Erosion balance in the watersheds of the western Paris Basin by high-frequency monitoring of discharge and suspended sediment in surface water     

Benoît Laignel  Emmanuel Dupuis  Alain Durand  Jean-Paul Dupont  Emmanuel Hauchard  Nicolas Massei 《Comptes Rendus Geoscience》2006,338(8):556-564

An accurate quantification of erosion, based on high-frequency monitoring of river discharge and suspended sediment fluxes is proposed for two watersheds in the western Paris Basin, a sensitive area with respect to erosion phenomena. This continuous monitoring makes it possible to include flood events of short duration, but significant erosion potential. The obtained erosion rate (16 and 21 t?km^?2?yr^?1) is among the weakest of the planet (3.5 to 18?000 t?km^?2?yr^?1). However, this annual balance does not reflect the behaviour of these rivers which can be torrential in certain cases. To cite this article: B. Laignel et al., C. R. Geoscience 338 (2006).  相似文献   

Origine des eaux des émergences karstiques chlorurées du Languedoc-Roussillon     

Olivier Hébrard  Séverin Pistre  Nicolas Cheynet  Jean Dazy  Christelle Batiot-Guilhe  Jean-Luc Seidel 《Comptes Rendus Geoscience》2006,338(10):703-710

The origin of chloride-rich karstic spring waters representative of the Languedoc-Roussillon region has been investigated with a hydrochemical approach. To this end, the major and trace elements most often used in the study of saline environments have been considered (Cl, SO₄, Br, B, Li). This study allowed distinguishing the different end-members of the various chloride-rich karstic spring waters (evaporitic, marine, geothermal). Associated with the Cl, Br and B contents, the Li/SO₄ ratio appeared as a relevant tracer for the determination of the origin of lithium and by extension of the considered waters. To cite this article: O. Hébrard et al., C. R. Geoscience 338 (2006).  相似文献   

L'inclinométrie,un nouvel outil pour le suivi temporel des aquifères ?     

Thibault Rerolle  Nicolas Florsch  Muriel Llubes  Frédéric Boudin  Laurent Longuevergne 《Comptes Rendus Geoscience》2006,338(11):775-786

This study explores the sensitivity of tilt measurements to hydrogeologic phenomena in order to use them to characterise aquifers and explain the signals observed on the instruments. The challenge is to separate the hydrogeological contribution from other phenomena that affect this type of measurements. First, we applied the theory propounded by Farell (1972) and Pagiatakis (1990) to simple hydrogeological cases. Then a simulation of the tiltmeter signal obtained in the Seine valley reveals that the order of magnitude is significant: the signal of a load with hydrologic origin therefore represents a significant part of any tiltmeter signal. Moreover, it can be interpreted in hydrogeological terms: it depends directly on the load gradient through a convolution formalism. Consequently, it is possible to imagine a use of the tiltmeter in hydrogeology to characterise, to a certain extent, mass transfer of water in the ground. To cite this article: T. Rerolle et al., C. R. Geoscience 338 (2006).  相似文献   

Seasonal effect on vertical positioning by Satellite Laser Ranging and Global Positioning System and on absolute gravity at the OCA geodetic station, Grasse, France     

J. Nicolas  J.-M. Nocquet  M. Van Camp  T. van Dam  J.-P. Boy  J. Hinderer  P. Gegout  E. Calais  M. Amalvict 《Geophysical Journal International》2006,167(3):1127-1137

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Effects of Drying on the Low-Frequency Electrical Properties of Tournemire Argillites   总被引：1，自引：0，他引：1  

Philippe Cosenza  Ahmad Ghorbani  Nicolas Florsch  André Revil 《Pure and Applied Geophysics》2007,164(10):2043-2066

Nearly water-saturated argillite samples (initial water content near 3.4 wt%) were cored from an undisturbed area of an underground facility of the French Institute for Radioprotection and Nuclear Safety (IRSN), located at Tournemire (Aveyron, France). These samples were subjected to the following desiccation path: (a) A desaturation phase during which the samples were dried at ambient temperature conditions, relative humidity equal to 43% in average and (b) a heating phase during which the same samples were heated at four temperature levels from 70°C up to 105°C. During both phases, the low-frequency complex resistivity (0.18Hz–12 kHz) was recorded by a four-electrode device. The amplitude of the complex resistivity was extremely sensitive to water content change. At the end of the isotherm desaturation phase, it was multiplied by a factor of 3 to 5. During the heating phase, the resistivity increased by more than two orders of magnitude compared to the initial state. The percentage of Frequency Effect shows a low sensitivity to water content changes during the desaturation stage while it increased by two orders of magnitude during the heating phase. This result confirms that low-frequency spectral signature is extremely sensitive to textural changes (i.e., thermal-induced microcracking in this case) that occurred during heating. Moreover, the complex resistivity of the samples shows a strong anisotropy (a ratio of 10 between both amplitudes measured in the perpendicular directions). The classical Cole-Cole model cannot be used to fit the experimental data obtained in the heating phase. A generalized formulation of this model is required and was successfully applied to represent the complex resistivity data.  相似文献   

Limited Consequences of Seagrass Decline on Benthic Macrofauna and Associated Biotic Indicators     

