[Concentration and distribution characterization of polycyclic aromatic hydrocarbons in airborne particles with different sizes].

Airborne particles with different sizes were collected in 2003 at two sampling sites(urban border and suburban area) of Beijing. Compositions of polycyclic aromatic hydrocarbons were detected by GC/MS. The results show that total concentrations of 17 PAHs ranged between 0.84 and 152.23 ng/m3, in urban border area were 1.07 - 6.60 times higher than those measured in suburban area. The total concentration of PAHs increased with decreasing ambient temperature (winter > autumn > spring > summer). About 68.4% - 84.7% of PAHs were absorbed on particles having aerodynamic diameter < or = 2.0 microm. The distribution of PAHs varies with the size of the molecules. Nearly bimodal distribution was found for two- and three-rings PAHs, four- to six-rings PAHs, however, followed unimodal distribution. The overall mass median diameter (MMD) for PAHs decreases with increasing molecular weight. Higher pollution level of PAHs in wintertime is probably ascribed to domestic heating and lower ambient temperature.