Pub Date : 2025-12-16DOI: 10.1016/j.atmosenv.2025.121748
Sofia Fellini , Dipanjan Majumdar , Pietro Salizzoni , Maarten van Reeuwijk
Vegetation is increasingly used in urban areas to improve microclimate and reduce pollutant exposure, yet its effect on pollutant dispersion within street canyons remains complex. This study combines high-resolution wind tunnel experiments and Large-Eddy Simulations (LES) using uDALES to provide a detailed three-dimensional characterization of airflow and pollutant concentration along the canyon.
Special attention is given to the consistent scaling of velocity and scalar fields, using friction velocity and canyon geometry as reference quantities, and to the role of tree drag length in aligning the aerodynamic resistance of physical and numerical vegetation. The simulations reproduce key mean-flow structures, including large-scale recirculations, but tend to underestimate turbulent kinetic energy and local scalar fluxes.
By jointly analyzing high-resolution wind-tunnel experiments and LES, we (i) confirm the spanwise and longitudinal concentration patterns observed experimentally, (ii) assess their sensitivity to the modeled tree drag, (iii) provide the first detailed experimental–numerical comparison of rooftop mean and turbulent mass fluxes, showing that bulk canyon ventilation exhibits no systematic dependence on tree number or drag intensity, and (iv) identify the specific strengths and limitations of each approach. This integrated analysis offers novel insights into the interplay between trees, turbulence, and boundary-layer forcing, informing strategies for modeling urban ventilation and pollutant dispersion in tree-lined streets.
{"title":"Three-dimensional pollutant dispersion in tree-lined urban canyons: Combined wind-tunnel and LES analysis","authors":"Sofia Fellini , Dipanjan Majumdar , Pietro Salizzoni , Maarten van Reeuwijk","doi":"10.1016/j.atmosenv.2025.121748","DOIUrl":"10.1016/j.atmosenv.2025.121748","url":null,"abstract":"<div><div>Vegetation is increasingly used in urban areas to improve microclimate and reduce pollutant exposure, yet its effect on pollutant dispersion within street canyons remains complex. This study combines high-resolution wind tunnel experiments and Large-Eddy Simulations (LES) using uDALES to provide a detailed three-dimensional characterization of airflow and pollutant concentration along the canyon.</div><div>Special attention is given to the consistent scaling of velocity and scalar fields, using friction velocity and canyon geometry as reference quantities, and to the role of tree drag length in aligning the aerodynamic resistance of physical and numerical vegetation. The simulations reproduce key mean-flow structures, including large-scale recirculations, but tend to underestimate turbulent kinetic energy and local scalar fluxes.</div><div>By jointly analyzing high-resolution wind-tunnel experiments and LES, we (i) confirm the spanwise and longitudinal concentration patterns observed experimentally, (ii) assess their sensitivity to the modeled tree drag, (iii) provide the first detailed experimental–numerical comparison of rooftop mean and turbulent mass fluxes, showing that bulk canyon ventilation exhibits no systematic dependence on tree number or drag intensity, and (iv) identify the specific strengths and limitations of each approach. This integrated analysis offers novel insights into the interplay between trees, turbulence, and boundary-layer forcing, informing strategies for modeling urban ventilation and pollutant dispersion in tree-lined streets.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"367 ","pages":"Article 121748"},"PeriodicalIF":3.7,"publicationDate":"2025-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787871","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}
Pub Date : 2025-12-15DOI: 10.1016/j.atmosenv.2025.121750
Egide Kalisa , Donnabella Lacap-Bugler , Matthew Adams , Jiaqi Bi , Antoine Nsabimana , Gabriel Habiyaremye , Glorieuse Uwizeye , Timothy Lawrence , Kevin Lee , Kazuichi Hayakawa , Stephen Pointing , Stephen DJ. Archer
Exposure to particulate matter (PM) is a major global health concern, yet the potential relationships between its chemical and microbial components remains poorly understood, particularly in rapidly urbanizing, understudied settings. This study presents an integrated assessment of polycyclic aromatic hydrocarbons (PAHs), nitrated PAHs (NPAHs), bacteria, and fungi in both fine (PM2.5) and coarse (PM10) aerosols across urban, roadside, and rural sites in sub-Saharan Africa, with a focus on Rwanda across dry and wet seasons. Microbial analysis revealed that the richness and community structure of the airborne bacterial and fungal communities varied with land-use type, linked with PAH/NPAH abundance, PM size fraction, and season. Spearman correlation coefficient confirmed that bacterial communities were more strongly associated with PAH and NPAH compounds, whereas fungal communities were shaped primarily by environmental factors. One bacterial genus, Sphingobium, exhibited evidence of selective enrichment within the PAH rich PM2.5 size fraction, highlighting the potential for direct interaction between the biological and chemical compositions in air. We provide a critical baseline for African cities where air quality data are scarce. Current air quality standards, which prioritize chemical thresholds, overlook the biological burden carried by PM.
