A Study On The Threshold Effect Of Urban Population Size On Environmental Pollution

The 18 th of the National People’s Congress made the ecological civilization as one of the constructions of socialist modernization and put forward the new idea of beautiful China. But with the rapid development of China’s economy and society, environmental pollution has become an important bottleneck of economic and social development, and has become the focus study for many scholars. However, the city economic development and environmental pollution may have different degree of relationships because of the difference of the urban population scale which can be characterized by interval effect. So, whether the urban population scale has a relationship with environment pollution? Whether they have a certain threshold effect, namely the urban population reaches a certain scale can exacerbate or reduce the environmental pollution? Specific to the regional analysis, what are the common points and differences such as the country’s eastern, central and western regions? All these issues are need to be further studied and discussed which will provide a theoretical and practical reference for China’s population, economy and environment.Based on the Environmental Kuznets Curve(EKC) hypothesis, considering the industrial SO2 and waste water emissions, the paper establishes the threshold regression model which Hansen first proposed to analysis the effect of population scale on environmental pollution using the 286 Chinese cities panel data from 2000 to 2012. Especially from the angle of national urbans and regions, the paper explores whether the environmental pollution has a threshold effect of population scale and explores the factors to influence the environment pollution under different levels of population scale.The research results show that as an important channel of influencing the level of economic development, the population scale has a significant threshold effect to environmental pollution from the perspective of national urban. If the population scale in the threshold of $460000 to $5 million range, the economic development will aggravate the environmental pollution, but if the population scale is less than 460000 or above 5 million, the economic development will reduce the environmental pollution, and most of cities in our country are in the period of the economic development is bad for the environment. From the perspective of the regions, different regions have different threshold effects and threshold values. Therefore, it is urgent to coordinate the population、economy and environment to develop harmoniously, such as control population scale reasonably、adjust the industrial structure gradually and improve the level of technology.