We investigated variations of ozone (O 3), its precursors, and their influence on photochemical reactivity by applying a photochemical box model to field data from three cities (Nantong, Xuzhou, and Yancheng) in the Yangtze River Delta. The photochemical box model was coupled with the near-explicit mechanism (Master Chemical Mechanism, MCM version 3.2) for the degradation of volatile organic compounds (VOCs), which provided detailed descriptions of different pathways for photochemical O 3 formation and related atmospheric photochemical reactivity based on observed data. Alkanes were the most important VOC group overall, while the contributions of aromatics and alkenes varied by city. The highest levels of O 3 and VOCs (indicating more severe photochemical pollution) were found in Nantong. This induced a higher contribution of O 3 photolysis to HO x production and promoted OH-HO 2 propagation, resulting in maximum HO x (OH + HO 2) and higher O 3 formation rates from RO 2 + NO. In Yangchen, the highest occurrence of alkenes resulted in the maximum contribution of ozonolysis to HO x production. In Nantong, the highest levels of NO 2 and HO 2 led to the greatest contributions of OH + NO 2 and HO 2 + HO 2 to HO x destruction. However, the longest OH chain length was found in Xuzhou, suggesting that O 3 production was most efficient there. Although vehicular emissions were the dominant sources of VOCs overall, industrial emissions in Nantong, solvent usage in Xuzhou and vehicular emissions in Yancheng were the most important VOC sources for O 3 formation. These results show that appropriate photochemical pollution control measures should consider both the emission sources and photochemical reactivities of VOCs.
- Atmospheric photochemical reactivity
- Volatile organic compounds
- Yangtze River Delta
ASJC Scopus subject areas
- Atmospheric Science