Quantifying methane oxidation in a landfill-cover soil by gas push–pull tests

• Published in: Waste management (Elmsford) 2009-09, Vol.29 (9), p.2518-2526
• Main Authors: Gómez, K.E., Gonzalez-Gil, G., Lazzaro, A., Schroth, M.H.
• Format: Article
• Language: English
• Subjects: ACETYLENE; Applied sciences; CARBON ISOTOPES; Carbon Isotopes - analysis; Chemical Fractionation; EMISSION; Exact sciences and technology; Extraction; General treatment and storage processes; Inhibitors; Kinetics; MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; METHANE; Methane - analysis; Methane - metabolism; Methylococcaceae - metabolism; Microorganisms; Other wastes and particular components of wastes; OXIDATION; Oxidation-Reduction; Pollution; Polymerase Chain Reaction; RARE GASES; Rate constants; REACTION KINETICS; Refuse Disposal; SANITARY LANDFILLS; Soil (material); Soil - analysis; Soil Microbiology; Waste management; WASTES
• ISSN: 0956-053X; 1879-2456
• DOI: 10.1016/j.wasman.2009.05.011

Methane (CH 4) oxidation by aerobic methanotrophs in landfill-cover soils decreases emissions of landfill-produced CH 4 to the atmosphere. To quantify in situ rates of CH 4 oxidation we performed five gas push–pull tests (GPPTs) at each of two locations in the cover soil of the Lindenstock landfill (Liestal, Switzerland) over a 4 week period. GPPTs consist of the injection of a gas mixture containing CH 4, O 2 and noble gas tracers followed by extraction from the same location. Quantification of first-order rate constants was based upon comparison of breakthrough curves of CH 4 with either Ar or CH 4 itself from a subsequent inactive GPPT containing acetylene as an inhibitor of CH 4 oxidation. The maximum calculated first-order rate constant was 24.8 ± 0.8 h −1 at location 1 and 18.9 ± 0.6 h −1 at location 2. In general, location 2 had higher background CH 4 concentrations in vertical profile samples than location 1. High background CH 4 concentrations in the cover soil during some experiments adversely affected GPPT breakthrough curves and data interpretation. Real-time PCR verified the presence of a large population of methanotrophs at the two GPPT locations and comparison of stable carbon isotope fractionation of CH 4 in an active GPPT and a subsequent inactive GPPT confirmed that microbial activity was responsible for the CH 4 oxidation. The GPPT was shown to be a useful tool to reproducibly estimate in situ rates of CH 4 oxidation in a landfill-cover soil when background CH 4 concentrations were low.