Effects of decarbonation treatments on δ13C values in marine sediments

Three different methods for decarbonating sediment samples prior to carbon isotope analyses were compared with each other: A, treating the sample with 10% HCl; B, treating the sample with 10% HCl followed by a twofold rinse with deionized water; C, acid fuming with 36% HCl in a desiccator. Whereas, method A and method B gave comparable results, method C gave poor results, since not all of the carbonate was eliminated, especially in samples with high carbonate content, and then interfered with the isotope measurements. Therefore, it is suggested to wash the samples after a treatment with acid (Method B) to avoid deleterious effects of HCl fumes on the elemental analyser and mass spectrometer.