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| Titel |
Improved quantification of microbial CH4 oxidation efficiency in arctic wetland soils using carbon isotope fractionation |
| VerfasserIn |
I. Preuss, C. Knoblauch, J. Gebert, E.-M. Pfeiffer |
| 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. 4 ; Nr. 10, no. 4 (2013-04-16), S.2539-2552 |
| Datensatznummer |
250018202
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| Publikation (Nr.) |
 copernicus.org/bg-10-2539-2013.pdf |
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| Zusammenfassung |
| Permafrost-affected tundra soils are significant sources of the
climate-relevant trace gas methane (CH4). The observed accelerated
warming of the arctic will cause deeper permafrost thawing, followed by
increased carbon mineralization and CH4 formation in water-saturated
tundra soils, thus creating a positive feedback to climate change.
Aerobic CH4 oxidation is regarded as the key process reducing CH4
emissions from wetlands, but quantification of turnover rates has remained
difficult so far. The application of carbon stable isotope fractionation
enables the in situ quantification of CH4 oxidation efficiency in
arctic wetland soils. The aim of the current study is to quantify CH4
oxidation efficiency in permafrost-affected tundra soils in Russia's Lena
River delta based on stable isotope signatures of CH4. Therefore, depth
profiles of CH4 concentrations and δ13CH4 signatures were
measured and the fractionation factors for the processes of oxidation
(αox) and diffusion (αdiff) were determined.
Most previous studies employing stable isotope fractionation for the
quantification of CH4 oxidation in soils of other habitats (such as
landfill cover soils) have assumed a gas transport dominated by advection
(αtrans = 1). In tundra soils, however, diffusion is the
main gas transport mechanism and diffusive stable isotope fractionation
should be considered alongside oxidative fractionation. For the first time,
the stable isotope fractionation of CH4 diffusion through
water-saturated soils was determined with an
αdiff = 1.001 ± 0.000 (n = 3). CH4
stable isotope fractionation during diffusion through air-filled pores of the
investigated polygonal tundra soils was
αdiff = 1.013 ± 0.003 (n = 18). Furthermore, it was
found that αox differs widely between sites and horizons
(mean αox = 1.017 ± 0.009) and needs to be
determined on a case by case basis. The impact of both fractionation factors
on the quantification of CH4 oxidation was analyzed by considering both
the potential diffusion rate under saturated and unsaturated conditions and
potential oxidation rates. For a submerged, organic-rich soil, the data
indicate a CH4 oxidation efficiency of 50% at the anaerobic–aerobic
interface in the upper horizon. The improved in situ quantification of
CH4 oxidation in wetlands enables a better assessment of current
and potential CH4 sources and sinks in permafrost-affected ecosystems
and their potential strengths in response to global warming. |
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