Metal Transport by Organic Carbon in the Amazon Basin

The Amazon basin is the largest river catchment area in the world. It contributes about 20% of the world\u27s fluvial hydrological input. Samplings were done during low water levels (March 1995) on one tributary of the Amazon, the Rio Negro. Sequential tangential ultrafiltration (STUF) was used to separate total organic matter. The cut-off values were at 0.22 μm, 100 kD and 5 kD, while the organic pool separations were done for particulate, colloidal and dissolved material. Total organic carbon (TOC) fraction-size analysis was done for each group. Copper complexing capacity measurements were done by fluorescence quenching. Fluorescence intensities were measured on site. The results show that particulate and colloidal organic carbon are the predominant TOC forms in the black water river. In the case of the white water river, the dissolved fraction is the predominant organic carbon form. The complexing capacity for the Rio Negro waters is supported by the dissolved molecules, with some contribution from the particulate and dissolved fractions. Similar behaviour was observed for the white river water. The correlation observed between TOC and the fluorescence intensity shows an apparent quantum yield varying between 43 and 104 mKalle/ppm of carbon for the contribution of black waters to the total organic carbon. (1 Kalle = 0.1 mg of quinine sulphate per litre of 5 mM H2SO4.) Electromobility of the organic material is about 1 μS cm-1 per ppm of carbon. In mixing area studies, association of STUF with fluorescence intensity measurements provide relevant information for understanding the phenomena occurring in these areas

Characterization of the Ceara Costal Zone Organic Matter Inputs

International audienceMangroves are extremely sensitive to the global climate change and urbanization impacts. To understand the effect of the urbanization on the organic matter of the coastal zone of Ceará State in north eastern Brazil, a seasonal filed campaigns were carried on in two most environmentally significant river/mangrove systems in the region; the Cocó river, in the metropolitan region of the huge city of Fortaleza, and the Pacoti River, an environmental protection area, without urban influence, on the east coast of the state. A spatial study was also done along the Jaguaribe river, which is the largest river in the state also connected to the largest mangrove area. Organic matter characterization by dissolved organic carbon, spectrofluorescence and fluorescence quenching and metal complexation capacity shows clearly that under urban pressure, the produced organic matter in mangrove area is different, meaning that carbon budget and pollutant fate have to be revised to take in account this difference

Water analysis with the help of tensor canonical decompositions

Coopération universitaire et scientifique Franco-VietnamienneInternational audienceRaw data are collected in five measurement locations along the Var river. It is assumed that some locations interact with each other, whereas others do not. In such a context, we are interested in determining the contribution of each location and in better understanding the water exchanges that are involved. Organic components can also be identified thanks to methods such as Canonical Polyadic decompositions (CP) (sometimes known as Parafac), applied to 3D fluorescence spectra calculated from the collected samples. The expected impact is a more efficient detection of polluting matters in water

Dissolved organic matter dynamics in the pristine Krka River estuary (Croatia)

The karstic Krka River is characterized by having lower dissolved organic carbon (DOC) concentrations (~30 μM) than coastal seawater (~60 μM). This peculiarity, together with the pristine nature of this area, makes the Krka River estuary a natural laboratory where it is possible to discriminate among the different dissolved organic matter (DOM) sources (riverine, marine and produced in-situ) and to study the main processes of DOM production and removal. The hypothesis behind this work is that in winter, due to the high discharge of the river, most of the DOM has a terrestrial signature, whereas in summer autochthonous DOM compose the main fraction of the DOM pool because of the reduced discharge, the high temperature and primary production. Our data shows that DOM in the river mainly consists of terrestrial molecules, as suggested by the high chromophoric content and low spectral slope (S275–295) values, as well by the predominance of humic-like substances. DOM in the seawater features the concentration and optical properties of the “typical” marine DOM from open sea waters. In summer, low riverine discharge and high temperature promote the intense biological activity, with an increase in DOC concentrations of up to 148 μM, resulting in a non-conservative behavior of DOM in the estuary. The high stratification combined with a decoupling between production and removal processes can explain the observed DOM accumulation. In the bottom layer DOM was released and quickly removed when oxygen was available, whereas in hypoxic waters the production of DOC, chromophoric DOM (CDOM) and fluorescent DOM (FDOM) was linearly related to oxygen consumption. Our work highlights the need of further studies combining chemical and biological information in order to gain new insights into the main processes responsible for DOM dynamics in this system

Correction to: Microplastics in seawater: sampling strategies, laboratory methodologies, and identification techniques applied to port environment

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Bourdieusian Reflections on Language: Unavoidable Conditions of the Real Speech Situation

