Establishing experimental characterization of the thermal conductivity of limestone substrate under different water saturation indices to improve heat transfer knowledge
Geothermal heat exchangers are currently dimensioned using mathematical models that only consider conductive heat transfers where water content is not considered. However, considering water could improve geothermal exchange dimensioning. To understand the effect of water on thermal conductivity, we focus on the unsaturated zone characterized by its capacity to store and transfer heat and, also, strongly affected by variations in water content. Heterogeneous limestones in an unsaturated zone over a depth of 20 m deep were investigated in the laboratory. To measure the thermal conductivity at different water contents, two methods were considered: (1) the direct thermal conductivity method and (2) an indirect estimation through acoustic measurements using an empirical model originally developed for dry conditions. The applicability of this empirical approach beyond its initial domain is therefore explored. Both methods show coherent results in dry conditions (λ dry = 1.5 and 1.3 W. m -1 .K -1 for direct and indirect methods) highlighting the usefulness of the indirect, and easier, method. For saturated or partially saturated materials however, the indirect method presents apparent inconsistencies, while for some samples, of rather massive appearance, only slightly altered and fractured, water content has a relatively low impact on thermal conductivity. This indirect approach, when used with a dry-based empirical model, shows clear limitations in capturing the effect of water in the pores of complex rocks. The direct method, which directly measures the thermal conductivity of a small area at the sample surface, shows an increase in thermal conductivity with water saturation. Finally, we discuss the limits of both methods considering the microstructures of the samples.
(International Journal of Thermal Sciences. vol. 229, n° 1290-0729, pp. 111091, 01/11/2026)
BRGM, ISTO, BRGM, INSU - CNRS, UO, CNRS, LOMC, ULH, NU, CNRS, ISTO, BRGM, INSU - CNRS, UO, CNRS, LaMé, UO, UT, NEOLAiA, INSA CVL, INSA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Structures surimposées des dunes aquitaines : description et compréhension des facteurs de mise en place
Le littoral aquitain se caractérise par de vastes champs dunaires s’étendant sur 5-7km à l’intérieur des terres, majoritairement fixés par une forêt de pin maritime. Trois grands ensembles morphologiques peuvent être distingués: i) la dune bordière, façonnée par des actions de gestion depuis le XIXᵉ siècle, ii) les dunes barkhanoïdes, qui s’étendent sur 3-5km vers l’intérieur des terres et iii) les dunes paraboliques, les plus distales. Les dunes barkhanoïdes, sujet de cette étude, présentent une grande diversité de morphotypes correspondant à différents stades de leur développement: forme chaotique de petites dimensions, rides barkhanoïdes ou barkhanes individualisées. On dénombre jusqu’à 7 à 10 séries de dunes, plus ou moins parallèles les unes aux autres, dont la hauteur de crête augmente vers l’intérieur des terres. Au sud du Bassin d’Arcachon, les dunes sont plus massives, accolées en méga-rides-barkhanoïdes, pouvant atteindre localement 70m d’altitude (Biscarrosse). Malgré cette diversité (spatiale, dimensions), on constate que quelques que soit leur forme et leur taille, les dunes barkhanoïdes présentent toutes des structures surimposées. Le LiDAR-HD (©IGN) a permis de révéler ces structures de second ordre sur l’ensemble du littoral Aquitain. Deux types de morphologies sont identifiées (Billieres-Kim et al., soumis): des dépôts surimposés parallèles à la crête (superimposed bedforms) et des structures ondulantes régulières, perpendiculaire à la dune (wavy patterns). Bien que mentionnées dans la littérature, ces structures de 2nd ordre restent peu étudiées, tant du point de vue de leurs dimensions que des processus et conditions prévalents à leur formation. L’approche couplée LiDAR-Géoradar, constitue une approche performante pour étudier ces structures, à la fois en identifiant les caractéristiques de surface et en imageant avec grande précision l’architecture interne des dunes. Par ailleurs, les dunes du Pilat et du Trencat (33) sont deux systèmes dunaires transgressifs actifs, qui présentent des structures de 2nd ordre similaires mais de plus faibles dimensions. La comparaison entre dunes actives et anciennes dunes fixées permettra, par analogie, de s’interroger sur les forçages ayant gouverné leur mise en place au cours des derniers siècles, de replacer l’émergence de ces structures dans l’évolution des systèmes dunaires aquitains, et plus largement de la façade atlantique.
