EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Clumped isotope analysis in nitrous oxide by mid-IR laser spectroscopy: analytical developments and validation

Kristýna Kantnerová1,2, Longfei Yu1, Daniel Zindel3, Mark S. Zahniser4, David D. Nelson4, Béla Tuzson1, Lukas Emmenegger1, Mayuko Nakagawa5, Sakae Toyoda6, Naohiro Yoshida5,6, Stefano M. Bernasconi2, and Joachim Mohn1
Kristýna Kantnerová et al.
  • 1Laboratory for Air Pollution / Environmental Technology, Empa, CH-8600 Dübendorf, Switzerland (
  • 2Department of Earth Sciences, ETHZ, CH-8092 Zürich, Switzerland
  • 3Laboratory of Physical Chemistry, ETHZ, CH-8093 Zürich, Switzerland
  • 4Center for Atmospheric and Environmental Chemistry, Aerodyne Research, Inc., Billerica, Massachusetts 01821, United States
  • 5Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, 152-8550, Japan
  • 6Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, Yokohama, 226-8502, Japan

Nitrous oxide (N2O) has been for long a major focus of all greenhouse gas accounting agreements. Understanding the mechanisms of its formation and clarifying its sources and sinks are highly important for mitigating N2O emissions. In this context, measuring the doubly substituted isotopocules of N2O can add new and unique opportunities to fingerprint and constrain the biogeochemical N2O cycle, similar to other atmospheric species such as CO2, CH4, and O2.

We address this challenging research field by developing and validating a laser spectroscopic technique for selective analysis of the eight most abundant N2O isotopic species including the doubly substituted isotopocules 14N15N18O, 15N14N18O, and 15N15N16O. This method is based on quantum cascade laser absorption spectroscopy (QCLAS) and reaches a precision of 0.01 – 0.20 ‰ with 1 – 2 min spectral averaging on samples of 4 μmol of N2O in N2 at 4 hPa.

Furthermore, we have established a new reference frame combining two independent approaches: (1) clumped N2O isotopocule abundances were linked to stochastic distribution by equilibrating the N–O bond in the N2O molecule over activated Al2O3 at 100 and 200 °C, and (2) individual isotopocule concentrations were calibrated using a set of high-accuracy gravimetric N2O-in-N2 gas mixtures. The latter approach, applied for the first time to clumped isotope measurements, has a particular potential in realizing regular multi-point calibration for species like 15N15N16O, because no procedure for equilibration of the N–N bond has been successful yet.

Results of the validation measurements, using the QCLAS method and calibration approach, are presented for a large range of δ values (approx. 100 ‰ for d15N and d18O). Inter-comparison measurements with high-resolution mass spectrometry show compatible results for bulk isotopic composition (d15N, d(458+548)), but superior performance of QCLAS for determining site-selectivity (SP, SP18). In summary, this work provides new methodological basis for the measurements of clumped N2O isotopes and has a high potential to stimulate future research in the N2O community by establishing a new class of reservoir-insensitive tracers and molecular-scale insights.

How to cite: Kantnerová, K., Yu, L., Zindel, D., Zahniser, M. S., Nelson, D. D., Tuzson, B., Emmenegger, L., Nakagawa, M., Toyoda, S., Yoshida, N., Bernasconi, S. M., and Mohn, J.: Clumped isotope analysis in nitrous oxide by mid-IR laser spectroscopy: analytical developments and validation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6726,, 2020


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