Atmospheric Environment最新文献

{"title":"Evaluation of GOSAT-IM, NASA-GEOS and NOAA-CT terrestrial ecosystem and oceanic flux datasets using the GEOS-Chem model to simulate the seasonal cycle of tropospheric CO2","authors":"M. Krishnapriya ,&nbsp;A. Bhuvana Chandra ,&nbsp;Rabindra Kumar Nayak ,&nbsp;S. Allahudheen ,&nbsp;Yogesh Tiwari ,&nbsp;V.K. Dadhwal ,&nbsp;M.V. Ramana ,&nbsp;G. Srinivasrao ,&nbsp;Prakash Chauhan","doi":"10.1016/j.atmosenv.2025.121719","DOIUrl":"10.1016/j.atmosenv.2025.121719","url":null,"abstract":"<div><div>This study evaluates the sensitivity of the GEOS-Chem atmospheric transport model to three CO₂ surface flux databases—GOSAT-IM, NASA-GEOS, and NOAA CarbonTracker (NOAA-CT)—in simulating the tropospheric CO₂ seasonal cycle during 2010–2014. Model outputs, generated using common anthropogenic emissions and meteorological forcing, were compared against NOAA-ESRL GLOBALVIEW in situ observations from 54 stations worldwide. All simulations coherently reproduced the observed latitudinal gradient, with high CO₂ concentrations (greater than 395 ppm) in the northern sub-polar region driven by fossil fuel emissions and shallow winter boundary layers, and lower concentrations (below 390 ppm) over the southern oceans due to strong uptake and vertical mixing. Among the simulations, the one using NOAA-CT input data showed the highest correlation (greater than 0.95) with observations in the northern mid-latitudes. This high correlation is attributed to the fluxes being constrained by actual observations. The simulation with GOSAT also captured the seasonal amplitudes in the northern hemisphere, although with lesser agreement, while the simulation with NASA-GEOS underestimated observed amplitudes in the tropics. Regional discrepancies, especially in the tropical and southern hemispheric regions, highlight the influence of convective processes and uncertainties in the flux datasets. Horizontal advection dominated seasonal variability at polar stations, whereas vertical transport was more important in the tropics. These findings emphasize the need for improved time-varying flux products, better parameterizations for vertical mixing, and the integration of new satellite observations to reduce model biases. This study highlights the crucial role of surface flux datasets, particularly the spatiotemporal resolution and observational constraints embedded in them in simulating the global CO₂ seasonal cycle. Among the evaluated datasets, NOAA-CT most accurately captured the phase, amplitude, and transport-driven dynamics of atmospheric CO₂, reinforcing its utility in model-data for carbon cycle assessments.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"367 ","pages":"Article 121719"},"PeriodicalIF":3.7,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterization and influencing factors of hydroxymethanesulfonate (HMS) in the North China plain: integration of field measurements and theoretical calculations","authors":"Chun Chen ,&nbsp;Haijie Zhang ,&nbsp;Yele Sun ,&nbsp;Junling Li ,&nbsp;Zhiqiang Zhang ,&nbsp;Jian Gao ,&nbsp;Rui Gao ,&nbsp;Lianfang Wei ,&nbsp;Nan Ma ,&nbsp;Wanyun Xu ,&nbsp;Pingqing Fu","doi":"10.1016/j.atmosenv.2025.121731","DOIUrl":"10.1016/j.atmosenv.2025.121731","url":null,"abstract":"<div><div>Hydroxymethanesulfonate (HMS) is a key secondary organosulfur compound formed through aqueous-phase or heterogeneous atmospheric processes, significantly affecting the atmospheric sulfur budget. However, the relationship between HMS and PM_2.5 components, as well as its formation mechanism, remains insufficiently explored. This study presents a comprehensive analysis of HMS at two sites in the North China Plain (NCP). Using offline filter analysis combined with theoretical calculations, we found that the HMS mass concentration in Gucheng during the winter of 2019 averaged 2.58 ± 2.56 μg/m³, approximately 1.5 times of that in Beijing during winter and 5.0 times of that in Beijing during autumn. This elevated concentration in Gucheng is attributed to higher relative humidity, elevated particle pH, and higher precursor concentrations. Correlation analyses demonstrated that aerosol liquid water content (AWC) is a key factor influencing HMS formation, while ammonium and nitrate may also contribute significantly. Theoretical calculations suggest that HMS formation primarily occurs through the reaction between SO₃²⁻ and HCHO, with an additional contribution from the reaction of HSO₃⁻ with HCHO. Aqueous H₂O and NH₃ can act as catalysts, reducing the reaction barrier between HSO₃⁻ and HCHO from 9.76 kcal/mol (uncatalyzed) to 5.01 and 6.48 kcal/mol, respectively, thus promoting HMS formation. Increasing concentrations of aqueous H₃O⁺ and NH₄⁺ during polluted periods do not exhibit a catalytic effect but instead strongly inhibit HMS formation. These results indicate that a comprehensive consideration of the combined effects of various aqueous species is essential in atmospheric models.