HAL-BRGM, les publications scientifiques en libre accès du BRGM
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Thermodynamic study of the ternary system CoSO4-NiSO4-H2O
No full textInternational audienceCobalt sulfate and nickel sulfate are two compounds used to produce lithium-ion batteries (LiBs), alloys or mixed crystals of CoxNi1-xSO4•6H2O, which have applications in photonics as UV bandpass filters [1] . While processes to recycle both compounds from scraps are already established, chemical behavior of their electrolytes in brines is still poorly described.This study aims to investigate the chemical behavior of the CoSO4-NiSO4-H2O system, combining experimental and modeling approaches to improve the thermodynamic description of the system in the temperature range between 10 and 50°C. In the first step, the binary systems NiSO4-H2O and CoSO4-H2O were investigated in this temperature range. Then, the 25°C isothermal section of the ternary system was determined using a homemade apparatus conceived at the SMS laboratory named D.I.T.A. (Discontinuous Isoperibolic Thermal Analysis) [2] . This allowed us to determine the chemical composition of the partial solid solution CoxNi1-xSO4•6H2O at 25°C. On the modeling part, previous Pitzer descriptions of NiSO4-H2O and CoSO4-H2O binary systems [3,4] were combined with the experimental data acquired in this study to extend the model's applicability to the ternary system NiSO4-CoSO4-H2O. This model includes a thermodynamic description of the solid solution. Calculations were done with the geochemical software PheeSCALE, which is dedicated to saline systems [5]
Stability and rheological characterization of colloidal gas aphrons: influence of xanthan gum and sodium dodecyl sulfate
No full textInternational audienceThis study explores the stability and rheological properties of colloidal gas aphrons (CGAs) prepared with varying concentrations of xanthan gum (XG) and sodium dodecyl sulfate (SDS). Static stability was assessed by monitoring CGA volume changes over time in a graduated cylinder, while dynamic flow behavior was analyzed using a rotational rheometer to measure yield stress and viscosity at different shear rates. Rheological models were employed to characterize CGA behavior. The results showed that increasing the concentrations of XG and SDS enhanced the structural stability and viscoelastic properties of CGAs. The CGAs exhibited non-Newtonian fluid behavior, which the Herschel-Bulkley-Papanastasiou model accurately described. Yield stress and viscosity increased with higher XG concentrations, demonstrating the system’s ability to maintain high viscosity at low shear rates while exhibiting shear-thinning behavior at higher shear rates. An optimal combination of XG and SDS concentrations was identified, which improved CGA stability, prolonged liquid retention, and minimized bubble coalescence. These findings provide important insights into how CGAs remain stable and flow. This knowledge will help in using CGAs in different industries and environmental processe
Reconstruction of Effective Cross-Sections from DEMs and Water Surface Elevation
No full textInternational audienceKnowledge of river bathymetry is crucial for accurately simulating river flows and floodplain inundation. However, field data are scarce, and the depth and shape of the river channels cannot be systematically observed via remote sensing. Therefore, an efficient methodology is necessary to define effective river bathymetry. This research reconstructs the bathymetry from existing global digital elevation models (DEMs) and water surface elevation observations with minimum human intervention. The methodology can be considered a 1D geometric inverse problem, and it can potentially be used in gauged or ungauged basins worldwide. Nine global DEMs and two sources of water surface elevation (in situ and remotely sensed) were analyzed across two study areas. Results highlighted the importance of preprocessing cross-sections to align with water surface elevations, significantly improving discharge estimates. Among the techniques tested, one that combines the slope-break concept with the principles of mass conservation consistently provided robust discharge estimates for the different DEMs, achieving good performance in both study areas. Copernicus and FABDEM emerged as the most reliable DEMs for accurately representing river geometry. Overall, the proposed methodology offers a scalable and efficient solution for cross-section reconstruction, supporting global hydraulic modeling in data-scarce regions
Qualité des sols et zéro artificialisation nette (ZAN): développements méthodologiques sur Rennes Métropole (France)
