(673f) Aerosol Composition and Sources in the Atlanta Area Measured by High Resolution Mass Spectrometry

The extent to which human activities affect secondary organic aerosol (SOA) formation and evolution is highly uncertain and poorly understood. It is established that aerosol formed from biogenic sources is the dominant contributor to global SOA. However, there exists an apparent contradiction that OA is predominately “modern” (indicative of a biogenic origin) but often correlates with anthropogenic tracers. The Atlanta area is characterized by high emissions of both biogenic and anthropogenic sources, ambient measurements in such areas can provide invaluable insights into the interaction of biogenic and anthropogenic emissions. In this study, a High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) is deployed at four different sites (~ 3 weeks at each site) in the Atlanta area, including: Jefferson Street (urban), Yorkville (rural, 55km NW of Atlanta), a roadside site (near Highway 75/85), and a near roadside site (Georgia Tech campus). Georgia Tech and Emory have recently been awarded an EPA health center (Southeastern Center for Air Pollution & Epidemiology, SCAPE) to study health effects of air pollution. The deployment of the HR-ToF-AMS overlaps with the SCAPE measurements to take advantage of all the co-located gas and particle phase data from SCAPE. The HR-ToF-AMS provides quantitative measurement of non-refractory submicron aerosol composition and size distribution with high time resolution. Total mass concentrations and diurnal trends of organics, nitrate, sulfate, ammonium, and chloride at each sampling site are reported. Elemental analyses are performed to determine elemental composition of the bulk OA, including oxygen/carbon (O/C), hydrogen/carbon (H/C), and nitrogen/carbon (N/C) ratios. Positive matrix factorization (PMF) is used to deconvolve the OA into different components, reflecting OA of different sources and/or photochemical processing.  Preliminary PMF results are presented to show the relative importance of hydrocarbon-like organic aerosols (HOA) and different types of oxygenated organic aerosols (OOA), which are surrogates of primary and secondary OA, respectively. Based on the measurement results obtained at the four different sampling sites, the effect of anthropogenic emissions on SOA formation would be discussed.