AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Measurements of In-situ SOA Formation Using an Oxidation Flow Reactor at GoAmazon2014/5
BRETT PALM, Suzane Simoes de Sa, Pedro Campuzano-Jost, Douglas Day, Weiwei Hu, Roger Seco, Jeong-Hoo Park, Alex Guenther, Saewung Kim, Joel Brito, Florian Wurm, Paulo Artaxo, Lindsay Yee, Gabriel Isaacman-VanWertz, Allen H. Goldstein, Rodrigo A. F. Souza, Antonio O. Manzi, Oscar Vega, Julio Tota, Matt Newburn, Lizabeth Alexander, Scot Martin, William Brune, Jose-Luis Jimenez, University of Colorado
Abstract Number: 576 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract During GoAmazon2014/5, ambient air was exposed to controlled concentrations of OH or O$_3 in-situ using an oxidation flow reactor (OFR). Oxidant exposures ranged from hours–several weeks of equivalent atmospheric oxidation. Oxidized air was sampled by several instruments (e.g., HR-AMS, ACSM, PTR-TOFMS, SMPS, CCN) at both the T3 site (IOP1: Feb 1–Mar 31, 2014, and IOP2: Aug 15–Oct 15, 2014) and T2 site (between IOPs and into 2nd IOP). Oxidation of ambient air in the OFR led to significant and dynamic SOA formation. In general, more SOA was produced during the nighttime than daytime, and more in the dry season (IOP2) than wet season (IOP1). The maximum amount of SOA produced during nighttime from OH oxidation ranged from less than 1 microgram/m$^3 to greater than 10 micrograms/m$^3. O$_3 oxidation of ambient air also led to SOA formation, although much less than from OH oxidation. Variations in the amount of SOA formation often, but not always, correlated with measured gas-phase biogenic and/or anthropogenic SOA precursors (e.g., SV-TAG sesquiterpenes, PTR-TOFMS aromatics, isoprene, and monoterpenes). PMF factor analysis and comparisons to SOA precursors measured at GoAmazon2014/5 will be discussed in order to investigate anthropogenic vs biogenic SOA formation. The total SOA mass formed in the OFR was ~10x larger than could be explained by aerosol yields of measured primary VOCs, suggesting that most SOA was formed from intermediate sources such as S/IVOCs (e.g., VOC oxidation products or evaporated POA), consistent with previous OFR field and lab studies. To verify the SOA yields of VOCs under OFR experimental conditions, atmospherically-relevant concentrations of several monoterpenes, sesquiterpenes, isoprene, or toluene were added into ambient air in the OFR and oxidized by OH or O$_3. SOA yields were similar to published yields from chamber studies. Results will be compared to observations from other recent campaigns.