Isotopic variation of molecular hydrogen in 20-375 hydrothermal fluids as detected by a new analytical method

• Published in: Journal of geophysical research. Biogeosciences 2010-07, Vol.115 (G03)
• Main Authors: Kawagucci, Shinsuke, Toki, Tomohiro, Ishibashi, Junichiro, Takai, Ken, Ito, Michihiro, Oomori, Tamotsu, Gamo, Toshitaka
• Format: Article
• Language: English
• ISSN: 2169-8953; 2169-8961
• DOI: 10.1029/2009JG001203

Molecular hydrogen (H2) is one of the most important energy sources for subseafloor chemolithoautotrophic microbial ecosystems in the deep-sea hydrothermal environments. This study investigated stable isotope ratios of H2 in 20-375 hydrothermal fluids to evaluate usefulness of the isotope ratio as a tracer to explore the H2-metabolisms. Prior to the observation, we developed an improved analytical method for the determination of concentration and stable isotope ratio of H2. This method achieved a relatively high sensitivity with a detection limit of 1 nmol H2 within an analytical error of 10ppt in the dDH2 value. The dDH2 values in the high-temperature fluids were between -405ppt and -330ppt, indicating the achievement of the hydrogen isotopic equilibrium between H2 and H2O at around the hydrothermal end-member temperature. In contrast, several low-temperature fluids showed apparently smaller dDH2 values than those in the high-temperature fluids in spite of a negligible dDH2 change due to flu