References of "Brouyère, Serge"
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See detailContinuous monitoring of transient groundwater fluxes using the Finite Volume Point Dilution Method
Jamin, Pierre ULg; Brouyère, Serge ULg

Conference (2016, July)

Groundwater flux is the driving force of solute contaminant dispersion through aquifers. Accurate groundwater flux measurement and monitoring is thus crucial for assessing the fate of contaminants in the ... [more ▼]

Groundwater flux is the driving force of solute contaminant dispersion through aquifers. Accurate groundwater flux measurement and monitoring is thus crucial for assessing the fate of contaminants in the saturated zone. Unfortunately, classical measurement such as pumping or slug tests based on the Darcy’s law and hydraulic gradient may lead to cumulated errors and provide no more than a snapshot measurement only representative of a given time. There is a need for a technique able to perform a continuous monitoring of groundwater fluxes, and moreover in aquifer where rapid changes of groundwater fluxes occur such as aquifers influenced by surface water, by nearby pumping or by fast precipitation recharge. Alternative methods, such as point dilution tracer tests to obtain a direct measurement of local groundwater fluxes, are promising In this study, the Finite Volume Point Dilution Method (FVPDM) was applied to continuously monitor groundwater fluxes of the alluvial aquifer of the River Meuse, in Liège (Belgium). The experimental setup consisted in the monitoring of a transient groundwater fluxes generated by a step pumping test that lasted 40 hours. Two FVPDM were performed simultaneously in two piezometers screened in two different part of the aquifer. Piezometric heads were also monitored in several piezometer located around the pumping well. Next to this original experimental setup, a mathematical solution has been developed to interpret data from FVPDM performed under transient state in order to deduce the continuous evolution of groundwater flux. The experiment demonstrated the ability of the FVPDM for monitoring transient groundwater fluxes, even if the changes of groundwater flux occurs rapidly. The FVPDM turned out to be very sensitive to small changes in groundwater flux. The FVPDM interpretation also showed that the upper part of the aquifer is affected by slower groundwater fluxes than the lower and coarser part. Furthermore, distinct hydraulic behavior were determined between the upper and lower part of the aquifer. This could not have been revealed by conventional pumping tests using only drawdown data for interpretation. The mathematical solution allowed to determine the groundwater flux at every moment of the test even if the FVPDM had not reached the stabilized phase that usually guarantee its good precision. These results illustrate the great interest of the FVPDM method for monitoring of contaminant fluxes in groundwater if coupled with a real time measurement of contaminant concentration. One of the main perspective is to perform a long term (several months) monitoring of groundwater fluxes in an aquifer influenced by river stages variations in order to prove the ability of the FVPDM for continuous long term monitoring and better characterize the exchanges between groundwater and surface water. [less ▲]

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See detailMulti-species measurements of nitrogen isotopic composition reveal the spatial constraints and biological drivers of ammonium attenuation across a highly contaminated groundwater system
Wells, Naomi S.; Hakoun, Vivien ULg; Brouyère, Serge ULg et al

in Water Research (2016), 98

Groundwater under industrial sites is characterised by heterogeneous chemical mixtures, making it difficult to assess the fate and transport of individual contaminants. Quantifying the in-situ biological ... [more ▼]

Groundwater under industrial sites is characterised by heterogeneous chemical mixtures, making it difficult to assess the fate and transport of individual contaminants. Quantifying the in-situ biological removal (attenuation) of nitrogen (N) is particularly difficult due to its reactivity and ubiquity. Here a multi-isotope approach is developed to distinguish N sources and sinks within groundwater affected by complex industrial pollution. Samples were collected from 70 wells across the two aquifers underlying a historic industrial area in Belgium. Below the industrial site the groundwater contained up to 1000 mg Nl-1 ammonium (NH4 +) and 300 mg N l-1 nitrate (NO3-), while downgradient concentrations decreased to ~1 mg l-1 DIN ([DIN] = [NH4+-N] + [NO3--N] + [NO2--N]). Mean δ1534 N-DIN increased from ~2‰ to +20‰ over this flow path, broadly confirming that biological N attenuation drove the measured concentration decrease. Multi-variate analysis of water chemistry identified two distinct NH4+ sources (δ15N-NH4+ from -14‰ and +5‰) within the contaminated zone of both aquifers. Nitrate dual isotopes co-varied (δ15 N: -3‰ - +60‰; δ18O: 0‰ - +50‰) within the range expected for coupled nitrification and denitrification of the identified sources. The fact that δ15N-NO2- values were 50‰ to 20‰ less than δ15N-NH4+ values in 40 the majority of wells confirmed that nitrification controlled N turnover across the site. However, the fact that δ15N-NO2- was greater than δ15N-NH4+ in wells with the highest [NH4+] shows that an autotrophic NO2- reduction pathway (anaerobic NH4+ oxidation or nitrifier-denitrification) drove N attenuation closest to the contaminant plume. This direct empirical evidence that both autotrophic and heterotrophic biogeochemical processes drive N attenuation in contaminated aquifers demonstrates the power of multiple N isotopes to untangle N cycling in highly complex systems. [less ▲]

