Assessment of distribution, contamination, ecological risks, and sources of heavy metals in soil from metal recycling sites

Developing the metal recycling industry to meet the demand for green resource recycling and utilization has raised environmental concerns. However, long-term processing and stacking of waste heavy metals (HMs) may lead to negative impacts on the soil environment. This study investigated the distribution of HMs such as, Cd, Cu, Pb, Hg, Ni, Co, and V, in soil from metal-recycling sites. A total of 63 soil samples were collected to assess the degree of soil contamination by HMs and trace the sources of HMs. The single pollution index was calculated based on the background values of reference elements to determine the level of HMs pollution. Except for As, the average concentrations of seven HMs in the surface soil exceeded their background values. It is worth noting that according to the geo-accumulation index (Igeo) and pollution load index (PLI) revealed that Hg, Cu, and Pb exhibited relatively high pollution levels, while the potential ecological risk index (RI) and Nemerow risk index (NRI) indicated that Hg and Cd posed higher ecological risks. The source apportionment results indicate that As, Cd, Cu, Pb, and Hg have significant homology, mainly derived from the composite source of human activities and natural sources; V mainly comes from industrial process sources; Ni and Hg mainly come from atmospheric deposition sources; Co is mainly influenced by natural factors. This study provides reference for implementing pollution control measures and promoting precise remediation work in areas affected by metal recycling activities.