Abstract: This study was undertaken to assess the impact of particle size distribution on the heavy metal concentrations and chemical fractions in urban surface dusts in Shanghai. The result showed that there was 47.4% of surface dusts under 75 μm, higher than other fractions. It showed obvious difference in the spatial distribution of heavy metals in urban surface dusts, Zn had the highest concentration in the commercial district, while Cr in the industrial district and Pb in the residential district. Heavy metals were mainly existed in the smaller particle size fractions and the 75 μm part contained the highest concentration. A five-step sequential extraction of urban surface dusts showed that Zn occurred predominantly in the carbonate bound fraction and reducible fraction, while Cr was the highest in the residual fraction and Pb in the reducible fraction. Considering the exchangeable and carbonate fractions, the comparative mobility of the metals in urban surface dusts probably decreased in the following order: Zn> Pb> Cr.

Key words: urban surface dust, heavy metal, chemical fraction, particle size distribution, urban surface dust, heavy metal, chemical fraction