Analysis of compound pollution characteristics of PM2.5 and O3 and their meteorological causes in Tai'an city from 2014 to 2021
Based on surface meteorological observation data,air pollutant monitoring data from 2014 to 2021 in Tai'an city,and ERA5 reanalysis data provided by the European Centre for Medium-Range Weather Forecasts(ECMWF),this study analyzes the characteristics of PM2.5 and O3 compound pollution,the meteorological cau-ses,and the interactions between PM2.5 and O3 during compound pollution periods in this region.The results show that compound pollution by PM2.5 and O3 is a significant issue in Tai'an city,with monthly exceedance hours showing a unimodal distribution and significant seasonal variation characteristics.The compound pollution is more likely to occur under conditions of high temperature,high relative humidity,and low wind speed.Using Principal Component Analysis(PCA)and K-means clustering methods,the weather patterns associated with compound pol-lution in Tai'an city are classified into five types:rear of high pressure type,uniform pressure field type,saddle field type,front of weak low pressure type,and bottom of high pressure type,with the rear of high pressure type showing the highest frequency of compound pollution occurrence.Analysis of the interactions between PM2.5 and O3 in Tai'an city indicates significant correlations in both winter and summer.In summer,atmospheric oxidation is dominated by O3 oxidation,and the contribution rate of atmospheric PM2.5 concentration under various photochemi-cal intensity levels shows that primary emissions surpass secondary formation.In winter,with weak atmospheric ox-idation,increasing PM2.5 concentrations,lead to reduced direct solar radiation and decreased O3 peak concentra-tions,indicating that PM2.5 has an inhibitory effect on O3 formation.
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