Characterization of volatile organic compounds (VOCs) around the Chinese Spring Festival and International Labour Day in the urban area of Shanghai, China

Volatile organic compounds (VOCs) have been recognized as important precursors in the production of tropospheric ozone and secondary organic aerosol. Studies on the concentration, speciation, and chemical reactivity of VOCs are necessary to further understand the formation process of atmospheric pollution. Gas chromatography with flame ionization detection (GC/FID) was employed to monitor VOCs in the urban area of Shanghai during Chinese Spring Festival (from Jan. 19th to Feb. 7th, 2009) and the International Labor Day (from Apr. 23rd to Jun. 5th, 2009) and 56 kinds of VOCs were detected. Two peaks in the morning and evening were observed in the diurnal profile of VOCs, consistent with the rush hours, suggesting that the atmosphere in the urban area of Shanghai was mainly affected by vehicle emissions. The average mixing ratio of VOCs in the urban area of Shanghai was (28.39±18.35)×10-9. The major components of the VOCs were alkanes (46.6%), aromatics (27.0%), alkenes (15.1%), and acetylene (11.2%). The OH radical loss rate and the ozone formation potential were applied to access the chemical reactivity of VOCs. There was a significantly positive correlation between the mixing ratio and the chemical reactivity. The chemical reactivity of the atmosphere in the urban area of Shanghai was similar to that of ethylene. The alkenes and aromatics were the dominant species for the chemical reactivity. For the OH radical loss rate, the alkenes and aromatics accounted for 51.2% and 31.8%, respectively; and for the ozone formation potential, they accounted for 30.2% and 53.4%, respectively. Considering individual compounds, propylene, ethylene, toluene, xylenes, and butenes were the most important contributors to ozone formation in the atmosphere in the urban area of Shanghai.