Photochemical Production of Sulfate and Methanesulfonic Acid from Dissolved Organic Sulfur in Natural Waters

Despite its abundance, its importance in biological processes and its influence on metal bioavailability, the biogeochemical cycle of dissolved organic sulfur (DOS) in aquatic systems is still poorly understood. Recent high-resolution mass spectrometry studies showed a selective loss of organic sulfur during photodegradation of dissolved organic matter (DOM), which was hypothesized to be associated with the production of sulfate. Here we present evidence of ubiquitous production of sulfate and small non-volatile S-containing compounds during photodegradation of DOM samples from a wide range of natural environments. Our estimates indicate that photoproduction of sulfate in the ocean exceeds that of carbonyl sulfide and carbon disulfide by at least two orders of magnitude, suggesting that photodegradation plays a significant role in the aquatic and atmospheric cycle of DOS.