Distributions and Influencing Factors of Heavy Metals in Soils from Zhenjiang and Yangzhou, China

Heavy metal pollution in surface soils poses significant environmental and health risks, yet the factors driving its spatial distribution remain poorly understood in certain regions. This study investigates the distribution and key influencing factors of heavy metal contamination in surface soils across Zhenjiang and Yangzhou, Jiangsu Province, China. This study analyzed the chemical compositions of 449 soil samples from the study area. Descriptive statistics, stepwise multiple regression, and the random forest (RF) method were employed to identify the key factors affecting the distribution and migration of heavy metals in soils. According to the national standards for soil risk screening values, cadmium (Cd) and mercury (Hg) were identified as the most heavily contaminated heavy metals in the study area. The average concentrations of Cd and Hg were 2.38 and 2.32 times higher than the provincial soil background values, respectively. A substantial proportion of samples exceeded the risk screening thresholds established for agricultural land. Key factors influencing the distribution of heavy metals in surface soils include soil iron oxides, pH, total organic carbon (Corg.), cation exchange capacity (CEC), and weathering intensity, as represented by the Chemical Index of Alteration (CIA). By integrating advanced data analysis techniques, this study provides new insights into the mechanisms governing heavy metal pollution in soils, offering a foundation for targeted soil management and pollution mitigation strategies.