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The Chinese authorities issued the "Guiding Opinions on Further Deepening the Reform of the Household Registration System" in 2014. This policy maintained strict controls on urban hukou in megacities, while slightly less stringent controls were applied in large cities. However, the restrictions on obtaining urban hukou were significantly relaxed in medium-sized cities and completely lifted in small cities. This study examines the causal effects and underlying mechanisms of hukou reform on urban innovation in cities of different sizes, using DID method based on a quasi-natural experiment by the 2014 hukou reform in China. The findings suggest that the hukou reform can significantly promote urban innovation, with particularly strong positive effects observed in large cities in the eastern region, small- and medium-sized cities in the central and western regions, as well as cities with favourable conditions for innovation. The primary mechanisms in which hukou reform influences urban innovation involve enhancing both the quantity and quality of urban labor force, as well as creating a better environment for innovation in cities. [ABSTRACT FROM AUTHOR]

AbstractIn limited-resourced Latin-American cities, adapting urban regulations and capturing value offers great potential for developing affordable land. We explored what counts for the significant variance in local land management implementation within Buenos Aires Metropolitan Region. Analysed municipalities successfully developed high-quality instruments to expand affordable land markets. However, local planning effectiveness does not find limits in the quality of planning itself. Depending on the municipalities’ relative location within the metro area, the national-level pipeline infrastructure plans, the politically driven finance choices, and divergent administration protocols favour or hinder the capacity to implement an effective urban land development strategy at local levels. [ABSTRACT FROM AUTHOR]

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Urban informality remains a central challenge for those engaged in understanding and transforming global South cities. There have been calls to develop new conceptual language geared to this challenge and much debate around the degree to which it might be subsumed within global urban theory. We argue that theories of informal urbanism need to be grounded in an understanding of how it works to sustain livelihoods, moving beyond studies of informal settlement, street vending and transport to understand the synergies, interrelations and interdependencies between them. Informal vending and transport provide employment and produce cheap goods and mobility; informal settlement produces affordable housing in key locations with access and mobility. 'Inventraset' is a portmanteau concept that links in formal ven ding, tra nsport and set tlement into a dynamic urban assemblage that is invent ive, tra nsgressive and set tled. This model is demonstrated through an empirical study of the spatial logic of the inventraset triangle within the megacities of Manila and Jakarta. Here the informal is normal, whether displayed in the intensities of transit nodes and street markets or camouflaged within zones of exclusion. This is not an 'informal city' but one where informal street vending, transport and settlement are geared to formal spatial and governance structures in different ways in different neighbourhoods − an assemblage of informal/formal and of vending/transport/settlement without which the urban economy would collapse. This is a call not simply to rename the informal but to understand it as a mode of production that is more than the inverse of the formal. [ABSTRACT FROM AUTHOR]

Concerns about climate change are driving the development of novel technologies for mitigation and adaptation. Some of them include electricity generating and water harvesting based on atmospheric humidity. The latter is already commercial and can generate 50 L of drinking water per day per capita for dozens of people; however, besides energy, operation requires sufficient levels and durations of humidity and temperature. Our study focuses on the 33 megacities of the world, characterising the humidity and heat stress regimes during the last decade, using data from meteorological stations in their vicinity, and ranking them by their exposure and vulnerability to intense heat stress and their suitability to use these moisture‐reliant technologies. Our findings indicate the dominance of severe heat stress conditions in megacities located in developing countries. Ranking the megacities according to the intensity and duration of the heat stress shows the annual, monthly and hourly courses. The five most affected are the cities of Chennai, Bangkok, Kolkata, Karachi and New Delhi. Seven megacities suffer continuous, at least 12 h, of intense heat stress during 1–4 months. The ranking also considered the level of income of the countries, hence their vulnerability. On an annual basis, approximately half of the megacities are highly suited for moisture‐reliant technologies, among them megacities ranked as the top three in exposure to intense heat stress conditions—Chennai, Bangkok and Kolkata. When focusing on the humid season, 27 out of 33 megacities (82%) obtain suitable conditions for the new technologies and thus can benefit from them, at least part of the year. The implementation of humidity technologies for green energy and clean water could be of great help as our world gets more populated, warmer with higher water demand, especially for populations with insufficient infrastructure and resources. [ABSTRACT FROM AUTHOR]

The idea of a modern city is hardly construed from the prism of religion, even though the Tower of Babel has been discursively engaged as an agenda of building a megacity with an interplanetary goal. During the development and expansion of Christianity, cathedrals, with their elaborate architectural aesthetics and frequently as the only spectacular buildings in the provinces, became sites of ecclesiastical and political power. In Nigeria, although the mainline churches followed the cathedralization pattern of Western Christianity, the Pentecostal churches preferred the establishment or construction of prayer camps as the earliest mode of development and sacralization of space. However, there is a transition from prayer camps to prayer cities, with the latter conceived as a deliberate urbanization policy that embraces modern facilities. Using ethnographic and analytical methods, I study the Mountain of Fire and Miracles Ministries' Prayer City near Lagos, Nigeria, a "city" built on and sustained by prayer culture, and a "city" that invigorates urban life. [ABSTRACT FROM AUTHOR]

Rapid morphological and socioeconomic changes have accelerated the urbanization process and urban land use transformation in China. Megacities comprise clusters of urban cities and exhibit both newly formed and well-developed urban land use development beyond administrative boundaries. It is necessary to distinguish the changing effects of spatial-varying driving factors on newly formed urban land uses from well-developed built-up areas in megacities. This study proposed a multi-spatial urbanization framework to quantify region-level socioeconomics, cluster-level ecological morphologies, and grid-level urban functional morphologies. A three-level Bayesian hierarchical model was developed to investigate the impacts of multi-spatial driving factors on urban land use transformation in megacities. The study period focused on the urbanization process between 2000 and 2018 in Guangdong–Hong Kong–Macao Greater Bay Area (GBA). Results revealed that compared with well-developed urban built-up land, changing impacts of three-level driving factors in urban land use transformation could be captured based on the proposed Bayesian hierarchical model. The region-level total population was associated with increasing possibilities in forming new residential land than the well-developed ones in 35 districts/counties/cities in GBA. Cluster-level ecological attributes with higher proportion, lower edge density of urban built areas, and lower-degree ecological complexity showed increasing probability on newly formed industrial and public land. Grid-level urban functional factors including public transportation density and shopping/dining distribution exhibited significantly decreasing probability (coefficients: −2.12 to −0.51) on contributing newly formed land uses compared with the well-developed areas, whereas business/industry distribution represented higher (coefficients: 0.99 and 0.15) and lower probabilities (coefficient: −0.22) of forming industrial/public land and residential land separately. This research shows a new attempt to distinguish multi-spatial morphological and socioeconomic effects in urban land use transformation in megacities. [ABSTRACT FROM AUTHOR]

