城市群已成为当今世界城市化与区域发展的新趋势.如何准确地认知和评价城市群建设对我国环境尤其是空气质量的影响是需要关注的重点问题.本文通过构建双重差分模型实证检验了中国五大城市群建设对空气质量的影响.研究发现：城市群建设降低了城市群城市AQI、PM₁₀和PM_2.5浓度；产业集聚改善了空气质量，第二产业产值占GDP的比重、人口密度和经济发展水平均恶化了空气质量；季节和气象因素也对空气质量产生影响，冬春季节的城市空气污染高于夏秋季节；各城市群建设对空气质量的影响也不尽相同.本文的政策启示是：要坚持高质量发展理念继续推进城市群建设，科学合理规划城市群发展；坚持创新驱动，推动城市群发展向集约型经济增长模式转变；建立城市群空气污染联防联控机制，促进城市群的经济和环境协调发展.

在全球化、快速城市化和新技术革命的背景下,要素流与网络关系构成的“流空间”愈发重要,城市网络结构不断受到冲击与重塑,人地关系矛盾日益凸显,区域空间组织模式及其环境效应已成为环境经济地理学研究的重要议题。本文利用腾讯位置大数据,构建了2015—2018年288个地级以上城市之间的人口迁徙网络,采用社会网络分析和面板空间计量模型,对中国城市网络演化格局及其环境效应进行实证分析。结论如下：① 中国城市网络联系强度高的城市主要分布在“胡焕庸线”东侧的京津冀、长三角、珠三角和成渝城市群组成的菱形结构;城市网络密度和关联性逐渐增强,度数和中介中心性呈现多中心和分散化的发展趋势。② 中国城市空气质量总体有所好转,空间上呈现显著的集聚特征;88.89%的城市空气质量指数（AQI）下降,PM_2.5、PM₁₀、SO₂、CO和NO₂年均浓度有所下降,而O₃年均浓度有所上升。③ 中国城市网络对环境质量的影响主要来源于城市网络外部性所带来的空间溢出效应;城市网络中节点权力地位和影响力的增强,提高了借用规模和借用技术,从而促进环境质量提升。④ 度数中心性提升了东部、中部和东北地区的环境质量,减少了PM_2.5、PM₁₀、SO₂和O₃的年均浓度,增加了CO的年均浓度;而中介中心性则提高了西部地区的环境质量,降低了NO₂的年均浓度。

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 PM2.5, 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 PM2.5, 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.

城市网络研究已成为国际上城市研究的前沿学术领域并渐成热点,外部性作为城市网络的本质属性,对城市网络的演化及城市与区域的发展均具有重要意义。论文从集聚外部性与网络外部性比较的视角切入,重点对城市网络外部性形成机理、效用和测度方法等方面的研究进展进行梳理和评述。其中,协同效应、整合效应和规模借用被认为是城市网络外部性形成的重要原因。而城市网络外部性的效用研究较多集中在2个方面：一是关注要素流动对知识扩散和创新的促进作用,二是关注城市网络对竞争力提升和经济增长的影响。从已有文献来看,城市网络外部性测度研究主要涉及识别和估算2种类型,包括3种常用方法：关联分析、回归分析和空间计量分析。未来需要进一步关注的问题包括城市网络的外部性理论认识、外部性量度方法以及经验研究问题。

Urban network research has become the frontier academic field of international urban research and has gradually become a hot spot. At present, the related literature on "urban network" mostly focuses on conceptual discussion, dimension analysis, and network structure analysis. Research on the influence of network on regional economic development is relatively weak. Externality, as an essential attribute of urban network, is of great significance to the evolution of urban network and the development of cities and regions. This article starts from a comparison of agglomeration externalities with urban network externalities, focusing on the review and evaluation of the formation mechanism, utility, and measurement methods of urban network externalities. The synergy effect, integration effect, and borrowing size are considered important reasons for the formation of urban network externalities. The research on the effectiveness of urban network externalities focuses on two aspects. The first is the role of factor flow in promoting knowledge diffusion and innovation, and the second is the impact of urban network on competitiveness and economic growth. Based on the existing literature, the research on the measurement of urban network externalities mainly involves identification and estimation, including three common methods: correlation analysis, regression analysis, and spatial econometric analysis. The existing empirical research on externalities is still mostly based on static analysis and lacks dynamic consideration. To a large extent, the existing research has insufficient theoretical framing and insufficient explanatory power, often resulting in the discovery of conditional associations, but not causal relationships. The Western research on urban network externalities is relatively early and mainly focuses on the global and regional dimensions, while Chinese scholars focus on the national and regional dimensions. In terms of empirical methods and objects, Chinese scholars have also made some innovations based on the study of world city network. The issues that need further attention in the future include theoretical understanding of urban network externalities, externality measurement methods, and empirical research.