{"title":"Variability of airborne microbial communities and associations with organic pollutants in African air particulate matter across land-use types","authors":"Egide Kalisa , Donnabella Lacap-Bugler , Matthew Adams , Jiaqi Bi , Antoine Nsabimana , Gabriel Habiyaremye , Glorieuse Uwizeye , Timothy Lawrence , Kevin Lee , Kazuichi Hayakawa , Stephen Pointing , Stephen DJ. Archer","doi":"10.1016/j.atmosenv.2025.121750","DOIUrl":"10.1016/j.atmosenv.2025.121750","url":null,"abstract":"<div><div>Exposure to particulate matter (PM) is a major global health concern, yet the potential relationships between its chemical and microbial components remains poorly understood, particularly in rapidly urbanizing, understudied settings. This study presents an integrated assessment of polycyclic aromatic hydrocarbons (PAHs), nitrated PAHs (NPAHs), bacteria, and fungi in both fine (PM<sub>2</sub>.<sub>5</sub>) and coarse (PM<sub>10</sub>) aerosols across urban, roadside, and rural sites in sub-Saharan Africa, with a focus on Rwanda across dry and wet seasons. Microbial analysis revealed that the richness and community structure of the airborne bacterial and fungal communities varied with land-use type, linked with PAH/NPAH abundance, PM size fraction, and season. Spearman correlation coefficient confirmed that bacterial communities were more strongly associated with PAH and NPAH compounds, whereas fungal communities were shaped primarily by environmental factors. One bacterial genus, <em>Sphingobium</em>, exhibited evidence of selective enrichment within the PAH rich PM<sub>2</sub>.<sub>5</sub> size fraction, highlighting the potential for direct interaction between the biological and chemical compositions in air. We provide a critical baseline for African cities where air quality data are scarce. Current air quality standards, which prioritize chemical thresholds, overlook the biological burden carried by PM.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"367 ","pages":"Article 121750"},"PeriodicalIF":3.7,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787875","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}
Pub Date : 2025-12-12DOI: 10.1016/j.atmosenv.2025.121741
Joaquín Sancho Val, Carlos Cajal Hernando, Lourdes Martínez de Baños
Urban air pollution requires analytical tools that capture complex temporal dynamics while remaining interpretable for policy purposes. This study applies Functional Principal Component Analysis (FPCA) to hourly concentrations of NO, PM10, and PM2.5 measured in 2024 at eight monitoring stations in Madrid. By transforming high-dimensional time series into smooth functional data, FPCA identifies dominant modes of variability and reveals structural differences among sites.
Across all pollutants, the first three components explained more than 85% of total variance. PC1 represented the main seasonal cycle, PC2 reflected short-term fluctuations driven by traffic and meteorology, and PC3 captured episodic peaks. The score plots highlighted consistent clustering: background stations (Casa de Campo, Sanchinarro) showed low levels and weak seasonality; traffic-oriented stations (Plaza Elíptica, Cuatro Caminos, Escuelas Aguirre) displayed high concentrations and stronger cycles; and intermediate sites (Castellana, Plaza Castilla, Méndez Álvaro) exhibited mixed patterns.
These findings confirm FPCA as an efficient diagnostic framework for air quality assessment, offering both dimensionality reduction and interpretability. Beyond methodological value, the approach enables classification of monitoring sites and supports targeted mitigation strategies. FPCA thus provides a transferable tool for urban air quality management and a solid basis for functional data analysis in environmental policy contexts.
城市空气污染需要分析工具来捕捉复杂的时间动态，同时保持可解释的政策目的。本研究将功能主成分分析（FPCA）应用于2024年马德里8个监测站测量的NO2、PM10和PM2.5每小时浓度。通过将高维时间序列转换为平滑的功能数据，FPCA识别出变异的主要模式，并揭示了站点之间的结构差异。在所有污染物中，前三个成分解释了85%以上的总方差。PC1代表了主要的季节周期，PC2反映了交通和气象驱动的短期波动，PC3捕获了偶发性峰值。得分图突出了一致的聚类：背景站（Casa de Campo, Sanchinarro）水平低，季节性弱；以交通为导向的车站（Plaza Elíptica、Cuatro Caminos、Escuelas Aguirre）表现出较高的集中度和较强的周期性；中间站点（Castellana、Plaza Castilla、msamundez Álvaro）呈现混合模式。这些发现证实了FPCA作为空气质量评估的有效诊断框架，提供了降维和可解释性。除了方法价值之外，该方法还有助于对监测点进行分类，并支持有针对性的缓解战略。因此，FPCA为城市空气质量管理提供了一个可转移的工具，并为环境政策背景下的功能数据分析提供了坚实的基础。
{"title":"Functional data analysis of air quality time series in Madrid Using FPCA and splines","authors":"Joaquín Sancho Val, Carlos Cajal Hernando, Lourdes Martínez de Baños","doi":"10.1016/j.atmosenv.2025.121741","DOIUrl":"10.1016/j.atmosenv.2025.121741","url":null,"abstract":"<div><div>Urban air pollution requires analytical tools that capture complex temporal dynamics while remaining interpretable for policy purposes. This study applies Functional Principal Component Analysis (FPCA) to hourly concentrations of NO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>, PM<sub>10</sub>, and PM<sub>2.5</sub> measured in 2024 at eight monitoring stations in Madrid. By transforming high-dimensional time series into smooth functional data, FPCA identifies dominant modes of variability and reveals structural differences among sites.</div><div>Across all pollutants, the first three components explained more than 85% of total variance. PC1 represented the main seasonal cycle, PC2 reflected short-term fluctuations driven by traffic and meteorology, and PC3 captured episodic peaks. The score plots highlighted consistent clustering: background stations (Casa de Campo, Sanchinarro) showed low levels and weak seasonality; traffic-oriented stations (Plaza Elíptica, Cuatro Caminos, Escuelas Aguirre) displayed high concentrations and stronger cycles; and intermediate sites (Castellana, Plaza Castilla, Méndez Álvaro) exhibited mixed patterns.</div><div>These findings confirm FPCA as an efficient diagnostic framework for air quality assessment, offering both dimensionality reduction and interpretability. Beyond methodological value, the approach enables classification of monitoring sites and supports targeted mitigation strategies. FPCA thus provides a transferable tool for urban air quality management and a solid basis for functional data analysis in environmental policy contexts.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"367 ","pages":"Article 121741"},"PeriodicalIF":3.7,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787890","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}
