[A-AS11] 大気化学

[AAS11-22] Four- and Five-Carbon Dicarboxylic Acids Present in Secondary Organic Aerosol Produced from Anthropogenic and Biogenic Volatile Organic Compounds

*佐藤 圭¹、池盛 文数²、Ramasamy Sathiyamurthi¹、伏見 暁洋¹、熊谷 貴美代³、飯島 明宏⁴、森野 悠¹ (1.国立研究開発法人国立環境研究所、2.名古屋市環境科学調査センター、3.群馬県衛生環境研究所、4.高崎経済大学)

キーワード：揮発性有機化合物、二次有機エアロゾル、環境チャンバー、化学反応機構、エアロゾル発生源解析

Dicarboxylic acids detected in atmospheric aerosol have traditionally been believed to be secondary organic aerosol (SOA) tracers. However, the sources of dicarboxylic acids in atmospheric organic aerosols have not been fully characterized. To better understand precursors of dicarboxylic acids in ambient SOA, we studied C4–C9 dicarboxylic acids present in SOA formed from the oxidation of toluene, naphthalene, α-pinene, and isoprene. C4–C9 dicarboxylic acids present in SOA were analyzed by offline derivatization gas chromatography–mass spectrometry. We revealed that C4-C5 dicarboxylic acids including succinic acid, maleic acid, fumaric acid, malic acid, DL-tartaric acid, and meso-tartaric acid are produced by the photooxidation of toluene, whereas trace levels of limited C4 dicarboxylic acids were produced by the photooxidation of the other three precursor VOCs (Fig. 1 [1]). These results agreed with previous field studies [2,3]. Since meso-tartaric acid barely occurs in nature, it is a potential aerosol tracer of photochemical reaction products. In SOA particles from toluene, we also detected a compound and its isomer with similar mass spectra to methyltartaric acid standard; the compound and the isomer are tentatively identified as 2,3-dihydroxypentanedioic acid isomers. The ratio of detected C4–C5 dicarboxylic acids to total toluene SOA mass had no significant dependence on the initial VOC/NOx condition. Trace levels of maleic acid and fumaric acid were detected during the photooxidation of naphthalene. Malic acid was produced from the oxidation of α-pinene and isoprene. A trace amount of succinic acid was detected in the SOA produced from the oxidation of isoprene. C6–C9 dicarboxylic acids were not detected for the photooxidation of all precursor VOCs.

References.
[1] Sato, K.; Ikemori, F., Ramasamy, S., Fushimi, A., Kumagai, K., Iijima, A., Morino, Y. Four-and Five-Carbon Dicarboxylic Acids Present in Secondary Organic Aerosol Produced from Anthropogenic and Biogenic Volatile Organic Compounds. Atmosphere 2021, 12, 1703.
[2] Röhrl, A.; Lammel, G. Determination of malic acid and other C4 dicarboxylic acids in atmospheric aerosol samples. Chemosphere 2002, 46, 1195–1199. https://doi.org/10.1016/s0045-6535(01)00243-0.
[3] Kawamura, K.; Ikushima, K. Seasonal changes in the distribution of dicarboxylic acids in the urban atmosphere. Environ. Sci. Technol. 1993, 27, 2227–2235. https://doi.org/10.1021/es00047a033.