[Spatiotemporal Distribution Characteristics of Co-pollution of PM 2.5 and Ozone over BTH with Surrounding Area from 2015 to 2021].

PM _2.5 and ozone co-pollution, which are harmful to not only human health but also the social economy, has become the pivotal issue in air pollution prevention and synergistic control, especially in Beijing-Tianjin-Hebei and its surrounding areas and "2+26" cities. It is necessary to analyze the correlation between PM _2.5 and ozone concentration and explore the mechanism of PM _2.5 and ozone co-pollution. In order to study the characteristics of PM _2.5 and ozone co-pollution in Beijing-Tianjin-Hebei with its surrounding area, ArcGIS and SPSS software were used to analyze the correlation between air quality data and meteorological data of the "2+26" cities in Beijing-Tianjin-Hebei and its surrounding areas from 2015 to 2021. The results indicated:① PM _2.5 pollution constantly decreased from 2015 to 2021, and the pollution was concentrated in the central and southern parts of the region; ozone pollution showed a trend of fluctuation and presented a pattern of "low in the southwest and high in the northeast" spatially. In terms of seasonal variation, PM _2.5 concentration was mainly in the order of winter>spring ≈ autumn>summer, and O ₃ -8h concentration was in the order of summer>spring>autumn>winter. ② In the research area, days with PM _2.5 exceeding the standard continued to decline, whereas days with ozone exceeding the standard fluctuated, and days with co-pollution decreased significantly; there was a strong positive correlation between PM _2.5 and ozone concentration in summer, with the highest correlation coefficient of 0.52, and a strong negative correlation in winter. ③ Comparing the meteorological conditions of typical cities during the ozone pollution period with that of the co-pollution period, the co-pollution occurred under the temperature range of 23.7-26.5℃, humidity of 48%-65%, and S-SE wind direction.