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Trace elements generally contaminate wild fish, particularly in megacities, necessitating guided consumption practices. This study investigated the bioaccumulation of trace elements in wild fish from Chongqing City in June 2021. We evaluated their contamination and associated health risks to establish consumption guidance based on fish size. Our results indicate that the concentrations of Zn, Pb, Cr, and As were relatively high, with some fish exceeding the maximum residue limits. Herbivorous and pelagic fish generally exhibited lower bioaccumulation of most trace elements, except for Cr and As, which were higher in pelagic species. The contamination indices (Pi) for Cr, Pb and As were consistently above 0.2, indicating widespread contamination. The most contaminated fish typically measured around 19 cm in length and weighed approximately 90 g. Only the maximum target hazard quotients (THQ) for As, Cr, and Hg exceeded 1, with a notably high ratio of THQ(As) > 1, highlighting concerns over arsenic contamination. The THQ(As) remained below 1 for adults across all fish species, whereas for children, species such as Onychostoma sima, Pseudohemiculter dispar, and Parabramis pekinensis exceeded this threshold. Fish safe for adult consumption generally measured 13 cm in length and weighed 20 g, and for children, 16 cm and 25 g. Consequently, selecting larger fish is likely to reduce the consumption of contaminated fish, thereby decreasing health risks to the public. The centralization of contaminated fish with high risk in specific size range confirmed fish size could be used to gauge the contamination and health risk of fish. [ABSTRACT FROM AUTHOR]

This study aims to assess how the construction patterns within residential communities influence the adolescent myopia using general survey. In a private high school from a megacity in mid-west China, a questionnaire gathered data on the 10th-grade students' level of myopia, home address, and some potential confounding factors. Additionally, satellite digital images were utilized to calculate the proportion of shadow area (PSA) and the proportion of greenness area (PGA) within a 500 m×500 m area centered on each student's home address. Correlations between myopia levels and PSA, along with other variables, were analyzed. The prevalence of mild, moderate, and high myopia were 39.2%, 32.5%, and 8.3%, respectively. A negative correlation was observed between myopia levels and PSA, albeit marginally significant (r=-0.189*, P = 0.05). Upon dividing the sample into higher and lower PSA groups using a cut-off point of 20%, a significant difference in myopia levels was evident (χ2 = 8.361, P = 0.038), while other confounding factors remained comparable. In conclusion, high-rise apartment constructions, which often cast more shadows on digital satellite maps, may not exacerbate myopia progression. Instead, they could potentially serve as a protective factor against adolescent myopia in densely populated megacities, as they allow for more ground space allocation. [ABSTRACT FROM AUTHOR]

Green infrastructure (GI) in cities plays significant role to provide various ecosystem services and enhance the urban health wellbeing. Recently, rapid urbanization and climate change has become one of the serious challenges to GI that may cause deterioration of urban environmental sustainability. This study aims to assess the pattern of place attachment and pro-environmental behaviour (Pro-environmental behaviour) towards GI in Kolkata megacity, India. Questionnaire survey was performed to glean the pattern of place attachment and pro-environmental behaviour from urban and peri-urban GI from multiple perspectives. The questionnaire used was divided into five major parts, namely-socio-demographic profile of the respondents, and place attachment, positive perception to GI, environmental attitudes, and environmentally responsible towards the GI. Results showed that the respondents had a high level of place attachment with GI (with mean score of 2.5 out of 5). The respondents showed positive perception towards GI stating the GI play significant role in maintaining good environment (mean score 4.5 out of 5). The overall mean score (%) of positive environmental attitudes was much higher (4.17) than negative environmental attitudes indicating that respondents held positive environmental attitudes towards GI. the mean score related to environmentally responsible attitude (ERA) clearly indicated that there were high levels of ERA towards GI. The study’s findings offer valuable insights into the human-nature relationship in large cities, highlighting the need for the development, monitoring, and management of GI. [ABSTRACT FROM AUTHOR]

In the last three decades, the world has experienced a rapid emergence of megacities. The increasing demographics, urbanization, and water demand brought severe and undesired effects on the quantity and quality of their water resources. A prime example is Lagos (Nigeria, West Africa), which is projected to become the world's largest city by 2100, and faces water scarcity challenges common to other megacities of developing countries. A literature review reveals the vast gap between water demand and regulated supply, inadequate knowledge and information on the current state of water (re)sources, and major, yet unregulated, use of groundwater. It further highlights the impacts of uncontrolled wastewater discharge into surface waters and aquifers, the role of increasing paved surfaces and blocked drainages on flooding, the inadequate supply of potable water, and the unsustainable abstraction of groundwater. Here, we examine the potential of managed aquifer recharge (MAR) to address these recurrent challenges across the megacity. The analysis reveals the opportunities and potential risks associated with the capture of wastewater, storm water, and brackish surface water for MAR. These waters, after appropriate treatment and subsurface storage may bridge the growing water supply–demand gap and mitigate the effects of groundwater (over)exploitation, including aquifer depletion, saltwater intrusion and land subsidence. Immediate efforts should focus on improving the conceptual and quantitative knowledge of Lagos' hydrogeology and groundwater resources through comprehensive spatial–temporal groundwater monitoring and socio‐economic studies of groundwater access and use. The insights provided may inform other fast‐growing coastal megacities in Africa and the wider developing world. This article is categorized under:Science of Water > Water and Environmental ChangeEngineering Water > Water, Health, and SanitationHuman Water > Value of WaterScience of Water > Hydrological Processes [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]

