Developing Accelerator Mass Spectrometry Capabilities for Anthropogenic Radionuclide Analysis to Extend the Set of Oceanographic Tracers
Developing Accelerator Mass Spectrometry Capabilities for Anthropogenic Radionuclide Analysis to Extend the Set of Oceanographic Tracers
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DOI：
10.3389/fmars.2022.837515
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发表时间：
2022-03
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通讯作者：
K. Hain;M. Martschini;Fadime Gülce;M. Honda;J. Lachner;M. Kern;J. Pitters;F. Quinto;A. Sakaguchi;P. Steier;A. Wiederin;Alexander Wieser;A. Yokoyama;R. Golser
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作者：
K. Hain;M. Martschini;Fadime Gülce;M. Honda;J. Lachner;M. Kern;J. Pitters;F. Quinto;A. Sakaguchi;P. Steier;A. Wiederin;Alexander Wieser;A. Yokoyama;R. Golser
最近在维也纳环境研究加速器（VERA）的加速器质谱（AMS）在探测效率和同量异位素抑制方面取得的重大进展为在超低环境浓度下分析其他长寿命放射性核素提供了可能性。这些放射性核素，包括233 U，135 Cs，99 Tc和90 Sr，将成为重要的海洋示踪剂的应用，由于它们在海水中的一般保守的行为。特别是233 U/236 U和137 Cs/135 Cs的同位素比值，因为不受元素分馏的影响，已被证明是识别排放源的有力指纹。改进的检测效率使我们能够分析所有主要的长寿命锕系元素，即，236 U、237 Np、239、240 Pu、241 Am以及非常罕见的233 U在西北太平洋深度剖面的相同10 L水样中。为此，实施了基于萃取色谱法（单个UTEVA®柱）的简化且非常灵活的化学纯化程序，其可以通过DGA®柱扩展用于Am纯化。该程序使用参考材料IAEA-381/385进行了验证。随着预计从AMS离子源中提取锕系元素作为氟化物分子的电离效率的额外增加，化学处理的进一步减少可能成为可能。该方法成功地应用于一组示例性的空气过滤器样品。为了可靠地定量测定237 Np浓度，正在与日本筑波大学合作开发236 Np加标材料。离子激光相互作用质谱（ILIAMS）是一种有效抑制稳定等压背景的新技术，它为裂变碎片135 Cs、99 Tc和90 Sr提供了前所未有的检测灵敏度。相应的装置现在已完全投入使用，并且所实现的同量异位素抑制因子>105原则上允许检测环境中的上述放射性核素。特别是对于90 Sr分析，这种新方法已经在选定的参考材料（例如，IAEA-A-12）并已准备好应用于海洋学研究。我们估计，仅（1-3）L的海水样品体积就足以分别用于90 Sr和135 Cs的分析。
Recent major advances in Accelerator Mass Spectrometry (AMS) at the Vienna Environmental Research Accelerator (VERA) regarding detection efficiency and isobar suppression have opened possibilities for the analysis of additional long-lived radionuclides at ultra-low environmental concentrations. These radionuclides, including 233U, 135Cs, 99Tc, and 90Sr, will become important for oceanographic tracer application due to their generally conservative behavior in ocean water. In particular, the isotope ratios 233U/236U and 137Cs/135Cs have proven to be powerful fingerprints for emission source identification as they are not affected by elemental fractionation. Improved detection efficiencies allowed us to analyze all major long-lived actinides, i.e., 236U, 237Np, 239,240Pu, 241Am as well as the very rare 233U, in the same 10 L water samples of a depth profile from the northwest Pacific Ocean. For this purpose, a simplified and very flexible chemical purification procedure based on extraction chromatography (a single UTEVA® column) was implemented which can be extended by a DGA® column for Am purification. The procedure was validated with the reference materials IAEA-381/385. With the additional increase in ionization efficiency expected for the extraction of actinides as fluoride molecules from the AMS ion source, a further reduction of chemical processing may become possible. This method was successfully applied to an exemplary set of air filter samples. In order to determine the quantitative 237Np concentration reliably, a 236Np spike material is being developed in collaboration with the University of Tsukuba, Japan. Ion-Laser Interaction Mass Spectrometry (ILIAMS), a novel technique for the efficient suppression of stable isobaric background, has been developed at VERA and provides unprecedented detection sensitivity for the fission fragments 135Cs, 99Tc, and 90Sr. The corresponding setup is fully operational now and the isobar suppression factors of >105 achieved, in principle, allow for the detection of the mentioned radionuclides in the environment. Especially for 90Sr analysis, this new approach has already been validated for selected reference materials (e.g., IAEA-A-12) and is ready for application in oceanographic studies. We estimate that a sample volume of only (1–3) L ocean water is sufficient for 90Sr as well as for 135Cs analysis, respectively.