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Dans les pays du Sahel, le développement de l’agriculture irriguée est une des solutions pour améliorer la sécurité alimentaire. À travers l’exemple du sud-ouest du Niger, cette étude montre que le développement d’une irrigation à faible coût est possible par pompage de l’eau des nappes phréatiques, ressource renouvelable et mieux répartie dans l’espace que les eaux de surface. Les ressources en eau et en terres irrigables de la zone ont été localisées, quantifiées et leur potentiel à long terme réévalué à partir de données actualisées. Les résultats montrent que 50 000 à 160 000 ha (3 à 9 % de la surface totale cultivée) pourraient être mis en valeur par la petite irrigation à partir des eaux souterraines les plus accessibles (jusqu’à 20 m de profondeur). Cette estimation est du même ordre de grandeur que celle déjà avancée pour les seules eaux de surface, doublant ainsi le potentiel irrigable de la zone.

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of European Journal of Water Quality is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Larhyss Journal is the property of Biskra University, Research Laboratory in Subterranean & Surface Hydraulics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents the results of a survey carried out in 2010 aimed at evaluating the type and quality of the groundwater resources of the Bangui region of the Central African Republic. This work is the first step towards the development of groundwater resources in the Central African Republic in order to find alternatives to direct pumping from the Ubangi River and provide the population of the suburbs with a safer drinking water supply from deep boreholes. By combining both geological and hydrogeochemical approaches, it appears that the geology of Bangui is favourable to the development of a secure and sustainable water supply from groundwater provided that the conditions of exploitation would be constrained by the local authorities. The deep Precambrian carbonate aquifers, known as the Bimbo and Fatima formations, are identified as target resources in view of the relatively good quality of their water from the chemical point of view, and the semi-confined structure of the aquifers that prevents the mixing with shallow aquifers that are already strongly affected by domestic and industrial pollution. The main difficulty in terms of exploitation is to appreciate the depth of the resource and the more or less fractured/palaeo-karstified type of the porosity. EditorZ.W. Kundzewicz CitationDjebebe-Ndjiguim, C.L., Huneau, F., Denis, A., Foto, E., Moloto-a-Kenguemba, G., Celle-Jeanton, H., Garel, E., Jaunat, J., Mabingui, J., and Le Coustumer, P., 2013. Characterization of the aquifers of the Bangui urban area, Central African Republic, as an alternative drinking water supply resource.Hydrological Sciences Journal, 58 (8), 1760–1778. [ABSTRACT FROM PUBLISHER]

The present study aims to investigate the impact of anthropogenic factors on the quality of groundwater in some wells and springs in the region of Meknes, used for the various purpose by the local population. This work was conducted for a duration of 6 months by monthly withdrawal from February to July 2013. The main physico-chemical and biological components of water quality have been measured and a principal component analysis (PCA) was performed based on the average values of each parameter, it was able to reveal the existence of a relatively strong spatial variation of these descriptors, making it appear four groups of very well differentiated and unequal stations: the first two groups together five wells and two springs provide a good quality water or slightly polluted and the last two which contain the other wells where the water is very polluted. [ABSTRACT FROM AUTHOR]

The main objective of this work is the study of the quality of surface and underground waters of the Bouchegouf region (Guelma, Algeria) based on pollution indices calculation. Two charts illustrating water quality were elaborated taking into account 10 intake water points covering the whole studied zone. Both charts relate to the periods of low and high waters for the year 2007. The results indicate that pollution is not vertical. In period of high waters, water quality is from good to very good (4

Copyright of Irrigation & Drainage is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: We present an analysis of daily water discharge and suspended sediment concentration measurements for the three main drainage basins in Nepal, on the basis of recent published papers. We first show how precipitation-discharge data can be used to highlight the impact of groundwater storage on the annual hydrological cycle of Himalayan rivers. Then, we show how the concentration of suspended sediment in rivers varies at the year scale depending on the river discharge cycle, as well as how the release of groundwater impacts the concentration of materials in rivers. Finally, we propose a new conceptual model for the mobilization and transportation of material within the monsoonal discharge cycle in the central Himalayas. [Copyright &y& Elsevier]

