Stable Carbon Isotope Fractionation of 1,2-Dichloropropane during Dichloroelimination by Dehalococcoides Populations

The isotope fractionation of 1,2-dichloropropane (1,2-D) during dichloroelimination to propene by Dehalococcoides populations was explored in laboratory experiments in order to provide data for the characterization of the fate of 1,2-D in heterogeneous subsurface systems. Compound specific stable carbon isotope analysis (CSIA) was used to determine the bulk enrichment factors (epsilon(bulk)), reactive position specific enrichment factors (epsilon(reactive)), and apparent kinetic isotope effect (AKIE) values for 1,2-D dichloroelimination in two district Dehalococcoides-containing cultures. The epsilon(bulk) factors calculated in the two cultures were statistically identical, -10.8 +/- 0.9 and -11.3 +/- 0.8 parts per thousand, even though the cultures were derived from geographically distinct locations. AKIE values for 1,2-D dichloroelimination assuming stepwise and concerted reaction mechanisms were approximately 1.033 and 1.017, respectively. These values are within the range of previously reported values for dichloroelimination reactions and were equivalent to values reported for biotic 1,2-dichloroethane and abiotic 1,1,2,2,-tetrachloroethane and pentachloroethane dichloroelimination reactions.