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81.
Pierre-Yves Pascal John W. Fleeger Fernando Galvez Kevin R. Carman 《Marine pollution bulletin》2010,60(12):2201-2208
Increased atmospheric CO2 concentrations are causing greater dissolution of CO2 into seawater, and are ultimately responsible for today’s ongoing ocean acidification. We manipulated seawater acidity by addition of HCl and by increasing CO2 concentration and observed that two coastal harpacticoid copepods, Amphiascoides atopus and Schizopera knabeni were both more sensitive to increased acidity when generated by CO2. The present study indicates that copepods living in environments more prone to hypercapnia, such as mudflats where S. knabeni lives, may be less sensitive to future acidification. Ocean acidification is also expected to alter the toxicity of waterborne metals by influencing their speciation in seawater. CO2 enrichment did not affect the free-ion concentration of Cd but did increase the free-ion concentration of Cu. Antagonistic toxicities were observed between CO2 with Cd, Cu and Cu free-ion in A. atopus. This interaction could be due to a competition for H+ and metals for binding sites. 相似文献
82.
Paul R. J. Saey Clemens Schlosser Pascal Achim Matthias Auer Anders Axelsson Andreas Becker Xavier Blanchard Guy Brachet Luis Cella Lars-Erik De Geer Martin B. Kalinowski Gilbert Le Petit Jenny Peterson Vladimir Popov Yury Popov Anders Ringbom Hartmut Sartorius Thomas Taffary Matthias Zähringer 《Pure and Applied Geophysics》2010,167(4-5):499-515
Activity concentration data from ambient radioxenon measurements in ground level air, which were carried out in Europe in the framework of the International Noble Gas Experiment (INGE) in support of the development and build-up of a radioxenon monitoring network for the Comprehensive Nuclear-Test-Ban Treaty verification regime are presented and discussed. Six measurement stations provided data from 5 years of measurements performed between 2003 and 2008: Longyearbyen (Spitsbergen, Norway), Stockholm (Sweden), Dubna (Russian Federation), Schauinsland Mountain (Germany), Bruyères-le-Châtel and Marseille (both France). The noble gas systems used within the INGE are designed to continuously measure low concentrations of the four radioxenon isotopes which are most relevant for detection of nuclear explosions: 131mXe, 133mXe, 133Xe and 135Xe with a time resolution less than or equal to 24 h and a minimum detectable concentration of 133Xe less than 1 mBq/m3. This European cluster of six stations is particularly interesting because it is highly influenced by a high density of nuclear power reactors and some radiopharmaceutical production facilities. The activity concentrations at the European INGE stations are studied to characterise the influence of civilian releases, to be able to distinguish them from possible nuclear explosions. It was found that the mean activity concentration of the most frequently detected isotope, 133Xe, was 5–20 mBq/m3 within Central Europe where most nuclear installations are situated (Bruyères-le-Châtel and Schauinsland), 1.4–2.4 mBq/m3 just outside that region (Stockholm, Dubna and Marseille) and 0.2 mBq/m3 in the remote polar station of Spitsbergen. No seasonal trends could be observed from the data. Two interesting events have been examined and their source regions have been identified using atmospheric backtracking methods that deploy Lagrangian particle dispersion modelling and inversion techniques. The results are consistent with known releases of a radiopharmaceutical facility. 相似文献
83.
84.
Morphology,structure and kinematics of a rainfall controlled slow‐moving Andean landslide,Peru
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Swann Zerathe Pascal Lacroix Denis Jongmans Jersy Marino Edu Taipe Marc Wathelet Walter Pari Lionel Fidel Smoll Edmundo Norabuena Bertrand Guillier Lucile Tatard 《地球表面变化过程与地形》2016,41(11):1477-1493
The large slow‐moving landslide of Maca is located in the upper Colca valley (southern Peru), a region characterized by a well pronounced rainy period, and intense and recurrent sustained seismicity. The landslide, developed in deep lacustrine deposits, has recently accelerated, threatening the Maca village. This work aims at understanding the rupture mechanism and the causes of the recent landslide reactivation/acceleration. We present a multidisciplinary characterization of the Maca landslide that includes: (i) geological and morphological mapping in the field; (ii) remote sensing analysis using an historical aerial photograph of 1955 and the Pléiades satellite images (2013); (iii) global positioning system (GPS) including time‐series of surveys over 13 years, and continuous measurements over 14 months; (iv) a geophysical campaign with deep electrical resistivity tomography profiles acquired across the landslide mass. Our study shows that this 60 Mm3 landslide, which can be classified as a clay/silt compound landslide, moved by 15 m between 2001 and 2014 with a large inter‐annual velocity variation (up to a factor of 500) depending on the rainfall intensity. We suggest that these dramatic changes in velocity are the result of the combination of a threshold mechanism and the short intense rainy season in Peru. This study reveals three main driving factors acting at different timescales: (i) over several decades, the river course has significantly changed, causing the Maca landslide reactivation in the 1980s due to the erosion of its toe; (ii) at the year scale, a minimum amount of rainfall is required to trigger the motion and this amount controls the landslide velocity; (iii) transient changes in slide velocity may occur anytime due to earthquakes. This study particularly highlights the non‐linear behaviour of the motion with rainfall. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
85.
