Exploration of radioactive cesium distribution in forest soil using gamma-ray spectral survey

• Project/Area Number: 26660133
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Forest science
• Research Institution: Forestry and Forest Products Research Institute
• Principal Investigator: YASUDA Yukio 国立研究開発法人森林総合研究所, 森林防災研究領域, 主任研究員 (50353892)
• Co-Investigator(Renkei-kenkyūsha): OHTANI Yoshikazu 国立研究開発法人森林総合研究所, 森林防災研究領域, 研究専門員 (90353614) ; TSUBOYAMA Yoshio 国立研究開発法人森林総合研究所, 研究ディレクター (10353773)
• Research Collaborator: HIRUTA Toshihide 福島県・農林水産部, 森林整備課, 主査
• Project Period (FY): 2014-04-01 – 2017-03-31
• Project Status: Completed (Fiscal Year 2016)
• Budget Amount: ¥3,900,000 (Direct Cost: ¥3,000,000、Indirect Cost: ¥900,000); Fiscal Year 2016: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2015: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2014: ¥2,600,000 (Direct Cost: ¥2,000,000、Indirect Cost: ¥600,000)
• Keywords: 放射性セシウム / 森林土壌 / ガンマ線

Outline of Final Research Achievements

We attempted to develop a new technique to measure radioactive cesium concentration and its depth distribution in forest soil using energy spectra of gamma ray on forest floor. This technique will not require soil samplings and permit simple and quick measurements.
Gamma ray spectra measured on forest floor clearly showed energy peaks from radioactive cesium (Cs-137, Cs-134). Peak counts of gamma-ray photon calculated around the detected peaks had significant correlation with the amounts of radioactive cesium contained in soil per unit area. This linear relationship was able to apply to estimate the actual cesium amounts in Fukushima forests. However, estimations of the depth distribution using gamma-ray spectra were difficult, since radioactive cesium still remained near the surface of forest soil.

Research Products

• [Presentation] スペクトルサーベイメータによる土壌中放射性セシウム濃度の非破壊測定の試み (2017)
  • Author(s): 安田 幸生、大谷 義一
  • Organizer: 日本農業気象学会
  • Place of Presentation: 北里大学十和田キャンパス（青森県十和田市）
  • Year and Date: 2017-03-27
• [Presentation] 森林内除染処理から４年経過後の土壌中放射性セシウム濃度の鉛直分布 (2016)
  • Author(s): 安田 幸生、大谷 義一
  • Organizer: 東北森林科学会
  • Place of Presentation: 岩手大学農学部（岩手県盛岡市）
  • Year and Date: 2016-08-25
• [Presentation] 森林土壌中における放射性物質濃度と放射線量率の深度分布 (2014)
  • Author(s): 安田幸生、大谷義一、蛭田利秀、渡部秀行、橘内雅敏
  • Organizer: 東北森林科学会
  • Place of Presentation: コラッセふくしま（福島県福島市）
  • Year and Date: 2014-09-01 – 2014-09-02
• [Presentation] 立木樹幹の線減衰係数の測定 (2014)
  • Author(s): 大谷義一、安田幸生、坪山良夫
  • Organizer: 東北森林科学会
  • Place of Presentation: コラッセふくしま（福島県福島市）
  • Year and Date: 2014-09-01 – 2014-09-02