Source mechanisms and transport patterns of tropospheric bromine monoxide: findings from long-term multi-axis differential optical absorption spectroscopy measurements at two Antarctic stations
<p>The presence of reactive bromine in polar regions is a widespread phenomenon that plays an important role in the photochemistry of the Arctic and Antarctic lower troposphere, including the destruction of ozone, the disturbance of radical cycles, and the oxidation of gaseous elemental mercur...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2023-03-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/23/3207/2023/acp-23-3207-2023.pdf |
| _version_ | 1811155029411758080 |
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| author | U. Frieß K. Kreher R. Querel H. Schmithüsen D. Smale R. Weller U. Platt |
| author_facet | U. Frieß K. Kreher R. Querel H. Schmithüsen D. Smale R. Weller U. Platt |
| author_sort | U. Frieß |
| collection | DOAJ |
| description | <p>The presence of reactive bromine in polar regions is a widespread phenomenon that plays an important role in the photochemistry of the Arctic and Antarctic lower troposphere, including the destruction of ozone, the disturbance of radical cycles, and the oxidation of gaseous elemental mercury. The chemical mechanisms leading to the heterogeneous release of gaseous bromine compounds from saline surfaces are in principle well understood. There are, however, substantial uncertainties about the contribution of different potential sources to the release of reactive bromine, such as sea ice, brine, aerosols, and the snow surface, as well as about the seasonal and diurnal variation and the vertical distribution of reactive bromine. Here we use continuous long-term measurements of the vertical distribution of bromine monoxide (BrO) and aerosols at the two Antarctic sites Neumayer (NM) and Arrival Heights (AH), covering the periods of 2003–2021 and 2012–2021, respectively, to investigate how chemical and physical parameters affect the abundance of BrO. We find the strongest correlation between BrO and aerosol extinction (<span class="inline-formula"><i>R</i>=0.56</span> for NM and <span class="inline-formula"><i>R</i>=0.28</span> for AH during spring), suggesting that the heterogeneous release of <span class="inline-formula">Br<sub>2</sub></span> from saline airborne particles (blowing snow and aerosols) is a dominant source for reactive bromine. Positive correlations between BrO and contact time of air masses, both with sea ice and the Antarctic ice sheet, suggest that reactive bromine is not only emitted by the sea ice surface but by the snowpack on the ice shelf and in the coastal regions of Antarctica. In addition, the open ocean appears to represent a source for reactive bromine during late summer and autumn when the sea ice extent is at its minimum. A source–receptor analysis based on back trajectories and sea ice maps shows that main source regions for BrO at NM are the Weddell Sea and the Filchner–Ronne Ice Shelf, as well as coastal polynyas where sea ice is newly formed. A strong morning peak in BrO frequently occurring during summer and that is particularly strong during autumn suggests a night-time build-up of <span class="inline-formula">Br<sub>2</sub></span> by heterogeneous reaction of ozone on the saline snowpack in the vicinity of the measurement sites. We furthermore show that BrO can be sustained for at least 3 d while travelling across the Antarctic continent in the absence of any saline surfaces that could serve as a source for reactive bromine.</p> |
| first_indexed | 2024-04-10T04:26:04Z |
| format | Article |
| id | doaj.art-6332970f0c29429bbac08fe49bdf76d0 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-04-10T04:26:04Z |
| publishDate | 2023-03-01 |
| publisher | Copernicus Publications |
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| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-6332970f0c29429bbac08fe49bdf76d02023-03-10T11:57:22ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242023-03-01233207323210.5194/acp-23-3207-2023Source mechanisms and transport patterns of tropospheric bromine monoxide: findings from long-term multi-axis differential optical absorption spectroscopy measurements at two Antarctic stationsU. Frieß0K. Kreher1R. Querel2H. Schmithüsen3D. Smale4R. Weller5U. Platt6Institute of Environmental Physics, Heidelberg University, Heidelberg, GermanyBK Scientific GmbH, Mainz, GermanyNational Institute of Water and Atmospheric Research, Lauder, New ZealandAlfred Wegener Institute for Polar and Marine Research, Bremerhaven, GermanyNational