Accumulation Characteristics and Pollution Evaluation of Heavy Metals in Soils of Wuhan City

The accumulation characteristics of Hg,As,Cd,Pb,Cr and Cu in 0-20 cm topsoil were studied by means of area sampling and laboratory detection from various suburbs and urban districts in Wuhan city,and the pollution status of those heavy metals were evaluated with the pollution index based on the background level of heavy metals in topsoil from Hubei province.The result showed that the average concentrations of Hg,As,Cd,Pb,Cr,and Cu in topsoil from urban districts were all higher than those from suburbs.By comparison to the background concentration of soil elements in Hubei province,Hg,Pb,and Cd contents in urban topsoils accumulated significantly,especially in traffic areas,industrial districts and park districts,and their average contents exceeded corresponding standard levels 186.1%,83.2% and 76.6%,respectively.The contents of Hg,Cd,Pb,and Cu also had significant accumulation in Wuhan suburb soils.Among the suburb soils,the average content of Hg in woodland soils exceeded its standard level 266.8%.Besides As in woodland which exceeded background value 13.8%,the contents of As in vegetable field,dry land,and paddy soils,and Cr in all suburban soils were all lower than the background level of heavy metals in topsoils of Hubei province.According to single-factor evaluation results,the pollution index of Hg,As,Cd,Pb,Cr,and Cu in soils of Wuhan were all less than 0.7.Cd pollution in soils was most serious,followed by As,Hg,Cu,Cr,and Pb.Comprehensive evaluation showed that soil pollution index were all less than 0.7 from both various use type in suburbs and different function districts in urban,which indicated topsoils in Wuhan kept the clean non-polluting condition.