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Bioretention cells remove increasingly small microplastics from stormwater
No full textInternational audienceMicroplastics are a suite of pollutants of increasing concern within the aquatic, atmospheric and terrestrial environments. In particular, stormwater runoff is a significant entry pathway of microplastics into the downstream environment. In our previous study, we showed that microplastics greater than 106 μm in size can be efficiently removed and retained from stormwater using a bioretention cell, a type of green infrastructure. Over time microplastics, plastic particles in the range of 1 μm to 5 mm, fragment into increasingly small particles due to mechanical and/or biological stresses and sunlight exposure. With increasingly small size, microplastics pose increasing threats to humans and other organisms. Asmicroplastic size gets smaller, there is a higher risk of transfer via bioretention soil pores toward surface water, groundwater, or the hydraulically connected municipal systems. A bioretention cell, located in Vaughan, Ontario, was monitored over 2 years in 2018 and 2019. Stormwater samples were collected from its inlet and outlet where the drainage area consisted of a parking lot made of recycled rubber tire pavers. Previous results for microplastics > 106 μm, showed an 84 % concentration decrease from 186 to 31 microparticles/ L at the bioretention inletand outlet respectively. In this work, we will present new results on the fate of the > 25 μm size range that highlighted an average 67 % concentration decrease between the inlet and outlet of the bioretention cell. These new results demonstrate that this conventionally designed bioretention cell continues to effectively remove microplastics down to 25 μm
Vineyard Management and Its Impacts on Soil Biodiversity, Functions, and Ecosystem Services
No full textInternational audienceHealthy soils form the basis of sustainable viticulture, where soil characteristics have a direct impact on wine quantity and quality. Soil not only provides water and nutrients to vines, but is also a living medium containing micro- and macroorganisms that perform many ecological functions and provide ecosystem services. These organisms are involved in many processes, from decomposing organic matter to providing minerals to vine roots. They also control diseases, pests, and weeds, in addition to improving the soil structure in terms of its capacity to retain water and nutrients. Related to decomposition processes, the carbon content of vineyard soils influences fertility, erosion and biogeochemical cycles, with significant implications for the global climate. However, common agricultural practices represent strong threats to biodiversity and associated ecosystem services provided by vineyard soils. As consumers increasingly consider environmental aspects in their purchase decisions, winegrowers have to adapt their vineyard management strategies, raising the demand for sustainable pest- and weed-control methods. This article presents a comprehensive review of the impacts of vineyard practices on the soil ecosystem, biodiversity, and biodiversity-based ecosystem services, and provides future prospects for sustainable viticulture
Quels livres pour apprendre à lire ? Les logiques d’un répertoire au cours préparatoire
No full textInternational audience131 primary school teachers were surveyed three times during school year 2013-2014 on the picture books read in class during the two previous weeks. The book list obtained – titles, writers and publishers - shows what types (narrative, expository…) and genres (traditional tales, poetry, etc.) teachers prefer, as well as the extent to which they use books prescribed by the national curriculum or which form part of a specific reading programme. This list raises the issue of what influences teachers’ choices, revealing multiple influences, from curricular prescriptions, publishers’ policies, and beyond these, from the notion of what “legitimate” children’s literature should be. It also shows how choices are, above all, determined by learning objectives, such as word identification and text comprehension.Une enquête a été réalisée auprès de 131 enseignants de cours préparatoire sur les livres lus par les élèves ou aux élèves en classe dans le cadre de la recherche Lire-écrire au CP conduite en 2013-2014. Elle permet d’établir le répertoire des lectures – titres, auteurs, éditeurs – et de donner les caractéristiques de celui-ci – types, genres, caractère patrimonial, appartenance éventuelle aux listes de prescriptions, à un manuel. Est posée ensuite la question des logiques qui président à sa constitution, en mobilisant les notions de culture scolaire et de littératie. Sont ainsi mises en évidence des influences multiples (listes officielles, éditeurs et, de manière plus diffuse, conception de ce qu’est une littérature de jeunesse légitime), mais surtout le poids des exigences liées aux objectifs de l’apprentissage de la lecture au cours préparatoire : apprendre à déchiffrer et apprendre à comprendre les textes
Internal relocation as a relevant and feasible adaptation strategy in Rangiroa Atoll, French Polynesia
