Search results for "COPPER"
showing 10 items of 3029 documents
A Study Using X-ray Absorption and Emission Spectroscopy of Dioxygen-Binding Xerogels Incorporating Cyclam Units Complexed with Copper Salts.
2005
X-ray absorption spectroscopy was used to elucidate how hybrid xerogels complexed with CuCl2 could reversibly bind molecular dioxygen. Difference EXAFS analyses at the Cu K-edge suggest that dioxygen could bridge two Cu atoms in a μ-η1:η1 peroxo-like conformation with unequal Cu···O distances. Only the short distance (RCu–O1 = 1.86 ± 0.01 A) was unambiguously determined and looks typical of a CuII site. The Cu···Cu internuclear distances would be rather long: RCu–Cu ≈ 4.0 A (3.9 A) for the oxygenated (oxygen-free) xerogels. Cl K-edge EXAFS spectra revealed the pre-existence in the oxygen-free xerogels of CuI sites with short Cl–Cu bonds (2.11 ± 0.03 A). Pentacoordinate CuII sites with a lon…
Dynamics of copper and zinc sedimentation in a lagooning system receiving landfill leachate.
2013
9 pages; International audience; This study characterises the sediment dredged from a lagooning system composed of a settling pond and three lagoons that receive leachates from a municipal solid waste (MSW) landfill in France. Organic carbon, carbonate, iron oxyhydroxides, copper (Cu) and zinc (Zn) concentrations were measured in the sediment collected from upstream to downstream in the lagooning system. In order to complete our investigation of sedimentation mechanisms, leachates were sampled in both dry (spring) and wet (winter) seasonal conditions. Precipitation of calcite and amorphous Fe-oxyhydroxides and sedimentation of organic matter occurred in the settling pond. Since different di…
L'évolution des premières métallurgies extractives du cuivre
2003
International audience; L'histoire de la métallurgie extractive débute avec le cuivre. Malgré la rareté, des témoignages archéologiques, l'étude des sites d'extraction et notamment des déchets permet depuis peu de caractériser, au moins partiellement, les premiers procédés. Ainsi, on arrive aujourd'hui à documenter ce qui fut une véritable révolution au tout début de cette métallurgie, quand, d'une activité à faible production durant le Chalcolithique et le début de l'âge du Bronze, on passe progressivement à une véritable production de masse vers le milieu et la fin de l'âge du Bronze. Les premiers procédés sont non scorifiants, ils séparent mal le stérile du métal, et conduisent à des per…
Ultrafiltration as a Means to Investigate Copper Resistance Mechanisms in Soil Bacteria
1999
Copper is a trace element of major concern for agricultural soils. It exhibits a high toxicity against microorganisms and is widely introduced into soils as a component of pesticide treatments or urban wastes such as sewage sludges or refuse composts. In most French vineyards, “Bordeaux mixture” (copper sulfate) has been applied for more than a century, sometimes leading to copper concentrations in soils much higher than the threshold values (100 mg kg−1 in France). Microorganisms exposed to high concentrations of copper or other trace elements are known to develop resistance mechanisms and represent a suitable material for the study of such processes, both at a physiological and molecular …
Copper Dynamics and Impact on Microbial Communities in Soils of Variable Organic Status
2008
International audience; The effect of soil organic status on copper impact was investigated by means of a microcosm study carried out on a vineyard soil that had been amended with varying types of organic matter during a previous long-term field experiment. Soil microcosms were contaminated at 250 mg Cu kg−1 and incubated for 35 days. Copper distribution and dynamics were assessed in the solid matrix by a sequential extraction procedure and in the soil solution by measuring total and free exchangeable copper concentrations. Copper bioavailability was also measured with a whole-cell biosensor. Modifications of microbial communities were assessed by means of biomass-C measurements and charact…
Le goût moisi-terreux du vin : contribution à la caractérisation cinétique et métabolique des moisissures associées à ce défaut organoleptique
2011
Some microorganisms that co-exist on the grapevine may have beneficial effects on the quality of wine whereas others may be at the origin of organoleptic deviations. In the last decade, several mouldy or earthy odors have been highlighted in various wine regions from France. (-)-geosmin was found to be the major compound responsible for this deviation, along with Botrytis cinerea and fungi belonging to the genus Penicillium, since they were frequently isolated from “earthy-musty” odor grapes. The extent of damage on the quality of wines, motivated our study on the caracterisation of grape rot fungi. First of all, the microflora of grapes from Burgundy vineyards was identified (morphological…
Importance of relating chemical to biological data in microcosms studies to asses s impact of copper on soil bacteria
2007
International audience
Extraction of copper and iron from soil with siderophores of fluorescent pseudomonads
2009
Due to the application for more than 100 years of copper to French vineyards to combat fungal diseases of vines copper levels have been reported in vineyard soils up to several hundred milligrams of copper/kg of soil. There are now concerns about the ecotoxicity effects of copper accumulation. One potential way to remediate copper accumulation is phytoextraction. Furthermore, there may be potential to enhance the phytoextraction process by augmenting the process using beneficial bacterial species. Our research has involved investigating the potential to use fluorescent pseudomonads, a key group of bacteria that produce siderophores (iron-scavenging compounds), to enhance phytoextraction of …
Copper binding capacity of root exudates of cultivated plants and associated weeds
2001
International audience; Cu binding to root exudates of two cultivated plants, wheat (Triticum aestivum) and rape (Brassica napus), and two weeds associated with wheat, dog daisy (Matricaria inodora) and cornflower (Centaurea cyanus), was studied in vitro under hydroponic and sterile conditions. Nutrient solutions were prepared with or without P. A MetPLATE microbiological test was used to assess the metal complexing capacity of root exudates. In the P-deficient solutions, no exudation was observed for any of the four plants; consequently, no Cu binding occurred. When P was present in the nutrient solutions, the plant exudates displayed differing abilities to complex Cu. No difference was de…
Crémations et monument funéraire campaniformes à Genlis « le Nicolot » (Côte-d'Or, France)
2021
The building of the high-speed rail track linking the Rhine to the Rhone led to the discovery of two Bell Beaker burials in an Iron Age cemetery located in the plain to the east of Dijon. The Tilles plain is an alluvial environment, shaped by the valleys of the Tille and the Ouche and populated since Late Prehistory, particularly during the Bell Beaker and Early Bronze periods, which have yielded settlements located on the rivers. These burials are the first funerary features discovered in the area.The two Bell Beaker cremation burials excavated at Genlis "le Nicolot" are remarkable, as still too little is known of the funerary practices of the period in the east of France and in particular…