Summer air temperature,reconstructions from the last glacial stage based on rodents from the site Taillis-des-Coteaux (Vienne), Western France     

Aurélien Royer  Christophe Lécuyer  Sophie Montuire  Jérôme Primault  François Fourel  Marcel Jeannet 《Quaternary Research》2014

The oxygen isotope composition of phosphate from tooth enamel of rodents (δ¹⁸O_p) constitutes a valuable proxy to reconstruct past air temperatures in continental environments. This method has been applied to rodent dental remains from three genera, Arvicola sp., Microtus sp. and Dicrostonyx sp., coming from Taillis-des-Coteaux, Vienne, France. This archaeological site contains an exceptionally preserved sedimentary sequence spanning almost the whole Upper Palaeolithic, including seven stratigraphic layers dated from 35 to 17 cal ka BP. The abundant presence of rodent remains offers the opportunity to quantify the climatic fluctuations coeval of the various stages of human occupation of the site. Differences between δ¹⁸O_p values of Arvicola sp. and Microtus sp. teeth are interpreted as the result of heterochrony in tooth formation as well as differences in ecology. Mean δ¹⁸O_p values of Microtus sp. are preferentially used to reconstruct summer air temperatures, which range from 16.0 ± 3.7 to 19.1 ± 3.1°C throughout the sedimentary sequence; however, the highest variability is observed during the last glacial maximum.  相似文献   

A combined modelling and geochemical study of the fate of terrigenous inputs from mixed natural and mining sources in a coral reef lagoon (New Caledonia)   总被引：1，自引：0，他引：1  

Fernandez JM  Ouillon S  Chevillon C  Douillet P  Fichez R  Le Gendre R 《Marine pollution bulletin》2006,52(3):320-331

Open-cast mining for Ni, Cr and Co was conducted in the south-west part of New Caledonia during the 20th century. Abandoned mining and prospecting sites were severely affected by erosion, resulting in an increase in the load of terrigenous particles transported to the coral reef lagoon. This article assesses the impact of a typical small catchment area (La Coulée River, 85 km2 watershed) on two bays (Boulari and Sainte Marie) located near Noumea, New Caledonia's main city. This multi-disciplinary study combines geochemical, sedimentological, and hydrodynamic approaches. Ni and Cr concentrations contained in the geochemical matrix phase of the pelitic fraction were determined. The study of the geochemical signatures together with sedimentological data and 3D numerical simulations of the transport of non-settling particles throughout the lagoon demonstrated that terrigenous inputs from the Coulée River were mainly transported and deposited along the shoreline, reaching areas as distant as Sainte Marie Bay. Although quantitatively low (about 3% of the pelite mass of the bay sediments), the terrigenous inputs in Sainte Marie Bay originating from the Coulée River could be traced. The metal content in suspended matter was over 7000 mg kg(-1) for Ni and 4200 mg kg(-1) for Cr.  相似文献   

Assessment of heavy metals in soil and terrestrial isopod <Emphasis Type="Italic">Porcellio laevis</Emphasis> in Tunisian industrialized areas     

Chedliya Ghemari  Christophe Waterlot  Anas Ayari  Julie Leclercq  Francis Douay  Karima Nasri-Ammar 《Environmental Earth Sciences》2017,76(17):623

In this study, data on several metals (Cd, Pb, Zn and Cu) in soil and isopod Porcellio laevis taken at 21 sites from the most important industrial areas in Tunisia (Bizerte, Nabeul, Zaghouan, Sfax and Gabes) were presented. Heavy metal concentrations in both soil samples and isopods were determined using atomic absorption spectrometry. Soil contamination was estimated using the contamination factor (CF). On the other hand, the bioaccumulation factor (BAF) was determined to estimate metal accumulation in isopods. The CF values show that the level of contamination varies between sampled soils, which may be due to the source of pollution at each site. The BAF values allow defining the order of accumulation in P. laevis which was classified for the majority of the sampled sites as a macro-concentrator of Cu and Zn and a deconcentrator of Cd with some exceptions. A principal component analysis (PCA) was conducted between soil properties (pH, OM and CaCO₃) and metal concentrations in soils. Through PCA, we obtained four groups in which soils were distinguished by their physicochemical properties and their metal concentrations. Moreover, linear multiple regressions with a downward stepwise procedure were conducted to test the relationships between the physicochemical parameters and metal concentrations in both soils and isopods. Thus, positive correlations (0.78 < R ² < 0.99) were obtained for Pb considering dataset from the groups 1, 2 and for Zn with data of groups 2 and 3. Finally, results showed that P. laevis could be used as a bio-indicator for monitoring and reducing the impact of pollution in terrestrial ecosystems.  相似文献   

