Chinese Megacities Research Articles

Value-driven Contention in China: Forms, Tactics and State Responses

Abstract This research challenges the conventional wisdom that value-driven protests in China are exceedingly rare and face harsh state repression. Drawing on a hand-coded, multi-source dataset of over 3,100 protests in three Chinese megacities from 2014 to 2016, we identify 67 protests that reveal a hitherto unknown underbelly of everyday, value-driven contention. Qualitatively, we identify three main forms of contentious performances. Quantitatively, we show how value-driven protesters combine non-disruptive tactics with ambitious targets and virtually never extract concessions. Surprisingly, we find that such protests are less often policed and repressed than other protests. They are also never met with violence from non-state actors. We provide three interpretations for the counter-intuitive finding on repression. This study shows that the Chinese state coexists with a non-negligible amount of explicitly regime-critical contention. It adopts a containment strategy, tolerating a certain extent of value-driven performances when the risk of spill-over into wider society is limited.

Low Methane Emissions from the Natural Gas Distribution System Indicated by Mobile Measurements in a Chinese Megacity Hangzhou

Low Methane Emissions from the Natural Gas Distribution System Indicated by Mobile Measurements in a Chinese Megacity Hangzhou

Optimized Resource Allocation for Sustainable Development in Beijing: Integrating Water, Land, Energy, and Carbon Nexus

Chinese megacities face significant challenges in reducing carbon emissions while balancing economic growth and social welfare. This study constructs an innovative multi-objective optimization model, the SD-NSGA-III model, integrated with a System Dynamics (SD) model and using the Non-dominated Sorting Genetic Algorithm III (NSGA-III) to optimize resource allocation in Beijing. The model targets environmental, economic, and social goals by establishing a water–land–energy–carbon (WLEC) nexus for analyzing resource allocation strategies and carbon reduction pathways under various constraints. Scenario simulations under the efficiency-oriented scenario indicated a potential reduction in energy carbon emissions of 81.4% by 2030. The fairness-oriented scenario revealed significant trade-offs between equity and emission reductions, emphasizing the need for balanced strategies. Introducing constraints on resources and economic growth significantly reduced median energy carbon emissions to 80 million tons by 2030. These findings demonstrate the effectiveness of the SD-NSGA-III model in providing actionable strategies for achieving carbon neutrality and sustainable development in cities.

Analysis of the spatial characteristics and driving forces of underground consumer service space in Chinese megacities based on multi-source data

Underground consumer service spaces (UCSS) offer new solutions for urban residents’ daily needs, but existing studies on their distribution and driving forces are often fragmented and overshadowed by research on other underground spaces, lacking targeted analysis. This study examines UCSS in the central urban areas of seven representative Chinese megacities. Using spatial analysis methods like kernel density estimation, multi-distance spatial clustering, and geographical detectors, the spatial characteristics and driving forces of UCSS are analyzed alongside aboveground consumer service spaces (ACSS). Results show that both ACSS and UCSS exhibit multi-centered, concentric spatial patterns, though UCSS demonstrates higher spatial aggregation. Unlike other underground public spaces (UPS), UCSS relies more on service industry agglomeration and market factors, while other UPS are more influenced by surrounding development intensity. UCSS follows the core principles of central place theory but deviates from the market-driven patterns typical of ACSS. Socioeconomic conditions and transportation infrastructure form the foundational basis for UCSS distribution, while service industry agglomeration, market dependence, and land development intensity exert more direct influence. The commercial atmosphere and existing underground space development play critical roles in UCSS distribution. Two key spatial scales for understanding UCSS distribution are the strong influence zones of shopping malls and metro stations, and high-density urban areas.

