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| Titel |
Overview of the 2007 and 2008 campaigns conducted as part of the Greenland Summit Halogen-HOx Experiment (GSHOX) |
| VerfasserIn |
J. L. Thomas, J. E. Dibb, J. Stutz, R. Glasow, S. Brooks, L. G. Huey, B. Lefer |
| 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 ; 12, no. 22 ; Nr. 12, no. 22 (2012-11-16), S.10833-10839 |
| Datensatznummer |
250011601
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| Publikation (Nr.) |
 copernicus.org/acp-12-10833-2012.pdf |
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| Zusammenfassung |
| From 10 May through 17 June 2007 and 6 June through 9 July 2008 intensive
sampling campaigns at Summit, Greenland confirmed that active bromine
chemistry is occurring in and above the snow pack at the highest part of the
Greenland ice sheet (72°36´ N, 38°25´ W and 3.2 km above sea
level). Direct measurements found BrO and soluble gas phase Br− mixing
ratios in the low pptv range on many days (maxima < 10 pptv).
Conversion of up to 200 pg m−3 of gaseous elemental mercury (GEM) to
reactive gaseous mercury (RGM) and enhanced OH relative to HO2 plus
RO2 confirm that active bromine chemistry is impacting chemical cycles
even at such low abundances of reactive bromine species. However, it does
not appear that Bry chemistry can fully account for observed
perturbations to HOx partitioning, suggesting unknown additional
chemical processes may be important in this unique environment, or that our
understanding of coupled NOx-HOx-Bry chemistry above sunlit
polar snow is incomplete. Rapid transport from the north Atlantic marine
boundary layer occasionally caused enhanced BrO at Summit (just two such
events observed during the 12 weeks of sampling over the two seasons). In
general observed reactive bromine was linked to activation of bromide
(Br−) in, and release of reactive bromine from, the snowpack. A coupled
snow-atmosphere model simulated observed NO and BrO at Summit during a three
day interval when winds were weak. The source of Br− in surface and
near surface snow at Summit is not entirely clear, but concentrations were
observed to increase when stronger vertical mixing brought free tropospheric
air to the surface. Reactive Bry mixing ratios above the snow often
increased in the day or two following increases in snow concentration, but
this response was not consistent. On seasonal time scales concentrations of
Br− in snow and reactive bromine in the air were directly related. |
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