[Composition Characteristics and Sources of Non-polar Organic Compounds in PM_2.5 in the Background Atmosphere of...

In order to explore the composition and source characteristics of non-polar organic compounds (NPOCs) in atmospheric fine particulate matter in the Yangtze River Delta region, 129 PM_2.5 samples were collected at the Regional Atmospheric background station in Lin'an from December 2019 to November 2020. Including polycyclic aromatic hydrocarbons (PAHs), n-alkanes, and hopanes, the main sources of organic aerosols were investigated using molecular tracers, eigen ratios, and orthogonal matrix factorization models. The results showed that the average annual mass concentration of PM_2.5 in Lin'an was approximately (32.36±20.44) μg·m^-3, and the average annual mass concentration of NPOCs was approximately (59.05±40.39) ng·m^-3, showing the seasonal characteristics of being high in winter and low in summer. n-alkanes mainly came from fossil fuels and biomass (grass, wood, etc.) burning, followed by cuticle wax emission from higher plants. PAHs mainly came from the mixed contribution of non-fossil sources such as coal burning motor vehicle emissions and biomass combustion. Hopanes were mainly derived from motor vehicle emissions, which were also affected by coal burning in winter. Backward trajectory cluster analysis and potential source analysis showed that Lin'an was mainly affected by external air mass transport. Combined with the orthogonal matrix-factor decomposition model, NPOCs observed during the sampling period were analyzed, and non-fossil sources such as coal burning sources, transportation emission sources, and biomass combustion were obtained. In winter, transportation sources were the main source, accounting for 59%. In spring and summer, coal burning was the main source, accounting for 58% and 57%, respectively. In autumn, biomass combustion and other non-fossil sources dominated, accounting for 64%.