An ecological risk assessment for heavy metals of the lead-zinc ore tailings

The structure of Pb, Zn, Cu and Cd in lead zinc ore tailing soils in Yongzhou, Hunan is analyzed by the optimized BCR sequential extraction procedure. The content and proportion of heavy metals of the mine are measured. Meanwhile, the ecological risks are evaluated with the Lars Hakanson’s potential ecological risk exponential method. The analysis shows that the content of heavy metals is very high, reaching the level of serious pollution. The order of metal pollution degrees are Cd>Pb>Cu>Zn. On the other hand, it is very possible that the heavy metals may combine together as compounds or cling to the crystal form of clay. Since the form of soluble acid and free metals are very little, it is not an easy job for metal eluting or restoration of plants. Yet it is possible to take out those heavy metals adopting the chemical extraction technology. DTPA and EDTA, indicated by a research, both have iterative value and strong conformity effect. So they are effective elutriants to restore the polluted soil. A chemical extraction method is put forward in this paper.