As one of the most dynamic economic zones in China, the Yangtze River Delta has further increased its economic output,becoming more open to foreign investment and international cooperation over the past 30 years.Its e...As one of the most dynamic economic zones in China, the Yangtze River Delta has further increased its economic output,becoming more open to foreign investment and international cooperation over the past 30 years.Its economic stability and coordination have been strengthened;and the process of regional integration continues to accelerate.展开更多
The transformation of Chengdu Tianfu New Area,a state-level new district,from the first site of constructing the“Park City”to the representative of the“Park City”,contains a unique path of“Chinese Style Governanc...The transformation of Chengdu Tianfu New Area,a state-level new district,from the first site of constructing the“Park City”to the representative of the“Park City”,contains a unique path of“Chinese Style Governance”.To expand the diverse paths of constructing megacities,the current research references the nudge theory of behavioral science,adopts the extended case method,and takes Chengdu Tianfu New Area as a typical case to summarize the“nudge”path of“Party City”construction.The study found that the government achieves the lock-in effect by the priming mechanism and uses the nudge strategy of improving environment and guiding public opinion,thereby helping the people make free choices.It realizes the framework effect by the salience mechanism and uses the strategies of highlighting key information and optimizing information delivery methods,which directly affects the behavior of the public.It achieves the commitment effect by the comparison mechanism,including the horizontal comparison and vertical comparison strategies,and gradually realizes the policy goals.It realizes the social norm effect by the imitation mechanism and uses the strategies of creating peer pressure and playing celebrity effect,which in turn influence people’s choices.With the help of the“nudging”mechanism,the construction of the park city has realized the interactive cycle of“government output-citizen feedback”and achieved the goal of“making great change through small actions”.As a new behavioral intervention tool,“nudging”provides an alternative explanation for the construction of the park city in Tianfu New Area and opens up new ideas for the construction of megacities.This study concludes that the construction of megacities can achieve the goal of“common return”through different ways and provides practical inspiration for future urban construction.展开更多
Inter-city mobility is one of the most important issues in the UN Sustainable Development Goals,as it is essential to access the regional labour market,goods and services,and to constrain the spread of infectious dise...Inter-city mobility is one of the most important issues in the UN Sustainable Development Goals,as it is essential to access the regional labour market,goods and services,and to constrain the spread of infectious diseases.Although the gravity model has been proved to be an effective model to describe mobility among settlements,knowledge is still insufficient in regions where dozens of megacities interact closely and over 100 million people reside.In addition,the existing knowledge is limited to overall population mobility,while the difference in inter-city travel with different purposes is unexplored on such a large geographic scale.We revisited the gravity laws of inter-city mobility using the 2.12 billion trip chains recorded by 40.48 million mobile phone users’trajectories in the Jing-Jin-Ji Region,which contains China’s capital Beijing.Firstly,unlike previous studies,we found that non-commuting rather than commuting is the dominant type of inter-city mobility(89.3%).Noncommuting travellers have a travel distance 42.3%longer than commuting travellers.Secondly,we developed more accurate gravity models for the spatial distribution of inter-city commuting and non-commuting travel.We also found that inter-city mobility has a hierarchical structure,as the distribution of inter-city travel volume follows Zipf’s law.In particular,the hierarchy of non-commuting travel volume among the cities is more in line with an ideal Zipf distribution than commuting travel.Our findings contribute to new knowledge on basic inter-city mobility laws,and they have significant applications for regional policies on human mobility.展开更多
Background China’s 35 largest cities,including Wuhan,are inhabited by approximately 18%of the Chinese popula-tion,and account for 40%energy consumption and greenhouse gas emissions.Wuhan is the only sub-provincial ci...Background China’s 35 largest cities,including Wuhan,are inhabited by approximately 18%of the Chinese popula-tion,and account for 40%energy consumption and greenhouse gas emissions.Wuhan is the only sub-provincial city in Central China and,as the eighth largest economy nationwide,has experienced a notable increase in energy con-sumption.However,major knowledge gaps exist in understanding the nexus of economic development and carbon footprint and their drivers in Wuhan.Methods We studied Wuhan for the evolutionary characteristics of its carbon footprint(CF),the decoupling relation-ship between economic development and CF,and the essential drivers of CF.Based on the CF model,we quantified the dynamic trends of CF,carbon carrying capacity,carbon deficit,and carbon deficit pressure index from 2001 to 2020.We also adopted a decoupling model to clarify the coupled dynamics among total CF,its accounts,and eco-nomic development.We used the partial least squares method to analyze the influencing factors of Wuhan’s CF and determine the main drivers.Results The CF of Wuhan increased from 36.01 million t CO_(2)eq in 2001 to 70.07 million t CO_(2)eq in 2020,a growth rate of 94.61%,which was much faster than that of the carbon carrying capacity.The energy consumption account(84.15%)far exceeded other accounts,and was mostly contributed by raw coal,coke,and crude oil.The carbon deficit pressure index fluctuated in the range of 8.44-6.74%,indicating that Wuhan was in the relief zone and the mild enhancement zone during 2001-2020.Around the same time,Wuhan was in a transition stage between weak and strong CF decoupling and economic growth.The main driving factor of CF growth was the urban per capita residen-tial building area,while energy consumption per unit of GDP was responsible for the CF decline.Conclusions Our research highlights the interaction of urban ecological and economic systems,and that Wuhan’s CF changes were mainly affected by four factors:city size,economic development,social consumption,and technological progress.The findings are of realistic significance in promoting low-carbon urban development and improving the city’s sustainability,and the related policies can offer an excellent benchmark for other cities with similar challenges.展开更多
