It remains to be clarified whether environmental regulation has a driving effect on green total factor productivity in resource-based cities, through what path and whether there is heterogeneity of city types. This paper selects panel data of 113 resource-based cities in China from 2004 to 2019, and uses non-radial and non-angular SBM model and GML index to measure green total factor productivity of resource-based cities. Then, this paper empirically tests the intermediary effect of scientific and technological innovation, foreign direct investment and industrial structure optimization and the heterogeneity among different type cities. The results show that: (1) The effect coefficient of environmental regulation on green total factor productivity of resource-based cities is significantly positive. Both industrial structure optimization and foreign direct investment play a significant positive mediating effect, while scientific and technological innovation plays an indirect inhibiting effect. (2) The heterogeneity test of city types shows that technological innovation plays a positive mediating role in growing and mature cities, and an indirect inhibiting role in regenerating cities; the foreign direct investment has a positive mediating effect in the declining cities, and negative in regenerating cities; the industrial structure optimization plays a positive mediating effect in growing and mature cities. (3) The comparative mediation effect results in the whole-sample regression shows that the intermediary effect of industrial structure optimization, foreign direct investment and scientific and technological innovation decrease step by step; the mediating effects of industrial structure optimization account for nearly 80%, and the direct effect of environmental regulation is greater than the overall mediating effect. Growing and mature cities mainly exert intermediary effects through scientific and technological innovation and industrial structure optimization, declining cities mainly exert intermediary effects through foreign direct investment, and regenerating cities mainly exert intermediary effects through scientific and technological innovation and foreign direct investment. The robustness test shows that the results are reliable. Finally, this paper puts forward policy suggestions from the aspects of establishing the externality constraint mechanism of resource development and pollution emissions, and adopting the environmental regulation policy of classified guidance and local conditions, etc.

Based on the panel data of 114 resource-based cities in China from 2011 to 2018, the entropy weight method is used to calculate the high-quality development index of each resource-based city. The influence and its mechanism of market-oriented environmental regulation tool on the high-quality development of resource-based cities are discussed by using systematic GMM model, static panel threshold model and dynamic panel threshold model. The results show that: (1) From 2011 to 2018, while the overall level of high-quality development of resource-based cities in China is improving, there also exists a phenomenon of widening extreme differences, and the spatial differences show a distribution pattern of "high in the east and low in the west". Specifically, the high-quality development index is the highest in the eastern region, followed by the northeastern region, whereas it is lower in the central region and the lowest in the western region. (2) Market incentive environmental regulation tools have a significant positive influence on the high-quality development of resource-based cities, that is, the improvement of the intensity of market incentive environmental regulation tools will significantly improve the high-quality development level of resource-based cities. In addition, a systematic GMM model is adopted to avoid possible endogenous problems in the regression and improve the robustness of the empirical results. Moreover, after we use the robust approach of gradually adding control variables and changing lag terms, the regression results are still consistently significant, which further proves the robustness of the results. (3) The positive effect of market incentive environmental regulation tools on the high-quality development of resource-based cities is regulated and restricted by the level of urban low-carbon living influence structure. There exists a threshold in the relationship between market incentive environmental regulation tools and high-quality development level of resource-based cities, that is, when the urban low-carbon living index exceeds a certain threshold level, the positive effect of market incentive environmental tools on its high-quality development is strengthened. The corresponding political implications are further analyzed based on the above empirical results.

