Analysis of the Causes of an O3 Pollution Event in Suqian on 18–21 June 2020 Based on the WRF-CMAQ Model

Abstract

In recent years, O3 pollution events have occurred frequently in Chinese cities. Utilizing the WRF-CMAQ model, this study analyzed the causes of an O3 pollution event in Suqian on 18–21 June 2020, considering meteorological conditions, process analysis, and source analysis. It also designed 25 emission reduction scenarios to explore more effective O3 emission reduction strategies. The results show that meteorological conditions such as temperature and wind field play an important role in the formation and accumulation of O3. During the heavy pollution period, the contribution of vertical transport (VTRA) and horizontal transport (HTRA) to O3 concentration is significantly enhanced. The photochemical reactions of precursors, such as NOx and VOCs transported from long distances and O3 directly transported to Suqian from other regions, contribute greatly to O3 pollution in Suqian; local sources contribute very little, between 12.22% and 18.33%. Based on the simulation of 25 emission reduction scenarios, it was found that excessive emission reduction of NOx is not conducive to the reduction of O3 concentration, and it is best to control the emission reduction ratio at about 10%. Without affecting normal production and life, it is recommended to reduce VOCs as much as possible, particularly those generated by traffic sources.