Natural gas will continue to replace coal in the process of global energy structure reform, but its leakage potential can delay the realization of global carbon neutrality. To quantify its impact, we established a carbon dioxide (CO2) and methane (CH4) flux detection platform on the 220 m platform of the Institute of Atmospheric Physics, Chinese Academy of Sciences, located in northwestern Beijing. The observation results indicated that the daily mean CO2 and CH4 fluxes were 12.21 +/- 1.75 mu mol m-2 s-1 and 95.54 +/- 18.92 nmol m-2 s-1, respectively. The fluxes were significantly correlated with natural gas consumption, indicating that natural gas has become a common source of CH4 and CO2, the combustion of which releases CO2, while its leakage processes emit CH4. Vehicle-based identification demonstrated that CH4 can escape at the production, storage and use stages of natural gas. Based on natural gas consumption data, the upper limit of the calculated natural gas leakage rate in Beijing reached 1.12 % +/- 0.22 %, indicating that the contribution of CH4 to climate change could reach 23 % of that of CO2 on a 20-year scale. Natural gas leakage was estimated to delay the time for China to achieve carbon neutrality by at least almost four years.

Dust aerosols profoundly impact regional air quality and radiative forcing, yet their long-term trends and driving mechanisms over China remain poorly constrained. This study evaluates dust historical simulations from 10 Coupled Model Intercomparison Project Phase 6 (CMIP6) models and their multi-model ensemble mean (MME) against MODIS satellite observations and MERRA-2 reanalysis, focusing on spring dust cycle trends over North China during 2000-2014. The results show that the MME captures the spatial heterogeneity of spring dust trends: increasing in western regions and decreasing in central/eastern areas. However, it exhibits substantial biases relative to MODIS, particularly failing to reproduce the pronounced declining dust optical depth (DOD) trends in the Gobi Desert (GD) and Northeast China (NEC), despite simulating the observed increasing trend (2.9 & times; 10-3 yr-1) in the Taklamakan Desert (TD). Dust budget analysis reveals regionally distinct drivers: emission-dominated processes in the TD correspond to an increasing dust trend, whereas deposition-dominated conditions in the NEC align with a declining trend, with consistent MME trends of all dust variables in both regions. Although both MME and MERRA-2 show a decreasing dust trend in the GD, the region exhibits substantial intermodel discrepancies in simulated emission and deposition processes, which also deviate from MERRA-2, indicating considerable uncertainties in simulating the key dust processes in this region. This study highlights the necessity of clarifying regional heterogeneities in dust trends for robust radiative forcing assessments and projections. Refining dust emission/deposition parameterizations and optimizing particle size distribution representation in climate models is critical to enhancing dust cycle simulation credibility.

Atmospheric nitrate (NO3-), a key component of fine particulate matter (PM2.5), significantly impacts air quality and climate. This study investigates decadal variability (2013-2022) of PM2.5-associated NO3- in Beijing using continuous real-time measurements, meteorological normalization, and source identification. Results reveal an annual NO3- decline of 4.8 %, driven by stringent clean air policies like "coal-to-gas" initiatives, with autumn and winter reductions (-8.6 %/yr and -8.4 %/yr, respectively) outpacing other seasons due to targeted emission controls. Despite progress, NO3- remains elevated (11.7 +/- 15.8 mu g/m(3)), contributing 33.0 % to PM2.5 by 2022, underscoring persistent secondary formation under high oxidation capacity. Diurnal patterns show high nocturnal and morning values (shallow boundary layers and traffic emissions) and minima at 16:00-18:00 (volatilization and deep boundary layers), while absent weekend effects reflect unregulated traffic and sustained residential activity. Meteorological normalization attributes 78.4 % of NO3- decline to emission controls, emphasizing policy efficacy, yet chemical feedbacks (enhanced NOx-to-HNO3 conversion) and transboundary transport challenge further mitigation. The interplay between local emissions and regional transport significantly shaped the variability of PM2.5-associated NO3- in Beijing from 2013 to 2022. The nonparametric wind regression analyses identify northwest and southern hotspots, with shifting source regions post-2018 highlighting growing contributions from southern industrial zones. Based on the potential source contribution function and concentration weighted trajectory methods, it can be found that dominant source regions of NO3- and its precursor (NOx) were located south of Beijing. Findings advocate interaction of policy, chemistry, and meteorology in shaping PM2.5 composition, integrated NH3-NOx controls and regional coordination, offering critical insights for optimizing air quality strategies in rapidly urbanizing regions globally.

