Environmental economic geography emerges as a reflection of the marginalization of the environment within the discipline of economic geography. It seeks to re-establish the linkage between economic geography and the environment. After almost two decades of development, environmental economic geography is still suffering from its poly-vocal, fragmented, and marginalized issues. This study scrutinizes the debates over the research agenda on environmental economic geography and reviews two primary strands of the literature. On this basis, this study discusses challenges for the future development of environmental economic geography. This study comes to four conclusions. Firstly, the development of environmental economic geography follows the theoretical advances in economic geography. It explore how environmental changes modify the spatial patterns of economic development. It also investigate how the spatial configuration of economic activities responds to the rising environmental risks and intensifying resource scarcity. Two research themes emerge, namely environmental governance and green transition. Secondly, environmental economic geography uses the theoretical framework of the Global Value Chain (GVC) and Global Production Network (GPN) to investigate how firms and regions can simultaneously upgrade in environmental and economic terms. It also seeks to establish the linkages between GVC/GPN governance and environmental governance. On the other hand, environmental economic geography identifies environmental regulation as a locational factor and examines its role in the location choice model. The empirical result offers various counter-examples for classical hypotheses, such as the Pollution Haven Hypothesis, the Porter Hypothesis, and the Environmental Kuznets Curve Hypothesis. Thirdly, environmental economic geography combines its theoretical interests with the theoretical advances in evolutionary economic geography. Particularly, the regional diversification theory and the path creation theory are incorporated into the empirical studies of environmental economic geography, which seek to unravel the conditions and processes of green transitions. Based on these theories, recent studies also offer some predictors for the regional green transition. Lastly, this study proposes that environmental economic geography is still suffering from the divergence between natural science and social science on research paradigm. Besides, the theoretical development of environmental economic geography is subject to a late-comer disadvantage. In this regard, it requires environmental economic geography to become more problem-oriented in the future, embracing the opportunities embedded in the issues for China’s sustainable development.

In recent years, the concept of sustainability transitions and its related research have increasingly drawn attention from economic geographers. Sustainability transitions studies aim to investigate the multi-scalar causality of mechanisms and spatial dynamics on how regional green technologies, consuming markets and industrial transformations emerge and develop over time. This research strand has become one of the emerging topics in both evolutionary economic geography and environmental economic geography. To better capture the progress of sustainability transitions studies, this paper conducts a bibliometrics-based literature review based on 2453 articles in the field during the past two decades. Besides, through an in-depth critical review on geographies of transitions, this paper identifies several key theoretical problems and shortcomings in the geographies of transitions literature. It has addressed the theoretical merits and value of economic geography for improving sustainability transitions studies. The findings of the paper are: (1) As one of the most promising research themes in innovation studies, sustainability management and environment science, sustainability transition studies have been increasingly disciplinarily pluralistic. The economic geographical research on sustainability transitions, in particular, focuses on three key research topics, including the co-evolution mechanisms between technologies and societies in regional new green industrial path development, multi-scalar driving forces and agency-structure interactive mechanisms of sustainability transitions, the role of transitions in shaping environmental economic and socio-spatial impacts, and the varieties of transition mechanisms. (2) There are in general three perspective advantages of economic geography for transitions studies that can be identified, namely, spatio-temporal sensitivity, spatial varieties of transition mechanisms, processes and impacts/outcomes, and place embeddedness of new socio-technical regimes in industrial systems and its geographies of legitimation. (3) Three orientations for economic geography to enhancing transitions studies are identified: deepening of geographical concepts (including place, scale and space), interactions and integrations with different approaches in economic geography (namely, transitions with evolutionary, institutional, and geographical political economy), and construction avenues for comprehensive analytical frameworks (integration of geographically multi-scalar perspective with multi-level perspectives, and that of regional innovation systems perspective with the approach of technological innovation systems. (4) Three promising research agendas on geographies of transitions in China are proposed, namely, localized transitions research by incorporating the role of Chinese-specific national contexts, green niche development and spatial mechanisms of its transitions, and regional new industrial path development and its related transition studies.

