Spatial variation, health risk assessment and transfer model of heavy metals in a soil-rice system: A case study in the typical production field of Southeastern China

The spatial variation and transfer characteristics of heavy metals (HMs) in the soil-rice system are important for revealing HM pollution in rice production areas and guaranteeing the safety of rice products. In this research, 95 pairs of topsoil (0-20cm) and their corresponding rice samples from a production area of southeastern China were collected. The pollution status, spatial variation characteristics, and HMs transfer models were studied using geostatistical analysis, health-risk assessment, and principal component analysis. Results indicated that the mean total concentrations of cadmium (Cd), copper (Cu), lead (Pb), zinc (Zn) and nickel (Ni) were 0.21, 28.65, 27.02, 38.50, and 98.75 mg/kg, respectively. Cadmium posed the highest potential ecological risk, although the overall regional risk remained moderate. The maximum Cd concentration in rice grains exceeded the national food-safety limit (GB2762-2017) by threefold, indicating a tangible risk of Cd accumulation and associated health impacts for local consumers. Children exhibited a higher exposure risk to HMs than adults, especially for Cd and Cu. The spatial distributions of HMs in rice were similar to those in soils, reflecting that the concentration of HMs in soil affected the accumulation of HMs in rice. The spatial distribution patterns of enrichment index revealed stronger transfer capacities for Ni, Zn, and Cd in the western region, with contamination hotspots for multiple HMs identified in the north-central zone. Soil physicochemical properties were shown to significantly govern HM transfer.