Les zones tampons humides artificielles pour réduire les pollutions des nappes par les pesticides issus des réseaux de drainage : une innovation en marche ?

Pesticides carried off by surface runoff or tile drainage system can be mitigated through “buffer zones” such as buffer strips and constructed wetlands. Buffer strips can be qualified as successful innovations since they switched from an experimental stage to their adoption in the regulatory texts and by the farmers. Constructed wetlands, still at the experimental stage in France, have required a compromise between a technical optimum and the requests of the farmers to be implemented for a first time. From an ex-post perspective for buffer strips and an ex-ante evaluation for constructed wetlands, this study analyses their transition from the concept phase to their appropriation by users. Those two devices follow each a different deployment approach but the implementation of a binding regulation, still not established for constructed wetlands, is the common denominator.Le maintien de « zones tampons » telles que les bandes enherbées permet de capter les transferts superficiels de produits phytosanitaires et les Zones Tampons Humides Artificielles (ZTHA), les transferts par les réseaux de drainage. Les premières peuvent être qualifiées d'innovations réussies dans le sens où elles sont passées d'un stade expérimental vers une adoption dans les textes réglementaires et par la profession agricole. Les deuxièmes, encore au stade expérimental, ont nécessité un compromis entre un optimum technique et les requêtes des agriculteurs, afin d'être diffusées une première fois. En nous basant sur une analyse ex-post pour les bandes enherbées et ex-ante pour les ZTHA, nous analysons leur passage depuis la phase de conception vers leur appropriation par les usagers. Le déploiement de ces deux dispositifs suit deux approches différentes mais la mise en place d'une réglementation contraignante, encore non instaurée pour les ZTHA, est le dénominateur commun

Tracing and hydraulic modelling to assess the hydraulic performance of a constructed wetland

Constructed wetlands are widely used to protect sensitive water resources from non-point source pollution from agriculture. Their potential to remove nitrate and pesticides increases with the water residence time and a uniform distribution of the inflow over the wetland area. Over the hydrological season, inflow variations greatly modify the theoretical residence time. The knowledge of the corresponding variations of the hydraulic performance constitutes a gap for the better management of treatment wetlands, especially for wetland with heterogeneous vegetation implementation. The aim of this work is to investigate how the hydraulic performance changes with the flow rate in a partly vegetated wetland. The study site, a 0.5 ha wetland, is located in an area of intensive cereal crop production in Northern France. The three-dimensional hydrodynamic model Delft3D-Flow was used to simulate flow through vegetation, forced by observed meteorological conditions. It was calibrated on continuous outflow concentration measurements and unmanned aerial vehicle (UAV) images during a 13 d tracing experiment with rhodamine WT. The simulated hydraulic performance indicators matched satisfactorily with observed values thanks to the detailed description of the vegetation. Simulations for the locally usual flow range and for a fixed water depth showed a limited increase of the hydraulic performance with the flow rate. This shows that conducting a tracing at low flow is sufficient to assess the average hydraulic performance of a wetland.</p

Localisation de réseau de drainage agricole par tomographie de résistivité électrique en mode de suivi temporel

9ème colloque GEOFCAN, Orsay, FRA, 13-/11/2014 - 14/11/2014International audienceLa pose d'un réseau de drain dans un sol agricole permet la maîtrise du risque d'engorgement des terres en eau lors de période de pluies importantes. Cependant le positionnement de ce réseau est très souvent perdu. Dans le but de réaliser un protocole permettant la localisation de drain agricole à faible diamètre, des profils de tomographie de résistivité électrique (ERT) 3D en mode de suivi temporel ont été réalisés. Associés à une expérimentation d'injection d'eau par l'aval d'un réseau de drains ils ont permis de suivre la réhumectation et l'infiltration provoquées par cette injection. La modélisation au cours du temps de ces zones d'infiltration a permis la localisation et l'évaluation du système de drain

Hydraulic & Design Parameters in Full-Scale Constructed Wetland & Treatment Units: Six Case Studies

The efficiency of pond and constructed wetland (CW) treatment systems, is influenced by the internal hydrodynamics and mixing interactions between water and aquatic vegetation. In order to contribute to current knowledge of how emergent real vegetation affects solute mixing, and on what the shape and size effects are on the mixing characteristics, an understanding and quantification of those physical processes and interactions was evaluated. This paper presents results from tracer tests conducted during 2015-2016 in six full-scale systems in the UK under different flow regimes, operational depths, shapes and sizes, and in-/outlet configurations. The aim is to quantify the hydraulic performance and mixing characteristics of the treatment units, and to investigate the effect of size and shape on the mixing processes. Relative comparison of outlet configuration, inflow conditions, and internal features between the six different treatment units showed variations in residence times of up to a factor of 3. A key outcome of this study, demonstrated that the width is a more important dimension for the efficiency of the unit compared to the depth. Results underlined the importance of investigating hydrodynamics and physics of flow in full-size units to enhance treatment efficiency and predictions of water quality models

