World Congress of Soil Science Logo 18th World Congress of Soil Science
July 9-15, 2006 - Philadelphia, Pennsylvania, USA
International Union of Soil Sciences

Monday, 10 July 2006 - Friday, 14 July 2006

This presentation is part of 141: 2.3B Molecular Approaches to Microbial Ecology in Soils - Poster

Methane Oxidation in Landfill Cover Soils as Revealed by PLFA Analyses and Δ13C Measurements.

Andrea Watzinger1, Frank Rasche2, Michael Pfeffer3, Thomas Reichenauer2, and Michael Stemmer4. (1) Univ of Natural Resources and Applied Life Sciences, Peter Jordan-Strasse 82, Wien, Austria, (2) ARC Seibersdorf Research, Seibersdorf, Austria, (3) Federal Research and Training Centre for Forests, Natural Hazards and Landscape, Wien, Austria, (4) Austrian Agency for Health and Food Safety, Wien, Austria

The atmospheric concentration of CH4, an important greenhouse gas, has increased by a factor of 2.5 since the pre-industrial era. 13 % of the global anthropogenic emissions derive from landfills. Microbial methane oxidation in the recultivation layer of landfill sites reduces CH4 emissions from landfills. Understanding the microbial organisms involved helps to improve the design of an appropriate landfill cover. Samples were collected from four different depths of 0.6 m deep lysimeters filled with a recultivation substrate (compost-gravel mixture). The lysimeters were fumigated with an artificial landfill gas (100 l CH4 m-2 d-1) and irrigated with landfill leachate for two years. The microbial methane oxidizing community was investigated by measurements of phospholipid fatty acids (PLFA), ergosterol and quinone. In addition, incorporation of methane into PLFAs of soil microorganism was studied by isotopic means owing to the fact, that the isotopic ratio of the artificial methane supplied was lower (δ13C ~ -50 ) than the recultivation substrate (δ13C ~ -26 ). The total amount of bacterial PLFAs and especially the PLFAs including methanotrophs Typ I (14:0 PLFA, 16:1 isomers) and Typ II (18:1 isomers) increased by a factor of 6, 13 and 11 respectively under fumigation. The methanotrophic biomarker 16:1ω8 and 18:1ω8 PLFAs were detected but in many cases not baseline separated. The 16:1ω8 PLFA pattern was consistent and reflected in 14:0 and 16:1 PLFAs, which was not the case for the typ II methanotrophic biomarker (18:1ω8 PLFA). Concerning the soil depth distribution, 18:1 PLFAs (α-proteobacteria, which include Typ II methanotrophs) were found at lower soil depth than Typ I methanotrophs. Under landfill leachate irrigation, the methanotrophic population shifted closer to the surface, and 18:1 PLFA contents were decreased. Ubiquinone 8 and 10, respective indicators for γ-proteobacteria (including Typ I methanotrophs) and α-proteobacteria (including Typ II methanotrophs) supported the results obtained by 14:0 and 16:1 and 18:1 PLFA measurements. The fungal biomarkers (18:2ω6,9 PLFA and ergosterol) increased up to five times in the upper layer under landfill gas fumigation, but fungi growth was inhibited under landfill leachate irrigation. However, fungal PLFA was not depleted in 13C. Therefore, fungi unlikely took part in the carbon circling deriving from methane. Gram positive bacteria, which are predominately carbon degraders, were also depleted in 13C and their δ13C distribution followed the depth profile of methanotrophic PLFAs. Secondary depletion of 13C might have occurred either through degradation of methanotrophic bacteria or exopolymeric substances excreted by methanotrophs. Although methane addition increased both 18:1 and 16:1 PLFA concentrations, 18:1 isomers were not depleted in 13C. In contrast, 14:0 and 16:1 PLFAs showed δ13C values of -45 to -50 . Assumingly, methane oxidation was predominately carried out by Typ I methanotrophs, e.g. Methylomonas spp. (14:0 PLFA). Cy17:0 PLFA, which relates to sulfate reducing bacteria, was 13C depleted at lower soil depth indicating a possible involvement in anaerobic oxidation of methane. No effect of landfill leachate irrigation was found on the depletion of 13C in methanotrophs, while gram positive bacteria were depleted more under landfill leachate treatment. To conclude, methane oxidation in the landfill cover used was primarily done by typ I methanotrophs. Secondary turnover of the bound carbon involved gram positive bacteria but no fungi.

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