ABSTRACT
This chapter attempts to determine if there were direct aqueous-phase photochemical sources of peroxides to cloud waters. It is possible to get some measure of the importance of aqueous-phase photo-production as a source of peroxides to cloud drops by comparing measured rates of aqueous-phase photoformation with field measurements of peroxides in cloud waters. Models of atmospheric water drop chemistry have traditionally focused on gas-to-drop partitioning of peroxides and peroxyl radicals as the sole sources of aqueous-phase peroxides. Aqueous-phase photoproduction will be relatively more important, with respect to gas-to-drop transfer, in the spring, fall, and winter compared to the summer. Initial aqueous-phase photochemical production rates are correlated with cloud water fluorescence. This suggests that the fluorescent compounds contribute significantly to peroxide photoproduction. Aqueous-phase photochemical peroxide production occurred in samples from all five sites and in nearly all of the samples irradiated.
