Spatial distribution characteristics and risk assessment of heavy metals in soils of Southern Xinjiang oases

The oasis is the most important territorial system of human-earth relationships in the hyper-arid zone. With the socioeconomic development, increasingly serious environmental problems have occurred in the oases. But current research major focus on the soil water balance of oases while ignore the spatial characteristics and risks of heavy metals in soils. Therefore, taking Southern Xinjiang, a typical hyper-arid zone, as a case study site, we collected soil samples from 15 major oases in the region and analyzed the spatial characteristics and risks of eight heavy metals (Cr, Ni, Cu, Zn, As, Cd, Pb, Hg). Through spatial autocorrelation analysis, the contamination index method, the geoaccumulation index method, and risk assessment methods, the analysis results show that (1) the overall concentration of soil heavy metals in the oases of Southern Xinjiang is low and relatively uniformly distributed, and there is a small-scale aggregation. (2) The eight heavy metals in the study area exhibit significant spatial distribution differences, with varying concentrations, but none exceed the risk screening values. The content of 8 heavy metals in the soil of the Southern Xinjiang oasis ranges from 0.01 to 62.73 mg/kg, in descending order of Zn > Cr > Ni > Cu > Pb > As > Cd > Hg. Among them, Zn, Cr, and Ni have the highest concentrations, while Cd, As, and Pb show significant deviations from background values. (3) Except for Cd and Hg, there is no overall ecological risk from soil heavy metals in the soils of most Southern Xinjiang oases. (4) None of the oasis soils in the study area have shown non-carcinogenic risks from heavy metals, but there are some carcinogenic risks for children, which are related to the accumulation of heavy metals and the specificity of the children’s population. This study fills a key gap in soil heavy metal research in oasis areas, offering valuable data for future research and policy. Future work should focus on remediation technologies like phytoremediation and microbial treatments, along with targeted policies to reduce pollution risks, especially for vulnerable populations.