10:15 AM - 10:30 AM
[AAS04-21] Characteristics of Atmospheric Photochemical Pollution at a Comprehensive Site in Guangzhou, China
Keywords:Photochemical Pollution, Guangzhou
Guangzhou, one of China’s megacities, is beset with frequent occurrence of atmospheric photochemistry events. In this study, online instruments were used to simultaneously monitor NMHCs, NOx and O3 at Guangzhou Panyu Atmospheric Composition Station (GPACS) of the China Meteorological Administration (CMA), from June 2011 to May 2012, in order to obtain their characteristics, NMHCs reactivity and the control strategies for atmospheric photochemistry. The results showed that during the observation period, the seasonal variation of O3 mixing ratio was lower in spring and winter compared to summer and autumn, which was opposite that for NMHCs and NOx. O3 mixing ratio began to show a net increase at 8:00LT, likely due to the breakup of the nocturnal boundary layer and increased photochemistry, while a net decrease in O3 mixing ratio occurred at about 15:00LT, due to the fact that sunlight and its associated photochemistry begin to decrease, leading to low OH radicals and the titration of O3 by emissions of NOx. In terms of NMHCs, aromatics had the largest O3 formation potential, among which toluene, xylenes, ethylbenzene, 1,2,4-trimethylbenzene and 1,3,5-trimethybenzene were the most important species, with a total contribution of about 44%. Weekday/weekend O3 differences in the morning and at midday largely depend on how much the O3 precursors are affected by the different intensity of anthropogenic activities. Although the increase of biogenic NMHCs emissions at midday reverses the sensitivity of O3 production from NMHCs-sensitive to NOx-sensitive, high-reactive NMHCs and NOx control can be effective for reducing peak O3 mixing ratios in Guangzhou. Further investigation based on numerical models is required to reach more robust conclusions.