Isotopic characterization of chlorinated solvents-laboratory and field results

Pure-phase chlorinated solvent delta(13)C and delta(37)Cl values of tetrachloroethylene (PCE), trichloroethylene (TCE), and 1,1,1 -trichloroethane (TCA) from a new solvent batch from Dow and PPG were analyzed and compared to values obtained from a previous chlorinated solvent batch. These analyses were performed to determine if each chlorinated solvent had a distinct delta(13)C and/or delta(37)Cl value associated with each manufacturer. Results indicate that the delta(13)C and the delta(37)Cl values of TCA do not remain consistent from batch to batch. However, the delta(37)Cl values for PCE and TCE did remain consistent from batch to batch. Furthermore, these tests show a consistent and significant delta(13)C difference between PPG and DOW PCE that could allow the use of C-13/C-12 in conjunction with Cl-37/Cl-36 ratios for fingerprinting applications. Chlorinated solvent/water solutions having known delta(13)C and delta(37)Cl values were used to lest a purge-and-trap unit to extract chlorinated solvents for isotope analyses. These results show that the purge-and-trap unit produces both accurate and reproducible results for dissolved chlorinated solvent delta(13)C and delta(37)Cl analyses. The delta(13)C and delta(37)Cl reproducibility of the purge-and-trap unit was better than 0.9 parts per thousand and 0.4 parts per thousand, respectively. The purge-and-trap unit was tested at a field site that has a well-defined plume of dissolved PCE emanating from a dry cleaner located in Angus, Ontario. The delta(13)C and delta(37)Cl data suggest that the PCE forming the core of the groundwater plume is related to one manufacturer. The results of this study along with results from a chlorinated solvent contaminated site affected by biodegradation show the potential of C-13/C-12 and Cl-37/Cl-36 ratios for isotopic fingerprinting applications on the field of organic contaminant hydrogeology. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.