Real-Time Continuous Characterization of Secondary Organic Aerosol Derived from Isoprene Epoxydiols in Downtown Atlanta, Georgia, Using the Aerodyne Aerosol Chemical Speciation Monitor

Real-time continuous chemical measurements of fine aerosol were made using an Aerodyne Aerosol Chemical Speciation Monitor (ACSM) during summer and fall 2011 in downtown Atlanta, Georgia. Organic mass spectra measured by the ACSM were analyzed by positive, matrix factorization (PMF), yielding three conventional factors: hydrocarbon-like organic aerosol (HOA), semivolatile oxygenated organic aerosol (SV-OOA), and low-volatility organic aerosol (LV-OOA). An additional OOA factor that contributed 33 +/- 10% of the organic mass was resolved in summer. This facto had a mass spectrum that strongly correlated (r(2) = 0.74) to that obtained from laboratory-generated secondary organic aerosol (SOA) derived from synthetic isoprene epoxydiols (IEPDX). Time series of this additional factor is also well correlated (r(2) = 59) with IEPDX-derived SOA tracers from filters collected in Atlanta but less correlated (r(2) < 0.3) with a methactylic acid epoxide (MAE)-derived SOA tracer, alpha-pinene SOA tracers, and a biomass burning tracer (i.e., levoglucosan), and primary emissions. Our analyses suggest IEPDX as the source of this additional factor, which has some correlation with aerosol acidity (r(2) = = 0.3), measured as H+ (nmol m(-3)), and sulfate mass loading (r(2) = 0.48), consistent with prior work showing that these two parameters promote heterogeneous chemistry g us of IEPDX to form SOA.