Soil Heavy Metal Pollution Assessment in the Sewage Irrigation Region of Shijiazhuang City

To investigate the influences of sewage irrigation on soil environment,the study is conducted in the sewage irrigation area of Shijiazhuang.The concentrations of the heavy metals Hg,Pb,Cr,Cd,As,Cu and Zn in the topsoils are analyzed,and the soil environmental quality on the basis of the environmental background value criteria is evaluated by the single-factor contaminant index and Nemerow multi-factor index method,respectively.Furthermore,the spatial variability of soil pollution of heavy metals is researched with the Kriging interpolation method.The results indicated that the average contents of heavy metals in the soil exceed the background values,of which,Cd is the dominant pollution element and its contents are much higher than the background value;Hg is the second pollution element,and other heavy metals are in slightly polluted states while As is not in the polluted state.The integrated contamination index of all samples has exceeded 1 and is over slightly polluted grades.The single-factor polluted index and the synthesis polluted index are different in different research regions.In general,pollution is distributed in the Dongming Channel and the main river of the Xiao River as the pollution center and gradually falls on both sides,moderately and seriously polluted areas in the study area account for nearly more than half of the total area.