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 (PM_2.5) and ozone (O₃), 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), PM_2.5, sulfur dioxide (SO₂), nitrogen dioxide (NO₂) and carbon monoxide (CO) have improved. Compared with the air quality guidelines given in the GAQG, PM₁₀, PM_2.5, NO₂ and O₃ have certain effects on human health. The spatial aggregation of PM₁₀ and PM_2.5 decreased year by year, while the spatial aggregation of O₃ increased with the change in time, and the distribution of NO₂ pollution had no obvious aggregation. Comprehensive analysis showed that the pollution problems of particulate matter, NO₂ and O₃ in CCEC need to be further controlled.

With the development of industry, agriculture, and aquaculture, excessive ammonia nitrogen mainly involving ionic ammonia (NH₄⁺) and molecular ammonia (NH₃) has inevitable access to the aquatic environment, posing a severe threat to water safety. Photocatalytic technology shows great advantages for ammonia nitrogen removal, such as its efficiency, reusability, low cost, and environmental friendliness. In this study, CP (g-C₃N₄/CoP) composite materials, which exhibited high-efficiency ammonia nitrogen removal, were synthesized through a simple self-assembly method. For the optimal CP-10 (10% CoP) samples, the removal rate of ammonia nitrogen reached up to 94.8% within 80 min under visible light illumination. In addition, the nitrogen selectivity $S\left(N_2\right)$ is about 60% for all oxidative products. The high performance of the CP-10 photocatalysts can be ascribed to the effective separation and transmission of electron–hole pairs caused by their heterogeneous structure. This research has significance for the application of photocatalysis for the remediation of ammonia nitrogen wastewater.