Minerva Research Group, Max Planck Institute for Chemistry, Mainz 55128, Germany.
State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China.
Environ Sci Technol. 2023 Aug 29;57(34):12571-12582. doi: 10.1021/acs.est.2c09851. Epub 2023 Aug 21.
Acidity is one central parameter in atmospheric multiphase reactions, influencing aerosol formation and its effects on climate, health, and ecosystems. Weak acids and bases, mainly CO, NH, and organic acids, are long considered to play a role in regulating atmospheric acidity. However, unlike strong acids and bases, their importance and influencing mechanisms in a given aerosol or cloud droplet system remain to be clarified. Here, we investigate this issue with new insights provided by recent advances in the field, in particular, the multiphase buffer theory. We show that, in general, aerosol acidity is primarily buffered by NH, with a negligible contribution from CO and a potential contribution from organic acids under certain conditions. For fogs, clouds, and rains, CO, organic acids, and NH may all provide certain buffering under higher pH levels (pH > ∼4). Despite the 10to 10 lower abundance of NH and organic weak acids, their buffering effect can still be comparable to that of CO. This is because the cloud pH is at the very far end of the CO multiphase buffering range. This Perspective highlights the need for more comprehensive field observations under different conditions and further studies in the interactions among organic acids, acidity, and cloud chemistry.
酸度是大气多相反应的一个核心参数，影响着气溶胶的形成及其对气候、健康和生态系统的影响。弱酸碱，主要是 CO、NH 和有机酸，长期以来被认为在调节大气酸度方面发挥作用。然而，与强酸和强碱不同，它们在特定气溶胶或云滴系统中的重要性和影响机制仍有待阐明。在这里，我们利用该领域的最新进展提供的新见解，特别是多相缓冲理论，研究了这个问题。我们表明，一般来说，气溶胶酸度主要由 NH 缓冲，CO 的贡献可以忽略不计，在某些条件下有机酸可能有一定的贡献。对于雾、云和雨，CO、有机酸和 NH 在较高 pH 值（pH > ∼4）下可能都具有一定的缓冲能力。尽管 NH 和有机弱酸的丰度低了 10 到 10 倍，但它们的缓冲作用仍可与 CO 相媲美。这是因为云的 pH 值处于 CO 多相缓冲范围的非常末端。本观点强调了在不同条件下进行更全面的现场观测以及进一步研究有机酸、酸度和云化学之间相互作用的必要性。