Pollution characterization and multi-index ecological risk assessment of microplastics in urban rivers from a Chinese megacity

Currently, a comprehensive understanding of the pollution risks of microplastics (MPs) in urban river ecosystems is still lacking. This study investigated the spatial distribution and morphological characteristics of MPs in surface waters of major rivers in Shenzhen, a megacity in China, using laser direct infrared (LDIR) imaging. A promisingly comprehensive risk assessment method, MultiMP, was first proposed in this study, taking into account the multidimensional characteristics of MPs including abundance, size, shapes, and polymer types. The results showed that MPs were widespread and highly heterogeneous, and the abundance of MPs ranged from 38 to 18380 particles/L, with an average of 2305 particles/L. Morphologically, polyamide (PA) (average 53.7 %), 30–50 µm (73.8 %), and pellet (65.7 %) were the predominant MPs types. Driving factors analyses revealed geographical distance, salinity, water temperature, and total nitrogen had relatively higher impacts on the abundance and morphology of MPs. The MultiMP results indicated that most of the river sampling sites and five major basins in Shenzhen were at moderate to high-risk levels. Polymer type and abundance had a relatively high impact on the environmental risk of MPs in the region. These findings contribute to improving the insights and management of the MPs pollution risks in megacity water bodies.

Source apportionment and health-risk assessment of PM2.5-bound elements in indoor/outdoor residential buildings in Chinese megacities

Particulate matter with a diameter of 2.5 μm or smaller (PM2.5) in indoor environments originates from both indoor and outdoor sources, influencing associated human health risks through different compositions. This study simultaneously collected and analyzed indoor and outdoor PM2.5 samples in three major Chinese megacities—Beijing, Shanghai, and Shenzhen—to characterize PM2.5 sources and assess their health impacts. A total of seven distinct sources, both indoor and outdoor, were identified for PM2.5: indoor activities, metal smelting, industrial activities, soil dust, vehicle emissions, coal combustion, and fuel oil combustion. Indoor activities accounted for approximately 20% of the residential indoor PM2.5, with the remainder predominantly due to outdoor PM2.5 infiltration. The contributions of indoor activities to noncarcinogenic and carcinogenic risks ranged from 3.6% to 28.5%, whereas outdoor PM2.5 sources posing greater health risks. The cumulative noncarcinogenic risks for adults in Beijing, Shanghai, and Shenzhen were 0.99, 1.15, and 0.72, respectively, slightly higher than those for children. The cumulative carcinogenic risks for adults were approximately five times those for children, with values of 6.90 × 10−5, 6.34 × 10−5, and 6.83 × 10−5, respectively, all surpassing the acceptable limit. Noncarcinogenic risks were predominantly attributed to Ni, Co, and Mn, contributing over 80% to the total risk, while Cr was the primary contributor (>89%) to carcinogenic risks. Indoor exposure accounting for over 80% of noncarcinogenic and carcinogenic risks for adults, and exceeding 90% for children. This study provides significant insights into the effective control of PM2.5 pollution and the reduction of health risks from a source perspective.

Segmented assimilation trajectories of physician trust among internal migrants in Shanghai, China: A cross-sectional study

Physician trust is necessary for improving physician–patient relationships and maintaining an effective health-care system. Most studies on the theory of segmentation assimilation have mainly focused on comparing immigrants in different countries and few studies have applied segmented assimilation to clarify physician–patient relationships, especially physician trust among internal migrants in the context of Chinese megacities. A random sample of 1200 internal migrants was collected through an online questionnaire conducted in Shanghai from August to December 2021. An exploratory K-means cluster analysis and multivariate logistic regression models were employed to identify patterns of segmented assimilation and examine their relationships with physician trust, as well as the factors influencing physician trust among internal migrants in Shanghai. Results show four main patterns were revealed, namely first-generation classic assimilation, first-generation integrative assimilation, first-generation segmentation, and second-generation underclass assimilation, supporting the theory of segmented assimilation. Association between assimilation pattern and physician trust was observed. A relationship was found between assimilation patterns and trust in physicians. Migrants belonging to the first-generation classic and integrative assimilation groups exhibited a higher level of trust in doctors compared to those in the segmented assimilation groups. Additionally, undergraduate and postgraduate education attainment, an annual income of <400 000 yuan, visiting the physician ≥2 times in the past year, and self-rated health status before and after population floating were significant contributing factors for good physician trust. The government can implement corresponding measures to maintain physician trust, improve cultural adaptability instead of only at the economic level among internal migrants, achieving the facilitation of their understanding of the health system and health service utilization to increase physician trust.

