Search

The major climatic forcing parameters on Earth climate are temperature and the atmospheric concentrations of CO2. Even if their evolutions covaried to the first-order, the geological record show periods with non-linear evolution between those two parameters. Such delinking requires accurate paleoclimate reconstructions with implications for the modelling studies of our future climate.pCO2 and Sea Surface Temperature (SST) reconstructions are usually quantified using proxies relying on both the organic matter produced by coccolithophores (UK37’ index and δ13Calkenones) and calcite of foraminiferal tests (δ11B, δ18O, Mg/Ca). These proxies have been very useful for a variety of paleoclimatic advances, yet present unresolved and potentially important biases. As an example, alkenone carbon isotopes are not able to register low to moderate pCO2 levels (Badger et al., 2019). This is notoriously a major issue for paleoclimate reconstructions of the last 6 My (Plio-Pleistocene period).Our approach is to use a unique archive – the coccoliths – for determination of coeval SST and pCO2. Coccoliths are small calcite plates produced by unicellular photosynthetic algae called coccolithophores. They are a very promising substrate to analyse for paleoclimate studies because they calcify in the uppermost water column and because their isotopic ratios are sensitive to both photosynthesis and calcification (Hermoso et al. 2020). Therefore, these isotopic ratios provide physiological and metabolic information about coccolithophores of the past. In order to infer paleoclimates from the sedimentary archives, we have to deconvolve the isotopic biological imprint (vital effect) from the environment signal. For the evaluation of the vital effects, we have undertaken a large-scaled culture experiments with various strains of coccolithophore grown under various CO2 concentrations and pH (Le Guevel et al. in prep). Even if we have managed culture until 1400ppm and 7.55 unit of pH, we were particularly interested in low pCO2 and high pH conditions because the bibliography is lacking of vital effect for Plio-Pleistocène applications. All the selected strains produce coccoliths within the size range of the one we find predominantly in the marine sediments throughout geological times.We document a large decrease of the carbon differential vital effect with the CO2 concentration increase between Gephyrocapsa oceanica and Coccolithus braarudii. This is consistent with previous studies but the absolute values are slightly different and we provide a more precise dataset at low to moderate pCO2 than the previous ones (Rickaby et al., 2010; Hermoso et al., 2016). We propose the first study of the oxygen and carbon vital effect of the Helicosphaera carteri group with combined CO2/pH changes. Taken together, the culture data and measurements of the isotopic composition of the calcite biominerals allows better paleoreconstructions of SST and aqueous CO2.

Cities are responsible for more than 70% of the global CO2 emissions and thus play an important role in mitigating climate change. Mayors and local governments have been taking measures to reduce urban CO2 emissions and to reach carbon neutrality. In order to evaluate their efforts, a series of high-resolution city-scale emission inventories were established. Top-down inversion modeling is a widely-used complementary solution to reduce the uncertainties in traditional bottom-up emission inventories. It combines atmospheric modeling and measurements to optimize the greenhouse gas estimates using Bayesian inference methods.The Mexico City Metropolitan Area (MCMA) is one of the largest megacities in the world. Its annual CO2 emissions have grown from 42.1 Mt to 66.0 Mt from 2012 to 2018. The Mexico government has planned to reduce 65.2 Mt CO2 emission during the period 2021-2030. To assess local CO2 emission reduction strategies, a French-Mexican project Mexico City regional Carbon impacts (MERCI-CO2) deployed a network of in-situ and column CO2 observation instruments in MCMA. The CO2 concentration gradients are assimilated in our inversion system based on the WRF-Chem model to improve the inventory estimates of CO2 emissions in and outside MCMA.Various options on meteorological drivers, domain sizes, physics, dynamics schemes and spectral nudging of the WRF modeling system over MCMA were quantitatively evaluated for model performance. A series of meteorological parameters were taken into account for the comparison between simulations and in-situ observations, LiDar analysis as well as WMO radiosonde observations. For the purpose of CO2 simulation, the most studied variables are those related to the dispersion of the ambient air, including air temperatures, wind speeds, wind directions and mixing heights. These sensitivity tests helped to define the optimal model configuration.The CO2 concentration maps over MCMA during 3 typical months (January, May and July) were reconstructed by the double-nesting 5-km resolution WRF-Chem model, coupled with the local emission inventories from UNAM and the global emission inventories ODIAC scaled by temporal scaling factors. The evaluation of CO2 simulations were based on CO2 in-situ measurements by PICARRO and column measurements (XCO2) by FTIR at an urban site UNA and at the background station ALZ. Along with the evaluation, we also analyzed the temporal and spatial distribution of CO2 signals, as well as the area impacted by anthropogenic fluxes and by biogenic fluxes. Based on our analysis, we assessed the potential of our network to constrain the urban emissions, defined the potential locations for future stations, and defined a “background index” to represent the suitability to build a background station.After the ground validation of the modeling system, we performed a 1-year inversion over the MCMA from 30 March 2018 to 30 March 2019. According to the assimilation of concentration gradients between the urban station and the rural station, the inversion adjusted the prior anthropogenic emission from UNAM and ODIAC estimates, in parallel with prior biogenic fluxes from the CASA model and background concentrations by CarbonTracker 2019B global inversion system. An ensemble of inversion configurations was constructed. The reference configuration optimizes three components: fossil fuel sources, biogenic fluxes and background concentrations to generate separate scaling factors for each block of 5 days. The sensitivity tests include several temporal error correlation length scales between continuous days, varying time windows over each day, a separation of the activity sectors (traffic), a filter over the MCMA, varying data screening and block sizes, to evaluate the performances of the inversion, and to specify the impact of our various configurations. The same system was also used to assimilate carbon monoxide concentrations, collected at the two stations since December 2018.; Les villes sont responsables de plus de 70% des émissions mondiales de CO2. De nombreuses municipalités se sont engagées à réduire les émissions de CO2 urbaines. Afin d'évaluer l'impact des Plans Climat, des inventaires d'émissions de gaz à effet de serre sont établis à l'échelle de la ville. La modélisation par inversion atmosphérique offre une solution complémentaire capable de réduire les incertitudes pour ces inventaires d'émissions. Elle combine la modélisation du transport atmosphérique et les mesures de concentrations en gaz à effet de serre pour affiner les estimations des émissions issues des inventaires.La zone métropolitaine de Mexico (MCMA) est l'une des plus grandes mégalopoles du monde. Les émissions annuelles de CO2 dans la MCMA sont passées de 42,1 millions de tonnes à 66,0 millions de tonnes entre 2012 et 2018. Le gouvernement mexicain a prévu de réduire les émissions de CO2 de 65,2 millions de tonnes au cours de la période 2021-2030. Afin d'évaluer quantitativement les stratégies de réduction des émissions de CO2, un projet franco-mexicain intitulé "Impacts du carbone dans la région de Mexico" (MERCI-CO2) a déployé un réseau d'instruments d'observation du CO2 in situ et en colonne dans la région de Mexico. Les gradients de concentration de CO2 sont assimilés dans un système d'inversion basé sur le modèle de transport atmosphérique WRF-Chem pour améliorer l'estimation préalable des émissions de CO2 à l'intérieur et à l'extérieur de la MCMA.J'ai évalué les performances du modèle atmosphérique sous diverses configurations. Afin de quantifier les erreurs les plus impactantes pour la simulation des concentrations en CO2 atmosphérique, le travail de thèse s'est focalisé sur les erreurs de simulation des températures de l'air, des vitesses et directions du vent et les hauteurs de mélange, en utilisant des données collectées aux stations météorologiques de la région mais également issues d'un instrument LiDar ainsi que de radiosondes. Ces tests de sensibilité ont permis de définir la configuration optimale du système de modélisation.Des cartes de concentration de CO2 au-dessus de la MCMA sur trois périodes caractéristiques des conditions météorologiques de la région (janvier, mai et juillet) ont été simulée par le modèle WRF-Chem à la résolution de 5 km, en utilisant deux inventaires d'émissions: inventaire local préparé par les chercheurs de l'UNAM et un inventaire d'émissions globales, ODIAC, ajusté par des facteurs d'échelle temporels. Parallèlement à l'évaluation sur la base de mesures in-situ de CO2 en surface et de mesures de colonne (XCO2) par FTIR, j'ai également analysé les distributions temporelle et spatiale des signaux de CO2, ainsi que la zone impactée par les flux anthropiques et la variation des flux biogéniques. Sur la base de cette analyse, j'ai évalué le potentiel de quantification du réseau actuel, y compris l'emplacement de la station de fond, tout en étudiant les emplacements potentiels de nouvelles stations.Une inversion sur une année complète a été réalisée du 30 mars 2018 au 30 mars 2019. En se basant sur l'assimilation des gradients entre la station urbaine UNA et la station d'altitude ALZ, l'inversion a ajusté les émissions anthropiques issues des deux inventaires ainsi que les flux biogéniques du modèle CASA et les concentrations de fond du modèle CarbonTracker 2019B. Un ensemble de plusieurs inversions a été réalisé pour mieux quantifier les incertitudes en faisant varier les covariances d'erreur temporelles, en variant la fenêtre d'assimilation, en séparant les secteurs d'activités (trafic routier), en appliquant un masque sur la MCMA, et en filtrant les données de gradients en CO2. Cet ensemble permet d'améliorer les performances de l'inversion et de spécifier l'impact du signal urbain et des différentes composantes du système. Une dernière expérience m'a permis d'étudier l'impact de l'assimilation des concentrations en CO, dont les observations débutent en décembre 2018.

National audience; Humans are messy, and not just here on Earth (Bohannon, 2015). On November 15, 2021, a Russian anti-satellite test produced more than 1,500 pieces of orbital debris that threatened the crew of the international space station. The crew members sheltered in capsules in case they had to evacuate. So far, more than 8000 tons of orbital debris have been generated from human space missions. Moreover, the dawn of ‘space tourism’, a term popularized by recent space missions, marks an acceleration of the era of spaceindustrialization. While recent reports have focused on space collisions induced by space debris, there is actually little discussion on the effect of space industrialization on the earth's environment. Here, we review the impacts of space debris on earth's environment. About 23,000 objects larger than a softball, more than about 10 cm, amounting to a total weight of 8000 tons, are actually orbiting the earth at speeds up to 17,500 miles per hour. By reflecting and scattering sunlight, man-made space objects and debris have increased the night sky brightness on earth by approximately 10% of the luminance of a typical naturalnight sky. Upon burning, some space debris consumes ozone and release carbon dioxide, which may—unlike in the lower atmosphere—induce cooling and contraction of the thermosphere due to increased heat shedding via infrared radiation. Rocket and plane propellants are likely to pollute the earth’s atmosphere and deplete the stratosphericozone. The falloff of nuclear powered engines and parts may cause large radioactive pollution. As a consequence, mitigation guidelines for orbital debris have been proposed by some countries, though with limited success to date.

