Temporal And Spatial Distribution Characteristics And Influencing Factors Of Tropospheric NO₂ Vertical Column Concentration In Shaanxi Province Based On Satellite Remote Sensing Data

In recent years,with the development of industry and the acceleration of urbanization,a large number of atmospheric pollutants are discharged into the atmosphere,which poses a serious threat to human health,food security,economic development and environmental quality.Shaanxi Province is a major energy province.At the same time,Guanzhong is a densely populated area with rapid urbanization.In recent years,the problem of atmospheric environmental pollution has become increasingly prominent.In order to fully understand and evaluate the problem of atmospheric pollution in Shaanxi Province,this paper used the NO2 concentration data of ground stations in Shaanxi Province to verify the NO2 vertical column density(VCD)in the troposphere observed by satellite was verified,and then the temporal and spatial distribution of NO2 VCD in the troposphere in Shaanxi Province was analyzed,GeoDa software was used to analyze the correlation of NO2 VCD in the troposphere of Shaanxi Province.The spatial spillover effect and human factors of NO2 VCD in the troposphere of Shaanxi Province were analyzed by Using Stata software and spatial econometric model.Finally,Hybrid Single-Particle Lagrangian Integrated Trajectory Model(HYSPLIT)was used to analyze the backward trajectory and clustering trajectory of air pollutants in Shaanxi Province,as well as the main transport path of pollutants.Potential Source Contribution Function Analysis(PSCF)and concentration weight trajectory analysis were used.Concentration Weighted Field(CWT)was used to calculate the PSCF and CWT values of NO2 in different seasons in northern Shaanxi,Guanzhong and southern Shaanxi,and to clarify the distribution of potential sources of pollutants.The main conclusions of this paper are as follows:(1)The concentration of NO2 column in troposphere monitored by OMI remote sensing satellite is in good agreement with the concentration of NO2 observed on the ground.Therefore,OMI data can be used to analyze the temporal and spatial variation of NO2 concentration in the troposphere of Shaanxi Province.It is found that the seasonal variation of NO2 column concentration is winter>autumn>spring>summer.The distribution of grade 5 concentration of NO2 in winter in Shaanxi Province is concentrated in Guanzhong area,which indicates that the pollution degree of NO2 in Guanzhong area is relatively high,and the pollution center is Xi'an city.From 2005 to 2012,the average NO2 column concentration in Shaanxi Province continued to rise,reaching the highest level in 2012,then began to decline,and the NO2 pollution situation improved.(2)There is a strong positive spatial spillover effect of NO2 pollution in Shaanxi Province,and the spillover effect is increasing.The concentration of NO2 vertical column in the troposphere increases by 1%,and that in the adjacent cities increases by 0.311%.The concentration of NO2 in the troposphere vertical column in Guanzhong area has a strong aggregation effect,and the interaction between cities is greater.Per capita GDP,GDP of secondary industry as a proportion of total production value,ownership of civil vehicles,urban per capita Road area are positively correlated with NO2 vertical column concentration in the troposphere of Shaanxi Province.Energy consumption per unit GDP,total import and export,green space area of gardens and operation cost of waste gas treatment facilities are negatively correlated with NO2 vertical column concentration in the troposphere of Shaanxi Province.(3)Affected by the northwest monsoon in winter and spring,the airflow trajectory in Shaanxi Province is mainly northwest direction,which has long airflow trajectory and fast moving speed.In summer and autumn,influenced by the southwest monsoon and Southeast monsoon,the airflow trajectory is mainly in the southwest and Southeast directions.The airflow trajectory in this direction is shorter and the moving speed is slower.The concentration of NO2 corresponding to the cluster trajectory in winter and spring in Shaanxi Province was higher than that in summer and autumn,indicating that the concentration of NO2 was higher in winter and spring.The NO2 concentration corresponding to clustering trajectory in northwest direction and local clustering trajectory is larger than that in southeast direction and northwest direction.(4)The spatial distribution of WPSCF and WCWT of NO2 in Shaanxi Province is similar,and the high value areas are mainly concentrated in Shaanxi Province,northeastern Gansu Province,Ningxia,western Inner Mongolia and other regions.The spatial distribution of WPSCF and WCWT varies with season.In winter and spring,WPSCF and WCWT mainly distribute in the Northwest direction,and move southward in summer and autumn.The high values of WPSCF and WCWT are winter>spring>autumn>summer.The distribution range of the potential sources of severe pollution(WPSCF>0.7)has seasonal differences,with the widest distribution in winter,the second in spring and the smallest in summer.