Laminations sédimentaires et variabilité climatique et océanographique haute-fréquence sur la marge péruvienne
Le Système d’Upwelling Péruvien (PUS) et la Zone à Oxygène minimum (OMZ) qui y est associée font partie des régions les plus marquées par les variations climatiques de type El Niño Southern Oscillation (ENSO), tant à l’échelle interannuelle qu’à l’échelle décennale. Or, peu d’enregistrements de l’impact de l’ENSO sur cette zone géographique atteignent ces résolutions temporelles, malgré des conditions propices à la conservation de dépôts sédimentaires laminés.Nous avons analysé ces archives sédimentaires à l’échelle de la lamine et en utilisant des marqueurs sédimentologiques, micro paléontologiques et géochimiques afin de retracer les variations de tous les paramètres susceptibles de répondre aux changements climatiques(précipitations, productivité, dénitrification, températures océaniques de surface). Cette approche nous a permis de disposer d’un enregistrement complet des conditions environnementales dans l’OMZ du Pérou à des échelles pluri-annuelle à multidécennale, ce qui est inégalé sur des périodes au-delà du dernier millénaire. Nous avons ainsi pu mettre en évidence une forte empreinte de la circulation de Walker sur le PUS. Cet impact est modulé par les régions extra tropicales de l’hémisphère Nord, en particulier par l’Oscillation Nord-Atlantique (NAO) à l’échelle multidécennale, par la circulation thermohaline à l’échelle centennale et par l’Anticyclone Sibérien à l’échelle millénaire.
(04/06/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
DNA alterations and effects on growth and reproduction in Daphnia magna during chronic exposure to gamma radiation over three successive generations
This study examined chronic effects of external Cs-137 gamma radiation on Daphnia magna exposed over three successive generations (F0, F1 and F2) to environmentally relevant dose rates (ranging from 0.007 to 35.4mGyh-1). Investigated endpoints included survival, growth, reproduction and DNA alterations quantified using random-amplified polymorphic DNA polymerase chain reaction (RAPD-PCR). Results demonstrated that radiation effects on survival, growth and reproduction increased in severity from generation F0 to generation F2. Mortality after 21 days at 35.4mGyh-1 increased from 20% in F0 to 30% in F2. Growth was affected by a slight reduction in maximum length at 35.4mGyh-1 in F0 and by reductions of 5 and 13% in growth rate, respectively, at 4.70 and 35.4mGyh-1 in F2. Reproduction was affected by a reduction of 19% in 21 day-fecundity at 35.4mGyh-1 in F0 and by a delay of 1.9 days in brood release as low as 0.070mGyh-1 in F2. In parallel, DNA alterations became significant at decreasing dose rates over the course of F0 (from 4.70mGyh-1 at hatching to 0.007mGyh-1 after ~21 days) and from F0 to F2 (0.070mGyh-1 at hatching to 0.007mGyh-1 after ~21 days), demonstrating their rapid accumulation in F0 daphnids and their transmission to offspring generations. Transiently more efficient DNA repair leading to some recovery at the organism level was suggested in F1, with no effect on survival, a slight reduction of 12% in 21 day-fecundity at 35.4mGyh-1 and DNA alterations significant at highest dose rates only. The study improved our understanding of long term responses to low doses of radiation at the molecular and organismic levels in a non-human species for a better radioprotection of aquatic ecosystems. © 2015 Elsevier B.V.
