Heavy Metal Concentrations of Agricultural Soils and Vegetables from Dongguan,Guangdong Province,China

A total of 118 of agricultural soil and 43 of vegetable samples were collected from Dongguan,Guangdong Province.The spatial distribution,sources,accumulation characteristics and potential risk of heavy metals in the agricultural soils and vegetables were depicted in details by three different approaches,including total contents of 8 metal elements in soils and vegetables,GIS maps and multivariate analysis of heavy metals in soils in the study.The results show that there are higher accumulation of heavy metals such as Cu,Zn,Ni,Pb,Cd and Hg in agricultural soils,and the contents of Pb(65.38 mg kg-1) and Hg(0.24 mg kg-1) are 1.82 and 2.82 times of background contents of the corresponding heavy metals in soils of Guangdong Province,respectively.There are about 3.4% of Cu,5.9% of Ni,1.7% of Cd and 28% of Hg in all collected soil samples from all investigated sites which have overran the contents for heavy metals of China Environmental Quality Standard for Soils(GB15618-1995,Grade Ⅱ).The pollution characteristics of multi-metals in soils are mainly reflected by Hg.There are different sources to 8 metal elements in soils,Cu,Zn,Ni,Cr and As are predominantly derived from parent materials,and Pb,Hg and Cd are affected by anthropogenic activity.The spatial distribution shows that Cu,Zn,Ni,Cr,Pb,As and Hg contents of agricultural soils are high in west and low in east,and Cd contents are high in northwest,southeast and low in southwest in Dongguan.The ratios of vegetable samples with Ni,Pb and As concentrations higher than the Maximum Levels of Contaminants in Foods(GB2762-2005) are 4.7%,16.3% and 48.8%,respectively.The order of bioconcentration factors(BCF) of heavy metals in vegetables is:Cd Zn Cu As Ni Hg Cr Pb.