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See detailHeat tracer test in an alluvial aquifer: field experiment and inverse modelling
Klepikova, Maria; Wildemeersch, Samuel; Hermans, Thomas ULg et al

in Journal of Hydrology (2016), 540

Using heat as an active tracer for aquifer characterization is a topic of increasing interest. In this study, we investigate the potential of using heat tracer tests for characterization of a shallow ... [more ▼]

Using heat as an active tracer for aquifer characterization is a topic of increasing interest. In this study, we investigate the potential of using heat tracer tests for characterization of a shallow alluvial aquifer. A thermal tracer test was conducted in the alluvial aquifer of the Meuse River, Belgium. The tracing experiment consisted in simultaneously injecting heated water and a dye tracer in an injection well and monitoring the evolution of groundwater temperature and tracer concentration in the pumping well and in measurement intervals. To get insights in the 3D characteristics of the heat transport mechanisms, temperature data from a large number of observation wells closely spaced along three transects were used. Temperature breakthrough curves in observation wells are contrasted with what would be expected in an ideal layered aquifer. They reveal strongly unequal lateral and vertical components of the transport mechanisms. The observed complex behavior of the heat plume is explained by the groundwater flow gradient on the site and heterogeneities in the hydraulic conductivity field. Moreover, due to high injection temperatures during the field experiment a temperature-induced fluid density effect on heat transport occurred. By using a flow and heat transport numerical model with variable density coupled with a pilot point approach for inversion of the hydraulic conductivity field, the main preferential flow paths were delineated. The successful application of a field heat tracer test at this site suggests that heat tracer tests is a promising approach to image hydraulic conductivity field. This methodology could be applied in aquifer thermal energy storage (ATES) projects for assessing future efficiency that is strongly linked to the hydraulic conductivity variability in the considered aquifer. [less ▲]

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See detailHeat tracer test in an alluvial aquifer: field experiment and inverse modelling
Klepikova, Maria; Wildemeersch, Samuel; Jamin, Pierre ULg et al

Poster (2016, April 20)

Using heat as an active tracer for aquifer characterization is a topic of increasing interest. In this study, we investigate the potential of using heat tracer tests for characterization of a shallow ... [more ▼]

Using heat as an active tracer for aquifer characterization is a topic of increasing interest. In this study, we investigate the potential of using heat tracer tests for characterization of a shallow alluvial aquifer. A thermal tracer test was conducted in the alluvial aquifer of the Meuse River, Belgium. The tracing experiment consisted in simultaneously injecting heated water and a dye tracer in a piezometer and monitoring the evolution of groundwater temperature and tracer concentration in the recovery well and in monitoring wells. To get insights in the 3D characteristics of the heat transport mechanisms, temperature data from a large number of observation wells distributed throughout the field site (space-filling arrangement) were used. Temperature breakthrough curves in observation wells are contrasted with what would be expected in an ideal layered aquifer. They reveal strongly unequal lateral and vertical components of the transport mechanisms. The observed complex behavior of the heat plume was explained by the groundwater flow gradient on the site and heterogeneity of hydraulic conductivity field. Moreover, due to high injection temperatures during the field experiment a temperature-induced fluid density effect on heat transport occurred. By using a flow and heat transport numerical model with variable density coupled with the pilot point inverse approach, main preferential flow paths were delineated. [less ▲]

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See detailRessources en eau au Bénin: Problématique, enjeux et défis d’une gestion durable
Tossou, Yao ULg; Orban, Philippe ULg; Ruthy, Ingrid ULg et al

Scientific conference (2016, March 12)

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See detailUse of dual carbon-chlorine isotope analysis to assess the degradation pathways of 1,1,1-trichloroethane in groundwater
Palau, Jordi; Jamin, Pierre ULg; Badin, Alice et al

in Water Research (2016)

