The estuarine geochemical reactivity of Zn isotopes and its relevance for the biomonitoring of anthropogenic Zn and Cd contaminations from metallurgical activities: Example of the Gironde fluvial-estuarine system, France
Zinc stable isotopes measurements by MC-ICP-MS, validated by laboratory intercalibrations, were performed on wild oysters, suspended particles and filtered river/estuarine water samples to provide new constraints for the use of Zn isotopes as environmental tracers. The samples selected were representative of the long range (400 km) transport of metal (Zn, Cd, etc.) contamination from former Zn-refining activities at Decazeville (i.e. δ66Zn > 1‰) and its phasing out, recorded during 30 years in wild oysters from the Gironde Estuary mouth (RNO/ROCCH sample bank). The study also addresses additional anthropogenic sources (urban and viticulture) and focuses on geochemical reactivity of Zn in the turbidity gradient and the maximum turbidity zone (MTZ) of the fluvial Gironde Estuary. In this area, dissolved Zn showed a strong removal onto suspended particulate matter (SPM) and progressive enrichment in heavy isotopes with increasing SPM concentrations varying from δ66Zn = −0.02‰ at 2 mg/L to +0.90‰ at 1310 mg/L. These signatures were attributed to kinetically driven adsorption due to strongly increasing sorption sites in the turbidity gradient and MTZ of the estuary. Oysters from the estuary mouth, contaminated sediments from the Lot River and SPM entering the estuary showed parallel historical evolutions (1979–2010) for Zn/Cd ratios but not for δ66Zn values. Oysters had signatures varying from δ66Zn = 1.43‰ in 1983 to 1.18‰ in 2010 and were offset by δ66Zn = 0.6–0.7‰ compared to past (1988) and present SPM from the salinity gradient. Isotopic signatures in river-borne particles entering the Gironde Estuary under contrasting freshwater discharge regimes during 2003–2011 showed similar values (δ66Zn ≈ 0.35 ± 0.03‰; 1SD, n = 15), i.e. they were neither related to former metal refining activities at least for the past decade nor clearly affected by other anthropogenic sources. Therefore, the Zn isotopic signatures in Gironde oysters reflect the geochemical reactivity of Zn in the estuary rather than signatures of past metallurgical contaminations in the watershed as recorded in contaminated river sediments. The study also shows that the isotopic composition of Zn is strongly fractionated by its geochemical reactivity in the Gironde Estuary, representative of meso–macrotidal estuarine systems.
(Geochimica et Cosmochimica Acta. vol. 170, n° 0016-7037, pp. 108-125, 01/12/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFREMER, ULB
Photodynamical mass determination of the multiplanetary system K2-19
K2-19 is the second multiplanetary system discovered with K2 observations. The system is composed of two Neptune size planets close to the 3: 2 mean-motion resonance. To better characterize the system we obtained two additional transit observations of K2-19b and five additional radial velocity observations. These were combined with K2 data and fitted simultaneously with the system dynamics ( photodynamical model) which increases the precision of the transit time measurements. The higher transit time precision allows us to detect the chopping signal of the dynamic interaction of the planets that in turn permits to uniquely characterize the system. Although the reflex motion of the star was not detected, dynamic modelling of the system allowed us to derive planetary masses of M-b = 44 +/- 12 M-circle plus and M-c = 15.9 +/- 7.0 M-circle plus for the inner and the outer planets, respectively, leading to densities close to Uranus. We also show that our method allows the derivation of mass ratios using only the 80 d of observations during the first campaign of K2.
(Monthly Notices of the Royal Astronomical Society. vol. 454, n° 0035-8711, pp. 4267--4276, 01/12/2015)
LAM, AMU, INSU - CNRS, CNES, CNRS, IPAG, OSUG, UJF, Grenoble INP, INSU - CNRS, IRSTEA, USMB [Université de Savoie] [Université de Chambéry], CNRS, INSU - CNRS, CNES, CNRS, IASTRO, CAB, INTA, CSIC, LPNHE, UPMC, IN2P3, UPD7, CNRS, CAB, INTA, CSIC, LAGRANGE, UNS, INSU - CNRS, UniCA, CNRS, UniCA, AIM (UMR7158 / UMR_E_9005 / UM_112), CEA, INSU - CNRS, UPD7, CNRS, COMUE UCA, OATo, INAF, IAP, UPMC, INSU - CNRS, CNRS, ObsGE, UNIGE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CFHT, INSU - CNRS, NRC, CNRS, UH, UNSA, CESR, UT3, Comue de Toulouse, INSU - CNRS, CNRS
Sea level monitoring and sea state estimate using a single geodetic receiver
(Remote Sensing of Environment. vol. 171, n° 0034-4257, pp. 261-277, 01/12/2015)
MINT, LIFL, Inria, CNRS, Inria, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, CNES, OMP, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LIENSs, INSU - CNRS, ULR, CNRS
Centennial-scale variations in diatom productivity off Peru over the last 3000 years
(The Holocene. vol. 26, n° 0959-6836, pp. 520-531, 30/11/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CAU
African humid periods triggered the reactivation of a large river system in Western Sahara
The Sahara experienced several humid episodes during the late Quaternary, associated with the development of vast fluvial networks and enhanced freshwater delivery to the surrounding ocean margins. In particular, marine sediment records off Western Sahara indicate deposition of river-borne material at those times, implying sustained fluvial discharges along the West African margin. Today, however, no major river exists in this area; therefore, the origin of these sediments remains unclear. Here, using orbital radar satellite imagery, we present geomorphological data that reveal the existence of a large buried paleodrainage network on the Mauritanian coast. On the basis of evidence from the literature, we propose that reactivation of this major paleoriver during past humid periods contributed to the delivery of sediments to the Tropical Atlantic margin. This finding provides new insights for the interpretation of terrigenous sediment records off Western Africa, with important implications for our understanding of the paleohydrological history of the Sahara.
