Université de Neuchâtel

Evidence of Substantial Carbon Isotope Fractionation among Substrate, Inorganic Carbon, and Biomass during Aerobic Mineralization of 1,2-Dichloroethane by Xanthobacter autotrophicus

Hunkeler, Daniel ; Aravena, R

In: Applied and Environmental Microbiology, 2000, vol. 66, no. 11, p. 4870-4876

Carbon isotope fractionation during aerobic mineralization of 1,2-dichloroethane (1,2-DCA) by Xanthobacter autotrophicus GJ10 was investigated. A strong enrichment of 13C in residual 1,2-DCA was observed, with a mean fractionation factor α ± standard deviation of 0.968 ± 0.0013 to 0.973 ± 0.0015. In addition, a large carbon isotope fractionation between biomass and inorganic...

Université de Neuchâtel

Hydrogen and Carbon Isotope Fractionation during Aerobic Biodegradation of Benzene

Hunkeler, Daniel ; Andersen, N ; Aravena, R ; Bernasconi, M ; Butler, B.J

In: Environmental Science & Technology, 2001, vol. 35, no. 17, p. 3462-3467

The main aim of the study was to evaluate hydrogen and carbon isotope fractionation during biodegradation of benzene as a possible tool to trace the process in contaminated environments. Aerobic biodegradation of benzene by two bacterial isolates, Acinetobacter sp. and Burkholderia sp., was accompanied by significant hydrogen and carbon isotope fractionation with hydrogen isotope...

Université de Neuchâtel

Carbon and Chlorine Isotope Ratios of Chlorinated Ethenes Migrating through a Thick Unsaturated Zone of a Sandy Aquifer

Hunkeler, Daniel ; Aravena, R ; Shouakar-Stash, O ; Weisbrod, N ; Nasser, A ; Netzer, L ; Ronen, D

In: Environmental Science & Technology, 2011, vol. 45, p. 8247-8253

Compound-specific isotope analysis (CSIA) can potentially be used to relate vapor phase contamination by volatile organic compounds (VOCs) to their subsurface sources. This field and modeling study investigated how isotope ratios evolve during migration of gaseous chlorinated ethenes across a 18 m thick unsaturated zone of a sandy coastal plain aquifer. At the site, high concentrations of...

Université de Neuchâtel

Assessing chlorinated ethene degradation in a large scale contaminant plume by dual carbon–chlorine isotope analysis and quantitative PCR

Hunkeler, Daniel ; Abe, Y ; Broholm, M.M ; Jeannottat, S ; Westergaard, C ; Jacobsen, C.S ; Aravena, R ; Bjerg, P.L

In: Journal of Contaminant Hydrology, 2011, vol. 119, p. 69-79

The fate of chlorinated ethenes in a large contaminant plume originating from a tetrachloroethene (PCE) source in a sandy aquifer in Denmark was investigated using novel methods including compound-specific carbon and chlorine isotope analysis and quantitative real-time polymerase chain reaction (qPCR) methods targeting Dehaloccocides sp. and vcrA genes. Redox conditions were...

Université de Neuchâtel

Monitoring Biodegradation of Methyl tert-Butyl Ether (MTBE) Using Compound-Specific Carbon Isotope Analysis

Hunkeler, Daniel ; Butler, B.J ; Aravena, R ; Barker, J.F

In: Environmental Science & Technology, 2001, vol. 35, no. 4, p. 676-681

Methyl tert-butyl ether (MTBE), the most common gasoline oxygenate, is frequently detected in surface water and groundwater. The aim of this study was to evaluate the potential of compound-specific isotope analysis to assess in situ biodegradation of MTBE in groundwater. For that purpose, the effect of relevant physical and biological processes on carbon isotope ratios of MTBE was...

Université de Neuchâtel

Determination of Compound-Specific Carbon Isotope Ratios of Chlorinated Methanes, Ethanes, and Ethenes in Aqueous Samples

Hunkeler, Daniel ; Aravena, R

In: Environmental Science & Technology, 2000, vol. 34, no. 13, p. 2839-2844

Compound-specific carbon isotope ratio analysis is a promising tool to assess the origin and fate of organic contaminants in groundwater. The aim of this study was to develop and evaluate a reliable, fast method to determine carbon isotope ratios of chlorinated methanes, ethanes, and ethenes in aqueous samples. Direct solid-phase microextraction (dSPME) and headspace solid-phase microextraction...

Université de Neuchâtel

Monitoring Microbial Dechlorination of Tetrachloroethene (PCE) in Groundwater Using Compound-Specific Stable Carbon Isotope Ratios : Microcosm and Field Studies

Hunkeler, Daniel ; Aravena, R ; Butler, B.J

In: Environmental Science & Technology, 1999, vol. 33, p. 2733-2738

The determination of compound-specific stable isotope ratios is a promising new tool to assess biodegradation of organic compounds in groundwater. In this study, the occurrence of carbon isotope fractionation during dechlorination of tetrachloroethene (PCE) to ethene was evaluated in a PCE-contaminated aquifer and in a microcosm that was based on aquifer material from the site. In the microcosm,...

Université de Neuchâtel

Carbon Isotope Fractionation during Microbial Dechlorination of Trichloroethene,cis-1,2-Dichloroethene, and Vinyl Chloride : Implications for Assessment of Natural Attenuation

Bloom, Y ; Aravena, R ; Hunkeler, Daniel ; Edwards, E ; Frape, S.K

In: Environmental science & technology, 2000, vol. 34, no. 13, p. 2768-2772

Carbon isotope fractionation during dechlorination of chlorinated ethenes was investigated using a methanogenic microbial enrichment culture. Subcultures were amended with trichloroethene (TCE), cis-1,2-dichloroethene (cis-DCE), and vinyl chloride (VC), respectively. Carbon isotope ratios and concentrations of reactants and of all dechlorination products were monitored during two...

Université de Neuchâtel

Compound-Specific Chlorine Isotope Analysis : A Comparison of Gas Chromatography/Isotope Ratio Mass Spectrometry and Gas Chromatography/Quadrupole Mass Spectrometry Methods in an Interlaboratory Study

Bernstein, A ; Shouakar-Stash, O ; Ebert, K ; Laskov, C ; Hunkeler, Daniel ; Jeannottat, Simon ; Sakaguchi-Söder, K ; Laaks, J ; Jochmann, M.A ; Cretnik, S ; Jager, J ; Haderlein, S.B ; Schmidt, T.C ; Aravena, R ; Elsner, M

In: Analytical Chemistry, 2011, vol. 83, p. 7624-7634

Chlorine isotope analysis of chlorinated hydrocarbons like trichloroethylene (TCE) is of emerging demand because these species are important environmental pollutants. Continuous flow analysis of noncombusted TCE molecules, either by gas chromatography/isotope ratio mass spectrometry (GC/IRMS) or by GC/quadrupole mass spectrometry (GC/qMS), was recently brought forward as innovative analytical...

Université de Neuchâtel

Effect of source variability and transport processes on carbon isotope ratios of TCE and PCE in two sandy aquifers

Hunkeler, Daniel ; Chollet, N ; Pittet, X. ; Aravena, R ; Cherry, J. A. ; Parker, B. L.

In: Journal of Contaminant Hydrology, 2004, vol. 274, no. 1-4, p. 265-282

Chlorinated ethenes often migrate over extended distances in aquifers and may originate from different sources. The aim of this study was to determine whether stable carbon isotope ratios remain constant during dissolution and transport of chlorinated ethenes and whether the ratios can be used to link plumes to their sources. Detailed depth-discrete delineation of the carbon isotope ratio in a...