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Imported air pollution has a significant impact on urban air quality. Relevant studies have shown that many urban air pollution events are not resourced by local emissions but are imported by air pollution from surrounding areas transported across regions. The prevention and control of air pollution is very necessary. However, the existing supervision of urban air quality mostly relies on ground monitoring stations, which are extremely limited in time and space, and cannot satisfy continuous time-space air pollution research. Therefore, aiming at the problem of urban air pollution control, this paper used MERRA-2 reanalysis data and ground monitoring data to establish a "Time-Longitude-Latitude" three-dimensional pollution curve, and then a genetic algorithm was used to optimize its fitting. This study finally reconstructed the imported air pollution transmission route. This paper takes an air pollution event that occurred in Xuzhou City, China, on 12 January 2020, as an example. Through the analysis of aerosol optical depth (AOD), particulate matter (PM), wind speed, and other factors, we found the source, transmission route, and impact time of this pollution. We have verified the correctness and accuracy of the reconstructed contamination transport paths. It is proved that the method is universal and it can quickly and accurately restore the air pollution transmission route and identify the urban imported air pollution transmission entrance. This method will also provide strong data support for the division of responsibilities of environmental protection departments in various regions for severe air pollution transmission events and provide effective governance ideas for the prevention and control of imported air pollution in recipient cities. [ABSTRACT FROM AUTHOR]

With rapid urbanization, the economic agglomeration within cities is associated with severe air pollution. Urban spatial structure adjustment has been recognized as an effective strategy for improving air quality. However, the research on how to mitigate air pollution originating from economic agglomeration through urban spatial structure adjustment is unclear. Therefore, based on panel data for municipal cities in the Yangtze River Delta (YRD) region during 2008–2018, this study empirically tests the transmission mechanisms among economic agglomeration, urban spatial structure, and air pollution. We use the combination of the social network analysis (SNA) and two-stage least squares (2SLS) methods to verify the effect of economic agglomeration on air pollution. Economic agglomeration's indirect effect on air pollution through urban spatial structure is further tested using mediating effect model and cross-section comparisons. When exploiting an exogenous order rank of node city importance for instrument variable (IV), our finding shows that increasing economic agglomeration by 10% increases air pollution by 12%. In addition, in market forces, monocentricity brings about economic agglomeration's pollution effect, while polycentricity leads to agglomeration's environmental benefits improvement. However, a government-led exogenous polycentricity greatly mitigates economic agglomeration's pollution effect, while in cities with monocentricity, agglomeration slightly increases air pollution. Compared with market power, our paper stresses government intervention in promoting urban spatial structure in terms of polycentric development could be more helpful for improving agglomeration's environmental benefits in China's YRD region. [ABSTRACT FROM AUTHOR]

Based on the panel data of various daily air pollution indicators of 288 prefecture-level cities in China from January 1, 2015 to December 31,2018, this paper takes the first round of central environmental protection inspection (CEPI) as a quasi-natural experiment, and empirically analyzes its impact on urban air pollution by using multi-period difference-in-difference (DID) method. The results show that: (1) the first round of five batches of environmental inspection and two batches of "looking back" have significantly reduced the concentration of seven pollutants; (2) The first five batches of environmental inspection have a stronger impact on reducing air pollution than "looking back"; Moreover, in the short tel·in after the inspection, it still has a significant reduction effect on air pollution; (3) The impact of central environmental protection inspection on air pollution shows strong heterogeneity in different batches of inspections, urban scale and economic development level, as well as the air quality level of cities before the inspection. The research results of this paper provide corresponding policy recommendations and decision-making basis for the Chinese central government to further deepen the reform of environmental protection supervision mechanism and promote the emissions of multiple pollutants mitigation. [ABSTRACT FROM AUTHOR]

