LEON-BLOOM project - Origin, spatial and temporal dynamics of cyanobacteria blooms in lake Léon, France
Lake Léon (Landes) has recently experienced important cyanobacteria blooms, leading to severe restrictions on recreational activities of this popular tourist waterbody of the Atlantic coast in France. To investigate the origins of these algal blooms, the dynamics of biological patterns, and to provide management strategies for mitigation, the "Léon-Bloom" research project established a collaboration between environmental watershed managers and research scientists. The project aims to identify the potential sources of algal growth and gain a better understanding of their spatial and temporal dynamics. The project is structured in several workpackages, each investigating a potential mechanism. (1) Firstly, nutrient fluxes from the watershed are analyzed, including the use of passive phosphorus samplers. We also set up an experimental design to investigate the role temperature, light and phosphorus on the development of phytoplankton biomass. (2) Secondly, a chemical analysis of the lake’s sediments is carried out resorting to sediment coring and experimentation to measure the potential of phosphorus release under anoxic conditions. (3) Thirdly, the role of temperature and oxygen on phytoplankton composition will be assessed using a statistical modeling approach. We measured temperature and oxygen in several stations of the lake to calibrate these models using autonomous high-frequency sensors. (4) The phytoplankton community is studied both spatially and temporally, at the taxonomic and algal group level. Cyanotoxins are also regularly monitored. Finally, two modeling-based workpackages will focus on (5) analyzing the role of wind in the spatial distribution of the plankton community and physical parameters and (6) developing remote sensing methods for monitoring algal concentrations in this lake. Ultimately, we aim to decipher the relative contribution of wind, nutrients (fluxes and internal release), and environmental variables, to understand the conditions of cyanobacterial blooms emergence.
(21/05/2025)
UR EABX, INRAE, ECLA, USMB [Université de Savoie] [Université de Chambéry], INRAE, OFB, OFB - DRAS, OFB, UMR ISPA, Bordeaux Sciences Agro, INRAE, RECOVER, AMU, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, OFB Service EcoAqua, OFB - DRAS, OFB
Rescuelog : Collecte numérique et reporting des interventions de sauveteurs à l’océan avec (ru)ODK, Shiny et SK8
Les plages du Sud-Ouest de la France présentent des risques élevés de noyades, nécessitant des dispositifs de surveillance efficaces. Le projet Rescuelog modernise la collecte et l’analyse des données sur les interventions de sauveteurs grâce à un workflow entièrement intégré dans l’écosystème R. Les interventions sont enregistrées via des tablettes Android utilisant ODK Collect, les données étant ensuite extraites avec ruODK (Mayer 2020) et structurées dans une base PostgreSQL après validation. Des données environnementales, incluant les prévisions météo et marines, sont enrichies via l’API de Météo-France grâce au package httr2 (Wickham 2023). Ces données alimentent un modèle prédictif, construit avec tidymodels (Kuhn and Wickham 2020), permettant d’anticiper les jours à haut risque de noyade. Ce modèle est versionné et stocké grâce au package vetiver (Silge 2023), puis exploité par une application Shiny déployée via le service sécurisé SK8 (SK8 Team 2024) d’INRAE. Cette solution démontre la capacité des outils R à proposer des workflows robustes, sécurisés et scalables pour des problématiques opérationnelles critiques comme la prévention des noyades.
(18/05/2025)
UR EABX, INRAE, UR ETTIS, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A new open boundary condition for Boussinesq-type models, applied to irregular wave fields
We present a novel approach to handle open boundary conditions for a Boussinesq-type wave model coupled with the nonlinear shallow water equations. Traditional methods for managing open boundaries --- such as sponge layers and source functions --- are computationally intensive and require ad hoc calibration. To address this, we reformulate the Boussinesq equations as a system of conservation laws with nonlocal flux and a rapidly decaying source term. This reformulation is adapted to generate waves at the boundary of the numerical domain, from surface elevation data in situations where both incoming and outgoing waves are present. The proposed numerical scheme employs a MacCormack prediction-correction strategy combined with finite volume and finite difference methods, preserving key physical properties and ensuring stability. Comparison with laboratory experiments demonstrates that our approach avoids boundary reflection issues. In particular, it is able to accurately reproduce infragravity waves associated with a random wave field propagating over a sloping beach. This work opens important perspectives for improving phase-resolving coastal wave models, with the aim of forecasting complex random wave conditions in natural environments.
