Assessment and Source Analysis of Soil Heavy Metal Pollution under Different Land Use Types in the Yixun River Basin
Land use types profoundly influence the accumulation, speciation, and ecological risk of heavy metals through differences in human activity intensity, pollution input pathways, and soil self-regulation capacity. This study investigated soils of different land use types in Longhua County, downstream of the Yixun River Basin, central Chengde City, Hebei Province. Using the Nemerow Index and Potential Ecological Risk Index, the overall regional pollution was mild (Pn=1.65) with low ecological risk (RI=121.17). Main pollutants were Cd, Pb, Zn, and Hg, with Cd and Hg as primary ecological risk factors. Construction land exhibited moderate pollution and medium risk, with a Nemerow Index of 2.37 and average RI of 190.78, significantly exceeding other land use types. PMF model identified four pollution sources: pedogenic parent material natural source (43.54% contribution) dominating Cr, Cu, Ni, Zn enrichment; metallogenic parent material natural source (19.88%) controlling Cd spatial differentiation; agricultural-transportation mixed source (24.79%) driving As and Pb accumulation; and industrial source (11.93%) causing local Hg enrichment. Natural sources contributed 63.42% of total heavy metals, being the primary contributor. As was generally below background values, not constituting pollution; Pb exceeded standards but posed low ecological risk; industrial Hg enrichment in construction land presented high pollution and ecological risk, requiring priority control.