DEN-Service d'Etude du Comportement des Radionucléides (SECR), CEA, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France.
DEN-Service d'Etude du Comportement des Radionucléides (SECR), CEA, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France.
Chemosphere. 2018 Dec;213:472-480. doi: 10.1016/j.chemosphere.2018.09.064. Epub 2018 Sep 14.
The transport of emerging organic contaminants through the geosphere is often an environmental issue. The sorption of organic compounds slows their transport in soils and porous rocks and retardation is often assessed by extrapolation of batch experiments. However, transport experiments are preferable to strengthen migration data and modelling. In this context, we evaluated the adsorption of various organic acids by means of through-diffusion experiments in a sedimentary clay-rich rock (Callovo-Oxfordian, East of Paris Basin, France). A low diffusivity of organic anions was quantified with effective diffusion coefficients, D, ranged between 0.5 and 7 10 m s. These values indicated an organic anion exclusion. As for chloride, the porosity accessible to organic anions was lower than that of water: ε(organic anions) < ε(water). The partial exclusion of organic anions from rock porosity was linked to both charge and size effects. A significant retardation was observed for organic anions such as oxalate, citrate or α-isosaccharinate. Yet, retardation measured by diffusion experiments was significantly lower than expected from batch experiments on crushed samples. An empirical correction factor is proposed to account for a possible decrease of retardation with accessible porosity of diffusing solute. This feature has significant implications for the estimation of migration parameters of organic compounds in the environment.
新兴有机污染物在地质环境中的迁移通常是一个环境问题。有机化合物的吸附会减缓它们在土壤和多孔岩石中的迁移，而滞后通常通过批量实验的外推来评估。然而，为了加强迁移数据和模型的建立，进行传输实验是更好的选择。在这种情况下，我们通过在沉积粘土丰富的岩石（法国巴黎盆地东部的卡洛夫-牛津阶）中进行的贯穿扩散实验来评估各种有机酸的吸附。通过有效扩散系数 D 来量化有机阴离子的低扩散率，其范围在 0.5 到 7×10-9 m2 s-1 之间。这些值表明有机阴离子被排斥。与氯化物一样，有机阴离子可及的孔隙度低于水：ε（有机阴离子）<ε（水）。有机阴离子从岩石孔隙中部分排除与电荷和大小效应有关。草酸盐、柠檬酸盐或α-异蔗糖酸盐等有机阴离子表现出明显的滞后现象。然而，扩散实验测量的滞后现象明显低于粉碎样品的批量实验预期。提出了一个经验修正因子，以解释扩散溶质可及孔隙度对滞后的可能降低。这一特性对环境中有机化合物迁移参数的估计具有重要意义。
