AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Investigation of the Impact of Anthropogenic Pollution on Isoprene-derived Secondary Organic Aerosol (SOA) in PM2.5 Collected at Birmingham, AL during the 2013 Southern Oxidant and Aerosol Study (SOAS)
WERUKA RATTANAVARAHA, Kevin Chu, Sri Hapsari Budisulistiorini, Matthieu Riva, Ying-Hsuan Lin, Theran P. Riedel, Eric Edgerton, Karsten Baumann, Hongyu Guo, Rodney J. Weber, Elizabeth Stone, Zhenfa Zhang, Avram Gold, Jason Surratt, University of North Carolina at Chapel Hill
Abstract Number: 659 Working Group: Source Apportionment
Abstract Isoprene is the most abundant biogenic volatile organic compound (BVOC) emitted into the atmosphere. Studies have also shown that isoprene-derived SOA accounts for a substantial mass fraction of fine particulate matter (PM2.5). Recent work suggests that composition may affect PM2.5 toxicity, raising concerns with the effectiveness of current air quality standards in protecting human health. Chamber studies provide evidence that SOA formation is enhanced by the interaction of BVOC oxidation products with acidic sulfate aerosols from anthropogenic sources. Since control is practical only for anthropogenic contributions, understanding of how anthropogenic emissions impact biogenic SOA formation is critical for the development of effective control strategies.
In this study, high-volume PM2.5 filter samples were collected during the 2013 SOAS campaign at the Birmingham, AL ground site to investigate the impact of anthropogenic pollution on isoprene-derived SOA. Two sampling protocols were employed: (1) collection of day-time and nighttime filters and (2) collection of four filters per day to better resolve diurnal variations. Samples were chemically characterized by ultra-performance liquid chromatography/electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry and gas chromatography/electron ionization mass spectrometry (GC/EI-MS) with prior trimethylsilylation. PM2.5 sample analysis was supplemented by meteorological data and air quality measurements from collocated instruments operated by the South-Eastern Aerosol Research and Characterization (SEARCH) network. Our results indicate that isoprene-derived SOA constituents contribute significantly to the PM2.5 mass, with isoprene epoxydiol (IEPOX)-derived SOA contributing ~13% and methacrolein (MACR)-derived SOA contributing ~1% to the total organic carbon loading. Preliminary findings indicate only weak correlation between SOA tracers and aerosol acidity. Multivariate linear regression on the correlation between MACR-derived organosulfate, production rate of NO$_3, liquid water content (LWC), and particle acidity (H+ activity) suggests that the production rate of NO$_3 is a significant predictor of the MACR-derived organosulfate formation (p < 0.05), while LWC and particle acidity are not.