Photodegradation of 2-(2-hydroxy-5-methylphenyl) benzotriazole(UV-P) in coastal seawaters: Important role of DOM

摘要

Benzotriazole UV stabilizers (BT-UVs) have attracted concems due to their ubiquitous occurrence in the aquatic environment,and their bioaccumulative and toxic properties.However,little is known about their aquatic environmental degradation behavior.In this study,photodegradation of a representative of BT-UVs,2-(2-hydroxy-5-methylphenyl) benzotriazole (UV-P),was investigated under simulated sunlight irradiation.Results show that UV-P photodegrades slower under neutral conditions (neutral form) than under acidic or alkaline conditions (cationic and anionic forms).Indirect photodegradation is a dominant elimination pathway of UV-P in coastal seawaters.Dissolved organic matter (DOM) from seawaters accelerate the photodegradation rates mainly through excited triplet DOM (3DOM*),and the roles of singlet oxygen and hydroxyl radical are negligible in the matrixes.DOM from seawaters impacted by mariculture exhibits higher steady-state concentration of 3DOM*([3DOM*]) relative to those from pristine seawaters,leading to higher photosensitizing effects on the photodegradation.Halide ions inhibit the DOM-sensitized photodegradation of UV-P by decreasing [3DOM*].Photodegradation half-lives of UV-P are estimated to range from 24.38 to 49.66 hr in field water bodies of the Yellow River estuary.These results are of importance for assessing environmental fate and risk UV-P in coastal water bodies.