Characterisation of chlorinated hydrocarbons from chlorine and carbon isotopic compositions: scope of application to environmental problems

A set of chlorinated hydrocarbons (TCE, PCE, DCM, 1,1,1-TCA, chloroform) provided by four manufacturers has been isotopically characterised for both C and Cl, using a new sensitive method. A very large range of delta C-13 (from -51.66 to -24.07%/PDB) associated with a very large range of delta Cl-37 (from -2.7 to +3.4%/SMOC) was obtained. This range of delta Cl-37 is much larger than that of inorganic Cl (+/-1% SMOC) and most individual solvents show a very distinct delta Cl-37 compared to inorganic Cl isotopic signatures. Moreover, delta Cl-37/delta C-13 pairs are distinct from one solvent/manufacturer to another. In a delta C-13 versus delta Cl-37 diagram, delta Cl-37/delta C-13 pairs show different trends for the products of a single manufacturer compared to another. This suggests that Cl isotopic compositions are probably highly fractionated during organic synthesis. The delta Cl-37 values can be interpreted in terms of the probable manufacturing processes. Unlike the data published previously, With one exception, all the new results for samples reported here have positive delta Cl-37 values which might differentiate natural Cl from that derived from degradation. This method has significant potential as a tool for investigating environmental pollution problems; in particular, it offers the possibility for validating models of transport and fate of pollutants. (C) 2001 Elsevier Science Ltd. All rights reserved.