HAL-BRGM, les publications scientifiques en libre accès du BRGM
Not a member yet
14098 research outputs found
Sort by
Evidence of Geological Control on the Hydrological Response of Tropical Volcanic Catchments
No full textInternational audienceThe aim of this study is to assess the key drivers of runoff generation in permeable volcanic catchments, and notably the role of geology. Therefore, the hydrological response of 28 catchments located on the tropical volcanic Island of la Réunion, characterised by strong climatic forcing and geological contrasts, was studied. High‐frequency measurements (15‐min time step) of radar rainfall and discharge records over the 2014–2022 period were analyzed to develop a hydroclimatic database including 4591 storm‐flood events. At the annual scale, results show regional patterns in the rainfall‐runoff relationship, associated with the geological age and the local climate. Our results provide evidence of windward/leeward and geological effects on hydrological response at both the annual and flood event scales, with a significant correlation between the event‐scale runoff coefficient and annual rainfall. Combined with a statistical analysis of the data, including the application of a random forest algorithm, results suggest the importance of antecedent saturation conditions, preferentially occurring on the older and more weathered geology, while younger geology displayed a more episodic pattern. This study contributes to increasing our understanding of the hydrological behaviour of tropical volcanic catchments, by analysing the relative importance of climate and geology in controlling the catchments' hydrological response, which may help improve water management and flood prediction
Impact du Martelage sur les Propriétés Acoustiques : Caractérisation Microstructurale d’un Corpus de Gongs et Cymbales du Musée de la musique
No full textMatériaux dans les instruments de musique, matériaux synthétiques et architecturés; GSAM - Acoustique Musicale: GVB - Vibro acoustique et Contrôle du BruitNational audienceDans le procédé de fabrication des idiophones en bronze tels que les gongs et les cymbales, l'étape du martelage à froid est primordiale car elle permet d'accorder et de modifier finement le timbre et les variations sonores de ces instruments. Soutenu par la Fondation des Sciences du Patrimoine, ce projet de thèse vise à comprendre le rôle acoustique du martelage pour les gongs, en tentant d'établir un lien entre les propriétés microstructurales et vibratoires des alliages de bronze. Cette problématique s’appuie sur un corpus de gongs et de cymbales provenant d’Asie du Sud-Est conservés au Musée de la musique, produits entre le 18ème et le 20ème siècle, et présentant différentes typologies de martelage. La littérature sur les procédés de fabrication montre toute l'importance de la trempe, un type de traitement thermique inhabituel pour les bronzes, qui permet d'obtenir des propriétés mécaniques spécifiques rendant possible le martelage et le travail d'accordage. La présente communication propose premièrement, de rechercher et identifier les phases martensitiques typiques de cette trempe au sein du corpus par diffraction de rayons X (ligne DiffAbs, synchrotron SOLEIL) ; deuxièmement, de présenter le protocole d’analyse modale permettant de mesurer l’impact de l’écrouissage sur les propriétés vibratoires (fréquences et amortissements modaux) d’échantillons dont la composition d’alliage, la géométrie et l'état métallurgique sont contrôlés. À terme, le travail permettra de comprendre l’effet du martelage et des propriétés microstructurales sur les propriétés acoustiques des gongs et cymbales
Water policy in New Caledonia: Governmentality, multi-scale politics, and the commons
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/615578/)International audienceThe notion of “shared water policy” lies at the centre of the new NC water policy. Though it conveys an idea of commons, the new NC water policy is hybrid as it combines governmentality (measurement and calculation) and commons as analytical lenses offers a new perspective on emerging tensions related to water policy and the difficulties water managers and policy-makers face in crafting institutional innovations. This chapter first explores the conceptual rationale of the “shared water policy” and proposes a conceptual approach of water policy as a water-centered assemblage. Then, the focus on water policy “from below” follows the encounters of local and indigenous water conceptions and practices with new water assemblages driven by mining extraction and governmental anchoring in different localities in NC. It analyses the colonial legacy, exploring the structure, linkages, tensions and gaps between “traditional water” and “modern water” through these encounters. The case study approach ultimately highlights how local water policy entangles elements of governmentality, commodification and the commons against the background of localized fault-lines, memories and expectations
The VKP water management committee: An inspiring and successful experience for water management and stakeholder engagement
