Hydrogeochemical modelling of soil salinisation, alkalinisation and sodification : presentation and calibration of the PASTIS model

International audienceModélisation hydrogéochimique des processus de salinisation, alcalinisation et sodisation des sols: présentation et calage du modèle PASTIS. L'irrigation est indispensable à l'amélioration de la productivité agricole des terres dans les régions arides. Cependant, elle peut conduire localement à une dégradation progressive des propriétés physicochimiques des sols et une baisse de la fertilité, Ces processus de salinisation des sols ont été mis en évidence dans différents périmètres irrigués dans les pays sahéliens comme le Mali, le Sénégal ou le Niger. La prévision et la prévention de ces risques requièrent une meilleure compréhension et quantification des relations entre le régime hydrique sous l'influence de l'irrigation et l'évolution des propriétés des sois. Dans ce but, le développement d'un modèle intégrant les différents déterminants physiques et chimiques de ces évolutions représente un outil pour l'évaluation et la conception de stratégies d'irrigation. Le modèle PASTIS couplant les flux hydriques, le transport des solutés et les réactions géochimiques est présenté. Les échanges ioniques et la précipitation ou dissolution des minéraux sont modélisés sous la forme d'une cinétique d'ordre 1. Une expérimentation a été mise en oeuvre sur un monolithe de sol équipe pour le prélèvement de la solution à différentes profondeurs. Les isothermes d'échange ont été calées à partir d'expérimentation en réacteur fermé. La dispersion hydrodynamique a été calée par une méthode inverse à partir de l'élution des chlorures. Les courbes d'élution des cations K, Ca, Na et Mg mettent en évidence l'existence d'un non-équilibre et un coefficient cinétique pour les échanges de cations a été utilisé pour le calage du modèle. Le modèle reproduit correctement l'élution des différents solutés. (Résumé d'auteur

Evidencing the role of plants vs soils in the understanding of 137Cs phyto availability using a coupled experimental and modelling approach

International audience137Cs is a radionuclide with a half-life of 30 years that is commonly found in soils after nuclear fallout due to nuclear incidents or atmospheric nuclear weapon testing. Due to their properties of accumulation and retention, soils are key compartments for the transfer of contaminants such as 137Cs in the trophic chain. Ingestion of contaminated agricultural products being one of the main component of human exposure, it is essential to be able to predict the fate of 137Cs throughout the soil-plant continuum.The contaminant mobility into the soil, its transfer to the plant and its final distribution between all components are generally described by simple models (equilibrium-based, linear distributions). These models are operational but are not able to account for the variability of soils and plants encountered.Bioavailability is function of both soil physico-chemical characteristics, that impact the environmental availability, and plant physiology which determines the uptake rate and accumulation. The aim of this work is to highlight the preponderant factors controlling the 137Cs bioavailability in the soil-solution-plant continuum by using a model that account for both soil and plant characteristics. The proposed mechanistic model is based on thermodynamic reactions describing the interactions of Cs with the different soil reactive components, coupled with a physiological model of root absorption.Series of experiments were conducted to produce a contrasted data set of 137Cs soil to plant transfer. For those experiments, 2 different plants with contrasted Cs uptake capacities (Millet, Mustard) and 3 different soils with varying texture and mineralogy have been studied. Three weeks exposure studies were conducted with the RHIZOtest® which is a normative device to assess the bioavailability of contaminants in soil. They were completed with batch experiments aiming at characterizing the environmental availability of Cs in soils. A large range of 137Cs soil to plant transfer rates was measured for the different soil/pant combinations. For example a contrasted bioavailability of 137Cs was observed, with the same plant accumulating 10% to 40% of total Cs’s stock depending on the soils. We also observed that during the time of the experiment the plant had absorbed most of the estimated environmental available Cs.Modelling those experiments allowed us to highlight the main soil and plant properties that have a great impact on the contaminant mobility. For example, plant physiological factors were the main driver of bioavailability in condition where environmental availability was not limited (e.g. sandy soils), whereas their roles were reduced in soils with high 137Cs sorption capacity. Such a model may help to reduce uncertainties in the prediction of 137Cs transfer to plants in environmental risk assessment, with a great potential to cover a large range of soils and plants

Écologie de Pseudomonas syringae dans un bassin versant (Vers un modèle de transfert)

