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Title: Tracing the origin and fate of methane in waterlogged oxic soil using flux, biomarker and stable isotope probing methods
Author: Lim, Katie Lian Hui
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2013
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Oxic soils are generally classed as a sink for atmospheric methane (CH4), as methanotrophy far outweighs internal production. However, CH4 production can be stimulated in such soils by exposure to wet conditions, or even cause them to act as a net CH4 source. The work detailed in this thesis was carried out with the aims of investigating the nature and distributions of the microbial communities controlling CH4 cycling in waterlogged aerobic soils, and assessing their potential to respond to marginal increases in soil moisture and aeration conditions caused by climate-change induced precipitation. The concentration of archaeol in its free and conjugated forms was investigated within three oxic soils using gas chromatography/mass spectrometry (GC/MS) in combination with selected ion monitoring (SIM). Archaeol was proposed to be a biomarker for methanogenic biomass in such soils on the basis that trends in abundance differed from Thaumarchaeota-derived crenarchaeol. Phospholipid and glycosidic archaeol seemed to derive from extant and fossilised methanogen biomass, respectively. Observed trends in concentrations were attributed to carbon contents and soil moisture, due to their association with the development of anoxic microniches and substrate availability. The presence and distribution of glycerol dialkyl glycerol tetraethers (GDGTs), detennined by high performance liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry (HPLC/ APCI-MS), were investigated within two highmoisture, oxic soils. As with archaeol, trends in distribution were driven by organic matter content and soil moisture. Bacteria-derived GDGTs dominated at both sites. Isoprenoid GDGTs I and II-IV derived from a mutual archaeal source, potentially methanogens; however, distributions did not reflect archaeol concentrations.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available