Search Results (82)

Nitrogen oxides (NO_X) are important precursors of ozone and secondary aerosols. Accurate and timely NO_X emission estimates are essential for formulating measures to mitigate haze and ozone pollution. Bottom–up and satellite–constrained top–down methods are commonly used for emission inventory compilation; however, they have limitations of time lag and high computational demands. Here, we propose a machine learning model, WOA-XGBoost (Whale Optimization Algorithm–Extreme Gradient Boosting), to retrieve NO_X emissions. We constructed a dataset incorporating satellite observations and conducted model training and validation in the Shandong region with severe NO_X pollution to retrieve high spatiotemporal resolution of NO_X emission rates. The 10–fold cross–validation coefficient of determination (R²) for the NO_X emission retrieval model was 0.99, indicating that WOA-XGBoost has high accuracy. Validation of the model for the other year (2019) showed high agreement with MEIC (Multi–resolution Emission Inventory for China), confirming its strong robustness and good temporal transferability. The retrieved NO_X emissions for 2021–2022 revealed that emission rate hotspots were located in areas with heavy traffic flow. Among 16 prefecture–level cities in Shandong, Zibo exhibited the highest NO_X rate (>1 μg/m²/s), explaining its high NO₂ pollution levels. In the future, priority areas for emission reduction should focus on heavy industry clusters such as Zibo and high traffic urban centers. Full article

Currently, China’s urbanization has entered a stage of high-quality development, and rapid urban growth has led to a series of environmental pollution issues, with haze pollution caused by delicate particulate matter (PM2.5) increasingly becoming a focal point for scholars. This paper focuses on Xi’an, Wuhan, Taiyuan, and Lanzhou, exploring the relationship between PM2.5 concentrations using methods such as the Pearson correlation coefficient (PCC), dominance analysis (DA), and ordinary least squares regression (OLSR). The results indicate that (1) Xi’an’s built environment is distributed radially, Wuhan is circular, Taiyuan is grid-like, and Lanzhou is strip-shaped; (2) Xi’an, Wuhan, Taiyuan, and Lanzhou exhibited different development patterns between 2014 and 2022, with Xi’an experiencing rapid urban expansion but lagging infrastructure, while Wuhan focused on improving post-urbanization quality. Taiyuan and Lanzhou advanced expansion and infrastructure construction simultaneously. (3) The regression coefficients of PM2.5 concentration concerning factors such as building density, green space density, road density, and water density in Xi’an are relatively high. In contrast, the regression coefficients of urban spatial structure factors in Wuhan, Taiyuan, and Lanzhou show consistency. This study provides a basis for reducing PM2.5 and explores the interaction and contribution relationship between urban spatial structure and PM2.5, offering a new research perspective for promoting urban sustainable development. Full article

As a new window for opening up in the new era, whether the China Free Trade Pilot Zones (PFTZs) can effectively balance urban economic development and environmental sustainability remains a topic that warrants further exploration. This study employs the PFTZ policy as a quasi-natural experiment and constructs a difference-in-differences model to empirically investigate the impact and mechanism of the PFTZ policy on haze pollution using city-level data from 2005 to 2020 in China. The study finds that: (1) the PFTZ policy significantly reduces haze pollution, and the results remain robust using the historical opening of treaty ports as an instrumental variable; (2) the PFTZ policy reduces haze pollution through the learning effect, demonstration effect, and agglomeration effect; and (3) the haze reduction effect of PFTZs is particularly pronounced inland and in areas with high public environmental awareness. The results directly address the key question of whether the PFTZ policy can foster sustainable economic development. It provides empirical evidence on how the PFTZ policy balances environmental sustainability and economic growth and draws policy recommendations for formulating more sustainable development strategies. Full article

As an important means of regulating pollution emissions, environmental regulation is crucial for reducing urban PM2.5. However, previous studies have mainly focused on the emission reduction effect of formal environmental regulations and neglected the role played by informal environmental regulations represented by environmental information disclosure. We employed a multiperiod difference-in-differences (DID) model to assess the effectiveness of EID policies in mitigating PM2.5 emissions and to investigate their abatement mechanism by focusing on green innovation and industrial structure. The findings indicate that the implementation of EID policies significantly reduces PM2.5 emissions. Mechanism tests reveal that EID promotes PM2.5 reductions by fostering green innovation and upgrading industrial structure. In addition, the impact of EID policy is more marked in resource-based cities and those located in interior regions. This study contributes to the reduction in urban haze emissions in China, offering empirical evidence and policy recommendations for the further implementation of environmental information disclosure. Full article

