Methanotrophic activity in a diffusive methane/oxygen counter- gradient in an unsaturated porous medium
Urmann K, Norina E S, Schroth M H, Zeyer J

Swiss Global Change Abstract Ref. # 08.1-217

Type of Publication:
Reviewed Journal Article

Source:
Journal of Contaminant Hydrology, 2007, V94, N1-2, OCT 30, pp 126-138.

Abstract:
Microbial methane (CH4) oxidation is a main control on emissions of this important greenhouse gas from ecosystems such as contaminated aquifers or wetlands under aerobic conditions. Due to a lack of suitable model systems, we designed a laboratory column to study this process in diffusional CH4/O-2 counter-gradients in unsaturated porous media. Analysis and simulations of the steady-state CH4, CO2 and O-2 gas profiles showed that in a 15-cm-deep active zone, CH4 oxidation followed first-order kinetics with respect to CH4 with a high apparent first-order rate constant of similar to 30 h(-1). Total cell counts obtained using DAPI-staining suggested growth of methanotrophic bacteria, resulting in a high capacity for CH4 oxidation. This together with apparent tolerance to anoxic conditions enabled a rapid response of the methanotrophic community to changing substrate availability, which was induced by changes in O-2 concentrations at the top of the column. Microbial oxidation was confirmed by a similar to 7 parts per thousand enrichment in CH4 stable carbon isotope ratios along profiles. Using a fractionation factor of 1.025 +/- 0.0005 for microbial oxidation estimated from this shift and the fractionation factor for diffusion, simulations of isotope profiles agreed well with measured data confirming large fractionation associated with microbial oxidation. The designed column should be valuable for investigating response of methanotrophic bacteria to environmental parameters in future studies.

URL: link

ProClim- Category:
1.3 Soil and Lithosphere

Discipline(s):
Toxicology , Geochemistry + Geophysics , Pedology , Water Resources

Main Keywords:
in situ hybridization; landfill cover soil; oxidation activity; carbon; consumption; emission; oxygen; CH4; quantification; fractionation

Author's Keywords:
column; counter gradient; profile; methane emissions; methane oxidation; stable isotope fractionation

Reprint from:
K Urmann, ETH, Inst Biogeochem & Pollutant Dynam, Univ Str 16, CH 8092 Zürich, Switzerland ; Research Address: ETH, Inst Biogeochem & Pollutant Dynam, CH 8092 Zürich, Switzerland ; Email: Karina.urtnann@env.ETHz.ch

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