Real-Time Characterization of Fine Aerosol Composition during the First Year of Continuous Operation at the Look Rock, TN ASCENT Site
NICOLAS ALIAGA 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: 550
Working Group: Coast to Coast Campaigns on Aerosols, Clouds, Chemistry, and Air Quality
Abstract
A near yearlong (2023-2024) real-time chemical characterization of fine aerosol (PM2.5) was conducted as part of the Atmospheric Science and Chemistry Measurement Network (ASCENT) at the Look Rock, TN site in Great Smoky Mountains National Park, which serves as the network’s rural, background site in the Southeastern United States. A Time-of-Flight Aerosol Chemical Speciation Monitor (ToF-ACSM, Aerodyne Research, Inc.) was used to provide real-time composition measurements of non-refractory fine aerosol, allowing us to conduct positive matrix factorization for identifying distinct organic aerosol components indicative of varying sources and atmospheric chemical processes. Fine aerosol characterization was assisted by the colocation of other ASCENT instruments: an AE33 aethalometer (Aerosol Magee Scientific) and Xact 652i (Sailbri Cooper, Inc.) for near real-time black carbon and metals measurements, respectively, and a 3839W89 Scanning Mobility Particle Sizer (TSI, Inc.) for near real-time fine aerosol size characterization. Fine aerosol composition measured during 2023-2024 will be compared against measurements and source apportionment results obtained from the 2013 field campaigns at Look Rock using a Quadrupole ACSM (Aerodyne Research, Inc.). The 2023-2024 PM2.5 aerosol composition is predominantly organic, and when compared to the 2013 PM1 baseline, demonstrates a substantial reduction (up to 70%) in particulate sulfate concentration, with average winter and spring sulfate declining to approximately ~0.4 µg m-3 and ~0.5 µg m-3, respectively. Potential implications of changing inorganic composition on organic aerosol components at Look Rock will be considered. The 2023-2024 dataset is additionally marked by the presence of several short-term high aerosol concentration events presumed to result from smoke plumes derived from sources such as local prescribed burning and the 2023 Canadian wildfires.