Two-step water splitting with Zn/Fe₃O₄ - ZnFe₂O₄ reaction system is suggested for H₂ generation to utilize concentrated solar heat. When mixture of Zn and Fe₃O₄ was heated to 873 K and steam was passed through, the H₂ was obtained in 93.4% of the theoretical yield. Formation of ZnFe₂O₄ with several zinc content (Zn_xFe_3-xO₄; 0.2≤x≤l) and ZnO was determined by XRD and Mössbauer spectroscopy. The yield of ZnO was 26-29%, which shows the ratio of the competition-reaction (H₂O Zn system) effects less in the total H₂ yield. O₂ generation (also energy storage) step can be proceeded at the temperature of ca. 1800 K. The reaction took place very fast, and it can be seen that a large amount of O₂ was released from irradiated ZnFe₂O₄. The stoichiometry and the reaction mechanism of the system are discussed upon the analyses for the solid product.

抄録全体を表示

The populations of Microcystis cells and the concentrations of a hepatotoxic group of compounds they produce, known as microcystins, were measured in 6 typical eutrophicated lakes in Japan to gain insight into spatial and temporal variations in microcystin production. The formation of water-bloom by the genus Microcystis was confirmed in all the surveyed lakes, and microcystins type LR, RR and YR were detected. In 5 of the 6 lakes, M. aeruginosa was the dominant species, but these 5 lakes were further classified into two groups according to the percentages of the three species of microcystins found inside M. aeruginosa cells. In Group 1, M. aeruginosa containing almost equal percentages of the three microcystins was detected, but in Group 2, Microcystis containing mainly type LR and RR and almost no type YR was detected. The content of microcystins in the cells varied between each lake, and also varied markedly during the summer season. In July and August, when the water temperature is high, almost all the microcystins in the lakes remained inside the cells. Only small amounts were eluted into the lake water.

抄録全体を表示