滇西地区土壤重金属来源解析及空间分布

Source identification and spatial distribution of soil heavy metals in Western Yunnan

以滇西重金属地质高背景区为研究区,系统采集了4193件表层土壤样品,分析测试了As、Cd、Cr、Cu、Hg、Ni、Pb和Zn 8种重金属元素的含量,综合运用相关分析、主成分分析和单因素方差分析等经典统计方法探讨了土壤重金属来源和土壤重金属含量与成土母质、土地利用方式之间的关系,并利用地统计方法对重金属的空间分布特征进行了分析.结果表明:(1)研究区8种重金属含量平均值均超过全国土壤背景值,但是低于农用地污染风险筛选值;与云南省土壤背景值相比,As、Cd、Cu、Ni、Pb和Zn含量平均值与云南省背景值相当,Hg和Cr的平均含量分别是其背景值的2.35和1.60倍,土壤重金属存在不同程度累积现象.(2)Cr、Cu和Ni主要受成土母质的控制;Cd、Zn和Pb主要受人类活动影响,人为来源主要为铅锌矿开采选冶、交通运输和煤炭燃烧,Cd、Zn在一定程度上受成土母质的影响;As和Hg以人为来源为主,受汞矿采选、农业活动及煤炭燃烧的影响.(3)不同成土母质和土地利用方式的土壤中重金属含量差异显著.Cd、Cr、Cu、Hg和Ni在沉积岩母质区土壤中平均含量最高;草地中As、Cd、Cr、Cu、Hg、Ni、Zn平均含量最高.(4)Cu、Ni、Cr高值区与沉积岩母质区及区内分布的铜矿和铁矿空间耦合性良好;Pb、Cd和Zn的高值区与区内的铅锌矿分布范围基本一致;As和Hg高值区与区内汞矿等热液型金属矿的分布具有较高的空间一致性,在人类活动密集地区也呈高背景分布.

A total of 4193 samples of surface soils were collected in the high background area of heavy metals in Western Yunnan,and the contents of eight heavy metals(As,Cd,Cr,Cu,Hg,Ni,Pb and Zn)were analyzed.The sources of soil heavy metals and the relationship between soil parent materials and land use patterns were discussed by using correlation analysis,principal component analysis(PCA)and one-way analysis of variance(ANOVA).Moreover,the spatial distribution characteristics of soil heavy metals were analyzed by geostatistics.-The average contents of eight heavy metals in study area were higher than the national soil background value,but lower than the pollution risk screening value.The average As,Cd,Cu,Ni,Pb and Zn contents were equivalent to the background value of soils in Yunnan Province,and the average contents of Hg and Cr were 2.35 and 1.60 times greater than the background value,indicating heavy metals have been accumulated in different degrees in surface soils.The Cr,Cu and Ni in surface soils are mainly controlled by parent materials.However,Cd,Zn and Pb are mainly affected by human activities,including mining activities,transportation and coal combustion,and Cd and Zn are affected by parent materials to a certain extent.The As and Hg are predominantly anthropogenic sources,which include mining activities,agricultural activities and coal combustion.The average Cd,Cr,Cu,Hg and Ni concentrations were the highest in the soils derived from sedimentary rocks,and the average As,Cd,Cr,Cu,Hg,Ni and Zn concentrations were the highest in grassland.High-Cu,Ni and Cr concentrations occur in the western and southern part of study area,and are spatially associated with the occurrence of sedimentary rocks and copper,iron and mercury deposits in the area.The areas with high Pb,Cd and Zn contents are largely consistent with the distribution of Pb,Zn and Hg ore deposits in study area.High-As and Hg concentrations in surface soils has a high spatial consistency with the distribution of hydrothermal metal deposits such as lead-zinc deposits and mercury deposits,and also shows a high background characteristic in areas with intensive human activities.