Heavy metal pollution and ecological risk assessment of tailings in the Qinglong Dachang antimony mine, China.

ABSTRACT

The pollution of heavy metals and their harm to human health and the ecological environment have caused widespread concern. In this research, we collected Qinglong antimony mine tailings (8-meter deep) and then analyzed the content changes, geochemical behavior, and ecological risk assessment of 7 heavy metals (Sb, As, Cr, Cd, Cu, Zn, Pb) in the tailing profile, providing a theoretical basis for strengthening the source control and risk control of heavy metals. In addition, the chemical forms of Sb and As were analyzed, and the relationship between their forms and their physical and chemical properties was analyzed by redundancy analysis (RDA). The results showed that the concentrations of Sb (671.97-13896.62 mg/kg), As (287.38-657.36 mg/kg), Cu (27.61-74.48 mg/kg), and Cd (0.49-1.76 mg/kg) in the tailings greatly exceeded their background values, those of Pb (15.67-125.74 mg/kg) and Cr (22.69-185.88 mg/kg) moderately exceed their background values, while that of Zn (41.66-94.48 mg/kg) was slightly below its background value. Among the chemical forms of Sb and As, the residual fraction (F4) had the highest concentration. RDA showed that the pH and tailing particle size were significantly correlated with the chemical species content of Sb and As (p < 0.05). The improved Igeo analysis showed that the tailings were extremely polluted with Sb; highly polluted with As; uncontaminated to moderately polluted with Cd, Cu, and Pb; and uncontaminated with Zn and Cr, and the average Igeo values were in the following order Sb >As > Pb > Cd > Cu > Zn > Cr. The potential environmental risk index showed that Sb and As imposed a serious risk and Cr, Cd, Cu, Pb, and Zn imposed a low risk, which was basically consistent with the results of the improved Igeo values. This research provides comprehensive theoretical approaches to better understand the source control and risk control of heavy metals in tailing ponds.