Dataset Information

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

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.

SUBMITTER: Hara K

PROVIDER: S-EPMC6138753 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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

Hara Keiichiro K Osada Kazuo K Yabuki Masanori M Takashima Hisahiro H Theys Nicolas N Yamanouchi Takashi T

Scientific reports 20180914 1

Polar sunrise activates reactive bromine (BrOx) cycle on the Antarctic coasts. BrOx chemistry relates to depletion of O3 and Hg in polar regions. Earlier studies have indicated "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 BrOx activation other than the heterogeneous reactio ...[more]

PMID: 30218011

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Project description:As sources of reactive halogens, snowpacks in sea ice regions control the oxidative capacity of the Arctic atmosphere. However, measurements of snowpack halide concentrations remain sparse, particularly in the high Arctic, limiting our understanding of and ability to parameterize snowpack participation in tropospheric halogen chemistry. To address this gap, we measured concentrations of chloride, bromide, and sodium in snow samples collected during polar spring above remote multi-year sea ice (MYI) and first-year sea ice (FYI) north of Greenland and Alaska, as well as in the central Arctic, and compared these measurements to a larger dataset collected in the Alaskan coastal Arctic by Krnavek et al. (2012). Regardless of sea ice region, these surface snow samples generally featured lower salinities, compared to coastal snow. Surface snow in FYI regions was typically enriched in bromide and chloride compared to seawater, indicating snowpack deposition of bromine and chlorine-containing trace gases and an ability of the snowpack to participate further in bromine and chlorine activation processes. In contrast, surface snow in MYI regions was more often depleted in bromide, indicating it served as a source of bromine-containing trace gases to the atmosphere prior to sampling. Measurements at various snow depths indicate that the deposition of sea salt aerosols and halogen-containing trace gases to the snowpack surface played a larger role in determining surface snow halide concentrations compared to upward brine migration from sea ice. Calculated enrichment factors for bromide and chloride, relative to sodium, in the MYI snow samples suggests that MYI regions, in addition to FYI regions, have the potential to play an active role in Arctic boundary layer bromine and chlorine chemistry. The ability of MYI regions to participate in springtime atmospheric halogen chemistry should be considered in regional modeling of halogen activation and interpretation of satellite-based tropospheric bromine monoxide column measurements.

Dataset Information

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

Publications

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

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