The research on location and relocation of polluting enterprises, including their associated mechanisms, is a hot topic in environmental economic geography, which has attracted extensive attention of scholars and policy makers. Existing studies have explored the influencing factors of local government environmental regulations on the entry and exit, spatial distribution and industrial transfer of polluting enterprises from the perspective of formal institutions, while relatively ignoring the role of informal institutional factors such as local social capital, residents’ environmental awareness and corporate environmental responsibility which also has a potential impact on enterprise exit. Based on the Chinese industrial enterprises data in 2011, China General Social Survey (CGSS) data and urban statistical yearbook data, this paper constructs China’s urban scale social capital from three aspects of social norms, social networks and social trust, and uses the binary logit regression model to explore the impact of social capital and environmental regulation on the exit of Chinese polluting enterprises. The results show that:(1) The role of environmental regulation has been verified with a threshold effect in the promotion of environmental regulation on the exit of polluting enterprises. (2) Social normative factors, such as public environmental awareness and corporate environmental responsibility, constitute external informal environmental pressure on the survival of polluting enterprises and positively support the exit of polluting enterprises; However, social trust and social network have no direct and significant effect on polluting enterprises as expected. (3) Interactive model shows that social capital has a positive interaction with environmental regulation in area with high environmental regulation, which can form a positive relation between formal and informal systems. Such relation constitutes a strong driving force for polluting enterprises withdraw from the local market. This study suggests that informal institutional environment has an important impact on the survival of polluting enterprises and there are rich interactive activities with environmental regulation. The present study explains influence mechanism of polluting enterprises exit from the perspective of social capital, which complements the existing research on environmental regulation from the informal institutional aspect. Meanwhile, it provides a practical reference for the sustainable operation of polluting enterprises and the formulation of environmental governance policies.

Environmental justice studies focus on the spatial justice of people's life quality. With the rapid development of urbanization and industrialization, industrial pollution has led to intensifying environmental degradation. Due to the spatial distribution of polluting enterprises, the levels of environmental degradation vary among urban settlements in the city. Recently, this variance has become a major environmental justice concern in China. Based on this understanding, it is imperative to understand the relationship between distribution of polluting enterprises and the social characteristics of the regional population from the spatial and temporal perspective. Cities with many industrial enterprises can lead to differential distributions in residential settlements. Guangzhou, a typical city, is selected as the empirical case. Based on a collection of enterprise census of 1995, 2004 and 2013 and the population census data of 1990, 2000 and 2010, this study analyzed the distribution of polluting enterprises and its spatial changes using ArcGIS visualization tool, and further examined the spatio-temporal changes of relationship between polluting enterprises and sociodemographic characteristics of regional population in Guangzhou by geographic weighted regression model. We find that the clustering of polluting enterprises has transferred from the central city to the suburban and border areas. The regression results reveal that old people and immigrants had become the main groups greatly affected by enterprise pollution in the 1990s, whereas differences among social classes including social stability, educational level and income level are related to the spatial distribution of polluting enterprises since 2000. This change of spatial relationship reflects the reconfiguration of urban industries and socio-spatial differentiation in modern Guangzhou. Further analysis discovers that the spatially influenced environmental injustice of pollution evolves from insignificance to a significantly city-wide relationship between different social classes and the pollution burden of enterprises. This evolution is different from the characteristics and mechanisms in a Western context. Compared to their Western counterparts, the public environmental resources are endowed with commodity attributes and the fundamental driving force to redistribute spatial environmental benefits through profit capture under the Chinese social market system. Based on our findings, this research further calls attention to seriously considering the environmental rights of low-income classes and emphasizing the need of public participation when making relevant policies.