(Aquatic Toxicology. vol. 163, n° 0166-445X, pp. 27-36, 01/06/2015)
IRSN/PRP-ENV/SERIS/LECO, IRSN/PRP-ENV/SERIS, IRSN, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRSN
Metal detoxification and gene expression regulation after a Cd and Zn contamination: An experimental study on Danio rerio
(Chemosphere. vol. 128, n° 0045-6535, pp. 125-133, 01/06/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Impact of the winter 2013–2014 series of severe Western Europe storms on a double-barred sandy coast: Beach and dune erosion and megacusp embayments
The winter of 2013/2014 was characterized by a striking pattern of temporal and spatial extreme storm wave clustering in Western Europe. The 110-km long Gironde coast, SW France, was exposed to the most energetic wave conditions over the last 18 years. The period was outstanding in terms of the available energy to move sediment and cause large-scale erosion with the 2-month average significant wave height (Hs) exceeding 3.6 m, just below the 0.95 quantile, and 4 distinct 10-year return period storms with Hs > 9 m. These storm waves caused unprecedented beach and dune erosion along the Gironde coast, including severely damaged sea defences at the coastal towns. At the end of the winter, dune erosion scarp height was highly variable alongshore and often exceeded 10 m. Megacusp embayments were observed along the Gironde coast with an average alongshore spacing of 1000 m in the south progressively decreasing to 500 m in the north, with an average cross-shore amplitude of 20 m. While beach megacusps were previously observed to systematically couple to the inner bar along the Gironde coast during low- to moderate-energy wave conditions, severe storm-driven megacusp embayments cutting the dune were found to be enforced and coupled to the outer crescentic bar. A detailed inspection of the 1500 m-long bimonthly topographic surveys of Truc Vert beach shows that in early January 2014 the outstanding shore-normal incident storm swell ‘Hercules’, with Hs and peak wave period Tp peaking at 9.6 m and 22 s, respectively, triggered the formation of a localized megacusp embayment with the erosion scarp height exceeding 6 m in its centre where the dune retreat reached 30 m. The subsequent storms progressively smoothed the megacusp by the end of the winter, mostly through severe erosion of the megacusp horns. Because of the very long period (16 s < Tp < 23 s) storm waves with persistent shore-normal incidence, the well-developed outer crescentic bar observed prior to the winter did not straighten. Instead, the outer-bar three-dimensionality developed further, particularly during ‘Hercules’. Our observations indicate that both the antecedent outer sandbar morphology and storm wave characteristics, including period and angle of incidence, govern patterns of beach and dune erosion along open multiple-barred sandy coasts during severe storms.
(Geomorphology. vol. 238, n° 0169-555X, pp. 135-148, 01/06/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Effects of short flexible seagrass Zostera noltei on flow, erosion and deposition processes determined using flume experiments
Innovative flume experiments were conducted in a recirculating straight flume. Zostera noltei meadows were sampled in their natural bed sediments in the field at contrasting stages of their seasonal growth. The aims of this study were: (i) to quantify the combined effects of leaf flexibility and development characteristics of Zostera noltei canopies on their interaction with hydrodynamics; and (ii) to quantify the role of Zostera noltei meadows in suspended sediment trapping and bed sediment resuspension related with changes in hydrodynamic forcing caused by the seasonal development of seagrasses. Velocity within the canopy was significantly damped. The attenuation in velocity ranged from 34 to 87% compared with bare sediments and was associated with a density threshold resulting from the flow-induced canopy reconfiguration. The reduction in flow was higher in dense canopies at higher velocities than in less dense canopies, in which the reduction in flow was greater at low velocities. These contrasted results can be explained by competition between a rough-wall boundary layer caused by the bed and a shear layer caused by the canopy. The velocity attenuation was associated with a two to three-fold increase in bottom shear stress compared with unvegetated sediment. Despite the increase in near-bed turbulence, protection of the sediment against erosion increased under a fully developed meadow, while sediment properties were found to be the main factor controlling erosion in a less developed meadow. Deposition fluxes were higher on the vegetated bed than on bare sediments, and these fluxes increased with leaf density. Fewer freshly deposited sediments were resuspended in vegetated beds, resulting in an increase in net sediment deposition with meadow growth. However, in the case of a very high leaf area index, sediment was mostly deposited on leaves, which facilitated subsequent resuspension and resulted in less efficient sediment trapping than in the less developed meadow.
