滇池周边磷矿复垦区土壤重金属污染特征研究

Characteristics of Heavy Metals in Reclaimed Soils of A Phosphorite-mining Area around Dianchi Lake

长期开采磷矿所产生的重金属残留将给矿区复垦后的农业或林业生产带来环境风险。选取云南省滇池周边某磷矿区的复垦区作为研究区域,分析了复垦区内不同土地利用类型在不同复垦年限下土壤中铜(Cu)、镉(Cd)、铬(Cr)、铅(Pb)、锌(Zn)、钛(Ti)、锰(Mn)、钒(V)、镍(Ni)、钴(Co)等10种重金属的含量,并利用综合污染指数法、地累积指数法和潜在生态风险指数法对重金属污染程度与生态风险进行了评价。综合指数法和潜在生态风险指数法分析结果均表明,Cd为各复垦区的首要污染物;而地累积指数法分析结果显示,大多数复垦区域的首要污染物为Pb。综合而言,各复垦区的首要污染物为Cd和Pb。其中,停采恢复区土壤中重金属含量最高,生态风险也最高。随复垦年限增加,农田和林地土壤中的重金属含量均有所下降,这表明矿区复垦降低了土壤重金属含量与生态风险,改善了环境质量,但在较短的复垦年限下种植农作物或林木仍存在一定的环境风险。各重元素的相关性分析结果显示:复垦区土壤中Cd、Pb和Cr的污染特征具有较高的相似性,且在复垦区中常会出现其中2~3种元素的复合污染。因此,在对复垦区中土壤重金属污染进行防控时,除需对首要污染物进行污染防控外,应根据复合污染特征考虑多污染物协同防控的效果和效益,降低污染防控的边际成本。

In China, heavy metal residues from long-term phosphorite-mining exhibit environmental risks to agricultural or forestry practices in reclaimed mining area. In this study, the contents of 10 kinds of heavy metal （Cu, Cd, Cr, Pb, Zn, Ti, Mn, V, Ni and Co） in reclaimed soils with different land-uses under different reclamation years of a phosphorite-mining area around Dianchi Lake were analyzed. Indexes of comprehensive pollution, geoaccumulation, and potential ecological risk were evaluated to assess the heavy metal pollution and its ecological risk. Results from comprehensive index and potential ecological risk index showed that Cd was the primary pollutant in reclamation areas and result of the geoaccumulation index indicated that the primary pollutant in most reclamation areas was Pb. On the whole, the primary pollutants in the reclamation areas were Cd and Pb. Highest content of heavy metals and highest ecological risk in the soils of the restoration zone were found. With the increase of rehabilitated years, the heavy metals in the soil of farm land and forest declined, indicating that reclamation in the mining area reduced the abundance of heavy metals and their ecological risks. Meanwhile, planting crops or trees grown in reclaimed soils under short reclamation years were still at risk. Clustering analysis showed that the pollution characteristics of Cd, Pb, and Cr in the soil were significant similar. Combined pollution of two or three heavy metals was often found in the reclamation area. In conclusion, it is not only the prevention and control of primary heavy metals should be conducted but also the cooperative control of the combined pollution of manifold heavy metals in order to enhance treatment effect and reduce treatment cost.