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"367 ","pages":"Article 121731"},"PeriodicalIF":3.7,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unveiling the causes of winter haze in southern Sichuan via observations and explainable machine learning","authors":"Gaofeng Zhou ,&nbsp;Junjie Wang ,&nbsp;Wenting Lv ,&nbsp;Yingjie Li ,&nbsp;Yuan Li ,&nbsp;Xuefeng Zhang ,&nbsp;Li Han ,&nbsp;Tao Jiang","doi":"10.1016/j.atmosenv.2025.121728","DOIUrl":"10.1016/j.atmosenv.2025.121728","url":null,"abstract":"<div><div>The Sichuan Basin is one of China's most haze-prone regions due to its unique topography and stagnant meteorological conditions. To understand the winter haze formation mechanisms in the Sichuan Basin, a field campaign was conducted in a previously identified pollution hotspot (Southern Sichuan, December 2024 to February 2025). During this campaign, PM_2.5 concentration averaged 63.79 ± 42.92 μg m⁻³, and we identified three haze episodes (H1-H3) during this campaign. The chemical speciation of fine aerosol was characterized using a quadrupole aerosol chemical speciation monitor (Q-ACSM), and the apportionment of organic aerosols (OAs) was solved by EPA PMF 5.0. The results indicated that OAs dominated the PM_2.5 composition throughout this campaign, with OA concentrations particularly high in H1 (64.63 ± 20.77 μg m⁻³) and H2 (64.11 ± 19.05 μg m⁻³). Biomass burning organic aerosols (BBOA) and oxygenated organic aerosols (OOA) were the primary contributors to these high concentrations. The haze episodes resulted mainly from early-stage biomass burning emissions and less-aged OOA, occurring concurrently with the highest levels of aerosol liquid water content (ALWC), suggesting the humid air can favor the formation of haze. In addition to local emissions, regional transport synergized with meteorological conditions also significantly contributed to haze formation during this campaign, especially in H2 (38.2 %), quantified by a machine learning based deweathering analysis. This study underscores the intricate interplay between emissions, regional transport, and meteorology in driving haze formation in the Sichuan Basin and demonstrates the utility of machine learning aided diagnostics for source attribution and regulatory insights.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"367 ","pages":"Article 121728"},"PeriodicalIF":3.7,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145734459","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of ambient air pollutants on influenza-like illness, influenza A and influenza B: A nationwide time-series study in China","authors":"Xi Huang ,&nbsp;Dina Wang ,&nbsp;Qing Zhang ,&nbsp;Dayan Wang ,&nbsp;Yuelong Shu ,&nbsp;Shenglan Xiao","doi":"10.1016/j.atmosenv.2025.121729","DOIUrl":"10.1016/j.atmosenv.2025.121729","url":null,"abstract":"<div><div>Influenza is a serious respiratory infection that imposes significant public health challenges. However, the precise impact of pollutants on influenza virus activity remains unclear. In this study, we aimed to investigate the effects of different air pollutants on the incidence of influenza-like illness (ILI), influenza A (Flu A), and influenza B (Flu B) in China based on nationwide air pollution and influenza data from 554 sentinel hospitals across 30 provinces and municipalities from 2014 to 2017. A Distributed Lag Nonlinear Model (DLNM) was employed to discern the lagged effects of six distinct air pollutants, namely PM2.5, PM10, O₃, CO, SO₂, and NO₂, on the incidence of ILI, Flu A, and Flu B. Our analysis indicated that the relationship between air pollutants and influenza varied among ILI, Flu A, and Flu B, with Flu B being more sensitive to SO₂ than Flu A. Elevated levels of air pollutants were generally associated with an increased risk of influenza; however, relative risks declined slightly at extreme concentrations of PM2.5, SO₂, and NO₂. These results highlight the complex associations between air pollution and influenza.