No full textInternational audienceSoil is a limited resource under pressure due to anthropic activities and climate change. Therefore, it is important to take it into account in territorial spatial planning, to preserve best soils and restore some degraded ones. Rennes Metropolis considers that No net land take objective cannot be dissociated from land degradation neutrality. In this frame, it has the ambition to take soils into account in a quantitative but also in a qualitative way, by developing a spatial tool able to assess the performances of planning scenarios. The objective here is to present the qualitative approach of soils that was developed within the QuaSoZan project to feed the tool under construction. The approach considers that soil ecological multifunctionality is a way to represent soil quality, which may be degraded by artificialisation, and especially sealing, as well as by contamination. To map soil multifunctionality, the French MUSE method was adapted, to fill the lack of knowledge on urban areas and gain precision. Four indicators of ecological functions were assessed: carbon storage (C), biodiversity storage (B), infiltration capacity (I) and agronomic value (A) of soils. A downscaled version of the regional soil map (50 m large cells) and associated intrinsic soil characteristics (eg. texture, pH, coarse elements) extracted from the regional soil database were used to assess the agronomic value of soils. Extrapolation to the urban area considered a slight alteration of soil agronomic value on vegetated zones. An existing layer of the soil infiltration capacity was used. A poor agronomic value and infiltration capacity are considered in sealed areas. The carbon and biodiversity storage use a relationship between land use and regional and national statistics respectively. The assessed soil multifunctionality is derived from the combination of the 4 soil ecological functions indicators, by summing the score obtained for each function (1 to 5: very bad to very good), giving rise to a score ranging from 4 (very poor) to 20 (very good). About 15 % of the Rennes Metropolis territory shows low soil multifunctionality (4-7 score), which is linked mainly to sealed surfaces. About 32 % shows medium multifunctionality (11-13 score), 50 % high multifunctionality (14-16 score) and only 3 % with very high multifunctionality (17 or 18 score). A total of 39 combinations of CBIA soil functions are obtained. To make the multifunctionality map more understandable, 15 clusters of combinations are made. 6 of them are more frequent: the types with low carbon, high biodiversity, high agronomic values, and medium to high infiltration capacity represent 29 % and 19 % respectively. It is mainly linked to soil used for agriculture (crops). The produced soil multifunctionality and typology maps offer a state of knowledge on soils that is useful for territorial spatial planning. It is a way to represent soil quality and to raise awareness on soils. It can help to identify the soils that need to be preserved, and those that could be artificialized. Soil contamination maps are going to serve as an additional indicator of soil degradation. Soil sampling on main soil typologies is also planned to check the accuracy of the spatial model. Tests by Rennes Metropolis are also in progress to cross the typology of soils with surface information (including vegetation type and ecological protection zones) to produce stake maps, where further soil studies are necessary. Replicability eƯorts were made so that the developed method can be applied in other French territories. The replicability at international scale will depend on the data available. Adaptations are probably going to be necessary
Influence of force field on clay–water contact angle determination using molecular dynamics
No full textInternational audienceClay minerals wettability is a key property for predicting water distribution and pollutant migration in natural or artificial materials. This study attempted to understand the difference in hydrophilicity due to the exchange of structural hydroxyl groups by fluorine atoms, observed in a number of clays. To this end, contact angles of water droplets on hydroxylated and fluorinated talcs were calculated from molecular simulations with two different force fields (one non-polarizable and one polarizable). In parallel, careful measurements of contact angles on a hydroxylated talc monocrystal were undertaken in order to assess the ability of the force fields to reproduce experiments. As expected, fluorinated talc was slightly more hydrophobic than hydroxylated talc for both force fields. Moreover, although the two force fields lead to fluid properties at the interface that were significantly different, the associated contact angles (and related works of adhesion) remained quite close to each other and to contact angles obtained on similar silica-type surfaces. These contact angles overestimated the experimental ones. This could be tentatively assigned to the presence of steps on monocrystal surfaces that could slightly increase the hydrophilicity of the surface, resulting in slightly lower contact angles. When analyzing more carefully the differences between both force fields, it appeared that the use of a polarizable force field resulted in a higher depletion of the fluid close to the surface. This could indicate less attraction between the fluid and the solid and a lesser constraint for the fluid
Managed Aquifer Recharge suitability mapping in Eastern Ethiopia (Dire Dawa, Harar, Jijiga areas)
