Laboratory Studies of Icy Regoliths in Relation to Observations of Minor Bodies in the Outer Solar System     

Levasseur-Regourd  A.Chantal 《Earth, Moon, and Planets》2003,92(1-4):337-343

Observing the properties of solar lightscattered by TNOs is (up to now) the only way to obtain information on the physical properties of their surfaces. As such observations, performed near backscattering, become available, it is important to stress the significance of the phase angle and wavelength dependences of the linear polarization of the scattered light. At small phase angles, a narrow spike in brightness and a significantly negative polarization could be typical of icy regoliths, actually expected to be formed by alteration of icy bodies surfaces. Accurate experimental simulations of icyaggregates and regoliths formation that should take place with the ICAPS facility on board the ISS are presented, with emphasis on light scattering measurements providing a link between remote observations of TNOs and physical properties of their surfaces.  相似文献   

The effects of ram pressure stripping on cluster galaxies     

Bernd Vollmer  Chantal Balkowski  Veronique Cayatte 《Astrophysics and Space Science》2002,281(1-2):359-362

We investigate the effects of ram pressure stripping of spiral galaxies using a numerical model that is directly confronted with interferometric observations. The current status of our research is presented. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

Projections of future floods and hydrological droughts in Europe under a +2°C global warming   总被引：1，自引：0，他引：1  

Philippe Roudier  Jafet C. M. Andersson  Chantal Donnelly  Luc Feyen  Wouter Greuell  Fulco Ludwig 《Climatic change》2016,135(2):341-355

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Long-term changes in a Mediterranean benthic community: Relationships between the polychaete assemblages and hydrological variations of the Rhône River     

Chantal Salen-Picard  Denise Arlhac 《Estuaries and Coasts》2002,25(6):1121-1130

Long-term changes in a macrobenthic, muddy community of the French Mediterranean coast, near the mouth of the Rhône River, were studied using 14 samples collected between 1963 and 1996 at 70-m depth. No drastic change in the community was observed over this time period. A factor correspondence analysis (FCA) performed with the most frequent polychaete species revealed that 3 sample groups were related to trends in the Rhône River discharge. Between 1965 and 1976, the effects of dumping events close to the study site acted in synergy with river drought leading to a drop in the abundance of the most common species of the community (e.g.,Sternaspis scutata). Floods were observed to be the main factor structuring the polychaete assemblages. These floods were subsequently followed, over a period of several years, by peaks of opportunistic species (Heteromastus filiformis, Prionospio cirrifera) and, with a time lag of 1 or 2 yr, by peaks ofS. scutata. Autumn and early winter floods were mainly the result of heavy rainfalls on the Mediterranean part of the drainage basin. They transported large amounts of mineral and particulate organic matter that increased the surface and subsurface deposit feeders assemblages. Late winter and spring floods originated from the north of the basin. They proportionally brought more dissolved material and were followed by developments of suspension and surface deposit feeders. Eutrophication of the area due to increased nitrate concentrations in the river is suggested to be responsible for the abundance, since the 1980s, of small-sized deposit feeders. There is a good parallel between the cumulative mean deviations of the river discharge and the quantity of soles caught in the area with a time lag of 4 yr between these two curves. These results may be of value to the management of the regional resources.  相似文献   

How to model shallow water‐table depth variations: the case of the Kervidy‐Naizin catchment,France     

Jrme Molnat  Chantal Gascuel‐Odoux  Philippe Davy  Patrick Durand 《水文研究》2005,19(4):901-920

