Molecular compositions and sources of organic aerosols from urban atmosphere in the North China plain during the wintertime of 2017

PM_2.5 samples were collected from Liaocheng, a typical city in the North China Plain, during a winter haze episode around 2017 Chinese Spring Festival (Lunar New Year, LNY) to investigate the impact of firework on organic aerosols. A comparison of PM_2.5 concentrations during different periods, with different air mass origins, and under different pollution situations was done. Organic compounds including normal alkanes (n-alkanes), polycylic aromatic hydrocarbons (PAHs), saccharides, and organic acids in PM_2.5 aerosols were determined by GC/MS. Sources were analyzed by diagnostics ratios and principal component analysis/multiple linear regression (PCA/MLR) model. The results showed that fireworks burning has significant impacts on fine particle pollution. During the haze period, a sharp increase in n-alkanes, PAHs, saccharides, and fatty acids were observed, but the influence of fireworks burning on n-alkanes concentration is minor. The concentrations of carcinogenic PAHs during haze and LNY periods were more than three times higher than those in the clean period, indicating that PAHs were more carcinogenic during the two periods. In addition, the estimated ILCR for children and adults were both about three times higher than those in the clean periods, suggesting a moderate potential carcinogenic risk in Liaocheng. The higher concentration and the dominance of levoglucoan in the total saccharides suggested that the biomass burning is the predominance source of saccharides. Both the ratios of C_18:1/C_18:0 and BaP/BeP were the highest during the haze period, indicating that aerosols in the haze period were more oxidized. According to the source precise molecular tracers and the PCA-MLR model, coal combustion, biomass burning, and vehicle emissions were the major sources of organic compounds in PM_2.5 aerosols during the winter in Liaocheng, cooking activity and firework burning had impact on organic aerosols obviously during LNY. Our data provided first analysis of the molecular distributions and sources of organic aerosols during Chinese Spring Festival in Liaocheng and their potential effects on human health.