This study explores the spatial patterns of particulate matter (PM) in the megacity of Delhi. A GRIMM aerosol spectrometer is used to analyze different aerodynamic diameters (PM10, PM2.5, PM1.0), inhalable, thoracic, and alveolic particles, and black carbon (BC) at six prominent locations in Delhi during summer and winter. Additionally, metals (Pb, Fe, Ca, Al, Zn), along with silicon and sulfur, are analyzed using an ED-XRF spectrometer over the sampling locations during the summer season. The sampling site data are interpolated using the Kriging method to generate spatial maps to explore the air pollution problem in Delhi. East Delhi is observed to be the most polluted site, while Guru Gobind Singh Indraprastha University (GGSIPU) is the least polluted site. We further observe a high correlation between Al-Fe, Al-Ca, Zn-Pb, Ca-Fe, and S-Zn, indicating their common source of emission. Aerosols are also found to be highly enriched with metals like Al, S, Fe, Zn, and Pb, suggesting strong anthropogenic sources of these metals. Construction activities, resuspended dust, an increased number of vehicles, faulty agricultural practices, and soil could be recognized as major sources of the particulate concentration in an urban area like Delhi. [ABSTRACT FROM AUTHOR]

Abstract This study aims to assess how the construction patterns within residential communities influence the adolescent myopia using general survey. In a private high school from a megacity in mid-west China, a questionnaire gathered data on the 10th-grade students’ level of myopia, home address, and some potential confounding factors. Additionally, satellite digital images were utilized to calculate the proportion of shadow area (PSA) and the proportion of greenness area (PGA) within a 500 m×500 m area centered on each student’s home address. Correlations between myopia levels and PSA, along with other variables, were analyzed. The prevalence of mild, moderate, and high myopia were 39.2%, 32.5%, and 8.3%, respectively. A negative correlation was observed between myopia levels and PSA, albeit marginally significant (r=-0.189*, P = 0.05). Upon dividing the sample into higher and lower PSA groups using a cut-off point of 20%, a significant difference in myopia levels was evident (χ2 = 8.361, P = 0.038), while other confounding factors remained comparable. In conclusion, high-rise apartment constructions, which often cast more shadows on digital satellite maps, may not exacerbate myopia progression. Instead, they could potentially serve as a protective factor against adolescent myopia in densely populated megacities, as they allow for more ground space allocation.

The largest cities in Russia, just like other megacities in the world, are facing the challenges of a new reality. Fiscal policy actively helps to counter these challenges, among other things. The purpose of the study is to identify fiscal tools for large cities to respond to global challenges. The methodology consisted in the fact that, based on a unique database compiled by the authors on the budgets of the ten largest cities in Russia from 2011 to 2021, a comparative study of theirparameters was carried out (tax and non-tax revenues by types, intergovernmental fiscal transfers by types, expenses by industry classification), their structures and dynamics. The results obtained indicate that the cities are very different and a lot of budget parameters, in principle, do not depend on the budget policy of the city, as they are determined by regional legislation, for example, transferred tax deduction standards or transferred spending powers. At the same time, it is concluded that cities retain the ability to pursue an independent budget policy, for example, by managing the structure of expenditures, which was transformed in a certain way during periods of crisis. That is an element of scientific novelty. To a greater extent, this statement is true for such a megacity as Moscow, which really showed a high degree of independence in times of crisis. Other large cities generally do not have sufficient independence in terms of opportunities to replenish their budgets and spend funds, and they have to rely on transfers from budgets at a higher level. The practical significance for higher-level government bodies lies in confirming the thesis about the need to implement a differentiated budget policy for cities that fall into different groups according to the level of budgetaryprovision.

The escalation of climate change has challenged urban sustainable development, especially in the top globally vulnerable countries. This paper investigates the role of social capital in shaping the resilience of residents in Ho Chi Minh City, Vietnam's first mega urban, based on survey data from 300 households, using a stratified sampling strategy to reflect the urban and suburban population structure of the city-dwellers with the application of PLS-SEM. The study highlights the significant role of bridging social capital, drawing on established research and theories, which emphasizes the importance of diverse social networks in enhancing problem-solving, optimism, material resources, and social resources. Additionally, the study uncovers the impact of bonding social capital, particularly in terms of enhancing material and social resources, underscoring the cultural inclination towards close-knit networks within Vietnamese society. Structural barriers associated with vertical networks are identified, implying the need to promote the role of linking social capital in enhancing resilience. The study confirms the cruciality of addressing socio-economic factors and promoting access to formal support systems for bolstering overall resilience among urban residents in Ho Chi Minh City and beyond. The results enrich the current literature when operationalizing and exploring the nexus of social capital and resilience multi-dimensionally in a mega urban setting of an emerging country for new pathways to achieve sustainability. [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]

Megacities are the main sources of carbon emissions and are pillars of socioeconomic development due to economic prosperity, industrial development, and population agglomeration. Taking the megacity of Shenzhen, China, as an example, this research explored the advantages of low-carbon transformation in both climate change mitigation and socioeconomic progress. Soft linking of the Low Emissions Analysis Platform (LEAP) model with input–output analysis demonstrates that adopting feasible low-carbon transformation strategies has the potential to reverse the ongoing trend of carbon emission growth in Shenzhen, resulting in a peak before 2025. The peaks in carbon intensity and carbon emissions per capita occurred earlier than those in total carbon emissions. Furthermore, a total low-carbon investment of 462.04 billion CNY could yield approximately 799.49 billion CNY in output, 311.42 billion CNY in value-added, and 156.10 billion CNY in resident remuneration and create 1.79 million job opportunities during policy implementation. Taking into account both the reduction in carbon emissions and the socioeconomic benefits of low-carbon transformation, this research elucidates a potential pathway for Shenzhen to achieve synergy between mitigating climate change and promoting socioeconomic development, thus offering a valuable model for cities facing similar challenges. [ABSTRACT FROM AUTHOR]

Abstract Urban green space is a direct way to improve the carbon sink capacity of urban ecosystems. The carbon storage assessment of megacity green spaces is of great significance to the service function of urban ecosystems and the management of urban carbon zoning in the future. Based on multi-period remote sensing image data, this paper used the CASA model and the InVEST model to analyze the spatio-temporal variation and driving mechanism of carbon storage in Shenzhen green space and discussed the applicability of the two models to the estimation of carbon storage in urban green space. The research results showed that, from 2008 to 2022, in addition to the rapid expansion of construction land, the area of green space and other land types in Shenzhen showed a significant decrease trend. The estimation results of the carbon storage model showed that the carbon storage of green space shows a significant trend of reduction from 2008 to 2022, and the reduction amounts are 0.8 × 106 t (CASA model) and 0.64 × 106 t (InVEST model), respectively. The evaluation results of the model show that, in megacities, the spatial applicability of InVEST model is lower than that of CASA model, and the CASA model is more accurate in estimating the carbon storage of urban green space. The research results can provide a scientific basis for the assessment of the carbon sink capacity of megacity ecosystems with the goal of "dual carbon".

