HAL-BRGM, les publications scientifiques en libre accès du BRGM
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Corrosion behavior of API 5L X65 steel in synthetic CallovianOxfordian pore water under extreme simulated storage conditions
No full textInternational audienceThis study examines the corrosion behavior of API 5L X65 carbon steel, a candidate material for high-level radioactive waste linings in France, when exposed to synthetic Callovian-Oxfordian (Cox) clay pore water. The experiments simulate some of the most severe conditions that could arise due to environmental changes in the storage environment during the evolution of a waste repository system. At atmospheric pressure, three distinct gas mixtures were selected for the study: anoxic (CO₂:1 %, N₂: 99 % representative of the actual atmosphere of the Cox pore water), oxic (O₂: 20%, N₂: 80%), and sulfide-rich (CO2: 20 %, H2S: 0.8 %, N2: 79.8 %) at temperatures of 25 and 80°C. Electrochemical techniques, including Linear Polarization Resistance (LPR), Electrochemical Impedance Spectroscopy (EIS), and Tafel extrapolation, were employed to measure corrosion current densities and elucidate corrosion mechanisms over immersion periods of 70 to 100 hours. Corrosion rates in anoxic conditions were relatively low in the beginning (10–30 µm/year), and slightly increased with the disturbance induced by the Tafel method. Protective effects of siderite (FeCO₃) and iron sulfide layers were highlighted in anoxic conditions but were insufficient to prevent corrosion in the long term under oxic and sulfide-rich conditions. Corrosion rates were the highest in oxic conditions, reaching up to 7 mm/year at 80°C, controlled by oxygen diffusion and reduced passivity due to insufficient protective layers. Sulfides also accelerated corrosion, with rates up to 1.5 mm/year at 80°C, attributed to the formation of less protective iron sulfide layers, cathodic activation by sulfide adsorption and the decrease of pH (from 7 to 4) due to H+ release. Higher corrosion rates were observed at 80°C across all conditions. This work confirms and recalls the critical need to manage environmental factors in waste repositories, particularly oxygen ingress and sulfide production, to minimize corrosion risks and ensure the longevity of containment systems, by using such materials as cemento-bentonitic filling material for the lining
The geoheritage inventory process in Occitanie (southern France): focus on Devonian to Permian sites
No full textInternational audienceIn France, the inventory of geoheritage was established by law in 2007. This inventory is managed at national level by the National Commission of Geoheritage (CNPG). Each french region has a Regional Commission for Geological Heritage (CRPG), which draws up an inventory of geological heritage sites and updates their knowledge in line with evolving concepts and scientific advances. In Occitanie (south of France), this inventory is carried out by a multidisciplinary group of geoscientists whose work is supervised, in particular, by the french geological survey (BRGM).Occitanie exhibits a great geodiversity related to the Variscan orogeny, as its territory includes the southern part of the french Massif Central, including the black mountain, and the eastern part of the Pyrenees, particularly in the axial and north-Pyrenean zones.These geoheritage sites, depending on their specific features, cover all the geological disciplines involved in understanding the history of the Variscan orogen: magmatic, metamorphic and tectonic aspects, as well as the sedimentary basins associated with the various stages in the evolution of the orogen, from a sedimentological, palaeontological and stratigraphic point of view. This presentation will highlight the region's most iconic geoheritage sites in the Variscan context.</div
Qualification des modèles de microclimat et des outils de simulation : une intercomparaison académique
No full textInternational audienceIn recent decades, numerous urban microclimate models have been developed to address various applications, such as diagnosing urban overheating and evaluating heat mitigation strategies using green or grey solutions. These models account for complex physical interactions; however, their qualification and validation remain significant challenges due to their complexity and the lack of a standardized framework and comprehensive reference datasets.This paper presents the first step of a comprehensive qualification and validation methodology through the definition of an academic benchmark and its application to four urban microclimate models. The proposed methodology follows an incremental phenomenological approach, systematically analysing heat transfer processes within an idealized street canyon with well-defined conditions across four cases: shortwave radiation, longwave radiation, aeraulics, and their coupling with heat conduction and storage in walls and ground. The benchmark aims to analyse the behaviour of different microclimate models, quantify deviations between simulation results, and identify their underlying sources within the physical models. This