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Your search keyword '"Michard, G."' showing total 109 results
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109 results on '"Michard, G."'

11. Geochemical signatures in Lac Pavin (Massif Central, France): New evidences from METANOX program (2006-2008)

Author

Jézéquel, D., Viollier, E., Michard, G., Lopes, F., Groleau, A., Sarazin, G., Prévot, F., Thiam, A., Harrault, L., Darmoul, Y., Lazar, H., Agrinier, P., Busigny, V., Assayag, N., Ader, M., Lafortune, S., Moreira, M., Guillon, F., Albéric, Patrick, Motelica-Heino, Mikael, Binet, S., Tomé, L., Abrir, G., Bergonzini, L., Huon, S., Tassin, Bruno, Bonhomme, Céline, Saad, M., Poulin, Michel, Gamblin, Y., Vieira, A., Centre d'Enseignement et de Recherche Eau Ville Environnement (CEREVE), AgroParisTech-École des Ponts ParisTech (ENPC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12), and Enpc, Ist

Subjects
[SDE] Environmental Sciences, [SDE]Environmental Sciences
Published
2008

12. Modélisation biogéochimique de l'oxydation anaérobie du méthane dans un lac de cratère, le lac Pavin, Massif Central

Author

Lopes, F., Viollier, E., Jézéquel, D., Thiam, A., Groleau, A., Sarazin, G., Prévot, F., Michard, G., Abril, G., Tassin, Bruno, Bonhomme, Céline, Enpc, Ist, Centre d'Enseignement et de Recherche Eau Ville Environnement (CEREVE), and AgroParisTech-École des Ponts ParisTech (ENPC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)

Subjects
[SDE] Environmental Sciences, [SDE]Environmental Sciences
Published
2007

14. Annual budget of chemical elements in a eutrophic lake, Aydat lake (Puy-de-Dôme), France

Author

Michard, G., Sarazin, G., Jézéquel, D., Albéric, Patrick, Ogier, S., Institut de Physique du Globe de Paris (IPGP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre d'Orléans (ISTO), Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), and Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)

Subjects
water geochemistry, eutrophic lake, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, major and trace elements, annual inventory
Abstract

International audience; An annual survey of the chemical composition both in dissolved and particulate phases of a eutrophic lake was performed from September 1995 to October 1996. All major elements and many trace elements were analyzed in the tributary and in the water column. Element fluxes were determined via sediment traps. Several sediment cores and interstitial water samples were also analyzed. From these data, a method to calculate element budgets was derived. Chemical elements can be classified into five main groups: (1) Low solubility elements are at or below detection limits in dissolved fractions and exhibit a nearly constant ratio to Al in all solid phases: Al, Ti, REE, Be, Th, Zr. (2) High solubility elements occur essentially in the dissolved phase: alkali and alkaline earth, Cl, B. Within this group, the cations exhibit some reactivity: they are removed from solution in the surface layer of the lake and released at the water–sediment interface or within the sediment. (3) biogenic elements are efficiently trapped within the lake, with about 70–75% of Si and P supplied to the lake in the dissolved form and only 25 to 30% exported as dissolved species. (4) Elements with different oxidation states (Fe, Mn, Co) show an extensive recycling within the lake. Inputs represent only 20–50% of the amount released annually into solution. (5) C and N inputs exceed outputs, suggesting that a significant amount of nitrogen escapes from the lake as N2 and some C may escape as CO2.

Published
2001
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15. Dynamique de dissolution d'une montmorillonite par des acides organiques

Author

Gaucher, E.C., Denaix, Laurence, Beaucaire, C., Michard, G., Unité de recherche Science du Sol (USS), Institut National de la Recherche Agronomique (INRA), and ProdInra, Migration

Subjects
[SDV] Life Sciences [q-bio], [SDE] Environmental Sciences, [SDV]Life Sciences [q-bio], [SDE]Environmental Sciences
Published
1997

27. Manganese dioxide concretions on granite outcrops in an intertidal area (cove of Belmont, France), II. Rapid manganese dioxide formation during the mixing of freshwater and seawater

Author

Boulègue, J., Renard, D., Michard, G., Boulad, A.P., and Chantret, F.

Abstract

The mixing of a freshwater spring (Carré Douce) with seawater in the intertidal area of the cove of Belmont leads to the non-conservative behaviour of Mn, Co and U. Mn, Co and U have a larger concentration in Carré Douce water than in seawater. At the contact of sea-water and atmosphere, Mn is oxidized in manganese dioxide. Co and U precipitate with MnO2. Owing to the preferential incorporation of 233U in MnO2, an isotopic effect is observed during the deposition of U. It is linked to the oxidation of U(IV) on MnO2and possible substitution of Mn2+by U6+in poorly cristallized MnO2. These characteristics are also found in the concretions forming on the granite outcrops in the cove of Belmont. These results can be of importance in understanding some processes related to the submarine hydrothermal Fe-Mn deposits.

Published
1978
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29. Synthèse des différentes études sur le manganèse des fonds océaniques

Author

Michard, G, Boulad, A- P, Boulegue, J, Grimaud, D, Kornprobst, C, Lavergne, D, and Renard, D

Subjects
Histoire Ifremer
Abstract

Core samples and related interstitial waters obtained during oceanographic cruises (Walda, Transpac 1 and 2) were studied. A model is proposed to explain the origin of manganese at the sediment sea water boundary. One source of the manganese of ferromanganese nodules can be deduced by the concentration mechanism described. Ni, Cu, Co, Zn are trapped within ferromanganese nodules by adsorption from sea water. [NOT CONTROLLED OCR]

Published
1977

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