COMPOUND SPECIFIC CHLORINE AND CARBON ISOTOPIC ANALYSES OF TCE AND CIS-DCE: APPLICATION TO A FRACTURED CONTAMINANT SITE

A former hazardous waste transfer station was responsible for a large contaminant spill in the town of Smithville, Ontario, where an estimated 2,000 to 4,000 liters of trichloroethene (TCE) was released into a fractured dolostone aquifer between 1978 and 1985. Previous lab and field studies have shown that fractionation of the stable isotopes of chlorine and carbon occurred as TCE and cis-1,2-dichloroethene (cis-DCE) were microbially dechlorinated. Compound specific (TCE and cis-DCE) isotopic analyses of both chlorine and carbon isotopes were conducted on groundwater samples to assess whether biologically remediated dechlorination occurred at this site. Current results of samples collected in the field show large ranges in both δ³⁷Cl and δ¹³C values. Furthermore, large variations in the relative concentration of TCE, cis-DCE, and other degradation products were observed.