title: Modelling the photochemical fate of ibuprofen in surface waters.
abstract: We show that the main photochemical processes involved in the phototransformation of anionic ibuprofen (IBP) in surface waters are the reaction with (•)OH, the direct photolysis and possibly the reaction with the triplet states of chromophoric dissolved organic matter ((3)CDOM). These conclusions were derived by use of a model of surface water photochemistry, which adopted measured parameters of photochemical reactivity as input data. The relevant parameters are the polychromatic UVB photolysis quantum yield (Φ(IBP) = 0.33 ± 0.05, μ±σ), the reaction rate constant with (•)OH (k(IBP,•OH)=(1.0 ± 0.3)⋅10(10) M(-1) s(-1)), the (1)O(2) rate constant (k(IBP,)( ¹O₂)= (6.0 ± 0.6)⋅10(4) M(-1) s(-1)), while the reaction with CO(3)(-•) can be neglected. We adopted anthraquinone-2-sulphonate (AQ2S) and riboflavin (Ri) as CDOM proxies and the reaction rate constants with the respective triplet states were k(IBP,3AQ2S)=(9.7 ± 0.2)⋅10(9) M(-1) s(-1) and k(IBP,3Ri) = 4.5⋅10(7) M(-1) s(-1). The reaction with (3)CDOM can be an important IBP sink if its rate constant is comparable to that of (3)AQ2S, while it is unimportant if the rate constant is similar to the (3)Ri* one. The photochemical pathways mainly lead to the transformation (oxidation and/or shortening) of the propanoic lateral chain of IBP, which appears to be significantly more reactive than the isobutyl one. Interestingly, none of the detected intermediates was produced by substitution on the aromatic ring.
authors: Dipartimento di Chimica Analitica, Università di Torino, Via P. Giuria 5, 10125 Torino, Italy. davide.vione@unito.it
authors: Davide
authors: D
authors: Vione
authors: Pratap Reddy
authors: PR
authors: Maddigapu
authors: Elisa
authors: E
authors: De Laurentiis
authors: Marco
authors: M
authors: Minella
authors: Marco
authors: M
authors: Pazzi
authors: Valter
authors: V
authors: Maurino
authors: Claudio
authors: C
authors: Minero
authors: Sofia
authors: S
authors: Kouras
authors: Claire
authors: C
authors: Richard
mesh_terms: D000042:Absorption / Q000528:radiation effects; D000880:Anthraquinones / Q000737:chemistry; D006863:Hydrogen-Ion Concentration / Q000528:radiation effects; D017665:Hydroxyl Radical / Q000737:chemistry; D007052:Ibuprofen / Q000302:isolation & purification*; D007700:Kinetics; D008956:Models, Chemical; D010777:Photochemistry / Q000379:methods*; D010782:Photolysis / Q000528:radiation effects; D012256:Riboflavin / Q000737:chemistry; D012395:Rose Bengal / Q000737:chemistry; D013481:Superoxides / Q000737:chemistry; D013499:Surface Properties / Q000528:radiation effects; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*
chemical_list: D000880:Anthraquinones; D014874:Water Pollutants, Chemical; D013481:Superoxides; D012395:Rose Bengal; D017665:Hydroxyl Radical; D012256:Riboflavin; D007052:Ibuprofen