T01_P04

Radiocarbon analysis of methane

Gentz T¹,  Höhn M¹, Grotheer H¹, Kattein L¹, Mollenhauer G¹

¹AWI-Bremerhaven, Bremerhaven, Germany

Methane (CH₄) is the most abundant organic compound in the atmosphere and its influence on the global climate is subject to widespread and ongoing scientific discussion. Two sources of atmospheric methane are the release of methane from the ocean seafloor, as well as from thawing permafrost.

In recent years the origin, sediment and water column processes and subsequent pathways of methane have received growing interest in the scientific community. ^13C/¹²C ratio measurements can be used to determine the methane source (biogenic or thermogenic), but potential formation/alteration processes by microbes are not yet fully understood.

Radiocarbon analysis can help to understand these carbon cycling processes. The presented method is a novel approach for the radiocarbon age determination of methane. A modified PreConn is used to separate methane from other gases such as CO₂ in a gaseous sample. Afterwards, the purified methane is transferred to a furnace and oxidized to CO₂. Subsequently, produced CO₂ is concentrated on a custom-made zeolite trap, which can be connected to a novel sampling unit implemented into the GIS system (by Ionplus AG) for direct CO₂ measurements on a MICADAS. The zeolite trap has ¼“ quick-fit connectors (Swagelok) that allow to detach the trap from the oxidation unit and to re-attach it in the GIS. Initial testing showed minimal blank carbon incorporation associated with sample storage, transfer and handling of the custom-build zeolite trap.

Here we will present the setup of the method, first results of the blank determination as well as precision of common standard gases.