Pollution characteristics and risk assessment of heavy metals in soil around a lead-zinc smelting waste residue dump in southwest China

In order to explore the spatial distribution characteristics and ecological risks of heavy metals in the slag dump site and the surrounding soil, 8 elements including As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in the soil were detected in a waste lead and zinc smelting slag dump site in southwest China. Spatial distribution characteristics of heavy metals were summarized, the impacts of existing forms on their migration and infiltration were analyzed, and the risks of their pollution status were assessed by using a variety of assessment methods. The results showed that the distribution of heavy metals in the slag dump site was consistent with the direction of surface runoff, and they penetrated into deep soil. It is difficult for As, Cd and Cu to further migrate along the surface runoff in the form of ions, while Pb and Zn still have relatively large ion mobility, and will further diffuse to the surrounding and deep soil. According to the comprehensive pollution index, the upper slag stacking area is seriously polluted, and the pollution elements mainly come from As. At the same time, the contents of As and Cd showed extremely strong ecological toxicity, which makes the region exhibits a strong ecological risk. The research results provide a theoretical basis and reference for further soil remediation in this region.