L'évaluation en 1-2H

Étant spécialisées dans le premier cycle de l’école primaire, nous avons choisi de traiter un sujet s’inscrivant dans les degrés s’y rapportant. Notre travail de mémoire traite du thème de l’évaluation en 1-2H et plus particulièrement des pratiques des enseignantes exerçant dans le canton du Jura. Dans le présent travail, nous abordons différents aspects de l’évaluation, tels que les formes, les outils, les différents types de régulation et les critères découlant du Plan d’études romand (2010). Nous nous intéressons également aux appréciations utilisées par les enseignantes et à la transmission d’informations aux parents d’élèves. Plus particulièrement, nos objectifs de recherche sont de saisir comment les enseignantes parlent des outils d’évaluation, de déterminer les différents changements qu’impliquent l’introduction du Plan d’étude romand (PER) dans la thématique de l’évaluation, ainsi que de connaître les différents enjeux en ce qui concerne la transmission des évaluations aux parents et aux autres acteurs intervenant dans le cadre scolaire

Mobile uranium(IV)-bearing colloids in a mining-impacted wetland

Tetravalent uranium is commonly assumed to form insoluble species, resulting in the immobilization of uranium under reducing conditions. Here we present the first report of mobile U(IV)-bearing colloids in the environment, bringing into question this common assumption. We investigate the mobility of uranium in a mining-impacted wetland in France harbouring uranium concentrations of up to 14,000 p. p. m. As an apparent release of uranium into the stream passing through the wetland was observable, we examine soil and porewater composition as a function of depth to assess the geochemical conditions leading to this release. The analyses show the presence of U(IV) in soil as a non-crystalline species bound to amorphous Al-P-Fe-Si aggregates, and in porewater, as a distinct species associated with Fe and organic matter colloids. These results demonstrate the lability of U(IV) in these soils and its association with mobile porewater colloids that are ultimately released into surface water

Phylogenetic comparison of Desulfotomaculum species of subgroup 1a and description of Desulfotomaculum reducens sp. nov.

A genome and physiological comparison was made of the type strains of Desulfotomaculum species belonging to subgroup 1a and of Desulfotomaculum reducens strain MI-1. Phenotypically, Desulfotomaculum reducens strain MI-1 can be distinguished from the other described Desulfotomaculum species of subgroup 1a by its ability to grow with propionate and butyrate. In addition, the strain is able to use a variety of metals as electron acceptors. Metal reduction has not been tested in the other species, but seems likely based on our genome analysis. Phylogenetic 16S rRNA gene sequence analysis and the average nucleotide identity between the genomes of the species of subgroup 1a show that strain MI-1 represents a novel species within the Desulfotomaculum 1a subgroup, Desulfotomaculum reducens sp. nov. The type strain is MI-1T.A. J. M. S. acknowledges the financial support of the Netherlands Ministry of Education, Culture and Science (ERC grant 323009 and Gravitation grant 024.002.002)

Growth and persistence of an aerobic microbial community in Wyoming bentonite MX-80 despite anoxic in-situ conditions

Microbial activity has the potential to enhance the corrosion of high-level radioactive waste disposal canisters, which, in the proposed Swiss deep geological repository, will be embedded in bentonite and placed in the Opalinus Clay rock formation (OPA). Twelve stainless-steel cylindrical vessels (referred to as modules) containing bentonite were deployed in an anoxic borehole in OPA for up to 5.5 years. Carbon steel coupons were embedded in the bentonite. Individual modules were retrieved after 1, 1.5, 2.5 and 5.5 years. Enumeration of aerobic and anaerobic heterotrophs and sulfate-reducing bacteria (SRB) revealed microbial growth for 1.5 years followed by a decline or a stagnation in microbial viability. It was surprising to observe the growth of aerobic heterotrophs followed by their persistent viability in bentonite, despite the nominally anoxic conditions. In contrast, SRB numbers remained at very low levels. DNA-based amplicon sequencing confirmed the persistence of aerobes and the relatively low contribution of anaerobes to the bentonite microbiome. Bentonite dry density, in-situ exposure time, and bioavailable trapped oxygen are observed to shape the bentonite microbial community in the clay.EM

Colloidal Size and Redox State of Uranium Species in the Porewater of a Pristine Mountain Wetland

Uranium (U) speciation was investigated in anoxically preserved porewater samples of a natural mountain wetland in Gola di Lago, Ticino, Switzerland. U porewater concentrations ranged from less than 1 μg/L to tens of μg/L, challenging the available analytical approaches for U speciation in natural samples. Asymmetrical flow field-flow fractionation coupled with inductively coupled plasma mass spectrometry allowed the characterization of colloid populations and the determination of the size distribution of U species in the porewater. Most of the U was associated with three fractions: <0.3 kDa, likely including dissolved U and very small U colloids; a 1–3 kDa fraction containing humic-like organic compounds, dispersed Fe, and, to a small extent, Fe nanoparticles; and a third fraction (5–50 nm), containing a higher amount of Fe and a lower amount of organic matter and U relative to the 1–3 kDa fraction. The proportion of U associated with the 1–3 kDa colloids varied spatially and seasonally. Using anion exchange resins, we also found that a significant proportion of U occurs in its reduced form, U(IV). Tetravalent U was interpreted as occurring within the colloidal pool of U. This study suggests that U(IV) can occur as small (1–3 kDa), organic-rich, and thus potentially mobile colloidal species in naturally reducing wetland environments

Active sulfur cycling in the terrestrial deep subsurface

The deep terrestrial subsurface remains an environment where there is limited understanding of the extant microbial metabolisms. At Olkiluoto, Finland, a deep geological repository is under construction for the final storage of spent nuclear fuel. It is therefore critical to evaluate the potential impact microbial metabolism, including sulfide generation, could have upon the safety of the repository. We investigated a deep groundwater where sulfate is present, but groundwater geochemistry suggests limited microbial sulfate-reducing activity. Examination of the microbial community at the genome-level revealed microorganisms with the metabolic capacity for both oxidative and reductive sulfur transformations. Deltaproteobacteria are shown to have the genetic capacity for sulfate reduction and possibly sulfur disproportionation, while Rhizobiaceae, Rhodocyclaceae, Sideroxydans, and Sulfurimonas oxidize reduced sulfur compounds. Further examination of the proteome confirmed an active sulfur cycle, serving for microbial energy generation and growth. Our results reveal that this sulfide-poor groundwater harbors an active microbial community of sulfate-reducing and sulfide-oxidizing bacteria, together mediating a sulfur cycle that remained undetected by geochemical monitoring alone. The ability of sulfide-oxidizing bacteria to limit the accumulation of sulfide was further demonstrated in groundwater incubations and highlights a potential sink for sulfide that could be beneficial for geological repository safety