Facing the severe problem of agricultural non-point source pollution, the diffusion and adoption of environmentally-friendly agricultural technology is of decisive significance to the modernization and the revitalization of ecology in rural China. However, environmentally-friendly agricultural technology is currently hard to promote and with a low acceptance in rural areas. Previous studies have proved that social network is an effective way and foundation for technology diffusion. Correspondingly, this paper constructs a theoretical framework of environmentally-friendly agricultural technology innovation diffusion from the perspective of social networks. Through the quantitative analysis of questionnaire data of 3015 households in 10 counties and cities of Guangdong Province from 2018 to 2020 and the fieldwork observation of non-point source agricultural pollution control in this province, this paper concludes that there are four stages of environment-friendly agricultural technology diffusion: (1) Initial stage: discrete and simple technical interaction among rural households emerges. (2) Single-core stage: single core such as elite farmer has formed and technology starts to diffuse through kinship network. (3) Multi-core stage: there have been several elite farmers and the diffusion goes through occupational network rather than kinship. (4) High-level interaction stage: agricultural economic organization and agricultural entrepreneur have been established; functional network has been formed. Behind the four stages, individual farmers keep on accumulating their own material, human and social capital to achieve the upgrade of their node level, also known as the process of technology diffusion, from disorder to formalization. Correspondingly, there are four main influencing factors of the diffusion of environmentally-friendly agricultural technology: individual resource endowment, technology effectiveness and perception, technology diffusion channels and external environment. These factors play different roles in different stages. The results of this study can be beneficial to the understanding of the underlying mechanism of environmentally-friendly agricultural technology diffusion in rural China, and are of policy significance for the diffusion and adoption of similar technologies. According to the stage characteristics of the diffusion of new technology, the government needs to guide and promote the mode of communication in accordance with local conditions.

As an essential loop in China′s low-carbon transition progresses, energy-intensive industries played irreplaceable roles in achieving carbon peak and carbon neutral goals. Based on the industrial upstream and downstream linkages, this study attempts to compare the changes between the production- and consumption-based carbon emissions, construct China's embodied carbon emission networks through industrial linkages, measure the embodied carbon transfer efficiency between upstream and downstream industries, trace the carbon risk transmission of energy-intensive industries, and identify the key nodes and paths under low-carbon transition. The main conclusions are as follows:(1) There remains a huge gap between the production- and consumption-based carbon emissions. The direct carbon emissions of energy-intensive industries accounted for about 80% in China's overall industrial system, while the corresponding consumption-based carbon emissions accounted for less than 10%. (2) The embodied carbon transfer efficiencies of petroleum processing, chemical raw materials and products, non-ferrous metal processing industries′ upstream and downstream are relatively high, while the embodied carbon transfer efficiencies of the electricity production and supply, non-metallic mineral products, and ferrous metal processing industries' upstream and downstream are relatively low. (3) Along with the increase of the industrial linkages, the proportion of energy intensive industries' embodied carbon emissions decreased by the production layer, and the key nodes and paths in carbon risk transmission of energy-intensive industries are different. (4) The carbon emission reduction per unit of value added in energy-intensive industries including electricity production and supply, ferrous metal processing, and non-metallic mineral products were higher than that of other energy-intensive industries, with relatively high carbon emission reduction efficiencies and more significant carbon emission reduction efficiencies. Through constructing the embodied carbon emission networks through industrial linkages and identifying the key nodes and paths of carbon risk transmission under low-carbon transition, this study is expected to provide practical quantified supports and policy implications for the sustainable low-carbon transition and potential risk prediction related to China's energy-intensive industries.

E-commerce and other new forms of consumption have developed rapidly in recent years, and their impact on carbon emissions can not be ignored. In terms of the spatial decomposition and the embodied carbon transfer, based on the research of the carbon footprint in the e-commerce express box life cycle, we study the geographic spatial couplings between the e-commerce behavior and carbon footprint in the raw material production, manufacture and consumption stages, and analyse the pattern characteristics of the emissions by stage and aggregate at provincial level, and the network layout of the embodied carbon emission transfer with the express flow. The results show that the carbon emissions in the raw material stage are mostly in the location of wood raw material suppliers, while the carbon emissions in the production stage are highly coupled with the location of express delivery, and the carbon emissions in the utilization stage are coupled with the location of express receiving area. The carbon emissions of e-commerce express box cartons in China of every stage are highly concentrated. The carbon emissions in the raw material stage are mainly concentrated in Guangxi, while in the production and consumption stages are concentrated in Guangdong, Zhejiang and Jiangsu, showing a general distribution pattern of "more in the eastern region and less in the western region; more in the southern region and less in the northern region". Provinces with higher total carbon emissions are mostly driven by production, while provinces with lower total carbon emissions are mostly driven by consumption. The embodied carbon emission transfer network presents a "hub-and-spoke" structure of "net outflow in few provinces, while net inflow in most provinces". Zhejiang and Guangdong, accounting for about 80% of the net outflow, are the largest places of departure of the embodied carbon emission inflow of most provinces, while Beijing is the sample with the largest net inflow. The division of responsibilities based on the embodied carbon emission transfer is an important factor of management decision, while the green packaging has made a great contribution to emission reduction, so it is urgent to seek technological breakthrough, and the carbon emissions of new consumption forms deserve long-term attention.