Tianjin is the third largest megacity and the fastest growth area in China,and consequently faces the problems of surface ozone and haze episodes.This study measures and characterizes volatile organic compounds （VOCs...Tianjin is the third largest megacity and the fastest growth area in China,and consequently faces the problems of surface ozone and haze episodes.This study measures and characterizes volatile organic compounds （VOCs）,which are ozone precursors,to identify their possible sources and evaluate their contribution to ozone formation in urban and suburban Tianjin,China during the HaChi （Haze in China） summer campaign in 2009.A total of 107 species of ambient VOCs were detected,and the average concentrations of VOCs at urban and suburban sites were 92 and 174 ppbv,respectively.Of those,51 species of VOCs were extracted to analyze the possible VOC sources using positive matrix factorization.The identified sources of VOCs were significantly related to vehicular activities,which specifically contributed 60％ to urban and 42％ to suburban VOCs loadings in Tianjin.Industrial emission was the second most prominent source of ambient VOCs in both urban and suburban areas,although the contribution of industry in the suburban area （36％） was much higher than that at the urban area （16％）.We conclude that controlling vehicle emissions should be a top priority for VOC reduction,and that fast industrialization and urbanization causes air pollution to be more complex due to the combined emission of VOCs from industry and daily life,especially in suburban areas.展开更多
COVID-19 pandemic has forced to lockdown entire India starting from 24th March 2020 to 14th April 2020(first phase), extended up to 3rd May 2020(second phase), and further extended up to 17th May 2020(third phase) wit...COVID-19 pandemic has forced to lockdown entire India starting from 24th March 2020 to 14th April 2020(first phase), extended up to 3rd May 2020(second phase), and further extended up to 17th May 2020(third phase) with limited relaxation in non-hotspot areas. This strict lockdown has severely curtailed human activity across India. Here, aerosol concentrations of particular matters(PM) i.e., PM,PM, carbon monoxide(CO), nitrogen dioxide(NO), sulphur dioxide(SO), ammonia(NH) and ozone(O), and associated temperature fluctuation in four megacities(Delhi, Mumbai, Kolkata, and Chennai)from different regions of India were investigated. In this pandemic period, air temperature of Delhi,Kolkata, Mumbai and Chennai has decreased about 3 ℃, 2.5 ℃, 2 ℃ and 2 ℃ respectively. Compared to previous years and pre-lockdown period, air pollutants level and aerosol concentration(-41.91%,-37.13%,-54.94% and-46.79% respectively for Delhi, Mumbai, Kolkata and Chennai) in these four megacities has improved drastically during this lockdown period. Emission of PMhas experienced the highest decrease in these megacities, which directly shows the positive impact of restricted vehicular movement. Restricted emissions produce encouraging results in terms of urban air quality and temperature, which may encourage policymakers to consider it in terms of environmental sustainability.展开更多
Measurements of column-averaged dry-air mole fractions of carbon dioxide and carbon monoxide,CO_(2)(XCO_(2))and CO(XCO),were performed throughout 2019 at an urban site in Beijing using a compact Fourier Transform Spec...Measurements of column-averaged dry-air mole fractions of carbon dioxide and carbon monoxide,CO_(2)(XCO_(2))and CO(XCO),were performed throughout 2019 at an urban site in Beijing using a compact Fourier Transform Spectrometer(FTS)EM27/SUN.This data set is used to assess the characteristics of combustion-related CO_(2)emissions of urban Beijing by analyzing the correlated daily anomalies of XCO and XCO_(2)(e.g.,ΔXCO andΔXCO_(2)).The EM27/SUN measurements were calibrated to a 125HR-FTS at the Xianghe station by an extra EM27/SUN instrument transferred between two sites.The ratio ofΔXCO overΔXCO_(2)(ΔXCO:ΔXCO_(2))is used to estimate the combustion efficiency in the Beijing region.A high correlation coefficient(0.86)betweenΔXCO andΔXCO_(2)is observed.The CO:CO_(2)emission ratio estimated from inventories is higher than the observedΔXCO:ΔXCO_(2)(10.46±0.11 ppb ppm^(−1))by 42.54%-101.15%,indicating an underestimation in combustion efficiency in the inventories.DailyΔXCO:ΔXCO_(2)are influenced by transportation governed by weather conditions,except for days in summer when the correlation is low due to the terrestrial biotic activity.By convolving the column footprint[ppm(μmol m-2 s-1)-1]generated by the Weather Research and Forecasting-X-Stochastic Time-Inverted Lagrangian Transport models(WRF-X-STILT)with two fossil-fuel emission inventories(the Multi-resolution Emission Inventory for China(MEIC)and the Peking University(PKU)inventory),the observed enhancements of CO_(2)and CO were used to evaluate the regional emissions.The CO_(2)emissions appear to be underestimated by 11%and 49%for the MEIC and PKU inventories,respectively,while CO emissions were overestimated by MEIC(30%)and PKU(35%)in the Beijing area.展开更多
Rural-to-urban migration and globalized trade are swelling cities worldwide,but these forces are perhaps more powerfully concentrated in Dhaka,Bangladesh,than anywhere on earth.Born of a natural disaster 50 years ago,...Rural-to-urban migration and globalized trade are swelling cities worldwide,but these forces are perhaps more powerfully concentrated in Dhaka,Bangladesh,than anywhere on earth.Born of a natural disaster 50 years ago,the world’s most densely-populated country faces multiple environmental challenges.Water,with seasonal monsoons,is both a blessing and a curse.A one meter rise in sea level,for example,would displace as many as 25 million Bangladeshis,and cause the largest mass migration in history.Each drought,flood,or cyclone drives scores of environmental refugees from rural areas to the capital city of Dhaka,where air and water pollution run rampant.Recent rapprochement with India over decades-long boundary disputes offers hope that environmental cooperation in the vulnerable Bay of Bengal can follow.展开更多
Several factors may contribute to on-going challenges for spatial planning and policy in megacities such as Rome, including rapid population shifts, poorly organized areas, and lack of data through which monitoring ur...Several factors may contribute to on-going challenges for spatial planning and policy in megacities such as Rome, including rapid population shifts, poorly organized areas, and lack of data through which monitoring urban growth and land use change. This research was conducted to examine past and current effects of the urbanization process, occurred over the large Roman urban system, on the basis of multi-source and multi-temporal optical remote sensing (RS) data, collected between 1990 and 2013. These changes were then validated via Geographic Information System (GIS) techniques, in a particular procedure applied to urban land/agricultural transformations. The proposed approach, based on geo-statistical methods, was used to calculate the index of innovative space (AP Index), useful for the monitoring of the urban sprawl phenomenon. Strong evidence of urban expansion over the north-eastern quarter of the city, accompanied by environmental degradation and loss of biodiversity, is provided. Urban infill developments are expected to emerge in the south-eastern areas too, and these might increase urban pressure as well. In conclusion, RS and GIS technologies together with ancillary data can be used to assist decision makers in preparing future plans to find out appropriate solutions to urbanization encroachment.展开更多
