Characterization and comparison of riverine, lacustrine, marine and estuarine dissolved organic matter by ultra-high resolution and accuracy Fourier transform mass spectrometry

Dissolved organic matter (DOM) is an important component in the global carbon cycle and knowledge of its chemical composition is crucial for understanding its role in biogeochemical cycles and its interaction with pollutants in aquatic systems. Changes in DOM could drastically affect carbon fluxes, and the toxicity and distribution of pollutants. This study reports DOM characterization and comparison by ultra-high resolution and accuracy Fourier transformed ion cyclotron resonance mass spectrometry (FT-ICR-MS) of samples from an estuarine, a marine, a riverine and a lacustrine system of southeastern Brazil (SE Brazil). The MS screening of DOM showed ions corresponding to several classes of constituents such as synthetic surfactants, lignins, lipids and sulfur polyoxygenated (CHOS) constituents. The CHOS constituents and the synthetic surfactants displayed higher abundance for riverine and lacustrine samples which have higher human impact than the marine and estuarine samples. We hypothesized that these CHOS compounds are formed in situ by the addition of inorganic sulfur anions such as sulfide or bisulfide to lignin derived compounds via Kraft reactions.