Cities are responsible for more than half of all greenhouse gas emissions. While many cities have committed to emission reduction trajectories, many lack the infrastructure to develop their emissions budgets. The measurement of CO2 plumes from cities by satellite imagery, coupled with atmospheric inversion methods, could allow quantifying direct CO2 emissions from cities, or at least detecting trends in their evolution.OCO-3, with its Snapshot Area Maps (SAMs) mode, is the first instrument to provide 2D (≈80km*80km) images of the total CO2 column at high resolution (≈2km*2km). In particular, these SAMs target atmospheric plumes of CO2 from cities and powerplants, with the goal of quantifying their emissions. Methods to estimate these emissions must be reliable and fast to process all available images (several thousands for OCO-3), whose number will increase with the CO2M and GeoCarb missions. The inversion methods by direct flux calculation (Integrated Mass Enhancement, Cross-Sectional and Source Pixel) or with a Gaussian plume model require little computation time. This thesis aims to evaluate the accuracy of these CO2 plume inversion methods and to study the favorable cases in terms of target and observation condition. This is done in a theoretical framework (atmospheric transport simulations) and by applying the methods to acquired SAMs.We quantify and analyze the different sources of error of these methods in detail using satellite pseudo-images of plumes, first over Paris and then over 31 cities in the world. The error of these methods is mainly due to errors in the estimation of the background concentration (XCO2 concentration that does not come from the city emissions) and in the estimation of the effective wind that carried the plume. We show, with a decision tree learning method, the sensitivity of the error on the emission estimate to the variability of the wind direction in the PBL and to the city's emission budget. The set of pseudo-images for which the emissions are large (>2.1ktCO2/h) and the wind direction variability low (2.1ktCO2/h) et la variabilité de la direction du vent faible (

In the actual context of energetic transition, the photocatalysis community is strongly interested in the reduction of carbon dioxide (CO2). This thesis work aims at better understand the complex phenomenon associated to this reaction and the photocatalytic materials, by using quantum chemistry methods. The objectives can be divided in two axes. In a first time, the determination of the feasibility of a heterojunction involving MoS2 (a promising material limiter by its small bandgap). In a second time, the investigations of the CO2 photoreduction mechanisms on this material.In a first part, we explore the evolution of the position of the conduction band and valence band for some heterostructures composed of 2D-MoS2 and TiO2 anatase surfaces. In particular, we study various TiO2 surfaces, interaction modes (physical and chemical), MoS2 sizes and chemical compositions of the interface. The results identify the nano-structuration parameters that have an influence on the electronic structure of the junction and that have an influence on the charge migration expected (type I, type II or Z-scheme). In a second part, the steps of the CO2 reduction mechanism are studied under different conditions of hydrogenation and hydroxylation of the MoS2 edge. Mechanisms leading to the formation of formic acid or carbon monoxide are identified. This study is performed thanks to the surface charging approach, that manage to explicitly simulate the impact of the electrochemical potential on the energy of the reactional intermediates.; Dans un contexte de transition énergétique, la communauté de la photocatalyse s’intéresse actuellement à la réduction de dioxyde de carbone (CO2). Ces travaux de thèse visent à mieux comprendre les phénomènes complexes liés à cette réaction et aux matériaux photocatalytiques via l’utilisation de méthodes de chimie quantique. Les objectifs sont d’une part, de déterminer la faisabilité d’une hétérojonction impliquant MoS2 (un matériau prometteur mais limité par son faible « bandgap ») et d’autre part, d’étudier les mécanismes de photoréduction du CO2 sur ce matériau.Dans un premier temps, nous explorons l’évolution de la position des bandes de conduction et valence pour différentes hétérostructures constituées d’un feuillet 2D-MoS2 et d’une surface de TiO2-anatase. En particulier, différentes surfaces de TiO2, différents modes d’interaction (chimique ou physique), tailles de MoS2 et compositions chimiques de l’interface sont étudiées. Les résultats identifient les paramètres de nano-structures ayant une influence sur la structure électronique de la jonction et ayant une influence sur le mécanisme de migration attendu (type I, type II ou schéma en Z). Dans un second temps, les étapes du mécanisme de réduction du CO2 en acide formique ou en monoxyde de carbone sur les sites de MoS2 sous différentes conditions d’hydroxylation et d’hydrogénation sont étudiées. Cette étude est menée grâce à la méthode de la surface chargée, qui permet de simuler explicitement l’impact du potentiel électrochimique sur l’énergie des intermédiaires réactionnels.

International audience; A pan-European GIS focused on gas hydrates has been developed in the GARAH project (https://geoera.eu/projects/garah4/) to assess for the first time the gas hydrate related risk along the European continental margins. Several factors and variables have been taken into account to assess the abundance of sediment-hosted gas hydrates and to estimate the safe storage volume of CO2 as mixed gas hydrates in deep-sea sediments. The baseline scenario is that gas hydrate occurrence is only possible in seafloor areas where pressure (bathymetry) and seafloor temperature conditions are inside the theoretical gas hydrate stability zone (GHSZ) and that the injected CO2(l) is expected to percolate downwards or upwards to the neutral buoyancy level (NBZ) depending on the CO2 quality and on the seafloor depth. In the Bay of Biscay, the safe CO2 deep offshore storage capacity is estimated in both cases (pure CO2 or 96%ml CO2). The French EEZ storage volume estimate of 3,422 km3 is of the same order of magnitude as the total Spanish EEZ storage volume estimate of 3,700 km3. There is, however, a big difference resulting from the seafloor depth: in the French zone, almost all the stored volume is occupied by gas hydrates, whereas in the Spanish zone, about the half (1,728 km3) is occupied by CO2 in hydrate phase and the other half (1,972 km3) by liquid CO2. This GIS-database has been conceived as a first step or base-line for future gas hydrate related research.

Species identification is currently a strong limitation to wild pollinator studies. It requires killing specimens for laboratory analyses, which can pose ethical issues in some programs of conservation biology and citizen science. The recent development of image-based identification tools using machine learning could challenge the current paradigm of required specimen euthanasia for species identification. However, to be accurate, these new methods call for standardized images or images of precise characters that are difficult or even impossible to obtain on live specimens. To facilitate the acquisition of these pictures, we tested twoin-situCO2 anesthesia protocols using material easily available, even in citizen science programs. We measured the time of anesthesia of 196 flower visitors belonging to the Hymenoptera and Diptera orders. The most efficient protocol enabled us to anesthetize 90% of the specimens for more than a minute with a marginal mortality (1.5%). Anesthesia time increased with specimen size in Hymenoptera and decreased with air temperature. Diptera were less sensitive to anesthesia. Further analyses would be required to investigate the potential sublethal effects of these anesthesia. These preliminary results suggest nonetheless that CO2-based anesthesia could help the development of non-lethal methods of wild pollinator identifications. L’anesthésie sur le terrain par machine à soda, un moyen de faciliter le développement de méthodes non létales d’identification des abeilles sauvages et autres visiteurs floraux L’une des limites actuelles à l’étude des pollinisateurs sauvages est la difficulté d’identifier ces insectes au niveau de l’espèce. Le développement d’outils d’identification sur images par intelligence artificielle ouvre de nouvelles perspectives par rapport au paradigme actuel d’euthanasie des spécimens pour les identifier en laboratoire. Cependant, l’obtention d’images de référence standardisées ou de caractères morpho-anatomiques précis nécessaires à ces outils est difficile, voire impossible sur un spécimen actif. Pour faciliter l’obtention de ces photos, nous avons testé deux protocoles d’anesthésie au CO2 de spécimens sur le terrain avec un matériel accessible au grand public. Nous avons mesuré le temps d’anesthésie sur 196 visiteurs de fleurs, hyménoptères et diptères. Avec le protocole le plus performant, 90% des insectes étaient anesthésiés pendant plus d’une minute. La mortalité due au traitement était marginale (1,5%). La durée de l’anesthésie augmentait avec la température de l’air, ainsi qu’avec la taille des spécimens chez les hyménoptères. Les diptères étaient moins sensibles à l’anesthésie que les hyménoptères. Des études complémentaires seraient nécessaires pour appréhender les effets sublétaux potentiels de ces anesthésies. Néanmoins, l’anesthésie au CO2 sur le terrain pourrait faciliter le développement de méthodes non-létales d’identification des pollinisateurs.

The intensive use of fossil resources, their depletion and the environmental issues it caused makes the research of alternative and sustainable energy sources of great interest. In this field, ethanol and Hydrogen represent energy carriers of a high potential to replace oil. Ethanol, is already used as an alternative. However, it has some drawbacks (low energy density and high hydrophilicity) that can be overcome with the upgrade of ethanol to n-butanol via the Guerbet reaction. The second alternative is hydrogen as it has high energetical density. However, due to its gaseous form and flammability it suffers from safety, transportation and storage issues. To overcome these issues, chemical storage in formic acid (FA) via hydrogenation of CO2 is a solution that creates a virtuous cycle of energy storage based on FA/CO2. The project implied the use of innovative η5-Oxocyclohexadienyl ruthenium complexes, structurally related to the Shvo catalyst, developed by our partner. Using homogeneous catalysis, the bifunctional properties and the Metal-Ligand cooperation of the catalyst have been evaluated in base-free reduction of ketones. The base-free hydrogenation and the base-free transfer hydrogenation with iso-propanol and FA were investigated and a broad scope of ketone applied. Then, the catalysts were studied in more challenging reactions in the domain of sustainable energy involving hydrogenation and dehydrogenation processes. Hence, the Guerbet reaction to upgrade ethanol into n-butanol was studied. The base-free hydrogen storage associated with CO2 hydrogenation to FA and the reverse reaction were also studied. We performed the unprecedented base-free hydrogen storage cycle.; L'utilisation intensive des ressources fossiles, leur épuisement et les problèmes environnementaux causés rendent la recherche de nouvelles sources d'énergie durables essentielle. Dans ce domaine, l’éthanol et l'hydrogène sont des vecteurs énergétiques prometteurs. L'éthanol, est déjà utilisé comme alternative mais il présente des inconvénients (faible densité énergétique, hydrophilie) pouvant être surmonté en transformant l'éthanol en n-butanol par la réaction de Guerbet. La seconde solution est l'hydrogène possédant des propriétés énergétiques élevées mais, souffrant de problèmes de sécurité, de transport et de stockage (gaz inflammable). Pour surmonter ces défauts, le stockage chimique de l’hydrogène en acide formique (AF) via l’hydrogénation de CO2 est une possibilité créant ainsi un cycle vertueux de stockage énergétique avec le couple AF/CO2. Le projet implique l'utilisation de complexes η5-Oxocyclohexadienyl ruthénium, apparentés à celui de Shvo, développé par notre partenaire. Par la catalyse homogène, les propriétés bifonctionnelles et la coopération Métal-Ligand du catalyseur ont été évaluées dans la réduction sans base de cétones soit par hydrogénation ou hydrogénation par transfert avec l'i-propanol ou l’AF. Ensuite, les complexes ont été testés dans des réactions du domaine de l'énergie impliquant des processus d'hydrogénation/déshydrogénation. Ainsi, la réaction de Guerbet, pour transformer de l'éthanol en n-butanol a été étudié. De même, le stockage sans base d'hydrogène par l'hydrogénation du CO2 en AF et la déshydrogénation de l’AF en H2 ont été effectués. Enfin, nous avons réalisé un cycle de stockage de l’hydrogène sans base inédit.

International audience; The emission of greenhouse gases such as carbon dioxide (CO2) is considered the most acute issue of the 21st century around the globe. Due to this fact, significant efforts have been made to develop rigorous techniques for reducing the amount of CO2 in the atmosphere. Adsorption of CO2 in metal–organic frameworks (MOFs) is one of the efficient technologies for mitigating the high levels of emitted CO2. The main aim of this study is to examine the aptitudes of four advanced intelligent models, including multilayer perceptron (MLP) optimized with Levenberg-Marquardt (MLP-LMA) and Bayesian Regularization (MLP-BR), extreme learning machine (ELM), and genetic programming (GP) in predicting CO2 uptake in MOFs. A sufficiently widespread source of data was used from literature, including more than 500 measurements of CO2 uptake in13 MOFs with various pressures at two temperature values. The results showed that the implemented intelligent paradigms provide accurate estimations of CO2 uptake in MOFs. Besides, error analyses and comparison of the prediction performance revealed that the MLP-LMA model outperformed the other intelligent models and the prior paradigms in the literature. Moreover, the MLP-LMA model yielded an overall coefficient of determination (R2) of 0.9998 and average absolute relative deviation (AARD) of 0.9205%. Finally, the trend analysis confirmed the high integrity of the MLP-LMA model in prognosticating CO2 uptake in MOFs, and its predictions overlapped perfectly the measured values with changes in pressure and temperature.

International audience; Breslow intermediates are very often elusive species whose application in frustrated Lewis pair (FLP) chemistry is unprecedented. Described herein is the use of a masked form of an O-borylated Breslow (OBB) intermediate that performs FLP-type activation of the carbonyl function of five different benzaldehyde derivatives with complete diastereoselectivity. The resulting compounds are characterised in solution by NMR spectroscopy (compounds 4–8) and in solid state by X-ray diffraction analysis (compounds 4–6). A combined kinetic and theoretical investigation reveals the associative nature of the rate determining step and suggests that the OBB intermediate part is never released during the whole process.