In the process of new urbanization,the population of megacities is increasing rapidly,the scale of cities is expanding,and the supply of service facilities has been unable to meet the demand.As an important carrier of...In the process of new urbanization,the population of megacities is increasing rapidly,the scale of cities is expanding,and the supply of service facilities has been unable to meet the demand.As an important carrier of urban governance and urban management,the police station should properly deal with the existing problems in the urban police stations,and improve the quality of life of residents by optimizing urban service facilities,which is of great significance for the implementation of people-oriented new urbanization.Taking Changping District of Beijing as an example,this study pointed out that there were many problems in police stations in Changping District.For example,the area of land is not up to the standard,the service capacity is not up to the demand,and the facilities are not up to the demand.Then,three planning strategies:adjusting the planning standards of facilities,optimizing the spatial layout of facilities,and strengthening the later guarantee of facilities were put forward,so as to improve people’s satisfaction with life,promote the high-quality development of new urbanization,and provide reference for the supplement of service facilities in megacities.展开更多
As urbanization expands＇ into the suburbs of Chinese cities, the conversion of farmers into citizens with urban social protection is becoming an important issue facing Chinese megacities. Taking Beijing as an example...As urbanization expands＇ into the suburbs of Chinese cities, the conversion of farmers into citizens with urban social protection is becoming an important issue facing Chinese megacities. Taking Beijing as an example, this paper has calculated the one-off urbanization cost of farmers in China and arrived at the results of 500, 000 yuan per person for urbanization of centralized target regions in the suburb and 200, 000 yuan per person for urbanization of scattered target regions in the exurb. This paper considers that a diversified cost sharing mechanism should be put into place for the step-by-step urbanization of farmers. In addition, policy recommendations are proposed regarding the functional transformation of collective economic organizations, eradication of the urban-rural divide, enhancement of land system innovation and policy improvements for urbanization of rural residents.展开更多
Objective Improvement in the quality of life is reflected in the narrowing of the gap between healthadjusted life expectancy(HALE)and life expectancy(LE).The effect of megacity expansion on narrowing the gap is rarely...Objective Improvement in the quality of life is reflected in the narrowing of the gap between healthadjusted life expectancy(HALE)and life expectancy(LE).The effect of megacity expansion on narrowing the gap is rarely reported.This study aimed to disclose this potential relationship.Methods Annual life tables were constructed from identified death records and population counts from multiple administrative sources in Guangzhou,China,from 2010 to 2020.Joinpoint regression was used to evaluate the temporal trend.Generalized principal component analysis and multilevel models were applied to examine the county-level association between the gap and social determinants.Results Although LE and HALE in megacities are increasing steadily,their gap is widening.Socioeconomic and health services are guaranteed to narrow this gap.Increasing personal wealth,a growing number of newborns and healthy immigrants,high urbanization,and healthy aging have helped in narrowing this gap.Conclusion In megacities,parallel LE and HALE growth should be highly considered to narrow their gap.Multiple social determinants need to be integrated as a whole to formulate public health plans.展开更多
Adaptation is the pursuit of active, deliberate measures to enhance humankind’s capacity to manage water supply and attenuate demand in the face of climate uncertainty. This article contends that worsening constraint...Adaptation is the pursuit of active, deliberate measures to enhance humankind’s capacity to manage water supply and attenuate demand in the face of climate uncertainty. This article contends that worsening constraints upon freshwater due to climate variability demand concerted, imaginative, science-based solutions. These solutions must join creative management to co-production of climate knowledge. Through a series of case studies, we analyze the need for adaptation approaches to prevail over climate variability, and the role of these factors to facilitate their implementation. We also examine how translation of climate knowledge is helping spur adaptation at various spatial levels. These experiences point to the challenges in adaptation, and the adversity various regions will be faced if we do not.展开更多
Space monitoring of aerosol optical depth (AOD) trends over megacities can serve as a potential space indicator of global anthropogenic air-pollution changes. Three space aerosol sensors, MODIS-Terra, MODIS-Aqua and M...Space monitoring of aerosol optical depth (AOD) trends over megacities can serve as a potential space indicator of global anthropogenic air-pollution changes. Three space aerosol sensors, MODIS-Terra, MODIS-Aqua and MISR, were used in order to study recent decadal trends of AOD over megacities around the world. Space monitoring of AOD trends has the advantage of global coverage and applies the same approach to detecting AOD trends over different sites. In spite of instrumental and time differences among the three sensors investigated, their global pictures of AOD trends over the 189 largest cities in the world are quite similar. The increasing AOD trends over the largest cities in the Indian subcontinent, the Middle East, and North China can be clearly seen. By contrast, megacities in Europe, the north-east of US, and South-East Asia show mainly declining AOD trends. In the cases where all three sensors show similar signs of AOD trends, the results can be considered as reliable. This is supported by the observed trends in surface solar radiation, obtained by using network pyranometer measurements in North and South China, India, and Europe. In the cases where the three sensors show differing signs of AOD trends (e.g. South America), additional research is required in order to verify the obtained AOD trends.展开更多
