Kinetics of Methane Oxidation in a Landfill Cover Soil: Temporal Variations, a Whole-Landfill Oxidation Experiment, and Modeling of Net CH4 Emissions

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• 作者：Jean E. Bogner ; Kurt A. Spokas ; and Elizabeth A. Burton
• 刊名：Environmental Science & Technology
• 出版年：1997
• 出版时间：September 1997
• 年：1997
• 卷：31
• 期：9
• 页码：2504 - 2514
• 全文大小：278K
• 年卷期：v.31,no.9(September 1997)
• ISSN：1520-5851

文摘

Rates and controlling variables for methanotrophicoxidationof methane at a northeastern Illinois landfill with pumpedgas recovery were examined in a field study from Juneto December 1995. Cover materials consisted of a simpleclay-topsoil sequence without geomembranes. Through useof a static enclosure (closed chamber) technique supplemented by soil gas concentration profiles and fieldincubations, the study concentrated on proximal (near gasrecovery well) and distal (between well) sites establishedin 1994. A personal computer-based three-dimensionalfinite-difference model was also developed which includes bothgaseous mass transfer (CH₄, CO₂,O₂) and microbial CH₄oxidation. Mass transfer is modeled through amodifiedchemical potential gradient within a cubic network ofnodes; a strict mass balance for each gas is maintainedthrough successive timesteps. Methane-oxidizingconditionswith no net CH₄ emissions to the atmospherepersistedinto full winter conditions in December, 1995. Rates ofCH₄oxidation (negative fluxes) from closed chamberexperimentswere similar to rates obtained from in vitrofieldincubations with initial headspace CH₄ at ambientatmosphericconcentrations (1-2 ppmv). Composited data from thechamber tests and field incubations demonstrated thatoxidation rates were able to rapidly increase over 4 orders ofmagnitude as a direct kinetic response to broad ranges ofinitial CH₄ concentrations (from ambient to 8.4 vol %).Themaximum observed rate was 48 g m^-2day^-1. Kinetic plotsindicated at least two major trophic groups of methanotrophs: a CH₄-limited group (low CH₄; ambientO₂) and an O₂-limited group (high CH₄; subambient O₂).The whole-landfill CH₄ oxidation experiment was conducted over a2day period when the pumped gas recovery system wasshut down and restarted; oxidation rates increased andthendecreased more than 2 orders of magnitude in responseto changing CH₄ concentrations. Although themodelingrelies on theoretical considerations for both gaseous fluxanddevelopment of microbial populations, the LandfillCH₄Emissions Model requires a limited number of inputvariablesand provides a practical tool for order-of-magnitudeprediction of net CH₄ fluxes at fieldsites.