Evolution of European carnivorous mammal assemblages through the Palaeogene

The rise of Carnivora (Mammalia: Laurasiatheria) is an important evolutionary event that changed the structure of terrestrial ecosystems, starting at the dawn of the Eocene, 56 Mya. This radiation has been mainly analysed in North America, leaving the evolution of carnivoran diversity in other regions of the globe poorly known. To tackle this issue, we review the evolution of terrestrial carnivorous mammal diversity (Mesonychidae, Oxyaenidae, Hyaenodonta and Carnivoramorpha) in Europe. We reveal four episodes of intense faunal turnovers that helped establish the dominance of carnivoramorphans over their main competitors. We also identify two periods of general endemism. The remaining time intervals are characterized by dispersals of new taxa from North America, Asia and Africa. The European Palaeogene carnivorous mammal fauna appears to have been almost constantly in a transient state, strongly influenced by dispersals. Many of the bioevents we highlight for European carnivorous mammals are probably best seen as ecosystem-wide responses to environmental changes. In contrast to the North American record, European hyaenodonts remain more diverse than the carnivoramorphans for the entire Eocene. The replacement of hyaenodonts by carnivoramorphans as the most diverse and dominant predators only occurred after the ‘Grande Coupure’ at 33 Mya, about 16 Myr later than in North America

Predisposal conditioning, treatment, and performance assessment of radioactive waste streams

Before the final disposal of radioactive wastes, various processes can be implemented to optimise the waste form. This can include different chemical and physical treatments, such as thermal treatment for waste reduction, waste conditioning for homogenisation and waste immobilisation for stabilisation prior to packaging and interim storage. Ensuring the durability and safety of the waste matrices and packages through performance and condition assessment is important for waste owners, waste management organisations, regulators and wider stakeholder communities. Technical achievements and lessons learned from the THERAMIN and PREDIS projects focused on low- and intermediate-level waste handling is shared here. The recently completed project on Thermal Treatment for Radioactive Waste Minimization and Hazard Reduction (THERAMIN) made advances in demonstrating the feasibility of different thermal treatment techniques to reduce volume and immobilise different streams of radioactive waste (LILW) prior to disposal. The Pre-Disposal Management of Radioactive Waste (PREDIS) project addresses innovations in the treatment of metallic materials, liquid organic waste and solid organic waste, which can result from nuclear power plant operation, decommissioning and other industrial processes. The project also addresses digitalisation solutions for improved safety and efficiency in handling and assessing cemented-waste packages in extended interim surface storage

Influence de la radiolyse alpha sur la dissolution de UO2 en milieu réducteur

Dans le cadre des recherches sur le stockage du combustible nucléaire usé en site géologique profond, nous avons évalué la vitesse de dissolution, R, de UO2 sous forme colloïdale en conditions réductrices et soumis à un rayonnement a. Nous avons constaté que : - En absence d'irradiation, la solubilité des colloïdes de UO2 est conforme aux données de la littérature pour des matériaux plus volumineux, ~ 10-9 M dans NaCl 1M, pH 6. - Sous un flux de particules a provenant d'un cyclotron, R et [H2O2] diminuent avec la quantité de solide irradié et augmentent avec le débit de dose. La simulation d'irradiation par ajout d'H2O2 laisse supposer que cette espèce radiolytique est suffisante pour représenter les mécanismes de dissolution lors de l'irradiation par un faisceau a. - En cas de dopage d'UO2 avec l'émetteur a (225Ac) les valeurs de R sont cohérentes avec la littérature pour des solides de même activité spécifique, bien que le débit de dose soit 105 fois plus faible.As part of research program for the performance of spent nuclear fuel in geological disposal, we have determined the dissolution rate, R, of UO2 colloids under reducing conditions and a-radiation. We have observed that : - Without irradiation, the solubility of UO2 colloids was in good agreement with literature data on bulk material, ~10-9 M in NaCl 1M, pH 6. - Under the a particles beam of a cyclotron, R and [H2O2] decreases with the quantity of irradiated solid and increases with the dose rate. The simulation of the radiolysis experiments by the addition of H2O2 allowed to conclude that this radiolytic specie was sufficient to represent the dissolution mechanism. - In case of doping of UO2 with the emitter 225Ac the R-values were in good agreement with literature for solids with the same specific activity despite a dose rate 105 times lower.NANTES-BU Sciences (441092104) / SudocSudocFranceF

Pyrite oxidation by nitrate and nitrite in sodium bicarbonate solution under anoxic and abiotic conditions

