Regional Characteristics and Background Concentration Estimation of Ozone in Ningbo City During the Warm Season of 2022
To study the regional characteristics of ozone in Ningbo during the warm season of 2022(April-October),principal component analysis(PCA)was conducted on the basis of ozone monitoring data in 11 cities of Zhejiang Province,including 53 National Control Stations and 20 Ningbo City Evaluation Stations.The background ozone concentration of Ningbo was estimated by TCEQ method.The results of PCA identified four principal components in Zhejiang Province.The variance contribution of PC1 was 65.6%,which was interpreted as the regional background concentration of ozone;the variance contribution of PC2,PC3 and PC4 was 14.2%,7.5%and 2.6%respectively,which was interpreted as the influence of factors such as intraregional transport,local circulation and local photochemical generation on ozone concentration.Two principal components could be identified in Ningbo City.The variance contribution of PC1 was 83.0%,which could be interpreted as the urban concentration of ozone in Ningbo City,and the variance contribution of PC2 was 7.0%,which could be interpreted as the influence of land-sea breeze on ozone concentration.According to the TCEQ method,the regional background concentration of ozone in Ningbo was 87 μg/m3,which was 9 μg/m3 higher than that in 2021.In summer(July-August),the higher regional background concentration and higher concentration produced by local photochemical resulted in a rise of ozone concentration by 35 μg/m3,which was the main reason for the high ozone concentration in 2022.The background concentrations of ozone obtained by the two methods had a strong correlation,the correlation coefficient was 0.88,and the results of PCA method were slightly higher than that of TCEQ method,meanwhile,analysis results from these two methods demonstrated that both higher regional background concentrations and stronger locally generated ozone concentration contributed to the 2022 high ozone concentration events.
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