Characterization and Source Apportionment of Ambient PM2.5 in Atlanta, Georgia: On-Road Emission, Biomass Burning and SOA Impact Bo Yan 260 Pages Directed by Drs. Armistead G. Russell and Mei Zheng Various airborne PM2.5 samples were collected in the metropolitan Atlanta and surrounding areas, which are directly impacted or dominated by on-road mobile and other typical urban emissions, regional transport sources, prescribed burning plumes, wildfire plumes, as well as secondary sources with anthropogenic and biogenic nature in origin. Detailed PM2.5 chemical speciation was conducted including over one hundred of GC/MS-quantified organic compounds, organic carbon (OC), water-soluble organic carbon (WSOC), elemental carbon (EC), ionic species, and tens of trace metals. Day-night, seasonal and spatial variations of PM2.5 characterization were also studied. Contributions of PM2.5 major sources were identified quantitatively through the receptor source apportionment models. These modeling results, especially on-road mobile source contributions and secondary organic carbon (SOC) were assessed by multiple approaches. Furthermore, new season- and location-specific source profiles were developed in this research to reflect real-world and representative local emission characterizations of on-road mobile sources, aged prescribed burning plumes, and wildfire plumes. Secondary organic aerosol (SOA), a major component of PM2.5 in the summer, was also explored for sources and contributions.