Exploration tree approach to estimate historical earthquakes Mw and depth,test cases from the French past seismicity     

Paola Traversa  David Baumont  Kévin Manchuel  Emmanuelle Nayman  Christophe Durouchoux 《Bulletin of Earthquake Engineering》2018,16(6):2169-2193

The estimation of the seismological parameters of historical earthquakes is a key step when performing seismic hazard assessment in moderate seismicity regions as France. We propose an original method to assess magnitude and depth of historical earthquakes using intensity data points. A flowchart based on an exploration tree (ET) approach allows to apply a consistent methodology to all the different configurations of the earthquake macroseismic field and to explore the inherent uncertainties. The method is applied to French test case historical earthquakes, using the SisFrance (BRGM, IRSN, EDF) macroseismic database and the intensity prediction equations (IPEs) calibrated in the companion paper (Baumont et al. Bull Earthq Eng, 2017). A weighted least square scheme allowing for the joint inversion of magnitude and depth is applied to earthquakes that exhibit a decay of intensity with distance. Two cases are distinguished: (1) a “Complete ET” is applied to earthquakes located within the metropolitan territory, while (2) a “Simplified ET” is applied to both, offshore and cross border events, lacking information at short distances but disposing of reliable data at large ones. Finally, a priori-depth-based magnitude computation is applied to ancient or poorly documented events, only described by single/sporadic intensity data or few macroseismic testimonies. Specific processing of “felt” testimonies allows exploiting this complementary information for poorly described earthquakes. Uncertainties associated to magnitude and depth estimates result from both, full propagation of uncertainties related to the original macroseismic information and the epistemic uncertainty related to the IPEs selection procedure.  相似文献   

Invigorating hydrological research through journal publications   总被引：1，自引：1，他引：0  

Nevil Quinn  Günter Blöschl  András Bárdossy  Attilio Castellarin  Martyn Clark  Christophe Cudennec 《水文科学杂志》2018,63(8):1113-1117

Editors of several journals in the field of hydrology met during the General Assembly of the European Geosciences Union—EGU in Vienna in April 2017. This event was a follow-up of similar meetings held in 2013 and 2015. These meetings enable the group of editors to review the current status of the journals and the publication process, and to share thoughts on future strategies. Journals were represented at the 2017 meeting by their editors, as shown in the list of authors. The main points on invigorating hydrological research through journal publications are communicated in this joint editorial published in the above journals.  相似文献   

Effects of porosity and composition on seismic wave velocities and elastic moduli of lower cretaceous rocks,central Lebanon     

Mohamed K. Salah  Mohammad Alqudah  Ahmad K. Abd El-Aal  Christophe Barnes 《Acta Geophysica》2018,66(5):867-894

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Experimentally-controlled carbon and oxygen isotope exchange between bioapatites and water under inorganic and microbially-mediated conditions     

Antoine Zazzo  Christophe Lécuyer  André Mariotti 《Geochimica et cosmochimica acta》2004,68(1):1-12

Modern bone and enamel powders have reacted at 301 K with ¹³C- and ¹⁸O-labelled waters under inorganic and microbial conditions. The aim of the study is to investigate the resistance of stable isotope compositions of bioapatite carbonate (δ¹³C, δ¹⁸Oc) and phosphate (δ¹⁸Op) to isotopic alteration during early diagenesis. Rapid and significant carbon and oxygen isotope changes were observed in the carbonate and phosphate fractions of bone apatite before any detectable change occurred in the crystallinity or organic matter content. These observations indicate that chemical alterations of bone apatite are likely to start within days of death. Enamel crystallites are much more resistant than bone crystallites, but are not exempt of alteration. Non removable carbon and oxygen isotope enrichments were measured in the carbonate phase of bone (50-90%) and enamel (40%) after the acetic acid treatment. This result indicates that a significant part of ¹³C and ¹⁸O-labelled coming from the aqueous fluid has been durably incorporated into the apatite structure, probably through isotopic exchange or secondary carbonate apatite precipitation. As a result, acetic acid pre-treatments that are currently used to remove exogenous material by selective dissolution, are not adequate to restore pristine δ¹³C and δ¹⁸Oc values of fossil apatites. Under inorganic conditions, kinetics of oxygen isotope exchange are 10 times faster in carbonate than in phosphate. On the opposite, during biologically-mediated reactions, the kinetics of oxygen isotope exchange between phosphate and water is, at least, from 2 to 15 times faster than between carbonate and water. Enamel is a more suitable material than bone for paleoenvironmental or paleoclimatical reconstructions, but interpretations of δ¹⁸Op or δ¹³C values must be restricted to specimens for which no or very limited trace of microbial activity can be detected.  相似文献   

