Concentration,influencing factors,and transport characteristics of PM2.5 and O3 in southern Sichuan from 2015 to 2020
With the economic development of southern Sichuan,ground-level ozone(O3)and particulate matter less than 2.5 μm in aerodynamic diameter(PM2.5)have emerged as major pollutants detrimental to human health.In response to air pollution challenges,the Chinese Government implemented the"Air Pollution Prevention and Control Action Plan"in 2013 and the"Three-Year Action Plan to Win the Blue Sky Defense War"in 2018.This study evaluates the effectiveness of control measures for PM2.5 and O3 in southern Sichuan post-implementa-tion and aims to provide a theoretical and scientific basis for the coordinated management of these pollutants.We analyze the temporal variations in PM2.5 and O3 concentrations in four cities in southern Sichuan(Zigong,Nei-jiang,Luzhou,and Yibin)from 2015 to 2020.Zigong,identified as the most polluted among the cities,serves as a case study to investigate the correlations between PM2.5 and O3 concentrations and various influencing factors.The study utilizes backward trajectory clustering,source emission intensity analysis,and potential source analysis to as-sess the impact of regional pollutant transport on Zigong.The results indicate that:1)From 2015 to 2020,the an-nual average concentration of PM2.5 in southern Sichuan showed a declining trend with a 38.9％reduction,while the annual average concentration of O3 showed a slight increasing trend,rising by 8.2％.These trends suggest that current control strategies are effective for PM2.5 but may be insufficient for O3,highlighting the need for enhanced O3 management strategies.2)The monthly average PM2.5 concentration exhibits a"U"shape,with the lowest val-ues in July and August and the highest from December to February.In contrast,the monthly average O3 concentra-tion exhibits an"M"shape,peaking in July and August with secondary peaks in April and May.These patterns suggest that PM2.5 control should be prioritized in winter,while O3 control should be emphasized in spring and summer.3)In Zigong,PM 2.5 concentration shows significant positive correlations with CO,NO2,and SO2 concen-trations,while O3 concentration is significantly positively correlated with temperature and negatively correlated with relative humidity.4)The regional transport of PM2.5 and O3 in Zigong is predominantly influenced by local air masses.Radiation levels and anthropogenic emission intensities along air trajectories significantly affect PM2.5 and O3 concentrations.The primary potential source areas for these pollutants are located within the Sichuan Basin and parts of Guizhou.Given the regional transport influnece,there is a need for strengthened regional collaborative governance,joint prevention and control efforts,enhanced source control,accelerated replacement of VOC-contai-ning materials,and increased utilization of clean energy soucres.The study employs Pearson correlation analysis to preliminarily identify relationships between PM2.5 and O3,and various influencing factors.Future research will in-clude a more quantitative analysis of these relationships,including the impact of temperature on photochemical re-actions,the role of relative humidity in PM2.5 wet deposition,and the effects of atmospheric diffusion conditions on pollutant concentrations.These analyses will provide precise quantification of the specific impacts of each influ-encing factor on PM2.5 and O3 pollution,thereby enhancing the objectivity and reliability of the research findings.
PM2.5 and O3temporal variationbackward trajectorypotential source contribution functionconcen-tration weighted trajectory
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