Relatively little is known regarding the spatial variability of microbial communities in aquifers where well fouling is an issue. In this study 2 water wells were installed in an alluvial aquifer located adjacent to the North Saskatchewan River and an associated piezometer network developed to facilitate the study of microbial community structure, richness, and diversity. Carbon utilization data analysis revealed reduced microbial activity in waters collected close to the wells. Functional PCR and quantitative PCR analysis indicated spatial variability in the potential for iron-, sulphate-, and nitrate-reducing activity at all locations in the aquifer. Denaturing gradient gel electrophoresis analysis of aquifer water samples using principal components analyses indicated that the microbial community composition was spatially variable, and denaturing gradient gel electrophoresis sequence analysis revealed that bacteria belonging to the genera Acidovorax, Rhodobacter, and Sulfuricurvum were common throughout the aquifer. Shannon's richness ( H′) and Pielou's evenness ( J′) indices revealed a varied microbial diversity ( H′ = 1.488-2.274) and an even distribution of microbial communities within the aquifer ( J′ = 0.811-0.917). Overall, these analyses revealed that the aquifer's microbial community varied spatially in terms of composition, richness, and metabolic activity. Such information may facilitate the diagnosis, prevention, and management of fouling. [ABSTRACT FROM AUTHOR]

Copyright of Biotechnologie, Agronomie, Societe et Environnement is the property of Les Presses Agronomiques de Gembloux and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study quantifies experimentally the influence of groundwater on the thermal conductivity measurements via thermal response tests (TRT) in a fractured hard rock with low matrix permeability. An artificial groundwater flow towards a nearby well was induced by groundwater extraction and a TRT performed simultaneously. The results were compared with a TRT performed 24 days later in the same well without groundwater extraction. The effect of the groundwater flow is shown indirectly by the enhanced effective thermal conductivity and directly through the comparison of temperature profiles before and 4 h after both TRTs. Simulations in FEFLOW show that a groundwater flow velocity of 130-1,300 m d through one open horizontal fracture of small volume increases the effective thermal conductivity by 11 % in the studied system. [ABSTRACT FROM AUTHOR]

Abstract: The demand for acceptable thermal comfort conditions within the London Underground network has grown over the years. The operation of the network generates a large heat load, with high temperatures recorded in summer in train and on platforms. Different cooling methods and new sources of cooling have been proposed for cooling the network. Of the new sources of cooling proposed, groundwater cooling is the first to be tried. London Underground Limited unique characteristics of being close to the aquifer of the central London basin, rivers and also because they pump over 30 million litres of water from the network every day make it an ideal site for this technology. This paper investigates thermal issues within London Underground network and presents an overview of groundwater cooling schemes for the network. [Copyright &y& Elsevier]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: The current use of untreated river water for drinking purposes by the population of French Guiana has important impacts on public health. Consequently, groundwater is of major importance as a possible alternative drinking water supply to reduce these impacts. Since French Guiana belongs to the Guyana Shield, sustainable water management can be expected to depend increasingly on water from fissured aquifers in hard rocks. Groundwater samples were collected from shallow drill holes in the densely populated coastal area, and deeper wells in the basement (around Cayenne and along the Maroni and Oyapock rivers). This study reports on major and trace elements for which Na+ and Ca2+ excess with regard to Cl reflect the role of water-rock interaction, as well as Sr and Nd isotopes that reflect the role of the different lithologies. δ18O and δD in waters give constraints on the water cycle (recharge and evaporation processes). [ABSTRACT FROM AUTHOR]

Two ways of connecting numerical hydrological models that have significantly differently sized calculation time steps are compared. A model for rainfall-runoff and surface water flow (SOBEK) is connected to a model for groundwater flow (TRIWACO). Data exchange between the two models takes place at the end of each larger time step. In the 'explicit' connection, both models calculate every time step only once, after which the algorithm moves to the next time step. In the 'implicit' connection, the same time step is recalculated with the exchanged data until the resulting exchanged values converge. Due to the iteration, implicit connections require more calculation time, which can only be justified if it leads to significant improvements of model predictions. By simulating the hydrological situation of the Huewelerbach basin in Luxembourg, this work shows that implicit and explicit connections can indeed lead to significantly different calculation results. Citation Vergroesen, A. J. J., van de Giesen N. C. & van de Ven, F. H. M. (2010) Comparison of implicit and explicit connection of fast- and slow-flowing components of a water system. Hydrol Sci. J. 55(3), 287-302. [ABSTRACT FROM AUTHOR]