Caractériser la dissémination des bio-agresseurs est un enjeu majeur pour la gestion et la prédiction des maladies en santé des plantes. Face aux limites des approches usuelles en pathologie végétale, une nouvelle vision a été proposée abordant les paradigmes d histoire de vie des agents phytopathogènes en dehors des limites du système hôte-pathogène. Parmi ces agents phytopathogènes, les études sur P.syringae sont celles qui ont contribuées le plus à ce nouveau courant de pensée et dont on connaît le mieux l histoire de vie en relation avec ses réservoirs non hôtes . L espèce est détectée dans de nombreux compartiments du cycle de l eau, des précipitations jusqu aux rivières et eaux d irrigation, en passant par les plantes sauvages et le manteau neigeux. L ensemble de ces observations ont soulevé de nouvelles questions sur la manière dont P. syringae se dissémine au travers de ces environnements et sur les processus impactant sur la dynamique des populations à l échelle d un bassin versant. Ces recherches se sont donc intéressées à ses processus dans des précipitations jusqu aux cours d eau alpins dans l optique d acquérir des données pour la modélisation des flux de P. syringae. Elles ont mis en évidence les populations résidentes de la litière et la survie sa survie dans le sol, processus jamais identifiés à l histoire de vie de P. syringae. Elles ont également caractérisé (i) les conditions propices à son transport via les précipitations, (ii) le rôle du manteau neigeux comme réservoir et protecteur des populations des prairies alpines et (iii) ont mis en évidence la chimie de l eau comme indicateur témoin de la dynamique des populations des les rivières. Ces observations suggérant un transport de P. syringae dans le sol, nous l avons quantifiée à travers des études de terrain et des simulations en laboratoire.Enfin, l ensemble des données de ces recherches couplées à des outils SIG et des modèles météorologiques et hydrologiques ont permis de proposé un modèle sur les flux de P.syringae des habitats naturels vers les agro-systèmes.The characterization of the spread of bio-agressors spread is a major issue for themanagement of plant health and the prediction of disease emergence. Given thelimitations of conventional approaches in plant pathology, a new vision has beenproposed addressing paradigms life history of plant pathogens outside the limits of thecrop host-pathogen system. Among the plant pathogens, studies on P. syringae are thosethat have contributed the most to this new way of thought for which life history inrelation to "non host" reservoirs has been highlighted. The species is found in manycompartments of the water cycle, from precipitation to rivers and irrigation water, wildplants and snowpack. All these observations have raised new questions about how P.syringae spreads through these environments and on the processes impactingpopulation dynamics at the scale of a watershed. This research was therefore interestedin these processes with the objective to acquire data for modeling the tranfer of P.syringae through the watershed. They highlighted the resident populations of litter andtheir survival in the soil, processes never identified in association with the life history ofP. syringae. They also revealed (i) the conditions for transport via precipitations, (ii) therole of snowpack as a reservoir and protector of the populations in alpine meadows and(iii) showed that water chemistry can be used as an indicator of the populationdynamics in headwaters. These observations suggested a transport of P. syringae via thesoil that we subsequently characterized through field studies and laboratorysimulations. Finally, all data from this research combined with GIS tools andmeteorological and hydrological models have permitted us to propose a model of theflux of P. syringae of natural habitats to agricultural systems.AVIGNON-Bib. numérique (840079901) / SudocSudocFranceF

In situ modeling of PAH dynamics in agricultural soils amended with composts using the “VSOIL” platform

In situ modeling of PAH dynamics in agricultural soils amended with composts using the “VSOIL” platform. EGU 2017, European Geophysical Union General Assembly 201

Ethical aspects of registry-based research in the Nordic countries

National health care registries in the Nordic countries share many attributes, but different legal and ethical frameworks represent a challenge to promoting effective joint research. Internationally, there is a lack of knowledge about how ethical matters are considered in Nordic registry-based research, and a lack of knowledge about how Nordic ethics committees operate and what is needed to obtain an approval. In this paper, we review ethical aspects of registry-based research, the legal framework, the role of ethics review boards in the Nordic countries, and the structure of the ethics application. We discuss the role of informed consent in registry-based research and how to safeguard the integrity of study participants, including vulnerable subjects and children. Our review also provides information on the different government agencies that contribute registry-based data, and a list of the major health registries in Denmark, Finland, Iceland, Norway, and Sweden. Both ethical values and conditions for registry-based research are similar in the Nordic countries. While Denmark, Finland, Iceland, Norway, and Sweden have chosen different legal frameworks, these differences can be resolved through mutual recognition of ethical applications and by harmonizing the different systems, likely leading to increased collaboration and enlarged studies

