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Georges Aouad Valérie Geoffroy Jean-Marie Meyer Jean-Louis Crovisier Denis Damidot Peter Stille 《Comptes Rendus Geoscience》2005,337(15):1340-1347
The influence of microorganisms on mineral alteration is not easy to determine in environmental conditions, because of the difficulty to raise for comparison purposes an identical but abiotic system. Another problem in this context is the choice of reliable tracers to evaluate the alteration rate of materials during in vitro experiments. To face such difficulties, we elaborated a defined medium allowing both the growth of Pseudomonas aeruginosa and a precise measurement of the elements solubilized from the minerals. Thanks to this medium, we were able to quantitatively determine the amounts of major elements solubilized from the materials in the presence of bacterial growth, compared to a sterile system. Moreover, the analysis by ICP-MS of trace elements was possible after a chromatographic treatment, which selectively eliminated 99% of the sodium content of the medium. To cite this article: G. Aouad et al., C. R. Geoscience 337 (2005). 相似文献
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《水文科学杂志》2013,58(3)
Abstract Abstract Generating pulses and then converting them into flow are two main steps of daily streamflow generation. Three pulse generation models have been proposed on the basis of Markov chains for the purpose of generating daily intermittent streamflow time series in this study. The first one is based on two two-state Markov chains, whereas the second uses a three-state Markov chain. The third model uses harmonic analysis and fits Fourier series to the three-state Markov chain. Results for a daily intermittent streamflow data series show a good performance of the proposed models. 相似文献
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Kathryn A. Matthews Michael T. Murrell Steven J. Goldstein Andrew J. Nunn Deborah E. Norman 《Geostandards and Geoanalytical Research》2011,35(2):227-234
Here we report uranium and thorium isotopic ratios and elemental concentrations measured in solid reference materials from the USGS (BHVO‐2G, BCR‐2G, NKT‐1G), as well as those from the MPI‐DING series (T1‐G, ATHO‐G). Specifically created for microanalysis, these naturally‐sourced glasses were fused from rock powders. They cover a range of compositions, elemental concentrations and expected isotopic ratios. The U‐Th isotopic ratios of two powdered source materials (BCR‐2, BHVO‐2) were also characterised. These new measurements via multi‐collector thermal ionisation mass spectrometry and multi‐collector inductively coupled plasma‐mass spectrometry can now be used to assess the relative performance of techniques and facilitate comparison of U‐Th data amongst laboratories in the geoscience community for in situ and bulk analyses. 相似文献
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Résumé Cette étude compare, pour la région sud du Québec (Canada), différents estimateurs des courbes intensité–durée–fréquence (IDF) basés sur les séries de durées partielles (SDP) et sur celles des maximums annuels (SMA). Deux modèles ont été considérés pour les SMA, le premier utilisant un paramètre local (SMA-1), et le second utilisant deux paramètres locaux (SMA-2). Pour les SDP, les séries ont été construites en fixant, d'une part, un seuil régional (SDP-1) et, d'autre part, le nombre moyen régional de dépassements du seuil (SDP-2). Les quantiles et les intervalles de confiance à 90% des différents modèles ont été estimés et comparés. Le modèle SDP-1 a été finalement retenu puisque, d'après la littérature, il conviendrait à une région comme celle sous étude dont l'hétérogénéité est raisonnable. Par ailleurs, le modèle SDP-1 reproduit relativement bien les quantiles et probabilités empiriques. Les quantiles générés, à chaque site, par ce modèle régional sont comparés à ceux obtenus à partir d'un modèle SDP local. Citation Kingumbi, A. & Mailhot, A. (2010) Courbes Intensité–Durée–Fréquence (IDF): comparaison des estimateurs des durées partielles et des maximums annuels. Hydrol. Sci. J. 55(2), 162–176. 相似文献
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Emmanuelle Lemaire Gwenaël Abril Rutger De Wit Henri Etcheber 《Comptes Rendus Geoscience》2002,334(4):251-258
In the Gironde Estuary, most part of phytoplanktonic material carried by the rivers is mineralised in the maximum turbidity zone (MTZ). In order to follow the degradation of the phytoplanktonic material into the MTZ, we developed an in vitro approach based on the monitoring of phytoplanktonic pigments. Algal material from two chlorophytes (Scenedesmus suspicatus Chaudat and Chlamydomonas sp.) was incubated in the dark during 28 days into water samples from the Gironde estuary MTZ, at variable suspended solid concentrations (SPM) as well as in a sterilised turbid sample. First order decay constants of chlorophylls a and b and lutein increased by a factor 3 to 5 between SPM of 0 and . The production of pheophytin a in the presence of particles and the lack of degradation in the sterilised turbid sample confirmed the effect of attached bacteria on the particles. To cite this article: E. Lemaire et al., C. R. Geoscience 334 (2002) 251–258. 相似文献
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《水文科学杂志》2013,58(6)
