Radioiodine (¹²⁹I) poses a potential risk to human health and the environment at several U.S. Department of Energy sites, including the Hanford Site, located in southeastern Washington State. Experimental studies and numerical modeling were performed to provide a technical basis for field-scale modeling of iodine sorption and transport behavior. The experiments were carried out using six columns of repacked contaminated sediments from the Hanford Site. Although iodate has been determined to be the dominant iodine species at the Hanford Site, the sorption and transport behaviors of different iodine species were investigated in a series of column experiments by first leaching sediments with artificial groundwater (AGW) followed by AGW containing iodate (IO₃^–), iodide (I^–), or organo-iodine (2-iodo-5-methoxyphenol, C₇H₇IO₂). Ferrihydrite amendments were added to the sediments for three of the columns to evaluate the impact of ferrihydrite on ¹²⁹I attenuation. The results showed that ferrihydrite enhanced the iodate sorption capacity of the sediment and retarded the transport but had little effect on iodide or organo-I, providing a technical basis for developing a ferrihydrite-based remedial strategy for iodate under oxidizing conditions. Data from the column transport experiments were modeled using the linear equilibrium Freundlich isotherm model, the kinetic Langmuir adsorption model, and a distributed rate model. Comparisons of the experimental data and modeling results indicated that sorption was best represented with the distributed rate model with rates and maximum sorption extents varying by iodine species and ferrihydrite treatment. However, the linear Freundlich isotherm (K_d) model was also found to fit the laboratory experimental data relatively well, suggesting that the K_d model could also be used to represent iodine transport at the field scale.

中文翻译：

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汉福德沉积物中放射性碘吸附和传输的实验和数值研究

放射性碘 ( ¹²⁹ I) 对美国能源部的多个站点（包括位于华盛顿州东南部的汉福德站点）的人类健康和环境构成潜在风险。进行了实验研究和数值模拟，为碘吸附和传输行为的现场尺度模拟提供了技术基础。实验是使用来自汉福德遗址的六列重新填充的污染沉积物进行的。尽管碘酸盐已被确定为汉福德遗址的主要碘物种，但通过一系列柱实验研究了不同碘物种的吸附和传输行为，首先用人工地下水（AGW）浸出沉积物，然后用含有碘酸盐的AGW（IO ₃ ^– )、碘化物(I ^– )或有机碘(2-碘-5-甲氧基苯酚，C ₇ H ₇ IO ₂ )。将水铁矿修正物添加到三个柱的沉积物中，以评估水铁矿对¹²⁹ I 衰减的影响。结果表明，水铁矿增强了沉积物对碘酸盐的吸附能力并延缓了迁移，但对碘化物或有机碘影响不大，为开发氧化条件下基于水铁矿的碘酸盐修复策略提供了技术基础。使用线性平衡 Freundlich 等温线模型、动力学 Langmuir 吸附模型和分布速率模型对柱传输实验的数据进行建模。实验数据和建模结果的比较表明，吸附最好用分布式速率模型来表示，其中速率和最大吸附程度因碘种类和水铁矿处理而异。然而，线性弗罗因德利希等温线（K _d）模型也被发现与实验室实验数据拟合得相对较好，这表明K _d模型也可用于表示现场尺度的碘传输。