Satellites provide global coverage for monitoring atmospheric greenhouse gases, crucial for understanding global climate dynamics. However, their temporal and spatial resolutions fall short in detecting urban‐scale variations. To enhance satellite reliability over urban areas, this study presents the first comprehensive analysis of long‐term observations of column‐averaged dry air mole fractions of CO2, CH4, and CO (XCO2, XCH4, XCO) using two ground‐based fourier transform infrared spectrometers, EM27/SUNs, in a megacity. With over 2 years of observations, our study shows that EM27/SUN measurements can effectively capture the daily and seasonal variability of XCO2, XCH4, and XCO over Seoul, a megacity with complex topography and various emission sources. In addition, we use the advantage of having multiple greenhouse gas satellites targeting Seoul to compare with the EM27/SUNs. Our study highlights the importance of EM27/SUN observations in Seoul to identify the need for improvements in satellites to monitor greenhouse gas behaviors and emissions in urban areas. Plain Language Summary: This study examines how accurately satellites can monitor greenhouse gases over urban atmospheres to understand climate change. While satellites are good at covering large areas, they struggle to detect changes in cities. To improve these setbacks, this study uses ground‐based instruments to measure greenhouse gases over 2 years and test satellite reliability over Seoul, a megacity with various emission sources as well as a complex terrain for observation. This study shows that the newly developed ground‐based instruments, EM27/SUNs, are effective in tracking daily and seasonal changes in greenhouse gas concentrations and are useful tools in improving the validity of satellite observations in urban areas. The study suggests that using ground‐based observations in addition to satellite data adapted for urban area monitoring is important for understanding greenhouse gas emissions in major cities like Seoul. Key Points: First results of long‐term EM27/SUN measurements and satellite comparisons over SeoulEM27/SUN effective in monitoring greenhouse gases and assessing validity of satellite measurements over urban areasSatellites need higher resolutions and locally validated algorithms for urban monitoring [ABSTRACT FROM AUTHOR]

We present a new method for estimating NOx emissions and effective lifetimes from large cities based on NO2 measurements from the TROPOspheric Monitoring Instrument (TROPOMI) (PAL dataset, May 2018–November 2021). As in previous studies, the estimate is based on the downwind plume evolution for different wind directions separately. The novelty of the presented approach lies in the simultaneous fit of downwind patterns for opposing wind directions, which makes the method far more robust (i.e., less prone to local minima with nonphysically high or low lifetimes) than a single exponential decay fit. In addition, the new method does not require the assumption of a city being a "point source" but also derives the spatial distribution of emissions. The method was successfully applied to 100 cities worldwide on a seasonal scale. Fitted emissions generally agree reasonably with the Emissions Database for Global Atmospheric Research (EDGAR) v6 (R=0.72) and are on average 14 % lower, while estimated uncertainties are still rather large (≈ 30 %–50 %). Lifetimes were found to be rather short (2.44 ± 0.68 h) and show no distinct dependency on season or latitude, which might be a consequence of discarding observations at high solar zenith angles (>65 °). The main limitations of this and similar methods are the underlying assumptions of steady state (meaning constant emissions, wind fields and chemical conditions) within about 100 km downwind from a city, which is probably a simplification that is too strong in order to reach higher accuracies. [ABSTRACT FROM AUTHOR]

The Alborz Mountains are among the areas exhibiting high tectonic and seismic activity in northern Iran. Studying key parameters of tectonic structures, including quantitative analysis and observational studies, in such active regions is essential to identify potential active faults and assess the consequent seismic hazards. This study focuses on seismicity and seismotectonics by analyzing seismic parameters, including b-value, mean seismic activity rate, earthquake recurrence time, seismic moment, and fractal dimension derived from micro and teleseismic data. The b-values vary between 0.6 and 1.1 in the tectonically active parts of the study area, corresponding with the reverse/thrust and strike-slip active faults. Large earthquakes might be prone to occur at 10–25 km depth because both catalogues show low b-values (b < 1.0) concentrations at this depth range. The high fractal dimension (> 1.5), high seismic activity rate, large seismic moment parameters, and its continuously increasing trend. Short recurrence periods (20–50 years) of M 6.5 events also emphasize the high seismic activity and high seismic hazard. On the other hand, the prevalence of low b-values is notably observed in areas encompassing densely populated cities such as Rasht, Lahijan, Amol, Babol, Sari, Behshahr, Gorgan, and the megacity of Tehran. Furthermore, we have identified asperities where the Gorgan Plain, the Khazar, and the Alamutrud Fault Zones are located. These findings emphasize the seismic hazard potential in the identified areas and urban centers within the study area. Therefore, particular attention should be directed towards areas exhibiting low b-values when assessing and mitigating seismic hazards. It underscores the necessity for additional focus on seismic hazard assessment and implementation of mitigation strategies in the Alborz region. [ABSTRACT FROM AUTHOR]

This paper argues for normative visioning as an underdeveloped component of adaptation planning. Multi-stakeholder and normative approaches to future visioning offer generative moments when creativity can meet the power to act required for critical, including transformative, adaptation. Including normative methods with community and city actors in adaptation planning allows for alternative narratives of development to arise as a basis for deeper conversation and potential action on the root causes of vulnerability and risk. A specific visioning approach is tested for four megacities – Istanbul, Kathmandu, Nairobi and Quito. Relations between current and future states of development and resilience are found to be both aligned (congruent or contingent) and in opposition (countervailing or constrained) shaping strategy for policy setting. These data are combined with additional work from London, Kolkata, New York and Lagos to pilot a City Resilience Challenge Index (CRCI), indicating to policy-makers whether and how cities are currently moving away from, rather than towards, envisioned trajectories of vulnerability reduction and adaptation. In the future, the CRCI might provide a global tool to track the progress of cities towards climate resilient development and, by doing so, to increase ambition and galvanize action. [ABSTRACT FROM AUTHOR]

Ebenezer Howard is one of the foundational figures of town planning. His Garden Cities of To-morrow envisions a Utopian synthesis of the urban and the rural to enhance the well-being of residents, in contrast to the industrial megalopolis of the late 19th century. While realized Garden Cities took many forms different from Howard's original layout, this is the one we find in the urban roots of the deep past. About 4350 BCE we see the formation of large, circular, decentralized settlements in what is today central Ukraine. Elsewhere, in the Brazilian Amazon between 1200 and 1600 CE, we see a transformation of the jungle into a vast park landscape filled with clusters of circular settlements, with horticultural land-use in between them. In addition to similarities in planning, these past settlements also involve the social aspect of countering inequality and fostering freedom and cooperation. This paper explores the possibility of Garden Cities in the past and the implications of decentralized 'rurban' landscapes from the deep history perspective of archaeology. [ABSTRACT FROM AUTHOR]

There are thousands of volatile organic compound (VOC) species in ambient air, while existing techniques can only detect a small part of them (approximately several hundred). The large number of unmeasured VOCs prevents us from understanding the photochemistry of ozone and aerosols in the atmosphere. The major sources and photochemical effects of these unmeasured VOCs in urban areas remain unclear. The missing VOC reactivity, which is defined as the total OH reactivity of the unmeasured VOCs, is a good indicator for constraining the photochemical effect of unmeasured VOCs. Here, we identified the dominant role of anthropogenic emission sources in the missing VOC reactivity (accounting for up to 70 %) by measuring missing VOC reactivity and tracer-based source analysis in a typical megacity in China. Omitting the missing VOC reactivity from anthropogenic emissions in model simulations will remarkably affect the diagnosis of sensitivity regimes for ozone formation, overestimating the degree of VOC-limited regimes by up to 46 %. Therefore, a thorough quantification of missing VOC reactivity from various anthropogenic emission sources is urgently needed for constraints of air quality models and the development of effective ozone control strategies. [ABSTRACT FROM AUTHOR]