(Nature Communications. vol. 6, n° 2041-1723, pp. 8751, 10/11/2015)
LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], GM, IFREMER, L3AB, UB, INSU - CNRS, CNRS, OASU, UB, INSU - CNRS, ULR, CNRS, INRAE, LAB, UB, INSU - CNRS, CNRS, UB, RMCA, SHOM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GEOAZUR 6526, IRD, UPMC, UNS, INSU - CNRS, UniCA, CNRS, CEFREM, UPVD, INSU - CNRS, CNRS, IMRS
Architecture et dynamique sédimentaire d'une pente carbonatée moderne : exemple de la pente nord de Little Bahama Bank (LBB), Bahamas
Cette étude présente les architectures et la dynamique sédimentaire de la pente carbonatée au nord de Little Bahama Bank (Bahamas) à partir des données de sondeur multifaisceaux, de sondeur de sédiments (Chirp) et de sismique multitraces Haute Résolution (HR) issues de la mission Carambar 1(2010). Une analyse morpho-sédimentaire de surface permet de définir les grands domaines physiographiques et les éléments architecturaux de la pente et précise la répartition spatiale des sédiments dans le contexte actuel de haut niveau marin relatif. Elle révèle une pente dominée par de la boue de périplate-forme avec différents niveaux d’induration et entaillée par des glissements et des canyons sous marins.La variabilité spatiale du transfert de boue depuis la plate-forme vers la pente, couplée à l’évolution latérale de l’intensité du courant des Antilles est à l’origine de grandes différences morphologiques d’est en ouest. Dans la partie occidentale, la pente est environ deux fois plus étendue que dans la partie orientale,elle s’apparente à un système progradant. La pente orientale, quant à elle, est marquée par des processus de bypass. En effet, cette partie est caractérisée par de nombreux canyons sous-marins se poursuivant par des sillons distributaires alimentant des zones de dépôts distales confinées. Une étude intégrée permet la caractérisation à haute résolution des glissements et des canyons et la proposition d’un modèle déformation. Ces éléments architecturaux sont initiés par des déstabilisations intra-pente et leur évolution est contrôlée par des épisodes d’érosion régressive, la sédimentation pélagique et les écoulements gravitaires boueux. Enfin, une analyse sismo-stratigraphique permet de reconstituer l’évolution tectono-sédimentaire de la pente de l’Albien à l’Actuel en lien avec le contexte géodynamique des Caraïbes, l’eustatisme et la production carbonatée sur la plate-forme.
(05/11/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Gas- and Particle-Phase Products from the Chlorine-Initiated Oxidation of Polycyclic Aromatic Hydrocarbons
The chlorine atom (Cl)-initiated oxidation of three polycyclic aromatic hydrocarbons (PAHs; namely, naphthalene, acenaphthylene, and acenaphthene) was investigated. Experiments were performed in an atmospheric simulation chamber using a proton transfer reaction time-of-flight mass spectrometer (TOF-MS) and an aerosol TOF-MS to characterize the oxidation products in the gas and particle phases, respectively. The major products identified from the reaction of Cl atoms with naphthalene were phthalic anhydride and chloronaphthalene, indicating that H atom abstraction and Cl addition reaction pathways are both important. Acenaphthenone was the principal product arising from reaction of Cl with acenaphthene, while 1,8-naphthalic anhydride, acenaphthenone, acenaphthenequinone, and chloroacenaphthenone were all identified as products of acenaphthylene oxidation, confirming that the cylcopenta-fused ring controls the reactivity of these PAHs toward Cl atoms. Possible reaction mechanisms are proposed for the formation of these products, and favored pathways have been suggested. Large yields of secondary organic aerosol (SOA) were also observed in all experiments, and the major products were found to undergo significant partitioning to the particle-phase. This work suggests that Cl-initiated oxidation could play an important role in SOA formation from PAHs under specific atmospheric conditions where the Cl atom concentration is high, such as the marine boundary layer.
