| Based on the acquisition of heavy metal data from 216 topsoil samples of the agricultural land in Baoshan District,a typical region of Shanghai City,the content,distribution characteristics and sources of the heavy metals in agricultural soil of Shanghai Baoshan District were analyzed with the methods of combining multivariate statistics and geo-statistical.The results show that the average concentrations of the Cd,Hg,As,Cr,Pb,Cu and Zn in agricultural soil of Baoshan District are 0.195,0.148,7.44,82.5,29.1,33.2 and 124.5 mg·kg-1,they are lower than the secondary standards of the national soil environment; but the average concentrations of the Cd,Hg,Cr,Pb,Cu and Zn are more than background values of soil in Shanghai.Especially the Cd,Hg,Zn,they are 1.50,1.48,1.45 times higher than the background values,showing a net cumulative trend.The results of correlation analysis and factor analysis show that the sources of these elements can be divided into three categories; the Zn,Cd,Hg and Pb as one class; the Cr and Cu as another class; the As in a separate category.The concentrations of the former two classes are much higher than the background value,implying mainly from various human activities; the content of the As is almost the same as the background value of soil,it has the lowest degree of variation.Spatial structure analysis shows that the distribution of the As is influenced by the soil structural variations,such as soil parent material,topography,and other elements are mainly affected by random factors of human activities.Through the probability distribution of contour lines of the critical value,it can be found that the Cd,Zn,Cr,Cu,Hg come mainly from the point sources of pollution,but the source of Pb is relatively dispersed. |
