A Pollutant transport investigated through an expansive clay

In the framework of domestic waste disposals, the in-situ compaction of soil is usually used to obtain engineered clay barriers with suitable confining properties. Permeability and pollutant retention are the major properties which should be investigated in this context for barrier evaluation. Considering clay barriers in contact with waste leachates, they may be saturated by solutes of various chemical compositions, including in particular toxic heavy metals. In this context, the expansive Fo-Ca clay, a natural Ca-smectite from the Paris basin of Ypersian (Sparnacian) age, was chosen because of its very low permeability and ability for pollutant retention through cationic exchanges. The smectic is associated with kaolinite (up to 20%), and minor quartz, calcite, goethite and gypsum

Détermination indirecte des limites d'Atterberg par gravimétrie dynamique.

Ce travail présente une nouvelle méthode de mesure des limites d'Atterberg par dessiccation dynamique. En effet, pour certaines argiles polluées ou des mélanges d'argiles, les méthodes classiques ne peuvent pas être mises en œuvre. Le principe de détermination des limites de liquidité (WL) et plasticité (WP) par cette méthode de dessiccation est présenté. Les valeurs des limites d'Atterberg obtenues sur des argiles courantes se révèlent peu différentes de celles déterminées par la méthode de Casagrande. Ces résultats permettent de considérer cette méthode comme une caractérisation physique des boues argileuse

Simulation of pollutant transport investigated through an expansive clay.

In the framework of domestic waste disposals, the in-situ compaction of soil is usually used to obtain engineered clay barriers with suitable confining properties. Permeability and pollutant retention are the major properties which should be investigated in this context for barrier evaluation. Considering clay barriers in contact with waste leachates, they may be saturated by solutes of various chemical compositions, including in particular toxic heavy metals. In this context, the expansive Fo-Ca clay, a natural Ca-smectite from the Paris basin of Ypersian (Sparnacian) age, was chosen because of its very low permeability and ability for pollutant retention through cationic exchanges. The smectic is associated with kaolinite (up to 20%), and minor quartz, calcite, goethite and gypsum

Modelling of metal polluant leaching through a smectite.

International audienceLaboratory tests are performed to characterise the soaking and retention properties of a clay barrier (Fo-Ca) under controlled homogeneous conditions. A physical model that allows calculating the retention properties and kinetics observed during the test is then detailed, and lastly simulations are examined using various soaking conditions. The results show the model predictions of cumulative cation concentrations in leachates (i.e. copper retention by clay). These curves are accurately fit by the model with the experimental data for the leaching phenomena. Clay retention capacity until reaching a physical limit in the exchanges is evidenced as well, with this limit being input into the model as the clay CEC

Default in plasma and intestinal IgA responses during acute infection by Simian Immunodeficiency Virus.

International audienceABSTRACT: BACKGROUND: Conflicting results regarding changes in mucosal IgA production or in the proportions of IgA plasma cells in the small and large intestines during HIV-infection have been previously reported. Except in individuals repeatedly exposed to HIV-1 but yet remaining uninfected, HIV-specific IgA are frequently absent in mucosal secretions from HIV-infected patients. However, little is known about the organization and functionality of mucosal B-cell follicles in acute HIV/SIV infection during which a T-dependent IgA response should have been initiated. In the present study, we evaluated changes in B-cell and T-cell subsets as well as the extent of apoptosis and class-specific plasma cells in Peyer's Patches, isolated lymphoid follicles, and lamina propria. Plasma levels of IgA, BAFF and APRIL were also determined. RESULTS: Plasma IgA level was reduced by 46 percent by 28 dpi and no IgA plasma cells were found within germinal centers of Peyer's Patches and isolated lymphoid follicles. This lack of a T-dependent IgA response occurs although germinal centers remained functional with no sign of follicular damage, but a prolonged survival of follicular CD4+ T-cells and normal generation of IgG plasma cells is observed. Whereas the average plasma BAFF level was increased by 4.5-fold and total plasma cells were 1.7 to 1.9-fold more numerous in the lamina propria, the relative proportion of IgA plasma cells in this effector site was reduced by 19 percent (duodemun) to 35 percent (Ileum) at 28 dpi. CONCLUSION: Our data provide evidence that SIV is unable to initiate a T-dependent IgA response during the acute phase of infection and favors the production of IgG (ileum) or IgM (duodenum) plasma cells at the expense of IgA plasma cells. Therefore, an early and generalized default in IgA production takes place during the acute of phase of HIV/SIV infection, which might impair not only a virus-specific antibody response but also IgA responses to other pathogens and vaccines as well. Understanding the mechanisms that impair IgA production during acute HIV/SIV infection is crucial to improve virus-specific response in mucosa and control microbial translocation

Etude de la transformation de precurseurs citriques pour la synthese de BaTiO_3 sous forme divisee, frittee ou de couches minces

SIGLEINIST T 76659 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Transport de polluant à travers une argile gonflante : étude du cuivre infiltré sous pression dans un matériau argileux sous contrainte.

