ABSTRACT
Understanding and quantifying the biogeochemical cycle of N2O is essential to develop effective N2O emission mitigation strategies. This study presents a novel, fully automated measurement technique that allows simultaneous, high-precision quantification of the four main N2O isotopocules (14N14N16O, 14N15N16O, 15N14N16O and 14N14N18O) in ambient air. The instrumentation consists of a trace gas extractor (TREX) coupled to a quantum cascade laser absorption spectrometer, designed for autonomous operation at remote measurement sites. The main advantages this system has over its predecessors are a compact spectrometer design with improved temperature control and a more compact and powerful TREX device. The adopted TREX device enhances the flexibility of the preconcentration technique for higher adsorption volumes to target rare isotope species and lower adsorption temperatures for highly volatile substances. All system components have been integrated into a standardized instrument rack to improve portability and accessibility for maintenance. With an average sampling frequency of approximately 1 h–1, this instrumentation achieves a repeatability of 0.09, 0.13, 0.17 and 0.12 ‰ for δ15Nα, δ15Nβ, δ18O and site preference of N2O, respectively, for pressurized ambient air. The repeatability for N2O mole fraction measurements is better than 1 ppb (parts per billion, 10–9 moles per mole of dry air).
Acknowledgements
Sakae Toyoda, Naohiro Yoshida and Yuma Watanabe are kindly acknowledged for conducting IRMS measurements within the inter-laboratory comparison conducted in early 2016. Furthermore, we would like to thank Marco Weber for his technical support during the construction of the TREX device and Juanfernando Angel-Ramelli for his support with LabVIEW adaptations.
Disclosure statement
No potential conflict of interest was reported by the authors.
ORCID
Erkan Ibraim http://orcid.org/0000-0002-1246-4369
Eliza Harris http://orcid.org/0000-0002-7102-8305
Béla Tuzson http://orcid.org/0000-0001-7442-5405
Lukas Emmenegger http://orcid.org/0000-0002-9812-3986
Johan Six http://orcid.org/0000-0001-9336-4185
Joachim Mohn http://orcid.org/0000-0002-9799-1001
Notes
* Originally presented at the Joint European Stable Isotopes User Group Meeting JESIUM 2016, Ghent University, Belgium, 4–9 September 2016.