• A novel spatial general equilibrium model was constructed and the impact of air pollution on urban residents' welfare in China was studied. • Empirical study shows air pollution significantly reduces urban residents' welfare and migration cost reduces the negative impact of air pollution on the welfare of urban residents. • Policy suggestions suggested that air pollution should be balanced against the welfare of residents, and should not be cleaned up by "one size fits all" in the early stages of economic development. Air pollution and its effects are important issues of human society. However, few literatures on the effect of air pollution on urban residents' welfare considered the cost of migration. This paper constructs a novel spatial general equilibrium model and studies the impact of air pollution on urban residents' welfare in 274 cities at and above the prefectural level in China from 2007 to 2017, and investigates the role of migration costs. The theoretical analysis and empirical research show that air pollution has a significant negative impact on the welfare of residents. Further, the simulation results indicate that the reduction of migration cost and the improvement of air quality accounts for roughly 24.65% improvement of resident's welfare from 2007 to 2017 in China. Another conclusion is that there is an inverted U-shaped relationship between resident's welfare and air pollution. On another side, migration costs play a moderating role in the impact path of air pollution on residents' welfare. When the migration costs fall, it will help residents to move out of cities with poor air quality and improve the resident's welfare. The policy suggestions are as follows: (1) In the process of sustainable development, local governments need to coordinate the phased characteristics between air pollution and residents' welfare, effectively improve the livable degree of city and urban economic sustainability, and prevent the brain drain caused by excessive migration of residents. (2) Local governments should lower the migration costs between cities by deepening the reform of the household registration system, so as to promote the free flow of labor and ultimately improve the welfare of residents. [ABSTRACT FROM AUTHOR]

Urban air pollution is the most serious environmental pollution problem in China. It not only causes serious losses to our economy, but also brings great hidden dangers to the physical and mental health of urban residents. Therefore, it is urgent to prevent and control air pollution. Air quality prediction and forecasting must be carried out to prevent air pollution. Timely and accurate air quality prediction can not only help urban managers to make scientific and effective preventive measures, but also provide more healthy and safe travel strategies for urban residents. China's air monitoring system is gradually improving, its scale is expanding, and a large amount of air quality data is accumulating. With the rapid expansion of data scale, the traditional method of air quality prediction technology has been unable to deal with these massive data. In this paper, 365 sets of air pollutant data from January 1, 2018 to December 31, 2018 in Shen Zhen were used as experimental objects. The improved SAPSO algorithm and PSO algorithm were used to optimize the parameters of SVM model and construct the air quality evaluation model. By analyzing the classification results of air quality grade, selecting relevant data and using partial least squares, the correlation coefficient matrix is established for the classification results, and the pollutant factors affecting air quality in Shenzhen are obtained. The results are ideal, which provides a scientific theoretical basis for the prevention and control of air pollution and urban management planning. [ABSTRACT FROM AUTHOR]

Emissions from ships stand as one of the principal contributors to air pollution in coastal areas. China has implemented the Domestic Ship Emission Control Area (DECA) policy progressively since 2016 to alleviate sulfur oxide and particulate matter pollution in coastal cities by limiting the sulfur content in marine fuel oil. This study utilizes Synthetic Difference-in-Differences model to construct a counterfactual framework for evaluating the DECA policy effect on air quality of cities in the Yangtze River Delta, the Pearl River Delta, and the Bohai Rim region. Results revealed that DECA policy significantly reduced the urban sulfur dioxide (SO 2) concentrations of YRD, BR, and PRD regions by 9.93 %, 8.64 %, and 7.09 %, respectively. However, the policy's efficacy in restraining fine particulate matter (PM 2.5) concentrations was found to be non-significant. This study further estimated the dynamic changes in SO 2 concentration in coastal cities of different regions in the DECA coverage. The results showed that the DECA policy generally began to significantly reduce SO 2 concentration levels in the second year after implementation, and with the tightening of the DECA policy, the reduction effect followed a growing-and-then-falling trend. Finally, the paper offers policy recommendations to further reduce ship emissions, aligned with recent emission reduction advancements. • Assessing the impact of China's DECA on coastal urban air pollution using a synthetic difference-in-differences model. • DECA effectively reduces SO 2 concentrations in coastal cities, yet its control over PM 2.5 levels is limited. • The impact of DECA varies across regions, with the most significant effects in the YRD, followed by BR and the PRD. • Several policy recommendations are proposed to optimize the effectiveness of DECA. [ABSTRACT FROM AUTHOR]

