HR: 1340h
AN: B43A-0891    [Abstracts]
TI: In-Situ Quantification of Methanotrophic Activity in a Landfill Cover Soil Using Gas Push-Pull Tests
AU: Gomez, K E
EM: katherine.gomez@env.ethz.ch
AF: Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Universitaetstr. 16, Zurich, CH-8092, Switzerland
AU: Gonzalez-Gil, G
EM: graciela.gonzalez@epfl.ch
AF: Current address: Laboratory for Environmental Biotechnology, EPFL, Lausanne, CH-1015, Switzerland
AU: * Schroth, M H
EM: martin.schroth@env.ethz.ch
AF: Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Universitaetstr. 16, Zurich, CH-8092, Switzerland
AU: Zeyer, J
EM: josef.zeyer@env.ethz.ch
AF: Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Universitaetstr. 16, Zurich, CH-8092, Switzerland
AB: Landfills are both a major anthropogenic source and a sink for the greenhouse gas CH4. Methanogenic bacteria produce CH4 during the anaerobic digestion of landfill waste, whereas, methanotrophic bacteria consume CH4 as it is transported through a landfill cover soil. Methanotrophs are thought to be ubiquitous in soils, but typically exist in large numbers at oxic/anoxic interfaces, close to anaerobic methane sources but exposed to oxygen required for metabolism. Accurate in-situ quantification of the sink strength of methanotrophs in landfill cover soils is needed for global carbon balances and for local emissions mitigation strategies. We measured in-situ CH4 concentrations at 30, 60, and 100 cm depth at 18 evenly spaced locations across a landfill cover soil. Furthermore, we performed Gas Push-Pull Tests (GPPTs) to estimate in-situ rates of methanotrophic activity in the cover soil. The GPPT is a gas-tracer test in which a gas mixture containing CH4, O2, and non-reactive tracer gases is injected (pushed) into the soil followed by extraction (pull) from the same location. Quantification of CH4 oxidation rates is based upon comparison of the breakthrough curves of CH4 and tracer gases. We present the results of a series of GPPTs conducted at two locations in the cover soil to assess the feasibility and reproducibility of this technique to quantify methanotrophic activity. Additional GPPTs were performed with a methanotrophic inhibitor in the injection gas mixture to confirm the appropriate choice of tracers to quantify CH4 oxidation. Estimated CH4 oxidation rate constants indicate that the cover soil contains a highly active methanotrophic community.
DE: 0412 Biogeochemical kinetics and reaction modeling (0414, 0793, 1615, 4805, 4912)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting