Etude de la réactivité et l’efficacité de rétention des éléments traces métalliques dans les stations d'épuration de Bordeaux et leurs apports métalliques dans les eaux de la section Garonnaise de l'estuaire de la Gironde
Cette thèse s’intègre dans l’axe 3 du programme « ETIAGE » qui a associé pendant quatre ans (2010-2014) la Lyonnaise des Eaux, la Communauté Urbaine de Bordeaux (CUB), l’AEAG, et le FEDER, région Aquitaine avec l’université de Bordeaux, le CNRS et IRSTEA. L’objectif de l’axe 3 était de documenter les apports métalliques du bassin versant de la CUB aux eaux de la section garonnaise de l’estuaire de la Gironde. Ce vaste estuaire européen est l’un des plus turbides au monde, avec en période d’étiage la présence devant Bordeaux d’une zone de turbidité maximum (ZTM, >1 g.L-1 de MES en surface) qui transporte des particules estuariennes et des éléments traces potentiellement toxiques. Les travaux de cette thèse se sont focalisés sur les apports métalliques via le fonctionnement des deux principales stations d’épuration (STEP) de la CUB. De ce fait, l’objectif de cette recherche est d’analyser en détail les concentrations, les flux et la réactivité de huit contaminants métalliques définis comme prioritaires par l’Union Européenne Cr, Cu, Cr, Hg, Ni, Pb, Zn, As, et le contaminant émergent Ag, des STEP de la CUB. Les taux d’abattement calculés sont importants, de l’ordre de 80 % pour la majorité des métaux, essentiellement lors de l’étape de décantation. Malgré cette efficacité, les apports en éléments traces métalliques (ETM) urbains via les STEP pendant les épisodes orageux et dans des situations de faible débit peuvent augmenter les concentrations et les flux dans l’estuaire fluvial de la Gironde et ainsi avoir des conséquences sur la qualité des eaux estuariennes. Les concentrations en Ag sont supérieures aux concentrations normales de bruit de fond dans l’estuaire fluvial de la Gironde, faisant de Ag un excellent traceur urbain. Le traitement dans les STEP concentre les ETM dans les boues extraites dont les concentrations métalliques restent en-deçà des normes d’épandage. Toutefois, les concentrations en éléments traces peuvent être de 15 (Ag) à 30 (Cu) fois supérieures aux concentrations naturelles du bruit de fond en raison du fort enrichissement des boues en Hg, Ag, Cr, Cu et Zn. De plus, environ 70 % des éléments traces Cd, Ag, Pb, Cu, et Zn contenus dans ces boues sont potentiellement biodisponibles et peuvent avoir un impact néfaste à court et long terme sur les environnements récepteurs. En raison de l’augmentation prévisible de la démographie des villes côtières, les résultats de cette étude participent à l’élaboration de nouveaux concepts et outils (récupération, recyclage, valorisation) pour améliorer quantitativement et qualitativement les rejets urbains solides et liquides.
(23/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Genomic and gene expression responses to genotoxic stress in PAC2 zebrafish embryonic cell line
PAC2 cell line is, along most of the developed zebrafish cell lines, poorly characterized concerning its response to genotoxicants. To define the PAC2 cell line response to different forms of genotoxic stress, we exposed the cells to model genotoxic agents (benzo[a]pyrene, B[a]P, and ethyl methanesulfonate) and subsequently monitored DNA damage and alterations by using the battery of tests, including the Comet assay, quantitative random-amplified polymorphic DNA and amplified fragment length polymorphism. The expression of several DNA repair (xpc, xpd, hr23b, rad51, msh2) and oxidative stress response (sod (Cu/Zn)) genes was monitored as well. To obtain an indication of the PAC2 cell line metabolizing capacity, the expression of genes belonging to cyp1, cyp2 and cyp3 families was assessed upon exposure to B[a]P. Genotoxic responses were observed in all the used methods, and quantitative random-amplified polymorphic DNA and amplified fragment length polymorphism proved to be more sensitive by revealing DNA alterations even when the Comet assay indicated lack of significant damage. The PAC2 cell line demonstrated basal and B[a]P-induced expression of several cyp genes, suggesting its ability to metabolize indirect acting xenobiotics to a certain point. Based on these results, PAC2 cells seem to be sensitive zebrafish in vitro model in the genotoxicity assessment of the direct acting genotoxicant; however, they are less sensitive toward the indirect acting genotoxicant due to their limited metabolizing properties.
(Journal of Applied Toxicology. vol. 35, n° 0260-437X, pp. 1381-1389, 21/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Preliminary Assessment of SARAL/AltiKa Observations over the Ganges-Brahmaputra and Irrawaddy Rivers
Radar altimetry has demonstrated strong capabilities for the monitoring of water levels of lakes, rivers and wetlands over the last 20 years. The Indo-French SARAL/AltiKa mission, launched in February 2013, is the first satellite radar altimetry mission to carry onboard a Ka-band sensor. We propose here to evaluate the potential of this new instrument for land hydrology through comparisons with other altimetry-derived stages and discharges in the Ganges-Brahmaputra and Irrawaddy river basins using its first year of data. Due to the lack of concomitant in situ measurements for the current period, Jason-2 data, previously evaluated against in situ gauge records, were used as reference. Comparisons between Jason-2 and SARAL-derived water levels and discharges, and Jason-2 and Envisat (which flew the same orbit as SARAL from 2002 to 2010) –derived ones, was performed. Time-series of only one year of SARAL-derived water levels and discharges present better performances (lower RMSE and higher R, generally greater than 0.95) than the ones derived from Envisat when compared to Jason-2.