Ⅰ. MAIN TRAFFIC PROBLEMS IN THE MEGACITIES IN CHINA (1) Road capacity is far from enough The road space per capita in China’s megacities has long been very limited and it is only recently did it began to increase fr...Ⅰ. MAIN TRAFFIC PROBLEMS IN THE MEGACITIES IN CHINA (1) Road capacity is far from enough The road space per capita in China’s megacities has long been very limited and it is only recently did it began to increase from 2.8 to 6.6 square meters.But, fast as it is, this change still cannot meet the demand of the growing urban traffic volume with an average annual rate of 20 percent. At present,among the 34 cities populated over one million people each in China, 27 are being suffered by展开更多
China has witnessed unprecedented urbanization over the past decades. The rapid expansion of urban population has been dominantly contributed by the floating population from rural areas, of which the spatiotemporal pa...China has witnessed unprecedented urbanization over the past decades. The rapid expansion of urban population has been dominantly contributed by the floating population from rural areas, of which the spatiotemporal patterns, driving forces, and multidimensional effects are scrutinized and evaluated in this study by using the latest national censuses conducted in 2000 and 2010. Analysis based on the county-level data comes to conclusions as follows. The spatial pattern of floating population has remained stable over the first decade of the new century. The top 1% cities with the largest floating population received 45.5% of all migrants in China. As the rapid development of mega-city regions, the coastal concentration areas of floating population tended to geographically united as a whole, whereas the spatial distribution of migrants within each region varied significantly. The migrant concentration area in the Yangtze River Delta was the largest and its expansion was also the most salient. However, the floating population has growingly moved into provincial capitals and other big cities in the inland regions and its gravity center has moved northward for around 110 km during the study period. The spatial pattern of floating population has been formed jointly by the state and market forces in transitional China and the impacts of state forces have been surpassed by those of market forces in the country as a whole. The attractiveness of coastal cities and counties to the floating population comes mainly from the nonagricultural employment opportunities and public services, reflecting that long-distance and long-term migrants have moved coastward not only to gain employment but also to enjoy city life. By contrast, in the central and western regions, places with a higher economic development level and at a higher administrative level are more attractive to floating populations, demonstrating that the state remains to play an important role in allocating economic resources and promoting regional development in inland China. As the main body of new urban residents, the floating population has contributed substantially to the elevation of the urbanization levels of migrant-sending and -receiving places, by 20.0% and 49.5% respectively. Compared with ex- tensively investigated interprovincial migrants, intra-provincial migrants have higher intention and ability to permanently live in cities and thus might become the main force of China＇s urbanization in the coming decades. The internal migration has also reshaped China＇s urban system in terms of its hierarchical organization and spatial structure.展开更多
Current global urbanisation processes are leading to new forms of massive urban constellations. The conceptualisations and classifications of these, however, are often ambiguous, overlap or lag behind in scientific li...Current global urbanisation processes are leading to new forms of massive urban constellations. The conceptualisations and classifications of these, however, are often ambiguous, overlap or lag behind in scientific literature. This article examines whether there is a common denominator to define and delimitate–and ultimately map–these new dimensions of cityscapes. In an extensive literature review we analysed and juxtaposed some of the most common concepts such as megacity, megaregion or megalopolis. We observed that many concepts are abstract or unspecific, and for those concepts for which physical parameters exist, the parameters are neither properly defined nor used in standardised ways. While understandably concepts originate from various disciplines, the authors identify a need for more precise definition and use of parameters. We conclude that often, spatial patterns of large urban areas resemble each other considerably but the definitions vary so widely that these differences may surpass any inconsistencies in the spatial delimitation process. In other words, today we have tools such as earth observation data and Geographic Information Systems to parameterise if clear definitions are provided. This appears not to be the case. The limiting factor when delineating large urban areas seems to be a commonly agreed ontology.展开更多
Carbonyl-containing volatile organic compounds （cVOCs） are important precursors of atmospheric photochemical reactions in the formation of ozone, smog and other air pollutants. China＇s megacities are economically d...Carbonyl-containing volatile organic compounds （cVOCs） are important precursors of atmospheric photochemical reactions in the formation of ozone, smog and other air pollutants. China＇s megacities are economically developed and densely populated metropolitan areas, usually with a population over ten million; they drive the rapid growth of surrounding urban clusters. So far, 21 cVOCs have been detected in the atmosphere of these megacities. The average annual total concentration of cVOCs is 55.6 μg/m^3, an alarmingly high level. Vehicle emissions, industrial discharges, excessive use of organic solvents and other factors have led to a situation where hazardous formaldehyde, acetaldehyde and acetone account for 62.4 percent of the total atmospheric concentration of cVOC in Chinese cities. In a quantitative evaluation using daily exposure levels, cancer risk and hazardquotient, we found that the excessive levels of atmospheric cVOCs in Beijing, Shanghai and Guangzhou pose serious health risks to their inhabitants. Air pollution persists, despite the brief improvements in air quality brought about by the air quality campaign undertaken during major intemational events like the 2008 Olympic Games, the 2010 Asian Games, and the 2010 World Expo. The health risks caused by atmospheric cVOCs in Chinese cities require close attention.展开更多
文摘As one of the most dynamic economic zones in China, the Yangtze River Delta has further increased its economic output,becoming more open to foreign investment and international cooperation over the past 30 years.Its economic stability and coordination have been strengthened;and the process of regional integration continues to accelerate.
