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

We made 3-year sampling of aerosols and blowing snow in 2004-2006 at Syowa Station, Antarctica. Water-soluble constituents were determined with ion chromatograph. Polar sunrise activates reactive bromine (BrO_x) cycle on the Antarctic coasts. BrO_x chemistry relates to depletion of O₃ and Hg in polar regions. Earlier studies have pointed out "blowing snow" as a source of atmospheric BrOx. However, surface O₃ 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. This study shows 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 O3 depletion at Syowa Station occurred in aerosol enhancement because of SSA dispersion during the polar sunrise. Amounts of the 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 BrOx cycles via heterogeneous reactions on SSA.