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Karst springs, groundwater dependent ecosystems and global changes: a few examples from France
No full textInternational audienceIn addition to the habitat they provide to microbiological fauna (Griebler and Avramov 2015), groundwaters contribute to numerous ecosystem services, including the production and distribution of high-quality water and the feeding of groundwater-dependent aquatic ecosystems such as rivers, lakes and wetlands. This role is particularly important during dry periods, when the water stored in aquifers supplies significant quantities to surface waters that are at low flow.Springs are the interface between aquifers and surface water, making them ideal sites for monitoring groundwater and its ability to provide services to downstream ecosystems. Among these, karst springs are particularly noteworthy for the quantity of water they convey to a specific point. Karst accounts for 21.6% of Europe's surface area (Chen et al. 2017) and some of the ecosystem services it provides have been already described by Goldsheider (2012). However, the supply of water to aquatic ecosystems remains a largely undervalued and understudied feature.In this presentation, we highlight the role of karstic springs in various ecohydrological contexts of France (Fig. 1) and the risks that dependant ecosystems will face in a context of global changes.The Argens is a river that flows through the Triassic limestones of Provence Verte. With a constant temperature throughout the year, the bouillidoux karst springs help to regulate the river's temperature by decreasing it in summer and increasing it in winter. The section of river downstream from the spring is a thermal refugee that is home to significant biodiversity, like other thermal refugees in the south of France. However, these are vulnerable to climate change, which will alter the way they function, as well as the respective inflows of groundwater and surface water, and the temperatures of these waters.The Vise Spring is a submarine karst spring located in the Thau Lagoon in southern France, on the Mediterranean coast. Its karst hydrosystem regularly supplies freshwater to the lagoon, contributing to its quality and ecological balance. Shellfish farming is a major activity here, but other uses of the groundwater also coexist: thermal water for the Balaruc Spa and drinking water supply for neighbouring villages. This spring is the site of regular flow reversals, which cause salt water intrusion from the lagoon into the karst aquifer, disrupting the hydro-ecological balance of the lagoon (Ladouche et al. 2023). The chronic drop in the water level in the aquifer, linked to repeated droughts and the increasing use of groundwater, is leading to an acceleration in the number of flow reversal phenomena. In addition, the particular geometry of the site makes it vulnerable to long-term or even permanent flow reversal and salt water intrusion.The karst springs of the Loue and Lison Rivers are among the largest in France in terms of flow. They emerge in the Jura Mountains and feed the Loue River, which draws most of its flow from the surrounding limestone plateaux. For more than a decade, numerous contaminations of the rivers have led to fish kills, linked in particular to major inputs of nutrients flowing through the karst aquifers. Farming practices linked to cattle rearing for cheese production need to be improved to reduce inputs in the upstream basins.These karst springs, which are highly sensitive to climate change and modifications in land use in their catchment areas, constitute sentinels of global change. As vectors of groundwater, they link upstream and downstream ecosystems and guarantee major ecosystem services. Monitoring them is vital for gaining a better understanding of their ecological functions, which depend on their hydrogeological functions. In this context, a new research project called SentinelSpringS is starting within the Water4All program, with colleagues from Portugal, Italy, Poland, Denmark and Malta, in order to propose a better framework for managing groundwater resources and associated springs
Syn-tectonic emplacement of Li-bearing pegmatites related to detachment faulting in the Dahongliutan pegmatite belt, Western Kunlun, NW China
