Risk Assessment of Heavy Metals in Typical Karst Soils and Analysis of Potential Influencing Factors

The southwestern region of Yunnan Province, China, is characterized by typical karst landforms, where the elevated concentration of soil heavy metals has had significant impacts on the local environment. The objective of this study was to investigate the spatial distribution of soil heavy metals (Cu, Zn, Pb, Cd, and Cr) and identify the influencing factors in the target area using geo-detector and spatial interpolation techniques. The average concentration of chromium (Cr) in the study area exceeded the background level of soil elements in Yunnan Province, being 1.35 times higher than the background value. The concentrations of the other heavy metals did not exceed the background levels, although individual sampling points showed values above the standard. In terms of spatial distribution, the high-concentration areas for all five heavy metals were primarily located in the central part of the study area. GeoDetector analysis revealed that soil pH, soil organic matter, GDP, evapotranspiration, rainfall, and land-use type were the main factors influencing soil heavy metal. Interaction detector analysis showed that the results of factor interactions led to either non-linear or two-factor enhancement. Among Cu, Zn, and Cd, the strongest interacting combination was found between pH and organic carbon (OC). This study clarifies the factors affecting soil heavy metal concentrations in karst regions and provides a scientific evaluation method and decision-making support for similar areas with high background values. The findings hold significant scientific value and practical implications.