Risk-Targets Identification and Source Apportionment Associated with Heavy Metals for Different Agricultural Soils in Sunan Economic Region, China

Rapid socio-economic transition is often accompanied by intensive anthropogenic activities, leading to a significant build-up of heavy metals within farmland soils. However, this unwanted outcome may not be fully uniform but exhibit spatial variability, particularly involving different land uses. Based on 1839 topsoil samples from China’s Sunan Economic Region, this study estimated the contamination profiles and associated ecological risks posed by five heavy metals (As, Cd, Cr, Pb, and Hg) across cash-crop and cereal-crop soils. Further, we applied a combination of geostatistics and positive matrix factorization (PMF) model to identify the targeted zones, priority pollutants, and their underlying sources to pave the way for formulating detailed and fine-scale risk-mitigation strategies. Our results revealed that heavy metal pollution in Sunan displayed significant spatial variability, predominantly influenced by localized Hg and Cd accumulation, with more severe contamination observed in cash-crop soils compared to cereal-crop soils. The 232,532 ha of agricultural land could be designated as the targeted zones in which excessive Hg and Cd accumulation can be identified as the priority pollutants contributing to potential ecological risk. PMF modeling also suggested that within targeted zones, Cd accumulation was predominantly driven by intensive agrochemical application, whereas multiple sources simultaneously determined Hg accumulation. Our findings offer valuable guidance for optimizing land management strategies aimed at mitigating agricultural soil degradation driven by intensive anthropogenic activities. In addition, the integrated approach highlighted the crucial values in aspects to spatially identify risk-targeted zones and priority pollutants.