Julia Mitzscherling, Anja M. Schleicher, S. Genderjahn, Marie Bonitz, Dirk Wagner
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引用次数: 0
摘要
由于具有膨胀能力,压实膨润土是高放射性核废料深层地质处置库的合适缓冲材料。然而,这只适用于保持膨胀能力的情况。因此,膨润土必须对不断变化的温度、湿度、渗透流体或微生物活动保持稳定。在批量实验中,我们研究了微生物和热-水-地球化学对未压实膨润土 MX-80 膨胀能力的综合影响。膨润土暴露在不同离子强度的液体和膨润土菌中。在不同的温度和湿度条件下,通过计数菌落形成单位监测细菌的生长情况,同时使用原位 XRD 评估膨润土的膨胀能力。膨润土的存在延长了 S. bentonitica 的存活时间。然而,电子显微镜、X 射线衍射和 ICP-OES 分析表明,膨润土既没有与 S. bentonitica 发生相互作用,其膨胀能力或元素组成也没有发生显著变化。不过,膨胀能力和衍射峰强度受液体离子强度和暴露时间的影响而大大降低。这项研究突出表明,膨润土在不同程度上受到热-水-地球化学和微生物过程的影响,潜在核废料储存库中不同共存因素的复杂性是安全评估中需要考虑的重要因素。
Assessing the Microbial Impact on the Performance of Bentonite Clay at Different Thermo-Hydro-Geochemical Conditions
Because of its swelling capacity, compacted bentonite clay is a suitable buffer material in deep geological repositories for high-level nuclear waste. However, this only applies if the swelling capacity is maintained. Accordingly, bentonites have to be stable to changing temperature, humidity, infiltrating fluids or microbial activity. In batch experiments, we investigated combined microbial and thermo-hydro-geochemical effects on the swelling capacity of uncompacted bentonite MX-80. Bentonite was exposed to fluids of different ionic strength and the bacterium Stenotrophomonas bentonitica. Bacterial growth was monitored by counting colony-forming units while the swelling capacity of bentonite was evaluated using in situ XRD at varied temperatures and humidity. The presence of bentonite prolonged the survival of S. bentonitica. However, electron microscopy, XRD and ICP-OES analyses showed neither an interaction of S. bentonitica with bentonite, nor significant changes in the swelling capacity or element composition. The swelling capacity and diffraction peak intensity were, however, strongly reduced by the ionic strength of the fluid and the exposure time. The study highlights that bentonite is affected by thermo-hydro-geochemical and microbial processes to different degrees and that the complexity of different co-occurring factors in potential nuclear waste repositories is important to consider in safety assessments.