(27/10/2026)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Land–sea thermal decoupling and iceberg discharges in the western North Atlantic during Heinrich Stadials 5–3
Abrupt climate changes of the last glacial period, including Dansgaard–Oeschger cycles and Heinrich Stadials (HSs), were contemporaneous with profound disruptions of the Atlantic Meridional Overturning Circulation (AMOC). However, their impacts on the western North Atlantic and adjacent North American continent remain poorly resolved. Here we present a high-resolution multiproxy reconstruction from core MD99-2203 (Cape Hatteras, 35° N), integrating mineralogical and reworked dinocyst data, pollen and foraminiferal assemblages, and iLOVECLIM model simulations to identify HSs and investigate vegetation–ocean linkages during HSs 5–3. In contrast to the western European margin, each HS is marked by continental cold conditions coeval with warm sea surface temperatures (SST) and the onset of iceberg-rafted debris (IRD) deposition near Cape Hatteras, yet the regional landscape remained dominated by open forests. A close up of HS 4 reveals a distinct two-phase structure: an early stage of synchronous cooling in land and SST, associated with peak IRD deposition in the Ruddiman Belt, followed by a post-surge phase when ice-rafted debris reached 31–35° N. During this phase, cold and dry continental conditions contrasted with anomalously warm sea surface temperatures, generating enhanced land–sea thermal gradients. This contrast increased humidity and, together with rising atmospheric CO2 concentration, may have triggered transient forest recovery, which coincided with subsequent surface cooling. Comparisons with transient iLOVECLIM simulations successfully capture the early phase and reveal insightful spatially heterogeneous feedbacks in the later period. Our results reveal complex, evolving land–ocean interactions during abrupt climate events, providing new insights into regional climate dynamics and impacts of AMOC weakening.
(Quaternary Science Reviews. vol. 389, n° 0277-3791, pp. 110141, 01/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IPMA, CCMAR, UAlg, HNHP, MNHN, UPVD, CNRS
Estimating plastic export from estuaries into the sea using an estuarine-mass-balance model
Estuaries act as an interface between rivers and the sea, and therefore play a key role in transporting plastic to the sea. However, plastic transport in estuaries is complex and estuary-to-sea export is still very uncertain. This study presents a macroplastic mass-balance model that can be applied to specific estuaries, and produces export estimates similar to previous studies. The daily plastic export from estuary to sea during the wet season was estimated to be 290 kg for the Rhine-Meuse Estuary (RME), and 19,431 kg for the Saigon Estuary, where the discharge into the sea is 3.5 times larger for the RME, compared to the Saigon Estuary. Due to limited river discharge measurements for the Saigon Estuary, a yearly simulation could only be performed for the RME, corresponding to an export of 13,300 kg. These estimates fall within the uncertainty range of previous studies. Deposition and remobilization from riverbanks resulted in the largest model fluxes, with magnitudes of 20 t/d for the RME and 430 t/d for the Saigon Estuary. At the same time, the model is most sensitive to the uncertainty in parameters related to deposition. Our results demonstrate that with the right measurements, making reliable estimates of estuary-to-sea export is possible. However, uncertainty in plastic transport processes, like deposition and remobilization, leads to poorly constrained parameters and increased overall model uncertainty. Automated sensors, targeted field experiments, and improved model structure can enhance export estimates and further improve understanding of plastic dynamics in estuaries.
