Hisashi Nirei

Distribution and seasonal variation of methanotrophs in trichloroethylene contaminated groundwater

Seasonal variations in distribution of methanotrophs in trichloroethylene (TCE)-contaminated groundwater in Chikura, Chiba, Japan were investigated. The hydrostratigraphic units of the area consisted of three aquifers which extended over 30-m depth. High concentrations of dissolved methane and high electric conductivity were observed in the bottom aquifer influenced by fossil water confined below, because of its location on the edge of a naturally dissolved methane field. Methanotrophs were distributed throughout the three aquifers. Their abundance was low in the zone of low-dissolved methane and high-dissolved oxygen, while high numbers were observed in the zone of high-dissolved methane and low-dissolved oxygen. Groundwater level decreased in the season of low precipitation. In the first aquifer, seasonal variation of dissolved methane showed the opposite pattern to that of groundwater level. In this aquifer, a seasonal variations in the number of methanotrophs and dissolved methane were positively correlated. This was explained by calculating that dissolved methane regulated the abundance of methanotrophs in the first aquifer. Although in every aquifer, the pH was within the suitable range for TCE degradation by methanotrophs and indigenous methanotrophs had TCE degradation ability, variations in the numbers of methanotrophs did not show significant correlation with TCE concentrations in groundwater in any aquifer.

A Potential Lower–Middle Pleistocene GSSP with Excellent Magnetostratigraphy Along the West Pacific Margin: The Chiba Section, Central Japan

The Chiba section in Japan represents a potential global boundary stratotype section and point (GSSP) for the Lower–Middle Pleistocene Subseries/Subepoch. The proposed GSSP is placed at the base of the Byakubi ash bed, a regional marker directly correlated to the Matuyama–Brunhes magnetic reversal, which is the primary guide for the Lower–Middle Pleistocene boundary. The Byakubi ash bed occurs within the 2000-m-thick Kazusa Group, which was deposited in bathyal to shelf palaeoenvironments during the Early and Middle Pleistocene. In addition to the numerous marine stratigraphies already studied, this section offers potential correlation to Chinese loess stratigraphy.

Medical Geology in Japan

The relationship between medical treatment and geology in Japan has an old history. However, the distribution of man-made strata deserves special mentioning in the geology of the Japanese Archipelago. The population density of Japan is high, and the man-made strata abruptly increased due to consequences of high economic growth, mass production, and mass consumption. Therefore this chapter describes the background and the different methods used in solving environmental problems linked to man-made pollution, the geological environment, and health in Japan.