The stable carbon isotope biogeochemistry of acetate and methane in freshwater environments

Miscellaneous · Sun Jan 01 00:00:00 EST 1989

OSTI ID:5546270

Gelwicks, J T

Methane produced in freshwater sediments, where acetate is the major substrate utilized by methanogenic bacteria, is commonly depleted in {sup 13}C. Variations in the carbon-isotopic composition of methane have been related to flows of acetate carbon to various fates within microbial communities. To examine these processes, the isotopic compositions of biogenic methane and its sedimentary sources (acetate and CO{sub 2}) were considered along with related isotope effects. A method of preparation for carbon isotope analyses of both carbons in acetate was developed. Uncertainties in measurements are less than 0.4{per thousand} for samples greater than 5 {mu}mol of acetate. Advantages of this technique include good separation of acetate from other compounds and the applicability to samples containing micromolar quantities of acetate. Carbon kinetic isotope effects associated with synthesis of acetate from CO{sub 2} by Acetobacterium woodii were measured by isotopic analyses of CO{sub 2}, methyl-carbon, and total acetate. Closed systems allowing construction of complete mass balances at varying stages of growth were utilized, and the effects of the partitioning of carbon between CO{sub 2} and HCO{sub 3}{sup {minus}} were taken into account. For the overall reaction total carbonate {yields} total acetate, the isotope effect measured {minus}58.6 {plus minus} 0.7{per thousand}; there is no evidence for intramolecular isotopic ordering in the acetate. Carbon isotope effects associated with synthesis of methane from acetate by Methanosarcina barkeri and by a natural community of methanogens were measured in closed system experiments. For the process of methyl-carbon {yields} methane, the isotope effect measured {minus}21.5 {plus minus} 1.3{per thousand}.

• Research Organization: Indiana Univ., Bloomington, IN (United States)
• OSTI ID: 5546270
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ACETATES
BIOGEOCHEMISTRY
METHANE
METHANOGENIC BACTERIA
GROWTH
SEDIMENTS
CONTAMINATION
CARBON 13
FRESH WATER
ISOTOPE EFFECTS
TRACER TECHNIQUES
WATER POLLUTION
ALKANES
BACTERIA
CARBON ISOTOPES
CARBOXYLIC ACID SALTS
CHEMISTRY
EVEN-ODD NUCLEI
GEOCHEMISTRY
HYDROCARBONS
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
MICROORGANISMS
NUCLEI
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
POLLUTION
STABLE ISOTOPES
WATER
540320* - Environment
Aquatic- Chemicals Monitoring & Transport- (1990-)
560300 - Chemicals Metabolism & Toxicology