Enhanced anaerobic transformations of carbon tetrachloride by soil organic matter

Journal Article · Wed Dec 01 04:00:00 EST 1999 · Environmental Toxicology and Chemistry

DOI:https://doi.org/10.1897/1551-5028(1999)018<2703:EATOCT>2.3.CO;2· OSTI ID:20012769

Collins, R; Picardal, F

Anaerobic, reductive dehalogenation of carbon tetrachloride (CT) by Shewanella putrefaciens 200 is enhanced by the presence of a high-organic-carbon soil. In microbial incubations without soil, 29% of the initial 3 ppm CT was transformed after 33 h, whereas 64% was transformed after only 18 h when soil was present. In sterile, biomimetic systems using a chemical reductant, 20 mM dithiothreitol, similar results were observed, suggesting that abiotic electron-transfer mediators in the soil were catalyzing the reaction. Destruction of 62% of the soil organic carbon by H{sub 2}O{sub 2} resulted in a soil that was less effective in enhancing CT dechlorination. Following separation of the soil organic matter into three humic fractions, the humic acid (HA) fraction catalyzed the dechlorination reaction to a greater extent than did the fulvic acid (FA) fraction, and both were more effective than the fraction containing humin and inorganic minerals. The results are consistent with a mechanism involving humic functional groups that serve as electron-transfer mediators able to enhance the reductive transformation of CT in the presence of a microbial or chemical reductant. Humic functional group analyses showed that the FA contained more total acidity and carboxylic acidity than did the HA; however, both fractions contained similar amounts of total carbonyl groups and quinone carbonyls. Abiotic, HA-mediated CT transformation was observed regardless of whether dithiothreitol was present or not. At circumneutral pH, HA-mediated CT transformation required the presence of dithiothreitol. At pH 8.7, HA-mediated reductive CT transformation occurred both in the absence or presence of dithiothreitol although the transformation was greater in the presence of a reductant. Trichloromethane (chloroform [CF]) production at pH 8.7 was much lower than at circumneutral pH, and volatile organic compounds other than CF were not detected as products in any case.

• Research Organization: Indiana Univ., Bloomington, IN (US)
• OSTI ID: 20012769
• Journal Information: Environmental Toxicology and Chemistry, Journal Name: Environmental Toxicology and Chemistry Journal Issue: 12 Vol. 18; ISSN ETOCDK; ISSN 0730-7268
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ANAEROBIC CONDITIONS
BIODEGRADATION
CARBON TETRACHLORIDE
ORGANIC MATTER
REMEDIAL ACTION
SOILS