Air quality degradation due to high levels of atmospheric particulate matter (PM) of various size fractions and the associated potentially toxic trace elements (PTEs) is a global concern. This article provides a thorough review and analysis of the temporal and spatial distribution of PM and PTEs in Bangladesh, offering a comprehensive assessment with other megacities worldwide based on existing literature. This study provides insights into the sources and transport mechanisms of PM and their link to human health. The level of PM was consistently high in Dhaka (capital of Bangladesh), with occasional higher levels in the surrounding cities. Different functional areas within Bangladesh show varying levels of PM, with total suspended particulates (TSP) being notably prevalent. When compared to megacities worldwide, African and Asian megacities, like India, Pakistan, Nigeria, and Egypt, exhibited higher PM concentrations. The concentration of PM-associated PTEs varies significantly among megacities and PM10 tends to have relatively higher concentrations of PTEs compared to other fractions in Bangladesh. Pb in ambient air was found across most megacities, with a temporal increase in Bangladesh. TSP exhibited the highest relative Pb content, followed by PM10 and PM2.5. Temporal factors, geographic locations, meteorological conditions, and anthropogenic activities contribute to the variation in PM and associated PTEs concentration in Bangladesh and global megacities. Ultimately, this study would aid policymakers in assessing the magnitude of PM pollution in Bangladesh compared to other megacities considering regional factors. [ABSTRACT FROM AUTHOR]

The COVID‐19 pandemic perturbed air pollutant emissions as cities shut down worldwide. Peroxyacyl nitrates (PANs) are important tracers of photochemistry that are formed through the oxidation of non‐methane volatile organic compounds in the presence of nitrogen oxide radicals (NOx = NO + NO2). We use satellite measurements of free tropospheric PANs from the Suomi‐National Polar‐orbiting Partnership Cross‐track Infrared Sounder (CrIS) over eight of the world's megacities. We quantify the seasonal cycle of PANs over these megacities and find seasonal maxima in PANs correspond to seasonal peaks in local photochemistry. CrIS is used to explore changes in PANs in response to the COVID‐19 lockdowns. Statistically significant changes to PANs occurred over four megacities: with decreases over Los Angeles and Delhi, and increases over Mexico City and Beijing in the winter. Our analysis suggests that large perturbations in NOx may not result in significant declines in NOx export potential of megacities. Plain Language Summary: The COVID‐19 pandemic led to the lockdown of urban centers worldwide, drastically perturbing the concentrations of global air pollutants. Peroxyacyl nitrates (PANs) are important photochemical pollutants formed from reactions between NOx and volatile organic compounds, which were substantially reduced during the pandemic. We use satellite measurements of PANs from the Suomi‐National Polar‐orbiting Partnership Cross‐track Infrared Sounder in the free troposphere over and surrounding eight of the world's megacities. Seasonal cycles of PANs are pronounced and the seasonal maxima correspond to seasonal peaks in local photochemistry. Significant changes to PANs in response to COVID‐19 occurred over four out of the eight cities: PANs decreased over Los Angeles and Delhi, and PANs increased over Mexico City and Beijing in the winter. Our results indicate that large changes in NOx may not result in equally significant changes to PANs and the NOx export potential of megacities. Key Points: There are pronounced seasonal cycles of peroxyacyl nitrates (PANs) over each megacity that align with seasonal maximums in photochemistryObserved free tropospheric mixing ratios of PANs during COVID‐19 were significantly different over four out of eight surveyed megacitiesSensitivity of free tropospheric PANs to the abundance of precursors is seasonally dependent in some locations [ABSTRACT FROM AUTHOR]

The determinants of smartphone use for urban transportation purposes in developing countries, particularly in the cities of the Middle East and North Africa, have not been thoroughly investigated so far. This study aims to clarify the individual, mobility, and perception-related correlates of smartphone use specifically for ordering vehicles via ride-sourcing in medium-sized and large cities as well as the megacities of the region. The four cities of Cairo and Alexandria in Egypt and Beirut and Jounieh in Lebanon were taken as casestudy cities. An overall sample of 3,285 face-to-face interviews was undertaken between late 2022 and early 2023 using a questionnaire focusing on individual, household, mobility, and perceptions of the respondents. The research depends on a chi-square test of independence and Binary logistic regression to answer three research questions: Are the levels of smartphone use for transportation purposes significantly different in the countries of Egypt and Lebanon? What are the correlates of smartphone use for transportation purposes in the four casestudy cities? What are the differences among the correlates of smartphone use for transportation purposes in the four case-study cities? The results of a Chisquare test of independence show that there is a highly significant difference between the smartphone use levels for transportation purposes among the four case-study cities: in subsamples in the Egyptian and Lebanese capitals, there is a stronger tendency to use smartphones for transportation. Moreover, the model fit based on Binary Logistic regression shows that age, trip generation for non-commute purposes, perceived ease of using ride-sourcing apps, perceived security when using public transportation, education status, and gender are significantly correlated with smartphone use. These explanatory variables function somehow differently in the case-study cities, but in general, there are strong similarities among the four cities. In conclusion, the results of this study can be used to reduce personal car use and strengthen shared mobility in the cities of the Middle East and North Africa region. [ABSTRACT FROM AUTHOR]

