Historical impact of Kosa on Japanese land to enhance soil ability to retain radiocesium

2018 Fiscal Year Final Research Report

• Project/Area Number: 16H06188
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Plant nutrition/Soil science
• Research Institution: Kyoto Prefectural University
• Principal Investigator: Nakao Atsushi 京都府立大学, 生命環境科学研究科, 准教授 (80624064)
• Research Collaborator: Elliott Crawford ジョージア州立大学 ; Tanaka Ryoji 岡山大学 ; Eguchi Tetsuya 農研機構 ; Naruse Toshiro 元兵庫教育大学 ; Kubotera Hideo 農研機構 ; Takahara Hikari 京都府立大学
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 石英の酸素同位体比 / K-Ar年代 / 放射性セシウム捕捉ポテンシャル / XRD / 古環境解析

Outline of Final Research Achievements

The enhancement effect of historical accumulation of Kosa-dust on the ability of soils to retain radiocesium (RCs) was hypothesized. To verify this hypothesis, mineral particles with a diameter of <20μm, a typical size range of Kosa-dust, were isolated from cumulative volcanic or peaty layers and subjected to the chemical, mineralogical, and isotopic analyses.
This study obtained the following achievements that 1) higher inclusion of Kosa-dust, evidenced by K-Ar dating and quartz-δ18O values, well associated with both higher mica content and the ability of soils to retain RCs, 2) volcanic soils further away from volcanic craters have higher ability to retain RCs, and 3) higher deposition of Kosa-dust under the colder paleoclimate was much more important to enhance the ability of sols to RCs than that under warmer period.

Free Research Field

土壌化学

Academic Significance and Societal Importance of the Research Achievements

黄砂が土壌の機能を規定する因子になり得ることは，福島原発事故が起こるまでほとんど見過ごされてきた。しかし，とりわけ日本においては地質史を通じた黄砂の飛来量が大きいため，放射性セシウム固定能を大きく高める効果があり，火山灰への黄砂混入比が高い黒ボク土ほどその固定能が大きいことが初めて実証された。この成果は，黒ボク土の放射性セシウム固定能に地点間差が生じる要因を新しい視点から証明しており，黄砂が供給する知られざる生態系サービスの解明という点で高い学術的があり，放射性セシウムの土壌-植物間での移行量予測に有用な知見を供給したという点で高い社会的意義を持っている。