Effects of inorganic anions on carbon isotope fractionation during Fenton-like degradation of trichloroethene

Understanding the magnitude and variability in isotope fractionation with respect to specific processes is crucial to the application of stable isotopic analysis as a tool to infer and quantify transformation processes. The variability of carbon isotope fractionation during Fenton-like degradation of trichloroethene (TCE) in the presence of different inorganic ions (nitrate, sulfate, and chloride), was investigated to evaluate the potential effects of inorganic anions on carbon isotope enrichment factor (epsilon value). A comparison of epsilon values obtained in deionized water, nitrate solution, and sulfate solution demonstrated that the epsilon values were identical and not affected by the presence of nitrate and sulfate. In the presence of chloride, however, the epsilon values (ranging from-6.3 +/- 0.8 to 10 +/- 1.3 parts per thousand) were variable and depended on the chloride concentration, indicating that chloride could significantly affect carbon isotope fractionation during Fenton-like degradation of TCE. Thus, caution should be exercised in selecting appropriate e values for the field application of stable isotope analysis, as various chloride concentrations may be present due to naturally present or introduced with pH adjustment and iron salts during Fenton-like remediation. Furthermore, the effects of chloride on carbon isotope fractionation may be able to provide new insights about reaction mechanisms of Fenton-like processes. (C) 2016 Elsevier B.V. All rights reserved.