Dynamic Network Analysis Of Urban Haze Pollution In Beijing-Tianjin-Hebei Region

In recent years,haze pollution has seriously affected human physical and mental health,urban environment,national economy-related industries and the development of our society.As a regional air pollution problem,how to carry out urban cooperative governance of haze pollution in the region has become a major and overarching problem.As the “worst-hit area” of haze pollution in China,the interaction of haze pollution among cities in Beijing-Tianjin-Hebei region has aggravated the extent of haze pollution in the region.However,the extent of haze pollution transmission and interaction between cities is inconformity.Thus,further study of dynamic asymmetric tail correlation of haze pollution between cities within the region has important practical significance for the joint prevention and control of haze pollution in the entire region.This paper firstly used the Pearson correlation coefficient to reflect the correlation of haze pollution between cities.Static undirected weighted network of haze pollution in Beijing-Tianjin-Hebei region was constructed.Then,three kinds of methods were used in nodes importance ranking,including degree and cluster coefficient,network efficiency and vulnerability and comprehensive node importance evaluation method.This paper synthetically analyzed nodes importance and extracted a sub-network of haze pollution in Beijing-Tianjin-Hebei region which has a strong internal correlation.On this basis,the daily average PM2.5 concentration data of nine cities in Beijing-Tianjin-Hebei region haze pollution sub-network from October 28,2013 to October 9,2018 were selected as samples.And the evolution process of dynamic network of haze pollution in BeijingTianjin-Hebei region was analyzed based on the samples.Firstly,the time series was transformed into 1435 time segments.Secondly,the tail threshold was determined by Hill diagram and error limit comparison verification.Meanwhile,the best Copula function was selected by AIC and BIC.Then,the dynamic asymmetric upper-tail correlation coefficient was derived based on Copula function.The dynamic asymmetric upper-tail correlation between two cities was calculated and the causal effect of asymmetric correlation was analyzed.Finally,on the basis of the dynamic asymmetric upper-tail correlation coefficient of two cities,a dynamic directed weighed network of haze pollution in Beijing-Tianjin-Hebei region was established.And the evolution process of the dynamic network was analyzed through the network average edge weight,cluster coefficient and network efficiency.In addition,the edge linking state between nodes in Beijing-Tianjin-Hebei haze pollution network was analyzed in detail.The results show that the overall correlation extent of Beijing-Tianjin-Hebei haze pollution network is higher in the early and late states of the entire time series,but lower in the middle state.The general edge linking state of Beijing-Tianjin-Hebei haze pollution network reflects that the haze pollution from other cities has a positive impact on Tianjin and Cangzhou.And in most periods,haze pollution from Baoding has affected most cities except Xingtai.At the end of this paper,four targeted policy recommendations were put forward based on the results of empirical research:(1)Placing the focus of supervision on the three key cities with high nodes importance.So that the connectivity efficiency of the urban haze pollution network of Beijing-Tianjin-Hebei region will be reduced.Thus,the secondary spread of haze pollution in the entire Beijing-Tianjin-Hebei region will be curbed.(2)Further revising and improving relevant policies and regulations on air pollution prevention and control,breaking through the constraints of traditional administrative systems and making cross-sectoral and inter-departmental cooperation.(3)taking active measures to slow down or interrupt the transmission of haze pollutants along the main transmission routes of haze pollutants and strengthening the supervision and control of pollution sources such as factories on the key transmission routes of pollutants.(4)Establishing a big data information service center in Beijing-Tianjin-Hebei region to conduct real-time monitoring and early warning of haze pollution.