Small angle neutron scattering (SANS) data are reported from a system that models the contamination of a clay - organic matter soil from a fuel spillage. The soil was represented as an aqueous dispersion of the synthetic clay mineral Laponite coated with lysine, and the contaminant was a representative jet fuel, quadricyclane, mixed with the detergent cetyltrimethylammonium bromide (CTAB). The adsorbed surface coverage on the clay was estimated. It is shown that the presence of adsorbed lysine considerably enhances the subsequent adsorption of both CTAB and quadricyclane. It is demonstrated that the SANS technique can contribute to the general problem of environmental remediation and retention by probing the interactions of pollutants and clay surfaces. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To verify previous conclusions on the use of bacterial indicators suggested in regulations and to investigate virological quality of groundwater, a 1-year study was undertaken on groundwater used as a source of drinking water in 3 provinces in Canada. Raw water from 25 municipal wells was sampled during a 1-year period for a total of 167 samples. Twenty-three sites were selected on the basis of their excellent historical bacteriological water quality data, and 2 sites with known bacteriological contamination were selected as positive controls. Water samples were analyzed for general water quality indicators (aerobic endospores, total coliforms), fecal indicators (Escherichia coli, enterococci, somatic and male-specific coliphages), total culturable human enteric viruses (determined by cell culture and immunoperoxidase), noroviruses (analyzed by reverse-transcriptase - polymerase chain reaction (RT-PCR)), adenovirus types 40 and 41 (analyzed by integrated cell culture (ICC) - PCR), and enteroviruses and reoviruses types 1, 2, and 3 (analyzed by ICC-RT-PCR). General water quality indicators were found very occasionally at the clean sites but were frequently present at the 2 contaminated sites. Only one of 129 samples from the 23 clean sites was positive for enterococci. These results confirm the value of raw water quality historical data to detect source water contamination affecting wells that are vulnerable. Samples from the 2 contaminated sites confirmed the frequent presence of fecal indicators: E. coli was found in 20/38 samples and enterococci in 12/38 samples. Human enteric viruses were not detected by cell culture on MA-104 cells nor by immunoperoxidase detection in any sample from the clean sites but were found at one contaminated site. By ICC-RT-PCR and ICC-PCR, viruses were found by cytopathic effect in one sample from a clean site and they were found in 3 samples from contaminated sites. The viruses were not detected by the molecular methods but were confirmed as picornaviruses by electron microscopy. Noroviruses were not detected in any samples. The results obtained reinforce the value of frequent sampling of raw water using simple parameters: sampling for total coliforms and E. coli remains the best approach to detect contamination of source water by fecal pollutants and accompanying pathogens. The absence of total coliforms at a site appears to be a good indication of the absence of human enteric viruses. La présente étude a été entreprise pour déterminer la qualité microbiologique d'eaux souterraines servant de sources d'eau potable municipales dans 3 provinces canadiennes ainsi que de valider les conclusions d'une étude précédente sur l'utilisation des indicateurs microbiologiques proposés dans certaines réglementations. L'eau brute de 25 puits municipaux a été analysée pendant une période d'un an pour un total de 167 échantillons. Les puits furent sélectionnés sur la base d'une bonne qualité bactériologique de l'eau brute, à l'exception de 2 puits servant de contrôles positifs où l'eau était contaminée. Les échantillons d'eau ont été analysés pour des paramètres de qualité générale (endospores aérobies, coliformes totaux), indicateurs de pollution fécale (Escherichia coli, entérocoques, coliphages somatiques et mâles-spécifiques), virus