Alain Bourg | Université De Pau Et Des Pays De L'adour (original) (raw)

Papers by Alain Bourg

Riverbank Filtration: Understanding Contaminant Biogeochemistry and Pathogen Removal, 2002

ORGANIC MATTER AS THE DRIVING FORCE IN THE SOLUBILIZATION OF Fe AND Mn DURING RIVERBANK FILTRATIO... more ORGANIC MATTER AS THE DRIVING FORCE IN THE SOLUBILIZATION OF Fe AND Mn DURING RIVERBANK FILTRATION ALAIN CM. BOURG and MONIKA AM KEDZIOREK Environmental Hydrogeochemistry Group University of Pau Helioparc Pau-Pyrenees 64053 Pau Cedex ...

Environmental Technology Letters, 1982

ABSTRACT ADSORP is a simple BASIC computer program conceived for the determination of the equilib... more ABSTRACT ADSORP is a simple BASIC computer program conceived for the determination of the equilibrium speciation of trace elements. Only one family (REDEQL 2, MINEOL and GEOCHEM) among the existing programs can already take adsorption processes into account. ADSORP differs from them in (1) the definition of the adsorption process, (2) the introduction of the adsorption of trace element complexes, and (3) the simplicity of the mathematics (method of convergence).

Journal français d’hydrologie, 1979

Applied Geochemistry, 1996

The solubilisation of Ni, Cd and Pb from 3 model components of soils and sediments is investigate... more The solubilisation of Ni, Cd and Pb from 3 model components of soils and sediments is investigated as a function of pH. In presence of increasing acidity, Ni, Cd and Pb are strongly solubilised from kaolinite and amorphous ferric hydroxide. Metal solubility tends to decrease, on the other hand, when humic acid is present. The quantity of metal solubilised from the dual-component, amorphous ferric hydroxide-humic acid system is smallest in the pH range 3.5 to 5.5. In the system kaolinite-humic acid, the solubility is highest at neutral pH. In these solid mixtures, metal solubility is always minimal (close to nil) in the pH range between the pHm, of the humic acid and the pH,,, of the mineral solid. The solubilisation of heavy metals from soils and sediments is highly pH-dependent but does not always increase with decreasing pH. The solubility of Cd, Ni and Pb depends not only on pH but also on interactions between soil components.

Agu Fall Meeting Abstracts, Dec 1, 2005

Bentonite (a strongly-swelling, smectite-rich clay) is commonly used in engineered barriers and g... more Bentonite (a strongly-swelling, smectite-rich clay) is commonly used in engineered barriers and geosynthetic liners for the isolation of landfills and contaminated sites. Bentonite barriers are under consideration in several countries as potential components of deep geological repositories for high-level radioactive waste. Because of the low hydraulic conductivity of water-saturated bentonite, molecular diffusive processes contribute significantly to the transport of solutes through such barriers. In the present study, we discuss the results of numerous studies of the diffusion of water and cations (Na+, Sr2+) in water-saturated bentonite carried out during the last decade. We note that the pore space of compacted, water-saturated Na-bentonite contains a significant fraction of nanopores, the nanometer-thin smectite interlayers. We develop a new conceptual model of the apparent diffusion coefficient (Da) of water and ions in water-saturated bentonite that accounts for diffusion in two compartments: the interlayer nanopores and larger macropores. We show that our model can explain all available experimental data of the apparent diffusion coefficient of water and cations (Na+, Sr2+) with a single fitted parameter, a geometric factor G = 4.0 ± 1.6, for all bentonites studied (with montmorillonite contents between 35 and 100 %), in a broad range of partial montmorillonite dry density (0.2 to 1.7 kg dm-3, the mass of montmorillonite per combined volume of montmorillonite and pore space).

Clays and Clay Minerals, Jun 1, 2006

Environ Sci Technol, 2007

Sodium bentonites are used as barrier materials for the isolation of landfills and are under 24 c... more Sodium bentonites are used as barrier materials for the isolation of landfills and are under 24 consideration for a similar use in the subsurface storage of high-level radioactive waste. The 25 performance of these barriers is determined in large part by molecular diffusion in the bentonite 26 pore space. We tested two current models of cation diffusion in bentonite against experimental 27 data on the relative apparent diffusion coefficients of two representative cations, sodium and 28 strontium. On the 'macropore/nanopore' model, solute molecules are divided into two categories, 29 with unequal pore-scale diffusion coefficients, based on location: in macropores or in interlayer 30 nanopores. On the 'surface diffusion' model, solute molecules are divided into categories based 31 on chemical speciation: dissolved or adsorbed. The macropore/nanopore model agrees with all 32 experimental data at partial montmorillonite dry densities ranging from 0.2 (a dilute bentonite 33 gel) to 1.7 kg dm -3 (a highly compacted bentonite with most of its pore space located in 34 interlayer nanopores), whereas the surface diffusion model fails at partial montmorillonite dry 35 densities greater than about 1.2 kg dm -3 . 36 37

