Atmospheric Environment最新文献

{"title":"Development of a multiple solution mixing mechanism based aerosol component retrieval method for polarimetric satellite measurements","authors":"Ying Zhang ,&nbsp;ChaoYu Yan ,&nbsp;Zhengqaing Li ,&nbsp;Haoran Gu ,&nbsp;Yisong Xie","doi":"10.1016/j.atmosenv.2025.121120","DOIUrl":"10.1016/j.atmosenv.2025.121120","url":null,"abstract":"<div><div>Aerosols chemical components from different sources significantly affect climate change and air quality. In this study, we developed a satellite-based aerosol component retrieval method based on multiple solution mixing mechanism (MSMM) to extract global aerosol component from POLDER polarimetric satellite observations from 2008 to 2012. The MSMM calculates the complex refractive index using the Lorentz-Lorenz relation and constrains the solute fraction with κ-Köhler theory to retrieve the following components: black carbon (BC), ammonium nitrate-like inorganic salts (AN), dust (DU), sea salt (SS), water-soluble organic matter (WSOM), water-insoluble organic matter (WIOM), and aerosol water content (AW). By analyzing the spatial distribution and seasonal characteristics of the seven aerosol components over a five-year period, we captured the significant patterns of each aerosol component over global anthropogenic and natural hotspot emission regions. The five-year average and the seasonal patterns of each component during 2008 show significant changes, consistent with our expectations and previous studies. The pattern of global brown carbon (BrC), which is estimated by the possible tracer substances, is correlated with the fire radiative power. After analyzing the time series changes of each component in different regions for five years, we fine that the fine-mode fraction of aerosol component mass concentration in the central-eastern region of China declined about 6.05% from 2008 to 2010, which is closely related to the strong implementation of environmental protection policies. Also, we find the global aerosol component mass fraction in 2012 shows anomalies, especially a significant increase in the AW component, which is explained by the high frequency of extreme weather. The aerosol components retrieved by the MSMM are comparable with MERRA-2, with the correlations up to 0.94 for BC and 0.88 for DU in representative regions. More comprehensive species of aerosol components can be obtained using the MSMM method than MERRA-2, which can be applied to future satellite observations with higher spatial resolution.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"349 ","pages":"Article 121120"},"PeriodicalIF":4.2,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143520097","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":"Analysis of contrasting aerosol indirect effects in liquid water clouds over the northern part of Arabian Sea","authors":"Kashif Anwar ,&nbsp;Khan Alam ,&nbsp;Abdulhaleem H. Labban ,&nbsp;Yangang Liu ,&nbsp;Naila","doi":"10.1016/j.atmosenv.2025.121123","DOIUrl":"10.1016/j.atmosenv.2025.121123","url":null,"abstract":"<div><div>The extensive daily statistics of aerosol properties, cloud properties, and their mutual correlations provide crucial information for better assessing future climate change. In this paper, 14 years (2010–2023) of data from the Moderate Resolution Imaging Spectroradiometer (MODIS) are analyzed over the northern part of Arabian Sea (Latitude: 21°–25° N and Longitude: 62°–68° E) to assess the characteristics of aerosols and clouds and their relationships under different meteorological conditions. When aerosol optical depth (AOD) is less than ∼ 0.7, the observations exhibit a positive correlation between AOD and cloud droplet effective radius (CDR) but negative correlations between AOD and cloud droplet number concentration (CDNC), between AOD and cloud optical depth (COD), between AOD and cloud liquid water path (CLWP), and between AOD and cloud geometrical thickness (H). The corresponding aerosol-cloud correlations change signs when the AOD values are larger than 0.7. However, the single folded positive AOD-cloud fraction (CF) relationship is observed in both AOD regimes. Similar correlations are also observed between