Impacts of air pollution are not limited to human health and ecosystems, but are also important for building materials. The main objective of this study is the quantification and mapping of air pollution effects on the materials, namely the soiling effect of modern glass. An integrated modelling approach was implemented to quantify and analyze the spatial distribution of glass soiling due to exposure to air pollution. The methodology is based on an integrated modelling approach (transportation-emissions-dispersion modelling) applied with high spatial resolution for Coimbra (Portugal) urban area and compared with national scale modelling, showing the important contribution of local pollution sources affecting spatial variability in the soiling effect. Air quality data from CAMS (Copernicus Atmosphere Monitoring Service) were used to quantify the soiling effect at national scale. The results are presented and analyzed in terms of haze. The results obtained at national scale suggest that the average time to reach a 1% haze is 320 days, and this time is reduced to 180 days in the most affected areas. However, urban scale modelling applied with a detailed characterization of local pollution sources in Coimbra provides significantly different results and reveals that in the most affected areas, near road traffic, 1% haze could be reached in approximately 80 days. The methodology proposed and implemented in this study provides relevant information for the maintenance and preservation of building materials and highlights the importance of integrated modelling with high spatial resolution for the assessment of the soiling effect in the built environment. Full article

Increasing urbanization in China has caused severe haze pollution in Chinese cities in recent years. This study investigates the impact of urban spatial development mode on haze pollution from the leapfrog spatial dimension. We constructed a dataset containing LandScan population dynamic statistical data, PM2.5 surface concentration data, and urban economic statistical data and adopted ordinary least squares (OLS) and instrumental variable methods. The findings indicate that the polycentric spatial structure within the city increases the PM2.5 levels, indicating that the urban monocentric spatial development mode is conducive to alleviating haze pollution. The use of the core explanatory variables, lagged by one and two periods, and of the number of Qing Dynasty walls as the instrumental variable confirm the robustness of the benchmark results. The heterogeneity analysis demonstrates that, in cities with underdeveloped public rail transit, the monocentric spatial development mode has a more obvious effect on reducing haze pollution. The results of the influence mechanism test show that the urban polycentric spatial development mode aggravates urban haze pollution, mainly by encouraging residents to travel by private transport, thereby increasing energy consumption. The obtained research results provide a sufficient basis for taking appropriate measures to govern haze pollution in Chinese cities from the perspective of polycentric spatial development mode. Full article

This paper uses panel data from 284 Chinese cities from 2004 to 2020 and employs a dynamic spatial panel Durbin model to re-examine the relationship between industrial agglomeration, environmental regulation, and haze pollution. It further adopts a dynamic spatial moderation effect model to explore the spatial regulatory mechanism of environmental regulation. The results show that both local and neighboring industrial agglomeration have a significant “inverted U-shaped” relationship with local haze pollution, and the scale cumulative optimization effect can only be effectively played after the industrial agglomeration level of the locality and neighboring areas exceeds the inflection point. Local environmental regulation significantly inhibits haze pollution, while neighboring environmental regulation plays a promoting role. The moderating effect of environmental regulation on the relationship between industrial agglomeration and haze pollution shows spatial heterogeneity in the local and neighboring areas. Local environmental regulation has a “U-shaped” non-linear moderating effect while neighboring environmental regulation has a positive linear moderating effect. Therefore, the government should pay attention to the joint effort and coordinated advancement of industrial agglomeration and environmental regulation to further reduce urban haze pollution and enhance urban air quality. Full article

In this study, online ambient volatile organic compounds (VOCs) were collected at an urban site of Zhengzhou in Central China during February 2018. The VOCs characteristics, source contributions and the Chinese New Year (CNY) effects have been investigated. During the sampling period, three haze periods have been identified, with the corresponding VOCs concentrations of (92 ± 45) ppbv, (62 ± 18) ppbv and (83 ± 34) ppbv; in contrast, the concentration during non-haze days was found to be (57 ± 27) ppbv. In addition, the festival effects of the CNY were investigated, and the concentration of particulate matter precursor decreased significantly. Meanwhile, firework-displaying events were identified, as the emission intensity had been greatly changed. Both potential source contribution function (PSCF) and the concentration weighted trajectory (CWT) models results indicated that short-distance transportation was the main influencing factor of the local VOCs pollution, especially by transport from the northeast. Source contribution results by the positive matrix factorization (PMF) model showed that vehicle exhaust (24%), liquid petroleum gas and natural gas (LPG/NG, 23%), coal combustion (21%), industrial processes (16%) and solvent usages (16%) were the major sources of ambient VOCs. Although industry and solvents have low contribution to the total VOCs, their secondary organic aerosol (SOA) contribution were found to be relatively high, especially in haze-1 and haze-3 periods. The haze-2 period had the lowest secondary organic aerosol potential (SOAp) during the sampling period; this is mainly caused by the reduction of industrial and solvent emissions due to CNY. Full article

