Photochemical formations of lower aldehydes and lower fatty 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 on clear summer days in central Japan. Photochemical formations of lower aldehydes (C 1–C 3) and lower fatty acids (C 2–C 6) were investigated in the cooperative field observation of meteorology and chemistry in summer, 1983, 1984 and 1986. Measurements were made at 3-h intervals at inland sites along the LRT route. Aldehydes and fatty acids were produced by the photochemical oxidation of anthropogenic hydrocarbons during the LRT. The concentrations of aldehydes and fatty acids increased in the daytime and decreased at night. The ratios of aldehydes and fatty acids to CO and to acetylene were similar to that of O 3. The increase of the aldehyde concentrations during the LRT compared well with those calculated from a gas-phase chemistry model (Chang, 1987, Pr.D. Thesis; Atkinson, 1990, Atmospheric Environment 24A, 1–41). However, model-predicted concentrations of acetic acid were smaller than the observed result. The model prediction was improved with the addition of the production mechanism of acetic acid suggested by Moortgat et al. (1989, Chem. Phys. Lett. 160, 443–447) and Madronich et al. (1990, Geophys. Res. Lett. 17, 2361–2364).