Methane Emissions in UK: Deciphering Regional Sources with Mobile Measurements and Isotopic Characterisation

Giulia Zazzeri

Research output: ThesisDoctoral Thesis

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UK national inventories suggest that methane emissions for waste, gas
transmission and coal mining sectors have decreased since 1990. Inventories are compiled from statistical databases multiplied by pre-defined emission factors.This “bottom-up” approach may produce precise but highly inaccurate estimates, since databases might be incomplete and emission factors poorly established.
Methane stable isotope analysis, coupled with mole fraction measurement, has
been used to link isotopic signature to methane emissions from the leading
methane sources in UK, such as landfills, gas leaks, sewage works and coal mines, and verify the consistency of UK emission inventories. A mobile Picarro G2301 CRDS analyser was installed in a vehicle, together with an anemometer and a Hemisphere GPS receiver, to measure atmospheric methane mole fractions and their relative location. When methane plumes were located and intercepted, air samples were collected for δ13C-CH4 isotopic analysis by CF-GC-IRMS (Continuous Flow-Gas Chromatography-Isotopic Ratio Mass Spectroscopy). The bulk signature of the methane plume into the atmosphere from the whole source area was obtained by Keeling plot analysis, and a δ13C-CH4 signature, with the relative uncertainty, allocated to each methane source investigated. The averaged δ13C-CH4 signature measured for landfill sites around the London region was -58 ±3 ‰, whereas the δ13C-CH4 signature for gas leaks was fairly constant at -36 ±2 ‰.
Diurnal studies were carried out in central London and Egham, measuring the
methane isotopic composition and mole fractions of air samples collected over a 24 hours period. The mean δ13C-CH4 source signature recorded in central London was -40.2 ±2.6 (2SD) ‰, revealing the primacy of fossil CH4 emissions in the CH4 budget.
From the isotopic characterisation of methane sources, the contribution to the
methane budget and the local distribution of methane sources given in inventories could be validated.
Original languageEnglish
Awarding Institution
  • Royal Holloway, University of London
  • Lowry, David, Supervisor
Award date1 Apr 2016
Publication statusPublished - 2016

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