Investigation of heavy metal and polycyclic aromatic hydrocarbons contamination in street dusts in urban Beijing

This paper investigated the contamination levels of heavy metal and polycyclic aromatic hydrocarbons(PAHs) in street dusts in different functional areas in urban Beijing.Results show that the mean concentrations of Cd,Hg,Cr,Cu,Ni,Pb and Zn in street dusts in Beijing are 710 ng/g,307 ng/g,85.0 μg/g,78.3 μg/g,41.1 μg/g,69.6 μg/g and 248.5 μg/g,respectively,which are significantly lower than those in most cities around the world and Shenyang,Shanghai in China.The mean concentration of ∑16PAHs in street dusts in Beijing is 0.398 μg/g,which is also lower than those of Handan,Tianjin and Shanghai.Non-parametric Friedman test demonstrates significant differences of heavy metal contents on street dusts from different functional zones.Street dusts in residential area and parks have lower heavy metal and PAHs concentrations than the street dusts from areas of high traffic density.The concentrations of heavy metals follow the order ZnCrCuPbNiCdHg,which is consistent with the situation in other cities around the world.The geoaccumulation index analysis shows that street dust in urban Beijing is moderately polluted by Cd,Zn and Cu,little polluted by Cr and Pb and practically unpolluted by Ni.The contamination levels of ∑16PAHs on street dusts vary greatly in different functional zones with parks little polluted,residential areas moderately to strongly polluted and traffic related areas strongly polluted to extremely polluted.Mass loading of heavy metals and PAHs is largely associated with street dusts of size range 300 μm.Therefore,the urban sweeping vehicles should update the dust sweeping devices to remove not only the fine particle but also the coarser particles.