Development of prediction model for ambient dose rate based on the analysis of radiocesium dynamics in forest environment

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K16201
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Environmental impact assessment
• Research Institution: University of Tsukuba
• Principal Investigator: Kato Hiroaki 筑波大学, 生命環境系, 准教授 (90732636)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 福島第一原子力発電所事故 / 林内空間線量率 / 放射性セシウム / 移行状況 / 樹種

Outline of Final Research Achievements

In order to clarify the influence of the distribution and transfer of radiocesium in the forest on the fluctuation of air dose rate in the forest, radiocesium redistribution in association with rainwater and litterfall was monitored in the forest in Kawamata and Namie, Fukushima Prefecture. We developed double exponential model which simulate vertical distribution of radiocesium in forest. Furthermore, we analyzed huge dataset of air dose rate which was measured in the experimental forests and by regional monitoring campaign by local governments and related ministries in the wide area forest in Fukushima prefecture, the influence of tree species on temporal trend of the air dose rate was clarified. In addition, we developed a method to correct the variation of the measured air dose rate based on variation of moisture content at the forest floor and using the advance rainfall index.

Free Research Field

環境放射能

Academic Significance and Societal Importance of the Research Achievements

森林では大気からの初期沈着から放射性セシウムの分布が時間経過とともに変化してゆく。そのため、福島原発事故の環境影響の解明と被ばく線量評価のためには、森林域の空間線量率の変化傾向と変動要因を解明することが長期的な線量予測に不可欠である。本研究では、樹種毎の林内の放射性セシウムの移行状況とあわせて相補的に解析することにより、樹種毎の林内空間線量率の時間変化傾向及び樹種間の差異の発生要因を明らかにした。以上の研究成果は、森林の空間線量率の長期予測と被ばく評価に資するのみならず、福島事故由来の放射性核種をトレーサーとした林内物質循環の理解の深化に貢献する科学的知見を提供しうる。