title: Photochemical degradation of sunscreen agent 2-phenylbenzimidazole-5-sulfonic acid in different water matrices.
abstract: The occurrence of sunscreen agents in natural environment is of scientific concern recently due to their potential risk to ecology system and human beings as endocrine disrupting chemicals (EDCs). In this work the photodegradation mechanism and pathways of sunscreen agent 2-phenylbenzimidazole-5-sulfonic acid (PBSA) were investigated under artificial solar irradiation with the goal of assessing the potential of photolysis as a transformation mechanism in aquatic environments. The quantum yield of PBSA direct photolysis in pH 6.8 buffer solution under filtered mercury lamp irradiation was determined as 2.70 × 10(-4). Laser flash photolysis (LFP) experiments confirmed the involvement of PBSA radical cation (PBSA(·+)) during direct photolysis. Acidic or basic condition facilitated PBSA direct photolysis in aqueous solution. Indirect photolysis out-competes direct photolysis as a major process for PBSA attenuation only at higher level of photosensitizers (e.g., NO3(-) > 2 mM). Thus, direct photolysis is likely to be the major loss pathway responsible for the elimination of PBSA in natural sunlit surface waters, while indirect photolysis (e.g., mediated by HO·) appeared to be less important due to a general low level of steady-state concentration of HO· ([HO·]ss) in natural surface waters. Direct photolysis pathways of PBSA includes desulfonation and benzimidazole ring cleavage, which are probably initiated by the excited triplet state ((3)PBSA*) and radical cation (PBSA(·+)). Conversely, hydroxylation products of PBSA and 2-phenyl-1H-benzimidazole as well as their ring opening intermediates were found in nitrate-induced PBSA photolysis, suggesting the indirect photodegradation was primarily mediated by HO and followed a different mechanism.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, PR China; Université Lyon 1, UMR CNRS 5256, Institut de recherches sur la catalyse et l'environnement de Lyon (IRCELYON), 2 Avenue Albert Einstein, F-69626 Villeurbanne, France. Electronic address: yuefei.ji@ircelyon.univ-lyon1.fr.
authors.forename: Yuefei
authors.initials: Y
authors.lastname: Ji
authors.forename: Lei
authors.initials: L
authors.lastname: Zhou
authors.forename: Ya
authors.initials: Y
authors.lastname: Zhang
authors.forename: Corinne
authors.initials: C
authors.lastname: Ferronato
authors.forename: Marcello
authors.initials: M
authors.lastname: Brigante
authors.forename: Gilles
authors.initials: G
authors.lastname: Mailhot
authors.forename: Xi
authors.initials: X
authors.lastname: Yang
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Chovelon
mesh_terms: D001562:Benzimidazoles / Q000737:chemistry*; D010777:Photochemistry / Q000379:methods*; D013451:Sulfonic Acids / Q000737:chemistry*; D013473:Sunscreening Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D001562:Benzimidazoles; D013451:Sulfonic Acids; D013473:Sunscreening Agents; D014867:Water; C499767:ensulizole
keywords: 2-Phenylbenzimidazole-5-sulfonic acid; Degradation pathways; Photolysis; Sunscreen agent; Water matrix