资源环境科技发展态势分析平台

We investigated variations of ozone (O₃), 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 O₃ 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 O₃ and VOCs (indicating more severe photochemical pollution) were found in Nantong. This induced a higher contribution of O₃ photolysis to HO_x production and promoted OH-HO₂ propagation, resulting in maximum HO_x (OH + HO₂) and higher O₃ formation rates from RO₂ + 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 NO₂ and HO₂ led to the greatest contributions of OH + NO₂ and HO₂ + HO₂ to HO_x destruction. However, the longest OH chain length was found in Xuzhou, suggesting that O₃ 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 O₃ formation. These results show that appropriate photochemical pollution control measures should consider both the emission sources and photochemical reactivities of VOCs.