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EFFECTS OF THREE CONCENTRATIONS OF MIXED FATTY ACIDS ON DECHLORINATION OF TETRACHLOROETHENE IN AQUIFER MICRO- COSMS
Citation:
Gibson, S. A., D. S. Roberson, H. H. Russell, AND G W. Sewell*. EFFECTS OF THREE CONCENTRATIONS OF MIXED FATTY ACIDS ON DECHLORINATION OF TETRACHLOROETHENE IN AQUIFER MICRO- COSMS. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 13(3):453-460, (1994).
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Description:
Chloroethenes are among the most common organic contaminants of ground water. The biotransformation of these compounds by reductive dechlorination is a promising technology for in situ treatment. The effects of three concentrations of a fatty acids mixture on the reductive dehalogenation of tetrachloroethene (PCE) were studied in methanogenic microcosms. These microcosms were constructed with slurries of aquifer solids collected from an area impacted both by aviation gasoline and chlorinated ethenes at Traverse City, Michigan. The microcosms were amended with approximately 30 µM PCE and one of three concentrations (0.1, 1, or 10 mM total acids) of a mixture of low-molecular-weight organic acids, or were part of a control set that received no amendment. The observed lag or adaptation times before the onset of PCE dehalogenation were 51 d (10 mM acids), 65 d (1 mM acids), 86 d (0.1 mM acids), and >233 d (no acids). After 233 d of incubation, no PCE was detectable in any of the fatty-acid-supplemented microcosms, but 23 to 27 µM of combined tri- and dichloroethenes (TCEs, DCEs) was detected. PCE was not dechlonnated in microcosms without a fatty acid supplement. Although there were observed differences in the length of the lag time, the amount of ultimately dechlorinated PCE was similar. A zero-order rate constant of 0.3 µM d−1 was calculated for PCE dechlorination and for TCE dechlorination for the two series of microcosms receiving 0.1 and 1.0 mM fatty acid supplements. Of the fatty acids tested in the mixture, butyrate oxidation appeared to be the most probable link to PCE dechlorination.
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