Laser spectroscopy; Trace gases; Methane isotopes; Quantum cascade laser
Eyer Simon, Tuzson Bela, Popa M. Elena, van der Veen Carina, Röckmann Thomas, Rothe Michael, Brand Willi A., Fisher Rebecca, Lowry Dave, Nisbet Euan G., Brennwald Matthias S., Harris Eliza, Zellweger Christoph, Emmenegger Lukas, Fischer Hubertus, Mohn Joachim (2016), Real-time analysis of d13C- and dD-CH4 in ambient air with laser spectroscopy: method development and first intercomparison results, in Atmospheric Measurement Techniques
, 9, 263-280.
Eyer Simon, Tuzson Bela, Stadie Nicolas, Borgschulte Andreas, Emmenegger Lukas, Mohn Joachim (2014), Methane preconcentration by adsorption: a methodology for materials and conditions selection, in Adsorption
, 20(5-6), 657-666.
Röckmann Thomas, Eyer Simon (shared first author), van der Veen Carina, Popa M. Elena, Tuzson Bela, Monteil Guillaume, Houweling Sander, Harris Eliza, Brunner Dominik, Fischer Hubertus, Zazzeri Giulia, Lowry Dave, Nisbet Euan G., Brand Willi A., Necki Jaroslaw M., Emmenegger Lukas, Mohn Joachim, In-situ observations of the isotopic composition of methane at the Cabauw tall tower site, in Atmospheric Chemistry and Physics Discussions
The total global methane source is relatively well known but the strength of each source component and their trends are not. Since the major source categories and the OH sink have distinct isotopic signatures in d13C-CH4 and dD-CH4, high-frequency and high-precision measurements of the these parameters would improve the constrains for emission sources and the global budget. However, isotope-ratio mass-spectrometry (IRMS), the standard analytical tool for stable isotope ratios in trace gases, is generally a laboratory-based technique which limits temporal and spatial resolution capabilities.Alternatively, absorption spectroscopy in the mid-infrared is a direct method to distinguish between all relevant CH4 isotopic species because of their characteristic rotational-vibrational transitions. Within this project we will thus develop an instrument to continuously monitor 12CH4, 13CH4 and CH3D, and the respective isotope rations d13C-CH4 and dD-CH4, based on state of the art quantum cascade laser absorption spectrometry (QCLAS). The instrument will be based on recently developed 7.5 µm, continuous wave room temperature lasers (cw-RT-QCL) and a novel astigmatic multipath cell with an optical path length of 200 m. To obtain the necessary precision of 0.1‰ (d13C-CH4) and 1‰ (dD-CH4), the QCLAS will be coupled to an automated, liquid-nitrogen free preconcentration unit. Validation will include the careful evaluation of fractionation effects, methan concentration dependence, as well as direct comparison with state of the art IRMS.The project is based on the work of one PhD student and the strong competence in laser spectroscopy, trace gas monitoring and IRMS of the involved research partners.