Characteristics, source apportionment and chemical conversions of VOCs based on a comprehensive summer observation experiment in Beijing

Based on the observation data of VOCs in the Beijing atmosphere in the summer of 2016, this study analyzed the variation characteristics of the VOCs concentration and composition with time. The potential impacts of each component on ozone and secondary organic aerosol (SOA) production were compared. The results showed that the concentration of alkane was the highest in the total VOCs in Beijing, followed by oxygenated VOCs (OVOCs) and aromatics, and the lowest concentration was of acetonitriles. The concentration of VOCs peaked in the morning (7:00–9:00 a.m.) and evening (8:00–10:00pm), and the value decreased significantly in the afternoon. During the observation period, the contributions of ethylene, acetaldehyde, propylene and m/p-xylene were the highest among the ten substances that contributed the most to the ozone formation potential (OFP) in atmospheric VOCs in Beijing. The greatest potential for SOAP in the atmosphere was caused by aromatic hydrocarbons. The contribution rate was much higher than the contribution rates of other hydrocarbons (96.91%). The 10 substances that contributed the most to the secondary organic aerosol potential (SOAP) by atmospheric VOCs are benzene species. The substance with the highest contribution rate was toluene, where the contribution rate was 25.79%. Based on backward trajectories and the potential source contribution function (PSCF), short-distance transport was the main source influencing VOCs pollution, especially transport from the south. Six potential sources were identified by positive matrix factorization (PMF), industrial sources, solvent usage and fuel evaporation were the main sources of VOCs pollution during the observation period, and the contributions to VOCs during the observation period were 30.24%, 24.62%, 15.59% respectively.