(14/05/2025)
LJLL (UMR_7598), SU, CNRS, UPCité, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IMB, UB, Bordeaux INP, CNRS
Biomonitoring of azole fungicides in free-living blackbird plasma using on-line solid-phase extraction coupled to liquid chromatography-tandem mass spectrometry (SPE HPLC-MS/MS)
In this study, a rapid and sensitive method using on-line solid-phase extraction (SPE) coupled to liquid chromatography - tandem mass spectrometry (SPE HPLC-MS/MS) was developed to analyse 15 azole fungicides currently used in vineyards in blackbird plasma samples. The monitored fungicides included 13 triazoles (cyproconazole, difenoconazole, epoxiconazole, fenbuconazole, flusilazole, flutriafol, metconazole, penconazole, propiconazole, tebuconazole, tetraconazole, triadimefon, triadimenol) and 2 imidazoles (imazalil and prochloraz). After a rapid preparation step by protein precipitation with acetonitrile on 25 µL of plasma samples, final extracts diluted with Milli-Q water were analyzed by on-line SPE-LC-MS/MS in positive electrospray mode (ESI+) using the dynamic multi-reaction monitoring mode (dMRM). Following optimization, method validation was achieved through studies of linearity, sensitivity, accuracy, precision, and sample extract conservation. The limits of quantification (LOQs) obtained for a low volume of plasma (25 µL) ranged from 0.01 to 0.43 ng g−1 plasma, except for triadimenol (1.37 ng g−1). Finally, the validated method was successfully applied to 34 Eurasian blackbird plasma samples, with blackbirds from different habitats (city, forest, vineyards) submitted to contrasted azole pressures. Five of them were detected, tebuconazole and tetraconazole being the predominant ones. As expected, azoles concentrations were more elevated in blackbirds sampled in vineyards where most of these fungicides are used.
(Journal of Chromatography A. vol. 1748, n° 0021-9673, pp. 465725, 10/05/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEBC, ULR, CNRS, INRAE
Molecular characterization of organic aerosols in urban and forested areas of Paris using high-resolution mass spectrometry
In order to study aerosols in environments influenced by anthropogenic and biogenic emissions to variable extents, PM1 samples were collected during summer 2022 in the greater Paris area (ACROSS campaign, Atmospheric Chemistry Of the Suburban Forest, 14 June to 25 July) at two locations that represent the urban Paris and the suburban forested areas. They were analyzed using high-resolution mass spectrometry (HRMS) together with total carbon (TC) with a thermo-optical method. Both sites are compared here to explore differences in aerosol composition from urban and forested environments. The TC analysis shows similar organic carbon (OC) concentrations at both sites (3.2 ± 1.8 µg m−3 for Paris and 2.9 ± 1.5 µg m−3 for Rambouillet) and higher elemental carbon (EC) values in the urban area. Both OC and EC concentrations did not show significant variations for daytime and nighttime conditions. This work highlights the influence of anthropogenic inputs on the chemical composition of urban and forested areas, derived from the presence of CHO and CHON compounds but also the detection of two sulfur-containing compounds (C5H12SO7 and C10H17NSO7), which could be tentatively assigned as organosulfates. A smaller number of aromatic compounds were observed for clean periods that better represent the local biogenic and anthropogenic contributions in Rambouillet and Paris, respectively.