In recent decades, the use of CO₂ as a carbon source has gained considerable interest due to its non-toxicity and abundance. CO₂ represents an attractive renewable resource to decrease the massive consumption of fossil fuels as well as the environmental difficulties associated with their exploitation. More recently, the development of new strategies for carboxylic acids synthesis has emerged as these compounds are versatile starting materials for the fine chemical industry. However, due to the inherent stability of CO₂, the use of highly reactive and waste-generating substrates is often needed. The present project finds interest in developing new systems for reductive carboxylation reactions, catalyzed by transition metals, allowing to avoid the use of polluting co-reactants. This work first focuses on the study of different catalytic systems activities, previously selected through a literature study.Using a high throughput screening approach, some promising systems for the reductive carboxylation reaction of C₂H₄, in the presence of the reducing agent Et₃SiH, have been identified and then optimized in terms of conversion and selectivity. The second part of the manuscript aims at understanding the corresponding reaction mechanisms giving access to the targeted alkyl and alkenyl silyl esters. In particular, it describes the structural investigations carried out on the catalytic intermediate species generated in situ from ruthenium precursors and bidentate phosphine ligands. The knowledge acquired through experimental NMR studies, supplemented by DFT calculations, allowed to propose several reaction mechanisms potentially involved.; Au cours des dernières décennies, l’utilisation du CO₂ comme matière première carbonée a suscité un intérêt considérable de par sa non toxicité et son abondance. Le CO₂ représente une ressource renouvelable attrayante pour pallier à la consommation massive de ressources fossiles et aux difficultés environnementales liées à leur exploitation. Plus récemment, le développement de nouvelles stratégies de synthèse d’acides carboxyliques, molécules polyvalentes pour la chimie fine, ont vu le jour. Néanmoins, en raison de la stabilité inhérente du CO₂, l'utilisation de substrats hautement réactifs et générateurs de déchets est souvent nécessaire. Le présent travail doctoral s’est intéressé au développement de nouveaux systèmes pour les réactions de carboxylation réductrice, catalysées par des métaux de transition, permettant de s’affranchir de co-réactifs polluants.Ces travaux de thèse s’intéressent d’abord à l’étude de l’activité de différents systèmes catalytiques, préalablement sélectionnés au travers d’une étude de la littérature existante. En utilisant une approche de criblage à haut débit, certains systèmes prometteurs pour la réaction de carboxylation réductrice du C₂H₄, en présence du réducteur Et₃SiH, ont été identifiés puis optimisés en termes de conversion et de sélectivité. La seconde partie du manuscrit vise à la compréhension des mécanismes réactionnels donnant accès aux esters d'alkyle et d'alcényl silylés désirés. Elle décrit en particulier l’élucidation structurale des espèces catalytiques intermédiaires générées in situ à partir de précurseurs au ruthénium et de ligands phosphine bidentés. Les connaissances acquises à travers des études RMN expérimentales, complétées par des calculs DFT, ont permis de proposer plusieurs mécanismes réactionnels potentiellement mis en jeu.

The understanding and prediction of the processes involved in the convective dissolutionof carbon dioxide (CO2) in brine are of major concern for storage applications and toreach the 2050 carbon neutral target. Indeed, the efficiency of the CO2 storage processin deep saline aquifers is related to the dissolution rate of CO2 in brine. The latterincreases when the mass transfer switches from pure diffusion to convection. This thesispresents an experimental study of the convective dissolution of CO2 at high pressure,and in three-dimensions (3D), i.e. in the Rayleigh-Taylor regime. The experimentswere carried out in pure water and in salted water for multiple salt compositions andconcentrations. In this study, we develop a non-destructive experimental approachbased on the dynamic shadowgraphy method, and a high-pressure cell adapted for thecharacterisation of convection with or without a temperature gradient. The resultsobtained with homogeneous temperature show that the injection pressure of CO2 playsa dominant role on the dissolution rate, and influences the shape of the 3D convectivepatterns. The analysis of the refractive index variations over time shows that the onsettime of convection is a function of the solutal Rayleigh number following a power-law,which is independent of the brine composition and its height. To allow the up-scalingto the saline aquifers scale, the results are rationalised with dimensionless equations.At these scales, convection induced by the Soret effect in the liquid mixture could besignificant. Thus, the influence of a temperature gradient was checked. These lateststudies have been carried out on fluids mimicking the water-CO2 system on Earth, andunder reduced-gravity conditions., Comprendre et prédire les mécanismes impliqués dans la dissolution convective du dioxyde de carbone (CO2) dans la saumure est un enjeu majeur pour atteindre la neutralité carbone en 2050. En effet, l'efficacité du procédé de stockage du CO2 dans les aquifères salins profonds est associée au taux de dissolution du CO2 dans la saumure. Ce dernier augmente lorsque le mode de transfert de masse devient rapidement convectif. Ce mémoire de thèse présente une étude expérimentale de la dissolution convective du CO2 à haute pression et en trois dimensions (3D), c'est-à-dire en régime de Rayleigh-Taylor. Les expériences ont été réalisées dans de l'eau pure, puis de l'eau salée à différentes compositions et concentrations de sel. L'approche expérimentale non-destructive développée dans cette étude repose sur l'ombroscopie dynamique et une cellule haute pression adaptée pour la caractérisation de la convection en présence ou non de gradients de température. Les résultats obtenus à température homogène montrent que la pression d'injection du CO2 joue un rôle prépondérant sur le taux de dissolution et influence les motifs 3D de convection. L'analyse des variations moyennes d'indice de réfraction au cours du temps montre que le temps de mise en place de la convection en fonction du nombre de Rayleigh solutal suit une loi puissance indépendante de la composition de la saumure et de sa hauteur. Les résultats sont rationalisés avec des équations adimensionnelles permettant leur projection aux échelles des aquifères salins. A ces échelles, la convection induite par effet Soret dans le mélange liquide, due à la présence du gradient géothermique, devient non négligeable et a été étudié dans le dernier chapitre de ce mémoire. Ces dernières études ont été menées sur des fluides mimant le système eau + CO2 sur Terre ainsi qu'en impesanteur.

This paper presents a laser source designed to measure CO2 mixing ratio and wind speed at 2.05 µm using the DIfferential Absorption Lidar (DIAL) method with coherent detection. The all-fiber part of the laser offers robustness, high spatial and spectral quality and versatility. The main limitation in a single-frequency fiber laser source weighs on the signal peak power, which is limited by stimulated Brillouin scattering (SBS). The second part is a single-pass free-space amplifier able to achieve higher peak power, while maintaining low alignment sensitivity. We use a Ho:YLF crystal which is a good candidate to perform efficient power scaling at 2.05 µm. For 200 ns laser pulses, we achieved 1.2 mJ at 20 kHz and 9 mJ at 1 kHz repetition rate., Cet article présente une source laser conçue pour mesurer le rapport de mélange du CO2 et la vitesse du vent à 2,05 μm en utilisant la méthode DIAL (DIfferential Absorption Lidar) en détection cohérente. La partie entièrement fibrée du laser offre robustesse, haute qualité spatiale et spectrale et polyvalence. La principale limitation d'une source laser à fibre mono-fréquence est la puissance crête atteignable, qui est limitée par la diffusion Brillouin stimulée (SBS). La deuxième partie est un amplificateur en espace libre à un seul passage capable d'atteindre une puissance crête plus élevée, tout en maintenant une faible sensibilité à l'alignement. Nous utilisons un cristal Ho:YLF qui est un bon candidat pour réaliser une montée en puissance efficace à 2,05 μm. Pour des impulsions laser de 200 ns, nous avons atteint 1,2 mJ à 20 kHz et 9 mJ pour une fréquence de répétition de 1 kHz.

In order to develop an alternative to petroleum-based compounds in synthetic chemistry, the molecules present in biomass have been the subject of increasing study in recent years. Carboxylic acids have been particularly studied in the context of decarboxylating reactions. Indeed, the extrusion of a carbon dioxide (CO₂) molecule into carboxylic acids, or derivatives, allows the formation of a highly reactive fragment. With this approach, we have been interested in the reactivity of alkyl formates in particular in the context of hydroalkylation reactions by organometallic catalysis of compounds with unsaturations such as alkenes, carbonyl derivatives or imines. We have also explored the reactivity of carboxylic acids to perform dynamic exchanges between CO₂ and sulphur dioxide (SO₂) to synthesise sulphones directly from the latter., Afin de développer une alternative aux composés pétrosourcés dans la chimie de synthèse, les molécules présentent dans la biomasse font l'objet d'étude croissant ces dernières années. Les acides carboxyliques ont été particulièrement étudiés dans le cadre de réactions décarboxylantes. En effet, l'extrusion d'une molécule de dioxyde de carbone (CO₂) dans les acides carboxyliques, ou dérivés, permet la formation de fragment très réactif. Avec cette approche, nous nous sommes intéressés à la réactivité des formiates d'alkyles notamment dans le cadre de réactions d'hydroalkylation par transfert par catalyse organométallique de composés présentant des insaturations comme les alcènes, dérivés carbonylés ou bien les imines. Nous avons également exploré la réactivité d'acides carboxyliques pour réaliser des échanges dynamiques entre du CO₂ et du dioxyde de soufre (SO₂) pour synthétiser des sulfones directement à partir de ce dernier.

In August 2021 took place in northern Scandinavia the MAGIC-2021 campaign, dedicated to the Monitoring of Atmospheric composition and Greenhouse gases through multi-Instruments Campaigns. Gathering 17 research teams from 7 countries, the campaign involved a large suite of instruments and payloads (ground-based, balloon-borne, and airborne). Among them, an original combination of two airborne lidars was deployed onboard the same aircraft (SAFIRE ATR42): on one side DLR’s CHARM-F direct detection lidar for CH4 and CO2 measurement in IPDA mode (Integrated Path Differential Absorption), and on the other side ONERA’s LIVE coherent lidar for range-resolved vertical wind vector profiles.The scientific goal of this double-lidar experiment was to record greenhouse gas (GHG) concentration and wind data with very good temporal and spatial matching, so as to characterize GHG atmospheric transport and infer regional fluxes. Indeed, the boreal region is known to host significant sources of CH4, either anthropogenic (gas and oil platforms) or natural (wetlands, peat bogs, lakes…). Moreover, high latitudes are generally considered to be a sink for atmospheric CO2, but this effect could be strongly impacted by the rapid warming at these latitudes. However, due to the low population density and harsh environment, the boreal area is poorly covered by in-situ instrumentation. Therefore, airborne measurements appear as a preferred solution in these conditions.The airborne campaign was based in Kiruna (Sweden), and lasted 10 days. Though it suffered from poor weather conditions, six flights were successfully completed by the ATR42 above northern Sweden, Finland, and Norway. CHARM-F and LIVE lidars operated nominally during those flights, collecting hours of data in various sky conditions (clear, haze, broken clouds…). The expected precision of CHARM-F and LIVE lidars were respectively around 0.3% for integrated columns of CH4 and CO2 (10 km-along track averaging) and 0.6 m/s for horizontal wind (2.5 km along-track averaging, for average aerosol load in France). The paper will detail the payload arrangement, and review CHARM-F and LIVE lidars main properties. The data processing work is currently in progress, but selected preliminary results of measured collocated GHG columns and wind profiles will be shown and discussed., En août 2021 a eu lieu dans le nord de la Scandinavie la campagne MAGIC-2021, dédiée à la surveillance de la composition atmosphérique et des gaz à effet de serre à travers des campagnes multi-instruments. Rassemblant 17 équipes de recherche de 7 pays, la campagne impliquait une large gamme d'instruments et de charges utiles (au sol, en ballon et aéroportées). Parmi eux, une combinaison originale de deux lidars aéroportés a été déployée à bord du même avion (SAFIRE ATR42) : d'un côté le lidar à détection directe CHARM-F du DLR pour la mesure du CH4 et du CO2 en mode IPDA (Integrated Path Differential Absorption), et de l'autre côté le lidar cohérent LIVE de l'ONERA pour les profils de vecteur vent verticaux résolus en distance.L'objectif scientifique de cette expérience à double lidar était d'enregistrer des données de concentration de gaz à effet de serre (GES) et de vent avec un très bon appariement temporel et spatial, afin de caractériser le transport atmosphérique des GES et d'en déduire les flux régionaux. En effet, la région boréale est connue pour abriter d'importantes sources de CH4, soit anthropiques (plateformes gazières et pétrolières), soit naturelles (zones humides, tourbières, lacs…). De plus, les hautes latitudes sont généralement considérées comme un puits de CO2 atmosphérique, mais cet effet pourrait être fortement impacté par le réchauffement rapide à ces latitudes. Cependant, en raison de la faible densité de population et de l'environnement hostile, la zone boréale est mal couverte par l'instrumentation in situ. Les mesures aéroportées apparaissent donc comme une solution privilégiée dans ces conditions.La campagne aéroportée était basée à Kiruna (Suède) et a duré 10 jours. Bien qu'il ait souffert de mauvaises conditions météorologiques, six vols ont été effectués avec succès par l'ATR42 au-dessus du nord de la Suède, de la Finlande et de la Norvège. Les lidars CHARM-F et LIVE ont fonctionné nominalement pendant ces vols, collectant des heures de données dans diverses conditions de ciel (clair, brumeux, nuages ​​fragmentés…). La précision attendue des lidars CHARM-F et LIVE était respectivement d'environ 0,3 % pour les colonnes intégrées de CH4 et de CO2 (moyenne de 10 km le long de la trajectoire) et de 0,6 m/s pour le vent horizontal (moyenne de 2,5 km le long de la trajectoire, pour une charge moyenne d'aérosols en France). L'article détaillera l'agencement de la charge utile et passera en revue les principales propriétés des lidars CHARM-F et LIVE. Le travail de traitement des données est actuellement en cours, mais des résultats préliminaires sélectionnés de colonnes de GES et de profils de vent mesurés au même endroit seront présentés et discutés.