entériques humains totaux cultivables, norovirus (RT-PCR) et l'ICC-PCR pour les adénovirus 40 et 41, ICC-RT-PCR les entérovirus et les réovirus 1, 2 et 3. Les indicateurs de qualité générale étaient quasiment absents des 23 puits de bonne qualité alors qu'ils étaient fréquemment retrouvés aux 2 puits contaminés. Seulement un des 129 échantillons en provenance des 23 puits présentant une bonne qualité était positif pour les entérocoques. Ces résultats confirment la valeur des données historiques de l'eau brute pour déterminer la contamination d'un puits vulnérable. Des indicateurs de pollution fécale ont été retrouvés fréquemment dans les échantillons prélevés aux 2 puits contaminés. Escherichia coli a été retrouvé dans 20/38 échantillons contre 12/38 pour les entérocoques dans les échantillons en provenance des 2 sites contaminés. Aucun virus entérique humain cultivable n'a été retrouvé aux 23 puits de bonne qualité par culture cellulaire sur MA-104 et détection par immunoperoxydase, mais ont été retrouvés a un site contaminé. Par les méthodes d'ICC-RT-PCR et ICC-PCR, des virus ont été détectés dans un échantillon d'un site de bonne qual [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Air sparging represents an innovative groundwater remediation technology, which has been proved to be capable of restoring aquifers that have been polluted by volatile and (or) biodegradable contaminants, such as petroleum hydrocarbons. This paper presents the design, the installation, and the pulsed operation of an in-well air sparging system at the site of a Greek petroleum refinery. The geographical position, the hydrologeoly, and the contamination features of the chosen study area develop special conditions that, along with the fact that the existing refinery is still active, greatly determine the applicability and the effectiveness of the specific technology. The area that was used for the application of the technology covered almost 600 m2 and included five air injection wells and four additional monitoring wells. The pulsed operation of the installed system lasted about 5 months and the results of frequent groundwater sampling and analysis indicate an important decline in total petroleum hydrocarbons (TPH) and benzene-toluene-ethylbenzene-xylene (BTEX) concentrations (up to 99%). However, prior to any attempt to expand the application of air sparging within the facilities of the refinery, special attention should be given to the eccentricities of the site and the ability of the technology to confront more persistent contaminants, such as methyl tertiary-butyl ether (MTBE). Le barbotage à l’air est une technologie d’assainissement innovatrice pour l’eau souterraine et il s’est avéré adéquat pour restaurer les aquifères pollués par des contaminants volatils et (ou) biodégradables, tels que les hydrocarbures pétroliers. Cet article présente la conception, l’installation et le fonctionnement pulsé d’un système de barbotage à l’air dans un puits d’une raffinerie de pétrole en Grèce. L’emplacement géographique, l’hydrogéologie et les caractéristiques de la contamination de la zone à l’étude ont conduit à des conditions spéciales qui, ajoutées au fait que la raffinerie est toujours en opération, déterminent grandement l’applicabilité et l’efficacité de la technologie spécifique. La zone d’utilisation de la technologie couvrait environ 600 m2 et comprenait cinq puits d’injection et quatre puits de surveillance additionnels. Le fonctionnement pulsé du système installé a duré environ cinq mois; les résultats de l’échantillonnage fréquent de l’eau souterraine et des analyses indiquent une diminution importante des concentrations en hydrocarbures pétroliers totaux et en benzène-toluène-éthylbenzène-xylène (BTEX) (jusqu’à 99 %). Toutefois, avant de penser à étendre l’utilisation du barbotage à l’air à d’autres secteurs de la raffinerie, il faut porter une attention spéciale aux conditions spéciales du site et à la capacité de la technologie à faire face à des contaminants plus persistants, tels que l’éther méthyltertiobutylique (MTBE). [ABSTRACT FROM AUTHOR]

