Methane contributes substantially to global warming as the second most important anthropogenic greenhouse gas. Methane sources are diverse and remain poorly quantified and not well understood. The radiocarbon (14C) content of these emissions is of growing interest since it can be used as a tool for a methane source apportionment (Lassey et al., 2007). Indeed, contemporary methane (e.g. agriculture, biomass burning) contains present-day 14C levels whereas fossil methane (e.g. fossil fuels, geologic sources) is 14C-free. However, this task is challenging given the very large amounts of methane required and its very low concentration in the atmosphere. Methane is usually cryogenically separated from other trace gases (mainly CO and CO2) but cross contamination remains an issue difficult to overcome (Pack et al., 2015). Our research aims at enabling the extraction of methane from various kinds of environments (atmosphere, fresh waters and wetlands) and performing 14C measurements with the AMS MICADAS in our laboratory (Szidat et al., 2014). We adapt and develop analytical setups to preconcentrate methane directly in the field in order to bring small samples to the lab where methane is purified and prepared for 14C measurements. We develop a preparative gas chromatography technique to obtain pure methane from the preconcentrated samples and prepare them for 14C analysis with an AMS.