(Marine Geodesy. vol. 38, n° 0149-0419, pp. 568-580, 20/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Ischnomesus harrietae sp. nov., a new benthic asellote (Crustacea: Isopoda: Ischnomesidae) from bathyal bottoms of the southern Bay of Biscay
A new species of Ischnomesidae (Crustacea: Isopoda: Asellota), Ischnomesus harrietae sp. nov. is described from the southern Bay of Biscay. This new species is distinctive due to the presence of numerous pedestal setae arranged in longitudinal rows on pereonite 5. Because of this morphological peculiarity, it can be easily distinguished from the four other Ischnomesus species previously reported from bathyal/abyssal bottoms of the European continental margin. Within its known distributional area, the new species inhabits sandy and muddy bottoms between 619 and 1099 m, with a maximum abundance of 41.8 individuals per 100 m2 recorded at approximately 700 m on the Arcachon Plateau. Another new species is also reported, Ischnomesus sp.1, represented by one specimen only and briefly described. An identification key to European species of Ischnomesus is provided.
(Zootaxa. vol. 3911, n° 1175-5326, pp. 201, 19/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Elasmopus thalyae sp. nov. (Crustacea: Amphipoda: Maeridae), a new benthic species from soft and hard bottoms of Arcachon Bay (SE Bay of Biscay)
A new species of Elasmopus is described and figured from specimens collected in different benthic communities of Arcachon Bay. It can be distinguished from its closest relative E. rapax by the palmar ornamentation of male gnathopod 2 propodus (shelf and 2 teeth). It preferentially lives on hard bottoms (in mussel fouling of navigation buoys, Sabellaria spinulosa reefs, algal rocky bottoms, Laminaria and Saccorhiza bulbs and as epibiont on the carapace of Maja brachydactyla) but also less abundantly on naked sandy bottoms. An identification key of Atlantic and Mediterranean European species is also given.
(Zootaxa. vol. 3905, n° 1175-5326, pp. 107, 09/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UB
Process-based modeling of cross-shore sandbar behavior
A coupled wave–current–sediment transport beach profile model is used to simulate cross-shore sandbar evolution on the time scale from days to months comprising both rapid offshore and slow onshore migrations. The discrimination of four modes of sediment transport driven by velocity and acceleration skewness, mean currents and slope effects allows addressing the dominant hydrodynamic processes governing cross-shore sandbar behavior. Acceleration–skewness-induced transport systematically results in a slow onshore sandbar migration together with a slow bar growth. Velocity–skewness-induced transport can drive onshore and offshore bar migrations with substantially larger rates. Mean–current-induced sediment transport systematically drives an offshore bar migration with either bar growth or decay. Slope effects essentially act as a damping term. The water level above the sandbar crest mainly influences the sandbar migration direction, while wave obliquity regulates the magnitude of the migration rates and is crucial to accurately simulate offshore sandbar migration during energetic obliquely incident waves. The inclusion of acceleration skewness is a necessary requirement to accurately reproduce the onshore migration of shallow sandbars. Detailed inter-site comparison of best-fit model parameters shows large differences meaning that free parameters attempt to compensate some mispecifications of the physics in the model. Although this also applies to other existing beach profile models, this suggests that this model needs further improvements including, for instance, the contribution of the injection of breaking wave turbulence onto the bed to sand stirring.
(Coastal Engineering. vol. 95, n° 0378-3839, pp. 35-50, 01/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Hydrothermal Activity and Paleoenvironments of the Atlantis II Deep
The Atlantis II Deep is a 65 km2 topographic depression located in the axial trough of the Red Sea at 2,000 m depth. The depression traps 17 km3 of hot and dense brines fed by hydrothermal fluids. This chapter reviews numerous data collected during the last 50 years. Chemical and isotopic data suggest that the processes that lead to the formation of the Atlantis II Deep brines are similar to those that produce open ridge black smoker fluids, but the recharging fluid is sea water in the case of sediment-free ridges, whereas it is sea water that has dissolved evaporites in the case of the Atlantis II Deep. The monitoring of temperature indicates that the heat flux was 0.54 × 109 W between 1965 and 1995. After 1995, the heat flux became 10 times lower. The substratum of the Atlantis II Deep consists of MORB-type basalts, which are covered with 0- to 30-m-thick metalliferous sediments. The solid fraction contains biogenic calcareous and/or siliceous components and silico-clastic detrital particles diluted by metalliferous sediment, which consists of metal oxides, sulphides, carbonates, sulphates, and silicates that precipitated from the hydrothermal fluids. The redox interface between the deepest brine layer and sea water is a major place of mineral precipitation. During glacial periods before the Holocene, the redox boundary was located above the brine–sea water boundary, so that hydrothermal metals spread over a large area of the Red Sea bottom.
