## 3 Results and Discussions
### Spatial Distribution Characteristics of PM\({}_{2.5}\) in Chenzhou City
Figure 5: Spatial patterns of annual average concentrations of SO\({}_{2}\), CO, NO\({}_{2}\), and PM\({}_{2.5}\)/PM\({}_{10}\) in Chenzhou City (**(a)** Annual average concentration spatial distribution of SO\({}_{2}\) (**b**) Annual average concentration spatial distribution of CO (**c**) Annual average concentration spatial distribution of NO\({}_{2}\) (**d**) Annual average concentration spatial distribution of PM\({}_{2.5}\)/PM\({}_{10}\)) (note: the illustration was crafted utilizing ArcGIS software, specifically version 10.2. For further reference, the software can be accessed at 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)). across the five principal regions, with correlation coefficients surpassing 0.60. With the exception of the central and western zones, CO in the remaining three areas also demonstrates a marked correlation with PM\({}_{2.5}\). This suggests a significant homology between PM\({}_{2.5}\) and PM\({}_{10}\), NO\({}_{2}\), and CO within these locales. The primary sources of NO\({}_{2}\) are vehicular exhaust emissions and coal combustion, while SO\({}_{2}\) and CO predominantly originate from industrial discharges and fossil fuel burning. High concentrations of SO\({}_{2}\) are evident in Linwu County, Jiahe County, and the western reaches of Guiyang County within Chenzhou City. Notably, Linwu County serves as a principal hub for non-ferrous metals in Chenzhou, encompassing prominent mining locals such as the Sanshiliuwan Mining Area and the Ganxi River Basin Mining Area. Jiahe County stands renowned as a coal mining epicenter in Chenzhou, whereas the southeastern expanse of Guiyang County hosts substantial industrial parks with heightened fossil fuel combustion emissions. In Figure 5b,c, elevated concentrations of CO and NO\({}_{2}\) are prominently observed in the central and western sectors of Chenzhou City. The underlying factors contributing to these high-concentration zones of CO mirror those of SO\({}_{2}\). Specifically, the presence of industrial parks in Chenzhou's central and western regions, coupled with substantial fossil fuel emissions, accounts for this phenomenon. The topographical barrier formed by the Nanjing Mountains' midsection and the southern segment of the Luoxiao Mountains obstructs pollutant dispersion to the southwest. Within the industrial park, the transportation of raw materials and finished goods is predominantly facilitated by heavy-duty diesel vehicles. Concurrently, the central urban expanse of Chenzhou witnesses a dense vehicular presence, precipitating significant vehicular exhaust emissions and consequently elevated NO\({}_{2}\) levels in the central and western sectors. Furthermore, the inverse relationship between PM\({}_{2.5}\) and O\({}_{3}\) suggests that fluctuations in PM\({}_{2.5}\) concentrations can modulate solar radiation intensity, consequently influencing O\({}_{3}\) production indirectly. This dynamic may also be attributed to the presence of certain precursors common to both PM\({}_{2.5}\) and O\({}_{3}\), facilitating their convergence. The annual average ratio of PM\({}_{2.5}\) to PM\({}_{10}\) is markedly elevated in the central and western regions, as illustrated in Figure 5. This elevation underscores the heightened severity of PM\({}_{2.5}\) pollution in these areas, a trend in alignment with the annual average PM\({}_{2.5}\) distribution depicted in Figure 4. Conversely, on the periphery of the central city, the annual average PM\({}_{2.5}\) to PM\({}_{10}\) ratio in the eastern regions remains comparatively subdued, signaling PM\({}_{10}\) as the predominant pollutant therein. Beyond anthropogenic emission sources, this phenomenon can also be attributed to the influence of southward sand and dust transport.