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Enhanced anaerobic biotransformation of carbon tetrachloride in the presence of reduced iron oxides
Author(s) -
Kim Sanggoo,
Picardal Flynn W.
Publication year - 1999
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620181005
Subject(s) - shewanella putrefaciens , chemistry , lepidocrocite , reaction rate constant , biotransformation , transformation (genetics) , carbon tetrachloride , dithiothreitol , anoxic waters , goethite , hydroxide , nuclear chemistry , environmental chemistry , inorganic chemistry , kinetics , organic chemistry , biochemistry , bacteria , biology , adsorption , quantum mechanics , genetics , physics , gene , enzyme
Rates of anaerobic transformation of carbon tetrachloride (CT) by the facultative anaerobe Shewanella putrefaciens 200 were increased by the presence of Fe(III)‐containing minerals. In batch reactors with amorphous, Fe(III)‐hydroxide and S. putrefaciens, CT transformation rates could be modeled by a first—order expression in which the pseudo—first‐order rate constant was linearly proportional to the initial concentration of Fe(III)‐oxide. Subsequent measurement of soluble and acid—extractable Fe(II) showed that increased CT transformation rates were proportional to microbially reduced, surface—bound Fe(II), rather than soluble Fe(II). In biomimetic experiments using 20 mM dithiothreitol (DTT) as a reductant, rates of transformation of CT by DTT were low in the absence of Fe(III)‐oxides. However, in the presence of iron oxides, DTT was able to transform CT at elevated rates. Results again strongly suggested that surface—bound Fe(II) was primarily responsible for the reductive transformation of CT. Results suggested that the surface area of the iron mineral determines the rate of CT transformation by affecting the extent of iron reduction. Chloroform (CF) was the only transformation product identified and production of CF was nonstoichiometric. In microbial and abiotic experiments with Fe(III) oxides, the percentage of the transformed CT recovered as CF decreased even though the rate and extent of CT transformation was increased. Overall, our results have important implications for an improved understanding of possible microbial and geochemical interactions in the environmental transformation of chlorinated organic pollutants and for modeling of CT transformation rates in anaerobic, iron—bearing sediments.