Understanding the interplay between emissions and meteorology is critical for air quality management, yet quantifying emission-related changes under unfavorable atmospheric conditions remains challenging. This research employs a natural experiment during the meteorologically demanding 2025 Victory Day military parade to evaluate the effectiveness and meteorological vulnerability of air quality control measures. Analysis of a decade (2016–2025) of high-resolution observed PM2.5 chemical speciation data from Beijing, alongside data from the Beijing–Tianjin–Hebei and its surrounding regions (“2 + 36 cities”), demonstrates substantial and sustained air quality enhancements. The “2 + 36 cities” experienced a 55.9% reduction in mean PM2.5 concentrations and a notable convergence of inter-city variability. Beijing's PM2.5 levels decreased by 50%, with secondary inorganic components, particularly nitrate (NO3−), becoming more prominent. Five major sources were consistently identified by the Positive Matrix Factorization model, with secondary formation and vehicular emissions remaining the most significant contributors. Meteorological normalization reveals that the 33.1% PM2.5 decrease during the 2025 study period, compared to the 2016–2024 baseline, was primarily associated with the anthropogenic-related component (−34.4%), with a minor meteorological contribution (+1.3%). However, on the parade day, stagnant and humid conditions, together with regional transport, resulted in a significant +43.2% meteorological penalty, largely negating the concurrent anthropogenic-related decrease (−35.7%). Furthermore, the meteorology-related contribution increased secondary inorganic components by 41.1%, counteracting their anthropogenic decline (−40.3%). This study provides evidence for an adaptive, sustainable air quality management framework in regions where secondary particulate pollution can be strongly amplified by unfavorable meteorological conditions.

This study investigates the spatiotemporal dynamics of urban greenhouse gases amidst energy transition, aiming to assess the emission reduction effectiveness of Beijing's "coal-to-gas" and "coal-to-electricity" policies and to pinpoint the key sources arising from the subsequent structural shifts in the emission profile. We analyzed greenhouse gas concentrations from 1993 to 2024 using gas chromatography. Vertical profile data across the 8-240 m atmospheric layer from 2022 to 2024 were obtained using a pod-based measurement system installed on a 325-m meteorological tower. The results show that the CO2 growth rate initially increased and then decreased during the 1993-2024 period, and the difference in CO2 concentration between the ground and upper air decreased by 20-56% compared to the historical maxima. These trends demonstrate that the energy transition has effectively mitigated the increase in CO2 concentration. A concurrent deceleration in the growth rates of CH4 and N2O was also observed, albeit with less pronounced changes in their vertical gradients. This mitigation is largely linked to the shift from landfill disposal to waste incineration and the promotion of new energy vehicles. In contrast, SF6 emissions increased steadily from 2008 to 2024, primarily driven by growing electricity demand and the expansion of the semiconductor industry. The recent eight-year average growth rate reached 0.52 ppt yr-1. These findings underscore the power and semiconductor sectors as critical domains for targeted SF6 emission control.

While the solubility of atmospheric elements critically influences their toxicity and environmental mobility, global understanding of water-soluble hazardous elements (WSHEs) in PM2.5 remains limited. To address this, PM2.5 samples were collected from July 2021 to March 2022 across six major cities in the Beijing-Tianjin-Hebei region and its surroundings (BTHs). Total elemental concentrations (all cities) and water-soluble fractions (Beijing) were quantified via inductively coupled plasma mass spectrometry (ICP-MS), focusing on Cd, V, Cr, Ni, Se, As, Mn, and Pb. Regional analyses revealed synchronized pollution patterns across BTHs, driven by shared industrial/energy activities. In Beijing, WSHEs constituted 25.0-39 .3 % of total concentrations, with Cd (35.7 %) and Mn (39.3 %) showing peak solubility. WSHE levels rose during air quality deterioration but declined during dust storms due to crustal sources with low solubility. Key drivers of solubility included particle acidity, liquid water content, and organic carbon, emphasizing atmospheric processing (e.g., acid dissolution) as a bioaccessibility amplifier. Positive Matrix Factorization identified vehicular emissions (38 %) and coal combustion (20 %) as dominant WSHE sources, followed by waste incineration (20 %), metal smelting (14 %), electronics manufacturing (6 %), and dust (2 %). Coal and vehicular sources contributed disproportionately to bioaccessible elements, whereas dust-derived elements exhibited minimal solubility. These results highlight the elevated health risks from anthropogenic WSHEs and the urgency of prioritizing sector-specific controls (e.g., accelerating vehicle electrification, phasing out residential coal) over broad PM2.5 reduction strategies. The study establishes a mechanistic link between emission sources, atmospheric aging, and elemental bioaccessibility, offering actionable insights for mitigating toxic elements exposure in megacities.