International audience; This work aims to compare two deposition methods to highlight the strong influence of the induced morphology on the sensitive film conductivity. Lanthanum oxycarbonate films have been deposited by drop coating and screen printing for carbon dioxide detection. The measurements are based on a change in resistance and provide sensitive responses to carbon dioxide concentrations in a humid environment maintained at 50%. Electrical measurements were made under 5 000 ppm of carbon dioxide in synthetic air. Our results highlighted the close link between the morphology of the sensitive layers and the electrical responses of the sensors, and therefore the need to master the deposition technique.

International audience; The aviation sector contributes to anthropogenic climate change through both CO 2 and non-CO 2 radiative effects. The CO 2 effect is considered to be much more certain than the non-CO 2 effects, yet there are relatively few studies that quantify it. Building on the scientific literature on burden sharing in the wake of the "Brazilian proposal", we discuss how to best attribute a fraction of the CO 2 radiative forcing to the aviation sector. For this we use the OSCAR compact Earth System model to estimate a contribution of aviation to the CO 2 concentration of 2.18 ppm in 2018. We further estimate the aviation contribution to the 2018 CO 2 radiative forcing to be 34.6, 32.6, 32.2 and 28.8 mW m − 2 for the proportional, differential, time-sliced and marginal methods, respectively. The time-sliced method has our preference because it is invariant upon disaggregation or recombination and can differentiate the relative impacts of early and late emissions. It leads to a radiative forcing estimate that is 12% larger than the residual method that is commonly used despite not being additive. This work has implications on the total-to-CO 2 RF ratio and the assessment of potential mitigation measures involving a trade-off between the CO 2 and non-CO 2 radiative effects of aviation. ☆ T. Gasser acknowledges support from the Austrian science fund (project P-31796). O. Boucher and D. Hauglustaine acknowledge support from the Direction Générale de l'Aviation Civile through the Convention N • 2021-39 relative to "Aviation & Climate".

Crop cultivation of northern peatlands emitted large amount of CO2 over the period 850–2010., When a peatland is drained and cultivated, it behaves as a notable source of CO2. However, we lack temporally and spatially explicit estimates of carbon losses from cultivated peatlands. Using a process-based land surface model that explicitly includes representation of peatland processes, we estimate that northern peatlands converted to croplands emitted 72 Pg C over 850–2010, with 45% of this source having occurred before 1750. This source surpassed the carbon accumulation by high-latitude undisturbed peatlands (36 to 47 Pg C). Carbon losses from the cultivation of northern peatlands are omitted in previous land-use emission assessments. Adding this ignored historical land-use emission implies an 18% larger terrestrial carbon storage since 1750 to close the historical global carbon budget. We also show that carbon emission per unit area decrease with time since drainage, suggesting that time since drainage should be accounted for in inventories to refine land-use emissions from cultivated peatlands.

International audience; The reduction of global warming potential gases emissions in industrial refrigeration devices requires the development of efficient cycles using low GWP gases. The supercritical C02 cycle assisted by a transcritical two phase ejector is a nice example of such cycles. The design of such ejectors is not obvious and an intense development of performance prediction tools is observed in literature especially regarding two-phase CFD modeling. The two phase flow CFD models are limited today by their lack of flexibility and difficulties to empirically calibrate them. The main drawback of classical Hertz-Knudsen or HRM phase change models is their difficulty to simultaneously predict the mass flow rate and the outlet velocity of the primary flow of the ejector. These two parameters are responsible of the entrainment ratio an ejector at given operating conditions and geometry. This paper presents a thermal phase change model that introduces a non symmetric interfacial area density formulation for two-phase liquid-gas CO 2 ejectors. This formulation describes the gas-liquid interface as bubbles at low void fractions and as droplets at high void fractions. The model results are compared to experimental results of literature. It appeared that bubbles number density affects mainly the primary flow rate and the droplets number density affects the outlet velocity of the primary nozzle and thus the mixture pressure and the secondary flow rate.

International audience

The objective of the thesis was to develop and characterize asymmetric mixed matrix membranes containing metal-organic frameworks (MOF) for CO2 separation from air. Gas separation in dense polymer membranes is limited by the trade-off between permeability and selectivity. To improve CO2 separation, some authors had highly permeable and selective fillers like MOF to the polymer matrix. These membranes are called mixed matrix membrane (MMM). The use of asymmetric membrane structures rather than dense allows the increase of the permeability. In this work, asymmetric Matrimid membranes were also prepared with two MOF (HKUST-1 and ZIF-8) to improve the CO2 separation. However, HKUST-1 was quickly abandonned due to its large crystals size. The prepared asymmetric membranes presented some micro-perforations on their dense skin. It was necessary to cover them by spray-coating with a second polymer. Pebax 2533 and 1657 were used for their high permselectivity to CO2. In order to make comparisons with the scarce data available in the bibliography, we also tested a coating with poly(dimethyl siloxane) (PDMS). As this technique improved the permselectivities of the membranes, we also tested the influence of the ZIF-8 in the cover layer. ZIF-8 improved the permselectivities of the membranes and showed similar properties than with ZIF-8 in the asymmetric membrane. The thesis highlighted the importance of the dispersion of the filler to obtain high-performance membranes.; L’objectif de ce travail de thèse à été d’élaborer et de caractériser des membranes à matrice mixte polymère / réseau organométallique (MOF) destinées à la séparation du CO2 de l’air. La séparation des gaz par les membranes denses en polymère est limitée par un compromis qu’il faut atteindre pour obtenir de fortes perméabilités et sélectivités. Il est possible d’améliorer les propriétés de séparation au CO2 des membranes en ajoutant à la matrice polymère des charges très perméables et sélectives, comme les MOF. Ces membranes sont appelées membranes à matrice mixte (MMM). L’utilisation d’une structure membranaire asymétrique plutôt que dense permet également d’augmenter les perméabilités. Dans ce contexte, nous avons élaboré des membranes asymétriques en Matrimid dans lesquelles nous avons dispersé deux types de MOF d’origine commerciale, l’HKUST-1 et le ZIF-8 connus pour posséder de très bonnes propriétés de séparation du CO2. L’HKUST-1 a rapidement été abandonné car ses cristaux étaient de trop grandes tailles, et donc inadaptés à nos membranes. Il s’est très vite avéré que les membranes asymétriques préparées possédaient quelques micro-perforations sur leur peau dense qui anhilaient leurs propriétés de séparation. Il a donc été nécessaire de les recouvrir d’une couche d’un second polymère. Pour ce faire, nous avons déposé par pulvérisation des copolymères à bloc polyamide - polyéther (Pebax de grades 2533 et 1657) qui sont connus pour posséder de bonnes permsélecitivés au CO2. Afin de réaliser des comparaisons avec les rares données disponibles dans la bibliographie, nous avons également testé un recouvrement par du poly(diméthyle siloxane) (PDMS). Cette technique ayant améliorée les propriétés de permsélectivité des membranes, nous avons également testé l’influence de la présence du ZIF-8 dans la couche de recouvrement. Sa présence améliore les permsélectivités des membranes, et elle évite d’utiliser du ZIF-8 dans la membrane asymétrique ce qui réduit les coûts de fabrication. La thèse a mis en évidence l’importance de la dispersion de la charge pour obtenir des membranes performantes.

A set of three commercial zeolites (13X, 5A, and 4A) of two distinct shapes have been characterized: (i) pure zeolite powders and (ii) extruded spherical beads composed of pure zeolite powders and an unknown amount of binder used during their preparation process. The coupling of gas porosimetry experiments using argon at 87 K and CO2 at 273 K allowed determining both the amount of the binder and its effect on adsorption properties. It was evidenced that the beads contain approximately 25 wt% of binder. Moreover, from CO2 adsorption experiments at 273 K, it could be inferred that the binder present in both 13X and 5A zeolites does not interact with the probe molecule. However, for the 4A zeolite, pore filling pressures were shifted and strong interaction with CO2 was observed leading to irreversible adsorption of the probe. These results have been compared to XRD, IR spectroscopy, and ICP-AES analysis. The effect of the binder in shaped zeolite bodies can thus have a crucial impact on applications in adsorption and catalysis.

This work reports on an all-fiber pulsed laser source for simultaneous remote sensing of C O 2 concentration and wind velocity in the 2.05 µm region. The source is based on a polarization-maintaining master oscillator power amplifier (MOPA) architecture. Two narrow-linewidth master oscillators for ON-line/OFF-line C O 2 differential absorption lidar operation alternately seed a four-stage amplifier chain at a fast switching rate up to 20 kHz. The MOPA architecture delivers laser pulses of 120 µJ energy, 200 ns duration (600 W peak power) at 20 kHz pulse repetition rate (2.4 W average power). The output linewidth is lower than 5 MHz, close to the pulse Fourier transform limit, and the beam quality factor is M 2 = 1.12 . The source also provides a pre-amplified 20 mW local oscillator with a relative intensity noise of − 160 d B / H z that ensures optimal performance for future coherent detection.

Weathering of silicate rocks at a planetary surface can draw down CO$_2$ from the atmosphere for eventual burial and long-term storage in the planetary interior. This process is thought to provide an essential negative feedback to the carbonate-silicate cycle (carbon cycle) to maintain clement climates on Earth and potentially similar temperate exoplanets. We implement thermodynamics to determine weathering rates as a function of surface lithology (rock type). These rates provide upper limits that allow estimating the maximum rate of weathering in regulating climate. This modeling shows that the weathering of mineral assemblages in a given rock, rather than individual minerals, is crucial to determine weathering rates at planetary surfaces. By implementing a fluid-transport controlled approach, we further mimic chemical kinetics and thermodynamics to determine weathering rates for three types of rocks inspired by the lithologies of Earth's continental and oceanic crust, and its upper mantle. We find that thermodynamic weathering rates of a continental crust-like lithology are about one to two orders of magnitude lower than those of a lithology characteristic of the oceanic crust. We show that when the CO$_2$ partial pressure decreases or surface temperature increases, thermodynamics rather than kinetics exerts a strong control on weathering. The kinetically- and thermodynamically-limited regimes of weathering depend on lithology, whereas, the supply-limited weathering is independent of lithology. Our results imply that the temperature-sensitivity of thermodynamically-limited silicate weathering may instigate a positive feedback to the carbon cycle, in which the weathering rate decreases as the surface temperature increases., Comment: Accepted for publication in The Planetary Science Journal

The aim of this dissertation was to quantify the economic impact of connecting electricity systems in the presence of interacting, and sometimes competing, policy objectives. The GCC region was chosen because the countries are substantial energy consumers, due partly because of the government interventions in prices and quantities in the transformation and end-use sectors. This dissertation directly incorporated the role of on prices and quantity interventions in the study of energy system interconnectivity. The framework was extended to a regional energy system under autarky and cooperation to quantify the mismatch in gains among the member states with and without interventions.The mixed-complementarity problem (MCP) approach was utilized in this dissertation, which enabled price and quantity interventions of agents to appear as market clearing conditions in an equilibrium problem. The MCP formulated in this dissertation was designed specifically for a multi-sector energy system in one country, then extended to multiple interconnected countries. A recursive dynamic solution algorithm was employed to approximate lack of perfect foresight of agents in the model.The first set of results demonstrated the MCP formulation and its viability to studying price and quantity interventions in Saudi Arabia. A static analysis of the six GCC countries quantified the economic losses from heterogeneous intervention schemes in each country and how they impede electricity exchange. The multi-country, multi-period analysis (through 2030) examined how subsidy reform, electricity exchange, and carbon pricing policies interact. It was shown how sequencing subsidy reforms before implementing electricity exchange or carbon pricing is a prerequisite for producing a net economic gain.; L’objectif de cette thèse est de quantifier l’impact économique de la connexion des systèmes électriques en présence d’objectifs politiques pluriels, et parfois concurrents. La région du CCG a été choisie car les pays qu’elle inclue sont d’importants consommateurs d’énergie du fait d’interventions gouvernementales sur les prix et les quantités, tant au niveau de la transformation que de l’utilisation finale. Cette thèse incorpore directement le rôle des interventions sur les prix et les quantités dans l’étude de l’interconnection du système énergétique. Le cadre d’analyse a été étendu à un système énergétique régional autarcique mais coopératif, afin de quantifier l’incidence des interventions sur les gains des Etats membres.La modélisation avec complémentarité mixte (MCP) utilisée dans cette thèse permet de faire apparaître les interventions sur les prix et quantités comme des conditions de compensation du marché à l’équilibre. L’approche MCP formulée dans cette thèse a été conçue spécifiquement pour un système énergétique multi-sectoriel dans un seul pays tout d’abord, puis étendue à plusieurs pays interconnectés ensuite. Un algorithme de résolution dynamique récursive a été utilisé pour appréhender le manque de prévoyance parfaite des agents.Une première analyse permet de valider la formulation MCP du problème pour étudier les interventions en matière de prix et de quantité en Arabie saoudite. Une seconde analyse, statique, sur les six pays du CCG quantifie les pertes économiques causées par les programmes d’intervention hétérogènes dans chaque pays et la manière dont ils entravent l’échange d’électricité. La troisième analyse, multi-pays et pluriannuelle (jusqu’en 2030), examine quant à elle comment la réforme des subventions, l’échange d’électricité et les politiques de tarification du carbone interagissent. Elle démontre que le séquençage des réformes, privilégiant la suppression des subventions avant la mise en oeuvre de l’échange d’électricité ou la tarification du carbone, est une condition préalable à l’obtention d’un gain économique net.