Identifying high-risk volatile organic compounds in residences of Chinese megacities: A comprehensive health-risk assessment

Indoor volatile organic compounds (VOCs) pose considerable health hazards. However, research on hazardous VOCs in Chinese residences has been conducted on a limited spectrum. This study used Monte Carlo simulations with data from Beijing, Shanghai, and Shenzhen to assess VOC health risks in Chinese homes. We identified high-risk VOCs and analyzed the impact of geographic location, age group, activity duration, and inhalation rate on VOC exposure, including lifetime risks. Formaldehyde, acrolein, naphthalene, and benzene posed the highest risks. Notably, acrolein made the leading contribution to non-cancer risks across all megacities. Naphthalene had elevated cancer and non-cancer risks in Shenzhen. This study highlights the need to investigate acrolein and naphthalene, which are currently unregulated but pose substantial health risks. The cumulative cancer risk (TCR) decreases from adults to children, while the cumulative non-cancer risk (HI) is higher for children. In all cities, the average TCR for adults exceeds the tolerable threshold of 10−4, and the average HI values surpass the safety threshold of 1. Nearly 100 % of the population faces a lifetime cancer risk above 10−4, and over 71 % face a non-cancer risk exceeding 10 (tenfold the benchmark). This study underscores the critical need for developing control strategies tailored to VOCs.

Sustainable Approaches to Oily Sludge Management in Chinese Megacities

Sustainable Approaches to Oily Sludge Management in Chinese Megacities

Composition and Sources of Organic Aerosol in Two Megacities in Western China Using Complementary Mass Spectrometric and Statistical Techniques.

Over 300 daily PM2.5 filter samples were collected in two western Chinese megacities, Xi'an and Chongqing, from October 2019 to May 2020. Their aqueous extracts were nebulized simultaneously to an aerosol mass spectrometer (AMS) and a recently developed extractive electrospray ionization (EESI) mass spectrometer, for bulk and near-molecular organic aerosol (OA) composition, respectively. Carbonate was quantified using EESI and a total organic carbon analyzer to separate inorganic carbon from dust. Via isotopically-labelled internal standards and positive matrix factorization, seven water-soluble sources were quantified separately using the AMS- and EESI-based analyses, with consistent types, concentrations, and correlations. These include dust, solid fuel combustion (SFC)-related, nitrogen- (and sulfur-) containing, summer/winter oxygenated OAs, and a cigarette-related OA only in EESI. When accounting for water-solubility, SFC-related OAs were the largest (53%) sources in Chongqing, while dust (consisting of 77% OA and 23% carbonates) was the largest (30%) source in Xi'an. Overall, this study presents one of the first times that complementary mass spectrometric techniques independently resolved consistent OA sources-with added chemical information-over multiple seasons and locations of complex pollution. The methods and quantified sources are essential for subsequent chemical, modelling, and health studies, and policy making for air pollution mitigation.

Enhancing urban identity through the refined management of architectural styles: insights from Wuhan

ABSTRACT The shaping of urban features is profoundl influenced by the underlying urban context, and architectural features and style management are important parts of the protection and cultivation of urban identity. However, in China, oversight in managing the urban context often results in neglect of the cultural values embedded in architectural aspects at the micro level. This, in turn, contributes to the convergence and disorder of urban architectural features and styles. This study builds upon the significance of the urban context and takes the typical Chinese megacity Wuhan as a case study. First, the research systematically outlines the diachronic development of architectural features and styles in Wuhan and meticulously analyses the prevailing problems. Subsequently, an evaluation is conducted on the efficacy of existing architectural features and style management policies and the approval processes for architectural schemes. Finally, the research formulates a comprehensive architectural feature and style management and implementation system that harmonizes Wuhan’s urban cultural heritage and urban identification characteristics. This paper aims to contribute to the refinement of urban identity management and the preservation of architectural diversity to foster a more cohesive and culturally resonant urban environment in Wuhan.

