The isoMET project on ambient CH4 monitoring, source signature information and modelling

Methane (CH4) is a greenhouse gas (GHG) with both anthropogenic and natural sources. It also contributes to air quality problems through its role in tropospheric ozone formation. Key source categories of anthropogenic CH4 emissions in Europe are the agricultural sector (~50 %), waste (~22 %), and energy (~15 %), which makes them the focus of intense research for developing mitigation actions. Stable isotope ratio measurement in CH4 provide the information needed to verify emissions by source type. To provide comparable and accurate atmospheric CH4 isotope ratios, there is an increasing need to develop metrological harmonized measurements protocols and procedures. In addition, there is a lack of a metrological infrastructure for source signature information needed to interpret atmospheric isotope ratio measurements, as well as an assessment of uncertainties in atmospheric transport models and inverse estimates of Europe's CH4 emissions. Here, we present the isoMET project that aims to (a) develop a harmonised in situ CH4 isotope dataset of ambient air in Europe to resolve compatibility issues of measurements of δ13C or δ2H in CH4 across multiple laboratories, b) develop a sustainable metrological infrastructure for a dataset for δ13C(CH4) and δ2H(CH4)-emissions source measurements in Europe and to evaluate the potential for source apportionment through clumped isotopes, c) use atmospheric chemistry transport modelling to inform the work in (a) and (b), creating estimates of the minimum measurement requirements for deployed instruments.   References [1] isoMET project available at: https://www.npl.co.uk/21grd04-isomet [2] J. A. Nwaboh, J. Mohn, M. Fatima, T. Arnold, V. Ebert, Metrology for European emissions verification on methane isotopes (isoMET), CCQM GAWG-IRWG Workshop on Carbon Dioxide and Methane Stable Isotope Ratio Measurements, LATU (Uruguay), 2023 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).