Urbanization contributes to declines in biodiversity of moths, but how it acts in megalopolises is unclear. In this study, I hypothesized that relative abundance of species within the family Saturniidae changes within megalopolises in eastern and midwestern North America. After compiling records from iNaturalist.org, I assessed 3,272 saturniid observations in areas of low and high human population density around East Coast and Midwest megalopolises including New York City, Philadelphia, Baltimore, Washington, and Chicago. From rural counties to cities, observations of Antheraea polyphemus increased by 15% while those of all other saturniids decreased by 63%–99%, depending on species. Species with greatest percentage decrease were Dryocampa rubicunda and Anisota senatoria. In cities, observations of A. polyphemus surpassed those of all other saturniids combined. These observations were nearly five times greater than observations of Actias luna, the saturniid with the next highest number of observations. By contrast, in rural counties, observations of the three saturniids (A. luna, A. polyphemus and Eacles imperialis) with the most observations differed by 25% or less. The proportion of saturniid observations specific to A. polyphemus more than doubled from rural counties to cities in each of the five metropolitan regions and in each of New York City's five boroughs except for the borough of Staten Island. The proportion of saturniid observations specific to A. polyphemus was essentially the same in Staten Island compared to less populous rural counties outside the city. Expansive tracts of natural forest in Staten Island likely blunted increases in abundance of A. polyphemus relative to other saturniids. Relative abundance of A. polyphemus in megalopolises increased in proportion to human population density on a subcontinental scale. On a local scale, environmental conditions potentially moderated this increase. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to create a methodological approach for identifying priority areas for science and technology (S&T) development and its empirical application within the city of Moscow. This research uncovers a wide range of multicultural and multidisciplinary global trends that will affect the development of major cities in an era of complexity and uncertainty, including the inherent complexity of urban contexts, demographic and socioeconomic trends, as well as scientific and ecological factors. Design/methodology/approach: The methodological approach is based on classic foresight instruments. Its novelty lays in the blending of qualitative and quantitative methods specially selected as the most appropriate for the identification of S&T areas in an era of complexity and uncertainty, including horizon scanning, bibliometric analysis, expert surveys and the construction of composite indexes with respect to the scope and resources of the research and the selected object for empirical application – Moscow, which is one of the world's largest megacities. The analysis was performed for the period of 2009–2018 and expert procedures took place in 2019. Findings: As a result, 25 global trends were identified, evaluated and discussed over the course of an expert survey and subsequent expert events. Ten priority areas of S&T development were determined, including 62 technological sub-areas within them and the most important market niches for all identified technological sub-areas, which could be useful for the world's megacities. The results of this study are illustrated using the construction sector. Based on the conducted research and results, a list of recommendations on S&T policy measures and instruments were suggested, including the creation of the Moscow Innovation Cluster, which by the end of 2023 contained more than 6,000 projects and initiatives, selected using the findings of this investigation. Originality/value: This research contributes to the existing literature and research agenda of setting priorities for S&T development and shows how it can be done for a megacity. The blended foresight methodology that was created within the study satisfies the criteria of scientific originality, is repeatable for any interested researcher, is applicable to any other city in the world and demonstrates its high efficiency in empirical application. It could be used for creating new agenda items in S&T policy, setting S&T priorities for a megacity and integrating the results into decision-making processes. This study provides recommendations on the further implementation of the designed methodology and results into a policymaking system. Moreover, the example of the Moscow Innovation Cluster, which was created based on the results of our research, demonstrates these recommendations' practical significance in real life, which is quite valuable. The limitation of this study is that it is not devoted to urban planning issues directly or the promotion of R&D areas; it is about setting promising S&T priorities in an era of complexity and uncertainty for megacities. [ABSTRACT FROM AUTHOR]

The importance of sustainable transport development is being increasingly realised in China. However, the understanding of social sustainability in the transport sector remains inadequate. Transport social impact assessment (SIA) at the local level, especially for small- to medium-sized cities, lacks systematic guidance. As a starting point for improving social sustainability in the transport sector, this research explores transport SIA practices in different-sized Chinese cities. Following a critical review of transport planning and appraisal documents collected from 83 sample cities in mainland China, 5 categories were identified based on the characteristics of their transport SIA practices. It was found that except for a few megacities, transport SIA in Chinese cities is generally weak, compared to developed countries. SIA has received little attention and had limited influence on decision-making in transport planning in China. Current guidance on transport SIA in China is relatively general and ambiguous compared to many developed countries, an established transport SIA framework and indicator set for local governments to refer to are lacking. The disparities in transport SIA among different-sized Chinese cities and different project types are significant. Interviews with Chinese transport practitioners were conducted to further explore the gaps in transport SIA practices and the potential for improvement. Based on the interview analysis, key aspects for improving transport SIA practices in China have been provided. [ABSTRACT FROM AUTHOR]

PM2.5 is one of the major contributors to air pollution in India, resulting in poor air quality and human health issues. The current study explores the applicability of TTAinterfaceTrendAnalysis (an 'R' language-based Graphical User Interface package) in estimating the annual and month-wise trends in PM2.5 over five Indian megacities (New Delhi, Kolkata, Mumbai, Hyderabad, and Chennai). The package offers a one-stop solution for various statistical analyses such as data imputation, outlier detection, trend analysis, data smoothing, diagnostic tests, etc. The trends are estimated using seven (2014–2020) years of PM2.5 data. All estimated month-wise trends of PM2.5 over the study cities were found to be statistically non-significant. Annual trends (both with and without applying data smoothing techniques) were found to be statistically significant with magnitudes ranging between − 0.27 and − 5.2 µg m−3 y−1 (negative sign indicates a declining trend). Autocorrelation analysis and normality tests are also conducted using the inbuilt options of TTAinterfaceTrendAnalysis. Results obtained are thoroughly discussed and compared with those of similar contemporary studies. To our knowledge, the current study is the first to apply TTAinterfaceTrendAnalysis for quantifying long-term trends in PM2.5. The sensitivity of the trend estimates due to the inclusion of COVID-19 lockdown PM2.5 data was also examined. The net impact of lockdown on the PM2.5 long-term trend ranged between − 0.13 and 2.29 µg m−3 y−1 across the study cities. [ABSTRACT FROM AUTHOR]

Enhanced ozone (O3) pollution has emerged as a pressing environmental concern in China, particularly for densely populated megacities and major city clusters. However, volatile organic compounds (VOCs), the key precursors to O3 formation, have not been routinely measured. In this study, we characterize the spatial and temporal patterns of VOCs and examine the role of VOCs in O3 production in five cities (Dongying (DY), Rizhao (RZ), Yantai (YT), Weihai (WH), and Jinan (JN)) in the North China Plain (NCP) for two sampling periods (June and December) in 2021 through continuous field observations. Among various VOC categories, alkanes accounted for the largest proportion of VOCs in the cities. For VOCs, chemical reactivities, aromatic hydrocarbons, and alkenes were dominant contributors to O3 formation potential (OFP). Unlike inland regions, the contribution to OFP from OVOCs increased greatly at high O3 concentrations in coastal regions (especially YT). Model simulations during the O3 episode show that the net O3 production rates were 27.87, 10.24, and 10.37 ppbv/h in DY, RZ, and JN. The pathway of HO2 + NO contributed the most to O3 production in JN and RZ, while RO2 + NO was the largest contributor to O3 production in DY. The relative incremental reactivity (RIR) revealed that O3 formation in DY was the transitional regime, while it was markedly the VOC-limited regime in JN and RZ. The O3 production response is influenced by NOx concentration and has a clear daily variation pattern (the sensitivity is greater from 15:00 to 17:00). The most efficiencies in O3 reduction could be achieved by reducing NOx when the NOx concentration is low (less than 20 ppbv in this study). This study reveals the importance of ambient VOCs in O3 production over the NCP and demonstrates that a better grasp of VOC sources and profiles is critical for in-depth O3 regulation in the NCP. [ABSTRACT FROM AUTHOR]

This article investigates the processes and politics of slum demolitions in the megacity of Mumbai. Scholars of subaltern urbanism have celebrated the political agency and entrepreneurial ability of the metonymic slums in Mumbai. This article argues instead that paying close attention to the dynamics of the lived realities within informal settlements directs us to the limits of ethnographic and archival imagination where fixers operating within the 'para-legal' are practicing a new subaltern urbanism, one that is attentive to the complexity of community within the metonymic slum. Through a detailed analysis of the practices of two fixers, this article shows how, by placing themselves at crucial nodes in the demolition and rehabilitation process, the fixers, on the one hand, were able to delay the displacement of residents; on the other, they created hierarchies in the distribution of resettlement benefits. Focusing on the quotidian practices of fixers operating within the demolished informal settlement brings forth a complicated and contradictory politics that ensure the existence of diverse non-privatized land tenures in the city. [ABSTRACT FROM AUTHOR]

