Important contributions of sea-salt aerosols to atmospheric bromine cycle in the Antarctic coasts

Polar sunrise activates reactive bromine (BrO(x)) cycle on the Antarctic coasts. BrO(x) chemistry relates to depletion of O(3) and Hg in polar regions. Earlier studies have indicated “blowing snow” as a source of atmospheric BrO(x). However, surface O(3) depletion and BrO enhancement occurs rarely under blowing snow conditions at Syowa Station, Antarctica. Therefore, trigger processes for BrO(x) activation other than the heterogeneous reactions on blowing snow particles must be considered. Results of this study show that enhancement of sea-salt aerosols (SSA) and heterogeneous reactions on SSA are the main key processes for atmospheric BrO(x) cycle activation. Blowing snow had Br(−) enrichment, in contrast to strong Br(−) depletion in SSA. In-situ aerosol measurements and satellite BrO measurements demonstrated clearly that a BrO plume appeared simultaneously in SSA enhancement near the surface. Results show that surface O(3) depletion at Syowa Station occurred in aerosol enhancement because of SSA dispersion during the polar sunrise. Amounts of depleted Br(−) from SSA were matched well to the tropospheric vertical column density of BrO and BrO(x) concentrations found in earlier work. Our results indicate that SSA enhancement by strong winds engenders activation of atmospheric BrO(x) cycles via heterogeneous reactions on SSA.