[Characteristics of Multi-metal Pollution and Associated Health Risks in the Soil-rice System of a Typical...

Heavy metal contamination of agricultural soils poses a significant global challenge to sustainable development. While extensive studies have focused on heavy metal pollution in soil-rice systems using indoor pot experiments, most remain limited to small-scale, localized "point" analyses, lacking comprehensive research on the soil-rice systems in regions. Addressing this gap, the present study systematically analyzed soil and rice samples from the southern Shanghai rice-growing region. The Integrated Contamination Quality Index (IICQ) was utilized to assess the degree and spatial dispersion of heavy metal pollution within the soil-rice system. This research delved into the various factors that influence the bioaccumulation of heavy metals in rice grains. Furthermore, employing the Human Health Risk Assessment (HHRA) model, the potential risks associated with consuming such rice were meticulously evaluated. The findings revealed that Cd, Ni, and Pb concentrations in the soil exceeded background levels for Shanghai but remained below China's agricultural land risk screening thresholds. Cr and Ni exceeded safety standards in 30.4% of rice samples, and As surpassed limits at certain sampling points; other heavy metals remained within acceptable levels. Rice exhibited a low bioaccumulation capacity for soil heavy metals (BF < 1), though soil properties influenced heavy metal accumulation in rice. Heavy metals in the soil exhibited similar sources. The health risk assessment indicated potential non-carcinogenic and carcinogenic risks from As, as well as Cr for children, with HI > 1 and TCR > 1.0×10^-4, suggesting combined exposure risks. The IICQ evaluation classified the study of soil heavy metal contamination as predominantly mild, with the soil-rice system exhibiting mild to moderate contamination. Further optimization of soil management practices is required to reduce heavy metal migration and accumulation in the soil-rice system, focusing on protecting vulnerable groups, such as children, to ensure the safe utilization of farmland soils.