Accommodation coefficient of HOBr on deliquescent sodium bromide aerosol particles

[摘要] Uptake of HOBr on sea salt aerosol, sea salt brine or ice is believed to be akey process providing a source of photolabile bromine (Br₂) and sustainingozone depletion cycles in the Arctic troposphere. In the present study, uptake of HOBr on sodium bromide (NaBr) aerosol particles was investigated atan extremely low HOBr concentration of 300 cm^-3 using the short-livedradioactive isotopes ^83-86Br. Under these conditions, at maximum oneHOBr molecule was taken up per particle. The rate of uptake was clearly limited by the mass accommodation coefficient, which was calculated to be0.6 ± 0.2. This value is a factor of 10 larger than estimates used in earlier models. The atmospheric implications are discussed using the boxmodel "MOCCA'', showing that the increase of the accommodation coefficientof HOBr by a factor of 10 only slightly affects net ozone loss, but significantly increases chlorine release.

[学科分类] 大气科学