Improvements in ambient CH4 isotope ratio measurements – the isoMET project

Atmospheric observations provide a reality check on the true efficacy of climate change mitigation policy. Methane (CH₄) is a potent greenhouse gas (GHG) with multiple complex sources. Stable isotope ratio measurements for CH₄ provide the fingerprints necessary to verify emissions by source type. The isoMET project focuses on improving ambient air CH₄ isotope ratio monitoring capabilities both in the laboratory and field. This project also targets improvements in the quality of CH₄ isotopic source signature information as well as modelling necessary to make top-down emissions estimates with sectorial attribution.

Here, we present a new metrological infrastructure, developed within the isoMET project, for a dataset for CH₄ isotope source signature measurements. In addition, information on new state-of-the-art CH₄ calibration reference materials, developed in the project, will be provided. Latest results from the project on analytical advances in high-resolution mass spectrometry and laser spectroscopy for doubly substituted isotopic species of CH₄ (¹³CH₃D, ¹²CH₂D₂) will be shown. In addition, we present results on laboratory and field intercomparison, demonstrating the capability of e.g. optical isotope ratio measurements (OIRS) for δ¹³C, δ²H, Δ¹³CH₃D and Δ¹²CH₂D₂ measurements in CH₄. Finally, the use of atmospheric chemistry transport modelling to direct the measurement strategy for optimal emissions estimation will be demonstrated.

References

[1] isoMET project available at: https://www.npl.co.uk/21grd04-isomet

[2] J. A. Nwaboh, J. Mohn, F. Mehr, T. Arnold, V. Ebert, CCQM GAWG-IRWG Workshop on Carbon Dioxide and Methane Stable Isotope Ratio Measurements, LATU (Uruguay), 2023

[3] Mehr Fatima, Javis Nwaboh, Joachim Mohn, Tim Arnold, and Volker Ebert, EGU 2024, EGU24-20560, https://doi.org/10.5194/egusphere-egu24-20560

Acknowledgements: The project 21GRD04 isoMET project has received funding from the European Partnership on Metrology, co-financed from the European Union’s Horizon Europe Research and Innovation Programme and by the Participating States.  Empa has received funding from the Swiss State Secretaritat for Education, Research and Innovation (SERI).