Carbon isotope fractionation during abiotic reductive dehalogenation of trichloroethene (TCE)

Dehalogenation of trichloroethene (TCE) in the aqueous phase, either on palladium catalysts with hydrogen as the reductant or on metallic iron, was associated with strong changes in δ13C. In general, the δ13C of product phases were more negative than those of the parent compound and were enriched with time and fraction of TCE remaining. For dehalogenation with iron, the δ13C of TCE and products varied from −42‰ to + 5‰. For the palladium experiments, the final product, ethane, reached the initial δ13C of TCE at completion of the dehalogenation reaction. During dehalogenation, the carbon isotope fractionation between TCE and product phases was not constant. The variation in δ13C of TCE and products offers a new monitoring tool that operates independently of the initial concentration of pollutants for abiotic degradation processes of TCE in the subsurface, and may be useful for evaluation of remediation efficiency.