precipitable water vapor (PWV) and CDR, CDNC, COD, H, CF and CLWP, together with a positive correlation between PWV and AOD. Further isolation of the environmental effects from aerosol effects by stratifying AOD and cloud data into different LTS and PWV bins shows that the signature of the well-known Twomey effect is observed under high LTS-high PWV conditions, while an opposite effect (anti-Twomey) is observed under low PWV conditions, regardless of LTS values. Additionally, negative correlations between AOD and COD, AOD and CLWP, and AOD and H are observed under low LTS, regardless of PWV conditions, with a slight positive correlation when AOD &gt;0.4 under high LTS and PWV conditions.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"348 ","pages":"Article 121123"},"PeriodicalIF":4.2,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143474527","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":"Dosimetry simulations of ultrafine particles deposition to the human respiratory tract and transport to the olfactory region for female receptors","authors":"Eleftheria Chalvatzaki ,&nbsp;Sofia Eirini Chatoutsidou ,&nbsp;Lila Diapouli ,&nbsp;Maria I. Gini ,&nbsp;Manousos I. Manousakas ,&nbsp;Evangelia Samoli ,&nbsp;Kostas Eleftheriadis ,&nbsp;Mihalis Lazaridis","doi":"10.1016/j.atmosenv.2025.121103","DOIUrl":"10.1016/j.atmosenv.2025.121103","url":null,"abstract":"<div><div>The regional deposited dose of ultrafine particles in the respiratory tract and their transport to the olfactory region was investigated through an existing particle dosimetry model (Exposure Dose Model 2, ExDoM2). The original dosimetry model was adapted to include a methodology that uses numerical modelling for the transport of ultrafine particles from the nose to the olfactory region. The mass dose to the oesophagus, blood, and lymph nodes was also calculated. Four different cases were studied: heating, traffic, nucleation events and background levels. The results showed that deposition in the olfactory region decreased with increasing particle size (from 0.40 % to 0.12 %). The majority of particles were estimated to penetrate into the thoracic region with 36 % of particles within the size range 14–33 nm deposited in the alveolar-interstitial region, followed by the tracheobronchial (21 %), the extrathoracic (11 %) and olfactory (&lt;0.5 %) regions. In addition, a comparison between the mass, surface, and number doses indicated different governing sources such as a higher number dose was obtained during nucleation (10.5 × 10⁸ particles), while higher mass (9.4 × 10⁻² μg) and surface (7.1 × 10¹² nm²) dose was obtained during heating periods. Simulations also indicated that after clearance, 56.9 % of ultrafine particles were found in the alveolar region, a finding that is linked to their small size and low clearance rate of this region. Nevertheless, the dose per unit surface area and the dose per cell in the olfactory region were higher than in the alveolar-interstitial region.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"348 ","pages":"Article 121103"},"PeriodicalIF":4.2,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143488444","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Synergistic effects of synoptic and quasi-biweekly timescale atmospheric circulation patterns on PM2.5 concentration in South Korea","authors":"Seyeong Lee ,&nbsp;Jeong-Hun Kim ,&nbsp;Maeng-Ki Kim ,&nbsp;Sang-Hyun Lee ,&nbsp;Cheol-Hee Kim","doi":"10.1016/j.atmosenv.2025.121122","DOIUrl":"10.1016/j.atmosenv.2025.121122","url":null,"abstract":"<div><div>In recent years, South Korea has continued to experience high PM_2.5 events despite government efforts, posing a significant threat to human life. This study examines the relationship between high winter PM_2.5 concentrations in South Korea and atmospheric circulation patterns on synoptic and quasi-biweekly timescales. During the winters of 2018–2022, periodicities of 4–8 and 8–26 days were observed in PM_2.5 concentrations, playing a crucial role in high PM_2.5 events. Composite analysis revealed that while atmospheric conditions during high PM_2.5 events shared similar characteristics, their intensity and spatial extent varied. An