Quasi-liquid layer on ice surfaces in the global environment: In-situ observation by controlling atmospheric gas and water vapor pressure

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K05604
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Biological physics/Chemical physics/Soft matter physics
• Research Institution: Hokkaido University
• Principal Investigator: Nagashima Ken 北海道大学, 低温科学研究所, 助教 (60436079)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 氷 / 疑似液体層 / 大気化学 / 酸性ガス / 不均一反応

Outline of Final Research Achievements

Surfaces of ice have attracted considerable attention as “reaction sites” where atmospheric gases cause various chemical reactions. In addition, the ice crystal surfaces near melting point are covered with quasi-liquid layers (QLLs). We directly visualized effects of acidic gases (HNO3 and HCl) on ice surfaces by advanced optical microscopy.
In the presence of acidic gas, QLLs were not pure bulk water but acidic solution. In the case of the HNO3 droplets, the ice-droplet interface grows evenly by vapor-liquid-solid growth mechanism. In contrast, in the case of HCl droplets, the growth of ice starts from the ice-droplet-vapor interface (contact lines) and the subsequent growth proceeded on the surface of the droplets, resulting in the embedding of the droplets in the ice crystals.

Free Research Field

結晶成長

Academic Significance and Societal Importance of the Research Achievements

氷表面における酸性ガスの反応は、オゾン層の破壊や二酸化窒素ガス等の有毒ガス生成を促進すると言われている。氷表面を覆うnmオーダー厚みの疑似液体層はこういった反応に関与すると考えられているが不明点が多い。研究代表者は高分解能光学顕微鏡で疑似液体層を直接観察することによって、地球大気に含まれるようなわずかppbオーダーの酸性ガスであっても氷表面の疑似液体層の安定性を高め、存在温度や存在形態を変化させることを発見した。