[Evolution Characteristics of PM and O and Their Synergistic Effects on Atmospheric Compound Pollution in Tangshan].

The concentrations of atmospheric pollutants PM, O, SO, NO, and CO together with the meteorological factors of temperature （）, relative humidity （RH）, wind speed, and other relevant data in Tangshan from 2015 to 2021 were collected to study the variation characteristics of PM and O at different periods in Tangshan City in the past seven years and their influencing factors, to discuss the contributions of air mass transport to PM and O pollution, and to reveal the synergistic influence mechanism of PM and O on atmospheric compound pollution by using correlation analysis and backward trajectory cluster analysis techniques. The results showed that PM concentrations in Tangshan decreased year by year from 2015 to 2021, whereas O concentration showed a unimodal trend, with the peak appearing in 2017. Both PM and O concentrations showed obvious seasonal variation trends； PM was characterized by the highest concentration in winter and the lowest concentration in summer, whereas O was characterized by the highest concentration in summer and the lowest concentration in winter.