Composition characteristics and source implications of biomarkers in PM2.5 at a typical urban area of Chongqing

Seventy-seven PM2.5 samples covering four seasons from October 2015 to August 2016 were collected at an urban site of Chongqing University Campus A. These samples were analyzed for biomarkers including n-alkanes, UCM, hopanes and steranes to reveal the composition characteristics, seasonal variation and assess their source implications. The results showed that the annual average concentrations of Σn-alkanes (C11~C38) and UCM were 328.69ng/m3 and 2.52 μg/m3, respectively. Both of them are the highest in winter, lowest in summer. The PMF analysis of 28n-alkanes identified 4source categories, including fossil fuel combustion (23.45%), fossil fuel residue (29.1%), biomass burning (21.35%) and plants wax emission (26.1%). The ratio of UCM to alkanes (U: R) ranged from 1.29 to 3.33. Possibly owning to the high temperature and intense light, the activities of microorganisms and plants were vigorous and resulted in the lowest U: R value in summer. The annual average of Ts/Tm, C30αβ/C31αβ(22R) and C31αβ(22S)/(22S+22R) for hopanes were 1.15, 5.26 and 0.59, respectively, indicating sources from high-maturity petroleum hydrocarbons, such as the exhaustion from motor vehicles. The annual average of C29αββ/(ααα+αββ) and C29ααα(20S)/(20S+20R) for steranes were 0.40 and 0.53, respectively, indicating sources from fossil fuel residues with high thermal maturity. PSCF analysis showed that the potential source areas of Σn-alkanes were mainly in southeastern Sichuan, western Chongqing and their adjacent areas; while the potential source areas of UCM were mainly in southeastern Sichuan. © 2021, Editorial Board of China Environmental Science. All right reserved.