Carbon dioxide (CO2) is a major greenhouse gas in the atmosphere and has large impacts on climate change. Its fossil fuel (CO2ff) and biogenic (CO2bio) sources are well investigated, while CO2 emissions from human respiration (CO2hr), a subset of CO2bio, have received less attention. Especially as a source of carbon emissions in densely populated megacities, the role of CO2hr emissions in the carbon cycles was largely neglected. Here we fully characterize the respiratory CO2 emission rates (CERs) of Chinese people for the first time. Using the example of the megacity Beijing in China, we estimate the CO2hr emissions and present a method for quantifying its fraction in the atmospheric CO2 based on radiocarbon (14C) measurements and inventory data sets. The results show that males and females have similar age trends in CERs, but the gender difference is significant, especially between the ages of 20 and 60, the average CERs was 33% higher for males than for females (P < 0.05). The CO2hr emissions were about 22.2 ± 0.6 kt CO2 per day, which was equivalent to 7.5% of daily CO2ff emissions in winter. The proportion is likely to be twice in summer due to the seasonal fluctuations of fossil fuel emissions. More importantly, the respiratory emissions could increase atmospheric CO2 concentration by about 2 ppm, accounting for 14% ± 6% of average CO2bio concentration in winter. This study highlights the importance of human respiration in carbon emissions in megacities and has implications for a better understanding of the regional carbon budget. Plain Language Summary: Human respiration is an important CO2 source in densely populated areas, and its emission can be estimated by the "bottom‐up" method, just like fossil fuel emissions. However, as a key parameter in the estimate of CO2 emissions from human respiration, the variability of the CO2 emission rate is the main source of uncertainty. Another challenge is how to separate it from other atmospheric CO2 sources, which is related to the estimation of real carbon sources and sinks in natural ecosystems. Taking Beijing as a case study, we combined inventory data sets and radiocarbon (14C) measurements to quantitatively evaluate the contribution of human respiratory emission in a megacity in China, and further isolate the emissions from fossil fuels and biogenic CO2 sources. Although human breathing carbon emissions do not belong to the carbon that can be reduced, ignoring the contribution of human respiration would lead to a corresponding overestimation of carbon emissions from fossil fuel or biogenic sources. This pilot study is helpful to arouse people's attention to human respiratory CO2 emissions and inspire the evaluation method of human respiratory emissions. Key Points: We fully characterized the respiratory CO2 emission rates of Chinese people for the first timeAn approach was developed to quantify the respiratory CO2 concentration in the atmospheric CO2Human respiration should be considered in the regional carbon budget and CO2 monitoring [ABSTRACT FROM AUTHOR]

Urban green space is a direct way to improve the carbon sink capacity of urban ecosystems. The carbon storage assessment of megacity green spaces is of great significance to the service function of urban ecosystems and the management of urban carbon zoning in the future. Based on multi-period remote sensing image data, this paper used the CASA model and the InVEST model to analyze the spatio-temporal variation and driving mechanism of carbon storage in Shenzhen green space and discussed the applicability of the two models to the estimation of carbon storage in urban green space. The research results showed that, from 2008 to 2022, in addition to the rapid expansion of construction land, the area of green space and other land types in Shenzhen showed a significant decrease trend. The estimation results of the carbon storage model showed that the carbon storage of green space shows a significant trend of reduction from 2008 to 2022, and the reduction amounts are 0.8 × 106 t (CASA model) and 0.64 × 106 t (InVEST model), respectively. The evaluation results of the model show that, in megacities, the spatial applicability of InVEST model is lower than that of CASA model, and the CASA model is more accurate in estimating the carbon storage of urban green space. The research results can provide a scientific basis for the assessment of the carbon sink capacity of megacity ecosystems with the goal of "dual carbon". [ABSTRACT FROM AUTHOR]

Although the points systems for hukou conversion in Chinese megacities have been discussed in detail, the issue of policy equity has received scant attention. Drawing on policy documents and on interviews with urban-to-urban migrants in Beijing and Shenzhen, this article examines the issue of equity in the current points systems. Our analysis is based on three features of policy equity: policy declarations of equity, equity in conditions of hierarchy, and lack of transparency. The difference in perceptions of equity between the migrants in Beijing and those in Shenzhen, and their implications in terms of policy implementation were also analysed. Shenzhen's points system was perceived as more equitable than that of Beijing's. We found inequities arose from variations in the policy design between different levels of government and in the policy implementation between cities. To promote consolidation of policy equity, we need to create a governance model that will not only encourage local authorities to promote equity in their policy-making but also ensure effective oversight of the implementation of the resulting practice. [ABSTRACT FROM AUTHOR]

The growth of gated communities and the omnipresence of video surveillance have changed urban life considerably in the last decades. Especially in cities governed by neoliberal public policies and widespread fear of crime, residents search for security, social status, and shared services in fortified enclaves where video cameras watch everybody who enters their premises. These developments are not restricted to private space, and affluent neighborhoods in megacities are eager to adopt a wide range of surveillance technology to protect their citizens. Eight years ago, the affluent municipality of Lo Barnechea in the metropolitan region of Santiago, Chile, installed a surveillance balloon in a residential area. The local security forces currently operate six balloons, and residents have become accustomed to the ever-present gaze of aerial video cameras. This article contrasts the presence of this technology in a megacity against different perspectives on surveillance and urbanism. A consideration of its panoptic features leaves an unsatisfactory explanation. Citizens actively participate in generating public policies and smart technology for public safety, as is characteristic of a maximum security society. The surveillance balloons have become a sustainable element in the urban landscape and an appreciated part of the social fabric of the residential neighborhoods. [ABSTRACT FROM AUTHOR]

Abstract 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.

