AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Monoterpene Oxidation Products Dominate Organic Aerosol Mass in Centreville, Alabama during the SOAS Field Campaign
HAOFEI ZHANG, Lindsay Yee, Ben Lee, Michael Curtis, Dave Worton, Gabriel Isaacman-VanWertz, Claudia Mohr, Felipe Lopez-Hilfiker, John Offenberg, Michael Lewandowski, Tad Kleindienst, Melinda Beaver, Amara Holder, William Lonneman, Kenneth Docherty, Mohammed Jaoui, Havala Pye, Weiwei Hu, Douglas Day, Pedro Campuzano-Jost, Jose-Luis Jimenez, Joel A. Thornton, Allen H. Goldstein, University of California, Berkeley
Abstract Number: 304 Working Group: Aerosol Chemistry
Abstract Comprehensively characterizing atmospheric organic aerosol (OA) composition is crucial to understanding its origins and environmental impacts. The extreme chemical complexity of OA has been a barrier to progress in this field. Here, we provide new constraints on OA origins through molecular-level speciation coupled to bulk measurements of fossil vs. modern carbon and oxygenated OA at Centreville, Alabama, during summer 2013, as part of the Southern Oxidant and Aerosol Study (SOAS) field campaign. 254 ambient aerosol samples were collected at 4-hour time resolution and analyzed using a Thermal Desorption Two-Dimensional Gas Chromatography High-resolution Time-Of-Flight Mass Spectrometer (TD-GC×GC/HTOF-MS) with on-line trimethylsilylation derivatization to obtain clear chemical separation with extensive ranges of volatility and polarity. This off-line measurement was complemented by on-line analysis of OA chemical composition using a high-resolution time-of-flight chemical ionization mass spectrometer with a filter inlet for gases and aerosols (FIGAERO-HRToF-CIMS) using iodide-adduct (I-) ionization.
By comprehensively analyzing OA chemical composition combining the two molecular-level approaches, we determined that monoterpene secondary OA (MTSOA) contributes more than half of total fine OA (PM1) mass, significantly higher than current regional model predictions. The time series of the measured MTSOA correlate strongly with the total of oxygenated OA (OOA) factors resolved by AMS-PMF analysis, suggesting that the majority of oxidized OA during SOAS are MTSOA. Moreover, characterized anthropogenic OA (POA + anthropogenic SOA) which have < 10% of total OA mass account for almost all the fossil carbon mass measured by radiocarbon (14C) analysis, confirming that most OA at SOAS are modern carbon.