Pollution Characteristics and Pollution Risk Evaluation of Heavy Metals in Soil of Lead-zinc Mining Area

In order to analyze the pollution characteristics and evaluate the pollution risk of heavy metals in soil in lead-zinc mining areas, soil samples in a lead-zinc mining area in Hunan province were collected and analyzed. The mineral compositions were analyzed by X-ray diffraction (XRD) method. The soil samples were digested by microwave digestion instrument, and then the concentration of heavy metals detected by inductively coupled plasma mass spectrometry (ICP-MS). The heavy metal forms were analyzed by method proposed by the European Communities Bureau of Reference (BCR). Finally, the heavy metal pollution potential environmental risk was assessed. The results show that the soil components mainly include quartz, feldspar, kaolinite and montmorillonite, etc. The pollution level for different heavy metals is in the order of Zn＞Pb＞Ni＞Cd＞Cu＞Cr＞As. The heavy metals have different leaching behaviors in different leaching experiments, and Ni possesses the highest proportion of residual state, while Zn has the highest proportion of acid extractable state. The pollution index and potential ecological risk index of heavy metals in soil are high on the whole. Cd possesses the highest single pollution index with the Nemerow comprehensive index of 1 472.98. Cd also possesses the highest environmental risk coefficient with the comprehensive pollution index RI of up to 25 380.63 that exceeds the high ecological risk threshold by 211.51 times.