Heavy metal contamination and risk assessment with uncertainty analysis in agricultural soils at a rural–urban interface
Abstract
As traditional pollution risk assessments fail to comprehensively consider the conbined effects of individual element toxicity and pollutant species, a modified geoaccumulation index ( I geo ) was proposed to identify priority trace metals and assess pollution risk characteristics in agricultural soils at a rural–urban interface area. Seventy agricultural soil samples were collected and analyzed for 6 heavy metals (Cr, Ni, Cu, Zn, Cd, Pb). To account for uncertainty from spatial heterogeneity in soil heavy metals and model parameters in the risk assessment model, a health risk model coupled with probabilistic triangular fuzzy numbers (TFN) was utilized to evaluate human health risks from three primary exposure pathways. The average concentrations of Cr, Ni, Cu, Zn, Cd, and Pb (mg kg −1 ) were 75.3, 22.6, 44.0, 189, 0.63, and 106, respectively, indicating elevated accumulation of Cd and Pb. The proposed I geo index determined elevated pollution risk levels comparable to the conventional index. Notably, Cd was identified as a priority trace metal to control due to its severe contamination risk ( I m = 3.3). The health risk model revealed no significant non-carcinogenic or cancer risk for adults. However, health risk for children were determined to be unacceptable, with a hazard index (HI) value > 1.0 and a total carcinogenic risk (TCR) > 1.0E−04. Ingestion was identified as the primary pathway of exposure to soil heavy metals. The TFN-based probabilistic assessment indicated higher cancer risk for children than the deterministic method. This difference may be attributed to Cr, which has moderate spatial variability and contributes substantially to health risk. This study provides new insights into pollution and human health risk from soil heavy metals, which can be used to generate strategies to prioritize decision-making on soil heavy metal pollution remediation and risk management in soil environments.