Technical University of Denmark, Department of Environmental Engineering, Risø Campus, Roskilde DK-4000, Denmark.
China Institute of Atomic Energy, Beijing 102413, China.
Anal Chem. 2020 May 5;92(9):6709-6718. doi: 10.1021/acs.analchem.0c00688. Epub 2020 Apr 21.
The atomic ratio of Cs/Cs is a powerful fingerprint for distinguishing the source terms of radioactive contamination and tracing the circulation of water masses in the ocean. However, the determination of the Cs/Cs ratio is very difficult due to the ultratrace level of Cs (<0.02 mBq/m) and Cs (<2 Bq/m) in the ordinary seawater samples. In this work, a sensitive method was developed for determination of Cs concentration and Cs/Cs ratio in seawater using chemical separation combined with thermal ionization mass spectrometry (TIMS) measurement. Cesium was first preconcentrated from seawater using ammonium molybdophosphate-polyacrylonitrile column chromatography and then purified using cation exchange chromatography to remove the interferences. With this method, decontamination factors of 6.0 × 10 for barium and 1800 for rubidium and a chemical yield of more than 60% for cesium were achieved. By using glucose as an activator, the ionization efficiency of cesium was significantly improved to 50.6%, and a constant high current of Cs (20 V) can be maintained for more than 180 min, which ensures sensitive and reliable measurement of low level Cs and Cs. Detection limits of 4.0 × 10 g/L for both Cs and Cs for 200 mL seawater were achieved, which enables the accurate determination of Cs concentration and Cs/Cs ratio in a small volume of seawater samples (<200 mL). The developed method has been validated by analysis of seawater reference material IAEA-443. Seawater samples collected from the Greenland Sea, Baltic Sea, and Danish Straits have been successfully analyzed for Cs concentrations and Cs/Cs ratios, and the results showed that Cs concentrations in the seawater of the Baltic Sea is much higher than that in the Greenland Sea, which is attributed to the high deposition of Chernobyl accident derived radiocesium in the Baltic Sea region.
铯/铯原子比是区分放射性污染源项和追踪海洋水团循环的有力指纹。然而，由于普通海水中铯（<0.02 mBq/m）和铯（<2 Bq/m）的痕量水平，铯/铯比的测定非常困难。在这项工作中，开发了一种使用化学分离结合热电离质谱（TIMS）测量的灵敏方法，用于测定海水中的铯浓度和铯/铯比。首先，使用钼酸铵-聚丙烯腈柱色谱法从海水中预浓缩铯，然后使用阳离子交换色谱法进行纯化，以去除干扰。用这种方法，钡的去污因子为 6.0×10，铷的去污因子为 1800，铯的化学收率超过 60%。通过使用葡萄糖作为活化剂，铯的电离效率显著提高到 50.6%，并且可以保持超过 180 分钟的 Cs（20 V）恒定高电流，这确保了低水平 Cs 和 Cs 的敏感和可靠测量。对于 200 mL 海水，Cs 和 Cs 的检测限分别为 4.0×10 g/L，这使得可以准确测定小体积海水中的 Cs 浓度和 Cs/Cs 比（<200 mL）。通过对 IAEA-443 海水标准物质的分析验证了所开发的方法。成功分析了来自格陵兰海、波罗的海和丹麦海峡的海水样品中的 Cs 浓度和 Cs/Cs 比，结果表明，波罗的海海水中的 Cs 浓度明显高于格陵兰海，这归因于切尔诺贝利事故放射性铯在波罗的海地区的高沉积。
