Abstract:Profile soil of a manganese mining area in Guizhou province was sampled to determine contents of Cu, Zn, Cr, Mn, Pb and Cd. Occurrence forms of heavy metals were analyzed by improved BCR continuous extraction method, and the risk assessment was evaluated by risk assessment coding method (RAC) and secondary phase vs. primary value method (RSP). The results show that: 1) Average mass concentration of Cd, Cr, Cu, Zn, Pb and Mn in soil of the study area is 2.63, 126.39, 48.95, 751.8, 37.28 and 4 992.88 mg/kg respectively, which is all higher than the background value of Guizhou soil. From vertical distribution of soil heavy metals, content of heavy metals shows no obvious regularity because the soil in the mining area is affected by more man-made influence. 2) Occurrence forms of different heavy metals vary greatly. Main occurrence form of Cd is weakly acid insoluble state, Pb and Mn are mainly reducible state, Cr, Zn and Cu are mainly residual state, and the effective forms of Cd and Cu show the characteristics of enrichment in the surface layer. 3) The results of potential ecological risk assessment show that, in the study area, risk of Cd in soil has a higher risk of pollution, while risk of Cu, Mn, Zn, Pb and Cr in soil mainly has low and medium risk. The pollution risk of bioavailable form components of Cd and Cu in soil of different depth sections drop gradually with increase of depth.