title: Isotope Fractionation Associated with the Indirect Photolysis of Substituted Anilines in Aqueous Solution.
abstract: Organic micropollutants containing aniline substructures are susceptible to different light-induced transformation processes in aquatic environments and water treatment operations. Here, we investigated the magnitude and variability of C and N isotope fractionation during the indirect phototransformation of four para-substituted anilines in aerated aqueous solutions. The model photosensitizers, namely 9,10-anthraquinone-1,5-disulfonate and methylene blue, were used as surrogates for dissolved organic matter chromophores generating excited triplet states in sunlit surface waters. The transformation of aniline, 4-CH3-, 4-OCH3-, and 4-Cl-aniline by excited triplet states of the photosensitizers was associated with inverse and normal N isotope fractionation, whereas C isotope fractionation was negligible. The apparent 15N kinetic isotope effects (AKIE) were almost identical for both photosensitizers, increased from 0.9958±0.0013 for 4-OCH3-aniline to 1.0035±0.0006 for 4-Cl-aniline, and correlated well with the electron donating properties of the substituent. N isotope fractionation is pH-dependent in that H+ exchange reactions dominate below and N atom oxidation processes above the pKa value of the substituted aniline's conjugate acid. Correlations of C and N isotope fractionation for indirect phototransformation were different from those determined previously for the direct photolysis of chloroanilines and offer new opportunities to distinguish between abiotic degradation pathways.
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology , CH-8600 Dübendorf, Switzerland.|Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich , CH-8092 Zürich, Switzerland.
authors.forename: Marco
authors.initials: M
authors.lastname: Ratti
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology , CH-8600 Dübendorf, Switzerland.
authors.forename: Silvio
authors.initials: S
authors.lastname: Canonica
authors.affiliation: Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich , CH-8092 Zürich, Switzerland.
authors.forename: Kristopher
authors.initials: K
authors.lastname: McNeill
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology , CH-8600 Dübendorf, Switzerland.
authors.forename: Jakov
authors.initials: J
authors.lastname: Bolotin
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology , CH-8600 Dübendorf, Switzerland.|Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich , CH-8092 Zürich, Switzerland.
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Hofstetter
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry*; D000880:Anthraquinones / Q000737:chemistry; D002247:Carbon Isotopes; D005591:Chemical Fractionation; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008751:Methylene Blue / Q000737:chemistry; D009587:Nitrogen Isotopes; D010084:Oxidation-Reduction; D010782:Photolysis; D012996:Solutions; D014867:Water / Q000737:chemistry*
chemical_list: D000814:Aniline Compounds; D000880:Anthraquinones; D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D012996:Solutions; C042834:9,10-anthraquinone; D014867:Water; C023650:aniline; D008751:Methylene Blue