According to United Nations projections, future global urban growth will mostly occur in Asian megacities. In this study, a Cellular Automata based Artificial Neural Network (CA-ANN) model is used to simulate the future land use and land cover (LULC) over Delhi megacity (India). Delhi, projected to become the world's most populated city by 2030, is an example of a data poor city in Asia, having millions of climate vulnerable people. The CA-ANN model of Modules for Land Change Simulation (MOLUSCE), an open-source plugin, is first tested to simulate the LULC for 2009. Based on good validation results-structural similarity (SSIM; 0.8288), overall accuracy (79.78 %), kappa index of agreement (KIA; 77.25 %), and minimum validation overall error (0.0379), the same model set-up is used to carry out LULC simulation for 2030. This model is found to be simple, efficient, and computationally less expensive tool, and can be used to model future LULCs with a minimal set of inputs, a constraint often found in data poor cities. Results show continued increase in built-up area from 38.3 % (2014) to 53.8 % (2030), at the expense of cultivable areas, forests, and wastelands. The study incorporates past and future LULC change trajectories to highlight the changing LULC dynamics of the megacity from 1977 to 2030. Rate of urban sprawl, calculated using compound annual growth rate (CAGR) is projected to be 2.51 % for 2014–2030, substantially higher than the estimates for 2006–2014 (0.62 %). Further, the past and future urban growth patterns for Delhi are found to mimic other big Asian cities. The database generated from the present study has wide applicability for scientific research community, governmental bodies, profit and non-profit organizations for topics concerning-future urban climate research, climate risk and adaption policy frameworks, climate finance budgeting, future town planning, etc.

Effective waste separation at the source is vital for sustainable waste management globally. However, motivating people to participate in waste separation can be challenging, especially in developing countries' megacities, where rapid urbanization and surging solid waste trends are prevalent. A survey conducted in Bangkok, Thailand, provides valuable insights into the factors that encourage waste separation at the source among individuals from diverse backgrounds. The study involved 456 respondents, an effect size of 0.35, a 95 % confidence level, and a 5 % margin of error. The sample groups were divided into four modules based on their lifestyles and analysed waste separation intention and behaviour using an extended theory of planned behaviour and a structural equation model. The results showed that attitude is a critical and fundamental factor influencing intention, while intention and trust in the recycling system are the most significant factors influencing waste separation behaviour. Furthermore, the significant factors influencing waste separation intention and behaviour for each module differ, highlighting the need for specific strategies to promote waste separation among individuals with diverse lifestyles in megacities. These findings are of immense value and can be confidently used by governors or policymakers worldwide to combat waste management challenges.

The expansion of urban agglomerations and the accompanying increase in the severity of environmental problems require special attention to ensure a comfortable urban environment. One of the ways to solve this problem is to create an ecological framework in the megacity, formed by quasi-natural biocenoses, created within the application of the concept of rewilding. This article reviews the main current trends and approaches to the implementation of rewilding; discusses positive and negative environmental effects of the transformation of urban ecosystems within rewilding; presents an analytical review of available techniques and options for rewilding in various megacities around the world.

Understanding sources of oxygenated volatile organic compounds (OVOCs) in the atmosphere still has large uncertainties. In this study, an improved OVOC source apportionment model was developed by principal component analysis and multiple linear regression based on the online monitoring of nonmethane hydrocarbons (NMHCs) and OVOCs in a dense urban agglomeration in the winter. The modeled concentrations were in good agreement with the measured concentrations (R2 = 0.56–0.97). The concentrations of major OVOCs, except for 2‐methylacrolein, were greatly affected by anthropogenic sources (15.8%–76.8%) and secondary generation (0.0%–51.7%), while transport and natural sources contributed to 0.0%–26.8% and 0.0%–32.0%, respectively. The selection of isoprene as the natural tracer led to an underestimation of the OVOC species from primary emission and an overestimation from natural sources. In addition, photochemical reactions significantly reduced the simulation accuracy of the model for NMHCs in the afternoon, with the R2 of 0.60 ± 0.23, which was lower than the overall value of 0.82 ± 0.11. However, the R2 for OVOCs (0.83 ± 0.14) did not decrease significantly in the afternoon due to the compensation of secondary oxidation. Furthermore, the concentration gradient distribution of the species gradually changes from a normal distribution to an exponential normal distribution with a decrease in concentration, the accuracy of the model was influenced by the degree of matching between tracer and species concentration gradient as species concentration change. Developing models with additional tracers at different concentration levels may enhance the robustness of the OVOC source apportionment model without increasing its complexity. Plain Language Summary: The precision of oxygenated volatile organic compound (OVOC) source apportionment models is subject to external factors that affect the accuracy of the analysis. Thus, understanding their sources in the atmosphere still has large uncertainties. In this study by measuring the full spectrum of VOCs, we developed a source apportionment model. The model had good agreement with the measured concentrations (R2 = 0.56–0.97) and quantified main sources of OVOCs, except for 2‐methylacrolein, as follows: (a) anthropogenic sources (15.8%–76.8%), (b) secondary generation (0.0%–51.7%), (c) regional transport (0.0%–26.8%), and (d) natural sources (0.0%–32.0%). However, due to the selection of isoprene as the natural source tracer, the concentrations of OVOCs were higher in the natural source category and lower in the anthropogenic source category. In addition, the photochemical reaction can reduce the simulation accuracy of NMHCs with the R2 of 0.60 ± 0.23, but has little effect on the simulation accuracy of OVOCs (R2 = 0.83 ± 0.14). A downside of the model is that the predicted concentrations are higher at low concentration gradients and lower at high concentration gradients. Thus, we recommend implementing a model with more tracers at different concentration levels in order to improve the source apportionment results. [ABSTRACT FROM AUTHOR]

