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

Better understanding and applications of ammonium 12-molybdophosphate-based diffusive gradient in thin film techniques for measuring Cs in waters

International audienceChang (1998) and Murdock et al. (2001) performed numerous laboratory and field experiments to define the application scope of the AMP-DGT method. Briefly, the response of AMP-DGT was pH independent in synthetic freshwater (pH 2 – 10) and in sea waters (pH 4.5 – 10) for 8 h of deployment time. During this deployment time, no influence of Na+ (50 µmol L-1 – 0.5 mol L-1) and Ca2+ concentrations (5 µmol L-1 – 10 mmol L-1) were observed at pH 5.5 on Cs uptake by DGT from water. Correct DGT performances were obtained up to 1 month deployment time during field application in the Llyn Trawsfydd Lake (pH 6.1 – 8), before being progressively decreased to 81 % of the expected value after 5 months deployment time. The changes in DGT performances over time were possibly linked to the growth of algae / bacteria biofilm, the temperature impact on diffusion coefficient and the chemical degradation of AMP shown by a gradual loss of its characteristic yellow color. Concerning the last point, factors causing AMP binding gel degradation in DGT unit were not discussed, and their consequences on the accumulation of Cs by AMP-DGT samplers were not clearly identified. This study is dealing with an evaluation of AMP-DGT method under unfavourable conditions to maintain stable AMP binding gel in DGT unit, such as moderately basic environmental water (pH 7 – 9). Laboratory experiments were designed: (i) to identify factors controlling AMP binding gel degradation during storage and DGT deployment and (ii) to assess the possible impact of AMP degradation over time on the DGT response in waters with various chemical composition. Conclusions on potential limitations of AMP-DGT methods will finally be discussed for a better use of this technique for field applications

Assessment of co–contaminant effects on uranium and thorium speciation in freshwater using geochemical modelling

Speciation modelling of uranium (as uranyl) and thorium, in four freshwaters impacted by mining activities, was used to evaluate (i) the influence of the co–contaminants present on the predicted speciation, and (ii) the influence of using nine different model/database combinations on the predictions. Generally, co–contaminants were found to have no significant effects on speciation, with the exception of Fe(III) in one system, where formation of hydrous ferric oxide and adsorption of uranyl to its surface impacted the predicted speciation. Model and database choice on the other hand clearly influenced speciation prediction. Complexes with dissolved organic matter, which could be simulated by three of the nine model/database combinations, were predicted to be important in a slightly acidic, soft water. Model prediction of uranyl and thorium speciation needs to take account of database comprehensiveness and cohesiveness, including the capability of the model and database to simulate interactions with dissolved organic matter. Measurement of speciation in natural waters is needed to provide data that may be used to assess and improve model capabilities and to better constrain the type of predictive modelling work presented here

Iodine budget in forest soils: Influence of environmental conditions and soil physicochemical properties

International audienceDue to its longevity, radioisotope 129I is a health concern following potential releases in the environment which raises questions about residence and exposure times relevant for risk assessments. We deter¬mined 127I concentrations (as a surrogate for 129I) in a series of French forest soils (i.e. litters, humus and mineral soils) under different vegetation and climate conditions in order to identify the major processes affecting its accumulation and persistence in the soil column. The input fluxes linked to rainfall, throughfall and litterfall were also characterized. Main results obtained showed that: (i) rainfall iodine concentrations probably influenced those of litterfall through absorption by leaves/needles returning to the ground; (ii) throughfall was the major iodine input to soils (mean = 83%), compared to litterfall (mean = 17%); (iii) humus represented a temporary storage of iodine from atmospheric and biomass deposits; (iv) iodine concentrations in soils depended on both the iodine inputs and the soil's ability to retain iodine due to its organic matter, total iron and aluminium concentrations; (v) these soil properties were the main factors influencing the accumulation of iodine in the soil column, resulting in residence times of 419-1756 years; and (vi) the leaching of iodine-containing organic matter dissolved in soil solution may be an important source of labile organic iodine for groundwater and streams

RadoNorm – towards effective radiation protection based on improved scientific evidence and social considerations – focus on RADON and NORM

RadoNorm aims to manage risks from exposures to radon and naturally occurring radioactive material (NORM) to promote effective radiation protection based on improved scientific evidence and social considerations. It supports the European Member States and the EU Commission (EC) in implementing the Basic Safety Standards for protection against ionising radiation hazards at the legislative, executive, and operational levels (Directive 2013/59/EURATOM). The project is grounded on (1) implementation of multidisciplinary and innovative research and technologies, (2) integration of education and training, and (3) dissemination of project results targeting a broad stakeholder community including the public, regulators, and policymakers. The objectives are achieved through scientific research-related topics (exposure, dosimetry, biology, epidemiology, societal aspects), cross-cutting topics (education and training, dissemination, ethics) and project management. The project will yield guidelines at legal, executive and operational levels. It will enable consolidated and harmonised decision-making in the field of radiation protection, considering societal aspects and sustainable knowledge transfer. The project contributes to EC activities to strengthen radiation protection in a consistent and joint manner, as has already been done through the establishment of radiation protection platforms, the promotion of projects (e.g., DoReMi, OPERRA) and the partnership CONCERT-EJP. The outcomes may also impact future recommendations

Detailed plan for the COMET WP3 initial research activity - list of research projects and goals, participants and timing

Detailed plan for the COMET Work Package (WP) 3

Transfert d\u27un mélange Zn-Cd-Pb dans un dépôt fluvio-glaciaire carbonaté. Approche en colonnes de laboratoire

