Case studies of the oxidation of sulphur dioxide in a hill cap cloud using ground and aircraft based measurements
Gallagher, M. W.; Downer, R. M.; Choularton, T. W.; Gay, M. J.; Stromberg, I.; Mill, C. S.; Radojevic, M.; Tyler, B. J.; Bandy, B. J.; Penkett, S. A.; Davies, T. J.; Dollard, G. J.; Jones, B. M. R.
Журнал:
Journal of Geophysical Research: Atmospheres
Дата:
1990
Аннотация:
Two case studies are presented which investigate the aqueous phase oxidation of sulfur dioxide (SO<sub>2</sub>) within a cap cloud on the summit of Great Dun Fell (847 m above sea level) in England. Data gathered by aircraft showed that hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) concentrations in the free troposphere were much greater than near the ground and that entrainment of air containing H<sub>2</sub>O<sub>2</sub>, into the cap cloud could provide a significant supply of oxidant. These findings suggest that the entrainment of H<sub>2</sub>O<sub>2</sub> into cloud systems may be important to the oxidation of SO<sub>2</sub>, particularly in the absence of large concentrations of ammonia gas, which may favor oxidation by ozone. It is also shown that the apparent reaction rate of H<sub>2</sub>O<sub>2</sub> within the cloud is consistent with our previous estimates made and were substantially larger than would be predicted from laboratory studies in bulk solutions (Chandler et al., 1988b). Sulphate, (SO<sub>4</sub><sup>2−</sup>), production was observed when significant concentrations of SO<sub>2</sub> were present. The measured concentrations of the principal species involved in one of the case studies were consistent with model predictions which take account of SO<sub>2</sub> oxidation by H<sub>2</sub>O<sub>2</sub> and O<sub>3</sub> and an enhanced H<sub>2</sub>O<sub>2</sub>‐SO<sub>2</sub> reaction rate.
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