新疆于田县绿洲区土壤重金属空间分布特征与影响因素

Spatial Distribution Characteristics and Influence Factors of Soil Heavy Metal Contents in Oasis Area of Yutian County,Xinjiang

以新疆于田县绿洲区为研究区,对1 165组表层土壤样品的重金属元素含量进行测定。通过综合运用多元统计分析、地统计学、空间自相关理论、空间分析和GIS技术相结合的方法,对研究区土壤重金属含量和空间分布特征及影响因素进行分析。结果表明:1 165组土壤采样点中,有3个取样点超过风险筛选值,非农用地土壤重金属元素含量均值均低于新疆土壤背景值,农用地中Cd、Hg、Cr含量均值大于新疆土壤背景值; Cd、Pb的变异函数理论模型为指数模型,Hg、As、Cr、Cu、Ni、Zn的变异函数理论模型为球状模型,Cd块金系数小于25%,说明Cd有较强的空间相关性,其他元素块金系数介于25%～50%之间,有明显的空间相关性;土壤重金属空间自相关莫兰指数均大于0。县域尺度内,土壤重金属具有一定的空间正相关分布,其空间分布格局总体呈从研究区中心向四周含量逐渐减小的趋势。土壤重金属元素含量在不同成土母质、土壤类型和土地利用类型下呈现的分布特征不同。Hg、As、Pb、Cr、Cu、Ni、Zn具有相同的来源,其含量还受土壤质地的影响。

Totally 1 165 surface soil samples for heavy metal analysis were collected in oasis area of Yutian County, Xinjiang. Spatial distribution and influence factors of heavy metal elements in soils in the study area were analyzed by means of multivariate statistical analysis, geostatistics, spatial autocorrelation, spatial analysis and GIS technology. Results showed that among 1 165 soil samples, three of which had As contents greater than the risk screening values. Average contents of heavy metal elements in non-agricultural lands were lower than that of soil background values in Xinjiang. Average values of Cd, Hg and Cr contents in agricultural land were greater than that of soil background values in Xinjiang. The theoretical models for variation function of Cd and PB were exponential model, while the theoretical models for variation function of Hg, As, Cr, Cu, Ni and Zn were spherical model. Nugget value of Cd was less than 25%, indicated a relatively strong spatial correlation. Nugget value of other elements ranged between 25% and 50%, indicated significant spatial correlations. As for soil heavy metals, the Moran s I indexes of spatial autocorrelation were greater than 0. There was a positive spatial correlation distribution of soil heavy metal elements in the county scale. And the spatial distribution of soil heavy metal contents in oasis area of Yutian County showed a general decreasing trend from the center of the study area to surrounding areas. Distribution of soil heavy metal contents in the Yutian County varied in different parent materials, soil types and land use patterns. Hg, As, Pb, Cr, Cu, Ni and Zn in soils derived from the same source. However, the contents were affected by soil texture as well.