is achieved through the intercomparison of simulation results, incorporating reference data with a known standard deviation where available.The results show good agreement between models for solar radiation, infrared radiation, and heat conduction but reveal significant deviations in surface convection, stressing the need for further research into convection modelling and its influence on coupled processes. Additionally, the results confirm the suitability of the proposed methodology in identifying the sources of deviations between models. This benchmark provides a robust framework for model qualification and is expected to be widely adopted in future studies.Au cours des dernières décennies, plusieurs modèles de microclimat urbain ont été développés et utilisés pour diverses applications. Ces modèles permettent de diagnostiquer les surchauffes urbaines ou d'évaluer différentes stratégies d'atténuation de la chaleur, basées par exemple sur des solutions vertes ou grises, en tenant compte de toutes les interactions physiques. Cependant, leur validation reste un défi pour la recherche, en raison de leur complexité et de l'absence d'un cadre de qualification commun. Cet article propose et met en œuvre la première étape d'une méthodologie de qualification commune progressive par le biais d'un benchmark sur une étude de cas académique idéale, correspondant à un canyon de rue. La méthodologie proposée vise à analyser d'abord, de manière aussi indépendante que possible, les différents phénomènes physiques simulés, tels que le rayonnement solaire, le rayonnement infrarouge, l'aéraulique et la conduction thermique, puis leur couplage. Cette méthodologie a été appliquée à quatre modèles de microclimat urbain : MATHIS, SOLENE-Microclimat, SOLENE-SUSHI et TRABOULE-ProLB, mettant en évidence leurs capacités respectives, leurs similitudes et leurs différences. Dans l'ensemble, les résultats montrent une bonne correspondance pour le rayonnement solaire, le rayonnement infrarouge et la conduction thermique, mais des écarts significatifs pour la convection à la surface. Ces résultats soulignent l'importance de poursuivre les travaux de recherche sur la modélisation de la convection. Ils montrent également la pertinence de la méthodologie développée afin d'évaluer l'origine des divergences entre les modèles. Par conséquent, cette méthodologie devrait être appliquée plus largement à l'avenir
Un outil d’aide à la décision pour élaborer une stratégie collective de sécurisation de l’AEP
No full textInternational audienceGrowing pressure on water resources is posing new challenges for stakeholders in the drinking water supply (DWS) sector, calling on them to think collectively on a larger scale than that on which they currently operate. To support these evolutions, the present article proposes an original decision-support approach, combining a participatory approach and modeling. The approach is based on the co-construction and participatory use of a hydro-economic model simulating the operation of the drinking water supply system, taking into account interdependencies between drinking water supply management entities (through shared resources and interconnection infrastructure). This approach makes it possible to explore different prospective scenarios, to collectively plan for future drinking water supply security on a relevant scale. The approach was implemented in Sud-Finistère (Brittany, France), engaging the different stakeholders involved with drinking water management in the region. It has built a shared vision of the challenges facing drinking water management in the region, and quantified the future water deficits for different prospective scenarios co-constructed with stakeholders. Various types of results and indicators, notably maps, are available for analysis to identify any limiting factors and bottlenecks. Building on these diagnoses, the approach has made it possible to assess the effectiveness of multiple adaptation measures and combinations of measures co-constructed by stakeholders. The simulations provide objective information on the expected effects of the measures, facilitating dialogue between stakeholders who may have differing preconceptions as to their effectiveness, thereby fuelling collective planning on the actions to be implemented to secure future drinking water security. The proposed approach was positively evaluated by the participants. It is replicable in other regions where needed.Les tensions croissantes sur les ressources en eau posent de nouveaux défis aux acteurs de l’alimentation en eau potable (AEP), les invitant à réfléchir collectivement à une échelle plus large que celle à laquelle ils fonctionnent actuellement. Pour accompagner ces évolutions, cet article propose une démarche d’aide à la décision originale, combinant approche participative et modélisation. La démarche s’appuie sur la co-construction et l’utilisation participative d’un modèle hydro-économique simulant le fonctionnement du système d’approvisionnement en eau potable, prenant en compte les interdépendances entre les collectivités (ressources partagées, interconnexions). L’approche