Quantitative analysis of chemical reaction rates in deliquesced aerosol particles at high ionic strengths

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K17876
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 63010:Environmental dynamic analysis-related
• Research Institution: Tohoku University (2022-2023); Kanazawa University (2021)
• Principal Investigator: Gen Masao 東北大学, 多元物質科学研究所, 助教 (50774535)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: エアロゾル / 大気化学反応

Outline of Final Research Achievements

Nitrogen dioxide (NO2) hydrolysis in deliquesced aerosol particles forms nitrous acid and nitrate and thus impacts air quality, climate, and the nitrogen cycle. Traditionally, it is considered to proceed far too slowly in the atmosphere. However, the significance of this process is highly uncertain because kinetic studies have only been made in dilute aqueous solutions but not under high ionic strength conditions of the aerosol particles. Here, we use laboratory experiments, air quality models, and field measurements to examine the effect of the ionic strength on the reaction kinetics of NO2 hydrolysis. We find that high ionic strengths (I) enhance the reaction rate constants (kI) by more than an order of magnitude compared to that at infinite dilution (kI=0), yielding log10(kI/kI=0) = 0.04I.

Free Research Field

大気化学

Academic Significance and Societal Importance of the Research Achievements

エアロゾルの反応速度定数への高イオン強度の影響は未だ解明されず、従来の研究ではバルク反応領域から得られた速度定数がエアロゾルの反応速度定数として代用されてきた。本研究の成果では、高イオン強度条件の影響に係る実験的検討を行い、エアロゾル相での反応速度定数は、バルク溶液（イオン強度がゼロ）に比べて、何倍もから高いことを示した。この成果は、従来のバルク溶液から得られた反応速度論は大気エアロゾル中で起こる化学反応には適用できないことが示唆され、大気化学研究におけるイオン強度の重要性が高まると考えられる。