Measurements of in-situ SOA Formation Using an Oxidation Flow Reactor at GoAmazon2014/5

Tuesday, 15 December 2015: 14:40
3008 (Moscone West)
Brett B Palm1, Suzane S de Sá2, Pedro Campuzano Jost3, Douglas A Day4, Weiwei Hu1, Roger Seco5, Jeong-Hoo Park6, Alex B Guenther7, Saewung Kim7, Joel Brito8, Florian Wurm9, Paulo Artaxo9, Lindsay Yee10, Gabriel A Isaacman-VanWertz10, Allen H Goldstein10, Rodrigo Augusto Ferreira de Souza11, Antonio O Manzi12, Jose Oscar Vega Bustillos13, Julio Tota14, Matt K Newburn15, M. Lizabeth L Alexander16, Scot T Martin2, William H Brune17 and Jose L Jimenez18, (1)University of Colorado at Boulder, Boulder, CO, United States, (2)Harvard University, Cambridge, MA, United States, (3)University of Colorado Boulder, Boulder, CO, United States, (4)CIRES, Boulder, CO, United States, (5)University of California Irvine, Dept. of Earth System Science, Irvine, CA, United States, (6)NIER National Institute of Environmental Research, Incheon, South Korea, (7)University of California Irvine, Irvine, CA, United States, (8)Universidade de São Paulo, Instituto de Física, São Paulo, Brazil, (9)USP University of Sao Paulo, São Paulo, Brazil, (10)University of California Berkeley, Berkeley, CA, United States, (11)Organization Not Listed, Washington, DC, United States, (12)National Institute for Amazon Research (INPA), Manaus, AM, Brazil, (13)IPEN Nuclear Energy Research Institute, Sao Paulo, Brazil, (14)Federal University of Western Para, Santarem, Brazil, (15)Pacific Northwest National Laboratory, Environmental Molecular Sciences Laboratory, Richland, WA, United States, (16)Pacific Northwest National Laboratory, Richland, WA, United States, (17)Pennsylvania State University Main Campus, University Park, PA, United States, (18)University of Colorado at Boulder, Dept. of Chemistry and Biochemistry, Boulder, CO, United States
During GoAmazon2014/5, ambient air was exposed to controlled concentrations of OH or O3 in-situ using an oxidation flow reactor (OFR). Oxidation ranged from hours–several weeks of aging. Oxidized air was sampled by several instruments (e.g., HR-AMS, ACSM, PTR-TOF-MS, 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 µg/m3 to greater than 10 µg/m3. O3 oxidation of ambient air also led to SOA formation, although much less than from OH oxidation. Preliminary PMF factor analysis showed that the less-oxidized OOA (LO-OOA) factor was produced at up to several days OH aging, while at longer ages the more-oxidized OOA (MO-OOA) factor was formed and LO-OOA was depleted. HOA, BBOA, and IEPOX-SOA factors were not formed in the reactor, just depleted at high ages (though at different rates). More detailed PMF results will be presented. 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). The 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 VOCs were added individually into ambient air in the OFR and oxidized by OH or O3. SOA yields were similar to published chamber yields.