Université Paris-Saclay, CEA, Service d'Etude du Comportement des Radionucléides, 91191 Gif-sur Yvette, France; Géosciences Montpellier, CNRS-INSU - Montpellier University, 34095 Montpellier Cedex 5, France.
Université Paris-Saclay, CEA, Service d'Etude du Comportement des Radionucléides, 91191 Gif-sur Yvette, France.
J Contam Hydrol. 2022 Jun;248:103989. doi: 10.1016/j.jconhyd.2022.103989. Epub 2022 Mar 14.
Diffusion is the main transport process of water and solutes in clay-rich porous media owing to their very low permeability, so they are widely used as barriers against contaminant spreading. However, the prediction of contaminant mobility can be very complicated when these media are partially water-saturated. We conducted diffusion experiments for water (HTO and HDO) and ions (Na and I) through partially water saturated compacted kaolinite, a weakly charged clay material, to quantify the distinct diffusive behavior of these species. The osmosis method was used to set kaolinite samples at 67, 86 and 100% saturation. The results showed that desaturation led to a sharp decrease in diffusive rates by factors of 6.5, 18 and 35 for HTO, I and Na, respectively, from 100 to 67% of the degree of saturation. Thus, to interpret water diffusivities, we proposed a model taking into account the diffusion of water in both gas and liquid phases, using diffusion data obtained for ions, considered as inert species. This model was capable of properly predicting water diffusive flux, especially at a low degree of saturation (67% saturation), for which the assumption made for the occurrence of air phase continuity throughout the sample appears to be more relevant than at 86% saturation.
扩散是水和溶质在富粘土多孔介质中的主要传输过程，因为其渗透率非常低，所以它们被广泛用作防止污染物扩散的屏障。然而，当这些介质部分水饱和时，预测污染物的迁移能力可能会非常复杂。我们通过部分水饱和的压实高岭石进行了水（HTO 和 HDO）和离子（Na 和 I）的扩散实验，以量化这些物质的独特扩散行为。渗透压法将高岭石样品设置在 67%、86%和 100%饱和度下。结果表明，饱和度从 100%降至 67%时，HTO、I 和 Na 的扩散速率分别急剧下降了 6.5、18 和 35 倍。因此，为了解释水的扩散系数，我们提出了一个模型，该模型考虑了气相和液相中的水扩散，使用了离子的扩散数据，这些离子被认为是惰性物质。该模型能够很好地预测水的扩散通量，特别是在饱和度较低（67%饱和度）的情况下，这一假设对于样品中整个空气相连续性的出现似乎比在 86%饱和度时更为相关。
