矿区周边土壤中重金属形态分析及污染风险评价

摘要

为了解某矿区周边土壤的重金属污染状况及污染程度，以广西河池市某矿区周边6处矿山和农田土壤为研究对象，采用湿法消解和BCR连续提取法研究了土壤中重金属( Cd、Zn、Pb和Cu)的总量及形态分布，并用次生相与原生相比值法( RSP)评价了土壤中重金属潜在的生态风险。结果表明，样品中重金属呈现一定的富集效应，总量超过当地土壤背景值和土壤环境质量标准值，从总量超标倍数看，其污染程度为Cd>Zn>Pb抑Cu。 BCR结果显示，离矿山较近的5个采样点的可提取态重金属均占总量的50%以上，有较强的生物有效性和毒性，最远的采样点的重金属主要存在于残渣态中(>60%)，可提取态低于40%。 RSP结果显示，离矿山较近的两个采样点的重金属污染风险最高( RSP在1.62~3.20)，矿山周边3个采样点有轻度或中度的的污染风险(RSP在1.11~2.16)，离矿山最远的采样点几乎没有污染风险(RSP在0.42~0.67)。说明该矿区周边土壤重金属活性较大，离矿区越近，污染风险越高。%In order to understand the pollution condition and level of heavy metals in a mining area and surrounding soils, the contents and speciation distribution of heavy metals ( Cd, Zn, Pb and Cu) in six mine/farmland soils surrounding mine area in Hechi city of Guangxi province were stud-ied by the wet digestion method and BCR sequential extraction procedure . The potential ecological risk of heavy metals in the soils was evaluated by the ratio of secondary phase and primary phase ( RSP) . The results showed that the enrichment of heavy metals in the soils was observed, and the contents of heavy metals were higher than the background values of the local soils, and the values of soil environmental quality standard ( SEQS) . According to the total contents of heavy metals in the soil, the sequence of heavy metal pollution level was obtained as Cd>Zn>Pb-Cu. The results of BCR method showed that the extractable heavy metals in five sampling points near the mines were account for at least 50% of the total amount, so the extractable heavy metals had strong bioavail-ability and toxicity. The heavy metals in the farthest sampling point were mainly found in residual form (>60%) , the heavy metals in extractable form were less than 40%. The results of RSP meth-od showed that, two sampling points near the mines showed the highest pollution risk ( RSP 1. 62~3. 20 ) , three sampling points surrounding the mines showed the mild or moderate pollution risk ( RSP 1. 11~2. 16 ) , the farthest sampling point showed little pollution risk ( RSP 0. 42~0. 42 ) . It indicated that heavy metal in the soil samples are highly active, and the nearer the mining area, the higher the risk of pollution.