Soil erosion assessment using RUSLE model in the Congo Nile Ridge region of Rwanda     

Enan M. Nyesheja  Attia M. El-Tantawi  Fidele Karamage  Christophe Mupenzi  Jean Baptiste Nsengiyumva 《自然地理学》2019,40(4):339-360

This research assessed the soil erosion threat in the Congo Nile Ridge Region of Rwanda. The study forecasted erosion by applying the Revised Universal Soil Erosion (RUSLE) with five factors (rainfall, soil, topography, cover management, and support practices) and spatial data. About 85.5% of the area under investigation was predisposed to erosion with unsustainable average soil loss rates of > 1 t/ha/yr. The outcomes of the research highlighted that the average rate of estimated soil loss in the region prone to erosion was > 63.62 t/ha/yr, resulting in an overall annual predicted soil loss of approximately 44 × 10⁶ t in 2016. All of the districts studied have steep slope gradients (30.4%–36.1%) and high annual rainfall totals (1199–1484 mm/yr), except Rubavu district. More than 88.8% of croplands had unsustainable average soil loss rates of > 1 t/ha/yr. The analysis indicated that both terracing and strip cropping have the potential to reduce rates of soil loss in the farmland, by 64.4% and 10.4%, respectively. The results of this study will serve as a baseline for soil erosion mitigation and land-use planning in the study area and Rwanda at large.  相似文献   

Persistent organic pollutants (POPs) in killer whales (Orcinus orca) from the Crozet Archipelago, southern Indian Ocean     

Marie Noël  Lance Barrett-Lennard  Christophe Guinet  Neil Dangerfield  Peter S. Ross   《Marine environmental research》2009,68(4):196-202

Persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and dibenzofurans (PCDFs), are ubiquitous environmental contaminants of which significant concentrations are reported in upper trophic level animals. In 1998, we collected blubber biopsy samples (n = 11) from killer whales (Orcinus orca) inhabiting the coastal waters around Possession Island, Crozet Archipelago, southern Indian Ocean, for contaminant analyses. Despite inhabiting an isolated region far removed from industrial activities, these killer whales can presently be considered among the most PCB-contaminated cetaceans in the southern hemisphere, with concentrations ranging from 4.4 to 20.5 mg/kg lipid weight (lw). PCDD levels ranged from below the detection limit (5 ng/kg) to 77.1 ng/kg lw and PCDF levels from below the detection limit (7 ng/kg) to 36.1 ng/kg lw. Over 70% of our study animals had PCB concentrations which exceeded a 1.3 mg/kg PCB threshold established for endocrine disruption and immunotoxicity in free-ranging harbour seals, suggesting that organic contaminants cannot be ruled out as an additional threat to this declining population.  相似文献   

Scientific detector workshop 2022 on-sky performance verification of near-infrared e−APD technology for wavefront sensing and demonstration of e−APD pixel performance to improve the sensitivity of large science focal planes     

Gert Finger  Frank Eisenhauer  Reinhard Genzel  Christopher Mandla  Ian Baker  Domingo Alvarez  Antonio Amorim  Wolfgang Brandner  Christophe Dupuy  Casey Deen  Derek Ives  Leander Mehrgan  Manfred Meyer  Karin Perraut  Guy Perrin  Jörg Stegmeier  Christian Straubmeier  Harald J. Weller  Vincent Isgar 《Astronomische Nachrichten》2023,344(8-9):e20230069

Near-infrared adaptive optics as well as fringe tracking for coherent beam combination in optical interferometry require the development of high-speed sensors. Because of the high speed, a large analog bandwidth is required. The short exposure times result in small signal levels which require noiseless detection. Both requirements cannot be met by state-of-the-art conventional CMOS technology of near-infrared arrays as has been attempted previously. A total of five near-infrared SAPHIRA 320 × 256 pixel HgCdTe e⁻APD arrays have been deployed in the wavefront sensors and in the fringe tracker of the VLTI instrument GRAVITY. The current limiting magnitude for coherent exposures with GRAVITY is m_k = 19, which is made possible with ADP technology. New avalanche photo-diode array (APD) developments since GRAVITY include the extension of the spectral sensitivity to the wavelength range from 0.8 to 2.5 μm. After GRAVITY a larger format array with 512 × 512 pixels has been developed for both AO applications at the ELT and for long integration times. Since dark currents of <10⁻³ e⁻/s have been demonstrated with 1Kx1K e⁻APD arrays and 2Kx2K e⁻APD arrays have already been developed, the possibilities and adaptations of e⁻APD technology to provide noiseless large-format science-grade arrays for long integration times are also discussed.  相似文献