International audience; Autonomous low-pressure hydrogen on demand system was found promising to supply fuel cell technology for light or short distance mobility applications. Among the various hydrogen production technologies, the hydrolysis reaction method of magnesium-based materials is one of the most suitable. Magnesium (Mg) powder ball milled with the simultaneous addition of graphite and nickel under Ar was used as the hydrolysis reagent for hydrogen production. The effects of the solution composition (i.e. NaCl, NH4Cl and HCl) and the temperature (i.e. from 0 °C to 60 °C) of the solution on the hydrolysis performances were discussed. The hydrolysis reaction was complete (i.e. yield = 100%) in less than 5 minutes, except that performed at 0 °C, regardless the hydrolysis solution. The activation energy of the reaction decreases with lowering the pH of the hydrolysis solution. Semi-quantitative analysis was performed to evaluate the variation of CH4, CO, CO2 and moisture contents in the hydrogen produced by the hydrolysis. The exothermicity of the reaction and the composition of the hydrolysis solution showed a major impact on the purity of hydrogen. Under standard pressure and ambient temperature conditions, the hydrolysis of magnesium-based materials is considered as a clean hydrogen production technique. Our results should be taken as the starting point to evaluate the purity of the hydrogen produced by the hydrolysis of Mg-based materials according to the ISO standard 14687:2019.

The objective of this project is to develop a comprehensive reaction for the synthesis of styrene carbonate from styrene in the presence of CO2 and a clean oxidant: O2. Salophen-R-M (R = Me2N, Et2N, tBu and M = Mn, Ni and Cr) catalysts were synthesized and their co-catalytic activity for the cycloaddition reaction of CO2 on styrene oxide was evaluated in the presence of Bu4NBr; Salophen-Me2N-Cr showed the best results: 99% yield obtained after 3h at 80°C. Salophen-R-M complexes were grafted onto mesoporous silica {NH2}-SBA-15 by covalent bonding. In parallel, the binding of quaternary ammonium salts was optimized by ex-situ grafting on SBA-OH. These catalytic materials were tested for the formation of styrene carbonate, with yields higher than those obtained in solution thanks to the synergy effect linked to the presence of silanols. The Salophen-Me2N-Cr catalyst was tested in the Mukaiyama epoxidation reaction of styrene in the presence of O2. A 50% yield of styrene oxide was obtained under reaction conditions similar to those used in cycloaddition. The overall reaction was performed in the presence of Bu4NBr and Salophen-Me2N -Cr catalysts at 80°C under 3.5 bar O2 and 11 bar CO2. A maximum yield of styrene carbonate of 31% was obtained after a two-step reaction of oxidation (3h) and cycloaddition (20h)., Ce projet a pour objectif la mise au point d’une réaction globale de synthèse de styrène carbonate à partir du styrène en présence de CO2 et d’un oxydant propre : O2. Les catalyseurs Salophen-R-M (R = Me2N, Et2N, tBu et M = Mn, Ni et Cr) ont été synthétisés et leur activité co-catalytique pour la réaction de cycloaddition de CO2 sur le styrène oxyde a été évaluée en présence de Bu4NBr ; Salophen-Me2N-Cr a présenté les meilleurs résultats : 99% de rendement obtenu après 3h à 80°C. Les complexes Salophen-R-M ont été greffés sur silice mésoporeuse {NH2}-SBA-15 par liaison covalente. En parallèle, le greffage de sels d’ammonium quaternaires a été optimisé par voie ex-situ sur SBA-OH. Ces matériaux catalytiques ont été testés pour la formation de styrène carbonate, avec des rendements supérieurs à ceux obtenus en solution grâce à l’effet de synergie lié à la présence de silanols. Le catalyseur Salophen-Me2N-Cr a été testé en réaction d’époxydation Mukaiyama du styrène en présence de O2 Un rendement en styrène oxyde de 50% a été obtenu dans des conditions de réaction similaires à celles utilisées en cycloaddition. La réaction globale a été effectuée en présence de catalyseurs Bu4NBr et Salophen-Me2N-Cr à 80°C sous 3,5 bar O2 et 11 bar CO2. Un rendement maximum en styrène carbonate de 31% a été obtenu après réaction en deux étapes distinctes d’oxydation (3h) puis de cycloaddition (20h).

This study is a continuation of our previous geochemical monitoring finding at the injection wells of Rousse 1 ( Total CCS pilot, Lacq- Rousse, France) where it was identified that the soil CO₂ mole fraction (χc) evolution in subsoil was negatively correlated with the level of the water table and the CO₂ sources were attributed to the CO₂-rich aquifers. However, it is still unclear whether this relationship exists in the forest ecosystem, representing a significant proportion of the CO₂ atmospheric budget. For this reason, this thesis focuses on monitoring the gas exchange and its main driver of the transport process between soil (-1 m), subsoil (-6 m), and biosphere. We developed and implemented an in-situ geochemical monitoring system for continuous monitoring of CO₂ mole fraction in the subsoil coupled with a micrometeorological monitoring system using a pre-established flux tower in the forest Ecosystem (Montiers, Lorraine Region, France). This soil gas measurement infrastructure combining borehole measurement with micrometeorological measurement offers great possibilities for long-term in-situ and continuous gas monitoring to derive the vertical distribution of CO₂. Thus, this infrastructure allowed the observation of the temporal dynamics in soil-gas CO₂ research. During the study periods, the ecosystem acted as a net carbon sink with a mean annual NEE, GPP, and Reco of -453±122 gC m-2y-1, -1468 ±109 gC m-2y-1, and 1052 ±88 gC m-2y-1 consecutively. The Carbon exchange, climate, and environmental drivers during the drought episodes were compared with long-term reference data recorded from 2014 to 2017. In contrast with some previous research where GPP and Reco parallelly decreased during the drought episodes, our site showed Reco is more sensitive to drought than GPP, resulting in a significant increase in Net Ecosystem exchange. Reco decreased by 20%, and 26% were found in Summer and Autumn (2018-2019) relative to the ref erence years (2014-2017). This study shows strong empirical shreds of evidence that wind turbulence plays a significant role in driving the deep soil CO₂ concentration. We hypothesize that this could be due to pressure pumping effects where it decreases the CO₂ molar fraction in the soil during high turbulence and increasing the CO₂ storage in deep soil during low turbulence. This study also demonstrates that permeability significantly reduced during wet periods diminishing molecular diffusion and advection. This study also revealed a strong biotic influence on CO₂ production. The δ¹³CCO₂ values in our site subsoil can be attributed to respiration and decomposition of the C3 plants. These biological origins of soil CO₂ are highly likely increases air density resulting in gravitational percolation that leads the CO₂ stored in a deeper layer of soil. The relationship of subsoil gases also emphasizes that biogenic components dominate the origins and controlling process of subsoil CO₂ while the geochemical process plays an insignificant role., Ce travail de recherche s'inscrit dans le prolongement de différentes études conduites notamment dans le cadre du pilote de Capture Transport et Stockage du CO₂ (pilote Total CCS, Lacq- Rousse, France) relatives au suivi des mécanismes de transfert des gaz (CO₂ et CH₄) dans les compartiments Géosphère/Biosphère/Atmosphère. De ces études, il était ressorti que l'évolution de la fraction molaire de CO₂ (χc) dans le sous-sol karstique du plateau du Jurançon était négativement corrélée aux battements de la nappe phréatique située à -45m via des mécanismes de dissolution/dégazage. Cependant, il n'est pas encore clair si cette relation existe dans l'écosystème forestier, qui représente importante de l'échange de CO₂ atmosphérique. Dans ce contexte, cette thèse se concentre sur la surveillance des échanges gazeux et de leurs processus de transport au sein de la zone critique, entre le sous-sol (-6 m), le sol (-1 m) et le couvert végétal (+50m). Nous avons développé et mis en place un système de surveillance géochimique in situ en puits dédiés pour le suivi continu de la fraction molaire de CO₂ dans le sous-sol et le sol couplé à un système de surveillance micrométéorologique utilisant une tour de flux préétablie dans l'écosystème forestier (Montiers, Région Lorraine, France). Au cours des périodes d'étude allant de Juin 2018 à Décembre 2020, l'écosystème a agi comme un puits de carbone net avec une moyenne annuelle des paramètres d’échange d'écosystème net (NEE), de productivité primaire brute (GPP) et de respiration de l'écosystème (Reco) de -453±122 gC m-2y-1, -1468 ±109 gC m-2y-1, et 1052 ±88 gC m-2y-1 respectivement. L’échange de carbone, les données météorologiques et les facteurs environnementaux durant les épisodes de sécheresse ont été comparés aux données de référence à long terme enregistrées durant les années allant de 2014 à 2017. Contrairement à certaines recherches précédentes où les paramètres NEE et Reco ont diminué parallèlement pendant les épisodes de sécheresse, les données enregistrées sur site ont montré que le paramètre Reco est plus sensible à la sécheresse que le paramètre NEE, ce qui a entraîné une augmentation significative de l'échange net au sein de l'écosystème. Ainsi, durant les périodes de sécheresses d’été et d’automne (2018-2019), le paramètre de respiration de l’écosystème (Reco) a diminué de 20 %, et 26 % par rapport aux années de référence (2014-2017). Les traitement statistique des données comparées sous-sol/sol/couvert végétal, montre des preuves empiriques solides que la turbulence du vent, mesurée au travers du paramètre de vitesse de frottement (u*) joue un rôle important dans la variabilité des concentrations de CO₂ dans les sols même jusqu’à des profondeurs de -6m, ce qui n’avait jamais été établi. Nous supposons que cela pourrait être dû aux effets de pompage de la pression qui diminue la fraction molaire de CO₂ dans le sol lors de fortes turbulences et augmente le stock age du CO₂ dans les sols profonds lors de faibles turbulences. Cette étude a aussi démontre le rôle de l’hydrométrie du sol sur ces processus d’échanges. En effet, en périodes humides, la perméabilité est considérablement réduite ce qui diminue la diffusion et l'advection moléculaires. Cette étude a également révélé une forte influence biotique sur la production de CO₂. Les valeurs de δ¹³CCO₂ dans le sous-sol de notre site peuvent être attribuées à la respiration et à la décomposition des plantes en C3. Ces origines biologiques du CO₂ du sol entraine très probablement des augmentations de la densité de l'air ce qui conduit à faire migrer le CO₂ stocké vers les couches plus profondes du sol par le biais d’un mécanisme de percolation gravitationnelle. La relation des gaz du sous-sol souligne également que les composants biogéniques dominent les origines et le processus de contrôle du CO₂ du sous-sol alors que le processus géochimique joue un rôle insignifiant.

