Modeling study of ozone source apportionment over the Pearl River Delta in 2015.

In recent years, the concentration of fine particulate matter has decreased gradually in the Pearl River Delta (PRD) region, but the ozone (O3) concentration remains high and has become the primary air pollutant. In this study, using a three-dimensional numerical model [nested air quality prediction modeling system (NAQPMS)] coupled with an on-line source apportionment module, the contribution of different source regions and source categories to the O3 concentration in the PRD region was quantified. A comparison with observation data confirmed that the NAQPMS adequately reproduced surface O3 concentrations in different seasons. Compared with biogenic emissions, anthropogenic precursors play a dominant role in O3 production. In Guangzhou city, among different source categories, mobile emission is the largest contributor (accounting for approximately 40%), followed by industry emissions (20%-24%). Regional control measures for solvent use and mobile emissions are effective for reducing O3 concentration. In the PRD region, self-contribution is more significant in daytime (∼40%) than in nighttime (∼10%) on average. Among the source regions outside PRD, the northern part of Guangdong province, Jiangxi province, and Fujian province are important contributors. Within the PRD region, the self-contribution of each city increases by 12%-32% during O3 episodes (>80 ppbv) compared with the annual mean contribution. The contribution of the entire PRD region and the entire Guangdong province is 46%-63% and 63%-74% in PRD cities during O3 episodes. These results indicate that regional collaboration on emission control within PRD or Guangdong province is effective for reducing O3 episodes in the PRD region. In addition, because long-range transport from regions outside Guangdong province played an important role in the O3 concentration in the PRD region, long-term emission control measures throughout China in subsequent years should be propitious to further reduce the annual O3 level and improve air quality in the PRD region.