The impact of organic nitrates on summer ozone formation in Shanghai, China

Abstract. Organic nitrates serve as important secondary oxidation products in the atmosphere, playing a crucial role in the atmospheric radical cycles and influencing the production of secondary pollutants (ozone (O₃) and secondary organic aerosols). However, field measurements of organic nitrates are scarce in China, and a comprehensive localized mechanism for organic nitrates is absent, hindering effective pollution mitigation strategies. In this study, we conducted measurements of ambient gaseous organic nitrates and examined their effects on local O₃ production at a polluted urban site in eastern China during summer. The average daytime concentrations of alkyl nitrates (ANs) and peroxy nitrates (PNs) throughout the campaign were 0.5±0.3 ppbv and 0.9±0.7 ppbv, respectively, with peaks reaching up to 1.6 ppbv and 3.6 ppbv. An observation-constrained box model, incorporating an updated mechanism for organic nitrates, was employed to assess the environmental impact of these compounds. The model results indicated that PNs production inhibited the daytime O₃ production by 16 % (0.8 ppbv/h), which is relatively low compared to previous studies. Furthermore, scenario analyses revealed that production yields (α) of ANs would alter the response of O₃ formation to precursors due to varying compositions of volatile organic compounds. Our results suggest that blind pollution control may cause ineffective pollution prevention and highlight the necessity of a thorough understanding on organic nitrate chemistry for local O₃ control strategy.