In this study, an isotope dilution method specifically designed to detect anaerobic methane oxidation (AOM) in methanogenic wetland soils was developed. A range of anaerobic soils and sediments were screened for AOM potential. Methane and carbon dioxide emissions were investigated in strictly anoxic microcosms to which <sup>13</sup>C-labelled methane was added, and changes in the concentration and <sup>12</sup>C/<sup>13</sup>C isotope ratios of methane and carbon dioxide were subsequently measured and used to calculate the separate components of the methane flux. The results indicated that certain soils can oxidise methane oxidation anaerobically. The clearest evidence for AOM was provided by minerotrophic fen soil (pH 6.0) in Bin Forest, which is derived from ultra-basic and serpentine till. In the Bin Forest fresh soil anoxic microcosms, net consumption of methane was observed, and the amount of headspace <sup>13</sup>C-CO<sub>2</sub> increased at a greater rate than the <sup>12+13</sup>C-CO<sub>2</sub>, further proof of methane oxidation. Net methane production was observed in soil from Murder Moss, an alkaline site, pH 6.5, with a strong calcareous influence, but the <sup>13</sup>C-CH<sub>4</sub> and <sup>13</sup>C-CO<sub>2</sub> data indicated co-occurrence of AOM in this soil. Anaerobic methane oxidation was not observed in the other, lower pH soils. There was no evidence that amending anoxic slurries with up to 5.0 mM sulphate or nitrate solutions promoted anaerobic methane oxidation. Overall, this study provided good evidence for anaerobic methane oxidation in some wetland soils, and suggested that models predicting methane flux from wetland soils to the atmosphere could be improved by better understanding of the process.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:509213 |
| Date | January 2009 |
| Creators | Riekie, Gail Jocelyn |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=59018 |
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