In recent years, ozone (O₃) pollution has become a prominent air quality concern in the Sichuan Basin (SCB). Based on surface O₃ measurements from 22 cities between 2015 and 2024, this study investigates the evolution of extreme O₃ pollution events and their underlying causes. While the average O₃ concentration, the number of affected cities, and the total O₃ pollution hours have all increased during the past decade, extreme O₃ concentrations have shown a significant decline since 2020. These trends suggest that O₃ pollution in the SCB has become more spatially extensive and less intense. Decomposition analysis attributed ~75% of the post-2020 decline in extreme O₃ concentrations to precursor emission reductions, with meteorological variability explaining the remaining ~25%. Satellite observations of formaldehyde (HCHO) and nitrogen dioxide (NO₂) column densities indicate a regional shift in O₃ formation regimes across the SCB, with many areas transitioning from VOC (volatile organic compound)-limited to transitional or NO_x (nitrogen oxide)-limited conditions. This shift likely contributed to the broader spatial extent and longer duration of O₃ pollution in recent years. Model sensitivity simulations and Integrated Reaction Rate (IRR) analysis demonstrate that reductions in precursor emissions, particularly NO_x, directly weakened daytime photochemical O₃ production and disrupted NO_x-driven radical propagation under transition and NO_x-limited conditions, collectively driving the observed decline in extreme O₃ concentrations.

The concentration of atmospheric ozone (O₃) pollution is showing a rapid growing tendency, and O₃ pollution has become one of the bottleneck issues that restrict the continuous improvement of air quality in China. In this study, we first identified the primary factors based on the source apportionment of O₃, then used factor analysis to divide these selected factors into economic and environmental categories. The geographical detector model was used to analyze the impact of factors and their interactions on O₃ concentration in 41 cities in the Yangtze River Delta (YRD) region in 2020. The results showed that forest coverage ranked first among all the detected factors, suggesting a strong relationship between the regional O₃ concentration and forest coverage. The driving factors of economic activity were ranked as follows: actual utilization of foreign capital (0.400) > gross domestic product (GDP) per capita (0.387) > proportion of tertiary industry (0.360) > urbanization rate (0.327) > per capita consumption expenditure (0.194) > research and development (R&D) of full-time equivalents of industrial enterprises above designated size (0.182) > number of industrial enterprises (0.126). The interaction between any two factors enhanced their influence on O₃ concentration more than any single factor, indicating that the variability of regional O₃ concentration was an outcome of a combination of multiple factors. This study could provide recommendations for the prevention and control of O₃ pollution and the development of ecological integration in the YRD region.

Rivers emit substantial amounts of carbon dioxide (CO₂) to the atmosphere, yet its response to heavy rainfall remains unclear with intensive anthropogenic disturbances. To fill the knowledge gap, this study investigated the dynamic variability of CO₂ partial pressure (pCO₂) and CO₂ emissions flux at the Chaohu Lake Basin, a watershed under intensive anthropogenic perturbations, based on field campaigns across diverse river systems during dry season, normal season, and post-rainfall periods. Results demonstrated marked differences in aquatic pCO₂ across river types, with urban rivers (3949 µatm) exhibiting significantly higher levels than non-urban counterparts (1423 µatm). Rainfall events elevated riverine pCO₂, but the effect size varied between river types (urban river versus non-urban river). In non-urban rivers, pCO₂ following heavy rainfall (2461 μatm) was significantly higher (p < 0.05) than those observed during both dry season (1096 μatm) and normal season (712 μatm). In contrast, urban rivers demonstrated only marginal pCO₂ elevation after rainfall (20–30%). Statistical analysis revealed that discharge, total nitrogen (TN), total phosphorus (TP), and ammonia nitrogen (NH₄⁺-N) showed significantly positive correlations with pCO₂, while dissolved oxygen (DO) and pH exhibited significantly negative correlations with pCO₂. Overall, rivers in the Chaohu Lake Basin act as significant sources of atmospheric CO₂, with an annual mean CO₂ emission flux of 297.84 mmol·m⁻²·d⁻¹, and the heavy rainfall events amplify riverine CO₂ emissions (629.91 mmol·m⁻²·d⁻¹), with observed enhancement effects exceeding 300% compared to baseline conditions. To accurately estimate the CO₂ emissions from human-dominated rivers, future research should emphasize the impacts of extreme or heavy rainfall events.

Climate change alters climatic factors, which in turn affect the suitability of crops to grow. Winter wheat is a major crop in the Beijing-Tianjin-Heibei region of China. To assess the climate factors on winter wheat production, the meteorological data (temperature, precipitation, sunshine, etc.) from 25 stations in the target region the Beijing-Tianjin-Hebei region of China from 1961 to 2010, the winter wheat yield data from 1978 to 2010, and the growth stages were used. A model of the suitability of light, temperature, and water was subsequently developed to quantitatively analyze the spatial and temporal variability of the suitability of the winter wheat to the climate of the region. Temperature suitability was high during the sowing and grouting periods (temperature suitability peaks at 0.941 during grouting) and lowest in the rejuvenation period. In terms of spatial distribution, it is strong in the south and low in the north, and it exhibits a gradual increase in interannual variation. Precipitation suitability fluctuates steadily, with a peak in the tillering stage and a trough in the jointing stage. In terms of spatial distribution, it is highest in the northeast and decreases in the west; in inter-annual changes, it fluctuates strongly with weak overall growth. Sunshine suitability is stable at 0.9 or above. In spatial distribution, it is high in the northwest and low in the southeast, and it decreases slowly in the interannual variations. The trend of climatic suitability is consistent with temperature and precipitation, showing a pattern of falling first and then rising. In terms of spatial distribution, the overall climate suitability is high in the south and low in the north. In inter-annual changes, climate suitability generally increases slowly. Temperature and precipitation are key factors. Moisture stress became the most important factor for winter wheat cultivation in the region. Sunshine conditions are typically sufficient. This study provides a theoretical basis for a rational layout of winter wheat growing areas in the Beijing-Tianjin-Hebei region and the full utilization of climatic resources.