ANALYSIS OF POLLUTION CHARACTERISTICS AND INFLUENCING FACTORS OF AIR POLLUTANTS IN BEIJING AND TIANJIN, CHINA

In this study, we analysed the air quality status, air pollution characteristics and their relationship with meteorological factors in Beijing and Tianjin in 2019. The main PM10, PM2.5, and CO have a greater impact on the Air quality index (AQI). The correlation between O-3 and AQI is strong in spring and summer, but weak in autumn and winter. The air quality of Beijing is better than that in Tianjin in 2019, and the air quality in the study area is greatly affected by particulate matter. In terms of spatiotemporal variations, Beijing's pollutants are mainly concentrated in the central city. Among them, SO2 pollution is the most serious in the northeastern of the city, and O-3 pollution is concentrated in the central and northwestern. In Tianjin, the concentrations of CO and NO2 are relatively high in the central and northeastern of the city, and the concentrations of PM2.5, PM10, SO2 and O-3 are relatively high in the west and northwest. Except that O-3 concentration in spring and summer is higher than that in other seasons and the concentration in winter is the lowest, other pollutions generally show the characteristics that spring and winter are higher than other seasons. The correlation between SO2, NO2, CO, PM2.5, PM10 is highly positive. Except SO2, and NO2 other pollutants are usually negatively correlated with Ps in each season. Pollutants are mostly positively correlated with temperature, while O-3 is generally positive correlate with temperature only in autumn, and NO2 is negatively correlated with temperature in autumn. We can see that the dominant wind direction in Beijing is North (N) direction, while the higher wind speed in Tianjin is concentrated in the North (N) and North-northwest (NNW) directions. The backward trajectory transmission path of Tianjin in January and February shows that the airflow mainly comes from the north and northwest of China.