THE DEGRADABILITY OF PARTICULATE ORGANIC MATTER IN THE GIRONDE ESTUARY, FRANCE   总被引：4，自引：0，他引：4  

林荣根 《中国海洋湖沼学报》1994,12(2):106-113

The degradability of particulate organic matter(POM)in the Gironde Estuary(France)was measuredusing the incubation technique.The influence of sample treatment and incubation conditions on the re-sults was evaluated.A mathematical model was successfully used to describe the various degradationcurves.Results showed that the upstream POM had very high degradability;the central estuaryPOM had low degradability;and that the mouth POM degradability was between that of central POM(low degradability)and marine POM(high degradability).  相似文献   

African Easterly Waves and convective activity in wet and dry sequences of the West African Monsoon     

Christophe Lavaysse  Arona Diedhiou  Henri Laurent  Thierry Lebel 《Climate Dynamics》2006,27(2-3):319-332

Janicot and Sultan (Geophys Res Lett 28(3):523–526, 2001) and Sultan et al. (J Clim 16(21):3389–3406, 2003) showed evidence of an intraseasonal signal of Sahelian rainfall corresponding to wet and dry sequences of the West African Monsoon. Using NCEP/NCAR reanalysis, NOAA outgoing longwave radiation (OLR) and observed daily rainfall over West Africa from 1968 to 1990, this paper investigates the variability of 3 to 5-day African Easterly Waves (AEWs), convection and their relationship with rainfall in these wet and dry sequences. The mean daily value rainfall during wet sequences is twice the mean value during dry sequences but the number of dry or wet sequences per year is not correlated with the annual rainfall. Wet sequences account for 39% of the annual accumulated rainfall while dry sequences account for 22%. The number of 3 to 5-day AEWs increases during wet years in wet sequences and the activity tends to be larger during wet years in both wet and dry sequences. These AEWs explain 40% of the accumulated rainfall during wet sequences whereas they contribute to 26% of the accumulated rainfall observed during dry sequences. Generally, they contribute to the increase of rainfall during these sequences. Mean convection is stronger and there are twice as many low OLR days (<225W/m²) during wet than dry sequences. The mean rainfall for days with high convective activity (convective days) is also twice as great during wet sequences. Rainfall that occurs during days without low OLR (weak convection with warm cloud tops or isolated deep convection) contributes to 69% of the total rainfall during dry sequences and 45% during wet sequences. A composite study was performed from day D ₀−10 to day D ₀+10 in each sequence. Wet (dry) sequences of the African monsoon start with a decrease (slight increase) of the negative meridional Ertel Potential Vorticity (PV) gradient at 700 hPa, associated with an increase (decrease) of the spectral density of AEWs. During the wet sequence, the African Easterly Jet (AEJ), detected by 700 hPa zonal wind, decreases and moves northward, whereas the Tropical Easterly Jet (TEJ), detected at 200 hPa, increases and shifts southward. Convective activity increases from D ₀−6 to D ₀−3 and remains high for 4 days in wet sequences. The daily rainfall increases (decreases) between D ₀−6 and D ₀ and returns to the mean value at D ₀+4 for wet (dry) sequences.  相似文献   

The location of infinite electrodes in pole–pole electrical surveys: consequences for 2D imaging     

Henri Robain  Yves Albouy  Michel Dabas  Marc Descloitres  Christian Camerlynck  Pierre Mechler  Alain Tabbagh 《Journal of Applied Geophysics》1999,41(4):588

In 2D-multielectrode electrical surveys using the pole–pole array, the distance to ‘infinite electrodes' is actually finite. As a matter of fact, the available cable length generally imposes a poor approximation of theoretical location of these electrodes at infinity. This study shows that in most of the cases, the resulting apparent resistivity pseudosection is strongly distorted. Numerical simulation validated by field test also shows that a particular finite array provides results that are as close as possible to the ones of the ideal pole–pole array. This is achieved when two conditions that are weaker than an infinite location are fulfilled: (i) the ‘infinite electrodes' are placed symmetrically on both sides of the in-line electrodes with a spread angle of 30° and (ii) the length of ‘infinite lines' is at least 20 times the greatest distance between in-line electrodes. The electrical 2D image obtained with this enhanced array is the least distorted one with respect to the pole–pole image. The apparent resistivities are generally underestimated, but this deviation is almost homogeneous. Though the shift cannot be determined a priori, the interpretation of such an image with direct or inverse software designed for pole–pole data provides an accurate interpretation of the ground geometry.  相似文献   

Precise Quantitative Determination of Niobium at Low Level Concentrations in Geological Samples by WD-XRF     

Joël Etoubleau  Pierre Cambon  Henri Bougault  Jean-Louis Joron 《Geostandards and Geoanalytical Research》1999,23(2):187-195

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Organic matter dynamics and budgets in the turbidity maximum zone of the Seine Estuary (France)     

Josette Garnier  Gilles Billen  Stéphanie Even  Henri Etcheber  Pierre Servais 《Estuarine, Coastal and Shelf Science》2008

