Diffusive parameters of tritiated water and uranium in chalk

Descostes, Michaël; Pili, Éric; Felix, O.; Frasca, B.; Radwan, J.; Juery, A.

doi:10.1016/j.jhydrol.2012.05.018

Cited by 10 publications

(13 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The Fickian diffusion coefficients D d selected here are listed in Table 1. These values of D d are generally similar to those reported in other chalk diffusion studies; 28,32 however, the D d value for Silurian dolomite is an order of magnitude higher than "usual" estimates, further illustrating a deviation from expected Fickian diffusion. 45 The plots in Figure 3 show that varying the value of D d in the Fickian BTC (i) controls the duration until the first arrival of tracer�in this case, seen as first values of log 10 (1 − C/C 0 ) < 0�as well as (ii) the rate of transition as the long-time tail falls to a slope of −0.5.…”

Section: ■ Results and Discussionsupporting

confidence: 86%

“…With these assumptions, a limited number of experimental measurements to estimate the actual values of D d have been reported. These experiments generally involve the use of a diffusion cell in which a section of (water-saturated) porous rock, often a cylindrical core of diameter 25–75 mm and thickness 7–25 mm is sandwiched between inlet and outlet reservoirs of liquid; − at the start of an experiment, the inlet reservoir liquid contains an inert chemical tracer (e.g., bromide) with a specified concentration C 0 , while the initial concentration in the outlet reservoir and in the section of fully liquid saturated porous rock is C = 0.…”

Section: Introductionmentioning

confidence: 99%

“…Analytical solutions of Fick’s law are “most convenient” when considering diffusion along a semi-infinite domain, wherein the outlet plane is sufficiently far from the inlet reservoir such that C = 0 even at very long times. However, the small dimensions of the experimental setups described above enable the outlet concentration to increase significantly, e.g., up to C / C 0 = 0.65, while the inlet reservoir concentration decreases accordingly, over experiment durations of ∼30–100 days. ,,, Fitting the BTCs measured in such situations requires the use of (nonsemi-infinite boundary condition) solutions that account for the evolving equilibration between inlet and outlet …”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Diffusion in Porous Rock Is Anomalous

Rajyaguru,

Metzler,

Dror

et al. 2024

Environ. Sci. Technol.

View full text Add to dashboard Cite

Molecular diffusion of chemical species in subsurface environmentsrock formations, soil sediments, marine, river, and lake sedimentsplays a critical role in a variety of dynamic processes, many of which affect water chemistry. We investigate and demonstrate the occurrence of anomalous (non-Fickian) diffusion behavior, distinct from classically assumed Fickian diffusion. We measured molecular diffusion through a series of five chalk and dolomite rock samples over a period of about two months. We demonstrate that in all cases, diffusion behavior is significantly different than Fickian. We then analyze the results using a continuous time random walk framework that can describe anomalous diffusion in heterogeneous porous materials such as rock. This methodology shows extreme long-time tailing of tracer advance as compared to conventional Fickian diffusion processes. The finding that distinct anomalous diffusion occurs ubiquitously implies that diffusion-driven processes in subsurface zones should be analyzed using tools that account for non-Fickian diffusion.

show abstract

Section: ■ Results and Discussionsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Diffusion in Porous Rock Is Anomalous

Rajyaguru,

Metzler,

Dror

et al. 2024

Environ. Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…The effective diffusion coefficient of tritiated water in the Champagne chalk has been measured in the laboratory: 4.0×10 −10 m 2 .s −1 for a porosity around 40% (Descostes et al, 2009). …”

Section: Hydrogeological Parametersmentioning

confidence: 99%

Reactive transport modelling of groundwater chemistry in a chalk aquifer at the watershed scale

Mangeret

Windt

Crançon

2012

Journal of Contaminant Hydrology

View full text Add to dashboard Cite

“…Notwithstanding the above, the Chalk aquifer is still far too often visualized as a homogeneous porous medium (Brenner et al, 2018), rather than a karstic aquifer. Only a few studies have considered the role of lithological heterogeneity and stratigraphical discontinuities on groundwater flow (Descostes et al, 2012;Gallagher et al, 2012;Barhoum et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Stratigraphical influence on chalk cave development in Upper Normandy, France: implications for chalk hydrogeology

Ballesteros¹,

Farrant²,

Nehmé³

et al. 2020

IJS

View full text Add to dashboard Cite

Classically, the Upper Cretaceous Chalk Group aquifer of northwest Europe is conceptualized as a homogenous dual-porosity aquifer, with high porosity related to its fine-grained porous matrix, and intermediate hydraulic conductivity associated with fractures. However, an increasing number of hydrological studies visualize the Chalk as a heterogeneous karst aquifer due to the localised presence of dissolutionally enlarged conduits. Field investigation suggests that cave development is guided by distinct stratigraphical and tectonic discontinuities within the rock mass. Identifying which potential inception horizons within the Chalk aquifer are favoured, and why, is important for developing future robust conceptual models of groundwater behaviour. This study focusses on the Chalk of the Upper Normandy region in France where karstic conduits are common and are linked to major sources of groundwater for public water supply. We analyse the geometry and geomorphology of six chalk caves exposed in the Seine Valley with an aggregated length of over 5.7 km, along with other caves in southern England, and identify the key inception horizons associated with their development. The data shows that prominent Turonian, Coniacian and Santonian hardgrounds have influenced the development of 68% of the studied caves length, with sheet-flints and marl seams also playing a prominent role. Caves developed on or between hardgrounds typically display a complex interlinked anastomotic passage network, whereas passages subjected to paragenetic conditions caused by a high sediment flux tend to be concentrated into fewer, larger conduits. The new evidence from Normandy and Southern England demonstrates the role of lithostratigraphy, and in particular stratigraphical discontinuities on conduit development. The data reinforces the idea that the Chalk aquifer should be viewed as a heterogeneous triple porosity karstic aquifer, in which conduit development is influenced by key stratigraphical discontinuities. This improved conceptual model can be used to develop better groundwater flow models and improved catchment delineation.

show abstract

Diffusive parameters of tritiated water and uranium in chalk

Cited by 10 publications

References 46 publications

Diffusion in Porous Rock Is Anomalous

Diffusion in Porous Rock Is Anomalous

Reactive transport modelling of groundwater chemistry in a chalk aquifer at the watershed scale

Stratigraphical influence on chalk cave development in Upper Normandy, France: implications for chalk hydrogeology

Contact Info

Product

Resources

About