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"367 ","pages":"Article 121729"},"PeriodicalIF":3.7,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683967","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lead sources detected in Manila's air after the phase-out of leaded gasoline","authors":"Mengli Chen ,&nbsp;Jariya Kayee ,&nbsp;Armin Sorooshian ,&nbsp;Grace Betito ,&nbsp;Paola Angela Bañaga ,&nbsp;Rachel A. Braun ,&nbsp;Maria Obiminda Cambaliza ,&nbsp;Melliza Templonuevo Cruz ,&nbsp;Alexander B. MacDonald ,&nbsp;James Bernard Simpas ,&nbsp;Connor Stahl ,&nbsp;Iravati Ray ,&nbsp;Reshmi Das ,&nbsp;Zunya Wang ,&nbsp;Xianfeng Wang","doi":"10.1016/j.atmosenv.2025.121727","DOIUrl":"10.1016/j.atmosenv.2025.121727","url":null,"abstract":"<div><div>The global phase-out of leaded gasoline marked a major milestone in pollution control, yet modern uses of lead (Pb) continue to pose significant health risks, especially in low- and middle-income countries. In the Philippines, significant data gaps still exist despite increasing exposure. This study presents to the best of our knowledge, the first Pb isotopic fingerprinting of atmospheric aerosols in Metro Manila, Philippines, covering fine (0.56–1 μm) and coarse (5.6–10 μm) fractions, collected in 2018–2019. Results show that local sources, mainly industrial activities (45–62 %) and fossil fuel combustion (30–45 %), are now the dominant contributors to airborne Pb, while a minor legacy leaded gasoline and geogenic Pb persists (&lt;18 %) through soil resuspension. Stable isotopes show no clear seasonal pattern. Together with 25 fold higher Pb concentration in the fine fraction, these indicate limited transboundary input. Regional comparison highlights overlapping Pb isotopic composition across Southeast Asia, but is distinct from areas farther north due to intensive coal use in China. The consistency between isotopic fingerprinting and Positive Matrix Factorization (PMF) results demonstrates the value of combining methods for robust source apportionment. These findings demonstrate the continuing importance of isotopic monitoring for distinguishing contemporary and legacy Pb sources and informing targeted air quality management in rapidly developing regions.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"367 ","pages":"Article 121727"},"PeriodicalIF":3.7,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Integrating surface-based in-situ and satellite observations to characterize CO2 and CH4 emission hotspots in Houston, USA","authors":"Irfan Karim ,&nbsp;Bernhard Rappenglück","doi":"10.1016/j.atmosenv.2025.121713","DOIUrl":"10.1016/j.atmosenv.2025.121713","url":null,"abstract":"<div><div>This study integrates in-situ and satellite observations to characterize urban greenhouse gas (GHG) emissions across Houston, Texas USA. Surface-based background concentrations show seasonal reductions from ∼435 to ∼410 ppm for carbon dioxide (CO₂) due to photosynthetic uptake, and from ∼2.02 to ∼1.88 ppm for methane (CH₄) predominantly due to oxidation by the hydroxyl radical (OH). Boundary layer height corrected excess CO₂ and CH₄ (ΔCO₂, ΔCH₄) peak in winter (∼139.4 ppm, ∼5.5 ppm) and drop in summer (∼5.6 ppm, ∼0.08 ppm), highlighting emission seasonality. The observed annual ΔCH₄/ΔCO₂ ratio (9.4 ppb ppm⁻¹) exceeds EDGAR and EPA inventory estimates by 65–70 %, and spatial mapping identifies key CH₄ hotspots - such as McCarty and Blue Ridge landfills - with ratios larger than 40–70 ppb ppm⁻¹, which are severely underrepresented in emission inventories.</div><div>Satellite-derived enhancements from OCO-3 and TROPOMI offer broader coverage but lack sensitivity to surface plumes. For example, in situ bivariate plots show sharp ΔCO₂ enhancements &gt;30 ppm and ΔCH₄ up to ∼0.3 ppm over industrial zones like the Ship Channel, while satellite ΔXCO₂ (∼5–7 ppm) and ΔXCH₄ (∼0.03–0.04 ppm) show moderate enhancements over the urban core. TROPOMI NO₂ (∼1 × 10⁻⁴ μmol/m²) and HCHO (∼2.0 × 10⁻⁴ mol/m²) enhancements further confirm co-located industrial emissions. This synthesis underscores the value of combining surface and satellite data for robust urban emission assessments and improved emission inventory evaluation.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"366 ","pages":"Article 121713"},"PeriodicalIF":3.7,"publicationDate":"2025-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145622271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fine-scale estimates of ammonia emissions from South Asian croplands under changing climate","authors":"Ali Ismaeel ,&nbsp;Jin Wu ,&nbsp;Amos P.K. Tai","doi":"10.1016/j.atmosenv.2025.121705","DOIUrl":"10.1016/j.atmosenv.2025.121705","url":null,"abstract":"<div><div>Ammonia (NH₃) emissions significantly impact air quality and the Earth's radiation balance through their interactions with other atmospheric chemical species to form particulate matter. Reducing NH₃ emissions from croplands without compromising productivity is challenging due to the widespread and diffuse nature of NH₃ sources. In the absence of direct monitoring networks, emission inventories provide