Content,Source and Speciation of Heavy Metal Elements of Street Dusts in Baoji City

Heavy metal concentrations in street dust of Baoji City were investigated by using X-Ray fluorescence spectrometry(XRF) and atomic adsorption spectrometry(AAS).The results show that the mean concentrations of Cu,Pb,Zn,Mn,Co,Ni,Cr and Cd are 123.2,408.4,715.1,804.2,15.9,48.8,126.7 and 5.5 μg·g-1,respectively,which are higher than those of the element background values of International,Chinese,and Shaanxi Soil,especially for Cu,Pb,Zn and Cd.The source of heavy metal elements in street dust of Baoji City was identifed by multivariate statistics analysis(correlation analysis,principal component analysis and cluster analysis),and the results show that Ni and Cr mainly originate from natural source(local soil);Cu,Pb,Mn and Co have mixed sources of human activities(industry and traffic) and nature(local soil);Zn and Cd represent traffic and industry sources.At the same time,the speciation characteristics of heavy metals in street dust of Baoji City were investigated by using the modified BCR sequential extraction procedure and ICP-MS.The results show that Mn,Co,Ni and Cr are dominated by residue(over 48.52%),Zn and Cd mainly exist in acetic acid extractable part(44.43% and 44.08%),Cu is rich in oxidizable(48.22%) and residual(37.65%) parts,Pb is mainly in reducible part(45.42%).The order of mobility of heavy metal elements is Cd(90.11%) Pb(82.33%) Zn(79.32%) Cu(62.35%) Mn(51.48%) Co(29.02%) Ni(23.62%) Cr(18.68%),in which of them,Cd,Pb,Zn,Cu and Mn have stronger transformation(over 50%) and higher potential harm.