Angelaki Maria, d'Erceville Jill, Donaldson D James, George Christian
Universite Claude Bernard Lyon 1, CNRS, IRCELYON, UMR 5256, Villeurbanne, F-69100, France.
Department of Chemistry, University of Toronto, 80 George Street, Toronto, Ontario, Canada M5S 3H6.
J Am Chem Soc. 2024 Sep 25;146(38):25889-25893. doi: 10.1021/jacs.4c07356. Epub 2024 Sep 16.
Recent studies have shown that the air-water interface of aqueous microdroplets is a source of OH radicals and hydrogen peroxide in the atmosphere. Several parameters such as droplet size, salt, and organic content have been suggested to play key roles in the formation of these oxidants. In this study, we focus on the effect of acidity on the spontaneous interfacial hydrogen peroxide formation of salt-containing droplets. NaSO, NaCl, and NaBr bulk solutions, at the range of pH 4 to 9.5, were nebulized, using ultra high-purity N/O (80%/20%), and HO was measured in the collected droplets. All of the experiments were performed in = 292 ± 1 K and humidity levels of 90 ± 2%. For NaSO and NaCl, the HO concentration was increased by ∼40% under alkaline conditions, suggesting that OH enriched environments promote its production. When CO was added in the ultrapure air, HO was observed to be lower at higher pH. This suggests that dissolved CO can initiate reactions with OH radicals and electrons, impacting the interfacial HO production. HO formation in NaBr droplets did not display any dependence on the pH or the bath gas, showing that secondary reactions occur at the interface in the presence of Br, which acts as an efficient interfacial source of electrons.
最近的研究表明，水性微滴的气-水界面是大气中羟基自由基和过氧化氢的一个来源。已有人提出，诸如液滴大小、盐分和有机物含量等几个参数在这些氧化剂的形成过程中起着关键作用。在本研究中，我们聚焦于酸度对含盐液滴自发形成界面过氧化氢的影响。使用超高纯N/O（80%/20%）对pH值在4至9.5范围内的NaSO、NaCl和NaBr本体溶液进行雾化，并对收集到的液滴中的HO进行测量。所有实验均在温度为292 ± 1 K、湿度为90 ± 2%的条件下进行。对于NaSO和NaCl，在碱性条件下HO浓度增加了约40%，这表明富含OH的环境会促进其生成。当在超纯空气中添加CO时，观察到在较高pH值下HO含量较低。这表明溶解的CO会引发与OH自由基和电子的反应，影响界面HO的生成。NaBr液滴中HO的形成对pH值或浴气均无依赖性，这表明在存在Br的情况下，界面会发生二次反应，Br作为一种有效的界面电子源。