the crucial basis for designing and implementing emission control measures. In South Asia (SA), knowledge of NH₃ emissions at the regional scale is limited by the coarse-resolution global emission inventories, which carry significant uncertainties due to generalized emission factors. Here, we estimated remote sensing-based NH₃ emissions from SA croplands at a 250-m spatial resolution between 2003 and 2020 by incorporating local knowledge of farming practices. Our estimates reveal that an average of 5.7 Tg NH₃ is emitted annually from SA croplands. We found a ∼25 % increase in total NH₃ emissions over the period, attributable to cropland expansion and a shift toward more fertilizer-demanding crop cultivation. A comparison of the modeled annual NH₃ fluxes with global emission inventories reveals discrepancies in the range of −10 to +30 %. The comparison of total column NH₃ concentrations retrieved from satellite observations and simulated by chemical transport model simulations using our fine-scale NH₃ emission inventory shows a high correlation coefficient (<em>r</em> ≥ 0.47) but indicates an average bias of −21 %. We estimated that without adopting any mitigation strategies to reduce NH₃ emissions, future climate change under specific Shared Socioeconomic Pathway (SSP2-RCP4.5) will exacerbate environmental pollution by increasing NH₃ volatilization by 6 % in the 2050s. However, mitigation strategies, such as incorporating fertilizers into the soil at the time of crop sowing, could decrease NH₃ emissions by 18 % even under future climate conditions, relative to current levels. Our work highlights the importance of strategic agricultural management to make the SA food systems more sustainable and resilient to climate change.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"366 ","pages":"Article 121705"},"PeriodicalIF":3.7,"publicationDate":"2025-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145691535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deciphering aerosol impacts: Unravelling long-term AOD trends and radiative forcing across key regions","authors":"Gopika Gupta ,&nbsp;B.L. Madhavan ,&nbsp;M. Venkat Ratnam","doi":"10.1016/j.atmosenv.2025.121693","DOIUrl":"10.1016/j.atmosenv.2025.121693","url":null,"abstract":"<div><div>Assessing long-term changes in Aerosol Optical Depth (AOD) together with Aerosol Radiative Forcing Efficiency (ARFE, defined as radiative forcing per unit visible AOD) provides critical insight into the evolving role of different aerosol species in regional climate forcing. In this study, we analyse two decades of AOD trends (2001–2020) across eight climatically diverse regions using a multivariate regression framework, and quantify species-specific radiative effects with the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model. The regions were chosen to represent contrasting trends in total AOD. Our results show that sulfate aerosols, which account for the largest share of AOD over India (∼36–45 %), are the primary driver of increasing AOD and associated atmospheric warming. Black carbon (BC), although contributing only a minor fraction to total AOD (2–10 %), emerges as the dominant warming agent across most regions, with particularly strong forcing signals over the Middle East. In contrast, sea-salt (SS) aerosols exert the largest cooling influence, most prominently over the Southern African (SAF) region, partially offsetting warming from absorbing species. Europe, despite an overall decline in AOD, exhibits a slight increase in SS that sustains a regional cooling effect. These findings demonstrate that species composition, vertical distribution, and optical properties govern ARFE more strongly than the total AOD magnitude alone. By linking AOD trends with species-resolved radiative forcing efficiency across multiple regions, this study advances the interpretability of ARFE as a climate indicator and highlights its potential to inform policy-relevant assessment of aerosol-driven warming and cooling.