基金supported by General Project of National Social Science Fund[Grant number.22BZZ077],Study on Efficiency Improvement Mechanism of Rural Relative Poverty Governance Driven by Big Data.
文摘The transformation of Chengdu Tianfu New Area,a state-level new district,from the first site of constructing the“Park City”to the representative of the“Park City”,contains a unique path of“Chinese Style Governance”.To expand the diverse paths of constructing megacities,the current research references the nudge theory of behavioral science,adopts the extended case method,and takes Chengdu Tianfu New Area as a typical case to summarize the“nudge”path of“Party City”construction.The study found that the government achieves the lock-in effect by the priming mechanism and uses the nudge strategy of improving environment and guiding public opinion,thereby helping the people make free choices.It realizes the framework effect by the salience mechanism and uses the strategies of highlighting key information and optimizing information delivery methods,which directly affects the behavior of the public.It achieves the commitment effect by the comparison mechanism,including the horizontal comparison and vertical comparison strategies,and gradually realizes the policy goals.It realizes the social norm effect by the imitation mechanism and uses the strategies of creating peer pressure and playing celebrity effect,which in turn influence people’s choices.With the help of the“nudging”mechanism,the construction of the park city has realized the interactive cycle of“government output-citizen feedback”and achieved the goal of“making great change through small actions”.As a new behavioral intervention tool,“nudging”provides an alternative explanation for the construction of the park city in Tianfu New Area and opens up new ideas for the construction of megacities.This study concludes that the construction of megacities can achieve the goal of“common return”through different ways and provides practical inspiration for future urban construction.
基金supported by the National Natural Science Foundation of China(Grant Nos.41925003&42130402)the Beijing Municipal Social Science Foundation(Grant No.20JCB073)。
文摘Inter-city mobility is one of the most important issues in the UN Sustainable Development Goals,as it is essential to access the regional labour market,goods and services,and to constrain the spread of infectious diseases.Although the gravity model has been proved to be an effective model to describe mobility among settlements,knowledge is still insufficient in regions where dozens of megacities interact closely and over 100 million people reside.In addition,the existing knowledge is limited to overall population mobility,while the difference in inter-city travel with different purposes is unexplored on such a large geographic scale.We revisited the gravity laws of inter-city mobility using the 2.12 billion trip chains recorded by 40.48 million mobile phone users’trajectories in the Jing-Jin-Ji Region,which contains China’s capital Beijing.Firstly,unlike previous studies,we found that non-commuting rather than commuting is the dominant type of inter-city mobility(89.3%).Noncommuting travellers have a travel distance 42.3%longer than commuting travellers.Secondly,we developed more accurate gravity models for the spatial distribution of inter-city commuting and non-commuting travel.We also found that inter-city mobility has a hierarchical structure,as the distribution of inter-city travel volume follows Zipf’s law.In particular,the hierarchy of non-commuting travel volume among the cities is more in line with an ideal Zipf distribution than commuting travel.Our findings contribute to new knowledge on basic inter-city mobility laws,and they have significant applications for regional policies on human mobility.
基金Hunan Provincial Natural Science Foundation of China(2022JJ40193).
文摘Background China’s 35 largest cities,including Wuhan,are inhabited by approximately 18%of the Chinese popula-tion,and account for 40%energy consumption and greenhouse gas emissions.Wuhan is the only sub-provincial city in Central China and,as the eighth largest economy nationwide,has experienced a notable increase in energy con-sumption.However,major knowledge gaps exist in understanding the nexus of economic development and carbon footprint and their drivers in Wuhan.Methods We studied Wuhan for the evolutionary characteristics of its carbon footprint(CF),the decoupling relation-ship between economic development and CF,and the essential drivers of CF.Based on the CF model,we quantified the dynamic trends of CF,carbon carrying capacity,carbon deficit,and carbon deficit pressure index from 2001 to 2020.We also adopted a decoupling model to clarify the coupled dynamics among total CF,its accounts,and eco-nomic development.We used the partial least squares method to analyze the influencing factors of Wuhan’s CF and determine the main drivers.Results The CF of Wuhan increased from 36.01 million t CO_(2)eq in 2001 to 70.07 million t CO_(2)eq in 2020,a growth rate of 94.61%,which was much faster than that of the carbon carrying capacity.The energy consumption account(84.15%)far exceeded other accounts,and was mostly contributed by raw coal,coke,and crude oil.The carbon deficit pressure index fluctuated in the range of 8.44-6.74%,indicating that Wuhan was in the relief zone and the mild enhancement zone during 2001-2020.Around the same time,Wuhan was in a transition stage between weak and strong CF decoupling and economic growth.The main driving factor of CF growth was the urban per capita residen-tial building area,while energy consumption per unit of GDP was responsible for the CF decline.Conclusions Our research highlights the interaction of urban ecological and economic systems,and that Wuhan’s CF changes were mainly affected by four factors:city size,economic development,social consumption,and technological progress.The findings are of realistic significance in promoting low-carbon urban development and improving the city’s sustainability,and the related policies can offer an excellent benchmark for other cities with similar challenges.