中国生态文明建设和“健康中国”战略强调切实治理影响人口健康的环境问题,建设健康人居环境。论文基于2000年和2010年中国人口普查资料以及2005年和2015年各省级行政单元1%人口抽样调查等数据资料,论文使用探索性空间分析方法刻画中国城市人口死亡率的时空变化特征,并采用空间回归方法,揭示城市PM_2.5的平均浓度对人口死亡率的影响及其空间溢出效应,以及社会经济因素对PM_2.5—人口死亡率关联的调节效应。结果表明：① 中国城市人口死亡率的空间分布特征呈现明显的异质性,高死亡率地区早期集聚分布于西南地区,2005年后在西南地区、华北地区、华东地区和华中地区呈现逐渐集聚分布态势。低死亡率地区长期集中分布于西北地区、东北地区、长三角地区、珠三角地区和京津两市。② 人口死亡率的分布存在空间关联性,高—高类型地区早期集中分布于西南地区,后期向东扩展;低—低类型地区主要分布于北疆、内蒙古西部和广东省及其周边地区。③ 城市PM_2.5浓度对人口死亡率具有显著的正向影响,并且对邻近地区的人口死亡率具有显著的空间溢出效应。④ 中国城市PM_2.5浓度对人口死亡率的影响存在学历差异和城乡差异,地区高学历人群集聚可降低PM_2.5的健康风险,城镇化发展进程缓慢则会加重PM_2.5的健康风险。研究旨在为防范空气污染暴露导致的健康风险、建设健康人居环境提供科学依据。

污染密集型产业空间转移规律及其动力机制研究正在成为区域可持续发展研究的热点领域之一。利用2000~2010年江苏省13个省辖市的统计数据,运用空间分析及面板数据分析模型,探讨该省污染密集型产业空间转移特征及作用机制。结果发现：江苏省依然是国际污染密集型产业的承接地,其污染密集型产业分布呈现以苏锡常地区为核心向外围逐渐下降的“核心-边缘”型空间格局,并显示出“扩散-集聚-扩散”的空间演化趋势,苏北地区正在成为苏南地区的“污染避难所”;发展阶段和实际利用外资是江苏省承接污染密集型产业的主要因素,实际利用外资是实现污染密集型产业向江苏转移的主要形式;技术创新、产业结构是驱动污染密集型产业由苏南、苏中向苏北转移的主要因素;政府调控是影响污染密集型产业转移的主要手段。因此,应通过加大产业结构转型升级和技术创新力度、改善政府调控、加强环境监管等措施促进污染密集型产业布局优化。

The spatial relocation of pollution-intensive industries and its associated mechanism are becoming increasingly hot in regional sustainable development. Using a statistical panel data, the characteristics of spatial relocation of pollution-intensive industries in Jiangsu are explored, and further, the mechanism of it is discussed, based on the spatial analysis and statistical modeling. Three important findings are gotten. First, the pollution-intensive industries demonstrated a downward trend in the industrial system of Jiangsu Province in the last 10 years. Spatially, the pollution-intensive industries gradually moved from Jiangsu’s core areas. More specifically, the growth rate of pollution-intensive industries originally followed a pattern of South Jiangsu>Middle Jiangsu>North Jiangsu, however, in the most recent years, this pattern has changed to North Jiangsu>Middle Jiangsu>South Jiangsu. The proportion of pollution-intensive industry in South Jiangsu increased in early years but then decreased. In middle Jiangsu and North Jiangsu, it increased slowly in early years but recently accelerated. Second, before 2005, the concentration ratio of pollution-intensive in most cities along the Changjiang River increased, however, that of the cities of North Jiangsu decreased. After 2005, Jiangsu Province adopted a policy of accelerating the development of North Jiangsu, and many pollution-intensive industries were relocated from South Jiangsu to North Jiangsu. These pollution-intensive industries include Textile Industry, Paper Making and Paper Product, Oil Processing, Coking and Nuclear Fuel Processing, Raw Chemical Materials and Chemical Products, Chemical Fiber Manufacturing, Nonmetal Mineral Products and Smelting and Pressing of Ferrous Metals. Spatially, the pollution-intensive industry demonstrated a pattern of decentralization, then centralization, and most recently returned to decentralization. Finally, Jiangsu Province undertakes the international pollution-intensive industries, while North Jiangsu is the "Pollution Haven" for pollution-intensive industries in South Jiangsu. Because North Jiangsu was at a preliminary industrialization stage, it became an undertaking area to attract foreign capital and to promote pollution-intensive industries. Technological innovation and the industrial structure policy are the other driving forces for the relocation of pollution-intensive industries from South Jiangsu to Middle Jiangsu, and then North Jiangsu. Government regulation affected the pollution-intensive industries as a primary mean of industrial relocation. In summary, industry upgrading, technological innovation, and improved government regulation which more focuses on environmental control, environmental monitoring, but other related measures are the primary means to optimize the spatial layout of pollution-intensive industries.