Exploring the production of spatial inequality in dockless bicycle sharing in Shenzhen

There have been rising concerns over the unequal geographical distribution of bicycle sharing services in cities. Previous research on inequalities of urban bikeshare has often focused on quantitatively mapping inequalities with big data from travel records. It has thus been unable to examine the causes, reproduction mechanisms, and consequences of observed spatial inequalities in detail. Using the case of Shenzhen, a Chinese megacity with strong governmental control on mobility and a historical legacy of urban segregation, this study aims to achieve a nuanced understanding of the mechanism through which operators, regulators, and users of dockless bicycle sharing interact to produce and reproduce inequalities in accessing and using the service. To achieve this, this study adopts a mixed-method approach consisting of GIS mapping analysis, survey, and interviews with cyclists and experts. The result shows that both the use frequency and perceived accessibility of dockless bicycles are higher in wealthier and more central neighbourhoods. Moreover, strong governmental regulation in the form of a designated parking system, fleet quota distribution and point-based service evaluation have reproduced and enhanced spatial inequalities in dockless bicycle use and access. The findings contribute to the literature by demonstrating how preexisting urban infrastructure and certain regulatory arrangements interact to form a reproduction cycle of inequalities in accessing and using dockless bicycles that favours more central and well-off neighbourhoods at the expense of marginalized communities in Shenzhen.

Atmospheric H2O2 during haze episodes in a Chinese megacity: Concentration, source, and implication on sulfate production

Atmospheric hydrogen peroxide (H2O2), as an important oxidant, plays a key role in atmospheric chemistry. To reveal its characteristics in polluted areas, comprehensive observations were conducted in Zhengzhou, China from February 22 to March 4, 2019, including heavy pollution days (HP) and light pollution days (LP). High NO concentrations (18 ± 26 ppbv) were recorded in HP, preventing the recombination reaction of two HO2• radicals. Surprisingly, higher concentrations of H2O2 were observed in HP (1.5 ± 0.6 ppbv) than those in LP (1.2 ± 0.6 ppbv). In addition to low wind speed and relative humidity, the elevated H2O2 in HP could be mainly attributed to intensified particle-phase photoreactions and biomass burning. In terms of sulfate formation, transition-metal ions (TMI)-catalyzed oxidation emerged as the predominant oxidant pathway in both HP and LP. Note that the average H2O2 oxidation rate increased from 3.6 × 10−2 in LP to 1.1 × 10−1 μg m−3 h−1 in HP. Moreover, the oxidation by H2O2 might exceed that of TMI catalysis under specific conditions, emerging as the primary driver of sulfate formation.

Metal-containing nanoparticles in road dust from a Chinese megacity over the last decade: Spatiotemporal variation and driving factors

As a crucial sink of metal-containing nanoparticles (MNPs), road dust can record their spatiotemporal variations in urban environments. In this study, taking Shanghai as a representative megacity in China, a total of 272 dust samples were collected in the winter and summer of 2013 and 2021/2022 to understand the spatiotemporal variations and driving factors of MNPs. The number concentrations of Fe-, Ti-, and Zn-containing NPs were 3.8 × 106 − 8.4 × 108, 2.3 × 106–1.4 × 108, and 6.0 × 105–2.3 × 108 particles/mg, respectively, according to single particle (sp)ICP-MS analysis. These MNPs showed significantly higher number concentrations in summer than in winter. Hotspots of Fe-containing NPs were more concentrated in industrial and traffic areas, Zn-containing NPs were mainly distributed in the central urban areas, while Ti-containing NPs were abundant in areas receiving high rainfall. The structural equation model results indicates that substantial rainfall in summer can help remove MNPs from atmospheric PM2.5 into dust, while in winter industrial and traffic activities were the primary contributors for MNPs. Moreover, the contribution of traffic emissions to MNPs has surpassed industrial one over the last decade, highlighting the urgency to control traffic-sourced MNPs, especially those from non-exhaust emissions by electric vehicles.

