Impact of atmospheric O₃ and NO₂ on the secondary sulfates in real atmosphere

As an important component of secondary aerosols, sulfate plays a crucial role in regulating atmospheric radiative balance and influencing the secondary formation of ozone (O₃). In real atmosphere, atmospheric oxidants NO₂ and O₃ can promote the oxidation of SO₂ to form sulfate (SO₄^2-) through multiphase chemistry that occur at different time scales. Due to the combined impact of meteorology, pollution sources, atmospheric chemistry, etc., time-scale dependence of SO₂-SO₄^2- conversion makes the impact of NO₂/O₃ on it more complex. In this study, based on long-term time series (2013-2020) of air pollution variables from seven stations in Hong Kong, the Multifractal Detrended Cross-Correlation Analysis (MFDCCA) method has been employed to quantify the cross-correlations between SO₂ and SO₄^2- in real atmosphere at different time scales, for examining the time-scale dependence of SO₂-SO₄^2- conversion efficiency. Furthermore, the Pearson correlation analysis has been used to study the influence of NO₂/O₃ on SO₂-SO₄^2- conversion, and the regional and seasonal differences have been analyzed by considering factors such as meteorology, pollution sources, and regional transport. Changes in the main components of secondary aerosols are closely linked with the co-control of regional PM_2.5 and O₃. Therefore, the exploration of the impact of co-existing NO₂/O₃ gases on the secondary formation of sulfates in real atmosphere is significant.