Dissolved organic matter (DOM) as a collective term for a very complex mixture of organic compounds in aqueous environments is one of the biggest organic carbon reservoirs on earth. The biggest part of this organic matter is refractory as it is not utilized by microorganisms. Although DOM occurs all over the world and is able to influence the global climate by absorption and release of climate impacting gases its biogeochemistry is very little understood.
Ultrahigh resolution mass spectrometry via Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) provides unprecedented information on the molecular composition of DOM. Molecular formulae can be assigned to thousands of masses resolved by FT-ICR-MS within the complex mixture of DOM. Structural analysis of the compounds remains very complicated, though, due to the high number of isomers for each molecular formulae.
Especially sulfur containing compounds in DOM are little analyzed, yet, and offer a broad research topic in organic geochemistry. Sulfur compounds are on the one hand produced directly by living organisms and on the other hand by complex abiotic reactions via reactive sulfide intermediates. Possibly occurring sulfur containing functional groups in DOM samples are analyzed by using diverse selective derivatization reactions and different mass spectrometric analysis methods at the FT-ICR mass spectrometer. All experiments are verified by model compounds. Furthermore, hypotheses about production and fate of the organic sulfur compounds shall be analyzed by interdisciplinary experiments.