The open burning of municipal solid waste (MSW) remains a prevalent yet underreported source of greenhouse gas (GHG) and air pollutant emissions, particularly in developing and transition economies. This study updates the 2006 IPCC activity inventory methods and subsequent refinements to quantify emissions from open waste burning (OWB) in Asian countries. The emissions from OWB were estimated using updated emission factors for particulate matter 10 μm (PM10), 2.5 μm (PM2.5), carbon monoxide (CO), nitrogen oxides (NOx), sulphur dioxide (SO2), and dioxins, estimating a total release of approximately 16.51 Megatons (Mt) of CO, 1.50 Mt of PM10, 1.42 Mt of PM2.5, 0.50 Mt of NOx, and 0.20 Mt of SO2 annually. The total annual climate impact is estimated at 249 Mt CO2-equivalents (CO2e), with South Asia accounting for over 39 % of these emissions owing to high population densities and limited formal waste services. These findings highlight the urgent need to explicitly incorporate open burning in national emission inventories and waste strategies while also strengthening institutional capacity, regulatory enforcement, and community-based interventions to reduce this overlooked source of pollution and climate impact.
{"title":"Assessment of environmental impact of open waste burning activity in Asia and Pacific: A methodological update","authors":"Bimastyaji Surya Ramadan , Lakshitha Chathuranga Paranagamage , Miho Hayashi , Premakumara Jagath Dickella Gamaralalage , Dennis Mwaniki , Andreea Baias , Francesca Calisesi , Samuel Wahome Maina , Mehmet Dogu Karakaya , Masaki Yabitsu","doi":"10.1016/j.atmosenv.2025.121747","DOIUrl":"10.1016/j.atmosenv.2025.121747","url":null,"abstract":"<div><div>The open burning of municipal solid waste (MSW) remains a prevalent yet underreported source of greenhouse gas (GHG) and air pollutant emissions, particularly in developing and transition economies. This study updates the 2006 IPCC activity inventory methods and subsequent refinements to quantify emissions from open waste burning (OWB) in Asian countries. The emissions from OWB were estimated using updated emission factors for particulate matter 10 μm (PM<sub>10</sub>), 2.5 μm (PM<sub>2.5</sub>), carbon monoxide (CO), nitrogen oxides (NO<sub>x</sub>), sulphur dioxide (SO<sub>2</sub>), and dioxins, estimating a total release of approximately 16.51 Megatons (Mt) of CO, 1.50 Mt of PM<sub>10</sub>, 1.42 Mt of PM<sub>2.5</sub>, 0.50 Mt of NO<sub>x</sub>, and 0.20 Mt of SO<sub>2</sub> annually. The total annual climate impact is estimated at 249 Mt CO<sub>2</sub>-equivalents (CO<sub>2</sub>e), with South Asia accounting for over 39 % of these emissions owing to high population densities and limited formal waste services. These findings highlight the urgent need to explicitly incorporate open burning in national emission inventories and waste strategies while also strengthening institutional capacity, regulatory enforcement, and community-based interventions to reduce this overlooked source of pollution and climate impact.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"367 ","pages":"Article 121747"},"PeriodicalIF":3.7,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787891","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}
Pub Date : 2025-12-11DOI: 10.1016/j.atmosenv.2025.121746
Ravi Kumar Kunchala , Imran Girach , Chiranjit Das , Chaithanya Jain , Pramit Kumar Deb Burman , Mahesh Pathakoti , Prabir K. Patra , Yogesh K. Tiwari , M. Venkat Ratnam , Vinayak Sinha , Vinu Valsala , Manish Naja , S. Venkataramani , Naveen Chandra , S Suresh Babu , Mehul R Pandya , Haseeb Hakkim , Savita Datta , Vaishnavi Jain
India is the 3rd largest emitter of fossil fuel carbon dioxide (CO2), highlighting the critical need to understand CO2 dynamics for effective carbon management. This study investigates the CO2 variability and its dynamics over India using ground-based in situ measurements (11 sites), satellite observations and model simulations. The analyses reveal distinct diurnal and seasonal patterns, along with a consistent increasing trend with global-mean CO2 concentrations. The amplitude of seasonal cycles (SCAs) vary geographically, with deeper SCAs observed in northern India and shallower ones in the south, primarily influenced by the monsoon system and temperature-dependent vegetation dynamics. The lowest SCA is observed over the high-altitude site at Hanle in north India (7.4 ppm), followed by the coastal sites at Pondicherry (8.0 ppm) and Thumba (8.5 ppm) in south India. The deepest SCA of 26.7 ppm is observed at Mohali, with one of the peaks observed in November attributed to crop residue burning in the Indo-Gangetic Plain. We have used an Atmospheric Chemistry Transport Model (ACTM) to understand spatial and temporal variations in CO2. The model simulates the phase of the SCAs reasonably well at only a few sites, e.g., Thumba, Gadanki, and fails to capture details at most sites. Coarse horizontal resolution of ACTM (2.8o 2.8°) limits the reproduction of observed diurnal pattern at the sites near strong fluxes. Satellite observations of total column CO2 (XCO2) anomalies (2014–2024) show negative values (indicative of sink) over India during post-monsoon season, and positive values (indicative of source) during premonsoon season. The regional mean XCO2 SCA (5.45–5.65 ppm), trend (2.44–2.51 ppm y−1) and interannual variability in growth rates (∼1.0–3.9 ppm y−1) are consistently estimated from two satellites during 2009–2024.
