Unsaturated low-volatile organic compounds have been observed in atmospheric aerosol particles (e.g., aerosols from plants, cooking, and biomass burning) and human skin. Understanding their chemical fates through reactions with ozone at the relevant interfaces is crucial to elucidating the multiphase chemical mechanisms and predicting their environmental and health impacts. In this work, heterogeneous ozonolysis of two endocyclic unsaturated organic aerosol proxies (4-cyclohexene-1,2-diacid and shikimic acid) were studied in a flow tube reactor under different O₃ exposure levels and relative humidities (30%, 60%, and 90%). Our results show strong RH dependence for the oxidation kinetics due to aerosol phase state change and secondary chemistry (e.g., parent acids reacting with the produced Criegee Intermediates). The observed multifunctional products are explained by the various Criegee Intermediates mechanisms and later-generation reactions. Three processes that lead to the evolution of first-generation carbonyl products were revealed in light of independent measurements: (1) intramolecular aldol reactions; (2) peroxide oxidation of aldehydes (i.e., Baeyer–Villiger reactions); and (3) decarboxylation induced by hydrogen peroxide. Furthermore, organic peroxides were observed to form from accretion reactions between the Criegee Intermediates and the parent compounds as well as the later-generation multifunctional products. The proposed mechanisms can be a key extension to the current understanding of heterogeneous ozonolysis of unsaturated organic aerosol.

中文翻译：

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内环不饱和有机气溶胶代理的异质臭氧分解：对学员中间动力学和后代反应的影响。

在大气气溶胶颗粒（例如，来自植物，烹饪和生物质燃烧的气溶胶）和人体皮肤中发现了不饱和的低挥发性有机化合物。通过与相关界面处的臭氧反应了解它们的化学命运，对于阐明多相化学机理并预测其对环境和健康的影响至关重要。在这项工作中，在不同O ₃下，在流管反应器中研究了两种内环不饱和有机气溶胶代理（4-环己烯1,2-二酸和sh草酸）的异质臭氧分解。暴露水平和相对湿度（30％，60％和90％）。我们的结果表明，由于气溶胶的相态变化和第二化学反应（例如，母酸与生成的Criegee中间体发生反应），RH对氧化动力学的依赖性强。各种Criegee中间体机制和后代反应解释了所观察到的多功能产品。根据独立的测量，揭示了导致第一代羰基产物进化的三个过程：（1）分子内醛醇缩合反应；（2）醛的过氧化物氧化（即，Baeyer-Villiger反应）；（3）过氧化氢引起的脱羧作用。此外，在Criegee中间体与母体化合物以及下一代多功能产品之间的积聚反应中观察到有机过氧化物的形成。所提出的机制可以是对不饱和有机气溶胶非均相臭氧分解的当前理解的关键扩展。