基金supported by the Tianjin Fundamental Research Program of the Tianjin Committee of Science and Technology (Grant No. 10JCYBJC050800)the National Special Science and Technology Program for Non-Profit Industry of the Ministry of Environmental Protection (Grant No. 200909022)+2 种基金the 973 Program (Grant No. 2011CB403402)the National Natural Science Foundation of China (NSFC) (Grant No. 40875001)the Basic Research Fund of the Chinese Academy of Meteorological Sciences (Grant No. 2008Z011)
文摘Tianjin is the third largest megacity and the fastest growth area in China,and consequently faces the problems of surface ozone and haze episodes.This study measures and characterizes volatile organic compounds （VOCs）,which are ozone precursors,to identify their possible sources and evaluate their contribution to ozone formation in urban and suburban Tianjin,China during the HaChi （Haze in China） summer campaign in 2009.A total of 107 species of ambient VOCs were detected,and the average concentrations of VOCs at urban and suburban sites were 92 and 174 ppbv,respectively.Of those,51 species of VOCs were extracted to analyze the possible VOC sources using positive matrix factorization.The identified sources of VOCs were significantly related to vehicular activities,which specifically contributed 60％ to urban and 42％ to suburban VOCs loadings in Tianjin.Industrial emission was the second most prominent source of ambient VOCs in both urban and suburban areas,although the contribution of industry in the suburban area （36％） was much higher than that at the urban area （16％）.We conclude that controlling vehicle emissions should be a top priority for VOC reduction,and that fast industrialization and urbanization causes air pollution to be more complex due to the combined emission of VOCs from industry and daily life,especially in suburban areas.
文摘COVID-19 pandemic has forced to lockdown entire India starting from 24th March 2020 to 14th April 2020(first phase), extended up to 3rd May 2020(second phase), and further extended up to 17th May 2020(third phase) with limited relaxation in non-hotspot areas. This strict lockdown has severely curtailed human activity across India. Here, aerosol concentrations of particular matters(PM) i.e., PM,PM, carbon monoxide(CO), nitrogen dioxide(NO), sulphur dioxide(SO), ammonia(NH) and ozone(O), and associated temperature fluctuation in four megacities(Delhi, Mumbai, Kolkata, and Chennai)from different regions of India were investigated. In this pandemic period, air temperature of Delhi,Kolkata, Mumbai and Chennai has decreased about 3 ℃, 2.5 ℃, 2 ℃ and 2 ℃ respectively. Compared to previous years and pre-lockdown period, air pollutants level and aerosol concentration(-41.91%,-37.13%,-54.94% and-46.79% respectively for Delhi, Mumbai, Kolkata and Chennai) in these four megacities has improved drastically during this lockdown period. Emission of PMhas experienced the highest decrease in these megacities, which directly shows the positive impact of restricted vehicular movement. Restricted emissions produce encouraging results in terms of urban air quality and temperature, which may encourage policymakers to consider it in terms of environmental sustainability.
基金supported by grants from the National Key Research and Development Program of China(Grant No.2017YFB0504000)National Natural Science Foundation of China(Grant No.41875043)+2 种基金the Strategic Priority Research 275 Program of the Chinese Academy of Sciences(Grant No.XDA17010102)External Cooperation Program of the Chinese Academy of Science(Grant No.GJHZ1802)Youth Innovation Promotion Association,CAS.
文摘Measurements of column-averaged dry-air mole fractions of carbon dioxide and carbon monoxide,CO_(2)(XCO_(2))and CO(XCO),were performed throughout 2019 at an urban site in Beijing using a compact Fourier Transform Spectrometer(FTS)EM27/SUN.This data set is used to assess the characteristics of combustion-related CO_(2)emissions of urban Beijing by analyzing the correlated daily anomalies of XCO and XCO_(2)(e.g.,ΔXCO andΔXCO_(2)).The EM27/SUN measurements were calibrated to a 125HR-FTS at the Xianghe station by an extra EM27/SUN instrument transferred between two sites.The ratio ofΔXCO overΔXCO_(2)(ΔXCO:ΔXCO_(2))is used to estimate the combustion efficiency in the Beijing region.A high correlation coefficient(0.86)betweenΔXCO andΔXCO_(2)is observed.The CO:CO_(2)emission ratio estimated from inventories is higher than the observedΔXCO:ΔXCO_(2)(10.46±0.11 ppb ppm^(−1))by 42.54%-101.15%,indicating an underestimation in combustion efficiency in the inventories.DailyΔXCO:ΔXCO_(2)are influenced by transportation governed by weather conditions,except for days in summer when the correlation is low due to the terrestrial biotic activity.By convolving the column footprint[ppm(μmol m-2 s-1)-1]generated by the Weather Research and Forecasting-X-Stochastic Time-Inverted Lagrangian Transport models(WRF-X-STILT)with two fossil-fuel emission inventories(the Multi-resolution Emission Inventory for China(MEIC)and the Peking University(PKU)inventory),the observed enhancements of CO_(2)and CO were used to evaluate the regional emissions.The CO_(2)emissions appear to be underestimated by 11%and 49%for the MEIC and PKU inventories,respectively,while CO emissions were overestimated by MEIC(30%)and PKU(35%)in the Beijing area.
