Pollution Characteristics and Risk Assessment of Heavy Metals in Agricultural Soils Across Different Regions of China

ABSTRACT To evaluate the contamination levels and ecological risks of heavy metals (HMs) in agricultural soils, 85 soil samples were collected from 14 provinces across China. The concentrations of seven heavy metals (Mn, Zn, Cr, Pb, Cu, Ni, and As) were measured, with mean values of 509.83, 87.38, 64.07, 26.92, 35.10, 29.16, and 12.21 mg/kg, respectively. Spatial distribution analysis revealed that the total concentrations of ΣHMs in soils across 14 provinces exhibited a descending regional gradient: southern China (mean: 129.14 mg/kg) > central China (117.85 mg/kg) > northwestern China (102.77 mg/kg) > northeastern China (99.84 mg/kg). To circumvent spurious correlations inherent in traditional source apportionment methods, this study employs a ternary ensemble strategy integrating compositional data analysis, SELBAL, and principal component/partial matrix factorization to analyze HM sources in interregional agricultural soils across China. The study indicates that HMs in farmland soils primarily originate from natural factors associated with bedrock and composite sources, including industrial production and motor vehicle exhaust emissions, as well as atmospheric deposition processes. The ecological risk assessment revealed no detectable pollution risks for Cr, Mn, and Ni, whereas As, Zn, Pb, and Cu exhibited relatively low contamination levels. Monte Carlo modeling was employed to conduct quantitative assessments of health risks, revealing oral ingestion as the primary exposure pathway. As was identified as the predominant noncarcinogenic risk factor, whereas Ni was identified as the core carcinogenic risk factor.