Emerging investigator series: a holistic approach to multicomponent EXAFS: Sr and Cs complexation in clayey soils,Environmental Science: Processes & Impacts

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Emerging investigator series: a holistic approach to multicomponent EXAFS: Sr and Cs complexation in clayey soils
Environmental Science: Processes & Impacts ( IF 4.3 ) Pub Date : 2021-06-21 , DOI: 10.1039/d1em00121c
Pieter Bots ₁ , M Josick Comarmond , Timothy E Payne , Katharina Gückel , Rebecca J Lunn , Luca Rizzo , Alexandra E P Schellenger , Joanna C Renshaw

Affiliation

Strontium and caesium are fission products of concern at many nuclear legacy sites and Cs is additionally a significant consideration at sites in the aftermath of nuclear accidents and incidents. Such sites require long-term management to minimize the risk of such contaminants to the environment and the public. Understanding the geochemical speciation of Sr and Cs in situ in the soils and groundwater is essential to develop engineered management strategies. Here we developed and utilized a comprehensive approach to fitting the EXAFS of Sr and Cs adsorption to single mineral phases and a composite clayey soil. First, a shell-by-shell fitting strategy enabled us to determine that Sr surface complexes involve the formation of bidentate edge sharing complexes with anatase and illite-smectite, and form at the silicon vacancy sites at the kaolinite basal surfaces. Cs surface complexes form at the silicon vacancy sites at the illite-smectite and kaolinite basal surfaces. Second, using a subsequent holistic approach we determined the predominance of these complexes within a composite clayey soil. Sr was dominated by complexation with illite-smectite (72–76%) and to a lesser extent with kaolinite (25–30%) with negligible complexation with anatase, while Cs complexed roughly equally to both illite-smectite and kaolinite. The presented approach to fitting EXAFS spectra will strengthen predictive modelling on the behaviour of elements of interest. For example, the details on Sr and Cs speciation will enable predictive modelling to characterise their long-term behaviour and the design and validation of evidence-based engineering options for long-term management of nuclear legacy sites.

中文翻译：

新兴研究者系列：多组分 EXAFS 的整体方法：粘土质土壤中的 Sr 和 Cs 络合

锶和铯是许多核遗留场址关注的裂变产物，Cs 也是核事故和事故后场址的重要考虑因素。此类场地需要长期管理，以尽量减少此类污染物对环境和公众的风险。原位了解 Sr 和 Cs 的地球化学形态在土壤和地下水中，对于制定工程管理策略至关重要。在这里，我们开发并利用了一种综合方法将 Sr 和 Cs 吸附的 EXAFS 拟合到单一矿物相和复合粘土。首先，逐壳拟合策略使我们能够确定 Sr 表面复合物涉及与锐钛矿和伊利石-蒙脱石形成双齿边缘共享复合物，并在高岭石基底表面的硅空位处形成。Cs 表面复合物在伊利石-蒙脱石和高岭石基底表面的硅空位处形成。其次，使用随后的整体方法，我们确定了这些复合物在复合粘土中的优势。Sr 主要与伊利石-蒙脱石 (72-76%) 络合，与高岭石 (25-30%) 的络合程度较低，与锐钛矿的络合可忽略不计，而 Cs 与伊利石-蒙脱石和高岭石的络合大致相同。所提出的拟合 EXAFS 光谱的方法将加强对感兴趣元素行为的预测建模。例如，关于 Sr 和 Cs 形态的详细信息将使预测建模能够表征它们的长期行为，以及设计和验证用于核遗产站点长期管理的循证工程选项。

更新日期：2021-06-28

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