anticyclonic anomaly was observed in the upper levels over the Korean Peninsula, and the dipole pattern of the mean sea level pressure (MSLP) weakened the Siberian High, reducing northerly winds and weakening the East Asian winter monsoon. Under this atmospheric circulation, both low planetary boundary layer height (PBLH) and stable atmosphere contribute to high PM_2.5 concentrations along with weak ventilation. Anticyclonic anomalies associated with trough intensity originated from different sources: synoptic-scale anomalies from the North Atlantic (∼13 days prior) and quasi-biweekly anomalies from Siberia (∼8 days prior), propagating southeastward as precursor signals. PM_2.5 transport contributions differed by timescale: synoptic events were dominated by transport from eastern China, while quasi-biweekly events showed greater contributions from northern China. When overlapping, these timescales exhibited a synergistic effect, creating more favorable conditions for extreme high-concentration events.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"348 ","pages":"Article 121122"},"PeriodicalIF":4.2,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143512488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Addressing the advantages and limitations of using Aethalometer data to determine the optimal absorption Ångström exponents (AAEs) values for eBC source apportionment","authors":"Marjan Savadkoohi ,&nbsp;Mohamed Gherras ,&nbsp;Olivier Favez ,&nbsp;Jean-Eudes Petit ,&nbsp;Jordi Rovira ,&nbsp;Gang I. Chen ,&nbsp;Marta Via ,&nbsp;Stephen Platt ,&nbsp;Minna Aurela ,&nbsp;Benjamin Chazeau ,&nbsp;Joel F. de Brito ,&nbsp;Véronique Riffault ,&nbsp;Kostas Eleftheriadis ,&nbsp;Harald Flentje ,&nbsp;Martin Gysel-Beer ,&nbsp;Christoph Hueglin ,&nbsp;Martin Rigler ,&nbsp;Asta Gregorič ,&nbsp;Matic Ivančič ,&nbsp;Hannes Keernik ,&nbsp;Marco Pandolfi","doi":"10.1016/j.atmosenv.2025.121121","DOIUrl":"10.1016/j.atmosenv.2025.121121","url":null,"abstract":"<div><div>The apportionment of equivalent black carbon (eBC) to combustion sources from liquid fuels (mainly fossil; eBC_LF) and solid fuels (mainly non-fossil; eBC_SF) is commonly performed using data from Aethalometer instruments (AE approach). This study evaluates the feasibility of using AE data to determine the absorption Ångström exponents (AAEs) for liquid fuels (AAE_LF) and solid fuels (AAE_SF), which are fundamental parameters in the AE approach. AAEs were derived from Aethalometer data as the fit in a logarithmic space of the six absorption coefficients (470–950 nm) versus the corresponding wavelengths. The findings indicate that AAE_LF can be robustly determined as the 1st percentile (PC1) of AAE values from fits with R² &gt; 0.99. This R²-filtering was necessary to remove extremely low and noisy-driven AAE values commonly observed under clean atmospheric conditions (i.e., low absorption coefficients). Conversely, AAE_SF can be obtained from the 99th percentile (PC99) of unfiltered AAE values. To optimize the signal from solid fuel sources, winter data should be used to calculate PC99, whereas summer data should be employed for calculating PC1 to maximize the signal from liquid fuel sources. The derived PC1 (AAE_LF) and PC99 (AAE_SF) values ranged from 0.79 to 1.08, and 1.45 to 1.84, respectively. The AAE_SF values were further compared with those constrained using the signal at mass-to-charge 60 (<em>m/z</em> 60), a tracer for fresh biomass combustion, measured using aerosol chemical speciation monitor (ACSM) and aerosol mass spectrometry (AMS) instruments deployed at 16 sites. Overall, the AAE_SF values obtained from the two methods showed strong agreement, with a coefficient of determination (R²) of 0.78. However, uncertainties in both approaches may vary due to site-specific sources, and in certain environments, such as traffic-dominated sites, neither approach may be fully applicable.