A theoretical study of chemical kinetic control in the scavenging of pollutant gases by cloud and rain drops

Abstract

Theoretical models that describe the uptake of trace gases by water drops falling at terminal velocity in air have been extended to include the effects of aqueous phase chemical processes that occur on time scales comparable with or greater than that over which the relevant physical scavenging processes operate. In particular, the case of reversible dervative formation by the absorbed species has been treated, and illustrated by application to the absorption of acetaldehyde under conditions prevailing in the atmosphere. In addition, the relative influences of aqueous phase chemistry and of convective-diffusion on the efficiency of the scavenging process have been explored more generally, using the revised models. A brief comparison of the factors controlling the uptake of sulfur dioxide, dichloromethane, and acetaldehyde is presented.