(Journal of Physical Chemistry A. vol. 119, n° 1089-5639, pp. 11170-11181, 02/11/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Precise indices based on n-alkane distribution for quantifying sources of sedimentary organic matter in coastal systems
Precise indices based on n-alkane signatures were developed in order to determine the sources and composition of sedimentary organic matter (SOM) in coastal systems. The Arcachon Bay (France), a well-studied temperate lagoon, was used as an example of a complex coastal system sheltering a wide diversity of OM sources. Three main groups of sources were well discriminated from their n-alkane signatures: seagrass (Zostera sp.) produced mainly n-C17, n-C19, n-C21, n-C23 and n-C25 alkanes, algae (Rhodophyta, Chlorophyta) produced n-C15 and n-C17 and the terrigenous input [Quercus sp., Spartina sp. and river suspended particulate OM (SPOM)] was characterized by n-C25, n-C27, n-C29, n-C31 and n-C33. From the above and literature n-alkane fingerprints, we developed a set of indices (n-alkane ratios) to quantify the contribution of these three major sources of the SOM. At the Arcachon Bay scale, they indicated that SOM was composed mainly of seagrass (ca. 53 ± 19%) and terrestrial (ca. 41 ± 17%) material, followed by algae (ca. 6 ± 9%). Moreover, the new n-alkane indices exhibited more relevant spatial patterns than classical ones – the TAR (C27 + C29 + C31/C15 + C17 + C19; terrestrial to aquatic ratio) and the Paq (C23 + C25/C23 + C25 + C29 + C31; aquatic plant %) – with a greater contribution from marine sources in the central part of the lagoon where a high density of Zostera seagrass was observed. Therefore, the development of precise indices adapted to the local diversity of OM sources is needed when using n-alkanes for quantifying the source composition of SOM in complex coastal systems.
(Organic Geochemistry. vol. 88, n° 0146-6380, pp. 69-77, 01/11/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Organic matter characterization and distribution in sediments of the terminal lobes of the Congo deep-sea fan: Evidence for the direct influence of the Congo River
The terminal lobe complex of the Congo River submarine fan sits on the abyssal Atlantic plain, at 5000 m water depth, 760 km offshore from the river mouth estuarine area. While most rivers deliver particulate material to the continental shelf, particulate matter from the Congo River largely bypasses the shelf and is transported by turbidity currents through the Congo submarine canyon system. We determined the quantity and quality of the organic matter reaching the terminal lobe complex at five sites with marked morphological differences that may influence the distribution of organic matter. A suite of bulk geochemical (% OC, δ13Corg, δ15N, C: N), 137Cs and palynofacies analyses were done on cores collected from the terminal lobe area. These results were also compared to the composition of sediments collected upstream at the Malebo Pool (Congo River). Distal lobe complex sediments contain high amounts of terrestrial organic carbon (3–5 wt.%) that is homogeneously distributed in surficial (22 cm) and deeper sediments (580 cm) silty–clay facies. Strongly altered soil-derived organic matter with well-preserved land plant detritus from the Congo River predominates. A terrestrial soil origin for the particulate load was confirmed by the elevated 137Cs activity in lobe sediments. The vertical distribution of the 137Cs signal suggests that there has been a massive arrival of terrestrial sediments since 1963, consistent with a turbiditic origin. From the locations surveyed, we estimate a maximum accumulation of terrestrial organic carbon of ca. 1 kg OC m− 2 y− 1 for the distal lobe. However, transport modifies the organic matter both in terms of quantity and quality. Observed differences were attributed to preferential degradation of nitrogenous matter during diagenesis and to the addition of highly remineralized marine organic matter. Results from our temporal reference site (E) suggest that organic matter may be preserved in turbidite facies for thousands of years. The good preservation state of the accumulated organic matter shows that turbiditic lobe complexes should be considered as a sink for terrestrial organic carbon in the deep ocean.
(Marine Geology. vol. 369, n° 0025-3227, pp. 182-195, 01/11/2015)
iSTeP, INSU - CNRS, SU, CNRS, LECOB, SU, CNRS, OOB, SU, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, OCEANIS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GM, IFREMER, IFREMER, LEMAR, IRD, IFREMER, UBO EPE, CNRS
Combined effects of pollutants and salinity on embryo-larval development of the Pacific oyster, Crassostrea gigas
For several years, low larval recruitment has been observed in Arcachon Bay, in southwest France. Exposure to pollutants could partly account for the reduction of early life stages of the Pacific oyster. This study evaluated the effects of copper and S-metolachlor in combination with salinity on the early life stages of Crassostrea gigas. Embryos were exposed to concentrations of copper (1, 10 and 50 μg L(-1)) or S-metolachlor (10, 100 and 1000 ng L(-1)) and six salinities (18, 21, 24, 27, 30 and 33 u.s.i). Embryotoxicity was measured by considering both the percentage of abnormalities and arrested development in D-shaped larvae. Embryo-larval development was only affected at salinities ≤24 u.s.i, which have never been observed during C. gigas reproduction period in Arcachon Bay. Both contaminants had an effect at environmental concentrations. Our results suggest that copper and metolachlor toxicity was enhanced with decreasing salinity.
(Marine Environmental Research. vol. 113, n° 0141-1136, pp. 31-38, 01/11/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS