title: New insight into photo-bromination processes in saline surface waters: the case of salicylic acid.
abstract: It was shown, through a combination of field and laboratory observations, that salicylic acid can undergo photo-bromination reactions in sunlit saline surface waters. Laboratory-scale experiments revealed that the photochemical yields of 5-bromosalicylic acid and 3,5-dibromosalicylic acid from salicylic acid were always low (in the 4% range at most). However, this might be of concern since these compounds are potential inhibitors of the 20α-hydroxysteroid dehydrogenase enzyme, with potential implications in endocrine disruption processes. At least two mechanisms were involved simultaneously to account for the photo-generation of brominated substances. The first one might involve the formation of reactive brominated radical species (Br, Br(2)(-)) through hydroxyl radical mediated oxidation of bromide ions. These ions reacted more selectively than hydroxyl radicals with electron-rich organic pollutants such as salicylic acid. The second one might involve the formation of hypobromous acid, through a two electron oxidation of bromine ions by peroxynitrite. This reaction was catalyzed by nitrite, since these ions play a crucial role in the formation of nitric oxide upon photolysis. This nitric oxide further reacts with superoxide radical anions to yield peroxynitrite and by ammonium through the formation of N-bromoamines, probably due to the ability of N-bromoamines to promote the aromatic bromination of phenolic compounds. Field measurements revealed the presence of salicylic acid together with 5-bromosalicylic and 3,5-dibromosalicylic acid in a brackish coastal lagoon, thus confirming the environmental significance of the proposed photochemically induced bromination pathways.
authors.affiliation: UMR HydroSciences 5569, Montpellier University, 15 Avenue Ch. Flahault, 34093 Montpellier cedex 5, France.
authors.forename: Fatima
authors.initials: F
authors.lastname: Tamtam
authors.forename: Serge
authors.initials: S
authors.lastname: Chiron
mesh_terms: D001959:Bromates / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D054879:Halogenation; D009569:Nitric Oxide / Q000737:chemistry; D009573:Nitrites / Q000737:chemistry; D010084:Oxidation-Reduction; D030421:Peroxynitrous Acid / Q000737:chemistry; D055668:Photochemical Processes; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D020156:Salicylic Acid / Q000737:chemistry*; D054712:Salinity; D062065:Wastewater / Q000737:chemistry; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D001959:Bromates; D005609:Free Radicals; D009569:Nitric Oxide; D009573:Nitrites; D030421:Peroxynitrous Acid; D000644:Quaternary Ammonium Compounds; D020156:Salicylic Acid; D062065:Wastewater; D014867:Water; D014874:Water Pollutants, Chemical; C027664:hypobromous acid