大型金属矿山不同环境介质中重金属元素化学形态分布特征--以甘肃金昌市和白银市为例

Chemical Forms of Heavy Metals in Soil and Sediments around Jinchuan and Baiyin Mines,Gansu Province

重金属元素在环境介质中的存在形态及各形态比例是决定其迁移性和生物可利用性的重要因素。采用BCR法连续提取过程对大型金属矿山周围土壤和水体沉积物中Cd、Cr、Cu、Ni、Pb和Zn化学形态的分析结果表明，土壤和水体沉积物中不同重金属元素化学形态分布有很大差异，总体而言，Cd以弱酸提取态为主（约占60％），Cr以残渣态为主，占90％以上，Cu以可氧化态为主（约占60％）．Ni和Pb以可还原态为主．分别约占50％和60％，Zn以残渣态为主，约占45％。不同区域土壤中重金属元素各形态质量分数之和依次为厂区外围〉尾矿坝旁〉农田，各形态分布也与总量具有相似的变化趋势。金昌市矿山环境介质中重金属以Cu和Ni为主，白银市以Cd、Cu和Pb为主．重金属元素的生物可利用态和潜在可利用态质量分数高，平均约占各金属总量的60％～90％，对周围环境具有很大的潜在生态危害性。

The chemical forms of heavy metals in soil and sediments were analyzed by BCR sequence extraction procedure and the concentrations of each extraction fraction were determined using ICP-AES. The results show that chemical forms for each heavy metal are in different distributions and so are the different forms of the same metal. It has been revealed that the various portions of heavy metals are present in acid -soluble/exchangeable, reducible, oxidisable and residual fractions, where Cd is mainly in acid-soluble/ exchangeable fraction and oxidizable fraction, Cr and Zn aremainly in residual fraction, Cu is mainly in oxidizable fraction, Ni and Pb are mainly in reducible fraction. The concentrations of summation or single of speciation of heavy metals in various mediums were in the descending order： mill and smelter, tailings dam and farmland. The potential availability of Cu, Ni, Cd, and Pb of soil and sediment in Baiyin are higher than those in Jinchang city. This shows that it has great potential harm to the surroundings.