permet d’explorer différents scénarios prospectifs pour réfléchir de façon collective à la sécurisation de l’AEP à une échelle pertinente. La démarche a été mise en œuvre dans le Sud Finistère, mobilisant les différents acteurs de la gestion de l’eau potable du territoire. Elle a permis de construire une vision partagée des enjeux de gestion de l’AEP sur le territoire, d’anticiper et de quantifier les déficits ressources-besoins des collectivités pour différents scénarios d’évolutions futures co-construits avec les parties prenantes. Différents types de résultats et d’indicateurs, notamment des cartographies, sont analysables en sortie de simulation pour identifier les éventuels facteurs limitants et points de blocage. Face à ces diagnostics, la démarche a permis d’évaluer l’efficacité de multiples mesures et combinaisons de mesures d’adaptation proposées par les acteurs. Les simulations fournissent une base d’information objective sur les effets attendus des mesures, facilitant le dialogue entre des parties prenantes pouvant avoir des a priori divergents quant à leur efficacité, et alimentant ainsi la réflexion sur les actions à entreprendre pour orienter favorablement l’avenir. La démarche proposée a été évaluée positivement par les participants. Elle est reproductible sur d’autres territoires
Assessing seasonal forecast performance to predict crop irrigation requirements to support water management decision-making in the Mediterranean region
No full textInternational audienceIrrigation water management in the Mediterranean region faces major challenges due to climate variability changes. To address this reality, tools that support early decision-making are increasingly needed. While seasonal forecasts (SWF) have demonstrated potential to assist the agricultural sector, their practical application in irrigation management remains limited. This study evaluates the accuracy and skill of raw (non-bias-corrected) SWF in predicting weather and climatic demand conditions, crop cycle duration estimated using the growing degree day (GDD) approach and crop irrigation water requirements across the Mediterranean region, focusing on how seasonality and location factors may influence their usefulness. The Lucefecit Collective Irrigation Scheme (Portugal), the Crau irrigated area (France), and the Thessaly Plain (Greece) were selected as key irrigation locations in the Mediterranean region. Durum wheat and maize were selected as representative autumn-winter (AW) and spring-summer (SS) crops, respectively. SWF data were generated within the HubIS project (PRIMA/ 0006/2019) using the Weather Research and Forecasting system. The results showed that SWF performance varied by predicted variable, season, and location. Overall, the forecasts were more accurate in predicting matic demand (ETo) than precipitation, with mean absolute errors (MAE) of 17.0-170.3 mm and 94.8-438.6 mm, respectively. Higher irrigation demands were predicted, especially in SS, as SWF tended to overestimate ETo to 20 %), underestimate seasonal accumulated precipitation (up to 90 %), underestimate temperature (up to degrees C) and extend crop cycles (up to 60 days). Irrigation requirements anomaly signals were better captured wheat than for maize. SWF exhibited less skill than the long-term (10-years) weather observed average in almost all cases, except for AW ETo predictions in Portugal. Nevertheless, the range of irrigation requirements (for wheat 0-489 mm and for maize 563-960 mm) suggests SWF hold potential for early irrigation water management, which could be better achieved with appropriate forecast data corrections
: Contribution aux actions 2024
No full textDans le cadre du groupe de travail « Analyse Multi-Critères » (GT AMC) appliquée à l’évaluation des projets de gestion des inondations, des fonctions de dommage à différents types d’enjeux ont été développées à partir de l’année 2011. Cependant, dans un contexte dit torrentiel, la genèse des dommages fait intervenir des processus différents que ceux considérés pour des autres types d'aléa inondation. En effet, les approches actuelles d'estimation des dommages liés aux crues torrentielles s'orientent vers des fonctions d'endommagement par classes d'intensité d'aléa au lieu de fonctions de dommages continues, comme celles proposées par la méthode officielle française.Parmi les différentes méthodes proposées dans la littérature pour estimer les dommages dans des contextes plus larges que ceux de l’inondation fluviale classique, celle qui a été mise en œuvre en Suisse par l'office fédéral de l'environnement (OFEV) est particulièrement intéressante. Cet intérêt se fonde sur différents éléments. D'abord cette méthode s'oriente vers un objectif d'évaluation des projets de gestion des inondations qui comporte de similitudes avec la méthode AMC PAPI préconisée en France. En plus, elle est issue d’un territoire où le patrimoine architectural est assez similaire à celui du territoire français métropolitain de montagne. Troisièmement, elle a recours à des indices d'endommagement définis dans différents contextes d'inondation, y compris le contexte torrentiel. Et dernièrement, elle couvre de très larges enjeux (bâtis, réseaux, infrastructures). Ces éléments permettent de considérer la méthode suisse comme un bon candidat pour pallier à court terme l'absence de méthodologie spécifiquement française d'estimation des dommages dans des contextes de crues torrentielles. L'objectif de ce rapport est, donc, de proposer des recommandations d'estimation des dommages aux enjeux bâtis en contexte torrentiel s’appuyant sur une adaptation de la méthode Suisse au contexte français
