http://hdl.handle.net/2268/88 Chercher dans ce canal chercher http://orbi.ulg.ac.be/simple-search http://hdl.handle.net/2268/150493 Titre: Les sulfures dans les filons Sn-W de Panasqueira (Portugal). Approche du problème de l'argent. <br/> <br/>Auteur, co-auteur: Pirard, Eric <br/> <br/>Résumé: Etude des paragenèses minérales de la mine de Panasqueira. Microanalyses des sulfures. Pistes pour améliorer la récupération de l'argent dans les installations de traitement du minerai. Pavonite, Schapbachite, Mathildite.; Detailed study of mineral parageneses in the Panasqueira ore deposit. Microanalysis of sulphide phases. Suggestions for better recovery of silver in the mineral processing plant. Pavonite, Schapbachite, Mathildite. Fri, 14 Jun 2013 12:22:52 GMT http://hdl.handle.net/2268/150413 Titre: BIERSET – Réhabilitation de la carrière Lemaire - Piézomètres de contrôle - Prélèvements d’eau du 18 mars 2013 <br/> <br/>Auteur, co-auteur: Orban, Philippe; Dassargues, Alain Fri, 14 Jun 2013 07:16:02 GMT http://hdl.handle.net/2268/150339 Titre: ASSESSMENT LAND DEGRADATION USING OPTICAL REMOTE SENSING AND GIS IN SALOUM ESTUARY, SENEGAL <br/> <br/>Auteur, co-auteur: Dieng, Ndeye Maguette <br/> <br/>Résumé: The present study aims at assessing consequences of salinization during the last three decades in this estuary with regard to land, biodiversity and water degradation. In this respect, Landsat images (1984, 1992, 1999 and 2010) were used to investigate regional time series land use/land cover. These were classified into six land-use/land-cover types: water bodies, high mangrove, low mangrove, denuded and salty soils (locally called “Tan”), savannah/rainfed agriculture and forestland. Change detection analysis of land and mangrove degradation was assessed using GIS techniques. Spectral analysis indicated that from 1984 to 2010, mangroves and savannah/rainfed agriculture are converted to “tan” (denuded and salty soils). In addition, these results showed that significant changes in land-use/land-cover occur within the whole estuary system and reflecting therefore environmental degradation, such as land desertification and salinization, and vegetation degradation which reflect the advanced of salinity Thu, 13 Jun 2013 10:03:36 GMT http://hdl.handle.net/2268/150337 Titre: Assessing the consequences of salinization in Saloum estuary system by land use and land cover change analysis <br/> <br/>Auteur, co-auteur: Dieng, Ndeye Maguette; Dinis, Joel; Faye, Serigne; Caetano, Mario <br/> <br/>Résumé: The saltwater contamination constitutes a serious problem in Saloum estuary, due to the intermittent and reverse tide flows of the Saloum River. This phenomenon is caused by the runoff deficit, which forces the advance of saltwater 60 km upstream, contaminating surface water and, thus, causing the degradation of biodiversity and large areas of agricultural soils in this region. The present study aims to evaluate the consequences of saltwater contamination in the last three decades in this estuary by assessing the land cover dynamics over this period. Land cover dynamics evaluation consists in tracking the landscape changing process over time to identify land cover transitions. These transitions are closely related to the ecosystem state condition and can be used to assess the combined impacts of both natural and human-induced phenomena over a given period of time. In this study, a special attention was given to the mangrove degradation and to the temporal progression of the salty barren soils locally called “Tan”. The lost of mangrove areas to “Tan” and the general increase of salty barren soil areas can reflect the increase of the level of salinization in the study area over the time period under consideration. To fulfill this objective, four Landsat satellite images from the same season in the years 1984, 1992, 1999 and 2010 were used to infer a time series land use and land cover maps of the Saloum estuary area. In addition to satellite imagery, rainfall record was used to evaluate climatic variation in terms of high to low precipitation during the time span considered. Thu, 13 Jun 2013 09:35:14 GMT http://hdl.handle.net/2268/150108 Titre: Multivariate statistics to understand the geochemical processes induced by groundwater pollution Multi-scale applying <br/> <br/>Auteur, co-auteur: Gesels, Julie; Joniau, Claire; Batlle-Aguilar, Jordi; Dassargues, Alain; Brouyère, Serge <br/> <br/>Résumé: Different hydrogeochemical approaches (classical diagrams, spatial distribution maps, geochemical equations and multivariate statistics) are combined to obtain a global understanding of the hydrogeochemical processus at regional and at local scale. Mon, 10 Jun 2013 12:17:10 GMT http://hdl.handle.net/2268/150098 Titre: A combined hydrochemical, isotopic and multivariate statistics approach for pollutant source identification