Impacts of cloud water droplets on the OH production rate from peroxide photolysis

Abstract

Understanding the difference between observed and modeled concentrations of HO_x radicals in the troposphere is a current major issue in atmospheric chemistry. It is widely believed that existing atmospheric models miss a source of such radicals and several potential new sources have been proposed. In recent years, interest has increased on the role played by cloud droplets and organic aerosols. Computer modeling of ozone photolysis, for instance, has shown that atmospheric aqueous interfaces accelerate the associated OH production rate by as much as 3–4 orders of magnitude. Since methylhydroperoxide is a main source and sink of HO_x radicals, especially at low NO_x concentrations, it is fundamental to assess what is the influence of clouds on its chemistry and photochemistry. In this study, computer simulations for the photolysis of methylhydroperoxide at the air–water interface have been carried out showing that the OH production rate is severely enhanced, reaching a comparable level to ozone photolysis.