Determination of I-129 in aerosols using pyrolysis and AgI-AgCl coprecipitation separation and accelerator mass spectrometry measurements
Determination of I-129 in aerosols using pyrolysis and AgI-AgCl coprecipitation separation and accelerator mass spectrometry measurements
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使用热解和 AgI-AgCl 共沉淀分离和加速器质谱测量测定气溶胶中的 I-129
DOI：
10.1039/c8ja00248g
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发表时间：
2018
影响因子：
3.4
通讯作者：
Ning Chen
中科院分区：
文献类型：
--
作者：
Luyuan Zhang;Xiaolin Hou;Yunchong Fu;Miao Fang;Ning Chen
在核事故和核应急期间，空气传播的放射性碘是放射性污染的运输和扩散以及辐射暴露评价的关键问题。关于气溶胶中长寿命的碘的信息对于重建短寿命和高放射性的碘的水平和分布以及了解碘的大气循环至关重要。然而，在远离核污染源的偏远地区，气溶胶129I浓度较低，难以测量。本文采用高温热解和AgI-AgCl共沉淀法分离，结合高灵敏度加速器质谱（AMS）测量，建立了一种测定玻璃纤维过滤器收集的气溶胶中129I的新方法。值得注意的是，尽管对不同碘种的热解行为进行了研究，发现存在差异，但所有的碘都可以定量回收。碘酸盐在500℃以上的温度下分解为碘，从气溶胶中释放出来。热解过程中碘的化学收率为81.5±5.8%。与碱灰化分离与溶剂萃取相结合的方法相比，气溶胶样品中129I的检出限为1.3 × 104原子/ m3，至少将所需的气溶胶样本量减少了三倍。对于在亚洲收集的129I/127I比值为（0.1-10）× 10−9的气溶胶样品，1000 m3空气的体积足以测定129I。该方法用于分析在中国内陆城市西安收集的气溶胶样本。观察到129I浓度范围为（0.38-5.19）× 105原子/ m3, 129I/127I比率为（21.7-252）× 10−10，与福岛核事故前日本和西班牙收集的数据相当，但远低于北欧的数据。
Airborne radioactive iodine is a key concern for the transport and dispersion of radioactive contamination and radiation exposure evaluation during nuclear accidents and nuclear emergency preparedness. Information about long-lived 129I in aerosols is vital for the reconstruction of the level and distribution of short-lived and highly radiotoxic 131I, as well as for understanding the atmospheric cycling of iodine. However, aerosol 129I concentration is difficult to measure due to its low concentration in remote areas, away from nuclear pollution sources. In this study, a novel method for the determination of 129I in aerosols collected on a glass fiber filter was developed using high-temperature pyrolysis and AgI–AgCl coprecipitation for separation coupled with highly sensitive accelerator mass spectrometry (AMS) measurements. It is worth noting that even though the pyrolysis behaviors of various iodine species were investigated and found to be different, all of the iodine can be quantitatively recovered. Iodate was released from the aerosols through its decomposition to iodine at temperatures over 500 °C. The chemical yield of iodine during pyrolysis was 81.5 ± 5.8%. The detection limit for 129I in the aerosol samples was 1.3 × 104 atoms per m3, at least reducing the required aerosol sample size by a factor of three, in contrast to the method using alkaline-ashing separation coupled to solvent extraction. For aerosol samples collected in Asia with 129I/127I ratios of (0.1–10) × 10−9, a volume of 1000 m3 air is sufficient for the determination of 129I. The developed method was used to analyse aerosol samples collected in Xi'an, an inland Chinese city. It is observed that 129I concentrations ranged within (0.38–5.19) × 105 atoms per m3, with 129I/127I ratios of (21.7–252) × 10−10, which are comparable to those collected in Japan before the Fukushima nuclear accident and Spain, while much lower than those observed in Northern Europe.