Ablation laser couplée à l'ICP-MS-HR : outil pour l'étude du comportement d'élément d'intérêt dans l'environnement

The High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS) coupled to a laser ablation system (LA) is known as a powerful analytical technique for the determination of major, minor and trace elements in solid materials due to its multiple advantages. Within the framework of this thesis, specific developments have been made, such as the set up of a 2D quantitative elemental mapping method and the quantification method using the sum normalization strategy by summation of the element oxides to 100% (w/w). This work includes sample preparation, data acquisition and processing. The analytical developments carried out during this thesis were applied to two scientific projects,the quantification of uranium in oak tree rings (Quercus petraea) dated for the chronological monitoring of contamination related to mining and the analysis of elements in Callovo-Oxfordian (COx) claystone necessary to understand its retention properties as part of the assessment of the safety of deep geological radioactive waste storage. The development of 2D elemental mapping has shown a heterogeneous distribution of uranium at the surface of tree rings that does not allow precise quantification; HR-ICP-MS in solution mode has proved to be more appropriate. The analysis of the distribution of elements naturally present in COx and their "lability" made it possible to evaluate "in situ" Kd values that could be compared to data determined by the "batch" or "bottom-up" approaches. The LA-HR-ICP-MS was also used to characterize COx retention capacities on intact samples doped with europium.La Spectrométrie de Masse à Plasma à Couplage Inductif Haute Résolution (ICP-MS-HR) couplée à un système d’ablation laser (AL) s’est imposée de par ses multiples avantages comme une technique d’analyse performante pour la détermination des éléments majeurs, mineurs et traces dans les matériaux solides. Dans le cadre de cette thèse, des développements spécifiques ont été réalisés avec la technique, comme la mise en place d’une méthode de cartographie chimique quantitative 2D et l’installation d’une méthode de quantification basée sur la somme à 100% (m/m) des éléments sous forme d’oxydes. Ce travail inclut la préparation des échantillons, l’acquisition et le traitement des données. Les développements analytiques réalisés au cours de cette thèse ont été appliqués à deux projets scientifiques, la quantification de l’uranium dans des cernes de chênes (Quercus petraea) datés pour le suivi chronologique de contamination en lien avec l’exploitation minière et l’analyse des éléments dans les argilites du Callovo-Oxfordien(COx) nécessaire à la compréhension de ses propriétés de rétention dans le cadre de l’évaluation de la sûreté du stockage géologique profond des déchets radioactifs. La mise au point de la cartographie multi-élémentaire 2D a mis en évidence une distribution hétérogène de l’uranium à la surface des cernes ne permettant pas une quantification précise ; l’ICP-MS-HR en mode solution s’est avéré mieux adapté. L’analyse de la distribution des éléments naturellement présents dans le COx et leur «labilité » a permis de remonter à des valeurs de Kd "in situ" qui ont pu être comparées à des données déterminées par l’approche « batch » ou« bottom-up ». L’utilisation de la technique AL-ICP-MS-HR a servi également à caractériser les capacités de rétention du COx sur des échantillons intacts dopés avec de l’europium

Laser ablation coupled with ICP-MS-HR : tool for studying the behaviour of elements of interest in the environment

La Spectrométrie de Masse à Plasma à Couplage Inductif Haute Résolution (ICP-MS-HR) couplée à un système d’ablation laser (AL) s’est imposée de par ses multiples avantages comme une technique d’analyse performante pour la détermination des éléments majeurs, mineurs et traces dans les matériaux solides. Dans le cadre de cette thèse, des développements spécifiques ont été réalisés avec la technique, comme la mise en place d’une méthode de cartographie chimique quantitative 2D et l’installation d’une méthode de quantification basée sur la somme à 100% (m/m) des éléments sous forme d’oxydes. Ce travail inclut la préparation des échantillons, l’acquisition et le traitement des données. Les développements analytiques réalisés au cours de cette thèse ont été appliqués à deux projets scientifiques, la quantification de l’uranium dans des cernes de chênes (Quercus petraea) datés pour le suivi chronologique de contamination en lien avec l’exploitation minière et l’analyse des éléments dans les argilites du Callovo-Oxfordien(COx) nécessaire à la compréhension de ses propriétés de rétention dans le cadre de l’évaluation de la sûreté du stockage géologique profond des déchets radioactifs. La mise au point de la cartographie multi-élémentaire 2D a mis en évidence une distribution hétérogène de l’uranium à la surface des cernes ne permettant pas une quantification précise ; l’ICP-MS-HR en mode solution s’est avéré mieux adapté. L’analyse de la distribution des éléments naturellement présents dans le COx et leur «labilité » a permis de remonter à des valeurs de Kd "in situ" qui ont pu être comparées à des données déterminées par l’approche « batch » ou« bottom-up ». L’utilisation de la technique AL-ICP-MS-HR a servi également à caractériser les capacités de rétention du COx sur des échantillons intacts dopés avec de l’europium.The High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS) coupled to a laser ablation system (LA) is known as a powerful analytical technique for the determination of major, minor and trace elements in solid materials due to its multiple advantages. Within the framework of this thesis, specific developments have been made, such as the set up of a 2D quantitative elemental mapping method and the quantification method using the sum normalization strategy by summation of the element oxides to 100% (w/w). This work includes sample preparation, data acquisition and processing. The analytical developments carried out during this thesis were applied to two scientific projects,the quantification of uranium in oak tree rings (Quercus petraea) dated for the chronological monitoring of contamination related to mining and the analysis of elements in Callovo-Oxfordian (COx) claystone necessary to understand its retention properties as part of the assessment of the safety of deep geological radioactive waste storage. The development of 2D elemental mapping has shown a heterogeneous distribution of uranium at the surface of tree rings that does not allow precise quantification; HR-ICP-MS in solution mode has proved to be more appropriate. The analysis of the distribution of elements naturally present in COx and their "lability" made it possible to evaluate "in situ" Kd values that could be compared to data determined by the "batch" or "bottom-up" approaches. The LA-HR-ICP-MS was also used to characterize COx retention capacities on intact samples doped with europium

