Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093.
Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093.
Proc Natl Acad Sci U S A. 2021 Jan 12;118(2). doi: 10.1073/pnas.2018397118.
Aerosols impact climate, human health, and the chemistry of the atmosphere, and aerosol pH plays a major role in the physicochemical properties of the aerosol. However, there remains uncertainty as to whether aerosols are acidic, neutral, or basic. In this research, we show that the pH of freshly emitted (nascent) sea spray aerosols is significantly lower than that of sea water (approximately four pH units, with pH being a log scale value) and that smaller aerosol particles below 1 μm in diameter have pH values that are even lower. These measurements of nascent sea spray aerosol pH, performed in a unique ocean-atmosphere facility, provide convincing data to show that acidification occurs "across the interface" within minutes, when aerosols formed from ocean surface waters become airborne. We also show there is a correlation between aerosol acidity and dissolved carbon dioxide but no correlation with marine biology within the seawater. We discuss the mechanisms and contributing factors to this acidity and its implications on atmospheric chemistry.
气溶胶对气候、人类健康和大气化学都有影响，而气溶胶的 pH 值在气溶胶的物理化学性质中起着重要作用。然而，气溶胶是酸性、中性还是碱性，目前仍存在不确定性。在这项研究中，我们表明，新排放（初生）的海水喷雾气溶胶的 pH 值明显低于海水（约四个 pH 值单位，其中 pH 值是对数刻度值），并且直径小于 1 微米的较小气溶胶颗粒的 pH 值甚至更低。这些在独特的海洋-大气设施中进行的初生海水喷雾气溶胶 pH 值测量提供了令人信服的数据，表明当海洋表面水形成的气溶胶成为空气传播物时，酸化会在几分钟内“跨越界面”发生。我们还表明，气溶胶酸度与溶解二氧化碳之间存在相关性，但与海水中的海洋生物学没有相关性。我们讨论了这种酸度的机制和影响因素及其对大气化学的影响。
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