Actuellement, lors du stockage de déchets ménagers et industriels, une barrière argileuse est mise en place en fond et sur les flancs des alvéoles, pour respecter la réglementation en terme de perméabilité et permettre la rétention des polluants. Dans ce domaine, un des enjeux scientifiques est la prédiction du comportement à long terme des argiles gonflantes utilisées comme barrière de confinement. Dans cette optique, des essais de laboratoire reproduisant les conditions hydrauliques in situ d'un site de stockage ont été effectués à l'aide d'une cellule œdométrique munie d'un système d'injection approprié (Jullien et Lecomte, 2000). Les expériences ont été réalisées avec la Fo-Ca, matériau argileux naturel choisi pour ses propriétés de gonflement, sa faible perméabilité et sa capacité d'échanges cationiques. La Fo-Ca, d'âge Yprésien et issue du bassin de Paris, contient plus de 80% de minéraux argileux (dont 80% d'interstratifiés smectite-kaolinite et 20% de kaolinite) et comme phases mineures, du quartz, de la goethite, de la calcite et du gypse. Des travaux antérieurs (Jullien et al., 2002) ont permis de tester les performances de la Fo-Ca soumises à des sollicitations chimio-hydro-mécaniques lors de l'infiltration sous pression de solutions de nitrate de cuivre. Les lixiviats obtenus sont analysés par spectrométrie d'absorption atomique, caractérisant ainsi l'aptitude de rétention du matériau argileux en fonction du temps (figure 1). Ces échantillons d'argile compactés puis infiltrés peuvent ainsi être considérés comme un système soumis à un paramètre externe x(t) et délivrant une réponse y(t)

Road LCA: the dedicated ECORCE tool and database

International audienceAbstractPurposeThis paper presents a specific tool called “ECORCE” (French acronym for ECO-comparator applied to Road Construction and Maintenance) dedicated to the road pavement life cycle assessment. This tool aims to reduce the consumption of materials, water, and energy by means of evaluating impacts.MethodsThe environmental assessment has been based on the LCA framework established by the SETAC and ISO 14040 series of standards, as well as by NFP 01010 for French products. The pavement life cycle is divided into the initial construction and maintenance operations. Several functional units can be defined in order to compare roads or road layers that have been designed to offer the same service. The system is built by selecting the processes to be considered during the impact assessment; this selection step relies on lists of main processes, such as road materials, road equipment, and material transport. The keys to building this tool were to specifically propose simple functionalities for road engineers and researchers, allow for quick case study implementation, and display a user-friendly interface. Moreover, the tool takes into account civil engineering practices and provides a set of dedicated data related to road materials, road works, and earthworks. ECORCE also allows easily changing input data (geometry, operations, materials, and transport distances); its output screens and tables offer several approaches to investigating environmental LCA results on roads.Results and discussionIt becomes possible to compare not only the materials used in a given layer but also the pavement structures composed of several layers using various mixed materials. Lastly, the tool is able to assess initial construction and maintenance policies. Various road structures and their associated traffic conditions may be examined with ECORCE. Results obtained with the tool are detailed in the paper for a highway case study aimed at demonstrating its possible uses. These results highlight that the relative magnitude of impacts from each main process can be analyzed for road design optimization.ConclusionsThe tool reveals that road pavement materials have more impact than other processes such as transport and non-road equipment running within the life cycle. The investigation of standard road practices can thus focus on various alternative materials and pavement structures, depending on the configurable functional units already implemented in the tool, as explained in this paper. The highway case study and accompanying sensitivity testing campaign serve to discuss the benefits of this tool

Evaluation environnementale de la production de granulats naturels en exploitation de carrière (indicateurs, modèles et outils)

Les granulats naturels, seconde matière première consommée en France, sont élaborés à partir de roche, ressource non renouvelable. La prise de conscience de l importance de la protection de l environnement et des impacts associés à l élaboration de produits manufacturés, favorise le développement de méthodes destinées à mieux approcher les impacts de leur production. Dans ce contexte, ce travail concerne l évaluation environnementale d exploitations industrielles en carrière. Il s appuie sur une collecte de données de sites utiles à cette évaluation, suivie de la réalisation d un modèle d évaluation globale des consommations d énergie, rejets atmosphériques et émissions sonores générées lors de l élaboration de granulats. Ce modèle, basé sur des indicateurs, est conçu pour être paramétrable selon la nature pétrographique du site (roche meuble ou massive). La mise au point d un outil d évaluation, nommé CADUR (CArrière DURable) permet i) d obtenir des données environnementales relative à la production de granulats naturels ; ii) de mettre en évidence que le paramètre prépondérant de l évaluation en carrière est la configuration elle-même de l exploitation considérée ; iii) de suivre, pour l exploitant, l évolution de ces performances, d en comprendre les raisons et de quantifier l effet d éventuelles modifications. Vis-à-vis des données de sites collectées, les résultats fournis par CADUR offrent une relative bonne précision. Ils montrent des écarts, avec les données réelles, inférieurs à 10 % pour les consommations énergétiques et à 5 % concernant les niveaux sonores.ORLEANS-BU Sciences (452342104) / SudocORLEANS-ISTO (452342307) / SudocSudocFranceF