in a regional aquifer <br/> <br/>Auteur, co-auteur: Gesels, Julie; Joniau, Claire; Knöller, Kay; Brouyère, Serge <br/> <br/>Résumé: In an urban and industrial context, a detailed hydrogeochemical characterization of groundwater has been performed in an alluvial aquifer, with the aim of determining the origin of the inorganic contaminations and the main processes involved that contribute to a poor groundwater quality. Mon, 10 Jun 2013 11:40:21 GMT http://hdl.handle.net/2268/150093 Titre: Diffuse urban and industrial groundwater pollution with metallic trace elements A comparison between affected and unaffected areas <br/> <br/>Auteur, co-auteur: Gesels, Julie; Dollé, Fabien; Leclercq, Julie; Brouyère, Serge <br/> <br/>Résumé: For metalic trace elements, spatially distributed background concentrations will be defined as a function of geological and hydrogeological context and considering the impact of diffuse pollution. Mon, 10 Jun 2013 11:13:53 GMT http://hdl.handle.net/2268/149855 Titre: Evaluation des ressources en eau souterraine dans le bassin de Dargol (Liptako - Niger) <br/> <br/>Auteur, co-auteur: Abdou Babaye, Maman Sani Wed, 05 Jun 2013 12:45:10 GMT http://hdl.handle.net/2268/149474 Titre: ETUDE HYDROGEOCHIMIQUE DES EAUX DE LA NAPPE DU CONTINENTAL TERMINAL DU SALOUM : RELATION EAU DE SURFACE – EAU SOUTERRAINE <br/> <br/>Auteur, co-auteur: Dieng, Ndeye Maguette; Orban, Philippe; FAYE, Serigne; Dassargues, Alain; Mall, Ibrahima <br/> <br/>Résumé: L’évaluation de l’état actuel de la qualité des eaux de la nappe du Continental Terminal et du fleuve Saloum a été réalisée grâce à l’analyse de 44 échantillons d’eau souterraine et 3 échantillons d’eau de surface collectés en saison humide. Les analyses des ions majeurs et les mesures de la conductivité électrique (CE) ont démontré que les eaux de la nappe du CT du Saloum étaient largement contaminées par la salinisation (CE comprise entre à 750 et 2800 µS/cm) au niveau de la zone côtière à l’ouest et au nord sur une bande longeant le fleuve Saloum. Dans ces zones, les eaux ont désormais des faciès chimiques chlorurés sodiques venant de faciès au départ bicarbonatés calciques des eaux souterraines peu contaminées. Au niveau de certains points, la composition des eaux souterraines devient sensiblement la même que celle des eaux du fleuve Saloum. Les diagrammes binaires (Na versus Cl, Na/Cl versus Cl, [Ca + Mg] versus HCO3 et [(Ca+Mg) - (HCO3+SO4)] versus (Na-Cl)) ont permis de définir les processus géochimiques et les phénomènes de mélange impliqués dans la minéralisation des eaux. Suivant la répartition des valeurs de conductivité électrique et des types d’eaux, une zonation a été cartographiée Wed, 29 May 2013 15:48:14 GMT http://hdl.handle.net/2268/149390 Titre: La valse des métaux critiques - Où sont les métaux pour les technologies du futur ? <br/> <br/>Auteur, co-auteur: Pirard, Eric <br/> <br/>Résumé: De l’Age de la Pierre à l’Age du Lithium, nous n’avons eu de cesse de perfectionner nos technologies. Progressant dans la découverte et la compréhension de notre environnement, nous nous sommes mis à exploiter toutes les ressources naturelles disponibles. Aujourd’hui, il n’y a pratiquement aucun élément du tableau de Mendeleïev qui ne trouve son champ d’application spécifique : du lithium dans les batteries à l’indium dans les écrans en passant par le tantale dans les capacités. Baignant quotidiennement dans un tel univers d’abondance, nous en oublions d’où proviennent ces ressources. Nous avons refoulé cette question au plus profond de nous-mêmes et avons poussé le syndrome NIMBY (not in my backyard) jusqu’à atteindre le NIMYCON (not in my continent). Depuis quelques années, l’Europe vit un réveil brutal. Elle réalise qu’elle ne produit que 3 % des métaux alors qu’elle en consomme plus de 20 %. Elle réalise que toute son industrie est dépendante de pays émergents qui ont l’ambition de développer un tissu industriel puissant sur base de leur accès aux ressources. L’Europe serait-elle un continent maudit ? Aurait-elle épuisé ses ressources ? Est-elle condamnée à dépendre de pays tiers pour poursuivre sa fuite en avant vers les « hautes technologies ? Nullement, mais il est évident qu’il n’y aura pas de ré-industrialisation sans une réflexion sur les matières premières. Le mot d’ordre aujourd’hui est Resource Efficiency. Certains traduisent cela par la nécessité de mettre au point des nouveaux matériaux moins gourmands en matières premières ou évitant l’utilisation d’éléments dits « critiques ». Mais en réalité, dans un monde avide de technologies qui voit le nombre de consommateurs croître sensiblement, il faudra nécessairement ouvrir de nouvelles mines et veiller à ne plus disperser dans l’environnement les métaux que nous en aurons laborieusement extraits. Pour l’Europe, cela signifie concrètement qu’il est temps de relancer la prospection