No full textInternational audienceGroundwater constitutes a major water resource in Ethiopia: according to Kebede (2013), groundwater provides 90% of domestic supply (including the supply of fast-growing cities such as Addis Ababa, Nazret, Gondar, Awasa, Dire Dawa, etc.), 95% of industrial uses, and 80% of the total national supplies. However, these groundwater resources are not evenly distributed as the geological framework of Ethiopia is complex. Managed Aquifer Recharge (MAR) is seen as an appropriate tool for managing existing assets and augment water availability in stressed aquifers of Ethiopia. The country has a geo-climatic context favorable to MAR projects whereby groundwater shall be considered as a water bank recharged during surplus surface water periods (rainy season) and pumped during the dry season. However, it shall be stressed that successful MAR implementation is not feasible anywhere and it requires careful planning.A scientific collaboration on MAR between the MoWE (Ministry of Water & Energy) and BRGM (French Geological Survey) has started in 2023 with the support of the French Development Agency (AFD). The main objectives of this collaboration are to develop a methodology for MAR suitability mapping at regional scale and then to carry out pre-feasability studies in two favorable areas. This pilot project is located around the towns of Dire Dawa, Harar, and Jijiga (eastern Ethiopia), a region where groundwater resources are critical to meet the growing water demand linked to population growth and development.The MAR suitability mapping is performed using existing datasets within a multi-criteria analysis framework. The main criteria are climate and precipitation, the proximity of runoff or watercourses, the proximity and the depth of sufficiently porous and permeable reservoir layers, and the predisposition of land to receive MAR. The resulting map is then validated by field surveys (geology and hydrogeology)
The Tectonic Responses in the Overriding Plate During the Tethyan Convergence and the Progressive Extrusion Process in Sundaland: Insights From the Wuliangshan Massif, SE Tibetan Plateau
No full textInternational audienceThe overriding plate commonly accumulates less strain than the subducted plate during continental collision. Analyzing plate interactions from the perspective of the overriding plate provides important insights into orogenic dynamics. In the southeastern Tibetan Plateau, the Wuliangshan massif, as a key region of the overriding plate, records tectonic events related to the closure of both the Paleo-Tethys and Neo-Tethys. In this study, we present detailed structural analysis, Titanium-in-quartz geothermometry, and zircon U-Pb and Hf isotopic data. These results indicate that the Wuliangshan massif experienced rapid subsidence and deposition within a short period from 260 to 250 Ma in a back-arc tectonic setting. The polyphase deformation events were recognized in the Wuliangshan massif. The ductile syn-metamorphism D 1 event, characterized by a top-to-the-SE ductile shearing under middle-to high-temperature conditions, represents the tectonic response to the collision between the Sibumasu block and the Indochina block occurred at ca. 250-246 Ma. The D 2 deformation is expressed by E-directed thrusts and E-verging folds coeval with a slaty cleavage. The D 3 deformation is marked by SW-directed thrusts and SW-verging folds. The D 2 and D 3 events correspond to positive flower structures related to transpression along the Chongshan-Lancang River fault and the Ailaoshan-Red River fault, respectively. The D 2 -related Chongshan-Lancang River fault accommodated the southward extrusion of the western part of Sundaland occurred at 32-27 Ma. The southeastward extrusion of the entire Sundaland was accommodated by the D 3 -related Ailaoshan-Red River fault at 27-23 Ma.</div
The science-society interface: a key to a regional adaptation framework
No full textArticle d'opinion pour le projet REGILIENCE (projet Horizon Europe de la Mission Adaptation de la Commission Européenne. Cet article met en avant l’interface science-société renforcée comme clé de l'adaptation au changement climatique dans les Régions Ultrapériphériques (RUP).THE CLIMATE RESILIENCE CLUSTERSmall islands are "sentinels" of climate change impacts. This is particularly true for Réunion Island, a French overseas and European Union Outermost Region in the South West Indian Ocean. It is home to a rich diversity of terrestrial and marine ecosystems and characterized by a pronounced topography and significant climatic contrasts. The island's economy relies mainly on vulnerable and exposed sectors (agriculture, tourism, transport, energy supply). Combined with its insularity and geographical isolation, limited local resources, and dependence on external trade, it makes it particularly sensitive. At last, frequent exposure to climate-driven natural hazards, like tropical cyclones, heavy rainfall, flash floods, landslides, droughts and heatwaves, combined with a fragile socio-economic system, amplify this vulnerability.Navigating the complex challenges of climate change adaptation requires strategies tailored to this local context. A dynamic and functional science-society interface is central to ensure that scientific knowledge feeds policy and planning, and that societal needs and local realities shape research initiatives and outputs. However, building this interface on Réunion Island faces several interconnected challenges
Typologie géomorphologique des systèmes falaise–estran : application aux côtes rocheuses de Charente-Maritime