Ammonia (NH3) is a significant precursor for secondary inorganic aerosol, in order to better study the impacts of NH3 on PM2.5 pollution in Fenwei Plain in China, hourly-resolved NH3 and water-soluble ions (WSI) were measured at an urban site in Taiyuan from 1 December 2021 to 30 November 2022. Hourly NH3 concentrations ranged from 0.7 to 40.2 mu g m(-3), with an average concentration of 10.2 +/- 5.0 mu g m(-3). Due to the impacts of meteorology and emission sources, NH3 exhibited apparent seasonal variations: summer > autumn > spring > winter. Diurnal variations of NH3 concentrations showed higher values during the daytime except in autumn. Cluster analysis of backward trajectories suggested that the southern short-distance air mass from Taiyuan Basin had the highest concentrations of TNHx (NH3+NH4+) and PM2.5. The analysis by conditional probability function and weighted concentration weighted trajectory function showed the rough consistency between the distribution of the TNHx and PM2.5 in four seasons. The analysis of hourly excess NH3 showed that Taiyuan's atmosphere was always ammonia-sufficient. SOR (nSO(4)(2-)/(nSO(4)(2-) + nSO(2))) and NOR (nNO(3)(-)/(nNO(3)(-) + nNO(2))) increased with NHR (nNH(3)/(nNH(4)(+)+nNH(3)); n denotes the molar concentration) and RH in four seasons, indicating that the gas-particle conversion of NH3 promoted the formation of SO42- and NO3- under high RH condition. The critical total ammonia concentrations (CTACs) in spring, summer, autumn, and winter were 63 %, 61 %, 60 %, and 53 %, respectively. Considering the current difficulty in reducing NH3 and WSI concentration decreased linearly with the reduction of TNO3 (NO3- + HNO3), controlling NOx emissions is more effective for PM2.5 pollution mitigation in Taiyuan.

Although it is known that downward transport from the upper boundary layer contributes significantly to the surface ozone (O3) concentration, the factors influencing vertical O3 exchange remain unclear. To solve this problem, a platform for observing the vertical exchange flux of O3 in the urban canopy was established in Beijing. The observation results revealed that the city functioned as an O3 sink. The daily variation in the O3 flux was highly consistent with the development of the boundary layer structure, peaking at -15.2 nmol·m-2·s-1 at midday, when the level of the convection was the highest. Combining ground-based remote sensing data, the observation days were divided into forced and free convection days, and the free convection days were further subdivided into low-, medium-, and high-O3 days on the basis of the maximum 8-h moving average O3 concentration. Intense free convection promoted the upward exchange of surface nitrogen dioxide (NO2), the chemical reaction process of generating O3 at high altitudes and the downward exchange of O3 in the upper boundary layer, thereby exacerbating surface O3 pollution. This research highlights the importance of NOX emission reduction, which reduces the vertical circulation of NO2-O3 driven by free convection, thus effectively controlling O3 pollution.

Waterlogging is a major stress that impacts the chrysanthemum industry. Large-scale germplasm screening for identifying waterlogging-tolerant resources in a quick and accurate manner is essential for developing new cultivars with improved waterlogging tolerance. To overcome this phenotyping bottleneck, consumer-grade digital cameras have been used to acquire the red-green-blue (RGB) images of 180 chrysanthemum cultivars and their wild relatives under waterlogging stress and well-watered conditions. A total of 103 image-based digital traits (i-traits), including 10 morphological i-traits and 93 texture i-traits, were extracted and systematically analyzed. Most of these i-traits presented high coefficients of variation (CVs) and broad-sense heritability (H 2 ), with an average CV of 34.04 ​% and an average H 2 of 0.93. We identified several novel texture i-traits associated with the hue (H) component, which strongly correlated with the traditional waterlogging tolerance index, the membership function value of waterlogging (MFVW) (R ​= ​0.63-0.77). We further employed the random forest (RF) and gradient boosting tree (GBT) machine learning algorithms to predict aboveground biomass and MFVW on the basis of different i-trait datasets. The RF model achieved superior predictive performance, with a coefficient of determination (R 2 ) of up to 0.88 for shoot weight and 0.86 for MFVW. Moreover, a subset of the top 13 most important i-traits could accurately predict MFVW (R 2  ​> ​0.80) via the cross-validation method. A total of 10 highly tolerant resources were selected by traditional and RGB-based evaluation, and 50 ​% belonged to Artemisia. Our findings confirmed that RGB-based technology provides a promising novel approach for quantifying waterlogging response that contributes to future breeding programs and genetic dissection for waterlogging tolerance.