The aim of this work is threefold: (1) to identify the main characteristics of water‐table variations from observations in the Kervidy‐Naizin catchment, a small catchment located in western France; (2) to confront these characteristics with the assumptions of the Topmodel concepts; and (3) to analyse how relaxation of the assumptions could improve the simulation of distributed water‐table depth. A network of piezometers was installed in the Kervidy‐Naizin catchment and the water‐table depth was recorded every 15 min in each piezometer from 1997 to 2000. From these observations, the Kervidy‐Naizin groundwater appears to be characteristic of shallow groundwaters of catchments underlain by crystalline bedrock, in view of the strong relation between water distribution and topography in the bottom land of the hillslopes. However, from midslope to summit, the water table can attain a depth of many metres, it does not parallel the topographic surface and it remains very responsive to rainfall. In particular, hydraulic gradients vary with time and are not equivalent to the soil surface slope. These characteristics call into question some assumptions that are used to model shallow lateral subsurface flow in saturated conditions. We investigate the performance of three models (Topmodel, a kinematic model and a diffusive model) in simulating the hourly distributed water‐table depths along one of the hillslope transects, as well as the hourly stream discharge. For each model, two sets of parameters are identified following a Monte Carlo procedure applied to a simulation period of 2649 h. The performance of each model with each of the two parameter sets is evaluated over a test period of 2158 h. All three models, and hence their underlying assumptions, appear to reproduce adequately the stream discharge variations and water‐table depths in bottom lands at the foot of the hillslope. To simulate the groundwater depth distribution over the whole hillslope, the steady‐state assumption (Topmodel) is quite constraining and leads to unacceptable water‐table depths in midslope and summit areas. Once this assumption is relaxed (kinematic model), the water‐table simulation is improved. A subsequent relaxation of the hydraulic gradient (diffusive model) further improves water‐table simulations in the summit area, while still yielding realistic water‐table depths in the bottom land. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Macrofaunal density, biomass and composition of estuarine sediments and their relationship to the river plume of the Rhone River (NW Mediterranean)     

Rachel Hermand  Chantal Salen-Picard  Elisabeth Alliot  Claude Degiovanni 《Estuarine, Coastal and Shelf Science》2008,79(3):367-376

This study investigates species community patterns and sediment relationships of benthic macrofauna off the Rhone river delta. Along a WE transect, changes in diversity, density, biomass and trophic structure were coupled with the mean extension of the river dilution plume. Species number and diversity were at a minimum off the river mouth, below the area of the minimum surface salinity. Density decreased by a factor 2 and biomass by a factor 5 from the fluvial to the marine system. These features are due to high overload of terrestrial organic matter in the river prodelta as evidenced by the carbon isotopic signature of surface sediment and by pigment content. On the basis of a non-metric MDS analysis and of Dufrêne and Legendre method (1997), groups of stations and characteristic species associated were identified. These species, mainly small capitellids, spionids, lumbrinerids and sternaspids, correspond to a successional dynamic in response to changes in sedimentation conditions, mainly in organic matter quality of the surface sediment. The succession observed in space was similar to described in macrotidal estuaries and off other deltaic systems all over the world and to that observed in time following the Rhone river severe flood events. Results suggest that organic matter quality is an important factor with regard to benthic macrofauna successions and recovery mechanisms following disturbances. The differences observed between the Rhone deltaic system and the general model of relations between shelf processes and discharge of large rivers are attributed to a more regular supply of organic material from terrestrial origin on the Rhone continental shelf.  相似文献   

Diel variability of glycolate in the eastern tropical Atlantic Ocean     

Christophe Leboulanger  Louise Oriol  Henri Jupin  Chantal Desolas-gros 《Deep Sea Research Part I: Oceanographic Research Papers》1997,44(12):2131-2139

The concentration of dissolved glycolate in sea water was measured by high performance liquid chromatography in the eastern tropical Atlantic Ocean during the Eumeli 4 oceanographic cruise in June 1992. Diurnal concentrations of glycolate reached 74 kg 1⁻¹ 1⁻¹ in mesotrophic waters and 17 μg 1⁻¹ 1 in oligotrophic waters. At midday total dissolved glycolate exceeded 1 g of carbon per m² of ocean, decreasing strongly during the night (less than 0.1 g of carbon per m²). At the three stations studied, glycolate carbon difference between night and day in the water column was of the same order as the daily primary production estimated by incorporation of ¹⁴C0₂. Disappearance of this compound at night suggested a rapid consumption by heterotrophic organisms. These data suggest that glycolate excretion by phytoplankton may be important, and possibly influenced by ambient nutrient concentrations. Further, with glycolate representing up to 50% of daily productivity, our estimates of the total biological reduction of C0₂ need to be re-examined.  相似文献   

