淮南煤矿复垦区土壤重金属形态分布及污染评价

Speciation Distribution Characteristics of Heavy Metals in Reclamation Area of Coal Mine and Its Pollution Assessment in Huainan

采用Tessier连续提取法,分析淮南矿区煤矸石充填和挖深垫浅2种复垦区土壤中Zn、Ni、Cr、Mn和Pb的赋存形态特征。结果表明:煤矸石充填复垦区土壤Zn含量分别是淮南土壤背景值和未复垦对照土壤的24.14,4.38倍,具有明显的累积现象。Ni、Cr、Mn和Pb均未超过国家土壤环境质量二级标准。而挖深垫浅复垦区土壤各重金属含量均小于煤矸石充填复垦土。淮南2种复垦区除煤矸石充填复垦土壤中Zn外,其余重金属含量均偏低。形态分析表明,2种复垦区Zn、Ni、Cr以残渣态为主,Mn和Pb以铁锰氧化物结合态和残渣态为主。表明复垦土壤受人为活动的干扰相对较小,自然来源是影响其含量的主要因素。但Mn和Pb在还原条件下容易释放,对环境造成潜在危害。基于形态的次生相与原生相比值法评价结果表明,在2个复垦区中,Mn污染最严重,为重度污染,Zn、Cr和Ni均无污染;煤矸石充填复垦区Pb为轻度污染;挖深垫浅复垦区Pb为中度污染。煤矸石充填复垦区土壤重金属RSP的大小为Mn>Pb>Ni>Cr>Zn;挖深垫浅复垦区为Mn>Pb>Ni>Zn>Cr。

Samples were collected around reclamation area of coal mine in Huainan.Five steps sequential extraction method was applied to investigate the speciation distribution characteristics and contents of five heavy metals（Zn,Ni,Cr,Mn,Pb）in the reclamation soil filled with coal gangue and reclamation soil of deeping-digging and shallow-filling.The result indicated that the content of Zn in reclamation soil filled with coal gangue was 24.14,4.38 times higher than the background value of Huainan and reference soil.The total contents of four heavy metals（Ni,Cr,Mn,Pb）in reclamation soil were not beyond National Soil Environmental Quality Standard of Grade Ⅱ.The contents of four heavy metals（Ni,Cr,Mn,Pb）in reclamation soil of deeping-digging were lower than that in reclamation soil filled with coal gangue.The contents of heavy metals except Zn in reclamation soil filled with coal gangue were lower in Huainan.Speciation analysis indicated that in both reclamation soil,Zn,Ni,Cr were mainly composed with residual fraction.While Mn,Pb were dominated by Fe-Mn oxide form and residual fraction.The content of Zn,Ni,Cr,Mn,Pb were mainly controlled by nature source.The heavy metals of Mn,Pb would produce a potential danger to environment in the reduction condition.By ratio of secondary phase to primary phase（RSP）,it showed that in the two reclamation soils,Zn,Cr,Ni were clean,and Mn was polluted heaviest in all heavy metals.But Pb was mostly slightly polluted and mostly moderately polluted in reclamation soil filled with coal gangue and in reclamation soil of deeping-digging and shallow-filling respectively.The risk order of RSP of the heavy metal in reclamation soil filled with coal gangue and in reclamation soil of deeping-digging and shallow-filling was MnPbNiCrZn and MnPbNiZnCr respectively.