*Article* **Temporal and Spatial Distribution Analysis of Atmospheric Pollutants in Chengdu–Chongqing Twin-City Economic Circle**

**Ning Qi 1,\*, Xuemei Tan <sup>1</sup> , Tengfei Wu 2,\*, Qing Tang <sup>3</sup> , Fengshou Ning <sup>1</sup> , Debin Jiang <sup>1</sup> , Tengtun Xu <sup>1</sup> , Hong Wu <sup>1</sup> , Lingxiao Ren <sup>4</sup> and Wei Deng <sup>5</sup>**


**Abstract:** In order to study the temporal and spatial distribution characteristics of atmospheric pollutants in cities (districts and counties) in the Chengdu–Chongqing Twin-city Economic Circle (CCEC) and to provide a theoretical basis for atmospheric pollution prevention and control, this paper combined Ambient Air Quality Standards (AAQS) and WHO Global Air Quality Guidelines (GAQG) to evaluate atmospheric pollution and used spatial correlation to determine key pollution areas. The results showed that the distribution of atmospheric pollutants in CCEC presents a certain law, which was consistent with the air pollution transmission channels. Except for particulate matter with an aerodynamic diameter equal to or less than 2.5 µm (PM2.5) and ozone (O<sup>3</sup> ), other pollutants reached Grade II of AAQS in 2020, among which particulate matter with an aerodynamic diameter equal to or less than 10 µm (PM10), PM2.5, sulfur dioxide (SO<sup>2</sup> ), nitrogen dioxide (NO<sup>2</sup> ) and carbon monoxide (CO) have improved. Compared with the air quality guidelines given in the GAQG, PM10, PM2.5, NO<sup>2</sup> and O<sup>3</sup> have certain effects on human health. The spatial aggregation of PM<sup>10</sup> and PM2.5 decreased year by year, while the spatial aggregation of O<sup>3</sup> increased with the change in time, and the distribution of NO<sup>2</sup> pollution had no obvious aggregation. Comprehensive analysis showed that the pollution problems of particulate matter, NO<sup>2</sup> and O<sup>3</sup> in CCEC need to be further controlled.

**Keywords:** spatial autocorrelation; Moran's I; air pollution transmission channels; ambient air quality standards; WHO Global Air Quality Guidelines