Ce que les questions environnementales font aux professions scientifiques et techniques : expertise, délimitation des frontières et réflexivité: Entre production scientifique, injonction à l’interdisciplinarité et réponses aux politiques publiques : le Service Géologique National
No full textInternational audienceIn France, the energy transition and environmental challenges are reshaping the issues related to subsurface resources. This presentation explores how organizations like BRGM are incorporating the social sciences and humanities to support public policies and site rehabilitation. Interdisciplinarity is redefining the boundaries between scientific knowledge and local knowledge, in response to the rise of citizen critiques and private initiatives. BRGM has launched several collaborations to integrate these diverse forms of knowledge, notably with PEPR poject and OFREMI. The aim is to discuss the potentials and limitations of these interdisciplinary approaches.En France, la transition énergétique et les enjeux environnementaux renouvellent les défis liés aux ressources du sous-sol. Cette communication explore comment des organismes comme le BRGM intègrent les sciences humaines et sociales pour accompagner les politiques publiques et la réhabilitation des sites. L’interdisciplinarité redéfinit les frontières entre savoirs scientifiques et savoirs locaux, face à l’émergence de critiques citoyennes et d’initiatives privées. Le BRGM a engagé plusieurs collaborations pour intégrer ces savoirs, notamment avec les PEPR -Sous-Sol et l'OFREMI. L'objectif est de discuter des possibilités et limites de ces approches croisées
Prospects for improving the food and economic security of smallholder maize-based farming systems: a farmer typology approach in Zimbabwe
No full textInternational audienceApproximately 70% of communal farmers in Zimbabwe live in poverty, struggling to meet basic needs and provide for their families. These farmers face significant challenges in accessing essential services and resources. This situation makes them a critical subject for study, particularly in the context of smallholder farming systems in sub-Saharan Africa. This study aims to enhance the existing body of knowledge by incorporating a participatory approach and statistical analysis to characterize smallholder farmers and examine their economic and food security status. Methods We employed principal component analysis (PCA) and hierarchical cluster analysis (HCA) to classify farmers based on various factors such as cultivated land, livestock ownership, family labor availability, off-farm activities, and remittance receipt. Data was collected from 248 randomly selected households across three purposively chosen wards in the Murehwa district, Zimbabwe. Results The analysis identified four distinct farm clusters: Cluster 1: Highly resource-constrained households, Cluster 2: Moderately resource-endowed households without off-farm income, Cluster 3: Moderately resource-endowed households with access to off-farm income, Cluster 4: Highly resource-endowed households All clusters primarily cultivated maize, their main food source, but showed significant variations in their economic and food security status. The clusters also differed in their levels of resource access, with notable distinctions in the availability of family labor and off-farm income. Discussion These findings highlight the need for targeted interventions that provide essential inputs, such as affordable seeds and legumes, to promote crop diversification. Additionally, the study advocates for promoting alternative income sources, such as small livestock and beekeeping, which can enhance food and economic security by reducing the reliance on crop production alone, particularly in the face of uncertain agricultural conditions. These strategies are crucial for improving the livelihoods and resilience of smallholder farmers in Zimbabwe and similar contexts in sub-Saharan Africa
Déploiement de la géothermie profonde en région Centre-Val de Loire : un argumentaire à destination des acteurs locaux basé sur des analyses sociales, économiques et environnementales
