Molecular Geochemistry: Analyses of Evolution of Earth and Life based on Speciation from Atomic Scale

2014 Fiscal Year Final Research Report

• Project/Area Number: 22224011
• Research Category: Grant-in-Aid for Scientific Research (S)
• Allocation Type: Single-year Grants
• Research Field: Geochemistry/Astrochemistry
• Research Institution: The University of Tokyo (2014); Hiroshima University (2010-2013)
• Principal Investigator: TAKAHASHI Yoshio 東京大学, 理学(系)研究科(研究院), 教授 (10304396)
• Co-Investigator(Kenkyū-buntansha): TANIMIZU Masaharu 海洋研究開発機構, 高知コア研究所, サブリーダー (20373459) ; SAKAGUCHI Aya 筑波大学, 数理物質科学研究科, 准教授 (00526254) ; UEKI Tatsuya 広島大学, 大学院理学研究科, 准教授 (10274505) ; KATSUMOTO Yukiteru 広島大学, 大学院理学研究科, 助教 (90351741) ; MITSUNOBU Satoshi 静岡県立大学, 環境科学研究所, 助教 (70537951)
• Project Period (FY): 2010-04-01 – 2015-03-31
• Keywords: 化学種解明 / XAFS / モリブデン / タングステン / セリウム異常 / 酸化還元状態 / セレン / ヒ素

Outline of Final Research Achievements

We studied solid-water distribution and isotopic fractionation of trace elements during adsorption on solid media in seawater based on speciation analysis such as by X-ray absorption fine structure (XAFS). The distribution and isotopic information for various elements were interpreted systematically to establish accurate estimation methods of paleoredox condition and change of their concentrations under various redox conditions in seawater. In this study, following results were obtained: (i) multiple analyses of isotopes of Mo and W provide accurate redox information, (ii) combination of cerium stable isotope and degree of Ce anomaly can be also an accurate redox probe, (iii) oxidation states of selenium and arsenic in barite can contain redox information when the barite was precipitated, and (iv) a clear relationship was found between adsorption structure on the solid media and solubility of the elements during adsorption reactions.

Free Research Field

地球化学、環境化学