Global warming is a great challenge faced by all mankind. The continued increase in greenhouse gas emissions will have a negative impact on agricultural production, socio-economic activities and human life, and ultimately hinder the process of achieving global sustainable development. This study attempts to introduce the variable of digital economy development into the research framework of carbon emission impact factor theory to systematically examine the effect of digital economy development on urban carbon emissions. This study was conducted to investigate the spatial effects of the digital economy on urban carbon emissions. Based on the panel data of 286 cities from 2011 to 2017, this study analyzes the impact of digital economy development on urban carbon emissions using the spatial Durbin model and the spatial DID model. The main conclusions are as follows:(1) There is spatial heterogeneity in the development pattern of digital economy, and the development pattern changes from "multi-point" sporadic distribution to "cluster" agglomeration, but the gap between the development levels of cities has not been narrowed, and the Yangtze River Delta becomes an important digital economy agglomeration area. (2) The digital economy has a significant negative effect on urban carbon emissions, and the findings are robust to the introduction of the exogenous policy shock of "smart cities". Moreover, there is spatial heterogeneity in this effect, with the negative effect of digital economy on carbon emissions being stronger in the eastern region, and the influence of digital economy is stronger in regions located within urban agglomerations. (3) In order to investigate the spatial decay characteristics of the spillover effect of the digital economy on urban carbon emissions, the spillover effect analysis of the multi-distance economic circle is carried out, and it is found that the spillover effect of the digital economy on carbon emissions peaks at 1100 km. (4) The coverage of digital infrastructure does not have a significant negative effect on carbon emissions in the region, while digital industry development, digital innovation capacity and digital inclusive finance all have a significant negative effect on carbon emissions in the region and neighboring areas. This study adds to the lack of research on the digital economy and carbon emissions, and provides some theoretical reference for the study of the environmental improvement effects of the digital economy.

Based on the number of patent applications in the field of solar and wind energy submitted in 367 cities in China, we measure the technological innovation ability of China's new energy industry. Then this industry’s innovation phases, spatial distributions, spatial correlations and influencing factors between 2001 and 2018 are explored by means of Gini coefficient, spatial autocorrelation and spatial measurement model. Results show that: (1) The technology innovation and development in China's new energy industry presents an overall growing trend, with obvious phase characteristics and different changing trends. Oil crisis and financial crisis are two important events in the development process, where national incentive policies also play an important role. (2) The Gini Index of the eastern region where innovation outputs are mainly concentrated shows little change; in contrast, the Gini Index of the central and northeastern regions shows a decline trend. On the other hand, the innovation ability is weak in the western region, with the largest difference in innovation ability related to new energy technologies. (3) High level innovation hotspots are widely distributed across developed cities. (4) The Moran's I value for technological innovation capabilities in solar and wind energy is both positive and rising, indicating that there is a significant spatial correlation in terms of new energy technological innovation capabilities in cities, and the spatial agglomeration gradually intensifies. The H-H cluster areas are mainly distributed in the Beijing-Tianjin-Hebei region, the Yangtze River Delta region and the Pearl River Delta region, while the H-L cluster areas are mainly distributed in the provincial capitals of central and western regions, with no obvious driving effect for neighboring cities, or with only limited radiation effect. (5) Economic foundation, education level, industrialization level, electricity demand, human capital, technology investment level, environmental regulation, resource endowment and urban innovation ability all have some impact on the development of the new energy industry’s technological innovation of cities. According to the four major regional factors, the influence and constraints of the development in solar and wind energy technology innovation have obvious regional heterogeneity. The level of economic development is the primary driving factor and an important foundation for bolstering the technological innovation and development of the new energy industry. The regional effects of environmental regulations, industrial structures and resource endowments are significantly different.

