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New Insights into Spatially Distributed Simulations of Nitrogen Reactive Transport in the Unsaturated-Saturated Continuum at the Catchment Scale: Can a Paradigm Shift Be Achieved by Coupling Physically-Based and Lumped Models ?
No full textInternational audienceDiffuse groundwater contamination from non-point sources, particularly nitrate originating from agricultural activities, continues to pose a significant challenge to water resource management at the European scale. Physically based, process-oriented modelling tools have demonstrated their effectiveness at fine spatial scales—such as field plots or small experimental catchments—particularly when supported by high-resolution monitoring networks. A conventional approach for extending the applicability of these models to larger catchment scales involves the coupling of one-dimensional (1D) models, which simulate variably saturated flow and reactive solute transport in the soil and unsaturated zone, with three-dimensional (3D) groundwater flow and transport models. While such multi-scale model coupling appears promising for representing the continuum of surface to subsurface processes, it remains limited by three major constraints: the increasing complexity of the 1D models often overemphasizes soil processes relative to deeper subsurface dynamics; inconsistencies in water and mass balance calculations arise from discrepancies in the representative elementary volumes used across models; and the limited availability of high-quality data, particularly for the unsaturated zone, inhibits robust model calibration and parameterization. These methodological and practical constraints hinder the routine application of such coupled models at national or continental scales, where detailed geological, hydrological, and land-use information is often lacking. Additionally, the structural and parametric uncertainties associated with representing coupled surface–subsurface processes exacerbate these limitations.To address these challenges, this study proposes a novel modelling paradigm based on the integration of a spatially distributed, lumped conceptual model—designed to simulate water and nitrogen fluxes in the soil and unsaturated zone—with a physically based numerical model of saturated groundwater flow and solute transport. Conceptual lumped models, which represent dominant hydrological and biogeochemical processes with reduced data requirements, have been shown to offer a satisfactory balance between process representation and parsimony. The proposed modelling framework allows for the spatial discretization of geological and hydrogeological heterogeneities, the incorporation of temporally variable agricultural practices, and a reduction in model complexity while maintaining process relevance. This integrated modelling system was implemented through the development of new computational modules within the MARTHE software platform (developed by the French Geological Survey—BRGM), which supports the simulation of water flow, energy, and solute transport in hydrosystems. The numerical architecture of this software facilitates seamless simulation of coupled hydrological and geochemical processes, and mitigates mass balance issues typically encountered when interfacing multiple software platforms.This approach was applied to a 94 km² catchment in western France, which serves as a drinking water source and has experienced a sustained increase in nitrate concentrations since the 1990s, primarily attributable to historical agricultural intensification. The model satisfactorily reproduced the spatial and temporal dynamics of groundwater levels, surface discharge, and spring flows, including a karstic resurgence. Model performance metrics indicated strong agreement with observed nitrate concentration trends across multiple observation points (including karstic springs, stream gauges, and piezometers). Model outputs highlighted key controls on nitrogen dynamics at the catchment scale, including the spatial and temporal variability of organic fertilizer application, preferential flow in the karst network, and the interactions between surface and subsurface compartments. Furthermore, the model was used to simulate future nitrate trajectories under a suite of climate and land-use change scenarios, revealing the strong legacy effect associated with nitrate accumulation in the unsaturated zone and the associated system inertia. These results demosntrate the potential of the proposed modelling framework to enhance predictive understanding of nitrate fate and transport at the catchment scale. The approach offers a robust and scalable tool to support integrated water resource management and policy development in the context of diffuse agricultural pollution
Méthodologie pour l'exploration des aquifères offshore (ANR Aquimer, Roussillon, sud France)
