Frost flower influence on springtime boundary-layer ozone depletion events and atmospheric bromine levels

Springtime boundary layer ozone depletion events have been observed in both the Arctic and Antarctic. It has been suggested that these bromine-catalyzed depletion events may be caused by bromine released from frost flowers. We have measured the pH and ion concentrations of snow and frost flowers in the Ross Island, Antarctica area and find that if these are representative, frost flowers are unlikely to be a direct source of atmospheric bromine. The pH of the sampled frost flowers is too alkaline to support the release of molecular bromine resulting from the heterogeneous reaction of HOBr with Br ions. It is more likely that frost flowers are a source of aerosol bromine from which gas-phase bromine can be released through subsequent reactions in aerosol form or on the snow pack.