A 1 year study was undertaken on groundwater that was a source of drinking water in the province of Quebec, Canada. Twelve municipal wells (raw water) were sampled monthly during a 1 year period, for a total of 160 samples. Using historic data, the 12 sites were categorized into 3 groups: group A (no known contamination), group B (sporadically contaminated by total coliforms), and group C (historic and continuous contamination by total coliforms and (or) fecal coliforms). Bacterial indicators (total coliform, Escherichia coli, enteroccoci), viral indicators (somatic and male-specific coliphages), total culturable human enteric viruses, and noroviruses were analyzed at every sampling site. Total coliforms were the best indicator of microbial degradation, and coliform bacteria were always present at the same time as human enteric viruses. Two samples contained human enteric viruses but no fecal pollution indicators (E. coli, enterococci, or coliphages), suggesting the limited value of these microorganisms in predicting the presence of human enteric viruses in groundwater. Our results underline the value of historic data in assessing the vulnerability of a well on the basis of raw water quality and in detecting degradation of the source. This project allowed us to characterize the microbiologic and virologic quality of groundwater used as municipal drinking water sources in Quebec. [ABSTRACT FROM AUTHOR]

In 1982 diesel fuel migrated from a well lease site into underlying fractured bedrock contaminating the groundwater-bearing zone approximately 30 m below ground surface. Historical contaminant concentrations, geochemical indicators, and microbiological data were analysed to evaluate natural attenuation, specifically intrinsic bioremediation. Evidence of microbial activity was provided by most probable number (MPN) and commercial biological activity reaction tests (BART™). Laboratory microcosms using groundwater from the site were incubated under aerobic and anaerobic conditions with electron acceptor and nutrient amendment to assess microbial activity. Aerobic biodegradation rates were determined by measuring mineralization of 14C-dodecane. Nutrient amendment combined with a higher temperature (28 °C) increased the first-order aerobic biodegradation rate to 0.0066 d–1 from 0.0002 d–1 at 10 °C. Anaerobic biodegradation rates were calculated from depletion of total extractable hydrocarbons (TEH) over 717 d at 10 °C. Nutrient addition increased the anaerobic first-order biodegradation rate to 0.0016 from 0.0005 d–1. Data from these laboratory microcosms indicate that the current slow rates of intrinsic bioremediation may be enhanced with nutrient addition. [ABSTRACT FROM AUTHOR]

Soils and geologic deposits derived from marine shale often contain elevated levels of arsenic. The source of arsenic is iron sulfide minerals. Oxidative weathering breaks down the iron sulfide minerals and potentially releases undesirable levels of arsenic into the surrounding pore water. Equilibration experiments on a weathered marine shale containing naturally elevated levels of native arsenic and on a mixture of weathered shale and calcareous till were conducted under aerobic conditions to determine how much arsenic was released into pore water and the mechanism responsible for limiting soluble arsenic concentrations. Aqueous phase arsenic released from the shale was less than 10 µg/L for aerobic conditions. Soluble arsenic concentrations were low considering the high total As concentrations in the shale (30 µg As/g shale). Over 4 times as much solution arsenic was released from the higher pH shale–till mixture compared to the acid shale alone. Adsorption and desorption was the mechanism that controlled the concentration of aqueous phase arsenic. [ABSTRACT FROM AUTHOR]

Trichloroethylene (TCE) is a prevalent contaminant of groundwater that can be cometabolically degraded by indigenous microbes. Groundwater contaminated with TCE from a US Department of Energy site in Ohio was used to characterize the site-specific impact of phenol on the indigenous bacterial community for use as a possible remedial strategy. Incubations of 14C-TCE-spiked groundwater amended with phenol showed increased TCE mineralization compared with unamended groundwater. Community structure was determined using DNA directly extracted from groundwater samples. This DNA was then analyzed by amplified ribosomal DNA restriction analysis. Unique restriction fragment length polymorphisms defined operational taxonomic units that were sequenced to determine phylogeny. DNA sequence data indicated that known TCE-degrading bacteria including relatives of Variovorax and Burkholderia were present in site water. Diversity of the amplified microbial rDNA clone library was lower in phenol-amended communities than in unamended groundwater (i.e., having Shannon–Weaver diversity indices of 2.0 and 2.2, respectively). Microbial activity was higher in phenol-amended ground water as determined by measuring the reduction of 2-(p-iodophenyl)-3(p-nitrophenyl)-5-phenyl tetrazolium chloride. Thus phenol amendments to groundwater correlated with increased TCE mineralization, a decrease in diversity of the amplified microbial rDNA clone library, and increased microbial activity.Key words: community structure, trichloroethylene, degradation, groundwater. [ABSTRACT FROM AUTHOR]

Stable isotopes of nitrogen and oxygen are important tools for investigating the occurrence of denitrification in groundwater. Previous investigators have noted a linear relationship between δ15N and δ18O field data collected from shallow groundwater systems, but the reason for such a linear correlation is not clear. In this study, we represent denitrification reactions using parallel, first-order kinetics, and reaction rate constants that depend on the nitrogen or oxygen isotope present in nitrate. The derived mathematical relationship between δ15N and δ18O indicates that nitrogen and oxygen isotopes should fractionate at a constant ratio. Using the laboratory reaction rate constants obtained by Olleros (1983), our equations give a theoretical fractionation ratio value of b = 0.51. A review of published field studies in which denitrification in groundwater has been confirmed, and δ15N and δ18O data has been collected, shows that the mean fractionation ratio value is 0.55 (standard deviation = 0.08, n = 6). The field values therefore agree well with the predicted fractionation ratio value of b = 0.51. It is concluded that a linear relationship between δ15N and δ18O values, with a slope (b) close to 0.51, provides additional, unambiguous evidence that denitrification is responsible for nitrate concentration decline and enrichment in nitrogen isotope values in shallow groundwater. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Résumé: Des analyses chimiques et isotopiques des eaux ont été utilisées, conjointement à des analyses pétrographiques et chimiques des roches, pour déterminer l'origine des ions chlorure dans les eaux souterraines de la nappe de Chtouka-Massa (Maroc). Il apparaît que la formation schisteuse qui constitue le substratum de la nappe étudiée est à l'origine des fortes teneurs en Cl- mesurées dans certaines eaux souterraines. Dans ces schistes, une partie du chlorure est probablement contenue dans les biotites, et passe en solution lors de l'altération de ces minéraux. Toutefois, l'exceptionnelle richesse en chlorure de ces schistes est difficile à expliquer sans admettre qu'ils contiennent aussi des minéraux chlorurés de type évaporitique. Pour citer cet article : S. Krimissa et al., C. R. Geoscience 336 (2004). [Copyright 2004 Elsevier]