Despite enhancements in pollution control measures in southwestern China, detailed assessments of PM_2.5 dynamics following the implementation of the Clean Air Action remain limited. This study explores the PM_2.5 concentrations and their chemical compositions during the winter haze period of 2017 across four major urban centers—Chengdu, Chongqing, Guiyang, and Kunming. Significant variability in mean PM_2.5 concentrations was observed: Chengdu (71.8 μg m⁻³) and Chongqing (53.3 μg m⁻³) recorded the highest levels, substantially exceeding national air quality standards, while Guiyang and Kunming reported lower concentrations, suggestive of comparatively milder pollution. The analysis revealed that sulfate, nitrate, and ammonium (collectively referred to as SNA) constituted a substantial portion of the PM_2.5 mass—47.2% in Chengdu, 62.2% in Chongqing, 59.9% in Guiyang, and 32.0% in Kunming—highlighting the critical role of secondary aerosol formation. The ratio of NO₃⁻/SO₄²⁻ and nitrogen oxidation ratio to sulfur oxidation ratio (NOR/SOR) indicate a significant transformation of NO₂ under conditions of heavy pollution, with nitrate formation playing an increasingly central role in the haze dynamics, particularly in Chengdu and Chongqing. Utilizing PMF for source apportionment, in Chengdu, vehicle emissions were the predominant contributor, accounting for 33.1%. Chongqing showed a similar profile, with secondary aerosols constituting 36%, followed closely by vehicle emissions. In contrast, Guiyang’s PM_2.5 burden was heavily influenced by coal combustion, which contributed 46.3%, reflecting the city’s strong industrial base. Kunming presented a more balanced source distribution. Back trajectory analysis further confirmed the regional transport of pollutants, illustrating the complex interplay between local and distant sources. These insights underscore the need for tailored, region-specific air quality management strategies in southwestern China, thereby enhancing our understanding of the multifaceted sources and dynamics of PM_2.5 pollution amidst ongoing urban and industrial development. Full article

This study selects the entropy method to measure the comprehensive index of green finance and 2011–2020 panel data covering 283 cities in China; describes spatial and temporal evolution, the migration of the centre of gravity, and discrete trends in green finance and urban haze pollution; and empirically examines the effect of green finance on urban haze pollution using static and dynamic spatial Durbin models. The study revealed that Chinese urban haze pollution significantly decreased during the sample period and that the hotspot emission area shifted to the northeast. Green finance experienced significant advancement, transitioning from a lower stage to a higher stage and becoming more geographically focused. Green finance mainly suppresses urban haze pollution through spatial spillover effects, and such spatial spillover effects change from positive to negative over time. Regarding regional heterogeneity, the effect on the western region is positive, the effects on the central and eastern regions are negative, and there is a spatial spillover effect “from promotion to inhibition” in the eastern region. Due to the heterogeneity in resource endowments, green finance in nonresource-based cities has a greater impact on haze pollution than does green finance in other cities, and in the long term, it has a significant inhibitory effect on haze pollution. This study reveals the effect of green finance on urban haze pollution from a dynamic perspective and, in doing so, it not only provides a new path for joint governance of haze pollution between cities but also provides more accurate guidance for the government to formulate policies for different regions and regions with different resource endowments. Full article

During rapid urbanization, microclimate environment deterioration through events such as haze pollution and heat waves has continuously occurred in cities, which greatly affects the living environment, production activities, and health of urban residents. Therefore, it is particularly necessary to explore methods for controlling and optimizing the urban microclimate environment. In this paper, based on the mechanism of the effect of urban spatial structure at street-level on the distribution of atmospheric particulate matter, an indicator system that can be employed to comprehensively describe and quantify urban morphological structure at street-level was constructed from eight aspects: the spatial morphology of street-valleys, intensity of land use and development, geometric structure of buildings, inhomogeneity of buildings, roughness of the underlying surface, distribution of ecological landscapes, 3D architectural landscape morphology, and ventilation potential. Furthermore, using satellite remote sensing images and vector thematic maps of Shanghai, indicator factors were quantified by applying GIS technique. The intrinsic mechanism of the influence of the urban morphology on the diffusion and transport of atmospheric particulate matter was comprehensively analyzed by combining statistical methods and data mining algorithm, and eight key dominant factors were identified that can be considered to improve the urban ventilation conditions and help control urban air pollution, namely, the land use intensity, urban canopy resistance, vegetation cover, spatial congestion rate, comprehensive porosity, height-to-gross floor area ratio, building density, and average building volume ratio. As such, according to the quantitative analysis results for various combinations of the dominant factors, a spatial optimization strategy at street-level that can help improve the urban air quality was proposed in terms of identifying the pathways through which urban spatial elements affect the distribution of particulate matter, i.e., controlling the source–flow diversion–flow convergence process. Full article