Despite significant improvements in particulate pollution, ozone (O₃) levels have unexpectedly worsened in Shandong Province, China (SDP), which is one of the world’s hotspots for O₃ pollution. This review aims to summarize O₃ pollution studies in SDP and highlight the challenges faced by current research efforts. The interaction between O₃ chemistry and meteorological conditions has exacerbated O₃ pollution in SDP, with frequent increases in nighttime O₃ levels. Both local emissions and regional transport play significant roles in O₃ pollution, with O₃ production being particularly sensitive to VOCs in most cities. The worsening O₃ pollution has led to increased health risks and ecological damage. This review provides a comprehensive overview of O₃ pollution in SDP, covering formation mechanisms, in-situ measurements, source analyses, and the health and ecological impacts. It is recommended that monitoring networks be scientifically optimized, urgent mitigation strategies for VOCs and NOx be implemented, and collaborative research efforts be intensified to address O₃ pollution at regional scales.

Although particulate Fe has a significant impact on human health, atmospheric chemical reactions, air quality, climate change, and ecosystems, there is a lack of long-term continuous hourly observation on particulate Fe in the megacity of Beijing, limiting research on these issues. To address this gap, this study continuously measured hourly concentrations of Fe in PM2.5 from October 2018 to October 2022 in Beijing. The results indicate an overall decline in Fe concentrations, consistent with previous studies in Beijing. This decline can be attributed to multiple factors, such as reduced coal consumption, restrictions on biomass burning, increased use of clean energy, advanced technologies for industrial emission reduction, and efforts to control fugitive dust. Seasonal variations in Fe concentrations were similar across the various years, with higher mean concentrations in spring, fall, and winter, and lower levels in summer. Daily variations in PM2.5-bound Fe concentrations exhibited two peaks, influenced by changes in emission intensity and the evolution of the planetary boundary layer. The solubility of PM2.5-bound Fe exhibited a wide range, varying from 4 % to 95 %, surpassing previously reported source-specific values. This variability can be attributed to acid dissolution effects and complexation behaviors. Nonparametric wind regression analysis identified distinct hotspots (higher concentrations) in the northwest wind sector at wind speeds of approximately 5-15 km/h, which are associated with blowing dust and dust storms. Additionally, the potential source contribution function analysis identified high-potential source areas were precisely located in the northwestern, western, and southern regions of Beijing, rather than primarily in the southern areas recorded in a previous study. This research provides valuable insights for studying the health effects and migration and transformation of nutrient elements, particularly particulate Fe, in Beijing.

Exploring the vertical variation in volatile organic compounds (VOCs) in background regions can provide information on the spatial distribution of pollutants, providing a scientific basis for atmospheric pollution prevention and control strategies. From 15 August to 5 September 2023, at the Southeast Tibet Mountain Comprehensive Environmental Observation Station (SETS), a tethered balloon was used to sample VOCs every 100 m from the ground to 1000 m. A total of 403 air bag samples were collected, and 39 vertical profiles of VOCs were obtained. Ninety-two VOC species were detected. The VOC concentration at the SETS did not change significantly vertically, and the average VOC concentration was 11.1 +/- 2.4 ppbv. The main components were alkanes (51.4 %), alkenes (18.7 %), and halohydrocarbons (18.1 %). There was no obvious diurnal change in VOCs and no significant difference between the different layers. When the surface VOC concentration was less than 10 ppbv, the concentrations, components, and sources of VOCs were evenly distributed vertically, and the main sources of VOCs at different heights were vehicle exhaust and background. When the surface VOC concentration exceeded 10 ppbv, the VOC concentration gradually decreased with height. The proportion of alkanes in surface VOCs increased, and the source was mainly vehicle exhaust. This study confirmed that VOCs are vertically homogeneous in the background of the Tibetan Plateau, emphasizing the importance of vehicle emissions as a potential source of VOCs.

