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Advances in Air Pollution Control and Air Quality Improvement in...
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Advances in Air Pollution Control and Air Quality Improvement in Chinese Megacity Clusters: From Formation Mechanisms to Mitigation Strategies

A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Air Quality".

Deadline for manuscript submissions: 30 June 2026 | Viewed by 2136

Special Issue Editors

Prof. Dr. Guangli Xiu

E-Mail Website
Guest Editor
School of Resources and Environmental Engineering, East China University of Science and Technology, Shanghai 200237, China
Interests: air quality; regional air transportation; ozone and aerosol; environmental health; emerging pollutants
Dr. Lian Duan

E-Mail Website
Guest Editor
School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093, China
Interests: atmospheric environment; environmental data science; environmental exposure assessment and population health risk

Special Issue Information

Dear Colleagues,

Megacity clusters in China, such as the Yangtze River Delta, Beijing-Tianjin-Hebei and Pearl River Delta, serve as critical engines for economic development while facing persistent challenges from complex air pollution.

This Special Issue seeks to compile pioneering research that elucidates the physical and chemical mechanisms governing air pollution formation and evolution in these densely populated regions. We particularly encourage submissions employing innovative methodological frameworks, including but not limited to, machine learning-enhanced prediction systems; coupled meteorology–chemistry modeling at high resolutions; advanced source apportionment techniques integrating chemical speciation with multivariate statistical approaches and novel exposure-risk assessment paradigms. Investigations evaluating the efficacy of emission control policies and analyzing the ancillary air quality benefits associated with carbon neutrality pathways are strongly welcomed.

By broadening the geographic scope to encompass key Chinese megacity clusters while emphasizing methodological innovation, this collection aims to establish an international forum for knowledge exchange and to provide robust scientific support for the next generation of air quality management strategies in urbanized regions globally.

Prof. Dr. Guangli Xiu
Dr. Lian Duan
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Atmosphere is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • megacity clusters
  • multipollutant air quality
  • emission control policy
  • advanced source apportionment
  • long-term trend analysis
  • health and environmental effects
  • coupled meteorology-chemistry model

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Published Papers (3 papers)

