T03_P02

A new online ramped oxidation (ORO) system for improved coupled thermal and radiocarbon  dissection of complex natural organic matter

Bolandini M¹, Bröder L¹, De Maria D², Eglinton T¹, Wacker L²

¹D-ERDW - Biogeoscience Group, ETH, Zürich, Switzerland, ²D-PHYS - Laboratory for Ion Beam Physics (LIP), ETH, Zürich, Switzerland

The coupling of serial or ramped pyrolysis and oxidation to carbon isotope measurements provides insights into the relationships between thermal activation energies and age distributions of natural organic materials. It therefore helps to elucidate controls on organic matter reactivity. The conventional approach involves heating of a bulk sample with a defined temperature ramp, simultaneous oxidation of thermal decomposition products, and collection of the resulting to CO₂ for subsequent ¹⁴C analysis.

The newly developed online ramped oxidation (ORO) system has been designed to sequentially trap and release evolved CO₂ via a customized interface to a gas-accepting source of an accelerator mass spectrometer (AMS), facilitating higher thermal and isotopic resolution of organic constituents. This is achieved via a two-stage oven that regulates the decomposition and subsequent oxidation of carbonaceous compounds to CO₂ in a mixture of He and O₂. This is coupled with a double zeolite trap interface (DTI, De Maria et al. 2021) that modulates the collection and transfer of evolved CO₂ to the AMS system for ¹⁴C measurement.

A functioning prototype of the ORO system has been developed to perform initial combustion tests. To this end, blanks, standard material, and samples from complex matrices such as soils, river, lake, and marine sediments are being measured and results compared with reference data.