Pyrite reactivity with nitrate and nitrite was assessed in long-term batch tests to assess its possible oxidation in anoxic conditions at pH 8.5, at room temperature and atmospheric pressure. This was done in the frame of compatibility studies of nitrate-containing radioactive waste with a pyrite-containing clay host rock for geological disposal. Abiotic pyrite suspensions were prepared under inert atmosphere in 15 mM bicarbonate medium, as this simulates the inorganic carbon and pH conditions in the pore water of Boom Clay, which is a potential host rock for geological disposal in Belgium. Two forms of pyrite powder were used, formed via different genetic pathways and exhibiting a different morphology, namely pyrite obtained by crushing a large crystal cluster and pyrite extracted from Boom Clay by flotation. The reactivity of these two pyrite forms with nitrate and nitrite is reported and compared. Overall, after 2–2.5 years under abiotic conditions and inert atmosphere, no significant reaction between crushed pyrite and nitrate was detected, while a very limited reaction was observed between Boom Clay pyrite and nitrate. Between pyrite and nitrite, which is known to be more reactive than nitrate, a slow reaction took place for both forms of pyrite, with no significantly higher reactivity with the Boom Blay pyrite. The variability between the replicates of Boom Clay pyrite were also larger than for crushed pyrite. Overall, nitrate and nitrite induced a very limited, if any, oxidation reaction of the pyrite powders. These observations are important in assessing the safety of geological disposal of nitrate-containing radioactive waste

Surface-mediated redox activity in the Pyrite – Nitrate/nitrite – Hydrogen system under conditions relevant for the geological disposal of bituminized waste in Boom Clay

The reactivity of a system with pyrite powder, nitrate or nitrite, and hydrogen in a 15 mM sodium bicarbonate solution was assessed over the course of 2 years in the frame of compatibility studies of nitrate-containing bituminized radioactive waste with the host rock for final disposal. A series of batch tests was performed with pyrite suspensions in bicarbonate solution to which nitrate or nitrite was added before filling the headspace of the recipient with a constant, and non-renewed, volume of 100% pure hydrogen gas (initial PH2 1.5 bara). Under anoxic conditions and at room temperature, hydrogen reacted readily with nitrate and nitrite in the presence of pyrite powder. Ammonia was formed while hydrogen was consumed. Based on the XPS analyses of the pyrite surface and the absence of dissolved pyrite oxidation products, the pyrite surface was not oxidized. Moreover, no reaction between hydrogen and nitrate or nitrite was observed in the absence of pyrite. This reaction was thus clearly mediated by the Boom Clay pyrite surface. The reducing atmosphere kept the pyrite surface intact and protected it from precipitation of carbonates from the medium, thus effectively preventing pyrite surface deactivation, previously observed under anoxic conditions in the absence of H2. Overall, only 5% of the 0.1 M of nitrate that was added to the tests, was reduced over the course of 2 years, without complete consumption of H2. Nitrite was added in a lower concentration of 0.05 M, but was more reactive: about 50% of nitrite was reduced, producing stoichiometric amounts of ammonia, and nearly depleting the H2 in the gas phase. The possible consequences of these processes for the final repository performance are also discussed

CARNAGES – Une analyse critique du succès des Canivores (Mammalia)

Pourquoi sommes-nous aujourd'hui entourés par un seul groupe de mammifères carnassiers (les Carnivora), alors qu'au moins trois autres groupes de mammifères placentaires (Hyaenodonta, Mesonychia, Oxyaenidae) étaient en compétition avec les carnivores il y a 50 millions d'années ? Ces quatre groupes de mammifères partagent une caractéristique importante: la présence de dents spécialisées dédiées à la « découpe » de la viande, les dents carnassières. Traditionnellement, leur présence/absence ainsi que leur position dans la mâchoire ont été considérées comme des caractéristiques cruciales pour discriminer les différents groupes de mammifères carnassiers. Depuis les années 1990, les paléontologues ont étudié en détail le succès des carnivores ainsi que leurs adaptations clés. Il est ainsi apparu que les Carnivora ont surpassé, en Amérique du Nord, les Hyaenodonta, les Mesonychia et les Oxyaenidae durant l'Éocène, en particulier aux alentours de 50 millions d'années, lorsque les carnivores ont augmenté en nombre et se sont diversifiés. Des études portant sur l'écomorphologie des mammifères carnassiers ont révélé que les carnivores ont vraisemblablement réussi grâce à la position antérieure des dents carnassières par rapport aux autres mammifères carnassiers. Il a en effet été suggéré que le succès de l'évolution des carnivores pouvait résulter de la vaste gamme d'adaptations dentaires (c'est-à-dire une grande variété de régimes) conférée par cette position particulière de leurs dents carnassières. Afin de tester cette hypothèse, nous avons analysé la richesse spécifique des mammifères carnassiers européens ainsi que l’évolution de leur masse corporelle durant le Paléogène. Étonnamment, notre enquête suggère que les résultats de cette compétition sont diamétralement opposés en Amérique du Nord et en Europe : les carnivores ne se sont pas « imposés » en Europe dès l'Éocène inférieur. Il ressort, en outre, que la « Grande Coupure de Stehlin » marque, en Europe, le début de la domination des carnivores sur les autres mammifères carnassiers.CARNAage

