[Molecular Composition and Source Apportionment of Fine Organic Aerosols in Autumn in Changchun]

Organic aerosols have attracted increasing attention recently due to their significant contribution to fine particles (PM_2.5) and their complex components and sources. In this study, a total of 40 PM_2.5 samples were collected simultaneously with high-volume samplers in Changchun from 16^th Oct to 29^th Nov 2016. Organic carbon (OC), elemental carbon (EC), non-polar organic compounds including n-alkanes, polycyclic aromatic hydrocarbons (PAHs), and hopanes, and levoglucosan in atmospheric fine particles were analyzed. The main sources of organic aerosols were identified by molecular markers, diagnostic ratios, and a principal component analysis-multiple liner regression (PCA-MLR) model. The results showed that the average mass concentration of PM_2.5 was (79.0±55.7) μg·m^-3, and the averaged OC and EC mass concentrations were (20.7±15.6) μg·m^-3 and (2.2±1.1) μg·m^-3, which accounted for 26.2% and 2.8% of PM_2.5, respectively. The total average concentration of the tested non-polar organic compounds was (186.3±104.5) ng·m^-3 and, in descending order, this was composed of n-alkane (101.3±67.0) ng·m^-3, polycyclic aromatic hydrocarbons (81.4±46.0) ng·m^-3, hopanes (3.8±1.9) ng·m^-3. The PCA-MLR model results showed that the relative contributions of the main sources of organic aerosols were coal combustion (47.0%), biomass burning (42.6%), and traffic emission (10.4%).