Recently, deep learning techniques, specifically semantic segmentation, have been employed to extract visual features from street images, a dimension that has received limited attention in the investigation of the connection between subjective and objective road environment perception. This study is dedicated to exploring and comprehending the factors influencing commuters' perceptions of the road environment, with the aim of bridging the gap in interpreting environmental quality in Thailand. Semantic segmentation was applied to identify visual objects, expressed as a percentage of pixels represented in 14,812 street images from the Bangkok Metropolitan Region. Subjective road environment perception was assessed through a questionnaire, with a total of 3600 samples collected. Both sets of data were converted to average values per grid, with a grid size of 500 × 500 square meters, resulting in a total of 631 grids with data points. Finally, a multiple linear regression model was employed to analyze the relationship between the ratios of objects obtained from street images via semantic segmentation and human sensory perception of the road environment. The findings from this analysis indicate that the attributes of distinct object classes have a notable impact on individuals' perceptions of the road environment. Visual elements such as infrastructure, construction, nature, and vehicles were identified as influential factors in shaping the perception of the road environment. However, human and object features did not exhibit statistical significance in this regard. Furthermore, when examining different road environments, which can be categorized into urban, community, and rural contexts, it becomes evident that these contexts distinctly affect the perceptions of various road environments. Consequently, gaining a comprehensive understanding of how street environments are perceived is crucial for the design and planning of neighborhoods and urban communities, facilitating the creation of safer and more enjoyable living environments. [ABSTRACT FROM AUTHOR]

The surge in plastic debris poses a critical global concern, driven by escalated consumption, accumulation, and enduring persistence in the environment. This study sought to evaluate the composition and relative abundance of plastic debris on Manora and Sandpit beaches in Karachi, Pakistan. Employing 24 transects, each with a fixed length of 100 m and a variable width of 25 m (corresponding to beach width at the sampling site) during the lowest tides, the sampling sites were determined using GPS coordinates. Plastics exceeding 2.5 cm were meticulously collected, then subjected to thorough cleansing, washing, and drying processes. Subsequently, adhering to the OSPAR Guideline for Monitoring Marine Litter on Beaches (2010), the plastics were sorted, enumerated, and categorized into ten predetermined waste categories. The designated transects carried 57.5 ± 44.17 plastic items 100 m-1 and weighed 568.37 ± 432.76 g 100 m-1. Notably, branded plastic items predominated in terms of quantity, typically falling within the size range of 2.5 to 10 cm. The primary source of plastic pollution at these beaches stems from land-based littering, notably from local communities and beach visitors engaged in recreational activities. Contrary to the trend observed in heavily frequented global beaches, the present study unveils relatively low plastic debris on the designated Karachi beaches To safeguard Pakistan’s coastal and marine resources, the study advocates for the adoption of effective waste management practices in the area. [ABSTRACT FROM AUTHOR]

This study examines viewers' characteristics and operational dynamics of football viewing centres (FVCs) in Agege, Lagos Megacity, Nigeria. It anchors on the "theory of happiness" and the microeconomic vitality of FVCs using a mixed-methods approach. The results of the descriptive and inferential statistics revealed that most viewers can afford subscriptions for digital TV in their homes, yet patronize the FVCs. Factors attributed to patronage are happiness, excitement, and other social opportunities, with some perspectives of leisure and microeconomic vitality benefits. Finally, the study suggests a new policy direction to mitigate the negative effects of unplanned areas resulting in the proliferation of FVCs. [ABSTRACT FROM AUTHOR]

Several epidemiological studies have demonstrated that particulate matter (PM) in air pollution can be involved in the genesis or aggravation of different cardiovascular, respiratory, perinatal, and cancer diseases. This study assessed the in vitro effects of PM10 on the secretion of cytokines by a human monocytic cell line (THP-1). We compared the chemotactic, pro-inflammatory, and anti-inflammatory cytokines induced by PM10 collected for two years during three different seasons in five different Mexico City locations. MIP-1α, IP-10, MCP-1, TNF-α, and VEGF were the main secretion products after stimulation with 80 μg/mL of PM10 for 24 h. The THP-1 cells showed a differential response to PM10 obtained in the different sites of Mexico City. The PM10 from the north and the central city areas induced a higher pro-inflammatory cytokine response than those from the south. Seasonal pro-inflammatory cytokine secretion always exceeded anti-inflammatory secretion. The rainy-season-derived particles caused the lowest pro-inflammatory effects. We concluded that toxicological assessment of airborne particles provides evidence supporting their potential role in the chronic exacerbation of local or systemic inflammatory responses that may worsen the evolution of some chronic diseases. [ABSTRACT FROM AUTHOR]

