Search results for "Geochemistry"
showing 10 items of 2967 documents
Effets à long terme de l'apport répété de déchets organiques sur l'évolution de la matière organique et des éléments trace métalliques dans un sol sa…
2002
The distribution of trace metal elements (ETM) in soils depends on physico-chemical characteristics of the soil (pH, redox potential …) and does not remain fixed during time. The objective of this work was to study the long-term effects of the organic waste applications (sewage sludge and manure) on the evolution of the ETM and the organic matter in a cultivated soil. This study was made on the acid sandy soil of the experimental site of Ambarès (Gironde) set up in 1974 by the INRA of Bordeaux. During 20 years, this soil, cultivated in maize, received various organic applications (manure 10 t ha-1 year-1, sludges 10 t ha-1 year-1 and sludges 100 t ha-1 year-1), which stopped in 1993. This s…
Enhancements of the refractory submicron aerosol fraction in the Arctic polar vortex: feature or exception ?
2014
In situ measurements with a four-channel stratospheric condensation particle counter (CPC) were conducted at up to 20 km altitude on board the aircraft M-55 Geophysica from Kiruna, Sweden, in January through March (EUPLEX 2003, RECONCILE 2010) and in December (ESSenCe 2011). During all campaigns air masses from the upper stratosphere and mesosphere were subsiding inside the Arctic winter vortex, thus initializing a transport of refractory aerosol into the lower stratosphere (Θ 3 were generally detected. Up to 8 of these 11 particles per cm3 were found to contain thermo-stable (at 250 °C) residuals with diameters of 10 nm to about 1 μm. Particle mixing ratios (150 mg−1) and fractions of non-…
Isotopic biomarkers.
2011
5 pages
Paléoclimats : l'enregistrement des variations climatiques.
2014
240 pages; National audience; Ce livre traite de la reconstitution des climats anciens aux échelles de temps utilisées en géosciences : de la centaine de millions d’années à l’échelle des générations humaines. Après une présentation des principaux acteurs du système climatique et des supports de l’enregistrement géologique des variations climatiques, l’auteur présente les principales étapes de l’évolution du climat de la Terre.Ce nouveau manuel, outre la présence d’exercices intégralement corrigés, intègre les résultats les plus récents en matière de recherches sur les paléoclimats et porte notamment sur les récents développements de la théorie de la terre « Boule de neige », les premiers r…
Quelques questions concernant la contribution de matière organique fossile dans le cycle supergène.
2003
Bien qu'observée depuis plus d'un siècle dans les cours d'eau, les sédiments et plus récemment dans les sols (un exemple parmi d'autres : [1]), la contribution potentielle de carbone organique (Corg) que nous qualifierons de géologique et libéré par l'altération des formations géologiques n'a que rarement été, excepté [2], prise en compte dans les bilans globaux concernant le cycle supergène (références dans [3]). Pourtant les formations géologiques classiquement reconnues comme contenant du Corg. représentent plus de 50% des surfaces continentales. Une estimation de ce que nous pouvons appeler une production organique liée à l'érosion chimique des roches carbonatées (carbonates, shales) a …
Looking inside rodent teeth: δ18O analysis used to reconstruct the environment of MIS 3 in Northeastern Iberia
2018
International audience; Small mammals (insectivores, bats and rodents) are one of the most useful tools to reconstruct Quaternary environment. Recent studies have demonstrated the relation between the stable oxygen isotopes (mainly δ18O) from biogenetic phosphates from rodent teeth with the δ18O from meteoric water; that at the same time can be potentially related with palaeotemperatures. This work explores the palaeoenvironment reconstructions based on the δ18O composition of phosphates from enamel of rodent teeth (mainly Murinae and Arvicolinae) to approach to the Marine Isotope Stage 3 (ca. 60-30 ka) in Northeastern Iberia. Fourteen new δ18O analyses from current samples are presented, c…
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…
Dissolved silica in the Garonne River waters : changes in the weathering dynamics
2000
The major ion chemistry of the Garonne River is indicative of seasonal variations in the weathering dynamics of the drainage basin. Using the geochemical model MEGA for calculation of the contribution of atmospheric CO2 to the total bicarbonate fluxes exported by the Garonne River allows estimations of the concentrations of the major dissolved elements that originate from silicate- and carbonate-rock weathering. The molecular ratio SiO2/Al2O3 was calculated for the 1989–1992 period to identify the main type of weathering in the Garonne River, and montmorillonite was shown to be the major mineral occurring in the weathering products. The seasonal variations of the SiO2/Al2O3 ratio also showe…
Leaching of oryzalin and diuron through undisturbed vineyard soil columns under outdoor conditions
2006
12 pages; International audience; Field studies monitoring herbicide pollution in the vineyards of Burgundy (France) have revealed that drinking water reservoirs are contaminated with several pre-emergence herbicides. An assessment of the leaching of two such herbicides, diuron and oryzalin, was therefore performed using lysimeters, under outdoor conditions, from May 2001 to May 2002. Four vineyard soils from Vosne-Roman?(Burgundy) were chosen along a topolithosequence: a rendosol and three calcosols. After 673 mm of rainfall, greater amounts of diuron than oryzalin were measured in percolates: respectively 0.10-0.84% and 0.02-0.43% of applied herbicide, depending on soils. Measurements for…
Lead isotopes of the carbonate-hosted Kabwe, Tsumeb, and Kipushi Pb-Zn-CU sulphide deposits in relation to Pan African orogenesis in the Damaran-Lufi…
1999
Lead isotope ratios of galena from the carbonate-hosted massive sulphide deposits of Kabwe (Pb-Zn) and Tsumeb (Pb-Zn-Cu) in Zambia and Namibia, respectively, have been measured and found to be homogeneous and characteristic of upper crustal source rocks. Kabwe galena has average isotope ratios of 206/204Pb = 17.997 ± 0.007, 207/204Pb = 15.713 ± 0.010 and 208/204Pb = 38.410 ± 0.033. Tsumeb galena has slightly higher 206/204Pb (18.112 ± 0.035) and slightly lower 207/204Pb (15.674 ± 0.016) and 208/204Pb (38.276 ± 0.073) ratios than Kabwe galena. The isotopic differences are attributed to local differences in the age and composition of the respective source rocks for Kabwe and Tsumeb. The homog…