Speciation characteristics and risk assessment of heavy metals in soils from different functional zones of the lead-zinc mine

In order to investigate the distribution of heavy metals and pollution characteristics in soil of the Youxi lead-zinc mine, the authors collected samples from different functional areas (tailings area, smelting area, abandoned smelting area and mining area), and detected the content of heavy metals and chemical speciation. Both primary phase (RSP) and secondary phase enrichment factors were employed to assess heavy metal pollution. The results show that the values of Pb, Zn, Cd exceed the National Soil Environmental Standard Grade Ⅲ, the maximum values of Cd, Cu, Pb, Zn exist in abandoned smelting area, the maximum value of Cr appears in the mining area but remains within standard permission. Cd has the highest percentage in weak acid extractive form relative to the other elements, Cu has the highest proportion of exchangeable form, and Pb, Zn, Cr are mainly existent in residual form. The result of RSP method shows the descending order of Cu(1.15)＞Cd(0.80)＞Pb(0.59)＞Zn(0.57)＞Cr(0.54), the pollution degree of different functional areas shows the descending order of tailing area>smelting area>abandoned smelting area>mining area. The results of SPEF show that the Youxi lead-zinc mining area has been obviously polluted by anthropogenic sources. Zn has the highest degree of potential ecological risks in tailing area and mining area. The highest degree of potential ecological risk of Pb exists in abandoned smelting area and smelting area. The order of pollution assessment of functional areas is tailing area>smelting area>abandoned smelting area>mining area.