Carbon and Hydrogen Isotope Fractionation of Benzene, Toluene, and o -Xylene during Chemical Oxidation by Persulfate

Experiments were performed to investigate the carbon and hydrogen isotope fractionation of benzene, toluene, and o -xylene (BTX) during chemical oxidation by unactivated persulfate at two concentrations (8 and 20 g/L). Carbon enrichment ( e C ) values of −1.7 ± 0.1‰ for benzene, −0.64 ± 0.1‰ for toluene and −0.36 ± 0.04‰ for o -xylene were obtained. No significant hydrogen enrichment ( e H ) was observed for benzene, while the hydrogen enrichment for toluene and o -xylene were −20 ± 3‰ and −23 ± 2‰, respectively. The dual isotope plot ( ∆ δ 13 C vs. ∆ δ 2 H) for benzene and o -xylene revealed a distinct fractionation trend compared to the majority of the biodegradation data compiled from the literature; however, no unique trend was observed for toluene. The significant carbon and/or hydrogen enrichment, and the distinct trend observed on the dual isotope plot suggest that compound specific isotope analysis (CSIA) can potentially be used to monitor the chemical oxidation of BTX by persulfate, and to distinguish treatment areas where persulfate or biodegradation reactions are occurring for benzene and o -xylene.