Inverse hydrochemical models of aqueous extracts tests

Zheng, Liange; Samper, Javier; Montenegro, Luís

doi:10.1016/j.pce.2008.05.012

Cited by 17 publications

(13 citation statements)

References 34 publications

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“…This makes it difficult to derive the chemical composition of the original pore water from the aqueous extract data (Bradbury and Baeyens, 1998;Sacchi et al, 2001). The inference of dissolved concentration for reactive species requires geochemical modeling based on mineralogical data (Bradbury and Baeyens, 1997, 2003Pearson et al, 2003;Fernández and Rivas, 2005;Zheng et al, 2008a). Aqueous extract tests and cation exchange population are available in sections 19, 28 and 29 (Fernández and Rivas, 2003).…”

Section: Inference Of Pore Water Composition From Aqueous Extract Datamentioning

confidence: 99%

A coupled THC model of the FEBEX in situ test with bentonite swelling and chemical and thermal osmosis

Zheng

Samper

Montenegro

2011

Journal of Contaminant Hydrology

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The performance assessment of a geological repository for radioactive waste requires quantifying the geochemical evolution of the bentonite engineered barrier. This barrier will be exposed to coupled thermal (T), hydrodynamic (H), mechanical (M) and chemical (C) processes. This paper presents a coupled THC model of the FEBEX (Full-scale Engineered Barrier EXperiment) in situ test which accounts for bentonite swelling and chemical and thermal osmosis. Model results attest the relevance of thermal osmosis and bentonite swelling for the geochemical evolution of the bentonite barrier while chemical osmosis is found to be almost irrelevant. The model has been tested with data collected after the dismantling of heater 1 of the in situ test. The model reproduces reasonably well the measured temperature, relative humidity, water content and inferred geochemical data. However, it fails to mimic the solute concentrations at the heater-bentonite and bentonite-granite interfaces because the model does not account for the volume change of bentonite, the CO 2 (g) degassing and the transport of vapor from the bentonite into the granite. The inferred HCO 3 -and pH data cannot be explained solely by solute Page 2 of 54 transport, calcite dissolution and protonation/deprotonation by surface complexation, suggesting that such data may be affected also by other reactions.

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Section: Inference Of Pore Water Composition From Aqueous Extract Datamentioning

confidence: 99%

A coupled THC model of the FEBEX in situ test with bentonite swelling and chemical and thermal osmosis

Zheng

Samper

Montenegro

2011

Journal of Contaminant Hydrology

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“…Because of the low water content (high solid/liquid ratio as well), the pore-water chemistry at the initial state can only be measured indirectly by squeezing conducted at higher water content or aqueous extract. But both methods introduce artifacts and alter the geochemical system, resulting geochemical modeling needing be employed to retrieve the aqueous ion concentrations at low water content (Zheng et al 2008). Any uncertainties associated with the geochemical models affect concentration levels at low water content (the water content at the initial state).…”

Section: Mineralogical Compositionmentioning

confidence: 99%

Generic Argillite/Shale Disposal Reference Case

Zheng¹,

Colon²,

Bianchi³

et al. 2014

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“…Aqueous extract data were interpreted with the inverse hydrochemical model of Zheng et al (2008) by assuming that the initial clay pore water is in equilibrium with quartz, calcite, dolomite and pyrite.…”

Section: Numerical Modelmentioning

confidence: 99%

“…Chemical data obtained from aqueous extract tests ( AET data (Bradbury and Baeyens, 1998;Sacchi et al 2001;Zheng et al, 2008). Measured AET data must be re-interpreted to infer the pore water chemical composition of the clay samples.…”

Section: Testing Computed Concentrations With Inferred Datamentioning

confidence: 99%

“…The reactive transport model is based on the geochemical model of Pearson et al (2003) and is calibrated using mineralogical and aqueous extract data from Fernández et al (2006). The inverse hydrochemical model of Zheng et al (2008) is used to estimate the chemical composition of pore water of clay samples from aqueous extract data. The model is used to evaluate changes in porosity and permeability of the rock caused by mineral dissolution/precipitation.…”

Section: Introductionmentioning

confidence: 99%

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A coupled THMC model of FEBEX mock-up test

Zheng¹,

Samper²

2008

Physics and Chemistry of the Earth, Parts A/B/C

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During the construction and operational phases of a high-level radioactive waste (HLW) repository constructed in a clay formation, ventilation of underground drifts will cause desaturation and oxidation of the rock. The Ventilation Experiment (VE) was performed in a 1. calcite and siderite, precipitation of ferrihydrite, dolomite and gypsum and cation exchange. pH in the unsaturated rock varies from 7.8 to 8 and is buffered by calcite. Computed changes in the porosity and the permeability of Opalinus clay in the unsaturated zone caused by oxidation and mineral dissolution/precipitation are smaller than 5%. Therefore, rock properties are not expected to be affected significantly by ventilation of underground drifts during construction and operational phases of a HLW repository in clay.

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Inverse hydrochemical models of aqueous extracts tests

Abstract: Aqueous extract test is a laboratory technique commonly used to measure the amount of soluble salts of a soil sample after adding a known mass of distilled water. Main uncertainties are related to kinetic calcite dissolution and variations in CO 2 (g) pressure.2/32

Cited by 17 publications

References 34 publications

A coupled THC model of the FEBEX in situ test with bentonite swelling and chemical and thermal osmosis

A coupled THC model of the FEBEX in situ test with bentonite swelling and chemical and thermal osmosis

Generic Argillite/Shale Disposal Reference Case

A coupled THMC model of FEBEX mock-up test

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