Elucidation of iodine activation mechanism in polar regions

• Project/Area Number: 18K03746
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17020:Atmospheric and hydrospheric sciences-related
• Research Institution: Aichi University of Technology (2023); Kyushu University (2018)
• Principal Investigator: YABUSHITA AKIHIRO 愛知工科大学, 工学部, 教授 (70371151)
• Project Period (FY): 2018-04-01 – 2024-03-31
• Project Status: Completed (Fiscal Year 2023)
• Budget Amount: ¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000); Fiscal Year 2020: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000); Fiscal Year 2019: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000); Fiscal Year 2018: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
• Keywords: ヨウ素 / ヨウ化物イオン / オゾン / 二酸化窒素 / キャビティリングダウン分光 / 不均一反応 / 氷 / 極域環境 / 極域 / 吸収分光 / レーザー / キャビティーリングダウン分光

Outline of Final Research Achievements

High concentrations of iodine (I2) and iodine monoxide radical (IO) have been observed in the Weddell Sea, which cannot be explained solely by biological releases. This observation suggests that there are other sources of production, such as inorganic chemical reactions. In this study, iodine compounds released from the photooxidation of iodide ions (I－) in ice and from the ice surface by the reaction of ozone (O3) or nitrogen dioxide (NO2) with the surface of frozen aqueous solutions containing iodide ions (I－) was studied in order to identify the source of these iodine compounds. The results suggested that reactions in/on ice, such as sea ice and snow ice, can be a source of iodine release in polar regions. The mechanism of iodine activation was elucidated.

Academic Significance and Societal Importance of the Research Achievements

ヨウ素原子は微量ながら触媒サイクルにより対流圏オゾン濃度を減少させたり、エアロゾルを生成したりして気候に影響を与えている。極域で生物放出のみでは説明できない高濃度のヨウ素が観測されていたが、本研究により新たな放出源を明らかにすることができた。
氷表面上での不均一反応によって気相中に放出されたガス種の高感度計測装置を開発した。雪氷や海氷での反応は、本研究の反応以外にも極域大気に影響を及ぼしているため今後の不均一反応機構の研究に役立つ。

Research Products

• [Journal Article] Experimental determination of the photooxidation of aqueous I- as a source of atmospheric I2 (2019)
  • Author(s): Kosuke Watanabe, Shohei Matsuda, Carlos A. Cuevas, Alfonso Saiz-Lopez, Akihiro Yabushita, Yukio Nakano
  • Journal Title: ACS Earth and Space Chemistry Volume: 印刷中 Issue: 4 Pages: 669-679
  • DOI: 10.1021/acsearthspacechem.9b00007
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Improved model for the isosteric heat of adsorption and impacts on the performance of heat pump cycles (2018)
  • Author(s): Azahar Fatin Hazwani M.、Mitra Sourav、Yabushita Akihiro、Harata Akira、Saha Bidyut Baran、Thu Kyaw
  • Journal Title: Applied Thermal Engineering Volume: 143 Pages: 688-700
  • DOI: 10.1016/j.applthermaleng.2018.07.131
  • Peer Reviewed / Int'l Joint Research
• [Presentation] H2Oを介したO2・I-間の電荷移動励起についての理論的研究 (2018)
  • Author(s): 水上渉，薮下彰啓, 原田明，青木百合子
  • Organizer: 第12回分子科学討論会
• [Presentation] Measurement of effective quantum yields for the photolysis of aqueous I- and estimation of atmospheric I2 emission rate (2018)
  • Author(s): Kosuke Watanabe, Shohei Matsuda, Carlos A. Cuevas, Alfonso Saiz-Lopez, 〇Akihiro Yabushita, Yukio Nakano
  • Organizer: 2018 joint 14th iCACGP Symposium and 15th IGAC Science Conference
• [Presentation] 海洋中でのヨウ化物イオン光化学反応による大気中へのヨウ素の放出速度 (2018)
  • Author(s): 薮下彰啓
  • Organizer: 第10回 大気・雪氷・海洋間の物質循環と極域への物質輸送に関する研究小集会
• [Remarks]
  • URL: http://www.mm.kyushu-u.ac.jp/lab_07/