We present a new method for estimating NOx emissions and effective lifetimes from large cities. As in previous studies, the estimate is based on the downwind plume evolution for different wind directions separately. The novelty of the presented approach lies in the simultaneous fit of downwind patterns for opposing wind directions, which makes the method far more robust (i.e. less prone to local minima with nonphysically high or low lifetimes) than a single exponential decay fit. In addition, the new method does not require the assumption of a city being a 'point source', but derives also the spatial distribution of emissions. The method was successfully applied to 100 cities worldwide on seasonal scale. Fitted emissions generally agree reasonably with EDGAR v6 (R=0.76) and are on average 16 % lower, while estimated uncertainties are still rather large (≈ 30–50 %). Lifetimes were found to be rather short (2.44±0.68 h) and show no distinct dependency on season or latitude, which might be a consequence of discarding observations at high solar zenith angles (>65°). Main limitations of this (and similar) methods are the underlying assumptions of steady state (meaning constant emissions, wind fields and chemical conditions) within about 100 km downwind from a city, which is probably a too strong simplification in order to reach higher accuracies. [ABSTRACT FROM AUTHOR]

Precipitation induced by tropical cyclones (TCs) over cities is associated with both TC duration and urbanization; however, observational evidence of the impacts of TC duration and urbanization on precipitation in megalopolises is limited. In this study, the Yangtze River Delta (YRD) of eastern China is taken as a typical region because this region has been experiencing both rapid urbanization processes and frequent TC attacks. During 1979-2018, we find reduced translation speed and increased meandering of TCs over the YRD, resulting in increased TC duration and the proportion of TC stalling in this region. The correlation between TC duration and TC-induced precipitation amount is significant across the YRD region but is relatively weak in areas with faster urbanization expansion rates. Long-term increases in TC-induced precipitation are found in both rural and urban areas but are larger for urban areas. Urbanization plays an important role in enhancing TC-induced precipitation over urban areas of the YRD region. Areas with faster urbanization expansion rates and longer TC durations have larger TC-induced precipitation, suggesting that urban expansion and TC duration jointly amplify TC-induced precipitation. Our findings suggest that urban planners, in areas potentially affected by TCs, should consider adaptation measures to mitigate the impacts of urban rainstorms amplified by the combined effects of TCs and urbanization. [ABSTRACT FROM AUTHOR]

We study how a significant relaxation of internal migration restrictions affects labor market outcomes of incumbent migrants and natives, exploiting the 2014 hukou reform in China, which substantially removed the migration barriers of cities with an urban population below 5 million (nonmegacities). Using a difference-in-differences method, we find that migrants' wages in nonmegacities experienced approximately a 2.6%–7.9% decline relative to that in megacities after the policy. The policy had nonnegative impacts on the wages of natives in nonmegacities. These results suggest that the downward wage pressure imposed by new migrants falls primarily on incumbent migrants rather than on natives. [ABSTRACT FROM AUTHOR]

This study assessed the regional differences of PM2.5 (fine particulate matter) concentration and secondary components in China. Through chemical analysis (Thermal/Optical Carbon Analyzer and ion chromatography) and statistical tools (SPSS and Origin software), PM2.5 samples' concentration and main components were estimated and compared in Tianjin and Guangzhou in December 2016. The average PM2.5 mass concentration was 148 μg/m3 in Tianjin and 62 μg/m3 in Guangzhou, indicating heavy air pollution in both cities. Organic carbon constituted 15% of PM2.5 in Tianjin, while that accounted for 25% in Guangzhou. The concentration of the secondary organic carbon accounted for 40% and 33% of organic carbon in Tianjin and Guangzhou, respectively. The ionic components in Tianjin made up 49% of PM2.5, while those of Guangzhou were responsible for 36% locally. The sulfate oxidation ratio reached 0.41 in Tianjin and 0.53 in Guangzhou while the nitrate oxidation ratio was 0.23 and 0.14 in the two cities, respectively. These results indicated high secondary conversion rate in PM2.5 pollution in both cities and suggested that PM2.5 mass concentration could not fully reflect its environmental and health effects, and so more attentions should be paid to the effects of its components, especially secondary components. In addition, the results could provide a scientific basis for making policies concerning air pollution control and developing strategies of air quality improvement. [ABSTRACT FROM AUTHOR]

There are thousands of VOC species in ambient air, while existing techniques can only detect a small part of them (~ several hundred). The large number of unmeasured VOCs prevents us from understanding the photochemistry of ozone and aerosols in the atmosphere. The major sources and photochemical effects of these unmeasured VOCs in urban areas remain unclear. The missing VOC reactivity, which is defined as the total OH reactivity of the unmeasured VOCs, is a good indicator to constrain the photochemical effect of unmeasured VOCs. Here, we identified the dominant role of anthropogenic emission sources in the missing VOC reactivity (accounting for up to 70 %) by measuring missing VOC reactivity and tracer-based source analysis in a typical megacity in China. VOC reactivity from anthropogenic emissions will remarkably affect the diagnosis of sensitivity regimes for ozone formation, overestimating the degree of VOC-limited regime by up to 46 %. Therefore, a thorough quantification of missing VOC reactivity from various anthropogenic emission sources is urgently needed for constraints of air quality models and the development of effective ozone control strategies. [ABSTRACT FROM AUTHOR]

Understanding the relationship between city size and resilience is crucial for informed decisions on preparedness and interventions in building resilient cities. This study addresses this issue by dividing urban resilience into four components: stability, redundancy, resourcefulness, and connectivity. Using the above evaluation framework, we assessed the spatial–temporal variations in the relationship between city size and resilience in the Yangtze River Economic Belt from 2005 to 2020. The findings shows that, overall, resilience increased in the cities, with larger populations and spatial scales showing greater resilience, but both megacities and small cities experienced a decline in resilience. In terms of the four components of resilience, most of the region's cities have roughly equal connectivity and stability, but redundancy and resourcefulness vary by city size and location. Specifically, downstream and larger cities demonstrated better crisis resolution and innovation. The dominant coupling coordination states showed antagonism between population and resilience. Upstream areas experienced a mismatch between "low resilience" and "large population", while a moderate coordination existed between spatial scale and resilience. Further, it was found that factors hindering urban resilience varied according to city size. Cities with a population of <3 million faced low connectivity and limited transformation capacity. Those with a population of 3–5 million had moderate connectivity limitations, while cities with a population >5 million faced energy and aging population challenges. This study contributes to urban resilience discourse by providing a conceptual understanding and empirical analysis of the impact of city size on resilience. [ABSTRACT FROM AUTHOR]

Making the connection between the function and structure of networked systems is one of the fundamental issues in complex systems and network science. Urban traffic flows are related to various problems in cities and can be represented as a network of local traffic flows. To identify an empirical relation between the function and network structure of urban traffic flows, we construct a time-varying traffic flow network of a megacity, Seoul, and analyze its global efficiency with a percolation-based approach. Comparing the real-world traffic flow network with its corresponding null-model network having a randomized structure, we show that the real-world network is less efficient than its null-model network during rush hour, yet more efficient during non-rush hour. We observe that in the real-world network, links with the highest betweenness tend to have lower quality during rush hour compared to links with lower betweenness, but higher quality during non-rush hour. Since the top betweenness links tend to be the bridges that connect the network together, their congestion has a stronger impact on the network's global efficiency. Our results suggest that the spatial structure of traffic flow networks is important to understand their function. [ABSTRACT FROM AUTHOR]

