Study on the Occurrence States of Heavy Metals in Street Dusts of Beijing City and Their Environmental Effects

The street dusts (≤100 μm) were collected from NW-SE transects inside the sixth ring road in Beijing. Tessier sequential extraction method was used for the study on distribution of heavy metals of As, Cd, Cr, Hg, Pb and Zn in five fraction states including exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter and residual, respectively. The results from the study showed that Cd presented higher affinity to the exchangeable fraction and the bound to carbonates fraction. Pb, Hg, Zn and As presented similar affinity to the organic fraction. Pb presented the dominant in the Fe-Mn oxide fraction and As and Cr existed mainly in the residual fraction. The apparent mobility and potential bioavailability for these 6 highly contaminating elements are in order of Cd＞Zn＞Pb＞Cr＞Hg＞As.