The aim of this work is to investigate the valorization of carbon dioxide through the CO₂ methanation and the CO₂ reforming of methane reactions. Alumina, ceria and mesoporous silica were chosen as the catalytic support materials. The wet impregnation technique was used in order to add an active phase of 15 xt% nickel (Ni), 1 wt% ruthenium (Ru) or a combination or the two metals (Ni-Ru) on each of the stabilized supports. The obtained catalysts were calcined at 550°C, and then characterized using X-Ray Diffraction (XRD), Nitrogen adsorption/desorption, H₂-Temperature Programmed Reduction (H₂-TPR), and CO₂-Temperature Programmed Desorption (CO₂-TPD). Characterization results of Ni and/or Ru catalysts supported on CeO₂, Al₂O₃, and KIT-6 showed that all supports and catalysts present a type IVa isotherms typical to mesoporous materials and that the formed RuO₂ species were well-dispersed when the CeO₂ is used as a support and in the bi-metallic catalysts. The reduction of NiO was enhanced in the presence of CeO₂ support given its redox properties. The presence of RuO₂ also led to a facilitated NiO reduction in the bi-metallic catalysts. In the CO₂ methanation reaction, a first part compared the catalytic activity of the different active phases on the same support. In each case, the bi-metallic Ni-Ru catalyst exhibited the highest conversions at 350°C which was linked to a possible good RuO₂ dispersion and NiO reducibility observed in these catalysts. Moreover, regardless of the active phase used, the catalytic activity of the catalysts depended on the type of the support. The order of reactivity obtained was : CeO₂ supported catalysts > KIT-6 suported catalysts > Al₂O₃ supported catalysts. In the second part, KIT-6 was promoted with different CeO₂ percentages and impregnated with the same studied active phases in an attempt to create more economical and stable catalysts. A good dispersion of RuO₂ species, an ameliorated active phase reducibility at lower temperatures, and an enhancement in the basic properties were observed following the promotion with Ce ans as the percentage of Ce in the catalyst increased. This ultimately led to higher catalytic performances especially for the bi-metallic 15Ni1Ru/CeₓKIT-6 catalysts. The stability study showed that the 15Ni1Ru/CeO₂ catalyst exhibited good catalytic activity in terms of CO₂ conversion (70%) and CH₄ selectivity (99%) and showed no deactivation for 24h on stream. In the CO₂ reforming of methane, CeO₂ supported catalysts showed lower catalytic activity when compared to Al₂O₃ supported catalysts. However, they showed more resistance to carbon formation as proven by the thermal analyses and the XRD performed on the spent catalysts. The effect of adding Ce to Al₂O₃ on the physico-chemical properties and the catalytic performances was then investigated. The addition of Ce was found to cause a partial destruction of the porous structure, strengthen the weak basic sites of the catalysts and enhance the catalytic activity. The 15Ni1Ru/Ce-Al₂O₃ catalyst showed higher activity and stability during a 12 hour stability test compared to the non-promoted counter-part. The three different mesoporous silicas (15Ni/KIT-6, 15Ni/SBA-15, 15Ni/SBA-16) were then synthesized using the wet impregnation technique, characterized and compared for their activity and stability in the CO₂ reforming reaction. In the dynamic tests, 15Ni/SBA-16 was the best performing catalyst due to its strong metal-support interactions and high contribution from strong basic sites. However, the 15Ni/KIT-6 catalyst was able to maintain a good activity and stability even at higher gas hourly space velocities GHSVs. Finally, among the Ni/Ce-KIT-6, 1Ru/Ce-KIT-6 and 15Ni1Ru/Ce-KIT-6 catalysts, the latter was the most active in the DRM reaction and maintained a stable high CO₂ conversion (97% for 12 hours). Despite the deposition of graphitic carbon during the stability test, the catalyst was not desactivated., L'objectif de ce travail est d'étudier la valorisation du CO₂ par méthanation et reformage à sec du méthane. L'alumine, la cérine et la silice mésoporeuse ont été choisies comme support catalytique. La technique d'imprégnation humide est utilisée pour ajouter une phase active de 15% de nickel (Ni), 1% de ruthénium (Ru) ou une combinaison des deux métaux (Ni-Ru) sur chacun des supports stabilisés. Les catalyseurs obtenus ont été calcinés à 550°C, puis caractérisés par la Diffraction des Rayons X (DRX), l'adsorption/désorption d'azote, la Réduction en Température Programmée sous hydrogène (RTP-H₂) et la Désorption en Température Programmée (DTP-CO₂). Les résultats de la caractérisation des catalyseurs supportés sur CeO₂, Al₂O₃ et KIT-6 montrent que tous les supports et catalyseurs présentent des isothermes de type IVa typique des matériaux mésoporeux. Les espèces RuO₂ formées sont bien dispersées lorsque CeO₂ est utilisé comme support et dans les catalyseurs bimétalliques. La réduction de NiO est renforcée en présence de CeO₂ à cause de ses propriétés redox. La présence de RuO₂ a conduit à une plus grande réductibilité de NiO dans les catalyseurs bimétalliques. Une première partie a comparé l'activité catalytique des différentes phases actives (le Ni, Ru ou le Ni-Ru) sur le même support (CeO₂, l'Al₂O₃ ou le KIT-6) pour la réaction de méthanation. Dans chaque cas, le catalyseur bimétallique (Ni-Ru) présentait les conversions les plus élevées à 350°C. Ceci peut être lié à une bonne dispersion de RuO₂ et bonne réduction de NiO. De plus, quelle que soit la phase active utilisée, l'ordre de réactivité obtenu était : catalyseurs supportés sur CeO₂> catalyseurs supportés sur KIT-6> catalyseurs supportés sur Al₂O₃. Dans la seconde partie, le support KIT-6 est promu avec différents pourcentages de CeO₂ et imprégné avec les mêmes phases actives étudiées. Une bonne dispersion des espèces RuO₂, une réduction à des températures plus basses et une amélioration des propriétés basiques sont observées en présence de Ce et en fonction de sa teneur dans le matériau. Ceci a conduit à des performances catalytiques plus élevées, en particulier pour les catalyseurs bimétalliques 15Ni1Ru/CeₓKIT-6. L'étude de stabilité a montré que le catalyseur 15Ni1RU/CeO₂ présente une bonne activité en termes de conversion de CO₂ (70%) et de sélectivité CH₄ (99%) et ne présente pas de désactivation sur une durée de 24h. Lors de l'étude de la réaction de reformage à sec du méthane, les catalyseurs supportés sur CeO₂ ont montré une activité catalytique inférieure par rapport aux catalyseurs supportés sur Al₂O₃. Néanmoins, ces catalyseurs ont montré une plus grande résistance à la formation de carbone. L'effet de l'ajout de cérium sur le support Al₂O₃ a ensuite été étudié. L'addition de cérium a causé une destruction partielle de la structure poreuse, tout en renforçant les sites basiques faibles et augmentant l'activité catalytique des catalyseurs. Le catalyseur 15Ni/Ce-Al₂O₃ a montré une activité et une stabilité élevées pendant un test de stabilité de 12h. Trois solides supportés à base de nickel sur silices mésoporeuses (15Ni/KIT-6, 15Ni/SBA-15 et 15Ni/SBA-16) ont été synthétisées en utilisant la technique d'imprégnation humide et ensuite caractérisées. La stabilité et l'activité de ces matériaux a été étudié dans la réaction de reformage à sec du méthane. Dans les tests dynamiques, le 15Ni/SBA-16 s'est montré le plus performant en raison de ses fortes interactions métal-support et de sa forte basicité. Enfin, parmi les catalyseurs 15Ni/Ce-KIT-6, 1Ru/Ce-KIT-6 et 15Ni1Ru/Ce-KIT-6, le solide 15Ni1Ru/Ce-KIT-6 était le plus actif dans la réaction de reformage à sec du méthane et maintenait une conversion de CO₂ élevée et stable (97% pendant 12H). Le catalyseur n'a pas été désactivé malgré le dépôt de carbone graphitique lors du test de stabilité.

Simple Summary Our climate is changing and the world population is growing to an estimated 10 billion people by 2050. This may cause serious problems in global food supply, protection of the environment and safeguarding Earth’s biodiversity. To face these challenges, agriculture will have to adapt and a key element in this will be the development of “future-proof” crops. These crops will not only have to be high-yielding, but also should be able to withstand future climate conditions and will have to make very efficient use of scarce resources such as water, phosphorus and minerals. Future crops should not only sustainably give access to sufficient, nutritious, and diverse food to a worldwide growing population, but also support the circular bio-based economy and contribute to a lower atmospheric CO2 concentration to counteract global warming. Future-proofing our crops is an urgent issue and a challenging goal that only can be realized by large-scale, international research cooperation. We call for international action and propose a pan-European research and innovation initiative, the CropBooster Program, to mobilize the European plant research community and all interested actors in agri-food research and innovation to face the challenge. Abstract The realization of the full objectives of international policies targeting global food security and climate change mitigation, including the United Nation’s Sustainable Development Goals, the Paris Climate Agreement COP21 and the European Green Deal, requires that we (i) sustainably increase the yield, nutritional quality and biodiversity of major crop species, (ii) select climate-ready crops that are adapted to future weather dynamic and (iii) increase the resource use efficiency of crops for sustainably preserving natural resources. Ultimately, the grand challenge to be met by agriculture is to sustainably provide access to sufficient, nutritious and diverse food to a worldwide growing population, and to support the circular bio-based economy. Future-proofing our crops is an urgent issue and a challenging goal, involving a diversity of crop species in differing agricultural regimes and under multiple environmental drivers, providing versatile crop-breeding solutions within wider socio-economic-ecological systems. This goal can only be realized by a large-scale, international research cooperation. We call for international action and propose a pan-European research initiative, the CropBooster Program, to mobilize the European plant research community and interconnect it with the interdisciplinary expertise necessary to face the challenge.

Objective: To investigate voice quality changes of patients treated by transoral laser cordectomy (TLC) for early glottic cancer according to the type of cordectomies. Methods: A total of 164 consecutive male patients with an early glottic cancer were prospectively recruited from the Department of Otolaryngology—Head and Neck Surgery of the Georges Pompidou European Hospital. Depending on the tumor characteristics, patients benefited from type I to VI CO2 cordectomy regarding the European Laryngological Society classification. The following voice quality outcomes were pre- to postoperatively assessed: voice handicap index (VHI), perceptual grade of dysphonia, roughness, breathiness, maximum phonation time, and acoustic parameters. Results: Fifty-five patients with Tis, T1, or T2 vocal fold cancer completed the study (mean age: 61.7 years). Of these patients, 34 and 21 composed group 1 (types I-III TLC) and group 2 (types IV-VI TLC), respectively. Voice handicap index, grade of dysphonia, and breathiness significantly improved from pre- to 3- and 6-month posttreatment in group 1. In group 2, only VHI significantly improved from pre- to 3- and 6-month posttreatment. Acoustic and aerodynamic measurements did not change throughout the postoperative course. Patients with types I to III TLC exhibited better postoperative voice outcomes compared to those treated by types IV to VI TLC. Conclusion: Irrespective to the types of TLC, the subjective voice quality of patients treated by CO2 laser cordectomy for early glottic cancer significantly improved from pre- to 3- and 6-month posttreatment. The usefulness of aerodynamic and acoustic measurements as postoperative outcomes of voice quality changes remain controversial and require future studies considering multidimensional assessment of voice.

International audience

Contexte - Les conditions météorologiques extrêmes (gels, précipitations extrêmes, sécheresses automnale ou printanière) ont tendance à se multiplier, perturbant les pratiques agricoles,entraînant des pertes de rendement ou l’abandon de la culture. Les effets de la hausse des températures ou de l’allongement de l’ensoleillement sont plus marqués sur les dates de récoltepar exemple.Mais peut-on prévoir l’impact de ces changements climatiques sur les espèces adventices ?¾ effets diReCts - Les interactions entre caractéristiques climatiques, pratiques culturales et traits biologiques dechaque espèce rendent les prévisions difficiles. La hausse des températures peut avoir des effets directs sur l’aire de répartition de certaines adventices ou leur date de levée ; la hausse du taux de gaz carbonique peut favoriser les plantes en C3 ; les stress abiotiquespeuvent sélectionner les espèces les plus tolérantes.¾ effets indiReCts - La complexité de la problématique « adventices/ changement climatique » est en grande partie liée au fait que les systèmes de culture vont évoluer de façon beaucoupplus rapide qu’au cours des dernières décennies. À court et moyen termes, l’adaptation des pratiques culturales pourra dans une certaine mesure compenser les évolutions climatiques.