(Marine Pollution Bulletin. vol. 230, n° 0025-326X, pp. 119793, 01/09/2026)
WUR, IGE, IRD, INSU - CNRS, CNRS, INRAE, Fédération OSUG, UGA, Grenoble INP, UGA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Évolution des environnements sédimentaires au cours de la formation de la flèche du Cap Ferret : approche par géoradar et carottage
La flèche du Cap Ferret, située le long de la façade atlantique en Gironde, s’est formée au cours des 3 000 dernières années. Initialement ce littoral était caractérisé par la présence de l’embouchure tidal de la Leyre. La formation progressive de cette flèche du Cap Ferret et la migration de l’embouchure vers le sud, ont progressivement transformé ce littoral, passant d’un environnement ouvert à un environnement lagunaire semi-abrité. La chronologie et la dynamique sédimentaire associées à ces changements paléo- environnementaux restent cependant peu étudiées. Pour cela, un carottage de 15 m de profondeur couplé à un profil géoradar (antenne 100 MHz) ont été réalisés dans la partie nord de la flèche (Claouey, à proximité du VFF). Quatre unités morpho-sédimentaires distinctes sont identifiées. L'unité basale U1 (dont le toit atteint ~ -4.4 m NGF) correspond à un dépôt de sable gris coquillier (au moins 5.5 m d’épaisseur) caractéristique d’un remplissement de chenal. Drapant U1, U2 présente des sables moyens jaune et des réflecteurs radars fortement pentés (~15°), indiquant le sens de migration de barres intertidales et marquant le développement de la flèche et de sa base. U3 vient draper U2. C’est un niveau de sable jaune caractérisé par des réflecteurs radars subhorizontaux, interprété comme une accumulation de dépôts de sable marins puis éoliens. Ainsi, cette succession sédimentaire enregistre les principaux changements paléo-environnementaux, offrant une première caractérisation détaillée de l’évolution de la dynamique sédimentaire passée de ce littoral et la formation de la flèche du Cap Ferret.
(03/08/2026)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Nationwide monitoring of seabirds reveals species- and site-specific legacy PFAS contamination in French coastal areas
Per-and poly-fluoroalkyl substances (hereafter PFAS) are widespread and persistent compounds that pose a threat to human and wildlife health. Wildlife monitoring is essential to understand the extent of PFAS contamination and its ecological drivers. Seabirds are good bioindicators of PFAS contamination of the marine environment, yet some areas, including the French coastlines, remain poorly covered. Here, we quantified 11 legacy PFAS in the plasma of 9 seabird species (n = 340 chicks) from 30 sites along the French Atlantic and Mediterranean coasts. Linear perfluorooctanesulfonic acid was by far the most abundant PFAS. Oceanic piscivorous species (Northern gannets Morus bassanus, black-legged kittiwakes Rissa tridactyla and Scopoli's shearwaters Calonectris diomedea) had the highest PFAS concentrations compared to Larus sp. gulls and shags Gulosus aristotelis. Overall, Mediterranean seabirds had lower perfluoroalkyl sulfonic acid and higher perfluoroalkyl carboxylic acid concentrations compared to Atlantic seabirds. At a finer spatial scale, chicks sampled near estuaries had a slightly higher PFAS burden, suggesting local riverine inputs. This first large-scale survey of PFAS in French seabirds reveals substantial heterogeneity in PFAS contamination across French coastal environments. Future work should address the sources of this PFAS contamination and quantify its toxicological consequences, given that sampled chicks may be at risk based on previous avian studies reporting PFAS-related health effects.
