Assessing the reactions of iodine (I) in soil is critical to evaluate radioiodine exposure and understand soil-to-crop transfer rates. Our mechanistic understanding has been constrained by method limitations in assessing the dynamic interactions of iodine between soil solution and soil solid phase over short periods (hours). We use microdialysis to passively extract soil solution spiked with radioiodine (129I- and 129IO3-) to monitor short-term (≤40 h) in situ fixation and speciation changes. We observed greater instantaneous adsorption of 129IO3- compared to 129I- in all soils and the complete reduction of 129IO3- to 129I- within 5 h of addition. Loss of 129I from solution was extremely rapid; the average half-lives of 129I- and 129IO3- in soil solution were 4.06 and 10.03 h, respectively. We detected the presence of soluble organically bound iodine (org-129I) with a low molecular weight (MW) range (0.5-5 kDa) in all soils and a slower (20-40 h) time-dependent formation of larger MW org-I compounds (12-18 kDa) in some samples. This study highlights the very short window of immediate availability in which I from rainfall or irrigation remains in soil solution and available to crops, thus presenting significant challenges to phytofortification strategies in soil-based production systems.

中文翻译：

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土壤溶液中的短期碘动力学。

评估土壤中碘（I）的反应对于评估放射性碘的暴露和了解土壤到作物的转移速率至关重要。在评估短时间内（小时）土壤溶液和土壤固相之间碘的动态相互作用时，方法的局限性限制了我们对机理的理解。我们使用微渗析法被动提取掺有放射性碘（129I-和129IO3-）的土壤溶液，以监测短期（≤40 h）原位固定和形态变化。我们观察到在所有土壤中129IO3-的瞬时吸附均高于129I-，并且在添加后5小时内将129IO3-完全还原为129I-。解决方案中的129I损失非常迅速；土壤溶液中129I-和129IO3-的平均半衰期分别为4.06和10.03 h。我们检测到在所有土壤中均存在低分子量（MW）范围（0.5-5 kDa）的可溶性有机结合碘（org-129I），较大的MW org-在某些样品中，I化合物（12-18 kDa）。这项研究突出了立即可用的窗口非常短，降雨或灌溉中的I仍然保留在土壤溶液中并可供农作物使用，因此对基于土壤的生产系统中的植物强化策略提出了重大挑战。