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| Titel |
Mercury dynamics in the Rocky Mountain, Colorado, snowpack |
| VerfasserIn |
X. Faïn, D. Helmig, J. Hueber, D. Obrist, M. W. Williams |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 6 ; Nr. 10, no. 6 (2013-06-13), S.3793-3807 |
| Datensatznummer |
250018284
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| Publikation (Nr.) |
 copernicus.org/bg-10-3793-2013.pdf |
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| Zusammenfassung |
| Gaseous elemental mercury (GEM) was monitored at the Niwot Ridge (NWT)
Long-Term Ecological Research (LTER) site (Colorado, USA, 40° N)
from interstitial air extracted from the snowpack at depths ranging from the
snow surface to 10 cm above the soil. A highly dynamic cycling of mercury
(Hg) in this mid-latitude snowpack was observed. Patterns were driven by
both GEM production in surface snow and GEM destruction in the deeper
snowpack layers. Thorough mixing and vertical transport processes were
observed through the snowpack. GEM was photochemically produced near the
snow-air interface throughout the entire winter, leading to enhanced GEM
levels in interstitial air of surface snow of up to 8 ng m−3. During
low-wind periods, GEM in surface snow layers remained significantly above
ambient air levels at night as well, which may indicate a potential weak GEM
production overnight. Analyses of vertical GEM gradients in the snowpack
show that surface GEM enhancements efficiently propagated down the snowpack,
with a temporal lag in peak GEM levels observed with increasing depth.
Downward diffusion was responsible for much of these patterns, although
vertical advection also contributed to vertical redistribution. Destruction
of GEM in the lower snowpack layers was attributed to dark oxidation of GEM.
Analysis of vertical GEM / CO2 flux ratios indicated that this GEM
destruction occurred in the snow and not in the underlying soil. The strong,
diurnal patterns of photochemical GEM production at the surface ultimately
lead to re-emission losses of deposited Hg back to the atmosphere. The NWT
data show that highest GEM surface production and re-emissions occur shortly
after fresh snowfall, which possibly resupplies photoreducible Hg to the
snowpack, and that photochemical GEM reduction is not radiation-limited as
it is strong even on cloudy days. |
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