(pp. 235-249, 01/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Turbidity in the fluvial Gironde Estuary (southwest France) based on 10-year continuous monitoring: sensitivity to hydrological conditions
Climate change and human activities impact the volume and timing of freshwater input to estuaries. These modifications in fluvial discharges are expected to influence estuarine suspended sediment dynamics, and in particular the turbidity maximum zone (TMZ). Located in southwest France, the Gironde fluvial-estuarine system has an ideal context to address this issue. It is characterized by a very pronounced TMZ, a decrease in mean annual runoff in the last decade, and it is quite unique in having a long-term and high-frequency monitoring of turbidity. The effect of tide and river flow on turbidity in the fluvial estuary is detailed, focusing on dynamics related to changes in hydrological conditions (river floods, periods of low discharge, interannual changes). Turbidity shows hysteresis loops at different timescales: during river floods and over the transitional period between the installation and expulsion of the TMZ. These hysteresis patterns, that reveal the origin of sediment, locally resuspended or transported from the watershed, may be a tool to evaluate the presence of remained mud. Statistics on turbidity data bound the range of river flow that promotes the upstream migration of TMZ in the fluvial stations. Whereas the duration of the low discharge period mainly determines the TMZ persistence, the freshwater volume during high discharge periods explains the TMZ concentration at the following dry period. The evolution of these two hydrological indicators of TMZ persistence and turbidity level since 1960 confirms the effect of discharge decrease on the intensification of the TMZ in tidal rivers; both provide a tool to evaluate future scenarios.
(Hydrology and Earth System Sciences. vol. 19, n° 1027-5606, pp. 2805-2819, 01/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Paleomagnetic and geochemical record from cores from the Sea of Marmara, Turkey: Age constraints and implications of sapropelic deposition on early diagenesis
We present results of a multi-proxy analysis of two sediment cores from the Marmara Sea. The cores were ana- lyzed using paleomagnetic and geochemical measurements. Two sapropels are documented in the last 11 kyr and are recorded in several locations across the Marmara Sea. These two sapropels have contrasting magnetic prop- erties. The magnetic record is affected by intense early diagenesis; the most recent upper sapropelic layer has low remanence and susceptibility values. A record of paleomagnetic inclinations could still be isolated above the dia- genesis front and is compared with secular variation models. The lower sapropel is identified in the deep part of the oldest studied core (Klg07) and has distinct magnetic properties characterized by high remanence and sus- ceptibility values. Using the magnetic properties it is possible to constrain bottom water ventilation and recon- nection episodes between the Marmara Sea and the Black Sea following the sea level rise during the last glacial to inter-glacial transition. ; Peer reviewed
(Marine Geology. vol. 360, n° 0025-3227, pp. 40-54, 01/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Sedimentary records of past earthquakes in Boraboy Lake during the last ca 600 years (North Anatolian Fault, Turkey)
Multiproxy sedimentological analyses along 4.9 m-long sequence of Boraboy Lake, which is located on the central eastern part of the North Anatolian Fault (NAF), reveal the sedimentary traces of past large earthquakes in the region. The lake has a relatively large catchment area (10 km2) compared to its size (0.12 km2), which renders sedimentation sensitive to heavy rain/storm events. Accordingly, the background sedimentation, which is composed of faintly laminated reddish/yellowish brown clayey silt, is frequently interrupted by organic-rich intercalations probably due to heavy rain/storm events transporting terrestrial plant remains from the densely vegetated catchment. In addition to frequent organic-rich intercalations, the background sedimentation is interrupted by four mass-wasting deposits (MWD) of which thickness range is between 15 and 50 cm. High-resolution ITRAX μXRF data confirms higher homogeneity along the MWDs (E1–E4) compared to the background sedimentation. Based on 137Cs and 210Pbxs dating and radiocarbon chronology, three MWDs detected in Boraboy sequence (E2, E3 and E4) temporally correlate with large historical earthquakes along the NAF; the 1943 Tosya (Ms = 7.6) and/or 1942 Niksar-Erbaa (Ms = 7.1), the 1776 Amasya-Merzifon and the 1668 North Anatolian (Ms = 7.9) earthquakes. The youngest MWD in the sequence (E1), which is dated to early 2000s, does not correlate with any strong earthquake in the region. This MWD was probably a single mass-wasting event due to routine overloading and oversteepening on the delta front formed by the main inlet of the lake. In subaqueous paleoseismology, coevality of multi-location mass-wasting events is used as a criterion to assign a seismic triggering mechanism, and to rule out mass-wasting events due to routine overloading/oversteepening of subaqueous slopes. Within this context, Boraboy sequence provides a valuable example to discuss sedimentological imprints of single- vs. multi-source MWDs.
(Palaeogeography, Palaeoclimatology, Palaeoecology. vol. 433, n° 0031-0182, pp. 1-9, 01/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS