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| Titel |
Using carbon isotope fractionation for an improved quantification of CH4 oxidation efficiency in Arctic peatlands |
| VerfasserIn |
I. Preuss, C. Knoblauch, J. Gebert, E.-M. Pfeiffer |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250065470
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| Zusammenfassung |
| Much research effort is focused on identifying global CH4 sources and sinks to estimate their
current and potential strength in response to land-use change and global warming. Aerobic
CH4 oxidation is regarded as the key process reducing the strength of CH4 emissions in
wetlands, but is hitherto difficult to quantify.
Recent studies quantify the efficiency of CH4 oxidation based on CH4 stable isotope
signatures. The approach utilizes the fact that a significant isotope fractionation occurs when
CH4 is oxidized. Moreover, it also considers isotope fractionation by diffusion. For field
applications the ‘open-system equation’ is applied to determine the CH4 oxidation
efficiency:
fox = (δE – δP)/ (αox – αtrans)
where fox is the fraction of CH4 oxidized; δE is δ13C of emitted CH4; δP is δ13C of
produced CH4; αox is the isotopic fractionation factor of oxidation; αtrans is the isotopic
fractionation factor of transport.
We quantified CH4 oxidation in polygonal tundra soils of Russia’s Lena River Delta
analyzing depth profiles of CH4 concentrations and stable isotope signatures. Therefore, both
fractionation factors αox and αtrans were determined for three polygon centers with differing
water table positions and a polygon rim.
While most previous studies on landfill cover soils have assumed a gas transport
dominated by advection (αtrans = 1), other CH4 transport mechanisms as diffusion have to
be considered in peatlands and αtrans exceeds a value of 1. At our study we determined
αtrans = 1.013 ± 0.003 for CH4 when diffusion is the predominant transport mechanism.
Furthermore, results showed that αox differs widely between sites and horizons (αox = 1.013
± 0.012) and has to be determined for each case.
The impact of both fractionation factors on the quantification of CH4 oxidation was
estimated by considering both the potential diffusion rate at different water contents and
potential oxidation rates. Calculations for a water saturated tundra soil indicated a CH4
oxidation efficiency of 88% in the upper horizon.
Using carbon isotope fractionation improves the in situ quantification of CH4 oxidation in
wetlands and thus the assessment of current and potential CH4 sources and sinks in these
ecosystems. |
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