¹²⁹I 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 ¹²⁹I 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 ¹²⁹I was much weaker than for ¹²⁷I 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.

¹²⁹ I是源自核燃料循环的碘的主要放射性同位素之一，由于其半衰期较长，因此可以在环境中持续发现。在沿海海洋环境中，已知诸如海带（或海带）之类的棕色大型藻类自然具有最高的碘积累率，并且是释放到大气中的生物挥发性碘化化合物的重要来源。因此，这些海藻可能被放射性碘显着标记，但也可能具有潜在的载体。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海带指骨的天然样品进行成像年轻的孢子体，收集在英吉利海峡南海岸的两个不同地点（Roscoff和Goury）。激光解吸电离（LDI）和解吸电电离技术（DESI），加上质谱，证实无机我的优势^-当在微切片施加物种新鲜藻类的表面上，以及外围碘定位。此外，在Roscoff附近收集的藻类样品的小苗表面或菌柄切片中未检测到放射性同位素¹²⁹ I，但在趾状乳杆菌中检测到了放射性同位素129I。样品在拉海牙附近的古里收集，在那里发生了从奥拉诺拉海牙后处理厂产生的受控液体放射性排放。在亚细胞尺度上，通过二次离子质谱（nano-SIMS）进一步分析了来自两个位点的藻类叶片样品的冷冻固定显微切片，得出相似的结果。即使检测到¹²⁹的信号也比¹²⁷弱得多在来自古里（Goury）的样品中，化学成像显示出放射性和稳定碘同位素之间在细胞外分布方面存在一些差异。LDI和nano-SIMS共同是藻类样品中碘同位素的检测和定位以及对海洋环境中放射性和稳定碘吸收机制的更好了解的互补而强大的技术。