Temporal uranium records of oak tree rings (QuercusPetraea) by(LA)-HR-ICP-MS from a former uranium mining site (Rophin,France)

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U(VI) retention in compact Callovo-Oxfordian clay stone at temperature (20–80 °C); What is the applicability of adsorption models?

International audienceIn the context of the radioactive waste management in deep geological formations, U(VI) retention by intact Callovo-Oxfordian claystone (COx) was studied by percolation-type experiments at 20 and 80 degrees C. The experimental results were confronted with modelling prediction based on a published adsorption model developed from dispersed media in the 20-80 degrees C temperature range. For the experiments at 20 degrees C, the adsorption model allowed to explain the results for the intact system; the retention was weak (R-d similar to 10 L.kg(-1)) and the analysis of the COx phases at the end of the experiment confirmed a retention of U by the clay fraction. The adsorption model in temperature also explained the observed trend of increasing retention with increasing temperature. However, it underestimated the temperature effect on the adsorption of U(VI) by the COx clay fraction, and other phases contributed to the retention. Solid-state analysis of the percolation-doped samples indicated a reactivity in the order pyrite>clay>calcite phases. The transposition of the knowledge at 20 degrees C from the dispersed system to the intact medium was therefore not possible at 80 degrees C for the studied U(VI)/COx system

Temporal uranium records of oak tree rings (QuercusPetraea) by(LA)-HR-ICP-MS from a former uranium mining site (Rophin,France)

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Uranium quantification of oak tree rings (Quercus petraea) from a former uranium mining site by High Resolution Inductively Coupled Plasma Mass spectrometry in Laser Ablation and Solution modes

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Investigation of europium retention on Callovo-Oxfordian clay rock (France) by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and percolation experiments in microcells

International audienceClay-rock formations are under investigation in several countries as a potential host of radioactive waste repositories. In order to assess the long-term safety of these concepts, retention distribution data (Rd) are needed to describe the interaction between radionuclides and natural rock. While Rd values obtained from batch-type experiments with dispersed material are essential for the development of retention models, it is also important to generate retention data under more realistic conditions, in particular with compact samples. Specifically, the literature data on strongly retained radionuclides proves to be very scarce. The present study focuses on the retention of europium (Eu) at trace concentrations on clay samples extracted from the Callovo-Oxfordian (COx) formation in France. Rd values obtained with compact COx samples are assessed by a methodology coupling percolation experiments (in pressurized microcells), performed using submillimeter-sized samples in thickness, and Laser Ablation Inductively Coupled Plasma Mass Spectrometry measurements. The Rd found at trace concentrations under non-transient conditions are high (Rd > 104 mL g−1) and in agreement with those recorded under classical batch-type conditions or those deduced from the distribution of naturally-occurring Eu between the pore water and the clay rock. They can be described by modeling with existing sorption databases, considering an adsorption process only on the clay fraction. This was validated by solid state LA-ICP-MS analyses of one of the Eu-spiked COx samples; the added europium was found exclusively in the COx clay fraction

Nickel Retention on Callovo-Oxfordian Clay: Applicability of Existing Adsorption Models for Dilute Systems to Real Compact Rock

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Uranium retention in a Callovo-Oxfordian clay rock formation: From laboratory-based models to in natura conditions

International audienceFor the performance assessment of radioactive waste disposal, it is critical to predict the mobility of radionuclides in the geological barrier that hosts it. A key challenge consists of assessing the transferability of current knowledge on the retention properties deduced from model systems to in natura situations. The case of the redox-sensitive element uranium in the Callovo-Oxfordian clay formation (COx) is presented herein. Extensive experimental work was carried out with respect to parameters affecting uranium speciation (pH, PCO2, [Ca] and redox potential) with illite, COx clay fraction and raw COx claystone. The “bottom-up” approach implemented, with illite and montmorillonite as reactive phases, quantitatively explains the adsorption results of U(VI) and U(IV) on COx. While retention is high for U(IV) (Rd∼104 L kg−1), it remains very low for U(VI) (Rd∼4 L kg−1) due to the formation of soluble ternary Ca(Mg)–U(VI)-carbonate complexes. The applicability of the sorption model was then assessed by comparing predictive analyses with data characterizing the behavior of naturally-occurring U ( 70 L kg−1. (Elsevier

URANIUM BEHAVIOR IN CALLOVO-OXFORDIAN CLAY ROCK FORMATION; FROM LABORATORY-DERIVED MODELS TO IN-SITU KD VALUES

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