The extremely complex and variable chemical composition of dissolved organic matter (DOM) often poses seemingly insurmountable problems to understand the role of DOM in the transformation of aquatic contaminants. The case of light-induced reactions of DOM is particularly challenging. This contribution reviews the efforts made during the last three decades to mimic, using model compounds, the activity of DOM as a promoter and inhibitor in the indirect phototransformation of organic contaminants. Aromatic ketones have been employed since the early 1990s as surrogates of DOM chromophores with the aim of producing primarily excited triplet states as reactive intermediates. With their help, excited triplet states of DOM (<sup>3</sup>DOM*) were proposed as main reactive species initiating the oxidative transformation of organic contaminants. In later studies on <sup>3</sup>DOM*-induced transformations of aromatic amine contaminants, phenolic compounds were utilized to simulate the inhibition of these reactions by DOM antioxidant moieties. The newest example in this review deals with the use of electron-poor phenols to photo-generate the corresponding phenoxyl radicals, used to mimic the still poorly characterized DOM-derived “long-lived” photooxidants. The latter appear to be relevant reactive intermediates for the transformation of electron-rich contaminants at the typical low concentrations observed in surface waters. In conclusion, aromatic ketone and phenolic moieties were suggested to be key players in the photochemistry of DOM.

Using model compounds to understand the photochemistry of dissolved organic matter and the fate of aquatic contaminants in sunlit natural waters

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.