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

Keiichiro Hara; Kazuo Osada; Masanori Yabuki; Hisahiro Takashima; Nicolas Theys; Takashi Yamanouchi

doi:10.1038/s41598-018-32287-4

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

Sci Rep. 2018 Sep 14;8(1):13852. doi: 10.1038/s41598-018-32287-4.

Authors

Keiichiro Hara¹, Kazuo Osada², Masanori Yabuki³, Hisahiro Takashima⁴, Nicolas Theys⁵, Takashi Yamanouchi⁶

Affiliations

¹ Department of Earth System Science, Faculty of Science, Fukuoka University, Fukuoka, Japan. harakei@fukuoka-u.ac.jp.
² Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan.
³ Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto, Japan.
⁴ Department of Earth System Science, Faculty of Science, Fukuoka University, Fukuoka, Japan.
⁵ Belgian Institute for Space Aeronomy, Brussels, Belgium.
⁶ National Institute of Polar Research, Tokyo, Japan.

Abstract

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 indicated "blowing snow" as a source of atmospheric BrO_x. 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. 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 O₃ 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.