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Zopfi, Jakob
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Zopfi, Jakob
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- PublicationAccès libreIntrinsic biodegradation potential of aromatic hydrocarbons in an alluvial aquifer - Potentials and limits of signature metabolite analysis and two stable isotope-based techniques(2011)
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Firstly, a stable carbon isotope-based field method allowed quantifying biodegradation of monoaromatic compounds in situ and confirmed the degradation of naphthalene. No evidence could be deduced from stable isotope shifts for the intrinsic biodegradation of larger molecules such as methylnaphthalenes or acenaphthene. Secondly, using signature metabolite analysis, various intermediates of the anaerobic degradation of (poly-) aromatic and heterocyclic compounds were identified. The discovery of a novel metabolite of acenaphthene in groundwater samples permitted deeper insights into the anaerobic biodegradation of almost persistent environmental contaminants. A third method, microcosm incubations with 13C-labeled compounds under in situ-like conditions, complemented techniques one and two by providing quantitative information on contaminant biodegradation independent of molecule size and sorption properties. Thanks to stable isotope labels, the sensitivity of this method was much higher compared to classical microcosm studies. The 13C-microcosm approach allowed the determination of first-order rate constants for 13C-labeled benzene, naphthalene, or acenaphthene even in cases when degradation activities were only small. The plausibility of the third method was checked by comparing 13C-microcosm-derived rates to field-derived rates of the first approach. Further advantage of the use of 13C-labels in microcosms is that novel metabolites can be linked more easily to specific mother compounds even in complex systems. This was achieved using alluvial sediments where 13C-acenaphthyl methylsuccinate was identified as transformation product of the anaerobic degradation of acenaphthene. - PublicationAccès libreEvaluating the fate of chlorinated ethenes in streambed sediments by combining stable isotope, geochemical and microbial methods(2009)
; - PublicationAccès libreCarbon and chlorine isotope fractionation during aerobic oxidation and reductive dechlorination of vinyl chloride and cis-1,2-dichloroethene(2009)
; - PublicationAccès libreEffect of molecule size on carbon isotope fractionation during biodegradation of chlorinated alkanes by Xanthobacter autotrophicus GJ10
; The effect of the number of carbon and chlorine atoms on carbon isotope fractionation during dechlorination of chlorinated alkanes by Xanthobacter autotrophicus GJ10 was studied using pure culture and cell-free extract experiments. The magnitude of carbon isotope fractionation decreased with increasing carbon number. The decrease can be explained by an increasing probability that the heavy isotope is located at a non-reacting position for increasing molecule size. The isotope data were corrected for the number of carbons as well as the number of reactive sites to obtain reacting-site-specific values denoted as apparent kinetic isotope effect (AKIE). Even after the correction, the obtained AKIE values varied (on average 1.0608, 1.0477, 1.0616, and 1.0555 for 1,2-dichloroethane, chloropentane, 1,3-dichloropentane and chlorobutane, respectively). Cell-free extract experiments were carried out to evaluate the effect of transport across the cell membrane on the observed variability in the AKIE values, which revealed that variability still persisted. The study demonstrates that even after differences related to the carbon number and structure of the molecule are taken into account, there still remain differences in AKIE values even for compounds that are degraded by the same pure culture and an identical reaction mechanism.