Carbon isotope fractionation of chlorinated ethenes during oxidation by Fe2+ activated persulfate

The increased use of persulfate (S2O82−) for in situ chemical oxidation to treat groundwater and soils contaminated by chlorinated hydrocarbon compounds (CHCs) requires unbiased methods to assess treatment performance. Stable carbon isotope analysis offers a potential tool for assessing the in situ treatment performance of persulfate at sites contaminated with CHCs. This study investigated the extent of C isotope fractionation during oxidation of tetrachloroethene (PCE), trichloroethene (TCE) and cis-dichloroethene (cis-DCE) by persulfate activated by ferrous ion (Fe2+). An average carbon isotope enrichment factor εbulk of −4.9‰ for PCE, −3.6‰ for TCE and −7.6‰ for cis-DCE were obtained in batch experiments. Variations in the initial S2O82−/Fe2+/CHC molar ratios did not result in any significant differences in carbon isotope fractionation. The occurrence of carbon isotope fractionation during oxidation and the lack of dependence of enrichment factors upon the S2O82−/Fe2+/CHC molar ratio demonstrate that carbon isotope analysis can potentially be used at contaminated sites as an additional technique to estimate treatment efficacy during oxidation of CHCs by Fe2+ activated persulfate. [Display omitted] ► The performance of in situ chemical oxidation (ISCO) is still difficult to assess. ► We investigated the potential of carbon isotope analysis as a new assessing tool. ► C isotope of PCE, TCE and DCE oxidized by persulfate activated by Fe2+ was measured. ► Enrichment factors of −4.9‰ for PCE, −3.6‰ for TCE and −7.6‰ for cisDCE were obtained. ► Carbon isotope can potentially be used to estimate the ISCO treatment efficacy.