The main purpose of this paper is to shed light on Pierre Bourdieu’s conception of language. Although he has dedicated a significant part of his work to the study of language and even though his analysis of language has been extensively discussed in the literature, almost no attention has been paid to the factthat Bourdieu’s account of language is based on a number of ontological presuppositions, that is, on a set of universal assumptions about the very nature of language. This article aims to fill this gap in the literature by offering a detailed overview of 10 key features which, from a Bourdieusian point of view, can be regarded as inherent in language. On the basis of this enquiry,the study seeks todemonstrate that——contraryto commonbelief——there is not only a Bourdieusian sociology of language but also a Bourdieusian philosophy of language, which provides a useful theoretical framework for examining the unavoidable conditions of the real speech situation. The paper draws to a close by reflecting on the flaws and limitations of Bourdieu’s approach to language

Impact de l' intensification thérapeutique avec autogreffe de cellules souches hématopoïétiques sur la survie sans évènement des lymphomes indolents

PARIS-BIUM (751062103) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocSudocFranceF

Devenir du séléniate dans les sols (mise en évidence expérimentale et modélisation des phénomènes d'hystérèse de sorption/désorption)

Dans le contexte des futurs stockages des matières nucléaires en couches géologiques profondes, le transfert desélénium 79 des eaux de nappes vers la biosphère, par le biais de l irrigation, est un des scenarii envisagés parl ANDRA. Le sol servirait alors d interface entre la géosphère et la biosphère.Le modèle actuellement utilisé pour évaluer la mobilité de nombreux éléments dans le sol repose sur une représentationsimple de leur distribution entre la quantité adsorbée sur le sol et la quantité restante en solution (modèleKd), considérée comme instantanée, réversible et linéaire avec la concentration de contamination. Ce modèleprésente des lacunes vis-à-vis du sélénium puisque ce dernier peut être présent sous différents états redoxqui contrôlent sa mobilité et dont les cinétiques de transformation entre ces états sont peu connues (Se(-II), Se(0),Se(IV) et Se(VI)).Dans le but d améliorer les prédictions faites sur la mobilité du sélénium dans un sol, le séléniate (Se(VI)), qui estla forme la plus mobile, a été utilisé pour étudier ses interactions vis-à-vis de deux sols différents (sol B et sol R).Un modèle cinétique, alternatif au modèle Kd, a été développé pour décrire l évolution des stocks de Se(VI) ensolution, en considérant une fraction de sélénium associée au sol de façon réversible (potentiellement mobile) etune fraction stabilisée sur le sol (fixée pseudo-irréversiblement). Ce modèle intègre des cinétiques de stabilisationbiotique et abiotique sur le sol, et une cinétique de réduction en solution.Afin d acquérir les paramètres des modèles, des expériences en batchs et en réacteurs à flux ouvert avecl utilisation de sacs à dialyse ont été réalisées. L acquisition des paramètres a permis de confronter les modèlescinétiques et Kd dans différents scenarii réalistes de contamination (chronique ou séquentielle) d un sol de surfacepar du 79Se(VI).De plus, les mécanismes de sorption du Se(VI) au sein des deux sols ont été évalués en batch avec l ajout de compétiteursspécifiques vis-à-vis de certains sites pouvant sorber ce dernier (acides humiques et carbonates de calcium).Ceci a été complété avec l étude de la sorption du Se(VI) sur des phases pures commerciales (silice, hydroxyded aluminium, goethite, bentonite, carbonate de calcium et acides humiques) ou extraites d un sol (substanceshumiques), pour différentes concentrations en Se(VI) (10-8, 10-6 et/ou 10-3 mol/L), de l impact de l ajout dephases pures réactives, dans les sols, sur la sorption du Se(VI).Il a été montré que le Se(VI) était sorbé sous la forme de complexes de sphères externes (CSE) au sein du sol Rpour des concentrations inférieures à 10-6 mol/L, tandis que dans le sol B, la majorité était sorbée sous la formesde complexes de sphère internes (CSI). La formation de CSE étant réversible et instantanée, l utilisation du modèleKd était donc suffisante pour décrire la sorption du Se(VI) au sein du sol R, dans les expériences en réacteursà flux ouvert.A contrario, pour le sol B, il a été montré que le modèle Kd, contrairement au modèle cinétique, présentait deslacunes pour décrire la sorption pseudo-irréversible du Se(VI), engendrée par la formation de CSI.Il a été montré que les mécanismes biotiques étaient majoritaires au sein du sol B, en raison de l apport de nutrimentspour les microorganismes, par l utilisation de sacs à dialyse en cellulose régénérée. Cependant les mécanismesabiotiques ont aussi eu lieux au sein du sol B.14/256Les études sur les phases pures