No full textInternational audienceThe Late Triassic to Early Jurassic (ca. 220 to 190 Ma) Dahongliutan pegmatite belt, located in the Western Kunlun orogenic belt, NW China, is a newly discovered, large Li-Be ore district comprising > 320 individual rare-metal pegmatites. The pegmatite belt was emplaced in a post-orogenic setting in relation with a ductile shear zone related to the Dahongliutan detachment fault, which is spatially and temporally related to post-orogenic exhumation. Deformed spodumene pegmatites, mostly striking NW with dip angle of 50 ~ 80°, occur within or adjacent to the NW-striking detachment fault. We present new field observations, mineralogical, geochemical and geochronological results from the Dahongliutan pegmatite belt, which lead to the following conclusions: 1) High-medium temperature/middle-to-low pressure metamorphic rocks and granitoids were intruded by ductile-deformed spodumene-bearing pegmatites during development of the gneissic domes; 2) Spodumene pegmatites from the Aktas, Kalaka, Bailongshan and Longmenshan deposits record two age groups, a first one during the Upper Triassic at ca. 212–205 Ma, and a second one during the Lower Jurassic at ca. 195–193 Ma, as revealed by in-situ Rb–Sr dating of micas and U–Pb dating of columbite-group minerals; 3) Textural observations and geochemical analyses of coexisting quartz and spodumene further indicate that ductile deformation provided favorable conditions for enrichment of Li and Be in pegmatites. The Western Kunlun-Songpan Ganzi rare-metal pegmatite belt shows a close spatial and genetic relationship with ductile shear zones induced by detachment faulting, making it a potential proxy for exploration targeting of Li-Be-mineralized occurrences at the regional scale as well as in other metallogenic provinces worldwide
Effect of cement water contacting an aged cementitious grout on the dissolution rates of inactive nuclear glass SON68
No full textInternational audienceThe long-term behavior of high-level radioactive waste glass depends on the mineralogical and geochemical interactions between the various components of the multibarrier system, under geological repository conditions. The present study focuses on SON68 glass alteration in synthetic cement water and at 50 • C and 70 • C. While pH > 10, the glass dissolution rates were lower when contacting synthetic cement water than deionized water. This effect stems from the high Ca concentration and the presence of Si in the porewater. The initial dissolution rates at low reaction progress (3.4 ± 1.0 × 10 -2 g m -2 d -1 at 50 • C and 1.9 ± 0.8 × 10 -2 g m -2 day -1 at 70 • C) and the long-term dissolution rates at high reaction progress (1.5 ± 0.5 × 10 -5 g m -2 day -1 at 50 • C and 6.7 ± 1.0 × 10 -5 g m -2 day -1 at 70 • C), were two times to one order of magnitude lower than the rates determined in deionized water. The cement water has a beneficial effect on glass dissolution rates which were dependent on pH, Si, and Ca concentrations
Poljes, a pre-structuration of the hydrosystems in plateau karsts, the example of the Jura mountain (Fr)
No full textInternational audienceThe aim of this work is to analyze - through the prism of poljes - the development of karst networks and the organization of underground drainage in the case of plateau karsts. The methodology combines various approaches: i) surface morphology, ii) speleogenesis and iii) hydrogeology. The study site is the Loue basin, located in the french Jura Mountains. It is a typical plateau karsts, with its high karstification degree (around a hundred karst networks over 100 m, several karst springs with an average flow superior to 1 m3/s), and its extensive hydrogeological knowledge of karst hydrosystems (several hundred dye tracer tests available). First, a detailed surface morphological mapping has shown that the current plateaus correspond to ancient depressions with relatively flat, elliptical bottoms, and large extension (~ 400 km²). These plateaus are enclosed between the raised hydrological barriers of anticlines (fold systems). We interpreted these depressions as paleo-poljes. Currently perched 150 m above the base level, they only have a residual hydrological functioning, i.e. the lowest of them are subject to occasional flooding by exceeding the infiltration capacity of the ponors. Second, the analysis of numerous dye tracer tests within the largest karst hydrosystems has enabled us to determine their current recharge area. A strong spatial correlation between the geometry of the recharge area and the paleo-poljes suggests that the poljes plays a pre-structuring role in the organisation of the underground drainage. Third, the analysis of the horizontal galleries (relative altitude and endokarst forms) shows several significant levels and different speleogenetic processes (paragenesis, alteration) that can be linked to ancient local base levels contemporary of the hydrological functioning of the paleo-poljes (regular and long periods of flooding). Finally, our results enable us to propose a new conceptual model of plateau karsts in the Jura Massif, highlighting the role of poljes in karstogenesis and in the hydrogeological compartmentation of current hydrosystems
Simulating Shoreline and Nearshore Changes: The LX-ST Model
