Distribution and abiotic degradation of chlorinated solvents in heated field samples

The objective of this study was to evaluate the abiotic degradation of tetrachloroethylene (PCE) in contaminated soil and groundwater samples obtained from the Camelot Cleaners Superfund site, West Fargo, ND. The field samples were incubated at temperatures of 25, 55, 75, and 95 degrees C in sealed ampules containing aqueous, gas, and solid phases for periods of up to 75 days to simulate thermal treatment temperatures. Aqueous PCE concentrations increased with incubation temperature but remained constant over time. The degradation of dolomite to form CO2 facilitated the transfer of sorbed-phase PCE from the solid to the aqueous phase in heated ampules. While compounds associated with PCE degradation were detected in the heated ampules, these compounds were also detected in ampules with PCE-free Camelot soil and were attributed to soil diagenesis rather than PCE degradation. Trichloroethylene underwent hydrogenolysis to form cis-DCE at 95 degrees C, and TCE levels decreased with first-order half-lives of 157 days at 55 degrees C and 26 days at 95 degrees C. The relatively small decrease in total PCE levels after 75 days of heating at 95 degrees C suggests that abiotic degradation of PCE will not result in significant mass reduction during thermal treatment of the Camelot Cleaners Superfund site.