Concentrations of particulate organic compounds in atmosphere

This study investigated the distribution of organic matters in airborne aerosols. Field observations were made at Takasaki and Karuizawa, which are located along the route of the long-range transport of photochemical air pollution in summer, in two urban areas (Okaya and Nagano) in late autumn and early winter, in a rural area (Nakano) in late autumn and in a mountainous area (Happo) in autumn. Organic matter in airborne aerosol was collected on a quartz fiber filter using a high-volume air sampler for 3 days to a week. Organic compounds collected on the filter were extracted with dichlorometane and subsequently with methanol, and the extracts were subjected to GC/FID and GC/MS analyses. Pinonaldehyde, C17-C33 n-alkanes, C12-C26 fatty acids, dicarboxylic acids, phthalic acids, benzoic acid, lower molecular unresolved mixtures (LUCM) and higher molecular unresolved mixtures (HUCM) were detected in the airborne aerosols. The total concentrations of the analyzed matter accounted for approximately 20% of the organic carbon (OC) in any of the samples. Pinonaldehyde, dicarboxylic acids and phthalic acids, which are produced by photochemical reaction in the atmosphere, were more abundant in summer. Concentrations of long-chain fatty acids and UCM (LUCM + HUCM) increased in rural Nakano in late autumn, probably due to the vegetative burning of asparagus fields nearby. A large part of the analyzed matter was made up of anthropogenic compounds (n-alkanes, dicarboxylic acids, phthalic acids, benzoic acid and UCM), while biogenic ones (pinonaldehyde, n-alkanes and fatty acids) were minor contributors to the airborne aerosols. In the mountainous area, pinonaldehyde, oxalic acid and LUCM were considered to be produced by photochemical reactions during transport to Happo.