(Atmospheric Chemistry and Physics. vol. 25, n° 1680-7316, pp. 4885-4905, 09/05/2025)
LISA (UMR_7583), INSU - CNRS, UPEC UP12, CNRS, UPCité, CAM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, INERIS
Atmospheric stability of six particulate biogenic secondary organic aerosol markers towards photolysis, hydroxyl radicals and ozone
This study aimed to investigate the kinetics of the heterogeneous reactions of six biogenic secondary organic aerosol (BSOA) markers of atmospheric interest, i.e. the terebic, terpenylic, cis-pinonic, pinic, 3-methyl-1,2,3-butanetricarboxylic (MBTCA) and β-caryophyllinic acids. For this purpose, these compounds were individually adsorbed onto silica model particles and exposed either to solar irradiation, hydroxyl radicals, or ozone. Marker concentrations extracted from particles were subsequently analyzed by liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (LC-QTOF/MS). Pseudo-first-order rate constants were derived from simulations (using either exponential functions or the tangent slope at t0) of particulate marker concentration decays as a function of exposure time to different oxidants or light. Second-order rate constants were calculated considering the oxidant concentrations under different experimental conditions. The overall atmospheric lifetime of each marker was calculated, revealing that β-caryophyllinic acid is the most reactive compound studied, with a lifetime of <14.3 min, followed by cis-pinonic acid (8.6 h), MBTCA (19 h), pinic acid (>2.8 days), terpenylic acid (>4.8 days), and terebic acid (>5.8 years).This work confirms that the atmospheric stability of some BSOA markers is insufficient, to justify their relevance as tracers of particle formation or aging processes.
(Chemosphere. vol. 380, n° 0045-6535, pp. 144453, 09/05/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Predicting individual’s decision to enter the water at a high-energy recreational surf beach in France
Objectives To predict beachgoer decision to enter the water at a high-energy surf beach, in southwest France. Methods We built a unique multidisciplinary database combining data collected by an on-site beachgoers survey, weather stations, marine buoys and tidal reconstruction. Human, weather and meteocean factors were considered as potentially predictive of beachgoer behaviour. We employed a logistic regression analysis to predict beachgoers’ decision to enter the water on any given day at a high-energy recreational beach. Results We demonstrated that both environmental and human factors influence a beachgoer’s decision to enter the water. Daily mean wave height and daily mean insolation duration were significant predictors at the p<0.001 level, while age, place of residence and self-confidence in swimming out of a rip current were significant at the p<0.05 level or higher. Beachgoers were more likely to enter the water on sunny days with lower waves. Younger individuals, those living outside the Landes département, and those who declared themselves to be ‘confident’ or ‘uncertain’ about their ability to swim out of a rip current expressed a higher propensity to enter the water. Our model has an accuracy, F-Score, precision and recall of 71%, 73%, 86%, 79%, respectively. Conclusions Beachgoer exposure on any given day can ultimately be predicted by coupling our model with beach attendance models. This would allow for the design of rescue and preventive operations on days with high expected exposure. While models based solely on environmental factors can be used to forecast beach risks, incorporating human factors into the model provides valuable insight for crafting prevention messages. In this regard, lifeguards could engage more actively with beach users to deliver appropriate safety messages.
(Injury Prevention, n° 1353-8047, pp. ip-2024-045574, 08/05/2025)
UR ETTIS, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Estimating Contaminated Soil Volumes Using a Generative Neural Network: A Hydrocarbon Case in France
The estimation of the volumes of contaminated soil to be treated is a crucial step in soil remediation. Numerous techniques exist for estimating the distribution of pollutants in soils, such as inverse distance weighting, kriging, Gaussian sequential simulation, and sequential indicator simulation. Unfortunately, these methods require significant computational resources to achieve precise estimations. Moreover, both kriging and Gaussian simulation require the transformation of non-normal distributions, often seen in hydrocarbon contamination, to produce accurate results. In this paper, we propose a generative neural network to generate 3D maps of contaminant distributions without prior training, and to estimate the contaminated volumes. This differentiates this work from other Deep Learning approaches that necessitate training data. The proposed method relies on a convolutional neural network for image reconstruction and inpainting. Rather than solely depending on the concentration of chemicals determined in the laboratory, we utilize hyperspectral imaging data from soil cores to achieve a more precise depiction of soil contaminants. We assess the proposed method using a synthetic 3D dataset and a real case of hydrocarbon pollution on a polluted site in France. The method demonstrates competitive performance with efficiently managed computation time, achieved through the use of GPU accelerator. This study offers a new, practical way to improve soil pollution management using fast, and data-driven techniques.
