Carbon and chlorine isotope fractionation of chlorinated aliphatic hydrocarbons by evaporation

Two pure solvents (trichloroethene and dichloromethane) were evaporated at room temperature (24 +/- 1 degrees C). The carbon and chlorine isotopic com positions of the residual solvents were measured as a function of the fract ion remaining. Isotopic fractionation factors (alpha) derived From these ex perimental results are 1.00031 +/- 0.00004 for C and 0.99818 +/- 0.00022 fo r Cl in trichloroethene, and 1.00065 +/- 0.00002 for C and 0.99952 +/- 0.00 006 for Cl in dichloromethane. The negative correlation between delta(13)C and delta(37)Cl values caused by evaporation of chlorinated aliphatic hydro carbons can be used to distinguish evaporation from biodegradation in conta minated systems. (C) 1999 Published by Elsevier Science Ltd. All rights res erved.