title: Sulfur and oxygen isotope fractionation during benzene, toluene, ethyl benzene, and xylene degradation by sulfate-reducing bacteria.
abstract: We examined the oxygen and sulfur isotope fractionation of sulfate during anaerobic degradation of toluene by sulfate-reducing bacteria in culture experiments with Desulfobacula toluolica as a type strain and with an enrichment culture Zz5-7 obtained from a benzene, toluene, ethylbenzene, and xylene (BTEX)-contaminated aquifer. Sulfur isotope fractionation can show considerable variation upon sulfate reduction and may react extremely sensitively to changes in environmental conditions. In contrast, oxygen isotope fractionation seems to be less sensitive to environmental changes. Our results clearly indicate that oxygen isotope fractionation is dominated by isotope exchange with ambient water. To verify our experimental results and to test the applicability of oxygen and sulfur isotope investigations under realistic field conditions, we evaluated isotope data from two BTEX-contaminated aquifers presented in the recent literature. On a field scale, bacterial sulfate reduction may be superimposed by processes such as dispersion, adsorption, reoxidation, or mixing. The dual isotope approach enables the identification of such sulfur transformation processes. This identification is vital for a general qualitative evaluation of the natural attenuation potential of the contaminated aquifer.
authors.affiliation: Departments of Isotope Hydrology and Isotope Biogeochemistry, Umweltforschungszentrum (Centre for Environmental Research) Leipzig-Halle, Theodor-Lieser-Strasse 4, 06120 Halle/Saale, Germany. kay.knoeller@ufz.de
authors.forename: Kay
authors.initials: K
authors.lastname: Knöller
authors.forename: Carsten
authors.initials: C
authors.lastname: Vogt
authors.forename: Hans-Herrmann
authors.initials: HH
authors.lastname: Richnow
authors.forename: Stephan M
authors.initials: SM
authors.lastname: Weise
mesh_terms: D001554:Benzene / Q000378:metabolism; D001555:Benzene Derivatives / Q000378:metabolism; D001673:Biodegradation, Environmental; D020564:Deltaproteobacteria / Q000378:metabolism*; D005618:Fresh Water / Q000737:chemistry; D006841:Hydrocarbons, Aromatic / Q000378:metabolism*; D010103:Oxygen Isotopes / Q000032:analysis*; D013431:Sulfates / Q000378:metabolism*; D013460:Sulfur Isotopes / Q000032:analysis*; D016999:Sulfur-Reducing Bacteria / Q000378:metabolism; D014050:Toluene / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000378:metabolism*; D014992:Xylenes / Q000378:metabolism
chemical_list: D001555:Benzene Derivatives; D006841:Hydrocarbons, Aromatic; D010103:Oxygen Isotopes; D013431:Sulfates; D013460:Sulfur Isotopes; D014874:Water Pollutants, Chemical; D014992:Xylenes; D014050:Toluene; D001554:Benzene; C004912:ethylbenzene