International audience

This research aims at developing and optimizing a powerful technological breakthrough in the CO2 capture/release treatment using Layered Double Hydroxides (LDHs) that have a strong affinity for carbonate, CO32-. The electrochemical control of the oxidation state of the multiple valence cations, constituting the lamellar sheets, is the core process. The co-precipitation of Co/Fe LDH was optimized for electrochemical cycling according to: CoII6FeIII2(CO3)(OH)16 + (x/2)CO32- ⇆ CoII(6-x)CoIII(x)FeIII2 (CO3)(1+x/2)(OH)16 + xe- The combination of X-Ray diffraction, vibrational and absorption spectroscopies as well as physical and chemical analyses provides a deep insight into Co/Fe-based LDH formation mechanism. Ferrihydrite, onto which Co2+ is adsorbed, is the key reaction intermediate in the synthesis of LDH Co/Fe. The adsorption of Co2+ is responsible for redox phenomena that induce the formation of a metastable LDH (FeII/CoIII). The evolution of this metastable material leads to the final LDH material (CoII/FeIII). The analysis of the thermal behavior of materials, by High Temperature X-ray Diffraction and by Thermo-Gravimetry coupled with Gas Chromatography, enabled to specify the formulation of the synthesized LDHs (Co3,14Fe2(OH)10,28(CO3), xH2O) and to define their operating temperature range (less than 160 °C). As part of the energy integration of the process, heat exchangers, for energy recovery or preheating of certain flows, will therefore have to be implemented for the use of Co/Fe LDH in a CO2 capture process in which hot gases can reach up to 600°C. The coupling of cyclic voltammetry (in the range 0.44 -1.41 V/SHE), quartz crystal microbalance and grazing-incidence wide-angle X-ray scattering, at Synchrotron Soleil, enabled to determine the oxidation-reduction heterogeneous kinetic constant of the CoIII/CoII redox couple constituting the LDHs brucitic layers (k°= 2.5 x 10-4 m/s, a = 0.6, ß = 0.4). The process of CO2 capture and release was implemented on LDH aqueous slurries in two-compartments electrochemical reactors. The analyzes were carried out in a NaHCO3/Na2CO3 buffer solution pH 9 (I.S 0.05M). The coupling of electrochemical measurements by electrolysis at an applied potential, and potentiometric by alkalinity titration, allowed the calculation of the efficiency of redox reactions. The percentage of electroactive Co ranges from 5 to 12%. Furthermore, experiments showed that the mass transport coefficient (km) of LDHs towards the electrode is 4.72x10-5 m/s; the electrochemical oxidation and reduction constants of cobalt are respectively 1.48x10-3 s-1 and 1.27x10-3 s-1. Under optimal cycling conditions (0.84 and 0.24 V/SHE respectively for the oxidation and reduction of Co, with a Co concentration of 0.39x10-2 M), the efficiency of the process, for one cycle of capture and release, is higher than 170 kg of CO2 per ton of LDH. This result suggests particularly interesting perspectives for the optimization of an electrolytically supported process of capture and release of CO2 using Co/Fe LDHs., Ce travail de thèse s'inscrit dans le cadre du projet ADEME CALICE "Procédé de captage et libération du CO2 assisté par électrolyse utilisant des matériaux de type brucitique". Il vise à développer une technologie de rupture dans le domaine du traitement d'effluents gazeux contenant du CO2, en vue de sa valorisation. Le procédé repose sur la modification des valencedes espèces redox actives constitutives des feuillets du matériau pour moduler sa capacité d'échange anionique et assurer le captage et la libération du CO2, sous forme d'anions inorganiques. Décrits dans la bibliographie comme matériaux capables d'assurer jusqu'à 5000 cycles électrochimiques d'oxydation et de réduction, les HDLs Co/Fe ont été sélectionnés comme matériaux d'intérêt, susceptibles d'assurer le captage et la libération des anions HCO3- et/ou CO32- ; les atomes de cobalt, aux degrés d'oxydation II et III, constituent les entités électroactives. Le mécanisme de formation des HDLs Co/Fe, par coprécipitation à pH variable, a été étudié pour des valeurs de pH comprises entre 2 et 11. La ferrihydrite, sur laquelle Co2+ s'adsorbe, est l'intermédiaire réactionnel clé de la synthèse des HDLs Co/Fe. L'adsorption de Co2+ est responsable de phénomènes d'oxydoréduction qui induisent la formation d'un HDL métastable (FeII/CoIII) dont l'évolution conduit au matériau HDL final (CoII/FeIII). L'analyse du comportement thermique des matériaux a permis de préciser la formulation des HDLs synthétisés (Co3,14Fe2(OH)10,28(CO3), xH2O) et de définir leur domaine thermique d'application potentielle (inférieur à 160°C) en vue de leur utilisation dans un procédé de capture du CO2 contenu dans des gaz chauds issus d'installations industrielles dont la température peut atteindre 600°C. Dans le cadre de l'intégration énergétique du procédé, des échangeurs thermiques, pour la récupération d'énergie ou le préchauffage de certains flux, devront par conséquent être mis en œuvre. Le couplage des techniques électrochimiques, gravimétrique et de diffraction de rayons X, au synchrotron Soleil, a permis de déterminer le potentiel standard apparent du couple CoIII/CoII (1,23 V/ESH), la constante cinétique d'oxydo-réduction du couple CoIII/CoII constitutifs des feuillets du HDL (k° = 2,5 x10-4 m/s, a = 0,6, b = 0,4) et d'analyser les mécanismes physico-électrochimiques associés à l'oxydation de CoII et à la réduction de CoIII de telle sorte que : CoII6CoIIIFeIII2[(OH)16][CO3], zH2O + 0,5x CO32- ⇆ CoII6-xCoIIIxFeIII2[(OH)16][CO3](1+0,5x),(z-z')H2O + z'H2O + xe- Le procédé de captage et libération du CO2 a été mis en œuvre sur des solides de type HDLs utilisés sous forme de pulpes dans des réacteurs électrochimiques à deux compartiments, en milieu aqueux. Les analyses ont été conduites dans une solution tampon NaHCO3/Na2CO3 à pH 9 (FI 0,05M). Le couplage des électrolyses à potentiel imposé et du suivi de l'alcalinité a permis de calculer le rendement des réactions redox. Le pourcentage de Co redox actif est compris entre 5 et 12%. Le coefficient de transport de matière électroactive vers la surface de l'électrode, km, est égal à 4,72x10-5 m/s ; les constantes réactionnelles électrochimiques d'oxydation et de réduction du cobalt, qui quantifient l'efficacité de l'interaction matière/électrode, sont respectivement égales à 1,48x10-3 s-1 et 1,27x10-3 s-1. Dans les conditions optimales de cyclage (0,84 et 0,24 V/ESH respectivement pour l'oxydation et la réduction de Co, avec une concentration de Co de 4 10-3 M), le rendement du procédé est supérieur à 170 kg de CO2 par tonne de HDL et par cycle. Ce résultat laisse présager des perspectives intéressantes pour l'optimisation d'un procédé, assisté par électrolyse, de capture et de libération du CO2 par des HDLs Co/Fe.

TanSat is the 1st Chinese carbon dioxide (CO2) measurement satellite, launched in 2016. In this study, the University of Leicester Full Physics (UoL‐FP) algorithm is implemented for TanSat nadir mode XCO2 retrievals. We develop a spectrum correction method to reduce the retrieval errors by the online fitting of an 8th order Fourier series. The spectrum‐correction model and its a priori parameters are developed by analyzing the solar calibration measurement. This correction provides a significant improvement to the O2 A band retrieval. Accordingly, we extend the previous TanSat single CO2 weak band retrieval to a combined O2 A and CO2 weak band retrieval. A Genetic Algorithm (GA) has been applied to determine the threshold values of post‐screening filters. In total, 18.3% of the retrieved data is identified as high quality compared to the original measurements. The same quality control parameters have been used in a footprint independent multiple linear regression bias correction due to the strong correlation with the XCO2 retrieval error. Twenty sites of the Total Column Carbon Observing Network (TCCON) have been selected to validate our new approach for the TanSat XCO2 retrieval. We show that our new approach produces a significant improvement on the XCO2 retrieval accuracy and precision when compared to TCCON with an average bias and RMSE of −0.08 ppm and 1.47 ppm, respectively. The methods used in this study can help to improve the XCO2 retrieval from TanSat and subsequently the Level‐2 data production, and hence will be applied in the TanSat operational XCO2 processing., Key Points First using O2 A and 1.61 um CO2 band approaching TanSat XCO2 retreivalDevelopment a method on radiometric correction of TanSat L1B data in O2 A and 1.61 um CO2 Validation of new TanSat retrieval against TCCON and recived significant improved results compare to previously retrieval

International audience; The low hydrate formation rate, the low gas selectivity and the low gas storage capacity have been proved as the major bottlenecks for a successful application of CO2 capture process using gas hydrates. Aluminum nanoparticles has an important specific area, which can lead to high heat and mass transfer efficiency, large gas dissolution, fast nucleation, and formation rate. In this work, CO2-CH4 hydrate formation with and without aluminum nanoparticles was investigated. Herein, the promoting mechanism and effects of aluminum nanoparticles concentrations for an initial pressure of 4.0 MPa and temperature of 274.15 K on CO2-CH4 hydrate formation process were studied experimentally. The obtained results showed that the nanoparticles of Al, beyond a certain minimum concentration, slightly enhanced the gas dissolution, notably improved the gas consumption by crystallization and dramatically improved the gas capture selectivity. These positive effects were observed at the beginning of the process and after that became negative.

International audience; The present work aims at applying Machine Learning approaches to predict CO2 viscosity at different thermodynamical conditions. Various data-driven techniques including multilayer perceptron (MLP), gene expression programming (GEP) and group method of data handling (GMDH) were implemented using 1124 experimental points covering temperature from 220 to 673 K and pressure from 0.1 to 7960 MPa. Viscosity was modelled as function of temperature and density measured at the stated conditions. Four backpropagation-based techniques were considered in the MLP training phase; Levenberg-Marquardt (LM), bayesian regularization (BR), scaled conjugate gradient (SCG) and resilient backpropagation (RB). MLP-LM was the most fit of the proposed models with an overall root mean square error (RMSE) of 0.0012 mPa s and coefficient of determination (R2) of 0.9999. A comparison showed that our MLP-LM model outperformed the best preexisting Machine Learning CO2 viscosity models, and that our GEP correlation was superior to preexisting explicit correlations.

International audience; In order to develop a new process to eliminate acid gases from natural gas, it is important to consider phase equilibrium properties. New solid-liquid equilibrium data were determined concerning the ternary system CO 2 + H 2 S + CH 4. The experimental technique is based on visual synthetic method. The new experimental data were compared to predictions given by the Predictive Peng-Robinson equation of state (PPR78), PSRK UNIFAC, Peng-Robinson with Huron-Vidal mixing rules and GERG 2008 models coupling with classical approach or Jager and Span for solid phase. The results have shown that the model selected for the fluid phase has more impact that the model considered for the solid phase. New binary interaction parameters of Peng-Robinson equation of state were fitted only on our experimental data and it was found that the obtained values are very different from the value used for Vapor Liquid Equilibrium computation.

International audience; The oxidative dry reforming of CH4 (ODRM) was studied at 500-800°C in harsh conditions (CH4/CO2/O2/N2 = 1:0.7:a:N2 with 20% of CH4, 96,000 mLh-1gcat-1 and a varying from 0 up to 0.5) on CeNiXAl0.5HZOY (0.5 ≤ x ≤ 5) nano-oxyhydride catalysts. At low temperature (500-600°C), the conversion of CH4 reaches the thermodynamic limit while those of CO2 overcomes the predicted value in particular at 500°C. At 600°C with an O2/CH4 ratio of 0.3, the CeNi2Al0.5HZOY catalyst allows getting CH4 and CO2 conversions of about 63% and 50 %, respectively, and a H2/CO ratio of about 1.3, without carbon formation. The physico-chemical characterizations performed before and after test show the existence of strong interactions existing between Ni2+ cations with other cations and the presence of nano-oxyhydride compound. The mixed oxide based nano-materials corresponding to hydride reservoirs with the presence of Ni2+ cations are shown to be highly active, selective and stable catalysts.