No full textThis paper presents LX-ST, a numerical model that simulates shoreline and nearshore evolution over medium-to long-term timescales across diverse sandy coastal environments. It combines the reduced-complexity shoreline model LX-Shore with the shoreface profile translation tool ShoreTrans, enabling it to capture shoreline changes and 3D nearshore morphology. LX-ST accounts for sea-level rise, sediment transport, complex features like artificial structures (e.g., seawalls, groynes), and natural morphologies (e.g., dunes and barriers). The model is tested on synthetic cases, demonstrating its ability to simulate complex coastal configurations. It is then applied to a 5-km beach-dune system in southwest France, which includes a 1.2-km-long seawall. Results show good agreement with observed past shoreline changes and reveal how LX-ST can predict future coastal trajectory shifts, including the eventual retreat and potential disappearance of the beach fronting the seawall. These findings underscore the model's utility in forecasting shorelin
From Waste to Resources: Circular Economy Solutions for Wind Turbine Materials in the EU Through 2050
No full textInternational audienceRenewable energy sources, such as wind turbines (WTs), are of primary importance in reducing the use of fossil fuels while simultaneously fulfilling the growing demand for electricity. The increased deployment of WT in the coming decades to achieve decarbonisation objectives will result in an increased demand for materials embedded in WT, such as steel, zinc and some that are critical raw materials like Neodymium (Nd), Dysprosium (Dy) in permanent magnets (PM) and copper (Cu). The implementation of a circular economy, with an increased focus on reuse and recycling, will enhance the European Union (EU) resilience and mitigate potential supply chain disruptions. This work presents a dynamic material flow analysis (MFA) that tracks the materials utilized in the entire EU WT sector (both onshore and offshore) throughout the whole life cycle, until the year 2050. This study combines an inflow-driven model, based on historical data from existing wind farms up to 2023, with a stock-driven model for the period 2024-2050. The inflow-driven model is applied at the level of individual wind parks, while the stock-driven model is at country level. Moreover, the model integrates material intensities (MIs) derived from literature review, for seven distinct types of WT, including their external cables and foundations, distinguishing between onshore and offshore wind parks. The MFAs and MIs are combined to determine the mass of components, materials and elements that can be recovered through the application of circular economy principles from the waste generated by wind turbines. The volume of recovered material is evaluated through three distinct scenarios, each reflecting a specific level of ambition. The initial scenario assumes a continuation of current practices, thereby maintaining the existing recycling capacities. The second scenario represents an increase in recycling rates across Europe, driven by enhanced recycling capacities, improved collection rates, and a reduction in waste sent to landfill or energy recovery facilities. The third scenario assumes that a more circular economy can be achieved by promoting the extension of product lifetimes, improved repair, reuse and replacement of components. The lifetime model of WTs, based on data from operational and decommissioned EU wind turbines data, indicates that their actual lifetime often exceeds the theoretical lifespan announced by the manufacturers, with 60% of turbines dismantled after 25 years. This extended lifespan may potentially impact the efficacy of recycling initiatives, given the possibility of fewer wind turbines reaching their designated end-of-life. Nevertheless, it is anticipated that the quantity of wind turbines undergoing dismantling will increase over time. It is estimated that by 2030, over 300 tonnes of Nd and 40 tonnes of Dy may become available from dismantled WTs in the EU. The different scenarios will show the amount of materials that can be obtained from recovered waste and the impact of circular economy on the supply chain disruptions
Transport properties estimation from coupled acoustic and electric characterization in heterogeneous limestones
No full textFluid flow in aquifers is mainly controlled by heterogeneities present at different scales, from microporosity to fractures, especially for carbonate formations. Predicting transport properties becomes tremendously difficult in complex environments like vadose zones. We investigated acoustic and electrical properties coupled to hydraulic and structure measurements of limestone samples from the vadose zone of the Beauce aquifer at the O-ZNS platform (Villamblain, France). At first sight, the different samples present highly heterogeneous features defined as macropores (fractures, cracks, dissolution vugs, microporosity). Our petrophysical characterization shows that the transport properties are scattered for the samples with important macropores resulting in a poor permeability-porosity relationship. The velocity-porosity relationship with empirical models shows fair correlations that allows to differentiate samples with respect to their structures. In the case of microstructural sample, the porosity can be well predicted. However, we also show that the presence of macropores leads to an uncomplete porosity characterization. On another side, we demonstrate the relevance and usefulness of complex conductivity measurement in carbonates characterization for permeability prediction. Indeed, based on some well-known models calibrated for sillicoclastic samples, permeability can be correctly estimated by choosing the right structural parameters. Finally, we use a multimethod approach based on a joint interpretation of acoustic and electrical properties, allowing an improved characterization of the sample properties