du sous-sol et de développer une culture du recyclage intelligente et écologique. Il y a là un champ d’opportunités à saisir pour l’innovation et le développement de technologies qui sont restées trop longtemps dans l’ombre! Le Resource Efficiency c’est aussi extraire les métaux des minerais et des déchets électriques et électroniques en utilisant des procédés moins gourmands en énergie, en eau et en matière. Au travers de quelques exemples choisis, cet exposé présentera l’évolution des technologies et la nature des matières premières utilisées. Partant de la géochimie d’un simple jardin de banlieue, il introduira le concept de gisement qui est indispensable à une bonne compréhension des ressources et des réserves que recèle encore notre sous-sol. Suscitant la réflexion sur la nécessité de maintenir une industrie extractive, cette présentation analysera aussi les difficultés tant sociologiques que technologiques à mener à bien un recyclage efficace des ressources. Par la nature des exemples et l’accent mis sur le recyclage, cette conférence vient en complément de celle consacrée à « Ressources dans le Rouge pour les Technologies Vertes ? » qui est disponible en PodCast sur le site http://www.reflexions.ulg.ac.be (rubrique Décryptage). Tue, 28 May 2013 12:08:39 GMT http://hdl.handle.net/2268/149387 Titre: Reinventing Docimasy <br/> <br/>Auteur, co-auteur: Pirard, Eric Tue, 28 May 2013 12:03:21 GMT http://hdl.handle.net/2268/149381 Titre: Automated characterisation of intergrowth textures in mineral particles. A case study <br/> <br/>Auteur, co-auteur: Perez-Barnuevo, Laura; Pirard, Eric; Castroviejo, Ricardo <br/> <br/>Résumé: The characterisation of mineral texture has been a major concern for process mineralogists, as liberation characteristics of the ores are intimately related to the mineralogical texture. While a great effort has been done to automatically characterise texture in unbroken ores, the characterisation of textural attributes in mineral particles is usually descriptive. However, the quantitative characterisation of texture in mineral particles is essential to improve and predict the performance of minerallurgical processes (i.e. all the processes involved in the liberation and separation of the mineral of interest) and to achieve a more accurate geometallurgical model. Driven by this necessity of achieving a more complete characterisation of textural attributes in mineral particles, a methodology has been recently developed to automatically characterise the type of intergrowth between mineral phases within particles by means of digital image analysis. In this methodology, a set of minerallurgical indices has been developed to quantify different mineralogical features and to identify the intergrowth pattern by discriminant analysis. The paper shows the application of the methodology to the textural characterisation of chalcopyrite in the rougher concentrate of the Kansanshi copper mine (Zambia). In this sample, the variety of intergrowth patterns of chalcopyrite with the other minerals has been used to illustrate the methodology. The results obtained show that the method identifies the intergrowth type and provides quantitative information to achieve a complete and detailed mineralogical characterisation. Therefore, the use of this methodology as a routinely tool in automated mineralogy would contribute to a better understanding of the ore behaviour during liberation and separation processes. Tue, 28 May 2013 11:56:42 GMT http://hdl.handle.net/2268/148612 Titre: Modélisation régionale et locale sur base des données de la carte géologique <br/> <br/>Auteur, co-auteur: Orban, Philippe Thu, 16 May 2013 19:28:25 GMT http://hdl.handle.net/2268/148411 Titre: Amenability for processing of oolitic iron ore concentrate for phosphorus removal <br/> <br/>Auteur, co-auteur: Ionkov, Krassimir; Gaydardzhiev, Stoyan; Bastin, David; Correa de Araujo, Armando; Lacoste, Marine <br/> <br/>Résumé: Beneficiation routes aimed at dephosphorisation of oolitic gravity magnetic concentrate and involving a combination of roasting, re-grinding, magnetic separation and water and acid leaching are investigated. Roasting was carried out at 900ºC for one hour without or with lime or sodium hydroxide as roasting additives. When additives were used, cement phases of Si-Al-Na-Ca-O type were detected as well as the mineral giuseppettite. During the thermal process sodium silicate is liquefied and the newly formed phases coat the oolites and penetrate inside the cracks. Energy Dispersive Spectroscopy analysis has indicated that the zone surrounding the oolites consists of Na, Al and Si phases with part of phosphorus being captured there. As a result of the alkaline roasting, goethite is partly transformed to magnetite and this reduction is reinforced with an increase in sodium hydroxide dosage. Investigation