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| Titel |
Temperature and sunlight controls of mercury oxidation and deposition atop the Greenland ice sheet |
| VerfasserIn |
S. Brooks, C. Moore, D. Lew, B. Lefer, G. Huey, D. Tanner |
| 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 ; 11, no. 16 ; Nr. 11, no. 16 (2011-08-15), S.8295-8306 |
| Datensatznummer |
250010005
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| Publikation (Nr.) |
 copernicus.org/acp-11-8295-2011.pdf |
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| Zusammenfassung |
| We conducted the first ever mercury speciation measurements atop the
Greenland ice sheet at Summit Station (Latitude 72.6° N, Longitude 38.5° W,
Altitude 3200 m) in the Spring and Summer of 2007 and 2008. These
measurements were part of the collaborative Greenland Summit
Halogen-HOx experiment (GSHOX) campaigns investigating the importance
of halogen chemistry in this remote environment. Significant levels of BrO
(1–5 pptv) in the near surface air were often accompanied by diurnal dips in
gaseous elemental mercury (GEM), and in-situ production of reactive gaseous
mercury (RGM). While halogen (i.e. Br) chemistry is normally associated with
marine boundary layers, at Summit, Greenland, far from any marine source, we
have conclusively detected bromine and mercury chemistry in the near surface
air. The likely fate of the formed mercury-bromine radical (HgBr) is further
oxidation to stable RGM (HgBr2, HgBrOH, HgBrCl...), or thermal
decomposition. These fates appear to be controlled by the availability of
Br, OH, Cl, etc. to produce RGM (Hg(II)), versus the lifetime of HgBr by
thermal dissociation. At Summit, the production of RGM appears to require a
sun elevation angle of >5 degrees, and an air temperature of <−15 °C.
Possibly the availability of Br, controlled by photolysis J(Br2),
requires a sun angle >5 degrees, while the formation of RGM from HgBr
requires a temperature <−15 °C . A portion of the deposited RGM is
readily photoreduced and re-emitted to the air as GEM. However, a very small
fraction becomes buried at depth. Extrapolating core samples from Summit to
the entire Greenland ice sheet, we calculate an estimated net annual
sequestration of ~13 metric tons Hg per year, buried long-term under
the sunlit photoreduction zone. |
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