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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 1 | Copyright
Atmos. Chem. Phys., 18, 385-403, 2018
https://doi.org/10.5194/acp-18-385-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 12 Jan 2018

Research article | 12 Jan 2018

Highly controlled, reproducible measurements of aerosol emissions from combustion of a common African biofuel source

Sophie L. Haslett1, J. Chris Thomas2, William T. Morgan1, Rory Hadden2, Dantong Liu1, James D. Allan1,3, Paul I. Williams1,3, Sekou Keita4, Cathy Liousse5, and Hugh Coe1 Sophie L. Haslett et al.
  • 1Centre for Atmospheric Science, University of Manchester, Manchester, M13 9PL, UK
  • 2School of Engineering, University of Edinburgh, Edinburgh, EH9 3JL, UK
  • 3National Centre for Atmospheric Science, University of Manchester, Manchester, M13 9PL, UK
  • 4L'Université Félix Houphoët-Boigny, VPV34, Abidjan 01, Côte d'Ivoire
  • 5Laboratoire d'Aérologie, Université Paul Sabatier Toulouse III, Toulouse, France

Abstract. Particulate emissions from biomass burning can both alter the atmosphere's radiative balance and cause significant harm to human health. However, due to the large effect on emissions caused by even small alterations to the way in which a fuel burns, it is difficult to study particulate production of biomass combustion mechanistically and in a repeatable manner. In order to address this gap, in this study, small wood samples sourced from Côte D'Ivoire in West Africa were burned in a highly controlled laboratory environment. The shape and mass of samples, available airflow and surrounding thermal environment were carefully regulated. Organic aerosol and refractory black carbon emissions were measured in real time using an Aerosol Mass Spectrometer and a Single Particle Soot Photometer, respectively. This methodology produced remarkably repeatable results, allowing aerosol emissions to be mapped directly onto different phases of combustion. Emissions from pyrolysis were visible as a distinct phase before flaming was established. After flaming combustion was initiated, a black-carbon-dominant flame was observed during which very little organic aerosol was produced, followed by a period that was dominated by organic-carbon-producing smouldering combustion, despite the presence of residual flaming. During pyrolysis and smouldering, the two phases producing organic aerosol, distinct mass spectral signatures that correspond to previously reported variations in biofuel emissions measured in the atmosphere are found. Organic aerosol emission factors averaged over an entire combustion event were found to be representative of the time spent in the pyrolysis and smouldering phases, rather than reflecting a coupling between emissions and the mass loss of the sample. Further exploration of aerosol yields from similarly carefully controlled fires and a careful comparison with data from macroscopic fires and real-world emissions will help to deliver greater constraints on the variability of particulate emissions in atmospheric systems.

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Wood burning is chaotic, so the particles emitted can be difficult to study in a repeatable way. Here, we addressed this problem by carefully controlling small wood fires in the lab. We saw three burning phases, which could be told apart chemically; we also saw evidence of these in measurements of wood burning in London in 2012. Controlled experiments like this help us to understand why emissions are so variable and to recognise burning conditions just from the particles seen in the atmosphere.
Wood burning is chaotic, so the particles emitted can be difficult to study in a repeatable way....
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