Photochemical formation of particulate dicarboxylic acids under long-range transport in central Japan

Abstract

Long-range transport (LRT) of photochemical air pollution from the coastal area with large emission sources to the inland mountainous region occurs very frequently in the central Japan region on clear summer days. It is caused by local winds and the transport route is almost-fixed geographically. Along this route, behavior of dicarboxylic acids in the airborne aerosols was investigated in the cooperative field observation of meteorology and chemistry. Measurements were made every 3-h at inland sites. The concentrations of dicarboxylic acids as well as NO 3 − and total organic C increased in the daytime and decreased at night. The maximum are attained when the transported air mass was arrived at the sampling sites. These diurnal variations were similar to that of O 3. In the daytime, although the phthalates (di- n-butyl and dioctyl), n-alkanes (C 21C 32) and pinon aldehyde were abundant in the airborne aerosols, the dicarboxylic acids (C 2C 10) were the most abundant species and the total concentrations attained from 30 to 50% of the total organic particulate matter. In addition, of the dicarboxylic acids, more than 70% were estimated to be produced by photochemical reactions in the daytime. Thus, it was concluded that most of the dicarboxylic acids were produced by the photochemical oxidation of anthropogenic compounds during LRT.