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ABIOTIC DEGRADATION OF TRICHLOROETHYLENE UNDER THERMAL REMEDIATION CONDITIONS
Citation:
COSTANZA, J., E. L. DAVIS, J. D. MULHOLLAND, AND K. D. PENNELL. ABIOTIC DEGRADATION OF TRICHLOROETHYLENE UNDER THERMAL REMEDIATION CONDITIONS. DOI10/1021/es0502932, J. Schnoor (ed.), ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 39(17):6825-6830, (2005).
Impact/Purpose:
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Description:
The degradation of TCE (C2HCl3) to carbon dioxide (CO2) and chloride (Cl-) has been reported to occur during thermal remediation of subsurface environments. The overall goal of this study was to evaluate abiotic degradation of TCE at elevated temperatures in sealed ampules containing aqueous, gas, and solid phases. The effects of dissolved oxygen content and solid phase composition on TCE degradation rates and products formed was determined by incubating ampules at 22 and 120 °C for periods of up to 40 days. First-order rate coefficients for TCE disappearance ranged from 1.2 to 6.2 10-3 day-1 at 120 °C (half-life = 111-591 days), regardless of the oxygen content and presence of Ottawa sand. The rate of TCE disappearance increased by more than one order-of-magnitude (half-life = 13-44 days) in ampules containing 1% (wt) goethite and Ottawa sand. These findings suggest that the rate of TCE degradation in heated, three-phase systems is relatively insensitive to oxygen content, but may increase substantially in the presence of iron bearing minerals. In all experiments, the TCE degradation products detected were naturally occurring, non-chlorinated carbon compounds including carbon monoxide, carbon dioxide, glycolate, and formate along with chloride. Less than 10% of the initial amount of TCE present was transformed into carbon degradation products and chloride. There was also evidence of the formation of dichloroacetylene, an unstable and spontaneously explosive compound.
