TY - JOUR
T1 - Isotope fractionation associated with the direct photolysis of 4-chloroaniline
AU - Ratti, Marco
AU - Canonica, Silvio
AU - McNeill, Kristopher
AU - Erickson, Paul R.
AU - Bolotin, Jakov
AU - Hofstetter, Thomas B.
N1 - Publisher Copyright:
© 2015 American Chemical Society.
PY - 2015/4/7
Y1 - 2015/4/7
N2 - Compound-specific isotope analysis is a useful approach to track transformations of many organic soil and water pollutants. Applications of CSIA to characterize photochemical processes, however, have hardly been explored. In this work, we systematically studied C and N isotope fractionation associated with the direct photolysis of 4-Cl-Aniline used as a model compound for organic micropollutants that are known to degrade via photochemical processes. Laboratory experiments were carried out at an irradiation wavelength of 254 nm over the pH range 2.0 to 9.0 as well as in the presence of Cs+ as a quencher of excited singlet 4-Cl-Aniline at pH 7.0 and 9.0. We observed considerable variation of C and N isotope enrichment factors, C and N, between -1.2 ± 0.2‰ to -2.7 ± 0.2‰ for C and -0.6 ± 0.2‰ to -9.1 ± 1.6‰ for N, respectively, which could not be explained by the speciation of 4-Cl-Aniline alone. In the presence of 1 M Cs+, we found a marked increase of apparent 13C-kinetic isotope effects (13C-AKIE) and decrease of 4-Cl-Aniline fluorescence lifetimes. Our data suggest that variations of C and N isotope fractionation originate from heterolytic dechlorination of excited triplet and singlet states of 4-Cl-Aniline. Linear correlations of 13C-AKIE vs 15N-AKIE were distinctly different for these two reaction pathways and may be explored further for the identification of photolytic aromatic dechlorination reactions.
AB - Compound-specific isotope analysis is a useful approach to track transformations of many organic soil and water pollutants. Applications of CSIA to characterize photochemical processes, however, have hardly been explored. In this work, we systematically studied C and N isotope fractionation associated with the direct photolysis of 4-Cl-Aniline used as a model compound for organic micropollutants that are known to degrade via photochemical processes. Laboratory experiments were carried out at an irradiation wavelength of 254 nm over the pH range 2.0 to 9.0 as well as in the presence of Cs+ as a quencher of excited singlet 4-Cl-Aniline at pH 7.0 and 9.0. We observed considerable variation of C and N isotope enrichment factors, C and N, between -1.2 ± 0.2‰ to -2.7 ± 0.2‰ for C and -0.6 ± 0.2‰ to -9.1 ± 1.6‰ for N, respectively, which could not be explained by the speciation of 4-Cl-Aniline alone. In the presence of 1 M Cs+, we found a marked increase of apparent 13C-kinetic isotope effects (13C-AKIE) and decrease of 4-Cl-Aniline fluorescence lifetimes. Our data suggest that variations of C and N isotope fractionation originate from heterolytic dechlorination of excited triplet and singlet states of 4-Cl-Aniline. Linear correlations of 13C-AKIE vs 15N-AKIE were distinctly different for these two reaction pathways and may be explored further for the identification of photolytic aromatic dechlorination reactions.
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U2 - 10.1021/es505784a
DO - 10.1021/es505784a
M3 - Article
C2 - 25719866
AN - SCOPUS:84926433995
SN - 0013-936X
VL - 49
SP - 4263
EP - 4273
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 7
ER -