An intercomparison of four regional air quality models is performed in the tropical megacity of São Paulo with the perspective of developing a forecasting system based on a model ensemble. Modeled concentrations of the main regulated pollutants are compared with combined observations in the megacity center, after analyzing the spatial scale of representativeness of air monitoring stations. During three contrasting periods characterized by different types of pollution events, the hourly concentrations of carbon monoxide (CO), nitrogen oxides (NOx), sulfur dioxide (SO2), and particulate matter (PM2.5 and PM10) modeled by the ensemble are in moderate agreement with observations. The median of the ensemble provides the best performance (R ≈ 0.7 for CO, 0.7 for NOx, 0.5 for SO2, 0.5 for PM2.5, and 0.4 for PM10) because each model has periods and pollutants for which it has the best agreement. NOx concentration is modeled with a large inter‐model variability, highlighting potential for improvement of anthropogenic emissions. Pollutants transported by biomass burning events strongly affect the air quality in São Paulo and are associated with significant inter‐model variability. Modeled hourly concentration of ozone (O3) is overestimated during the day (≈20 ppb) and underestimated at night (≈10 ppb), while nitrogen dioxide (NO2) is overestimated at night (≈20 ppb). The observed O3 concentration is best reproduced by the median of the ensemble (R ≈ 0.8), taking advantage of the variable performance of the models. Therefore, an operational air quality forecast system based on a regional model ensemble is promising for São Paulo. Plain Language Summary: Forecasting air quality in megacities is particularly difficult due to the diversity and temporal variability of emission sources. São Paulo is the largest metropolitan area in South America and has no operational air quality forecast. We perform an intercomparison of four regional air quality models with the perspective of developing an air quality forecasting system. During three contrasting periods characterized by different types of pollution events, we analyze the modeled concentrations of the main regulated pollutants (trace gases and aerosols) compared to observations from the São Paulo air quality monitoring network. The modeled concentrations of the main regulated pollutants agree well with the observations range of variation, although we show the potential in improving the treatment of anthropogenic emissions. In addition, the long‐range transport of pollutants due to forest fires strongly affects the air quality in São Paulo and also reduces the performance of the models. The observed hourly ozone concentration is well reproduced by the models, and its median has the best performance, taking advantage of the capabilities of each model. Therefore, an operational air quality forecasting system for the megacity of São Paulo is promising. Key Points: An ensemble of regional air quality models performs well in the São Paulo megacity for the main regulated pollutants (CO, NOx, O3, SO2, PM2.5, and PM10)Transport of pollutants due to biomass burning events, affecting strongly the air quality of the megacity, is represented with high variability by the ensembleIn the center of the megacity, the median of the regional model ensemble leads to the best performance for these pollutants compared to each model that composes it [ABSTRACT FROM AUTHOR]

The urban built environment, comprising structures, roads, and various facilities, plays a key role in the formation of urban heat islands, which inflict considerable damage upon human society. This phenomenon is particularly pronounced in urban areas characterized by the rapid growth and concentration of populations, a global trend, notably exemplified in megacities such as Bangkok, Thailand. The global trend of urbanization has witnessed unprecedented growth in recent decades, with cities transforming into megametropolises that profoundly impact changes in urban temperature, specifically the urban heat island (UHI) phenomenon induced by the rapid growth of urban areas. Elevated urban concentrations lead to increased city density, contributing to higher temperatures within the urban environment compared to the surrounding areas. The evolving land-use surface has assumed heightened significance due to urban development, necessitating accelerated efforts to mitigate urban heat islands. This study aims to quantify the influence of urban growth on urban surface temperature in Bangkok and its surrounding areas. The inverse relationship between urban temperature and land surface temperature (LST), coupled with urban area density, was examined using Landsat 5 and 8 satellite imagery. The analysis revealed a positive correlation between higher temperatures and levels of urban growth. Areas characterized by high-rise structures and economic activities experienced the most pronounced impact of the heat island phenomenon. The city exhibited a notable correlation between high density and high temperatures (high–high), signifying that increased density contributes to elevated temperatures due to heat dissipation (significant correlation of R2 = 0.8582). Conversely, low-temperature, low-density cities (low–low) with a dispersed layout demonstrated effective cooling of the surrounding area, resulting in a significant correlation with lower local temperatures (R2 = 0.7404). These findings provide valuable insights to assist governments and related agencies in expediting planning and policy development aimed at reducing heat in urban areas and steering sustainable urban development. [ABSTRACT FROM AUTHOR]

Cairo has been described as a city of dualities, in the sense of its conflict between the traditions of the past and the modern values of the present. The city has witnessed rapid transformations in terms of its sociocultural aspects due to political, economic and religious changes. In his work, the acclaimed and legendary Egyptian filmmaker Youssef Chahine portrayed such changes in his 1991 short semi-documentary Al-Qahira Munawwara bi Ahlaha (Cairo as Told by Youssef Chahine) in surrealistic and flâneurie ways. This article breaks down Chahine's visual interpretation of Cairo to reveal his sense of in-betweenness as a form of urban surrealism. The film offers fragmented episodes of Cairo that are assembled to reflect Chahine's imagination and collective memory. In filming Cairo, Chahine transformed his portrait of the city into a self-reflexive illustration of a filmmaker who expresses deep admiration for Cairo and its inhabitants. [ABSTRACT FROM AUTHOR]

The rapid growth of urbanization in China has led to a substantial escalation in the demand for civil aviation services, consequently propelling China to the third-largest contributor of carbon emissions within the aviation sector. Using the 2012–2021 data on takeoffs and landings of civil aviation aircraft in China, the aircraft engine emission factor database of the Base of Aircraft Data (BADA) from EUROCONTROL, this paper investigates the spatial-temporal distribution characteristics of atmospheric pollutants, primarily carbon emissions from Chinese civil aviation aircraft in 19 megacities. The results indicate that (1) China's aviation CO2 emissions equivalent between 2012 and 2022 has been on an upward trajectory, peaking at 186.53 MT in 2019 with an average annual growth of 12.52%. The trend, albeit momentarily interrupted by the COVID-19 pandemic, appears to persist. (2) CO2 constitutes the highest proportion of aircraft emissions at 83.87%, with Cruise Climb Descent (CCD) cycle emissions accounting for 96.24%. CO2 and NOX, with the highest increase rates in the CCD and Landing and Takeoff (LTO) phases, respectively, are identified as the chief culprits in aviation-related greenhouse effects. (3) There is a marked spatial imbalance, with 19 megacities contributing 62.08% of total CO2 emissions, compared to the 207 least-emitting cities contributing just 9.29%. (4) The pattern of city carbon emissions is changing, with rapid growth rates in the western cities of Xinjiang, Tibet, Shaanxi, and Guizhou, and varied growth rates among megacities. The implications of this study emphasize the urgency for advancements in aviation fuel technology, rigorous management of CCD phase pollutants, strategic carbon emission controls in populous cities, fostering green aviation initiatives in western regions, diverse carbon mitigation tactics, and strengthening the precision and surveillance of aviation carbon accounting systems. Collectively, this study paints a grand picture of the complexities and challenges associated with China's urban sprawl and aviation carbon emissions. [ABSTRACT FROM AUTHOR]

