Source Apportionment of Organic Aerosol Informed by ASCENT Instrumentation at Look Rock, Great Smoky Mountains National Park
NICOLAS A. BUCHENAU, Cade Christensen, James Renfro, Bill Hicks, Roya Bahreini, Ann M. Dillner, Armistead G. Russell, Nga Lee Ng, Jason Surratt, University of North Carolina at Chapel Hill
Abstract Number: 606
Working Group: Source Apportionment
Abstract
The Atmospheric Science and Chemistry Measurement Network (ASCENT) site in Look Rock, Great Smoky Mountains National Park is intended to characterize the aerosol typical of the rural Southeastern United States and is located between sources of biogenic and anthropogenic emissions. Deployment of ASCENT instrumentation to Look Rock, especially the time-of-flight aerosol chemical speciation monitor (TOF-ACSM, Aerodyne Research Inc.) has demonstrated the predominance of organic aerosol within PM2.5 at the site, which occurs in the context of a long-term decline in sulfate aerosol. Understanding the origins of organic aerosol at Look Rock may shed light on aerosol formation processes contributing to much of the background aerosol found in the rural Southeastern United States. Source apportionment of TOF-ACSM organic mass spectra using positive matrix factorization (PMF) is used to characterize organic aerosol (OA) types at Look Rock in 2024. The additional ASCENT instrumentation, the Aethalometer AE33 (Magee Scientific), Scanning Mobility Particle Sizer (SMPS, TSI Inc.), and Xact 625i (Sailbri Cooper Inc.) provide additional context on aerosol physical and chemical properties to aid in interpreting TOF-ACSM source apportionment results. Source apportionment of 2024 ASCENT Look Rock data are compared against prior source apportionment studies which analyzed data collected at Look Rock in 2013. PMF analysis reveals the presence of hydrocarbon-like organic aerosol (HOA) in 2024, a component of OA previously unobserved in 2013. In addition, PMF of 2024 data confirms the continued presence of biomass burning aerosol, isoprene-derived secondary organic aerosol (SOA), and oxidized SOA.