Case studies of the oxidation of sulphur dioxide in a hill cap cloud using ground and aircraft based measurements

Data gathered by aircraft showed that hydrogen peroxide (H₂O₂) concentrations in the free troposphere were much greater than near the ground and that entrainment of air containing H₂O₂, into the cap cloud could provide a significant supply of oxidant. These findings suggest that the entrainment of H₂O₂ into cloud systems may be important to the oxidation of SO₂, 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 H₂O₂ 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). -from Authors