Evidence for sustainably reducing secondary pollutants in a typical industrial city in China: Co-benefit from controlling sources with high reduction potential beyond industrial process.

Under China's strict industrial control measures, the reduction of secondary pollutants (O₃ and secondary organic aerosols [SOA]) and precursors (volatile organic compounds [VOCs] and NOx) caused by industrial processes has encountered bottlenecks. In this study, the net O₃ formation rate (Net [O₃]) in summer and the self-reaction rate between peroxy radicals (Self-Rnxs) in winter are used to characterize the formation potentials of O₃ and SOA, respectively. Assuming that the precursor reduction ratio based on emission inventories is approximately equal to that based on observed concentrations, this study combines emission inventory and observation-based model (OBM) methods to indicate the potential source of secondary pollutants reduction. The findings show that strict control measures implemented by local governments, particularly those targeting industrial processes and fossil fuel combustion, are effective in reducing VOCs and NOx emissions during summer, and the two sources result in 3.8 % and 5.3 % decrease in the Net (O₃), respectively. Similarly, control measures focusing on industrial processes help to significantly reduce VOCs emissions during winter, resulting in an 8.0 % decrease in Self-Rnxs. However, current measures for industrial processes are stringent and have little potential for further reduction. Therefore, additional sources with higher reduction potentials beyond industrial processes should be subject to stringent controls in industrial cities. Given the limited emission reduction potential associated with industrial processes, this study provides perspectives for sustained reduction of secondary pollutants in industrial cities.