Compound-specific δ13C analysis of DOC in groundwater by LC-TIC/TOC-continuous flow IRMS

Full text: The isotopic composition of both dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in groundwater can now be routinely analysed by an automated total inorganic and organic carbon (TIC/TOC) instrument interfaced with a continuous flow isotope ratio mass spectrometer (CF-IRMS). The TIC/TOC analyzer uses a helium carrier gas compatible with the CF-IRMS. This allows rapid, automated analysis of concentration and 13C composition for these two important carbon components in groundwaters. Having developed this new method, we now add a preparation step where DOC components are separated by liquid chromatography and fraction collector, allowing the analysis of 13C in specific DOC compounds. This provides insights into the consumption and production of organic carbon substrates during bacterial degradation of DOC. Applications with leachate-contaminated groundwaters and methanogenic groundwaters are presented. (author)