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| Titel |
Technical Note: Simultaneous measurement of sedimentary N2 and N2O production and a modified 15N isotope pairing technique |
| VerfasserIn |
T.-C. Hsu, S.-J. Kao |
| 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 (2013-12-03), S.7847-7862 |
| Datensatznummer |
250085452
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| Publikation (Nr.) |
 copernicus.org/bg-10-7847-2013.pdf |
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| Zusammenfassung |
| Dinitrogen (N2) and/or nitrous oxide (N2O) are produced through
denitrification, anaerobic ammonium oxidation (anammox) or nitrification in
sediments, of which entangled processes complicate the absolute rate
estimations of gaseous nitrogen production from individual pathways. The
classical isotope pairing technique (IPT), the most common 15N nitrate
enrichment method to quantify denitrification, has recently been modified by
different researchers to (1) discriminate between the N2 produced by
denitrification and anammox or to (2) provide a more accurate denitrification
rate under considering production of both N2O and N2. In case 1,
the revised IPT focused on N2 production being suitable for the
environments of a low N2O-to-N2 production ratio, while in case 2,
anammox was neglected. This paper develops a modified method to refine
previous versions of IPT. Cryogenic traps were installed to separately
preconcentrate N2 and N2O, thus allowing for subsequent measurement
of the two gases generated in one sample vial. The precision is better than
2% for N2 (m/z 28, m/z 29 and m/z 30), and 1.5% for
N2O (m/z 44, m/z 45 and m/z 46). Based on the six m/z peaks of
the two gases, the 15N nitrate traceable processes including N2 and
N2O from denitrification and N2 from anammox were estimated.
Meanwhile, N2O produced by nitrification was estimated via the
production rate of unlabeled 44N2O. To validate the applicability
of our modified method, incubation experiments were conducted using sediment
cores taken from the Danshuei Estuary in Taiwan. Rates of the aforementioned
nitrogen removal processes were successfully determined. Moreover, N2O
yield was as high as 66%, which would significantly bias previous IPT
approaches if N2O was not considered. Our modified method not only
complements previous versions of IPT but also provides more comprehensive
information to advance our understanding of nitrogen dynamics of the
water–sediment interface. |
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