Gasoline and electric vehicle ownership rationing over time: Lottery vs. First-come-first-served schemes

This paper addresses the ownership rationing issues of gasoline vehicles (GV) and electric vehicles (EV) in a given time horizon. A state-owned vehicle manufacturer is assumed to be the producer of these vehicles. Two typical rationing schemes for the GV and EV ownership that have been implemented in some Chinese megacities, namely a simultaneous lottery scheme for both GV and EV and a hybrid scheme consisting of lottery for GV and first-come-first-served (FCFS) for EV, are investigated. Multi-period social cost minimization models are proposed for determining the optimal auto quota (i.e., the number of vehicles to be produced) and the optimal frequency of ownership allocation for each scheme in the given time horizon. In the proposed models, residents’ heterogeneity is considered in terms of their values of time (VOTs). The properties of the proposed models are analytically explored, and a comparison between the lottery mode and the FCFS mode is made. The results show that the lottery mode outperforms the FCFS mode in terms of the total social cost. The VOT threshold of the subsequent participants in auto rationing schemes tends to be higher than that of the preceding participants. The decision of EV subsidy should be cautiously made due to a tug of war between the resultant decreased pollutant emissions and increased traffic congestion. The implementation of the auto ownership rationing schemes can cause inequity issue in terms of the changes of travel costs of different-income residents. A Pareto-improvement strategy is presented to balance equity and efficiency of the rationing schemes.

Responses of the Urban Atmospheric Thermal Environment to Two Distinct Heat Waves and Their Changes With Future Urban Expansion in a Chinese Megacity

AbstractThis study investigates the responses of the urban atmospheric thermal environment to two distinct heat waves in Hefei, China, and explores potential changes associated with future urban expansion. During the Event 1, characterized by clear and dry conditions, the western Pacific subtropical high limits water vapor influx, resulting in a significant cooling effect in rural area due to higher surface latent heat flux. The urban heat island (UHI) intensity, calculated using surface temperature and 2‐m temperature, reaches 5.2°C and 1.7°C during the Event 1, respectively. Although Event 2, characterized by cloudy and humid conditions, exhibits weaker UHI and urban dry island effects, it remains highly unfavorable for human comfort. During distinct heat waves, the vertical extent of the warming effect induced by future urban expansion varies, which can be attributed to environmental factors, such as atmospheric stability and near‐surface wind speed.

Citizenization or Talent Recruitment? The Development of China’s Points-Based Hukou Channels

ABSTRACT Points-based channels for accessing urban citizenship (hukou) have spread in a context where the Chinese central authorities have sought to facilitate migrant workers’ access to hukou, a process named ‘citizenization’ (shiminhua). This multicase study analyses policy documents, media coverages, commercial agencies’ explanations and migrants’ online comments to retrace the development of points-based hukou channels between 2010 and 2022 in seven Chinese megacities. Although points-based hukou channels were initially meant for fostering migrant ‘citizenization’, they have been increasingly used for recruiting the most desirable migrants, so-called ‘talents’. Intended to facilitate the urban integration of long-term ordinary migrant workers, the new points-based channels used criteria related to length of residence instead of mainly level of economic capital. However, adapting to guidelines imposed from the central or provincial governments while pursuing their own interests, municipal governments have made the channels more selective and more complex over the years. The discrepancy between the hopes generated by the promise of citizenization through points-based channels and the complexity of their workings and selectivity generates disappointment, and gives rise to many complaints voiced by ordinary citizens.

Significantly underestimated traffic-related ammonia emissions in Chinese megacities: Evidence from satellite observations during COVID-19 lockdowns

Ammonia (NH3) plays an important role in the formation of atmospheric particulate matter, but the contribution of traffic-related emissions remains unclear, particularly in megacities with a large number of vehicles. Taking the opportunity of the stringent COVID-19 lockdowns implemented in Beijing and Shanghai in 2022, this study aims to estimate the traffic-related NH3 emissions in these two megacities based on satellite observations. Differences between urban and suburban areas during the lockdown and non-lockdown periods are compared. It was found that despite different dominating sources, the overall NH3 concentrations in urban and suburban areas were at a similar level, and the lockdown resulted in a more prominent decrease in urban areas, where traffic activities were most heavily affected. The traffic-related contribution to the total emission was estimated to be ∼30% in megacities, and ∼40% in urban areas, which are about 2–10 times higher than that in previous studies. The findings indicate that the traffic-related NH3 emissions have been significantly underestimated in previous studies and may play a more critical role in the formation of air pollution in megacities, especially in winter, when agricultural emissions are relatively low. This study highlights the importance of traffic-related NH3 emissions in Chinese megacities and the need to reassess the emissions and their impacts on air quality.

