Depth-Dependent isotope dynamics in karst reservoirs: Multi-Decadal monitoring insights from French caves
Understanding the stable oxygen isotope (δ18O/δD) compositions in rainwater and cave drip water within karst systems is essential for past climatic reconstructions all over the world. However, the relationship between cave drip water isotopes and upper karst infiltrated water and reservoirs remains unclear. Over twenty years, we monitored eight caves in France, from North to South: Arcy-sur-Cure, Villars, Cussac, Pech-Merle, Chauvet, Orgnac, Niaux, and Clamouse, collecting 3,000 dripping water samples from 32 drip points to measure δ18O and δD isotopes. As already observed in many cave sites, the isotopic composition of drip waters shows temporal stability with a Coefficient of Variation (CV) below 7 %, suggesting effective rainfall mixing during infiltration period. However, putting all these data on cave vertical cross sections, we observed subtle decreasing gradients in the averaged dripping δ18O values. For the first time in a multi-cave study, a clear logarithmic decrease of δ18O and δD with depth is found. Deeper sites show more negative isotopic values, especially in shallower zones (<50 m). In order to better understand these gradients, we used the hydrologic KarstFor model which revealed the importance of overflow mechanisms and of evapotranspiration (ETP) in driving this depth-dependent isotopic effect. These findings emphasize the significance of incorporating depth-dependent reservoir dynamics when analyzing isotopes in cave environments, advocating for a nuanced understanding of karst hydrological processes in affecting stalagmite δ18O.
(Journal of Hydrology. vol. 656, n° 0022-1694, pp. 133028, 01/08/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GLACCIOS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GEOTRAC, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Evolución tridimensional del frente dunar de la playa de l’Auir (2008-2022)
Las dunas son espacios interrelacionados con las playas que presentan un elevado dinamismo y un gran interés ambiental y social. Su estudio a grandes escalas espaciales y temporales se encuentra limitado por la dificultad de obtener datos altimétricos precisos de forma eficiente. Su caracterización tridimensional empleando técnicas de teledetección resulta de gran interés para cuantificar los cambios sedimentarios y analizar el conjunto del sistema playa-duna. Los vuelos LiDAR, junto al reciente desarrollo métodos fotogramétricos de reaprovechamiento de fotografías aéreas, permiten la obtención de series históricas de datos tridimensionales de alta precisión del frente costero. Se ha caracterizado la evolución del frente dunar de la playa de l'Ahuir, en Gandia (Valencia), a partir de cambios volumétricos y caracterización morfométrica derivada de perfiles tomados, a su vez, sobre 9 modelos digitales de superficie entre 2008 y 2022. Los resultados muestran una fase de importantes ganancias sedimentarias durante el periodo 2009-2015 (más de 12000 m3), que aparece asociada a un periodo de relativamente baja intensidad en los temporales costeros. Posteriormente, y pese a la alternancia de ligeras ganancias y pérdidas de sedimento en la playa emergida entre los MDS anuales, el frente dunar se encuentra en una fase de estabilidad y ligeras ganancias, presentando una ganancia neta de cerca de 26000 m3 para el conjunto del periodo 2008-2022. A diferencia de otros cordones dunares de la costa valenciana, el sector de l’Ahuir no se ha visto erosionado de forma asociada al temporal Gloria en enero de 2020. El análisis aporta información morfológica de gran interés para la caracterizar el estado sedimentario de la playa de l’Ahuir y monitorizar sus cambios, demostrando su potencial para suministrar datos de gran precisión y con gran cobertura espacial y temporal.
(Revista de Teledetección, n° 1133-0953, 31/07/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
In situ analysis of single secondary organic aerosol from the ozonolysis of α-pinene using laser trapping and Raman spectroscopy
To form secondary organic aerosols (SOAs) from volatile α-pinene via ozone oxidation reactions, the generation of low-vapor pressure compounds capable of acting as condensation nuclei is essential. Both laboratory and field studies have identified low-volatile dimers as key components in SOA formation. Although mechanisms involving stabilized Criegee intermediates and peroxy radicals have been proposed for dimer formation in the gas phase, the detailed processes of SOA formation remain widely debated due to the high diversity of reaction products and the inherent complexity of their formation mechanisms. To clarify certain steps of the SOA formation mechanism from ozone-initiated oxidation of α-pinene, a laser trapping technique coupled with Raman spectroscopy was employed for in situ analysis of individual SOA particles. In this study, single micrometer-sized α-pinene SOA particles were successfully trapped in air. To our knowledge, this represents the first successful application of laser trapping of α-pinene SOA particles directly in air. An intense Raman peak observed at about 852 cm−1 was attributed to the O–O stretching vibration of peroxides. This finding provides direct evidence for the presence of peroxy functional groups in the dimers, likely formed via stabilized Criegee intermediates. These results demonstrate the capability of laser trapping combined with Raman spectroscopy to detect specific molecular features, such as peroxide bonds, within α-pinene-derived SOAs in air.