No full textInternational audienceLes falaises rocheuses de Charente-Maritime s’étendent sur 60 km et sont principalement entaillées dans des formations calcaires et marno-calcaires du Jurassique supérieur et du Crétacé supérieur. Elles sont associées à des estrans de diverses natures, incluant des plateformes rocheuses, des accumulations de galets, de sable ou de vase. La morphologie des falaises, à l’échelle départementale, est hétérogène, avec des variations significatives de hauteurs, pentes et composition lithologique. Cette diversité complique l’analyse des dynamiques côtières et limite les approches comparatives. Ce travail propose une méthode visant à élaborer une typologie des falaises de Charente-Maritime, en tenant compte du système « estran-falaise ».Une première tentative de typologie morphologique construite sur l’étude du front de falaise, basée sur des critères lithologiques et topographiques et une classification à dire d’expert a été réalisée par Jean-Baptiste (2021). Les limites de ce travail ont été montrées (Béranger et al., 2024). Afin d’améliorer cette typologie, cette étude propose une méthodologie qui prend en compte le système « estran-falaise ». Cette approche se base sur une acquisition multi-data (terrain, télédétection, SIG). Son originalité réside dans l’intégration des descripteurs de l’estran, un facteur clé dans la dissipation de l’énergie des vagues et potentiellement dans l’érosion des falaises (Earlie et al., 2018 ; Vann Jones et al., 2018 ; Krier-Mariani et al., 2023 ; Matsumoto et al., 2024). L’estran est caractérisé par sa nature (rocheux, sableux, vaseux) et sa topographie (largeur, pente, morphologie). La falaise est décrite par la prise en compte de trois groupes d’indicateurs : la topographie (hauteur, pente, orientation, sous-cavage), la lithologie (matériaux, formations allochtones et autochtones du sommet de falaise), la structure (fracturations, pendage et orientation des stratigraphies). Ces groupes d’indicateurs, composants le système « estran-falaise », sont impliqués dans la morphodynamique des côtes rocheuses à falaise (Payot et al., 2015).Le linéaire côtier à falaises de Charente-Maritime est segmenté à partir d’imagerie aérienne oblique, en fonction des discontinuités morphologiques (failles, lithologie, hauteur) Cela a permis d’identifier plus d’une centaine de segments « falaise-estran ». Cette segmentation est validée sur le terrain, puis des points de collecte sont générés en SIG pour optimiser l’acquisition des données. Des logs litho-stratigraphiques sont levés, et un indice GSI (Hoek et Marinos, 2000) est attribué à chaque point d’observation. Les autres indicateurs sont collectés sur le terrain ou par télédétection et SIG, puis transposés aux segments homogènes. La classification repose sur une Analyse Factorielle de Données Mixtes (AFDM) pour réduire la dimensionnalité des données. Une Classification Ascendante Hiérarchique (CAH) permet ensuite de regrouper les segments en classes homogènes. Cette typologie des systèmes « estran-falaise » constituera une base d’analyse des dynamiques érosives et des mouvements gravitaires à l’échelle départementale
Source-to-Sink Evolution of Volcano-Sedimentary Li-B Deposits at Rhyolite Ridge, Southwestern Nevada
No full textInternational audienceVolcano-sedimentary lithium (Li) and boron (B) deposits at Rhyolite Ridge, Nevada (USA), are poised for development and represent a critical opportunity to secure domestic supplies of these strategic mineral resources. Despite their significance, the sources of Li and B, the geochemical processes responsible for mineralization, and their connection to a proposed caldera in the central Silver Peak Range remain poorly understood. This study integrates detailed geologic mapping with new petrographic, geochemical, and geochronologic data from mineralized lacustrine strata of the Cave Spring formation and underlying volcanic rocks to assess the source-to-sink evolution of Li-B enrichment at Rhyolite Ridge. The Rhyolite Ridge and Argentite Canyon formations (ca. 6.1–5.8 Ma) consist of peraluminous to metaluminous rhyolitic and trachytic tuffs and lavas that include the distinctive Rhyolite Ridge tuff (ca. 6.0 Ma). These rocks exhibit unusually high Li (mean = 73 ppm; maximum = 352 ppm) and B (mean = 160 ppm; maximum = 817 ppm) concentrations, substantially higher than typical upper continental crust, with no clear correlation between Li and B; mild and spatially variable hydrothermal alteration is characterized by sericite, K-feldspar, or disseminated carbonate, along with depleted rare earth element patterns in more altered samples. Drill hole geochemical data from the overlying Cave Spring formation (ca. 5.8–4.7 Ma) indicate that mineralization occurs in stratiform claystone and marl, characterized by a depletion in transition metals and notable enrichment in Li, B, and other incompatible trace elements at concentrations 6 to 30 times higher than typical upper continental crust. Li and B were likely supplied by supergene weathering of surrounding volcanic rocks, possibly with additional input from early hydrothermal fluid circulation in the basin. We propose a regional stratigraphic correlation of the Rhyolite Ridge tuff supported by a new U-Pb date of 6.05 ± 0.08 Ma for an Li-enriched rhyolite tuff in the nearby Montezuma Range and strong compositional similarities in mineralogy and geochemistry from both outcrop and subsurface data across Clayton Valley, the Silver Peak Range, and northern Fish Lake Valley. This correlation suggests that the Rhyolite Ridge tuff erupted from a source in the Montezuma Range and was emplaced in an ~80-km-long, NW-SE–oriented paleovalley and that it is the probable source of Li in brine and volcano-sedimentary deposits throughout the greater Clayton Valley region