Journal of Hydrology, Feb 1, 2009

SummaryAlluvial aquifers are largely used as groundwater resource since large flow rates can be o... more SummaryAlluvial aquifers are largely used as groundwater resource since large flow rates can be obtained due to infiltration from the neighboring river. Reductive conditions in the infiltration flow path, caused by the degradation of organic matter, can induce effects detrimental to water quality, such as dissolution of Mn and Fe from the aquifer sediments. In the absence of any direct relationship between the redox potential (Eh) and reductive conditions favorable to manganese and/or iron reduction, we propose a quantitative approach, the electron trapping capacity (ETC). It is calculated using dissolved O 2 and NO 3 concentrations in groundwater, weighted for the quantity of electrons these two species can trap during the oxidation of organic matter. This approach, tested on several field and laboratory investigations, indicates that reductive dissolution of manganese and iron oxyhydroxides occurs for an ETC lower than 0.2 mmol L -1. Exceptions to that threshold value are observed when Mn-rich groundwater flows too fast out of a reduced zone into an oxidizing environment to permit equilibrium precipitation of Mn oxyhydroxides.

Applied Geochemistry, Aug 15, 2008

Assessments of bentonite barrier performance in waste management scenarios require an 23 accurate... more Assessments of bentonite barrier performance in waste management scenarios require an 23 accurate description of the diffusion of water and solutes through the barrier. A two-24 compartment macropore/nanopore model (on which smectite interlayer nanopores are treated as 25 a distinct compartment of the overall pore space) was applied to describe the diffusion of 22 Na + 26 in compacted, water-saturated Na-bentonites and then compared with the well-known surface 27 diffusion model. The two-compartment model successfully predicted the observed weak ionic 28 strength dependence of the apparent diffusion coefficient (D a ) of Na + , whereas the surface 29 diffusion model did not, thus confirming previous research indicating the strong influence of 30 interlayer nanopores on the properties of smectite clay barriers. Since bentonite mechanical 31 properties and pore water chemistry have been described successfully with two-compartment 32 models, the results in the present study represent an important contribution toward the 33 construction of a comprehensive two-compartment model of compacted bentonite barriers. 34 35 36

Environmental Science and Technology, Jan 12, 2007

Journal of Colloid and Interface Science, Aug 15, 2007

Proton uptake on montmorillonite edge surfaces can control pore water pH, solute adsorption, diss... more Proton uptake on montmorillonite edge surfaces can control pore water pH, solute adsorption, dissolution kinetics and clay colloid behavior in engineered clay barriers and natural weathering environments. Knowledge of proton uptake reactions, however, is currently limited by strong discrepancies between reported montmorillonite titration data sets and by conflicting estimates of edge structure, reactivity and electrostatics. In the present study, we show that the apparent discrepancy between titration data sets results in large part from the widespread use of an erroneous assumption of zero specific net proton surface charge at the onset of titration. Using a novel simulation scheme involving a surface chemistry model to simulate both pretreatment and titration, we find that montmorillonite edge surface chemistry models that account for the "spillover" of electrostatic potential from basal onto edge surfaces and for the stabilization of deprotonated Al-Si bridging sites through bond-length relaxation at the edge surface can reproduce key features of the best available experimental titration data (the influence of pretreatment conditions on experimental results, the absence of a point of zero salt effect, buffer capacity in the acidic pH range). However, no combination of current models of edge surface structure, reactivity and electrostatics can quantitatively predict, without fitted parameters, the experimental titration data over the entire range of pH (4.5 to 9) and ionic strength (0.001 to 0.5 mol dm −3 ) covered by available data.

Trace Metals in Sea Water, 1983

Inorganic and Nuclear Chemistry Letters

Comptes rendus de l'Académie des sciences. Série II, Mécanique, physique, chimie, sciences de l'univers, sciences de la terre