文摘Rural-to-urban migration and globalized trade are swelling cities worldwide,but these forces are perhaps more powerfully concentrated in Dhaka,Bangladesh,than anywhere on earth.Born of a natural disaster 50 years ago,the world’s most densely-populated country faces multiple environmental challenges.Water,with seasonal monsoons,is both a blessing and a curse.A one meter rise in sea level,for example,would displace as many as 25 million Bangladeshis,and cause the largest mass migration in history.Each drought,flood,or cyclone drives scores of environmental refugees from rural areas to the capital city of Dhaka,where air and water pollution run rampant.Recent rapprochement with India over decades-long boundary disputes offers hope that environmental cooperation in the vulnerable Bay of Bengal can follow.
文摘Several factors may contribute to on-going challenges for spatial planning and policy in megacities such as Rome, including rapid population shifts, poorly organized areas, and lack of data through which monitoring urban growth and land use change. This research was conducted to examine past and current effects of the urbanization process, occurred over the large Roman urban system, on the basis of multi-source and multi-temporal optical remote sensing (RS) data, collected between 1990 and 2013. These changes were then validated via Geographic Information System (GIS) techniques, in a particular procedure applied to urban land/agricultural transformations. The proposed approach, based on geo-statistical methods, was used to calculate the index of innovative space (AP Index), useful for the monitoring of the urban sprawl phenomenon. Strong evidence of urban expansion over the north-eastern quarter of the city, accompanied by environmental degradation and loss of biodiversity, is provided. Urban infill developments are expected to emerge in the south-eastern areas too, and these might increase urban pressure as well. In conclusion, RS and GIS technologies together with ancillary data can be used to assist decision makers in preparing future plans to find out appropriate solutions to urbanization encroachment.
基金Youth Fund Project of the National Natural Science Foundation of China(51608009)Youth Top Talent Training Project of Support Plan for the Construction of High-level Teachers of Beijing Municipal Colleges and Universities in 2019(CIT&TCD201904010).
文摘In the process of new urbanization,the population of megacities is increasing rapidly,the scale of cities is expanding,and the supply of service facilities has been unable to meet the demand.As an important carrier of urban governance and urban management,the police station should properly deal with the existing problems in the urban police stations,and improve the quality of life of residents by optimizing urban service facilities,which is of great significance for the implementation of people-oriented new urbanization.Taking Changping District of Beijing as an example,this study pointed out that there were many problems in police stations in Changping District.For example,the area of land is not up to the standard,the service capacity is not up to the demand,and the facilities are not up to the demand.Then,three planning strategies:adjusting the planning standards of facilities,optimizing the spatial layout of facilities,and strengthening the later guarantee of facilities were put forward,so as to improve people’s satisfaction with life,promote the high-quality development of new urbanization,and provide reference for the supplement of service facilities in megacities.
基金supported by CASS Innovation Project"Study on the Evaluation and Improvement of Urbanization Quality in the Chinese Mainland."
文摘As urbanization expands＇ into the suburbs of Chinese cities, the conversion of farmers into citizens with urban social protection is becoming an important issue facing Chinese megacities. Taking Beijing as an example, this paper has calculated the one-off urbanization cost of farmers in China and arrived at the results of 500, 000 yuan per person for urbanization of centralized target regions in the suburb and 200, 000 yuan per person for urbanization of scattered target regions in the exurb. This paper considers that a diversified cost sharing mechanism should be put into place for the step-by-step urbanization of farmers. In addition, policy recommendations are proposed regarding the functional transformation of collective economic organizations, eradication of the urban-rural divide, enhancement of land system innovation and policy improvements for urbanization of rural residents.
基金supported by the Guangdong Basic and Applied Basic Research Foundation[grant 2020A1515011294,2020A1515110230,and 2021A1515011765]the China Postdoctoral Science Foundation[grant 2021M693594]+1 种基金the Guangzhou Municipal Health Commission[grant No.2021-2023-12,No.20201A011054]Guangzhou Municipal Science and Technology Bureau[grant 2021BRP004]。
文摘Objective Improvement in the quality of life is reflected in the narrowing of the gap between healthadjusted life expectancy(HALE)and life expectancy(LE).The effect of megacity expansion on narrowing the gap is rarely reported.This study aimed to disclose this potential relationship.Methods Annual life tables were constructed from identified death records and population counts from multiple administrative sources in Guangzhou,China,from 2010 to 2020.Joinpoint regression was used to evaluate the temporal trend.Generalized principal component analysis and multilevel models were applied to examine the county-level association between the gap and social determinants.Results Although LE and HALE in megacities are increasing steadily,their gap is widening.Socioeconomic and health services are guaranteed to narrow this gap.Increasing personal wealth,a growing number of newborns and healthy immigrants,high urbanization,and healthy aging have helped in narrowing this gap.Conclusion In megacities,parallel LE and HALE growth should be highly considered to narrow their gap.Multiple social determinants need to be integrated as a whole to formulate public health plans.
文摘Adaptation is the pursuit of active, deliberate measures to enhance humankind’s capacity to manage water supply and attenuate demand in the face of climate uncertainty. This article contends that worsening constraints upon freshwater due to climate variability demand concerted, imaginative, science-based solutions. These solutions must join creative management to co-production of climate knowledge. Through a series of case studies, we analyze the need for adaptation approaches to prevail over climate variability, and the role of these factors to facilitate their implementation. We also examine how translation of climate knowledge is helping spur adaptation at various spatial levels. These experiences point to the challenges in adaptation, and the adversity various regions will be faced if we do not.