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/615576/)International audienceBefore the launch of the participatory process aimed at implementing a Shared Water Policy in 2018, several local consultations had been initiated at the beginning of the 2010s in catchment areas where concurrent water uses were becoming problematic. The very first experience of participation in New Caledonia took place in 2015 with the Voh-Koné-Pouembout local water management committee. This local experience was one of the cornerstones of the methodology used for the Shared Water Policy. This chapter recounts this shared experience. The municipalities of Voh-Koné- and Pouembout villages, located in the North-West of New Caledonia, faced unprecedented development generated by the establishment of an international scale nickel mining industrial complex, the Koniambo Nickel Project, from 2006 onwards. To cope with the risks of shortages, quality degradation and conflict over water rights, the Northern Province created a local water committee (the Water Management Committee of Voh-Koné-Pouembout—VKP WMC) to facilitate regional development while safeguarding water resources. The VKP WMC members (experts, customary leaders, farmers, etc.) have developed an integrated water resource management program using participatory methods. The authors, directly involved in this local participation process, describe the tools they used to facilitate water management coordination. This experience of governance was unique to New Caledonia and has been praised by all its members for its ability to unite and coordinate actions that benefit the population
Des bauxites tropicales à l'exhumation orogénique : la datation (U-Th)/He révèle la tectonique polyphasique dans le sud de la France
No full textNational audienc
Post-exposure recovery of Microcystis aeruginosa from nanoplastics stress: metabolic adaptation and damage resilience
No full textInternational audienceDespite the ubiquitous distribution of nanoplastics (NPs) in global aquatic ecosystems, microbial adaptive strategies during the post-exposure period remain largely unexplored. In this study, Microcystin aeruginosa treated with 5 and 50 mg/L polystyrene (PS) for 15 days and then were transferred to PS-free medium for 15 days to study toxicology and post-exposure effects. The results showed that 5 and 50 mg/L PS inhibited algal growth, with inhibition rates of 6.82% and 9.34% at the end of exposure, respectively, while M. aeruginosa resumed growth on the fourth day of the post-exposure period. In addition, PS enhanced microcystins (MCs) biosynthesis and release in a dose-dependent manner during exposure, while phased variations were observed in MCs production and release during recovery. Transcriptome analysis revealed that 5 mg/L PS inhibited cell growth by disrupting cellular structures, inducing oxidative stress, altering lipid metabolism, and suppressing protein synthesis. These effects were largely reversible during the recovery phase, except for irreversible damage to the algal cell membrane. KEGG pathway analysis identified significant suppression of carbohydrate and energy metabolism during exposure, with subsequent reactivation during post-exposure. These findings suggest that M. aeruginosa may mitigate PS-induced oxidative stress through glucose accumulation and reduced energy expenditure
Granites et mineralisations filoniennes (Au et Sn-W) en contexte tardi orogenique (Chaıne Hercynienne, Galice centrale, Espagne) – Hommage a Eric
No full textNational audience>Le Domaine Schisteux de Galice Centrale (DSGC) se situe dans le Nord-Ouest de l'Espagne (Galice) et appartient à la zone interne de la chaîne hercynienne. Trois épisodes de déformation affectent le secteur. Durant l'événement D3 (métamorphisme MP-HT), le DSGC est affecté par la mise en place de quatre générations successives de granites nommés G1 (ca. 335 Ma), G2 (ca. 322 Ma), G3 (ca. 318 Ma) et G4 (ca. 303 Ma). Autour des granites G2 et G3, des minéralisations filoniennes à Au et Sn-W se sont formées. Les filons aurifères sont spatialement associés aux granites G3 alors que les minéralisations filoniennes Sn-W sont associées aux granites G2. Le massif G3 de Boborás, hôte des minéralisations Au de Brués et le massif composite G1-G2 de Beariz, hôte des minéralisations Sn-W ont été plus spécifiquement étudiés. L'étude structurale confirme le rôle du contrôle régional sur la forme allongée N-S de ces granites et démontre l'existence d'un continuum de déformation depuis l'emplacement des granites jusqu'à la formation des minéralisations. Les données pétro-structurales, minéralogiques et géochronologiques sont en faveur d'un même évènement minéralisateur et d'un âge proche des granites voisins, ce qui situerait les filons aurifères autour de 318 Ma et les filons SnW vers 322 Ma. Un modèle général de formation est proposé dans lequel l'ensemble des granites se met en place au cours d'une phase de déformation associant un serrage E-W et une déformation cisaillante à vergence nord. Cet évènement tectonique, interprété en terme d'extrusion latérale en réponse à la poursuite de la convergence EW, se localise dans une demi-cuillère limitée à l'Est par une zone de cisaillement dextre (échelon dextre des granites G3) et vers l'Ouest par la zone de cisaillement senestre de Couzo. Les minéralisations se forment à la faveur d'instabilités mécaniques formées au toit des plutons. Ainsi, le rôle des granites est à la fois thermique et rhéologique (instabilité, lien spatial) mais aussi chimique puisque la nature des minéralisations (Sn-W ou Au) dépend de la nature et de l'âge des granites environnants
Towards standardized microbial hydrogen consumption testing in the subsurface: harmonized field sampling and enrichment approaches
