As one of China’s emerging urban agglomerations, the Changzhutan urban area is suffering from regional composite air pollution. Previous studies mainly focus on single cities or world-class urban agglomerations, which cannot provide a scientific basis for air pollution in emerging urban agglomerations. This paper proposes the latest high-resolution emission inventory through the emission factor method and compares the results with the rest of the urban agglomeration. The emission inventory shows that the estimates for sulfur dioxide (SO₂), nitrogen oxides (NO_X), particulate matter 10 (PM₁₀), particulate matter 2.5 (PM_2.5), volatile organic compounds (VOCs), and ammonia (NH₃) emission are 132.5, 148.9, 111.6, 56.5, 119.0, and 72.0 kt, respectively. From the 3 × 3 km emission grid, the spatial difference of air pollutant emissions in the Changzhutan urban agglomeration was more obvious, but the overall trend of monthly pollutant discharge was relatively stable. Depending on the source apportionment, SO₄²⁻, OC, and NO₃⁻ are the main chemical constituents of PM_2.5, accounting for 13.06, 8.24, and 4.84 μg/m³, respectively. Simultaneously, industrial emissions, vehicle exhaust, and dust are still three main sources that cannot be ignored. With the support of these data, the results of this study may provide a reference for other emerging urban agglomerations in air quality.

Analysis of chemical composition characteristics of PM_2.5 under different pollution degrees can reveal the changes of pollution sources. In order to make clear the evolution process of PM_2.5 compositions in autumn and winter, PM_2.5 samples were continuously collected and analyzed at Liaocheng city, China. The collected samples were classified as clean days (CLD), mild-moderate pollution days (MMD) and severe-serious pollution days (SSD). It was concluded that with the increase of pollution degrees, the concentrations of water-soluble ions and carbon components increased significantly, while elements only increased slightly. In addition, as the pollution degrees increased, the percentage of NO₃⁻, SO₄²⁻ and NH₄⁺ increased significantly, from 23.0% in CLD to 49.0% in SSD, while the percentage of other components decreased, especially crust material. The PMF analyzed results showed that secondary transformation (36.7%), combustion sources (20.4%), secondary organic aerosols (SOA) (11.7%), vehicle sources (11%), dust (10.5%) and industrial processes (9.7%) were the main sources of PM_2.5 during autumn and winter in Liaocheng. The contribution of secondary transformation reached 57% at the SSD level, which indicated that it was the main reason for the increase of PM_2.5 concentrations. The air mass mainly came from five paths to Liaocheng. The secondary transformation contribution of the air mass with short transmission distance was higher, while the contribution of the dust was higher from the long distance.

Pollutants emission, meteorological conditions, secondary formation, and pollutants transport are the main reasons for air pollution. A comprehensive air pollution analysis was conducted from the above four aspects in the autumn–winter seasons of 2017–2018 and 2018–2019 at Xingtai, China. In addition, the relationship between PM_2.5 and O₃ was also studied from the aspects of secondary formation and meteorological conditions to find the rules of cooperative management of PM_2.5 and O₃ combined pollution. Taking measures of concentrated and clean heating and controlling biomass burning could make the concentrations of EC, K⁺ and SO₄²⁻ decrease. The variation trends of PM_2.5 and O₃ concentration in the autumn–winter season of Xingtai were different, and with the increase in secondary formation effects, the concentration of O₃ decreased. Furthermore, the key meteorological conditions that affected O₃ and PM_2.5 formation were temperature and relative humidity, respectively. The relationships of NOR (nitrate oxidation rate) and SOR (sulfate oxidation rate) against temperature presented a “U” shape, suggesting that gas-phase oxidation and gas–solid-phase oxidation were all suppressed at a temperature of around 4 °C. The cities located in the east had more pollutant transporting effects during the pollution processes of Xingtai, and the main transport routes of O₃ and PM_2.5 were not all the same.

Beijing-Tianjin-Hebei (BTH) and its surrounding areas are one of the most polluted regions in China. Xingtai, as a heavy industrial city of BTH and its surrounding areas, has been experiencing a severe PM_2.5 pollution in recent years, characterized by extremely high concentrations of PM_2.5. In 2014, PM_2.5 mass concentrations monitored by online instruments in urban areas of Xingtai were 116, 77, 128, and 200 µg m⁻³ in spring, summer, autumn and winter, respectively, with annually average concentrations of 130 µg m⁻³ exhibiting 3.7 times higher than National Ambient Air Quality Standard (NAAQS) value for PM_2.5 (35 µg m⁻³). To identify PM_2.5 emission sources, ambient PM_2.5 samples were collected during both cold and warm periods in 2014 in urban areas of Xingtai. Organic carbon (OC), sulfate, nitrate, ammonium and elemental carbon (EC) were the dominant components of PM_2.5, accounting for 13%, 11%, 12%, 11% and 8% in the cold period, respectively, and 11%, 12%, 9%, 6%, and 5% in the warm period, respectively. Source apportionment results indicated that coal combustion (24.4%) was the largest PM_2.5 emission source, followed by secondary sulfate (22.2%), secondary nitrate (18.4%), vehicle exhaust dust (12.4%), fugitive dust (9.7%), construction dust (5.5%), soil dust (3.4%) and metallurgy dust (1.6%). Based on PM_2.5 source apportionment results, some emission control measures, such as replacing bulk coal with clean energy sources, controlling coal consumption by coal-fired boiler upgrades, halting operations of unlicensed small polluters, and controlling fugitive and VOCs emission, were proposed to be implemented in order to improve Xingtai’s ambient air quality.

Precise construction of asymmetric bimetallic coordination sites is important for developing efficient Fenton-like catalysts, but stabilizing such structures on nitrogen-rich carbon supports remains challenging. Herein, an ultrasmall CoSn particle-supported C2N catalyst (CoSn/C2N) was prepared through a supramolecular assembly-assisted pyrolysis strategy using melamine, cyanuric acid, CoPc, SnPc, and oxalic acid as precursors. The obtained CoSn/C2N exhibited a flower-like architecture assembled from ultrathin wrinkled nanosheets, with highly dispersed CoSn particles mainly distributed at 1.0–1.2 nm. XANES, EXAFS fitting, and WT-EXAFS analyses revealed the partially oxidized states of Co and Sn, confirmed Co–Sn coordination, and demonstrated strong coupling between the bimetallic particles and the C2N. Benefiting from this unique local structure, CoSn/C2N efficiently activated peroxymonosulfate for sulfachloropyridazine degradation, achieving complete removal within 10 min with an apparent rate constant of 0.25 min-1, higher than those of Co/C2N and Sn/C2N. The CoSn/C2N/PMS system maintained high activity over a broad pH range, resisted interference from common ions and humic acid, and retained complete removal after five cycles. Quenching experiments and EPR spectra identified singlet oxygen as the dominant reactive species, indicating a 1O2-mediated nonradical oxidation pathway. This work provides a feasible strategy for designing C2N-confined bimetallic catalysts for antibiotic wastewater treatment.