The application of STXM and μFT-IR to characterize sedimentary organic matter in the Opalinus clay

Clay-rich formations with low organic carbon content are considered as host formations for radioactive waste disposal. Examples are the Callovo-Oxfordian argillite (France) and the Opalinus Clay (Switzerland). The natural organic matter can have an impact on the chemical clay stability and can be the source of strongly radionuclide complexing hydrophilic compounds. The investigated clay sample originates from the Opalinus clay (Benken). 1.1 wt. % of the total organic carbon inventory could be released by alkaline extraction. C-, K-, Ca- edge Scanning Transmission X-Ray microscopy (STXM) and synchrotron μFT-IR microcopy was used for identification of the spatial distribution of clay organic matter and mineral dependent organic matter functionality. The results show the complexity of the organic inventory and could be used to identify possible sources of hydrophilic organic compounds.