Spatial Variability And Environmental Risk Assessment Of Heavy Metal Pollution Of Cultivated Land In Xinghua Plain Based On GIS

The pollution of heavy metals in cultivated land is grave increasingly with the development of industry and agriculture. The contaminants of heavy metals in soils affect remarkably the growth, yield and quantity of crops due to theirs' bad transferability, long detaining time and difficulty of being decomposed . Hence , it is necessary to investigate the pollution and spatial variability of heavy metals and predict their potential environmental risk in regional cultivated land. This will have a realistic sense on preventing the pollution of soil heavy metals .improving the soil environment quality and guaranteeing people's health .The Xinghua plain belonging to one of four plains in Fujian province was selected for the study, based on the investigating samplings and analyzing contents, GIS and Geostatistic softwares were used to carry out a series of studies. First,we explored the semi-variance functions and the fitted models for the contents of observed heavy metal samples ,then analyzed different interpolation models of 8 kinds of heavy metal(As,Hg,Pb,Cd,Cr,Ni,Cu,Zn) contents.Secondly , we select an optimal spatial interpolation model and analyzed the spatial variability and pollution state of 8 kinds of heavy metals through setting up spatial grids of 100m×100m .Thirdly, we made an assessment on the environmental risk and obtained divisions of 8 kinds of heavy metals by using potential environmental risk index .The results showed,The average contents of total-As,Hg,Pb,Cd,Cr,Ni,Cu,Zn were 5.956mg/kg,0.360 mg/kg ,49.939 mg/kg ,0.120 mg/kg,43.053mg/kg, 18.527 mg/kg,26.042 mg/kg and 78.085mg/kg respectively,the average contents of the remaining six heavy metals were lower obviously than the natural background criteria of national soil quality standard except for Hg and Pb, the total variability trend of 8 kinds of heavy metal contents was:Cd>As>Hg>Cr>Pb>Zn>Cu>Ni.The semi-variograms of soil As , Hg, Pb, Cu, Zn were fitted by exponential models ,while Cd, Cr, Ni were fitted by spherical models. The spatial correlation distance of As is the largest, the next is Cu ,the smallest was Hg, the spatial correlation distance of the other five kinds of heavy metals was , 1280—6530m. The order of spatial variability indictor( Co/Co+C) was Cd (12.7%) < Hg (27.0%)