Fate of Dimethylsilanediol (DMSD) via Indirect Photolysis in Water

Dimethylsilanediol (DMSD) is the common degradation product of ubiquitous polydimethylsiloxane (PDMS) and volatile methylsiloxanes (VMS) in water and soil. Given the high solubility of DMSD in water, the further degradation of DMSD in this compartment is of particular importance. While DMSD appears relatively resistant to degradation in standard hydrolysis or biodegradation studies, it may degrade by indirect photolysis in surface waters through oxidation by hydroxyl radicals. The formation of hydroxyl radicals is governed by nitrate ions or other promoters in the presence of sunlight. In this study, we investigated the impact of nitrate ions on the oxidative decomposition of DMSD in water under simulated solar light. When exposed to solar light, DMSD can degrade all the way to the natural, mineralized substances, namely carbon dioxide (in the form of carbonic acid) and silicic acid, via the intermediate methylsilanetriol (MST).