污染密集型产业转移及影响机理研究已成为区域可持续发展的研究热点之一。利用长江三角洲地区2000-2010年面板数据,运用ArcGIS空间分析工具,探讨污染密集型产业的时空格局演变特征及转移规律,构建计量学模型,定量地揭示其转移的驱动机理。结果表明：①近十年来,长江三角洲地区的污染密集型产业具有空间转移特征,转移方向基本符合沪宁—沪杭甬交通线,呈现由中心城市到外围城市、由集中到分散转移态势;②污染密集型产业转移主要受到外向度和劳动力成本拉动,而与经济发展水平呈负相关,环境规制、产业结构、创新能力均产生重要推动作用。③长江三角洲地区经济发展目前已逐渐摆脱依赖污染密集型产业的迹象,但污染密集型产业区位仍未发生根本性改变。

The world is moving further toward economic globalization and trade liberalization. Industrial relocation is an important way to upgrading the industrial structure and promoting regional coordinated development, which usually assumes relocating industrial production from prosperous zones to less developed zones. Against the background, it has become a hotspot in the research of regional sustainable development in the places where the pollution-intensive industry is relocated and what causes the pollution.Based on the panel data of the Yangtze River Delta from 2000 to 2010 and using spatial analysis tool of ArcGIS, this paper explores the characteristics and regularities of spatial-temporal pattern of pollution-intensive industry, and comes to a quantitative conclusion on the driving mechanism of pollution-intensive industry's relocation by constructing a metrological model. Results suggest: (1) In the last 10 years, the phenomenon of pollution-intensive industry's relocation is found in the Yangtze River Delta. The direction of its relocation coincides with Shanghai-Nanjing railway and Shanghai-Hangzhou-Ningbo railway. Moreover, the general trend is from the center to the periphery, which is an accelerated diffusion trend. Generally, the speed of diffusion is faster in the latter 5 years than in the former 5 years, but it has been a little slower since 2008; (2) There are many factors contributing to the relocation of pollution-intensive industry in the Yangtze River Delta, among which export-oriented degree and labor costs help pollution-intensive industry to relocate, while the intensity of environmental governance, industrial structure and innovation capability prevent pollution-intensive industry from relocating to destination. What’s more, economic development level is negatively related to the relocation. Given that, it is concluded that the economic development of the Yangtze River Delta is independent to pollution-intensive industry, which contributes less to the growth of GDP nowadays than 10 years ago. However, the Yangtze River Delta has not got rid of the position of "Pollution haven", because the location of pollution-intensive industry has not changed fundamentally, and Shanghai, Nanjing and Hangzhou remain to be on centre stage of pollution-intensive industry in the Yangtze River Delta, as well the export-oriented degree is particularly noticeable in this region. To some extent, this is related to the recent economic downturn after the financial crisis in 2008. Hence, it is an arduous task and long way to upgrade the overall industrial structure, in order to maintain the sustained regional development. Furthermore, the need for more serious environmental supervision is urgent, so government should pay more attention to the coordination between industrial development and environmental protection.

快速的城市化和经济发展在改善我们物质生活的同时,也因其剧烈人为活动导致了严重的环境污染,尤其是近年来以细颗粒物(PM_2.5)为首要污染物的城市与区域空气污染问题凸显。而传统的研究更注重孤立地开展空气污染或城市化的研究,缺乏对二者相互耦合关系的综合研究。本文以中国近年来广受关注的以PM_2.5为首要污染物的城市空气污染为切入点,系统地分析总结了在城市化与PM_2.5时空格局演变及其影响因素方面的主要研究进展,包括研究框架、主要方法和相关的主要研究成果等。指明该领域的研究已从空间格局分析逐步深入到健康影响、社会经济驱动等相关方向,并已延伸至复合主题的研究。未来,开展更为深入细致的研究,对于拓展城市与景观生态学的理论体系,了解城市化与城市空气质量的影响关系,解析不同城市发展阶段所面临的城市空气质量问题,将具有重要的科学与现实意义。

Urbanization is essentially a geographical concentration of population and industry, and change of landscape patterns. The proportion of the urbanized population in China has increased to more than 50% during the recent decade. The rapid growth in such a short time period has not only led to an improvement of material wealth and a higher standard of living, but also caused severe environmental pollution, particularly the air pollution in many urbanized regions of China. In this research, multi-resolution remote sensing images, meteorological records, environmental monitoring data, and ground survey records were employed at multiple scales to understand the relationship between rapid urbanization and urban air quality, taking PM2.5 concentration as an indicator of air quality. The key findings are in the following three areas: (1) The spatial-temporal patterns of PM2.5 concentration in China; (2) The spatial-temporal patterns of the relationship between urban PM2.5 pollution and rural PM2.5 pollution in China's major cities; and (3) The linkage between urbanization and PM2.5 concentration at global, regional, city, and local scales. The results of this research also encourage different approaches to urbanization study in order to mitigate the negative impact caused by urban air pollution, both in China and in other rapidly developing mid- and low-income countries.