Biogeochemical modelling of anaerobic vs. aerobic methane oxidation in a meromictic crater lake (Lake Pavin, France)
Methane is a powerful greenhouse gas and its concentration in the atmosphere has increased over the past decades. Methane produced by methanogenic Archae can be consumed through aerobic and anaerobic oxidation pathways. In anoxic conditions found in freshwater environments such as meromictic lakes, CH4 oxidation pathways involving different terminal electron acceptors such as NO 3 , SO2 4 , and oxides of Fe and Mn are thermodynamically possible. In this study, a reactive transport model was developed to assess the relative significance of the different pathways of CH4 consumption in the water column of Lake Pavin. In most cases, the model reproduced experimental data collected from the field from June 2006 to June 2007. Although the model and the field measurements suggest that anaerobic CH4 oxidation may contribute to CH4 consumption in the water column of Lake Pavin, aerobic oxidation remains the major sink of CH4 in this lake.
(Applied Geochemistry. vol. 26, n° 0883-2927, pp. 1919-1932, 28/10/2026)
LGE, UPD7, IPG Paris, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LMGE, UBP, UdA, CNRS, ISTO, INSU - CNRS, UO, UT, NEOLAiA, CNRS
Modeling biogeochemical processes in sediments from the Rhône River prodelta area (NW Mediterranean Sea)
In situ oxygen microprofiles, sediment organic carbon content, and pore-water concentrations of nitrate, ammonium, iron, manganese, and sulfides obtained in sediments from the Rhône River prodelta and its adjacent continental shelf were used to constrain a numerical diagenetic model. Results showed that (1) the organic matter from the Rhône River is composed of a fraction of fresh material associated to high first-order degradation rate constants (11-33 yr−1); (2) the burial efficiency (burial/input ratio) in the Rhône prodelta (within 3 km of the river outlet) can be up to 80 %, and decreases to ~20 % on the adjacent continental shelf 10-15 km further offshore; (3) there is a large contribution of anoxic processes to total mineralization in sediments near the river mouth, certainly due to large inputs of fresh organic material combined with high sedimentation rates; (4) diagenetic by-products originally produced during anoxic organic matter mineralization are almost entirely precipitated (>97 %) and buried in the sediment, which leads to (5) a low contribution of the re-oxidation of reduced products to total oxygen consumption. Consequently, total carbon mineralization rates as based on oxygen consumption rates and using Redfield stoichiometry can be largely underestimated in such River-dominated Ocean Margins (RiOMar) environments.
(Biogeosciences. vol. 8, n° 1726-4170, pp. 1351-1366, 28/10/2026)
IPGP, INSU - CNRS, UPD7, UR, IPG Paris, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, NIOO-KNAW, LAERO, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNRS, BIAF, UA, OCEANIS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Copper addition by organic matter degradation in the freshwater reaches of a turbid estuary
This study reports on the relationship between copper (Cu) behavior and organic matter (OM) transformation along the turbidity gradient in the freshwater reaches of the Gironde Estuary. During a one-year survey, surface water and suspended particulate matter (SPM) were sampled at least monthly at three sites along the Garonne Branch, representing the main fluvial branch of the Gironde Estuary. Additionally, a longitudinal high resolution profile was sampled along the Garonne Branch, covering the turbidity gradient from the river water endmember to the maximum turbidity zone (MTZ). Seasonal variability and spatial distribution of Cu in both the dissolved phases (<0.2μm, Cu0.2 and <0.02μm, Cu0.02) and particulate Cu (CuP) clearly suggested Cu0.2 addition during summer, that increased the Cu0.2 concentrations by a factor ~2, mainly manifested by an increase in the Cu0.02 fraction. At the annual timescale (2004), this internal Cu reactivity increased Cu0.02 fluxes in the Garonne Branch by ~20% (3.6tyear-1), with the equivalent of ~2.9tyear-1 derived from the CuP fraction and ~0.7tyear-1 from the colloidal (0.02-0.2μm) fraction, without involving and/or affecting the CuC18 (hydrophobic metal-organic complexes) fraction.Combining data on Cu speciation with the results obtained by several independent techniques (DOC and POC measurements, 3D-fluorescence, and TEM) suggested close relationships between Cu behavior and OM transformation/restructuration along the turbidity gradient in the Garonne Branch. The observed Cu0.02 addition was related to increasing humification (humification index HIX increased from 9 to 12, network formation) and labile OM degradation (Iγ/Iα ratio decreased from 0.70 to 0.44), going along with decreasing DOC and POC concentrations. Mass-balances suggest that in the studied system, degradation of OM may account for the release of ~25μmol potentially bioaccessible Cu0.02 per mole of particulate organic carbon mineralized. \textcopyright 2011 Elsevier B.V.