(Mathematical Geosciences, n° 1874-8961, 05/05/2025)
LITIS - App, LITIS, ULH, NU, UNIROUEN, NU, INSA Rouen Normandie, INSA, NU, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Beach-dune dynamics and coastal management along the North-Médoc coastline, southwest France: a decade of morphological change and erosion mitigation
The North-Médoc coastline, exposed to energetic waves and meso-macro tides and exhibiting major erosion hotspots, has experienced notable changes in beach and dune volumes over the last decades due to a combination of natural forcings and human interventions, including coastal defenses and beach nourishment. Annual LiDAR data (2011-2023) combined with interspersed annual GNSS surveys were used to quantify spatial and temporal variations in beach-dune topography along approximately 14.5 km of coastline. Beach-dune changes along the North-Médoc coast over the past decade were influenced by multiple factors at varying scales. (1) Long-term changes, such as chronic erosion or accretion of up to 7 m/yr, are mainly inherited from large-scale shoal welding originating from the estuary mouth (internal forcing). (2) Coastal structures have localized impacts on shoreline dynamics, sometimes altering trajectories. While alongshore structures stabilize the shoreline, they may cause issues at their ends. Cross-shore structures, like groynes, have variable effects; for instance, extending one of the groyne after winter 2013-14 led to rapid accretion, widening beach, and raising elevations updrift. This accreting area is now used as a sediment extraction area to nourish the eroding southern beaches. (3) Interannual shoreline variability, linked to winter wave height fluctuations driven by climate modes of atmospheric variability, overlaps with trends from (1) and (2). However, this external forcing is more pronounced farther from the estuary, indicating a continuum from external forcing on open coasts to internal processes near the estuary.
(Geomorphology. vol. 482, n° 0169-555X, pp. 109758, 01/05/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM
Experimental and computational analysis of the DNA damage induced in zebrafish, Danio rerio, early life stages after exposure to tritiated thymidine
Tritium is an ubiquitous radioactive hydrogen isotope. It is found in all environmental compartments, in three different forms: tritiated water (HTO), gaseous tritium (HT) and organically bound tritium (OBT). Once internalized in the organism, it can either be found free in the tissues (TFWT) or bound to organic matter (OBT). This study aims to assess if tritiated thymidine, an organic form of tritium, induces DNA breaks once internalized in a model organism and its DNA. To do so, both experimental procedures and nanodosimetry simulations have been used. Zebrafish embryos (3.5 hpf, hours post fertilization) were exposed to three tritiated thymidine activity concentrations (7.5, 40, 110 kBq/mL, leading to internal dose rates of 22, 170 and 270 μGy/h) for four days. Individuals were sampled after 1 and 4 days of exposure and DNA break levels were assessed by the comet assay. Results showed that, even at the lowest activity concentration, tritiated thymidine induced DNA breaks in both embryos (1 dpf) and larvae (4 dpf). It was also highlighted that there was no increase nor decrease in DNA break level between 1 and 4 dpf, except in the case of the exposure to 170 μGy/h, where a slight decrease was observed. Geant4-DNA Monte Carlo simulations, performed on two spherical zebrafish nuclei of two different radii (2.5 and 5 μm), highlighted that organic tritium mainly induced single strand breaks (SSB). The results also showed that most of the damage was indirectly induced. Those results, combined with various experimentations, expose tritiated thymidine genotoxic pathways that could lead to both short- and long-term health effects.
(Journal of Environmental Radioactivity. vol. 285, n° 0265-931X, pp. 107682, 01/05/2025)
IRSN/PSE-ENV/SERPEN/LECO, IRSN/PSE-ENV/SERPEN, IRSN, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRSN/PSE-SANTE/SDOS/LDRI, IRSN/PSE-SANTE/SDOS, IRSN