|Abstract Title:||Isotopic signatures of urban methane emissions in London, UK|
|Presenter Name:||Mrs Julianne Fernandez|
|Company/Organisation:||Royal Holloway University of London|
Abstract Information :
The challenge of understanding complex urban methane (CH4) emissions has been a growing interest worldwide. The UK National Atmospheric Emission Inventory (NAEI) heavily bases fossil fuel emissions on population density. Due to this, fugitive emissions from gas distribution and sewage systems, water treatment facilities, and out-of-service landfills, may be overestimated especially if leaking natural gas infrastructure is present. Mobile campaigns are being conducted in 3 UK cities (London, Birmingham, and Swansea) to measure emissions at close proximity and identify contributing sources. Presented here is the current progress of the London region surveys. Since May 2018, mobile surveys have been conducted targeting specific boroughs on a day basis. For spatial control, the driving strategy was to pass each 10x10 km grid square (British National Grid) of each surveyed borough. The survey vehicle is equipped with continuous mobile instruments measuring concentrations of CH4, CO2, and H2O (Picarro G2301 CRDS & A0941 Mobile Module) and concentrations of CH4/C2H6 (LGR Ultraportable CH4/C2H6 analyzer), allowing for the identification of natural gas leaks from other source category emissions. Air samples have been collected from a roof top inlet connected to a bag pump to fill 3L flexfoil bags. These samples were then analyzed for CH4 concentration and stable isotopic analysis of Î´13C-CH4 =13C/12C using an IsoPrime Trace Gas continuous flow gas chromatograph isotope ratio mass spectrometer (CF GC-IRMS) at the Royal Holloway University of London. Background baselines of CH4 concentrations and isotopic ratios for each surveyed borough has been determined and distinguished from the various plumes of high concentrations. The regional source signatures were then calculated using Keeling plot analysis. This research contributes to the trans-European mobile measurements on the MEthane goes MObile, MEasurements and MOdeling (MEMO2) project to examine temporal and spatial variations of different CH4 sources, and to the United Nations CCAC project to assess the distribution of midstream/downstream losses in the gas distribution system. Overall, a better understanding of urban CH4 will be gained using high precision stable isotopic source apportionment, benefitting future government policy in regulating anthropogenic contributions of hydrocarbon emissions.