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| Titel |
Year-round N2O production by benthic NOx reduction in a monomictic south-alpine lake |
| VerfasserIn |
C. V. Freymond, C. B. Wenk, C. H. Frame, M. F. Lehmann |
| 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. 12 ; Nr. 10, no. 12 (2013-12-20), S.8373-8383 |
| Datensatznummer |
250085486
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| Publikation (Nr.) |
 copernicus.org/bg-10-8373-2013.pdf |
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| Zusammenfassung |
| Nitrous oxide (N2O) is a potent greenhouse gas, generated through
microbial nitrogen (N) turnover processes, such as nitrification, nitrifier
denitrification, and denitrification. Previous studies quantifying natural
sources have mainly focused on soils and the ocean, but the potential role
of terrestrial water bodies in the global N2O budget has been widely
neglected. Furthermore, the biogeochemical controls on the production rates
and the microbial pathways that produce benthic N2O in lakes are
essentially unknown. In this study, benthic N2O fluxes and the
contributions of the microbial pathways that produce N2O were assessed
using 15N label flow-through sediment incubations in the eutrophic,
monomictic south basin of Lake Lugano in Switzerland. The sediments were a
significant source of N2O throughout the year, with production rates
ranging between 140 and 2605 nmol N2O h−1 m−2, and the
highest observed rates coinciding with periods of water column
stratification and stably anoxic conditions in the overlying bottom water.
Nitrate (NO3−) reduction via denitrification was found to be the
major N2O production pathway in the sediments under both
oxygen-depleted and oxygen-replete conditions in the overlying water, while
ammonium oxidation did not contribute significantly to the benthic N2O
flux. A marked portion (up to 15%) of the total NO3− consumed
by denitrification was reduced only to N2O, without complete
denitrification to N2. These fluxes were highest when the bottom water
had stabilized to a low-oxygen state, in contrast with the notion that
stable anoxia is particularly conducive to complete denitrification without
accumulation of N2O. This study provides evidence that lake sediments
are a significant source of N2O to the overlying water and may produce
large N2O fluxes to the atmosphere during seasonal mixing events. |
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