Measurements of in-situ SOA Formation and Chemistry Using an Oxidation Flow Reactor at GoAmazon2014 and Other Campaigns
Brett B Palm1,2, Pedro Campuzano-Jost3, Doug A Day4,5, Weiwei Hu6,7, Amber M Ortega7,8, Suzane S de Sá9, Roger Seco10, Jeong-Hoo Park11, Alex B Guenther10, Saewung Kim12, Joel Ferreira De Brito13, Florian Wurm13, Paulo Artaxo13, Ryan M Thalman14, Jian Wang15, Lina Hacker16, Astrid Kiendler-Scharr17, Lindsay Yee18, Gabriel A Isaacman-VanWertz19, Allen H Goldstein20, Rodrigo Augusto Ferreira de Souza21, Antonio O Manzi22, Jose Oscar Vega Bustillos23, Julio Tota24, Matt K Newburn25, M. Lizabeth L Alexander26, Scot T Martin27, William H Brune28, Jose L Jimenez29,30 and BEACHON-RoMBAS Collaborators, (1)University of Colorado at Boulder, Boulder, United States, (2)University of Colorado at Boulder, Cooperative Institute for Research in Environmental Sciences, Boulder, CO, United States, (3)University of Colorado Boulder, Department of Chemistry and Cooperative Institute for Research in Environmental Sciences, Boulder, United States, (4)Cooperative Institute for Research in Environmental Sciences (CIRES), Boulder, United States, (5)University of Colorado at Boulder, Chemistry, Boulder, United States, (6)Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China, (7)Cooperative Institute for Research in Environmental Sciences, Boulder, CO, United States, (8)University of Colorado at Boulder, Boulder, CO, United States, (9)Harvard University, School of Engineering and Applied Sciences, Cambridge, MA, United States, (10)University of California Irvine, Department of Earth System Science, Irvine, CA, United States, (11)National Center for Atmospheric Research, Boulder, CO, United States, (12)University of California Irvine, Department of Earth System Science, Irvine, United States, (13)USP University of Sao Paulo, São Paulo, Brazil, (14)Brookhaven National Laboratory, Upton, NY, United States, (15)Brookhaven Natl Lab, Upton, United States, (16)Forschungszentrum Jülich, Institute for Energy and Climate Research: Troposphere (IEK-8), Jülich, Germany, (17)Forschungszentrum Jülich GmbH, Institute of Climate and Energy Systems, Troposphere (ICE-3), Jülich, Germany, (18)University of California Berkeley, Department of Environmental Science, Policy, & Management, Berkeley, CA, United States, (19)University of California Berkeley, Berkeley, CA, United States, (20)University of California Berkeley, Department of Civil & Environmental Engineering, Berkeley, CA, United States, (21)Universidade do Estado do Amazonas, Manaus, AM, Brazil, (22)Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil, (23)IPEN Nuclear Energy Research Institute, Sao Paulo, Brazil, (24)Federal University of Western Pará, Santarém, Brazil, (25)Pacific Northwest National Laboratory, Environmental Molecular Sciences Laboratory, Richland, WA, United States, (26)Pacific Northwest National Laboratory, Richland, WA, United States, (27)Harvard University, Department of Earth and Planetary Sciences, Cambridge, MA, United States, (28)Pennsylvania State University, University Park, PA, United States, (29)Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado Boulder, Boulder, United States, (30)Cooperative Institute for Research in Environmental Sciences (CIRES) and Department of Chemistry, Boulder, United States
Abstract:
During several recent field campaigns including GoAmazon2014, ambient gases and particles were exposed to controlled concentrations of OH, O3 or NO3 in-situ using a Potential Aerosol Mass oxidation flow reactor. Oxidant exposure in the reactor ranged from an hour to several weeks of equivalent atmospheric residence time, allowing the study of SOA formation and chemistry over long time scales. Oxidized air from the reactor was sampled directly (e.g., HR-AMS, ACSM, PTR-TOFMS, SMPS, CCN), and these results were compared with collocated biogenic and anthropogenic tracers (e.g., SV-TAG sesquiterpenes and PTR-TOFMS aromatics, isoprene, and monoterpenes). In all studies, OH oxidation of ambient air in the reactor led to substantial SOA mass production (often several µg/m3 of SOA) during times of high precursor gas concentrations. While SOA production correlated with measured gas-phase precursors, the total mass formed in the reactor was generally several times larger than could be explained by the aerosol yields of measured VOC’s. This suggests that a majority of gases that formed SOA in the reactor were not the primary VOCs considered as traditional SOA precursors. Additionally, most of the SOA mass increase occurred in the first day of equiv. atmospheric aging, suggesting that ambient SOA is predominantly formed close to emission sources of precursors with gas-phase reaction lifetimes of <1 day. At a remote Colorado pine forest site (during BEACHON-RoMBAS), the mainly biogenic aerosol formed in the reactor from <1 equivalent day of oxidation had an atomic O:C of 0.54, similar to the existing ambient aerosol O:C of 0.61. As OH exposures increased (up to 10-20 equivalent days), the OA became highly oxidized (O:C>1) and partially revolatilized, demonstrating the competing effects of functionalization/condensation at low exposures vs. fragmentation/evaporation reactions for high exposures. SOA formation from O3 and NO3 oxidation correlated with biogenic gas-phase precursors, but led to smaller (<0.5 µg/m3) SOA production, consistent with the ability for OH to achieve more generations of oxidation than O3 or NO3. Measurements taken in a variety of biogenic ecosystems with a wide range of anthropogenic influence were compared, allowing investigation of the effects of anthropogenic pollution on SOA formation.
