Size distributions and dry deposition fluxes of particulate polycyclic aromatic hydrocarbons (PAHs) at several sites in Korea in 1999

The atmospheric size distributions of particulate polycyclic aromatic hydrocarbons (PAHs) and their deposition fluxes were measured at four sites in August and at three sites in November 1999, in Korea. The total ambient particulate PAHs concentrations at each site ranged between 6.7 and 128.7 ng m^-3. In November, the total PAHs concentrations at Inchon (IC) were the highest, followed by Yangsuri (YS) and Seoul (SE). This trend is contrary to the expectation that the total PAHs concentrations at IC and SE be higher than that at YS because IC and SE are highly industrialized large cities and YS is rural area. The size distributions of individual PAHs in IC and SE show trimodal in Dp ≤ 9 μm while the particulate PAHs in YS were distributed evenly to fine- and coarse-size particles. These results suggest that YS has local sources in addition to transport of PAHs emitted from urban sources. The measured dry deposition fluxes of total PAHs ranged from 6.9 to 12.6 μg m^-2 day^-1 in August, and from 5.9 to 8.5 μg m^-2 day ^-1 in November. Individual PAH fluxes were dominated by high molecular weight (MW) PAHs at all sampling sites in August. But dry deposition fluxes of low MW PAHs were higher than high MW PAHs at all sampling sites in November. This result indicates that major sources of ambient PAHs have seasonal variety. The Sehmel-Hodgson model was used to estimate dry deposition velocities as a function of particle size for the multistep deposition model calculation. The calculated fluxes agreed fairly well with the measured fluxes, and it was shown that large particles (Dp > 9 μm) are more important than small particles (Dp > 9 μm) in particulate dry deposition of PAHs.