The Dynamic Redox Chemistry of Metals in the Troposphere

9303024 Hoffmann根据加州理工学院目前的研究，已经确定近岸大陆对流层中铁的氧化还原循环涉及溶解和气溶胶表面物种，并且主要受与含铁（III）的各种相和物种共存的可氧化有机化合物的水平控制。这些共存的有机化合物被Fe(III)（可溶性配合物和金属氧化物多晶）热氧化和光辅助氧化生成羧酸。这种化学相互依赖性与海洋层云中Fe（II）和CH3二氧化碳浓度之间观察到的强相关性是一致的。此外，当草酸盐和甲酸盐等电子供体存在时，辐照的环境气溶胶粒子已被证明能产生相对高浓度的h2o2。这些结果表明，被照射的云和雾霾气溶胶可能为对流层中的空气包裹提供过氧化氢的原位来源。这一结果是对全球对流层化学在大气氧化能力来源方面具有重要意义的重大发现。根据正在进行的关于大气中铁的动态化学的研究（NSF Grant ATM-9015775），建立了以下研究目标：1)实验确定了从海洋和大陆（农村和城市）环境中收集的云、雾和雨水中铁的各种化学形态和氧化态；2)表征了大气水滴中参与氧化还原循环的铁和锰的固相，并追踪了它们的来源。

9303024 Hoffmann Based on current research a Caltech, it has been determined that the redox cycle of Fe in near-shore continental troposphere involves both dissolved and aerosol surface species and it is controlled primarily by level of oxidizable organic compounds that co-exist with the various phases and species containing Fe(III). These co-existing organic compounds undergo thermal and photo- assisted oxidation by Fe(III) species (soluble complexes and metal oxide polymorphs) to yield carboxylic acids. This chemical interdependency is consistent with the strong correlation observed between the concentrations of Fe(II) and CH3 carbon dioxide in marine stratus clouds. In addition, irradiated ambient aerosol particles have been shown to produce relatively large concentrations of h2o2 when electron donors such as oxalate and formate are present. These results suggest that illuminated clouds and haze aerosol may provide an in situ source of hydrogen peroxide to air parcels in the troposphere. This result is a major finding of significance to global troposphere chemistry in regards to sources of oxidizing capacity in the atmosphere. In light of the on-going research (NSF Grant ATM-9015775 on the dynamic chemistry of iron in the atmosphere, the following research objectives have been established: 1) experimentally determine the various chemical forms and oxidation states of Fe in cloud-, fog- and rainwater collected from marine and continental (both rural and urban) environments, 2) characterize the solid- phase of Fe and Mn, which participate in redox cycles in atmospheric water droplets, and trace their sources to the atmosphere.