Aqueous-phase chemical reactions in the atmosphere

Full text: Energy production strongly impacts on the environment in particular, to the increase of the atmospheric loads of acidic gases and particle loading e.g. to the acid rain environmental problem. Scientific evidence has shown these depositions can harm ecosystems and human health. The known Antarctic ozone hole and dramatic drops in concentration of ozone caused by the release of free chlorine2 and bromide2 from sea salt occurred in marine boundary layer at sunrise are well known examples of such negative impact of heterogeneous chemical reactions on the Environment. During the past two decades great strides have also been made toward understanding aqueous-phase chemical reactions in cloud droplets, in particular, those involved transition metal ions (TMI). The knowledge how these metal ions accelerate chemical reactions in the droplet phase will help to develop and evaluate a relevant role of TMI in the atmosphere and probably others aqueous-phase atmospheric processes. In contrast to a fairly extensive knowledge of gas phase reactions in the troposphere, current understanding of cloud chemistry yet not well determined. Despite their low water volume content in the gas (typically 10-7 vol/vol), the droplets provide an ideal reaction media to occurrence of chemical reactions in the atmosphere especially which involve TMI which might act as efficient catalysts and hence to much more efficient aqueous phase reaction pathways then the respective uncatalyzed gas phase reactions. Iron-catalyzed SO2 removal from the gas phase is of the largest interest for the droplet chemistry. Its extensive study during the past 10-15 years is motivated largely by a need to reproduce SO2 rate depletion in the troposphere. Much less attention was paid to the analysis of a role of TMI in these processes. Many aspects of this problem are still far from certain. The so-called classical model of S(IV) oxidation is insufficient to account for many phenomena and observations even for the simplest case. The extent the catalytic activity of TMI is influenced by atmospheric radical fluxes, by UV light absorption and by uptake different organic or inorganic constituents from the gas phase are still far from certain and need to be investigated in more details. Also reliable SO2 removal rate predictions in the atmosphere as well as others pollutants removal rates including radioactive nuclides and consequently the forecasts of real distances from a source of the pollutants to the location where they can actually be deposited onto the earth's surface are not possible without detailed knowledge of cloud processes