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"367 ","pages":"Article 121693"},"PeriodicalIF":3.7,"publicationDate":"2025-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145651835","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Short-term effects of exposure to heat waves and ambient ozone on mortality: a case-crossover study","authors":"Xinyao Lian ,&nbsp;Jiajia Ji ,&nbsp;Guomin Chen ,&nbsp;Shuai Jiang ,&nbsp;Weiqi Liang ,&nbsp;Xindou Chen ,&nbsp;Jianhui Guo ,&nbsp;Yaqi Wang ,&nbsp;Yingbin Fu ,&nbsp;Jia Zhang ,&nbsp;Xiaoheng Li ,&nbsp;Jing Li ,&nbsp;Yi Song","doi":"10.1016/j.atmosenv.2025.121706","DOIUrl":"10.1016/j.atmosenv.2025.121706","url":null,"abstract":"<div><div>The individual and joint effects of short-term exposure to heat waves and ozone (O₃) on mortality, particularly on nervous system disease mortality, need further investigation, as global warming leads to frequent heat waves and increased O₃ concentrations. Heat waves were identified when the daily maximum apparent temperature reached or exceeded the temperature threshold (the 90th percentile of the temperature in 2019–2023) for at least 2, 3, or 4 consecutive days. High-level O₃ was defined as daily maximum 8-h average O₃ concentrations above 100 μg/m³. Based on 51,073 death cases from the Shenzhen Mortality Surveillance System in 2019–2023, we found significant individual and joint effects of short-term exposure to heat waves and high-level O₃ on mortality, including all-cause non-accidental mortality, circulatory disease mortality, and nervous system disease mortality, employing a case-crossover design and conditional logistic regression models. Excess fractions of all-cause non-accidental deaths, circulatory disease deaths, and nervous system disease deaths attributable to heatwave and high levels of O₃ exposure could be as high as 6.42 %, 8.28 %, and 13.21 %. In addition, we found that the elderly and males were more susceptible to joint exposure to heat waves and O₃. This study provided a reference for the development of a region-specific early warning system for joint heat waves and O₃, and highlighted the priority protection of susceptible populations during heatwaves and higher O₃ levels.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"366 ","pages":"Article 121706"},"PeriodicalIF":3.7,"publicationDate":"2025-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145622260","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A year-long observational analysis of atmospheric trace gases and particulate matter in Kathmandu","authors":"Dikra Prasad Bajgai ,&nbsp;Sagar Adhikari ,&nbsp;Arshini Saikia ,&nbsp;Bertrand Bessagnet ,&nbsp;Suresh Pokhrel ,&nbsp;Govinda Lamichhane ,&nbsp;Deepak Gyawali ,&nbsp;Ravi Sahu ,&nbsp;Qianggong Zhang","doi":"10.1016/j.atmosenv.2025.121704","DOIUrl":"10.1016/j.atmosenv.2025.121704","url":null,"abstract":"<div><div>Kathmandu Valley is one of the most densely populated cities in Nepal, facing significant air quality challenges. This study presents a comprehensive analysis based on twelve months of continuous air quality measurement data collected at the Khumaltar Air Quality Monitoring Station (ICIMOD AQMS), which is located in the southern part of the Kathmandu Valley. The study investigates particulate matter (PM₁₀, PM_2.5, PM<span><math><msub><mrow></mrow><mrow><mi>C</mi></mrow></msub></math></span> (PM₁₀–PM_2.5)) alongside trace gases (O₃, NO<span><math><msub><mrow></mrow><mrow><mi>X</mi></mrow></msub></math></span>, SO₂, and CO), focuses on their seasonal, diurnal variations, interspecies correlations, potential sources, and the impact of regional atmospheric transport. The results reveal that the annual PM_2.5 concentration (49 <span><math><mrow><mi>μ</mi><mtext>g</mtext><mspace></mspace><msup><mrow><mtext>m</mtext></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msup></mrow></math></span>) largely exceeds the WHO air quality guideline of 5 <span><math><mrow><mi>μ</mi><mtext>g</mtext><mspace></mspace><msup><mrow><mtext>m</mtext></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msup></mrow></math></span>. Pollutant concentrations show clear seasonal variation, with peaks during the winter and pre-monsoon seasons, and a noticeable decline during the monsoon. A strong correlation (r = 0.82, p = 0.00) between PM_2.5 and NO<span><math><msub><mrow></mrow><mrow><mi>X</mi></mrow></msub></math></span> indicates that fossil fuel combustion is a dominant source of fine particulate pollution. During the pre-monsoon season, O₃ concentrations occasionally exceed 100 ppb (8-hr running average), with seasonal diurnal concentration observed close to 90 ppb in the afternoon. The study found that temperature and relative humidity significantly influence coarse PM levels, with a strong negative correlation (r = −0.89, p = 0.00) between coarse PM and the relative humidity, suggesting less resuspension under moist conditions. Furthermore, this study highlights the severe air pollution in the Kathmandu Valley throughout the year, driven primarily by local emissions, with regional atmospheric transport further contributing to poor air quality.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"366 ","pages":"Article 121704"},"PeriodicalIF":3.7,"publicationDate":"2025-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145623420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}