A three-dimensional mathematical model is developed for simulating the transport of dissolved contaminants originating from a well-defined, multicomponent nonaqueous phase liquid (NAPL) source containing polycyclic aromatic hydrocarbon (PAH) compounds in groundwater. The dissolution process for each NAPL component is envisioned to occur in a successive series of small dissolution intervals (or pulses). The equilibrium aqueous phase concentration of each component and the source dimensions are assumed to remain constant for the duration of each dissolution interval. The model accounts for possible solidification of PAH components as the NAPL source dissolves. Aqueous phase contaminant concentrations resulting from each dissolution interval are calculated using an existing analytical solution. A synthetic PAH-rich NAPL mixture consisting of benzene and eight PAH components is used for model simulations. The model is useful for evaluation and prediction of downstream aqueous phase contaminant concentrations resulting from dissolution of a PAH-rich NAPL source. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In London and Merseyside in the UK, which are served by deep underground railway networks, rising water tables are proving an increasing problem, leading to a serious deterioration of track, traction supply and signalling systems. Also in these transport systems there is an increasing demand for an energy efficient and environmentally sustainable comfort cooling system. This paper outlines a novel cooling system that aims to reduce the water table by using the groundwater for ‘free’ cooling the railway network. This paper investigates the potential for cooling the underground network and trains in this way. It uses a purposely-developed mathematical model to show that additional cooling to the existing rolling stock may be provided, by cooling the tunnels within which they operate. It has been shown theoretically, that by cooling the air within the tunnels by 9K, the temperature in the typical carriage operating under peak load conditions will reduce by approximately 6K to a much more acceptable level. Finally the paper identifies areas for further work, that are required in order to realise the preferred way of achieving a sustainable cooling scheme. [Copyright &y& Elsevier]

Numerical models are useful tools to evaluate problems and design remedial measures relative to groundwater seepage. They provide information for decision-making and guidance for collecting new data. Most users do not know in detail how the numerical code works. However, they must be sure that it gives reliable predictions for the problem under study. The major questions relative to the computer calculations are as follows: Can the results of the code be trusted? Under which conditions and to what extent are its predictions uncertain? This paper describes an approach that can be followed by model users to evaluate the results of a groundwater numerical code. This approach is relatively general, although each code is unique and may require specific controls. It begins with simple problems and progressively moves towards more complex problems: from steady-state to unsteady-state conditions, from one- to three-dimensional problems, and from saturated to saturated–unsaturated conditions. This approach is illustrated with a commercial code that passed the successive tests.Key words: groundwater, numerical code, quality control, saturated and unsaturated seepage.Les modèles numériques sont des outils utiles pour évaluer les problèmes et concevoir les mesures curatives relatives à l'écoulement souterrain. Ils fournissent de l'information pour prendre des décisions, et des indications pour recueillir de nouvelles données. La plupart des utilisateurs ne savent pas en détail comment fonctionne le code numérique. Cependant, ils doivent être sûrs qu'il donne des prédictions fiables pour le problème étudié. Les principales questions relatives aux calculs de l'ordinateur sont : Peut-on se fier aux résultats du code? Dans quelles conditions ses prédictions sont-elles incertaines? et De combien? Cet article décrit une approche qui peut être suivie par les utilisateurs pour évaluer les résultats d'un code numérique d'écoulement souterrain. Cette approche est relativement générale, même si chaque code est unique et peut nécessiter des contrôles spécifiques. Elle débute par des problèmes simples et passe progressivement aux problèmes plus complexes : du régime permanent au régime transitoire, des problèmes 1D aux problèmes 3D, et des conditions saturées aux conditions saturées et non saturées. Cette approche est illustrée à l'aide d'un code commercial qui a réussi les tests successifs.Mots clés : eau souterraine, code, contrôle de la qualité, écoulement saturé et non saturé. [ABSTRACT FROM AUTHOR]