Seasonal characteristics of the gaseous and particulate PAHs at a roadside station in Seoul, Korea

Gaseous and particulate PAHs were measured at a roadside station in Seoul, Republic of Korea and 16 PAH compounds were analyzed in order to investigate the seasonal variation of the roadside PAHs concentrations, evaluate the toxicity from the PAHs, and identify the contribution of vehicular emissions. Evident seasonal variation was observed both in the gaseous and particulate PAH concentrations though the degree of the variation was lower than the non-road urban area and background measurements. From the toxicity analysis, it was revealed that the toxic PAH compounds were mostly associated with particulates with the highest toxicity in winter. The considerable toxicity of the roadside PAHs indirectly implies that the toxicities of PAHs in tunnel could be a level of significant concern in Seoul. The distributions of individual PAH compounds in the gas and particle phases were more variable at the roadside station than the tunnel, since the roadside measurements are more susceptible to variable sources although the major source is vehicular emission. From the analysis of PAH profiles, the toxicity analysis, and the source evaluation using the diagnostic ratios, it was suggested that the PAH concentrations in spring might be particularly influenced by the transport of PAHs produced by biomass burning from China and/or North Korea.