Compound-specific isotope analysis (CSIA) is a powerful tool to track contaminant fate in groundwater. However, the application of CSIA to chlorinated ethanes has received little attention so far. These ... [more ▼]

Compound-specific isotope analysis (CSIA) is a powerful tool to track contaminant fate in groundwater. However, the application of CSIA to chlorinated ethanes has received little attention so far. These compounds are toxic and prevalent groundwater contaminants of environmental concern. The high susceptibility of chlorinated ethanes like 1,1,1-trichloroethane (1,1,1-TCA) to be transformed via different competing pathways (biotic and abiotic) complicates the assessment of their fate in the subsurface. In this study, the use of a dual C-Cl isotope approach to identify the active degradation pathways of 1,1,1-TCA is evaluated for the first time in an aerobic aquifer impacted by 1,1,1-TCA and trichloroethylene (TCE) with concentrations of up to 20 mg/L and 3.4 mg/L, respectively. The reaction-specific dual carbon-chlorine (C-Cl) isotope trends determined in a recent laboratory study illustrated the potential of a dual isotope approach to identify contaminant degradation pathways of 1,1,1-TCA. Compared to the dual isotope slopes (Δδ13C/Δδ37Cl) previously determined in the laboratory for dehydrohalogenation / hydrolysis (DH/HY, 0.33 ± 0.04) and oxidation by persulfate (∞), the slope determined from field samples (0.6 ± 0.2, r2 = 0.75) is closer to the one observed for DH/HY, pointing to DH/HY as the predominant degradation pathway of 1,1,1-TCA in the aquifer. The observed deviation could be explained by a minor contribution of additional degradation processes. This result, along with the little degradation of TCE determined from isotope measurements, confirmed that 1,1,1-TCA is the main source of the 1,1-dichlorethylene (1,1-DCE) detected in the aquifer with concentrations of up to 10 mg/L. This study demonstrates that a dual C-Cl isotope approach can strongly improve the qualitative and quantitative assessment of 1,1,1-TCA degradation processes in the field. [less ▲]

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See detailHow heterogeneity of the K-field influences a heat plume in a shallow alluvial aquifer: responses from a heat tracer test
Klepikova, Maria; Jamin, Pierre ULg; Orban, Philippe ULg et al

in Abstract book (2016, January 26)

Simultaneous solute and heat tracer test provides essential information for a reliable assessment of low temperature geothermal systems. The actual efficiency of ‘open systems’, including heat storage ... [more ▼]

Simultaneous solute and heat tracer test provides essential information for a reliable assessment of low temperature geothermal systems. The actual efficiency of ‘open systems’, including heat storage projects, is strongly affected by the heterogeneity of the hydraulic conductivity field (K-field). It could be also useful for assessing the cumulative impacts of numerous projects in urban areas on the groundwater resources. Using field data from a solute and heat tracer test conducted in the alluvial aquifer of the Meuse River (Belgium), an inverse problem of parameter estimation is solved. The tracing experiment consisted in simultaneously injecting heated water and a dye tracer in a piezometer and monitoring the evolution of groundwater temperature and tracer concentration in the recovery well and in monitoring wells. To get insights in the 3D characteristics of the heat plume, an arrangement of three transects of observation wells was used. The breakthrough curves measured in the recovery well showed that heat transfer in the alluvial aquifer is slower and more dispersive than solute transport. Recovery is very low for heat while in the same time it is measured as relatively high for the solute tracer. This is due to the fact that heat transport is a thermal diffusion dominated process. For conditions corresponding to high Peclet numbers, the hydraulic conductivity is the primary calibration parameter for predicting heat plume distribution. Heat diffusion is larger than molecular diffusion, implying that exchange between groundwater and the porous medium matrix is far more significant for heat than for solute tracers. [less ▲]

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See detailLe bassin du Triffoy et les eaux souterraines : Exemple de caractérisation des échanges entre nappe et rivière
Briers, Pierre ULg; Descy, Jean-Pierre; Schmit, Flore et al

in Atlas du Karst Wallon - Bassins versants du Hoyoux et de la Solières (2016)

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See detailHydrogéologie du bassin du Hoyoux
Briers, Pierre ULg; Jamin, Pierre ULg; Ruthy, Ingrid ULg et al

in Atlas du Karst Wallon - Bassins versants du Hoyoux et de la Solières (2016)

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See detailDélivrable D3.3 Bilans hydrogéologiques
Schmit, Flore; Hallet, Vincent; Briers, Pierre ULg et al

Report (2016)

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