Chromophoric Dissolved Organic Matter (CDOM) has a major impact on aquatic ecosystems through its absorption of light and photochemical reactions. The nature of the light absorbing species that produce the optical and photochemical properties of CDOM remain incompletely understood. Further, these properties can vary by source and be altered by thermal and photochemical reactions. The contribution of various functional groups to the optical and photochemical properties exhibited by CDOM is needed to address this issue. This study examines the reactions of several series of model quinones with dithionite and sulfite, ultimately to test for the presence of quinones in CDOM from various sources as well as to better understand the reaction mechanisms. Current results on a series of methyl-substituted quinones reduced with sodium dithionite and sodium sulfite show that their reactivity depends on the degree of substitution, the substitution pattern, and the reduction potentials. Ongoing studies are examining the reactions of methoxy-substituted quinones, naphthoquinones, and anthraquinones. The change in optical properties observed for these model quinones following reaction with dithionite and sulfite will be compared with those obtained following reaction with CDOM to estimate the overall contribution of quinones to the optical properties of CDOM from a variety of sources. These studies should also provide a greater understanding of the reactions of quinones with sulfur-based reductants.

Reaction of quinones with sodium dithionite and sodium sulfite: Examining quinone reactivity in chromophoric dissolved organic matter

ACS Spring 2022

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