N2O source partitioning in soils using N-15 site preference values corrected for the N2O reduction effect

A - Papers appearing in refereed journals

Wu, D., Koster, J. R., Cardenas, L. M., Bruggemann, N., Lewicka-Szczebak, D. and Bol, R. 2016. N2O source partitioning in soils using N-15 site preference values corrected for the N2O reduction effect. Rapid Communications In Mass Spectrometry. 30 (5), pp. 620-626.

AuthorsWu, D., Koster, J. R., Cardenas, L. M., Bruggemann, N., Lewicka-Szczebak, D. and Bol, R.
Abstract

RationaleThe aim of this study was to determine the impact of isotope fractionation associated with N2O reduction during soil denitrification on N2O site preference (SP) values and hence quantify the potential bias on SP-based N2O source partitioning. MethodsThe N2O SP values (n=431) were derived from six soil incubation studies in N-2-free atmosphere, and determined by isotope ratio mass spectrometry (IRMS). The N-2 and N2O concentrations were measured directly by gas chromatography. Net isotope effects (NIE) during N2O reduction to N-2 were compensated for using three different approaches: a closed-system model, an open-system model and a dynamic apparent NIE function. The resulting SP values were used for N2O source partitioning based on a two end-member isotopic mass balance. ResultsThe average SP0 value, i.e. the average SP values of N2O prior to N2O reduction, was recalculated with the closed-system model, resulting in -2.6 (+/- 9.5), while the open-system model and the dynamic apparent NIE model gave average SP0 values of 2.9 parts per thousand (+/- 6.3) and 1.7 parts per thousand (+/- 6.3), respectively. The average source contribution of N2O from nitrification/fungal denitrification was 18.7% (+/- 21.0) according to the closed-system model, while the open-system model and the dynamic apparent NIE function resulted in values of 31.0% (+/- 14.0) and 28.3% (+/- 14.0), respectively. ConclusionsUsing a closed-system model with a fixed SP isotope effect may significantly overestimate the N2O reduction effect on SP values, especially when N2O reduction rates are high. This is probably due to soil inhomogeneity and can be compensated for by the application of a dynamic apparent NIE function, which takes the variable reduction rates in soil micropores into account. Copyright (c) 2016 John Wiley & Sons, Ltd.

KeywordsBiochemical Research Methods; Chemistry, Analytical; Spectroscopy
Year of Publication2016
JournalRapid Communications In Mass Spectrometry
Journal citation30 (5), pp. 620-626
Digital Object Identifier (DOI)doi:10.1002/rcm.7493
PubMed ID26842583
Open accessPublished as non-open access
FunderBiotechnology and Biological Sciences Research Council
Chinese Scholarship Council
Funder project or codeSustainability
ISSN09514198
0951-4198
PublisherWiley
Grant ID201306350130

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