No full textInternational audienceHydrogen (H₂) will play a crucial role in Europe’s green energy transition, necessitating efficient storage solutions such as underground storage in salt caverns or porous media. However, the potential microbial H₂ consumption in these subsurface environments poses risks to storage stability and safety, and its magnitude remains relatively unexplored. Within the HyLife-CETP project, we developed a brine sampling protocol for the field operators and tested a standardized laboratory procedure for estimating microbial hydrogen consumption rates in these original brine samples, combining precise gas, chemical, and genetic analyses. Four labs tested and compared the developed enrichment protocol in a round-robin-like test using artificial brine and the hydrogen-consuming, sulfate-reducer Oleidesulfovibrio alaskensis as a reference strain. This test revealed consistent trends in microbial hydrogen consumption and corresponding pH increase across labs, indicating that the developed protocol effectively captures the overall microbial activity. However, inter-laboratory variability in the reported H 2 consumption quantity, ranging from 19.8 to 61%, highlights how metabolic activity, analytical approaches, and sample handling variations can affect results. Most importantly, abiotic hydrogen loss, particularly leakage from experimental bottles, was identified as a significant factor affecting accurate hydrogen consumption estimation, and we tested different measures to reduce abiotic losses. Our developed protocol effectively detected microbial hydrogen consumption and identified associated metabolic processes, supporting its robustness for studying microbial activity in underground storage systems. In addition, the findings underscore the natural biological variability inherent to growth tests, particularly in hydrogen-utilizing systems
User interface design principles for peer-to-peer distributed databases for ecological citizen science projects
No full textInternational audienceCitizen science, where participants from outside of academia contribute to data collection or analysis, is an important approach in ecological studies that can significantly improve both modelling outcomes and community participation. However, all ecological citizen science platforms developed to date rely on centralised server architecture for data storage and communication with citizen scientists, which can lead to unsustainable server maintenance costs for project managers as well as data sovereignty issues for the concerned communities, thereby endangering project resilience and sustainability after the end of a funded project. Distributed databases, which rely on peer-to-peer technology to store and share data, can address these concerns, but they are complex and conceptually different from centralised systems. As such, their use involves a very steep learning curve that hinders their adoption by citizen science practitioners in ecology, where neither project leaders nor end users are experts in peer-to-peer technologies. In this article, the authors use formal and open-ended feedback from workshops with academics to discuss how well-planned user interface design can be used to facilitate the adoption of peer-to-peer distributed databases in citizen science and provide generalisable key recommendations for the implementation of user interfaces in citizen science applications. In particular, we discuss several key conceptual differences between centralised and distributed applications, such as key-pair authentication and eventual consistency, that must be efficiently and visually communicated to end users. While there is extremely limited literature available on user interface design for distributed systems (and none so far in the ecological field), we find that lessons learned from other fields transfer well to the field of ecological citizen science, that well-designed user interfaces are key to the adoption of new technologies, and that simplicity and efficiency in interface design are more important than showing average users the details of how the underlying technology works. We propose these recommendations as a blueprint for future research and development of citizen science applications based on peer-to-peer distributed database technologies
Suivi des processus d'intrusions salines dans l'aquifère sédimentaire complexe côtier du Plio-Quaternaire du Roussillon
No full textInternational audienceLes eaux souterraines qui s’écoulent sous la plaine du Roussillon (Pyrénées Orientales) au sein des aquifères multicouches constitués de formations alluviales du Quaternaire, surmontant des niveaux de sables et d'argiles du Pliocène représentent une ressource en eau majeure pour ce territoire. Placées en situation d’Alerte depuis plus de 2 ans, elles sont soumises à un risque croissant d’intrusion d’eau de mer, d’autant qu’une partie non négligeable de ces aquifères se prolongent sur plusieurs dizaines de kilomètres sous la mer Méditerranée. L’observatoire hydrogéophysique Dem'Mer qui a été mis en place en bordure littorale pour suivre le comportement piézométrique et physico-chimique (conductivité, température) des eaux souterraines circulant dans les différents niveaux perméables décrits au sein de cet aquifère multicouche est un outil précieux pour le suivi des processus d’intrusion. Les séries temporelles de niveaux d'eau, de conductivité électrique et de température des eaux souterraines qui s’écoulent au droit de l’observatoire en direction de la mer permettent de mettre en évidence l’intrusion d’eau de mer dans les formations superficielles et des écoulements d’eau douce ascendants en profondeur. Ces observations indiquent que des volumes non négligeables d’eau douce soient stockés, ou s’écoulent lentement, dans sa partie off-shore, que l’on cherche à imager avec des outils géophysiques en forage et en mer. Les principaux processus d’écoulement d’eau souterraine et d’influence des forçages météo-marins que l’on observe au niveau de cet observatoire seront décrits à partir des données disponibles et les différentes hypothèses concernant la présence d’une ressource d’eau douce off-shore seront présentées