A Model Study Of Halogen Chemsrtry In The Marine Atmospheric Boundary Layer

The gas and aqueous phase chemistry in the marine atmospheric boundary layer has been studied by model MECCA. A special focus was the study of the reaction cycles of halogen compounds, including acid catalyzed mechanism of halogen activation in sea salt aerosols, the role of halogen radicals in ozone destruction and oxidation of DMS by BrO ,etc.Acid catalyzed mechanism is a useful way to transform unreactive Br? to reactive substance such as HOBr aq and Bra q.When HO2 exists, the total net reaction is aerosols uptake acid gases, the autocatalytic bromine activation cycle consumes H + which implies the need for acidification of the sea salt aerosol to form HOBr .The gas phase concentration of O3 is important for these cycles because the production of BrO and therefore also the O3 destruction is catalyzed by O3 . If O3 concentration is low ,halogen activation is slowed down .Compared to sea salt aerosol, the presence of sulfate aerosol particles is more important for the halogen activation .Due to the lager surface area and the lower pH of the sulfate aerosol.At sunrise (high solar zenith angle) the solar spectrum in the lower troposphere is shifted to longer wavelengths resulting in a delay of O3 photolysis relative to Br2 and BrCl . This causes a delay in the photolysis initiated production of OH and HO2 relative to the production of Br ,leading to an increase in BrO concentration and O3 destruction in sunrise. And then the HO2 concentration will increase gradually and lead to a minimum of BrO concentration. In winter, the solar zenith angle is different with summer, the solar spectrum is shifted to greater...