No full textInternational audienceThe recent identification of large quantities of fresh to low saline waters in marine sedimentary prisms requires to revisit our knowledge of the water cycle and to integrate these volumes of freshwater and their mixing with saline water in the management of coastal aquifers. Characterization of such systems is rendered difficult by their position offshore, which limits the possible acquisitions (technical constrains, costs, …). It is therefore necessary to set up 1) tools that can be mobilized to characterize the distribution of water of varying salinity in the offshore domain, and 2) an integrative approach to better understand these distributions and their evolution. The AQUIMER project will take as a case study a potential submarine mega-aquifer, the Plio-Quaternary aquifer of Roussillon (South of France), well known onshore, and. Its continuation offshore is imaged in the marine domain by numerous seismic profiles. AQUIMER will develop tools and methods to characterize these complex objects in terms of volumes, distribution and dynamics of circulation and mixing. In particular, AQUIMER will develop and deploy onshore and offshore geophysical techniques at different scales and resolutions to image resistivity variations in the ground and sub- sea floor (up to 15 km from the coast). The resistivity data obtained will be inverted by integrating all the geological data via the compilation of a predictive model of facies and lithologies variations. This will allow 1) to define the reservoir and lithological properties variations and 2) to better constrain the variations of the resistivity related to rock-related resistivity signal and so to better deconvolute the pore water salinity-related signal. Finally, the results will be integrated into a hydrogeological model on the scale of the entire onshore- offshore hydrosystem to constrain the dynamics of flow and mixing between freshwater and saltwater, and better understand their evolution. The resulting approaches will be applicable to other aquifers in the Mediterranean realm and in many settings around the world.La mise en évidence récente de grandes quantités d’eaux douces à peu salées dans des sédiments dépôts sédimentaires sous-marins invite à revisiter la connaissance du cycle de l’eau et à intégrer ces volumes d’eau douce et leurs dynamiques dans la gestion des aquifères côtiers. La connaissance de ces systèmes est limitée par leur position en mer qui limite les acquisitions (contraintes techniques, coût, ...). Il est donc n´nécessaire de mettre en place 1) des outils mobilisables pour caractériser la distribution des eaux de salinités variables dans le domaine offshore, 2) une démarche d’intégration permettant de mieux comprendre ces distributions et leur évolution. Le projet AQUIMER prend pour cas d’étude un potentiel méga-aquifère sous-marin, l’aquifère plio-quaternaire du Roussillon), bien connu `a terre, et dont l’extension en mer est imagée par de nombreux profils sismiques. AQUIMER mettra en place des outils et méthodes pour caractériser ces aquifères complexes en termes de volumes, distribution et dynamique de circulation et de mélange. En particulier, AQUIMER développera et mobilisera des techniques géophysiques à terre et en mer, à différentes ´échelles et résolutions, pour imager les variations de résistivité `a l’échelle de l’aquifère jusqu’`a 15 km en mer. Les données de résistivités obtenues seront inversées en intégrant l’ensemble des données géophysiques et géologiques via la réalisation d’un modèle prédictif de faciès et variations lithologiques. Ceci permettra 1) de d´définir la variation des propriétés réservoirs et lithologiques et 2) de mieux contraindre les variations du signal de résistivité lié à la roche pour mieux déconvoluer le signal de salinité des eaux porales. Les résultats seront ensuite intégrés dans un modèle hydrogéologique terre-mer qui questionnera les processus `a l’origine des distributions des masses d’eau, leur signature géophysiques, et les dynamiques d’écoulement et de mélange eaux douces - eaux salées et leurs évolutions dans le temps. L’approche développée pourra être appliquée autour de la Méditerranée et `a d’autres aquifères présentant des configurations similaires. Ce projet (ANR-24-CE01-1184) est financé par l’Agence Nationale de la Recherche
Tracing Nd–Fe–B Permanent Magnet Supply Chains Using Nd and B Isotope ratios