Urban air pollution is an important issue facing China in the midst of rapid urbanization and economic development. To investigate the regional air quality characteristics and its drivers in Northeast China, this paper compares the spatial and temporal characteristics of air quality between cities and analyzes the influence of socioeconomic variables by using statistical analysis methods and geographic model. The results show that the air quality index (AQI) showed a downward trend in time and decreased from southwest to northeast in space. The duration of heavy pollution condition was not only controlled by the distribution of pollutant concentrations, but also influenced by the topography. Based on the mean concentrations of the 6 pollutants, 37 cities were divided into 4 categories by cluster analysis, reflecting the levels and characteristics of pollution. The level of industrialization was the most important cause for air quality, followed by the size of the city and the degree of economic development. The AQI predicted by geographic weighted regression model (GWR) showed a lower goodness of fit in developed cities, indicating that the factors controlling air quality are more complex in these regions. The influence of different socioeconomic metrics on AQI showed large spatial differences. AQI was more sensitive to variations in socioeconomic metrics in less developed small and medium-sized cities. This study provides a theoretical basis for revealing the causes of urban air pollution and formulating pollution control measures in Northeast China. [ABSTRACT FROM AUTHOR]

To investigate whether information infrastructure can improve air quality, this paper presents an empirical study based on urban data for 2015 to 2018. To analyse regional differences in the impact of information infrastructure on air pollution, we used full sample and subsample data to make estimates respectively. The results show that information infrastructure can significantly reduce air pollution. However, there are regional differences in this effect, which is only significant in the eastern part of China. Information infrastructure can reduce air pollution in two ways: improving the quality of traditional infrastructure and improving energy efficiency In addition, the robustness test results are consistent with the above results. Finally, we put forward some suggestions for the future construction and application of information infrastructure. • Measuring information infrastructure with the technological index. • Information infrastructure can significantly reduce urban air pollution. • Traditional infrastructure and energy efficiency can act as influence mechanisms. • Information infrastructure has different effects on air quality in different regions. [ABSTRACT FROM AUTHOR]

The urgent and global concern of environmental problems transcends local and regional boundaries, posing significant challenges for policymakers in developing countries. Amid conflicting economic and environmental goals, evaluating the efficacy of regulatory policies becomes increasingly critical. This study investigates the effectiveness of public policy in incentivizing developing nations to prioritize environmental regulation, with a specific focus on China's most recent environmental policy, the Ecological Environmental Protection Plan. Using multilevel modeling and difference-indifferences estimation with data from six of China's most populous cities between 2014 and 2019, we see evidence of air quality improvements following the implementation of the policy. Furthermore, we observe greater enhancements in air quality in the cities most affected by the institutional details of the policy. This shows that well-crafted public policy can improve air quality, providing crucial insights for policymakers and scholars alike. [ABSTRACT FROM AUTHOR]

Understanding the complex impact of air pollution is crucial to assessing exposure risk and defining public health policies in China. However, the evidence and hence knowledge of how urban activity responds to air pollution are limited. In this paper, we propose to use geotagged check-in records on Weibo, a Tweeter-like platform, to systematically investigate the effect of air pollution on urban activity. Based on panel models, we found clear evidence that such effect exists and varies between pollutants, visitors and residents, and different activity types. Typically, SO 2 has the largest impact, followed by PM 2.5 , NO 2 , and PM 10 ; local citizens' activities are more susceptible than visitors; leisure-related activity has a sensitivity at least twofold higher than work-related activities. Additionally, we tested hypotheses about the heterogeneous effect. We confirmed the role of Income and air quality, showing that people who live in richer and more polluted cities are more likely to experience the effects of air pollution. Specifically, people who live in a more polluted city with 100 unit increments in AvgAQI show on average the same sensitivity as those who live in a less polluted city and earn about 20.3 thousand yuan more in average Income. This reveals new insights about environmental injustice in China. By presenting a portrait of the spatial heterogeneity, we argued that environmental injustice in terms of air pollution is not just about the difference in exposure risk measured based on population distribution, rather the measurement should also consider the disparity derived from urban activity. Secondly, new injustice may arise in underdeveloped areas where manufacture industry is transferred to but people barely take avoidance behavior. Finally, the map also reveals the general neglect of the detrimental effect of light air pollution, which we speculate is partly due to China's comparatively low standard in governmental regulations. We believe our finding contributes significantly to exposure risk assessment and environmental justice debates. Hence it highlights the necessity and urgency of public healthy polices that spread the health consequence of air pollution, especially in the underdeveloped region. • Assessing exposure risk in China. • How urban activity responds to air pollution. • Using geo-tagged check-ins on Weibo, a Twitter-like platform, to investigate effects of air pollution on urban activity. [ABSTRACT FROM AUTHOR]