Construction and application of economic resilience evaluation model for megacities.

Economic resilience provides a new perspective for megacities to achieve sustainable development when facing multiple shocks, and its accurate evaluation is an essential prerequisite for optimizing urban governance. There are currently no generally accepted methods for empirical evaluation or measuring economic resilience, and the present study aims to contribute to in both the research field and methodology. The present study sets dimensions and indicators based on economic resilience's theoretical and empirical research and used Decision Making Trial and Evaluation Laboratory (DEMATEL) and Interactive Structural Modeling (ISM) methods to exclude the effect indicators and divide the indicator hierarchy, respectively. Subsequently, the present study conducts model validation using Chinese megacities as a case study. The game theory weighting method, which combines the Analytic Hierarchy Process (AHP) and Entropy methods, is used to calculate indicator weights, and the VIKOR (VIseKriterijumska Optimizacija i KOmpromisno Resenje) method is used to evaluate and compare economic resilience of megacities. The research findings indicate that the evaluation model constructed in the present study included 15 indicators (after excluding three effect indicators) divided into four levels. After merging the levels, they correspond to three dimensions: resistance, recoverability, and adaptability. In addition, using Chinese megacities as a case study, the evaluation results found that Beijing, Shanghai, and Shenzhen have high economic resilience, Tianjin and Guangzhou have moderate economic resilience, Chengdu has low economic resilience, and Chongqing has the lowest economic resilience. This result is consistent with previous studies and verifies the model's effectiveness. The present study also found that megacities with lower levels of economic resilience exhibit a more significant upward trend, as well as the highest and higher proportion of economic resilience in Chinese megacities depending on time passes, indicating that megacities' economic resilience is weakening. The evaluation result obtained in the present study is more specific, precise, and focused on depicting the distribution differences and development trends of economic resilience at the urban level.

Variations of source-specific risks for inhalable particles-bound PAHs during long-term air pollution controls in a Chinese megacity: Impact of gas/particle partitioning

Gas/particle (G/P) partitioning is a determining factor that drives the behavior of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere. To comprehend the variations and impacts of PAHs G/P partitioning on inhalation risks from different sources, atmospheric PAHs in Chengdu were studied from January 2009 to January 2021. Chengdu's air quality demonstrated improvement, with a noticeable decline in PM10 (from 238 to 103 μg m−3), PM10-bound PAHs mass concentrations (from 0.08 to 0.01 μg m−3), as well as PAHs inhalation non-cancer (from 63.5 to 7.1) and cancer risks (from 6.2 × 10−5 to 7.7 × 10−6). Decreasing trends were also observed in the concentrations of organic carbon (OC) and the values of absorptive G/P partitioning coefficient (Kp, OM) from 2009 to 2020, indicating a slight decrease in the PM absorptive capacity. A positive matrix factorization (PMF) model utilized three distinct datasets: PMFpp (particle-phase PAHs only), PMFtot (total PAHs concentrations), and PMFpp/gas (particle-phase in parallel with gas-phase PAHs). PMFpp and PMFpp/gas provide reasonable source apportionment and source-specific risk results. However, daily variations in source contributions of PMFtot were found to be unreasonable. PMFpp/gas and PMFtot could identify a source of low molecular weight PAHs (LPAHs) related to temperature, and a significantly positive correlation between LPAHs and temperature was discovered. Gas/particle partitioning of PAHs showed a notable impact on source-specific risks associated with coal and biomass combustion (CC&BC). The findings contribute to our understanding of the variation in PAHs G/P partitioning and the PM absorptive capacity resulting from effective air pollution control in China. Additionally, they offer prerequisite information for incorporating semi-volatile organic compounds in source apportionment and source-specific risk assessment.