AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Real-time Continuous Characterization and Quantification of Isoprene Epoxydiol (IEPOX)-Derived Secondary Organic Aerosol in Downtown Atlanta, Georgia Using the Aerodyne Aerosol Chemical Speciation Monitor (ACSM)
SRI HAPSARI BUDISULISTIORINI, Manjula Canagaratna, Philip Croteau, Wendy Marth, Karsten Baumann, Eric Edgerton, Stephanie Shaw, Eladio Knipping, John Jansen, Roger Tanner, Douglas Worsnop, John Jayne, Jason Surratt, University of North Carolina at Chapel Hill
Abstract Number: 604 Working Group: Source Apportionment
Abstract Real-time continuous measurements of the chemical composition of PM$_1 were made using an Aerodyne Aerosol Chemical Speciation Monitor (ACSM) during the summer and fall seasons of 2011 at Jefferson Street, Atlanta, Georgia, one of the research sites of the Southeastern Aerosol Research and Characterization (SEARCH) network.
The organic mass spectra measured by the ACSM were analyzed with positive matrix factorization (PMF), yielding three conventional factors: hydrocarbon-like organic aerosol (HOA), semi-volatile oxygenated organic aerosol (SV-OOA), and low-volatility oxygenated organic aerosol (LV-OOA). In addition to these conventional factors, in the summer PMF analysis we found an additional OOA factor that contributed on average to 32.2% to the total organic aerosol loading.
The time series of this additional factor is not correlated to anthropogenic pollutant tracers (i.e., NOx, NOy, EC, and CO) but shows a moderate correlation to SO$_(4), temperature, aerosol acidity and odd oxygen. These correlations suggest that the factor has a low-volatility and a temperature dependence that is consistent with that of biogenic VOC emissions. Comparison of this factor’s ACSM mass spectrum with that from an aerosol mass spectrometer (AMS) previously collected by our laboratory suggests that isoprene epoxydiol (IEPOX)-derived SOA may be the source of this additional factor.
In order to further investigate the source of this factor, we chemically analyzed low-volume PM$_2.5 filter samples collected from the same site by GC/MS for IEPOX-derived SOA tracers. A strong correlation (r = 0.90) was found between the additional factor and the sum of the IEPOX-SOA tracers, while the other factors were weakly or uncorrelated to the sum of the IEPOX-SOA tracers.
Results from our filter analyses constitute strong evidence that the additional OOA factor is attributable to IEPOX-derived SOA in the Atlanta metropolitan area. This finding illustrates the important contribution of isoprene oxidation to biogenic SOA in the Southeastern United States.