The carbon neutrality target is not only China′ s commitment to climate governance, but also the endogenous demand for high-quality economic development. This paper, based on China′s energy consumption, land utilization pattern and input-output data, is aimed to conduct research on China's inter-provincial ecological security, coordinated development and carbon ecological compensation in the context of basic theoretical framework of ecological footprint. The conclusions of this paper are as follows. (1) Ecological security and regional coordination level continue to decline, which present the characteristics of regional convergence. From 2000 to 2017, the ESI index of China as a whole rose from 1.08 to 3.06, and the ECI index decreased from 1.413 to 1.261. The level of ecological security and coordinated development in 24 provincial-level regions declined. The level of ecological security and coordinated development showed an obvious trend of consistency, i.e., low coordinated development level in regions with low security level, and high coordinated development level in regions with high security level. (2) China is witnessing rapidly growing ecological "debt". Regional ecological compensation shows the following characteristics:eastern China "pays compensation", western China "accepts compensation", and central China "maintains a balance". Based on different policy objectives, this paper designs two ecological compensation schemes:"net zero emission" and "net zero contribution". Under the "net zero emissions" scheme, China's ecological compensation payments increased from $1334.57 million to $83819.61 million during the study period, a 60-fold increase over 17 years. On the regional compensation structure, the three coastal economic zones are long-term compensation payment areas, but the proportion of compensation payment in the whole country is gradually declining; correspondingly, the proportion of compensation payment in the middle reaches of the Yellow River and the middle reaches of the Yangtze River increased rapidly. Under the net zero contribution compensation scheme, China-wide compensation achieves accounting balance. Regionally, eastern China pays for carbon offsetting, western China is compensated, and central China can basically keep the balance.

Based on the data of 61 prefecture-level cities in the Yellow River Basin from 2005 to 2017, this paper constructed the input-output index system of green development efficiency, and used various spatial econometric models to examine the spatio-temporal pattern characteristics and influencing factors of green development efficiency in the study area. The following conclusions can be drawn as follows. (1) The regional differences of green development efficiency are gradually widening, evolving from “small differences and high efficiency” to “large differences and low efficiency” totally, which indicates that the club convergence characteristics of green development efficiency are obvious. (2) Scale efficiency makes significant contribution to the growth of green development efficiency, showing that large-scale agglomeration and intensive development are still an important guarantee for the improvement of green development efficiency. However, science and technology have not yet played an important driving role in improving the green development efficiency. In the future, improving the level of science and technology in this basin is the key to optimizing and improving the green development efficiency. (3) There is an obvious spatial reliable correlation of green development efficiency within the study period, and the regional spatial agglomeration featured with similar green development efficiency level is significant. (4) The spatial distributions of green development efficiency are obviously diverse, and the regional differences between the east-west distribution and north-south distribution of high-efficiency areas are prominent, which mainly shows a cluster development stimulated with urban agglomeration. and reflects that the green development efficiency of the study basin has a circular cumulative path dependent effect. The influencing factors of green development efficiency in the Yellow River Basin can be attributed to the adjustment effect of industrial structure, the growth effect of economic development, the demonstration effect and spillover effect of science and technology, the government regulation mechanism and market-oriented mechanism. Finally, Tobit regression model is used to analyze the influencing intensity and direction of industrial structure, economic development, science and technology, government regulation and marketization level on green development efficiency in the Yellow River Basin and its subzones.

