher than the background values of Guangxi soils, respectively, with pollution severity ranked as: Zn > Pb > Cr > As > Ni > Hg > Cu. Source apportionment identified three primary pollution sources: (1) traffic-related emissions, contributing significantly to Ni (81.08%), Pb (63.07%), As (48.32%), and Cu (28.87%); (2) industrial activities, contributing to Hg (36.81%) and Cr (25.79%); and (3) mixed anthropogenic activities with natural background sources, contributing minimally to Zn (3.08%) and Cu (2.86%). Health risk assessment indicated non-carcinogenic risk probabilities of 2.8% for adults and 43.1% for children, while unacceptable carcinogenic risk probabilities were 0.03% for adults and 18.5% for children, with As identified as the primary carcinogenic substance. These findings underscore the urgent need for strict control of traffic emissions and agricultural non-point source pollution, enhanced industrial waste management, and regular monitoring with source-specific remediation of key pollutants, particularly As, to ensure regional ecological security and protect resident health.