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| Titel |
Fate of mercury in tree litter during decomposition |
| VerfasserIn |
A. K. Pokharel, D. Obrist |
| 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 ; 8, no. 9 ; Nr. 8, no. 9 (2011-09-09), S.2507-2521 |
| Datensatznummer |
250006116
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| Publikation (Nr.) |
 copernicus.org/bg-8-2507-2011.pdf |
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| Zusammenfassung |
| We performed a controlled laboratory litter incubation study to assess
changes in dry mass, carbon (C) mass and concentration, mercury (Hg) mass
and concentration, and stoichiometric relations between elements during
decomposition. Twenty-five surface litter samples each, collected from four
forest stands, were placed in incubation jars open to the atmosphere, and
were harvested sequentially at 0, 3, 6, 12, and 18 months. Using a mass
balance approach, we observed significant mass losses of Hg during
decomposition (5 to 23 % of initial mass after 18 months), which we
attribute to gaseous losses of Hg to the atmosphere through a gas-permeable
filter covering incubation jars. Percentage mass losses of Hg generally were
less than observed dry mass and C mass losses (48 to 63 % Hg loss per
unit dry mass loss), although one litter type showed similar losses. A field
control study using the same litter types exposed at the original collection
locations for one year showed that field litter samples were enriched in Hg
concentrations by 8 to 64 % compared to samples incubated for the same
time period in the laboratory, indicating strong additional sorption of Hg
in the field likely from atmospheric deposition. Solubility of Hg, assessed
by exposure of litter to water upon harvest, was very low (<0.22 ng Hg g−1
dry mass) and decreased with increasing stage of decomposition for all
litter types. Our results indicate potentially large gaseous emissions, or
re-emissions, of Hg originally associated with plant litter upon
decomposition. Results also suggest that Hg accumulation in litter and
surface layers in the field is driven mainly by additional sorption of Hg,
with minor contributions from "internal" accumulation due to preferential
loss of C over Hg. Litter types showed highly species-specific differences
in Hg levels during decomposition suggesting that emissions, retention, and
sorption of Hg are dependent on litter type. |
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