The extent of carbon isotope fractionation during degradation of 1,1,1-trichloroethane (1,1,1-TCA) by a base-catalyzed persulfate (S2O82-) treatment system was investigated. Significant destruction of 1,1,1-TCA was observed at a pH of similar to 12. An increase in the NaOH:S2O82- molar ratio from 0.2:1 to 8:1 enhanced the reaction rate of 1,1,1-TCA by a factor of similar to 5 to yield complete (>99.9%) destruction. An average carbon isotope enrichment fractionation factor which was independent of the NaOH:S2O82- molar ratio of -7.0 +/- 0.2 parts per thousand, was obtained. This significant carbon isotope fractionation and the lack of dependence on changes in the NaOH:S2O82- molar ratio demonstrates that carbon isotope analysis can potentially be used in situ as a performance assessment tool to estimate the degradation effectiveness of 1,1,1-TCA by a base-catalyzed persulfate system. (C) 2013 Elsevier B.V. All rights reserved.