Dynamics of Urban Atmospheric Conditions under Emission Mitigation Pathways

Rapid urbanization and industrialization have led to complex atmospheric pollution characterized by coincident high levels of PM2.5 and ozone (O3) . This study establishes a high-resolution "Emission-Meteorology-Chemistry" simulation system using the WRF-CMAQ model to evaluate the air quality response to three mitigation pathways-structural adjustment (S1), end-of-pipe control (S2), and deep decarbonization (S3)-in the Yangtze River Delta (YRD) region. The results indicate that while all scenarios reduce PM2.5, the Deep Decarbonization (S3) pathway provides the most significant co-benefits, reducing urban PM2.5 by 58.5% to 32.1μg/m3. In contrast, O3 exhibits a strong non-linear response; the S2 scenario triggers a "Chemical Penalty," increasing peak MDA8 ozone by +5.2% due to the weakened NOx titration effect in VOC-limited urban cores. Integrated Process Rate (IPR) and EKMA analysis reveal that only the S3 pathway, through synchronous NOx and VOCs reductions (>60%), successfully crosses the "EKMA Ridgeline" and suppresses the atmospheric oxidizing capacity (AOC) by slowing the HOx radical propagation rate by 84.8%. The findings suggest that achieving carbon neutrality goals is a prerequisite for overcoming the ozone bottleneck. This study proposes a "Spatially Differentiated and Temporally Dynamic" control strategy, prioritizing VOCs abatement in urban cores and strict management of industrial emissions during peak photochemical hours to achieve synergistic pollution and carbon reduction.