2022 年 37 巻 2 号 p. 117-126
Understanding various source contributions of secondary organic aerosols (SOAs) is important for devising strategies to alleviate PM2.5 pollution. We measured anthropogenic and biogenic secondary organic markers and dicarboxylic acids, all of which are photooxidation products in PM2.5, both during the day and at night in Maebashi, Gunma, a suburban site in the Kanto region, in the summer of 2018. The results showed that concentrations of organic carbon and water-soluble organic carbon in PM2.5 increased during the daytime. Concentrations of 2,3-dihydroxy-4-oxopentanoic acid (DHOPA), a toluene-derived marker, and phthalic acid (PhA), a naphthalene-derived marker, were higher during the day than at night on days with high O3 levels. As for α-pinene-derived markers, 3-methylbutane-1,2,3-tricarboxlic acid (MBTCA), 3-hydroxy glutaric acid, and pinic acid concentrations also increased during the daytime. However, pinonic acid concentrations did not show a clear difference between day and night. Levoglucosan, the molecular marker for biomass burning, was observed at a low concentration. Concentrations of DHOPA, PhA, and MBTCA were positively correlated with average O3 concentrations. These results indicated that photochemical reactions increased the concentrations of anthropogenic and biogenic SOAs. This study confirmed that anthropogenic and biogenic SOAs contributed to increased PM2.5 level in the summer in Maebashi.