Urbanization and industrialization of cities have resulted in elevated concentration of particulate matters and the compounds contained in them in the air. From among the compounds present in the air, polycyclic aromatic hydrocarbons are very important because of their carcinogenicity and potential hazardous effects on the environment. In this research, through active air sampling in 17 points of the air of the most industrial city of Iran, we dealt with the analysis, source identification, and risk assessment of PAHs within a one-year period. The air samples were taken using PTFE filter based on NIOSH and EPA-TO/13A guidelines and SKC pump that average of flow rate of 3 L/min on the PMI2.5 was performed. In order to achieve a logical outcome for decision-making on the policies of the studied metropolis to mitigate air pollution, meteorological parameters were also measured, and the effect of each of them was tested on PAHs using SPSS software. The results indicated that the concentration of PM2.5 particles within the one-year period was higher than the value set by WHO and EPA guidelines. On the other hand, across all of the measurement stations, PAHs compounds were observed, suggesting that PAHs are a common pollutant across the city of Karaj. The ΣPAHs concentration within one year was 8.72–16.11 ng/m3. Benzo (a) pyrene (BaP), one of the dangerous hydrocarbons to the human health, claimed an above standard concentration among the other compounds. It was also found that factors such as transport fleet, car fule, diesel car, burning of biomass and coal are sources of PAHs. Also, PAHs had a direct relationship with temperature and pressure. Humidity and wind speed had a negative and poor correlation with PAHs. Finally, the results of incremental lifetime cancer risk (ILCR) estimations indicated that the carcinogenicity risk values in the studied region are acceptable. [ABSTRACT FROM AUTHOR]

Due to the rapid urbanization and climate change, one of the pressing problems confronting Chinese cities lies in air pollution. Especially during recent years, most cosmopolitan cities in China suffer from thick smog caused by PMs. It is reported that such air pollution has close relations with traffic-related pollutants, such as NO2. Meteorological condition contributes significantly to long-range transport sources and has remarkable influences on the distribution of the above pollutants. Thus, it is necessary to quantitatively analyze such influential patterns. In this paper, taking Chengdu as an illustrative example, the meteorological and pollutant statistics in 4947 h are collected and fitted with 8 meteorological parameters of PM2.5, PM10, and NO2 through linear regression method. And data is analyzed and compared on the hourly, daily, weekly, and monthly basis, respectively. Results show that hourly and daily data focus on fluctuations that affected by multiple interferences other than meteorological influences. When hourly values of PM2.5, PM10, and NO2 exceed 175 μg/m3, 250 μg/m3, and 125 μg/m3, respectively, discrete values that cannot be explained by meteorological influences increase notably, while weekly and monthly variations illustrate more tendencies, and communicable patterns that decisively influenced by meteorology can be extracted among 3 pollutants. By comparing the results in 4 timescales, respectively, similar principal meteorological factors are involved in fitting processes. Thirdly, visibility (V), wind speed (WS), precipitation (P), and cloud condition (CC) are the most influential factors and served as main parameters in linear regressions within 4 timescales. Air temperature (AT) and dew temperature (DT) are less influential factors by daily and weekly data but are served as main parameters when it goes to hourly and monthly data and function as variables that signify tendency variances in linear regressions, while relative humidity (RH) and barometric pressure (BP) are lest influential factors and have limited effect on fitting results. This work can provide guidance and reference for urban planning optimization and air environment protection in cities with air quality control considerations impacted by local climatic conditions. [ABSTRACT FROM AUTHOR]

We examined the relationship between city size and environmental efficiency and found sequential growth of environmental efficiency in 282 Chinese cities from 2003 to 2019 and also tested the mechanism of industrial transfer. The empirical results show that as the period advances, the relationship between the environmental efficiency of cities and the city size changes from an upward-sloping straight line to a "U-shaped" structure, indicating that the urbanization advantages of megacities are shifting to large or medium-sized cities. This shift is the result of the industrial transfer. The government should refrain from excessive market interventions in industrial shifts. Simultaneously, it should facilitate population mobility in large cities and enhance public services for medium-sized cities. Small cities undergoing population decline should not be hindered. [ABSTRACT FROM AUTHOR]

Suburban railways in megacities exert a pivotal role in propelling urbanization and shaping urban agglomeration. However, previous study endeavors have overlooked the transformations occurring in urban expansion along suburban railways, with a particular dearth of attention on the spatio-temporal evolution of landscape ecology and urban function. Therefore, this study employs the megacity of Beijing as an example. It utilizes remote sensing and point-of-interest (POI) data spanning from 2008 to 2022 to construct an indicator system from two essential dimensions: urban form and function. We explored the spatio-temporal characteristics of alterations in urban expansion within the gradient buffer zone adjacent to the suburban railway network in Beijing. The results showed that: (1) The rates of urban expansion were highest in 2008–2013 and lowest in 2013–2018; moreover, suburban railways had the greatest impact on the built-up area within 2–4 km along the route, and the impact gradually decreased beyond 4 km. (2) The direction of urban expansion shifted northward in the direction of latitude and eastward in the direction of longitude from 2008 to 2022, with the shift in latitude being more distinct. (3) The number of urban functions gradually increased from 2008 to 2018, but the number of medical services suddenly increased and the number of other urban functions decreased from 2018 to 2022; in addition, urban functions other than scenic spots were mainly distributed in the main urban areas, with very few clusters distributed near stations. (4) The landscape shape index became more irregular and fragmented from the center along the route to the edge of the buffer zone from 2008 to 2013, and the degree of fragmentation was highest in the 2–4 km buffer zone. In summary, this paper analyzes the spatio-temporal characteristics of urban expansion along suburban railways through four indexes, namely expansion rate, expansion direction, urban function, and landscape shape, and the results of this study are of great significance to the development and planning of suburban railways in megacities. [ABSTRACT FROM AUTHOR]

This study investigates the development trend of smart-green cities, focusing on seven megacities in China. It addresses three issues that are common in urban green development, including the relationship between "smart" and "green", the scenario analysis of green development, and the uniqueness of megacities in green development. System dynamics modeling is applied. The simulation results reveal an "S"-shaped development curve for both aspects, indicating a gradual and accelerating growth pattern. Notably, the curve representing energy consumption lags behind the curve for smart city development by approximately three years. After 2030, when the smart city construction is expected to be completed, the proportion of the tertiary industry and investment in science and technology will play a significant role in limiting energy consumption. This study concludes by providing policy suggestions, including the need for long-term plans with phased targets, considering the specificity of megacities, and addressing external influences. [ABSTRACT FROM AUTHOR]

