[A-AS07] 大気化学

[AAS07-13] 酸性粒子存在下でのα-ピネンの酸化過程からの二次有機エアロゾルの生成収率の増大と低揮発性成分の生成

*猪俣 敏¹、佐藤 圭¹、森野 悠¹、江波 進一¹、谷本 浩志¹、Deng Yange¹、Ramasamy Sathiyamurthi¹、飯沼 賢輝² (1.国立研究開発法人国立環境研究所、2.沖縄科学技術大学院大学)

キーワード：α-ピネン、光酸化、オゾン反応、二次有機エアロゾル、SOA収率、有機硫酸エステル

Secondary organic aerosols (SOAs) affect human health and climate change; however, the factors (e.g., temperature, acidity of pre-existing particles, and oxidants) influencing their formation are not sufficiently understood. The temperature and acidity dependence of SOA yields and chemical components of SOA from α-pinene ozonolysis and α-pinene photooxidation under low NO_x conditions were systematically investigated under 278–298 K temperatures in the presence of neutral ((NH₄)₂SO₄) and acidic (H₂SO₄ + ((NH₄)₂SO₄)) seeds by using a compact chamber. The slight negative temperature dependence of the SOA yields was observed and the enthalpies of vaporization were estimated to be 25–48 kJ mo^–1, which is in agreement with the value of 40 kJ mol^–1 applied in the CMAQ model. The SOA yields increased ~10–30 % with the increase in the acidity of seed particles ([H⁺] = 220 nmol m^–3) at low SOA mass loadings. Those increases were thought to be caused by the formation of low- and extremely low-volatility organic compounds such as dimer esters and organosulfates, which were measured by means of negative electrospray ionization liquid-chromatography time-of-flight mass spectrometry coupled to ion mobility spectrometry. To achieve better simulation of monoterpene SOA formation in the SOA module of the model, we propose that the conversion rate (τ^–1) of semi-volatile organic compounds (SVOCs) to non-volatile compounds (NVOCs) should be faster under acidic conditions compared with that under neutral conditions.