[A-AS06] 大気化学

[AAS06-P26] Do hypohalous acids play important roles on sulfate formation in the Antarctic atmosphere?

*石野 咲子¹、服部 祥平¹、Savarino Joel²、Chen Qianjie³、Shao jingyuan^3,4、吉田 尚弘^1,5、Alexander Becky³ (1.東京工業大学 物質理工学院、2.Institut des Geosciences de l’Environnement, Universite Grenoble Alpes/CNRS, France、3.Department of Atmospheric Sciences, University of Washington, USA、4.Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, China、5.Earth-Life Science Institute, Tokyo Institute of Tehcnology, Japan)

キーワード：南極、硫酸エアロゾル、反応性臭素、17O異常

Br_y (= HBr + HOBr + Br₂ + BrO + BrNO₂ + BrNO₃ + Br) is thought to play important roles in atmospheric chemistry in the Antarctic boundary layer through e.g., ozone destruction by Br atoms and oxidation of dimethyl sulfide by BrO [1,2]. A series of studies has indicated that a major source of Br_y in coastal Antarctica is blowing-snow which takes a part of brine on the sea ice surface to the atmosphere [3,4]. Therefore, it has been suggested that the importance of Br_y is limited at Dumont d’Urville (DDU; 66°40'S, 140°01'E), one of coastal Antarctic stations where the sea ice extent is relatively low compared to other coastal stations and highly exposed to the continental winds from the East Antarctic plateau [5]. Nevertheless, ¹⁷O-excess (Δ¹⁷O ≒ δ¹⁷O – 0.52 x δ¹⁸O) of atmospheric sulfate (SO₄^2-) at DDU showed relatively low values in spring compared to autumn, which indicates the possibility of a significant contribution of hypohalous acids (HOBr, HOCl) to aqueous S(IV) oxidation in the spring time [6].
To test this hypothesis, we simulate ¹⁷O excess of SO₄^2- using 3D chemical transport model (GEOS-Chem) in which reactions of S(IV) and hypohalous acids were recently implemented. We discuss the results by comparison of the observations at DDU with those from Concordia (75°06'S, 123°33'E), the inland Antarctic station which is located more than 1,000 km away from the sea ice.

References:
[1] Saiz-Lopez et al. (2008), ACP, Vol.8, p.887-900, doi: 10.5194/acp-8-887-2008
[2] Read et al. (2008), ACP, Vol.8, p.2985-2997, doi: 10.5194/acp-8-2985-2008
[3] Yang et al. (2008), GRL, Vol.35, L16815, doi: 10.1029/2008GL034536
[4] Lieb-Lappen and Obbard (2015), ACP, Vol.15, p7537-7545, doi: 10.5194/acp-15-7537-2015
[5] Legrand et al. (2009), JGRA, Vo.114, D20, doi: 10.1029/2008JD011667
[6] Ishino et al. (2017), ACP, Vol.17, p.3713-3727, doi:10.5194/acp-17-3713-2017