Carbon isotopic composition of bacterial methane in a soil incubation experiment: Contributions of acetate and CO[sub 2]/H[sub 2]

Journal Article · Sun Aug 01 04:00:00 EDT 1993 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(93)90350-6· OSTI ID:5591338

Sugimoto, Atsuko; Wada, Eitaro ^[1]

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1. Mitsubishi Kasei Inst. of Life Sciences, Tokyo (Japan)

Anaerobic incubations of paddy soil collected from Konosu, Japan, were carried out for 10 weeks to clarify the general principles that govern the variation of carbon isotopic composition of bacterial methane from freshwater areas. The concentrations and isotopic compositions of CH[sub 4], CO[sub 2], and acetate produced in the incubated system were measured. The [delta][sup 13]C value of biogenic CH[sub 4] was highly variable ranging from [minus]60 to [minus]33[per thousand], corresponding to changes in its formation pathways: acetate fermentation and CO[sub 2]/H[sub 2] reduction. Acetate accumulated only during the first week. After it became depleted, acetate production completely limited CH[sub 4] production. The [delta][sup 13]C value of the methyl carbon of acetate, which was accumulated with addition of inhibitor for methanogenesis, ranged from [minus]43 to [minus]30[per thousand], after acetate depletion. The [delta][sup 13]C value of CH[sub 4] from CO[sub 2]/H[sub 2] reduction was estimated to be [minus]77 to [minus]60[per thousand]. An enrichment in [sup 13]C of CO[sub 2] localized around the site of methanogenesis was suggested. CO[sub 2] produced in situ during methanogenesis (e.g., CO[sub 2] from carboxyl group of acetate) was possibly utilized as well. Using the above [delta][sup 13]C values of two endmembers of CH[sub 4], the change of acetate contribution for CH[sub 4] production was calculated: less than 12% until week 1, 65 to 100% at weeks 1 to 3, 16 to 28% at weeks 3 to 5, and 35 to 40% after week 5. Variability of CH[sub 4] [delta][sup 13]C resulted from the difference in contribution of each biological process. Also, the [delta][sup 13]C value of CH[sub 4] was a useful indicator for assessing the contribution of each process to methane production in sulfate depleted freshwater areas. 50 refs., 6 figs., 4 tabs.

• OSTI ID: 5591338
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 57:16; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

09 BIOMASS FUELS
090900* -- Biomass Fuels-- Processing-- (1990-)
ACETIC ACID
ALKANES
ANAEROBIC CONDITIONS
BIOLOGICAL PATHWAYS
BIOSYNTHESIS
CARBON 13
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON ISOTOPES
CARBON OXIDES
CARBOXYLIC ACIDS
CHALCOGENIDES
ELEMENTS
EVEN-ODD NUCLEI
HYDROCARBONS
HYDROGEN
ISOTOPE RATIO
ISOTOPES
LIGHT NUCLEI
METHANE
MICROORGANISMS
MONOCARBOXYLIC ACIDS
NONMETALS
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
SOILS
STABLE ISOTOPES
SYNTHESIS