随着经济的全球化，全球各国在经济发展和科技合作等领域均呈现出日益紧密的联系。改革开放以来，我国十分重视国际贸易的发展，积极加入WTO等贸易组织，经历了一段繁荣的贸易发展时期。而贸易的发展离不开交通基础设施的支持，近些年我国大力发展交通基础设施建设，其中高铁的身影处处可见。当前已经成为全球第二大经济体的中国拥有着全球最长的铁路里程。发达的交通基础设施不仅使人们的出行更加便利，也促进了资源要素和科学技术的交流，为出口贸易的发展提供了新的机遇。当前，由于中美贸易战、新冠疫情的冲击等等，全国出口贸易发展的大环境不容乐观。在“双循环”的背景下，我国是否可以通过升级交通基础设施来达到促进出口贸易的可持续发展，尤其是近些年交通基础设施的大力建设是否能够促进更加低碳、绿色的出口贸易，这些是值得深入研究的。基于以上背景，本文基于中国工业企业数据库、中国城市数据库、中国海关数据库和中国工业企业绿色数据库等研究高铁开通对出口贸易及其环境效应的影响。
文章首先介绍了关于交通基础设施升级、出口贸易与空气污染的选题背景，从理论和实践层面详细阐述了研究意义，并交代了文章主要的研究内容和结构安排，对研究方法和文章的创新点与不足也进行了说明。国内外文献综述主要分析了出口贸易、交通基础设施，以及它们与环境污染之间的关系。本研究对贸易的环境效应，交通基础设施与国际贸易，以及交通的环境和经济效应等相关研究分别展开述评分析。本文通过纳入环境要素的H-O扩展模型和“中心-外围”理论对研究内容展开理论分析。基于此，文章采用地级市面板数据检验了城市出口的环境效应、交通基础设施升级对出口贸易的影响，以及交通基础设施升级对贸易引致的污染排放强度的影响。为缓解模型的内生性，文章选取了近代通商口岸数据和海外市场可达性作为出口贸易的工具变量，选取明朝驿站数据和1962年铁路线路数据作为高铁的工具变量。为检验上述研究的传导机制，本研究对城市出口通过技术创新影响空气污染的过程进行了机制检验，从集聚效应、外资效应和技术效应等方面对高铁与出口贸易之间的关系进行了机制检验，从竞争效应和成本效应等角度对高铁与出口环境效应的关系进行了机制检验。此外，本研究基于我国企业级面板数据，通过实证进一步验证了交通基础设施对出口贸易引致的污染物排放影响的研究，并从空间角度出发，验证了高铁对出口贸易环境影响的空间溢出效应。
文章主要得出如下结论：（1）出口贸易会增加空气污染。东、中部城市和出口依赖城市一般都拥有较高的出口贸易水平，其边际环境效应更为显著。此外，技术创新的中介作用凸显。（2）高铁对出口贸易存在积极影响。高铁开通总体上为贸易企业带来集聚效应、外资机会和技术潜力。（3）高铁会显著降低贸易企业的污染物排放强度。由于城市内竞争效应和成本效应的存在，企业会尽可能通过技术引入和清洁生产来抵消要素价格上涨和环境处罚所带来的成本。此外，创新效应和绿色效应也是贸易企业污染物排放强度下降的重要原因。（4）高铁对出口贸易环境效应的影响存在空间溢出效应。周边地区出口引致的污染情况与本地区存在很强的关联性，表现为“一荣俱荣，一损俱损”的关系。针对上述分析，本文提出如下几点政策建议：（1）重视高铁在出口贸易经济中的作用。（2）积极利用高铁优势，优化出口贸易结构。（3）注重欠发达地区的出口贸易的可持续发展。（4）重视贸易企业合理布局。时刻把握贸易企业动向，合理配置环保资源。（5）考虑特征差异，因地制宜制定城市环境政策。（6）强化城市间的要素流动和经济合作，促进绿色发展。（7）加强城市出口对绿色技术创新的国际学习。
本文的创新点在于：第一，在研究视角上，文章从城市层面研究了交通基础设施升级对出口贸易引致污染排放的影响。第二，研究方法上，使用DID方法将由高铁开通所代表的基础设施质量提升影响效应从城市固定效应中识别出来。同时，在出口贸易和交通基础设施升级的内生性问题处理上，本研究采用新颖的工具变量，有效地控制了二者的内生性问题，使得本研究的结论更具稳健性和可信度。本研究还尝试把高铁产生的空间溢出效应加入到实证中，较好的提升了模型的准确度和可信度。第三，研究方案设计上，从出口贸易环境效应、交通基础设施升级与出口贸易，再到交通基础设施升级对出口贸易环境效应的影响展开分析。并在企业层面和空间层面对以上研究的核心展开进一步验证。第四，研究数据选取上，本研究将主要匹配 “中国工业企业数据库”、“海关贸易数据库”和“工业企业污染排放数据库”三大数据库，并匹配至城市层面，与城市统计数据库共同构建城市平衡面板数据，研究交通设施对出口贸易环境排放的影响。此外，研究还将技术创新分为传统技术创新和绿色技术创新，研究城市出口引致技术创新的绿色导向，更能准确揭示城市出口对空气污染的影响渠道。

With the globalization of the economy, countries around the world are increasingly connected in the fields of economic development and scientific and technological cooperation. Since the reform and opening up, my country has attached great importance to the development of international trade, actively joined the WTO and other trade organizations, and experienced a period of prosperous trade development. The development of trade is inseparable from the support of transportation infrastructure. In recent years, my country has vigorously developed transportation infrastructure, among which high-speed rail can be seen everywhere. China, which has now become the world's second largest economy, has the longest railway mileage in the world. Developed transportation infrastructure not only makes people's travel more convenient, but also promotes the exchange of resource elements and science and technology, providing new opportunities for the development of export trade. At present, due to the Sino-US trade war, the impact of the new crown epidemic, etc., the overall environment for the development of national export trade is not optimistic. Under the background of "dual circulation", whether my country can promote the sustainable development of export trade by upgrading transportation infrastructure, especially whether the vigorous construction of transportation infrastructure in recent years can promote more low-carbon and green export trade, These are worth looking into. Based on the above background, this paper studies the impact of the opening of high-speed rail on export trade and its environmental effects based on the China Industrial Enterprise Database, China City Database, China Customs Database, and China Industrial Enterprise Green Database.