of redistribution of phosphorous shows that it could be only partly separated if leaching is not accompanied by re-grinding and physical separation. The recommended dosage of the reductive agent for the final flowsheet is 8 % mass ratio to concentrate. Grinding to a mean size of 0.040 mm, with water and acid leaching and double magnetic separation creates conditions to obtain a high-quality iron concentrate with 65.97 % Fe and recovery of 92.43 %, with simultaneous decrease in the phosphorus content from 0.71 % to 0.05 %. Mon, 13 May 2013 15:32:38 GMT http://hdl.handle.net/2268/148027 Titre: Time variyng groundwater flux measurement using a single well tracer technique <br/> <br/>Auteur, co-auteur: Jamin, Pierre; Brouyère, Serge; Bour, Olivier; LeBorgne, Tanguy; Goderniaux, Pascal <br/> <br/>Résumé: Contaminant mass discharge measurements are often performed at given times or integrated over a certain period of time, using active or passive sampling techniques. One problem arising is that such measurements may not be representative of the temporal dynamics of the mass discharge variations. These variations can be caused by fluctuations in contaminant concentrations or, more frequently, by changes in the groundwater fluxes. Pollutant mass fluxes are typically estimated through a combination of solute concentrations and groundwater fluxes measured across a control plane made of several multi-level wells. Accurate measurements of local transient Darcy fluxes have been recognized as the weakest points in most of the developed techniques for groundwater contaminant mass flux measurements. The main objective here is to extend the FVPDM technique for temporal monitoring of groundwater fluxes and to demonstrate its ability to be used in combination with passive sampling devices for measurement of contaminant mass fluxes in groundwater. The Finite Volume Point Dilution Method (FVPDM) is a single well tracer technique for the measurement of local groundwater fluxes based on the continuous injection of tracer at very low injection rate (Brouyère et al. 2008). These developments are based on the application of the adapted technique on a case study in a fractured granitic aquifer in Ploemeur (France). This application investigates transient groundwater fluxes that are controlled by pumping in a well nearby the tested piezometers. Long monitoring time series have been recorded under these controlled conditions of transient groundwater flow. Results show the high sensivity of the FVPDM technique to small variations in groundwater flow velocities and its aptitude for long term monitoring of groundwater fluxes. The comparison between the results of FVPDM and classical point dilution tests performed in same conditions shows close correlation. Interpretation of FVPDM tests in transient conditions have been developed together with an evaluation of the uncertainties that can happen if the frequency of the groundwater flow variations is high. The tests carried on the Ploemeur site also illustrate the first ever application of the FVPDM technique between a double-packer system used for the investigation of a defined layer of an aquifer. This innovative application of the FVPDM using packers opens concrete perspectives for investigation of vertical heterogeneities of groundwater fluxes across a well. Tue, 07 May 2013 14:34:50 GMT http://hdl.handle.net/2268/148026 Titre: Quantification and monitoring of contaminant mass fluxes in heterogeneous subsurface media <br/> <br/>Auteur, co-auteur: Jamin, Pierre; Brouyère, Serge <br/> <br/>Résumé: Since the beginning of the years 2000, a consensus has been growing among the scientific, technical and decision makers community concerning the fact that the characterisation and the management of contaminated sites have to be performed in terms of contaminant flux metrics instead of to be based on a simplistic study of pollutant concentration coming from piezometers randomly spread over the site. Contaminant plumes and associated pollutant mass fluxes are extremely variable in space as well as in time. The scientific and technical challenge is to capture this double heterogeneity in order to consider it explicitly or statistically for the management of a contamination issue. This requires (1) the interception of the entire contaminated groundwater flowing section with a control panel; (2) the ability to measure and to calculate accurately groundwater and contaminant fluxes across that panel; and (3) the repetition of the measurement to bring out the spatial and the temporal variation of contaminant fluxes. This research project aims to develop an integrated pollutant flux measurement approach for contaminated groundwater at the scale of the contaminant plume. This approach lays on a triple integration of (1) single well tracing techniques – (2) passive sampling – (3) control