No full textInternational audienceRare earth elements (REEs) are critical raw materials for renewable energy technologies, particularly through their role in Nd–Fe–B permanent magnets. These magnets are essential components of wind turbines and electric vehicle motors. Ensuring a transparent and sustainable supply of REEs, especially Nd, is fundamental to mitigating future resource risks (Balaram, 2019; Liu et al., 2023). Within the framework of the MaDiTraCe project, we investigated elemental and isotopic signatures of Nd and B along the Nd–Fe–B magnet value chain, from concentrates to finished magnets.The sample set comprised ore concentrates from Bayan Obo (China) and Mountain Pass (USA), metallic intermediates from CEA-Liten (Nd–Pr and FeB alloys, ribbons, powders, magnets), two commercial ribbons of Japanese and European origin, and eight magnets sourced from a single wind turbine. Nd isotope ratios were measured for all samples using MC-ICP-MS (NeptunePlus, UGent-A&MS) and TIMS (Finnigan MAT262, BRGM). B isotope ratios were determined with TIMS along the magnet production chain.The results reveal distinct Nd isotopic signatures between Bayan Obo and Mountain Pass concentrates, providing a robust basis for distinguishing between these deposits. However, no linked ore–concentrate samples were available, and thus it cannot be determined whether isotopic signatures are fully preserved during beneficiation. Within the magnet production chain, Nd isotope ratios exhibit no measurable fractionation despite extensive metallurgical processing, and intra-magnet variability is negligible. This demonstrates that Nd isotope ratios reliably preserve signatures from the alloy through to the final product. Distinct isotopic signatures in commercial ribbons, relative to each other and to the two major deposits, point to potential variability within a deposit, contributions from minor deposits, or blending of concentrates from different origins.B isotopes show no fractionation across the production chain, from FeB alloy precursors to sintered magnets. δ¹¹B values remain stable within each magnet and across processing steps, demonstrating B’s utility for tracing processing integrity. However, the narrow δ¹¹B range of industrial borax feedstocks, such as the Kramer deposit (USA) and Kırka deposit (Turkey) (Smith & Medrano, 1996; Helvacı et al., 2017, Palmer & Swihart, 1996; Swihart et al., 1996), limits their potential for provenance discrimination.Together, these findings highlight the strong potential of Nd isotope ratios as a tracer linking concentrates to final Nd–Fe–B products, while the B isotope ratio provides complementary information for verifying processing consistency. This combined isotopic approach contributes to the development of robust tools for critical mineral traceability in renewable energy supply chains. REFERENCES Balaram, V. (2019). Rare earth elements: A review of applications, occurrence, exploration, analysis, recycling, and environmental impact. Geoscience Frontiers, 10, 1285–1303.Helvacı, C., et al. (2017). Mineralogy and origin of borate deposits. Ore Geology Reviews, 80, 536–553.Liu, S. L., Fan, H. R., Liu, X., Meng, J., Butcher, A. R., Yann, L., Yang, K. F., & Li, X. C. (2023). Geological characteristics and REE mineralization of the giant Bayan Obo deposit, Inner Mongolia, China. Ore Geology Reviews, 157, 105428. https://doi.org/10.1016/j.oregeorev.2023.105428Smith, R., & Medrano, M. (1996). Boron resources in South America. Economic Geology, 91, 191–205.Palmer, M. R., & Swihart, G. H. (1996). Boron isotope geochemistry: An overview. In E. S. Grew & F. C. Hawthorne (Eds.), Boron: Mineralogy, Petrology, and Geochemistry (Reviews in Mineralogy, Vol. 33, pp. 709–744). Mineralogical Society of America. Swihart, G. H., McBay, E. H., Smith, D. H., & Sietke, J. W. (1996). A boron isotopic study of a mineralogically zoned lacustrine borate deposit: The Kramer deposit, California, U.S.A. Chemical Geology, 127, 241–250
Chronology of mobile pastoralists settlements and dairy exploitation in neolithic Iran through compound-specific radiocarbon analyses of archaeological pottery
No full textInternational audienceAgropastoralism developed in southwest Asia in the 9th millennium BC. The Zagros mountains in Iran are one of the centres of goat domestication. The management of caprine herds and the climatic constraints of this region led to the development of pastoralism with seasonal mobility. The temporary campsites of mobile pastoral groups, which were probably occupied on several occasions, generally include ceramic and lithic materials that are not very distinctive. The dearth of organic materials conventionally used for 14 C dating provides challenges in establishing the chronology of the settlements. Therefore, the development of CSRA of lipids in ceramic vessels provides a unique alternative to resolve the chronology of such campsites. We study first the lipid preservation in about 400 ceramics from Neolithic permanent settlements, open-air campsites, and cave campsites of pastoral groups. It showed a reliance on both carcasses and dairy products of their caprine herds. The overall low lipid preservation led to performing 14C measurements on less than 100 µg of C of lipids in ceramic, which diverged from the routine method with sample sizes over 200 µg of C. We therefore employed the EA-GIS interface linked to ECHoMICADAS to do gas measurements on single lipid. Despite the relatively low precision obtained on the measurements, we were able to: (1) provide chronological context to prospection surveys in the Zagros; (2) show a reuse of three open-air and cave campsites across several centuries or millennia; (3) demonstrate dairy exploitation in the ceramic vessels by pastoral groups in the Zagros mountains was already established during the 7th millennium BC