{"title":"Carbon dioxide (CO2) variations across India: Synthesis of observations and model simulations","authors":"Ravi Kumar Kunchala , Imran Girach , Chiranjit Das , Chaithanya Jain , Pramit Kumar Deb Burman , Mahesh Pathakoti , Prabir K. Patra , Yogesh K. Tiwari , M. Venkat Ratnam , Vinayak Sinha , Vinu Valsala , Manish Naja , S. Venkataramani , Naveen Chandra , S Suresh Babu , Mehul R Pandya , Haseeb Hakkim , Savita Datta , Vaishnavi Jain","doi":"10.1016/j.atmosenv.2025.121746","DOIUrl":"10.1016/j.atmosenv.2025.121746","url":null,"abstract":"<div><div>India is the 3rd largest emitter of fossil fuel carbon dioxide (CO<sub>2</sub>), highlighting the critical need to understand CO<sub>2</sub> dynamics for effective carbon management. This study investigates the CO<sub>2</sub> variability and its dynamics over India using ground-based in situ measurements (11 sites), satellite observations and model simulations. The analyses reveal distinct diurnal and seasonal patterns, along with a consistent increasing trend with global-mean CO<sub>2</sub> concentrations. The amplitude of seasonal cycles (SCAs) vary geographically, with deeper SCAs observed in northern India and shallower ones in the south, primarily influenced by the monsoon system and temperature-dependent vegetation dynamics. The lowest SCA is observed over the high-altitude site at Hanle in north India (7.4 ppm), followed by the coastal sites at Pondicherry (8.0 ppm) and Thumba (8.5 ppm) in south India. The deepest SCA of 26.7 ppm is observed at Mohali, with one of the peaks observed in November attributed to crop residue burning in the Indo-Gangetic Plain. We have used an Atmospheric Chemistry Transport Model (ACTM) to understand spatial and temporal variations in CO<sub>2</sub>. The model simulates the phase of the SCAs reasonably well at only a few sites, e.g., Thumba, Gadanki, and fails to capture details at most sites. Coarse horizontal resolution of ACTM (2.8<sup>o</sup> <span><math><mrow><mo>×</mo></mrow></math></span> 2.8°) limits the reproduction of observed diurnal pattern at the sites near strong fluxes. Satellite observations of total column CO<sub>2</sub> (XCO<sub>2</sub>) anomalies (2014–2024) show negative values (indicative of sink) over India during post-monsoon season, and positive values (indicative of source) during premonsoon season. The regional mean XCO<sub>2</sub> SCA (5.45–5.65 ppm), trend (2.44–2.51 ppm y<sup>−1</sup>) and interannual variability in growth rates (∼1.0–3.9 ppm y<sup>−1</sup>) are consistently estimated from two satellites during 2009–2024.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"367 ","pages":"Article 121746"},"PeriodicalIF":3.7,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787893","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}
Pub Date : 2025-12-11DOI: 10.1016/j.atmosenv.2025.121744
Michael P. Perring , Laurence Jones , Katrina Sharps , Felicity Hayes
The atmospheric pollutants nitric oxide (NO) and nitrogen dioxide (NO2) (collectively referred to as NOx) remain persistent constituents in the lower atmosphere. Here, we provide a state-of-knowledge overview of their sources, their biochemical and physiological roles in plants, and their consequences for ecosystems, exploring duality in their impacts. Ecosystem exposure to these pollutants is increasing in areas of the globe. Vegetative harm arises from oxidising and acidifying influences on biochemical and metabolic properties following stomatal uptake of NOx with conflicting information on whether NO and NO2 act differentially. Emergent general consequences include altered plant physiology, structure and function, with effects on vegetative growth, flowering and community composition e.g. loss of bryophytes and lichens. There is also evidence of negative effects on insect health and behaviour. Yet, recent evidence points to both NO and NO2 acting as plant signalling molecules and, in some ecosystems, providing a critical source of nutrients to sustain plant growth. The exogenous supply of NO from donor molecules, as well as endogenous NO, can mediate vegetation response to environmental stressors. Ecological responses are modulated by environmental factors (e.g. available nutrients) and other atmospheric constituents such as ozone, carbon dioxide and ammonia. We urgently need studies in realistic environments, including contemporary/future atmospheric conditions, to understand ecosystem consequences arising from atmospheric NOx exposure. Research needs to consider interactions among endogenous NO production in plants, stomatal uptake of NOx, and atmospheric NO to NO2 ratios to estimate risks to vegetation and ecosystems.
