[A-AS09] Atmospheric Chemistry

[AAS09-19] Intensive observation for the understanding of the formation of photochemical oxidants at an urban aera of Tokyo in 2023

*Satoshi Inomata¹, Hiroshi Tanimoto¹, Jun Matsumoto², Yashuhiro Sadanaga³, Takahiro Shioji³, Shungo Kato⁴, Takeru Sasaki⁴, Izumi Kobashi⁴, Hiroshi Tsurumaru⁵ (1.National Institute for Environmental Studies, 2.Waseda University, 3.Osaka Metropolitan University, 4.Tokyo Metropolitan University, 5.Tokyo Metropolitan Research Institute for Environmental Protection)

Keywords:Photochemical oxidant, Volatile organic compound, Reactive nitrogen oxide, Peroxy acetyl nitrate, Aldehydes

In Japan, concentrations of precursors of photochemical oxidants such as nitrogen oxides (NOx) and non-methane hydrocarbons (NMHCs) are decreasing year by year, but an improvement of photochemical oxidant concentration level is recently stagnant. To elucidate the reason, we have planned seasonal intensive observations in Tokyo, in which comprehensive measurements of speciated reactive nitrogen NOy and non-methane volatile organic compounds are performed. In the intensive observation, NO, NO₂, ΣPANs (peroxyacyl nitrates), ΣONs (organic nitrates), HONO, HNO₃, H₂O₂, SO₂, O₃, 28 NMHCs, and 10 oxygenated volatile organic compounds (OVOCs) were measured simultaneously. The ΣPNs and ΣONs were measured by thermal dissociation-cavity attenuated phase shift (CAPS) spectroscopy. The HONO, HNO₃, and H₂O₂ were measured by negative ion chemical ionization mass spectrometry using I⁻·(H₂O)_n as the reagent ion. The NMHCs and OVOCs were measured by selected ion flow tube mass spectrometry and the data of NMHCs were compared and corrected with the data from gas chromatography/flame ionization detector (GC/FID). The observation was carried out at an urban site (Tokyo Metropolitan Research Institute for Environmental Protection) in 2023. Since PANs were formed at the early time of the days in the presence of relatively high concentrations of acetaldehyde and an enhancement of PANs in the morning seems to bring a rapid rising of O₃, it is thought that small OVOCs such as acetaldehyde may play an important role on recent photochemistry related to the ozone formation in urban area of Japan.