Abstract 126Sn is a long-lived fission product and as such a waste relevant radioisotope. Understanding its fate under deep-geological repository conditions is a requirement for a complete safety assessment. Yet, due to a limited knowledge of its hydrogeochemical properties, the solubility and speciation of tin in a nuclear waste repository remain uncertain. In Belgium, Boom Clay (BC) is investigated as a potential host rock. It contains a significant amount of dissolved organic matter (DOM), which was shown to strongly influence the mobility of several radionuclides and notably of tetravalent actinides. By chemical analogy, the speciation, sorption and mobility of Sn(IV) in BC is also assumed to be controlled by its binding to DOM. However, the Sn-DOM complexation was never quantified in relevant repository conditions. In this work, the complexation of Sn with BC DOM was investigated under present-day BC conditions and in synthetic seawater as representative of more saline conditions. The ultrafiltration technique was used to quantify the amount of Sn bound to DOM. The two investigated repository conditions yielded nearly identical binding constants, evidencing a low influence of salinity on the level of binding of Sn to BC DOM. BC DOM forms strong complexes with Sn that would significantly increase Sn solubility in BC pore waters. The investigated range of Sn and DOM concentration (DOMtot/Sntot = 2.8 × 102 to 5.7 × 103)also showed that the binding constants are dependent on the metal loading (5.0

中文翻译：

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储存库条件下 Sn 与 Boom Clay 天然有机物的络合

摘要 126Sn 是一种长寿命裂变产物，因此是一种与废物相关的放射性同位素。了解其在深层地质处置库条件下的命运是完整安全评估的必要条件。然而，由于对其水文地球化学特性的了解有限，锡在核废料储存库中的溶解度和形态仍然不确定。在比利时，Boom Clay (BC) 被调查为潜在的主岩。它含有大量溶解有机物 (DOM)，已证明这会强烈影响几种放射性核素的迁移率，尤其是四价锕系元素的迁移率。通过化学类比，也假设 BC 中 Sn(IV) 的形态、吸附和迁移率受其与 DOM 的结合控制。然而，Sn-DOM 络合从未在相关存储库条件下量化。在这项工作中，Sn 与 BC DOM 的络合在当今的 BC 条件下和在合成海水中作为更多盐分条件的代表进行了研究。超滤技术用于量化与 DOM 结合的锡量。两个研究的储存库条件产生了几乎相同的结合常数，证明盐度对 Sn 与 BC DOM 结合水平的影响很小。BC DOM 与 Sn 形成强复合物，这将显着增加 Sn 在 BC 孔隙水中的溶解度。Sn 和 DOM 浓度的研究范围（DOMtot/Sntot = 2.8 × 102 到 5.7 × 103）也表明结合常数取决于金属负载（5.0 超滤技术用于量化与 DOM 结合的锡量。两个研究的储存库条件产生了几乎相同的结合常数，证明盐度对 Sn 与 BC DOM 结合水平的影响很小。BC DOM 与 Sn 形成强复合物，这将显着增加 Sn 在 BC 孔隙水中的溶解度。Sn 和 DOM 浓度的研究范围（DOMtot/Sntot = 2.8 × 102 到 5.7 × 103）也表明结合常数取决于金属负载（5.0 超滤技术用于量化与 DOM 结合的锡量。两个研究的储存库条件产生了几乎相同的结合常数，证明盐度对 Sn 与 BC DOM 结合水平的影响很小。BC DOM 与 Sn 形成强复合物，这将显着增加 Sn 在 BC 孔隙水中的溶解度。Sn 和 DOM 浓度的研究范围（DOMtot/Sntot = 2.8 × 102 到 5.7 × 103）也表明结合常数取决于金属负载（5.0