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See detailFlux-based Risk Assessement of the impact of Contaminants on Water resources and ECOsystems
Jamin, Pierre ULg; Dujardin, Juliette; Crèvecoeur, Sophie et al

Report (2012)

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See detailFlux-based risk assessment of the impact of contamnants on water ressources and ecosystems - FRAC-WECO.
Jamin, Pierre ULg; Dujardin, J.; Crévecoeur, Sophie et al

Report (2012)

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See detailBenzene dispersion and natural attenuation in an alluvial aquifer with strong interactions with surface water
Batlle-Aguilar, Jordi; Brouyère, Serge ULg; Dassargues, Alain ULg et al

in Journal of Hydrology (2009)

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 ... [more ▼]

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. [less ▲]

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See detailPlasmids for heavy metal resistance in Alcaligenes eutrophus CH34: Mechanisms and applications
Collard, Jean-Marc; Corbisier, Philippe; Diels, Ludo et al

in FEMS Microbiology Reviews (1994), 14

Alcaligenes eutrophus CH34 is the main representative of a group of strongly related strains (mostly facultative chemolithotrophs) that are well adapted to environments containing high levels of heavy ... [more ▼]

Alcaligenes eutrophus CH34 is the main representative of a group of strongly related strains (mostly facultative chemolithotrophs) that are well adapted to environments containing high levels of heavy metals. It harbors the megaplasmids pMOL28 and pMOL30 which carry resistance determinants to Co2+, Ni2+, CrO42-, Hg2+, Tl+, Cd2+, Cu2+ and Zn2+. Among the best characterized determinants are the cnr operon (resistance to Co, Ni) an pMOL28 and the czc operon on pMOL30 (resistance to Co, Cd and Zn). Although the two systems reveal a significant degree of amino acid similarity in the structural genes, the regulation of the operons is different. The resistance mechanism in both cases is based on efflux. The efflux mechanism leads to a pH increase outside of the cytoplasmic membrane. Metals are sequestered from the external medium through the bioprecipitation of metal carbonates formed in the saturated zone around the cell. This latter phenomenon can be exploited in bioreactors designed to remove metals from effluents. The bacteria are immobilized on composite membranes in a continuous tubular membrane reactor (CTMR). The effluent continuously circulates through the intertubular space, while the external surface of the tubes is in contact with the growth medium. Metal crystals are eventually removed by the effluent stream and collected on a glass bead column. The system has been applied to effluents containing Cd, Zn, Co, Ni and Cu. By introducing catabolic plasmids involved in the aerobic degradation of PCBs and 2,4-D into metal-resistant A. eutrophus strains, the application range was widened to include effluents polluted with both organic and inorganic substances. Biosensors have been developed which are based on the fusion of genes induced by metals to a reporter system, the lux operon of Vibrio fischeri. Bacterial luciferases produce light through the oxidation of fatty aldehydes. The gene fusions are useful both for the study of regulatory genes and for the determination of heavy metal concentrations in the environment. [less ▲]

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