Source Apportionment of Ground-Level Ozone and Assessment of Emission Reduction Strategies in Shenyang, China

This study presents an in-depth analysis of ground-level ozone (O3) episodes in Shenyang from May to July 2019, utilizing advanced source apportionment modeling techniques: Ozone Source Apportionment Technology (OSAT), Geographic Ozone Assessment Technology (GOAT), and the High-order Decoupling Direct Method (HDDM). The research aimed to characterize the sources of O3 and assess the potential impact of emission reduction strategies on O3 concentrations. The results demonstrate that reducing emissions of both NOx and VOCs can lower O3 levels, with VOC controls proving to be more effective. During the ozone season, regional transport was identified as the dominant contributor to pollution, accounting for approximately 90% of the total, while local sources (sources within Shenyang’s administrative boundary) contributed only about 10%. On days with severe pollution, the long-range transport of O3 precursors was found to be the primary driver of Maximum Daily 8 h average O3 (MDA8 O3) exceedances in Shenyang. This study indicates that local measures alone are insufficient to eliminate O3 exceedances; for instance, in some scenarios, even with a simultaneous 60% reduction in both local anthropogenic VOCs and NOx emissions, MDA8 O3 levels would not meet the national standard of 160 µg·m−3. Therefore, effective mitigation strategies must include regionally coordinated, time-dependent controls. This study also highlights that local industrial and mobile sources contribute to over 70% of ozone formation, suggesting that targeting these sectors could yield the most significant local benefits. This research underscores the need for a comprehensive approach to O3 management, combining both local and regional efforts to address the complex issue of ground-level ozone pollution.