Contamination and source-oriented health risk assessment of heavy metals in sediments: a case study of the Yixun River Basin, China.

As a result of their tendency to enter various ecosystems, bioavailable heavy metals (HMs) have become major human public health concerns. The diverse characteristics and variations in the bioavailable forms of various HMs can cause a range of specific health risks. To verify this, sources of HMs in the sediments of the Yixun river basin were identified, with a focus on studying the aggregation and risks of HMs in various speciation forms. The results showed that the HMs in the sediments were, in order of concentration: Ti > Mn > Zn > Ni > Cu > Pb. The major sources of pollution in the sediments were mining (39.86%), industrial activities (18.24%), and agricultural activities (12.32%). For adults and children, the non-carcinogenic hazard indexes were 0.37 and 1.88, respectively-thus indicating significant non-carcinogenic health impacts on children. These impacts were mainly attributed to the enrichment of Pb bound to Fe-Mn oxides in sediments from agricultural pollution, leading to a hazard quotient of > 1 for children through dermal exposure pathways. Given that industrial pollution contributed the most to the total carcinogenic risk index value, the carcinogenic risks for both adults and children were relatively significant. However, although mining represents the primary source of HMs in river sediments, it is not the main source of health risks in the Yixun river basin, owing to the low bioavailability of the HMs forms in the region. This study confirmed that mining activities can lead to HMs enrichment in river basin sediments, but that the health risks arising from agricultural and industrial sources also merit enhanced monitoring.