V. Tu Do  Hugues Blanchet  Xavier de Montaudouin  Nicolas Lavesque 《Estuaries and Coasts》2013,36(4):795-807

Marine phanerogams are ecosystem engineers, as their presence induces major environmental changes that impact on the benthic fauna. Consequently, modifications to the structure of benthic communities would be expected to be associated with seagrass decline. Since 2005, Zostera noltii seagrass beds in Arcachon Bay (France), the largest in Europe, have undergone a severe decline. Twelve stations distributed throughout the lagoon were sampled in 2002, and all were found to be densely planted at that time. Subsequently, the same stations were revisited in 2010 and seagrass cover had drastically decreased by that time. Based on benthic macrofauna, multidimensional scaling (MDS) analysis identified four groups. Years were separated. In 2002, two groups were distinct in relation to the water body, since in 2010 separation between the two other groups was related to seagrass occurrence. When looking at community structure and dominant species there were moderate differences within and between years, independent of seagrass decline. Seagrass loss did not drastically modify the species composition as they were preserved in the remaining seagrass patches. However, there was a drop in macrofauna abundance in unvegetated muddy compared with abundance in the remaining seagrass areas. Epifauna was particularly affected by seagrass decline. Among biotic indicators based on macrofauna, multivariate indicator MISS (Macrobenthic Index in Sheltered Systems) was in agreement with the similarity of macrofauna structure among groups, while other tested indicators performed badly in relation to seagrass occurrence. However, no index detected seagrass loss, highlighting the necessity of maintaining a separate survey on seagrass cover.  相似文献   

Recommendation system to determine suitable and viable hiking routes: a prototype application in Sierra de las Nieves Nature Reserve (southern Spain)     

Jesús Vías  José Rolland  María Luisa Gómez  Carmen Ocaña  Ana Luque 《Journal of Geographical Systems》2018,20(3):275-294

This paper describes a system for recommending hiking routes to help manage hiking activities in a protected area. The system proposes various routes, based on five criteria that maximize some aspects of hikers’ requirements (by analyzing the viability and difficulty of the trails) and also those of protected areas managers (by proposals to relieve congestion in areas already used for hiking and to promote awareness of new ones, as a contribution to environmental education). The recommendation system uses network analysis, multi-criteria decision analysis and geographic information system by free software tools: PgRouting, PostgreSQL and PostGIS. This system has been tested in Sierra de las Nieves Nature Reserve (Andalusia, Spain). Of the 182 routes obtained by the system, 62 (34%) are considered viable for hikers in Sierra de las Nieves, taking into account the type of user most likely to visit this protected area. Most routes have a high difficulty level, which is coherent with the mountainous character of the protected area.  相似文献   

A model for assessing iceberg hazard     

Bigg  Grant R.  Cropper  T. E.  O’Neill  Clare K.  Arnold  Alex K.  Fleming  A. H.  Marsh  R.  Ivchenko  V.  Fournier  Nicolas  Osborne  Mike  Stephens  Robin 《Natural Hazards》2018,92(2):1113-1136

Natural Hazards - With the polar regions opening up to more marine activities but iceberg numbers more likely to increase than decline as a result of global warming, the risk from icebergs to...  相似文献   

Coral- and oyster-microbialite patch reefs in the aftermath of the Triassic–Jurassic biotic crisis (Sinemurian,Southeast France)     

Simon Boivin  Mélanie Gretz  Bernard Lathuilière  Nicolas Olivier  Annachiara Bartolini  Rossana Martini 《Swiss Journal of Geoscience》2018,111(3):537-548

The end of the Triassic and the Early Jurassic are intervals characterised by profound biotic and environmental changes, accompanied by dramatic decreases in marine fauna diversity. Corals were strongly affected and assemblages underwent a severe reduction; compared with those of the Upper Triassic, the Early Jurassic is traditionally defined as holding a “reef gap”. A Sinemurian coral-microbialites patch reef, located in southern France in the Hérault department (Le Perthus locality), is here described. This bioconstruction developed in a shallow mixed siliciclastic-carbonate inner ramp setting. The reef volume is composed of up to 70% of an intercoral facies mostly microbialites, with subordinated sediments (approximately 20–30% of the intercoral facies). Therefore, the patch reef can be defined as a coral-microbialite bioconstruction, in which microbialites were the main framebuilders. The coral assemblage has low diversity and is dominated by massive to branching colonies of Chondrocoenia clavellata. This highlights the reef diversity after the T/J boundary crisis. The Le Perthus patch reef could have acted as an edge for the dominant currents and probably induced reductions in hydrodynamic energy and sedimentation on one of its sides. Consequently, it could have triggered the growth of small lateral bioconstructions, composed of oysters and microbialites, uniquely on one of its sides. The evolution of the facies shows that the Le Perthus patch reef grew in a shallowing-upward setting accompanied by an increase in siliciclastic inputs. The rate of bioerosion and the faunal assemblage suggest that the bioconstructions could have been developed in a mesotrophic environment.  相似文献   

Correction to: Characterization,modeling, and remediation of karst in a changing environment     

Zexuan Xu  Nicolas Massei  Ingrid Padilla  Andreas Hartmann  Bill Hu 《Environmental Earth Sciences》2018,77(15):560

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