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"349 ","pages":"Article 121121"},"PeriodicalIF":4.2,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143520084","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Revealing the chemical composition and sources of carbonaceous aerosols in PM2.5: Insights from the Omicron-22 lockdown in Shanghai","authors":"Lian Duan ,&nbsp;Huimin Yu ,&nbsp;Fengwen Wang ,&nbsp;Tareq Hussein ,&nbsp;Tian Lin ,&nbsp;Zhigang Guo","doi":"10.1016/j.atmosenv.2025.121115","DOIUrl":"10.1016/j.atmosenv.2025.121115","url":null,"abstract":"<div><div>The COVID-19 pandemic, particularly the Omicron-22 lockdown in Shanghai, provided a unique opportunity to examine the influence of lockdown and decreasing human activities on the urban atmosphere environment. Here, we explored the chemical compositions and sources of carbonaceous aerosols during the pre-lockdown, lockdown, and post-lockdown periods in 2022, Shanghai. The mean concentrations of organic carbon (OC) and element carbon (EC) were 4.40 ± 1.58 and 1.05 ± 0.41 μg/m³ pre-lockdown, 1.60 ± 0.99 and 0.30 ± 0.13 μg/m³ during lockdown, and 2.66 ± 2.01 and 0.47 ± 0.19 μg/m³ post-lockdown, respectively. Normal alkanes (n-alkanes) and polycyclic aromatic hydrocarbons (PAHs) concentrations were 27.5 ± 9.77 and 1.81 ± 1.34 ng/m³ pre-lockdown, 10.6 ± 5.84 and 1.50 ± 0.67 ng/m³ during lockdown, and 7.27 ± 3.86 and 1.44 ± 0.23 ng/m³ post lockdown, respectively, with a further decline noted post-lockdown. A notable decrease in carbonaceous aerosols was observed during the lockdown. Carbonaceous aerosols showed a marked decrease during the lockdown, with OC and EC increasing by 60% post-lockdown, while n-alkanes and PAHs continued to decline. Although the composition of OC, EC, and PAHs remained stable, n-alkanes, particularly C₂₉-C₃₄, significantly increased due to plant wax emissions. Source apportionment indicated that coal combustion and industrial emissions were the primary contributors across all periods, with reduced transport emissions having limited impact on OC, EC, and PAH sources. This study highlights the air quality improvements from reduced anthropogenic activities, offering insights for future pollution mitigation policies.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"348 ","pages":"Article 121115"},"PeriodicalIF":4.2,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143474448","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":"Deep learning calibration model for PurpleAir PM2.5 measurements: Comprehensive Investigation of the PurpleAir network","authors":"Masoud Ghahremanloo ,&nbsp;Yunsoo Choi ,&nbsp;Mahmoudreza Momeni","doi":"10.1016/j.atmosenv.2025.121118","DOIUrl":"10.1016/j.atmosenv.2025.121118","url":null,"abstract":"<div><div>The limited number of PM_2.5 monitoring stations from the Environmental Protection Agency (EPA) across the Contiguous United States (CONUS) restricts PM_2.5 monitoring and associated policymaking efforts. Low-cost PM_2.5 stations, such as those from the PurpleAir network, offer a vital alternative to expand coverage in regions not monitored by the EPA. However, the accuracy of PurpleAir measurements has been questioned. This study introduces a deep learning (DL) approach, specifically a deep convolutional neural network (DeepCNN), to align hourly PM_2.5 data from PurpleAir with EPA PM_2.5 observations across the CONUS for the year 2021. Utilizing over nine million samples from 1595 PurpleAir stations located within 5 km of EPA stations, the DeepCNN demonstrates significant improvements in the agreement between PurpleAir and EPA observations. It increases the correlation coefficient (R) with EPA observations from 0.58 to 0.85 and reduces the mean absolute bias (MAB) from 4.99 to 2.98 μg/m³, achieving a 40% reduction in bias. The state-wise cross-validation also underscores the model's generalizability, with an average 11% improvement in R values and a 13% reduction in bias between PurpleAir and EPA PM_2.5 measurements in various states. Comparative analysis reveals that the accuracy of our DL-enhanced PurpleAir PM_2.5 (PM-DL) data significantly surpasses that of five previously established PurpleAir correction models, which show low R values of 0.55–0.58 and MABs ranging from 4.21 to 6.43 μg/m³ when validated against EPA data. This study underscores the need for more sophisticated models to better align PurpleAir PM_2.5 measurements to EPA standards. The PM-DL data can substantially mitigate the scarcity of reliable institutional PM_2.5 observations across the CONUS. By aligning PurpleAir PM_2.5 data with EPA observations, our model has the potential to augment the existing network with over ten thousand accurate monitoring stations, significantly expanding upon the nearly one thousand EPA stations currently in operation.