The expansion of impervious surface area (ISA) in megacities of China often leads to land surface temperature (LST) aggregation effects, which affect living environments by impacting thermal comfort levels, thus becoming an issue of public concern. However, from an urban–rural synchronous comparison perspective, the study of LST responses to ISA changes is still lacking in the central coastal megalopolises of China. To solve this issue, a collaborative methodology of artificial digitization—fully constrained least squares mixed pixel decomposition—split-window algorithm—PCACA model was established for Qingdao using land use dataset and remote sensing images. The conclusions are below. Long time series of land use monitoring indicated that the expansion ratios of urban and rural areas were 131.29% and 43.42% in the past 50 years (i.e., from 1970 to 2020). Within urban and rural areas, a synchronous ISA increase was observed, with ratios of +9.14% (140.55 km2) and +7.94% (28.04 km2), respectively. Higher ratios and area changes were found in the urban regions, and a similar ISA change pattern in both urban and rural regions was captured by the ISA horizontal epitaxial expansion and vertical density enhancement. Further, the horizontal gradient effect displayed that the mean LSTs were 28.75 °C, 29.77 °C and 31.91 °C in the urban areas and 28.73 °C, 29.66 °C and 31.65 °C in the rural areas in low-, medium-, and high-density ISAs. The vertical density effect showed that the LST change was 1.02 °C and 2.14 °C in the urban areas but 0.93 °C and 1.99 °C in the rural areas during the ISA-density transition from low- to medium- and from medium- to high-density, respectively. Potential surface thermal indicators were assessed, and the urban regions displayed higher sensible heat flux (280.13 W/m2) compared to the rural regions (i.e., 274.76 W/m2). The mechanism effect of the ISA changes on LST in the urban and rural regions was revealed. These findings form a new comparative perspective of the urban–rural synchronous change in the central coastal megalopolis of China and can provide a practical reference for relevant studies. [ABSTRACT FROM AUTHOR]

The synergistic development of metropolitan areas led by megacities is considered a driving force in achieving regional coordination and the high-quality development of urban agglomerations. Extant studies have often neglected the spatial structure of metropolitan areas under the guidance of megacities. This study sought to explore the radiation effect of central cities, the development capacity of metropolitan subcentral cities, and the intermediary role of metropolitan hub cities in the metropolitan area. Based on the modified gravitational model and social network analysis, we constructed a spatial connection network of the Shanghai metropolitan area with districts and counties as the basic research units and analyzed the characteristics from two perspectives: network hierarchy and network structure. Our results indicated the following: (1) The connection strength of the metropolitan area decreased from the center of the network to the periphery. (2) The polycentric pattern was gradually forming, but a significant gap remained between the radiation range and capacity of central and subcentral cities. (3) The clustering phenomenon in the metropolitan area was significant, and the degrees of internal connection and external radiation ability of each subgroup differed. (4) The core–edge structure as obvious, but its intermediary role in the network was relatively weak. Our findings revealed the spatial relationship pattern of metropolitan areas led by megacities and have implications for formulating scientific policies to promote the coordinated spatial development of metropolitan areas and the high-quality development of urban agglomerations. A high-quality urban agglomeration is highly significant, and coordination and balanced development among cities has become a pressing need. In recent years, many scholars have researched how to improve the quality of urban agglomeration development. The construction of metropolitan areas—the basic unit of urban agglomeration—plays a strategic role in urban agglomeration. Accordingly, analyzing the spatial connection networks in metropolitan areas led by megacities is necessary. In response, this study explored the network hierarchy and structure of a notable metropolitan area led by megacities, the Shanghai metropolitan area, to uncover valuable findings about the radiation effect of central cities, the development capacity of metropolitan subcentral cities, and the intermediary role of metropolitan hub cities in promoting the coordinated development of metropolitan areas. These findings offer useful insights for policymakers seeking to promote the coordinated spatial development of metropolitan areas, optimize their spatial structure, and promote high-quality urban agglomeration. [ABSTRACT FROM AUTHOR]

We employ the data of 290 cities in China from 2006 to 2019 as a research sample and use the Multi‐period DID method to test the policy shock of National E‐commerce Demonstration Cities (NEDC) pilots on high‐end service industry agglomeration. We find that after becoming pilot cities, the specialized agglomeration level of its high‐end service industry increases by about 14.1% on average, and the diversified agglomeration level decreases by about 2.7% on average. And NEDC policy can affect the spatial agglomeration of high‐end service industry through three channels: Enhancing the inclusiveness of digital finance, improving the degree of market competition, and promoting regional innovation ability. Moreover, NEDC policy has the characteristics of spatial heterogeneity. NEDC policy has a significant spillover effect on the specialized agglomeration of high‐end service industry in the first‐tier cities, while the second‐tier cities show the characteristics of diversification dispersion. In addition, NEDC policy has a more obvious impact on the agglomeration effect of high‐end service industry under the radiation and driving effect of megalopolis. [ABSTRACT FROM AUTHOR]

Pollution from vehicular emissions is a major cause of poor air quality observed in many urban and semi-urban towns and cities. As such, this study was conducted to assess air quality and the spatiotemporal distribution of vehicular and traffic-related pollutants in several air sheds of Lagos megacity, the economic nerve centre of Nigeria. A setup of low-cost air quality sensors comprising five (5) units was deployed between November 2018 and February 2019 within traffic corridors in the heart of the city. Diurnal variation of pollutants indicated that carbon dioxide (CO2) peaked during the early hours of the day, total oxide (Ox = NO2+O3) peaked at mid-day while carbon monoxide (CO) had two distinct peaks which correspond to morning and evening rush hours. Nitrogen dioxide (NO2) concentration peaked during evening hours. Average concentrations are NO2 (97.1 ± 9.7) ppb, Ox (78.6 ± 27.2) ppb, CO2 (450.1 ± 31.2) ppm, and CO (2285.63 ± 743.7) ppb. Average concentrations of pollutants were above thresholds set by the World Health Organization (WHO) except for NO2 which was within the range permissible limits. The implication of this is that the atmosphere is polluted due to elevated concentrations of airborne pollutants, an indication which is of both health and environmental concern. The air quality index (AQI) indicates that the quality of ambient air varies from good to very unhealthy for Ox, and unhealthy to very unhealthy for CO, while AQI for PM2.5 and PM10 showed hazardous at all the sampling locations except at UNILAG where it is unhealthy for the sensitive group. For all of the sampling sites, conditional bivariate probability function (CBPF) plots show a significant agreement with the location of known pollution sources. [ABSTRACT FROM AUTHOR]

We present a novel and efficient approach that enables the evaluation of environmental quality in cities worldwide using high-resolution satellite imagery, based on a new green index (GI) through multivariate analysis, to compare the proportion of urban green spaces (UGSs) with built and impervious surfaces. High-resolution images were used to perform a supervised classification of 25 districts in the city of São Paulo, Brazil. Only 11 districts showed higher urban forests, green spaces, green index, and green vs. built values, and impervious surface proportions with lower impervious and built spaces. On the other hand, the remaining districts had higher population densities and unfavorable conditions for urban ecosystem development. In some cases, urban green spaces were three-times smaller than the built and impervious surfaces, and none of the districts attained a high green quality index (0.75 to 1). Artificial intelligence techniques improved the precise identification of land cover, particularly vegetation, such as trees, shrubs, and grasses. The development of a novel green index, using multivariate statistical analysis, enhanced positive interactions among soil cover classes, emphasizing priority areas for enhancing environmental quality. Most of them should be prioritized by decision makers due to the low environmental quality, as identified by the low green index and worse ecosystem services, well-being, and health outcomes. The method can be employed in many other cities to enhance urban ecosystem quality, well-being, and health. The green index and supervised classification can characterize pastures, degraded forest fragments, and guide forest restoration techniques in diverse landscapes. [ABSTRACT FROM AUTHOR]

