Comparisons of carbonaceous aerosols based on hourly data between two typical pollution events in heavily polluted zhengzhou

Carbonaceous aerosols (CA) have a profound impact on both the environment and climate, and in particular, secondary organic aerosols play multiple roles in different types of pollution events. In this study, high-resolution CA data were collected in four seasons in 2020 with organic carbon (OC) and elemental carbon (EC) components quantified by thermo-optical analysis at an urban site in the traffic-hub city of Zhengzhou, China. The concentration of ozone (O3) and fine particulate matter (PM2.5) were synchronously obtained by online analyzers. The characteristics and sources of CA on O3 and haze pollution days were analyzed in combination with hourly gaseous pollutants and meteorological data. OC and EC concentrations increased by 28 and 20 % on O3 pollution days compared to warm clean days and increased by 75 and 81 % on haze pollution days compared to cold clean days. The highest concentrations of secondary organic carbon (SOC) were observed in winter. SOC concentrations on O3 pollution days and haze pollution days were 1.4 and 1.7 times of corresponding clean days, respectively. Positive matrix factorization model results showed that CA was mainly from SOC (42 %), gasoline vehicles (27 %), and coal combustion (20 %). Compared with clean days, the contribution of coal combustion increased by 8 % on O3 pollution days, and the contribution of SOC increased by 5 % on haze pollution days, indicating that the primary and secondary pollution both significantly impact the air pollution in Zhengzhou city. SOC is more affected by local and surrounding areas during both O3 and haze pollution days. On O3 pollution days and haze pollution days, SOC has a positive correlation with O3 and relative humidity (RH), respectively, indicating that O3 and RH promote the generation of SOC.