Lixiviation du béton et son incidence sur l'environnement

National audienceL'objectif de ce travail est d'étudier le comportement du béton dans un environnement de lessivage important à travers le comportement de certains éléments. Pour ceux, nous avons mis en place un protocole de lixiviation de matériau broyé par une solution d'eau pure de pH 6 (représentatif de celui d'une eau de pluie) en système fermé. L'importance des constructions en béton et la pollution atmosphérique importante provoquant un lessivage permanent de ces matériaux de construction, justifie cette étude. La présence dans les produits de fusion des fourneaux des cimentiers de plus en plus de métaux qui se trouvent incorporer dans le ciment milite également pour ce travail

REE minerals in Catalão II, Goias, Brazil

National audienceThe REE minerals pyroxenites and sövites of Catalão II show a substantial enrichment in REE from the magmatic stage. The activity of carbonate and CO32-/ PO43- ratio have played an important role in the formation of REE-carbonate-phosphates, which are an intermediate form between REE-rich apatite and REE-rich carbonate. The magmatic enrichment in REE and Ti, favored by the presence of a carbonate phase, correlate to a high activity of CO32- and activities of Ti and Na specially in the carbonatite. This feature explains the low enrichment in phosphate (apatite vein) in Catalão II compared to Catalão I, which is rich in apatite vein. In the weathering stage, these minerals interact with the fluid surface and lose some of their REE and Ba. The exchange reactions between pyrochlore and ground water are generally consistent with relatively low pH, low activities of Na+, Ca2+, F-and elevated activities of Ba2+ /or Ce3+. Significant amounts of Ba were derived from barite dissolution with some silicate contribution, whereas the Ce might come, either from dissolved REE-carbonate minerals or from the pyrochlore themselves through selective immobilisation of Ce as Ce4+

Evaluation of the metallic contamination impact on 'Mytilus Edulis' mussel at the level of the mouth of Sebou's estuary, Marocco

International audienceThe understanding of the bioaccumulation phenomenon of heavy metals in the living substance is of an extreme complexity. This is due to the interpenetration of several parameters which influence this bioaccumulation such as: the physico-chemical characteristics of the study area, the chemical properties of the contaminant and the biologic factors of the organism. This work constitutes, using Mytilus edulis as bioindicator, a contribution to study the metal contamination at different points of the mouth of Sebou's estuary. The samples were collected during the spring and the summer of the year 2005. The obtained results reveal a contamination of the study area by all the measured metals especially by lead, cadmium and chromium. This study allowed also discerning the existence of a variation in the accumulation of heavy metals according to Mytilus edulis size, as it was reported in the literature. Indeed, it showed that the small mussels accumulate heavy metals more than the big, mainly for manganese, chromium and cadmium. Seven trace metals (Mn, Cu, Cr, Pb, Co, Fe and Cd) were detected in the four studied organs (hepatopancreas, gills, gonads and muscle); the variations was least or more significant according to the organ. So, we conclude that the bioaccumulation does not make in a strictly selective way

Spectroscopie d'etats excites au voisinage de la premiere limite d'ionisation du krypton et de l'argon

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Lixiviation du béton ett son incidence sur l'environnement

International audienc

Lixiviation du béton ett son incidence sur l'environnement

International audienc

Overview of PM₁₀, PM_2.5 and BC and Their Dependent Relationships with Meteorological Variables in an Urban Area in Northwestern Morocco

At an urban site in Kenitra, Morocco, two aerosol size fractions (PM2.5 and PM10) were sampled for four seasons to characterize the seasonal trends of particulate (PM) and carbonaceous (BC) aerosols. An in-depth statistical analysis of the lag-effects of meteorology on collected data was investigated using uni- and multivariate linear regression analyses. The results revealed significant seasonal trends for PM10, PM2.5, and BC. PM concentrations showed the maximum values in autumn (61.4 ± 24.5 µg/m3 for PM10 and 21.2 ± 8.2 µg/m3 for PM2.5), while the minimum was observed in winter (40.2 ± 17.1 µg/m3) for PM10 and in summer (14.3 ± 3.3 µg/m3) for PM2.5. High BC concentrations were recorded in summer (6.3 ± 4.2 μg/m3, on average). The relative humidity 1–2 days earlier showed a higher negative correlation with the PM concentrations (except in winter), and the temperature 1–3 days earlier showed a negative correlation with the PM2.5 in winter and summer and a positive one with the PM10 in autumn. Wind speed was negatively associated with PM10 on the current day in winter and 3 days earlier in summer. However, diverse effects of wind speed on PM2.5 were observed (negative in summer and positive in spring). These results confirm the important role of meteorology in the formation of urban air pollution with pronounced variations in different seasons

Capabilities of elemental analysis by EDXRF for geochemistry

International audienceElemental analyses of 10 geological samples from Morocco and some Standard Reference Materials were performed by Energy Dispersion X-Rays Fluorescence, Wavelength Dispersion X-Rays Fluorescence and Neutron Activation Analysis techniques in order to assess the accuracy and sensitivity of the concentrations determined with regard to requirements in geochemical exploration. The possibilities of utilization of EDXRF as an appropriate and economic technique for the analysis of various elements which are important in interpretation of geochemical data were evaluated

Evaluation of airborne particulate matter pollution in Kenitra City Morocco

Two size fractions of atmospheric particulate matter < 2.5 µm and 2.5-10 µm were collected in Kenitra City from February 2007 to February 2008. The sampling was done using a Gent Stacked sampler on nuclepore polycarbonate filters and the collected filters were analyzed using Total Reflection X-Ray Fluorescence (TXRF) and Atomic Absorption Spectroscopy (AAS). The particulate matter trends show higher concentrations during the summer as compared to other seasons. The highest concentrations were obtained for Ca in coarse particles and Fe for fine particles. However, the lowest concentrations were observed for Cd in both particulate sizes. The principal component analysis (PCA) based on multivariate study enabled the identification of soil, road dust and traffic emissions as common sources for coarse and fine particles

WD-XRFand ICP-AES analysis methods and their application to sediments of two moroccan rivers (Boufekrane and Oum er Rbia)

International audienceThis paper examines Wavelengths Dispersive X-Ray Fluorescence (WD-XRF) and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) as complementary techniques to analyse major and trace elements. A set of Geostandard samples were analyzed and statistical methods were applied to the results. In the second part of this paper, the concentrations of Al, Cr, Fe, Ni, Cu Zn and Pb in sediments of two Moroccan rivers, Oum Er Rbia and Boufekrane, were determined. This study shows that the metal distribution in Oum Rbia sediments is homogeneous throughout the studied area. Whereas in Boufekrane sediments, enrichment was observed downstream (for Al, Cr, Fe, Ni) and inside the city of Meknes (for Cu, Zn and Pb). The Oum Er Rbia river sediments show significantly higher concentrations of Al, Fe, Cr, Ni, Cu and Zn. These higher concentrations can be attributed to the geological features of this river. The Boufekrane river sediments show higher Pb concentrations probably due to the pottery industry activities in the watershed