No full textNational audienceThe Centre Val-de-Loire region sees deep geothermal energy as a virtuous energy solution for the region, but to date it has not been widely deployed. To encourage its use, the region has financed a research project of regional interest, called "AMIGO". The project is being co-ordinated by BRGM in partnership with LEO (Laboratoire d'Économie d'Orléans), AFPG (Association Française des Professionnels de la Géothermie), AMORCE (Association d'accompagnement des collectivités et des acteurs dans la transition énergétique) and AgreenTech Valley (national cluster dedicated to digital technologies for plant-based industries). Its aim is to draw up a set of arguments to help local authorities and private-sector players in the region to choose between the various possible sources of renewable energy for district heating networks, industrial processes or heating crops in greenhouses. To develop this argument, the phases of the project are: (1) to understand the position of the stakeholders with regard to deep geothermal energy, and (2) to gather the key information in the territorial context (socio-economic and environmental aspects of a deep geothermal energy project, information on the geothermal resource, demand for heat in the territory). This article presents the progress made in the process of constructing the argument, in particular the results of (1) the analysis of the positioning of stakeholders in the region and (2) the economic and environmental analysis of a deep geothermal energy project.La géothermie profonde est vue par la région Centre Val-de-Loire comme une solution énergétique vertueuse pour le territoire, cependant, à ce jour, elle y reste peu déployée. Aussi, pour favoriser sa mise en œuvre, la région a financé un projet de recherche d’intérêt régional, appelé « AMIGO ». Ce projet est coordonné par le BRGM en partenariat avec le LEO (Laboratoire d'Économie d'Orléans), l'AFPG (Association Française des Professionnels de la Géothermie), l’AMORCE (Association d'accompagnement des collectivités et des acteurs dans la transition énergétique) et AgreenTech Valley (Cluster national dédié aux technologies numériques pour les filières végétales). Il a pour objectif d’établir un argumentaire pour aider les collectivités locales et les acteurs privés de la région à choisir entre les différentes sources d'énergie renouvelable possibles pour les réseaux de chauffage urbain, les processus industriels ou le chauffage des cultures sous serres. Pour développer cet argumentaire, les phases du projet sont : (1) comprendre le positionnement des acteurs vis-à-vis de la géothermie profonde, et (2) rassembler les informations clés dans le contexte territorial (aspects socio-économiques et environnementaux d’un projet de géothermie profonde, informations sur la ressource géothermale, demande de chaleur sur le territoire). Cet article présente les avancées dans le processus de construction de l’argumentaire, en particulier les résultats (1) de l’analyse du positionnement des acteurs de la région et (2) de l’analyse économique et environnementale d’un projet de géothermie profonde
Evolution of the crustal reservoir feeding La Palma 2021 eruption. Insights from phase equilibrium experiments and petrologically derived time scales
No full textInternational audienceCrystallization experiments were performed on three representative samples of the 2021 La Palma eruption at variable temperatures (920-1150°C), pressures (100-400 MPa), and H2O-CO2 ratios in order to shed light on the pre-eruptive reservoir architecture and evolution. Experimental data reveal that La Palma crustal reservoir was at 300 MPa (10 km), at a temperature of 1065°C with a melt water content of 2-3 wt%, lying in the stability field of amphibole. Mineral compositional zoning along with experimental constraints and whole rock data, show that a cold magma body (850-950°C), likely a remnant of previous eruptive episodes at La Palma, was rejuvenated by hotter magmas that increased the temperature of the bottom portion of the reservoir up to 1135°C. Time scales derived from olivine diffusion profiles show that such a reactivation started 10-15 years prior to eruption, and was marked by at least four different injections from a deep mantle reservoir at ≥25 km. This sequence is corroborated by geophysical signals and changes of surficial fluid geochemistry monitored during that period. Olivine zoning further indicates that the last mafic recharge prior to eruption onset occurred in mid-October 2018, and was followed by a post-injection cooling phase which continued up to the date of the eruption, during which the top portion of the rejuvenated body re-entered the stability field of amphibole. This cooling period preceding the eruption could in part explain the absence of pre-eruptive seismic signals at ~10 km, as revealed by the revision of the precursory seismic catalogue since 2017. Once initiated, the eruption drained the 300 MPa body, which in turn activated the deep-seated mantle reservoir, lying at >500-600 MPa, which supplied fresh, hotter and volatile-rich magma, that was emitted during the second half of the eruptive episode. Amphibole breakdown documented in first emitted magmas is related to decompression and not to overheating of the resident magmas. The fact that the rocks emitted during the first half of the eruption do not bear textural or compositional evidence for a mafic recharge occurring a short time prior the eruption suggest that the eruption triggering is linked to the internal evolution of the reservoir (volatile build-up) or to external factors.div>