Monday, 11 January 2016
It is important to perform studies on the reactions occurring within raindrops or cloud droplets in order to understand the role of heterogeneous chemistry in the atmosphere. Several in-situ measurements have given significant concentrations of transition metals in wet aerosol, cloud, rain, fog, or snow. However, there is still large uncertainly in the understanding of the reactivity of transition metal ions (TMI) in aqueous solution. This creates difficulties in evaluating the impact of cloud chemistry on the atmosphere. Iron (Fe), is the major metal involved in chemical interactions occurring in atmospheric liquid phase and are principally related to the homogeneous aqueous phase chemistry. The production of iron(IV) (ferryl, FeIVO2+) in the environment may be possible through a reaction of Fe(II) with ozone and as an intermediate in the Fenton reaction. Ferryl ion has the potential oxidative role in cloud water. Tthe reactivity and products of reactions of ferryl with constituents of atmospheric droplet will be presented. Assessment of the ferryl oxidative capacity in cloud droplets will be presented. The mechanism and role of the ferryl-substrate system in the atmosphere will be discussed. Manganese also interacts with the chemistry of HO, HO2, and sulfur to influence the oxidizing capacity of the atmospheric aqueous phase. Manganese(II)-Mn(III) redox chemistry plays an important role in the radical chemistry of troposphere by destroying major atmospheric oxidants, O3 and H2O2. Examples of the reactions are: Mn2+ + OH → Mn3+ + OH- and Mn(III) + H2O2 → Mn2+ + HO2 + H+. Manganese(III) generated by such reactions may also react with other constituents of atmospheric water phases. The impact of Mn(III) to the chemistry of atmospheric liquid phase will be given.
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