Impacts of Anthropogenic Emission Reduction and Meteorological Conditions on PM2.5 Pollution in Typical Cities of Beijing-Tianjin-Hebei in Winter

This study used sampling analysis and a CAMx-PSAT coupling model to analyze the components, transmission, and source apportionment of PM2.5 in Beijing and Tangshan in January 2018. The results showed that in January 2018, water-soluble inorganic ions (WSIIs) accounted for 49.59% and 39.13% of PM2.5 mass concentrations in Beijing and Tangshan, respectively. The ratios of NO3- to SO42- were 2.02 and 1.51, respectively, indicating that pollution in both cities was dominated by mobile sources. In Beijing and Tangshan, PM2.5 accounted for 48.74% and 30.67% of transmission, respectively. Regional transmissions were mainly contributed by neighboring areas, northwest masses, and southwest masses. However, the contribution of the southwest passage to pollution in the respective cities increased by 9.65% and 15.02% during pollution periods. The principal sources contributing to PM2.5 pollution in Beijing were mobile and dust sources. Secondary ions were more obviously affected by regional contributions, mobile and industrial sources had the most significant effect in Tangshan, and most particulate matter and sulfate were contributed by local emissions. From 2013 to 2018, the dominant component of WSIIs changed from sulfate to nitrate while the main pollution sources changed from coal-fired and industrial sources to mobile and dust sources. Meanwhile, in January 2018, the meteorological factors were more favorable for pollution mitigation than in 2013. The meteorological impact of secondary ions is closely related to the lower relative humidity in 2018, compared to 2013. © 2021, Science Press. All right reserved.