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| Titel |
Bromide and other ions in the snow, firn air, and atmospheric boundary layer at Summit during GSHOX |
| VerfasserIn |
J. E. Dibb, L. D. Ziemba, J. Luxford, P. Beckman |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 20 ; Nr. 10, no. 20 (2010-10-20), S.9931-9942 |
| Datensatznummer |
250008843
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| Publikation (Nr.) |
 copernicus.org/acp-10-9931-2010.pdf |
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| Zusammenfassung |
| Measurements of gas phase soluble bromide in the boundary layer and in firn
air, and Br− in aerosol and snow, were made at Summit, Greenland
(72.5° N, 38.4° W, 3200 m a.s.l.) as part of a larger investigation
into the influence of Br chemistry on HOx cycling. The soluble bromide
measurements confirm that photochemical activation of Br− in the snow
causes release of active Br to the overlying air despite trace
concentrations of Br− in the snow (means 15 and 8 nmol Br− kg−1 of snow in 2007 and 2008, respectively). Mixing ratios of soluble
bromide above the snow were also found to be very small (mean <1 ppt both
years, with maxima of 3 and 4 ppt in 2007 and 2008, respectively), but these
levels clearly oxidize and deposit long-lived gaseous elemental mercury and
may perturb HOx partitioning. Concentrations of Br− in surface
snow tended to increase/decrease in parallel with the specific activities of
the aerosol-associated radionuclides 7Be and 210Pb. Earlier work
has shown that ventilation of the boundary layer causes simultaneous
increases in 7Be and 210Pb at Summit, suggesting there is a pool
of Br in the free troposphere above Summit in summer time. Speciation and
the source of this free tropospheric Br− are not well constrained, but
we suggest it may be linked to extensive regions of active Br chemistry in
the Arctic basin which are known to cause ozone and mercury depletion events
shortly after polar sunrise. If this hypothesis is correct, it implies
persistence of the free troposphere Br− for several months after peak
Br activation in March/April. Alternatively, there may be a ubiquitous pool
of Br− in the free troposphere, sustained by currently unknown sources
and processes. |
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