{"title":"Nitric oxide (NO) and nitrogen dioxide (NO2): A state-of-knowledge review of their roles in, and consequences for, vegetation and ecosystems","authors":"Michael P. Perring , Laurence Jones , Katrina Sharps , Felicity Hayes","doi":"10.1016/j.atmosenv.2025.121744","DOIUrl":"10.1016/j.atmosenv.2025.121744","url":null,"abstract":"<div><div>The atmospheric pollutants nitric oxide (NO) and nitrogen dioxide (NO<sub>2</sub>) (collectively referred to as NO<sub>x</sub>) remain persistent constituents in the lower atmosphere. Here, we provide a state-of-knowledge overview of their sources, their biochemical and physiological roles in plants, and their consequences for ecosystems, exploring duality in their impacts. Ecosystem exposure to these pollutants is increasing in areas of the globe. Vegetative harm arises from oxidising and acidifying influences on biochemical and metabolic properties following stomatal uptake of NO<sub>x</sub> with conflicting information on whether NO and NO<sub>2</sub> act differentially. Emergent general consequences include altered plant physiology, structure and function, with effects on vegetative growth, flowering and community composition e.g. loss of bryophytes and lichens. There is also evidence of negative effects on insect health and behaviour. Yet, recent evidence points to both NO and NO<sub>2</sub> acting as plant signalling molecules and, in some ecosystems, providing a critical source of nutrients to sustain plant growth. The exogenous supply of NO from donor molecules, as well as endogenous NO, can mediate vegetation response to environmental stressors. Ecological responses are modulated by environmental factors (e.g. available nutrients) and other atmospheric constituents such as ozone, carbon dioxide and ammonia. We urgently need studies in realistic environments, including contemporary/future atmospheric conditions, to understand ecosystem consequences arising from atmospheric NO<sub>x</sub> exposure. Research needs to consider interactions among endogenous NO production in plants, stomatal uptake of NO<sub>x</sub>, and atmospheric NO to NO<sub>2</sub> ratios to estimate risks to vegetation and ecosystems.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"367 ","pages":"Article 121744"},"PeriodicalIF":3.7,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145920692","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}
Pub Date : 2025-12-11DOI: 10.1016/j.atmosenv.2025.121717
Felipe Aranda , Lina Castro , Tomás R. Bolaño-Ortiz , Felipe McCracken
Black Carbon (BC), generated mainly by the incomplete combustion of fossil fuels, reduces snow albedo by increasing solar radiation absorption, which enhances surface warming and accelerates snow ablation. This effect is particularly relevant in snow-dominated basins near emission sources. However, limited atmospheric and depositional BC measurements restrict the assessment of its spatial and temporal variability in mountain catchments. This study estimates past (2006–2022) and future (2023–2035) atmospheric BC levels in the Juncalillo River basin, Central Andes of Chile. BC concentrations in snow (BCCS) were inferred using an asymptotic radiative transfer model (ART) and subsequently used to estimate atmospheric BC through a statistical model. Future BC was projected under two contrasting scenarios: (1) climate change conditions using the IPSL-CM5A-MR GCM with Quantile Delta Mapping, and (2) increased vehicular traffic on the CH-60 road (primary emission source in the basin). BCCS ranged from 160 to 520 ng g−1, with 11–20 % higher values within 1 km of the road. Atmospheric BC in 2006–2022 averaged 0.12 μg m−3 at the basin scale, with a non-significant increasing trend. Climate change projections suggest reduced BC (mean 0.10 μg m−3) with a significant negative trend, whereas the traffic-based scenario predicts an increase to 0.21 μg m−3 and a significant positive trend. These contrasting outcomes highlight the need to explicitly consider BC emission sources when evaluating future cryosphere changes in mountain basins.
