AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Ozone Reactions with Squalene: Particle Seeding and Formation
BREANN COFFARO, Clifford Weisel, Rutgers, The State University of New Jersey
Abstract Number: 868 Working Group: Indoor Aerosols
Abstract Particulate matter (PM) has been reported to form from the reaction of ozone and squalene, a natural component of skin oil. These particles contain carbonyls and organic acids, which can be potential respiratory and ocular irritants, so indoor exposures are of concern. A controlled reaction chamber was used to investigate the conditions that lead to particulate formation from squalene-ozone (SqO) reactions arising through nucleation mechanisms. Particle counts were analyzed with a TSI Condensation Particle Counter. Initial experiments with filtered background ambient air containing PM levels of 1,000-4,000 particles (#/cc) often resulted in the formation of an additional 5,000-10,000 #/cc about 20-60 minutes after the introduction of ozone during the spring and summer. During the fall and winter, particle formation was less consistent suggesting that the composition of the background particles is important in serving as nucleation sites. Spring and summer particles typically have higher organic content. An immediate large spike in PM counts (20,000 #/cc) was observed if new squalene was placed in the reaction chamber after the PM returned to background levels during the spring/summer, suggesting the presence of some residual organic nucleation particles. To further evaluate the role of nucleation in SqO particle formation, two sources of particles often present indoors were examined: PM formed by a heated nichrome wire and secondary organic aerosols formed from limonene and ozone. The nichrome wire particles, which are predominantly inorganic, did not result in particles produced from the SqO reaction while particles from the limonene ozone reactions resulted in formation of approximately 55,000 #/cc almost immediately after the introduction of the squalene. These results suggest that organic nucleation particles are an important component for the formation of particles from the reaction of ozone with squalene which influences indoor air counts and PM composition.