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安定同位体比は環境中に存在する物質の挙動や生成メカニズムを解明する非常に優れたパラメーターであり、地球上における様々な化学種の循環、生命活動及び地球環境変動を知る上で必要不可欠な存在である。筆者らはこれまでに、バイカル湖のAcademician Ridgeから得られた約10mの湖底柱状堆積物試料Ver98-1 St.5 (53°44'33"N, 108°24'35"W; Water depth,325m)に含まれる有機炭素・窒素・硫黄の存在量と安定同位体比、及び個々の有機分子の安定炭素同位体比を測定し、バイカル湖における生物活動の変遷を解析した(Watanabe et al., 2003a, 2003b, 2004)。本稿では安定硫黄同位体比を中心にこれまでの結果をまとめ、今後の展開について報告する。\\Variations in stable isotopic compositions of TOC, TN, TS and pyrite sulfur in the Lake Baikal sediment core (Ver98-1 St.5) are interpreted as proxies for climatic and environmental changes that can be of local, regional, and even global significance. Rapid δ^<34>S_<py> decreases at climate transition periods suggest that active sulfate reduction by SRB occurred at the water-sediment interface in the transition from cool to warm periods. This result implies that the [SO_4^<2->] increase and less oxic conditions took place in the climate transition periods. The rapid increase of precipitation with warming could give rise to the [SO_4^<2->] increase in the lake. The decrease of dissolved oxygen concentrations at sediment surface could be caused by the weakening of deep water ventilation. Also, δ^<15>N_<TN> excursions suggest low vertical mixing and low nutrient condition in these periods. Fluctuations of lake water circulation and depositional conditions correspond to global climatic and environmental changes.

第17回名古屋大学タンデトロン加速器質量分析計シンポジウム平成16(2004)年度報告 Proceedings of the 17th symposiumon Researches Using the Tandetron AMS System at Nagoya University in 2004\日時:平成17 (2005)年1月24日(月)、25日(火) 会場:名古屋大学シンポジオン Date:January 24th and 25th, 2005 Place:Nagoya University Symposion Hall



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