Institute of Water and Atmospheric Research, Lauder, New ZealandAlfred Wegener Institute for Polar and Marine Research, Bremerhaven, GermanyInstitute of Environmental Physics, Heidelberg University, Heidelberg, Germany<p>The presence of reactive bromine in polar regions is a widespread phenomenon that plays an important role in the photochemistry of the Arctic and Antarctic lower troposphere, including the destruction of ozone, the disturbance of radical cycles, and the oxidation of gaseous elemental mercury. The chemical mechanisms leading to the heterogeneous release of gaseous bromine compounds from saline surfaces are in principle well understood. There are, however, substantial uncertainties about the contribution of different potential sources to the release of reactive bromine, such as sea ice, brine, aerosols, and the snow surface, as well as about the seasonal and diurnal variation and the vertical distribution of reactive bromine. Here we use continuous long-term measurements of the vertical distribution of bromine monoxide (BrO) and aerosols at the two Antarctic sites Neumayer (NM) and Arrival Heights (AH), covering the periods of 2003–2021 and 2012–2021, respectively, to investigate how chemical and physical parameters affect the abundance of BrO. We find the strongest correlation between BrO and aerosol extinction (<span class="inline-formula"><i>R</i>=0.56</span> for NM and <span class="inline-formula"><i>R</i>=0.28</span> for AH during spring), suggesting that the heterogeneous release of <span class="inline-formula">Br<sub>2</sub></span> from saline airborne particles (blowing snow and aerosols) is a dominant source for reactive bromine. Positive correlations between BrO and contact time of air masses, both with sea ice and the Antarctic ice sheet, suggest that reactive bromine is not only emitted by the sea ice surface but by the snowpack on the ice shelf and in the coastal regions of Antarctica. In addition, the open ocean appears to represent a source for reactive bromine during late summer and autumn when the sea ice extent is at its minimum. A source–receptor analysis based on back trajectories and sea ice maps shows that main source regions for BrO at NM are the Weddell Sea and the Filchner–Ronne Ice Shelf, as well as coastal polynyas where sea ice is newly formed. A strong morning peak in BrO frequently occurring during summer and that is particularly strong during autumn suggests a night-time build-up of <span class="inline-formula">Br<sub>2</sub></span> by heterogeneous reaction of ozone on the saline snowpack in the vicinity of the measurement sites. We furthermore show that BrO can be sustained for at least 3 d while travelling across the Antarctic continent in the absence of any saline surfaces that could serve as a source for reactive bromine.</p>https://acp.copernicus.org/articles/23/3207/2023/acp-23-3207-2023.pdf |
| spellingShingle | U. Frieß K. Kreher R. Querel H. Schmithüsen D. Smale R. Weller U. Platt Source mechanisms and transport patterns of tropospheric bromine monoxide: findings from long-term multi-axis differential optical absorption spectroscopy measurements at two Antarctic stations Atmospheric Chemistry and Physics |
| title | Source mechanisms and transport patterns of tropospheric bromine monoxide: findings from long-term multi-axis differential optical absorption spectroscopy measurements at two Antarctic stations |
| title_full | Source mechanisms and transport patterns of tropospheric bromine monoxide: findings from long-term multi-axis differential optical absorption spectroscopy measurements at two Antarctic stations |
| title_fullStr | Source mechanisms and transport patterns of tropospheric bromine monoxide: findings from long-term multi-axis differential optical absorption spectroscopy measurements at two Antarctic stations |
| title_full_unstemmed | Source mechanisms and transport patterns of tropospheric bromine monoxide: findings from long-term multi-axis differential optical absorption spectroscopy measurements at two Antarctic stations |
| title_short | Source mechanisms and transport patterns of tropospheric bromine monoxide: findings from long-term multi-axis differential optical absorption spectroscopy measurements at two Antarctic stations |
| title_sort | source mechanisms and transport patterns of tropospheric bromine monoxide findings from long term multi axis differential optical absorption spectroscopy measurements at two antarctic stations |
| url | https://acp.copernicus.org/articles/23/3207/2023/acp-23-3207-2023.pdf |
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