In order to study the impact of control measures on air quality in Kunshan City during the COVID-19 pandemic in 2022,this paper analyzed the variation characteristics of atmospheric pollutants,especially ozone concentration during the pre-epidemic and control periods,the spatial distribution,causes and sources of ozone pollution were researched.The results showed that under the pandemic control measures,the concentration of primary pollutants decreased progressively,while O3-8 h concentration increased significantly,and the pollution was the most severe during middle period of epidemic control,obviously surpassing the historical level in the same period.The high values of O3-8 h were mainly concentrated in the western(New&High-tech Industrial Development Zone)and northwestern areas of the city,showed a significant increase compared to 2021.The spatial distribution of the reduction rate of NO2 and the rise rate of O3-8 h showed a good correspondence,the regions with high NO2 reduction also had high O3-8 h increase.They also showed a nonlinear correlation,when the NO2 concentration reached a critical value,the ozone concentration decreased accordingly.The daily change of ozone showed an obvious"single-peak"pattern with a significant increase in amplitude during the typical pollution events,ozone concentration was significantly positive correlation with air temperature,visibility and sunshine,and negative correlation with relative humidity and air pressure.Combined with the wind direction and backward trajectory cluster analysis,the air masses of pollution mainly came from Zhejiang Province,Anhui Province,accounting for about 64%of the total input air masses.
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