International audience; Aviation emissions are estimated to contribute to 5 % (2–14 %, 90 % likelihood range) of the anthropogenic radiative forcing of climate with an uncertainty dominated by non-CO2 effects (Lee et al., 2010). Even if the level of scientific understanding is considered to be high by the IPCC for present-day aviation CO2 impact compared to other non-CO2 forcers (e.g. ozone, aerosols and contrails), the future (2050) aviation CO2 climate impact remains highly uncertain. One major reason of these varying estimates is linked to the inherent assumptions made in the development of future global emission scenarios such as the one from international aviation (Boucher et al., 2016). Hence, using the compact Earth System Model (ESM) OSCARv2.2 we quantify the climate impact of present and future (up to 2100) civil aviation carbon dioxide (CO2) emissions using eight aviation scenarios ranging from 386 Mt CO2/year (Factor 2 scenario) to 2338 Mt CO2/year (ICAO/CAEP scenario) in 2050. This approach will allow quantifying the uncertainty due to the difficulty to estimate the future mitigation effort. Another originality of the paper is that the influence of other emission sectors is evaluated using two background Representative Concentrations Pathways (RCP2.6 and RCP6.0). Results show that in 2050, on a climate trajectory in line with the Paris Agreement limiting the global warming below 2 °C (RCP2.6), the impact of the aviation CO2 emissions ranges from 26 ± 2 mK (1.4 % of the total global warming associated with all fossil fuel emissions) for an ambitious mitigation strategy scenario (Factor 2) to 39 ± 4 mK (2.0 % of the total global warming) for the least ambitious mitigation scenario of the study (ICAO-CAEP). On the longer term, if no significant emission mitigation is implemented for the aviation sector, the associated warming could further increase and reach a value of 100 mK in 2100 (ICAO/CAEP), which corresponds to 5.2 % of the total global temperature increase from total fossil fuel CO2 emissions under RCP2.6.

International audience; Interest and effort in re-introducing civil supersonic transport (SST) airplanes as a means of travel have surged in the past decade. Current major endeavours are underway for both commercial and business supersonic vehicles. The value proposition for these aircraft exists for high-networth individuals and business-class travellers who value time savings more than the potential cost associated with supersonic travel. Although these new SSTs in development will be more fuel-efficient than the SSTs of the past, they will have higher relative fuel burn (FB) than current subsonic aircraft flying the same routes. Burning more fuel while having less passengers (pax) on board per trip yields significantly higher FB per passenger for these operations. However, the relatively small market capturable by supersonic commercial operations means that in the broader scope of global aviation, the effect of increased FB per pax on fleet-level carbon dioxide (CO2) emissions is unknown. In addition, due to uncertainties in the effectiveness of sonic boom reduction technologies,it remains unclear whether supersonic over-land flight will be permitted in the future. Part I of this twopart study aims to formulate a methodology that employs a bottom-up approach for estimating the demand of supersonic commercial operations in coming decades, using only publicly available subsonic baseline-fleet data. The constraints and limitations identified while using publicly available data is key to understanding the data requirements for executing market assessment studies of this type. Part II of two-part study will fill many of the gaps identified in this public-data-only Part I, in order to refine the study process and results. After proposing the bottom-up methodology for estimating demand, the procedure is implemented and the environmental impact of the estimated market is determined. The results identify a supersonic commercial flight demand of 47 to 786 daily, global flights in 2035, growing to 71 to 1,180 daily, global flights in 2050, corresponding to low and high demand scenarios, respectively. These fleets will contribute an approximate 1.96 to 28.61 megatonnes (MT) of CO2 to global aviation emissions in 2035, growing to 3.01 to 43.08 MT of CO2 in 2050. These emissions in 2035 and 2050 represent a 0.21 to 3.12% and 0.33 to 4.69% increase in CO2 emissions with respect to the 2018global subsonic commercial aviation fleet.

This study investigates and compares soil moisture and hydrology projections of broadly used land models with permafrost processes and highlights the causes and impacts of permafrost zone soil moisture projections. Climate models project warmer temperatures and increases in precipitation (P) which will intensify evapotranspiration (ET) and runoff in land models. However, this study shows that most models project a long-term drying of the surface soil (0–20 cm) for the permafrost region despite increases in the net air–surface water flux (P-ET). Drying is generally explained by infiltration of moisture to deeper soil layers as the active layer deepens or permafrost thaws completely. Although most models agree on drying, the projections vary strongly in magnitude and spatial pattern. Land models tend to agree with decadal runoff trends but underestimate runoff volume when compared to gauge data across the major Arctic river basins, potentially indicating model structural limitations. Coordinated efforts to address the ongoing challenges presented in this study will help reduce uncertainty in our capability to predict the future Arctic hydrological state and associated land–atmosphere biogeochemical processes across spatial and temporal scales.

Periodic Mesoporous Organosilica Nanoparticles (PMONPs) are nanoparticles of high interest for nanomedicine applications. These nanoparticles are not composed of silica (SiO2). They belong to hybrid organic&ndash, inorganic systems. We considered using these nanoparticles for CO2 release as a contrast agent for High Intensity Focused Ultrasounds (HIFU). Three molecules (P1&ndash, P3) possessing two to four triethoxysilyl groups were synthesized through click chemistry. These molecules possess a tert-butoxycarbonyl (BOC) group whose cleavage in water at 90&ndash, 100 &deg, C releases CO2. Bis(triethoxysilyl)ethylene E was mixed with the molecules Pn (or not for P3) at a proportion of 90/10 to 75/25, and the polymerization triggered by the sol-gel procedure led to PMONPs. PMONPs were characterized by different techniques, and nanorods of 200&ndash, 300 nm were obtained. These nanorods were porous at a proportion of 90/10, but non-porous at 75/25. Alternatively, molecules P3 alone led to mesoporous nanoparticles of 100 nm diameter. The BOC group was stable, but it was cleaved at pH 1 in boiling water. Molecules possessing a BOC group were successfully used for the preparation of nanoparticles for CO2 release. The BOC group was stable and we did not observe release of CO2 under HIFU at lysosomal pH of 5.5. The pH needed to be adjusted to 1 in boiling water to cleave the BOC group. Nevertheless, the concept is interesting for HIFU theranostic agents.

International audience; Plants regularly encounter abiotic constraints, and plant response to stress has been a focus of research for decades. Given increasing global temperatures and elevated atmospheric CO2 levels and the occurrence of water stress episodes driven by climate change, plant biochemistry, in particular, plant defence responses, may be altered significantly. Environmental factors also have a wider impact, shaping viral transmission processes that rely on a complex set of interactions between, at least, the pathogen, the vector, and the host plant. This review considers how abiotic stresses influence the transmission and spread of plant viruses by aphid vectors, mainly through changes in host physiology status, and summarizes the latest findings in this research field. The direct effects of climate change and severe weather events that impact the feeding behaviour of insect vectors as well as the major traits (e.g., within-host accumulation, disease severity and transmission) of viral plant pathogens are discussed. Finally, the intrinsic capacity of viruses to react to environmental cues in planta and how this may influence viral transmission efficiency is summarized. The clear interaction between biotic (virus) and abiotic stresses is a risk that must be accounted for when modelling virus epidemiology under scenarios of climate change.

International audience; Le dioxyde de carbone (CO2) n'a été formellement identifié que durant la seconde moitié du xviiie siècle. Mais, depuis la Renaissance, on pouvait constater sa nocivité dans une ­anfractuosité volcanique située près de Naples : des animaux, le plus souvent des chiens, étaient soumis au gaz insidieux qui s y accumulait, afin de satisfaire la curiosité des voyageurs. Ainsi naquit le mythe de la « Grotte du chien », bientôt répliquée avec succès à Royat-Chamalières. C'est l'incroyable histoire de cette attraction pluriséculaire, ancêtre des dispositifs de vulgarisation scientifique, que retrace cet ouvrage.

The carbonylation reaction provides access to many organic molecules with high added value, but involves the use of carbon monoxide, a flammable and highly toxic gas. On the contrary, carbon dioxide is a non-toxic, inexpensive, non-flammable gas, and its use as a raw material to produce CO in situ is therefore an interesting path, both from a safety and environmental point of view. The objective of this thesis was therefore to convert CO2 into CO by plasma, then to use the CO formed to carry out a carbonylation reaction, both steps in microfluidic systems. First, the palladium-catalysed aminocarbonylation reaction was studied in a gas/liquid microreactor, and the operating parameters were optimized to obtain a total conversion of the substrate to amide. Secondly, the decomposition of CO2 into CO in a plasma microreactor was optimized to maximize the volume concentration of CO formed. Finally, the serial combination of the two microreactors allowed the synthesis of the amide starting from CO2 with a conversion of 70%, in a total residence time of less than 2 min, at a temperature of 50 °C and atmospheric pressure. Thus, the association of microfluidics and plasma is proving to be a very promising route for the rapid and clean organic synthesis of carbonyl molecules. Direct aminocarbonylation, without catalyst and by plasma activation, has also been explored, and the first results open up encouraging prospects., La réaction de carbonylation permet d'accéder à de nombreuses molécules organiques à forte valeur ajoutée, mais implique l'utilisation de monoxyde de carbone, un gaz inflammable et hautement toxique. Au contraire, le dioxyde de carbone est un gaz non toxique, peu coûteux, ininflammable, et son utilisation comme matière première pour produire du CO in situ est donc une voie intéressante, tant d’un point de vue sécurité qu’environnemental. L’objectif de cette thèse a donc été de convertir le CO2 en CO par plasma, puis d'utiliser le CO formé pour réaliser une réaction de carbonylation, le tout en systèmes microfluidiques. Dans un premier temps, la réaction d’aminocarbonylation catalysée au palladium a été étudiée dans un microréacteur gaz/liquide, et les paramètres opératoires ont été optimisés de manière à obtenir une conversion totale du substrat en amide. Dans un deuxième temps, la décomposition du CO2 en CO dans un microréacteur plasma a été optimisée de façon à maximiser la concentration volumique de CO formé. Finalement, la combinaison en série des deux microréacteurs a permis la synthèse de l’amide en partant du CO2 avec une conversion de 70%, en un temps de séjour total inférieur à 2 min, à une température de 50°C et à pression atmosphérique. Ainsi, l'association de la microfluidique et du plasma se révèle être une voie très prometteuse pour la synthèse organique rapide et propre de molécules carbonylées. L’aminocarbonylation directe, sans catalyseur et par activation plasma, a été également explorée, et les premiers résultats ouvrent des perspectives encourageantes.

The utilization of cold plasmas in combination with an heterogeneous catalyst has recently proven to boost the kinetically impeded CO2 hydrogenation reaction at low temperatures, i.e. without any source of external heating. Nevertheless, there is a complete lack of understanding about the real effect of the plasma, as well as on its coupling to a catalytic system. Moreover, the cylindrical-shaped fixed bed reactors tested so far do not allow a proper control of the physical phenomena, i.e. heat-energy and mass transfer, hindering the industrial application of this hybrid process. The present PhD subject proposes the construction of milli-structured reactors for CO2 hydrogenation. By means of an optimized distribution of the plasma discharge, this configuration will permit the accurate diagnosis of the interaction between the plasma and the catalytic solid phase, and thus, a better understanding of the bulk effects of the coupled plasma-catalytic phenomena. In this sense, the energy practically provided by the plasma can be tailored to fit the requirements of the catalytic reaction. Furthermore, a better control of heat and mass transfer will be gained through the milli-structuration of the catalytic system., L'utilisation de plasmas froids en combinaison avec un catalyseur hétérogène a récemment permis d'accélérer significativement la réaction d'hydrogénation de CO2 à basses températures, c'est-à-dire sans aucune source de chauffage externe. Néanmoins, il existe un manque total de compréhension de l'effet réel du plasma, ainsi que de son couplage à un système catalytique. En outre, les réacteurs conventionnels à lit fixe testés jusqu'à présent ne permettent pas un contrôle correct des phénomènes physiques, en particuliers les transferts de chaleur et de matière, ce qui freine l'application industrielle de ce procédé hybride. Le présent sujet de doctorat propose la construction de réacteurs milli-structurés pour l'hydrogénation du CO2. Grâce à une distribution optimisée de la décharge du plasma, cette configuration permettra un diagnostic précis de l'interaction entre le plasma et la phase solide catalytique, et donc une meilleure compréhension du couplage plasma-catalyse. Egalement, ce dispositif permettra de mieux adapter l'énergie fournie par le plasma aux besoins de la réaction catalytique. Enfin, un meilleur contrôle de la chaleur et du transfert de masse sera obtenu grâce à la milli-structuration du système catalytique.