| The sustainable development of the environment was closely related to the development of the city,and the environment with sustainable and healthy development can provide good development conditions for the city and its residents.With the increase of national control of fine particles(PM2.5),PM2.5 in the air presented a downtrend year by year,while ozone?O3?showed a rising trend year by year,and gradually becoming the main pollutant affecting air quality.At present,the study on air quality rules was mainly based on the monitoring data of large-scale and sparse state-controlled air quality monitoring stations.In recent years,a large number of intensive air quality monitoring stations deployed in various cities had provided the possibility for the study on the rules of air quality change in small-scale regions.On the basis of small scale and intensive air quality monitoring data,the study on the temporal and spatial change rules of important pollutant O3 in the rising trend was of great significance to the decision for the regional pollution control of O3.Taking Lanzhou City as the research object,in this paper,it selected the time series data of O 3 and its influencing factors on over 500 air quality monitoring stations in this city from November 2017 to October 2018,and used the complex network related theories and methods to study the dynamic relationship of O3 in Lanzhou City and its influencing factors,and the interactions of the pollutant O3 between urban areas.The detailed research contents were as follows.Fristly,the Vector Autoregressive model?VAR?of O3 in Lanzhou City and its influencing factors like nitrogen dioxide?NO2?,PM2.5,temperature?Temp?was constructed to analyze the dynamic influence relationships of NO2,PM2.5 and Temp on O3.The lag order of the model was determined according to the factor stationarity test and model characteristics.The VAR model with 4 lag period was constructed by AR characteristic root test.Using Granger causality test,generalized impulse response and variance decomposition,the dynamic influences of PM2.5,NO2,Temp on O3 were analyzed.The results showed that the influences of PM2.5 on O3 were negatively correlated,the influences of Temperature,NO2 on O3 were positively correlated,and the influences of NO2 and Temp on O3 were more obvious.Temp was an uncontrollable factor and there was a conversion relationship between NO2 and O3,and therefore,for the control of the urban pollutant O3,it was necessary to strictly control the emission of NO2.Secondly,the correlation fluctuation network model of NO2 and O3 in Lanzhou City was constructed to analyze the dynamic influence relationships between NO 2 and O3 in time series.The correlation between NO2 and O3 was processed by coarse granulation and symbolization,and the change sequence about the influence degree of NO2 on O3 was obtained.This sequence was used as network node to construct the correlation fluctuation network of NO2 and O3 in Lanzhou City.The dynamic influence relationships between NO2 and O3 were obtained by analyzing network features such as node degree,node strength,node betweenness,average shortest path of network,diameter of network and clustering coefficient of network.The results showed that the transformation period of NO2 on O3 can last for up to three days,and the correlation fluctuation network between NO2 and O3 in Lanzhou City had the characteristics of“small-world”networks,and the node strength had the heterogeneity.Through the excavation of the influence rules on NO2 and O3 and its network characteristics,it provided a reasonable theoretical basis for controlling O3 pollution.Thirdly,the spatial correlation network model of the interregional O 3 was constructed to analyze the interactions of the interregional O3 pollution.The air quality monitoring station in Qilihe district of Lanzhou City was used as the network node,the correlated coefficient probability density distribution and the most connected subgraph were used to determine the optimal connection threshold of the network edge,the spatial correlation network of O3 was constructed,and the proposed node important algorithm?CNODE?and transfer entropy theory were used to analyze the influence relationship between the regions of urban O3 pollution.The results showed that the spatial correlation network of O3 had the nature of community,the key nodes excavated from the network belonged to the same community,and the key nodes belonged to the adjacent regions in real space,which had the different effects of O3 on other nodes in the spatial correlation network of O3.Therefore,in the joint control of the pollutant O3,the impact of O3 pollution on other areas can be reduced by strengthening the pollution control of O3 in key areas,and the O3 pollution in noncritical areas can be treated in combination with their own situations and the extents to which other regions affect them. |
PDF Full Text Request