Fumiaki Tsunomori

Mechanisms of hydrogen generation during the mechanochemical treatment of biotite within D2O media

The mechanism of hydrogen generation during the mechanochemical treatment of biotite was examined by grinding experiments using a ball mil in H2O or D2O as a grinding media. From the linear relationship between the amount of generated hydrogen and the increase of the surface area of ground powders, the hydrogen productivity of biotite is estimated to be 0.036 μmol/m2, which agrees with the previous results in spite of the difference in the grinding conditions. D2 analyses by a mass spectrometry indicate that the produced amount of D2 accounts for only 10% of the total hydrogen and that more than 90% of hydrogen takes a form of a mixture of HD and H2. The observed isotope distribution clearly indicates that hydroxyls within the crystal structure can be a major source for the generation of hydrogen. Hydrogen generation originated from hydroxyls may indicate the higher hydrogen productivity of phyllosilicates than those of quartz and alkali feldspar.

Radon concentration distributions in shallow and deep groundwater around the Tachikawa fault zone

Groundwater radon concentrations around the Tachikawa fault zone were surveyed. The radon concentrations in shallow groundwater samples around the Tachikawa fault segment are comparable to previous studies. The characteristics of the radon concentrations on both sides of the segment are considered to have changed in response to the decrease in groundwater recharge caused by urbanization on the eastern side of the segment. The radon concentrations in deep groundwater samples collected around the Naguri and the Tachikawa fault segments are the same as those of shallow groundwater samples. However, the radon concentrations in deep groundwater samples collected from the bedrock beside the Naguri and Tachikawa fault segments are markedly higher than the radon concentrations expected from the geology on the Kanto plane. This disparity can be explained by the development of fracture zones spreading on both sides of the two segments. The radon concentration distribution for deep groundwater samples from the Naguri and the Tachikawa fault segments suggests that a fault exists even at the southern part of the Tachikawa fault line.