(Chemosphere. vol. 385, n° 0045-6535, pp. 144581, 29/07/2025)
HU, ISM, UB, INC-CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Lack of data and misperception of open science limit the scope of Cantabrian brown bear body mass studies, not misinterpretation of results: Reply to comment by García-Vázquez (2025)
This manuscript responds to the comment of García-Vázquez on our recent paper, especially regarding the decline in body mass of the Cantabrian brown bear during the Holocene. The observations of García-Vázquez are reviewed point by point, addressing methodological aspects, that is, the use of the Viranta equation, the mass estimation of the specimen SH5-97-T29-35 and radiocarbon dating, as well as her ethical questions about the use of previously published data. Re-evaluations show that (1) the errors noted do not significantly affect the original conclusions of Fidalgo et al. and, (2) the use of thirdparty data was carried out in compliance with both legal regulations and open science principles. The new analyses maintain the pattern of declining bear body size after 7000-4500 years ago, without any conclusive evidence to link this phenomenon to the introduction of firearms in historical times. Neither this nor any alternative hypotheses are discarded, though. The importance of integrative meta-analyses in data-poor contexts is highlighted, and their legitimacy in the framework of collaborative and open science is defended, provided that sources of data are cited.
(The Holocene. vol. 35, n° 0959-6836, pp. 1196 - 1199, 29/07/2025)
MNCN, CSIC, NMBU, IDEES, UNICAEN, NU, ULH, NU, UNIROUEN, NU, CNRS, IRIHS, UNIROUEN, NU, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A continuous 500‐year sediment record of inundation by local and distant tsunamis in South‐Central Chile (40.1°S)
Abstract Chile's west coast is frequently struck by megathrust earthquakes and tsunamis, as illustrated by the CE 2010 Maule ( M w 8.8) and CE 1960 Valdivia ( M w 9.5) events. Despite numerous palaeoseismic and palaeotsunami studies, uncertainties remain regarding the rupture extent and tsunamigenic potential of M w 8–9 earthquakes. This study examines the sedimentary record of Laguna Gemela West, a coastal lake at 5–6 m a.s.l. and of 17.5 m depth. It is separated from the Pacific by a 400 m long channel bordered by northward‐propagating dunes and controlled by Pleistocene sandstones forming a knickpoint in the channel profile. Multiple sedimentary proxies (e.g. grain‐size, X‐CT, XRF scanning) identified five distinct sand‐enriched layers, interpreted as tsunami deposits. Age‐depth modelling (based on 137Cs and 14C) allowed linking these deposits to the CE 2010, 1960, 1837, 1737 and 1575 megathrust earthquakes. While historical records confirm significant tsunamis in CE 2010, 1960, 1837 and 1575, no reports exist for a CE 1737 tsunami. However, a potential tsunami deposit and evidence for subsidence were found at the nearby Chaihuín site, albeit with large dating uncertainty (CE 1600–1820). The more precise age for a sand layer at Laguna Gemela West (CE 1672–1746) supports the occurrence of a local tsunami in CE 1737. Additionally, deposits linked to the CE 1837 and 2010 events suggest tsunamis can impact sites >100 km adjacent to megathrust ruptures. A second pulse in the uppermost sand layer may reflect the CE 2011 Japan tsunami, which reached a similar height (~1.6 m a.s.l.) in the nearest tide gauge as the CE 2010 tsunami. Unlike coastal plain sites, which often require coseismic subsidence for deposit preservation, coastal lakes can capture a more complete tsunami history. This study highlights their complementary role in palaeotsunami research, providing insights in local, regional and transoceanic tsunami events.
(Depositional Record, n° 2055-4877, 28/07/2025)
UGent, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ICT
Benchmarking shoreline prediction models over multi-decadal timescales
Robust predictions of shoreline change are critical for sustainable coastal management. Despite advancements in shoreline models, objective benchmarking remains limited. Here we present results from ShoreShop2.0, an international collaborative benchmarking workshop, where 34 groups submitted shoreline change predictions in a blind competition. Subsets of shoreline observations at an undisclosed site (BeachX) over short (5-year) and medium (50-year) periods were withheld from modelers and used for model benchmarking. Using satellite-derived shoreline datasets for calibration and evaluation, the best performing models achieved prediction accuracies on the order of 10 m, comparable to the accuracy of the satellite shoreline data, indicating that certain beaches can be modelled nearly as well as they can be remotely observed. The outcomes from this collaborative benchmarking competition critically review the present state-of-the-art in shoreline change prediction as well as reveal model limitations, facilitate improvements, and offer insights for advancing shorelineprediction capabilities.
(Communications Earth & Environment. vol. 6, n° 2662-4435, pp. 581, 24/07/2025)
UNSW, USGS, TU Delft, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM, UC / UniCan, CSIRO, ULISBOA
Effects of high overvoltages on the treatment of PFAS in water
The chemical structure of per-polyfluoroalkyl substances (PFAS), based on strong C-F bonds makes them extremely stable in the natural environments. Plasma technologies have a strong potential for degrading PFAS in water. Understanding of the plasma removal mechanisms is necessary to improve the efficiency and to better control the by-products. Here three types of discharges with the same deposition energy were investigated for plasma removal of PFAS. An AC and a nanosecond high voltage pulse discharge were used in a wire-to-water surface configuration, whereas an atmospheric pressure fast ionization wave was generated in a 3-pins configuration over the water surface.