(Environment International. vol. 214, n° 0160-4120, pp. 110386, 01/08/2026)
CEBC, ULR, CNRS, INRAE, LIENSs, INSU - CNRS, ULR, CNRS, LPO, PatriNat, MNHN, IRD, CNRS, OFB - DSUED, OFB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CCEM, IFREMER, MIVEGEC, CNRS, IRD [Occitanie], IRD, UM, CEN Corse, BEEP, IFREMER, UBO EPE, CNRS, LPTC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Chronic exposure to sodium fluoride or to tebuconazole disrupts the thyroid hormone and immune systems during early development of rainbow trout (Oncorhynchus mykiss)
Over the past 20 years, there has been a growing interest in endocrine-disrupting chemicals (EDCs) found in both terrestrial and aquatic environments. These substances have garnered attention from scientists, the public and regulatory bodies, with many being classified as substances of very high health concern. Only recently, disruption of the thyroid hormone system (THS) by EDCs has also attracted significant attention: In vertebrates, the THS interacts with various physiological systems, including the immune system (IS), and plays a crucial role in development. It can also influence the microbial diversity in certain tissues. The main objective of this study was to investigate the potential impact of sodium fluoride (NaF) on the THS and IS in rainbow trout ( Oncorhynchus mykiss ), a species of both economic and environmental importance. For this end, trout were exposed from the embryonic stage (48 h post-fertilisation) to the juvenile stage for 7 months. Fish were subjected to 1.5 mg F-/L or 5 mg F-/L and 20 µg/L tebuconazole (TBZ; positive control) monitored daily and sampled after 3 and 7 months of exposure to assess potential disruption to the thyroid hormone and immune systems. Results document that chronic exposure to NaF or TBZ during early life stages of rainbow trout induces a broad range of sublethal effects, including physiological condition, immune competence, endocrine regulation and organ morphology. Although mortality was reduced, most probably due to the antifungal activity of TBZ, the consistent alterations observed in thyroid hormone dynamics and immune parameters clearly indicate a deterioration of overall health.
(Aquatic Toxicology. vol. 297, n° 0166-445X, pp. 107867, 01/08/2026)
VIMEP, ANSES, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ANSES, VU, COS, UB
Evaluating migration hazard for recently remobilized managed coastal dunes
Sparsely vegetated or unvegetated coastal dunes are inherently dynamic, regardless of their size (Hesp et al., 2022). A salient characteristic of these dunes is their landward migration, driven by prevailing onshore winds, at rates that can exceed several meters per year. The rapid evolution of freely evolving coastal dunes inevitably raises concerns about the burial of infrastructure and more generally, the back dune areas. In a context where dune system remobilization is emerging as a nature-based management solution with multiple benefits (ecological reconnection, chronic marine erosion and sea-level rise effects mitigation), precise, spatially explicit quantitative assessments of dune migration hazards are essential. This is more critical given the trends of increasing urbanization and the concentration of socio-economic interests in coastal zones. Along the 230 km of the Aquitaine coast (southwest France), coastal dunes, which landscape is largely inherited from nearly two centuries of management, stabilization, and episodic mechanical re-profiling, have undergone spontaneous remobilization over the past decade (Nicolae Lerma et al., accepted). Across extensive sectors, dunes have transitioned from geometrically fixed, vegetated forms to aerodynamic, transgressive dunes (Figure 1a). This shift presents both opportunities and challenges for short- and long-term management strategies but also raises critical questions about accommodating rapid migration rates and evolving dune morphology. Current approaches to assessing burial hazards often overlook key parameters, such as interannual wind variability, climate change-induced trends in forcing, dune and back-dune morphology, and sediment budgets. Furthermore, methods relying on historical migration rates are inapplicable in regions where dunes were artificially stabilized during the 20th century through management interventions. Using annual airborne LiDAR data (Figure 1b.) and simulations with the morphodynamic model DUNA (Kombiadou et al., 2023, Figure 1c.), we analyze the factors influencing the migration speed of recently unvegetated dunes. We also investigate the impact of hybrid management strategies (designed to either accelerate or mitigate dune remobilization) at large spatial scales (hundreds of meters to tens of kilometers).