Organic matter was studied in the turbidity maximum zone (TMZ) of the Seine Estuary during 8 tidal cycles from April to October in 2001, 2002 and 2003, covering a salinity range from 0 to 27. The hydrological conditions were quite varied (extremely wet in 2001, unusually dry in 2003). A particularly striking feature is the high organic matter content in the suspended solids (SS) of the Seine estuary (4–5%).  相似文献   

Variations of the suspended matter and the particulate organic carbon in the entry of the Gironde Estuary,France   总被引：1，自引：0，他引：1  

Lin Rong-gen  Etcheber Henri 《中国海洋湖沼学报》1994,12(1):54-60

The effects of using different types of glass fiber filters (GF/F, GF/C) and of sample treatments were evaluated. Studies on the variation of suspended matter (SM) and particulate organic carbon (POC) showed that: 1) the transversal and day to night variations are important and must be taken into account in order to get a correct river flux; 2) no regular seasonal variations of SM and POC were observed, as they are controlled essentially by the climatological, hydrologic, physiochemical, biological, and geological conditions of the drainage area. Contribution No 2246 from the Institute of Oceanology, Chinese Academy of Sciences.  相似文献   

The relationship between seismic and aseismic motions induced by forced fluid injections   总被引：1，自引：1，他引：0  

Fran?ois Henri Cornet 《Hydrogeology Journal》2012,20(8):1463-1466

The injection of fluid into a rock mass results in variations of effective stresses that sometimes generate induced seismicity. These effective stress field variations depend on the diffusion process, which depends, in turn, on the magnitude of the pore pressure variation relative to the total stress. Four diffusion mechanisms are distinguished: diffusion through a poroelastic rock mass, and diffusion in preferential directions controlled either by slip along preexisting fractures, or by the development of fresh shear zones, or by hydraulic fracturing. More importantly, in some instances, this diffusion process also generates non-seismic motions that, in turn, influence the seismic activity, in particular when injection stops.  相似文献   

A New Single Vacuum Furnace Design for Cosmogenic 3He Dating     

Laurent Zimmermann  Pierre Henri Blard  Pete Burnard  Sarah Medynski  Raphael Pik  Nicolas Puchol 《Geostandards and Geoanalytical Research》2012,36(2):121-129

Helium‐3 is a stable cosmogenic isotope that can be used to determine the time interval during which a rock sample has been at or close to the Earth’s surface. As a result of the high production rate of ‘cosmogenic’³He (≈ 130 at g^?1 year^?1) and the low detection limit of modern mass spectrometers, it is possible to date exceptionally young surfaces (≈ 1000 years). The precision and accuracy of cosmogenic ³He measurements depend critically on the passive helium blank (produced by the metalwork of the extraction furnace) which can be significant relative to the sample signals. We have developed and constructed, at the CRPG (Nancy, France), a new high temperature furnace (< 1500 °C) to extract helium in minerals such as apatite, pyroxene and olivine at 1050, 1350 and 1450 °C, respectively. The furnace demonstrated an excellent helium extraction yield (> 99% for olivine and pyroxene for heating times of 20–30 min and temperatures in the range 1050–1450 °C) and low residual helium contributions (the blank, obtained under the same analytical conditions as for sample extraction: 1 × 10^?15 mole ⁴He and < 4 × 10^?21 mole ³He). This is approximately an order of magnitude lower than those reported by other laboratories using conventional furnaces.  相似文献   

Superimposed tectonic and hydrothermal events during the late-orogenic extension in the Western French Massif Central: a structural and ⁴⁰Ar/³⁹Ar study     

Jean-Yves Roig  Michel Faure  & Henri Maluski 《地学学报》2002,14(1):25-32

In the Western French Massif Central, the Argentat fault is a major structure through which As–Au fluids percolated in the Late Carboniferous along brittle fractures. New petrostructural investigations show that an early ductile normal-dextral faulting, coeval to leucogranite emplacement took place during the Late Visean syncollisional extension of the belt and was accompanied by a hydrothermal event marked by the growth of muscovites whose ⁴⁰Ar/³⁹Ar ages cluster around 335 Ma. This early fluid channelling is associated with brittle deformation only in the hangingwall of the Argentat fault, whereas ductile deformation is restricted to the footwall. These results provide new evidence for the upper crust implication during the syncollisional extension in the French Massif Central. This study stresses the interest of a detailed multimethod analysis to characterize hydrothermal processes, especially in basement areas where the tectonic, plutonic and metamorphic evolution is polyphased.  相似文献   

Predicting the occurrence of sand banks in the North Sea     

H. Henriët van der Veen  Suzanne M. J. H. Hulscher 《Ocean Dynamics》2009,59(5):689-696

Sand banks have a wavelength between 1 and 10 km, and they are up to several tens of meters high. Also, sand banks may have an impact on large-scale human activities that take place in the North Sea like sand mining, shipping, offshore wind farms, etc. Therefore, it is important to know where sand banks occur and what their natural behavior is. Here, we use an idealized model to predict the occurrence of sand banks in the North Sea. The aim of the paper is to research to what extent the model is able to predict the occurrence of sand banks in the North Sea. We apply a sensitivity analysis to optimize the model results for a North Sea environment. The results show that the model correctly predicts whether or not sand banks occur for two thirds of the North Sea area.  相似文献