Subterranean radioiodine contamination at the Hanford Site in Washington State is believed to be present as iodide, iodate, and organo-I species, with iodate being the predominant form. Because these species have different sediment-sorption characteristics, understanding their distribution is important for developing an accurate understanding of iodine migration in the subsurface. Herein, we report a novel, rapid technique for simultaneous iodine speciation (iodide/iodate) and isotopic ratio ( 129 I/ 127 I) measurements using ion chromatography (IC) joined with collision/reaction cell inductively coupled plasma mass spectrometry (ICP-MS), collectively referred to as IC-ICP-MS. This approach employs online dynamically regenerated eluent suppression post chromatographic separation of the samples and collision cell technology, with pure oxygen as a collision gas for the active suppression of 129 Xe (which naturally exists in the argon supplied to the ICP source) to rapidly (< 15 min) achieve precise and reproducible results. Speciated standard reference materials yielded detection limits for 127 I of approximately 23.8 ng/L for iodate and 24.3 ng/L for iodide, and for 129 I of approximately 1.81 ng/L for iodate and 2.62 ng/L for iodide. The method was demonstrated by analyzing groundwater samples from six wells from 129 I-contaminated regions of the Hanford Site; iodate was the primary species for both 127 I and 129 I. Small quantities of 127 I-iodide were also detected in most of the samples, but all 129 I-iodide results were below the detection limit. An interference from molybdenum prevented the estimation of organo-iodine concentrations but did not affect the iodate and iodide results. This new analytical capability will enable rapid, simultaneous characterization of speciated inorganic iodine in vadose zone sediments and groundwater samples at levels below the US federal drinking water standard for 129 I of 1 pCi/L (~ 5.6 ng/L).

中文翻译：

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使用 IC-ICP-MS 评估环境样品中低浓度的碘形态和 129I/127I 比率

华盛顿州汉福德基地的地下放射性碘污染被认为以碘化物、碘酸盐和有机 I 物种的形式存在，其中碘酸盐是主要形式。由于这些物种具有不同的沉积物吸附特性，因此了解它们的分布对于准确了解地下碘迁移非常重要。在此，我们报告了一种使用离子色谱 (IC) 结合碰撞/反应池电感耦合等离子体质谱 (ICP-MS) 同时测量碘形态（碘化物/碘酸盐）和同位素比 ( 129 I/ 127 I) 的新型快速技术)，统称为 IC-ICP-MS。这种方法采用在线动态再生洗脱液抑制后色谱分离样品和碰撞池技术，使用纯氧作为碰撞气体主动抑制 129 Xe（自然存在于供应给 ICP 源的氩气中），以快速（< 15 分钟）获得精确且可重现的结果。特定标准参考物质的 127 I 碘酸盐检测限约为 23.8 ng/L，碘化物检测限为 24.3 ng/L，129 I 碘酸盐检测限约为 1.81 ng/L，碘化物检测限约为 2.62 ng/L。该方法通过分析来自 Hanford Site 的 129 个 I 污染区域的 6 口井的地下水样品进行了验证；碘酸盐是 127 I 和 129 I 的主要物质。在大多数样品中也检测到少量 127 I-碘化物，但所有 129 I-碘化物结果都低于检测限。钼的干扰阻止了有机碘浓度的估计，但不影响碘酸盐和碘化物的结果。这种新的分析能力将能够快速、同时表征包气带沉积物和地下水样品中低于美国联邦饮用水标准的 129 I 1 pCi/L (~ 5.6 ng/L) 中的特定无机碘。