title: Comparative study of microbial dechlorination of chlorinated ethenes in an aquifer and a clayey aquitard.
abstract: In order to determine whether natural attenuation of chlorinated ethenes by microbial activity occurs in aquitards, sediments at a site contaminated with tetrachloroethene were vertically studied by drilling. The distribution of microbes (Dehalococcoides group and anaerobic hydrogen producers) and the ability of the sediments to sustain microbial dechlorination were determined in an aquitard as well as in an aquifer. Close-spaced sampling revealed the existence of large populations of Dehalococcoides and H(2)-producing bacteria, especially in the organic-rich clayey aquitard rather than in the aquifer. The vinyl chloride reductase gene was also detected in the clay layer. Furthermore, incubation experiments indicated that the clay sediment could sustain transformations of tetrachloroethene at least to vinyl chloride. In contrast, no significant transformation was observed in the aquifer sand. Our results indicate that dechlorination of tetrachloroethene by bacteria can take place in an organic-rich clayey aquitard, and that organic-rich clay may also be important in the natural attenuation in an adjacent aquifer, possibly supplying a carbon source or an electron donor.
authors.affiliation: Institute for Geo-resources and Environments, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan. takeuchi-mio@aist.go.jp
authors.forename: Mio
authors.initials: M
authors.lastname: Takeuchi
authors.forename: Yoshishige
authors.initials: Y
authors.lastname: Kawabe
authors.forename: Eiji
authors.initials: E
authors.lastname: Watanabe
authors.forename: Toshio
authors.initials: T
authors.lastname: Oiwa
authors.forename: Manabu
authors.initials: M
authors.lastname: Takahashi
authors.forename: Kenji
authors.initials: K
authors.lastname: Nanba
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Kamagata
authors.forename: Satoshi
authors.initials: S
authors.lastname: Hanada
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Ohko
authors.forename: Takeshi
authors.initials: T
authors.lastname: Komai
mesh_terms: D000538:Aluminum Silicates / Q000032:analysis; D001421:Bacteria, Anaerobic / Q000145:classification / Q000378:metabolism; D001673:Biodegradation, Environmental; D044822:Biodiversity; D041862:Chloroflexi / Q000145:classification / Q000378:metabolism; D000077215:Clay; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D019015:Geologic Sediments / Q000032:analysis / Q000382:microbiology*; D007564:Japan; D012336:RNA, Ribosomal, 16S / Q000032:analysis / Q000235:genetics; D012997:Solvents / Q000032:analysis / Q000378:metabolism; D013750:Tetrachloroethylene / Q000032:analysis / Q000378:metabolism*; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000378:metabolism; D014881:Water Supply / Q000032:analysis*
chemical_list: D000538:Aluminum Silicates; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D012997:Solvents; D014874:Water Pollutants, Chemical; D000077215:Clay; D013750:Tetrachloroethylene