[Analysis of Change Trend and Influencing Factors of PM-O Pollution in Tianjin from 2013 to 2020].

The change trend, relationship, and influencing factors of PM and O concentrations were analyzed by using a Kolmogorov-Zurbenko (KZ) filter coupled with stepwise multiple linear regression analysis and the spatiotemporal resolution monitoring data of PM and O and meteorological data observed in Tianjin from 2013 to 2020. The results showed that a significant decreasing trend of PM concentrations by 50.0% was observed from 2013 to 2020, whereas an increasing trend for O concentrations by 25.

[Assessment of Emission Reduction Effect of Major Air Pollution Control Measures on PM Concentrations During 13th Five-Year Period in Tianjin].

The emission reduction effect of major air pollution control measures on PM concentrations was assessed using air quality simulations based on the calculation data of emission reductions from different air pollution control measures and the high spatiotemporal resolution online monitoring data of PM during the 13th Five-Year Period in Tianjin. The results showed that the total emission reductions of SO, NO, VOCs, and PM from 2015 to 2020 were 4.77×10, 6.

[Characteristics and Meteorological Factors of PM-O Compound Pollution in Tianjin].

The characteristics, pollutant concentration distribution, and key meteorological factors of PM-O compound pollution in Tianjin were analyzed based on the high-resolution online monitoring data of PM, Oand meteorological data observed in Tianjin from 2013 to 2019. Total PM-O compound pollution was 94 days and showed a decreasing trend by year; a significant decreasing trend of PM-O compound pollution days were observed in the early stage, with a decline rate of 52.2% from 2013 to 2015.

[Characteristics and Sources of PM-O Compound Pollution in Tianjin].

The characteristics and sources of PM-O compound pollution were analyzed based on the high-resolution online monitoring data of PM, O and volatile organic compounds(VOCs) observed in Tianjin from 2017 to 2019. The results showed that total PM-O compound pollution was 34 days, which only appeared between March and September and slightly increased by year. The peak value of (O)(301-326 μg·m) appeared when (PM) ranged from 75 μg·m to 85 μg·m.