Dehydrochlorination of 1,1,1-trichloroethane and pentachloroethane by microbially reduced ferruginous smectite.
Reduction of structural Fe(III) in smectite clay minerals has been identified as a means to promote dechlorination of polychlorinated ethanes, but its environmental significance has yet to be fully assessed because Fe reduction has normally been achieved by agents uncommon in the environment (e.g., dithionite). This study reports the dehydrochlorination of pentachloroethane and 1,1,1-trichloroethane in the presence of ferruginous smectite reduced by two cultures of microorganisms, Shewanella oneidensis strain MR-1 (MR-R) and an enrichment culture from rice paddy soils (PS-R), in aqueous suspension under anoxic conditions. Microbially reduced ferruginous smectite facilitated dehydrochlorination of 1,1,1-trichloroethane to 1,1-dichloroethene with up to 60% conversion within 3 h of incubation time. In contrast, no formation of 1,1-dichloroethene was observed after incubation of 1,1,1-trichloroethane with chemically reduced ferruginous smectite for 24 h. Microbially reduced ferruginous smectite by MR-R and PS-R promoted the dehydrochlorination of pentachloroethane to tetrachloroethene by 80 and 15%, respectively, after 3 h of incubation time. The conversion of pentachloroethane to tetrachloroethene in the presence of chemically reduced ferruginous smectite after 24 h was 65%. These results indicate that structural Fe(II) in clay minerals has the potential to be an important reductant controlling the fate of organic chemicals in contaminated sediments.
Department of Environmental Science, Policy, and Management, University of California, Hilgard Hall 3110, Berkeley, California 94720-3110, USA. jcervini@nature.berkeley.edu
Javiera
J
Cervini-Silva
Joel E
JE
Kostka
Richard A
RA
Larson
Joseph W
JW
Stucki
Jun
J
Wu
D002713:Chlorine / Q000737:chemistry* / Q000378:metabolism; D004980:Ethane / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism; D005290:Ferric Compounds / Q000737:chemistry* / Q000378:metabolism; D005765:Gastrointestinal Agents / Q000737:chemistry* / Q000378:metabolism; D006843:Hydrocarbons, Chlorinated / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D020592:Shewanella / Q000145:classification / Q000378:metabolism*; D017640:Silicates; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis; D014240:Trichloroethanes / Q000737:chemistry* / Q000378:metabolism
D005290:Ferric Compounds; D005765:Gastrointestinal Agents; D006843:Hydrocarbons, Chlorinated; D017640:Silicates; D012989:Soil Pollutants; D014240:Trichloroethanes; C024566:1,1,1-trichloroethane; D002713:Chlorine; C033214:Smectite; D004980:Ethane; C016036:pentachloroethane