176 research outputs found
Hydrodynamic and solid residence time distribution in a circulating fluidized bed: experimental and 3D computational study
No full textVertical profiles of local pressure, horizontal profiles of net vertical solid mass flux, and residence time distributions (RTD) of the solid phase are experimentally assessed in the riser of a small scale cold Circulating Fluidized Bed of 9 m high having a square cross section of 1111 cm. Air (density 1.2 kg/m3, dynamic viscosity 1.8×10-5 Pa.s) and typical FCC particles (density 1400 kg/m3, mean diameter 70 mm) are used. The superficial gas velocity is kept constant at 7 m/s while the solid mass flux ranges from 46 to 133 kg/m2/s. The axial dispersion of the solid phase is found to decrease when increasing the solid mass flux. Simultaneously, 3D transient CFD simulations are performed to conclude on the usability of the eulerian-eulerian approach for the prediction of the solid phase mixing in the riser. The numerical investigation of the solid mixing is deferred until later since the near-wall region where the solid phase downflow and mixing are predominant is not well predicted in spite of well-predicted vertical profiles of pressure
d13C pattern of dissolved inorganic carbon in a small granitic catchment: the Strengbach case study (Vosges mountains, France)
No full textThe transfers and origins of dissolved inorganic carbon DIC. were studied for a year in a soil–spring–stream system in
the Strengbach catchment, Vosges mountains, France. This 80 ha experimental research basin is located on the eastern side
of the mountains, at an altitude ranging from 883 to 1146 m.a.s.l. and is mainly covered by spruce 80%.. Brown acid and
podzolic soils developed on a granitic basement, and, as a result, the DIC originates solely from CO2 generated by oxidation
of soil organic matter. The d13CDIC. in catchment waters is highly variable, from about y22‰ in the springs and
piezometers to about y12‰ in the stream at the outlet of the catchment. In the springs, pronounced seasonal variations of
d13C exist, with the DIC in isotopic equilibrium with the soil CO that has estimated d13DIC 2 C of about y24‰ in winter and
y20‰ in summer. These seasonal variations reflect an isotopic fractionation that seems only induced by molecular
diffusion of soil CO2 in summer. In stream water, seasonal variations are small and the relatively heavy DIC y12‰ on
average. is a result of isotopic equilibration of the aqueous CO2 with atmospheric CO2
Données actuelles sur les transferts d'atrazine dans l'environnement
No full textLes différentes voies de dispersion de l'atrazine dans les sols et l'environnement sont examinées, et les résultats discutés en relation avec les méthodes d'approche respectives. Pour ce qui concerne la volatilisation, les données de la littérature sont limitées et discordantes, car les mesures sont le plus souvent menées dans des conditions très éloignées de la réalité: les valeurs rencontrées pour cette voie de transfert vont, suivant les auteurs, de 0,017 à 60% de la dose appliquée au sol en 72 h. Les travaux menés en vue d'étudier les transferts par ruissellement ou par lessivage sont nombreux et font appel le plus souvent à des expérimentations réalisées en conditions naturelles - travail au niveau de la parcelle- où semi-naturelles - modèles placés sous conditions naturelles - Ces transferts sont particulièrement observables au cours des 2 mois qui suivent l'application du produit. Leur intensité et leur durée sont essentiellement influencées par le climat, le travail du sol et le couvert végétal. Sur une période d'un an, les pertes en atrazine varient de 0,2 à 2% de la dose appliquée pour le ruissellement, et de 0,005 à 2% pour le lessivage. Enfin, il est à noter que l'atrazine est en partie métabolisée dans le sol et que la pollution des nappes phréatiques peut être due davantage à son métabolite chloré, le dé-éthylatrazine, qu'à l'herbicide lui-même.The movement of atrazine in the environment. The different ways in which atrazine is dispersed in soils and in the environment are considered, and the results discussed in relation to the respective methods of study. Literature data regarding volatilization are limited and inconsistent, as measurements are frequently carried out in conditions dissimilar to those in the field: from one author to another, values found range between 0.017 and 60% of applied doses volatilized in 72 hours. Studies related to the transfers by run-off or leaching are numerous, and frequently use experiments carried out under natural conditions, ie experimental plots, or semi-natural, ie outdoor model experiments. These transfers occur mainly during the 2 first months following application of the chemical. Their intensity and duration are mainly influenced by climate, soil management, and the nature of plant cover. Within a 1 year period, the reported losses in atrazine generally range between 0.2 and 2.0% of the applied doses for run-off, and between 0.005 and 2.0% for leaching. It should be noted that atrazine is partly metabolized in soil, and that pollution of phreatic levels can therefore be due more to its chlorinated metabolite (de-ethylatrazine), rather than to the herbicide itself
Superficial evolution of Amazonian bauxite deposits
No full textWe evaluate the contribution of present pedogenetic processes under tropical humid forest of Central Amazonia (Brazil), to the accumulation of aluminium, in deep soil horizons. -from Author
Interactions of diuron with dissolved organic matter from organic amendments.
No full textDiuron is frequently detected in some drinking water reservoirs under the Burgundy vineyards, where organic amendments are applied. The environmental effect of these amendments on pesticide transport is ambiguous: on the one hand it could enhance their retention by increasing soil organic carbon content; on the other hand, dissolved organic matter (DOM) could facilitate their transport. Elutions were performed using columns packed with glass beads in order to investigate DOM-diuron interactions, and the possible co-transport of diuron and DOM. Four organic amendments (A, B, C and D) were tested; C and D were sampled at fresh (F) and mature (M) stages. An increase in diuron leaching was observed only for A and D-F amendments (up to 16% compared to the DOM-free blank samples), suggesting a DOM effect on diuron transport. These results could be explained by the higher DOM leaching for A and D-F compared to B, C-F, C-M and D-M increasing diuron-DOM interactions. These interactions seem to be related to the aromatic and aliphatic content of the DOM, determining formation of hydrogen and non-covalent bonds. The degree of organic matter maturity does not seem to have any effect with amendment C, while a reduction in diuron leaching is observed between DF and D-M. After equilibrium dialysis measurement of diuron-DOM complexes, it appeared that less than 3% of the diuron applied corresponded to complexes with a molecular weight > 1000 Da. Complexes < 1000 Da could also take part in this facilitated transport
Effect of light on humic substances: production of reactive species
No full textInternational audienc
SYSGENET: a meeting report from a new European network for systems genetics
No full textThe first scientific meeting of the newly established European SYSGENET network took place at the Helmholtz Centre for Infection Research (HZI) in Braunschweig, April 7-9, 2010. About 50 researchers working in the field of systems genetics using mouse genetic reference populations (GRP) participated in the meeting and exchanged their results, phenotyping approaches, and data analysis tools for studying systems genetics. In addition, the future of GRP resources and phenotyping in Europe was discusse
- …