文摘Space monitoring of aerosol optical depth (AOD) trends over megacities can serve as a potential space indicator of global anthropogenic air-pollution changes. Three space aerosol sensors, MODIS-Terra, MODIS-Aqua and MISR, were used in order to study recent decadal trends of AOD over megacities around the world. Space monitoring of AOD trends has the advantage of global coverage and applies the same approach to detecting AOD trends over different sites. In spite of instrumental and time differences among the three sensors investigated, their global pictures of AOD trends over the 189 largest cities in the world are quite similar. The increasing AOD trends over the largest cities in the Indian subcontinent, the Middle East, and North China can be clearly seen. By contrast, megacities in Europe, the north-east of US, and South-East Asia show mainly declining AOD trends. In the cases where all three sensors show similar signs of AOD trends, the results can be considered as reliable. This is supported by the observed trends in surface solar radiation, obtained by using network pyranometer measurements in North and South China, India, and Europe. In the cases where the three sensors show differing signs of AOD trends (e.g. South America), additional research is required in order to verify the obtained AOD trends.
文摘Ⅰ. MAIN TRAFFIC PROBLEMS IN THE MEGACITIES IN CHINA (1) Road capacity is far from enough The road space per capita in China’s megacities has long been very limited and it is only recently did it began to increase from 2.8 to 6.6 square meters.But, fast as it is, this change still cannot meet the demand of the growing urban traffic volume with an average annual rate of 20 percent. At present,among the 34 cities populated over one million people each in China, 27 are being suffered by
基金The New Teachers＇ Scientific Research Program funded by Beijing Forestry University, No.BLX2013028 National Natural Science Foundation of China, No.41371166
文摘China has witnessed unprecedented urbanization over the past decades. The rapid expansion of urban population has been dominantly contributed by the floating population from rural areas, of which the spatiotemporal patterns, driving forces, and multidimensional effects are scrutinized and evaluated in this study by using the latest national censuses conducted in 2000 and 2010. Analysis based on the county-level data comes to conclusions as follows. The spatial pattern of floating population has remained stable over the first decade of the new century. The top 1% cities with the largest floating population received 45.5% of all migrants in China. As the rapid development of mega-city regions, the coastal concentration areas of floating population tended to geographically united as a whole, whereas the spatial distribution of migrants within each region varied significantly. The migrant concentration area in the Yangtze River Delta was the largest and its expansion was also the most salient. However, the floating population has growingly moved into provincial capitals and other big cities in the inland regions and its gravity center has moved northward for around 110 km during the study period. The spatial pattern of floating population has been formed jointly by the state and market forces in transitional China and the impacts of state forces have been surpassed by those of market forces in the country as a whole. The attractiveness of coastal cities and counties to the floating population comes mainly from the nonagricultural employment opportunities and public services, reflecting that long-distance and long-term migrants have moved coastward not only to gain employment but also to enjoy city life. By contrast, in the central and western regions, places with a higher economic development level and at a higher administrative level are more attractive to floating populations, demonstrating that the state remains to play an important role in allocating economic resources and promoting regional development in inland China. As the main body of new urban residents, the floating population has contributed substantially to the elevation of the urbanization levels of migrant-sending and -receiving places, by 20.0% and 49.5% respectively. Compared with ex- tensively investigated interprovincial migrants, intra-provincial migrants have higher intention and ability to permanently live in cities and thus might become the main force of China＇s urbanization in the coming decades. The internal migration has also reshaped China＇s urban system in terms of its hierarchical organization and spatial structure.
文摘Current global urbanisation processes are leading to new forms of massive urban constellations. The conceptualisations and classifications of these, however, are often ambiguous, overlap or lag behind in scientific literature. This article examines whether there is a common denominator to define and delimitate–and ultimately map–these new dimensions of cityscapes. In an extensive literature review we analysed and juxtaposed some of the most common concepts such as megacity, megaregion or megalopolis. We observed that many concepts are abstract or unspecific, and for those concepts for which physical parameters exist, the parameters are neither properly defined nor used in standardised ways. While understandably concepts originate from various disciplines, the authors identify a need for more precise definition and use of parameters. We conclude that often, spatial patterns of large urban areas resemble each other considerably but the definitions vary so widely that these differences may surpass any inconsistencies in the spatial delimitation process. In other words, today we have tools such as earth observation data and Geographic Information Systems to parameterise if clear definitions are provided. This appears not to be the case. The limiting factor when delineating large urban areas seems to be a commonly agreed ontology.
基金supported by the National Natural Science Foundation of China Fund(No.40975077)the National Natural Science Foundation of China and Guangdong Province Joint Fund(No.U1201232)
文摘Carbonyl-containing volatile organic compounds （cVOCs） are important precursors of atmospheric photochemical reactions in the formation of ozone, smog and other air pollutants. China＇s megacities are economically developed and densely populated metropolitan areas, usually with a population over ten million; they drive the rapid growth of surrounding urban clusters. So far, 21 cVOCs have been detected in the atmosphere of these megacities. The average annual total concentration of cVOCs is 55.6 μg/m^3, an alarmingly high level. Vehicle emissions, industrial discharges, excessive use of organic solvents and other factors have led to a situation where hazardous formaldehyde, acetaldehyde and acetone account for 62.4 percent of the total atmospheric concentration of cVOC in Chinese cities. In a quantitative evaluation using daily exposure levels, cancer risk and hazardquotient, we found that the excessive levels of atmospheric cVOCs in Beijing, Shanghai and Guangzhou pose serious health risks to their inhabitants. Air pollution persists, despite the brief improvements in air quality brought about by the air quality campaign undertaken during major intemational events like the 2008 Olympic Games, the 2010 Asian Games, and the 2010 World Expo. The health risks caused by atmospheric cVOCs in Chinese cities require close attention.