The Yangtze River Delta is a demonstration area for China's high-quality integrated development and an important area for China to achieve its peak dioxide emissions by 2030 and carbon neutrality targets by 2060. In the context of the transformation of China's administrative region economy to an integrated economy, the regional integration of the Yangtze River Delta has reduced administrative barriers and optimized the allocation of factors. At the same time, what impact does it have on urban carbon emissions? Based on the panel data of prefecture level and above cities in China, this paper regards the issuance of The Regional Planning of Yangtze River Delta as a quasi-natural experiment, using the difference-in-difference (DID) method to estimate the effects of regional integration in the study area on urban carbon emissions. Furthermore, by using the mediation effect model, we identify the possible internal mechanism of regional integration on carbon emission effects. The results showed that regional integration policy of this delta in 2010 significantly reduced urban carbon emissions, and after a series of robustness tests such as the parallel trend test, PSM-DID and placebo test were still true. From the perspective of dynamic effects, the carbon emission reduction effect appeared in the third year after the issuance of regional integration policy. At the same time, compared with general hierarchy cities, regional integration had a greater effect on carbon emissions reduction of high hierarchy cities. Mechanism verification showed that regional integration policy aggravated urban carbon emissions through the strengthening of economic links between cities, and reduced urban carbon emissions by promoting the upgrading of the industrial structure and the improvement of urban technology. From the perspective of better achieving the goal of high-quality integration in the Yangtze River Delta, it is suggested that the delta should actively explore the cooperation mechanism of carbon emission reduction and green development between cities, and establish a green development evaluation index system that can be monitored and operated. Besides, we should focus on the green transformation of industries and increase investment in green technology research and development among cities in the Yangtze River Delta.

Resource and environmental constraints pose severe challenges to China's energy consumption. Smog can be seen as a concentrated outbreak of long-term accumulation of structural contradictions in terminal energy consumption. With the help of K-means clustering, spatial correlation analysis and other methods, this paper systematically studies the spatiotemporal characteristics and structural evolution of the terminal energy consumption of 30 provincial-level units. Furthermore, the spatial measurement model is used to explore the impact of terminal energy consumption on environmental pollution from multiple perspectives. The results show that: (1) Per capita terminal energy consumption of each provincial-level unit has increased to varying degrees during the study period, but the inter-provincial differences are still significant. (2) In terms of terminal energy consumption, during the study period there is a significant positive spatial correlation, indicating the existence of spatial agglomeration characteristics, and the formation of a variety of spatial agglomeration types. (3) As for terminal energy consumption structure, due to large differences in resource endowments and industrial structures, various types in different provincial-level units show diversified evolutionary characteristics. (4) Through spatial econometric model testing, it is found that terminal energy consumption has a significant positive impact on the air quality index, and this impact differs in different energy consumption types. There are obvious differences between the structure and different regions. (5) Based on the research conclusions, targeted countermeasures and suggestions for energy consumption and structural optimization are put forward, in order to provide ideas and references for reducing carbon emissions and improving air quality. Finally, this article attempts to explain the impact of energy on air pollution from the consumption side of energy, but the production side of energy and the intermediate stage of processing and conversion may also form a more complex path of impact on environmental pollution, which is worthy of further analysis. In addition, with the continuous advancement of environmental protection technology, China's clean energy continues to increase, gradually transforming from auxiliary energy to main energy, and a clean, low-carbon, safe and efficient energy system is being built. Therefore, the complex relationship between clean energy production, consumption, resource allocation, technological innovation, and market-oriented reforms, and air quality will become the focus of subsequent exploration.

As the economic development entered the transitional stage, the limitation and drawbacks of the traditional extensive growth model of land-based development has become more obvious, which not only causes excessive consumption of resources, but also leads to prominent environmental problems. Urban development is facing pressures from economic growth and environmental protection. In China, it is worthy to study what action strategy the local governments will implement when facing this dilemma as the agent of the central government. It has been found that local governments often transfer industrial land with large area and low land price to promote local economic development. However, there have been fewer studies on the regional environmental influences and effects caused by industrial land transfer. Whether the local government has considered the resource and environmental constraints in the process of industrial land transfer? What are the characteristics of its current industrial land transfer behavior? What are the environmental effects and what is the internal mechanism? To answer these questions, this study develops a variable lag panel data regression model using 284 cities data from 2015 to 2019, in which the independent variable is the urban annual air quality index (AQI), and the core explanatory variable is the transfer area of different types of industrial land. The conclusions are as follows. (1) First, the expansion of industrial land will significantly exacerbate urban air quality, and the influence has spatial heterogeneity. (2) The way of industrial land transfer has a significant impact on the urban environmental quality. The environmental pollution of industrial land transferred by agreement is greater than that of industrial land transferred by bidding, auction and listing. The larger the scale of land transferred by agreement, the worse the urban air quality would be. (3) The choice of industry is an internal mechanism on how the transfer of industrial land affects quality urban air. Local governments prefer to supply lands for pollution-intensive industry by agreement, which results in exacerbated environmental quality. This is different from the standpoint holding that industry projects are always of poor quality thus aggravating environmental quality. The study indicates how the local governments’ land supply behavior affects urban air quality from the perspective of industrial selection mechanism, thus expanding the existing literature and providing policy references for urban ecological civilization construction.

