2018 Fiscal Year Final Research Report

Metal accumulation and retention mechanism in lichen, and applicability of radioactive fallout evaluation

Research Project

PDF

Project/Area Number	16K12627
Research Category	Grant-in-Aid for Challenging Exploratory Research
Allocation Type	Multi-year Fund
Research Field	Modeling and technologies for environmental conservation and remediation
Research Institution	Japan Atomic Energy Agency
Principal Investigator	Dohi Terumi 国立研究開発法人日本原子力研究開発機構, 福島研究開発部門福島研究開発拠点福島環境安全センター, 技術副主幹 (50469821)
Co-Investigator(Kenkyū-buntansha)	高橋嘉夫東京大学, 大学院理学系研究科(理学部), 教授 (10304396) 大村嘉人独立行政法人国立科学博物館, 植物研究部, 研究主幹 (40414362) 町田昌彦国立研究開発法人日本原子力研究開発機構, システム計算科学センター, 研究主席 (60360434)
Project Period (FY)	2016-04-01 – 2019-03-31
Keywords	地衣類 / セシウム / ストロンチウム / ヨウ素 / 第一原理計算 / EXAFS / 環境モニタリング
Outline of Final Research Achievements	Lichens are known to accumulate and retain metals and radionuclides. However, little is known about these mechanisms. Here we studied the relationships between their morphology or physiological characteristics and metal accumulation, and retention. We focused on elements; Cs, Sr, I. An absorption experiments of these elements were carried out. The distributions of the elements in lichen tissues were observed by electron microscope. In addition, chemical state analysis and model calculation were combined to investigate factors related to accumulation. As the results, we found that Cs and Sr distributed in cortex mainly. It was suggested that the difference between the morphology and the amounts of Cs and Sr was not shown in relative species. The binding stabilities between lichen secondary metabolites and Cs were also evaluated. The high stability was shown in usnic acid under alkaline conditions, though the stabilities of all metabolites were similar under neutral conditions.
Free Research Field	地球科学
Academic Significance and Societal Importance of the Research Achievements	地衣類中の面積あたりの放射性Cs量はこれまで実環境下の試料で形態の違い（生殖器官の密度）が要因との議論もなされてきたが、対象種については栄養繁殖器官による形態差が表面積を左右しない可能性が示されたのは大きな成果であった。地衣体組織内部のCsおよびSrの主な分布状況を初めて視覚的に示すことができたことも重要な成果である。さらにCsと地衣類の二次代謝物や細胞壁成分との錯体安定性の評価結果を示すことができたのは世界で初めての成果であり、化学状態分析結果と組み合わせた評価によってより具体的な保持状態の検討が進展するものと期待される。