Evaluation on the Pollution of Agricultural Soil Heavy Metal in Guangzhou City

The methods of single pollution index,single average pollution index,arithmetic mean,weighted average,the Nemerow pollution index,cluster analysis and principal component analysis were adopted to evaluate the pollution of soil heavy metals,such as Cu,Pb,Zn,Cr,Ni,Cd,As and Hg,in suburb area of Guangzhou City.From aspect of frequency distribution of single pollution index,Hg has the most pollution frequency among the eight heavy metals,which means that the frequencies are all great of slight pollution,middle degree pollution and heaviest pollution of Hg,being 25.4%,9.3% and 16.1% respectively.Next to it are Cd and Zn,both having high frequencies of slight pollution,middle degree pollution and heaviest pollution.The eight heavy metals are classified into 4 groups by the cluster analysis,and the first group includes Pb,Ni,As,Cr,and Cu,the second group is Zn,the third group and the fourth group are Cd and Hg, respectively.The pollution indexes of the first group are the lowest,while the fourth is the highest.In principal component analysis,the first two principal components can explain 67.81% of the information,and the first one can explain nearly 50% of the information in particular.The first principal component mainly reflects the enrichment degree of Cu,Pb,Zn,Ni,Cd,As and Hg,while the second principal component reflects the enrichment information of Cr and Ni and the release information of Hg.