ont montré que seuls l hydroxyde d aluminium (pH 5,2 et 8) et la goethite (pH 5,2)pouvaient sorber le Se(VI) respectivement de manière pseudo-irréversible et réversible (pour [Se(VI)] < 10-6mol/L).Enfin, il a été montré que l ajout de certaines phases pures (goethite et hydroxyde d aluminium) au sein des deuxsols, pouvait entrainer une augmentation ou une diminution de la sorption du Se(VI) par rapport à celle attendue(additivité réactionnelle). Les interactions solide/solide directes et/ou indirectes, (la plus connue étant le coating)peuvent être à l origine de la difficulté d évaluation, de manière générique, de la sorption du Se(VI) au sein dusol, connaissant seulement sa composition élémentaire.In the context of future storage of nuclear material in deep geological layers, the transfer of selenium-79 fromgroundwater to biosphere through irrigation is one of the scenarios considered by the ANDRA (National Agency forRadioactive Waste Management). So, the soil would act as an interface between the geosphere and biosphere.Actually the model adopted to evaluate the element mobility in soil is based on a simple representation of itsdistribution between the quantity adsorbed on the soil and the amount remaining in the solution (KD model). Suchdistribution is considered as instantaneous, reversible and linear with the concentration of contamination. Thismodel has some inadequacies with respect to selenium because this latter can be present in different redox statesthat control its mobility and whose transformation kinetics among states are poorly known (Se(-II), Se(0), Se(IV)and Se(VI)). In order to improve predictions on the mobility of selenium in soil, selenate (Se(VI)) - which is themost mobile form - has been used to study its interactions with respect to two different soils (soil B and soil R). Akinetic model, alternative to the Kd model, has been developed to describe the evolution of stocks of Se(VI) insolution. This model considers that a fraction of selenium is associated with soil in a reversibly way (potentiallymobile) and a portion of it is stabilized in soil (pseudo-irreversibly fixed). This model integrates on one hand, inthe soil, kinetics of biotic and abiotic stabilization and on the other hand, in solution, a reduction kinetic.With the goal of acquiring the parameters of the models, various experiments using dialysis bags have been effectuated,both in batch and with open-flow reactors. The parameter acquisition has allowed kinetic and Kd modelsto be compared in different realistic scenarios of contamination (chronic or sequential) of a surface soil with79Se(VI). In addition, the sorption mechanisms of Se(VI) have been evaluated in the two soils in batch adding specificcompetitors (humic acid and calcium carbonates) that can sorb on solid sites such as selenate. This study hasbeen completed with the analysis of the sorption of Se(VI) on pure phases available on the market (silica, aluminumhydroxide, goethite, bentonite, calcium carbonate and humic acids) or extracted from a soil (humic substances).This investigation has been carried out at different concentrations of Se(VI) (10-8, 10-6 et/ou 10-3 mol/L). Inaddition, some pure reactive phases have been added to the soil in order to study the solid-solid interaction havinga role on the sorption of Se(VI).This study has underlined that in the R-soil Se(VI) was sorbed in the form of outer sphere complexes (OSC) at concentrationslower than 10-6 mol/L, whereas in B-soil, the majority were sorbed as inner sphere complexes (ISC). Asthe formation of OSC is reversible and instantaneous, in experiments with open-flow reactors, the use of Kd modelwas sufficient to describe the sorption of Se(VI) in R-soil. On the contrary, for soil B, the study has shown that theKd model, unlike the kinetic model, was inadequate to describe the pseudo-irreversible sorption of Se(VI), causedby the formation of ISC. Due to the supply of nutrients for microorganisms, it has been shown that biotic mechanismspredominated in soil B, due to the utilization of cellulose dialysis bags. However, abiotic mechanisms tookplaces in soil B, too.The studies on pure phases have shown that only aluminum hydroxide (pH 5.2 and 8) and goethite (pH 5.2) couldsorb Se(VI), respectively in a pseudo-irreversible and reversible way (for [Se(VI)] < 10-6 mol/L).Moreover, it has been shown that, in both soils, the addition of some pure phases (goethite and aluminum hydroxide),could cause an increase or a decrease of the sorption of Se(VI) with respect to the one expected (additivityreaction).This study has shown that, knowing only the element composition of the soil, it is not sufficient to evaluate thesorption of selenate without any experimentation.TOULON-Bibliotheque electronique (830629901) / SudocSudocFranceF

Les céramiques injectées sous pression (une situation clinique après 20 ans)

LYON1-BU Santé Odontologie (693882213) / SudocSudocFranceF