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"348 ","pages":"Article 121118"},"PeriodicalIF":4.2,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143474526","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":"Modeling comparison of precipitation schemes and implications on aerosol diameter treatment for better sulfate aerosol production in the early summer rainy season over Northeast Asia","authors":"S. Itahashi ,&nbsp;N.K. Kim ,&nbsp;Y.P. Kim ,&nbsp;M. Song ,&nbsp;C.H. Kim ,&nbsp;K.S. Jang ,&nbsp;K.Y. Lee ,&nbsp;H.J. Shin ,&nbsp;J.Y. Ahn ,&nbsp;J.S. Jung ,&nbsp;Z. Wu ,&nbsp;J.Y. Lee ,&nbsp;Y. Sadanaga ,&nbsp;S. Kato ,&nbsp;N. Tang ,&nbsp;A. Matsuki","doi":"10.1016/j.atmosenv.2025.121117","DOIUrl":"10.1016/j.atmosenv.2025.121117","url":null,"abstract":"<div><div>In 2020, the Fine Particle Research Initiative in East Asia considering National Differences (FRIEND) project was launched to understand air quality issues over Northeast Asia better. In the FRIEND project, high-temporal-resolution measurements of gas and aerosol concentrations were taken simultaneously at five key sites in Northeast Asia. In this study, we used the dataset at Beijing in China, Seoul in Republic of Korea, and Noto in Japan. The second FRIEND campaign was conducted in early summer from June 1 to 30, 2021. Compared with the results of the first FRIEND campaign conducted in winter, it was revealed that the fraction of sulfate aerosol (SO₄²⁻) had dramatically increased in the upwind region of Northeast Asia (Beijing and Seoul). This period corresponds to the early rainy season in Northeast Asia; therefore, the role of the aqueous-phase oxidation process could be increased in SO₄²⁻ production. However, accurate modeling of precipitation is still challenging because of the parameterization in the meteorological model. Thus, we investigated the microphysics and cumulus schemes in the meteorological model and conducted 10 simulations. All schemes underestimated the precipitation amount and the cloud fraction. Hence, SO₄²⁻ concentration was underestimated with a lower conversion ratio from sulfur dioxide (SO₂) to SO₄²⁻ (F_S) at Beijing, Seoul, and Noto. At Seoul, the SO₄²⁻ concentration was underestimated with the aerosol ion monitor (AIM) measurements, corresponding to PM_2.5, but had an acceptable performance level. The SO₄²⁻ concentration at Seoul was sensitive to microphysics and cumulus schemes. However, the SO₄²⁻ concentration was compared with aerosol chemical speciation monitors (ACSMs), corresponding to PM_1.0, in Beijing and Noto, and showed greater underestimation. The sensitivities of SO₄²⁻ concentration to the precipitation schemes were small at Beijing and Noto. The simulated aerosol diameter shifted to a coarser range (1–2.5 μm) in the second campaign compared with the first campaign dataset with increasing temperature and relative humidity. The international measurement network in the FRIEND project demonstrates that the modeled aerosol diameter treatment must be revised carefully.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"349 ","pages":"Article 121117"},"PeriodicalIF":4.2,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143562439","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unexpected changes in occurrence and sources of chromophoric dissolved organic matter in PM2.5 driven by the clean air action over Xi'an, China","authors":"Xin Zhu ,&nbsp;Qingcai Chen ,&nbsp;Tong Sha ,&nbsp;Yue Yin ,&nbsp;Jinwen Li ,&nbsp;Zimeng Zhang ,&nbsp;Jiale Ding ,&nbsp;Tengfei Xu","doi":"10.1016/j.atmosenv.2025.121116","DOIUrl":"10.1016/j.atmosenv.2025.121116","url":null,"abstract":"<div><div>Chromophoric dissolved organic matter (CDOM) in atmospheric PM significantly impacts climate and health. However, China's air pollution control on CDOM is unclear. To evaluate the effect of the Blue Sky Defense Battle (BSDB) on the pollution characteristics