(Science of the Total Environment. vol. 409, n° 0048-9697, pp. 1539--1549, 28/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UB
Non-steady state modeling of early diagenetic processes following a major flood event in the Rhône prodelta (NW Mediterranean Sea, France)
(28/10/2026)
EDF R&D STEP, EDF R&D, EDF [E.D.F.], EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, LPGN, UN, CNRS, IPGP, INSU - CNRS, UPD7, UR, IPG Paris, CNRS
Suivi de la contamination des tributaires du Bassin d'Arcachon par les pesticides et tests écotoxicologiques sur diatomées
L'échantillonnage passif des substances organiques de synthèse suscite un intérêt croissant depuis son apparition par son gain de représentativité temporelle, sa facilité de mise en ½uvre et son coût acceptable. Depuis le début des années 1990, plusieurs dispositifs ont été développés pour échantillonner différents types de contaminants. Le Polar Organic Chemical Integrative Sampler (POCIS) est l'outil le plus adapté à l'échantillonnage des pesticides pour différentes applications (e.g. monitoring ; appui à l'écotoxicologie), en particulier grâce à l'utilisation d'un composé de performance et de référence (PRC). L'objectif de cette étude est de caractériser la pollution à pesticides dans neuf des principaux tributaires du Bassin d'Arcachon. Des POCIS ont été déployés pour l'échantillonnage des pesticides neutres (i.e. 1
(pp. 1, 28/10/2026)
UR REBX, CEMAGREF, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Evolution taxonomique de biofilms diatomiques en condition de décontamination métallique expérimentale après colonisation sur site contaminé
Le système fluvio-estuarien de la Gironde (France) est soumis depuis plus d'un siècle à une contamination polymétallique (Cd et Zn) s'étendant du Lot jusqu'à l'estuaire de la Gironde. Des études géochimiques ont montré que les apports en Cd et Zn proviennent essentiellement d'un site industriel spécialisé dans le traitement du minerai de zinc, localisé environ 400 km en amont de l'estuaire. Depuis 2007, un important plan de remédiation du site industriel a été mis en place. Ces travaux devraient durer jusqu'en 2012. Dans ce contexte de gestion corrective, et en référence à l'état initial de contamination déterminé par des études antérieures (programme national Ecodyn), cette étude s'intègre dans le cadre d'un projet ANR pluridisciplinaire (RESYST) et a pour objectif d'étudier l'impact de la mise en place de la remédiation sur les biofilms diatomiques. Afin de caractériser les cinétiques de récupération des diatomées, une étude expérimentale de décontamination du biofilm a été menée en laboratoire. La colonisation des biofilms s'est déroulée durant 24 jours sur un site subissant les rejets métalliques industriels et parallèlement sur un site en amont sans métaux, considéré comme témoin. Les biofilms ont ensuite été ramenés et maintenus en laboratoire durant 56 jours en condition de décontamination, ou de contamination artificielle à partir de solutions de Cd et de Zn. Différentes analyses ont été réalisées du niveau communautaire - mesures de la bioaccumulation métallique, des densités cellulaires et investigations taxonomiques - jusqu'au niveau individuel : déformation des frustules. Après 56 jours de décontamination, les concentrations en Cd dans les biofilms montrent une forte décroissance mais restent significativement supérieures aux concentrations mesurées dans les biofilms témoins. Par ailleurs, les inventaires taxonomiques ne permettent pas de mettre en évidence une restauration des communautés diatomiques dans les biofilms en décontamination comparativement à la condition témoin. En effet, après 56 jours de décontamination, malgré l'apparition d'espèces opportunistes sensibles aux métaux, pouvant être liées aux conditions expérimentales, les espèces résistantes aux métaux présentes initialement après colonisation sur site contaminé, persistent en abondances élevées dans les biofilms en décontamination. A la lumière de ces premiers résultats sur le comportement des biofilms diatomiques en conditions expérimentales de décontamination, l'amélioration de l'état chimique de l'hydrosystème naturel apparaît rapidement mais un éventuel retour au bon état écologique préconisé dans la DCE semble différé avec la persistance d'espèces tolérantes aux métaux. Ces résultats seront confrontés aux investigations menées en parallèle in situ afin de révéler ou non les prémices d'un retour au bon état écologique.
(pp. 1, 28/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR REBX, CEMAGREF
X-ray fluorescence microchemical analysis and autoradiography applied to cave deposits: speleothems, detrital rhythmites, ice and prehistoric paintings
This article presents recent research on the sedimentary endokarstic infillings in connection with the new contributions of geochemical analysis by autoradiography and X-ray fluorescence (portable analyser, core scanner, micro-XRF, microprobe) in the context of the ‘Climanthrope’ ANR programme. Coupled with sedimentological analysis (stratigraphy, laser grain size analysis, micromineralogy, and micromorphology), geochemical analysis and imaging refine the study of underground deposits such as carbonated sediments (speleothems), rhythmites, subterranean ice, and prehistoric cave paintings. Formed following a seasonal cycle, stalagmites and rhythmites are likely to provide important data not only on the two main parameters of regional climate, i.e. hydrology and temperature, but also on human impacts (speleothems in urban tunnels) and the rural environment. The microdebris and dusts sampled in subterranean ice record the palaeoenvironment by snow trapping. Parietal paintings can be studied directly with a portable XRF analyser without sampling. In every case, the notion of the ‘site effect’ is discussed for four French examples (Pyrenees, Aquitaine, Charente, Rhône) and three foreign examples (Italy, Chile, China).
