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| Titel |
Emissions of greenhouse gases and selected volatile organic compounds from UK moorland burning estimated using open-path FTIR spectrometry and burnt area measures. |
| VerfasserIn |
Thomas Smith, Katherine Allen, Robert Marrs, Michael Harris, John Dold, Martin Wooster |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250049283
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| Zusammenfassung |
| In the UK, approximately 3,000 km2 of heather moorland is managed by controlled burning
(muirburn), with individual heather patches of between  0.2 and 10 ha in area subject to
burning on a seasonal rotational basis. This management plan amounts to an annual total of Â
120 - 360 km2 of heather moorland burning each year. Full assessment of the atmospheric
effects of such open vegetation fires generally requires spatio-temporally resolved data on the
chemical makeup and magnitude of the smoke emissions. This is usually obtained via
multiplication of the amount of fuel consumed [M] by an emission factor [EFx],
representing the amount of chemical species [x] released per kilogram of dry fuel burned.
Unfortunately, emission factors for heather burning muirburns do not yet exist. This
work details new emission factors for muirburns, derived via open-path Fourier
Transform Infrared (OP-FTIR) spectroscopic measurements of the muirburn smoke
plumes.
In March 2010, two moorland sites near Debdon in Northumberland, UK, were used for a
series of experimental controlled burns. These burns are intended to be the first in a series of
experimental UK burns designed for studying emissions from rural fires. The OP-FTIR
system was positioned downwind of each experimental fire plot. The spectrometer was
aligned to view an infrared lamp located at a distance of 20 - 80 m and along a
path approximately parallel to the burning plot edge. As smoke advects across the
spectrometer-lamp path, the IR absorption by the various smoke constituents is recorded in
the measured spectra. The position and depth of the absorption features are then analysed
to retrieve the total number of molecules of each key IR absorbing gas species
present in the open-path, from which emission ratios and emission factors are then
derived.
Using a spectral forward model coupled to a non-linear least squares fitting procedure, the
IR spectra were used to derive the pathlength-amounts of CO2, CO, CH4, NH3,
C2H4, C2H6 and CH2O at six different muirburn fires. The emission ratio of each
gas to CO2 was used to first establish emission ratios and then emission factors
for each gas species, using the carbon mass balance approach. The variation in
emission factors for both heather and gorse fires was examined, along with the
variability caused by differing combustion efficiencies and fuel (vegetation) chemical
composition.
To calculate total UK moorland emissions, it is necessary to multiply the derived
emission factors (EFx) by the total amount of fuel consumed by moorland burning (M). To
estimate total fuel consumption, estimates of total UK moorland burnt area are taken from the
UK’s National Atmospheric Emission Inventory and were multiplied by estimates of
fuel density and combustion completeness, derived from data on historic burns
in both Northumberland and the Peak District National Park. These calculations
represent the first reliable, full measurement-based estimates of the total mass of
CO2, CO, CH4, NH3, C2H4, C2H6 and CH2O emitted by UK moorland burning. |
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