Geophysical imaging in carbonate critical zone highlights the significant of deep weathering
No full textInternational audienceWithin the critical zone, rock weathering plays a fundamental role in controlling subsurface water storage and transfer. In karstic carbonate settings -particularly sensitive to dissolution and erosion -characterizing the geometry and properties of weathered rocks is essential. This study proposes a conceptual model of weathered zones in the subsurface of the critical zone, based on an integrated imaging framework. The study site is in a dolomitic karst area (Larzac observatory, Southern France).First the properties of weathered and unweathered rocks are analyzed on rock samples using petrological observations and petrophysical measurements. Weathered rocks appear as unconsolidated, highly porous material, resulting from dissolution at the grain boundaries of the dolomite without any significant mineralogical change from the unweathered rock. Various geophysical methods (GPR, Gravimetry, ERT, SRT) are used to identify and image the weathered areas in subsurface. The weathered rocks form numerous corridors (several meters long) both at the surface and at depth, aligned with the fractures and known caves.By integrating multidisciplinary data from samples and field, we infer the potential presence of water in these weathered zones. This leads to a refined conceptual model of karst subsurface architecture, where weathered rocks may serve as preferential reservoirs for groundwater within the critical zone.</p
Comment se partager l’eau comme bien commun ?
No full textInternational audienceCe chapitre questionne la manière de se partager l’eau en tant que bien commun, en exposant les difficultés associées puis en présentant des pistes pour y arriver, basées notamment sur le cadre institutionnel existant en France.L’accès à l’eau est un défi ancien, souvent relevé par des aménagements hydrauliques pour capter l’eau, adossés à des règles encadrant son accès et ses usages. Le changement climatique vient bousculer les équilibres progressivement atteints et remet en avant la question du partage de l’eau d’une ressource par nature commune mais devenue rare. C’est l’objet de ce chapitre. Après avoir détaillé les raisons de la difficulté de ce partage, il propose des principes et modalités opérationnelles pour y parvenir, soulignant notamment l’importance du dialogue territorial. Il présente enfin une manière d’adapter le référentiel d’action publique existant pour faire face à un défi supplémentaire : le changement climatique est en effet caractérisé par des incertitudes multiples qui ne facilitent pas le partage d’une eau « incertaine »
Comment combiner le rafraîchissement adiabatique direct et indirect dans une unité de traitement d'air pour des bâtiments tertiaires résilients
No full textInternational audienceIn this article we propose various indicators to highlight the performances and the resilience of an air-handling unit (AHU) that can integrate both direct and indirect adiabatic cooling. This combined adiabatic strategy enhances the cooling performance during heatwaves. We developed the control strategy of the integrated system into a TRNSYS numerical model. Considering continental, Mediterranean, arid subtropical and equatorial climates, we analyzed best operation strategies for a typical office building. The multicriteria approach highlights the lower efficiency under equatorial climates. The system performs better in arid environments, in this case study the Mediterranean climate is better regarding the water consumption while the subtropical arid climate is better regarding the fan consumption.Dans cet article, nous proposons divers indicateurs pour mettre en évidence les performances et la résilience d'une unité de traitement d'air(CTA) pouvant intégrer à la fois un module de rafraîchissement adiabatique direct et indirect.Cette stratégie adiabatique combinée améliore les performances de refroidissement pendant les vagues de chaleur. Nous avons développé lastratégie de contrôle du système intégré dans un modèle numérique TRNSYS.En tenant compte des climats continental, méditerranéen, subtropical aride et équatorial, nous avons analysé les meilleures stratégies de fonctionnement pour un immeuble de bureaux type.L'approche multicritères met en évidence une efficacité moindre sous les climats équatoriaux. Le système fonctionne mieux dans les environnements arides. Dans cette étude de cas, le climat méditerranéen est plus avantageux en termes de consommation d'eau, tandis que le climat subtropical aride est plus avantageux en termes de consommation des ventilateurs