and sources of CDOM, we comprehensively analyzed 1,428 PM_2.5 samples in Xi'an (2016-2022). Compared with the pre-BSDB period, we found a 17% increase in the air quality index and a 42% reduction in CDOM pollution levels. Furthermore, in winter, carbonaceous aerosol concentrations notably declined, with OC decreased by 25% and EC by 74%. Additionally, CDOM in Xi'an was predominantly composed of humic chromophores (80%), and the highly oxygenated humic-like substances (HO-HULIS) declined by 34%, effectively reducing the potential oxidative toxicity risks. Source apportionment results from the excitation-emission matrix fluorescence fingerprinting technique with the non-negative matrix factorization (NMF) model demonstrated that the effective control of combustion sources was the main driver of changes in atmospheric concentrations, chemical composition, and optical properties. Based on the NMF model analysis of carbonaceous aerosol, the source contributions of atmospheric oxidation and photochemical reactions increased after the BSDB indicating the limited control of the secondary sources. Additionally, the ineffective control of dust sources and the increasing contribution of external transport to CDOM after the BSDB highlighted the importance of effective dust management and regional collaborative control. Despite the decline in PM_2.5 levels, the rise in toxic components (HO-HULIS) indicated ongoing challenges for health-focused pollution control.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"348 ","pages":"Article 121116"},"PeriodicalIF":4.2,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143480689","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":"HONO chemistry affected by relative humidity and ammonia in the North China Plain during winter","authors":"Haiyan Ran ,&nbsp;Jingwei Zhang ,&nbsp;Yu Qu ,&nbsp;Juan Yang ,&nbsp;Yong Chen ,&nbsp;Yele Sun ,&nbsp;Chaoyang Xue ,&nbsp;Yujing Mu ,&nbsp;Junling An","doi":"10.1016/j.atmosenv.2025.121114","DOIUrl":"10.1016/j.atmosenv.2025.121114","url":null,"abstract":"<div><div>Nitrous acid (HONO) is a critical precursor of the hydroxyl radical (OH) and plays a pivotal role in atmospheric photochemistry. Although nitrogen dioxide (NO₂) heterogeneous reactions (HET) on ground and aerosol surfaces are widely recognized as major paths of HONO production, their influencing factors are not well characterized in air quality models, limiting the understanding of HONO formation and the quantification of their regional impact. In this study, a novel parameterization scheme for the NO₂ uptake coefficient, including the effects of solar radiation, relative humidity (RH) and ammonia (NH₃), was developed and coupled into the Weather Research and Forecasting model with Chemistry. Nine simulation scenarios were designed to assess the impacts of RH and NH₃ on HONO chemistry and O₃ levels in the North China Plain (NCP). The results showed that the RH-impacted HET contributed 10−25% of HONO, with a significant increase of more than 35% during the haze periods; whereas the NH₃-impacted HET contributed 15% of nighttime HONO and &lt;5% of noontime HONO, playing a more significant role in rural areas. Vertically, the RH-impacted HET contribution to nighttime HONO concentrations remained 26−31% at an altitude of 700–900 m due to the higher RH levels (50−60%) during the haze periods; whereas the NH₃-impacted HET contribution was minor above 500 m owing to the fast-decreasing NH₃ concentrations with height. When RH exceeded the turning point (70%), nighttime HONO was suppressed by up to 1 ppb in eastern NCP. The combination of RH and NH₃ produced a ground daily maximum 8h averaged O₃ enhancement of 6–14 μg m⁻³ during the haze periods, exceeding the effect of solar radiation. These findings deepen our understanding of the role of RH and NH₃ in HONO chemistry and imply the importance of reasonably expressing HET in air quality models.</div></div>","PeriodicalId":250,"journal":{"name":"Atmospheric Environment","volume":"348 ","pages":"Article 121114"},"PeriodicalIF":4.2,"publicationDate":"2025-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143453631","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}