Abstract The western reservoirs represent the principal groundwater system in Morocco. Demographic, industrial and agricultural developments during the last decade have markedly altered groundwater quality. The Mamora coastal aquifer system is among the Atlantic systems which are most heavily threatened by pollution. Agricultural and industrial activities, and rapid urban growth contribute to the pollution of the groundwater. Contamination transport is facilitated by a high permeability of the aquifer formations. In order to assess the actual groundwater quality of the Mamora aquifer and to understand the influence of the factors generating the pollution, an extensive multidisciplinary research programme is in progress, with hydrochemistry and microbiology playing essential roles. The present paper concerns the spatial distribution of physico-chemical parameters in the groundwater, subjected to domestic, industrial and agricultural pollution. Fifty-seven samples were analysed for several parameters (Ca2+, Mg2+, Na+, K+, Cl?, SO4 2?, HCO3 ?, NO3 ?, pH, electrical conductivity and temperature). The microbiological analysis of 143 samples reveals the presence of four kinds of indicator bacteria in the groundwater resources: faecal Streptococci, faecal coliform, Escherichia coli and Clostridium. The physico-chemical results and bacteriological monitoring show that the nitrate and bacteria concentrations exceed the maximum admissible levels, notably around pumping stations in the sectors of Sidi Taibi, Sidi Ahmed Taleb and Aïn Sbaâ. Contamination is generated by uncontrolled anthropogenic activities and accentuated by the high intrinsic vulnerability of the aquifer system. Several parameters appeared to exceed admissibility standards. Measures are recommended to prevent groundwater pollution in the region. 相似文献
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《水文科学杂志》2013,58(4)
Abstract The issue of data size (length) requirement for correlation dimension estimation continues to be the nucleus of criticisms on the (low) correlation dimensions reported for hydrological series. The present study addresses this issue from the viewpoints of both the existing theoretical guidelines and the practical reality. For this purpose, correlation dimension analysis is carried out for various data sizes from each of three types of series: (a) stochastic series (artificially generated using a random number generation technique); (b) chaotic series (artificially generated using the Henon map equation); and (c) hydrological series (real flow data observed on the Göta River in Sweden). The outcomes of the analysis of the (artificial) stochastic and chaotic series are used as a basis for interpreting the outcomes of the hydrological series. It is found that reliable dimension results for the stochastic and chaotic series are obtained even when the data size is only a few hundred points (i.e. no underestimation of dimension for small data sizes is visible), with no significant change in the scaling regimes (of the dimension plots) with respect to data size. This implies that the dimension results obtained for the hydrological series even with a few hundred points are also close to the actual ones. The insignificant difference in the scaling regimes for the various data sizes further supports this point. These results lead to the conclusions that: (1) the issue of data size requirement for correlation dimension estimation is more of a myth than reality; (2) the dimension estimates reported thus far for hydrological series could indeed be close to the actual ones (unless influenced by factors other than data size, e.g. delay time, noise, zeros, intermittency). 相似文献
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Alain Coulomb 《Comptes Rendus Geoscience》2010,342(1):75-78
This study aims at commenting the article by Romano and Lugrezi (2007). Four main facts are brought to light: the temperature data used by Romano and Lugrezi were not sea temperatures, but air temperatures measured inside the Marseille tide gauge building; the sea temperature data still exist and were already exploited in at least three studies; these sea temperature data were never used to correct the tide gauge recordings for any effect in the computation of mean sea levels; the sea temperature was not measured in the tide gauge well, but outside of the building. 相似文献
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《水文科学杂志》2013,58(2)
Abstract The study of changes in annual rainfall in the Lake Chad basin during the 20th century is based on the analysis of 47 stations, i.e. a total of about 1600 station-years for the time series with more than 25 years of data. As previously observed in western and Sahelian Africa, robust tests of shift in time series identify a significant change in mean from the beginning of the 1960s between the latitudes 11 and 13°N, and a little later in this decade for the northern stations. The analysis of decadal rainfall shows that the 1950s decade was very humid and the next three decades were drier. These dry conditions were more and more severe until the 1980s. Data available after 1990 do not show any inversion in the trend. The annual rainfall decreases from south to north, and the regional gradient has changed from 1.5 mm km?1 in the 1950s to 1.2 mm km?1 in the 1980s between the latitudes 10 and 14°N. 相似文献
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