Dust storms have the ability to transport and deposit contaminants and nutrients, such as iron (Fe), to downwind regions through atmospheric processes. However, there is a lack of reported data on the high-resolution variations and deposition of particulate iron in multiple locations during dust storms. This study aimed to address this gap by employing standardized analytical methods to measure the concentrations of PM10, PM2.5, and PM2.5- associated Fe in Taiyuan, Beijing, Tianjin, Ji'nan, and the Bohai Bay of China during the dusty events of 2021. A total of 13 blowing sand or dust storms were recorded, with average PM10 and PM2.5 concentrations of 262 +/- 322 and 85 +/- 652, 171 +/- 403 and 53 +/- 448, 153 +/- 211 and 57 +/- 315, and 207 +/- 249 and 63 +/- 301 mu g/m3 at the above-mentioned sites, respectively. These elevated concentrations were attributed to stronger winds in northern China and severe wind erosion in the sand source areas. During these events, the average concentrations of PM2.5-bound Fe reached 2730.2 +/- 4587.9, 2030.2 +/- 3877.9, 1342.1 +/- 2251.4, and 1785.1 +/- 2536.6 ng/m3 in Taiyuan, Beijing, Tianjin, and Ji'nan, respectively, with the highest concentrations recorded as 48.8, 48.0, 29.2, and 22.7 mu g/m3. A significant positive correlation was observed between Fe and Si in PM2.5 in the four cities, with higher Fe/Si slopes recorded in or near the source regions, while the homogenized Fe/Si values were observed after long-distance transport. The mean dry deposition fluxes (FFe) of PM2.5-bound Fe were calculated as 0.34 +/- 0.64, 0.31 +/- 0.91, 0.21 +/- 0.56, and 0.17 +/- 0.28 mg/m2/d for Taiyuan, Beijing, Tianjin, and Ji'nan, respectively, based on both hourly observation data and model-based calculations of dry deposition velocities. It is worth noting that FFe decreased from west to east in China, consistent with a previous study that showed a decrease in dust deposition rates with increasing transport distances. Peaks in FFe corresponded to the highest concentrations of PM2.5-associated Fe, indicating that these concentrations played a significant role in Fe. Furthermore, the atmospheric deposition of dissolved Fe from blowing sand or dust storm events was found to contribute to carbon fixation in the Bohai region of China, providing a range of 7.8 x 104-3.9 x 106 mol. This research provides valuable insights into the quantitative relationship between atmospheric deposition and marine productivity during dust events.

Situated in close proximity to the Korea Peninsula and the Japan Islands, Shandong Province in China (SDP) has emerged as a focal point for global attention due to its significant surface ozone (O3) and aerosol pollution. Despite this attention, there are notable gaps in knowledge across various interconnected research domains, encompassing climate change, atmospheric circulation, anthropogenic emissions, and the chemistry of O3 and aerosols. The impact of frequent heat waves on regional O3 and aerosol pollution remains unclear, while our comprehension of atmospheric circulation dynamics and the chemistry involved with O3 and aerosols is still hampered by substantial limitations. The unique topography and geographical setting of SDP, with its complex interplay of factors like sea-land breezes, mountain-valley winds, and urban heat islands, make it an ideal location for investigating the dynamics of O3 and aerosol chemistry. Moreover, it is essential to explore the effects of transboundary transport on O3 and aerosol pollution and delve into the underlying mechanisms contributing to their combined pollution effects. To bridge these knowledge gaps, the Innovative Collaboration-Based Ozone and Aerosol Observation Network in Northeast Asia has been established through collaborative efforts involving the Bureaus of Ecology and Environment, Meteorology in SDP, and the Chinese Academy of Sciences. This network encompasses various components, including air quality and weather stations, a network of low-cost air quality sensors, monitoring stations focused on atmospheric photochemical smog and aerosol chemical speciation, and vertical measurement systems targeting O3 and its precursor gases (utilizing light detection and ranging, balloon sounding, and drone-based measurements), as well as measurements conducted via vehicles and ships. Additionally, preliminary findings from this comprehensive observational campaign will be shared. SIGNIFICANCE STATEMENT: This research aims to understand how climate change, atmospheric circulation, and pollution from ozone and aerosols interact in northeast Asia, particularly in Shandong Province. By establishing a comprehensive observation network, we seek to uncover the dynamics of air pollution in diverse environments. Our work provides crucial data to improve air quality and inform climate change mitigation strategies, emphasizing the importance of interdisciplinary collaboration and sustained monitoring efforts to address environmental challenges. This initiative not only enhances scientific understanding but also fosters regional cooperation and contributes significantly to global atmospheric science.