The article first introduces the background of the topic selection on the upgrading of transportation infrastructure, export trade and air pollution, elaborates the research significance from the theoretical and practical levels, and explains the main research content and structural arrangement of the article, as well as the innovation of research methods and articles. The points and shortcomings are also explained. The literature review at home and abroad mainly analyzes export trade, transportation infrastructure, and their relationship with environmental pollution. This study reviews and analyzes the environmental effects of trade, transportation infrastructure and international trade, and the environmental and economic effects of transportation. This study conducts a theoretical analysis of the research content from the H-O expansion model and the "center-periphery" theory incorporating environmental elements. Based on this, this paper uses the panel data of prefecture-level cities to examine the environmental effects of urban exports, the impact of transportation infrastructure upgrades on export trade, and the impact of transportation infrastructure upgrades on the intensity of pollution emissions caused by trade. In order to alleviate the endogeneity of the model, the paper selects the data of modern trading ports and the accessibility of overseas markets as the instrumental variables of export trade, and selects the data of Ming Dynasty post stations and the data of railway lines in 1962 as the instrumental variables of high-speed rail. In order to test the transmission mechanism of the above research, this study conducted a mechanism test on the process of urban exports affecting air pollution through technological innovation, and conducted a mechanism test on the relationship between high-speed rail and export trade from the aspects of agglomeration effect, foreign investment effect and technological effect. , from the perspectives of competition effect and cost effect, the mechanism test is carried out on the relationship between high-speed rail and export environmental effect. In addition, based on my country's enterprise-level panel data, this study further verifies the research on the impact of transportation infrastructure on pollutant emissions caused by export trade through empirical evidence, and from a spatial perspective, verifies the spatial spillover effect of high-speed rail on the environmental impact of export trade.
The article mainly draws the following conclusions: (1) Export trade will increase air pollution. The eastern and central cities and export-dependent cities generally have a higher level of export trade, and their marginal environmental effects are more significant. In addition, the mediating role of technological innovation is prominent. (2) High-speed rail has a positive impact on export trade. The opening of high-speed rail generally brings agglomeration effects, foreign investment opportunities and technological potential to trading companies. (3) High-speed rail will significantly reduce the pollutant emission intensity of trading enterprises. Due to the existence of competition effect and cost effect in the city, enterprises will try their best to offset the cost caused by the increase in factor prices and environmental penalties through the introduction of technology and cleaner production. In addition, the innovation effect and green effect are also important reasons for the decline of pollutant emission intensity of trading enterprises. (4) The impact of high-speed rail on the environmental effect of export trade has a spatial spillover effect. There is a strong correlation between the pollution caused by the export of the surrounding areas and the local area, which is manifested in the relationship of "one prosperous, one loss and one loss". In response to the above analysis, this paper puts forward the following policy suggestions: (1) Pay attention to the role of high-speed rail in the export trade economy. (2) Actively utilize the advantages of high-speed rail to optimize the structure of export trade. (3) Pay attention to the sustainable development of export trade in underdeveloped areas. (4) Pay attention to the rational distribution of trade enterprises. Always keep abreast of the trends of trading enterprises and rationally allocate environmental protection resources. (5) Taking into account the differences in characteristics, formulate urban environmental policies according to local conditions. (6) Strengthen the flow of factors and economic cooperation between cities to promote green development. (7) Strengthen the international study of green technology innovation in urban exports.
The innovations of this paper are: First, from the perspective of research, the paper studies the impact of the upgrading of transportation infrastructure on the pollution emissions caused by export trade from the city level. Second, in terms of research methods, the DID method is used to identify the impact effect of infrastructure quality improvement represented by the opening of high-speed rail from the city fixed effect. At the same time, in dealing with the endogenous problems of export trade and transportation infrastructure upgrading, this study uses novel instrumental variables to effectively control the endogenous problems of the two, making the conclusions of this study more robust and credible. This study also tried to add the spatial spillover effect produced by high-speed rail into the empirical evidence, which improved the accuracy and credibility of the model. Third, in the design of the research plan, the analysis is carried out from the environmental effect of export trade, the upgrading of transportation infrastructure and export trade, and the impact of the upgrading of transportation infrastructure on the environmental effect of export trade. And the core of the above research is further verified at the enterprise level and the space level. Fourth, in the selection of research data, this research will mainly match the three major databases of "China Industrial Enterprise Database", "Customs Trade Database" and "Industrial Enterprise Pollution Emission Database", and match them to the city level, and build a city together with the city statistical database. Balanced panel data to study the impact of transportation facilities on environmental emissions from export trade. In addition, the research divides technological innovation into traditional technological innovation and green technological innovation, and studies the green orientation of technological innovation caused by urban exports, which can more accurately reveal the impact channels of urban exports on air pollution.