Vignette d'image

Hunkeler, Daniel

Nom
Hunkeler, Daniel
Affiliation principale
Fonction
Professeur.e ordinaire
Email
daniel.hunkeler@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/142
_
0000-0003-3525-9736

Résultat de la recherche

Filtres

51
5
Réinitialiser les filtres

Paramètres

Voici les éléments 1 - 5 sur 5
  • Publication
    Accès libre
    Intrinsic biodegradation potential of aromatic hydrocarbons in an alluvial aquifer - Potentials and limits of signature metabolite analysis and two stable isotope-based techniques
    (2011)
    Morasch, Barbara
    ;
    Hunkeler, Daniel 
    ;
    Zopfi, Jakob 
    ;
    Temime, B
    ;
    Höhener, Patrick
    Three independent techniques were used to assess the biodegradation of monoaromatic hydrocarbons and low-molecular weight polyaromatic hydrocarbons in the alluvial aquifer at the site of a former cokery (Flémalle, Belgium).
    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.
  • Publication
    Accès libre
    Quantification of biodegradation for o-xylene and naphthalene using first order decay models, Michaelis–Menten kinetics and stable carbon isotopes
    (2009)
    Blum, P.
    ;
    Hunkeler, Daniel 
    ;
    Weede, M
    ;
    Beyer, C
    ;
    Grathwohl, P
    ;
    Morasch, Barbara
    At a former wood preservation plant severely contaminated with coal tar oil, in situ bulk attenuation and biodegradation rate constants for several monoaromatic (BTEX) and polyaromatic hydrocarbons (PAH) were determined using (1) classical first order decay models, (2) Michaelis–Menten degradation kinetics (MM), and (3) stable carbon isotopes, for o-xylene and naphthalene. The first order bulk attenuation rate constant for o-xylene was calculated to be 0.0025 d−1 and a novel stable isotope-based first order model, which also accounted for the respective redox conditions, resulted in a slightly smaller biodegradation rate constant of 0.0019 d−1. Based on MM-kinetics, the o-xylene concentration decreased with a maximum rate of kmax=0.1 μg/L/d. The bulk attenuation rate constant of naphthalene retrieved from the classical first order decay model was 0.0038 d− 1. The stable isotope-based biodegradation rate constant of 0.0027 d−1 was smaller in the reduced zone, while residual naphthalene in the oxic part of the plume further downgradient was degraded at a higher rate of 0.0038 d−1. With MM-kinetics a maximum degradation rate of kmax=12 μg/L/d was determined. Although best fits were obtained by MM-kinetics, we consider the carbon stable isotope-based approach more appropriate as it is specific for biodegradation (not overall attenuation) and at the same time accounts for the dominant electron-accepting process. For o-xylene a field based isotope enrichment factor εfield of −1.4 could be determined using the Rayleigh model, which closely matched values from laboratory studies of o-xylene degradation under sulfate-reducing conditions.
  • Publication
    Accès libre
    Evidence for in situ degradation of mono-and polyaromatic hydrocarbons in alluvial sediments based on microcosm experiments with 13C-labeled contaminants
    (2007)
    Morasch, Barbara
    ;
    Höhener, P.
    ;
    Hunkeler, Daniel 
    A microcosm study was conducted to investigate the degradation of mono- and polyaromatic hydrocarbons under in situ-like conditions using alluvial sediments from the site of a former cokery. Benzene, naphthalene, or acenaphthene were added to the sediments as 13C-labeled substrates. Based on the evolution of 13C-CO2 determined by gas chromatography isotope-ratio mass spectrometry (GC-IRMS) it was possible to prove mineralization of the compound of interest in the presence of other unknown organic substances of the sediment material. This new approach was suitable to give evidence for the intrinsic biodegradation of benzene, naphthalene, and acenaphthene under oxic and also under anoxic conditions, due to the high sensitivity and reproducibility of 13C/12C stable isotope analysis. This semi-quantitative method can be used to screen for biodegradation of any slowly degrading, strongly sorbing compound in long-term experiments.

