Modeling explicit tropospheric oxidation through identifying volatile organic compound (VOC) sources, their impact on air quality and their signatures in South China.

摘要

Photochemical smog, characterized by high concentrations of ozone (O 3) and fine particles, is of great concern in the urban areas like the Pearl River Delta (PRD). Ambient O3 and its precursors were simultaneously measured for the first time at a site within the inland PRD region (WQS) and a site in Hong Kong (TC) from 22 October to 01 December 2007, in order to improve our understanding of the interplay of O3 pollution between Hong Kong and the inland PRD region, to explore the relationships between O3 and its precursors, and to identify the key volatile organic compound (VOC) species and emission source categories contributing to the O3 formation. Ratio analyses for trace gases and VOCs and back trajectory calculation revealed that the air masses arriving at WQS were more aged due to regional influence, whereas the air masses at TC were mainly affected by local emissions and/or regional transport.;An observation-Based Model (OBM) was employed to determine the O 3-precursor relationship. At both sites, O3 production was found to be VOC-limited. Anthropogenic hydrocarbons played a key role in O 3 production, while reducing NO emissions aided the build up of O 3 concentrations. The contribution of carbonyls to O3 formation was firstly input in the OBM by using measured data, the results showed that the net O3 production derived from the OBM agreed better with the observed O3 increment after hourly carbonyl concentrations were included.;A photochemical trajectory model was developed and used for the first time to simulate the formation of photochemical pollutants at WQS, Guangzhou during photochemical pollution episodes between 12 and 17 November, 2007. Calculated photochemical ozone creation potential (POCP) indices indicated that alkanes and oxygenated organic compounds had relatively low reactivity, while alkenes and aromatics presented high reactivity. Analysis of the emission inventory found that the sum of 60 of the 139 VOC species accounted for 91% of the total POCP-weighted emission. The findings obtained in this study would advance our knowledge of air quality in the PRD region, and provide useful information to local government on effective control of photochemical smog in the region.