Impact of aerosol-radiation interaction and heterogeneous chemistry on the winter decreasing PM2.5 and increasing O3 in Eastern China 2014–2020

In the context of the prevalent winter air quality issues in China marked by declining PM_2.5 and rising O₃, this study employed a modified WRF-Chem model to examine the aerosol radiation interaction (ARI), heterogeneous chemistry (AHC), and their combined impact (ALL) on the variations in O₃ and PM_2.5 during the 2014–2020 in eastern China. Our analysis confirmed that ARI curtailed O₃ while elevating PM_2.5. AHC reduced O₃ through heterogeneous absorption of NO_x and hydroxides while notably fostering fine-grained sulfate, resulting in a PM_2.5 increase. Emission reductions mitigated the inhibitory impact of ARI on meteorological fields and photolysis rates. Emission reduction individually without aerosol feedback led to a 5.43 ppb O₃ increase and a 22.89 µg/m³ PM_2.5 decrease. ARI and AHC amplified the emission-reduction-induced (ERI) O₃ rise by 1.83 and 0.31 ppb, respectively. The response of ARI to emission diminution brought about a modest PM_2.5 increase of 0.31 µg/m³. Conversely, AHC, acting as the primary contributor, caused a noteworthy PM_2.5 decrease of 4.60 µg/m³. As efforts concentrate on reducing PM_2.5, the promotion of ARI on PM_2.5 counterbalanced the efficacy of emission reduction and the AHC-induced strengthening of PM_2.5 decrease. The ALL magnified the ERI O₃ increase by 38.9% and PM_2.5 decrease by 18.7%. Sensitivity experiments with different degrees of emission reduction demonstrated a consistent linear relationship between the ALL-induced enhancement of O₃ increase and PM_2.5 decrease to the ERI PM_2.5 decline. Our investigation revealed the complex connection between emissions and aerosol feedback in influencing air quality.