No full textInternational audienceAtoll islands face increasing coastal risks (coastal erosion and marine flooding) due to climate change, especially sea-level rise. To face increasing coastal risks, various adaptation options are considered by atoll countries and territories, including in particular hard protection (preferred option to date), Nature-based Solutions (increasingly used) and island raising (considered a longer-term solution and a potential alternative to international migration, e.g. in the Maldives). Internal relocation within the same atoll island or atoll, which refers to long-term community movement from one threatened island area or island to a safer island area or island, has previously been disregarded by scholars as a potentially relevant climate adaptation strategy. However, in low-lying coastal areas, it offers real potential to address the dual context of increasing climate risks and the shrinking of the solution space. This paper assesses the potential of internal relocation for atolls by applying to Rangiroa Atoll, French Polynesia, Central Pacific, a two-fold assessment framework questioning its physical relevance ( are some islands high enough to host settlements in the future?) and its societal feasibility ( are the political-institutional and socio-economic conditions in place? Are people willing to relocate ?). The findings show that internal relocation is both relevant and feasible on Rangiroa Atoll and should therefore serve as a pillar to develop robust in situ adaptation pathways in this atoll
Methodological Aspects in the Theory of Mathematical Working Spaces
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Detuning optimization of nonlinear mistuned bladed-disks
No full textInternational audienceOne major industrial challenge is to consider the detuning as a technological means to reduce the dynamical amplifications induced by mistuning. Due to technological evolutions, the nonlinear geometrical effects induced by the large displacements cannot longer be neglected. Recently, methodologies for the robust analysis of detuned/mistuned bladed-disks in presence of geometrical nonlinearities have been developed. A full analysis of the detuning optimization of mistuned bladed-disks with finite displacements is carried out on a 12 bladed-disk finite element model. The paper is based on a computational methodology previously developed by the authors. It insists on the necessity to carefully optimize all the involved numerical parameters to get the nonlinear mistuned response of each considered detuned configuration with an optimal balance between response accuracy and computational costs. We then have to be very careful with the construction of an adapted scalar quantity of interest for defining the detuning optimization problem. Direct computations allowing for all possible detuned configurations to be considered allow for obtaining a full data basis. A meticulous post-processing shows the existence of a few detuned configurations, that inhibits the mistuning amplification effects of the pure mistuned bladed-disk
South African dust contribution to the high southern latitudes and East Antarctica during interglacial stages
No full textInternational audienceMineral dust is a natural tracer of atmospheric composition and climate variability. Yet, there is still much to be known about the Southern Hemisphere dust cycle. Major efforts have attempted to solve the puzzle of the origin of the potential source areas contributing dust to the Southern Ocean and East Antarctica. Here we present a comprehensive geochemical characterization of a source area, whose role as a dust supplier to high latitude environments has significantly been underestimated. Sediments collected within the major dust-producing areas along the Namibian coast in Southern Africa (Kuiseb, Omaruru and Huab river catchments and the Namib Sand Sea region), were analyzed for radiogenic isotope ratios and rare earth element concentrations. We find that during warm periods, the Southern African dust signature can be found in archives of the Southern Hemisphere, especially in the Atlantic sector of the Southern Ocean and peripheral areas of the East Antarctic plateau
Le dessin à main levée, un révélateur du rapport des élèves à la figure géométrique
No full textInternational audienceIn this article we explore the topic of freehand drawing, a technique that has seldom been studied in the research on geometry education. We also delve into the origins of freehand drawing in mathematics teaching in France. Using an exercise in which students aged 9 to 11 must convert a shorttext description into a hand-drawn image, we study the students’ behaviour and interactions amongst each other from a semiotics perspective. Our analysis reveals the potential role that freehand drawing plays in the development of geometric reasoning (which is fundamental to conceptualizing geometric objects), in broadening the scope of tool-assisted drawing, and in fostering a dialectic between freehand and tool-assisted drawing.Cet article explore le dessin à main levée, un type de dessin peu étudié dans les recherches en didactique de la géométrie. Il essaie de circonscrire la genèse de ce type de dessin dans l’enseignement des mathématiques (en France). Il s’appuie sur l’activité d’élèves de 9–11 ans confrontés à une tâche de conversion d’un court texte en un dessin à main levée. Les actions des élèves et les interactions entre pairs sont analysées d’un point de vue sémiotique. Ces analyses permettent de révéler le rôle potentiel du dessin à main levée dans le développement de raisonnements géométriques, source de conceptualisation des objets géométriques, d’enrichir la vision du dessin instrumenté, et de promouvoir une dialectique entre dessin à main levée et dessin instrumenté
