Atmospheric pollution constitutes one of the key environmental challenges hindering Atmospheric pollution is a key environmental challenge constraining the sustainable development of Gansu Province’s land-based Belt and Road corridor and its regional ecological barrier function. The spatiotemporal heterogeneity of aerosol optical depth (AOD) profoundly impacts regional environmental quality. Based on MODIS AOD, NCEP reanalysis, and emission data, this study employed trend analysis (Mann–Kendall test) and attribution analysis (multiple linear regression combined with LMG and Spearman correlation) to investigate the spatiotemporal evolution of AOD over Gansu Province during 2009–2019 and its meteorological and emission drivers. Key findings include the following: (1) AOD exhibited significant spatial heterogeneity, with high values concentrated in the Hexi Corridor and central regions; monthly variation showed a unimodal pattern (peak value of 0.293 in April); and AOD generally declined slowly province-wide during 2009–2019 (52.8% of the area showed significant decreases). (2) Following the implementation of the Air Pollution Prevention and Control Action Plan in 2013 (2014–2019), AOD trends stabilized or declined in 99.8% of the area, indicating significant improvement. (3) Meteorological influences displayed distinct regional-seasonal specificity—the Hexi Corridor (arid zone) was characterized by strong negative correlations with relative humidity (RH2) and wind speed (WS) year-round, and positive correlations with temperature (T2) in spring but negative in summer in the north; the Hedong region (industrial zone) featured strong positive correlations with planetary boundary layer height (PBLH) in summer (r > 0.6) and with T2 in spring/summer; and the Gannan Plateau (alpine zone) showed positive WS correlations in spring and weak positive RH2 correlations in spring/autumn, highlighting the decisive regulatory role of underlying surface properties. (4) Emission factors (PM_2.5, ${\mathrm{SO}}_4^{2-}$, ${\mathrm{NO}}_3^{-}$, ${\mathrm{NH}}_4^{+}$, OM, and BC) dominated (>50% relative contribution) in 80% of seasonal scenarios, prevailing in most regions (Hexi: 71–95% year-round; Hedong: 68–80% year-round; and Gannan: 69–72% in spring/summer). Key components included BC (contributing > 30% in 11 seasons, e.g., 52.5% in Hedong summer), ${\mathrm{NO}}_3^{-}$ + ${\mathrm{NH}}_4^{+}$ (>57% in Hexi summer/autumn), and OM (20.3% in Gannan summer, 19.0% province-wide spring). Meteorological factors were the primary driver exclusively in Gannan winter (82%, T2-dominated) and province-wide summer (67%, RH2 + WS-dominated). In conclusion, Gansu’s AOD evolution is co-driven by emission factors (dominant province-wide) and meteorological factors (regionally and seasonally specific). Post-2013 environmental policies effectively promoted regional air quality improvement, providing a scientific basis for differentiated aerosol pollution control in arid, industrial, and alpine zones.

Oxidative stress is a central mechanism underlying the toxicity of fine particulate matter (PM_2.5); however, the source-specific chemical drivers of particle-associated oxidative potential remain incompletely understood. In this study, the oxidative potential (OP) of ambient PM_2.5 in Xi’an was investigated during winter and summer using the dithiothreitol (DTT) assay, with particular emphasis on the toxicological roles of water-soluble metals and emission sources. PM_2.5 exhibited significantly higher volume-normalized OP (DTT_v) in winter, indicating an enhanced particle-associated oxidative stress burden during the heating period. Notably, although water-soluble metals accounted for only a minor fraction of PM_2.5 mass, interpretable machine learning analysis (XGBoost–SHAP) identified potassium and manganese as dominant contributors to OP, highlighting the importance of biomass burning tracers and redox-active transition metals in particle-mediated reactive oxygen species generation. Source apportionment further revealed pronounced seasonal contrasts: dust sources contributed substantially to wintertime OP primarily due to their large mass loading, whereas traffic-related emissions dominated OP in summer owing to their high intrinsic oxidative toxicity. Overall, these findings suggest that variations in PM_2.5 oxidative potential are more closely associated with chemical composition and source-specific oxidative activity than with particle mass alone, providing additional insight into the factors influencing PM-related health risks.

Ambient aerosols exert growing influences on atmospheric radiative forcing, precipitation, and climate change over the Tibetan Plateau (TP), yet observational constraints on their chemical characteristics remain sparse in this high‐altitude region. A 2‐month field study was conducted during the pre‐monsoon season at Yarlung Tsangpo Grand Canyon, the primary water vapor channel into the TP, to investigate aerosol sources and chemical evolution in this critical corridor. The campaign‐averaged mass concentration of submicron aerosols was 5.68 μg m ⁻³ , dominated by secondary species (78.2%). Notably, a large contribution (27.8%) of aqueous‐phase‐processed oxygenated organic aerosol (aq‐OOA) was observed in the early pre‐monsoon period, closely linked to elevated aerosol liquid water (ALW) and transboundary transported biomass‐burning emissions. Our results highlight the importance of ALW‐involved aqueous‐phase processing of secondary aerosols associated with South Asian outflow in this moisture‐rich channel, which is crucial for evaluating their interactions with clouds and impacts on precipitation in the southeastern TP.

Black carbon (BC) aerosol critically influences climate and haze, yet the mechanisms driving its coating and light absorption enhancement remain poorly understood. Here, we show that BC in Beijing is coated by ammonium nitrate via photochemistry. Laboratory experiments, quantum calculations, and machine learning reveal a new pathway: hydroxyl groups on photoaged BC surfaces promote nitric acid formation in the presence of NO ₂ , which then neutralizes with ammonia to produce ammonium nitrate. Mie simulations demonstrate that this coating drives enhanced light absorption alongside haze intensification. Our findings bridge a key gap between laboratory studies and field observations, elucidating the aging and coating mechanisms of BC in a typical megacity.