Aqueous-Phase Photochemical Formation of Hydrogen Peroxide and Hydroxyl Radical in Clouds and Fogs

9307171大气水滴中过氧化氢(HoOH)和羟基自由基(OH)的浮士德水相反应在对流层化学中起着至关重要的作用，但对这些氧化剂对水滴的来源的了解尚不完整。虽然氢氧化氢和氢氧化氢的气滴分配已经得到了大量的研究，但作为这些氧化剂向大气水滴的来源的水相光化学反应的关注相对较少。这项研究的目的是：(A)确定几年来从几个地点收集的真实云水和雾水中HoOH和OH光形成的量子产率和阳光速率，(B)确定HoOH和OH光形成的季节依赖性，(C)比较水相光化学和气滴分配作为HoOH和OH的来源对大气水滴的相对重要性，(D)评估真实大气水的化学和物理参数，作为HoOH和OH光形成速率和OH寿命的预测因子(基于机理考虑)，(E)确定与云和雾化学有关的化合物光形成HoOH的速率和量子产率；(F)增加对真实大气水中氧化剂光化学形成的机制的了解，并形成单独的化合物。该项目将表征从几个高海拔地点获得的真实云和雾水中HoOH和OH的光形成。此外，还将对个别有机化合物明确定义的水溶液的HoOH光形成进行调查研究。总体而言，这项建议的结果将允许更准确地了解HoOH和OH的来源到云和雾滴。这将提高我们对过氧物、硫、碳、铁和其他元素的大气化学循环的理解。这一新知识将加强我们对硫酸和硫酸盐气溶胶形成的预测，这些影响酸沉积和硫酸盐气溶胶所产生的全球冷却效应。

9307171 Faust Aqueous-phase reactions of hydrogen peroxide (HOOH) and hydroxyl radical (OH) in atmospheric water drops play crucial roles in the chemistry of the troposphere, yet knowledge of the sources of these oxidants to the water drops is incomplete. While gas-to- drop partitioning of HOOH and OH has received much study, comparatively little attention has been focussed on aqueous-phase photochemical reactions as sources of these oxidants to atmospheric water drops. The objectives of this research are: (a) determination of quantum yields and sunlight rates of HOOH and OH photo-formation in authentic cloud and fog waters collected over several years from several locations, (b) determination of the seasonal dependence of HOOH and OH photo-formation, (c) comparisons of the relative importance of aqueous-phase photochemistry versus gas-to-drop partitioning as sources of HOOH and OH to atmospheric water drops, (d) to evaluate chemical and Physical parameters of authentic atmospheric waters as predictors (based on mechanistic considerations) of the HOOH and OH photo-formation rates and of the OH lifetime, (e) to determine rates and quantum yields of HOOH photo-formation from compounds of relevance to cloud and fog chemistry, and (f) to increase the understanding of mechanisms responsible for photochemical formation of the oxidants in authentic atmospheric waters and form the individual compounds. The project will characterize the photo-formation of HOOH and OH in authentic cloud and fog waters obtained form several high elevation sites. Additionally, survey studies will be carried out on the HOOH photo-formation form well-defined aqueous solutions of individual organic compounds. Overall, the results form this proposal will allow for a more accurate understanding to the sources of HOOH and OH to cloud and fog drops. This will improve our understanding of the atmospheric chemical cycles of peroxides, sulfur, carbon, iron, and other elements. This new knowledge will enhance our predictions of sulfuric acid and sulfate aerosol formation that affect acid deposition and the global cooling effect exerted by sulfate aerosols.