Evolution of European carnivorous mammal assemblages through the Palaeogene

The rise of Carnivora (Mammalia: Laurasiatheria) is an important evolutionary event that changed the structure of terrestrial ecosystems, starting at the dawn of the Eocene, 56 Mya. This radiation has been mainly analysed in North America, leaving the evolution of carnivoran diversity in other regions of the globe poorly known. To tackle this issue, we review the evolution of terrestrial carnivorous mammal diversity (Mesonychidae, Oxyaenidae, Hyaenodonta and Carnivoramorpha) in Europe. We reveal four episodes of intense faunal turnovers that helped establish the dominance of carnivoramorphans over their main competitors. We also identify two periods of general endemism. The remaining time intervals are characterized by dispersals of new taxa from North America, Asia and Africa. The European Palaeogene carnivorous mammal fauna appears to have been almost constantly in a transient state, strongly influenced by dispersals. Many of the bioevents we highlight for European carnivorous mammals are probably best seen as ecosystem-wide responses to environmental changes. In contrast to the North American record, European hyaenodonts remain more diverse than the carnivoramorphans for the entire Eocene. The replacement of hyaenodonts by carnivoramorphans as the most diverse and dominant predators only occurred after the ‘Grande Coupure’ at 33 Mya, about 16 Myr later than in North America

Predisposal conditioning, treatment, and performance assessment of radioactive waste streams

Before the final disposal of radioactive wastes, various processes can be implemented to optimise the waste form. This can include different chemical and physical treatments, such as thermal treatment for waste reduction, waste conditioning for homogenisation and waste immobilisation for stabilisation prior to packaging and interim storage. Ensuring the durability and safety of the waste matrices and packages through performance and condition assessment is important for waste owners, waste management organisations, regulators and wider stakeholder communities. Technical achievements and lessons learned from the THERAMIN and PREDIS projects focused on low- and intermediate-level waste handling is shared here. The recently completed project on Thermal Treatment for Radioactive Waste Minimization and Hazard Reduction (THERAMIN) made advances in demonstrating the feasibility of different thermal treatment techniques to reduce volume and immobilise different streams of radioactive waste (LILW) prior to disposal. The Pre-Disposal Management of Radioactive Waste (PREDIS) project addresses innovations in the treatment of metallic materials, liquid organic waste and solid organic waste, which can result from nuclear power plant operation, decommissioning and other industrial processes. The project also addresses digitalisation solutions for improved safety and efficiency in handling and assessing cemented-waste packages in extended interim surface storage

Predisposal conditioning, treatment, and performance assessment of radioactive waste streams

International audienceBefore the final disposal of radioactive wastes, various processes can be implemented to optimise the waste form. This can include different chemical and physical treatments, such as thermal treatment for waste reduction, waste conditioning for homogenisation and waste immobilisation for stabilisation prior to packaging and interim storage. Ensuring the durability and safety of the waste matrices and packages through performance and condition assessment is important for waste owners, waste management organisations, regulators and wider stakeholder communities. Technical achievements and lessons learned from the THERAMIN and PREDIS projects focused on low- and intermediate-level waste handling is shared here. The recently completed project on Thermal Treatment for Radioactive Waste Minimization and Hazard Reduction (THERAMIN) made advances in demonstrating the feasibility of different thermal treatment techniques to reduce volume and immobilise different streams of radioactive waste (LILW) prior to disposal. The Pre-Disposal Management of Radioactive Waste (PREDIS) project addresses innovations in the treatment of metallic materials, liquid organic waste and solid organic waste, which can result from nuclear power plant operation, decommissioning and other industrial processes. The project also addresses digitalisation solutions for improved safety and efficiency in handling and assessing cemented-waste packages in extended interim surface storage