panel. Spatial and temporal variability of groundwater fluxes will be quantified by the point dilution tracing method derived from the “FVPDM” technique (Brouyère et al. 2008). In the same time, the amount of pollutant flowing through the same location will be determined by the adequate passive sampling technique (PS). The integration of these two measures in an interpretation schema based on mathematical and numerical modelling will allow quantifying contaminant fluxes and their variability over time. The adaptation at the scale of the contaminant plume will be based on a logging-type use of techniques, repeated along the vertical axis of the monitoring wells and repeated from one well to an other of a control panel implanted to intercept the plume. All the research results and developed techniques will then be integrated into a complete measurement system (PS-FVPDM), mobile and easily usable on field. The whole development and testing will take place on several pilot contaminated test site located in various hydrogeological context. Tue, 07 May 2013 14:27:51 GMT http://hdl.handle.net/2268/148025 Titre: Coupling heat and salt tracer experiment for the estimation of heat transfer and solute transport parameters <br/> <br/>Auteur, co-auteur: Wildemeersch, Samuel; Jamin, Pierre; Orban, Philippe; Hermans, Thomas; Brouyère, Serge; Dassargues, Alain <br/> <br/>Résumé: Geothermal energy is a promising source of energy in the context of sustainable development. Therefore, very low enthalpy geothermal systems (open or closed) are increasingly considered for heating or cooling houses and offices using groundwater energy. However, prior to the development of such systems, a feasibility study and an impact study of the system on groundwater ressources are required. Thereliability of such studies is highly dependent on the quality of the estimation of heat transfer parameters. This highlights the necessity of estimating properly such parameters. The objective of this study is to combine the use of heat and salt tracers to estimate simultaneously heat transfer and solute transport parameters in an alluvial aquifer. Additionally, coupling heat and salt tracing experiments is particularly useful for comparing heat transfer and solute transport processes occurring in the subsurface. An experimental field site, located near Liege (Belgium), is equipped with 21 piezometers drilled in the alluvial deposits of the Meuse River. These alluvial deposits are composed of a loess layer (3 m) overlying a sand and gravel layer which constitutes the alluvial aquifer (7 m). The coupled tracing experiment consists in injecting simultaneously heated water and salt in a piezometer and monitoring the evolution of groundwater temperature and salt concentration in a series of control panels set perpendicularly to groundwater flow. This coupled tracing experiment is then simulated using a numerical model. The estimation of heat transfer and solute transport parameters is obtained by calibrating this numerical model using inversion tools. The present study proposes a methodology coupling heat and salt tracing experiment for estimating heat transfer parameters at the field scale. Furthermore, this coupled tracing experiment shows that the comportment of heat and solute in the subsurface presents key differences. Tue, 07 May 2013 14:24:55 GMT http://hdl.handle.net/2268/147930 Titre: Downscaling transient climate change with a stochastic weather generator for the Geer catchment, Belgium <br/> <br/>Auteur, co-auteur: Blenkinsop, Steve; Harpham, C.; Burton, A.; Goderniaux, Pascal; Brouyère, Serge; Fowler, H.J. <br/> <br/>Résumé: The coarse resolution of climate models creates the need for future scenarios which are downscaled to an appropriate spatial scale. Considerable effort has been devoted to the development of downscaling methods but a number of important issues remain in the development of robust, usable climate scenarios. These include the incorporation of various sources of uncertainty into future scenarios and the production of scenarios at timescales relevant to planners. This paper describes a new procedure which addresses these issues by producing a multi-model ensemble of transient climate change scenarios. This method couples an existing stochastic rainfall model to a new, transient implementation of a weather generator, using changes projected by an ensemble of regional climate model (RCM) experiments. The methodology is demonstrated by the generation of transient scenarios of daily rainfall, temperature and potential evapotranspiration (PET) for the Geer catchment in Belgium for the period 2010 to 2085. The utility of these scenarios is demonstrated by assessing the changes projected by the simulated time series of several temperature indices. The Geer is projected to experience a decrease in the occurrence of