Visualization of Abscess Formation in a Murine Thigh Infection Model of Staphylococcus aureus by 19F-Magnetic Resonance Imaging (MRI)

Background: During the last years, 19 F-MRI and perfluorocarbon nanoemulsion (PFC) emerged as a powerful contrast agent based MRI methodology to track cells and to visualize inflammation. We applied this new modality to visualize deep tissue abscesses during acute and chronic phase of inflammation caused by Staphylococcus aureus infection. Methodology and Principal Findings: In this study, a murine thigh infection model was used to induce abscess formation and PFC or CLIO (cross linked ironoxides) was administered during acute or chronic phase of inflammation. 24 h after inoculation, the contrast agent accumulation was imaged at the site of infection by MRI. Measurements revealed a strong accumulation of PFC at the abscess rim at acute and chronic phase of infection. The pattern was similar to CLIO accumulation at chronic phase and formed a hollow sphere around the edema area. Histology revealed strong influx of neutrophils at the site of infection and to a smaller extend macrophages during acute phase and strong influx of macrophages at chronic phase of inflammation. Conclusion and Significance: We introduce 19 F-MRI in combination with PFC nanoemulsions as a new platform to visualize abscess formation in a murine thigh infection model of S. aureus. The possibility to track immune cells in vivo by this modality offers new opportunities to investigate host immune response, the efficacy of antibacterial therapies and th

Disentangling the complexity of groundwater dependent social-ecological systems

Groundwater resources are part of larger social-ecological systems. In this chapter, we review the various dimensions of these complex systems in order to uncover the diversity of elements at stake in the evolution of an aquifer and the loci for possible actions to control its dynamics. Two case studies illustrate how the state of an aquifer is embedded in a web of biophysical and sociopolitical processes. We propose here a holistic view through an IGM-scape that describes the various possible pathways of evolution for a groundwater related social-ecological system. Then we describe the elements of this IGM-scape starting with physical entities and processes, including relations with surface water and quality issues. Interactions with society bring an additional layer of considerations, including decisions on groundwater abstraction, land use changes and even energy related choices. Finally we point out the policy levers for groundwater management and their possible consequences for an aquifer, taking into account the complexity of pathways opened by these levers

Functional overlap of microtubule assembly factors in chromatin-promoted spindle assembly

Author Posting. © American Society for Cell Biology, 2009. This article is posted here by permission of American Society for Cell Biology for personal use, not for redistribution. The definitive version was published in Molecular Biology of the Cell 20 (2009): 2766-2773, doi:10.1091/mbc.E09-01-0043.Distinct pathways from centrosomes and chromatin are thought to contribute in parallel to microtubule nucleation and stabilization during animal cell mitotic spindle assembly, but their full mechanisms are not known. We investigated the function of three proposed nucleation/stabilization factors, TPX2, {gamma}-tubulin and XMAP215, in chromatin-promoted assembly of anastral spindles in Xenopus laevis egg extract. In addition to conventional depletion-add back experiments, we tested whether factors could substitute for each other, indicative of functional redundancy. All three factors were required for microtubule polymerization and bipolar spindle assembly around chromatin beads. Depletion of TPX2 was partially rescued by the addition of excess XMAP215 or EB1, or inhibiting MCAK (a Kinesin-13). Depletion of either {gamma}-tubulin or XMAP215 was partially rescued by adding back XMAP215, but not by adding any of the other factors. These data reveal functional redundancy between specific assembly factors in the chromatin pathway, suggesting individual proteins or pathways commonly viewed to be essential may not have entirely unique functions.This work was supported by the American Cancer Society (grant PF0711401 to T. J. Maresca), the National Cancer Institute (grant CA078048-09 to T. J. Mitchison) and the National Institutes of Health (grant F32GM080049 to J. C. Gatlin and grant GM24364 to E. D. Salmon)

Stabilité thermique de la couche active d’une cellule solaire organique par réticulation

Date du colloque : 11/2012</p

The Chikungunya Epidemic on La Réunion Island in 2005–2006: A Cost-of-Illness Study

For a long time, studies of chikungunya virus infection have been neglected, but since its resurgence in the south-western Indian Ocean and on La Réunion Island, this disease has been paid greater amounts of attention. The economic and social impacts of chikungunya epidemics are poorly documented, including in developed countries. This study estimated the cost-of-illness associated with the 2005–2006 chikungunya epidemics on La Réunion Island, a French overseas department with an economy and health care system of a developed country. “Cost-of-illness” studies measure the amount that would have been saved in the absence of a disease. We found that the epidemic incurred substantial medical expenses estimated at €43.9 million, of which 60% were attributable to direct medical costs related, in particular, to expenditure on medical consultations (47%), hospitalization (32%) and drugs (19%). The costs related to care in ambulatory and hospitalized cases were €90 and €2000 per case, respectively. This study provides the basic inputs for conducting cost-effectiveness and cost-benefit evaluations of chikungunya prevention strategies