<p>Atmospheric nitrate and sulfate are major components of particulate matter (PM) in China. Mechanisms driving their rapid production are highly concerned but remain unresolved yet. Here we explored the formation of nitrate and sulfate based on hourly observations and estimation in 2019. Calculations based on diurnal nitrogen oxidation ratio implied that nocturnal nitrate production generally outweigh daytime OH oxidation in winter while the opposite was true in other seasons. Nitrate production rate via daytime OH oxidation (P(HNO₃)_NO2+OH) showed the highest values in noon hours while the production rate of nocturnal NO₃ radicals (P(NO₃)_noc) decreased from sunset to sunrise. Both seasonal P(HNO₃)_NO2+OH and P(NO₃)_noc presented high values in summer and low values in winter. Estimation indicated that nitrate formation generally dominated NO₃ radical loss pathways in winter with the fraction larger than 52%. Further analysis implied that the elevated O₃ can enhance nocturnal nitrate production in winter via regulating P(NO₃)_noc. As for sulfate, overall heterogeneous sulfate production presented high values in winter and low values in summer while homogenous sulfate production via OH oxidation showed the opposite seasonal trends. Calculations based on the observed Cu concentrations and the chemical kinetics of heterogeneous Cu-catalyzed SO₂ oxidation by NO₂ suggested the role of this pathway can reach the maximum on the day of Chinese Spring Festival which related to the setting off of fireworks and firecrackers. Our estimation also indicated that aqueous sulfate production, especially H₂O₂ oxidation, may be mostly responsible for the high sulfate in summer.</p>