東京大学 · 環境科学
Yoshio Takahashi教授の研究室は、環境中における希土類元素や重金属の挙動、特に鉄・マンガン・ヒ素の化学的挙動とその環境影響を、XANES分析や連続抽出法を用いて解明しています。特に水田土壌や大気中の鉄酸化物がヒ素をどのように固定・移動させるかを、現場測定と実験的アプローチで解明しています。また、希土類酸化物を含む非線形光学性酸化物ガラスの結晶化制御についても、二次高調波発生法を用いて材料設計に貢献しています。
Figures are computed from collected data and may differ slightly.
The behavior of As in paddy fields is of great interest considering high As contents of groundwater in several Asian countries where rice is the main staple. We determined the concentrations of Fe, Mn, and As in soil, soil water, and groundwater samples collected at different depths down to 2 m in an experimental paddy field in Japan during the cycle of flooded and non-flooded periods. In addition, we measured the oxidation states of Fe, Mn, and As in situ in soil samples using X-ray absorption
Abstract. In the North Pacific, transport and deposition of mineral dust from Asia appear to be one of major sources of iron which can regulate growth of phytoplankton in the ocean. In this process, it is essential to identify chemical species of iron contained in Asian dust, because bioavailability of iron in the ocean is strongly influenced by the solubility of iron, which in turn is dependent on iron species in the dust. Here, we report that clay minerals (illite and chlorite) in the dusts ne
Transparent optical nonlinear crystallized glasses with the composition of 25La2O3 25B2O3 50GeO2, stoichiometric to ferroelectric stillwellite-type LaBGeO5 crystalline phase, have been prepared by a two-step heat-treatment (first heat treatment: T1=670 °C, t1=10 h, second heat-treatment: T2, t2), and their second harmonic (SH) intensities have been examined using the Maker fringe method. The samples obtained by heat treatments at T2=720∼725 °C for t2=3 h show only surface crystallization and exh
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