Empirical study of the origin and concentration mechanism of iodine in sedimentary rocks of the Northern Tertiary system of northern Hokkaido, Japan.

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K04971
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 31020:Earth resource engineering, Energy sciences-related
• Research Institution: Northern Advancement Center for Science ＆ Technology
• Principal Investigator: MURAKAMI Takuma 公益財団法人北海道科学技術総合振興センター, 幌延地圏環境研究所, 研究員 (30422760)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: ヨウ素 / 第三系堆積岩 / 地下水 / 北海道北部

Outline of Final Research Achievements

High concentrations (several tens of mg/L) of iodine have been observed in groundwater in northern Hokkaido. These concentrations, particularly in the Soya coal-bearing Fm, the Masuhoro Fm, and the Yuchi Fm, exceed 40 mg/L, comparable to those found in groundwater from iodine deposits in Japan. To clarify the migration and concentration process of iodine within these formations, this study analyzed iodine and other halogen elements, as well as iodine isotope ratios, in groundwater and rocks from the sedimentary formations. The results suggest that halogen element ratios are effective tracers for the migration of iodine in groundwater, and that high iodine concentrations in the formation are strongly influenced by iodine concentrated in marine sediments. Additionally, the isotope analysis indicated the influence of formation older than the geological age of the embryonic strata, consistent with previous studies.

Free Research Field

地球化学

Academic Significance and Societal Importance of the Research Achievements

北海道北部の地下水中における高濃度ヨウ素の起源解明により、地層内におけるヨウ素の移行や濃集のメカニズムの解明は国内外のヨウ素鉱床の形成過程の理解、それに伴う新たなヨウ素資源の探査・発掘に寄与すると考えられる。また地層内におけるヨウ素の移行メカニズムの理解は高レベル放射性廃棄物の地層処分分野への応用の点でも重要である。