AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
NO3-initiated Oxidation of Isoprene: Oxidation Mechanism and Aerosol Formation
BELLAMY BROWNWOOD, Juliane Fry, Reed College
Abstract Number: 605 Working Group: Aerosol Chemistry
Abstract Secondary organic aerosol from NO3-initiated isoprene oxidation in nighttime conditions has been thought to be extremely low, due to the high volatility and small size of the isoprene precursor. Previous studies have showed low but highly variable secondary organic aerosol (SOA) yields. We present alkyl nitrate and SOA yields measured in the Reed Environmental Chamber (REC) and Simulation of Atmospheric PHotochemistry In a Large Reaction Chamber (SAPHIR) under varying chemical regimes (RO2 + RO2, RO2 + NO3, RO2 + HO2, and RO2 unimolecular reactions) and varying total aerosol mass loading. In the smaller REC chamber, we observe low organonitrate yields, around 10% total (gas + particle) alkyl nitrate (AN) yield. In contrast, in the larger SAPHIR Chamber we observe consistently higher organonitrate molar yields of ~ 40 %. We model observed yields in terms of absorptive partitioning and assess partitioning coefficients (Kp). Observed differences in yields and partitioning across the two chambers may be due to proportionally much higher wall losses in the smaller chamber when aerosol loading is low.