frost days with a corresponding shortening of the frost season and lengthening of the growing season. By examining a large ensemble of transient scenarios the range of uncertainty in these projections is assessed, but further, it is suggested that additional information on the projected timing of specified threshold events or system responses may be provided which could aid planners in assessing the likely timescales of required interventions and adaptation responses. Mon, 06 May 2013 09:33:11 GMT http://hdl.handle.net/2268/147928 Titre: Is it worth protecting groundwater from diffuse pollution with agri-environmental schemes? A hydro-economic modeling approach Journal of Environmental Management <br/> <br/>Auteur, co-auteur: Hérivaux, Cécile; Orban, Philippe; Brouyère, Serge <br/> <br/>Résumé: In Europe, 30% of groundwater bodies are considered to be at risk of not achieving the Water Framework Directive (WFD) ‘good status’ objective by 2015, and 45% are in doubt of doing so. Diffuse agricultural pollution is one of the main pressures affecting groundwater bodies. To tackle this problem, the WFD requires Member States to design and implement cost-effective programs of measures to achieve the ‘good status’ objective by 2027 at the latest. Hitherto, action plans have mainly consisted of promoting the adoption of Agri- Environmental Schemes (AES). This raises a number of questions concerning the effectiveness of such schemes for improving groundwater status, and the economic implications of their implementation. We propose a hydro-economic model that combines a hydrogeological model to simulate groundwater quality evolution with agronomic and economic components to assess the expected costs, effectiveness, and benefits of AES implementation. This hydro-economic model can be used to identify cost-effective AES combinations at groundwater-body scale and to show the benefits to be expected from the resulting improvement in groundwater quality. The model is applied here to a rural area encompassing the Hesbaye aquifer, a large chalk aquifer which supplies about 230,000 inhabitants in the city of Liege (Belgium) and is severely contaminated by agricultural nitrates. We show that the time frame within which improvements in the Hesbaye groundwater quality can be expected may be much longer than that required by the WFD. Current WFD programs based on AES may be inappropriate for achieving the ‘good status’ objective in the most productive agricultural areas, in particular because these schemes are insufficiently attractive. Achieving ‘good status’ by 2027 would demand a substantial change in the design of AES, involving costs that may not be offset by benefits in the case of chalk aquifers with long renewal times. Mon, 06 May 2013 09:16:46 GMT http://hdl.handle.net/2268/147926 Titre: Benzene dynamics and biodegradation in alluvial aquifers affected by river fluctuations <br/> <br/>Auteur, co-auteur: Batlle-Aguilar, Jordi; Morasch, Barbara; Hunkeler, Daniel; Brouyère, Serge <br/> <br/>Résumé: The spatial distribution and temporal dynamics of a benzene plume in an alluvial aquifer strongly affected by river fluctuations was studied. Benzene concentrations, aquifer geochemistry datasets, past river morphology and benzene degradation rates estimated in situ using stable carbon isotope enrichment were analysed in concert with aquifer heterogeneity and river fluctuations. Geochemistry data demonstrated that benzene biodegradation was on-going under sulphate reducing conditions. Long-term monitoring of hydraulic heads and characterisation of the alluvial aquifer formed the basis of a detailed modelled image of aquifer heterogeneity. Hydraulic conductivity was found to strongly correlate with benzene degradation, indicating that low hydraulic conductivity areas are capable of sustaining benzene anaerobic biodegradation provided the electron acceptor (SO42-) does not become rate limiting. Modelling results demonstrated that the groundwater flux direction is reversed on annual basis when the river level rises up to two meters, thereby forcing the infiltration of oxygenated surface water into the aquifer. The mobilisation state of metal trace elements such as Zn, Cd and As present in the aquifer predominantly depended on the strong potential gradient within the plume. However, infiltration of oxygenated water was found to trigger a change from strongly reducing to oxic conditions near the river, causing mobilisation of previously immobile metal species and vice versa. Monitored natural attenuation appears to be an appropriate remediation strategy in this type of dynamic environment provided that aquifer characterisation and targeted monitoring of redox conditions is adequate and electron acceptors remain available until concentrations of toxic compounds reduce to acceptable levels. Mon, 06 May 2013 08:53:49 GMT