[Organic Aerosols and Source Analysis of Fine Particles in the Background of Shiwanda Mountain, Guangxi]

The non-polar compounds in atmospheric fine particles (PM_2.5) mainly include polycyclic aromatic hydrocarbons (PAHs) and normal alkanes (n-alkanes), etc., which are usually used to identify the source of the air pollution and have a great important impact on human health and the environment. To study the pollution characteristics and sources of non-polar organic aerosols in the background point PM_2.5 in Guangxi, from November 2017 to October 2018, 17 types of PAHs and 20 types of n-alkanes were analyzed on PM_2.5 samples collected in the field. It was found that the annual average concentrations of PAHs and n-alkanes were 4.28±4.25 ng·m^-3 and 13.7±14.72 ng·m^-3, respectively. The seasonal change was as follows:winter[(7.86±5.19) ng·m^-3, (27.51±16.90) ng·m^-3]>spring[(2.73±1.76) ng·m^-3, (7.64±4.71) ng·m^-3]>autumn[(2.34±145) ng·m^-3, (7.01±4.55) ng·m^-3]>summer[(1.91±1.67) ng·m^-3, (3.98±3.12) ng·m^-3]. In PAHs, 5-ring and 6-ring molecules accounted for more than 60%, followed by low- and medium-ring molecules (4-ring and 3-ring). The high molecular weight of n-alkanes was relatively high (C29>C31>C27), and the odd and even carbon numbers were significantly different. In addition, combined with the feature ratio method, principal component analysis method, and backward trajectory joint verification, it was found that 41.5% of non-organic aerosols in winter were affected by maritime traffic emissions and ocean source transportation, and 36.7% of the pollution was explained by the coal burning and local biomass burning; 25.2% of the pollution in spring came from biomass combustion and transportation, and 45.0% was attributed to marine transportation in the southern part of the study area and higher plant wax emissions pollution; 53.4% of pollution in summer came from polluted ship emissions, and 10.6% of pollution came from transportation in Southwest Thailand Source transportation. The organic aerosols at the background sites in Guangxi were affected by the combined effects of local emissions and transmission sources.