{"title":"Spatiotemporal variation of black carbon in snow surface and atmosphere in an upper basin of central Chilean Andes: A retrospective analysis and future projections","authors":"Felipe Aranda , Lina Castro , Tomás R. Bolaño-Ortiz , Felipe McCracken","doi":"10.1016/j.atmosenv.2025.121717","DOIUrl":"10.1016/j.atmosenv.2025.121717","url":null,"abstract":"<div><div>Black Carbon (BC), generated mainly by the incomplete combustion of fossil fuels, reduces snow albedo by increasing solar radiation absorption, which enhances surface warming and accelerates snow ablation. This effect is particularly relevant in snow-dominated basins near emission sources. However, limited atmospheric and depositional BC measurements restrict the assessment of its spatial and temporal variability in mountain catchments. This study estimates past (2006–2022) and future (2023–2035) atmospheric BC levels in the Juncalillo River basin, Central Andes of Chile. BC concentrations in snow (BCCS) were inferred using an asymptotic radiative transfer model (ART) and subsequently used to estimate atmospheric BC through a statistical model. Future BC was projected under two contrasting scenarios: (1) climate change conditions using the IPSL-CM5A-MR GCM with Quantile Delta Mapping, and (2) increased vehicular traffic on the CH-60 road (primary emission source in the basin). BCCS ranged from 160 to 520 ng g<sup>−1</sup>, with 11–20 % higher values within 1 km of the road. Atmospheric BC in 2006–2022 averaged 0.12 μg m<sup>−3</sup> at the basin scale, with a non-significant increasing trend. Climate change projections suggest reduced BC (mean 0.10 μg m<sup>−3</sup>) with a significant negative trend, whereas the traffic-based scenario predicts an increase to 0.21 μg m<sup>−3</sup> and a significant positive trend. These contrasting outcomes highlight the need to explicitly consider BC emission sources when evaluating future cryosphere changes in mountain basins.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"367 ","pages":"Article 121717"},"PeriodicalIF":3.7,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145920693","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}
Pub Date : 2025-12-11DOI: 10.1016/j.atmosenv.2025.121745
Michael Hedges , Max Priestman , Marc Chadeau-Hyam , Rudy Sinharay , Alison E. Kent , Frank J. Kelly , David C. Green
Subway systems provide an important mode of sustainable urban public transportation reducing traffic congestion and vehicle emissions. However, there are increasing concerns over the elevated levels of particulate matter (PM) concentrations found in the subway and the potential health effects from train-related emissions. These emission sources are common worldwide with the highest concentrations driven by lack of ventilation, tunnel depth and distance from tunnel openings. The aim of this study was to assess PM2.5 mass concentrations, particle number concentrations and particle number size distributions by taking measurements inside a train carriage in a London Underground deep-tunnelled line. A fully portable, battery powered Mobile Reference Station (MoRS) was developed to obtain simultaneous measurements of oxides of nitrogen, ozone and all size fractions of PM in train carriages across 16 distinct Bakerloo Line subway journeys. In the tunnelled sections of the Bakerloo line mean PM2.5 concentrations were 343 (115) μg m−3, with mean concentrations peaking at 550 (45) μg m−3 at Marylebone Station. A moderate negative correlation between PM2.5 and NO2 was demonstrated likely influenced by a complex relationship linking tunnel depth, ventilation, ambient air, PM2.5 and NO2 concentrations. PM2.5 concentrations and particle size distributions were seen to be driven by the piston effect of moving trains and settling processes. Using particle number size distributions, ultrafine particles were found to constitute 84 % of subway particle number concentrations with 99 % of subway particles having a diameter less than 530 nm. Lung Deposited Surface Area (LDSA) was used to estimate PM exposure during the subway journeys. Importantly, total LDSA for PM2.5 was higher in the subway than at a London roadside site. Overall, this study provides a basis to begin to control specific train related emission sources and to improve air quality management through focused mitigation strategies in the London Underground and worldwide subway systems.
{"title":"Exposure assessment and particle number size distribution in train carriages in the London subway","authors":"Michael Hedges , Max Priestman , Marc Chadeau-Hyam , Rudy Sinharay , Alison E. Kent , Frank J. Kelly , David C. Green","doi":"10.1016/j.atmosenv.2025.121745","DOIUrl":"10.1016/j.atmosenv.2025.121745","url":null,"abstract":"<div><div>Subway systems provide an important mode of sustainable urban public transportation reducing traffic congestion and vehicle emissions. However, there are increasing concerns over the elevated levels of particulate matter (PM) concentrations found in the subway and the potential health effects from train-related emissions. These emission sources are common worldwide with the highest concentrations driven by lack of ventilation, tunnel depth and distance from tunnel openings. The aim of this study was to assess PM<sub>2.5</sub> mass concentrations, particle number concentrations and particle number size distributions by taking measurements inside a train carriage in a London Underground deep-tunnelled line. A fully portable, battery powered Mobile Reference Station (MoRS) was developed to obtain simultaneous measurements of oxides of nitrogen, ozone and all size fractions of PM in train carriages across 16 distinct Bakerloo Line subway journeys. In the tunnelled sections of the Bakerloo line mean PM<sub>2.5</sub> concentrations were 343 (115) μg m<sup>−3</sup>, with mean concentrations peaking at 550 (45) μg m<sup>−3</sup> at Marylebone Station. A moderate negative correlation between PM<sub>2.5</sub> and NO<sub>2</sub> was demonstrated likely influenced by a complex relationship linking tunnel depth, ventilation, ambient air, PM<sub>2.5</sub> and NO<sub>2</sub> concentrations. PM<sub>2.5</sub> concentrations and particle size distributions were seen to be driven by the piston effect of moving trains and settling processes. Using particle number size distributions, ultrafine particles were found to constitute 84 % of subway particle number concentrations with 99 % of subway particles having a diameter less than 530 nm. Lung Deposited Surface Area (LDSA) was used to estimate PM exposure during the subway journeys. Importantly, total LDSA for PM<sub>2.5</sub> was higher in the subway than at a London roadside site. Overall, this study provides a basis to begin to control specific train related emission sources and to improve air quality management through focused mitigation strategies in the London Underground and worldwide subway systems.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"367 ","pages":"Article 121745"},"PeriodicalIF":3.7,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787889","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}
