EGU23-11383
https://doi.org/10.5194/egusphere-egu23-11383
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Capabilities of CH4 source apportionment using atmospheric 14CH4 measurements: Switzerland as a case study

Thomas Laemmel1,2, Dylan Geissbühler1,2, Stephan Henne3, Dominik Brunner3, Markus Leuenberger2,4, and Sönke Szidat1,2
Thomas Laemmel et al.
  • 1Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
  • 2Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
  • 3Empa, Laboratory for Air Pollution/Environmental Technology, Dübendorf, Switzerland
  • 4Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland

Methane (CH4) is the second most important anthropogenic greenhouse gas after carbon dioxide (CO2). Main CH4 sources are linked to the human use of fossil fuels (oil, gas, coal) and human-related or natural biogenic processes such as agriculture, waste management or wetlands. While biogenic emissions of CH4 contain present-day atmospheric radiocarbon (14C) levels, CH4 derived from fossil sources is 14C-free so that 14CH4 measurements can be used as a source apportionment proxy to distinguish fossil from biogenic CH4 sources.

A dedicated setup to analyze 14CH4 was developed at the Laboratory for the Analysis of Radiocarbon with AMS, University of Bern. Typical samples are 60L of atmospheric air collected in bags, which, after extraction, result in about 60 µg carbon in CH4-derived CO2 form, enough for a 14C gas measurement on a MICADAS (Mini Carbon Dating System) accelerator mass spectrometer.

Since 2019, biweekly air samplings have been  conducted at three sites in Switzerland: the high altitude research station Jungfraujoch (3580 m asl) considered as a European continental background station, a tall tower in Beromünster and an urban site in Bern. A fourth site (with a tall tower) in Sottens has been visited since June 2021.

Beside these in situ measurements, an atmospheric 14CH4 transport model was developed to simulate 14CH4 values for each sampling. It is based on the Lagrangian transport and dispersion model FLEXPART, two CH4 emission inventories (Meteotest EKAT for Switzerland, TNO-CAMS v4.2 for the rest of Europe), a priori 14CH4 signatures for each emission type and the weather model COSMO. 14CH4 emissions from pressurized water reactors (PWR) of nuclear power plants in Switzerland and neighboring countries are also taken into consideration.

This contribution will show the in situ 14CH4 measurements as well as corresponding simulations and emphasize that the sporadic transport of 14CH4 emitted from PWRs is greatly influencing the overall signal measured over the Swiss Plateau making CH4 source apportionment for this region very challenging.

How to cite: Laemmel, T., Geissbühler, D., Henne, S., Brunner, D., Leuenberger, M., and Szidat, S.: Capabilities of CH4 source apportionment using atmospheric 14CH4 measurements: Switzerland as a case study, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11383, https://doi.org/10.5194/egusphere-egu23-11383, 2023.