Department of Forest Soils, Forestry and Forest Products Research Institute (FFPRI), Tsukuba, Ibaraki, 305-8687, Japan.
Extension and Protection Division, Private Forest Department, Forestry Agency, Chiyoda, Tokyo, 100-8952, Japan.
Sci Rep. 2023 Jun 5;13(1):9144. doi: 10.1038/s41598-023-35852-8.
Radiocesium (Cs) released in the Fukushima Dai-ichi Nuclear Power Plant accident is still cycling in the forest ecosystem. We examined the mobility of Cs in the external parts-leaves/needles, branches, and bark-of the two major tree species in Fukushima, Japanese cedar (Cryptomeria japonica) and konara oak (Quercus serrata). This variable mobility will likely lead to spatial heterogeneity of Cs and difficulty in predicting its dynamics for decades. We conducted leaching experiments on these samples by using ultrapure water and ammonium acetate. In Japanese cedar, the Cs percentage leached from current-year needles was 26-45% (ultrapure water) and 27-60% (ammonium acetate)-similar to those from old needles and branches. In konara oak, the Cs percentage leached from leaves was 47-72% (ultrapure water) and 70-100% (ammonium acetate)-comparable to those from current-year and old branches. Relatively poor Cs mobility was observed in the outer bark of Japanese cedar and in organic layer samples from both species. Comparison of the results from corresponding parts revealed greater Cs mobility in konara oak than in Japanese cedar. We suggest that more active cycling of Cs occurs in konara oak.
福岛第一核电站事故中释放的放射性铯（Cs）仍在森林生态系统中循环。我们研究了福岛两种主要树种——日本扁柏（Cryptomeria japonica）和柯那拉栎（Quercus serrata）的外部部分（叶子/针叶、树枝和树皮）中 Cs 的迁移性。这种可变性可能导致 Cs 的空间异质性，并在未来几十年内难以预测其动态。我们使用超纯水和乙酸铵对这些样本进行了淋溶实验。在日本扁柏中，当年针叶中浸出的 Cs 百分比为 26-45%（超纯水）和 27-60%（乙酸铵）-与旧针叶和树枝中的 Cs 百分比相似。在柯那拉栎中，叶片中浸出的 Cs 百分比为 47-72%（超纯水）和 70-100%（乙酸铵）-与当年和旧树枝中的 Cs 百分比相当。日本扁柏的外树皮和两种物种的有机层样本中 Cs 的迁移性较差。对相应部分的结果进行比较表明，柯那拉栎中的 Cs 迁移性大于日本扁柏。我们认为，柯那拉栎中 Cs 的循环更为活跃。
