Effect of confining pressure on the diffusion of HTO, 36Cl− and 125I− in a layered argillaceous rock (Opalinus Clay): diffusion perpendicular to the fabric

Loon, Luc R. Van; Soler, Josep M.; Jakob, A.; Bradbury, Michael E.

doi:10.1016/s0883-2927(03)00047-7

Cited by 105 publications

(65 citation statements)

References 11 publications

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“…Measurements of diffusion of both water (measured using HTO) and chloride have also been made on several samples from Mont Terri. The ratio of the diffusion porosity for chloride to that of HTO is also between 0.5 and 0.7 (Pearson et al, 2003, Table A10.8;Van Loon et al, 2003, 2004. As a consequence, the value obtained from the overcore samples is the highest reliable value measured on…”

Section: Gradients In Pore Water Compositionmentioning

confidence: 99%

Biogeochemical processes in a clay formation in situ experiment: Part B – Results from overcoring and evidence of strong buffering by the rock formation

Koroleva¹,

Lerouge²,

Mäder³

et al. 2011

Applied Geochemistry

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An in-situ Porewater Chemistry (PC) experiment in the Opalinus Clay formation was carried out at the Mont Terri underground rock laboratory (Jura Mountains, Switzerland) for a period of five years. A traced water with a composition close to that expected in the formation was continuously circulated and monitored in a packed-off borehole to achieve diffusive equilibration. An unwanted microbial perturbation changed the water composition, characterized by reduction of sulphate combined with increasing sulphide, increasing alkalinity, decreasing pH and increasing P(CO 2 ). In contrast, the main cations (Na, Ca, Mg) remained remarkably constant during the experiment, thus indicating the strong buffering of the formation via cation and proton exchange as well as carbonate dissolution/precipitation reactions.After five years, the 4.5 m long vertical test interval was overcored and Opalinus clay samples were analyzed along ca. 15 cm long radial profiles. The analytical investigations included mineralogy (XRD, SEM-EDX), bulk parameters (water content, density, C, S), cation exchange capacity and occupancy, aqueous leachates for Cl -, Br -, SO 4 2-and water and carbonate stable isotopes. Emphasis was put on best sample preparation and conservation techniques.Results show that the distribution of non-reactive tracers (Br -and 2 H) follows the expected out/in-diffusion profiles compatible with the time-dependent boundary conditions in the test interval of the borehole. Although some experimental features remain unresolved (e.g. high content of leachable sulphate compared to test interval), the distribution of reactive tracers (in porewater, on the clay exchanger and in the solid phase) demonstrate the very extensive buffer capacity of the Opalinus Clay formation towards chemical disturbances, such as those induced by microbial sulfate reduction and oxidation of an organic carbon source.

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Section: Gradients In Pore Water Compositionmentioning

confidence: 99%

Biogeochemical processes in a clay formation in situ experiment: Part B – Results from overcoring and evidence of strong buffering by the rock formation

Koroleva¹,

Lerouge²,

Mäder³

et al. 2011

Applied Geochemistry

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“…In many applications of the through-diffusion technique, this condition may be violated. It requires experimental design to ensure that this condition is achieved [Lü and Viljanen, 2002;Lü and Ahl, 2005;Van Loon et al, 2003b], or at a minimum, verification of this condition through sampling. Moridis [1999] provides examples demonstrating the potential errors that would arise if this condition is violated.…”

Section: Time-lag Methodsmentioning

confidence: 99%

“…An immobile thin film may exist surrounding particle grains because of adhesive forces (the diffuse double layer). The influences of this adhesion have been shown to be solute dependent, as in the case of anion exclusion [Schön, 1996;Van Loon et al, 2003a, 2003bAppelo and Wersin, 2007]. Highly structured, inaccessible water may also occur in interlayers of clay minerals.…”

Section: Introductionmentioning

confidence: 99%

“…The intrinsic diffusion coefficient is estimated by measuring the flux of the tracer through the porous sample over time, as described by Fick's laws of diffusion. Theoretically, the effective, or transport, porosity can be derived from the early time, or transient-state, data from a through-diffusion experiment, though there is much debate over the accuracy of these derived effective porosities [Grathwohl, 1998;Van Loon et al, 2003b;Appelo and Wersin, 2007;Motellier et al, 2007]. Some of this difficulty arises from the method of estimation of the effective porosity from through-diffusion experimental data.…”

Section: Introductionmentioning

confidence: 99%

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Comparison of modeling methods for the determination of effective porosities and diffusion coefficients in through‐diffusion tests

Benning

Barnes

2009

Water Resources Research

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[1] Diffusion coefficients and effective, or transport, porosities are important parameters in the assessment of the fate and transport of contaminants in fractured rock systems and when contaminant transport needs to be considered in zones of low to negligible advective flows. This study presents and discusses various solutions, analytical and semianalytical, to Fick's law for the typical through-diffusion experiment and applies these solutions to the results of three through-diffusion experimental data sets. These through-diffusion experiments were conducted on two natural breccia samples, with bulk measured porosities of approximately 13.7% and 16.8%, and one manufactured porous plate sample with a bulk measured porosity of 40.9%, such that the samples displayed order of magnitude differences in their diffusivities. For each experiment, the derived effective porosities and intrinsic diffusion coefficients for each method are compared. It was shown that the semianalytical solution provides an improved method for reliably estimating the effective porosity from through-diffusion experimental data; however, there is little difference between methods in the derived intrinsic diffusion coefficients.

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“…In this sense, the diffusion of various radionuclides through compacted swelling clays and argillaceous rocks has been extensively evaluated in laboratory tests by obtaining the e , primarily by through-diffusion experiments. The literature on through-diffusion experiments is vast but important references are: Molera and Eriksen [6], in which the diffusion of 22 [7], who applied through-diffusion and the complementary out-diffusion method to study the diffusion of HTO, Opalinus Clay under different confining pressures; and Glaus et al [8], who investigated the diffusion of HTO, 22 …”

Section: Introductionmentioning

confidence: 99%

Suitability of various materials for porous filters in diffusion experiments

et al. 2014

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Abstract:The suitability of different porous materials (stainless steel, VYCOR ® glass, Al 2 O 3 and PEEK) for use as confining filters in diffusion experiments was evaluated by measuring the effective diffusion coefficients ( e ) of neutral (HTO) and ionic solutes (NaSeO 4 2− ) in the materials in through-diffusion experiments.For stainless steel filters, the e values of the target solutes correlated satisfactorily with their bulk diffusion coefficient in water ( w ); thus, the diffusion process in the stainless steel filters was primarily controlled by the diffusivity of the solvated ions. For the remaining materials, the e and w values were also correlated for the target solutes, and the geometric factors were in the sequence: VYCOR ® glass < Al 2 O 3 < PEEK. Stainless steel and VYCOR ® glass were the most appropriate materials because of their high e values, but a specific interaction of caesium with VYCOR ® glass was hypothesised because the e values obtained for this solute were slightly higher than expected.

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Effect of confining pressure on the diffusion of HTO, 36Cl− and 125I− in a layered argillaceous rock (Opalinus Clay): diffusion perpendicular to the fabric

Cited by 105 publications

References 11 publications

Biogeochemical processes in a clay formation in situ experiment: Part B – Results from overcoring and evidence of strong buffering by the rock formation

Biogeochemical processes in a clay formation in situ experiment: Part B – Results from overcoring and evidence of strong buffering by the rock formation

Comparison of modeling methods for the determination of effective porosities and diffusion coefficients in through‐diffusion tests

Suitability of various materials for porous filters in diffusion experiments

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