Japan Geoscience Union Meeting 2015

Presentation information


Symbol A (Atmospheric and Hydrospheric Sciences) » A-HW Hydrology & Water Environment

[A-HW24] Isotope Hydrology 2015

Mon. May 25, 2015 9:00 AM - 10:45 AM 301A (3F)

Convener:*Masaya Yasuhara(Geological Survey of Japan, AIST), Kohei Kazahaya(Geological Survey of Japan, AIST), Shinji Ohsawa(Institute for Geothermal Sciences, Graduate School of Science, Kyoto University), Masaaki Takahashi(The National Institute of Advanced Industrial Science and Technology), YUICHI SUZUKI(Faculty of Geo-Environmental Sience,Rissho University), Futaba Kazama(Social Cystem Engineering, Division of Engineering, Interdiciplinary Graduate School of Medical and Engineering, University of Yamanashi), Kazuyoshi Asai(Geo Science Laboratory), Chair:Masaya Yasuhara(Geological Survey of Japan, AIST), Shiho Yabusaki(Faculty of Symbiotic Systems Science, Fukushima University)

9:00 AM - 9:30 AM

[AHW24-01] Microbial methane production and denitrification in deep aquifer associated with the accretionary prisms

*Hiroyuki KIMURA1, Makoto MATSUSHITA1, Shugo ISHIKAWA1 (1.Shizuoka University)

Keywords:accretionary prisms, groundwater, subsurface microorganisms, methane production, denitrification

To understand microbial potential of degradation of organic compounds, fermentation, methanogenesis, and denitrification in deep aquifer associated with the accretionary prism, the deep groundwater and natural gas samples were collected from 14 deep wells that were drilled to the aquifer. We performed a series of geochemical and microbiological analyses of the samples. Consequently, methane was the predominant component of the natural gas (51.4 to 99.4%). On the other hand, the natural gas samples containing N2 (0.6 to 48.6%) were found in some samples. Stable carbon isotopic analysis suggested that the methane was derived from both biogenic processes and thermogenic reaction. Phylogenetic analysis targeting bacterial 16S rRNA genes indicated the dominance of H2-producing fermentative bacteria in the groundwater. In addition to the fermentative bacteria, 16S rRNA genes related to denitrifying bacterium were identified at the sites where N2 was detected from the natural gas. Phylogenetic analysis targeting archaeal 16S rRNA genes revealed the dominance of hydrogenotrophic methanogens in the groundwater. Anaerobic incubations using the groundwater amended with organic substrates indicated H2 accumulation and rapid methane production. These results suggested that methane in the deep aquifer is produced by a syntrophic consortium of H2-producing fermentative bacteria and hydrogenotrophic methanogens in a wide range of deep aquifer associated with the accretionary prism in Southwest Japan. In addition to methane production, microbial denitrification using methane or organic matters as electron donors seems to be present in the deep aquifer associated with the accretionary prisms.