(20/07/2025)
EM2C, CNRS, LSPM, USPC, CNRS, LPTC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Water Wars: competition between native and exotic isoetid species
Among several global changes, invasion by exotic species is often pointed out as responsible for the decline of native species. Indeed, in the competition for space and resources, fast-growing species are generally more efficient than native ones. The natural lakes along the Aquitaine coast are home to unique and protected populations of isoetid macrophytes, which are declining in the last decades. The present study aims at testing the potential competition between the native isoetid Lobelia dortmanna and the exotic isoetid Sagittaria graminea, both coexisting in Lake Cazaux-Sanguinet, France. To achieve this, we set up a multi-year monitoring program across 1x1m quadrats, with three conditions: native species only, exotic species only, and mixed condition when both species occurred. Each individual in the quadrat was spatially mapped and its photosynthetic activity was measured, as well as its leaf length and width. Sediment samples were also collected to analyze differences in organic matter content and granulometry between the quadrats. Preliminary results show that, while substrate analysis indicates similar biotopes for both species, their co-occurrence triggered significant physiological and morphological responses. Additionally, the native and exotic species appeared to follow different patterns of spatial distribution. However, these first results did not necessarily indicate a negative effect of the exotic species on the native one. Further field sampling in the coming years will help clarify the temporal spatial dynamics of the two species.
(20/07/2025)
UR EABX, INRAE, ECLA, USMB [Université de Savoie] [Université de Chambéry], INRAE, OFB, LPTC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Persistence of a wind-driven fire regime in Mediterranean France over the past 8200 years revealed by a marine paleoecological record
Data on paleofire activity in southeastern France during the Holocene are still lacking thus limiting our capability to anticipate fire regime shifts under climate change. Here, we present a 8.2 ky-long high-resolution time-series of microscopic charcoal (microcharcoal) particles from a marine sediment core retrieved from the Rhone prodelta, in the Gulf of Lions (NW Mediterranean Sea). Fire frequency, episodes, size and types of burnt vegetation were determined by quantifying microcharcoal and analysing its morphometry. Our results indicate an increase in biomass burning and fire frequency combined with a decrease in the mean elongation ratio from the Northgrippian (8.2–4.2 ka) to the Meghalayan (4.2–0 ka) stage. This pattern is interpreted as reflecting a shift from the burning of graminoids in closed mesophytic forests during the Northgrippian to the burning of shrub communities in open Mediterranean habitats during the Meghalayan. We also identified 20 fire episodes over the past 8.2 ka, occasionally coinciding with human occupations. Large fires occurred during cold events and summer droughts conditions of the Northgrippian. We relate this finding to negative phases of the North Atlantic Oscillation (NAO) and increased fuel load under wet winter conditions and fuel flammability under dry and strong summer winds. Besides climate and vegetation, human activity is likely to be an additional driver of fire during the Meghalayan. Southeastern France is currently identified as a region with a high wind-driven fire risk, although its fire regime analysis is biased by intensive fire suppression. We suggest that wind-driven large fires is an inherent element of fire and weather patterns in this area rather than the result of fire suppression strategies leading to uncontrollable large fires.
(The Holocene. vol. 35, n° 0959-6836, pp. 961-976, 13/07/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEFE, EPHE, PSL, CNRS, IRD [Occitanie], IRD, INRAE, Institut Agro, UM, UMPV, IMBE, AU, AMU, CNRS, CEFREM, UPVD, INSU - CNRS, CNRS, UMLP, LCE, CNRS, UMLP, UBFC, LOCEAN-VOG, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, EPOC
Analyse des tendances de contaminations historiques multi-métalliques dans les archives sédimentaires de la Saône (années 1940 - actuel)
In order to understand the evolution of metallic contaminant flux in the Saone River towards Lyon over time, two sediment cores were studied. These cores provide records spanning over 80 years with relatively continuous and homogeneous deposition. Age models were established based on radionuclide profiles (137Cs and 210Pb), defining high deposition rates (1–2 cm. yr⁻¹) that enable to study contaminant trends at high temporal resolution. These analyses reveal distinct contamination phases linked to the industrial history of the basin. Based on the chronology covered by these sediment archives, copper, lead, and cadmium contamination can be identified as early as the 1950s, with peaks extending during the 1970s. Later, while contamination levels of these metals, silver reaches maximal concentrations at two periods, in the 1970s and 1980s, and then during the 1990s. Within the industrial context of the basin, silver contamination can be associated with the photographic industry. These findings show that secondary channels of the Saone River have been affected by multi-metallic contamination accumulated since the 1950s. They act as pollution archives, enabling the reconstruction of the consequences of anthropogenic activities on river ecosystems. Moreover, this stock of metallic contaminants requires integrated management within the framework of secondary channel restoration efforts.
(09/07/2025)
LEHNA, UCBL, ENTPE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, EVS, ENS de Lyon, Mines Saint-Étienne MSE, IMT, UL2, UJML, INSA Lyon, INSA, UJM, ENTPE, ENSAL, CNRS, ALLHiS, UJM