Leibniz Universität Hannover, Institut für Radioökologie und Strahlenschutz, D-30419 Hannover, Germany.
Sci Rep. 2013 Oct 18;3:2988. doi: 10.1038/srep02988.
The contamination of Japan after the Fukushima accident has been investigated mainly for volatile fission products, but only sparsely for actinides such as plutonium. Only small releases of actinides were estimated in Fukushima. Plutonium is still omnipresent in the environment from previous atmospheric nuclear weapons tests. We investigated soil and plants sampled at different hot spots in Japan, searching for reactor-borne plutonium using its isotopic ratio ²⁴⁰Pu/²³⁹Pu. By using accelerator mass spectrometry, we clearly demonstrated the release of Pu from the Fukushima Daiichi power plant: While most samples contained only the radionuclide signature of fallout plutonium, there is at least one vegetation sample whose isotope ratio (0.381 ± 0.046) evidences that the Pu originates from a nuclear reactor (²³⁹⁺²⁴⁰Pu activity concentration 0.49 Bq/kg). Plutonium content and isotope ratios differ considerably even for very close sampling locations, e.g. the soil and the plants growing on it. This strong localization indicates a particulate Pu release, which is of high radiological risk if incorporated.
福岛事故后对日本的污染主要针对易挥发的裂变产物进行了调查，但对钚等锕系元素的调查却很少。福岛估计仅有少量锕系元素释放。钚仍然存在于以前大气核武器试验造成的环境中。我们研究了在日本不同热点地区采集的土壤和植物，利用其同位素比值²⁴⁰Pu/²³⁹Pu 寻找反应堆携带的钚。通过使用加速器质谱法，我们清楚地证明了福岛第一核电站的 Pu 释放：虽然大多数样本仅含有放射性核素沉降钚的特征，但至少有一个植被样本的同位素比值（0.381 ± 0.046）表明 Pu 源自核反应堆（²³⁹⁺²⁴⁰Pu 活度浓度 0.49 Bq/kg）。即使是非常接近的采样地点，钚含量和同位素比值也有很大差异，例如土壤和生长在其上的植物。这种强烈的本地化表明存在颗粒状 Pu 释放，如果被人体摄入，将带来很高的放射性风险。
