[Characteristics of Ambient VOCs at the Shuangliu Site in Chengdu, China, During Summer and Autumn].

To better understand the characteristics and sources of ambient volatile organic compounds (VOCs) in a polluted area in Chengdu, which requires air pollution control, samples were collected hourly at the Shuangliu site from August 2016 to December 2016. Online gas chromatography/mass spectrometry and a flame ionization detector (GC/MS-FID) were used to analyze the mixing ratios and compositions of the VOCs. During the sampling period, the average mixing ratios of the VOCs were (45.15±43.74)×10-9. Alkanes contribute the most to the total volatile organic compounds (TVOCs), followed by aromatics (22%), halocarbon (17%), oxygenated volatile organic compounds (OVOCs; 15%), alkenes (9%), acetylene (7%), and acetonitrile (1%). Acetone, dichloromethane, acetylenes, ethylene, toluene, m/p-xylenes, propane, 1,2-dichloroethane, and methyl ethyl ketone are the dominant species. By calculating the OH loss rate, the chemical reactivity of the VOCs was estimated. Aromatics contribute the most to the total VOC reactivity, followed by alkenes. The most reactive species are styrene, m/p-xylenes, isoprene, and ethylene. Two biomass burning events were detected during the sampling period. The average mixing ratio of TVOCs is 57.65×10-9, which significantly increased during the national holiday. The mixing ratios of several C2-C5 alkenes, halocarbons, and OVOCs increased the most during the national holiday. The diurnal patterns of critical non-methane hydrocarbons (NMHCs) and OVOCs are consistent with the emission sources in this area. The VOC characteristics at the sampling site are mainly influenced by local industrial sources.