Toward 3D Deep Mineral Imaging: CSEM, ERT, and IP Strategies for Depths Beyond 1 Km
No full textInternational audienceThis study outlines a robust workflow for imaging deep-seated mineral deposits using Electrical Resistivity Tomography (ERT), Induced Polarization (IP), and Controlled-Source Electromagnetics (CSEM) at depths beyond 1 km. Deep-target surveys pose significan technical and logistical challenges, requiring careful planning of current injection parameters, array geometry, and instrumentation.To address these challenges, we evaluated survey strategies through synthetic modeling to guide decisions on injection period, source power, and the use of nodal systems. These pre-survey assessment enabled an optimized balance between signal quality, depth sensitivity, and field efficiency.A large-scale 3D field survey was conducted at the Koillismaa Layered Intrusion Complex in Finland, targeting mafic-ultramafic intrusion from a depth of 1.4 km. Using 25 long transmitter dipoles (∼1 km) and 114 receiver stations utilising nodal system which allows much flexible configuration at the field site across ∼200 km2.Inversion results from ERT and CSEM revealed deep conductive features, with CSEM identifying three distinct anomalies in greater detail. The IP model also captured a phase anomaly aligned with a known mafic-ultramafic intrusion. This work demonstrate the effectiveness of the proposed approach and support its broader application in deep mineral exploratio
Microfluidics for geosciences: metrological developments and future challenges
No full textInternational audienceThis review addresses the main metrological developments over the past decade for microfluidics applied to geosciences. Microfluidic experiments for geosciences seek to decipher the complex interplay between coupled, multiphase, and reactive processes in geological porous media, e.g., for groundwater management, soil remediation, gas storage in geological reservoirs, or geothermal energy. The guiding principle is to represent natural or engineered processes in a controlled environment to observe, characterize, and model them. When microfluidic experiments are associated with advanced metrology techniques, they provide direct visualization of the processes and measurements of transport mechanisms, chemical reactions, interfacial processes, or mixing within the pore space. In this review, we present the state of the art in metrological approaches to microfluidics for geosciences, including measuring velocity fields, fluid and solute saturations, tracking chemical reactions, and combining experimental and computational microfluidics. The upscaling from microfluidics to the reservoir scale is discussed. Finally, we outline future challenges related to metrological advancements and the integration of artificial intelligence in microfluidics
Guidelines for the FAIRt publication of Terrestrial Laser Scanner Data in Geomorphic Research
No full textInternational audienceThe increasing dissemination of data from Terrestrial or Permanent Laser Scanning (TLS/PLS) topographic surveys in geomorphology requires the establishment of clear recommendations for their publication. The work presented here proposes a framework to ensure that published datasets comply with the FAIRt (Findable, Accessible, Interoperable, Reusable, trustworthy) principles, with a particular attention on the documentation of theprocessing steps. This facilitates the evaluation of the relevance of published point clouds and their reuse. Central to this proposal is a set of structured metadata that is essential to document acquisition conditions, methodological choices and processing parameters in order to understand how the published cloud was obtained and what it can be used for.The framework presented in this article is organised into three distinct parts: the essential perimeter of publication, without which the cloud cannot be exploited, pre-processing and processing. These recommendations are accompanied by concrete examples of datasets to illustrate their implementation. To ensure the long-term interoperability of distribution, it is recommended that the LAS format be used as the standard for TLS clouds, associated with a GeoJSON file of metadata. This approach constitutes a component of a long-term preservation process, which is based on the use of open sharing and storage platforms. This standard is therefore intended to be a support tool for researchers, structuring publication practices while remaining open to adapt to future technological and scientific developments. Designed for TLS acquisitions, it could be extended to photogrammetric point clouds if specific photogrammetric processing information is provided