Photolysis of atrazine: Role of triplet dissolved organic matter and limitations of sensitizers and quenchers.

Bin Wu, William A Arnold, Limin Ma

Water research 2021 Feb 15

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Atrazine, a widely used herbicide, is susceptible to photolysis. The role of triplet excited states of chromophoric dissolved organic matter (3CDOM*) in the photolysis of atrazine, however, is not well understood. The direct photolysis of atrazine under irradiation sources (natural sunlight/environmentally relevant simulated solar light) and its indirect photochemical reactivity with model triplet photosensitizers (benzophenone, 2-acetonaphthone, 3'-methoxy-acetophenone, 4-carboxybenzophenone, rose bengal, methylene blue, and anthraquinone-2-sulphonate) was investigated. The reactivity of the model sensitizers and DOM (Suwannee River natural organic matter, river/lake water, and wastewater effluent), were compared. The direct photolysis quantum yield was determined as 0.0196 mol Einstein-1 in a solar simulator and 0.00437 mol Einstein-1 under natural sunlight. Considerable photosensitization was induced by triplet state (n-π*) model sensitizers, while insignificant effects on atrazine loss were discerned in natural organic matter even when oxygen, a triplet quencher, was removed. The triplet sensitizers benzophenone and 2-acetylnaphthone reacted with L-histidine and 2-propanol that were intended to quench/ scavenge 1O2 and hydroxyl radical •OH, respectively, and benzophenone reacted with NaN3 as a 1O2 scavenger and furfuryl alcohol as a 1O2 trapping agent, indicating quenchers may have unanticipated effects when using model sensitizers. Atrazine loss via reaction with 3DOM* will be relevant only in selected conditions, and this work provides a more comprehensive view on the use of model photosensitizers to mimic triplet 3DOM*. Copyright © 2020. Published by Elsevier Ltd.

Citation

Bin Wu, William A Arnold, Limin Ma. Photolysis of atrazine: Role of triplet dissolved organic matter and limitations of sensitizers and quenchers. Water research. 2021 Feb 15;190:116659