COMPUCEA 2nd generation performance evaluation

COMPUCEA (Combined Procedure for Uranium Concentration and Enrichment Assay) is used for on-site analytical measurements in support of joint Euratom-IAEA inspections during physical inventory verification (PIV) campaigns in European Low-Enriched Uranium (LEU) fuel fabrication plants. The analyses provided on site during the PIV involve the accurate determination of the uranium element content and of the U-235 enrichment in verification samples (uranium product samples of solid form , i.e. powders, pellets) selected by the Safeguards inspectors. These samples are dissolved and then measured by energy-dispersive X-ray absorption edge spectrometry (L-edge densitometry) to obtain the uranium elemental content and gamma spectrometry with a Lanthanum-bromide detector for the U-235 abundance determination. The second generation of COMPUCEA equipment is compact, rugged and ready-to use directly after transport, no cooling of the detectors with liquid nitrogen is required. A software package for comfortable instrument control and data handling has been implemented. The paper describes the technique, setup and calibration procedure of the instrument. Results from PIV campaigns and comparisons between COMPUCEA results with data obtained by remote analysis with a qualified primary analytical method are presented, which demonstrate the performance of the technique. The achieved uncertainties are well within the international target values. First results obtained with a sandwich detector configuration for enhanced detection efficiency of the passive gamma spectrometry and a small separate X-ray fluorescence unit for the pre-screening of the samples for their Gd content are discussed.JRC.E.7-Nuclear Safeguards and Forensic

La plateforme de modélisation « VSoil »

National audienc

Central retinal vein occlusion in young population: risk factors and outcomes

ObjectiveTo evaluate the risk factors and outcomes of central retinal vein occlusion (CRVO) in young patients (< 40 years).MethodsIn this retrospective monocentric case series, we included young patients (<40 years) with CRVO. Patients’ medical files were analyzed focusing on demographic characteristics, suspected risk factors, ophthalmic work-up, visual acuity (VA), treatment, and outcomes.ResultsA total of 54 eyes of 52 patients were included. Central retinal vein occlusion was considered idiopathic in 13 patients (25%). The main risk factors identified were ocular hypertension (20.4%), inflammation (20.4%), high blood pressure (14.8%), and coagulation abnormality (11.1%). Final VA was lower in patients with high blood pressure and inflammation when compared to patients with no risk factor (p = 0.03 and 0.04, respectively). Intravitreal injections were needed in 23 eyes (42.6%) and 19 eyes (35.2%) received panretinal photocoagulation treatment.ConclusionCentral retinal vein occlusion is frequently associated with risk factors in young patients (75% of patients). In addition to the usual factors found in older patients, such as ocular hypertension and high blood pressure, coagulation abnormality and inflammation were also among the risk factors identified. Young patients with CRVO should be evaluated for the presence of risk factors and patients with high blood pressure or inflammatory findings should be followed carefully since they have a worse outcome

Les avancées de la recherche dans le domaine de la modélisation des interactions sol-arbre

Les outils de modélisation au service de la politique, de la planification et de la gestion forestière ne permettent pas encore une évaluation simultanée de l’impact des changements globaux et de la gestion sur les différentes fonctions écologiques et productives assurées par les écosystèmes forestiers. Nous proposons un état des lieux des modèles disponibles dans les différentes disciplines que sont la dendrométrie, l’écophysiologie et les sciences du sol et comment l’intégration des concepts de ces trois disciplines peut permettre d’élaborer les outils nécessaires au gestionnaire. In fine, ces nouveaux outils devront être suffisamment complets pour répondre à des questions à l’échelle de l’écosystème ; distinguer ce qui relève du processus générique de ce qui reste site-dépendant ; permettre de définir puis simuler des scénarios de gestion variés et innovants en environnement incertain, avec des contraintes de plus en plus fortes ; et être documentés et référencés pour garantir leur pérennité et leur utilisation