大冶龙角山矿区农田土壤重金属形态分布及其来源

为研究大冶龙角山矿区某溪流段沿岸农田土壤基本理化性质和重金属分布情况,采用Tessier五步连续提取法提取并测定土壤中Mn、Cu、Zn、Pb、Cr、Ni和Cd 7种重金属的形态与含量,并分析了重金属含量与土壤Fe和S含量之间的相关性。结果表明:所有重金属在大部分取样点总含量均超出湖北省土壤背景值;Cu和Cd总含量超过土壤环境质量三级标准(GB 15618—1995)限值,Zn、Pb、Cr和Ni符合土壤环境质量二级标准;Mn、Cu、Zn、Pb、Ni和Cd均以残渣态和铁锰氧化物结合态为主,Pb、Cr和Cd存在一定比例的可交换态。矿山矿石组分主要为黄铁矿和黄铜矿,且Mn、Cu、Zn、Pb和Cd的铁锰氧化物结合态、残渣态以及总含量的分布均与土壤Fe和S含量分布表现出较好的正相关关系,表明硫化物矿物开采引发了重金属Mn、Cu、Pb、Zn和Cd在该矿区农田土壤中的累积与污染。

Speciation, distribution and sources of heavy metals in agricultural soils from the mining area of Longjiao Mountain in Daye City

In this work,the physical and chemical properties of soil and distribution of heavy metals were determined along the river in the mining area of Longjiao Mountain in Daye City.Tessier five-step sequential extraction procedure was used to determine different speciation of heavy metals including Mn,Cu,Zn,Pb,Cr,Ni and Cd.The correlation between the contents of heavy metals and Fe,S in soils was analyzed.The results indicated that the contents of all heavy metals in almost selected soils exceeded the soil background values of Hubei Province.The total contents of Cu and Cd were higher than the soil environmental quality standard (Grade Ⅲ)(GB 15618-1995) limits,and the total contents of Zn,Pb,Cr,and Ni were lower than the level of the soil environmental quality standard(Grade Ⅱ).Mn,Cu,Zn,Pb,Ni and Cd mainly existed as residual fraction and the Fe-Mn oxide fraction,and some Pb,Cr,and Cd existed as ion-exchangeable fraction.Pyrite and chalcopyrite were found to be the main components in mine ores.The contents of Mn,Cu,Pb,Zn,and Cd existing as residual fraction,Fe-Mn oxide fraction,and their total contents exhibited significantly positive correlation with total contents of Fe and S in soils.These results further suggested that the accumulation of Mn,Cu,Pb,Zn and Cd was resulted from the exploitation of sulfide minerals.