Urban skyways, in which an elevated pedestrian-friendly layer of the city is applied to the existing urban fabric, have evolved from radical conceptual proposals in the mid-twentieth century, such as the continuous monument by SuperStudio, to increasingly realised proposals over the last 30 years, such as the highline project in Manhattan. Developed as either networks that respond to harsh climatic conditions, or solutions that aim to reclaim part of the city for pedestrian use, their use has been additive rather than integrative, in most cases culminating in elevated walkways. This article proposes an alternative approach to the utilisation of urban skyways within existing cities, in which the question of habitation is a primary driver. The research involved the application of sequential evolutionary simulations, to locations in the city of Paris, as an algorithmic approach to achieve multiple conflicting objectives. The results demonstrate the value of urban skyways as habitable spaces that respond to the city as well as being informed by it, in which issues of overpopulation, lack of public space, climatic response and urban farmlands—all of which impact most megacities today—shape the urban decision-making process. [ABSTRACT FROM AUTHOR]

This article contributes to research on Lyotard and sounds by taking up the urban as an ensemble that is immediately a matter of sound and education, approaching pedagogy not as a tactic but as a sonic mode of and relation to thought. It begins by exploring the sounding state of the contemporary urban environment as it's organised around the production and circulation of information and knowledge. Hearing and listening in this urban setting are privatised such that the possibility of sonic interruptions is foreclosed. The article turns next to Jean-François Lyotard's writing on the urban, which positions urbanism as a system that demands exchange and communication and as a social form that doesn't avoid or repress interruptions, but rather consumes and absorbs them as sources of new accumulation. Connecting Lyotard's urbanism with his work on writing and sound, the article then articulates three forms of sonic pedagogy: hearing, listening, and not listening. In this pedagogical schema, the primary problem of the urban today is that hearing and listening dominate at the expense of not listening. This configuration positions students as deficient adults who must grow up as quickly as possible, thereby depriving the student of the ability to be and remain a student. The sonic pedagogies developed in the article, then, have the potential to resist the privatising listening practices of the urban that compel opacity into transparency and to potentially reconfigure the urban around exposure to thought and childhood. [ABSTRACT FROM AUTHOR]

In order to illustrate pollution characterization, source apportionment, and risk assessment of VOCs in Beijing, Baoding, and Shanghai, field observations of CO, NO, NO2, O3, and volatile organic compounds (VOCs) were conducted in 2019. Concentrations of VOCs were the highest in Beijing (105.4 ± 52.1 ppb), followed by Baoding (97.1 ± 47.5 ppb) and Shanghai (91.1 ± 41.3 ppb). Concentrations of VOCs were the highest in winter (120.3 ± 61.5 ppb) among the three seasons tested, followed by summer (98.1 + 50.8 ppb) and autumn (75.5 + 33.4 ppb). Alkenes were the most reactive VOC species in all cities, accounting for 56.0%, 53.7%, and 39.4% of ozone formation potential in Beijing, Baoding, and Shanghai, respectively. Alkenes and aromatics were the reactive species, particularly ethene, propene, 1,3,5-trimethylbenzene, and m/p-xylene. Vehicular exhaust was the principal source in all three cities, accounting for 27.0%, 30.4%, and 23.3% of VOCs in Beijing, Baoding, and Shanghai, respectively. Industrial manufacturing was the second largest source in Baoding (23.6%) and Shanghai (21.3%), and solvent utilization was the second largest source in Beijing (25.1%). The empirical kinetic modeling approach showed that O3 formation was limited by both VOCs and nitric oxides at Fangshan (the suburban site) and by VOCs at Xuhui (the urban site). Acrolein was the only substance with an average hazard quotient greater than 1, indicating significant non-carcinogenic risk. In Beijing, 1,2-dibromoethane had an R-value of 1.1 × 10−4 and posed a definite carcinogenic risk. [ABSTRACT FROM AUTHOR]

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Green areas are essential for life in cities and for the conservation of ecosystem services in the case of megacities such as Mexico City. Green areas mitigate air pollution, reduce the temperature, and promote infiltration to feed the aquifers that, in the case of Mexico City, supply 68% of the water. Additionally, food production and recreational usage are important for the population. In the years 2017 and 2018, the chemical composition of wet deposition in the southern part of Mexico City was analyzed, daily and weekly. The study area is located in the greenest part of Mexico City, an important site for water recharge and carbon sequestration. Mexico City, like other megacities of high- and low-income countries, faces serious problems of air pollution. The purpose of this study was to measure the amount of total nitrogen and sulfur that is available in a natural reserve located inside the National Autonomous University of Mexico, and conductivity, pH, rain volume, and anions and cations were analyzed as well. Eighteen months of data were analyzed in order to understand the atmospheric deposition in and anthropogenic influence on an urban green natural area from the southern part of the city. Although both stations are less than 2 km apart, there are significant differences in their chemical composition; however, no differences were found for precipitation and pH, indicating that each station provides a local contribution, depending on local events and sources. Samples included rain events match for both sampling sites, with 67% of the samples in the same rain event match. Nonetheless, when only volume is compared for each year, both tests showed no significant difference (pv = 0.520). Throughout the year, various rainfall rates occur at the CU-CCA and REPSA stations, and the rainy season presents during the May–October period; the median value registered for both monitoring stations was 780 mL, and maximal rainfall was 4780 mL presenting at the CU-CCA station. [ABSTRACT FROM AUTHOR]

The article analyzes the relationship between the shape of the city and the COVID-19 crisis. During the hegemony of the neoliberal pattern of capital accumulation, the capitalist city became a space for the production and reproduction of capitalist social relations. The shape of the city is composed of proletarian and bourgeois zones, and it is the stage for class struggle. Furthermore, the contemporary city has expanded beyond its biophysical limits and has become a megalopolis or a regional system of urban corridors. However, this expansion has led to the degradation of territories and the emergence of problems in social reproduction. The shape of the city has also generated destructive infrastructure and degrading urban metabolism. In this context, the neoliberal city presents itself as a total socio-environmental metabolic collapse and has contributed to the production of various pathologies, including infectious and chronic diseases. The article highlights diseases related to the mutagenesis or synthesis of new types of viruses, such as Sars-H5N1, H1N1, MERS, and Sars-CoV-2, which are generated due to the environmental degradation of territories. It is mentioned that institutional measures derived from pharmaceutical, nanotechnological, and biotechnological capital groups have exacerbated the problems related to living in the neoliberal city. Additionally, it is pointed out that the production of sick bodies is related to the global network of cities that constitutes the center of the capitalist world market. [Extracted from the article]