There is always a debate about the relationship between foreign direct investment and its domestic environmental outcome. The Pollution Haven Hypothesis argues that multinational firms in developed countries will relocate their dirty production to some developing countries to seek low compliance costs but the Pollution Halo Hypothesis emphasizes that multinational firms transfer their green knowledge and practice to the host country bringing favorable environmental benefits to domestic firms. This paper aims to examine the environmental spillover effects of foreign firms on domestic firms. Specifically, this paper compares the emissions intensity of SO₂ (sulfur dioxide) and COD (Chemical Oxygen Demand) between foreign and domestic firms and their spatiotemporal evolution using matching data of pollution emissions and production from industrial firms in China between 1999 and 2012, and then, uses an econometric model to identify the environmental spillover effects of geographic agglomeration of foreign firms. The results show that: (1) during the study period, the total emissions of SO₂ and COD of Chinese industrial firms showed a gradual decline, mainly due to the reduction of the total emissions of domestic firms, while the total emissions of foreign firms did not change significantly. (2) During the study period, the SO₂ and COD emission intensity of domestic firms decreased rapidly and gradually caught up with that of foreign firms. Domestic firms with low emission intensity in China are mainly located in the coastal areas with a relatively high level of economic development; meanwhile the emission intensity of inland areas has experienced a rapid decline. (3) Empirically, for both within and between industries, the geographical agglomeration of foreign firms can significantly reduce the emission intensity of domestic firms, but the effect and significance of intra-industry spillovers are higher than that of inter-industry. The environmental spillovers of foreign firms can affect domestic firms through three channels: labor mobility, competition effect and the embedding effect of local production network. In terms of the embedding of local production network, empirical evidence shows that the backward link can show environmental spillover effects, while the forward link effect is not significant. In the heterogeneity analysis, compared with high-efficiency firms, low-efficiency firms can benefit from environmental spillover effects by labor mobility or embedding in foreign production network, but cannot obtain environmental spillovers from the competitive effects.

Under the background of globalization, rapid urbanization and new technological revolution, the "flow space" composed of factor flow and network relationship was becoming more and more important, the city network structure was constantly impacted and reshaped, the contradiction of man-land relations was becoming increasingly prominent, the regional spatial organization patterns and its environmental effect have become an important topic of environmental economic geography research. In this paper, we used Tencent location big data to establish population migration network among 288 China's cities above prefecture level from 2015 to 2018, and employed social network analysis and panel spatial econometric model to empirically analyze the evolution patterns of city network and its environmental effects in China. The results show that: (1) Cities with high connection strength in China's city network are mainly distributed in the rhombus structure consisting of the Beijing-Tianjin-Hebei, Yangtze River Delta, Pearl River Delta, and Chengdu-Chongqing urban agglomerations in the region east of the Hu Huanyong Line. China's city network density and relevance were gradually increasing, and degree centrality and betweenness centrality presented a trend of multi-center and decentralization. (2) On the whole, China's urban air quality has improved, showing significant agglomeration characteristics in space. Ambient Air Quality Index (AQI) decreased in 256 cities (88.89% of the country's total number). The annual average concentrations of PM_2.5, PM₁₀, SO₂, CO, and NO₂ declined while that of O₃ increased. (3) The impact of China's city network on environmental quality were mainly due to the spatial spillover effect brought by the externality of the city network. The enhancement of the city's degree centrality could increase the ability of the borrowing size and borrowing technology to gain development advantages, thereby promoting the improvement of environmental quality. (4) The upgrade of city's degree centrality has improved the environmental quality of the eastern, central and northeastern regions, reducing the annual average concentration of PM_2.5, PM₁₀, SO₂ and O₃, but that of CO was increasing, while the enhancement of city's betweenness centrality has improved the environmental quality of the western region and significantly reduced the annual average concentration of NO₂.