石家庄污灌区土壤中铬分布特征

Distribution characteristics of Cr in the soil of Shijiazhuang sewaged-irrigation area

采集石家庄污灌区内土壤表层和深层样品及垂直剖面样品,测定样品中Cr质量比,采用ArcGIS软件和Surfer软件制作Cr的平面分布和垂向分布图,分析了当地Cr分布特征。结果表明,由于外源污染物强烈影响着表层土壤Cr的分布,深层土壤中的Cr受外源影响较小,石家庄污灌区内表层土壤Cr质量比远高于深层,其均值达到深层的1.37倍。研究区内土壤表层和深层都形成了具有独立成因的Cr高值区,二者高值区的分布不吻合。垂向分布上,Cr表现出沿水流方向由排污点逐渐向下迁移的趋势,迁移过程中Cr主要富集在黏土层,其最高值均位于黏土质层,表明Cr的垂向分布受土质的影响。另外,垂向上Cr高值点偏向城镇密集的河道东侧,这表明排污口的位置分布对Cr分布也有影响。

The present paper is aimed to introduce the findings on the horizontal and vertical distribution of Cr in the soil of Shijiazhuang sewagedirrigation area. The data we have quoted in this paper are based on the soil samples taken from the topsoil, deep soil and the soil column of the area. In accordance with the actual analysis of the different contents of Cr in the samples, we have drawn the map of the horizontal and vertical distribution of Cr by using an ArcGIS and Surfer softwares. The results of our analysis show that the content of Cr in the topsoil turns to be much higher than that in the deep soil. Vertically speaking, the influential factors of Cr in the soil are the soil structure and the location of the sewage ouffalls. And, horizontally speaking, the mean value of Cr content in the topsoil has worked out at about 89.41 mg/kg, with that of deep soil being 65.31 mg/kg, which is 1.37 times as much as that of the latter. That may attribute to the distribution of Cr in the surface soil strongly influenced by ex ogenous, whereas the influence of exogenous is weaker in the deep soil. The higher content of Cr in the surface and deep layer may at tribute to the independent causes, with the distribution of the higher content areas due to the different characteristic features between both layers. The distribution of Cr in the soil column shows there is a ten dency in vertical soil with Cr moving down with the water from the sewage discharge outlet to the other parts of the river. The main in fluential factor of Cr vertical distribution is the soil texture, particu larly with the clay features of strong adsorption function on the heavy metals. Therefore, Cr has been mainly enriched in the clay layers vertically, and the highest contents of Cr in the 3 longitudinal profiles are all in the clay layers. And, more specifically speaking, the urban areas by the Xiao River sides, such as Luancheng, Zhaoxian and other places on the eastern side of the channel, the higher content of Cr may attribute to the location of the sewage discharge outlets that affects the result of Cr vertical distribution. The results will be valu able in distribution and migration of pollutants in this sewage irrigation area.