Investigating The Environment Kuznets Curve And Interaction Relationship Between China’s Urbanization And Air Environment

Air pollution as one of the major global environmental problems, has increasingly raised common concern from academia, community and governments. Meanwhile, China has been become the world’s largest developing country and the second largest economy, since the reform and opening up at 1980s. However, ecological environment pollution, especially for the air pollution, also has been seriously exacerbated with the rapid economic development, low energy efficiency and large pollution emissions during the last three decades. In recent 20 years, air pollution has broken out intensively in China which American and European countries had been suffered for a hundred years. Thus, the air pollution incidents such as haze, have become the "new normal" with the rapidly urbinazation. Moreover, considering the industry of China is undergoing transforming and upgrading, accompanied by three major strategies including "coordinated development of Beijing, Tianjin and Hebei" "the Belt and Road" and "the Yangtze River economic belt", more strict requirements have been put forward to improve urban air environment quality, which also meet the building of new pattern urbanization road, the coordinated developing of regional and the constructing of ecological civilization.Thus, the study on interaction relationship between urbanization and air environment is not only an important extension study on urbanization and ecological environment coupling relations but also an important basis for future sustainable urban development and environmental policy formulation.Facing the "new normal" that environment is worsening continually, the economic is growing rapidly and urbanization is expanding extraordinarily in China, it deserves a further discussion about these questions, such as what is the kind of relationship between air environment and urban development and urban economic growth? Will the rapid urbanization development lead to worsening air pollution, or could eventually lead to improvements in the air environment, and how is the interaction mechanism between the two?Based on the above, this paper chooses prefecture or above level cities of China as the main study object and sieves 274 cities among them based on the continuity of the index data. The spatial distribution patterns and evolution trends of three conventional pollutants including SO2, NO2, and PM10 were analyzed during 2004-2013 in these cities. To determine the impact on air quality deriving from social and economic development of the city, four indicators including populational urbanization rate, urban population size, built-up area and the proportion of secondary industry were selected in this paper. Then by choosing urbanization rate and per capita GDP as mainly explained variable, General Panel Regression Model and Spatial Panel Regression Model were built respectively for Environmental Kuznets Curve (EKC) test which can reflect the effect of urbanization on air environment. Lastly, using Panel Vector Auto-regression model (PVAR) and Coupled Coordination Degree model (CCDM), this paper discussed the response law and coupled coordination mode between urbanization and air environment system and proposed corresponding suggestions for Chinese new pattern urbanization development.The main work and the conclusions of this paper are as follows:(1) Systematically revealing the spatio-temporal evolution pattern of three main air pollutants and IAQI value in the 274 cities during 2004-2013From the point of temporal evolution pattern, there is a trend to slow down in the early phases but a worsening trend in the last phases for the air pollution of these 274 cities in general. The evolution pattern differed with each atmospheric pollutants, in particular, PM10 is not a common but a relatively harmful one among the three air pollutants. According to Daniel’s result of trend test, the index IAQI of Chinese urban air quality is decreased generally with the rank correlation coefficient of γs at -0.648 (at the significant of 0.05), this means that the air quality has become relatively better especially for the cities in coastal area. From the point of spatial evolution pattern, the air quality differed with cities but the spatial pattern of urban air pollution remained the same. In north China (Beijing, Tianjin city and Hebei province) and some cities in Shandong province, the air has been heavily polluted and they are also the key areas of which air pollution should be controlled cooperatively. With respect to SO2, the concentration has been decreased obviously in the air with higher concentrations dotted sporadically in some areas of Beijing, Tianjin city, Hebei and Shandong province. The air pollution deriving from SO2 of southwest China has been controlled. However, the air pollution attributed to NO2 is not improved dramatically and the spatial pattern also does not change fundamentally, with the main air-polluted areas including north China, Shandong province and Yangtze River Delta. The PM10 pollution in China becomes improved first and then deteriorated. Although the heavily air-polluted areas have reduced, the distribution of the PM10 pollution showed a concentrated and contiguous-pieces trends, especially for the areas of Beijing, Tianjin and Hebei in North China and Shandong and Xinjiang Uygur Autonomous Region and Gansu Province in northwest China. This suggests that there no significantly improvement for the controlling of PM10 in China over recent decades.