title: Monitoring in situ biodegradation of benzene and toluene by stable carbon isotope fractionation.
abstract: Intrinsic biodegradation of benzene and toluene in a heavily contaminated aquifer at the site of a former hydrogenation plant was investigated by means of isotope fractionation processes. The carbon isotope compositions of benzene and toluene were monitored in two campaigns within a time period of 12 months to assess the extent of the in situ biodegradation and the stability of the plume over time. The Rayleigh model, applied to calculate the extent of biodegradation and residual theoretical concentrations of toluene, showed that in situ biodegradation was a relevant attenuation process. The biodegradation rate constant for toluene was estimated to be k = 5.7+/-0.5 microM/d in the groundwater flow path downstream of the source area. The spatial distribution of the carbon isotope composition of benzene indicated that in situ biodegradation occurred at marginal zones of the plume where concentrations were lower than 30 mg/L. The vertical structure of the benzene plume provided evidence for in situ degradation processes at the upper and lower fringes of the plume. The results show that isotope fractionation can be used to quantify the extent of microbial in situ degradation in contaminated aquifers and to develop conceptual models for natural attenuation approaches.
authors.affiliation: Department of Bioremediation UFZ-Centre for Environmental Research Leipzig-Halle, Permoserstrasse 15, D-04318 Leipzig, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Vieth
authors.forename: Matthias
authors.initials: M
authors.lastname: Kästner
authors.forename: Mario
authors.initials: M
authors.lastname: Schirmer
authors.forename: Holger
authors.initials: H
authors.lastname: Weiss
authors.forename: Stefan
authors.initials: S
authors.lastname: Gödeke
authors.forename: Rainer U
authors.initials: RU
authors.lastname: Meckenstock
authors.forename: Hans H
authors.initials: HH
authors.lastname: Richnow
mesh_terms: D001554:Benzene / Q000032:analysis*; D001555:Benzene Derivatives / Q000032:analysis*; D001673:Biodegradation, Environmental; D002244:Carbon / Q000032:analysis; D002247:Carbon Isotopes / Q000032:analysis; D002250:Carbon Radioisotopes; D005742:Gasoline; D005858:Germany; D008956:Models, Chemical; D013997:Time Factors; D014050:Toluene / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014992:Xylenes / Q000032:analysis
chemical_list: D001555:Benzene Derivatives; D002247:Carbon Isotopes; D002250:Carbon Radioisotopes; D005742:Gasoline; D014874:Water Pollutants, Chemical; D014992:Xylenes; D014050:Toluene; D002244:Carbon; D001554:Benzene; C004912:ethylbenzene