AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Effects of Secondary Organic Aerosol coating on the Morphological Properties of Soot Aggregates from Three Sources
KAISER LEUNG, Elijah G. Schnitzler, Wolfgang Jaeger, Jason S. Olfert, University of Alberta
Abstract Number: 334 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Soot aggregates are a large contributor to global climate change and have different morphological properties such as primary particle size, effective density, and mobility diameters. The purpose of this study is to determine whether soot from difference sources with different initial morphological properties will restructure differently when coated with secondary organic aerosols (SOA). Monodispersed soot aggregates from a diesel engine generator, an inverted diffusion burner, and a McKenna burner underwent restructuring due to SOA derived from p-xylene in photo-oxidation chamber experiments. Soot aggregates were generated by a diesel Yanmar YDG3700 generator, combustion of methane using an inverted diffusion burner, or combustion of ethylene using a McKenna burner. All sources were treated to eliminate any volatile organic chemicals (VOCs) present, size-selected by differential mobility analyzer, injected into a smog chamber, and exposed to the oxidation products of p-xylene to form SOA coatings. The mobility diameter collected for the diesel generator were 70 nm, 100 nm, and 150 nm and the sizes collected for both the inverted burner and McKenna burner were 100 nm, 150 nm, 200 nm, and 250 nm. As the initial mobility diameter increased, the calculated percentage of diameter change also increased; with the diesel soot collapsing from a range of 1.2% to 11.8%, the inverted burner from 3.0% to 27.8%, and the McKenna burner from 0.8% to 16.0%. For comparable initial mobility diameters, the soot from the diesel generator collapsed significantly more relative to the inverted and McKenna burner. Effective density was also calculated for each source and it was determined that the soot aggregates from the diesel generator were the lowest, ranging from 0.38 to 0.47 kg/m$^3. For similar initial mobility diameters the effective density for the McKenna burner ranged from 0.50 to 0.689 kg/m$^3 and for the inverted burner ranged from 0.66 to 0.74 kg/m$^3.