Based on the dual pressures of economic transformation and energy conservation and emission reduction faced by resource-based cities, this paper empirically measures the carbon emission efficiency of 114 resource-based cities in China from 2004 to 2019 by using a three-stage super-efficiency SBM model, and discusses the efficiency differences, spatio-temporal evolution and sources of differences by using the methods of Dagum Gini coefficient, kernel density estimation and QAP regression analysis. The results show that: (1) After the environmental factors and random interference is removed, the average carbon emission efficiency of resource-based cities decreases to 0.230, but the overall trend is on the rise. (2) The areas with high carbon emission efficiency are concentrated in regenerating and mature cities, and the distribution is relatively scattered. The low value areas are mainly growing and declining cities, and they are clustered in northeast, central and other regions. (3) The carbon emission efficiency of resource-based cities varies greatly, among which the contribution rate of inter-group difference is the highest, but it shows a downward trend; The differences within the groups of regenerating and mature cities are relatively stable, while the differences within the groups of growing and declining cities are gradually expanding. (4) The differences of population density, per capita disposable income and the number of large-scale enterprises will significantly expand the differences of carbon emission efficiency of resource-based cities, and the differences in population density, population structure and disposable income of residents have a significant heterogeneous impact on the differences in carbon emission efficiency of different types of resource-based cities. Considering the characteristics of carbon emission efficiency of resource-based cities, this paper puts forward the following policy implications: Firstly, according to the types of resource-based cities, we should adopt emission reduction schemes that suit local conditions. Secondly, we should increase investment in low-carbon innovation and promote green transformation of industry. Resource-based cities can increase R&D investment by imitating innovation, and make low-carbon innovation more directional and targeted. At the same time, resource-based cities should encourage enterprises to carry out green technological transformation and upgrading. Thirdly, we will promote green consumption mode and strengthen emission reduction of residents. The government should enhance residents' cognitive level of consumption emission reduction ability and encourage consumers to make low-carbon consumption. Moreover, the government should explore green financial innovation, establish individual carbon credit and carbon account system, and encourage residents' participation in green financial market.

Green development is an important manifestation of the high-quality transformation of resource-based cities. The study develops a green development efficiency evaluation system, using MinDs model, Theil index, Geodetector and other methods, to measure green development efficiencies in resource-based cities of Western China from 2001 to 2019, and analyzes the spatiotemporal heterogeneity characteristics and associated driving factors. The main conclusions are as follows: (1) The green development efficiency of resource-based cities in the western region is bounded by 2015, showing a trend of "rising first and then falling", the green development efficiency change trends of different types of cities are quite different, resource-based cities in Northwest China and Guangxi have shown an upward trend as a whole, resource-based cities in Southwest China and Inner Mongolia have shown a downward trend in recent years, growing cities have developed relatively stable, mature and regenerating cities have declined significantly after 2017, and declining cities have shown an upward trend. (2) The green development efficiency of resource-based cities in the western region is characterized by a normal distribution with a small number of extremely low and extremely high intervals, and a large number of intermediate scores. (3) The problem of spatial unevenness of green development efficiency is still serious. Changes in the efficiencies of mature cities in northwest and southwest regions are the dominant factors for expanding gaps in the efficiencies of resource-based cities in Western China. (4) Economic development, urbanization, city size expansion and technological innovation can significantly increase the green development efficiency of resource-based cities in the whole study area. Moreover, the driving factors of green development efficiency of resource-based cities in different spatial ranges and different life cycles have their own characteristics. The research has practical significance for improving the green development efficiency of various resource-based cities in the western region of China.

Coastal resource-based cities are spatial carriers with highly intertwined land resources and sea resources. From the perspective of cross-system impact, the spatial governance will help to break through the limitations of the transformation and development of resource-based cities, and maximize the comprehensive efficiency of resources. Firstly, this paper clarifies the complexity of cross-system impact and the diversity of coastal resources, and takes spatial resources as the core element of the study. Secondly, it emphasizes the ecological-economic-social "integrated efficiency" of the whole land and sea system, and takes "land-sea coordination" as a guide to deepen the connotation of high-quality development of coastal resource-based cities. Thirdly, it explores the spatial governance path of "key resource identification-spatial efficiency evaluation-spatial resource regulation" for high-quality development. Concretely, we select key resources by identifying cross-system impact scope, conducting resource spatial surveys, and determining the resource combination mode. Furthermore, a resource spatial efficiency evaluation framework including "comprehensive efficiency evaluation" and "cross-system impact correction" is established to clarify the differences of various spatial efficiencies, and provide a decision-making basis for spatial governance. Finally, according to the results of spatial efficiency evaluation, combined with the requirements of territorial spatial planning, this paper puts forward beneficial regulation and control methods for the high-quality development of coastal resource-based cities, in the four aspects of resource spatial optimization, regional resource integration, total space allocation and development mode guidance.