Gas-phase H₂O₂ is a prominent oxidant in the atmosphere. It also induces lung tissue damage and forest decline. Although it is known that ozonolysis of gas-phase alkenes leads to H₂O₂ formation at high relative humidities (RHs), little is known about this chemistry via gas-surface heterogeneous oxidation. Here, we quantitatively investigated the formation of H₂O₂ from surface ozonolysis of unsaturated lipids commonly found in human skin oil and atmospheric aerosol. This process is initiated by water reacting with Criegee intermediates (CIs), forming α-hydroxyhydroperoxides (α-HHPs) as the key intermediate products. α-HHPs are thermally stable molecules that act as reservoirs of H₂O₂ under dry conditions, prior to rapid decomposition to release H₂O₂ in the presence of water vapor. The upper limit of the α-HHP lifetime derived from oxidized methyl oleate was roughly 2 min at 50% RH. The molar H₂O₂ yields (relative to ozone consumption) vary from 7% to 35% for triolein, methyl oleate, and squalene, with no significant dependence on relative humidity from 50% to 80%. In contrast, oleic acid has the lowest H₂O₂ yield (∼2%), likely due to a more competitive reaction between CIs and its carboxylic acid headgroup. The implications of this chemistry in atmospheric and indoor environments are discussed.

中文翻译：

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通过不饱和脂质的多相臭氧分解形成气相过氧化氢

气相H ₂ O ₂是大气中的主要氧化剂。它还引起肺组织损伤和森林退化。尽管已知气相烯烃的臭氧分解会在高相对湿度（RH）下形成H ₂ O ₂，但对于这种化学方法通过气体表面非均相氧化知之甚少。在这里，我们定量研究了人类皮肤油和大气气溶胶中常见的不饱和脂质的表面臭氧分解过程中H ₂ O ₂的形成。水与Criegee中间体（CIs）反应，形成α-羟基氢过氧化物（α-HHPs）作为关键中间产物，从而引发了这一过程。α-HHP是热稳定的分子，可作为H的储库₂ O ₂在干燥条件下，然后在水蒸气存在下迅速分解释放H ₂ O ₂。在50％RH下，源自氧化油酸甲酯的α-HHP寿命上限约为2分钟。三油精，油酸甲酯和角鲨烯的摩尔H ₂ O ₂产率（相对于臭氧消耗量）从7％到35％不等，相对湿度从50％到80％没有显着依赖性。相反，油酸的H ₂ O ₂收率最低（〜2％），这可能是由于CI和其羧酸头基之间更具竞争性的反应。讨论了这种化学在大气和室内环境中的含义。