    A method based on 13C-labeled substrates was developed to determine the intrinsic biodegradation potential of aromatic pollutants under oxic and under anoxic conditions.
  • Publication
    Accès libre
    Deposition, persistence and turnover of pollutants: First results from the EU project AquaTerra for selected river basins and aquifers
    (2007)
    Barth, J. A. C.
    ;
    Steidle, D.
    ;
    Kuntz, D.
    ;
    Gocht, T.
    ;
    Mouvet, C.
    ;
    von Tümpling, W.
    ;
    Lobe, I.
    ;
    Langenhoff, A.
    ;
    Albrechtsen, H.-J.
    ;
    Janniche, G. S.
    ;
    Morasch, Barbara
    ;
    Hunkeler, Daniel 
    ;
    Grathwohl, P.
    Deposition, turnover and movement of persistent organic pollutants (POP) were investigated in the EU integrated project “AquaTerra”, which is among the first funded environmental projects within the 6th Framework Program by the European Commission. Project work integrates across various disciplines that range from biogeochemistry, environmental engineering, computer modelling and chemistry to socio-economic sciences. Field study areas are the river basins of the Ebro, the Meuse, the Elbe and the Danube as well as the 3-km2 French catchment of the Brévilles Spring. Within the first 2 years of the project more than 1700 samples of atmospherically deposited particles, sediments, and water have been collected in the above-mentioned systems. Results show clear spatial patterns of deposition of polyaromatic hydrocarbons (PAHs) with the highest rates in the Meuse Basin. For local inputs, in the Brévilles sandy aquifer, the contamination of the groundwater by the pesticides atrazine (AT) and deethylatrazine did not decrease even 5 years after their agricultural inputs were stopped. On the other hand, herbicides such as mecroprop (MCPP), and PAHs, were at least partially degraded microbiologically in laboratory studies with soils and aquifer material from selected sites. For sediment transport of contaminants, new flood sampling techniques revealed highest deposition rates of β-hexachlorocyclohexane (β−HCH) in river sediments at hotspot areas on the Mulde River in the Bitterfeld region (Elbe Basin, Germany). These selected preliminary results of AquaTerra help to improve fundamental understanding of persistent organic pollutants (POP) in the environment.
  • Publication
    Accès libre
    Benzene dispersion and natural attenuation in an alluvial aquifer with strong interactions with surface water
    Batlle-Aguilar, Jordi
    ;
    Brouyère, Serge
    ;
    Dassargues, Alain
    ;
    Morasch, Barbara
    ;
    Hunkeler, Daniel 
    ;
    Höhener, Patrick
    ;
    Diels, Ludo
    ;
    Vanbroekhoven, Karolien
    ;
    Seuntjens, Piet
    ;
    Halend, Henri
    Field and laboratory investigations have been conducted at a former coke plant, in order to assess pollutant attenuation in a contaminated alluvial aquifer, discharging to an adjacent river. Various organic (BTEX, PAHs, mineral oils) and inorganic (As, Zn, Cd) compounds were found in the aquifer in concentrations exceeding regulatory values. Due to redox conditions of the aquifer, heavy metals were almost immobile, thus not posing a major risk of dispersion off-site the brownfield. Field and laboratory investigations demonstrated that benzene, among organic pollutants, presented the major worry for off-site dispersion, mainly due to its mobility and high concentration, i.e. up to 750 mg L-1 in the source zone. However, benzene could never be detected near the river which is about 160 m downgradient the main source. Redox conditions together with benzene concentrations determined in the aquifer have suggested that degradation mainly occurred within 100 m distance from the contaminant source under anoxic conditions, and most probably with sulphate as main oxidant. A numerical groundwater flow and transport model, calibrated under transient conditions, was used to simulate benzene attenuation in the alluvial aquifer towards the Meuse River. The mean benzene degradation rate used in the model was quantified in situ along the groundwater flow path using compound-specific carbon isotope analysis (CSIA). The results of the solute transport simulations confirmed that benzene concentrations decreased almost five orders of magnitude 70 m downgradient the source. Simulated concentrations have been found to be below the detection limit in the zone adjacent to the river and consistent with the absence of benzene in downgradient piezometers located close to the river reported in groundwater sampling campaigns. In a transient model scenario including groundwater–surface water dynamics, benzene concentrations were observed to be inversely correlated to the river water levels, leading to the hypothesis that benzene dispersion is mainly controlled by natural attenuation.