Impact of aerosol-radiation interaction and heterogeneous chemistry on the winter decreasing PM and increasing O in Eastern China 2014-2020.

In the context of the prevalent winter air quality issues in China marked by declining PM and rising O, 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 O and PM during the 2014-2020 in eastern China. Our analysis confirmed that ARI curtailed O while elevating PM. AHC reduced O through heterogeneous absorption of NO and hydroxides while notably fostering fine-grained sulfate, resulting in a PM 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 O increase and a 22.89 µg/m PM decrease. ARI and AHC amplified the emission-reduction-induced (ERI) O rise by 1.83 and 0.31 ppb, respectively. The response of ARI to emission diminution brought about a modest PM increase of 0.31 µg/m. Conversely, AHC, acting as the primary contributor, caused a noteworthy PM decrease of 4.60 µg/m. As efforts concentrate on reducing PM, the promotion of ARI on PM counterbalanced the efficacy of emission reduction and the AHC-induced strengthening of PM decrease. The ALL magnified the ERI O increase by 38.9% and PM decrease by 18.7%. Sensitivity experiments with different degrees of emission reduction demonstrated a consistent linear relationship between the ALL-induced enhancement of O increase and PM decrease to the ERI PM decline. Our investigation revealed the complex connection between emissions and aerosol feedback in influencing air quality.