Five early-stage sustainable urban water management innovations in India are examined utilizing diffusion of Innovations theory. Cases are described using grey literature, surveys, and qualitative insights derived from interviews with innovators (N = 5). Potential future adopters (PFA's) were also surveyed (N = 31), and their attitudes toward adoption is discussed. We identify alignments and misalignments between the goals, perceptions, adoption attitudes, and modes of communication between innovators and PFA's. Innovators and PFA's were largely aligned in their assessment of two innovation characteristics considered 'most important' (namely relative advantage and compatibility), but not aligned regarding simplicity (rated 'most important') or other 'moderately important' to 'less important' innovation characteristics (trialability, observability, and reinvention). We identify the role of communication channels between innovators and PFA's, and suggest that innovators might work to better emphasize the simplicity of their approaches to maximize the likelihood of adoption. Finally, we identify opportunities for future research in this under-studied domain. [ABSTRACT FROM AUTHOR]

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Greater Cairo, the largest megacity of the Middle East North Africa (MENA) region, is currently suffering from major aerosol pollution, posing a significant threat to public health. However, the main sources of pollution remain insufficiently characterized due to limited atmospheric observations. To bridge this knowledge gap, we conducted a continuous 2-month field study during the winter of 2019–2020 at an urban background site, documenting for the first time the chemical and physical properties of submicron (PM1) aerosols. Crustal material from both desert dust and road traffic dust resuspension contributed as much as 24 % of the total PM1 mass (rising to 66 % during desert dust events), a figure not commonly observed in urban environments. Our observations showed significant decreases in black carbon concentrations and ammonium sulfate compared to data from 15 years ago, indicating an important reduction in both local and regional emissions as a result of effective mitigation measures. The diurnal variability of carbonaceous aerosols was attributed to emissions emanating from local traffic at rush hours and nighttime open biomass burning. Surprisingly, semi-volatile ammonium chloride (NH4Cl) originating from local open biomass and waste burning was found to be the main chemical species in PM1 over Cairo. Its nighttime formation contributed to aerosol water uptake during morning hours, thereby playing a major role in the build-up of urban haze. While our results confirm the persistence of a significant dust reservoir over Cairo, they also unveil an additional source of highly hygroscopic (semi-volatile) inorganic salts, leading to a unique type of urban haze. This haze, with dominant contributors present in both submicron (primarily as NH4Cl) and supermicron (largely as dust) modes, underscores the potential implications of heterogeneous chemical transformation of air pollutants in urban environments.

IntroductionDuring the global COVID-19 pandemic, densely populated megacities engaged in active international exchanges have faced the most severe impacts from both the disease and the associated infodemic. This study examines the factors influencing public participation behavior on government microblogs in these megacities during the pandemic. It guides megacities in disseminating epidemic information, promoting knowledge on epidemic prevention, managing public opinion, and addressing related matters.MethodsUtilizing the elaboration likelihood model’s central and peripheral routes, drawing on an empirical analysis of 6,677 epidemic-related microblogs from seven Chinese megacities, this study analyses the influence mechanisms influencing public participation behavior and reveals the regulatory role of confirmed case numbers. Meanwhile,a qualitative comparative analysis examines and discusses diferent confgurations of ixn fuential factors.ResultsThe study reveals that microblog content richness demonstrates a U-shaped impact on public participation behavior. Conversely, content interaction, content length, and the number of fans positively impact participation, while update frequency has a negative impact. Additionally, the number of new confrmed cases positively regulates the impact of microblog content and publisher characteristics on public participation behavior. Public participation behavior also varies based on publishing time and content semantic features. This study further revealed the different confgurations of influential factors by QCA method.ConclusionThis study reveals the impact mechanism of the microblog content and publisher characteristics on public participation behavior. It also demonstrates the regulatory role of newly confrmed cases in the way content and publishers’ characteristics influence public participation behavior. This study is of great significance for the operation of government microblogs, the release of emergency information, and the promotion of public participation.

Street trees provide critical ecosystem services and economic benefits that support urban livelihoods. To effectively manage street trees over the long term and maximise their benefits, information on their abundance, composition, and distribution is needed. Unfortunately, a lack of data is prevalent in most cities, particularly those in the developing countries. To address this, species, basal diameter, height, and location of 4,017 street trees were collected from all 16 local government areas (LGAs) of Lagos metropolis (two wards per LGA) to assess their abundance, composition, and distribution. Forty-six species, 37 genera, and 25 families were identified, with Polyalthia longifolia (27.3 %) being the most prevalent species. Most (87 %) of the trees were non-native, and the highest percentage (78.1 %) had basal diameters between 20 and 40 cm. The LGAs which harbour the wealthiest neighbourhoods in Lagos (Ikeja and Eti-osa), have higher species abundance and richness. The Gini coefficient is 0.81, indicating unequal distribution of street trees within different LGAs that made up the metropolis. These results highlight the need to plant a diverse set of species, particularly native species that can provide multiple benefits. The information obtained in this study could provide insights into which species should be planted and where they are most needed to ensure distributional equity. Future studies could seek to understand the key limitations of street tree establishment and management in Lagos metropolis.

With the rapid economic development, megacities have gathered a large number of population and industries, and a series of “urban diseases” have also emerged. To alleviate these problems, various administrative measures have been taken to control population and optimize industrial distribution. Meanwhile, home-purchase restriction (HPR) has been introduced to control the soaring housing prices. Existing research focuses on the impact of policy on its own market, without paying attention to the linkage between markets and spillover effect. We take Beijing, the capital of China, as an example to study the impact of the HPR on the population distribution and industry development of megacities. By analyzing the industry location quotient and population economy matching degree, we conclude that HPR effectively promotes the efficiency of population and industry dispersal, but increases the mismatching between industry and population. City is a typical intelligent system that gathers various intelligent agents, and the development of its population and industry is the fundamental evolution of the system. This paper explores the role of policies in the evolution of urban intelligent systems, and therefore has important theoretical and practical significance for intelligent systems.

