AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Soot Aggregate Restructuring due to Coatings of Secondary Organic Aerosol from Aromatic Precursors
ELIJAH G. SCHNITZLER, Jason S. Olfert, Wolfgang Jaeger, University of Alberta
Abstract Number: 418 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Soot aggregates are emitted from many sources, such as biomass burning and diesel engines, and have a significant warming effect on climate. The extent of this effect depends on the optical and morphological properties of the aggregates, and these properties evolve during the lifetime of the aggregates. For example, aggregates can be coated by neat liquids, such as sulfuric acid, or complex mixtures of compounds, such as the array of semi-volatile oxidation products present in secondary organic aerosol (SOA). Such coatings, through surface tension effects, tend to restructure and, more specifically, compact the aggregates. Past studies have characterized aggregate restructuring due to neat liquids, including sulfuric acid and oleic acid, and mixtures, including SOA derived from alpha-pinene, toluene, and isoprene. In this study, we further characterized aggregate restructuring due to SOA derived from aromatic precursors, including benzene, toluene, para-xylene, and ethylbenzene. Two sets of experiments were carried out. In the first set, the maximum change in aggregate diameter due to SOA coatings was measured for initially 100, 150, 200, and 250 nm aggregates, using a tandem differential mobility analyzer. Briefly, soot aggregates were dried, denuded, neutralized, classified, and injected into a smog chamber; an aromatic SOA precursor and hydrogen peroxide were injected into the chamber; and the chamber was irradiated with black lights. In the second set of experiments, the coating mass was measured using a centrifugal particle mass analyzer, and the coating mass dependence of aggregate restructuring was determined for coatings derived from each SOA precursor.