The influence of in-cloud chemical reactions on the formation of ozone in polluted atmospheres

Ozone (O{sub 3}) is a harmful secondary air pollutant produced during the photochemical oxidation of emitted nitrogen oxides (NO + NO{sub 2} = NO{sub x}) and organic compounds in polluted areas. Previous studies of O{sub 3} pollution consider only gas-phase reactions among pollutants. However, several recent cloud chemistry studies show that chemical processes occurring in clouds significantly influence O{sub 3} formation. Unfortunately, existing studies on the influence of heterogeneous-phase chemistry on O{sub 3} formation have examined only a limited set of chemical conditions, and have not considered the effects of clouds under polluted urban conditions. In this paper, the authors apply a comprehensive photochemical reaction model that includes several important aqueous-phase reactions to a wide range of pollutant concentration conditions. Concentrations of primary pollutants NO{sub x} and NonMethane HydroCarbons (MMHC) range from heavily polluted to cleaner, more remote conditions. The results of this study can be used to assess O{sub 3} formation in polluted boundary layers that are partially covered by clouds.