DEN-Service d'Etude du Comportement des Radionucléides (SECR), CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette, France.
PSL Research University, Chimie ParisTech-CNRS, Institut de Recherche de Chimie Paris, 11 rue Pierre et Marie Curie, F-75005, Paris, France.
Chemosphere. 2017 Aug;181:296-303. doi: 10.1016/j.chemosphere.2017.04.086. Epub 2017 Apr 21.
The release and transport of anthropogenic organic matter through the geosphere is often an environmental criterion of safety. Sedimentary rocks are widely studied in this context as geological barriers for waste management. It is the case of Callovian-Oxfordian claystone (COx), for which several studies report adsorption of anthropogenic organic molecules. In this study, we evaluated and reviewed adsorption data of polar organic molecules on COx claystone. Experiments were performed on raw claystone, decarbonated and clay fractions. Adsorption isotherms were measured with adsorbates of various polarities: adipate, benzoate, ortho-phthalate, succinate, gluconate, oxalate, EDTA, citrate. A significant adsorption was observed for multidentate polycarboxylic acids as evidenced with phthalate, succinate, oxalate, gluconate, EDTA and citrate (R = 1.53, 3.52, 8.4, 8.8, 12.4, 54.7 L kg respectively). Multiple linear regression were performed as a statistical analysis to determine the predictors from these adsorption data. A linear correlation between adsorption data (R) and dipole moment (μ) of adsorbates was evidenced (R = 0.91). Molecules with a high dipole moment, μ(D) > 2.5, displayed a significant adsorption, R≫1 L kg. A qualitative correlation can be easily estimated using the water/octanol partition coefficient, P, of adsorbates (R = 0.77). In this case, two opposite trends were distinguished for polar and apolar molecules. The use of organic carbon content in sediments is relevant for predicting adsorption of apolar compounds, log (P)>+1. The oxides/clays contents may be relevant regarding polar molecules, log (P)<-1. The proposed scheme offers a general methodology for investigation of geo-barriers towards heterogeneous organic plumes.
人为有机物质通过地质圈的释放和传输通常是环境安全的一个标准。在这方面，沉积岩被广泛研究作为废物管理的地质屏障。这正是卡洛维安-牛津粘土岩（COx）的情况，针对该岩石已经有多项研究报告了对人为有机分子的吸附作用。在本研究中，我们评估和回顾了 COx 粘土岩对极性有机分子的吸附数据。实验在原状粘土岩、脱碳酸和粘土部分上进行。使用不同极性的吸附质（己二酸、苯甲酸、邻苯二甲酸、琥珀酸、葡萄糖酸、草酸盐、EDTA、柠檬酸盐）测量了吸附等温线。多齿多羧酸表现出明显的吸附作用，这一点可以从邻苯二甲酸、琥珀酸、草酸盐、葡萄糖酸、EDTA 和柠檬酸盐的实验结果中得到证明（R 值分别为 1.53、3.52、8.4、8.8、12.4 和 54.7 L kg）。作为一种统计分析方法，我们进行了多元线性回归，以从这些吸附数据中确定预测因子。吸附数据（R）与吸附质的偶极矩（μ）之间存在线性相关性（R = 0.91）。具有高偶极矩，μ(D) > 2.5 的分子表现出显著的吸附作用，R≫1 L kg。使用吸附质的水/辛醇分配系数 P 可以很容易地估计出这种定性相关性（R = 0.77）。在这种情况下，对于极性和非极性分子，可以区分出两种相反的趋势。对于非极性化合物，使用沉积物中的有机碳含量预测吸附作用是相关的，log（P）>+1。对于极性分子，氧化物/粘土含量可能是相关的，log（P）<-1。所提出的方案为研究针对非均相有机羽流的地质屏障提供了一种通用方法。
