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What can we learn from N2O isotope data? – Analytics,processes and modelling |
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| Authors: | Longfei Yu Eliza Harris Dominika Lewicka-Szczebak Matti Barthel Margareta RA Blomberg Stephen J Harris Matthew S Johnson Moritz F Lehmann Jesper Liisberg Christoph Müller Nathaniel E Ostrom Johan Six Sakae Toyoda Naohiro Yoshida Joachim Mohn |
| Institution: | 1. Laboratory for Air Pollution & Environmental Technology, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, Dübendorf, CH-8600 Switzerland;2. Department of Ecology, University of Innsbruck, Sternwartestrasse 15, Innsbruck, A-6020 Austria;3. Centre for Stable Isotope Research and Analysis (KOSI), Büsgen Institute, Georg-August University of Göttingen, Germany;4. Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland;5. Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, SE-10691 Sweden;6. School of Biological, Earth and Environmental Sciences, UNSW, Sydney, NSW, Australia
Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW, Australia;7. Department of Chemistry, University of Copenhagen, Universitetsparken 5, Copenhagen Ø, DK-2100 Denmark;8. Department of Environmental Science, University of Basel, Basel, Switzerland;9. Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark;10. Institute of Plant Ecology (IFZ), Justus-Liebig University Giessen, Heinrich-Buff-Ring 26, Giessen, 35392 Germany School of Biology and Environmental Science and Earth Institute, University College Dublin, Belfield, Dublin 4, Ireland;11. Department of Integrative Biology and DOE Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI, USA;12. Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, Yokohama, 226-8502 Japan |
| Abstract: | The isotopic composition of nitrous oxide (N2O) provides useful information for evaluating N2O sources and budgets. Due to the co-occurrence of multiple N2O transformation pathways, it is, however, challenging to use isotopic information to quantify the contribution of distinct processes across variable spatiotemporal scales. Here, we present an overview of recent progress in N2O isotopic studies and provide suggestions for future research, mainly focusing on: analytical techniques; production and consumption processes; and interpretation and modelling approaches. Comparing isotope-ratio mass spectrometry (IRMS) with laser absorption spectroscopy (LAS), we conclude that IRMS is a precise technique for laboratory analysis of N2O isotopes, while LAS is more suitable for in situ/inline studies and offers advantages for site-specific analyses. When reviewing the link between the N2O isotopic composition and underlying mechanisms/processes, we find that, at the molecular scale, the specific enzymes and mechanisms involved determine isotopic fractionation effects. In contrast, at plot-to-global scales, mixing of N2O derived from different processes and their isotopic variability must be considered. We also find that dual isotope plots are effective for semi-quantitative attribution of co-occurring N2O production and reduction processes. More recently, process-based N2O isotopic models have been developed for natural abundance and 15N-tracing studies, and have been shown to be effective, particularly for data with adequate temporal resolution. Despite the significant progress made over the last decade, there is still great need and potential for future work, including development of analytical techniques, reference materials and inter-laboratory comparisons, further exploration of N2O formation and destruction mechanisms, more observations across scales, and design and validation of interpretation and modelling approaches. Synthesizing all these efforts, we are confident that the N2O isotope community will continue to advance our understanding of N2O transformation processes in all spheres of the Earth, and in turn to gain improved constraints on regional and global budgets. |
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