Origin of 13C-enriched methane in the crater lake Towada, Japan

Rieko Nishimura, Urumu Tsunogai, Junichiro Ishibashi, Hiroshi Wakita, Yukihiro Nojiri

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11 Citations (Scopus)

Abstract

Concentration and stable carbon isotopic composition (δ13C) of CH4 are determined in a water column of an 327 m deep oxic oligotrophic crater lake, Lake Towada in Japan. The results of CTD measurements show relatively high temperature and high conductivity in the lower part of the column, possibly derived from hot springs at the crater wall approximately 150 m deep. The vertical profile of CH4 concentration shows two sharp maxima of 68 and 69 nmol/kg at depths of 20 and 150 m, respectively. The δ13C value of CH4 at 20 m is -55‰PDB, suggesting microbial production in and around the lake. In contrast, the δ13C value of CH4 at 150 m is +11‰PDB, which suggests some secondary isotopic alternation processes peculiar to hot spring-derived CH4 in the oxic water column, such as rapid aerobic microbial oxidation.

Original languageEnglish
Pages (from-to)277-283
Number of pages7
JournalGEOCHEMICAL JOURNAL
Volume33
Issue number4
DOIs
Publication statusPublished - 1999

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

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