某锰矿区土壤剖面重金属形态迁移转化特征及生态风险评价

对贵州省某锰矿区剖面土壤进行采样，测定其中Cu、Zn、Cr、Mn、Pb和Cd含量，并采用改进的BCR连续提取法分析重金属的赋存形态，利用风险评价编码法（RAC）及次生相与原生相比值法（RSP）对其进行风险评价。结果表明，1）研究区域土壤中Cd、Cr、Cu、Zn、Pb和Mn的质量浓度平均值分别为2.63、126.39、48.95、751.8、37.28和4 992.88 mg/kg，均高于贵州土壤背景值。从土壤重金属垂向分布来看，由于矿区土壤受到较多人为影响，导致土壤垂向重金属元素含量未表现出明显的规律性。2）不同重金属的赋存形态分布差异较大，Cd的主要赋存形态为弱酸溶态，Pb、Mn均以可还原态为主，Cr、Zn和Cu均以残渣态为主，其中Cd、Cu元素有效态均表现出在表层富集的特征。3）潜在生态风险评价结果表明，研究区域土壤Cd有较高的污染风险，土壤Cu、Mn、Zn、Pb和Cr以中低风险为主。不同剖面深度土壤Cd和Cu生物有效形态组分污染风险均呈由浅至深逐渐降低的趋势。

Speciation Transformation and Ecological Risk Assessment of Heavy Metals in Soil Profile of a Manganese Ore Area

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.