Chemical Speciation of Heavy Metals and Trace Element in Urban Street Dusts of Beijing, China

Sequential extraction was used to characteristic the heavy metals (Cd, Cr, Zn, Cu, Ni and Pb) and trace element (As) studied in these urban dusts. The ratio of the average total content (F1+F2+F3+F4+R) to the corresponding background value of Beijing soil decreased in the order of Cd>Pb>Cu>Zn>Ni>Cr>As. For fraction distribution, residual form predominated among for Zn, Ni, Cr and Pb. Oxidizable fraction was the leading fraction for Cd and Cu and was the second dominated fraction for Zn and Ni. The results of Risk assessment code (RAC) showed the medium environmental risk of Cd was found in Dongcheng and East 4thRing districts, while a high environmental risk for Cr was present in Xizhimen and Yongdingmen areas.