Stable hydrogen, carbon and chlorine isotope measurements of selected chlorinated organic solvents

Stable hydrogen isotopes of two chlorinated solvents, trichloroethylene (TCE) and 1,1,1-trichloroethane (TCA), provided by five different manufacturers, were determined and compared to their carbon and chlorine isotopic signatures. The isotope ratio for δ2H of different TCEs ranged between +466.9‰ and +681.9‰, for δ13C between −31.57‰ and −27.37‰, and for δ37Cl between −3.19‰ and +3.90‰. In the case of the TCAs, the isotope ratio for δ2H ranged between −23.1‰ and +15.1‰, for δ13C between −27.39‰ and −25.84‰, and for δ37Cl between −3.54‰ and +1.39‰. As well, a column experiment was carried out to dechlorinate tetrachloroethylene (PCE) to TCE using iron. The dechlorination products have completely different hydrogen isotope ratios than the manufactured TCEs. Compared to the positive values of δ2H in manufactured TCEs (between +466.9‰ and +681.9‰), the dechlorinated products had a very depleted δ2H (less than −300‰). This finding has strong implications for distinguishing dechlorination products (PCE to TCE) from manufactured TCE. In addition, the results of this study show the potential of combining 2H/1H analyses with 13C/12C and 37Cl/35Cl for isotopic fingerprinting applications in organic contaminant hydrogeology.