Analysis and interpretation of ambient data for CO2, CH4 and CO recorded in Southwest London during 2000 to 2012

Ivan Hernandez

Research output: ThesisDoctoral Thesis

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CO2 and CH4 current levels are the highest recorded during the Anthropocene
epoch due, mostly, to emissions from anthropogenic activities. These emissions
have modified the biochemical cycle of C and earth’s thermal equilibrium. In
contrast, CO emissions have decreased since 2000 following the strict controls on vehicle emissions. Atmospheric observations can be used to detect trends and changes in CO2, CH4 and CO concentrations, and also, to locate and characterize natural and anthropogenic sources. In situ measurements of atmospheric CO2, CH4 and CO have been performed at Royal Holloway University of London since 2000 to 2012 and standardised using NOAA calibration gases.
CO2, CH4 and CO varied on time scales ranging from minutes to inter-annual and annual cycles. Diurnal cycles were observed and varied with the length daylight which influences the net soil uptake of CO2, the concentration of OH radicals and, the degree of vertical mixing. There is a greater influence of CO2 and CO anthropogenic emissions during weekdays when fossil fuel use and combustion processes are higher than at weekends not observed for CH4. CO2 showed an increasing trend of 2.45 ppm yr-1 data for the whole dataset; a higher rate of increase than the observed global trend due to higher regional combustion emissions such as airplanes, houses and cars on highly loaded motorways. By contrast, CO showed a progressive decline not linear, but if linearized the decline rate was 15.3 ppb CO yr-1, while CH4 concentration remained steady.
The data set was split into 8 categories (45°) using wind sector analysis. This shows that the greatest concentrations for the three carbon gas are recorded from the NE, E and SE sectors. The lowest concentrations were observed for air from the S and SW sectors. Back trajectory and meteorological analysis of the data confirmed that the dominant sources of CO2, CH4 and CO are anthropogenic emissions from Greater London area and the dense local road network to the East of the measurement site.
Nowadays, compared with Mace Head (West Ireland) data, the CO2 measured at
Egham is slightly higher than at Mace Head while CO and CH4 is not far above
Atlantic background levels during large periods of the year when prevailing S-SW
winds reach the site. The Egham record implies that controls on CO emissions
subsequent to legislation have been extremely successful the UK.
Original languageEnglish
Awarding Institution
  • Royal Holloway, University of London
  • Clemitshaw, Kevin, Supervisor
  • Lowry, David, Supervisor
  • Nisbet, Euan, Advisor
Thesis sponsors
Award date1 Nov 2014
Publication statusUnpublished - 2014


  • long-term trend
  • seasonal cycle
  • Air pollutants

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