不同湿度下辐照怀俄明型膨润土中天然有机物的特征

IF 3.1 3区 地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS
C.M. James Neurauter , Nivetha Srikanthan , Huan Tong , Mehran Behazin , Myrna J. Simpson
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引用次数: 0

摘要

怀俄明型膨润土(MX-80;美国怀俄明州)将用于加拿大废核燃料长期贮存的深层地质贮存库(DGR)。膨润土中的天然有机物(NOM)可能会成为微生物的营养源,并有可能影响废燃料容器的性能。以前的调查表明,NOM 在 MX-80 中的浓度很低,并且已经发生了广泛的成岩变化,但对模拟 DGR 条件下的 NOM 化学性质了解有限。特别值得关注的是,由于怀俄明型膨润土中存在由水辐射分解产生的活性物质,伽马辐射可能会改变 NOM 的溶解和反应性。在这项研究中,在不同的湿度水平(20%、40%、60%和 80%)和室温条件下,采用互补的分子水平技术,对总伽马辐射剂量为 100 kGy(1.08 kGy/h,93 h)的 NOM 化学性质进行了研究。经过处理的样品显示出相对较低的总有机碳浓度(0.074-0.232%),没有证据表明总碳、有机碳和无机碳浓度有任何重大变化。固态 13C NMR 光谱检测到辐照后固相 NOM 化学成分没有变化。在水分含量为 80% 的情况下,NOM 的溶解度随辐照的增加而显著提高,这表明较高的水饱和度可能会提高溶解有机物(DOM)的产量。溶液状态下的 1H 核磁共振(NMR)和紫外可见光分析并未发现 DOM 成分有任何显著差异。更灵敏的定向化合物分析表明,在较低的含水量水平(20% 和 40%)下,正构烷醇的总浓度明显下降。一些单个化合物的浓度在毫微克级也有显著差异,包括在水分含量较高(60% 和 80%)时的正二十八烷醇和几种正烷酸。这些发现表明,在拟议的 DGR 的预期初始条件下,MX-80 中的大部分 NOM 仍保持化学稳定。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Characterization of natural organic matter in Wyoming-type bentonites irradiated at varied moisture levels

Wyoming-type bentonite clay (MX-80; Wyoming, USA) will be used in a deep geological repository (DGR) for the long-term storage of used nuclear fuel in Canada. The natural organic matter (NOM) found in bentonite may serve as a microbial nutrient source and potentially compromise the performance of the used fuel containers. Previous investigations indicate that NOM is present in low concentrations in MX-80 and has undergone extensive diagenetic alteration, though limited knowledge is available regarding NOM chemistry under simulated DGR conditions. Of particular concern is the possibility for gamma-radiation to alter NOM dissolution and reactivity due to the presence of reactive species generated by water radiolysis in Wyoming-type bentonites. In this study, NOM chemistry was investigated using complementary molecular-level techniques following exposure to a total gamma-radiation dose of 100 kGy (1.08 kGy/h for 93 h) at varied moisture levels (20%, 40%, 60% and 80%) and room temperature. Treated samples exhibited relatively low total organic carbon concentrations (0.074–0.232%), with no evidence of any major changes in total, organic, and inorganic carbon concentrations. Solid-state 13C NMR spectroscopy detected no changes in solid-phase NOM chemistry after irradiation. Solubilization of NOM increased significantly with radiation exposure at 80% moisture, suggesting higher levels of water saturation may enhance dissolved organic matter (DOM) production. Solution-state 1H nuclear magnetic resonance (NMR), and UV–Vis analyses did not identify any significant differences in DOM composition. More sensitive, targeted compound analysis revealed significant decreases in total n-alkanol concentration at lower moisture content levels (20% and 40%). Several individual compound concentrations also differed significantly at the nanogram-level, including n-octacosanol and several n-alkanoic acids at elevated moisture levels (60% and 80%). These findings suggest the majority of NOM in MX-80 remains chemically stable under the anticipated initial conditions of the proposed DGR.

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来源期刊
Applied Geochemistry
Applied Geochemistry 地学-地球化学与地球物理
CiteScore
6.10
自引率
8.80%
发文量
272
审稿时长
65 days
期刊介绍: Applied Geochemistry is an international journal devoted to publication of original research papers, rapid research communications and selected review papers in geochemistry and urban geochemistry which have some practical application to an aspect of human endeavour, such as the preservation of the environment, health, waste disposal and the search for resources. Papers on applications of inorganic, organic and isotope geochemistry and geochemical processes are therefore welcome provided they meet the main criterion. Spatial and temporal monitoring case studies are only of interest to our international readership if they present new ideas of broad application. Topics covered include: (1) Environmental geochemistry (including natural and anthropogenic aspects, and protection and remediation strategies); (2) Hydrogeochemistry (surface and groundwater); (3) Medical (urban) geochemistry; (4) The search for energy resources (in particular unconventional oil and gas or emerging metal resources); (5) Energy exploitation (in particular geothermal energy and CCS); (6) Upgrading of energy and mineral resources where there is a direct geochemical application; and (7) Waste disposal, including nuclear waste disposal.
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