The Zuckerburg Institute for Water Research, The Jacob Blaustein Institutes for Desert Studies, Ben Gurion University of the Negev, Midreshet Ben Gurion 84990, Israel.
Geological Survey of Israel, Jerusalem 9550161, Israel.
Sci Total Environ. 2018 Dec 1;643:260-269. doi: 10.1016/j.scitotenv.2018.06.162. Epub 2018 Jun 22.
In the context of geological disposal of radioactive waste, one of the controlling mechanisms for radionuclide migration through subsurface strata is sorption to mobile colloidal bentonite particles. Such particles may erode from the repository backfill or bentonite buffer and yield measurable (0.01-0.1 g/L) concentrations in natural groundwater. The extent of sorption is influenced by colloid concentration, ionic strength, radionuclide concentration, and the presence of competing metals. Uranium (VI) and cesium sorption to bentonite colloids was investigated both separately and together in low ionic strength (2.20 mM) artificial rainwater (ARW) and high ionic strength (169 mM) artificial groundwater (AGW; representative of a fractured carbonate rock aquitard). Sorption experiments were conducted as a factor of colloid concentration, initial metal concentration and opposing metal presence. It was shown that both U(VI) and Cs sorption were significantly reduced in AGW in comparison to ARW. Additionally, the sorption coefficient K of both metals was found to decrease with increasing colloid concentration. Competitive sorption experiments indicated that at high colloid concentration (1-2 g/L), Cs sorption was reduced in the presence of U(VI), and at low colloid concentration (0.01-0.5 g/L), both Cs and U(VI) Ks were reduced when they were present together due to competition for similar sorption sites. The results from this study imply that in brackish carbonate rock aquifers, typical of the Israeli northern Negev Desert, both U(VI) and Cs are more likely to be mobile as dissolved species rather than as colloid-associated solids.
在放射性废物的地质处置中，放射性核素通过地下地层迁移的控制机制之一是被可移动的胶体膨润土颗粒吸附。这些颗粒可能会从储存库回填物或膨润土缓冲层中侵蚀出来，并在天然地下水中产生可测量的（0.01-0.1g/L）浓度。吸附程度受胶体浓度、离子强度、放射性核素浓度和竞争金属的存在影响。分别和一起在低离子强度（2.20mM）人工雨水（ARW）和高离子强度（169mM）人工地下水（AGW；代表断裂碳酸盐岩含水层）中研究了铀（VI）和铯对膨润土胶体的吸附。吸附实验是作为胶体浓度、初始金属浓度和相反金属存在的因素进行的。结果表明，与 ARW 相比，AGW 中的 U(VI)和 Cs 吸附均显著降低。此外，还发现两种金属的吸附系数 K 随着胶体浓度的增加而降低。竞争吸附实验表明，在高胶体浓度（1-2g/L）下，当存在 U(VI)时，Cs 的吸附会减少，而在低胶体浓度（0.01-0.5g/L）下，当它们同时存在时，由于对相似的吸附位点的竞争，Cs 和 U(VI)的 Ks 都会减少。本研究的结果表明，在以色列北部内盖夫沙漠典型的咸碳酸盐岩含水层中，U(VI)和 Cs 更有可能作为溶解态物质而不是胶体相关固体迁移。
