Source Apportionment of Regional Ozone Pollution Observed at Mount Tai, North China: Application of Lagrangian Photochemical Trajectory Model and Implications for Control Policy

Abstract

AbstractTo better understand the characteristics and trace the sources of regional ozone (O3) in the North China Plain (NCP), we analyzed 1‐year continuous observations obtained at Mount Tai in 2018 and compared with previous data from 2006–2009. In the warm seasons (April–September), O3 pollution (defined as a maximum daily 8‐h average O3 mixing ratio that exceeds 75 ppbv) occurred frequently (59%–92% of days) and O3 concentrations significantly increased (especially in July–September) from 2006–2009 to 2018. We applied the Lagrangian photochemical trajectory model, built on the coupling of the Lagrangian backward trajectory model and Master Chemical Mechanism box model, to identify the source regions, key precursors, and emission sectors. The NCP was identified as the major source region with an average contribution of 74% ± 27% to the regional O3 concentrations during the O3 episodes in April–September. Regional O3 formation was highly NOx‐sensitive in air masses traveling from the southern part of the NCP but limited by anthropogenic hydrocarbons (especially alkenes) in air masses from the northern part of the NCP. The reduction of emissions from transportation and industry sectors would significantly reduce the regional O3 concentrations. Biomass burning also exerts a significant influence on regional O3 concentrations under certain circumstances. This study demonstrates that the regional background O3 at mountaintop levels is a good indicator of surface O3 pollution over a wide spatial coverage, and provides guidance for regional collaboration on emission control to mitigate photochemical air pollution over the NCP.