Volatile organic compounds (VOCs) are the key precursors of ozone (O3) and secondary organic aerosol (SOA) formation.
To identify the variation in VOCs emission sources, simultaneous VOCs measurements were conducted for one year at a
suburban site (Xianlin Campus of Nanjing University (NJU)) in Nanjing, a highly polluted city of the Yangtze River Delta (YRD) region in China. The annual average concentration of VOCs at NJU was observed to be 18.95 ± 14.95 ppbv, with alkanes, alkenes and aromatics contributing 67.5%, 13.6% and 18.9%, respectively, of the total mass concentration. The ratios for i-pentane/n-pentane and m,p-xylene/ethylbenzene showed that the ambient VOCs at NJU were affected by fuel evaporation and long-distance transport. A positive matrix factorization (PMF) model was applied for source apportionment of the VOCs, and seven factors were identified. Vehicle exhaust, evaporation, natural gas (NG) and aged air masses, combustion and synthetic industries, solvents and painting, petrochemical plants and mixed industrial sources were estimated to contribute 23.5%, 16.3%, 15.9%, 14.6%, 13.2%, 10.8% and 5.6%, respectively. The contribution from traffic emissions (i.e., vehicle exhaust) exceeded that suggested by a local emission inventory (9.7%). The concentration-weighted trajectory (CWT) model revealed that the highly polluted air masses arriving at NJU originated in the industrial areas of northeastern Nanjing and the YRD. The contributions from petrochemical plants, solvents and painting, and aged air masses were found to be increased during O3 and PM2.5 pollution days in suburban areas, indicating the importance of reducing industrial emissions and jointly controlling VOCs on a regional scale.

Publisher's version