Developing Damage State-Dependent Fragility Models for Reinforced Concrete Buildings Under Flood and Seismic Hazards
No full textRegistration for Poster Presentation - 7th Global Summit of GADRI (gadri.net)International audienceAs built environments face increasing exposure to multiple hazards, exacerbated by factors such as climate change and urban expansion, there is a growing need for methodologies to assess multi-risk impacts throughout a structure's lifespan. This study focuses on developing damage state-dependent fragility models for reinforced concrete buildings commonly found in French city centers. The analysis considers two major hazards prevalent in Southern France, especially in the Nice region: earthquakes (including mainshock-aftershock sequences) and flooding. These hazards pose threats to structural stability, necessitating an in-depth assessment of their cumulative and sequential effects. Fragility models are developed using Monte Carlo simulations, where both the sequence and intensity of hazard events are randomized to encompass all possible loading scenarios. The resulting state-based fragility models provide probabilistic estimates of transitioning between different damage states based on the intensity of either hazard. Furthermore, the developed models are hazard-specific, with differences analyzed based on the physics of damage absorption, considering the distinct ways in which seismic forces and flood loads impact the structure. This differentiation allows for a more accurate assessment of how buildings deteriorate under different hazard types and sequences. By integrating data from in-building seismological sensors and data-driven updates of a building's damage state, the developed mode can enhance situational awareness of structural integrity in the context of crisis management and allow for the prediction of how a building's vulnerability evolves throughout its lifecycle, supporting more effective risk management and resilience planning.</div
L’apport des données hydrodynamiques pour caractériser les tempêtes détectées au sein d’archives sédimentologiques et historiques
No full textInternational audienceL'étude et la datation précises des impacts sédimentologiques de dépôts de tempêtes situés dans des zones basses côtières en arrière de cordons dunaires constituent un défi important dans les environnements macrotidaux. Pour relever ce défi, nous proposons une méthode basée sur le croisement entre sédimentologie, analyse d'archives historiques, statistiques et modélisation hydrodynamique. Le site de la Petite Mer de Gâvres, dans le sud de la Bretagne, a été retenu comme étant un espace macrotidal pertinent le long de la côte atlantique française. L'analyse des carottes sédimentaires a permis d'identifier six dépôts de washover. Le croisement avec les données météo-marines de réanalyse et les sources historiques a suggéré qu'ils ont été causés par les événements de 1896, 1924, 1950, 1974, 1990 (quatre tempêtes) et 1999 (deux tempêtes). Ces hypothèses ont été confirmées par les données de réanalyse via le calcul de la période de retour conjointe des hauteurs significatives des vagues et des niveaux d'eau (marée + surcote) et l'utilisation de la formule de Stockdon pour estimer si le niveau de l'eau par rapport au niveau de la crête de dune. Pour toutes les tempêtes identifiées comme étant à l'origine des dépôts de washover datés, la hauteur significative des vagues était toujours exceptionnellement forte, soulignant l'effet clé de ce paramètre. Enfin, les avantages et les limites de cette méthode composite employée pour documenter les tempêtes historiques ont été soulignés ; notamment en mettant en lumière l'exemple du dépôt de tempête daté à 1973 ± 1.5an, qui était précédemment associé à l'évènement du 13 février 1972 mais qui a été corrigé avec celui du 11 février 1974 grâce aux modèles hydrodynamiques
MASSIRE PROJECT: STRENGTHENING NETWORKS FOR AGRICULTURAL AND RURAL INNOVATION IN OASES AND ARID ZONES OF THE MAGHREB
No full textThe Massire Project (2019–2024) was a research-for-development project implemented by a consortium of research and education institutions from Morocco, Algeria, Tunisia and France. It was funded by IFAD, with a financial contribution of project academic partners. The project aimed to strengthen agricultural and rural innovation systems in the oases and arid zones of Morocco, Algeria, and Tunisia. Addressing challenges such as resource vulnerability, biodiversity loss, and social inequalities, the project facilitated sustainable development pathways through innovative, participatory, and inclusive approaches