HR: 1340h
AN: B43B-0160    [Abstracts]
TI: Methanotrophy in London, UK, Landfill Topsoil: Microbiology, Stable Carbon Isotopes, Seasonal Variation and Laboratory Model Study
AU: * Sriskantharajah, S
EM: s.sriskantharajah@gl.rhul.ac.uk
AF: Dept of Geology, Royal Holloway, University of London, Egham Hill, Egham, TW20 0EX United Kingdom
AU: Fisher, R
EM: r.fisher@gl.rhul.ac.uk
AF: Dept of Geology, Royal Holloway, University of London, Egham Hill, Egham, TW20 0EX United Kingdom
AU: Lowry, D
EM: d.lowry@gl.rhul.ac.uk
AF: Dept of Geology, Royal Holloway, University of London, Egham Hill, Egham, TW20 0EX United Kingdom
AU: Grassineau, N
EM: n.grassineau@gl.rhul.ac.uk
AF: Dept of Geology, Royal Holloway, University of London, Egham Hill, Egham, TW20 0EX United Kingdom
AU: Nisbet, E G
EM: e.nisbet@gl.rhul.ac.uk
AF: Dept of Geology, Royal Holloway, University of London, Egham Hill, Egham, TW20 0EX United Kingdom
AB: Landfill is a major source of methane emissions into the atmosphere. Aerobic soil is also a good sink of methane, as it is inhabited by methane consuming bacteria, methanotrophs. Methanotrophic bacteria were cultured from landfill soil samples. Three genera of methanotrophs were cultured: {\it Methylocaldum}, {\it Methylosinus} and {\it Methylomonas}. Interestingly, the only established members of the {\it Methylocaldum} genus are all thermophilic, whilst those isolated in this study are mesophilic. This suggests that those {\it Methylocaldum} methanotrophs found in landfills may have migrated from hot spring natural settings. Representatives of each genera were inoculated into a simple topsoil model and subjected to variations in temperature, methane concentration and incubation periods. As expected, temperature greatly affected methane oxidation, but methane concentration affected the rate of oxidation far more than expected. The model study implies that the complete combustion of methane to carbon dioxide is greatly affected by temperature and methane availability, whilst the effect on the uptake of methane is not as great. Seasonal variations in methane concentrations within the topsoil were monitored over a one year period from November 2002 to October 2003 and show that methane flow through the topsoil, and consequently methanotrophy, is strongly controlled by meteorology, mainly air temperature and pressure. Generally, methanotrophy was low during colder months and higher at during warmer months, but changes in air pressure complicate this by controlling the rate of flow of methane through the topsoil. $\delta$$^{13}$C analyses of methane and carbon dioxide emitted from landfill topsoil showed that there was a great deal of methanotrophic activity during the warmer months of 2003, with most fractionation of residual methane occurring during August. During the heat wave experienced in the UK in August 2003, the $\delta$$^{13}$C from borehole samples of methane in the anaerobic zone shifted from -57$\permil$ to -16$\permil$ at a depth of 5cm. Results derived from this study indicate that with careful engineering of landfill sites and other sources of methane emissions, methanotrophic bacteria could be employed more intensively as biological methane removal systems. This would alleviate greenhouse gas emissions.
DE: 0315 Biosphere/atmosphere interactions
DE: 0322 Constituent sources and sinks
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting