Impact of dust storms on the organic composition in the ambient aerosol

To better understand the impact of dust storm (DS) events on the ambient aerosol organic composition in Seoul, samples of solvent-extractable organic compounds in the atmospheric particulate matter with an aerodynamic diameter of less than or equal to a nominal 10 μm (PM₁₀) were collected for 3 months (March-May) in 2007 and characterized. The results of the statistical analysis suggested that during the DS events the ambient PM₁₀ concentration increased, the n-alkanes concentrations decreased, and the PAH concentrations show no trend, although they increased slightly. The distributions of n-alkanes and PAH species showed that among n-alkanes only C₂₅ and C₂₇ species in the non-DS samples increased compared to in the DS samples. Since C₂₅ and C₂₇ species are mainly emitted from plants, this suggests that the impact of biogenic emissions of n-alkanes was reduced during the DS periods. Among PAHs, only the concentration of Fluoranthene increased in a statistically significant manner during the DS period, and only the 1,3,5-Triphenylbenzene level was higher during the non-DS period. The backward trajectory analysis results showed that the air parcels over Seoul did not show much difference between DS and non-DS days. The average level of n-alkanes per unit mass of PM₁₀ was statistically lower in the DS samples, while those of the PAHs showed no statistically significant differences between the DS and non-DS samples.