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 and 0.9 ± 0.7 ppbv, respectively, with peaks reaching up to 1.6 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 PN production inhibited the daytime O3 production by 16 % (0.8 ppbv h−1), 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 (VOCs). Our results suggest that blind pollution control may cause ineffective pollution prevention and highlight the necessity of a thorough understanding of organic nitrate chemistry for local O3 control strategy.