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| Titel |
Kinetics of N2O production and reduction in a nitrate-contaminated aquifer inferred from laboratory incubation experiments |
| VerfasserIn |
D. Weymann, H. Geistlinger, R. Well, C. Heide, H. Flessa |
| 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 ; 7, no. 6 ; Nr. 7, no. 6 (2010-06-20), S.1953-1972 |
| Datensatznummer |
250004848
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| Publikation (Nr.) |
 copernicus.org/bg-7-1953-2010.pdf |
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| Zusammenfassung |
| Knowledge of the kinetics of N2O production and reduction in
groundwater is essential for the assessment of potential indirect emissions
of the greenhouse gas. In the present study, we investigated this kinetics
using a laboratory approach. The results were compared to field measurements
in order to examine their transferability to the in situ conditions. The study site
was the unconfined, predominantly sandy Fuhrberger Feld aquifer in northern
Germany. A special characteristic of the aquifer is the occurrence of the
vertically separated process zones of heterotrophic denitrification in the
near-surface groundwater and of autotrophic denitrification in depths beyond
2–3 m below the groundwater table, respectively. The kinetics of N2O
production and reduction in both process zones was studied during long-term
anaerobic laboratory incubations of aquifer slurries using the 15N
tracer technique. We measured N2O, N2, NO3-,
NO2-, and SO42- concentrations as well as parameters of
the aquifer material that were related to the relevant electron donors, i.e.
organic carbon and pyrite. The laboratory incubations showed a low
denitrification activity of heterotrophic denitrification with initial rates
between 0.2 and 13 μg N kg−1 d−1. The process was carbon
limited due to the poor availability of its electron donor. In the
autotrophic denitrification zone, initial denitrification rates were
considerably higher, ranging between 30 and 148 μg N kg−1 d−1,
and NO3- as well as N2O were completely removed
within 60 to 198 days. N2O accumulated during heterotrophic and
autotrophic denitrification, but maximum concentrations were substantially
higher during the autotrophic process. The results revealed a satisfactory
transferability of the laboratory incubations to the field scale for
autotrophic denitrification, whereas the heterotrophic process less
reflected the field conditions due to considerably lower N2O
accumulation during laboratory incubation. Finally, we applied a
conventional model using first-order-kinetics to determine the reaction rate
constants k1 for N2O production and k2 for N2O
reduction, respectively. The goodness of fit to the experimental data was
partly limited, indicating that a more sophisticated approach is essential
to describe the investigated reaction kinetics satisfactorily. |
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