En milieu périurbain, l\u27emploi de techniques d\u27infiltration pour l\u27évacuation des eaux pluviales entraîne des risques de contamination des sols et des nappes phréatiques. L\u27étude vise à améliorer la compréhension des mécanismes hydrauliques et chimiques impliqués dans le devenir des polluants au cours de leur transfert dans un dépôt fluvio-glaciaire carbonaté de l\u27est lyonnais utilisé en fond de bassin d\u27infiltration. Le travail a été réalisé à l\u27échelle du laboratoire sur des colonnes de dépôt fluvio-glaciaire tamisé à 1 cm. La source de pollution est un mélange équimolaire artificiel Zn-Cd-Pb à 10-3 mol.l-1.Des expériences de traçage, associées à des phases de modélisation (modèle MIM), ont mis en évidence le fonctionnement hydrodynamique du dépôt en fonction de sa teneur en eau et de la vitesse d\u27écoulement. A saturation, l\u27écoulement est fortement régionalisé (50 % de régions mobiles). En conditions non saturées, l\u27écoulement se fait de façon plus homogène. Cette particularité semble être une conséquence de la distribution granulométrique du dépôt étudié. Les interactions entre les métaux et le dépôt ont été étudiées par des expériences en conditions statiques et en conditions dynamiques, associées à des phases de modélisation (modèle PHREEQC). D\u27un point de vue qualitatif, les réactions prépondérantes sont la dissolution de la calcite du dépôt fluvio-glaciaire, la précipitation des métaux sous forme carbonatée (cérusite ou hydrocérussite pour Pb, espèce mixte non identifiée pour Cd et Zn), et les réactions d\u27échange cationique. La rétention des métaux au cours de leur transfert apparaît fortement influencée par la cinétique chimique de dissolution de la calcite et la cinétique physique d\u27échange entre régions mobile et immobile. Elle est maximale pour des écoulements en conditions non saturées et à faibles vitesses

Transfert d'un mélange Zn-Cd-Pb dans un dépôt fluvio-glaciaire carbonate (approche en colonnes de laboratoire)

En milieu périurbain, l'emploi de techniques d'infiltration pour l'évacuation des eaux pluviales entraîne des risques de contamination des sols et des nappes phréatiques. L'étude vise à améliorer la compréhension des mécanismes hydrauliques et chimiques impliqués dans le devenir des polluants au cours de leur transfert dans un dépôt fluvio-glaciaire carbonaté de l'est lyonnais utilisé en fond de bassin d'infiltration. Le travail a été réalisé à l'échelle du laboratoire sur des colonnes de dépôt fluvio-glaciaire tamisé à 1 cm. La source de pollution est un mélange équimolaire artificiel Zn-Cd-Pb à 1 o-3 mol.-1. Des expériences de traçage, associées à des phases de modélisation (modèle MIM), ont mis en évidence le fonctionnement hydrodynamique du dépôt en fonction de sa teneur en eau et de la vitesse d'écoulement. A saturation, l'écoulement est fortement régionalisé (50 % de régions mobiles). En conditions non saturées, l'écoulement se fait de façon plus homogène. Cette particularité semble être un conséquence de la distribution granulométrique du dépôt étudié. Les interactions entre les métaux et le dépôt ont été étudiées par des expériences en conditions statiques et en conditions dynamiques, associées à des phases de modélisation (modèle PHREEQC). D'un point de vue qualitatif, les réactions prépondérantes sont la dissolution de la calcite du dépôt fluvio-glaciaire, la précipitation des métaux sous forme carbonatée (cérusite ou hydrocérussite pour Pb, espèce mixte non identifiée pour Cd et Zn), et les réactions d'échange cationique. La rétention des métaux au cours de leur transfert apparaît fortement influencée par la cinétique chimique de dissolution de la calcite et la cinétique physique d'échange entre régions mobile et immobile. Elle est maximale pour des écoulements en conditions non saturées et à faibles vitesses.The use of stormwater infiltration basins in urban area can generate a risk of contamination for soils and groundwater. The aim of this work is ta increase the knowledge of the hydraulic and the chemical mechanisms implied in the transfer of pollutants. The porous matrix studied is a carbonated fluvio-glacial deposit usually found in the infiltration basins of the Lyon area. Some columns were designed at the laboratory scale, with the fluvio-glacial deposit sieved at 1 cm. The pollution studied was a mixture of Zn-Cd-Pb - 1 o 3 mol. -1. Some flow tracer .experiments coupled with modeling (MIM model) were used to characterize the hydrodynamic behaviour of the columns, as a function of water content and flow rate. At saturation, the flow is divided in mobile (50 %) and immobile regions whereas for unsaturated conditions, the flow is more homogeneous. This property seems to be a consequence of the particle size distribution of the fluvio-glacial deposit. The interactions between the metals and the fluvio-glacial deposit were studied thanks to batch and transfer experiments, coupled with modeling (PHREEQC model). From a qualitative point of view, the main reactions are the dissolution of the fluvio-glacial deposit's calcite, the metals precipitation in a carbonated form (cerusite and hydrocerussite for Pb, an unknown mixed specie for Cd and Zn) and the cationic exchange reactions. During the transfer, the metals retention is governed by the chemical kinetic dissolution of the calcite and by the physical kinetic exchange between the mobile and the immobile regions. The retention is maximized for transfer in unsaturated conditions and law flow rates.VILLEURBANNE-DOC'INSA LYON (692662301) / SudocSudocFranceF

The radioecology education and training platform

The Radioecology Education and Training Platform is a website focal point for students and professionals interested in radioecology. The platform presents an overview of education and training course modules within radioecology/environmental radioactivity presently offered by the STAR consortium