Isotope fractionation factors controlling isotopocule signatures of soil-emitted N2O produced by denitrification processes of various rates

A - Papers appearing in refereed journals

Lewicka-Szczebak, D., Well, R., Bol, R., Gregory, A. S., Matthews, G. P., Misselbrook, T. H., Whalley, W. R. and Cardenas, L. M. 2015. Isotope fractionation factors controlling isotopocule signatures of soil-emitted N2O produced by denitrification processes of various rates. Rapid Communications In Mass Spectrometry. 29 (3), pp. 269-282.

AuthorsLewicka-Szczebak, D., Well, R., Bol, R., Gregory, A. S., Matthews, G. P., Misselbrook, T. H., Whalley, W. R. and Cardenas, L. M.
Abstract

RATIONALEThis study aimed (i) to determine the isotopic fractionation factors associated with N2O production and reduction during soil denitrification and (ii) to help specify the factors controlling the magnitude of the isotope effects. For the first time the isotope effects of denitrification were determined in an experiment under oxic atmosphere and using a novel approach where N2O production and reduction occurred simultaneously. METHODSSoil incubations were performed under a He/O-2 atmosphere and the denitrification product ratio [N2O/(N-2+N2O)] was determined by direct measurement of N-2 and N2O fluxes. N2O isotopocules were analyzed by mass spectrometry to determine O-18, N-15 and N-15 site preference within the linear N2O molecule (SP). An isotopic model was applied for the simultaneous determination of net isotope effects () of both N2O production and reduction, taking into account emissions from two distinct soil pools. RESULTSA clear relationship was observed between N-15 and O-18 isotope effects during N2O production and denitrification rates. For N2O reduction, diverse isotope effects were observed for the two distinct soil pools characterized by different product ratios. For moderate product ratios (from 0.1 to 1.0) the range of isotope effects given by previous studies was confirmed and refined, whereas for very low product ratios (below 0.1) the net isotope effects were much smaller. CONCLUSIONSThe fractionation factors associated with denitrification, determined under oxic incubation, are similar to the factors previously determined under anoxic conditions, hence potentially applicable for field studies. However, it was shown that the O-18/N-15 ratios, previously accepted as typical for N2O reduction processes (i.e., higher than 2), are not valid for all conditions. Copyright (c) 2014 John Wiley & Sons, Ltd.

KeywordsBiochemical Research Methods; Chemistry, Analytical; Spectroscopy
Year of Publication2015
JournalRapid Communications In Mass Spectrometry
Journal citation29 (3), pp. 269-282
Digital Object Identifier (DOI)doi:10.1002/rcm.7102
PubMed ID26411625
Open accessPublished as non-open access
FunderBiotechnology and Biological Sciences Research Council
German Research Foundation (DFG)
Funder project or codeDelivering Sustainable Systems (SS) [ISPG]
Publisher's version
ISSN09514198
0951-4198
PublisherWiley
Grant IDWe/1904-4
BBE0015801

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