Detoxification of heavy metals attributed to biological and non-biological complexes in soils around copper producing areas throughout China

Previously risk evaluation did not consider soil composition and the in-situ existing forms for heavy metals in soils would be altered during sequential extraction. It necessitates exploring the detoxification pathways of heavy metals using real soil biological/non-biological components and then linking them to risk evaluation of heavy metals. In this study, we focused on the potential health risks associated with heavy metals, enzyme/extracellular polymeric substances (EPS)-producing bacteria associated with heavy metal resistance, and non-biological compositions in soils from typical copper producing areas throughout China. This study showed that 83% of the monitored regions in 7 provinces throughout China posed unacceptable health risks using prediction models. Details include Pb (1.21) and Hg (3.60) with unacceptable non-cancer hazards, As (1.44E-04) with unacceptable cancer risks, and highly unaccept-able risks associated with groundwater ingestion from soil leaching. The production processes and pe-riods as well as ore composition accounted for the distributions of heavy metals in soils through principal component analysis. Linkage between heavy metals, soil biological and non-biological components were built using redundancy models. Based on the results, two possible existing forms were revealed for detoxification of heavy metals. First, the ternary complex of heavy metal, phosphate and Fe (hydr)oxide were formed for multiple metals, where the urease and catalase were up-regulated. Second, the bac-terial EPS complexed with Fe (hydr)oxides was formed in soils with Cr of low risks and high total N/total P ratios. Therefore, we recommended insight into pollution sources and existing forms of heavy metals to control risks. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study focuses on the potential health risks associated with heavy metals in soils from typical copper producing areas in China, and the biological and non-biological components in the soil; using prediction models, it was found that the majority of monitored regions posed unacceptable health risks; two possible existing forms for detoxification of heavy metals were revealed, suggesting the need for understanding pollution sources and existing forms of heavy metals to control risks.