Laurence Jouniaux Alexis Maineult Véronique Naudet Marc Pessel Pascal Sailhac 《Comptes Rendus Geoscience》2009,341(10-11):928-936
The self-potential (SP) method is a passive geophysical method based on the natural occurrence of electrical fields on the Earth's surface. Combined with other geophysical methods, SP surveys are especially useful for localizing and quantifying groundwater flows and pollutant plume spreading, and estimating pertinent hydraulic properties of aquifers (water table, hydraulic conductivity). Laboratory experiments have shown that the involved coupling coefficients mainly depend on the fluid chemistry, conductivity and pH, and on the soil or rock properties. The interpretation of SP observations can be done qualitatively, for instance, by correlation of SP gradients with water fluxes (through electrokinetics) or salt fluxes (through electro-diffusion). In recent years, the interpretation has been improved with the help of modelling or/and inversion of the Poisson equation and endeavours to estimate hydraulic parameters by means of the intensity of electric current sources caused by underground flows. 相似文献
86.
The assessment of OpenStreetMap (OSM) data quality has become an interdisciplinary research area over the recent years. The question of whether the OSM road network should be updated through periodic data imports from public domain data, or whether the currency of OSM data should rather rely on more traditional data collection efforts by active contributors, has led to perpetual debates within the OSM community. A US Census TIGER/Line 2005 import into OSM was accomplished in early 2008, which generated a road network foundation for the active community members in the US. In this study we perform a longitudinal analysis of road data for the US by comparing the development of OSM and TIGER/Line data since the initial TIGER/Line import. The analysis is performed for the 50 US states and the District of Columbia, and 70 Urbanized Areas. In almost all tested states and Urbanized Areas, OSM misses roads for motorized traffic when compared with TIGER/Line street data, while significant contributions could be observed in pedestrian related network data in OSM compared with corresponding TIGER/Line data. We conclude that the quality of OSM road data could be improved through new OSM editor tools allowing contributors to trace current TIGER/Line data. 相似文献
87.
Finn Løvholt Sylfest Glimsdal Carl B. Harbitz Natalia Zamora Farrokh Nadim Pascal Peduzzi Hy Dao Helge Smebye 《Earth》2012,110(1-4):58-73
In the aftermath of the 2004 Indian Ocean tsunami, a large increase in the activity of tsunami hazard and risk mapping is observed. Most of these are site-specific studies with detailed modelling of the run-up locally. However, fewer studies exist on the regional and global scale. Therefore, tsunamis have been omitted in previous global studies comparing different natural hazards. Here, we present a first global tsunami hazard and population exposure study. A key topic is the development of a simple and robust method for obtaining reasonable estimates of the maximum water level during tsunami inundation. This method is mainly based on plane wave linear hydrostatic transect simulations, and validation against results from a standard run-up model is given. The global hazard study is scenario based, focusing on tsunamis caused by megathrust earthquakes only, as the largest events will often contribute more to the risk than the smaller events. Tsunamis caused by non-seismic sources are omitted. Hazard maps are implemented by conducting a number of tsunami scenario simulations supplemented with findings from literature. The maps are further used to quantify the number of people exposed to tsunamis using the Landscan population data set. Because of the large geographical extents, quantifying the tsunami hazard assessment is focusing on overall trends. 相似文献
88.
