Roles of volatile organic compounds in photochemical ozone formation in the atmosphere of the Pearl River Delta, southern China

Whole air samples were simultaneously collected at two sites in the Pearl River Delta (PRD), namely Wan Qing Sha (WQS) in Guangzhou, and Tung Chung (TC) in Hong Kong on eight selected days from 23 October to 1 December 2007, in order to investigate the composition and temporal patterns of volatile organic compounds (VOCs), and the relative contributions of VOCs to ozone (O3) formation in the PRD region. The total volatile organic compound (TVOC) mixing ratios at WQS were higher than those at TC, so were the trace gases, i.e. SO2, CO, and O3, indicating that the air pollution in Guangzhou was more serious. Ozone formation potentials (OFPs) of VOCs were estimated using maximum incremental reactivity (MIR) and the kOH method (reactivity of VOC with OH radical) to assess the relative effects of VOCs on O3 formation. The results showed that regional scale O3 formation in the PRD region can be mainly attributed to a relatively small number of VOC species, including formaldehyde, m,p-xylene, toluene, o-xylene, ethene, and isoprene. Based on the OFPs of VOC species and principle component analysis results, it is concluded that VOCs from solvent usage and vehicular emission made major contributions to O3 formation at both sites. The findings obtained in this study provide useful information to local government on effective control of VOC emissions in this region.