(Sedimentology. vol. 62, n° 0037-0746, pp. 997-1023, 01/06/2015)
DYNECO, IFREMER, NIOZ, LIENSs, INSU - CNRS, ULR, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Contamination des sols franciliens par les éléments métalliques et les micropolluants organiques
Dans le cadre de la phase 6 du programme PIREN-Seine, l’action « Cartographie de la contamination des sols » s’est focalisée sur la contamination des sols à large échelle spatiale. Si aujourd’hui certaines bases de données existent pour la contamination des sols (base de données GIS Sol sur les éléments traces métalliques, les hydrocarbures aromatiques polycycliques, les polychlorobiphényls, les dioxines et les pesticides organochlorés), la contamination des sols reste méconnue pour certaines molécules d’intérêt émergent. Dans ce contexte, 105 molécules ont été recherchées dans les sols, incluant les métaux et éléments majeurs (n=23), les hydrocarbures aromatiques polycycliques (HAP, n=15), les polychlorobiphényles (PCB, n=19), les phtalates (PAE, n=7), les polybromodiphényléthers (PBDE, n=8), les alkylphénols (n=7), les composés perfluoroalkylés (PFAS, n=22) et 4 substances individuelles (bisphénol A (BPA), tétrabromobisphénol A (TBBPA), hexachlorobenzène (HCB) et pentachlorobenzène (PeCB)). La stratégie d’échantillonnage visait, d’une part, à caractériser la contamination physico-chimique de divers sols franciliens, et d’autre part, à étudier l’influence de l’occupation des sols. Dans ce but, 32 sols répartis dans des zones urbaines et rurales ont été échantillonnés et analysés (Figure 1). Ils ont été prélevés au moyen d’une tarière sur les dix premiers centimètres du sol. La première partie de cette étude s’est consacrée à la caractérisation globale de la contamination des sols par les métaux et les micropolluants organiques. Selon le métal considéré, les teneurs métalliques varient de quelques mg/kg à plusieurs milliers de mg/kg. Pour les polluants organiques, ces teneurs varient entre 0,1 µg/kg et plusieurs milliers de µg/kg. Globalement, la contamination des sols par les micropolluants organiques est caractérisée par la prédominance des HAP (∑15HAP, 150-55 000 µg/kg), suivi des PAE (∑7PAE, 10-1 700 µg/kg) et des AP (∑7AP, 30-330 µg/kg). Très loin derrière ce premier groupe, on retourne les PCB (∑19PCB, 1-71 µg/kg) suivis par les PBDE (∑8PBDE, 0,3-13 µg/kg) et les PFAS (∑22PFAS, 0,2-3,2 µg/kg). Les distributions de composés et les niveaux de contaminations dans ces sols sont globalement comparables aux niveaux mentionnés dans la littérature, bien que certaines molécules comme les PFAs soient extrêmement peu documentées. D’un sol à un autre, la contamination des sols par les AP, les PAE et les PFAS ne semble varier que faiblement (d90/d10 < 10), alors que les niveaux de contamination pour les PCB et les PBDE et dans une plus forte mesure les HAP fluctuent plus fortement. Même si certaines études mentionnent des corrélations entre polluants, carbone organique (COP) et black carbon (BC), ces travaux n’ont pas mis en évidence l’une ou l’autre de ces corrélations. Le second objectif de cette synthèse visait à étudier l’influence de l’occupation des sols. Pour une majorité de polluants et le COP, aucune différente significative n’apparait entre les sols urbains et ruraux. Les seules différences significatives observées concernent le BC, le Cu, le Zn. Bien que non significatives, certaines tendances apparaissent cependant pour les HAP, les PBDE, les PCB ou les PFAS pour les micropolluants organiques ou le Sr pour les métaux. Les sols localisés sous le panache des vents dominants d’Ile-de-France (axe sud-ouest / nord-est) n’apparaissent pas plus contaminés que d’autres sols. Ces résultats témoignent à la fois de la contamination plus importante des sols urbains comparativement aux sols ruraux, mais également d’une diffusion importante de ces molécules à travers les apports atmosphériques. Cette observation s’explique par l’utilisation de ces molécules pendant plusieurs décades, dans des gammes plus ou moins variées d’applications qui a conduit à une dissémination importante de ces composés et à une pollution de fond dans les sols franciliens. Certains sites se démarquent néanmoins, et ce pour plusieurs familles de contaminants, probablement en raison de la présence de source locales. La dernière partie de cette synthèse se consacrait à l’évaluation du stock de polluants contenu dans les premiers centimètres du sol et à la comparaison de ce stock aux flux atmosphériques. Pour des polluants comme les ∑15HAP, le Pb et dans une moindre mesure le Zn, Cu, Cd, ∑7PAE et ∑7AP, les stocks de polluants dans le sol sont très nettement supérieurs aux flux atmosphériques. Pour ces polluants, la faible contribution atmosphérique pourrait s’expliquer par 1) la rémanence de ces molécules dans les sols, 2) l’exposition du sol à travers les années et donc, à l’intégration de la pollution sur une période relativement longue, et 3) les émissions passées de ces molécules et les stocks importants constitués au cours des années. Une tendance moins marquée est observée pour les PFAS et les PBDE.
