Fate of TCE in Heated Fort Lewis Soil

This study explores the transformation of trichloroethene (TCE) caused by heating contaminated soil and groundwater samples obtained from the East Gate Disposal Yard (EGDY) located in Fort Lewis, WA. After field samples transferring into glass ampules and introducing 1.5 μmol of TCE, the sealed ampules were incubated at temperatures of 25, 50, and 95 °C for periods of up to 95.5 days. Although TCE was completely transformed into cis-1,2-dichloroethene (cis-DCE) after 42 days at 25 °C by microbial activity, this transformation was not observed at 50 or 95 °C. Chloride levels increased after 42 days at 25 °C corresponding to the mass of TCE transformed to cis-DCE, were constant at 50 °C, and increased at 95 °C yielding a TCE degradation half-life of 1.6−1.9 years. These findings indicate that indigenous microbes contribute to the partial dechlorination of TCE to cis-DCE at temperatures of less than 50 °C, whereas interphase mass transfer and physical recovery of TCE will predominate over in situ degradation processes at temperatures of greater than 50 °C during thermal treatment at the EGDY site.