Pascal Terray 《Climate Dynamics》2011,36(11-12):2171-2199
The main goal of this paper is to shed additional light on the reciprocal dynamical linkages between mid-latitude Southern Hemisphere climate and the El Ni?o-Southern Oscillation (ENSO) signal. While our analysis confirms that ENSO is a dominant source of interannual variability in the Southern Hemisphere, it is also suggested here that subtropical dipole variability in both the Southern Indian and Atlantic Oceans triggered by Southern Hemisphere mid-latitude variability may also provide a controlling influence on ENSO in the equatorial Pacific. This subtropical forcing operates through various coupled air?Csea feedbacks involving the propagation of subtropical sea surface temperature (SST) anomalies into the deep tropics of the Atlantic and Indian Oceans from boreal winter to boreal spring and a subsequent dynamical atmospheric response to these SST anomalies linking the three tropical basins at the beginning of the boreal spring. This atmospheric response is characterized by a significant weakening of the equatorial Atlantic and Indian Inter-Tropical Convergence Zone (ITCZ). This weakened ITCZ forces an equatorial ??cold Kelvin wave?? response in the middle to upper troposphere that extends eastward from the heat sink regions into the western Pacific. By modulating the vertical temperature gradient and the stability of the atmosphere over the equatorial western Pacific Ocean, this Kelvin wave response promotes persistent zonal wind and convective anomalies over the western equatorial Pacific, which may trigger El Ni?o onset at the end of the boreal winter. These different processes explain why South Atlantic and Indian subtropical dipole time series indices are highly significant precursors of the Ni?o34 SST index several months in advance before the El Ni?o onset in the equatorial Pacific. This study illustrates that the atmospheric internal variability in the mid-latitudes of the Southern Hemisphere may significantly influence ENSO variability. However, this surprising relationship is observed only during recent decades, after the so-called 1976/1977 climate regime shift, suggesting a possible linkage with global warming or decadal fluctuations of the climate system. 相似文献
89.
RésuméLe bassin carbonifère des Cévennes, voisin du décrochement sénestre de Villefort, a été étudié en intégrant les données sédimentologiques, les données structurales du socle et du remplissage, ainsi que les données de la pétrologie métamorphique du socle. Le remplissage du bassin est contrôlé par des failles subméridiennes induisant une subsidence localisée en début d’ouverture. Cette subsidence devient plus régionale en fin d’histoire. Un grenat mangane- sifère est associé aux minéraux du faciès schistes verts, des blastes d’andalousite recoupent l’ensemble. Cette association minéralogique indique un gradient de température de 50°C/km. Ce gradient est semblable au gradient estimé dans le bassin sur la matière organique. La schistosité porte trois familles de linéation : 1- une famille à biotite-chlorite-quartz, orientée N45 ± 20° et associée à la mise en place des nappes cévenoles; 2- une famille à minéraux phylliteux dont l’orientation est située autour de N90 et associée à l’ouverture du bassin; 3- une famille à minéraux phylliteux orientée NO horizontale sur des plans de schistosité redressés près de la faille de Villefort. La schistosité régionale est affectée par des plis asymétriques, des bandes de cisaillement et des zones cata- clasées, le tout ayant une cinématique en faille normale vers l’Est. Les relations entre ces différentes structures suggèrent un continuum de déformation depuis des niveaux ductiles jusqu’à des niveaux fragiles. Le remplissage du bassin est affecté par des décrochements parallèles à la faille de Ville- fort. Le bassin des Cévennes s’est donc ouvert dans un contexte extensif est-ouest sur une croûte épaissie. La région a ensuite été reprise par des décrochements nord-sud dont celui de Villefort. 相似文献
90.
The influence of humic acids (HA) on the retention of Th(IV) onto the surface of Fe oxides has been investigated. Thorium (IV) is here considered as an analogue of tetravalent radionuclides (Zr, Hf, U, Np, Pu). Hematite (α–Fe2O3) and gœthite (α–FeOOH) have been chosen as model phases because of their widespread presence in the earth's crust. Retention experiments were performed by batch procedure at constant ionic strength and varying pH in the range 2–10; the HA concentration varied in the range 1–100 mg l−1. Compared with the former data obtained on the retention of Th(IV) with the same hematite sample free of HA, the study of a ternary system (i.e. hematite–HA–Th), clearly shows the influence of HA on the retention mechanisms of Th(IV) even in neutral to slightly alkaline medium. In particular, it is illustrated that the retention of Th(IV) onto Fe oxides closely depends upon the ratio between humic and surface (Fe oxide) sites. This ratio has to be greater than a critical value in order to impede the sorption of Th(IV). 相似文献