Pub Date : 2025-12-11DOI: 10.1016/j.atmosenv.2025.121742
Lijing Zhang , Pingping Liu , Hongyu Yan , Yuhao Dong , Shaozhong Guo , Hongmei Xu
"Iron-fisted Smog Control '1 + 9' Action Plan" in Shaanxi Province in 2017 promoted clean heating in rural households including "coal-to-gas" and "coal-to-electricity" conversions. This study collected PM2.5 samples in Xi'an during three periods (pre-, mid-, and post-policy implementation from 2016 to 2021) and quantified policy-driven changes in particulate toxicity and underlying influence factors through DCFH-based oxidative potential (OP) measurements. The results demonstrated significant decreases in characteristic metals from residential combustion sources (As, Pb, K) alongside increases in vehicular emission tracers (Cu, Mn) during policy implementation. A progressive decline in OP (16.28 ± 2.43, 14.41 ± 2.59, and 13.77 ± 2.62 nM H2O2 m−3 in pre-, mid-, and post-policy implementation periods) confirmed the efficacy of clean energy projects in reducing oxidative stress potential. OP showed strong positive correlations (R = 0.35–0.47, P < 0.01) with water-soluble toxic metals (Fe, Cu, Mn). The source apportionment of PM2.5 OP was conducted using a combined approach of positive matrix factorization and multilayer perceptron. The results revealed that the contribution of residential combustion sources to OP decreased from 32.1 % before the policy implementation to 25.9 % afterward, showing a significant response to the clean energy policies enacted in the Guanzhong region. Meanwhile, in the post-policy period, vehicle emissions (37.3 %) surpassed residential combustion as a major contributor to OP. This study verifies that policy interventions focusing on replacing scattered coal and biomass burning effectively reduced PM2.5 OP through decreasing toxic coal/biomass combustion components (As, Pb, K), achieving dual-control strategies targeting both mass concentration and toxicity reduction in precision air pollution management.
{"title":"Reshaping metal composition and sources to reduce PM2.5 oxidative potential by clean energy policies in Xi'an, China","authors":"Lijing Zhang , Pingping Liu , Hongyu Yan , Yuhao Dong , Shaozhong Guo , Hongmei Xu","doi":"10.1016/j.atmosenv.2025.121742","DOIUrl":"10.1016/j.atmosenv.2025.121742","url":null,"abstract":"<div><div>\"Iron-fisted Smog Control '1 + 9' Action Plan\" in Shaanxi Province in 2017 promoted clean heating in rural households including \"coal-to-gas\" and \"coal-to-electricity\" conversions. This study collected PM<sub>2.5</sub> samples in Xi'an during three periods (pre-, mid-, and post-policy implementation from 2016 to 2021) and quantified policy-driven changes in particulate toxicity and underlying influence factors through DCFH-based oxidative potential (OP) measurements. The results demonstrated significant decreases in characteristic metals from residential combustion sources (As, Pb, K) alongside increases in vehicular emission tracers (Cu, Mn) during policy implementation. A progressive decline in OP (16.28 ± 2.43, 14.41 ± 2.59, and 13.77 ± 2.62 nM H<sub>2</sub>O<sub>2</sub> m<sup>−3</sup> in pre-, mid-, and post-policy implementation periods) confirmed the efficacy of clean energy projects in reducing oxidative stress potential. OP showed strong positive correlations (R = 0.35–0.47, P < 0.01) with water-soluble toxic metals (Fe, Cu, Mn). The source apportionment of PM<sub>2.5</sub> OP was conducted using a combined approach of positive matrix factorization and multilayer perceptron. The results revealed that the contribution of residential combustion sources to OP decreased from 32.1 % before the policy implementation to 25.9 % afterward, showing a significant response to the clean energy policies enacted in the Guanzhong region. Meanwhile, in the post-policy period, vehicle emissions (37.3 %) surpassed residential combustion as a major contributor to OP. This study verifies that policy interventions focusing on replacing scattered coal and biomass burning effectively reduced PM<sub>2.5</sub> OP through decreasing toxic coal/biomass combustion components (As, Pb, K), achieving dual-control strategies targeting both mass concentration and toxicity reduction in precision air pollution management.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"367 ","pages":"Article 121742"},"PeriodicalIF":3.7,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787930","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}
Pub Date : 2025-12-10DOI: 10.1016/j.atmosenv.2025.121737
Suresh K. R. Boreddy, Prashant Hegde, Mukunda M. Gogoi, S. Suresh Babu
High-latitude regions are particularly susceptible to the impacts of climate change and global warming. Organic aerosols are widespread and play a vital role in the Earth's climate; therefore, monitoring their molecular distributions, sources, and formation processes is essential. The present study investigates water-soluble dicarboxylic acids and related secondary organic compounds in aerosols from the Gruvebadet observatory in Ny-Ålesund during summer 2023 to gain insights into the formation processes of secondary organic aerosols (SOA) in the Arctic atmosphere. The results indicate that oxalic acid (C2) was the most abundant, followed by succinic (C4) and phthalic (Ph) acids, as well as malonic (C3) and azelaic (C9) acids. The higher abundance of C4 over C3 (on average) suggests relatively fresh emission sources. The high fumaric-to-maleic (F/M) ratios (mean: 1.14 ± 0.46) and diacids-C/TC ratios (16.4 ± 6.67 %) indicate that photochemical processes were a significant source of diacids throughout the sampling period. The mass diagnostic ratios indicate that the photochemical oxidation of unsaturated fatty acids (UFAs) enriched in the sea-surface micro-layer is the primary source of SOA, followed by the oxidation of aromatic hydrocarbons (AHCs). Furthermore, quantification of C2 associated with the photooxidation of UFAs was conducted using a linear relationship-based approach. The results show that on average, 61 ± 20 % (range: 9–83 %) of C2 was derived from the oxidation of UFAs, with the rest was attributed to the photooxidation of AHCs. The present study also highlighted potential uncertainties in using regression-based source apportionment of C2 with bootstrap analysis. These findings will improve our understanding of the transformation processes of organic aerosols, which are vital for climate modellers to accurately estimate SOA mass and its climatic effects, especially in the Arctic environment.