Will high-speed rail improve air quality, or make it worse? We use data of 270 cities in China from 2000 to 2018 to study the impact of high-speed rail (HSR) on air pollution. Based on the difference-indifference (DID) model, the regression results show that high-speed rail has reduced air pollution. But the results also show geographic differences. In underdeveloped areas, HSR will increase urban air pollution. The main mechanism is that HSR has affected the industrialization level and the entry of polluting enterprises. Especially in underdeveloped cities, HSR will increase industrial output and attract more polluting companies, which is not conducive to environmental governance. [ABSTRACT FROM AUTHOR]

Road traffic has changed as an essential source of influential urban air pollution in China. This study developed the Spatial Durbin Model to analyze the spatial spillover effects on air pollution caused by urban transportation infrastructure. The results show that high-emission areas congregate in the eastern region of China, which reflects noticeable spatial spillover effects and agglomeration characteristics as high-emission "clubs." When the traffic construction 1 1 Traffic construction area refer to the acreage of street area within the city in this paper. area increases by 1%, the air pollution level will increase 3.2% as accompanied. The improvement of the transportation infrastructure will bring out economic development. The speed of air pollution generated by the resources consumed by economic development is higher than that of technological improvement in the economic transition period to reduce air pollution. In contrast, economic growth and air pollution exacerbation represent a U-shaped curve connection. Most provinces remain in a stage where air pollution worsened with economic growth. [ABSTRACT FROM AUTHOR]

The development of urban agglomeration further deteriorates the air pollution status arising from urbanization. However, disparities in the urbanization process across different urban agglomerations may shape unique regional air pollution characters, and further complicate its driving mechanism. In this study, 11 urban agglomerations with different urbanization levels in China thus were chosen as the case study areas, to explore the spatiotemporal heterogeneity of PM2.5 and its potential driving difference related to the urbanization process from a multi-urban agglomeration perspective. The ground-monitored PM2.5 data and socioeconomic panel data (2015–2018) were processed using multiple statistical analysis methods, and the main findings of this study can be generated as followed: (1) significant spatial heterogeneity characteristics of PM2.5 pollution were recognized across the study area. And even though obvious improvement in the air quality during the study period, PM2.5 concentration remains at a high level for most of the urban agglomerations. (2) Urbanization process has a substantial contribution to regional PM2.5 pollution, and significant differences of the urbanization factors on PM2.5 concentration across the urban agglomerations assigned with various urbanization levels were emphasized. The significance of this study is to provide insight into the relationship of the urbanization process on PM2.5 pollution in different urban agglomerations and to offer a scientific basis for regional cooperation for air pollution regulation among multiple urban agglomerations. [ABSTRACT FROM AUTHOR]

The "comparative attitude" of urban agglomerations involves multidimensional perspectives such as infrastructure, ecological protection, and air pollution. Based on monitoring station data, comparative studies of multispatial, multitimescale and multiemission pollution sources of air quality on 19 urban agglomerations during the 13th Five-Year Plan period in China were explored by mathematical statistics. The comparison results are all visualized and show that clean air days gradually increased and occurred mainly in summer, especially in South and Southwest China. PM2.5, PM10 and O3 were still the main primary pollutants. PM2.5 is mainly concentrated in December, January and February, and PM10 is mainly concentrated in October–November and March–April. The O3 pollution in the Pearl River Delta and Beibu Gulf urban agglomerations located in the south is mainly concentrated from August to November, which is different from others from May to September. Second, from 2015 to 2019, the increasing rate of O3 concentration in any hour is higher than that of particulate matter (PM). Diurnal trends in O3 concentration in all directions also showed a single peak, with the largest increments that appeared between 13:00 and 16:00, while the spatial distribution of this peak was significantly regional, earlier in the east but later in the west. Third, this analysis indicated that the annual average air quality index (AQI) showed a gradually decreasing trend outward, taking the Central Plain urban agglomeration as the center. The ambient air pollutants are gradually moving southward and mainly concentrated in the Central Plains urban agglomeration from 2015 to 2019. Furthermore, in each urban agglomeration, the cumulative emission of PM2.5 is consisted of the four average emissions, which is approximately 2.5 times of that of PM10, and industries are the main sources of PM2.5, PM10 and VOCs (volatile organic compounds). VOCs and NOX increased in half of the urban agglomerations, which are the reasons for the increase in ozone pollution. The outcomes of this study will provide targeted insights on pollution prevention in urban agglomerations in the future. [ABSTRACT FROM AUTHOR]