(28/05/2015)
LEESU, UPEM, ENPC, UPEC UP12, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GEDI, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, METIS, UPMC, EPHE, PSL, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LPTC, UB, CNRS
Contamination de l'atmosphère par les composés perturbateurs endocriniens en Ile-de-France
(27/05/2015)
SISYPHE, UPMC, EPHE, PSL, PSL, CNRS, LEESU, UPEM, ENPC, UPEC UP12, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LPTC, UB, CNRS
Evidence for an Unrecognized Secondary Anthropogenic Source of Organosulfates and Sulfonates: Gas-Phase Oxidation of Polycyclic Aromatic Hydrocarbons in the Presence of Sulfate Aerosol
In the present study, formation of aromatic organosulfates (OSs) from the photo-oxidation of polycyclic aromatic hydrocarbons (PAHs) was investigated. Naphthalene (NAP) and 2-methylnaphthalene (2-MeNAP), two of the most abundant gas-phase PAHs and thought to represent “missing” sources of urban SOA, were photochemically oxidized in an outdoor smog chamber facility in the presence of nonacidified and acidified sulfate seed aerosol. Effects of seed aerosol composition, acidity and relative humidity on OS formation were examined. Chemical characterization of SOA extracts by ultra performance liquid chromatography coupled to electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry revealed the formation of OSs and sulfonates from photo-oxidation in the presence of sulfate seed aerosol. Many of the organosulfur compounds identified in the smog chamber extracts were also measured in urban fine aerosol collected at Lahore, Pakistan, and Pasadena, USA, demonstrating that PAH photo-oxidation in the presence of sulfate aerosol is a hitherto unrecognized source of anthropogenic secondary organosulfur compounds, and providing new PAH SOA tracers.
(Environmental Science and Technology. vol. 49, n° 0013-936X, pp. 6654-6664, 12/05/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
On The Impact of a Series of Severe Storms on a Double-Barred Sandy Coast: Dune Erosion and Megacups Embayments
The winter of 2013/2014 was outstanding in terms of the available energy to move sediment and caused large-scale unprecedented erosion of the Gironde coast (France), comprising the onset of megacusp embayments cutting the dune with a typical alongshore and cross-shore lengthscale of O (100 m) and O(10 m), and a dune erosion scarp height often exceeding 10 m. Megacusps are found to be coupled to the outer crescentic sandbar and triggered by the outstandingly high-energy, long-period and normally-incident storm wave event Hercules on January 6-7. Our observations indicate that both the antecedent outer sandbar morphology and storm wave characteristics, including period and angle of incidence, govern patterns of beach and dune erosion along open multiple-barred sandy coasts during severe storms.
(11/05/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, WRL, UNSW, BRGM, OASU, UB, INSU - CNRS, ULR, CNRS, INRAE
Trilobites and inarticulate brachiopods from the Devonian Floresta Formation of Colombia: a review
The study of Devonian Colombian trilobites and inarticulate brachiopods allows to recognize two biostratigraphic levels within the Floresta Formation. The first level, in the lower part of the formation, is late Emsian in age, and yields 14 distinct trilobite taxa, including Colombianaspis carvalhoae gen. et sp. nov. The second one, in the upper part of the formation, is assigned to the Givetian based on the co-occurrence of the genera Dipleura and Greenops; this is the first record of a Givetian age for the upper part of the Floresta Formation. The inarticulate brachiopods collected from the uppermost part of the formation suggest a Givetian age. Inarticulate brachiopods as well as the trilobites show close affinities with the North Eastern Americas Realm, but they also suggest European affinities. The late Emsian occurrence of calmoniids from Colombia is indicative of restricted faunal exchanges with the Malvinokaffric Realm.
(Bulletin of Geosciences. vol. 90, n° 1214-1119, pp. 331-358, 01/05/2015)
UNAL, CR2P, MNHN, UPMC, CNRS, LDO, INSU - CNRS, UBO EPE, CNRS