Heat transfer characterization in a shallow aquifer using heat and dye tracer tests

Very low enthalpy geothermal systems (open or closed) are increasingly considered for heating or cooling houses and offices using groundwater energy combined with heat pumps. However, the design and the impact of current shallow geothermal systems are often set up and assessed in a semi-empirical way. In our country, this situation seems accepted by most of the private partners but not by the authorities and responsible administrations evaluating the impact on groundwater with a mid- to long-term perspective. A rigorous methodology is needed based on a physically based estimation of heat transfer parameters. In this study, the simultaneous use of heat and dye tracers allows estimating simultaneously heat transfer and solute transport parameters in an alluvial aquifer. The 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 loam layer (3 m) overlying a sand and gravel layer which constitutes the alluvial aquifer (7 m). The tracing experiment consisted in injecting simultaneously heated water and a dye tracer in a piezometer and monitoring the evolution of groundwater temperature and tracer concentration in a series of control panels set perpendicularly to the main groundwater flow. Results showed drastic differences between heat transfer and solute transport due to the main influence of thermal capacity of the saturated porous medium. The tracing experiment was then simulated using a numerical model and the best estimation of heat transfer and solute transport parameters is obtained by calibrating this numerical model using inversion tools. The developed concepts and tests may lead to real projects of various extents that can be now optimized by the use of a rigorous and efficient methodology at the field scale

Proposition d'un support d'aide à la décision pour l'amélioration de l'accès à une eau souterraine de meilleure qualité dans un contexte de contamination géogénique au fluorure au Bénin, Afrique de l'Ouest

High concentrations of fluoride (up to 7 mg/L) are observed in the hard crystalline aquifers in the central part of Benin (Department of Collines) while the WHO recommended standard is 1.5 mg/L. The drinking of water with high fluoride contents affects human heath as dental fluorosis which already occurs frequently in the region. The hydrogeochemical investigations in the area reveal that the origin of fluoride in groundwater is geogenic with an important contribution of ferromagnesian minerals, mainly biotite. This work aims to carry out a double cartography at the scale of the Department of Collines for: (i) an estimation map of the fluoride concentration in the groundwater by ordinary kriging and (ii) a probability map to exceed the WHO guideline value of fluoride in water (1.5 mg/L) by indicator kriging. Beside the cartography, analysis of the spatial structure of the data (groundwater fluoride content) through variograms calculation was also carried out. This analysis shows a strong link between spatial structure of fluoride contents in groundwater and the dominant geological layer structures, corroborating the geogenic origin of fluoride. The proposed maps could be useful as decision support for policymakers and water resources managers for the appropriate locations of further groundwater extraction wells to limit or avoid fluoride risk areas

Time of day is associated with paradoxical reductions in global signal fluctuation and functional connectivity.

The brain exhibits substantial diurnal variation in physiology and function, but neuroscience studies rarely report or consider the effects of time of day. Here, we examined variation in resting-state functional MRI (fMRI) in around 900 individuals scanned between 8 AM and 10 PM on two different days. Multiple studies across animals and humans have demonstrated that the brain's global signal (GS) amplitude (henceforth referred to as "fluctuation") increases with decreased arousal. Thus, in accord with known circadian variation in arousal, we hypothesised that GS fluctuation would be lowest in the morning, increase in the midafternoon, and dip in the early evening. Instead, we observed a cumulative decrease in GS fluctuation as the day progressed. Although respiratory variation also decreased with time of day, control analyses suggested that this did not account for the reduction in GS fluctuation. Finally, time of day was associated with marked decreases in resting-state functional connectivity across the whole brain. The magnitude of decrease was significantly stronger than associations between functional connectivity and behaviour (e.g., fluid intelligence). These findings reveal time of day effects on global brain activity that are not easily explained by expected arousal state or physiological artefacts. We conclude by discussing potential mechanisms for the observed diurnal variation in resting brain activity and the importance of accounting for time of day in future studies

Characterizing background concentrations in groundwater bodies of the Brussels region: example of the Landenian sands (BR03)

Caractérisation de la concentration de référence de certains paramètres chimiques présents naturellement dans les masses d’eau souterraine captives du Socle et du Crétacé (BR01) et du Landénien (BR03) en Région de Bruxelles-Capital

Right ventricular function in transcatheter mitral and tricuspid valve edge-to-edge repair

Since transcatheter edge-to-edge repair (TEER) has become a valuable therapy in the treatment of both, mitral (MR) and tricuspid regurgitation (TR), the question of optimized patient selection has gained growing importance. After years of attributing rather little attention to the right ventricle (RV) and its function in the setting of valvular heart failure, this neglect has recently changed. The present review sought to summarize anatomy and function of the RV in a clinical context and aimed at presenting the current knowledge on how the RV influences outcomes after TEER for atrioventricular regurgitation. The anatomy of the RV is determined by its unique shape, which necessitates to use three-dimensional imaging methods for detailed and comprehensive characterization. Complex parameters such as RV to pulmonary artery coupling (RVPAc) have been developed to combine information of RV function and afterload which is primary determined by the pulmonary vasculature and LV filling pressure. Beyond that, TR, which is closely related to RV function also plays an important role in the setting of TEER. While mitral valve transcatheter edge-to-edge repair (M-TEER) leads to reduction of concomitant TR in some patients, the prognostic value of TR in the setting of M-TEER remains unclear. Overall, this review summarizes the current state of knowledge of the outstanding role of RV function and associated TR in the setting of TEER and outlines the unsolved questions associated with right-sided heart failure

Note de travail relative à l’adaptation de la méthodologie pour l’analyse de la vulnérabilité des nappes profondes et/ou de second niveau (tâche TD3)

Convention relative à la valorisation et au développement du module SIG de cartographie de la vulnérabilité des eaux souterraines et de risques – APSÛ-GIS

ESU-ESO2 (Deliverable D02): Description of results relating to sampling campaigns at basin scale

Convention pour la caractérisation complémentaire des masses d’eau dont le bon état dépend de l’interaction des eaux de surface et des eaux souterraines - ESU-ESO

Interest of the Assimilation of Surface Melt Extent Derived From Passive and Active Microwave Satellites Into the Regional Climate Model MAR Over the Antarctic Peninsula

editorial reviewedMelting ice sheets are a major contributor to the rising sea level. At the Liège University, the Regional Climate Model MAR (Modèle Atmosphérique Régional) has been developed to monitor and study the current and future evolution of various properties of ice sheets. However, uncertainties remain on the surface melt extent upon Antarctic ice sheets as models are subject to error propagation and need some external data to model the climate. In Antarctica, unlike Greenland, the produced surface meltwater does not leave the ice sheet through visible rivers in which the quantity of meltwater can be estimated. Remote sensing is then the only product able to provide an estimation of the surface melt extent with a satisfying spatial and temporal coverage. The assimilation of melt spatial extent estimated by remote sensing allows the mitigation of the uncertainties linked to the models as well as a better quantification of the melt quantity. In this research, active (Sentinel-1) and passive (AMSR2 & SSMIS) microwave satellite data are assimilated into MAR model over the Antarctic Peninsula, where surface melt has caused hydrofracturing and destabilization of ice shelves in the past. The assimilation of the different satellite products is also conducted to study the effect of spatial resolution on melt detection, Sentinel-1 having a pixel size of a few meters while passive satellites are at the 10km scale. This difference can be crucial upon the Peninsula as Foehn effects are occurring locally and can generate local surface melt, not detectable while using a coarser resolution