The popularisation of mobile information technology has provided access to the living habits and activity trajectories of residents and enabled the accurate measurement of the impact of urban haze disasters on residents’ lives, supporting urban haze risk response. Using the main urban area of Gaoyou City as a case study, this study identifies the spatial range and trajectory characteristics of the daily activities of residents in a haze disaster environment, based on air pollution monitoring and resident travel positioning data. We constructed an evaluation index system to measure the corresponding relationship between residential activities and haze disasters. The results indicate that the interference with residential activities and the adaptability of built environments are key indicators for evaluating urban resilience in haze environments, with weights of 0.57 and 0.43, and correlation indices of 0.67 and 0.81, respectively. The interference with residential activities and the adaptability of built environments exhibit spatial characteristics of cold and hot ‘multi-core’ agglomeration and ‘strip’ agglomeration, respectively. Specific indicators show that the residential activity exposure index is significantly influenced by the built environment factor index, with the vegetation coverage index showing a significant positive correlation (0.837) and the public transportation facility accessibility index showing a significant negative correlation (−1.242). Planning should focus on improving the adaptability of the built environment or reducing the interference with residential activities and enhancing the matching degree of the two at the spatial facility level. Full article

Environmental pollution significantly impacts the urbanization process. Despite the well-documented influence of urban scale on pollution, understanding of the specific effects of pollution at the urban scale remains limited. This study aims to further the understanding of the impact of pollution on urban scales by analyzing pollution variations and mechanisms. This study investigated city-level panel data in China, specifically assessing different pollutant emissions and their linkage to resident health. This study found that pollution has contrasting effects on urban land and population scales. It leads to expansion in urban land but has crowding-out effects on population scales. Notably, pollution from haze was found to increase urban mortality to a greater extent than pollution from industrial sources. Furthermore, this research found that increasing healthcare expenditures for urban residents can offset the negative impact of pollution on population growth and promote coordinated urbanization. This study emphasizes the importance of local government investment in medical services and public expenditures to mitigate the harmful effects of pollution on health, which can substantially prevent population outflows. Furthermore, stronger environmental protection measures can prevent urban land development sprawl resulting from pollution. In conclusion, this study highlights the need for a balanced approach to pollution control and urban development to achieve sustainable and high-quality urbanization. Full article

Haze pollution not only has negative impact on public health and air quality, but also has restricted China’s industrial upgrading and high-quality development, and Chinese urban agglomerations are one of the areas hardest hit of haze pollution. In the process of China’s economic transformation, local governments will adopt local protectionism, leading to market segmentation. This is a phenomenon that refers to the distortion of resource allocation by local governments for the sake of vested interests and the existence of segmentation in commodity markets. This behavior is considered to be one of the important factors causing haze pollution. As Yangtze River Delta urban agglomerations are considered to be one of the earliest, fastest growing, and most mature for market integration in China, there is a lack of empirical testing on the impact of market segmentation on haze pollution in this urban agglomeration. Based on urban panel data from the period of 1998–2018 and the market segmentation index calculated by the relative price method, we use the dynamic spatial Durbin model and generalized space two-stage least squares method to explore the effect of market segmentation in urban agglomeration on haze pollution; the results are as follows: (1) Market segmentation significantly exacerbates haze pollution, in other words, haze pollution will increase by 2.14% when market segmentation increases by 1%. (2) Cities with a high degree of market segmentation and high levels of haze pollution have the potential to reduce pollution through market integration in the future. (3) Market segmentation in surrounding regions also has a significant worsening effect on haze pollution in the region. The indirect effect of market segmentation is 3.67 times that direct effect, indicating that the spatial spillover effect of market segmentation on haze pollution is greater than its own impact. (4) Mechanism analysis finds that it will aggravate haze pollution by hindering economic scale, industrial structure, and technological progress when the degree of market segmentation is high. Full article

The rapid economic growth of China has caused significant adverse effects on the environment. Meanwhile, technological innovation, a fundamental driver of economic development and social progress, plays a pivotal role in mitigating haze pollution. This study comprehensively examines the influence of technological innovation on haze pollution in the Yangtze River urban agglomeration, using the STIRPAT model and analyzing research data from 2004 to 2020. Additionally, the study investigates the specific moderating role of urban spatial structure in the relationship between technological innovation and haze pollution. The findings reveal that technological innovation in the middle reaches of the Yangtze River urban agglomeration can effectively curtail haze pollution, and its impact extends to surrounding areas through spillover effect. The polycentric urban spatial structure significantly enhances the haze-reducing effect of technological innovation in the region. Notably, in cities with a strong level of environmental regulation, the urban spatial structure plays a substantial role in augmenting the haze-reducing impact of technological innovation. The policy implications of this research underscore the importance of continuous improvement in technological innovation within the middle reaches of the Yangtze River urban agglomeration. To address haze pollution in future development, the adoption of a polycentric development strategy and the establishment of sound environmental governance policies are recommended. Full article