The use of an aqueous reductant (Na-dithionite) with pH buffer (K-carbonate, pH 12) was evaluated in this laboratory study as a potential remedial approach for removing Fe oxide associated iodine and enhancing pump-and-treat extraction from iodine-contaminated sediments in the unconfined aquifer in the 200 West Area of the Hanford Site. X-ray fluorescence data of untreated sediment indicated that iodine was largely associated with Fe (i.e., potentially incorporated into Fe oxides), but XANES data was inconclusive as to valence state. During groundwater leaching, aqueous and adsorbed iodine was quickly released, then additional iodine was slowly released potentially from slow dissolution of one or more surface phases. The Na-dithionite treatment removed greater iodine mass (2.9x) at a faster rate (1-4 orders of magnitude) compared to leaching with groundwater alone. Iron extractions for untreated and treated sediments showed a decrease in Fe(III)-oxides, which likely released iodine to aqueous solution. Solid phase inorganic carbon and aqueous Ca and Mg analysis further confirmed that significant calcite dissolution did not occur in these experiments meaning these phases did not release significant iodine. Although it was expected that, after treatment, 127I concentrations would eventually be lower than untreated sediments, continued, elevated iodine concentrations for treated samples over 750 h were observed for leaching experiments. Stop flow events during 1-D column leaching suggested that some iodide precipitated within the first few pore volumes. Further, batch extraction experiments compared iodine-129/127 removal and showed that iodine-129 was more readily removed than iodine-127 suggesting that the two are present in different phases due to their different origins. Although significantly greater iodine is removed with treatment, the long-term leaching needs to be investigated further as it may limit dithionite treatment at the field scale.

中文翻译：

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原位还原溶解从含水层沉积物中去除Iodine-129。

在此实验室研究中，评估了使用带有pH缓冲液（碳酸钾，pH 12）的水性还原剂（连二亚硫酸钠）作为去除Fe氧化物相关碘并增强从碘中抽提的潜在补救方法。汉福德遗址西区200号无限制含水层中被污染的沉积物。未经处理的沉积物的X射线荧光数据表明，碘与Fe大量相关（即可能掺入Fe氧化物中），但XANES数据对于价态尚无定论。在地下水浸出过程中，含水碘和吸附的碘迅速释放，然后缓慢释放出一个或多个表面相，从而缓慢释放出额外的碘。连二亚硫酸钠处理去除了更多的碘（2。与仅使用地下水进行淋洗相比，速度提高了（9x）（1-4个数量级）。未处理和处理过的沉积物的铁提取物显示出Fe（III）-氧化物的减少，这很可能将碘释放到水溶液中。固相无机碳以及Ca和Mg水溶液的分析进一步证实，在这些实验中未发生方解石的明显溶解，这意味着这些相不会释放出明显的碘。尽管可以预期，在处理后，127I浓度最终将低于未处理的沉积物，但在浸出实验中，观察到在750 h内持续观察到碘浓度升高。一维柱浸出过程中的停止流动事件表明，在最初的几个孔体积内沉淀了一些碘化物。进一步，分批提取实验比较了碘129/127的去除效果，并显示碘129比碘127更容易去除，这表明两者由于其来源不同而存在于不同的相中。尽管通过处理去除了明显更高的碘，但是仍需要进一步研究长期浸出，因为这可能会限制田间规模的连二亚硫酸盐处理。