Influence Of Meteorology And Space Transport On Ozone Pollution In Typical Cities Of Shandong Province

In recent years,ozone（O₃）has gradually become another major air pollutant after PM_2.5,and it is also the main component of photochemical smog,which has become the focus of research due to its complex influencing factors.O₃ pollution in Shandong Province is a key problem restricting its air quality improvement.Owing to obvious regional differences in characteristics and causes of O₃ pollution,the analysis of its characteristics and formation mechanism in different regions can provide a reference for the formulation of regionally differentiated control measures for O₃ in Shandong Province.Taking Jinan,Linyi,Qingdao,and Weihai as representative cities,this study analyzed the temporal and spatial variation characteristics of O₃ concentration from 2014 to 2019.The GAM model was used to analyze the nonlinear relationship between O₃ concentration and meteorological conditions and the concentration of other polluting gases.Potential Source Contribution Function（PSCF）and Concentration Weighted Trajectory（CWT）methods were used to analyze the characteristics of O₃ pollution affected by regional transport.The main conclusions are as follows:（1）From 2014 to 2019,the annual average concentration of O₃ and the annual 90th percentile concentration of O₃-8h in the four cities showed an upward trend of varying degrees.The O₃exceeding rate and the number of days exceeding the standard in Jinan and Linyi increased since2014,and the exceeding rates in 2019 were 26.0%and 19.2%,respectively.Qingdao and Weihai had a relatively low degree of exceeding the standard,and the exceeding rate did not exceed 10%in recent years.The annual average concentrations in Jinan from 2014 to 2019,Linyi from 2015to 2019,Qingdao in 2017,and Weihai in 2014 and 2019 exceeded the national secondary standard（160μg/m³）.（2）The temporal variation of O₃ concentration had obvious regional differences.Jinan and Linyi showed a“single peak”and peaked in June,while coastal cities of Qingdao and Weihai showed a“double peak type”,with peaks in May and August or September.The diurnal variation trends all showed an obvious“single peak”,and the difference between the daytime peak value and the nighttime trough value in Jinan and Linyi was significantly higher than that in Qingdao and Weihai.The seasonal variation of O₃ concentration in four cities was higher in spring and summer.（3）The GAM model study showed that O₃ had a complex nonlinear relationship with the concentration of meteorological elements and other pollutants,and the sensitivity of O₃concentration to meteorological elements and other pollutants varied in different cities.Compared with coastal cities,O₃ pollution in inland cities was more significantly affected by meteorological factors,which was related to the influence of sea breeze transmission in coastal cities.Through collinearity diagnosis,the multicollinearity influencing factors were eliminated(Jinan and Linyi removed SO₂,CO and PM₁₀,Qingdao City removed SO₂ and PM₁₀,Weihai removed P（pressure）,SO₂ and PM₁₀).The main driving factors of O₃ in each representative city were T（temperature）,SH（sunshine hours）and RH（relative humidity）in Jinan;RH,T and SH in Linyi;SH,CO and T in Qingdao;CO,PM_2.5 and RH in Weihai.（4）By establishing the GAM model of the two-way interaction of influencing factors,it was found that the interaction terms of Jinan and Linyi had a higher interpretation rate for O₃concentration,which was mainly represented by“meteorological elements+meteorological elements”,among which T,RH,SH and other influencing factors were main factors.Qingdao and Weihai were mainly in the form of“meteorology+pollutants”,and the interaction terms between RH,SH and pollutants were most.In general,the generation and change mechanisms of O₃ in the four cities were not the same,which needed further research.（5）The results of backward trajectory clustering,PSCF and CWT analysis of the O₃ pollution days in four cities showed that the regional air mass transport had a greater impact on the O₃concentration,and the O₃ pollution levels were significantly different in different trajectory directions.The O₃ pollution in Jinan and Linyi was mainly related to the southerly air flow,while Qingdao and Weihai were mainly affected by the air flow from the surrounding inland cities.In conclusion,the prevention and control of O₃ pollution in Shandong Province needs to take regional differentiated control measures and strengthen joint prevention and control between cities.