UBC Theses and Dissertations
Measurements of black carbon properties during cloud, biomass burning, and free tropospheric conditions at a marine boundary layer site and high elevation mountain site Schroder, Jason C.
Black carbon is a subset of the total atmospheric aerosol population that is formed in the incomplete combustion of fossil fuels, biofuels, and biomass. This research focused on the properties of black carbon particles measured in the boundary layer and free troposphere, as well as the activation of black carbon particles by cloud droplets. The primary motivation for this research is to increase our understanding of the properties of black carbon under these different atmospheric conditions. A single particle soot photometer was used to study properties of black carbon particles incorporated into cloud droplets at two field locations: 1) a marine boundary layer site, and 2) a high elevation mountain site. At both sites, a size dependence on the fraction of black carbon incorporated into cloud droplets was observed; and for small (<100 nm) diameters, black carbon was efficiently incorporated into droplets. In addition, at the marine boundary layer site, thick coatings were observed on the small diameter black carbon particles that were incorporated into the droplets, which was consistent with theory. The single particle soot photometer was also used at a high elevation mountain site to investigate properties of black carbon from biomass burning and black carbon within the free troposphere. The average mass concentration of black carbon was found to be significantly higher (approximately 9x) during periods of biomass burning than within the free troposphere, yet had similar mass median diameters. Coating thicknesses of black carbon containing particles during the two subsets of data were also investigated. Average coating thicknesses for black carbon core diameters between 140 to 160 nm was 55 nm when sampling in the free troposphere, but approximately 32 nm when sampling air masses influenced by biomass burning. The results presented in this dissertation increase our understanding of the properties of black carbon particles and how they vary as a function of location and type of air mass sampled. This information can be used to further constrain computer models that are used to predict how black carbon can affect climate.
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