## 4 Discussions  
The conspicuous seasonal variations in the average concentrations of PM2.5 and PM10 observed in Chenzhou City from March 2022 to March 2023 predominantly stem from seasonal climatic conditions. Winter and autumn typically denote the drier epochs in Chenzhou City, potentially hindering the dispersion and attenuation of particulate matter  
Figure 9: Seasonal variations in PM2.5 Concentration-Weighted Trajectories across Chenzhou City (**a**) Spring trajectory (**b**) Summer trajectory (**c**) Autumn trajectory (**d**) Winter trajectory) (note: the illustration was crafted utilizing ArcGIS software, specifically version 10.2. For further reference, please visit the following URL: [[https://www.arcgis.com/index.html](https://www.arcgis.com/index.html)]([https://www.arcgis.com/index.html](https://www.arcgis.com/index.html)) (accessed on 16 October 2023)). in the atmosphere, thereby augmenting the concentrations of PM\({}_{2.5}\) and PM\({}_{10}\). Conversely, the moisture-laden conditions prevalent during spring and summer foster the removal of particulate matter, culminating in reduced average concentrations. Moreover, the intensified demand for heating during winter catalyzes heightened combustion activities and emissions, potentially intensifying PM\({}_{2.5}\) and PM\({}_{10}\) concentrations, especially in the absence of rigorous pollution control measures. Winter and autumn are anticipated to mark the peaks of industrial production and activity in Chenzhou City--endeavors often associated with significant emissions of particulate matter, thus exacerbating pollution levels. Additionally, fluctuations in traffic volume, influenced by weather conditions or other determinants, can amplify vehicular emissions, further impacting PM\({}_{2.5}\) and PM\({}_{10}\) concentrations. Furthermore, specific natural phenomena, such as dust storms or wind-driven particulate matter, can exert a profound influence on particulate matter concentrations during specific seasons, notably in spring. The heightened concentrations of PM\({}_{2.5}\) observed in Chenzhou City during autumn and winter are likely the result of the confluence of seasonal climatic conditions, increased heating demand, escalated industrial activities, and amplified vehicular traffic. In contrast, the exacerbation of PM\({}_{10}\) pollution in spring and summer can be ascribed to the influence of humid climatic conditions, precipitation, and natural emissions. To effectively mitigate and reduce particulate matter pollution, a comprehensive examination of these potential factors is essential. Concurrently, the implementation of tailored control measures and policy interventions is imperative. In the realm of spatial distribution, the annual average PM\({}_{2.5}\) concentrations in Chenzhou City manifest a pollution gradient distinguished by \"ascending concentrations from the north to the south in the eastern and central sectors, with attenuated levels prevailing in the west.\" This spatial configuration could be shaped by a confluence of factors. Firstly, in terms of demographic distribution and economic activities, the eastern and central regions of the city stand as epicenters of burgeoning urbanization and industrialization. In contrast, the western expase retains its predominantly agrarian and pristine character, potentially yielding fewer emission sources. Secondly, the interplay of topographical contours and meteorological conditions is instrumental in delineating this spatial disparity. The topography exerts a profound influence on wind dynamics and speeds, subsequently modulating the dispersion trajectories of pollutants. Additionally, indigenous meteorological conditions may foster the aggregation of pollutants in discrete locales, resulting in areas of amplified concentration. In areas with pronounced annual average PM\({}_{2.5}\) concentrations, such as the Beihu District and Suvian District, the conspicuous pollution levels might be intricately correlated with localized industrial endeavors, vehicular activities, and domestic emissions.