Université Paris-Saclay, CEA, Service d'Etude du Comportement des Radionucléides, Gif-sur-Yvette, France.
Institut Curie, PSL University, Université Paris-Saclay, CNRS UMS 2016, INSERM US43, Multimodal Imaging Center, Orsay, France.
J Environ Radioact. 2021 May;231:106552. doi: 10.1016/j.jenvrad.2021.106552. Epub 2021 Feb 22.
I is one of the main radioisotopes of iodine derived from the nuclear fuel cycle that can be found sustainably in the environment due to its long half-life. In coastal marine environment, brown macroalgae, such laminariales (or kelps), are known to naturally feature highest rates of iodine accumulation, and to be an important source of biogenic volatile iodinated compounds released to the atmosphere. These seaweeds are therefore likely to be significantly marked by but also potential vectors of radioactive iodine. In order to better understand the chemical and isotopic speciation of iodine in brown algal tissues, we combined mass spectrometry-based imaging approaches in natural samples of Laminaria digitata young sporophytes, collected at two different locations along the south coast of the English Channel (Roscoff and Goury). Laser desorption ionization (LDI) and desorption electrospray-ionization techniques (DESI), coupled with mass spectrometry, confirmed the predominance of inorganic I species on the surface of fresh algae, and a peripheral iodine localization when applied on micro-sections. Moreover, radioactive isotope I was not detected on plantlet surface or in stipe sections of algal samples collected near Roscoff but was detected in L. digitata samples collected at Goury, near La Hague, where controlled liquid radioactive discharges from the ORANO La Hague reprocessing plant occur. At the subcellular scale, cryo-fixed micro-sections of algal blade samples from both sites were further analyzed by secondary ion mass spectrometry (nano-SIMS), leading to similar results. Even if the signal detected for I was much weaker than for I in samples from Goury, the chemical imaging revealed some differences in extracellular distribution between radioactive and stable iodine isotopes. Altogether LDI and nano-SIMS are complementary and powerful techniques for the detection and localization of iodine isotopes in algal samples, and for a better understanding of radioactive and stable iodine uptake mechanisms in the marine environment.
碘-131 是核燃料循环中碘的主要放射性同位素之一，由于其半衰期长，因此可以在环境中持续存在。在沿海海洋环境中，褐藻（如马尾藻）被认为是碘积累率最高的天然物质，也是向大气中释放生物源挥发性碘化化合物的重要来源。因此，这些海藻很可能被放射性碘显著标记，同时也是放射性碘的潜在载体。为了更好地了解褐藻组织中碘的化学和同位素形态，我们结合了基于质谱的成像方法，对在英吉利海峡南岸的两个不同地点（Roscoff 和 Goury）收集的年轻海带孢子体的 Laminaria digitata 自然样本进行了研究。激光解吸电离（LDI）和解吸电喷雾电离技术（DESI）与质谱相结合，证实了新鲜藻类表面无机碘物种的优势，并且当应用于微切片时，碘会发生外围定位。此外，在 Roscoff 附近采集的植物幼体表面或藻茎切片中未检测到放射性同位素 I，但在 La Hague 附近的 Goury 采集的 L. digitata 样品中检测到了放射性同位素 I。在亚细胞尺度上，对来自两个地点的藻类叶片样品的冷冻固定微切片进一步进行了二次离子质谱（nano-SIMS）分析，得到了相似的结果。尽管在 Goury 采集的样品中检测到的 I 信号比 I 弱得多，但化学成像揭示了放射性碘和稳定碘同位素在细胞外分布上的一些差异。总之，LDI 和 nano-SIMS 是检测和定位藻类样品中碘同位素的互补且强大的技术，有助于更好地理解放射性碘和稳定碘在海洋环境中的摄取机制。