(13/07/2026)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ONF
PFAS Data Hub: An open data portal featuring geovisualisation
Per-and polyluoroalkylated substances (PFAS) are a group of man-made chemical substances used in everyday products and industry processes since the 1950s. They contain carbon-fluorine bonds, among the strongest in chemistry, resulting in intrinsic or indirect extreme environmental persistence and earning them the nickname "forever chemicals". In a context of growing awareness of PFAS toxicity and widespread pollution, the Forever Pollution Project (FPP), a cross-border journalistic investigation, compiled data on measured and estimated PFAS contamination across Europe, published as an interactive map. In this data paper we present the PFAS Data Hub (PDH), a project building upon the FPP dataset and reprocessing it using a more robust and transparent methodology. We incorporated several additional data sources, most of which are automatically updated on a monthly basis. To our knowledge, this constitutes the only compilation of PFAS contamination data at the European scale. It is intended to support research projects across a wide range of different disciplines, and to be used as a source of information by journalists, citizens and civil society organisations. The data, as well as a geovisualisation tool with filtering and export options, is available on the PDH website: https://pdh.cnrs.fr.
(03/07/2026)
LIS, AMU, UTLN, CNRS, PRODIG (UMR_8586 / UMR_D_215 / UM_115), UP1, IRD, SU, CNRS, UPCité, IRISSO, PSL, CNRS, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Continuous speleothem record from central Tunisia (the Mine cave) reveals climatic events for the last 27 ka
The Last Deglaciation, a key period punctuated by many climatic events, has been recorded in several natural archives but, it has been rarely recorded continuously on speleothems because of the presence of stops in their growth rate due to cold/dry climates. Here we present the results of a stalagmite (Min-stm2) from the Mine Cave (Oueslatia, Tunisia) that cover continuously the last 27 ka BP after a very slow growth between 120 ka to 35 ka. The time resolution, calculated with twenty-eight U/Th dating points and a 1 mm sampling space for stable isotopes, reaches 24 years during the Bølling-Allerød (BA) period, while it was the lowest (330 a/mm) during the Younger Dryas (YD). The growth rate (GR) curve reveals a sudden growth increase at 27.5 ± 0.08 ka BP, a key point in the stalagmite history, demonstrating that infiltration due to a humid and a relatively temperate climate started again at least in Tunisia. More vigorous northwesterly winds combined with the southern displacement of the ITCZ belt may explain this abrupt hydrological change. Despite of extreme cold climate that occurred N-Mediterranean area (i.e. Western Europe) during the Last Glacial Maximum (LGM) and the Oldest Dryas, the studied stalagmite kept a sustained GR showing a quite high humidity in the N-Tunisia area. The Last Deglaciation is here clearly marked by a large decrease in the calcite δ18O and δ13C between maximum values at 21.9 ka, denoting the coldest conditions, and minimum values at 8.5 ka coinciding with the warmest conditions. Even if the isotopic curves nicely mimic the ice and marine core records of the deglaciation, detailed events show some noticeable differences. For example, the stalagmite δ13C at the end of the BA is interrupted by a rapid and pronounced isotopic increase denoting colder conditions after 13.3 ± 0.1 ka BP which could be related to the IACP (Intra Allerød Cold Period). GR during the YD appears extremely slow. The Holocene onset, at about 11.7 ± 0.09 a BP, is marked by a gradual decrease in δ18O and δ13C until 8.3 ka associated with high GR suggesting increased precipitation. Despite the high time resolution during this period (better than 40 years), the 8.2 ka event is not recorded, marking a different sensitivity compared with more western and northern speleothem records. While the δ18O continuously increased after the Holocene optimum at 8.3 ka, a positive excursion occurred on the δ13C between 8.3 ka and 6.3 ka suggesting a reduction in the vegetation activity. This is likely due to increased seasonality with drier spring/summer conditions and humid autumn/winter and/or lower CO2 dissolution in the soil water during infiltration. The comparison with a former studied stalagmite from the same cave brings precious information about the local influences in recording detailed climatic variations.
(Quaternary Science Reviews. vol. 384, n° 0277-3791, pp. 109921, 01/07/2026)
LMRE, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, UTM, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, IGEC, Xjtu, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, UNIROUEN, NU, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS