The Zuckerburg Institute for Water Research, The Jacob Blaustein Institutes for Desert Studies, Ben Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben Gurion, 8499000, Israel.
Nuclear Research Center of the Negev, Negev, PO Box 9001, Beer Sheva, 84190, Israel.
Water Res. 2016 Sep 1;100:88-97. doi: 10.1016/j.watres.2016.04.075. Epub 2016 May 7.
Colloid facilitated transport of radionuclides has been implicated as a major transport vector for leaked nuclear waste in the subsurface. Sorption of radionuclides onto mobile carrier colloids such as bentonite and humic acid often accelerates their transport through saturated rock fractures. Here, we employ column studies to investigate the impact of intrinsic, bentonite and humic acid colloids on the transport and recovery of Ce(III) through a fractured chalk core. Ce(III) recovery where either bentonite or humic colloids were added was 7.7-26.9% Ce for all experiments. Greater Ce(III) recovery was observed when both types of carrier colloids were present (25.4-37.4%). When only bentonite colloids were present, Ce(III) appeared to be fractionated between chemical sorption to the bentonite colloid surfaces and heteroaggregation of bentonite colloids with intrinsic carbonate colloids, precipitated naturally in solution. However, scanning electron microscope (SEM) images and colloid stability experiments reveal that in suspensions of humic acid colloids, colloid-facilitated Ce(III) migration results only from the latter attachment mechanism rather than from chemical sorption. This observed heteroaggregation of different colloid types may be an important factor to consider when predicting potential mobility of leaked radionuclides from geological repositories for spent fuel located in carbonate rocks.
胶粒的运移促进了放射性核素的迁移，这被认为是地下渗漏核废料的主要迁移载体。放射性核素被诸如膨润土和腐殖酸之类的可动载体胶体吸附通常会加速它们通过饱和岩石裂缝的迁移。在这里，我们通过柱实验研究了内在胶体、膨润土胶体和腐殖酸胶体对放射性铈（Ce(III)）通过破裂白垩岩心的迁移和回收的影响。在所有实验中，添加膨润土或腐殖酸胶体时，Ce(III)的回收率为 7.7-26.9% Ce。当两种载体胶体都存在时，Ce(III)的回收率更高（25.4-37.4%）。当仅存在膨润土胶体时，Ce(III)似乎在膨润土胶体表面的化学吸附和膨润土胶体与天然存在于溶液中的内在碳酸盐胶体的异质聚集之间进行了分配。然而，扫描电子显微镜（SEM）图像和胶体稳定性实验表明，在腐殖酸胶体悬浮液中，胶体促进的 Ce(III)迁移仅源于后一种附着机制，而不是源于化学吸附。当预测位于碳酸盐岩中的乏燃料地质处置库中泄漏放射性核素的潜在迁移性时，这种不同胶体类型的异质聚集可能是一个需要考虑的重要因素。