This study explores the spatial patterns of particulate matter (PM) in the megacity of Delhi. A GRIMM aerosol spectrometer is used to analyze different aerodynamic diameters (PM10, PM2.5, PM1.0), inhalable, thoracic, and alveolic particles, and black carbon (BC) at six prominent locations in Delhi during summer and winter. Additionally, metals (Pb, Fe, Ca, Al, Zn), along with silicon and sulfur, are analyzed using an ED-XRF spectrometer over the sampling locations during the summer season. The sampling site data are interpolated using the Kriging method to generate spatial maps to explore the air pollution problem in Delhi. East Delhi is observed to be the most polluted site, while Guru Gobind Singh Indraprastha University (GGSIPU) is the least polluted site. We further observe a high correlation between Al-Fe, Al-Ca, Zn-Pb, Ca-Fe, and S-Zn, indicating their common source of emission. Aerosols are also found to be highly enriched with metals like Al, S, Fe, Zn, and Pb, suggesting strong anthropogenic sources of these metals. Construction activities, resuspended dust, an increased number of vehicles, faulty agricultural practices, and soil could be recognized as major sources of the particulate concentration in an urban area like Delhi.

Interest in the study and characterization of aerosols has been growing given its multiple connections with air quality and climate. However, the limited ground-based stations for measurements in many countries are not enough to completely study a big city or a region. Low-cost technology arises as a viable alternative to improve the spatial resolution of measurements. This study aims to demonstrate that the properties of aerosols may change within a megacity and that is advisable to segment measurements according to their characteristics. We measured the optical properties of aerosols in the outskirts of Buenos Aires and compared the data obtained with AERONET data from the city center. This is the first study of its kind in the region. The comparison of concentration, sizes, and types of aerosols shows differences between the sites regardless of the background levels that they share regionally. While the city center has a strong influence from traffic and sea particles and levels of pollution typical of a dense city, the outskirts present several aerosol sources and characteristics of a semi-rural site with a moderate influence of anthropogenic sources.

Background: Increased attention has been paid to humid-heat extremes as they are projected to increase in both frequency and intensity. However, it remains unclear how compound extremes of heat and humidity affects morbidity when the climate is projected to continue warming in the future, in particular for a megacity with a large population. Methods: We chose the Wet-Bulb Globe Temperature (WBGT) index as the metric to characterize the humid-heat exposure. The historical associations between daily outpatient visits and daily mean WBGT was established using a Distributed Lag Non-linear Model (DLNM) during the warm season (June to September) from 2013 to 2015 in Shanghai, a prominent megacity of China. Future morbidity burden related to the combined effect of high temperature and humidity were projected under four greenhouse gases (GHGs) emission scenarios (SSP126, SSP245, SSP370 and SSP585). Results: The humid-heat weather was significantly associated with a higher risk of outpatient visits in Shanghai than the high-temperature conditions. Relative to the baseline period (2010–2019), the morbidity burden due to humid-heat weather was projected to increase 4.4 % (95 % confidence interval (CI): 1.1 %–10.1 %) even under the strict emission control scenario (SSP126) by 2100. Under the high-GHGs emission scenario (SSP585), this burden was projected to be 25.4 % (95 % CI: 15.8 %–38.4 %), which is 10.1 % (95 % CI: 6.5 %–15.8 %) more than that due to high-temperature weather. Our results also indicate that humid-hot nights could cause large morbidity risks under high-GHGs emission scenarios particularly in heat-sensible diseases such as the respiratory and cardiovascular disease by the end of this century. Conclusions: Humid heat exposures significantly increased the all-cause morbidity risk in the megacity Shanghai, especially in humid-hot nights. Our findings suggest that the combined effect of elevated temperature and humidity is projected to have more substantial impact on health compared to high temperature alone in a warming climate.

AbstractThe urbanization process has significantly intensified surface urban heat island (SUHI) effects in the Bangkok Metropolitan Region (BMR). However, understanding the evolution of the urban thermal environment is challenging due to the difficulty in obtaining consistent remote sensing data of the cloud-prone landscape in the BMR. In this study, the data fusion algorithm was utilized to fill cloud-induced data gap and create high spatiotemporal-resolution data by blending Landsat and MODIS remote sensing images. The fused data was used to retrieve land surface temperature (LST) for winter months from 2000 to 2020. The spatiotemporal variations in SUHI were then captured using spatial cluster analysis. Finally, gradient analysis and geographically weighted regression (GWR) were employed to analyse the effects of land cover composition on LST. The SUHI intensity in winter increased from 4.40 °C in 2000 to 5.76 °C in 2020. The areal percentage of SUHI hot spots increased from 24.86% to 29.13%. The gradient analysis results indicated that vegetation with a density higher than 0.3 had a significant effect on LST compared to low-density areas. The woody lands were more effective in lowering LST than cultivated lands. These results provide useful information for developing heat mitigation strategies in the metropolitan regions.

Heavy metal pollution in roadside soil may harm humans, animals, plants, and local ecosystems. This study aimed to explore the sources and potential ecological risks of heavy metals in soils of roadside trees under different land uses, using soil samples collected from 136 roads across 16 administrative districts in Shanghai. The contents, pollution characteristics, potential ecological risks, and sources of seven heavy metals were analyzed, including Cr, Ni, Cd, Pb, As, Cu, and Zn. Results showed that (1) land use patterns affected the heavy metal contents, with industrial and construction areas showing higher contents while agricultural and forestry areas lower; (2) the ranking of heavy metal pollution levels was Cd > As > Pb > Cu > Ni > Cr > Zn. Cd exhibited the highest potential ecological risk, falling within the moderate to considerable potential ecological risk interval; (3) the sources of Cu, Zn, Cr, Ni, Cd, and Pb were associated with traffic emissions, whereas As had independent other sources and Pb in industrial and construction areas was also influenced by industrial emissions. These results provide valuable references on the control of heavy metal pollutants and the management of land uses in megacities. [ABSTRACT FROM AUTHOR]