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Research

30 pages, 18009 KB  
Article
A Multi-Agglomeration Assessment of Air Quality Responses to Top-Down NOx Emission Changes: Insights from Trends in Surface NO2 and O3 Across Urban China (2014–2021)
by Yang Shen, Shuzhuang Feng, Rui Zhang, Chenchen Peng, Zihan Yang, Yuanyuan Yang and Guoen Wei
Atmosphere 2026, 17(3), 313; https://doi.org/10.3390/atmos17030313 - 19 Mar 2026
Viewed by 327
Abstract
China’s stringent clean air policies have substantially reduced nitrogen oxides (NOx) emissions, leading to a general decline in nitrogen dioxide (NO2). However, surface ozone (O3) pollution remains severe, creating a complex challenge due to the non-linear relationship [...] Read more.
China’s stringent clean air policies have substantially reduced nitrogen oxides (NOx) emissions, leading to a general decline in nitrogen dioxide (NO2). However, surface ozone (O3) pollution remains severe, creating a complex challenge due to the non-linear relationship between O3 and its precursors. To disentangle the drivers behind these trends, this study quantifies the impacts of interannual variations in top-down constrained NOx emissions on surface NO2 and O3 concentrations from 2014 to 2021 across mainland China and five national urban agglomerations. We employed the WRF-CMAQ model with a fixed-emission simulation approach, using an observationally optimized NOx emission inventory derived from the assimilation of surface NO2 measurements. Results reveal that NO2 reductions were predominantly emission-driven (>80% post-2017), with declines most pronounced in winter. A strong linear consistency was found between interannual changes in top-down NOx emissions and attributed NO2 concentration variations, validating the methodology. In contrast, O3 responses to NOx reductions were spatially and seasonally heterogeneous, reflecting a non-linear photochemical regime. In major urban agglomerations (e.g., Beijing–Tianjin–Hebei (BTH), Yangtze River Delta (YRD), Pearl River Delta (PRD)), NOx reductions post-2018 showed limited effectiveness in mitigating summertime O3 and even increased O3 in spring and autumn, indicating a prevalent VOC-sensitive regime where NOx reduction can disinhibit O3 formation. Conversely, certain provinces (e.g., Anhui, Shanxi, Jilin) exhibited O3 decreases, suggesting a NOx-sensitive regime. The area benefiting from NOx reductions expanded steadily in summer after 2017 but not in other seasons. This study confirms the efficacy of NOx-focused policies for reducing primary NO2 pollution but highlights that mitigating persistent O3 requires a strategic shift to synergistic, region-specific control of volatile organic compounds alongside NOx, informed by local chemical sensitivity. Full article
(This article belongs to the Special Issue Advances in Air Pollution Control and Air Quality Improvement in Chinese Megacity Clusters: From Formation Mechanisms to Mitigation Strategies)
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23 pages, 2424 KB  
Article
High-Time-Resolution Aerosol Chemistry and Machine-Learning Sensitivity Reveal a Highland Triad Mechanism Driving PM2.5 in Xining (Qinghai–Tibet Plateau)
by Zihong Liang, Xiaofeng Hu, Anan Qi, Guojuan Qu, Weijun Song and Chunyan Sun
Atmosphere 2026, 17(2), 200; https://doi.org/10.3390/atmos17020200 - 13 Feb 2026
Viewed by 825
Abstract
Fine particulate matter (PM2.5) formation mechanisms in fragile highland ecosystems remain inadequately constrained, particularly regarding thermodynamic non-linearities (aerosol pH, liquid water content) and their interaction with geochemical modulation. Here, we present comprehensive year-long online measurements from Xining, Qinghai-Tibet Plateau, integrating hourly [...] Read more.
Fine particulate matter (PM2.5) formation mechanisms in fragile highland ecosystems remain inadequately constrained, particularly regarding thermodynamic non-linearities (aerosol pH, liquid water content) and their interaction with geochemical modulation. Here, we present comprehensive year-long online measurements from Xining, Qinghai-Tibet Plateau, integrating hourly measurements of water-soluble ions, inorganic elements, and gaseous precursors with ISORROPIA-II thermodynamic modeling and ensemble machine learning. Median pH was 4.38 but exhibited two distinct pH regimes (14.8% pH < 3.0, 11.5% pH > 7.2), with acute acidification enhancing toxic metal solubility (Fe, Pb by 3-5×), and it posed distinct ecological risks. Our analysis reveals a distinct “highland mechanism triad” governing PM2.5 dynamics: (1) winter meteorological confinement amplifying dust-catalyzed sulfate formation (SOR = 0.68); (2) spring alkaline dust buffering (pH > 7.2) that titrates NH3 and suppresses nitrate formation (NOR < 0.10); and (3) summer photochemical oxidation constrained by chronic NH3 limitation within an oxidant-excess regime. Random Forest achieved optimal prediction for the chemically active inorganic fraction (RMSE = 6.63 μg/m3, R2 = 0.91) by learning regime-specific non-linearities, with local sensitivity analysis identifying Ca2+, SO42−, and Al as chemically sensitive drivers (S > 0.35) while revealing NH3’s seasonally variable influence (rank 15 in winter, significant in summer; S > 0.28), subsequently complemented by global SHAP analysis, which further revealed NO3− as the most robust predictor (ranking 1st–2nd) and captured NH3’s non-linear threshold effects (). Positive Matrix Factorization apportioned secondary aerosols (30.11%) within a unique alkaline–dust matrix. These findings demonstrate that highland PM2.5 inorganic chemistry operates through fundamentally different pathways than lowland photochemical haze, with acid-induced toxic metal activation providing a new target for ecological protection in this fragile ecosystem. Seasonally adaptive mitigation is required: concurrent SO2-NH3 control in winter, dust suppression infrastructure in spring, and agricultural NH3 capture in summer. This integrated framework provides a transferable methodology for air-quality management in alkaline dust-dominated, NH3-limited highland ecosystems (>2000 m). Full article
(This article belongs to the Special Issue Advances in Air Pollution Control and Air Quality Improvement in Chinese Megacity Clusters: From Formation Mechanisms to Mitigation Strategies)
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20 pages, 2875 KB  
Article
Characteristics and Sources of Particulate Matter During a Period of Improving Air Quality in Urban Shanghai (2016–2020)
by Xinlei Wang, Zheng Xiao, Lian Duan and Guangli Xiu
Atmosphere 2026, 17(1), 99; https://doi.org/10.3390/atmos17010099 - 17 Jan 2026
Viewed by 487
Abstract
Following the implementation of the Shanghai Clean Air Act, this study investigates the evolution of air pollution in central Shanghai (Putuo District) by analyzing continuous monitoring data (2016–2020) and chemical speciation of particulate matter (2017–2018). The results confirm a transition toward a “low [...] Read more.
Following the implementation of the Shanghai Clean Air Act, this study investigates the evolution of air pollution in central Shanghai (Putuo District) by analyzing continuous monitoring data (2016–2020) and chemical speciation of particulate matter (2017–2018). The results confirm a transition toward a “low exceedance rate and low background concentration” regime. However, short-term exceedance episodes persist, generally occurring in winter and spring, with significantly amplified diurnal variations on exceedance days. Distinct patterns emerged between PM fractions: PM10 exceedances were characterized by a single morning peak linked to traffic-induced coarse particles, while PM2.5 exceedances showed synchronized diurnal peaks with NO2, suggesting a stronger contribution from vehicle exhaust. Source apportionment revealed that mineral components (21.61%) and organic matter (OM, 21.02%) dominated in PM10, implicating construction and road dust. In contrast, PM2.5 was primarily composed of OM (26.73%) and secondary inorganic ions (dominated by nitrate), highlighting the greater importance of secondary formation. The findings underscore that sustained PM2.5 mitigation requires targeted control of gasoline vehicle emissions and gaseous precursors. Full article
(This article belongs to the Special Issue Advances in Air Pollution Control and Air Quality Improvement in Chinese Megacity Clusters: From Formation Mechanisms to Mitigation Strategies)
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