Measuring carbonaceous particles in air using light absorption and thermal/optical approaches

Student thesis: Doctoral ThesisDoctor of Philosophy


Carbonaceous aerosols from a variety of sites and emission sources were investigated by filter based light absorption and thermal-optical techniques to provide information on sources of airborne particles and their physical properties. Major differences were found between solid fossil fuel and vehicle emissions in thermal-optical analysis. Solid fuel emissions were characterised by high organic carbon (OC) and pyrolytic carbon (PC) content. Vehicle emissions were characterised by high elemental carbon (EC) and negligible PC. These results agreed with the high EC proportion measured at a roadside location and the dominance of OC and PC at the rural and urban sites. Results from thermo-optical analysis also revealed differences between summer and winter samples which were indicative of greater oxidation of OC during summer. A new method was developed to visualise the information from thermal-optical analyses. Termed the “absorption versus evolved carbon (AVEC) plot”, this presentation provides insight into the physical properties of particles such as the mass absorption cross section (σ). It helps to assess the effect of laser instability on the split between OC and EC, and to detect early OC evolution. The AVEC plot also provided information about the optical properties of carbonaceous particles from different sources and showed that PC has a larger value of σ than sample EC, contrary to a key assumption in thermal-optical analysis that they are the same. Using EUSAAR and NIOSH (Quartz) protocols on non-ambient samples, large amounts of evolved carbon were found near the split points which would lead to large uncertainties on the OC and EC concentrations. Aethalometer and light absorption measurements of equivalent black carbon (eBC) in the London Underground were confounded by both the iron content of the aerosol and by the particle size, highlighting a weakness of this technique in non-ambient environments. It was not possible to determine specific metrics from light absorption and thermal-optical techniques to enable source apportionment, but indicative source metrics may prove useful markers in primary matrix factorisation. These include the Angstrom coefficient (α) and loading correction factor (k) from the eBC measurements, and PC, OC peaks, EC and σ from the thermal-optical analysis.
Date of Award1 Jun 2019
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorGary Fuller (Supervisor)

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