(2) Analyzing and comparing the evolution laws of Environmental Kuznets Curve based on per Urban Capita GDP and Urbanization Rate systemUsing fixed effect model and random effect model, this study regresses and fits the four indicators of air quality including average annual concentration of the main pollutants such as SO2, NO2 and PM10 and the comprehensive quality index IAQI with six indicators reflecting urban development such as per capita GDP, urbanization rate, the proportion of the secondary industry and built-up area after examining the stability of panel data. The result indicates that no matter in the GEKC or UEKC system, the relationship between Chinese urban development and air quality is not completely in accordance with inverted "N" curve and different pollutants evolve in different ways. Over the ten years, the SO2 concentration of urban air has been reduced to the inflection point of improvement as the economy developing which is in accordance with the N-shaped curve with the point of deterioration and improvement at 15,444 and 74,051 yuan in GEKC system, respectively whereas with the deterioration and improvement point at 25.7% and 59.9% of the urbanization rate in UEKC system, respectively. On the contrary, the relationships between NO2, PM10 concentration, comprehensive index of air quality with the urban economic development all meet the "U" curve. Moreover, the air pollution is deteriorating continually and undergoing the ascent stage. Thus, there were no improvement points for these indicators with the point of deterioration appearing at 19909,40759 and 44,356 yuan and 8.8%,45.75% and 61% the urbanization rate in the two systems, respectively). Since the performing of twelfth five-year plan, China has been struggling to control the emission of nitrogen oxide and the NO2 concentration has tended to reach the point of improvement. However, the pollution of PM10 has still become deteriorating which reflected by the increasing concentration of PM2.5 with the application of the novel ambient air quality standard.In addition, the indicator of per capita GDP failed to pass the significance test through the four models in the UEKC system when the urbanization rate acting as the main explanatory variable. Therefore, it is worth putting into practice and simulating scientifically based on the perspective of the urbanization to discuss the evolutionary pattern and law of the environment quality.(3) Establishing a new analysis framework of the evolution of air quality Environmental Kuznets curve based on ESDA-Spatial EconometricsThe global spatial correlation analysis results of ESDA showed that the air pollution showed a significant spatio positive correlation, and it is suitable for spatial measurement regression test. The results of local spatial correlation analysis revealed that gathering zones with heavier air pollution derived from the air quality indexes mainly distributed in Beijing, Tianjin, Hebei province in North China and other adjacent areas such as Shandong, Henan with a transfer trend in different years. At the same time, the scope range and number of the low-low gathering cities with better air quality have increased. As the spatial correlation between urban economic development and air environmental quality deepened by industrial transfer and air diffusion, the spatial spillover effects of pollution also has been further demonstrated.Through establishing the Environmental Kuznets Curve spatial regression models (Spatial Econometrics Model), it was found that the concentration levels of air quality is closely related to urbanization, per capita GDP, the built-up area and changes in the industrial structure. From the point of spatial autoregressive coefficients, whether in SGEKC or SUEKC system, the four indicators all ranked as p IAQI>p PM10>p NO2 >p SO2 (the latter three are relatively close about 0.25) and all have passed the 1% level of significance test. It can be conclude that the comprehensive value of urban air environment quality IAQI resulted from the integrated impacts and was more affected by the air pollutant diffusion from the adjacent city than single space value of the single contaminant value. Similar to the common panel test results, there is a "N" or "U" curve relationship between per capita income, urbanization development and urban air quality (SO2, NO2, PM10, IAQI) but no classic inverted "U" type curve at the present stage of China, when environmental degradation is rising. But taking the spatial econometric panel interaction factors into account, the inflection point of deterioration moved to the left and the inflection point of improvement lagged behind, indicating the deteriorating of air pollution accelerated by the diffusion of pollutants between the cities which to some extent delayed the improvement in air quality. It further showed that air quality was extremely hard to be improved for the single city and was potentially affected by the outer city. As a result of the existence of space pollution overflow, the areas with stricter environmental regulation such as Beijing and Tianjin can’t get all the benefits from the regulation. Thus, it is imperative to strengthen regional cooperation to control air pollution.