Aliphatic and aromatic hydrocarbons in marine biota and coastal sediments from the Gulf and the Gulf of Oman     

Tolosa I  de Mora SJ  Fowler SW  Villeneuve JP  Bartocci J  Cattini C 《Marine pollution bulletin》2005,50(12):1619-1633

The composition and spatial distribution of aliphatic and polycyclic aromatic hydrocarbons (PAHs) were investigated in biota and coastal sediments from four countries surrounding the Gulf (Bahrain, Qatar, United Arab Emirates and Oman). The levels of total petroleum hydrocarbons (TPH), aliphatic unresolved mixture and PAHs in sediments and biota were relatively low compared to world-wide locations reported to be chronically contaminated by oil. Only in the case of the sediments collected near the BAPCO oil refinery in Bahrain, having concentrations of 779 μg g⁻¹ total petroleum hydrocarbon equivalents and 6.6 μg g⁻¹ ∑PAHs, can they be categorized as chronically contaminated. Some evidence of oil contamination was also apparent in sediments and bivalves around Akkah Head and Abu Dhabi in the UAE, and near Mirbat in Oman. Contaminant patterns in sediments and biota indicated that the PAHs were mainly from fossil sources, with the exception of the high PAH concentrations in sediments near the BAPCO refinery that contained substantial concentrations of carcinogenic PAH combustion products.  相似文献   

Sr and Nd isotopes as tracers of clastic sources in Lake Le Bourget sediment (NW Alps, France) during the Little Ice Age: Palaeohydrology implications     

Marie Revel-Rolland  Fabien Arnaud  Marc Desmet  Chantal Alibert 《Chemical Geology》2005,224(4):183-200

Geochemical methods (major elements and Sr, Nd isotopes) have been used to (1) characterize Lake Le Bourget sediments in the French Alps, (2) identify the current sources of the clastic sediments and estimate the source variability over the last 600 years. Major element results indicate that Lake Le Bourget sediments consist of 45% clastic component and 55% endogenic calcite. In addition, several individual flood levels have been identified during the Little Ice Age (LIA) on the basis of their higher clastic content (> 70%).Potential sources of Lake Le Bourget clastic sediments have been investigated from Sr and Nd isotope compositions. The sediments from the Sierroz River and Leysse River which are mainly derived from the Mesozoic Calcareous Massifs are characterised by lower ⁸⁷Sr/⁸⁶Sr ratios and slightly lower ?_Nd(0) ratios than the Arve River sediments which are derived from the Palaeozoic Mont-Blanc External Crystalline Massifs. The Rhône River appears to have been the main source of clastic sediments into the lake for the last 600 years, as evidenced by a similar Sr and Nd isotopic compositions analyzed in core B16 sediments (⁸⁷Sr/⁸⁶Sr = 0.719, ?_Nd(0) = − 10) and in the sediments of the Rhône River (⁸⁷Sr/⁸⁶Sr = 0.719, ?_Nd(0) = − 9.6).The isotopic signatures of flood events and background samples from core B16 in Lake Le Bourget are also similar. This indicates that prior to ∼ 1800, the inputs into the lake have remained relatively homogeneous with the proportion of clastic component mainly being a function of the palaeohydrology of the Rhone River. Early human modification (deforestation and agriculture) of the lake catchment before the 1800s appears to have had little influence on the source of clastic sediments.  相似文献   

Modelling the thermal evolution of slow-spreading ridge segments and their off-axis geophysical signature     

Sébastien Gac  Chantal Tisseau  Jérôme Dyment  Jean Goslin 《Geophysical Journal International》2006,164(2):341-358

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