(Géomorphologie : relief, processus, environnement. vol. 17, n° 1266-5304, pp. 407-426, 28/10/2026)
ADES, UBM, CNRS, CENBG, UB, IN2P3, CNRS, AMPERE, ECL, UCBL, INSA Lyon, INSA, CNRS, EDYTEM, USMB [Université de Savoie] [Université de Chambéry], CNRS, Fédération OSUG, TRACES, EHESS, UT2J, Comue de Toulouse, MCC, Inrap, CNRS, Inrap, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GEOTOP, EPM, UdeM, UQAT, UQAR, UQAM, ArScAn, UP1, UP8, UPN, MCC, CNRS
Potentiel of TerraSAR-X imagery for mapping intertidal coastal wetlands
This work presents preliminary results about the use of TerraSAR-X imagery for mapping intertidal habitats (oyster parks, seagrass meadows of Zostera noltii, sediments) along coastal lagoons (Arcachon lagoon, France). The combination of SAR and optical data appears to be useful to improve the discrimination of the various sediment and vegetation covers into classification schemes. Unlike optical imagery which may lead to misinterpret sediment type, the potential of the multi-polarization SAR data is assessed notably regarding its efficiency for separating intertidal (Z. noltii) from supratidal salt-marsh vegetation species (spartina, salicornia, and so on). TerraSAR-X imagery is also an excellent highlighter of areas colonized by oysters (both cultivated and invasive ones) due to their relevant roughness signature among neighbored facies. In contrast, mapping methods based on optical data alone often do not perform well because of the presence of algae on oyster shelves. Moreover, potential exists for discrimating unvegetated soils but biofilm-covered from low-vegetated ones. As a conclusion, TerraSAR-X imagery offers many tracks to increase the performance of thematic mapping products along intertidal environments, in complement of optical data.
(pp. 9, 28/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMR TETIS, Cirad, CEMAGREF, IRSTEA
Bilan des gaz à effet de serre d’origine agricole: oxyde nitreux et méthane
Les bilans agricoles d’émissions de méthane (CH4) et de l’oxyde nitreux (N2O) ont été réalisés à l’échelle du bassin de la Seine, sur la base de mesures acquises sur les sols et dans le réseau hydrographique. Le réseau hydrographique émet environ 140 103 kg N-N2O et 170 103 kg C-CH4 auxquelles s’ajoutent les émissions par les zones humides estimées à 500 – 800 103 kg NN2O et 400 - 4000 103 kg C-CH4. Ces émissions indirectes représentent environ 10% et 1% des émissions directes par les sols agricoles pour le N2O et le CH4 respectivement. Les émissions directes sont en majorité celles des sols arables 10400 103 kg N-N2O pour le N2O, alors que les émissions directes du CH4 sont essentiellement liées à la digestion entéro-gastrique du cheptel, et en particulier des bovins, soit 194660 103 kg C-CH4. Les sols sont un puits pour le CH4 : - 10000 103 kg C-CH4.. Les émissions de N- N2O et de CCH4représentent 12.3 106 tonnes CO2 équivalent an-1. A ces émissions, il faut ajouter celles émises par le fuel pour les activités agricoles et celles liées à la fabrication des engrais synthétiques qui représentent respectivement 0.1% et 10%.
(pp. 18 p., 28/10/2026)
SISYPHE, UPMC, EPHE, PSL, PSL, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, EGC, INRA
Glacial-interglacial vegetation dynamics in South Eastern Africa coupled to sea surface temperature variations in the Western Indian Ocean
Glacial-interglacial fluctuations in the vegetation of South Africa might elucidate the climate system at the edge of the tropics between the Indian and Atlantic Oceans. However, vegetation records covering a full glacial cycle have only been published from the eastern South Atlantic. We present a pollen record of the marine core MD96-2048 retrieved by the Marion Dufresne from the Indian Ocean ∼120 km south of the Limpopo River mouth. The sedimentation at the site is slow and continuous. The upper 6 m (spanning the past 342 Ka) have been analysed for pollen and spores at millennial resolution. The terrestrial pollen assemblages indicate that during interglacials, the vegetation of eastern South Africa and southern Mozambique largely consisted of evergreen and deciduous forests. During glacials open mountainous scrubland dominated. Montane forest with Podocarpus extended during humid periods was favoured by strong local insolation. Correlation with the sea surface temperature record of the same core indicates that the extension of mountainous scrubland primarily depends on sea surface temperatures of the Agulhas Current. Our record corroborates terrestrial evidence of the extension of open mountainous scrubland (including fynbos-like species of the high-altitude Grassland biome) for the last glacial as well as for other glacial periods of the past 300 Ka.
(Climate of the Past. vol. 7, n° 1814-9324, pp. 1209 - 1224, 28/10/2026)
MARUM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, NIOZ