高纬度地区特别容易受到气候变化和全球变暖的影响。有机气溶胶分布广泛，在地球气候中起着至关重要的作用；因此，监测它们的分子分布、来源和形成过程是必不可少的。本研究调查了2023年夏季美国Ny Gruvebadet观测站-Ålesund气溶胶中的水溶性二羧酸和相关的二次有机化合物，以深入了解北极大气中二次有机气溶胶（SOA）的形成过程。结果表明，草酸（C2）含量最多，其次为琥珀酸（C4）和邻苯二甲酸（Ph），丙二酸（C3）和壬二酸（C9）。C4的丰度高于C3（平均），表明排放源相对较新鲜。富马/马来酸（F/M）比值（平均值：1.14±0.46）和二酸- c /TC比值（16.4±6.67%）表明，在整个采样期间，光化学过程是二酸的重要来源。质量诊断比值表明，海洋表层微层富集的不饱和脂肪酸（UFAs）的光化学氧化是SOA的主要来源，其次是芳香烃（AHCs）的氧化。此外，使用基于线性关系的方法对与ufa光氧化相关的C2进行了量化。结果表明，平均61±20%（范围：9 - 83%）的C2来源于ufa的氧化，其余来源于AHCs的光氧化。本研究还强调了使用基于回归的C2源分配与bootstrap分析的潜在不确定性。这些发现将提高我们对有机气溶胶转化过程的理解，这对于气候建模者准确估计SOA质量及其气候影响至关重要，特别是在北极环境中。
{"title":"Secondary organic aerosol formation in the arctic (Ny-Ålesund) atmosphere during summer: inferences from water-soluble dicarboxylic acids and related compounds","authors":"Suresh K. R. Boreddy, Prashant Hegde, Mukunda M. Gogoi, S. Suresh Babu","doi":"10.1016/j.atmosenv.2025.121737","DOIUrl":"10.1016/j.atmosenv.2025.121737","url":null,"abstract":"<div><div>High-latitude regions are particularly susceptible to the impacts of climate change and global warming. Organic aerosols are widespread and play a vital role in the Earth's climate; therefore, monitoring their molecular distributions, sources, and formation processes is essential. The present study investigates water-soluble dicarboxylic acids and related secondary organic compounds in aerosols from the Gruvebadet observatory in Ny-Ålesund during summer 2023 to gain insights into the formation processes of secondary organic aerosols (SOA) in the Arctic atmosphere. The results indicate that oxalic acid (C<sub>2</sub>) was the most abundant, followed by succinic (C<sub>4</sub>) and phthalic (Ph) acids, as well as malonic (C<sub>3</sub>) and azelaic (C<sub>9</sub>) acids. The higher abundance of C<sub>4</sub> over C<sub>3</sub> (on average) suggests relatively fresh emission sources. The high fumaric-to-maleic (F/M) ratios (mean: 1.14 ± 0.46) and diacids-C/TC ratios (16.4 ± 6.67 %) indicate that photochemical processes were a significant source of diacids throughout the sampling period. The mass diagnostic ratios indicate that the photochemical oxidation of unsaturated fatty acids (UFAs) enriched in the sea-surface micro-layer is the primary source of SOA, followed by the oxidation of aromatic hydrocarbons (AHCs). Furthermore, quantification of C<sub>2</sub> associated with the photooxidation of UFAs was conducted using a linear relationship-based approach. The results show that on average, 61 ± 20 % (range: 9–83 %) of C<sub>2</sub> was derived from the oxidation of UFAs, with the rest was attributed to the photooxidation of AHCs. The present study also highlighted potential uncertainties in using regression-based source apportionment of C<sub>2</sub> with bootstrap analysis. These findings will improve our understanding of the transformation processes of organic aerosols, which are vital for climate modellers to accurately estimate SOA mass and its climatic effects, especially in the Arctic environment.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"367 ","pages":"Article 121737"},"PeriodicalIF":3.7,"publicationDate":"2025-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787892","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}
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