(4) Describing the interaction between urbanization development and the environmental air quality response relationship based on panel vector autoregressive model (PVAR)On the basis of the panel data of 274 cities in 2004-2013, this paper estimated the pulse response between the four air environmental indicators and urbanization rate, and analyzed the bidirectional dynamic coupling characteristics between the air qualities of the eastern, central, western, coastal and inland regions and the urbanization development. The results showed that there is a two-way interactive relationship between the regional urbanization and the air quality, which means that the urbanization can affect the air quality whereas the deteriorating of air quality has obvious negative effect on urbanization. The results of the impulse response analysis showed a significant regional difference between the region’s urbanization development and air quality in China’s eastern, central and western regions. The contradiction between urbanization and air quality in eastern and western regions is the most outstanding among these regions but is relatively weak in the middle region. This also reflected the two-way coupling relationship between urbanization and air quality in different developing stages in the three big regions. The east and west region is still in a low-level stage when urbanization and the air pollution are still inhibiting mutually.The impact response and variance decomposition results of different pollutants were varied with regions. Overall, the impact responses of urbanization on air environment indicators is decreased as PMio > SO2 > NO2. The air pollution has been worsened with the increasing population urbanization rate in all the regions except for the cities in the western region with SO2 concentrations decreasing. And with respect to the feedbacks impacting, the cumulative response values of the air environment indicators are negative in the cities of all the regions except for SO2 in the eastern cities. Thus, it can be concluded that NO2、PM10 and IAQI restricted the level of urbanization’s improvement with different extents and the restricting extent increases as time goes on.As a whole, it should not ignore the negative effect of the population, economic agglomeration on environment pollution with pursuing to expand the urban population scale and the economic density individually during the process of urbanization. In the future, the dynamic monitoring system should be established between the urban population scale and air pollution data to determine the threshold values of urbanization and pollution. Moreover, an early warning system linking the spatial distribution of human economic activity and pollution should be built. It was also paid more attention to reduce negative effect of the air pollution on urbanization development by proposing corresponding macroeconomic regulation and control strategy in the planning, industry, technology, etc.(5) Dynamically evaluating the provincial scale of coupling between urbanization and air environment system coordinating role process and comparing the action relation and model difference between different provinces and regionsThe coupling mechanism was complicated between the urbanization and air environment system elements, which were indicated on two aspects including the stress effect of urbanization on the ecological environment and the restriction effect of the ecological environment on urbanization. Based on this, this paper choose 20 urbanization indicators impacting on air environment and 12 air environment indexes impacting on urbanization and determined the index weights using the structure entropy weight method and mean squared deviation method. And then the evaluation system for the comprehensive level and the coupling coordination degree evaluation model (CCDM) of urbanization and air environment was established. The results showed that: ① Provincial urbanization comprehensive level score presents certain spatial heterogeneity and regularity. The score distribution is basically consistent with the law of China’s population density contrast line (Hu Huanyong line). Furthermore, the provincial urbanization level distributed with a pattern of spatial agglomeration and differed rarely between different provinces indicating the strengthening of spatial homogeneity. To realize the regional coordinated development and narrow the regional differences, it needs to pay more attention to the regional cooperation and spatial diffusion during the future developing of urbanization. ② During 2000-2013, the coupling coordination model of urbanization and air environment in different provinces has been experiencing the development from uncoordinated stage to transformation period and no high-level coordination phase was found, indicating that the air pollution is still more outstanding in the process of urbanization in Chia. From the point of the time sequence, disharmony period was mainly concentrated in 2005 and more than half of the provinces entered into the developing phase of the transformation period after 2006. From the point of type, after 2006, more and more provinces gradually undergone a transformation developing phase with the systems developing harmonically and air environment lagging and they all get rid of uncoordinated period in 2012. This also indicated that the development of urbanization and the air environment system has maintained a basic coordination development trend after "12th Five-Year". Therefore, in the future, in order to promote the construction of new urbanization, it needs not only to control the size of the population urbanization and to improve the city’s functional structure constantly, but also to focus the regional coordination on air quality improving.The main innovation of this paper lies in:using spatial analysis method and spatial econometric model, regarding urbanization as the main explanatory variable to develop and extending the Environmental Kuznets Curve theory of air pollution. Considering that the socioeconomic impacts of social factors such as urbanization and the natural factors including atmospheric circulation and climatic temperature in different seasons both effected on urban ambient air quality in different period, the future research should not only focus on the relationship mechanism between the urban scale, transformation and upgrading of industrial structure and air quality, but also to improve the spatial weight matrix by embedding with the wind speed, direction and other natural elements in spatial econometrics model.